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WR Review Memo - 1591 Park Road Memorandum To: Rachel Arsenault, Associate Planner From: Joe Seidl, Water Resources Engineer CC: Charles Howley, Public Works Director/City Engineer George Bender, Assistant City Engineer Charlie Burke, Public Works Operations Manager Date: 09/06/2024 Re: 1591 Park Road Conditional Use Permit Project Overview The property owner seeks a conditional use permit to establish a contracting yard at 1591 Park Road. Contractor yards typically store construction and landscaping materials and equipment. These materials may include dirt, sand, construction debris, salt, fuel, and raw building materials such as lumber and concrete blocks. Equipment might include trucks and construction vehicles like skid steers, excavators, and bulldozers. Due to the nature of these materials and equipment, contractor yards have a higher risk of pollutant transport, especially because materials like dirt and salt can be easily eroded by wind and water. Historically, this property served as a public works building for the City of Chanhassen and had a similar use. The applicant has provided supporting documents for the conditional use permit request, which were reviewed by the Water Resources Department. These documents include: · Overall Site Plan (Moore Engineering Inc., dated 5/31/24) · Contractor Yard Site Plan (Moore Engineering Inc., dated 5/31/24) · Stormwater Memo (Moore Engineering Inc., dated 8/9/24) · Contractor’s Yard Exhibit (Moore Engineering Inc., dated 8/9/24) · Drainage Plan Exhibit (Moore Engineering Inc., dated 8/9/24) Documented Water Resources Issues In May 2023, City staff visited the site in response to complaints about its condition. The site exhibited numerous erosion and sediment control issues, including missing best management practices (BMPs) like perimeter controls, insufficient buffer areas, large areas of disturbed soil, and uncovered stockpiles. These issues led to sediment and pollutants entering the onsite wetland/stormwater pond and potentially impacting downstream City infrastructure and local water resources. The site also showed failing stormwater infrastructure, exacerbating sediment and erosion problems. The Erosion and Sediment Control Inspection Report of May 5, 2023, details the site’s past condition and is included as a reference to this memo. Spring 2023 – Photo of Stockpile and Depressional Area Spring 2023 – Photo of Contractor’s Yard Since 2023, the owner has addressed some of the onsite issues by removing stockpiles and installing silt fence and other Erosion and Sediment Control BMPs. However, disturbed soils and failing stormwater infrastructure remain onsite. Wetlands A small depression in the southwest corner of the property appears to have wetland characteristics, with wetland vegetation observed during staff inspections conducted in 2023. This area is classified as a wetland on the City’s GIS inventory. Aerial photographs from 1969 and subsequent observations indicate the presence of standing water in this depression since the late 1980s/early 1990s. A review of older site plans from the 1980’s indicates the presence of a depression/channel that was modified with the development of the site. It is possible that the intent of the modifications was to create a stormwater management feature, however more detailed review is required to make an official Wetland Conservation Act decision. It is recommended that the applicant conduct a wetland delineation to confirm whether this depression is a jurisdictional wetland. If classified as such, the site should comply with Article 20-6 Wetland Protection of the City Code, which includes establishing buffer areas and potentially wetland restoration. If the area is classified as a stormwater management feature, then the applicant could use this area to manage the runoff generated by the site. Drainage The site primarily drains to the southwest into the onsite wetland/stormwater pond. From there, stormwater flows southwest through a railroad ditch system into a City maintained wet pond before discharging into Bluff Creek. The northern part of the site drains into the City storm sewer along Park Road, with stormwater eventually reaching Riley Creek. There is limited onsite stormwater infrastructure including pipes and catch basins which appear to be private as they act to drain private property, are not contained in easements, and do not benefit the public. The proposed plans will not significant alter the existing drainage patterns. Some existing impervious surfaces will be removed and revegetated, and new stormwater infrastructure, including bituminous curbs and stabilized curb cuts, are proposed to help manage runoff. The Contractor Site Plan includes temporary BMPs like hay bales and silt fences for interim site management. A new bituminous drive lane was added in 2023 without permits. No new permanent BMPs for stormwater management are currently proposed. Erosion Control The exact area of disturbance is unclear but appears to exceed 5,000 square feet. If the disturbance is over one acre, the project will require a General Permit Authorization to Discharge Stormwater Associated with Construction Activity (NPDES Construction Permit). The project must comply with Section 19-145 of the City Code regarding Erosion and Sediment Control. Given the disturbance size and sediment transport concerns, the applicant should submit an Erosion and Sediment Control Plan adhering to City regulations. All erosion control measures must be installed and inspected by City staff before site grading/construction begins. If disturbance exceeds one acre, a Stormwater Pollution Prevention Plan (SWPPP) should be included in the next submittal. The site is within the Riley Purgatory Bluff Creek Watershed District (RPBCWD). The district requires an erosion and sediment control permit if the site grades 50 cubic yards or more of earth or disturbs 5,000 square feet or more of area. The applicant should confirm whether these thresholds are met and secure all necessary permits, including after-the-fact permits. Stormwater Management The City's Code Section 20-232 outlines General Issuance Standards for Conditional Use Permits. Relevant standards include: Sec 20-232 General Issuance Standards The planning commission shall recommend a conditional use permit and the council shall issue such conditional use permits only if it finds that such use at the proposed location: a. Will not be detrimental to or endanger the public health, safety, comfort, convenience or general welfare of the neighborhood or the city. b. Will be consistent with the objectives of the city's comprehensive plan and this chapter. e. Will be served adequately by essential public facilities and services, including streets, police and fire protection, drainage structures, refuse disposal, water and sewer systems and schools; or will be served adequately by such facilities and services provided by the persons or agencies responsible for the establishment of the proposed use. City Code requires that site be in compliance with the objectives of Chanhassen’s Comprehensive Plan. The Local Stormwater Management Plan (LSWMP) is part of the city’s Compressive Plan. The first three goals of the LSWMP are: Goal 1. Promote abstraction through infiltration, reuse and other methods where practicable to do so to provide flood protection, ground water recharge and improved water quality. Goal 2. Achieve water quality standards in lakes, streams, and wetlands consistent with their designated uses and established classifications. Goal 3. Protect and rehabilitate wetlands to maintain or improve their function and value. When not properly managed, a contractor’s yard increases pollution risks to downstream water resources and can increase maintenance needs on downstream stormwater infrastructure. This would not align with the goals of the LSWMP and as a result a contractor’s yard requires proper stormwater management facilities in order to meet the goals of the City’s LSWMP. The onsite wetland/stormwater pond is in disrepair and there have been documented erosion and sediment control issues that have very likely impacted local water quality. To comply with City Code and the LSWMP, it is recommended that the applicant develop a comprehensive stormwater management plan, including: · Paved surfaces for maintenance · Develop and implement an Erosion and Sediment Control Plan · Permanent private stormwater management facilities meeting water quality standards · Assessment and repair of existing stormwater infrastructure · Covered storage facilities · Schedule of regular maintenance activities as needed to manage the contractor’s yard (practices to contain sediment, fuel, and other runoff associated with contracting yards) · Execution of an Operations and Maintenance Agreement to ensure the functionality of the private stormwater infrastructure onsite. The project is also subject to RPBCWD rules and regulations. The applicant should confirm any applicable rules and obtain necessary permits as part of the Conditional Use Permit. WATER RESOURCES CONDITIONS: 1. It is the developer’s responsibility to ensure that permits are received from all other agencies with jurisdiction over the project (i.e. Carver County, RPBCWD, Board of Water and Soil Resources, MnDOT, etc.) prior to the commencement of construction activities. 2. The applicant shall complete a wetland delineation onsite to confirm if the depressional area is a jurisdictional wetland. If any area onsite is determined to be a jurisdictional wetland then the applicant shall revise plans to meet all applicable city code regulations. The Wetland delineation shall be completed within 3 months after the approval of the Conditional Use Permit. 3. The applicant and their Engineer shall work with City staff in amending the construction plans, dated May 31, 2024, and August 9, 2024 prepared by Moore Engineering Inc. to fully satisfy construction plan comments and concerns within 6 months after the approval of the Conditional Use Permit. 4. The applicant shall provide updated plans and models to demonstrate that the contractor’s yard site is meeting water quality standards. A permanent BMP to manage the runoff generated by the contractor’s yard is anticipated. These models shall be submitted as part of all future submittals. 5. The applicant shall create a storm water management plan approved by staff to describe how the site is meeting city requirements including water quality and erosion control. The stormwater management plan including site improvements shall be executed within 12 months after the approval of the Conditional Use Permit. 6. The developer shall enter into encroachment agreements for all existing and proposed improvements located in public easements. The encroachment agreements shall be recorded within 12 months after the approval of the Conditional Use Permit.