HomeMy WebLinkAboutStorm Drainage Report Final - PLN General - 7/1/2003 t
PLANNING
FINAL STORM DRAINAGE REPORT FOR: J Bar A WM-STORAGE
LOCATED IN BELFAM WASSINGTON
Judy 1,2003
FOR
J Bar D
P.O_Boa 1461
Poulsbo,WA 98370
(360)509-0119
PREPARED BY:
Team 4 Engsnaering
5819 NE Minder Roed
Poulsbo,WA.98370
(360)297-5560
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TABLE OF CONTENTS
L LOCATION PC. 3
IL PREDEVELOPMENT SITE CONDITIONS PG. 3
IIL UPSTREAM ANALYSIS PG. 3
IV. DOWNSTREAM ANALYSIS PG. 4
V. DESCRIPTION OF PROPOSED DEVELOPMENT PG. 4
VL OVERVIEW OF PROPOSED STORMWATER MANAGEMENT FACILITIES PG. 4
VII. TECHNICAL REQUIREMENTS PG.4
VIIL HYDROLOGICAL ANALYSIS PG. 5
IX. STORMWATER QUALITY ENHANCEMENT FACILITIES PG.8
X. EROSION AND SEDIMENT CONTROL PG.8
FIGURES
FIGURE 1 VICINITY MAP PG. 10
FIGURE 2 PREDEVELOPED SITE MAP PG. 11
FIGURE 3 SOILS MAP PG. 12
FIGURE 4 DEVELOPED CONDITIONS SITE MAP PG. 13
EXHIBITS
EXHIBIT 1 HYDROLOGIC SOIL GROUPS PG. 14
EXHIBIT 2 CURVE NUMBERS PG. 15
EXHIBIT 3 MANNING'S COEFFICIENTS PG. 16
EXHIBIT 4 100 YR,24 HR LSOPLUVIAL PG. 17
ATTACHMENTS
ATTACHMENT 1 BIOSWALE DESIGN PG. 18
2
I. LOCATION
The proposed development is located on a 5.34 acre parcel, in the Northwest quarter of
the Northwest quarter of Section 32 Township 23 North, Range 1 West, W.M., in Mason
County, Washington. The site is situate in Belfair and is immediately east of Navy Yard
Highway. The Assessor's Parcel Number for the site is 123325000020.
Adjacent projects include the Belfair Baptist Church to the north, and the Belfair Doctoes
Clinic to the south.
H. PRE-DEVELOPMENT SITE CONDITIONS
The site is approximately 5.34 acres and contains three drainage basins. The western
portion of the site is currently developed and contains a storage facility. The area to be
developed encompasses some of all three basins and is labeled basin PreDev. The
remaining basin areas consist of native vegetation and are the remnants of a logged off
area. All remaining undeveloped drainage basin areas are located on the upper portion of
the property and discharge storm waters to the north and south away from the project site.
Their respective areas are not used in the calculations. See Figure 2—Pre-Development
Site Map.
The DOE Manual assumes the conditions of the site in 1988 were established second
growth forest. For the purposes of this analysis, this pre-grading site condition of
established second growth forest has been used.
The soils on site are listed in the"Soil Survey of Mason County Area, Washington"
prepared by the United States Department of Agriculture, Soil Conservation Service as
Everett gravelly sandy loam, 15 to 30 percent slopes. See Figure 3 —Soils Map. The
Everett soil group is listed as Hydrologic Group A in Table HI-1.6 of the DOE
Stormwater Manual—Hydrologic Soil Group in the Puget Sound Basin. Soil logs
excavated on the site for this project show data consistent with the SCS mapping.
Water for domestic use and fire flow are serviced from Belfair Water District. An eight-
inch main is located on the west of the Navy Yard Highway and an 8" line has been
brought under the highway via a boring. Sanitary is on-site disposal. The primary and
reserve drainfields for all buildings are located to the south and east of existing building
A5.
III. UPSTREAM ANALYSIS
There are no basins upstream of this proposed project to analyze therefore there is no
analysis used in the following calculations.
3
IV. DOWNSTREAM ANALYSIS
All runoff from the JBarD Mini-Storage project flows west to the infiltration ditches
located on the west side of the project, adjacent to the Navy Yard Highway. The roofs
will also be infiltrated in trenches located in between each set of buildings.
V. DESCRIPTION OF PROPOSED DEVELOPEMT
The developed site contains three drainage basins. The developed area is labeled basin
PostDev. The remaining undeveloped drainage basin areas are located in the upper
portion of the project and drain the north and south into the adjoining second growth
forest next to the development area. See Figure 4—Developed Conditions Site Map.
The site is owned by Jesse Wallace et al and is located in the UGA of Belfair. The owner
proposes to build an additional 3 buildings in like fashion of the existing 5 buildings. The
new buildings will use extended services from the existing facilities as needed.
VI. OVERVIEW OF PROPOSED STORM WATER MANAGEMENT
FACILITIES
The portion of the site, which will be developed, is Everett series with long term high
infiltration capacity(hydrologic soil group A). Therefore the selected method of
Stormwater Management for the project is Infiltration. A new Stormwater collection,
conveyance, treatment and infiltration system is proposed to handle the additional paved
areas located on the westerly edge of the proposed addition.
The building roofs will discharge to individual infiltration trenches. Each set of buildings
will be equipped with one trench for each half of the roof. The trenches have been sized
using Waterworks software version 6.1.6.8 in conjunction with the DOE manual. Note
that the west half of building"F" is being infiltrated in the pavement trench since the
existing trench was not sized for the future expansion.
The paved and landscaped areas will be graded for surface flow and storm drain flow
discharging to a bioswale. The bioswale is designed to provide Quality enhancement for
the 6 month, 24 hour storm event. The bioswale will discharge to a Spill Containment
Oil/Water separator to an underground infiltration trench. These facilities will provide
infiltration of runoff for the 100 yr., 24 hr. storm for most paved and landscaped areas on
the developed site. A small portion of the pavement in the area of expansion will not be
collected in the new system, but will be collected and treated in an existing onsite system.
VII. TECHNICAL REQUIREMENTS
The DOE Stormwater Management Manual defines technical requirements.
• The Water Quantity Mitigation facilities will be infiltration trenches
designed to retain the 100 year, 24 hour, type 1 A storm.
4
• The Water Quality Mitigation facilities will be a bioswale designed to
provide treatment for the 6 month, 24 hour storm event. This design event
is equivalent to 64% of the 2 year, 24 hour, type 1 A storm for the
developed condition.
VIII. HYDROLOGIC ANALYSIS
Runoff computations utilize the SCS-based hydrograph method, Santa Barbara Urban
Hydrograph (SBUH) method with Type 1 A rainfall distribution.
The hydrological analysis was performed using StormShed (Release 6.1.6.8) by
Engenious Systems, Inc.
Other parameters are as follows:
• Runoff Curve Numbers (CN), Type 1 A Storm; See Exhibit 2 - Table 5-2
Modified Curve Numbers.
• Manning Coefficients; See Exhibit 3 - Table 5-3 Manning
Coefficients/"IC" Factors.
• 100 year, 24 hour Precipitation Isopluvial; See Exhibit 4.
1. ROOF AREAS
The roof runoff from the buildings will be infiltrated in infiltration trenches constructed
using washed rock for drainfields. The volume of trench required was computed using
software as mentioned above.
The footprint of each building proposed is 4,600 S.F. (0.1060 ac.) with a ridgeline
dividing the roof area in half. Using the infiltration rate for sand at 6 in/hr and a 40' long
10'wide trench, the design dictates that a 3' deep trench be used to service 4,600 sf of
roof area.
Running C:\Program Fi les\StormShed\RLP-rooftop Report.pgm on Thursday, July 10, 2003
Summary Report of all RLPooI Data
Project Precips
[2 yr] 3.00 in
[10 yr] 5.00 in
[100 yr] 7.00 in
BasinlD Peak Q Peak T Peak Vol Area Method Raintype Event
------- (cfs) (hrs) (ac-ft) ac /Loss
Roof(92x50) 0.0747 8.00 0.0254 0.11 SBUH/SCS TYPEIA 2 yr
Roof(92x50) 0.1263 8.00 0.0437 0.11 SBUH/SCS TYPEIA 10 yr
Roof(92x50) 0.1777 8.00 0.0620 0.11 SBUH/SCS TYPEIA 100 yr
5
Drainage Area: Roof(92x50)
Hyd Method: SBUH Hyd Loss Method: SCS CN Number
Peak Factor: 484.00 SCS Abs: 0.20
Storm Dur: 24.00 hrs Intv: 10.00 min
Area CN TC
Pervious 0.0000 ac 78.00 0.00 hrs
Impervious 0.1100 ac 98.00 0.08 hrs
Total 0.1100 ac
Supporting Data:
Impervious CN Data:
p-rooftop 98.00 0.1100 ac
Impervious TC Data:
Flow type: Description: Length: Slope: Coeff: Travel Time
Fixed dummy 0.00 ft 0.00% 5.0000 5.00 min
HydID Peak Q Peak T Peak Vol Cont Area
------- (cfs) (hrs) (ac-ft) (ac)
roof-out2yr 0.06 2.33 0.0298 0.1100
roof-outl0yr 0.06 2.17 0.0459 0.1100
roof-out 1 00yr 0.06 1.33 0.0627 0.1100
Node ID: Infil-rooftop
Desc: Manhole structure
Start El: 100.0000 ft Max El: 108.0000 ft
Contrib Basin: Contrib Hyd:
Length Width Void Ratio
40.0000 ft 10.0000 ft 30.00
Bottom area only with infiltration
Control Structure ID: Infil-rate - Infiltration control structure
Descrip: Multiple Orifice
Start El Max El Increment
100.0000 ft 105.0000 ft 0.10
Infil: 6.00 in/hr Multiplier: 1.00
RLPCOMPUTE [RLP-rooftop]SUMMARYd
2 yr MatchQ=PeakQ=0.0747 cfs Peak Out Q: 0.0556 cfs-Peak Stg: 100.37 ft-Active Vol: 43.99 cf
10 yr MatchQ=PeakQ= 0.1263 cfs Peak Out Q: 0.0556 cfs-Peak Stg: 101.25 ft-Active Vol: 149.58 cf
100 yr MatchQ=PeakQ=0.1777 cfs Peak Out Q: 0.0556 cfs-Peak Stg: 102.61 ft-Active Vol: 312.65 cf
2. ASPHALTIC & LANDSCAPED AREAS
The runoff from the rest of the developed site will be infiltrated in infiltration trench
constructed using washed rock for drainfields. The volume of trench required was
computed using software as mentioned above.
The areas remaining to be collected and treated are-
6
• The west half of building"F"(2,300 sf)
• The pavement (0.3 5 ac)
• Landscaped areas (0.17 ac)
• Some undeveloped areas are contributory (1.04 ac)
Using the infiltration rate for sand at 6 in/hr and a 60' long 30'wide trench; the
design dictates that a 3' deep trench be used to service the rest of the developed area.
Running C:\Program Files\StormShed\RLP Report.pgm on Thursday, July 10, 2003
Summary Report of all RLPool Data
Project Precips
[2 yr] 3.00 in
110 yr] 5.00 in
[100 yr] 7.00 in
BasinlD Peak Q Peak T Peak Vol Area Method Raintype Event
------ (cfs) (hrs) (ac-ft) ac /Loss
PostDev 0.2716 8.00 0.0953 1.61 SBUH/SCS TYPE1A 2yr
PostDev 0.4594 8.00 0.2064 1.61 SBUH/SCS TYPE1A 10yr
PostDev 0.6927 8.00 0.3556 1.61 SBUH/SCS TYPE1A 100yr
Drainage Area: PostDev
Hyd Method: SBUH Hyd Loss Method: SCS CN Number
Peak Factor: 484.00 SCS Abs: 0.20
Storm Dur: 24.00 hrs Intv: 10.00 min
Area CN TC
Pervious 1.2100 ac 45.65 0.35 hrs
Impervious 0.4000 ac 98.00 0.08 hrs
Total 1.6100 ac
Supporting Data:
Pervious CN Data:
Est. Second Growth Forest 42.00 1.0400 ac
Lawn & Landscaping 68.00 0.1700 ac
Impervious CN Data:
pavement 98.00 0.3500 ac
structures 98.00 0.0500 ac
Pervious TC Data:
Flow type: Description: Length: Slope: Coeff: Travel Time
Sheet Est. Second Growth Forest 300.00 ft 20.00% 0.4000 21.26 min
Shallow 2:1 Cut Slope 85.00 ft 50.00% 11.000 0.18 min
Impervious TC Data:
Flow type: Description: Length: Slope: Coeff: Travel Time
Fixed dummy 0.00 ft 0.00% 5.0000 5.00 min
HydID Peak Q Peak T Peak Vol Cont Area
------- (cfs) (hrs) (ac-ft) (ac)
east-out2yr 0.25 2.50 0.1171 1.6100
east-outlOyr 0.25 1.67 0.2101 1.6100
east-out100yr 0.25 1.33 0.3581 1.6100
7
Node ID: Infil-east
Desc: Manhole structure
Start El: 100.0000 ft Max El: 108.0000 ft
Contrib Basin: Contrib Hyd:
Length Width Void Ratio
60.0000 ft 30.0000 ft 30.00
Bottom area only with infiltration
Control Structure ID: Infil-rate - Infiltration control structure
Descrip: Multiple Orifice
Start El Max El Increment
100.0000 ft 105,0000 ft 0.10
Infil: 6.00 in/hr Multiplier: 1.00
RLPCOMPUTE [RLP] SUMMARY
2 yr MatchQ=PeakQ= 0.2716 cfs Peak Out Q: 0.2500 cfs-Peak Stg: 100.14 ft-Active Vol: 73.51 cf
10 yr MatchQ=PeakQ=0.4594 cfs Peak Out Q: 0.2500 cfs-Peak Stg: 100.78 ft-Active Vol:419.15 cf
100 yr MatchQ=PeakQ=0.6927 cfs Peak Out Q: 0.2500 cfs-Peak Stg: 102.46 ft-Active Vol: 1327.32 cf
IX STORMWATER QUALITY ENHANCEMENT FACILITIES
The Stormwater quality enhancement will be provided by a bioswale sized to treat the 6
month storm. The 6 month storm runoff rate from Basin PostDev is calculated as 64% of
the two year storm runoff rate. The two year storm peak discharge as calculated by
Waterworks is as follows;
2 yr Flow Time Volume 6 Month
Summary: 0.2716 cfs 8.00 hrs 4153 cf—0.0953 acft 0.1740 cfs
As presented in Attachment 1 —Bioswale Design Worksheet, for an 8-foot wide bioswale
with slopes at 1.00 percent the minimum length to meet the required 300-second contact
time for the 0.174 cfs design flow rate of the basin labeled PostDev is 47 lineal feet.
The proposed bioswale is located on a slope of approximately 14%. In order to have a
bioswale that slopes at 1% a terraced bioswale is being proposed.
X. EROSION AND SEDIMENT CONTROL
The developed area is small in acreage, with moderate ground slopes and combined with
the fact that the soils are sandy, the potential for erosion and sedimentation problems is
low. Erosion and sedimentation control measures will be installed as the first work on the
site. The TESCP includes the following elements;
• Filter Fabric Fence along the west boundary.
• Stabilized construction entrance.
• Installation of a Sedimentation Trap. (20'x10')
At this point the TESCP changes to a Maintenance Program. Elements of the
maintenance program extend beyond maintenance of the above described facilities to
8
application of best management practices to include slope stabilization, covering exposed
areas, and other measures as included in the project notes, "Minimum Erosion and
Sedimentation Control Requirements" and "General Erosion and Sedimentation Control
Requirements".
9
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AREAS
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FIGURE 4 DEVELOPED SITE CONDITIONS
STORMWATER MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN
Table III-1.6 Hydrologic Soil Groups fo•Soils in the Puget Sound Basin
Hydrologic Soil Hydrologic Soil
Soil Type
Group Soil Type Group
Agnew C Colter
Ahl B C
Aits Crater ND
Alderwood C Dabob ND
Arents,Alderwood Delphi D
B Dickim ND
--7
Aroma, Evs,roa B Dimal
Baldhill Ashoo B �p°Or D
BarnasWo B Earimool C
Baumgard B Eld�kk C
Beausite B Elwell B
Belfast C Eayuatzel B
Bellingham D Everett
Bellingham variant C Everson A.
Boisistfofon B Galvin
Bow D
Briscot
D Getchell A
D Gila
Buckley B
C Godfrey D
Cagey
roonwater B G
Cagey C A
Carisborg Grove C
Casey
ND Harstine C
Cassole Hannit ry D ND
Cathcart B Hoh ND
Centralia Hoko ND
Chesaw 8
Chehalis B Hoo dal n CD
Cinebar A Hoypus ND
Clellem B Huel ND
Clayton Wisinole ND
Coastal beach*& B Jonas B
variable Jumps, ND
Ka�pD CID Kaleloch
Katule C c
Kilchis Remo D
Kitsap
C Republic B
Klaus C ND Roberwash variable
KlonLaws ND Salal C
Lies C
Lebam
C Saikum B
B
Lummi Sam namish D
San Juan Lynnwood ND N D
LysND Scamman D
Mal ND Schneider
Ma! g
Manley C Seattle D
Mashel B Sekiu
B ND
Maytown Semiahmoo D
McKenna C Shalear D
McMurray Shano y ND g
Melbourne Shelton C
Menzel B Si C
Mixed Alluvial ND Sinclair Cvariable Skipopa
Molson B D
Mukilteo Skykomish B
N&ff C/D Snahopiah ND
Nat B Snohomish D
A Solduc
National ND g
Neilton Soileks ND
A Spars D
IIi-1-9 FEBRUARY, 1992
IT
• 1
STORMWATER MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN
Table III-1.3 SCS Western Washington Runoff Curve Numbers
(Published by SCS in 1982) Runoff curve numbers for selected agricultural,
suburban and urban
land use for Type lA rainfall distribution, 24-hour storm duration.
LAND USE DESCRIPTION CURVE NUMBERS BY
HYDROLOGIC SOIL GROUP
A B C D
Cultivated land 1 : winter condition 86 91 94 95
Mountain open areas: low growing brush & grasslands 74 82 89 92
Meadow or pasture: 65 78 85 89
Wood or forest land: undisturbed 42 64 76 81
Wood or forest land: young second growth or brush rush 55 72 81 86
Orchard: with cover crop 81 88 92 94
Open spaces, lawns, parks, golf courses, cemeteries,
landscaping.
Good condition: grass cover on L758 of the 68 80 86 90
area
Fair condition: grass cover on 50-75% of 77 85 90 92
the area
Gravel roads & parking lots: 76 85 89 91
Dirt roads & parkin lots: 72 82 87 89
Impervious surfaces, pavement, roofs etc. 98 98 98 98
Open water bodies: lakes, wetlands, ponds etc. 100 100 100 100
Single family residential(2) :
Dwelling Unit/Grose Acre %Impervious(3) Separate curve number
1.0 DU/GA 15 shall be selected for
1.5 DU/GA 20 pervious & impervious
2.0 DU/GA 25 , portions of the site
2.5 DU/GA 30 or basin
3.0 DU/GA 34
3.5 DU/GA 38
4.0 DU/GA 42
4.5 DU/GA 46
5.0 DU/GA 48
5.5 DU/GA 50
6.0 DU/GA 52
6.5 DU/GA 54
7.0 DU/GA 56
PUD's, condos, apartments, %impervious
commercial businesses & must be
industrial areas computed
(1) For a more detailed description of agricultural land use curve numberei refer
to National Engineering Handbook, Sec. 4, Hydrology, Chapter 9, August 1972.
(2) Assumes roof and driveway runoff is directed into street/storm system.
(3) The remaining pervious areas (lawn) are considered to be in good
condition for these curve numbers.
III-1-12 FEBRUARY, 1992
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STORMWATER MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN
124 123 122 121
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NOAA ATLAS 2, Volume IX
ISOPLUVIALS F 100-YR 24•HR PRECIPITATION
TION 50 55 60 65 Prepared by U.S Department of C coerce
IN TENTHS OF N INCH Nafionsl Oceanic and AtmosphancAliministration
Netionsi Weather Service,Office of NydrolotY
Prepared for U.S.Department of A iculture,
Son Conservation Service,Engineers 9 Division
124 123 122
121
III-1-46 FEBRUARY, 9992
BIOSWAL.E DESIGN WORKSHEEY
Project Name JBarD mini-storage Job No. 005A
By: RDC
Client Jesse Wallace Date: 7/9/2003
Q=(1.486/n)"A"R^2/3*S^1/2
where: Q= Flow Rate, in cfs input: B= 8 ft.
V= Velocity, in fps S= 0.01 ft./ft.
n= Roughness coefficient, Q 2yr= 0.2716 cfs
A= Area of cross section, in sf Q 100yr= 0.6927 cfs
R= Hydraulic Radius
S= Slope, in f/f calculate:
Q Match= 0.64(Q 2yr)= 0.174 cfs
requirements: n= 0.2 max
3 to 1 sideslopes
Q match d A R V find: Q Match 0.190 cfs
check: d<0.25 YES
0.000 0.00 0.000 0.000 0.000 select: V= 0.157 fps
0.033 0.05 0.408 0.051 0.081 calculate: L req'd= 47 lin. Ft.
0.108 0.10 0.830 0.103 0.130
0.174 0.13 1.108 0.137 0.157
0.359 0.20 1.720 0.211 0.209
0.533 0.25 2.188 0.265 0.243
0.359 0.20 1.720 0.211 0.209 check stability:
0.693 0.29 2.572 0.309 0.269
0.969 0.35 3.168 0.373 0.306 find: Q 100yr 0.693 cfs
1.229 0.40 3.680 0.426 0.334 check: V<3.0 ? YES
1.517 0.45 4.208 0.478 0.361 d<1.0 ? YES
1.830 0.50 4.750 0.528 0.385
2.169 0.55 5.308 0.576 0.409
2.531 0.60 5.880 0.623 0.430
2.915 0.65 6.468 0.667 0.451
3.320 0.70 7.070 0.710 0.470
3.745 0.75 7.688 0.750 0.487
4.188 0.80 8.320 0.788 0.503
4.649 0.85 8.968 0.823 0.518
5.127 0.90 9.630 0.857 0.532
5.619 0.95 10.308 0.888 0.545