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ENG_WRC Memo 3703 South Cedar Drive (ENG) Memorandum To: MacKenzie Young-Walters, Associate Planner From: Erik Henricksen, Project Engineer CC: Charles Howley, Public Works Director/City Engineer George Bender, Assistant City Engineer Date: 10/25/2021 Re: Variance Review at 3703 South Cedar Drive – Planning Case #2021-25 The Engineering Department has reviewed the variance submittal for 3703 South Cedar Drive. These comments are divided into two categories: general comments and proposed conditions. General comments are informational points to guide the applicant in the proper planning of public works infrastructure for this project, to inform the applicant of possible extraordinary issues and/or to provide the basis for findings. Proposed conditions are requirements that Engineering recommends be formally imposed on the application in the final order. Note that references to the “City Standards” herein refer to the City of Chanhassen Standard Specifications and Detail Plates. General Comments/Findings 1. Any and all utility and transportation plans submitted with this application have been reviewed only for the purpose of determining the feasibility of providing utility and transportation facilities for the project. A recommendation of variance approval does not constitute final approval of details, including but not limited to alignments, materials and points of access, utility connections or discharge, that are depicted or suggested in the application. The applicant is required to submit detailed construction drawings for the project, as applicable. The City of Chanhassen Engineering and Public Works Departments will review plans, in detail, when they are submitted and approve, reject or require modifications to the plans or drawings based upon conformance with City Standards, the Chanhassen Code of Ordinances and the professional engineering judgment of the City Engineer. 2. It is the opinion of the Engineering Department that the proposed variance can be developed in near accordance with the requirements of the Chanhassen Code of Ordinances (as it pertains to Engineering and Public Works requirements) and City Standards, provided it fully addresses the comments and conditions contained herein, and can be approved. 3. The applicant is requesting a number of variances to facilitate the construction of a single family home at 3703 South Cedar Drive (Site). These include lot cover, front yard setback, side yard setback, and shoreland setback variances. Engineering and Public Works has no comment regarding the front yard and side yard setback variances. There are no public drainage and utility easements currently on the property and none are being requested by staff in concert with the variance requests. 4. The applicant is proposing a lot coverage variance. The Site currently has 2,948 SF of hardcover on the 5,899 SF property, or 50% lot coverage of the Site. The proposed change to the Site’s total hardcover based on the provided submittals would provide a reduction of 2.4%, or 137 SF , for a total proposed lot cover of 2,811 SF, or 47.6%. Even though there is a reduction of total hard cover the Site is still above the allowable lot coverage (25%) under Ordinance and would require a variance. The proposed reduction of lot coverage by 137 SF alone would not result in a measurable water quality benefit to the riparian Site, which is directly adjacent to Lake Minnewashta. Additional measures must be taken to improve stormwater management, reduce impervious surfaces on the Site, and to mitigate the amount of stormwater runoff being diverted into Lake Minnewashta. While it may not be possible to achieve a total of 25% lot coverage on the Site, the applicant shall submit updated plans that illustrate the use of pervious paver systems, in accordance with Ordinances (Sec. 20-921), to the maximum extent possible. The use of pervious paver systems will help reestablish a more natural hydrologic balance, reduce runoff volume associated with impervious surfaces, all while providing water quality treatment by reducing the concentration of po llutants. Areas such as the driveway, sidewalk, and patios should be constructed with pervious paver systems (an approximate 1046 SF reduction of the proposed impervious surfaces). Additionally, a permanent 20’ native vegetated buffer must be installed along the shoreline. The native vegetated buffer will provide additional water quality protections through filtering pollutants, nutrients and sediments while helping to improve ecosystem health and function. See proposed conditions 1 and 2. 5. The applicant is proposing a shoreland setback variance. The proposed variance request is to maintain the existing 40.8 foot structure setback from the ordinary high water level of Lake Minnewashta. The required setback per Ordinance from the ordinary high water level in the Shoreland Management District is 75 feet. The applicant justifies that if there were no variance approved for the shoreland setback that the buildable home area would equate to about a 75 square foot home, which staff agrees would be a constrained area. As many of the lots in the surrounding neighborhood have similar constraints, the City has granted shoreland setback variances to allow for a more reasonable use of the property. As such, staff recommends approval of the proposed 40.8 foot structure setback as long as proposed conditions 1 and 2 are adhered to in order to mitigate stormwater runoff being diverted into Lake Minnewashta while improving the overall health of the ecosystem and function. Lastly, while Engineering and Public Works is recommending approval of the discussed variances in association with the proposed conditions, any and all improvements on the Site must meet applicable jurisdictional requirements. See proposed condition 3. Proposed Conditions 1. The applicant shall supply updated construction plans that utilize to the maximum extent possible the use of pervious paver systems in accordance with Sec. 20-921 of City Ordinances. Areas such as the driveway, sidewalk, and patios must be considered in the design of these systems. 2. A permanent 20’ native vegetated buffer must be installed along the shoreline using species native to the ecotype with permanent buffer monuments. The buffer may work around the path and stairs. The buffer must be designed and installed by an experienced professional in native shoreline restoration. Design plans must be approved by the Water Resources Administrator/Engineer. 3. The installation of any improvements on the Site shall meet all applicable jurisdictional requirements, including but not limited to the Minnesota Department of Natural Resources and the Minnehaha Creek Watershed District, and all applicable permits shall be obtained prior to any site improvements.