05-10-1999 Council Packet - Laserfiche WebLink

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site designer has been in contact with the City's On-Site Septic Systems Manager, Steve Weckman. Staff will attach a septic report as an Exhibit to this report when it is available. ACCESS The preliminary plat has been reviewed by the City Engineer. The proposed location for the private road appears acceptable. It has been sent to Hennepin County for review. The proposed street section will need to be 28* to meet city standards because the number of units to be served exceeds 7. Water from the private road shall ^ diverted from Old Crystal Bay Road (County Road 84). GRADING There is an existing ditch on this parcel which serves as a drainage way for a pond. A driveway for proposed Lot 3 may cross this ditch. If so, it should not impede flows through the existing ditch. The final plan needs to identify all structures to be removed. A grading and erosion control plan should be submitted for the entire site for review. Erosion controls should be in place before any grading to protect the wetland. Erosion control measures will be required during construction of the houses emd septic sites. DRAINAGE The site is located within the French Lake Drainage district. The site drains southerly to an existing wetland along the south edge of the site. Storm water drains to the wetland from the north to the south. The flow from the north is routed through an existing ditch. Ditch stabilization may be required if the flow will continue to route through it. An alternative would be to install storm sewer to convey flows from north of the site to the stormwater management pond. The pond would need to be sized if this is the proposed drainage method. There is a 36" pipe for a southerly outlet of the existing wetland. The city's proposed stormwater management plan states that water quantity may be a problem downstream and recommends restricting the size of the pipe to 27". Reducing the outlet pipe would result in a reduction of the rate of stormwater downstream but would increase the high water level of the wetland to 966. The City Engineer will need to review the wetland outlet sizing after a drainage area map, storm sewer, and ponding calculations are provided. The calculations should be based on the total drainage area that flows into the wetland. The plans will need to be submitted to the Minnehaha Creek Watershed District (MCWD). EASEMENTS The City Engineer has recommended that a 10 ’ trail easement be dedicated along the west property line adjacent to Old Crystal Bay Road. Internal and perimeter drainage and utility easements shall be provided 5' along all interior lot lines and 10' along perimeter lines. Drainage easements shall be #2477 Stickney 250 & 340 Old Crystal Day Road South Subdivision PC-4/19/99 page~6