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Email from Lori Haak 11-5-04 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 Mak Sweidan, Engineer fi/! ,f!{ '7 .~. t)/L. FROM: DATE: November 8, 2004 SUBJ: Preliminary Plat Review for Hidden Creek Meadows LUR No. 04-16 Upon review of the plans dated October 15,2004, prepared by Ryan Engineering, I offer the following comments: GRADING, DRAINAGE & EROSION CONTROL The plans propose to grade about 75% of the site for the 23. new house pads, proposed street ending with a cul-de-sac, and a storm water pond. The proposed grading will prepare the site for full basement, lookout, and walkout-type dwellings. The plan proposes a retaining wall in the back yard of Lot 8, Block 1. It appears the wall will be some six to eight feet in height. The applicant should be aware that any retaining wall over 4 feet will require a building permit and must be designed by a Minnesota Registered Professional Structural Engineer. Also, the retaining wall must be 20 feet off the back of the building pad to provide adequate area for a backyard and deck. The existing site drains to a wetland along the south side of the parcel. Under developed conditions, the street, front yards and most of the house roofs and rear yard drainage will be conveyed via storm sewer to a proposed storm water pond for treatment prior to discharging to the existing wetland. The proposed development will be required to meet the existing stormwater runoff rates for. the 10- and 100-year, 24-hour storm events. The applicant has done a good job of attempting to preserve the existing drainage pattern of the wetland on the site through the use of a storm sewer culvert. Where the proposed street has bisected the wetland, the culvert will act as a conduit and allow the water to flow as it would under existing conditions. There is an area in the rear yard of Lot 10, Block 1 that will need to be revised to prevent trapping water behind the curb. Also, staff recommends that storm sewer and catch basins be added in Pipewood Lane between Lots 1 and 2, Block 1 to capture and treat additional site runoff prior to it flowing off-site. Staff has received drainage calculations for the development and only minor revisions are necessary. The proposed pond is required to be designed to National Urban Runoff Program (NURP) standards. The storm sewer will have to be designed for a 10-year, 24-hour storm event. Drainage and utility easements will 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 November 8, 2004 Page 2 need to be dedicated on the final plat over the public storm drainage system including the pond, drainage swales, and wetlands up to the 100-year flood level. The minimum utility easement width must be 20 feet wide. The applicant has included silt fence around the grading perimeter. Adjacent to the pond and wetlands, silt fence type II must be used. A 75-foot minimum rock construction entrance must be added to the entrance that will be accessed during construction. In addition, an erosion control blanket will be required for the steep slopes along the north property line of the site. The applicant should be aware that any off-site grading will require an easement from the appropriate property owner. All disturbed areas must be sodded or seeded and mulched within two weeks of grading completion. UTILITIES Municipal sewer and water service is available to the site from existing mains, which run along the eastern property line and from Pipewood Lane on the southwest comer of the parcel. The applicant is proposing to extend sewer and water lines along the proposed streets to service the proposed lots. The watermain will be looped through the site to avoid stagnant water issues. According to the City's Finance Department records, there is a remaining assessment balance of $25,477.05 on the parcel. This balance is required to be paid at the time of final plat recording. Since the developer will be responsible for extending lateral sewer and water mains, the sanitary sewer and water connection charges will be waived. However, the sanitary sewer and water hookup charges will still be applicable for each lot. The 2004 trunk hookup charge is $1,458 for sanitary sewer and $2,814 for watermain. Each of these charges is based on the number of SAC units calculated by the Metropolitan Council. Sanitary sewer and watermain hookup fees may be specially assessed against the parcel at the time of building permit issuance. Public utility improvements are required to be constructed in accordance with the City's latest edition of Standard Specifications and Detail Plates. Detailed construction plans and specifications must be submitted at the time of final plat for staff review. The applicant is required to finance all of the proposed improvements. The applicant will also be required to enter into a development contract with the City and to supply the necessary financial security in the form of a letter of credit or cash escrow to guarantee installation of the improvements and the conditions of final plat approval. Permits from the appropriate regulatory agencies must be obtained, including but not limited to the MPCA, Department of Health, MnDOT, etc. Bob Generous November 8, 2004 Page 3 STREETS The plans propose to extend Pipewood Lane, as the main road, approximately 1300 feet within the site. The public streets are shown within a 60-foot right-of- way, as per City ordinance along with street pavement widths of 3 I-feet back-to- back and a 45.5-foot radius on the cul-de-sac. Staff is concerned with the tight curb radius on the cul-de-sacs. In order to accommodate emergency fire vehicles, the curb radius must be a minimum of 30 feet. Due to the long length of the proposed cul-de-sac and the practice of having two connections int%ut of developments, staff is recommending that the existing gravel road known as Cartway Lane be connected to the proposed cul-de-sac at the eastern border of the site. This will be an interim connection until the properties to the north develop and Cartway Lane is vacated. RECOMMENDED CONDITIONS OF APPROVAL 1. Prior to final plat approval, a professional civil engineer registered in the State of Minnesota must sign all plans. 2. Prior to final platting, storm sewer design data with a drainage map will need to be submitted for staff review. The storm sewer will have to be designed for a lO-year, 24-hour storm event. The pond is required to be designed to National Urban Runoff Program (NURP) standards. Drainage and utility easements will need to be dedicated on the final plat over the public storm drainage system including ponds, drainage swales, and wetlands up to the 100-year flood level. The minimum utility easement width shall be 20 feet wide. 3. Type II silt fence must be used adjacent to all ponds and wetlands. A 75-foot minimum rock construction entrance must be added to the entrance that will be accessed during construction. In addition, an erosion control blanket is required for the steep slopes along the north property line of the site. The applicant should be aware that any off-site grading would require an easement from the appropriate property owner. All disturbed areas must be sodded or seeded and mulched within two weeks of grading completion. 4. The remaining utility assessment due payable to the City at the time of final plat recording is $25,477.05. In addition, the sanitary sewer and water hookup charges will be applicable for each of the new lots. The 2004 trunk utility hookup charges are $1,458 per unit for sanitary sewer and $2,814 per unit for water. Each of these charges is based on the number of SAC units calculated by the Metropolitan Council. 5. Public utility improvements will be required to be constructed in accordance with the City's latest editions of Standard Specifications and Detail Plates. Bob Generous November 8, 2004 Page 4 Detailed construction plans and specifications will be required at the time of final platting. The applicant will also be required to enter into a development contract with the City and supply the necessary financial security in the form of a letter of credit or cash escrow to guarantee installation of the improvements and the conditions of final plat approval. Permits from the appropriate regulatory agencies must be obtained, including but not limited to the MPCA, MNDOT, Department of Health, etc. 6. A registered structural engineer must design any retaining walls in excess of four feet in height. This will also require a building permit. 7. Show all of the existing and proposed easements on the plans. 8. Show all of the existing utilities on the plans. 9. The proposed development is required to meet the existing storm water runoff rates for the 10- and 100-year, 24-hour storm events. 10. The walk-out elevation of the proposed homes must be a minimum of 3 feet higher than the adjacent pond or wetland high-water-Ievel. 11. Revise the plans to show a 30-foot minimum curb radius on the cul-de-sacs. 12. On the utility plan: a. Show the proposed storm manhole rim and invert elevations. b. Show the proposed culvert invert elevations. c. Add a note "any connection to existing structures must be core drilled. " 13. On the grading plan: a. Show the benchmark used for the site survey. b. Show all emergency overflow elevations. c. Show all proposed contour elevations. d. Show the location of the 75-foot rock construction entrance. e. Show the retaining wall top and bottom elevations. f. Show the proposed NWL and HWL of the pond. 14. On the plat sheet revise the street right-of-way adjacent to Cartway Lane from 33.5 ft to 43.5 ft. 15. The existing temporary pavement turnaround for Pipewood Lane just south of this site must be removed when Pipewood Lane is extended. Any disturbed area must be sodded and restored. 16. The retaining wall in the rearyard of Lot 8, Block 1 must be 20 feet off the back of the building pad. Bob Generous November 8, 2004 Page 5 17. Add storm sewer and catch basins in Pipewood Lane between Lots 1 and 2. 18. Revise the rearyard grading of Lot 10, Block 1 to prevent trapping water behind the curb. 19. The existing gravel road known as Cartway Lane must be connected to the proposed cul-de-sac at the eastern border of the site. c: Paul Oehme, Public Works Director/City Engineer Matt Saam, Assistant City Engineer. g:\eng\projects\hidden creek meadows\ppr.doc