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BOLTON 2638 Shadow Lane Suite 200 & M E N K Chaska, MN 55318-1172 Real People.Real Solutions. Ph: (952)448-8838 Fax: (952)448-8805 Bolton-Menk.com November 2, 2017 City of Orono Attn: Adam Edwards 2750 Kelley Parkway Orono, MN 55356 RE: #2017—01341 1020 Mooney Lake Drive Engineering Review#1 Dear Adam: As requested, we have completed an engineering review of the documents submitted for the above referenced project. We offer the following observations, comments, and recommendations for your consideration: 1. As part of development of Mooney Lake Preserve, each individual lot(except Lots 4 & 8, Blk 2) must provide stormwater management facilities capable of restricting proposed peak runoff rates to that of existing and retaining a volume equal to 1"over new impervious surfaces on site. The rain gardens proposed to provide stormwater management are more than adequately sized to meet requirements. 12. Drainage and Utility Easements should be revised to adequately cover stormwater management facilities used to meet governmental requirements, including access to the outlet control device. 3. Perimeter erosion control measures and protection fencing should be installed by the Contractor and inspected by City prior to any land disturbance. Contractor must provide 24 hour notice prior to inspection. 4. Biologs should be installed in swales after grading is complete to limit potential for erosion prior to establishment of vegetation. 15. Erosion control blanket should be installed on all slopes of 3:1 to limit erosion potential. 6. The applicant should consider earth overflows reinforced with Turf Reinforcement Mat in lieu of the proposed 0.5' weirs for the rain garden outlets. The basins appear to be sized adequately to accommodate a larger outlet, and the earth overflows may appear more aesthetically pleasing than hard infrastructure. In addition, the larger outlet would provide for less concentrated flow and thus less potential for erosion. ../7. The culvert indicated under the driveway to direct flow to the entrance rain garden should have a minimum 12"diameter to limit potential for clogging. 8. The proposed contours on the west side of the entrance rain garden should be revised to ensure runoff does not bypass the facility. A minimum 12" depth in the swale should be provided leading to the rain garden to limit potential for bypass. v9. The proposed contours on the north side of the east rain garden should be revised to ensure runoff does not bypass the facility. The 995 contour should be indicated closer to the rain garden to eliminate potential for bypass. H:\ORNO\C13113299\2017-01341-1020 Mooney Lake Drive\1020MooneyLakeDrive-1.docx Bolton&Menk is an equal opportunity employer.