HomeMy WebLinkAbout976500009 Drainage Report
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DRAINAGE, EROSION, AND SEDIMENT CONTROL
PLAN FOR PARCEL 0976500009
Prepared for:
Seahome Services, Inc.
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EXPIRES 8-25-07 I
NORTHWESTERN TERRITORIES, INC. 717 S. Peabody St. Port Angeles, WA 98362,360-452-8491
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DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
Prepared For Seahome Services, Inc.
December 2005
For the Property Described as Tax # 976500009
Section 4, Township 28 North, Range 1 East, W.M.
Jefferson County, Washington
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Prepared by
NORTHWESTERN TERRITORIES, INC.
717 S. Peabody Street
Port Angeles, Washington 98362
Phone 360-452-8491 Fax 360-452-8498
Web Site www.nti4u.com
E-mail info@nti4u.com
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SEAHOME SERVICES, INC. PROJECT
PORT LUDLOW VICINITY MAP
fI NORTHWESTERN TERRITORIES, INC.
Engineers - Land Surveyors - Geologists
Construction Inspection ~ Materials Testing
NTI 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360)452-8491
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DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
for
PARCEL 976500009
Seahorne Services, Inc. Project Neighborhood Map
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DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
for
PARCEL 976500009
Seaborne Services, Inc. Project Area Map
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EROSION AND SEDIMENT CONTROL PLAN
PREPARED FOR:
SEAHOME SERVICES, INC.
INSTALL ADDmONAL SILT FENCING JUST ABOVE:
THE UNE OF ORDINARY HIGH WA7ER ONLY IF
WORK WILL EXPOSE SOILS ON THE SLOPE ABOVE
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"NORTHWESTERN TERRITORIES, INC.
Engineers - Land Surveyors - Geologists
Construction Inspection - Materials Testing
NTI 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360)452-8491
EXTEND SILT FENCING 15 FEET
BEYOND UMrrs OF EXPOSED
SOIL
ROU7E ALL RUNOFF FROM ROOF
DRAINS, CURTAIN DRAINS, INTER-
CEPTION DITCHES AND THE UKE
TO THE T1GHTLlNE PIPE TO BE
ROUTED DOWN THE STAIRS PER
THE DRAINAGE REPORT.
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50 25 0 50
SCALE IN FEET
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STANDARD TEMPORARY EROSION AND SEDIMENT CONTROL PLAN NOTES
· All erosion and sediment control Best Management Pmctices shall be selected, constructed, and
maintained in accordance with the Washington Department of Ecology Stormwater Management
Manual for Western Washington (current edition).
· The construction and maintenance of erosion and sediment control measures shall be the
responsibility of the contractor. The contractor shall not deviate from the approved plans without
prior approval from the Jefferson County Public Works Department. The contractor shall have a
set of approved plans on the site whenever construction is in progress.
· The erosion and sediment control measures depicted on this plan are minimum requirements to
meet anticipated site conditions. AB conditions dictate during construction, the contractor shall
implement additional measures as necessary to ensure erosion and sediment control.
· Construction vehicle access shall be limited to one route, whenever possible. Quarry spalls or
crushed rock shall be applied to the access in order to prevent sediment from being transported
onto roads. If this should occur, roads shall be cleaned thoroughly by shoveling or sweeping.
· Clearing shall be phased so that only areas that are being worked are exposed. All exposed and
unworked soils shall be stabilized by appropriate Best Management Practices. From October 1
through April 30, unworked soils shall not be left exposed for more than 2 days. From May 1
through September 30, unworked soils shall not be left exposed for more than 7 days.
· All erosion and sediment control measures shall be maintained in a satisfactory condition until
such time as land disturbing activities are completed and the potential for onsite erosion has
passed.
· The contractor shall request inspection of temporary erosion and sediment control measures by
the Jefferson County Public Works Department [(360) 385-9160] as soon as practicable after
installation.
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DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
for
PARCEL 9765??oo9
ABSTRACT
This project consists of the construction of a beach access stair system and related
work on a one acre parcel at 7701 Oak Bay Road, Port Ludlow, Washington. This
plan also provides for the construction of a tightline pipe to convey stormwater
runoff from the existing improvements as well as a future home.
The pre-development runoff is not calculated since the system will discharge directly
to marine waters. The post-development runoff is estimated based on a standard 24
hour storm having mean recurrence intervals of 25 years. Post-development runoff
is used to design the tightline stormwater pipe.
Construction phase erosion and sediment control measures are proposed to prevent
soil from leaving the site during construction of the improvements. A detail
drawings for erosion control measures is included at the beginning of this report.
The following BMPs shall be implemented in addition to any that may later be
necessary due to changing or unforeseen site conditions.
1. Silt fencing shall be installed below the limits of any work which will
expose soil to the elements for more than 24 hours. The location of the silt
fencing is shown on the Erosion and Sediment Control Plan map included
at the beginning of this report.
2. Additional silt fencing shall be installed just above the line of ordinary
high water if any work will expose soils on the slope above the beach for
more than 24 hours.
3. Existing runoff from roof drains, interception ditches, and tightline pipes
shall be routed to the tightline pipe to be constructed down the beach
access stair system per this plan. The stair assembly shall include a six
inch diameter tightline pipe to transport stormwater runoff from the
uplands to discharge immediately above the line of ordinary high water.
The pipe shall be rigidly secured to the stair assembly. The discharge
point shall be at ground level into a basin of quarry spalls for energy
dissipation.
4. Runoff from future structures shall be routed to the same tightline pipe
down the beach access stair system.
5. Silt fencing shall be installed across the lower limit[~~~,:~:~~'-U~ rr~l
co~struction and shall extend 25 feet beyond the li~ii_ lof ally eAposet!. ~ t 1 ! I [
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DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
for
PARCEL 976500009
CONTENTS
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I. PROJECT OWRVIEW .................. ............ .... ...................... ................................1
A. Project Description......... .... ............ ........................... ...... ................ ....... ...... .... 2
B. Existing Site Conditions ...................... ....... ................ .............. .... .... .... ..... ...... 2
1. Topography... .......... .... .......... ...... ...... ........ .................................................. 2
2. Vegetation........... .......................... .... ........................ ...... .... .... .... ................ 4
3. Drainage. .... ............................ ................ .......... ............ .............................. 6
C. Adjacent Areas ....... .......................... ........... ............. .......... .... .... ........ .............. 8
II. DESIGN CRITERIA............ .................... ................ ..................... .............. ...........8.
A. Soils......................... .... ......................... .... .......... ...... ........ .......... ......... ........ ...... 8
B. Rainfall. ...... ........ .... ..................... ..... .... ............ ........ .... .............. ............. ....... 10
C. Hydrologic Model.................... .... ...... ............. ...... ...... ........ .............. ..... .... ...... 11
D. Time of Concentration.... .............. .......................... .... .... .......... ...................... 12
1. Predevelopment Condition. ...... .......... .... ...... ........ ...... ................ ...... ........ 12
2. Predevelopment Time of Concentration.................................................. 15
3. Post-development Condition .................................................................... 15
4. Post-development Time of Concentration ................................................ 17
III. R'UN'OFF ......................... ...... ................. ................. ........................ ........ .... ......... .17
A. Pre-development Runoff .. .... .... ...... ............. ...... .............. .... .......... ........ ......... 17
B. Post-development Runoff....... .... ................... ....... ........ .... ...... .... ............ .... ..... 17
C. Mitigation............. .......... ........ ...... ...... .............. .............. .......... .... ........... ....... 18
IV. EROSION AND SEDIMENT CONTROL PLAN ...............................................18
A. Site Specific Construction Phase BMPs ........................................................ 19
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B. Stabilization and Sediment Trapping (Erosion and Sediment
Control Requirement Number 1)................................................................... 20
1. Stabilization of Exposed Soils.................................................................. 20
2. Sediment Trapping. .............. ...... ............... .... .......... ........... ....... ............... 23
C. Delineate Clearing and Easement Limits (Erosion and
Sediment Control Requirement Number 2) .................................................. 25
D. Protection of Adjacent Properties (Erosion and Sediment
Control Requirement Number 3)................................................................... 25
E. Timing and Stabilization of Sediment Trapping Measures
(Erosion and Sediment Control Requirement Number 4)............................ 26
1. Timing of Installation of BMPs ............................................................... 26
2. Stabilization of slopes of structural BMPs.............................................. 26
F. Cut and Fill Slopes (Erosion and Sediment Control
Requirement Number 5) ............................... ........... ............. ...................... 26
G. Controlling Off-Site Erosion (Erosion and Sediment Control
Requirement Number 6) .............................. .............. ...... .............................. 26
H. Stabilization of Temporary Channels and Outlets (Erosion
and Sediment Control Requirement Number 7)........................................... 27
I. Underground Utility Construction (Erosion and Sediment
Control Requirement Number 9)...................................................................27
J. Construction Access Routes (Erosion and Sediment Control
Requirement Number 10) ...... .......... .......... ......................................... ...... ..... 28
K. Removal of Temporary BMPs (Erosion and Sediment
Control Requirement Number 11)................................................................. 28
L. Dewatering Construction Sites (Erosion and Sediment
Control Requirement Number 12)................................................................. 29
M. Control of Pollutants Other than Sediment (Erosion and
Sediment Control Requirement Number 13) ................................................ 29
1. Control of Toxic Substances. ...... .............. ............. .......... ............ ............. 29
2. Petroleum Spills.................. ............. ...... .................................... ........ ...... 30
N. Maintenance (Erosion and Sediment Control Requirement
Number 14)....... .............................................. .................................... ............ 30
O. Financial Responsibility............ .......... ....................... ...................... ............. 31
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DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
for
PARCEL 976500009
Photo 1
I. PROJECT OVERVIEW
This project consists of the construction of a beach access stair system and related work on
a one acre parcel at 7701 Oak Bay Road, Port Ludlow, Washington. This plan also provides
for the construction of a tightline pipe to convey stormwater runoff from the existing
improvements as well as a future home. Photo 1 shows the building site and the view
beyond to Hood Canal on the eastern end of the parcel. The existing layout of the site is
shown on the area and site maps included at the beginning of this report. A geotechnical
report for the site was prepared by this office and provides additional information about the
site.
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A. Project Description
This project consists of the construction of a beach access stair system. The drainage,
sediment and erosion control features of the plan are directed toward the stair system
but they also provide for the eventual construction of a home on the parcel.
B. Existing Site Conditions
The following summary of site conditions represents existing conditions.
1. Topography
The site is somewhat long and narrow with the axis oriented east and west as shown
on the Area and Site Maps included at the beginning of this report. The geotechnical
report prepared by this office discusses the topography in more detail. The ground
generally slopes to the east, toward the beach, but there is some slope to a small
ravine located off the parcel to the north.
Photo 2
Photo 2 is a view of the small ravine to the north, taken from the top of the slope at
the parcel's northern boundary. n.' '-~'"-rEE' m\l
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Photo 3 is an air photo of the area. The parcel is indicated by the white arrow. The
small ravine is located to the north (right on photo) of the parcel.
Photo 3
Photo 4 is a view of the cabin from near the top of the marine slope. Note the rise on
the left (south) side of the parcel.
Photo 4
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Photo 5
Photo 5 shows the driveway through the upper (western) part of the parcel. The
small ravine is out of sight on the left.
2. Vegetation
The site is heavily vegetated with natural vegetation. The upper part is forested
with very heavy brush and ground cover. Photo 6 shows typical vegetation on the
upper part of the parcel.
Photo 6
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Photo 7
Photo 7 shows vegetation in the vicinity of the existing cabin. Note the dense ground
cover. Also obvious in these photos is the preponderance of plants that grow well
with copious amounts of water. This indicates an excess of surface water runotfwith
little infiltration on the upper (western) portion of the parcel. Photo 8 shows
vegetation on the lower (eastern) part of the parcel.
Photo 8
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Photo 9
Photo 9 shows ground cover vegetation on the slope above the beach. The brush is
very dense here making views of the actual ground surface difficult to obtain.
3. Drainage
The building site presently drains in sheet flow to the north and east. As noted
above, the ground on the upper (western) part of the parcel is not particularly
permeable and produces much runoff.
Photo 10
Some effort has been made to collect this runoff with piping as shown in Photo 10.
The network of small pipes extends around the cabin and attempts to control the
runoff from the upper part of the parcel.
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Photo 11
Photo 11 shows a part of this system further downstream, to the south of the cabin.
Drainage across the lower portion of the uplands is primarily by sheet flow across
the lawn shown in Photo 12 with some runoff going onto adjacent properties to the
north (in the background of the photo) and the rest over the slope to the west (right
background of the photo).
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C. Adjacent Areas
The site is surrounded by rural residential lands on the north and south sides. Oak Bay
Road, a County road, lies a short distance to the west from the parcel. Hood canal forms
the eastern side of the parcel. The Area Map included at the beginning of this report
shows a good overview of the neighborhood.
Photo 13
Photo 13 shows beach front homes on the north side of the parcel.
II. DESIGN CRITERIA
The following criteria are specific to this project site and will not apply to other properties,
even those that may be nearby.
A. Soils
The site may be found on map number 52 of the Soil Survey of Jefferson Countv Area,
publ~shed by the U. S. Soil Conservation Service, a portir.,~fWh....iC,f.l.,...~;.Fer. -'I', e.;
as FIgure 1. , r;. r 'l' ~:, t!..~ It I \Ji L6 u. . ... I.
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Figure 1
Figure 1 can be compared with the Area Maps at the beginning of this report for
orientation.
Map number 52 predicts that the soils on this site are type cm, Cassolary sandy loam
on slopes ranging between 15 and 30 percent.
The Soil Survey of Jefferson County Area describes Cassolary sandy loam as being well
drained soils on uplands formed of reworked glacial and marine sediments. The well
drained descriptor appears to apply well to the soils on the lower part of the parcel,
below the cabin. The gravel content of the soils exposed on the marine slope does not
agree well with the Cassolary soil description. The soils above the cabin are not as well
drained and may be closer related to the Swantown gravelly loam, (SuB) soils, shown to
the immediate north on the soils map.
Cassolary soils belong to hydrologic group C while Swanto~~~iliiaG.: ~~t'~ Jil~l
This report ~sumes that the soils above the cabin are S't;~,'. _)~.wn and those e 0 ':11 111,( I
Cassolarysods. ;:' \,! 0 EC 2 2 2005 ! lj /
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Photo 14 shows an exposed section of soils to the north of the cabin. Note the random
gravel content and the very sandy fines.
Photo 14
B. Rainfall
The total amount of precipitation falling over a 24 hour period during a storm having a
mean recurrence interval of 2 years, will be 1.5 inches. This information was taken
from a 2 year, 24 hour Isopluvial Map published by the U.S. Soil Conservation Service,
a portion of which is reproduced here as Figure 2. The project location is marked on the
map.
3tN
30N
29N
28N
27N
Figure 2
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The isopluviallines represent total precipitation in 24 hours, in tenths of inches. 2 year
rainfall data is used in the calculation of times of concentration for the site.
The total amount of precipitation falling over a 24 hour period during a storm having a
mean recurrence interval of 25 years, will be 2.8 inches. This information was taken
from a 25 year, 24 hour Isopluvial Map published by the U.S. Soil Conservation Service,
a portion of which is reproduced here as Figure 3. The project location is marked on the
map.
3tN
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30N
29N
28N
27N
26N
HOUR
(IF
Figure 8
The rainfall distribution is assumed to be a Type IA distribution per standard practice
in the area.
C. Hydrologic Model
Because hydrologic and hydraulic calculations are only performed for the purpose of
sizing the tightline pipe system, there is no need for a continuous hydrologic simulation.
Only the peak. flow is needed.
This plan uses a hydrograph based method of calculating runoff which is described in
Urban Hydrology for Small Watersheds, Technical Release No. 55, and the Western
Washington Supplement to Technical Release No. 55, both published by the U. S. Soil
Conservation Service. This same type of method is given in the King County Surface
Water Design Manual, published by the King County Public Works Department, and
the 1992 Stormwater Management Manual for the Puget Sound Basin (The Tecltnical
Manual) published by the Washington State Department of Ecolo~r" ~1--'-- ~ -""-~ -"1
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This method yields runoff volumes that are significantly different from those
determined using the rational method.
This plan uses the suggested runoff curve numbers given in Table 2-2a of Technical
Release No. 55.
D. Time of Concentration
The length of time that it takes a drop of rainfall to travel from the uppermost point of a
basin to the point of discharge from the basint or to the point where flows are to be
calculated, is referred to as the time of concentration (Tc). This is the sum of the time it
takes for runoff to flow across the various types of flow channels as it crosses the basin.
For this project the time of concentration is little affected by development since the new
home site is located near the bottom of the drainage basin (entire parcel).
The following calculations are per Section 111-1.4.2, pages 111-1-13 through 111-1-16, of
the Washington State Department of Ecology's STORMWATER MANAGEMENT
MANUAL FOR THE PUGET SOUND BASIN. THE TECHNICAL MANUAL, (DOE).
1. Predevelopment Condition
The time of concentration is first determined for the existing condition of the basin.
a. Unconcentrated Flow
Immediately after falling to the ground, rainwater initially travels as
unconcentrated sheet flow for a period of time (Tt) calculated by:
0.80
0.42 (NsL)
Tt = -------------------- = 51.79 min
0.527 0.4
(P2) (SO)
Where:
Ns = 0.800
P2 = 1.5
SO = 0.0500
L = 150
= Sheet flow Manning's n (DOE Table 111-1.4)
= 2 yr, 24 hr rainfall (in)
= Slope of flow path (ftlfl;)
= Length (L) of flow path (fiij...f.".'~~ -.,----... ~'111'\J7' fr'" m-~
,,' \ I "l'? f1\
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This is flow across the upper (western) portion of the parcel through ground
cover as shown in Photo 15
Photo 15
b. Shallow Concentrated Flow
As sheet flows run together and become concentrated, they travel as shallow
concentrated flow for a period of time (Tt) calculated by:
L
Tt = -------------------- = 2.36 min
60 Ks SQRT(SO)
Where: Ks = 5
SO = 0.0800
L = 200
= Velocity factor (Ks) (per DOE Table 111-1.4)
= Slope of flow path (ft/ft)
= Length (L) of flow path (ft)
This is flow through the brush alongside the road shown in Photo 16.
l: I~
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Photo 16
c. Open Channel (Intermittent) Flow
Flows next travel through intermittent open channels for a period of time (Tt)
calculated by:
L
Tt = ----------------- = 0.38 min
60 Kc SQRT(SO)
Where: Kc = 17
SO = 0.1500
L = 150
= Velocity factor (Kc) (DOE Table 111-1.4)
= Slope of flow path (ft/ft)
= Length (L) of flow path (ft)
This is flow down the grassy slopes below the cabin as shown in Photo 17.
1_ [ i [E]~I!
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Photo 17
2. Predevelopment Time of Concentration
As noted above, the time of concentration (Tc) is the sum of the time it takes for
runoff to flow across the various types of flow channels as it crosses the basin. For
the predevelopment condition:
Tc = the sum of the various Tt's = 54.52 min
This is rounded to 55 min for use in further calculations.
3. Post-development Condition
The time of concentration is next determined for the proposed, post-developed
condition of the basin. There is little change in time of concentration from the pre-
developed to the post-developed condition since most changes in land use will occur
in areas where flows are already relatively rapid, allowing little opportunity for the
increased flow velocities that will reduce the time of concentration.
15
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a. Unconcentrated Flow
Immediately after falling to the ground, rainwater initially travels as
unconcentrated sheet flow for a period of time (Tt) calculated by:
0.80
0042 (NsL)
Tt = -------------------- = 51.79 min
0.527 004
(P2) (SO)
Where: Ns = 0.800
Ps = 1.5
SO = 0.0500
L = 150
= Sheet flow Manning's n (per DOE Table HIlA)
= 2 yr, 24 hr rainfall (in)
= Slope of flow path (ftift)
= Length (L) of flow path(ft)
This is unchanged from the pre-development condition.
b. Shallow Concentrated Flow
As sheet flows run together and become concentrated, they travel as shallow
concentrated flow for a period of time (Tt) calculated by:
L
Tt = -------------------- = 1.31 min
60 Ks SQRT(SO)
Where: Ks = 9
SO = 0.0800
L = 200
= Velocity factor (Ks) (per DOE Table HI-1A)
= Slope of flow path (ftJit)
= Length (L) of flow path (ft)
This is reduced from the pre-developed condition.
c. Open Channel (Intermittent) Flow
As shallow concentrated flows from several sources run together, they cut open
channels that flow as intermittent streams. Flows travel through these
intermittent open channels for a period of time (Tt) calculated by:
'_.._~-~
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L
Tt = -------------------- = 0.65 min
60 Kc SQRT(SO)
Where: Kc = 10
SO = 0.1500
L = 150
= Velocity factor (Kc) (per DOE Table 111-1.4)
= Slope of flow path (Nfl;)
= Length (L) of flow path (ft)
This will be increased from the pre-developed condition due to the replacement of
the existing grass with natural vegetatioin.
4. Post-development Time of Concentration
As noted above, the time of concentration (Tc) is the sum of the time it takes for
runoff to flow across the various types of flow channels as it crosses the basin. For
the post-development condition:
Tc = the sum of the various Tt's = 53.74 min
This is rounded to 54 min for use in further calculations.
III. RUNOFF
While not necessary for the purposes of this report, pre-development runoff was calculated
for the site. These values are reported but calculations are not included. Full calculations
for post-development flow at the 25 year level are included in Appendix I.
A Pre-development Runoff
A catalog of assumed pre-development conditions and calculations of the pre-
development, weighted runoff curve numbers is included in Appendix I. These are the
conditions that were assumed to prevail before development of the site.
Under these conditions, the site has a weighted runoff curve number of 86.9.
Complete calculations of the pre-development runoff are contained in Appendix I. The
pre-development runoff is calculated to be 0.83 cfs for the 25-year storm.
B. Post-development Runoff
A catalog of assumed post-development conditions and calculations of the post-
development, weighted runoff curve numbers is also included in Appendix I. These are
the conditions that will prevail after development of the site.
If-----.. - '--'--\1
Under these conditions, the site will have a weighted runott~J.;D.J:b~ of ~'i.~ ~r" II
'.' "T--~Ii II,
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Complete calculations of the post-development runoff are contained in Appendix I. The
post-development runoff is calculated to be 0.95 cfs for the 25-year storms, a slight
increase from the predevelopment rate.
C. Mitigation
Construction phase erosion and sediment control measures are proposed to prevent soil
from leaving the site during construction of the improvements. A detail drawing for
erosion control measures is included at the beginning of this report.
To mitigate increased levels of runoff from the future full development of this parcel,
and to provide a higher level of protection against erosion of the marine slope, existing
runoff from roof drains, interception ditches, and tightline pipes shall be routed to the
tightline pipe to be constructed down the beach access stair system per this plan. Runoff
from future structures shall also be routed to the same tightline pipe down the beach
access stair system.
Design (sizing) calculations, including flood routing calculations, are included in
Appendix I. The stair assembly shall include a six inch diameter tightline pipe to
transport stormwater runoff from the uplands to discharge immediately above the line
of ordinary high water. The pipe shall be rigidly secured to the stair assembly. The
discharge point shall be at ground level into a basin of quarry spalls for energy
dissipation.
To mitigate potential erosion and sediment impacts, the requirements of the erosion and
sediment control plan shall be followed. Site specific mitigation measures are listed near
the beginning of the erosion and sediment control plan. General guidelines and
recommendations are in following sections.
IV. EROSION AND SEDIMENT CONTROL PLAN
This portion of the plan was prepared with the goal of preventing damage to adjoining or
downstream properties due to erosion and sediment deposition and preventing the
degradation of the quality of the receiving waters during the construction phase of this
project.
To ensure that the provisions of this Erosion and Sediment Control Plan are followed
during construction, the complete text of this Erosion and Sediment Control Plan should be
included in the construction plans for this project. Where formal construction plans will not
be prepared for all or portions of the work, a copy of this document should be made
available to the contractor and appropriate subcontractors. Subcontractors that will not be
receiving copies should be made aware of the plan's existence and advised where copies can
be obtained. ! ~'~}1 k~. ~-''"~t?'" U;-\l
Water quality controls, commonly referred to as Bes. t M~.,..~~.Mt Practice., or BM.P. ...~.I.
necessary to prevent three distinct types of impacts. The fimt ldtnsWEt o~ ~65f d Il~gS
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the result of soils being taken up by running water. This type of damage typically consists
of rilling, rutting and loss of topsoil. The next type of damage is the degradation of water
quality that occurs as the water transports the smaller soil particles. The last type of
damage occurs when the running water reduces its velocity and drops the suspended soils.
The Erosion and Sediment Control features (BMPs) of this plan are designed to address all
three types of damage with the emphasis on preventing the initial soil uptake. Successful
prevention of soil uptake will also prevent damage caused by degradation of water quality
and by soil deposition. While the measures described below for preventing soil uptake
should theoretically prevent any removal of soil, common sense advises that additional
measures will be necessary and indeed, the DOE Manual requires additional measures.
These additional measures will allow deposition of transported soils under controlled
conditions before flows leave the project site or enter the receiving waters.
The site specific types of BMPs and their locations are described immediately below in sub-
section A. Specific details of the BMPs and the standards required by the DOE manual
follow as sub-sections B - O.
A. Site Specific Construction Phase BMPs
The following BMPs shall be implemented in addition to any that may later be
necessary due to changing or unforeseen site conditions.
1. Silt fencing shall be installed below the limits of any work which will expose soil
to the elements for more than 24 hours. The location of the silt fencing is shown
on the Erosion and Sediment Control Plan map included at the beginning of this
report.
2. Additional silt fencing shall be installed just above the line of ordinary high
water if any work will expose soils on the slope above the beach for more than 24
hours.
3. Existing runoff from roof drains, interception ditches, and tightline pipes shall be
routed to the tightline pipe to be constructed down the beach access stair system
per this plan. The stair assembly shall include a six inch diameter tightline pipe
to transport stormwater runoff from the uplands to discharge immediately above
the line of ordinary high water. The pipe shall be rigidly secured to the stair
assembly. The discharge point shall be at ground level into a basin of quarry
spalls for energy dissipation.
4. Runoff from future structures shall be routed to the same tightline pipe down the
beach access stair system.
5. Silt fencing shall be installed across the lower limits of any future home
construction and shall extend 25 feet beyond the limits of any exposed soil.
~f~ r-~~~ <<~- ""-~nd fE fTh1
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It is expected that minor adjustments, especially the installation of additional BMPs
where an unexpected need arises, will be necessary during the construction phase of
this project. For this reason, discussions of various BMPs that are not specifically
required are included below. These BMPs should be considered as being held in ready
reserve against the possibility that they will be needed.
The following subsections discuss the various BMPs that may be lD.corporated in this
plan. Reasons for their use, limitations and benefits associated with specific BMPs, and
additional information are provided.
B.
Stabilization and Sediment Trapping
Requirement Number 1)
These requirements are to be considered general in nature and provide a framework for
deciding when and where various BMPs should be utilized. They are intended to provide
guidance in quickly selecting BMPs for use in unexpected situations. They apply to
both soils that are not yet at final grade and to those that are at final grade, including
soil stockpiles.
(Erosion and Sediment Control
1. Stabilization of Exposed Soils
The stabilization of exposed soils is the single most important element of this plan.
If exposed soils are protected such that soil particles are not picked up by running
water, erosion will not occur. Protection of exposed soil consists of four main areas
of effort.
a. Minimize Disturbance of Vegetation
Existing vegetation on the site comprises the best overall protection against
erosion. To protect this resource and to keep the risk of erosion at a minimum,
clearing and grading activities outside of the areas necessary to construct the
improvements shall be kept to an absolute minimum. Patches of existing
vegetation that are within the clearing/grading limits and may be left intact
without hindering the project, shall be left alone whenever possible.
Care shall be taken that existing vegetation is left intact wherever possible
around the perimeter of the project and particularly along the lower side of the
project. Vegetation in drainage corridors and immediately below soil disturbing
activities is the most valuable and as such is to be provided with the most
protection.
b. Minimize the Length of Time the Soil is Unprotected
Where grading is necessary for construction activities, the grading should be
delayed as long as reasonably possible to minimize the length of time that the
soil is exposed to the elements.
Where exposure of bare soil is necessary to accomplish re:!!.~" ~=.~- s "7~1E u'~
work, such portions ~f the :work should be c?mpleted ~ro#t) .." . II Ii!
the chance of an erOSIve ramfall event catchmg the soIl ~~N~ cted. ; I t r
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c. Ensure Prompt Revegetation of Disturbed Areas
Every effort shall be made to ensure a healthy stand of protective vegetation is
established as soon as possible. Reseeding of areas which are to be planted with
grass shall be accomplished within 14 days if grading opera,~on's are completed
within a planting season. If grading operations are completed outside of a
planting season, reseeding shall occur within 7 days following the beginning of
the next planting season. If substantial portions of the project are ready for
reseeding at the beginning of or during a planting season, such portions may be
promptly reseeded without waiting for completion of work on oth~r portions of
the project.
Planting seasons are considered to be between March 1 and May 15 and between
August 15 and October 1 where irrigation is impractical. Where irrigation is
practical, the planting season is considered to be between March 1 and
October 1.
.----- "~'- -."--;:-1
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The following seed mix has been tested and found to be adequate for use for
erosion control and for slope stabilization in Western Washington:
Seed Type Percent by Weight
Chewing Fescue 40
Colonial Bentgrass,
Var. Astoria 10
Perennial Rye 40
White Clover 10
100
Other mixes, selected with regard for the soils, uses of the site, method of
application, and expected weather may be used if desired. The recommendations
of the seed supplier should be sought and strongly considered in selecting a mix.
If the season or construction scheduling will not allow prompt revegetation of an
area where construction activities have been completed, the area should be
covered with plastic sheeting, straw, mulch or other covering chosen to match
the situation and with due regard for the length of time that the area is expected
to remain uncovered.
d. Protective Coverings
Protective coverings are highly recommended for application to exposed soils that
are not being actively worked for an extended period of time. An extended period
of time is considered to be 2 days between October 1 and April 30 or 7 days
between May 1 and September 30.
Protective coverings include plastic sheeting, straw, mulch, commercial sod and
other coverings. The particular type of protective covering used should be chosen
based on the steepness of the slope of the area to be covered, the size or the area
to be covered, the time of year, the length of time the covering will remain,
proximity to wetlands or other sensitive. areas,' the amount of existing vegetation
between the exposed soil and the downhill project boundary, cost, and the visual
impact of the covering.
The best covering is existing vegetation, which should be disturbed as little as
possible. Commercial sod is the next best covering but its use is often precluded
by cost. Clear plastic sheeting is suitable for steep slopes but is difficult to apply
and maintain in moderate to high winds. Black plastic sheeting is not
appropriate during growing seasons except for short periods of time. Loose
straw, either straight from bales or shredded, makes an adequate ground
covering on gentle to moderately steep slopes (no steeper thaD: 2 horiz.()l!.tal to 1
verti~al) if it is wet to the point of limpness. Straw is ~~. ..~ (f~~!il t~ef!
the distance from the top to the toe of the slope is no mom tti '~.' 'Q
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Early application of gravel bases, pavements, and special landscaping items such
as washed rock over plastic sheeting is considered to be a suitable protective
covering where otherwise required.
2. Sediment Trapping ,-
Stormwater runoff from areas of exposed soil shall not be permitted to leave the
project site without first having passed through an appropriate sediment trapping
system or device. The type of sediment trap should be chosen based on the potential
for erosion from exposed soils, the expected velocity and depth of flows, the
proximity to downstream sensitive areas, and the length of time that the upstream
soils will remain exposed to the elements.
a. Sheet Flow Through Grassy or Heavily Vegetated Areas
Runoff from exposed slopes that are less than 150 feet from top to bottom
(measured along the slope) can be adequately treated by routing flows through
bands of dense grass or other heavy vegetation. The vegetated band should be a
minimum of one fifth as wide as the width of the exposed slope, but no narrower
than 10 feet. For example, a band of exposed soil 75 feet wide should have a
minimum of 15 feet of dense grass for sediment trapping.
The vegetated band width above is for a slope no steeper than 10 percent. Where
the slope of the vegetated area is between 10 and 20 percent, add 50 percent to
the minimum width. Where the slope is greater than 20 percent, the minimum
width should be doubled.
For this type of sediment trapping system to be effective, flows must cross the
vegetated area in sheet flows. If flows are expected to arrive at the vegetated
band in concentrated flows, creation of a small artificial delta may be necessary
to force a sheet flow.
b. Grassy Swales
Grassy swales are used to treat runoff from larger areas than sheet flows across
bands of vegetation. Although grassy swales are usually thought of as
permanent features, they can often be utilized during the construction phase.
Unfortunately, there is usually insufficient time before the main construction
effort to reshape landforms to provide the necessary slopes, widths, etc., and
grow vegetation in the swale. Either an area must be found that is already
vegetated and that meets the minimum requirements for a grassy swale or
commercial sod must be placed along the sides and bottoms of the swale
immediately after the swale is constructed.
The following standard requirements for grassy swales~e takeIlJr.om.",~_
D~aft ~tox:nwater Guidelines published by the WaShin~.,. f -.....'..'~...' S@t~t~~R~XJ~ "" r;.. ~l.
Flshenes m 1990 and are recommended for use here.,.:.aY~r&-~" '..1 ! Iii!
, II , ;1
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More specific design criteria are more appropriate for use on large or complex
sites.
i. Soils
Gravelly and coarse sandy soils should be avoided in order to maximize water
contact with vegetation and the soil surface. .
ii. Design Criteria
The grassy swale should be designed based on a two-year, 24-hour peak flow
and the following:
(A) Velocity
Velocities should be less than 1.50 feet per second.
(B) Depth of Flow
The flow depth should be less than 4 inches.
(C) Slope
The longitudinal slope should average two to four percent. Rock or log
check dams or terraces should be installed as necessary to achieve slopes
of less than four percent.
lll. Dimensions
Grassy swales should be located to obtain maximum length. If less than 200
feet long, the width should be increased by an amount proportional to the
reduction below 200 feet in order to obtain the same area of vegetation
contact.
iv. Side Slopes
Side slopes should be no steeper than three horizontal to one vertical.
c. Interceptor Swales
Interceptor swales are shallow trenches constructed with a single pass of a large
dozer equipped with one to three ripper teeth. The preferred configuration of
ripper teeth for construction of interceptor swales is two teeth positioned on the
outside of the ripper assembly. This type of swale construction will tear through
existing sod without removing it. Leaving the sod in place will protect against
erosion of the swale bottom on steeper slopes.
Swales thus constructed are intended to intercept sheet flows and infiltrate them
into the soil. When flows are greater than can be infiltrated, the swales will
provide a path for runoff of excess flows. Such excess flows will run along the
swale until they are either infiltrated or they enter interceptor!:JlitcJ!~~__._ _ .
'-'"-tF 1. r; l~ f"
Interceptor swales are especially effective adjacent to prop~H~ . It.. ~(
more or less straight up and down a slope and where only ~~~i ows are to be ~l
'" \ i D EC 2 2 2005
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intercepted. In order to be effective, the surface of the ground must not be
regraded during the life of the swale. Grading or blading of the surface of these
swales will defeat their purpose.
Construction of interceptor swales causes only minimal disruption of the ground
contours. For this reason the swales need not be removed or otherwise treated at
the end of their usefulness. "
d. Other Sediment Trapping Devices and Systems
Many other effective sediment trapping systems and devices are listed in Table
11-2.1 of the 1992 DOE Manual. Complete details and descriptions of them are
included elsewhere in the DOE Manual. They should be used where appropriate
and as described in the Manual.
C. Delineate Clearing and Easement Limits (Erosion and Sediment Control
Requirement Number 2)
Appropriate clearing limits, property lines, easement lines, and similar boundaries shall
be determined prior to starting construction. Clearing, grubbing, grading and similar
operations shall not begin until the appropriate limits are staked in the field. Once
these stakes are set, care shall be taken that the stakes are not disturbed.
D. Protection of Adjacent Properties (Erosion and Sediment Control Requirement
Number 3)
As required by the DOE Manual, no flows from exposed or disturbed soils are to leave
the project site without first having been treated with some type of sediment
trapping/filtering system or device. The proposed arrangement of these devices and
systems is described above. The individual items are discussed in more detail in the
section on Sediment Trapping above.
The protective measures shown on the site plan are designed to prevent sediment
deposition on adjacent properties. To the extent that the various items are constructed
as designed and other work on the site progresses as envisioned, sediment should not be
deposited on neighboring properties.
Last minute changes in other items of work on this project, responses to previously
unknown site conditions, or unexpected weather may require that revisions to the
sediment trapping provisions of this plan be made rapidly. To this end, the previous
section on Sediment Trapping contains design criteria, comments, information about
BMPs, and similar information that is intended to be used in rapidly responding to
changing needs and changing site conditions. As soon as a previously unexpected threat
to adjacent properties becomes apparent, sufficient measures shall be taken to either
eliminate the source of the threat or to provide an adequate level of defense against the
threat. The measures taken shall provide a level of defense against sediment deposition
on adjacent properties at least as secure as those provided by the remainder of this
plan. "~-"-~'-\l'
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E. Timing and Stabilization of Sediment Trapping Measures (Erosion and
Sediment Control Requirement Number 4)
It is essential that the various sediment trapping systems and devices be constructed
prior to exposing the upslope soils to the elements. Both the timing of construction of
the measures and the stabilization of the slopes of the structural BMPl;l are mandatory
parts of this plan. '._
1. Timing of Installation ofBMPs
In keeping with the goal of providing positive sediment trapping or removal for all
runoff from exposed soils before the runoff leaves the project site, no soil shall be
exposed, or grading operations performed, until all of the required BMPs in the
drainage path below the area to be exposed have been completed. Clearing,
grubbing, and grading operations necessary for the construction of the BMPs are
excepted from this requirement.
2. Stabilization of slopes of structural BMPs
It is critical that the slopes of ditches, berms, ponds, and similar structural items be
stabilized. These slopes will not only shed as much silt as any other exposed slope,
but their erosion could cause the failure of the structural BMP. This could easily
result in the failure of the BMP to perform its task of forcing sediment deposition to
occur in a controlled location. This would leave open the potential for erosive
transport of soil from a much larger area than that originally exposed on the slope of
the BMP.
F. Cut and Fill Slopes (Erosion and Sediment Control Requirement Number 5)
Newly created slopes shall be covered or otherwise protected as provided for elsewhere
in this plan.
The faces of newly created fill slopes shall be well compacted. Since it is often
impossible for typical compaction equipment to adequately compact the outer one to
three feet of a fill, it will be necessary for compaction equipment to be operated up and
down the face of the slope after the fill is completed. Operating tracked equipment in
this manner will provide a certain amount of slope roughness which is desirable in
slowing the velocity of running water and in retaining seed and fertilizer.
After cut or fill slopes are covered, they should be monitored to ensure that the covering
is functioning as intended and that rills are not forming under or through the covering.
G. Controlling Off-Site Erosion (Erosion and Sediment Control Requirement
Number 6)
The BMPs specified by this plan are intended to prevent damage to downstream and/or
adjoining properties. To the extent that construction of this project is performed as
intended and all elements. of this plan are implemented, there should be no off-site
erosion. It is possible that extensive covering of slopes and similar practices could
increase the volume of peak floods, especially if a storm even~great~r than a"t1Vo_~~--~'l
~vent w~re to occ~ before the site were completely reveget ;~~a,~ ~ ~~~~~ m\ !
infiltratIon/detentIOn systems completed. . \ I) r-:":'" ...:.....-.-.---.--'\ \ \ II:
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The possibility of this occurring increases significantly if construction is delayed and
exposed slopes must be covered through a winter rainy season instead of having been
successfully revegetated. While this is not expected to occur, is possible that the
vagaries of the construction trade will cause this to happen. If this does occur,
downstream drainage channels shall be inspected before the end of the Fall planting
season and an inventory made of areas where increased flows would reasonably be
expected to cause. erosion. Such areas shall then be protected in a manner consistent
with the goals and guidelines included within this plan. Those BMPs noted above as
being held in "ready reserve" on this project may be brought up to active status by their
use in such off-site situations.
H. Stabilization of Temporary Channels and Outlets (Erosion and Sediment Control
Requirement Number 7)
Channels, slopes, embankments, trenches, and similar areas of disturbed soil which are
required for the implementation of this erosion control plan shall be subject to the same
erosion control requirements as other portions of the project. In addition to the general
protective requirements, specific armoring methods are included in the appropriate
details.
1. Underground Utility Construction (Erosion and Sediment Control Requirement
Number 9)
Underground utility construction shall proceed subject to the following criteria.
A major source of potentially contaminated flows is from pumping or otherwise
dewatering trenches. For this reason, flows discharged from pumping or other
method of trench dewatering shall be closely monitored and, except where there is
no visible turbidity, treated as described below in the Section titled "Dewatering
Construction Sites."
Where feasible, no more than 500 feet of trench shall be opened at one time.
Where consistent with safety and space considerations, stockpiles of excavated soils
shall be placed on the uphill side of the trench. Any such stockpiles shall be
protected from erosion as provided for in this plan.
Trenches shall be backfilled and revegetated as soon as reasonably possible
following placement of utilities. Wherever trenches run more or less straight up and
down a slope, either the backfill shall be mounded over the trench or waterbars or
similar BMPs shall be utilized as necessary to prevent the backfilled trench from
becoming a water course. Simply covering the exposed soil may not prevent the
trench from conveying waters.
Where the upstream end of a pipe is subject to inundation, it shall be temporarily
capped or plugged at the end of each day's work to prevent soil from being washed
into the pipe.
27
.'..f' ..r,.....)..~ . fi::. a~ -. ~~ q 'ld l~ rn.' -\1, <
Ill. ..::. ...'" L... U '-i '- : I'
. . -~,., . - t
i I ii'l r-DE~2~_~~J Ilh 1
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The underground utility locate service, 1-800-424-5555, shall be called a minimum of
48 hours (2 working days) prior to beginning any excavation and arrangements
made to have all buried utilities marked.
J. Construction Access Routes (Erosion and Sediment Control Requirement
Number 10)
It is expected that minor amounts of soil will be tracked onto paved roads, especially
when unexpected circumstances such as rains and delays occur. To prevent this from
becoming a nuisance or source of sedimentation, the roa~s shall be cleaned thoroughly
at the end of each day if there is evidence of any significant accumulation of soil.
Sediment shall be removed from roads by shoveling or sweeping and be transported to a
controlled sediment disposal area. Washing of the street shall be allowed only after
sediment is removed in this manner. Wherever construction, delivery, and similar
vehicles enter paved roads from this project, the following provisions shall be followed to
minimize the transport of soil onto the paved road.
During periods of dry weather (where the soil is too dry to adhere to the tires of
construction vehicles) construction vehicles may access paved streets directly from the
project site with monitoring and occasional sweeping of the paved street as necessary to
prevent accumulations of soil.
During periods of wet weather (where soil readily adheres to the tires of vehicles) the
vehicles may access graveled roads directly from the project site as necessary, but shall
not access paved roads without first having been routed over areas where existing grass
or other vegetation remains or routed down a minimum of 150 feet of graveled road.
Access routes over grass or other vegetation shall be changed occasionally to ensure that
wheel ruts are not allowed to develop and that the vegetation is not unduly worn down.
K. Removal of Temporary BMPs (Erosion and Sediment Control Requirement
Number 11)
Temporary Erosion Control Facilities shall be promptly (within 60 days) removed, once
their presence is no longer required. During their removal, any entrapped sediment
shall be disposed of in suitable locations on the project site where they will not be
subject to erosion. Disturbed areas left after the removal of sediments shall be promptly
stabilized.
As an alternate to the removal of entrapped sediments, they may be stabilized in place
by the application of suitable BMPs such as sodding, mulching, seeding, etc.
In no case shall sediments be left in a channel or where they would be washed into
receiving waters by the next storm. The role of the Erosion Control Facilities is to
prevent sediments from entering waters, not to merely delay it until after construction
is comple~.
28
[r~'~ fI:"---::--- . '~'.._. . -'~.'-'---\l
,,' ..:lI;,. . f' ': """-' ..,'"
i'P" <i a; u Wi ~ fJlli
rh10Ec 2 2 2O~~IUY
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L. Dewatering Constmction Sites (Erosion and Sediment Control Requirement
Number 12)
Discharges from pumps used in dewatering trenches or other portions of a constmction
site shall be dispersed by one of the following methods:
Directing flows onto existing heavily vegetated areas. If this is. done, the flows shall
be directed against objects such as old tires or stumps, capable of dismpting
concentrated flows.
Directing flows onto a pad constmcted of clean, pit run gravel or washed drain rock
or pea gravel. The pad shall be a minimum of 15 feet square and flows shall be
directed into a circle of 6 - 8 inch diameter stones to assist in dispersing flows into
sheet flows.
Directing flows directly into a grassy swale or other sediment trapping BMP,
constructed per this plan.
In no case shall flows discharged from a pump be allowed to remain as a concentrated
flow. Every effort shall be made to break the flows into sheet flows.
In all cases, flows from dewatering shall be routed through a sediment trapping BMP
before being released off of the site.
M. Control of Pollutants Other than Sediment (Erosion and Sediment Control
Requirement Number 13)
All potential pollutants other than sediments that may occur on the site during the
construction process shall be handled and disposed of in a manner that does not cause
contamination of stormwater.
1. Control of Toxic Substances
No toxic or noxious substances shall be used, stored or disposed of on or off the
project site in conjunction with the project except in full compliance with all
applicable federal, state and local laws and regulations and the recommendations of
the supplier of the substance. The product label or instructions for use and the
Material Safety Data Sheets (MSDS) for such products shall be kept on the site until
the product has been used up or removed from the site and properly disposed of.
While not commonly thought of as a hazardous material, common fertilizer can be
very damaging if allowed to enter receiving waters. Fertilizers shall only be used in
accordance with the recommendations of the supplier and any concentrations such
as dribbles or leaks shall be cleaned up.
In the event of a spill or other unusual event involving toxic or hazardous materials, .
wo~k in the vicinity shall be immediately stopped. ~'.,.... ..... f~.... t~.r~~.~,~ '~.' " (-",,\1.
notified: , : I ) . r-:='- U2_~...!!__~~_~...., I n \ l
, 'c. ,'" I I" i"
i '~'" 1:! "~ [
, ", l-
i IDE C 2 2 2005 : l; t
, ."
29
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Washington State Department of Ecology, (206) 459-6000 during normal
business hours or (206) 753-2353 after hours.
If the incident presents a threat to life, health, or property, the Fire and Police
Departments shall be notified by dialing 911.
2. Petroleum Spills
The following requirements are included to ensure compliance with Part 40 of CFR
112 in cases where SPeC Plans are required. They shall be followed on all projects.
Storage of fuel for construction vehicles and fueling of construction vehicles shall be
performed in accordance with the following requirements:
a. Driver Training
All employees assigned to operate fuel trucks will be properly trained in
appropriate regulations and safety procedures. Training shall include proper
inspection and use of tanks, hatches, valves, pumps, hoses and fuel delivery
equipment.
b. Fueling of Vehicles
Fuel nozzles shall be locked when not attended and hoses shall be rewound or
otherwise properly stored when not in use. Unattended fueling which relies on
the proper operation of automatic shutoff nozzles shall not be permitted.
c. Parking of Fuel Tankers
Parking areas for fuel trucks shall be selected such that spills will not leave the
area. Fuel trucks shall not be parked closer than 25 feet to a conveyance BMP
such as a grassy swale or interceptor swale. When fuel trucks must be taken to
other portions of the project to fuel equipment, they must be continuously
attended or returned to. the staging/storage area. Fuel trucks shall be locked
with the wheels chocked when unattended and not in use.
d. Containment of Spills
Spills shall be immediately diked and every effort made to stop spillage. Each
fuel truck shall carry a long handled shovel for use in containing spills. In the
event of a spill, the U. S. Environmental Protection Agency, Seattle, Washington
(206) 442-1263, shall be notified as soon as possible. If the magnitude ofthe spill
is such that it presents an immediate threat to life, health, or property, it shall
be promptly reported by dialing 911.
N. Maintenance (Erosion and Sediment Control Requirement Number 14)
Thi~ section constitutes the Op~ration and M~tenance r~~~l"fq:r~~~r~~to~a~~,l
sediment control BMPs used dunng the constructlon Pbase'1~.,.~i!rGIect~\j lb, 111.',)\ i
i \ 0 EC 2 2 2005 ! f"j
. -.-.._."'-_..--~ .1
30
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Most of the various BMPs required to maintain water quality during the construction
phase of this project are of a temporary nature. They are neither intended nor expected
to remain in service for months at a time. The typical BMP often has a life expectancy
. of only 6 - 12 weeks unless time and effort are expended to bring it back to its original
condition.
Foul weather, rough use, overloading and similar conditions will reduce the life of these
items. It is critical that all of the erosion and sediment control BMPs be maintained in
their intended condition until they have served their purpose and are ready to be
removed.
The project foreman shall inspect the various parts of the system at least once daily
during rainy weather. In addition, the foreman shall perform additional inspections
during or immediately after significant rainfall. Any damaged or non-functioning
components of the system shall be repaired before noon of the next day.
In addition to verifying that the various BMPs are functioning as intended, the foreman
shall check for formation of rills, deposits of silt and similar indications that the system
is not functioning properly. If it is found that the system is not performing its role in
preventing erosion and sedimentation, additional BMPs shall be provided as necessary.
Specific maintenance instructions for the various erosion and sediment control BMPs
are contained in the DOE Manual.
O. Financial Responsibility
Construction, operation, maintenance, replacement, and final removal of the erosion
and sedimentation control BMPs is an integral part of the construction of this project.
When referenced as such by the construction contract or similar documents, this plan
forms a part of the construction plans for this project. In such cases the erosion and
sedimentation control work is covered under applicable financial instruments such as
the contractor's and developer's bonds to the same extent as all other items of work
shown in the construction plans.
r. ;..... c...~) -I~=--' li \:jj f~ r~\~
, ..,.. '1 u lb I 'I
; l L. r;"'" -~-'--\'. i \ I.
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i Hi! 0 EC 2 2 2005 i l~
31
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Appendix I
Drainage Calculations
I rf~)) Ire~-'''~ff ~f~in I
"L(.:..r. ....----.--- '~..... i'...d
iDEe 2 2 2005 itl,' i
~".".. "," ""~' .'>~_...._.",
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File: SEAH01.WB2 Date: December 10, 2005
I
BASIN DATA
PROJECT: Seahome Services, Inc. drainage
I
Predevelopment
---------------------------------------------------------------
I
Area:
Cn:
Tc:
Undetained
1.0000 (Ac) +
86.9
55 (min)
Detained
0.0000 (Ac)
100.0
55 (min)
Total
1.0000 (Ac)
I
Postdevelopment Basin Data
---------------------------------------------------------------
I
Undetained Detained
Area: 0.9082 (Ac) + 0.0918 (Ac)
en: 86.6 98.0
Tc: 54 (min) 54 (min)
Total
1.0000 (Ac)
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RAINFALL
I
24 hr rainfall depth
----------------------------------
2 yr storm:
25 yr storm:
100 yr storm:
1. 50 (in)
1.80 (in)
3.30 (in)
I
PREDEVELOPMENT RUNOFF
I
----------------------------------
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2 yr storm:
25 yr storm:
100 yr storm:
I
POSTDEVELOPMENT RUNOFF
I
Peak Runoff From
Undeveloped Port'n
(Undetained)
------------------ -----(Qpos1)-----
2 yr storm: 0.0455 (cfs)
25 yr storm: 0.0732 (cfs)
100 yr storm: 0.2441 (cfs)
I
I
Peak
Runoff From
Entire Basin
------------------ -----(Qpos)------
2 yr storm: 0.0629 (cfs)
25 yr storm: 0.0947 (cfs)
100 yr storm: 0.2855 (cfs)
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Peak
Basin Rainfall
------(Qr)-------
0.4901 (cfs)
0.5881 (efs)
1.0781 (efs)
Peak
Pre-Devt Runoff
------(Qpre)-----
0.0519 (cfs)
0.0827 (efs)
0.2712 (cfs)
Peak Runoff From
Developed Port'n
(Detained)
-----(Qpos2)-----
0.0175 (cfs)
0.0215 (efs)
0.0415 (efs)
DEe 2 2 2005
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PROJECI': Seahome Services, Inc. drainage
RUNOFF CURVE NUMBER CALCULAT IONS
Total Parcel Size lacres) ,
......-----......---.....--.....---------..................-------.........---.........--......-....--...--------.....--------------............----------....--..-------...----------------------------------...-...---..----.....--...
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PRE-DEVELOPMENT
I Impervious (detained)
Runoff 1 Runoff
Area Curve No. I Area Curve No.
Land Use (acres) (Cn) (A x Cnl I Land Use lacres) (Co) lA x Cn)
-------------------------------------------------------------------------------- 1 -------------------------------------------------------_______________________.
YOWl9 Second Growth TidleJ: and bl1l8h 0.65040 86.00 55.93 1 YOIIIlg Second Growth Timber and bIiiih 0.0??oo 86.00
Gnvel driveway 0.12000 91.00 10.92 I Gnvel driveway 0.00000 91.00
Roof. 0.02300 98.00 2.25 1 Roof. 0.00000 98.00
Lawn/landscaping 0.20660 86.00 17.77 1 Lawn/hndacaping 0.00000 86.00
Revegetated iteas, Illtural 0.00000 85.00 I RaYe98tated areas, Illtural 0.00000 85.00
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1
1
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98.00 I
-----00----1
86.88 I
1.000 I
----00-----1
86.88 I
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86.9 I Weighted Average Runoff Curve Number of Impervious Portion (rounded)
Pervious (undetained)
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Subtotal Pervious Area =
Remainder Area =
I. 00000
0.00000
Total Pervious Area =
Total Impervious Area =
Total Impervious Area =
0.00000
100.00
0.00
1.00000
0.00000
Total Area =
100.00
1.00000
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Weighted Average Runoff Curve Number of Pervious Portion (rounded)
100.0
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Predeveloprnent Weighted Average Runoff Curve Number of Entire Parcel (rounded) 86.9
----...-----------------------------..---......------------------------...------...-----------------------------------------...------------------------------------------------
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POST -DEVELOPMENT
I Impervious (detained)
Runoff I Runoff
Area Curve No. I Area Curve No.
Land Use (acres) (Cnl (A x Cn) I Land Use (acres) (Co) fAx Cnl
-------------- ------------------ 00______-----------------------___00______------ 1 -----00--____ 00________________________________________________________________
Younq SeCond Growth 'liIIber and bl1l8h 0.43820 86.00 37.69 I YOUIlg Second Growth 'filIber and brush 0.00000 86.00
Gnvel driveway 0.14000 91.00 12.74 1 Gravel driveway 0.0??oo 91.00
Roofs 0.00000 98.00 1 Roofs 0.09180 98.00
Lawn/landscaping 0.15000 86.00 12.90 1 Lawn/landscaping 0.00000 86.00
Revegetated areas, Illtural 0.18000 85.00 15.30 I Revegetated areas, Illtural 0.00000 85.00
1
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1
1
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98.00 -0.00 1
-----------1
78.63 1
0.908 1
-----------1
86.57 1
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86.6 1 Weighted Ave. Runoff Curve
Pervious (undetained)
I
9.00
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Subtotal Pervious Area =
Remainder Area =
0.90820
-0.00000
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Total Pervious Area =
Total Impervious Area =
0.90820
0.09180
Total Impervious Area =
0.09180
9.00
0.09
I
Total Area =
98.00
1.00000
Weighted Ave. Runoff Curve Number of Pervious Portion (rounded I =
fYiou~Po\Q9n~j1F~1
f, 'j 'i' \.....'" r~~' t ,
~~:"l ,\J C, . ~ \ 1 1
" !,; ... .-- .', ",\
--~:"""---\l' \:
\ " I:
\ 0 EC 2 2 2005 {;i \
. -----,
98.0
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Postdeveloprnent Weighted Average Runoff Curve Number of Entire Parcel (rounded) 87.6
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PROJECT: Seahome Services, Inc. drainage
25 yr storm (B)
-------------------------------------------------------------
Total Basin Area = 43560 sq ft =
Storm Duration =
Peak Rainfall Intensity =
Total Rainfall Volume
Total, 24 hr rainfall =
Standard SCS Type 1A
24 hr hyetograph (adj'd)
from King Co Drn Manual
1.0000 Ac
24 hr
0.588 cfs
6534 cu ft
1. 80 'in
Rainfall Data
-----------------------------------
------------------------
Time % Cumulative
(min) Precip % Precip
o
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
310
320
330
340
350
360
370
380
0.00
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.50
0.50
0.50
0.50
0.50
0.50
0.60
0.60
0.60
0.60
0.60
0.60
0.70
0.70
0.70
0.70
0.70
0.70
0.82
0.82
0.82
0.82
0.82
0.82
0.95
0.95
0.95
0.95
0.00
0.40
0.80
1.20
1.60
2.00
2.40
2.80
3.20
3.60
4.00
4.50
5.00
5.50
6.00
6.50
7.00
7.60
8.20
8.80
9.40
10.00
10.60
11. 30
12.00
12.70
13.40
14 .10
14.80
15.62
16.44
17 . 26
18.08
18.90
19.72
20.67
21. 62
22.57
23.52
Time
(hrs)
0.00
0.17
0.33
0.50
0.67
0.83
1.00
1.17
1.33
1. 50
1. 67
1.83
2.00
2.17
2.33
2.50
2.67
2.83
3.00
3.17
3.33
3.50
3.67
3.83
4.00
4.17
4.33
4.50
4.67
4.83
5.00
5.17
5.33
5.50
5.67
5.83
6.00
6.17
6.33
Total
Basin
Rainfall
P
(cfs)
0.0000
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0545
0.0545
0.0545
0.0545
0.0545
0.0545
0.0653
0.0653
0.0653
0.0653
0.0653
0.0653
0.0762
0.0762
0.0762
0.0762
0.0762
0.0762
0.0893
0.0893
0.0893
0.0893
0.0893
0.0893
0.1035
0.1035
0.1035
0.1035
Cumulative
Precip Precip
Depth Depth
Pr Pre
(in) (in)
0.0000
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0090
0.0090
0.0090
0.0090
0.0090
0.0090
0.0108
0.0108
0.0108
0.0108
0.0108
0.0108
0.0126
0.0126
0.0126
0.0126
0.0126
0.0126
0.0148
0.0148
0.0148
0.0148
0.0148
0.0148
0.0171
0.0171
0.0171
0.0171
0.0000
0.0072
0.0144
0.0216
0.0288
0.0360
0.0432
0.0504
0.0576
0.0648
0.0720
0.0810
0.0900
0.0990
0.1080
0.1170
0.1260
0.1368
0.1476
0.1584
0.1692
0.1800
0.1908
0.2034
0.2160
0.2286
0.2412
0.2538
0.2664
"'__'.,_n
O. 2, r .~. 1'il 11 s;
o . 2 .t.. \.c:;i J l;~~
0.3' "/,/ r-- --'-..----,----,
0.3~lt~'11 I
'11"'1., DEe 2 2 '101l'i .
0.34u2 I...~, I
0.3550 I
0.3721 '
0.3892
0.4063
0.4234
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PROJECT: Seahome Services, Inc. drainage
25 yr storm (B)
-------------------------------------------------------------
Total Basin Area = 43560 sq ft =
Storm Duration =
Peak Rainfall Intensity =
Total Rainfall Volume
Total, 24 hr rainfall =
Standard SCS Type 1A
24 hr hyetograph (adj'd)
from King Co Drn Manual
1.0000 Ac
24 hr
0.588 cfs
6534 cu ft
1. 80 in "
Rainfall Data
-----------------------------------
------------------------
Time % Cumulative
(min) Precip % Precip
390
400
410
420
430
440
450
460
470
480
490
500
510
520
530
540
550
560
570
580
590
600
610
620
630
640
650
660
670
680
690
700
710
720
730
740
750
760
770
0.95
0.95
1.33
1.33
1.33
1.80
1.80
3.40
5.40
2.70
1.80
1. 34
1.34
1.34
0.88
0.88
0.88
0.88
0.88
0.88
0.88
0.88
0.88
0.88
0.88
0.88
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.57
24.47
25.42
26.75
28.08
29.41
31. 21
33.01
36.41
41.81
44.51
46.31
47.65
48.99
50.33
51. 21
52.09
52.97
53.85
54.73
55.61
56.49
57.37
58.25
59.13
60.01
60.89
61.61
62.33
63.05
63.77
64.49
65.21
65.93
66.65
67.37
68.09
68.81
69.53
70.10
Time
(hrs)
6.50
6.67
6.83
7.00
7.17
7.33
7.50
7.67
7.83
8.00
8.17
8.33
8.50
8.67
8.83
9.00
9.17
9.33
9.50
9.67
9.83
10.00
10.17
10.33
10.50
10.67
10.83
11. 00
11.17
11. 33
11.50
11. 67
11.83
12.00
12.17
12.33
12.50
12.67
12.83
Total
Basin
Rainfall
P
(ets)
0.1035
0.1035
0.1448
0.1448
0.1448
0.1960
0.1960
0.3703
0.5881
0.2940
0.1960
0.1459
0.1459
0.14 59
0.0958
0.0958
0.0958
0.0958
0.0958
0.0958
0.0958
0.0958
0.0958
0.0958
0.0958
0.0958
0.0784
0.0784
0.0784
0.0784
0.0784
0.0784
0.0784
0.0784
0.0784
0.0784
0.0784
0.0784
0.0621
Cumulative
Precip Precip
Depth Depth
Pr Pre
(in) (in)
0.0171
0.0171
0.0239
0.0239
0.0239
0.0324
0.0324
0.0612
0.0972
0.0486
0.0324
0.0241
0.0241
0.0241
0.0158
0.0158
0.0158
0.0158
0.0158
0.0158
0.0158
0.0158
0.0158
0.0158
0.0158
0.0158
0.0130
0.0130
0.0130
0.0130
0.0130
0.0130
0.0130
0.0130
0.0130
0.0130
0.0130
0.0130
0.0103
0.4405
0.4576
0.4815
0.5054
0.5294
0.5618
0.5942
0.6554
0.7526
0.8012
0.8336
0.8577
0.8818
0.9059
0.9218
0.9376
0.9535
0.9693
0.9851
1.0010
1.0168
1.0327
1.0485
1. 0643
~ :W.6 [~ ff; -,[;'" fl fvf~' r:', ,,:',1
~ .,,, L~.. U d u;;; I~ \'1
1..9[---..'--._." .,!.".
, .. \ i: I I,
1 J 1 d ;1
1:ilj4~; DEe 22 2005 liLli'
1.1479, I" ~
1. 1608
1.1738
1.1867
1.1997
1.2127
1.2256
1. 2386
1.2515
1. 2618
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PROJECT: Seahome Services, Inc. drainage
25 yr storm (B)
-------------------------------------------------------------
Total Basin Area = 43560 sq ft =
Storm Duration =
Peak Rainfall Intensity =
Total Rainfall Volume
Total, 24 hr rainfall =
Standard SCS Type 1A
24 hr hyetograph (adj'd)
from King Co Drn Manual
1.0000 Ac
24 hr
0.588 cfs
6534 cu ft
1. 80 in
Rainfall Data
-----------------------------------
------------------------
Time % Cumulative
(min) Precip % Precip
780
790
800
810
820
830
840
850
860
870
880
890
900
910
920
930
940
950
960
970
980
990
1000
1010
1020
1030
1040
1050
1060
1070
1080
1090
1100
1110
1120
1130
1140
1150
1160
0.57
0.57
0.57
0.57
0.57
0.57
0.57
0.57
0.57
0.57
0.57
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.43
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
70.67
71. 24
71.81
72.38
72.95
73.52
74.09
74.66
75.23
75.80
76.37
76.87
77 .37
77.87
78.37
78.87
79.37
79.87
80.37
80.87
81. 37
81. 87
82.37
82.80
83.20
83.60
84.00
84.40
84.80
85.20
85.60
86.00
86.40
86.80
87.20
87.60
88.00
88.40
88.80
Time
(hrs)
13.00
13.17
13.33
13.50
13.67
13.83
14 .00
14.17
14.33
14.50
14.67
14.83
15.00
15.17
15.33
15.50
15.67
15.83
16.00
16.17
16.33
16.50
16.67
16.83
17.00
17 .17
17.33
17.50
17.67
17 .83
18.00
18.17
18.33
18.50
18.67
18.83
19.00
19.17
19.33
Total
Basin
Rainfall
P
(ds)
0.0621
0.0621
0.0621
0.0621
0.0621
0.0621
0.0621
0.0621
0.0621
0.0621
0.0621
0.0545
0.0545
0.0545
0.0545
0.0545
0.0545
0.0545
0.0545
0.0545
0.0545
0.0545
0.0545
0.0468
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
Cumulative
Precip Precip
Depth Depth
Pr Prc
(in) (in)
0.0103
0.0103
0.0103
0.0103
0.0103
0.0103
0.0103
0.0103
0.0103
0.0103
0.0103
0.0090
0.0090
0.0090
0.0090
0.0090
0.0090
0.0090
0.0090
0.0090
0.0090
0.0090
0.0090
0.0077
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
1.2721
1. 2823
1. 2926
1.3028
1.3131
1. 3234
1.3336
1.3439
1. 3541
1. 364 4
1.3747
1. 3837
1.3927
1. 4017
1.4107
1. 4197
1.4287
1.4377
1. 4467
1. 4557
1. 4647
1.4737
1. 4827
1. 4904
1.4976
1.5048
1.5120
1.519~~__._ ,.. -'----:-1
1.5264['f:)') ~~ ~ [2 ~'\!
1. 533f>.. I.., I.............'.. - -'---. -.-. '.~.. ...'..... ...ll.... \1......... .1...
. I .', "'; I I t ~ ,
1.54081', .: !~
~:~:~~: Ii DEe 22 2005 :[,~i
1.5624
1. 5696 "'~-
1. 5768
1.5840
1.5912
1. 5984
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PROJECT: Seahome Services, Inc. drainage
25 yr storm (B)
-------------------------------------------------------------
Total Basin Area = 43560 sq ft =
Storm Duration =
Peak Rainfall Intensity =
Total Rainfall Volume
Total, 24 hr rainfall =
Standard SCS Type 1A
24 hr hyetograph (adj'd)
from King Co Drn Manual
1 .0000 Ac
24 hr
0.588 cfs
6534 cu ft
1.80 in '."
Rainfall Data
-----------------------------------
------------------------
Time % Cumulative
(min) Precip % Precip
1170
1180
1190
1200
1210
1220
1230
1240
1250
1260
1270
1280
1290
1300
1310
1320
1330
1340
1350
1360
1370
1380
1390
1400
1410
1420
1430
1440
1450
1460
1470
1480
1490
1500
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.40
0.00
0.00
0.00
0.00
0.00
0.00
100.00
89.20
89.60
90.00
90.40
90.80
91.20
91. 60
92.00
92.40
92.80
93.20
93.60
94.00
94.40
94.80
95.20
95.60
96.00
96.40
96.80
97.20
97.60
98.00
98.40
98.80
99.20
99.60
100.00
100.00
100.00
100.00
100.00
100.00
100.00
Time
(hrs)
19.50
19.67
19.83
20.00
20.17
20.33
20.50
20.67
20.83
21.00
21.17
21. 33
21. 50
21. 67
21.83
22.00
22.17
22.33
22.50
22.67
22.83
23.00
23.17
23.33
23.50
23.67
23.83
24.00
24.17
24.33
24.50
24.67
24.83
25.00
Total
Basin
Rainfall
P
(ets)
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0436
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
Cumulative
Preeip Preeip
Depth Depth
Pr Pre
(in) (in)
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0072
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
1.8000
1.6056
1.6128
1. 6200
1. 6272
1. 6344
1. 6416
1.6488
1. 6560
1.6632
1. 6704
1. 6776
1. 6848
1.6920
1. 6992
1. 7064
1. 7136
1. 7208
1. 7280
1. 7352
1. 7424
1. 7496
1.7568
1. 7640
1.7712
1. 7784
1.7856
1.7928
~ : ~~rt~ ~:--'_.'1e -~'l
1. 80qW1.! 1------------1
~:~~d~\\1 DEe 22 2005 I
1. 8000 I
1. 8000 \
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Date: 12-10-105 PIPE HEAD LOSS
Pipe diameter (inches) : 6 D == 0.50 ft
Flow (one only) GPM: Q 0.10cfs
CFS: 0.1 Q 44.88 gpm
Length of pipe (feet) : 800 L == 800 ft
Friction factor
------------------
Hazen-Williams (C) : 150 (50-200) HI 0.15 ft 0.06
Mannings (n) : 0.0082 ( .005-.05) HI 0.10 ft 0.04
Darcy-Weisbach (f) : 0.014 (.01-1) HI 0.09 ft 0.04
. - ---\1
".1, ~ rm. \ t
~) L::: i I
---.------. \', !.',
r-- ".. ','."
I I,.
I H)H
I DEe 2 2 2005 jI)
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