HomeMy Public PortalAboutStormwater Management Guidance Document
CHAPTER 272
STORMWATER MANAGEMENT BYLAW
GUIDANCE DOCUMENT
(JUNE 22, 2022)
Brewster Planning Department
2198 Main Street
Brewster, MA 02631-1898
(508) 896-3701 x1133
brewplan@brewster-ma.gov
Town of Brewster Stormwater Management Bylaw
Effective March 4, 2022 Page 1 of 10
Chapter 272
Stormwater Management Bylaw
Purpose and Objectives
A. The purpose of this Bylaw is to protect, maintain, and enhance public health,
safety, environment, and general welfare of the Town by preventing or
diminishing adverse effects of construction-site and post-construction stormwater
runoff. Proper management of stormwater runoff will minimize damage to public
and private property and infrastructure, safeguard the health, safety, environment,
and general welfare of the public, protect water and aquatic resources, protect and
enhance wildlife habitat, and promote groundwater recharge to protect surface
and groundwater drinking supplies. This Bylaw seeks to meet that purpose
through the following objectives:
Establish minimum stormwater management standards and design criteria for the regulation and
control of stormwater runoff quantity and quality;
Encourage the use of nonstructural stormwater management, better site design, and low impact
development practices such as preserving natural resources and open space, reducing impervious
surface area, and increasing infiltration;
Establish provisions for the long-term responsibility for, and maintenance of, structural
stormwater control facilities and nonstructural stormwater best management practices to ensure
that they continue to function as designed and pose no threat to public safety;
Establish provisions to ensure there is an adequate funding mechanism, including surety, for the
proper review, inspection, and long-term maintenance of stormwater facilities implemented as
part of this Bylaw;
Establish the Town of Brewster’s legal authority to ensure compliance with the provisions of this
bylaw through permitting, inspection, monitoring, and enforcement; and
Comply with state and federal statutes and regulations relating to stormwater discharges
including Total Maximum Daily Load requirements and with the General Permit for Stormwater
Discharges from Small Municipal Separate Storm Sewer Systems in Massachusetts (MS4
Permit), issued by the U.S. Environmental Protection Agency and the Massachusetts Department
of Environmental Protection.
Definitions
The following definitions shall apply in the interpretation and implementation of this Bylaw.
Additional definitions may be adopted by separate regulation.
ALTERATION OF DRAINAGE CHARACTERISTICS: Any activity on an area of land that
changes the water quality, force, direction, timing, or location of runoff flowing from the area.
Such changes include: change from distributed runoff to confined or discrete discharge; change
in the volume of runoff from the area; change in the peak rate of runoff from the area; and
change in the recharge to groundwater on the area.
APPLICANT: Any person, individual, partnership, association, firm, company, corporation,
trust, authority, agency, department, or political subdivision, of the Commonwealth or the
Federal government, to the extent permitted by law, requesting a Stormwater Permit.
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Effective March 4, 2022 Page 2 of 10
BEST MANAGEMENT PRACTICE (BMP): Schedules of activities, practices (and prohibitions
of practices), structures, vegetation, maintenance procedures, and other management practices to
prevent or reduce the discharge of pollutants to Waters of the United States. BMPs also include
treatment requirements, operating procedures, and practices to control plant site runoff, spillage
or leaks, sludge or waste disposal, or drainage from raw material storage.
CLEAN WATER ACT: The Federal Water Pollution Control Act (33 U.S.C. § 1251 et seq.) as
hereafter amended.
CLEARING: Any activity that removes the vegetative surface cover.
COMMON PLAN OF DEVELOPMENT: - A "larger common plan of development or sale" is a
contiguous area where multiple separate and distinct construction activities may be taking place
at different times on different schedules under one plan.
EROSION: The wearing away of the land surface by natural or artificial forces such as wind,
water, ice, gravity, or vehicle traffic and the subsequent detachment and transportation of soil
particles.
GRADING: Changing the level or shape of the ground surface.
GRUBBING: The act of clearing land surface by digging up roots and stumps.
IMPERVIOUS SURFACE: Any surface that prevents or significantly impedes the infiltration of
water into the underlying soil. This can include but is not limited to: roads, driveways, parking
areas and other areas created using nonporous material; buildings, rooftops, structures, solar
panels, artificial turf, and compacted gravel or soil.
INFILTRATION: The act of conveying surface water into the ground to permit groundwater
recharge and the reduction of stormwater runoff from a project site.
LAND DISTURBANCE ACTIVITY: Any activity that causes a change in the position or
location of soil, sand, rock, gravel, or similar earth material; results in an increased amount of
runoff or pollutants; measurably changes the ability of a ground surface to absorb waters;
involves clearing, grading, or excavating, including grubbing; or results in an alteration of
drainage characteristics.
LOW IMPACT DEVELOPMENT (LID): site planning and design strategies that use or mimic
natural processes that result in the infiltration, evapotranspiration or use of stormwater in order to
protect water quality and associated aquatic habitat.
MS4 PERMIT: General Permit for Stormwater Discharges from Small Municipal Separate
Storm Sewer Systems in Massachusetts.
MUNICIPAL SEPARATE STORM SEWER SYSTEM (MS4) or MUNICIPAL STORM
DRAIN SYSTEM: The system of conveyances designed or used for collecting or conveying
stormwater, including any road with a drainage system, street, gutter, curb, inlet, piped storm
drain, pumping facility, retention or detention basin, natural or man-made or altered drainage
channel, reservoir, and other drainage structure that together comprise the storm drainage system
owned or operated by the Town of Brewster.
NEW DEVELOPMENT: Any construction activities or land alteration on an area that has not
previously been developed to include impervious surface.
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OPERATION AND MAINTENANCE PLAN: A plan setting up the functional, financial and
organizational mechanisms for the ongoing operation and maintenance of a stormwater
management system to ensure that it continues to function as designed.
OWNER: A person with a legal or equitable interest in property.
PERSON: An individual, partnership, association, firm, company, trust, corporation, agency,
authority, department or political subdivision of the Commonwealth or the federal government,
to the extent permitted by law, and any officer, employee, or agent of such person.
RECHARGE: The process by which groundwater is replenished by precipitation through the
percolation of runoff and surface water through the soil.
RECORD: Recorded in the Barnstable County Registry of Deeds; if registered land is affected,
filed with the recorder of the Land Court of Massachusetts.
REDEVELOPMENT: Development, rehabilitation, expansion, demolition, construction, land
alteration, or phased projects that disturb the ground surface, including impervious surfaces, on
previously developed sites.
RUNOFF: Rainfall, snowmelt, or irrigation water flowing over the ground surface.
SEDIMENT: Mineral or organic soil material that is transported by wind or water, from its
origin to another location; the product of erosion processes.
SEDIMENTATION: The process or act of deposition of sediment.
SITE: The areal extent of construction and land disturbance activities, including but not limited
to the creation of new impervious surface and improvement of existing impervious surface.
STORMWATER AUTHORITY: The Town of Brewster Planning Board or its authorized
agent(s), acting pursuant to this Bylaw to administer, implement, and enforce this Bylaw and to
adopt regulations pursuant to it.
STORMWATER PERMIT: A permit issued by the Stormwater Authority, after review of an
application, plans, calculations, and other supporting documents, in accordance with the
provisions of this Bylaw.
TOTAL MAXIMUM DAILY LOAD (TMDL): A regulatory plan (authorized by the Clean
Water Act) that identifies the amount of a pollutant that a waterbody can assimilate without
exceeding its water quality standard for that pollutant.
WATERCOURSE: A natural or man-made channel through which water flows or a stream of
water, including a river, brook, or underground stream.
WATERS OF THE COMMONWEALTH: All waters within the jurisdiction of the
Commonwealth, including, without limitation, rivers, streams, lakes, ponds, springs,
impoundments, estuaries, wetlands, coastal waters, groundwater, and Waters of the United States
as defined under the Federal Clean Water Act as hereafter amended.
Authority
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Effective March 4, 2022 Page 4 of 10
This Bylaw is adopted under authority granted by the Home Rule Amendment of the
Massachusetts Constitution and the Massachusetts home rule statutes, and pursuant to the
regulations of the federal Clean Water Act found at 40 CFR 122.34.
Administration
A. The Stormwater Authority shall administer, implement, and enforce this Bylaw.
Any powers granted to or duties imposed upon the Stormwater Authority may be
delegated in writing by the Stormwater Authority to its employees or agents.
B. The Brewster Planning Board shall be the Stormwater Authority. For projects that
fall within the jurisdiction of the Brewster Wetlands Protection Bylaw (Brewster
General Bylaw Chapter 172), the Conservation Commission shall be the authority
to implement and enforce this Bylaw. The Stormwater Authority may designate
an agent to enforce this Bylaw.
C. This Bylaw is not intended to interfere with, abrogate, or annul any other Town of
Brewster bylaw, rule or regulation, statute, or other provision of law. The
requirements of this Bylaw should be considered minimum requirements, and
where any provision of this Bylaw imposes restrictions different from those
imposed by any other bylaw, rule or regulation, or other provision of law,
whichever provisions are more restrictive or impose higher protective standards
for human health or the environment shall be considered to take precedence.
Applicability
A Stormwater Permit shall be required for any of the following, except for an activity exempted
under Section 6 of this Bylaw:
A. Any land disturbance activity that will disturb 10,000 square feet or more, or
smaller land disturbance activities that are part of a larger common plan of
alteration or development that will disturb 10,000 square feet or more;
B. Any new development or redevelopment that will result in a net increase in
impervious surface area by 500 square feet or more, or smaller activities that are
part of a larger common plan of alteration or development that will result in a net
increase in impervious surface area by 500 square feet or more; or
C. Any land disturbance activity, new development, or redevelopment that, over a
two-year period, will result in a cumulative land disturbance of more than 10,000
square feet and/or a cumulative net increase in impervious surface area of more
than 500 square feet to land that is part of a larger parcel held in common
ownership or control at any time since said date. For the purposes of this Section,
ownership by related or jointly controlled persons or entities shall be considered
common ownership. In such cases, the new activity is prohibited until either:
(1) All activities that previously disturbed land and/or increased impervious
surface area as described in this Section are brought into full compliance
with the requirements and standards of this Bylaw, or
(2) The application for permit under this Bylaw for the new activity includes
bringing the land previously disturbed and/or the impervious surface area
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Effective March 4, 2022 Page 5 of 10
previously increased into full compliance with the requirements and
standards of this Bylaw. If the involved land is not currently held in
common ownership, all owners of the involved land must jointly apply for
the permit.
D. A development or alteration of land shall not be segmented or phased in a manner
to avoid compliance with this Bylaw.
Exemptions
The following activities are exempt from the requirements of this Bylaw, provided that such
activities utilize the best practical measures to avoid any negative impacts on stormwater quality,
runoff rate, and volume.
A. Any work or projects for which all necessary approvals and permits, including
building permits, have been issued before the effective date of this Bylaw.
B. Maintenance and improvement of land in agricultural or aquacultural use, as
defined by the Massachusetts Wetlands Protection Act regulation 310 CMR
10.04.
C. Maintenance of existing landscaping, gardens, or lawn areas associated with a
residential dwelling conducted in such a way as to not cause a nuisance.
D. Construction of fencing that will not substantially alter existing terrain or drainage
patterns.
E. Construction of utilities other than drainage (gas, water, electric, telephone, etc.)
that will not alter terrain, ground cover, or drainage patterns or result in discharge
of sediment or other pollutants to the MS4 or to a Watercourse or Waters of the
Commonwealth.
F. Emergency repairs to existing utilities (gas, water, electric, telephone, drainage,
etc.) or emergency repairs to any stormwater management facility that poses a
threat to public health or safety, as determined by the Stormwater Authority.
G. Maintenance or resurfacing (not including reconstruction) of an existing public or
private way, parking area, or driveway, provided that such activity does not
increase impervious surface area and that resurfacing does not disturb the
pavement subbase.
Stormwater Management Regulations
A. The Stormwater Authority shall promulgate and periodically amend Stormwater
Management Regulations relating to the terms, conditions, definitions,
enforcement, fees (including application, inspection, and/or consultant fees),
delegation of authority, procedures, and administration of this Bylaw. Failure of
the Stormwater Authority to issue such regulations, or a legal declaration of their
invalidity by a court, shall not act to suspend or invalidate the effect of this
Bylaw.
B. The Stormwater Authority may establish a Minor Stormwater Permit for specific
activities.
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(1) The purpose of the Minor Stormwater Permit is to simplify the permitting
process under this Bylaw by waiving certain submission requirements,
provided a set of predetermined eligibility criteria and performance
standards are met.
(2) The eligibility criteria, performance standards, and submission
requirements for Minor Stormwater Permits shall be outlined in the
Stormwater Management Regulations promulgated in accordance with this
Bylaw.
(3) The Stormwater Authority may allow Minor Stormwater Permits to be
approved by one or more agents of the Stormwater Authority rather than
by a majority of Stormwater Authority members.
C. The Stormwater Authority may establish criteria, procedures, and standards for
off-site compliance with post-construction stormwater management performance
standards established in the Stormwater Management Regulations promulgated
under this Bylaw.
Performance Standards
A. Performance standards shall be defined as part of the Stormwater Management
Regulations promulgated under this Bylaw.
B. Unless specifically altered by this Bylaw or its regulations, the Stormwater
Authority will use the latest accepted versions of the Massachusetts Stormwater
Management Regulations as contained in the Massachusetts Wetlands Protection
Act Regulations at 310 CMR 10.05 (6)(k) and the Massachusetts Stormwater
Handbook as issued by the Massachusetts Department of Environmental
Protection for criteria, policy, standards, stormwater systems design and
engineering, compliance documentation requirements, and general information
for the execution of the provisions of this Bylaw.
C. Unless specifically altered in this Bylaw and its regulations, the Stormwater
Authority shall presume that stormwater management practices designed,
constructed, and maintained in accordance with the Massachusetts Stormwater
Management Handbook meet the performance standards of this Bylaw. For
requirements that are inconsistent between the Massachusetts Stormwater
Management Handbook and the MS4 Permit, the Stormwater Authority will
enforce the more stringent of the requirements.
Procedures
A. A Stormwater Permit must be obtained prior to the commencement of any
construction or land disturbance activity for which such a permit is required. An
Applicant seeking a permit shall file an appropriate application with the
Stormwater Authority in a form and containing information as specified in this
Bylaw and in regulations adopted by the Stormwater Authority.
B. Each application must be accompanied by the appropriate application fee as
established by the Stormwater Authority. Applicants shall pay the application fee
before the review process commences. The Stormwater Authority, or its
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designated agent, is authorized to retain a Registered Professional Engineer (PE)
or other professional consultant to advise the Stormwater Authority on any or all
aspects of the application and/or the project’s compliance with conditions of a
Stormwater Permit. The Stormwater Authority may require the applicant to pay
reasonable costs to be incurred by the Stormwater Authority for the employment
of outside consultants pursuant to Stormwater Authority regulations as authorized
by M.G.L. c. 44, §53G.
C. To obtain a Stormwater Permit, the applicant must show that site design,
construction-site stormwater management, and post-construction stormwater
management will meet the standards established by the Stormwater Authority in
its regulations, which shall be at least as stringent as the relevant requirements of
the MS4 Permit and the Massachusetts Stormwater Handbook.
D. The Stormwater Permit shall include measures to ensure adequate long-term
operation and maintenance of stormwater management design features and BMPs.
E. The Stormwater Authority may impose requirements, including but not limited to
the following:
(1) A requirement that funds for future operation and maintenance be set aside
in a dedicated fund or escrow account;
(2) A permanent permit condition requiring compliance with an Operation
and Maintenance Plan;
(3) A permanent permit condition requiring that the property owner submit an
annual report or certification regarding operation and maintenance;
(4) A requirement to record the Operation and Maintenance Plan (or notice
thereof);
(5) A requirement that a legal instrument be put in place establishing
responsibility for operation and maintenance of a stormwater BMP serving
more than one lot.
Consent to Entry onto Property
By signing the permit application, the Applicant consents to the entry of members of the
Stormwater Authority or its authorized agents on the property while the application is under
review to verify the information in the application, and at any time after a Stormwater Permit is
issued to inspect for compliance with Stormwater Permit conditions.
Inspection and Site Supervision
The Stormwater Authority or its designated agent shall make inspections to verify and document
compliance with the Stormwater Permit.
Surety
The Stormwater Authority may require the applicant to post surety before the start of land
disturbance or construction activity. The form of the surety shall be approved by the Stormwater
Authority and be in an amount deemed sufficient by the Stormwater Authority to ensure that the
work will be completed in accordance with the permit. If the project is phased, the Stormwater
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Authority may release part of the surety as each phase is completed in compliance with the
permit.
Funds held pursuant to this Section shall be deposited in a separate account pursuant to M.G.L. c.
44, §53G1/2. Surety shall be in the form of a surety bond, irrevocable letter of credit, or cash.
All interest shall be held within said account; surety shall be released upon satisfaction of all
Permit requirements; upon satisfaction of all Permit requirements, applicant shall request, in
writing, to the Town Treasurer, that the funds be released, the funds shall not be released until
the Stormwater Authority certifies, in writing, that all requirements of the Permit have been met.
If the permittee defaults on any obligations imposed by the Permit, the Stormwater Authority
may (after notification of the permittee) inform the holder of the security (and the municipal
treasurer if the treasurer is not holding the funds) of the default, in which event the Town shall be
entitled to the security funds to complete the outstanding permit requirements.
Waivers
A. The Stormwater Authority, or its authorized agent, may waive strict compliance
with any requirement of this Bylaw if it finds that:
(1) Application of some of the requirements is unnecessary or impracticable
because of the size or character of the development activity or because of
the natural conditions at the site;
(2) The project is consistent with the purposes and intent of this Bylaw; and
(3) The project provides substantially the same level of protection to the
public health, safety, environment, and general welfare of the Town as
required by this Bylaw.
B. Any person seeking a waiver shall submit a written waiver request. Such a request
shall be accompanied by an explanation or documentation supporting the waiver
request.
C. Waiver requests, except those for activities eligible for Minor Stormwater
Permits, shall be discussed and voted on at a public meeting for the project.
D. Waiver requests for Minor Stormwater Permits may be approved by one or more
agents of the Stormwater Authority rather than by a majority of Stormwater
Authority members.
E. If in the opinion of the Stormwater Authority or its authorized agent, additional
time or information is required for review of a waiver request, the Stormwater
Authority may continue a meeting to a date announced at the meeting. In the
event the Applicant objects to a continuance or postponement, or fails to provide
requested information, the waiver request shall be denied.
Enforcement
The Stormwater Authority or its authorized agent shall enforce this Bylaw, and any associated
regulations, orders, violation notices, and enforcement orders and may pursue all civil and
criminal remedies for such violations.
A. Criminal and Civil Relief.
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(1) Any person who violates the provisions of this Bylaw, or any associated
regulations, permit, or order issued thereunder, may be subject to criminal
penalties and prosecution in a court of competent jurisdiction and/or a fine
of not more than $300 per violation. Each day or part thereof that such
violation occurs or continues shall constitute a separate offense.
(2) The Stormwater Authority may seek injunctive relief in a court of
competent jurisdiction restraining the person from activities which would
create further violations or compelling the person to perform abatement or
remediation of the violation.
B. Orders.
(1) The Stormwater Authority’s authorized agent may issue a written order to
enforce the provisions of this Bylaw or any associated regulations or
permit. Violations include, without limitation, failure to obtain a
Stormwater Permit for an activity subject to this Bylaw, or failure to
follow the requirements of a Stormwater Permit, or any other
authorization issued pursuant to this Bylaw or regulations issued
hereunder. The written order may require the violator to remediate the
non-compliance and/or any adverse impact caused by it, including without
limitation:
(a) A requirement to cease and desist from the land-disturbing activity
until there is compliance with this Bylaw and provisions of the
Stormwater Permit or other authorization;
(b) Maintenance, installation, or performance of additional erosion and
sediment control measures;
(c) Monitoring, analyses, and reporting;
(d) Remediation of erosion and sedimentation resulting directly or
indirectly from the land-disturbing activity;
(e) Construction, reconstruction, repair, or maintenance of stormwater
BMPs or any other aspect of the post-construction stormwater
management system;
(f) Remediation of adverse impacts resulting from improper
construction or operation of the post-construction stormwater
management system; and/or
(g) A requirement to eliminate discharges, directly or indirectly, into
the MS4, a watercourse, or into the Waters of the Commonwealth.
(2) Any order under this section may be appealed to the Stormwater Authority
within five (5) days of the date of said order. All appeals shall be heard
and decided within thirty (30) days. The decision of the Stormwater
Authority shall be final.
(3) If the Stormwater Authority or its authorized agent determines that
abatement or remediation of contamination is required, the order shall set
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forth a deadline by which such abatement or remediation must be
completed. Said order shall further provide that, should the violator or
property owner fail to abate or perform remediation within the specified
deadline, the Town of Brewster may, at its option, undertake such work,
and expenses thereof shall be charged to the violator.
(4) Within 30 days after completing all measures necessary to abate the
violation or to perform remediation, the violator and the property owner
will be notified of the costs incurred by the Town, including
administrative costs. The violator or property owner may file a written
protest objecting to the amount or basis of costs with the Stormwater
Authority within 30 days of receipt of the notification of the costs
incurred. If the amount due is not received by the expiration of the time in
which to file a protest or within 30 days following a decision of the
Stormwater Authority affirming or reducing the costs, or from a final
decision of a court of competent jurisdiction affirming or reducing the
costs, the costs shall constitute a municipal charge for purposes of M.G.L.
c.40, §58, and a lien may be imposed on the property for the amount of the
unpaid charge, pursuant to M.G.L. c.40, §58. Interest shall begin to accrue
on any unpaid costs at the statutory rate provided in M.G.L. c. 59, §57 on
the 31st day after the costs first become due.
C. Noncriminal disposition. As an alternative to criminal prosecution or civil action,
the Town may elect to utilize the noncriminal disposition procedure set forth in
M.G.L. c. 40, §21D, in which case designated agents of the Stormwater Authority
shall be the enforcing persons. The penalty for the first violation shall be a
warning. The penalty for the second violation shall be $100. The penalty for the
third and subsequent violations shall be $300. Each day or part thereof that such
violation occurs or continues shall constitute a separate offense.
D. Entry to perform duties under this Bylaw. To the extent permitted by local, state
or federal law, or if authorized by the owner or other party in control of the
property, the Stormwater Authority, its agents, officers, and employees may enter
upon privately owned property for the purpose of performing their duties under
this Bylaw and regulations and may make or cause to be made such examinations,
surveys or sampling as the Stormwater Authority deems reasonably necessary.
E. Appeals. The decisions or orders of the Stormwater Authority shall be final.
Further relief shall be appealed to a court of competent jurisdiction.
F. Remedies not exclusive. The remedies listed in this section are not exclusive of
any other remedies available under any applicable federal, state, or local law.
Severability
The provisions of this Bylaw are hereby declared to be severable. If any provision, paragraph,
sentence, or clause of this Bylaw or the application thereof to any person, establishment, or
circumstances shall be held invalid, such invalidity shall not affect the other provisions or
application of this Bylaw.
Town of Brewster
Stormwater Management Regulations
Adopted Date: February 23, 2022
Effective Date: March 4, 2022
Table of Contents
Section 1. Purpose 2
Section 2. Definitions 2
Section 3. Authority 2
Section 4. Applicability 3
Section 5. Administration 3
Section 6. Performance Standards 9
Section 7. Construction Inspections 14
Section 8. Long -Term Operation and Maintenance 15
Section 9. Surety 17
Section 10. Severability 17
Appendix A. Definitions 18
Appendix B. Stormwater Management Plan Checklists 22
Appendix C. Fee Schedule 30
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Section 1. Purpose
The purpose of these Regulations is to protect, maintain, and enhance public health, safety,
environment, and general welfare by establishing minimum requirements and procedures to
mitigate the adverse effects of stormwater runoff, decreased groundwater recharge, erosion and
sedimentation, and nonpoint source pollution, as more specifically addressed in the Town of
Brewster Stormwater Management Bylaw (Chapter 272).
Section 2. Definitions
2.1. The definitions contained herein apply to the Brewster Stormwater Management Bylaw
and the Regulations adopted thereunder. Terms not defined in this section shall be
construed according to their customary and usual meaning unless the context indicates a
special or technical meaning.
2.2. Definitions are provided in Appendix A of these Regulations.
Section 3. Authority
3.1. The regulations contained herein have been adopted by the Stormwater Authority in
accordance with § 272-7 of the Stormwater Management Bylaw.
3.2. Pursuant to § 272-4 of the Stormwater Management Bylaw, the Brewster Planning Board
is the Stormwater Authority. For projects that fall within the jurisdiction of the Brewster
Wetlands Protection Bylaw (Chapter 172), the Conservation Commission shall be the
authority to implement and enforce this Bylaw. The Stormwater Authority may designate
an agent(s) to enforce this Bylaw.
3.3. The Stormwater Authority may periodically amend these regulations pursuant to § 272-7
of the Stormwater Management Bylaw.
3.4. Nothing in these Regulations is intended to replace or be in derogation of the
requirements of any other Brewster bylaw. These Regulations should be considered
minimum requirements, and where any provision of these Regulations impose restrictions
different from those imposed by any other bylaw, rule or regulation, or other provision of
law, whichever provisions are more restrictive or impose higher protective standards for
human health or the environment shall be considered to take precedence.
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Section 4. Applicability
All activities subject to the Stormwater Management Bylaw (as set forth in § 272-5 of the
Stormwater Management Bylaw) shall obtain a Stormwater Permit before commencing
construction or land -disturbance activities. Exemptions are established in § 272-6 of the
Stormwater Management Bylaw. The following provides further guidance on activities that do
not require a Stormwater Permit:
• Paving an existing gravel, crushed shell, or dirt driveway, road, or parking area, provided
that the area of land disturbance is less than 10,000 square feet, and the expansion of
impervious surface area is less than 500 square feet. Gravel, crushed shell, and dirt
driveways, roads, and parking areas are defined as impervious surfaces per Appendix A
of these Regulations and § 272-2 of the Stormwater Management Bylaw. Therefore,
paving of those surfaces does not constitute creation of new impervious surface area;
• Construction or repair of subsurface septic system components; and
• Replacement of an existing roof.
Proposed raised decks are excluded from the calculation of new impervious surface area if:
• The ground area beneath the proposed deck is presently bare ground or landscaped,
including lawn, and is proposed to remain pervious,
• There will not be a roof constructed over the proposed deck, and
• The proposed deck will be constructed in such a manner to allow rainfall to pass
through to the ground below. An example of this is the typical wooden deck with
expansion spaces between the boards that form the deck surface.
The following criteria shall apply for determining eligibility for Minor Stormwater Permit and
Major Stormwater Permit categories:
4.1. Minor Stormwater Permit
A. Any combination or series of construction or land disturbance activities that, over a
two-year period, will result in a net increase in impervious area of 500 square feet to
2,500 square feet and/or will result in land disturbances of 10,000 square feet to
20,000 square feet.
4.2. Major Stormwater Permit
A. Any alteration, disturbance, development, or redevelopment that does not meet the
eligibility criteria for Minor Stormwater Permit.
Section 5. Administration
5.1. Stormwater Permit applications shall be administered as follows:
A. Minor Stormwater Permit applications shall be reviewed and acted upon by the
Designated Agent of the Stormwater Authority. The Town Planner, Conservation
Administrator, Department of Public Works (DPW) Director, or Building
Commissioner shall be the Designated Agent, depending on the other reviews and
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approvals to which the project is subject. Review by the Stormwater Authority is not
required for Minor Stormwater Permits.
B. Major Stormwater Permit applications shall be reviewed and acted upon by the
Stormwater Authority.
5.2. Application Procedures
A. The Applicant shall submit to the Stormwater Authority (for a Major Permit) or
Designated Agent (for a Minor Permit) a completed application for a Stormwater
Permit. The Stormwater Permit Application package shall include:
(1) A completed Application Form with original signatures of all property owners;
(2) Digital and printed copies of the Stormwater Management Plan, prepared in
accordance with the Stormwater Management Plan Checklist in Appendix B of
these Regulations; and
(3) Payment of the Application Fee in accordance with the Fee Schedule in
Appendix C of these Regulations.
B. The Stormwater Authority (for a Major Permit) or Designated Agent (for a Minor
Permit) shall make a determination as to the completeness of the application and
adequacy of the materials submitted. No review shall take place until the application is
determined complete.
5.3. Fees
A. Each application shall be accompanied by the appropriate Application Fee, as detailed
in Appendix C of these Regulations.
B. The Stormwater Authority or Designated Agent may, at the Applicant's expense,
retain a registered Professional Engineer (PE) or other professional consultant to
advise the Stormwater Authority on any or all aspects of the Application.
(1) Purpose. As provided by M.G.L. Ch. 44 §53G and the Stormwater
Management Bylaw, the Stormwater Authority may impose reasonable fees for
the employment of outside consultants, engaged by the Stormwater Authority,
for specific expert services to assist the Stormwater Authority in its review of
applications for Stormwater Permits and oversight of permit compliance.
(2) Consultant Services. Specific consultant services may include, but are not
limited to, technical or legal review of the permit application and associated
information, on -site monitoring during construction, or other services related to
the project deemed necessary by the Stormwater Authority. The consultant
shall be chosen by, and report only to, the Stormwater Authority or its staff.
Notice. The Stormwater Authority shall give written notice to the Applicant of
the selection of an outside consultant. Such notice shall state the identity of the
consultant, the amount of the fee to be charged to the applicant, and a request
for payment of said fee in its entirety. Such notice shall be deemed to have
been given on the date it is mailed or delivered. No such costs or expenses
(3)
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shall be incurred by the Applicant if the application or request is withdrawn
within five (5) business days of the date notice is given.
(4) Payment of Fee. The fee must be received prior to the initiation of consulting
services. The Stormwater Authority may request additional consultant fees if
the review requires a larger expenditure than originally anticipated or new
information requires additional consultant services. Failure by the Applicant to
pay the consultant fee specified by the Stormwater Authority within ten (10)
business days of the request for payment, or refusal of payment, shall be cause
for the Stormwater Authority to deny the application based on lack of
sufficient information to evaluate whether the project meets applicable
performance standards. An appeal stops the clock on the above deadline; the
countdown resumes on the first business day after the appeal is either denied or
upheld.
Special Account. Funds received pursuant to these Regulations shall be
deposited with the municipal treasurer, who shall establish a special account
for this purpose. Expenditures from this special account may be made at the
direction of the Stormwater Authority without further appropriation as
provided in M.G.L. Ch. 44 §53G. Expenditures from this account shall be
made only in connection with a specific project or projects for which a
consultant fee has been collected from the applicant. Expenditures of accrued
interest may also be made for these purposes.
(6) Appeals. The Applicant may appeal the selection of the outside consultant to
the Select Board, who may only disqualify the outside consultant selected on
the grounds that the consultant has a conflict of interest or does not possess the
minimum required qualifications. The minimum qualifications shall consist of
either an educational degree or three or more years of practice in the field at
issue or a related field. Such an appeal must be in writing and received by the
Select Board and a copy received by the Stormwater Authority, so as to be
received within ten (10) business days of the date consultant fees were
requested by the Stormwater Authority. The required time limits for action
upon the application shall be extended by the duration of the administrative
appeal.
Return of Unspent Fees. When the Stormwater Authority's review of a permit
application and oversight of the permitted project is complete, any balance in
the special account attributable to that project shall be returned within thirty
(30) business days. The excess amount, including interest, shall be repaid to
the Applicant or the Applicant's successor in interest. For the purpose of these
Regulations, any person or entity claiming to be an Applicant's successor in
interest shall provide the Stormwater Authority with appropriate
documentation. A final report of said account shall be made available to the
Applicant or Applicant's successor in interest.
5.4. Right of Entry
Filing an application for a permit grants the Stormwater Authority or its agent permission
to enter the property to verify the information in the application and to inspect for
(5)
(7)
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compliance with permit conditions. During the application process, the Stormwater
Authority, its employees and agents (including consultants) may conduct site visits of the
project site to review information presented in the application.
5.5. Public Meeting
A. A public meeting is not required for Minor Stormwater Permit applications.
B. For Major Stormwater Permit applications, the Stormwater Authority shall hold a
meeting in accordance with the Massachusetts Open Meeting Law. For projects or
activities that require issuance of a Stormwater Permit in addition to other approvals or
permits, the Stormwater Authority shall hold a coordinated meeting on all
jurisdictional project aspects in accordance with its own regulations and procedures.
5.6. Action by the Stormwater Authority or Designated Agent
A. Minor Stormwater Permit
(1) The Designated Agent shall act upon a Minor Stormwater Permit Application
within thirty (30) business days of the date the Designated Agent determines
the application is complete or after receipt of expert review by outside
consultants if deemed necessary in accordance with Section 5.3.B.
(2) The Designated Agent may:
a. Approve the Minor Stormwater Permit Application and issue a permit if it
finds that the performance standards and requirements set forth herein
have been met;
b. Approve the Minor Stormwater Permit Application and issue a permit
with conditions, modifications, or restrictions that the Designated Agent
determines are required to ensure that the performance standards and
requirements set forth herein are met;
c. Disapprove the Minor Stormwater Permit Application and deny the permit
if it finds that the performance standards and requirements set forth herein
have not been met; or
d. Disapprove the Minor Stormwater Permit Application "without prejudice"
where an applicant fails to provide requested additional information or
review fees that in the Designated Agent's opinion are needed to
adequately describe or review the proposed project.
Final approval, if granted, shall be endorsed on the Stormwater Permit by the
signature of the Designated Agent.
(4) Appeal of Disapproved Applications
a. The Applicant may appeal a permit denial by the Designated Agent by
requesting the Stormwater Authority review the application. Such review
shall take place with a public meeting as described in Section 5.5 and shall
be subject to any review fees or additional submittal requirements as
specified in these Regulations.
B. Major Stormwater Permit
(3)
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(1) The Stormwater Authority shall take final action within thirty (30) business
days from the public meeting as described in Section 5.5, unless such time is
extended by agreement between the Applicant and Stormwater Authority.
(2) The Water Quality Review Committee will provide comments on Major
Stormwater Permit applications for those projects that require a Special Permit
under the Water Quality Protection District (Chapter 179, Article XI).
The Stormwater Authority may:
a. Approve the Major Stormwater Permit Application and issue a permit if it
finds that the performance standards and requirements set forth herein
have been met;
b. Approve the Major Stormwater Permit Application and issue a permit with
conditions, modifications, or restrictions that the Stormwater Authority
determines are required to ensure that the performance standards and
requirements set forth herein are met;
c. Disapprove the Major Stormwater Permit Application and deny the permit
if it finds that the performance standards and requirements set forth herein
have not been met; or
d. Disapprove the Major Stormwater Permit Application "without prejudice"
where an applicant fails to provide requested additional information or
review fees that in the Stormwater Authority's opinion are needed to
adequately describe or review the proposed project.
(4) Final approval, if granted, shall be endorsed on the Stormwater Permit by the
signature of the majority of the Stormwater Authority or by the Stormwater
Authority chair or other designated Stormwater Authority member, as
consistent with the Stormwater Authority (Planning Board or Conservation
Commission) standard procedures.
(3)
5.7. Project Delay
If the project associated with an approved Stormwater Permit has not been completed
within three (3) years of permit issuance, the Permit shall expire. At the request of the
Applicant, the Stormwater Authority or Designated Agent may extend the Permit or
require the Applicant to apply for a new permit. Any request for extension shall be
submitted in writing no later than thirty (30) business days prior to the expiration of the
Stormwater Permit. The Stormwater Authority or Designated Agent may require updates
to the project to comply with current regulations and standards as a condition of the
permit extension.
5.8. Project Changes
The Permittee, or their agent, shall notify the Stormwater Authority or Designated Agent
in writing of any change of a land -disturbing activity authorized in a Stormwater Permit
before any change occurs. If the Stormwater Authority or Designated Agent determines
that the change is significant, based on the performance standards in Section 6 and
accepted construction practices, the Stormwater Authority or Designated Agent may
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February 23, 2022 Page 7 of 30
require that an amended Stormwater Permit application be filed and a public meeting
held. If any change from the Stormwater Permit occurs during land disturbing activities,
the Stormwater Authority or Designated Agent may require the installation of interim
erosion and sedimentation control measures before approving the change.
5.9. Stormwater Management Certificate of Compliance (SMCC)
A. No SMCC is required for work approved under a Minor Stormwater Permit.
B. Within two (2) years after completion of construction or land disturbance activities
permitted under a Major Stormwater Permit, the Permittee shall submit in writing a
request for a SMCC. The Permittee must complete the following actions before the
Stormwater Authority will consider the request for SMCC:
(1) Within six (6) months after completion of construction and land disturbance
activities, the Permittee shall submit certified as -built plans from a registered
Professional Engineer (PE), surveyor, or Certified Professional in Erosion and
Sediment Control (CPESC). The as -built plans must depict all structural and
non-structural stormwater management systems, including subsurface
components, and impervious and pervious surface areas on site. Any
discrepancies from the approved Stormwater Management Plan should be
noted in the cover letter.
(2) The Permittee shall record the approved Operation and Maintenance Plan,
including the as -built plans, with the Barnstable County Registry of Deeds.
The Permittee shall complete and document the first year of stormwater best
management practice (BMP) operation and maintenance, in accordance with
the approved Operation and Maintenance Plan and Stormwater Permit
conditions.
C. Upon written request by the Permittee, the Stormwater Authority shall assess whether
the work has been completed in substantial conformance with the approved
Stormwater Management Plan and any conditions of the Stoiiniwater Permit. Upon
determination that permit conditions have been met, the Stormwater Authority shall
issue a SMCC.
D. It is the responsibility of the Permittee to request, in writing, the issuance of a SMCC.
A Permittee who fails to request a SMCC within two (2) years after completion of
construction and land disturbance activities may be found in noncompliance with the
Stormwater Management Bylaw and face applicable enforcement actions.
E. After issuance of the SMCC, the Stormwater Authority may periodically review
ongoing compliance with Stormwater Permit conditions, including long-term
operation and maintenance. If it finds that permit conditions have not been met, the
Stormwater Authority may revoke the SMCC and take action in accordance with §
272-14 of the Stormwater Management Bylaw. For projects that have been issued a
Water Quality Certificate under the Water Quality Protection District (Chapter 179,
Article XI), the Water Quality Review Committee will conduct a compliance review
every three years and will work with the Stormwater Authority to ensure ongoing
compliance with Stormwater Permit conditions.
(3)
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5.10. Waivers
A. The Stormwater Authority or Designated Agent may waive strict compliance with any
requirement of these Regulations, if it finds that:
(1) Application of some of the requirements is unnecessary or impracticable
because of the size or character of the development activity or because of the
natural conditions at the site;
(2) The project is consistent with the purposes and intent of the Stormwater
Management Bylaw; and
The project provides substantially the same level of protection to the public
health, safety, environment, and general welfare of the Town as required by the
Stormwater Management Bylaw.
B. Any Applicant seeking a waiver shall submit a written waiver request. Such a request
shall be accompanied by an explanation or documentation supporting the waiver
request.
C. Waiver requests for Minor Stormwater Permits may be approved by the Designated
Agent rather than by a majority of Stormwater Authority members.
D. Waiver requests for Major Stormwater Permits shall be discussed and voted on at a
public meeting for the project. If, in the opinion of the Stormwater Authority,
additional time or information is required for review of a waiver request, the
Stormwater Authority may continue a meeting to a date announced at the meeting. In
the event the Applicant objects to a continuance or postponement, or fails to provide
requested information, the waiver request shall be denied.
(3)
Section 6. Performance Standards
6.1. Construction -Site Stormwater Management
A. Projects eligible for Minor Stormwater Permits shall meet the construction -site
stormwater management performance standards detailed in Section 6.1.B to the
maximum extent practicable. At a minimum, controls for erosion, sediment, and
construction wastes shall be implemented to prevent nuisance conditions, such as
sediment or debris washouts onto abutting properties and public rights of way.
B. For Major Stormwater Permits, projects shall implement practices to control
construction -related erosion, sedimentation, and wastes in accordance with the most
recent versions of the Massachusetts Stormwater Handbook and the Massachusetts
Erosion and Sedimentation Control Guidelines for Urban and Suburban Areas, or
more stringent standards as specified in these Regulations. The following performance
standards shall be met.
(1) Natural Resource Protection: Before commencing land disturbance activities,
the limits of permitted disturbance areas shall be marked with high -visibility
flagging, fencing, and/or signage. Areas designated for revegetation and/or
infiltration -based stormwater practices shall be marked with flagging, fencing,
and/or signage to restrict use of heavy vehicles and equipment in these areas to
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February 23, 2022 Page 9 of 30
avoid soil compaction. Tree protection shall be installed around the dripline for
all trees to be preserved. Buffers and other restricted areas shall be maintained
as required in a wetlands protection authorization from the Brewster
Conservation Commission or MassDEP.
(2) Area of Disturbance: Clearing and grading shall only be performed within
areas needed to build the project, including structures, utilities, roads,
recreational amenities, post -construction stormwater management facilities,
and related infrastructure. Such areas shall be staked to ensure that the work is
completed within the appropriate areas. Construction activities shall be phased
to minimize the area of disturbed soil at any one time.
Soil Stabilization: The time that soil is exposed shall be minimized by
stabilizing dormant areas as work progresses. Exposed areas shall be
vegetated, hydromulched, protected with erosion control blankets, or otherwise
stabilized within 14 days after land disturbance activities have permanently
ceased or will be temporarily inactive for 14 or more days. Vegetative cover
shall be prepared in the fall to ensure that exposed areas have cover before the
first freeze.
(4) Stockpiles: Materials shall not be stored or stockpiled near a storm drain or a
wetland resource area. Stockpiled materials that will be unused for 14 or more
days shall be covered with roof, tarp, or temporary seeding (of soil stockpiles).
Perimeter controls shall be installed around stockpile and staging areas.
Perimeter Controls: Perimeter sediment controls, such as silt fencing and filter
tubes, shall be installed around downgradient boundaries, along all resource
areas, and around stockpile and staging areas. Compost socks and straw bale
shall be free of invasive species. Perimeter controls shall not be removed until
the drainage areas have been permanently stabilized.
(6) Stabilized Construction Entrance: Track -out controls (e.g., gravel apron) shall
be installed at each construction entrance to remove sediment from vehicles
and prevent tracking onto public roads. Where sediment has been tracked -out
from the site, paved roads, sidewalks, or other paved areas shall be swept or
vacuumed at the end of the workday. Sediment shall not be swept, hosed, or
otherwise deposited into any stormwater conveyance, storm drain inlet, or
waterbody.
Inlet Protection: Filter bags, filter tubes, or other inlet protection controls shall
be installed to prevent sediment from entering downgradient storm drains. Inlet
controls shall not be removed until the drainage areas have been permanently
stabilized.
(8) Runoff Diversion: Runoff shall be intercepted and diverted away from
disturbed areas with berms, swales, or pipes toward stabilized outlets.
Conveyances shall be stabilized with vegetation, erosion control blankets,
check dams, or similar practices to slow velocities and prevent erosion.
Sediment Removal: Sediment traps and basins shall be used to remove
suspended solids from runoff before it discharges from the site. Traps and
(3)
(5)
(7)
(9)
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basins shall be designed to use baffles, multiple cells, and other practices to
maximize the flow path and settling time. Sediment controls shall not be
removed until the drainage areas have been permanently stabilized.
(10) Dewatering: Dewatering activities shall use tanks, filter bags, or other practices
to remove sediment before discharge. Water shall not be discharged in a
manner that causes erosion or flooding of the site or receiving waters.
(11) Outlet Protection: Pipe outlets shall have stone aprons, level spreaders, or other
energy dissipation practices installed to prevent erosion.
(12) Construction Waste Management: Trash, debris, and sanitary wastes shall be
removed from the site on a regular basis. Dumpsters shall be covered at the end
of every workday and before rain events. Dumpsters shall not be allowed to
leak or otherwise discharge to any stormwater conveyance, storm drain inlet,
or waterbody. Concrete mixers shall be washed out only in designated areas
with liners. Demolition debris, discarded building materials, concrete truck
wash out, chemicals, litter, and sanitary wastes shall not be discharged to the
MS4 and shall be disposed of in compliance with all local, state, and federal
requirements.
(13)Post-Construction BMPs: Stormwater management facilities to be used after
construction shall not be used as BMPs during construction unless otherwise
approved by the Stormwater Authority. Many technologies are not designed to
handle the high concentrations of sediments typically found in construction
runoff, and thus must be protected from construction -related sediment
loadings.
(14)Dust Control: Dust control shall be used during grading operations. Dust
control methods may consist of grading fine soils on calm days only or
dampening the ground with water.
(15) Inspection and Maintenance: Erosion and sediment controls shall be inspected
as needed and at a minimum before and after rain events. Accumulated
sediments shall be removed, and erosion and sediment controls shall be
repaired or replaced as needed to ensure they perform as intended.
6.2. Post -Construction Stormwater Management
Projects that do not involve the development or redevelopment of impervious surfaces are
exempt from meeting Post -Construction Stormwater Management performance
standards.
A. Minor Stormwater Permits
(1) Projects eligible for Minor Stormwater Permits shall evaluate and, unless
impracticable, implement Low Impact Development (LID) planning and
design strategies. LID practices may include, but not be limited to, protection
and restoration of natural resources, minimizing impervious surfaces, grading
to direct runoff onto pervious surfaces, and soil decompaction and amendments
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February 23, 2022 Page 11 of 30
to improve infiltration capacity. Further guidance on LID practices may be
found in the Massachusetts Stormwater Handbook.
(2) Projects shall implement at least one stormwater BMP to mitigate the impacts
from stormwater runoff and pollutants generated from impervious surfaces on
the property. The Applicant may select a BMP type including but not limited
to:
i. Impervious area disconnection
ii. Rain barrel for roof runoff
iii. Rain garden
iv. Pervious pavement
v. Dry well
vi. Infiltration trench
vii. Vegetated swale
(3)
Stormwater BMPs shall be designed in accordance with the Massachusetts
Stormwater Handbook and shall have a storage volume equivalent to 1 inch
multiplied by the net increase in impervious surface area or by 500 square feet
of impervious surface area, whichever is greater. Sizing of infiltration BMPs
may be adjusted using a BMP sizing tool provided by the Stormwater
Authority.
B. Major Stormwater Permits
(1) At a minimum, Major Stormwater Permit projects shall comply with the
Massachusetts Stormwater Standards and the MS4 Permit. Design of
stormwater management systems shall be consistent with the requirements of
the Massachusetts Stormwater Handbook, or more stringent standards as
specified in these Regulations.
(2) Applicants shall evaluate and, unless infeasible, implement LID planning and
design strategies. LID practices shall include, but not be limited to, protection
and restoration of natural resources, minimizing impervious surfaces, grading
to direct runoff onto pervious surfaces, and soil decompaction and amendments
to improve infiltration capacity. Further guidance on LID practices may be
found in the Massachusetts Stormwater Handbook. If the Applicant finds that
LID practices are infeasible, the Applicant shall demonstrate which LID
practices were evaluated and reasons why those practices were deemed
infeasible.
Selection and design of stormwater BMPs shall be optimized for the removal
of phosphorus and nitrogen. Infiltration BMPs, bioretention, and constructed
stormwater wetlands are recommended for reducing the concentration of
nutrients in stormwater discharges. Additional guidance on BMP performance
for phosphorus and nitrogen removal may be found in the MS4 Permit.
(3)
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(4) Drainage analyses and design calculations shall use precipitation depths based
on 90% of the NOAA Atlas 141 upper confidence interval for the project
location, also known as "NOAA Plus". These "Plus" values are calculated by
multiplying the NOAA Atlas 14 upper confidence interval by 0.9.
BMPs located on commercial or industrial land use areas shall be designed to
allow for shutdown and containment to isolate the drainage system in the event
of an emergency spill or other unexpected event.
(6) New Development
a. Stormwater management systems for new development shall be designed
to remove, at a minimum, 90% of the average annual load of Total
Suspended Solids (TSS) and 60% of the average annual load of Total
Phosphorus (TP) generated from the total post -construction impervious
surface area on the site. Average annual pollutant removal requirements
may be achieved through one of the following methods:
i. Installing stormwater BMPs that provide the required pollutant removal
based on calculations developed using EPA Region 1's BMP
Accounting and Tracking Tool (2016), the MS4 Permit methodology,
or other BMP performance evaluation tool provided by the Stormwater
Authority; or
ii. Retaining the volume of runoff equivalent to, or greater than, 1.0 inch
multiplied by the total post -construction impervious surface area on the
site; or
iii. Providing a combination of retention and treatment that achieves the
above standards.
Redevelopment
a. Redevelopment activities that are exclusively limited to maintenance and
improvement of existing roadways (including widening less than a single
lane, adding shoulders, correcting substandard intersections, improving
existing drainage systems, and repaving projects) shall improve existing
conditions unless infeasible and are exempt from the requirements of
Section 6.2.C(7)b.
b. Stormwater management systems for redevelopment shall be designed to
remove, at a minimum, 80% of the average annual load of TSS and 50%
of the average annual load of TP generated from the total post -
construction impervious surface area on the site. Average annual pollutant
removal requirements may be achieved through one of the following
methods:
i. Installing stormwater BMPs that provide the required pollutant removal
based on calculations developed using EPA Region 1's BMP
Accounting and Tracking Tool (2016), the MS4 Permit methodology,
(5)
(7)
NOAA Atlas 14 Precipitation Frequency Data Server https://hdsc.nws.noaa.gov/hdsc/pfds/
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February 23, 2022 Page 13 of 30
or other BMP performance evaluation tool provided by the Stormwater
Authority; or
ii. Retaining the volume of runoff equivalent to, or greater than, 0.8 inch
multiplied by the total post -construction impervious surface area on the
site; or
iii. Providing a combination of retention and treatment that achieves the
above standards.
Section 7. Construction Inspections
7.1. For Minor Stormwater Permit projects, inspection requirements will be determined by the
Designated Agent based on the proposed project's scale and complexity.
7.2. For Major Stormwater Permit projects, the following inspection requirements shall apply:
A. The Stormwater Authority may, at its discretion, require a pre -construction meeting
prior to the start of clearing, excavation, construction, or land disturbing activity by
the Applicant. The Permittee's technical representative, general contractor, or other
authorized person(s) shall meet with the Stormwater Authority to review the permitted
plans and their implementation.
B. For projects subject to the NPDES Construction General Permit, construction may not
commence until the Permittee has submitted EPA's approval of the Construction
General Permit Notice of Intent to the Stormwater Authority and posted the final
Stormwater Pollution Prevention Plan (SWPPP) at the site.
C. The approved Stormwater Management Plan bearing the signature of approval of the
Stormwater Authority shall be maintained at the site during the progress of the work.
D. The Stormwater Authority or its designated agent may inspect the site at the following
stages, at a minimum:
(1) Initial Site Inspection: An inspection may be made of erosion and
sedimentation controls and signage prior to any land disturbance to assess
overall effectiveness and functioning to protect resources.
(2) Stormwater Management System Excavation Inspection: An inspection may be
made of the excavation for the stormwater management system to ensure
adequate separation of the stormwater system from groundwater and presence
of approved soil type.
Stormwater Management System Inspection: An inspection may be made of
the completed stormwater management system, prior to backfilling of any
underground drainage or stormwater conveyance structures.
(4) Final Inspection: An inspection may be made of the completed stormwater
management system and final site stabilization to confirm as -built features and
other permit conditions.
E. Inspections will be conducted by a "qualified person" from the Stormwater Authority
or a third party hired to conduct such inspections. A "qualified person" is a person
(3)
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knowledgeable in the principles and practice of erosion and sediment controls and
pollution prevention, who possesses the appropriate skills and training to assess
conditions at the construction site that could impact stormwater quality, and the
appropriate skills and training to assess the effectiveness of any stormwater controls
selected and installed to meet the requirements of these Regulations.
F. The Permittee shall notify the Stormwater Authority at least five (5) business days
before each of the following events, to keep the Stormwater Authority informed of
construction progress and to facilitate timely inspections by the Stormwater Authority:
(1) Commencement of construction, with erosion and sedimentation control
measures in place and stabilized;
(2) Site clearing has been substantially completed;
(3) Rough grading has been substantially completed;
(4) Excavation for stormwater BMPs has been completed;
(5) Subsurface components of stormwater BMPs have been installed, prior to
backfilling;
(6) Stormwater BMP surface features have been substantially completed;
(7) Final grading has been substantially completed;
(8) Close of the construction season; and,
(9) Final landscaping (permanent stabilization) and project final completion.
G. Permittee Inspections. The Permittee, or their agent, shall conduct and document
inspections of all erosion and sediment control measures no less than weekly or as
specified in the permit, and prior to and following anticipated storm events. The
purpose of such inspections will be to determine the overall effectiveness of the
Erosion and Sedimentation Control Plan, and the need for maintenance or additional
control measures as well as verifying compliance with the Stormwater Management
Plan. The Permittee, or their agent, shall submit monthly reports to the Stormwater
Authority or designated agent in a format approved by the Stoitiiwater Authority.
Section 8. Long -Term Operation and Maintenance
8.1. For Minor Stormwater Permits, the Permittee shall maintain post -construction stormwater
BMPs to ensure that they continue to function as intended.
8.2. For Major Stormwater Permits, the Permittee shall meet the following requirements:
A. The Permittee shall ensure that all components of the proposed Stormwater
Management Plan are functioning according to manufacturer or design specifications
for the life of the system. All components shall be maintained in good condition and
promptly repaired, in accordance with the approved Operation and Maintenance Plan.
This shall constitute a perpetual condition of any Major Stormwater Permit issued
under these Regulations.
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B. To ensure adequate long-term operation and maintenance of stormwater management
practices, the Stormwater Authority or Designated Agent may require Permittees to
implement one or more of the following procedures, depending on the scale and
complexity of the project:
(1) Submit an annual certification documenting the work that has been done over
the last 12 months to properly operate and maintain the stormwater control
measures. The certification shall be signed by the person(s) or authorized agent
of the person(s) named in the permit as being responsible for ongoing
operation and management.
(2) Establish a dedicated fund or escrow account in the form of a Bond, Insurance
Policy, or similar instrumentality, to be maintained for a number of years and
for an amount specified by the Stormwater Authority. Such fund or account
may be used by the applicant to perform its operation and maintenance
responsibilities or, if the Stormwater Authority finds that the applicant has
failed to comply with the Permit, by the Stormwater Authority to perform or
cause to be performed the required operation and maintenance tasks.
Pay to the Town an amount specified by the Stormwater Authority in
compensation for its acceptance of ownership of privately constructed BMPs.
(4) Establish a maintenance contract between with the Stormwater Authority
whereby the Stormwater Authority will perform or cause to be performed the
required operation and maintenance tasks.
(3)
8.3. Recording
For Major Stormwater Permits, the Operation and Maintenance Plan shall be recorded
with the Barnstable County Registry of Deeds prior to issuance of a Stormwater
Management Certificate of Compliance by the Stormwater Authority pursuant to Section
5.9 of these Regulations.
8.4. Record Keeping
A. The Permittee shall keep records of all inspections, maintenance, and repairs and shall
retain the records for at least five (5) years. These records shall be made available to
the Stormwater Authority or Designated Agent during inspection of the stormwater
management structure or system and at other reasonable times upon request.
B. The Stormwater Authority or Designated Agent may request written records
documenting maintenance of the system, including receipts of inspection or cleaning
services, and/or may physically inspect the systems to ensure that the proper
maintenance has been carried out. Failure of the Permittee to maintain the stormwater
management system in reasonable order and condition, in conformance with the
approved Operation and Maintenance Plan, shall be considered a violation of these
Regulations and shall be subject to enforcement action in accordance with § 272-14 of
the Stormwater Management Bylaw.
8.5. Changes to Ownership and/or Operation and Maintenance Plans
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A. The Permittee shall notify the Stormwater Authority or Designated Agent of changes
in ownership or assignment of financial responsibility for O&M of the stormwater
management system or any changes to the Operation and Maintenance Plan within
thirty (30) business days of the change. The Permittee shall also be responsible for
informing prospective new owners of the requirements of the existing Operation and
Maintenance Plan. This shall be an on -going requirement of any Major Stormwater
Permit issued.
Section 9. Surety
For Major Stormwater Permits, the Stormwater Authority may require the Applicant to post
surety before the start of land disturbance or construction activity. The form of the surety shall be
approved by the Stormwater Authority and be in an amount deemed sufficient by the Stormwater
Authority to ensure that the work will be completed in accordance with the Permit. If the project
is phased, the Stormwater Authority may release part of the surety as each phase is completed in
compliance with the permit.
Funds held pursuant to this Section shall be deposited in a separate account pursuant to M.G.L. c.
44, §53G1/2. Surety shall be in the form of a surety bond, irrevocable letter of credit, or cash.
All interest shall be held within said account; surety shall be released upon satisfaction of all
Permit requirements; upon satisfaction of all Permit requirements, Applicant shall request, in
writing, to the Town Treasurer, that the funds be released. The funds shall not be released until
the Stormwater Authority certifies, in writing, that all requirements of the Permit have been met.
If the Permittee defaults on any obligations imposed by the Permit, the Stormwater Authority
may (after notification of the Permittee) inform the holder of the security (and the municipal
treasurer if the treasurer is not holding the funds) of the default, in which event the Town shall be
entitled to the security funds to complete the outstanding permit requirements.
Section 10. Severability
The invalidity of any section, provision, paragraph, sentence, or clause of these Regulations shall
not invalidate any other section, provision, paragraph, sentence, or clause thereof, nor shall it
invalidate any permit or determination that previously has been issued.
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Appendix A. Definitions
ABUTTER: The owner(s) of land adjacent to regulated activity.
ALTERATION OF DRAINAGE CHARACTERISTICS: Any activity on an area of land that
changes the water quality, force, direction, timing, or location of runoff flowing from the area.
Such changes include: change from distributed runoff to confined or discrete discharge, change
in the volume of runoff from the area; change in the peak rate of runoff from the area; and
change in the recharge to groundwater on the area.
APPLICANT: Any person, individual, partnership, association, firm, company, corporation,
trust, authority, agency, department, or political subdivision of the Commonwealth or the Federal
government, to the extent permitted by law, requesting a Stormwater Permit.
BEST MANAGEMENT PRACTICE (BMP): Schedules of activities, practices (and prohibitions
of practices), structures, vegetation, maintenance procedures, and other management practices to
prevent or reduce the discharge of pollutants to Waters of the United States. BMPs also include
treatment requirements, operating procedures, and practices to control plant site runoff, spillage
or leaks, sludge or waste disposal, or drainage from raw material storage.
CERTIFIED PROFESSIONAL IN EROSION AND SEDIMENT CONTROL (CPESC): A
certified specialist in soil erosion and sediment control. This certification program, sponsored by
the Soil and Water Conservation Society in cooperation with the American Society of
Agronomy, provides the public with evidence of professional qualifications.
CLEAN WATER ACT: The Federal Water Pollution Control Act (33 U.S.C. § 1251 et seq.) as
hereafter amended.
CLEARING: Any activity that removes the vegetative surface cover.
COMMON PLAN OF DEVELOPMENT: A "larger common plan of development or sale" is a
contiguous area where multiple separate and distinct construction activities may be taking place
at different times on different schedules under one plan.
DESIGNATED AGENT: Staff of the Planning, Conservation, Public Works, and Building
Departments designated by the Stormwater Authority to review and act upon Minor Stormwater
Permit applications.
EROSION: The wearing away of the land surface by natural or artificial forces such as wind,
water, ice, gravity, or vehicle traffic and the subsequent detachment and transportation of soil
particles.
EROSION AND SEDIMENTATION CONTROL PLAN: A document containing narrative,
drawings and details developed by a registered Professional Engineer (PE) or a Certified
Professional in Erosion and Sedimentation Control (CPESC), which includes best management
practices, or equivalent measures designed to control surface runoff, erosion, and sedimentation
during pre -construction and construction related land disturbing activities.
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EROSION CONTROL: The prevention or reduction of the movement of soil particles or rock
fragments due to stormwater runoff.
GRADING: Changing the level or shape of the ground surface.
GRUBBING: The act of clearing land surface by digging up roots and stumps.
IMPERVIOUS SURFACE: Any surface that prevents or significantly impedes the infiltration of
water into the underlying soil. This can include but is not limited to: roads, driveways, parking
areas and other areas created using nonporous material; buildings, rooftops, structures, solar
panels, artificial turf, and compacted gravel or soil.
INFILTRATION: The act of conveying surface water into the ground to permit groundwater
recharge and the reduction of stormwater runoff from a project site.
LAND DISTURBANCE ACTIVITY: Any activity that causes a change in the position or
location of soil, sand, rock, gravel, or similar earth material; results in an increased amount of
runoff or pollutants; measurably changes the ability of a ground surface to absorb waters;
involves clearing, grading, or excavating, including grubbing; or results in an alteration of
drainage characteristics.
LOW IMPACT DEVELOPMENT (LID): Site planning and design strategies that use or mimic
natural processes that result in the infiltration, evapotranspiration, or use of stormwater in order
to protect water quality and associated aquatic habitat.
M.G.L.: Massachusetts General Laws.
MASSACHUSETTS STORMWATER MANAGEMENT STANDARDS: The performance
standards as further defined by the Massachusetts Stormwater Handbook, issued by the
Department of Environmental Protection, and as amended, that coordinate the requirements
prescribed by state regulations promulgated under the authority of the Massachusetts Wetlands
Protection Act M.G.L. c. 131 §. 40 and Massachusetts Clean Waters Act M.G.L. c. 21, §. 23-56
to prevent or reduce pollutants from reaching water bodies and control the quantity of runoff
from a site.
MS4 PERMIT: General Permit for Stormwater Discharges from Small Municipal Separate
Storm Sewer Systems in Massachusetts.
MUNICIPAL SEPARATE STORM SEWER SYSTEM (MS4) or MUNICIPAL STORM
DRAIN SYSTEM: The system of conveyances designed or used for collecting or conveying
stormwater, including any road with a drainage system, street, gutter, curb, inlet, piped storm
drain, pumping facility, retention or detention basin, natural or altered drainage channel,
reservoir, and other drainage structure that together comprise the storm drainage system owned
or operated by the Town of Brewster.
NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM (NPDES)
STORMWATER DISCHARGE PERMIT: A permit issued by the Environmental Protection
Agency that authorizes the discharge of pollutants to Waters of the United States.
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NEW DEVELOPMENT: Any construction activities or land alteration on an area that has not
previously been developed to include impervious surface.
NONPOINT SOURCE POLLUTION: Pollution from many diffuse sources caused by rainfall or
snowmelt moving over and through the ground. As the runoff moves, it picks up and carries
away pollutants finally depositing them into a water resource area.
OPERATION AND MAINTENANCE PLAN: A plan setting up the functional, financial and
organizational mechanisms for the ongoing operation and maintenance of a stormwater
management system to ensure that it continues to function as designed.
OWNER: A person with a legal or equitable interest in property.
PERSON: An individual, partnership, association, firm, company, trust, corporation, agency,
authority, department or political subdivision of the Commonwealth or the federal government,
to the extent permitted by law, and any officer, employee, or agent of such person.
PUBLIC SHADE TREES: All trees within a public way or on the boundaries thereof, as defined
within Massachusetts General Law Chapter 87 (Public Shade Tree Law).
RECHARGE: The process by which groundwater is replenished by precipitation through the
percolation of runoff and surface water through the soil.
RECORD: Recorded in the Barnstable County Registry of Deeds; if registered land is affected,
filed with the recorder of the Land Court of Massachusetts.
REDEVELOPMENT: Development, rehabilitation, expansion, demolition, construction, land
alteration, or phased projects that disturb the ground surface, including impervious surfaces, on
previously developed sites.
RUNOFF: Rainfall, snowmelt, or irrigation water flowing over the ground surface.
SEDIMENT: Mineral or organic soil material that is transported by wind or water, from its
origin to another location; the product of erosion processes.
SEDIMENTATION: The process or act of deposition of sediment.
SITE: The areal extent of land disturbance and construction activities, including but not limited
to the creation of new impervious surface and improvement of existing impervious surface.
STABILIZATION: The use, singly or in combination, of mechanical, structural, or vegetative
methods, to prevent or retard erosion.
STORMWATER AUTHORITY: The Town of Brewster Planning Board or its authorized
agent(s), acting pursuant to the Town of Brewster Stoiiiiwater Management Bylaw (Chapter 272)
to administer, implement, and enforce the Bylaw and to adopt regulations pursuant to it.
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STORMWATER: Stormwater runoff, snow melt runoff, and surface runoff and drainage.
STORMWATER MANAGEMENT CERTIFICATE OF COMPLIANCE (SMCC): A document
issued by the Stormwater Authority which states that all conditions of an issued Stormwater
Permit have been met and that a project is currently in compliance with the conditions set forth
in the permit.
STORMWATER PERMIT: A permit issued by the Stormwater Authority, after review of an
application, plans, calculations, and other supporting documents, in accordance with the
provisions of the Town of Brewster Stormwater Management Bylaw (Chapter 272).
TOTAL MAXIMUM DAILY LOAD (TMDL): A regulatory plan (authorized by the Clean
Water Act) that identifies the amount of a pollutant that a waterbody can assimilate without
exceeding its water quality standard for that pollutant.
TOTAL SUSPENDED SOLIDS (TSS): A measure of undissolved organic or inorganic particles
in water.
TOTAL PHOSPHORUS (TP): A measure of the total dissolved and particulate forms of
phosphorus.
WATERCOURSE: A natural or man-made channel through which water flows or a stream of
water, including a river, brook, or underground stream.
WATERS OF THE COMMONWEALTH: All waters within the jurisdiction of the
Commonwealth, including, without limitation, rivers, streams, lakes, ponds, springs,
impoundments, estuaries, wetlands, coastal waters, groundwater, and Waters of the United States
as defined under the Federal Clean Water Act as hereafter amended.
WETLAND RESOURCE AREA: Areas specified in the Massachusetts Wetlands Protection Act
M.G.L. c. 131, § 40 and in the Brewster Wetlands Protection Bylaw (Chapter 172).
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Appendix B. Stormwater Management Plan Checklists
Minor Stormwater Permit Applications
The application for a Minor Stormwater Permit shall contain sufficient information for the
Designated Agent to evaluate the environmental impact, effectiveness, and acceptability of the
measures proposed by the Applicant to reduce adverse impacts from stormwater runoff during
and after construction.
The Applicant shall submit one digital copy and two (2) printed copies of the Minor Permit
application package. The Minor Permit application package shall include:
A. Completed Application Form with original signatures of all property owners;
B. Narrative describing the proposed work including:
(1) Existing and proposed site conditions (including structures, vegetation, and
drainage),
(2) The square footage of the proposed land disturbance area, existing impervious
surface area, and proposed impervious surface area,
(3) Proposed low impact development practices, and
(4) Proposed measures to control erosion, sediment, and wastes during
construction and to mitigate any long-term stormwater impacts.
C. For proposed stormwater BMPs, if applicable, calculations for the stormwater volume
to be managed. The volume may be calculated using the following formulas, or using
a BMP sizing tool provided by the Stormwater Authority:
(1) Stormwater volume (cubic feet) = impervious surface area (square feet) x 1
inch x 1 foot / 12 inches
(2) Stormwater volume (gallons) = stormwater volume (cubic feet) x 7.48 gallons /
cubic foot
D. For proposed stormwater BMPs, if applicable, a description of anticipated
maintenance activities and schedule to ensure that the stormwater BMP continues to
function as intended. A stormwater BMP maintenance guide, provided by the
Stormwater Authority and customized as needed for the project, may be used to meet
this requirement.
E. A drawing, map, or plan that shows:
(1) Existing site features including structures, pavement, trees, plantings, and
stonnwater management systems, etc.;
(2) Proposed work including proposed stormwater management systems and limits
of disturbance; and
(3) Proposed erosion and sedimentation controls.
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Major Stormwater Permit Applications
The Stormwater Management Plan shall contain sufficient information for the Stormwater
Authority to evaluate the environmental impact, effectiveness, and acceptability of the site
planning process and the measures proposed by the applicant to prevent adverse impacts from
stormwater runoff during and after construction.
The applicant shall submit one digital copy and twelve (12) printed copies of the Stormwater
Management Plan. Stormwater Management Plans submitted for consideration shall contain the
following minimum components:
1. Site Plan;
2. Stormwater Management Report; and
3. Operation and Maintenance Plan.
More information than the minimum required herein may be required by the Stormwater
Authority, provided such information is reasonably necessary for the proper evaluation of the
Stormwater Management Plan. Additional plans, such as but not limited to utility plan,
landscaping plan, etc., may be required for more complex projects.
Site Plan
The Site Plan shall be prepared to fully detail and explain the intentions of the Applicant. Site
Plan sheets shall be prepared at a standard scale (1" = 20', 1" = 40', or 1" = 80', whichever is
appropriate to the size of the proposal). All sheets shall include a reasonable numbering system
with an appropriate title block, north arrow, signature block, and legend identifying any
representative symbols used on the sheet in question.
Design Certification: Each plan sheet shall show the seal and signature of an Engineer,
Landscape Architect, or Surveyor, as appropriate to the data.
The Site Plan shall include the following sheets (pages), at a minimum:
A. Existing Conditions Sheet
The Existing Conditions sheet shall contain all the necessary information to convey existing
surface features and drainage patterns. It shall contain a topographical survey plan prepared
by a Surveyor, including the following information:
1. Name, seal, and signature of the Surveyor who performed the survey.
2. Date(s) of the survey.
3. Reference to all deeds, plans of record, and other information used to establish the
existing property lines, the layout of all streets and ways, and public and private
easements, including deed references to the abutting lots.
4. Locus, prepared at a scale not smaller than 1" = 1200' and a minimum extent of
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one mile diameter. Major streets, buildings, brooks, streams, rivers, or other
landmarks should be shown on the Locus with sufficient clarity to be easily
discernible.
5. Existing property lines, public and private easements, and road layouts with
bearings and distances. All distances shall be in feet and decimals of a foot and all
bearings shall be given to the nearest ten seconds. The error of closure shall not
exceed one to ten thousand.
6. Boundary of the entire property held in common ownership by the Applicant
regardless of whether all or part is being developed at this time.
7. Acreage of the property to the nearest tenth of an acre.
8. Existing monuments.
9. Location and name of all abutters as they appear on the most recent tax list,
including owners of the property on the opposite side of all streets abutting the
property.
10. Location, names, status (i.e., public or private), and present widths of streets and
sidewalks bounding, approaching, or within reasonable proximity of the property,
showing both roadway widths and right-of-way width.
11. Location of all test pits, borings, percolation tests, or similar, in or adjacent to the
development. Logs of observed groundwater elevations and other test data shall
be included in the Stormwater Management Report.
12. Location of all existing buildings and structures on the property and within
reasonable proximity of the perimeter of the property.
13. Location of all existing wells and septic systems that can be observed and/or are
on file with the Health Department, on the property and within reasonable
proximity of the perimeter of the property.
14. Features within and abutting the property, including but not limited to, waterways,
water bodies, drainage ditches, streams, brooks, stone walls, fences, curbing,
walkways and other paths (paved or unpaved), utility and light poles, buildings
and other structures, ledge outcrops, wooded areas, public shade trees and all
other trees greater than four (4) inches in diameter at breast height (4'/2 feet above
grade), and historic sites.
15. Location and identification of resource areas regulated under the Massachusetts
Wetlands Protection Act or the Brewster Wetlands Protection Bylaw, including
areas located within the property and areas outside of the property with buffer
zones or offsets that may intersect the property. This shall include wetlands and
associated offsets and buffer zones, isolated lands subject to flooding (ILSF),
bordering land subject to flooding (BLSF), and riverfront protection areas. If a
currently valid delineation for the property does not exist, wetland boundaries
shall be delineated in the field with numbered flags by a qualified wetlands
specialist, surveyed, and shown on the plan(s) with reference to the flag numbers.
The date of any Resource Area Delineation, Determination of Applicability,
Order of Conditions, or other applicable decision from the Brewster Conservation
Commission shall be indicated on the plans.
16. Location of aquifer protection zones, including Zone 1 and Zone II as defined in
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February 23, 2022 Page 24 of 30
the Brewster Water Quality Protection Bylaw, Chapter 179 Article XI.
17. Location of all existing above- and below -ground utilities and all associated
appurtenances within and abutting the property. All utility pipe types, sizes,
lengths, and slopes shall be provided, as well as utility structure information,
including rim and invert elevations.
18. Existing topography within the property and within reasonable proximity of the
perimeter of the property. Topography shall be provided at a minimum one -foot
contour intervals. The plan survey datum shall be the National American Vertical
Datum 1988 (NAVD88), and this reference shall be identified on the plans.
19. Stormwater flow direction.
B. Proposed Conditions Sheet
The Proposed Conditions sheet shall indicate all proposed site improvements, including but
not limited to structures, buildings, sidewalks, handicap ramps, parking areas, curb type and
limits, walls, fences, landscaped areas, and the proposed location of all utilities, as described
below:
1. All applicable information from the Existing Conditions sheet. The proposed
improvements shall be overlaid on the existing conditions and shown in a darker
line weight.
2. The boundaries of the site, the outline or footprint of all proposed buildings,
structures, parking areas, walkways, loading facilities, or significant landscaping
features shall be shown.
3. All means of vehicular access for ingress and egress to and from the site onto the
public streets. Plans should show the size and location of driveways and curb cuts.
4. The location of all public shade trees and all other trees over four (4) inches in
diameter at breast height (4'/2 feet above grade) to be removed.
5. The location and type of all above -ground and below -ground utilities.
6. The existing and proposed above- and below -ground stormwater management
system, with pipe sizes, lengths, slopes, and materials including conveyances,
catch basins, manholes, culverts, headwalls, detention and/or retention basins,
treatment units, infiltration systems, and outlet pipes/structures. Rim and invert
elevations shall be provided for all structures and other appurtenant features.
7. Proposed contours indicating the finished grades of all proposed construction in
the site. The plan shall show how the proposed grades will tie in to the existing
grades within and outside of the limit of disturbance. The grades should be
provided at a minimum one -foot contour intervals. Walls, curbing and any other
features creating a break in grade shall be shown, including proposed top and
bottom grades.
8. Stormwater flow direction.
C. Erosion and Sediment Control Sheet
The Erosion and Sediment Control sheet shall contain sufficient information to demonstrate
that erosion will be minimized and sediment contained as part of a land disturbance activity,
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including the following:
1. All applicable information from both the Existing and Proposed Conditions
sheets. The proposed development information shall be shown in a darker line
weight.
2. Location of the proposed limit of land disturbance activity, to be lined by
perimeter sediment controls in downgradient areas and along all resource areas.
3. Location of anti -tracking area at each construction entrance.
4. Inlet and outlet erosion and sediment controls at all existing and proposed
drainage structures.
5. Tree protection for all public shade trees and all other trees over six inches in
caliper proposed to remain.
6. Seeding, sodding, or revegetation plans and specifications for all unprotected or
unvegetated areas.
7. Location and design of all structural erosion and sediment control measures, such
as grade stabilization practices, temporary drainage swales, dewatering devices,
and temporary sedimentation basins.
8. Location of all proposed construction stockpiling and staging areas with
appropriate erosion and sediment control measures.
9. Location of areas designated for revegetation or infiltration -based BMPs, with
notes indicating that soil compaction shall be avoided in those areas.
10. Notes detailing the proposed operation, maintenance, and inspection schedule for
all erosion and sedimentation control measures, including proposed schedule for
street sweeping of adjacent roadways and paved areas.
11. Notes indicating that demolition debris, discarded building materials, concrete
truck wash out, chemicals, litter, and sanitary wastes may not be discharged to the
MS4 and must be legally disposed of.
12. Where a site is located in whole or in part within the floodplain, a Floodplain
Contingency Plan shall be included. The Floodplain Contingency Plan shall
describe the steps necessary to stabilize the site during construction in the event
that a flood watch is declared by the National Weather Service.
13. Where a project is also subject to coverage under a National Pollutant Discharge
Elimination System (NPDES) Construction General Permit issued by the EPA,
submission of the Stormwater Pollution Prevention Plan (SWPPP) shall be
required prior to commencement of land disturbance activities.
D. Construction Details Sheet
The Construction Details sheet should provide information regarding the component parts of
the construction, illustrating how they fit together. The sheet shall show the following:
1. Typical construction details of all proposed stormwater management system
devices, including but not limited to conveyances, catch basins, manholes,
headwalls, sub -drains, detention and retention systems, and other stormwater
management system structures.
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2. Landscaping details including, but not limited to, tree plantings, shrubs,
perennials, fences, walls, guard rails, street furniture, and other specialty items, if
applicable.
3. Construction details for all hard surfaces, including but not limited to, roadways,
sidewalks, driveways, loading docks, handicap ramps, permeable pavers, and
curbing.
4. Erosion and sediment control details that for components included in the Erosion
and Sediment Control Plan.
5. Where site constraints or differing conditions require work that deviates from
"typical details," specific construction details shall be provided.
6. All proposed work within the public right-of-way shall conform to Town of
Brewster and/or MassDOT Standard Details, where applicable.
Stormwater Management Report
A separate Stormwater Management Report shall be submitted with the Stormwater Permit
Application. It shall be prepared and stamped by an Engineer, and shall contain the following
information:
1. Contact Information. The name, address, and telephone number of all persons
having a legal interest in the property and the tax reference number and parcel
number of the property or properties affected.
2. Description of the watershed that the site is located in, the immediate
downgradient waterbody(s) that stormwater runoff from the site discharges to, the
impairment status and Total Maximum Daily Load (TMDL), if applicable, of the
watershed and waterbody(s), and the pollutant(s) of concern.
3. Description of the existing and proposed soil conditions (including Hydrologic
Soils Group [HSG] classification published by the National Resources
Conservation Service [NRCS]), land use, land cover, estimated high groundwater
elevations, design points, drainage patterns, and proposed stormwater
management practices.
4. Description of proposed work within proximity of regulated wetland resources,
aquifer protection zones, earthwork within 4 feet of seasonal high groundwater
elevations, and other sensitive environmental areas.
5. Description of the low impact development (LID) site planning and design
techniques considered for the project and an explanation as to why they were
included or excluded from the project.
6. Description of the existing and proposed stormwater management system,
including all proposed BMPs incorporated in the project design.
7. Description of all soil testing conducted in the study area, including sieve
analyses, tests for saturated hydraulic conductivity, test pits, or soil borings. Soils
information shall be based on field investigations by a Soil Evaluator approved by
the Commonwealth of Massachusetts, or by an Engineer. Testing shall be
performed in accordance with Volume 3 of the Massachusetts Stormwater
Handbook (dated February 2008, as amended) and these Rules and Regulations.
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Raw test data shall be provided in an appendix to the report.
8. Narrative describing the methodology used to conduct the hydrologic and
hydraulic analyses of the site and the design of the proposed stormwater
management system.
9. Tables comparing existing and proposed impervious areas, peak stormwater
runoff rates, and total stormwater runoff volumes for each design point and for the
2-, 10-, 25-, and 100 -year design storms.
10. Narrative and calculations demonstrating compliance with the Massachusetts
Stormwater Management Standards.
11. Narrative and calculations demonstrating compliance with the requirements of
Section 6 of these Regulations, including estimated reductions to annual average
load of total suspended solids (TSS) and annual average load of total phosphorus
(TP). Calculations shall be completed using the Environmental Protection Agency
(EPA) Region 1's BMP Accounting and Tracking Tool (2016), the Massachusetts
MS4 Permit methodology, or other BMP performance evaluation tool provided by
the Stormwater Authority.
12. Description of any impacts to the floodplain and floodway and a summary of
compensatory flood storage calculations, if appropriate.
13. Description of existing and proposed groundwater recharge on the site, including
quantitative summary of existing and proposed recharge volumes, and summary
of groundwater mounding analysis, if applicable.
14. Plans showing existing and proposed drainage areas, including any off -site
contributions, and time of concentration travel flow -paths. Study design points
should be indicated on the plan.
15. If applicable, a map showing the location of the site overlaid on the Federal
Emergency Management Agency's (FEMA) Flood Insurance Rate Map (FIRM)
for the Town of Brewster, or other appropriate information pertaining to location
of the floodplain and floodway boundaries in relation to the site.
16. Appendix containing all drainage calculations for existing and proposed
conditions, including hydrologic analysis of the site, hydraulic analysis of the
proposed drainage system, and calculations supporting the design of all BMPs
that will control stormwater runoff pollutants, peak rates, and volumes.
17. Massachusetts Department of Environmental Protection (MassDEP) Checklist for
Stormwater Report, stamped and signed by a registered Professional Engineer
(PE) licensed in the Commonwealth of Massachusetts to certify that the
Stormwater Management Plan is in accordance with the criteria established in the
Massachusetts Stormwater Management Standards, Brewster Stormwater
Management Bylaw, and these Regulations.
Operation and Maintenance Plan
An Operation and Maintenance (O&M) Plan, in accordance with the Massachusetts Stormwater
Management Standards, shall be included with the Stormwater Management Plan. The purpose
of the plan is to identify the actions necessary to ensure that stormwater management systems
and BMPs function as designed, in perpetuity.
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At a minimum, the O&M Plan shall contain:
1. The name(s) of the Owner of all components of the system, and the name(s) and
address(es) of the Responsible Party for O&M of each component, if different
from the Owner.
2. A plan that is prepared to scale and shows the location of all stormwater
management system components and all discharge points.
3. A description of all BMPs, including proper operating parameters and how the
Owner will determine if a BMP is not functioning properly.
4. A description of long-term source control and pollution prevention measures.
5. An inspection log and a description of all inspection and maintenance procedures,
responsibilities, and frequencies. Where applicable, this schedule shall refer to the
Maintenance Criteria provided in the Stormwater Handbook or the EPA National
Menu of Stormwater Best Management Practices or equivalent;
6. An inspection and maintenance schedule for all routine and non -routine
maintenance tasks to be performed.
7. Minimum qualifications for personnel that will perform inspections and
maintenance.
8. Snow storage procedures and locations in accordance with the MassDEP Snow
Disposal Guidance, dated December 11, 2020, as amended. Snow shall not be
stored or disposed of in any proposed stormwater BMP.
9. A list of easements held to access any BMPs.
10. An estimated O&M budget.
11. A copy of the As -built Plan prepared in accordance with Section 5.9 of these
Regulations, upon project completion.
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Appendix C. Fee Schedule
Fee
Minor Stormwater Permit Application
$50
Major Stormwater Permit Application
$100
Consultant Services and Technical Review
Determined on a case -by -case basis
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Brewster Stormwater Management Bylaw
Frequently Asked Questions
What is stormwater and why does it matter?
Stormwater is rain and snow melt that doesn’t soak into the ground but instead flows over impervious surfaces
such as roofs, pavement, and gravel driveways. As stormwater flows, it picks up soil, animal waste, road salt,
fertilizer, trash, and other pollutants that can impact our ponds, coastal waters, and drinking water.
Land disturbance activities, such as clearing, construction, and creation of impervious surfaces, can increase
stormwater runoff and pollutants if not managed properly. Runoff from disturbed lands also impacts the
town’s storm drainage systems, exacerbating road flooding during large storms and necessitating more
frequent maintenance and upgrades.
What activities trigger the bylaw?
With some exceptions, the bylaw applies to projects that
will, over a 2-year period:
1) Disturb over 10,000 square feet of land.
And/or
2) Increase impervious surface area by over 500 square
feet.
A project that meets either of these thresholds must
apply for a Stormwater Permit.
Would a Stormwater Permit be required for these projects?
Yes No
Clearing a quarter-acre forest to create a
landscaped yard.
Building a 600-square-foot addition onto an
existing house.
Expanding an existing parking lot to add 4
parking spaces.
Constructing a new home on a vacant lot.
Building a 400 square-foot garage and then
adding a 400 square-foot patio the next year.
Reconstructing a 1,000-foot length of road.
Installing a large solar array in a field.
Paving an existing gravel driveway (< 10,000 sq.
ft.) without expanding it.
Installing or repairing a septic system.
Demolishing a structure and reconstructing it
within the same footprint (assuming
construction disturbs < 10,000 sq. ft. land area).
Maintaining an existing landscaped property.
Building a new 600-square-foot driveway and
converting the old 400-square-foot driveway
into lawn. (This would only increase impervious
surface area by 200 square feet).
Installing solar panels on a roof or over an
existing parking lot.
Commonly Used Terms
Land disturbance: Any activity that causes a change
in the position or location of soil, sand, rock,
gravel, or similar earth material; results in an
increased amount of runoff or pollutants;
measurably changes the ability of a ground surface
to absorb waters; involves clearing, grading, or
excavating, including grubbing; or results in an
alteration of drainage characteristics.
Impervious surface: Any surface that prevents
water from soaking into the underlying soil. This
can include roofs, solar panels, artificial turf, and
paved, gravel, or crushed-shell roads, driveways,
parking areas, and sidewalks.
What does the Stormwater Management Bylaw require?
As described in the Brewster Stormwater Management Regulations, the size of a project will determine the
stormwater permitting requirements that must be met. Small projects may qualify for a minor permit, which
has simpler procedures and requirements than for a major permit.
Minor Permits. Small projects that will disturb between 10,000 – 20,000 square feet of land or will increase
impervious surface area by 500 - 2,500 square feet will require a minor permit. These projects can use simple,
non-engineered practices to prevent sediment from washing offsite during construction and to soak rain into
the ground after construction. Minor permit applications can be approved administratively by the Town
Planner, Building Commissioner, Conservation Agent, or DPW Director.
Rain Barrel Drywell Rain Garden
Major Permits. Larger projects (above 20,000 square feet of land disturbance or 2,500 square feet increase in
impervious surface area) will need to provide construction-site and post-construction stormwater
management in accordance with the Massachusetts Stormwater Handbook and the Massachusetts MS4
General Permit. These requirements are similar to those for projects under Conservation Commission
jurisdiction. Major permit applications will be acted upon by the Conservation Commission if the project is
within jurisdiction of the Wetlands Protection Bylaw, or by the Planning Board for all other projects.
Bioretention Basin Permeable Pavement
Brewster Stormwater Management Bylaw
Guide for Minor Stormwater Permit Applicants
This fact sheet provides guidance to applicants for a Minor Stormwater Permit under the Brewster Stormwater
Management Bylaw. Please refer to the Stormwater Management Regulations for more detail.
Does my project qualify for a Minor Permit?
You can apply for a Minor Stormwater Permit if your project falls within or below the following thresholds:
Cumulative area of land disturbance between 10,000
and 20,000 square feet over a 2-year period, and
Net increase of impervious surface area between 500
and 2,500 square feet over a 2-year period.
If your project’s land disturbance or net impervious surface
area are above those thresholds, you will need to apply for a
Major Stormwater Permit.
How do I apply for a Minor Permit?
Download and fill out the Town of Brewster Stormwater
Management Permit Application. In the space provided for
“Detailed Project Description”, include the following
information:
A description of the proposed work,
The square footage of the proposed area of land
disturbance, the existing impervious surface area, and
the proposed impervious surface area,
Low-impact development strategies that will be
incorporated into the project,
Proposed measures to control erosion, sediment, and
wastes during construction, and
Proposed stormwater practices to manage runoff after
construction.
Attach the following to your application form:
A drawing, map, or plan that shows existing site features, proposed site features, limits of land
disturbance, proposed construction-site erosion and sedimentation controls, and proposed post-
construction stormwater practices,
A page showing your calculations for the stormwater volume to be managed and sizing of the proposed
post-construction stormwater practices, and
A page describing the anticipated maintenance activities and schedule to ensure that the stormwater
practices continue to function as intended.
If your project is subject to the Wetlands Protection Bylaw (i.e., if it is within 100 feet of a wetland), submit your
application to the Conservation Department. Otherwise, submit your application to the Planning Department.
TIP
Is your project just barely above the 500 or 2,500-
square-foot thresholds for net impervious surface
area? With good design, you might be able to get
below those thresholds. Look for ways to reduce
the area of existing and new impervious surfaces.
For example, can you make the new driveway
narrower? Revegetate unused parking spaces?
Commonly Used Terms
Land disturbance: Any activity that causes a
change in the position or location of soil, sand,
rock, gravel, or similar earth material; results
in an increased amount of runoff or
pollutants; measurably changes the ability of a
ground surface to absorb waters; involves
clearing, grading, or excavating, including
grubbing; or results in an alteration of
drainage characteristics.
Impervious surface: Any surface that prevents
water from soaking into the underlying soil.
This can include roofs, solar panels, artificial
turf, and paved, gravel, or crushed-shell roads,
driveways, parking areas, and sidewalks.
Brewster Stormwater Management Bylaw
Guide for Minor Stormwater Permit Applicants
Where can I go for help?
Please reach out to the Planning Department, Conservation Department, or the Department of Public Works for
guidance on the Stormwater Management Regulations, application process, resources, and examples. You can
also hire an engineer or landscape architect to assist you with the design and permit application.
What are low impact development strategies?
Low impact development (LID) planning and design strategies
aim to enhance a landscape’s ability to slow, filter, and soak in
rain. Applicants for Minor Permits must evaluate and
implement LID strategies unless it is impracticable due to cost
or site constraints. Some strategies that you might consider
include:
Minimize the area of impervious surfaces on your
property,
Slope new impervious surfaces toward vegetated areas,
where runoff can soak in,
Till, amend, and densely seed your lawn to improve
drainage and reduce erosion,
Protect and care for trees on your property, and
Plant trees and native plants to replace mowed lawn.
What is construction-site stormwater management?
The Regulations list best practices for construction-site stormwater management in Section 6.1. Minor Permit
projects must implement these practices unless they are impracticable due to cost or site constraints. At a
minimum, projects must control erosion, sediment, and construction wastes to prevent nuisance conditions, such
as sediment or debris washouts onto abutting properties and public rights of way.
Inlet Protection Tree Protection Covered and Contained Stockpiles
Association to Preserve Cape Cod meadow in Dennis, MA
Brewster Stormwater Management Bylaw
Guide for Minor Stormwater Permit Applicants
What are post-construction stormwater practices?
Minor Permit projects must install at least one stormwater practice (also known as stormwater best management
practice, or BMP) to mitigate the impacts of stormwater runoff and pollutants generated from impervious
surfaces on the property. Some common practices to consider are rain barrels, dry wells, rain gardens, permeable
pavers, and directing runoff toward vegetated areas (impervious area disconnection).
Rain Barrel Drywell Rain Garden Permeable Pavers
How do I select and design my stormwater practices?
Step 1. Understand Your Site Conditions
Before selecting a stormwater practice, it is helpful to first
understand conditions on your property and which
stormwater practices are suitable for those conditions.
Soils
Most properties in Brewster have sandy soils that allow
water to soak in quickly. These are called “high
permeability” soils. Disconnection and infiltration
practices work best in permeable soils.
Some properties in Brewster have clay soils that drain
water slowly. These are called “low permeability” soils.
Rain barrels and rain gardens work best in these
conditions but may require simple soil amendments.
If you are not sure if your property has high or low permeability soils, view the soils map on the Town of
Brewster GIS Map Viewer. Areas shown as Hydrologic Soil Group (HSG) A or HSG B have high permeability;
areas shown as HSG C or HSG D have low permeability.
Groundwater Table
Stormwater practices that soak water into the ground should be located in areas that are dry in the
springtime. If you have frequent spring ponding or basement flooding when it has not been raining, the
groundwater table on your property might be too high for stormwater to infiltrate.
Slope
Most stormwater practices should be in an area that is flat or gently sloped (i.e., a vertical drop of 5 feet over
horizontal distance of 100 feet).
Commonly Used Terms
Stormwater practice: Sometimes referred to as
best management practice (BMP), methods used
to collect, cleanse, and infiltrate stormwater.
Impervious surface: Any surface that prevents
water from soaking into the underlying soil. This
can include roofs, solar panels, artificial turf, and
paved, gravel, and crushed-shell roads,
driveways, parking areas, and sidewalks.
Infiltration: Soaking water into the ground.
Permeability: Soil characteristic that describes
how easily water can drain through it.
Brewster Stormwater Management Bylaw
Guide for Minor Stormwater Permit Applicants
Available Space
It may be helpful to measure the area on your property to see if you have enough space for your desired
practice. Stormwater infiltration practices should be placed at least 10 feet from building foundations and
property lines, 50 feet from septic system leach fields and surface waters, and 100 feet from private wells.
Step 2. Select Your Stormwater Practice
Use the matrix below to identify stormwater practices that might be suitable for your property.
Stormwater
Practices
Source of Stormwater Soils and Groundwater Slope Available Space
Roof Driveway
/Parking Patio
High
Permeability,
Dry Area
Low
Permeability
or Wet Area
Flat or
Gently
Sloping
Steep
Slopes
< 100
ft2
> 100
ft2
Dry Well X X X X
Permeable Pavers X X X X X X
Rain Garden X X X X * X X
Infiltration Trench X X X X X X
Rain Barrel X X X X X
Impervious Area
Disconnection X X X X X X X
*Low permeability soils can be amended to improve permeability, and the system size is increased to account for poor soils
Step 3. Calculate the Volume of Stormwater to Manage
For Minor Permits, the Brewster Stormwater Management Regulations require that an applicant install one or
more stormwater practices that are sized to manage 1 inch of runoff from the net impervious surface area
(proposed minus existing impervious surface area) or 500 square feet, whichever is greater.
Impervious surface area is the square footage of land covered by roof, driveway, parking
area, patio, and other hardscapes on your property.
To calculate the volume of runoff to manage, use the following equation:
STORMWATER VOLUME TO MANAGE (ft3) = IMPERVIOUS SURFACE AREA (ft2) × 0.083 (ft)
If the stormwater practice is designed to infiltrate runoff and will be located in an area with very sandy soils
where water soaks in immediately, you may apply a 20% reduction to the required stormwater volume and
calculate volume using the following equation.
STORMWATER VOLUME FOR SANDY SOIL INFILTRATION (ft3) = STORMWATER VOLUME (ft3) × 0.8
Step 4. Design your Stormwater Practice
Refer to the fact sheet for your selected stormwater practice for instructions on where to place your practice and
how to design it.
Step 5. Plan for Maintenance
Stormwater practices must be maintained to ensure that they continue to function as intended. Maintenance
typically includes periodic inspections of the stormwater practice, cleaning out accumulated sediment, leaves, and
other debris, and taking care of plants (e.g., for rain gardens). For more information about the maintenance
activities and schedule, refer to the fact sheet for your selected stormwater practice.
ft = feet
ft2 = square feet
ft3 = cubic feet
gal = gallons
Structural BMPs - Volume 2 | Chapter 2 page 23
Bioretention Areas & Rain Gardens
Standard Description
2 - Peak Flow N/A
3 - Recharge An exfiltrating bioretention area provides groundwater recharge.
4 - TSS
Removal
90% TSS removal credit with adequate pretreatment
5 - Higher
Pollutant
Loading
Can be used for certain land uses with higher potential pollutant loads if lined and sealed
until adequate pretreatment is provided. Adequate pretreatment must include 44% TSS
removal prior to infiltration. For land uses that have the potential to generate runoff with
high concentrations of oil and grease such as high intensity use parking lots and gas stations,
adequate pretreatment may also include an oil grit separator, sand filter or equivalent. In
lieu of an oil grit separator or sand filter, a filtering bioretention area also may be used as a
pretreatment device for infiltration practices exfiltrating runoff from land uses with a potential
to generate runoff with high concentrations of oil and grease.
6 - Discharges
near or to
Critical Areas
Good option for discharges near cold-water fisheries. Should not be used near bathing
beaches and shellfish growing areas.
7 -
Redevelopment
Suitable with appropriate pretreatment
Ability to meet specific standards
Pollutant Removal Efficiencies
Total Suspended Solids (TSS) 90% with vegetated filter strip or equivalent•
Total Nitrogen 30% to 50% if soil media at least 30 inches•
Total Phosphorus 30% to 90%•
Metals • (copper, lead, zinc, cadmium) 40% to 90%
Pathogens (coliform, e coli) Insufficient data•
Description: Bioretention is a technique that uses
soils, plants, and microbes to treat stormwater
before it is infiltrated and/or discharged.
Bioretention cells (also called rain gardens in
residential applications) are shallow depressions
filled with sandy soil topped with a thick layer of
mulch and planted with dense native vegetation.
Stormwater runoff is directed into the cell via
piped or sheet flow. The runoff percolates through
the soil media that acts as a filter.
There are two types of bioretention cells: those
that are designed solely as an organic filter
filtering bioretention areas and those configured
to recharge groundwater in addition to acting as
a filter exfiltrating bioretention areas. A filtering
bioretention area includes an impermeable
liner and underdrain that intercepts the runoff
before it reaches the water table so that it may
be conveyed to a discharge outlet, other best
management practices, or the municipal storm
drain system. An exfiltrating bioretention area
has an underdrain that is designed to enhance
exfiltration of runoff into the groundwater.
Structural BMPs - Volume 2 | Chapter 2 page 24
Advantages/Benefits:
Can be designed to provide groundwater recharge and preserves the natural water balance of the site•
Can be designed to prevent recharge where appropriate•
Supplies shade, absorbs noise, and provides windbreaks•
Can remove other pollutants besides TSS including phosphorus, nitrogen and metals•
Can be used as a stormwater retrofit by modifying existing landscape or if a parking lot is being resurfaced•
Can be used on small lots with space constraints•
Small rain gardens are mosquito death traps•
Little or no hazard for amphibians or other small animals•
Disadvantages/Limitations:
Requires careful landscaping and maintenance•
Not suitable for large drainage areas•
Special Features:
Can be lined and sealed •
to prevent recharge where
appropriate
Adequate pretreatment is •
essential
Not recommended in areas •
with steep slope
Depth of soil media depends •
on type of vegetation that is
proposed
Soil media must be 30 inches •
deep to achieve removal of
nitrogen
Activity Frequency
Inspect and remove trash Monthly
Mow 2 to 12 times per year
Mulch Annually
Fertilize Annually
Remove dead vegetation Annually
Prune Annually
Maintenance
adapted from the Vermont Stormwater Manual
Structural BMPs - Volume 2 | Chapter 2 page 25
Bioretention Areas & Rain Gardens
Not all bioretention cells are designed to exfiltrate. Only the
infiltration requirements are applicable to bioretention cells
intended to exfiltrate.
Applicability
Bioretention areas can provide excellent pollutant
removal for the “first flush” of stormwater runoff.
Properly designed and maintained cells remove
suspended solids, metals, and nutrients, and can
infiltrate an inch or more of rainfall. Distributed
around a property, vegetated bioretention areas
can enhance site aesthetics. In residential
developments they are often described as “rain
gardens” and marketed as property amenities.
Routine maintenance is simple and can be handled
by homeowners or conventional landscaping
companies, with proper direction.
Bioretention systems can be applied to a wide
range of commercial, residential, and industrial
developments in many geologic conditions; they
work well on small sites and on large sites divided
into multiple small drainage areas. Bioretention
systems are often well suited for ultra-urban settings
where little pervious area exists. Although they
require significant space (approximately 5% to 7% of
the area that drains to them), they can be integrated
into parking lots, parking lot islands, median strips,
and traffic islands. Sites can be retrofitted with
bioretention areas by replacing existing parking lot
islands or by re-configuring a parking lot during
resurfacing. On residential sites, they are commonly
used for rooftop and driveway runoff.
Effectiveness
Bioretention areas remove pollutants through
filtration, microbe activity, and uptake by plants;
contact with soil and roots provides water quality
treatment better than conventional infiltration
structures. Studies indicate that bioretention areas
can remove from 80% to 90% of TSS. If properly
designed and installed, bioretention areas remove
phosphorus, nitrogen, metals, organics, and bacteria
to varying degrees.
Bioretention areas help reduce stress in watersheds
that experience severe low flows due to excessive
impervious cover. Low-tech, decentralized
bioretention areas are also less costly to design,
install, and maintain than conventional stormwater
technologies that treat runoff at the end of the pipe.
Decentralized bioretention cells can also reduce
the size of storm drain pipes, a major component
of stormwater treatment costs. Bioretention areas
enhance the landscape in a variety of ways: they
improve the appearance of developed sites, provide
windbreaks, absorb noise, provide wildlife habitat,
and reduce the urban heat island effect.
Planning Considerations
Filtering bioretention areas are designed with
an impermeable liner and underdrain so that
the stormwater may be transported to additional
BMPs for treatment and/or discharge. Exfiltrating
bioretention areas are designed so that following
treatment by the bioretention area the stormwater
may recharge the groundwater.
Both types of bioretention areas may be used to treat
runoff from land uses with higher potential pollutant
loads. However, exfiltrating bioretention areas may
be used to treat runoff from land uses with higher
potential pollutant loads, only if pretreatment has
been provided to achieve TSS removal of at least 44%.
If the land use has the potential to generate runoff
with high concentrations of oil and grease, other
types of pretreatment, i.e., a deep sump catch basin
and oil grit separator or a sand filter, is required prior
to discharge of runoff to an exfiltrating bioretention
area. A filtering bioretention area may also be
used as a pretreatment device for an exfiltrating
bioretention area or other infiltration practice that
exfiltrates runoff from land uses with a potential to
generate runoff with high concentrations of oil and
grease.
To receive 90% TSS removal credit, adequate
pretreatment must be provided. If the flow is piped to
the bioretention area a deep sump catch catch basin
and sediment forebay should be used to provide
pretreatment. For sheet flow, there are a number or
pretreatment options. These options include:
A vegetated filter strip, grass channel or water •
quality swale designed in accordance with the
specifications set forth in Chapter 2.
A grass and gravel combination. This should •
consist of at least 8 inches of gravel followed
by 3 to 5 feet of sod. (source: North Carolina
Stormwater Manual, 2007, http://h2o.enr.state.nc.us/su/
documents/Ch12-Bioretention_001.pdf)
Pea diaphragm combined with a vegetated filter •
strip specially designed to provide pretreatment
for a bioretention area as set forth in the following
table. (source: Georgia Stormwater Manual and
Claytor and Schuler 1996)
Structural BMPs - Volume 2 | Chapter 2 page 26
Bioretention areas must not be located on slopes
greater than 20%. When the bioretention area is
designed to exfiltrate, the design must ensure vertical
separation of at least 2 feet from the seasonal high
groundwater table to the bottom of the bioretention
cell.
For residential rain gardens, pick a low spot on the
property, and route water from a downspout or sump
pump into it. It is best to choose a location with full
sun, but if that is not possible, make sure it gets at
least a half-day of sunlight.
Do not excavate an extensive rain garden under large
trees. Digging up shallow feeder roots can weaken
or kill a tree. If the tree is not a species that prefers
moisture, the additional groundwater could damage
it. Size the bioretention area using the methodology
set forth in Volume 3.
Design
Size the bioretention area to be 5% to 7% of the area
draining to it. Determine the infiltrative capacity
of the underlying native soil by performing a soil
evaluation in accordance with Volume 3. Do not use
a standard septic system (i.e., Title 5) percolation test
to determine soil permeability.
The depth of the soil media must be between 2 and
4 feet. This range reflects the fact that most of the
pollutant removal occurs within the first 2 feet of
soil and that excavations deeper than 4 feet become
expensive. The depth selected should accommodate
the vegetation. If the minimum depth is used, only
shallow rooted plants and grasses my be used. If
there is a Total Maximum Daily Load that requires
nitrogen to be removed from the stormwater
dischrges, the bioretention area should have a soil
media with a depth of at least 30 inches, because
nitrogen removal takes place 30 inches below the
ground surface. If trees and shrubs are to be planted,
the soil media should be at least 3 feet.
Size the cells (based on void space and ponding
area) at a minimum to capture and treat the required
water quality volume (the first 0.5 inch or 1 inch
of runoff) if intended to be used for water quality
treatment (Stormwater Standard No. 4), the required
recharge volume if used for recharge (Stormwater
Standard No. 3), or the larger of the two volumes if
used to achieve compliance with both Stormwater
Standards 3 and 4.
Cover the bottom of the excavation with coarse
gravel, over pea gravel, over sand. Earlier designs
used filter fabric as a bottom blanket, but more
recent experiences show that filter fabric is prone to
clogging. Consequently, do not use fabric filters or
sand curtains. Use the Engineered Soil Mix below.
Engineered Soil Mix for Bioretention Systems
Designed to Exfiltrate
The soil mix for bioretention areas should be a •
mixture of sand compost and soil.
o 40 % sand,
o 20-30% topsoil, and
o 30-40% compost.
The soil mix must be uniform, free of stones, •
stumps, roots or similar objects larger than 2
inches. Clay content should not exceed 5%.
Soil pH should generally be between 5.5-6.5, a •
range that is optimal for microbial activity and
adsorption of nitrogen, phosphorus, and other
pollutants.
Use soils with 1.5% to 3% organic content and •
maximum 500-ppm soluble salts.
The sand component should be gravelly sand that •
meets ASTM D 422.
Sieve Size Percent Passing
2-inch 100
¾-inch 70-100
¼-inch 50-80
U.S. No. 40 15-40
U.S. No. 200 0-3
The topsoil component shall be a sandy loam, •
loamy sand or loam texture.
The compost component must be processed •
from yard waste in accordance with MassDEP
Guidelines (see http://www.mass.gov/dep/recycle/
reduce/leafguid.doc). The compost shall not
contain biosolids.
Parameter Impervious Area Pervious Areas (lawns, etc.)
Maximum inflow approach length
(feet)
35 75 75 100
Filter strip slope (max=6%)<2%>2%<2%>2%<2%>2%<2%>2%
Filter strip minimum length (feet)10 15 20 25 10 12 15 18
Dimensions for Filter Strip Designed Specially to Provide Pretreatment for Bioretention Area
Structural BMPs - Volume 2 | Chapter 2 page 27
On-site soil mixing or placement is not allowed if
soil is saturated or subject to water within 48 hours.
Cover and store soil to prevent wetting or saturation.
Test soil for fertility and micro-nutrients and, only
if necessary, amend mixture to create optimum
conditions for plant establishment and early growth.
Grade the area to allow a ponding depth of 6 to 8
inches; depending on site conditions, more or less
ponding may be appropriate.
Cover the soil with 2 to 3 inches of fine-shredded
hardwood mulch.
The planting plan shall include a mix of herbaceous
perennials, shrubs, and (if conditions permit)
understory trees that can tolerate intermittent
ponding, occasional saline conditions due to road
salt, and extended dry periods. A list of plants that
are suitable for bioretention areas can be found at
the end of this section. To avoid a monoculture, it
is a good practice to include one tree or shrub per
50 square feet of bioretention area, and at least 3
species each of herbaceous perennials and shrubs.
Invasive and exotic species are prohibited. The
planting plan should also meet any applicable local
landscaping requirements.
All exfiltrating bioretention areas must be designed
to drain within 72 hours. However, rain gardens are
typically designed to drain water within a day and are
thus unlikely to breed mosquitoes.
Bioretention cells, including rain gardens, require
pretreatment, such as a vegetated filter strip. A stone
or pea gravel diaphragm or, even better, a concrete
level spreader upstream of a filter strip will enhance
sheet flow and sediment removal.
Bioretention cells can be dosed with sheet flow, a
surface inlet, or pipe flow. When using a surface
inlet, first direct the flow to a
sediment forebay. Alternatively,
piped flow may be introduced
to the bioretention system via an
underdrain.
For bioretention cells dosed
via sheet flow or surface inlets,
include a ponding area to allow
water to pond and be stored
temporarily while stormwater
is exfiltrating through the cell.
Where bioretention areas
are adjacent to parking areas, allow three inches
of freeboard above the ponding depth to prevent
flooding.
Most bioretention cells have an overflow drain
that allows ponded water above the selected
ponding depth to be dosed to an underdrain. If the
bioretention system is designed to exfiltrate, the
underdrain is not connected to an outlet, but instead
terminates in the bioretention cell. If the bioretention
area is not designed to exfiltrate, the underdrain is
connected to an outlet for discharge or conveyance
to additional best management practices.
Construction
During construction, avoid excessively compacting
soils around the bioretention areas and accumulating
silt around the drain field. To minimize sediment
loading in the treatment area, direct runoff to the
bioretention area only from areas that are stabilized;
always divert construction runoff elsewhere.
To avoid compaction of the parent material, work
from the edge of the area proposed as the location of
an exfiltrationg bioretention cell. Never direct runoff
to the cell until the cell and the contributing drainage
areas are fully stabilized.
Place planting soils in 1-foot to 2-foot lifts and
compact them with minimal pressure until the
desired elevation is reached. Some engineers suggest
flooding the cell between each lift placement in lieu
of compaction.
Maintenance
Premature failure of bioretention areas is a significant
issue caused by lack of regular maintenance.
Ensuring long-term maintenance involves sustained
public education and deed restrictions or covenants
for privately owned cells. Bioretention areas require
careful attention while plants are being established
Bioretention Maintenance Schedule
Activity Time of Year Frequency
Inspect & remove trash Year round Monthly
Mulch Spring Annually
Remove dead vegetation Fall or Spring Annually
Replace dead vegetation Spring Annually
Prune Spring or Fall Annually
Replace entire media &
all vegetation
Late Spring/early
Summer
As needed*
* Paying careful attention to pretreatment and operation & maintenance can extend the
life of the soil media
Structural BMPs - Volume 2 | Chapter 2 page 28
and seasonal landscaping maintenance thereafter.
In many cases, a landscaping contractor working
elsewhere on the site can complete maintenance
tasks. Inspect pretreatment devices and bioretention
cells regularly for sediment build-up, structural
damage, and standing water.
Inspect soil and repair eroded areas monthly. Re-mulch
void areas as needed. Remove litter and debris monthly.
Treat diseased vegetation as needed. Remove and
replace dead vegetation twice per year (spring and fall).
Proper selection of plant species and support during
establishment of vegetation should minimize—if not
eliminate—the need for fertilizers and pesticides.
Remove invasive species as needed to prevent these
species from spreading into the bioretention area.
Replace mulch every two years, in the early spring. Upon
failure, excavate bioretention area, scarify bottom and
sides, replace filter fabric and soil, replant, and mulch.
A summary of maintenance activities can be found on
the previous page.
Because the soil medium filters contaminants from
runoff, the cation exchange capacity of the soil media
will eventually be exhausted. When the cation
exchange capacity of the soil media decreases,
change the soil media to prevent contaminants
from migrating to the groundwater, or from being
discharged via an underdrain outlet. Using small
shrubs and plants instead of larger trees will make it
easier to replace the media with clean material when
needed.
Plant maintenance is critical. Concentrated salts in
roadway runoff may kill plants, necessitating removal
of dead vegetation each spring and replanting. The
operation and maintenance plan must include
measures to make sure the plants are maintained.
This is particularly true in residential subdivisions,
where the operation and maintenance plan may
assign each homeowner the legal responsibility
to maintain a bioretention cell or rain garden on
his or her property. Including the requirement
in the property deed for new subdivisions may
alert residential property owners to their legal
responsibilities regarding the bioretention cells
constructed on their lot.
Cold Climate Considerations
Never store snow in bioretention areas. The
Operation and Maintenance plan must specify where
on-site snow will be stored. All snow dumps must
comply with MassDEP’s guidance. When bioretention
areas are located along roads, care must be taken
during plowing operations to prevent snow from
being plowed into the bioretention areas. If snow
is plowed into the cells, runoff may bypass the cell
and drain into downgradient wetlands without first
receiving the required water quality treatment, and
without recharging the groundwater.
References
Center for Watershed Protection, 2000, Bioretention
as a Water Quality Best Management Practice, Article
110 from Watershed Protection Techniques; http://
www.cwp.org/Downloads/ELC_PWP110.pdf
Federal Highway Administration , YEAR, Bioretention
Fact Sheet, http://www.fhwa.dot.gov/environment/
Low Impact Development Center, 2003, Drainage
– Bioretention Specification, http://www.
lowimpactdevelopment.org/epa03/biospec.htm
Prince Georges County, 2002, Bioretention Manual,
http://www.goprincegeorgescounty.com/der/
bioretention.asp
Puget Sound Action Team, 2005, Low Impact
Development, Pp. 174 - 184 http://www.psat.wa.gov/
Publications/LID_tech_manual05/LID_manual2005.
pdf
U.S. Environmental Protection Agency, 1999,
Stormwater Technology Fact Sheet, Bioretention, EPA
832-F-99-012, http://www.epa.gov/owm/mtb/biortn.
pdf
U.S. Environmental Protection Agency, 2005, National
Management Measures to Control Nonpoint Source
Pollution from Urban Areas, Publication Number
EPA 841-B-05-004, Pp. 5-29 http://www.epa.gov/nps/
urbanmm/
University of North Carolina,
www.bae.ncsu.edu/topic/bioretention
www.bae.ncsu.edu/stormwater/PublicationFiles/
DesigningRainGardens2001.pdf
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Structural BMPs - Volume 2 | Chapter 2 page 84
Description: Dry wells are small excavated pits,
backfilled with aggregate, and used to infiltrate
uncontaminated runoff from non-metal roofs or
metal roofs located outside the Zone II or Interim
Wellhead Protection Area of a public water supply
and outside an industrial site. Do not use dry wells
to infiltrate any runoff that could be significantly
contaminated with sediment and other pollutants.
Never use dry wells to infiltrate runoff from land
uses with higher potential pollutant loads, including
parking lot runoff.
Dry Wells
Advantages/Benefits:
Applicable for runoff from non-metal roofs and •
metal roofs located outside of the Zone IIs or
IWPA of a public water supply, and outside
industrial sites
Can reduce the size and cost of downstream •
BMPs and/or storm drains.
Feasible for new development and retrofit •
areas
Provides groundwater recharge •
Disadvantages/Limitations:
Clogging likely when used for runoff other than •
that from residential rooftops.
May experience high failure rate due to •
clogging.
Only applicable in small drainage areas of one •
acre or less.
When located near buildings, potential issues •
with water seeping into cellars or inducing
cracking or heaving in slabs
Overflow from roof leader must be directed •
away from sidewalks or driveways
Standard Description
2 - Peak Flow N/A
3 - Recharge Provides groundwater recharge.
4 - TSS
Removal
80% TSS removal for runoff from
non-metal roofs and runoff from
metal roofs that are located
outside the Zone II or Interim
Wellhead Protection Area of a
public water supply and outside an
industrial site.
5 - Higher
Pollutant
Loading
May not be used for runoff from
land uses with higher potential
pollutant loads, May not be used
for runoff from metal roofs located
at industrial sites.
6 - Discharges
near or to
Critical Areas
Within a Zone II or IWPAmay
be used only for runoff from
nonmetal roofs. Outside a Zone
II or Interim Wellhead Protection
Area, may be used for both metal
and nonmetal roofs provided the
roof is not located on an industrial
site.
7 -
Redevelopment
For rooftop runoff from non-metal
roofs and from metal roofs located
outside a Zone II or IWPA and
outside industrial sites.
Ability to meet specific standards
Pollutant Removal Efficiencies
Total Suspended Solids (TSS) 80% •
Nutrients (Nitrogen, phosphorus) Insufficient data•
Metals (copper, lead, zinc, cadmium) Insufficient data•
Pathogens (coliform, e coli) Insufficient data•
Structural BMPs - Volume 2 | Chapter 2 page 85
Activity Frequency
Inspect dry wells.After every major storm in the first few months
after construction to ensure proper stabilization
and function. Thereafter, inspect annually.
Measure the water depth in the observation
well at 24- and 48-hour intervals after a storm.
Calculate clearance rates by dividing the drop in
water level (inches) by the time elapsed (hr).
See activity
Maintenance
Special Features
For uncontaminated runoff from non-metal roofs. May be used for runoff from metal roofs located
outside the Zone II or Interim Wellhead Protection Area of a public water supply and outside an
industrial site. A metal roof is a roof made of galvanized steel or copper.
LID Alternative
Take advantage of LID site design credit and direct runoff from non-metal roofs to a qualifying pervious
area. See Volume 3 for information on disconnecting roof runoff.
Consider green roof.
adapted from the University of New Hampshire
Structural BMPs - Volume 2 | Chapter 2 page 94
Description: Infiltration trenches are shallow
excavations filled with stone. They can be
designed to capture sheet flow or piped
inflow. The stone provides underground
storage for stormwater runoff. The stored
runoff gradually exfiltrates through the
bottom and/or sides of the trench into the
subsoil and eventually into the water table.
Infiltration Trenches
Advantages/Benefits:
Provides groundwater recharge.•
Reduces downstream flooding and •
protects stream bank integrity for small
storms.
Preserves the natural water balance of the •
site.
Provides a high degree of runoff pollution •
control when properly designed and
maintained.
Reduces the size and cost of downstream •
stormwater control facilities and/or storm
drain systems by infiltrating stormwater in
upland areas.
Suitable where space is limited.•
Disadvantages/Limitations:
High failure rates due to improper siting, •
inadequate pollution prevention and
pretreatment, poor design, construction
and maintenance.
Use restricted to small drainage areas. •
Depending on runoff quality, potential risk •
of groundwater contamination.
Requires frequent maintenance. •
Susceptible to clogging with sediment.•
Standard Description
2 - Peak Flow Full exfiltration trench systems may be
designed for peak rate attenuation
3 - Recharge Provides groundwater recharge.
4 - TSS
Removal
80% TSS removal credit when
combined with one or more
pretreatment BMPs.
5 - Higher
Pollutant
Loading
May be used if 44% of TSS is removed
with a pretreatment BMP prior to
infiltration. For some land uses with
higher potential pollutant load an
oil grit separator or equivalent must
be used prior to discharge to the
infiltration structure. Infiltration must
be done in compliance with 314 CMR
5.00.
6 - Discharges
near or to
Critical Areas
Highly recommended with
pretreatment to remove at least 44%
TSS removal prior to discharge.
7 -
Redevelopment
Suitable with pretreatment.
Ability to meet specific standards
Pollutant Removal Efficiencies
Total Suspended Solids (TSS) 80% with pretreatment•
Total Nitrogen 40% to 70%•
Total Phosphorus 40% to 70%•
Metals • (copper, lead, zinc, cadmium) 85% to 90%
Pathogens • (coliform, e coli) Up to 90%
Structural BMPs - Volume 2 | Chapter 2 page 95
Activity Frequency
Inspect units and remove debris Every 6 months and after every major storm
Remove sediment from pretreatment BMPs Every 6 months and after every major storm
Maintenance
Special Features:
LID Alternative:
High failure rate without adequate pretreatment and regular maintenance
Reduce impervious areas
Bioretention areas
adapted from the University of New Hampshire
Structural BMPs - Volume 2 | Chapter 2 page 96
Infiltration Trenches
Infiltration trenches can be designed for complete
exfiltration or partial exfiltration, where a portion of
the runoff volume is directed to the trench and the
remainder is conveyed to other BMPs.
Full Exfiltration Trench Systems
Infiltration trenches must be sized to provide storage
and exfiltration of the required water quality volume.
Full exfiltration systems also provide control of
peak discharges and water quality treatment for
all storm events equal to or less than the design
storm selected. In selecting the design storm, the
minimum peak rate attenuation storm event must
include the 2- and 10-year 24-hour storm events and
may include the 100-year 24-hour storm event, if the
runoff from that storm will increase flooding up- or
downstream of the site. An emergency overflow
channel is required to discharge runoff volumes in
excess of the design storm. Economic and physical
constraints can restrict the use of full exfiltration
systems. Generally, it is not practical to provide
storage for large infrequent storms, such as the
100-year storm.
Partial or Water Quality Exfiltration Trench Systems
These systems exfiltrate a portion of the runoff,
while the remainder is conveyed to other BMPs.
At a minimum, they must be sized to exfiltrate
the recharge volume required by Stormwater
Management Standard 3. There are two methods
of partial infiltration. The first relies on off-line
treatment where a portion of the runoff, or the “first-
flush,” is routed from the main channel to the trench
by means of a weir or other diversion structure. The
second method is on-line, and uses a perforated pipe
at the top of the trench. This underdrain must be
placed near the top of the trench. Refer to the design
section below. After the trench fills to capacity,
excess runoff is discharged through the perforated
pipe and directed to other BMPs.
Applicability
Infiltration trenches always require a pretreatment
BMP. For sheet flow, pretreatment BMP structures
that may be used include vegetated filter strips and
pea stone gravel diaphragms. For piped flow, a
sediment forebay should be used.
Infiltration trenches are feasible at sites with gentle
slopes, permeable soils, and where seasonal high
groundwater levels are at least two feet below
the bottom of the trench. MassDEP recommends
providing greater depths from the bottom of the
trench to seasonal high groundwater elevation to
reduce the potential for failure. Depth to bedrock
will need to be evaluated to determine if use of an
infiltration trench is feasible.
Contributing drainage areas must be relatively small
and not exceed 5 acres. Infiltration trenches are
suitable for parking lots, rooftop areas, local roads,
highways, and small residential developments.
Infiltration trenches are adaptable to many sites
because of their thin profile. Table IT.1 lists the
recommended site criteria. Infiltration trenches can
be used in upland areas of larger sites to reduce the
overall amount of runoff and improve water quality
while reducing the size and costs of downgradient
BMPs.
Infiltration trenches are effective at mimicking
the natural, pre-development hydrological regime
at a site. Full exfiltration systems that have been
carefully designed may be capable of controlling
peak discharges from the 2-year and 10-year 24-hour
storm.
Planning Considerations
MassDEP highly recommends using infiltration
trenches near Critical Areas. They may be used to
treat stormwater discharges from areas of higher
potential pollutant loads, provided 44% of TSS is
removed prior to infiltration. For some land uses with
higher potential pollutant load, an oil grit separator or
equivalent device may be required prior to discharge
to the infiltration trench. When an oil/grit separator
is used, pipe the runoff to the infiltration trench.
Discharges from land uses with higher potential
pollutant loads require compliance with 314 CMR
5.00.
Before planning infiltration trenches, carefully
evaluate the subsurface of the site including soils,
depth to bedrock, and depth to the water table. Make
sure soils have a minimum percolation rate of 0.17
inches per hour.
Make the slopes of the contributing drainage area
less than 5%. Infiltration trenches have extremely
high failure rates, usually due to clogging, so
pretreatment is essential. Infiltration trenches are not
intended to remove coarse particulate pollutants, and
generally are difficult to rehabilitate once clogged.
Typical pretreatment BMPs for infiltration trenches
Structural BMPs - Volume 2 | Chapter 2 page 97
include oil grit separators, deep sump catch basins,
vegetated filter strips, pea stone gravel diaphragms,
or sediment forebays.
Clogging can be an issue even when infiltrating
uncontaminated rooftop runoff as well, so it is
important to implement some form of pretreatment
to remove sediments, leaf litter, and debris to ensure
the proper functioning of the trench and allow for
longer periods between maintenance.
Consider the impacts of infiltrating stormwater on
nearby resources. Infiltration trenches need to be set
back outside Zone Is and Zone As for public drinking
water supplies. Finally, avoid creating groundwater
mounds near Chapter 21e sites that could alter
subsurface flow patterns and spread groundwater
pollution.
Design
See the following for complete design references:
Maryland Stormwater Design Manual, Volumes I and II. October
2000. Maryland Department of Environment. Baltimore, MD.
The volume and surface area of an infiltration
trench relate to the quantity of runoff entering the
trench from the contributing area, the void space,
and the infiltration rate. Because the infiltration
trench is filled with stone, only the space between
the stone is available for runoff storage. Effective
designs call for infiltration trenches to be filled with
1.5-inch to 3.0-inch diameter clean washed stone.
Conduct a geotechnical study to determine the final
soil infiltration rate below the trench. For sizing
purposes, assume a void ratio of 0.4.
Take a minimum of two borings or observation
pits for each infiltration trench. For trenches over
100 feet long, include at least one additional boring
or pit for each 50-foot increment. Take borings or
dig observation pits at the actual location of the
proposed infiltration trench to determine localized
soil conditions.
Base the design of the infiltration trench on the soil
evaluation set forth in Volume 3. The minimum
acceptable rate is 0.17 inches per hour. Never use
the results of a Title 5 percolation test to estimate an
infiltration rate, as these tend to greatly overestimate
the rate that water will infiltrate into the subsurface.
Place the maximum depth of the trench at least two
feet above the seasonal high water table or bedrock,
and below the frost line.
Table IT.1 - Site Criteria for Infiltration Trenches
1. The contributing drainage area to any individual infiltration trench should be restricted to 5 acres or less.
2. The minimum depth to the seasonal high water table, bedrock, and/or impermeable layer should be 2 ft. from
the bottom of the trench.
3. The minimum acceptable soil infiltration rate is 0.17 inches per hour. Infiltration trenches must be sized in
accordance with the procedures set forth in Volume 3.
4. A minimum of 2 soil borings should be taken for each infiltration trench. Infiltration trenches over 100 ft. in length
should include at least one additional boring location for each 50 ft. increment. Borings should be taken at the
actual location of the proposed infiltration trench so that any localized soil conditions are detected.
5. Infiltration trenches should not be used at sites where soils have 30% or greater clay content, or 40% or greater
silt clay content. Infiltration trenches will not function adequately in areas with hydrologic soils in group D and
infiltration will be limited for hydrologic soils in group C.
6. Infiltration trenches should not be placed over fill materials.
7. The following setback requirements apply to infiltration trench installations:
Distance from any slope greater than 5% to any surface exposed trench: minimum of 100 ft.•
Distance from any slope greater than 20% to any underground trench: minimum of 100 ft.•
Distance from septic system soil absorption system: minimum of 50 ft.•
Distance from any private well: minimum of 100 feet, additional setback distance may be required depending •
on hydrogeological conditions.
Distance from any public groundwater drinking water supplies: Zone I radius, additional setback distance may •
be required depending on hydrogeological conditions.
Distance from any surface water supply and its tributaries: Zone A •
8. Distance from any surface water of the Commonwealth (other than surface drinking water supplies and their
tributaries): minimum of 150 ft downslope and 100 ft upslope.
9. Distance from any building foundations including slab foundations without basements: minimum of 20 ft.
Structural BMPs - Volume 2 | Chapter 2 page 98
Include vegetated buffers (20-foot minimum) around
surface trenches. Place permeable filter fabric 6 to
12 inches below the surface of the trench, along
the sides, and at the bottom of the trench. Use filter
fabric, especially at the surface to prevent clogging;
if failure does occur, it can be alleviated without
reconstructing the infiltration trench. Another option
is to place twelve inches of sand at the bottom of the
trench.
Install an observation well at the center of the trench
to monitor how quickly runoff is clearing the system.
Use a well-anchored, vertical perforated PVC pipe
with a lockable above-ground cap.
The visible surface of the trench may either be stone
or grassed. Stone is easier to rake out when clogged.
If it is vegetated with grasses, use fabric above the
stone to keep the soil that serves as the planting
medium from clogging the stone. When trenches are
designed to accept sheet flow, take into account the
grass surface when determining how much of the
runoff will exfiltrate into the trench.
A perforated pipe underdrain is sometimes used as
part of the design. The purpose of the underdrain is
to facilitate exfiltration into the parent soil. Except for
underdrains placed between different trench cells,
MassDEP does not allow underdrains placed near the
bottom of the trench. Placement of an underdrain
near the bottom of the trench reduces the amount
of treatment and exfiltration, because more water is
conveyed through the underdrain to the outlet point
when it rains than exfiltrates into the surrounding
soils.
Construction
Table IT.2 presents the minimum construction criteria
for infiltration trenches. Take precautions before and
during construction to minimize the risk of premature
failure of the infiltration trench. First, prevent heavy
equipment from operating at the locations where
infiltration trenches are planned. Heavy equipment will
compact soil and adversely affect the performance of
the trench. Isolate the areas where the trenches will be
located by roping them off and flagging them.
Construct infiltration trenches only after the site has
been stabilized. Never use trenches as temporary
sediment traps during construction. Use diversion
berms or staked and lined hay bales around the
perimeter of the trenches during their construction.
Excavate and build the trench manually or with
light earth-moving equipment. Deposit all excavated
material downgradient of the trench to prevent re-
deposition during runoff events.
Line the sides and bottom of the trench with
permeable geotextile fabric. Twelve inches of sand
(clean, fine aggregate) may be substituted or used in
addition on the bottom. Place one to three inches of
clean, washed stone in the lined trench and lightly
compact the stone with plate compactors, to within
approximately one foot of the surface. Place fabric
filter over the top, with at least a 12-inch overlap on
both sides. An underground trench may be filled with
topsoil and planted. A surface trench may be filled
with additional aggregate stone.
Divert drainage away from the infiltration trench
until the contributing drainage area is fully stabilized,
including full establishment of any vegetation.
Table IT.2 - Construction Criteria for Infiltration Trenches
1. Infiltration trenches should never serve as temporary sediment traps for construction.
2. Before the development site is graded, the area of the infiltration trench should be roped off and flagged to
prevent heavy equipment from compacting the underlying soils.
3. Infiltration trenches should not be constructed until the entire contributing drainage area has been stabilized.
Diversion berms should be placed around the perimeter or the infiltration trench during all phases of construction.
Sediment and erosion controls should be used to keep runoff and sediment away from the trench area.
4. During and after excavation, all excavated materials should be placed downstream, away from the infiltration
trench, to prevent redeposition of these materials during runoff events. These materials should be properly handled
and disposed of during and after construction.
Light earth-moving equipment should be used to excavate the infiltration trench. Use of heavy equipment causes
compaction of the soils in the trench floor, resulting in reduced infiltration capacity.
Structural BMPs - Volume 2 | Chapter 2 page 99
Maintenance
Because infiltration trenches are prone to failure
due to clogging, it is imperative that they be
aggressively maintained on a regular schedule.
Using pretreatment BMPs will significantly reduce
the maintenance requirements for the trench itself.
Removing accumulated sediment from a deep sump
catch basin or a vegetated filter strip is considerably
less difficult and less costly than rehabilitating a
trench. Eventually, the infiltration trench will have
to be rehabilitated, but regular maintenance will
prolong its operational life and delay the day when
rehabilitation is needed. With appropriate design
and aggressive maintenance, rehabilitation can be
delayed for a decade or more. Perform preventive
maintenance at least twice a year.
Inspect and clean pretreatment BMPs every six
months and after every major storm event (2 year
return frequency). Check inlet and outlet pipes to
determine if they are clogged. Remove accumulated
sediment, trash, debris, leaves and grass clippings
from mowing. Remove tree seedlings, before they
become firmly established.
Inspect the infiltration trench after the first several
rainfall events, after all major storms, and on
regularly scheduled dates every six months. If the
top of the trench is grassed, it must be mowed on a
seasonal basis. Grass height must be maintained to
be no more than four inches. Routinely remove grass
clippings leaves and accumulated sediment from the
surface of the trench.
Inspect the trench 24 hours or several days after
a rain event, to look for ponded water. If there is
ponded water at the surface of the trench, it is likely
that the trench surface is clogged. To address surface
clogging, remove and replace the topsoil or first layer
of stone aggregate and the filter fabric. If water is
ponded inside the trench, it may indicate that the
bottom of the trench has failed. To rehabilitate a
failed trench, all accumulated sediment must be
stripped from the bottom, the bottom of the trench
must be scarified and tilled to induce infiltration, and
all of the stone aggregate and filter fabric or media
must be removed and replaced.
REFERENCES:
California Stormwater Quality Association, 2003, California
Stormwater BMP Handbook 1 of 7, New Development and
Redevelopment, Infiltration Trench, Practice TC-10, http://
www.cabmphandbooks.com/Documents/Development/
TC-10.pdf
Center for Watershed Protection, Stormwater
Management Fact Sheet, Infiltration Trench, http://www.
stormwatercenter.net/Assorted%20Fact%20Sheets/
Tool6_Stormwater_Practices/Infiltration%20Practice/
Infiltration%20Trench.htm
Center for Watershed Protection, Stormwater
Design Example, Infiltration Trench, http://www.
stormwatercenter.net/Manual_Builder/infiltration_design_
example.htm
Duchene, M., McBean, E.A., Thomson, N.R., 1994,
Modeling of Infiltration from Trenches for Storm-Water
Control, Journal of Water Resources Planning and
Management, Vol. 120, No. 3, pp. 276-293
Dewberry Companies, 2002, Land Development
Handbook, McGraw Hill, New York, pp. 521, 523.
Georgia Stormwater Management Manual, Section 3.2.5,
Infiltration Trench, Pp. 3.2-75 to 3.2-88, http://www.
georgiastormwater.com/vol2/3-2-5.pdf
Guo, James C.Y., 2001, Design of Infiltration Basins for
Stormwater, in Mays, Larry W. (ed.), 2001, Stormwater
Collection Systems Design Handbook, McGraw-Hill, New
York, pp. 9.1 to 9.35
Livingston, E.H. 2000. Lessons Learned about
Successfully Using Infiltration Practices. Pp 81-96 in
National Conference on Tools for Urban Water Resource
Management and Protection Proceedings of Conference
held February 7-10, 2000 in Chicago, IL. EPA/625/R-00/001
Metropolitan Council, 2001, Minnesota Urban Small Sites
BMP Manual, Infiltration Trenches, Pp. 3-169 to 3-180 http://
www.metrocouncil.org/Environment/Watershed/BMP/
CH3_STInfilTrenches.pdf
U.S. EPA, 1999, Stormwater Technology Fact Sheet,
Infiltration Trench, EPA 832-F-99-019, http://www.epa.gov/
owm/mtb/infltrenc.pdf
Structural BMPs - Volume 2 | Chapter 2 page 118
Description: Porous pavement is a paved surface
with a higher than normal percentage of air voids
to allow water to pass through it and infiltrate into
the subsoil. This porous surface replaces traditional
pavement, allowing parking lot, driveway, and
roadway runoff to infiltrate directly into the soil
and receive water quality treatment. All permeable
paving systems consist of a durable, load-bearing,
pervious surface overlying a stone bed that stores
rainwater before it infiltrates into the underlying
soil. Permeable paving techniques include porous
asphalt, pervious concrete, paving stones, and
manufactured “grass pavers” made of concrete
or plastic. Permeable paving may be used for
walkways, patios, plazas, driveways, parking stalls,
and overflow parking areas.
Porous Pavement
Advantages/Benefits:
Reduce stormwater runoff volume from paved •
surfaces
Reduce peak discharge rates. •
Increase recharge through infiltration. •
Reduce pollutant transport through direct •
infiltration.
Can last for decades in cold climates if properly •
designed, installed, and maintained
Improved site landscaping benefits (grass pavers •
only).
Can be used as a retrofit when parking lots are •
replaced.
Disadvantages/Limitations:
Prone to clogging so aggressive maintenance •
with jet washing and vacuum street sweepers is
required.
No winter sanding is allowed.•
Winter road salt and deicer runoff concern •
near drinking water supplies for both porous
pavements and impervious pavements.
Soils need to have a permeability of at least 0.17 •
inches per hour.
Special care is needed to avoid compacting •
underlying parent soils.
Standard Description
2 - Peak Flow Provides peak flow attenuation
for small storms.
3 - Recharge Provides groundwater recharge.
4 - TSS
Removal
80% TSS Removal credit if
storage bed is sized to hold
½-inch or 1-inch Water Quality
Volume, and designed to drain
within 72 hours.
5 - Higher
Pollutant
Loading
Not suitable.
6 - Discharges
near or to
Critical Areas
Not suitable especially within
Zone IIs or Zone A’s of public
water supplies.
7 -
Redevelopment
Suitable.
Ability to meet specific standards
Pollutant Removal Efficiencies
Total Suspended Solids (TSS) 80% •
Nutrients • (Nitrogen, phosphorus) Insufficient data
Metals • (copper, lead, zinc, cadmium) Insufficient data
Pathogens • (coliform, e coli) Insufficient data
Structural BMPs - Volume 2 | Chapter 2 page 119
Maintenance
Special Features
Most appropriate for pedestrian-only areas and for low-volume, low-speed areas such as overflow
parking areas, residential driveways, alleys, and parking stalls.
Activity Frequency
Monitor to ensure that the paving surface drains
properly after storms
As needed
For porous asphalts and concretes, clean the
surface using power washer to dislodge trapped
particles and then vacuum sweep the area. For
paving stones, add joint material (sand) to replace
material that has been transported.
As needed
Inspect the surface annually for deterioration Annually
Assess exfiltration capability at least once a year.
When exfiltration capacity is found to decline,
implement measures from the Operation and
Maintenance Plan to restore original exfiltration
capacity.
As needed, but at least once a year
Reseed grass pavers to fill in bare spots.As needed
adapted from the University of New Hampshire
Structural BMPs - Volume 2 | Chapter 2 page 120
Porous Pavement
Applicability
Porous pavement, also known as permeable paving,
is appropriate for pedestrian-only areas and for
low-volume, low-speed areas such as overflow
parking areas, residential driveways, alleys, parking
stalls, bikepaths, walkways, and patios. It can be
constructed where the underlying soils have a
permeability of at least 0.17 inches per hour. Porous
paving is an excellent technique for dense urban
areas, because it does not require any additional
land. Porous pavement can be successfully installed
in cold climates as long as the design includes
features to reduce frost heaving.
Porous paving is not appropriate for high traffic/
high speed areas, because it has lower load-bearing
capacity than conventional pavement. Do not
use porous pavement in areas of higher potential
pollutant loads, because stormwater cannot be
pretreated prior to infiltration. Heavy winter sanding
will clog joints and void spaces. On some highways,
MassHighway Department uses an Open Graded
Friction Course (OGF) that has a permeable top coat
but an impermeable base course. MassDEP provides
no Water Quality or Recharge Credit for OGC,
because it does not provide treatment or recharge.
The primary benefit of OGF pavements is reductions
in noise and hydroplaning.
Effectiveness
Porous pavement provides groundwater recharge
and reduces stormwater runoff volume. Depending
on design, paving material, soil type, and rainfall,
porous paving can infiltrate as much as 70% to 80%
of annual rainfall. To qualify for the Water Quality
and Recharge Credits, size the storage layer to hold
the Required Water Quality or Required Recharge
Volume, whichever is larger, using the Static Method,
and design the system to dewater within 72 hours.
Porous pavement may reduce peak discharge
rates significantly by diverting stormwater into the
ground and away from pipe-and-basin stormwater
management systems, up to the volume housed
in the storage layer. Grass pavers can improve site
appearance by providing vegetation where there
would otherwise be pavement. Porous paving can
increase the effective developable area of a site,
because the infiltration provided by permeable
paving can significantly reduce the need for large
stormwater management structures.
Planning considerations
Porous paving must not receive stormwater from
other drainage areas, especially any areas that are
not fully stabilized.
Use porous paving only on gentle slopes (less than
5%). Do not use it in high-traffic areas or where it will
be subject to heavy axle loads.
Consider the setback requirements when considering
porous pavement:
Considerations Setback Requirements
Slope Less than 5%
Septic system
soil absorption system 50 feet
Private well 100 feet
Public well Outside the Zone 1
Public reservoir Outside the Zone A
Surface Waters 100 feet
Cellar Foundations 20 feet
Slab Foundations 10 feet
Property Lines 10 feet
Minimum depth 2 feet vertical separation above
seasonal high groundwater
from bottom of storage layer
Frost Line Below frost line
Bedrock
Porous paving reduces the need for other stormwater
conveyances and treatment structures, resulting in
cost savings.
Permeable paving also reduces the amount of land
needed for stormwater management.
Design
There are three major types of permeable paving:
Porous asphalt and pervious concrete.• Although
it appears to be the same as traditional asphalt
or concrete pavement, it is mixed with a very low
content of fine sand, so that it has from 10%-25%
void space.
As with any stormwater
exfiltration system, determine if
it is feasible in locations
with high bedrock. Presence
of bedrock near land surface
reduces the ability of soils to
exfiltrate to groundwater.
Structural BMPs - Volume 2 | Chapter 2 page 121
Paving stones• (also known as unit pavers) are
impermeable blocks made of brick, stone, or
concrete, set on a prepared sand base. The joints
between the blocks are filled with sand or stone
dust to allow water to percolate to the subsurface.
Some concrete paving stones have an open cell
design to increase permeability.
Grass pavers• (also known as turf blocks) are a
type of open-cell unit paver in which the cells are
filled with soil and planted with turf. The pavers,
made of concrete or synthetic material, distribute
the weight of traffic and prevent compression of
the underlying soil.
Each of these products is constructed over a storage
bed.
Storage Bed Design
The University of New Hampshire has developed
specifications for storage beds used in connection
with porous asphalt or pervious concrete. According
to UNH, the storage bed should be constructed
as indicated in Figure PP 1 with the following
components from top to bottom:
a 4-inch choker course comprised of uniformly •
graded crushed stone,
a filter course, at least 12 inches thick, of poorly •
graded sand or bankrun gravel to provide
enhanced filtration and delayed infiltration
a filter blanket, at least 3 inches thick, of pea •
stone gravel to prevent material from entering the
reservoir course, and
a reservoir course of uniformly graded crushed •
stone with a high void content to maximize
the storage of infiltrated water and to create
a capillary barrier to winter freeze thaw. The
bottom of the stone reservoir must be completely
flat so that runoff can infiltrate through the entire
surface.
The size of the storage bed may have to be increased
to accommodate the larger of the Required Water
Quality and the Required Recharge Volume.
If paving stones or grass pavers are used, a top course
of sand that is one inch thick should be placed above
the choker coarse.
Overflow Edge
Some designs incorporate an “overflow edge,” which
is a trench surrounding the edge of the pavement.
The trench connects to the stone reservoir below the
surface of the pavement and acts as a backup in case
the surface clogs.
Preparation of Porous Asphalt
Care must be taken in batching and placing porous
asphalt. Unless batched and installed properly,
porous pavement may have a reduced exfiltration
ability. At Walden Pond State Reservation, several of
the areas paved with porous asphalt did not meet the
target exfiltration rate. Cores were taken and it was
found that the batches had more sand and/or asphalt
than was specified, and those sections had to be
removed and repaved.
It is critical to minimize the amount of asphalt binder.
Using greater amounts of asphalt binder could lead to
a greater likelihood of “binder” or asphalt drawdown
and clogging of voids. Sun light heating can liquefy
the asphalt. The liquefied asphalt then drains into the
voids, clogging them. Such clogging is not remedied
by power washing and vacuuming. The topcoat in
such instances needs to be scarified and resurfaced.
The University of New Hampshire has prepared
detailed specifications for preparing and installing
pourous asphalt that are intended to prevent asphalt
problems.
Additional Design Considerations
Provide an open-graded subbase with minimum •
40% void space.
Use surface and stone beds to accommodate •
design traffic loads
Generally, do not use porous pavement for slopes •
greater than 5 %.
Do not place bottom on compacted fill.•
Provide perforated pipe network along bed •
bottoms for distribution
Provide a three-foot buffer between the bed •
bottom and the seasonal high groundwater
elevation, and a two-foot buffer for bedrock.
Cold Weather Design Considerations
Porous pavement performs well in cold climates.
Porous pavement can reduce meltwater runoff
and avoid excessive water on the road during the
snowmelt period.
In cold climates, the major concern is the potential
for frost heaving. The storage bed specifications
prepared by the University of New Hampshire
address this concern.
Structural BMPs - Volume 2 | Chapter 2 page 122
Maintenance
In most porous pavement designs, the pavement itself
acts as pretreatment to the stone reservoir below.
Consequently, frequent cleaning and maintenance
of the pavement surface is critical to prevent
clogging. To keep the surface clean, frequent vacuum
sweeping along with jet washing of asphalt and
concrete pavement is required. No winter sanding
shall be conducted on the porous surface.
As discussed, designs that include an “overflow
edge” provide a backup in case the surface clogs.
If the surface clogs, stormwater will flow over the
surface and into the trench, where some infiltration
and treatment will occur. For proper maintenance:
Post signs identifying porous pavement areas. •
Minimize salt use during winter months. If •
drinking water sources are located nearby (see
setbacks), porous pavements may not be allowed.
No winter sanding is allowed.•
Keep landscaped areas well maintained to •
prevent soil from being transported onto the
pavement.
Clean the surface using vacuum sweeping •
machines monthly. For paving stones, periodically
add joint material (sand) to replace material that
has been transported.
Regularly monitor the paving surface to make •
sure it drains properly after storms.
Never reseal or repave with impermeable •
materials.
Inspect the surface annually for deterioration or •
spalling.
Periodically reseed grass pavers to fill in bare •
spots.
Attach rollers to the bottoms of snowplows to •
prevent them from catching on the edges of grass
pavers and some paving stones.
Adapted from:
MassDEP, Massachusetts Nonpoint Source Pollution
Management Manual, 2006.
References
Ferguson, Bruce, K., Porous Pavements, 2005, CRC
Press. Taylor and Francis Group, Boca Raton
UNH, 2007, UNHSC Design Specifications for Porous
Asphalt Pavement and Infiltration
Beds, Revised October 2007, http://www.unh.edu/erg/
cstev/pubs_specs_info/unhsc_pa_apec_07_07_final.
pdf
Asphalt Pavement for Stormwater Management,
http://www.unh.edu/erg/cstev/pubs_specs_info/
porous_ashpalt_fact_sheet.pdf
University of New Hampshire Center for Stormwater
Technology Evaluation and Verification; this research
group tests and evaluates stormwater BMPs on the
UNH campus.
An article about the use of permeable pavers at •
the Westfarms Mall in Connecticut.
Case Studies from Uni-Group USA, a block paver •
manufacturer.
The Nonpoint Education For Municipal Officials •
program at the University of Connecticut has
been involved in numerous permeable paving
pilot projects.
Permeable paver specifications courtesy of the •
Low Impact Development Center.
Porous pavement design and operational criteria •
from the US Environmental Protection Agency,
which also publishes a Low Impact Development
Page. Also see this report on a Field Evaluation
of Permeable Pavements for Stormwater
Management (PDF.)
New Jersey Stormwater Best Management •
Practices Manual February 2004.
Structural BMPs - Volume 2 | Chapter 2 page 123
Description: Cisterns and rain barrels are
structures that store rooftop runoff and reuse it for
landscaping and other non-potable uses. Instead
of a nuisance to get rid of, consider rooftop runoff
as a resource that can be reused or infiltrated. In
contrast, conventional stormwater management
strategies take rooftop runoff, which is often
relatively free of pollutants, and direct it into the
stormwater treatment system along with runoff
from paved areas.
Rain Barrels & Cisterns
Advantages/Benefits:
Can reduce water demand for irrigation or other •
non-potable uses.
Property owners save money on water bills by •
using stored water for landscape purposes.
Public water systems may experience lower •
peak demand in summer.
When properly installed, rain barrels and •
cisterns reduce stormwater runoff volume for
small storms.
Disadvantages/Limitations:
Provides mosquito-breeding habitat unless •
properly sealed.
May need to be disconnected and drained in •
winter to avoid cracking of storage structure
Standard Description
2 - Peak Flow Provides peak flow attenuation for
small storms.
3 - Recharge Provides no groundwater
recharge.
4 - TSS
Removal
The roof surface can be deducted
from the impervious area used
to calculate the Required Water
Quality Volume for sizing other
structural treatment BMPs, a)
when rain barrel or cistern is
sized to store the Required Water
Quality Volume for the roof surface
(0.5 inch or 1.0 inch), b) stored
water is used within 72-hours or
discharged to an infiltration BMP,
and c) the system is designed to
operate year round.
5 - Higher
Pollutant
Loading
Not applicable.
6 - Discharges
near or to
Critical Areas
Not applicable.
7 -
Redevelopment
Suitable.
Ability to meet specific standards
Pollutant Removal Efficiencies
Offers no primary pollutant removal benefits•
Rooftop Runoff presumed to be clean• 1
1Although MassDEP presumes rooftop runoff to be clean for purposes of the Stormwater Management Standards, research
indicates higher PAHs in runoff from asphalt shingled roofs and zinc from metal roofs. USGS research in Texas indicates
rooftop runoff contains mercury. Before using rooftop runoff for vegetable gardens, investigate the quality of the runoff,
especially when using larvicides in rain barrels or cisterns for mosquito control.
Structural BMPs - Volume 2 | Chapter 2 page 124
Maintenance
Special Features
Direct overflow from rain barrels and cisterns to a dry well, infiltration trench, rain garden, bioretention
area, or other infiltration BMP sized to recharge the overflow volume.
Activity Frequency
Maintenance requirements for cisterns and rain barrels are minimal. These requirements include the
following: Inspecting the unit twice a year, larviciding for mosquito control, disconnecting and draining
the system prior to winter to prevent cracking, and replacing or repairing any worn-out pieces.
Structural BMPs - Volume 2 | Chapter 2 page 125
Rain Barrels & Cisterns
Applications and Design Principles
The most common approach to roof runoff storage
involves directing each downspout to a 55-gallon rain
barrel. A hose is attached to a faucet at the bottom of
the barrel and water is distributed by gravity pressure.
A more sophisticated and effective technique is
to route multiple downspouts to a partially or fully
buried cistern with an electric pump for distribution.
Where site designs permit, cisterns may be quite
large, and shared by multiple households, achieving
economies of scale. Stored rainwater can be used
for lawn irrigation, vegetable and flower gardens,
houseplants, car washing, and cleaning windows.
The roof surface can be deducted from the
impervious surfaces used to determine the Required
Water Quality Volume for sizing other structural
treatment practices, only when a) the cistern or
barrel can store the required water quality volume
for the roof surface, b) the stored water is used or
discharged to an infiltration BMP within 72-hours,
and c) the system is designed to operate 365 days a
year.
Cisterns and rain barrels can provide benefits by
reducing the required water quality volume and
peak discharge rates depending on the amount of
storage available at the beginning of each storm. One
rain barrel may provide a useful amount of water
for garden irrigation, but it will have little effect on
overall runoff volumes, especially if the entire tank is
not drained between storms. Improve effectiveness
by having more storage volume and by designing the
system with a continuous discharge to an infiltration
structure, so that there is always storage available for
retention. To operate the system year-round, bury or
insulate the unit. State Plumbing Code requirements
apply to cisterns and rain barrels located within 10
feet of a building. All applicable requirements of
the Massachusetts State Plumbing or State Building
Codes must be met.
Cisterns and rain barrels are applicable to most
commercial and residential properties where there is
a gutter and downspout system to direct roof runoff
to the storage tank. They take up little room and
can be used in dense urban areas. Rain barrels and
cisterns are excellent retrofit techniques for almost
any circumstance. Rain barrels are covered plastic
tanks that can hold from 50 to 100 gallons with a
hole in the top for downspout discharge, an overflow
outlet, and a valve and hose adapter at the bottom.
They are used almost exclusively on residential
properties. Plastic rain barrels are typically installed
above ground. They must be disconnected prior to
the winter, and the barrel drained completely to
prevent the barrel from cracking.
Because rain barrels rely on gravity flow, place
them near, and slightly higher than, the point of use
(whether a garden, flower bed, or lawn). Route the
overflow outlet to a dry well, bioretention area, rain
garden or other infiltration BMP. It is important for
property owners to use the water in rain barrels on
a regular basis, otherwise the barrels can fill up and
prevent additional roof runoff from being stored.
Each house should have the appropriate number
of rain barrels or an appropriately sized cistern. A
one-inch storm produces over 620 gallons of water
from a 1,000 square foot roof. Assuming a rain barrel
capacity of 55 gallons, it would take 11 rain barrels
to store one inch of runoff from 1,000 square feet of
roof.
Cisterns are partially or fully buried tanks with a
secure cover and a discharge pump; they provide
considerably more storage than barrels, as well as
pressurized distribution. They are less susceptible
to cracking induced by expansion of freezing water
when buried below grade. Cisterns can collect water
from multiple downspouts or even multiple roofs,
and then distribute this water wherever it needs to
go via an electric pump. Property owners may use
one large tank or multiple tanks in series. Either
way, direct the overflow for the systems to a dry
well or other infiltration mechanism so that if the
cistern is full, excess roof runoff is infiltrated, and
not discharged to the stormwater treatment system.
Some cisterns are designed to continuously discharge
water into infiltration units at very slow rates, so that
the tank slowly empties after a storm, providing more
storage for the next storm. The cisterns must also be
designed to dewater in 72 hours or less.
Design
Because of the low pressure of the discharge, rain
barrels are most effectively used with a drip irrigation
system. Secure rain barrels against disturbance
by children or animals. Seal any openings with
mosquito netting. If present, place the cistern’s
continuous discharge outlet so that the tank does
not empty completely. This ensures water availability
at all times, and provides some storage capacity for
every storm. A diverter at the cistern inlet can redirect
Structural BMPs - Volume 2 | Chapter 2 page 126
the “first flush” of runoff, which is more likely to have
particulates, leaves, and air-deposited contaminants
washed off the roof. Keep leaves and debris out
of the storage tank by placing a screen at the top
of the downspout. Hide rain barrels and cisterns
with shrubs or other landscaped features. Direct
overflow from rain barrels and cisterns to a dry well,
infiltration trench, rain garden, bioretention area, or
other infiltration BMP sized to recharge the overflow
volume. Use pond routing methods to design cisterns
or rain barrels to account for retention of early runoff
in the storage tank. Include access ports for any
subsurface cisterns. Confined space entry training
may be needed to enter large cisterns. MassDEP does
not require treatment of runoff from non-metal roofs
prior to infiltration.
Maintenance
Maintenance requirements for rain barrels are
minimal and consist only of inspecting the unit
as a whole and any of its constituent parts and
accessories twice a year. The following components
should be routinely inspected and either repaired or
replaced as needed:
Roof catchment,• to ensure that trash and
particulate matter are not entering the gutter and
downspout to the rain barrel.
Gutters,• to ensure that no leaks or obstructions
are occurring.
Downspouts,• to assure that no leaks or
obstructions are occurring.
Entrance at rain barrel,• to ensure that there are
no obstructions and/or leaks occurring.
Rain barrel,• to check for potential leaks, including
barrel top and seal.
Runoff / overflow pipe,• to check that overflow is
draining in non-erosive manner.
Spigot,• to ensure that it is functioning correctly.
Any accessories,• such as rain diverter, soaker
hose, linking kit, and additional guttering.
Apply larvicides in strict accordance with all Mass. •
Department of Agricultural Resources Pesticide
Bureau regulations to prevent mosquitoes from
reaching adulthood.
Add bleach or other chemicals annually to •
kill bacteria present in the system. A qualified
professional should determine appropriate
treatment.
Drain the system before winter• if it is located
above ground or partially exposed, to prevent
cracking.
Disconnect the system from roof leaders in the •
fall, if water is not intended to be used during the
winter, unless the runoff is directed to a qualifying
stormwater infiltration practice.
When the cistern or barrel is connected to a •
stormwater recharge system, remove particulates
trapped in the cistern or rain barrel annually
to limit clogging of the stormwater infiltration
system.
Adapted from:
MAPC Low Impact Development Toolkit. For more information,
go to www.mapc.org/lid and www.arc-of-innovation.org.
Additional Information
http://www.rainwaterrecovery.com/about.html
www.crwa.org (Charles River Watershed Association)
Horsley Witten Group, Inc. *Remember, this information is great for most sites, but if your property
is really steep or you have complicated drainage issues, please do reach out to a professional to help
you!
Build it and Clean Water will Come!
A Rain Garden Guide for Homeowners Michelle West, P.E.
Michelle is a senior water resources engineer with more than 18 years of professional experience. With a background in both
engineering and natural resources, she is passionate about using her skills to restore the natural world while improving the
human experience. Have you joined the rain garden craze yet? Inspired by an article, your neighbor’s rain garden, or our Rain Garden Wednesdays on Instagram? Want to do your part to improve your local water quality and wildlife habitat? It’s easier than you think!
What is a Rain Garden? Rain gardens are actually very simple. They are just shallow depressions – too shallow to even call a hole! – with plants. But, rain gardens are not just isolated depressions placed randomly out in a yard. They are specifically sized and placed to absorb stormwater runoff, the water that flows from your built impervious surfaces such as rooftops, driveways, roads, parking lots, and even compacted lawn areas when it rains. And that’s it! Well, not quite, since rain gardens do take a bit of planning and physical labor, which we will get to in a bit.
Cross-section of a typical rain garden Maybe the better question to ask is “why a rain garden”? What’s so bad about stormwater runoff? Why all the fuss? It’s just rainwater straight from the sky – isn’t that natural? Unfortunately, no. All of those impervious surfaces that we built for our shelter and transportation prevent the clean rainwater from soaking into the ground like it did before we developed the land. Dirt, fertilizer, soaps, oils, metals, and even animal poop build up on these hard surfaces and get carried away with the stormwater. In addition to creating water pollution, when your runoff joins up with your neighborhood’s runoff, it can cause flooding and erosion, damage infrastructure, degrade aquatic ecosystems, and close shellfishing areas and beaches. While runoff from just your home or business may not cause much of a problem, the cumulative impact from everyone’s home and business really does. Rain gardens are one beautiful way to “break the impervious chain” of roof to downspout to driveway to road to stream, pond, or bay. They use soils and plants to filter pollutants and help water soak in rather than run off. Please remember that rain gardens are NOT ponds or wetlands - they should drain in less than 24 hours after a rainfall. Use the four-step process below to create one at your house!
Horsley Witten Group, Inc. *Remember, this information is great for most sites, but if your property
is really steep or you have complicated drainage issues, please do reach out to a professional to help
you!
These graphics show how “breaking the impervious chain” slows, cleans, and reduces the stormwater
leaving a site.
Step 1 – Site Selection This step really is the most important. Choosing the wrong location for your rain garden can at best, waste your time and money, and at worst, cause drainage issues in your yard. So, take your time with Step 1!
Walk your property to get the general lay of the land.
Where does the water go? Determine existing stormwater flow paths.
Note the location of underground pipes, trees, structures, property lines, septic systems, etc.
What kind of soils do you have? (e.g., sand, clay, etc.) Areas of well-drained sand are ideal but not mandatory.
Pick a good general location for your rain garden. Try to avoid areas that: X Are within 10 ft of a wall or basement, 2 ft of a sidewalk/driveway; and 50 ft of a septic system X Stay consistently wet X Have high groundwater or bedrock X Are under trees or on steep slopes or where getting water into and out of the rain garden is difficult.
Helpful Tip - Existing flat areas are the best, at least on your shoulders and back if you are digging it by hand!
Step 2 - Design Now that you have a general location, you can get to the fun part – designing your rain garden! You do not need to be an engineer to complete this step, I promise (although I understand how hollow that sounds coming from an engineer…)! While it is important to understand roughly how big your rain garden should be, this does not have to be an exact calculation - there is a lot of wiggle room here. Most importantly, have fun with the shape and look of your rain garden!
Horsley Witten Group, Inc. *Remember, this information is great for most sites, but if your property
is really steep or you have complicated drainage issues, please do reach out to a professional to help
you!
Don’t be afraid to make a sketch! You don’t need to be an artist to jot down a meaningful sketch that
helps you visualize your yard and find a great place for your rain garden.
Estimate impervious areas (IA) draining to your rain garden. This is the size (ft2) of your rooftops, driveways, patios, etc., that are uphill from your rain garden. So it may just be a portion of your roof or half of your driveway, while the other half drains to the other side of your yard. Don’t over count!
Size the rain garden (RG) surface area to hold at least 1 inch of rain (P=0.08 ft). One inch is a good target to shoot for since 90% of all storm events in the Northeast are 1 inch or less, causing the majority of all stormwater pollution. Typical rain gardens are 100-200 ft2.
Choose a ponding depth (D). This is not a depth of permanent standing water, but instead, the maximum depth of water during and immediately after a rain event. Typical rain gardens are 6
inches deep (D=0.5 ft) – you can go deeper for sandy soils (up to 8”), whereas tight soils (with a lot of silt or clay) require a larger surface area with shallower depths (minimum 3”). Now wait, you say, this is starting to sound like math! But you promised! Never fear – you can use the cheat sheet in Table 1 to figure out your rain garden surface area. Just pick your ponding depth and size of impervious area, and we did the math for you! But if you love equations like I do, you can do your own calculations with the following equation:
RG (ft2) = IA (ft2) * P (ft)
D (ft)
Horsley Witten Group, Inc. *Remember, this information is great for most sites, but if your property
is really steep or you have complicated drainage issues, please do reach out to a professional to help
you!
And that’s it – now you now how big your rain garden needs to be! What’s next?
Amend soils if necessary to improve infiltration and provide organic matter for plants. Add a 3” layer of coarse sand for sites with clayey soils or 3” of leaf compost for really sandy sites.
Helpful Tip - For a 100 ft2 rain garden, a 3” layer of amendments = 1 cubic yard
Figure out how to get the water in your garden, and perhaps more importantly, how it will get out during really big storms. For inlets, consider using an extended downspout or pipe, vegetated or stone-lined swales, diversion berms, or just direct the surface flow over lawn. The key is to make sure you don’t have erosion at the inlet location – use rock if you see erosion. For overflows, just make sure you know where the water will go if the rain garden overflows: X Avoid directing overflow to other properties or structures
Make berms higher near buildings
Direct flows over lawns or into existing drain inlets or wherever the stormwater goes today.
Helpful Tip - Remember, you are not creating more water than you had before – the drainage area is the same. Rather, you are actually reducing the total amount of runoff with your rain garden. So as long as you are not redirecting runoff in a completely different direction, the rain garden should be improving conditions, not creating new problems!
Pick your plants!
Use plant species tolerant to both wet and dry conditions.
Native species are preferred and DO NOT plant invasive vegetation X Avoid using edible plants, particularly if treating driveway or road runoff
Provide for variable heights, color, leaf shape (trees, shrubs, herbaceous) X Avoid placing woody vegetation at inflow/outflow locations to avoid clogging
Consider visual appeal and wildlife habitat in all seasons (e.g., fall flowers for pollinators; winter berries for birds, etc.)
Horsley Witten Group, Inc. *Remember, this information is great for most sites, but if your property
is really steep or you have complicated drainage issues, please do reach out to a professional to help
you!
But wait, which plants do I use? Don’t worry if you are not a master gardener! You can usually ask at your local nursery or find a list online. There is probably a rain garden plant list for your location, but the recommended species are pretty similar throughout the Northeast, so don’t worry if you can’t find one for your specific area. Here are two example lists you can start with from UMASS and APCC:
https://ag.umass.edu/landscape/fact-sheets/rain-gardens-way-to-improve-water-quality
https://apcc.org/raingardens/apcc-rain-garden-plant-list.pdf
You can also find lists of invasive species to avoid in your area. Here is a sample list of the invasive species in Massachusetts: https://www.mass.gov/service-details/invasive-plants
Step 3 – Install Now that you’ve got your hand sketch of your rain garden location and design, it’s time to get your hands dirty. Round up your friends and family, or even better, your neighbors (maybe they’ll want one next!), to help you with the installation. Don’t forget to do the following before you get started, though:
Check with the Town or City to see if you need a permit and call for utility locations before you dig!
Mark the excavation footprint with string or spray paint.
Spray-painted location of a rain garden – the solid line indicates bottom of bed and the dotted line is
for the top of slope, leaving space to provide gentle side slopes rather than vertical walls.
Install erosion & sediment controls if necessary (like silt fence or silt sock).
Find a place to stockpile materials.
Remove grass (reuse, if possible).
Helpful Tip – Use a tarp for stockpiling materials to make cleanup so much easier!
Horsley Witten Group, Inc. *Remember, this information is great for most sites, but if your property
is really steep or you have complicated drainage issues, please do reach out to a professional to help
you!
Now, you are ready for the actual work!
Start digging! Dig to the desired ponding depth (3-8”) along with another 2-3” if you are adding a mulch layer. May also need to over-dig another 3-6” to aerate compacted soils or for adding soil amendments. Use excavated material to create berms if needed.
Mix any amendments into the native soil with shovels and rakes.
Be sure to make the bottom of ponding area flat. This is the most important part of the install. The rain garden should fill up uniformly like a bathtub.
Helpful Tip - You can check this easily at home using two stakes, a string, a string level, and a measuring tape!
Install inlet and overflow components.
Plant! Arrange plants first, then remove from containers. Loosen root-bound plants and dig holes 2x wider than the root ball. Leave room for mulch layer if adding. Plugs can go in after mulch.
Add mulch/organic surface layer (1-3”) or just around plants (preferred). Protect small plants.
Helpful Tip - Don’t be afraid to “decorate” with rocks, particularly any you found while you were digging! Looks cool and saves you time and effort to get rid of them.
Horsley Witten Group, Inc. *Remember, this information is great for most sites, but if your property
is really steep or you have complicated drainage issues, please do reach out to a professional to help
you!
Turn on water to inspect flow path and to soak plants. If your inlet is a roof downspout, it is fun to spray water on your roof and watch the rain garden in action!
Clean up site. Remove any erosion controls once area is stabilized (i.e., the plants and/or seed are well established!).
Pat yourself on the back and enjoy your rain garden!
Table 2 – Sample rain garden supply list
Step 4 – Maintain Unfortunately, yes, your rain garden will need to be maintained like everything else. But the level of effort required is really based on how “nice” you want it to look. If you are going for the more wild, natural look, maintenance will be pretty minimal. If you want it to be a more ornamental feature in your yard, then you will need to keep up with it just like your other ornamental beds.
Inspect your rain garden after storms and during regular landscaping activities. Be sure to look for: X Weeds and invasive plants X Sediment build-up X Debris and trash X Dying plants and grasses
X Erosion/gullying X Inlet/outlet clogging X Standing water/drainage issues
Maintenance activities will include:
Vegetation pruning and trimming
Debris and sediment removal
Plant and mulch replacement
Stabilization of any eroded areas with rock or plants
Soil amendments for areas that pond water >24 hours after rain X No fertilization is recommended
We hope this helps you put a rain garden in at your house! If you want to use a downloadable rain garden App on your smart phone or tablet, we recommend the one that our friends at the University of Connecticut developed: http://nemo.uconn.edu/raingardens
Rain Garden Supply List Qu Unit Notes
Materials
Compost for 3 inches of soil amendments 1.5 cy Mix compost with existing soil for bottom of RG
Mulch, 2 inches with extra for blending existing beds 1.5 cy
Tarps for stockpiles 3-4 ea
Plants 100 ea See RG sketch for proposed layout
Washed stone for downspouts 1 cf couple of bags should do
Non-woven filter fabric for use under the stone inlet and overflow – (roll 6’ wide)6 sf only need a pretty small strip
Fabric staples 1 box
Grass seed for stabilizing disturbed areas outside of rain garden 1 bag or re-use sod
Erosion controls (silt fence or silt sock)50 ft
~30 ft for downgradient of RG and ~20 ft for
around soil stockpile if needed
Spray paint for marking garden footprint 1 can
Gloves
Tape measure
Shovels (both spade and flat)
Rake
Pitchfork
Stakes and string
Tools
String level
Hammer
Trowel
Utility knife for cutting fabric
Hose for watering
Wheelbarrow