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Final - Eng & WR Review Memo - Santa Vera Phase II Memorandum To: Eric Maass, Planning Director From: Mackenze Grunig, Project Engineer 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: 8/4/2025 Re: Santa Vera Apartments Site Plan Review - City Planning Case No. 2025-07 PROJECT OVERVIEW The Applicant is requesting preliminary site plan review of a 28 unit multi-family apartment project located just north of downtown Chanhassen. Construction plans and Stormwater Reports developed by Measure Group dated July 21, 2025 were reviewed by staff. The proposed design would create 1.11 acres of new impervious area in the form of an apartment building, parking lots, sidewalks, and streets. Stormwater is proposed to be managed by two storm water ponds along Laredo Dr. GRADING & DRAINAGE In the existing condition stormwater on the site generally flows from west to east. City Center Park, which borders the property to the west, is located at a high point, with runoff leaving the park in all directions including runoff that flows through the Santa Vera site. On the project site, stormwater primarily flows overland through a conveyance depression that directs most of the sites runoff to three catch basins located at a low point along Laredo Drive. Currently, stormwater from the site is collected and conveyed by public infrastructure, including storm sewers and wet ponds, before ultimately discharging into Lotus Lake. There are no public or private stormwater Best Management Practices (BMPs) located on the property. As a result, pollutants generated on-site are carried downstream and treated solely by the City’s infrastructure. The project site lies in an older area of Chanhassen that was developed in the 1960s and 1970s, before current stormwater management standards were adopted. As a result, the area lacks sufficient BMPs, contributing to higher pollutant loads reaching Lotus Lake. The redevelopment of the Santa Vera property presents an opportunity to address these deficiencies by incorporating stormwater treatment measures that go beyond current regulatory requirements. PROPOSED CONDITIONS Under the proposed development plan, the site will be mass graded to accommodate new apartment buildings, a parking lot, driveways, and stormwater reuse basins. Drainage patterns will remain generally consistent with existing conditions. The northern portion of the site will remain unchanged and continue draining toward the storm sewer on Saratoga Drive. Runoff from the proposed buildings, parking lot, driveway, and part of the existing apartment building will be collected via storm sewer and directed to the stormwater reuse basins located on the east portion of the site adjacent to Laredo Drive. These reuse basins will be connected by storm sewer and discharge to the existing storm sewer system on Laredo Drive through a single outlet. Stormwater treatment for the proposed impervious surfaces will be provided through a combination of stormwater basins and a reuse system designed for irrigation. The site is currently zoned as Planned Unit Development (PUD). However, preliminary development plans propose changes in the previously approved PUD and relief from sections of city code to facilitate the proposed plan. In return, it is recommended that the applicant provide enhanced water quality treatment to reduce the burden on downstream stormwater infrastructure. The stormwater basins along Laredo Drive appear to be too high in elevation to direct and treat stormwater from the adjacent area, however there appears to be an opportunity to route stormwater from Saratoga Drive into the proposed stormwater basins. Additional engineering calculations are needed to understand if this is a viable option. As such it is recommended that the applicant work with staff to optimize the stormwater design and assess opportunity’s to provide stormwater treatment in excess to the requirements. If the design was reconfigured to treat stormwater by the public ROW the city may provide relief to the project by reducing stormwater development fees and/or taking on the ownership and maintenance of the stormwater treatment system depending on the amount of excess stormwater treatment provided. SANITARY SEWER AND WATERMAIN The applicant is proposing construction of 4” PVC for the sanitary sewer and 6” for the watermain. Service connections are proposed to be separate 4” fire & 2” domestic for water and 4” for sanitary sewer. Plans that illustrate the profile of the utilities along with their size and material are required for review and approval prior to final plan approval. The proposed sanitary sewer and watermain are undersized in order for the City to own and maintain them. The applicant is expected to complete the revisions and coordinate additional reviews in order to identify if any of the proposed utilities are private or publicly owned. TRAFFIC A traffic study for the proposed Santa Vera Apartments was completed by TC2 on July 18, 2025, by Matt Pacyna. The project proposes to continue using the three existing access points: two on Laredo Drive and one on Santa Vera Drive. The adjacent street network—Laredo Drive (1,300 ADT), Santa Vera Drive (700 ADT), and Kerber Boulevard (4,000 ADT)—remains within the capacity thresholds for their respective classifications. City staff has reviewed the study and found the estimated trip generation to be relatively low. During peak hours, 24 vehicles are expected to exit and 21 to enter the site. The development is projected to add approximately 256 daily trips, with the majority of the additional traffic distributed 75/25 between Laredo Drive and Santa Vera Drive. Even with this increase, the affected streets are projected to remain within their functional classification capacities. An addition to the traffic study shall be made to incorporate a traffic sight line review at the access to Santa Vera Dr. and both access points on Laredo Dr. The applicant shall update the construction plans with any additional information following this addition. EROSION CONTROL The proposed development will create greater than one (1) acre of land disturbance and therefore will be subject to the General Permit Authorization to Discharge Stormwater Associated with Construction Activity Under the National Pollution Discharge Elimination/State Disposal System (NPDES Construction Permit). A Surface Water Pollution Prevention Plan (SWPPP) was included in the preliminary site plan submittal. The SWPPP is a required submittal element for final site plan review along with the Erosion and Sediment Control Plan (ESCP) in accordance with Section 19-145 of City Ordinance. No earth disturbing activities may occur until the SWPPP is formally approved. This SWPPP shall be a standalone document consistent with the NPDES Construction Permit and shall contain all required elements of the permit. The SWPPP will need to be updated as the plans are finalized, when the contractor and their sub- contractors are identified, and as other conditions change. An updated SWPPP shall be submitted and approved prior to recording the final site plan agreement. All erosion and sediment control BMP’s shall be installed and inspected prior to initiation of site grading activities. STORM WATER MANAGEMENT Article VII, Chapter 19 of City Code describes the required storm water management development standards. Section 19-141 states that “these development standards shall be reflected in plans prepared by developers and/or project proposers in the design and layout of site plans, subdivisions and water management features.” These standards include abstraction of runoff and water quality treatment resulting in the removal of 90% total suspended solids (TSS) and 60% total phosphorous (TP). The proposed project is located within the Riley Purgatory Bluff Creek Watershed District (RPBCWD) and is therefore subject to the watershed’s rules and regulations. A RPBCWD permit will be required for final site plan approval. A Stormwater Management Report is required to be submitted for review to confirm all applicable stormwater management requirements are being met. This includes rate control, volume abstraction and water quality requirements among others. The site proposes to meet stormwater management requirements through the use of stormwater basins and reuse system. The applicant shall confirm that the reuse system will provide enough water for the proposed irrigation system based on the drainage area and the storage in the tank. A backup potable connection may be needed. Currently the TSS removal requirements and TP removal requirements are being met on site. The applicant shall provide final versions of all modeling (HydroCAD and MIDS) and Stormwater Management Report to address remaining comments and confirm rate, volume and water quality requirements are met as part of the final site plan approval. The stormwater basins do not appear to meet the 3-foot freeboard requirements to the existing and proposed buildings onsite. As such the applicant shall revise the design to meet the stormwater design requirements outlined in city code. The proposed stormwater management systems shown in the preliminary site plan are to be privately owned and maintained. An operations and maintenance plan is required to ensure that the private stormwater infrastructure is maintained in good working order. The maintenance plan includes descriptions of maintaining the BMPs, maintenance schedule, responsible party, and information on how the system will be cleaned out. The applicant shall submit an updated stormwater operations and maintenance including all required exhibits plan as part of the final plan submittal. WATER RESOURCES RECOMMENDATIONS: 1. The developer shall enter into a site plan agreement with the City and provide necessary financial security to guarantee compliance with the terms of site plan approval and construction of infrastructure onsite. 2. 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. 3. The developer and their Engineer shall work with City staff in amending the construction plans, dated July 21, 2025, developed by Measure Group to fully satisfy construction plan comments and concerns. Final construction plans will be subject to review and approval by staff prior to recording the site plan agreement. 4. An Operations and Maintenance plan for all proposed private stormwater management systems including the inspection frequency, maintenance schedule, and responsible party shall be submitted with the final plans. 5. The applicant shall provide updated H&H and water quality modelling with the final plan submittal. 6. The design shall be updated to meet the city’s freeboard requirement. ENGINEERING: 1. The developer shall enter into Encroachment Agreements for private improvements (e.g., retaining walls and monument signage) located within the 10-foot wide public drainage and utility corridor abutting the right-of-way prior to issuance of building permits. 2. The applicant and their Engineer shall work with City staff in amending the construction plans. Final construction plans will be subject to review and approval by staff prior to start of construction. 3. Retaining walls shall be privately owned and maintained. All walls four feet and greater in height shall be engineered. 4. All sanitary sewer mains and watermains will be publicly owned and maintained after acceptance of the public improvements by the City Council. These utilities shall be covered by a Drainage and Utility Easement which shall be large enough for the owner to own and maintain. Applicant shall loop the watermain through the site from Santa Vera Dr to Laredo Dr, and this watermain shall be publicly owned and maintained. 5. The applicant will be required to enter into a Development Contract with the City and all applicable securities and fees provided prior to recording of the final plans. 6. Applicant shall provide a color coded map identifying what improvements are public and what are private with final plans. 7. Chanhassen engineering standards require 6” minimum for sanitary sewer service pipe. 8. It is the applicant’s responsibility to ensure that permits are received from all other agencies with jurisdiction over the project (i.e. Army Corps of Engineers, DNR, MnDOT, Carver County, RPBC Watershed District, Board of Water and Soil Resources, PCA, MDH, MPCA, etc.). Applicant shall provide a copy of all permits prior to starting construction. 9. The construction plans show connecting into an existing sanitary sewer main. That main shall be cleaned and televised prior to connection and the video provided to the project engineer for review. 10. City Standard Detail Plates shall be included in the construction plan set and displayed in a layout format of 2 rows by 4 columns for consistency with City expectations.