HomeMy WebLinkAboutDrainage, Erosion, and Pollution Prevention Report - GEO General - 5/5/2008 V `
Drainage, Erosion & Pollution Prevention Report
Werdall Logging and Single Family Residence
Parcel 12216 2100001 _
Mason County,Washington
May 5, 2008
Project#0243
r
Prepared For:
Jeff and Pam Werdall
PO Box 2517
P��,CLYDFST
Belfair, Washington 98528 � wo WASH 9Ik
Prepared By. /sly
Envirotech Engineering ��a ,p�43045�0 w�
74 NE Hurd Road S,GIST G�
Belfair, Washington 98528
Phone: 360-275-9374 a 2°�Z
EXPIRES JAN-49;2009--
Fax: 360-275-4789
TABLE OF CONTENTS
Section Page
1.0 PROJECT DESCRIPTION 1
2.0 EXISTING CONDITIONS 1
3.0 INFILTRATION RATES/SOILS REPORTS 2
4.0 HYDROLOGIC/HYDRAULIC ANALYSIS 2
4.1 Hydrologic Summary 2
4.2 Best Management Practices 3
4.3 Drainage Tributary to the Project 3
4.4 Drainage System Beyond the Project 3
4.5 Wells and Septic Systems 3
4.6 Flood Analysis 3
5.0 FACILITY SIZING AND DOWNSTREAM ANALYSIS 3
5.1 Catch Basin 4
5.2 Roof/Foundation Infiltration Trench 4
5.3 Surface Runoff Infiltration Trench 4
5.4 Vegetated Filter Strip 5
6.0 CONSTRUCTION SEQUENCE AND PROCEDURE 5
7.0 TEMPORARY EROSION CONTROL 5
7.1 Stabilized Construction Entrance 6
7.2 Silt fence 6
8.0 PERMANENT EROSION CONTOL 7
9.0 INSPECTION AND MAINTENANCE 7
9.1 Inspection and Maintenance Schedule 8
9.2 Inspection and Maintenance Responsibility 8
10.0 CONTROL OF POLLUTANTS OTHER THAN SEDIMENTS 8
11.0 PROJECT ENGINEER'S CERTIFICATION 9
APPENDIX
Appendix A-Hydrologic Information and Computer Input/Output
1.0 PROJECT DESCRIPTION
Envirotech Engineering (Envirotech) has completed this drainage report for a vacant
property identified as parcel number 1221-62-100001 located in Mason County,
Washington (Project).
Information pertaining to the Project was provided by Jeff and Pam Werdell, project
owners, and general assumptions by Envirotech. The proposed development and land
disturbing activities includes constructing single family structures with a total of 4311
square feet (so of roof surface, approximately 13,200 sf of gravel surfaced driveway, and
selective timber harvesting. Timber harvesting primarily includes the area beyond 50 feet
from the top of the 60% slope, and includes trees greater than 4 inches in diameter. All
stumps and underbrush will be minimally disturbed.
The proposed stormwater management plan includes collecting runoff from the roofs and
foundations of each structure, and tightlining to infiltration trenches; allowing runoff from
the driveway to be distributed over a large vegetated and re-vegetated green area; and,
collecting a substantial amount of surface runoff, and re-distributing into a series of
infiltration trenches.
2.0 EXISTING CONDITIONS
The Project is currently undeveloped vacant land with an existing decommissioned logging
road. No recent clearing of vegetation was apparent on the property. The Project consists
of moderate to highly dense vegetation, including cedars, firs, alders, ferns, grasses,
blackberries, and other trees and shrubbery common to the Northwest. Beyond the
property lines, vacant land exists immediately to the east, with sparse development to the
north and south. The State Highway 302 right-of-way (ROW) with associated drainage
and paved roadway exists adjacent to the west, with single family development beyond.
The Project is situated within moderate to steep sloping terrain. Site grades are
moderately sloped at about 27% where development and the majority of logging is
expected to take place. Steep descending slopes of up to approximately 60% are located
on the southeast portion of the property, with a vertical relief of approximately 56 feet.
Ascending slopes near the northeast property corner are approximately 15%. There are no
water bodies or apparent wetlands located upslope from the proposed development.
Stormwater runoff originating upslope from anticipated building locations are expected to
be moderate due to the existing topography. Drainage within most of the property limits
appears to sheet flow in a westerly direction, with an exception near the descending 60%
slope. Watershed from this slope basically sheet flows in a southeast direction to the
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bottom of an adjacent ravine. All stormwater originating from this property is expected to
be intercepted by the above mentioned ravine or drainage facilities in the State ROW.
Ultimately, excess water from this property is conveyed less than '/2 mile to the west
before emptying into North Bay of the Case Inlet. During the site visit, running surface
water was not present within 300 feet of the planned building locations. Excessive scour,
erosion or other indications of past drainage problems were not observed at or near the
Project. Overall, the earth near the Project surface consists of moderate permeable soils
that is an engineering property relating to average groundwater drainage.
3.0 INFILTRATION RATES/ SOILS REPORTS
Information on infiltration rates and soil conditions pertaining to the Project was
accomplished by Envirotech. One percolation test was completed for this Project after the
preparation of the geotechnical report, and measured to be 4.3 in/hr. Soils are primarily a
loamy sand per the USDA textural classification. A geotechnical report was prepared for
this Project, dated October 18, 2007.
4.0 HYDROLOGIC/HYDRAULIC INFORMATION
Information in this section includes a hydrologic summary of parameters, best
management practices utilized for the design, drainage patterns beyond the project, and
flood information.
4.1 Hydrologic Summary
The Santa Barbara Urban Hydrograph (SBUH) method was utilized for estimating peak
design flows. The SBUH method is based on a runoff curve number approach, and uses
Soil Conservation Service (SCS) equations for computing soil absorption and precipitation
excess This analysis is based on a Type IA rainfall distribution and a 24 hour storm
duration. Volume was calculated using the SCS equation, and facility sizing is based on a
conservative infiltration rate and the 100yr-24hr design storm.
The following design parameters were used for stormwater drainage design:
• Design storm, 100yr-24hr;
• 6.4 inches from the 100yr-24hr design storm;
• Hydraulic soil group `A';
• Curve Number of 98 for impervious areas;
• Curve Number of 42 for pre-existing conditions; and,
• Curve Number of 55 for disturbed conditions.
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4.2 Best Management Practices
Best Management Practices (BMPs) for this project includes a type 30 catch basin to
collect roof and foundation water, infiltration trenches, and vegetative areas for surface
runoff. Vegetation will be permanently established within the disturbed areas to the
recommended procedures in the stormwater management plans and specifications.
4.3 Drainage Tributary to the Project
The drainage to the Project is very minimal due to the topography and small upland
watershed. This runoff appears to be a sheet flow.
4.4 Drainage System Beyond the Project
Drainage from the site is directed into the adjacent roadside drainage channel located
along the west side of State Route 302. The drainage channel leads to a culvert, and
ultimately into Case Inlet.
4.5 Wells and Septic Systems
Records, research and site observations revealed no indication of existing or proposed
wells or septic systems located within the setback distances for stormwater infiltration
facilities identified in the Stormwater Management Manual for Western Washington. The
location of the proposed septic drainfield is portrayed on the plan sheets.
4.6 Flood Analysis
The immediate project is not situated within a flood zone, or contain or abut a stream,
therefore an analysis of the 100-year flood is not required. Furthermore, indications of
flooding within or near the Project were not observed during a site visit. The stream
located within the southeast portion of the property is geologically separated from the
proposed development, and approximately 50 feet lower than the planned residence.
5.0 FACILTY SIZING AND DOWNSTREAM ANALYSIS
Proposed facilities for this project includes a type 30 catch basin, roof/ foundation
infiltration trenches, surface runoff infiltration trench, and green areas for driveway runoff.
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Fax: 360-275-4789 Parcel No. 12216 2100001
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5.1 Catch Basin
The catch basin is designed to be a type 30, and can accommodate the 25yr-24hr design
storm without difficulty. Stormwater entering the catch basin exits through a 6-inch
diameter corrugated CPEP solid pipe that has the capacity which greatly exceeds the 25yr-
24hr design storm.
5.2 Roof/Foundation Infiltration Trench
The infiltration trench for the roof and foundation drains were sized based on the 100yr-
24hr design storm. Location and details of the trench is provided in the plans and
specifications. Section 4.1 of this report depicts the hydrologic summary of parameters
used in this analysis.
The peak design flow rate from the 100yr-24hr design storm are estimated to be, Q =
0.206 cfs. The volume of runoff was determined to be approximately, V= 2200 cf. Excess
water from foundation drains were not accounted for, however, a very conservative
infiltration rate of 3.1 in/hr was utilized in lieu of the measured 4.3 in/hr. This is depicted
in the output spreadsheet in Appendix A of this report.
The following is a summary of design parameters for the infiltration trench for the roofs
and foundations:
-Total Length: 100 ft
Bottom width: 3 ft
-Depth: 3 ft
-Drawdown: 30 hr
5.3 Surface Runoff'Infiltration Trench
The infiltration trench for a large portion of the surface runoff were sized based on the
100yr-24hr design storm. Location and details of the interceptor drain and trenches are
provided in the plans and specifications. Section 4.1 of this report depicts the hydrologic
summary of parameters used in this analysis.
The peak design flow rate from the 100yr-24hr design storm are estimated to be, Q =
0.195 cfs. The volume of runoff was determined to be approximately, V = 5900 cf. This is
depicted in the output spreadsheet in Appendix A of this report.
The following is a summary of design parameters for the infiltration trench for the surface
runoff.
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Fax: 360-275-4789 Parcel No. 12216 21 00001
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•Total Length: 240 ft
•Bottom width: 3 ft
*Depth: 3 ft
•Drawdown: 30 hr
5.4 Vegetated Filter Strip
Runoff from the gravel surfaced driveway is designed to sheet flow over green areas with
a flow length of up to 320 feet. The green area will be selectively harvested. However,
stumps and underbrush will remain undisturbed as much as possible. Additionally,
denuded areas will be re-vegetated per the requirements in the stormwater management
plan.
6.0 CONSTRUCTION SEQUENCE AND PROCEDURE
The following includes the recommended construction sequence and procedure for project
development:
1. Construct stabilized construction entrance, if necessary.
2. Install silt fencing.
3. Complete selective harvesting.
4. Perform initial earthwork, subexcavation, fill, and rough grading based on approved
design.
5. Install additional temporary erosion control facilities, if necessary.
6. Maintain all temporary erosion and sediment control facilities, as needed, in order to
provide the required protection of downstream water quality.
7. Construct infiltration trenches.
8. Complete project and permanent erosion control in order to stabilize the project.
9. Remove temporary erosion sedimentation control facilities after construction is
complete, the site is sufficiently stabilized, and accepted by the County.
7.0 TEMPORARY EROSION CONTROL
The primary methods used for trapping sedimentation before it reaches off-site storm
drainage systems or adjoining properties includes a stabilized construction entrance and
silt fencing. Based on the soil classification of the Project soils, the upper 4 feet of soils
have a low to moderate erodibility factor.
------------------
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7.1 Stabilized Construction Entrance
Details and location regarding the stabilized construction entrance shall be constructed
according to the detailed engineering plans and specifications. The stabilized construction
entrance shall be constructed according to the following general guidelines:
• Material shall range from 4 inches to 8 inches quarry spalls.
• Construction entrance extents shall extend to a minimum depth of 12 inches, a
minimum width of 20 feet (or ingress/ egress width), and a minimum length of
50 feet.
• Construction entrance surface shall be sloped at least I% in the direction
shown on the engineering plans.
• If the pad does not adequately remove mud from the vehicle wheels, the
wheels shall be hosed off before the vehicle leaves the site.
7.2 Silt Fence
Silt fencing shall be located and installed according to the details provided on the
engineering plans and specifications with the following materials and guidelines:
1. FILTER FABRIC SHALL BE PURCHASED IN A CONTINUOUS ROLL AND CUT TO THE
LENGTH OF THE BARRIER TO AVOID USE OF JOINTS. WHEN JOINTS ARE NECESSARY,
FILTER CLOTH SHALL BE SPLICED TOGETHER ONLY AT A SUPPORT POST, WITH A
MINIMUM 6-INCH OVERLAP, AND SECURELY FASTENED AT BOTH ENDS TO THE POST.
2. POSTS SHALL BE SPACED A MAXIMUM OF 6 FEET APART AND DRIVEN SECURELY INTO
THE GROUND (MINIMUM OF 30 INCHES).
3. A TRENCH SHALL BE EXCAVATED APPROXIMATELY 8 INCHES WIDE AND 12 INCHES
DEEP ALONG THE LINE OF POSTS AND UPSLOPE FROM THE BARRIER. THIS TRENCH SHALL
BE BACKFILLED WITH WASHED GRAVEL.
4. WHEN STANDARD STRENGTH FILTER FABRIC IS USED, A WIRE MESH SUPPORT FENCE
SHALL BE FASTENED SECURELY TO THE UPSLOPE SIDE OF THE POSTS USING HEAVY
DUTY WIRE STAPLES AT LEAST 1 INCH LONG,TIE WIRES OR HOG RINGS. THE WIRE SHALL
EXTEND INTO THE TRENCH A MINIMUM OF 4 INCHES AND SHALL NOT EXTEND MORE
THAN 24 INCHES ABOVE THE ORIGINAL GROUND SURFACE.
5. THE STANDARD STRENGTH FILTER FABRIC SHALL BE STAPLED OR WIRED TO THE
FENCE, AND 20 INCHES OF THE FABRIC SHALL BE EXTENDED INTO THE TRENCH. THE
FABRIC SHALL NOT EXTEND MORE THAN 24 INCHES ABOVE THE ORIGINAL GROUND
SURFACE. FILTER FABRIC SHALL NOT BE STAPLED TO EXISTING TREES.
6. WHEN EXTRA-STRENGTH FILTER FABRIC(MONOFILAMENT), AND CLOSER POST
SPACING IS USED,THE WIRE MESH SUPPORT FENCE MAY BE ELIMINATED. IN SUCH A
CASE, THE FILTER FABRIC IS STAPLED OR WIRED DIRECTLY TO THE POSTS WITH ALL
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OTHER PROVISIONS OF ABOVE NOTES APPLYING.
7.FILTER FABRIC FENCES SHALL NOT BE REMOVED BEFORE THE UPSLOPE AREA HAS
BEEN PERMANENTLY STABILIZED.
8.FILTER FABRIC FENCES SHALL BE INSPECTED IMMEDIATELY AFTER EACH RAINFALL
AND AT LEAST DAILY DURING PROLONGED RAINFALL. ANY REQUIRED REPAIRS SHALL
BE MADE IMMEDIATELY.
9. SILT FENCES WILL BE INSTALLED PARALLEL TO ANY SLOPE CONTOURS.
10. CONTRIBUTING LENGTH TO FENCE WILL NOT BE GREATER THAN 100 FEET,
11. DO NOT INSTALL BELOW AN OUTLET PIPE OR WEIR.
12. INSTALL DOWNSLOPE OF EXPOSED AREAS.
13. DO NOT DRIVE OVER OR FILL OVER SILT FENCES.
8.0 PERMANENT EROSION CONTROL AND SITE RESTORATION
Site restoration and permanent erosion control includes a gravel surfaced driveway, and
stabilization of exposed soils with vegetation. Due to the adequate amount of topsoil,
additional topsoiling and/ or mulching may not be necessary. Specific details regarding
permanent erosion are illustrated on the engineered plans and specifications.
9.0 INSPECTION AND MAINTENANCE
The following subsections provides details regarding inspection and maintenance schedule,
inspection and maintenance responsibility.
Stabilized Construction Entrance
The stabilized construction entrance shall be inspected at reasonable increments. Increased
usage of the construction entrance warrants more frequent inspections. Additional rock
shall be added periodically to maintain proper function of the pad.
Silt Fence
All silt fencing shall be inspected immediately after each rainfall and at least daily during
prolonged rainfall. Any required repairs shall be made immediately.
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Permanent Vegetation
Permanent vegetation, shall initially be inspected regularly to insure establishment and
healthy growth. Once established, vegetation may need to be periodically fertilized for
continuous growth. Vegetation shall be re-established in areas, if necessary.
9.1 Inspection and Maintenance Schedule
While active construction is in process, all temporary erosion and sediment control
facilities shall be inspected and immediately maintained if necessary per the requirements
provided above and on the plan sheets. In the event that construction activities are
discontinued for at least 4 consecutive days, the owner shall be responsible for the
inspection, and immediate maintenance if necessary, of all temporary erosion and sediment
control facilities immediately after storm events, and at least once every 7 days.
In addition to the aforementioned inspection and maintenance schedule, the owner shall
install additional erosion and sediment control facilities if proposed erosion and sediment
control measures prove to be inadequate.
9.2 Inspection and Maintenance Responsibility
Inspection and maintenance of all temporary erosion and sedimentation control facilities
shall ultimately be the responsibility of the following owner or assigned representative:
Jeff and Pam Werdall
PO Box 2517
Belfair, Washington 98528
10.0 CONTROL OF POLLUTANTS OTHER THAN SEDIMENTS
Potential source of pollutants may occur from spills, leaks, excessive usage, ordinary
usage, or vandalism of several pollutants including the following:
• Fuel/Oil
• Solvent/Degreaser
• Dust
• Pesticide
• Herbacide
• Fertilizer
• Other Chemicals
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Fax: 360-275-4789 Parcel No. 12216 21 00001
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None of these pollutants are expected to originate from existing property conditions. The
proposed development is expected to include typical single family activities. Average daily
traffic is expected to be no more than 10 for the proposed Project. The proposed green
area should be sufficient for controlling pollutants generated on-site due to the proposed
site conditions.
Additional pollutant sources during construction are possible. The potential sources of
pollution with regards to the proposed development may be released into the stormwater.
Control of pollutants other than sediments include the following:
• All pollutants other than sediments shall be handled and disposed of in a
manner that does not cause contamination of stormwater.
• Cover, containment and protection from vandalism shall be provided for all
chemicals, liquid products, petroleum products, and non-inert wastes present
on the project site.
• Maintenance and repair of heavy equipment and vehicles involving oil changes,
hydraulic system drain down, solvent and de-greasing cleaning operations, fuel
tank drain down and removal, and other activities which may result in
discharge or spillage of pollutants to the ground or into stormwater runoff
must be conducted using spill prevention measures, such as drip pans.
Contaminated surfaces shall be cleaned immediately following any discharge or
spill incident. Emergency repairs may be performed on-site using temporary
plastic placed beneath and, if raining, over the vehicle.
• Wheel wash or tire bath wastewater shall be discharged to a separate on-site
treatment system or to the sanitary sewer, if available.
• Application of agricultural chemicals including fertilizers and pesticides shall be
conducted in a manner, and at application rates that will not result in loss of
chemical to stormwater runoff. Manufacturers' recommendations for
application rates and procedures shall be followed.
11.0 PROJECT ENGINEER'S CERTIFICATION
I hereby state that this drainage, erosion/ sediment control & pollution prevention plan for
Werdall Logging and Single Family Residence has been prepared by me or under my
supervision and meets the standard of care and expertise which is usual and customary in
this community for professional engineers.
- --- -------------------------------------------- --
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Fax: 360-275-4789 Parcel No. 12216 21 00001
May 5, 2008
Please contact Michael Staten at 360-275-9374 if you have any questions, comments, or
require additional information.
Sincerely,
Envirotech Engineering
EL cLYDp S
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EXPIRES JAN 10,2009
Michael Staten, P.E.
Project Manager
Envirotech Engineering Drainage Report
Ph. 360-275-9374 Page 10 of 10 Werdall Single Family Residence
Fax: 360-275-4789 Parcel No. 12216 2100001
May 5, 2008
APPENDIX A
HYDROLOGIC INFORMATION
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Single Event Hydrograph Method summo emina" is staraae
w, bottom width (ft) -"3
input condition 1 condition 2 I, length of trench (ft) UOL; 1 0
Design Storm 100yr-24hr d, trench depth (ft) 3
P, precipitation depth (in) T4 reduction of storage due to rock (%) 50
CN, curve number 56-- 98 s, trench slope (ft/ft) 0.01
v, trench volume (cf) 1140
Al, proposed area of change (so 49W 0
L1, flow length (ft) 500 0 SCS trench storage
L2, flow length (ft) 0 0 volume out Infiltration drawdown net volume(available space)
s1, slope (ft/ft) 0.27 0.01 (cf) (cfs) (hr) (co
s2, slope (ft/ft) 0 0 5858.38 0.055 29.74 Total
R, hydraulic radius OA ' 0.1 1181.9267 0.055 6 857.3329
n, Manning's roughness coeff. 0.011 2363.8533 0.055 12 574.6658
3545.78 0.055 18 291.9987
f, infiltration rate (in/hr) 0 3939.7556 0.055 20 197.7763
d, subsurface distance (ft) 3 0 distance from bottom of 4333.7311 0.055 22 103.5539
pond to impermeable, 4530.7189 0.055 23 56.44277
output water, or different soil 4727.7067 0.055 24 9.331582
SCS Curve Number Equations
S= 8.18 0.20 Max. natural detention due to infiltration, storage, etc. Condition 1, 2 (in) S=1000/CN-10
Qd = 1.75 6.16 Runoff depth over area for condition 1, 2 (in)
V= 5858.38 0.00 Runoff volume for condition 1, 2 (cubic feet)
Total Volume
k= 0.80 29.16 time of concentration velocity factor(ft/sec) k=(1.49*R^0.667)/n
v1= 0.42 2.92 velocity of flow(ft/sec) v=k*SQRT(s)
v2= 0.00 0.00 velocity of flow(ft/sec)
Tt1= 20.00 0.00 Travel time (min) Tt=U(60*v)
Tt2= 0.00 0.00 Travel time (min)
Tc= 20.00 0.00 Time of concentration (min) Tc=Tt1+Tt2+....Ttm
w= 0.20 1.00 routing constant w=dt/(2Tc+dt)
Santa Barbara Urban H dro ra h Method Add Snowmelt Factor to h eto ra h if elevation is above 1000 feet
Condition 1 Condition 2 Total
Time Type IA Rainfall Incre. Rain accu. Rain Accum. Incre. Tot. Runoff It Des. Flow Accum. Incre. Tot. Runoff It Des. Flow Des. Flow
hr Distribution dec. in in Runoff in Runoff in in cfs Rate cfs Runoff in Runoff in in cfs Rate cfs Rate cfs
0.0 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
0.2 0.004 0.026 0.026 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
0.3 0.004 0.026 0.051 0.000 0.000 0.000 0.000 0.000 0.001 0.001 0.001 0.000 0.000 0.000
0.5 0.004 0.026 0.077 0.000 0.000 0.000 0.000 0.000 0.005 0.005 0.005 0.000 0.000 0.000
0.7 0.004 0.026 0.102 0.000 0.000 0.000 0.000 0.000 0.014 0.009 0.009 0.000 0.000 0.000
0.8 0.004 0.026 0.128 0.000 0.000 0.000 0.000 0.000 0.026 0.012 0.012 0.000 0.000 0.000
1.0 0.004 0.026 0.154 0.000 0.000 0.000 0.000 0.000 0.040 0.014 0.014 0.000 0.000 0.000
1.2 0.004 0.026 0.179 0.000 0.000 0.000 0.000 0.000 0.056 0.016 0.016 0.000 0.000 0.000
1.3 0.004 0.026 0.205 0.000 0.000 0.000 0.000 0.000 0.073 0.017 0.017 0.000 0.000 0.000
1.5 0.004 0.026 0.230 0.000 0.000 0.000 0.000 0.000 0.091 0.018 0.018 0.000 0.000 0.000
1.7 0.004 0.026 0.256 0.000 0.000 0.000 0.000 0.000 0.110 0.019 0.019 0.000 0.000 0.000
1.8 0.005 0.032 0.288 0.000 0.000 0.000 0.000 0.000 0.135 0.025 0.025 0.000 0.000 0.000
2.0 0.005 0.032 0.320 0.000 0.000 0.000 0.000 0.000 0.161 0.026 0.026 0.000 0.000 0.000
2.2 0.005 0.032 0.352 0.000 0.000 0.000 0.000 0.000 0.188 0.027 0.027 0.000 0.000 0.000
2.3 0.005 0.032 0.384 0.000 0.000 0.000 0.000 0.000 0.215 0.027 0.027 0.000 0.000 0.000
2.5 0.005 0.032 0.416 0.000 0.000 0.000 0.000 0.000 0.243 0.028 0.028 0.000 0.000 0.000
2.7 0.005 0.032 0.448 0.000 0.000 0.000 0.000 0.000 0.271 0.028 0.028 0.000 0.000 0.000
2.8 0.006 0.038 0.486 0.000 0.000 0.000 0.000 0.000 0.306 0.034 0.034 0.000 0.000 0.000
3.0 0.006 0.038 0.525 0.000 0.000 0.000 0.000 0.000 0.340 0.035 0.035 0.000 0.000 0.000
3.2 0.006 0.038 0.563 0.000 0.000 0.000 0.000 0.000 0.376 0.035 0.035 0.000 0.000 0.000
3.3 0.006 0.038 0.602 0.000 0.000 0.000 0.000 0.000 0.411 0.036 0.036 0.000 0.000 0.000
3.5 0.006 0.038 0.640 0.000 0.000 0.000 0.000 0.000 0.447 0.036 0.036 0.000 0.000 0.000
3.7 0.006 0.038 0.678 0.000 0.000 0.000 0.000 0.000 0.483 0.036 0.036 0.000 0.000 0.000
3.8 0.007 0.045 0.723 0.000 0.000 0.000 0.000 0.000 0.525 0.042 0.042 0.000 0.000 0.000
4.0 0.007 0.045-- 0.768 0.000 0.000 0.000 0.000 0.000 0.568 0.043 0.043 0.000 0.000 0.000
4.2 0.007 0.045 0.813 0.000 0.000 0.000 0.000 0.000 0.611 0.043 0.043 0.000 0.000 0.000
4.3 0.007 0.045 0.858 0.000 0.000 0.000 0.000 0.000 0.654 0.043 0.043 0.000 0.000 0.000
4.5 0.007 0.045 0.902 0.000 0.000 0.000 0.000 0.000 0.697 0.043 0.043 0.000 0.000 0.000
4.7 0.007 0.045 0.947 0.000 0.000 0.000 0.000 0.000 0.740 0.043 0.043 0.000 0.000 0.000
4.8 0.008 0.052 1.000 0.000 0.000 0.000 0.000 0.000 0.791 0.051 0.051 0.000 0.000 0.000
5.0 0.008 0.052 1.052 0.000 0.000 0.000 0.000 0.000 0.842 0.051 0.051 0.000 0.000 0.000
5.2 0.008 0.052 1.105 0.000 0.000 0.000 0.000 0.000 0.893 0.051 0.051 0.000 0.000 0.000
5.3 0.008 0.052 1.157 0.000 0.000 0.000 0.000 0.000 0.944 0.051 0.051 0.000 0.000 0.000
5.5 0.008 0.052 1.210 0.000 0.000 0.000 0.000 0.000 0.995 0.051 0.051 0.000 0.000 0.000
5.7 0.008 0.052 1.262 0.000 0.000 0.000 0.000 0.000 1.046 0.051 0.051 0.000 0.000 0.000
5.8 0.010 0.061 1.323 0.000 0.000 0.000 0.000 0.000 1.106 0.060 0.060 0.000 0.000 0.000
6.0 0.010 0.061 1.384 0.000 0.000 0.000 0.000 0.000 1.166 0.060 0.060 0.000 0.000 0.000
6.2 0.010 0.061 1.444 0.000 0.000 0.000 0.000 0.000 1.225 0.060 0.060 0.000 0.000 0.000
6.3 0.010 0.061 1.505 0.000 0.000 0.000 0.000 0.000 1.285 0.060 0.060 0.000 0.000 0.000
6.5 0.010 0.061 1.566 0.000 0.000 0.000 0.000 0.000 1.345 0.060 0.060 0.000 0.000 0.000
6.7 0.010 0.061 1.627 0.000 0.000 0.000 0.000 0.000 1.405 0.060 0.060 0.000 0.000 0.000
6.8 0.013 0.086 1.713 0.001 0.001 0.001 0.004 0.001 1.490 0.085 0.085 0.000 0.000 0.001
7.0 0.013 0.086 1.798 0.003 0.002 0.002 0.014 0.004 1.575 0.085 0.085 0.000 0.000 0.004
7.2 0.013 0.086 1.884 0.007 0.004 0.004 0.023 0.010 1.660 0.085 0.085 0.000 0.000 0.010
7.3 0.018 0.115 1.999 0.015 0.008 0.008 0.045 0.020 1.774 0.114 0.114 0.000 0.000 0.020
7.5 0.018 0.115 2.115 0.026 0.011 0.011 0.061 0.033 1.888 0.114 0.114 0.000 0.000 0.033
7.7 0.034 0.218 2.332 0.055 0.028 0.028 0.157 0.063 2.104 0.216 0.216 0.000 0.000 0.063
7.8 0.054 0.346 2.678 0.118 0.063 0.063 0.351 0.140 2.448 0.344 0.344 0.000 0.000 0.140
8.0 0.027 0.173 2.851 0.157 0.039 0.039 0.219 0.198 2.619 0.172 0.172 0.000 0.000 0.198
8.2 0.018 0.115 2.966 0.186 0.029 0.029 0.161 0.195 2.734 0.115 0.115 0.000 0.000
8.3 0.013 0.086 3.052 0.209 0.023 0.023 0.127 0.174 2.820 0.085 0.085 0.000 0.000 0.174
8.5 0.013 0.086 3.137 0.233 0.024 0.024 0.134 0.157 2.905 0.085 0.085 0.000 0.000 0.157
8.7 0.013 0.086 3.223 0.258 0.025 0.025 0.140 0.149 2.990 0.085 0.085 0.000 0.000 0.149
8.8 0.009 0.056 3.279 0.275 0.017 0.017 0.095 0.136 3.047 0.056 0.056 0.000 0.000 0.136
9.0 0.009 0.056 3.336 0.292 0.017 0.017 0.097 0.120 3.103 0.056 0.056 0.000 0.000 0.120
9.2 0.009 0.056 3.392 0.310 0.018 0.018 0.100 0.112 3.159 0.056 0.056 0.000 0.000 0.112
9.3 0.009 0.056 3.448 0.329 0.018 0.018 0.102 0.107 3.215 0.056 0.056 0.000 0.000 0.107
9.5 0.009 0.056 3.505 0.347 0.019 0.019 0.105 0.106 3.271 0.056 0.056 0.000 0.000 0.106
9.7 0.009 0.056 3.561 0.367 0.019 0.019 0.107 0.106 3.327 0.056 0.056 0.000 0.000 0.106
9.8 0.009 0.056 3.617 0.386 0.020 0.020 0.109 0.107 3.383 0.056 0.056 0.000 0.000 0.107
10.0 0.009 0.056 3.674 0.406 0.020 0.020 0.111 0.108 3.440 0.056 0.056 0.000 0.000 0.108
10.2 0.009 0.056 3.730 0.427 0.020 0.020 0.114 0.110 3.496 0.056 0.056 0.000 0.000 0.110
10.3 0.009 0.056 3.786 0.447 0.021 0.021 0.116 0.112 3.552 0.056 0.056 0.000 0.000 0.112
10.5 0.009 0.056 3.843 0.469 0.021 0.021 0.118 0.114 3.608 0.056 0.056 0.000 0.000 0.114
10.7 0.009 0.056 3.899 0.490 0.022 0.022 0.120 0.116 3.664 0.056 0.056 0.000 0.000 0.116
10.8 0.007 0.046 3.945 0.508 0.018 0.018 0.100 0.114 3.710 0.046 0.046 0.000 0.000 0.114
Single Event Hydrograph Method 3> rllllrlrirwlrwse tre+�c�store
w, bottom width (ft)
Input condition 1 condition 2 I, length of trench (ft) 9887790
Design Storm 100yr-24hr d, trench depth (ft) 3
P, precipitation depth (in) reduction of storage due to rock (%) 50
CN, curve number s' 98 s, trench slope (ft/ft) 0.01
v, trench volume (cf) 1140
Al, proposed area of change (sf) 40M 0
L1, flow length (ft) 500 0 SCS trench storage
L2, flow length (ft) 0 0 volume out Infiltration drawdown net volume(available space)
s1, slope (ft/ft) 0.27 0.01 (cf) (cfs) (hr) (cf)
s2, slope (ft/ft) 0 0 5858.38 0.055 29.74 Total
R, hydraulic radius Q11r- 0.1 1181.9267 0.055 6 857.3329
n, Manning's roughness coeff. 0& 0.011 2363.8533 0.055 12 574.6658
3545.78 0.055 18 291.9987
f, infiltration rate (in/hr) 3 V 0 3939.7556 0.055 20 197.7763
d, subsurface distance (ft) 3 0 distance from bottom of 4333.7311 0.055 22 103.5539
pond to impermeable, 4530.7189 0.055 23 56.44277
Output water, or different soil 4727.7067 0.055 24 9.331582
SCS Curve Number Equations
S= 8.18 0.20 Max. natural detention due to infiltration, storage, etc. Condition 1, 2 (in) S=1000/CN-10
Qd = 1.75 6.16 Runoff depth over area for condition 1, 2 (in)
V= 5858.38 0.00 Runoff volume for condition 1, 2 (cubic feet)
W38 Total Volume
k= 0.80 29.16 time of concentration velocity factor(ft/sec) k=(1.49*R^0.667)/n
v1= 0.42 2.92 velocity of flow(ft/sec) v=k*SQRT(s)
v2= 0.00 0.00 velocity of flow (ft/sec)
Tt1= 20.00 0.00 Travel time (min) Tt=L/(60*v)
Tt2= 0.00 0.00 Travel time (min)
Tc= 20.00 0.00 Time of concentration (min) Tc=Tt1+Tt2+....Ttm
w= 0.20 1.00 routing constant w=dt/(2Tc+dt)
Santa Barbara Urban H dro ra h Method Add Snowmelt Factor to h eto ra h if elevation is above 1000 feet
Condition 1 Condition 2 Total
Time Type IA Rainfall Incre. Rain accu. Rain Accum. Incre. Tot. Runoff It Des. Flow Accum. Incre. Tot. Runoff It Des. Flow Des. Flow
hr Distribution dec. in in Runoff in Runoff in in cfs Rate cfs Runoff in Runoff in in cfs Rate cfs Rate cfs
0.0 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
0.2 0.004 0.026 0.026 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
0.3 0.004 0.026 0.051 0.000 0.000 0.000 0.000 0.000 0.001 0.001 0.001 0.000 0.000 0.000
0.5 0.004 0.026 0.077 0.000 0.000 0.000 0.000 0.000 0.005 0.005 0.005 0.000 0.000 0.000
0.7 0.004 0.026 0.102 0.000 0.000 0.000 0.000 0.000 0.014 0.009 0.009 0.000 0.000 0.000
0.8 0.004 0.026 0.128 0.000 0.000 0.000 0.000 0.000 0.026 0.012 0.012 0.000 0.000 0.000
1.0 0.004 0.026 0.154 0.000 0.000 0.000 0.000 0.000 0.040 0.014 0.014 0.000 0.000 0.000
1.2 0.004 0.026 0.179 0.000 0.000 0.000 0.000 0.000 0.056 0.016 0.016 0.000 0.000 0.000
1.3 0.004 0.026 0.205 0.000 0.000 0.000 0.000 0.000 0.073 0.017 0.017 0.000 0.000 0.000
1.5 0.004 0.026 0.230 0.000 0.000 0.000 0.000 0.000 0.091 0.018 0.018 0.000 0.000 0.000
1.7 0.004 0.026 0.256 0.000 0.000 0.000 0.000 0.000 0.110 0.019 0.019 0.000 0.000 0.000
1.8 0.005 0.032 0.288 0.000 0.000 0.000 0.000 0.000 0.135 0.025 0.025 0.000 0.000 0.000
2.0 0.005 0.032 0.320 0.000 0.000 0.000 0.000 0.000 0.161 0.026 0.026 0.000 0.000 0.000
2.2 0.005 0.032 0.352 0.000 0.000 0.000 0.000 0.000 0.188 0.027 0.027 0.000 0.000 0.000
2.3 0.005 0.032 0.384 0.000 0.000 0.000 0.000 0.000 0.215 0.027 0.027 0.000 0.000 0.000
2.5 0.005 0.032 0.416 0.000 0.000 0.000 0.000 0.000 0.243 0.028 0.028 0.000 0.000 0.000
2.7 0.005 0.032 0.448 0.000 0.000 0.000 0.000 0.000 0.271 0.028 0.028 0.000 0.000 0.000
2.8 0.006 0.038 0.486 0.000 0.000 0.000 0.000 0.000 0.306 0.034 0.034 0.000 0.000 0.000
3.0 0.006 0.038 0.525 0.000 0.000 0.000 0.000 0.000 0.340 0.035 0.035 0.000 0.000 0.000
3.2 0.006 0.038 0.563 0.000 0.000 0.000 0.000 0.000 0.376 0.035 0.035 0.000 0.000 0.000
3.3 0.006 0.038 0.602 0.000 0.000 0.000 0.000 0.000 0.411 0.036 0.036 0.000 0.000 0.000
3.5 0.006 0.038 0.640 0.000 0.000 0.000 0.000 0.000 0.447 0.036 0.036 0.000 0.000 0.000
3.7 0.006 0.038 0.678 0.000 0.000 0.000 0.000 0.000 0.483 0.036 0.036 0.000 0.000 0.000
3.8 0.007 0.045 0.723 0.000 0.000 0.000 0.000 0.000 0.525 0.042 0.042 0.000 0.000 0.000
4.0 0.007 0.045 0.768 0.000 0.000 0.000 0.000 0.000 0.568 0.043 0.043 0.000 0.000 0.000
4.2 0.007 0.045 0.813 0.000 0.000 0.000 0.000 0.000 0.611 0.043 0.043 0.000 0.000 0.000
4.3 0.007 0.045 0.858 0.000 0.000 0.000 0.000 0.000 0.654 0.043 0.043 0.000 0.000 0.000
4.5 0.007 0.045 0.902 0.000 0.000 0.000 0.000 0.000 0.697 0.043 0.043 0.000 0.000 0.000
4.7 0.007 0.045 0.947 0.000 0.000 0.000 0.000 0.000 0.740 0.043 0.043 0.000 0.000 0.000
4.8 0.008 0.052 1.000 0.000 0.000 0.000 0.000 0.000 0.791 0.051 0.051 0.000 0.000 0.000
5.0 0.008 0.052 1.052 0.000 0.000 0.000 0.000 0.000 0.842 0.051 0.051 0.000 0.000 0.000
r
5.2 0.008 0.052 1.105 0.000 0.000 0.000 0.000 0.000 0.893 0.051 0.051 0.000 0.000 0.000
5.3 0.008 0.052 1.157 0.000 0.000 0.000 0.000 0.000 0.944 0.051 0.051 0.000 0.000 0.000
5.5 0.008 0.052 1.210 0.000 0.000 0.000 0.000 0.000 0.995 0.051 0.051 0.000 0.000 0.000
5.7 0.008 0.052 1.262 0.000 0.000 0.000 0.000 0.000 1.046 0.051 0.051 0.000 0.000 0.000
5.8 0.010 0.061 1.323 0.000 0.000 0.000 0.000 0.000 1.106 0.060 0.060 0.000 0.000 0.000
6.0 0.010 0.061 1.384 0.000 0.000 0.000 0.000 0.000 1.166 0.060 0.060 0.000 0.000 0.000
6.2 0.010 0.061 1.444 0.000 0.000 0.000 0.000 0.000 1.225 0.060 0.060 0.000 0.000 0.000
6.3 0.010 0.061 1.505 0.000 0.000 0.000 0.000 0.000 1.285 0.060 0.060 0.000 0.000 0.000
6.5 0.010 0.061 1.566 0.000 0.000 0.000 0.000 0.000 1.345 0.060 0.060 0.000 0.000 0.000
6.7 0.010 0.061 1.627 0.000 0.000 0.000 0.000 0.000 1.405 0.060 0.060 0.000 0.000 0.000
6.8 0.013 0.086 1.713 0.001 0.001 0.001 0.004 0.001 1.490 0.085 0.085 0.000 0.000 0.001
7.0 0.013 0.086 1.798 0.003 0.002 0.002 0.014 0.004 1.575 0.085 0.085 0.000 0.000 0.004
7.2 0.013 0.086 1.884 0.007 0.004 0.004 0.023 0.010 1.660 0.085 0.085 0.000 0.000 0.010
7.3 0.018 0.115 1.999 0.015 0.008 0.008 0.045 0.020 1.774 0.114 0.114 0.000 0.000 0.020
7.5 0.018 0.115 2.115 0.026 0.011 0.011 0.061 0.033 1.888 0.114 0.114 0.000 0.000 0.033
7.7 0.034 0.218 2.332 0.055 0.028 0.028 0.157 0.063 2.104 0.216 0.216 0.000 0.000 0.063
7.8 0.054 0.346 2.678 0.118 0.063 0.063 0.351 0.140 2.448 0.344 0.344 0.000 0.000 0.140
8.0 0.027 0.173 2.851 0.157 0.039 0.039 0.219 0.198 2.619 0.172 0.172 0.000 0.000
8.2 0.018 0.115 2.966 0.186 0.029 0.029 0.161 0.195 2.734 0.115 0.115 0.000 0.000 0.195
8.3 0.013 0.086 3.052 0.209 0.023 0.023 0.127 0.174 2.820 0.085 0.085 0.000 0.000 0.174
8.5 0.013 0.086 3.137 0.233 0.024 0.024 0.134 0.157 2.905 0.085 0.085 0.000 0.000 0.157
8.7 0.013 0.086 3.223 0.258 0.025 0.025 0.140 0.149 2.990 0.085 0.085 0.000 0.000 0.149
8.8 0.009 0.056 3.279 0.275 0.017 0.017 0.095 0.136 3.047 0.056 0.056 0.000 0.000 0.136
9.0 0.009 0.056 3.336 0.292 0.017 0.017 0.097 0.120 3.103 0.056 0.056 0.000 0.000 0.120
9.2 0.009 0.056 3.392 0.310 0.018 0.018 0.100 0.112 3.159 0.056 0.056 0.000 0.000 0.112
9.3 0.009 0.056 3.448 0.329 0.018 0.018 0.102 0.107 3.215 0.056 0.056 0.000 0.000 0.107
9.5 0.009 0.056 3.505 0.347 0.019 0.019 0.105 0.106 3.271 0.056 0.056 0.000 0.000 0.106
9.7 0.009 0.056 3.561 0.367 0.019 0.019 0.107 0.106 3.327 0.056 0.056 0.000 0.000 0.106
9.8 0.009 0.056 3.617 0.386 0.020 0.020 0.109 0.107 3.383 0.056 0.056 0.000 0.000 0.107
10.0 0.009 0.056 3.674 0.406 0.020 0.020 0.111 0.108 3.440 0.056 0.056 0.000 0.000 0.108
10.2 0.009 0.056 3.730 0.427 0.020 0.020 0.114 0.110 3.496 0.056 0.056 0.000 0.000 0.110
10.3 0.009 0.056 3.786 0.447 0.021 0.021 0.116 0.112 3.552 0.056 0.056 0.000 0.000 0.112
10.5 0.009 0.056 3.843 0.469 0.021 0.021 0.118 0.114 3.608 0.056 0.056 0.000 0.000 0.114
10.7 0.009 0.056 3.899 0.490 0.022 0.022 0.120 0.116 3.664 0.056 0.056 0.000 0.000 0.116
10.8 0.007 0.046 3.945 0.508 0.018 0.018 0.100 0.114 3.710 0.046 0.046 0.000 0.000 0.114