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HomeMy Public PortalAbout06-14-2011MEDINA PLANNING COMMISSION AGENDA TUESDAY, JUNE 14, 2011 7:00 P.M. CITY HALL (2052 County Road 24) 1. Call to Order 2. Public Comments on items not on the agenda 3. Update from City Council proceedings 4. Planning Department Report 5. Approval of May 10, 2011 draft Planning Commission minutes. 6. Continued Public Hearing - Ordinance Amendment - Chapter 8 of the Medina Zoning Code to codify the City's stormwater management regulations. 7. Discussion — Off -premise signage and "Directional" signage 8. City Council Meeting Schedule 9. Adjourn POSTED IN CITY HALL JUNE 10, 2011 MEMORANDUM TO: Mayor Crosby and Members of the City Council FROM: Dusty Finke, City Planner; through City Administrator Chad Adams DATE: June 2, 2011 SUBJ: Planning Department Updates June 7, 2011 City Council Meeting Ordinance Updates A) Storm water/LID Ordinance — Planning staff have been working with Engineering on this project. The ordinance was presented to the Planning Commission at their May meeting, and they recommended a number of changes and tabled the ordinance until their next meeting. B) Animal Regulations — staff has prepared the ordinance amendment as directed by the City Council related to limitations on keeping pets and private kennel licenses. Staff intends to present the ordinance for Council review at the June 7 meeting. Land Use Application Reviews A) Marx Conservation Design Subdivision — 2700 and 2900 Parkview Drive — Wally. Marx has requested review of a CD-PUD Concept Plan for a subdivision which would allow a density bonus (10 lots) and flexibility to lot size and setback requirements and place a portion of their property into Conservation Easements. Staff has conducted a preliminary review and has tentatively scheduled a Public Hearing for the June 14 Planning Commission meeting. B) Pemtom Stage I Plan — N of Highway 55 and W of CR 116 — The City Council adopted a resolution of approval for the Stage I plan at the May 17 City Council meeting. Staff has been working with the applicant who is planning to apply for Stage II and preliminary plat for the single-family portion of the development. C) J. Cavanaugh Plat — 805 Hamel Road — Joe Cavanaugh has requested subdivision of his property into three single-family lots at the southwest corner of Hamel Road and Pinto Drive. Staff has conducted a preliminary review and determined the application is incomplete, and the applicant recently submitted additional information. The Planning Commission tabled the Public Hearing at their January 11, requesting more information related to drainage and stormwater management. D) Enclave of Medina Subdivision — 3212 Hunter Drive — The City Council approved the final plat and development agreement at the May 17 meeting and staff is working with the applicant to meet all of the requirements of the development agreement so that work can begin. E) Puptown Text Amendment and CUP — 810 Tower Drive — the City Council adopted a resolution of approval at the May 17 meeting, and staff will close the file and await a building permit application. F) White Variance — 4642 Brook Street — The City Council adopted a resolution of approval at the May 17 meeting, and staff will close the file and await a building permit application. G) Ringer Lot Combination, Comp Plan Amendment and Rezoning — 1700 Deerhill Road — The City Council adopted the lot combination, Comprehensive Plan amendment, and Planning Department Update Page 1 of 2 June 7, 2011 City Council Meeting rezoning at the May 17 meeting. Staff has assisted the applicant to finalize these approvals and submit the application for Ag Preserve status and will now close the file. H) Hunter Ridge Farm Plat — 1382 Hunter Drive — the Council approved the final plat at the April 5 meeting, and staff will assist the property owner with finalizing the project. I) Fortuna Farms Plat — 1425 Tamarack Drive — the Council approved the preliminary plat resolution on November 22, 2010, and staff awaits an application for final plat approval. J) Holy Name Cemetery — The City Council approved the Site Plan Review and CUP at the April 19 meeting, and staff is working with the applicant on the conditions of approval. K) Wrangler's Restaurant — 32 Hamel Road — the Council approved resolutions on July 21, 2009. The City Council granted until August 10, 2011 for the applicant to final the plat. Additional Projects A) Private Dog Kennels — staff has been assisting the City Clerk and Police with the coordination of two requests for private dog kennel licenses. One is a request for 7 dogs in a home at 1822 Morgan Road and the other is a request for 12 small dogs in a home at 25 Hamel Road. B) Water Resource Services RFP — staff has been fielding questions from firms considering submitting a proposal. C) Development Fee Survey — staff responded to a survey being coordinated by the City of Ramsey which will provide good information on how Medina's development fees compare to other communities. D) Housing Policy — The City Council held a workshop with Interfaith Outreach to discuss opportunities prior to the May 3 meeting and directed staff to conduct additional research on a possible partnership for project(s) in the City. E) Zoning Enforcement (Hamel Station tree removal) — The applicant reported that plantings have been installed to remediate the ordinance violations but the plantings on -site differed significantly from the remediation plan. The applicant has provided a list of plants, and staff will review and potentially schedule an inspection. F) Zoning Enforcement (manure management inspections) — Staff has been inspecting both commercial horse facilities and private horse facilities currently under a CUP requiring manure management. Planning Department Update Page2of2 June7,2011 City Council Meeting Also Present: City Council member Elizabeth Weir, City Planner Dusty Finke and 1 2 3 4 5 6 7 CITY OF MEDINA PLANNING COMMISSION Draft Meeting Minutes Tuesday, May 10, 2011 1. Call to Order: Chair Charles Nolan called the meeting to order at 7:00 p.m. 8 Present: Plannin o ssioners John Anderson, Kathleen Marti 9 Charles Nolan, obin l �ia 1�.eiad d Kent Williams. 10 11 Absent: None , �j �� ' � ak. '� k 12 13 14 Dan Edgerton from Bonestroo. 15 16 17 2. Public Comments on items not on the agenda 18 19 No public comments. 20 21 22 3. Update from City Council proceedings 23 24 Council member Elizabeth Weir presented a report of recent activities and decisions 25 by the City Council. 26 27 28 4. Planning Department Report 29 30 Finke provided an update of upcoming Planning projects and noted that there will 31 likely be more ordinances for reviews in coming months as well. 32 33 34 5. Approval of the April 12, 2011 Draft Planning Commission meeting minutes. 35 36 Motion by V. Reid, seconded by Martin, to approve the April 12, 2011 minutes 37 with minor modifications to pages four and five. Motion carried unanimously. 38 39 40 6. Public Hearing - Ordinance Amendment - Chapter 8 of the Medina Zoning Code 41 to codify the City's stormwater management regulations. 42 Edgerton presented the staff report. He summarized various types of stormwater 43 improvements which are commonly constructed to meet objectives, such as are 44 included in the ordinance. Edgerton stated that the ordinance is intended to 45 implement the City's Surface Water Management Plan. The primary objectives of 46 the ordinance are to control the rate and volume of stormwater runoff and to improve 1 1 water quality by reducing phosphorus. The ordinance establishes the thresholds that 2 determine the type of projects which will trigger the requirement to install 3 improvements. Edgerton stated that the Stormwater Manual is meant to describe how 4 to complete necessary calculations and also to describe the types of improvements 5 allowed by the City. This Manual will be updated often to include new technologies 6 in stormwater improvements which are constantly improving. 7 8 Edgerton described the approximate construction costs of various stormwater 9 improvements which could be installed if a project triggered the ordinance. He 10 stated that most of the ordinance and manual were very technical in nature. He 11 summarized two primary policy questions which the Planning Commission needed to 12 provide direction: 1) the scale of the project which would require improvements; and 13 2) whether volume control requirements on expansion projects should apply to the 14 whole site, or just the new hardcover. 15 16 Commissioners discussed the differences between residential and commercial 17 projects. Commissioners discussed if rural projects which may disturb over an acre 18 would actually bring up less of a need to treat runoff than work in a denser 19 neighborhood. 20 21 Nolan suggested the possibility of a less onerous review process which could apply to 22 individual homeowners. Commissioners expressed support for a system by which 23 improvements could be installed without hiring an engineer to complete modeling. 24 25 Edgerton stated that he believed it would be possible to include a calculation of rain 26 garden size within the Stormwater Manual so that a property owner could avoid the 27 modeling and design costs. 28 29 Nolan stated that it seems like the cost of design and improvement should be linked to 30 the cost of the proposed construction, perhaps a "not to exceed" exemption. Finke 31 stated that staff would not like to utilize actual project cost, but attempt to address this 32 concern by setting a reasonable threshold for when improvements are required. 33 34 Public Hearing opened at 8:18 p.m. 35 36 Martin stated that a homeowner should also not be expected to prepare the 37 Maintenance Agreement. Finke noted that the City would prepare a template to use. 38 Finke stated that the maintenance, and the City's enforcement of the maintenance, 39 was very important so that they are successful at improving water quality for the 40 amount of money invested in them. 41 42 Public Hearing closed at 8:27 p.m. 43 44 The Commission discussed state and watershed water quality mandates. Edgerton 45 stated that the City has set a goal to reduce phosphorus loading by 20%. 46 2 1 Finke stated that an important discussion point in the ordinance is related to 2 expansion projects. The current language would require a property owner who 3 wished to expand their parking lot by 10 stalls to treat the stormwater for not only the 4 10 stalls, but also for all of the existing hardcover. 5 6 Martin stated that it appears that the Surface Water Management Plan says that the 7 volume control requirement should only apply to the disturbed area. 8 9 Edgerton described the potential cost impact of an expansion project. 10 11 Williams inquired if the ordinance couldn't require a 30% reduction over the 12 disturbed area to improve water quality, but still link the amount of improvement to 13 the scale of the project. 14 15 Commissioners discussed the potential impacts to a property owner of requiring a 16 20% reduction for the whole site or a 30% of a reduction over the new hardcover. 17 18 Martin stated that she believes a requirement to reduce the phosphorus by 30% of the 19 disturbed area seems inconsistent with the language in the Surface Water 20 Management Plan which states 20% over the disturbed. 21 22 Williams inquired what language would allow requiring the reduction over the whole 23 site would seem inconsistent as well. fit„,' a�" " `. 24 25 Finke read language under the volume control requirements of the Surface Water 26 Management plan that stated that sites should maintain runoff volume to the extent 27 practical. 28 29 The consensus of the Commission was to require the 20% reduction over only the 30 disturbed portion of the site during an expansion project. 31 32 Martin inquired if it would be possible for a Planning Commissioner to assist with 33 proofreading of ordinances. She stated that when she reads an ordinance, she often 34 gets distracted by clerical and grammatical changes that she sees are needed. 35 36 Commissioners discussed options by which Planning Commissioners could assist the 37 process. 38 39 Nolan inquired if there was any additional feedback for the stormwater ordinance 40 before the Commission would table it and have staff prepare revisions. 41 42 Motion by V. Reid, seconded by Anderson, to table discussion of the ordinance and 43 to direct staff to make the changes discussed. Motion carried unanimously. 44 45 Commissioners discussed the threshold for smaller residential projects. 46 3 b 1 Finke noted that the discussion had still left alone the acre of disturbance. 2 3 Nolan stated that the threshold for him is related to how streamlined the design and 4 administrative review process was. 5 6 V. Reid stated that she was concerned with making the process too onerous for 7 smaller projects. 8 9 10 7. City Council Meeting Schedule 11 May 17, 2011 — Williams 12 June 7, 2011 — Anderson and Nolan 13 14 15 8. Adiourn 16 Motion by V. Reid, seconded by R. Reid, to adjourn the meeting at 9:27 p.m. 17 Motion carried unanimously. (Absent: Martin) 4 Agenda Item: 6 Memorandum 4 Bonestroo To: Dusty Finke Project: Stormwater Management Ordinance Date: 6/9/11 From: Dan Edgerton Client: City of Medina Re: Ordinance and Design Manual File No: 000190-10031-1 Attached are the 2nd draft Stormwater Management Ordinance and Stormwater Design Manual for the City of Medina. The ordinance and design manual have been revised to reflect comments received in the 5/10/11 Planning Commission meeting. Key revisions to the ordinance and design manual are as follows: Ordinance • Redevelopment has been redefined as Major Expansion Project and Minor Expansion Project. • Applicability has been revised: o Reflects the change to Major and Minor Expansion Projects o Clarifies what activities are governed by rate control, volume control, and water quality treatment o Provides a raingarden (or similar stormwater improvement) approach for single-family residential projects • Maintenance: Slightly modifies the subdivision on maintenance Design Manual • Volume Control has been revised to reflect only new impervious area (and not 20% of existing area as well) • Volume Control has been revised from 1" over new impervious surface to 1.1", to reflect the latest statewide requirement • Volume Control for Single-family Residences: A simplified procedure for single-family residences has been provided, which includes a formula for sizing of a raingarden and a standard detail for the raingarden. Some requirements for maximum size of raingarden and provision of draintile have been included as well. 2335 Highway 36 W St. Paul, MN 55113 Tel 651-636-4600 Fax 651-636-1311 www.bonestroo.com CITY OF MEDINA ORDINANCE NO. XXX An Ordinance Pertaining to the Management of Stormwater Adding Section 828.33 to the Medina Zoning Ordinance The City Council of the City of Medina, Minnesota Ordains as Follows: Section 828.33. Stormwater Management Subd. 1. Purpose Land development projects, and associated increases in impervious cover, alter the hydrologic response of local watersheds. Increases in stormwater runoff rates and volumes, flooding, erosion, sediment transport and deposition, and water -borne pollutants can be controlled and minimized through the regulation of stormwater runoff. The purpose of this ordinance is to protect and safeguard the health, safety, and welfare of the public by regulating stormwater runoff in order to protect local water resources from degradation. This ordinance seeks to meet this purpose through the following objectives: a) minimize increases in stormwater runoff rates from any development in order to reduce flooding, siltation and erosion and in order to maintain the integrity of stream channels, b) minimize increases in nonpoint source pollution caused by stormwater runoff from development which would otherwise degrade local water quality, c) minimize the total annual volume of surface water runoff that flows from any specific site during and following development so as not to exceed the predevelopment hydrologic regime to the maximum extent practicable, d) ensure that these management controls are properly maintained and pose no threat to public safety, and e) implement stormwater management controls to help meet current and future total maximum daily load (TMDL) goals, to address the need to improve water quality, and to meet objectives in the Local Surface Water Management Plan. The provisions of this Ordinance are adopted under the authority of the City of Medina Code. These provisions apply to all developments within the areas of the City of Medina. The application of this Ordinance and provisions expressed herein shall be the minimum stormwater management requirements and shall not be deemed a limitation or repeal of any other powers granted by State statute. The City of Medina shall be responsible for the coordination and enforcement of the provisions of this Ordinance. Ordinance No. XXX May 26, 2011 Subd. 2. Incorporation by Reference The Medina Stormwater Design Manual is incorporated by reference by the City of Medina. The Manual shall serve as the official guide for stormwater principles, methods, and practices for proposed development activities. Subd. 3. Definitions For the purpose of this Ordinance, the following definitions describe the meaning of the terms used in this Ordinance: a) "Applicant" means a property owner or agent of a property owner who has filed an application for a stormwater management permit. b) "Channel" means a natural or artificial watercourse with a definite bed and banks that conducts continuously or periodically flowing water. c) "Impervious Area" means those surfaces that cannot effectively infiltrate rainfall (e.g., building rooftops, pavement, sidewalks, gravel, driveways, etc.). d) "Land Disturbance Activity" means any activity that changes the volume or peak discharge rate of stormwater runoff from the land surface. This may include the grading, digging, cutting, scraping, or excavating of soil, placement of fill materials, paving, construction, substantial removal of vegetation, or any activity that bares soil or rock or involves the diversion or piping of any natural or fabricated watercourse. e) "Maintenance Agreement" means a legally recorded document that acts as a property deed restriction, and which provides for long-term maintenance of stormwater management practices. f) "Major Expansion Project" means any construction, alteration, or improvement which disturbs one acre or more in area and where the existing land use is commercial, industrial, institutional, or multi -family residential. g) "Minor Expansion Project" means any construction, alteration, or improvement which disturbs more than 1,000 square feet and less than one acre in area and where the existing land use is commercial, industrial, institutional, or multi -family residential. h) "New Development" means: a. Any subdivision, as defined by law. For the purposes of this section, a subdivision creating less than three new single-family detached lots shall not be considered New Development. b. Construction of a principal structure on an existing vacant lot. For the purposes of this section, construction of a detached single-family home shall not be considered New Development. c. Redevelopment of a property which results in the removal of more than 50 percent of the market value of the principal structure and such removal is followed by reconstruction. For the purposes of this section, redevelopment of a single-family detached home shall not be considered New Development. i) "Nonpoint Source Pollution" means pollution from any source other than from any discernible, confined, and discrete conveyances, and shall include, but not be limited to, Ordinance No. XXX 2 Month XX, 2011 pollutants from agricultural, silvicultural, mining, construction, subsurface disposal and urban runoff sources. j) "Off -Site Facility" means a stormwater management measure located outside the subject property boundary described in the permit application for land development activity. k) "Responsible Party" means the entity which will be responsible for ownership and maintenance of Stormwater Treatment Practices 1) "Site" means: a. For "New Development" any tract, lot or parcel of land or combination of tracts, lots, or parcels of land, which are in one ownership, or are contiguous and in diverse ownership where development is to be performed as part of a unit, subdivision, or project. b. For a "Major Expansion Project or Minor Expansion Project" the area of new construction, as shown on an approved site plan, or the original parcel. Final determination of the applicable area for stormwater management shall be made by the City of Medina. m) "Stop Work Order" means an order issued which requires that all construction activity on a site be stopped. n) "Stormwater Management" means the use of structural or non-structural practices that are designed to reduce stormwater runoff pollutant loads, discharge volumes, and/or peak discharge rates. o) "Stormwater Management Plan" means a set of drawings or other documents submitted by a person as a prerequisite to obtaining a stormwater management approval, which contain all of the information and specifications pertaining to stormwater management. p) "Stormwater Runoff' means flow on the surface of the ground, resulting from precipitation. q) "Stormwater Treatment Practices (STPs)" means measures, either structural or nonstructural, that are determined to be the most effective, practical means of preventing or reducing point source or nonpoint-source pollution inputs to stormwater runoff and waterbodies. r) "Water Quality Volume (WQv)" means the runoff storage volume needed to treat the specified phosphorus loading as determined in the Medina Stormwater Manual. s) "Watercourse" means a permanent or intermittent stream or other body of water, either natural or fabricated, which gathers or carries surface water. t) "Watershed" means the total drainage area contributing runoff to a single point. Subd. 4. Applicability This Ordinance shall be applicable to all subdivision,site plan, building permit or grading permit applications, unless eligible for an exemption or granted a waiver by the City. The Ordinance also applies to land development activities that are smaller than the minimum applicability criteria if such activities are part of a larger common plan of development that meets the following applicability criteria, even though multiple separate and distinct land development activities may take place at different times on different schedules. In addition, all plans must also be reviewed by local environmental protection officials to ensure that post construction runoff levels are consistent with any local and regional watershed plans. Ordinance No. XXX 3 Month XX, 2011 To prevent the adverse impacts of stormwater runoff, the City has developed a set of performance standards that must be met at sites where Land Disturbance Activity is proposed. These standards apply to the following conditions: A. New Development: Rate control standards apply to all New Development. Volume control and water quality treatment standards apply to New Development disturbing one (1) acre or more of land. B. Major Expansion Projects: Rate control, volume control, and water quality treatment standards apply to Major Expansion Projects. C. Minor Expansion Projects: Rate control standards apply to all Minor Expansion Projects. Volume control and water quality treatment standards apply to Minor Expansion Projects increasing impervious area by 1,000 square feet or more. D. Single-family residential projects: Installation of a raingarden or similar stormwater improvement as described in the Medina Stormwater Design Manual shall be required upon construction, alteration, or improvements on existing single-family residential property disturbing one acre or more of land AND increasing impervious area by 1,000 square feet or more. The following activities may be exempt from these stormwater performance criteria: A. Agricultural activity that is consistent with an approved soil conservation plan or a timber management plan prepared or approved by the City of Medina, as applicable. B. Repairs to any Stormwater Treatment Practice deemed necessary by the City of Medina. C. Emergency actions as declared by the City of Medina. D. New Development, Major or Minor Expansion Projects, or single-family residential projects below the thresholds described above. Subd. 5. General Performance Criteria for Stormwater Management Unless determined by the City to be exempt or granted a waiver, all site designs shall establish Stormwater Management Practices to control the peak flow rates and pollutants of stormwater discharge associated with specified design storms and runoff volumes, as detailed in the Medina Stormwater Design Manual. These practices should seek to use pervious areas for stormwater treatment and to infiltrate stormwater runoff from driveways, sidewalks, rooftops, parking lots, and landscaped areas to the maximum extent practical to provide treatment for both water quality and quantity. Subd. 6. Permit or Plat Approval Required No landowner or land operator shall receive a building permit or plat approval from the City until first meeting the requirements of this Ordinance prior to commencing the proposed activity. Subd. 7. Application Requirements Unless otherwise exempted by this Ordinance, a stormwater management submittal must include the following as a condition for its consideration: Ordinance No. XXX 4 Month XX, 2011 a) a Stormwater Management Plan; b) a Maintenance Agreement; The Stormwater Management Plan shall be prepared to meet the requirements of Subd. 5 of this Ordinance; the Maintenance Agreement shall be prepared to meet the requirements of Subd. 11 of this Ordinance. Subd. 8. Application Procedure (a) Applications for Land Disturbance Activity permits or plat approvals must be filed with the City of Medina on any regular business day. (b) A copy of this application shall be forwarded to City of Medina for staff review and approval. (c) Applications shall include the following: five copies of the Stormwater Management Plan, five copies of the Maintenance Agreement, and any required review fees. Subd. 9. Permit or Plat Approval Duration Approved plans issued under this section shall be valid from the date of approval through the date the City of Medina notifies the owner that all stormwater management practices have passed the final inspection required under approved conditions, or the approval is revoked. Subd. 10. Waivers for Providing Stormwater Management Every Applicant shall provide for stormwater management, unless a waiver is granted. Requests to waive the Stormwater Management Plan requirements shall be submitted to the City for approval. The minimum requirements for stormwater management may be waived in whole or in part upon written request of the applicant, if at least one of the following conditions applies: a) It can be demonstrated that the proposed development is not likely to impair attainment of the objectives of this Ordinance. b) Alternative minimum requirements for on -site management of stormwater discharges have been established in a stormwater management plan that has been approved by the City of Medina. c) Provisions are made to manage stormwater by an off -site facility. The off -site facility is required to be in place, to be designed and adequately sized to provide a level of stormwater control that is equal to or greater than that which would be afforded by on - site practices and has a legally obligated entity responsible for long-term operation and maintenance of the stormwater practice. In instances where one of the conditions above applies, the City may grant a waiver from strict compliance with stormwater management provisions that are not achievable, if acceptable mitigation measures are provided. Ordinance No. XXX 5 Month XX, 2011 Subd. 11. Stormwater Treatment Maintenance Plan and Agreement During the application process, the City shall determine who the Responsible Party will be for ownership and maintenance of all Stormwater Treatment Practices. The Responsible Party shall enter into an agreement with the City that documents all responsibilities for operation and maintenance of all Stormwater Treatment Practices. Such responsibility shall be documented in a maintenance plan and executed through a Maintenance Agreement. The Maintenance Agreement shall be executed and recorded against the parcel. a) Maintenance Agreement The stormwater Maintenance Agreement shall be in a form approved by the City, and shall, at a minimum: 1. Designate the owner or other Responsible Party, which shall be permanently responsible for maintenance of the structural or nonstructural measures. 2. Pass responsibility for such maintenance to successors in title. 3. Grant the City and its representatives the right of entry for the purposes of inspecting all Stormwater Treatment Practices at reasonable times and in a reasonable manner. This includes the right to enter a property when the City has a reasonable basis to believe that a violation of this division or Maintenance Agreement is occurring or has occurred and to enter when necessary for abatement of a public nuisance or correction and enforcement of a violation of this division or agreement. 4. Allow the City to repair and maintain the facility, if necessary maintenance is not performed after proper and reasonable notice to the Responsible Party. The agreement shall permit the City to certify the costs of the maintenance/correction to the taxes for the subject property. 5. Include a maintenance plan that contains, but is not limited to the following: a. Identification of all structural Stormwater Treatment Practices. b. A schedule for regular inspection, monitoring, and maintenance for each practice. Monitoring shall verify whether the practice is functioning as designed and may include, but is not limited to quality, temperature, and quantity of runoff. c. Identification of the responsible party for conducting the inspection, monitoring, and maintenance for each practice. 6. Identify a schedule and format for reporting compliance with the Maintenance Plan to the City. b) Inspection of Stormwater Facilities Inspection programs may be established on any reasonable basis, including but not limited to: routine inspections; random inspections; inspections based upon complaints or other notice of possible violations; inspection of drainage basins or areas identified as higher than typical sources of sediment or other contaminants or pollutants; inspections of businesses or industries of a type associated with higher than usual discharges of contaminants or Ordinance No. XXX 6 Month XX, 2011 pollutants or with discharges of a type which are more likely than the typical discharge to cause violations of state or federal water or sediment quality standards or the NPDES stormwater permit; and joint inspections with other agencies inspecting under environmental or safety laws. Inspections may include, but are not limited to, reviewing maintenance and repair records; sampling discharges, surface water, groundwater, and material or water in drainage control facilities; and evaluating the condition of drainage control facilities and other stormwater treatment practices. c) Right -of -Entry for Inspection When any new Stormwater Treatment Practice is installed on private property, or when any new connection is made between private property and a public drainage control system, sanitary sewer, or combined sewer; the property owner shall grant to the City of Medina the right to enter the property at reasonable times and in a reasonable manner for the purpose of inspection. This includes the right to enter a property when it has a reasonable basis to believe that a violation of this Ordinance is occurring or has occurred, and to enter when necessary for abatement of a public nuisance or correction of a violation of this Ordinance. d) Records of Installation and Maintenance Activities The Responsible Party shall make records of the installation and of all maintenance and repairs, and shall retain the records for at least three (3) years. These records shall be made available to the City of Medina during inspection of the facility and at other reasonable times upon request. e) Failure to Maintain Practices If a responsible party fails or refuses to meet the requirements of the Maintenance Agreement, the City, after reasonable notice, may correct a violation of the design standards or maintenance needs by performing all necessary work to place the facility in proper working condition. In the event that the Stormwater Treatment Practice becomes a danger to public safety or public health, the City shall notify the party responsible for maintenance of the stormwater management facility in writing. Upon receipt of that notice, the Responsible Party shall have thirty days to apply maintenance and repair of the facility in an approved manner. After proper notice, the City may assess the owner(s) of the facility for the cost of repair work and any penalties; and the cost of the work shall be a lien on the property, or prorated against the beneficial users of the property, and may be placed on the tax bill and collected as ordinary taxes by the county. Subd. 12. Performance Bond/Security The City shall require the submittal of a performance security or bond prior to issuance of a permit in order to insure that the Stormwater Treatment Practices are installed by the permit holder as required by the approved Stormwater Management Plan. The amount of the installation performance security shall be the total estimated construction cost of the Stormwater Treatment Practices approved, plus 50%, or 150% of estimated construction cost. The performance security shall contain forfeiture provisions for failure to complete work specified in the Stormwater Management Plan. Ordinance No. XXX 7 Month XX, 2011 The installation performance security shall be released in full only upon submission of "as built plans" and written certification by a registered professional engineer that the Stormwater Treatment Practice has been installed in accordance with the approved plan and other applicable provisions of this Ordinance. The City will make a final inspection of the Stormwater Treatment Practice to ensure that it complies with the approved plan and the provisions of this Ordinance. Provisions for a partial pro -rata release of the performance security based on the completion of various development stages can be done at the discretion of the City. Subd. 13. Notice of Construction Commencement The Applicant must notify the City in advance before the commencement of construction. Regular inspections of the Stormwater Treatment Practice construction shall be conducted by the staff of the City or certified by a professional engineer or their designee. All inspections shall be documented and written reports prepared that contain the following information: • the date and location of the inspection, • whether construction is in compliance with the approved stormwater management plan, • variations from the approved construction specifications, • any violations that exist. If any violations are found, the Applicant shall be notified in writing of the nature of the violation and the required corrective actions. No added work shall proceed until any violations are corrected and all work previously completed has received approval by the City. Subd. 14. As Built Plans All Applicants are required to submit actual "as built" plans for any Stormwater Treatment Practices located on -site after final construction is completed. As -built plans must show the final design specifications for all Stormwater Treatment Practices, and the plans must be certified by a professional engineer. A final inspection by the City is required before the release of any performance securities can occur. Subd. 15. Violations Any development activity that is commenced or is conducted contrary to this Ordinance may be restrained by injunction or otherwise abated in a manner provided by law. (a) Notice of Violation When the City determines that an activity is not being carried out in accordance with the requirements of this Ordinance, it shall issue a written notice of violation to the owner of the property. The notice of violation shall contain: I) the name and address of the owner or applicant, 2) the address when available or a description of the building, structure, or land upon which the violation is occurring, 3) a statement specifying the nature of the violation, 4) a description of the remedial measures necessary to bring the development activity into compliance with this Ordinance and a time schedule for the completion of such remedial action, Ordinance No. XXX 8 Month XX, 2011 5) a statement of the penalty or penalties that shall or may be assessed against the person to whom the notice of violation is directed, and 6) a statement that the determination of violation may be appealed to the City by filing a written notice of appeal within fifteen (15) days of service of notice of violation. (b) Stop Work Orders Persons receiving a notice of violation will be required to halt all construction activities. This "Stop Work Order" will be in effect until the City confirms that the development activity is in compliance and the violation has been satisfactorily addressed. Failure to address a notice of violation in a timely manner can result in civil, criminal, or monetary penalties in accordance with the enforcement measures authorized in this Ordinance. (c) Civil and Criminal Penalties In addition to or as an alternative to any penalty provided herein or by law, any person who violates the provisions of this Ordinance shall be guilty of a misdemeanor and subject to prosecution. Such person shall be guilty of a separate offense for each day during which the violation occurs or continues: (d) Restoration of Lands Any violator may be required to restore land to its undisturbed condition. In the event that restoration is not undertaken within a reasonable time after notice, the City may take necessary corrective action, the cost of which shall become a lien upon the property until paid. Subd. 16. Holds on Occupation Permits Occupation permits will not be granted until corrections to all stormwater practices have been made and accepted by the City, or a financial guarantee in a form acceptable to the City has been submitted to ensure completion. Subd. 17. Revocation of Approval Revocation of the stormwater approval may be made by the City if requirements within this ordinance are not fulfilled, or the owner or Applicant is unable to fulfill the ordinance requirements. If an approval is revoked, the applicant must resubmit a Stormwater Management Plan. Subd. 18. Appeals Any person aggrieved by the action of any official charged with the enforcement of this Ordinance, as the result of the disapproval of a properly filed application for a permit or plat approval, issuance of a written notice of violation, or an alleged failure to properly enforce the Ordinance in regard to a specific application, shall have the right to appeal the action to the City. (a) The Applicant shall submit the appeal in writing and include supporting documentation. (b) City staff shall make a decision on the appeal within 45 days of receipt of a complete appeal application. Ordinance No. XXX 9 Month XX, 2011 (c) The Applicant may appeal the decision of city staff to the city council. This appeal must be filed with the City within 30 days of city staff's decision. Subd. 19. Compatibility with Other Permit and Ordinance Requirements This Ordinance is not intended to interfere with, abrogate, or annul any other Ordinance, rule or regulation, statute, or other provision of law. The requirements of this Ordinance should be considered minimum requirements, and where any provision of this Ordinance imposes restrictions different from those imposed by any other Ordinance, 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. Subd. 20. Severability If the provisions of any article, section, subsection, paragraph, subdivision or clause of this Ordinance shall be judged invalid by a court of competent jurisdiction, such order of judgment shall not affect or invalidate the remainder of any article, section, subsection, paragraph, subdivision or clause of this Ordinance. This Ordinance shall become effective upon its adoption and publication. Adopted by the city council of the city of Medina this XX day of May, 2011. T.M. Crosby, Jr., Mayor ATTEST: Douglas S. Reeder, Interim City Administrator -Clerk Published in the South Crow River News this XX day of May, 2011. Ordinance No. XXX 10 Month XX, 2011 MED1NA CITYOF _ Stormwater Design Manual City of Medina May 2011 Project No. 000190-10031-0 Bonestroo MEDINA — STORMWATER DESIGN GUIDE Table of Contents Table of Contents 1 1.0 Design Overview 2 2.0 Procedure for Reviewing Stormwater Management Plans 2 3.0 Submittal Requirements 24.0 List of Acceptable Practices 5 5.0 Guidance on Stormwater Treatment Practice (STP) 6 6.0 Basic Sizing Criteria 7 7.0 Design Examples 14 8.0 Stormwater Treatment Practice Detail Drawings 15 9.0 Construction Specifications 15 10.0 Checklists 16 Appedndix A Infiltration Rates for Infiltration STPs 18 City of Medina Stormwater Design Guide Bonestroo Page 1 000190-10031-0 MEDINA — STORMWATER DESIGN GUIDE 1.0 Design Overview The City of Medina's Local Surface Water Management Plan (LSWMP) identifies the goals and policies that define the City's stormwater management program. Medina's stormwater requirements were written meet the City's goals to preserve, protect, and manage its water resources as well as to meet federal, state, and watershed stormwater regulations. Additionally, the City of Medina will need to meet the pollutant reduction requirements of current and future total maximum daily loads (TMDLs) specified for waterbodies in whose watershed it resides. 2.0 Procedure for Reviewing Stormwater Management Plans All new development and redevelopment will require the submittal of a stormwater management plan. It is highly recommended that a concept plan be submitted prior to the preparation of a final stormwater management plan. The concept plan identifies basic site information, locations of proposed development features, and preliminary locations and sizing of stormwater treatment practices. The concept plan allows the review to be conducted in conjunction with a preliminary development plan or site plan. The review of a concept plan helps to identify major issues related to regulatory oversight of the planned development. It is less time consuming and more efficient to evaluate proposed development plans with this step of the review process. The final plan provides more detailed design information for the proposed stormwater practices, and includes much more detail in terms of hydrologic conditions and site features. The general review process, from the submittal of the concept and final plans to the issuance of the Stormwater Management Plan approval, is summarized in the following five steps. 1) What permits, or approvals, are required for the project site, and what waivers and/or exemptions are applicable? 2) Are the selected practices appropriate for this site? 3) Are the practices designed to meet the minimum performance criteria? 4) Does the Plan meet other resource protection requirements as specified in the City of Medina Code? 5) Are provisions for long-term maintenance adequate? 3.0 Submittal Requirements Requirements for Stormwater Management Plan Approval Stormwater Management Plan Required for All Developments No application for development, or redevelopment, will be approved unless it includes a stormwater management plan detailing how runoff and associated water quality impacts resulting from the development will be controlled or managed. This plan must indicate whether stormwater will be managed on -site or off -site and, if on -site, the general location and type of practices. The stormwater management plan must be signed by a licensed professional engineer in the State of Minnesota, who will verify that the design of all stormwater management practices meet City of Medina Stormwater Design Guide Bonestroo Page 2 000190-10031-0 the submittal requirements outlined in the Submittal Checklist found in the stormwater design manual. No building permit, grading permit, sediment control permit, or plat approval shall be issued until a satisfactory final stormwater management plan, or a waiver thereof, shall have undergone a review and been approved by the City of Medina after determining that the plan or waiver is consistent with the requirements of this manual. Stormwater Management Conceptual Plan Requirements (Optional) A stormwater management concept plan submittal is optional, but highly encouraged. A concept plan submittal has a greater chance of identifying major obstacles and can facilitate alternative stormwater management arrangements in a timely fashion. If a concept plan is submitted for review, it should include sufficient information (e.g., maps, hydrologic calculations, etc) to evaluate the environmental characteristics of the project site. This information should show the potential impacts of all proposed development of the site, both present and future, on the water resources, and show the effectiveness and acceptability of the measures proposed for managing stormwater generated at the project site. The intent of this conceptual planning process is to determine the type of stormwater management measures necessary for the proposed project, and ensure adequate planning for management of stormwater runoff from future development. To accomplish this goal the following information shall be included in the concept plan: 1. A map (or maps) indicating the location of existing and proposed buildings, roads, parking areas, utilities, structural stormwater management and sediment control facilities. The map(s) will also clearly show proposed land use with tabulation of the percentage of surface area to be adapted to various uses; drainage patterns; locations of utilities, roads and easements; the limits of clearing and grading; a written description of the site plan and justification of proposed changes in natural conditions may be required. 2. Sufficient engineering analysis to show that the proposed stormwater management measures are capable of controlling runoff from the site in compliance with the Stormwater Design Manual. 3. A written or graphic inventory of the natural resources at the site and surrounding area as it exists prior to the commencement of the project and a description of the watershed and its relation to the project site. This description should include a discussion of soil conditions, forest cover, topography, wetlands, and other native vegetative areas on the site. Particular attention should be paid to environmentally sensitive features that provide particular opportunities or constraints for development. 4. A brief written description of the required maintenance burden for the proposed stormwater management facility. 5. The concept plan may also consider the maximum development potential of a site under existing zoning, regardless of whether the applicant presently intends to develop the site to its maximum potential. For development or redevelopment occurring on a previously developed site, an applicant should include within the concept plan measures for controlling existing stormwater runoff discharges from the site in accordance with the standards of this Manual to the maximum extent practicable. After review of the concept plan and modifications are made to that plan as deemed necessary by the City of Medina, a final stormwater management plan may be submitted for approval. Stormwater Management Plan Requirements (Required) The final stormwater management plan shall include all of the information required in the Final Stormwater Management Plan checklist found at the end of the Medina Stormwater Design Manual. This includes: City of Medina Stormwater Design Guide Bonestroo Page 3 000190-10031-0 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. Topographic Base Map A 1" = 200' topographic base map of the site which extends a minimum of fifty (50) feet beyond the limits of the proposed development and indicates existing surface water drainage including streams, ponds, culverts, ditches, and wetlands; current land use including all existing structures; locations of utilities, roads, and easements; and significant natural and manmade features not otherwise shown. 3. Calculations Hydrologic and hydraulic design calculations for the predevelopment and postdevelopment conditions for the design storms specified in this manual. Such calculations shall include: 1. design storm frequency, amount, and duration, 2. time of concentration, 3. Runoff Curve Numbers or runoff coefficients, 4. peak runoff rates and total runoff volumes for each watershed area, 5. pond and wetland high-water levels and storage volumes, 6. infiltration rates, where applicable, 7. culvert capacities, 8. flow velocities, 9. data on the change in rate and volume of runoff for the design storms referenced in the Medina Stormwater Design Manual, and 10. documentation of sources for all computation methods and field test results. 4. Soils Information If a stormwater management control measure depends on the hydrologic properties of soils (e.g., infiltration basins), then soils information (e.g., Hennepin County Soil Survey, soil boring data, or soils report) shall be submitted. The soils report shall be based on on -site boring logs or soil pit profiles. The number and location of required soil borings or soil pits shall be determined based on what is needed to determine the suitability and distribution of soil types present at the location of the control measure. 5. Maintenance and Repair Plan The design and planning of all stormwater management facilities shall include detailed maintenance and repair procedures to ensure their continued function. These plans will identify the parts or components of a stormwater management facility that need to be maintained and the equipment and skills or training necessary. Provisions for the periodic review and evaluation of the effectiveness of the maintenance program and the need for revisions or additional maintenance procedures shall be included in the plan. • Landscaping plan The applicant must present a detailed plan for management of vegetation associated with stormwater features after construction is finished, including who will be responsible for the maintenance of vegetation at the site and what practices will be employed to ensure that adequate vegetative cover is preserved. • Maintenance Easements The applicant must ensure access to all stormwater treatment practices at the site for the purpose of inspection and repair by securing all the maintenance easements needed on a City of Medina Stormwater Design Guide Bonestroo Page 4 000190-10031-0 permanent basis. Maintenance easements will be recorded with the plat, and will remain in effect, even if the title of the property is transferred to a new owner. • Maintenance Agreement The applicant must execute an easement and an inspection and maintenance agreement binding on all subsequent owners of land served by an on -site stormwater management measure in accordance with the requirements of this manual. • Other Environmental Permits The applicant shall assure that all other applicable environmental permits have been or will be acquired for the site. 4.0 List of Acceptable Practices In the development of the stormwater management practice appropriate for the development or redevelopment, infiltration (water quality volume) is foremost in importance to apply in the design. Filtration is warranted when site conditions do not allow for an effective infiltration facility. For flooding or rate control, detention systems are typically the preferred practice. Alternative practices may be approved at the discretion of the City Engineer. Infiltration Systems: • Infiltration Trench • Infiltration Basin • Raingarden • Underground Storage Filtration Systems: • Surface Sand Filter • Underground Sand Filter • Perimeter Sand Filter • Organic Filter • Bioretention System • Raingarden • Pervious Pavement • Underground Storage • Tree Trench Detention Systems: • Wet Pond • Multiple Pond System • Extended Detention Basin • Micro -pool Extended Detention Basin • Dry Detention Ponds • Underground Storage • Other, as approved by the City of Medina Wetlands: • Shallow Wetland • Pond/Wetland System Open Channel Systems: City of Medina Stormwater Design Guide Bonestroo Page 5 000190-10031-0 " Dry Swale " Wet Swale " Grass Swale " Natural channel, or stream 5.0 Guidance on Stormwater Treatment Practice (STP) Designers are expected to follow the nine step screening process for stomwater treatment practice (STP) selection detailed in Chapter 7 of the Minnesota Stormwater Manual. Stormwater Treatment Practices will be scrutinized using the same matrices found in Chapter 7 as part of the review process. Deviations from recommended guidance in the Minnesota Stormwater Manual will require detailed written explanation. Approval of any deviation from the Minnesota Stormwater Manual guidance will be at the discretion of the City of Medina. The 9 step screening process that should be used in the BMP selection process is as follows: 1. Investigate Pollution Prevention Opportunities: Evaluate the site to look for opportunities to prevent pollution sources on the land from becoming mobilized by runoff. 2. Design Site to Minimize Runoff: Assess whether any better site design techniques can be applied at the site to minimize runoff and therefore reduce the size of structural BMPs. Better site design considers the following principles in the design of the STP: " Preserves Natural Areas " Reduction of Impervious Areas and Distributing Stormwater " Reducing Impervious Cover 3. Select Temporary Construction Sediment Control Techniques: Check to see what set of temporary sediment control techniques will prevent erosion and minimize site disturbance during construction. 4. Identify Receiving Water Issues: Understand the regulatory status of the receiving water to which the site drains. Depending on the nature of the receiving water, certain BMPs may be promoted, restricted, or prohibited, or special design or sizing criteria may apply. 5. Identify Climate and Terrain Factors: Climate and terrain conditions vary widely across the state, thus designers need to explicitly consider how each regional factor will influence the BMPs proposed for the site. 6. Evaluate Stormwater Treatment Suitability: Not all BMPs work over the wide range of storm events that need to be managed at the site, so designers need to choose the type or combination of BMPs that will provide the desired level of treatment. 7. Assess Physical Feasibility at the Site: City of Medina Stormwater Design Guide Bonestroo Page 6 000190-10031-0 Each development site has many physical constraints that influence the feasibility of different kinds of BMPs; designers confirm feasibility by assessing eight physical factors at the site. 8. Investigate Community and Environmental Factors: Each group of BMPs provides different economic, community, and environmental benefits and drawbacks; designers need to carefully weigh these factors when choosing BMPs for the site. 9. Determine Any Site Restrictions and Setbacks: Check to see if any environmental resources or infrastructure is present that will influence where a BMP can be located at the development site. 6.0 Basic Sizing Criteria Proposed stormwater management plans must incorporate Volume Control, Water Quality Control, and Rate Control as the basis for stormwater management in the proposed development plan. All proposed stormwater management practices must fulfill Volume Control, Water Quality, and Rate Control sizing requirements. 6.1 Volume Control Requirements Volume control measures are required on projects to meet the water quality criteria of the City of Medina's Local Surface Water Management Plan. Volume control shall be required for proposed new impervious area. If an applicant can demonstrate that the volume control standard has been met, then the water quality sizing criteria shall be considered satisfied. 6.1.1 Volume Control Calculations Depending on applicability, a proposed development shall have one of the following Stormwater Treatment Practices (STP): an infiltration STP or a filtration STP that collects and treats the following volume of stormwater runoff: Volume calculation for Infiltration Practice (VCinf): VCinf (cf) = 1.1" x (1/12) x (area of proposed new impervious area in sq. ft.) Volume Calculation for Filtration Practice (VCfil): VCfil (cf) = VCinf x 1.5 If volume control is infeasible due to site restrictions such as tight soils, contaminated soils, or lack of separation between facility and groundwater (minimum 3' of separation), the site may employ a management practice that demonstrates a reduction in 20% phosphorus loading over existing conditions. Specifications for this practice are detailed in the Water Quality Control section. Volume Control for Single-family Residences In lieu of providing a stormwater management plan documenting that the volume control requirements are being met, single-family residences can satisfy the volume control requirement with the construction of a bioretention facility, or raingarden. The surface area of the base City of Medina Stormwater Design Guide 4' Bonestroo Page 7 000190-10031-0 (bottom of fill) of the raingarden shall be determined by the amount of new impervious area being added to the property. The base area required in the raingarden shall be calculated using the following formula: Base of Raingarden (square feet) = 0.0733 x Area of New Impervious (square feet) The raingarden design shall follow the Medina Typical Rain Garden Detail for Single Family Home. Impervious area draining to a single raingarden shall not exceed 0.5 acres. Multiple raingardens are acceptable to treat impervious areas greater than 0.5 acres in size. Draintile shall be provided as needed, in accordance with the Typical Rain Garden Detail. Additional design guidance may be found in the 2005 Minnesota Stormwater Manual in Chapter 12-6, Bioretention. Volume Control with Irrigation Irrigation as an STP may receive full credit towards satisfying the VCinf requirement in lieu of using on -site infiltration. However, acceptance of this practice will be determined on a site -by - site basis subject to the approval of the City of Medina City Engineer. 6.3 Water Quality Control The water quality control standard shall be considered satisfied, if the volume control standard has been satisfied. In the event that that it is infeasible to meet the volume control standard due to contaminated soils, site constraints, etc., the proposed management practice will need to detain and treat a sufficient volume of stormwater to achieve a phosphorus load reduction of 20% from existing conditions using an approved Stormwater Treatment Practice (STP). The 20% reduction requirement does not apply to land use classifications for meadow, forested, open space, or wetland land use, see Table 1. These areas are considered natural condition areas and no additional phosphorus reduction is needed from these areas. Water quality treatment for these natural condition areas shall be controlled to existing phosphorus loading conditions only. If unable to apply an infiltration or filtration management practice due to site physical constraints, then justification shall be documented and submitted for approval by the City Engineer. Approval of a waiver from the Volume Control requirement will be evaluated on a case -by -case basis. Demonstration that the water quality criteria have been met shall be done using PondNet, or other approved water quality modeling method. If using PondNet, then the event mean concentrations found in Table 2 shall be used. The volume required using PondNet would be known as the Water Quality Volume (WQv) required for the proposed development. Table 1: Event Mean Concentrations for PondNet Modelin Land Use Phosphorus (P) Runoff Concentration (PPB) Row Crop Agriculture 540 Pasture 350 Meadow* 200 Rural Residential 255 Urban Residential 450 Forested* 200 Commercial, Industrial 350 Open Space* 200 Golf Course 550 Right -of -Way 400 Wetland* 200 City of Medina Stormwater Design Guide Bonestroo Page 8 000190-10031-0 * - Natural Condition Area A Microsoft ExcelTM version of PondNet can be made available upon request to the City of Medina. 6.4 Rate Control Post development discharge rates must be less than or equal to existing conditions discharge rates for the 1 -year (2.4 -inch), 10 -year (4.1 -inch) and 100 -year (5.9 -inch) NRCS Type II, 24 -hour storm events. In some cases where there is the potential for adverse downstream impacts, the rate control requirement may be more stringent than the existing conditions standard. Ultimately, the stormwater system will be managed so that development, redevelopment, and other infrastructure projects do not overburden the existing downstream system for the design event. All runoff calculations shall be according to the methodology described in the Natural Resources Conservation Service's Technical Release 55, "Urban Hydrology for Small Watersheds" (commonly referred to as TR-55). Example acceptable modeling software includes HydroCAD and XP- SWMM. Other methodology may be used with prior approval by the City. Composite curve numbers shall not be used; instead, proposed contributing areas shall be broken into one of the cover types in Table 2. Curve numbers for each land use shall be chosen based on Table 2. Table 2: Curve Numbers for Use in Hydrologic Computations Hydrologic Soil Group Cover Type A B C D Open Water 100 100 100 100 Pasture 68 79 86 89 Meadow 30 58 71 78 Forested 55 55 70 77 Developed Open Space' 61 61 74 80 Impervious Areas2 98 98 98 98 Agricultural Land3 Peak Growth Formula Row Crop - Fallow 77 86 91 94 Row Crop — Average 72 81 88 91 Gravel Road 76 85 89 91 Wetlands 98 98 98 98 1 Lawns, parks, golf courses, other grassy areas, etc. 2 Streets, parking lots, roofs, driveways, etc. 3 Where existing conditions are characterized by agricultural land use, the 'peak growth" curve number should be utilized. Calculation of the peak growth curve number is based on the following formula: CN average = % * (CN normal peak growth + CN fallow), or CN normal peak growth = 2 * (CN average) - CN fallow City of Medina Stormwater Design Guide Bonestroo Page 9 000190-10031-0 For example, for row crop agriculture and hydrologic soil group B, the peak growth curve number is 76. This is based on average and fallow curve numbers of 81 and 86, respectively. A Type II 24 -hour rainfall distribution with, average antecedent moisture conditions, should be utilized for runoff calculations. The recommended minimum outlet diameter is 6 -inches due to plugging susceptibility and may supersede the rate control requirement for the 2 -year event. Infiltration will not be considered when determining rate control or freeboard. Waterbodies should be modeled with the starting water level at their outlet elevation. City standard detail plates should be utilized for pond outlet structures. It is recommended that outlet structures be designed in three phases with a primary outlet structure and secondary overflow structure routed to the storm sewer and a defined emergency overflow as the tertiary outlet structure. Bounce of water level within the wetlands shall be maintained according to the following table: Table 3: Bounce Restriction for Runoff Directed Through Wetlands Protection Classification Additional Protection Requirements Bounce - Change in water level due to runoff event Preserve Maintain bounce at or below existing conditions Manage 1 Maintain bounce at or below existing conditions plus 0.5 feet Manage 2 Maintain bounce at or below existing conditions plus 1.0 feet Manage 3 No quantity requirement The following items shall be considered in the management of landlocked basins: • The flood levels established for landlocked basins shall take into consideration the effects of water level fluctuations on trees, erosion, and property values. Steeply sloped shorelines subject to slope failure and shoreline damage should not be in contact with floodwaters for extended periods. • The capacity of proposed outlets to landlocked basins should not be so small as to cause extended duration of high water levels that would result in damage to upland vegetation. Exceptions to this policy include basins that are strictly regional stormwater management basins and not formerly wetlands. Exceptions also include wetlands converted to regional stormwater management basins through mitigation of the affected wetland areas. City of Medina Stormwater Design Guide Bonestroo Page 10 000190-10031-0 6.5 Freeboard Elevation separations of buildings with respect to ponds, lakes, streams, and storm water features shall be designed as follows: 1. At least two feet of vertical separation is required from an area's emergency overflow elevation to the lowest opening of a home. In areas where this separation is not or cannot be provided, we require additional analysis showing that the 100 -year back-to- back storm event does not impact adjacent homes. 2. Drainage easements and outlots for ponds, lakes, wetlands, streams etc. shall encompass an area to the calculated one foot above the 100 -year HWL. 6.6 Stormwater Treatment Practice Design Standards 6.6.1 Storm Sewers 1. Manhole spacing shall not exceed 400 feet. 2. Where more than one pipe enters a structure, a catch basin/manhole shall be used. 3. Storm sewer pipe should match top of pipe to top of pipe unless grade constraints prevent this. In that case, hydraulic calculations will be necessary to verify that excessive surcharging will not occur. 4. Storm water pipes shall be designed utilizing the Rational Method. Channel design shall be hydrograph method only. All methods are subject to the City Engineer's approval. 5. Lateral systems shall be designed for the 10 -year rainfall using the Rational Method. State Aid roadway storm sewer shall be designed per the State Aid requirements. 6. The minimum full flow velocity within the storm sewer should be 3 feet per second (fps). The maximum velocity shall be 10 fps, except when entering a pond, where the maximum velocity shall be limited to 6 fps. 7. Trunk storm sewer should be designed at a minimum to carry 100 -year pond discharge in addition to the 10 -year design flow for directly tributary areas. The following table may be used for the calculation of peak rates using the Rational Method: Table 3: Rational Method Runoff Coefficients for Storm Sewer Design Cover Type 10 -Year Runoff Coefficient Single-family Residential 0.4 Multi -family Residential 0.5 Commercial 0.7 Industrial 0.7 Parks, Open Space 0.2 Ponds, Wetlands 1.0 8. For storms greater than the 10 -year event, and in the case of plugged inlets, transient street ponding will occur. For safety reasons, the maximum depth in streets should not exceed 1.5 feet at the deepest point. 9. To promote efficient hydraulics within manholes, manhole benching shall be provided to 1/2 diameter of the largest pipe entering or leaving the manhole. City of Medina Stormwater Design Guide 4' Bonestroo Page 11 000190-10031-0 10. Vaned grate (3067V) catch basin castings shall be used on all streets. 11. The maximum design flow at a catch basin for the 10 -year storm event shall be 3 cubic feet per second (cfs), unless high capacity grates are provided. Catch basins at low points will be evaluated for higher flow with the approval of the City Engineer. 12. All structures located in the street are to be a minimum of four feet deep (rim to invert) and a minimum of three feet deep elsewhere. Two -by -three catch basins are to be four feet deep. 13. The last structure in the street prior to discharging into a pond is to be a minimum of five feet deep with a four -foot deep sump, where appropriate. 6.6.2 Outlet and Inlet Pipes 1. Inlet pipes of stormwater ponds should be extended to the pond normal water level whenever possible. 2. Outfalls with velocities greater than 4 fps into channels, where the angle of the outfall to the channel flow direction is greater than 30 -degrees, requires energy dissipation or stilling basins. 3. Outfalls with velocities of less than 4 fps, that project flows downstream into a channel in a direction 30 -degrees or less from the channel flow direction, generally do not require energy dissipaters or stilling basins, but will require riprap protection. 4. In the case of discharge to channels, rip rap should be provided on all outlets to an adequate depth below the channel grade and to a height above the outfall or channel bottom. Rip rap should be placed over a suitably graded filter material and filter fabric to ensure that soil particles do not migrate through the riprap and reduce its stability. Riprap should be placed to a thickness at least 2.5 times the mean rock diameter to ensure that it will not be undermined or rendered ineffective by displacement. If riprap is used as protection for overland drainage routes, grouting may be recommended. 5. Discharge velocity into a pond at the outlet elevation shall be 6 fps or less. Riprap protection is required at all inlet pipes into ponds from the NWL to the pond bottom. 6. Where outlet velocities to ponds exceed 6 fps, the design should be based on the unique site conditions present. Submergence of the outlet or installation of a stilling basin approved by the City is required when excessive outlet velocities are experienced. 7. Submerged outlet pipes from ponds are not allowed. 6.6.3 Channels and Overland Drainage 1. Overland drainage routes where velocities exceed 4 fps should be reviewed by the City Engineer and approved only when suitable stabilization measures are proposed. 2. Open channels and swales are recommended where flows and small grade differences prohibit the economical construction of an underground conduit. Open channels and swales can provide infiltration and filtration benefits not provided by pipe. 3. The minimum grade in all unpaved areas shall be 2%. 4. Maximum length for drainage swales shall be 400 feet. 5. Channel side slopes should be a maximum of 4:1 (horizontal to vertical) with gentler slopes being desirable. 6. Rock riprap should be provided at all points of juncture. Particularly between two open channels and where storm sewer pipes discharge into a channel. City of Medina Stormwater Design Guide ' Bonestroo Page 12 000190-10031-0 7. Open channels should be designed to handle the expected velocity from a 10 -year design storm without erosion. Riprap or concrete liners may need to be provided. 8. Periodic cleaning of an open channel is required to ensure that the design capacity is maintained. Therefore, all channels should be designed to allow easy access for equipment. 6.6.4 Ponds 1. Maximum allowable pond slopes above the outlet elevation are 4:1. 2. All constructed ponds and wetland mitigation areas shall have an aquatic or safety bench around their entire perimeter. The aquatic bench is defined as follows: a. Cross -slope no steeper than 10:1. b. Minimum width 10 feet. c. Located from pond outlet elevation to one foot below pond outlet elevation. 3. All constructed ponds shall be provided a maintenance access from an adjacent roadway. The maintenance access shall be provided in the form of an easement no narrower than 20 feet. The maintenance access shall have a longitudinal slope no steeper than 6:1 and minimal cross slope. Maintenance access routes, due to their extra width, also serve well as emergency overflow (EOF) routes. 4. All constructed ponds and wetland mitigation areas shall have a maintenance access bench around sufficient perimeter to provide access to all inlets and outlets. The maintenance bench should be located within a designated outlot, or within a permanent easement. The maintenance bench should extend from the outlet elevation to 1 foot above the outlet elevation and its cross slope should be no steeper than 10:1. The maintenance bench shall connect to the maintenance access. 5. Maximum pond wet volume depth is 8 feet. 6. Mean depth for wet ponds should be a minimum of 4 feet. If the pond is smaller than 3 acre-feet in volume, mean depths of 3 to 4 feet may be used. Mean depth is defined as the area at outlet elevation divided by the wet volume. 7. All ponds shall be graded to one -foot below design bottom elevation. This "hold down" allows sediment storage until site restoration is complete. 8. The top berm elevation of ponds shall be a minimum of one foot above the 100 -year pond HWL. 9. Grading shall not block or raise emergency overflows from adjoining properties unless some provision has been made for the runoff that may be blocked behind such an embankment. 10. All ponds shall have a protected EOF. 6.6.5 Infiltration/Filtration Practices 1. Sizing of filtration/infiltration practices shall be in conformance with the volume control requirements of this manual. 2. When designing an infiltration practice for volume control and water quality management, on -site testing and detailed analysis are strongly encouraged in order to determine the infiltration rates of the proposed infiltration facility. Documented site - specific infiltration or hydraulic conductivity measurements (double -ring infiltrometer) City of Medina Stormwater Design Guide Bonestroo Page 13 000190-10031-0 completed by a licensed soil scientist or engineer is required. In the absence of a detailed analysis, the saturated infiltration rates listed in the Table 4: Infiltration Rates for Infiltration STPs, found in Appendix A of this manual, must be used. A piezometer shall be installed in order to ascertain the level of the local groundwater table and demonstrate at least three (3) feet of separation between the bottom of the proposed facility and the groundwater. The soil boring is required to go to a depth of at least five feet below the proposed bottom of the facility, or STP. The soils must be classified using the Unified Soil Classification system. The least permeable soil horizon will dictate the infiltration rate. Infiltration practices shall be designed to infiltrate the required runoff volume within 48 hours. 3. Pretreatment, in the form of ponds, forebays or filter strips or other approved methods shall be provided for all infiltration areas. Pretreatment upstream of volume management practices is a key element in the long-term viability of infiltration areas. The level of pretreatment varies largely depending on the BMP and drainage area. Local watershed district, City staff, and Minnesota Stormwater Manual recommendations will be utilized for determining the appropriate level of pretreatment on a case -by -case basis. 4. The infiltration practice cannot be used within fifty (50) feet of a municipal, community or private well, unless specifically allowed by an approved wellhead protection plan. 5. The infiltration practice cannot be used for runoff from fueling and vehicle maintenance areas and industrial areas with exposed materials posing contamination risk, only if the infiltration practice is designed to allow for spill containment. 6. The infiltration practice cannot be used in HSG types C & D soils without soil corrections. 7. Vegetation of infiltration/filtration practices shall be as shown on the BMP details of the City of Medina Detail Standards. A plan for the management of vegetation shall be included in the stormwater management plan. 8. If soils are unsuitable for infiltration, then filtration may be used with drain tile, provided in accordance with the BMP Details of the City of Medina Detail Standards. 9. Subgrade soils for infiltration/filtration practices shall be as presented in the BMP Details of the City of Medina Detail Standards. Assume a 30% void ratio for the purposes of volume calculations. 10. For infiltration benches adjacent to ponds, benches shall have slopes no steeper than 5:1 over the proposed infiltration zone. A slope of 10:1 is preferred. The Minnesota Stormwater Manual cites concerns with locating infiltration features immediately adjacent to ponds. To address this, benches shall be located to maintain hydraulic separation from the saturated zone of the pond in order to decrease the infiltration potential over time. 6.6.6 Emergency Overflow Paths 1. Emergency Overflows (EOF) should be sized with a minimum bottom width of five feet and 4:1 side slopes. 2. The maximum flow depth in EOFs should be less than or equal to one foot as calculated for a 100 -year back-to-back storm event. 7.0 Design Examples City of Medina Stormwater Design Guide Bonestroo Page 14 000190-10031-0 Design process for each of the acceptable Stormwater Treatment Practice is detailed in Chapter 12 of the Minnesota Stormwater Manual. 8.0 Stormwater Treatment Practice Detail Drawings Please refer to the City of Medina Engineering Details. 9.0 Construction Specifications Construction specifications and details are found in the Minnesota Stormwater Manual in Chapter 12 for each of the acceptable BMPs, unless otherwise restricted by this ordinance. City of Medina Stormwater Design Guide Bonestroo Page 15 000190-10031-0 10.0 Checklists Final Stormwater Management Plan Checklist • Applicant information o Name, legal address, and telephone number • Common address and legal description of site • Signature or stamp of registered engineer • Vicinity map • Existing and proposed mapping and plans (recommended scale of 1" = 50' or greater detail) which illustrate at a minimum: o Existing and proposed topography (minimum of 2 -foot contours recommended) o Perennial and intermittent streams o Mapping of predominant soils from USDA soil surveys as well as location of any site -specific borehole investigations that may have been performed o Location and boundaries of resource protection areas such as wetlands, lakes, ponds, and other setbacks (e.g., stream buffers, drinking water well setbacks, septic setbacks) o Location of existing and proposed roads, buildings, and other structures o Location of existing and proposed utilities (e.g., water, sewer) o Location of existing and proposed conveyance systems such as grass channels, swales, and storm drains o Existing and proposed drainage boundaries, including off -site drainage boundaries o Flow paths o Location of floodplain/floodway limits and relationship of site to upstream and downstream properties and drainages o Location and dimensions of proposed channel modifications, such as bridge or culvert crossings o Location, size, maintenance access, and limits of disturbance of proposed structural stormwater management practices • Representative cross-section and profile drawings and details of structural stormwater management practices and conveyances (i.e., storm drains, open channels, swales, etc.) which include: o Existing and proposed structural elevations (e.g., invert of pipes, catchbasins, etc.) o Design water surface elevations o Structural details of outlet structures, embankments, spillways, stilling basins, grade control structures, conveyance channels, etc. o Logs of borehole investigations that may have been performed along with supporting geotechnical report. • Hydrologic and hydraulic analysis for all structural components of stormwater system (e.g., storm drains, open channels, swales, management practices, etc.) for applicable design storms including: o Existing condition analysis for runoff rates, volumes, velocities, and water surface elevations showing methodologies used, design parameters, and supporting calculations o Proposed condition analysis for runoff rates, volumes, velocities, water surface elevations, and routing showing the methodologies used, design parameters, and supporting calculations o Final sizing calculations for structural stormwater management practices including contributing drainage area, storage, high water level, peak inflow and outflow, and outlet configuration City of Medina Stormwater Design Guide Bonestroo Page 16 000190-10031-0 o Stage -discharge or outlet rating curves and inflow and outflow hydrographs for storage facilities (e.g., stormwater ponds and wetlands) o Analysis, computations, and supporting materials indicating that water quality and quantity design criteria are being met o Final analysis of potential downstream impact/effects of project, where necessary o Dam breach analysis, where necessary • Maintenance plan which will include: o Name, address, and phone number of responsible parties for maintenance. o Description of annual maintenance tasks o Description of applicable easements o Description of funding source o Minimum vegetative cover requirements o Access and safety issues o Testing and disposal of sediments that will likely be necessary • Waiver requests Checklists for Construction Inspection Construction Inspection Checklists for each of the approved Stormwater Treatment Practice are available in Appendix D of the Minnesota Stormwater Manual. Bioretention — p.685 Media Filter System — p.687 Vegetative Filter System — p.689 Infiltration Trench — p.691 Infiltration Basin — p.693 Stormwater Pond/Wetland — p.695 Checklists for Operation & Maintenance Operations & Maintenance Checklist for each of the approved Stormwater Treatment Practice are available in Appendix D of the Minnesota Stormwater Manual. Bioretention — p.702 Media Filter System — p.704 Vegetative Filter System — p.706 Infiltration Trench — p.708 Infiltration Basin — p.708 Stormwater Pond/Wetland — p.710 City of Medina Stormwater Design Guide Bonestroo Page 17 000190-10031-0 MEDINA — STORMWATER DESIGN GUIDE Appendix A Table 4: Infiltration Rates for Inf Itration STPs Corresponding Unified Soil Classification Infiltration Rate (inches/hour) GW — Well -graded or well -graded gravel with sand GP — Poorly graded gravel or poorly graded gravel with sand 1.63 GM - Silty gravel or silty gravel with sand SW — Well -graded sand or well -graded sand with gravel SP — Poorly graded sand or poorly graded sand with gravel 0'8 SM — Silty sand or silty sand with gravel 0.6 ML — Silt OL — Organic silt or organic silt with sand or gravel or gravelly organic silt 0.3 GC — Clay gravel or clayey gravel with sand SC — Clayey sand or clayey sand with gravel 0.2 CL — Lean clay or lean clay with sand or gravel or gravelly lean clay CH — Fat clay or fat clay with sand or gravel or gravelly fat clay OH — Organic clay or organic clay with sand or gravel or gravelly organic clay MH — Elastic silt or elastic silt with sand or gravel <0.2 Source: Minnesota Stormwater Manual City of Medina Stormwater Design Guide Bonestroo Page 18 000190-10031-0 Agenda Item: 7 MEMORANDUM TO: Planning Commission FROM: Dusty Finke, City Planner DATE: June 9, 2011 MEETING: June 14, 2011 Planning Commission SUBJ: Discussion: Off -premise signage and Directional Signage Background Within the past month, staff has received two requests for signage from owners of commercial property who do not directly abut a major roadway. One owner requested a monument sign on the property in front of their lot. The other owner requested a simpler "directional sign" along a City street directing traffic down the side street. Current City regulations prohibit off -premise signage, and there are no standards for granting directional signage in the right-of-way. Staff seeks direction from the Planning Commission and City Council if there is interest in evaluating these restrictions. The Planning Department had intended to address a minor amendment to the sign ordinance later in the year, dealing with applicability and the City's new zoning districts. If the Commission and Council provide direction, staff could include a discussion related to off -premise and directional signage. Quick Research Staff conducted very preliminary research on how other communities regulate these types of signage. Generally, cities do not allow an advertising sign for one property owner on another's property. The exception to this clearly is a coordinated development such as a PUD. Almost every city allows shared signage in these circumstances. Brooklyn Park and Plymouth are two examples of communities which would allow off -premise signage even when the development of the sites were not linked. Brooklyn Park would allow more advertising signage while the City of Plymouth only allows smaller directional signage. With regards to directional signage within the City right-of-way, most communities do not have standards, but defer to MnDOT on signage on state/federal highways. . Brief Staff Analysis The purpose of the sign ordinance is as follows: Section 815.01. Purpose. It is hereby declared by the city council that the aesthetic and safety interests of the city are reasonably promoted by the provisions of this ordinance. Accordingly, it is the intent and purpose of this ordinance to provide for the orderly and harmonious display of signs within the city; to aid in the identification of properties and enterprises for the convenience Discussion: Page 1 of 4 June 14, 2011 Off -Premise and Directional Signage Planning Commission Meeting 11 of the public; to avoid the erection of displays which produce deleterious and injurious effects to adjacent properties and to the natural beauty of the environment; to provide for the safety of the traveling public by limiting the distractions, hazards, and obstructions; to minimize visual clutter and encourage a positive visual environment; and to promote the mental and physical health, safety and welfare of the public. On one hand, directional signage in the right-of-way and allowing off -premise signage would likely lead to an increase in signage at certain locations in the community (intersections, along major corridors, etc.). On the other hand, the signage would help with way -finding, perhaps reduce u -turns, and perhaps support local business. It should be noted that with regards to off -premise signage, the overall amount of signage on each lot could still be regulated. If that is the case, the property owner on the corner would essentially be using up some of their signage rights and the amount of allowed signage may not need to be increased. In practice, however, every property does not use the absolute maximum signage allowed and would likely have some to transfer to another. Attachment 1. City of Plymouth regulations related to Off -site Directional Signage Discussion: Page 2 of 4 June 14, 2011 Off -Premise and Directional Signage Planning Commission Meeting Attachment 1 City of Plymouth regulations for off -site Directional Signage (b) Off -Site Directional Signs. (1) In addition to other freestanding signs permitted in the applicable zoning district, off -site directional signs are permitted for businesses, apartment complexes, or institutions that are not located on a minor arterial or a major collector street. Such uses may display one (1) off -site directional sign on private property that abuts a minor arterial or major collector street, subject to the following requirements: a. Off -site directional signs may be located in any zoning district. b. There shall be no more than one (1) off -site directional sign for each business, apartment complex or institution. c. collector street. d. Off -site directional signs shall be located at the major intersection nearest to the business, apartment complex or institution displaying the sign. e. corner. Off -site directional signs shall be visible from a minor arterial or major There shall be no more than one (1) off -site directional sign per intersection f. Off -site directional signs shall not exceed four (4) square feet in surface area or eight (8) feet in height. g. Off -site directional signs shall not be illuminated. h. traffic to a specific location. i. review and permitting by the Zoning Administrator. J. triangle. At least seventy-five (75) percent of the surface area shall be used to direct Off -site directional signs cannot be transferred to any other entity without Off -site directional signs shall be located outside of the sight visibility k. No off -site directional sign shall be located on any property without the written consent of the current property owner. The applicant for the sign permit shall be responsible to obtain written consent from subsequent property owners. 1. Off -site directional signs required by the City of Plymouth for public safety purposes are subject to the above requirements. Such signs may exceed four (4) square feet in area to accommodate an affected location address. Discussion: Page 3 of 4 June 14, 2011 Off -Premise and Directional Signage Planning Commission Meeting 1 (Amended by Ord. No. 2001-26, 08/14/01 (2) One (1) off -site directional sign for properties located in commercial or industrial districts may be located on an abutting premises if deemed necessary by the Zoning Administrator in order to avoid confusion to the traveling public and assist emergency vehicles in locating the premises, provided all the following conditions are met: a. The signage rights are designated in a recorded easement or similar instrument. b. The premises served by the off -site directional sign shall not have direct access to a public street. c. The off -site directional sign shall be located on a premises that 1) provides access to the premises served by the off -site directional sign, and 2) has access on an arterial or collector roadway. d. At least seventy-five (75) percent of the surface area shall be used to direct traffic to a specific location. e. The sign shall comply with all other ordinance requirements, except that the maximum height of such sign shall not exceed five (5) feet. Discussion: Page 4 of 4 June 14, 2011 Off -Premise and Directional Signage Planning Commission Meeting