Loading...
HomeMy WebLinkAboutWPO201800084 Calculations 2019-05-21GEMENT SHIMP PRO CI LAND PLANNING ENGINEERING ENGINEERING May 21, 2019 Mr. John Anderson Department of Community Development 401 McIntire Road Charlottesville, VA 22902 APPROVED by the Albemarle County Community Development Department Date 06/11/2019 File WP0201800084 Regarding: WPO 201800084 Royal Fern Phase 2 SWM Calculation Packet Dear John, Enclosed is the stormwater calculation packet for Royal Fern Phase 2. This is development will occupy a site that has an area of 8.55 acres. The disturbed area is 8.70 acres. The proposed stormwater design meets the runoff requirements set forth in 9VAC25-870-95 as the Part IIC regulations are applicable to the project per 9VAC25-870-47. After research of the approved site plan for Sterling University Housing (SDP 200100129), it was determined that the storm sewer which conveys runoff from the Royal Fern Phase 2 site (T.M. 76 P. 46A & 54) drains into the wet pond on the adjacent Cavalier Crossing Apartments property (TMP 76-54A1). This pond was designed to manage and beat runoff from a fully -built Royal Fern Phase 2 site, listed in the approved SWM calculation packet for SDP 2001000129 as the "western residue of the Heischman property". The pond was designed under VA Part IIC regulations. This design included storm sewer construction on the Royal Fern Phase 2 site. Construction was completed before 2014 while the Part IIC regulations were still in effect as the governing VSMP ordinance. Per 9VAC25-870-47 (B), "Land -disturbing activities that obtain an initial state permit or commence land disturbance prior to July 1, 2014, shall be conducted in accordance with the Part 11 C (9VAC25-870-93 at seq.) technical criteria of this chapter. Such projects shall remain subject to the Part 11 C technical criteria for two additional state permit cycles." Only one permit cycle has completed since the pond was approved, so Part IIC regulations are applicable to the Royal Fern Phase 2 project. Since the Royal Fern Phase 2 site falls under Part IIC regulations, and since the pond to which site runoff shall drain was designed to treat a fully developed site, the Royal Fern Phase 2 project must be constructed within the original pond design parameters to achieve SWM compliance. The proposed design for Royal Fern Phase 2 has less onsite impervious area than the original drainage area used for the pond design, so nutrient treatment and downstream natural channel requirements are satisfied. The proposed design for Royal Fern Phase 2 directs runoff into the storm sewers constructed under SDP 2001000129 at rates that do not exceed the capacity of the system, so manmade channel requirements are satisfied. Overall Pond Adequacy. Total Drainage Area Original Design Assumption vs. As -built Conditions The pond was originally approved with SDP 2001000129 to treat a total area of 60.26 acres @ CN=89 (ref. SDP 200100129 "SWM and BMP Report, Sterling University Housing" sheet 6). The pond was revised with WPO 201500094 and expanded to treat runoff from an additional 12.46 acres, increasing the total drainage area to 72.72 acres @ CN=88 (ref. WPO 201500094 "Fifth Street Place VSMP Plan" sheet SWM-10). To identify if the pond remains adequate, the current total as -built drainage area to the pond was re -analyzed. This was compared to the current approved design listed in WPO 201500094. SDP 200100129 Design WPO 201500094 Design Current As -Built Conditions Drainage Area 60.26 Acres 72.72 Acres 71.83 Acres Curve Number (CN) 89 (63% Imp.) 88 (63% Imp.) 78 (45% Imp.) This analysis revealed that the current drainage area is 71.83 acres @ CN=78. This is 0.89 acres less than the current design drainage area of 72.72 acres, and has a lower curve number due to less actual impervious area than assumed in the original design. This reveals that the pond is still adequate for the total drainage area and can safely manage the peak runoff from this area. Onsite SWM Hydraulic Comparison: Pond & Storm Sewer Design Assumptions Vs. New Plan Conditions WPO 201500094 did not change the land cover assumptions used for the Royal Fern Phase 2 site, and since the land cover assumptions for this area were more clearly listed in the SWM calculation packet for SDP 200100129, we have compared the proposed plan condition with the land cover and peak flow rate design assumptions from SDP 200100129. Onsite Design Assumption data was obtained from SDP 200100129, "SWM and BMP Report, Sterling University Housing" sheets 14 & 20. The results are shown in the table below. Onsite Design New Onsite Plan Assumption Condition Land Cover 80% Impervious 42.7% Impervious (6.9 Ac. Max Imp) (3.65 Ac. Imp) Original Inlet: E1 10 yr runoff: 10 yr runoff: (New Plan Inlet: Str. X) 51.11 cis 29.04 cfs Original Inlet: C1 10 yr runoff: 10 yr runoff: (New Plan Inlet: Str. M7) 45.58 cis 43.44 cfs The new plan for Royal Fern Phase 2 falls within the original design assumptions for this property because the total impervious area onsite is less than the original design, and because the total flow to each existing inlet intended to convey runoff from this property to the pond is less than the original design. This reveals that no revisions are necessary to the existing storm sewer conveyance to the pond because the new Royal Fern Phase 2 plan complies with the original hydraulic design for the site. Onsite SWM Nutrient Treatment Comparison: Pond Design Assumptions Vs. Existing Conditions Since the new plan has less onsite impervious cover than the original design for the site, the pond will provide full nutrient treatment for the site runoff. However, since the pond was expanded with WPO 201500094, we investigated if the pond's as -built condition is sufficient to provide the treatment for both the original area and for the added area from WPO 201500094. SDP200100129 Required Design WP0201500094 Added Requirements Total Required After WP0201500094 Current Pond As -Built Forebay 528 CY* 174 CY Addition*" 702 CY Total 714 CY Quality Volume 4220 CY* 828 CY Addition*" 5048 CY Total 6848 CY *Ref. SDP 200100129 `SWM and BMP Report Sterling University Housing"sheet 20 **Ref: WPO 201500094 "Fifth Street Place VSMP Plan"sheet SWM-10 The pond has sufficient volumes to provide the design nutrient treatment. Thus the Royal Fern Phase 2 site nutrient treatment requirements are achieved by the existing pond. Pond Adequacy Conclusions Since the current total drainage area to the pond is smaller and less impervious than the approved design area, we can conclude that the pond remains adequate and will continue to operate within its intended parameters. Since the Royal Fern Phase 2 proposed site has less impervious cover and less peak runoff to the existing storm sewers than the approved design, we can conclude that the storm sewers which convey runoff to the pond are adequate, and that the pond hydraulic design remains adequate. Since the wet pond current as -built conditions exceed the required forebay and treatment volume than the approved design, we can conclude that the pond is adequate to provide the approved nutrient treatment amounts. These conclusions mean that the Royal Fern Phase 2 site is fully treated by the existing wet pond and that no downstream improvements are necessary to achieve runoff quality or quantity requirements. If you have any questions please do not hesitate to contact me at: keane(a),shimp-enoineerino.com or by phone at 434- 299-9843. Contents: Post-Dev Runoff Calculations: Post-Dev Drainage Spreadsheet Post-Dev Ditch and Structure Drainage Map Offsite Drainage Map Post-Dev Land Cover VDOT LD-204 Inlet Capacity VDOT LD-229 Culvert Capacity VDOT LD-268 Ditch Capacity Pond Drainage Analysis Pond Drainage Map — Aerial Photography Pond Drainage Map — Topographic Wet Pond As -Built Volumes Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report Appendix 1: Selection from SDP 200100129 SWM Calculation Packet SWM and BMP Report Sterling University Housing, Sheets 1-21 Appendix 2: Selection from SDP 201500094 VSMP Plan and SWM As -Built Fifth Street Place VSMP Plan, Sheets SWM-1, SWM-4D, SWM-7 — SWM-10 Fifth Street Place Stormwater As -Built, Sheets SWM-0 — SWM-1A Post-Dev Runoff Calculations: Post-Dev Drainage Spreadsheet Post-Dev Ditch and Structure Drainage Map Offsite Drainage Map Post-Dev Land Cover VDOT LD-204 Inlet Capacity VDOT LD-229 Culvert Capacity VDOT LD-268 Ditch Capacity Sediment Basin Caclulations ROYAL FERN PH. 2 Inlet Drainage Area Summary Impervious C 0.9 Pervious C 0.3 To Area Impervious Turf C A D2 5,890 2,651 3,240 0.57 0.14 E9 14,050 6,323 7,728 0.57 0.32 E8 6,970 3,137 3,834 0.57 0.16 E7A 15,810 7,115 8,696 0.57 0.36 E7 9,920 4,464 5,456 0.57 0.23 19 50,730 19,277 31,453 0.53 1.16 E5 22,270 10,022 12,249 0.57 0.51 H6 48,100 21,645 26,455 0.57 1.10 E4 11,780 5,301 6,479 0.57 0.27 E3 37,370 7,474 29,896 0.42 0.86 G4 27,050 18,935 8,115 0.72 0.62 G3 7,500 5,250 2,250 0.72 0.17 F4 60,980 6,098 54,882 0.36 1.40 EIA 1 41,490 1 15,766 1 25,724 0.53 1 0.95 L5 11,050 8,840 2,210 0.78 0.25 L4A 20,950 14,665 6,285 0.72 0.48 L4 7,600 6,080 1,520 0.78 0.17 M4A 11,770 8,239 3,531 0.72 0.27 M2A 6,400 4,480 1,920 0.72 0.15 M2 10,690 7,483 3,207 0.72 0.25 r '- r�iil_ „r 1. __ /. ; � ----- PAST-DEV DITCH & ,: "\ INLET DRAINAGE MAP i i ribili r 41480 9F ail r V0 - tr_ — _ __— - N r __ ■ %" -- \ ash ram' _ _ _ _ i - ) - TO D1 9 F4 �— gym. O r. r. / 41 , \ r! Irk ;� Aj i' r �L//� `��J_ �/ -_I r �� ✓ ✓ r �� �� r - :: `.fib J , 50930 SF i wo �r r , ■ �� I I - � C� fA � � 1 �� � —G� i i � `�' ■ �,, �r V /E - Oe,- TO ES EY 2s� / 'ac29050 SF a' T G3 ■ �`. S . �O 1e 0 SF n i -TO E3 \ � \ .. 1 • - �� 14d� a29920TO 'SF r 922'10 aF 39340 3F TO Ea o r I I ^ao eavo SFTO E9 � ■ 1— ]5810 SF 4050 3F 1 �a° a L, ` ■ �T/ �,_/ �i �i�i il0� - i'o ].4A _ YS i f� TO 2 TO HB 51590 IF I \ 8100 SF - 110 SF 0 590 SF•> A o 7600 SF 4F sop Da r ' wW A / TO M4A 11790 SF Yo / �r1rINS I / - /'TOMS�/ B.84 AC �.AV `,`; 80 0 80 160 240 AW 75% IMP moo Scale: 1"-80' ROYAL FERN OFFSITE DRAINAGE MAP 200 0 200 400 600 Scale: 1 I E; 0 i ■ i 0 i 0) 0 19 0 n 0 0 ROUTE VARIABLE WIDTH R/W -�- HWY.P.B.XI 2 7 THRU 262 _ C 0 Cml F i 8 c ROYAL FERN T-DEV LAND COVER MAP POSTDEV LAND COVER MANAGED TURF a HSG B=4.90 AC NEW IMPERVIOUS: =3.65 AC TOTAL SITE: 8.55 AC IMPERVIOUS COVER: 42.7% w 0 80 160 240 ROYAL FERN PHASE 2 LD-204 Stormwater Inlet Computations Inlets on Grade Only Sag Inlets Only m c m "v y E d t5 Z N n a o m m () C m N W t r m X A z E115 ~ m C N C m L G m O- o w o o 2 w hl= z' _c u 0 ¢' S o Clo 0 e- r7 r m o o o 0 21 M 1 2 3 4 5 6 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 (ft) (ac) (in)hr) (cfs) _(cfs)_(cfs) (T) V) ('I') (ft) (%) (cfs) (cis) ft (% 0) D2 DI-3B 6 0.14 0.57 0.08 4.0 0.31 0.00 0.31 0.013 0.020 0.020 0.08 1.55 0.15 100.0% 0.31 0.00 7.5 0.58 0.00 0.58 1.95 0.16 100.0% 0.58 0.00 E9 DI-3B 14 0.32 0.57 0.18 4-0 0.74 0.00 0.74 0.013 0.100 0.020 0.08 1.57 0.15 100.0% 0.74 0.00 7.5 1.38 0.00 1.38 2.00 0.16 100.0% 1.38 0.00 E8 DI-313 12 0.16 0.57 0.09 4.0 0.36 0.00 0.36 0.013 0.100 0.020 0.08 "0 0.15 100.0% 0.36 0.00 7.5 0.68 0.00 0.68 0.08 1.64 0.15 100.0% 0.68 0.00 EM DI-3B 12 0.36 0.57 0.21 4.0 0.83 0.00 0.83 0.013 0.030 0.020 0.08 2.26 0.17 100.0% 0.83 0.00 7.5 1.55 0.00 1.55 4.26 0.21 100.0% 1.55 0.00 E7 DI-3B 12 0.23 0.57 0.13 4.0 0.52 0.00 0.52 0.013 0.030 0.020 0.08 1.90 0.16 100.0% 0.52 0.00 7.5 0.97 0.00 0.97 3S3 0.19 100.0% 0.97 0.00 19 YARD DRAIN 3x3 1.16 0.53 0.61 4.0 2.46 0.00 2.46 0.013 0.030 0.300 0.08 0.17 1 0.17 2.08 7.5 4.61 0.00 4.61 0.26 1 0.26 8.36 E5 DI-3B 12 0.51 0.57 0.29 4.0 1.17 0.00 1.17 0.013 0.030 0.020 0.08 3S9 0.19 100.0% 1.17 0.00 2.38 7.5 2.19 0.00 2.19 5.67 0.24 99.3% 2.17 0.02 H6 ES-1 2.5 1.10 0.57 0.63 4.0 2.52 0.00 2.52 0.015 0.030 0.200 0.08 0.32 1 0.32 1.59 7.5 4.72 0.00 4.72 0.48 1 0.48 24.00 E4 DI-3B 10 0.27 0.57 0.15 4.0 0.62 0.00 0.62 0.013 0.030 0.030 0.08 1.91 0.16 100.0% 0.62 0.00 7.5 1.16 0.00 1.16 3S6 0.19 100.0% 1.16 0.00 E3 DI-7 44 0.86 0.42 0.36 4-0 1.44 0.00 1.44 0.015 0.030 0.020 0.08 0.12 0.5 0.24 3.17 7.5 2.70 0.00 2.70 0.18 0.5 0.36 3.78 G4 DI3C 6 0.62 0.72 0.45 4.0 1.79 0.00 1.79 0.013 0.300 0.020 0.08 0.19 0.5 0.38 3.67 7.5 3.35 0.00 3.35 0.28 0.5 0.56 8.22 G3 DI-3C 6 0.17 0.72 0.12 4.0 0.50 0.00 0.50 0.013 0.300 0.020 0.08 0.08 0.5 0.16 1.00 7.5 0.93 0.00 0.93 0.12 0.5 0.24 1.51 F4 YARD DRAIN 3x3 1.40 0.36 0.50 4.0 2.02 0.00 2.02 0.013 0.030 0.020 0.08 0.18 1 0.18 2.09 7.5 3.78 0.00 3.78 0.27 1 0.27 2.39 E1A DI-3C 6 0.95 0.53 0.50 4-0 2.01 0.00 201 0.013 0.030 0.020 0.08 0.20 0.5 0.40 3.06 7.5 3.77 0.00 3.77 0.31 0.5 0.62 5.69 L5 DI-313 10 0.25 0.78 0.20 4.0 0.79 0.00 0.79 0.013 0.029 0.020 0.08 2.41 0.17 100.0% 0.79 0.00 7S 1.48 0.00 1.48 4.41 0.21 100.0% 1.48 0.00 L4A DI-313 12 0.48 0.72 0.35 4.0 1.39 0.00 1.39 0.013 0.020 0.020 0.08 4.82 0.22 100.0% 1.39 0.00 7.5 2.60 0.00 2.60 7.02 0.26 99.1% 2.57 0.02 L4 DI-3C 6 0.17 0.78 0.14 4.0 0.54 0.00 0.54 0.013 0.020 0.020 0.08 0.08 0.5 0.16 1.05 7.5 1.02 0.00 1.02 0.13 0.5 0.26 1.61 M4A DI-3B 10 0.27 0.72 0.19 4.0 0.78 0.00 0.78 0.013 0.023 0.020 0.08 2.73 0.17 100.0% 0.78 0.00 7.5 1.46 0.00 1.46 4.75 0.22 100.0% 1.46 0.00 M2A DI3C 6 0.15 0.72 0.11 4.0 0.42 0.00 0.42 0.013 0.018 0.020 0.08 0.07 0.5 0.14 0.89 7.5 0.79 0.00 0.79 0.11 0.5 0.22 1.35 M2 DI-1 4x4 0.25 012 0.18 4.0 0.71 0.00 0.71 0.013 0.018 0.020 0.08 0.07 0.5 0.14 5.65 LD-229 Storm Drain Design Computations ROYAL FERN PHASE 2 From To Catch. Runoff Incrementl Accum. I Total Total Total Up Down Pipe Invert Pipe Pipe Velocity Flow time Structure Structure Area Coef AC AC TOC Intensity Flow Invert Invert Length Slope Diameter Capacity Increment (acres) (min) (in/hr) (cfs) Elev. Elev. (ft) % (in) (cfs) (ft/s) (min) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 D2 D1 0.14 0.57 0.08 0.08 5.00 6.81 0.52 454.00 450.00 119.15 3.36% 15 12.8 5.0 0.39 E9 E8 0.32 0.57 0.18 0.26 5.00 6.81 1.78 438.50 438.00 29.00 1.72 % 15 9.2 5.8 0.08 E8 E7 0.16 0.57 0.09 0.35 5.08 6.79 2.39 437.80 429.20 169.86 5.06% 15 15.7 9.3 0.30 E7A E7 0.36 0.57 0.21 0.21 5.00 6.81 1.41 430.00 429.20 29.00 2.76% 15 11.6 6.3 0.08 E7 E6 0.23 0.57 0.13 0.69 5.16 6.76 4.66 429.00 420.20 109.77 8.020/, 15 19.8 13.1 0.14 19 18 1.16 0.53 0.61 0.61 5.00 6.81 4.19 428.50 427.20 111.07 1.17% 15 7.6 6.0 0.31 18 17 0.00 0.00 0.00 0.61 5.47 6.68 4.11 427.00 424.20 180.58 1.55% 15 8.7 6.6 0.46 17 E6 0.00 0.00 0.00 0.61 5.92 6.55 4.03 424.00 422.00 91.44 2.19% 15 10.4 7.4 0.21 E6 E5 0.00 0.00 0.00 1.30 5.67 6.62 8.63 420.00 414.20 93.86 6.180/6 15 17.4 13.8 0.11 E5 E4 0.51 0.57 0.29 1.60 5.79 6.59 10.51 414.00 412.20 76.80 2.34 % 18 17.4 10.1 0.13 H6 H5 1.10 0.57 0.63 0.63 5.00 6.81 4.29 437.00 430.20 130.00 5.23% 15 16.0 11.1 0.20 H5 E4 0.00 0.00 0.00 0.63 5.20 6.75 4.25 430.00 412.20 227.18 7.84% 15 19.6 12.8 0.30 E4 E3 0.27 0.57 0.15 2.38 5.31 6.72 15.99 412.00 411.00 43.54 2.30% 24 37.2 11.2 0.06 E3 E2 0.86 0.42 0.36 2.74 5.37 6.70 18.36 410.80 408.20 81.69 3.18% 24 43.7 13.1 0.10 G4 G3 0.62 0.72 0.45 0.45 5.00 6.81 3.04 416.00 415.20 34.33 2.33% 15 10.7 7.5 0.08 G3 E2 0.17 0.72 0.12 0.57 5.08 6.79 3.88 415.00 411.50 42.28 8.28% 15 11.7 8.6 0.08 F4 F3 1.40 0.36 0.50 0.50 5.00 6.81 3.43 422.00 414.20 74.28 10.50% 15 22.7 13.3 0.09 F3 E2 0.00 0.00 0.00 0.50 5.09 6.78 3.42 414.00 408.20 93.27 6.22% 15 17.5 11.4 0.14 E2 E7 0.00 0.00 0.00 3.81 5.23 6.74 25.72 408.00 405.82 58.78 3.71% 30 85.6 15.1 0.06 EtA E1 0.95 0.53 0.50 0.50 5.00 6.81 3.42 412.00 409.00 58.21 5.15% 15 15.9 10.3 0.09 E1' X 0.00 0.00 0.00 4.32 5.29 6.73 29.04 405.62 405.27 16.51 2.120/6 36 97.1 11.9 0.02 L5 L4 0.25 0.78 0.20 0.20 5.00 6.81 1.35 429.00 427.00 51.39 3.890/6 15 13.8 7.1 0.12 L4A L4 0.48 0.72 0.35 0.35 5.12 6.78 2.35 427.80 427.00 108.16 0.74%, 15 6.0 4.6 0.39 L4 M3 0.17 0.78 0.14 0.68 5.39 6.70 4.56 426.80 419.40 61.50 12.03% 15 24.3 15.2 0.07 M5' M4 8.84 0.75 6.63 6.63 10.00 5.62 37.29 425.22 417.31 86.48 9.15% 36 218.6 21.8 0.07 M4A M4 0.27 0.72 0.19 0.19 5.00 6.81 1.32 438.00 434.00 27.60 14.49% 15 26.6 11.2 0.04 M4 M3 0.00 0.00 0.00 6.82 10.07 5.61 38.30 417.11 415.80 50.13 2.61% 36 116.7 14.8 0.06 M3 M2 0.00 0.00 0.00 7.50 10.12 5.60 42.03 415.60 412.76 106.10 2.68% 36 118.3 15.3 0.12 M2A M2 0.15 0.72 0.11 0.11 5.00 6.81 0.72 426.00 422.56 23.10 14.89% 15 27.0 9.5 0.04 M2' M1 0.25 0.72 0.18 7.79 10.24 5.58 43.44 412.56 411.30 122.29 1.03% 36 67.7 10.1 0.20 "Existing Culvert Section ROYAL FERN PHASE 2 Modified LD-268 Roadside and Median Ditch Desi n Form Ditch C A CA Tc 110 010 Side Slope :1 L 1 R - - Min. Slope Ft/Ft Max Slope Ft/Ft Allowable Velocity On Protective Lining EC-2: n=.05 EC-3: n=.15 I Velocity I Depth I On I Velocity I Depth 9 0.36 1.46 0.53 5.0 7.05 3.71 3 3 0.01 0.04 4.0 0.19 2.28 0.81 10 0.57 1.79 1.02 5.0 7.05 7.21 4 4 0.02 0.04 4.0 0.36 2.66 0.87 11 0.57 0.33 0.19 5.0 7.05 1.35 3 3 0.09 0.11 4.0 0.07 2.99 0.39 'Velocity calculations performed using average slope for this application Royal Fern Ph. 2 Orange cells need input, white cells are calculations. Basin 1 Step 1: Preliminary Design Top of Dam 426.0 Downstream Toe of Dam 418.0 Barrel length (ft) 110.0 Slope of principal spillway barrel (%) 4.30/0 Step 2: Calculate Runoff Rational Method Drainage Area (ac) 5.24 C 0.6 12 4.3 125 6.6 Q2 (cfs) 13.5 Q25 (cfs) 20.8 Step 3: Principal Spillway From Plate 3.14-8 Spillway Capacity with emergency spillway (cfs) 20.8 Riser Diameter (in) 36 Actual head (ft) 1.00 QP (max) 29.0 Step 4: Emergency Spillway From Table 3.14-C Required spillway capacity 0.0 HP 0.0 b - Bottom width (ft) 0 Basin 1 S - slope of exit channel (ft/foot) 0.00 X - minimum length of exit channel (ft) 0 Sten 5: Grade Basin Design Parameters Maximum Top of wet Storage 423.0 Required Wet + Dry Storage (cf) 18,958 Wet Storage Required Volume (cy) 351 Required Volume (ct) 9,479 Minimum Standpipe Invert 419.4 Cleanout Required Volume (cy) 173 Cleanout Required Volume (cf) 4,669 Design Elevation Area s. 418.0 4,500 Bottom of Wet Storage 418.5 4,915 419.5 5,774 Cleanout Elevation 420.0 6,240 421.0 7,210 Top of Wet Storage 7,698 Cleanout Volume (cf) Wet Storage Volume (cf) 17,427 Wet Storage Volume (cy) 645 Dry Storage Required Volume (cy) Required Volume (cf) Maximum Top of Dry Storage Bottom of Dry Top of Dry Dry Storage Volume (cf) 351 9,479 424.0 Design Elevation Area (s Storage 421.0 7,210 422.0 8,234 Storage 423.0 9.290 16,484 Basin 1 Dry Storage Volume (cy) 611 Step 6: Final Details Upstream Toe of Dam 418.0 Principle Spillway Elevation 423.0 Trash rack and anti -vortex device From Table 3.14 D: Diameter (in) 54 Height (in) 17 From Retention Basin Design and Plate 3.14-B: Head on barrel (ft) 5.0 Q, (max) 32.5 Barrel diameter (in) 24 Dewatering Orifice Design Riser Height 5.0 h (ft) 1.0 S (cf) 16,484 Q (cfs) 0.76 A (sf) 0.159 d (ft) 0.449 Dewatering Orifice Diameter (in) 6 Flexible Tubing Diameter (in) 8 Baffle Calculation Length of Flow (L) (R) 225 Effective Width (We) (ft) 70 L/We 3.2 Baffles Required? no 1992 TABLE 3.14-D CONCENTRIC TRASH RACK AND ANTI -VORTEX DEVICE DESIGN TABLE 3.14 Riser Diam., in. Cylinder Height, inches Minimum Size Support Bar Minimum Top Diameter, inches Thickness, gage Thickness Stiffener 12 18 16 6 #6 Rebar or 1% x 16 ga. 1% x 3/16 angle (F&C) 15 21 16 7 ^ 18 27 16 8 " ^ 21 30 16 11 16 ga.(C), 14 ga.(F) 24 36 16 13 27 42 16 15 36 54 14 17 #8 Rebar 14 ga.(C), 12 ga.(F) 42 60 16 19 " 48 72 16 21 1'/W pipe or 1'/4 x 14 ga.(C), 10 1'/4 x 1/4 angle ga.(F) 54 78 16 25 " " _ 60 90 14 29 hh" pipe or 1% x 12 ga.(C), 8 - hh x'/4 angle ga.(F) 66 96 14 33 2" pipe or 2 x 2 x 12 ga.(C), 8 2 x 2 x'/4 3/16 angle ga.(F) angle w/stiffener 72 102 14 36 2% x 21h x 1/4 angle 78 114 14 39 21h" pipe or 2 x 2 x ^ '/4 angle 84 120 12 42 21/2" pipe or 21h x 21/2 x 21h x 2�h x �/4 angle 5/16 angle Note,: The criterion for sizing the cylinder is that the area between the inside of the cylinder and the outside of the riser is equal to or greater than the area inside the riser. Therefore, the above table is invalid for use with concrete pipe risers. Note2: Corrugation for 12"-36" pipe measures 2W x 1h"; for 42" -84" the corrugation measures 5" x 1" or 8" x 1". Note3: C = corrugated; F - flat. Source: Adapted from USDA-SCS and Carl M. Henshaw Drainage Products Information. III - 104 1992 Riser Inflow Curves —+ Legend Weir flw. %-9.739 Or"I' "......... Orifice flw. Oe-3.7e2 O2rX � mono VAi If01MA ■EE 1MMA row, "Iffm4mot ®1A �O, i f"dwArr, ne 9 ,r�iyf�ii7�wnnuu�s ■■■■■■unni /!I'Vi%►III ■111116ii11 ���■■■■�1111111'. MY Source: USDA-SCS III - 97 3.14 Plate 3.14-8 O O M e 1992 3.14 saON n- P 00 ORPPPu Nmm nnmaa w www r"www wwwww .•i.N,ww ... "n"" .NN mWnnm maP w ws," rw4ww . Nwwr aaPw. s«.N Nmerya nnmmm r�g�w wraa� °mwww�P.."�" �a: 2 9 .NNN9 mmnnn nmmmm aaaaaao F j mP.^ anRn9i N N aTNa mNMnn .4a N NNNVP q VVnnn nnmmm mmm 0P (6�j1 ""nN d� �^ Ra ao>ossaaxam ««., ���.. ..NaN N��nsm maryme m n nnn wnw n �� os.xryN N sa�"w�s�amaa Nn««N ��a.. ....N NNNNN NNm ee a µ P�Nmm «.Nnm a P amP.... n.N mnmPm w«N.N n m.P� " www 7 anss;g sxa n �a 2 4soap � ae� mm-oa -a ss aes :xa nary „, �e �s�m aa: rya ss sassP...`= �p 4 0o mo_ m nn J 8 V�nnm N m V� sy Nn mRPPN wNw w.ri r"www ""w.l« rwwrPPPPgO �8 M a Pm � Nm «m Nm :asasa mm m F R' NN�m Reee� 6 PN sassaa «N«N. «N«N« NN«« �aN N n a N.N mnm " "".."" N«««« m •E" .,wwwN ««:Am"_� .NS�RR8A Source: USDA-SCS III-99 Pond Drainage Analysis Pond Drainage Map — Aerial Photography Pond Drainage Map — Topographic Wet Pond As -Built Volumes v 4SE, �O 0.BO 416 m l.� 4B0 v 73.42 ACRES 'TOTAL TO F �15 ACRES IMPERVIOUS 'dry �a9z ERES PERVIOUS � ,. A R - P A - _ — -- a Rfb � 4c 464� '6a C a � 0 LA do 4 FERN PH.2 ID O ov 0 460 % o EDO O 0 p Oi ROYAL_ FERN TOPOGRAPHIC POND DRAINAGE MAP ACTUAL POND DRAINAGE INFO Includes Built —Out Royal Fern Ph. 2 Area. All Areas are HSG B. Pervious — Areas are assumed to be turf, for most conservative analysis. —c = ACTUAL POND DRAINAGE AREA: Pervious Area=39.73 Ac. CN=61 Impervious Area=32.10 Ac. CN=98 Total Area=71.83 Ac. Weighted CN-78 44.7% Impervious Area �T 0 NOTE: This drainage area is 0.89 cc. smaller than the design pond drainage area. This difference is due to updated drainage area analysis based on the current GIS topography. a Q0 DESIGN POND DRAINAGE INFO DESIGN POND DRAINAGE AREA: From WPO 201500094 12.53 Ac.-5th St Apartments, CN-86 60.19 Ac.—Other Area to Pond, CN=89 Total Area=72.72 Ac, Weighted CN-88 63% Impervious Area THE ACTUAL POND DRAINAGE AREA, INCLUDING THE PROPOSED ROYAL FERN \ PHASE 2 DEVELOPED SITE, HAS LESS TOTAL DRAINAGE AREA AND LESS IMPERVIOUS AREA THAN THE DESIGN AND THUS FALLS WITHIN THE DESIGN PARAMETERS AS ANALYZED IN WPO 201 500094. 300 0 300 600 90 Royal Fern Phase 2 Wet Pond As -Built Volumes TREATMENT VOLUME ELEV1 AREA1 VOLUMEI ELEV2 AREA2 VOLUME2 SUM VOLUME SUM VOL CF 388 12100 0 0 0 0 0.0 390 15774 27874 0 0 27874 1032.4 0 391 2386 0 27874 1032.4 392 19423 35197 392 4996 3691 66762 2472.7 394 21932 41355 394 7443 12439 120556 4465.0 395.78 39416 64338.1 0 184894.1 6847.9 FOREBAY ELEV AREA VOLUME SUM VOLUME SUM VOL CF 397 4328 0 0 0.0 398 7127 5727.5 5727.5 212.1 399.7 9306 13557.2 19284.7 714.2 Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report Precipitation Frequency Data Server https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html'?Iat=38.0062&... NOAA Atlas 14, Volume 2, Version 3 Location name: Charlottesville, Virginia, USA' Latitude: 38.0062', Longitude:-78.5199' j Elevation: 453.03 ft" - source: ESRI Maps source'. USGS POINT PRECIPITATION FREQUENCY ESTIMATES G.M. Bonnin. D. Martin, B. Lin, T Parzytwk, MYekta. and D. Riley NOAA, National Weather Service, Silver Spring, Maryland PF tabular I PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Average recurrence Interval (years) Duratlonr i^^ ' 0.352 Z 0.419 IL0.4491 10 ' 0.552 . 25 50 0.675 100 0.725 200 0.772 500 1000 FO.622 0.828 0.873 5-min (0.317-0.391) (0.378-0.466) (0.4 ,42-0.544).(0.496-0.611) (0.556-0.686) (0.601-0.745) (0.642-0.799) (0.679-0.851) (0.721-0.915) (0.753-0.969) 0.563 0.670 0.786 0.883 0.991 1.08 1.15 1.22 1.37 1.38 �10-min (0.506-0.625) 0.703 (0.605-0.744)(0.708-0.872)(0.793-0.978)I F 0.842 0.995 1.12 (0.886-1.09) (0.957-1.19), (1.02-1.27) 1.46 (1.08-1.35) 11 1.54 (1.14-1.45) (1.19-1.53) 126 1.36 1.65 1_1_ 173 5-min (0.03-0.781) (0.760-0.936) (0.895-1.10 ) ( 1.00-1.24) (1.12-1.39) (121-1.50 ) ( 1.29-1.61 ) ( 1.36-1-70 ) (1.44-1.82) (1.49-1.92) 0964 1.16 1.41 1.62 1.86 2.05 F 2.23 2.40 2.62 2.80 30-min J (0.868-1.07) 1.20 (1.05-1.29) j 1.46 (1.27-1.57) (1.45-1.79) (1.66-2.05) 11 (1.83-2.26) (1.98-2.46) (2.12-2.65) (2.28-2.90) (2.41-3.10) 1.81 2.11 2.48 2.78 3.07 3.37 .76 4.08 F360-min (1.08-1.34) (1.32-1.62) 1-75 (1.63-2.01) 2.19 1 (1.89-2.33) 257 (2.21-2.73) 3.06 (2A7-3.06) 3.47 (2.72-3.39) 3.89 (2.97-3.72) 4.32 (3.28-4.16) 4.92 (3.52-4.53) 5.42 1.44 F2-hr (1.27-1.65) (1.53-2.00) (1.92-2.49) (2.26-2.92) (2.67-3.47) (3.01-3.93) (3.35-4.40) (3.70-4.89) (4.16-5.57) (4.54-6.16) 1.58 1.91 2.39 2.81 3.34 3.8o 426 4.74 5.40 5.96 3-hr IF (1.38-1.82) (1.67-2.20) (2.09-275) (2.44-3.22) (2.90-3.83) (3.27-4.33) (3.65-4.86) (4.03-5A7) (4.53-6.17) (4.95-6.81) 2.02 F 2.44 F 3.03 F 3.57 F 4.29 F 4.92 5.57 F 6.28 F 7.29 FS.16 6-hr (1.79-2.29) (2.15-2.76) 1 (2.67-3.43) (3.13-4.03) (3.74-4.84) (4.25-5.53) (4.78-6.27) 1 (5.33-7.07) (6.09-8.21) (6.73-9.21) 2.55 3.07 3.83 4.53 5.52 6.39 7.33 8.37 9.90 11.3 n12-hr (2.25-2.92) (2.71-3.52) 11 (3.36-4.38) (3.97-5.18) (4.79-6.27) 11 (5.50-7.25) (6 23-8.32) (7.02-9.48) (8.14-11.2) (9.11-12.8) 3.05 3.69 4.72 &a 6.as 7.95 9.16 10.5 12.5 14.2 �24-hr .(2.74-3.42) (3.32-4A4) (4.23-5.28) (4.98-6.22) (6.08-7.62) (7.00-8.82) (8.00-10.1) (9.07-11.6) (10.6-13.8) (11.9-15.7) 5.54 6.52 77 7.94 9.12 11.8 13.9 7 7-5.6 3.59 4.36 10.4 2-day (3.22-4.01) (3.91-4.87) (4.96-6.19) (5.82-7.26) (7.03-8_82) (SA3-10.1) (9.09-11.6) (10.2-13.1) (11.8-15.5) (13.2-17.4) 3.83 4.64 5.89 6.93 8.42 9.68 11.0 1-2-514.7 16.5 3-day (3.48-4.23) (4.21-5.13) 4.92 (5.34-6.52) 624 (6.26-7.65) 733 (7.57-9.29) 8.91 (8.64-10.7) 10-2 (9.78-12.2) 11.7 (11.0-13.8) 13.2 1 (12.7-162) 15.5 (14.1-18.3) 17.4 4.06 4day (3.73-4A5) (4.51-5.39) (5.72-6.85) (6.70-8.03) (8.11-9.75) (9.26Al2) (10.5-12-8) ( 11.8-14.5) (13.64Z0) (15.1-19.1) 4.72 5.68 7.10 826 9.94 11.3 12.a 14A 16.8 18.7 7-day (4.34-5.13) (5.23-6.18) (6.53-7.72) (7.58-8.99 ) (9.07-10.8) (10.3-12.3 ) (11.6-13.9 ) ( 12.9-15.7 ) (14.8-18.3) (16.3-20.5) 5.34 6.41 7.92 9.14 10.9 12.3 13.a 15.3 17.6 19-4 10day 4 ( .94 5.77) (5.94-6.93) (7.32-8.55) (8.44-9.86) (9.98-11.7) (11.2-13.2) (12.5-14.9) (13.8-16.6 ) (157-19.1) (17.2-21.1) 7.02 8.37 1o.1 11-5 13.3 14b 16.3 17.8 19.9 215 20 (6.58 7.50) (7.85-8.94) (9.47-10.8) (10.7-12.3) (12-4-142) 11 (13.7-15.8) (15.1-17.4) (16.4-19.1) 11 (182-21-4) (19.5-23.2) 8.61 10-2 12.1 13.5 15.3 16R 18.1 19.5 21.3 22.6 30-day (8.11-9.15) (9.62-10.8) (11.4-12.8) (12.7-14.3) (14.4-16.3) (15.7-17.8) (16.9-19-3) ( 18.1-20.7) (19.7-22.7) (20.8-24.2) 10.7 12.7 14.8 16.4 18.5 20.0 21.5 22.9 24.7 26.1 4$-flay (10.2-11.4) (12.0-13.4) (14.0-15.7) (15.5-17.4) (17.4-19.6)� (18.8-21.2) (20.2-22.8) (21.4-24.3) 1 (23.0-26.3) (24.2-27.8) 12.6 14.8 17.1 16.8 21.0 22.6 24.2 25.6 275 28.8 60-0ay (12.0-13.3) (14.1-15.6) (16.2-18.1) (17.8-19.9) (19.9-22.1) (21.3-23.8) (22.7-25.5) (24.1-27.1) (257-29.1) (26.9-30.6) 1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90 % confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5 %. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Too PF graphical 1 of 4 5/30/2018. 9:48 AM Precipitation Frequency Data Server https://hdsc.nws.noaa.gov/hdsc/pfdslpfds_printpage.html?tat=38.0062&... c r9 Mi 10 5 ro PDS-based depth -duration -frequency (DDF) curves Latitude: 38.0062°, Longitude:-78.5199° _.-_:...:... _:.....:-.... ....................... II. ....: ..... .'. L L L L N N r4 rppp re 6 � o N o a s o A A h N 1 rri O �1 rC'1f� Duration 0 25 c c 20 0 ter- 1 2 5 10 25 50 100 200 500 1000 Average recurrence interval (years) NOAA Atlas 14, Volume 2, Version 3 Created (GMT): Wed May 30 13:48:24 2018 Back to Too Maps & aerials Small scale terrain Average recurrence interval (years) —1 2 5 10 25 50 100 200 500 1000 Duration 5-rnm — 2day — 10-min — 3day 15-min — 4-day — 30amn — 7-day — 60-min — 10-day — 2dr — 20-day — 3fir — 30day — 6-hr — 45day — 12-hr — 60-day — 24-hr 2of4 5/30/2018, 9:48 AM Precipitation Frequency Data Server https://hdsc.nws.noaa.gov/hdsc/pfdslpfds_printpage.html?tat=38.0062&... AS Moon DUDLEY MOUNTAIN 3km �I 2mi z Large scale terrain E Washington, D.C.* Al R SIP �-- yfla jso uige $ id Nilan VIRGINIA IA I Rich -T � Lynchburg A, aoan„r" 100km B� 60mi Norfo Large scale map 0 " An (/// Washington " "ginia Haniconhurg M- Nah /ry` lo�unlu_n_ I )Fichmo l Lynchburg } Black burg ;,Roanoke Uu l II � Norte 60mi Large scale aerial 3of4 5/30/2018, 9:48 AM 3 Hydrologic Soil Group—Albemade County, Virginia 3 m b M°UWN W 016N 717270 ]i7310 717410 717480 3 -�' Map Sole: 1:Z170IFprirfiedm Blandk pe(17'x 11")slce N Metes 0 30 60 121 i8D A 0 100 2ID 400 Om Map PNedmn: Web Vector Cm ax r�atF : WCS84 Edgets: U1M Zone 17N WGS84 USDA Natural Resources Conservation Service 717MD 717M 7170M 717760 7178M 71M 717 718M Web Soil Survey National Cooperative Soil Survey Sia B W 0' 16" N 5/29/2018 Page 1 of 4 MAPLEGEND Area of Interest (AOI) Area of Interest(AOI) Solis Sol Rating Polygons 0 A 0 AID 0 B Q BID 0 0 CID 0 D 0 Not rated or not available Soil Rating Lines ~ A ~ AID �y B py B/D w C CID ^r D 0 Not rated or not available Soil Rating Points 13 A ❑ AID ❑ B ❑ BID Hydrologic Soil Group —Albemarle County, Virginia ® C CID D 0 Not rated or not available Water Features Streams and Canals Transportation � Rails py Interstate Highways ,r✓ US Routes Major Roads Local Roads Background . Aerial Photography MAP INFORMATION The soil surveys that comprise your AOI were mapped at 1:15,800. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Albemarle County, Virginia Survey Area Data: Version 11, Oct 11, 2017 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Apr 22, 2015—Mar 10, 2017 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. USDA Natural Resources Web Soil Survey 5/29/2018 Conservation Service National Cooperative Soil Survey Page 2 of Hydrologic Soil Group —Albemarle County, Virginia Hydrologic Soil Group Map unit. symbol Map un@ name Rating Acres in AOI Percent of AOI 21C Culpeper tine sandy B 0.4 1.3% loam, 7 to 15 percent slopes 21D Culpeper fine sandy B 0.7 2.3% loam, 15 to 25 percent slopes 27B Elioak loam, 2 to 7 B 12.7 42.6% percent slopes 27C Elioak loam, 7 to 15 B 1.6 5.3% percent slopes 27D Elioak loam, 15 to 25 B 4.0 13.3% percent slopes 34B Glenelg loam, 2 to 7 B 5.6 18.9% percent slopes 34C Glenelg loam, 7 to 15 B 1.5 5.0% percent slopes 39D Hazel loam, 15 to 25 B 3.4 11.3% percent slopes Totals for Area of Interest 29.8 100.0% USDA Natural Resources Web Soil Survey 5/29/2018 Conservation Service National Cooperative Soil Survey Page 3 of 4 Hydrologic Soil Group —Albemarle County, Virginia Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long -duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink -swell potential, soils that have a high water table, soils that have a claypan or Gay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff.- None Specked Tie -break Rule: Higher USDA Natural Resources Web Soil Survey 5/29/2018 Conservation Service National Cooperative Soil Survey Page 4 of 4 Appendix 1: Selection from SDP 200100129 SWM Calculation Packet SWM and BMP Report Sterling University Housing, Sheets 1-21 Storm Water Management and BMP Report Sterling University Housing Albemarle County, Virginia 14 December 2001 Rev.03/01/02 /%i r, McKEE,CARSON CONSULTING ENGINEERS LANDSCAPE ARCHITECTS • PLANNERS 301 EAST HIGH STREET CHARLOTTESVILLE, VIRGINIA 22902 804-979-7522 TABLE OF CONTENTS Introduction 3 Project Description 3 Hydrologic Methodology & Assumptions 3 Summary 4 Pre -Development Drainage Area Map 5 Post -Development Drainage Area Map 6 Inlet Drainage Area Map 7 Time of Concentration Calculations 8-9 Culvert Capacity Checks 10-11 Ditch Capacity Checks 12-13 Storm Drain Design 14-16 Inlet Design 17 Storm Sewer Structure Schedule 18 BMP Computations Worksheet 19 Sediment Forebay Calculations 20 Water Quality Volume Requirements 21 PondPack Output — Pre -development Model Appendix A PondPack Output — Post -development Model Appendix B Public Road Drainage Calculations Appendix C INTRODUCTION Enclosed are the calculations for the Sterling University Housing project located between Fifth Street Extended, Old Lynchburg Road and Interstate 64. This report includes the BMP phosphorous removal spreadsheet, drainage area maps, inlet calculations, storm drainage pipes and structures capacity calculations, and the PondPack hydrologic calculations, including the land use (curve number) calculations, for the entire drainage area leaving the project site. PROJECT DESCRII'TION The proposed site consists of approximately 15 acres of undeveloped land. The construction property is bounded on the south by Fifth Street Extend, on the west by Old Lynchburg Road, the western residue of the Heischman property, and the Covenant School, on the north by Interstate 64, and on the east by the eastern residue of the Heischman property. The existing land cover is mostly wooded and brushy. There is an existing sediment basin/storm water management pond on the property that was designed and built for the Jefferson National Bank (JNB) project in 1994. This project will utilize the existing JNB pond for managing its storm water runoff. The original storm water pond design has been modified to account for the development of this property. Additionally, the original pond design has been revised to manage storm water from the future development of the western residue of the Heischman property (8 acres) and a portion of the eastern residue of the Heischman property (1.5 acres). The pre -development drainage area to the pond is approximately 40 acres. The post -development drainage area to the pond expands to approximately 60 acres and requires all of the Heischman western residue post -developed storm runoff to be routed through the Sterling University Housing storm pipe system to the storm water pond HYDROLOGIC METHODOLOGY & ASSUMPTIONS The SCS Unit Hydrograph Method was used to compute and route the peak flows through the revised storm water pond. Due to their small drainage areas, the proposed storm water inlets and pipes were designed using the Rational Method to compute peak flows for the 10-year storm. The post -development drainage areas and cover coefficients (curve number and "C" value) were computed assuming full build -out of this project shown on the approved preliminary plan. The curve numbers for the SCS method and the runoff coefficient C values were taken from the Virginia Department of Conservation and Recreation's 1992 Virginia Erosion and Sediment Control Handbook. This development (including the Heischman western and portion of eastern residue) will be required to detain the post -development 10-year storm runoff and release it at a rate less than or equal to the pre -development 10-year storm peak runoff rate from the existing pond. Pre -development condition in this case was assumed to be the current state of development of the drainage basin, or in other words, the JNB site plus the undeveloped Sterling and Heischman parcels routed through the existing pond and pond structures. This site (including the Heischman western and portion of eastern residue) will also be required to provide storm water quality measures to remove pollutants as measured by the phosphorus loads. SUMMARY In order to handle the proposed development (Sterling and Heischman western residue and a portion of eastern residue), the existing JNB pond will have to be enlarged and the existing outlet structure and existing emergency spillway will have to be modified. The proposed modifications to the existing outlet structure are to plug the existing intermediate stage orifices, add 2 —15" intermediate stage orifices at the new water surface elevation 396.5, and to raise the top elevation to 404.50. The proposed modification to the existing emergency spillway is to raise the spillway from 404.50 to 405.00 which also increase its width from 10' to 12'. The pre -development 10-year storm currently creates a discharge of 49.60 cfs from the existing pond outlet point. The 10-year storm post - development peak discharge from the improved pond will be 43.90 cfs at the pond outlet. The calculations show that the 10-year post -development release rate from the proposed pond is less than the 10-year pre -development storm peak rate. Additionally, the spillway structures for the improved pond will handle the 100-year storm without causing damage to the dam. The total impervious area for this site (including the Heischman western and portion of eastern residue) is 683,892 sq. ft. This is 63% of the total site areas. The calculated phosphorus removal requirement is 63%. The proposed pond improvements will include a sediment forebay, an aquatic bench around the dam at the perimeter of the water surface, and will also utilize an existing wetland bench. This should adequately address the water quality issues for this site. According to the Albemarle County Design Manual, these BMP's will normally remove 50-65% of the phosphorus. In summary, the improved JNB pond will sufficiently meet the County's storm water management requirements for the Jefferson National Bank (now Wachovia) facility, Sterling University Housing project, the future development of the entire western residue of the Heischman property, and the future development of a portion of the eastern residue of the Heischman property. Additionally, the improved JNB pond will sufficiently meet the County's storm water quality requirements for the Sterling University Housing project, the future development of the entire western residue of the Heischman property, and the future development of a portion of the eastern residue of the Heischman property. E 39D 17C ,1 14 .. - 1 1 ' .... ........ ..•• .-' •.•gyp ./ z:7.' ^` i f ` 34C f -' ` r .ItFSt RESrDuf .. - k, - SOILS LIST MAP NUMBER 2TB3C&D 34D 39D r_ _-- ---- --- 1.6a 390 16 - 39E 390, l'• ' 278 EDWENt A9N E EXISG SPdNO r SB• r -' f r -.a i-21P 390 ! r F r ' ENOE� % 1-1 • r _. ..: t Egi i._ r t 27C f 17C f / DA : 440 41 f Ol01P,$El Tc a252 1 OF {" 0000 ; ' 0 t FROM 1 rtoq Its opEarh ; 27B ,'•. idaft NAME ELIOAK LOAM GLENEG LOAM HAZEL LOAM HYDROLOGIC GROUP • • AIfrE WKEE CARSON CrMMIFN6EN6NEEN9 LEN05C• m,cHnas LmaO NEN! 001 Um High Sew LNNau fi, VA VQW f(m4r," x meluwreonam aNw.umrE..N=rr3e c..=o. uL U) O x Q !W!� F-� O C7 W W � Project No.: Sa1c Date: Revised: 0110 1'=300' 12/14/01 ini SOILS LIST MAP HYDROLOGIC A NUMBER NAME GROUP - 27B d C & D ELIOAK LOAM C 34B & C & D GLENELG LOAM B 39D HAZEL LOAM C -------------- 39E-- -- ` - \- ,�` •�• 278' '\ - _ - - - `+ ;\ i I 39D ; PROPOgD PRO$�CT S/ITE SWM POND _ 7 i. 34C I', 34B390 �a > \\ I 1 27C N � t i 27C •\, ` i _ l ... 7 1 DA 6h.26 ACRiS' 27B CN ' 1 Oi01POST1 : 43. 0 CFS - i Tc 21.6 MINUT$ \` 1 I - 1 OA 10of /%ICE MCIEE CAPSON CONEULMO ENOMEERa L"HWE MCRRECra LA 0"ERE M E. Nyn 8bERt Chs E .VA 2290E ew-07afuE rwrmtlu�rnwnam Project Na: 0110 Sale. 1-=300• Dale: 12/14/01 Re\tised: _................ 11 /YID --_ - - - - ----- - - - - -- McKHCARSC LE B-3 r ca SWM POND Or by G B 1 < B-2 z z A-1 r A-2 > /O A-3 . cn A-4 /... . P W6 Ael`h C 1 f A-5 II ?rIazte-ocla PC- Ck l.rLr lun� 1 I J.J CO L = Oc v Z 0 �k= 65°�Zz - z5`5. f sic L I'IGl �, = Z.Z% Im 2 J F e o l ce .tr�I: o, C a/1 vl DekJe1 epe rX lc� Ci)l1�7LP�(A�PDpr� r""10WJ �5 Ire—bOel-bee / . rrl YPJ- v,�C'.J- Sane a5 �re- deoel-oP4 f� _ L =5o` tc, _ =z 0.S m F(Dj-y" " �P;r/-- I-� &z3 �-. 12- -R/5 �z = 0m Ib O//v- iY!?G/iv4 v/�/V/;,sir / j-''U✓,%"..t CND 4/vz CHART 10 180 10,000 16e 8,000 EXAMPLE 13) 6. 156 6,000 0•42 inch. (3.} t«tl 6. 5,000' 0.120 cfe 5. 144 5. 4,000 v • Her6. 132 0 feet 4 3,000 III 2.3 e.e 5. 4. 120 (2) 2.1 7.4 2,000 (3) 2.2 1.7 4• 3. 108 3. �0m1w 96 1,000 r 1.2 �irA4e / 3. 84 800 yW = -3. V / 2• -_ 2- 600 / i 500 Z. 72 400 3 = 300 t = I.5 1.5 2 Z ty I.S 60 V 200 F z Z w C) 54 / Q — � 0 48 w 100 Z W > ¢ 80 D 42 V 6p �W L0 L0 5 HW ENTRANCE ¢ 10 o 'o— 40 SCALE D TYPE w W r . / 6 t 30 0) Sao'. edge .11n 3 .9 .9 w H nead.all .9 a 33 20 (z) wool..•e.an W 30 nua..0 x •8 .B II (}j Graau «d '8 � Pnpelln� 27 10 .T .T 24 6 T 6 Te «. .del. (2) .' (3) ereleCt 5 Mrl.enlell71..ce1.(1). Me. 21 ..e 11'.19M I.clihd He. tnr..en 4 0 end 9 cola, « noon. « • 6 , 6 3 ill.e1re1N• ,6 18 2 .S 1.0 Liz HEADWATER DEPTH FOR HEADWATER SCALES 253 CONCRETE PIPE CULVERTS REVISED MAY1964 WITH INLET CONTROL eUREAU 0( P BLZC t10A0e JAIL lld3 I81 I -ND SPC7ieN F-/ CHART 10 ISO 10, 000 168 8.000 EXAMPLE 6. 156 6,000 0142 inert« 13.3 1«1) 6. 5. 5,000 Q. izo.1. 44 6. 5. 4,000 ww . Rw 132 D r.a a. 3,000 pl Z.] e.e 5' 4. 120 l21 2.1 ].• 2.000 (3) 2.2 7.7 4• 3' 108 'D 96 1,000 3 Soo / 500 72 400 to = L� 3 300*� 1.5 1.5 = N ¢ 1.5 Z 60 V 200 / F _ _ / W 0 54 - Q O_ W O 00 = > 48 / ¢ 60 J Q = 60. c 42 /o- �So r(w SCALE ENTRANCE 10 ¢ i 40 D TYPE W f _ 36 � 30 (1) So.an Wa. with < •9 .9 .9 W 4 hub.11 � q 33 U Q 20 (2) o 30 � n«a..0 S •0 .6 l3) Gros« ..a '8 1\ 27 •' I«Lcllq I 10 24 �j 8 .7 .T T 6 T. ... .cal. (2) .r (3) P10.0 21 5 n.rh«Nu] I. w.b Ul, tnu 4 u. .lraynt Lc1inN IFf. tnre..n D wad D .c.N., « n.«.... .6 3 111.014f.a. 18 2 15 ®' .5 L .5 Liz HEADWATER DEPTH FOR HEADWATER SCALES 253 CONCRETE PIPE CULVERTS REVISED MAY*64 WITH INLET CONTROL SURE" OF VVYL.IC ROPOS J 11421 181 i�- Ditch near G-1 -- 2 year computations Worksheet for Triangular Channel Project Description Worksheet G-1 Ditch Flow Element Triangular Channel Method Manning's Formula Solve For Channel Depth Input Data Mannings Coefficient 0.030 Slope 33.30 % Left Side Slope 2.00 ft/ft (H:V) Right Side Slope 2.00 ff/ft (H:V) Discharge 0.53 cfs Results Depth 0.21 ft Flow Area 0.1 ft2 Wetted Perimeter 0.95 ft Top Width 0.85 ft Critical Depth 0.34 ft Critical Slope 2.75 % Velocity 5.93 ft/s —31 6rG- 3 TyPE f� Velocity Head 0.55 ft Specific Energy 0.76 ft Froude Number 3.22 Flow Type Supercritical Notes: A = 0.13 Ac. C = 0.75 12 = 5.4 in/hr 110 = 7.1 in/hr (based on Tc = 5.0 min.) 02 = 0.13'.75`5.4 = 0.53 CFS Q10 = 0.13'.75'7.1 = 0.69 CFS Project Engineer: Eliot Fendig e:\...\0110 design\final drainage calcs.fm2 McKee Carson FlowMaster v6.0 [614b] 1/14/2002 1:44 PM © Haeslad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA (203) 755-1666 Page 1 1s Ditch near G-1 -- 10 year Computations Worksheet for Triangular Channel Project Description Worksheet G-1 Ditch Flow Element Triangular Channel Method Manning's Formula Solve For Channel Depth Input Data Mannings Coefficient 0.030 Slope 33.30 % Left Side Slope 2.00 ft/ft (H:V) Right Side Slope 2.00 f Jft (H:V) Discharge 0.69 cfs Results Depth 0.23 ft Flow Area 0.1 ft' Wetted Perimeter 1.04 ft Top Width 0.93 ft Critical Depth 0.37 ft Critical Slope 2.66 % Velocity 6.34 fUs Velocity Head 0.62 ft Specific Energy 0.86 ft Froude Number 3.27 Flow Type Supercritical Notes: A = 0.13 Ac. C = 0.75 12 = 5.4 in/hr 110 = 7.1 in/hr (based on Tc = 5.0 min.) Q2 = 0.13*.75*5.4 = 0.53 CFS Q10 = 0.13'.75`7.1 = 0.69 CFS Project Engineer: Eliot Fendig eA..A0110 design\final drainage calcs.fm2 McKee Carson FlowMaster v6.0 [614b] 1/1412002 1:46 PM © Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA (203) 755-1666 Page 1 PROJECT STORM SEWER DESIGN LOCATION COMPUTATIONS DESCRIPTION All pipes 15' and greater are RCP (n=0.013): all pipes less than 15' are PVC (n=0.010) -- unless Otherwise noted. FROM TO AREA DRAIN. 'A' RUNOFF COEF. CA INLET TIME RAINFALL RUNOFF O INVERT ELEVATIONS LENGTH SLOPE DIA. CAPACITY VEL. FLOW TIME REMARKS POINT POINT ACRES C INCRE MENT ACCUM- ULATEO MINUTES IN./HR C.F.S. UPPER END LOWER END FT. ,a IN. C.F.S. F.P.S. MIN. it 2 (31 41 5 (6) 7 (8) (9) 101 (11) (121 13) (14) (15) 16) (171 1181 A-8 A-7 1 0.37 0.80 0.30 0.30 5.0 7.1 2.13 412.40 411.78 123.04 0.50 15 4.91 3.55 0.6 DI.3A H=3.92' F-1 A-7 1 0.16 0.75 0.12 0.12 5.0 7.1 0.85 414.83 41 L78 54.49 5.60 15 16.44 670 0.1 01.3A H=3.92' A-7 A-6 1.36 0.80 1.09 1.51 5.6 6.9 10.42 411.68 409.90 355.51 0.50 21 12.05 529 1.1 01-1 H=5.97" -1''. A-6 13.90 0.75 10.43 10.43 13.6 4.9 51.11 407.50 407.22 37.90 0.75 36 62.13 923 0.1 ES-1 Al-4 Al-3 0.50 0F0 0,20 0.20 5.0 7.1 1.42 423.50 422.00 75.03 2.001 8 2.39 6.75 0.2 YD A2.1 Al-3 0.03 0.40 0.01 0.01 5.0 7.1 0.07 422.60 422.00 56.96 1.05 4 0.27 2.-8 0.4 YO Al-3 At-2 0.20 0.60 0.12 0.33 5.4 6.9 2.28 422.00 419.03 99.02 3.00 8 2.93 873 0.2 YO Al-2 Al-1 0.14 0.50 0.07 0.40 5.6 6.9 2.76 419.03 416.87 61.81 3.50 8 3.16 9.57 0.1 YO Al-1 A-6 0.33 0.50 0.17 0.57 5.7 6.8 3.881 416.87 411.35 84.92 6.50 8 4.31 13.07 0.1 YO A-6 A-5 1.32 0.75 0.99 11.99 13.7 4.9 58.75 407.12 405.76 271.56 0.50 42 76.52 8.25 0.5 DI.4AA H=13.38' D-1 A-5 0.32 0.80 0.26 0.26 5.0 7.1 1.85 421.47 420.871 60.16 1.00 15 6.95 4.541 0.2 DI-3AH=3.92- A-5 A-4 0.12 0.90 0.11 12.36 14.2 4.8 59.33 405.66 405.18 96.93 0.50 42 76.52 8.27 02 DI.4AA MOD. H=21.54' - ' A-4 13.81 0.75 10.36 10.36 17.4 4.4 45.58 414.00 412,60 139.65 1-00 36 71.74 10.16 0.2 ES-1 A3-5 A3-4 0.18 0.70 0.13 0.13 SA 7.1 0.92 424.69 422.71 99.02 2.00 6 1.11 5 C4 0.3 YD A3.4 A3-3 0.14 0.70 0.10 0.23 5.3 7.0 1.611 422.71 422.09 31.00 2.00 8 2.39 6.94 0.1 YD A3-3 A3-2 0.22 0.65 0.14 0.37 5.4 6.9 2.551 422.09 419.12 99.02 3.00 8 2.93 8.8AI 0.2 YD A3-2 A3.1 0.19 0,70 0.13 0.50 5.6 6.9 3.45 419.12 415.83 65.81 5.00 8 3.78 11.47 0.1 YD A3-1 A-4 0.10 0.60 0.06 0.56 5.7 6.8 3.61 415.83 414.19 27.36 6.00 8 4.14 12.57 0.0 YD A4-4 A4-3 0.04 0.90 0.04 0.04 5.0 7.1 0.28 424.73 424.28 8.94 5.00 4 0.60 6 3- 00 Trench A4-3 A4-2 0.08 0.55 0.04 0.08 5.0 7.1 0.57 424.28 423.75 26.53 2.00 6 1.11 5.3z 0.1 YD A4-2 A4-1 0.07 0.70 0.05 0.13 SA 7.0 091 423.75 422.70 52.54 2.00 6 1.11 5.93 0.1 YD A4-1 A-4 0.06 0.60 0.04 0.17 5.2 7.0 1.19 422.70 419.57 78.25 4.00 6 1.57 8.25 0.2 YO A52 A5-1 0.01 0.50 0.0t 0.01 5.0 7.1 007 424.62 424.46 18.00 2.00 4 0,38 3.13! 0.1 YO A5-1 A-4 0.011 0.501 0.01 0.021 5.1 7-01 01431 424.46 423.98 2422 2.00 4 0.38 3 Trl 0.1 YD A6-1 A-4 0.10 0601 0.06 0 06 5.0 7.1 043 425.43 422,42 75-21 4.00 4 0.53 E 321 02 YD A-4 A3 O.T 0.75 0.56 24.09 17.6 4.3 103,59 405,08 402,94 356.56 0.60 46 119.68 1C.'! 0.6 DI-4AA MOD. H=20.13' A-3 A-2 1 0.211 0.851 C.1E 24.271 18.21 4.3 104 35 402841 402.16 110.25 0.60 48 119.66 10.C5! 02 DI-4AA H=19.75' s PROJECT STORM SEWER DESIGN LOCATION COMPUTATIONS DESCRIPTION All pipes 15' and greater are RCP (n=0.013); all pipes less than 15" are PVC (n=0.010) --unless otherwise noted. FROM TO AREA DRAIN.'A' RUNOFF COEF. CA INLET TIME RAINFALL RUNOFF O INVERT ELEVATIONS LENGTH SLOPE DIA. CAPACITY VEL. FLOW TIME REMARKS POINT POINT ACRES C INCRE MENT ACCUM- ULATED MINUTES IN./HR C.F.S. UPPER END LOWER END FT qe IN. C.F.S. F.P.S. MIN. (1) (2) (3) 4 (5) (6) 7 (8) 9 10 (11) (12 13 14 (15) 161 117 18) 82-5 82.4 0.03 0.45 0.01 0.01 5.0 7.1 0.07 428.80 428.37 42.63 1,00 4 0.27 2.44 0.3 YD B2.4 82-3 0.03 0.40 0.01 0.02 5.3 7.0 0.14 428.37 428.14 23.28 1.00 4 0.27 2.92 0.1 YD B2.3 B2-2 0.07 0.75 0.05 0.07 5.4 6.9 0.48 428.30 427.91 38.70 1.00 6 0.78 3.97 0.2 YD B2-2 82.1 0.08 0.75 0.06 0.13 S.6 6.9 0.90 427.91 426.30 80.49 2.00 6 1.11 5.92 0.2 YD B2-1 S-4 0.09 0.75 0.07 0.20 5.8 6.8 1.36 426.30 421.98 163.27 2.65 8 2.75 7.44 0.4 YD B-4 B-3 0.20 0.75 0.15 0.35 6.2 6.7 2.35 421.40 417.83 78.30 4.56 15 14.84 8.38 0.2 DI-3A H=3.92' B•3 B-2 1.32 0.85 1.12 1.47 6.4 6.6 9.70 417.73 411.63 250.08 2.44 15 10.85 9.36 0.4 DI-1 H=4.27' 81-3 81-2 0.44 0.50 0.22 0.22 5.0 7.1 1.56 420.98 419.37 80.49 2.00 8 2.39 6.89 0.2 YD B1-2 Bt•1 0.33 0.50 0.17 0.39 5.2 7.0 2.73 419.37 418.14 35.21 3.50 6 3.16 9.56 0.1 YD Bt-1 8.2 0.03 0.40 0.01 0.40 5.3 7.0 2.80 418.85 414.39 127.51 3.50 8 3.16 9.58 0.2 YD B-2 B•1 1.01 0.75 0.76 2.63 6.8 6.5 17.10 411.53 408.74 66.00 4.23 18 23.24 13.56 0.1 DI-3A H=8.00' B-1 A-2 0.78 0.85 0.66 3.29 6.9 6.5 21.39 408.64 405.36 131.17 2.50 21 26.95 11.70 0.2 DI-3A H=7.77' A-2 A-11 0.00 0.00 0.00 27.56 18.4 4.2 115.75 402.08 401.95 16.60 0.75 48 133.81 11.24 0.0 MH-1 G-2 G•1 82.13 0.50 41.07 41.07 20.0 4.0 164.28 403.50 395.20 113.43 7.32 54 572.29 29.47 0.1 JB-1 w/ rate H-2 H•1 0.31 0.85 0.26 0.26 5.0 7.1 1.85 405.36 399.00 33.83 18.80 15 30.13 12.92 0.0 DI-3AH=8.00' 11.5 11-4 0.03 0.45 0.01 0.01 5.0 7.1 0.07 426.15 425.72 42.63 1.00 4 0.27 2.44 0.3 YD 11.4 11.3 0.02 0.35 0.01 0.02 5.3 7.0 0.14 425.72 425.49 23.28 1.00 4 0.27 2.92 0.1 YD 11.3 11•2 0.06 0.80 0.05 0.07 5.4 6.9 0.48 425.65 425.26 38.70 1.00 6 0.78 3.97 0.2 YD 11-2 11.1 0.05 0.70 0.04 0.11 5.6 6.9 0.76 425.261 424.50 53.00 1.43 6 0.94 5.01 0.2 YD Inlet o U O O O ° N c i e N N - W 3 3 En to `• k7 N `�' .i t �.�J 4 7 L W t. i a 9 tl E Y O �d Remarks 8 A-8 3A 2.5 - 0.37 0.80 030 030 4.0 1.18 0,0016G 20 0.020 2.0 6.1 0.19 0.39 0.49 1.9 sum eir F-1 3A 2.5 0.16 075 0.12 0.12 40 0.48 0.0020 0.048 2.0 6.7 0.11 0.39 028 0.8 sumptweir A-7 1 4.0 1.36 0.80 1.09 1.09 40 4.35 0.0031 0.020 2.0 0.24 3.8 sump/weir A-6 4AA 4.0 1.32 0.75 099 099 40 396 0.0023 0,020 2.0 7.6 0.37 0.39 0.95 f0.3 sum weir 0-1 3A 2.5 0.32 0.80 0.26 0.26 CO 1.02 00001 0.058 2.0 6.1 0.17 0.39 0.44 1.7 sum eir A-5 4AA 4.0 0.12 0.90 0.11 0.11 4.0 0.43 0 00020 0.020 0.013 1 8 2,0 1.11 0 083 4,15 0,93 351 0.146 0.156 5.4 0.74 0.91 0.39 0.04 overflow to A•4 A-4 4AA 4.0 - 0,75 075 0.56 0.56 4.0 2.25 0.04020 0010 2.0 7.6 026 0.39 0.67 9.1 sumpAveir A-3 4AA 4.0 0.21 0.85 0.18 0.18 40 071 000020 0.038 20 7.6 0.12 0.39 0.31 1.0 sump/weir Bd 3A 25 0.20 0.75 0.15 0.15 40 O60 000 0.60 0020 0020 2.0 6.1 0.12 0.39 0.31 1.2 sumphveir 8.3 1 4.0 1.32 0.85 1.12 2 40 a0 0.00 a.a9 0.028 0.020 20 0.25 4.2 sum elr B-2 3A 2.5 - 101 0.75 0.76 0.76 4,0 303 0.0) 3.03 0.015 0.020 2.0 6.1 0.36 0.39 0.92 9.75umphveir 0-1 3A 25 0.78 0.85 0.66 0.66 4.0 2.65 000 2.65 0.024 0.020 2.0 6.1 0.33 0.39 0.85 8.1 sumplweir H-2 3A 2.5 - 0.31 085 0.26 0.26 4.0 105 7.00 1.05 0.001 0.020 2.0 1 6.1 0.78 0.39 0.46 1.7 sumpMeir STORM SEWER STRUCTURE SCHEDULE STRUCTURE ID STRUCTURE TYPE NORTH EAST TOP ELEV INVERT IN INVERT OUT PIPE DESCRIPTION A-1 -_ GS-1 �. 530613 533712 40196 - _ 5306 16 5320 52 408 44- 402 18 402.08 MH-1 _ 71025 LF 48" _ RCP Yiil _ _ OuO% - A-3 - - _____ _A-4 _ ---DI.JCC; _ _ DI-4CC MOD_ 5232_ 29 _ 520897 _ 5238- 6 _ 4882.88 _ 422 59 f 02 94 405.18 _ 402 84___ 35G 5G Lf- 48" HOP tut 0 60"/ 425 26 405 08 96 93 LF 42" R_CP__9 0 50- DI-4CC MOD. 5262.02 4801.76 406.76 405.66 A-5 427.37 420.50 40990 407A2 27453 _ LF J2' RCP Gil 05t1% A-6 D1-4CC _ 5474 65 4628.11 355.50 LF 2 "RCP fa 050 A-7 DI-1 582211 a55290 41774 41178 411.68 123 04 LF 15" RCP 4u 0 60_% A-8 DI-3C 59a4 73 4542 80 416.32 41240 A-2 MH-1 530616 5320 52 408.44 402 18 402.08 131.17 LF 18" RCP N 5.53 _ 8-9 DI-3A 5a27.78 527138 416.31 409.53 409.43 66.00 LF t8" RCP n 3 00% _ 8-2 DI-3A 5397.87 5194,19 419.57 411.51 411.41 DI-i 5663 43 St35 09 250.08 LF 15" P.CPM2.50% _ _ f�. 3_ 422.00 11 4.86 417 76 l3_4_ _ DI-3A _ 5727 OS 78 30 LFi5"RCP_ U 4 21 5t80 73 a25.34 421.40 f A-4 4CC MOD. 520697 4882.88 425.26 412.60 405.08 -C-1--ES-1 _ _.94_ 139.65 LF 3G' _ IiCf� i� 1.00% 5_074.25 4821 _ 114.00 _ ---- ---- DI-aCC MOD 5282 02 4807 46 427 37 A-5 420.87 46568 425.42 421.47 60.16 LF 15" RCP ra 100% D-1 DI.3C 5277.53 4743 63 5474 65 4628-11 3790 LF 336"R_CP _ FLid_07,;% A-6 DI-4CC 42050 407 22 407.12 545313 459692 E-1 ES-1 407.50 A•7 DI-1 582211 d55290 41774 41176 411.68 54 49 LF 15" RCP Fu1 5_60% F-1 DI-3C - 5837.74 450070 418.75 414.83 G-t -- HEADWALL 5937.Ot 4355 06 395.20 0-2 5835 25 a335 73 403.50 ------ 113 43 LF 54 - RCP rd 7 J2% 43-1 9{100 _ �ES-1 5935 46 4378 97 H-1 _ 399.00 D1L3A 690293. 33.83 LFi5' _ RCP r,� 8 90 H-2 4388.28- 412.86 405.36 Short Version BMP Computations For Worksheets 2 - 6 Albemarle County Water Protection Ordinance: Modified Simple Method Plan: Sterling university Housing Water Resources Area: Development Area Preparer: McKee Carson Date: 12/14/2001 Revised: 3/1/2002 Project Drainage Area Designation Project site + Heischman Western Residue L storm pollutant export in pounds, L = (P(Pj)Rv/12 j t C(A)2.72 ] Rv mean runoff coefficient, Rv = 0.05 + 0.009(I) Pj small storm correction factor, 0.9 1 percent imperviousness P annual precipitation, 43" in Albemarle A project area in acres in subject drainage area, A = 25.10 C pollutant concentration, mg/I or ppm target phosphorus f factor applied to RR V required treatment volume in cy, 0.5" over imperv. area = A(I)43560(0.5/12y27 RR required removal , L(post) - f x L(pre) °%RR removal efficiency, RR100/L(post) Impervious Cover Computation (values in feet & square feet) Item pre -development Area post -development Area Roads Length Width subtotal Length Width subtotal 0 0 0 0 0 0 0 0 0 0 Driveways Length Width no. subtotal Length Width no. subtotal and walks 0 0 0 0 0 0 0 0 Parking Lots 1 2 3 4 1 2 3 4 0 0 0 Structures Area no. subtotal Area no. subtotal 0 0 0 0 0 0 0 0 0 0 0 0 Actively -grazed pasture & Area Area yards and cultivated turf 0 x 0.08 = 0 0 x 0.08 = 0 Active crop land Area Area 0x0.25= 0 0x0.25= 0 Other Impervious Areas 0 683892 Impervious Cover 0% 63% 1(pre) I(post) Rv(post) V 2$,y85 cf 0.61 1055.4 New Development (For Development Areas, existing impervious cover <= 20%) C f I (pre)* Rv(pre) L(pre) L(post) RR %. RR Area Type 0,70 1.00 20% 0.23 35.44 94.45 59.01 62% Development Area 0.35 11.00 0% 0.05 3.85 47.22 43.37 92% Drinking Water Watersheds 0.40 1.00 1% 0.06 5.19 53.97 48.78 90% Other Rural Land ' min. values Redevelopment (For Development Areas, existing impervious cover> 20%) C If I (pre)' Rv(pre) L(pre) L(post) RR %. RR Area Type 0.70 0.90 20% 0.23 35.44 94.45 62.55 66% Development Area 0.35 0.85 0% 0.05 3.85 47.22 43.95 93% Drinking Water Watersheds 0.40 0.85 1% 0.06 5.19 53.97 49.55 92% Other Rural Land Interim Manual, Page 70 rev. 31 March 1998 GEB 'L0 S21 (Y) tni t4er`,�� S� 1L I5 Ac1rs TnIP rvIoIAS A('eq r�e �man We - Jere ReSl;dnC U•{%� C.CeS NASSu^,t 50O�u-i--peroous//1� 1 rea = 61 Acrec, t*5Ck Aa f=r,irfn ZPS.dAf- ^ 5-AcresQ &07 pr.,ruw-t, _ I crc- Ienef.rVio�S 'rtr<w 15.7 Acf-cS 9� r'eat Sed �lenl rare / VJ ILA-A�( �. . = 15. � Atrts'x 0,25;,c,1cs = I Z ; �c6/R- x 9 5j560 R/AUc, =Z7F4Jc( = 52,8 o-1 I Anew 753 129 `} ZIT50 50�0 TorcCJ-, / V o��M4 Vo),5"n(cF) 0 1OZ4 I,0Z.1 61157 10,I Z5 r13o C voLknic- ?roo,4jeo( MD cr) > vol-Amc �U V..'rCA L� We+ 4 x VV QV TienUt - 00 I / Iota x CO r W �7crm.,nc�l ?aal. 55 c Co�i�«r tle��t .o,. _V�►Nmt sG-n Cey�------- - 33s_ o O zo 'ad 39t 5- 9 `toy y 0 Z-`i /46.3 Appendix 2: Selection from SDP 201500094 VSMP Plan and SWM As -Built Fifth Street Place VSMP Plan, Sheets SWM-1, SWM-4D, SWM-7 — SWM-10 Fifth Street Place Stormwater As -Built, Sheets SWM-0 — SWM-1A EXISTING WET POND EXPANS 01M L_ I I > E m ERGENCY SPILLWAY 263 C.Y. OF VDOT EC1, CLASS 1,; RIP. -RAP INSTALL VDOT \EC-3 UNDER 'RIP -RAP" k� A ---RE-FER-TO---_ STM-1 PROFILE VSMP PLAN o 11111111A EXPANDED FORBAY AREA EXISTING POND RISER N. TS. "CONTRACTOR SHALL CLEAN OUT THE EXISTING RISER STRUCTURE AND DRAW DOWN THE POND TO THE DESIGN WATER SURFACE ELEVATION OF 396.50 EXISING 48" RISER__, CREST 0 404.50 - - - - - - - - - - --- 1DQ_jYB_5TDRM_@_4Q7Da - - - - - - - - - - - - - - - - - - - - - - - J(LY3 _5TQRM JA,,51 --R-4 . . . . . . . . . . . . . . . . . . — — — — — — — — — I 1R__510R)%L A AU-75 — — — — — — — — — — — — — — — — — — - — — — — — — — — j _y L 51 QB bL _9_A0_00 L — — — — — — — — — — — — — — — — — — TOP OF POND @ 396.50 EXISTING AND PROPOSED i-n (2) EXISTING 15" ORIFICE MAINTAIN INV. ELEVATION I W-0- --*-10, N-N 396.50. PROVIDE (2) SAFETY AQUATIC PLASTIC SOLUTIONS BENCH BENCH STORMRAX OR APPROVED BOTTOM OF POND 0 388.00 EQUAL. EXISTING AND PROPOSED .FER TO 6 PROF1 AP PLAN (2) PROPOSED 18" ORIFICE INV, ELEVATION 400.50. PROVIDE (2) PLASTIC SOLUTIONS STORMRAX OR APPROVED EQUAL. EXISTING RISER AND OUTFALL PIPE 30"0 RCP FLOW 3A IN19114 ON& VA17,1121111111 REFER TO P/\-STM-8 PROFILE VSMP PLAN /3\5 0. \ 40' S(--A:-L IN FN�! 11 A "Aia VDOT EC-3 LINING rhfet �Pond #1 (Ex. Riser) VA DEQ, Stommoater De-sigin Specification No. 14 (Level 1) P t2 NINAH"A Date. 8/4/201. 5 County/Cfty: Albemarle la La 8 0 & �a ,wu� Cc I�� ResrOalii Event i,00 inches u I a imn BMW Drairmigc, Ama Suunmwy (A&�rvs) 0 a T_ Totals 1_LsndCoVfr Rv ia Ed So-i- I 9L m > T! P (,--',V 0 L; 0. 0,9C Uj 7T I ............. j ------ ------ - - -------- - - ---- i 0100) 1) GTJ 22 iC . ... . .... ........ . Fw .. . ....... _j 11 12 CL Totals Rvc0efficwatts A soils I R soi k C suds O Sc ms h® LU or sto Uj 0.04 rMlant.'aaged Tl�urf 0_1 5 1 0, 2C ----------- ....... Imp e i-vio us Cover 0 - 9�1 0,95 Cl) U) DeT.errnlne Requlm�,d MiniMptim Sur -face Aria rig Dninagc Area] "Recommendpd" --- ------- - - - - - _-_---- - - - - < Mimunum Suif,­_e Area I IV" 6UG 1[31A� of ContibutinG Drainage Arcal "Recorm-n-ended" ,eAi c,,a 4 270 If,- N111 n i rn u im S u f f a Provided i OK - Sirface.Arcii Mwiled Moets, Design Require;tients Su, ricace Are P t z 'r"p- n ri a c, Are Determine Provided Treatmeea Vmumv, ........... - ------ > VCILI Elevation Area A2,SCM Aj,' 2 V, I -------------- - --------------------- 5,367 0 0 0 UD 12 202 5,754 16, 9 .,'i 5,652 21jIlu 41-1 oci 16,96fi 628 392.00 t 6,164 18,184 21,N7 833 6,266 29,293 - - - ------ - r --- -- -------- ----- - -------------T i 6573 10,41-1 �i,47f, 35,763 0- --i— ­_11 --- -------- 4�­­---------------------- Uj 7, 105 '20,312 6,837 42,601 1,578 0- ------------- t 1,867 -1 2 3, 4 74 7,mlz 50,409 - — - - ------------------ - --------- --------- ------ 9,()22 26,329 4,388 54,797 2�030 ------------- ---------- --- U) co Di�tem,.aaa Pequimd TrPatment Vcdr n- Volume from " Remaining Runoff Upstmam Rk Kul-lolMcAuctiOri i 1 0 I. volume LL C) prictic, I:_J LD� ------- perviousAnc;,� 3862 1-863 Bioretention I & 2 - ----------- ---- - — - - - -------- < TurfArea 124 10 -1 , , 504 B(orctention I FA 2 ------ ------- LL1 Tv V v, v0junno reduced by an mpst,,eafn BNAIP < 'fV provi dr,"i 18K - TrcatrTic m', Volume Prot/ dod Moets Desion Requi,omo.-ItS DetOrmine prc-vided FwLay volum,�! LO < Aea U ff-A2+�qr(w 2) Vo our 0, V0 Elevation lume. suirn Volume sum (D 2 C4 il) 1 4 0K.I 3� 141 0 0 0 4 1A , 874 J_ 350T 130 LU 03 ------- 4,289 7790 2S9 LU z 14,339 4473 W,263 380 Lij Ld 39700 S,F,38 1G,219 966 48-0 --------- -- 39------ � I,- z Z: 8-00 (�,(525 6125 i9,091 707 w ---------- -- 67 2 7,143 26,234 972 1 7,6 3 �< - A 3 9 9. C11 0 40000 8,7-1,9 24,1639 8, 2;,, 0 34,454 00 ------ - ----- R, N te mi ne R," ui re d Fa tray Vo I urrie (Z) -J�K,� Target Rainfall €+ ertt 0 ZS firches, comments .............. . . .... . . .. .. . . ..... & . .. ... ....... F �V' orbay Vol urnQ Required 4,701 Ift, Forbaw Yolume Provided 8,220 JOK-FobayVole me Provided i[4-GFiretif)Depth1 6.60 NI—eet- s Design Requimments Fo�hay De.pth Provided N31 Oetetrninn Requimd Ge.aynenji - ------ - ---- ----- Length ui'Sho� to Fiovit Path 320 ------- ---------- po LS-hortestFl0i'v Pad:hlovn�all Lengthl "�0.5 Ov-,-,Il i erigtl� 415 -Z -P, nidc� OK - GeorrieLy Prodded Dleets Design Requiremepts aLo i i0vefallLength 0,77 1)� I I - ------ ------ - — — ------ "J_ 00 --------- - --- -- ---- ---- -------- Ii n= try Uj W i -,it h 1-15 LL Lengrh/ Width] ��2 ------- . .... . .... Length Width J-26 lun]tios; DOES NOT MEEI'DESIGN REQUIREMIENTS "Existing Canidtion" --- ------- ......... -------- - DetRrinlne Actepab!e Water Dopa� ------ ------ ---- -- Ci N n Death '02 lirl if)PI rt Rate [ET( iticrthly In lt,at o ri Lo .s lin NNFI LU for S 24 lin Ir, s,co mo,asured Base Flow Rate 0 [MBI 0 ------ - CLUSa 2. ILA d ft2j Q EMERGENCY SPILLWAY N. T S. mawvm� Zml �1% G Nry r —CREST OF EMER E M _161 0� 40,5,F WFIRY -%41&, SPILLWAY @ 405.00 24" VDOT EC-1 CLASS I RIP -RA• CONNECT TO EXISTING EMERGENCY SPILLWAY 2 a' LO 0 4 09 '' ,•'hY y �' � +«,-. wY-i�• at.3.Y6L l y, 4aR+tfd .t'+�.-`-5�5� .... ... i , 3� ,.. � ... ........_.. � � -..... ^4 - _ �,r�`.. w. 'Y - NN \ \` � � ' V \ "'NW W �� V/ - "W '+Y V'- W WETLAND TYP. W W �� _ W � W sl/W V/ W W W V V` W 4 W 4ts 20' 10, 0 20' 40' 60' SCALE 1"= 20' Uj' CN G+3 Ill L p( ppgg U6 (} � UB F 0 LL W LU .. Lo G Z co r T� 4J ` ^ �W b c Z � 00 00 � LTl m t J �x La t � 6 C ti f G 3 OVERALL PRE DEVELOPED DRAINAGE .AREA MAP — " 1 / -/, �'�&' _ `.. ,� _ �. �% /�t #�G" �� � `•mar - , � E M.r W EXISTING LANDCOVER MAP ,« ` a 4 TOT — 8,7 AL SITE AREA — 16 27 AC (70 21 .F.) EX. FOR ED AREA/ OPEN SPACE = 571;517 S.F. (fi3.12 AC) � r v / ' I » G P! ' EST Y / » c v a e v x IV T pW r r 1 » s y Er e'Py»r / 3 t EX. MANAGED TURF AREA= 104,245 S.F. (2.39 AC) r. LLJ «� Lli < _I I f ' - 14.7 % pqy crj Y, i EX, IMPERVIOUS AREA= 32,959 S.F. (0.76 AC) t 4.7 % Pq E _ ' e,+' ) " 1 J/ cc l r � »W ,.i �. 1.•' _ / r '� » 1 . a » » i » » a , / yy���� »a A na' » » » r a / 1 • / 1 / w s a o a w / r P " T » °� » t dT ! 4 t r• � �4 » x o » « . » LL a rj uj I r t < pggg r. _ pa t� t r' SCALE iN FEE f < OVERALL POST DEVELOPED DRAINAGE AREA MAP �— co CD Luuj a it Lu _ h ` � W s, r' -J e � 'rx�vKsenao Y{ /Yv..,.... - � � Y, fir•: / JA' v _..� .-.;.�•�:.,-,�'..•..•.•• +� •.-. w �_'`' « LANDCOVER lPROPOSEDMAP � :.•' ate.. :; " r ::.: •.: TOTAL SITE AREA = 16.27 AC (708,721 S.F.a • e ra :r ✓ „ , •�.Xw:��`�• — PROP. FORESTED REA(OPENS ACE 77 1 1S.F.F1.77 AC l AQ� ✓ �.. o 10.9 IV s9 PROP. MANAGED TURF AREA= 357,192 S.Fa (8.20 AC) �, Z_ lw 48.8 d 1. 8 0 v a r, r f , + u ev . , , r•••.`.• Yf �' —�' PROP. IMPERVIOUS AREA- 274,428 S.F. (6.30 AC) / e, ♦,r e Y •s r° s: •ea a e• , i +r e°r r' 0 0 , r r• ,•r n .y s , r s ' so • s , o• , , e• ' ♦ e ♦ e ," •s: -,•a°♦ -.aryh A °r♦ it Y i.,_.._.. � a",'�h"+.�` /) t♦'r,^+^r-, • r , r , , e . •/ • % 1 •G i - 9 38.7 /o 0 . .:..... .. ♦: i u Lij CL • , e+nr r° is a ♦.n; s< •r. , _i /� • t e ' t: r, ./ G f •q,• ,/ • . Lu e •. •.e G: / n +C / r , , r• e• „ t • •e • „ „ :e „ 1 •,o j � r, r r r ry f - /_" SCAEE IN FEET m LIJ -J AT NIX I A T- ill1,�11PI/ n. /Z/ j I, Z f 0 7 Z / LoAc=675 31 N m 1IJ 2`7 -N A, "X TC=C fy co .0 LU C�s LLI w C = ZI-Y 16 -------- ------ /Ac—iD =6.T 18 20 lv c0.47 i T LIJ = I& 0.50 ti" g"I Z V) L 014 _3 71— E jg, 3-3 C 6Tc- c; =0.15 A 31 C 6-1 SCALL IN FFI-7 0 D.A. = 72.72 Ac, CN = 88 Tc = 21.6 min. WEIGHTED CN: 12.53 AC.— 5TH STREET APARTMENTS @ CN = 86 (SEE SHEET SWM-8) 60.19 AC. OFF —SITE TO POND @ CN = 89 (SEE STERLING POND REPORT) D.A. = 1.60 Ac. CN 91 Tc = 7.7 min. WEIGHTED CN: 1.13 AC.VIMPERVIOUS @ CN = 98 0.34 AC. TURF @ CN = 74 0.13 AC. FORESTED @ CN = 70 BMP DRAINAGE AREA NOTES: BIORETENTION 1 DRAINAGE AREA CONSISTS OF INLET AREAS 18, 20, & 22, BIORETENTION 2 DRAINAGE AREA CONSISTS OF INLET AREA 16. SEE SHEET SWM-9 FOR INLET DRAINAGE AREAS. FIFTH STREET PLACE STORMWATER AS=BUILT ALBEMARLE COUNTY, VIRGINIA MAGISTERIAL DISTRICT SCOTTSVILLE z O JEFFERSON I I Mq� sT U) PARK AVE > �� LLl 7J FwgrFRsr g a << z rn n W Q O rn m U o° � U z Q A Q� 9G mJ�O N RR�S RO 5� P 2 PROPOSED OFF -SITE 40 MONpCpN R� SANITARY SEWER IMPROVEMENTS O LtJ Q Q z o NPROPOSED ,��Fti i WW W 5TH STREET PLACE 5 CpI d c LIJ DEVELOPMENT QO ST. �PS W j Z o� W O ::) o If U L VICINITY MAP = w Q O LU Scale: 1" = 2000' � F) m v U- Q 00 z N Lo LU W Y d LLl Y Q eo pj Z Q z = Q m Lu U U O � SHEET DESCRIPTION VIA 0 SWM-0 COVER SHEET _j SWM-1 AS -BUILT POND DETAILS 6 0 SWM-1A AS -BUILT FOREBAY REFURBISHMENT Z SWM-2 AS -BUILT BIORETENTION DETAILS SWM-4 I SWM-6 OVERALL DRAINAGE AS -BUILT O 11`Oa SWM-5A - SWM-5E AS -BUILT STORM PROFILES SWM -9 AS -BUILT INLET DRAINAGE AREA MAP q� o N cn "Zt U Co ti Cq ON LLJ Z (j J E- Co 0 4 �UT/4� N o N 3 C w N L / V a SURVEY NOTES: eFFpRE �o'� t. BENCHMARKS ARE PROVIDED ALONG THE 5TH STREET MEDIAN. 2. DATUM AS FOLLOWS. BEFORE YOU DIG GALL o HORIZONTAL — NAD 83 (GRID NORTH VIRGINIA STATE PLANE, SOUTH ZONE) „ r, VERTICAL — NAVD 88 PROTECT YOURSELF, GIVE THREE 3. AS —BUILT SURVEY DATA PROVIDED BY ROUDABUSH, GALE do ASSOCIATES, INC. WORKING DAYS NOTICE L : f- fEXISTING POND RISER r• r IN- t f • • • iI:3l (2) PROPOSED 18" ORIFICE CREST 0 -,•- I � 1 • ; �� - ,,, retlLi%kl • INV. ELEVATION 400750-.= 7XISTING AND PROPOSED APPROVED EQUAL. (2) EXISTING 15" ORIFICE MAINTAIN INV. ELEVATION EXISTING RISER 396.50. PROVIDE (2) AND OUTFALL LNG&jgTEgEp SAFET* PLASTIC SOLUTIONS PIPE J f • i APPROVED EQUAL.1 • 1 .. Ll��r 01 _ 1 cRi:9bY:? PROPOSED 0 391.00-394.00 OUT iIbi1L! MEMNON?'@ .f pig av till 11 I .\ I y i \ \ f, �♦ ' �}� ieef� rely o-C, pxAo iep ';- s� +�p�� ♦�♦ . ,•s . fir. Y � 4 l f } �o L L i 1 • t .�� � �! a �1. �, • L} •.ae, s •.,1 .. ..-G 1r� 1 �� l� •!� � \ Q y7+« « .. ,.:r' :fir ..va.,gp,'a�frreeiif 1 .�;, `�1��:.�4 :±`ay.�`+i �isriy�i. ��Y•`rass�ii C•e �e a+ee•+.. F� wi see «' �� �� ' e+er"t�`�+re+ f�Sr•IrNeE1«•�,�#• t 1� 1N7 �l'�'°�"• ►��e� Pjs�� j "•�g►M. ,� , • • • ,3.S�jt j / , .. P �II/ �ie;�.�, , , � ice, ,• ej•�� ` � �~.r.../ _ ram: �F--< �•�'� rx, T: �:� .r,: 4 - s •iteh� e i rY • z` RP., '111111111 I t`\.100%10` 0_yr.mpg� . SFA-z aye afr �` + o � +'.r i ! c ♦iA 1p° <if "�N�"��6':•rtrp> • i��SP,► a� a Erb +sra r�•r �I1I�,rt I : S ♦ , ii�t"t• `. , , s . y r. .► is � ..rr � s•,�•z���ti ,,j, , ,erg, {`yam ..��,��•- _ t >�%0%401 4 �Nq gg LEGEND EXISTING CONTOUR PROPOSED kSBUILT i Wet Pond #1(Ex. Riser) VA DEQ StormWater Desgin Specification No,14 (Level 1) Design by: SNR Checked by: MMM Date: 8/4/2015 County/City: Albemarle Runoff RatluT ().()aLevel 1 data input cells ctlon Credit Target Rainfall Event 1.00 inchas�� calw1 incells constant values BMP Drainage Area Summary (Acres) Landcover Type AoIIs BSoiis CSoils DSoils Totals Landcover Rv Impervious 000 0.00 5.18 0.00 5.18 0.95 _ Managed __.._ Forest/Open Space 000� 0.00 0.00 6.00 5.64 0.36 0.00 0,00 564 0.3b 022 0.04 7orals Rv Coefficients _ Asoils 85oils CSoils DSoils Forest/Open Space D 02 0 03 0.04 0.05 Managed Turf 0.15 020 0.22 025 impervious Cover 0.95 0.95 095 0 95 J Determine Required Minimum Surface Area Mini Maximum Surface Area Sur#use Area Provided 14 610 ft' 9#2� ft' n Dralna a Area]Recmnmended [3% of Contributing Drainage Areal ""Recommended Ol. Surface Araa Rrovided Meets Dell n Regmrrments - � Determine Provided Treatment Volume ___.._. .......... _.._.... ....._. ._ .. ..-_ .. ........ __.-___. .. ... _.___ .., _.__.___-_ .. Elevation Area Al+A2+sgr(Al A2) Volume Volume Sum Volume Sum if I) ft') ­_(fi) (it))(fill W) HOCKENC _.- 391.06_-- -8yi•-® __..-..,._�r9r.H® j-t56a® 1 }}B;`i. 392 00 fi;3GrF 'f9-}86 393.00 394 395 00 {r968 ?-i8S •H>-7'}} 26;512 ,., 'tTi6661 ' _._ 34o-2e ® 396.58 .. 8',,31 Determine Required Treatment Volume Volume from Upstream RR Runoff Remaining Runoff Prac Reductian Comments Practice Volume (ft ft' ft' Impervious Area 3862 0 17863 Bioretention 1 & 2 Turf Area 784 0 4504 8ioretention 1 & 2 Tv { 22,367{ir (100"11v*A/12) volume reduced by an upstream BMP 'TV provided OK Treatment Volume Provided Meets Design Requirements - Determine Provided Forbay, Volume _ Elevation (ft)(fill Area Al+A]+sgr(At"A2) (fill Volume Volume Sum {(t' (FI') Volume Sum (vd' _._ T - __- {r6z"T }9 75 23428 8}f9 aA,65y '2'783'480 398.00 486h36 -6 i35- i9Q41- -1.94 . -8,220 04,464 471;16--... . .. __.. _. __. Determine. Required Forbay Volume Target Rainfall Event 025 inch e Comments iinperaous Acerige 518 -pA�cres F-- -- ForhayVolumeRequlrad --- - 4,701 --- fr' ---- _- -_- (025/12`A ,,�"43560j Forbay Volume Provided OK - Forbay Volume Provided Meets Design Requirements [4 6 reet in Depth] Forbay Depth 6.00 it OK- Forbay Depth Provided Meets Design Requirements Determine Required Geomerty Length of Shortest Flow Path 320 If Comments Overall Length 415 If - I[Shorlest Flow Path / Overall Length) > 0.5 - Ratio SFP/ Overall Length 0.77 umtlCsS OK - Geometry Provided Meets Design Requirements length 145 If Width 115 if (LanglhJ Width) 22 length/ Width 126 umtless DOES NOT MEET DESIGN REQUIREMENTS **Existing Conidt onM° Determine Acceptable Water Depth Avg Design Depth 102 in is Design Requirements 5ummertvap Rale B m [ET] (DP>ET+INF+RES MBj MonthlyinfdtrationLoss _ _ 7 Ile JINFJ _- Reservoiraf Water for FS Measured 3ase Flow Rafe 24 0 in in (MB] _ 0 cfs Qft/s' ` 2.597x6 (12"/!t /SA of and ft�) EMERGENCY SPILLWAY N. T.S. -CREST OF EXISTING VDOT EC-3 / BERM Q 408.00 LINING _ -CREST OF EMERGENCY J W ¢ U Zz Q J � W W W a �> W W O z N O H W ^ _ W Q J_ m m L Q U) 01) N o 2 U g S 00 r W W Y �_ z Y <i DD Q z i ¢ 00 o W U U �T1IA It"00 Do O ;:ft V)rn F a � z\" uj Q. J Cr J > MO �- W CO O � N 'CL`CL � J o J ill a ro o U S C IRA JIM •��� s�'Wllm ICI • • I�� �\ 69.7 CY OF VDOT EC - CLASS I, RIP -RA \ 1.5' DEPT \(TO BE PLACED OVE \ \ FILTER FABRI( m:. f r T q S ♦ ', I�III 4 0 . �j.. I ram,,, ice. ` < �,���' /� fi J 1;1 �a�•�• �.•�i�I1 �� .►- ►' � � `� � �� '� •� ��` ���, ��:� - _. � `fie._ �\� 1 • •� • • "..��llllllllllllllllll��i,:<����'��� �� Nab MR I -ram � :,,:` ►�♦��. \ ,� .�I�I • A • GEOTEXTILE I FABRIC mI 10YR POND ELE ,T"__,_._.._ _._ .. _ 1 OYR CHANNEL ELEV/ t BOT OF RIP -RAP ELEV;395-G Cal 0+20.00 i 05.0 405.0 10YR PON ELEV. i — I EXISTING GRADE ' GABION BASKETS - _ I BOT ELEV = 315 00 GEOTEXTILE FABRIC 1OYRCHANNEL EL V. - _ 12" CLASS 1, RIP RAP PROPOSED GRADE f UNDERDRAIN / REMOVABLE / ( Q 00 CAP ON UPSTREAM ND NWSE. V, / :7I5 GEOTEXTILE )FABRIC I Friction Method Manning Formula Solve For Normal Depth Input O Roughness Coefficient 0.076 Channel Slope 0.01300 fyft Left Side Slope 2.00 Wit (H;V) Right Side Slope 2,00 fVft (H:V) Bottom Width 1000 it Discharge 37600 ft'/s p t � ro„...-., h M1% f`' /�'l.?Y ✓ /KT" 'rY k. M �✓b �4 � � i Y$A "'d �.i'nf".5d "M ^y 5� v' �'T��'r1„..ax-t.:v^.4�...�ry�3.,',� F^4ss',�r'S�✓.at3w�akv,�� n:�,f!4.'M",�°':+':1. n"��''�YS���^a:'Fs Normal Depth 4.52 ft Flow Area 86.13 ft' Wetted Perimeter 30.22 it Hydraulic Radius 2.85 ft Top Width 28.09 ft Critical Depth 2.89 it Critical Slope 0.07496 ft/ft Velocity 4.37 fJs Velocity Head 0.30 ft Specific Energy C82 ft Froude Number 0.44 Flow Type Subcntical LEGEND EXISTING _ CONTOUR PROPOSED _ CONTOUR ASBUILT CONTOUR z O 111 tY z a Q o N W< i � r Z w a U_) U f- z m Q z0 a w� > U_ W W w W O WQ U Q U) W in w = w¢ o �w LL. Q F_ J m UNDERDRAIN NOTES: t 1. ALL PIPING WITHIN THE UNDERDRAIN SYSTEM SHALL HAVE A U) MINIMUM SLOPE OF 0.5% AND SHALL BE CONSTRUCTED OF N Q SCHEDULE 40 OR SR35 SMOOTH WALL PVC PIPE. Igo 2. A MINIMUM OF 4 ROWS OF PERFORATIONS SHALL BE PROVIDED AROUND THE DIAMETER OF THE PIPE AND THE PERFORATIONS SHALL w BE PLACED 6-IN ON CENTER WITHIN EACH ROW FOR THE ENTIRE _j 00 LENGTH OF EACH DRAINAGE LATERAL. PERFORATIONS SHALL BE o Iv o 3/8-IN IN DIAMETER. C) 00 N 3. UNDERDDRAIN PIPES SHALL HAVE A MINIMUM OF 12-IN OF STONE ABOVE AND ON EACH SIDE OF THE PIPE. LU LLL1 Y LU Y Q 00 r, JO' tii ~ U W p SECTION 'C' -- - _-' o W 0 0 ° I GEOr�XTtl_L' FABRIC BOT OF RIP -RAP 1-6' I UNDERDRAIN FI FV- -i95100 0 a omz c rn M N LU CV)� �Nco 0. LU CO F= Q o J O � W nl c w 't5 C ro � La n w