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Resolution Exhibit C <br /> • <br /> 6835 <br /> BO LTO N 2638 Shadow Lane <br /> Suite 200 <br /> & M E N K Chaska, MN 55318-1172 <br /> Real People.Real Solutions. Ph:(952)448-8838 <br /> Fax:1952)448-8805 <br /> Botton-Menk.com <br /> January 9, 2018 <br /> City of Orono <br /> Attn: Jeremy Barnhart <br /> 2750 Kelley Parkway <br /> Orono,MN 55356 <br /> RE: Preliminary Plat Application 18-3999 <br /> Southways Addition <br /> Engineering Review#1 <br /> Dear Jeremy: <br /> As requested, I have completed an engineering review of the documents submitted for the above <br /> referenced project. In addition,Adam Edwards has provided comments for inclusion with this review. <br /> We offer the following observations, comments,and recommendations for your consideration: <br /> 1.0 GENERAL: <br /> 1.1 Stormwater management for the site to meet regulatory requirements is proposed through use <br /> of wet retention basins. The following should be considered regarding the proposed system: <br /> a. Volume control and water quality measures must be provided as well to meet NPDES <br /> requirements. Plans should be revised to include volume reduction equal to 1"of runoff <br /> from the new impervious surface. If infiltration is considered infeasible, other methods of <br /> volume reduction must be considered. It appears that there are sufficient areas high <br /> enough above the water table to provide localized filtration practices or amended soils. <br /> Also,the overall estimate of Total Suspended Solids(TSS)and Total Phosphorus(TP) <br /> from proposed improvements must be reduced from pre-project conditions. Calculations <br /> detailing volume control and water quality compliance must be submitted for review and <br /> approval. If the applicant pursues a design with less than the normally required infiltration <br /> volume,sequencing of design to provide treatment to maximum extent practical must be <br /> provided. <br /> b. An Outlet Control Structure(OCS)that provides skimming must be installed on the wet <br /> retention ponds in order to keep floatables in ponds. The following should be considered <br /> regarding OCS design: <br /> i. The inlet pipe from the pond to the OCS should be submerged with back slope from the <br /> OCS to the pond to facilitate maintenance. The normal water level should be <br /> controlled by a weir in the structure or the outlet pipe. The inlet pipe should be one <br /> nominal size larger than the outlet pipe to limit flow control and turbulence at the pond <br /> interface. <br /> ii. A sloped rim should be utilized,per City Standard Details,with the bottom of the rim <br /> placed at the predicted 100 year high water level. <br /> iii. A trashguard should be installed on the outlet pipe. <br /> c. Wet retention basins must provide a minimum 1800 cubic feet per acre of drainage area. <br /> The stage-storage curves for permanent pools must be submitted for review to verify <br /> H:\ORNO\C13115486\z-18.3999_Brackets Point\Southways_PrePlatReview-1 2018-01-09.docx <br /> Bolton&Menk is an equal opportunity employer. <br />