HomeMy WebLinkAboutSWP272320(1) i
a
CONCEPT ENGINEERING, INC.
j 455 Rainier Boulevard North,Suite 200
Issaquah,Washington 98027
i ., .. (206)392-8055 Fax: (206)392-0108
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DRAINAGE CALCULATIONS FOR
' U.S. RENTALS
' CITY OF RENTON, WASHINGTON
' Prepared for:
Treece & Company
i 320 2nd Ave. South, Suite 200
Kirkland, WA 98033
Phone: (206) 822-2577
' FAX: (206) 822-8758
By:
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Kirk R. Smith, P.E. N
' April 11, 1997 JUN 2 0 1997
REVISED June 20, 1997 DCv�S;ION
CIVIL ENGINEERING/SURVEYING/LAND USE PLANNING
' TABLE OF CONTENTS
' Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Summary of Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
' Basin Summaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Runoff Curve Number and Time of Concentration . . . . . . . . . . . . . . . . . . . . . 8
' Detention Pond Design Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
' Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Backwater Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
' Drainage Area Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
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' INTRODUCTION
' The following design report presents the design of the stormwater control facilities for
the proposed 4.17 acre U.S. Rentals site at the intersection of Lind Ave. and SW 34th
St.
Existing Drainage Conditions
' The project site is currently a vacant parcel (Lot 8 of Burlington Northern Binding Site
Plan). The parcel was filled approximately 18 years ago. The existing ground cover
consists of mainly pasture grass in poor condition. The site is extremely flat with
several shallow depressions. A 30 foot wide railroad easement borders the east side
of the site. This railroad line has ditches on either side of the tracks which collect
runoff from a portion of the site. The general overall slope is from east to west at an
average slope of 0.2 percent.
The site has two storm drainage stubs available, one on each frontage road.
However, neither is currently receiving runoff from the site. The east and south sides
of the site have been or are under development and will intercept any surface flow
from upstream areas.
Proposed Drainage Conditions
' Runoff from parking, equipment and material storage, landscaping and roof areas will
be conveyed via sheet flow to perimeter biofiltration swales. These perimeter swales
' convey the treated water to a combination detention/water quality pond located in the
southern portion of the site. This pond will have 2-3 feet of dead storage to enhance
water quality through settling of sediments prior to discharge from the site.
A multi-orifice flow control structure is provided at the outlet from the pond. Post-
detention peak outflows will be at or below the pre-developed peak runoff rates for
the 2, 10 and 100 year storm events. The control structure outlet is connected to a
12 inch storm drainage stub near the midpoint of the west property line along Lind
Avenue. This stubs connects with a 60 inch storm drain pipe along the west side of
Lind Avenue. The 60 inch continues north to the Lind-SW 34th St. intersection and
then turns west and continues down SW 34th St for approximately 1/4 mile until
' reaching Springbrook Creek.
Per discussions with Scott Woodbury of the City of Renton, a tailwater condition from
' Springbrook Creek exists in the 60-inch culvert during storm events. Mr. Woodbury
said that development projects in the area have been required to base their
conveyance analyses on a 2-year tailwater elevation of 14.6 (NAVD 88). Converted
' to the vertical datum used in the site plans for this project, the tailwater elevation is
1 1 .26 feet. This tailwater was used in the backwater analysis for this project.
' Core and Special Requirements
' Following is a description of how the 1990 King County Surface Water Design Manual
core and special requirements were addressed in this design.
' CORE REQUIREMENT #1 - Discharge at the natural location:
As described above, two drainage stubs have been provided to the site; both connect
to a 60-inch system leading to Springbrook Creek. The proposed system will connect
to the stub in Lind Ave.
' CORE REQUIREMENT #2 - Off-site analysis:
The upstream and downstream systems are described above.
CORE REQUIREMENT #3 - Runoff control:
A stormwater detention pond will control runoff from the developed site and release
at the existing condition peak runoff rates for the 2, 10, and 100-year, 24-hour storm
' events. Designing the system to the 100-year event resulted in a storage volume of
11 ,738 cubic feet, which is greater than the 10,201 cubic feet that would have been
provided if the system had been designed to the 10-year storm with a 30% factor of
' safety added. Biofiltration swales have been provided as required.
CORE REQUIREMENT #4 - Conveyance system:
' A uniform flow conveyance analysis has been provided for the proposed swales. A
backwater conveyance analysis was performed for the proposed pipes.
' CORE REQUIREMENT #5 - Temporary erosion and sedimentation control plan:
A TESC plan has been prepared consisting of construction sequence, gravel
construction entrance, perimeter silt fencing, and a sediment pond.
' SPECIAL REQUIREMENT #5 - Special Water Quality Controls:
A water quality pond (wetpond) has been provided since the proposed site plan
contains more than 1 acre of impervious surfaces subject to vehicular use or the
storage of chemicals.
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' SUMMARY OF RESULTS
PROPOSED DETENTION SYSTEM
Total Area of Project Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.17 acres
Post-Devel- Post- Design Detention
Design Pre-Developed oped Pond Developed Water Storage
Storm Peak Discharge Inflow Release Surface volume
(cfs) Rate Elevation
(cfs) (cfs) (ft) (cf)
W.Q. NA 0.45 0.26 13.53 243
2 0.45 1 .76 0.44 14.06 4575
' 10 0.91 2.68 0.89 14.44 7847
' 100 1 .47 3.69 1 .29 14.86 11747
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BASIN SUMMARIES
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1/2/97 1:22:34 pm Treece & Company
US Rentals - Lind Ave. & SW 34th St.
SBUH m aph-Analysis-------------------------
Preliminary
R/D Sizing
BASIN SUMMARY
BASIN ID: DEV-002 NAME: POST-DEV 2-YEAR 24-HR STORM
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 4.17 Acres BASEFLOWS: 0.00 cfs
RAINFALL TYPE. . . . : KC24HR PERV IMP
PRECIPITATION. . . . : 1.95 inches AREA. . : 0.42 Acres 3.75 Acres
TIME INTERVAL. . . . : 10.00 min CN. . . . : 90.00 98.00
' TC. . . . : 10.00 min 10.00 min
ABSTRACTION COEFF: 0.20
PEAK RATE: 1.76 cfs VOL: 0.58 Ac-ft TIME: 480 min
BASIN ID: DEV-002W NAME: POST-DEV WATER QUALITY STORM
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 4.17 Acres BASEFLOWS: 0.00 cfs
RAINFALL TYPE. . . . : KC24HR PERV IMP
PRECIPITATION. . . . : 0.65 inches AREA. . : 0.42 Acres 3.75 Acres
TIME INTERVAL. . . . : 10.00 min CN. . . . : 90.00 98.00
TC. . . . : 10.00 min 10.00 min
ABSTRACTION COEFF: 0.20
' PEAK RATE: 0.44 cfs VOL: 0.15 Ac-ft TIME: 480 min
BASIN ID: DEV-010 NAME: POST-DEV 10-YEAR 24-HR STORM
SBUH METHODOLOGY
' TOTAL AREA. . . . . . . : 4 .17 Acres BASEFLOWS: 0.00 cfs
RAINFALL TYPE. . . . : KC24HR PERV IMP
PRECIPITATION. . . . : 2 .85 inches AREA. . : 0.42 Acres 3.75 Acres
TIME INTERVAL. . . . : 10.00 min CN. . . . : 90.00 98.00
TC. . . . : 10.00 min 10.00 min
ABSTRACTION COEFF: 0.20
PEAK RATE: 2.67 cfs VOL: 0.88 Ac-ft TIME: 480 min
BASIN ID: DEV-100 NAME: POST-DEV 100-YEAR 24-HR STORM
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 4.17 Acres BASEFLOWS: 0.00 cfs
RAINFALL TYPE. . . . : KC24HR PERV IMP
PRECIPITATION. . . . : 3 .85 inches AREA. . : 0.42 Acres 3 .75 Acres
TIME INTERVAL. . . . : 10.00 min CN. . . . : 90.00 98 .00
TC. . . . : 10.00 min 10.00 min
ABSTRACTION COEFF: 0.20
PEAK RATE: 3 .69 cfs VOL: 1.23 Ac-ft TIME: 480 min
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1/2/97 1:22:34 pm Treece & Company
US Rentals - Lind Ave. & SW 34th St.
SBUH
' Preliminary Hydrograph Analysis
R/D Sizing
BASIN SUMMARY
BASIN ID: EX-002 NAME: PRE-DEV 2-YEAR 24-HOUR STORM
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 4 .17 Acres BASEFLOWS: 0.00 cfs
RAINFALL TYPE. . . . : KC24HR PERV IMP
PRECIPITATION. . . . : 1.95 inches AREA. . : 4.17 Acres 0.00 Acres
TIME INTERVAL. . . . : 10.00 min CN. . . . : 88 .00 0.00
TC. . . . : 60.00 min 0.00 min
ABSTRACTION COEFF: 0.20
PEAK RATE: 0.44 cfs VOL: 0.32 Ac-ft TIME: 490 min
BASIN ID: EX-010 NAME: PRE-DEV 10-YEAR 24-HOUR STORM
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 4 .17 Acres BASEFLOWS: 0.00 cfs
RAINFALL TYPE. . . . : KC24HR PERV IMP
PRECIPITATION. . . . : 2 .85 inches AREA. . : 4.17 Acres 0.00 Acres
TIME INTERVAL. . . . : 10.00 min CN. . . . : 88.00 0.00
TC. . . . : 60.00 min 0.00 min
ABSTRACTION COEFF: 0.20
PEAK RATE: 0.91 cfs VOL: 0.59 Ac-ft TIME: 490 min
' BASIN ID: EX-100 NAME: PRE-DEV 100-YEAR 24-HOUR STORM
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 4 .17 Acres BASEFLOWS: 0.00 cfs
RAINFALL TYPE. . . . : KC24HR PERV IMP
PRECIPITATION. . . . : 3.85 inches AREA. . : 4.17 Acres 0.00 Acres
TIME INTERVAL. . . . : 10.00 min CN. . . . : 88.00 0.00
TC. . . . : 60.00 min 0.00 min
ABSTRACTION COEFF: 0.20
PEAK RATE: 1.47 cfs VOL: 0.90 Ac-ft TIME: 490 min
1/2/97 1:22:34 pm Treece & Company
US Rentals - Lind Ave. & SW 34th St.
SBUH
Preliminary aph-Analysis-------- ---- -----------
Preliminary R/D Sizing
HYDROGRAPH SUMMARY
' PEAK TIME VOLUME
HYD RUNOFF OF OF Contrib
NUM RATE PEAK HYDRO Area
cfs min. cf\AcFt Acres
1 0.445 490 14004 cf 4.17
2 0.909 490 25513 cf 4.17
3 1.470 490 39205 cf 4.17
4 1.761 480 25082 cf 4.17
5 2 .675 480 38466 cf 4.17
6 3.685 480 53450 cf 4.17
7 0.445 480 6393 cf 4.17
' 14 0.442 550 25082 cf 4.17
15 0.891 540 38491 cf 4.17
16 1.289 530 53453 cf 4.17
17 0.259 510 6394 cf 4.17
RUNOFF CURVE NUMBER
TIME OF CONCENTRATION
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CURVE NUMBER SELECTION
The fill soil was assumed to correspond to hydrologic soil group C. A Curve Number
(CN) value of 88 was used for the pre-developed conditions. This was determined by
taking an average of the "fair" and "good" conditions for open space and lawns. A
CN value of 90 was chosen for the pervious areas in the post-developed condition.
TIME OF CONCENTRATION
A conservative time of concentration of 60 minutes was used for the pre-developed
conditions. Due to the extremely flat topography with several small depressions, a
typical calculation with a friction coefficient and slope is not appropriate.
A post-developed T, of 10 minutes has been used. The actual calculated Tr's for the
east and west Swale basin are slightly more than 10 minutes, thus the analysis
predicts more conservative peak runoff rates and volumes for the post-developed
condition.
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■ DETENTION BASIN DESIGN DATA
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US Rentals - Lind Ave . & SW 34th St .
SBUH Hydrograph Analysis
R/D Sizing
STAGE STORAGE TABLE
TRAPEZOIDAL BASIN ID No. SP-1
Description: DETENTION STORAGE POND
Length: 155 . 00 ft . Width: 50 . 00 ft .
Side Slope 1 : 3 Side Slope 3 : 3
Side Slope 2 : 3 Side Slope 4 : 3
Infiltration Rate : 0 . 00 min/inch
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STAGE <----STORAGE----> STAGE <----STORAGE----> STAGE <----STORAGE----> STAGE <----STORAGE---->
_(ft)_===cf-==_==Ac=Ft=--__(ft)_===cf===-==Ac=Ft=---_(ft)-===cf===_==Ac=Ft=_-_-(ft)-===cf===_==Ac=Pt=_--
13.50 0.0000 0.0000 13.90 3199 0.0734 14.30 6600 0.1515 14.70 10206 0.2343
13.60 781.16 0.0179 14.00 4030 0.0925 14.40 7482 0.1718 14.80 11141 0.2558
13.70 1575 0.0362 14.10 4874 0.1119 14.50 8377 0.1923 14.90 12088 0.2775
13.80 2381 0.0547 14.20 5730 0.1316 14.60 9285 0.2132 15.00 13049 0.2996
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US Rentals - Lind Ave . & SW 34th St .
SBUH Hydrograph Analysis
R/D Sizing
STAGE DISCHARGE TABLE
COMBINATION DISCHARGE ID No. DC-1
Description: COMBO DISCHARGE #1
Structure : DO-1 Structure :
Structure : DNW-1 Structure :
Structure :
STAGE <--DISCFIARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE--->
' -(ft)=====cfo=====-----====(ft)=====cfa=====_____====(ft)=====cfs====______====(ft)=====cfra
13.25 0.0000 14.00 0.4245 14.80 1.1596 15.60 1.5013
13.30 0.1096 14.10 0.4519 14.90 1.3751 15.70 1.5417
13.40 0.1898 14.20 0.6714 15.00 1.6651 15.80 1.5810
13.50 0.2451 14.30 0.7761 15.10 1.2790 15.90 1.6194
13.60 0.2900 14.40 0.8610 15.20 1.3266 16.00 1.6568
13.70 0.3288 14.50 0.9353 15.30 1.3725
13.80 0.3635 14.60 1.0025 15.40 1.4168
13.90 0.3952 14.70 1.0645 15.50 1.4597
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US Rentals - Lind Ave . & SW 34th St .
SBUH Hydrograph Analysis
R/D Sizing
STAGE DISCHARGE TABLE
NOTCH WEIR ID No. DNW-1
Description: NOTCH WEIR ON 18" RISER
Weir Length: 1 . 0000 ft . Weir height (p) : 0 . 2500 ft .
Elevation 14 . 75 ft . Weir Increm: 0 . 10
STAGS <--DISCHARGS---> STAGE <--DISCHARGE---> STAGS <--DISCHARGE---> STAGS <--DISCHARGE--->
(ft) ---cfe-- ------- (ft) ---cfe-- ------- (ft) ---cfe-- ------- (ft) ---cfS-- -------
14.75 0.0000 14.80 0,0371 14,90 0.1978 15,00 0,4358
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US Rentals - Lind Ave . & SW 34th St .
SBUH Hydrograph Analysis
R/D Sizing
STAGE DISCHARGE TABLE
MULTIPLE ORIFICE ID No . DO-1
Description: MULTIPLE ORIFICE DISCHARGE
Outlet Elev: 13 . 25
Elev: 11 . 25 ft Orifice Diameter: 4 . 2500 in.
Elev. 14 . 10 ft Orifice 2 Diameter: 4 . 7500 in.
STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE--->
(ft) ---cfe-- ------- (ft) ---cfo-- ------- (ft) ---cfe-- ------- (ft) ---cfe-- -------
13 25 0.0000 14.00 0 4245 14.80 1.1225 15.60 1.5013
13.30 0.1096 14.10 0.4519 14.90 1.1773 15.70 1.5417
13.40 0.1898 14.20 0.6714 15.00 1.2293 15.80 1.5810
1 13.50 0.2451 14.30 0.7761 15.10 1.2790 15.90 1.6194
13.60 0.2900 14.40 0.8610 15.20 1.3266 16.00 1.6568
13.70 0.3288 14.50 0.9353 15.30 1.3725
13.80 0.3635 14.60 1.0025 15.40 1.4168
13.90 0.3952 14.70 1.0645 15.50 1.4597
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US Rentals - Lind Ave . & SW 34th St .
SBUH Hydrograph Analysis
R/D Sizing
STAGE DISCHARGE TABLE
BROAD CRESTED WEIR ID No. DOW-1
Description: EMERGENCY OVERFLOW SPILLWAY
cd: 3 . 2100 Weir length: 6 . 0000 ft .
El : 15 . 50 ft . Weir Increm: 0 . 10
STAGE <--DISCHARGE---> STAGE —DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE--->
(ft) ---cfo-- ------- (£t) ---cfo-- ------- (ft) ---cfo-- ------- (ft) ---cfe-- -------
15.50 0.0000 15.70 1.8605 15.90 5.6520 16.00 8.1713
15.60 0.6334 15.80 3.S44S 16.00 8.1713
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US Rentals - Lind Ave . & SW 34th St .
SBUH Hydrograph Analysis
R/D Sizing
DISCHARGE TABLE====____________________
1 RISER DISCHARGE ID No. DR-1
Description: 18" CMP OVERFLOW RISER
Riser Diameter (in) : 18 . 00 elev: 15 . 00 ft
1 Weir Coefficient . . . : 9 . 739 height : 16 . 00 ft
Orif Coefficient . . . : 3 . 782 increm: 0 . 10 ft
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STAGS <--DISCHARGE---> STAGE r-DISCHARGE-- STAGE <--DISCHARGE---> STAGS <--DISCHARGE--->
1 -(ft)=====cfs ====(ft)=====cfs=====_____====`ft)=====cfs (ft)=====cfe=====________
15.00 0.0000 15.20 1.3066 15.50 5.1649 15.80 7.6111
15.00 0.0000 15.30 2.4004 15.60 6.5914 15.90 8.0728
15.10 0.4620 15.40 3.6957 15.70 7.1196 16.00 8.5095
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US Rentals - Lind Ave . & SW 34th St .
SBUH Hydrograph Analysis
R/D Sizing
LEVEL POOL TABLE SUMMARY
MATCH INFLOW -STO- -DIS- <-PEAK-> STORAGE
<--------DESCRIPTION---------> (cfo) (cfe) --id- --id- <-STAGE> id VOL (cf)
2-YEAR, 1 5' POND 0.44 1.76 SP-1 cDC-1 14.06 14 4575.29 cf
10-YEAR, 1.5' POND ........... 0.91 2.67 SP-1 DC-1 14.44 15 7847.14 cf
100-YEAR, 1.5' POND . ......... 1.47 3.69 SP-1 DC-1 14.86 16 11738.61 cf
W.Q. STM, 1.5' POND .......... 0.00 0.44 SP-1 DC-1 13.53 17 242.60 cf
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' GENERAL
The water quality design consists of two elements:
1 . Biofiltration Swale
2. Wetpond
CODE THRESHOLDS
The threshold for biofiltration treatment of impervious surface runoff is 5,000 sq. ft. subject to
vehicular use or storage. The site proposes approximately 2.5 acres of such surfacing and thus is
' over this threshold. The threshold for a wetpond (Special Requirement #5) is 1 acre of impervious
surface subject to vehicular use or storage, and for the site to be within one mile of a Class 1 or 2
stream. Springbrook Creek is classified as a Class 2S stream and lies approximately 1/4 mile west
' of the site. Therefore, a wetpond is required.
DESIGN PARAMETERS & METHOD
' The design parameters listed in the 1990 KCSWDM have been used to determine the required
biofiltration swale and wetpond size. The site design utilizes perimeter swales to provide in excess
of the required biofiltration surface area. These swales converge at a combination detention/water
' quality pond. The results are summarized below:
East Swale
2-year Peak Runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.64 cfs
DesignFlow Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 inches
' Required Bottom Width for 200 If Swale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.00 ft
Equivalent Bottom Area Required 200 ft'
Provided Bottom Area for 460 If Swale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 920 ft'
Actual Channel Slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.002 ft/ft
Actual 2-Year Peak Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.79 ft/sec
Actual 100-Year Peak Runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 .32 cfs
' Actual 100-Year Peak Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.98 ft/sec
West Swale
' 2-year Peak Runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.65 cfs
Design Flow Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 inches
Required Bottom Width for 200 If Swale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.03 ft
Equivalent Bottom Area Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 ft'
Provided Bottom Area for 384 If Swale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 684 ft2
' Actual Channel Slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.002 ft/ft
Actual 2-Year Peak Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.79 ft/sec
Actual 100-Year Peak Runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 .33 cfs
Actual 100-Year Peak Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.98 ft/sec
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Water Quality Pond (Wetpond)
Water Quality Storm Peak Runoff, QN,q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 639 cfs
Water Quality Storm Runoff Volume, VWq . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 393 ft
Impervious Surface Tributary to Wetpond, A,, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125,000 ft
Required Wetpond Surface Area, A, (1 % of At_Wq) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1250 ft3
Required Wetpond Dead Storage Volume = VWq 6393 ft
' Proposed Wetpond Surface Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7755 ft2
Proposed Wetpond Dead Storage Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13,210 ft3
' Both the biofiltration swales and the wetpond will require seeding with a wetland-type vegetation
consistent with the 1990 KCSWDM.
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US Rentals - Lind Ave . & SW 34th St .
SBUH Hydrograph Analysis
' 100-Year Backwater Analysis
REACH SUMMARY
Hydraulic Gradeline for Reach HGL-MN
<-FROM-> -TO- <FLOW> floss Ent HGL EntLoss ExtLoaa OutLet Inlet AppHead BndHead JunHead HeadWtr -cb/mh-
--------------------cfa--=loan-_=Blev==-=-loss=-==loco----EleV=---Elev=--=loss=--=loss=-==loss=-==B1eV=--=Rim==
cb-exst 11.26
' CB-01 cb-exat 3.69 0.94 12.20 0.07 0.34 12.61 13.17 0.34 0.31 0.00 13.14 17.80
CB-02 CB-01 3.69 2.01 15.14 0.07 0.34 15.55 14.63 0.34 0.11 0.00 15.32 17.00
INL-03 CB-02 3.69 0.05 15.38 0.34 15.72 15.30 0.00 0.00 0.00 15.72 16.00
' Network Reach N-MAIN
REACH <-AREA> <-DIA> LBNGTH SLOPE < n > DSGN Q PIPE Ndepth %Depth Vact Vfull C Area
ID (Ac) (ft) (ft) ft/ft ------ (cfs) (ft) ------ (fps) (fps)
---------------------------------------------------------------------
----------------------------
-------------------------------------------------------------------------------------------------
P-03 4.17 1.00 6.03 0.0414 0.0120 3.69 43.49 0.48 48.09 9.86 11.07
P-02 4.17 1.00 221.50 0.0065 0.0120 3.69 >=100$ Pressure flow 4.69 4.40
P-01 4.17 1.00 103.50 0.0269 0.0120 3.69 54.01 0.55 54.73 8.38 8.92
PIPE REACH ID No. P-01
From: CB-01 To : cb-exst
Pipe Diameter: 1 . 0000 ft n: 0 . 0120
Pipe Length 103 . 5047 ft s : 0 . 0269
Up invert 11 . 8000 ft down invert : 9 . 0200 ft
' Collection Area: 4 . 1700 Ac .
Design Flow 3 . 6852 cfs Dsgn Depth: 0 . 55 ft
Pipe Capacity 6 . 8227 cfs
Design Vel 8 . 3771 fps Travel Time : 0 . 21 min
Pipe Full Vel 8 . 9152 fps
PIPE REACH ID No . P-02
From: CB-02 To : CB-01
Pipe Diameter: 1 . 0000 ft n: 0 . 0120
Pipe Length 221 . 5038 ft s : 0 . 0065
Up invert 13 . 2500 ft down invert : 11 . 8000 ft
Collection Area: 4 . 1700 Ac .
Design Flow 3 . 6852 cfs Dsgn Depth: ft
Pipe Capacity 3 . 3683 cfs
Design Vel 4 . 6921 fps Travel Time : 0 . 79 min
Pipe Full Vel 4 . 4013 fps (surcharged tt)
2�
6/20/97 10 : 59 : 49 am Concept Engineering page 2
' US Rentals - Lind Ave . & SW 34th St .
SBUH Hydrograph Analysis
100-Year Backwater Analysis
REACH SUMMARY
1 PIPE REACH ID No. P-03
From: INL-03 To: CB-02
Pipe Diameter: 1 . 0000 ft n: 0 . 0120
1 Pipe Length 6 . 0343 ft s : 0 . 0414
Up invert 13 . 5000 ft down invert : 13 . 2500 ft
Collection Area : 4 . 1700 Ac .
Design Flow 3 . 6852 cfs Dsgn Depth: 0 .48 ft
Pipe Capacity 8 . 4737 cfs
' Design Vel 9 . 8632 fps Travel Time : 0 . 01 min
Pipe Full Vel 11 . 0725 fps
i
1
i
1
i
i
1
1
1
2�
6/20/97 10 : 50 : 21 am Concept Engineering page 1
US Rentals - Lind Ave . & SW 34th St .
SBUH Hydrograph Analysis
25-Year Backwater Analysis
REACH SUMMARY
Hydraulic Gradeline for Reach HGL-MN
-FROM- <--TO--> <FLOW> £loos Ent HGL BntLoes ExtL000 OutLet Inlet AppHead BndHead JunHead HeadWtr -cb/mh-
-------- -------- cfs -loos- -Elsv-- --loos- --lose- --Blev- --Blew- --lose- --lose- --loss- --Elev- --Rim--
cb-exot 11 26====----
CB-01 cb-exst 3.18 0.70 11.96 0.05 0.25 12.26 13.01 0.25 0.23 0.00 12.98 17.80
CB-02 CB-01 3.18 1.50 14.48 0.05 0.25 14.78 14.47 0.25 0.08 0.00 14.61 17.00
INL-03 CB-02 3.18 0.04 14.65 0.25 14.90 15.04 0.00 0.00 0.00 15.04 16.00
Network Reach N-MAIN
REACH <-AREA> <-DIA> LENGTH SLOPE < n > DSGN Q % PIPE Ndepth %Depth Vact Vfull C-Area
' ID (Ac) (ft) (ft) ft/ft ------ (cfs) ------ (ft) ------ (fps) (fps)
P-03 4.17 1.00 6.03 0.0414 0.0120 3.18 37.53 0.44 44.22 9.49 11.07
' P-02 4.17 1.00 221.50 0.0065 0.0120 3.18 94.42 0.83 83.46 4.54 4.40
P-01 4.17 1.00 103.50 0.0269 0.0120 3.18 46.62 0.50 50.08 8.08 8.92
PIPE REACH ID No . P-01
From: CB-01 To: cb-exst
Pipe Diameter: 1 . 0000 ft n: 0 . 0120
Pipe Length 103 . 5047 ft s : 0 . 0269
' Up invert 11 . 8000 ft down invert : 9 . 0200 ft
Collection Area : 4 . 1700 Ac .
Design Flow 3 . 1804 cfs Dsgn Depth: 0 . 50 ft
Pipe Capacity 6 . 8227 cfs
Design Vel 8 . 0814 fps Travel Time : 0 . 21 min
Pipe Full Vel 8 . 9152 fps
PIPE REACH ID No. P-02
From: CB-02 To: CB-01
Pipe Diameter: , 1 . 0000 ft n: 0 . 0120
Pipe Length 221 . 5038 ft s : 0 . 0065
Up invert 13 . 2500 ft down invert : 11 . 8000 ft
Collection Area: 4 . 1700 Ac .
Design Flow 3 . 1804 cfs Dsgn Depth: 0 . 83 ft
Pipe Capacity 3 . 3683 cfs
Design Vel 4 . 5415 fps Travel Time : 0 . 81 min
Pipe Full Vel 4 . 4013 fps
2y
6/20/97 10 : 50 : 22 am Concept Engineering page 2
US Rentals - Lind Ave . & SW 34th St .
SBUH Hydrograph Analysis
25-Year Backwater Analysis
REACH SUMMARY
PIPE REACH ID No . P-03
From: INL-03 To: CB-02
Pipe Diameter: 1 . 0000 ft n: 0 . 0120
' Pipe Length 6 . 0343 ft s : 0 . 0414
Up invert 13 . 5000 ft down invert : 13 . 2500 ft
' Collection Area : 4 . 1700 Ac .
Design Flow 3 . 1804 cfs Dsgn Depth: 0 . 44 ft
Pipe Capacity 8 . 4737 cfs
' Design Vet 9 . 4938 fps Travel Time : 0 . 01 min
Pipe Full Vel 11 . 0725 fps
' pgqixnGE AREA MAP
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Fair" '
B-twelve Associates, Inc.
December 5, 1996
Mr. Peter Powell
Powell Development Company
737 Market Street '
Kirkland, Washington 98033
RE: Orillia Lot #8 - Wetland Determination
B-twelve Job#96-174
Dear Peter,
This letter describes our findings in regards to jurisdictional wetlands on your property
known as Lot #8, located on the east side of Lind Avenue, in the City of Renton,
Washington (the "site" see Exhibit A). Specifically, the site is a 4.173 acre irregularly
shaped parcel of land with Lind Avenue bordering the west side of the site, Burlington
Northern rail spurs along the south and east side of the site, and a commercial property
along the north side of the site.
METHODS
On October 15 and November 25, 1996, I inspected the site to determine if any
jurisdictional wetlands exist(ed) on your property. A combination of field indicators
(including vegetation, soils, and hydrology) were used to determine the presence of a
wetland. Soil colors were identified using the 1990 Edited and Revised edition of the
Munsell Soil Color Charts (Kollmorgen Instruments Corp. 1990). The site was
inspected using the methodology described in the Corps of Engineers Wetlands
Delineation Manual (Dept. of the Army, 1987). This is the methodology recognized
by the US Army Corps of Engineers and the City of Renton for wetland eterminations
and delineations at the time of our field work. 4-
EXISTING DOCUMENTATION JAN 2 i 1997
OEVELOpMr--,
Prior to visiting the site, a review of several natural resource inventory rmf iANNINGI.
conducted. Resources reviewed included the King County Soil Survey (Snyder et al.
1973-see Exhibit B), the National Wetlands Inventory Map (see Exhibit C) and the City
of Renton Critical Areas Inventory (see Exhibit D).
1103 West Meeker Street, Suite C • Kent, WA 98032-5751 • (206) 859-0515 • Fax (206) 852-4732
Powell-Lot #81#96-174
B-twelve Associates, Inc.
December 5, 1996
Page 2
According to the Soil Survey for King County Area, Washington (Snyder et al. 1973),
the entire site is mapped as containing Snohomish series (So) soils (see Exhibit B).
Snohomish soils are a poorly drained silt loam formed in alluvium and are considered
hydric soils according to the publication Hydric Soils of the United States (USDA
NTCHS Pub No.1491, 1991). However, the entire site was filled in 1974, burying the
mapped Snohomish series under gravelly fill. Additional fill was placed on the site in
1982/83 by the owner at that time (Burlington Northern Railroad). Soil pits excavated
throughout the site reveal gravelly fill material with various colors and textures.
Review of Terra Associates, Inc. Geotechnical report prepared for the site and dated 2-
9-96, indicates that there is approximately 5 feet of compacted (preloaded) fill material
over the native soils. The Terra report also indicates that the groundwater level on the
site was generally at a depth of 7 feet below existing grades.
Data collection for the King County Soil Survey was conducted between 1966-1969.
The Survey states that the mapping and documentation represents conditions in 1969.
Since the filling took place after 1969, this unit of fill missed being mapped as Urban
soils (Ur) as were other areas filled prior to 1969. Urban soils are not considered
hydric soils. Additionally, a recent interpretation by the US Army Corps of Engineers
in 1995 results in the Corps not regulating wetlands formed in legally placed fill
material in the valley.
According to the NWI map for the site, there are no wetlands or streams on or near the
site (see Exhibit Q.
According to the City of Renton Wetland Inventory, there are two (2) small areas of
wetland located near the west side of this property (see Exhibit D). According to the
inventory sheets, these wetlands are described as Reference No. W-33, and, are
isolated emergent wetlands located on fill. These wetlands are described as vegetated
with bentgrass (Agrostis spp.) and "grasses". It should be noted that this inventory was
comprised using aerial photographs arld a "windshield survey" in 1991. Therefore,
other than looking from the road at the site, a thorough on-site inspection of the areas
designated as wetlands was not conducted for this inventory.
OBSERVATIONS
The site is vegetated with a mix of colonizing grasses and forbs. It appears that the site
is mowed on a regular basis, allowing the low growing bentgrass to remain dominant.
Other species found in abundance on the site include cat's ear (Hypochaeris radicata),
red clover (Trifolium pratense) and English plantain (Plantago lanceolata).
Powell-Lot #81#96-174
B-twelve Associates, Inc.
December 5, 1996
Page 3
Soils on the site consist of a compact, gravelly, sandy fill material >20" in depth.
During our October 15 site visit the entire site was dry with no evidence of wetland
hydrology. During our November 25, 1996 site visit, several areas of ponding were
observed on the compact fill where the recent heavy snow had melted. However, these
observations were taken outside of the growing season and do not appear indicative of
growing season hydrology. Additionally, these areas were dominated by cat's ear, a
non-hydrophytic species.
In conclusion, several areas of facultative wetland vegetation (bentgrass) were observed
on the site. However, as our attached data sheets indicate, the entire site has been
filled and, other than during heavy periods of precipitation outside of the growing
season, we have not observed any water on the site, As a result, we have concluded
that no wetlands are present on the site.
If you have any questions or require additional information, please feel free to contact
me at (206) 859-0515.
Sincerely,
B-twelve Associates, Inc. '.,-Pot Wetle d1�1+
i10 N
Ed Sewall
Senior Wetland Ecologist 00021,2
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B-there Associates,L►c.
®� l=col<�girnl Syslrme DcsiRn fi_ Manngcnicnt
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(206)859-0515 Fax(206)852-4132
Job# . 9G-/ 9 Date: /z--f-96 POWELL DEVELOPMENT CO.
Drawls by: £stS Scale: P LOT#8
Revised: Checked by:_ CITY OF RENTON, WA
EXfUBI'I' I3: Soils Map
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1103 W.Mcckcr si_saitr.C Kent, \VA 98032
(206)859-0515 rax(206)852-4732
Job## : W-t74 ,pate: /2 - -f -94 POWELL DEVELOPMENT CO.
Drawn by:.as Scale: :'-L000- LOTTl8
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I)-t«•elve Associates,Inc.
®® ---- ---ing Date- F.coiogicni Systems Design A N1nnnP,cment
111nI7p
1103 W.Pireker St.,Suite.C Kent,NA 98032
(206)859-0515 Fax(206)852-4732
Job# : %-174 Date: tt - -f-- U POWELL DEVELOPMENT CO.
Drawn lyy: fps Scale. !"-i 000- LOW
Revised: Checked by:____ CITY Or RENT'ON, WA
EXIMI1' D:
CITY or, REN'i'ON CRITiCAL AR'-,Aq INVENTORY
WETLANDS AND STREAM CoRIZID(,-)RS
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Ecol(fRicnl Systems Design fi Mnnagcment
1103 W.kteeker S1..Suiie.C Kent,WA 98032
(206)859 0515 Fax(206)852-4732
Job# /7-1' Date: 12 -4 POWELL DEVELOPMENT CO.
Dra)tm by: ;F'yf Scale: / /000' L07'#8
Re vise d.•____ Checked by:_ A CITY OF RENTON, IVA
WETLAND DETERMINATION DATA FORM
(US A1711y Cotps of Engineers Wetlands Delineation Alantial, January 1987)
B-TIVELVE ASSOCIATES, INC.
Proiect: Pow, lo f n. 8 Job#: 04 /74 Investigator: Ed Sewall Date:
Jurisdiction: State: Sample Point //: UPN/ Wetland:
Atypical areas analysis: ars old /l!
Problem areas analysis:No
VEGETATION
Dominant plant species Stratum Indicator Coverage
1. r4C BU
3. r
4.
5.
6.
7.
8.
9.
10.
it. _
12.
13.
14. _
15.
% of species OBL, FACW and/or FAC: 5V Nydrophytic vegetation criteria met: Yes No(M4 rein`at1
Continents:
SOILS
Mapped Soil Series: SN�1,�..•s On Ilydric Soils List?: No Drainage Class: /
Deplh(0 in) Matrix color Mottle color 'Text e
16 in. Ioya- 313
in.
_in.
Indicators present:_hislosol,_histic epipedon,_sulfidic odor,_aquic moisture re.gime,_reducing conditions,
_gleying,_concretions,_hi h surficial organic content, organic streaking, _mottling
Ilydric soil ct•itet•ia met: Yes Basis: IVa f.1-4 r tA. /r.I._f
Comments: 1-45 F%/c y ?d .r
11YDROLOGY
Inundated: Y/ } Depth of Standing water. Saturated: Y/ Depth to saturated soil:
Indicators present:_inundated,_saturated upper 12",_water enarks,_drift lines,—sediment deposits
drainage patterns,Toxidized rhizos heres,_waler stained leaves p
Weiland hydrology criteria met: Yes tNo_Basis:_ tJ e I .C\-\or S
Comments:
SUMMARY OF CRITERIA
Ifydrophylic vegetation: Y/N Flydric soils: YAWetla�(I hydrology: )
Data point meets the criteria r f a jrn i.alic tinnal n etland?: Yes
COMMENTS-
m. .
WETLAND DETERMINATION DATA FORM
(US ilnnJI Corps of E►►gineets Wetlands Delineation A1an►►al, January 1987)
B-TIVEL ICE ASSOCIATES, INC.
Project: • ��ti<�l L.T 8 Job#: le Investigator: Ed Sewall Date: 25--14
Junsdiction:_ � lz State: a,a Sample Point N: DPII Z- Wetland:
Atypical areas analysis: w e.s
Problem areas analysis: ^'o
VEGETATION
Dominant plant species Stratum lndica(or Coverage %
2. c,
4.
5.
G.
7.
8.
9.
10.
11.
12.
13.
14.
15.
% of species OBL, FACW and/or FAC: SD Nydropkytic vegetation criteria met: Yes N Mareinal )
Comments:
SOILS )
Mapped Soil Series: ar o lrenr3� On llydric Soils List?&_e�)Nii Drainage Class:
Depth(0 in) Matrix olor Mottle colsr ,Texhl e>J
AG in.
in.
in.
Indicators present:_hislosol,. histic epipedon,_sullidic odor,_aduic moisture regime,_reducing conditions,
___gleying,_concretions,_hi h , ficial organic content, organic streaking, _mottling
Nydric soil criteria met: Yes Basis: /-0e-
Comments:— W,;S F. � -- 1, TVs Fc
HYDROLOGY
Inundated:_Y& Depth of Standing water: Sa(urated: Yd) Depth to saturated soil:
Indicators present:_inundated,_saturated upper 12",_water marks,_driR lines,_sediment deposits
drainage pattern hs,`oxidized rhinos res,_water stained leaves
Weiland hydrology crirer-ia met: Yes o ' Basis: e ��. 1V/x _
Comments:
SUPINTARY OF CRITERIA
liydtophytic vege(ation: Y/N Ilydric soils: Y/ _ WgQand hydrology: YK�)
Data point meets the criteria of a jurisdictional metland?: Yes(.
COMMENTS:
:<dldm.X 7.dm
1VETLAND DE'TIERMINATION DATA FORM
(US Anny Cotps of Engineers Wetlands Delineation Manual, Jammy 1957)
B-TNrLVE, ASSUCIAT rS, INC.
Proiect: • Y o, ,�.�( G I 8 Job#:f -/74 Investigator: Ed Se►vall Date: // z5-' 7G
Jurisdiction: izs.l:• ' State: �4 Sample Point#: DPN 3 Wetland:
Atypical areas analysis: o Id { lJJ
Problem areas analysis: /VO
VEGETATION
Dominant plant species Straturn Indicator Coverage %
2. i�, rya i��.. /./. h/
4.
5.
6.
7.
8.
9.
l0.
11.
12.
13. --
14. --
15.
% of species OBL, FACW an /or FAC: Hydrophytic vegetation criteria met Y No Marginal
Comments:_
solLs
Mapped Soil Series: On Ilydric Soils List?: (Ya No Drainage Class:
Depth(0 in) Matrix color Mottle color 'Textu gg /
in.
in.
Indicators presenl:_histosol,_histic epipedon,,_sullidic odor,_aquic moisture regime,—reducing conditions,
gleying,_concret ions,_hr h surticial organic content,_organic streaking, _mottling
IJyd►icsoil cri►erianret: Yes Basis:
Comments: o/d { % /�c�r ,li r r g p r•
IIYDR0LU Y
Inundated: Y Depth of Standing water: Saturated: Y/ Depth to saturated soil:
Indicators present:_inundated,_saturited upper 12",_water marks,_drift lines,_sediment deposits
drainage patlerns,_oxidized rhizospheres,�water stained leaves
N
Weiland hydrology criteria met: Yes _Basis:
Comments:
SUAIAIARY OF CRITERIA Hydrophytic vegetation:(S51N llyd is soils: Woltilld hydrology: Ya
Data point meets the criteria of a jrn isdictional ivetland?: Ye. N_
COMMENTS:
rr �K 1.d,K
WETLAND DETERMINATION DATA F0101
(US A/711y Corps of Engineers Wetlands Delineation Rlanrral, January 1987)
B-TIVELVE ASSOCIATES, INC.
Project:_•I'o. . �-�� Job#: %-0 Investigator: Ed Sewall Date:
Jurisdiction: State: �/i Sample Point #: DP# 4 Wetland:
Atypical areas analysis: Fa 4..,) --
Problem areas analysis:
VEGETATION
Dominant plant species Stratum Indicator Coverage %
2.
3. ,
4.
5.
6.
7.
8.
9.
10.
I1.
12.
13.
14.
15.
% of species OBL, FACW and/or FAC: Hydrophytic vegetation criteria met: Yes No d6larginal•)
Continents: �---
SOILS l
Mapped Soil Series: ^''��n�_S✓�. On Ilydric Soils List?<J'J No Drainage Class: D
Depth(0 in) Matrix color Mottle color r .1,exlyre
/Gin. /OY/� 3l�_. 'r�.rel�
in.
in.
Indicators presenl:_histosol,_histic epipedon,^sullidic odor,^aquic moishire regime,_reducing conditions,
___gleying,_concretions,_hi h surficral organic content,_organic streaking, _mottling
Hydric soil criteria met: Yes b r Basis: 'e> . �1: c, l r
Continents: old 1;l Iry_) �r :,,;�! e�•. ., f� �fl •t a- ..,, tti r T irU
HYUROLO�CY i� 1
Inundated ' �I Depth of Standing water. / Saturated: ION De nth to saturated soil: r
Indicators present:_inundated, saturated tipper 12",—water rnarks,_drift lines,_sediment deposits
drainage patterns,_oxidized thizospheres,_water stained leaves /
Werland hydrology criteria met: Yes No 7 Basis:
Comments: i,,u-
SUMMARY OF CRITERIA
Hydrophytic vegetation: Y(o I lydric soils: Y/ _) W,tlnnd hydrology: Y/N
Darcy point meers the criteria ofa jutisdictionrrl wetlond?: Yes(No_.-)
CORIAIENTS:
M-77.1.11 .
JUN-20-1997 15:37 FROM CONCEPT ENGINEERING, INC TO 2352541 P.01i02
CONCEPT ENGINEERING, INC-
a55 Rainier Bovievara Norm, Suite 200
_ Issaquah. Washington 98027
(206) 392-8065 FAX (206) 392-0108
FAX TRANSMITTAL LETTER
To: Clint Morgan Firm Name: City of Renton
cc: Bart Treece
Fax Number: 235-2541
From: Kirk Smith Fax Number: (206) 392-0108
Date: June 20, 1997 (4:33pm) Job No. 96401
Number of Pages Transmitted: a (Total includes this cover page)
If you do not receive all the pages, call (206) 392-8055.
RE: U.S. Rentals - Response to storm drainage comments
Clint:
Following is a response to your storm drainage comments for the U.S. Rentals project
pertaining to the storm drainage report. The revised plans and report are being
resubmitted this afternoon by Bart Treece.
1 . Additional printouts from the WaterWorks program have been included in the
revised report that indicate the invert elevations used in the backwater analysis.
On the tailwater issue, I spoke with Scott Woodbury who had dealt with this
issue on the Farwest Steel site. He said the city required the conveyance
analysis to use the 2-year flood elevation of Springbrook Creek at the outfa€i of
the 60-inch pipe system as the tailwater for the on-site conveyance analysis.
This elevation is 14.6 on NAVD 88 datum, and 11 .26 on the vertical datum of
the US Rentals site plan. The tailwater in the backwater analysis was adjusted
accordingly and an explanation was added to the introduction.
2. The overflow riser and emergency overflow spillway have been removed
from the combined orifice structure defined in WaterWorks for the purpose of
sizing the detention system. This did not change the design of the detention
system. The downstream pipe was analyzed in pond overflow conditions.
n,wr��era�Kirc,oeo,.rnx
a
TERRA ASSOCIATES, Inc.
Consultants in Geotechnical Engineering, Geology
and
Environmental Earth Sciences
January 23, 1997
FIR CIn_0 EVo yy Project NO.T-3065-1
FP / E.
MAR 1 0 1997
U.S. Rentals
c/o Mr. Bart Treece BUILDING DIVISION
Treece and Company
320- 2nd Avenue South, Suite 200
Kirkland,Washington 98033
Subject: Geotechnical Report Revision
U.S. Rentals
SW 34th Street and Lind Avenue
Renton, Washington
Reference: 1. Geotechnical Report,Warehouse/Office Facility,by Terra Associates, Inc.dated
February 9, 1996
Dear Mr.Treece:
We understand that the subject site will be developed by U.S. Rentals as a new rental facility. The proposed
construction will differ considerably from what we expected and evaluated in the referenced report.
Accordingly, you have asked us to review our recommendations with respect to the planned construction.
A preliminary grading plan for the project by Treece and Company dated January 3, 1997 shows that a
10,600 square foot office/rental building will be situated within the central portion of the site. With existing
site grades at Elev. 16, an approximately two-foot thick fill pad will be required to construct the building to
the proposed finished floor elevation of 18.5 feet. We understand the building will be of metal-frame
construction that will impose relatively light foundation loads. With the planned building, we expect
relatively low floor slab loading of approximately 150 to 200 pounds per square foot(psf).
As we discussed with you, the recommendations in our referenced report pertaining to site preparation and
foundation design would still be applicable for the revised site development. However, because of the
reduced building loads and the type of construction planned, we do not believe it will be necessary to
surcharge the site to the extent or magnitude recommended for the previously planned structure. The
revision to our surcharge recommendations is to reduce the four foot surcharge fill above the finished floor
subgrade elevation to a minimum of six inches. Following fill placement, monitoring for settlements should
be completed as previously recommended in our referenced report.
12525 Willows Road, Suite 101, Kirkland, Washington 98034 9 Phone (206) 821-7777
r'
Mr. Bart Treece
January 23, 1997
We estimate that the 2.5-foot thick fill pad will induce primary settlements of about 2-1/4 inches within the
peat and clayey silt layers underlying the building area. Analysis indicates that these settlements should
occur within about six weeks. The time rate for these expected settlements can be accelerated by placing
additional depth of surcharge fill. For four feet of surcharge fill above the finished subgrade elevation,
analysis indicates that the expected settlements would occur within two to three weeks.
Following successful completion of the preload program, we estimate that post-construction primary
settlements will range from 1/2 to 1 inch. Secondary compression of the peat layer beneath the building will
continue for several years once the primary settlements are complete. We estimate that over a 50 year
period, up to 1-1/2 inches of settlement will occur in addition to the primary settlements. Approximately 75
percent of the secondary settlements will occur within the initial ten years of the life of the structure.
Local variations in building loads and subsurface conditions will introduce a differential component to the
above settlements. Accordingly, you should expect some building movements and cracking of the floor slabs
during the initial years of the life of the structure.
If the risk of building settlement as discussed is not acceptable to you, then we recommend implementing the
surcharge program outlined in the referenced geotechnical report. Other than the modification to the building
surcharge, all other geotechnical recommendations for design and construction remain valid.
We trust the information presented is sufficient to meet your current needs. If you have any questions or
need additional information,please call.
Sincerely yours,
TERRA ASSOCIATES,INC.
Kevin P. Roberts, Pf,
Project Engineer
Theodore J. Sc P.1*4
Principal Engine
KPR/TJS:tmQN`�' �
e MES 6/18J 58
Project No.T-3065-1
Page No. 2
rl ` ........ ...
GEOTECHNICAL REPORT
Warehouse/Office Facility
SW 34th Street and Lind Avenue
Renton, Washington
?k
Project No. T-3065
L
a
.... .
Terra Associates, Inc.
Yak 4.. Y
4
Prepared for:
sp Powell Development Company
( . Kirkland, Washington
I February 9, 1996
L
TERRA ASSOCIATES, Inc.
Consultants in Geotechnical Engineering, Geology
and
Environmental Earth Sciences
r�
February 9, 1996
Project No. T-3065
Mr. Peter Powell
Powell Development Company
737 Market Street
j Kirkland, Washington 98033
Subject: Geotechnical Report
Warehouse/Office Facility
SW 34th Street and Lind Avenue
Renton, Washington
Dear Mr. Powell:
As requested, we have conducted a geotechnical engineering study for the subject project. In general, the site is
underlain by five to six feet of dense granular fill overlying two to four feet of clayey silt, organic silt, and peat.
These compressible soils are underlain by medium dense to dense alluvial sands. To reduce post-construction
settlements to what may be considered to tolerable levels, we recommend that the building area be pre-loaded
j with a surcharge fill. Following successful completion of the surcharge program, the proposed warehouse/office
facility may be constructed using conventional spread footings placed on the existing fill or on new structural
fill, as required. If the estimated post-construction differential settlements of 1/2 inch cannot be tolerated by the
construction, you should plan for deep foundation support or removal of the organic consolidating layer.
2 ;
The attached report describes our exploration and explains our recommendations in greater detail. We trust this
information is sufficient for your present needs. Please call if you have any questions or need additional
information.
Sincerely yours,
TERRA A Cal tsi
c`
Kevin P. Rb6erts, ,
z Project Engineer ``
T eodore J. Sc he per;P-r'
Principal-Engineer._ t_XPRES 6/f
cc: Mr. Bart Treece, Horton Dennis and Associates, Inc.
12525 Willows Road, Suite 101, Kirkland, Washington 98O.34 Phone (206) 821-7777
1
TABLE OF CONTENTS
Page
f 1.0 Project Description 1
2.0 Scope of Work 1
3.0 Site Conditions 2
3.1 Surface 2
_ 3.2 Soils 2
3.3 Groundwater 2
C 3.4 Seismic Hazards 3
4.0 Discussion and Recommendations 3
4.1 General 3
4.2 Site Preparation and Grading 4
4.3 Surcharge and Settlements 5
4.4 Spread Footing Foundations 6
4.5 Excavate and Refill Procedure 7
4.6 Timber Piling 7
4.7 Augercast Piling 8
4.8 Slab-on-grade Floors 8
4.9 Excavations 9
4.10 Utilities 9
4.11 Lateral Earth Pressures 9
4.12 Drainage 10
t. 4.13 Pavements 10
5.0 Additional Services 11
6.0 Limitations 11
Fi ures
y' Vicinity Map Figure 1
Exploration Location Plan Figure 2
Typical Settlement Marker Detail Figure 3
1 Reinforced Soil Wall Section Figure 4
Appendix
Field Exploration and Laboratory Testing Appendix A
i`.1
r�
Geotechnical Report
� Warehouse/Office Facility
SW 34th Street and Lind Avenue
Renton, Washington
i
-� 1.0 PROJECT DESCRIPTION
r j The project will consist of construction of a warehouse/office facility in Renton, Washington. The location of
J the project site is shown on the Vicinity Map, Figure 1. Horton Dennis and Associates, Inc. provided an
r
undated conceptual site plan showing the location of the warehouse facility and associated loading and parking
areas. The site plan shows a 65,400 square foot warehouse building occupying the central portion of the site.
Truck loading areas will be located at the eastern and western sides of the building. Parking areas will lie within
the northern and western sections of the site.
While specific design details are not available to us, we expect the warehouse building will be constructed using
pre-cast concrete tilt-up wall panels or masonry blocks. Grades at the site may be raised up four to six feet
above existing site grades to create a dock-high floor level. We anticipate building loads will be about three
kips per lineal foot along walls, 80 to 100 kips for columns, with floor loads of approximately 200 to 300
pounds per square foot(psf).
The recommendations in the following sections of this report are based on our understanding of the project's
1 design features. We should review final design drawings and specifications to verify that our recommendations
Jhave been properly interpreted and incorporated into project design.
i
2.0 SCOPE OF WORK
r j On January 9, 1996, we drilled two test borings at the site to depths of 28.5 and 29 feet below existing site
grades. We also reviewed and used test boring information from the adjacent Farnvest Steel site. Using the
information obtained from the subsurface exploration, we performed analyses to develop geotechnical
arecommendations for project design and construction. Specifically,this report addresses the following:
• Soil and groundwater conditions
• Site preparation and grading
• Foundation alternatives
n Surcharge and settlements
• Lateral earth pressures
• Slab-on-grade floors
• Utilities
• Pavements
0
Drainage requirements
February 9, 1996
Project No. T-3065
FI
3.0 SITE CONDITIONS
3.1 Surface
The subject site is located at the southeast corner of the intersection of SW 34th Street and Lind Avenue in
Renton, Washington. This location is shown on Figure 1. The site is bounded to the south and north by
undeveloped property and SW 34th Street, respectively. Lind Avenue bounds the site on the west. An open,
undeveloped parcel (Farwest Steel site)bounds the site on the east.
The site and vicinity are flat. An existing railroad spur track enters the northeastern corner of the property and
curves in a southwestward direction to join a track leading west of the site. We noted that the track was raised
slightly above surrounding grades. We observed shallow ditches filled with standing water adjacent to the spur
i
track.
:1
Vegetation at the site consisted of sparse grasses. Standing water was observed over much of the site at the time
of our visit. Stormwater drainage from adjacent roadways is directed to storm drains along curbs and gutters
iJ located along the northern and western margin of the site.
3.2 Soils
The soil conditions at the site generally consist of sand with gravel and silt fill overlying a variably thick layer of
compressible peat, clayey silt, or organic silt. The compressible soils were underlain by generally competent
sand and silty sand deposits.
Each boring showed fill soil comprised of sand with gravel and silt to a depth of about five feet. This material
was generally medium dense to dense, indicating it was compacted. The compressible native soils under the fill
consisted mostly of dark brown silty peat, gray organic silt, or gray to brown clayey silt. These soils occur at
1 five feet below existing grades and were between two and four feet thick. Interbeds of black to brown sand that
was fine to coarse-grained and loose to medium dense was found underlying the compressible layers. Borings
B-1'and B-2 were terminated within very dense horizons of the black sand.
The Geologic Map of the Renton Quadrangle, King County, TVashington by D.R. Mullineaux (1965) shows that
the soils are mapped as peat (Qlp). The peat seen in Boring B-I correlates with the published description of this
soil unit. Figures A-2 through A-4 in Appendix A present more detailed descriptions of the subsurface
conditions encountered in the test borings. The approximate test boring locations are shown on Figure 2.
3.3 Groundwater
We encountered groundwater in each of the test borings. Groundwater levels observed are recorded on the
Boring Logs. Water encountered near the ground surface appeared to consist of a perched zone of infiltration
from recent heavy rains. In general, the static groundwater table was found at a depth of about seven feet.
Annual and seasonal fluctuations in the depth of the groundwater table should be expected.
Page No. 2
1
February 9, 1996
Project No. T-3065
.1
3.4 Seismic Hazards
The Puget Sound area falls within Seismic Zone 3 as classified by the Uniform Building Code (UBC). Based on
the soil conditions encountered and the local geology, Table 16-J of the 1994 UBC indicates a site coefficient of
1.5 should be used in design of the structure.
We reviewed the results of our field and laboratory testing and assessed the potential for liquefaction of the
E� site's soils during an earthquake. Liquefaction is a phenomenon where there is a reduction or complete loss of
t J soil strength due to an increase in pore water pressure induced by vibrations from a seismic event. Based on the
information obtained and considering the additional confining stresses from the building and fill weight, it is our
opinion that the risk of liquefaction-related impacts to the structure are minimal.
4.0 DISCUSSION AND RECOMMENDATIONS
i ! 4.1 General
Based on our study, in our opinion, there are no geotechnical constraints that would preclude construction of the
proposed facility. The primary geotechnical concern for construction at this site is the two to four foot-thick
layer of clayey silt, organic silt, and silty peat at depths of five to nine feet below existing site grades.
Consolidation of these soils will occur when subjected to loads comparable to those expected from construction
of the warehouse/office building.
A fill surcharge program implemented prior to construction will consolidate the compressible soil layers and
11 induce most of the primary settlements under loads expected from the project. Once the primary settlements are
complete, lesser amounts of secondary settlement will continue throughout the life of the structure. These
secondary settlements are in addition to settlements that will occur from placement of the building's foundation.
Analysis indicates that over a 50 year span, one inch of total secondary settlement and 1/2 inch differential
settlement are expected. If the settlements cannot be tolerated by the facility, other foundation alternatives will
need to be considered. These alternatives can consist of:
• Overexcavation and removal of the organic soils and replacement with a structural engineered fill for
foundation support
• Piling support using either timber or augercast piling systems
The foundation option chosen for design of the facility will depend on how much risk of damage to the structure
a from differential settlement is acceptable to the owner. The following sections provide detailed
recommendations regarding the above issues and other geotechnical design considerations. These
recommendations should be incorporated into the final design drawings and construction specifications.
Page No. 3
L3
February 9, 1996
Project No. T-3065
4.2 Site Preparation and Grading
Following clearing, the fill surface should be proofrolled with heavy construction equipment prior to placement
of additional fill. Soft yielding areas should be overexcavated to firm bearing soil and replaced with structural
fill. Where excavations to achieve firm conditions are excessive, use of a geotextile fabric such as Mirafi 500X
in conjunction with limited overexcavation and replacement with a structural fill can be considered. Typically,
t
18 inches of clean granular structural fill over the fabric will achieve a stable subgrade.
Our laboratory test results show that the existing fill was above its optimum moisture content at the time of our
investigation, and that some of the fill contains up to 12 percent fines. These conditions may be difficult to
compact if the moisture conditions cannot be carefully controlled. Extreme care should be taken to ensure that
exposed surfaces of the on-site fill do not become disturbed due to weather and construction traffic. Moreover,
> I the ability to use these soils as structural fill will depend on their moisture content and the prevailing weather
conditions at the time of construction. It will be difficult to achieve proper compaction of these soils when their
moisture content is above optimum. When the moisture is excessive, the soil can be dried by aeration to a
moisture content which will allow for proper compaction.
We recommend that the structural fill required to achieve site grades consist of inorganic granular soil meeting
the following grading requirements:
c Maximum Aggregate Size 6 inches
i
Minimum Retained on the No. 4 Sieve 25 percent
JMaximum Passing the No. 200 Sieve 25 percent
(Based on the Minus 3/4-inch Fraction) (see following narrative)
If fill placement takes place during wet weather or if the moisture conditions of the fill material cannot be
controlled, consideration should be given to importing fill soil that conforms with the above gradation, but with
the maximum passing the No. 200 sieve reduced to five percent.
i Structural fill materials should be placed in uniform loose layers not exceeding 12 inches and compacted to a
�U) minimum of 95 percent of the soil's maximum density, as determined by ASTM Test Designation D-698
(Standard Proctor). The moisture content of the soil at the time of compaction should be within about two
percent of its optimum, as determined by this same ASTM method.
Prior to constructing foundations and floor slabs, we recommend probing or proofrolling the subgrade to
determine if any isolated soft and yielding areas are present. As discussed above, soft or yielding areas should
be overexcavated and filled to grade with structural fill or crushed rock.
Page No. 4
• February 9, 1996
Project No. T-3065
l
4.3 Surcharee and Settlements
For spread footing foundation support and slab-on-grade construction, we recommend placing a surcharge fill
f over the building area. The surcharge program is necessary to limit building settlements to what may be
considered tolerable levels. Our surcharge and settlement analysis is based on an assumed existing ground
surface elevation qf�f21feet. In addition, our analysis is based on a finished floor(top-of-slab)elevation of about
( ans
feet and the ant?eipated floor loads discussed above. We should review the final foundation and grading
in order to better assess expected settlements.
Primary Consolidation
The site grades should be raised using structural fill as outlined in the Site Preparation and Grading section.
Once grade is achieved, an additional four feet of fill should be placed as a surcharge. This surcharge fill does
not need to meet any special requirements other than having a minimum in-place unit weight of 125 pounds per
cubic foot (pcf). However, it may be advisable to use a good quality fill which could be used to raise grades in
other portions of the site, such as parking and driveway areas, if necessary.
We do not believe it is necessary to place a surcharge of fill within the parking and access easement areas.
However, the structural fill required in the pavement areas should be placed as soon as possible to allow enough
time for consolidation of the compressible layers and to reduce potential settlement impacts to pavement and
utilities.
The estimated total primary settlements under the recommended surcharge range from six to eight inches across
the building area. These settlements are expected to occur eight to ten weeks following full application of the
1 surcharge loading. The actual period for completion and magnitude of the primary settlements will be governed
by variations in subsurface conditions at the site. The rate of consolidation can be accelerated by placing an
additional thickness of fill surcharge. We estimate that placing an additional three feet of surcharge will reduce
the surcharge time by about 30 percent.
To verify the amount of settlement and the rate of movement, the surcharge program should be monitored by
installing settlement markers. A typical settlement marker installation is shown on Figure 3. The settlement
Q markers should be installed on the existing grade prior to placing any building or surcharge fills. Once installed,
elevations of both the fill height and marker should be recorded daily by a registered land surveyor until the full
height of the surcharge is in place. Once fully surcharged, readings should continue weekly until the anticipated
settlements have occurred.
It is critical that the grading contractor recognize the importance of the settlement marker installations. All
Q efforts must be made to protect the markers from damage during fill placement. It is difficult, if not impossible,
to evaluate the progress of the surcharge program if the markers are damaged or destroyed by construction
equipment. As a result, it may be necessary to install new markers and to extend the surcharging time to ensure
that settlements have ceased and that building construction can begin.
Page No.5
February 9, 1996
Project No. T-3065
sl
We recommend that the surcharge pad extend a minimum of five feet beyond the building perimeter and then
slope down at an inclination of 1:1 (Horizontal:Vertical). It appears that sections of the southeastern building
perimeter may be located close to the railroad spur that curves along the southern property line. If sufficient
area is not available to slope the surcharge, the surcharge may be supported at a near vertical inclination
(minimum 1:12) using a reinforced soil wall. Figure 4 shows a typical reinforced soil wall section.
t
Post-construction Settlements
Primary consolidation of compressible soils at the site will be achieved upon completion of the surcharge
program. Secondary consolidation will continue at the site throughout the life of the structure. During
secondary consolidation, you should expect a maximum post-construction settlement of one inch and differential
settlement of 1/2 inch. These values represent expected settlements over a 50 year period. We anticipate that
most of these settlements will occur within five to ten years after completion of the structure.
Impact ojSurcharge on Adjacent Roadway and Utilities
Depending on its location, the proximity of the surcharge fill pad to the adjacent railroad spur and roadways
may result in settlement of these structures due to soil beneath them being influenced by the pre-load fill pad.
We recommend placing monitoring points on the roadway curbs and pavement as necessary to record possible
movements during surcharge. A similar monitoring program should be implemented for the railroad spur if it
cannot tolerate possible settlement from the pre-load.
Sufficient monitoring points should be established since some of these points will likely be disturbed by traffic.
In addition, we suggest making a photographic survey of the curbs and pavement before placing the surcharge to
determine if any movement occurs during surcharging.
Similarly, if the pre-load fill pad is placed over or near underground utilities, they may experience vertical
` and/or lateral movement as a result of the stress changes in the soil associated with the placement of a pre-load
fill pad. Utility organizations should be prepared to relocate utilities as required prior to construction of the pre-
load, if necessary. We can better assess the level of risk to adjacent structures and utilities upon review of the
final plans.
4.4 Spread Footing Foundations
Following successful completion of the surcharge program, if the above estimated settlements are considered
tolerable, the building may be supported on conventional spread footing foundations bearing on a minimum of
four feet of structural fill. Existing competent fills may be included in determining the depth of the structural
fill. Perimeter foundations exposed to the weather should be at a minimum depth of 1.5 feet below final exterior
grades.
We recommend designing foundations for a net allowable bearing capacity of 3,000 psf. For short-term loads
such as wind and seismic, a 1/3 increase in this allowable capacity can be used. With the anticipated loads and
bearing stresses, the estimated total settlements are as discussed in the Post-construction Settlements section.
Page No. 6
February 9, 1996
Project No. T-3065
Y
For designing foundations to resist lateral loads, a base friction coefficient of 0.4 can be used. Passive earth
pressures acting on the side of the footing and buried portion of the foundation stem wall can also be considered.
We recommend calculating this lateral resistance using an equivalent fluid weight of 350 pcf. We recommend
not including the upper 12 inches of soil in this computation because they can be affected by weather or
disturbed by future grading activity. This value assumes the foundation will be constructed neat against
competent fill soil or backfilled with structural fill as described in the Site Preparation and Grading section. The
recommended lateral resistance value includes a safety factor of 1.5.
4.5 Excavate and Refill Procedure
6
For this procedure, the consolidating soil layer will be excavated and removed from below the foundations, with
grades then restored to the desired construction elevation using structural fill. Based on the information
l obtained, excavations of nine to ten feet below existing surface grades will be necessary. The excavation will
also need to be oversized to allow for placing structural fill a distance laterally from the edge of the foundation
jequal to 1/2 the depth of the fill below the foundation.
Once removed, grades can be restored using a structural fill placed and compacted in accordance with the
J recommendations in the Site Preparation and Grading section. The excavation to remove the clayey silt, organic
J silt, or peat layers will expose loose to medium dense silty sand and sand in a water-bearing condition.
Therefore, it will probably be necessary to place an initial 12 to 18 inch layer of quarry rock or railroad ballast
in order to establish a firm base on which to place the remaining portion of the structural fill. For this method of
obtaining support, spread footing foundations can be designed as discussed in the preceding section. Foundation
r settlements should be negligible, with less than 1/2 inch total settlement anticipated. This settlement will be
immediate, occurring as building loads are applied.
t..
4.6 Timber Pilino
Transferring structural loading below the consolidating layers with the use of timber piling can be considered.
�E Jj We estimate that timber piling with a minimum tip diameter of eight inches will achieve an allowable axial load
of 25 tons when driven into the medium dense, black to brown-gray sand at a minimum tip elevation of 20 feet
below existing surface grades. This allowable axial load takes into account potential negative loading caused by
downdrag on the pile due to consolidation of the organic layer under building fill and floor slab loading.
Full axial capacity can be used provided the piles are spaced at a minimum of three pile diameters. Closer
spacing in pile groups will require a reduction in the single pile capacity. This reduction will depend on the
number of piles in the pile group and the spacing used. For resistance to lateral loading, a lateral pile capacity of
Qsix tons can be used. Estimated pile settlements are 1/2 inch and less. Elastic shortening of the pile is not
included in the above value.
Page No. 7
O'
February 9, 1996
Project No. T-3065
:1
To successfully install timber piling at the site, it may be necessary to predrill the upper five to six feet of
existing fill soils. The pile driving hammer used to install the piles should have sufficient energy to drive the
piling to the estimated tip elevation without damaging the pile. For this purpose,we recommend the pile driving
equipment have a minimum rated energy of 15,000 foot-pounds with an efficiency factor of at least 70 percent.
We also recommend that prior to ordering and installing production piles, a minimum of three test piles be
driven at the site to verify anticipated tip elevations and establish driving criteria for use in evaluating
i production pile capacities. The test piles should be driven with the same equipment that will be used in the
production pile installation.
4.7 Augercast Piling
Augercast piling can be considered as an alternative to timber piling in transferring foundation loading below
the peat and gray-brown clayey silt layers. For 16-inch diameter pilings with a tip elevation of 20 feet below
existing surface grades, an allowable axial load of 30 tons is available for design. This loading takes into
E1 account the potential negative loading effects due to downdrag. Similar effects on the reduction of axial pile
capacity due to close spacing apply to augercast piles. For resistance to lateral loads, an allowable lateral pile
capacity of four tons is available. The estimated pile settlement is 1/2 inch and less. Elastic shortening of the
pile is not included in this value.
} Augercast piles are formed by the pressure injection of grout through a hollow stem auger which is slowly
retracted from the ground after advancement to the recommended tip elevation. The grout pressure used will
compress the soils within the immediate vicinity of the pile, thereby increasing to some extent the pile diameter
and the amount of grout required to construct the pile. For planning purposes, we suggest considering a 30
percent increase in the amount of grout necessary to form the pile.
t
To construct augercast piling, a higher than normal reliance on quality workmanship is required for successful
installations. It is extremely important that the grout pressure be consistent and uniform during the installation
1 and that retraction of the auger occurs at a slow uniform pace beneath a sufficient head of grout in the pile
_J column. The contractor should have adequate means for verifying grout pressure and estimating the volume of
grout used in construction of the piles. Because of the compression effects and the possible influence on
adjacent pile construction, the installation sequence should be based on a minimum pile spacing of five pile
diameters. Once the grout column has achieved its initial 24 hour set, pile construction between these spacings
can be completed.
4.8 Slab-on-trade Floors
With site preparation completed as described in the Site Preparation and Grading section, new structural fill soils
should be suitable for supporting slab-on-grade construction. Immediately below the floor slabs, we recommend
making an allowance for placing a six-inch layer of clean free-draining sand or gravel which has less than five
percent passing the No. 200 sieve. This capillary break will guard against wetting of the floor slab due to the
F underlying soil conditions.
Page No. 8
z
February 9, 1996
Project No. T-3065
P
IL
Where moisture via vapor transmission is not desired, a polyethylene vapor barrier should also be installed. We
suggest that this vapor barrier be placed on an initial four inch layer of the capillary break material and then
covered with the final two inches to help protect it during construction and to aid in uniform curing of the
f concrete floor slab. For slab thickness design, with respect to floor deflection due to traffic and point loadings, a
1 subgrade modulus of 300 pounds per cubic inch (pci)can be used.
Estimated floor slab settlements of less than 3/4 inch are expected due to post-primary consolidation. This
movement assumes that settlements due to required building fills would be allowed to occur prior to floor slab
construction.
4.9 Excavations
Excavations will need to be completed in accordance with local, state, or federal regulations. In accordance
with the Occupational Safety and Health Administration (OSHA), inorganic soils encountered at the site are
classified as Group C soils. Accordingly, excavations made within the native soils or fill at the site greater than
four feet in depth but not exceeding 20 feet in depth will need to be laid back with side slope gradients of 1.5:1.
r As another option, a trench shoring box to support excavations throughout the lower depth may be used in
conjunction with sloping of the upper portion of the excavation as outlined above. Because of groundwater
seepage within the upper fills, temporary dewatering of the excavation may need to be considered where
excavation depths exceed two to three feet below existing site grade. Excavations below depths of seven feet
will likely encounter the groundwater table and require more intensive dewatering efforts to maintain trench
stability.
4.10 Utilities
We recommend that all site utilities be bedded and backfilled in accordance with applicable American Public
Works Association (APWA) specifications. For site utilities within City rights-of-way, bedding and backfill
should be completed in accordance with City of Renton specifications. At a minimum, utility trench backfill
should be placed and compacted in accordance with recommendations presented in the Site Preparation and
Grading section. Where utilities will occur below unimproved areas, the degree of compaction can be reduced
to a minimum of 90 percent of the soil's maximum density as determined by the referenced ASTM standard.
Because of the potential for long-term settlements, utility pipe joints and connections should be flexible,
allowing for up to one inch of differential movement.
4.11 Lateral Earth Pressures
The magnitude of earth pressure development on retaining walls constructed in loading dock areas will partly
depend on the quality of backfill. Where fill is placed behind retaining walls, we recommend placing and
compacting it as structural fill. The fill should be compacted to a minimum of 95 percent of its maximum dry
unit weight as determined by ASTM Test Designation D-698 (Standard Proctor). To guard against the buildup
of hydrostatic pressure, wall drainage must also be installed as discussed in the Drainage section.
,., Page No. 9
r
rl
i ! February 9, 1996
Project No. T-3065
With granular backfill placed and compacted as recommended and drainage properly installed, we recommend
designing restrained walls for an at-rest earth pressure equivalent to a fluid weighing 50 pcf. A value of 35 pcf
may be used where the wall is unrestrained. These values do not include other surcharge loading such as from
fill backslopes or adjacent footings that may act on the wall. If such conditions will exist, the imposed loading
rmust be included in the wall design. Friction at the base of foundations and passive earth pressure will provide
resistance to these lateral loads. Values for these parameters are provided in the Foundations section.
4.12 Drainage
Surface
Final exterior grades should promote free and positive drainage away from the building areas at all times. Water
must not be allowed to pond or collect adjacent to foundations or within the immediate building area. We
recommend providing a gradient of at least three percent for a minimum distance of ten feet from the building
perimeter, except in paved locations. In paved locations, a minimum gradient of one percent should be provided
unless provisions are included for collection and disposal of surface water adjacent to the structure.
Subsurface
In our opinion, perimeter foundation drains will not be necessary if the area immediately adjacent the structure
is paved and positive surface drainage is maintained. If the grade is not positively drained away from the
structure or if it is landscaped,perimeter foundation drains should be installed.
a To guard against hydrostatic pressure development, retaining wall drainage must be installed. We recommend
that wall drainage consist of a minimum 12-inch thick layer of washed rock or pea gravel placed adjacent to the
wall. A four-inch diameter perforated pipe should be placed on a bed of gravel at the base of the wall footing
and gravel drainage column. The pipe should be directed to a suitable outlet.
4.13 Pavements
With subgrade soils prepared as described in the Site Preparation and Grading section, suitable support for
pavement construction should be provided. However, regardless of the compaction results obtained subgrades
must be in a stable non-yielding condition prior to paving. Immediately prior to paving, the area of the subgrade
should be proofrolled with heavy construction equipment to verify this condition.
The required pavement thickness is not only dependent upon the supportin capability of the subgrade soils but
also on the traffic loading conditions which will be applied. For light commercial vehicles and typical passenger
vehicle traffic,the following pavement sections are recommended:
• Two inches of asphalt concrete (AC)over four inches of crushed rock base (CRB)
• Two inches of AC over three inches of asphalt treated base (ATB)
Page No. 10
' 1
February 9, 1996
Project No. T-3065
For heavy truck traffic areas, we recommend the following pavement sections:
• Three inches of AC over six inches of CRB
• Three inches of AC over four inches of ATB
If there is a potential that pavement construction will be delayed until the wet winter months, the subgrade soils
must consist of a clean granular material as described in the Site Preparation and Grading section. In addition,
we strongly suggest that the subgrade be further protected by placing a layer of ATB, on which construction
traffic could access the project without excessively disturbing the subgrade soils. The ATB thickness for this
purpose should be four inches. Repair of failed ATB areas should be anticipated prior to final paving.
However, the overall integrity of the subgrade soils will be considerably less impacted if this protection is
provided.
Because of secondary compression of the clayey silt, organic silt, or peat layers, some degree of post-
construction settlement within the pavement structure should be anticipated. This settlement will probably result
in some longitudinal and transverse cracking of the pavement. Cracks in the pavement should be sealed in a
timely fashion to prevent excessive surface water infiltration into the subgrade soils.
r
5.0 ADDITIONAL SERVICES
Terra Associates, Inc. should review the final design and specifications in order to verify that earthwork and
foundation recommendations have been properly interpreted and incorporated in the project design. We should
also provide geotechnical services during construction in order to observe compliance with the design concepts,
` specifications, and recommendations. This will also allow for design changes if subsurface conditions differ
from those anticipated prior to the start of construction.
i
6.0 LIMITATIONS
We prepared this report in accordance with generally accepted geotechnical engineering practices. This report is
the property of Terra Associates, Inc. and is intended for specific application to the Warehouse/Office Facility
project in Renton, Washington. This report is for the exclusive use of Powell Development Company and their
authorized representatives. No other warranty, expressed or implied, is made.
The analyses and recommendations presented in this report are based upon data obtained from the test borings
a drilled on-site. Variations in soil conditions can occur, the nature and extent of which may not become evident
until construction. If variations appear evident, Terra Associates, Inc. should be requested to reevaluate the
recommendations in this report prior to proceeding with construction.
Page No. 11
�i15r1
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REFERENCE: THE THOMAS GUIDE, KING COUNTY, WASHINGTON, PAGES 655, 656, 685 AND 686, 1995 EDITION.
!J
VICINITY MAP
ROGeotechnicol
TERRA WAREHOUSE/OFFICE FACILITY
ASSOCIATES RENTON, WASHINGTON
Consultants Proj. No.3065 Date 1/96 Figure 1 7:1
w
2U B-6 I - --
PARKINw G c PARKING
CD
L 280
c'M PARKING
z
Ir
PARKING LOADING a
APPROXIMATE SCALE
1 100 0 100 200 feet
B-1 I
wood
BU LDI G B
g N ,400 F I
J i B-2
a . I LEGEND:
270 I i 1� APPROXIMATE BORING LOCATION
so " LOADING 60 APPROXIMATE BORING LOCATION
PARKING PARKING FROM TERRA ASSOCIATES REPORT
I
� T-3064, DATED FEBRUARY, 1996.
PARKING
ti
LIND AVENUE S.W. REFERENCE:
FACSIMILE OF SITE PLAN PROVIDED BY HORTON DENNIS
AND ASSOCIATES, INC., JOB No. UNKNOWN, UNTITLED
t AND UNDATED.
i�
EXPLORATION LOCATION PLAN
TERRA WAREHOUSE/OFFICE BUILDING
R#Geotechnical
ASSOCIATES RENTON, WASHINGTON
Consultants Proj. No.3065 Date 1/96 Figure 2
STEEL ROD
ERE
PROTECTIVE SLEEVE
-77
HEIGHT VARIES
SURCHARGE (SEE NOTES) SURCHARGE
I OR FILL OR FILL
i
NOT TO SCALE
i
NOTES:
: a
1. BASE CONSISTS OF 1/2" THICK, 2'x2' PLYWOOD WITH CENTER DRILLED 5/8" DIAMETER HOLE.
2. BEDDING MATERIAL, IF REQUIRED, SHOULD CONSIST OF CLEAN COARSE SAND.
3. MARKER ROD IS 1/2" DIAMETER STEEL ROD THREADED AT BOTH ENDS.
(� 4. MARKER ROD IS ATTACHED TO BASE BY NUT AND WASHER ON EACH SIDE OF BASE.
�J 5. PROTECTIVE SLEEVE SURROUNDING MARKER ROD SHOULD CONSIST OF 2" DIAMETER
PLASTIC TUBING. SLEEVE IS NOT ATTACHED TO ROD OR BASE.
6. ADDITIONAL SECTIONS OF STEEL ROD CAN BE CONNECTED WITH THREADED COUPLINGS.
7. ADDITIONAL SECTIONS OF PLASTIC PROTECTIVE SLEEVE CAN BE CONNECTED WITH PRESS—FIT
PLASTIC COUPLINGS.
8. STEEL MARKER ROD SHOULD EXTEND AT LEAST 6" ABOVE TOP OF PLASTIC PROTECTIVE SLEEVE.
9. STEEL MARKER ROD SHOULD EXTEND AT LEAST 1' ABOVE TOP OF FILL SURFACE.
TYPICAL SETTLEMENT MARKER DETAIL
TERRA WAREHOUSE/OFFICE FACILITY
ASSOCIATES RENTON, WASHINGTON
@Geotechnical Consultants Proj. No. 3065 Date 1/96 Figure 3
I
r
SLOPE 12:1(V:H) GEOTEXTILE FACING COMPACTED STRUCTURAL FILL
MINIMUM WRAP (typical) 95% MAX. DRY DENSITY t2%
OPTIMUM MOISTURE CONTENT
PER D-698 (STANDARD PROCTOR)
0.8H feet (TYPICAL)
3 feet
(TYPICAL)
H feet � . . . .. :- ;.. .. • • •.: . . • . .. •
18 in. (max.)
._J MIRAFI 5T
GEOGRID
(TYPICAL)
0 NOT TO SCALE
REINFORCED SOIL WALL SECTION
TERRA WAREHOUSE/OFFICE BUILDING
J ASSOCIATES RENTON, WASHINGTON
ROGeotechnicol Consultants Proj. No.3065 Date 1/96 Figure 4
U
2
cl
APPENDIX A
FIELD EXPLORATION AND LABORATORY TESTING
Warehouse/Office Facility
Renton, Washington
On January 9, 1996, we performed our field exploration using a truck-mounted hollow stem auger drill
rig. We explored subsurface soil and groundwater conditions at the site by drilling two hollow stem
P ] auger test borings to a maximum depth of 29 feet below existing grade. An additional test boring was
E_ drilled on the adjacent Farwest Steel site. This log is included in Appendix A as Boring B-6. The test
boring locations are shown on Figure 2. The Boring Logs are presented on Figures A-2 through A-4.
An engineer from our office maintained a log of each test boring as it was drilled, classified the soil
conditions encountered, and obtained representative soil samples. All soil samples were visually
classified in accordance with the Unified Soil Classification System shown on Figure A-1.
Representative soil samples were obtained from the test borings using sampling procedures outlined in
ASTM Test Designation D-1586. The samples were placed in jars or tubes (ring samples) and taken to
our laboratory for further examination and testing. The moisture content of each sample was measured
and is reported on the Boring Logs. Plasticity characteristics of the fine-grained soils were determined
by conducting Atterberg limit tests. Grain size analyses were performed on three of the samples. The
results of the grain size analyses are presented as Figures A-5 and A-6.
�J
0
Project No. T-3065
S�
MAJOR DIVISIONS LETTER GRAPH TYPICAL DESCRIPTION
SYMBOL SYMBOL
GRAVELS Clean GW Q: O.•G Well-graded gravels, gravel-sand mixtures, little
a)
Gravels •.Q•q• or no fines.
� uD (less than •• • • •• Poorly-graded gravels, gravel-sand mixtures, little
J c� a; More than GP • • • • ••
N 5% fines) • • • • • or no fines.
50% of coarse
fraction is GM Silty gravels, gravel-sand-silt mixtures, non-
O a) m larger than No. Gravels plastic fines.
Z0 4 sieve. with fines GC Clayey gravels, gravel-sand-clay mixtures, plastic
z oo F./• � fines.
SANDS Clean Well-graded sands, gravelly sands, little or
O 'n Sands SW no fines.
L.l w o 0
o z (less than {,::i:< ;: ;$;
More than :;:, Poorly graded sands or gravelly sands, little
5% fines) SP " „ .
t 50% of coarse ' "
Q !1--)
o �'.:{'3;� !3,'E%ss or no fines.
O � fraction is
I U o smaller than SM Silty sands, sand-silt mixtures, non-plastic fines.
2 No. 4 sieve. Sands
with fines SCmom
Clayey sands, sand-clay mixtures, plastic fines.
N SILTS AND CLAYS ML Inorganic silts and very fine sands, rock flour, silty or clayey fine sands or clayey sifts with slight plasticity.
J �
N
Inorganic clays of low to medium plasticity, gravelly
N Liquid limit is less than 50% CL clays, sandy clays, silty clays, lean clays.
E
-� z *0 0L Organic silts and organic clays of low plasticity.
LO
< C Z SILTS AND CLAYS M H Inorganic silts, micaceous or diatomaceous fine
O sandy or silty soils, elastic.
co
W
z
i 08 Liquid limit is greater than 50% CH Inorganic clays of high plasticity, fat clays.
�
E O H Organic clays of medium to high plasticity,
N organic silts.
HIGHLY ORGANIC SOILS PT Peat and other highly organic soils.
DEFINITION OF TERMS AND SYMBOLS
Standard Penetration T 2" OUTSIDE DIAMETER SPLIT
w Density Resistance in Blows/Foot I SPOON SAMPLER
0-4 2.4" INSIDE DIAMETER RING SAMPLER
Loose
Very loose 410 OR SHELBY TUBE SAMPLER
° Medium dense 10-30 P SAMPLER PUSHED
o Dense 30-50 SAMPLE NOT RECOVERED
< Very dense >50 Q WATER LEVEL (DATE)
WATER OBSERVATION STANDPIPE
Standard Penetration C TORVANE READINGS, tsf
} Consistency Resistance in Blows/Foot q u PENETROMETER READING, tsf
vVery soft 0 2 W MOISTURE, percent of dry weight
a o Soft 2-4 pcf DRY DENSITY, pounds per cubic foot
Medium stiff 4-8 LL LIQUID LIMIT, percent
—� Stiff 8-16 PI PLASTIC INDEX
Very stiff 16-32
E i Hard >32 N STANDARD PENETRATION, blows per foot
flJl SOIL CLASSIFICATION SYSTEM
i TERRA WAREHOUSE/OFFICE FACILITY
ASSOCIATES RENTON, WASHINGTON
Geotechnical Consultants
l _Prof. No. T-3065 Date 1/96 Figure A-1
: l
Boring No. B-1
D
Logged by: KPR
Date: 1/9/96
a�
Graph/h a (N) Water
t p / Relative Depth E Blows/ Content
I USCS Soil Description Density (ft ) foot (%)
Gray SAND with gravel and silt
fill cuttings, saturated bearing,
moist at 2 feet
FILL: Gray SAND with silt and few 37 9'7
gravel, medium-grained, moist. Dense
`EAR --------------y PEAT,------------------ ------------------------ T
n Dark brown silt 5
n n 3 59.6 Initially no
n PT nr amorphous, wet. Soft = recovery.
AnAAAAA
- - Re-drove
ML ; Gray to brown clayey SILT, sampler.
CL ii low plasticity, saturated. Medium Stiff T 7 64.4
Brown to gray SAND, fine to
Loose
very fine-grained, saturated. 10 I
10 to 11.5 feet black SAND 21 25.4
with silt, fine-grained, saturated. Medium Dense
I
21 27.1
"ff Black SAND, as above but with
"`•' Medium Dense
»>' trace of silt.
15
� 1 I
SW Black SAND, medium to 51 24.4
coarse-grained, saturated. Very Dense
20......................
.......:::.
•:::r:x::f" ':
�_ _____________________
Water added
Black SAND, medium-grained, Very Dense 73/10" 21.2
_• to hole to
saturated.
I
SP..,: control heave.
25
Black SAND, as above. Very Dense 50+ 30.0
Test boring terminated at 28.5 feet.
Hole plugged with 1 bag of bentonite chips mixed with cuttings.
Ponded surface water.
Groundwater encounterd at 7 feet.
st_(
BORING LOG
TERRA WAREHOUSE/OFFICE FACILITY
ASSOCIATES RENTON, WASHINGTON
Geotechnical Consultants
r Proj. No. T-3065 Date 1/96 Figure A 2
Boring No. B-2
Logged by: KPR
Date: 1/9/96
Graph/ Relative Depth 0 (N) Water
USCS Soil Description Blows/ Content
Density (ft•) a foot N
Brown sand with silt and few
gravel fill cuttings, fine to
j medium-grained, moist. 1
SP SM
FILL: Brown SAND with silt and Medium Dense 12 17.0
few gravel, medium-grained,
saturated.
FILL: As above but gray. 5
Gray organic SILT interbedded with 1 12 60.3 LL=85
I off I inch thick peat layers,low plasticity. Medium Stiff PL=46
' Dark gray silty SAND, very PI=39
SM fine-grained, saturated. Medium Dense 16 37.8
Black SAND, fine-grained, 10
saturated.
26 30.4
Black SAND, very fine to fine- 1
< : :: grained, with occasional 1 inch Medium Dense
++? thick layers of non plastic silt, I— 15
saturated.
Black to brown silty SAND with
interbeds of sandy SILT,very Medium Dense T
fine-grained, saturated. 1 17 36.5
SM �20
ML . .
Black to brown silty SAND with
interbeds of silt(as above). Very Dense
57 24.1
Black SAND, medium-grained,
saturated. 25
»�
SP
J Black SAND, as above but Very Dense 81 35.0
:.;;. fine grained.
Test boring terminated at 29 feet.
a Groundwater encountered at 2 feet.
Hole plugged with 1 bag of bentonite chips mixed with cuttings.
Bentonite slurry added to hole to control heave.
BORING LOG
TERRA WAREHOUSE/OFFICE FACILITY
RENTON, WASHINGTON
�. ASSOCIATES
Geotechnical Consultants
Proj. No. T-3065 Date 1/96 1 Figure A-3
Boring No. B-6
Logged by: KPR
Date: 1/11/96
a)
a
Graph/ Relative Dept E Blow(N) Water
s/ Content
USCS Soil Description Density (ft.) a foot N
V
I Brown-gray, gravelly medium-
grained silty sand FILL cuttings,
saturated.
SM FILL: Gray SAND with gravel, Dense 32 9.3
medium-grained, wet.
FILL: Gray SAND, medium- Loose r— 5
grained, saturated. 3 62.9
Dark brown PEAT, amorphous,-wet.-. Soft
----- - -- -- -- -- ----- -------
Gray sandy SILT,very fine-grained
IMLI Soft
ILT-1 I I I sand, saturated, medium plastic. 3 58.2 Unit wt=94.3 pcf
Gray silty SAND, very fine to Loose Bentonite slurry
—
fine-grained, saturated. 10 added to hole
to control heave
.1 1-Iffisv-i. �!11 rT... I Dark gray silty SAND, very fine
to fine-grained, saturated, grades Medium Dense
to black sand in sampler tip. 19 28.7
..........
.. ................
. .........
. ................
.. ......
Black SAND, fine to coarse..... .....
..... .....
Dense
SW *. grained, saturated.
...........
. ...........
.... 33 21.5
....................
I..,......%........'.4.,...'... - i
....................
.......... I............................
—20
- ----------------------------------------- ------------------------
Black SAND, medium to coarse- Very Dense
............... ....................
grained.
64 20.5
—25
Black SAND, as above. Very Dense 75 26.5
Page 1 of 2
BORING LOG
TERRA FARWEST STEEL
ASSOCIATES RENTON, WASHINGTON
Geotechnical Consultants Proi. No. T-3064 � Date 1/96 � Figure A-4
r i Boring No. B-6 (Continued)
Logged by: KPR
Date: 1/11/96
a)
+ Graph/ Relative Depth Q. (N) Water
USCS Soil Description Density foot (�)(ft ) Blows/ Content
�
Black SAND, as above. Very Dense
`;• 3 s>` 54 22.6
.::
35
Dark gray silty SAND with
trace clam shells, fine to
medium-grained, saturated. Loose 7 25.1
SM
40
aDark gray silty SAND, as above. T
58 29.8
Dark gray SAND with silt, trace
SP SMX. clamshells, very fine to fine- Very Dense
grained, saturated. 45
Dark gray silty SAND,with trace Loose
bits of wood,clam shells and to 10 36.9
clay, very fine to fine-grained, Medium Dense
saturated. 50
i
SM
LA
Dark gray silty SAND, as above. Loose 6 32.1
55
Dark gray silty SAND, as above. Medium Dense
28 24.2
Test boring terminated at 59 feet.
Ponded surface water.
Groundwater encountered at 7 feet.
Hole plugged with 2 bags of bentonite chips mixed with cuttings. Page 2 of 2
BORING LOG
TERRA FARWEST STEEL
REN ON, WASHINGTON
ASSOCIATES
Geotechnical Consultants
Proj. No. T-3064 I Date 1/96 1 Figure A 4
SIEVE ANALYSIS HYDROMETER ANALYSIS
SIZE OF OPENING IN INCHES NUMBER OF MESH PER INCH, U.S. STANDARD GRAIN SIZE IN MM
(V
\\\\ \ O O O O S 00 C> PO N CD O O O O O
1D d K) N .-- M N M N d t0 N O O O CO O O O O O O O
.•, 100 0
90 10
oCD
—
f l 80 — — 20
n O_ D n 70 _ 30 m
O fri -z:
> Z
C: 60 40 C7
7 j
M 50 — ---_ _ _ 50
W
-< 40 _ 60 U)
v M _
�. 30 70 M
oi t I _
20 80
� D
cn
z O D 10 90
O O O O O O O O O 00 c0 d- M N 00 f0 d r7 N 00 c0 d M N 00 c0 d M N
\ O O O CO (0 d r) N O O O O O O O O O O O
CN rM 04 O O O O O
O
> m GRAIN SIZE IN MILLIMETERS
D
COARSE I FINE I COARSE I MEDIUM FINE
z m D> COBBLES I GRAVELN FINES
r
�DC/)
z n Boring or De th Moisture
C Key Test
(fP.) USCS Description Content (�) LL PL
a • 8-1 2.5 SP-SM SAND with silt and some gravel
cn
0 B-1 17.5 SP-SW clean SAND
' 1f�flf .:!fir► ,wiwMi
SIEVE ANALYSIS HYDROMETER
SIZE OF OPENING IN INCHES GRAIN SIZE IN MM
:NNINE mom a:CMmm ME WOMEN MINEEN!
'MUM IMEMENEEN
a:����:�aa:�C� ,
MMOM
ME
ENIMINEWEEN
. CCM =CMIN Ommm CWCm4�amMINmIME C�=Saa:C
O� ,� ..NN�� . ■.. Mom.
on IMENEEN
ONNION
MOMINE
OWNWEEN
• CCC�CCa:���C������a�C:�::=ate C��
..���■■■■..MENEE
WOMIN WE
Moisture
Description
SAND with silt
• sandy
JUN-20-1997 15:37 FROM CONCEPT ENGINEERING, INC TO 2352541 P.02i02
3. The weir height is 0.25 feet and has been adjusted in the report.
4. The use of a 100-year analysis rather than a factor of safety of 1 .3 is
discussed on page 2 of the report under core requirement #3. The provided
detention volume is 1 1 ,738 cubic fleet, which is greater than the 10,201 cubic
feet that would have been provided if a 30% factor of safety had been added
to the 10-year volume.
5. A narrative addressing core and applicable special requirements has been
added to page 2.
6. The impervious area of the site is 163,425 square feet.
Please telephone me if you have any questions.
cc: Bart Treece 822-8758
Ho,NV4ERSSKIW f e9 01.F^X 2