HomeMy WebLinkAboutSWP272341(1) IX-
GEOTECHNICAL REPORT
Renton Chevron
South Grady Way and Talbot Road South
Renton, Washington
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Project No. T-3310
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4 Terra Associates, Inc.
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Prepared for:
Santa Property Development
Bellevue, Washington
XXX
October 19, 1996
SEP 18 1997
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to 4 TERRA ASSOCIATES, Inc.
~" r' Consultants iri Geotechnical Engineering, Geology
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Environmental Earth Sciences
October 19, 1996
Project No. T-3310
Mr. Mick Santa
Santa Property Development
4509 - 116th Avenue SE
Bellevue, Washington 98006
Subject: Geotechnical Report
Renton Chevron
South Grady Way and Talbot Road South
Renton, Washington
Dear Mr. Santa:
As requested, we have conducted a geotechnical engineering study for the subject project. The attached report
presents our findings and recommendations for the geotechnical aspects of project design and construction.
Our field exploration indicates the site is generally underlain by compressible alluvial sediments with medium
dense to very dense silty sand and silty gravel present approximately 20 feet below existing grades. We
observed groundwater at depths ranging from approximately four feet in the western portion of the site to ten
feet in the eastern portion.
The compressible soils will undergo significant total and differential settlements if subjected to the loads
anticipated for the project. Supporting the structures with an augercast pile foundation that transfers the building
loads through the loose sediments to the underlying bearing stratum will virtually eliminate the potential for
settlements due to load consolidation and, potentially, liquefaction.
Alternatively, the settlements may be pre-induced by placing a surcharge fill pad over the building areas for a
period necessary to effect primary consolidation of the compressible strata. Once primary consolidation is
complete, the structures may be constructed using a standard spread footing foundation. However, some risk of
damage will remain since secondary settlements will continue throughout the life of the structure. Moreover, the
risk for additional settlements due to liquefaction of saturated soils during a seismic event would still be present.
12525 Willows Road, Suite 101, Kirkland, Washington 98034 • Phone (206) 821-7777
Mr. Mick Santa
October 19, 1996
We appreciate the opportunity to be of service during the design phase of this project and look forward to
working with you during the final design and construction phases. We trust the information presented in this
report is sufficient for your current needs. If you have any questions or need additional information,please call.
Sincerely yours,
TERRA ASSOCIATE 1
J9t
John C. Sadle OM ' G>�y •o
Project Engin e, Geo
2 4 i0-K{-Ellp
Theodore J. Schep ALEw
Principal Engineer
JCS/TJS:ts I EXPIRES 6/18/ +
cc: Mr. Hal Grubb, Barghausen Consulting Engineers, Inc.
Project No. T-3310
- Page No. ii
TABLE OF CONTENTS
Page
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 3
3.4 Seismic 3
4.0 Discussion and Recommendations 4
4.1 General 4
4.2 Site Preparation and Grading 5
4.3 Surcharge 6
4.4 UST Excavation 7
4.5 Foundations 7
4.6 Slab-on-grade Floors 8
4.7 Drainage 9
4.8 Pavements 9
4.9 Utilities 10
5.0 Additional Services 10
6.0 Limitations 10
Fieures
Vicinity Map Figure 1
Exploration Location Plan Figure 2
Appendix
Field Exploration and Laboratory Testing Appendix A
(i)
Geotechnical Report
Renton Chevron
South Grady Way and Talbot Road South
Renton, Washington
1.0 PROJECT DESCRIPTION
The project will consist of a service station. Site improvements will include an approximately 2,400 square foot
station building, two separate buildings located to the north and east of the station building, a free-standing pump
island canopy, and three underground storage tanks (USTs). A preliminary Site Grading and Storm Drainage
Plan by Barghausen Consulting Engineers, Inc. shows site grades will be raised by approximately 1.5 to 3.5 feet.
The proposed floor elevation of the station building is Elev. 32.5, which is approximately 4.5 feet above the
existing ground surface.
At this time, we have not been provided with building plans or structural loads. We expect building construction
to consist of masonry block or metal framing with brick exterior finish. Floor slabs will be constructed at grade.
Based on our experience with similar projects, we expect that perimeter load-bearing walls will carry one to two
kips per linear foot. Individual interior columns may carry loads of 30 kips.
The recommendations contained in the following sections of this report are based on our understanding of the
above design features. If actual features vary or changes are made, we should review them in order to modify our
recommendations as required. We should review final design drawings and specifications to verify that our
recommendations have been properly interpreted and incorporated into project design.
2.0 SCOPE OF WORK
On August 22 and September 27, 1996, we performed our field exploration at the site using a rubber-tire backhoe
and a truck-mounted drill rig, respectively. Using the information obtained from the subsurface exploration, we
performed analyses to develop geotechnical recommendations for project design and construction. Specifically,
this report addresses the following:
• Soil and groundwater conditions
• Recommendations for import fill material
• Site preparation and grading
• Foundation suppoYt alternatives
October 19, 1996
Project No. T-3310
• Slab-on-grade support
• Excavations
• Utilities
• Pavements
3.0 SITE CONDITIONS
3.1 Surface
The site is located north and adjacent the intersection of South Grady Way and Talbot Road South in Renton,
Washington. The location of the site is shown on the Vicinity Map, Figure 1. The site is bounded by South
Grady Way to the south, Talbot Road South to the west, and the right-of-way for South 7th Street to the north.
Property use in the vicinity of the site is commercial and residential.
The site is currently vacant and vegetated with grasses, blackberries, and some large landscaping shrubs.
Topography at the site and in the general vicinity is relatively flat. Existing site improvements include a concrete
slab foundation in the north-central portion of the site, and several power poles. We understand that the slab
foundation was for an electrical substation that formerly occupied the site.
3.2 Soils
The soils encountered during our subsurface investigations generally consisted of 1.5 to 8 feet of uncontrolled fill
overlying very loose to loose fine-grained sands and silts to depths of approximately 20 feet. Below these depths,
the soils generally consisted of medium dense to very dense fine-grained to coarse-grained silty sands and silty
gravels. The native soils are interbedded with thin layers of dark brown fibrous peat at various depths.
The uncontrolled fill generally consisted of dry silty sand and coal mining tailings. However, we observed fill
materials in the western portion of the site that consisted of sand and gravel with several logs up to one foot in
diameter.
We observed caving and sloughing of the test pit sidewalls in Test Pits TP-1 through TP-5. Sloughing of the
sidewalls in Test Pits TP-1 through TP-4 occurred rapidly and inhibited excavation. Minor caving occurred in
Test Pit TP-5 below a depth of five feet.
Detailed descriptions of the subsurface conditions encountered are presented on the Test Pit Logs and Boring
Logs in Appendix A. The approximate locations of the test pits and borings are shown on the Exploration
Location Plan, Figure 2.
Page No. 2
October 19, 1996
Project No. T-3310
The Geologic Map of the Renton Quadrangle, King County, Washington by D.R. Mullineaux (1965) shows that
the soils at the site are mapped as modified land (fill), with native younger alluvial sands and silts mapped nearby.
The soils encountered at the site are consistent with the published description of these soils.
3.3 Groundwater
We observed groundwater seepage in all six of the test pits. Heavy seepage was encountered in Test Pits TP-1
through TP-4 which were excavated in the central portion of the site. The water table at these locations ranged
from 4 to 7.5 feet below the existing ground surface. Groundwater seepage in Test Pits TP-5 and TP-6 was
moderate to heavy below a depth of ten feet. We also observed isolated light groundwater seepage at 6.5 feet in
Test Pit TP-6. We encountered water-bearing soils to the termination depth of 39 feet in each boring.
Fluctuations in the groundwater levels will occur on a seasonal and annual basis. The groundwater table typically
will be at its highest elevation during the wet winter season and shortly thereafter. Given the time of year our
investigation was performed, it is our opinion that the observed groundwater levels are representative of the
seasonal low levels.
3.4 Seismic
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, from Table 16-J of the UBC, a site coefficient of 1.5 should
be used.
Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in
water pressure induced by vibrations. Liquefaction mainly affects geologically recent deposits of fine-grained
sands that are below the groundwater table. Soils of this nature derive their strength from intergranular friction.
The generated water pressure or pore pressure essentially separates the soil grains and eliminates this intergranular
friction,thus eliminating the soil's strength.
Coarser grain deposits of sands and gravels, if not isolated and confined, are normally not affected because their
hydraulic conductivity allows for drainage or dissipation of these excess pore pressures. Silts and clays are
normally not affected because of the cohesive component of their shear strength. The vibration source typically
considered in liquefaction analysis is a seismic event or earthquake. Structural damage due to liquefaction can
occur in one of three forms:
l. Excessive settlements
2. Complete foundation bearing capacity failure
3. Surface rupturing due to lateral spreading
Based on the soil and groundwater conditions we encountered, it is our opinion that there is a high risk for
liquefaction to occur at this site during an earthquake of Richter magnitude 6.5 or greater. Soils to a depth of 20
feet would likely be affected.
Page No. 3
October 19, 1996
Project No. T-3310
4.0 DISCUSSION AND RECOMMENDATIONS
4.1 General
Based on our study, it is our opinion that the proposed project is feasible from a geotechnical engineering
standpoint. Geotechnical considerations that will impact development as planned include the potentially
liquefiable, compressible soils encountered to depths of 20 feet below the existing ground surface and a shallow
groundwater table.
The very loose and compressible soils will not be suitable for support of the proposed structures if unacceptable
total and differential settlements are to be avoided. To mitigate this condition, we have considered the following
two alternatives:
1. Support structures on augercast piles
2. Surcharge the site
A pile foundation will virtually eliminate foundation settlements and potential impacts to the structure from
liquefaction of the loose soils during a seismic event. We expect that pile lengths at the site will be approximately
30 to 35 feet below the existing site grades. Resistance to uplift forces may require longer piles.
Foundations for Alternative 2 may be conventional spread footings. Surcharging the site with additional fill
above that required to establish grade should induce most of the potential primary settlement at the site. However,
lesser amounts of secondary settlement will continue throughout the life of the structure. In addition, there would
be a risk of additional settlements occurring during an earthquake if liquefaction of the underlying loose soils
occurs. If the owner is not willing to accept the risk for secondary post-construction settlements, the building
foundations should be supported on piling.
Excavations in the central and western portions of the site should be expected to encounter significant
groundwater at depths of four to seven feet below the existing site grades. The groundwater elevation in the
vicinity of the proposed USTs is approximately four feet below the existing grade. Dewatering will be required to
facilitate site excavation, excavation sidewall stability, and construction of the USTs. Depending on the time of
year that construction is initiated, groundwater levels may be slightly higher.
It will be necessary to provide measures for uplift resistance of the USTs due to the shallow groundwater. The
buoyant force acting on the USTs could increase significantly if liquefaction occurs during a seismic event.
The following sections provide detailed discussion and 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. 4
October 19, 1996
Project No. T-3310
4.2 Site Preparation and Grading
To prepare the site for construction, all vegetation, debris, organic surface soils, and other unsuitable materials
should be stripped and removed from the areas under construction. To prepare a suitable subgrade surface for
paved areas and placement of the building's structural fill pad, we recommend scarifying and recompacting the
existing shallow surficial fill at the site. Partial overexcavation and.recompaction of existing deeper fills (Test Pit
TP-3 and TP-4) is also recommended. The required extent of overexcavation,both laterally and vertically, will be
best evaluated in the field during construction. For planning purposes, a minimum depth of four feet should be
considered.
In general, the on-site soils contain a significant amount of fines and will be difficult to compact if the moisture
conditions cannot be carefully controlled. Extreme care should be taken to ensure that exposed surfaces of the
surficial soils do not become disturbed due to weather and construction traffic. Reuse of the existing site soils as
structural fill will depend on its moisture content and the prevailing weather conditions at the time of construction.
We recommend that the structural fill required to achieve site grades consist of inorganic relatively free-draining
granular soil meeting the following grading requirements:
Maximum Aggregate Size 6 inches
Minimum Retained on the No. 4 Sieve 25 percent
Maximum Passing the No. 200 Sieve 5 percent
(Based on the Minus 3/4-inch Fraction)
Structural fill materials should be placed in uniform loose layers not exceeding 12 inches and compacted to a
minimum of 95 percent of the soils' 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 placing fill, we recommend probing or proofrolling all exposed surfaces to determine if any isolated soft
and yielding areas are present. A representative of Terra Associates, Inc. should observe all proofrolling
operations. We also recommend field evaluations at the time of construction to verify stable subgrades.
If excessively yielding areas are observed, they should be cut to a firm subgrade and filled to grade with structural
fill. In pavement areas, if the depth of excavation to remove unstable soils is excessive, use of geotextile fabric
such as Mirafi 500X or equivalent in conjunction with structural fill can be considered to limit the depth of
removal. In general, a minimum of 18 inches of a clean granular structural fill over the geotextile fabric should
establish a stable bearing surface.
Page No. 5
October 19, 1996
Project No. T-3310
4.3 Surcharge
As previously discussed, support for building foundations and slabs-on-grade can be provided by surcharging the
building areas. The surcharge program is necessary to limit building settlements to what may be considered
tolerable levels. Our surcharge and settlement analysis is based on a finished floor elevation of 32.5 for the
station building. Grades in the vicinity of the two other structures will be raised approximately two feet.
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 three feet of fill should be placed as a surcharge in the vicinity of the station
building and the other building location. 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 that could be used to raise grades in other portions of the site, such as parking and driveway
areas, if necessary.
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). The estimated total primary settlements under the
recommended surcharge range from three to five inches. These settlements are expected to occur 8 to 12 weeks
following full application of the surcharge loading. The actual period for completion of the primary settlements
will be governed by variations in subsurface conditions at the site.
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 A-10. The settlement
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 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 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 building construction can begin.
Post-construction Settlements
Primary consolidation of compressible soils at the site will be achieved upon completion of the preloading.
During secondary consolidation, you should expect maximum post-construction total settlements of 1 to 1-1/4
inch and differential settlements of 1/2 to 3/4 inch. These values represent expected settlements over 50 years.
However, we anticipate that most of these settlements will occur within one to two years after completion of the
structure.
Page No. 6
October 19, 1996
Project No. T-3310
The surcharge program will not significantly reduce the liquefaction potential of the loose saturated silty sand
layers at the site. Additional total settlements of three to five inches could occur during a moderate earthquake
(magnitude 6.5 or greater). If the owner is not willing to accept the risk for these potential settlements, the
buildings should be supported on pile foundations.
4.4 UST Excavation
Due to the shallow depth to groundwater observed in the vicinity of the USTs, dewatering prior to excavation will
be required. To accomplish this, we recommend using a well point system. For design, the permeability of the
coarse-grained soils encountered in the area of the USTs can be taken as 0.1 centimeters per second(cm/s).
With excavation depths potentially reaching 10 to 12 feet below the ground surface, a single-stage well point
system should be adequate to dewater the excavation. Adequate dewatering of a deeper excavation may require a
multiple-stage well point system. We do not recommend using deep pumping wells for dewatering because they
have the potential to cause settlements across a much broader area than a well point system. The dewatering
contractor should develop details of the dewatering system.
Side slopes for an adequately dewatered excavation should be laid back at a minimum inclination of 1.5:1. The
excavation side slopes should be covered with durable reinforced plastic sheeting that is securely staked in place.
This plastic sheeting will prevent erosion of the slope and will contain any loose slope soils that slough off or are
dislodged from the slope face due to isolated seepage conditions.
The UST's will need to be anchored to resist buoyant forces. To account for potential increases in buoyant forces
during an earthquake, we recommend designing for a groundwater level at the surface plus three feet.
4.5 Foundations
Spread Footing
Following the successful completion of the surcharge program, if the estimated post construction settlements are
considered tolerable, the building may be supported on conventional spread footing foundations bearing on a
minimum of two feet of 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 2,000 pounds per square foot (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 previous section.
Page No. 7
October 19, 1996
Project No. T-3310
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 passive
value includes a safety factor of 1.5.
Augercast Piles
If deep foundation support is selected,we recommend using augercast piling. Augercast piles should be advanced
to achieve a minimum penetration of five feet into bearing stratum consisting of the dense to very dense silty
sands and silty gravels. This will require pile tip elevations of 30 feet below existing site grades. Actual pile
depths and corresponding lengths will vary in the field due to variations in depth to bearing stratum. At this
depth, allowable end-bearing and lateral pile capacities for varying pile diameters are as follows:
Pile Diameter Allowable End-Bearing Capacity
(inches) (tons)
14 20
16 30
18 40
The above allowable capacities are provided with a safety factor of two. These allowable capacities also account
for negative downdrag loading on the pile due to consolidation of the adjacent soils caused by fill loads or
liquefaction. All piles may be designed for the full load-carrying capacities recommended above, provided they
are spaced at least four pile diameters apart. Settlement of piles extending into the medium dense to very dense
soils is expected to be less than 1/4 inch for individual piles.
Additional load-carrying capacity and resistance to uplift forces will be provided by soil friction along the pile
shaft. We recommend using a value of 500 psf over the surface area of the pile for this purpose. The upper 20
feet of soil should not be considered in this design due to the potential for liquefaction during a seismic event.
Liquefaction will also eliminate lateral soil support within the upper 20 feet. With this considered, resistance to
lateral loads should be provided by battered piles.
4.6 Slab-on-grade Floors
If potential post-construction settlements are considered tolerable, then slabs-on-grade may be supported on the
structural fill subgrade prepared as recommended in the Site Preparation and Grading section. Immediately below
the floor slab, we recommend placing a four-inch thick capillary break layer of clean free-draining sand or gravel
that has less than three percent passing the No. 200 sieve. This material will reduce the potential for upward
capillary movement of water through the underlying soil and subsequent wetting of the floor slab.
Page No. 8
October 19, 1996
Project No. T-3310
Where moisture by vapor transmission is undesirable, a durable plastic membrane should be placed on the
capillary break layer. The membrane should be covered with one to two inches of clean, moist sand to guard
against damage during construction and to aid in curing of the concrete.
4.7 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
We recommend installing a continuous drain along the outside lower edge of the perimeter building foundations.
The foundation drains and roof downspouts should be tightlined separately to an approved discharge facility.
Subsurface drains must be laid with a gradient sufficient to promote positive flow to a controlled point of
approved discharge.
4.8 Pavements
Pavements should be constructed on subgrades prepared as described in the Site Preparation and Grading section.
Regardless of the degree of relative compaction achieved, the subgrade must be firm and relatively unyielding
before paving. Proofrolling the subgrade with heavy construction equipment should be completed to verify this
condition.
The pavement design section is dependent upon the supporting capability of the subgrade soils and the traffic
conditions to which it will be subjected. We expect moderate to heavy traffic loading. With a stable subgrade
prepared as recommended, we recommend the following pavement sections:
• Three inches of asphalt concrete (AC) over six inches of crushed rock base (CRB)
• Three inches of AC over four inches of asphalt treated base (ATB)
The paving materials used should conform to the Washington State Department of Transportation (WSDOT)
specifications for Class B asphalt concrete and CRB surfacing.
Long-term pavement performance will depend on surface drainage. A poorly-drained pavement section will be
subject to premature failure as a result of surface water infiltrating into the subgrade soils and reducing their
supporting capability. For optimum performance, we recommend surface drainage gradients of at least two
percent. Some degree of longitudinal and transverse cracking of the pavement surface should be expected over
time. Regular maintenance should be planned to seal cracks when they occur.
Page No. 9
October 19, 1996
Project No. T-3310
4.9 Utilities
Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA) or
City of Renton specifications. At minimum, trench backfill should be placed and compacted as structural fill as
described in the Site Preparation and Grading section. If buildings are pile supported, utility connections to the
structures should be capable of sustaining differential movements of up to three inches.
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 implemented in the project design. We should
also provide geotechnical services during construction 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.
6.0 LIMITATIONS
This report is the property of Terra Associates, Inc. and was prepared in accordance with generally accepted
geotechnical engineering practices. This report is intended for specific application to the Renton Chevron project
and for the exclusive use of Santa Property Development 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 on-site test pits
and borings. Variations in soil and groundwater 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. 10
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{1\\\ -N�M •Lit - ' t tJ,t;y r,•y,y•�Tz..rCL +x' �1."• >ns i a ,,. ,'s' 61• a t'.'f!
l` I,u1.o S��N C _ •y.1.1';,�"�'R.r'StY7 .1/'�Ci r+.,, I• �.�.t.,•p�-- - - ------ • .� s •C �I' !!T'
1
`.� ••'\C� ,�} � k? Tv:�yr- r= • Sl �■. Nl aII •'� .1 r i:_ C •Ne+• :•*a
\f- CAS r-Kf! •t J7r ; t , _ l� a/OrFa �. •` i nw:' :y Wn(k
to PC wwy¢rtt\\]] S - 'y } 1 'y •: t. I t I .ti i i ! {, `\. 'b••
IFso f O.4f 50 lFl 17 50 0 04k CB/y ' t-{,r ! ' �.ti�j
A.- t �bw1+ .•1`tt� J•�/;.. i__ ,r..y■Pr(.. -.� � :_ i� '`" 'e1•.[t Sr..NAE BOx
'f' d' •rA �•t, ,':aY iJf ,i r.`: _ a >.,q tt r� M1 III e, o A37.
'� \sL �\+ t "i' :a ��;I11'l�t•.t v� ' `•x-- — _ � .. d .�' .�1
� ` .?. \l r[ .,+y n;� A �_Q .�lM +�fir,.. o • }A+ o .t � '_... s� i,+
`` + :� •'•,._ -'t A f. I � i� +� _ • 1 Ex¢¢.J-sox
\ • M`, �:1;•\' D , •.4�!Y, �.AC�ZC a � a " e',i
' O _ � •�Lr. i ,sl t..�r4,�;;h'ry - `d L{ o - i f / �P
" ' •l�.• ` r. J.fe ;>Z *�..r ,,1.. 40 80 feet
T � -� {' ;:• {' - ," 'P0J` APPROY,IMATE SCALE
P- 1
Yam. \ ,,`••,,,� I !r� f 5
`Fj .e�` \�' \�r�`; :®. }' r.,, ' �• 40 0
i �� ,•S�'r t f; ?t,, 1 -,.) .�y LEGEND:
3 tie- • r •• "� APPROXIMATE TEST PIT LOCATION
a �. ..1•\. ;. 111 .BVS S70V-. ..ir.
\ i F/
(4 _\ _ i •,C i_'�??, Cz 5Cw1 J-oorCS LL
l R` APPROXIMATE BORING LOCATION
AI PE W.
REFERENCE:
GRADING AND STORM PLAN PREPARED BY
jr
\ � BARGHAUSEN CONSULTING ENGINEERS, INC.,
`;/"'EL JOB No. 5734, SHEET C4 OF 10, DATED
8/12/96_
t rat .
EXPLORATION LOCATION PLAN
`""°' '
TERRA
RoGeotechnical
RENTON CHEVRON
ASSOCIATES
�` RENTON, WASHINGTON
Consultants Proj. No.3310 Date 10/96 Figure 2
APPENDIX A
FIELD EXPLORATION AND LABORATORY TESTING
Renton Chevron
Renton,Washington
On August 22 and September 27, 1996, we performed our field exploration at the site using a rubber-tire
backhoe and a truck-mounted drill rig, respectively. We excavated six test pits to a maximum depth of 14 feet
below existing grade and two borings to a maximum depth of 39 feet. The approximate locations of the test pits
and borings are shown on Figure 2. The Test Pit Logs and Boring Logs are presented on Figures A-2 through
A-6.
An engineering geologist from our firm conducted the field exploration and classified the soil conditions
encountered, maintained a log of each test pit and boring, obtained representative soil samples, and observed
pertinent site features. All soil samples were visually classified in accordance with the Unified Soil
Classification System described on Figure A-1.
Representative soil samples obtained from the test pits and borings were placed in sealed containers and taken to
our laboratory for further examination and testing. The moisture content of each sample was measured and is
reported on the test pit logs. Grain size analyses were performed on six of the soil samples, the results of which
are shown on Figures A-7 through A-9. We determined the Atterberg limits of five samples. The results of this
analysis are shown on the Test Pit Logs and Boring Logs.
Project No. T-3310
MAJOR DIVISIONS LETTER GRAPH TYPICAL DESCRIPTION
SYMBOL SYMBOL
GRAVELS Clean GW O Q; .• Well-graded gravels, gravel-sand mixtures, little
a�
Gravels �.Q•q• •. or no fines.
(less than • • • • .• Poorly-graded ravels
J ai More than o GP • • • • • •
gravels, gravel-sand mixtures, little
— N 5/ fines) or no fines.
O 50% of coarse
fraction is GM ' • Silty gravels, gravel-sand-silt mixtures, non-
e a> > larger than No. Gravels plastic fines.
z4 sieve. with flues GC Clayey gravels, gravel-sand-clay mixtures, plastic
• fines.
Q o 00 ..
0 c� Clean
C'J SANDS Ian Well graded sands, gravelly sands, little or
0
Sands SW no fines.
uwj m Z (less than
More than a Poorly-graded sands or gravelly sands, little
+� c o 5/ fines) SP
50% o or no fines.
aCa
f coarse
O m c fraction is
U o " smaller than SM Silty sands, sand-silt mixtures, non-plastic fines.
No. 4 sieve. Sands
with flues SC Clayey sands, sand-clay mixtures, plastic fines.
SILTS AND CLAYS ML Inorganic silts and very fine sands, rock flour, silty or
(n N clayey fine sands or clayey silts with slight plasticity.
J_
LO
O '� > CL Inorganic clays of low to medium plasticity, gravelly
m W Liquid limit is less than 50% clays, sandy clays, silty clays, lean clays.
E
wp o No 0 L i i i i i i i Organic silts and organic clays of low plasticity.
< m z Inorganic silts, micaceous or diatomaceous fine
O SILTS AND CLAYS MH sandy or silty soils, elastic.
Co
w 1'
z 0 Liquid limit is greater than 50% CH Inorganic clays of high plasticity, fat clays.
L
m 0H Organic clays of medium to high plasticity,
organic silts.
HIGHLY ORGANIC SOILS PT ^ Peat and other highly organic soils.
DEFINITION OF TERMS AND SYMBOLS
J Standard Penetration T 2" OUTSIDE DIAMETER SPLIT
LU Density Resistance in Blows/Foot I SPOON SAMPLER
Very loose 0-4 2.4" INSIDE DIAMETER RING SAMPLER
Loose 4-10 OR SHELBY TUBE SAMPLER
° Medium dense 10-30 P SAMPLER PUSHED
0 Dense 30-50 * SAMPLE NOT RECOVERED
Very dense >50 ZZ WATER LEVEL (DATE)
Ci WATER OBSERVATION STANDPIPE
Standard Penetration C TORVANE READINGS, tsf
r Consistency Resistance in Blows/Foot qu PENETROMETER READING, tsf
vVery soft 0 2 W MOISTURE, percent of dry weight
o Soft 2-4 pcf DRY DENSITY, pounds per cubic foot
J Medium stiff 4-8 LL LIQUID LIMIT, percent
Stiff 8-16 Very stiff 16-32 PI PLASTIC INDEX
Hard >32 N STANDARD PENETRATION, blows per foot
SOIL CLASSIFICATION SYSTEM
TERRA RENTON CHEVRON
• ;' • ASSOCIATES RENTON, WASHINGTON
Geotechnical Consultants
Proj. No. T-3310 Date 10/96 Figure A-1
Test Pit No. TP-1
Logged by: JCS
Approximate Elev. 28.0
Date: 8/22/96
Depth USCS/ W
�ft'� Graph Soil Description %
(4 inches sod and topsoil) 25
FILL: Gray to black silty SAND and coal mine tailings, dry.
CH Mottled gray-brown CLAY, stiff, moist. qu=1.0 tons/ft2 39 LL= 56
PI = 28
Rusty brown SAND with gravel, fine to coarse grained sand,
SP ' 10
5 ?> fine gravel, medium dense,waterbearing.
Gray SAND with gravel, fine grained, sand, fine gravel, medium
SP € dense,waterbearing. 11
Test pit terminated at 8 feet due to sloughing of side walls.
10 Heavy groundwater seepage below 4 feet.
15
Test Pit No. TP-2
Logged by: JCS
Approximate Elev. 27.5
Date: 8/22/96
Depth
(ft ) USCS/ W
Graph Soil Description °�
0 °
ML SM (8 inches sod and topsoil)
Gray-brown SILT to silty SAND fine grained, medium dense moist.
Mottled rusty brown SAND with gravel, fine grained sand, fine 10
SP .>:'•:••`• gravel, medium dense, moist to wet.
Gray SAND with gravel to GRAVEL with sand, fine to medium
grained sand, fine gravel, medium dense,waterbearing.
Test pit terminated at 7 feet due to sloughing of sidewalls.
Heavy groundwater seepage below 4.5 feet.
10
15
TEST PIT LOGS
TERRA RENTON CHEVRON
-' - ASSOCIATES RENTON, WASHINGTON
. . •-
Geotechnical Consultants
Proj. No. T-3310 Date 10/96 Figure A-2
Test Pit No. TP-3
Logged by: JCS
Approximate Elev. 29.0
Date: 8/22/96
(ft.)h USCS/ W
Graph Soil Description /�
o
(4 inches sod and topsoil)
FILL: Gray silty SAND, minor debris (wood and glass).
zi" FILL: Mottled rusy brown SAND, fine grained, medium dense,
SP :: moist to wet, 2.5 foot diameter log at approximatley 3 feet.
z: ;•v
FILL: Gray SAND with gravel to GRAVEL with sand,fine to medium grained
SP GP sand,fine gravel,medium dense,waterbearing,1 foot diameter log at
approximately 6.5 feet.
plasticity,with highly decomposed peat. 82
Gray, elastic SILT,very soft,wet, moderate to high ILL= 53
10 PI 17
MH =
Test pit terminated at 10 feet due to sloughing of side walls.
Heavy groundwater seepage below 6 feet.
15
Test Pit No. TP-4
Logged by: JCS
Approximate Elev. 28.5
Date: 8/22/96
Depth
(ft.) USCS/ W
Graph Soil Description
FILL: Crushed gravel, gray silty SAND, and minor debris.
111 Mottled gray brown sandy SILT, fine grained, medium stiff to
ML stiff, moist to wet. (Possible Fill) qu=1.0 tons/ft2 LL= 46
43 PI =15
5
"`"'`•`•?' Gray SAND, fine grained, medium dense, wet to waterbearing.
30
10 ML Gray clayey SILT, very soft to soft, wet. qu<0.5 tons/ft2
Test pit terminated at 11 feet due to sloughing of sidewalls.
Heavy groundwater seepage below 7.5 feet.
15
TEST PIT LOGS
TERRA RENTON CHEVRON
ASSOCIATES RENTON, WASHINGTON
Geotechnical Consultants Proj. No. T-3310 Date 10/96 FFigure A-3
Test Pit No. TP-5
Logged by: JCS
Approximate Elev. 30
Date: 8/22/96
Depth(ft.) S /Graph Soil Description W
FILL: Gray silty SAND, coal mine tailings, dry.
Gray sandy SILT, fine grained, soft,wet to waterbearing,
[j interbedded with gray fine sand below 13 feet. qu<0.5 tons/ft2
ML
10 41
15 Test pit terminated at approximately 14 feet. Moderate to heavy groundwater
seepage below 10 feet. Minor caving below 5 feet.
Test Pit No. TP-6
Logged by: JCS
Approximate Elev. 30.5
Date: 8/22/96
Depth
(ft.) Graph Soil Description W
0
FILL: Gray silty SAND, coal mine tailings, dry.
Gray sandy SILT, fine grained, soft to medium stiff,with a few
5 wood timbers at various elevations. qu<0.5 tons/ft2
ML
10
Test pit terminated at 11 feet.
Light groundwater seepage at 6.5 feet, moderate below 10 feet.
15
TEST PIT LOGS
TERRA RENTON CHEVRON
PON ASSOCIATES RENTON, WASHINGTON
Geotechnical Consultants proj. No. T-3310 Date 10/96 Figure A-4
Boring No. B-2
Logged by: JCS
Date: 9/27/96 Approximate Elev. 30
a)
Graph/. Relative Depth 0- (N) Water qu Lab
E USCS Soil Description Density (ft-) Blows/ Content tons/ Test
foot ft2
U)
Fill.
6 23 2.75
Gray silty SAND, fine grained,wet. Loose
M
----------------------------------------------- --------------------
5
Gray SILT, low to medium plasticity,
wet, with thin lenses of brown Very Soft I 2 80.4 <0.5
fibrous peat.
Ll — 107
Gray SILT, low to medium plasticity, -
wet,with thin lenses of brown Medium Stiff - 5 37.8 o.5 LL=35
fibrous peat and thin lenses of fine - PI = 9
to medium grained sand — 15
Gray silty SAND, fine grained,
waterbearing. I 2 28.3
SM F Very Loose
20
As above. T
0 283.8
T --D-a rk-b-rown-P EAT,wet-------------------- ----Very-Soft------
25
............... SAND to SAND with Gray silty
........... 58.4 0.5
... 21 silt,
fine grained, waterbearing,
SM interbedded with thin lenses Medium Dense
of dark brown peat. 30
As above. 42 6.3
I Gray silty GRAVEL with sand, fine to
• coarse grained sand,fine gravel, Dense 35
• GM waterbearing.
As above, fine to coarse gravel. Very Dense I 74 6.0 0.5
Boring terminated at 39 feet.
Groundwater encountered at approximately 10 feet during drilling.
BORING LOG
,—,.... ..�477771 TERRA RENTON CHEVRON
..................
ASSOCIATES RENTON, WASHINGTON
Geotechnical Consultants Proj. No. T-3310 � Date 10/96 � Figure A-6
SIEVE ANALYSIS HYDROMETER ANALYSIS
SIZE OF OPENING IN INCHES NUMBER OF MESH PER INCH, U.S. STANDARD I GRAIN SIZE IN MM
\\ \\\\ \ N .ja 01 O O
N cn P. W N N�s ?co N co A a+ O O O O O O O) _F_ C4 IJ 00 01 .y. W N
♦,: 100 0
90 10
CD
O
CD � m 80 20
(n ;U m
c� O D n 70 30 m
0 T m �
60 40 c7
� _ O
N Z
50 50 cn
m
C0
40 60
v m
o. 30 - 70 m
_ _ G-)
z � _
o �
20 80
F7
;:U C-)
m�;U ;;U 10 90
zmDiL
o d Z
Z O L7 0 _ _ 100
Z (�J W N 0 0 O O O 00 Q� W N Co O> W N OOo O O 0 0 O 0 0 O
>= m S S g GRAIN SIZE IN MILLIMETERS m (n � � $
CO � � W N
D
z� D COBBLESDIUMINE FINES
r—
i=z U)
Z C/) Boring or Depth Moisture
Key Test Pit (ft.) USCS DescriptionCD Content N LL PL
• TP-1 4.0 SP poorly—graded SAND with gravel
0 TP-1 7.0 GP poorly—graded GRAVEL with sand
SIEVE ANALYSIS m M.,
OPENINGSIZE OF
► ��_��..f1■._ice ��`�� ...���..■■■._i,�
• ----.._.._- — -Lis
E.----......---
MI.■C__�■■■■.._i,=
. .. t��1.1;�9���CI�<d�Z•�►������I�Il�L!��iW�
Description
poorly—graded SAND with silt
•
•
• silty SAND MEN
SIEVE ANALYSIS HYDROMETER ANALYSIS
SIZE OF OPENING IN INCHES NUMBER OF MESH PER INCH, U.S. STANDARD GRAIN SIZE IN MM
L" O O O O� �a O N O O
N Q1 .A .aA N? � IV OO .A ? O CD
t.
100 0
'-� 90 10
(D 7 IT
s U) m 80 20
(n X m m
O x m ;:a
o n D n 70 30 m
E m
En
o rn z 60 40 c7
Cn D
z
50 50 cam/)
m
40 60 a)
� m �
30 70 m
z —f G-)
o =
—i
w 20 80
0
m 10 90
m
o p Z
CD Z O Cn 0 _ _ LEE11100
(D
C z �f 8 O O CO O O O O O 00 O W N f bo � � C"� N O O O O O O O O O O p
CD >= m O O GRAIN SIZE IN MILLIMETERS W N co 0) � w N O
= IN MEDIUM
Z m D COBBLESFINES
z r-
p z C/)
Z C/) Boring or Depth Moisture
Key Test Pit (ft.) USCS DescriptionCD Content (%) LL PL
a
• B-2 18.5 SM silty SAND
0 B-2 28.5 SM silty SAND
STEEL ROD
PROTECTIVE SLEEVE
:.. HEIGHT VARIES
SURCHARGE (SEE NorEs) :. SURCHARGE :
OR FILL OR FILL
NOT TO SCALE
NOTES:
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.
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
P#Geotechnical
TERRA RENTON CHEVRON
ASSOCIATES RENTON, WASHINGTON
Consultants Proj. No. 3310 Date 10/96 Figure A-10