HomeMy WebLinkAboutSWP272818 STORM DRAINAGE REPORT
FOR
BRONSON SHORT PLAT
RENTON,WASHINGTON
STORM DRAINAGE REPORT
FILE NO. 944-002-991
PREPARED BY
TOUMA ENGINEERS
6632 SOUTH 191ST PLACE, SUITE E-102
KENT, WA. 98032
(425)251-0665
July 19, 1999
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TABLE OF CONTENTS
I. PROJECT NARATIVE,VICINITY MAP
II. CORE& SPECIAL REQUIREMENTS
III. LEVEL I ANALYSIS
IV. DETENTION/BIOSWALE DESIGN
V. CONVEYANCE SYSTEM ANALYSIS
3
I. PROJECT NARRATIVE
S
PROJECT NARRATIVE
1-he subject property covers an area of approximately 1 .89 acres.
The proposed Taylor short plat is situated in the northeast end of the City.
Bounded on the south by the Plat of Windsor Hills Addition; on the west by the
Flat of Renton Stinset Heights; Bounded on the northeast by Block 23 of the Plat
Renton Highlands, and approximately 100 feet west of Edmonds Avenue NE and
100 feet southwesterly of Camas Avenue NE. Access to the property will be from
Bronson Place NE. Adjacent street improvements (Bronson Place NE) consist of
32 feet wide of asphaltic pavement, curb & gutters on both sides, sidewalks on
the west side only, sewer, water and storm systems. Street light is on existing
utility pole.
The project area is hilly, with slope ranges from 10% to 18%.
The City of Renton designates the site with the SF zoning. The SF zoning allows
for a minimum lot size of 4500 square feet and a maximum density of 8 units per
acre. The setbacks allowed in the SF zone are as follows: front yard setbacks, 15
feet; rear yard setbacks, 25 feet, and side yards setbacks, 5 feet on all interior
lots, and 15 feet on corner lots. The City of Renton Comprehensive Plan
designates the site as Single-Family Residence which is consistent with present
zoning.
The proposed development would create 7 single family lots with a minimum lot
area of 6261 sctcrare feet. Excluding the area to be dedicated for roadway and the
public use (10,164 sf) the dwelling unit density calculates at 4.2 units per net
developed area. The unit density calculates a lesser than the minirnurn 5.0 unit per
net area required by the SF zone. The steep slopes and configuration of the
property restrict consideration of additional lots to meet the Minirnunt unit.
requirements. Minimal grading will be required in order to prepare the final
residential lots. Public water and sewer are available along the south of the
property. There exists a 12-inch water main within a 30-foot public right-of-way
immediately south of the property and there exist a sanitary sewer system in
Bronson Place NE at adequate depth to provide sewer connection for this plat.
The area cover consists of overgrown and brushy covers for most of the site.
There exist few mature evergreen trees. The surface water sheet flows westerly
following natural drainage pattern. The storm is oriented westerly from the
property following an existing ditch within the a 30-foot public right-of-way,
directing the flows into exiting under ground storm system in Sunset Blvd NE.
Traffic circulation and access to the property is proposed to provide vehicular
access from Bronson Place NE. The internal street will consist of a short
cul =de =sac to be constructed in accordance with City's code and regulations.
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4
II. CORE REQUIREMENTS
Core Requirement#1. -Discharge at the Natural Location
The developed site runoff will collect in the bioswale, from where it will flow to the existing storm
drain under Sunset Blvd. NE,
Core Requirement#2. -Offsite analysis
See section 111, this report.
Core Requirement#3. -Runoff control
The runoff from road, cul-de-sac, and roofs will be detained in a detention vault. See section IV for design,
and hydrology. Water quality treatment will be provided thru biofiltration;the existing ditch downstream of
the site shall be enhanced to serve this purpose.
Core Requirement#4. -Conveyance system Design
The storm drainage system consists of catch basins and pipes, which have been checked for
peakflow capacity. It has been found that their capacity far exceeds the expected 100 yr. peakflow. The
roof runoff will be conveyed in 6" underground pipes. See Section V of this report for calculation of pipe
capacities.
Core Requirement#5. -Temporary erosion and sedimentation control
Temporary erosion and sedimentation control shall consist of siltfences, a construction entrance,
filter fabric over storm grates, and mulching. See plans.
Core Requirement#6. -Maintenance and operation
Maintenance involves having on-site catch basins cleared from sediments when necessary.
Core Requirement#7. -Bonds and liability N.A.
Special Requirement# 1. -Critical drainage areas N.A.
Special Requirement#2, -Compliance with an existing Master Drainage Plan(MDP) N.A.
Special Requirement#3. -Conditions requiring a MDP. N.A.
Special Requirement#4. -Adopted basin or community plans N.A.
Special Requirement#5. - Special water quality controls.N.A.
Special Requirement#6. - Coalescing plate oil/water seperators N.A.
Special Requirement#7. -Closed depressions N.A.
Special Requirement#8. -Use of lakes, wetlands or closed depressions for runoff control N.A.
Special Requirement#9. -Delineation of the 100 yr floodplain N.A.
Special Requirement#10. -Flood protection facilities for type 1 and type 2 streams N.A.
Special Requirement#11. -Geotechnical analysis and report N.A.
Special Requirement#12. - Soils analysis and report N.A.
6 Y
LEVEL - I ANALYSIS
INTRODUCTION
The project involves one parcel of land about 1 . 89 acres . The
property is situated in the northeast part of the City of Renton.
It is situated in the Renton Highland Plat, in the SE Quarter of
Section 8 , Township 23 North, Range 5 East, W .M. It is bounded on
the south by a 30-foot public right-of-way (undeveloped) . The
current Bronson Place NE terminates into the southerly boundary
of the site . Easterly, approximately 100 feet there exist Edmonds
Avenue NE, and the along the north and east there are several
developed single family lots which are served by Camas Avenue NE .
The soil type as classified by King County Soil Conservation
Service is Alderwood Soil (Agc) .
REVIEW OF RESOURCES
1 . City of Renton Aquifer Protection Area Map
2 . City of Renton Topographic Mapping, Scale 111= 40,0 '
3 . Soil Conservation Service
4 . City of Renton Zoning and Subdivision Ordinances
FIELD INSPECTION
Field inspection of the site area was performed on :in January,
1997 .
The property is presently vacant . The current improvements south
of the property, Bronson Place NE, consist of 32 feet of
asphaltic roadway, curb and gutters on both sides and concrete
sidewalks on one side . The property is served from Bronson Place
NE . Sewer and water are available to the site and will serve the
site adequately.
The topography of the site is oriented from east to west at
slopes ranging from 10 to 15 percent . The land cover mostly
wooded, consisting of fairly mature alder and cotton wood trees
were observed.
Page 1 of 2
LEVEL I ANALYSIS (Continued)
NARRATIVE
UPSTREAM ANALYSIS
In reviewing the upstream drainage flows it was ascertained that
a very small off-site area flows into the subject property.
Mostly consisted of back-yards of existing homes bordering the
northeast portion of the property . This was confirmed in
reviewing the aerial topographic mapping for the area, and the
actual topography performed for the site .
DOWNSTREAM ANALYSIS
Runoff from the proposed site sheet flows westerly along natural
swales orienting the flow toward backyards of adjacent
developments to the west . Thence the flow is directed westerly
and southwesterly to an existing ditch situated within a 30-foot
public right-of-way. The water in the ditch is collected into an
existing catch-basin in the right-of-way and thence is directed
into the storm system situated in Sunset Blvd NE .
SUMMARY
During our field inspection of the site we did not observe any
flooding problems . it appears that the downstream system
consisting of open ditches and under ground conveyance facilities
which are adequate to handle normal storms .
Page 2 of 2
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IV. RETENTION/DETENTION DESIGN
The required detention volume came out to be 3681 cubic feet. This corresponds to a detention vault
measuring 40 ft. by 18.4 ft,with a design depth of 5 ft. Water surface elevations are presented below for the
2, 10 and 100 yr. storms.
We designed this vault geometry to have a longitudinal support wall in the middle sothat the water will flow
from one end to the other,bend around, and flow to the outlet riser. See civil plans. This creates a longer
flow path, and may help settle out sediments;furthermore, it means more efficient construction.
PAGES FOLLOWING:
l. areas summary and peak flow summary
2. developed basin map
3. existing basin map
4. typical vault detail
5, vault outflow graphs
6, peak stage graph
7. hyd program input: vault design
8. hyd program output: vault design
9. hyd program output for routing hydrographs
10. SCS soils map
11. curve number table
12. 2 yr. isopluvial
13. 10 yr. isopluvial
14. 100 yr. isopluvial
15. 2 yr. hydrograph
16. 10 yr. hydrograph
17. 100 yr. hydrograph
18, time of conc. flow path-developed
19. time of conc. flow path-existing
20. time of concentration calculation
21. "n","k"values table
22. formulas for time of conc. calculations
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TALOR SHORT PLAT- Renton
Return Period 2 yr 10 yr
24hr. Precip. (inch) 2 2.9
Areas CN# Existing Developed to Pond
sf acres sf acres
impervious 98 2179 0.05 35095 0.81
2nd forest 81 82588 1.90 0 0.00
grass 86 44182 1.01 93858 2.15
Totals 1 1 128949 2.961 128953 2.96
Areas in Developed Conditions
total on-site : 82588 sf.= 1.90 ac./total to detention vault: 2.96 ac.
Impervious sf acres
on-site cul-de-sac& sidewalk 8964 measured 0.21
off-site road & side walk 1933 measured 0.04
roofs&driveways to pond 21000 7 lots x 3000sf 0.48
South boundary conc. walk 3198 6' x 533' 0.07
Total Impervious to Det. Pond 35095 0.81
Pervious
on-site lawns 52624 (82588-8964-21 OOO)sf 1.21
off-site lawns 35982 measured 0.83
off-site grass 5252 (8450-3198) sf. 0.12
Total Pervious 93858 2.15
Totals 128953 2.96
PEAK FLOWS, cfs
EVENT EXIST. DEVPD. VAULT OUTFLOW
2 YR 0.23 0.53 0.22
10 YR 0.54 0.95 0.49
100 YR 0.95 1.46 1.41
BASIN MAP
DEVELOPED CONDITIONS
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LAWN LANDSCAPING
35,982 sq.
P �F. Ty 0.83 acres
82,0'I F' sq:.ft.
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3000 sf
IMPERV.
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PER LQT
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1 � 1.90 dcres
ROAD & WALK 1 ,
8,964 sq.ft.
1 ,
0.21 acres '
-- 70
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1,93 q.ft
0.04 s ` 4450 sq. 0.073 AC. / 3198 SF. CONO WALK
361 `.\ 1
0.01 acres
OUTFLOW
POINT
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BASIN MAP
EXISTING CONDITIONS
PROPERTY
82,588 sq.ft.
1.90 acres
LAWNS & NDSCAP/NG
35,9 sq.ft.
�' fyG 0.83 acres ,
PROPERTY
82 588 sq.ft.
1.96 acres
OUTFLOW 79 s+ - o'90 acrest GRAS
POINT 1
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KING COUNTY, WASHINGTON, SURFACG WATER DI? SIGN MANUAL
FIGURE 4.4.6A TYPICAL DETEN'nON VAULT
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VAULT OUTFLOW PERFORMANCE
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RETURN INTERVAL(YEARS)
-�--EXISTING -f--DEVELOPED INFLOW f DEVELOPED OUTFLOW
DETENTION VAULT, 5 FT. RISER
PEAK STAGE
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RETURN INTERVAL(YEARS)
R
SUMMARY OF INPUT ITEMS
1) TYPE OF FACILITY: VAULT
2 ) STORAGE DEPTH(ft ) : 5 . 00
3) VERTICAL PERMEABILITY(min/in) : . 00
4) PRIMARY DESIGN HYDROGRAPH FILENAME : 6963dv10.hyd
5 ) PRIMARY RELEASE RATE(cfs ) : . 54
6) NUMBER OF TEST HYDROGRAPHS : 1
TEST HYD 1 FILENAME : 69603dv2 .hyd TARGET RELEASE(cfs ) : . 23
7 ) NUMBER-OF-ORIFICES, RISER-HEAD(ft ) , RISER-DIAM( in) : 2, 5 . 00, 12
8) ITERATION DISPLAY: NO
ENTER ITEM NUMBER TO BE REVISED (ENTER ZERO IF NO REVISIONS ARE REQUIRED) :
0
INITIAL STORAGE VALUE FOR ITERATION PURPOSES : 5796 CU-FT
BOTTOM ORIFICE : ENTER Q-MAX(cfs )
0. 3
DIA. = 2 . 22 INCHES
TOP ORIFICE : ENTER HEIGHT(ft)
3 . 05
DIA. = 2 . 52 INCHES
PERFORMANCE : INFLOW TARGET-OUTFLOW ACTUAL-OUTFLOW PK-STAGE STORAGE
DESIGN HYD: . 95 . 54 . 54 5 . 00 2829
TEST HYD 1 : . 53 . 23 . 23 3 . 02 1710
SPECIFY: D - DOCUMENT, R - REVISE, A - ADJUST ORIF, E - ENLARGE, S - STOP
E
ENLARGEMENT OPTION: ALLOWS FOR INCREASING STORAGE AT A SPECIFIED
STAGE HEIGHT, TO PROVIDE A FACTOR OF SAFETY.
ENTER: STORAGE-INCREASE() , STAGE-HEIGHT(ft)
3o ��� J T S T�'n ne-K/- pa c�
30, 5 j O v V4-Z- 5-1-7- Z)Z3.
PgRFOR14ANCE : INFLOW TARGET-OUTFLOW ACTUAL-OUTFLOW PK-STAGE STORAGE
DESIGN HYD : . 95 . 54 . 49 4. 46 3281
TEST HYD 1 : . 53 . 23 . 22 2 . 61 1920
SPECIFY: D - DOCUMENT, R - REVISE, A - ADJUST ORIF, E - ENLARGE, S - STOP
D
PERFORMANCE : INFLOW TARGET-OUTFLOW ACTUAL-OUTFLOW PK-STAGE STORAGE
DESIGN HYD: . 95 . 54 . 49 4. 46 3281
TEST HYD 1 : . 53 . 23 . 22 2 . 61 1920
STRUCTURE DATA: R/D-VAULT
ISER-HEAD VAULT-BOTTOM-AREA STOR-DEPTH STORAGE-VOLUME-
5 . 00 FT 736 . 4 SQ-FT 5 . 00 FT 3681 CU-FT 40.V .`
DOUBLE ORIFICE RESTRICTOR: DIA( INCHES) HT(FEET) Q-MAX(CFS)
BOTTOM ORIFICE: 2 . 22 . 00 . 300
TOP ORIFICE: 2 . 52 3 . 05 . 240
ROUTING DATA:
STAGE(FT) DISCHARGE(CFS) STORAGE(CU-FT) PERM-AREA(SQ-FT)
. 00 . 00 . 0 . 0
. 50 . 09 368. 2 . 0
1 . 00 . 13 736. 4 . 0
1 . 50 . 16 1104 . 6 . 0
2 . 00 . 19 1472 . 8 . 0
2 . 50 . 21 1841 . 0 . 0
3 . 00 . 23 2209 . 1 . 0
3 . 05 . 23 2246. 0 . 0
3 . 50 . 37 2577 . 3 . 0
4. 00 . 44 2945 . 5 . 0
4. 50 . 49 3313 . 7 . 0
5 . 00 . 54 3681 . 9 . 0
5 . 10 . 86 3755 . 5 . 0
5 . 20 1 . 43 3829 . 2 . 0
5 . 30 2 . 17 3902 . 8 . 0
5 . 40 2 . 97 3976. 5 . 0
5 . 50 3 . 26 4050 . 1 . 0
AVERAGE VERTICAL PERMEABILITY: . 0 MINUTES/INCH
SPECIFY: F - FILE, N - NEWJOB, P - PRINT IF/OF, R - REVISE, S - STOP
F
ENTER [d: ] [Path]filename[ . ext] FOR STORAGE OF ROUTING DATA:
6963VALT.DAT
SPECIFY: F - FILE, N - NEWJOB, P - PRINT IF/OF, R - REVISE, S - STOP
RESERVOIR ROUTING INFLOW/OUTFLOW ROUTINE
SPECIFY [d: ] [path]filename[ .ext] OF ROUTING DATA
6963VALT.DAT
DISPLAY ROUTING DATA (Y or N)?
N
ENTER [d: ] [path]filename[ . ext] OF COMPUTED HYDROGRAPH:
6963D100 .HYD
INFLOW/OUTFLOW ANALYSIS :
PEAK-INFLOW(CFS) PEAK-OUTFLOW(CFS) OUTFLOW-VOL(CU-FT)
1 . 46 1 . 41 29791
INITIAL-STAGE(FT) TIME-OF-PEAK(HRS) PEAK-STAGE-ELEV(FT)
. 00 8. 17 5 . 20
PEAK STORAGE : 3820 CU-FT
ENTER [d: ] [path]filename[ .ext] FOR STORAGE OF COMPUTED HYDROGRAPH:
69630100.HYD
SPECIFY: C - CONTINUE, N - NEWJOB, P - PRINT, S - STOP, R - REVISE
C
ENTER [d: ] [path]filename[ . ext] OF COMPUTED HYDROGRAPH:
6963DV10 .HYD
INFLOW/OUTFLOW ANALYSIS :
PEAK-INFLOW(CFS) PEAK-OUTFLOW(CFS) OUTFLOW-VOL(CU-FT)
. 95 . 49 19945
INITIAL-STAGE(FT) TIME-OF-PEAK(HRS) PEAK-STAGE-ELEV(FT)
. 00 9 . 00 4 . 47
PEAK STORAGE : 3290 CU-FT
ENTER [d: ] [path]filename[ .ext] FOR STORAGE OF COMPUTED HYDROGRAPH:
6963010 .HYD
SPECIFY: C - CONTINUE, N - NEWJOB, P - PRINT, S - STOP, R - REVISE
C
ENTER [d: ] [path]filename[ .ext] OF COMPUTED HYDROGRAPH:
69603DV2 .HYD
INFLOW/OUTFLOW ANALYSIS :
PEAK-INFLOW(CFS) PEAK-OUTFLOW(CFS ) OUTFLOW-VOL(CU-FT)
. 53 . 22 11743
INITIAL-STAGE(FT) TIME-OF-PEAK(HRS ) PEAK-STAGE-ELEV(FT)
. 00 10 . 50 2 . 65
PEAK STORAGE : 1950 CU-FT
ENTER [d: ] [path]filename[ .ext] FOR STORAGE OF COMPUTED HYDROGRAPH:
6960302 .HYD
SPECIFY: C - CONTINUE, N - NEWJOB, P - PRINT, S - STOP, R - REVISE
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WATER DESIGN MANUAL
KIN (; COUNTY, WAS 11 1 N (; 'I' () N, SU 11 FACII-
'FABLE 3.5.211 SCS WES'FEIZN WASHING'FON RUNOF
SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS In 1982)
Runoff curve numbers for selected agricultural, suburban and urban land use for Type to
rainfall distribution, 24-hour storm duration.
CURVE NUMBERS BY
HYDROLOGIC SOIL GROUP
�
LAND USE DESCRIPTION A B 'C D
Cultivated land(l): winter condition 86 91 94 95
Mountain open areas: low growing brush and grasslands 74 82 89 92
Meadow or pasture: 65 78 85 89
Wood or forest land: undisturbed 42 64 76 81
Wood or forest land: young second growth or brush 55 72 fbil) 86
Orchard: with cover crop 81 88 92 94
Open spaces, lawns, parks, golf courses, cemeteries,
landscaping.
good condition: grass cover on 75%
or more of the area 68 80 086) 90
fair condition: grass cover on 50%
to 75% of the area 77 85 90 92
Gravel roads and parking lots 76 85 89, 91
Dirt roads and parking lots 72 82 87 89
Impervious surfaces, pavement, roofs, etc. 98 96 98 98
Open water bodies: lakes, wetlands, ponds, etc. 100 100 100 100
Single Family Residential (2)
Dwelling Unit/Gross Acre % Impervious (3)1.0 DU/GA 15 Separate curve number
1.5 DU/GA 20 shall be selected
2.0 DU/GA 25 for pervious and
2.5 DU/GA 30 Impervious portion
3.0 DU/GA 34 of the site or basin
15 DU/GA 38
4.0 DU/GA 42
4.5 DU/GA 46
5.0 DU/GA 48
5.5 DU/GA so
6.0 DU/GA 52
6.5 DU/GA 54
7.0 DU/GA 56
Planned unit developments, % Impervious
condominiums, apartments, must be computed
commercial business and
Industrial areas.
(1) For a more detailed description of agricultural land use curve numbers refer to National Engineering
Handbook, Section 4, Hydrology, Chapter 9, August 1972.
(2) Assumes roof and driveway runoff Is directed Into street/storm system.
(3) The remaining pervious areas (lawn) are considered to be In good condition for these curve numbers.
3.5.2-3 2/89
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S .r- . S. `TYPE-1A RAINFALL DISTRIBUTION
ENTER: FREQ(YEAR) , DURATION(HOUR) , PRECIP( INCHES)
2 ,24,2
----------------------------------------------------------------------
******************** S.C. S . TYPE-1A DISTRIBUTION ********************
********* 2-YEAR 24-HOUR STORM **** 2 . 00" TOTAL PRECIP. *********
----------------------------------------------------------------------
ENTER: A(PERV) , CN(PERV) , A( IMPERV) , CN( IMPERV) , TC FOR BASIN NO. 1
82914 82 . 74, 0. 05 , 98 , 44. 5
DATA PRINT-OUT:
AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES)
A CN A CN
3 . 0 2 . 9 82 . 7 . 1 98 . 0 44. 5
PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT)
. 23 8 . 00 7481
ENTER [d: ] [path]filename[ . ext] FOR STORAGE OF COMPUTED HYDROGRAPH:
69603ex2 .hyd
SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP
C
----------------------------------------------------------------------
ENTER: A(PERV) , CN(PERV) , A( IMPERV) , CN( IMPERV) , TC FOR BASIN NO. 2
2 . 15 , 86 , 0. 81, 98, 32 . 5
DATA PRINT-OUT:
AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES)
A CN A CN
3 . 0 2. 2 86. 0 . 8 98 . 0 32 . 5
PEAK-Q(CFS) T-PEAK(HRS ) VOL(CU-FT)
. 53 7 . 83 11777
ENTER [d: ] [path]filename[ .ext] FOR STORAGE OF COMPUTED HYDROGRAPH:
69603dv2 .hyd
SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP
S .C . S . TYPE-1A RAINFALL DISTRIBUTION
ENTER: FREQ(YEAR) , DURATION(HOUR) , PRECIP( INCHES)
10,249? . 9
------------------------------------------------------------------
******************** S .C . S. TYPE-lA DISTRIBUTION ********************
********* 10-YEAR 24-HOUR STORM **** 2 . 90" TOTAL PRECIP. *********
---------------------------------------------------------------------
ENTER: A(PERV) , CN(PERV) , A( IMPERV) , CN( IMPERV) , TC FOR BASIN NO. 1
2 . 91, 82 . 74, 0 . 05 , 98, 44. 5
DATA PRINT-OUT :
AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES)
A CN A CN
3 . 0 2 . 9 82 . 7 . 1 98. 0 44. 5
PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT)
. 54 8 . 00 14623
ENTER [d: ] [path]filename[ . ext] FOR STORAGE OF COMPUTED HYDROGRAPH:
6963ex10 .hyd
SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP
c
----------------------------------------------------------------------
ENTER: A(PERV) , CN(PERV) , A( IMPERV) , CN( IMPERV) , TC FOR BASIN NO. 2
2 . 15 , 86, 0 . 81, 98, 32 . 5
DATA PRINT-OUT:
AREA(ACRES ) PERVIOUS IMPERVIOUS TC(MINUTES)
A CN A CN
3 . 0 2 . 2 86 . 0 . 8 98.0 32 . 5
PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT)
. 95 7 . 83 20013
ENTER [d: ] [path]filename[ .ext] FOR STORAGE OF COMPUTED HYDROGRAPH:
6963dv10.hyd
SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP
s
KING COUNTY DEPARTMENT OF PUBLIC WORKS
Surface Water Management Division
HYDROGRAPH PROGRAMS
Version 4. 21B
1 - INFO ON THIS PROGRAM
2 - SBUHYD
3 - MODIFIED SBUHYD
1
S .C . S . TYPE-1A RAINFALL DISTRIBUTION
ENTER: FREQ(YEAR) , DURATION(HOUR) , PRECIP( INCHES)
100 , 24 ,3 . 9
----------------------------------------------------------------------
******************** S.C . S . TYPE-lA DISTRIBUTION ********************
********* 100-YEAR 24-HOUR STORM **** 3 . 90" TOTAL PRECIP. *********
----------------------------------------------------------------------
S.C. S . TYPE-1A RAINFALL DISTRIBUTION
ENTER: FREQ(YEAR) , DURATION(HOUR) , PRECIP( INCHES)
2 ,24, 2
----------------------------------------------------------------------
******************** S.C.S. TYPE-lA DISTRIBUTION ********************
********* 2-YEAR 24-HOUR STORM **** 2 . 00" TOTAL PRECIP. *********
----------------------------------------------------------------------
ENTER: A(PERV) , CN(PERV) , A( IMPERV) , CN( IMPERV) , TC FOR BASIN NO. 1
82914 82. 74, 0. 05 , 98, 44 . 5
DATA PRINT-OUT:
AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES)
A CN A CN
3 .0 2 . 9 82 . 7 . 1 98. 0 44. 5
PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT)
. 23 8 . 00 7481
ENTER [d: ] [Path]filename[ . ext] FOR STORAGE OF COMPUTED HYDROGRAPH:
69603ex2 .hyd
SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP
c
----------------------------------------------------------------------
ENTER: A(PERV) , CN(PERV) , A( IMPERV) , CN( IMPERV) , TC FOR BASIN NO. 2
2 . 15 , 86, 0. 81, 98, 32 . 5
DATA PRINT-OUT:
AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES)
A CN A CN
3 . 0 2 . 2 86 . 0 . 8 98 . 0 32. 5
PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT)
. 53 7 . 83 11777
ENTER [d: ] [Path]filename[ .ext] FOR STORAGE OF COMPUTED HYDROGRAPH:
69603dv2 .hyd
SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP
TIME OF CONCENTRATION FLOW PATH
EXISTING CONDITIONS
N
i
1
of
1
e f
Lr s— h LF S�4%
2X000000
244 Lr S=18.0X F i=8.33% �-- LFS=14. %
.�--=�---- — L 41
r
r
60 LF S=
J
pCP
TIME OF CONCENTRATION FLOW PATH
DEVELOPED CONDITIONS
8.0
,
1 N
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14
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TABLE 3.5.2C "n" AND "k" VALUES USED IN TIME CALCULATIONS FOR HYDROGRAPHS
Sheet1
SBU HYDROGRAPH METHOD:
- ---------------
Existin Site Tic
SHEETTs= 0.42*(L*ns)^0.8/(P2"0.5*S^0.4)
ns S P2 (in.) T(min.)
0.15 0.04 2 9.62
0.15 0. 4472 2.73
0.25 0.0152 2 25.99
0.4 0.0833 2 4.90
T= L/(60*k*S"0.5)
L (ft) k S - -
CHANNEL 244 11 0.18
0.87
60 27 0.084 D. _
43 17 0.161 0.11
TIME OF CONCENTRATION 44.35 :44.5 min
Developed Site Tc
SHEET L(ft) ns S P2 (in.) T(min.)
103 0.15 0.04 2 9.62
_ 41 0.15 0.147 2 2.73
132 0.15 0.0152 2 17.27
-- 24 0.15 0.0833 2 2.24
L(ft) k S
CHANNEL 50 11 0.28 0.14
_-_ 134 27 0.15 0.21
81 42 0.15 0.08
30 42 0.005
- 0.17
TIME OF CONCENTRATION - -
32.47 =32.5 min
Trapezoidal Channel Analysis & Design
Open Channel - Uniform flow
Worksheet Name: 100 yr depth
Comment : 100 yr peak flow, normal depth
Solve For Depth
Given Input Data:
Bottom Width. . . . . 1 . 89 ft
Left Side Slope. . 3 . 00 : 1 (H:V)
Right Side Slope. 3 . 00: 1 (H:V)
Manning' s n. . . . . . 0 . 040
Channel Slope. . . . 0. 1800 ft/ft
Discharge. . . . . . . . 1 . 41 cfs
Computed Results :
Depth. . . . . . . . . . . . 0 . 15 ft
Velocity. . . . . . . . . 3 . 95 fps
Flow Area. . . . . . . . 0. 36 sf
Flow Top Width. . . 2 .80 ft
Wetted Perimeter. 2 . 85 ft
Critical Depth. . . 0 . 23 ft
Critical Slope. . . 0. 0426 ft/ft
Froude Number. . . . 1 . 95 (flow is Supercritical)
Open Channel Flow Module, Version 3 . 4 (c) 1991
Haestad Methods , Inc . * 37 Brookside Rd * Waterbury, Ct {06708
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
where
T� = time of concentration (min), and
m = number of flow segments
Sheet Flow: Sheet flow is flow over plane surfaces. It usually occurs in the headwater of streams. With
sheet flow, the friction value (n.) (a modified Manning's effective roughness coefficient that Includes the
effect of raindrop impact; drag over the plane surface; obstacles such as litter, crop ridges, and rocks; and
erosion and transportation of sediment) is used. These n, values are for very shallow flow depths of about
0.1 foot and are only used for travel lengths up to 300 feet. Table 3.5.2.0 gives Manning's n, values for
sheet flow for various surface conditions.
For sheet flow up to 300 feet, use Manning's kinematic solution to directly compute T,:
Sheet flow: Tt =
0.42 (n,L)o'e
(P2) o.s (So) o.c
where
T, = travel time (min),
n, = sheet flow Manning's effective roughness coefficient (from Table 3.5.2C),
L = flow length (ft),
P2 = 2-year, 24-hour rainfall (in), (see Figure 3.5.1 C) and
S. = slope of hydraulic grade line (land slope, ft/ft)
Velocity Equation
A commonly used method of computing average velocity of flow, once it has measurable depth, is the
following equation:
V = k
where:
V = velocity (ft/s)
k = time of concentration velocity factor (ft/s)
so = slope of flow path (ft/ft)
"k" is computed for various land covers and channel characteristics with assumptions made for hydraulic
radius using the following rearrangement of Manning's equation:
k = (1.49 (R) 0667 )/n;
where
R = an assumed hydraulic radius
n = Manning's roughness coefficient for open channel flow (from Table 4.3.76 in Chapter 4)
3.5.2-6 1/90
IV-b. BIO SWALE DESIGN
Bottom width= 1.89 ft.
3:1 side slopes
longitudiunal slope= 18%
length=200 ft
constructed swale depth= 1.15 ft
Respective Calculation Printouts:
1, 200 if design norm, design parameters solving bottom width
2. solve for 2Yr depth with actual swale parameters
3. solve for 100 Yr depth with actual swale parameters
Trapezoidal Channel Analysis & Design
' Open Channel - Uniform flow
Worksheet Name : design
Comment : bottom width design, 2 yr. peak flow
Solve For Bottom Width
Given Input Data:
Left Side Slope. . 3 . 00 : 1 (H:V)
Right Side Slope. 3 . 00 : 1 (H:V)
Manning' s n. . . . . . 0 . 350
Channel Slope. . . . 0 . 0200 ft/ft
Depth. . . . . . . . . . . . 0 . 33 ft
Discharge. . . . . . . . 0 . 22 cfs
Computed Results :
Bottom Width. . . . 1. 89 ft
Velocity. . . . . . . . . 0 . 23 fps
Flow Area. . . . . . . . 0 . 95 sf
Flow Top Width. . . 3 . 87 ft
Wetted Perimeter. 3 . 98 ft
Critical Depth. . . 0 . 07 ft
Critical Slope. . . 4 .4959 ft/ft
Froude Number. . . . 0 . 08 (flow is Subcritical )
Open Channel Flow Module, Version 3 . 4 (c) 1991
Haestad Methods , Inc. * 37 Brookside Rd * Waterbury Ct 06708
• Trapezoidal Channel Analysis & Design
Open Channel - Uniform flow
Worksheet Name : 2yr depth
Comment : 2 yr. peak flow, normal depth
Solve For Depth
Given Input Data:
Bottom Width. . . . . 1 . 89 ft
Left Side Slope. . 3 . 00 : 1 (H:V)
Right Side Slope. 3 .00 : 1 (H:V)
Manning' s n. . . . . . 0 . 040
Channel Slope. . . . 0. 1800 ft/ft
Discharge. . . . . . . . 0 . 22 cfs
Computed Results :
Depth. . . . . . . . . . . . 0. 05 ft
Velocity. . . . . . . . . 2 .08 fps
Flow Area. . . . . . . . 0. 11 sf
Flow Top Width. . . 2 . 20 ft
Wetted Perimeter. 2 . 22 ft
Critical Depth. . . 0 .07 ft
Critical Slope. . . 0 . 0587 ft/ft
Froude Number. . . . 1 . 67 (flow is Supercritical)
Open Channel Flow Module, Version 3 .4 (c) 1991
Haestad Methods , Inc. * 37 Brookside Rd * Waterbury, Ct 067 {8
8
V. CONVEYANCE SYSTEM ANALYSIS
Applying the manning equation to full flow in pipes,table below shows the minimum slopes for a 6"
diameter pipe to convey at least the 100 yr, developed peak flow of 1.41 cfs. All of the pipes have a
greater slope,sothat they convey over 1.41 cfs.
PIPE CAPACITIES
CPEP CAPACITY Q = 1.49/n *A"RA(2/3) "S^(1/2)
FULL FLOW, SO THAT R = A/P = D/4
Showing minimum slopes for 12" pipes
n L (ft) S D (ft) R v (fps) A(sf) Q (cfs)
0.012 57 0.0015 1 0.25 1.91 0.79 1.50 smooth wall
0.024 57 0.0055 1 0.25 1.83 0.79 1.44 single wall
Showing minimum slopes for 6" pipes
0.012 48 0.054 0.50 0.13 7.21 0.20 1.42 smooth wall
0.024 48 0.1 0.50 0.13 4.91 0.20 0.96 single wall