HomeMy WebLinkAboutdetention pond analysisDetention Pond Analysis
for
Meadow Creek Subdivision
Phases 4 & 5
Brazos County, Texas
November 2008
Developer:
Main Street Homes - CS, Ltd.
900 Congress Avenue, Suite L-100
Austin, Texas 78701
(512) 801-8832
Prepared By:
Civil Development, Ltd.
2033 Harvey Mitchell Parkway South
College Station, TeXas 77840
(979) 764-7743
0~- ~
Detention Pond Analysis
for
Meadow Creek Subdivision
Phases 4 & 5
Brazos County, Texas
November 2008
Developer:
Main Street Homes - CS, Ltd.
900 Congress Avenue, Suite L-100
Austin, Texas 78701
(512) 801-8832
Pre ap red X.
Civil Development, Ltd.
2033 Harvey Mitchell Parkway South
College Station, Texas 77840
(979) 764-7743
II//Y /1110 U
DETENTION POND ANALYSIS
MEADOW CREEK SUBDIVISION - PHASES 4 & 5
INTRODUCTION
The purpose of this report is to provide the hydrological analysis of the construction of the
detention ponds for Meadow Creek Subdivision - Phases 4 & S, and to verify that the
proposed detention system meets the requirements set forth by the Subdivision and
Development Regulations of Brazos County. Phases 4 & 5 comprise the remainder of the
Meadow Creek development.
GENERAL LOCATION AND DESCRIPTION
The project is located on a portion of a 75 acre tract located west of FM 2154 along the
south side of Koppe Bridge Road approximately 1 mile from Wellborn, Texas. The site
was cleared in 2005. The existing ground elevations range from Elevation 293 to
Elevation 324. The general location of the project site is shown on the vicinity map in
Exhibit A.
FLOOD HAZARD INFORMATION
The project site is located in the Peach Creek Drainage Basin. This entire site is located in
a Zone X Area according to the Flood Insurance Rate Map prepared by the Federal
Emergency Management Agency (FEMA) for Brazos County, Texas and incorporated
areas dated July 2, 1992, panel number 48041 C0200-C. Zone X Areas are determined to
be outside of the 500-year floodplain.
DEVELOPMENT DRAINAGE PATTERNS
Prior to development of the previous phases of the Meadow Creek Subdivision, the storm
water runoff from this site flowed in a southeasterly direction and left the site in an
existing drainage channel. This runoff flows into a tributary of Peach Creek and then into
the main branch of Peach Creek. Runoff from the adjacent properties to the northeast,
northwest and southwest also enter the Meadow Creek site. This runoff is accounted for in
the design of the drainage structures for this project. After development, the runoff will be
discharged at the same location as before the development.
DRAINAGE DESIGN CRITERIA
The design parameters for the storm sewer and detention facility analysis are as follows:
• The HEC-HMS computer program was utilized to determine peak storm water runoff
rates for the detention facility design.
• Design Storm Frequency
Detention facility analysis 2, 5, 10, 25, 50 and 100-year storm events
Runoff Curve Number (CN) - Detention Pond
The Brazos County Soil Survey shows the soils in the area to be classified as
hydrologic Group C & D soils. The pre-development CN is based on no
development on the site. The CN for the pre-development condition was
determined to be 69.7, which is consistent with the design on previous phases in the
subdivision. The post-development CN is based on development of Phases 1, 2, 3,
4 & 5 of the subdivision within the detention pond drainage area. The CN
calculations are found in Appendix A.
• Time of Concentration, tc - Calculations are based on the method found in the TR-55
publication. Refer to Table 1 for the equations and Appendices for calculations. The
runoff flow paths used for calculating the post-development times of concentration for
the detention pond analysis are shown on Exhibit B.
TABLE I - Time of Concentration (tc) and Lag Time Equations
The time of concentration was determined using methods found in TR-55, "Urban
Hydrologyfor Small Watersheds. " The equations are as follows:
Time of Concentration:
Tc = Tt(sheet flow) + Tt(concentrated sheet flow)
where: Tt = Travel Time, minutes
For Sheet Flow: Tt = 0.007 (n L)"
(PZ)o.s SOA where: Tt = travel time, hours
n = Manning's roughness coefficient
L = flow length, feet
P2 = 2-year, 24-hour rainfall = 4.5"
s = land slope, ft/ft
For Shallow Concentrated Flow: Tt = L / (60*V)
where: Tt = travel time, minutes
V = Velocity, fps
L = flow length, feet
From tc, Lag Times for use in EEC-HMS are computed by: Lag = 0.6* t,
Refer to Appendix A for calculations.
TABLE 2 - Pre- & Post-Development Runoff Information - Detention Evaluation
Dev.
Scenario
1 Drainage
Area #
(acres)
Area
1 (sq.mi.)
CN j
r
Tc
(min)
Lai Time
(min) (hr)
Pre
i 101 j
188.48
.2945 j
69.7 1
83.1
49.9 i
0.83
Pre
101 j
201.63
i .3150
69.7 I
83.1
49.9
0.83
Post
401 ;
32.79
j .0512
84.4
32.4 I
19.4
0.32
Post
i 402
104.71
i .1636 1
76.9
80.1 i
48.1
0.80
Post
j 403 1
1.56
1 .0024 '
86.6 j
12.8 1
7.7
0.13
Post
404 1
17.27
1 .0270
79.1 1
61.0 1
36.6
0.61
Post
1 405 1
11.96
' .0187
82.5 1
43.2
25.9 1
0.43
Post
1 406 i
15.3
.0239 1
88.2 i
29.6
17.8 1
0.30
Post
407
18.04
.0282 i
88.2 i
28.3
17.0 1
0.28
DETENTION FACILITY DESIGN
Four detention ponds have been constructed for the Meadow Creek Subdivision for
previous phases. An additional detention pond will be constructed and the size of one of
the existing ponds will be increased to control the peak discharge from this development
such that it is less than or equal to the pre-development peak discharge. No modifications
are proposed for existing Ponds 3 & 4 with this project, but the data in the computer model
has been adjusted to include as-built conditions so it accurately represents conditions in the
subdivision. All of the ponds act together as a single system to control runoff from the
site.
The total pre-development drainage area used in the analysis of previous phases was
188.48 acres, which was determined using USGS maps that offered the best available
topographic data at the time. Since then, newer and more accurate topographic maps from
the City of College Station have become available that show 2-foot contour intervals.
Using this more accurate information, the pre-development drainage area for the entire site
is 201.63 acres. Both areas were analyzed for this report. The runoff rates for Pre and
Post-Development Scenarios for the system are summarized in Table 3.1.
TABLE 3.1- Pre- & Post-Development Peak Discharge Comparison
Q?
Qs
Qio I
Q~s
Qso
Qioo
Meadow Creek Detention System
cfs
cfs
cfs
cfs
cfs
cfs
Pre-Development-188.48 acres
82
I 195
j 254 i
338
405
j 474
Pre-Development - 201.63 acres
87
j 209
1 272
362
433
I 508
Post Development - at main outfall from Pond 1
69
! 180
245 1
331 1
393
473
Decrease in Peak Discharge 188.48 acres
13
15
9
7
12
1
Decrease in Peak Discharge (201.63 acres)
18
29
j 27
31
40
35
Note: Pre and Post-Development flowrates are computed using a 12-hr storm duration with S minute
computation intervals.
The elevation-storage data and the storage-discharge data for the various ponds used in this
analysis are provided in Appendix C. The grading for Detention Ponds 1, 2A & 2B are
shown on Exhibits C & D.
As seen in Table 3.1, the Post-Development outflow from Detention Pond No. 1 is less
than the Pre-Development outflow for all storm events, even when compared to the smaller
basin size used in the original report for the subdivision. Detailed pre- and post-
development HEC-HMS outputs are provided in Appendices D through J.
Pond 1
The pond outlet structure is a concrete channel that is 10' wide and has a control structure
with 2 square openings that are 2' x 2' with a flowline elevation of 293.0. The control
structure also has a top crest elevation of 296.5, which allows additional weir flow over the
control structure. Also, there is an overflow spillway with a crest elevation of 297.5. This
spillway channel has a bottom width of 20', 3H:1 V side slopes and is lined with rock
riprap to prevent erosion of the channel. The top of the pond berm will be raised to
Elevation 300.5. The outlet and spillway details are shown on the Grading Plan for the
Phase 1 construction drawings. The outlet structure channel has dissipater blocks to
reduce the velocity of the discharge and rock riprap is used to control erosion.
Pond 2A
The existing pond outlet structure consists of 2-36" HDPE pipes with an upstream flowline
of 296.05. One of the 36" pipes will be capped at each end to reduce the amount of flow
out of this pond. Also, there is an overflow spillway with a crest elevation of 298.5. This
spillway channel has a bottom width of 10', 4H:1 V side slopes and is lined with concrete
to prevent erosion of the channel. Details are shown in Exhibit C. The top of the pond
berm will be raised to Elevation 303.5. The proposed grading to increase the size of the
pond is shown on Exhibits C & D. The outlet and spillway details are shown on the
grading plans for Phases 2 & 3. The outlet structure channel has concrete channel lining to
prevent erosion.
Pond 2B
The pond outlet structure consists of 1-42" HDPE pipe with a concrete box riser structure
on the upstream end. The top of the riser box is at Elevation 302. This structure has a
1'x1' opening at Elevation 298.5 and a 3.5' wide opening at Elevation 301.0. The
discharge from Pond 2B is controlled by the 2 openings in the riser structure until the
water surface in the pond reaches Elevation 302, at which point the 42" outlet pipe restricts
the flow from the pond. Also, there is an emergency overflow spillway with a crest
elevation of 304. This spillway channel has a bottom width of 120' and 4H:1V side
slopes. The top of the pond berm is at Elevation 305.2. The proposed grading of the pond
and the outlet and spillway details are shown on the Grading Plan, Exhibits C & D. The
outlet structure pipe will have a concrete headwall with dissipater blocks to control
erosion.
Ponds 3 & 4
No modifications are proposed for existing Ponds 3 & 4, and these ponds will continue to
function as previously designed.
TABLE 3.2 - Detention Pond Levels and Freeboard for 100 yr Rainfall Events
Pond 1
Pond 2A
Pond 2B
ioo post Dev. WSEL
299.6
! 302.8
304.1
To of Berm
300.5
303.5
305.2
_
Freeboard (ft.)
0.9
0.7
1.1
CONCLUSIONS
The five detention facilities analyzed in this report function together as a single system.
When analyzed together, the ponds reduce the peak runoff from the entire development to
levels below the peak flows for the pre-development conditions.
APPENDIX A
Detention Pond Design Data & Calculations:
SCS Curve Number Data
Meadowcreek Subdivision - Phase 1
SCS Curve Number Calculations
Drainage Area -101
Area - Ac. 188.48
sq. mi. 0.2945
Tc = 83.1
Lag = L = 0.6Tc = 49.9 min = 0.831 hrs
Weighted
Land Use Soil Type Area - Ac. CN II CN
Pasture (good)
C
54.73
74
21.5
Pasture (good)
D
26.62
80
11.3
Wooded (good)
C
58.08
70
21.6
Wooded (good)
D
39.87
77
16.3
Farmstead
C
4.50
82
2.0
Road
2.36
98
1.2
Water
2.32
100
1.2
Total - CN II
188.48
75.1
Average Runoff condition CN = 69.7
CN I = 57.1
ARC CN = CN 1+ 0.70(CN 11 - CN 1)
Meadow Creek Subdivision - Phases 4 & 5
SCS Curve Number Calculations
Post-Development
Drainage Area - 401
Area - Ac. 32.79
sq. mi. 0.0512
Tc = 32.4
Lag = L = 0.6Tc = 19.4 min = 0.324 hrs
Weighted
Land Use Soil Type Area - Ac. CN II CN
Pasture (good)
C
0.90
74
2.0
Pasture (good)
D
0.00
80
0.0
Wooded (good)
C
2.94
70
6.3
Wooded (good)
D
1.37
77
3.2
Developed Area
C
18.25
89
49.5
Developed Area
D
4.48
91
12.4
Open Space
C
4.85
74
10.9
Open Space
D
0.00
80
0.0
Farmstead
C
0.00
82
0.0
Road
0.00
98
0.0
Water
0.00
100
0.0
Total - CN II
32.79
84.4
Drainage Area - 402
Area - Ac. 104.71
sq. mi. 0.1636
Tc = 80.1
Lag = L = 0.6Tc = 48.1 min = 0.801 hrs
Weighted
Land Use Soil Type Area - Ac. CN II CN
Pasture (good)
C
49.34
74
34.9
Pasture (good)
D
34.55
80
26.4
Wooded (good)
C
11.10
70
7.4
Wooded (good)
D
0.00
77
0.0
Developed Area
C
1.98
89
1.7
Developed Area
D
0.00
91
0.0
Open Space
C
0.00
74
0.0
Open Space
D
0.00
80
0.0
Farmstead
C
4.64
82
3.6
Road
1.88
98
1.8
Water
1.22
100
1.2
Total - CN 11
104.71
76.9
Drainage Area - 403
Area - Ac. 1.56
sq. mi. 0.0024
Tc = 12.8
Lag = L = 0.6Tc =
7.7 min
=
0.128 hrs
Weighted
Land Use
Soil Type Area - Ac.
CN II
CN
Pasture (good)
C
0.00
74
0.0
Pasture (good)
D
0.00
80
0.0
Wooded (good)
C
0.00
70
0.0
Wooded (good)
D
0.00
77
0.0
Developed Area
C
0.00
89
0.0
Developed Area
D
0.93
91
54.3
Open Space
C
0.00
74
0.0
Open Space
D
0.63
80
32.3
Farmstead
C
0.00
82
0.0
Road
0.00
98
0.0
Water
0.00
100
0.0
Total - CN II
1.56
86.6
Drainage Area - 404
Area - Ac. 17.27
sq. mi. 0.0270
Tc = 61.0
Lag = L = 0.6Tc = 36.6 min = 0.610 hrs
Weighted
Land Use Soil Type Area - Ac. CN II CN
Pasture (good)
C
10.43
74
44.7
Pasture (good)
D
0.00
80
0.0
Wooded (good)
C
0.00
70
0.0
Wooded (good)
D
0.00
77
0.0
Developed Area
C
2.32
89
12.0
Developed Area
D
1.26
91
6.6
Open Space
C
0.15
74
0.6
Open Space
D
0.73
80
3.4
Farmstead
C
1.90
82
9.0
Road
0.48
98
2.7
Water
0.00
100
0.0
Total - CN 11
17.27
79.1
Drainage Area - 405
Area - Ac. 11.96
sq. mi. 0.0187
TC = 43.2
Lag = L = 0 6Tc = 25.9 min = 0.432 hrs
Weighted
Land Use Soil Type Area - Ac. CN II CN
Pasture (good).
C
0.00
74
0.0
Pasture (good)
D
0.00
80
0.0
Wooded (good)
C
1.70
70
9.9
Wooded (good)
D
4.26
77
27.4
Developed Area
C
0.23
89
1.7
Developed Area
D
5.22
91
39.7
Open Space
C
0.00
74
0.0
Open Space
D
0.55
80
3.7
Farmstead
C
0.00
82
0.0
Road
0.00
98
0.0
Water
0.00
100
0.0
Total - CN II
11.96
82.5
Drainage Area - 406
Area - Ac. 15.3
sq. mi. 0.0239
Tc = 29.6
Lag = L = 0.6Tc = 17.8 min = 0.296 hrs
Weighted
Land Use Soil Type Area - Ac. CN II CN
Pasture (good)
C
0.00
74
0.0
Pasture (good)
D
0.00
80
0.0
Wooded (good)
C
0.00
70
0.0
Wooded (good)
D
0.00
77
0.0
Developed Area
C
2.64
89
15.4
Developed Area
D
9.43
91
56.1
Open Space
C
0.24
74
1.2
Open Space
D
2.99
80
15.6
Farmstead
C
0.00
82
0.0
Road
0.00
98
0.0
Water
0.00
100
0.0
Total - CN 11
15.3
88.2
Drainage Area - 407
Area - Ac. 18.04
sq. mi. 0.0282
Tc = 28.3
Lag = L = 0.6Tc = 17.0 min = 0.283 hrs
Weighted
Land Use Soil Type Area - Ac. CN II CN
Pasture (good)
C
0.00
74
0.0
Pasture (good)
D
0.00
80
0.0
Wooded (good)
C
0.00
70
0.0
Wooded (good)
D
0.00
77
0.0
Developed Area
C
7.64
89
37.7
Developed Area
D
5.92
91
29.9
Open Space
C
3.62
74
14.8
Open Space
D
0.86
80
3.8
Farmstead
C
0.00
82
0.0
Road
0.00
98
0.0
Water
0.00
100
0.0
Total - CN 11
18.04
86.2
APPENDIX B
Time of Concentration Data
Meadowcreek Subdivision - Phase 4 & 5
Tc Calculations-Pre-Development
Drainage Area #101
Sheet Flow: n= 0.24 (dense grass)
P= 4.5
L=
300
Tt=
0.007(L*n)u-" =
(P)0.5*(S)0.4
Concentrated Flow 1: V=
L=
404
Tt=
U(60*V) _
Concentrated Flow 2: V=
L= 55
Tt= U(60*V) _
Flow Through Stream V=
#1 Segment #1:
L= 800
Tt= U(60*V) _
Flow Throuqh Stream V=
#1 Segment #2:
L= 1461
Tt= U(60*V) _
Flow Through Stream
#3 Segment #1:
L= 384
Tt= U(60*V)
Flow Through Stream
#3 Segment #2:
L= 581
Tt= U(60*V)
Elev,= 332.3 EIev2= 331.1 Slope= 0.0040
0.919 hours= 1 55.1 min I
2 fps (unpaved)
Elev,= 331.1 EIev2=
3.4 min
3.8 fps (unpaved)
Elev,= 326 EIev2=
0.2 min
2.02 fps (Manning's)
Elev,= 323 EIev2=
6.65 min 1
2,49 fps (Manning's)
Elev,= 313 EIev2=
9.8 min
1.51 fps (Manning's)
Elevl= 297 EIev2=
4.2 min
V=
V= 2.57 fps (Manning's)
Elev,= 296.5 EIev2=
3.8 min
326 Slope= 0.0126
323 Slope= 0.0545
313 Slope= 0.0125
297 Slope= 0.0110
296.5 Slope= 0.0013
293.5 Slope= 0.005
Tr=
83.1 min
Meadow Creek Subdivision - Phases 4 & 5
Tr Calculations-Post-Development
Drainage Area #401
Sheet Flow:
n=
0.24 (dense grass)
P=
4.5
L= 210
Slope=
0.0200
Tt= 0.007(L*n)u*"
=
0.363 hours=
21.8 min
(P)o.s*(S)o.4
Concentrated Flow 1:
V=
2.42 fps (unpaved)
L= 132
Slope=
0.0227
Tt= U(60*V)
_
0.9 min
Gutter Flow 1:
V=
1.85 fps (paved)
m.
L= 245
Slope=
0.0080
Tt= U(60*V)
=
2.2 min
Gutter Flow 2:
V=
2.2 fps (paved)
L= 300
Slope=
0.0123--
Tt= U(60*V)
=
2.3 min
Gutter Flow 3:
V=
1.92 fps (paved)
L= 59
Slope=
0.0090
Tt= U(60*V)
_
0.5 min
Gutter Flow 4:
V=
1.92 fps (paved)
L= 341
Slope=
0.0090
Tt= U(60*V)
_
3.0 min
Gutter Flow 5:
V=
1.85 fps (paved)
L= 119
Slope=
0.0080
Tt= U(60*V)
1.1 min
Flow Through Pipe s:
V=
4 fps (Manning's)
L= 94
Slope=
0,0080
Tt= U(60*V)
=
0.4 min
Flow Through Pipe 7:
V=
5 fps (Manning's)
L= 35
Slope=
0.0100
Tt= U(60*V)
=
0.1 min
Flow Through Channel 6:
V=
4 fps
L= 35
Slope=
0.0100
Tt= U(60*V)
=
0.1 min
Tc = 32.4 min
Drainage Area #402 (stopping at culvert)
Sheet Flow: n=
P=
L= 300
Tt= 0.007(L*n)".d =
0.24 (dense grass)
`4.5
Slope= 0.0100
0.637 hours= 38.2 min
P)0.5*(S)0.4
Concentrated Flow 1: V=
L= 330
Tt= U(60*V) _
17 fps (unpaved)
Slope= 0.0110,
3.2 min
Concentrated Flow 2: V=
L= 553
Tt= U(60*V) _
Concentrated Flow 3: V=
L= 684
Tt= U(60*V) _
Concentrated Flow 4: V=
L= 335
Tt= U(60*V) _
Culvert Flow: V=
L= 50
Tt= U(60*V) _
Concentrated Flow 5_ V=
L= 1135
Tt= U(60*V) _
Concentrated Flow 6: V=
L= 497
Tt= U(60*V) _
Channel Flow 1: V=
L= 152
Tt= U(60*V) _
2.15 fps (unpaved)
Slope= 0.0180
4.3 min
1.25 fps (unpaved)
Slope= 0.0060
9.1 min
1.75 fps (unpaved)
Slope= 0.0120
3.2 min
2.05 fps
Slope= 0.0100
0.4 min
1.35 fps (unpaved)
Slope= 0.0070
14.0 min
1.45 fps (unpaved)
Slope= 0.0080
F 5.7 min
1.25 fps (unpaved)
Slope= 0.0050
2.0 min
Tc= 80.1 min
Drainage Area #403
Sheet Flow: n= 0.24` (dense grass)
P= 4.5
L= 80 Slope= 0.0200
Tt= 0.007(L*n)" = 0.168 hours= 10.1 min
(P)0.5*(S)0.4
Concentrated Flow 1: V=
L= 21
Tt= U(60*V) _
Concentrated Flow 2: V=
L= 50
Tt= L/(60*V) _
Concentrated Flow 3: V=
L= 258
Tt= U(60*V)
6 fps (unpaved)
Slope= 0.2500
0.1 min
2 fps (unpaved)
Slope= 0.0060
0.4 min
2 fps(unpaved)
Slope= 0.0100
2.2 min
Tc = 12.8 min
Drainage Area #404
Sheet Flow: n=
P=
L= 300
Tt= 0.007(L*n)u-" _
0.24 (dense grass)
4.5
Slope= 0.0080
0.697 hours= I 41.8 min
P)0.5*(S)0.4
Concentrated Flow 1: V=
L= 840
Tt= U(60*V) _
1.45 fps (unpaved)
Slope= 0.0080=
9.7 min
Ditch Flow: V=
L= 280
Tt= U(60*V) _
Pipe Flow: V=
L= 40
Tt= U(60*V) _
Flow Through Channel #3: V=
L= 143
Tt= U(60*V)
Flow Through Pipe #3: V=
L= 24
Tt= U(60*V) _
Flow Throu h Pipe #V=
L= 31
Tt= U(60*V) _
Flow Through Pipe #1: V=
L= 83
Tt= U(60*V)
Flow Throuqh Pond #4: V=
L= 459
Tt= U(60*V) _
2.00 fps
Slope= 0.0070
2.3 min
4.00 fps
Slope= 0.0545
0.2 min
2.75 fps (Manning's)
Slope= 0.0200
F0.9 min
6.37 fps (Manning's)
Slope= 0.0100
F0.1 min
6.95 fps (Manning's)
Slope= 0.0100
0.1 min
7.02 fps (Manning's)
Slope= 0.0100
0.2 min
1.35; fps
Slope= 0.0070
5.7 min
Tc = 61.0 min
Drainage Area #405
Sheet Flow: n=
P=
L= 300
Tt= 0.007(L*n)u," _
0.24 (dense grass)
4.5
Slope= 0.0150--
0.542 hours= 32.5 min
(P)0.5*(S)0.4
Concentrated Flow 1: V=
L= 139
Tt= U(60*V) _
2.05 fps (unpaved)
Slope= 0.0150
1.1 min
Concentrated Flow 2: V=
L= 882
Tt= U(60*V) _
Flow Through Channel #5: V=
L= 86
Tt= U(60*V) -
Flow Through Pipe #5: V=
L= 30
Tt= U(60*V) _
Flow Through Pipe #4: V=
L= 34
Tt= U(60*V)
Flow Through Channel #4: V=
L= 143
Tt= U(60*V) _
1.80 fps (unpaved)
Slope= 0.0130
8.2 min
2.78-fps (Manning's)
Slope= 0.0191
0.5 min
7.12 fps (Manning's)
Slope= 0.0100
0.1 min
6.08 fps (Manning's)
Slope= 0.0060
0.1 min
3.44` fps (Manning's)
Slope= 0.0060
0.7 min
Tc = 43.2 min
Drainage Area #406 (to outlet structure between ponds)
Sheet Flow: n= 0.24 (dense grass)
P= 4.5
L= 162 Slope= 0.0200
Tt= 0.007(L*n)" = 0.280 hours= 16.8 min
(P)0.5*(S)0.4
Concentrated Flow 1: V=
L= 888'
Tt= U(60*V) _
Flow thru Pipe #10:
Flow thru Pipe #11:
Flow through Pond #2: V=
L= 266
Tt= U(60*V)
1.75 fps (unpaved)
Slope= 0.0120
8.5 min
0.1 min (from Manning's)
0.3 min (from Manning's)
1.15 fps (unpaved)
Slope= 0.0050
3.9 min
ITc= 29.6 min
Drainage Area #407
Sheet Flow: n=
P=
L= 125
Tt= 0.007(L*n)" -a
0.24` (dense grass)
4.5
Slope= 0.0100
0.316 hours= 19.0 min
P)0.5*(S)0.4
Gutter Flow 1: V=
L= 397
Tt= U(60*V) _
1.85 fps (paved)
Slope= 0.0080'
3.6 min
Gutter Flow 2: V=
L= 350
Tt= U(60*V) _
Flow Throuqh Pipe 30: V=
L= 40
Tt= U(60*V) _
Flow Through Pipe 29: V=
L= 252
Tt= L/(60*V) _
Flow Through Pipe 28: V=
L= 251
Tt= U(60*V) _
Flow Through Pipe 27: V=
L= 191
Tt= U(60*V) _
Flow Through Pipe 26: V=
L= 181
Tt= U(60*V) _
Flow Throuqh Pipe 25: V=
L= 161
Tt= U(60*V) _
Flow Through Pipe 24_ V=
L= 75
Tt= L/(60*V) _
2.90 fps (paved)
Slope= 0.0200
2.0 min
5 fps (Manning's)
Slope=
0.1 min
5 fps (Manning's)
Slope=
0.8 min
5 fps (Manning's)
Slope=
0.8 min
5 fps (Manning's)
Slope=
0.6 min
5 fps (Manning's)
Slope=
F0.6 min
5 fps (Manning's)
Slope=
0.5 min
5 fps (Manning's)
Slope=
0.3 min
Tc = 28.3 min
APPENDIX C
Detention Pond Design Data & Calculations:
Elevation-Storage-Discharge Data
Meadow Creek Subdivision - Phases 4 & 5
Detention Pond No. 1 Area-Capacity Data
V = H * {[A1 +A2 + (Al *A2)112] /3)
V = volume, ft2
A = area, ft2
H = difference in elevation, ft
POND NO. 1
Area - Capacity Data
Elevation
ft
Depth
ft
Area
ft2
Area
acres
Volume
(ac-ft)
Cumulative
ac-ft
90%
ac-ft
293.00
0.00
0
0.000
0.000
0.000
0.00
294.00
294.00
9,554
0.219
0.073
0.073
0.07
295.00
295.00
32,607
0.749
0.458
0.531
0.48
296.00
296.00
41,913
0.962
0.853
1.384
1.25
297.00
297.00
50,782
1.166
1.062
2.446
2.20
298.00
298.00
61,001
1.400
1.281
3.728
3.35
299.00
299.00
84,675
1.944
1.665
5.392
4.85
300.00
300.00
115,398
2.649
2.287
7.680
6.91
Detention Pond No. 1 Elevation Discharge Data
POND NO. 1
Elevation Discharge Data
Elevation
2-2.0' wide x 2- high openings
L=4.0' A =8.0 sf
10' wide
crest=296.5
Overflow Spillway
20" sw, 3H: IV side slopes
Total
Di
h
Elevation
Weir
Orifice
Weir
crest=297.5, n=0.030
sc
arge
ft
, depth (ft)
Q, cfs'
h, depth (ft)
Q, cfs2
, depth (ft)
Q, cfs'
, depth ft
Q, cfs'
Q, cfs
(ft)
293.0
0.0
0.0
0.0
0.0
-
-
-
0
293.0
294.0
1.0
12.0
-
-
-
12
294.0
295.0
2.0
34.0
-
-
-
34
295.0
296.0
2.0
55.0
-
-
-
-
55
296.0
297.0
-
-
3.0
67.0
0.5
10.6
-
77
297.0
298.0
-
4.0
77.0
1.5
55.1
0.5
18.0
150
298.0
299.0
5.0
86.0
2.5
118.6
1.5
113.2
318
299.0
300.0
-
6.0
94.5
3.5
196.4
2.5
300.0
591
300.0
1. Weir Equation Q = 3.0 * L * y3/2
2. Orifice Equation Q = 4.82 * A. * h'12
3. Overflow Spillway - Mannings Equation
Meadow Creek Subdivision - Phases 4 & 5
Detention Pond No. 2A Area-Capacity Data
V = H * {[A1 +A2 + (Al *A2)1121 /3)
V = volume, f:2
A = area, ft2
H = difference in elevation, ft
POND NO. 2A
Area - Capacity
Data
Elevation
ft
Depth
ft
Area
ft2
Area
acres
Volume
(ac-ft)
Cumulative
ac-ft
90%
ac-ft
296.05
0.00
0
0.000
0.000
0.000
0.00
297.00
0.95
14,557
0.334
0.106
0.106
0.10
298.00
1.95
100,047
2.297
1.169
1.275
1.15
299.00
2.95
133,535
3.066
2.672
3.947
3.55
300.00
3.95
143,602
3.297
3.180
7.127
6.41
301.00
4.95
150,966
3.466
3.381
10.508
9.46
302.00
5.95
158,795
3.645
3.555
14.063
12.66
303.00
6.95
166,638
3.825
3.735
17.798
16.02
Detention Pond No. 2A Elevation Discharge Data
POND NO. 2A
Elevation Discharge Data
Elevation
1-36" Pipe
n = 0.012
10' wide Concrete Overflow Spillway
Crest = 298.5
Total
Dischar
e
Elevation
HW, Depth
TW, Depth
Flow, Q
n =
0.012
g
ft
ft
ft
cfs
Depth, ft
Flow, Q cfs'
Q, cfs
(ft)
296.05
0.00
0.0
0.0
-
-
0
296.05
297.0
0.95
0.0
5.4
-
-
5
297.0
298.0
1.95
0.0
18.8
-
-
19
298.0
299.0
2.95
0.5
36.8
0.5
10.0
47
299.0
300.0
3.95
2.0
54.5
1.5
55.2
110
300.0
301.0
4.95
2.6
67.5
2.5
129.0
197
301.0
302.0
5.95
3.4
76.4
3.5
232.0
308
302.0
303.0
6.95
4.0
87.8
4.5
366.0
454
303.0
1. Overflow Spillway - Mannings Equation
Meadow Creek Subdivision - Phases 4 & 5
Detention Pond No. 2B Area-Capacity Data
V = H • {[A1+A2 + (A1'A2)1/) / 3)
V = volume, ft2
A = area, ft
H = difference in elevation, ft
POND NO. 2B
Area - Capacity Data
Elevation
ft
Depth
ft
Area
ft2
Area
acres
Volume
ac-ft
Cumulative
Volume
ac-ft
90%
Volume
(ac-ft)
298.5
0.00
0
0.000
0.000
0.000
0.00
299.0
0.50
12,630
0.290
0.048
0.048
0.04
300.0
1.50
65,655
1.507
0.819
0.868
0.78
301.0
2.50
83,526
1.917
1.708
2.576
2.32
302.0
3.50
88,165
2.024
1.971
4.546
4.09
303.0
4.50
92,893
2.133
2.078
6.625
5.96
304.0
5.50
97,729
2.244
2.188
8.812
7.93
305.0
6.50
103,025
2.365
2.304
11.116
10.00
Detention Pond No. 2B Elevation Discharge Data
POND NO. 2B
Elevat
ion Discharge Data
Elevation
VW x 1'H opening
Ao=1.0 sf
3.5' wide Opening & Outlet
Structure Overflow
L=3.5' Elev. 301
42" Pipe
120' wide
Overflow Spillway
120' BW, 4H:1V side slopes
Controlled
Discharge
Elevation
Orifice
Weir
Invert = 298.5
crest=304.0, n=0.035
HW, depth
TW, depth
Q'
, depth
QZ
HW, depth
TW, depth
Q
, depth
Q3
Q
ft
ft
ft
cfs
ft
cfs
ft
ft
cfs
ft
cfs
cfs
(ft)
298.5
0
-
0.0
-
-
0
0
-
-
0
298.5
299.0
0.5
-
1.1
-
-
0.5
-
-
1
299.0
300.0
1.5
0.5
4.8
-
-
1.5
-
-
5
300.0
301.0
2.5
0.5
6.8
-
-
2.5
-
-
7
301.0
302.0
3.5
1.2
7.3
1.0
10.5
3.5
-
-
]
j
18
302.0
303.0
4.5
3.1
-
-
-
4.5
3.1
77.9
-
78
303.0
304.0
5.5
3.8
-
-
-
5.5
3.8
92.2
-
92
304.0
305.0
6.5
4.0
-
-
-
6.5
4.0
109.1
1.0
352.0
447
305.0
1. Orifice Equation C=0.6
2. Weir Equation Q = 3.0' L * y3/2
3. Overflow Spillway - Mannings Equation
The outlet structure is a 4.5'x 4.5' concrete riser box with a 1' wide x 1' high opening at Elev.
298.5, a 3.5' wide weir opening at Elev. 301 and a top elevation of 302. The openings in the
outlet structure control the rate of discharge until the pond level reaches Elev. 302, at which
point the 42" pipe controls the discharge.
Meadow Creek Subdivision - Phases 4 & 5
Detention Pond No. 3 Area-Capacity Data
V = H * ([A1+A2 + (A1*A2)1121 /3)
V = volume, ft2
A = area, ft2
H = difference in elevation, ft
POND NO.3
Area - Ca aci Data
Elevation
ft
Depth
(ft)
Area
ft 2
Area
acres
Volume
(ac-ft)
Cumulative
Volume
ac-ft
90%
Cumulative
Volume
ac-ft
308.00
0.00
0
0.000
0.000
0.000
0.00
309.00
1.00
5,530
0.127
0.042
0.042
0.04
310.00
2.00
13,441
0.309
0.211
0.253
0.23
311.00
3.00
16,180
0.371
0.340
0.593
0.53
312.00
4.00
19,019
0.437
0.404
0.997
0.90
Detention Pond No. 3 Elevation Discharge Data
POND NO. 3
Elevation Discharge Data
Elevation
15" Pipe
n = 0.012
1.8' wide Concrete Overflow Spillway
Crest = 310
Total
Dischar
e
Elevation
Depth,
Flow, Q
n = 0.014
g
ft
ft
cfs
Depth, ft
Flow, Q cfs
Q, cfs
(ft)
308.0
0.0
0.0
0.0
0
0
308.0
309.0
1.0
3.1
-
-
3
309.0
310.0
2.0
5.8
0.0
-
6
310.0
311.0
3.0
8.2
1.0
12
20
311.0
312.0
4.0
10.0
2.0
50.6
61
312.0
Meadow Creek Subdivision - Phases 4 & 5
Detention Pond No. 4 Area-Capacity Data
V = H * ([A1 +A2 + (Al 'A2)'121 /3)
V = volume, ft2
A = area, ft2
H = difference in elevation, ft
POND NO. 4
Area - Ca aci Data
Elevation
ft
Depth
ft
Area
ft2
Area
acres
Volume
ac-ft
Cumulative
Volume
ac-ft
90%
Cumulative
Volume
ac-ft
311.00
0.00
0
0.000
0.000
0.000
0.00
312.00
1.00
3,929
0.090
0.030
0.030
0.03
313.00
2.00
10,430
0.239
0.159
0.189
0.17
314.00
3.00
15,306
0.351
0.294
0.483
0.43
315.00
4.00
18,915
0.434
0.392
0.875
0.79
316.00
5.00
22,624
0.519
0.476
1.351
1.22
Detention Pond No. 4 Elevation Discharge Data
POND NO.4
Elevation Discharge Data
Elevation
15" Pipe
n = 0.012
2.1' wide Concrete Overflow Spillway
Crest = 314.0
Total
Di
h
Elevation
Depth,
Flow, Q
n = 0.014
sc
arge
ft
ft
cfs
Depth, ft
Flow, Q cfs
Q, cfs
ft
311.0
0.0
0.0
-
-
0
311.0
312.0
1.0
3.1
-
-
3
312.0
313.0
2.0
5.8
-
-
6
313.0
314.0
3.0
8.2
-
-
8
314.0
315.0
4.0
10.0
1.0
12.5
23
315.0
316.0
5.0
11.5
2.0
57.8
63
316.0
APPENDIX D
Pre-Development HEC-HMS Output Data
for 188.48 acres
Project: Meadow Creek Simulation Run: Pre 2 yr 188 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Pre Dev 188
End of Run: 290ct2008, 13:15 Meteorologic Model: 2 yr 12 hr
Compute Time: 04Nov2008, 14:54:36 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
101
0.2945
81.6
280ct2008, 20:05
0.90
Existing topo
0.2945
81.7
280ct2008, 20:05
0.90
Outfall
0.2945
81.7
280ct2008, 20:05
0.90
Project: Meadow Creek Simulation Run: Pre 5 yr 188 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Pre Dev 188
End of Run: 290ct2008, 13:15 Meteorologic Model: 5 yr 12 hr
Compute Time: 04Nov2008, 14:55:44 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time.of Peak
Volume
(IN)
101
0.2945
195.1
280ct2008, 20:00
2.20
Existing topo
0.2945
195.0
280ct2008, 20:00
2.20
Outfall
0.2945
195.0
280ct2008, 20:00
2.20
Project: Meadow Creek Simulation Run: Pre 10 yr 188 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Pre Dev 188
End of Run: 290ct2008, 13:15 Meteorologic Model: 10 yr 12 hr
Compute Time: 04Nov2008, 14:53:34 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
101
0.2945
254.2
280ct2008, 20:00
2.95
Existing topo
0.2945
254.1
280ct2008, 20:00
2.95
Outfall
0.2945
254.1
280ct2008, 20:00
2.95
Project: Meadow Creek Simulation Run: Pre 25 yr 188 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Pre Dev 188
End of Run: 290ct2008, 13:15 Meteorologic Model: 25 yr 12 hr
Compute Time: 04Nov2008, 14:54:02 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
101
0.2945
337.9
280ct2008, 20:00
3.93
Existing topo
0.2945
338.0
280ct2008, 20:00
3.93
Outfall
0.2945
338.0
280ct2008, 20:00
3.93
Project: Meadow Creek Simulation Run: Pre 50 yr 188 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Pre Dev 188
End of Run: 290ct2008, 13:15 Meteorologic Model: 50 yr 12 hr
Compute Time: 04Nov2008, 14:55:11 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
101
0.2945
404.4
280ct2008, 20:00
4.81
Existing topo
0.2945
404.8
280ct2008, 20:00
4.81
Outfall
0.2945
404.8
280ct2008, 20:00
4.81
Project: Meadow Creek Simulation Run: Pre 100 yr 188 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Pre Dev 188
End of Run: 290ct2008, 13:15 Meteorologic Model: 100 yr 12 hr
Compute Time: 04Nov2008, 14:53:11 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
101
0.2945
473.9
280ct2008, 20:00
5.73
Existing topo
0.2945
473.9
280ct2008, 19:55
5.73
1
Outfall
0.2945
473.9
280ct2008, 19:55
5.73
APPENDIX E
Pre-Development HEC-HMS Output Data
for 201.63 acres
Project: Meadow Creek Simulation Run: Pre 2 yr 200 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Pre Dev 200
End of Run: 290ct2008, 13:15 Meteorologic Model: 2 yr 12 hr
Compute Time: 04Nov2008, 14:54:50 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
101
0.3150
87.2
280ct2008, 20:05
0.90
Existing topo
0.3150
87.4
280ct2008, 20:05
0.90
Outfall
0.3150
87.4
280ct2008, 20:05
0.90
Project: Meadow Creek Simulation Run: Pre 5 yr 200 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Pre Dev 200
End of Run: 290ct2008, 13:15 Meteorologic Model: 5 yr 12 hr
Compute Time: 04Nov2008, 14:55:59 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
101
0.3150
208.7
280ct2008, 20:00
2.20
Existing topo
0.3150
208.5
280ct2008, 20:00
2.20
Outfall
0.3150
208.5
280ct2008, 20:00
2.20
Project: Meadow Creek Simulation Run: Pre 10 yr 200 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Pre Dev 200
End of Run: 290ct2008, 13:15 Meteorologic Model: 10 yr 12 hr
Compute Time: 04Nov2008, 14:53:49 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
101
0.3150
271.9
280ct2008, 20:00
2.95
Existing topo
0.3150
271.7
280ct2008, 20:00
1
2.95
Outfall
0.3150
271.7
280ct2008, 20:00
2.95
Project: Meadow Creek Simulation Run: Pre 25 yr 200 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Pre Dev 200
End of Run: 290ct2008, 13:15 Meteorologic Model: 25 yr 12 hr
Compute Time: 04Nov2008, 14:54:17 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
101
0.3150
361.4
280ct2008, 20:00
3.93
Existing topo
0.3150
361.5
280ct2008, 20:00
3.93
Outfall
0.3150
361.5
280ct2008, 20:00
3.93
Project: Meadow Creek Simulation Run: Pre 50 yr 200 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Pre Dev 200
End of Run: 290ct2008, 13:15 Meteorologic Model: 50 yr 12 hr
Compute Time: 04Nov2008, 14:55:21 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
101
0.3150
432.6
280ct2008, 20:00
4.81
Existing topo
0.3150
433.0
280ct2008, 20:00
4.81
Outfall
0.3150
433.0
280ct2008, 20:00
4.81
Project: Meadow Creek Simulation Run: Pre 100 yr 200 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Pre Dev 200
End of Run: 290ct2008, 13:15 Meteorologic Model: 100 yr 12 hr
Compute Time: 04Nov2008, 14:53:20 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
101
0.3150
506.9
280ct2008, 20:00
5.73
Existing topo
0.3150
507.7
280ct2008, 20:00
5.73
Outfall
0.3150
507.7
280ct2008, 20:00
5.73
APPENDIX F
Post-Development HEC-HMS Output Data
Project: Meadow Creek Simulation Run: Post 5 yr 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Post Dev
End of Run: 290ct2008, 13:15 Meteorologic Model: 5 yr 12 hr
Compute Time: 04Nov2008, 14:57:47 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
401
0.0512
93.3
280ct2008, 19:25
3.54
402
0.1636
146.0
280ct2008, 19:55
2.82
403
0.0024
6.5
280ct2008, 19:10
3.76
404
0.0270
30.4
280ct2008, 19:45
3.02
405
0.0187
28.3
280ct2008, 19:30
3.35
406
0.0239
49.7
280ct2008, 19:20
3.92
407
0.0282
57.3
280ct2008, 19:20-
3.72
Jct.3
0.0720
81.2
280ct2008, 19:25
3.43
Jct.4
0.2638
198.9
280ct2008, 19:55
3.08
Jct.5
0.3150
181.8
280ct2008, 20:15
3.16
Jct 1
0.0294
26.9
280ct2008, 20:00
3.08
Jct 2
0.0481
37.1
280ct2008, 19:40
3.19
Junction-1
0.0000
0.0
280ct2008, 13:00
Junction-2
0.0000
0.0
280ct2008, 13:00
Outfall
0.3150
180.2
280ct2008, 20:25
3.16
Pond1
0.3150
180.2
280ct2008, 20:25
3.16
Pond2A
0.2638
163.3
280ct2008, 20:20
3.08
Pond2B
0.0720
42.5
280ct2008, 20:15
3.43
Pond3
0.0294
24.7
280ct2008, 20:10
3.08
Pond4
0.0270
26.0
280ct2008, 20:00
3.02
Reach 1
0.0481
37.0
280ct2008, 19:40
3.19
Project: Meadow Creek Simulation Run: Post 2 yr 12 hr
Start of Run: 280ct2008, 13:00 Basin Model:
End of Run: 290ct2008, 13:15 Meteorologic Model:
Compute Time: 04Nov2008, 14:57:15 Control Specifications
Volume Units: IN
Post Dev
2yr12hr
24 hr duration
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
401
0.0512
56.3
280ct2008, 19:25
1.83
402
0.1636
72.5
280ct2008, 19:55
1.31
403
0.0024
4.2
280ct2008, 19:10
2.01
404
0.0270
16.2
280ct2008, 19:45
1.45
405
0.0187
16.2
280ct2008, 19:30
1.69
406
0.0239
31.8
280ct2008, 19:20
2.14
407
0.0282
35.6
280ct2008, 19:20
1.98
Jct.3
0.0720
49.9
280ct2008, 19:25
1.76
Jct.4
0.2638
91.1
280ct2008, 19:55
1.50
Jct.5
0.3150
76.9
280ct2008, 19:30
1.56
Jct 1
0.0294
11.1
280ct2008, 20:10
1.50
Jct 2
0.0481
20.6
280ct2008, 19:35
1.57
Junction-1
0.0000
0.0
280ct2008, 13:00
Junction-2
0.0000
0.0
280ct2008, 13:00
Outfall
0.3150
69.3
280ct2008, 20:40
1.56
Pond 1
0.3150
69.3
280ct2008, 20:40
1.56
Pond2A
0.2638
65.4
280ct2008, 20:30
1.50
Pond2B
0.0720
12.1
280ct2008, 21:10
1.76
Pond3
0.0294
9.9
280ct2008, 20:25
1.50
Pond4
0.0270
10.8
280ct2008, 20:10
1.45
Reach 1
0.0481
20.6
280ct2008, 19:35
1.57
Project: Meadow Creek Simulation Run: Post 10 yr 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Post Dev
End of Run: 290ct2008, 13:15 Meteorologic Model: 10 yr 12 hr
Compute Time: 04Nov2008, 14:56:44 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
401
0.0512
108.6
280ct2008, 19:25
4.44
402
0.1636
181.4
280ct2008, 19:55
3.66
403
0.0024
7.4
280ct2008, 19:10
4.68
404
0.0270
37.0
280ct2008, 19:40
3.88
405
0.0187
33.5
280ct2008, 19:30
4.24
406
0.0239
57.0
280ct2008, 19:20
4.85
407
0.0282
66.1
280ct2008, 19:20
4.63
Jct.3
0.0720
96.2
280ct2008, 19:25
4.32
Jct.4
0.2638
262.0
280ct2008, 19:55
3.94
Jct.5
0.3150
248.1
280ct2008, 20:15
4.02
Jct 1
0.0294
35.4
280ct2008, 19:55
3.95
Jct 2
0.0481
52.4
280ct2008, 19:55
4.06
Junction-1
0.0000
0.0
280ct2008, 13:00
Junction-2
0.0000
0.0
280ct2008, 13:00
Outfall
0.3150
245.4
280ct2008, 20:20
4.02
Pond1
0.3150
245.4
280ct2008, 20:20
4.02
Pond2A
0.2638
221.9
280ct2008, 20:20
3.94
Pond2B
0.0720
62.1
280ct2008, 20:10
4.32
Pond3
0.0294
33.5
280ct2008, 20:00
3.95
Pond4
0.0270
34.1
280ct2008, 19:55
3.88
Reach 1
0.0481
52.2
280ct2008, 19:55
4.06
Project: Meadow Creek Simulation Run: Post 25 yr 12 hr
Start of Run: 280ct2008, 13:00 Basin Model:
End of Run: 290ct2008, 13:15 Meteorologic Model:
Compute Time: 04Nov2008, 14:57:00 Control Specifications
Volume Units: IN
Post Dev
25yr12hr
24 hr duration
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
401
0.0512
131.9
280ct2008, 19:25
5.58
402
0.1636
231.8
280ct2008, 19:55
4.73
403
0.0024
8.8
280ct2008, 19:10
5.84
404
0.0270
46.7
280ct2008, 19:40
4.98
405
0.0187
41.3
280ct2008, 19:30
5.36
406
0.0239
68.1
280ct2008, 19:20
6.02
407
0.0282
79.6
280ct2008, 19:20
5.79
Jct.3
0.0720
118.8
280ct2008, 19:25
5.45
Jct.4
0.2638
341.9
280ct2008, 19:50
5.04
Jct.5
0.3150
334.0
280ct2008, 20:10
5.13
Jct 1
0.0294
46.1
280ct2008, 19:50
5.05
Jct 2
0.0481
71.2
280ct2008, 19:50
5.17
Junction-1
0.0000
0.0
280ct2008, 13:00
Junction-2
0.0000
0.0
280ct2008, 13:00
Outfall
0.3150
331.4
280ct2008, 20:15
5.13
Pond 1
0.3150
331.4
280ct2008, 20:15
5.13
Pond2A
0.2638
297.4
280ct2008, 20:15
5.04
Pond2B
0.0720
80.9
280ct2008, 20:05
5.45
Pond3
0.0294
44.4
280ct2008, 20:00
5.05
Pond4
0.0270
44.3
280ct2008, 19:50
4.98
Reach 1
0.0481
71.1
280ct2008, 19:50
5.17
Project: Meadow Creek Simulation Run: Post 50 yr 12 hr
Start of Run: 280ct2008, 13:00 Basin Model: Post Dev
End of Run: 290ct2008, 13:15 Meteorologic Model: 50 yr 12 hr
Compute Time: 04Nov2008, 14:57:32 Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
Volume
(IN)
401
0.0512
149.7
280ct2008, 19:25
6.57
402
0.1636
270.9
280ct2008, 19:55
5.67
403
0.0024
9.9
280ct2008, 19:10
6.84
404
0.0270
54.2
280ct2008, 19:40
5.94
405
0.0187
47.3
280ct2008, 19:30
6.34
406
0.0239
76.6
280ct2008, 19:20
7.03
407
0.0282
89.8
280ct2008, 19:20
6.79
Jct.3
0.0720
137.0
280ct2008, 19:25
6.43
Jct.4
0.2638
392.2
280ct2008, 19:50
6.00
Jct.5
0.3150
395.7
280ct2008, 20:05
6.09
Jct 1
0.0294
53.8
280ct2008, 19:50
6.01
Jct 2
0.0481
85.1
280ct2008, 19:45
6.14
Junction-1
0.0000
0.0
280ct2008, 13:00
Junction-2
0.0000
0.0
280ct2008, 13:00
Outfall
0.3150
392.7
280ct2008, 20:10
6.09
Pond1
0.3150
392.7
280ct2008, 20:10
6.09
Pond2A
0.2638
351.2
280ct2008, 20:10
6.00
Pond2B
0.0720
88.8
280ct2008, 20:10
6.43
Pond3
0.0294
52.1
280ct2008, 19:55
6.01
Pond4
0.0270
51.8
280ct2008, 19:50
5.94
Reach 1
10.0481
84.9
280ct2008, 19:45
6.14
Project: Meadow Creek Simulation Run: Post 100 yr 12 hr
Start of Run: 280ct2008, 13:00
End of Run: 290ct2008, 13:15
Compute Time: 04Nov2008, 14:56:30
Basin Model: Post Dev
Meteorologic Model: 100 yr 12 hr
Control Specifications: 24 hr duration
Volume Units: IN
Hydrologic
Element
Drainage Area
(M12)
Peak Discharge
(CFS)
Time of Peak
401
0.0512
167.1
280ct2008, 19:20
402
0.1636
311.0
280ct2008, 19:55
403
0.0024
11.0
280ct2008, 19:10
404
0.0270
61.6
280ct2008, 19:40
1405
0.0187
53.2
280ct2008, 19:30
1406
0.0239
84.8
280ct2008, 19:20
407
0.0282
99.8
280ct2008, 19:20
Jct.3
0.0720
160.6
280ct2008, 19:30
Jct.4
0.2638
474.8
280ct2008, 19:55
Jct.5
0.3150
477.1
280ct2008, 20:05
Jct 1
0.0294
61.6
280ct2008, 19:50
Jct 2
0.0481
98.6 6
280ct2008, 19:40
Junction-1
0.0000
0.0
280ct2008, 13:00
Junction-2
0.0000
0.0
280ct2008, 13:00
Outfall
0.3150
472.6
280ct2008, 20:10
0.3150
472.6
280ct2008, 20:10
A
F
0.2638
422.6
280ct2008, 20:10
Pond2B
0.0720
126.
6
280ct2008, 19:55
Pond3
0.0294
60.0
280ct2008, 19:55
Pond4
0.0270
59.2
280ct2008, 19:50
Reach 1
0.0481
98.5
280ct2008, 19.45
Volume
(IN)
7.59
6.65
7.86
6.93
7.35
8.06
7.81
7.44
6.99
7.09
7.00
7.14
7.09
7.09
6.99
7.44
7.00
6.93
7.14
APPENDIX G
Post-Development Pond Elevations for 100-yr Event
From HEGHMS Output Data
Project: Meadow Creek
Simulation Run: Post 100 yr 12 hr Reservoir: Pond1
Start of Run:
280ct2008, 13:00 Basin Model:
Post Dev
End of Run:
290ct2008, 13:15 Meteorologic Model:
100 yr 12 hr
Compute Time:
04Nov2008, 14:56:30 Control Specifications:
24 hr duration
Volume Units: IN
Computed Results
Peak Inflow :
477.1 (CFS) Date/Time of Peak Inflow :
280ct2008, 20:05
Peak Outflow :
472.6 (CFS) Date/Time of Peak Outflow :
280ct2008, 20:10
Total Inflow :
7.09 (IN) Peak Storage :
6.0 (AC-FT)
Total Outflow :
7.09 (IN) Peak Elevation :
299.6 (FT)
Project: Meadow Creek
Simulation Run: Post 100 yr 12 hr Reservoir: Pond2A
Start of Run: 280ct2008, 13:00 Basin Model: Post Dev
End of Run: 290ct2008, 13:15 Meteorologic Model: 100 yr 12 hr
Compute Time: 04Nov2008, 14:56:30 Control Specifications: 24 hr duration
Volume Units: IN
Computed Results
Peak Inflow : 474.8 (CFS) Date/Time of Peak Inflow : 280ct2008, 19:55
Peak Outflow : 422.6 (CFS) Date/Time of Peak Outflow : 280ct2008, 20:10
Total Inflow : 6.99 (IN) Peak Storage : 15.3 (AC-FT)
Total Outflow : 6.99 (IN) Peak Elevation : 302.8 (FT)
Project: Meadow Creek
Sim
ulation Run: Post 100 yr 12 hr Reservoir: Pond2B
Start of Run:
280ct2008, 13:00 Basin Model:
Post Dev
End of Run:
290ct2008, 13:15 Meteorologic Model:
100 yr 12 hr
Compute Time:
04Nov2008, 14:56:30 Control Specifications:
24 hr duration
Volume Units: IN
Computed Result
s
Peak Inflow :
160.6 (CFS) Date/Time of Peak Inflow :
280ct2008, 19:30
Peak Outflow :
126.6 (CFS) Date/Time of Peak Outflow :
280ct2008, 19:55
Total Inflow :
7.44 (IN) Peak Storage :
8.1 (AC-FT)
Total Outflow :
7.44 (IN) Peak Elevation :
304.1 (FT)
Project: Meadow Creek
Simulation Run: Post 100 yr 12 hr Reservoir: Pond3
Start of Run: 280ct2008, 13:00 Basin Model: Post Dev
End of Run: 290ct2008, 13:15 Meteorologic Model: 100 yr 12 hr
Compute Time: 04Nov2008, 14:56:30 Control Specifications: 24 hr duration
Volume Units: IN
Computed Results
Peak Inflow : 61.6 (CFS) Date/Time of Peak Inflow: 280ct2008, 19:50
Peak Outflow : 60.0 (CFS) Date/Time of Peak Outflow : 280ct2008, 19:55
Total Inflow : 7.00 (IN) Peak Storage : 0.9 (AC-FT)
Total Outflow : 7.00 (IN) Peak Elevation : 312.0 (FT)
Project: Meadow Creek
Simulation Run: Post 100 yr 12 hr Reservoir: Pond4
Start of Run: 280ct2008, 13:00 Basin Model: Post Dev
End of Run: 290ct2008, 13:15 Meteorologic Model: 100 yr 12 hr
Compute Time: 04Nov2008, 14:56:30 Control Specifications: 24 hr duration
Volume Units: IN
Computed Results
Peak Inflow : 61.6 (CFS) Date/Time of Peak Inflow : 280ct2008, 19:40
Peak Outflow : 59.2 (CFS) Date/Time of Peak Outflow : 280ct2008, 19:50
Total Inflow : 6.93 (IN) Peak Storage : 1.2 (AC-FT)
Total Outflow : 6.93 (IN) Peak Elevation : 315.9 (FT)
EXHIBIT A
Drainage Area Map - Pre-Development
EXHIBIT B
Drainage Area Map - Post-Development, Pond Design
EXHIBIT C
Grading Plan - Sheet I of 2
EXHIBIT D
Grading Plan - Sheet 2 of 2