07/08/2020 P&Z Packet - Laserfiche WebLink

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Ms. Katie Larsen 7/012020 Page 4 Comments: 1. Pond 100 is discharging to a private ditch, which should be coordinated with the Rice Creek Watershed District and the City of Centerville. Discharge location is being verified with developer. Plunge Pool Energy Dissipator has been added to discharge location per discussion with watershed district and City. See comment 9 regarding the plunge pool energy dissipator design. Straight pipe has been approved by neighbors. Plunge pool is no longer needec 2. Sections of the storm sewer are located directly beneath the overhead powerlines and should be relocated. Revised. The storm sewer needs to be offset at least 20' from the proposed structure on Lot 5 Block 4. Per discussion, the storm sewer line has been raised as much as possible (0.5-feet). The pipe near the proposed structure will be approximately 9.3-feet below garage elevation. Would an open grate catch basin in place of the FES allow the storm pipe to be shallower between STMH 300 and CBMH 132? 3 Adjust storm c r that a ently rums thre gh Outlet G se that it fellevuo the a rh RLQ-0s;LQd NlA4Q that On Ar&r tA fAme sterm sewer to fellow the c;- -ph fAr eRtiFety OR this let, 2 additieRal StFUGtWeS would be required. G-atr--.h basin rneved further nerth te- red-i-Irue the assurned- future easGITIeRt in a petential fFGRt yard 4. The storm sewer that is part of the rear yard drainage system for Lots 6 & 7 of Block 2 is too close to the future houses. Applicant shall move the storm sewer to the west while maintaining a 20-ft offset from the overhead power line. Storm adjusted further back. Note that 20 feet from overhead power is not possible given the maintenance access location and the need to revise a storm manhole to a catch basin manhole for drainage purposes. We are still concerned that the storm sewer is too close to the proposed structures for Lots 6 & 7 of Block 2. Catch basin moved further to the north and to the west. 20-feet from the powerlines and 50-feet from the building pad. Moved as far west as possible. A 4:1 slope from the site boundary limits how far the catch basin can be pushed west. The storm pipe is now 45-ft min. from the building pad on Lot 7 Block 2. The applicant should extend the stub street further -5' to keep the pipe more parallel to lot lines. 5. The RA-Irth army.f wetlands An the figures sheuld hp ';;hplpd North arroi.y revised. \A/etlan.d line addled to legend R C B 50 added 7. HydrerAD rnedel updated to match grading plan 8. G1350) should be rne-d-eled- -;;R- -;; r--.-;;tr--.h basin 'R HydreGAD ("PeRd with *RS*gR*f*GaRt sterage"). if they are of freeboard from the low entry in the 100 yeaF oterm event), Revised to ponds with insignificant storage. Note th-at C-B v.(-As modeled as ponds to determine 9. Plunge Pool Energy Dissipator grading requires revision. The bottom of the plunge pool grading of 891.5 has no width in the middle of it and grading is not feasible. Recommend at least 4-feet bottom width to avoid erosion of slopes of pool. Confirm riprap size used at riprap check and overflow. Recommend a detail or notes regarding width and depth of riprap check and overflow, and note on how riprap size was determined. Straight pipe has been approved by the neighbors. Plunge pool is no longer needed. See WSB response under Stormwater Management, Comment 1. 10. Drainage Area S-10 is shown to flow to W-10. S-10 includes area east of Lots 12-20 of Block 4. Confirm the drainage path for flow to pass from south to north under proposed Red Oak Lane. Culvert to be installed under Red Oak Lane to maintain ditch flow. Developer is checking with homeowner to obtain easement to install culvert. The applicant needs to obtain a temporary easement or right -of -entry prior to construction in order to complete grading work that appears to extend beyond the right-of-way. Nadeau Acres Engineering Review