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HomeMy WebLinkAboutWPO201400074 Correspondence 2015-01-20 r.r SAIMP PROJECT MANAGEMENT CIVIL ENGINEERING LAND PLANNING ENGINEERING a January 20, 2015 Mr. Glenn Brooks Mr. Max Greene Regarding: SDP 2014-00074- Riverside Village WPO Plan Dear Mr. Brooks and Mr. Greene, I have attached 2 copies of the updated WPO plan and calculation set. Your comments and the changes we have made in response are below. Rev. 3:Please provide the SWPPP amendment. The updated SWPPP is attached to this submittal, with scans of the inspection logs and PPP. Rev. 3:Biofilter C:Inlet placement has short-circuited this facility. Curb cuts must be designed as curb inlets with not depression, and have outlet protection. The gabion baskets need a foundation, usually baskets are entrenched and stacked. Structure A4C and the detention pipe are drawn incorrectly and the wrong sizes. Biofilter B: This structure ponds too deeply for safety. The 24"pipe in the section appears incorrect. The gabions need a foundation, and the inlet pipe needs outlet protection. Provide anti-clogging measures. Specify excavation side slopes on sections. Biofilter C: Pre-treatment has been re-designed per the meeting on January 15. Pre-treatment is now achieved with a gravel diaphragm along the edge of pavement. The curb has been removed next to Biofilter C. Structure A4C has been updated in the biofilter cross-section to be shown consistently with the plan and profile views. Biofilter B: This BMP has been re-designed to keep the 10-yr maximum ponding depth below 2.0'. The 24" pipe has been re-drafted to include the connection to A2. The gabions now are shown as entrenched and stacked, and B1 now discharges into a rip-rap pre-treatment cell. The 3"orifice on structure A2 now specifies a pile of stone to prevent clogging. Side slopes on the sections of biofilter mix and gravel and now specified at 1:1. If you have any questions, please do not hesitate to contact me at your earliest opportunity. I may be reached at: Justinshimp-engineering.com or by phone at 434-953-6116. Best Res- p Ahh, stin Shimp, P.E. Shimp Engineering, P.C. • SH' IMP PROJECT MANAGEMENT CIVIL ENGINEERING LAND PLANNING ENGINEERING December 1, 2014 Mr. Glenn Brooks Mr. Max Greene Regarding: SDP 2014-00074- Riverside Village WPO Plan Dear Mr. Brooks and Mr. Greene, I have attached 2 copies of the updated WPO plan and calculation set. Your comments and the changes we have made in response are below. VSMP Comments: 3. Please revise the drawing to accurately reflect a forebay weir. The weirs shown do not appear sufficient. Perhaps Gabion baskets might work better in this situation, as a proper stone weir might take up too much space. The biofilter itself should not be part of the forebay area, so would not have media. In the case of facility C, it might be easier to fry and establish sheet flow into the facility and just a grass and stone entry similar to the examples in the VSMH. The forebays have been re-designed to use gabion baskets and to be 0.5' above the treatment elevations. One of the forebays in BMP C has been eliminated, as we found the VSWMH allows grass channels to serve as biofilter pre- treatments. Erosion and Sediment Control Comments: Thank you for the pipe profiles, however the outlet protection for Al could not be found on the profiles. The outlet protection for Al has been added to the profile. 3. Site conditions have changed. VDOT reports pipe could not be sleeved with 60"round pipe as proposed. Existing pipe is reported to be an old elliptical CMP. Please show new proposal for pipe repair under State ? Route 20. The plan and profile for the culvert extension have been updated to reflect field conditions. 6. Plan has a triangle with the#4 in it and states Sanitary Sewer MH Top 322.16. Please change the benchmark legend on the first page to match the benchmark location and datum on the plan sheet. ✓ The benchmark legend on the first page has been updated to match the benchmark shown on the plan. 9. Please show how site is protected from soil loss during the basin#1 conversions from Phase 2 to Phase 3; appears to require a complete re-construction of the basin. It appears the site will not be protected during 0K, conversion. Will the contractor use pump-around systems and filter boxes or filter bags? Site will need to be completely stabilized prior to final conversion. As discussed in our last meeting, a note has been added to C22 regarding the timing of the conversion of basin#1 to minimize the possibility of soil loss. 5: p hA�L� ca„vtas:0.4" �2v,M p )se 21 To p hAsi j� u• I( h- Po{- 401 (/to Led ,` „vokk s rve 4 C1pl.tjed PIL ' `Q - c, RSf A#ir` Ca !I GUE4A av04" CerJtrs;o- .n 10. As mentioned in our last meeting for this site;the proposed stormwater system D1 to D2B appears to be filled with water during a storm event and partially during the normal conditions pool elevation. The D1 pipe will be under water. The site work elevations do not appear to allow for the system to be elevated to resolve this issue. Can the system be installed at a later date after the site is deemed stabilized? Can an armored swale be installed until the phase 2 portion of the site is developed? As discussed in our last meeting, a note has been added to C22 requiring the contractor to regularly inspect and clean the pipe line to ensure that it is clean prior to the installation of the infiltration trench. e proposed contours on Sheet C22 do not appear constructible. The areas around the proposed basins do not appear to work until the final design is constructed. Please show that all phases of construction work and will not be cause for site delays due to constructability issues that may arise. The drafting of the contours has been updated to show that basin#2 can remain in place until Trailside Court has been graded and stabilized. ,X2. Inspection department has requested silt fence along the backs of curb or sidewalks to keep stormwater from flowing into the roads prior to final stabilization. This is only for the up-slope sides of the roads. Silt fence has been added to the back of the sidewalks that are uphill of Trailside Drive. /i3. The right-hand road stub-out should have a right-or-way diversion installed to prevent stormwater from flowing into the road. A right-of-way diversion has been added to the right-hand road stub-out. i/614. Please show a diversion or RWD into basin#1 for the road/turn-lane construction to capture as much of the site work as possible. A RWD has been added for basin#1 to capture flows from the Route 20 expansion. If you have any questions, please do not hesitate to contact me at your earliest opportunity. I may be reached at: Justinashimp-engineering.com or by phone at 434-953-6116. Best Regards, 7/ stin Shimp, P.E. Shimp Engineering, P.C.