HomeMy WebLinkAbout20182137.tiff4.10009
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PRELIMINARY DRAINAGE REPORT
For
CENTENNIA L TOOLS ;\: SE
25172 WCR 53
MERSEY, COLORADO
Prepared for:
Juan Cruz
P.O. Box 296
Kersey, Colorado 80644
Contact: Brandi McMullan
(970) 3373-3307
March 2018
or
S gm
S
Drexel, Barrell & CO.
Engineers 1' Surveyors
710 11th Avenue, Suite L-45
Greeley, Colorado 80631
(970) 351-0645
Project: 21075-00GRCV
Prepared By:
Mark A. Butler, P.E.
]ES LLC
March 27, 2018
Hayley Balzano
Weld County Planning Department
1555 N. 17th Avenue
Greeley, CO 80631
RE: Preliminary Drainage Report
25172 CR 53, Kersey, Colorado.
Dear Ms. Balzano:
We are pleased to submit, for your review and approval, Preliminary Drainage
Report for the Centennial Tools & Service LLC, USR Application.
The investigation and design within this report have been performed according
to the criteria established by the Weld County Storm Drainage Criteria as an
addendum to the Urban Storm Drainage Manual.
We sincerely appreciate your time and consideration in the review of this
project. If you should have any questions, please feel free to contact this
office.
Respectfully,
afrazie
Mark A. Butler, P.E.
Drexel, Barrell & Co.
"I hereby attest that this report for the preliminary drainage design for
Centennial Tools & Service LLC USR, was prepared by me (or under my
direct supervision) in accordance with the provisions of Weld County Storm
Drainage Criteria for the responsible parties thereof. I understand that W e l d
County does not and shall not assume liability for drainage facilities designed
by others."
%MA'
Mark A Butler, PE
Registered Professional Engineer
State of Colorado No. 33625
Preliminary Drainage Report
i i March 2018
Centennial Tools USR Drexel, Barrell & Co.
TABLE OF CONTENTS
HEADING PAGE
TABLE OF CONTENTS
a ago Oa a
I. GENE ' L LOCATION & DESCRIPTION.
A. Location
seal sssi*ss.Us•ss*sss.*Ssss*sssss•ssu.
44.*444.►►..44444'4**►..►.►........4444'44444444!4'44 44444444 4* 44444*444'444444444
B. Description of Property
C.
Proposed improvements... ...
•••••••••••••••••••••••••••••••
4444444444444444344443444444443444443443444444444444440 e•*** 444*444444*
iv
1
1
l
1
II. DRAINAGE BASINS & S "BASINS enema .noes ems nom seem •ssssns*ems s•••sssw.ems •s•sss•ssssss.sone
A. Major Basin Description 2
B. Existing Drainage Description ...••••••••••••••.••••••••••••• * • 4'.......e•••••••...••• OP • 4*•••••••••••••• 2
C. Existing Condition Runoff --. ---- --- -- - 444-- --- _ _ - - --. 2
----
III. DRAINAGE DESIGN CRITERIA
A. Hydrological criteria
......... •s SOW•s•••snn••sss•*s'•Rwsss•s•••••••••••illssese$••••••i•ns0•••••u44s•0000
**4* ** +4444444444444444*..•4444****44444.F4***+444444.4.444.4•••••••••••••••••••••••••••••••••••••••• •
2
2
H. Hydraulic Criteria 3
3
C. Waiver/Variance from criteria
44'4'4..444.4'44*4444444'4'4444444444*444444444'4...444.4
IV. DRAINAGE FACILITY DESIGN
A. eneral .4. 4 - -
B. Proposed Basin Runoff...........,...........
C. Detention Facility Details - - -
44444'44...44.4.4* 44444* 444' 40004
•sssssssssss••sssss*SW sfssssus••ss•s•sssssflee
.
444444.4.444444.4* 4444444. 4444444444* 444444* 44.44444444.444444444.4444444444
REFERENCES. ** * •••••••••••••••••••••••••••••••••• * • ** • * itt•••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••
APPENDICES
A. Vicinity Map
B. Soils Information from USDA NR "'oils Web Survey"
C. Hydrologic Computations
D. Proposed Stormwater Quality Pond Calculations
E. Charts, Tables and Graphs
BACK POCKET:
24"x36" Proposed Drainage Plan
3
3
3
4
4
Preliminary Drainage Report
Centennial Tools USR Drexel, Barrell & Co.
iii March 2018
I. GENERAL LOCATION & DESCRIPTION
A. Location
1. The project site is located in the North 1/2 of the Southwest 1/4 of the
Southwest 1/4 of Section 28, Township 5 North, Range 64 West, of the 6th
Principal Meridian, Weld County, Colorado.
2. The property address is 25172 CR 53 Kersey, Colorado 80644.
3. The drainage basin bounded as follows:
a. East, by WCR 53.
b. All other directions by 5 to 40 acre fa t steads with irrigated or
dryland pastures.
B. Description of Property
1. The total area of the property is 10.04 acres.
2. The east 2/3 of the property is currently dryland pasture. The existing
farmstead occupies the west third.
3. The "Soil Survey of Weld County Area, Colorado, Southern Part" prepared by
the U.S. Department of Agriculture, Soil Conservation Service, indicates that
the surface soils on the site consists of about a third of each Valent sand (0-3
percent slope), Valent sand (3-9 percent slope), and Vona loamy sand (3-5%
slope).
a. All three soil types are described as well drained soil, with a high
capacity to transmit water. All are classified in the 'A' hydrologic
group.
4. According to the FEMA Flood Insurance Rate Map (FIRM) Community Panel
No. 0 8123 177 E, the site is not located in a designated 100 -year floodplain
or floodway.
Fay.
C. Proposed improvements
1. The proposed improvements on the site include:
a. Construction of a 15,000 square foot building.
b. Installation of gravel parking and storage areas.
c. Construction of storm water detention.
Preliminary Drainage Report
Centennial Tools USR Drexel, Barrell & Co.
March 2018
II. DRAINAGE BASINS & SUB -BASINS
A. Major Basin Description
1. This agricultural area south of Kersey generally drains to the northeast. There
are some low points in the topography, offsite to the northeast, that appear to
collect runoff. The Latham Ditch is about two miles to the northeast and
functions a runoff collector.
B. Existing Drainage Description
1. The site slopes from west to east at approximately 2% slope. The low point is
the northeast corner. There are no defined drainage structures or ditches on the
site.
2. The east half of the asphalt County Road 53 runs off onto the site. There is no
defined roadside ditch.
C. Existing Condition Runoff
The undeveloped peak runoff rates and runoff coefficients associated with the
existing undeveloped conditions are presented in Table 1. The entire area, road
included was assumed to be undeveloped, imperviousness of 2.0%
TABLE 1: EXISTING CONDITIONS RUNOFF RATES
Basin
Area
(acres)
5 -year Runoff
Coefficients
10 -year
Coefficients
10
Peak
-year
Runoff
(cis)
100 -Year
Runoff
Coefficients
100 -year
Peak Runoff
(cis)
EX -1
10.04
0.01
0.01
0.25
0.13
6.28
III. DRAINAGE DESIGN CRITERIA
A. Hydrological Criteria
1. The All proposed drainage design will conform to Weld County Storm
Drainage Criteria and Urban Storm Drainage.
2. The design storm frequencies for un-urbanized land use are the 10 -year and
100 -year storm events per Weld Storm Drainage Criteria.
3. The Rational Method was utilized to calculated peak runoff rates.
a. Runoff coefficients and Imperviousness values are taken from Tables
6-3 and 6-5 of the Urban Storm Drainage Criteria Manual, volume 1
based on the 'A' Hydrologic Soils Group.
4. Rainfall intensities for the 1 -hour point rainfall were taken from the PF table
for Kersey Colorado, downloaded from NOAA Atlas 14, Volume 8, Version 2
Precipitation Frequency Data Server.
Preliminary Drainage Report
i i March 2018
Centennial Tools USR Drexel, Barrell & Co.
B. Hydraulic Criteria
1. According to Weld County Storm Drainage Criteria, Detention of the 100 -
year runoff will be required with discharge restricted to the 10 -year historic
runoff rate. Water Quality Capture Volume and associated restricted discharge
is required but the volume may be included in the 100 -year detention volume.
C. Waiver/Variance from Criteria
1. All aspects of the site drainage design and storm sizing will conform to the
Weld County Storm Drainage Criteria.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
No regrading of the site is anticipated except as required for building construction and
for the construction of a berm, full width of the east end of the site to create the storm
water detention pond. The entire site will sheet flow to the detention pond at the east
end as a single basin. An outlet structure constructed into the berm will provide the
required discharge restriction and outlet toward the historic drainage path.
B. Proposed Basin Runoff
The peak runoff rates and runoff coefficients associated with the site and , are
presented in Table 2. Runoff coefficients values are calculated per the Weld
County Storm Drainage Criteria using the current Urban Storm Drainage Criteria
Manual Tables 6-3 and 6-5, based on the 'A' Hydrologic Soils Group.
TABLE 2: DEVELOPED CONDITIONS RUNOFF RATES
Basin
Area
(acres)
5 -year
Coefficients
RunoffRunoff
10 -year
Coefficients
10 -year
Peak Runoff
(cfs)
100 -Year
Runoff
Coefficients
100 -year
Peak Runoff
(cis)
PR -1
10.04
0.20
0.20
5.52
0.32
16.79
Preliminary Drainage Report
Centennial Tools USR
March 2018
Drexel, Barrell & Co.
C. Detention Facility Details
1. The site will discharge to the proposed water quality/detention pond at the east
end of the site. Note that all elevations listed are based on Digital Terrain
Elevation Data, actual field surveyed elevations may vary.
a. The detention pond will be located in the open space, outside of the gravel
storage yard at the east end of the site. A proposed outlet structure will be
constructed at the northeast corner of the pond with invert at Elevation
4896.20 the existing ground elevation at the inside toe of the berm, 4.8 foot
high to top of free board.
b. The Water Quality Capture Volume for the pond was calculated to be 6,258
cubic feet and is achieved at the Water Surface Elevation of 4665.60. .
water quality control plate fixed to the front of the outlet structure will have
1 column &. 6 rows consisting of 11/16" diameter holes to regulate the 40 -
hour drain time.
c. During a larger storm events, the water surface elevation in the pond will
rise beyond the WQCV elevation of 4665.60 and overtop the water quality
control plat, spilling into the main compartment of the outlet structure. An
orifice plate with a 2-1/8 inch orifice will limit outflow to the 10 -year
historic allowable release rate of (0.25 cfs). This will happen up until the
height of the overflow weir is reached.
d. A 12" diameter RCP outlet pipe extending from the outlet structure through
the berm will discharge to the surface at the east property boundary.
e. During larger storm events, or plugging of the outlet structure the water
surface elevation in the pond may rise beyond the 100 -year water surface
elevation of 4667.20. In this case the overflow will pass through an i i foot
wide concrete overflow weir and rip rapped spillway beyond.
f. The pond will have over 1 foot of freeboard above the overflow weir crest,
elevation currently set at a minimum elevation of 4668.20.
V. REFERENCES
1. Weld County Storm Drainage Criteria.
2. Urban Storm Drainage Criteria Manual 2017, volumes I, II III
Preliminary Drainage Report
Centennial Tools USR Drexel, Barrell & Co.
iv March 2018
APPENDIX A
VICINITY MAP
ST HWY 34
KERSEY
54
N)
WCR 52
CesA
S TE
NOT TO ALE
VICINITY MAP
Drexel, Barrell & Co.
Engineers • Surveyors
DATE:
3/27/2018
JOB NO:
21172-00
DWG. ND,
VM
SHEET 1 OF
APPENDIX B
NRCS SOILS INFORMATION
USDA United States
Department of
Agriculture
N RCS
Natural
Resources
Conservation
Service
A product of the National
Cooperative Soil Survey,
a joint effort of the United
States Department of
Agriculture and other
Federal agencies, State
agencies including the
Agricultural Experiment
Stations, and local
participants
Custom Soil Resource
Report for
Weld County,
Colorado,
Southern Part
25172 WCR 53
March 22, 2018
40° 221 Oil
1
4U'° 21' 50" N
104° 33' 52" W
N
En
en
536980
N
A
537030
537430
537080
5`'x7080
537130
537134
Map Scale: 1:2,200 if printed on A landscape (11" x 8.5') sheet
Custom Soil Resource Report
Soil Map
537180
537180
Meters
0 30 OD 120 180
Feet
0 10(? 200' 400 600
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
9
537230
5372,30
537284
537280
53733)
537330
537380
537383
537430
l
5374,30
104° 33' 32" W
104° 33' 32" VQ`
40° 22'Q"N
40° 21' 54" N
Custom Soil Resource Report
MAP LEGEND
Area of Interest (AUDI)
Area of Interest (AOl )
Soils
1
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
w
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
c
a
.0
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
-4-f Rails
aso
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
MAP INFORMATION
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of thedetail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Weld County, Colorado, Southern Part
Survey Area Data: Version 16, Oct 10, 2017
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jul 17, 2015 Sep
22, 2016
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
10
Custom Soil Resource Report
Weld County, Colorado, Southern Part
69 Valent sand, 0 to 3 percent slopes
Map Unit Setting
National map unit symbol: 2tczd
Elevation: 3,000 to 5,210 feet
Mean annual precipitation: 13 to 20 inches
Mean annual air temperature: 48 to 52 degrees F
Frost -free period: 130 to 166 days
Farmland classification: Farmland of local importance
Map Unit Composition
\talent and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Valent
Setting
Landform: I nterd un es
Landform position (two-dimensional): Footslope, toeslope
Landform position (three-dimensional): Base slope
Down -slope shape: Linear
Across -slope shape: Linear
Parent material: Noncalcareous eolian sands
Typical profile
A - 0 to 5 inches: sand
AC - 5 to ?2 inches: sand
CI - 12 to 30 inches: sand
C2 - 30 to 80 inches: sand
Properties and qualities
Slope: 0 to 3 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Excessively drained
Runoff class: Negligible
Capacity of the most limiting layer to transmit water (Ksat): High to very high (6.00
to 39.96 inlhr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 1 percent
Salinity, maximum in profile: Nonsaline (0.1 to 1.9 mmhoslcm)
Available water storage in profile: very low (about 2.4 inches)
Interpretive groups
Land capability classification (irrigated): 4e
Land capability classification (non irrigated): 6e
Hydrologic Soil Group: A
Ecological site: Deep Sand (R067BY615CO), Sands (North) (PE 16-20)
(R072XA021 KS)
Hydric soil rating: No
13
Custom Soil Resource Report
Minor Components
Dailey
Percent of map unit: 5 percent
Landform: I nterdun es
Landform position (two-dimensional): Toeslope
Landform position (three-dimensional): Base slope
Down -slope shape: Linear
Across -slope shape: Concave
Ecological site: Deep Sand (R067BY015CO), Sandy (North) Draft (April 2010)
(PE 16-20) (R072XA022KS)
Hydric soil rating: No
Julesburg
Percent of map unit: 5 percent
Landform: I nterd un es
Landform position (two-dimensional): Toeslope
Landform position (three-dimensional): Base slope
Down -slope shape: Linear
Across -slope shape: Linear
Ecological site: Sandy Plains (R067BY024CO), Sandy (North) Draft (April 2010)
(PE 16-20) (R072XA022KS)
Hydric soil rating: No
Vona
Percent of map unit: 5 percent
Landform: I nterd un es
Landform position (two-dimensional): Toeslope
Landform position (three-dimensional): Base slope
Down -slope shape: Linear
Across -slope shape: Linear
Ecological site: Sandy Plains (R067BY024CO), Sandy (North) Draft (April 2010)
(PE 16-20) (R072XA022KS)
Hydric soil rating: No
70 Valent sand, 3 to 9 percent slopes
Map Unit Setting
National map unit symbol: 2tczf
Elevation: 3,050 to 5,150 feet
Mean annual precipitation: 12 to 18 inches
Mean annual air temperature: 48 to 55 degrees F
Frost -free period: 130 to 180 days
Farmland classification: Not prime farmland
Map Unit Composition
Valent and similar soils: 80 percent
Minor components: 20 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Custom Soil Resource Report
Description of Valent
Setting
Landform: Hills, dunes
Landform position (two-dimensional): Backslope, shoulder, footslope, summit
Landform position (three-dimensional): Side slope, head slope, nose slope, crest
Down -slope shape: Linear, convex
Across -slope shape: Linear, convex
Parent material: Noncalcareous eolian sands
Typical profile
A - 0 to 5 inches: sand
AC - 5 to ?2 inches: sand
CI - 12 to 30 inches: sand
C2 - 30 to 80 inches: sand
Properties and qualities
Slope: 3 to 9 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Excessively drained
Runoff class: Very low
Capacity of the most limiting layer to transmit water (Ksat): High to very high (6.00
to 3926 inlhr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 1 percent
Salinity, maximum in profile: Nonsaline (0.0 to 1.9 mmhoslcm)
Available water storage in profile: Very low (about 2.4 inches)
Interpretive groups
Land capability classification (irrigated): 4e
Land capability classification (nonirrigated): 6e
Hydrologic Soil Group: A
Ecological site: Deep Sand (R067BY015CO), Rolling Sands (R072XY109KS)
Hydric soil rating: No
Minor Components
Dailey
Percent of map unit: 10 percent
Landform: I nterd un es
Landform position (two-dimensional): Footslope, toeslope
Landform position (three-dimensional): Base slope
Down -slope shape: Linear
Across -slope shape: Concave
Ecological site: Deep Sand (R067BY015CO), Sands (North) (PE 16-20)
(R072XA021KS)
Hydric soil rating: No
Vona
Percent of map unit: 5 percent
Landform: Hills
Landform position (two-dimensional): Footslope, backslope, shoulder
Landform position (three-dimensional): Side slope, head slope, nose slope, base
slope
15
Custom Soil Resource Report
Down -slope shape: Linear
Across -slope shape: Linear
Ecological site: Sandy Plains (R067BY024CO), Sandy (North) Draft (April 2010)
(PE 16-20) (R072XA022 KS)
Hydric soil rating: No
Haxtun
n
Percent of map unit: 5 percent
Landform: I nterdun es
Landform position (two-dimensional): Footslope, toeslope
Landform position (three-dimensional): Base slope
Down -slope shape: Linear
Across -slope shape: Concave
Ecological site: Sandy Plains (R067BY024CO), Sandy Plains (R072XY111 KS)
Hydric soil rating: No
73 Vona loamy sand, 3 to 5 percent slopes
Map Unit Setting
National map unit symbol: 363s
Elevation: 4,600 to 5,200 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 55 degrees F
Frost -free period: 130 to 160 days
Farmland classification: Not prime farmland
Map Unit Composition
Vona and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transacts of the mapunit.
Description of Vona
Setting
Landform: Terraces, plains
Down -slope shape: Linear
Across -slope shape: Linear
Parent material: Alluvium and/or eolian deposits
Typical profile
HI - 0 to 6 inches: loamy sand
H2 - 6 to 28 inches: fine sandy loam
H3 - 28 to 60 inches: sandy loam
Properties and qualities
Slope: 3 to 5 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Very low
Capacity of the most limiting layer to transmit water (Ksat): High (1.98 to 6.00
inmr)
16
Custom Soil Resource Report
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 15 percent
Salinity, maximum in profile: Nonsaline to slightly saline (0.0 to 4.0 mmhoslcm)
Available water storage in profile: Moderate (about 6.5 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirhrigated): 4e
Hydrologic Soil Group: A
Ecological site: Sandy Plains (ROG7BY024CO)
Hydric soil rating: No
Minor Components
Remmit
Percent of map unit: 8 percent
Hydric soil rating: No
Valent
nt
Percent of map unit: 7 percent
Hydric soil rating: No
APPENDIX C
HYDROLOGIC COMPUTATIONS
e, DREXEL, BAR LL OO.
�Li
CIVIL ENGINEERS/LAND SURVEYORS
T
r Project: 25172
CR Job # 2117'2-0CRCV
53
Engineers/Surveyors Client: CENTENIAL TOOLS & SERVICES LLC Designed by: MAB Date: 2-23-2018
COMPOSITE RUNOFF COEFFICIENTS
EXISTING CONDITIONS:
Basin
Area
(sq. ft.)
Urban Drainage, Volume 1, 2016 Table 6-5 Type A NRCS Soil Group
Weighted
02
Weighted
C5
Weighted
C10
Weighted
C100
Weighted
Irrmperv.
Description
Percent Imp. "I"
02
05
C10
C1oo
'EX -1'
acres
10.04
Streets (Asphalt Pavement)
100%
0.84
0.86
0.87
0.89
0.00
0.00
0.00
0.00
0.0%
Drives & Walks
90%
0.73
0.75
0.77
0.81
0.00
0.00
0.00
0.00
0.0%
Roofs
90%
0.73
0.75
0.77
0.81
0.00
0.00
0.00
0.00
0.0%
Packed Gravel
40%
0.25
0.27
0.28
0.42
0.00
0.00
0.00
0.00
0.0%
437,560
Undeveloped
(Lawn/Bare Ground:
2%
0.01
0.01
0.01
0.13
0.01
0.01
0.01
0.13
2.0%
437,560
<<Total Area Total Weighted Runoff Coefficients C , C , C 1 o, O100 & I >o
� �
0.01
0.01
0.01
0.13
2.� f�
T
mr as im
DREXEL, BARRELL & CO.
CIVIL ENGINEERS/LAND SURVEYORS
TABLE 4-2
TIME OF CONCENTRATION
RATIONAL METHOD
PROJECT: 25172 CR 53
CALC. BY: MAB DATE: 3-23-2018
SUB -BASIN
DATA
INITIAL / OVERLAND
TIME (Ti) = 0,395(1.1-05)(L''2)I(So.3a)
TRAVEL TIME
(Tt) = (L)/(V*60) where V = CVS\V9 5
FINAL
URBAN BASINS
FINAL
REMARKS
Tc
Tc Check
Tc
(Min.)
CONTRIBUTING
BASINS
DESIGN
PT.
COEFF.
C5
AREA
(Ac)
LENGTH
(Ft)
A ELEV.
(ft)
SLOPE
(ft/ft)
Ti
(Min.)
LENGTH
(Ft)
A ELEV.
(ft)
SLOPE
(ftfft)
Conveyance
Coefficient (Cu)
VELOCITY
(Fps)
Tt
(Min.)
(Min.)
LENGTH
(ft)
Tc=(L/180)+10
EXISTING
BASINS
1
0.01
10.04
165
6
0.036
16.7
1180
22
0.019
20
2.73
7.2
23.9
23.9
'EX -1'
n
7/N
DREXEL BARRELL & CO. CIVIL ENGINEERS/LAND SURVEYORS
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
Client: CENTENIAL TOOLS & SERVICES LLC
PROJECT
JOE #
DATE:
CALL. BY:
CHECKED BY:
DESIGN STORM
25172 53
211 72-00CRCV
2/23/2018
MAB
CWK
HISTORIC
DIRECT RUNOFF
TOTAL RUNOFF
STREET
DESIGN STORM
AREA (ac.)
RUNOFF
COEFF.
Z
tc (min.)
(CA) (AC)
Z
SLOPE %
STREET
FLOW CFS
REMARKS
-
w
0in
10 -YEAR
1
' EX -1'
10.04
0.01
23.9
0.100
2.54
0.25
Existing
Conditions
100
-YEAR
1
'EX -1'
10.04
0.13
23.9
1.306
4.81
6.28
I
Existing
Conditions I
P- 0.869
P5= 1.14
** 1=((28.5*Px)/((lO+ter0.786))
P10= 1.42
Pion- 2.69
NOAA Atlas 14, Volume 8, Version 2
Kersey, Colorado One -Hour Point Rainfall
and USDCM Equation RA -5
�, DREXEL, BAR LL & CO.
a3,....).._
CIVIL ENGINEERS/LAND SURVEYORS
\a
,..-.Ht 1
Project:
25172 CR Job # 21172-0G RCV
53
Engineers/Surveyors Client: CENTENIAL TOOLS & SERVICES LLC Designed by: MAB Date: 2-23-2018
COMPOSITE RUNOFF COEFFICIENTS
PROPOSED CONDITIONS:
Basin
Area
(sq. ft.)
Urban Drainage, Volume 1, 2016 Table 6-5 Type D NRCS Soil Group
Weighted
C2
Weighted
C5
Weighted
Cio
Weighted
C1010
Weighted
Irnperv.
Description
Percent Imp. "I"
C2
C5
C10
C100
'PR -I'
acres
10.04
9,066
Streets (Asphalt Pavement)
100%
0.84
0.86
0.87
0.89
0.02
0.02
0.02
0.02
2.1%
4,130
Drives & Walks
90%
0.73
0.75
0.77
0.81
0.01
0.01
0.01
0.01
0.8% 1
23,019
Roofs
90%
0.73
0.75
0.77
0.81
0.04
0.04
0.04
0.04
4.7%
206,190
Packed Gravel
40%
0.25
0.27
0.28
0.42
0.12
0.13
0.13
0.20
18.8%
195,155
Undeveloped
(Lawn/Bare Ground)
2%
0.01
0.01
0.01
0.13
0.00
0.00
0.00
0.06
0.9%
437,560
<<Total Area Total Weighted Runoff Coefficients C2, C„ C10,C100 & I>>
0.18
0.20
0.20
0.32
27.4%
fl
IN
JIM
DREXEL, BARBELL & CO.
CIVIL ENGINEERS/LAND SliRVE YOBS
TABLE 4-2
TIME OF CONCENTRATION
RATIONAL METHOD
PROJECT: 25172 CR 53
CALC. BY: MAB DATE: 3-23-2018
SUB -BASIN
DATA
INITIAL ! OVERLAND
TIME (Ti) = 0.395(1,1-05)(LC' 2)f(S° 33)
TRAVEL TIME
(Tt) = (L)/(V*60) where V = Cs/S: 5
FINAL
Tc
. FINAL
REMARKS
Tc
(Min.)
CONTRIBUTING
BASINS
DESIGN
PT.
COEFF.
C5
AREA
(Ac)
LENGTH
(Ft)
A ELEV.
(ft)
SLOPE
(ftift)
Ti
(Min.)
LENGTH
(Ft)
A ELEV.
(ft)
SLOPE
(ftlft)
Conveyance
Coefficient (Cu)
VELOCITY
(Fps)
Tt
(Min.)
(Min.)
DEVELOPED BASINS
1
0.20
10.04
165
6
0.036
13.8
1180
22
0.019
20
2.73
7.2
21.0
21.0
'PR -1'
easi
A
DREXEL CARRELL SLI CO.
CIVIL ENGINEERS/LAND SURVEYORS STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE;
Client: CENTENIAL TOOLS & SERVICES LLC
PROJECT
JOB #
DATE:
CALL. BY:
CHECKED BY:
DESIGN STORM
25172 CR 53
21172-00G R CV
2/23/2018
MAB
CWK
DEVELOPED
DIRECT RUNOFF
TOTAL RUNOFF
STREET
DESIGN STORM
DESIGN
POINT
z
O
AREA (ac.)
RUNOFF
COEFF.
tc (min.)
-ce--.
I
a
C)
C)
c
I
-
-�
C
SLOPE %
STREET
FLOW CF
REMARKS
►RK
a
w
IY
�F
.1
10 -YEAR
1
'PR -1'
10.04
0.20
21.0
2.031
2.72
5.52
Developed
Conditions
100 -YEAR
1
PR -1'
10.04
0.32
21.0
3.261
5.15
16.79
Developed
Conditions
P2 0.869 P5 1.14
** I=((28.5*Px)/((l0+to)"0.786))
Pio= 1.42
P100= 2.69
NOAA Atlas 14, Volume 8, Version 2
Kersey, Colorado One -Hour Point Rainfall
and USDCM M Equation RA -5
APPENDIX D
PROPOSED
STORM WATER QUALITY
POND CALCULATIONS
dem
Lei
DREXEL, BARBELL irk CO.
CIVIL ENGINEERS I LAND SURVEYORS
Project: 25172 CR 53
Engineers/Surveyors Client: CENTENIAL TOOLS & SERVICES LLC
Job ## 21172-00
Date: 3/2312018
Designed by: MAB
WATER QUALITY CAPTURE VOLUME:
REQUIRED WATER QUALITY CAPTURE VOLUME FOR POND:
1. Basin Storage Volume
A) Tributary Area's Imperviousness Ratio (i = la / 100 )
B) Contributing Watershed Area (Area)
C) Water Quality Capture Volume (WQCV)
(WQCV =a* (0.91 *13-1.19*I2+0.78*I))
Where a = 1.0 based on 40 -hr. drain time
D) Design Volume: Vol = (WQCV / 12) * Area * 1.2
la -
.
I-
Area =
WQCV =
Vol =
Vol =
27.4 ° o
0.274
10.04 acres
0.1431 watershed inches
0.144 acre-feet
6,258 cubic -feet
2. Outlet Works
A) Outlet Type (Check One)
B) Depth at Outlet Above Lowest Perforation (H)
C) Recommended Maximum Outlet Area per Row, (Ao)
A = 1.8 (WQCV/b) 1 /c) Based on 40 -hr drain time
D) Perforation Dimensions:
i) Circular Perforation Diameter or
E) Number of Columns (nc, See Table 6a-1 For Max.)
F) Actual Design Outlet Area per Row (Ao)
G) Number of Rows (n)
H) Total Outlet Area (AO
Orifice Plate
2.2 feet
0.368 square inches
0.687
0.978
0.68
1
0.36
6
2.18
inches (11/16")
number
square inches
number
square inches
DREXEL, BARRELL & CO.
CIVIL ENGINEERS/LAND SURVEYORS
Project: 25172 CR 53
Engineers/Surveyors Client: CENTENIAL IAL TOOLS & SERVICES LLC
REQUIRED 100-yr. STORAGE VOLUME
RATIONAL FORMULA METHOD
Variables:
A=
Q0 UT =
100-yr,1-hour
10.04
L 0.274
0.25
2.69
acres
(Composite)
ft3is
inch
10 -year EX
Job # 21172-0C
Date: 2-23-201
Designed by: N
STORM
DURATION
(min)
INTENSITY
RAINFALL
(in/hr)
RUNOFF
VOLUME
(ft3)
OUTFLOW
VOLUME
(ft3)
STORAGE
VOLUME
(ft3)
STORAGE
VOLUME
(acre
-ft)
0
12.55
0
0
0
0.000
60
2.72
26,921
900
26,021
0.597
120
1.67
33,099
1,800
31,299
0.719
180
1.24
36,843
2,700
34,143
0.784
240
1.00
39,593
3,600
35,993
0.826
300
0.84
41,793
4,500
37,293
0.856
360
0.73
43,640
5,400
38,240
0.878
420
0.65
45,241
6,300
38,941
0.894
480
0.59
46,659
7,200
39,459
0.906
540
0.54
47,935
8,100
39,835
0.914
600
0.50
49,099
9,000
40,099
0.921
660
0.46
50,169
9,900
40,269
0.924
720
0.43
51,162
10,800
40,362
0.927
780
0.40
52,089
11,700
40,389
0.927
840
0.38
52,960
12,600
40,360
0.927
900
0.36
53,780
13,500
40,280
0.925
960
0.34
54,558
14,400
40,158
0.922
1020
0.33
55,297
15,300
39,997
0.918
1080
0.31
56,001
16,200
39,801
0.914
100-YR VOLUME 40,389 CF
raNy
®T-'
IMIlr S aMIMI
DREXEL, BARRELL & CO.
CIVIL ENGINEERS 1 LAND SURVEYORS
Project: 25172 CR 53
Job # 21172-00
Engineers/Surveyors Client: CENTENIAL TOOLS & SERVICES LLC
Designed by: MAB Date: 312312018
PROPOSED STORAGE VOLUME PROVIDED:
ELEVATION***
CONTOUR
(ft)
SURFACE
AREA
(ft�)
(A)
SURFACE
AREA
(f
2
(B)
DEPTH
CONTOURS
(ft)
BETWEEN
INCREMENTAL
VOLUME
f#
CUMULATIVE
VOLUME
ft
)
CUMULATIVE
VOLUME
(ac
-ft)
4663.40
357
0
0
0
0
0.000
4663.60
969
357
0.2
128
128
0.003
4663.80
1.707
969
0.2
264
392
0.009
4664.00
2,572
1,707
0.2
425
817
0.019
4664.20
3,562
2,572
0.2
611
1,427
0.033
4664.40
-
520
520
0.2
104
1,532
0.035
4664.00
1,250
1,250
0.2
250
1,781
0.041
4664.80
2,235
2,235
0.2
447
2,228
0.051
4665.00
3,476
3,476
0.2
695
2,924
0.067
4665.20
4,973
4.973
0.2
995
3,918
0.090
4665.40
6,725
6,725
0.2
1,345
5,263
0.121
4665.60
8,733
8,733
0.2
1,747
7,010
0.161
4665.80
10,997
10,997
0.2
2,199
9,209
0.211
4666.00
13,517
13,517
0.2
2,703
11,913
0.273
4666.20
16,263
16,263
0.2
3,253
15,165
0.348
4666.40
19,140
19,140
0.2
3,828
18,993
0.436
4666.60
21,996
21,996
0.2
4,399
23,393
0.537
4666.80
_
24,808
24,808
0.2
4,962
28,354
_
0.651
4667.00
27,575
27,575
0.2
5,515
33,869
0.778
4667.20
30,297
30,297
0.2
6,059
39,929
0.917
4667.40
32,975
32,975
0.2
6,595
46,524
1.068
4667.60
35,609
35,609
0.2
7,122
53,645
1.232
4667.80
38,197
38,197
0.2
7,639
61,285
1.407
4668.00
40,741
40,741
0.2
8,148
69,433
1.594
4668.20
43,241
43,241
0.2
8,648
78,081
1.792
* WOCV volume = 6,258 cubic feet See WOCV Worksheet WOCV elevation
** 100-yr. total volume = 40,389 cubic feet See 100-yr Required Storage Volume Worksheet
*** Note that all elevations listed are based on Digital Terrain Elevation Data, actual field surveyed elevations may vary.
INCREMENTAL VOLUME CALCULATED FROM EON: (1/3)*d*(A + B + (A*B)1!2)
POND INVERT
WOCV ELV.*
100-yr WSL**
FREEBOARD
a DREXEL, BARRELL & CO.
7FI CIVIL ENGINEERS / LAND SURVEYORS
1
Project: 21172-00
Job # 21172-00
Enginects/Surveyors Client: CENTENIAL TOOLS & SERVICE. Designed by: MAB Date: 3/23/2018
SIZING OF 100-YR. FLOW CONTROL ORIFICE FOR POND C:
Allowable release rate
Q10hist-
0.25 cfs
- Orifice opening in plate covering the outlet pipe will provide 10-yr historic release rate from outlet
structure as water surface elevation reaches the 100-yr. WSL
Pond outlet invert elevation =
100-yr WSL elevation =
difference = 3.80 ft
Orifice Flow Equation: Q=CdA(2gh)1/2
where:
4663.40
4667.20
o = 0.25 cfs Max. release rate
Cd = 0.65 Orifice Coefficient
100-yr depth 3.80 ft from pond design
3.64 ft (calculated adjust "h" to match)
h = 3.64 ft (Distance from 100-yr WSL to center of orifice opening)
g = 32.2 ft/secs gravity
A = 0.03 ft2 Area in sq . ft.
A = 3.62 in2 Area in sq . in.
Opening = 1.90 in. square or
Round = 2.15 in. 2 1/8 in. diameter
71.si.
mr
DREXEL, BARRELL CO.
CIVIL ENGINEERS I LAND SURVEYORS
Project: 25172 CR 53 Job # 21172-00
Engineers/Surveyors Client: CENTENIAL T E N I AL TOOLS & SERVICES Designed by: MAB Date: 3/23/2018
SIZING OF EMERGENCY OVERFLOW SPILLWAY FOR DETENTION POND:
- O100 Peak Runoff Rate = 16.79 cfs
Bottom Width of Weir
Side Slope Weir
Elev. for Weir Crest
Coef. for Rectangular Weir
Coef. for Trapezoidal Weir
L= 11 ft.
S= 4 Horizontal to Vertical
Ew= 4677.20 elevation
Cw= 3.1
Ct- 3.1
Water
Surface
Elevation
feet
Depth
of
Water
inches
Trapazoidal
Flowrate
Weir
cfs
4677.20
0.0
0.00
4677.25
0.6
0.40
4677.30
1.2
1.16
4677.35
1.8
2.20
4677.40
2.4
3.49
4677.45
3.0
5.04
4677.50
3.6
6.83
4677.55
4.2
8.86
4677.60
4.8
11.14
4677.65
5.4
13.66
4677.70
6.0
16.44
4677.75
6.6
19.47
4677.80
7.2
22.76
4677.85
7.8
26.32
4677.90
8.4
30.14
4677.95
9.0
34.23
4678.00
9.6
38.60
4678.05
10.2
43.24
4678.10
10.8
48.17
4678.15
11.4
53.39
4678.20
12.0
58.90
- Begin Overflow
- 6" depth limit*
- Limit of Freeboard
* Weld County Storm Drainage Criteria Sec. 23-12-90 indicates
that the emergency spillway must be capable of conyeying the
peak 100 -year storm at an overflow depth less than 6 inches.
NOTE: Output of Overflow Cacapity based on Trapezoidal Shaped
Spillway Calculated from USDCM Spreadsheet
NOTE: The detention pond will begin to overtop thru the spillway at
the NE corner of the site -historic route
APPENDIX H
CHARTS, TABLES
AND GRAPHS
Precipitation Frequency Data. Server https: /hdsc.n s.noaa.gov/hdsc/pfd pf _printpage.htmllat=403653 ..,
NOAA Atlas 14, Volume 8, Version 2
Location name: Kersey, Colorado, USA*
Latitude: 40.3653°, Longitude: -104.5625°
Elevation: 4679.93 ft**
* source: ESRI Maps
** source: USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
Sanja Pence, Deborah Martin. Sandra Pavlovic, Ishani Roy, Michael St. Laurent, Carl Trypaluk, Dale
Unruh, Michael Yekta, Geoifery Bonnin
NOAA, National Weather Service, Silver Spring, Maryland
PF tabular PF graphical Maps & aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1
Duration
5 -min
10 -min
15 -rain
30 -rain
60 -min
2 -hr
3 -hr
6 -hr
12 -hr
24 -hr
2 -day
3 -day
4 -day
7 -day
10 -day
20 -day
30 -day
45 -day
60 -day
Average recurrence interval (years)
1'
0.245
(0.199-0.303)
0.358
(0.292-0.444)
2
5
10
0.296 0.393
(0.241-0.367) (0.318-0.488)
0.433 0.575
(0.353-0.537) (0.466-0.715)
0.528
(0.430-p.655),
0.709 0.940
(0.577-0.878) (0.762-1.17)
0.437
(0.356-0.541)
0.587
(0.478-0.727)
0.730
(0.5950}.904)
0.873
(0.717-1.07)
0.485
(0.391-0.606)
0.701
(0.568-0.872)
0.869
(0.707-1.08)
0.710
(0.572-0.888)
0.866
(0.697-1.08)
1.16
(0.936-1.45)
1.14
(0.927-1.42)
1.42
(1.14-1.77)
1.03 1.35
(0.843-1.26) (1.1Q-1.66)
1.67
(1.36-2.07)
0.956
(0.789-1.17)
1.11 1.45
(0.918-1.36) (1.19-1.78)
1.10
(0.910-1.33)
1.27
(1.07-1.53)
1.51
(1.28-1.80)
1.74
(1.4a -2.06J
1.91
(1.63-2.24)
2.04
(1.75-Z38)
2.31
2.00-2.68)
1.29
(1.07-1.56)
1.68
(1.39-2.04)
1.79
(1.46-2.21)
2.07
(1.70-2.53)
1.52 1.97
(1.27-1.82)] (1.64-2.37)
1.78
(1.50-2.12)
2.05
(1.74-2.42)
2.22
(1.89-2.61)
2.35
(2.02-2.75)
2.69
(2.32-3.12)
2.55
(2.21-2.95)
2.97
(2.57-3.44)
3.27
(2.86-3.74)
3.85
(3.38-4.38)
4.56
4.02-5.16)
3.77
(3.29-4.32)
4.42
(3.87-5.03)
5.22
4.60-5.92)
5.13
(4.54-5.79)
5.90
(5.22-6.66)
2.40
(1.99-2.91)
2.26
(1.90-2.70)
2.60
(2.20-3.07)
2.77
(2.35-3.26)
2.91
(2.48-3.41)
b3.32
2.85-3.87)
2.71
(2.26-3.26)
3.08
(2.59-3.67)
3.26
(2.75-3.85)
3.41
(2.89-4.01)
3.86
(3.29-4.52)
3.67
(3.16-4.25)
4.58
(3.98-5.26)
4.25
(3.64-4.95)
5.23
(4.52-6.04)
5.32
(4.64-6.07)
6.27
(5.51-7.13)
7.11
(6.26-8.05)
6.04
(5.25-6.94)
7.11
(6.21-8.12)
8.06
(7.06-9.16)
25
50
0.631 l
(0.495-0.841)
0.924
(0.726-1.23)
1.13
(0.885-1.50)
0.758
(0.575-1.02)
100
0.897
(0.652-1.24)
I 200 I
1.05
(0.727-1.49)
1.11
1.31
1.54
(0.842-1.49)
(0.955-1.81)
(1.06-2.19)
1.35
(1.03-1.82)
1.60
(1.17-2.21)
1.51
(1.19-2.02)
1.86
(1.47-2.50)
2.21
(1.76-2.95)
1.82
(1.38-2.45)
2.25
(1.72-3.05)
2.69
(2.07-3.61)
2.16
(1.57-2.98)
2.69
(1.96-3.73)
1.88
(1.30-2.67)
2.53.
(1.75-3.60)
3.19
(2.21-4.54)
3.23 3.84
(2.38-4.45) (2.69-5.44)
500
1.27
(0.841-1.86)
1.87
(1.23-2.73)
2.28
(1.50-3.33)
2.38
(1.91-3.17)
2.71
(2.19-3.56)
3.07
(2.48-3.95)
3.41
(2.77-4.32)J
2.91
(2.25-3.89)
3.29
(2.56-4.34)
3.51
(2.60-4.82)
3.93
(2.93-5.32)
3.65
(2.85-4.74)
4.00
(3.15-5.13)
3.81
3.10-4.75)
3.99
(3.27-4.94)
4.14
(3.41-5.11)
4.63
(3.82-5.63)
4.41
(3.49-5.57)
4.59
(3.66-5.77)
4.75
(3.80-5.94)
5.25
(4.21-6.47)
4.28
(3.21-5..70)
4.64
(3.51-6.11)
5.05
(3.84-6.54)
5.24
(4.01-6.75)
5.40
(4.15-6.92)
5.88
(4.54-7.45)
4.19
(2.96-5.91)
3.07
(2.03-4.49)
3.91
(2.59-5.73)
4.75
(3.17-6.91)
5.21
(3.50-7.54)
4.65
3.31-6.48L
5.72
(3.88-8.18)
4.98
(3.56-6.82),
5.34
(3.85-7.24)
5.73
(4.16-7.65)
5.93
4.33-7.87)
6.09
(4.46-8.04)
6.55
4.83-8.53
5.99
(4.09 -8.44)
6.35
(4.38-8.85}
6.69
(4.65-9.20)
6.90
(4.83-9.43)
5.06
4.17-6.09)
6.12
5.08-7.27)
7.01
5.85-8.26)
8.21
(6.87-9.60)
9.29
(7.80-10.8)
5.68
(4.57-6.95)
6.79
(5.50-8.19)
7.74
(6.30-9.27)
9.02
(7.38-10.7)
6.31
(4.89-7.92)
7.45
(5.82-9.22)
8.44
(6.62-10.4)
9.79
(7.72-11.9)
10.2
(8.35-12.1)
11.0
(8.72-13.4)
6.95
(5.15-8.99)
8.10
(6.04-10.3)
9.13
(6.85-11.6)
10.5
(7.94-13.2)
11.8
(8.93-14.8)
7.06
(4.96-9.59)
7.45
(5.26-10.0)
7.81
(5.54-10.4)
8.94
(6.40-11.8)
10.0
(7.20-13.1)
11.5
(8.29-14.8)
12.8
(9.28-16.4)
1000
1.46
(0.927-2.14)
2.13
(1.36-3.14)
2.60
(1.66-3.83)
3.52
(2.24-5.17)
4.51
(2.87-6.63)
5.51
(3.54-8.01)
6.07
(3.92-8.77)
6.61
(4.31-9.47)
6.82
(4.49-9.66)
7.17
(4.78-10.1)
7.47
(5.02-10.4)
7.68
(5.20-1p.6)
7.84
(5.33-10.8)
8.16
(5.59-11...1
8.46
(5.84-11.5
9.57
(6.67-12.8)
10.6
(7.46-14.2)
12.1
[�8.55-16.1)
13.4
(9.53-17.7)
I Precipitation frequency (PF) estimates in this table are based on frequency analysis of 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 va pies.
Please refer to NOAA Atlas 14 document for more information.
Back to Top
PF graphical
1 of 4 3/23/2018, 11:50 AM
Table 6-3. Recommended percentage imperviousness values
Surface
Land
Characteristics
Use
or
Percentage
i
perviousness
(%)
Business:
Downtown Areas
95
Suburban
Areas
75
Residential
lots (lot
area only):
Single-family
2.5 acres or larger
12
0.75
2.5 acres
20
—
0.25
—
0.75 acres
30
0.25 acres or less
45
Apartments
75
Industrial:
Light
areas
80
Heavy areas
90
Parks, cemeteries
10
Playgrounds
15
Schools
55
Railroad
yard
areas
50
Undeveloped
Areas:
Historic
flow
analysis
2
Greenbelts, agricultural
Off -site
defined)
flow analysis
(when
land
use not
45
Streets:
Paved
100
Gravel (packed)
40
Drive and
walks
90
Roofs
90
Lawns,
sandy
soil
2
Lawns,
clayey
soil
2
6-8 Urban Drainage and Flood Control District
Urban Storm Drainage Criteria Manual Vol l e
March 2017
Table 6-4. Runoff coefficient equations based on NRCS soil group and storm return period
Storm
Return
Period
NRCS
Soil
Group
2 -Year
5 -Year
10 -Year
25 -Year
50 -Year
100 -Year
500 -Year
A
CA—
CA
C
=
CA
CA
CA
0.8411.302
0.8611.27°
0.87i1-232
0.8411.124
A
0.851+0.025
0.781+0.110
0.651+0.254
B
CB=
CB =
CB
CB =
CB=
CB =
CB
0.86i1.M88
0.471+0.426
0.8411.169
0.811+0.05
0.631+0.249
0.56H-0.328
0.371+0.536
C
D
COD—
CC.ID
CC
COD
GOOD
COD
0.83i1.122
0.821+0.035
0.741+0.132
/ii
0.561+0.319
0.491+0.393
0.411+0.484
cmD
0.321+0.588
Where:
CB
°A) imperviousness (expressed as a decimal)
Runoff coefficient for Natural Resources Conservation Service (NRCS) HSG A soils
Runoff coefficient for NRCS HSG B soils
= Runoff coefficient for NRCS 14SG C and D soils.
The values for various catchment imperviousness and storm return periods are presented graphicallin
Figures 6-1 through 6-3, and are tabulated in Table 6-5. These coefficients were developed for the
Denver region to work in conjunction with the time of concentration recommendations in Section 2.4.
Use of these coefficients and this procedure outside of the semi -arid climate found in the Denver region
may not be valid. The UD-Rational Excel workbook performs all the needed calculations to find the
runoff coefficient given the soil type and imperviousness and the reader may want to take advantage of
this macro- enabled Excel workbook that is available for download from the UDFCD's website
www.udfcd.org.
See Examples 7.1 and 7.2 that illustrate the Rational Method.
March 2017
Urban Drainage and Flood Control District 6-9
Urban Storm Drainage Criteria Manual Vol e 1
Table 6-5. Runoff coefficients, c
Total
%
or Effective
Impervious
NRCS
Soil Group
A
Hydrologic
2 -Year
5 -Year
10 -Year
25 -Year
50 -Year
100
-Year
500 -Year
2%
0.01
0.01
0.01
0.01
0.04
0.13
0.27
5%
0.02
0.02
0.02
0.03
0.07
0.15
0.29
10%
0.04
0.05
0.05
0.07
0.11
0.19
0.32
15%
0.07
0.08
0.08
0.1
0.15
0.23
0.35
20%
0.1
0.11
0.12
0.14
0.2
0.27
0.38
25%
0.14
0.15
0.16
0.19
0.24
0.3
0.42
30%
0.18
0.19
0.2
0.23
0.28
0.34
0.45
35%
0.21
0.23
0.24
0.27
0.32
0.38
0.48
40%
0.25
0.27
0.28
0.32
0.37
0.42
0.51
45%
0.3
0.31
0.33
0.36
0.41
0.46
0.54
50%
0.34
0.36
0.37
0.41
0.45
0.5
0.58
55%
0.39
0.4
0.42
0.45
0.49
0.54
0.61
60%
0.43
0.45
0.47
0.5
0.54
0.58
0.64
65%
0.48
0.5
0.51
0.54
0.58
0.62
0.67
70%
0.53
0.55
0.56
0.59
0.62
0.65
0.71
75%
0.58
0.6
0.61
0.64
0.66
0.69
0.74
80%
0.63
0.65
0.66
0.69
0.71
0.73
0.77
85%
0.68
0.7
0.71
0.74
0.75
0.77
0.8
90%
0.73
0.75
0.77
0.79
0.79
0,81
0.84
95%
0.79
0.81
0.82
0.83
0.84
0,85
0.87
100%
0.84
0.86
0.87
0.88
0.88
0.89
0.9
or
Impervious
Effective
NRCS
Soil
Group B
Total
%
Hydrologic
2 -Year
5 -Year
10
-Year
25 -Year
50 -Year
100
-Year
500 -Year
2.0
0.01
0.01
0.07
0.26
0.34
0.44
0.54
5%
0.03
0.03
0.1
0.28
0.36
0.45
0.55
10%
0.06
0.07
0.14
0.31
0.38
0.47
0.57
15%
0.09
0.11
0.18
0.34
0.41
0.5
0.59
20%
0.13
0.15
0.22
0.38
0.44
0.52
0.61
25%
0.17
0.19
0.26
0.41
0.47
0.54
0.63
30%
0.2
0.23
0.3
0.44
0.49
0.57
0.65
35%
0.24
0.27
0.34
0.47
0.52
0.59
0.66
40%
0.29
0.32
0.38
0.5
0.55
0.61
0.68
45%
0.33
0.36
0,42
0.53
0.58
0.64
0.7
50%
0.37
0.4
0.46
0.56
0.61
0.66
0.72
55%
0.42
0.45
0.5
0.6
0.63
0.68
0.74
60%
0.46
0.49
0.54
0.63
0.66
0.71
0.76
65%
0.5
0.54
0.58
0.66
0.69
0.73
0.77
70%
0.55
0.58
0.62
0.69
0.72
0,75
0.79
75%
0.6
0.63
0.66
0.72
0.75
0.78
0.81
80%
0.64
0.67
0,7
0.75
0.77
0.8
0.83
85%
0.69
0.72
0.74
0.78
0.8
0.82
0.85
90{%0
0.74
0.76
0.78
0.81
0.83
0.84
0.87
95%
0.79
0.81
0.82
0.85
0.86
0.87
0.88
100%
0.84
0.86
0.86
0.88
0.89
0.89
0.9
6-10 Urban Drainage and Flood Control District
Urban Storm Drainage Criteria. Manual Vol o
March 2017
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FOR THE MARKING OF UNDERGROUND
MEMBER UTIU11ES.
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DESIGN
POINT
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16,79
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Ent ine:no Surveyor.:
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BOLILLER ♦ ( I3EELFV
IMLORL6D MINES
PREPARED FORE
CENTENNIAL TOOLS
AND SERVICES LLG
P.C. BOX 296
KERSEY, CO 60644
CONTACT: JUAN I+IACIO CRUZ
(970)-31-2030
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ISSUE
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3/23/2018
DESIGNED BY;
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FILE NAME
ARR
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CO
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PROJECT NO. 21172-00GROV
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