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1 REPORT OF GEOTECHNICAL INVESTIGATION
WETLAND MITIGATION BANKING SITES
RENTON, WASHINGTON
1 FOR
1 CITY OF RENTON
March 27, 1995
DAMES & MOORE JOB NO. 00699-017-016
1
1 DAMES &. MOORE
1
1
i
_ DAMES & MOORE
' 500 MARKET PLACE TOWER, 2025 FIRST AVENUE, SEATTLE, WASHINGTON 98121
(206)728-0744 FAX: (206)727-3350
' March 27, 1995
' Mr. Scott Woodbury
Planning/Building/Public Works Department
City of Renton
Municipal Building
' 200 Mill Avenue South
Renton, Washington 98055
Report
Geotechnical Investigation and Consultation
' Wetland Mitigation Banking Sites
Renton, Washington
for
' City of Renton
Job No. 699-017-016
' Gentlemen:
We submit herewith three copies of our 'Report of Geotechnical Investigation, Wetland Mitigation
' Banking Sites, Renton,Washington." This investigation was performed according to your contract dated
January 17, 1995.
' We appreciate the opportunity to assist you on this project. If you or your design consultants have any
questions regarding our report, or should need further assistance, please do not hesitate to call us.
' Yours very truly,
TINS, DAMES & MOORE, INC.
wAS��1rC�
IZ� C.J. Shin, Ph.D., P.E.
' Project Engineer
23499
�/V\C�Q�
W. Martin McCabe, P.E.
EXPIRES: Z r2g"9 Associate
005\REPORTS\RENTON.R W P
00699-017-016
OFFICES WORLIM A
TABLE OF CONTENTS
' Page
' 1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2.0 SCOPE OF SERVICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .'. . . . . . . . . . . . I
' 3.0 SITE CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3.1 SURFACE CONDITIONS 2
' 3.2 SUBSURFACE CONDITION• . • . . - . . . . . • • . . . . , • . . • . . . . . . - . . . • . . . . • . . . 3
3.2.1 Site 1 3
3.2.2 Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.3 GROUNDWATER CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
' 4.0 LABORATORY TESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
' 5.0 IN-SITU INFILTRATION AND LABORATORY PERMEABILITY TEST RESULTS . . . . . . 4
6.0 ENGINEERING ANALYSES 5
' 6.1 SEEPAGE 5
7.0 EVAPORATION 6
' 8.0 CONCLUSIONS AND RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
' 8.1 FEASIBILITY OF WETLAND CREATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.2 WETLAND CONSTRUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.3 ONSITE SUITABLE STRUCTURAL FILL MATERIALS . . . . . . . . . . . . . . . . . . . . 7
' 8.4 PREPARATION OF WETLAND BOTTOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.5 PERMANENT SLOPE ANGLE 8
9.0 CLOSURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
' Appendix A - Site Exploration and Laboratory Testing
005\REPORTS\R ENTON.R W P
' 00699-017-016 DAMES & MOORE
' REPORT OF GEOTECHNICAL INVESTIGATION
WETLAND MITIGATION BANKING SITES
' RENTON, WASHINGTON
for
CITY OF RENTON
' 1.0 INTRODUCTION
' The proposed Wetland Mitigation Banking sites are located near the southern boundary of the City of
Renton. A vicinity map, Plate 1, is provided at the end of this report. The wetland mitigation banking
sites are engineered wetlands to be constructed for the purpose of replacement or enhancement of existing
' wetlands. The project includes two sites. Site 1 is about 31 acres in size and is located near the northwest
corner of SW 34th Street and Oakesdale Avenue SW. Site 2 is about 14 acres and is located near the
southeast corner of SW 34th Street and Oakesdale Avenue SW. We understand that the depth of the
' proposed wetland at Site 1 will be about 6 feet below the existing ground surface, and the depth of the
proposed wetland at Site 2 will be about 8 to 12 feet below the existing ground surface.
' 2.0 SCOPE OF SERVICES
' The purpose of this geotechnical investigation is to evaluate the feasibility of creating an engineered
wetland on the two sites. Specifically, our service includes the following:
1. Exploration of soil and ground-water conditions underlying the sites by excavating fiuv�SAX
test pits on Site 1 and five test pits on Site 2. The test pits were excavated with a rubber-
tired backhoe to maximum depths of up to 14 feet below current site grades.
' Representative samples were obtained from each soil stratum encountered in the test pits.
2. Installation of two piezometers on Site 1 and one piezometer on Site 2. The piezometers
were used for monitoring of groundwater fluctuation during the exploration program.
' 3. Performance of three in-situ subsurface infiltration tests on each site. The tests were
conducted according to King County Surface Water Design Manual. Test depths were
12 feet or less below site grade as field determined by our field engineer.
4. Laboratory testing to assess the pertin
ent physical characteristics of the site soils. Tests
include moisture content determination(ASTM test procedure D2216), gradation (ASTM
D422), compaction (ASTM D 1557), and laboratory permeability.
005\R EPORTS\RENTON.R W P
00699-017-016 1 DAMES & MOORE
' 5. Evaluation of the depth, quantity, and permeability of the on-site soils to evaluate the
availability and suitability of on-site soils to support wetland creation. Recommendations
' regarding excavation,stockpiling,placement,compaction,and other construction methods
are provided. Recommendations regarding the need for a synthetic impermeable liner,
including type, bedding, cover, etc., are also provided.
6. Evaluation of the suitabilityof the onsate soils for use as on-site or off-site fill materials.
' 7. Recommendation regarding site dewatering.
8. A written geotechnical report containing a test pit location plan,test pit logs, a description
of subsurface conditions, and our findings and recommendations.
' The site explorations were coordinated by an experienced field engineer from our staff who located the
test pits, obtained samples, and maintained a continuous log of each test pit. The engineer also conducted
the in-situ subsurface infiltration tests. Recovered soil samples were taken to our Seattle laboratory for
' further examination and testing. The results of the site exploration and laboratory testing form the basis
for our engineering analyses and recommendations commensurate with the scope of services described
' herein.
3.0 SITE CONDITIONS
The sites are located in the eastern portion of Green River valley. The sites are less than 1/2 mile from
the river. The general area is very flat. Most of the areas to the east of the sites are developed for
' commercial and industrial uses, whereas the areas to the west of the sites are undeveloped.
3.1 SURFACE CONDITIONS
Site 1 has a rectangular shape and Site 2 g p has a triangular shape. At the time of this report both sites were
' covered with sparse trees and patches of grass. The field exploration was conducted during the wet
season. Ponded water existed in the eastern and western portions of site 1, and
a=-en site 2. The surface soils at both sites were wet and soft.
A ditch about 5 feet wide exists near the western and northern boundaries of Site 1. The ditch is about
4—e&3,W feet deep andcontained about one foot of water during our field exploration.
Springbrook Creek runs parallel to the southeastern boundary of Site 2. The creek bottom was about 10
to 15 feet below the surrounding ground surface. Water in the creek was about 5 deep during our field
work.
0051R E PORTS\R E NTON.R W P
' 00699-017-016 2 DAMES & MOORE
3.2 SUBSURFACE CONDITION
P/C z orv�cfz/S
' The subsurface conditions at each site were investigated by excav tion of five test pits on each site.
Short-term monitoring of groundwater level was conducted using pizometers installed in the test pits.
Also, the in-situ infiltration rate of subsoils was tested using subsurface infiltration tests. Details of the
field exploration program are presented in Appendix A. The following paragraphs present the description
of the subsurface conditions at the two sites.
' 3.2.1 Site 1
' Site 1 is covered with fill soils about 2 to 3 feet in thickness. The materials include gravel, silty sand and
silt. The fill soils are underlain by alluvial deposits which include interbedded layers of silt, silty sand,
and sand. Our test pits were terminated in these soils. In general, the upper 4 to 10 feet of the alluvial
deposits is a soft silt, and the silt is underlain by a sand. The exception to this profile was found at the
center of the site where the surface fill soil was directly underlain by a sand (see Test Pit TP-3).
' 3.2.2 Site 2
' Site 2 has a soil profile similar to that of Site 1 except that the surface fill soils at Site 2 are slightly
thicker - in the range of 2 to 5 feet. The fill is also underlain by alluvial soils, and the upper 4 to 10 of
which is also a silt. The silt at Site 2 differs than that at Site 1 in two ways: (1) The interbedded sand
' layers at Site 2 are thicker, in the range about 2 to 2.5 feet in thickness, and (2) thin layers of peat are
common at Site 2.
3.3 GROUNDWATER CONDITIONS
Groundwater was encountered during test pit excavation and monitored in piezometers during the field
exploration program. The measurements are presented in TABLE 1.
' TABLE 1. Observation of Groundwater Level
Test Pit No. Time of Observation Groundwater below Approximated Groundwater
Ground Surface(ft) Elevation(ft)
' During Excavation 5 12.5
10:45 am, 2-1-95
TP-1-Site 1
Piezometer Reading 11:15 5.5 12
am, 2-3-95
Piezometer Reading 4.5 13
7:30 am, 2-7-95
TP-3-Site 1 During Excavation 5.8 13
3:40 pm, 2-1-95
005\R E PORTS\RENTON.R W P' 00699-017-016 3 DAMES & MOORE
' TABLE 1. Observation of Groundwater Level
' Test Pit No. Time of Observation Groundwater below Approximated Groundwater
Ground Surface(ft) Elevation(ft)
During Excavation 2 16
2:30 pm,2-1-95
' Tp-5-Site 1
Piezometer Reading 2.5 15.5
8:57 am, 2-2-95
' Piezometer Reading 3.8 14.2
4:25 pm, 2-7-95
During Excavation 8 8
Tp-4-Site 2 10:20, 2-7-95
' Piezometer Reading 8.1 7.9
7:35, 2-8-95
Note 1. Test Pit TP-5-Site 1 was located about 30 feet from the ditch, the bottom of which was about 2 to 3 feet below the
ground surface at the test pit. The ditch had about one foot of water during the excavation of the test pit.
Note 2. Test Pit TP-4-Site 2 was located about 90 feet from Springbrook Creek,the bottom of which was about 10 to 15 feet
' below the ground surface at the test pit. The creek had about 5 feet of water during the excavation of the test pit.
4.0 LABORATORY TESTING
' Representative samples were obtained during the field exploration. The samples were transported to our
Seattle laboratory for further examination and testing. The laboratory tests include moisture content
determinations, particle size analyses, compaction tests, and permeability tests. The moisture content test
results are presented in the test pit logs, the particle size analysis and compaction test results are presented
at the end of Appendix A. The permeability test results are presented in the next section.
5.0 IN-SITU INFILTRATION AND LABORATORY PE
RMEABILITY TEST RESULTS
iA total of 3 in-situ infiltration tests were conducted on each site. The purpose of the tests is to obtain an
estimate of the permeability of the in-situ soils. The tests were conducted according to the method
' presented in the King County Surface Water Design Manual. Test results are presented in TABLE 2.
A constant-head permeability test was conducted in the laboratory. The purpose of this test was to gain
' an estimate of the permeability of a compacted on-site silt soil. The test sample was prepared at a
moisture content of 25.5%, and a dry density of 93 pounds per cubic foot (pcf). The dry density
corresponds to about 93% of the maximum dry density based on the ASTM D1557 test method. The
permeability test was conducted in a Standard Proctor Mold according to ASTM D2434 test procedures.
The test result is also presented in TABLE 2.
005\R EPORTS\RENTON.R W P 00699-017-016 4 DAMES & MOORE
TABLE 2. In-situ Infiltration and Laboratory Permeability Test Results
Sample Location Test Type Sample Depth(ft) Soil Type Permeability (cm/sec)
TP-1-Site 1 Infiltration 10 sot 8.0 x 10'
TP-3-Site 1 Infiltration 11.6 Silty Sand 7.5 x 10'
TP-5-Site 1 Infiltration 11.6 Silty Sand 1.2 x 10'
TP-1-Site 2 Infiltration 5.5 Silt 5.5 x 1W
' TP-2-Site 2 Infiltration 8.5 Silt 2.2 x UP
TP-2-Site 2 Infiltration 8.5 Silt 6.5 x 10'
' TP-4-Site 1 Permeability 3 Silt 2.9 x lU'
6.0 ENGINEERING ANALYSES
6.1 SEEPAGE
One-dimensional seepage analyses were conducted to estimate the potential seepage loss from the bottom
of the proposed engineered wetlands. The analyses assume the presence of a 6-foot-thick silt layer below
the bottom of the proposed wetland at Site 1, and 3 feet thick silt layer below the bottom of the proposed
wetland at Site 2. Two groundwater levels were considered in the analyses: 1) at the bottom of the
wetlands, and 2) at the bottom of the silt layer. The former would simulate the groundwater condition
' during wet seasons and the latter would simulate the groundwater condition during dry seasons.
The seepage analyses utilize the permeability of the silt layer estimated from the in-situ infiltration and
I laboratory permeability tests. A synthetic flexible membrane liner (FML) having a permeability of 1 x
10' cm/sec was also considered in the seepage analyses. Only the soil or membrane at the bottom of the
wetland area was considered in the analysis, and the potential exfiltration losses from the relatively small
area constituting the sloping sides of the wetlands was ignored.
' TABLE 3 presents the results of the seepage analyses.
' TABLE 3. Results of Seepage Analysis
Location Seepage Loss in inches/day(gpm) Seepage Loss in inches/day (gpm)
(Without Membrane) (With Membrane)
' Dry Seasons Wet Seasons Dry Seasons Wet Seasons
Site 1 0.4 (400) 0.2 (200) 0.01 (12) 0.005 (6)
Site 2 2.9 (775) 0.9 (250) 0.07 (20) 0.04 (10)
Note: gpm = gallon per minute.
005\REPORTS\RENTON.R W P 00699-017-016 5 DAMES & MOORE
' 7.0 EVAPORATION
' The evaporation loss was estimated using the published information about the mean annual lake
evaporation of 24" in Seattle area (reference: Hydrologic Analysis & Design by Richard H. McCuen).
We assume that about 80% of the annual evaporation loss occurs in the dry seasons. Based on this
tassumption, the estimate shows that the evaporation loss in the dry seasons is about 0.1 inches/day for
both sites, or 50 gpm for Site 1, and 25 gpm for Site 2.
' Table 4 shows the combined seepage and evaporation losses for various conditions.
tTABLE 4. Combined Seepage and Evaporation Losses
Location Loss inches/day(gpm) Loss in inches/day(gpm)
(Without Membrane) (With Membrane)
Dry Seasons Wet Seasons Dry Seasons Wet Seasons
Site 1 0.5 (450) 0.2 (200) 0.11 (62) 0.005 (6)
' Site 2 3.0 (800) 0.9 (250) 0.17 (45) 0.04(10)
Note: gpm =gallon per minute.
' 8.0 CONCLUSIONS AND RECOMMENDATIONS
' 8.1 FEASIBILITY OF WETLAND CREATION
' Based on the results of our study, we are of the opinion that wetland creation at the proposed sites is
feasible. However, the water loss through seepage is relatively high for both sites during the dry seasons.
The necessary pool level for wetlands can be maintained through water replenishment, or reduction in
t seepage loss. The former will include both precipitation and hydraulic injection,the latter can be achieved
using a synthetic membrane installed at the bottom of the wetlands. A detailed hydrogeologic study in
the vicinity of the site, and a detailed water budget analysis are not within the scope of this study, but
' should be performed to assist in the selection of different options.
8.2 WETLAND CONSTRUCTION
The wetland construction should be conducted in the d season when the groundwater table is low. Our
dry
' field exploration was conducted in the wet period of the year. The observed groundwater table was
relatively close to the proposed wetland bottoms at both sites. We believe that during the dry season the
groundwater table will be at least a few feet lower than the observed levels. As such, we do not expect
' the need for site dewatering. However, we suggest that a few open test pits be 2x-oavation to confirm the
groundwater depth prior to construction.
005SREPORTS\RENTON.R W P
' 00699-017-016 6 DAMES & MOORE
' In the event site dewatering is required, we suggest dewatering using well points around the perimeter of
the site. The well point should be spaced about 10 to 15 feet, and installed to a depth about 5 feet below
' the proposed bottom of the wetland. The actual dewatering requirements may change depending on
conditions encountered during construction.
' Note that seepage from trapped water in pockets of sand and granular fill soils should be expected. The
water can most likely be handled by pumping from sump holes.
' Prior to wetland excavation, the drainage ditch that currently exists at the west and north sides of Site 1
should be diverted so that storm water will not flow into the excavation. At site 2, the elevation of the
bottom of the wetland may be relatively close to that of the bottom of Springbrook Creek which is running
parallel to the southeast boundary of the site. We understand that water in the creek level can be high
during or shortly after heavy rain storms. Due to the presence of sand layers in the subsoils, water can
potentially flow into the excavation from the creek bank during wet periods. The potential need for well-
point dewatering is greater in this area. Alternatively, consideration can be given to either a slurry cutoff
wall installed along the creek bank, or diversion of storm drainage away from creek inflow points during
' the construction period in order to reduce seepage from the creek.
' Wet soil conditions will likely present some operational problems for earthwork equipment. Use of
lightweight equipment is advised.
' 8.3 ONSITE SUITABLE STRUCTURAL FILL MATERIALS
In general, the fill soils found in the upper few feet of both sites are suitable structural fill materials. The
sand found below the surficial fill soils, for example in Test Pit TP-3-Site 1, is also suitable for structural
fill. However, the sand is usually interlayered with silt layers. Separation of the sand from the silt may
be difficult, and a predominant portion of the excavated soils from both Sites I and 2 will likely not be
' considered useable as structural fill.
' 8.4 PREPARATION OF WETLAND BOTTOM
The preparation of wetland bottom is critical. Note that our previous estimate of seepage loss is based
' on 6 feet of silt soil at the bottom of the wetland at Site 1 and 3 feet of silt soil at the bottom of the
wetland at Site 2. The actual distribution of soils in the vertical and lateral directions cannot be accurately
predicted. If a synthetic membrane is not used, the vertical continuity of low-permeability silt layers
' should be confirmed during construction at random locations throughout the wetland area in order to
validate design assumptions. Where bottom conditions are found to consist primarily of higher
' permeability sandy soils, removal and replacement with low permeability soils will be required.
005%REPORTS\RENTON.RW P' 00699-017-016 7 DAMES & MOORE
1
' The following paragraphs present the recommendations for the preparation with or without a synthetic
membrane.
' Bottom with Membrane: The membrane should have a minimum 20 mil thickness and a
permeability rating of 1 x 10'cm/sec or lower. The membrane should be installed at the bottom
' of the excavation by experienced contractor. Prior to membrane placement, so; ,at the bottom
w �* f� a �c .
of the excavation should be cleared of any sharp or oversized pa2clesv°-anr51d tracked to an even -
surface. The membrane should be covered by at least one foot of compacted onsite s1bil:'defails`L �
concerning anchorage, seaming and handling should be developed during the design phase.
Geosynthetic clay liners (GCL) are also acceptable low permeability alternatives to an FML.
Bottom without Membrane: We expect nonuniform soil conditions at the bottom of the wetlands.
In order to reduce the seepage loss, any primarily sandy soils exposed at the bottom of the
' excavation should be overexcavated by at least 2 feet and replaced with compacted onsite silt.
The compaction criteria for the silt is presented below. In the event that an insufficient amount
' of low permeability silt is encountered, the permeability of on-site sandy soils can be substantially
reduced by mixing with powdered bentonite clay. The mixing can be performed in-place by
dozer-towing of discing equipment.
' The following criteria should be used for the compaction of the silt:
' 1. The silt should be moisture conditioned to about 1 to 4% wet of the optimum moisture
content. Our laboratory test results indicate that the optimum moisture content of the silt
is 17.1% and the moisture content of the insitu silt is at least 29.8%. Hence, drying of
' the soil will likely be required prior to compaction.
2. The material should be placed in 6 inches lifts and compacted to a dry density that is at
least 95% of the maximum dry density as determined by ASTM D1698 test method.
' The wet-of-optimum moisture content is suggested so that the compacted soil will have a low
permeability.
' 8.5 PERMANENT SLOPE ANGLE
We recommend that the wetland banks be sloped to an angle no steeper than 3 horizontal to 1 vertical.
At the side of the wetland that borders Springbrook Creek, the top of the slope should be at least 50 feet
away from the creek bank.
005\REP0RTS\R ENTON.R W P
00699-017-016 8 DAMES & MOORS
9.0 CLOSURE
The recommendations presented in this report are provided for design purposes and are based on soil
conditions disclosed by field observations and subsurface explorations. Subsurface information presented
herein does not constitute a direct or implied warranty that the soil conditions between exploration
' locations can be directly interpolated or extrapolated or that subsurface conditions and soil variations
different from those disclosed by the explorations will not be revealed. The recommendations outlined
' in this report are based on the assumption that the proposed plan is consistent with that shown on Plate
1 and the description provided in this report. If, during construction, subsurface conditions different from
those disclosed by the exploration borings are observed, we should be advised at once so that we can
review these conditions, and if necessary, reconsider our design recommendations
OOSREPORTS\R ENTON.R W P
00699-017-016 9 DAMES & MOORE
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VICINITY MAP
_ Job No.00699-017-016 Wetland Mitigation
DAMES &MooxE Banking Sites
' PLATE 1
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00699_07.CDR
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_ Job No.00699-017-016 Wetland Mitigation
— DAMES &MOORE Banking Sites
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_ Job No.00699-017-016 Wetland Mitigation
DAMES &MooxE Banking Sites
' PLATE 3
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APPENDIX A
SITE EXPLORATION AND LABORATORY TESTING
FIELD EXPLORATION
A field exploration program comprised of six test pits at Site 1 and five test pits at Site 2 was
accomplished to help characterize the subsurface conditions at the sites. The locations of these test pits
' are shown on the Test Pit Location Plans, Plate 2, and Plate 3. The test pits were excavated with a Case
580, Extended backhoe. Whenever possible the test pits were excavated to the maximum reach of the
' backhoe at about 14 feet below ground surface. A six-inch diameter PVC pipe was installed in Test Pits
1, 3, and 5 on Site 1, and in Test Pits 1, 2 and 5 on Site 2. The pipes were used to conduct subsurface
infiltration tests. A one-inch diameter PVC pipe equipped with a sand pack at the bottom of the pipe was
1 installed in Test Pits 1 and 5 on Site 1, and in Test Pit 4 on Site 2. These pipes were used for the
monitoring of groundwater level during the field exploration program. Logs of all test pits are presented
on Plates A-1 through A-11. A key to symbols used on the test pit logs is shown on Plate A-12.
' All soils have been classified in accordance with the Unified Soil Classification System which is shown
on Plate A-13.
LABORATORY TESTING
' Soil samples recovered during the field exploration program were visually examined and classified in our
laboratory and a testing program was conducted to evaluate pertinent engineering properties.
Moisture contents were performed on selected soil samples. The test results are indicated adjacent to the
appropriate sample notations on the test pit logs. The gradation and compaction test results are presented
in Plates A-14, and A-15.
005\REPORTS\RENTON.R W P 00699-017-016 A-1 DAMES & MOORE
TP - 1 —Site 1
Surface Elevation: t17.5
0
GW Grayish brown fine to coarse gravel with trace
. `•,", of fines and occasional cobbles (moist) (fill)
(medium dense)
ML Grayish brown silt with trace to some fine sand
(moist) (fill) (soft)
29.5
2.5
MIL Gray silt with lenses of black fine to medium
sand(wet) (soft)
5
7.5
grades very soft and wet
10
' SM/SP Black fine to medium sand, trace to some fines
12.5 (wet) (medium dense)
rn
rn
r� Peat visible at 14 ft
Test Pit TP-1—Site 1 completed at a depth of
14 feet on 2-1-95. Piezometer installed at a
' > depth of 13 feet. Infiltration pipe installed at
0 15 a depth of 10 feet. Groundwater encountered at a
depth of 5 feet during excavation.
a
N
Ln
M
0' 17.5
I
Co
0
1 NOTE:
0
Groundwater encountered at a depth of 5 feet
during excavation.
01
01
' O
LOG OF TEST PIT Dames & Moore
' Job No. 00699-017-016 PLATE A-1
i
i TP —2— Site I
2� °�� Surface Elevation: t18
0
. SM Yellowish brown silty fine to medium sand
i (moist) (loose)
I ML Yellowish brown silt (moist) (medium stiff)
i 2.5
' Seepage at 4 ft
i 5 SP/SM Reddish brown fine to medium sand with trace to
some fines (wet) (loose)
Test Pit TP-2—Site 1 abandoned on 2-1-95 due to
7 5 caving at a depth of 7.0 feet.
iNo groundwater encountered during excavation.
1
10
i 12.5
rn
rn
0
N
1 �
0
15
J
N
i �
17.5
1 �
ro
0
0
0
1cn
cn
T
la
LOG OF TEST PIT Dames & Moore
iJob No. 00699-017-016 PLATE A-2
Job No. 00699-017-016 PLATE A—J
TP -4— Site 1
Surface Elevation: f 17
0 1 I I 1 OL Dark brown or anic silt with abundant roots
—(moist) (topsoil) (soft)
SW Brown fine to coarse sand with trace of
2� fines (moist) (fill) (loose)
Q:
2.5
I1•I1 OL Dark brown organic silt with abundant roots
I i I (wet) (soft) (old topsoil)
I I
29.8 ML Gray and brown to ers of silt with occasional
roots (moist) (soft
' 5
Layer (6 in) of brown medium to coarse sand and
7.5 fine to coarse gravel, occasional small cobble
ML Gray silt with some mottlin and occasional fine
roots (moist) (medium stiff
10 grades wet and soft
12.5
rn
rn
' o PT�OL Peat and dark gray organic silt (wet) (soft)
N Test Pit TP-4—Site 1 completed at a depth of
14 feet on 2-1-95. No groundwater encountered
' > during excavation.
0 15
D-
C,
17.5
1
oa
O
O
V
N
a
fl
' O
LOG OF TEST PIT Dames & Moore
Job No. 00699-017-016 PLATE A-4
TP —5 — Site I
Surface Elevation: t18
ML Yellowish brown silt with abundant roots
' (wet) (topsoil) (very soft)
Nrades with mottling and no roots
moist) (medium stiff)
MIL Brown fine to medium sandy silt (moist) (soft)
grades with lenses of brown silty fine to medium
sand (moist) (soft)
5
' 7.5
25.8s1 fines 41.5 10 SM Dark gray silty fine to medium sand (wet) (loose)
Test Pit TP-5—Site 1 abandoned on 2-1-95 due to
caving at a depth of 11 feet. Piezometer
installed at a depth of 10.5 feet. Infiltration
pipe installed at a depth of 11.6 feet.
Groundwater encountered at a depth of 2 feet
12.5 during excavation.
m
rn
r7
0
N
0 15
J
N
Ln
C,
17.5
Cn
r�
0
Cn
T
O
LOG OF TEST PIT Dames & Moore
' Job No. 00699-017-016 PLATE A-5
T- 6 — Site I
Surface Elevation: t22
0 :'.
GW Reddish brown sandy fine to coarse gravel with
abundant cobbles and trace of fines
r� (moist) (dense)
L
5.5% fines 6.3 ¢
2.5
Test Pit TP-6—Site 1 completed at a depth of
3 feet on 2-1-95.
' S
7.5
10
12.5
rn
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O
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0 15
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01
LOG OF TEST PIT Dames & Moore
Job No. 00699-017-016 PLATE A-6
' TP— 1 — Site 2
2 Surface Elevation: t16
0
j' SP/SM Yellowish brown fine to medium sand with some
fineto coarse gravel and trace of fines (wet)
' (fill) (medium dense)
' seepage at 2 feet
2.5
PT Peat and wood debris (wet)
MIL Reddish brown sandy silt with abundant roots
(moist) (medium stiff)
ML Gray silt with some roots (wet) (soft)
' 5
SP/SM Dark gra fine to medium sand with trace to some
7 5 fines(wet� (loose) (medium dense)
ML/OL Interbedded ray silt and dark gray organic silt
(moist) (soft
rTest Pit TP-1—Site 2 abandoned on 2-7-95 due to
10 caving at a depth of 9.5 feet. Infiltration pipe
installed at a depth of 5.5 feet.
' No groundwater encountered during excavation.
12.5
m
rn
0
N
CD 15
O
J
1 �
Ln
17.5
00
0
NOTE:
0
' o No groundwater encountered during excavation.
Ln
T
' O
LOG OF TEST PIT Dames & Moore
Job No. 00699-017-016 PLATE A-7
' TP -2—Site 2
Surface Elevation: t16
0
SP/SM Grayish brown fine to medium sand with roots in
the upper 6 inches (wet) (very loose) (fill)
ML/SM Layer of gray sandy silt and silty fine sand
(moist) (fill) (stiff and medium dense)
' 2.5
1 ML Dark gray silt with some roots (wet) (very soft)
' 05
seepage at 6 ft
7.5
PT/01- Peat and dark grayish brown organic silt
10 (wet) (soft)
' SP Black fine to medium sand, trace fines
(wet) (loose)
Test Pit TP-2—Site 2 abandoned on 2-7-95 at
a depth of 11.5 feet due to caving.
Infiltration pipe installed at a depth of 8.5
12.5 feet. No groundwater encountered during
o excavation.
m
r�
0
N
I >
0 15
ch
N
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17.5
I
M
O
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Co
U
o
LOG OF TEST PIT Dames & Moore
Job No. 00699-017-016 PLATE A-8
1 TP - 3 — Site 2
o63Q Surface Elevation: f16
0
SP/SM Yellowish brown fine to medium sand with trace of
fines and fine to coarse gravel at the
surface (moist) (fill) (medium dense)
5.5% fines 14.7
Maximum Dry
Density 123
pcf at 10.3% 2 5
PT Wood debris and seepage at 2.5 feet.
ML Reddish brown mottled fine sandy silt
(moist) (possible fill) (medium stiff)
ML Gray silt with some roots (moist) (soft)
5
grades mottled
16.3% fines 39.1 SP/SM Dark gray fine sand with trace to some fines
7 5 (wet) (medium dense)
ML Gray silt with seams of peat (wet) (very soft)
10
SP Black fine sand with trace of fines (wet) (loose)
<'_'t?s.
' Test Pit TP-3—Site 2 abandoned on 2-7-95 at a
12.5 depth of 12 feet due to caving.
No groundwater encountered during excavation.
rn
0
N
J
0 15
N
N
Q1
0 17.5
I
ro
0
0
Ln
o
T
J
LOG OF TEST PIT Dames & Moore
Job No. 00699-017-016 PLATE A-9
1 TP -4— Site 2
Surface Elevation: t16
0 ML Reddish brown fine sandy silt with abundant roots
__(moist) (topsoil) (very soft)
SM Grayish brown mottled silty fine to medium sand
(moist) (fill) (medium dense)
2.5
39.2% fines 33.0
,
grades wet
ML/PT Gray silt and peat (wet) (soft)
5
Reddish brown staining around abundant root holes
7.5
' — SP Grayish brown fine to medium sand (moist) (loose)
ML Gray silt (wet) (very soft)
10
ML Purplish brown silt with some fine sand
(wet) (soft)
seam of peat at 11 feet
` SP Black fine to medium sand (wet) (medium dense)
12.5 Test Pit TP-4—Site 2 abandoned on 2-7-95 at a
depth of 12.5 feet due to caving. Peizometer
installed at a depth of 12 feet.
Groundwater encountered at a depth of B feet
during excavation.
0
N
' 0 15
ch
LO
17.5
Co
Ln
0
Ln
D
N
O
LOG OF TEST PIT Dames & Moore
' Job No. 00699-017-01 6 PLATE A-10
TP - 5 — Site 2
Surface Elevation: t17
0
ML Dark brown silt with abundant roots
et) (topsoil) (very soft)
SM Dark brown fine sand with some silt (moist)
(loose) (possible fill)
20.95K fines 27.4
' 2.5
seepage at 3 feet
' 5
ML Dark gray silt with occasional wood debris
(wet) (soft)
7.5
10
grades with lenses of reddish brown silt at 10
feet (moist) (medium stiff)
1 SP Black fine sand, trace fines (moist) (loose)
m
rn
' o
N Test Pit TP—S—Site 2 completed at a depth of
14 feet on 2-7-95. Infiltration pipe installed at
> a depth of 8.5 feet below ground surface.
0
15 No groundwater encountered during excavation.
cn
cn
rn
0 17.5
i
0
0
Cn
N
a�
J LOG OF TEST PIT Dames & Moore
' Job No. 00699-017-01 6 PLATE A-1 1
' KEY:
Indicates depth of grabbed samples.
' NOTE:
The discussion in this report is necessary for
a proper understanding of the nature of the
subsurface materials.
KEY Dames & Moore
Job No. 00699-017-016 PLATE A-12
Major Divisions Graphic Letter Typical Descriptions
Symbol Symbol
Well-Graded Gravels,
.;.;.;�.4. GW Gravel-Sand Mixtures,
Gravel and Clean Gravels `• : Little or no Fines
' Gravelly Soils (little or no fines) 0 O Poorly-Graded Gravels,
O 0 GP Gravel-Sand Mixtures,
Coarse Grained O o Little or no Fines
Soils Silty Gravels,
GM Gravel-Sand-Silt Mixtures
More than 50% of Gravels with Fines
Coarse Fraction' a reciable amount( pp Clayey Gravels,
Retained on
No. 4 Sieve of fines) GC Gravel-Sand-Clay Mixtures
a a Well-Graded Sands,
4 0 0.4 SW Gravelly Sands,
Sand Clean Sand G�� Little or no Fines
and (little or no fines)
Sandy Soils Poorly-Graded Sands,
More than 50%o SP Gravelly Sands,
i of Material is Little or no Fines
Larger than
No. 200 Sieve Size Silty Sands,
More than 50% of SM Sand-Silt Mixtures
Coarse Fraction lit 11
Sands with Fines
Passingthrough (appreciable amount
g of fines) Clayey Sands,
No. 4 Sieve SC Sand-Clay Mixtures
' Inorganic Silts and Very Fine Sands,
ML Rock Flour, Silty or Clayey Fine Sands
or Clayey Silts with Slight Plasticity
Fine Grained Silts Liquid Limit Inorganic Gays of Low to Medium
Soils and Less than 50 CL Plasticity, Gravelly Clays, Sandy Clays,
Clays Silty Clays, Lean Clays
Organic Silts and Organic
OL Silty Clays of Low Plasticity
' Inorganic Silts, Micaceous or
MH Diatomaceous Fine Sand or
Silty Soils
More than 501% Silts Inorganic Clays of High
of Material is and Liquid Limit CH Plasticity, Fat Clays
Smaller than Clays Greater than 50
No. 200 Sieve Size
Organic Clays of Medium to
OH High Plasticity, Organic Silts
Peat, Humus, Swamp Soils
' Highly Organic Soil PT with High Organic Contents
M1
Note: Dual symbols are used to indicate borderline soil classifications.
iz
Unified Soil Classification System
Dames & Moore
' PLATE A-13
1
GRAVEL SAND
1 COBBLES SILT OR CLAY
Coarse Fine Coa. Medium Fine
U.S.Standard Sieve Size in Inches U.S.Standard Sieve Numbers I Hydrometer
' 3 3/4 3/8 4 10 20 40 100 200
100
' 80
i
60 ---- — - --- — —
1 PASSING
BY
WEIGHT (%)
1 40
i -
1
20 - - --- - - - - ---
�
0
1 1 00 TrT 1 1 1 01
GRAIN SIZE (mm)
' GRAIN SIZE DISTRIBUTION
1 SYMBOL BORING DEPTH DESCRIPTION % % %
NO. (ft) GRAVEL SAND FINES
0 TP-6-Site 1 0-3 It Fine to coarse sandy gravel 62.8 31.6 5.6
TP-3-Site 2 1.5 ft Fine to medium sand 5.0 89.5 5.5
1 REMARKS:
1 03-24-1995 Wetlands Mitigation Banking Sites DAMES & MOORE
' JOB NO.00699-017-016 PLATE A-14
1
i COMPACTION TEST
i 150
140
i 130
ZERO A/7 VOID R TIO
i 120
iDRY DENSITY
(pro 110
100
1
90
i
i 80
i 70
0 10 20 30 40
MOISTURE CONTENT (%)
1
SYMBOL SAMPLE DEPTH DESCRIPTION TEST OPTIMUM
iLOCATION (ft) METHOD MOISTURE(%)
O TP-4-Site 1 4 Gray and brown silt D1557A 17.1
iTP-6-Site 1 0-3 Reddish brown fine to coarse sandy gravel D1557C 8.1
TP-3-Site 2 1.5 Yellowish brown fine to medium sand D1557A 10.3
1
iREMARKS:
i L
-09-1995 Wetlands Mitigation Banking Sites DAMES & MOORE
iJOB NO. 00699-017-016 PLATE A-15
n
i
i_
l_
u