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desel From; Sent:; To: Cc: 5ubje+ Attact Tyler Maxson <Ty€er.Maxson@westwoodps.com> Tuesday, July 31, 2018 931 AM Tom Rledesel Daniel Parks Gem Lake Hy-Vee Plan Changes and Watershed Approval 18-15 Permit Withheld Letter 7-42-18.pdf TOM; ! Here's the list of changes that the watershed requested of us, which should be ail of the changes that were made to the plans: i. !f 1; Submit revised model using the MRCS. MSE3 rainfall distributions. j • We Have changed therainfall distribution. Could I ask why this is requiredlwhere that is t communicated? We almost always use Type1I and don't see where MSE3 is required in the rules. 2.1 Filtration rate used does not match the District's design rates. Based on soil borings, 0.8 ln�hr should be used. E The HydroCAD model's filtittion.rate has been adjusted to 0.8 in/hr. 3.,When using 0.8 lit/hr, the maximum ponding depth Is 1.6 feet. Revise ponds 2 and 3 such that they draw down within 48 hours, Shouldn°t this number be 3.2. feet (0.8 inlhr * 48 hr 1 ] 2.inlft w 3.2 ft)? If -so, we meet this r I drawdown requirenlent. 4.1 Update 1GO-year HWLs on the plans for the proposed filtration BMPs once revisions are complete. Dome Provide detailed print-out of storage curve from HydroCAD to confirm reported storage. volume. v Done and included in the report. 6. Revise the overflow elevation for the south pond: The detail shows 9W.31 while the model uses 960.21, This has been fixed. 7'.€ Revise pipe invert.fQr the south pond. The. plans show 956.5 while the model uses 956.29. e This has beei3 fixed. 56rrs ' pf these Issues were regarding the stormwater narrative or the stormwater model but may have caused small grad..ing changes to the ponds. [also. ttached the watershed's conditional approval letter permit. Aleas l let me know if you have. any more questions. Thanks, Tyler' 3 Tyler.Maxson GRAIWATE ENGENEER tyter, m a�son@wo slwood ps.co m Direct' 052) 697Z748 Ma?n : € (952)937-5150 1