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Memo from Mak Sweidan 2-14-06 CITY OF CHANHASSEN 7700 Market Boulevard PO Box 147 Chanhassen, MN 55317 Administration Phone: 952.227.1100 Fax: 952.227.1110 BUilding Inspections Phone: 952.227.1180 Fax: 952.227.1190 Engineering Phone: 952.227.1160 Fax: 952.227.1170 Finance Phone 952.227.1140 Fax: 952.227.1110 Park & Recreation Phone: 952.227.1120 Fax: 952.227.1110 Recreation Center 2310 Coulter Boulevard Phone: 952.227.1400 Fax: 952.227.1404 Planning & Natural Resources Phone: 952.227.1130 Fax: 952.227.1110 Public Works 1591 Park Road Phone: 952.227.1300 Fax: 952.227.1310 Senior Center Phone: 952.227.1125 Fax: 952.227.1110 Web Site www.ci.chanhassen.mn.us MEMORANDUM TO: Bob Generous, Senior Planner FROM: Mak Sweidan, Engineer ~ car February 14, 2006 DATE: SUBJ: Preliminary Plat Review of Powers Circle Land Use Review File No. 98-1 Upon review of the plans prepared by BRW dated January 4, 2006, I offer the following comments and recommendations: GRADING. DRAINAGE. EROSION CONTROL Approximately one-half of the parcel is proposed to be graded for the house pads and street layout. The existing topography contains a very steep, partially wooded slope along the westerly portion of the site. The westerly portion of the site contains a variety of trees, shrubs and conifers. In addition, two drainage ravines also intersect the parcel on this west slope. While previous upstream development has decreased the amount of runoff that flows through the ravines, they still act as a conduit to neighborhood drainage and need to be preserved. In an attempt to preserve the drainage ravines, the applicant has proposed drainage and utility easements over the ravines in Lots 3 and 4. Lot 5 is proposed to be "custom graded". As such, a detailed grading, drainage, tree removal and erosion control plan will be required at the time of building permit application for staff review and approval. The front and rear house pad elevation for all lots must be shown on the grading plan as well. Generally, the overland drainage will be directed towards the homes on Lots 3, 4 and 5. The grading plan does not adequately address how this drainage will be directed away from the homes. Staff is concerned about the volume of runoff flowing through the ravine along both sides of Lot 3. The applicant must submit hydrology calculations indicating the 100-year, 24-hour water elevations in each ravine near the proposed building pads under the proposed grading conditions. The lowest floor elevations for Lots 3 and 4 must be minimum three feet above this elevation. The grading plan shows that the front of Lot 3 will sheet drain over the private drive and to the front of the house pad on Lot 8. This drainage pattern must be adjusted so that runoff will not be directed to Lot 3. Staff recommends that the grading plan be revised prior to City Council consideration of the plat. The City 01 Chanhassen · A growing community with clean lakes, quality schools, a charming downtown, thriving businesses, winding trails, and beautiful parks. A great place to live, work, and play. Bob Generous February 14,2006 Page 2 This development is adjacent to Powers Boulevard (County Road 17), which is listed as a collector street in the City's Comprehensive Land Use Plan. According to City Code, the development will require screening of the adjacent lots from Powers Boulevard. The applicant has proposed a combination of landscaping and separated berms to accomplish the screening. The separated berms will provide openings for the runoff to drain out to Powers Boulevard as it does today. Staff has some concerns with the berming and screening in the rearyard area of Lot 1. The berm, which is meant to screen the rear of the house from Powers Boulevard, does not extend far enough south to screen any of the rear house pad. Staff is recommending that the berm be extended, approximately 40 feet, to the south and that the berm be raised to an elevation of 910 at the northeast comer of the lot. The applicant and/or contractor must supply the City Engineer with a haul route for review and approval prior to grading activities commencing. The applicant should be aware that any grading outside of the property limits will require a temporary easement. The existing site drains from west to east onto Powers Boulevard where an existing storm drainage system collects stormwater runoff and carries it north to a stormwater quality pond for pretreatment prior to discharging into a downstream wetland. The pond has been sized for development of this site and, as such, no on-site pond will be required for this development. The parcel was not assessed for any storm drainage improvements with the Powers Boulevard project and therefore will be responsible for surface water management fees. The plans propose two catch basins to convey stormwater runoff from Powers Circle and the property to the north into the existing drainage system in Powers Boulevard. There are also three proposed structures within the site to convey the stormwater from the northern ravine, private street, and a large portion of the lots to Powers Boulevard. In addition, storm drainage calculations for a lO-year and 100-year, 24-hour storm event must be submitted for review and approval along with a drainage area map. No increase in off-site runoff rates to the south will be allowed. The sanitary sewer and watermain must be removed from the grading plan. Erosion control measures and site restoration shall be developed in accordance with the NPDES Construction Permit. Silt fence is shown along the majority of the site perimeter where stormwater and sediment can run off the site. A 75-foot rock construction entrance has been shown at the proposed street access off of Powers Boulevard. In addition, tree preservation fencing needs to be added around any and all trees to be saved. Bob Generous February 14, 2006 Page 3 UTILITIES There is an existing home on the site which utilizes a well and septic system. Upon installation of the public utilities, the existing house will be required to abandon the septic tank and connect to the public sanitary sewer. The applicant will have the option of doing the same with the existing well. In the meantime, the existing septic and well locations need to be shown on the plans so they can be protected during construction. The site has not been previously assessed for utilities. As such, the site will be subject to one sanitary sewer and water connection charge for the installation of the existing stubs to the site. The 2006 connection charges for both sanitary sewer and water are $5,272/unit. The connection charges will be applied toward the first building permit that is pulled for the site. The property is also subject to sanitary sewer and water hook-up charges for all of the lots. The 2006 trunk utility hook- up charges are $1,575 per unit for sanitary sewer and $4,078 per unit for water. The 2006 SAC charge is $1,625 per unit. In addition, since the property is within the Lake Ann Sewer District, a sewer interceptor charge of $1,347 per unit and a sub-trunk charge of $1,412 per unit will be due on each lot. These charges are collected prior to each building permit issuance. In conjunction with the Powers Boulevard project, municipal sewer and water service was extended to serve this parcel and the one to the north. An 8-inch sewer line has been extended out along the northerly lot line of the site from Powers Boulevard. The plans propose on extending the sanitary line into the site and then going south to serve the lots. Staff is recommending that the southern most sanitary sewer manhole (#1) be moved within the paved portion of the private street. This will provide easier maintenance access for City utility workers. A 6-inch watermain is also proposed to be extended into the site along Powers Circle and then along the private street. The watermain must be extended to within five feet of the south property line for future looping with the property to the south. The plat must be revised to provide minimum 10 foot drainage and utility easements on each side of all public utilities. The applicant has included public sanitary sewer and watermain stubs off of the cul-de-sac for future development of the property to the north. Upon installation of these utilities, the house to the north will be within 150 feet of the sanitary sewer. As per City Code Section 19-41 (a), this house will then be required to connect to the sanitary sewer system within twelve months of the sewer becoming available. The applicant must be aware that drop manholes are required when the pipe inverts are greater than three feet apart. Bob Generous February 14, 2006 Page 4 Since all of the lots will have a lowest floor elevation of 930 or less, in-home pressure reducing water valves will be required on all lots. Utilities along the private street will need to have a drainage and utility easement dedicated over them. The minimum width will be 30 feet depending on the utility depth. The interior site storm sewer will also need to have a minimum 20-foot wide easement dedicated over it. Detailed utility construction plans and specifications in accordance with the City's latest edition of Standard Specifications and Detail Plates will be required for review and approval by the City Council at time of final plat consideration. Since the utilities and part of the street improvements will become owned and maintained by the City, the applicant must enter into a development contract with the City and provide financial security in the form of a letter of credit or cash escrow to guarantee construction of the public improvements. Permits from the appropriate regulatory agencies will be required, including but not limited to: Watershed District, MPCA, NPDES, Dept. of Health, Carver County, etc. STREETS Upon City Council approval at the September 29,2005 consent agenda, the development is subject to the $3,600/developable acre Arterial Collector Fee. All new developments within the Lyman Boulevard corridor are subject to this fee. The proceeds of this fee will fund the reconstruction of Lyman Boulevard. Access to the site is proposed by both a public street (Powers Circle) and a private street to serve up to four of the lots (1, 2, 3 and 4). There is no need to extend a public street to the south since the adjacent parcel has access from Oakside Circle. The parcel to the north will have access from Powers Circle. The preliminary plat also shows a future street access to the north. Staff is recommending that this street be stubbed out to the property line and constructed with this project. Staff would also recommend that the proposed driveway entrance to the north be revised and shifted further to west. The public street width and right-of-way for Powers Circle per City ordinance must be 31-feet back-to-back within a 60-foot wide right-of-way. Powers Circle must meet the City's requirements; therefore, the grade must be a maximum 7%. The private street must be paved to a minimum width of 20-feet and built to a 7- ton design. A turnaround area must be acceptable to the City's Fire Marshall and be provided along the private street, maximum slope of 7% (currently shown at 17 %). Minimum 100 foot pavement length at hammer head terminus (currently shown at 73 feet). The private street must be located within a 30-foot wide private easement and dedicated to the benefiting property owners. Bob Generous February 14,2006 Page 5 Access to the site from Powers Boulevard does have a right turn lane provided. Therefore, no additional turn lanes will be necessary. As a result of this project, both existing homes will be required to change addresses to correspond to the new street name. RECOMMENDED CONDITIONS OF APPROVAL 1. Lot 5 shall be designated as a "custom graded" lot. A detailed grading, drainage, tree removal and erosion control plan shall be submitted to the City at time of building permit application for review and approval. 2. The applicant and/or contractor shall supply the City Engineer with a detailed haul route for review and approval prior to site grading. 3. Shift the proposed northern parcel access off Powers Circle further to the west, stub it out to the north property line and construct with this project. The existing driveway for the property to the north shall be revised to come off of the new stub street. 4. The plans shall be revised as follows: a. Show the front and rear housepad elevations for all lots. b. Extend the berm in Lot 1 approximately 40 feet to the south and raise the elevation to a high of 910. c. Add a benchmark and legend to the plans. The legend should define all of the different line types, utilities, contours, etc. d. Move sanitary sewer manhole (#1) to within the paved portion of the private street. e. Extend the watermain to within five feet of the south property line of the site. f. Remove contour lines from the utility plan. g. Show the utilities in light shading on the grading plan. h. On the grading plan, the utilities show in double layout, revise accordingl y. 1. On the grading plan, extend the silt fence further north along the west side of Lot 3. J. On the grading plan, add a note to remove the north parcel access entrance off Powers Boulevard. k. Reroute the proposed storm sewer from CBMH2-Existing CB to be CBMH2-CBMH3. 1. Show the proposed utilities pipe class. m. On the utility plan, sanitary manhole #3 must be an outside drop manhole. Bob Generous February 14, 2006 Page 6 n. On the utility plan, add a note that any connection to existing structure must be core drilled. 5. The developer shall be responsible for the applicable surface water management fees. 6. The developer shall supply the City Engineer with storm drainage calculations for a lO-year and lOa-year, 24-hour storm event for review and approval along with a drainage area map. There shall be no increase in off-site runoff rates to the south. 7. Existing well and septic sites must be properly abandoned in accordance with City Code and the Minnesota Department of Health once the sewer and water lines become operational and are accepted by the City. 8. Detailed utility and street construction plans and specifications shall be prepared and submitted in accordance with the City's latest edition of Standard Specifications and Detail Plates for City Council approval at time of final plat consideration. 9. The developer shall enter into a development contract with the City and provide financial security in the form of a letter of credit or a cash escrow to guarantee construction of the public improvements and compliance with the Conditions of Approval. 10. All disturbed areas as a result of construction activities shall be immediately restored with seed and disc mulch or wood fiber blanket or sod within two weeks of completion of each activity in accordance with the NPDES Construction Permit 11. The applicant shall apply for and obtain permits from the appropriate regulatory agencies, i.e. Carver County, Watershed District, Health Department, MPCA, and NPDES and comply with their Conditions of Approval. 12. The developer shall include a drain tile system behind the curb to convey sump pump discharge from the units not adjacent to ponds and/or wetlands. This includes the private street. 13. Any offsite grading will require a temporary easement. 14. The site has not been previously assessed for utilities. As such, the site will be subject to one sanitary sewer and water connection charge for the Bob Generous February 14, 2006 Page 7 installation of the existing stubs to the site. The 2006 connection charges for both sanitary sewer and water are $5,272/unit. The connection charges will be applied toward the first building permit that is pulled for the site. The property is also subject to sanitary sewer and water hook-up charges for all of the lots. The 2006 trunk utility hook-up charges are $1,575/unit for sanitary sewer and $4,07/unit for water. The 2006 SAC charge is $1,625 per unit. In addition, since the property is within the Lake Ann sewer district, a sewer interceptor charge of $1,347/unit and a sub-trunk charge of $1,412/unit will be due on each lot. These charges are collected prior to each building permit issuance. 15. Due to the low floor elevation of the proposed lots, in-home pressure reducing water valves will be required on all lots with a lowest floor elevation of 930 or less. 16. Utilities along the private street will need to have a drainage and utility easement dedicated over them. The minimum width will be 30 feet depending on the utility depth. 17. As per City Code Section 19-41 (a), the house to the north will be required to connect to the sanitary sewer within twelve months of the sewer becoming available. 18. The private street must be paved to a minimum width of 20-feet, built to a 7-ton design and 7% maximum slope. A turnaround area must be acceptable to the City's Fire Marshall and provided along the private street. The private street must be located within a 30-foot wide private easement and dedicated to the benefiting property owners. 19. The interior site storm sewer will need to have a minimum 20-foot wide easement dedicated over it. 20. The developer shall submit the storm sewer sizing calculations for review and approval along with a drainage area map prior to final plat approval. 21. Add City Details Plate Nos. 1002, 1004, 1005, 1006,2001,2103,2109, 2201,2201,2202,2204,3101,3102,3106,5200,5203,5205,5206,5217, 5232, 5234, 5300 and 5301. 22. Upon City Council approval of the September 29, 2005 Consent Agenda, the development is subject to the $3,600/developable acre Arterial Collector Fee. All new developments along the Lyman Boulevard corridor are subject to this fee. The proceeds of this fee will fund the Bob Generous February 14, 2006 Page 8 reconstruction of Lyman Boulevard between Audubon Road and Powers Boulevard. 23. The applicant must submit hydrology calculations indicating the 100-year, 24-hour water elevations in each ravine near the proposed building pads under the proposed grading conditions. The lowest floor elevations for Lots 3 and 4 must be a minimum of three feet above this elevation. c: Paul Oehme, Director of Public Works/City Engineer Alyson Fauske, Assistant City Engineer g:\eng\projects\powers circle\powers circle ppr.doc