HomeMy WebLinkAboutWPO200800084 Plan - Other (not approved) Stormwater Management Plan 2008-08-07LEGEND:
aa�aa APPROXIMATE WETLAND LIMITS
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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:
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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
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LPOST = 6.14 X [.005 +0.009(IPOST)] X AREA
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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.
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EXISTING FIRE w
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FULL LOW IMPACT DEVELOPMENT (LID)
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TREAT PROPOSED DEVELOPMENT WITH SELECT
i WATER QUALITY PRETREATMENT PRACTICES
'> PROPOSED ROUTE 250
i LANDSCAPING STRIP
1 ••:
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IN ACCORDANCE WITH APPROVED STORMWATER•...•...:
MANAGEMENT CONCEPT PLAN BY OTHERS
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9WM 3-1
DRY DETENTION (UPSTREAM
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OF PROPOSED CULVERT, 1
RESERVING EXISTING STREAM
(INCLUDES BRIEF INJUNDATI.N
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FULL LOW IMPACT DEVELOPMENT (LID)
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_PRETREATMENT IN ACCORDANCE WITH
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NATIONAL LID HANDBOOK CRITERIA
AS PRE CONDITIONS)
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EXISTING FIRE w
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FULL LOW IMPACT DEVELOPMENT (LID)
- RETENTION BASINS
_PRETREATMENT IN ACCORDANCE WITH
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NATIONAL LID HANDBOOK CRITERIA
AS PRE CONDITIONS)
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9WM 3-1
DRY DETENTION (UPSTREAM
'
OF PROPOSED CULVERT, 1
RESERVING EXISTING STREAM
(INCLUDES BRIEF INJUNDATI.N
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MILAN -
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OF PROPOSED TENNIS COURTS
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EXISTING FIRE w
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PROPOSED SWM 3-1
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SWM 2-2
SERIES OF STEP -POOLS
SERVING AS STORMWATER
- RETENTION BASINS
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SERIES OF STEP -POOLS
SERVING AS STORMWATER
- RETENTION BASINS
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POTENTIAL STREAM
1C ANNEL RELOCATION '
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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
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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
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• 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
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• RETROFITS TO THE EXISTING PONDS ON EITHER SIDE OF THE PROPOSED GREEN TO IMPROVE THEIR PERFORMANCE RELATED TO STORMWATER MANAGEMENT. \ J \ 411
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• 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. / ,
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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'
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JOB#:3647
LEGEND: \ ��
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APPROXIMATE WETLAND LIMITS \v#
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APPROXIMATE STREAM CHANNEL LIMITS
POST -DEVELOPMENT DRAINAGE AREA
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R71 POST -DEVELOPMENT
SUBWATERSHED LABELS % \ \\o
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150' 0' 75' 150' 300' 450'
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JOB#:3647
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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)-`+•.�-.,,�
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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
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