Grading Plan and Stormwater management plan

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r Highway w St.P St.Paul,MN 5511 13 'il ff lO Tel 651-636-4600 Fax 651-636-1311 www.bonestroo.com May 28, 2009 Bonestroo Melanie Curtis Planning &Zoning Coordinator City of Orono Post Office Box 66 Crystal Bay, MN 55323 Re: 2687 Wayzata Boulevard File No. 000139-09000-2 Building Permit No. 2009-00122 Dear Melanie: We have reviewed the grading plan and stormwater management plan dated 5-19-09 for parking lot expansion and rain garden at 2687 Wayzata Boulevard. Our review includes a compliance check for Chapter 79 of Orono's Land Use Code. We have the following comments: • Concrete curb and gutter should be installed around the perimeter of the parking lot. • The discharge rates for the rain garden (4.63 cfs 10-year and 6.79 cfs 100-year event) exceed those of the existing conditions (2.96 cfs 10-year and 4.50 cfs 100- year event). All runoff rates for proposed conditions should be less than or equal to existing condition rates. • Geotechnical reports for the adjacent Crystal Bay Business Center indicated that parking lot pavement sections include a 12-inch select granular, 6-inch aggregate base, and 3-inch bituminous pavement section for normal duty pavement. Heavy duty pavement (drive lanes of the parking lot) was to have 24-inches select granular, 8-inches of aggregate base, and 4-inches of bituminous. We would recommend using these pavement sections or have the applicant submit a geotechnical report stating that the 6-inch aggregate base and 2.5-inch bituminous is sufficient. • Draintile should be provided for the rain garden. • The applicable code section is 79-7(c)(2) for all commercial or industrial sites in which land disturbance activities fill or excavate more than 100 cubic yards. • To bring this submittal in to compliance with the ordinance, the following information should be provided separately or on the grading plan. o Phasing plan. A phasing plan shall be provided that clearly indicates the areas in the order they are to be disturbed and restored. The phasing plan shall consider minimization of area and duration of exposed soil and unstable conditions, minimization of the disturbance of natural soil cover and vegetation, erosion and sediment control measure installation, weather conditions and the schedule for temporary and permanent restoration. The area and duration of each phase shall be indicated on the plan.