HomeMy WebLinkAboutRS_TIR_Logan Six_230807_v2.pdf
P.O Box 1478 ⬧ Everett, WA 98206 ⬧ P: 425.303.9363
info@insightengineering.net
TECHNICAL INFORMATION REPORT
For
Logan Tower Mixed Use
Prepared for
City of Renton
Renton City Hall - 6th Floor
1055 South Grady Way
Renton, WA 98057
Project Site Location:
302 Logan Ave N
Renton, WA 98057
Tax Id: 1823059264
IECO Project: 21-1157
Certified Erosion and Sedimentation Control Lead:
To be named by contractor
Stormwater Site Plan Prepared By:
Ryan J. Korte
TIR Preparation Date:
November 11, 2021
Date revised: February 7, 2023
Approximate Construction Date:
September 1, 2023
Applicant:
Andrew Kovach
2115 Colby Ave
Everett, WA 98201
425-259-0609
Contact:
IECO
P.O. Box 1478
Everett, WA 98206
425-303-9363
02/09/2023
Insight Engineering Co. – Technical Information Report 2/7/23
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TABLE OF CONTENTS
1.0 Project Overview ....................................................................................................................3
2.0 Conditions and Requirements Summary ............................................................................7
2.1 Conditions ....................................................................................................................................7
2.2 Requirements Summary ...............................................................................................................8
3.0 Offsite Analysis ....................................................................................................................13
4.0 Flow Control and Water Quality Analysis and Design ......................................................15
4.1 Existing Basin Summary ............................................................................................................15
4.2 Developed Basin Summary ........................................................................................................15
4.3 Water Quality .............................................................................................................................16
5.0 Conveyance Analysis and Design .......................................................................................17
6.0 Special Report and Studies .................................................................................................18
7.0 Other Permits .......................................................................................................................19
8.0 CSWPPP Analysis and Design ...........................................................................................24
9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant .............................28
10.0 Operations and Maintenance Manual ..............................................................................29
Figures
Figure 1 - Vicinity Map .................................................................................................................6
Figure 2 - Soil Map .....................................................................................................................11
Figure 3 - Downstream Analysis Map .......................................................................................14
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Acronyms and Abbreviations _________________________________________
BMP Best Management Practices
RSWDM Renton Surface Water Drainage Manual
DOE Department of Ecology
ESC Erosion and Sediment Control
IECO Insight Engineering Company
MR Minimum Requirement
NCSS National Cooperative Soil Survey
KCRS King County Road Standards
KCSWDM King County Surface water Drainage Manual
SWPPP Stormwater Pollution Prevention Plan
SWMMWW Stormwater Management Manual for Western Washington
TESC Temporary Erosion and Sediment Control
WWHM Western Washington Hydrology Model
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1.0 Project Overview
The proposed project “Logan Tower Mixed Use” is located at 302 Logan Ave N in Renton,
Washington. More generally, the project site is in Section 36, Township 28 North, and Range 4
East of the Willamette Meridian in King County, Washington. Please refer to the Vicinity Map
attached later in the section. This report will follow the Technical Information Report
requirements, per the 2022 Renton Surface Water Design Manual.
The site is currently undeveloped with lawn. The site contains one drainage basin that slopes
to the north side of the site. Please refer to the downstream analysis map for more details. As per the
Geotech report attached under Section 6.0 the site contains poorly graded sands with gravel.
The site contains 1.08 acres and is zoned as UC (Urban Center). The proposal is to construct
a ten-story mixed-use building with three levels of underground parking. The access to the site will
be from driveway entrances located on N 4th St and N 3rd St. Sewer and water utilities will be provided
by City of Renton. The water will be provided by City of Renton Water District.
The project is located within the Lower Cedar River drainage basin. The project is
subjected to the peak flow rate flow control standard matching existing conditions. The site is
located within the City’s Aquifer Protection Area (APA). The north half of the site is within Zone
1 of the APA and the south half falls in Zone 2. The project is subject to a full drainage review per
Figure 1.1.2.A (Flow Chart for Determining Type of Drainage Review Required) according to
section 1.1.2.4 (Full Drainage Review). The project is exempt from flow control per section 1.2.3
of the RSWDM the direct discharge exemption may be applied. The project meets the following
required criteria #1-5 as outlined on page 1-39 of the RSWDM.
Criteria #1: “The flowpath from the project site discharge point to the edge of the 100 -
year floodplain of the major receiving water will be no longer than a half mile, except for
discharges to Lake Washington.”
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The site discharge point is about 1,000-feet (0.19 miles) from the discharge point into the
lower Cedar River which is less then the maximum distance of 0.5 miles.
Criteria #2: “The conveyance system between the project site and the major receiving
water will extend to the ordinary high water mark, and will be comprised of manmade
conveyance elements (pipes, ditches, etc.) and will be within public right-of-way or a
public or private drainage easement.”
The downstream conveyance system will be comprised entirely of manmade conveyance
elements with most of the run within the public right-of-way crossing through one drainage
easement prior to discharging (at the ordinary high-water mark) to the lower Cedar River.
See downstream analysis in section 3.2 for a detailed description of the downstream flow.
Criteria #3: “The conveyance system will have adequate capacity24 to convey the 25-year
peak flow (per Core Requirement #4, Conveyance System), for the entire contributing
drainage area, assuming build-out conditions to current zoning for the equivalent area
portion (the area that is contained within an arc formed by the shortest, straight line distance
from the conveyance system discharge point to the furthermost point of the proposed
project) and existing conditions for the remaining area.”
The project will generate a peak discharge of 0.23 CFS in the 25-year developed storm.
This is very minimal and is not expected to aggravate any downstream problems.
Therefore, the proposal will not have any effect on the downstream corridor. A detailed
conveyance analysis will be performed for the construction submittal.
Criteria #4: The conveyance system will be adequately stabilized to prevent erosion,
assuming the same basin conditions as assumed in Criteria (c) above.”
The conveyance system will be adequately stabilized as it is an entirely a closed piped
system.
Criteria #5: “The direct discharge proposal will not divert flows from or increase flows to
an existing wetland or stream sufficient to cause a significant adverse impact.”
The site will continue to flow to its natural discharge point and will not divert any flows
from wetlands. No wetlands are present on or downstream of the site.
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The project is proposing to direct discharge to the existing drainage system along N 4th
Street that is maintained by the city. Water quality is exempt because the total PGIS is only 2,165
SF which is less than the threshold limit of 5,000 SF.
For on-site BMPs, as outlined in Appendix C Section C 2.1, full dispersion must be
considered first, however the required native vegetated cannot be achieved for this UC zoned
project. Full dispersion for the site is not feasible. Full infiltration was considered next, however
due to the large footprint of the proposed building and part of the site falling under APA Zone 2
full infiltration is infeasible as the required setbacks could not be met. Limited infiltration,
bioretention, and permeable pavement were also considered infeasible due to the Aquifer
Protection Area. The roof drains will be connected via a tight line connection to an existing catch
basin near the northwest corner of the lot along N 4th Street. Underground parking areas will be
connected to the sanitary sewer.
Insight Engineering Co. – Technical Information Report 2/7/23
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FIGURE 1. VICINITY MAP
Taken from City of Renton GIS
P.O. Box 1478 Everett, WA 98206
425-303-9363
Info@insightengineering.net
Figure 1 -Vicinity Map
Logan Tower Mixed Use
Renton, Washington
SCALE:
NTS
DATE
: 2/9/23 JOB #: 21-1157
BY
: RJK FILE NAME:
21-1157/doc/drainage report
SITE
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2.0 Conditions and Requirements Summary
2.1 Conditions
There are no conditions to date.
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2.2 Requirements Summary
1.2.1 Core Requirement #1: Discharge at the Natural Location
The project is proposing to direct discharge to the existing drainage system along N 4th Street that
is maintained by the city. Discharge from the developed site will continue to flow to the site’s
natural discharge location.
1.2.2 Core Requirement #2: Off-site Analysis
Refer to Section 3 for the level two downstream analysis.
1.2.3 Core Requirement #3: Flow Control
The project is exempt from flow control per section 1.2.3 of the RSWDM the direct discharge
exemption may be applied.
1.2.4 Core Requirement #4: Conveyance System
The roof drains will be connected via a tight line connection to an existing catch basin near the
northwest corner of the lot along N 4th Street. Underground parking areas will be connected to the
sanitary sewer.
1.2.5 Core Requirement #5: Construction Stormwater Pollution Prevention
During construction of the infrastructure for the project, temporary erosion control methods will
be implemented to prevent sedimentation and erosion using the methods outlined in section 1.2.5.1
of the 2017 RSWDM. Refer to the Grading and SWPPP Plan.
1.2.6 Core Requirement #6: Maintenance and Operations
An Operations and Maintenance Manual shall be provided for the construction submittal.
1.2.7 Core Requirement #7: Financial Guarantees and Liability
Bond and insurance in accordance with City of Renton’s requirements will be provided upon
request or at the behest of the owner during site construction.
1.2.8 Core Requirement #8: Water Quality
Water quality is exempt because the total PGIS is only 2,165 SF which is less than the threshold
limit of 5,000 SF.
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1.2.9 Core Requirement #9: On-Site BMPs
For on-site BMPs, as outlined in Appendix C Section C 2.1, full dispersion must be considered
first, however the required native vegetated cannot be achieved for this UC zoned project. Full
dispersion for the site is not feasible. Full infiltration was considered next, however due to the
large footprint of the proposed building and part of the site falling under APA Zone 2 full
infiltration is infeasible as the required setbacks could not be met. Limited infiltration,
bioretention, and permeable pavement were also considered infeasible due to the Aquifer
Protection Area. The roof drains will be connected via a tight line connection to an existing catch
basin near the northwest corner of the lot along N 4th Street. Underground parking areas will be
connected to the sanitary sewer.
Special Requirements – Section 1.3 of KCSWDM
1.3.1 Special Requirement #1: Other Adopted Area Specific Requirements
This project is not located in the “other adopted area” that require any area specific requirements.
1.3.2 Special Requirement #2: Flood Plain / Floodway Delineation
The project is not located within the 100-yr floodplain.
1.3.3 Special Requirement #3: Flood Protection Facilities
Stringent control for the site is not required.
1.3.4 Special Requirement #4: Source Controls
A SWPPP will be prepared and kept on site to meet DOE requirements upon construction plan
approval.
1.3.5 Special Requirement #5: Oil Control
This project is not considered as a high use development.
1.3.6 Special Requirement #6: Aquifer Protection Area
The project is located within Zones 1 & 2 of the Aquifer Protection Area. All proposed drainage
facilities and conveyance systems are closed systems. No open systems are proposed, therefore
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the project should not impose any negative impacts to the Aquifer Protection Area. Refer to the
appendix for the Groundwater Protection Areas map.
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FIGURE 2. SOIL MAP
P.O. Box 1478
Everett, WA 98206
425-303-9363
Info@insightengineering.net
Figure 2 - Soil Map
Logan Tower Mixed Use
Renton, Washington
SCALE:
NONE DATE: 2/9/23 JOB #: 21-1157
BY: RJK FILE NAME:
21-1157\docs\drainage report
SITE
SOILS LEGEND
Ur—Urban land
Insight Engineering Co. – Technical Information Report 2/7/23
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King County Area, Washington
Ur—Urban land
Map Unit Composition
• Urban land: 100 percent
• Estimates are based on observations, descriptions, and transects of the
mapunit.
Description of Urban Land
Interpretive groups
• Land capability classification (irrigated): None specified
• Land capability classification (nonirrigated): 8
• Hydric soil rating: No
\
Insight Engineering Co. – Technical Information Report 2/7/23
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3.0 Offsite Analysis
LEVEL 1 DOWNSTREAM ANALYSIS
A site reconnaissance was performed by Brian R. Kalab of Insight Engineering on October
22, 2021 to verify the downstream flow paths and observe any drainage problems downstream of
the site. The sky was overcast with a temperature of 45 degrees.
The site is currently undeveloped with lawn. The site contains one drainage basin that
slopes to the north side of the site.
3.1 Upstream Analysis
Based on the site reconnaissance and the topographic survey of the site, the upstream flows
appear to be minimal. Refer to the Downstream Analysis Map attached in the next page for more
details.
3.2 Downstream Analysis
Refer to the Downstream Analysis Map attached to the next pages for a visual description
of the downstream flow.
The outlet from the roof drain will be connected to the existing catch basin along the south
side of N 4th St. The flow travels east about 45-feet through 12-inch corrugated polyethylene pipe
(CPP) pipe to a CB on the east side of Logan Ave N. The flow then heads south for approximately
700-feet through 12-inch CPP to a CB. The pipe then upsizes to 24-inch CPP and continues south
for 70 more feet. The flow crosses to a CB on the west side of Logan Ave N via a 24-inch CPP.
The flow then travels southwest under the sidewalk and landscaping for approximately 180-feet
through corrugated metal pipe (CMP) to outlet into the Cedar River. This is where the downstream
observation was stopped. There did not appear to be any restrictions or erosion problems within 1
mile of the site.
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FIGURE 3. DOWNSTREAM ANALYSIS MAP
P.O. Box 1478 Everett, WA 98206
425-303-9363
Info@insightengineering.net
Figure 3 - Downstream Analysis Map
Logan Tower Mixed Use
Renton, Washington
SCALE:
NONE DATE: 2/9/23 JOB #: 21-1157
BY: RJK FILE NAME:
21-1157\docs\drainage report
Existing Flow
path
N
SITE
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4.0 Flow Control and Water Quality Analysis and Design
Total Site Area = 1.08 Acres
Clearing Limit = 1.11 Acres
Total Area Included in the Analysis = 1.11 Acres
4.1 Existing Basin Summary
Total Area Included in the Analysis = 1.11 Acres
Total Existing Impervious:
Existing Sidewalk = 0.01 Acres ( 590 SF)
Existing Road = 0.01 Acres ( 428 SF)
Total Impervious = 0.02 Acres (1,018 SF)
Pervious Areas = 1.09 Acres
Refer to the Existing Basin Map attached later in this section for more details.
4.2 Developed Summary
Total Area Included in the Analysis = 1.11 Acres
Total Developed Impervious:
Roof Area = 0.66 Acres (28,580 SF)
Driveway = 0.05 Acres ( 2,165 SF)
Sidewalk = 0.08 Acres ( 3,555 SF)
Existing Sidewalk = 0.01 Acres ( 590 SF)
Existing Road = 0.01 Acres ( 428 SF)
Total Impervious = 0.81 Acres (35,318 SF)
Pervious Areas = 0.30 Acres
Refer to the Developed Basin Map attached later in this section for more details.
LOGAN AVE NN. 3RD ST.
BURNETT ST. N.N. 4TH ST.EXISTING BASIN MAPIECSCALE: 1" = 0502550'
LOGAN AVE NN. 3RD ST.
BURNETT ST. N.N. 4TH ST.DEVELOPED BASIN MAPIECSCALE: 1" = 0502550'
Insight Engineering Co. – Technical Information Report 2/7/23
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4.3 Water Quality
Water quality is exempt because the total PGIS is only 2,165 SF which is less than the
threshold limit of 5,000 SF.
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5.0 Conveyance Analysis and Design
A detailed conveyance analysis will be included with the construction submittal.
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6.0 Special Reports and Studies
A. Geotechnical Report
B. Sensitive Areas Map
C. Watershed Map
D. Soil Amendment Calculations
Insight Engineering Co. – Technical Information Report 2/7/23
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A. Geotechnical Report
Preliminary Geotechnical
Investigation
Proposed Mixed Use Building
3xx Logan Avenue North
Renton, Washington
January 8, 2021
PRELIMINARY GEOTECHNICAL INVESTIGATION
RENTON, WASHINGTON
i
Table of Contents
1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2.0 PROJECT DESCRIPTION .............................................................................................. 1
3.0 SITE DESCRIPTION ....................................................................................................... 1
4.0 FIELD INVESTIGATION ............................................................................................... 1
4.1.1 Site Investigation Program ................................................................................... 1
5.0 SOIL AND GROUNDWATER CONDITIONS .............................................................. 2
5.1.1 Area Geology ........................................................................................................ 2
5.1.2 Groundwater ........................................................................................................ 3
6.0 GEOLOGIC HAZARDS ................................................................................................... 3
6.1 Erosion Hazard .................................................................................................... 3
6.2 Seismic Hazard .................................................................................................... 3
7.0 DISCUSSION ................................................................................................................... 4
7.1.1 General................................................................................................................. 4
8.0 RECOMMENDATIONS .................................................................................................. 5
8.1.1 Site Preparation ................................................................................................... 5
8.1.2 Temporary Excavations and Shoring .................................................................... 5
8.1.3 Erosion and Sediment Control.............................................................................. 7
8.1.4 Foundation Design ............................................................................................... 7
8.1.5 Concrete Retaining Walls ..................................................................................... 8
8.1.6 Slab on Grade ......................................................................................................10
8.1.7 Stormwater Management ....................................................................................11
8.1.8 Groundwater Influence on Construction .............................................................11
8.1.9 Utilities ...............................................................................................................11
8.1.10 Pavements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9.0 CONSTRUCTION FIELD REVIEWS ...........................................................................13
10.0 CLOSURE ...................................................................................................................13
LIST OF APPENDICES
Appendix A — Statement of General Conditions
Appendix B — Figures
Appendix C — Boring Logs
Appendix D — Liquefaction Analyses
PRELIMINARY GEOTECHNICAL INVESTIGATION
RENTON, WASHINGTON
January 8, 2021
1
PO Box 82243
Kenmore, WA 98028
cobaltgeo@gmail.com
206-331-1097
1.0 Introduction
In accordance with your authorization, Cobalt Geosciences, LLC (Cobalt) has completed a preliminary
geotechnical investigation for the proposed mixed-use building located at 3xx Logan Avenue North in
Renton, Washington (Figure 1).
The purpose of the geotechnical investigation was to identify subsurface conditions and to provide
geotechnical recommendations for foundation design, stormwater management, earthwork, soil
compaction, and suitability of the on-site soils for use as fill.
The scope of work for the geotechnical evaluation consisted of a site investigation followed by engineering
analyses to prepare this report. Preliminary recommendations presented herein pertain to various
geotechnical aspects of the proposed development, including foundation support of the building along
with liquefaction analyses.
2.0 Project Description
The project includes construction of a multi-story building with at grade retail space and potentially,
below grade parking. The building location and elevations have not been finalized. One option includes
three stories of below grade parking with cuts of about 37 feet. This report provides preliminary
recommendations for estimating and scoping purposes.
We should be notified if the planned construction changes and we should be provided with the final plans
when they become available so that we may update our recommendations and provide additional
analyses/reporting under a separate proposal, if necessary.
3.0 Site Description
The site is located at 3xx Logan Avenue North in Renton, Washington (Figure 1). The property consists
of one irregularly shaped parcel (No. 1823059264) with a total area of 47,081 square feet.
The property is undeveloped and surfaced with gravel and grasses. The site is nearly level to very slightly
sloping in multiple directions.
The site is bordered to the east by commercial buildings, to the north by N. 4th Street, to the west by Logan
Avenue N. and to the south by N. 3rd Street.
4.0 Field Investigation
4.1.1 Site Investigation Program
The geotechnical field investigation program was completed on December 23, 2020 and included drilling
and sampling two hollow stem auger borings with a truck mounted drill rig.
PRELIMINARY GEOTECHNICAL INVESTIGATION
RENTON, WASHINGTON
January 8, 2021
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PO Box 82243
Kenmore, WA 98028
cobaltgeo@gmail.com
206-331-1097
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 boring sampling are presented in Appendix C.
5.0 Soil and Groundwater Conditions
5.1.1 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 King County indicates that the site is underlain by Quaternary Alluvium
In this area, alluvium usually includes variable thicknesses of fine-grained materials overlying a relatively
thick sequence of poorly graded sands with gravel. These materials vary in density and composition with
depth and can include areas of organic debris, peat, and silt/clay.
Explorations
Boring B-1 encountered approximately 10 feet of loose to medium dense, silty-fine to fine grained sand
(Possible Fill over Alluvium). This layer was underlain by loose to very dense, fine to medium grained
sand trace to some gravel (Alluvium), which continued to the termination depth of the boring. It must be
noted that there were local interbeds and layers of organic material (some peat), silt and silty-sands, and
areas with coarser gravel at multiple depths below grade.
Boring B-2 encountered approximately 9 feet of loose to medium dense, silty-fine to fine grained sand
(Possible Fill over Alluvium). This layer was underlain by loose to very dense, fine to medium grained
sand trace to some gravel (Alluvium), which continued to the termination depth of the boring. This
boring also encountered interbeds as discussed above.
PRELIMINARY GEOTECHNICAL INVESTIGATION
RENTON, WASHINGTON
January 8, 2021
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206-331-1097
5.1.2 Groundwater
Groundwater was encountered approximately 10.5 to 12 feet below existing site elevations in B-1 and B-2
respoectively, during our investigation. We anticipate that this represents the regional groundwater table
in this area. Groundwater likely fluctuates between about 8 and 16 feet below site elevations during a
typical year.
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.
6.0 Geologic Hazards
6.1 Erosion Hazard
The Natural Resources Conservation Services (NRCS) maps for King County indicate that the site is
underlain by Urban Land. These soils generally have a slight to moderate erosion potential in a disturbed
state.
It is our opinion that soil erosion potential at this project site can be reduced through landscaping and
surface water runoff control. Typically, erosion of exposed soils will be most noticeable during periods of
rainfall and may be controlled by the use of normal temporary erosion control measures, such as silt
fences, hay bales, mulching, control ditches and diversion trenches. The typical wet weather season, with
regard to site grading, is from October 31st to April 1st. Erosion control measures should be in place before
the onset of wet weather.
6.2 Seismic Hazard
The overall subsurface profile corresponds to a Site Class E as defined by Table 1613.5.2 of the 2015
International Building Code (2015 IBC). A Site Class E applies to a soil profile that includes at least 10
feet of loose soils.
We referenced the U.S. Geological Survey (USGS) Earthquake Hazards Program Website to obtain values
for SS, S1, Fa, and Fv. The USGS website includes the most updated published data on seismic conditions.
The site-specific seismic design parameters and adjusted maximum spectral response acceleration
parameters are as follows:
PGA (Peak Ground Acceleration, in percent of g)
SS 144.30% of g
S1 54.00% of g
FA 0.9
FV 2.4
PRELIMINARY GEOTECHNICAL INVESTIGATION
RENTON, WASHINGTON
January 8, 2021
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PO Box 82243
Kenmore, WA 98028
cobaltgeo@gmail.com
206-331-1097
Additional seismic considerations include liquefaction potential and amplification of ground motions by
soft/loose soil deposits. The liquefaction potential is highest for loose sand with a high groundwater table.
Soil liquefaction is a state where soil particles lose contact with each other and become suspended in a
viscous fluid. This suspension of the soil grains results in a complete loss of strength as the effective stress
drops to zero as a result of increased pore pressures. Liquefaction normally occurs under saturated
conditions in soils such as sand in which the strength is purely frictional. However, liquefaction has
occurred in soils other than clean sand, such as low plasticity silt. Liquefaction usually occurs under
vibratory conditions such as those induced by seismic events.
To evaluate the liquefaction potential of the site, we analyzed the following factors:
1) Soil type and plasticity
2) Groundwater depth
3) Relative soil density
4) Initial confining pressure
5) Maximum anticipated intensity and duration of ground shaking
The commercially available liquefaction analysis software, LiqSVS was used to evaluate the liquefaction
potential and the possible liquefaction induced settlement for the existing site soil conditions. Maximum
Considered Earthquake (MCE) was selected in accordance with the 2012 ASCE, 2015 International
Building Code (2015 IBC) and the U.S. Geological Survey (USGS) Earthquake Hazards Program website.
For this site, we used a peak ground acceleration of 0.535g and a 7.0M earthquake in the liquefaction
analyses.
The analyses yielded total settlement on the order of 12.7 inches with corresponding differential
settlement of about 6.35 inches. From the analyses, the depth of the liquefiable zone was identified as
about 12 to 40 feet below grade in the area of B-1.
7.0 DISCUSSION
7.1.1 General
The site is underlain by likely areas of fill and at depth by variable composition alluvium which is locally
loose. The subsurface soils are locally liquefiable during/after certain seismic events between about 12
and 40 feet below grade.
Depending on the final building location, elevations, and loading, the structure may be supported on
several types of foundation systems. These include but are not limited to a mat/raft system, auger-cast
piles with grade beams, and compacted rock columns or geopiers.
Depending on the proposed cuts, temporary or permanent shoring could include soldier pile walls with
tieback anchors and potentially walers.
PRELIMINARY GEOTECHNICAL INVESTIGATION
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Significant de-watering systems will be required if excavations below the water table are proposed. The
groundwater table in this area is relatively shallow and continuous with depth. In other words,
groundwater is not perched and localized; therefore, continuous pumping of de-watering wells will be
required to construct the building. Water-tight shoring would be necessary to allow this type of system to
be effective.
8.0 Recommendations
8.1.1 Site Preparation
Based on our understating of the project, clearing and removal of near-surface soils will be necessary. We
recommend removal of all organic laden materials and any fill. Based on observations from the site
investigation program, it is anticipated that the stripping depth will be 6 to 12 inches. Deeper excavations
will be necessary below utilities, existing foundation elements (if present), and in any areas underlain by
undocumented fill materials.
The near-surface soils consist of silty-sand with gravel and poorly graded sands with silt. Soils with less
than 35 percent fines (passing the No. 200 sieve) may be used as structural fill provided they achieve
compaction requirements and are within 3 percent of the optimum moisture. These soils may only be
suitable for use as fill during the summer months, as they will be above the optimum moisture levels in
their natural state. These soils are variably moisture sensitive and may degrade during periods of wet
weather and under equipment traffic.
Imported structural fill should consist of a sand and gravel mixture with a maximum grain size of 3 inches
and less than 5 percent fines (material passing the U.S. Standard No. 200 Sieve). Structural fill should be
placed in maximum lift thicknesses of 12 inches and should be compacted to a minimum of 95 percent of
the modified proctor maximum dry density, as determined by the ASTM D 1557 test method.
8.1.2 Temporary Excavations
Based on our understanding of the project, we anticipate that the near surface grading could include local
cuts on the order of approximately 8 feet or less for utility placement. We anticipate that shoring will be
required for building foundations.
Excavations up to 8 feet in height, if required, should be sloped no steeper than 1.5H:1V
(Horizontal:Vertical) in loose fill and/or native soils. If an excavation is subject to heavy vibration or
surcharge loads, we recommend that the excavations be sloped no steeper than 2H:1V, where room
permits. Any deeper excavations will require shoring.
Temporary cuts should be in accordance with the Washington Administrative Code (WAC) Part N,
Excavation, Trenching, and Shoring. Temporary slopes should be visually inspected daily by a qualified
person during construction activities and the inspections should be documented in daily reports. The
contractor is responsible for maintaining the stability of the temporary cut slopes and reducing slope
erosion during construction.
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Temporary cut slopes should be covered with visqueen to help reduce erosion during wet weather, and the
slopes should be closely monitored until the permanent retaining systems or slope configurations are
complete. Materials should not be stored or equipment operated within 10 feet of the top of any
temporary cut slope.
Soil conditions may not be completely known from the geotechnical investigation. In the case of
temporary cuts, the existing soil conditions may not be completely revealed until the excavation work
exposes the soil. Typically, as excavation work progresses the maximum inclination of temporary slopes
will need to be re-evaluated by the geotechnical engineer so that supplemental recommendations can be
made. Soil and groundwater conditions can be highly variable. Scheduling for soil work will need to be
adjustable, to deal with unanticipated conditions, so that the project can proceed and required deadlines
can be met.
If any variations or undesirable conditions are encountered during construction, we should be notified so
that supplemental recommendations can be made. If room constraints or groundwater conditions do not
permit temporary slopes to be cut to the maximum angles allowed by the WAC, temporary shoring
systems may be required. The contractor should be responsible for developing temporary shoring
systems, if needed. We recommend that Cobalt Geosciences and the project structural engineer review
temporary shoring designs prior to installation, to verify the suitability of the proposed systems.
Shoring
Depending on the depth of planned cuts and final building elevations, temporary and/or permanent
shoring will be required. For a single-story depth basement level, we anticipate that cantilever soldier
piles with timber lagging will be adequate. At this depth, groundwater may be present near the base of the
excavation. Any deeper excavations will likely require water-tight shoring, de-watering wells, and walls
capable of resisting high lateral loads. These may include secant pile walls, sheet piles, soldier pile walls
with tiebacks, and/or combinations of these systems.
The following section includes preliminary recommendations for a typical soldier pile wall for a single-
story depth basement level.
Soldier piles typically consist of steel W or H-beams inserted into oversized drilled shafts, which are
backfilled with structural concrete, lean mix {Controlled Density Fill (CDF)}, or a combination of lean mix
to the base of the excavation and structural concrete below the excavation to anchor the soldier piles.
Due to the potential for local caving during drilling operations for the soldier pile holes due to soft soil
conditions and shallow groundwater, consideration should be given to using slurry or drilling fluid to
reduce the risk of caving of the pile holes during installation. If water is present within the pile hole at the
time of soldier pile concrete placement, the concrete should be placed starting at the bottom of the hole
with a tremie pipe and the column of concrete should be raised slowly to displace the water. Water will be
present along with caving soil conditions.
We recommend that soldier piles have a maximum spacing of eight feet on center. To account for arching
effects, lateral loading on the lagging can be reduced by 50 percent. Unlagged excavation heights should
not exceed three feet. No portion of the excavation should remain unsupported overnight. Lagging
sections may be up to 6 feet in height depending on stability.
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Cantilever soldier pile walls for this site may be designed based on an active lateral earth pressure of 40
pcf for a level backslope, provided the wall is unrestrained (not fixed; permitted to move at least 0.2
percent of the wall height). The pressure will act on the soldier pile width below the base of the excavation
as well. All applicable surcharge pressures should be included. A lateral uniform seismic pressure of 8H is
recommended for seismic conditions (active).
In front of the soldier piles, resistive pressure can be estimated using an allowable passive earth pressure
of 250 pcf acting over 2 times the soldier pile diameter, neglecting the upper 2 feet below the base of the
excavation. A factor of safety of 1.5 has been incorporated into the passive pressure value. A lateral
pressure reduction of 50 percent may be used for design of the lagging for a pile spacing of three
diameters. Lagging should be backfilled with 5/8 inch clean angular rock to minimize void spaces.
8.1.3 Erosion and Sediment Control
Erosion and sediment control (ESC) is used to reduce the transportation of eroded sediment to wetlands,
streams, lakes, drainage systems, and adjacent properties. Erosion and sediment control measures
should be implemented and these measures should be in general accordance with local regulations. At a
minimum, the following basic recommendations should be incorporated into the design of the erosion
and sediment control features for the site:
x Schedule the soil, foundation, utility, and other work requiring excavation or the disturbance of the
site soils, to take place during the dry season (generally May through September). However, provided
precautions are taken using Best Management Practices (BMP’s), grading activities can be completed
during the wet season (generally October through April).
x All site work should be completed and stabilized as quickly as possible.
x Additional perimeter erosion and sediment control features may be required to reduce the possibility
of sediment entering the surface water. This may include additional silt fences, silt fences with a
higher Apparent Opening Size (AOS), construction of a berm, or other filtration systems.
x Any runoff generated by dewatering discharge should be treated through construction of a sediment
trap if there is sufficient space. If space is limited other filtration methods will need to be
incorporated.
8.1.4 Preliminary Foundation Design Options
Due to the presence of liquefiable soils to variable depths below the property, it will be necessary to
support the building on a deep foundation system, rock columns, or on a mat/raft grade beam system.
Foundation options include auger-cast piles with grade beams, compacted rock columns, or a grade beam
raft/mat system. The following sections include preliminary recommendations for several of the
foundation support options.
Mat Foundations
It is our opinion that a rigid or flexible mat foundation system with interconnecting grade beams or
structural slab may be used to support the proposed building.
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A net allowable bearing pressure of 2,000 pounds per square foot (psf) may be used for design of the
mat/raft foundation at a depth of at least 3 feet below grade and on native soils. Local overexcavation
may be required. Any fill should be replaced with angular crushed rock. This bearing pressure may be
increased if deep cuts are proposed. These recommendations are preliminary only since the
recommendations are elevation specific.
Resistance to lateral footing displacement can be determined using an allowable friction factor of 0.40
acting between the base of foundations and the supporting subgrades. Lateral resistance for footings can
also be developed using an allowable equivalent fluid passive pressure of 250 pounds per cubic foot (pcf)
acting against the appropriate vertical footing faces (neglect the upper 12 inches below grade in exterior
areas). The allowable friction factor and allowable equivalent fluid passive pressure values include a
factor of safety of 1.5. The frictional and passive resistance of the soil may be combined without reduction
in determining the total lateral resistance.
Foundation excavations should be inspected to verify that the elements will bear on suitable material. It
should be noted that tipping may occur during/after certain seismic events, which could result in some
structural distress.
Exterior footings should have a minimum depth of 18 inches below pad subgrade (soil grade) or adjacent
exterior grade, whichever is lower. Once the final design plans have been determined, we should be
allowed to review the plans for conformance with our recommendations.
Rock Columns
Shallow perimeter and column footings supported on compacted rock columns or geopiers. We
anticipate that compacted rock columns/aggregate piers will need to extend about 35 feet below current
site elevations. Even with ground improvement, some structural damage and distress may occur
following certain seismic events (liquefaction). If structural damage is of primary concern, we
recommend supporting the building on auger-cast piles. We can provide auger-cast pile recommendations
and parameters upon request.
If deep cuts are planned and executed, the depth of aggregate piers will likely decrease. We can provide
additional input once the overall construction plan with elevations has been prepared.
Provided that the concrete grade beam footings are supported on a system of compacted rock columns, a
net allowable bearing pressure of 4,000 pounds per square foot (psf) may be used for design. Final
structural design should be prepared by a structural engineer experienced with aggregate piers. We
recommend that at least one load test be performed to verify adequate bearing capacity.
Resistance to lateral footing displacement can be determined using an allowable friction factor of 0.40
acting between the base of foundations and the supporting subgrades. Lateral resistance for footings can
also be developed using an allowable equivalent fluid passive pressure of 250 pounds per cubic foot (pcf)
acting against the appropriate vertical footing faces (neglect the upper 12 inches below grade in exterior
areas). The allowable friction factor and allowable equivalent fluid passive pressure values include a
factor of safety of 1.5. The frictional and passive resistance of the soil may be combined without reduction
in determining the total lateral resistance.
A representative of Cobalt should be present at the site during the installation to verify general
conformance with our recommendations.
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8.1.5 Reinforced Concrete Retaining Walls
The following table, titled Wall Design Criteria, presents the recommended soil related design
parameters for single story basement retaining walls with a level backslope. Contact Cobalt if an alternate
retaining wall system is used.
Wall Design Criteria
“At-rest” Conditions (Lateral Earth Pressure – EFD+) 60 pcf (Equivalent Fluid Density)
“Active” Conditions (Lateral Earth Pressure – EFD+) 40 pcf (Equivalent Fluid Density)
Seismic Increase for “At-rest” Conditions
(Lateral Earth Pressure)
25H* (Uniform Distribution) 1 in 2,500 year event
Seismic Increase for “At-rest” Conditions
(Lateral Earth Pressure)
15H* (Uniform Distribution) 1 in 500 year event
Seismic Increase for “Active” Conditions
(Lateral Earth Pressure)
8H* (Uniform Distribution)
Passive Earth Pressure on Low Side of Wall
(Allowable, includes F.S. = 1.5)
Neglect upper 12 inches, then 250 pcf EFD+
Soil-Footing Coefficient of Sliding Friction (Allowable;
includes F.S. = 1.5)
0.40
*H is the height of the wall; Increase based on one in 500 year seismic event (10 percent probability of being exceeded in 50 years), +
EFD – Equivalent Fluid Density
The stated lateral earth pressures do not include the effects of hydrostatic pressure generated by water
accumulation behind the retaining walls. Uniform horizontal lateral active and at-rest pressures on the
retaining walls from vertical surcharges behind the wall may be calculated using active and at-rest lateral
earth pressure coefficients of 0.3 and 0.5, respectively. The soil unit weight of 125 pcf may be used to
calculate vertical earth surcharges.
To reduce the potential for the buildup of water pressure against the walls, continuous footing drains
(with cleanouts) should be provided at the bases of the walls. The footing drains should consist of a
minimum 4-inch diameter perforated pipe, sloped to drain, with perforations placed down and enveloped
by a minimum 6 inches of pea gravel in all directions.
The backfill adjacent to and extending a lateral distance behind the walls at least 2 feet should consist of
free-draining granular material. All free draining backfill should contain less than 3 percent fines
(passing the U.S. Standard No. 200 Sieve) based upon the fraction passing the U.S. Standard No. 4 Sieve
with at least 30 percent of the material being retained on the U.S. Standard No. 4 Sieve. The primary
purpose of the free-draining material is the reduction of hydrostatic pressure. Some potential for the
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moisture to contact the back face of the wall may exist, even with treatment, which may require that more
extensive waterproofing be specified for walls, which require interior moisture sensitive finishes.
We recommend that the backfill be compacted to at least 90 percent of the maximum dry density based
on ASTM Test Method D1557. In place density tests should be performed to verify adequate compaction.
Soil compactors place transient surcharges on the backfill. Consequently, only light hand operated
equipment is recommended within 3 feet of walls so that excessive stress is not imposed on the walls.
Due to the likely presence of regional groundwater at shallow depths, permanent pump systems may be
required around the perimeter of the basement level.
8.1.6 Slab-on-Grade
We recommend that the upper 18 inches of the existing native soils within slab areas be re-compacted to
at least 95 percent of the modified proctor (ASTM D1557 Test Method). The type and depth of soil re-
compaction or removal and replacement is highly dependent on the elevation of any slabs. We can update
these recommendations once planned floor elevations have been determined. Note that these
recommendations may not be applicable for mat or raft foundation systems since they are essentially
large slabs.
Often, a vapor barrier is considered below concrete slab areas. However, the usage of a vapor barrier could
result in curling of the concrete slab at joints. Floor covers sensitive to moisture typically requires the
usage of a vapor barrier. A materials or structural engineer should be consulted regarding the detailing of
the vapor barrier below concrete slabs. Exterior slabs typically do not utilize vapor barriers.
The American Concrete Institutes ACI 360R-06 Design of Slabs on Grade and ACI 302.1R-04 Guide for
Concrete Floor and Slab Construction are recommended references for vapor barrier selection and floor
slab detailing.
Slabs on grade may be designed using a coefficient of subgrade reaction of 180 pounds per cubic inch (pci)
assuming the slab-on-grade base course is underlain by structural fill placed and compacted as outlined in
Section 8.1. A 4-6 inch thick capillary break material should be placed on the subgrade soils. This may
consist of pea gravel or 5/8 inch clean angular rock.
A perimeter drainage system is recommended around the residence and potentially within the slab
subgrade depending on the finish floor elevations. A perimeter drainage system should consist of 4 inch
diameter perforated drain pipes surrounded by a minimum 6 inches of drain rock wrapped in a non-
woven geosynthetic filter fabric to reduce migration of soil particles into the drainage system. The
perimeter drainage system should discharge by gravity flow to a suitable stormwater system.
Exterior grades surrounding buildings should be sloped at a minimum of one percent to facilitate surface
water flow away from the building and preferably with a relatively impermeable surface cover
immediately adjacent to the building.
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8.1.7 Stormwater Management
The site is underlain by local fill and at depth by saturated alluvium. While infiltration could be
considered, we anticipate that the site development will fully encompass the property limits, thereby
making infiltration infeasible.
We recommend detention (if required) with direct connection to City stormwater infrastructure. We can
provide additional recommendations upon request.
8.1.8 Groundwater Influence on Construction
Groundwater was encountered at about 10.5 feet below grade in B-1 and 12 feet in B-2.
Regional groundwater will be encountered below about 8 to 12 feet during certain years/seasons. If
excavations extend into the groundwater, water-tight shoring and de-watering wells may be required. We
can provide additional recommendations upon request; however, any de-watering system utilizing
pumping wells will require design by a hydrogeologist.
8.1.9 Utilities
Utility trenches should be excavated according to accepted engineering practices following OSHA
(Occupational Safety and Health Administration) standards, by a contractor experienced in such work.
The contractor is responsible for the safety of open trenches. Traffic and vibration adjacent to trench
walls should be reduced; cyclic wetting and drying of excavation side slopes should be avoided.
Depending upon the location and depth of some utility trenches, groundwater flow into open excavations
could be experienced, especially during or shortly following periods of precipitation.
In general, sandy and gravelly soils were encountered at shallow depths in the explorations at this site.
These soils have variable cohesion and low density and will have a tendency to cave or slough in
excavations. Shoring or sloping back trench sidewalls is required within these soils in excavations greater
than 4 feet deep.
All utility trench backfill should consist of imported structural fill or suitable on site soils. Utility trench
backfill placed in or adjacent to buildings and exterior slabs should be compacted to at least 95 percent of
the maximum dry density based on ASTM Test Method D1557. The upper 5 feet of utility trench backfill
placed in pavement areas should be compacted to at least 95 percent of the maximum dry density based
on ASTM Test Method D1557. Below 5 feet, utility trench backfill in pavement areas should be compacted
to at least 90 percent of the maximum dry density based on ASTM Test Method D1557. Pipe bedding
should be in accordance with the pipe manufacturer's recommendations.
The contractor is responsible for removing all water-sensitive soils from the trenches regardless of the
backfill location and compaction requirements. Depending on the depth and location of the proposed
utilities, we anticipate the need to re-compact existing fill soils below the utility structures and pipes. The
contractor should use appropriate equipment and methods to avoid damage to the utilities and/or
structures during fill placement and compaction procedures.
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8.1.10 Pavement Recommendations
The near surface subgrade native soils generally consist of silty-sand with gravel. These soils are rated as
good for pavement subgrade material (depending on silt content and moisture conditions). We estimate
that the subgrade will have a California Bearing Ratio (CBR) value of 10 and a modulus of subgrade
reaction value of k = 180 pci, provided the subgrade is prepared in general accordance with our
recommendations. These recommendations are for at grade conditions. Recommendations for
pavements at basement levels may differ somewhat. We can update these recommendations once plans
have been prepared.
We recommend that at a minimum, 18 inches of the existing subgrade material be moisture conditioned
(as necessary) and re-compacted to prepare for the construction of pavement sections. Deeper levels of
recompaction or overexcavation and replacement may be necessary in areas where fill and/or very poor
(soft/loose) soils are present. If dense soils are encountered, overexcavation may not be required.
Any soils that cannot be compacted to required levels should be removed and replaced with imported
structural fill. We anticipate the need for at least 6 inches of new structural fill over medium dense native
soils if the work occurs outside of the summer months when drying can occur.
The subgrade should be compacted to at least 95 percent of the maximum dry density as determined by
ASTM Test Method D1557. In place density tests should be performed to verify proper moisture content
and adequate compaction.
The recommended flexible and rigid pavement sections are based on design CBR and modulus of
subgrade reaction (k) values that are achieved, only following proper subgrade preparation. It should be
noted that subgrade soils that have relatively high silt contents will likely be highly sensitive to moisture
conditions. The subgrade strength and performance characteristics of a silty subgrade material may be
dramatically reduced if this material becomes wet.
Based on our knowledge of the proposed project, we expect the traffic to range from light duty (passenger
automobiles) to heavy duty (delivery trucks). The following tables show the recommended pavement
sections for light duty and heavy duty use.
ASPHALTIC CONCRETE (FLEXIBLE) PAVEMENT
LIGHT DUTY
Asphaltic Concrete Aggregate Base* Compacted Subgrade* **
2.5 in. 6.0 in. 12.0 in.
HEAVY DUTY
Asphaltic Concrete Aggregate Base* Compacted Subgrade* **
4.5 in. 8.0 in. 12.0 in.
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PORTLAND CEMENT CONCRETE (RIGID) PAVEMENT
Min. PCC Depth Aggregate Base* Compacted Subgrade* **
6.0 in. 6.0 in. 12.0 in.
* 95% compaction based on ASTM Test Method D1557
** A proof roll may be performed in lieu of in place density tests
The asphaltic concrete depth in the flexible pavement tables should be a surface course type asphalt, such
as Washington Department of Transportation (WSDOT) ½ inch HMA. The rigid pavement design is
based on a Portland Cement Concrete (PCC) mix that has a 28 day compressive strength of 4,000 pounds
per square inch (psi). The design is also based on a concrete flexural strength or modulus of rupture of
550 psi.
9.0 Construction Field Reviews
Cobalt Geosciences should be retained to provide part time field review during construction in order to
verify that the soil conditions encountered are consistent with our design assumptions and that the intent
of our recommendations is being met. This will require field and engineering review to:
Monitor and test structural fill placement and soil compaction
Observe deep foundation installation and testing
Observe slab-on-grade preparation
Geotechnical design services should also be anticipated during the subsequent final design phase to
support the structural design and address specific issues arising during this phase. Field and engineering
review services will also be required during the construction phase in order to provide a Final Letter for
the project.
10.0 Closure
This report was prepared for the exclusive use of Ambili Sukesa and their 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.
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Use of this report is subject to the Statement of General Conditions provided in Appendix A. It is the
responsibility of Ambili Sukesa 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:
DRAFT ONLY
Phil Haberman, PE, LG, LEG
Principal
PH/sc
APPENDIX A
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 party without the express written consent of Cobalt Geosciences and the
Client. Any use which a third party 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.
10.2
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APPENDIX B
Figures: Vicinity Map, Site Plan
N
Project
Location
Renton
WASHINGTON
VICINITY
MAP
FIGURE 1
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, WA 98028
(206) 331-1097
www.cobaltgeo.com
cobaltgeo@gmail.com
SITE
Proposed Mixed Use Building
3xx Logan Avenue North
Renton, Washington
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, WA 98028
(206) 331-1097
www.cobaltgeo.com
cobaltgeo@gmail.com
SITE PLAN
FIGURE 2
N
Proposed Mixed Use Building
3xx Logan Avenue North
Renton, Washington
APPENDIX C
Boring Logs & Laboratory Analyses
PT
Well-graded gravels, gravels, gravel-sand mixtures, little or no fines
Poorly graded gravels, gravel-sand mixtures, little or no fines
Silty gravels, gravel-sand-silt mixtures
Clayey gravels, gravel-sand-clay mixtures
Well-graded sands, gravelly sands, little or no fines
COARSE
GRAINED
SOILS
(more than 50%
retained on
No. 200 sieve)
Primarily organic matter, dark in color,
and organic odor Peat, humus, swamp soils with high organic content (ASTM D4427)HIGHLY ORGANIC
SOILS
FINE GRAINED
SOILS
(50% or more
passes the
No. 200 sieve)
MAJOR DIVISIONS SYMBOL TYPICAL DESCRIPTION
Gravels
(more than 50%
of coarse fraction
retained on No. 4
sieve)
Sands
(50% or more
of coarse fraction
passes the No. 4
sieve)
Silts and Clays
(liquid limit less
than 50)
Silts and Clays
(liquid limit 50 or
more)
Organic
Inorganic
Organic
Inorganic
Sands with
Fines
(more than 12%
fines)
Clean Sands
(less than 5%
fines)
Gravels with
Fines
(more than 12%
fines)
Clean Gravels
(less than 5%
fines)
Unified Soil Classification System (USCS)
Poorly graded sand, gravelly sands, little or no fines
Silty sands, sand-silt mixtures
Clayey sands, sand-clay mixtures
Inorganic silts of low to medium plasticity, sandy silts, gravelly silts,
or clayey silts with slight plasticity
Inorganic clays of low to medium plasticity, gravelly clays, sandy clays,
silty clays, lean clays
Organic silts and organic silty clays of low plasticity
Inorganic silts, micaceous or diatomaceous fine sands or silty soils,
elastic silt
Inorganic clays of medium to high plasticity, sandy fat clay,
or gravelly fat clay
Organic clays of medium to high plasticity, organic silts
Moisture Content Definitions
Grain Size Definitions
Dry Absence of moisture, dusty, dry to the touch
Moist Damp but no visible water
Wet Visible free water, from below water table
Grain Size Definitions
Description Sieve Number and/or Size
Fines <#200 (0.08 mm)
Sand
-Fine
-Medium
-Coarse
Gravel
-Fine
-Coarse
Cobbles
Boulders
#200 to #40 (0.08 to 0.4 mm)
#40 to #10 (0.4 to 2 mm)
#10 to #4 (2 to 5 mm)
#4 to 3/4 inch (5 to 19 mm)
3/4 to 3 inches (19 to 76 mm)
3 to 12 inches (75 to 305 mm)
>12 inches (305 mm)
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 0 to 5 percent of the soil
(i.e., slightly silty SAND, trace gravel).
Relative Density Consistency
(Coarse Grained Soils) (Fine Grained Soils)
N, SPT, Relative
Blows/FT Density
0 - 4 Very loose
4 - 10 Loose
10 - 30 Medium dense
30 - 50 Dense
Over 50 Very dense
N, SPT, Relative
Blows/FT Consistency
Under 2 Very soft
2 - 4 Soft
4 - 8 Medium stiff
8 - 15 Stiff
15 - 30 Very stiff
Over 30 Hard
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, WA 98028
(206) 331-1097
www.cobaltgeo.com
cobaltgeo@gmail.com
Soil Classification Chart Figure C1
Log of Boring B-1
Date: December 23, 2020
Contractor: EDI
Method: Hollow Stem Auger
Depth: 50.2’
Elevation: N/A
Logged By: PH Checked By: SC
Initial Groundwater: 10.5’
Sample Type: Split Spoon
Final Groundwater:
Material Description SPT N-Value
Moisture Content (%)Plastic
Limit
Liquid
Limit
10 20 30 400 50
4
8
12
16
20
24
28
32
36
40
End of Boring 50.2’
SM/
ML
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, WA 98028
(206) 331-1097
www.cobaltgeo.com
cobaltgeo@gmail.com
Proposed Mixed Use Building
3xx Logan Avenue North
Renton, Washington
Boring
Log
44
3
4
7
6
20
27
2
3
3
3
4
12
15
25
28
3
5
8
7
11
19
SP
Silt trace clay interbed at 23.25’
Organic materials present at 33’
Likely interbeds of silt and silty sand at multiple depths
48
52
5
5
4
Loose, silty-fine to fine grained sand with layers of silty-sand,
mottled yellowish brown to grayish brown, moist. (Fill and Alluvium)
Loose to very dense, fine to medium grained sand local organics
trace to some gravel locally with silt, grayish brown, moist to wet.
(Alluvium)
4
3
5
50/2
Log of Boring B-2
Date: December 23, 2020
Contractor: EDI
Method: Hollow Stem Auger
Depth: 34’
Elevation: N/A
Logged By: PH Checked By: SC
Initial Groundwater: 12’
Sample Type: Split Spoon
Final Groundwater:
Material Description SPT N-Value
Moisture Content (%)Plastic
Limit
Liquid
Limit
10 20 30 400 50
4
8
12
16
20
24
28
32
36
40
End of Boring 34’
SM/
ML
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, WA 98028
(206) 331-1097
www.cobaltgeo.com
cobaltgeo@gmail.com
Proposed Mixed Use Building
3xx Logan Avenue North
Renton, Washington
Boring
Log
44
1
4
6
1
4
3
2
1
2
5
12
15
5
9
10
SP
Organic materials present at 24’
Likely interbeds of silt and silty sand at multiple depths
48
52
3
13
12
Loose, silty-fine to fine grained sand with layers of silty-sand,
mottled yellowish brown to grayish brown, moist. (Fill and Alluvium)
Loose to very dense, fine to medium grained sand local organics
trace to some gravel locally with silt, grayish brown, moist to wet.
(Alluvium)
1
4
6
APPENDIX D
Liquefaction Analyses
SPT BASED LIQUEFACTION ANALYSIS REPORT
:: Input parameters and analysis properties ::
Analysis method:
Fines correction method:
Sampling method:
Borehole diameter:
Rod length:
Hammer energy ratio:
NCEER 1998
NCEER 1998
Standard Sampler
65mm to 115mm
3.28 ft
1.00
G.W.T. (in-situ):
G.W.T. (earthq.):
Earthquake magnitude M w:
Peak ground acceleration:
Eq. external load:
Project title :
Location :
SPT Name: SPT #1
10.50 ft
8.00 ft
7.00
0.54 g
0.00 tsf
Raw SPT Data
SPT Count (blows/ft)
50403020100Depth (ft)52
50
48
46
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
Raw SPT Data
Insitu
CSR - CRR Plot
CSR - CRR
10. 80. 60. 40. 20Depth (ft)50
48
46
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
CSR - CRR Plot
During earthq.
FS Plot
Factor of Safety
21. 510. 50Depth (ft)50
48
46
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
FS Plot
During earthq.
LPI
Liquefaction potential
3020100Depth (ft)50
48
46
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
LPI
During earthq.
CRR 7.50 clean sand curve
Corrected Blow Count N1(60),cs
50454035302520151050Cyclic Stress Ratio*0. 8
0. 7
0. 6
0. 5
0. 4
0. 3
0. 2
0. 1
0. 0
CRR 7.50 clean sand curve
Liquefaction
No Liquefaction
F.S. color scheme
Almost certain it will liquefy
Very likely to liquefy
Liquefaction and no liq. are equally likely
Unlike to liquefy
Almost certain it will not liquefy
LPI color scheme
Very high risk
High risk
Low risk
Project File:
Page: 1LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software
This software is registered to: Cobalt Geosciences
Raw SPT Data
SPT Count (blows/ft)
50403020100Depth (ft)52
50
48
46
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
Raw SPT Data
Insitu
CSR - CRR Plot
CSR - CRR
10. 80. 60. 40. 20Depth (ft)50
48
46
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
CSR - CRR Plot
During earthq.
FS Plot
Factor of Safety
21. 510. 50Depth (ft)50
48
46
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
FS Plot
During earthq.
Vertical Liq. Settlements
Cuml. Settlement (in)
1050Depth (ft)50
48
46
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
Vertical Liq. Settlements
During earthq.
Lateral Liq. Displacements
Cuml. Displacement (ft)
0Depth (ft)50
48
46
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
Lateral Liq. Displacements
During earthq.
:: Overall Liquefaction Assessment Analysis Plots ::
Project File:
Page: 2LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software
This software is registered to: Cobalt Geosciences
Test
Depth
(ft)
:: Field input data ::
SPT Field
Value
(blows)
Fines
Content
(%)
Unit
Weight
(pcf)
Infl.
Thickness
(ft)
Can
Liquefy
4.00 6 50.00 115.00 5.00 No
8.00 11 25.00 115.00 5.00 No
14.00 9 5.00 115.00 5.00 Yes
18.00 47 5.00 120.00 5.00 Yes
23.00 8 5.00 115.00 5.00 Yes
28.00 30 5.00 120.00 5.00 Yes
33.00 16 5.00 120.00 5.00 Yes
38.00 13 5.00 120.00 5.00 Yes
43.00 50 5.00 125.00 5.00 Yes
50.00 50 5.00 125.00 5.00 Yes
Abbreviations
Depth:
SPT Field Value:
Fines Content:
Unit Weight:
Infl. Thickness:
Can Liquefy:
Depth at which test was performed (ft)
Number of blows per foot
Fines content at test depth (%)
Unit weight at test depth (pcf)
Thickness of the soil layer to be considered in settlements analysis (ft)
User defined switch for excluding/including test depth from the analysis procedure
:: Cyclic Resistance Ratio (CRR) calculation data ::
CRR 7.5Depth
(ft)
SPT
Field
Value
CN CE CB CR C S (N 1)60 (N 1)60csαβFines
Content
(%)
σ v(tsf)
u o(tsf)
σ'vo(tsf)Unit
Weight
(pcf)
4.00 6 1.55 1.00 1.00 0.75 1.00 7 5.00 1.20 13 4.00050.00115.00 0.23 0.00 0.23
8.00 11 1.35 1.00 1.00 0.75 1.00 11 4.29 1.12 17 4.00025.00115.00 0.46 0.00 0.46
14.00 9 1.18 1.00 1.00 0.85 1.00 9 0.00 1.00 9 0.0995.00115.00 0.81 0.11 0.70
18.00 47 1.12 1.00 1.00 0.95 1.00 50 0.00 1.00 50 4.0005.00120.00 1.05 0.23 0.81
23.00 8 1.05 1.00 1.00 0.95 1.00 8 0.00 1.00 8 0.0905.00115.00 1.33 0.39 0.94
28.00 30 0.99 1.00 1.00 0.95 1.00 28 0.00 1.00 28 0.3485.00120.00 1.63 0.55 1.09
33.00 16 0.93 1.00 1.00 1.00 1.00 15 0.00 1.00 15 0.1635.00120.00 1.93 0.70 1.23
38.00 13 0.88 1.00 1.00 1.00 1.00 11 0.00 1.00 11 0.1205.00120.00 2.23 0.86 1.37
43.00 50 0.83 1.00 1.00 1.00 1.00 42 0.00 1.00 42 4.0005.00125.00 2.55 1.01 1.53
50.00 50 0.77 1.00 1.00 1.00 1.00 39 0.00 1.00 39 4.0005.00125.00 2.98 1.23 1.75
σ v:
u o:
σ'vo:
CN:
CE:
CB:
CR:
CS:
N1(60):
α, β:
N1(60)cs:
CRR7.5:
Total stress during SPT test (tsf)
Water pore pressure during SPT test (tsf)
Effective overburden pressure during SPT test (tsf)
Overburden corretion factor
Energy correction factor
Borehole diameter correction factor
Rod length correction factor
Liner correction factor
Corrected N SPT to a 60% energy ratio
Clean sand equivalent clean sand formula coefficients
Corected N1(60) value for fines content
Cyclic resistance ratio for M=7.5
Abbreviations
σ v, e q(tsf)
r d CSR MSF CSR eq,M=7.5 K si g m a
CSR *
:: Cyclic Stress Ratio calculation (CSR fully adjusted and normalized) ::
Depth
(ft)
Unit
Weight
(pcf)
u o, e q(tsf)
σ'vo,eq(tsf)
FSα
4.00 115.00 0.23 0.00 0.23 0.99 0.348 1.19 0.292 1.00 0.292 2.0001.00
8.00 115.00 0.46 0.00 0.46 0.98 0.345 1.19 0.289 1.00 0.289 2.0001.00
Project File:
Page: 3LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software
This software is registered to: Cobalt Geosciences
σ v, e q(tsf)
r d CSR MSF CSR eq,M=7.5 K si g m a
CSR *
:: Cyclic Stress Ratio calculation (CSR fully adjusted and normalized) ::
Depth
(ft)
Unit
Weight
(pcf)
u o, e q(tsf)
σ'vo,eq(tsf)
FSα
14.00 115.00 0.81 0.19 0.62 0.97 0.444 1.19 0.372 1.00 0.372 0.2671.00
18.00 120.00 1.05 0.31 0.73 0.96 0.481 1.19 0.404 1.00 0.404 2.0001.00
23.00 115.00 1.33 0.47 0.86 0.95 0.513 1.19 0.430 1.00 0.430 0.2081.00
28.00 120.00 1.63 0.62 1.01 0.93 0.529 1.19 0.443 1.00 0.443 0.7851.00
33.00 120.00 1.93 0.78 1.15 0.90 0.532 1.19 0.446 0.98 0.454 0.3601.00
38.00 120.00 2.23 0.94 1.30 0.87 0.525 1.19 0.440 0.96 0.458 0.2621.00
43.00 125.00 2.55 1.09 1.45 0.82 0.506 1.19 0.425 0.94 0.452 2.0001.00
50.00 125.00 2.98 1.31 1.67 0.75 0.471 1.19 0.395 0.91 0.433 2.0001.00
σv,eq:
uo,eq:
σ'vo,eq:
rd :
α:
CSR :
MSF :
CSR eq,M=7.5:
Ksigma:
CSR *:
FS:
Total overburden pressure at test point, during earthquake (tsf)
Water pressure at test point, during earthquake (tsf)
Effective overburden pressure, during earthquake (tsf)
Nonlinear shear mass factor
Improvement factor due to stone columns
Cyclic Stress Ratio (adjusted for improvement)
Magnitude Scaling Factor
CSR adjusted for M=7.5
Effective overburden stress factor
CSR fully adjusted (user FS applied)***
Calculated factor of safety against soi l l iquefaction
Abbreviations
1.00*** User FS:
:: Liquefaction potential according to Iwasaki ::
Depth
(ft)
FS F Thickness
(ft)
wz IL
4.00 2.000 0.00 9.39 0.004.00
8.00 2.000 0.00 8.78 0.004.00
14.00 0.267 0.73 7.87 10.556.00
18.00 2.000 0.00 7.26 0.004.00
23.00 0.208 0.79 6.49 7.845.00
28.00 0.785 0.21 5.73 1.885.00
33.00 0.360 0.64 4.97 4.855.00
38.00 0.262 0.74 4.21 4.735.00
43.00 2.000 0.00 3.45 0.005.00
50.00 2.000 0.00 2.38 0.007.00
29.84
IL = 0.00 - No liquefaction
IL between 0.00 and 5 - Liquefaction not probable
IL between 5 and 15 - Liquefaction probable
IL > 15 - Liquefaction certain
Overall potential I L :
:: Vertical settlements estimation for dry sands ::
Depth
(ft)
(N 1)60 τav p Gmax(tsf)
α b γ ε 15 Nc εNc(%)ΔS
(in)
Δh
(ft)
4.00 7 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.0005.00
Project File:
Page: 4LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software
This software is registered to: Cobalt Geosciences
:: Vertical settlements estimation for dry sands ::
Depth
(ft)
(N 1)60 τav p Gmax(tsf)
α b γ ε 15 Nc εNc(%)ΔS
(in)
Δh
(ft)
Abbreviations
τav:
p:
Gmax:
α, b:
γ:
ε15:
Nc:
εNc:
Δh:
ΔS:
Average cyclic shear stress
Average stress
Maximum shear modulus (tsf)
Shear strain formula variables
Average shear strain
Volumetric strain after 15 cycles
Number of cycles
Volumetric strain for number of cycles Nc (%)
Thickness of soil layer (in)
Settlement of soil layer (in)
0.000Cumulative settlemetns:
:: Vertical settlements estimation for saturated sands ::
Depth
(ft)
D 50(in)
q c/N e v(%)Δh
(ft)
s
(in)
8.00 0.01 2.10 0.00 5.00 0.000
14.00 0.10 4.04 5.36 5.00 3.216
18.00 0.10 4.04 0.00 5.00 0.000
23.00 0.10 4.04 5.80 5.00 3.480
28.00 0.10 4.04 1.70 5.00 1.019
33.00 0.10 4.04 3.53 5.00 2.115
38.00 0.10 4.04 4.55 5.00 2.728
43.00 0.10 4.04 0.00 5.00 0.000
50.00 0.10 4.04 0.00 5.00 0.000
Abbreviations
12.559Cumulative settlements:
D50:
qc/N:
ev:
Δh:
s:
Median grain size (in)
Ratio of cone resistance to SPT
Post liquefaction volumetric strain (%)
Thickness of soil layer to be considered (ft)
Estimated settlement (in)
:: Lateral displacements estimation for saturated sands ::
Depth
(ft)
(N 1)60 Dr(%)
γ max(%)
dz(ft)
LDI LD
(ft)
4.00 7 37.04 0.00 5.00 0.000 0.00
8.00 11 46.43 0.00 5.00 0.000 0.00
14.00 9 42.00 51.20 5.00 0.000 0.00
18.00 50 100.00 0.00 5.00 0.000 0.00
23.00 8 39.60 51.20 5.00 0.000 0.00
28.00 28 74.08 6.43 5.00 0.000 0.00
33.00 15 54.22 34.10 5.00 0.000 0.00
38.00 11 46.43 34.10 5.00 0.000 0.00
43.00 42 90.73 0.00 5.00 0.000 0.00
50.00 39 87.43 0.00 5.00 0.000 0.00
Project File:
Page: 5LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software
This software is registered to: Cobalt Geosciences
:: Lateral displacements estimation for saturated sands ::
Depth
(ft)
(N 1)60 Dr(%)
γ max(%)
dz(ft)
LDI LD
(ft)
0.00
Abbreviations
Cumulative lateral displacements:
Dr:
γmax:
dz:
LDI:
LD:
Relative density (%)
Maximum amplitude of cyclic shear strain (%)
Soil layer thickness (ft)
Lateral displacement index (ft)
Actual estimated displacement (ft)
Project File:
Page: 6LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software
References
⦁ Ronald D. Andrus, Hossein Hayati, Nisha P. Mohanan, 2009. Correcting Liquefaction Resistance for Aged Sands Using Measured
to Estimated Velocity Ratio, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 135, No. 6, June 1
⦁ Boulanger, R.W. and Idriss, I. M., 2014. CPT AND SPT BASED LIQUEFACTION TRIGGERING PROCEDURES. DEPARTMENT OF
CIVIL & ENVIRONMENTAL ENGINEERING COLLEGE OF ENGINEERING UNIVERSITY OF CALIFORNIA AT DAVIS
⦁ Dipl.-Ing. Heinz J. Priebe, Vibro Replacement to Prevent Earthquake Induced Liquefaction, Proceedings of the Geotechnique-
Colloquium at Darmstadt, Germany, on March 19th, 1998 (also published in Ground Engineering, September 1998), Technical
paper 12-57E
⦁ Robertson, P.K. and Cabal, K.L., 2007,Guide to Cone Penetration Testing for Geotechnical Engineering. Available at no cost at
http://www.geologismiki.gr/
⦁ Youd, T.L., Idriss, I.M., Andrus, R.D., Arango, I., Castro, G., Christian, J.T., Dobry, R., Finn, W.D.L., Harder, L.F., Hynes , M.E.,
Ishihara, K., Koester, J., Liao, S., Marcuson III, W.F., Martin, G.R., Mitchell, J.K., Moriwaki, Y., Power, M.S., Robertson, P.K.,
Seed, R., and Stokoe, K.H., Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF
Workshop on Evaluation of Liquefaction Resistance of Soils, ASCE, Journal of Geotechnical & Geoenvironmental Engineering,
Vol. 127, October, pp 817-833
⦁ Zhang, G., Robertson. P.K., Brachman, R., 2002, Estimating Liquefaction Induced Ground Settlements from the CPT, Canadian
Geotechnical Journal, 39: pp 1168-1180
⦁ Zhang, G., Robertson. P.K., Brachman, R., 2004, Estimating Liquefaction Induced Lateral Displacements using the SPT and CPT,
ASCE, Journal of Geotechnical & Geoenvironmental Engineering, Vol. 130, No. 8, 861 -871
⦁ Pradel, D., 1998, Procedure to Evaluate Earthquake-Induced Settlements in Dry Sandy Soils, ASCE, Journal of Geotechnical &
Geoenvironmental Engineering, Vol. 124, No. 4, 364-368
⦁ R. Kayen, R. E. S. Moss, E. M. Thompson, R. B. Seed, K. O. Cetin, A. Der Kiureghian, Y. Tanaka, K. Tokimatsu, 2013. Shear-
Wave Velocity–Based Probabilistic and Deterministic Assessment of Seismic Soil Liquefaction Potential, Journal of Geotechnical
and Geoenvironmental Engineering, Vol. 139, No. 3, March 1
LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software
SPT BASED LIQUEFACTION ANALYSIS REPORT
:: Input parameters and analysis properties ::
Analysis method:
Fines correction method:
Sampling method:
Borehole diameter:
Rod length:
Hammer energy ratio:
NCEER 1998
NCEER 1998
Standard Sampler
65mm to 115mm
3.28 ft
1.00
G.W.T. (in-situ):
G.W.T. (earthq.):
Earthquake magnitude M w:
Peak ground acceleration:
Eq. external load:
Project title :
Location :
SPT Name: SPT #1
10.50 ft
8.00 ft
7.00
0.54 g
0.00 tsf
Raw SPT Data
SPT Count (blows/ft)
50403020100Depth (ft)34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
Raw SPT Data
Insitu
CSR - CRR Plot
CSR - CRR
10. 80. 60. 40. 20Depth (ft)33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
CSR - CRR Plot
During earthq.
FS Plot
Factor of Safety
21. 510. 50Depth (ft)33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
FS Plot
During earthq.
LPI
Liquefaction potential
20100Depth (ft)33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
LPI
During earthq.
CRR 7.50 clean sand curve
Corrected Blow Count N1(60),cs
50454035302520151050Cyclic Stress Ratio*0. 8
0. 7
0. 6
0. 5
0. 4
0. 3
0. 2
0. 1
0. 0
CRR 7.50 clean sand curve
Liquefaction
No Liquefaction
F.S. color scheme
Almost certain it will liquefy
Very likely to liquefy
Liquefaction and no liq. are equally likely
Unlike to liquefy
Almost certain it will not liquefy
LPI color scheme
Very high risk
High risk
Low risk
Project File:
Page: 1LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software
This software is registered to: Cobalt Geosciences
Raw SPT Data
SPT Count (blows/ft)
50403020100Depth (ft)35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
Raw SPT Data
Insitu
CSR - CRR Plot
CSR - CRR
10. 80. 60. 40. 20Depth (ft)33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
CSR - CRR Plot
During earthq.
FS Plot
Factor of Safety
210Depth (ft)33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
FS Plot
During earthq.
Vertical Liq. Settlements
Cuml. Settlement (in)
8642Depth (ft)33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
Vertical Liq. Settlements
During earthq.
Lateral Liq. Displacements
Cuml. Displacement (ft)
0Depth (ft)33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
Lateral Liq. Displacements
During earthq.
:: Overall Liquefaction Assessment Analysis Plots ::
Project File:
Page: 2LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software
This software is registered to: Cobalt Geosciences
Test
Depth
(ft)
:: Field input data ::
SPT Field
Value
(blows)
Fines
Content
(%)
Unit
Weight
(pcf)
Infl.
Thickness
(ft)
Can
Liquefy
4.00 3 50.00 115.00 5.00 No
8.00 10 25.00 115.00 5.00 No
14.00 25 5.00 115.00 5.00 Yes
18.00 7 25.00 115.00 5.00 Yes
23.00 10 35.00 115.00 5.00 Yes
28.00 19 5.00 120.00 5.00 Yes
33.00 20 5.00 120.00 5.00 Yes
Abbreviations
Depth:
SPT Field Value:
Fines Content:
Unit Weight:
Infl. Thickness:
Can Liquefy:
Depth at which test was performed (ft)
Number of blows per foot
Fines content at test depth (%)
Unit weight at test depth (pcf)
Thickness of the soil layer to be considered in settlements analysis (ft)
User defined switch for excluding/including test depth from the analysis procedure
:: Cyclic Resistance Ratio (CRR) calculation data ::
CRR 7.5Depth
(ft)
SPT
Field
Value
CN CE CB CR C S (N 1)60 (N 1)60csαβFines
Content
(%)
σ v(tsf)
u o(tsf)
σ'vo(tsf)Unit
Weight
(pcf)
4.00 3 1.55 1.00 1.00 0.75 1.00 3 5.00 1.20 9 4.00050.00115.00 0.23 0.00 0.23
8.00 10 1.35 1.00 1.00 0.75 1.00 10 4.29 1.12 15 4.00025.00115.00 0.46 0.00 0.46
14.00 25 1.18 1.00 1.00 0.85 1.00 25 0.00 1.00 25 0.2855.00115.00 0.81 0.11 0.70
18.00 7 1.12 1.00 1.00 0.95 1.00 7 4.29 1.12 12 0.13125.00115.00 1.04 0.23 0.80
23.00 10 1.06 1.00 1.00 0.95 1.00 10 5.00 1.20 17 0.18535.00115.00 1.32 0.39 0.93
28.00 19 0.99 1.00 1.00 0.95 1.00 18 0.00 1.00 18 0.1965.00120.00 1.62 0.55 1.08
33.00 20 0.93 1.00 1.00 1.00 1.00 19 0.00 1.00 19 0.2065.00120.00 1.92 0.70 1.22
σ v:
u o:
σ'vo:
CN:
CE:
CB:
CR:
CS:
N1(60):
α, β:
N1(60)cs:
CRR7.5:
Total stress during SPT test (tsf)
Water pore pressure during SPT test (tsf)
Effective overburden pressure during SPT test (tsf)
Overburden corretion factor
Energy correction factor
Borehole diameter correction factor
Rod length correction factor
Liner correction factor
Corrected N SPT to a 60% energy ratio
Clean sand equivalent clean sand formula coefficients
Corected N1(60) value for fines content
Cyclic resistance ratio for M=7.5
Abbreviations
σ v, e q(tsf)
r d CSR MSF CSR eq,M=7.5 K si g m a
CSR *
:: Cyclic Stress Ratio calculation (CSR fully adjusted and normalized) ::
Depth
(ft)
Unit
Weight
(pcf)
u o, e q(tsf)
σ'vo,eq(tsf)
FSα
4.00 115.00 0.23 0.00 0.23 0.99 0.348 1.19 0.292 1.00 0.292 2.0001.00
8.00 115.00 0.46 0.00 0.46 0.98 0.345 1.19 0.289 1.00 0.289 2.0001.00
14.00 115.00 0.81 0.19 0.62 0.97 0.444 1.19 0.372 1.00 0.372 0.7661.00
18.00 115.00 1.04 0.31 0.72 0.96 0.483 1.19 0.405 1.00 0.405 0.3231.00
23.00 115.00 1.32 0.47 0.85 0.95 0.515 1.19 0.432 1.00 0.432 0.4281.00
28.00 120.00 1.62 0.62 1.00 0.93 0.531 1.19 0.445 1.00 0.445 0.4391.00
33.00 120.00 1.92 0.78 1.14 0.90 0.534 1.19 0.448 0.98 0.455 0.4541.00
Project File:
Page: 3LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software
This software is registered to: Cobalt Geosciences
σ v, e q(tsf)
r d CSR MSF CSR eq,M=7.5 K si g m a
CSR *
:: Cyclic Stress Ratio calculation (CSR fully adjusted and normalized) ::
Depth
(ft)
Unit
Weight
(pcf)
u o, e q(tsf)
σ'vo,eq(tsf)
FSα
σv,eq:
uo,eq:
σ'vo,eq:
rd :
α:
CSR :
MSF :
CSR eq,M=7.5:
Ksigma:
CSR *:
FS:
Total overburden pressure at test point, during earthquake (tsf)
Water pressure at test point, during earthquake (tsf)
Effective overburden pressure, during earthquake (tsf)
Nonlinear shear mass factor
Improvement factor due to stone columns
Cyclic Stress Ratio (adjusted for improvement)
Magnitude Scaling Factor
CSR adjusted for M=7.5
Effective overburden stress factor
CSR fully adjusted (user FS applied)***
Calculated factor of safety against soi l l iquefaction
Abbreviations
1.00*** User FS:
:: Liquefaction potential according to Iwasaki ::
Depth
(ft)
FS F Thickness
(ft)
wz IL
4.00 2.000 0.00 9.39 0.004.00
8.00 2.000 0.00 8.78 0.004.00
14.00 0.766 0.23 7.87 3.376.00
18.00 0.323 0.68 7.26 5.994.00
23.00 0.428 0.57 6.49 5.675.00
28.00 0.439 0.56 5.73 4.905.00
33.00 0.454 0.55 4.97 4.145.00
24.06
IL = 0.00 - No liquefaction
IL between 0.00 and 5 - Liquefaction not probable
IL between 5 and 15 - Liquefaction probable
IL > 15 - Liquefaction certain
Overall potential I L :
:: Vertical settlements estimation for dry sands ::
Depth
(ft)
(N 1)60 τav p Gmax(tsf)
α b γ ε 15 Nc εNc(%)ΔS
(in)
Δh
(ft)
4.00 3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.0005.00
Abbreviations
τav:
p:
Gmax:
α, b:
γ:
ε15:
Nc:
εNc:
Δh:
ΔS:
Average cyclic shear stress
Average stress
Maximum shear modulus (tsf)
Shear strain formula variables
Average shear strain
Volumetric strain after 15 cycles
Number of cycles
Volumetric strain for number of cycles Nc (%)
Thickness of soil layer (in)
Settlement of soil layer (in)
0.000Cumulative settlemetns:
:: Vertical settlements estimation for saturated sands ::
Depth
(ft)
D 50(in)
q c/N e v(%)Δh
(ft)
s
(in)
Project File:
Page: 4LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software
This software is registered to: Cobalt Geosciences
:: Vertical settlements estimation for saturated sands ::
Depth
(ft)
D 50(in)
q c/N e v(%)Δh
(ft)
s
(in)
8.00 0.01 2.10 0.00 5.00 0.000
14.00 0.10 4.04 2.00 5.00 1.203
18.00 0.10 4.04 4.23 5.00 2.540
23.00 0.10 4.04 3.18 5.00 1.909
28.00 0.10 4.04 3.04 5.00 1.822
33.00 0.10 4.04 2.90 5.00 1.743
Abbreviations
9.217Cumulative settlements:
D50:
qc/N:
ev:
Δh:
s:
Median grain size (in)
Ratio of cone resistance to SPT
Post liquefaction volumetric strain (%)
Thickness of soil layer to be considered (ft)
Estimated settlement (in)
:: Lateral displacements estimation for saturated sands ::
Depth
(ft)
(N 1)60 Dr(%)
γ max(%)
dz(ft)
LDI LD
(ft)
4.00 3 24.25 0.00 5.00 0.000 0.00
8.00 10 44.27 0.00 5.00 0.000 0.00
14.00 25 70.00 6.92 5.00 0.000 0.00
18.00 7 37.04 51.20 5.00 0.000 0.00
23.00 10 44.27 51.20 5.00 0.000 0.00
28.00 18 59.40 22.70 5.00 0.000 0.00
33.00 19 61.02 22.70 5.00 0.000 0.00
0.00
Abbreviations
Cumulative lateral displacements:
Dr:
γmax:
dz:
LDI:
LD:
Relative density (%)
Maximum amplitude of cyclic shear strain (%)
Soil layer thickness (ft)
Lateral displacement index (ft)
Actual estimated displacement (ft)
Project File:
Page: 5LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software
References
⦁ Ronald D. Andrus, Hossein Hayati, Nisha P. Mohanan, 2009. Correcting Liquefaction Resistance for Aged Sands Using Measured
to Estimated Velocity Ratio, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 135, No. 6, June 1
⦁ Boulanger, R.W. and Idriss, I. M., 2014. CPT AND SPT BASED LIQUEFACTION TRIGGERING PROCEDURES. DEPARTMENT OF
CIVIL & ENVIRONMENTAL ENGINEERING COLLEGE OF ENGINEERING UNIVERSITY OF CALIFORNIA AT DAVIS
⦁ Dipl.-Ing. Heinz J. Priebe, Vibro Replacement to Prevent Earthquake Induced Liquefaction, Proceedings of the Geotechnique-
Colloquium at Darmstadt, Germany, on March 19th, 1998 (also published in Ground Engineering, September 1998), Technical
paper 12-57E
⦁ Robertson, P.K. and Cabal, K.L., 2007,Guide to Cone Penetration Testing for Geotechnical Engineering. Available at no cost at
http://www.geologismiki.gr/
⦁ Youd, T.L., Idriss, I.M., Andrus, R.D., Arango, I., Castro, G., Christian, J.T., Dobry, R., Finn, W.D.L., Harder, L.F., Hynes , M.E.,
Ishihara, K., Koester, J., Liao, S., Marcuson III, W.F., Martin, G.R., Mitchell, J.K., Moriwaki, Y., Power, M.S., Robertson, P.K.,
Seed, R., and Stokoe, K.H., Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF
Workshop on Evaluation of Liquefaction Resistance of Soils, ASCE, Journal of Geotechnical & Geoenvironmental Engineering,
Vol. 127, October, pp 817-833
⦁ Zhang, G., Robertson. P.K., Brachman, R., 2002, Estimating Liquefaction Induced Ground Settlements from the CPT, Canadian
Geotechnical Journal, 39: pp 1168-1180
⦁ Zhang, G., Robertson. P.K., Brachman, R., 2004, Estimating Liquefaction Induced Lateral Displacements using the SPT and CPT,
ASCE, Journal of Geotechnical & Geoenvironmental Engineering, Vol. 130, No. 8, 861 -871
⦁ Pradel, D., 1998, Procedure to Evaluate Earthquake-Induced Settlements in Dry Sandy Soils, ASCE, Journal of Geotechnical &
Geoenvironmental Engineering, Vol. 124, No. 4, 364-368
⦁ R. Kayen, R. E. S. Moss, E. M. Thompson, R. B. Seed, K. O. Cetin, A. Der Kiureghian, Y. Tanaka, K. Tokimatsu, 2013. Shear-
Wave Velocity–Based Probabilistic and Deterministic Assessment of Seismic Soil Liquefaction Potential, Journal of Geotechnical
and Geoenvironmental Engineering, Vol. 139, No. 3, March 1
LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software
Insight Engineering Co. – Technical Information Report 2/7/23
- 20 -
B. Sensitive Areas Map
2,257
188
WGS_1984_Web_Mercator_Auxiliary_Sphere
Critical Areas Map
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
THIS MAP IS NOT TO BE USED FOR NAVIGATION
Notes
Legend
128 0 64 128 Feet
11/09/2021
City and County Labels
Addresses
Parcels
City and County Boundary
<all other values>
Renton
Erosion Hazard - High
Floodway
Special Flood Hazard Areas (100 year flood)
Landslide
Very High
High
Moderate
Unclassified
Slope City of Renton
>15% & <=25%
>25% & <=40% (Sensitive)
>40% & <=90% (Protected)
>90% (Protected)
Environment Designations
Natural
Shoreline High Intensity
Shoreline Isolated High Intensity
Shoreline Residential
Urban Conservancy
Jurisdictions
Streams (Classified)
<all other values>
Type S Shoreline
Type F Fish
Type Np Non-Fish
Type Ns Non-Fish Seasonal
Unclassified
Not Visited
Wetlands
Streets
Points of Interest
Parks
Waterbodies
2019.sid
Red: Band_1
Green: Band_2
Blue: Band_3
Insight Engineering Co. – Technical Information Report 2/7/23
- 21 -
C. Watershed Map
Thorton
Cree
k
R
o
c
k
Cr
eekR
e
x
Ri
verCe
d
a
r
R
i
v
er
C edar River BearCreek
K
e
l
sey CreekMay Creek
T
aylor Creek
N o r t h F o r k C e d a r R i v e r
T rou blesome C reekCoal Creek
ELW
ELW
EastLakeWashington
ELW
EastLakeWashington
ForbesCreek
JuanitaCreek
Kelsey
Creek
Lake
Union
Lower
Cedar
River
LyonCreek
May
Creek
McaleerCreek
Mercer
Island
Mercer
Slough
Thornton
Creek
Upper
Cedar
River
West Lake
Washington
West
LakeWashington
West
LakeWashingtonLake WashingtonLake
Ballinger
Green
Lake
Lake
Union
LakeDesire
Walsh Lake
ShadyLake
LakeTwelve
SpringLake
RetreatLake
ChesterMorseLake
Ce
d
a
r
R
i
v
e
rCedarRiverCedarRiver
ALGONA
AUBURN
BEAUX
ARTS
BELLEVUE
BLAC K
DIAM ON D
BLAC K
DIA M ON D
BOTHELL
BRIER
BURIEN
CARNATION CAR N AT ION
CARNATION
CLYDE
HILL
COV ING TO N
DES
M OIN ES
DUVALL
DUVALL
EDMONDS
FEDE RA L
WAY
HUNTS
POINT
I N D EX
ISSAQUAH
KENT KENT
KENT
KEN T
KENT
KEN T
KEN T
KEN T
KIRKLAND
KIRKLAND
MA PL E
VA LL EY
MEDINA
ME R C ER
I S LA N D
MO U N T L A KE
EDMONDS
LYNNWOOD
TER RA CE
NEWCASTLE
N ORM A N DY
PAR K
NORTHBEND
REDMOND
REDM ON D
REDM ON D
RENTON
SAM M AM ISH
SEATAC
SEATTLE
SNOQUALMIESNOQUALMIE
SNOQUALMIE
TUKW ILA
W OO D I N V IL LE
WOODW AY
YA RR OWPOINT
P ACIF IC
LAKE
FOREST
PARK
KENMORE
SHOR ELI N E
SEATTLE
SEATTLE
BELLEVUE
Department of Natural Resources and Parks
Water and Land Resources Division
N
Watershed Boundary
Basin Boundary
River
Stream
Major Road
Incorporated Area
Lake
Produced by:
King County IT Services, GIS, Visual Communications and Web Section
File Name: 1211_2650_CedarLkWashMap.ai skrau
November 2012
0 1 2 4 Miles
The
Lake Washington/Cedar River
Watershed
Insight Engineering Co. – Technical Information Report 2/7/23
- 22 -
D. Soil Amendment Calculations
11/9/21, 10:30 AM Achieving the Post-construction Soil Standard - King County
https://kingcounty.gov/depts/dnrp/solid-waste/compost-calculator.aspx 2/3
Compost and topsoil calculator for meeting post-
construction soil standards (King County Code
16.82)
Results
You have selected the Pre-Approved Compost Amendment Rate, which is
1.75 inches for turf applications.
Stockpile these quantities of site soil:
251.7 cubic yards of stockpiled site soil.
Order these quantities of compost and/or topsoil:
70.5 cubic yards of compost.
0.0 cubic yards of topsoil.
Amount of soil to
stockpile
Amount
compost
needed
Amount
topsoil needed
Option 1: Leave native soil
undisturbed N/A N/A N/A
Option 2: Amend existing soil in-
place
Areas:
Square footage in thousands =
***
Option 3: Import topsoil mix
Areas:
Square footage in thousands =
***
Option 4: Disturbed Soil - stockpile,
reapply and amend
Areas:
Square footage in thousands = 13068
251.7 cubic yards 70.5 cubic
yards *
Totals 251.7 cubic yards
stockpiled soil
70.5 cubic
yards *
Print Return
Step 4: Enter the results of the calculations for compost and/or topsoil needed from the table
above on the Soil Management Plan 1 MB, and attach a print-out of the calculation results to
the Plan. Submit to Department of Local Services, Permitting Division as part of the permitting
process.
Department of Local Services, Permitting Division reviewers will also use the calculator to verify
the compost and/or soil quantities that permit applicant must enter in the Soil Management Plan.
Note that separate calculation sheets are needed for turf and planting beds.
Insight Engineering Co. – Technical Information Report 2/7/23
- 23 -
7.0 Other Permits
Insight Engineering Co. – Technical Information Report 2/7/23
- 24 -
8.0 CSWPPP Analysis and Design
This Stormwater Pollution Prevention Plan (SWPPP) has been prepared as part of the
construction stormwater permit requirements for Logan Tower Mixed Use located at 15525 Lake
Shore Blvd NE in Lake Forest Park, Washington. More generally, the project site is in Section 36,
Township 28 North, and Range 4 East of the Willamette Meridian in King County, Washington.
The site contains 1.08 acres and is zoned as UC (Urban Center). The proposal is to construct a ten-
story mixed-use building with three levels of underground parking. The access to the site will be
from driveway entrances located on N 4th St and N 3rd St. The project is exempt from flow control
as section 1.2.3 of the RSWDM the direct discharge exemption may be applied to the project
because it meets all the required criteria outlined on page 1-39 of the RSWDM. The project is
proposing to direct discharge to the existing drainage system along N 4th Street that is maintained
by the city. Water quality is exempt because the total PGIS is only 2,165 SF which is less than the
threshold limit of 5,000 SF.
The purpose of this SWPPP is to describe the proposed construction activities and all
temporary and permanent erosion and sediment control (TESC) measures, pollution prevention
measures, inspection/monitoring activities, and recordkeeping that will be implemented during the
proposed construction project. The objectives of the SWPPP are to:
1. Implement Best Management Practices (BMPs) to prevent erosion and
sedimentation, and to identify, reduce, eliminate or prevent stormwater
contamination and water pollution from construction activity.
2. Prevent violations of surface water quality, ground water quality, or
sediment management standards.
3. Prevent, during the construction phase, adverse water quality impacts
including impacts on beneficial uses of the receiving water by controlling
peak flow rates and volumes of stormwater runoff at the Permittee’s outfalls
and downstream of the outfalls.
This SWPPP was prepared using the Ecology SWPPP Template. This SWPPP was prepared based
on the requirements set forth in the Construction Stormwater General Permit and in the Stormwater
Management Manual for Western Washington (SWMMWW 2014).
Insight Engineering Co. – Technical Information Report 2/7/23
- 25 -
The 13 BMP Elements
Element #1 – Mark Clearing Limits
To protect adjacent properties and to reduce the area of soil exposed to construction, the
limits of construction will be clearly marked before land-disturbing activities begin.
Element #2 – Establish Construction Access
Construction access or activities occurring on unpaved areas shall be minimized, yet where
necessary, access points shall be stabilized to minimize the tracking of sediment onto
public roads, and wheel washing, street sweeping, and street cleaning shall be employed to
prevent sediment from entering state waters.
Install the temporary construction entrance, according to the approved construction plans,
prior to any clearing or grading activities. Maintain until the access road is paved.
Element #3 – Control Flow Rates
In order to protect the properties and waterways downstream of the project site, stormwater
discharges from the site will be controlled. In general, discharge rates of stormwater from
the site will be controlled where increases in impervious area or soil compaction during
construction could lead to downstream erosion, or where necessary to meet local agency
stormwater discharge requirements. pond is proposed to control flow rates during grading
activity.
Element #4 – Install Sediment Controls
Install silt fencing, according to the approved plans, prior to any clearing or grading activities.
Maintain until all construction activities are completed.
Element #5 – Stabilize Soils
Exposed and un-worked soils shall be stabilized with the application of effective BMPs to prevent
erosion throughout the life of the project.
Apply temporary hydro-seed to exposed and un-worked soils, according to the approved
construction plans, as needed to prevent erosion during site grading. Apply permanent hydro-seed
to areas at final grade as site grading is completed.
Apply mulching to exposed and un-worked soils, according to the approved construction plans, as
needed to prevent erosion during site grading. Maintain until site grading is completed and
permanent hydro-seed is applied.
Cover stockpiles with plastic sheeting, according to the approved construction plans, as needed to
prevent erosion during site grading. Maintain until stockpiles are removed from site.
Element #6 – Protect Slopes
All cut and fill slopes will be designed, constructed, and protected in a manner than minimizes
erosion. The following specific BMPs will be used to protect slopes for this project.
Element #7 – Protect Drain Inlets
All storm drain inlets and culverts made operable during construction shall be protected to prevent
unfiltered or untreated water from entering the drainage conveyance system. However, the first
Insight Engineering Co. – Technical Information Report 2/7/23
- 26 -
priority is to keep all access roads clean of sediment and keep street wash water separate from
entering storm drains until treatment can be provided.
Element #8 – Stabilize Channels and Outlets
Where site runoff is to be conveyed in channels,or discharged to a stream or some other natural
drainage point, efforts will be taken to prevent downstream erosion.
Element #9 – Control Pollutants
All pollutants, including waste materials and demolition debris, that occur onsite shall be handled
and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping
and preventative measures will be taken to ensure that the site will be kept clean, well-organized,
and free of debris.
Element #10 – Control Dewatering
There will be no dewatering expected as part of this proposal. If it occurs, Baker tanks will be used
for dewatering.
Element #11 – Maintain BMPs
All temporary and permanent erosion and sediment control BMPs shall be maintained and repaired
as needed to assure continued performance of their intended function. Maintenance and repair shall
be conducted in accordance with each particular BMP’s specifications. Visual monitoring of the
BMPs will be conducted at least once every calendar week and within 24 hours of any rainfall
event that causes a discharge from the site. If the site becomes inactive, and is temporarily
stabilized, the inspection frequency will be reduced to once every month. All temporary erosion
and sediment control BMPs shall be removed within 30 days after the final site stabilization is
achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be removed
or stabilized on site. Disturbed soil resulting from removal of BMPs or vegetation shall be
permanently stabilized.
Element #12 – Manage the Project
Erosion and sediment control BMPs for this project have been designed based on the following
principles:
Design the project to fit the existing topography, soils, and drainage patterns; Emphasize erosion
control rather than sediment control; Minimize the extent and duration of the area exposed; Keep
runoff velocities low; Retain sediment on site; Thoroughly monitor site and maintain all ESC
measures and Schedule major earthwork during the dry season. The SWPPP shall be modified as
necessary to include additional or modified BMPs designed to correct problems identified.
Insight Engineering Co. – Technical Information Report 2/7/23
- 27 -
Revisions to the SWPPP shall be completed within seven (7) days following the inspection.
Element #13 – Protect On-site Stormwater Management BMPs for Runoff from Roofs and
Other Hard Surfaces
On-site stormwater management BMPs used for runoff from roofs and other hard
surfaces include: full dispersion, roof downspout full infiltration or dispersion
systems, perforated stub-out connections, rain gardens, bioretention systems,
permeable pavement, sheetflow dispersion, and concentrated flow dispersion. The
areas on the site to be used for these BMPs shall be protected from siltation and
compaction during construction by sequencing the construction in a fashion to
install these BMPs at the latter part of the construction grading operations, by
excluding equipment from the BMPS and the associated areas, and by using the
erosion and sedimentation control BMPs listed below. Additional requirements for
protecting these BMPs during the construction process, testing functionality, and
restoring functionality are needed at the final stage of the construction process.
Relevant BMPs
BMP C102: Buffer Zone BMP
C103: High Visibility Fence BMP
C200: Interceptor Dike and Swale BMP
C201: Grass-lined Channels BMP
C207: Check Dams BMP
C208: Triangular Silt Dike BMP
C231: Brush Barrier BMP
C233: Silt Fence BMP
C234: Vegetated Strip
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9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant
Bond and insurance in accordance with City of Renton’s requirements will be provided upon
request or at the behest of the owner during site construction.
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10.0 Operations and Maintenance Manual
The Operations and Maintenance Manual will be included with the construction submittal.