HomeMy WebLinkAboutWPO201900060 Calculations 2020-03-30UVA Foundation — Discovery Drive Development
COUNTY OF ALBEMARLE, VIRGINIA
VSMP WP02019-00060
DESIGN CALCULATIONS & NARRATIVE
MARCH 27, 2020
TIMMONS GROUP
!R VISION ACHIEVED THROUGH ❑URS.
Prepared by: Craig Kotarski, PE
Timmons Group
608 Preston Ave, Suite 200
Charlottesville, VA 22903
434.327.1688
o CRAIG Wv r. KWARSKI
Lic. NO. 0402048507
�3127120�
.'IONXL d�
Table of Contents
Section Title
Project Narrative
2 Pipe and Inlet Computations
LD204, LD229, LD347
3 Pipe Calculations
For existing pipe under Lewis & Clark Drive
LD229 for 10 year and 100 year storm
4 Drainage Subbasin Map — Developed Condition, Flat Branch — Tributary
to North Fork Rivanna River, UVA Research Park at North Fork
5 Lewis and Clark Drive — Stormwater Management Exhibit for Pond 1
6 USGS Geological Survey — Earlysville Quadrangle
7 Ultimate Buildout Conditions Exhibit
8 Final Site Plan — Sheet C6.1 — Stormwater Management Quantity
Project Narrative:
This project will be constructed in two phases. Phase 1 includes the construction of a
building addition and associated drainage, utilities, and landscaping at 1725 Discovery
Drive. The limits of disturbance totals 0.47 acres for this phase. Phase 2 includes the
construction of a new metal building, additional parking, as well as associated drainage,
utilities, and landscaping between 1725 and 1670 Discovery Drive. Also included in
Phase 2 of this project is the construction of the "Air Building". This is an anticipated
project addition that is still being designed. Understanding that this Air Building would
be just over 1 acre of impervious area, the limits of disturbance of the full Phase 2 of this
proposed project totals 2.71 acres for this phase. The total limits of disturbance for this
project totals 4.10 acres. Overall, the site drains through a pipe system to Analysis Point 1
and ultimately outfalls to a large wet pond (Pond 1) southeast of the site.
Stormwater Management Summar:
Per the document titled "Stormwater Management / BMP Analysis and Floodplain Study
for the UVA Research Park at Northfork" by Dewberry & Davis, October 1997, the
research park ponds have been master planned to handle both stormwater quantity and
quality requirements for the future build -out of the research park. The applicability of the
pond is conditioned on the pond being built as designed, and the CN value remaining
within the plan approved CN value. This Dewberry & Davis document lists approved
curve numbers and drainage areas based on the estimated future developed condition of
the UVA Research Park. Per the sheet "Drainage Subbasin Map — Developed Condition,
Flat Branch — Tributary to North Fork Rivanna River, UVA Research Park at North
Fork," dated July 23, 1997 (Section 4), the proposed development falls within Subbasin
C2. Subbasin C2 consists of 85.84 ac with a CN value of 82 (see Table 1). "UVA
Research Park — Pond 1 Analysis" dated March 27, 2020 demonstrates that Pond 1 was
built to satisfy water quantity and quality requirements. Additionally, the proposed CN
value remains within the plan approved CN value.
This development drains to the wet pond designated as Pond 1 in the "Lewis and Clark
Drive - Stormwater Management Exhibit for Pond 1" prepared December 19, 2018 by
Timmons Group (Section 5). This document lists approved curve numbers and drainage
areas based on the updated developed condition of the UVA Research Park. The subject
property falls within area C2 on this map. Drainage area C2 consists of 83.90 ac with a
CN value of 67 (see Table 1).
Based on the USGS topographic map (Section 6) for Earlysville, Virginia, the overall
watershed draining to Pond 1 is approximately 450 acres. Analysis downstream of Pond 1
is unnecessary since the project limits of disturbance (4.10 acres) is less than 1% of the
pond drainage area.
Area C2 was analyzed to determine the change in impervious and pervious surface area
resulting from this proposed Discovery Drive Development. These values have been
incorporated into the previously approved overall CN value for the drainage area. This
proposed development results in a net +2.52 acres impervious area which increases the
CN value to 69. This remains significantly below the approved full build out
development plan CN value of 82.
Both water quantity and quality requirements for this site will be met by utilizing the
existing Pond 1.
Existing Channel Adequacy Summary
The existing natural channel was analyzed according to 9VAC25-870-97.B and
9VAC25-840-40.19.
Per the NRCS Web Soil Survey, the soil type along the entire channel is 36C —
Hayesville Loam, which assuming the top layer of loam has washed away, is clay. From
Table 5-22 (VESCH), the permissible velocity for stiff clay is 5.0 feet per second.
The estimated ultimate development conditions of the drainage area utilizing this channel
are illustrated in the Exhibit in Section 7.
Based on the cross sections presented in the plans on Sheet C6.1 (included as Section 8),
and considering ultimate development conditions, the following criteria are met.
1. The 2-year velocity routed through the channel does not exceed 5 FPS at any
section.
2. The 10-year water surface elevation does not overtop the channel at any section.
Therefore, the channel is adequate to handle the stormwater conditions resulting from the
estimated ultimate development conditions, which includes this proposed development.
Approved Drainage Areas
and CN Values
7/23/1997
Area (Ac.)
CN
Al
57.25
79
A2
12.61
64
131
54.48
72
B2
48.56
80
C1
27.38
80
C2
85.84
82
D1
12.33
78
D2
84.03
86
E1
27.8
81
E2
17.28
83
F1
66.44
91
F2
31.64
91
G1
48.9
92
G2
49.05
92
Proposed Drainage Areas and
CN Values
3/27/2020
Area (Ac.)
CN
Al
56.35
60
A2
11.77
55
131
49.59
50
B2
47.79
67
C1
31.15
42
C2
83.90
69
D1
9.55
51
D2
81.90
70
E1
28.71
55
E2
16.91
38
F1
64.97
53
F2
30.75
54
G 1
47.53
76
G2
49.25
72
Table 1 — Drainage Areas and CN Values
FORM LD 204 STORMWATER INLET COMPUTATIONS SHEET 1 OF 1
LD204 PROJECT UVAF DISCOVERY DRIVE DESIGNER: KAM DATE 3/27/2020
CHECKED: AA UNITS ENGLISH
Sag Inlets
Only
INLETSOFT BY ENSOFTEC DATE: 3/27/2020
LD-229
STORM SEWER DESIGN COMPUTATIONS
STORM FREQUENCY 70
PROJECT: UVAF DISCOVERY DRIVE
LOCATION: ALBEMARLE COUNTY
COUNTY: Charlottesville
NOAA STATION:
Designed by: KAM
Checked by:
UNITS ENGLISH
PIPE
NO.
FROM POINT
TO POINT
DRAIN.
AREA
"A"
Acre
(3)
RUNOFF
COEFF.
"C"
(4)
CA
TOTAL
INLET
TIME
Minutes
(7)
RAIN
FALL
In/HrCFS
(8)(9)
RUNOFF
INVERT ELEVATIONS
LENGTH
ofPipe
Ft.
(12)
SLOPE
Ft./Ft.
(13)
SIZE
(Dia. Or
Span/Rise)
In.
(14)
SHAPE
Number
ofPipes
Capacity
CFS
(15)
Friction
Slope
Ft./Ft.
NORMAL FLOW
FLOW
TIME
Sec.
(17)
REMARKS
(18)
INCRE-
MENT
(5)
ACCUM-
ELATED
(6)
7ateralTotal
Q
UPPER
END
(10)
LOWER
END
(11)
Depth of
Flow, do
Ft.
Area of
Flow, An
SgFt
Hm
Ft.
Vn
FdSee
(16)
En
Ft.
REFERENCE
(1)
STA.
REFERENCE
(2)
STA.
300 TO EX
300
EX1
0.78
0.90
0.70
5.40
5.53
6.37
0.00
34.84
533.42
532.00
34.91
0.04068
24
Circular
1
49.43
0.02100
1.24
2.04
0.56
17.05
5.75
2.05
301
302
300
0.08
0.88
0.07
3.23
5.50
6.38
0.00
20.99
534.35
533.52
27.25
0.03046
24
Circular
1
42.77
0.00760
0.99
1.55
0.50
13.55
3.84
2.01
303
304
302
1 0.14
1 0.87
0.12
3.16
5.42
6.41
0.00
20.54
535.68
534.45
1 56.07
0.021941
24
1 Circular
1
1 36.30
0.00730
1.08
1.72
0.52
11.91
3.28
1 4.71
307
308
1
306
0.75
0.39
0.29
0.29
5.00
6.54
0.00
1.92
539.50
539.00
28.19
0.01774
15
Circular
1
9.32
0.00080
0.39
0.32
0.22
5.98
0.94
4.72
309
310
305
0.02
0.50
0.01
0.01
5.00
6.54
0.00
0.07
539.00
536.80
11.11
0.19802
8
Circular
1
5.83
0.00000
0.05
0.01
0.03
5.76
0.57
1.93
311
312
300
0.00
0.00
1.47
5.20
6.48
0.00
9.63
536.90
534.15
112.21
0.02451
15
Circular
1
10.96
0.01980
0.91
0.96
0.37
10.07
2.48
11.14
313
TRENCH
312
1.66
0.89
1.47
1.47
5.00
6.54
0.00
9.63
540.00
537.00
119.13
0.02518
15
Circular
1
11.11
0.01980
0.90
0.95
0.37
10.19
2.51
11.69
315
316
EX2
4.34
0.20
0.87
0.87
5.00
1 6.54
1 0.00
5.68
537.98
537.82
15.77
0.01015
15
Circular
1
7.05
0.00690
0.85
1 0.89
0.37
6.39
1.48
2.47
400 TO EX
400
EXIST
1.26
0.88
1.11
1.11
5.00
6.54
0.00
7.26
534.29
533.10
48.21
0.02468
15
Circular
l
10.99
0.01120
0.74
0.76
0.35
9.57
2.16
5.04
Ex 24 CPP
306
304
0.78
0.90
11 .70
3.03
5.28
6.45
0.00
19.76
538.97
535.76
111.34
0.02883
24
Ci-lar
l
1 41.61
0.00680
0.97
1.51
0.49
13.07
3.62
8.52
EX TO 306
EX
1
1306
5.04
0.40
2.03
2.03
5.00
6.54
0.00
13.27
544.23
538.97
I92.70
0.02730
24
Circular
I
40.49
0.00300
0.79
1.15
0.42
11.54
2.86
16.70
EX2-EX7
EX2
EX7
2.90
0.51
1.47
2.34
5.04
6.54
0.00
15.30
537.71
534.08
121.70
0.02983
24
Circular
1
42.33
0.00410
0.83
1.24
0.44
12.39
3.21
9.83
EX7-EXl
EX7
EXl
5.69
0.39
2.22
4.56
5.21
6.48
0.00
29.67
533.86
531.89
133.00
0.01481
24
Circular
l
29.83
0.01530
1.63
2.74
0.61
10.82
1 3.45
12.29
OUTFALL
EXl
I
JOUTFALL
0.27
0.71
0.19
10.15
5.57
6.36
0.00
65.05
526.42
524.99
31.00
0.04613
30
Circular
1
95.44
0.02230
1.51
3.11
0.70
20.92
8.31
1.48
LD-347 PROJECT: UVAF DISCOVERY DRIVE DESIGNED BY: KAM
HYDRAULIC GRADE LINE ANALYSIS
Checked: AA
INCIDENCE PROBABILITY Year
INLET
OR
JUNCTION
STA.
INVERT
EL.
OUTFLOW
PIPE
DEPTH
OF FLOW
OUTFLOW
PIPE
OUTLET
WATER
SURFACE
ELEV.
DIA.
PIPE
Do
(In/mm)
DESIGN
DISCH.
Oo
(CFS/CMS)
LENGTH
PIPE
Lo
(FtlM)
FRICTION
SLOPE, Sfo
(FT/FT)
(M/M)
FRICTION
LOSS
Hf
(Ft/M)
JUNCTION LOSS
SURFACE
FLOW
Adj. Ht
1.3
Ht
(FtlM)
Inlet
Shaping?
Y/N
0.5
Ht
(FtlM)
FINAL
H
(FtlM)
Inlet
Water
Surface
Elevation
Top of MH
Top of Inlet
Elev.
APPROX.
Adjustment?
V.
Contr.
Ho
(FtlM)
Vi
Vi'2/2g
Hi (Expn)
0.35'MAX.
(Vi2/2g)
SKEW
Angle
K
Bend
H
(FtlM)
Sum
HL
(FtlM)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
16
17
18
19
OUTFALL
I
1
527.490
EX1
524.990
2.50
527.490
30
64.560
31.00
0.02207
0.684
20.881
1.693
16.694
4.327
1.515
0.0
0.00
0.000
3.207
1.219
3.207
YES
1.604
2.288
529.778
540.210
O.K.
EX7
531.890
2.00
533.520
24
29.671
133.00
0.01532
2.038
10.823
0.455
12.385
2.382
0.834
0.0
0.00
0.000
1.288
14.369
1.675
NO
1.675
3.713
537.233
544.660
O.K.
EX2
534.080
2.00
537.233
24
15.298
121.70
0.00407
0.496
12.385
0.595
6.391
0.634
0.222
0.0
0.00
0.000
0.817
9.620
1.063
YES
0.531
1.027
538.541
542.540
O.K.
316
537.820
1.25
538.820
15
5.678
15.77
0.00688
0.109
1 6.391
0.159
0.000
0.000
0.000
0.0
0.00
0.000
0.159
5.678
0.206
YES
0.103
0.212
539.032
543.220
O.K.
300
532.000
2.00
533.600
24
31.654
34.91
0.01744
0.609
16.694
1.082
13.550
2.851
0.998
0.0
0.00
0.000
2.080
0.000
2.080
YES
1.040
1.649
535.249
542.540
O.K.
302
533.520
2.00
535.249
24
20.986
27.25
0.00766
0.209
13.550
0.713
11.911
2.203
0.771
0.0
0.00
0.000
1.484
0.447
1.484
YES
0.742
0.951
536.199
542.150
O.K.
304
534.450
2.00
536.199
24
20.539
56.07
0.00734
0.412
11.911
0.551
13.074
2.654
0.929
0.0
1 0.00
0.000
1.480
0.782
1.480
YES
0.740
1.152
537.351
544.380
O.K.
306
535.760
2.00
537.360
24
19.757
111.34
0.00679
0.756
13.074
0.664
11.541
2.068
0.724
0.0
1 0.00
0.000
1.387
0.000
1.387
YES
0.694
1.450
539.940
549.290
O.K.
308
539.000
1.25
540.000
15
1.917
28.19
0.00078
0.022
5.978
0.139
0.000
0.000
0.000
0.0
0.00
0.000
0.139
1.917
0.180
YES
0.090
0.112
540.112
543.450
O.K.
312
534.150
1.25
535.249
15
9.630
112.21
0.01980
2.221
10.072
0.394
10.189
1.612
0.564
0.0
0.00
0.000
0.958
0.000
0.958
YES
0.479
2.700
537.949
542.590
O.K.
TRENCH
537.000
1.25
538.000
15
9.630
119.13
0.01980
2.358
10.189
0.403
0.000
0.000
0.000
0.0
0.00
0.000
0.403
9.630
0.524
NO
0.524
2.882
540.899
541.880
O.K.
EX
538.970
2.00
540.570
24
13.267
192.70
0.00306
0.590
11.541
0.517
0.000
0.000
0.000
0.0
0.00
0.000
0.517
13.267
0.672
YES
0.336
0.926
545.018
550.930
O.K.
LD-229
STORM SEWER DESIGN COMPUTATIONS
STORM FREQUENCY 10
PROJECT: Discovery Drive Development
LOCATION: UVAF Research Park
COUNTY: Albemarle
NOAA STATION:
Designed by: A Fontaine
Checked by:
UNITS ENGLISH
PIPE
NO.
FROM POINT
TO POINT
DRAIN.
AREA
"A"
Aare
3
RUNOFF
COEFF.
"C"
4
CA
TOTAL
INLET
TIME
Minutes
7
RAIN
FALL
In/fir
8
RUNOFF
INVERT ELEVATIONS
LENGTH
of Pipe
Ft.
12
SLOPE
Ft./Ft.
13
SIZE
(Dia. Or
Span/Rise)
In.
14
SHAPE
Number
of Pipes
Capacity
CFS
15
Friction
Slope
Ft./Ft.
NORMALFLOW
FLOW
TIME
Sec.
17
REMARKS
(18)
INCRE-
MENT
5
ACCUM-
ULATED
6
Lateral
CFS
Tom]Q
CFS
9
UPPER
END
10
LOWER
END
11
Depth of
Flow, do
Ft.
Area of
Flow, An
SgFt
H.
Ft.
Vn
Ft/Sec
16
En
Ft.
REFERENCE
1
STA.
REFERENCE
2
STA.
EX
EW1
EW2
0.00
0.00
0.00
5.00
0.00
98.19
586.00
581.10
227.60
0.02153
72
Circular
1
621.42
0.00060
1.61
6.12
1 0.94
16.05
5.61
14.19
LD-229
STORM SEWER DESIGN COMPUTATIONS
STORM FREQUENCY 100
PROJECT: 1725 Discovery Drive Development
LOCATION: UVAF Research Park
COUNTY: Albemarle
NOAA STATION:
Designed by: A Fontaine
Checked by:
UNITS ENGLISH
PIPE
NO.
FROM POINT
TO POINT
DRAIN.
AREA
"A"
Aare
3
RUNOFF
COEFF.
"C"
4
CA
TOTAL
INLET
TIME
Minutes
7
RAIN
FALL
In/fir
8
RUNOFF
INVERT ELEVATIONS
LENGTH
of Pipe
Ft.
12
SLOPE
Ft./Ft.
13
SIZE
(Dia. Or
Span/Rise)
In.
14
SHAPE
Number
of Pipes
Capacity
CFS
15
Friction
Slope
Ft./Ft.
NORMALFLOW
FLOW
TIME
Sec.
17
REMARKS
(18)
INCRE-
MENT
5
ACCUM-
ULATED
6
Lateral
CFS
Tom]Q
CFS
9
UPPER
END
10
LOWER
END
11
Depth of
Flow, do
Ft.
Area of
Flow, An
SgFt
H.
Ft.
Vn
Ft/Sec
16
En
Ft.
REFERENCE
1
STA.
REFERENCE
2
STA.
EX
EW1
EW2
0.00
0.00
0.00
5.00
0.00
215.30
586.00
581.10
227.60
0.02153
72
Circular
1
621.42
0.00270
2.44
10.78
1 1.30
1 19.98
8.63
11.39
=e
r 1725 DISCOVERY DRIVE
.
=W ; ��n , - E �: SUBBASIN C2
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--------- 1---------- \
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NOTE:
DRAINAGE DIVIDES AND AREA NAMES ARE TAKEN FROM
"STORMWATER MANAGEMENT/BMP ANALYSIS AND
FLOODPLAIN STUDY FOR THE UVA RESEARCH PARK AT
NORTHFORK" BY DEWBERRY & DAVIS, DATED OCTOBER 1997.
1725 DISCOVERY DRIVE
LEGEND
171 HYDROLOGIC SOIL GROUP A, TURF
■ HYDROLOGIC SOIL GROUP A, WOODS
HYDROLOGIC SOIL GROUP B, TURF
HYDROLOGIC SOIL GROUP B, WOODS
HYDROLOGIC SOIL GROUP C, TURF
01 U HYDROLOGIC SOIL GROUP C, WOODS
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HYDROLOGIC SOIL GROUP D, WOODS
IMPERMEABLE SURFACES
AREA, IN ACRES CN VALUE
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LEWIS AND CLARK DRIVE - STORMWATER MANAGEMENT EXHIBIT FOR POND 1
December 19, 2018
DISCOVERY
DRIVE A
BUILDABLE AREA = 3.6 AC
ASSUME 80% IMPERVIOU;
LRABLE AR = .44 AC
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UVA FOUNDATION -DISCOVERY DRIVE DEVELOPMENT
ULTIMATE BUILDOUT CONDITIONS FOR CHANNEL EROSION CONSIDERATION
SCALE 1 "=150'
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0 150' 300'
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TIMMONS GROUP
YOUR VISION ACHIEVED THROUGH OURS.
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DRAINAGE AREA: 22.3 AC DRAINAGE AREA: 28.2 AC DRAINAGE AREA: 36.4 AC
CN: 67 CIN 68 CN: 70
_ _ - TC: 26 MIN TC: 27 MIN TC: 28 MIN
-- ----- - - - -_ __ ----- 2-YEAR Q: 16.77 CFS 2-YEAR Q: 22.01 CFS
_ _ _ _ _- - - _ _ __ - _ `\ 2-YEAR V: 3.65 FPS 2-YEAR V: 3.43 FPS 2 -YEA Q: 3 .56 CFS
10-YEAR Q: 43.25 CFS 10-YEAR Q: 55.25 CFS 2-YEAR V: 75.6 FPS
10-YEAR ELEV: 523.45' -YEAR ELEV: 510.73' -YEAR Q: 75.61 CFS
10-YEAR ELEV: 502.00'
540 540 525 525 520
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CHANNEL CROSS SECTIONS ,',' _= . `ON 'Ak
9+50 10+00 11+00 12+00 9+50
CROSS SECTION 1
HORIZ SCALE: 1"=50'
VERT SCALE: 1 `5
DRAINAGE AREA: 44.6 AC
CN: 72
TC: 29 MIN
2-YEAR Q. 43.57 CFS
2-YEAR V: 3.48 FPS
10-YEAR Q: 98.19 CPS
10-YEAR ELEV: 495.3V
515
10+00 D CROSS SECTION
HORIZ SCALE: 1"=50'
VERT SCALE: 1"=5
510
510
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505
505
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/
500
/
500
495
\
// 10-YR
WSE=495.31' 495
490
490
s+So 10,00 11+00 12+00
CROSS SECTION 4
HORIZ SCALE: 1"=50'
VERT SCALE: 1"=5
SCALE 1"=80'
0 80' 160'
515
515
510
510
505
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505
10-YR WSE
= 502.00'
F/
\
500
500
11+50 9+50 10+00 11+00 11+50
CROSS SECTION 3
HORIZ SCALE: 1"=50'
VERT SCALE: 1 "=5
DRAINAGE AREA: 61.0 AC
CN. 70
TC: 31 MIN
2-YEAR Q 50.02 CFS
2-YEAR V: 3.98 FPS
10-YEAR Q 118.95 CFS
10-YEAR ELEV: 481.57'
500
495
495
490
\
/
490
485
\
/
485
\
/
10-YR WSE =
481.57'
480
\ /
480
475
475
13+00 9+50 10+00 11+00 12+00 12+50
CROSS SECTION 5
HORIZ SCALE: 1 "=50'
VERT SCALE: 1"=5
WATER QUANTITY ANALYSIS - CHANNEL ADEQUACY
THE NATURAL CHANNEL WAS ANALYZED ACCORDING TO 9VAC25-870-97.B
AND 9VAC25-840-40.19.
PER THE NRCS WEB SOIL SURVEY, THE SOIL TYPE ALONG THE ENTIRE
CHANNEL IS 36C - HAYESVILLE LOAM, WHICH ASSUMING THE TOP LAYER OF
LOAM HAS WASHED AWAY IS CLAY. FROM TABLE 5-22 ESCH THE
N ).
PERMISSIBLE VELOCITY FOR STIFF CLAY IS 5.0 FPS.
THE ESTIMATED ULTIMATE DEVELOPMENT CONDITIONS OF THE DRAINAGE
AREA UTILIZING THIS CHANNEL ARE ILLUSTRATED ON THIS SHEET. THE
SHADED AREAS REPRESENT THE BUILDABLE AREA AND THE ASSUMPTION
IS THAT 80% OF THOSE AREAS WILL BE IMPERVIOUS. THE CN VALUE IS
SLIGHTLY DIFFERENT AT EACH CROSS SECTION BASED ON THIS ESTIMATED
DEVELOPMENT.
BASED ON THE CROSS SECTIONS ABOVE, AND CONSIDERING ULTIMATE
DEVELOPMENT CONDITIONS:
• 2-YEAR VELOCITY ROUTED THROUGH THE CHANNEL DOES NOT
EXCEED 5 FEET PER SECOND AT ANY SECTION.
• 10-YEAR WATER SURFACE ELEVATION DOES NOT OVERTOP THE
CHANNEL AT ANY SECTION,
THEREFORE THE CHANNEL IS ADEQUATE TO HANDLE THE STORMWATER
CONDITIONS RESULTING FROM THE ESTIMATED ULTIMATE DEVELOPMENT
CONDITIONS, WHICH INCLUDES THIS PROPOSED SITE PLAN.
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DESIGNED BY
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CHECKED BY
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