DNS BLD2021-0810+Infiltration_Report+7.23.2021_8.53.06_AM+2317835COBALT
G E 0 S C I E N C E S
Preliminary Infiltration Evaluation
Proposed Four Lot Plat
Parcel No. 00452000400800
Edmonds, Washington
February 27, 2019
PRELIMINARY INFILTRATION EVALUATION
EDMONDS, WASHINGTON
Table of Contents
i.o INTRODUCTION............................................................................................................. 1
2.0 PROJECT DESCRIPTION.............................................................................................. 1
3.0 SITE DESCRIPTION....................................................................................................... 1
4.o FIELD INVESTIGATION............................................................................................... 2
4.1.1 Site Investigation Program................................................................................... 2
5.0 SOIL AND GROUNDWATER CONDITIONS.............................................................. 2
5.1.1 Area Geology........................................................................................................ 2
5.1.2 Groundwater........................................................................................................ 3
6.o DISCUSSION................................................................................................................... 4
6.1.1 General.................................................................................................................4
7.o RECOMMENDATIONS.................................................................................................. 4
7.1.1 Water Quality and Regulatory Guidance............................................................... 4
7.1.2 Preliminary Infiltration Recommendations.......................................................... 4
8.o CLOSURE......................................................................................................................... 5
LIST OF APPENDICES
Appendix A
— Statement of General Conditions
Appendix B
— Figures
Appendix C
— Exploration Logs
Appendix D
— Sieve Analyses
PRELIMINARY INFILTRATION EVALUATION
EDMONDS, WASHINGTON
February 27, 2019
i.o Introduction
COBALT
GEOSCIENCES
In accordance with your authorization, Cobalt Geosciences, LLC (Cobalt) has completed a preliminary
infiltration evaluation for the proposed four lot plat located at 7901 - 240th Street SW in Edmonds,
Washington (Figure 1).
The purpose of the investigation was to identify subsurface conditions and to provide preliminary
recommendations for infiltration system design, including infiltration rates for use in shallow and deep
injection systems.
2.0 Project Description
The project includes subdivision of the parcel into four new lots followed by construction of four new
residences and an access roadway. The provided site plans indicate that the roadway will extend north
along the western portion of the property and the residences will be situated generally to fit a relatively
steep slope in the central portion of the property.
Stormwater management may include infiltration devices (if feasible), detention, rain gardens, and/or
detention systems. We should be provided with the plans to verify that our recommendations are valid.
Deep infiltration wells, known as Underground Injection Control (UIC) wells, could be utilized depending
on the depth to suitable soils with adequate clearance above groundwater.
3.0 Site Description
The site is located at 7901 — 240th Street SW in Edmonds, Washington (Figure 1). The property consists
of one rectangular shaped parcel (No. 00452000400800) with a total area of about o.9 acres.
Based on a review of historic aerial photographs, the property has previously been developed with
residential structures from at least 1958 up to the early to mid-196os.
Currently, the property is undeveloped and vegetated with grasses, ivy, blackberry vines, along with
variable diameter deciduous and evergreen trees.
The site slopes from west to east at variable magnitudes. There is a steep slope within the central portion
of the property that extends north to south and slopes to the east. The slope is generally 8 to 16 feet in
height and has magnitudes of 30 to ioo percent. The western and eastern portions of the property are
gently sloping to nearly level and the western portion appears to have been graded as an access roadway
at one time.
The site is bordered to the north, west, and east by residential developments and to the south by 240th
Street SW.
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Kenmore, WA 98028
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PRELIMINARY INFILTRATION EVALUATION
EDMONDS, WASHINGTON
February 27, 2019
4.o Field Investigation
4.1.1 Site Investigation Program
COBALT
G E 0 S C I E N C E S
The field investigation program was completed on August 30, 2018 and included excavating and sampling
five test pits within the property for subsurface analysis.
We also drilled two hollow stem auger borings on December 7, 2018 and January 11, 2019 to evaluate the
deeper subsurface soil and groundwater conditions. The borings were drilled using hollow stem auger
truck -mounted and track -mounted rigs.
Disturbed soil samples were obtained during drilling by using the Standard Penetration Test (SPT) as
described in ASTM D-1586. The Standard Penetration Test and sampling method consists of driving a
standard 2-inch outside -diameter, split barrel sampler into the subsoil with a 140-pound hammer free
falling a vertical distance of 30 inches. The summation of hammer -blows required to drive the sampler
the final 12-inches of an 18-inch sample interval is defined as the Standard Penetration Resistance, or N-
value. The blow count is presented graphically on the boring logs in this appendix. The resistance, or "N"
value, provides a measure of the relative density of granular soils or of the relative consistency of cohesive
soils.
The soils encountered were logged in the field and are described in accordance with the Unified Soil
Classification System (USCS).
A Cobalt Geosciences field representative conducted the explorations, collected disturbed soil samples,
classified the encountered soils, kept a detailed log of the explorations, and observed and recorded
pertinent site features.
The results of the explorations are presented on the logs enclosed in Appendix C. Laboratory analyses are
also included in Appendix D.
5.o Soil and Groundwater Conditions
5-m Area Geology
The site lies within the Puget Lowland. The lowland is part of a regional north -south trending trough that
extends from southwestern British Columbia to near Eugene, Oregon. North of Olympia, Washington,
this lowland is glacially carved, with a depositional and erosional history including at least four separate
glacial advances/retreats. The Puget Lowland is bounded to the west by the Olympic Mountains and to
the east by the Cascade Range. The lowland is filled with glacial and non -glacial sediments consisting of
interbedded gravel, sand, silt, till, and peat lenses.
The Geologic Map of the Edmonds East and West Quadrangle indicates that the site is underlain by
Vashon Glacial Till.
2
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PRELIMINARY INFILTRATION EVALUATION
EDMONDS, WASHINGTON
February 27, 2019
L � COBALT
GEOSCIENCES
Vashon Glacial Till is typically characterized by an unsorted, non -stratified mixture of clay, silt, sand,
gravel, cobbles and boulders in variable quantities. These materials are typically dense and relatively
impermeable. The poor sorting reflects the mixing of the materials as these sediments were overridden
and incorporated by the glacial ice.
Vashon Glacial Till is typically underlain by Vashon Advance Outwash. These materials consist of fine to
medium grained sand with local interbeds of silt. Regional groundwater is often located near the base of
the Vashon Advance Outwash unit. These deposits are typically permeable and suitable for infiltration of
stormwater runoff.
Test Pits
In general, the test pits encountered variable thicknesses of topsoil and vegetation underlain by up to 8
feet of loose to dense fill. The fill appears to be thickest along the upper bench in the western portion of
the property extending over and into the steep slope in the central portion of the property. The fill was
underlain by weathered and/or unweathered glacial till which consists of medium dense to very dense,
silty -fine to medium grained sand with gravel.
It appears that the site was graded on one or more occasions during previous site development activities.
The depth and extent of the fill could not be fully determined through test pit excavations due to access
limitations.
Soil Borings
Both borings encountered approximately 8 to 12 inches of topsoil and vegetation underlain by about 3 to
5.5 feet of loose to medium dense, silty -fine to medium grained sand with gravel and local debris (Fill).
This layer was underlain by approximately 18 to 23 feet of medium dense to very dense, silty -fine to
medium grained sand with gravel (Glacial Till). This layer was underlain by fine to medium grained sand
trace to some gravel (Advance Outwash), which continued to the termination depths of the borings.
5.1.2 Groundwater
Groundwater was not encountered in any of the test pits. We anticipate that perched groundwater could
be present at the site within 10 feet below existing grades during the winter and early spring months. This
groundwater would consist of shallow perched interflow between fill and weathered glacial till and
underlying unweathered glacial till.
Groundwater was not encountered in B-1 during our investigation. Groundwater was encountered in B-2
at a depth of 58 feet below grade. Groundwater was measured in B-2 on January 11, 2019 and February
15, 2019 at 57.2 and 56.8 feet below grade respectively.
This groundwater likely represents a more regional groundwater table and is generally consistent with the
elevation of nearby Lake Ballinger.
Water table elevations often fluctuate over time. The groundwater level will depend on a variety of factors
that may include seasonal precipitation, irrigation, land use, climatic conditions and soil permeability.
Water levels at the time of the field investigation may be different from those encountered during the
construction phase of the project.
3
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2o6-331-1097
PRELIMINARY INFILTRATION EVALUATION
EDMONDS, WASHINGTON
February 27, 2019
6.o DISCUSSION
6.1.1 General
COBALT
G E 0 S C I E N C E S
Shallow infiltration is limited due to the presence of variable thicknesses of low -permeability Vashon
Glacial Till.
Based on our field explorations, a moderately thick sequence of unsaturated and permeable Vashon
Advance Outwash is present beneath the low -permeability till and likely underlies the entire project area.
The unsaturated Vashon Advance Outwash has the capacity to infiltrate treated stormwater runoff via UIC
wells, allowing the water to slowly infiltrate downward to the regional Vashon Advance Outwash aquifer.
Alternatively, it may be feasible to utilize infiltration trenches or galleries excavated through the upper
glacial till and into the top of the underlying Vashon Advance Outwash. In either case, the depth to the
outwash soils will vary throughout the property. Excavations of 20 to 30 feet below existing grades will
likely be required to penetrate through the till and into the outwash soils.
7.o Recommendations
7.1.1 Water Quality and Regulatory Guidance
Stormwater that flows into the UIC wells or other infiltration systems should flow through pretreatment
facilities (bioretention swales or other approved devices/systems) designed to meet the Washington State
Department of Ecology's (DOE) water quality requirements presented in Guidance for UIC Wells That
Manage Stormwater Runoff, Publication Number 05-10-o67 (DOE UIC Manual, 2oo6) or any relevant
updated versions that are applicable to this project.
Treated stormwater flows that enter the UIC wells should be conveyed via an underdrain pipe below the
bioretention swales or other system. The bioretention swales or other system should be designed in
accordance with the 2014 DOE Stormwater Management Manual for Western Washington
requirements.
7.1.2 Preliminary Infiltration Recommendations
UIC Wells
We performed in situ infiltration tests in B-1 and B-2 in early February 2019. The testing included an
approximate 3 to 4 hour saturation period until a steady inflow rate was achieved. Measurements were
taken every minute to verify a consistent inflow rate and height of testing water above the base of the well.
Measurements were collected after the inflow was stopped until all of the water infiltrated beyond the well
zones.
Based on our calculations from the site testing in conjunction with sieve analyses on collected soil
samples, we estimate that new 6-inch diameter wells may be capable of infiltrating 20 gallons per minute
(gpm) of treated stormwater into the unsaturated outwash soils.
4
PO Box 82243
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2o6-331-1097
PRELIMINARY INFILTRATION EVALUATION
EDMONDS, WASHINGTON
February 27, 2019
L � COBALT
GEOSCIENCES
The infiltration receptor horizon (Vashon Advance Outwash) is not homogeneous. Deeper portions of the
Vashon Advance Outwash may have a lower infiltration rate because the grain size consists of finer sand
than the upper tested portions. Due to the depth to groundwater and a required minimum 5 feet
clearance above groundwater, the length of screen in UIC wells will likely be limited to about 15 feet.
Since the underlying outwash can vary in composition and the depth to outwash will vary throughout the
site, we recommend testing of at least two production wells in order to determine if additional or fewer
wells are required for the project. We should be provided with the site plans and details of both surface
and subsurface storm systems for review prior to submission for permitting.
Other Systems
The site is underlain by local areas of fill, glacial till, and at depth by advance outwash. Infiltration in fill
and glacial till is not feasible at this site. Infiltration is feasible in the underlying advance outwash
deposits; however, infiltration basins will require significant excavation in order to allow for infiltration
that DOE does not consider deep injection. DOE considers any system that includes an excavation or hole
that is deeper than the largest surface dimension and/or utilizes perforated pipe to disperse flow into the
subsurface soils to be UIC wells and must be constructed and maintained per their requirements (see
DOE Guidance for UIC Wells that Manage Stormwater). UIC wells must be registered with DOE.
If a large infiltration system is constructed at the site, we anticipate that excavations of at least 20 feet will
be required to penetrate through the glacial till and into the underlying outwash. Based on our testing
from the borings, a preliminary infiltration rate of 2 inches per hour may be used for the outwash soils.
The side walls (but not the bottom) of the deep infiltration gallery should be lined with a layer of non-
woven filter fabric (MIRAFI 14oN). The trenches/galleries are then to be filled with clean washed 3/4 to 1--
1/2 inch gravel or other approved clean rock up to the design elevation. The gravel particles should be
clean and not coated with mud. Depending on the system design, it may be necessary to cap the gallery
with a minimum thickness of `impermeable' fill. This could include on site glacial till compacted to at
least 95 percent of the modified proctor. It may be necessary to locally amend these soils with additional
fines (clay or silt) to prevent surface waters and precipitation from flowing into the infiltration system.
We can provide additional recommendations once a general stormwater management system is designed.
We should be provided with final plans for review to determine if the intent of our recommendations has
been incorporated or if additional modifications are needed. Verification testing of infiltration systems
should be performed during construction.
8.o Closure
This report was prepared for the exclusive use of Luke Shamp and his appointed consultants. Any use of
this report or the material contained herein by third parties, or for other than the intended purpose,
should first be approved in writing by Cobalt Geosciences, LLC.
The recommendations contained in this report are based on assumed continuity of soils with those of our
test holes, and assumed structural loads. Cobalt Geosciences should be provided with final architectural
and civil drawings when they become available in order that we may review our design recommendations
and advise of any revisions, if necessary.
5
PO Box 82243
Kenmore, WA 98028
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2o6-331-1097
PRELIMINARY INFILTRATION EVALUATION
EDMONDS, WASHINGTON
February 27, 2019
COBALT
GEOSCIENCES
Use of this report is subject to the Statement of General Conditions provided in Appendix A. It is the
responsibility of Luke Shamp who is identified as "the Client" within the Statement of General Conditions,
and its agents to review the conditions and to notify Cobalt Geosciences should any of these not be
satisfied.
Respectfully submitted,
Cobalt Geosciences, LLC
Original signed by:
Phil Haberman, PE, LG, LEG
Principal
PH/se
6
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Kenmore, WA 98028
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uwD \ 111 WIMAI
Statement of General Conditions
Statement of General Conditions
USE OF THIS REPORT: This report has been prepared for the sole benefit of the Client or its agent and
may not be used by any third parry without the express written consent of Cobalt Geosciences and the
Client. Any use which a third parry makes of this report is the responsibility of such third party.
BASIS OF THE REPORT: The information, opinions, and/or recommendations made in this report are
in accordance with Cobalt Geosciences present understanding of the site specific project as described by
the Client. The applicability of these is restricted to the site conditions encountered at the time of the
investigation or study. If the proposed site specific project differs or is modified from what is described in
this report or if the site conditions are altered, this report is no longer valid unless Cobalt Geosciences is
requested by the Client to review and revise the report to reflect the differing or modified project specifics
and/or the altered site conditions.
STANDARD OF CARE: Preparation of this report, and all associated work, was carried out in
accordance with the normally accepted standard of care in the state of execution for the specific
professional service provided to the Client. No other warranty is made.
INTERPRETATION OF SITE CONDITIONS: Soil, rock, or other material descriptions, and
statements regarding their condition, made in this report are based on site conditions encountered by
Cobalt Geosciences at the time of the work and at the specific testing and/or sampling locations.
Classifications and statements of condition have been made in accordance with normally accepted
practices which are judgmental in nature; no specific description should be considered exact, but rather
reflective of the anticipated material behavior. Extrapolation of in situ conditions can only be made to
some limited extent beyond the sampling or test points. The extent depends on variability of the soil, rock
and groundwater conditions as influenced by geological processes, construction activity, and site use.
VARYING OR UNEXPECTED CONDITIONS: Should any site or subsurface conditions be
encountered that are different from those described in this report or encountered at the test locations,
Cobalt Geosciences must be notified immediately to assess if the varying or unexpected conditions are
substantial and if reassessments of the report conclusions or recommendations are required. Cobalt
Geosciences will not be responsible to any party for damages incurred as a result of failing to notify Cobalt
Geosciences that differing site or sub -surface conditions are present upon becoming aware of such
conditions.
PLANNING, DESIGN, OR CONSTRUCTION: Development or design plans and specifications
should be reviewed by Cobalt Geosciences, sufficiently ahead of initiating the next project stage (property
acquisition, tender, construction, etc), to confirm that this report completely addresses the elaborated
project specifics and that the contents of this report have been properly interpreted. Specialty quality
assurance services (field observations and testing) during construction are a necessary part of the
evaluation of sub -subsurface conditions and site preparation works. Site work relating to the
recommendations included in this report should only be carried out in the presence of a qualified
geotechnical engineer; Cobalt Geosciences cannot be responsible for site work carried out without being
present.
LIVIWIJAZ 1WIII
Figures: Vicinity Map, Site Plan
8.2
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Kenmore, WA 98028
cobaltgeo ftmail. co m
206-331-1097
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APPENDIX C
Exploration Logs
Unified Soil Classification System (USCS)
MAJOR DIVISIONS
SYMBOL
TYPICAL DESCRIPTION
Clean Gravels
Gw
Well -graded gravels, gravels, gravel -sand mixtures, little or no fines
Gravels
(more than 50%
(less than 5%
fines)
GP
Poorly graded gravels, gravel -sand mixtures, little or no fines
COARSE
GRAINED
SOILS
of coarse fraction
retained on No. 4
sieve)
Gravels with
Fines
(more than 12%
fines)
GM
Silty gravels, gravel -sand -silt mixtures
GC
Clayey gravels, gravel -sand -clay mixtures
(more than 50%
retained on
Clean Sands
:•: sw
Well -graded sands, gravelly sands, little or no fines
No. 200 sieve)
Sands
(50% or more
of coarse fraction
(less than 5%
fines)
sP
Poorly graded sand, gravelly sands, little or no fines
passes the No. 4
sieve)
Sands with
Fines
sM
Silty sands, sand -silt mixtures
(more than 12%
fines)
sc
Clayey sands, sand -clay mixtures
ML
Inorganic silts of low to medium plasticity, sandy silts, gravelly silts,
FINE GRAINED
(50% or more
Silts and Clays
(liquid limit less
than 50)
Inorganic
cL
or clayey silts with slight plasticity
Inorganic clays of low to medium plasticity, gravelly clays, sandy clays
silty clays, lean clays
Organic rganic
oL
Organic silts and organic silty clays of low plasticity
passes the
MH
Inorganic silts, micaceous or diatomaceous fine sands or silty soils,
No. 200 sieve)
Silts and Clays
(liquid limit 50 or
more)
Inorganic
elastic silt
CH
Inorganic clays of medium to high plasticity, sandy fat clay,
or gravelly fat clay
Organic
OHOrganic
clays of medium to high plasticity, organic silts
HIGHLY ORGANIC
SOILS
Primarily organic matter, dark in color,
and organic odor
PT
Peat, humus, swamp soils with high organic content (ASTM D4427)
Classification of Soil Constituents
MAJOR constituents compose more than 50 percent,
by weight, of the soil. Major constituents are capitalized
(i.e., SAND).
Minor constituents compose 12 to 50 percent of the soil
and precede the major constituents (i.e., silty SAND).
Minor constituents preceded by "slightly" compose
5 to 12 percent of the soil (i.e., slightly silty SAND).
Trace constituents compose o to 5 percent of the soil
(i.e., slightly silty SAND, trace gravel).
Relative Density
(Coarse Grained Soils)
Consistency
(Fine Grained Soils)
N, SPT,
Relative
N, SPT,
Relative
Blows/FT
Density
Blows/FT
Consistency
0-4
Very loose
Under 2
Very soft
4 -10
Loose
2-4
Soft
10 - 30
Medium dense
4-8
Medium stiff
30 - 50
Dense
8 -15
Stiff
Over 50
Very dense
15 - 30
Very stiff
Over 3o
Hard
Grain Size Definitions
Description
Sieve Number and/or Size
Fines
<#200 (o.o8 mm)
Sand
-Fine
#200 to #40 (o.o8 to 0.4 mm)
-Medium
#40 to #10 (0.4 to 2 mm)
-Coarse
#10 to #4 (2 to 5 mm)
Gravel
-Fine
#4 to 3/4 inch (5 to 19 mm)
-Coarse
3/4 to 3 inches (19 to 76 mm)
Cobbles
3 to 12 inches (75 to 305 mm)
Boulders
>12 inches (305 mm)
1 Moisture Content Definitions 1
Dry Absence of moisture, dusty, dry to the touch
Moist Damp but no visible water
Wet Visible free water, from below water table
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, WA 98028
Soil Classification Chart
Figure Ci
(2o6) 331-1097
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Unified Soil Classification System (USCS)
MAJOR DIVISIONS
SYMBOL
TYPICAL DESCRIPTION
Clean Gravels
Gw
Well -graded gravels, gravels, gravel -sand mixtures, little or no fines
Gravels
(more than 50%
(less than 5%
fines)
GP
Poorly graded gravels, gravel -sand mixtures, little or no fines
COARSE
GRAINED
SOILS
of coarse fraction
retained on No. 4
sieve)
Gravels with
Fines
(more than 12%
fines)
GM
Silty gravels, gravel -sand -silt mixtures
GC
Clayey gravels, gravel -sand -clay mixtures
(more than 50%
retained on
Clean Sands
:•: sw
Well -graded sands, gravelly sands, little or no fines
No. 200 sieve)
Sands
(50% or more
of coarse fraction
(less than 5%
fines)
sP
Poorly graded sand, gravelly sands, little or no fines
passes the No. 4
sieve)
Sands with
Fines
sM
Silty sands, sand -silt mixtures
(more than 12%
fines)
sc
Clayey sands, sand -clay mixtures
ML
Inorganic silts of low to medium plasticity, sandy silts, gravelly silts,
FINE GRAINED
(50% or more
Silts and Clays
(liquid limit less
than 50)
Inorganic
cL
or clayey silts with slight plasticity
Inorganic clays of low to medium plasticity, gravelly clays, sandy clays
silty clays, lean clays
Organic rganic
oL
Organic silts and organic silty clays of low plasticity
passes the
MH
Inorganic silts, micaceous or diatomaceous fine sands or silty soils,
No. 200 sieve)
Silts and Clays
(liquid limit 50 or
more)
Inorganic
elastic silt
CH
Inorganic clays of medium to high plasticity, sandy fat clay,
or gravelly fat clay
Organic
OHOrganic
clays of medium to high plasticity, organic silts
HIGHLY ORGANIC
SOILS
Primarily organic matter, dark in color,
and organic odor
PT
Peat, humus, swamp soils with high organic content (ASTM D4427)
Classification of Soil Constituents
MAJOR constituents compose more than 50 percent,
by weight, of the soil. Major constituents are capitalized
(i.e., SAND).
Minor constituents compose 12 to 50 percent of the soil
and precede the major constituents (i.e., silty SAND).
Minor constituents preceded by "slightly" compose
5 to 12 percent of the soil (i.e., slightly silty SAND).
Trace constituents compose o to 5 percent of the soil
(i.e., slightly silty SAND, trace gravel).
Relative Density
(Coarse Grained Soils)
Consistency
(Fine Grained Soils)
N, SPT,
Relative
N, SPT,
Relative
Blows/FT
Density
Blows/FT
Consistency
0-4
Very loose
Under 2
Very soft
4 -10
Loose
2-4
Soft
10 - 30
Medium dense
4-8
Medium stiff
30 - 50
Dense
8 -15
Stiff
Over 50
Very dense
15 - 30
Very stiff
Over 3o
Hard
Grain Size Definitions
Description
Sieve Number and/or Size
Fines
<#200 (o.o8 mm)
Sand
-Fine
#200 to #40 (o.o8 to 0.4 mm)
-Medium
#40 to #10 (0.4 to 2 mm)
-Coarse
#10 to #4 (2 to 5 mm)
Gravel
-Fine
#4 to 3/4 inch (5 to 19 mm)
-Coarse
3/4 to 3 inches (19 to 76 mm)
Cobbles
3 to 12 inches (75 to 305 mm)
Boulders
>12 inches (305 mm)
1 Moisture Content Definitions 1
Dry Absence of moisture, dusty, dry to the touch
Moist Damp but no visible water
Wet Visible free water, from below water table
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, WA 98028
Soil Classification Chart
Figure Ci
(2o6) 331-1097
_
www.cobaltgeo.com
cobaltgeo(&gmail.com
Test Pit TP-i
USCS Graphic
Topsoil/Vegetation
SM Fill
4'............. X................................ ......
SM \ Weathered Glacial Till?
6' ............... ..................... .........
I
SM Glacial Till
y.
Test Pit TP-2
USCS
Graphic
Topsoil/Vegetation
1' ............................................. ...
SM Fill
2' ............ ............................. ......
SM \ Weathered Glacial Till
3' ............... .................../ ...........
SM Glacial Till i
0-1' Vegetation/Topsoil
1-4' Silty Sand with Gravel (SM)
Loose to medium dense, silty -fine to medium grained sand with
gravel and roots, dark yellowish brown to grayish brown, dry. (Fill)
4-6' Silty Sand with Gravel (SM)
Loose to medium dense, silty -fine to medium grained sand with
gravel, mottled yellowish brown to grayish brown, moist.
(Weathered Glacial Till?)
6-8' Silty Sand with Gravel (SM)
Dense to very dense, silty -fine to medium grained sand with gravel,
grayish brown, moist. (Glacial Till)
End of Test Pit 8'
No Groundwater
No Caving
0-1' Vegetation/Topsoil
1-2' Silty Sand with Gravel (SM)
Loose to medium dense, silty -fine to medium grained sand with
gravel and roots, dark yellowish brown to grayishb brown, dry. (Fill)
2-3' Silty Sand with Gravel (SM)
Loose to medium dense, silty -fine to medium grained sand with
gravel, mottled yellowish brown to grayish brown, dry to moist.
(Weathered Glacial Till)
3-10' Silty Sand with Gravel (SM)
Dense to very dense, silty -fine to medium grained sand with gravel,
grayish brown, moist. (Glacial Till)
End of Test Pit io'
No Groundwater
No Caving
Test Pit TP-3 Graphic
USCS ^� 0-2' Vegetation/Topsoil
Topsoil/Vegetation
2'........................................... ....
SM Weathered Glacial
Till
4................. .......................... .........{
SM Glacial Till '
2-4' Silty Sand with Gravel (SM)
Loose to medium dense, silty -fine to medium grained sand with
gravel, mottled yellowish brown to grayish brown, moist.
(Glacial Till)
4-7' Silty Sand with Gravel (SM)
Dense to very dense, silty -fine to medium grained sand with gravel,
grayish brown, moist. (Glacial Till)
End of Test Pit 7'
No Groundwater
No Caving
Proposed Four Lot Plat
24oth Street SW
Edmonds, Washington
TEST PIT
LOGS
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, WA 98028
(2o6) 331-1097
www.cobaltgeo.com
cobaltgeo@gmail.com
Test Pit TP-4
USCS Graphic
Topsoil/Vegetation
SM Fill
6' ............... ..................... .........
SM Glacial Till y
Test Pit TP-5
USCS Graphic
Topsoil/Vegetation
SM Fill
81 ............... ..................... .........
SM Glacial Till i
0-1' Vegetation/Topsoil
1-6' Silty Sand with Gravel (SM)
Loose to medium dense, silty -fine to medium grained sand with
gravel, asphalt, debris, and roots, dark yellowish brown to
grayish brown, dry. (Fill)
6-8' Silty Sand with Gravel (SM)
Dense to very dense, silty -fine to medium grained sand with gravel,
grayish brown, moist. (Glacial Till)
End of Test Pit 8'
No Groundwater
No Caving
0-1' Vegetation/Topsoil
1-8' Silty Sand with Gravel (SM)
Loose to medium dense, silty -fine to medium grained sand with
gravel, debris, and roots, dark yellowish brown to grayishb brown,
dry. (Fill)
8-1o' Silty Sand with Gravel (SM)
Dense to very dense, silty -fine to medium grained sand with gravel,
grayish brown, moist. (Glacial Till)
End of Test Pit io'
No Groundwater
No Caving
Proposed Four Lot Plat
24oth Street SW
Edmonds, Washington
TEST PIT
LOGS
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, WA 98028
(2o6) 331-1097
www.cobaltgeo.com
cobaltgeo@gmail.com
Log of Boring B-1
Date: December 7, 2018 Depth: 46.5' Initial Groundwater: None Observed
Contractor: EDI Elevation: - 358' Sample Type: Split Spoon
Method: Hollow Stem Auger Logged By: PH Checked By: SC Final Groundwater: N/A
3 0 0 Moisture Content (%)
Q Plastic Liquid
_ - U E 3 Limit Limit
t _ V
o o Material Description
o m V� o SPT N-Value
2 O 0 10 20 30 40 5
Vegetation/Topsoil
---
-
--
3
-------------------------------------------------
SM
Loose to medium dense, silty -fine to medium grained sand with
— 3
3
gravel and debris, dark yellowish brown to grayish brown, moist.
4
(Fill)
—6
-
SM
Medium dense to very dense, silty -fine to medium grained sand with
— 9
. ,
gravel, mottled dark yellowish brown to grayish brown, moist.
(Glacial Till)
— 12
-
12
—
—
14
15
— 15
=
—1 8
=
16
16
4.1 o Moisture
=
23
— 21
— 24
— 27
=
22
29
4.6%Moisture
50
---
SP
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Dense to very dense, fine to medium grained sand trace gravel,
grayish brown, moist. (Advance Outwash)
33
12
20
30
`
6.9% Moisture
36
13
s
16.9% Moisture
39
20
:N�
42
12
20
s
6.7% Moisture
30
45
19
32
-
9.8% Moisture
40
End of Boring 46.5'
48
Well Construction: Flush mount monument; 2-inch diameter pipe,
slotted from 33 to 43 feet; sand backfill up to 28 feet below grade.
51
Cobalt Geosciences, LLC
P.O. Box 82243 Proposed Short Plat
Kenmore, WA 98028 2 oth Street SW Boring
(2o6) 381-1097 79XX - 4
www.cobaltgeo.com Edmonds, Washington Log
cobaltgeopgmail.com
Log of Boring B-2
Date: January 11, 2019 Depth: 61.5' Initial Groundwater: 58'
Contractor: EDI Elevation: - 342.5' Sample Type: Split Spoon
Method: Hollow Stem Auger Logged By: PH Checked By: SC Final Groundwater: 57.2'
3 0 0 Moisture Content (%)
Q Plastic 1 Liquid
_ - U E 3 Limit Limit
t _ V
o o Material Description
o m � o SPT N-Value
0 :D O 0 10 20 30 40 50
Vegetation/Topsoil
---
-
-
--
---
SM
--------------------------------------------
Loose to medium dense, silty -fine to medium grained sand with
gravel and debris, dark yellowish brown to grayish brown, moist.
■
— 4
Fil1------------------------------------------
----
SM
Medium dense to very dense, silty -fine to medium grained sand with
=
gravel, mottled dark yellowish brown to grayish brown, moist.
—8
_
Glacial Till
— 12
Vp
— 16
-
—20
=
22
29
4.1 % Moisture
=
50
—24
=
1
SP
Dense to very dense, fine to medium grained sand trace gravel,
16
:'•,iy �',
grayish brown, moist. (Advance Outwash)
=
16
23
'
—2 8
22
J
_
29
•ti
— 32
_
50
22
'-N
— 36
29
% +
50
4.6% Moisture
— 40
22
29
`
50
44
12
+';
6.9%Moisture
20
30
_
48
13
18
16.9% Moisture
52
20
12
_
56
20
30
6.7% Moisture
60
9
32
4
9.8% Moisture
End of Boring 61.5'
64
Well Construction: Flush mount monument; 2-inch diameter pipe,
slotted from 37 to 57 feet; sand backfill up to 34 feet below grade.
68
Cobalt Geosciences, LLC
P.O. Box 82243 Proposed Short Plat
Kenmore, WA 98028 2 oth Street SW Boring
(2o6) 381-1097 79XX - 4
www.cobaltgeo.com Edmonds, Washington Log
cobaltgeopgmail.com
APPENDIX D
Laboratory Analyses
100
90
80
70
c
LL 60
a) 50
a 40
30
20
10
0
100
100
90
80
70
c
E 60
Q) 50
a 40
30
20
10
0
Particle Size Distribution - ASTM D 422
- - Extended Gradation Interpolation • Data - Gradation Functbn
• D10 (mm) • D30 (mm) • D60 (-)
---Gravel -----Sand ---Fines
d30 d10 O d60
B-1 at 17.5'
In
1 0.1 0.01 0.001
Grain Size (mm)
Particle Size Distribution - ASTM D 422
Extended Gradation Interpolation • Data - Gradation Function
• D10 (mm) • D30 (mm) • D60 (-)
---Gravel -SandFines
d30 a d10 O d60
0.68
1j0.52
0.34
100 10
B-1 at 37.5'
1 0.1 0.01 0.001
Grain Size (mm)
Material Properties
Description =
Edmonds
Soil ID =
B-1-17.5
Depth =
17.5
Max D Densl =
0.00
O timum Moisture =
0.00
WD Offset =
0
% Moisture Offset =
4.1
%> 3 In. •
0.00
%> 314In. •
13.40
% Gravel =
36.30
% Sand =
53.70
% Fines =
10.00
PL =
0.00
LL =
0.00
Cu =
41.00
Cc =
0.60
File Name
SP-..
Extrapolated Coefficients see Limitations on Input Screen
d10 d30 d60 Cu Cc
0.075 0.371 1 3.075 1 41.00 0.60
Material Properties
Description =
Edmonds
Soil ID =
B-1-37.5
Depth -
37.5
Max Dry Density =
0.00
Optimum Moisture =
0.00
WD Offset =
0
% Moisture Offset =
16.9
%> 3 In. -
0.00
%> 314In. -0.00
% Gravel =
2.00
% Sand =
96.00
% Fines =
0.00
PL =
0.00
LL =
0.00
Cu =
1.99
Cc =
1.16
File Name
SP
Extrapolated Coefficients see Limitations on In ut Screen
d10 d30 d60 Cu Cc
0.339 0.521 1 0.676 1 1.99 1 1.16
Cobalt Geosciences, LLC
COBALT24oth
Proposed Four Lot Plat
Street SW
Edmonds, Washington
SIEVE
ANALYSES
P.O. Box
Kenmore,, WA WA 98028
(2o6) 331-1097
www.cobaltgeo.com
cobaltgeo(&gmail.com
100
90
80
70
c
ii 60
c
50
a 40
30
20
10
0
Particle Size Distribution - ASTM D 422
Extended Gradation Interpolation ♦ Data - Gradation Function
• D10(mm) • D30(mm) • D60(mm)
-Gravel -Sand -Fines
d30 = d10 0 660
0.89
0.61
0.43
_
100 10 1 0.1 0.01 0.001
Grain Size (mm)
B-1 at 42.5'
100
90
80
70
c
ii 60
a) 50
a 40
30
20
10
0
Particle Size Distribution - ASTM D 422
Extended Gradation Interpolation • Data - Gradation E..o
0 D10 (mm) D30 (mm) • D60 (mm)
-Gmvel -Sand -Flnes
0 d30 0 d10 0 d60
0.68
0.50
0.29
100 10
B-1 at 45'
Martial Properties
Oescdptlon =
Edmonds
Soil ID -
B4-42.5
Depth =
42.5
Max Dry Density -
0.00
Optimum Moisture -
0.00
WD Offset =
0
% Moisture Offset =
6.7
%>3 in.=
0.00
%>314In. =0.00
% Gravel -
11.50
% Sand -
68.50
% Fines =
0.00
PL =
0.00
LL -
0.00
Cu =
2.08
Cc =
0.97
File Name
SP
EAra olated Coefficients see Limitations on Input Screen
d10 d30 d60 CuT Cc
0.428 1 0.60E 1 0.890 1 2.08 1 0.97
1 0.1 0.01 0.001
Grain Size (mm)
Proposed Four Lot Plat
24oth Street SW
Edmonds, Washington
Material Properties
Description =
Edmonds
Soil ID =
B-1-45
Depth =
45
Max Dry Density =
0.00
Optimum Moisture =
0.00
WD Offset =
0
% Moisture Oftet =
9.8
%>3In. =
0.00
%>314 In.
0.00
% Gravel =
2.80
% Sand =
97.00
% Fines =
0.20
PL =
0.00
LL =
0.00
Cu =
2.33
Cc-
129
File Name
SP
6dra olated Coeficients see Limitations on Input Screen
d10 d30 d60 CuT Cc
0.291 0.504 1 0.677 1 2.33 1 1.29
Cobalt Geosciences, LLC
SIEVE P.O. Box 82243
Kenmore, WA 98028
ANALYSES (2o6) 331-1097
www.cobaltgeo.com
cobaltgeo(&gmail.com
Particle Size Distribution - ASTM D 422
-- Extended Gradation Interpolation • Data - Gradation Function
• D10 (mm) • D30 (mm) • D60 (mm)
-Gravel -Sww -Flnes
0 d30 o d10 o d50
100
90
80
>- 70
(D
c
ii 60
c
(D 50
a 40
30
20
10
0
100
B-2 at 30'
10 1 0.1 0.01 0.001
Grain Size (mm)
Particle Size Distribution - ASTM D 422
---- Extended Gradation Interpolation
• Data
Gradation Function
• D10 (mm)
• 030 (mm)
• D60 (mm)
-Gravel
-Sand
-Fines
- d30
O d10
d60
100
90
80
a�
70
c
u- 60
c
a) 50
a. 40
30
20
10
0
•
0.72
0.46
0.30
100 10 1 0.1 0.01 0.001
Grain Size (mm)
B-2 at 35'
Proposed Four Lot Plat
24oth Street SW
Edmonds, Washington
Material Properties
Description =
Edmonds
Soil ID =
B-2-30
Depth =
30
Max Dry Density =
0.00
Optimum Moisture =
0.00
WD Otfset =
0
% Moisture Offset =
5.3
%>3In. =
0.00
%>314 in. =0.00
% Gravel =
0.00
% Sand -
99.80
% Fin" -
0.20
PL -
0.00
LL -
0.00
Cu
Cc=
1.04
File Name
SP
Extrapolated Coefficients see Limitations on In ut Screen
d10 d30 d60 Cu Cc
0.224 1 0.319 1 0.440 1 1.96 1 1.04
Material Properties
Description =
Edmonds
Soil ID =
B-2-35
Depth =
35
Max Dr Density=
0.00
Optimum Moisture =
0.00
WD Offset =
0
% Moisture Offsat -
4.7
%> 3 In. -
0.00
%>314 in. =0.00
% Gravel =
9.80
% Send =
90.00
% Fines =
0.20
PL .
0.00
LL =
0.00
Cu =
2.40
Ce=
0.98
Flla Nama
SP
Extrapolated Coefficients see Limita0ons on Input Screen
d10 d30 d60 Cu Cc
0.300 1 0.460 1 0.720 1 2.40 1 0.98
Cobalt Geosciences, LLC
SIEVE P.O. Box 82243
Kenmore, WA 98028
ANALYSES (2o6) 331-1097
www.cobaltgeo.com
cobaltgeo(&gmail.com
100
90
80
>` 70
m
c
ii 60
c
50
a 40
30
20
10
0
Particle Size Distribution - ASTM D 422
Ddended Gradation Interpolation ♦ Data - Gradation Function
D10 (mm) • D30 (mm) a D60 (MM)
-Gravel -Sand -Flnes
d30 O d10 O d60
100 10 1 0.1 0.01
Grain Size (mm)
B-2 at 40'
Particle Size Distribution - ASTM D 422
Extended Gradation Interpolation • Data - Gradation Function
e D10 (mm) • D30 (mm) • D60 (mm)
-Gravel -Sand -Fine.
d30 O 00 O d60
100
90
80
70
c
LL 60
c
50
a 40
30
20
10
0
100
B-2 at 50'
IN
0.56
0.39
0.30
1 0.1
Grain Size (mm)
0.001
Material Properties
Description =
Edmonds
Soil ID =
B-2-40
Depth =
40
Max Dry Density =
0.00
Optimum Moisture =
0.00
WD Ofset =
0
% Moisture Offset =
5
%>3In. =
0.00
%>314 in.
0.00
% Gravel =
1.70
% Sand =
97.50
% Fines =
0.80
Pl. =
0.00
ILL =
0.00
Cu =
2.S7
Cc =
0.93
File ..!Sp
EA- olaled Coefficients see Limitations on input Screen
d10 d30 d60 Cu Cc
0.279 0.432 0.718 1 2.57 i 0.93
0.01 0.001
Material Properties
Description =
Edmonds
Soil ID -
B-2-50
Depth =
50
Max Dry Density -
0.00
Optimum Moisture -
0.00
WD Otfset =
0
% Moisture Otfset =
7
%> 3 In. =
0.00
% > 314 In. =
0.00
% Gravel =
1.30
% Sand =
97.20
% Fines =
1.50
PL =
0.00
LL =
0.00
Cu =
1.s9
cc =
9.92
File Name
SP
E)drapolated Coeficients sea l.imttations on In ut Screen
d10 d30 d60 Cu Cc
0.299 0.395 0.565 1.89 0.92
Cobalt Geosciences, LLC
COSALT
7G E 0 S C I E N C E S
Proposed Four Lot Plat
24oth Street SW
Edmonds, Washington
SIEVE
ANALYSES
P.O. Box
Kenmore,, WA WA 98028
(2o6) 331-1097
www.cobaltgeo.com
cobaltgeo(&gmail.com