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Logan Place
Preliminary Technical Information Report
(Full Drainage Review)
Site Location:
129 Logan Ave S
Renton 98057
Parcel#:
569600-0150
Prepared for:
June Lu
5050 240th Pl. SE
Sammamish, WA 98029
(206)-650-0684
Junelu801@gmail.com
Schwin Chaosilapakul, P.E.
Nick Millman, E.I.T.
PATRICK HARRON & ASSOCIATES, LLC
14900 Interurban Avenue South, Suite 279
Seattle, WA 98168
PHA Project #: 20101
Date: April 28th, 2020
Revised: July 1st, 2020
14900 Interurban Ave. S, Suite 279
Seattle, WA 98168-4635
Ph: 206.674.4659
www.patrickharron.com
Engineering & Planning
Logan Place
Preliminary Technical Information Report
(Full Drainage Review)
PHA Project#: 20101
P:\2020\20101_129 Logan Place - Renton\Text\Storm Reports\20101_Logan Place_TIR.docx
Logan Place
Preliminary Technical Information Report
(Full Drainage Review)
PHA Project#: 20101
P:\2020\20101_129 Logan Place - Renton\Text\Storm Reports\20101_Logan Place_TIR.docx
TABLE OF CONTENTS
1. PROJECT OVERVIEW .................................................................................... 1
2. CONDITIONS AND REQUIREMENTS SUMMARY ................................ 10
3. OFF-SITE ANALYSIS ..................................................................................... 11
Task 1: Study Area Definition ................................................................................................11
Task 2: Resource Review .......................................................................................................11
Task 3: Site Description .........................................................................................................11
Task 4: Upstream Drainage System Description ...................................................................14
Task 5: Downstream Drainage System Description and Existing and Potential Problems ...14
4. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS
AND DESIGN ......................................................................................................... 15
Drainage Concept ...................................................................................................................15
5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN ............................... 18
6. SPECIAL REPORTS AND STUDIES ........................................................... 20
7. OTHER PERMITS ........................................................................................... 20
8. CSWPPP ANALYSIS AND DESIGN ............................................................. 20
9. BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION
OF COVENANT .................................................................................................... 20
10. OPERATIONS AND MAINTENANCE MANUAL ..................................... 20
LIST OF APPENDICES
Appendix A – Stormwater Site Plans
Appendix B – Storm Calculations
Appendix C – Operations & Maintenance Manual
Appendix D – Geotechnical Report
Appendix E – CSWPPP
LIST OF FIGURES
Figure 1 TIR Worksheet .................................................................................................................. 3
Figure 2 Vicinity Map ..................................................................................................................... 8
Figure 3 Proposed Conditions Exhibit ............................................................................................ 9
Figure 4 Aerial Photograph ........................................................................................................... 11
Figure 5 Existing Site Condition ................................................................................................... 12
Figure 6 NRCS Soil Description ................................................................................................... 13
Figure 7 Pipe Capacity .................................................................................................................. 18
Figure 8 Flow Frequency .............................................................................................................. 19
Logan Place
Preliminary Technical Information Report
(Full Drainage Review)
PHA Project#: 20101
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Logan Place
Preliminary Technical Information Report
(Full Drainage Review)
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1. PROJECT OVERVIEW
This Preliminary Technical Information Report (TIR) is submitted in support of the Building Permit
for the construction of a new, 9-unit apartment building with a parking garage on the first floor.
Project Data:
Address: 129 Logan Ave S
Renton 98057
Parcel Number: 569600-0150
Lot Area Total: 5,000 SF (0.115 Acres)
Zoning: Center Downtown (CD)
Drainage Basin: Lower Cedar River
This analysis was completed using the format set forth in the 2017 City of Renton Surface Water Design
Manual (CRSWDM). The project requires a Full Drainage Review as specified in Fig. 1.1.2.A of the
CRSWDM (See following page).
Project Description:
Please refer to Figure 2 – Vicinity Map and Figure 3 – Proposed Conditions Exhibit on the following
pages to aid in the project description.
The project proposes to demolish the existing single-family residence and all other existing structures
on site to construct a new apartment complex with a first-floor parking garage and associated
infrastructure.
The project site is located within the Peak Rate Flow Control Standard Area, but is exempt from Flow
Control based on a Peak Flow Rate increase of less than 0.15 cfs between the existing and developed
site conditions. Additionally, the project qualifies for Basic Exemption from flow control, since less
than 5,000 square feet of new plus replaced impervious area is proposed. See Section 4 and Appendix
B for details.
Direct connection to the existing storm main in Logan Ave S is proposed via underground pipes and
catch basins.
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Figure 1 – TIR Worksheet
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Logan Place
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Figure 2 – Vicinity Map
More generally the site is located within Section 18, Township 23 North, Range 5 East, Willamette
Meridian.
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Figure 3 – Proposed Conditions Exhibit
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2. CONDITIONS AND REQUIREMENTS SUMMARY
CORE REQUIREMENT #1: Discharge at the Natural Location
Stormwater runoff from the existing home (to be demolished) is dispersed over vegetation via splash blocks
on the northern and southern sides of the building. Post redevelopment, stormwater will be collected and
directed to the Logan Ave S. storm system.
CORE REQUIREMENT #2: Offsite Analysis
Minor upstream tributary runoff from adjacent properties. Downstream analysis is provided, see Section 3.
CORE REQUIREMENT #3: Flow Control Facilities
The project site is located within the Peak Rate Flow Control Standard Area but is exempt from Flow
Control, due to Basic Exemption and a Peak Flow Rate increase of less than 0.15 cfs from the developed
condition vs existing site conditions. See Appendix B.
CORE REQUIREMENT #4: Conveyance System
Conveyance capacity will be provided to handle peak flows from the 100-year storm event. See Section 5.
CORE REQUIREMENT #5: Erosion and Sediment Control
See Section 8.
CORE REQUIREMENT #6: Operations and Maintenance
An Operations and Maintenance Manual is provided in Appendix C of this report.
CORE REQUIREMENT #7: Financial Guarantees and Liability
Bond and liability assurances will be provided by the Owner or the Contractor.
CORE REQUIREMENT #8: Water Quality Facilities
The proposed area of Pollution Generating Impervious Surfaces (PGIS) is less than 5,000 sf. No water
quality treatment is required.
CORE REQUIREMENT #9: On-Site BMPs
The project proposes more than 2,000 sf of new plus replaced impervious surfaces, and so requires flow
control BMPs taken from the Small Lot BMP Requirements. See Section 4.
SPECIAL REQUIREMENT #1: Other Adopted Area-Specific Requirements
Not applicable.
SPECIAL REQUIREMENT #2: Flood Hazard Area Delineation
This property is not identified as a flood zone per FEMA flood analysis and King County iMap.
SPECIAL REQUIREMENT #3: Flood Protection Facilities
Not applicable.
SPECIAL REQUIREMENT #4: Source Controls
Not applicable.
SPECIAL REQUIREMENT #5: Oil Control
Not applicable.
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SPECIAL REQUIREMENT #5: Aquifer Protection Area
The site is located within Aquifer Protection Zone 1. Therefore a soils report is not required, and
infiltration BMPs are not allowed.
3. OFF-SITE ANALYSIS
Task 1: Study Area Definition
The study area covered consisted of the project site and upstream and downstream drainage areas near
the development property.
Task 2: Resource Review
The project site is located within the Lower Cedar River Drainage Basin, and the site is not located in
a critical drainage area. No erosion hazard or landslide hazard areas, or seismic hazard located on site.
The soils on the site have been classified as Urban Land by the NRCS (See Figure 5). Also included is
a Geotech Report in Appendix D.
Task 3: Site Description
Please refer to Figure 3 - Aerial Photograph, Figure 4 - Existing Site Conditions, and Figure 5 – NRCS
Soil Description below to aid in the following description.
Figure 4 – Aerial Photograph
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Figure 5 – Existing Site Conditions
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Existing Conditions
The 5,000 sf (0.115 ac) is currently developed with a single-family residence in the center of the
property. On the north side of the existing residence is a shared gravel driveway. The site topography
slopes gently to the north, at an average slope of approximately 4%.
The site is fronted by Logan Ave S to the east, and is bordered by another single-family residence to
the north, a small parking lot to the south, and the Renton High School parking lot to the west.
The site soil description per the National Resources Conservation Service is included below.
Figure 6 – NRCS Soil Description
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Task 4: Upstream Drainage System Description
Generally, the neighboring parking lot to the south slopes away from the project site. Therefore, sheet flow
entering the project site is expected to be minimal, and no significant impact to the proposed development is
anticipated.
Task 5: Downstream Drainage System Description and Existing and Potential Problems
The vast majority of onsite runoff from the site will be collected and directed to the Logan Ave S storm
system. The Logan Ave S storm main consists of a 24-inch concrete pipe and flows to the north. It
empties into the Lower Cedar River just over a quarter-mile from the project site. No drainage issues
are known to exist within the area, and no drainage issues are anticipated from this proposed
development.
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4. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS
AND DESIGN
Flow Control & BMP Requirements
The project site is located within the Peak Rate Flow Control Standard Area but is exempt from Flow
Control, due to Basic Exemption and a Peak Flow Rate increase of less than 0.15 cfs from the developed
condition vs existing site conditions. See Appendix B.
Per the CRSWDM (pg. 1-74 thru 1-77, Section 1.2.9.1), since the project proposes more than 2,000 sf
of new plus replaced impervious surfaces, adds less than ¾ acres of new pervious surface, and is
located on a lot smaller than 22,000 sf, Small Lot BMPs must be utilized to manage on-site runoff.
Drainage Concept
The storm drainage system proposed involves collection of stormwater runoff and direct connection to
the Logan Ave S storm system via underground pipes and catch basins.
The project site/lot is smaller than 22,000 sf (total property = 5,000 sf), and therefore, requires
stormwater management in accordance with the Small Lot BMP Requirements menu as provided in
the table below.
Please refer to Appendix A – Storm Plan and Developed Area Summary Table to aid in the following
description.
Small Lot BMP Requirements (Section C.1.2.9.2.1 of the 2017 CRSWDM)
BMP Rank BMP Infeasibility Description
1 Full Infiltration Site is within Aquifer Protection Zone 1.
Infiltration BMPs not permitted.
2 Limited Infiltration Site is within Aquifer Protection Zone 1.
Infiltration BMPs not permitted.
3 Rain Garden Site is within Aquifer Protection Zone 1.
Rain Garden BMP not permitted.
4 Bioretention Site is within Aquifer Protection Zone 1.
Bioretention BMP not permitted.
5 Permeable Pavement Site is within Aquifer Protection Zone 1.
Permeable Pavement BMPs not permitted.
6 Basic Dispersion Not enough room for flow path
* BMPs for Impervious Area equal to minimum of
10% for site/lot up to 11,000 sf 10% Impervious Area management not feasible for project.
* BMPS for Impervious Area equal to minimum of
20% for site/lot between 11,000 sf and 22,000 sf N/A
7 Reduced Impervious Credit Not viable, not enough pervious vegetation, and perf. pipe not permitted.
8 Native Growth Retention Credit Not viable, not enough space for required pervious vegetation.
9 Tree Retention Credit Not viable, trees not retainable for proposed development.
* Soil Amendment for New Pervious Surfaces Applied to all new pervious surfaces
* Perforated Pipe Connection Not utilized. Site is within Aquifer Protection Zone 1. Infiltration BMPs not
permitted.
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Existing Areas Summary Table:
EXISTING AREA SUMMARY
DESCRIPTION AREA (SF) (AC)
Total Site Area 5,000 0.115
Total Project Site Area 5,450 0.125
On-Site Areas
House Roof 1,145 0.026
Walkway 523 0.012
Shed Roofs 437 0.010
Shared Driveway* 1,483 0.034
On-Site Impervious Total 3,588 0.082
On-Site Pervious Total 1,412 0.032
Off-Site Areas
Sidewalk, Curb, & Gutter 261 0.006
Driveway* 158 0.004
Off-Site Impervious Total 419 0.010
Off-Site Pervious Total 31 0.001
Total Impervious Surface 4,007 0.092
Total Pervious Surface 1,443 0.033
*Pollution Generating Impervious Surface (PGIS) = 1,641 sf
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Proposed Areas Summary Table:
PROPOSED AREA SUMMARY
DESCRIPTION AREA (SF) (AC)
Site Area After Dedication 4,776 0.110
Total Project Site Area 5,450 0.125
On-Site Areas
Roof 3,070 0.070
Walkway (Courtyard) 189 0.004
Walkway (Paving Area) 516 0.012
Driveway* 161 0.004
On-Site Impervious Total 3,936 0.090
On-Site Pervious Total 840 0.019
Off-Site Areas
Sidewalk, Curb, & Gutter 328 0.008
Driveway* 270 0.006
Off-Site Impervious Total 598 0.014
Off-Site Pervious Total 76 0.002
Total Impervious Surface 4,534 0.104
Total Pervious Surface 916 0.021
*Total Pollution Generating Impervious Surface (PGIS) = 431 sf
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5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN
Minimum conveyance capacity of proposed storm systems provided is 0.151 cfs for a 4” diameter
pipe at 0.5% minimum allowable slope. Flows estimated for the 100-year peak developed flows for
project site areas is 0.097 cfs (See Figures 8 & 9 below). Adequate capacity is provided with the
proposed conveyance systems.
Figure 7 – Pipe Capacity
Using Hydraflow Express:
*Maximum pipe capacity = 0.151 cfs
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Figure 8 – Flow Frequency
Refer to Appendix B for Storm Calculation details.
Using Western Washington Hydrology Model 2012 (WWHM12):
* Peak flow rates are presented for 1 acre of Predeveloped 100% Forested condition and 1 acre of Developed
(Mitigated) 100% Impervious condition to establish a flow rate per acre (cfs/ac). Peak flow rates are calculated by
pro-rating actual tributary areas multiplied by cfs/ac.
100-year, 1 Acre Impervious Runoff = 0.775 cfs/ac
Total Project Site Area* = 5,450 sf (0.125 ac)
*Conservative assumption of fully impervious area
100-yr Outflow for Project Site Area = 0.775*0.125 = 0.097 cfs
Pipe Capacity > 100-year Outflow
0.151 cfs > 0.097 cfs → OK
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6. SPECIAL REPORTS AND STUDIES
Geotechnical Report (See Appendix D).
7. OTHER PERMITS
Demolition Permit.
Building Permit.
8. CSWPPP ANALYSIS AND DESIGN
See Appendix E.
9. BOND QUANTITIES, FACILITY SUMMARIES AND
DECLARATION OF COVENANT
Bond and liability assurances will be provided by the Owner or the Contractor.
Declaration of Covenant not required.
10. OPERATIONS AND MAINTENANCE MANUAL
An Operations and Maintenance Manual is included in Appendix C of this report.
Appendix A
Stormwater Site Plans
SITE
ABBREVIATIONS:PROJECT INFORMATIONPROJECT TEAM
LEGAL DESCRIPTION
BASIS OF BEARINGS
VERTICAL DATUM & CONTOUR INTERVAL
VICINITY MAP
LOGAN AVE S SECTION (LOOKING NORTH)
SITE CALLOUTS:
STORM CALLOUTS:
WATER & SEWER CALLOUTS:
DEDICATION AND EASEMENTS:
AREA INVENTORY:
Appendix B
Storm Calculations
WWHM12 Output
Hydrologic analysis was performed using continuous modeling with the Western Washington
Hydrologic Modeling Version 12 (WWHM12) program. WWHM12 output is provided within the
following sections.
Onsite:
According to Natural Resource Conservation Service (NRCS,) the soil of the site is classified as: Urban
land, with a slope of approximately 4%. Conservatively, the site was modeled using C Soils.
Existing vs Proposed Basin Model
Existing Basin:
Proposed Basin:
Flow Frequency:
Existing 100-yr Peak Flow = 0.081 cfs
Proposed 100-yr Peak Flow = 0.087 cfs
Peak Flow Increase = 0.006 cfs
Flow Control Facility Requirement exemption for Peak Flow Increase of < 0.15 cfs
0.006 cfs << 0.15 cfs → Flow Control Exemption
1-Acre Model for Pipe Capacity
Historic Basin:
Developed Basin:
Flow Frequency:
Appendix C
Operations & Maintenance
Appendix D
Geotechnical Report
Geotechnical Investigation
Proposed Apartment Building
129 Logan Avenue South
Renton, Washington
February 27, 2020
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 ........................................................................................ 5
8.1.3 Erosion and Sediment Control.............................................................................. 6
8.1.4 Foundation Design ............................................................................................... 6
8.1.5 Stormwater Management ..................................................................................... 8
8.1.6 Groundwater Influence on Construction .............................................................. 8
8.1.7 Utilities ................................................................................................................ 8
9.0 CONSTRUCTION FIELD REVIEWS ............................................................................ 9
10.0 CLOSURE .................................................................................................................... 9
LIST OF APPENDICES
Appendix A — Statement of General Conditions
Appendix B — Figures
Appendix C — Boring Log
Appendix D — Liquefaction Analyses
GEOTECHNICAL INVESTIGATION
RENTON, WASHINGTON
February 27, 2020
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 geotechnical
investigation for the proposed apartment building located at 129 Logan Avenue South 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. 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 five-story apartment building. We anticipate that the structure will
be wood framed and supported on a shallow foundation system. We have not received site plans or any
details regarding the proposed construction. We anticipate that building loads will be light to moderate
and that site grading will include cuts of 3 feet or less.
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, if necessary.
3.0 Site Description
The site is located at 129 Logan Avenue South in Renton, Washington (Figure 1). The property consists of
one rectangular shaped parcel (No. 5696000150) with a total area of 5,000 square feet.
The property is developed with a single-family residence and gravel driveway. The site and nearby areas
are nearly level and vegetated with ivy, grasses, blackberry vines, along with sparse areas of evergreen and
deciduous trees.
The site is bordered to the north by a residence, to the south by a commercial building, to the east by
Logan Avenue South, and to the west by a large commercial development.
4.0 Field Investigation
4.1.1 Site Investigation Program
The geotechnical field investigation program was completed on February 14, 2020 and included drilling
and sampling one hollow stem auger boring with a trailer mounted drill rig.
GEOTECHNICAL INVESTIGATION
RENTON, WASHINGTON
February 27, 2020
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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 3 feet of loose to medium dense, silty-fine to medium grained sand
(Fill). This layer was underlain by approximately 10 feet of medium dense, fine to medium grained sand
with gravel to gravel with sands (Alluvium). This layer was underlain by approximately 3 feet of medium
dense, fine to medium grained sand trace gravel (Alluvium). This layer was underlain by approximately 5
feet of fine to medium grained sand with gravel to gravel with sand (Alluvium). This layer was underlain
by medium dense to dense, fine to medium grained sand trace to some gravel (Alluvium), which
continued to the termination depth of the boring.
GEOTECHNICAL INVESTIGATION
RENTON, WASHINGTON
February 27, 2020
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PO Box 82243
Kenmore, WA 98028
cobaltgeo@gmail.com
206-331-1097
5.1.2 Groundwater
Groundwater was encountered approximately 14 feet below existing site elevations during our
investigation. We anticipate that this represents the regional groundwater table in this area.
Groundwater likely fluctuates between about 8 and 18 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
6.2 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.
6.3 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 dense soil profile within the upper 100
feet.
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 143.90% of g
S1 53.8% of g
FA 1.0
FV 1.5
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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 0.59g and a 7.0M earthquake in the liquefaction
analyses.
The analyses yielded total settlement on the order of 20.85 inches with corresponding differential
settlement of about 10.5 inches. From the analyses, the depth of the liquefiable zone was identified as
about 9 to 30 feet below grade in the boring.
7.0 DISCUSSION
7.1.1 General
The site is underlain by 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 9 and 30 feet
below grade.
The structure may be supported on a shallow foundation system bearing on auger-cast piles (with grade
beams), compacted rock columns (ground improvement); or on a shallow mat/raft foundation system.
There are additional foundation support options that could be utilized and can be discussed upon request
during the design phases of the project.
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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 large trees, existing foundation elements, 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 grading could include local cuts on the
order of approximately 4 feet or less for shallow foundation placement.
Excavations up to 6 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.
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
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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.
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:
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).
All site work should be completed and stabilized as quickly as possible.
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.
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 Foundation Design
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 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 3,000 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.
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 between 25 and 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.
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 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.
8.1.6 Groundwater Influence on Construction
Groundwater was encountered at 14 feet below grade in Boring B-1. Light amounts of perched
groundwater could be encountered in the near surface soils; however, we expect typical sump excavations
and pumps to be suitable to remove shallow groundwater, if necessary. Regional groundwater may be
encountered below 8 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.
8.1.7 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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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 June Lu 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.
Use of this report is subject to the Statement of General Conditions provided in Appendix A. It is the
responsibility of June Lu 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.
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Respectfully submitted,
Cobalt Geosciences, LLC
Original signed by:
Exp. 6/26/2020
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 Apartment Building
129 Logan Avenue South
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 Apartment Building
129 Logan Avenue South
Renton, Washington
B-1
Subject
Property
APPENDIX C
Boring Log
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
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Soil Classification Chart Figure C1
Log of Boring B-1
Date: February 14, 2020
Contractor: Geologic
Method: Hollow Stem Auger
Depth: 36.5’
Elevation: N/A
Logged By: PH Checked By: SC
Initial Groundwater: 14’
Sample Type: Split Spoon
Final Groundwater: 13’
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 36.5’
SP/
SM
Medium dense, fine to medium grained sand with gravel to fine
gravel with sand, yellowish brown to grayish brown, moist to wet.
(Alluvium)
Cobalt Geosciences, LLC
P.O. Box 82243
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Proposed Apartment Building
129 Logan Avenue South
Renton, Washington
Boring
Log
44
5
5
6
6
12
17
4
7
10
11
7
13
10
14
14
16
22
18
SP
SP
SP/
GP
Medium dense to dense, fine to medium grained sand,
grayish brown, wet. (Alluvium)
Medium dense, fine to medium grained sand to fine to medium
grained gravel with sand, grayish brown to olive gray, wet. (Alluvium)
48
52
7
8
11
SP/
GP
Loose, silty-fine to medium grained sand with layers of silty-sand,
dark yellowish brown to grayish brown, moist. (Fill)
Medium dense, fine to medium grained sand
trace to some gravel, grayish brown, wet. (Alluvium)
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
3.30 ft
1.00
Project title : Apartment Building
Location : 129 Logan Ave S.
SPT Name: SPT #1
14.00 ft
8.00 ft
7.50 ft
0.59 g
0.00 tsf
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 1.1.1.12 - SPT & Vs Liquefaction Assessment Software
This software is registered to: Cobalt Geosciences
:: Overall Liquefaction Assessment Analysis Plots ::
Project File:
Page: 2LiqSVs 1.1.1.12 - 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
5.00 11 12.00 110.00 5.00 Yes
10.00 19 12.00 110.00 5.00 Yes
15.00 29 12.00 110.00 5.00 Yes
20.00 17 12.00 115.00 5.00 Yes
25.00 20 12.00 115.00 5.00 Yes
30.00 28 12.00 115.00 5.00 Yes
35.00 40 12.00 115.00 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 ::
Depth
(ft)
SPT
Field
Value
α βFines
Content
(%)
Unit
Weight
(pcf)
5.00 11 1.51 1.00 1.00 0.75 1.00 12 1.55 1.03 14 4.00012.00110.00 0.28 0.00 0.28
10.00 19 1.28 1.00 1.00 0.85 1.00 21 1.55 1.03 23 0.25512.00110.00 0.55 0.00 0.55
15.00 29 1.13 1.00 1.00 0.85 1.00 28 1.55 1.03 30 0.48812.00110.00 0.83 0.03 0.79
20.00 17 1.06 1.00 1.00 0.95 1.00 17 1.55 1.03 19 0.20612.00115.00 1.11 0.19 0.93
25.00 20 1.00 1.00 1.00 0.95 1.00 19 1.55 1.03 21 0.22912.00115.00 1.40 0.34 1.06
30.00 28 0.95 1.00 1.00 1.00 1.00 27 1.55 1.03 29 0.38412.00115.00 1.69 0.50 1.19
35.00 40 0.90 1.00 1.00 1.00 1.00 36 1.55 1.03 39 4.00012.00115.00 1.98 0.66 1.32
Abbreviations
CSR MSF
:: Cyclic Stress Ratio calculation (CSR fully adjusted and normalized) ::
Depth
(ft)
Unit
Weight
(pcf)
FSα
5.00 110.00 0.28 0.00 0.28 0.99 0.380 1.00 0.380 1.00 0.380 2.0001.00
10.00 110.00 0.55 0.06 0.49 0.98 0.424 1.00 0.424 1.00 0.424 0.6021.00
15.00 110.00 0.83 0.22 0.61 0.97 0.505 1.00 0.505 1.00 0.505 0.9661.00
20.00 115.00 1.11 0.37 0.74 0.96 0.553 1.00 0.553 1.00 0.553 0.3731.00
25.00 115.00 1.40 0.53 0.87 0.94 0.581 1.00 0.582 1.00 0.582 0.3941.00
30.00 115.00 1.69 0.69 1.00 0.92 0.595 1.00 0.595 1.00 0.595 0.6441.00
35.00 115.00 1.98 0.84 1.13 0.89 0.596 1.00 0.596 0.99 0.604 2.0001.00
Project File:
Page: 3LiqSVs 1.1.1.12 - SPT & Vs Liquefaction Assessment Software
This software is registered to: Cobalt Geosciences
CSR MSF
:: Cyclic Stress Ratio calculation (CSR fully adjusted and normalized) ::
Depth
(ft)
Unit
Weight
(pcf)
FSα
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
Calculated factor of safety against soil liquefaction
Abbreviations
:: Liquefaction potential according to Iwasaki ::
Depth
(ft)
FS F Thickness
(ft)
wz
5.00 2.000 0.00 9.24 0.005.00
10.00 0.602 0.40 8.48 5.145.00
15.00 0.966 0.03 7.71 0.405.00
20.00 0.373 0.63 6.95 6.645.00
25.00 0.394 0.61 6.19 5.715.00
30.00 0.644 0.36 5.43 2.945.00
35.00 2.000 0.00 4.67 0.005.00
20.85
:: Vertical settlements estimation for dry sands ::
Depth
(ft)
p α b γ ΔS
(in)
Δh
(ft)
5.00 12 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.0005.00
Abbreviations
0.000Cumulative settlemetns:
:: Vertical settlements estimation for saturated sands ::
Depth
(ft)
Δh
(ft)
s
(in)
10.00 0.30 5.58 1.91 5.00 1.143
Project File:
Page: 4LiqSVs 1.1.1.12 - SPT & Vs Liquefaction Assessment Software
This software is registered to: Cobalt Geosciences
:: Vertical settlements estimation for saturated sands ::
Depth
(ft)
Δh
(ft)
s
(in)
15.00 0.10 4.04 0.74 5.00 0.444
20.00 0.30 5.58 2.23 5.00 1.337
25.00 0.10 4.04 2.68 5.00 1.605
30.00 0.10 4.04 2.05 5.00 1.232
35.00 0.10 4.04 0.00 5.00 0.000
Abbreviations
5.762Cumulative settlements:
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)
LDI LD
(ft)
5.00 12 48.50 0.00 5.00 0.000 0.00
10.00 21 64.16 22.70 5.00 0.000 0.00
15.00 28 74.08 3.54 5.00 0.000 0.00
20.00 17 57.72 22.70 5.00 0.000 0.00
25.00 19 61.02 22.70 5.00 0.000 0.00
30.00 27 72.75 11.40 5.00 0.000 0.00
35.00 36 84.00 0.00 5.00 0.000 0.00
0.00
Abbreviations
Cumulative lateral displacements:
Relative density (%)
Maximum amplitude of cyclic shear strain (%)
Soil layer thickness (ft)
Lateral displacement index (ft)
Actual estimated displacement (ft)
Project File:
Page: 5LiqSVs 1.1.1.12 - SPT & Vs Liquefaction Assessment Software
References
LiqSVs 1.1.1.12 - SPT & Vs Liquefaction Assessment Software
Appendix E
Construction Stormwater Pollution
Prevention Plan (CSWPPP)
CESCL REQUIREMENT
A Certified Erosion and Sediment Control Specialist shall be identified in the
Construction SWPPP and shall be onsite or oncall at all times. Certification may
be obtained by an approved training program that meets the erosion and sediment
control training criteria established by Ecology. If a preconstruction meeting is
held, this person shall attend. See attached BMPC160 Certified Erosion and
Sediment Control Lead (CESCL)
CESCL___________________________________
24hr Contact number:______________________
Fax number:______________________________
Address:_________________________________
_________________________________________
_________________________________________
ELEMENT 1: MARK CLEARING LIMITS
• Prior to beginning land disturbing activities, including clearing and grading, all clearing
limits, sensitive areas and their buffers, and trees that are to be preserved within the
construction area should be clearly marked, both in the field and on the plans, to prevent
damage and offsite impacts.
• Plastic, metal, or stake wire fence may be used to mark the clearing limits.
• The duff layer, native topsoil, and natural vegetation shall be retained in an undisturbed
state to the maximum extent practicable. If it is not practicable to retain the duff layer in
place, it should be stockpiled onsite, covered to prevent erosion, and replaced
immediately upon completion of the ground disturbing activities.
Element
#1 BMP Description
X C101 Preserving Natural Vegetation
X C102 Buffer Zones
X C103 High Visibility Plastic or Metal Fence
X C104 Stake and Wire Fence
Construction and silt fencing will be used to delineate the limits of clearing for the
project.
ELEMENT 2: ESTABLISH CONSTRUCTION ACCESS
• Construction vehicle access and exit shall be limited to one route if possible.
• Access points shall be stabilized with quarry spalls or crushed rock to minimize the
tracking of sediment onto public roads.
• Wheel wash or tire baths should be located onsite, if applicable.
• Public roads shall be cleaned thoroughly as needed to protect stormwater infrastructure
and downstream water resources. Sediment shall be removed from roads by shoveling
or pickup sweeping and shall be transported to a controlled sediment disposal area.
Street washing will be allowed only after sediment is removed in this manner.
• Street wash wastewater shall be controlled by pumping back onsite, or otherwise be
prevented from discharging untreated into systems tributary to state surface waters.
Element
#2 BMP Description
X C105 Stabilized Construction Entrance
C106 Wheel Wash
C107 Construction Road/Parking Area Stabilization
The proposed construction accesses will be on Logan Ave S, on the eastern
side of the property.
ELEMENT 3: CONTROL FLOW RATES
• Properties and waterways downstream from development sites shall be protected from
erosion due to increases in the volume, velocity, and peak flow rate of stormwater runoff
from the project site, as required by local plan approval authority.
• Downstream analysis is necessary if changes in flows could impair or alter conveyance
systems, stream banks, bed sediment or aquatic habitat. See Chapter 3 for offsite
analysis guidance.
• Where necessary to comply with Minimum Requirement #7, stormwater
retention/detention facilities shall be constructed as one of the first steps in grading.
Detention facilities shall be functional prior to construction of site improvements (e.g.
impervious surfaces).
• The local permitting agency may require pond designs that provide additional or different
stormwater flow control if necessary to address local conditions or to protect properties
and waterways downstream from erosion due to increases in the volume, velocity, and
peak flow rate of stormwater runoff from the project site.
• If permanent infiltration ponds are used for flow control during construction, these
facilities shall be protected from siltation during the construction phase and plans made
for restoration after construction.
Element
#3 BMP Description
C240 Sediment Trap
C241 Temporary Sediment Pond
The project area is less than 1 acre, and silt fencing will be utilized.
ELEMENT 4: INSTALL SEDIMENT CONTROLS
• Prior to leaving a construction site, or prior to discharge to an infiltration facility,
stormwater runoff from disturbed areas shall pass through a sediment pond or other
appropriate sediment removal BMP. Runoff from fully stabilized areas may be
discharged without a sediment removal BMP, but must meet the flow control
performance standard of Element #3, bullet #1. Full stabilization means concrete or
asphalt paving; quarry spalls used as ditch lining; or the use of rolled erosion products, a
bonded fiber matrix product, or vegetative cover in a manner that will
fully prevent soil erosion. The local permitting authority should inspect and approve
areas stabilized by means other than pavement or quarry spalls.
• Sediment ponds, vegetated buffer strips, sediment barriers or filters, dikes, and other
BMP’s intended to trap sediment onsite shall be constructed as one of the first steps in
grading. These BMP’s shall be functional before other land disturbing activities take
place.
• Earthen structures such as dams, dikes, and diversions shall be seeded and mulched
according to the timing indicated in Element #5.
• BMPs intended to trap sediment on site must be located in a manner to avoid
interference with the movement of juvenile salmonids attempting to enter off-channel
areas or drainages, often during nonstorm events, in response to rain event changes in
stream elevation or wetted area.
Element
#4 BMP Description
C230 Straw Bale Barrier
C231 Brush Barrier
C232 Gravel Filter Berm
X C233 Silt Fence
C234 Vegetated Strip
C235 Straw Wattles
C240 Sediment Trap
C241 Temporary Sediment Pond
C250 Construction Stormwater Chemical Treatment
C251 Construction Stormwater Filtration
The proposed sediment control measures are provided on Sheet C2.0 –
Erosion Control Plan. At minimum, the project will be required to have
downstream protection (compost socks, silt fencing, or equivalent), inlet
protection, and appropriate cover measures. The proposed plan is intended
as guidance and the Contractor shall be responsible for implementing and
maintaining appropriate sediment controls based on changing site
conditions.
ELEMENT 5: STABILIZE SOILS
• All exposed and unworked soils shall be stabilized by application of effective BMPs that
protect the soil from the erosive forces of raindrop impact, flowing water, and wind.
• Soils shall be stabilized as outlined below, where downstream water resources or
stormwater infrastructure may be negatively affected by sediments (i.e., runoff
discharges off the development site).
• From October 1 through April 30, no soils shall remain exposed and unworked for more
than 2 days. From May 1 to September 30, no soils shall remain exposed and unworked
for more than 7 days. This condition applies to all onsite soils, whether at final grade or
not. The local permitting authority may adjust these time limits if it can be shown that a
development site's erosion or runoff
potential justifies a different standard.
• Applicable practices include, but are not limited to, compost addition, temporary and
permanent seeding, sodding, mulching, plastic covering, soil application of
polyacrylamide (PAM), early application of gravel base on areas to be paved, and dust
control.
• Soil stabilization measures selected should be appropriate for the time of year, site
conditions, estimated duration of use, and potential water quality impacts that
stabilization agents may have on downstream waters or ground water.
• Soil stockpiles must be stabilized from erosion, protected with sediment-trapping
measures, and located away from storm drains, waterways, or drainage channels.
• Work on linear construction sites and activities, including right-of-way and easement
clearing, roadway development, pipelines, and trenching for utilities, shall not exceed the
capability of the individual contractor for his portion of the project to install the bedding
materials, roadbeds, structures, pipelines, and/or utilities, and to re-stabilize the
disturbed soils, in compliance with the applicable 2-day or 7-day criterion listed above.
Element
#5 BMP Description
C120 Temporary and Permanent Seeding
C121 Mulching
C122 Nets and Blankets
X C123 Plastic Covering
C124 Sodding
C125 Topsoiling
C126 Polyacrylamide for Soil Erosion Protection
C130 Surface Roughening
C131 Gradient Terraces
X C140 Dust Control
X C180 Small Project Construction Stormwater Pollution Prevention
Temporary and permanent cover measures shall be provided based upon plans and
Contractor’s discretion per site conditions during construction.
ELEMENT 6: PROTECT SLOPES
• Cut and fill slopes shall be designed and constructed in a manner that will minimize
erosion.
• Consider soil type and its potential for erosion.
• Reduce slope runoff velocities by reducing the continuous length of slope with terracing
and diversions, reduce slope steepness, and roughen slope surface.
• Offsite stormwater (run-on) shall be diverted away from slopes and disturbed areas with
interceptor dikes and swales. Offsite stormwater should be managed separately from
stormwater generated on the site.
• To prevent erosion, at the top of slopes collect drainage in pipe slope drains or protected
channels. Temporary pipe slope drains shall handle the peak flow from a 10-year, 24-
hour event; permanent slope drains shall be sized for a 25-year, 24-hour event. Check
dams shall be used within channels that are cut down a slope.
• Provide drainage to remove ground water intersecting the slope surface of exposed soil
areas.
• Stabilize soils on slopes, as specified in Element #5.
Element
#6 BMP Description
C120 Temporary and Permanent Seeding
C130 Surface Roughening
C131 Gradient Terraces
C200 Interceptor Dike and Swale
C201 Grass-Lined Channels
C204 Pipe Slope Drains
C205 Subsurface Drains
C206 Level Spreader
C207 Check Dams
C208 Triangular Silt Dike
The Contractor shall be responsible for protecting and stabilizing site slopes as
required.
ELEMENT 7: PROTECT DRAIN INLETS
• As needed to protect stormwater infrastructure and downstream water resources, all
storm drain inlets made operable during construction shall be protected so that
stormwater runoff shall not enter the conveyance system without first being filtered or
treated to remove sediment.
• All approach roads shall be kept clean, and all sediment and street wash water shall not
be allowed to enter storm drains without prior and adequate treatment, unless treatment
is provided before the storm drain discharges to waters of the State.
Element
#7 BMP Description
X C220 Storm Drain Inlet Protection
Both existing and proposed drain inlets shall be protected as required.
ELEMENT 8: STABILIZE CHANNELS AND OUTLETS
• All temporary onsite conveyance channels shall be designed, constructed and stabilized
to prevent erosion from the peak 10-minute flow velocity from a Type 1A 10-year 24-
hour frequency storm for the developed condition. Alternatively, the 10-year, 1-hour flow
rate indicated by an approved continuous runoff model, increased by a factor of 1.6, may
be used.
• Stabilization, including armoring material, adequate to prevent erosion of outlets,
adjacent stream banks, slopes and downstream reaches shall be provided at the outlets
of all conveyance systems.
Element
#8 BMP Description
C202 Channel Lining
C209 Outlet Protection
None required.
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.
• Cover, containment, and protection from vandalism shall be provided for all chemicals,
liquid products, petroleum products, and non-inert wastes present on the site (see
Chapter 173-304 WAC for the definition of inert waste). Onsite fueling tanks shall include
secondary containment.
• Maintenance and repair of heavy equipment and vehicles involving oil changes,
hydraulic system drain down, solvent and de-greasing cleaning operations, fuel tank
drain down and removal, and other activities which may result in discharge or spillage of
pollutants to the ground or into stormwater runoff must be conducted using spill
prevention measures, such as drip pans. Contaminated surfaces shall be cleaned
immediately following any discharge or spill incident. Report all spills to 911. Emergency
repairs may be performed onsite using temporary plastic placed beneath and, if raining,
over the vehicle.
• Wheel wash, or tire bath wastewater, shall be discharged to a separate onsite treatment
system or to the sanitary sewer if allowed by the local wastewater authority.
• Application of agricultural chemicals, including fertilizers and pesticides, shall be
conducted in a manner and at application rates that will not result in loss of chemical to
stormwater runoff. Manufacturers' label recommendations shall be followed for
application rates and procedures.
• Management of pH-modifying sources shall prevent contamination of runoff and
stormwater collected on the site. These sources include, but are not limited to, bulk
cement, cement kiln dust, fly ash, new concrete washing and curing waters, waste
streams generated from concrete grinding and sawing, exposed aggregate processes,
and concrete pumping and mixer washout waters.
• Construction sites with significant concrete work shall adjust the pH of stormwater if
necessary to prevent violations of water quality standards.
Element
#9 BMP Description
X C151 Concrete Handling
X C152 Sawcutting and Surfacing Pollution Prevention
The Contractor shall be responsible for controlling pollutants from construction
activities off the project site.
ELEMENT 10: CONTROL DE-WATERING
• All foundation, vault, and trench de-watering water, which has similar characteristics to
stormwater runoff at the site, shall be discharged into a controlled conveyance system,
prior to discharge to a sediment trap or sediment pond. Channels must be stabilized, as
specified in Element #8.
• Clean, non-turbid de-watering water, such as well-point ground water, can be discharged
to systems tributary to state surface waters, as specified in Element #8, provided the de-
watering flow does not cause erosion or flooding of the receiving waters. These clean
waters should not be routed through sediment ponds with stormwater.
• Highly turbid or otherwise contaminated dewatering water, such as from construction
equipment operation, clamshell digging, concrete tremie pour, or work inside a
cofferdam, shall be handled separately from stormwater at the site.
• Other disposal options, depending on site constraints, may include: 1) infiltration, 2)
transport offsite in vehicle, such as a vacuum flush truck, for legal disposal in a manner
that does not pollute state waters, 3) onsite treatment using chemical treatment or other
suitable treatment technologies, or 4) sanitary sewer discharge with local sewer district
approval.
The Contractor shall be responsible for discharging de-watering water in an
appropriate manner.
ELEMENT 11: MAINTAIN BMP’S
• All temporary and permanent erosion and sediment control BMP’s shall be maintained
and repaired as needed to assure continued performance of their intended function. All
maintenance and repair shall be conducted in accordance with BMP’s.
• Sediment control BMP’s shall be inspected weekly or after a runoff-producing storm
event during the dry season and daily during the wet season.
• All temporary erosion and sediment control BMP’s shall be removed within 30 days after
final site stabilization is achieved or after the temporary BMP’s are no longer needed.
Trapped sediment shall be removed or stabilized on site. Disturbed soil areas resulting
from removal of BMP’s or vegetation shall be permanently stabilized.
The Contractor shall be responsible for maintaining BMP’s to assure performance of
their intended function.
ELEMENT 12: MANAGE THE PROJECT
• Phasing of Construction - Development projects shall be phased where feasible in order
to prevent soil erosion and, to the maximum extent practicable, the transport of sediment
from the project site during construction. Revegetation of exposed areas and
maintenance of that vegetation shall be an integral part of the clearing activities for any
phase.
Clearing and grading activities for developments shall be permitted only if conducted pursuant
to an approved site development plan (e.g., subdivision approval) that establishes permitted
areas of clearing, grading, cutting, and filling. When establishing these permitted clearing and
grading areas, consideration should be given to minimizing removal of existing trees and
minimizing disturbance/compaction of native soils except as needed for building purposes.
These permitted clearing and grading areas and any other areas required to preserve critical or
sensitive areas, buffers, native growth protection easements, or tree retention areas as may be
required by local jurisdictions, shall be delineated on the site plans and the development site.
All plats shall include lot-specific grading plans, including information specified by the local
permitting authority such as finished grades, finished floor elevations, buildable areas, and
identified drainage outlets. This information would normally be submitted with the construction
drawings, but may be required prior to preliminary plat approval.
• Seasonal Work Limitations
From October 1 through April 30, clearing, grading, and other soil disturbing activities shall only
be permitted if shown to the satisfaction of the local permitting authority that silt-laden runoff will
be prevented from leaving the construction site through a combination of the following:
1. Site conditions including existing vegetative coverage, slope, soil type and proximity
to receiving waters; and
2. Limitations on activities and the extent of disturbed areas; and
3. Proposed erosion and sediment control measures.
Based on the information provided, and/or local weather conditions, the local permitting
authority may expand or restrict the seasonal limitation on site disturbance. If, during the course
of any construction activity or soil disturbance during the seasonal limitation period, silt-laden
runoff leaving the construction site causes a violation of the surface water quality standard or if
clearing and grading limits or erosion and sediment control measures shown in the approved
plan are not maintained, the local permitting authority may take enforcement action, including
but not limited to a notice of violation, administrative order, fine/penalty, stop-work order, or
correction notice.
The following activities are exempt from the seasonal clearing and grading limitations:
1. Routine maintenance and necessary repair of erosion and sediment control BMP’s;
2. Routine maintenance of public facilities or existing utility structures that do not (a)
expose the soil or (b) result in the removal of the soil's vegetative cover; and Self-
contained project sites, where there is complete infiltration of the water quality design
event runoff within the site.
3. Local governments may restrict clearing and grading activities where site conditions
may present a significant risk of impact to property or critical areas. Contact the local
permitting authority for information on specific site restrictions. In Olympia, except
where approved chemical treatment, full dispersion or infiltration is practiced,
clearing, grading, and other soil disturbing activities are prohibited in all watersheds
November through February, and in Green Cove, Percival, Woodard, and Ellis Creek
watersheds between October through April.
• Coordination with Utilities and Other Contractors
The primary project proponent shall evaluate, with input from utilities and other contractors, the
stormwater management requirements for the entire project, including the utilities, when
preparing the Construction SWPPP.
• Inspection and Monitoring
All BMP’s shall be inspected, maintained, and repaired as needed to assure continued
performance of their intended function. Site inspections shall be conducted by a person who is
knowledgeable in the principles and practices of erosion and sediment control. The person
shall have the skills to (1) assess site conditions and construction activities that could impact
stormwater runoff quality, and (2) assess erosion and sediment control measure effectiveness.
A Certified Erosion and Sediment Control Specialist shall be identified in the construction
SWPPP and shall be onsite or on-call at all times. Certification may be obtained an approved
training program that meets the erosion and sediment control training criteria established by
Ecology. If a pre-construction meeting is held, this person shall attend.
Sampling and analysis of the stormwater discharges from a construction site may be necessary
on a case-by-case basis to ensure compliance with standards. Monitoring and reporting
requirements may be established by the local permitting authority when necessary.
The following discharge standard applies:
Runoff leaving the construction site shall be free of settle able solids, as measured with an
Imhoff Cone and in accordance with Standard Methods for the Examination of Water and
Wastewater, most recent edition, American Water Works Association. "Free of settle able
solids" shall be defined as measuring less than 2.5 mL/L/hr, for storms up to the water quality
design event.1
The following surface water standard applies:
1. For storms up to the water quality design event, turbidity downstream of a
construction site may not increase more than 5 NTU, if upstream turbidity is 50 NTU
or less, and may not increase more than 10 percent, if upstream turbidity is over 50
NTU. To the extent practicable, samples should be taken far enough downstream so
that the construction site discharge has been well-mixed with the surface water.
2. Whenever inspection and/or monitoring reveals that the BMP’s identified in the
Construction SWPPP are inadequate, due to the actual discharge of or potential to
discharge a significant amount of any pollutant, appropriate BMP’s or design
changes shall be implemented as soon as possible.
• Maintaining an Updated Construction SWPPP - The SWPPP shall be retained onsite or
within reasonable access to the site.
The SWPPP shall be updated within 7 days to reflect any significant changes in the design,
construction, operation, or maintenance at the construction site that have, or could have, a
significant effect on the discharge of pollutants to waters of the state.
The SWPPP shall be updated within 7 days if during inspections or investigations by site staff or
local or state officials, it is determined that the SWPPP is ineffective in controlling pollutants
such that applicable discharge or surface water standards violations are apparent.
The objective is to control erosion and prevent sediment and other pollutants from leaving
the site during the construction phase of a project.
The Contractor shall be responsible for managing the construction phase of the
project within reasonable applications of the guidelines of this section and the
SWPPP.