HomeMy WebLinkAboutSWP272272(2) GEOTECHNICAL ENGINEERING REPORT
Proposed ARCO AM/PM Mini-Market
NWC South Grady Way at Talbot Road
Renton, Washington
ARCO PETROLEUM PRODUCTS COMPANY
MY Of793
E O E
[)ING DIVISION
ENVIRONMENTAL
ASSOCIATES, INC.
2227 112th Avenue North East, Suite 120
Bellevue,Washington 98004
(206)399-6041 (206)455-9025
Fax(206)455-2316
June 29 , 1992 JN 2100
Arco Products Company
7901 168th Avenue N.E. , Suite 107
Redmond, Washington 98052
Attention: Mr. Walt Tubandt, Manager-Site Acquisitions
Subject: GEOTECHNICAL ENGINEERING REPORT
Proposed ARCO AM/PM Mini-Market
NWC South Grady Way at Talbot Road South
Renton, Washington
Gentlemen:
Enclosed is the geotechnical engineering report for the proposed
ARCO AM-PM Mini-Market to be constructed on the northwest corner
of the intersection of South Grady Way and Talbot Road South in
Renton, Washington. The investigation was conducted and the
report prepared in accordance with generally recognized local
engineering practices and our understanding of ARCO needs and
policies. No other warranty, expressed or implied, is made.
The general purposes of our work were to evaluate subsurface soil
and groundwater conditions, to recommend procedures for grading
and drainage, and to develop foundation and; geotechnical
engineering recommendations for the new structures. Our
explorations revealed that the site is generally underlain by two
feet of sandy fill over loose soft alluvial deposits of sand and
silt which extend to at least nineteen feet below existing
grades. Groundwater was noted during drilling at between 7.5 and
12 . 5 feet below the existing ground surface. We recommend that
the new structures be founded on conventional continuous and
spread footings bearing on a minimum of one foot of compacted
granular structural fill or crushed rock (i.e. , 7/8" minus)
placed above a two-foot-thick layer of two to four-inch diameter
quarry spalls. Underground storage tanks should be installed in a
manner which accounts for buoyant forces. The pavement section
should be placed atop a minimum of one foot of compacted granular
structural fill .
lY l
Associate Offices: Oregon/San Francisco Bay Area
PROPOSED MINI-MARKET FACILITY/RENTON
June 29, 1992 Page 2
Although there may very well be subsurface variations between the test borings and conditions
not readily apparent from the surface, we expect the following subsurface interpretation to be
essentially correct except in the location of the backfilled excavations:
The grassy sandy ground surface is covered with two feet of sandy fill soils.
Below the fill soils, our test borings generally revealed loose to soft sandy silty
river-deposited soils the full depth of exploration. There were also layers of
gravel. Some of the layers penetrated during our exploration were moderately
dense. These soft and loose soils are moderately compressible. Groundwater
was noted in all of the borings between 7.5 to 12.5 feet below existing grades.
Conclusions and Recommendations
General
The following general geotechnical conclusions can be drawn from our field and laboratory test
data:
1) The loose and soft silty sandy alluvial (river-deposited) soils are moderately
compressible and will require bridging with an acceptable thickness of properly placed
fill soils. Our analysis indicates that those soils under building areas require bridging
with a minimum of one foot'of compacted granular structural fill placed atop two feet of
quarry spalls to provide the required 2000 pounds per square foot (psf) bearing to the
proposed structures.
2) We recommend over-excavation and replacement of at least the upper two feet of soil
in any backfilled excavations or loose pumping areas. Additional over-excavation and
replacement may be required depending upon site conditions and design requirements.
Replacement fill should be placed and compacted in a manner which meets the
requirements for structural fill. This will provide a dense unyielding surface for the
pavement above these areas. Structural fill should be placed in accordance with the
recommendations in "General Earthwork and Structural Fill".
3) Backfill in any excavations below pavement areas must be compacted to a minimum
of 90 percent of Modified Proctor (ASTM D-1557), except for the upper two feet below
the pavement subgrade, which must be compacted to a minimum of 95 percent of
Modified Proctor.
4) Silt is highly moisture sensitive and difficult to utilize as structural fill when wetter
than the optimum moisture content. If desired, "clean" granular fill soils or crushed rock
may be used as structural fill to hasten the construction process. If earthwork takes place
during inclement weather "clean" fill soils or crushed rock will be required. Soils
samples recovered in our June exploration revealed moisture contents up to twenty
percent over the estimated optimum moisture content.
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PROPOSED MINI-MARKET FACILITY/RENTON
June 29, 1992 Page 3
4) Groundwater was encountered at 7.5 to 12.5 feet below existing grades. We
recommend underground tanks be designed and installed in a manner which accounts for
buoyant forces. Drainage into the tank excavation should be anticipated and could
probably be controlled through the use of sump pumps which discharge to an appropriate
discharge facility.
Foundations
The proposed new structures may be supported on conventional continuous and spread footings
bearing on a minimum of one foot of compacted structural fill or crushed rock built up from a
base of two feet of dense unyielding quarry spalls that have been tapped into place with the end
of a trackhoe bucket. Quarry spalls are defined as two to four-inch-diaineter crushed basalt rock
or other approved equivalent. All foundations should bear at a minimum depth of twelve (12)
inches below the adjacent outside finish grade. A bearing pressure of two thousand (2000)
pounds per square foot (psf)may be assumed for,foundations bearing as described'above.
The bearing pressure may be increased by one-third to accommodate short term wind and
seismic loads. To provide protection against shear failure, we recommend continuous and spread
footings have minimum widths of sixteen(16)inches and twenty-four(24)inches,respectively.
Fill (including quarry spalls) placed under footings should extend out beyond the edges of the
footings a distance at least equal to one-half of the fill depth. For example, if two feet of
structural fill was placed below a sixteen-inch-wide continuous footing, the total minimum width
of the fill (and the excavation) would be forty inches.
We estimate that foundations bearing on two feet of properly compacted structural fill or crushed
rock placed atop two feet of unyielding quarry spalls will settle approximately three-quarters of
an inch both over the building area and differentially between building corners.
Lateral loads such as wind and seismic forces are accommodated by friction between the
foundation elements and the bearing soils and/or by passive earth pressure against the
foundations. However, passive earth pressure is only available if structural fill is used to backfill
against the foundation, or the foundation is poured against the existing soil. A coefficient of 0.40
may be used between the foundation elements and compacted structural fill and/or crushed rock.
The passive resistance of undisturbed native soils and structural fill may be taken to be an
equivalent fluid having the density of three hundred fifty (300)pounds per cubic foot (pef).
Based on our current project understanding, footing drains will probably be required for the
mini-market structure. We should be allowed to review the final plans in order to confirm this
preliminary opinion.
TMO
PROPOSED MINI-MARKET FACILITY/RENTON
June 29, 1992 Page 4
Slabs-on-Grade
Reinforced slab-on-grade floors are anticipated for the new structures. Slabs-on-grade may be
supported on a ininunutn of four inches of free-draining sand or gravel placed above one foot of
compacted structural fill. The quarry spall base is not required below the floor slab, although the
placement of the quarry spill base course under the entire structure would probably be expedient
from a construction standpoint. All loose soft zones should be repaired prior to placement of the
subslab fill which should meet the requirements for structural fill detailed below. A vapor
barrier such as a sheet of a 6-nil plastic membrane should be placed beneath the slab.
Site Drainage
The site should be graded so that surface water is directed away from the construction area.
Water should not be allowed to stand in any area where the foundations, pavements, or slabs are
to be constructed. Final site grades adjacent to the Mini-Market should be sloped away from the
structure for a distance of ten feet. Roof and surface water drains should discharge at an
appropriate discharge facility.
Excavations and Slopes
Temporary and permanent excavations and slopes for this project must meet all applicable
government safety regulations. Temporary cuts to a depth of four feet may be attempted vertical.
Excavation slopes greater than four feet in depth should be cut no steeper than 1.5:1 (H:V) from
the top of the slope to the excavation bottom. Flatter slopes may be required depending upon
local variations in soil conditions. All contractors working in excavations, especially where
previous backfilling has occurred, should anticipate slight to moderate sudden caving of the side
slopes.
The simplest method of placing the proposed tanks is to obtain temporary slope easements from
the city. If this is not possible, or does not provide the required clearance, and it is not possible
to move the underground tank location, then temporary shoring will be required and should be
designed to accommodate an active earth pressure of forty-five (45) pounds per cubic foot.
Drainage must be provided behind the temporary shoring to prevent the buildup of hydrostatic
pressure behind the walls.
The suitable choice of a shoring system, if it is required, is dependent upon a variety of factors,
many of which are under the contractor's control. For this reason, we suggest the shoring design
be the contractor's responsibility, with the understanding that his design will be submitted to the
structural and geotechnical engineers for review. We are available, and would be pleased to
assist with this design effort.
Whenever excavations and/or shoring is placed next to existing streets, utilities, and structures,
there exists the potential for damage. Therefore, we recommend the establishment of a
monitoring program to monitor the effect of the construction on adjacent facilities and structures.
As a minimum, the monitoring program should include visual surveying and photographing of
adjacent streets and property to detect any pre-existing distress and damage. Survey points may
also be established and monitored during construction.
PROPOSED MINI-MARKET FACILITY/RENTON
June 29, 1992 Page 5
Permanent cut and fill slopes should not exceed 2.5:1 (H:V). Water should not be allowed to
flow uncontrolled over the top of any slope. All permanently exposed slopes should be seeded
with appropriate vegetation to reduce erosion and improve stability of the surficial soil.
Pavement Section
All pavement subgrade areas must be in a stable non-yie:3ing condition prior to the placement of
aggregate base or crushed rock. We recommend the site be proof-rolled after the vegetation,
structures and any other deleterious material are removed, prior to placement of any structural
fill. We should be on-site to observe proof-rolling efforts. Any loose or soft areas revealed by
the proof-rolling should be over-excavated and replaced with compacted structural fill or crushed
rock. After proof-rolling, a blanket of one foot of compacted structural fill should be placed
under all proposed pavement areas.
The pavement section for lightly-loaded traffic and parking areas should consist of three inches
of asphalt concrete over four inches of crushed rock. Some maintenance and/or repair of limited
areas should be expected, especially around the dumpster, or where large trucks drive and park.
We recommend all fill under pavements on this project be compacted to a minimum of 95
percent of Modified Proctor(ASTM D-1557).
Where underground utilities will be removed from under the proposed pavements, we
recommend over-excavation and replacement with a minimum of two feet of properly compacted
structural fill.
General Earthwork and Structural Fill
Site construction should begin by stripping and clearing the building areas of any utilities, roots,
topsoil, vegetation, and any other deleterious material. Stripped materials should be removed
from the site.
Structural fill is defined as any fill placed below structures, including pavements, where the fill
soils would need to support loads without unacceptable deflections or shearing. Structural fill
should be placed above unyielding site soils in maximum eight-inch-thick loose lifts and
compacted to 95 percent of Modified Proctor (ASTM D-1557),except when that fill is more than
two feet below the proposed pavement subgrade. At those depths, a percent compaction of 90
percent of Modified Proctor is acceptable. Moisture-sensitive soils typically have a significant
percentage of fine-grained material. Much of the on-site soil is silt, and is moisture-sensitive.
This soil will be very difficult to place and compact as structural fill if these soils are wetter than
the optimum moisture content at the time of compaction. This should be anticipated as our test
results of the finer-grained soils consistently revealed moisture contents in excess of the
anticipated optimum moisture content. During wet weather or under wet conditions, structural
fill should consist of a granular soil having less that five percent silt or clay (measured on that
portion which passes the 3/4-inch sieve).
O-
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B-t
(MW-1)
O B-2
O
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B4 B3 00
00
Probable -
Direction of
Ground Water
Movement (EP
Planned layout of Arco AM/PM
Mini-Market
Approximate location of test borings
(monitoring well) by EAI, 6/92. N
1 Inch = 40 Feet
Site Exploration Plan
Planned Arco AM/PM Mini-Market Facility
" South Grady Way and Talbot Road South
ENVIRONMENTAL Renton,WA
ASSOCIATFS,INC. JOB NUMBER: DATE: LOGGED BY. PLATE
2100 6-5-92 TAJ 2
BORING B- 1
HEAD
Blows SPACE
Water Per ANALYSIS
mple sa Well Table Foot USCS DESCRIPTION (PPm)
c
1 m 19 Silty Sand (fine granular) with trace of HC<10
Gravel, light brown, damp, medium
5 dense.
o SM Silty Sand (fine granular) with trace of
2 0 4 Gravel, black to grey, moist, very loose. HC<10
0
10 c
a�
a�
L
U
U)
W
3 ?; 6 Sand (fine granular) with trace of Silt, HC<10
v medium dark brown.
15 Grades to silty Sand with trace Clay,
N dark gray, wet, loose.
4 16 ML Silt with Clay, with interbedded Sand, HC<10
dark grey, wet, very stiff.
20
• Boring terminated at 20 feet on 6-8-92.
• HC denotes hydrocarbon concentrations as measured in the headspace of a jar.
• Ground water monitoring well installed in boring.
• Well design
0-5 feet: 2" dia. PVC blank.
5-20 feet: 2" dia. PVC well screen (0.020° slot size)
• Depth to ground water measured at 6.67 feet, on 6-24-92.
TEST BORING LOG
Arco AM/PM Minimarket
Talbot Road S and S Grady Way
,a ENVIRONMENTAL Renton,WA
ASSOCIATES, INC. JOB NUMBER., DATE., LOGGED BY, PLATE
— - 2100 6-8-92 TAJ 3
BORING B-2
HEAD
Blows SPACE
Water Per ANALYSIS
Sample Table Foot uscS DESCRIPTION (PP-)
1 4 Silty Sand (fine granular) with trace of HC<10
Gravel, medium grey, moist, very loose.
5
sM
to
ML •.
2 3 Silty Sand (fine granular), grey, wet, very HC<10
loose. (organics noted)
10
nTfl3 2 ML Silt, medium grey, wet, soft. HC<10
15
sM ' Silty Sand (fine granular), grey, wet, loose.
4 9 Grades into coarse Sand, wet, loose. HC<10
• Boring terminated at 19 feet on 6-8-92.
• HC denotes hydrocarbon concentrations as measured in the headspace of a jar.
• No Hydrocarbon odors or visual indications of petrolium contamination.
• Depth to ground water measured at @ 8 feet during drilling, on 6-8-92.
TEST BORING LOG
/='f t Arco AM/PM Minimarket
4 Talbot Road ENVIRONMENTAL Renton,WA Grady Way
ASSOCIATES, INC.
?z
JOB NUMBER: DATE: LOGGED BY. PLATE
2100 6-8-92 TAJ 4
BORING B-3
I HEAD
Blows SPACE
Water per ANALYSIS
Sample Table Foot uscs DESCRIPTION (PP-)
ML Sandy Silt with interbedded coarse sand,
1 9 grey to black, moist, loose. HC<10
Grades into silty Clay
5
2 26 Sand (coarse granular), dark grey, wet, HC<10
medium dense.
I
10 :sM•
I
3 5 Sand (coarse granular), dark grey, wet, loose. HC<10
15
Silt with trace of Clay with interbedded Sand,
4 5 ML medium grey, wet, medium stiff. HC<10
1
1
I
i
- Boring terminated at 19 feet on 6-8-92.
- HC denotes hydrocarbon concentrations as measured in the headspace of a jar.
- No Hydrocarbon odors or visual indications of petrolium contamination.
- Depth to ground water measured at @ 8 feet during drilling, on 6-8-92.
1
I
TEST BORING LOG
Arco AM/PM Minimarket
Talbot Road S and S Grady Way
1p , ENVIRONMENTAL Renton,WA
ASSOCIATES,INC. JOB NUMBER: DATE: LOGGED BY. PLATE
�-" - 2100 6-8-92 TAJ 5
i
BORING B-4
HEAD
SPACE
Blows ANALYSIS
Water Sample Table Foo pert USCS DESCRIPTION (PPm)
1 6 ML Sandy Silt, dark grey, moist, soft. HC<10
5
2 5 : : Sand (coarse granular) with trace of Silt and HC<10
Clay, medium brown, moist, loose.
10 SM
3 4 Sand (coarse granular) with trace of Silt, dark HC<10
grey, wet, loose. (organics noted)
15
. . . . Sand (coarse granular) with trace of Gravel,
4 5 : :� dark grey, wet, loose. HC<10
• Boring terminated at 19 feet on 6-8-92.
• HC denotes hydrocarbon concentrations as measured in the headspace of a jar.
• No Hydrocarbon odors or visual indications of petrolium contamination.
• Depth to ground water measured at @ 12.5 feet during drilling, on 6-8-92.
TEST BORING LOG
Arco AM/PM Minimarket
= Talbot Road S and S Grady Way
ENVIRONMENTAL Renton,WA
ASSOCIATES,INC.
%� JOB NUMBER: DATE: LOGGED BY.
PLATE
' 2100 6-8-92 TAJ 6
70
60
CH
50
x
w
0
40
y' Alo�
U ,
N 30
a
J
D_
MH and OH
20
CL I
10
CL-ML I ML and OL
T
0
0 10 20 30 40 50 60 70 80 90 100
LIQUID LIMIT
Test Hole Depth (feet) L.L. P.L. Classification
B2 12 . 5 - 14 44 . 8 35--.6 ML
B4 2 . 5 - 4 32 .8 29 .8 ML
Plate 7
Plasticity Test Results
ARCO AM/PM Mini-Market
NWC- S. Grady Way at Talbot Road S.
Renton,Washington
Type of Material Native Soil
Source of Material SPT Sampler Tube
Test Procedure ASTM D1140/D422 Tested/Calc. By G. Eddy Date 6/12/92
Reviewed By M. Dodds Date 6/18/92
U.S.STD.SIEVE OPENINGS IN INCHES U.S.STANDARD SIEVE NUMBERS
3 2 1 YA 1 3/4 V2 % '/4 4 810 16 30 40 50 100 140 200
loo 0
90 10
80 i 20
1
70 30
►- m
urr
3 60 40
m o
Z 50 50 N
U. �
u 40 60
1 m
w n
a
30 70
AL
20 80
10 `0
0 100
100 50 10 5 1 0.5 0.1 0.074 0 01 0.002 0 (X)1
GRAIN SIZE IN MILLIMETERS
Plate 8
0 Boring #1; 2.5' - 4.0' Particle Size Gradation Chart
ARCO AM/PM Mini-Market
♦ Boring 0; 2.5' - 4.0' NWC - S. Grady Way at Talbot Rond S.
RCII1011, Washington