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DRAINAGE REPORT
URSA OPERATING COMPANY, BMC F PAD
March, 2017
PREPARED BY
65GM
I 18 WEST SIXTH STREET, SUITE 200
GLENWOOD SPRINGS, CO 81601
970.945.1004
970.945.5948 FAX
URSA Operating Company, BMC F March 2017
TABLE OF CONTENTS
SGM Project # 2006-479.062
Pad F_Drain Report.docx
1 Introduction 1
1.1 Purpose 1
1.2 Current Site 1
1.3 Methods Used
2 Hydraulic and Hydrologic Analysis
2.1 Off -Site Drainage
2.2 On -Site Drainage
2.3 Stormwater Detention
3 Hydraulic Analysis
4 Stormwater Quality Plan
APPENDIX
APPENDIX A - NOAA Atlas 14 Information
APPENDIX B - Rational Method Calculations
1
1
1
2
2
3
3
ii
URSA Operating Company, BMC F March 2017
1 Introduction
1.1 Purpose
The purpose of this drainage report is to provide calculations for storm water runoff volumes
to be detained on-site. This report contains a discussion of both off-site and on-site
drainage and the methodology used to design various drainage elements. The designed
drainage elements ensure that storm water runoff produced from the 24 hour storm will be
detained and treated on site to reduce possible contamination off-site.
1.2 Current Site
The project site is located in the unplatted portion of Battlement Mesa P.U.D. located South
of Stone Quarry Commons and the SI Gardner property. The Pad is located in the south
eastern portion of this unplatted parcel. BMC F is served by CR 308W near its south
terminus in Section 16 next to Monument Gulch. The site is sloping from east to west.
The project site, in its pre -developed condition, is located in a semiarid plateau region
between 5000 ft. and 6000 ft. in elevation. The vegetative cover consists of mostly pasture
grass intermixed with sage brush and juniper trees. A majority of the drainage basin for the
project is composed of hydraulic soil group C and D.
1.3 Methods Used
The Rational Method was used to produce a conservative set of hydrologic flood peak
calculations for sizing particular drainage elements (i.e., the Rational Method would predict
higher flood peaks than alternative methods). The Rational Method uses the equation
below:
Q = CiA Equation 1
where:
Q = flow rate (cfs)
C = runoff coefficient based on soil type and cover
i = rainfall intensity corresponding to the time of concentration
A = basin area (acres).
2 Hydraulic and Hydrologic Analysis
The project site in its developed condition will consist of a main gravel entrance road and
large gravel pad. Because only a small portion of the site is being developed, only these
areas will be analyzed in the detention calculations due to the rest of the site maintaining
historic flow patterns and characteristics. Drainage facilities will be provided to route
tributary/offsite flows around the pad into the common historic flow paths associated with the
property containing this pad.
2.1 Off -Site Drainage
In its developed condition, BMC F has some introduction of off-site surface drainage from a
smaller 36,090 square foot area immediately above the access roadway for the pad. Aside
from this area, the remaining offsite drainage tributary to the pad will be routed around the
1
URSA Operating Company, BMC F March 2017
pad. This offsite surface drainage generally exists in the form of sheet flow from above with
no incised tributary channels observed.
2.2 On -Site Drainage
The project site in its developed conditions will consist of 3.8 acres of a large gravel pad and
1,150' long tributary access road. Compared to historic conditions, construction of the
proposed developed conditions would produce a reduction in pervious ground cover,
resulting in a minor change to the runoff coefficient. This will result in an increase in peak
discharge of the 24 hour storm and detention will be needed for the stormwater flowing
across the developed site. Two borrow ditches are proposed for the access road
construction to route drainage to a detention pond for the increased runoff detention for the
roadway while collection ditches at the base of the pad will route flows to a detention pond
for the pad itself. The developed flows for the site are summarized below.
Table 1 Historic Vs. Developed Flow Rates (Access Road Pond)
Storm Return Period i 2 year (cfs) i 25 year (cfs) 1 100 year (cfs)
Historic Flow
Developed Flow
0.36
0.49
0.79 1.20
1.08 1.64
Table 2 Historic Vs. Developed Flow Rates (Pad Pond)
i Storm Return Period 2 year (cfs) 25 year (cfs) 100 year (cfs) I
Historic Flow 0.64 1.43 2.17
Developed Flow 1.03 2.28 3.47_1
The flows shown above are determined from a rainfall intensity corresponding to the 24 hour
storm and appropriate storm return period. These intensities and the flow calculations can
be seen in the appendix. Note that the time of concentration (or storm duration) used in the
analysis is 15 minutes.
2.3 Stormwater Detention
For the purpose of this report and this project, it will be required to detain the additional
stormwater runoff volume generated from the developed site from historic conditions. In order
to determine required detention, the developed and historic stormwater runoff volumes were
analyzed. Storm runoff volume was calculated from the 2 and 25 year, 24 hour storm
precipitation depth determined from the NOAA Atlas 14 information. These depths for each
storm return period can be seen in the appendix. The runoff volume of the site was calculated
from area of the developed site multiplied by the 2 and 25 year, 24 hour precipitation depth
and the weighted runoff coefficient for the appropriate site condition.
2
URSA Operating Company, BMC F
March 2017
Table 2 Stormwater Flow Summary (Access Road Pond)
Pond Location
Runoff
Coefficient
HistoricHistoric
(Historic)
Runoff
Coefficient
(Developed)
2 -YR Rainfall
Volume, CF
( )
25 -YR Rainfall
Volume, CF
Historic
( )
2 -YR Rainfall
Volume, CF
Develo ed
( P )
25 -YR Rainfall
Volume, CF
(Developed)
Pond Storage
Needed for
Detention, CF
(25 -YR)
Access Road Pond
0.5
0.7
321
711
438
970
259
Table 3 Stormwater Flow Summary (Pad F Pond)
Pond Location
Runoff
Coefficient
(Historic)
HistoricHistoric
Runoff
Coefficient
(Developed)
2 -YR Rainfall
Volume, CF
( )
25 -YR Rainfall
Volume, CF
Historic
( )
2 -YR Rainfall
Volume, CF
Develo ed
( P )
25 -YR Rainfall
Volume, CF
(Developed)
Pond Storage
Needed for
Detention, CF
(25 -YR)
BMC Pond F
0.5
0.7
580
1283
928
2052
769
The maximum calculated detention necessary to capture the stormwater runoff volume
generated from the 25 -year storm is approximately 259 cubic feet for the access road pond
and 769 cubic feet for the F Pad pond. Detention ponds with this capacity and drainage
features to convey water to the ponds will be provided on site. Pond specific size
calculations are attached in the appendix of this report.
3 Hydraulic Analysis
The site design will require various drainage features including ditches and culverts. These
will be required to divert the storm water runoff away from the site appropriately.
4 Stormwater Quality Plan
The main goal of the site design is to provide detention for the project, and ensure the post -
development peak discharge rates do not exceed the pre -development peak flow rates.
The only area where a significant increase in runoff coefficients occur is the gravel pad and
road. Detention ponds are sized appropriately and provide a location for sedimentation of
the storm water runoff generated from the developed site. The remaining site will remain
native vegetation and provide historic flow patterns and characteristics.
There is an increase of runoff generated with the construction the gravel pad and associated
access road. This increase in runoff is measurable, however; a detention pond will be
constructed just downstream of the respective pad, with a controllable outfall pipe and valve
structure. The controlling valves in the detention pond discharge pipes will each be left in
the normally open position at approximately 60% open. Alternatively, these valves can be
closed in the event of a non-compliant release, and further ensure no detrimental impact to
the surrounding area. A similar pond will be constructed for the access road.
In order to minimize any threat of property damage, the respective pond structures will have
an 18" culvert pipe installed at a higher elevation, along with the normal use 12" discharge
3
URSA Operating Company, BMC F March 2017
pipe, in order to facilitate conveying the 100 year storm event safely to the respective outfall
drainage features. Both proposed detention ponds will discharge into existing "natural
channel" drainage features. It is not anticipated for any additional erosion and
sedimentation protection beyond that proposed at the pipe outfalls. The operator will
monitor outfall locations to ensure there is no channel scour or additional erosion cause by
the detention pond outfall pipe. Supporting calculations have been included in the appendix
of this report.
Temporary erosion control measures will be required for the duration of construction. A
CDPHE Stormwater Permit for Construction activities will be obtained prior to construction
activities. Best Management Practices will be utilized during construction to control the
stormwater runoff during construction. Key temporary erosion control measures include
installation and maintenance of straw wattles, inlet protection, a stabilized construction
entrance and all necessary acceptable best management practices that would relate to this
project. See Ursa's Stormwater Management Plan (SWMP) for more details.
4
URSA Operating Company, BMC F March 2017
APPENDIX A —NOAA Atlas 14 Information
Appendix
5
Precipitation Frequency Data Server
Page 1 of 3
NOAA Atlas 14, Volume 8, Version 2
Location name: Parachute, Colorado, US*
Latitude: 39.4472°, Longitude: -108.0330°
Elevation: 5202 ft*
source: Google Maps
POINT PRECIPITATION FREQUENCY ESTIMATES
Sanja Perica, Deborah Martin, Sandra Pavlovic, Ishani Roy, Michael St. Laurent, Carl Trypaluk, Dale
Unruh, Michael Yekta, Geoffery Bonnin
NOAA, National Weather Service, Silver Spring, Maryland
PF tabular 1 PF graphical 1 Maps & aerials
PF tabular
PDS -based point precipitation frequency estimates with 90% confidence intervals (in inches)1
Average recurrence interval (years)
Duration
1
2
5
10
25
50
100
200
500
1000
5 -min
0.137
(0.110-0.173)
0.162
(0.130-0.205)
0.215
(0.172-0.273)
0.269
(0.215-0.344)
0.360
(0.284-0.500)
0.443
(0.336-0.618)
0.536
(0.391-0.769)
0.643
(0.446-0.948)
0.800
(0.531-1.22)
0.933
(0.595-1.42)
10 -min
0.200
(0.161-0.253)
0.237
(0.191-0.300)
0.314
(0.252-0.400)
0.394
(0.314-0.504)
0.527
(0.416-0.732)
0.648
(0.492-0.905)
0.785
(0.572-1.13)
0.941
(0.653-1.39)
1.17
(0.777-1.78)
1.37
(0.871-2.07)
15 -min
0.244
(0.197-0.309)
0.289
(0.233-0.366)
0.383
(0.308-0.487)
0.481
(0.383-0.614)
0.643
(0.507-0.893)
0.791
(0.600-1.10)
0.958
(0.698-1.37)
1.15
(0.797-1.69)
1.43
(0.948-2.17)
1.67
(1.06-2.53)
30 -min
0.309
(0.249-0.390)
0.389
(0.313-0.492)
0.534
(0.428-0.678)
0.667
(0.532-0.853)
0.872
(0.677-1.19)
1.05
(0.786-1.44)
1.23
(0.891-1.74)
1.44
(0.990-2.10)
1.73
(1.14-2.60)
1.96
(1.25-2.98)
60 -min
0.389
(0.313-0.492)
0.484
(0.390-0.613)
0.652
(0.523-0.828)
0.802
(0.639-1.03)
1.03
(0.792-1.38)
1.21
(0.908-1.66)
1.41
(1.01-1.98)
1.62
(1.11-2.35)
1.91
(1.26-2.87)
2.15
(1.37-3.26)
2 -hr
0.469
(0.382-0.586)
0.580
(0.472-0.725)
0.770
(0.624-0.966)
0.936
(0.754-1.18)
1.18
(0.917-1.56)
1.37
(1.04-1.85)
1.58
(1.15-2.18)
1.80
(1.25-2.57)
2.10
(1.40-3.09)
2.33
(1.51-3.49)
3 -hr
0.536
(0.439-0.665)
0.641
(0.525-0.796)
0.824
(0.672-1.03)
0.985
(0.798-1.23)
1.22
(0.959-1.61)
1.42
(1.08-1.89)
1.62
(1.19-2.22)
1.84
(1.29-2.60)
2.14
(1.44-3.13)
2.38
(1.55-3.53)
6 -hr
0.661
(0.548-0.809)
0.773
(0.639-0.947)
0.963
(0.794-1.18)
1.13
(0.924-1.39)
1.37
(1.08-1.77)
1.56
(1.20-2.05)
1.76
(1.31-2.38)
1.97
(1.40-2.75)
2.26
(1.54-3.25)
2.49
(1.64-3.64)
12 -hr
0.819
(0.685-0.989)
0.946
(0.791-1.14)
1.16
(0.967-1.41)
1.35
(1.12-1.64)
1.61
(1.29-2.05)
1.83
(1.43-2.36)
2.05
(1.54-2.73)
2.28
(1.64-3.13)
2.61
(1.79-3.69)
2.86
(1.91-4.11)
24 -hr
0.993
(0.840-1.18)
1.14
(0.964-1.36)
1.39
(1.17-1.67)
1.61
(1.35-1.94)
1.92
(1.56-2.41)
2.17
(1.71-2.76)
2.43
(1.85-3.18)
2.70
(1.97-3.65)
3.07
(2.15-4.29)
3.37
(2.28-4.77)
2 -day
1.17
(1.00-1.38)
1.35
(1.15-1.58)
1.64
(1.40-1.94)
1.90
(1.60-2.25)
2.26
(1.85-2.78)
2.55
(2.03-3.19)
2.84
(2.19-3.67)
3.16
(2.33-4.20)
3.58
(2.53-4.91)
3.92
(2.69-5.46)
3 -day
1.29
(1.11-1.50)
1.48
(1.27-1.73)
1.81
(1.55-2.12)
2.09
(1.78-2.46)
2.49
(2.05-3.04)
2.81
(2.26-3.49)
3.13
(2.43-4.00)
3.48
(2.58-4.58)
3.94
(2.81-5.36)
4.31
(2.99-5.95)
4 -day
1.39
(1.20-1.61)
1.59
(1.38-1.85)
1.94
(1.67-2.26)
2.24
(1.92-2.62)
2.67
(2.21-3.24)
3.01
(2.43-3.71)
3.36
(2.62-4.26)
3.72
(2.78-4.87)
4.22
(3.02-5.69)
4.60
(3.21-6.31)
7 -day
1.63
(1.42-1.87)
1.87
(1.62-2.14)
2.26
(1.96-2.60)
2.60
(2.24-3.00)
3.07
(2.56-3.68)
3.44
(2.80-4.19)
3.82
(3.01-4.78)
4.22
(3.18-5.44)
4.75
(3.44-6.32)
5.16
(3.64-6.99)
10 -day
1.85
(1.62-2.10)
2.10
(1.84-2.39)
2.52
(2.20-2.87)
2.87
(2.49-3.29)
3.37
(2.83-4.00)
3.76
(3.08-4.54)
4.16
(3.29-5.15)
4.56
(3.46-5.84)
5.11
(3.73-6.74)
5.54
(3.93-7.43)
20 -day
2.47
(2.19-2.77)
2.76
(2.45-3.10)
3.24
(2.86-3.64)
3.64
(3.19-4.11)
4.19
(3.55-4.89)
4.61
(3.83-5.47)
5.04
(4.04-6.14)
5.48
(4.21-6.88)
6.06
(4.48-7.84)
6.50
(4.68-8.57)
30 -day
2.99
(2.67-3.32)
3.33
(2.97-3.71)
3.89
(3.45-4.33)
4.34
(3.84-4.87)
4.96
(4.24-5.73)
5.43
(4.54-6.38)
5.90
(4.76-7.11)
6.37
(4.94-7.91)
6.98
(5.21-8.94)
7.44
(5.41-9.72)
45 -day
3.64
(3.27-4.01)
4.07
(3.66-4.49)
4.77
(4.27-5.27)
5.33
(4.74-5.92)
6.08
(5.22-6.93)
6.64
(5.57-7.70)
7.17
(5.83-8.55)
7.70
(6.01-9.46)
8.38
(6.29-10.6)
8.86
(6.50-11.5)
60 -day
4.18
(3.77-4.58)
4.72
(4.26-5.17)
5.57
(5.01-6.12)
6.25
(5.59-6.90)
7.13
56.14-8.07)
7.78
(6.56-8.95)
8.40
(6.85-9.92)
8.99
(7.05-10.9)
9.73
(7.34-12.2)
10.2
(7.57-13.2)
1 Precipitation frequency (PF) estimates in this table are based on frequency analysis o 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 dura ion 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 Top
PF graphical
http://hdsc.nws.noaa.gov/hdsc/pfds/pfds printpage.html?lat=39.4472&lon=-108.0330&dat... 9/30/2014
Precipitation Frequency Data Server
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Page 2 of 3
Average recurrence
interval
{years}
— 1
2
— 5
— 10
— 25
— 50
— 100
— 200
— 500
— 1000
Duration
— 5 -min — 2 -day
— 10 -min — 3 -day
15 -min --- 4 -day
— 30 -min — 7 -day
— 60 -min — 10 -day
— 24r — 20 -day
— 3 -he — 30 -day
— 6 -Sr — 45 -day
— 12 -hr — 60 -day
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US Department of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Office of Hydrologic Development
1325 East West Highway
Silver Spring, MD 20910
Questions?: HDSC.Questions(&noaa.gov
Disclaimer
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Precipitation Frequency Data Server
Page 1 of 3
NOAA Atlas 14, Volume 8, Version 2
Location name: Parachute, Colorado, US*
Latitude: 39.4472°, Longitude: -108.0330°
Elevation: 5202 ft*
source: Google Maps
POINT PRECIPITATION FREQUENCY ESTIMATES
Sanja Perica, Deborah Martin, Sandra Pavlovic, Ishani Roy, Michael St. Laurent, Carl Trypaluk, Dale
Unruh, Michael Yekta, Geoffery Bonnin
NOAA, National Weather Service, Silver Spring, Maryland
PF tabular 1 PF graphical 1 Maps & aerials
PF tabular
PDS -based point precipitation frequency estimates with 90% confidence intervals in inches/hour)1
Average recurrence interval (years)
Duration
1
2
5
10
25
50
100
200
500
1000
5 -min
1.64
(1.32-2.08)
1.94
(1.56-2.46)
2.58
(2.06-3.28)
3.23
(2.58-4.13)
4.32
(3.41-6.00)
5.32
(4.03-7.42)
6.43
(4.69-9.23)
7.72
(5.35-11.4L
9.60
(6.37-14.6)
11.2
(7.14-17.0)
10 -min
1.20
(0.966-1.52)
1.42
(1.15-1.80)
1.88
(1.51-2.40)
2.36
(1.88-3.02)
3.16
(2.50-4.39)
3.89
(2.95-5.43)
4.71
(3.43-6.76)
5.65
(3.92-8.33)
7.03
(4.66-10.7)
8.20
(5.23-12.4)
15 -min
0.976
(0.788-1.24)
1.16
(0.932-1.46)
1.53
(1.23-1.95)
1.92
(1.53-2.46)
2.57
(2.03-3.57)
3.16
(2.40-4.42)
3.83
(2.79-5.49)
4.59
(3.19-6.77)
5.72
(3.79-8.68)
6.66
(4.25-10.1)
30 -min
0.618
(0.498-0.780)
0.778
(0.626-0.984)
1.07
(0.856-1.36)
1.33
(1.06-1.71)
1.74
(1.35-2.37)
2.09
(1.57-2.88)
2.46
(1.78-3.49)
2.87
(1.98-4.19)
3.45
(2.28-5.20)
3.93
(2.50-5.96)
60 -min
0.389
(0.313-0.492)
0.484
(0.390-0.613)
0.652
(0.523-0.828)
0.802
(0.639-1.03)
1.03
(0.792-1.38)
1.21
(0.908-1.66)
1.41
(1.01-1.98)
1.62
(1.11-2.35)
1.91
(1.26-2.87)
2.15
(1.37-3.26)
2 -hr
0.234
(0.191-0.293)
0.290
(0.236-0.362)
0.385
(0.312-0.483)
0.468
(0.377-0.590)
0.589
(0.458-0.780)
0.687
(0.520-0.924)
0.789
(0.575-1.09)
0.898
(0.624-1.28)
1.05
(0.698-1.55)
1.17
(0.753-1.74)
3 -hr
0.178
(0.146-0.221)
0.213
(0.175-0.265)
0.274
(0.224-0.342)
0.328
(0.266-0.411)
0.407
(0.319-0.535)
0.471
(0.360-0.629)
0.539
(0.396-0.740)
0.611
(0.429-0.867)
0.712
(0.478-1.04)
0.792
(0.516-1.18)
6 -hr
0.110
0.129
0.161
0.189
0.228
0.261
0.294
0.329
0.377
0.416
(0.092-0.135)
(0.107-0.158)
(0.133-0.198)
(0.154-0.233)
(0.181-0.295)
(0.201-0.342)
(0.218-0.397)
(0.233-0.458)
(0.257-0.543)
(0.274-0.607)
12 -hr
0.068
(0.057-0.082)
0.079
(0.066-0.095)
0.096
(0.080-0.117)
0.112
(0.093-0.136)
0.134
(0.107-0.170)
0.152
(0.118-0.196)
0.170
(0.128-0.226)
0.190
(0.136-0.260)
0.216
(0.149-0.306)
0.237
(0.159-0.341)
24 -hr
0.041
(0.035-0.049)
0.048
(0.040-0.057)
0.058
(0.049-0.069)
0.067
(0.056-0.081)
0.080
(0.065-0.100)
0.091
(0.071-0.115)
0.101
(0.077-0.133)
0.113
(0.082-0.152)
0.128
(0.089-0.179)
0.140
(0.095-0.199)
2 -day
0.024
(0.021-0.029)
0.028
(0.024-0.033)
0.034
(0.029-0.040)
0.039
(0.033-0.047)
0.047
(0.038-0.058)
0.053
(0.042-0.066)
0.059
(0.046-0.076)
0.066
(0.048-0.087)
0.075
(0.053-0.102)
0.082
(0.056-0.114)
3 -day
0.018
(0.015-0.021)
0.021
(0.018-0.024)
0.025
(0.022-0.029)
0.029
(0.025-0.034)
0.035
(0.028-0.042)
0.039
(0.031-0.048)
0.044
(0.034-0.056)
0.048
(0.036-0.064)
0.055
(0.039-0.074)
0.060
(0.041-0.083)
0.014
0.017
0.020
0.023
0.028
0.031
0.035
0.039
0.044
0.048
4 -day
(0.012-0.017)
(0.014-0.019)
(0.017-0.024)
(0.020-0.027)
(0.023-0.034)
(0.025-0.039)
(0.027-0.044)
(0.029-0.051)
(0.031-0.059)
(0.033-0.066)
7 -day
0.010
(0.008-0.011)
0.011
(0.010-0.013)
0.013
(0.012-0.015)
0.015
(0.013-0.018)
0.018
(0.015-0.022)
0.020
(0.017-0.025)
0.023
(0.018-0.028)
0.025
(0.019-0.032)
0.028
(0.020-0.038)
0.031
(0.022-0.042)
10 -day
0.008
(0.007-0.009)
0.009
(0.008-0.010)
0.010
(0.009-0.012)
0.012
(0.010-0.0141
0.014
(0.012-0.017)
0.016
(0.013-0.0191
0.017
(0.014-0.021)
0.019
(0.014-0.024)
0.021
(0.016-0.028)
0.023
(0.016-0.031)
20 -day
0.005
(0.005-0.006)
0.006
(0.005-0.006)
0.007
(0.006-0.008)
0.008
(0.007-0.009)
0.009
(0.007-0.010)
0.010
(0.008-0.011)
0.011
(0.008-0.013)
0.011
(0.009-0.014)
0.013
(0.009-0.016)
0.014
(0.010-0.018)
30 -day
0.004
(0.004-0.005)
0.005
(0.004-0.005)
0.005
(0.005-0.006)
0.006
(0.005-0.007)
0.007
(0.006-0.008)
0.008
(0.006-0.009)
0.008
(0.007-0.010)
0.009
(0.007-0.011)
0.010
(0.007-0.012)
0.010
(0.008-0.013)
45 -day
0.003
(0.003-0.004)
0.004
(0.003-0.004)
0.004
(0.004-0.005)
0.005
(0.004-0.005)
0.006
(0.005-0.006)
0.006
(0.005-0.007)
0.007
(0.005-0.008)
0.007
(0.006-0.009)
0.008
(0.006-0.010)
0.008
(0.006-0.011)
60 -day
0.003
(0.003-0.003)
0.003
(0.003-0.004)
0.004
(0.003-0.004
0.004
(0.004-0.005)
0.005
(0.004-0.006)
0.005
(0.005-0.006)
0.006
(0.005-0.007)
0.006
(0.005-0.008)
0.007
(0.005-0.008)
0.007
(0.005-0.009)
1 Precipitation frequency (PF) estimates in this table are based on frequency analysis o 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 Top
PF graphical
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— 30 -min — 7 -day
— 60 -min — 10 -day
— 2 -hr — 20 -day
— 3 -hr — 30 -Clay
— 6 -hr — 45 -day
— 12 -hr — 60 -day
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US Department of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Office of Hydrologic Development
1325 East West Highway
Silver Spring, MD 20910
Questions?: HDSC.Questions(&noaa.gov
Disclaimer
http://hdsc.nws.noaa.gov/hdsc/pfds/pfds printpage.html?lat=39.4472&lon=-108.0330&dat... 9/30/2014
URSA Operating Company, BMC F March 2017
APPENDIX B — Rational Method Calculations
6
SIZING CATCH BASIN FOR ACCESS ROAD
Pad Description: URSA PAD F ACCESS ROAD- Developed Conditions
Date: 3/24/2017
Location: URSA Pad F Access Road, Parachute, Garfield County
Rainfall Intensity Data Table
Recurrence Interval (Years)
Duration (minutes)
2
10
25
100
10
0.278
0.455
0.615
0.938
15
0.339
0.555
0.750
1.140
30
0.450
0.767
1.010
1.440
60
0.558
0.923
1.180
1.630
To populate Data Table, refer to website below.
Area of Pad Calculations:
Coefficienst of Runoff:
Gravel Road:
Tributary undisturbed:
Rational Method: Q=CiA
Pad and Road Area:
Trib. area to Pad/Road:
CA Value:
CA Value:
Sum:
91760.00
55,670.00 squ. Ft.
36,090.00 squ. Ft.
Sum:
1.02 Acres
0.41 Acres
Peak Flow (Q, cfs)
Recurrence Interval (Years)
Duration (minutes)
2
10
25
100
10
0.399
0.654
0.884
1.348
15
0.487
0.797
1.077
1.638
30
0.646
1.102
1.451
2.069
60
0.802
1.326
1.695
2.342
Volume of Runoff (cf)
Recurrence Interval (Years)
Duration (minutes)
2
10
25
100
10
239.635
392.209
530.128
808.553
15
438.326
717.613
969.747
1474.015
30
1163.696
1983.456
2611.852
3723.828
60
2885.967
4773.741
6102.940
8430.333
http://hdsc.nws.noaa.gov/hdsc/pfds/pfds map cont.html
1.44 Acres
1.278 Acres
0.829 Acres
2.107 Acres
SIZING CATCH BASIN FOR WELL PAD
Pad Description: URSA PAD F - Historic Conditions
Date: 3/24/2017
Location: URSA Pad F, Parachute, Garfield County
Rainfall Intensity Data Table
Recurrence Interval (Years)
Duration (minutes)
2
10
25
100
10
0.278
0.455
0.615
0.938
15
0.339
0.555
0.750
1.140
30
0.450
0.767
1.010
1.440
60
0.558
0.923
1.180
1.630
To populate Data Table, refer to website below.
Area of Pad Calculations:
Coefficienst of Runoff:
Gravel Pad and Road:
Tributary undisturbed:
Rational Method: Q=CiA
Pad Area:
Trib. area to Pad:
0.5
0.5
CA Value:
CA Value:
Sum:
165,554.00 squ. Ft.
- squ. Ft.
1.90 Acres
0.00 Acres
Peak Flow (Q. cfs)
Recurrence Interval (Years)
Duration (minutes)
2
10
25
100
10
0.528
0.865
1.169
1.782
15
0.644
1.055
1.425
2.166
30
0.855
1.458
1.919
2.736
60
1.060
1.754
2.242
3.097
Volume of Runoff (cf)
Recurrence Interval (Years)
Duration (minutes)
2
10
25
100
10
316.97
518.78
701.21
1069.49
15
579.78
949.20
1282.70
1949.71
30
1539.24
2623.55
3454.74
4925.57
60
3817.32
6314.31
8072.47
11150.95
http://hdsc.nws.noaa.gov/hdsc/pfds/pfds map cont.html
1.90 Acres
( Worksheet: Pad F Outflow Pipe
Solve for. Discharge
ISI
1-1=Il1
Manning's Formula I
Mannings Coefficient:0.028
Channel Slops ft/ft
Depth: .00 fl
Diameter. l i 2.0
Discharge, 1.38 cfs
Flow Are. 0.8 11=
Wetted Perimeter:[ 3.14 ft
Tap Width 000 It
Critical Depth 0.50 It
Percent Full:7- 100.0
Critical Slope:r 00284661t)ft
Velocity: 1.76 Itis
Velocity Head: 0.05 It
Specific Energy: 1.05 It
Fronde Number 0.00
Maximum Discharge: 1.49 cfs
Discharge Full: 7- 1_30 cfs
Slope Full 0.007000 IVft
Flow Type: Subcrillcal
Solve j Report Cbse Help
3.801 Acres
0.000 Acres
Detention Volume Required (CF)
Recurrence Interval (Years)
Duration (minutes)
2
10
25
100
10
190
311
421
642
15
348
570
770
1170
30
924
1574
2073
2955
60
4843
6691
For pond sizing:
Contour Area
Detained
Volume
Cumm. Volume Comment
5827 598
5828 804 701 701
5829 1070 937 1638
DESIGN OVERFLOW CULVERT FOR 3.5 CFS
DRAIN CULVERT CAN BE AN 12" PIPE WITH A HEADGATE ON IT.
12" INVERT = 5827.0, PIPE LAID AT 0.70%
NORMAL MAINTENANCE WOULD ALLOW DRAINING OF THE POND
IN NON PRECIPITATION EVENTS AND COLLECTION OF SEDIMENT TO
MAINTAIN THE 25 YEAR VOLUME OF RUNOFF FROM PAD AND ROAD
1800
1600
1400
1200
1000
800
600
400
200
Stage/Storage
0
5827 8 5829
• Volume
Volume established at
5428.1 contour
Depth in pond:
1.1 feet