HomeMy Public PortalAbout4747381
October 2012
PERMEABLE INTERLOCKING CONCRETE PAVEMENT (PICP)
This document serves as an introduction to the design considerations for PICP when it is part of
a MSD stormwater management plan.
DESIGNER NOTES:
The designer should consider the following when designing a Permeable Interlocking Concrete
Pavement system:
1. Permeable Interlocking Concrete Pavement may be used to provide water quality volume
(WQv) provided it is designed and constructed in accordance with the March 16, 2012
Stand Alone Water Quality BMP policy change letter (Insert Link Here) or is used in
conjunction with a properly designed infiltration basin/trench, sand filter, or other
approved BMP per the 2000 Maryland Stormwater Design Manual. The supplemental
BMP shall be located downstream from the permeable interlocking concrete system, not
underneath it.
2. The design engineer shall reference the following resources published by the Interlocking
Concrete Pavement Institute; Permeable Interlocking Concrete Pavements Manual, and
the PICP Guide to Construction Specifications. The Permeable Design Pro software is
recommended to aid in the design; all are available from the www.icpi.org website. Also
reference the MSD Provisional Use Level approval letters for PICP to obtain additional
design guidelines, available at www.stlmsd.com.
3. Consideration should be given to the type of traffic loads placed upon the PICP. An
engineer experienced with pavement design shall provide input on this aspect early in the
design phase. The minimum pavement section subject to vehicular traffic shall be (from
top to bottom) 3 1/8 inch thick paving units, 2-inch thick bedding stone (typically ASTM
No. 8 or 9 stone), 4-inch thick layer of base stone (ASTM No. 57 or similar size), and a
layer of subbase stone (ASTM No. 2 or similar size), all underlain by MSD Type 4 filter
fabric (see note 11) where needed. The thickness of the subbase will vary depending on
storage and anticipated traffic loads as described in ICPI guidance literature. However, a
minimum 12-inch thick subbase will be required for all applications.
4. PICP will not be allowed on sites whose land use or activity generates higher
concentrations of hydrocarbons, trace metals or toxicants than are found in typical
stormwater runoff. Examples of such “hotspots” are listed in table 2.6 in the 2000
Maryland Stormwater Design Manual.
2
5. A perforated PVC underdrain system will be required. The horizontal and vertical
locations shall be determined by the design engineer, depicted on the drawings, and be in
general accordance with the MSD Permeable Interlocking Concrete Pavement detail.
6. To provide an infiltration bed, the primary underdrain system may be perched or
configured as internal water storage within the subbase rock. The perched height is
dependent on the infiltration characteristics of the underlying subgrade and the desired
storage. The underdrain system shall not be perched if the underlying soils are plastic or
plastic soils that have been stabilized with lime. Design the open graded storage bed to
completely drain within 12 to 72 hours.
7. When PICP is used in conjunction with stormwater runoff volume reduction practices,
MSD recommends the suitability and infiltration rates of the underlying soils shall be
confirmed by geotechnical evaluation prior to final design. Soil boring logs and a soil
survey shall accompany all test results. Designers shall also consider the depth of the
porous pavement system in determining the applicability of the information. If infiltration
testing is not conducted prior to design, then the underlying soils shall be assumed to
have an infiltration rate of 0.05 in/hr. (“default” subgrade saturated hydraulic
conductivity). If use of a greater design rate is desired for the purpose of estimating
volume reduction capabilities, at least one infiltration test shall be provided for each
onsite soil type where porous pavement is proposed. In no case shall the frequency of
testing be less than 1 per 5000 S.F of PICP. All infiltration test reports shall be submitted
for MSD review prior to final project approval.
8. Provide an overflow system or additional storage to prevent water in the open graded
storage bed from rising into the bedding course or PICP for the 2-yr, 24-hr storm event.
Any emergency overflow pipes placed within the subbase should discharge only when
the storage volume is exceeded. The horizontal and vertical location of all underdrains
and overflow systems shall be determined by the design engineer and shown on the plans.
Emergency overflow pipes and underdrains systems shall discharge to a storm water
structure or daylight to a stabilized outfall.
9. Observation wells should be provided in low areas within the permeable pavement
system, and shall extend to the bottom of the storage bed. The wells shall consist of a six
inch schedule 40 PVC pipe with cast iron frame and cover, as shown on the MSD PICP
details. The number of wells required on an installation will vary on a site specific basis,
and will be determined by the design engineer.
10. A minimum of 2 feet vertical clearance should be provided between the bottom of the
storage bed and the seasonally high water table.
11. Placing PICP over areas of recent fill or compacted fill is not optimal for infiltration.
12. The volume in the voids of the open graded base and storage bed shall be considered the
total water storage capacity. A void ratio not greater than 40 percent will be used to
calculate storage volume. No storage volume will be allowed in the paving units or
3
bedding stone layer. The emergency overflow apparatus, if any, should discharge only
when the storage volume is exceeded.
13. Prepared subgrade soil should be separated from the porous subbase. The prepared
subgrade soil shall be dry and, where needed, covered with MSD Type 4 filter fabric
(such as Mirafi 140N or approved equal) on the vertical sides of the typical section.
Separation of the prepared subgrade along the bottom of the section may be provided by
MSD Type 4 filter fabric or a well graded filter layer at the discretion of the design
engineer.
14. Subgrade should normally be compacted to a minimum density of 90% to 95% of the
theoretical density per AASHTO T 180. However, the designer should be aware that
increasing the subgrade density decreases its infiltration capacity. Since soil conditions,
grading requirements, and end user demands are site specific, this requirement shall be
considered from a case by case standpoint. A geotechnical engineer shall provide input in
balancing the infiltration and load bearing demands that the PICP must satisfy.
15. A permanent sign shall be posted warning that care should be taken during snow
plowing; and prohibit the following: resurfacing, the use of sand abrasives for winter tire
traction, and the use of power washers.
16. The property owner must execute a Maintenance Agreement with MSD, and the entire
PICP area shall be platted in a Reserve Area for Stormwater Management.
17. The design of the finished grade of the pavement surface shall take into consideration the
Americans with Disabilities Act (ADA) and local code requirements.
18. Subgrade should be flat, and where topography requires, terracing of the subgrade is
allowed. The volume of water stored behind each terrace will be considered part of the
infiltration bed.
PLAN NOTES:
The following notes, specifications, and details for Permeable Interlocking Concrete Pavements
shall be included on the plans proposed for MSD approval:
1. The contractor shall obtain the concrete paver manufacturer’s certification that the paving
units supplied to construct the PICP have been approved by MSD and meet the
requirements in ASTM C936. This certification shall be provided to the MSD Division
Inspector. The certification shall include the manufacturer’s name, and state that the PICP
supplied meets the ASTM C936 specifications, (testing should be current within previous
12 months) and that the paving materials meet all requirements as evaluated under the
manufacturer’s quality control program.
4
2. Prior to obtaining a construction permit from MSD to construct the permeable
interlocking concrete pavement (PICP) for a given project, the engineer providing the as-
built certification shall verify that the installing contractor has:
A. Past history demonstrating applicable experience.
B. The PICP installation contractor must have a current Level 1 certificate from the
Interlocking Concrete Pavement Institute’s concrete paver installer program.
3. The contractor shall prevent and divert sediment from entering the subbase and pavement
surface until the tributary areas are deemed stable by the assigned MSD inspector.
4. Vehicular traffic shall be prohibited on the PICP until the site is stable to prevent mud
from being deposited by vehicles.
5. No product or material substitutions are permitted unless previously approved by the
MSD plan review engineer or by the MSD field inspector assigned to the project. All
substitutions shall be presented to MSD through the engineer responsible for the design
of the PICP system.
6. Stone should be clean, washed, 90 percent fractured faces with a Los Angeles Abrasion
Index of less than 40 and conform to the grading requirements in ASTM D448.
7. Do not clean the paver surface with high-pressure hoses or abrasives. When cleaning is
necessary, combination cleaning machines that combine a wet spray and vacuum process
have been found to be effective.
8. A permanent sign shall be posted warning that care should be taken during snow
plowing; and prohibit the following: resurfacing, the use of sand abrasives for winter tire
traction, and the use of power washers.
9. At completion of the project, prior to final dedication, an as-built certification, signed and
sealed by a Missouri Professional Engineer, shall be provided.
MANUFACTURER’S PREQUALIFICATION:
The PICP manufacturer shall be responsible for establishing and maintaining a quality control
program to assure compliance with requirements in ASTM C936. Prior to use on projects
requiring MSD approval, the manufacture shall submit five (5) copies of a completed pervious
paving application as well as documentation describing the quality control program. The
completed application and other documentation shall be submitted to:
MSD BMP Committee
Metropolitan St. Louis Sewer District
2350 Market Street
St. Louis, Missouri 63103-2555
MATERIAL CERTIFICATION:
5
The contractor shall obtain the concrete paver manufacturer’s certification that the paving units
supplied to construct the PICP have been approved by MSD and meet the requirements in ASTM
C936. This certification shall be provided to the MSD Division Inspector. The certification shall
include the manufacturer’s name, and state that the PICP supplied meets the ASTM C936
specifications, (testing should be current within previous 12 months) and that the paving
materials meet all requirements as evaluated under the manufacturer’s quality control program.
CONTRACTOR PREQUALIFICATION:
Prior to obtaining a construction permit from MSD to construct the permeable interlocking
concrete pavement (PICP) for a given project, the engineer providing as-built certification shall
verify that the installing contractor has:
1. Past history demonstrating applicable experience.
2. The PICP installation contractor must have a current Level 1 certificate from the
Interlocking Concrete Pavement Institute’s concrete paver installer program.
AS-BUILT CERTIFICATION:
At completion of the project, prior to final dedication, an as-built certification, signed and sealed
by a Missouri Professional Engineer, shall be provided certifying:
1. The PICP system was built in accordance with the details, dimensions, and materials as
approved by MSD for this project.
2. The PICP system was installed by a qualified contractor, and has satisfied all applicable
quality control and performance tests.
3. The PICP system installation was witnessed by the certifying engineer or a
representative under his direct supervision.
6
7
8
PERVIOUS PAVEMENT AS-BUILT CERTIFICATION
DATE:
To: Metropolitan St. Louis Sewer District
Department of Engineering
Attn: Keith Milson
From: (Consultant Engineer’s Name)
Title:
Consulting Engineer Company Name & Address
Re: Engineering/Construction Certification for the following project:
MSD Project Name:
MSD P#:
Project Address:
For the project’s permeable pavement practice, this correspondence shall serve as a certification
of the following:
1. The Pervious Pavement was built in accordance with the details, dimensions, and
materials as approved by MSD for this project.
2. The Pervious Pavement was installed by a qualified contractor, and has satisfied
all applicable quality control and performance tests.
3. The Pervious Pavement installation was witnessed periodically by the certifying
engineer or a representative under their direct supervision.
Printed Name:
Discipline:
License No:
(P.E. seal with signature and date)