10521 19TH AVE SE 2022-05-23 - Laserfiche WebLink

• 0 Sabrina Fandler From: Erik Emerson Sent: Wednesday, March 28, 2018 4:56 PM To: Sabrina Fandler Subject: Silver Plaza - Review Comments for March 2018 Resubmittal Follow Up Flag: Follow up Flag Status: Flagged Sabrina, Robin and I have finished reviewing the latest submittal for the Silver Plaza project and have the following comments:- Drainage Report �Z) C t�P(E S w �1��%n✓ � /eL� 7�� V'�K /. S,Wft � SAiAr DkI 1. Update the table of contents. 2. Permanent Stormwater Control Plan o This section was added in the updated Drainage Report, but all of the information required per Volume I, Section 3.1.5 of the Stormwater Management Manual (SWMM) is not provided. o See Volume I, Section 3.1.5 of the SWMM for complete documentation requirements. R_ Fxhihits o Vicinity map — Missing: the route of stormwater to Silver Lake (provided instead on separate aerial map, which is not a required exhibit) and discussion or illustration of significant geographic features and sensitive/critical areas. o Site map - Missing: drainage from the site; routes of existing, construction, and future flows at all discharge points; length of travel from the farthest upstream end of the proposed conveyance to the proposed flow control and water quality treatment BMPs. o See Volume I, Section 3.1.7 of the SWMM for the complete listing of documentation requirements. 4. French Drain sizing calculations: o Manning n of 0.011 used for PVC pipe, but the value for PVC in DCSS Table 4.2.2(3) is 0.013. o PVC pipe sizing calculations were provided, but calculations and design details need to be provided for other components of the French Drain. 5. Minimum Requirement (MR) #6 — Runoff Treatment o See comments below for Sheet 6. 6. MR #7 — Flow Control o Delineate and map the extent of the flow control bypass area and call out the acreage on one of the maps provided. o The minimum orifice size provided of 0.45 inches is lower than the allowed minimum orifice size of 0.5-inch. This smaller orifice size may be allowed if the live storage were reduced to 3 feet in accordance with Volume III, Section 3.2.4 (Control Structures) of the SWMM. o WWHM modeling to size the flow control facility must properly account for dead storage. 7. MR #8 — Wetland Protection o If true, modify text to state that the project site does not discharge to wetlands upstream of the Silver Lake receiving water. The 300-foot threshold described in the Drainage Report does not apply to this minimum requirement. 8. MR #9 —Operation and Maintenance o Updates were made in the Drainage Report to satisfy the City's comments in their January 2018 letter, but those updates were not included in the stand-alone O&M Manual. Update the stand- alone 0&M Manual accordingly. CXJ2