03-23-1998 Council Packet - Laserfiche WebLink

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Bonestroo ^ J Rosene ■ Anderlik & Associates Engineers & Architects Match 19, 1998 Mr. Michael P. Gaffron Senior Planning Coordinator City of Orono Post Office Box 66 Crystal Bay. MN 55323 Re: Andersen Subdivision File No. 139-2321 Dear Mike; Bonnt'CO Rcsene Anderhk ,tnd Assoa-tees Inc n An Alfirm.irvc Action fiju.i/ Opportunity employe’ PrinciDAls C.to G Bone-.troo, PE • JO»«ph C AnOe^lik. PE • Mitrvin L Sorv.lM PE • PicnardE Turner PC • Glenn R Cook PE • Robert G Scnumcr't. PE • Jerry A Bourdon. PE • Robert W Roiene. PE and Susan V Eberlin C PA Senior Consultants Asiocuite PrincipAls Ho.vard A Santord. P? • Keith A Gordon PE • Robert R Pfefferle. PE • Richard ‘M Foster. PE • Dawid O Loskota PE • Robert C Rusiek A I A • Mark A Hanson. PE Michael T Rautmann PE • Ted K Field PE • Kenneth P Anderson, PE • Mark R Rolfs. PE • Sidney P Williamson. PE , L S • Robert F Kotsmith Officei St “aul Rochester Willmar and St CiOud MN • Mil'.v lukee. Wl C 's*\:' vjr Yesterday we received a mailing from Otto and Associates that included a preliminary plat, drainage calculations and a grading plan for the proposed seven lot Andersen subdivision. The site is located west of Old Crystal Bay Road South (C.R. 84) in the northwest quarter of Section 9. We have reviewed the submittal and observed that the plans and calculations contained some errors and omissions. The grading plan shows a storm water pond in the eastern corner of Lot 7. It appears that the poiul irjip. lutherly to a wetland on the east end of Maxwell Bay. The draft version of the City’s Surface Water ManagenR iii P»., ^SWMP) classifies this we-'and as being moderately susceptible to nutrient and sediment loading. We rerommend that pond cakulatioiis be submitted that identify both pre and post development peak flows and nutrient loading... In accordance with Lie SWMP ar.-.i to protect the downstream wetland, post development flows and nutrient loadings should not exceed pre tleveliipir.ei;: conditions. Wc al.so recommend that the following information be submitted or corrected: • A detailed drainage area map clearly showing pre and post development drainage areas, size of areas, runoff coefficients used and any assumptions used in the calculations. • Calculations showing pond sizing to meet NURP standards for the drainage area reaching the pond should be provided. The calculations submitted show that the pond is sized to treat the entire site (17.5 acres). • Corrected pool volume calculations. The contour areas provided in the calculations do not match the pond contour areas as measured on the drawing. • The pond should ha'. e :» 10:1 bench at the pond NW'L to provide a barrier of safety. • The Ftorm sewer design should be clarified. Do flows from CBMHI go to CBMH2 and then to MH1 ? Plans should show pipe si:'.es, pipe length and grade. • Storm sewer calculations should be provided to verify the proposed design. • Outlet slructu'c details and design should be provided. • A revised plan set should be submitted that shows specifically where the downstream drainage from the pond goes. If tl.e City choose.s to construct the trail south of the Luce Line on the west side of Old Crystal Bay Road, it is our recommendation that the trail be graded along the ea.>.t edge of the Andersen property as part of this project. Please contact me .t. (tH)4-4863) if you have any questions regarding this matter. Yours ver, truly. BONES rUOO. ROSENE, ANDERLIK & ASSOCIATES. INC. /07^ Tom Cc: Greg Gappa, City of Orono 2335 West Highway 36 ■ St. Paul, MN 55113 ■ 612-636-4600 ■ Fax; 612-636-1311