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Bonestroo Rosene Anderlik & 1 Associates Engineers & Architects September 15, 1999 Mr. Paul Weinberger Zoning Administrator/Planner City of Orono Post Office Box 66 Crystal Bay. MN 55323 Re: Willow View Subdivision File No. 139GEN-2522 Sc^etT’JO Arae*'»<t tnc ts .nr Cppor[vn$r/ irrs c/e* .“*• r: o.ns C::z G 3ore.:rc3 • Joiesn c Ance'b>i ?£ • r* t Scr/^tj PE • Cif*''* ^ Coo* ®E • "^cCe'C G SC^unirnt. P£ • A Bou^dor p£ • Hzztn i?oxe'*tf. P6 P E Turne*' P£ #r*o Susjn M EOer»«r. CPA . Ser s* Consultants Asscc^jee Prrc pjni Howard A Sanford. P£ • Kenn A Gordon. P£ • .?oocrt ^ Pfefferie. Pi. • ff.:-ard u/ Foste'' P£ • David O Losicota. P£ • f?oo<rt C. Russet. Ai A • Mart A Hanson. Pi • V*craS*drey P Vfc'.i:ian*son. Pi. l S • Rocert F Kctsmiin • Agnes M Ring • Allan R<ct Senmidt. P£ Cf* its St f'aui. Rocr*ester M/ iirrtr and St Ctoud. VN • Miiwac«ee. Wi wwwocnesrroo :om Dear Paul: We have reviewed the preliminary grading and utility plan for the proposed 49 lot Willow View subdivision. The site is located west of Willow Drive and south of County Road 6 in the southeast quarter of Section 28. We have the following comments in regards to engineering matters. 1. Sanitary Sewer: The preliminary sanitary sewer design appears acceptable. It should be noted that the proposed temporary bypass lift station along T.H. 12 needs to be in place before sewer service can be provided to the Willow View site. Final plans should include plan and profile views of the proposed sewer, sewer service locations and sanitary sewer details. Sanitary services should be located 3*feet downstream from water services. All sanitary and storm sewer manholes are required to have an exterior sealing sleeve as manufactured by Infi-Shield or an approved equal. Any connections to existing manholes shall be core drilled and a rubber boot installed. 2. Water Main: The proposed water main shown between Lots 12 and 13, Block 3 should be extended westerly and tied into the 12-inch water main installed as part of the new Orono Middle School project. The water main alignment should coincide with the utility easement on the school property located just south of the soccer fields. We also recommend extending the 8-inch water main northerly to the intersection of Willow Drive and County Road 6. This will allow for a futtire connection to the City of Medina’s water system. Final plans should include plan and profile views of the proposed water main, water main details and service locations. All water main shall be poly wrapped. 3. Grading: We recommend that the lowest basement elevations be at least 2-feet higher than the high water level (HWL) of the closest pond. Proposed basement elevations on some lots on Blocks 1,2 and 3 do not provide this 2-feet of freeboard. We would recommend revising the grading plan or basement elevations to allow a minimum of 2-feet of freeboard. It appears that ponds located in Outlet C will flood the property to the south when they reach their HVM-. We recommend revising the proposed grading plan so tha; ponded water is contained to at least 0.5-feet above the HWL. Block 5 appears to have a low, landlocked area behind the homes. This will result in drainage problems and additional storm sewer may be necessary. An erosion control plan should be submitted for review. 4. Siorm Sewer: The draft version of the City’s Surface Water M.tnagcment Plan (SWMP) shows that this si e lies within the Long Lake drainage district. The proposed grading plan shows ponding throughout the sire. It is unclear how all of the ponds are supposed to function. None of the ponds has an outlet shown. The pond in the northwest comer of the site has no inlet or outlet shown. The pipe shown between Lc's 6 and 7, Block 3 outlets to a wetland. All stonn sewer should outlet to a ponding area. All ponds should meet NURP standards. Ponds should have a 10:1 aquatic bench at the pond’s normal water 2335 West Highway 36 ■ St Paul. MN 55113 ■ 651-636*4600 • Fax: 651-636-1311