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if <br />Memo <br />Bonestroo <br />Rosene <br />Anderlic4 <br />Asfoctaces <br />CiiflMCrt 4 A k Mmcu <br />Projfeet Nann: Trinity Lutheran Church <br />To: Tom Kellogg <br />Rom: Lance Hoff <br />Ro: Drainage Review <br />Client: CItyofOrono <br />File No: 139-05-000 <br />Dale: 9-14-05 <br />Engineer. BKBM Engineers. MPLS <br />Submittai: Drainage Calculations, Rational Storm Sewer Design Calculations. Plans <br />Plan Sheets: Grading and Drainage. Storm Sewer, Details <br />Date of Plans: 9-6-05 <br />Date Received: 9-12-05 <br />1; <br />Summary of Recommendations <br />Based on our review of the Trinity Lutheran Church site, we offer the following comments. Grading and <br />drainage are generally good. Rato control requirement has been met for the site. The storm sewer has <br />been adequately designed. The only comments are In regards to water quality treatment, which has not <br />been addressed by the plans. Comments follow below: <br />1. The pond should be modified to include water quality treatment for the entire site. Treatment <br />should satisfy NURP requirements (wet volume equal to the runoff generated during a 2.5" <br />rainfall event). Our calculations show that 0.315 ac-ft of wet storage must be provided. <br />2. A10’ wide aquatic bench with slopes no steeper than 10:1 must be provided immediately below <br />theNWL <br />3. The pond outlet structure must be modified to provide skimming. <br />4. The pond inlet and outlet should be separated as much as feasible to prevent short circurting. <br />5. The pond EOF should be shown as armored to prevent erosion. Riprap or properly installed <br />permanent erosion control mat would be acceptable. <br />1 M <br />• ■ ■■ ' V; • <br />t ' ‘a <br />BoMttne, MMWMb AndwMwitf A mocMm. he.www.bonrnstroo.com