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HomeMy WebLinkAboutSDP200800114 Calculations 2008-07-14Stormwater Management & Erosion and Sediment Control Narrative Charlottesville Waldorf School Minor Site Plan Amendment to Phase -113) Albemarle County, Virginia July 1-I, 2008 MCKEECARSON CONSULTING ENGINEERS LANDSCAPE ARCHITECTS PLANNERS 301 EAST HIGH STREET ' CHARLOTTESVILLE, VIRGINIA 22902 434.979.7522 tel 434.977.1194 fax 4Vwv" , . nickeecar son.Com TABLE OF CONTENTS Project Descripticm Sturinwatcr N Io(r`,' Erosion and Sediment Control PROJECT I.)ESCRIPTION I7tc proposed miner situ plan amcndmernt is the addition of uctecl on Piers) and a ramp to the Phase 1 -13 ('I)P 2006- 000 -97, a major site plan amendment sllhr7iitt('cl om August 28, 2006) of a Waldorf School Project. Approximately 1, 00 sf (0.03 acres) of impervious areas are added in this proposed development. The proposed Waldorf School is located off of Iio Road in Albemarle, VA. ]nunediatcly to the south of the proposed site is the Village Square residential development. North of the entrance are several residential parcels fronting Rio Road. To the West of the site is Nleadoxv Creel:. And to the east across Rio Road is the Charlottesville Catholic School. METHODOLOGY The existing; Stormwater Management Facility, a retention pond, was analyzed for both water quantity and quality for Charlottesville Waldorf School phase -113 (WPO 2006- 000 -71). The drainage area for existing pond was approx. 5 acre. 1,V111cr Qiialitl in phase -113, water quuality control was achieved through the use of the existing; pond. The total water duality volume requirement for phase -1 B was approx. 1,547 cf (4 X Water Quality Volume) and the existing pond has the water retaining capacity of approx. 5, 334 cf. The new proposed development (in addition to phase -113) requires approx. 433 cf (-I X water quality volume from 1,300 sf impervious area) of water storage for water quality. Thus, pond is sized adequately to accommodate the water quality requirement of the proposed development. 1'VIIICY Q111717tity—as analyzed in WPO 2006- 000 -71, the 2 -vr and 10 -yr runoff in predevelopm ell t conditions was 6.13 cfs and 8.51 cfs respectively. The and 10 -vr post development discharge from the pond was 1.98 cfs and 4.82 cfs. The additional 2 -vr runoff due to the new proposed development is approx. 0.09 cfs(0.03 X 5.2 (0.9 - 0.35)). The additional 10 -yr runoff due to proposed development is approx. 0.11 cfs (0.03 X 6.7 (0.9- 0.35)). Thus, pond is sized adequately to accommodate the water quantity requirement of proposed development. EROSION AND SEDIMENT CONTROL The Erosion and Sediment Control measures proposed in Phase -113 would stay for this proposed development (Please refer WPO 2006- 000 -71 submitted on August 28, 2007). The railing and site disturbance is expected to be minor as the proposed building is constructed oil A note has been placed on the Grading and Utilities Plan requiring contractor to stabilize all the disturbed areas with temporary /permanent seeding and mulch at the end of the each work day. t Stormwater Management & Erosion and Sediment Control Narrative Charlottesville Waldorf School - Minor Site Plan Amendment to Phase -113) —5 50 Albemarle County, Virginia ( w July 14, 2008 MCKEECARSON CONSULTING ENGINEERS LANDSCAPE ARCHITECTS PLANNERS 301 EAST HIGH STREET ' CHARLOTTESVILLE, VIRGINIA 22902 434.979.7522 tel 434.977.1194 fax www.mckeecarson.com l - ABLL: () I CON I LNI S reject Dscripticm Sto rmwater IvIctliod logy Frosioll and Sediment Control PROJFCT DLSCRttT[ON flue proposed minor site plan ainendmeiit is the addition of a modular buildirig { ontili cicted on piers) and a ramip to the Phhase 1 -B (S;L)P ZOOh- 000 -97, a rniajor site plan ameri(iilucnt t,tikwtted on Atwust 28, 200 ()) of a Waldorf School Project Approximately 1.300 4 (0 ), acres) of inihc r ions areas are added lit this proposed deyeloptnent. I'he proposed Waldorf Schc -iol is located off of Rio Road in Albemarle, VA. linmediahcly to the south of the proposed site is the Village Square residential development. North of the entrance are several residential parcels fronting Rio Road. To the West of the site is Meatimv Creek. And to the gist across Rio Road is the Charlottesville Catholic School. METHODOLOGY The existing; Stormwater Management Facility, a retention pond, was analyzed for both water quantity and quality for Charlottesville Waldorf School phase - 1B (WPO 2006 - 000 - 71). The drainage area for existing pond was approx. 5 acre. Writer Qitalitit -- in phase - 113, water qualit}' control was achieved through the use of the existing pond. The total water quality volume requirement for phase -1 B was approx. 1,547 cf (4 X Water Quality Volume) and the existing; pond has the water retaining; capacity of approx. 5, 334 cf. The new proposed development (in addition to phase -113) requires approx. 433 cf (4 X water quality volume from 1,300 sf impervious area) of water storage for water quality. Thus, pond is sired adequately to accommodate the water qualitN' requirement of the proposed development. 6/'VWcr Qittmliti/ — as analyzed in WPO 2006 - 000 -71, the 2 -yr and 10 -yr runoff in predevelopmerit conditions was 6.43'cfs and 8.51 cfs respectively. The 2 -yr and 10 -yr post development discharge from the pond was 1.98 cfs and 1.82 cfs. The additional 2 - yr runoff due to the new proposed development is approx. 0.09 cfs(0.03 X 5.2 (0.9 - 0.35)). The additional 10 -yr runoff due to proposed development is approx. 0.11 cfs (0.03 X 6.7 (0.9- 0.35)). Thus, pond is sized adeguuately to accommodate the water quantity requirement of proposed development. EROSION AND SEDIMENT CONTROL The Erosion and Sediment Control measures proposed in Phase -113 would stay for this proposed developmert (Please refer WPO 2006- 000 -71 submitted on August 28, 2007). The grading and site disturbance is expected to be minor as the proposed building is constructed on piers. A note has been placed on the Grading and Utilities Plan requiring contractor to stabilize all the disturbed areas with temporary /permanent seeding; and tnulch at the end of the each work day.