HomeMy WebLinkAbout921185001 Stormwater Mgmt STORMWATER SITE PLAN
KENNETH AND MARTHA SMITH RESIDENCE
266 EAGLE RIDGE DR.
PORT HADLOCK, WA 98339
PARCEL NUMBER 921-185-001
Proponent
Kenneth and Martha Smith
2620 Kingsbridge Circle
Anchorage, Alaska 99504
Representative
Larry Johnson and Rob Gruye
Discovery Bay Construction
PO Box 1410
Port Townsend, WA 98368
(360) 385-4372
DEPT, OF COMiv ~: '~ "OvELOPMENT
iEXPIRES 3/28/0 q "]
~. z- o~ : APPROVED
Eric Page, P.E.
Willman Engineering, Inc. ~Y
PO Box 1375
Pon Hadlock, WA 98339 l~~~_~_ [
(360) 379-9661 ~n. ~ ~~~~
May 2, 2002
TABLE OF CONTENTS,,
L PROJECT OVERVIEW ...............................................................................................................
IL PLOT PLAN - (SEE ATTACHED STORMWATER AND TESC PLAN) ..................................
IlL CONDITIONS SUMMARY .........................................................................................................
IV. OFF SITE ANALYSIS .................................................................................................................. 3
V. ANALYSIS AND DESIGN OF STORMWATER FACILITIES ................................................. 4
VL SPECIAL REPORTS AND STUDIES ......................................................................................... 4
VH. BASIN AND COMMUNITY PLANNING AREAS ..................................................................... 4
VIII. OTHER PERMITS ....................................................................................................................... 4
IX. EROSION AND SEDIMENT CONTROL PLAN ........................................................................ 4
LARGE PARCEL EROSION AND SEDIMENT CONTROL PLAN ............................................... 4
PERMANENT STOtLMWATER QUALITY CONTROL PLAN ..................................................... 8
X. BOND QUANTITIES WORKSHEET .......................................................................................12
XL MAINTENANCE AND OPERATIONS ..................................................................................... 13
APPENDIX 'A' PROJECT VICINITY MAP
APPENDIX 'B' SOIL CONSERVATION SERVICE PROJECT AREA MAP
AND SOILS INFORMATION
APPENDIX 'C' HYDROLOGICAL CALCULATIONS
AND TIME OF CONCENTRATION CHART
APPENDIX 'D' INTERCEPTOR SWALE SIZING CALCULATIONS
APPENDIX 'E' CONVEYANCE PIPE SIZING CALCULATIONS
APPENDIX 'F' FLOW SPREADER TRENCH SIZING CALCULATIONS
ATTACHMENT STORMWATER AND TESC PLAN
I. PROJECT OVERVIEW
The applicant proposes construction of a single-family residence, garage, residential
landscaping, and appurtenances on a parcel with an area of 4.90 acres. The property is
described as Lot 1 of Eagle Ridge Large Lot Subdivision with Assessor's Parcel Number
921-185-001, and is accessed from Eagle Ridge Dr.
II. PLOT PLAN - (See Attached Stormwater and TESC Plan)
III. CONDITIONS SUMMARY
The existing ground in the proposed development area slopes from west to east, at slopes
ranging from seven to thirty percent. The elevations and orientations are similar to
adjacent properties to the north and south. The parcel has been logged, and is currently
vegetated with young second-growth deciduous trees and conifers.
The parcel contains no improvements with the exception of an existing dirt road. This
road begins at the proposed driveway entrance off of Eagle Ridge Dr. and wyes,
extending to the proposed home site and to the northwest comer of the parcel.
Surface Soil Conditions
The site soils are mapped in the Soil Survey of the Jefferson County Area, Washington,
August 1975, by the Soil Conservation Service (SCS). The soil type mapped in the
project vicinity is Clallam gravelly sandy loam (CmD). The SCS describes Clallam
gravelly sandy loam as a well-drained soil with a very slowly permeable layer at a depth
of twenty to forty inches. The SCS description of Clallam gravelly sandy loam is as
follows: The upper 23 inches of the soil is gravelly sandy loam that is grayish brown in
the upper three inches and dark grayish brown in the lower twenty inches. This is
underlain by a cemented layer.
Storm Drainage
Currently, and historically, stormwater enters the proposed development area from the
west and exits the parcel to the east as shallow sheet flow, and likely subsurface flow.
IV. OFF SITE ANALYSIS
Stormwater from the proposed development area will be routed to a stormwater dispersal
trench. Any overflow from this trench will be directed overland through a vegetated
buffer toward the parcel's east property line. This vegetated buffer is approximately 700
feet in length, therefore this project is not anticipated to impact the adjacent right-of-way
to the east. Water quality and quantity concerns will be addressed through dispersal of
the stormwater into this buffer. After permanent vegetation is established, exposed soils
will be minimized and risk of erosion from the project will be minimal.
V. ANALYSIS AND DESIGN OF STORMWATER FACILITIES
Stormwater runoff from the area proposed for development will be collected and routed
through surface swales, catch basins, and storm drainage piping. All collected and
controlled water will be directed into a stormwater flow dispersal trench. Prudent actions
and maintenance of facilities will ensure long term water quality.
The project alters approximately 1.20 acres of site cover, and site impervious area will be
approximately 7,000 s.f. (3.3 percent of the total parcel area). A Large Parcel Erosion
and Sediment Control Plan and Permanent Stormwater Quality Control Plan have been
developed, to the standards of the Stormwater Management Manual for the Puget Sound
Basin (SMM), February 1992 edition, and made a part of this report.
VI. SPECIAL REPORTS AND STUDIES
There are no other known special reports or studies relevant to this specific parcel.
VII. BASIN AND COMMUNITY PLANNING AREAS
There is no known basin plan for this locale.
VIII. OTHER PERMITS
A. An on-site septic system permit application has been prepared and submitted by
John Scott Fleming Engineering, Inc..
B. A building permit together with associated ntility work permits will be required
for the construction of the new home.
IX. EROSION AND SEDIMENT CONTROL PLAN
The total area of the site that will be disturbed is slightly greater than one acre. Further,
the project will create more than 5,000 square feet of impervious area. Minimum
Requirements #1 of Section 1-2.5, and Requirements #2 through #11 of Sections 1-2.6
through 1-2.15 of the SMM are therefore applicable. The Large Parcel Erosion and
Sediment Control Plan (LPESC) included here addresses Minimum Requirement #1. The
Permanent Stormwater Quality Control Plan (PSQC) included here addresses Minimum
Requirement #2 through # 11.
Lar.qe Parcel Erosion and Sediment Control Plan
This LPESC plan addresses the fifteen items required under Minimum Requirement #1,
Erosion and Sediment Control.
MINIMUM REQU1RE~NT #1: EROSION AND SEDIMENT CONTROL
Because the project includes land disturbing activity of' greater than one acre, Minimum
Requirements #1 through #15 of section I-2.5 apply:
1. Stabilization and Sediment Trapping
Criteria: All exposed and unworked soils shall be stabilized by suitable
application of BMPs. From October 1 to April 30, no soils shall remain
unstabilized for more than 2 days. From May 1 to September 30, no soils shall
remain unstabilized for more than 7 days. Prior to leaving the site, stormwater
runoff shall pass through a sediment pond or sediment trap, or other appropriate
It is believed that due to the permeable nature of the site soils, erosion is not
occurring at a fast rate. Prudent actions for continued stabilization for this area
include timing of excavations to occur during the dryer portions of the year,
covering of stockpiles of materials with visqueen sheeting during periods of
precipitation, and stabilization of' site soils with seeding and mulching as
necessary.
For the excavation of the home foundation, a silt fence will not need to be erected
around the lower portions of the excavation due to the presence of the vegetated
buffer. Any soils stockpiles will be erodible given steep slope of the spoils and
loose conditions, and should be covered with visqueen during inclement weather.
Inlet filters are required for the catch basins and yard drains.
Those areas that are disturbed, outside of the actual parking and building areas,
will be revegetated by seeding and/or landscaping concurrent with the final
grading and cleanup operations. Additional measures such as straw bale barriers
or silt fences will be employed as needed during construction.
2. Delineate Clearing and Easement Limits
Criteria: In the J~elc~ mark clearing limits and/or any easements, setbacks,
sensitive/critical areas and their buffers, trees and drainage courses.
The extent of clearing and grading is limited to the areas proposed for
development as depicted on the stormwater site plan. Clearing limits and
setbacks to sensitive/critical areas will be delineated in the field prior to the start
of construction.
3. Protection of Adjacent Properties
Criteria: Properties adjacent to the project site shall be protected from sediment
deposition.
The site shall be monitored during storm events and BMPs, such as hay bales and
silt fences, will be employed as needed to protect the adjacent parcels.
4. Timing and Stabilization of Sediment Trapping Measures
Criteria: Sediment ponds and traps, perimeter dikes, sediment barriers, and
other BMPs intended to trap sediment on-site shall be constructed as a first step
in grading. These BMPs shall be functional before land disturbing activities take
place. Earthen structures such as dams, dikes, and diversions shall be seeded and
mulched according to the timing indicated in Erosion and Sediment Control
Requirement # 1.
Permanent vegetation shall be used to provide final stabilization of the facilities
concurrent with final grading and landscaping operations.
5. Cut and Fill Slopes
Criteria: Cut and fill slopes shall be designed and constructed in a manner that
will minimize erosion. In addition, slopes shall be stabilized in accordance with
Erosion and Sediment Control Requirement # 1.
The project will not have any significant cut and fill slopes.
6. Controlling Off-Site Erosion
Criteria: Properties and waterways downstream from development sites shall be
protected from erosion due to increases in the volume, velocity, and peak flow
rate of stormwater runoff from the project site.
See #1 and #3 above.
7. Stabilization of Temporary Conveyance Channels and Outlets
Criteria: All temporary on-site conveyance channels shall be designed,
constructed and stabilized to prevent erosion from the expected velocity of flow
from a 2-year, 24-hour frequency storm for the developed condition. Stabilization
adequate to prevent erosion of outlets, adjacent streambanks, slopes and
downstream reaches shall be provided at the outlets of all conveyance systems.
No temporary conveyance channels and outlets are anticipated for this project.
8. Storm Drain Inlet Protection
Criteria: All storm drain inlets made operable during construction shall be
protected so that storrnwater runoff shall not enter the conveyance system without
first beingfiltered or otherwise treated to remove sediment.
The storm drain catch basins shall be protected by filter fence as detailed and
straw bale dams to prevent silt laden water from entering the storm drainage
system.
9. Underground Utility Construction
Criteria: The construction of underground utility lines shall be subject to the
following criteria:
(i) Where feasible, no more than 500feet of trench shall be opened at one time.
(lO Where consistent with safely and space considerations, excavated material shall be placed on
the uphill side of trenches.
O'iO Trench dewatering devices shall discharge into a sediment trap or sediment pond.
Underground utility installation shall conform to the guidelines set forth in the
Washington State Department of Ecology Stormwater Management Manual for
the Puget Sound Basin, latest edition (SMM).
10. Construction Access Routes
Criteria: Wherever construction vehicle access routes intersect paved roads,
provisions must be made to minimize the transport of sediment (mud) onto the
paved road. If sediment is transported onto a road surface, the roads shall be
cleaned thoroughly at the end of each day. Sediment shall be removed from roads
by shoveling or sweeping and be transported to a controlled sediment disposal
area. Street washing shall be allowed only after sediment is removed in this
manner.
Access to the site is from Eagle Ridge Dr., a paved private road. A temporary
construction entrance is proposed for this project, as shown on the design plans.
11. Removal of Temporary BMPs
Criteria: Ail temporary erosion and sediment control BMPs sha. ll be remove~,~
within 30 days after final site stabilization is achieved or afl'er the tempo~'!:~'
BMPs are no longer needed Trapped sediment shall be removed or stabilized on
site. Disturbed soil areas resulting from removal shall be permanently stabilized
All temporary erosion and sediment control measures shall be removed within
thirty days of final site stabilization or after the temporary measures are no longer
needed. Trapped sediment shall be removed or stabilized on site. Disturbed soil
areas resulting from removal of temporary BMPs shall be permanently stabilized.
12. Dewatering Construction Sites
Criteria: Dewatering devices shall discharge into a sediment trap or sediment
pond.
Foundation drains will discharge through a catch basin to remove sediment from
the waters to be discharged.
13. control of Pollutants Other Than Sediment on Construction Sites
Criteria: All pollutants other than sediment that occur on-site during
construction shall be handled and disposed of in a manner that does not cause
contamination of stormwater.
All pollutants that occur on-site during construction shall be handled and disposed
of in a manner that does not cause contamination of stormwater and that is
consistent with Washington State Department of Ecology Requirements. We do
not anticipate other pollutants will be generated with this residential project,
however, we acknowledge that proper response and disposal is essential.
14. Maintenance
Criteria: All temporary and permanent erosion and sediment control BMPs shall
be maintained and repaired as needed to assure continued performance of their
intended function. All maintenance and repair shall be conducted in accordance
with an approved manual.
All temporary and permanent erosion and sediment control measures employed
shall be maintained and repaired as needed to insure continued performance of
their intended function. Ail maintenance and repair shall be conducted in
accordance with the requirements of the SWMM.
15. Financial Liability
Performance bonding, or other appropriate financial instruments, shall be
required for all projects to ensure compliance with the approved erosion and
sediment control plan.
Jefferson County is not requiring a performance bond for this project.
Permanent Stormwater Quality Control Plan
This PSQC plan addresses Minimum Requirements #2 through #11.
MINIMUM REQUIREMENT #2, PRESERVATION OF NATURAL DRAINAGE
SYSTEMS
Criteria: Natural drainage patterns shall be maintained, and discharges from the
site shall occur at the natural location, to the maximum extent practicable.
There are no natural drainage ways in the area proposed for development. Rather,
natural flow exits the parcel as sheet flow downslope of the proposed
development area. As it is the requirement to maintain the natural drainage
pattern, a stormwater dispersal trench will be used to return the groundwater and
stormwater runoff to the ground and the surface downslope of the proposed
development area.
MINIMUM REQUIREMENT #3, SOURCE CONTROL OF POLLUTION
Criteria: Source control BMPs shall be applied to all projects to the maximum
extent practicable. Source control BMPs shall be selected, designed, and
maintained according to an approved manual.
An adopted and implemented basin plan (Minimum Requirement #9) may be used
to develop source control requirements that are tailored to a specific basin,
however, in all circumstances, source control BMPs shall be required for all
sites.
During construction, proper maintenance of construction equipment, to eliminate
leaks and spills, as well as adherence to the erosion and sediment control
requirements as set forth in the LPESC Plan, should help alleviate the potential
for pollution.
At build-out, proper maintenance of stormwater facilities, in compliance with
Section XI of this report, as well as the proper application of nutrients and
pesticides to landscape areas should help lessen the potential for pollution on a
long term basis.
Only direct on-site stormwater runoff should be allowed to enter the stormwater
infiltration system. No other discharges should be allowed.
MINIMUM REQUIREMENT #4, RUNOFF TREATMENT BMPs
Criteria: All projects shall provide treatment of stormwater. Treatment BMPs
shall be sized to capture and treat the water quality design storm, defined as the
&month, 24-hour return period storm. The first priority for treatment shall be to
infiltrate as much as possible of the water quality design storm, only if site
conditions are appropriate and ground water quality will not be impaired. Direct
discharge of untreated stormwater to ground water is prohibited. All treatment
BMPs shall be selected, designed, and maintained according to an approved
manual.
Stormwater treatment BMPs shall not be built within a natural vegetated buffer,
except for necessary conveyance systems as approved by the local government.
An adopted and implemented basin plan (Minimum Requirement #9) may be used
to develop runoff treatment requirements that are tailored to a specific basin.
Surface runoff' from the proposed development area will be directed to a
stormwater dispersal trench as shown on the plan. This dispersal trench will act
as an infiltration trench for most storm events, and those events not infiltrated will
be dispersed as shallow sheet flow to the vegetated buffer downslope of the
proposed development area.
MINIMUM REQUIREMENT #5, STREAMBANK EROSION CONTROL
Criteria: The requirement below applies only to situations where stormwater
runoff is discharged directly or indirectly to a stream, and must be met in addition
to meeting the requirements in Minimum Requirement #4, Runoff Treatment
BMPs:
Stormwater discharges to streams shall control streambank erosion by limiting
the peak rate of runoff from individual development sites to 50 percent of the
existing condition 2-year, 24-hour design storm while maintaining the existing
condition peak runoff rate for the lO-year, 24-hour and l O0-year, 24-hour design
storms. As the first priority, streambank erosion control BMPs shall utilize
infiltration to the fullest extent practicable, only if site conditions are appropriate
and ground water quality is protected. Streambank erosion control BMPs shall be
selected, designed and maintained according to an approved manual.
Stormwater treatment BMPs shall not be built within a natural vegetated buffer,
except for necessary conveyance systems as approved by the local government.
An adopted and implemented basin plan (Minimum Requirement #9) may be used
to develop streambank erosion control requirements that are tailored to a specific
basin.
Not Applicable.
MINIMUM REQUIREMENT #6, WETLANDS
Criteria: The requirements below apply only to situations where stormwater
discharges directly or indirectly through a conveyance system into a wetland, and
must be met in addition to meeting the requirements in Minimum Standard #4,
Runoff Treatment BMPs.
(a) Stormwater discharges to wetlands must be controlled and treated to the extent necessary to meet
the State Water Quality Standards, Chapter. 173-201 WAC, or Ground Water Quality Standards,
Chapter. 173-200 WAC, as appropriate.
Discharges to wetlands shall maintain the hydroperiod and flows of existing site conditions to the
extent necessary to protect the characteristic uses of the wetland. Prior to discharging to a
wetland, alternative discharge locations shall be evaluated, and natural water storage and
infiltration opportunities outside the wetland shall be maximized.
(c) Created wetlands that are intended to mitigate for loss of wetland acreage, function and value
shall not be designed to also treat stormwater.
(~t) In order for constructed wetlands to be considered treatment systems, they must be constructed
on sites that are not wetlands and they must be managed for stormwater treatment. If these
systems are not managed and maintained in accordance with an approved manual for a period
exceeding three years these systems may no longer be considered constructed wetlands.
Discharges from constructed wetlands to waters of the state (including discharges to natural
wetlands) are regulated under Chapter. 90.48 RCW, Chapter. 173-201 WAC, and Chapter. 173-
200 WAC.
(e) Stormwater treatment BMPs shall not be built within a natural vegetated buffer, except for
necessary conveyance systems as approved by the local government.
10
An adopted and implemented basin plan (Minimum Requirement #9) may be used
to develop requirements for wetlands that are tailored to a specific basin.
Not Applicable.
MINIMUM REQUIREMENT//7, WATER QUALITY SENSITIVE AREAS
Criteria: Where local governments determine that the Minimum Requirements do
not provide adequate protection of water quality sensitive areas, either on-site or
within the basin, more stringent controls shall be required to protect water
quality.
Stormwater treatment BMPs shall not be built within a natural vegetated buffer,
except for necessary conveyance systems as approved by the local government.
An adopted and implemented basin plan (Minimum Requirement #9) may be used
to develop requirements for water quality sensitive areas that are tailored to a
specific basin.
Not Applicable.
MINIMUM REQUIREMENT//8, OFF-SITE ANALYSIS AND MITIGATION
Criteria: All development projects shall conduct an analysis of off-site water
quality impacts resulting from the project and shall mitigate these impacts. The
analysis shall extend a minimum of one-fourth of a mile downstream from the
project. 7he existing or potential impacts to be evaluated and mitigated shall
include, at a minimum, but not be limited to:
(0 excessive sedimentation
(iO streambank erosion
(~0 discharges to ground water contributing or [sic] recharge zones
(~v) violations of water quality standards
(v) spills and discharges of priority pollutants
(i) Excessive sedimentation
See Minimum Requirement #1, Erosion and Sediment Control, Items 1-! 5, found
in the LPESC Plan.
(ii) Streambank Erosion
Not Applicable.
(iii) Discharges to groundwater contributing or [sic] recharge zones
Not Applicable.
11
(iv) Violations of water quality standards
Runoff entering the stormwater system is not expected to contain significant
contaminants. Proper dispersion of this stormwater will minimize the potential
for violation of water quality standards.
(v) Spills and discharges of priority pollutants
Not Applicable.
MINIMLrM REQUIREMENT//9, BASIN PLANNING
Criteria: Adopted and implemented watershed-based basin plans may be used to
modify any or all of the Minimum Requirements, provided that the level of
protection for surface or ground water achieved by the basin plan will equal or
exceed that which wouM be achieved by the Minimum Requirements in the
absence of a basin plan. Basin plans shall evaluate and include, as necessary,
retrofitting of BMPs for existing development an/or redevelopment in order to
achieve watershed-wide pollutant reduction goals. Standards developed from
basin plans shall not modify any of the above requirements until the basin plan is
formally adopted and fully implemented by local government. Basin plans shall be
developed according to an approved manual.
Not Applicable.
MINIMUM REQUIREMENT #10, MAINTENANCE AND OPERATIONS
Criteria: An operation and maintenance schedule shall be provided for all
proposed stormwater facilities and BMPs, and the party (or parties) responsible
for maintenance an operation shall be identified
See Section XI, Maintenance and Operations, in this report.
MINIMUM REQUIILEMENT//11, FINANCIAL LIABILITY
Criteria: Performance bonding or other appropriate financial instruments shall
be required for all projects to ensure compliance with these standards.
Jefferson County is not requiring a performance bond for this project.
X. BOND QUANTITIES WORKSHEET
Not Applicable.
Xl. MAINTENANCE AND OPERATIONS
Temporary Erosion and Sediment Control BMPs:
Silt fences, inlet protections, and hay bale check dams as well as all other BM~s
employed shall be inspected and cleaned after each large storm event, or when necessary.
Silt and other material removed shall be disposed of in accordance with the guidelines
established in the SMM. All other temporary and permanent measures employed shall be
maintained in accordance with the SMM.
The measures represented in this report are considered to be the minimum required to
stabilize the site and protect adjacent properties. The project area should be closely
monitored and other BMPs employed as needed.
Permanent Stormwater Facilities - Flow dispersal trenches:
After construction, the area downslope of the flow dispersal trench should be planted to
aid in evaporating water and oxygenating the soil. Examples of appropriate vegetation
are as follows:
1. Native vegetation of ferns, salal, rhododendrons and the like are preferred
because they are not water seeking and they are low maintenance.
2. Grasses, clovers, wildflowers and other low-growing ground covers are
acceptable.
3. Marsh grasses, elderberry, willow, maple, and alder are not acceptable
because their root systems seek water and can damage the flow dispersal
system.
All vegetation should be kept trim and manageable. Sunlight and wind aid in
evapotranspiration, but overgrown tangles impede the process.
The flow dispersal trench area is not appropriate as a place for storage, buildings, etc.
Permanent Stormwater Facilities- Catch basins:
Catch basins shall be maintained and repaired as needed to assure continued performance
of their intended function. Catch basins have a history of maintenance-related problems
and it is imperative that a good maintenance program be established for the proper
functioning. A typical problem is that sediment builds up inside the basin, restricting
flow to the outlet or causing the sediment to bypass the catch basin' s sump and continue
downstream to the flow dispersal facilities. To prevent this problem, catch basins should
be routinely cleaned out when half of their sediment storage capacity is reached.
13
APPENDIX 'A'
PROJECT VICINITY MAP
VICINITY MAP
1' = 5000'
Hadlock
Scow
Rd.
Robbins Rd.
OAK
Chimacum ~ BAY
Eagle Ridge Dr.,x,~
PROJECT
SITE
APPENDIX 'B'
SOIL CONSERVATION SERVICE PROJECT AREA MAP
SOILS INFORMATION
JEFFERSON COUNTY AREA, WASHI
R. lW.i R. 1E.
' · 1 FEET
I (Joins sheet 52) I
production of trees and for wildlife habitat and recreation firm; few fine roots penetrate upper few inches; medium acid;
areas. Small areas, less than 10 percent of the total acreage, diffuse, smooth boundary (12 to 16 inches thick)
C2--36 inches, very compact gravelly sandy loam glacial till.
are under cultivation and are used for pasture and diversified (Many feet thick)
home garden crops. Capability unit IVe-3; woodland group
. 4d2. The A2 horizon ranges from gray to grayish brown. The B2
horizons range from grayish brown to dark grayish brown. The
Cathcart gravelly silt loam, 30 to 50 percent slopes Clsim horizon is an olive-gray cemented layer that is 35 to 45
(C[ E) .--This steep soil is on glaciated uplands. Along the percent gravel and cobbles. Depth to the cemented layer ranges
upper part. of the slopes bedrock is at a depth of 24 to 30 from 20 to 40 inches. The A2 and B2 horizons range from strongly
acid to medium acid, and the Clsim horizon ranges from medium
inches, and along the lower part of the slopes it is at a depth acid to slightly acid.
of 30 to 40 inches.
Runoff is rapid, and the hazard of water erosion is severe. This soil is well drained. Permeability is moderate above
This soil is used mainly for production of trees and for the cemented layer. Roots penetrate to a depth of 20 to 40
recreation areas and wildlife habitat. Capability unit Vie-l; inches. This soil holds about 2 to 4 inches of water available
woodland group 4d2. for plants. Runoff is slow to medium, and the hazard of water
erosion is slight to moderate. The soil is saturated part of
the time during the rainy season, and at times water moves
Clallarn Series laterally, in places, above the cemented layer.
The Clallam series consists of well-drained soils that have Most of the acreage of this soil is used for gro~4ng pasture
a very slowly permeable cemented layer at a depth of 20 to of mixed grass and alfalfa or grass and clover. Home garden
40 inches. They are on uplands. Slopes range from 0 to 30 crops, berries, and vegetables are also grown. Capability
percent. Elevation ranges from $0 to 1,000 feet. These soils unit IVe-1; woodland group 4d2.
formed in glacial till under a forest of mixed coniferous and Clallam gravelly sandy loam, 15 to 30 percent slopes
deciduous trees. Native vegetation is mainly Douglas-fir, (CmD).--This hilly soil is on glacial terraces on the breaks
cedar, madrone, and willow. Annual precipitation ranges of canyons and steep drainageways.
from 18 to 25 inches. The average annual air temperature is Runoff is medium, and the hazard of water erosion is
49°F. The above 32°F growing season ranges from 240 to moderate. This soil is used mainly for production of trees
270 days, and thc above 28°F growing season ranges from and for wildlife habitat and recreation areas. Capability
300 to 330 days. These soils are associated mainly with unit Vie-l; woodland group 4d2.
Alderwood, Dick, Everett, Hoypus, Indianola, San~ Juan,
To~send, and Whidbey soils. Coastal Beaches
In a representative profile a thin layer of organic litter
covers the surface. Thc upper 23 inches of the soil is gravelly Coastal beaches (Co & CW) consist of sandy and gravelly
sandy loam that is gra)~ish brown in the upper 3 inches and sloping beaches in long, narrow strips. They are at the base
dark gra~sh brown in the lower 20 inches. This is underlain of coastal bluffs or lowlands bordering thc Pacific Ocean in
by a cemented layer, western Jefferson County and along the Straits of Juan de
More than 60 percent of the acreage of Clallam soils has Fuca, Admiralty Inlet, and Hood Canal in eastern Jefferson
been cleared and is used for pasture, hay, silage, berries, County.
orchards, small grains, and vegetable gardens. Wooded areas Coastal beaches have no vegetation and are subject to
are used as a source of woodland products and for wildlife continual wave action during high tides and storms.
habitat and recreation areas. This land type is used for clam and oyster production and
Clallam gravelly sandy loam, 0 to 15 percent slopes for recreation areas and wildlife habitat. Capability unit
(CmC).--This nearly level to rolling soil is on terraces. VIIIw-1; not assigned to a woodland group.
Most slopes range from 5 to 10 percent.
Representative profile 1,650 feet west and 660 feet north Cut and Fill Land
of southeast corner sec. 17, T. 30 N., R. I W.'
Cut and fill land (Gu) consists of landfills in iow, depres-
O1--2 inches to ~ inch, leaves, needles, and twigs, sional, wet or swampy areas. It is made up of a mixture of
02--~ inch to 0, ve~' dark grasdsh-brown (10YR 3/2), decom-
posed organic matter; strongly acid. many types of soil material. One of the largest areas of Cut
A2--4) to 3 inches, grayish~brown (10YR 5/2)gravelly sandy loam, and fill land is at the southwest end of Old Fort Flagler,
light gray (2.5Y 7'2) and white (2.5Y 8/2) dry; weak, fine, between the marine bluffs and the beach, where a swampy
granular structure' slightly hard, very friable, nonsticky, non-
plastic; man); roo~s; about 20 percent gravel; medium acid; area was filled for a gunnery range. Capability unit VIIIw-1;
abrupt, wavy boundary. (2 to 4 inches thick) not assigned to a woodland group.
B21--3 to 14 inches, dark grayish-brown (2.5Y 4/2) gravelly sandy
loam, light brownish gray (2.5Y 6/2) dry; weak, fine and me-
dium, subangular blocky structure; slightly hard, very friable, Dabob Series
nonsticky, nonplastic; many roots; few fine shot; about 35
percent gravel; medium acid; clear, wavy boundary. (8 to 19 The Dabob series consists of moderately well drained,
roches thick) very gravelly soils that have a very slowly permeable ce-
B22--14 to 23 inches, dark grayish-brown (2.5Y 4/2) gravelly mented layer at a depth of 20 to 36 inches. These soils are
sandy loam, light, brownish gray (2.5Y 6/2) dry; weak, me- '
dium and coarse, subangular blocky structure; slightly hard, on glacial terraces. Slopes range from 0 to 30 percent. Ele-
very friable, nonsticky, nonplastic; common roots; about 40 vation ranges from 100 to 800 feet. Thc Dabob soils formed
percen1 gravel (including a few cobbles)' medium acid; gradual, under a coniferous-deciduous forest-in very gravelly glacial
waw, boundary. (7 to 18 inches thick) till. Native vegetation is mainly Douglas-~fir, western hem-
C]sim--2:-; t(, 3(; ~nc'h~, olive-gray (5Y 4/2), weakly cemented lock, willow, madrone, rhododendron, salal, and evergreen
gravelly sandy loam, light gray (5Y 7/2) dry; common, medium
and coarse, dark yellowish-brown (10YR 4,/4) and brown huckleberry. Annual precipitation ranges from 25 to 45
(7.sYR 4/4) motile- massive; extremely hard, extremely inches. The average annual air temperature is 49°F. The
APPENDIX 'C'
HYDROLOGICAL CALCULATIONS
TIME OF CONCENTRATION CHARTS
JOB
· ~ ,: mm' 'm ' SHEET NO OF
·
CALCULATED BY DATE
. .
ENGINEERING, INC.
SCALE
)..i......i' ...... ..................................................... i ili ................. i
· - i --] .................................................................................................. : .....................................................
.................................................... * ...................................
............ * ................ i ................. t ................ ~ ................. ~ ...... ; i ; ~ ~ i ~ .............. } .................. i ................. ~ ................. ? ................ i ........ ! .................. r ................
.............. ~ ................................. L..,......i ................. ~.x._o_.~~ ..... ~,~..~:_...~.i
........... : ............... r .................................................. ! .......................... ~- -" ~ J j ~ ' - -i i ' ' i ! i ............. 'r ................................. ! .......... {"~ .................. T .......... ? .................
.....................~__~x.~~..~ ~ ........ ~ ,-.~.~..~._~....¥.~,- ........... ~....~ .............. ~, ................ ~ .................................. ~.., ............. ?.. ................. ,,' .................. ~ ................. ~ ................. ~ .................. , ................. ~ ................. ~ ................. ~ ................. , .................. ~ .................. ~ ................
~ : ~ ? ................. ? ................ i ............... ! .................. T ................
................. i ..................................................................................... il..~,~c~v~o.~ r~~~ r_~_~ ,~ ,~-~.-.~-~).._.~. ............. .O.......~.~..~..u..a.~.......i .............
................ ~ ................. :~ ................................. ~i ................................. ~-~-~¢~..~.-.~--~-~!.-o-i.~..~o-.....-x.~.~-~.~...~.----- i--.'~
: ~ . . ......... ~ .......... ~ ...... ; ................ ~- ............~ ...................................................................... ~ ...............................
'"'. i'" .'.'.'""';'ii.;.' .' i'.'..,'.'Z.'h?.~'.Z;i!~'i-~d~.-* ............ ~.~.~b..~.~L...C.~..?
........... i .............................................................................................................................................................................. ~ .......................................................................................................................................... i .......................................................................................................................................... r ...............
.......... 4 ............................. i ................. - ......... ' ..............
141 OAK BAY ROAD/P.O. BOX 1375 PORT HADLOCK, WA 98339 360-379-9661 360-379-0150 FAX d; - (
·
JOB
·
· ' SHEET NO. OF
CALCULATED BY DATE ,,
ENGINEERING, INC. ~.~c~o.~.
SCALE
.................. : ; ......... ; ........................ f i .... ; ................. ~ .................. ................. : ................. ! .................. ~ .................
.................... : .......................................... ~ ~"i '1 ~.~ ~. I/~ il..- J
~ = : ,,~ , i,,, -m ~~ ~ _ · ·
:~ .......... ~ :: , = c~,,to_~i_~.~.~..~:.:~ ..............................................................
i
~ :. ~~o ~_~ .................... i ............. i .......... i ......... i ................. i .........
................................................ :: ............... ~ ~~~_.L ............................................ i ~.........~:.~_~-o....~_..~:! .............. .......... ..................................
............... ; ................. : ............... ! ................ : ................. ~' '.- ~ ~ ! f~. ~ Id "..u' . ~ ~ ~ , .- - , , ~
................. ; .............. : .................. :. ............... :..........tl-.~..~.........~-.......- i ( !~,~:~?~,~-,,. ~',.~. i ,~a:4~!- i ,~,,.=...~;i i ~ -¥- ! --~ ....
: ~ ~ : '. i~J~~ L:,-: ~.~__.:~__.: .............. ~ ................ ~ ................. ~ ......... ~ ................ i .................
.............. : ............... ........... : .............. ~ .............. ................. i ................. i ........... ~__~.~_..~..~....~...~.,:---i-- i ........ i,,~~'~ =:, ' .o.._ i~ e~'
: : : : .... -: ........ : ........ ~ ................. ~ ................. ? ................. t ................. ~ ................. t .................. ! .................
: ~ k - v ~~_~i~ ......... e'a%.,..._~_.i ...... i ................. ! .................
...... : ............................. :. ................ ....................................... "=-_.: ........ : .... ~_~ .0 _~_...~ ................. ~ ............ : ................................. !~__~L~!__C~..~.~: : .~i,~.-~.~ ...................... : .
................ ~ ................................... ~ ................ ? ............. ~ o ,<_ ~ ~-~_~ ~~ :, = ~ ~ ~ ~ ....... i .............................. : ............. ! ................. i ......... : ..............
. ~ ...................................................... ................ : .............................. _.~..-...::...._i ................. i ....................................................................... i ................................................... i ................ : ...............................................................................................
............... ~ .................................. ........,......i..~,..t...-~__...~_.~/ .......... %'~ ......... .....~ ................... ~-~-~->-..~ ..................... ~-~ .......... i ..............................................
............................. ................ "-'"" :'"':' ........ :_ ...... i"-"'" :"' .......... ...... : ............... : ....... :'-': .....
: ~ ~ ::Yl~Hu'rf:~ .
...... :--i ....... :-: .... i i ' i
:-i
141 OAK BAY ROAD/P.O. BOX 1375 PORT HADLOCK, WA 98339 360-379'9661 360-379-0150 FAX
JOB
· .° t , ~' .. SHEET NO. OF .....
CALCULATED BY DATE
ENGINEERING, INC. c,,~,.o.~. OATI:
SCALE
. .
141 OAK BAY ROAD/RO. BOX 1375 ~RT HADL~K, WA 98339 360-379-9661 360-379-0150 F~ ~ -~
STORMWATER MANAGEMENT MANUAL FOR THE PUGET soUND BASIN
Table Iii-1.6 Hydrologic Soil Groups fos Soils in the Puget Sound Basin
Hydrologic Soll Hydrologic Soil
Soil TYl~ C_n, oup Soil Type Group
Agncw C Coit~r C
Ahl B Custer ND
Ai~ C Dabob ND
Alderwood C Delphi D
Ar~nts, Ald~rwood B Dick ND
Arents, Everett B Dinml D
Ashoe B Dupont D
~ B Badmont C
l~'ne, aon C Eda~dck C
Baumgard B Eld B
Baausite B Elwell B
Belfast C Esquatzel B
Balllngham D Everett A
Ballingham variant C Everson D
Boistfort B Galvin D
Bow D Getchell A
Briscot D Giles B
Buckiey C Godfrey D
Bunker B Greenwat~r A
Cagey C Grove C
Cartsborg ND Harstinc C
Casey ND Hartnit ND
Cassoiary. C Hoh ND
Cathcart B Hoko ND
Centralia B Hoodsport ND
Chehalis B Hoogdal C
Chesaw A Hoypus ND
Cincbar B Huel ND
Clallam C Indianola ND
Clayton B Joins B
Coastal beaches variable Jumpe ND
Kepowsin C/D Kalaloch C
Kamla C Remton D
Kilchis C Republic B
Kitaap C Riverwash variable
Klaus ND Rober C
Klonc ND Salal C
Lares C Saikum B
Lcbam B Sammamish D
Lummi ND San Juan ND
Lynnwood ND Scamman D
Lysmir ND Schneider B
Mai C Seattle D
Manicy B Sckiu ND
Maahei B Scmiahmoo D
Maytown C Shaicar D
McKcnm D Shano 'B
McMurray ND Shciton C
Melbourne B Si C
Menzei ND Sinclair C
Mixed Alluvial variable Skipopa D
Molson B Skykomish B
Mukilteo C/D Snahopish ND
Naif B Snohomish D
Nat'gar A Solduc B
National ND Solleks ND
Neiiton A Spare D
III-l-9 . FEBRUARY, 1992
STORMWATERMANAGEMENT MANUAL FOR THE PUGET SOUND BASIN
Table III-1.3 SCS Western Washington Runoff Curve Numbers
(Published by SCS in 1982) Runoff curve numbers for selected agricultural,
suburban and urban
la~d use for T~r~e lA rainfall distribution, 24-hour storm duration.
LAND USE DESCRIPTION CURVE NUMBERS BY
HYDROLOGIC SOIL GROUP
A B C D
Cultivated land(l)= winter condition 86 91 94 95
Mountain open areas= iow growing brush & grasslands 74 82 89 92
Meadow or pasture: 65 78 85 89
Wood or forest land= undisturbed 42 64 76 81
Wood or forest land= young second growth or brush 55 72 81 86
Orchard= with cover crop 81 88 92 94
Open spaces, lawns, parks, golf courses, cemeteries,
landscaping.
Good condition: grass cover on k75% of the 68 80 86 90
area
Fair condition: grass cover on 50-75% of 77 85 90 92
the area
Gravel roads & parking lots: 76 85 89 91
Dirt roads a parking lots: 72 82 87 89
Impervious surfaces, pavement, roofs etc. 98 98 98 98
Open water bodies: lakes, wetlands, ponds etc. 100 100 100 100
Single family residential(2):
Dwelling Unit/Gross Acre %Impervious(3) Separate curve number
1.0 DU/GA 15 shall be selected for
1.5 DU/GA 20 pervious & impervious
2.0 DU/GA 25 portions of the site
2.5 DU/GA 30 or basin
3.0 DU/GA 34
3.5 DU/GA 38
4.0 DU/GA 42
4.5 DU/GA 46 -~
5.0 DU/GA 48
5.5 DU/GA 50
6.0 DU/GA 52
6.5 DU/GA 54
7.0 DU/GA 56
PUD's, condos, apartments, %impervious
commercial businesses & must be
industrial areas computed
(1) For a more detailed description of agricultural land use curve numbers refer
to National Engineering Handbook, Sec. 4, Hydrology, Chapter 9, August 1972.
(2) Assumes roof and driveway runoff is directed into street/storm system.
(3) The remaining pervious areas (lawn) are considered to be in good
condition for these curve numbers.
III-1-12 FEBRUARY, 1992
STORMWATER MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN
124 123 122 121
_ i
!
~ f FRiD, t,~ HARBOR i'T; STANLEY
/
35 . . ...? ~
~',' ~,
4¢-,. ,1~
. ./
~ .
50~
/
35 ~' ADA~
WASHINGTON
Figure 25 ~5; 'NOAA ATLAS 2, Volume IX
ISOPL~IALS ~ 2-YR 24-HR PRECIPITATi~N IN Pre,.red by U.S. De,.~ment of C~merce
TENTHS OF A CH Nltlon~l Oce.nlc ~nd Atmo~Dheric ~mini~tration
; N~tion~l Weather Se~ice, Office of~Hydrology
- i ~ Pre~r~ for U.S. Dep~men~ of A~riculture.
~ ~ ~il Con~e~tion Service. Engineering Division
124 123 122 121
III-1-44 FEBRU~Y , 1992
STORMWATER MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN
124 123, 1221 121
\ ! /
,,
i F~IDAY HAR {PORT STANL
, \
/
175
TACuMA 30'
/
,50 .~
WASHINGTON
0 10 20 30 40
~ ' " ' MILES
Figure 27 j
ISOPLUVIALS 0F 10-YR 24-HR PRECIPITATION Prepare~ by U.~ De~ment of C~merce
National ~elnic In~ Atmospheric A~minJstratio~
IN TENTHS OFf AN INCH
!PreNr~ for U.S. Depl~me~t of A~Jculture.
~,~il Conae~at~on ~ce, Engineer~g Division
124 123 122 121
III-1-45 FEBRU~Y, 1992
STORMWATER MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN
124 123 122 121
45 ..4~
48
80 \
100",
WASHINGTON 40 ·
10 0 10 20 30 40
," ' ~' :- ] MILES ~---.-'"
Figure 30 -- NOAA ATLAS 2, Volume IX
;
ISOPLUVlALS (tF IO0-YR .24-HR PRECIPITI~TION
IN TENTHS OF iAN INCH Nltion.l Weather
: Prepared for U.S. Del~rtment
· Soil Conservation DivLsi(m
12' 123 122 12i
.... ,.... _~.,~..~ ~,.,, . , -
:' 111-1-46 'FEBRUARY ~ 1992
STORMWATER MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN
Table III-1.4 "n" AND "k" Values Used in Time Calculations for Hydrographs
"n~" Sheet Flow Equation Manning's Values (for the initial 300 ft. of travel) n~
Smooth surfaces (concrete, asphalt, gravel, or bare hand packed
soil)
0.011
Fallow fields or loose soil surface (no residue) 0.05
Cultivated soil with residue cover (s~ 0.20 ft/ft) 0.06
Cultivated soil with residue cover (s> 0.20 ft/ft) 0.17
Short prairie grass and lawns 0.15
Dense grasses 0.24
Bermuda grass 0.41
Range (natural) 0.13
Woods or forest with light underbrush 0.40
Woods or forest with dense underbrush 0.80
*Manning values for sheet flow only, from Overton and Meadows 1976 (See TR-55, 1986)
"k" Values Used in Travel Time/Time of Concentration Calculations
Shallow Concentrated Flow (After the initial 300 ft. of sheet flow, R = 0.1) k~
1. Forest with heavy ground litter and meadows (n = 0.10) 3
2. Brushy ground with some trees (n = 0.060) 5
3. Fallow or minimum tillage cultivation (n = 0.040) 8
4. High grass (n = 0.035) 9
5. Short grass, pasture and lawns (n = 0.030) 11
6. Nearly bare ground (n = 0.25) 13
7. Paved and gravel areas (n = 0.012) .. 27
Channel Flow {intermittent) {At the beg£nn£ng of vis£ble channels R ~ 0.2) kc
1. Forested swale with heavy ground litter (n = 0.10) 5
2. Forested drainage course/ravine with defined channel bed (n = 0.050) 10
3. Rock-lined waterway (n = 0.035) 15
4. Grassed waterway (n = 0.030) 17
5. Earth-lined waterway (n = 0.025) 20
6. CMP pipe (n = 0.024) 21
7. Concrete pipe (0.012) 42
8. Other waterways and pipe 0.508/n
Channel Flow (Continuous stream, R = 0.4) ~
9. Meandering stream with some pools (n.= 0.040) 20
10. Rock-lined stream (n = 0.035) 23
11. Grass-lined stream (n = 0.030) 27
12. Other streams, man-made channels and pipe 0.807/n**
III-l-16 ~BRUARY, 1992
KING COUNTY DEPARTMENT OF PUBLIC WORKS
Surface Water Management Division
HYDROGRAPH PROGRAMS Version 4.21B
I - INFO ON THIS PROGRAM
2 - SBUHYD
3 - MODIFIED SBUHYD
4 - ROUTE
5 - ROUTE2
6 - ADDHYD
7 - BASEFLOW
8 - PLOTHYD
9 - DATA
10 - RDFAC
11 - RETURN TO DOS
2
SBUH/SCS METHOD FOR COMPUTING RUNOFF HYDROGRAPH
STORM OPTIONS:
1 - S.C.S. TYPE-lA
2 - 7-DAY DESIGN STORM
3 - STORM DATA FILE
SPECIFY STORM OPTION:
1
S.C.S. TYPE-lA RAINFALL DISTRIBUTION
ENTER: FREQ(YEAR), DURATION(HOUR), PRECIP(INCHES)
2,24,1.0 ((m_~o~~)
******************** S.C.S. TYPE-lA DISTRIBUTION ********************
********* 2-YEAR 24-HOUR STORM **** 1.00" TOTAL PRECIP. *********
ENTER: A(PERV), CN(PERV), A(IMPERV), CN(IMPERV), TC FOR BASIN NO. 1
1.8,84,.16,98,42
DATA PRINT-OUT:
AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES)
A CN A CN
2.0 1.8 84.0 .2 98.0 42.0
PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT)
.03 8.17 1446
ENTER [d:][path]filename[.ext] FOR STORAGE OF COMPUTED HYDROGRAPH:
6month
FILE ALREADY EXIST; OVERWRITE (Y or N) ?
Y
SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP
n
STORM OPTIONS:
1 - S.C.S. TYPE-lA
2 - 7-DAY DESIGN STORM
3 - STORM DATA FILE
SPECIFY STORM OPTION:
1
S.C.S. TYPE-lA RAINFALL DISTRIBUTION
ENTER: FREQ(YEAR), DURATION(HOUR), PRECIP(INCHES)
2,24,1.5
******************** S.C.S. TYPE-lA DISTRIBUTION ********************
********* 2-YEAR 24-HOUR STORM **** 1.50" TOTAL PRECIP. *********
ENTER: A(PERV), CN(PERV), A(IMPERV), CN(IMPERV), TC FOR BASIN NO. 1
1.8,84,.16,98,42
DATA PRINT-OUT:
AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES)
A CN A CN
2.0 1.8 84.0 .2 98.0 42.0
PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT) .10 8.00 3428
ENTER [d:][path]filename[.ext] FOR STORAGE OF COMPUTED HYDROGRAPH:
2year
FILE ALREADY EXIST; OVERWRITE (Y or N) ?
Y
SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP
n
STORM OPTIONS:
1 - S.C.S. TYPE-lA
2 - 7-DAY DESIGN STORM
3 - STORM DATA FILE
SPECIFY STORM OPTION:
1
S.C.S. TYPE-lA RAINFALL DISTRIBUTION
ENTER: FREQ(YEAR), DURATION(HOUR), PRECIP(INCHES)
10,24,2.2
******************** S.C.S. TYPE-lA DISTRIBUTION ********************
********* lO-YEAR 24-HOUR STORM **** 2.20" TOTAL PRECIP. *********
ENTER: A(PERV), CN(PERV), A(IMPERV), CN(IMPERV), TC FOR BASIN NO. 1
1.8,84,.16,98,42
DATA PRINT-OUT:
AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES)
A CN A CN
2.0 1.8 84.0 .2 98.0 42.0
PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT) .25 8.00 6904
ENTER [d:][path]filename[.ext] FOR STORAGE OF COMPUTED HYDROGRAPH:
lOyear
FILE ALREADY EXIST; OVERWRITE (Y or N) ?
Y
SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP
n
STO~ OPT !ONS:
1 - S.C.S. TYPE-lA
2 - 7-DAY DESIGN STORM
3 - STORM DATA FILE
SPECIFY STORM OPTION:
1
S.C.S. TYPE-lA RAINFALL DISTRIBUTION
ENTER: FREQ(YEAR), DURATION(HOUR), PRECIP(INCHES)
100,24,3.0
******************** S.C.S. TYPE-lA DISTRIBUTION ********************
********* IO0-YEAR 24-HOUR STORM **** 3.00" TOTAL PRECIP. *********
ENTER: A(PERV), CN(PERV), A(IMPERV), CN(IMPERV), TC FOR BASIN NO. 1
1.8,84,.16,98,42
DATA PRINT-OUT:
AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES)
A CN A CN
2.0 1.8 84.0 .2 98.0 42.0
PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT) .46 8.00 11424
ENTER [d:][path]filename[.ext] FOR STORAGE OF COMPUTED HYDROGRAPH:
lOOyear
FILE ALREADY EXIST; OVERWRITE (Y or N) ?
Y
SPECIFY: C ~ CONTINUE, N - NEWSTORM, P - PRINT, S - STOP
S
i i i I
APPENDIX 'D'
INTERCEPTOR SWALE SIZING CALCULATIONS
· ' JOB
.
· SHEET NO. OF .....
CALCULATED BY DATE
ENGINEERING, INC.
SCALE
I
~ ~ '
~ = A -~=, ~ ~ '~ ~= ......... L-?' .......... ~ ........ ~ .......... ~ ....... ~ .............. ~ ..............
.............. ~ ................ ~ ................. ~ ........... ..... ~ .................. ~.._~.._,-~-~f ................ ~ .............. _~ .......................... >~ ................ ~,~_ ............... ~,__~ ..................................................... ~ /~--= : '~~]~ ................. ~,~f ............ :~ .............. ~:: ....... ................
........................ :. ............ ~ ................ ~ ................ ~_..~ ......... ~. ......... ~...~..?....~ ........... ~ .......... ~ ................ ~ ................. L..~.....7..~......L..~A.....~ ............ E....~:...~_..~...~......,........~.~ ................................ [~...~._..~ ....... ~ ..........
............................................... ~. .............. ~ ................. , ....................... ~ ........................... ~ ............................. 5 ................. ~ ....... ~ ................. ~ ............... ~ .......... ~ .......... ~ ............................. 7'~?'"""~ ................. ~ .............. ~ ........... ................ ~ ............... ~ ................. ~ ................. : ............ ~ ........................ ~ .................
........................... : ................................................................... ~ ........................... : .................................................................................................................................................. ~ ............... ~ ................................ ~ .................... : ...................................................................................................
................. :.. ~ ....... ~.~.~-~ ~__~.o~_~_z~ ...................................................... : ...... ~ ............ ~ ............. ~ ...... : ............. :___ ............................ ~ ............
.................. _~._:_~.O_d.l_ ~. ..~ .......................................... . ..................................
................ ~ ............................ ~ .............. ~ ................ ~ ............................ 7 .......... ~ ' ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ .
1 ~ OAK BAY ROAD/RO. BOX ~ 37~ ~RT HAD~K, WA 98339 360-S79-9661 360-~9-01
STORMWATER MANAGEMENT .M~_NUAL FOR THE PUOET SOUND BASIN
Table III-1.5 V&luem of t~e Roughness Coeff£cien~ "n"
Type of Channel Mann_,t~3's TYPe of Channel Manning's-
and Description "n' and Description "n"'
(Normal) (Normal)
,
, A. Constructed Cl~nnels 6. Sluggish.reaches, weedy 0.070
a. Earth, straight and uniform deep pools,
1. Clean~ recently completed 0.018 7. Very~.weedy, meches,-deep 0.100
2. Gravel, uniform section, 0.025 pools,-or fl~ys with
3. With sho~t grass, few 0.027. underbrush
weeds b. Mountain streams, no vegetation
b. Earth, winding and sluggish 0.025 in channel, :banks.usuailySteep,
1. No vegetation 0.025 trees and ~brush along banks
2. Grass, some weeds 0.030 sU~~~i~ stages
3. Dense weeds or-aquatic 1. Bottom:gravel,-:~bbles, and 0.040
plants In deep channels 0.035 few:~
4. Earth bottom and rubble 2. Bott~:CObbles with large 0.050
sides 0.030 bo~
· ,
5. Stony bottom and weedy a-2 R~i~ ~
banks 0.035 a~ P~m' ~!brush
6. Cobble bottom and dean 1. ShOrt~:grass. 0.030
sides 0.040 2. Highg~s 0.035
c. Rock lined b. Cultivated areas
1. Smooth and uniform 0.035 1. No crop 0.030
2. Jagged and irregular 0.040 2. Mature row crops 0.035
: d. Channels not maintained, 3. Mature field croPs 0.040
weeds and brush uncut c. Brush
1. Dense weeds, high as flow 1. Scattered:bruSh, heavy 0.050
depth 0.080 weeds
2. Clean bottom, brush on 2. ~Light brush and trees 0.060
sides 0.050 3. M~ium to~ ~h 0.070
3. Same, highest stage of 4. Heavy, dense :brush 0.100
flow 0.070 d. Trees · ·
4. Der-me brush, high stage 1. Dense willows, straight 0.150
B. Natural Streams 0.100 2. Cleared~.~withtree 0.040
B-1 Minor streams (top width at stu~i!
flood stage < 100 ft.) 3. S~ ~'with 0.060
a. Streanm on plain h iofspr°uts-
1. clean, straight, full stage 4. Heavy)~:of~timber,~a few 0.100
no riffs or deep pools 0.030 downt~;i:little
2. Same as above, but more und~~aoodstage
stones and weeds 0.035 belOW branches
3. Clean, winding, some 5. same!:iaS~abOve; but with 0.120
pools and shoals 0.040 floOd ~:~e.i ~Ching
4. Same as above, but some branc~s '
weeds 0.040 ":
.
5. Same as 4, but more
stones 0.050
I II-1-17 FEBRUARY, ::1992
APPENDIX 'E'
CONVEYANCE PIPE SIZING CALCULATIONS
JOB
~,B ~., SHEET NO. OF
CALCULATED BY DATE
ENGINEERING INC
SCALE
:
:
OAK BAY ROAD/P.O. BOX 1375 PORT HADLOCK, WA 98339 360-379-9661 360-379-0150 FAX ~-(
Pipe Capacity Calcul~.xis
This spreadsheet is designed to calculate flow capacity
and flow velocity for a silted or non-silted circular pipe
assuming open channel flow properties.
The principal formula is Manning's Equation.
INPUT VALUES
Manning's "n" for Pipe 0.0120
I
~anning's "n" for Invert Material 0.0000
Pipe Diameter (In.) 6.00
Pipe Slope, S (Ft/Ft) 0.0060
1
Depth of Invert Material (In.) 0.00
CALCULATED VALUES
nl 0.0120
n2 0.0000
r (Ft.) 0'25
y (Ft.) 0.00
At (SF) 0.20
Ab (SF) 0.00
P1 (Ft.) 1.57
P2 (Ft.) 0.00
"n" I 0.0120
A (SF) I 0.20
P (Ft.) 1.57
Maximum Capacity (CFS) 0.47
Flow Velocity (FPS) 2.40
Page I
Pipe Ca~y
I
This spreadsheet is designed to calculate ,flow capacity
and flow ve~ooi~ for a silted or non-~ilted circular pipe
assuming open channe~ flow properties, I
The principal fon~u)a is Manning's Equation,
INPUT VALUES
I
Manning's "n" for Pipe 0.0120
I
Manning's "n" for Invert Material 0.0000
1
Pipe Diameter (In.) 4.00
I
Pipe Slope, S (Ft/Ft) 0.1000
Depth of Invert Material (In.) 0.00
CALCULATED VALUES
nl 0.0120
n2 0.0000
r (Ft.) 0.17
y (Ft.) 0.00
At (SE) 0.09
Ab (SF) 0.00
P1 (Ft.) 1.05
P2 (Ft.) 0.00
"n" 0.0120
A (SF) 0.09
P (Ft.) 1.05
iMaximum Capacity (CFS) 0.65
Flow Velocity (FPS) 7.49
Page I
. Pipe Capacity Calculator, xls
This spreadsheet is designed to calculate flow capacity
and flow velocity for a silted or non-silted circular pipe
assuming open channel flow properties.
The principal formula is Manning's Equation.
INPUT VALUES
Manning's "n" for Pipe 0.0120
Manning's "n" for Invert Material 0.0000
Pipe Diameter (In.) 6.00
I
Pipe Slope, S (Ft/Ft) 0.0350
I 1
Depth of Invert Material (In.) 0.00
CALCULATED VALUES
nl 0.0120
n2 0.0000
r(Ft.) I 0.25
y (Ft.) 0.00
At (SF) 0.20
Ab (SF) 0.00
P1 (Ft.) 1.57
P2 (Ft.) 0.00
"n" 0.0120
n (SF) 0.20
P (Ft.) 1.57
Maximum Capacity (CFS) 1.14
Flow Velocity (FPS) 5.81
Page 1
inlet control conditions, which may be present or anticipated in the system,
are not specifically addressed.
Each pipe within the system is sized and sloped such that its barrel capacity at
normal full flow (computed by Manning's Equation) is equal to or greater than the
25-Year design flow. The nomograph in Figure III-2.1 can be used for an approximate
solution of Manning's Equation. For more precise results, or for partial pipe full
conditions, solve Manning's Equation directly:
V = 1.49 R~3 sla n
or, using the continuity equation, Q = AV
Q = 1.49 AR2/3sla
n
where:
Q = Discharge in cfs
V = Velocity in fps
A = Area in ft2
n = Manning's roughness coefficient in s-ft1/6 (see
Table III-2.2) ~
R = Hydraulic radius = area/wetted perimeter, in ft.
s = Slope of the energy grade line in ft/ft
For pipes flowing partially full, the actual velocity may be estimated from the
hydraulic properties shown in Figure III-2.1 by calculating Q~II and VhlI and using
the ratio .of Q4~ign/Qmll to find V and d (depth of flow).
Table III-2.2 provides the recommended Manning's "n" values for preliminary design
using the Uniform Flow Analysis Method for pipe systems. (Note, the "n" valves for
this method are 15% higher in order to account entrance, exit, junction, and bend
head losses.)
Table III-2.2 Manning's "n" Values for Pipes
Analysis Method
Type of Pipe Material Backwater Uniform
Flow Flow
A. Concrete pipe and CPEP-smooth interiOr pipe 0.014 0.012. ~
B. Annular Corrugated Metal Pipe or Pipe-Arch:
1.2-2/3" x 1/2" corrugation (riveted)
a. plain or fully coated 0.028 0.024
b. paved invert (40% of circumference paved):
(1) flow full depth 0.021 0.018
(2) flow 0.8 depth 0.018 0.016
(3) flow 0.6 depth 0.015 0.013
c. treatment 5 0.015 0.013
2.3" x 1" corrugation 0.031 0.027
3.6" x 2" corrugation (field bolted) 0.035 0.030
C. Helical 2-2/3" x 1/2" corrugation and CPEP-
single wall 0.028 0.024
D. Spiral rib metal pipe and PVC pipe 0.013 0.011
E. Ductile iron pipe cement lined 0.014 0 012
F. High density polyethylene pipe (butt fused only) 0.009 0.009
111-2-6 FEBRUARY, 1992
APPENDIX 'F'
FLOW SPREADER TRENCH SIZING CALCULATIONS
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~ SHEET NO, OF
CALCULATED BY. DATE,
ENGINEERING, INC.
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