HomeMy WebLinkAbout821103102 Stormwater Mgmt
DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
for
PARCEL 821.103.012
Prepared for:
EXPIRES 8-25-07
Dean Rosenthal
and
Irene Holt
NTI Engineering & Surveying
717 S. Peabody St., Port Angeles, WA 98362, 360-452-8491
DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
Prepared For Dean Rosenthal and Irene Holt
November 2006
For the Property Described as Tax # 821-103-012
Section 10, Township 28 North, Range 1 East, W.M.
Jefferson County, Washington
Prepared by
NTI ENGINEERING & SURVEYING
717 South Peabody Street
Port Angeles, Washington 98362
360-452-8491
I
DEAN ROSENTHAL & IRENE HOL THOME
TALA POINT VICINITY MAP
O NORTHWESTERN TERRITORIES, INC.
Engineers - Land Surveyors - Geologists
Construction Inspection - Materials Testing
NT I 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360) 452.8491
j
I
DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
for
PARCEL 821-103-012
Rosenthal and Holt Neighborhood Map
III
DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
for
PARCEL 821-103-012
Rosenthal and Holt Area Map
IV
DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
for
PARCEL 821-103-012
/.~
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~ PLOT PLAN
SITE MAP
v
I
SEE DETAIL DRAWING
FOR TlGHntNE DETAILS
NOTE: UNDERLYING BASE MAP
WAS PROVIDED BY MITCHELL
DESIGN
m PLOT PLAN
SILT FENCING OR
CONSTRUCTION FENCING
TO PROVIDE BOUNDARY
TO CONSTRUCTION
ACTIVITIES
EROS/ON CONTROL
MAP FOR
ROSENTHAL AND
HOL THOME
INSTALL SILT FENCING
/ WHERE INDICATED. ADJUST
LOCA TION PER TEXT OF
ACCOMPANYING REPORT
STABILIZED
CONSTRUCTION
ENTRANCE TO BE
PER DETAIL
DRAWING
O NORTHWESTERN TERRITORIES, INC.
Engineers - Land Surveyors - Geologists
Construction Inspection - Materials Testing
NTI 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360) 452-8491
PROVIDE <NONE> LF 12" CONCRETE
OR CORRUGATED METAL PIPE
TO MAINTAIN EXISTING DRAINAGE
(TEMPORARY INS TAL LA TlON)
4S
RcQ(/,
7RCO
(700 '
-0t1( .J
R = 25' MIN.
12" MIN.
4" TO 8" QUARRY SPALLS
PROVIDE FULL WIDTH OF
INGRESS/EGRESS AREA
STABILIZED CONSTRUCTION ENTRANCE
O NORTHWESTERN TERRITORIES, INC.
'"'1 Engineers - Land Surveyors - Geologists
Construction Inspection - Materials Testing
NT I 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360) 452-8491
MIRAFI 100 NS
OR EQUIVALENT
FlL TER FABRIC MA TERIAL
2" X 2" BY 74 GA WIRE
FABRIC OR EQUIVALENT
PROVIDE 3/4" - 1 1/2" WASHED
GRAVEL BACKFILL IN TRENCH AND
ON BOTH SIDES OF FlL TER FENCE
FABRIC ON THE SURFACE
2" X 4" WOOD POST
OR STEEL FENCE POST
MIRAFI 700 NS
OR EQUIVALENT
FlL TER FABRIC MA TERIAL
60" WIDE ROLLS - USE
STAPLES OR RINGS TO 7
ATTACH FABRIC TO WIR[ /
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Cl
Cl '"
l.r,
co
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I r ;O:,NUN[ ~
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I Cl
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SECTION
2" X 2" BY 74 GA WIRE
FABRIC OR EQUIVALENT
6' MAX
2" X 4" WOOD POSTS, STANDARD
OR BUTER, OR STEEL FENCE POST
ELEVA T10N
S/L T FENCE
O NORTHWESTERN TERRITORIES, INC.
Engineers - Land Surveyors - Geologists
Construction Inspection - Materials Testing
NT I 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360) 452.8491
ONE OR MORE MOBILE HOME OR SIMILAR AUGER
TYPE SOIL ANCHORS CAPABLE OF RESISTING A
TOTAL OF 5 TONS OF LATERAL FORCE, SET
BACK A MINIMUM OF 10 FEET FROM EDGE OF
BLUFF
1/2 IN DIA GALVANIZED WIRE~
ROPE OR CABLE, THREADED
THROUGH PIPE AS SHOWN
AND ATTACHED TO ANCHORS
WITH 2 OR MORE WIRE CLIPS
OR A SPLICED OR PRESSED
EYE.
INSERT 36" LENGTH OF
2" GAL V IRON PIPE
INSIDE OF CROSS BAR
FORMED OF HOPE
PIPE (WITH CAPS) AS
SHOWN.
DRILL A TOTAL OF 75 /
HOLES, EACH 1/2 INCH
IN DIAMETER, EVENL Y
SPACED (EXCEPT THRU
COUPLINGS) ALONG THE
HORIZONTAL PIPE MEMBER.
HOT BEND PIPE OR USE
LONG SWEEPS TO MATCH
SLOPE OF GROUND
BREAKS AND IRREGULARITIES IN
THE FACE OF THE BLUFF ARE
NOT SHOWN. PIPE JOINTS, LONG
SWEEPS, OR HOT BENDS MAY
BE USED TO MATCH THE PIPE TO
THE FACE OF THE BLUFF. PROVIDE
ADDITIONAL ANCHOR(S) AT BENDS
OF MORE THAN 10 DEGREES.
ALL THREE CAPS ON FLOW DISPERSER
TO BE THREADED AND REMOVABLE
CAP ON BOTTOM OF PIPE TO REST
AGAINST EYE OF ANCHOR. DRILL HOLE
IN CAP FOR CABLE. CAP MAYBE SLOTTED
TO ALLOW INSTALLATION AFTER PLACEMENT
OF CABLE. USE LARGE FENDER
WASHERS TO BACK UP PIPE CAP
/' _____ AS NECESSARY.
~ PLACE 12 INCH DIAMETER STONES UNDER
PIPE FOR ADDITIONAL ENERGY DISSIPA TION.
_____ STONES TO EXTEND A MINIMUM OF 2 FEET
_______ FROM HORIZONTAL PIPE IN ALL DIRECTIONS.
WELDED HOPE CROSS
MOBILE HOME OR SIMILAR AUG~
TYPE SOIL ANCHOR, SET IN FACE
OF BLUFF 12 INCHES ABOVE
ORDINARY HIGH WATER LINE
TIGHTLINE PIPE DETAIL
(ft NORTHWESTERN TERRITORIES, INC.
, Engineers - Land Surveyors - Geologists
Construction Inspection - Materials Testing
NT I 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360) 452-8491
\
DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
for
PARCEL 821-103-012
ABSTRACT
This project consists of the construction of a home and related work at Tala Point in
unincorporated Jefferson County in the State of Washington. This plan also provides
for the construction of a tightline pipe to convey stormwater runoff from both the
new and the existing improvements to a discharge to marine waters.
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 storm water pipe.
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.
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. Silt fencing may be
omitted where a buffer of undisturbed native vegetation or healthy lawn
exists for a minimum of 50 feet below the area of exposed soil. The
location of the silt fencing is shown on the Erosion and Sediment Control
Plan map included at the beginning of this report.
2. Runoff from new roof drains, interception ditches, and tightline pipes
shall be routed to a tightline pipe to be constructed down the bluff per this
plan. The tightline pipe shall be six inch diameter pipe securely attached
to the slope. It shall discharge to an energy dissipation structure located
just above the line of ordinary high water. Details are shown on the
drawing included at the beginning of this report.
3. Runoff from any future structures shall be routed to the same tightline
pIpe.
x
DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
for
PARCEL 821-103-012
CONTENTS
I. PROJECT OVERVIEW....................................................... .................................1
A. Project Description......................... .................................................................. 2
B. Existing Site Conditions.................................................................................. 2
1. Topography......................................................................... ........................ 2
2. Vegetation........ ......................... .................... ........................... ... ...... .......... 4
3. Drainage........ .............................................................._.............................. 4
C. Adjacent Properties...................... ................ _................................. .................. 4
II. DESIGN CRITERIA............................................................................................. 5
A. Soils................................................................................................................... 5
B. Rainfall............................................................................................................. 6
C. Hydrologic ModeL......................... .................................................... ................ 7
D. Time of Concentration................. ..................................................................... 7
1. Design Condition ................... .......................................... ......... ............. ..... 7
a. Unconcentrated Flow............ .......................... ........................................... 7
b. Shallow Concentrated Flow.. .......................... ........ ................ ............... ....8
c. Open Channel (Intermittent) Flow........................................................... 8
2. Time of Concentration.............. ........................................................ .......... 9
III. RUNOFF.................................................... ........................................ ................... 9
A. Post-development Runoff............................................................... .................. 9
B. Mitigation.................................... ............................................... .................... 10
IV. EROSION AND SEDIMENT CONTROL PLAN ...............................................10
A. Site Specific Construction Phase BMPs........................................................11
B. Stabilization and Sediment Trapping (Erosion and Sediment
Control Requirement Number 1)... ....................................... ......................... 11
1. Stabilization of Exposed Soils.. ......................... ....................... ................ 12
a. Minimize Disturbance of Vegetation.. ......................................... ............ 12
b. Minimize the Length of Time the Soil is Unprotected ...........................12
c. Ensure Prompt Revegetation of Disturbed Areas ..................................12
d. Protective Coverings................. .......... ...................... .............. ................. 14
2. Sediment Trapping.......................................................... ......................... 15
a. Sheet Flow Through Grassy or Heavily Vegetated Areas...................... 15
b. Grassy Swales........................................................................................... 15
Xl
I. Soils........................................................................................................... 16
11. Design Criteria .................................................. ....................................... 16
(A) Velocity.................................................................................................. 16
(B) Depth of Flow......................................... ............................... ................ 16
(C) Slope...................................................................................................... 16
Ill. Dimensions.................................................................... ........................... 16
IV. Side Slopes........................................................................................ ........ 16
c. Interceptor Swales........................................... ......................................... 16
d. Other Sediment Trapping Devices and Systems ....................................17
C. Delineate Clearing and Easement Limits (Erosion and
Sediment Control Requirement Number 2) .................................................. 17
D. Protection of Adjacent Properties (Erosion and Sediment
Control Requirement Number 3)........... ........... .................. ........... .......... ...... 17
E. Timing and Stabilization of Sediment Trapping Measures
(Erosion and Sediment Control Requirement Number 4)............................ 18
1. Timing oflnstallation of BMPs ....... .............. ...................... .............. ...... 18
2. Stabilization of slopes of structural BMPs .............................................. 18
F. Cut and Fill Slopes (Erosion and Sediment Control
Requirement Number 5) ........................................................................ ..... 18
G. Controlling Off-Site Erosion (Erosion and Sediment Control
Requirement Number 6) . .............................................................. ................. 18
H. Stabilization of Temporary Channels and Outlets (Erosion
and Sediment Control Requirement Number 7)........................................... 19
I. Underground Utility Construction (Erosion and Sediment
Control Requirement Number 9).................... ................... ............. ............... 19
J. Construction Access Routes (Erosion and Sediment Control
Requirement Number 10) ................................. ................. ....................... ..... 20
K. Removal of Temporary BMPs (Erosion and Sediment
Control Requirement Number 11)............ ...................... ............................... 20
L. Dewatering Construction Sites (Erosion and Sediment
Control Requirement Number 12)......... .................................................. ...... 21
M. Control of Pollutants Other than Sediment (Erosion and
Sediment Control Requirement Number 13)................................................ 21
1. Control of Toxic Substances................ ................ ...................... ............... 21
2. Petroleum Spills ....................................................................................... 22
a. Driver Training.................................. .......................................................22
b. Fueling of Vehicles............................... .................................................... 22
c. Parking of Fuel Tankers........................ ......... ....... ............................. ..... 22
d. Containment of Spills.......................... ................................................ ..... 22
N. Maintenance (Erosion and Sediment Control Requirement
Number 14)................................................ ..................................................... 22
O. Financial Responsibility................................ ....... ........................... ........... ... 23
X11
DRAINAGE, EROSION, AND SEDIMENT CONTROL PLAN
for
PARCEL 821-103-012
I. PROJECT OVERVIEW
This project consists of the construction ofa single family home and related work on a
single parcel at Tala Point in unincorporated Jefferson County in the State of Washington.
Maps of the area and site are 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,
with particular emphasis on the bluff.
Photo 1
Photo 1 shows the tip of Tala Point in a view taken via Google Earth. A tightline pipe will
be constructed from the top of the bluff to just above the line of ordinary high water. The
new home will be constructed near the lower right portion of the point shown in Photo 1
A. Project Description
This project consists of the construction of a new home for Dean Rosenthal and Irene
Holt. The limits of the new construction are shown on the maps included at the
beginning of this report. This plan provided for the construction of a tightline pipe from
the home site to the beach to convey stormwater runoff to marine waters. The assumed
area to be drained by the tightline outfall pipe is much larger that the actual footprint
of the home and driveway.
This plan provides for the installation of silt fencing and other erosion control measures
to provide protection against erosion during construction. Permanent water quantity
control will be provided by the tightline pipe down the bluff. The tightline pipe has been
sized to service the new roof area, new parking and driveway areas and any future
buildings.
B. Existing Site Conditions
The following summary of site conditions represents existing conditions.
1. Topography
The site resembles a long and narrow triangle as shown on the maps included at the
beginning of this report. The ground generally slopes to the northwest, toward the
beach. Figure 1 is an excerpt from a USGS topo map with the Project Location
marked.
Figure 1
2
The most striking feature of the parcel is the marine bluff to the northwest of the
home site. Photo 2 and Photo 3 show different views of this bluff.
Photo 2
Photo 3
3
The beach itself is relatively flat as shown in Photo 4.
Photo 4
2. Vegetation
The uplands portion of the site is presently vegetated with natural vegetation. Trees
and brush cover portions of the bluff. Natural stormwater falling on other than
impervious surfaces will be allowed to sheet flow across new lawn or landscaping of
natural vegetated strips before being introduced into the tightline pipe.
The photos and maps at the beginning of this report show more details of existing
vegetation.
3. Drainage
The largest runoff route from the parcel is subsurface. Water apparently infiltrates
into the upper sandy soils and percolates downward, eventually working its way to
marine waters below.
C. Adjacent Properties
The site is surrounded by rural residential lands on the south, west and east sides.
Hood Canal forms the northern boundary of the parcel.
The proposed work will not affect adjacent properties.
4
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 numbers 52 and 55 of the Soil Survey of Jefferson County
Area, published by the U. S. Soil Conservation Service, portions of which are combined
here as Figure 2.
Figure 2
Figure 2 can be compared with the Area Maps at the beginning of this report for
orientation.
These maps predict that the soils on this site are, from the beach upwards, types Co
(Coastal Beaches), KtE (Kitsap silt loam, 30-50 percent slopes), CfE (Cassolary sandy
loam, 30-50 percent slopes), and CfC (Cassolary sandy loam, 0-15 percent slopes).
5
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 approximately 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 3. The project
location is marked on the map.
;1t'~~ /I
~-I----~-- r'-..~ J ---- 9
j, if, I ! ---<. :~--, --r)-;-n rr-< \)
- - -ll-- : ------- ! -L--~I--+--~L"~'. ~~ r:\ I
2)/'1 I I I I I, ~
! I i I I L 'I'~
28N -~-l-r--r---T., -- i --T- -I ROS~tNTHiL & 40l T ~
---- i -----l----+ - +--+-~--- --+--+---h--;o
2;'t\i I Ii: ill 41 I (\ JF
2'N1l \ -r~Tr- I / /;
! ow 9W 8W -Yo 6{1 .'iP ,J1,j ,'H C'fl '1[;;
Figure 3
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 approximately 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 4. The project
location is marked on the map.
;2:]-=ILt. ..c.. r- 0)1.1 ,,~0\/
.?9N Iii : \' !1~i)r1v
28N-,--r-----r'i---ii-jROS$NTHAtL & 16L T =P~,
--t-l--~--+--.-+- !.'! . l--I-,-k'lv
27N ! I I I I I i I ,~i ;n !)
Ii . I . i. I I i I . \ i-
---.f----+----r -, -+---t-----+-~. -~.... . '.- '. '-f
76/; i I I \ I I : ~v j
;,)W I 9VV I 8v:"'V;' I 6(; i 5VV I "w I 3W :n~ U
1/V
Figure 4
6
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 Storm water Management Manual for the Puget Sound Basin (The Technical
Manual) published by the Washington State Department of Ecology.
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 basin, 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.
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. Design Condition
For this project the time of concentration is determined for rainfall falling on the
roof and being transported to the top of the bluff via a tightline pipe.
a. Unconcentrated Flow
Immediately after falling to the ground, rainwater initially travels as
unconcentrated sheet flow for a period of time (Tt) calculated by:
7
0.80
0.42 (NsL)
Tt = -------------------- = 0.21 min
0.527 0.4
(P2) (SO)
Where:
Ns = 0.011
P2 = 1.5
SO = 0.2500
L = 25
= Sheet flow Manning's n (DOE Table 111-1.4)
= 2 yr, 24 hr rainfall (in)
= Slope of flow path (ft/ft)
= Length (L) of flow path (ft)
This is flow across the roof surface at an assumed gentle angle (3:12 pitch)
and smooth surface.
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 = -------------------- = 0.31 min
60 Ks SQRT(SO)
Where: Ks = 27
SO = 0.0100
L = 50
= 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 rain gutters below the roof line.
c. Open Channel (Intermittent) Flow
Flows next travel through intermittent open channels for a period of time (Tt)
calculated by:
8
L
Tt = = 0.21 min
60 Kc SQRT(SO)
Where: Kc = 21
SO = 0.0800
L = 75
= Velocity factor (Kc) (DOE Table 111-1.4)
= Slope of flow path (ft/ft)
= Length (L) of flow path (ft)
This is flow through a tightline pipe from the home to a point near the top of the
bluff.
2. 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 = 0.73 min
This is rounded to 1 min for use in further calculations.
III. RUNOFF
Full calculations for post-development flow from the roof and driveway areas at the 100
year level are included in Appendix I.
A. 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 final development of the site.
Under these conditions, the site will have a weighted runoff curve number of 98.
Complete calculations of the post-development runoff are contained in Appendix I. The
post-development runoff is calculated to be 0.249 cfs for the 100-year storm.
9
B. 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.
Design (sizing) calculations, including flood routing calculations, are included in
Appendix I. The tightline pipe is designed to transport stormwater runoff from the
uplands to discharge immediately above the line of ordinary high water. The discharge
point shall be near ground level onto a pad of quarry spalls for energy dissipation as
shown on the drawing 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. Silt fencing may be omitted where a
buffer of undisturbed native vegetation or healthy lawn exists for a minimum of
50 feet below the area of exposed soil. The location of the silt fencing is shown on
the Erosion and Sediment Control Plan map included at the beginning of this
report.
2. Runoff from new and existing roof drains, interception ditches, and tightline
pipes shall be routed to a tightline pipe to be constructed down to just above the
beach per this plan.
3. Runoff from future structures shall be routed to the same tightline pipe down the
beach access stair system.
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.
10
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 forma I 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.
Water quality controls, commonly referred to as Best Management Practices, or BMPs, are
necessary to prevent three distinct types of impacts. The first consists of damage done as
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 site specific mitigation measures described above shall be implemented in addition
to any that may later be necessary due to changing or unforeseen site conditions.
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 incorporated 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
(Erosion and Sediment Control
11
both soils that are not yet at final grade and to those that are at final grade, including
soil stockpiles.
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 certain portions of the
work, such portions of the work should be completed promptly in order to reduce
the chance of an erosive rainfall event catching the soil unprotected.
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 operations 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 other 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
12
practical, the planting season IS considered to be between March 1 and
October 1.
13
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
Colonial Bentgrass,
Var. Astoria
Perennial Rye
White Clover
40
10
40
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 than 2 horizontal to 1
vertical) if it is wet to the point of limpness. Straw is generally effective where
the distance from the top to the toe of the slope is no more than 100 feet.
14
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 were taken from the
Draft Stormwater Guidelines published by the Washington State Department of
Fisheries in 1990 and are recommended for use here due to their simplicity.
15
More specific design criteria are more appropriate for use on large or complex
sites.
1. Soils
Gravelly and coarse sandy soils should be avoided in order to maximize water
contact with vegetation and the soil surface.
11. 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.
Ill. 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 ditches.
Interceptor swales are especially effective adjacent to property lines which run
more or less straight up and down a slope and where only sheet flows are to be
16
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
II-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.
17
E.
Timing and Stabilization of Sediment Trapping Measures
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 BMPs are mandatory
parts of this plan.
(Erosion and
1. Timing of Installation of BMPs
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 event greater than a two year
event were to occur before the site were completely revegetated and the stormwater
infiltration/detention systems completed.
18
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 ~ddition to the general
protective requirements, specific armoring methods are included in the appropriate
details.
I. 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.
19
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 roads 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
sta bilized.
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 completed.
20
L. Dewatering Construction Sites (Erosion and Sediment Control Requirement
Number 12)
Discharges from pumps used in dewatering trenches or other portions of a construction
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 disrupting
concentrated flows.
Directing flows onto a pad constructed 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 storm water.
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,
work in the vicinity shall be immediately stopped and the following agencies
notified:
21
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 SPCC 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 of the 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)
This section constitutes the Operation and Maintenance Manual for the erosion and
sediment control BMPs used during the construction phase of this project.
22
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.
23
APPENDIX 1
Subsection 1
Summary of various coefficients and operational values for the basin.
file: ROSNDRN1.WB2
Date: November 13, 2006
PROJECT: Rosenthal 25(30-3) drainage
BASIN DATA
Basin Data
---------------------------------------------------------------
Area:
Cn:
Tc:
Not Included
0.0000 (Ac) +
100.0
1 (min)
Included
0.2500 (Ac)
98.0
1 (min)
Total
0.2500 (Ac)
RAINFALL
2 yr storm:
25 yr storm:
100 yr storm:
1.50 (in)
2.80 (in)
3.20 (in)
Peak
Basin Rainfall
------(Qr)-------
0.1225 (cfs)
0.2287 (cfs)
0.2614 (cfs)
24 hr rainfall depth
----------------------------------
RUNOFF
2 yr storm:
25 yr storm:
100 yr storm:
Basin Runoff
------(Qpre)-----
0.1103 (cfs)
0.2168 (cfs)
0.2492 (cfs)
----------------------------------
APPENDIX I
Subsection 2
Catalog ofland uses in basin
PROJECT: Rosenthal 25 (30- 3) drainage
RUNOff CURVE NUMBER CALCULATIONS
Total Parcel Size (acres) =
0.25
Pervious (undetained)
- -- - - - - - - -- - - -- - -- - - - - -- - - -- - - - - - - -- -- - - - - - -- - - - - - -- -- - - - - - -- - --- - - --- -- --. --- --- - - - - - - - ----- -- -- -- - -- - - ---. -- - - - --- ---- - ---- - - --. - -- - - --. -- - ---- -. - -- -.- ---- ---- --
Land Use
Area
(acres)
Runoff
Curve No.
(Cn)
- -- -- - - - --- - - ----- - -- ---- - --- - ---- -- - - - - - ----- ------- ---- - - ---- -- ----- --- - -------
65.00
PRE-DEVELOPMENT
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
_U__n_u_ I
100.00 I
0.000 I
_uu______ I
100.00 I
I
100.0 I
Remaining undeveloped
Subtotal Pervious Area =
Remainder Area =
Total Pervious Area =
Total Impervious Area =
Total Area =
0.00000
0.00000
0.00000
0.00000
0.25000
D.25000
Weighted Average Runoff Curve Number of Pervious Portion (rounded)
(A x Cn)
98.00
Predevelopment Weighted Average Runoff Curve Number of Entire Parcel (rounded) =
Land Use
Impervious (detained)
Area
(acres)
Runoff
Curve No.
(Cn) (A x Cn)
-----.------ -- - ---- --- -- - - ---- ---- --- - -------- - --. - -- - - --- - -._-- ------ - ----. ----
24.50
Roof and/or driveway
Total Impervious Area = 0.25000
0.25000
98.00
24.50
0.25
98.00
98.0
Weighted Average Runoff Curve Number of Impervious Portion (rounded) 98.0
Land Use
Impervious (detained)
Area
(acres)
Pervious (undetained)
- - --- ---- - --- --- - --- ---- - - --- ----- - ----- -- ----- --- --- ---- - ------ - --- - ----- ---------- -- ---- - -. -- - - ---- ---- -------. -------- --- ---- ----- - -------- - ---- --- - ------ -- -- --- --
Remaining undeveloped
Subtotal Pervious Area =
Remainder Area =
Total Pervious Area =
Total Impervious Area =
Total Area =
Area
(acres)
0.00000
0.00000
0.00000
0.00000
0.25000
0.25000
Runo f f
Curve No.
(Cn)
Weighted Ave. Runoff Curve Number of Pervious Portion (rounded)
Land Use
- -- -- - - - - - -- -- - -- -- - - - -- - - --- - - - - - - - - - - - - - --- ---- -- -- - - - - - -- - - --- - - - --- - -- - - -- - --
65.00
POST-DEVELOPMENT
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
_n____n__ I
100.00 I
0.000 I
n___u____ I
100.00 I
I
]00.0 I
(A x Cn)
98.00
Runoff
Curve No.
(Cn) (A x Cn)
--- - - - - -- -- -- -- - - -- - - - - - --- -- - -- - - - - - - -- - - -- - - - - - - -- - - ----- -- - - - --- -- - -- -- - - - - --
24.50
Roof and/or driveway
Total Impervious Area = 0.25000
0.25000
98.00
24.50
0.25
- 98.00
Postdevelopment Weighted Average Runoff Curve Number of Entire Parcel (rounded) ~
Weighted Ave. Runoff Curve Number of Impervious Portion (rounded) 98.0
98.0
APPENDIX I
Subsection 3
Raw rainfall data for the design storms falling on the basin.
PROJECT: Rosenthal 25(30-3) drainage
100 yr storm (C)
-------------------------------------------------------------
Total Basin Area = 10890 sq ft =
Storm Duration =
Peak Rainfall Intensity
Total Rainfall Volume
Total, 24 hr rainfall
Standard SCS Type lA
24 hr hyetograph (adj'd)
from King Co Drn Manual
Time
(min)
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
% Cumulative
Preeip % Preeip
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.S2
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
0.2500 Ae
24 hr
0.261 efs
2904 eu ft
3.20 in
Rainfall Data
Total
Basin
Rainfall
P
(efs)
0.0000
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0242
0.0242
0.0242
0.0242
0.0242
0.0242
0.0290
0.0290
0.0290
0.0290
0.0290
0.0290
0.0339
0.0339
0.0339
0.0339
0.0339
0.0339
0.0397
0.0397
0.0397
0.0397
0.0397
0.0397
0.0460
0.0460
0.0460
0.0460
Cumulative
Preeip Preeip
Depth Depth
Pr Pre
(in) (in)
0.0000
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0192
0.0192
0.0192
0.0192
0.0192
0.0192
0.0224
0.0224
0.0224
0.0224
0.0224
0.0224
0.0262
0.0262
0.0262
0.0262
0.0262
0.0262
0.0304
0.0304
0.0304
0.0304
0.0000
0.0128
0.0256
0:0384
0.0512
0.0640
0.0768
0.0896
0.1024
0.1152
0.1280
0.1440
0.1600
0.17 60
0.1920
0.2080
0.2240
0.2432
0.2624
0.2816
0.3008
0.3200
0.3392
0.3616
0.3840
0.4064
0.4288
0.4512
0.4736
0.4998
0.5261
0.5523
0.5786
0.6048
0.6310
0.6614
0.6918
0.7222
0.7526
PROJECT: Rosenthal 25(30-3) drainage
100 yr storm (Cl
-------------------------------------------------------------
Total Basin Area = 10890 sq ft =
Storm Duration =
Peak Rainfall Intensity
Total Rainfall Volume
Total, 24 hr rainfall
Standard SCS Type 1A
24 hr hyetograph (adj'dl
from King Co Drn Manual
Time % Cumulative
(min) Preeip % Preeip
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
o . 2500 Ae
24 hr
0.261 efs
2904 eu ft
3.20 in
Rainfall Data
Total
Basin
Rainfall
P
(efs)
0.0460
0.0460
0.0644
0.0644
0.0644
0.0871
0.0871
0.1646
0.2614
0.1307
0.0871
0.0649
0.0649
0.0649
0.0426
0.0426
0.0426
0.0426
0.0426
0.0426
0.0426
0.0426
0.0426
0.0426
0.0426
0.0426
0.0348
0.0348
0.0348
0.0348
0.0348
0.0348
0.0348
0.0348
0.0348
0.0348
0.0348
0.0348
0.0276
Cumulative
Preeip Preeip
Depth Depth
Pr Pre
(in) (in)
0.0304
0.0304
0.0426
0.0426
0.0426
0.0576
0.0576
0.1088
0.1728
0.0864
0.0576
0.0429
0.0429
0.0429
0.0282
0.0282
0.0282
0.0282
0.0282
0.0282
0.0282
0.0282
0.0282
0.0282
0.0282
0.0282
0.0230
0.0230
0.0230
0.0230
0.0230
0.0230
0.0230
0.0230
0.0230
0.0230
0.0230
0.0230
0.0182
0.7830
0.8134
0.8560
0:8986
0.9411
0.9987
1.0563
1.1651
1.3379
1.4243
1.4819
1.5248
1.5677
1. 6106
1.6387
1.6669
1. 6950
1.7232
1.7514
1.7795
1.8077
1. 8358
1. 8640
1. 8922
1.9203
1.9485
1.9715
1.9946
2.0176
2.0406
2.0637
2.0867
2.1098
2.1328
2.1558
2.1789
2.2019
2.2250
2.2432
PROJECT: Rosenthal 25(30-3) drainage
100 yr storm (C)
-------------------------------------------------------------
Total Basin Area = 10890 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
Time
(min)
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
% Cumulative
Preeip % Preeip
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
0.2500Ae
24 hr
0.261 efs
2904 eu ft
3.20 in
Rainfall Data
Total
Basin
Rainfall
P
(efs)
0.0276
0.0276
0.0276
0.027 6
0.0276
0.0276
0.0276
0.0276
0.0276
0.0276
0.027 6
0.0242
0.0242
0.0242
0.0242
0.0242
0.0242
0.0242
0.0242
0.0242
0.0242
0.0242
0.0242
0.0208
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
Cumulative
Preeip Preeip
Depth Depth
Pr Pre
(in) (in)
0.0182
0.0182
0.0182
0.0182
0.0182
0.0182
0.0182
0.0182
0.0182
0.0182
0.0182
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0138
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
2.2614
2.2797
2.2979
2:3162
2.3344
2.3526
2.3709
2.3891
2.4074
2.4256
2.4438
2.4598
2.4758
2.4918
2.5078
2.5238
2.5398
2.5558
2.5718
2.5878
2.6038
2.6198
2.6358
2.6496
2.6624
2.6752
2.6880
2.7008
2.7136
2.7264
2.7392
2.7520
2.7648
2.7776
2.7904
2.8032
2.8160
2.8288
2.8416
PROJECT: Rosenthal 25(30-3) drainage
100 yr storm (C)
-------------------------------------------------------------
Total Basin Area = 10890 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
Time
(min)
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
% Cumulative
Preeip % Preeip
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
0.2500 Ae
24 hr
0.261 efs
2904 eu ft
3.20 in
Rainfall Data
Total
Basin
Rainfall
P
(efs)
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0194
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
Cumulative
Preeip Preeip
Depth Depth
Pr Pre
(in) (in)
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
3.2000
2.8544
2.8672
2.8800
2:8928
2.9056
2.9184
2.9312
2.9440
2.9568
2.9696
2.9824
2.9952
3.0080
3.0208
3.0336
3.0464
3.0592
3.072 0
3.0848
3.0976
3.1104
3.1232
3.1360
3.1488
3.1616
3.1744
3.1872
3.2000
3.2000
3.2000
3.2000
3.2000
3.2000
3.2000
APPENDIX I
Subsection 4
Runoff calculations for the design storms.
PH(),JI.:C'I': H():it~1I1Iidl ?~J(-.W-l) ,!r,.tiIL..-j{l"
(;'~rll~Tdt ilJll t)l il():.;1 dr~v(~I()p"'(:ont Huno( I Ilydl"oqrdph - SaIlL.:! lid I h,Jl"d llrhdll lIydru<J[dph Mel110d
ldO y' :,\ unn (A)
p(-~ I vi '.lU S ^ rea
PCI-vitHJS Portion of l3asLn
Runoff Curve Number, en
Time of Concentrat'n, Tc
Pot'l Max Nat'[ Det'n, S
Routing Coefficient, w
Time
(hrs)
[0.00)
[0.17 ]
[0.33)
[0.50J
[0.67 ]
[0.83)
[1.00J
[1.17 ]
[1. 33]
[1.50]
[1. 67)
[1. 83)
[2.00]
i2.17]
[2.33)
[".:,OJ
i:' .671
[=.83 ]
[3.00]
i 3.17]
[3 _ 33]
[3.50 )
[3.67 J
[3.83)
[4.00)
[4.17 ]
[4 .33]
[4.50)
(4 . 67 )
[4 .83]
[5.00]
[:'.17)
[5.33]
[5.50)
[5.67 )
[5.83 ]
[6.00)
[6.17 )
[6.33 ]
[6.50)
[6.67 )
[6.83 ]
[7.00]
[7.17 !
[7.33 ]
[7. :,OJ
[7.67 i
(7.83]
[8.00]
[8.17]
[8.33 ]
[8. :'0]
[B.671
[ (j. 8-) 1
[9.00j
[ 9. 171
1':'. DI
Cumulative
Excess Excess
Precip Precip
R Re
I in) I in)
0.0000
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0192
0.0192
0.0192
0.0192
0.0192
0.0192
0.0224
0.0224
0.0224
0.0224
0.022 4
0.0224
0.0262
0.0262
0.0262
0.0262
0.0262
0.0262
0.0304
0.0304
0.0304
0.0304
0.0304
0.0304
0.0426
0.0426
0.0426
0.0576
0.0576
0.1088
0.1728
0.0864
0.05-16
0.0429
0.0429
0.0429
0.0282
0.0282
0.0['82
0.0282
0.0000
0.0128
0.0256
0.0384
0.0512
0.0640
0.0768
0.0896
0.1024
0.1152
0.1280
0.1440
0.1600
0.1760
0.1920
0.2080
0.2340
0.2432
0.3624
0.3816
0.3008
0.3200
0.3392
0.3616
0.3840
0.4064
0.4288
0.4512
0.4736
0.4998
0.5261
0.5523
0.5786
0.6048
0.6310
0.6614
0.6918
0.7222
0.7526
0.7830
0.8134
0.8560
0.8986
0.9411
0."987
1.0563
1.1651
1.3379
1.4243
1.4819
1.5248
1.r~67"]
1 6106
1.6387
1 . (069
1.61)50
1.1"12
o sq fl
0.0000 Ae
100
1 min
0.0000 in
0.8333
Cumulative
Instan- Instan-
taneous taneous
Runoff Runoff
Oi Ve
lefs) (eu ft)
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
C.OOOO
0.0000
Routed
Runoff
Or
Icfs)
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
QrJedk
Vtou [ -
O.:~492 cts
2693 eu tt
Impervious Area
Impervious Portion of Basin
Runoff Curve Number, Cn
Time of Concentrat'n, Tc
Pot'l Max Nat'l Det'n, S
Routirlg Coefficient, w
Cumulative
Excess Excess
Precip Precip
R Re
(in) lin)
0.0000
0.0000
0.0000
0.0000
0.0005
0.0019
0.0030
0.0040
0.0049
0.0056
0.0062
0.0086
0.0093
0.0099
0.0105
0.0109
0.0114
0.0141
0.0146
0.0150
0.0153
0.0156
0.0159
0.0189
0.0192
0.0194
0.0196
0.0198
0.0200
0.0237
0.0238
0.0240
0.0242
0.0243
0.0244
0.0285
0.0286
0.0287
0.0288
0.0289
0.0290
0.0408
0.0409
0.0410
0.0557
0.0559
0.1060
0.1692
0.0849
0.0567
0.0422
0.04i'3
0.0 i'3
0.0 78
0.0 78
0.0 7>1
0.0 78
0.0000
0.0000
0.0000
0.0000
0.0005
0.0024
0.0054
0.0094
0.0143
0.0199
0.0261
0.0347
0.0439
0.0539
0.0643
0.0753
0.0866
0.1008
0.1153
0.1303
0.1457
0.1613
0.1772
0.1961
0.2152
0.2346
0.2542
0.2741
0.2941
0.3178
0.3416
0.3656
0.3898
0.4141
0.4386
0.4670
o . 4 956
0.5244
0.5532
0.5822
0.6112
0.6520
0.6929
0.7339
0.7897
0.8456
0.9516
1.1208
1.2057
1.2623
1.3046
1.3468
1.3891
1.4169
1.4447
1.4726
1.5004
10890 sq ft
0.2:'00 Ae
98.0
1 min
0.2041 in
0.8333
Cumulative
Instan- Instan-
taneous taneous
Runoff Runoff
Oi Ve
(efs) (eu ft)
0.0000
0.0000
0.0000
0.0000
0.0008
0.0028
0.0046
0.0061
0.0074
0.0085
0.0094
0.0129
0.0141
0.0150
0.0158
0.0166
0.0172
0.0214
0.0220
0.0227
0.0232
0.0236
0.0241
0.0285
0.0290
0.0294
o . 0297
0.0300
0.0303
0.0358
0.0361
0.0363
0.0366
0.0368
0.0370
0.0431
0.0433
0.0435
0.0436
0.0438
0.0439
0.0617
0.0619
0.0621
o . 0843
0.0846
0.1603
0.2559
0.1284
0.0857
0.0639
0.0639
0.0640
0.0420
0.0421
0.0421
0.0421
o
o
o
o
o
2
5
9
13
18
24
31
40
49
58
68
79
91
105
118
132
146
161
178
195
213
231
249
267
288
310
332
354
376
398
424
450
476
502
528
555
:'92
629
666
717
767
864
1017
1094
1146
1184
1222
1261
1286
1311
1336
1362
Routed
Runoff
Or
(efs)
0.0000
0.0000
0.0000
0.0000
0.0006
0.0026
0.0045
0.0059
0.0073
0.0083
0.0093
0.0124
0.0142
0.0147
0.0159
0.0164
0.0172
0.0207
0.0224
0.0223
0.0233
0.0235
0.0241
0.0278
0.0294
0.0290
0.0299
0.0298
0.0303
0.0348
0.0367
0.0359
0.0368
0.0366
0.0371
0.0420
0.0440
0.0430
0.0439
0.0435
0.0440
0.0586
0.063<:\
0.0607
0.0815
0.0864
0.146:'
0.2492
0.1541
0.07:'7
0.0742
0.0570
o . 0686
0.0426
0.0417
0_0423
0.0419
Total
Runoff
o
lefs)
0.0000
0.0000
O.OOOD
0.0000
0.0006
0.0026
0.0045
0.0059
o . 0073
0.0083
0.0093
0.0124
0.0142
0.0147
0.0159
0.81(,4
0.0172
0.0207
0.0224
0.0223
0.0233
0.0235
0.0241
0.027 8
0.0294
0.0290
0.0299
0.0298
0.0303
0.0348
0.0367
0.0359
0.0368
0.0366
0.0371
0.0420
0.0440
0.0430
0.0439
0.0435
0.044 0
0.0586
0.0639
0.060:
0.081c'
o . 08 64
0.1465
0.2492
0.1541
0.0757
0.0742
0.O:j7Q
0.0686
0.0426
o 04 l'I
0.0423
0.0419
l'j{(),JI.;C'I': j{():-)'~nl:lidl ?~)(]O-J) dl_dif1r-j(l"~
C(.:!f)CldI.10rl of P()~:itdevplopllh"d HunoJ.1 Hydtuqrdph - SanLeJ Bdrbdr.J Urban Hydl'ogrdph Method
100 yrc s I.o!'m (AI
Pervious Area
PerviolJs Portion of Basin
Runoff Curve Number, Cn
Time of Concentrat'n, Tc
Pot'l Max Nat'l Det'n, S
Routing Coefficient, w
Time
(hrs)
[9.50]
[9.67 J
[9.83)
[10.00)
[10.17]
[10.33J
[10.50)
[10.67J
[10.83]
[11. 00)
[11.17)
[11.33J
[11.50)
[11.67J
[11.83)
[12.00J
[12.17 J
[12.33)
[12.50)
[12.67 ]
[12.83)
[13.00J
[13.17J
[13.33J
[13.50)
[13.67)
[13.83]
[14.00)
[14.17J
[14.33)
[14.50)
[14.67 )
[14.83 ]
[15.00]
[15.17 )
[15.33J
[15.50)
[15.67 )
(15.83J
[16.00]
[ 16.17)
(16.33J
[16.50)
[16.67 )
[16.83J
[17.00]
[17.17]
[17.33]
[ 17. :'0)
[17.67 ]
[17.83)
[18.00)
[ 18 . 171
[ 18 . 33]
[18.50)
[18.671
[ 18.83]
Cumulative
Excess Excess
Prceeip Preeip
R Re
(in) (in)
0.0282
0.0282
0.0282
0.0282
0.0282
0.0282
0.0282
0.0282
0.0230
0.0230
0.0230
0.0230
0.0230
0.0230
0.0230
0.0230
o . 0230
0.0230
0.0230
0.0230
0.0182
0.0182
0.0182
0.0182
0.0182
0.0182
0.0182
0.0182
0.0182
0.0182
0.0182
0.0182
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0160
0.0138
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
1.7514
1 .7795
1.8077
1.8358
1.8640
1.8922
1. 9203
1.9485
1.9715
1.9946
2.0176
2.0406
2.0637
2.0867
2.1098
2.1328
2.1558
2.1789
2.2019
2.2250
2.2432
2.2614
2.2797
2.2979
2.3162
2.3344
2.3526
2.3709
2.3891
2.4074
2.4256
2.4438
2.4598
2.4758
2.4918
2.5078
2.5238
2.5398
2.5558
2.5718
2.5878
2.6038
2.6198
2.6358
2.6496
2.6624
2.6752
2.6880
2.7008
2.7136
2.7264
2.7392
2.7520
2.7648
2.7776
2 . 7 904
2.80J2
o sq ft
0.0000 Ae
100
1 min
0.0000 in
0.8333
Cumulative
Instan- Instan-
taneous
Runo f f
Qi
lefs)
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
G.OOOO
0.0000
0.0000
0.0000
taneous
Runoff
Ve
(eu ft)
Routed
Runoff
Qr
(efs)
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
Qpcdk -
VLotal
O. :!492 cfs
2693 eu ft
Impervious Area
impervious Portion at Basin
Runoff Curve Number, Cn
Time of Concentrat1n, Tc
Pot'l Max Nat'l Det'n, S
Routing Coefficient, w
Cumulative
Excess Excess
Preeip Preei p
R Re
(in) I in)
0.0278
0.0278
0.027 9
0.027 9
0.027 9
0.0279
0.0279
0.027 9
0.0228
0.0228
0.0228
0.0228
0.022 8
0.0228
0.0229
0.0229
0.0229
0.022 9
0.0229
0.0229
0.0181
0.0181
0.0181
0.0181
0.0181
0.0181
0.0181
0.0181
0.0181
0.0181
0.0181
0.0181
0.0159
0.0159
0.0159
0.0159
0.0159
0.0159
0.0159
0.0159
0.0159
0.0159
0.0159
0.0159
0.0137
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
1.5282
1.5561
1.5839
1.6118
1. 6396
1.667:'
1. 6954
1.7233
1.7461
1.7690
1.7918
1.8146
1.8375
1. 8 603
1. 8832
1.9060
1.9289
1.9518
1. 9746
1.9975
2.0156
2.0337
2.0518
2.0699
2.0881
2.1062
2.1243
2.1424
2.1605
2.17 87
2.1968
2.2149
2.2308
2.2467
2.2626
2.2785
2.2944
2.3103
2.3263
2.3422
2.3581
2.3740
2.3899
2.4058
2.4195
2.4322
2. 4450
2.4577
2.4704
2.4832
2.4959
2.5087
2.:'214
2.5341
2.:'469
2.5596
2.5723
10890 sq ft
0.2500 Ae
98.0
1 mln
0.2041 in
0.8333
Cumulative
Instan- Instan-
taneous taneous
Runoff Runoff
Qi Ve
(efs) (eu ft)
0.0421
0.0421
0.0421
0.0421
0.0422
0.0422
0.0422
0.0422
0.0345
0.0345
0.0345
0.0345
0.0346
0.0346
0.0346
0.0346
0.0346
0.0346
0.0346
0.0346
0.0274
0.027 4
0.027 4
0.027 4
0.0274
0.0274
0.0274
0.027 4
0.0274
0.0274
0.0274
0.0274
0.0241
0.0241
0.0241
0.0241
0.0241
0.0241
0.0241
0.0241
0.0241
0.0241
0.0241
0.0241
0.0207
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
1387
1412
1437
1463
1488
1513
1539
1564
1585
1605
1626
1647
1668
1688
1709
1730
1750
1771
1792
1813
1829
1846
1862
1878
1895
1911
1928
1944
1961
1977
1994
2010
2024
2039
2053
2068
2082
2097
2111
2126
2140
2154
2169
2183
2196
2207
2219
2230
2242
2253
2265
2277
2288
2300
2311
2323
2334
Routed
Runoff
Or
(efs)
0.0422
0.0420
0.0422
0.0421
0.0422
0.0421
0.0422
0.0422
0.0358
0.0337
0.0351
0.0342
0.0348
0.0344
0.0347
0.0345
0.0346
0.0345
0.0346
0.0346
0.0286
0.0266
0.0279
0.0270
0.0276
0.0272
0.0275
0.0273
0.0275
0.0274
0.0274
0.0274
0.0246
0.0237
0.0243
0.0239
0.0242
0.0240
0.0241
0.0240
0.0241
0.0241
0.0241
0.0241
0.0213
0.0191
0.0194
0.0192
0.0193
0.0192
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
Total
Runoff
o
(efs)
0.0422
0.0420
0.0422
0.0421
0.0422
0.0421
0.0422
0.0422
0.0358
0.0337
0.0351
0.0342
0.0348
0.0344
0.034,
0.034:'
0.034E
0.0345
0.0346
0.0346
0.0286
0.0266
0.0279
0.0270
0.0276
o . 0272
0.0275
0.0273
0.027 5
0.0274
0.027 4
0.027 4
0.0246
0.0237
0.0243
0.0239
0.0242
0.0240
0.0241
0.0240
0.0241
0.0241
0.0241
0.0241
0.0213
0.0191
0.0194
0.0192
0.0193
0.0192
0.0193
0.0193
0.0193
0.019:1
0.019'3
0.019'3
0.0191
PI~O.JECT: l{uscflUl.il ?~)(]O-]) drdin'-](Jf.~
C(~rwr..H iUfl ul P()~.;I ck>veJopmenl. Hunofr Hydrogrdpll - ~;d[ll(] Bd rbrl rd. IJrbd[1 liydroqldph M(~Lllod
100 yr :>Lorm (1\)
Pervious Area
Perv ious Por tion 0 f Basin
-------------------------------------------
Runoff Curve Number, Cn
Time of Concentrat1n, Tc
Po t '1 Ma x Na t '1 De t ' n, S
Routing Coefficient, w
Time
(hrs)
[19.00]
[19.17 J
[19.33]
[19.50)
[19. 67 )
[19.83 )
[20.00)
[20.17J
[20.33)
[20.50)
[20.67J
[20.83J
[21.00J
[21.17)
[21.33)
[21.50J
[21.67 ]
[21.83]
[22.00J
[22.17)
[22.33J
[22.50]
[22.67]
[22.83]
[23.00)
[23.17 )
[23.33)
[23.50J
[23.67 )
[23.83)
[24.00J
[24.17)
[24.33 )
[24.50)
[24.67 )
[24.83 ]
[25.00)
o sq ft
0.0000 Ae
100
1 min
0.0000 in
0.8333
-------------------------------------------
Cumulative
Excess Excess
Precip Precip
R Re
(in) (in)
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
3.2000
2.8160
2.8288
2.8416
2.8544
2.8672
2.8800
2.8928
2.9056
2.9184
2.9312
2.9440
2.9568
2.9696
2.9824
2.9952
3.0080
3.0208
3.0336
3.0464
3.0592
3.0720
3.0848
3.0976
3.1104
3.1232
3.1360
3.1488
3.1616
3.1744
3.1872
3.2000
3.2000
3.2000
3.2000
3.2000
3.2000
3.2000
Cumulative
Instan- Instan-
taneous taneous
Runoff Runoff
Qi Ve
(efs) (eu ft)
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
max
Routed
Runoff
Qr
(efs I
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
Qpeak ~
Vtotal ~
0.:2492 cfs
2693 eu ft
Impervious Area
Impervious Portiorl of Basin
-------------------------------------------
Runoff Curve Number, Cn
Time of Concentrat1n, Tc
Pot'l Max Nat'l Detln, S
Routing Coefficient, w
Cumulative
Excess Excess
Preeip Preeip
R Re
(in) (in)
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0128
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
2.9675
2.5851
2.5978
2.6106
2.6233
2.6360
2.6488
2.6615
2.6743
2.6870
2.6998
2.7125
2.7253
2.7380
2.7507
2.7635
2.7762
2.7890
2.8017
2.8145
2.8272
2.8400
2.8527
2.8655
2.8782
2.8910
2.9037
2.9165
2.9292
2.9420
2.9547
2.9675
2.9675
2.9675
2.9675
2.9675
2.9675
2.9675
10890 sq ft
0.2500 Ae
98.0
1 min
0.2041 in
O. 8333
Cumulative
Instan- Instan-
taneous taneous
Runoff Runoff
Qi Ve
(efs) (eu ft)
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
4.4883
max =
Routed
Runoff
Qr
(efs)
2346
2358
2369
2381
2392
2404
2415
2427
2438
2450
2462
2473
2485
2496
2508
2519
2531
2543
2554
2566
2577
2589
2600
2612
2624
2635
2647
2658
2670
2681
2693
2693
2693
2693
2693
2693
2693
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0032
-0.0021
0.0014
-0.0010
0.0006
-0.0004
0.2492
Total
Runoff
Q
(efs)
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0193
0.0032
-0.0021
0.0014
-0.0010
0.0006
-0.0004
0.2492
APPENDIX II
Sizing calculations for the outlet pipe.
Date: 11-14-06
Givens:
Change in elevation:
Estimated length of pipe:
Pipe dia:
Design flow:
Mannings n:
Pipe wall thickness:
Factor of Safety, Hydraulics:
Factor of Safety, Structural:
Factor of Safety, Pressure:
Head on dispersion holes:
Diameter of dispersion holes:
Ratio, hole area: wall area:
Cable sizinq:
Project: Rosenthall/Holt Drainage
Tiqhtline Outfall Desi9n Calculations
175 ft
300 ft
4in
0.2490 cfs
0.0120
0.200 in = t = 0.017 ft (used in weight calculations only)
2 at the 100 year storm event level
2 for the pipe entirely full of water
2 based on fully plugged outlet
1ft =h
0.5 in = d = 0.042 ft
3.00 % = Rh = percent of disperser walls consumed by holes
= H
= L
= D = 0.333 ft
= Q based on 24 hr,
100 year storm event
Weight of pipe when full = 3.14 x [ (0.333 ft ) + 2(0.017 ft ) ]^2 14 x 175 ft x 62.35 #/cf
4606lbs
(This assumes the density of the pipe material is equal to that of water)
Pipe Ratina:
Factor of Safety-Structural x
Minimum design strength of cable =
2
92121bs
Max pressure in pipe = 175 ft of head x 0.433 psi/ft x 2.00 Factor of Safety-Pressure =
152 psi
Check Pipe Hvdraulics:
Min slope = 2,650,000 x (0.0120)^2 x (0.2490 cfs x 2.000 FS-Hydraulics)^21 (4.00 in)^5.33 =
0.058491 ftlft
Capacity of Flow Disperser:
Actual available slope = So = 175 ft elevation loss 1300 ft pipe length =
0.5833 ftlft
Number of holes required = Q I q =
Flow, one dispersion hole = (0.50)^2 x -./(1.00) I 36.85 =
0.2490 I 0.0068 =
36.7 each
Length of Flow Disperser:
q=
0.0068 cfs
Factor of Safety-Hydraulics:
x
2
73.41 each
After rounding up, the number of holes required is = Nh =
74 each
The length of the flow disperser will be determined by the number of holes required to pass the
design flow. Allowing no more than 3.00% of the surface area of the pipe to be lost to holes yields
a minimum length of Ld for the disperser.
Length of disperser = Ld = Nh x (Area of one hole) I Rh I (pipe circumference) =
Reaction Force on Disperser:
74 x [3.14 x (0.50)^2 14] I 0.031 (3.14 x 4.00) 112 ftlin =
Add one foot for fittings:
+
3.21 feet
1
4.21 feet
The force that the design flow will exert on the disperser = Fr. From the momentum equation:
Fr = 4 x 62.35 Ib/cf x 0.249 cfs I 3.14 I 32.2 ftlsedsec I (0.3333)^2 =
5.531bs