HomeMy WebLinkAboutWWP272109 (17)' *AGRA AGRA Earth &
'
Earth & Environmental Environmental, Inc. 11335 NE 122nd Way
Suite 100
Kirkland, Washington
U.S.A. 98034-6918
' Tel (206) 820-4669
Fax (206) 821-3914
22 August 1996
6-91 M-1 1 154-0
City of Renton
' Planning, Building, Public Works Department
Wastewater Utility Division
200 Mill Avenue South
Renton, Washington 98055
Attention: Mr. John Hobson
Subject: Subsurface Exploration and Geotechnical Engineering Report
Proposed Higate Sewage Pump Station Elimination Project
Jones Avenue Northeast and Northeast 20th Street
Renton, Washington
' Dear Mr. Hobson:
This report presents the results of our subsurface exploration and geotechnical engineering
evaluation for the above referenced project. This scope of work was performed in accordance
with our contract dated 2 July 1996. The wetlands survey included in our contract was
subcontracted to Entranco, and the results of that portion of the project are presented under
separate cover. This report has been prepared in accordance with generally accepted
geotechnical engineering practices for the exclusive use of the City of Renton, and their agents
for specific application to this project. We recommend that we be allowed to review completed
project plans and specifications to ensure that our recommendations have been adequately
interpreted and incorporated into project design documents.
The purpose of this phase was to evaluate the subsurface conditions and geotechnical aspects
of project construction along the alignment from approximately project station 1 +30 to
' 11 +00. The current project plan calls for installation of a new 8 inch diameter PVC sewer line
with invert elevations between approximately 4 and 16 feet below existing grades along the
easement.
SUMMARY
• Our scope of work for this project included advancing four hollow stem auger soil
' borings to depths of approximately 20 feet below the existing ground surface.
Engineering & Environmental Services
City of Renton 6-91 M-11154-0
22 August 1996 Page 2
• The subsurface conditions observed in our explorations along the planned alignment
' generally consisted of loose to medium dense sand with trace to some silt, underlain in
three of the borings by dense to very dense silty gravelly sand.
' Groundwater was observed in each of the borings at depths ranging from approximately
0.5 to 6 feet, as noted on the boring logs. Dewatering operations are recommended in
advance of open excavations which penetrate more than approximately 2 feet below the
' groundwater level at the time of construction. For excavations penetrating less than 2
feet below groundwater levels, a system of pumped sumps in the sewer trench should
' provide adequate dewatering.
• The project appears feasible from a geotechnical standpoint with respect to the soil
' conditions observed in our explorations. Consideration will be required with respect to
temporary excavation shoring, temporary cut slope inclinations, and temporary
excavation dewatering during construction.
This summary is presented for introductory purposes only, and should be used in conjunction
with the full text of this report. The site location is indicated on the Location Map, Figure 1,
' the site and approximate locations of explorations accomplished for this study are presented
on the Site and Exploration Plan, Figure 2, and the exploration logs for subsurface explorations
completed for this study are appended to this report.
SITE AND PROJECT DESCRIPTION
The project site is located northeast of downtown Renton, in an area characterized primarily
' by single family residences and a small blueberry farm. Regional topography is rolling, with
gentle to moderate slope inclinations. The new sewer would be located in a relatively small
scale topographic depression, characterized by generally poor drainage.
' The new sewer alignment is relatively flat, with overall vertical relief of approximately 10 feet.
Ends of the new sewer would be located in City right - of - way along Jones Avenue Northeast
and Northeast 20th Street. The main section of the new sewer would be located in an
easement between private properties. Most of the easement is currently undeveloped and
covered with a thick growth of blackberry bushes and other vegetation. The pipe would cross
two shallow channels between project station 2+00 and 3+00, one of which contained
running water at the time of our exploration program.
' The new sewer would consist of slightly more than 1,000 feet of new 8-inch diameter plastic
sewer pipe, and four new manholes. Depths to invert elevation of the new pipe would vary
' between approximately 4 and 16 feet. Geotechnical considerations for construction of the new
sewer include excavation side slope inclinations, temporary shoring, and temporary dewatering.
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City of Renton 6-91 M-11 154-0
22 August 1996 Page 3
Project Area Geology
We researched the project area geology in the United States Department of Agriculture Soil
Conservation Service Soil Survey for King County, Washington, and in the Preliminary Geologic
Map of Seattle and Vicinity, Washington, by Waldron, Liesch, Mullineaux, and Crandell. In
addition, we reviewed the geotechnical report by Shannon and Wilson, Inc. Geotechnical Report
for the Gravity Sewerline. Higate Pump Station Elimination, Renton, Washington, Dated
November 1993. The Shannon and Wilson investigation included completion of three auger
borings within the rights of way for Jones Avenue Northeast and Northeast 20th Street. Based
on these information sources, the surficial soil conditions in the project area consist of loose
recessional sand and gravel, overlain by thin layers of surficial organic muck in some locations,
and generally underlain by very dense glacial till soils at depths.
SUBSURFACE EXPLORATION METHODS
Subsurface conditions were observed in four hollow stem auger soil borings completed in July
1996 by a local drilling company under subcontract to AGRA Earth & Environmental, Inc. (AEE).
The approximate boring locations are indicated on the attached Site and Exploration Plan, Figure
2. Exploration logs are included at the end of this report.
Hollow stem auger borings were advanced into soil utilizing a 3-inch inside diameter hollow -
stem auger. During the drilling process, samples were generally obtained at 2 % to 5 foot depth
intervals. The borings were continually observed and logged by a geologist from our firm.
' Standard Penetration Tests (SPT) were conducted through the auger casing.
Disturbed soil samples were obtained by using the Standard Penetration Test (SPT) procedure
' as described in ASTM:D-1586. This testing and sampling method consists of driving a standard
2-inch outside diameter split -barrel sampler a distance of 24 inches into the soil with a 140
pound hammer free -falling a distance of 30 inches. The number of blows for each 6-inch
' interval is recorded and the number of blows required to drive the sampler the last 12 inches
is considered the Standard Penetration Resistance ("N") or blowcount which is represented in
the boring logs. If a total of 50 blows is recorded within one 6 inch interval, the blowcount is
' recorded as 50 blows for the number of inches of penetration. The resistance, or "N" value,
provides a measure of the relative density of granular soils or the relative consistency of
' cohesive soils. The soil samples obtained from the split -barrel sampler were classified in the
field and a representative portions placed in moisture -tight containers. The samples were then
transported to our laboratory for further visual classification and laboratory testing.
' At the time of drilling, we installed short sections of PVC sprinkler pipe in two of the borings,
borings B-1 and B-3, to allow later measurement of groundwater levels after drilling was
' complete. The standpipes were removed and the holes sealed with bentonite clay once
readings were complete. The water levels estimated at the time of drilling, and measured
following drilling, are noted on the exploration logs.
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' City of Renton 6-91 M-11154-0
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1
The boring logs are based on interpretations of drilling action, inspection of the samples
secured, laboratory test results and field logs. The various types of soil are indicated, as well
as the depths where the materials or their characteristics changes. It should be noted that
these changes may have been gradual, and if the changes occurred between sample intervals,
they were interpreted.
Subsurface Conditions
' Subsurface conditions observed in our borings generally consisted of very loose to medium
dense sand with varying silt and gravel content. The soil conditions were generally variable,
and changes in soil conditions with depth and map locations were typical of the soil conditions
' in our borings. Most of the hollow stem auger soil borings penetrated below static groundwater
levels. Because of the granular nature of the site soils, soil "heave" was encountered during
' drilling below the groundwater interface. Heave occurs when groundwater enters the borings
and \ or the auger, carrying with it entrained particles of the subsurface soils. It is likely that
excavations on site will penetrate below the observed groundwater levels. The Tunnelmans
' Ground Classification for the soils observed in our borings at and above the pipe elevation is
"Flowing
' Laboratory Testing
A grain size analysis indicates the range of soil grain sizes included in a particular sample based
on particle diameter. Grain size analyses were performed on representative samples in general
accordance with ASTM:D-422. The results of the grain size determinations are presented at
the end of this report.
Moisture content determinations were performed in conjunction with grain size analyses in order
to aid in identification and correlation of soil types. The determinations were made in general
accordance with the test procedures described in ASTM:D-2216. The results of the tests are
shown on the exploration logs, and on laboratory test reports at the end of this report.
Groundwater Conditions
' Each of the four hollow stem auger borings completed for this study encountered water at
depths of approximately 0.5 to 6 feet below the existing ground surface at the time of drilling.
Two of the hollow stem auger borings, B-2 and B-5, were completed with short lengths of
sprinkler pipe to act as temporary open standpipe piezometers for monitoring groundwater
levels after drilling. Subsequent groundwater monitoring is noted on the boring logs included
' with this report. In general, our groundwater observations indicate that most or all of the
planned sewer line will be installed below the static groundwater level in saturated soil horizons.
Groundwater conditions should be anticipated to vary in response to changes in seasonal
precipitation, on and off site land usage, and other factors.
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' City of Renton 6-91 M-1 1 154-0
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CONCLUSIONS AND RECOMMENDATIONS
The proposed project appears feasible from a geotechnical standpoint with respect to the
subsurface conditions observed in our explorations. Construction of the new sewer line and
manholes will require temporary excavation shoring and dewatering. The following report
' sections present our conclusions and recommendations for specific aspects of the project.
Site Preparation
Prior to site grading, any site surface runoff and groundwater seepage should be collected and
routed away to a proper drainage to facilitate earthwork construction. Once surface runoff and
groundwater seepage are controlled, all areas of the site to be excavated should be stripped of
' all topsoil, vegetation, and existing paving, and the deleterious surficial material segregated
from native soil materials if they are suitable for reuse when excavated. We estimate that
' stripping depths will vary from approximately 6 inches to one foot below existing grades.
Any existing buried utilities on the site should be removed, relocated, abandoned, or worked
around as necessary. All utility work should be performed in accordance with applicable
Federal, State, and City regulations. Localized excavations below finished grades in road right
of way areas made for removal of utilities should be backfilled with structural fill as outlined
in the following section of this report.
Most or all of the excavations for the project will be below static groundwater levels and in
loose soil horizons. We recommend that shoring and dewatering plans and equipment be in
place before beginning any excavations for which shoring or dewatering may be required.
Shoring and dewatering considerations are discussed in subsequent sections of this report.
Because of the high silt content of some of the soils, some of the near surface site soils are
moisture sensitive. The silty soils are highly prone to disturbance when wet. To reduce site
' disturbance in areas to be paved, or other structural areas, the contractor should minimize
traffic above any prepared subgrade areas. During wet site conditions, the use of geotextile
reinforcement fabrics and a working surface of quarry spalls or sand and gravel may be required
' to protect the subgrade, especially from vehicular traffic. Earthwork during wet site conditions
may result in disturbance of the site soils and may require imported backfill or soil drying and
recompaction to repair the disturbed areas. If earthwork takes place during freezing conditions,
we recommend that the exposed subgrade be allowed to thaw and be recompacted prior to
placing subsequent lifts of structural fill or any permanent structure.
Structural Fill
All structural fill placed in excavations, placed below new pipes for pipe bedding, comprising
fill slopes or placed where future support of permanent structures of any kind is anticipated
should be placed in accordance with the recommendations herein for structural fill. Prior to the
placement of structural fill, all surfaces to receive fill should be prepared as previously
recommended. Structural fill should not be placed into standing water. If proper excavation
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City of Renton 6-91 M-1 1 154-0
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dewatering is not feasible, we should be contacted to provide situation -specific
recommendations for underwater fill placement.
Sewer lines constructed in open excavations should be supported by at le st 6 inches of
bedding material below the pipe invert. Pipes should also be supported below the spring line
with granular bedding material worked around the pipe by hand. The bedding aterial should
conform to Washington State Department of Transportation (WSDOT) Standard ecifications
for Road, Bridge, and Municipal Construction 9-03.15 Bedding Material fo igid Pi . If the
excavated native soils contain gravels larger than approximately 2 inches, the edding material
should also cover the pipe to protect it from damage caused by coarse gravel during
compaction. We anticipate that most of the excavated site soils will contain little coarse
gravel.
Structural fill should be placed in lifts not exceeding 8 inches in loose thickness if compacted
with conventional drum rollers or hand operated equipment. Fill placed in confined excavations
and compacted with vibratory "hoe packs" may be placed in loose lifts of up to 12 inches in
thickness when depths below finished grade exceed 4 feet. For the first lift of backfill above
new pipes, a single lift of 18 to 24 inches may be used to protect the pipe from damage caused
by compaction equipment. Closer than 4 feet to finish grade, all fill should be placed in 8-inch-
thick loose lifts, regardless of compaction method. Individual lifts should be compacted such
that a density of at least ent of the modified Proctor maximum dry density is achieved.
The upper 4 feet below paved roads should be compacted to at least 95 percent of the same
density standard. If buried pipes with crown elevations shallower than about 6.5 feet below
road subgrades are planned, some form of ductile iron sleeve or other structural reinforcing may
be warranted to protect the pipe during backfilling and road subgrade preparation. We
recommend that a representative from our firm be present during the placement of structural
fill to observe the work and perform a representative number of in place density tests. In this
way, the adequacy of earth work may be evaluated as grading progresses.
The suitability of soils used for structural fill depends primarily on the gradation and moisture
content of the soil when it is placed. As the fines content (that portion passing the U.S. No.
200 Sieve) of a soil increases, it becomes increasingly sensitive to small changes in moisture
content, and adequate compaction becomes more difficult or impossible to achieve. Soils
containing more than about 5 percent fines by weight, such as the majority of the site soils,
cannot be consistently compacted to the recommended degree when the moisture content is
more than approximately 2 percent above or below optimum. Based on our previous experience
with similar soils, it appears that the optimum moisture content of soils tested in the laboratory
varies from approximately 6 to 10 percent, and measured moisture contents of several selected
samples ranged from 6 to 26 percent. Only one of the eight samples tested had a moisture
content of less than 10 percent. We therefore anticipate that the majority of the site soils will
require reduction before they are suitable for reuse in structural fill
applications. Drying may be accomplished by means of scarifying and windrowing the soils
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' City of Renton 6-91 M-1 1 154-0
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during dry, warm weather conditions, or could be achieved with admixtures such as Portland
' cement or lime products thoroughly blended into the soils in specific proportions. If site soils
are to be reused, we recommend that excavated soils be protected from inclement weather and
surface water until moisture conditioning and compaction has been completed. If native soils
I
are left unprotected, rain or surface water could render otherwise suitable soils unusable
without additional effort to reduce moisture contents.
If imported soil is required for construction of compacted fills, we recommend that a clean, free
draining gravelly sand be used. Import material should contain no particles greater than
6 inches in diameter, and should contain less than 5 percent by weight passing the US Number
' 200 Sieve, based on that fraction passing the US Number 4 Sieve. All structural fill should be
free of organic material, roots, debris, and other deleterious materials. Imported fill material
that will be in contact with the pipe should meet the gradation requirements listed above for
' pipe bedding material. (�6;—��
' Sewer pipes installed above loose to medium dense native soils, and supported thoroughly by
compacted pipe bedding material, are anticipated to settle less than one inch contingent upon
adequate design and execution of excavation shoring, dewatering, and backfilling.
' Temporary Slopes
Temporary excavation slopes may be used in lieu of shoring where the necessary space is
' available and provided that existing structures, roadways, utilities or other sensitive elements
would not be adversely impacted. Slope stability during excavation is a function of many
factors, including: the presence and abundance of surface and groundwater; type and density
t of various soil strata; the depth of the cut; surcharge loading adjacent to the excavation, and
the length of time the excavation remains open.
' Consequently, it is exceedingly difficult to preestablish safe and maintenance free temporary
slope angles. Temporary slope stability should be made the responsibility of the contractor,
who is continuously on the job site and able to observe changes in the site soil and
' groundwater conditions and monitor the performance of the excavation. We recommend that
excavations be adequately sloped or braced to prevent injury of workman from local sloughing
and spalling. All cuts should be completed in accordance with applicable Federal, State, and
' local safety provisions and codes, including current OSHA and WISHA guidelines.
t For planning purposes, temporary cut slope inclinations on the order of _ 1 5H-2H• 1 V
(Horizontal: Vertical) should be Mannet 641�a :11:111+ Silty sand at least 2 fee
groundwater level. Temporary unshored excavations are not recommended less than 2 feet
' above the groundwater level. Perched groundwater conditions in the sidewalls of sloped
excavations may require substantially flatter cut slope angles or additional dewatering to
achieve stable temporary excavation side slopes.
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22 August 1996 Page 8
Permanent slopes above a pa d groundwater and surface water levels should be
' constructed at inclinations o 2H:1 V orizontal:Vertical) or flatter, and should be provided with
deep-rooted, prolific group as soon as possible after construction.
' Dewatering Considerations
Open excavations for pipeline construction will require dewatering to provide a stable
excavation base and to facilitate construction activities. Each of the four hollow stem auger
explorations encountered groundwater above the planned pipe invert elevation. Groundwater
levels should be expected to fluctuate.
' We recommend that dewatering be specified within the site soils to a depth of at least 2 feet
below anticipated base of excavation elevation. Such dewatering could minimize unstable
conditions and disturbance of the trench bottom, thereby reducing post construction pipe
' settlements and providing a more stable pipe foundation. It should be realized that dewatering
can cause ground settlement due to an increase in the effective stress of the dewatered soils.
' We recommend that the condition of adjacent structures be well documented prior to the start
of construction, as described in the Monitoring section of this report.
Dewatering activities could also affect the functioning of nearby groundwater wells or other
uses of groundwater resources nearby. Adverse effects such as increased turbidity, decreased
or eliminated well productivity, and general disruption of natural groundwater flow patterns are
' possible. Such effects could be either temporary or permanent. A thorough analysis of effects
of project dewatering on the existing groundwater conditions would require one or more aquifer
pump tests, which were beyond the scope of this study.
Based on the soil and groundwater conditions observed in our borings, we recommend that
dewatering be accomplished using pumped well points or drilled wells. Well points are effective
' when the depth of excavation is approximately 15 feet or less. Well points are usually two to
four inches in diameter, and consist of a pipe with a slotted lower section that is driven into the
ground to a predetermined depth using a drive hammer or vibratory driving system. A suction
' pump system is then lowered into the wells, removing water to the depth of the pump intake,
or at the maximum rate of the pump, whichever is less. Well points are typically installed in
advance of the excavation operations at spacings determined by experimentation in the field.
' The dewatering system is operated until the desired drawdown is achieved, construction
activities are completed in any given area, and dewatering is no longer required. Drilled
' dewatering wells work in a similar fashion except that larger diameter wells, and submersible
pumps are used. Submersible pumps allow dewatering to greater depths, at a relatively greater
cost than suction pumping methods.
' In locations where the planned depth of excavation is less than 2 feet below groundwater levels
at the time of construction, a system of pumped sumps could be used in lieu of well points.
Pumped sumps could consist of a suction pump intake situated inside of a perforated, gravel
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' City of Renton 6-91 M-11154-0
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filled bucket or drum. The drum is then placed below the planned excavation base and
activated to complete dewatering during construction activities. The number and spacing of
the sumps should be determined by the contractor in the field to meet the performance criteria
in the specifications.
' Ideally, a detailed dewatering design based on aquifer pump testing should be completed.
However, contractor designed systems are sometimes more cost effective. An experienced
' dewatering contractor can usually formulate an initial design, and modify the system as required
by performance testing to achieve the desired results. We recommend that the contractor be
' made responsible for final dewatering design based on the subsurface information observed in
our borings and the contractors experience and available equipment. This may be accomplished
by providing a performance - oriented specification for dewatering.
For preliminary design purposes, the following table presents our estimated permeability values
for some of the soil samples recovered from our borings. These permeability estimates are
' based on the grain size analyses completed for this study and methodology as outlined in the
manual Department of the Navy NAVFAC P-418 Dewatering and Groundwater Control. These
permeability estimates are based on the grain size analyses for discrete soil samples, and may
U
not be representative of the permeability of the formations from which they were retrieved.
Aquifer permeability values are dependent on structures and local variations of the soil deposits
which may not be accurately represented by the discrete soil samples.
TABLE 1
ESTIMATED SOIL PERMEABILITY VALUES
Boring Number
Sample Number
Depth
ft
Estimated Permeability
(cm/sec)
B-1
S-1
2.5
1 x 10-4
B-1
S-2
5
2 x 10-4
B-1
S-3
7.5
3 x 10-4
B-2
S-1
2.5
1 x 10-4
B-2
S-2
5
2 x 10-5
B-3
S-3
7.5
6 x 10-5
B-4
S-2
5
2 x 10-4
B-4
S-3
7.5
3 x 10-4
;; Earth & Environmental
' City of Renton 6-91 M-11154-0
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Dewatering activities will generate significant quantities and flow of groundwater. The water
is likely to be turbid and unsuitable for discharge into storm drainage systems without prior
treatment. Provisions should be made to collect and clarify dewatering fluid prior to discharging
from the site.
Dewatering Costs
Dewatering costs are dependent on many variables including contractor productivity and work
' schedules, time of year and groundwater conditions during construction, access conditions,
aquifer characteristics, and other factors. It is therefore difficult to estimate costs precisely for
dewatering operations. We have consulted Means Site Work and Landscape Cost Data, and
' talked briefly with a Anderson Dewatering, a local dewatering contractor, regarding this project.
Based on these information sources, the subsurface information gathered during our
1 investigation, and on the use of well points for excavations less than approximately 15 feet in
depth, we estimate a cost range of approximately $25 to $40 per foot of trench for dewatering
activities related to construction of the sewer. For precise estimates of dewatering costs, a
contractor should be provided with all available details for the proposed project and allowed to
prepare a detailed cost estimate.
Excavation Shoring
Based on the soil conditions observed in our explorations, and based on the site constraints,
excavation shoring will be required in most locations where open excavations are planned.
Shoring may consist of driven sheet piles, soldier piles, lagging, or "trench box" shoring. The
contractor should be allowed to use shoring of his choosing, however, we recommend that any
trench box shoring used be examined to confirm that it is recommended by the manufacturer
' to withstanding the lateral earth pressures described below.
We recommend that the contractor be made responsible for design and construction of
temporary excavation shoring, based on the following soil parameters. The following active and
at rest lateral earth pressures assume drained conditions (groundwater level at least 2 feet
below the base of the excavation), static (non - seismic) conditions, and no surcharges with a
lateral distance equal to the shoring depth at any given point. Surcharges may include
construction equipment or stockpiled materials, structures, roadways, slopes, or utilities.
Allowances should be added for such surcharges, as described subsequently. Shoring that is
free to deflect at the top a distance equal to 0.01 times the height of the retained cut should
be assumed to mobilize active earth pressures. Shoring designed using active earth pressures
will allow vertical settlement behind the shoring approximately equivalent to 0.01 H, where H
is the wall height. The maximum settlement effects will extend outward from the shoring a
distance approximately equal to the height of the retained cut, at which point the effects will
' gradually diminish with increasing distance from the shoring. Active earth pressure for the site
soils under the given conditions should be taken as 35 pounds per cubic foot (pcf), expressed
as and equivalent fluid weight.
Earth & Environmental
City of Renton 6-91 M-11154-0
22 August 1996 Page 11
Shoring that is restrained from lateral deflection at the top should be designed with at rest
lateral earth pressures. At rest pressures theoretically assume no horizontal movement of the
shoring, and therefore no settlement effects in the retained cut. In reality, some deflection and
settlement of the retained soils should be anticipated due to the fact that it is not possible to
construct a perfectly rigid shoring system. Shoring that is constructed closer than two times
the distance of the retained cut from settlement sensitive structures should be designed using
at rest lateral earth pressures. Where settlement sensitive structures are located near the
planned excavations, a program of adjacent structure monitoring should be developed, as
described subsequently. At rest lateral earth pressures under drained, static conditions should
be taken as 55 pcf, expressed as an equivalent fluid weight.
Shoring of undrained excavations is not recommended; however, if undrained soil conditions
occur behind shoring walls, we anticipate that active and at -rest lateral earth pressures of 85
pcf and 95 pcf, respectively, will be present.
Surcharges should be added to the above referenced lateral earth pressures to accommodate
construction equipment and supplies, roadways, or structures. Figure 3, Surcharge Pressures
Acting on Adjacent Shoring or Subsurface Walls, provides recommendations for determining
lateral earth pressures which correspond with specific surcharge conditions.
In the case of sheet pile or soldier pile and lagging shoring, resistance to active and at rest
lateral earth pressures will be achieved as a result of passive resistance against the portion of
the piles embedded below the excavation base. The following passive resistance value is based
on saturated soil conditions below the excavation base. An allowable passive resistance of 90
pcf, acting over two pile diameters in the case of soldier piles, should be used. An appropriate
factor of safety should be applied by the shoring designer to obtain a suitable allowable passive
earth pressure. Passive resistance within the uppermost 2 feet below the base of the
excavation should be neglected.
Shoring Monitoring
When excavations are made below the level of existing buildings, utilities or other
deflection -sensitive structures, there is risk of damage even if a well -designed shoring system
has been installed. Dewatering activities have the potential to cause similar settlement effects.
We recommend, therefore, that a systematic program of observations be conducted during the
project construction phase to document the effects of construction on adjacent facilities and
structures. We believe that such a program is advisable for two reasons. First, if excessive
movement is detected sufficiently early, it may be possible to undertake remedial measures
which could prevent or preclude serious or further damage to existing facilities or structures.
Secondly, in the unlikely event that problems do arise, the responsibility for damage may be
established more equitably if the cause and extent of the damage can be closely defined. In
situations where no settlement sensitive structures are located within a distance equal to 3
times the excavation depth (or depth of dewatering drawdown, whichever is greater),
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settlement damage as a result of excavation dewatering and shoring is less likely, and
monitoring may not be required.
The monitoring program should include measurements of the horizontal and vertical movements
I' of the adjacent structures and the shoring system itself. At least two reference lines should
be established adjacent to the excavation at horizontal distances back from the excavation face
of about'/sH and H, where "H" is the final excavation height. Monitoring of the shoring system
should include measurements of vertical and horizontal movements at the top of the shoring
approximately 5 feet on center. If local perched groundwater conditions are noted within the
excavation sidewalls, additional monitoring points should be established at the direction of the
' geotechnical engineer. The measuring system used for shoring monitoring should have vertical
and horizontal accuracy of at least 0.01 foot. All reference points on existing structures should
be installed prior to construction, and survey readings taken thereafter will depend on the
results of previous readings and the rate of construction. As a minimum, readings should be
taken about once a week throughout construction until the basement walls are completed and
' backfilled. Such readings should be reviewed by the geotechnical engineer as construction
progresses.
In order to establish the condition of existing facilities prior to construction, we recommend that
the owner and/or his representative make a complete inspection of pavements, structures,
utilities and other relevant facilities near the project site. This inspection should be directed
' towards documenting any existing signs of damage, particularly those caused by previous
settlement or lateral movement. The observations should be documented by pictures, notes,
survey drawings or other means of verification. The contractor should also establish the
existing conditions prior to construction for his own records.
� AG RA
Earth & Environmental
City of Renton
22 August 1996
6-91 M-11154-0
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CLOSURE
We appreciate the opportunity to be of service to you on this project. If you have any
questions or comments regarding this report, or require further information after reviewing this
report, please do not hesitate to call us.
Respectfully submitted,
AGRA Earth & Environmental, Inc.
v
Bruce . Guenz r WL
Senior Staff
DRY?)
games S. D an field, nt � " P.E.-i3'S�p"� E��'''
Vice Presid
EXP1fiE5 12 / 19 / 9
BWG/JSD/lad
Enclosure: Figure 1, Location Map
Figure 2, Site and Exploration Plan
Figure 3, Surcharge Pressures Acting on Adjacent Shoring or Subsurface Walls
Boring Logs B-1 Through B-4
Soil Grain Size Analyses Reports
�uf Earth & Environmental
wt
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-----EASEME---------------------------
I 15' NT PRpPOSED GRAVEL ACCESS ROAD
I�ROPOSED-140 STEEL CASING
EXISTING 15' CASEMENT
-- 7i00 --
T- - - - - - - - - - - - - - - - - - - - 7
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PROPOSED GRAVEL ACCESS ROAD
EXISTING M.H.
EXISTING 15' EASEMENT
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PROPOSED.8' SANITARY SEWER LINE
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LEGEND
BORING I4UMBER A14D APPROXIMATE
LOCATION
i
GROUND SURFACE
GROUND SURFACE
q x = mD
LINE LOAD
PRESSURE
UNIFORM LOAD q
ISOLATED FOOTING
°h = 0.64q(0—sinflcos2a)
LEVEL OF APPLICATION OF SURCHARGE LOAD, q,
WOULD VARY FROM GROUND SURFACE (FRONT
END LOADER) TO SOME DEPTH BELOW GROUND
SURFACE (FOOTING).
BASE OF EXCAVATION
CONTINUOUS FOOTING
PARALLEL TO EXCAVATION
11
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BASE OF EXCAVATION
BASE OF EXCAVATION
(FOR m > 0.4)
vh =1.28q m2 n
D (m2+ n2)2
(FOR m < 0.4)
ah=q 0.2n
D (0.16 + n2) 2
ORM LOAD DISTRIBUTION
ah = 0.4q
q = VERTICAL PRESSURE IN psf
FIGURE 3
W.O.
6-91M-11154-0
HIGATE PUMP STATION
*AC3RA
DESIGN
BWG
ELIMINATION PROJECT
Earth & Environmental
DRAWN
JMR
RENTON, WASHINGTON
11335 N.E. 122nd Way, Suite 100
Kirkland, WA, U.S.A. 98034-6918
DATE
AUG 1996
SURCHARGE PRESS. ACTING ON_ ADJACENT _
SCALE
N.T.S.
SHORING OR SUBSURFACE WALLS
AGRA EARTH k ENVIRONMENTAL, INC. DRAWING NO. \91\11154\PRESSURE.DWG
Higate Lift Station
PROJECT: Elimination Project
.. SOIL DESCRIPTION
A w Location: Brushy area near planned MHO3
Approximate ground surface elevation: 251 feet
0 Tdpsoil and sod
Very loose, saturated, mottled gray, fine SAND
with some silt to silty
5 f Grades to loose, saturated to wet, gray, fine
SAND with some silt
Grades to loose, saturated, gray; fine to medium
SAND with trace silt
�_ 10 4 Grades to medium dense with some silt
15 Dense, wet to saturated, gray, silty, gravelly, fine
SAND (Glacial Till -like) M—
edium dese n, saturated, gray, silty, fine SAND
with trace fine gravel
F 20
1- 25
30
Boring terminated at approximately
21.5 feet
LEGEND
2.00-inch OD split -spoon sample
Observed groundwater level
1/34/89 (ATD = at time of drilling)
NNE No groundwater encountered
W.O. 6-91 M-11154-0 BORING NO. 8-1
a
a
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0
PENETRATION RESISTANCE
Standard Blows per foot Other
10 20 30 40
8rtsi96
S-1
S-2
S-3
S-4 �
S-5
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Blowcount 15.
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0 20 40 60 80
MOISTURE CONTENT
Plastic limit Natural Liquid limit
AG R A
Earth & Environmental
11335 NE 122nd Way, Suite 100
Kirkland, Washington 98034-6918
100
Drilling method: HSA Hammer type: Cathead Date drilled: 23 July 1996 Logged by: B WG
Higate Lift Station
PROJECT: Elimination Project
w.o. 6-91 M-11154-0 BORING NO. 8-2
s SOIL DESCRIPTION
wLocation: Brushy area near planned MH#2
Q .. Approximate ground surface elevation: 256 feet
0 Topsoil and sod
Loose, damp, tan, fine SAND with some silt and
trace fine gravel
5 f Medium dense, wet, mottled gray, silty, gravelly,
fine SAND
r 10
r15
F 20
F 25
30
Grades to saturated, brown, with thin stringers of
sandy SILT
Very dense, wet to saturated, gray and brown,
silty, gravelly, fine SAND with thin stringers of silt
0
Boring terminated at approximately
21.5 feet
LEGEND
2.00-inch OD split -spoon sample
Observed groundwater level
L30189 (ATD = at time of drilling)
NNE No groundwater encountered
m
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PENETRATION RESISTANCE
Standard Blows per foot Other
10 20 30 40
----------
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S-2
AID
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0 20 40 60 80
MOISTURE CONTENT
Plastic limit Natural Liquid limit
my AG RA
Earth & Environmental
11335 NE122nd Way, Suite 100
Kirkland, Washington 98034-6918
Drilling method: HSA Hammer type: Cathead Date drilled: 22 July 1996
Page 1
of I
TESTING
Logged by: BWG
Higate Lift Station
PROJECT: Elimination Project
x SOIL DESCRIPTION
wLocation: Brushy area 2 10'E of MH#4 on Jones Ave.
ca .. Approximate ground surface elevation: 246 feet
0 ppsoil and sod
Loose, wet, mottled gray, silty, fine SAND with
trace fine gravel
5
Grades with silt stringers
Dense, wet to saturated, gray, silty, fine gravelly,
fine to coarse SAND
r 10 4— Grades to medium dense
F15
Grades to very dense
h 20
Boring terminated at approximately
20.5 feet
F 25
30 '
LEGEND
2.00-inch OD split -spoon sample
Observed groundwater level
2130189 (ATD = at time of drilling)
N/E No groundwater encountered
w.o. 6-91 M-11154-0 BORING NO. B-3
m o a PENETRATION RESISTANCE
a° a.m �F . 0
F¢ D I e 3 Standard Blows per foot Other
cm I Z 1 0 10 20 30 40
S-1 8/15/96 - -, - - - - -
ATD
i
S-2 _ --'--� --- �-
--'--
S-s -- -- -- - j
s 4 _A,
S-5 1
J ,
I S-6
i I
--,-- ----- -- - -;--
0 20 40 60 80
MOISTURE CONTENT
Plastic limit Natural Liquid limit
imp AG RA
Earth & Environmental
11335 NE 122nd Way, Suite 100
Kirkland, Washington 98034-6918
Page 1
of 1
TESTING
Drilling method: HSA Hammer type: Cathead Date drilled: 22 July 1996 Logged by: BWG
Higate Lift Station
PROJECT: Elimination Project W.O. 6-91 M-1 1 154-O BORING NO. B-4
x SOIL DESCRIPTION o PENETRATION RESISTANCE Page 1
w Location: 30' N of MH#4 on NE 20th St. 22 o ¢ ofg
A¢ F- a M I Standard Blows per foot Other
Approximate ground surface elevation: 251 feet Cn z , 3 0 10 20 30 ao so TESTING
' 0 Topsoil and sod
Very loose, wet to saturated, dark brown, silty,
organic, fine SAND AID
i
S-1 �- --�-- Mediumdense,dense, saturated, gray, silty, fine SAND
5 g y m,
i
S-2
Grades to fine to medium SAND with trace silt
S-3----i ------1-----
10 Blowcount
S 4 Overstated
_ ---- onheae
_---_----_
'v
-------------------:--------
15 Blowcount
' S-5 Overstated 1
-�- - - - - on Heave I
Grades to medium dense, wet, gray, silty, fine
gravelly, fine to coarse SAND -------;---- -- --' - -'--
i------ - - -
------------
20
I
S-5----------'---�------'-
I
Boring terminated at approximately
------- ;- -----
----;-------- 21.5 feet � �
25 �
i
--'-- - -- ---- -- !--=--
30
� 0 20 40 60 80 100
LEGEND MOISTURE CONTENT
c
C Plastic limit Natural Liquid limit
0 2.00-inch OD split -spoon sample
c
W , AG RA
a Observed groundwater level
r zi°o °° (ATD = at time of drilling) Earth & Environmental
w 11335 NE 122nd Way, Suite 100
NIE No groundwater encountered
a: Kirkland, Washington 98034-6918
a Drilling method: HSA Hammer type: Cothead Date drilled: 24 July 1996 Logged by: BWG
1
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GRAIN SIZE DISTRIBUTION
U.S. STANDARD SIEVE SIZE
HYDROMETER
���IIIRI■d�l■di�l�li�
■nm■iii��iu
1000.00 100.00 10.00 1.00 0.10 0.01 0.00
GRAIN SIZE IN MILLIMETERS
Coarse Fine Coarse Medium Fine Sift Clay
Exploration
Sample
Depth
Moisture
Fines
Soil Description
-*-�-�� B-1
S-1
2.6
22%
22%
Silly SAND
•-+-�-�-+ B-1
S-2
5.0
22%
19%
Silty SAND
- - - - B-1
S-3
7.6
25%
6%
SAND, some silt
A B-2
S-1
2.6
6%
16%
Silty SAND
Project Higate Lift Station Replacement
Work Order: 6-91 M-1 1154-0
Date: 7-31-96
*AGRA
Earth & Environmental
11335 NE 122nd Way
Suite 100
Kirkland, Washington 98034-6918
GRAIN SIZE DISTRIBUTION
SIZE OF OPENING IN INCHES
U.S. STANDARD SIEVE SIZE
INRII■�II�■IIIIY
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IIIIII�IIIIY■Illlil■�!!
IIIIII■
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1000.00 100.00 10.00 1.00 0.10 0.01 0.00
GRAIN SIZE IN MILLIMETERS
Coarse Fine Coarse Medium Fine Silt Clay
BOULDERS I COBBLES
Exploration
Sample
Depth
Moisture
Fines
Soil Description
•-+--•—♦♦ B-2
S-2
5.0'
13%
25%
Silty SAND, some gravel
•-�-•-•-+ B-3
S3
7.6
10%
36%
Silty SAND, some gravel
'- B-4
S-2
5.0'
26%
15%
Silty SAND
A, A� B-4
S3
7.5'
18%
6%
SAND, some silt
Project: Higate Lift Station Replacement
Work Order: 6-91 M-11154-0
Date: 7-31-96
40AGRA
Earth & Environmental
11335 NE 122nd Way
Suite 100
Kirkland, Washington 98034-6918
W-6574,-01
8WILSON, INC.
AFSHANNON
HD
'
GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS
FAIRBANKS
ANCHORAGE
SAINT LOUIS
BOSTON
November 5, 1993
Hammond, Collier & Wade -Livingstone
Associates, Inc.
4010 Stone Way North
Seattle, Washington 98103
Attn: Mr. Robin Nelson, P.E.
IRE: GEOTECHNICAL REPORT FOR THE GRAVITY SEWERLINE, HIGHGATE
PUMP STATION ELMUNATION, RENTON, WASHINGTON
This report presents the results of our, geotechnical study for the proposed 8-inch gravity
sewerline to be constructed as part of the Highgate pump station elimination project. The
purpose of our work was to evaluate soil and groundwater conditions along the pipeline align-
ment and to provide geotechnical recommendations for its installation. Our work included:
reviewing the U.S. Geological Survey (USGS) geologic map of the area, drilling three soil
borings, conducting laboratory tests on soil samples, performing engineering analysis to develop
design recommendations, and preparing this report.
Our work was done in accordance with the terms and conditions outlined in our confirming letter
to you dated October 22, 1993.
SITE AND PROJECT DESCRIPTION
The site is situated on the east side of Interstate 405 in Renton, Washington. As shown on
Figure 1, the 8-inch PVC or ductile iron sewerline will be installed along N.E. 20th Street and
Jones Avenue N.E. The total length of the pipe is expected to be 865 lineal feet, out of which
440 lineal feet will be along N.E. 20th Street and 425 lineal feet will be along Jones Avenue
N.E. As shown on Figure 2, the ground elevation at the site varies from 275 to 252 feet and
the pipeline elevation varies from 242 to 246 feet. The deepest section of the sewer would be
at the intersection of N.E. 20th Street and Jones Avenue N.E. (33 feet). A new manhole will
be constructed at this location.
We understand that two options are being considered for constructing this section of the
sewerline. Option 1 would consist of installing the pipe using the conventional cut -and -cover
400 NORTH 34TH STREET -SUITE 100
W-6574-01
P.O. BOX 300303
SEATTLE, WASHINGTON 98103
206.632.8020 FAX 206.633.6777
I
Hammond, Collier & Wade -Livingstone SHANNON 6WILrSON. INC.
Attn: Mr. Robin Nelson
November 5, 1993
' Page 2
method, whereby the sewerline would be installed by trenching and backfilling. This method
would involve closing one or both lanes of the existing roadway at any given time. Option 2
would involve pipe jacking or tunnel boring the sewerline. This method would consist of
' constructing two jacking pits, one along N.E. 20th Street and the other along Jones Avenue
N.E., at the approximate locations shown on Figure 2. This report presents geotechnical
recommendations for both options.
We understand that there are other options being considered to eliminate the existing Highgate
pump station. These options involve installing the proposed sewer around the wetlands (not
shown on Figure 1) which are located north of N.E. 20th Street and east of Jones Avenue N.E.
A creek flows through the wetland area. This study does not deal with these options.
SUBSURFACE EXPLORATIONS
The subsurface conditions along the sewerline alignment were explored by drilling three borings
(B-1 through B-3) at the locations shown on Figure 1. These locations were determined by
pacing from existing site features and should be considered approximate. The logs of borings
are presented on Figures 3 through 5. The geologic contacts shown on these logs should be
considered approximate.
The borings were drilled on August 20, 1993, using a truck -mounted B-61 drill rig equipped
with a hollow -stem auger. The rig was supplied and operated by Associated Drilling under
subcontract to Shannon & Wilson, Inc. Standard Penetration Tests (SPTs) were performed at
2.5-foot and 5-foot intervals in the boring in general accordance with the procedures outlined
in ASTM: D 1586. In the SPT, a 2-inch-outside diameter split -spoon sampler is driven three
6-inch increments into the bottom of the borehole using a 140-pound hammer dropped from a
height of 30 inches. The number of blows required to drive the sampler for each 6-inch
increment is recorded and the number of blows required to drive the sampler the last 12 inches
is termed the Standard Penetration Resistance (blow count or N-value). The N-value is plotted
on the boring logs. It provides a qualitative estimation of the relative density of cohesionless
soils and the consistency (stiffness) of cohesive soils. Samples obtained from the split -spoon
sampler are disturbed but representative of the soils encountered.
All samples retrieved from the borings were classified in the field, sealed in jars, and returned
to our laboratory in Seattle, where these classifications were rechecked (ASTM: D 2487-92) and
the moisture content of each sample was determined (ASTM: D 2216-92). The soil classifica-
W-6574-01
�II
d
Hammond, Collier & Wade -Livingstone SHANNON 6WILSON, INC.
Attn: Mr. Robin Nelson
November 5, 1993
Page 3
tions and moisture contents are presented on each boring log (Figures 3 through 5). In addition,
grain -size distributions of selected samples were determined in general accordance with the
"Department of Army Manual of Laboratory Soil Testing, Appendix V: Grain -Size Analysis."
The results are shown on Figures 6 and 7.
SUBSURFACE CONDITIONS
All three borings encountered very dense, silty, gravelly, fine to medium sand (locally sandy
silt) containing numerous cobbles and possibly boulders. This soil contained numerous seams
of water -bearing, slightly silty to silty, fine to coarse sand. Occasionally, it had a till -like
appearance. This soil was encountered at a depth of 6 inches in boring B-1, 18 feet in boring
B-2, and 6 feet in boring B-3. In boring B-2, this soil was overlain by loose, sandy grav-
el/gravelly sand and in boring B-3 it was overlain by very loose, silty, gravelly, fine to medium
sand containing organics.
Our conversation with some workers at a nearby site and our observations of the terrain along
the blueberry farm and existing pump station indicate that unsuitable loose sands and/or soft
clays/silts may be present along this section of the proposed pipeline. The presence and depths
of these soils could be determined by drilling an additional boring prior to construction.
Groundwater was not observed on drill rods at the time of drilling the borings on August 20th.
On September 4, however, water level readings taken in the piezometers installed in B-2 and
B-3 indicated water table at depths of 24 feet and 12 feet, respectively. In our opinion, this
' water is from the water -bearing seams within the very dense soil. It is also our opinion that,
in wet weather, the water levels will be higher and groundwater will be encountered perched
on top of this relatively impervious, very dense soil stratum.
CONCLUSIONS AND RECOMMENDATIONS
General
' Based on the results of the borings, we anticipate that soil at the proposed pipe invert elevation
would consist of very dense, silty, gravelly sand (locally sandy silt) containing cobbles and
scattered boulders (different soil could be encountered along the low-lying area adjacent to the
existing creek and blueberry farm, as previously stated). This soil is considered suitable for the
support of the pipeline provided it is maintained in an undisturbed condition. This soil is
i
W-6574-01
r"J
Hammond, Collier & Wade -Livingstone SHANNON &WILSON, INC.
Attn: Mr. Robin Nelson
November 5, 1993
Page 4
moisture sensitive; therefore, in wet weather, recommendations presented in the section "Wet
Weather Earthwork" should be followed.
In our opinion, the pipe could be installed by cut -and -cover method or by tunnel boring or pipe
jacking. We recommend that consideration be given to installing the pipe by cut -and -cover
technique as the presence of very dense, cobbly soil would make it difficult to jack the pipe and
maintain the required alignment, and an oversized bore, typically about 42 to 48 inches in
diameter, would be required to remove cobbles and boulders. While the pipe could be bored,
it is our opinion that there is a higher degree of uncertainty and, therefore, risk involved, which
could substantially impact the costs.
Excavation
We anticipate that the fill and near -surface native soils observed in borings B-2 and B-3 can be
excavated using conventional excavating equipment such as rubber -tire backhoes or tracked
hydraulic excavators. Excavation in such soils should not require unusual equipment or
procedures. Excavation through underlying very dense till -like soil, however, may be more
difficult, and the use of ripper teeth may facilitate excavation. In addition, cobbles and possibly
boulders would be encountered in this glacial soil and their presence should be anticipated by
the Contractor.
Unshored temporary excavation slopes may be possible along some shallow sections where space
permits. Consistent with conventional practice, temporary excavation slopes should be made
the responsibility of the Contractor since the Contractor is able to observe the nature and
conditions of the subsurface materials encountered, including groundwater, and has the responsi-
bility for methods, sequence, and schedule of construction. All temporary excavation slopes
should be accomplished in accordance with local, state, and federal safety regulations. For
' planning purposes, for excavations less than about 10 feet deep, we recommend that temporary
excavation slopes in the near -surface loose soils be no steeper than 1.5 horizontal to 1 vertical
(1.5H to 1V) and those in underlying dense soils be no steeper than 111 to 1V. Where less
competent soils or seepage zones are encountered, flatter slopes may be required. For purposes
of determining compliance with WAC 296-155, Part N, we expect the loose near -surface soils
should be classified as Type C soil while the underlying very dense soils would be Type A or
Type B, depending on their degree of cementation.
W-6574-01
Hammond, Collier & Wade -Livingstone SHANNON 6WILSON. INC.
Attn: Mr. Robin Nelson
November 5, 1993
M1 Page 5
Temporary Shoring
For temporary shored excavations, construction practice in the Seattle area generally utilizes
' trench box (for pipes installed by cut -and -cover method), interlocking steel sheet piles, a
combination of soldier piles and horizontal lagging, and/or steel plates and internal bracing
walers, although other methods of trench support are possible. Driving of sheet or soldier piles
by impact or vibratory hammers is probably not practical at this site due to the vibrations
produced and the density of the soil; therefore, partial or full -depth pre -drilling or pre -excavation
would likely be required for soldier pile installation. Regardless of the method selected, the
shoring system should provide adequate protection for workers and should prevent damage to
adjacent structures, utilities, streets, and other facilities. It is understood that the design of the
temporary shoring system and the method of construction will be the responsibility of the
Contractor. It is the Contractor's responsibility to monitor the stability of shored excavations
and take corrective measures if any deficiencies or potentially unstable conditions are encoun-
tered.
' Recommended lateral earth pressures for the design of a temporary shoring system are presented
on Figures 8 and 9. The recommended design values are based on soil classifications, soil
density or consistency, laboratory test results, and our engineering experience with similar soils
and conditions in the Greater Seattle area. Surcharge loading should be added to the lateral earth
pressures, as appropriate, depending on Contractor's proposed operation.
Please note that because the trench box is placed after excavation and may not fit snugly against
the excavation walls, a significant amount of soil deformation could take place; ground move-
ments can be severe, especially in the presence of groundwater and in the near -surface or loose
soils. The Contractor should be made responsible for all damages related to ground movements.
' Dewatering Considerations
1 Based on the available subsurface data, it is our current opinion that dewatering and groundwater
control at the site during construction can take place using measures such as sloping, ditching,
pumping from sumps, and subdrains. Should any significant seams of water -bearing sands be
encountered within glacial till, other measures - such as well points - could be required. The
contractor should evaluate the subsurface data from the logs and retain a hydrogeologist to design
the dewatering system, if necessary. Except as otherwise designed and/or specifically covered
in the contract, the Contractor should be made responsible for control of all surface and
groundwater encountered during construction. In this regard, sloping, slope protection, ditching,
' W-6574-01
u
J
Hammond, Collier & Wade -Livingstone SHANNON 6WILSON. INC.
Attn: Mr. Robin Nelson
November 5, 1993
Page 6
sumps, trench drains, dewatering, and other measures should be employed as necessary to permit
proper completion of the work.
Pipe Foundation and Bedding
Normal pipe bedding procedures should generally prove satisfactory along the proposed sewerline
I alignment. Bedding should provide a firm and uniform cradle for the pipe. We recommend
that the pipe be bedded on imported granular bedding material meeting the gradational require-
ments specified in the WSDOT/APWAI Standard Specifications, Section 9-03.16, "Bedding
Material for Flexible Pipe. " The granular bedding should extend at least 4 inches below the
bottom of the pipe and 12 inches above the top of the pipe. The bedding soil should be placed
' in lift thicknesses not exceeding 4 inches and should be carefully worked under and around the
pipe by shoveling, vibrating, tamping, or other approved procedures. It should be compacted
' to a dense and unyielding condition and to at least 90 percent of its Modified Proctor maximum
dry density (ASTM: D 1557). The subsequent backfill should be placed and compacted as
described in the following section.
The native soils encountered in our explorations at the proposed pipe grade are moisture -sensitive
and may become muddy and unstable in wet weather or wet conditions. If these soils become
disturbed during excavation, they should be overexcavated and replaced with imported pipe
bedding material. In extremely wet conditions, the soils should be replaced with 1-1/4-inch-
minus crushed rock meeting the gradational requirements unspecified in WSDOT/APWA
Standard Specifications, Section 9-03.9(3), "Crushed Surface -Base Course," except the fraction
passing the No. 200 sieve by weight (i.e., fines) should be limited to 5 percent.
In dry weather, if the foundation soils become loosened during excavation, they should be
recompacted provided their moisture content allows the requisite 90 percent compaction.
Fill Placement and Compaction
All subsequent fill backfill placed beneath or around structures, pavements, or other areas where
settlements are to be minimized, and all backfill that is to develop passive resistance should be
structural fill.
Washington State Department of Transportation and American Public Works Association:
1991 Standard Specifications for Road, Bridge, and Municipal Construction.
W-6574-01
11
11
fl
Hammond, Collier & Wade -Livingstone SHANNON 6WILSON, INC.
Attn: Mr. Robin Nelson
November 5, 1993
Page 7
Structural fill material should consist of a reasonably well -graded sand or sand and gravel, free
of organics and debris, with a maximum particle size of about 3 inches. It should contain not
more than 20 percent fines (material passing the No. 200 mesh sieve) by weight, based upon
wet sieving the soil fraction passing the 3/4-inch sieve. If earthwork takes place in wet weather
or wet conditions, no matter what time of the year, the fines content of structural fill material
should be no more than 5 percent. Fines should be non -plastic.
The native soils excavated from the trench may be reused as structural fill, provided their
moisture contents are suitable for obtaining proper compaction. The very dense, silty, gravelly,
fine to medium sand found in the borings generally appears to be at or near its optimum moisture
content and would probably achieve the necessary compaction in its present state. Under wet
conditions, this soil would become muddy and unstable and would not be suitable for reuse as
structural fill (see "Wet Weather Earthwork" for further details).
All structural fill should be placed in uniform layers and compacted to a dense and unyielding
condition and to at least 95 percent of its Modified Proctor maximum dry density, (ASTM: D
1557). In non-structural areas, where settlements equal to about 1 percent of the fill thickness
on the order of 1 inch or more is tolerable, the compaction requirement may be reduced to 92
percent. The compaction requirement may be further reduced in planting/landscape areas. In
general, the thickness of soil layers before compaction should not exceed 8 inches for heavy
equipment compactors and 4 inches for hand -operated mechanical compactors. For plate
compactors attached to backhoe buckets (i.e., hoe-pac), the thickness of soil layers should not
exceed 18 inches. Heavy mechanical compaction should not be allowed until the initial and
subsequent backfill is at least 2 feet above the top of the pipe.
As an alternative to the recommended pipe bedding and initial backfill, Controlled Density Fill
(CDF) could be used.
Lateral Pipe Support
Soil at the sides of the pipeline trench provide resistance to the lateral component of pipeline
pressure at corners. The magnitude of the available lateral resistance depends on the depth of
the pipe and the density of the soil. For thrust blocks located at least 5 feet below ground level
in loose soils, design should be based on a uniform pressure of 1,000 psf, and for blocks located
in medium dense soils, design could be based on 2,000 psf. Thrust blocks should have a
minimum bearing surface area of 4 square feet.
W-6574-01
n
Hammond, Collier & Wade -Livingstone SHANNON &WILSON, INC.
tAttn: Mr. Robin Nelson
November 5, 1993
Page 8
Pipe Jacking
Pipe jacking at this site could be accomplished using a continuous -flight auger or a boring
machine with a full -face cutterhead. The jacking pipe should be large enough to permit internal
access for removal of obstructions such as boulders and to allow flexibility in alignment control.
For this site, we expect a pipe with a minimum diameter of 42 inches will be required. The
auger should be recessed back from the end of the jacking pipe, if possible, to create a soil plug
which will inhibit soil loss and minimize potential settlement of the ground surface above.
Adjustments to the distance the auger is recessed may be necessary as soil conditions vary. We
expect that jacking pits about 30 feet long and 8 to 10 feet wide will be required. Such pits will
require shoring and some dewatering.
In order to reduce potential surface settlement, and to minimize frictional drag on the pipe, we
recommend that the Contractor be required to inject bentonite grout just behind the overcut ring
at the crown and sides of the pipe. This will require a bentonite agitator and pump capable of
mixing at least 20 gallons per minute and pumping at pressures in excess of 200 psi.
The Contractor should provide details on the equipment, material, and procedures for jacking
steel casing or carrier pipe. This would include the design and performance details for the
' jacking system and any lubricants required to reduce the frictional resistance between the soil
and pipe. In his design, the Contractor should consider the possibility of encountering cobbles
or boulders and the potential for isolated ravelling conditions from interlayered sand seams within
the very dense soils.
Prior to performing any bored excavations, we recommend a pre -construction survey be
implemented to document the conditions of the sidewalks, street pavement, utilities, and adjacent
buildings. In addition to the pre -construction survey, we recommend a monitoring program be
' implemented prior to construction to periodically evaluate the performance and workmanship
of the Contractor. In this case, a set of rigid pavement settlement markers consisting of a steel
' rebar and a pipe sleeve should be installed at regular intervals through the pavement and
anchored in the subbase soils.
Wet Weather Earthwork
The existing very dense site soils are moisture -sensitive. If earthwork is done in wet weather
' or under wet conditions, these soils could become muddy and difficult to place and compact if
their moisture content significantly exceeds the optimum. Therefore, if earthwork takes place
W-6574-01
Hammond, Collier & Wade -Livingstone SHANNION 6WILSON, INC.
Attn: Mr. Robin Nelson
November 5, 1993
Page 9
in wet weather or wet conditions, where control of soil moisture content is not possible, the
following recommendations should be followed:
a) Fill material should consist of clean, granular soil, of which not more than 5 percent
by weight should pass the No. 200 sieve, based on wet sieving of the soil fraction
passing the 3/4-inch sieve. Fines should be non -plastic. Such soil would have to be
imported to the site. The previously -described pipe bedding material would be suitable
for this purpose.
b) Earthwork should be accomplished in small sections and carried through to completion
to minimize exposure to wet weather. No soil should be left uncompacted so it can
soak up water. Soils which become too wet for compaction should be removed and
replaced with clean granular material.
c) The ground surface in the construction area should be sloped and sealed with a smooth
drum roller to promote the rapid runoff of precipitation and to prevent ponding of
water.
d) We recommend that the subgrade be protected with a compacted 8-inch-thick (mini-
mum) layer of clean, 1-1/4-inch-minus crushed rock.
' e) Slopes in work areas and soil stockpiles should be covered with plastic, and sloping,
ditching, sumps, dewatering and other measures should be employed as necessary to
permit proper completion of the work. Bales of straw and geotextile silt fences should
be used as appropriate to control soil erosion.
' f) Excavation and placement of fill should be observed on a full-time basis by a person
experienced in wet weather earthwork to determine that all unsuitable materials are
removed and that suitable compaction and site drainage is achieved.
' These recommendations for wet weather earthwork should be included in the contract specifica-
tions.
' Additional Considerations
There are existing utility trenches in the vicinity of the proposed sewerline alignment. These
trenches may have been loosely backfilled and caving conditions may occur in these trenches
during the excavation of the sewerline.
W-6574-01
I
1
11
1
1
Hammond, Collier & Wade -Livingstone
Attn: Mr. Robin Nelson
November 5, 1993
Page 10
LIMITATIONS
SHANNON 6WILSON, INC.
This report was prepared for the exclusive use of Hammond, Collier & Wade -Livingstone
Associates, Inc., and the City of Renton for specific application to the design of the project at
this site as it relates to the geotechnical aspects discussed herein. The data and report should
be provided to prospective contractors and/or the Contractor, for their information, but our
report, conclusions, and interpretations should not be construed as a warranty of subsurface
conditions included in this report.
The analyses, conclusions, and recommendations contained in this report are based on site
conditions as they presently exist and further assume that the explorations are representative of
the subsurface conditions throughout the site, i.e., the subsurface conditions everywhere are not
significantly different from those disclosed by the explorations. If, during construction,
subsurface conditions different from those encountered in these explorations are observed or
appear to be present, we should be advised at once so that we can review these conditions and
reconsider our recommendations, where necessary.
If there is a substantial lapse of time between the submission of this report and the start of work
at the site, or if conditions have changed due to natural causes or construction operations at or
adjacent to the site, we recommend that this report be reviewed to determine the applicability
of conclusions and recommendations considering the changed conditions and time lapse.
We recommend we be retained to review the geotechnical aspects of plans and specifications.
We also recommend we be retained to monitor the geotechnical aspects of construction,
particularly the excavations, shoring, sewerline installation, drainage, and earthwork. This
monitoring would allow us to evaluate the subsurface conditions as they are exposed during con-
struction and to determine that the work is accomplished in accordance with our recommenda-
tions.
The scope of our services for this report did not include any environmental assessment or
evaluation regarding the presence or absence of wetlands or hazardous or toxic materials in the
soil, surface water, groundwater, or air, on or below or around the site.
Unanticipated soil conditions are commonly encountered and cannot be fully determined by
merely taking soil samples or making test borings and pits. Such unexpected conditions
frequently require that additional expenditures be made to attain a properly constructed project.
Therefore, some contingency fund is recommended to accommodate such potential extra costs.
W-6574-01
Hammond, Collier & Wade -Livingstone SHANNON WILSON, INC.
Attn: Mr. Robin Nelson
November 5, 1993
' Page 11
To help you in understanding the use and limitations of our reports, Shannon & Wilson, Inc.
has prepared the attachment "Important Information About Your Geotechnical Engineering
Report. "
It has been a pleasure working on this project. If you have any questions, please do not hesitate
to call.
SHANNON & WILSON, INC.
' Mancj Sharma
Engineer
fl
Ralph N. Boirum, P.E.
Senior Associate
MS:RNB:TEK/dgw
Enclosures: Figure 1 -
Site and Exploration Plan
Figure 2 -
Sewerline Profiles
Figure 3 -
Log of Boring B-1
Figure 4 -
Log of Boring B-2
Figure 5 -
Log of Boring B-3
Figure 6 -
Grain Size Distribution
Figure 7 -
Grain Size Distribution
Figure 8 -
Earth Pressures for Temporary Braced Shoring
Figure 9 -
Earth Pressures, Temporary Shoring, Cantilevered or 1 Row of Braces
Important
Information About Your Geotechnical Engineering Report
W6574-01 XT2/W6574-Ikd/dgw
W-6574-01
NOTES
1. Base map provided by City of Renton.
2. This figure is not for construction purposes.
0 40 80
Scale in Feet
LEGEND
B-1 Boring Designation and
Approximate Location
To b Iz eb i. aA_.,and
r.
SEE SHE,
TO CxiStint rmmnhok (see r�uAel ) and
� -bo exis}in c� ,'v ^'►p station.
Z
ArrAox. pipe 9%oute
:: ::::::: ::::::: ::::::::'�.....:1:::::::::'::::::::: ::::::::: :......:: ::::::::---::::::::---
. . . . . . . . . . . . J. ... .��/ .l-:}. . . . ' : ' .a , . . . . .
i. . . . . . . . . . . . . . . . . . . l"'� i :
270� :....... • ` - -v': _ :::::; : _ ::::::: :::: ___-_ . _ : �_-_-- ' :.._ _ _.� .- ' i s _ �" ..........
Approximate _ __ _ _ { `-
:: ......::: ' ....... :—'Jacking Pit Location �_' ::::::: ::::::::: ::::::::: :::::: 4�- - • ---:: :
1}�> > x:crt m ale" �" .... .
::: ::::: : ' :::::: :... :.. i ...... . ::: A �sro.X.�,pt,ti�i�n. - '� �`'' ::::: FXIS7
.........
:l . �t..
2s _ _
Qf
:i: ,xi . . . _ , �` ... . . . . . .. . . . . . . . . ... . . . . .
L :::::::: :::::::.`. ::::::::: ::::: ���.z J �......... ..
ir rG . . . . . \ . . . . . . : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
..... ::::.. �A :.:.::. ; ...:..: ::....... • ......... ......... .... =- _ ____ -i i= ---- Ex_e
----
::::::::: ::::::::::::::. :::...::: :::::::.: :::.::::: .::::::.:
........................
24
PROFILE N.E. 20TH STREET
PROFILE JONES AVE. N.E.
_ _.......... ---- . - - -- - - - ----760. _Y..C_- - - - --- - - - - - _._... _ ..--- _ .. ...........................- - - -
.. .. � �; : .......: � ...... ......... � .. � t O N NOTE
4- �:
.... . .... . .. j ....... ......... ......... ... ..... �t :...... ....... .... .. .. } ...... o> .... .... Base map provided by City of Renton.
....... ......... .. .... ...... ;C:.....
.........:.........t _ —
N•
........ ... .. p
Ap roximafe�
...... ........ ... .. ....... ....... -i c Jacking Pit Location : . .... ....
j
PROFILE ; ..... ....... ....... ....... :::::::.. --- - - — —
cv o� — �.
�t --.._ ---' -- '- -- --- -- St._ .............. .... --- -- ----------I_..._ Vertical Scale m Feet
---- ----------._ _ -- - - - — -- --- - --- V rt' I S
�cv....... ......... ........ ... ...
... + : :::: :::::::: :: :::. ::: . :.: ::o::: J
ca " .:: j ... .. ` " 8 �° Horizontal Scale in Feet
:. i .... .. ::. :::.:::. ; „ PIP
' ... . . .. : j Vertical Exaggeration = 4X
.......-....... _...._...._.._._..:......... ... : _
_..._. ......__..._.. _......_............._..-- - -- - - -- .. .
. .. ... ....
... ti . - Proposed Gravity Sewerline
:: :::.:.... 3 88 % - _ Highgate Pump Station Elimination
....... ... .... ... .. .. .. Renton,
.1.4 9 - P1pE: G� c� Rento Washington
81O .
•. . . .. ......
. o SEWERLINE PROFILES
2
/331,� .. .. SELF. �. p.Op¢ .Fr! October 1993 W-6574
.... ... ..... . ..
? SHANNON & WILSON INC.
COm CO
_...... _._.. ..-..........._.. -- _...-._._..............................................._......._...:.........................._... ---N N — - ......__..............................._........_........_ ....... ...._...._....._.._ ................. .... . .. .. ons
•� � � �•� Geotechrrical and Environmental Consultants FIG
J
r
Ik l
L�
SOIL DESCRIPTION
li
-a li
Standard Penetration Resistance
s a
: -E
(140 lb. weight, 30" drop)
Surface Elevation: Approx. 261 Feet
o
C3 o
Blows per foot
0 20 40
Asphalt concrete
0.25
0.5 1=
0
: 48
Crushed rock/gravel
F'F-_�::f
21
: : : 50/3"
31
.........:.........
50/2'
Very dense, brown changing to gray at -16', silty,
10
gravelly, fine to medium SAND; numerous cobbles
41:
50/5 "
and probably boulders; dry to moist (locally
TILL -like)
.... . . ..... .
5=
. . : 95/10"
19.5 6=
20
.........:......
50/3"
........................................... .
BOTTOM OF BORING
COMPLETED 8-20-93
.................-....... ............ ........................
NOTE
Could not drill any further because of
cobbles or boulders.
............................................................ -
LEGEND 0 20 40
• % Water Content
I 2" O.D. split spoon sample Impervious seal
TT 3" O.D. thin -wall sample Water level
Sample not recovered Piezometer tip Proposed Gravity Sewerline
Highgate Pump Station Elimination
P Sample pushed Renton, Washington
Atterberg limits: 9
--�—�-- Liquid limit
LOG OF BORING B-1
Natural water content
Plastic limit October 1993 W-6574-01
The stratification lines represent the approx. boundaries
between soil types, and the transition may be gradual. S4IANNON & WILSON, INC. I FIG. 3
Geotechnical and Environmental Consultants
a
7
u
SOIL DESCRIPTION
U_
-o li
Standard Penetration Resistance
a
o r
(140 lb. weight, 30" drop)
Surface Elevation: Approx. 275 Feet
o C/)
c� o
Blows per foot
0 20 40
Asphalt concrete
0.9
ol
0
. :: ;
1=
�........
Loose, light brown, sandy GRAVEL/gravelly
2=
`
SAND; trace of silt; cobbles and possibly boulders;
0.
dry (FILL?)
31
4=
10
........................................................
5=
18
. . .
Very dense, brown (locally gray), silty, gravelly,
6
20
........
.........................
50/4"
fine to medium SAND (locally sandy SILT);
numerous seams of wet, slightly silty to silty, fine
7=
r>
to coarse sand; cobbles and possibly boulders;
4
. . . ."
moist (LOCALLY TILL -LIKE)
o)
8 =
30
.........:.........
.........................................................
50/5"
91
• : 50/5"
10
41 =
40
...................
.............�:.............. _ .........
100/4"
BOTTOM OF BORING
COMPLETED 8-20-93
50
.......................................................
LEGEND 0 20 40
• % Water Content
2" O.D. split spoon sample Impervious seal
TF 3" O.D. thin -wall sample Water level
Proposed Gravity Sewerline
Sample not recovered Piezometer tip
` Highgate Pump Station Elimination
Atterberg limits: P Sample pushed Renton, Washington
�--�--�-- Liquid limit
LOG OF BORING B-2
— Natural water content
Plastic limit October 1993 W-6574-01
The stratification lines represent the approx. boundaries
between soil types, and the transition may be gradual. SHANNON & WILSON, INC. I FIG. 4
Geotechnical and Environmental Consultants
II
1
P"
d
SOIL DESCRIPTION
ti
-a ti
Standard Penetration Resistance
AZ a
: z
(140 lb. weight, 30" drop)
Surface Elevation: Approx. 256 Feet
o U)
o
Blows per foot
0 20 40
Asphalt concrete
0.25
1=
0
Very loose, yellowish -brown to dark brown, silty,
gravelly, fine to medium SAND; organics; moist
ol
(FILL?)
2=
6
31
oo
.. . . . . .
........
: 50/4"
Very dense, brown changing to gray at -20', silty,
4=
10
- - ....- ...................
gravelly, fine to medium SAND (locally sandy silt);
.. . :: . 50/2"
seams of wet, slightly silty, medium to coarse
sand; cobbles and possilby boulders; moist
5=
od,
50/4"
(LOCALLY TILL -LIKE)
6=
20
...................
..............................:....... 0......... I.........
78/10"
25.5 7=
�. : 50/3"
BOTTOM OF BORING
COMPLETED 8-20-93
30
.............................................................
40
..........................................................
50
...... .................
.............................:....
LEGEND 0 20 40
• % Water Content
Z 2" O.D. split spoon sample Impervious seal
7T 3" O.D. thin -wall sample Water level
Proposed Gravity Sewerline
Piezometer tip
Sample not recovered p Highgate Pump Station Elimination
Atterberg limits: P Sample pushed Renton, Washington
--0—i-- Liquid limit
Natural water content LOG OF BORING B-3
Plastic limit August 1993 W-6574-01
The stratification lines represent the approx. boundaries
between soil types, and the transition may be gradual. SHANNON & WILSON, INC. I FIG. 5
Geotechnical and Environmental Consultants
P
rn
SIEVE ANALYSIS
SIZE OF OPENING IN INCHES NUMBER O
N
10 V In N
100
90
60
70
F.`
S
c�
60
m
w 50
Z
LL
Z 40
W
U
Cr
W
°' 30
20
10
0
0
N
HYDROMETER ANALYSIS
:H. U.S. STANDARD t� (+� GRAIN SIZ�pE� IN MMda p
0 ID
v 10 g N O O O O p O 0 p O C
—_ - 10
— w
—
i
I
NOTE
-----The size of samples in the above shown tests was -
limited by the size of the sampler. In our opinion,
the soil also contains numerous cobbles in most
--- and possibly boulders (see boring logs). - - ,--
Instances
-
------
-_—
-
--
_.
-
-
-
-
-
-
B- 3 -�
$ 5
----
}--!
t
r
--
-
-
i
---- ------------
—
A
I
20
30
L7
40 5t
}
m
60 N
Ir
�a
60 8
Z
W
U
70 Cr
n.
so
90
100
$ 0 0 o g 0 0 o w 0 a m N 00 to v of /y ': $ '$ o 0 0 0 8 o 3 o 0 p O CO IO ro N O
N GRAIN SIZE IN.MILLIMETERS o 0 0 0 o G
COBBLES COARSE I. FINE COARSE MEDIUMSAND FINE FINES
GRAVEL
SAMPLE
DEPTH -FT.
U.S.C.
CLASSIFICATION
W.C. %
LL
PL
PI
Proposed Gravity Sewerline
Highgate Pump Station Elimination
B-3
15.0-
SM
Brown, silty, gravelly SAND.
8.2
S- 5
16.5
Renton, Washington
GRAIN SIZE DISTRIBUTION
B-3
20.0-
ML
Gray, sandy SILT.
26.5
S-6
21.5
Set 1993 W-6574-01
SHANNON & WILSON, INC., FIG. 6
Geotechnical Consultants
r �r r r r r■� r� r r r r rr
P
SIEVE ANALYSIS
SIZE OF OPENING IN INCHES NUMBER O
pp N V
tp a 0) N 9
100
90
80
70
3 60
}
m
Ir w 50
Z
U.
Z 40
W
U
Ir
UJ
°' 30
20
10
0
HYDROMETER ANALYSIS
PER INCH. U.S. STANDARD a 1.� GRAIN SIZE IN.MMyp p
W (0
N O 10 8 N C O O O O O O O O O Q
_ 0
-1(-
Extra
-a
_..- NOTE
The size of samples in the above
shown tests was limited by the size of
the sampler. In our opinion, the soil-
- in
- r - --- -- -
-
- -- - _
- --
—
(-
-
-
-
- --
-
j
,--I--i
---
-
-- ---
also contains numerous cobbles
- most instances and possibly boulders
--- (see boring logs).
rrtr-,
_T_
—, I
.,, I-
20
30
Uj
c�
}
m
50 N
cc
a
60 1-
Z
w
U
70 W
a
80
90
100
S $ o m W g Cl)pN o ao a N .- CO �o a M N '; � 8 ao 0 No, o 8 `8 a o s 8
/`+ - GRAIN SIZE IN MILLIMETERS o O p p p
COBBLES COARSE I FINE ICOARSEJ MEDIUM I FINE FINES
GRAVEL SAND
SAIMOPLE
DEPTH -FT.
U.S.C.
CLASSIFICATION
yNAT.
LL
PL
PI
Proposed Gravity Sewerline
Highgate Pump Station Elimination
B-1
0.0-
SM
Gray -brown, silty, gravelly SAND.
8.3
Extra
5.0
Renton, Washington
GRAIN SIZE DISTRIBUTION
B-2
0.0-
GW
Brown, sandy GRAVEL.
2.1
Auger
7.0
B-2
20.0-
ML
Brown, slightly gravelly, sandy SILT.
9.3
S-6
21.5
Set 1993 W-6574-01
SHANNON & WILSON, INC,T
FIG. %
Geotechnical Consultants
1
1�
n
1
Surcharge
Loading (qS)
Loose, gravelly
SAND or sandy FILL
Internal _
Bracing
x
0.3gs
y = 125 pcf
= 330
24H
Ka = 0.30
Elev. x
H
Temporary
Shoring Wall
Very dense, silty,
gravelly SAND
y = 130 pcf
16H
0.2gs = 67.6 pcf
$= 420
Bottom of
Excavation
Ka = 0.20
Kp = 5.00
d
f
225 D — I Not to Scale
LEGEND
7W = Unit weight of water = 62.4 pcf
gs =Surcharge due to traffic,
7. Y = Total and bouyant unit weights of construction equipment and
soil, respectively other loadings
Ka,Kp = Active and passive earth pressure H = Depth of excavation below
coefficients, respectively present ground surface, feet
NOTES
1. This figure is for a temporary shoring system with multiple rows of braces.
It is not applicable to single brace -row or cantilevered shoring systems.
2. Groundwater level inside and outside excavation must be maintained at
least 2 feet below bottom of excavation at all times.
3. Earth and surcharge pressures to be combined. Pressure expressions
are in pounds per square foot (psf).
4. For soldier pile -and -lagging system, below the bottom of the excavation,
active pressures should be assumed to act over the width of the pile (B)
and passive pressures over twice the width of the pile (26) or pile spacing,
whichever is less.
APPROX.
BORING NO.
ELEVATION X
(FEET)
B-1
260.5
B-2
257
B-3
250
Z = Depth of water below bottom of
excavation = 2 feet minimum
D = Depth of pile embedment below
bottom of excavation
B = Soldier pile diameter, feet
d = Zone in which passive pressure should
be ignored. Recommend d = 2 feet
ueotemnicai ano tnvironmentai consuitants
Surcharge
Loading (qs)
H
Temporary
Shoring Wall
Bottom of
Excavation
x 0.3gs
0.2gs
/ 26(H+D-X)
Imo-- -� ► Not to Scale
LEGEND
pcf
qs =Surcharge due to traffic,
of construction equipment and
other loadings
H = Depth of excavation below
present ground surface, feet
�— 38X
26X it
d i
i
D
225 D -
I
water
= 62.4
unit weights
earth pressure
7W = Unit weight of
Y, Y = Total and bouyant
soil, respectively
Ka,Kp = Active and passive
coefficients, respectively
NOTES
1. This figure is for a temporary shoring system that is cantilevered or that
has a single row of braces.
2. Groundwater level inside and outside excavation must be maintained at
least 2 feet below bottom of excavation at all times.
3. Earth and surcharge pressures to be combined. Pressure expressions
are in pounds per square foot (psf).
4. For soldier pile -and -lagging system, below the bottom of the excavation,
active pressures should be assumed to act over the width of the pile (B)
and passive pressures over twice the width of the pile (2B) or pile spacing,
whichever is less.
5. Minimum embedment D equals H.
Loose, gravelly
SAND or sandy FILL
y = 125 pcf
$' = 330
Ka = 0.30
Elev. x
Very dense, silty,
gravelly SAND
y = 130 pcf
y = 67.6 pcf
$' = 42°
Ka = 0.20
Kp = 5.00
APPROX.
BORING NO.
ELEVATION X
(FEET)
B-1
260.5
B-2
257
B-3
250
Z = Depth of water below bottom of
excavation = 2 feet minimum
D = Depth of pile embedment below
bottom of excavation, min. = H
B = Soldier pile diameter, feet
d = Zone in which passive pressure should
be ignored. Recommend d = 2 feet
t W-6574-01
SHANNON & WILSON, INC. Attachment to Report Page 1 of 2
Geotechnical and Environmental Consultants Dated: November 5, 1993
To: _ Hammon o ier & W a e- ivingstone
Attn: Mr. Robin Nelson
' Important Information About Your Geotechnical Engineering/
Subsurface Waste Management (Remediation) Report
' GEOTECHNICAL SERVICES ARE PERFORMED FOR SPECIFIC PURPOSES AND PERSONS.
Consulting geotechnical engineers prepare reports to meet the specific needs of specific individuals. A report prepared for a civil
engineer may not be adequate for a construction contractor or even another civil engineer. Unless indicated otherwise, your consultant
prepared your report expressly for you and expressly for purposes you indicated. No one other than you should apply this report
for its intended purpose without first conferring with the consultant. No party should apply this report for any purpose other than
that originally contemplated without first conferring with the geotechnical engineer/geoscientist.
AN ENGINEERING REPORT IS BASED ON PROJECT -SPECIFIC FACTORS.
iA geotechnical engineering/subsurface waste management (remediation) report is based on a subsurface exploration plan designed
to consider a unique set of project -specific factors. Depending on the project, these may include: the general nature of the structure
and property involved; its size and configuration; its historical use and practice; the location of the structure on the site and its
orientation; other improvements such as access roads, parking lots, and underground utilities; and the additional risk created by scope -
of -service limitations imposed by the client. To help avoid costly problems, have the consulting engineer(s)/scientist(s) evaluate how
any factors which change subsequent to the date of the report, may affect the recommendations. Unless your consulting geotechnical/
civil engineer and/or scientist indicates otherwise, your report should not be used: 1) when the nature of the proposed project is changed
(for example, if an office building will be erected instead of a parking garage, or if a refrigerated warehouse will be built instead of
an unrefrigerated one, or chemicals are discovered on or near the site); 2) when the size, elevation, or configuration of the proposed
project is altered; 3) when the location or orientation of the proposed project is modified; 4) when there is a change of ownership;
or 5) for application to an adjacent site. Geotechnical/civil engineers and/or scientists cannot accept responsibility for problems which
may occur if they are not consulted after factors which were considered in the development of the report have changed.
I
SUBSURFACE CONDITIONS CAN CHANGE.
Subsurface conditions may be affected as a result of natural changes or human influence. Because a geotechnical/waste management
' engineering report is based on conditions which existed at the time of subsurface exploration, construction decisions should not be
based on an engineering report whose adequacy may have been affected by time. Ask the geotechnical/waste management consultant
to advise if additional tests are desirable before construction starts. For example, groundwater conditions commonly vary seasonally.
Construction operations at or adjacent to the site and natural events such as floods, earthquakes, or groundwater fluctuations may also
affect subsurface conditions and, thus, the continuing adequacy of a geotechnical/waste management report. The geotechnical/civil
engineer and/or scientist should be kept apprised of any such events, and should be consulted to determine if additional tests are
' necessary.
MOST GEOTECHNICAL RECOMMENDATIONS ARE PROFESSIONAL JUDGMENTS.
Site exploration and testing identifies actual surface and subsurface conditions only at those points where samples are taken. The data
were extrapolated by your consultant who then applied judgment to render an opinion about overall subsurface conditions. The actual
' interface between materials may be far more gradual or abrupt than your report indicates. Actual conditions in areas not sampled
may differ from those predicted in your report. While nothing can be done to prevent such situations, you and your consultant can
work together to help minimize their impact. Retaining your consultant to observe subsurface construction operations can be particu-
larly beneficial in this respect.
A REPORT'S CONCLUSIONS ARE PRELIMINARY.
The conclusions contained in your geotechnical engineer's report are preliminary because they must be based on the assumption that
conditions revealed through selective exploratory sampling are indicative of actual conditions throughout a site. Because actual
�l
Page 2 of 2
subsurface conditions can be discerned only during earthwork, you should retain your geotechnical engineer to observe actual conditions
and to finalize conclusions. Only the geotechnical engineer who prepared the report is fully familiar with the background information
needed to determine whether or not the report's recommendations based on those conclusions are valid and whether or not the
contractor is abiding by applicable recommendations. The geotechnical engineer who developed your report cannot assume
responsibility or liability for the adequacy of the report's recommendations if another party is retained to observe construction.
THE GEOTECHNICAL ENGINEERING/SUBSURFACE WASTE MANAGEMENT (REMEDIATION) REPORT IS
SUBJECT TO MISINTERPRETATION.
Costly problems can occur when other design professionals develop their plans based on misinterpretation of a geotechnical
engineering/subsurface management (remediation) report. To help avoid these problems, the geotechnical/civil engineer and/or scientist
should be retained to work with other project design professionals to explain relevant geotechnical, geological, hydrogeological and
waste management findings and to review the adequacy of their .plans and specifications relative to these issues.
BORING LOGS AND/OR MONITORING WELL DATA SHOULD NOT BE SEPARATED FROM THE
ENGINEERING/WASTE MANAGEMENT REPORT.
Final boring logs developed by the geotechnical/civil engineer and/or scientist are based upon interpretation of field logs (assembled
by site personnel), field test results, and laboratory and/or office evaluation of field samples and data. Only final boring logs and
data are customarily included in geotechnical engineering/waste management reports. These final logs should not, under any
circumstances, be redrawn for inclusion in architectural or other design drawings, because drafters may commit errors or omissions
in the transfer process.
To minimize the likelihood boring log
of or monitoring well misinterpretation, contractors should be given ready access to the complete
geotechnical engineering/waste management report prepared or authorized for their use. If access is provided only to the report
prepared for you, you should advise contractors of the report's limitations, assuming that a contractor was not one of the specific
persons for whom the report was prepared and that developing construction cost estimates was not one of the specific purposes for
which it was prepared. While a contractor may gain important knowledge from a report prepared for another party, the contractor
should discuss the report with your consultant and perform the additional or alternative work believed necessary to obtain the data
specifically for
appropriate construction cost estimating purposes. Some clients hold the mistaken impression that simply disclaiming
'
responsibility for the accuracy of subsurface information always insulates them from attendant liability. Providing the best available
information to contractors helps prevent costly construction problems and the adversarial attitudes which aggravate them to a
disproportionate scale.
READ RESPONSIBILITY CLAUSES CLOSELY.
Because geotechnical engineering/subsurface waste management,(remediation) is based extensively on judgment and opinion, it is far ,
less exact than other design disciplines. This situation has resulted in wholly unwarranted claims being lodged against geotechnical/
waste management consultants. To help prevent this problem, geotechnical/civil engineers and/or scientists have developed a number
of clauses for use in their contracts, reports and other documents. These responsibility clauses are not exculpatory clauses designed '
to transfer the engineer's or scientist's liabilities to other parties; rather, they are definitive clauses which identify where the engineer's
or scientist's responsibilities begin and end. Their use helps all parties involved recognize their individual responsibilities and take
appropriate.action. Some of these definitive clauses are likely to appear in your report, and you are encouraged to read them closely. '
Your engineer/scientist will be pleased to give full and frank answers to your questions. :
The preceding paragraphs are based on information provided by the
ASFE/Association of Engineering Firms Practicing in the Geosciences, Silver Spring, Maryland
1/93 ,
f;
WETLAND INVESTIGATION OF THE HIGHGATE
LIFT STATION ELIlMIENATION PROJECT
CITY OF RENTON, WASHINGTON
This report documents the results of a field investigation of the Highgate Lift Station
Elimination Project located in the City of Renton near Jones Avenue and NE 20th St (figure
1). The purpose of the investigation was to identify any areas within 75 feet of the proposed
lift station elimination project that could be classified as wetland pursuant to City of Renton
Ordinance No. 4346 (Figure 2). The City of Renton Wetland Inventory Map does list an area
marked as W-29 near the project site as City of Renton Wetlands (Figure 3).
DEFINITIONS AND METHODOLOGY
For the purpose of Section 404 of the Clean Water Act, a wetland is defined as an area
"inundated or saturated by surface or ground water at a frequency and duration sufficient to
support, and that under normal circumstances does support, a prevalence of vegetation
typically adapted for life in saturated soil conditions" (Federal Register 1986:41251).
The technical guidelines of the Federal Interagency Committee for Wetland Delineation
(1989) were used during the fieldwork. These guidelines are the result of a joint effort by the
US Army Corps of Engineers (COE), US. Fish and Wildlife Service (USFWS), Environmental
Protection Agency (EPA) and the Soil Conservation Service (SCS) to provide uniform
methods of wetland delineation. The interaction of vegetation, soils, and hydrology results in
the development of characteristics unique to wetlands. In general, hydrophytic vegetation,
hydric soil, and wetland hydrology must be found for an area to be classified as wetland.
These terms are defined as follows:
Hydrophytic vegetation "...is defined as macrophytic plant life growing in water, soil
or substrate that is at least periodically deficient in oxygen as a result of excessive water
content." (Federal Interagency Committee for Wetland Delineation 1989). The US. Fish and
Wildlife Service Wetland Indicator Status (WIS) ratings were used to make this determination.
The WIS ratings segregate plant species into ecological groups with similar abilities to
withstand saturated soil conditions. Going from high probability to low probability of being in
a wetland, these ratings are: obligate wetland (OBL), facultative wetland (FACW), facultative
(FAC), facultative upland (FACU), and upland (UPL) (See Table A for complete description).
"A hydric soil is a soil that in its undrained condition is saturated, flooded, or ponded
long enough during the growing season to develop anaerobic conditions that favor the growth
and regeneration of hydrophytic vegetation" (Soil Conservation Service 1985). The
morphological characteristics of the soils around the project were examined to determine
whether any could be classified as hydric according to the definition of the US. Soil
11
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LARGE PASTURE 1 I I
47
4-
EXISTING BERRY FARM
O
EXISTING SEWERS IN N.E. 20TH ST.
2
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EXISTING HIGATE
SEWAGE
lb
PUMP STATION
126.14
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4
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256 /4
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FIGURE #2
PROJECT AREA
MAP
HAMMOND, COLLIER & WADE — LIVINGSTONE ASSOCIATES, INC.
Conservation Service.
Wetland hydrology gives evidence of permanent or periodic inundation, or soil
saturation for a significant period (usually a week or more) during the growing season. Areas
with wetland hydrology are those where the presence of water has an overriding influence on
characteristics of vegetation and soils. While inundation and soil saturation are usually an
obvious indicator, lack of those conditions does not preclude a wetland determination. Other
indicators of wetland hydrology can include water marks, drift lines, water borne sediment
deposits, water stained leaves, and wetland drainage patterns.
FIELD SAMPLING PROCEDURES
Field work was conducted on May 18, 1993 by Marilyn Phelps of Cascade
Environmental Services to identify and delineate wetlands on the subject property. Mr. Robert
Bergstrom, project engineer for Hammond, Collier & Wade - Livingstone Associates
accompanied and provided information about the general layout and land use of the area.
Plant communities were inventoried, classified, and described by field inspection.
Representative areas were inspected for both upland and wetland areas at the project site.
Soil pits were dug to determine whether hydric soils were present and hydrologic
conditions were reviewed to help determine whether or not wetland conditions were present.
EXISTING CONDITIONS
General Project Description
The project area is a nearly flat, overgrown and brushy site with a small creek running
through the middle and a small pond on the northwest end of the site. The pond has a small
concrete dam at the north end that has been breached to allow more water to flow through.
The area to the east of the creek is relatively open with few trees and mostly blackberry vines
and stinging nettle vegetation. The area on both sides of the creek appears to have been
significantly altered over the years and in fact the perfectly straight streambed of the creek
suggests it has been changed from its original course. From N.E. 20th St. to about the middle
of the project area is an old gravel roadbed that has been overgrown with blackberry and
horsetail. There is an old barn or shed at the center of the project area and a long row of
Lombardy Poplars have been planted on the immediate west side of the creek. These extend
from N.E. 20th Street almost to the pond. Ornamental shrubs, fruit trees, and overgrown
grassy areas all suggest evidence of significant human development. The entire area is in a
residential neighborhood, although it is not densely populated.
There are three wetland areas on the site, all within 75 feet of the proposed lift station
elimination project (See figure 4). Site one extends along the east side of the creek from
immediately behind the garage of the residence on NE 20th Street to the north end of the
project area. It is a narrow band paralleling the creek and extending approximately 10-15 feet
due east. Site 2 is the area immediately surrounding the small pond at the northwest end of the
site. Site 3 is a shallow ditch approximately in the center of the project area. Due to the small
size of the wetlands and nearby stream, it does not appear to be directly connected to streams
with an average annual flow of at least 5 cubic feet per second, or perennial lakes. Thus, the
wetlands could probably be considered isolated and above the headwaters, as defined by the
COE. I emphasize, however, that the COE has ultimate authority to first determine whether or
not this area is a wetland under their jurisdiction, and then to determine its status with regard
to other water bodies in the vicinity.
There were several shallow (3" to 6" deep) channels on both sides of the creek running
perpendicular to it and into the creek. The soil in the ditches was wetter than the surrounding
soils and a few contained standing water indicating the present water table.
The soil of the project area has been mapped by the Soil Conservation Service as
belonging to the Shalcar (Sm) series surrounded by the Indianola (InQ series (Figure 5).
Shalcar muck is comprised of very poorly drained organic soils that are stratified with mineral
soils and overlie mineral soil material at a depth of 16 to 30 inches. Slopes are 0 to 1 percent.
Soil from this series is used for row crops and pasture. Indianola loamy fine sand is found on 4
to 15% slopes and is somewhat excessively drained. It is good for urban development as well
as growing timber.
For ease of description, the site will be described in two separate sections - 1.) the area
east of the creek and 2.) the area west of the creek.
1.) Site East of Creek
Vegetation
The vegetation along the east side of the creek was quite uniform. It was almost
entirely composed of blackberry brambles, stinging nettles, grasses and some horsetail. There
are no trees for at least 220' into the site. Nettles and horsetail are facultative or wetter, while
blackberry is occasionally found in wetlands. Based on observation and analysis, the
vegetation of the site would be classified as hydrophytic according to federal guidelines.
Soil
The soil on the 10-15' wide strip was saturated, black and mucky. It contained very
fine silt and organic matter extending to a depth of 12 inches or more. This description
satisfies the federal guidelines for hydric soil so the site does qualify as a wetland based on soil.
The soil east of the wetland area was somewhat mounded up and could possibly have been
dredged from the creek at one time. It was sandier and was not saturated or mucky. It is
possible that many of the blackberry brambles were growing from this area and spreading out
to the wetter area.
Hydrology
The existence of saturated soil is an indicator for wetland hydrology even in the
absence of any other evidence. Given that this site is also right next to a flowing creek, it is
presumed that the water table is at or near the surface. Therefore the site does qualify as a
wetland based on hydrology according to federal guidelines.
CONCLUSION
This site definitely displays wetland characteristics based on soil and hydrology. The
Vegetation indicators are not as strong, but this could be due to the fact that the original
vegetation has almost certainly been altered. It is likely that the site from the creek east for
several hundred feet has been used for pasture or row crops and has been allowed to grow up
in the past 10 years. Based upon observation and determination, this site does qualify as a
Category 3 (Lower Quality - Disturbed) wetland, under ordinance #4346 section 4-32-3-D3a.
2.) Site West of Creek
Vegetation
The vegetation in this area was much more diverse and included trees as well as both
wild and ornamental plants. The tree species included willow, cottonwood, alder and several
fruit trees. The Lombardy poplars were also on this side of the creek. The understory
included wild raspberry, buttercup, horsetail, and some nettles on the south end. The area
surrounding the small pond has grown up to grass and there were several ornamental shrubs in
the immediate vicinity. All of the native species observed were facultative or wetter which
satisfies the criteria for wetland vegetation.
Soils
The soil surrounding the pond for a distance of 10-20 feet was a saturated, very dark brown,
mucky, very fine silt extending to a depth of 12 inches or more. This satisfies the federal
requirement for hydric soil. There was also an area of similar type soil in a small depression
that ran into the creek about halfway through the project site. This area was approximately 5-
10 feet wide and the soil also met criteria for hydric soil. Both these soils fit the soil profile for
Shalcar soil which is listed as a hydric soil. The soil in the remainder of the site was also black
but was not saturated. It was gravely and quite compacted at the south end of the site. Mr.
Bergstrom stated that there had been an old gravel road at that location that was no longer in
use. The site conditions observed would agree with that statement. The soil along the rest of
the proposed project area was relatively loose, sandy, well drained, black and slightly organic
and did not display wetland characteristics such as gleying, mottling or evidence of saturation.
There was very little or no clay content in the soil and it did not feel sticky or "greasy." The
water table was not evident down to a depth of 18 inches in this soil. This description does not
fit the Shalcar soil series profile, nor does it fit the profile of the surrounding Indianola soil
series. For purposes of determination, it was not observed to be considered as a hydric soil
based on its characteristics. Therefore, the remainder of the site would not qualify as a
wetland based on soils.
Hydrology
This site displays evidence of considerable human intervention. The pond is obviously
manmade, as indicated by the dam, and the creek has very likely been dredged and/or
channeled. There is an old storage shed near the middle of the site and the old roadbed leading
to it. There has been deliberate effort made to divert, contain or otherwise manage the
hydrology of this site. The presence of saturated soil is enough to qualify the area around the
pond and ditch as a wetland based on hydrology. The manmade alterations of ditching and
channeling have effectively drained the other drier, slightly higher ground, removing any
hydrologic indicators of wetland status. That area would not now be considered as a wetland
based on hydrology.
CONCLUSION
This site does contain two small wetland areas. One was obviously manmade (the area
surrounding the pond) and the other may or may not have been manmade (the ditch). The rest
of the area does display some wetland characteristics (hydrophytic vegetation) but the drained
soils preclude it from meeting all the criteria for a true wetland. It is definitely a disturbed
area and it is difficult to determine what the original state of the entire area was.
Given that the site has been disturbed and is no longer in a true natural state, the two
wetland areas would qualify as Category 3 (Lower Quality - Disturbed ) wetland under
Ordinance #4346, section 4-32-3-D3a.
TABLE 1
Key to Wetland Indicator Status (WIS) Categories
Indicator Indicator
Category Symbol Definition
Obligate OBL Plants that occur almost always
(estimated probability >99%) in
wetlands under natural conditions,
but which may also occur rarely
(est. probability <1%) in non wetlands.
Facultative FACW Plants that occur usually (est.
Wetland probability >67% - 99%) in wetlands,
Plants but also occur (est. probability 1% -
33%) in non wetlands.
Facultative FAC Plants with a similar likelihood
Plants (est. probability 33% - 67%) of
occurring in both wetlands and
non -wetlands.
Facultative FACU Plants that occur sometimes (est.
Upland probability 1% - <33%) in wetlands,
Plants but occur more often (est. probab-
ility >67% - 99%) in non wetlands.
Obligate UPI, Plants that occur rarely (est.
Upland probability <1%) in wetlands, but
Plants occur almost always (est. probab-
ility >99%) in non wetlands under
natural conditions.
A + sign after the indicator symbol indicates a frequency toward the higher end of the
category (more frequently found in wetlands), and a - sign indicates a frequency toward the
lower end of the category (less frequently found in wetlands.)
Table 2 Plant Species and Indicator Symbol for
Vegetation at Project Site
Willow
Salix spp.
FACW
Red Alder
Alnus rubra
FAC
Cottonwood
Populous deltoides
FAC
Blackberry
Rubus discolor
FACU-
Raspberry
Rubus pedatus
FAC-
Buttercup
Ranunculus repens
FACW
Horsetail
Equisetum fluviatile
FACW
Stinging nettle
Urtica divica
FAC+
S 17
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FIGURE #3
CITY OF RENTON
WETLANDS
INVENTORY MAP
HAMMOND, COLLIER & WADE - LIVINGSTONE ASSOCIATES, INC.__!
/V 12;°��� WETLAND #2
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LARGE PASTURE
306
302 3
- -- 1. e.AM w•Ol'•
vA6i C5 16• To 4'..°c
WETLAND #1
EAST BANK OF CREEK,
s� NORTH OF
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FIGURE #4 12 y • �3 w .39 .790_�r..� S ♦ 3 78d 19 . b7 • 1 6 a% 497
PROJECT AREA ••• `. •�
SURVEY MAP EXISTING BERRY FARM
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RENTON 1.7 M1.
FIGURE #5
Scale 1:24 000 SOIL CONSERVATION
SERVICE
INVENTORY MAP
HAM M0ND, COLLIER & WADE — LIVINGSTONE ASSOCIATES, INC.—
SOIL SURVEY
King County Area
Washington
0
UNITED STATES DEPARTMENT OF AGRICULTURE
Soil Conservation Service
in cooperation with
WASHINGTON AGRICULTURAL EXPERIMENT STATION
Issued November 1973
gravelly coarse sand to very gravelly loamy sand.
Depth to the IIC horizon ranges from 18 to 36
inches.
Some areas are up to 5 percent included Alderwood
soils, on the more rolling and undulating parts of
the landscape; some are about 5 percent the deep,
sandy Indianola soils; and some are up to 25 percent
Neilton very gravelly loamy sands. Also included
in mapping are areas where consolidated glacial till,
which characteristically underlies Alderwood soils,
is at a depth of 5 to 15 feet.
Permeability is rapid. The effective rooting
depth is 60 inches or more. Available water capac-
ity is low. Runoff is slow, and the erosion hazard
is slight.
This soil is used for timber and pasture and for
urban development. Capability unit IVs-1; woodland
group 3f3.
Everett gravelly sandy loam, 5 to 15 percent
slopes (EvC).--This soil is rolling. Areas are
irregular in shape, have a convex surface, and range
from 25 acres to more than 200 acres in size. Run-
off is slow to medium, and the erosion hazard is
slight to moderate.
Soils included with this soil in mapping make up
no more than 25 percent of the total acreage. Some
areas are up to 5 percent Alderwood soils, which
overlie consolidated glacial till; some are up to
20 percent Neilton very gravelly loamy sand; and
some are about 15 percent included areas of Everett
soils where slopes are more gentle than 5 percent
and where they are steeper than 15 percent.
This Everett soil is used for timber and pasture
and for urban development. Capability unit VIs-1;
woodland group 3f3.
Everett gravelly sandy loam, 15 to 30 percent
slopes (EvD).--This soil occurs as long, narrow
areas, mostly along drainageways or on short slopes
between terrace benches. It is similar to Everett
gravelly sandy loam, 0 to 5 percent slopes, but in
most places is stonier and more gravelly.
Soils included with this soil in mapping make up
no more than 30 percent of the total acreage. Some
areas are up to 10 percent Alderwood soils, which
overlie consolidated glacial till; some are up to 5
percent the deep, sandy Indianola soils; some are
up to 10 percent Neilton very gravelly loamy sand;
and some are about 15 percent included areas of
Everett soils where slopes are less than 15 percent.
Runoff is medium to rapid, and the erosion hazard
is moderate to severe.
Most of the acreage is used for timber. Capa-
bility unit VIe-l; woodland group 3f2.
Everett-Alderwood gravelly sandy loams, 6 to 15
percent slopes (EwQ --This mapping unit is about
equal parts Everett and Alderwood soils. The soils
are rolling. Slopes are dominantly 6 to 10 percent,
but range from gentle to steep. Most areas are
irregular in shape and range from 15 to 100 acres
or more in size. In areas classified as Everett
soils, field examination and geologic maps indicate
16
the presence of a consolidated substratum at a depth
of 7 to 20 feet. This substratum is the same mate-
rial as that in the Alderwood soils.
Some areas are up to 5 percent included Norma,
Seattle, and Tukwila soils, all of which are poorly
drained.
Runoff is slow to medium, and the erosion hazard
is slight to moderate.
Most of the acreage is used for timber. Capabil-
ity unit VIs-l; woodland group 3f3.
Indianola Series
The Indianola series is made up of somewhat
excessively drained soils that formed under conifers
in sandy, recessional, stratified glacial drift.
These undulating, rolling, and hummocky soils are on
terraces. Slopes are 0 to 30 percent. The annual
precipitation is 30 to S5 inches, and the mean
annual air temperature is about 50' F. The frost -
free season is 150 to 210 days. Elevation ranges
from about sea level to 1,000 feet.
In a representative profile, the upper 30 inches
is brown, dark yellowish -brown, and light olive -
brown loamy fine sand. This is underlain by olive
sand that extends to a depth of 60 inches or more
(pl. I, right).
Indianola soils are used for timber and for urban
development.
Indianola loamy fine sand, 4 to 15 percent slopes
(InC).--This undulating and rolling soil has convex
slopes. It is near the edges of upland terraces.
Areas range from 5 to more than 100 acres in size.
Representative profile of Indianola loamy fine
sand, 4 to 15 percent slopes, in forest, 1,000 feet
west and 900 feet south of the northeast corner of
sec. 32, T. 25 N., R. 6 E.:
01--3/4 inch to 0, leaf litter.
B21ir--0 to 6 inches, broom (10YR 4/3) loamy fine
sand, brown (10YR 5/3) dry; massive; soft,
very friable, nonsticky, nonplastic; many
roots; slightly acid; clear, smooth boundary.
4 to 8 inches thick.
B22ir--6 to 15 inches, dark yellowish -brown (lOYR
4/4) loamy fine sand, brown (10YR 5/3) dry;
massive; soft, very friable, nonsticky, non -
plastic; common roots; slightly acid; clear,
smooth boundary. 6 to 15 inches thick.
C1--15 to 30 inches, light olive -brown (2.5Y 5/4)
loamy fine sand, yellowish brown (10YR 6/4)
dry; massive; soft, very friable, nonsticky,
nonplastic; common roots; slightly acid;
gradual, smooth boundary. 12 to 17 inches
thick.
C2--30 to 60 inches, olive (5Y 5/4) sand, light
brownish gray (2.5Y 6/2) dry; single grain;
loose, nonsticky, nonplastic; few roots;
slightly acid. Many feet thick.
There is a thin, very dark brown Al horizon at
the surface in some places. The B horizon ranges
from very dark grayish brown to brown and dark
yellowish brown. The C horizon ranges from dark
grayish brown to pale olive and from loamy fine sand
to sand. Thin lenses of silty material are at a
depth of 4 to 7 feet in some places.
Soils included with this soil in mapping make up
no more than 25 percent of the total acreage. Some
areas are up to 10 percent Alderwood soils, on the
more rolling and undulating parts of the landscape;
some are up to 8 percent the deep, gravelly Everett
and Neilton soils; some are up to 15 percent Kitsap
soils, which have platy lake sediments in the sub-
soil; and some are up to 15 percent Ragnar soils,
which have a sandy substratum.
Permeability is rapid. The effective rooting
depth is 60 inches or more. Available water capac-
ity is moderate. Runoff is slow to medium, and the
erosion hazard is slight to moderate.
This soil is used for timber and for urban devel-
opment. Capability unit IVs-2; woodland group 4s3.
Indianola loamy fine sand, 0 to 4 percent slopes
(InA).--This soil occupies smooth terraces in long
narrow tracts adjacent to streams. areas range from
about 3 to 70 acres in size.
Soils included with this soil in mapping make up
no more than 20 percent of the total acreage. Some
areas are up to 5 percent Alderwood soils, on the
more rolling and undulating parts of the landscape;
some are about 10 percent the deep, gravelly Everett
and Neilton soils; some are up to 10 percent Indian-
ola loamy fine sand that has stronger slopes; and
some areas are up to 10 percent the poorly drained
Norma, Shalcar, Tukwila soils.
Runoff is slow, and the erosion hazard is slight.
This soil is used for timber. Capability unit
IVs-2; woodland group 4s3.
Indianola loamy fine sand, 15 to 30 percent
slopes (InD).--This soil is along entrenched streams.
Soils included with this soil in mapping make up
no more than 25 percent of the total acreage. Some
areas are up to 10 percent Alderwood soils; some are
about 5 percent the deep, gravelly Everett and Neil -
ton soils; some are up to 15 percent Kitsap soils,
which have platy, silty lake sediments in the sub-
soil; and some are up to 15 percent Indianola loamy
fine sand that has milder slopes.
Runoff is medium, and the erosion hazard is moder-
ate to severe.
This soil is used for timber. Capability unit
VIe-1; woodland group 4s2.
Kitsap Series
The Kitsap series is made up of moderately well
drained soils that formed in glacial lake deposits,
under a cover of conifers and shrubs. These soils
are on terraces and strongly dissected terrace
fronts. They are gently undulating and rolling and
moderately steep. Slopes are 2 to 70 percent.
Platy, silty sediments are at a depth of 18 to 40
inches. The annual precipitation is 35 to 60 inches,
and the mean annual air temperature is about 50' F.
The frost -free season is 150 to more than 200 days.
Elevation ranges from about sea level to 500 feet.
In a representative profile, the surface layer
and subsoil are very dark brown and dark yellowish -
brown silt loam that extends to a depth of about 24
inches. The substratum is olive -gray silty clay
loam. It extends to a depth of 60 inches or more.
Kitsap soils are used for timber and pasture.
Kitsap silt loam, 2 to 8 percent slopes (KpB).--
This undulating soil is on low terraces of the major
valleys of the Area. Areas range from 5 acres to
more than 600 acres in size and are nearly circular
to irregular in shape. Some areas are one -eighth to
a half mile wide and up to 3 or 4 miles long.
Representative profile of Kitsap silt loam, 2 to
8 percent slopes, in pasture, 820 feet west and 330
feet south of east quarter corner of sec. 28, T. 25
N., R. 7 E.:
Ap--O to 5 inches, very dark brown (10YR 2/2) silt
loam, dark grayish brown (10YR 4/2) dry; mod-
erate, medium, granular structure; slightly
hard, very friable, nonsticky, nonplastic;
many roots; medium acid; abrupt, smooth bound-'
ary.
B2--5 to 24 inches, dark yellowish -brown (10YR 3/4)
silt loam, brown (10YR 5/3) dry; 2 percent
iron concretions; weak, coarse, prismatic
structure; slightly hard, friable, slightly
sticky, slightly plastic; many roots; slightly
acid; abrupt, wavy boundary. 18 to 21 inches
thick.
IIC--24 to 60 inches, olive -gray (SY 5/2) silty clay
loam, light gray (5Y 7/2) dry; many, medium
and coarse, prominent mottles of dark yellowish
brown and strong brown (10YR 4/4 and 7.SYR
5/8); moderate, thin and medium, platy struc-
ture; hard, firm, sticky, plastic; few roots
to a depth of 36 inches, none below; strongly
acid.
The A horizon ranges from very dark brown to dark
brown. The B horizon ranges from dark yellowish
brown to dark brown and from silt loam to silty clay
loam. The platy IIC horizon ranges from grayish
brown to olive gray and from silt loam to silty clay
loam that has thin lenses of loamy fine sand in
places. Brownish mottles are common in the upper
part of the IIC horizon.
Some areas are up to 10 percent included Alderwood
gravelly sandy loam; some are up to 5 percent the
very deep, sandy Indianola soils; and some are up to
5 percent the poorly drained Bellingham, Tukwila,
and Seattle soils.
Water flows on top of the substratum in winter.
Permeability is moderate above the substratum and
very slow within it. The effective rooting depth is
about 36 inches. Available water capacity is moder-
ate to moderately high. Runoff is slow to medium,
and the erosion hazard is slight to moderate.
This soil is used for timber and pasture. Capabil-
ity unit IIIe-l; woodland group M .
17
are 0 to 1 percent. The annual precipitation is 35
to 80 inches, and the mean annual air temperature is
about 500 F. The frost -free season ranges from 150
to 200 days. Elevation ranges from 25 to 750 feet.
In a representative profile, the surface layer is
r very dark brown muck about 14 inches thick. Below
this is 5 inches of grayish -brown silt loam and
dark -gray very fine sandy loam. The next 5 inches
is black and very dark brown muck. The underlying
material is mottled grayish -brown, dark -gray, black,
and very dark grayish -brown silt loam to loamy sand
that extends to a depth of 60 inches or more.
Shalcar soils are used for row crops and pasture.
Shalcar muck (Sm).--This nearly level soil is in
rounded and irregularly shaped areas that range from
1 to about 30 acres in size. Slopes are less than 1
percent.
Representative profile of Shalcar muck, in pas-
ture, 280 feet east and 1,220 feet north of center
of sec. 35, T. 22 N., R. 4 E.:
Oal--O to 9 inches, very dark brown (10YR 2/2) muck,
grayish brown (2.5Y 5/1) dry; many, large,
prominent, strong -brown (7.5YR 5/6) mottles
dry; moderate, medium, granular structure;
slightly hard, very friable, sticky, plastic;
many roots; medium acid; abrupt, smooth bound-
ary. 9 to 11 inches thick.
Oa2--9 to 14 inches, very dark brown (10YR 2/2) muck
and pockets of silt loam; muck is black (10YR
2/1), very dark brown (10YR 2/2), and brown
(10YR 4/3) dry; silt loam is light gray (10YR
7/2) dry; moderate, thin, platy structure;
slightly hard, very friable, slightly sticky,
slightly plastic; many roots; very strongly
acid; abrupt, smooth boundary. 3 to 5 inches
thick.
C1--14 to 16 inches, grayish -brown (2.5Y 5/2) silt
loam, light gray (2.5Y 7/2) dry; many, medium,
prominent, brown (7.5YR 4/4) and strong -brown
(7.5YR 5/6) mottles, brown (7.5YR 4/4) and
reddish yellow (7.5YR 7/6) dry; massive; hard,
firm, sticky, plastic; few roots; extremely
acid; clear, smooth boundary. 0 to 2 inches
thick.
C2--16 to 23 inches, dark -gray (SY 4/1) fine sandy
loam, gray (5Y 6/1) dry; many, medium, promi-
nent, dark -brown (7.SYR 3/2) and dark reddish -
brown (5YR 3/4) mottles, yellowish brown (10YR
5/8) and brownish yellow (10YR 6/6) dry;
massive; slightly hard, very friable, nonsticky,
nonplastic; few roots; extremely acid; clear,
wavy boundary. 0 to 10 inches thick.
Oa3--23 to 28 inches, black (10YR 2/1) and very dark
brown (10YR 2/2) muck and 25 percent dark -gray
(5Y 4/1) fine sandy loam, gray (5Y 6/1 and
5/1) dry; common, medium, prominent mottles of
yellowish brown (10YR 5/8) dry; moderate, thin,
platy structure; slightly hard, very friable,
slightly sticky, slightly plastic; few roots;
very strongly acid; clear, wavy boundary. 4
to 6 inches thick.
C3--28 to 60 inches, very dark grayish -brown (2.5Y
3/1) loamy sand, gray (5Y 5/1) dry; common,
medium, prominent, dark yellowish -brown (10YR
4/4) mottles and few, medium, prominent mottles
of yellowish brown (10YR 5/6 and 5/8) dry;
massive; soft, very friable, nonsticky, non -
plastic; few roots; very strongly acid.
The muck and mucky peat layers range in color
from black to very dark brown, have a combined thick-
ness of 16 to 28 inches, and occur within a depth
of 32 inches. Thin layers of mineral soil material
also occur within this depth in places. The mineral
C horizon is loamy sand to silty clay loam and is
mottled very dark grayish brown, gray, and olive
gray.
Some areas are up to 30 percent inclusions of the
very deep muck and mucky peat Tukwila and Seattle
soils; and some areas are up to 15 percent the poor-
ly drained Norma, Bellingham, Puget, and Snohomish
soils. Inclusions make up no more than 30 percent
of the total acreage.
Permeability is moderate in the organic layers
and moderate to rapid in the lower part of the pro-
file. There is a seasonal high water table at or
near the surface. If the water table is controlled,
the effective rooting depth is 60 inches or more. In
undrained areas, rooting depth is restricted. The
available water capacity is high. Runoff is ponded.
There is no erosion hazard.
This soil is used for row crops and pasture. Ca-
pability unit IIw-3; no woodland classification.
Si Series
The Si series is made up of moderately well drain-
ed soils that formed under grass and hardwoods, in
alluvium on stream terraces near North Bend. Slopes
are 0 to 2 percent. The annual precipitation is 70
to 80 inches, and the mean annual air temperature is
about 50° F. The frost -free season is about 150
days. Elevation ranges from 400 to 500 feet.
In a representative profile, the surface layer
and upper part of the subsoil are dark grayish -brown
silt loam about 25 inches thick. The lower part of
the subsoil, to a depth of 60 inches or more, is
mottled dark grayish -brown, very dark gray, and
olive -gray stratified silt loam, loamy sand, and
very fine sandy loam.
Si soils are used for row crops and pasture.
Si silt loam (Sn).--This soil is on stream ter-
races. Slopes are mostly less than 2 percent and
convex. Areas range from 2 to about 100 acres in
size.
Representative profile of Si silt loam, in pas-
ture, 1,650 feet south and 100 feet west of the
north quarter corner of sec. 34, T. 24 N., R. 8 E.:
Ap--O to 7 inches, dark grayish -brown (10YR 4/2)
silt loam, grayish brown (10YR 5/2) dry; weak,
medium, crumb structure; hard, very friable,
slightly sticky, slightly plastic; many roots;
medium acid; clear, smooth boundary. 6 to 9
inches thick.
29