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Home My WebLink AboutWPO200800084 Plan - Other (not approved) Stormwater Management Plan 2008-08-07LEGEND: aa�aa APPROXIMATE WETLAND LIMITS a a a a a APPROXIMATE STREAM CHANNEL LIMITS [71 APPROXIMATE OPEN WATER LIMITS FIN PROPOSED STORMWATER POND PROPOSED SHALLOW MARSH NI DETENTION BASIN DRY DETENTION UPSTREAM OF PROPOSED CULVERT PROPOSED STORM DRAINAGE MODIFICATION POTENTIAL UNDERGROUND DETENTION PROPOSED BUFFER/LANDSCAPING STRIP PROPOSED STREAM RELOCATION PROPOSED ROAD/PATH REALIGNMENT PROPOSED FULL LID TREATMENT SELECT WATER UALITY ENT CORDANCE WITH APPROVED STOPRACTICES IN RMWATER ER CONCEPTIP AN NOTE: THE LIMITS OF WATERS OF THE U.S., INCLUDING WETLANDS, SHOWN ON THIS MAP [EXCLUDING AREA SHOWN AS PENDING CONFIRMATION] WERE CONFIRMED BY THE U.S. ARMY CORPS OF ENGINEERS ON 10/06/03, CONFIRMATION #03-H0136-75. ORIGINAL (APPROVED) SWM CONCEPT PLAN HYDROLOGIC MODEL RESULTS MODIFIED SWM CONCEPT PLAN HYDROLOGIC MODEL RESULTS PRE -DEVELOPMENT PROPOSED ROUTED STORM EVENT PEAK FLOW AT OUTFALL PEAK FLOW AT OUTFALL (EXPRESSED AS PERCENTAGE OF SITE) = 53% (CFS) (CFS) 1 -YEAR 137.7 133.3 2 -YEAR 206.2 232.5 10 -YEAR 424.3 617.0 MODIFIED SWM CONCEPT PLAN HYDROLOGIC MODEL RESULTS WATER QUALITY CALCULATIONS: PRE -DEVELOPMENT PROPOSED ROUTED STORM EVENT PEAK FLOW AT OUTFALL PEAK FLOW AT OUTFALL (EXPRESSED AS PERCENTAGE OF SITE) = 53% (CFS) (CFS) 1 -YEAR 137.7 44.3 2 -YEAR 206.2 77.5 10 -YEAR 424.3 466.6 WATER QUALITY CALCULATIONS: w 'x, PROJECT AREA = 93.0 AC " TOTAL PROPOSED IMPERVIOUS AREA = 49.29 AC. R\ \ (EXPRESSED AS PERCENTAGE OF SITE) = 53% '> PROPOSED ROUTE 250 i LANDSCAPING STRIP EXISTING IMPERVIOUS COVER <20% � LPRE = 1.41 LB-TP/AC/YR X AREA IN ACCORDANCE WITH APPROVED STORMWATER•...•...: MANAGEMENT CONCEPT PLAN BY OTHERS LPRE = 1.41 LB-TP/AC/YR X 93.0 AC .......:.:..:::........�j LPRE = 1 31 .13 LB-TP/YR mEN -,L i Y \ LPOST = 6.14 X [.005 +0.009(IPOST)] X AREA \ LPOST = 6.14 X [.005 +0.009(53)] X 93.0 AC LPOST = 301.70 LB-TP/YR OF PROPOSED CULVERT, 1 RESERVING EXISTING STREAM (INCLUDES BRIEF INJUNDATI.N RR = LPOST - (LPRE X D 2 RR - 3101.7 LB-TP/YR-(131.13 LB-TP/YRX1.0) ..�� . ; . RR = 170.57 LB-TP/YR .. NOTE: SEE POTENTIAL WATER QUALITY TREATMENT MEASURES GRAPHIC FOR COMPLIANCE DEMONSTRATION. THE FINAL TYPE/CONFIGURATION I OF THE STORMWATER MANAGEMENT FACILITIES ARE SUBJECT TO CHANGE DURING DETAILED DESIGN, BUT SHALL PROVIDE THE MINIMUM , ` REQUIRED POLLUTANT REMOVAL SHOWN ABOVE. w.wwwww_ R� EXISTING FIRE w Sol w 'x, d i X FULL LOW IMPACT DEVELOPMENT (LID) R\ \ TREAT PROPOSED DEVELOPMENT WITH SELECT i WATER QUALITY PRETREATMENT PRACTICES '> PROPOSED ROUTE 250 i LANDSCAPING STRIP 1 ••: � r IN ACCORDANCE WITH APPROVED STORMWATER•...•...: MANAGEMENT CONCEPT PLAN BY OTHERS ! .......:.:..:::........�j \ \� \ mEN -,L i Y E, ............... �, ... .. .... I 9WM 3-1 DRY DETENTION (UPSTREAM ' OF PROPOSED CULVERT, 1 RESERVING EXISTING STREAM (INCLUDES BRIEF INJUNDATI.N \' 2 -ter,.. ................. ................. ..�� . ; . ... . .. .. w.wwwww_ R� EXISTING FIRE w Sol d i X FULL LOW IMPACT DEVELOPMENT (LID) R\ \ _PRETREATMENT IN ACCORDANCE WITH \ NATIONAL LID HANDBOOK CRITERIA AS PRE CONDITIONS) w.wwwww_ R� EXISTING FIRE w Sol d i m FULL LOW IMPACT DEVELOPMENT (LID) - RETENTION BASINS _PRETREATMENT IN ACCORDANCE WITH \ NATIONAL LID HANDBOOK CRITERIA AS PRE CONDITIONS) "z W r 0 (MODELED -DEVELOPMENT S >m SEN mEN -,L i Y E, a¢U 9WM 3-1 DRY DETENTION (UPSTREAM ' OF PROPOSED CULVERT, 1 RESERVING EXISTING STREAM (INCLUDES BRIEF INJUNDATI.N � C) MILAN - aao OF PROPOSED TENNIS COURTS w.wwwww_ R� EXISTING FIRE w Sol :Z PROPOSED SWM 3-1 � m m SWM 2-2 SERIES OF STEP -POOLS SERVING AS STORMWATER - RETENTION BASINS OtT� "z W m o S >m SEN mEN E, a¢U a � C) MILAN - :Z PROPOSED SWM 3-1 � m m SWM 2-2 SERIES OF STEP -POOLS SERVING AS STORMWATER - RETENTION BASINS OtT� "z W m o S >m SEN mEN a¢U POTENTIAL STREAM 1C ANNEL RELOCATION ' �:. AND VEGETATED BUFFER sWM 2-1 a*.a*:*.. OUTFAL / ^� IMPROVE EXISTING POND �. TO SERVE AS STORMWATER a MANAGEMENT FACILITY �' \ MODIFY STORNA DRAINAGE TO DISCHARGE DIRECTLY TO PROPOSED SWIM 2-1 (EXCEPT FOR CILFAN WATER OUTFALL DIRECTLY TO STREAM) TO PRESERVE STREAM CHANNEL UPSTREAM ` OF PROPOSED SWM 4 \\ (O�� PLAN FOR FRIVANNA VILLAGE THE ORIGINAL CONCEPT PLAN WAS - THIS PLAN DEPICTS MODIFICATIONS IN THE ORIGINAL STORMWATER THE REZ MANAGEMENT CONCEPT PREPARED BY THE COX COMPANIES IN CONJUNCTION WITH THE REZONING PROCESS FOR DEVELOPMEE SI MODIFICATIONS ARE PROPOSED IN CONJUNCTION ITTITHE WITH THE PERMITTING PROCESS TO AVOIDANINIMIZE IMPACTS TO JURISDICTIONAL AREAS TO TH THE EXTENT FEASRLE. ADDITIONALLY, EFFORTS HAVE BEEN MADE TO DETENTION EEMPLOYEO. THE MODIFIED PLAN ATTEMPTS TO MAINTAIN PROVIDED AND REDUCE THE AMOUNT OF UNDERGROUND INCREASE THE QUANTITY CONTROL D TVfPE OF THE PROPOSED FACILITIES. ORIGINALLY WATER \ - SAME GENERAL APPROACH OF THE ORIGINAL PLA, SOME ADJUSTMEN QUA NREL QUALITY TREATMENT COMPLIANCE WAS ADDRESSED IN RELATION TO OVERALL STRATEGY OF PRE-TRErATMENT, A MODICUM OF EMENDED -DETENTION, AND POLISHING TREATMENT THROUGH PONDANETLAND SYSTEMS AT THE OUTFALL HOWEVER, AS PART OF THE REVISED STORMWATER PLANNING PROVIDED HEREIN, \\ POTENTIAL WATER QUALITY TREATMENT MEASURERS HAVE BEEN IDENTIFIED WHICH WOULD SATISFY THE LLEVEL OF PRETREATMENT CALLED FOR IN THE REZONING PROCESS AND MEET OVERALL POLLUTANT REMOVAL REQUIREMENTS (SEE POTENTIAL WATER QUALITY THENMMENT MEASURES GRAPHIC). THE PROPOSED STORMWATER MODIFICATIONS SHOWN HEREIN CONSIST OF: Q� j " \ \ Ci \\ \\� \ CLEAN WATER PICKUP DISCHARGE DIRECTLY i T DEVELOPMENT LID i � C • INCREASED LEVEL OF PRETREATMENT IN THE WESTERNMOST SECTIONS OF THE DEVELOPMENT TO) CONSIST OF FULL LOW IMPAC DEVELO E T ( ) � \ ''�. \ TREATMENT IN ACCORDANCE WITH THE NATIONAL LID MANUAL. (^ lt. !�\\ 1� 1 I \ ' TO DOWNSTREAM CHANNEL) i I/ • REPLACEMENT OF THE RETENTION POND ADJACENT TO THE EXISTING FIRE STATION WITH A DRY DEIEMIEON FACILITY UPSTREAM OF THE PROPOSED ROADWAY ' 1 I J • RETROFITS TO THE EXISTING PONDS ON EITHER SIDE OF THE PROPOSED GREEN TO IMPROVE THEIR PERFORMANCE RELATED TO STORMWATER MANAGEMENT. \ J \ 411 y r / M c • THE PROPOSED POLISHING TREATMENT WITHIN THE PROPOSED PARK AREA CONSISTING OF A SERIES OF STEP POOL FEATURES REMAINS BUT THE DESIGNS HAVE BEEN ADJUSTED TO OPTIMIZE THE AVAILABLE STORAGE PROVIDED_ — • REPLACEMENT OF THE FINAL THREE STEP POOLS INCLUDED IN THE ORIGINAL PLAN WITH ENHANCEMENTfS/ADDITIONS TO THE EXISTING WETLANDS, SERVING AS��r' j \ ,, �..�✓ A SHALLOW MARSH DETENTION FACILfTY • ADDITION OFA DRY DETENTION COURT IN THE VICINITY OF THE PROPOSED TENNIS COURTS G DURINIG OF THE PROPOSED PATH. AS SHOWN THE AREA IS^,y. GRADED SUCH THAT THE TENNIS COURTS WILL BE INUNDATED WITH SHALLOWBRIEF PONDING DURINIG STORM EVENTS, WHICH DOES NOT APPEAR TO BEA Na f� CONCERN. / , n „o� SWM4 /� a </ 's ___ SHALLOW MARSH DETENTION UPSTREAM OF PROPOSED CULVERT \ (PRESERVE EXISTING WETLANDS AND CONSTRUCT ADDITIONAL) a a / PRESERVE STREAM /. CHANNEL UPSTREAM / OF PROPOSED SWM 4 I MODIFY STORM DRAINAGE TO OUTFALL DIRECTLY TO ROPOSED SWM 4 1 CONTOUR INTERVAL = 2 FEET 120' G 60' 120' 240' 360' i � m m U "z W m o S >m SEN mEN a¢U a � C) aao Z a °C a W uj au z Z (� Imo or O~a3 z (1) ui J V WW>w ��VQJ �=QZ a OZaw OQ> m P� o G REV) ONS DRAWN BY: DESIGNED BY: SMS OAP DATE: CHECKED BY: 8/7/08DAPANDB SCALE' ,.-,Zo' 1 SHEET: JOB#:3647 LEGEND: \ �� Y APPROXIMATE WETLAND LIMITS \v# M1 - APPROXIMATE STREAM CHANNEL LIMITS POST -DEVELOPMENT DRAINAGE AREA F R71 POST -DEVELOPMENT SUBWATERSHED LABELS % \ \\o �A A3 our2 POST -DEVELOPMENT OUTFALL % �� zi.Baac LOCATION � ,/�� `�, A j I ♦ �f 1 7 J\,� —� V ,/* M r _i A 9� F4 OF 1/6 P 40 oma ° 'T ----- I Y,�\ 1►�.� y l �, ��,P % ,� v-.- - .•moo , - uil��EN �/" �� • Orr , � 8��;r �.►�� ' V M F x ¢ � a as a a 3.02 AC PF1 O SECT U 1 Yxx^Fx l 1 z AC Y A1A % \\\\ y 489 AC \ ■ \\ CONTOUR INTERVAL = 2 FEET 7 150' 0' 75' 150' 300' 450' ZQ Q Z W �_ �. 9w DAZE: Omoz � Wa�O �W�v SCALE: Q - Zza J F NQQw JOB#:3647 p o� >_ m DRAW N BY: DESIGNED BY: SMS DAP DAZE: CHECKED BY. - Y:81808 81808 DAP/WDB SCALE: SHEET: SHEET: A G, JOB#:3647 )0 LEGEND: j� j PROPOSED STORMWATER POND PROPOSED SHALLOW MARSH DETENTION BASIN DRY DETENTION UPSTREAM OF PROPOSED CULVERT PROPOSED STORM DRAINAGE MODIFICATION POTENTIAL UNDERGROUND DETENTION PROPOSED BUFFER/LANDSCAPING STRIP PROPOSED STREAM RELOCATION PROPOSED ROAD/PATH REALIGNMENT PROPOSED FULL LID TREATMENT SELECT WATER QUALITY PRETREATMENT PRACTICES IN ACCORDANCE WITH APPROVED STORMWATER CONCEPT PLAN POTENTIAL FILTERRA LOCATION In NWE mull 1 114. um'! NOTE: THE LIMITS OF WATERS OF THE U.S., INCLUDING WETLANDS, SHOWN ON THIS MAP [EXCLUDING AREA SHOWN AS PENDING CONFIRMATION] WERE CONFIRMED BY THE U.S. ARMY CORPS OF ENGINEERS ON 10/06/03, CONFIRMATION #03-H0136-75. NOTE: THE POTENTIAL WATER QUALITY TREATMENT MEASURES REFLECTED HEREIN DO NOT REFLECT FINAL DESIGNS BUT MERELY ARE INTENDED TO DEMONSTRATE THE LEVEL OF PRE-TREATMENT REQUIRED. THE FINAL TYPE/CONFIGURATION OF THE STORMWATER MANAGEMENT FACILITIES ARE SUBJECT TO CHANGE DURING DETAILED DESIGN, BUT SHALL PROVIDE THE MINIMUM REQUIRED POLLUTANT REMOVAL SHOWN ABOVE. 7 I WATER QUALITY COMPLIANCE 1 st TIER TREATMENT 1 EXAMPLE PRE-TREATMENT - 'BLOCK IDI FILTERRA UNITS IBI_OR 2TENTION_1I BLOCK ID!IMPERVIOUS AREA IA_R_EA_IMP %OF_AREA TREATED ,REMOVAL(' % AC AC � - MI LB/YR - A 20 100 _ 445_- _ -- 4.85 , 3 r -__0.97_ --B- 65 11.96 7.77 50 17.2 1 B 18 - 16 C 40 9,62_ ---3.85 100 15.7_4_ C - 8,385 D 70 2.32 75 7.67 D 3-7 - _3.31 _ E 85 11.77 10.00 75 32.69 E 15-30 - F 40 6.40 2.56 0 0:00 F - - G 65 5.26 3.42 1 75 11.38 G 15 - 10 H 65 2.00 1.30 1 0 0.00 H - - II 10 18.93 1.89 1 0 0.00 1 - - J 75 2.40 1.80 5 0.29 1 _ K 70 3.20 2.240 0 00 K -_ L 85 13.30 1 11.31 1 75 36.94 L i 117-34 TOTAL 1 53 93.00 1 49.43 1 1 126.41 TOTAL 1 419-109 1 10,498 2nd TIER TREATMENT REMOVAL IFAD IILITY TYPE _ EFFICIENCY % WATER QUALITY VOLUME AVAILABLE IMPERVIOUS 'AREA TREATED I LOAD REMAOV ED [ac -ft] ac Ib mar �. SW M -1 1 DRY DETENTION - SWM 2-1 .(WET POND I_ 40 , iSWM 2 2 CONSTRUCTED WETLAND.- 30 - 0.62 0.23 - 496. 11.57 275 4.81 SWM -3- DRY DETENTION - �SWM 3 -2_ -WET POND 40 - 1.00 - - 8.00 18.67 SWM -4 CONSTRUCTED WETLAND 30 0.45 5.39 9.44 ',TOTAL 21.10 44.449 TOTAL PROPOSED TREATMENT = 1 st TIER = 2nd TIER TOTAL PROPOSED TREATMENT = 126.40 LB-TP/YR + 44.49 LB-TP/YR TOTAL PROPOSED TREATMENT = 170.90 LB-TP/YR TOTAL PROPOSED TREATMENT > REQUIRED POLLUTANT REMOVAL 170.90 LB-TP/YR > 170.57 LB-TP/YR LOCK A TREAT PROPOSED DEVELOPMENT WITH SELECT WATER QUALITY PRETREATMENT PRACTICES IN ACCORDANCE WITH APPROVED STORMWATER MANAGEMENT CONCEPT PLAN BY OTHERS „pRpJ 77 r LOW IMPACT DEVELOPMENT (LIU) PRETREATMENT IN ACCORDANCE ITH [-NATIONAL LID HANDBOOK CRITER' (MODELED AS PROPOSED ROUTE 250 P� LANDSCAPING 6TRIFULL • BLOCK C FULL LOW IMPACT DEVELOPMEM (LID) PRETREATMENT IN ACCORDANCE WITH NATIONAL LID HANDBOOK CRITERIA I ) (MODELED AS PRE -DEVELOPMENT CONDITIONS)-`+•.�-.,,� I , qq qq m g ^w >m mNN No .26 AN 6 a ,So moo 'mac W 0 ci�N m°�oN P. Fill FO -1 P-1 1 �0 OUTFAL EXISTING FIRE STATION MAY BE TREATED WITH STORMWATER RETROFITS TO MEET OVERALL \ j REM VACOMPLIANCE, PENDING FINAL DESIGN.(BLOCK H i I CONTOUR INTERVAL = 2 FEET 120' 0' 60' 120' 240' 360' APPROXIMATE WETLAND LIMITS APPROXIMATE STREAM CHANNEL LIMITS �-�- APPROXIMATE OPEN WATER LIMITS FEE J G� DPJ WN BY: DESIGNED BY. SMS DAP DATE: CHECKED BY soros DAPryVOB SCALE: i°=iza SHEET: A J, JOB#:364]