HomeMy WebLinkAbout1.03 DrainageDRAINAGE REPORT
for
THE DOG KENNEL FACILITY,
RESIDENTIAL DUPLEX, AND BIRD ENCLOSURE AREA
AT
THE HIGH LONESOME RANCH
GARFIELD COUNTY, COLORADO
SUBMITTED TO:
GARFIELD COUNTY BUILDING & PLANNING DEPARTMENT
108 8.111 STREET
GLENWOOD SPRINGS, COLORADO 81601
PREPARED FOR:
The High Lonesome Ranch
PO Box 88
Debeque, CO 81630
PREPARED BY:
Rhino Engineering, Inc.
1229 North 23rd Street, Suite 201
Grand Junction, Colorado 81501
February 25, 2009
RE Project No. 28053.02
"I hereby certify that this Drainage Report for the Dog Kennel Facility, Residential Duplex, and
Bird Enclosure is located in the NE' NW'/a of Section 9, Township 8S, Range 98W of the 6th
Principal Meridian in Garfield County, Colorado, was prepared by me or under my direct
supervision in accordance with the provisions of the Stormwater Management Manual for the
owners thereof. I understand that Garfield County does not and will not assume liability for
drainage facilities designed by others."
John Emil Kornfeld, P.E.
Registered Professional Engineer
State of Colorado No. 33064
FDR -CERTIFICATION PAGE
TABLE OF CONTENTS
1.0 LOCATION AND DESCRIPTION OF PROPERTY 1
A. Background 1
B. Property Location 1
C. Description of Property 1
D. Previous Investigations 2
2.0 DRAINAGE SYSTEM DESCRIPTION 2
A. Existing Drainage Conditions 2
B. Master Drainage Plan 2
C. Offsite Tributary Area 2
D. Proposed Drainage System Description 4
E. Drainage Facility Maintenance 4
3.0 DRAINAGE ANALYSIS AND DESIGN CRITERIA 5
A. Regulations 5
B. Development Criteria 5
C. Hydrologic Criteria 5
D. Hydraulic Criteria 5
4.0 POST CONSTRUCTION STORMWATER MANAGEMENT 5
5.0 CONCLUSIONS 6
A. Compliance with Manual 6
B. Design Effectiveness 6
6.0 REFERENCES 6
Appendix A
Appendix B
NRCS Soils Map
Drainage Calculations
APPENDICES
FIGURES
Figure 1 Proposed Improvements at The High Lonesome Ranch
Exhibit 1
Exhibit 2
Exhibit 3
EXHIBITS
Drainage Basin Map (USGS Quadrangle Map)
Existing Drainage Map (24" x 36" In Map Pocket)
Post -Development Drainage Plan (24" x 36" In Map Pocket)
FDR -TABLE OF CONTENTS
1.0 LOCATION AND DESCRIPTION OF PROPERTY
A. Background
This drainage report for the Dog Kennel Facility, Residential Duplex, and Bird Enclosure Area
was prepared by Rhino Engineering, Inc. The purpose of this report is to evaluate the impact (or
change) to the existing drainages, in relation to the historic drainage pattem and peak runoff, due
to the proposed improvements for The High Lonesome Ranch.
B. Property Location
The improvements are located north of Garfield County Road 200 (north of Debeque) on
approximately 40 acres of land owned by The Lonesome Ranch. Only about 5± acres of the total
40 acres are proposed for the improvements. The site will be accessed by a gravel road from
Garfield County Road 200. Garfield County Road (Garfield CR) 200 is accessed from Mesa
County Road X.5, north of Debeque.
By legal description, the property is located in the NE'/ NW''% of Section 9, Township 8S, Range
98W of the 6`h Principal Meridian in Mesa County. Refer to Figure 1 — General Location Map.
C. Description of Property
The 40 acre site is presently undeveloped. Proposed improvements will include a modular
duplex residential unit, a dog kennel facility, and a future bird enclosure. The property is
situated in a more or less remote area north of Debeque, north of Garfield CR 200. Current
vegetation on the site is high desert shrub and sagebrush with fair to good ground cover. The
general area slopes to the south. Two existing site drainages (washes) collect and convey runoff
from the offsite drainage basins through the site. Near the confluence of these two washes, a
much larger third wash from the east joins the two washes immediately north of Garfield CR
200. Runoff is conveyed under Garfield CR 200 near the confluence of the three washes. There
have historically been flooding and sediment problems at this culvert crossing, maintained by
Garfield County. Once clogging of the culvert occurs due to debris from the alluvial fan, runoff
then overtops the county road. There are no irrigation facilities on the site.
According to the Natural Resource Conservation Service (NRCS), the soils in this area consist
mostly of the Happle very channery sandy loam on the flatter slopes and Biedsaw-Sunup
gravelly loams on the steeper slopes. The Happle soil series is classified as Hydrologic Group B
and the Biedsaw-Sunup soils are classified as Hydrologic Group C soils. These soils are well
drained and are comprised of coarse grains soils. Refer to Appendix A for the soils map and
further information.
FDR -PAGE 1
1108°21' '0.00" 1 I _
l 80 20'
0.00"W
0
0
N
0
O
z
FIGURE i — PROPOSED IMPROVEMENTS
THE HIGH LONESOME RANCH
1 MILES
1000 YARDS
0 1 KILOMETER
2"E
I
1108°2 0.00" W
1 8°20' •0.00'4
Copyright (C) 1997, Maptech, Inc.
1108°19' 70.00" 1ilt
D. Previous Investigations
The project site is not included in any known master drainage plan nor is it located in a FEMA
designated floodplain.
2.0 DRAINAGE SYSTEM DESCRIPTION
A. Existing Drainage Conditions
The topography across the site varies of gently sloping alluvial fans to moderate sloping side
slopes rising from the fans. Slopes across the site average approximately 5% on the flatter areas
to near 40% on the steeper slopes. Drainage from this site flows into the Dry Fork drainage,
which lies about 500 feet south of Garfield CR 200. Refer to Exhibit 1 — Drainage Basin Map
and Exhibit 2 — Existing Drainage Map.
Construction of the improvements, i.e., the dog kennel facility, residential duplex, and future bird
enclosure, will not significantly impact the existing site drainage in terms of runoff. Increase in
runoff due to these facilities will be relatively minor. The primary drainage concern is how the
offsite drainages (runoff) may affect the location of these proposed facilities. The dog kennel
facility and the bird enclosure are situated near the outfall of the two offsite drainage basins
Discussion about the offsite drainages is included in the "C. Offsite Tributary Area" section
which follows. The proposed improvements will have negligible impact on site drainage due to
the minor amount of impervious disturbance the improvements will create in relation to the size
of the drainage. Therefore, no further discussion is provided for site runoff.
8. Master Drainage Plan
There are no known master drainage plans or adjacent developments which affect the site.
C. Offsite Tributary Area
The proposed improvements are located in the Dry Fork Drainage. More specifically, several
smaller unnamed natural drainages dissect the site. There are two main offsite drainage basins
that flow to the site and impact the site, especially the kennel facility. A third drainage basin,
including the steeper side slopes adjacent the duplex and kennels, also impacts the site. Refer to
the Site Plan/Post Development Drainage Plan.
Drainage Basin 1 flows near the proposed location of the kennel facility and Drainage Basin 2
drains near the future bird enclosure area. The residential duplex lies "around the slope" such
that any flows in Drainage Basin 1 will not directly impact the structure if proper routing is
maintained. There is not any development in either offsite drainage basin. Vegetation consists
mostly of desert shrub and sagebrush.
Magnetic Declination
Name: LONG POINT
Date: 2/13/2009
Scale: 1 inch equals 2000 feet
Location: 039° 23' 03.22" N 108° 19' 11.40" W NAD 27
Copyright (C) 1997, Maptech, Inc.
The 40 acre property is affected by offsite runoff from two drainage basins totaling 133± acres.
An SCS Curve Number of 85 is estimated for offsite conditions, as most of the offsite soils
include the Bledsaw-Sunup gravelly loams (C Hydrologic Soils). Runoff rates are presented in
Table I. Offsite runoff from the two drainage basins is shown below.
t 1.8(1.1-0.21)x300%=9.4min
26X
t _ 4400 ft — 4889s = 81.5 min
s 3.0 x 0.09o.s
t =t,+t,= 9.4min+ 81.5min = 90 9min
The time of concentration for Offsite Drainage Basin 2 is:
t _1.8(1.1-0.21)x300%_10.2 min
20X
3300ft — 4620s = 77.0min
S 2.7x0.07"
t = t, + is =10.2 min+ 77.0 min = 87.2 min
As mentioned above, a third drainage area, Basin 3, contributes minor runoff from the steeper
side slopes immediately north of the duplex and kennel facility. Runoff from this drainage area
can impact the location of these two structures and is therefore discussed below.
Table 1— Offsite Runoff
Drainage Basin Area 25 -Year Runoff 100 -year Runoff
(Ac) (cfs) (cfs)
Basin 1
Basin 2
Basin 3
93.6
39.6
3.2
37.3
17.1
6.0
57.0
26.0
7.3
D. Proposed Drainage System Description
Due to the proximity of Drainage Basin 1 outfall in relation to the location of the kennel facility,
conveyance of offsite stormwater through the site is imperative. The kennel facility and
residential duplex are situated on an alluvial fan that was formed by alluvial deposits from runoff
of Basin 1. Likewise, the bird enclosure area is also situated on a fan from deposits from Basin
2. Alluvial fans are generally active and ongoing erosional processes are dynamic. Alluvial
deposits will continue to pose a problem and therefore protection of the facilities is necessary.
Based on the natural topography, a combination of several hydraulic features are necessary. First
a berm is recommended east of the kennel. The berm should extend from the edge of the steeper
slopes to the south, beyond the kennels. This berm will divert runoff past the kennel thereby
protecting the facilities from stormwater and debris. Secondly, a vee shaped channel is
recommended and constructed between the kennel and duplex and the steeper side slopes to the
north. This swale will collect and convey runoff from Basin 3 to the west. An additional swale
should be constructed between the septic absorption field and the steeper side slopes to convey
and route stormwater away from the drain field. To insure proper protection of the absorption
field, a clay cut-off wall should also be constructed on the uphill side of the drain field. Runoff
from the swales will then drain under the access roadway to the facilities.
The berm to divert runoff and debris from Basin 1 beyond the kennel should have a top width of
4 feet with 4H:1 V side slopes. The height of the berm should be 6 feet to insure adequate
conveyance for major storm runoff and alluvial deposits associated with the stormwater runoff.
The berm should be seeded with native rangeland plants to insure stability of the embankment.
The vee swale should be a minimum of 2 feet depth with 4H:1 V side slopes. The minimum
slope should be 2.0%. If slopes exceed 3.0%, erosion protection should be used. Such protection
could be either riprap or permanent erosion control matting. Assuming a 2.0% slope, the normal
flow depth of the ditch is 0.8 feet for a flow rate of 7.2 cfs (100 -year peak flow). This ditch cross
section geometry should adequately convey offsite runoff from Basin 3. Refer to Appendix B for
calculations. Rip -rap aprons should be placed at the culvert inlet and outlet to prevent erosion.
Refer to Exhibit 3 — Post -Development Drainage Map for details.
Due to the nature of the bird enclosure, no structural hydraulic improvements are necessary for
runoff from Basin 3. However, it may be desirable to construct a berm upstream of the bird area
to route runoff away from this area. If the berm is constructed, it should divert runoff westerly
around the bird area and then returned naturally to the south. This runoff will then collect with
the runoff diverted by the berm at the kennel facility. This will maintain the historic drainage as
it flows southerly toward Garfield CR 200. If the berm is constructed, it should be similar to the
berm specifications to protect the kennel facility.
E. Drainage Facility Maintenance
Periodic maintenance of the berm and "cleaning" of the conveyance way beside the berm(s) will
be necessary.
5.0 CONCLUSIONS
A. Compliance with Manual
This drainage report complies with current Garfield County drainage criteria.
B. Design Effectiveness
The drainage facilities outlined in this report including culverts and ditches were designed to
effectively control impacts of storm runoff to adjacent properties.
6.0 REFERENCES
The following manuals, computer programs, and engineering reports were used as references in
the preparation of this report.
• Garfield County New Land Use Regulations (effective 1-1-09) for Article VII Standards,
Section 7-206 Drainage.
• Stormwater Management Manual, City of Grand Junction and Mesa County, May 2008.
• The NRCS method Technical Release 55 entitled "Urban Hydrology for Small
Watersheds" was used to calculate times of concentration.
• Hydraflow Hydragraphs 2004 Software was used to calculate runoff volumes and for
detention routing
• Denver Urban Drainage and Flood Control District Open Channel Design Version 1.01,
April 2004.
APPENDIX A
NRCS SOILS DATA
FDR -APPENDIX A
Web Soil Survey
'WHIM fitisatireetS4ItA
Contact Us ( Download Soils Data j Archived Soll Surveys j Glossary
Area of Interest (A0/)
Soil Map
Preferences Logout 1 Help
Soil Data Explorer
Shopping Cart (Free)
Page 1 of 2
View Soll Information By Use: All Uses
tiara ja'ed.3 ;Sb VPM
Intro to
Soils
Suitabllities and
Soil Properties
Limitations for Use and Qua ities
Ecological Site Soll
Assessment Reports
0
Search
0
Properties and Qualities Ratings
y�'41 tr4I51 Q 1
00
Soil Chemical Properties
00
Soil Erosion Factors
00
Soil Physical Properties
00
Soil Qualities and Features
AASHTO Group Classification (Surface)
Depth to a Selected Soil Restrictive Layer
Depth to Any Soll Restrictive Layer
Drainage Class
Frost Action
Frost -Free Days
Hydrologic Soil Group
r eW',. s. .YijI dil
View Options D 0
Map r
Table P1
Description of r
Rating
Rating Options P1
I— Detailed Description
Advanced Options (2)®
Aggregation Dominant Condition 11
Method ` _--
Component
Percent Cutoff -----•
Tie-break Rule .a; Lower
!..` Higher
4y/4t4,H}3sylgilE"p`I1F�w:Rdbi$ I
E
Map Unit Name a
y
Parent Material Name T
8
Representative Slope
C
Unified Soil Classification (Surface) o
0
00
Water Features G
Ma. — H drotogic Soil Group
411 Warning: Soil Ratings Map may not be valid at this scale.
You have zoomed In beyond the scale at which the soil map for this area is Intended to be used.
Mapping of soils Is done at a particular scale. The soil surveys that comprise your AOI were
mapped at 1:24,000. The design of map units and the level of detail shown in the resulting soil
map are dependent on that map scale.
Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail 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.
Tables — Hydrologic Soil Group —Summary By Map Unit
Summary by Map Unit — Douglas -Plateau Area, Colorado, Parts off Garfield and Mesa
counnea
Map unit symbol Map unit name
7 Biedsaw-Sunup gravelly
loam, 10 to 40 percent
slopes
cl
32 Dominguez clay loam, 3 to 8
percent slopes
44 Happle very channery sandy
loam, 3 to 12 percent slopes
Totals for Area of Interest
Rating Acres in AOl Percent of AOl
72.6. 63.0%
C 3.] 32%
B j
39.0 33.8%
115.3: 100.0%
escription — Hydrologic Soil Group
lydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups
ccording to the rate of water Infiltration when the soils are not protected by vegetation, are thoroughly
ret, and receive precipitation from long -duration storms.
he soils in the United States are assigned to four groups (A, B, C, and 0) and three dual classes (A/D,
/D, and C/D). The groups are defined as follows:
roup A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist
fainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate
water transmission.
roup B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of
oderately deep or deep, moderately well drained or well drained soils that have moderately fine texture
to moderately coarse texture. These soils have a moderate rate of water transmission.
Group C. Solis having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a
layer that Impedes the downward movement of water or soils of moderately floe texture or fine texture.
These soils have a slow rate of water transmission.
Group D. Soils having a very slow Infiltration rate (high runoff potential) when thoroughly wet. These
consist chiefly of clays that have a high shrink -swell potential, soils that have a high water table, soils
that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious
http://websoilsurvey.nres.usda.gov/app/WebSoilSurvey.aspx 2/17/2009
APPENDIX B
DRAINAGE CALCULATIONS
FDR -APPENDIX B
Hydrograph Summary Report
1
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
peak
(min)
Volume
(cuft)
Inflow
hyd(s)
Maximum
elevation
(ft)
Maximum
storage
(cuft)
Hydrograph
description
1
SCS Runoff
37.33
6
774
364,727
----
Basin 1
2
SCS Runoff
17.07
6
768
152,403
----
Basin 2
3
Rational
6.00
1
10
4,804
----
Basin 3
Kennels.gpw
Return Period: 25 Year
Wednesday, Feb 18 2009, 6:28 AM
Hydrafiow Hydrographs by Intelisolve
Hydrograph Summary Report
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
peak
(min)
Volume
(cuft)
Inflow
hyd(s)
Maximum
elevation
(ft)
Maximum
storage
(cuft)
Hydrograph
description
1
SCS Runoff
56.98
6
774
546,377
----
Basin 1
2
SCS Runoff
26.03
6
768
228,306
----
Basin 2
3
Rational
7.27
1
10
5,826
----
Basin 3
Cennels.gpw Return Period: 100 Year Wednesday, Feb 18 2009, 6:28 AM
Hydraflow Hydrographs by Intelisolve
Hydrograph IDF Curves
IDF file: The High Lonesome Ranch Kennels.IDF
Int. (in/hr)
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
0 5 10 15 20 25 30 35 40 45 50 55 60
7.00 — 100 -Yr
6.00 — - 25 -Yr
5.00
4.00
3.00
2,00
1.00
0.00
Time (min)
Hydraflow Hydrographs 2004
THR. LST
*********** *** HYDRO - Version 6.0 ***************
* HEC19 / Design Event vs Return Period Program
* Date of Run: 02-13-** *
THR
- -- Input File: C:\HYDRO\THR.HDO
IDF THR
__= IDF CURVE Option Selected ...
LOC 39 22 108 19
- -- The Latitude is 39 degrees, 22 minutes.
- -- The Longitude is 108 degrees, 19 minutes.
RPD 25
- -- The Selected Return Period is 25 years.
*** End of Command File
0
Page No 1
***** HYDRO ***** (Version 6.0) ***** Date 02-13-**
Page No 2
Duration 25 Yr
THR
IDF Curve for Various Return Periods
Intensities (in/h)
2 Yr 5 Yr 10 Yr
50 Yr 100 Yr
5 min 4.616 2.836 3.586 4.038 5.034 5.430
10 min 3.566 2.057 2.680 3.065 3.935 4.289
15 min 2.837 1.516 2.050 2.389 3.171 3.496
30 min 1.909 .941 1.323 1.572 2.165 2.417
60 min 1.185 .550 .796 .960 1.358 1.530
120 min .764 .355 .514 .619 .876 .987
4 h .446 .207 .300 .362 .512 .576
8 h .244 .113 .164 .197 .279 .315
16 h .128 .059 .086 .103 .146 .165
24 h .087 .040 .058 .070 .099 .112
0
THR
Intensity Curve for 25 Year Return Period
Rainfall Intensity (in/h) versus Duration (h)
4.62*
3.46*
2.31.
1.15. *
* *
.00
.00 6.00 12.00 18.00 24.00
***** HYDRO ***** (Version 6.0) ***** Date 02-13-**
Page No 3
THR
__= File Created on Intermediate Directory: THR.IDF
Page 1
RATING CURVE FOR TRAPEZOIDAL CHANNEL
ml 11 11 Z N
N f�
11 11
> 0
L
O_
a) 0 O a
m a 2 3 N
L_ O. O CO O Cl
'O 1 a5
W a) N C m
ID O O) 'O C N
E D C sC E
o t L C 0 O N
b 0 0) O
m J cc 2 J m 0
0
D 0
O j IL
IL Z
N
NNNNN
6
V
6
CD
0
CO
6
mr
0
CO
6
N
CO
O
CO
CO
O
s}
OD
O
N
CO
Ci
CO
CO
O
N
CO
O
CO
CO
O
m
CO
O
N
o m O COw
LL U
O
M
co
O
r
r`
CO
m
r
h
6
r
N
• r
N
r
N
N
COV
V
V
N
N
o
>.
Q.,
L a) d
CO
O
N
O
CO
N
u)
N
N
O)
(V
N
N
O
Ci
V
N
M
llOO
V
M
N
(D
C7
0
CO
ci
u)
O
4
IO
N
V
CO
V
7
N
CO
V
CO
CO
4
y)
a Vw
S m Cc
K
N
O
co M
Ci
0
mc
CO
0
d�
'
0
0)
V
0
CO
N
0
OD
N
0
CO
CO
6
CO
CO
0
CO
N
O
CO
h
6
N
CO
O
h
CO
O
'o d
a)
z a) l x
ii
r
v
0)
v
CO
ui
ID
m
V
r:
N
ed
r
Di
0)
Di
h
o
r
u)
r0i'
r
V
r
N
O
v'
r
CO
3
cr
LL Q a y
O
r
V
r
O
CI
0
N
N
COCJ
O
4
CO
4
CO
ui
CO
d
CO
O
Oi
N
6
m
r-cri
O
3
O N > w
LL 8)
N
0
w
0
h
06
0
O)
0
O
r
N
co.
V
IO
O
h
co.
STORMWATER MANAGEMENT MANUAL
RECOMMENDED IMPERVIOUSNESS VALUES
Land Use or Surface
Characteristic
Percentage
Imperviousness
Business
Commercial Areas
Neighborhood Areas
95
85
Residential
Single Family
Multi -unit (detached)
Multi -unit (attached)
gaff --acre lot or larger
Apartments
(see figures)
60
75
(see figures)
80
Industrial
Light industrial
Heavy industrial
80
90
Parks, cemeteries
5
Playgrounds
10
Schools
50
Railroad yards
15
Undeveloped Areas
Historic flow analysis
Greenbelts, agriculture
Off -site flow analysis
(when land use not defined)
2
7 -
45
Streets
Paved (concrete/asphalt)
Gravel
100
40
Drives and walks
90
Roofs
90
Lawns (all soils)
0
NOTE: The Imperviousness values are representative of land uses shown
and are for future development projections only. Impervious
values for existing land uses may vary.
Revision Delo
OR/CINAL ISSUE 3/27/06
WIT DiaEgiNa
REFERENCE:
UDFCD 2001. Urban Storm Drainage Criteria Manual, Volume 1
TABLE 701
STORMWATER MANAGEMENT MANUAL
RATIONAL FORMULA RUNOFF COEFFICIENTS
Equation:
CCD = KCD + (0.85813 - 0.78612 + 0.774i +0.04)
CA = KA + (1.3113 - 1.4412 +1.135i -0.12)
Ce = (CA +_ CCD)12
KCD VALUES
NRCS Soil
2 -year
5 -year
10 -year
25 -year
50 -year
100 -year
C and D
0
-0.101+0.11
-0.181+0.21
-0.281+33
-0.331+0.40
-0.391+0.46
A
0
-0.08i+0.09
-0.14i+0.17
0.191+0.24
-0.221+0.28
-0.251+0.32
Impervious
Decimal
Type A
2 -year
5 -year
10 -year
25 -year
50 -year
100 -year
0.1
0.00
0.06
0,14
0.20
0.24
0.28
0.2
0.06
0.13
0.20
0.26
0.30
0.33
0.3
0.13
0.19
0.25
0.31
0.34
0.37
0.4
0.19
0.25
0.30
0.35
0.38
0.41
0.5
0.25
0.30
0.35
0.40
0.42
0.45
0.6
0.33
0.37
0.41
0.45
0.47
0.50
0.7
0.42
0.45
0.49
0.53
0.54
0.56
0.8
0.54
0.56
0.60
0.63
0.64
0.66
0.9
0.69
0.71
0.73
0.76
0.77,
0.79
1.0
0.89
0.90
0.92
0.94
0.95
0.96
Impervious
Decimal
Type B
2 -year
5 -year
10 -year
25 -year
50 -year
100 -year
0.1
0.06
0.14
0.22
0.31
0.36
0.40
0.2
0.12
0.20
0.27
0.35
0.40
0.44
0,3
0.18
0.25
0.32
0.39
0.43
0.47
0.4
0.23
0.30
0.36
0.42
0.46
0.50
0.5
0.29
0.35
0.40
0.46
0.50
0.52
0.6
0.37
0.41
0.46
0,51
0.54
0.56
0.7
0.45
0.49
0.53
0.58
0.60
0.62
0.8
0.57
0.59
0.63
0.66
0.69
0.70
0.9
0.71
0.73
0.75
0.78
0.80
0.81
1
0.89
0.90
0.92
0.94
0.95
0.96
Impervious
Decimal
- Type C and D Soil
2 -year
-5-year
10 -year
25 -year
50 -year
100 -year
0.1
0.110.21
"
0.30
0.41
0.48
0.53
0.2
0.17
0:28"
0.34
0.44
0.50
0.55
0.3
0.22
0.30
0.38
0.47
0.53
0.57
0.4
0.28
0.35
0.42
0.50
0.55
0.58
0.5
0.34
0.40
0.46
0,53
0.57
0.60
0.6
0.41
0.46
0.51
0.57
0.61
0.63
0.7
0.49
0.53
0.57
0.62
0.66
0.68
0.8
0.60
0.63
0.66
0.70
0.73
0.74
0.9
0.73
0.75
0.77
0.80
0.83
0.83
1.0
0.89
0.90
0.92
0.94
0.96
0.96
Revision Dale
OR/GINAL ISSUE J/27/05
WET 1iN4pc
REFERENCE:
UDFCD 2001. Urban Storm Drainage Criteria Manual, Volume 1
TABLE 702
STORMWATER MANAGEMENT MANUAL
RUNOFF CURVE NUMBERS
Land Use or Surface Characteristic
Average
Imperv.
(%)
Runoff Curve Number
Soil Complex
A
B
C
D
Business
Commercial Areas
Neighborhood Areas
85.
70
89
80
92
87
94
91
95
93
Residential
Single Family (note 1)
Multi -unit (detached)
Multi -unit (attached)
Apartments
Industrial
Light
Heavy
(note 1)
60
75
80
74
83
86
83
89
91
88
92
93
91
94
94
Parks, cemeteries
80
90
86
92
91
94
93
96
94
96
Playgrounds
5
42
63
75.
81
10
45
65
76
82
Schools
50
69
80
86
89
Railroad yards
15
48
67
78
83
Irrigated Areas
Lawns, parks, golf course
Agriculture
Undeveloped Areas
Pre -development conditions
Greenbelts, agriculture
Off-site analysis when land use
Unknown
Outcrops
Streets/Roads
Paved
Gravel
Drives/Walks
0
0
39
39
61
61
74
74
80
80
2
2
45
70
40
40
66
80
62
62
78
87
74
85
80
80
88
94
100
40
98
63
98
76
98
84
98
87
90
92
94
96
96
Roofs
90
92
94
96
96
NOTE:
ESTIMATE IMPERVIOUS FROM FIGURES 703, 704, 705. THEN COMPUTE CURVE NUMBER, CN, FROM
EQUATION 708, BASED ON NRCS SOILS TYPE. USE OF THIS TABLE IS LIMITED TO EVALUATION OF
IMPERVIOUSNESS FOR FUTURE DEVELOPMENT PROJECTIONS WITHIN REGIONAL WATERSHED MASTER
PLANS, OR IN CONCEPTUAL DRAINAGE PLANS.
Rewsbn Oslo
ORIGINAL ISSUE . 3/27/06
acicErinta pc
REFERENCE:
SCS TECHNICAL RELEASE NO. 55 (1986)
TABLE 704
STORMWATER MANAGEMENT MANUAL
TRAVEL VELOCITY FOR RATIONAL METHOD
100
10
1
0.1
• Forest with heavy ground litter &
fallow
fallow or minimum tillage cultivation
A short grass, pasture & lawns
k nearly bare ground
.x.grassed waterway
*paved areas, sheet flow, &
.shallow gutter flow
•
0.001
0,01 0.1
Watercourse Slope (ft/ft)
1
1
Revision Dale
ORIGINAL /SSUE 3/27/05
WIC ENICIIFiNG. plc
REFERENCE:
Adapted from USDA, SCS 1975, Urban Hydrology for
Small Watersheds, TR 55
FIGURE 701