HomeMy WebLinkAbout34_RS_Drainage_Technical_Information_Report_TIR_230810_v1
Western Washington Division Eastern Washington Division
165 NE Juniper St., Ste 201, Issaquah, WA 98027 108 East 2nd Street, Cle Elum, WA 98922
Phone: (425) 392-0250 Fax: (425) 391-3055 Phone: (509) 674-7433 Fax: (509) 674-7419
www.EncompassES.net
TECHNICAL INFORMATION REPORT
For
Dreamliner Apartments
511 Airport Way
Renton, WA 98057
August 8th, 2023
Prepared by:
Samuel Salo
Encompass Engineering Job No. 20608
Prepared For:
Nord West Properties, LLC
14435 NE 40th ST. APT. B101
Bellevue, WA 98007
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Table of Contents
I. PROJECT OVERVIEW .............................................................................................................................. 1
II. CONDITIONS AND REQUIREMENTS SUMMARY .................................................................................... 7
III. OFFSITE ANALYSIS ............................................................................................................................... 11
IV. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY ANALYSIS AND
DESIGN ................................................................................................................................................ 16
V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN .................................................................................. 19
VI. SPECIAL REPORTS AND STUDIES ......................................................................................................... 19
VII. OTHER PERMITS .................................................................................................................................. 19
VIII. CSWPP PLAN ANALYSIS AND DESIGN ................................................................................................. 19
IX. BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION of COVENANT ................................. 19
X. OPERATION AND MAINTENANCE MANUAL ........................................................................................ 19
List of Figures
Figure 1 – TIR Worksheet
Figure 2 – Vicinity Map
Figure 3 – Soils Map and Legend
Figure 4 – Existing Conditions Map
Figure 5 – Developed Conditions Map
Figure 6 – Drainage Review Flow Chart
Figure 7 – Downstream Map
Figure 8 – Direct Discharge Contributing Areas Map
Appendix A
Geotechnical Engineering Report by The Riley Group, Inc. dated January 26, 2021
Appendix B
Operation and Maintenance Manual
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I. PROJECT OVERVIEW
Project: Dreamliner Apartments
Site Address: 511 Airport Way, Renton WA 98057 (See Vicinity Map)
Tax Parcel #: 722930-0580
Zoning District: CA- Commercial Arterial
Site Area: 16,000 SF (0.37 Acres)
Site Location: The site is in the City of Renton within the NE quarter of Section 18,
Township 23 North, Range 5 East, W.M, King County, Washington. The
site is located on the south side of Airport Way, approximately 120 feet
west of the intersection Logan Ave S and Airport Way.
Figure 2: Vicinity Map
Pre-developed Site Conditions
The project site is located in the City of Renton, consisting of a single parcel totaling 16,000 SF (0.37 Acres)
that is split zoned as Commercial Arterial (CA) and Center Downtown (CD). The site is currently accessed
from S Tillicum St, which acts as an alley to the south of the site. Access is also possible from Airport Way
via one of several driveway entrances built into the existing sidewalk. The site is bordered to the north
and south by City of Renton ROW, and to the east and west by commercial buildings, zoned CA to the
west and CD to the east.
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The site is currently undeveloped as an open grass field accessed from S Tillicum St which runs along the
southern boundary of the site. A small paved parking area exists in the northeast corner of the site. The
site almost entirely flat, with localized slopes of 0-1%. The property is located within the Lower Cedar
River drainage basin, and has two separate natural discharge areas. Runoff from the northern portion of
the site sheet flows into Airport Way and enters the COR storm system in a Type 1 CB in the curb line
before being conveyed to the north. Runoff from the southern portion of the site sheets flows into the
alley on S Tillicum St before sheet flowing to the west, eventually entering the COR storm system in a Type
1 CB on Shattuck Ave S. Runoff from these two flow paths converge within a ¼ of a mile; therefore, the
two separate Natural Discharge Areas create a single Threshold Discharge Area (TDA) for the site.
Ultimately, the stormwater is discharged into the Cedar river approximately 450 feet downstream of the
project site. See full downstream analysis in Section III of this Technical Information Report (TIR).
An Existing Conditions Map is included as Figure 4 at the end of this Section.
Critical Areas
According to COR Maps, the site is located in the High Seismic Hazard Area. Please see the Geotechnical
Engineering Report prepared by The Riley Group, Inc. dated January 26, 2021 included as Appendix A for
more discussion. In addition, the site is mapped in an Aquifer Protection Area/Wellhead Protection Area-
Zone 1.
Soils
Per the US Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS) Web Soil
Survey (WSS) information, the entire project site is considered Urban Land (Ur) (See Figure 3 on the
following page). Soils encountered in on-site investigations include “very soft to very stiff silt with varying
amounts of sand and very loose to very dense sand with varying amounts of silt and gravel and gravel with
varying amounts of silt and sand” per the Geotechnical Engineering Report prepared by The Riley Group,
Inc. dated January 26, 2021 (Appendix A).
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Figure 3: Soil Map and Legend
Developed Site Conditions
The project proposes the development of a six-level mixed-use apartment complex within the 16,000 SF
(0.37 Acres) parcel, as well as frontage improvements along Airport Way. The site will be accessed from
Airport Way via a driveway in the northwest corner of the site. Frontage improvements along Airport Way
will include an 8-foot sidewalk, an 8-foot landscape strip, as well as curb/gutter along the paved roadway.
Commercial storefronts and common space will also face Airport Way. Parking for the site will be provided
on the ground level of the structure.
The parcel is split zoned CA on the western portion of the parcel (approximately 75% of the site) and CD
on the eastern portion of the parcel (approximately 25% of the site). CA zoning allows for 75% maximum
building coverage provided parking is contained within the building. The proposed site includes 9,948 SF
(0.23 AC) of roof area, 2,191 SF (0.05 AC) of sidewalk, 599 SF (0.002 AC) of exposed driveway, and 3,262
SF (0.07 AC) of lawn/planter area.
Stormwater runoff from rooftop areas of the site will be conveyed directly to the adjacent Type 1 CB on
Airport Way just north of the site. The project meets the direct discharge exemption per Section 1.2.3.1
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of the 2022 RSWDM for flow control facilities as it drains to the Cedar River downstream of the Taylor
Creek confluence. Covered parking pollution generating impervious surfaces (PGIS) will drain to an
oil/water separator before being discharged to the sanitary sewer system located on S Tillicum St. south
of the project site. Exposed driveway areas will be conveyed directly to the storm system on Airport Way
as they total 599 SF. This is less than the 5,000 SF threshold for water quality treatment.
Please refer to the Core Requirements in Section II as well as Section IV of this TIR for additional discussion
on stormwater flow control and BMPs. A Developed Conditions Map is provided as Figure 5 at this end of
this Section.
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II. CONDITIONS AND REQUIREMENTS SUMMARY
The 2022 City of Renton Surface Water Design Manual (RSWDM) was utilized to determine and address
all core and special requirements. Based on the criteria specified in Figure 1.1.2.A of the RSWDM, the
project falls under Full Drainage Review. Per Section 1.1.2.4 of the RSWDM, the project must meet all nine
(9) core and all six (6) special requirements. See Figure 6 below for more information on how the type of
drainage review was determined.
Figure 6: Drainage Review Flow Chart
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Core Requirements
Core Requirement #1: Discharge at the Natural Location
The proposed development will follow existing drainage patterns in which runoff enters the City
of Renton storm system within a single TDA on Airport Way and is conveyed to its discharge point
in the Cedar River. Runoff from on-site roof and exposed driveway/parking areas will be conveyed
to the existing Type 1 CB located north of the project site in the curb line along the south side of
Airport Way.
Core Requirement #2: Offsite Analysis
A Level 1 Downstream analysis has been completed for the site and no existing or potential
problems have been identified. This analysis is included in Section III of this TIR.
Core Requirement #3: Flow Control Facilities
Based on the City of Renton’s flow control application map, the project site is located within the
Peak Rate Flow Control Standard (Existing Site Conditions). Flow control facilities are required to
match the developed peak discharge rates to existing site conditions peak discharge rates for 2-,
10-, and 100-year return periods.
However, this project meets the direct discharge exemption per Section 1.2.3.1 of the RSWDM,
as it drains to the Cedar River downstream of the Taylor Creek confluence. Therefore, no flow
control facilities are proposed for this project. See Section IV of this TIR for more details.
Core Requirement #4: Conveyance System
Conveyance has been designed in compliance with the requirements detailed in Section 1.2.4.1
of the 2022 RSWDM. See Section IV of this TIR for more details.
Core Requirement #5: Construction Stormwater Pollution Prevention
A temporary erosion and sediment control (TESC) plan providing details on best management
practices (BMPs) to be implemented during construction is included in the engineering plan set.
A Construction Stormwater Pollution Prevention Plan (CSWPPP) has been provided under
separate cover.
Core Requirement #6: Maintenance and Operations
An Operation and Maintenance Manual has been included as Appendix B.
Core Requirement #7: Financial Guarantees and Liability
The owner will arrange for any financial guarantees and liabilities required by the permit.
Core Requirement #8: Water Quality Facilities
As exposed PGIS surfaces on the project site total 599 SF, which is under the 5,000 SF threshold,
the project meets Exemption 1 in Section 1.2.8 of the RSWDM. Therefore, water quality facilities
are not required on the project site. All covered PGIS driveway/parking areas will drain to an
oil/water separator before discharging to the sanitary sewer system located on S Tillicum St. See
Section IV of this TIR for more details.
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Core Requirement #9: On-Site BMPs
This project is under 22,000 SF; therefore, it is subject to the Small Lot BMP Requirements detailed
in Section 1.2.9.2.1 in the RSWDM. BMPs have been considered for the future improvements in
the order they are listed in this section. As the site falls within Zone 1 of the Aquifer Protection
Area, open flow control facilities, BMP’s relying on infiltration, BMP’s relying on dispersion for
PGIS, and open conveyance systems are prohibited per Section 1.3.6 of the RSWDM. Further
design considerations are listed below. See Section IV of this TIR for further discussion on flow
control analysis.
Full Dispersion: Infeasible. The space required for an 100-foot native vegetated flowpath segment
is not available on the project site.
Full Infiltration: Infeasible. The Geotechnical Engineering Report prepared by The Riley Group, Inc.
dated January 26, 2021 (Appendix B) states that infiltration is infeasible based in native site soils
encountered in on-site borings. In addition, the site falls within a Wellhead Protection Area- Zone
1, which prohibits BMP’s relying on infiltration per section 1.3.6 of the RSWDM.
Limited Infiltration: Infeasible. BMP’s relying on infiltration are not feasible as described above.
Rain Gardens/Bioretention: Infeasible. BMP’s relying on infiltration are not feasible as described
above.
Permeable Pavement: Infeasible. Infeasible. BMP’s relying on infiltration are not feasible as
described above.
Basic Dispersion: Infeasible. The space required for 50-foot and 25-foot native vegetated
flowpaths are not available on the project site.
Reduced Impervious Surface Credit: Infeasible. Proposed impervious areas exceed the 10,000 SF
threshold on the site.
Native Growth Retention Credit: Infeasible. The necessary area to allow for 3.5 SF of native
vegetated surface for every SF of impervious surface is not available on the site.
Tree Retention Credit: Infeasible. No trees exist on the project site.
Soil Amendment: Feasible. All disturbed, pervious areas of the project will meet soil amendment
requirements as detailed in Section C.2.13 of the RSWDM.
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Special Requirements
Special Requirement #1: Other Adopted Area-Specific Requirements
Master Drainage Plans– N/A
Basin Plan – N/A
Salmon Conservation Plans- N/A
Lake Management Plans – N/A
Hazard Mitigation Plan- N/A
Shared Facility Drainage Plans – N/A
Special Requirement #2: Flood Hazard Area Delineation
The limits of this project do not lie within a delineated FEMA 100-year floodplain.
Special Requirement #3: Flood Protection Facilities
This project does not rely on or propose to modify/construct a new flood protection facility.
Special Requirement #4: Source Controls
The project is not a commercial building or development; therefore, this requirement is not
applicable.
Special Requirement #5: Oil Control
This project develops a site that has high-use site characteristics; therefore, all covered PGIS
driveway/parking areas will drain to an oil/water separator before discharging to the sanitary
sewer system located on S Tillicum St.
Special Requirement #6: Aquifer Protection Area
The site is located within an Aquifer Protection Area (1-Year Wellhead Capture Zone) per the pre-
application meeting. According to Section 1.3.6 of the RSWDM, open flow control facilities, open
conveyance systems and BMPs relying on infiltration are prohibited.
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III. DOWNSTREAM ANALYSIS
A Level 1 Downstream analysis has been conducted per the requirements in Section 1.2.2.1 of the
RSWDM. Please see Tasks 1 through 4 below for a summary of the results.
Task 1: Define and Map the Study Area
The area of analysis extends from the site discharge points along Airport Way at the northern boundary
of the site and S Tillicum St at the southern boundary of the site approximately 450 feet downstream to
where the stormwater discharges into the Cedar River. A Downstream Map is provided in Figure 7 below.
Figure 7: Downstream Map
Task 2: Review All Available Information on the Study Area
Per King county resources, there have been no significant drainage complaints within a quarter-mile
downstream of the site.
Task 3: Field Inspect the Study Area
A field inspection was performed by Encompass Engineering & Surveying on October 29, 2020. Please
refer to Task 4 for a detailed description of the downstream drainage system and analysis.
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Task 4: Describe the Drainage System
Runoff from the site is split into two Natural Discharge Areas (A & B), however these flowpaths converge
within a ¼ mile downstream of the site from the shortest flowpath, creating one Threshold Discharge Area
for the site. Runoff from Discharge Area A sheet flows (A1) into the alleyway on S Tillicum St at the
southwest corner of the site and sheet flows westward towards Shattuck Ave S. At the intersection of
Shattuck Ave S and S Tillicum St, the stormwater enters the City of Renton storm system in a Type 1 CB
(A2) and flows north through an 8” Poly pipe for approximately 50 feet to a Type 2 CB (A3). The stormwater
continues north through a 12” concrete pipe to the intersection of Airport Way and Shattuck Ave S where
it enters a series of two type 2 CB’s (A4 & A5). The stormwater then flows east on the north side of Airport
Way through a 12” concrete pipe until it enters a type 2 CB (B3) where it converges with stormwater from
Discharge Area B at a flowpath length of approximately 1,500 Feet.
Runoff from Discharge Area B sheet flows over the sidewalk at the northern boundary of the site and into
the gutter on the south side of Airport Way and into a Type 1 CB (B1). From here it flows northwest
through a 12” concrete pipe and into another type 1 CB (B2) in the median of the intersection of Airport
Way and Logan Ave S. This CB redirects the stormwater northwest where it connects to a type 2 CB (B3)
on the north side of Airport way where it converges with stormwater from Discharge Area A at a flowpath
length of 115 feet. This CB connects to a curbside type 1 CB (B4) and flows north on E Perimeter Rd through
a 12” concrete pipe where it enters a type 2 CB (B5) at the intersection of E Perimeter Rd and E Perimeter
Dr. The stormwater then flows northwest through a 24” concrete pipe and discharges into the Cedar River
(B6) at approximately 450 feet downstream of the site. This is where the downstream analysis was
concluded.
If conveyance system nuisance, severe erosion, severe flooding, or wetland hydrology problems are
identified downstream of the site under Core Requirement #2, additional impact analysis and/or
mitigation may be required. As discussed in Task 2, there have been no recent significant drainage
complaints within a quarter-mile downstream of the site. As no existing drainage or conveyance issues
have been recently identified, further impact analysis and mitigation of the downstream stormwater
system is not required. Please refer to the conveyance analysis in Section V of this TIR for additional
discussion and evaluation of the on-site conveyance system capacity. Photographs from the site visit are
included below.
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Element A1- Sheet flow to the west on S Tillicum St
Element A2- Stormwater from Discharge Area A enters COR storm system in Type 1 CB
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Element B1- Stormwater from Discharge Area B enters Type 1 CB on the south side of Airport Way at
the project site frontage
Element B3 & B4- Stormwater from Discharge Areas A & B converge in a Type 2 CB on the north side
of Airport Way.
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Element B6- Stormwater discharges into the Cedar River
Discharge Point
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IV. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND AND WATER
QUALITY FACILITY ANALYSIS AND DESIGN
Part A: Existing Site Hydrology
The project site is located in the City of Renton, consisting of a single parcel totaling 16,000 SF (0.37 Acres).
The site is currently undeveloped as an open grass field accessed from S Tillicum St which runs along the
southern boundary of the site. A small paved parking area exists in the northeast corner of the site. The
site almost entirely flat, with localized slopes of 0-1%. The property is located within the Lower Cedar
River drainage basin, and has two separate natural discharge areas. Runoff from the northern portion of
the site sheet flows into Airport Way and enters the COR storm system in a Type 1 CB in the curb line
before being conveyed to the north. Runoff from the southern portion of the site sheets flows into the
alley on S Tillicum St before sheet flowing to the west, eventually entering the COR storm system in a Type
1 CB on Shattuck Ave S. Runoff from these two flow paths converge within a ¼ of a mile; therefore, the
two separate Natural Discharge Areas create a single Threshold Discharge Area (TDA) for the site.
Ultimately, the stormwater is discharged into the Cedar river approximately 450 feet downstream of the
project site. See full downstream analysis in Section III of this Technical Information Report (TIR).
Per the US Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS) Web Soil
Survey (WSS) information, the entire project site is considered Urban Land (Ur). Soils encountered in on-
site investigations include “very soft to very stiff silt with varying amounts of sand and very loose to very
dense sand with varying amounts of silt and gravel and gravel with varying amounts of silt and sand” per
the Geotechnical Engineering Report prepared by The Riley Group, Inc. dated January 26, 2021 (Appendix
A).
Part B: Developed Site Hydrology
The project proposes the development of a six-level mixed-use apartment complex within the 16,000 SF
(0.37 Acres) parcel, as well as frontage improvements along Airport Way. The site will be accessed from
Airport Way via a driveway in the northwest corner of the site. Frontage improvements along Airport Way
will include an 8-foot sidewalk, an 8-foot landscape strip, as well as curb/gutter along the paved roadway.
Commercial storefronts and common space will also face Airport Way. Parking for the site will be provided
on the ground level of the structure.
Stormwater runoff from rooftop areas of the site will be conveyed directly to the adjacent Type 1 CB on
Airport Way just north of the site. The project meets the direct discharge exemption per Section 1.2.3.1
of the 2022 RSWDM for flow control facilities as it drains to the Cedar River downstream of the Taylor
Creek confluence. Covered parking pollution generating impervious surfaces (PGIS) will drain to an
oil/water separator before being discharged to the sanitary sewer system located on S Tillicum St. south
of the project site. The proposed site includes 9,948 SF (0.23 AC) of roof area, 2,191 SF (0.05 AC) of
sidewalk, 599 SF (0.002 AC) of exposed driveway, and 3,262 SF (0.07 AC) of lawn/planter area. Exposed
driveway areas will be conveyed directly to the storm system on Airport Way as they total 599 SF. This is
less than the 5,000 SF threshold for water quality treatment.
Part C: Performance Standards
Based on the City of Renton’s flow control map, the project site is located within the Peak Rate Flow
Control Standard (Existing Site Conditions). Flow control facilities are required to match the developed
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peak discharge rates to existing site conditions peak discharge rates for 2-, 10-, and 100-year return
periods.
This project is under 22,000 SF; therefore, it is subject to the Small Lot BMP Requirements detailed in
Section 1.2.9.2.1 in the RSWDM. The site falls within a Basic Water Quality treatment area in accordance
with Section 1.2.8.1.A of the RSWDM.
Part D: Flow Control System
This project meets the direct discharge exemption per Section 1.2.3.1 of the RSWDM, as it drains to the
Cedar River downstream of the Taylor Creek confluence, and the downstream flow path from the site to
the river is under ½ mile.
The conveyance system downstream will have adequate capacity to convey the 25-year peak flow for the
entire contributing area. Conveyance calculations were made for two specific pipes identified
downstream with the greatest tributary areas. The first is a 12” concrete storm pipe (identified as element
B4 in the Level 1 Downstream Analysis) which has an estimated tributary area of 4.8 Acres. The second is
a 24” concrete pipe which outfalls to the Cedar River (identified as element B5 in the Level 1 Downstream
Analysis) which has an estimated tributary area of 35.3 Acres. Pipe slopes were calculated based on upper
and lower invert elevations, as well as length provided by COR Maps records. Flows were calculated in
WWHM, assuming 95% of the tributary area as impervious, and 5% as pervious lawn in Type C soils. Based
on conveyance calculations using the Manning’s equation flow calculator, both of these downstream
pipes have sufficient capacity to convey the 25-year peak flow from the project site, as well as the entire
contributing area. Results of these calculation are shown in the table below, as well as Figure 8 on the
following page.
Existing
Pipe Slope
Total Contributing
Area
Required Capacity for
25-year peak flow (CFS)
Existing
Capacity (CFS)
12” Concrete Pipe
(Element B4)
2.25% 4.80 AC 2.97 6.23
24” Concrete Pipe
(Element B5)
1.35% 35.30 AC 21.70 30.63
Direct Discharge Downstream Pipe Capacity
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Figure 8- Direct Discharge Contributing Areas Map
Part E: Water Quality System
Exposed PGIS surfaces on the project site total 599 SF, which is under the 5,000 SF threshold; therefore,
the project meets Exemption 1 in Section 1.2.8 of the RSWDM. Water quality facilities are not required
on the project site. All covered PGIS driveway/parking areas will drain to the sanitary sewer system located
on S Tillicum St.
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V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN
Pipes used in the storm system were designed to handle the capacity of an 100-year storm event. Flows
of 0.2760 CFS will need to be conveyed during an 100-year storm according to WWHM using developed
site conditions. A 12” CPEP pipe will be used in areas of combined flow, which can convey up to 6.40 CFS
at 2%, greatly exceeding the design flow. See results from the Manning’s Equation Calculator below.
Manning’s Equation Calculator for a 12” Pipe
VI. SPECIAL REPORTS AND STUDIES
· Geotechnical Engineering Report by The Riley Group, Inc. dated January 26, 2021
VII. OTHER PERMITS
· Civil Construction Permit
· Building Permit
· Right-of-Way Use Permit
VIII. CSWPP PLAN ANALYSIS AND DESIGN
A CSWPPP will be provided with final engineering.
IX. BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION of
COVENANT
Bond Quantities, Facility Summary and Declaration of Covenant to be provided with Final Engineering.
X. OPERATION AND MAINTENANCE MANUAL
An Operation and Maintenance Manual is included as Appendix B.
Appendix A
Geotechnical Engineering Report by The Riley Group, Inc. dated January 26, 2021
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone 425.415.0551 ♦ Fax 425.415.0311
www.riley-group.com
GEOTECHNICAL ENGINEERING REPORT
PREPARED BY:
THE RILEY GROUP, INC.
17522 BOTHELL WAY NORTHEAST
BOTHELL, WASHINGTON 98011
PREPARED FOR:
DREAMLINER LLC
14545 NORTHEAST 57TH STREET
BELLEVUE, WASHINGTON 98007
RGI PROJECT NO. 2020-618-1
DREAMLINER MIXED USE
511 AIRPORT WAY
RENTON, WASHINGTON
JANUARY 26, 2021
Geotechnical Engineering Report i January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
TABLE OF CONTENTS
1.0 INTRODUCTION ............................................................................................................................... 1
2.0 PROJECT DESCRIPTION ............................................................................................................... 1
3.0 FIELD EXPLORATION AND LABORATORY TESTING .......................................................... 1
3.1 FIELD EXPLORATION ................................................................................................................................... 1
3.2 LABORATORY TESTING ................................................................................................................................ 2
4.0 SITE CONDITIONS ........................................................................................................................... 2
4.1 SURFACE .................................................................................................................................................. 2
4.2 GEOLOGY ................................................................................................................................................. 2
4.3 SOILS ....................................................................................................................................................... 2
4.4 GROUNDWATER ........................................................................................................................................ 2
4.5 SEISMIC CONSIDERATIONS ........................................................................................................................... 3
4.6 GEOLOGIC HAZARD AREAS .......................................................................................................................... 4
5.0 DISCUSSION AND RECOMMENDATIONS ................................................................................. 4
5.1 GEOTECHNICAL CONSIDERATIONS ................................................................................................................. 4
5.2 EARTHWORK ............................................................................................................................................. 4
5.2.1 Erosion and Sediment Control ..................................................................................................... 4
5.2.2 Stripping ....................................................................................................................................... 5
5.2.3 Excavations................................................................................................................................... 5
5.2.4 Site Preparation ........................................................................................................................... 6
5.2.5 Structural Fill ................................................................................................................................ 6
5.2.6 Cut and Fill Slopes ........................................................................................................................ 8
5.2.7 Wet Weather Construction Considerations ................................................................................. 8
5.3 FOUNDATIONS .......................................................................................................................................... 9
5.4 RETAINING WALLS ................................................................................................................................... 10
5.5 SLAB-ON-GRADE CONSTRUCTION ............................................................................................................... 10
5.6 DRAINAGE .............................................................................................................................................. 10
5.6.1 Surface ....................................................................................................................................... 10
5.6.2 Subsurface .................................................................................................................................. 11
5.6.3 Infiltration .................................................................................................................................. 11
5.7 UTILITIES ................................................................................................................................................ 11
5.8 PAVEMENTS ............................................................................................................................................ 11
6.0 ADDITIONAL SERVICES .............................................................................................................. 12
7.0 LIMITATIONS ................................................................................................................................. 12
LIST OF FIGURES AND APPENDICES
Figure 1 ..................................................................................................................... Site Vicinity Map
Figure 2 ............................................................................................... Geotechnical Exploration Plan
Figure 3 ............................................................................................... Retaining Wall Drainage Detail
Figure 4 ....................................................................................................Typical Footing Drain Detail
Appendix A .......................................................................... Field Exploration and Laboratory Testing
Geotechnical Engineering Report ii January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
Executive Summary
This Executive Summary should be used in conjunction with the entire Geotechnical
Engineering Report (GER) for design and/or construction purposes. It should be recognized
that specific details were not included or fully developed in this section, and the GER must
be read in its entirety for a comprehensive understanding of the items contained herein.
Section 7.0 should be read for an understanding of limitations.
RGI’s geotechnical scope of work included the advancement of four borings to approximate
depths of 40 to 51.5 feet below existing site grades.
Based on the information obtained from our subsurface exploration, the site is suitable for
development of the proposed project. The following geotechnical considerations were
identified:
Soil Conditions: The soils encountered during field exploration include very soft to very
stiff silt with varying amounts of sand and very loose to very dense sand with varying
amounts of silt and gravel and gravel with varying amounts of silt and sand.
Groundwater: Groundwater was encountered at about 10 feet during our subsurface
exploration.
Foundations: Foundations for the proposed building may be supported on conventional
spread footings bearing on a subgrade improved with Geopiers or Aggregate piers.
Slab-on-grade: Slab-on-grade floors and slabs for the proposed building can be supported
on a subgrade improved with Geopiers or Aggregate piers.
Pavements: The following pavement sections are recommended:
For asphalt surfaced areas: 3 inches of Hot Mix Asphalt (HMA) over 6
inches of crushed rock base (CRB) over 12 inches of gravel base
For concrete pavement areas: 5 inches of concrete over 4 inches of CRB
over 12 inches of gravel base
Geotechnical Engineering Report 1 January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
1.0 Introduction
This Geotechnical Engineering Report (GER) presents the results of the geotechnical
engineering services provided for the Dreamliner Mixed Use in Renton, Washington. The
purpose of this evaluation is to assess subsurface conditions and provide geotechnical
recommendations for the construction of a five story mixed use building. Our scope of
services included field explorations, laboratory testing, engineering analyses, and
preparation of this GER.
The recommendations in the following sections of this GER are based upon our current
understanding of the proposed site development as outlined below. If actual features vary
or changes are made, RGI should review them in order to modify our recommendations as
required. In addition, RGI requests to review the site grading plan, final design drawings
and specifications when available to verify that our project understanding is correct and
that our recommendations have been properly interpreted and incorporated into the
project design and construction.
2.0 Project description
The project site is located at 511 Airport Way in Renton, Washington. The approximate
location of the site is shown on Figure 1.
The site is currently a vacant lot with the eastern edge of the property an asphalt-paved
parking lot. RGI understands the site will be developed with a five story mixed use building
with commercial and parking on the lower floor and apartments above.
At the time of preparing this GER, building plans were not available for our review. Based
on our experience with similar construction, RGI anticipates that the proposed building will
be supported on perimeter walls with bearing loads of 10 to 20 kips per linear foot, and a
series of columns with a maximum load up to 400 kips. Slab-on-grade floor loading of 250
pounds per square foot (psf) are expected.
3.0 Field Exploration and Laboratory Testing
3.1 FIELD EXPLORATION
On January 13, 2021, RGI observed the drilling of four borings. The approximate exploration
locations are shown on Figure 2.
Field logs of each exploration were prepared by the geologist that continuously observed
the drilling. These logs included visual classifications of the materials encountered during
drilling as well as our interpretation of the subsurface conditions between samples. The
boring logs included in Appendix A represent an interpretation of the field logs and include
modifications based on laboratory observation and analysis of the samples.
Geotechnical Engineering Report 2 January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
3.2 LABORATORY TESTING
During the field exploration, a representative portion of each recovered sample was sealed
in containers and transported to our laboratory for further visual and laboratory
examination. Selected samples retrieved from the borings were tested for moisture
content and grain size analysis to aid in soil classification and provide input for the
recommendations provided in this GER. The results and descriptions of the laboratory tests
are enclosed in Appendix A.
4.0 Site Conditions
4.1 SURFACE
The subject site is a rectangular-shaped parcel of land approximately 0.37 acres in size. The
site is bound to the north by Airport Way, to the east by a commercial development, to the
south by South Tillicum Street, and to the west by a commercial development.
The existing site is vacant land vegetated with grass. A paved parking area is located on the
eastern edge of the site. The site is relatively flat with an overall elevation difference of less
than 5 feet.
4.2 GEOLOGY
Review of the Geologic Map of the Renton Quadrangle, King County, Washington by D. R.
Mullineaux (1965) indicates that the soil throughout of the site is mapped as Urban or
industrial land modified by widespread or discontinuous artificial fill (Map Unit afm).
Review of the boring logs show underlying native soils are consistent with alluvium (Map
Unit Qac), which is sand and gravel deposited by the Cedar River, including thin silt, clay,
and peat beds.
4.3 SOILS
The soils encountered during field exploration include very soft to very stiff silt with varying
amounts of sand and very loose to very dense sand with varying amounts of silt and gravel
and gravel with varying amounts of silt and sand.
More detailed descriptions of the subsurface conditions encountered are presented in the
borings included in Appendix A. Sieve analysis was performed on seven selected soil
samples. Grain size distribution curves are included in Appendix A.
4.4 GROUNDWATER
Groundwater was encountered at about 10 feet during our subsurface exploration.
It should be recognized that fluctuations of the groundwater table will occur due to
seasonal variations in the amount of rainfall, runoff, and other factors not evident at the
Geotechnical Engineering Report 3 January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
time the explorations were performed. In addition, perched water can develop within
seams and layers contained in fill soils or higher permeability soils overlying less permeable
soils following periods of heavy or prolonged precipitation. Therefore, groundwater levels
during construction or at other times in the future may be higher or lower than the levels
indicated on the logs. Groundwater level fluctuations should be considered when
developing the design and construction plans for the project.
4.5 SEISMIC CONSIDERATIONS
Based on the International Building Code (IBC), RGI recommends the follow seismic
parameters for design.
Table 1 2015/2018 IBC
Parameter 2015 Value 2018 Value
Site Soil Class1 E2
Site Latitude 47.4846
Site Longitude -122.2098
Short Period Spectral Response Acceleration, SS (g) 1.442 1.444
1-Second Period Spectral Response Acceleration, S1 (g) 0.54 0.492
Adjusted Short Period Spectral Response Acceleration, SMS (g) 1.298 1.732
Adjusted 1-Sec Period Spectral Response Acceleration, SM1 (g) 1.296 1.091
Numeric seismic design value at 0.2 second; SDS(g) 0.865 1.155
Numeric seismic design value at 1.0 second; SD1(g) 0.864 0.727
1. Note: In general accordance with Chapter 20 of ASCE 7-16, the Site Class is based on the average characteristics of the upper 100 feet
of the subsurface profile.
2. Note: ASCE 7-16 require a site soil profile determination extending to a depth of 100 feet for seismic site classification. The current
scope of our services does not include the required 100 foot soil profile determination. Borings extended to a maximum depth of 51.5
feet, and this seismic site class definition considers that very dense soil continues below the maximum depth of the subsurface
exploration. Additional exploration to deeper depths would be required to confirm the conditions below the current depth of
exploration. The site class E designation is valid only if the subgrade is improved to mitigate for the liquefaction potential of the soils
encountered up to 30 feet below grade and the proposed structures that have fundamental periods of vibration equal to or less than
0.5 seconds.
Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength
due to an increase in water pressure induced by vibrations from a seismic event.
Liquefaction mainly affects geologically recent deposits of fine-grained sands that are
below the groundwater table. Soils of this nature derive their strength from intergranular
friction. The generated water pressure or pore pressure essentially separates the soil grains
and eliminates this intergranular friction, thus reducing or eliminating the soil’s strength.
For liquefaction analysis, soil information was obtained from Borings B-1 and B-3. The
groundwater was assumed to be 10 feet. Analysis indicates the native soil below the
Geotechnical Engineering Report 4 January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
groundwater table will liquefy under severe earthquake ground motions (Magnitude 7 and
horizontal acceleration 0.535g, with settlement in the range of 6 to 8 inches. The analysis
is attached in Appendix B.
4.6 GEOLOGIC HAZARD AREAS
Regulated geologically hazardous areas include erosion, landslide, earthquake, wetland, or
other geological hazards. Based on the City of Renton GIS mapping, the site is mapped as a
Seismic Hazard Area. Review of the Liquefaction Susceptibility Map of King County,
Washington by Stephan P. Palmer, etc., (2004) indicates the soils in the area are mapped
as having a moderate to high liquefaction susceptibility during a seismic event.
5.0 Discussion and Recommendations
5.1 GEOTECHNICAL CONSIDERATIONS
Based on our study, the site is suitable for the proposed construction from a geotechnical
standpoint. Foundations for the proposed building can be supported on conventional
spread footings bearing on the native soils improved with aggregate piers or Geopiers. Slab-
on-grade floors can be similarly supported.
Detailed recommendations regarding the above issues and other geotechnical design
considerations are provided in the following sections. These recommendations should be
incorporated into the final design drawings and construction specifications.
5.2 EARTHWORK
Earthwork will include preparing foundation subgrade by installing aggregate piers or
Geopiers, installing utilities and preparing slab and pavement subgrades.
5.2.1 EROSION AND SEDIMENT CONTROL
Potential sources or causes of erosion and sedimentation depend on construction
methods, slope length and gradient, amount of soil exposed and/or disturbed, soil type,
construction sequencing and weather. The impacts on erosion-prone areas can be reduced
by implementing an erosion and sedimentation control plan. The plan should be designed
in accordance with applicable city and/or county standards.
RGI recommends the following erosion control Best Management Practices (BMPs):
Scheduling site preparation and grading for the drier summer and early fall months
and undertaking activities that expose soil during periods of little or no rainfall
Retaining existing vegetation whenever feasible
Establishing a quarry spall construction entrance
Geotechnical Engineering Report 5 January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
Installing siltation control fencing or anchored straw or coir wattles on the downhill
side of work areas
Covering soil stockpiles with anchored plastic sheeting
Revegetating or mulching exposed soils with a minimum 3-inch thickness of straw
if surfaces will be left undisturbed for more than one day during wet weather or
one week in dry weather
Directing runoff away from exposed soils and slopes
Minimizing the length and steepness of slopes with exposed soils and cover
excavation surfaces with anchored plastic sheeting (Graded and disturbed slopes
should be tracked in place with the equipment running perpendicular to the slope
contours so that the track marks provide a texture to help resist erosion and
channeling. Some sloughing and raveling of slopes with exposed or disturbed soil
should be expected.)
Decreasing runoff velocities with check dams, straw bales or coir wattles
Confining sediment to the project site
Inspecting and maintaining erosion and sediment control measures frequently (The
contractor should be aware that inspection and maintenance of erosion control
BMPs is critical toward their satisfactory performance. Repair and/or replacement
of dysfunctional erosion control elements should be anticipated.)
Permanent erosion protection should be provided by reestablishing vegetation using
hydroseeding and/or landscape planting. Until the permanent erosion protection is
established, site monitoring should be performed by qualified personnel to evaluate the
effectiveness of the erosion control measures. Provisions for modifications to the erosion
control system based on monitoring observations should be included in the erosion and
sedimentation control plan.
5.2.2 STRIPPING
Stripping efforts should include removal of pavements, vegetation, organic materials, and
deleterious debris from areas slated for building, pavement, and utility construction.
5.2.3 EXCAVATIONS
All temporary cut slopes associated with the site and utility excavations should be
adequately inclined to prevent sloughing and collapse. The site soils consist of very soft to
very stiff silt and very loose to very dense sand and gravel.
Accordingly, for excavations more than 4 feet but less than 20 feet in depth, the temporary
side slopes should be laid back with a minimum slope inclination of 1.5H:1V
(Horizontal:Vertical). If there is insufficient room to complete the excavations in this
manner, or excavations greater than 20 feet in depth are planned, using temporary shoring
to support the excavations should be considered. For open cuts at the site, RGI
recommends:
Geotechnical Engineering Report 6 January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
No traffic, construction equipment, stockpiles or building supplies are allowed at
the top of cut slopes within a distance of at least five feet from the top of the cut
Exposed soil along the slope is protected from surface erosion using waterproof
tarps and/or plastic sheeting
Construction activities are scheduled so that the length of time the temporary cut
is left open is minimized
Surface water is diverted away from the excavation
The general condition of slopes should be observed periodically by a geotechnical
engineer to confirm adequate stability and erosion control measures
In all cases, however, appropriate inclinations will depend on the actual soil and
groundwater conditions encountered during earthwork. Ultimately, the site contractor
must be responsible for maintaining safe excavation slopes that comply with applicable
OSHA or WISHA guidelines.
5.2.4 SITE PREPARATION
RGI anticipates that some areas of loose or soft soil will be exposed upon completion of
stripping and grubbing. The subgrade should moisture conditioned and compacted to a
firm and unyielding condition in order to achieve a minimum compaction level of 95
percent of the modified proctor maximum dry density as determined by the American
Society of Testing and Materials D1557-09 Standard Test Methods for Laboratory
Compaction Characteristics of Soil Using Modified Effort (ASTM D1557). In some areas, it
may be necessary to overexcavate and replace the native soils in order to provide a working
surface for the pier installation.
Subgrade soils that become disturbed due to elevated moisture conditions should be
overexcavated to reveal firm, non-yielding, non-organic soils and backfilled with
compacted structural fill. In order to maximize utilization of site soils as structural fill, RGI
recommends that the earthwork portion of this project be completed during extended
periods of warm and dry weather if possible. If earthwork is completed during the wet
season (typically November through May) it will be necessary to take extra precautionary
measures to protect subgrade soils. Wet season earthwork will require additional
mitigative measures beyond that which would be expected during the drier summer and
fall months.
5.2.5 STRUCTURAL FILL
Once stripping, clearing and other preparing operations are complete, cuts and fills can be
made to establish desired building grades. RGI recommends fill below the foundation and
floor slab, behind retaining walls, and below pavement and hardscape surfaces be placed
in accordance with the following recommendations for structural fill.
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Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
The suitability of excavated site soils and import soils for compacted structural fill use will
depend on the gradation and moisture content of the soil when it is placed. As the amount
of fines (that portion passing the U.S. No. 200 sieve) increases, soil becomes increasingly
sensitive to small changes in moisture content and adequate compaction becomes more
difficult or impossible to achieve. Soils containing more than about 5 percent fines cannot
be consistently compacted to a dense, non-yielding condition when the moisture content
is more than 2 percent above or below optimum. Optimum moisture content is that
moisture that results in the greatest compacted dry density with a specified compactive
effort.
Non-organic site soils are only considered suitable for structural fill provided that their
moisture content is within about two percent of the optimum moisture level as determined
by ASTM D1557. Excavated site soils may not be suitable for re-use as structural fill
depending on the moisture content and weather conditions at the time of construction. If
soils are stockpiled for future reuse and wet weather is anticipated, the stockpile should be
protected with plastic sheeting that is securely anchored.
The existing fill soils may be reusable as structural fill provided the soils can be moisture
conditioned and compacted. The silt native soils are not suitable for structural fill. We
expect it will be necessary to import clean, granular soils to complete site work that meet
the grading requirements listed in Table 2 to be used as structural fill. In the dry summer
and fall months the fines content may be increased if the soils will be covered by
impermeable surfaces prior to the wet season.
Table 2 Structural Fill Gradation
U.S. Sieve Size Percent Passing
4 inches 100
No. 4 sieve 22 to 100
No. 200 sieve 0 to 5*
*Based on minus 3/4 inch fraction.
Prior to use, an RGI representative should observe and test all materials imported to the
site for use as structural fill. Structural fill materials should be placed in uniform loose layers
not exceeding 12 inches and compacted as specified in Table 3. The soil’s maximum density
and optimum moisture should be determined by ASTM D1557.
Geotechnical Engineering Report 8 January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
Table 3 Structural Fill Compaction ASTM D1557
Location Material Type
Minimum
Compaction
Percentage
Moisture Content
Range
Foundations On-site granular or approved
imported fill soils: 95 +2 -2
Retaining Wall Backfill On-site granular or approved
imported fill soils: 92 +2 -2
Slab-on-grade On-site granular or approved
imported fill soils: 95 +2 -2
General Fill (non-
structural areas)
On-site soils or approved
imported fill soils: 90 +3 -2
Pavement – Subgrade
and Base Course
On-site granular or approved
imported fill soils: 95 +2 -2
Placement and compaction of structural fill should be observed by RGI. A representative
number of in-place density tests should be performed as the fill is being placed to confirm
that the recommended level of compaction is achieved.
5.2.6 CUT AND FILL SLOPES
All permanent cut and fill slopes should be graded with a finished inclination no greater
than 2H:1V. Upon completion of construction, the slope face should be trackwalked,
compacted and vegetated, or provided with other physical means to guard against erosion.
All fill placed for slope construction should meet the structural fill requirements as
described in Section 5.2.5.
Final grades at the top of the slopes must promote surface drainage away from the slope
crest. Water must not be allowed to flow in an uncontrolled fashion over the slope face. If
it is necessary to direct surface runoff towards the slope, it should be controlled at the top
of the slope, piped in a closed conduit installed on the slope face, and taken to an
appropriate point of discharge beyond the toe of the slope.
5.2.7 WET WEATHER CONSTRUCTION CONSIDERATIONS
RGI recommends that preparation for site grading and construction include procedures
intended to drain ponded water, control surface water runoff, and to collect shallow
subsurface seepage zones in excavations where encountered. It will not be possible to
successfully compact the subgrade or utilize on-site soils as structural fill if accumulated
water is not drained prior to grading or if drainage is not controlled during construction.
Attempting to grade the site without adequate drainage control measures will reduce the
amount of on-site soil effectively available for use, increase the amount of select import fill
materials required, and ultimately increase the cost of the earthwork phases of the project.
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Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
Free water should not be allowed to pond on the subgrade soils. RGI anticipates that the
use of berms and shallow drainage ditches, with sumps and pumps in utility trenches, will
be required for surface water control during wet weather and/or wet site conditions.
5.3 FOUNDATIONS
Following site preparation and grading, the proposed building foundation can be supported
on conventional spread footings bearing on subgrade soils improved with aggregate piers.
Aggregate piers are a proprietary system that is typically design build. Geopiers are
designed and installed by Geopier Foundation Company (800-371-7470) and Aggregate
piers are designed and installed by Hayward Baker (800-456-6548).
Perimeter foundations exposed to weather should be at a minimum depth of 18 inches
below final exterior grades. Interior foundations can be constructed at any convenient
depth below the floor slab. Finished grade is defined as the lowest adjacent grade within 5
feet of the foundation for perimeter (or exterior) footings and finished floor level for
interior footings.
Table 4 Foundation Design
Design Parameter Value
Allowable Bearing Capacity after Pier Installation 3,000 psf1
Friction Coefficient 0.35
Passive pressure (equivalent fluid pressure) 250 pcf2
Minimum foundation dimensions Columns: 24 inches
Walls: 16 inches
1. psf = pounds per square foot
2. pcf = pounds per cubic foot
The allowable foundation bearing pressures apply to dead loads plus design live load
conditions. For short-term loads, such as wind and seismic, a 1/3 increase in this allowable
capacity may be used. At perimeter locations, RGI recommends not including the upper 12
inches of soil in the computation of passive pressures because they can be affected by
weather or disturbed by future grading activity. The passive pressure value assumes the
foundation will be constructed neat against competent soil or backfilled with structural fill
as described in Section 5.2.5. The recommended base friction and passive resistance value
includes a safety factor of about 1.5.
With spread footing foundations designed in accordance with the recommendations in this
section, maximum total and differential post-construction settlements of 1 inch and 1/2
inch, respectively, should be expected.
Geotechnical Engineering Report 10 January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
5.4 RETAINING WALLS
If retaining walls are needed in the building area, RGI recommends cast-in-place concrete
walls be used. The magnitude of earth pressure development on retaining walls will partly
depend on the quality of the wall backfill. RGI recommends placing and compacting wall
backfill as structural fill. Wall drainage will be needed behind the wall face. A typical
retaining wall drainage detail is shown in Figure 3.
With wall backfill placed and compacted as recommended, and drainage properly installed,
RGI recommends using the values in the following table for design.
Table 5 Retaining Wall Design
Design Parameter Value
Allowable Bearing Capacity after Pier Installation 3,000 psf
Active Earth Pressure (unrestrained walls) 35 pcf
At-rest Earth Pressure (restrained walls) 50 pcf
For seismic design, an additional uniform load of 7 times the wall height (H) for
unrestrained walls and 14H in psf for restrained walls should be applied to the wall surface.
Friction at the base of foundations and passive earth pressure will provide resistance to
these lateral loads. Values for these parameters are provided in Section 5.3.
5.5 SLAB-ON-GRADE CONSTRUCTION
RGI recommends that the concrete slab-on-grade be placed on the subgrade soils improved
with aggregate piers. Immediately below the floor slab, RGI recommends placing a four-
inch thick capillary break layer of clean, free-draining sand or gravel that has less than five
percent passing the U.S. No. 200 sieve. This material will reduce the potential for upward
capillary movement of water through the underlying soil and subsequent wetting of the
floor slab. Where moisture by vapor transmission is undesirable, an 8- to 10-millimeter
thick plastic membrane should be placed on a 4-inch thick layer of clean gravel.
For the anticipated floor slab loading, we estimate post-construction floor settlements of
1/4- to 1/2-inch.
5.6 DRAINAGE
5.6.1 SURFACE
Final exterior grades should promote free and positive drainage away from the building
area. Water must not be allowed to pond or collect adjacent to foundations or within the
immediate building area. For non-pavement locations, RGI recommends providing a
Geotechnical Engineering Report 11 January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
minimum drainage gradient of 3 percent for a minimum distance of 10 feet from the
building perimeter. In paved locations, a minimum gradient of 1 percent should be
provided unless provisions are included for collection and disposal of surface water
adjacent to the structure.
5.6.2 SUBSURFACE
RGI recommends installing perimeter foundation drains. A typical footing drain detail is
shown on Figure 4. The foundation drains and roof downspouts should be tightlined
separately to an approved discharge facility. Subsurface drains must be laid with a gradient
sufficient to promote positive flow to a controlled point of approved discharge.
5.6.3 INFILTRATION
Based on native site soils, infiltration of stormwater is not feasible at the site.
5.7 UTILITIES
Utility pipes should be bedded and backfilled in accordance with American Public Works
Association (APWA) specifications. For site utilities located within the right-of-ways,
bedding and backfill should be completed in accordance with City of Renton specifications.
At a minimum, trench backfill should be placed and compacted as structural fill, as
described in Section 5.2.5. Where utilities occur below unimproved areas, the degree of
compaction can be reduced to a minimum of 90 percent of the soil’s maximum density as
determined by the referenced ASTM D1557. As noted, soils excavated on site may not be
suitable for use as backfill material. If on-site soils are or become unusable, imported
structural fill meeting the gradation provided in Table 2 should be used for trench backfill.
5.8 PAVEMENTS
Pavement subgrades should be prepared as described in Section 5.2 and as discussed
below. Regardless of the relative compaction achieved, the subgrade must be firm and
relatively unyielding before paving. The subgrade should be proof-rolled with heavy
construction equipment to verify this condition.
5.8.1 FLEXIBLE PAVEMENTS
With the pavement subgrade prepared as described above, RGI recommends the following
pavement sections for parking and drive areas paved with flexible asphalt concrete
surfacing.
For drive areas: 3 inches of Hot Mix Asphalt (HMA) over 6 inches of crushed rock
base (CRB) over 12 inches of gravel base
Geotechnical Engineering Report 12 January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
5.8.2 CONCRETE PAVEMENTS
With the pavement subgrade prepared as described above, RGI recommends the following
pavement sections for parking and drive areas paved with concrete surfacing.
For concrete pavement areas: 5 inches of concrete over 4 inches of CRB over 12
inches of gravel base
The paving materials used should conform to the WSDOT specifications for HMA, concrete
paving, CRB surfacing (9-03.9(3) Crushed Surfacing), and gravel base (9-03.10 Aggregate for
Gravel Base).
Long-term pavement performance will depend on surface drainage. A poorly-drained
pavement section will be subject to premature failure as a result of surface water
infiltrating into the subgrade soils and reducing their supporting capability.
For optimum pavement performance, surface drainage gradients of no less than 2 percent
are recommended. Also, some degree of longitudinal and transverse cracking of the
pavement surface should be expected over time. Regular maintenance should be planned
to seal cracks when they occur.
6.0 Additional Services
RGI is available to provide further geotechnical consultation throughout the design phase
of the project. RGI should review the final design and specifications in order to verify that
earthwork and foundation recommendations have been properly interpreted and
incorporated into project design and construction.
RGI is also available to provide geotechnical engineering and construction monitoring
services during construction. The integrity of the earthwork and construction depends on
proper site preparation and procedures. In addition, engineering decisions may arise in the
field in the event that variations in subsurface conditions become apparent. Construction
monitoring services are not part of this scope of work. If these services are desired, please
let us know and we will prepare a cost proposal.
7.0 Limitations
This GER is the property of RGI, Dreamliner LLC, and its designated agents. Within the limits
of the scope and budget, this GER was prepared in accordance with generally accepted
geotechnical engineering practices in the area at the time this GER was issued. This GER is
intended for specific application to the Dreamliner Mixed Use project in Renton,
Washington, and for the exclusive use of Dreamliner LLC and its authorized representatives.
No other warranty, expressed or implied, is made. Site safety, excavation support, and
dewatering requirements are the responsibility of others.
Geotechnical Engineering Report 13 January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
The scope of services for this project does not include either specifically or by implication
any environmental or biological (for example, mold, fungi, bacteria) assessment of the site
or identification or prevention of pollutants, hazardous materials or conditions. If the
owner is concerned about the potential for such contamination or pollution, we can
provide a proposal for these services.
The analyses and recommendations presented in this GER are based upon data obtained
from the explorations performed on site. Variations in soil conditions can occur, the nature
and extent of which may not become evident until construction. If variations appear
evident, RGI should be requested to reevaluate the recommendations in this GER prior to
proceeding with construction.
It is the client’s responsibility to see that all parties to the project, including the designers,
contractors, subcontractors, are made aware of this GER in its entirety. The use of
information contained in this GER for bidding purposes should be done at the contractor’s
option and risk.
USGS, 2020, Renton, Washington
7.5-Minute Quadrangle
Approximate Scale: 1"=1000'
0 500 1000 2000 N
Site Vicinity Map
Figure 1
01/2021
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Dreamliner Mixed Use
RGI Project Number:
2020-618-1
Date Drawn:
Address: 511 Airport Way, Renton, Washington 98057
SITE
B-1B-2B-3B-401/2021Corporate Office17522 Bothell Way NortheastBothell, Washington 98011Phone: 425.415.0551Fax: 425.415.0311Dreamliner Mixed UseRGI Project Number:2020-618-1Date Drawn:Address: 511 Airport Way, Renton, Washington 98057Figure 2Approximate Scale: 1"=30'0153060N= Boring by RGI, 01/13/21= Site boundaryGeotechnical Exploration Plan
Incliniations)
12" Over the Pipe
3" Below the Pipe
Perforated Pipe
4" Diameter PVC
Compacted Structural
Backfill (Native or Import)
12" min.
Filter Fabric Material
12" Minimum Wide
Free-Draining Gravel
Slope to Drain
(See Report for
Appropriate
Excavated Slope
01/2021
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Dreamliner Mixed Use
RGI Project Number:
2020-618-1
Date Drawn:
Address: 511 Airport Way, Renton, Washington 98057
Retaining Wall Drainage Detail
Figure 3
Not to Scale
3/4" Washed Rock or Pea Gravel
4" Perforated Pipe
Building Slab
Structural
Backfill
Compacted
Filter Fabric
01/2021
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Dreamliner Mixed Use
RGI Project Number:
2020-618-1
Date Drawn:
Address: 511 Airport Way, Renton, Washington 98057
Typical Footing Drain Detail
Figure 4
Not to Scale
Geotechnical Engineering Report January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
APPENDIX A
FIELD EXPLORATION AND LABORATORY TESTING
On January 13, 2021, RGI performed field explorations using a tracked drill rig. We explored
subsurface soil conditions at the site by observing the drilling of four borings to a maximum
depth of 51.5 feet below existing grade. The boring locations are shown on Figure 2. The
boring locations were approximately determined by measurements from existing property
lines and paved roads.
A geologist from our office conducted the field exploration and classified the soil conditions
encountered, maintained a log of each test exploration, obtained representative soil
samples, and observed pertinent site features. All soil samples were visually classified in
accordance with the Unified Soil Classification System (USCS).
Representative soil samples obtained from the explorations were placed in closed
containers and taken to our laboratory for further examination and testing. As a part of the
laboratory testing program, the soil samples were classified in our in house laboratory
based on visual observation, texture, plasticity, and the limited laboratory testing described
below.
Moisture Content Determinations
Moisture content determinations were performed in accordance with ASTM D2216-10
Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil
and Rock by Mass (ASTM D2216) on representative samples obtained from the exploration
in order to aid in identification and correlation of soil types. The moisture content of typical
sample was measured and is reported on the boring logs.
Grain Size Analysis
A grain size analysis indicates the range in diameter of soil particles included in a particular
sample. Grain size analyses was determined using D6913-04(2009) Standard Test Methods
for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis (ASTM D6913) on
seven of the samples.
Project Name:Dreamliner Mixed Use
Project Number:2020-618-1
Client:Dreamliner LLC
Boring No.: B-1
Date(s) Drilled:1/13/2021
Drilling Method(s):Hollow Stem Auger
Drill Rig Type:Track Rig
Groundwater Level:10'
Borehole Backfill:Bentonite Chips
Logged By:ELW
Drill Bit Size/Type:8" auger
Drilling Contractor:Bortec
Sampling Method(s):SPT
Location:511 Airport Way, Renton, Washington
Surface Conditions:Grass
Total Depth of Borehole:
Approximate
Surface Elevation:N/A
Hammer Data :140 lb, 30" drop, rope and
cathead
USCS SymbolML
GP
SW
SP
ML Moisture (%)66
8
14
18
32Recovery (%)Graphic LogRQD (%)MATERIAL DESCRIPTION
Tan SILT with some sand, very soft to soft, moist to wet
Trace wood debris
Brown sandy GRAVEL with trace silt, medium dense, water bearing
Brown SAND with some gravel and trace silt, medium dense, water bearing
4% fines
Brown SAND with some gravel and trace silt, medium dense, water bearing
Gray sandy SILT, soft to medium stiff, saturatedDepth (feet)0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30 Sample TypeSampling Resistance, blows/ft2
12
29
12
4Elevation (feet)Sheet 1 of 2
Project Name:Dreamliner Mixed Use
Project Number:2020-618-1
Client:Dreamliner LLC
Boring No.: B-1
USCS SymbolSP
GP
GP
SP Moisture (%)14
14
15Recovery (%)Graphic LogRQD (%)MATERIAL DESCRIPTION
Brown gravelly SAND with trace silt, dense, water bearing
Brown GRAVEL, dense, water bearing
Brown sandy GRAVEL, dense, water bearing
Brown SAND with some gravel, dense, water bearing
Boring terminated at 51' 6"Depth (feet)30
35
40
45
50
55
60 Sample TypeSampling Resistance, blows/ft38
46
42
34
35Elevation (feet)Sheet 2 of 2
Project Name:Dreamliner Mixed Use
Project Number:2020-618-1
Client:Dreamliner LLC
Boring No.: B-2
Date(s) Drilled:1/13/2021
Drilling Method(s):Hollow Stem Auger
Drill Rig Type:Track Rig
Groundwater Level:10'
Borehole Backfill:Bentonite Chips
Logged By:ELW
Drill Bit Size/Type:8" auger
Drilling Contractor:Bortec
Sampling Method(s):SPT
Location:511 Airport Way, Renton, Washington
Surface Conditions:Grass
Total Depth of Borehole:
Approximate
Surface Elevation:N/A
Hammer Data :140 lb, 30" drop, rope and
cathead
USCS SymbolGP
SP-SM
GP
ML
ML Moisture (%)6
16
9
37
31Recovery (%)Graphic LogRQD (%)MATERIAL DESCRIPTION
Gray sandy GRAVEL with some silt, dense, moist
Brown SAND with some silt and gravel, medium dense, water bearing
7% fines
Brown sandy GRAVEL with trace silt, loose, water bearing
Gray SILT with trace sand, soft to medium stiff, saturated
90% fines
Gray SILT with some sand, medium stiff, saturated
Trace organicsDepth (feet)0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30 Sample TypeSampling Resistance, blows/ft40
16
9
4
7Elevation (feet)Sheet 1 of 2
Project Name:Dreamliner Mixed Use
Project Number:2020-618-1
Client:Dreamliner LLC
Boring No.: B-2
USCS SymbolSM
GP Moisture (%)29
8
12Recovery (%)Graphic LogRQD (%)MATERIAL DESCRIPTION
Gray silty SAND, medium dense, saturated
Trace organics
Brown sandy GRAVEL with trace silt, medium dense, water bearing
Becomes very dense
Boring terminated at 40' 2"Depth (feet)30
35
40
45
50
55
60 Sample TypeSampling Resistance, blows/ft13
28
100/2"Elevation (feet)Sheet 2 of 2
Project Name:Dreamliner Mixed Use
Project Number:2020-618-1
Client:Dreamliner LLC
Boring No.: B-3
Date(s) Drilled:1/13/2021
Drilling Method(s):Hollow Stem Auger
Drill Rig Type:Track Rig
Groundwater Level:10'
Borehole Backfill:Bentonite Chips
Logged By:ELW
Drill Bit Size/Type:8" auger
Drilling Contractor:Bortec
Sampling Method(s):
Location:511 Airport Way, Renton, Washington
Surface Conditions:Grass
Total Depth of Borehole:
Approximate
Surface Elevation:N/A
Hammer Data :140 lb, 30" drop, rope and
cathead
USCS SymbolFill
SP
ML
SM Moisture (%)7
10
18
34
26Recovery (%)Graphic LogRQD (%)MATERIAL DESCRIPTION
Brown sandy GRAVEL with some silt, medium dense, moist (Fill)
Trace concrete debris
Brown gravelly SAND, medium dense, moist
Becomes water bearing
Gray SILT with some sand, soft, saturated
Brown silty SAND with trace gravel, medium dense, water bearing
23% finesDepth (feet)0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30 Sample TypeSampling Resistance, blows/ft20
27
29
3
13Elevation (feet)Sheet 1 of 2
Project Name:Dreamliner Mixed Use
Project Number:2020-618-1
Client:Dreamliner LLC
Boring No.: B-3
USCS SymbolSP
SM
GP
GP Moisture (%)17
13
13
10
8Recovery (%)Graphic LogRQD (%)MATERIAL DESCRIPTION
Brown sand with some gravel and trace silt, medium dense, water bearing
Brown to gray silty gravelly SAND, dense, water bearing
13% fines
Brown gravelly coarse SAND with trace silt, medium ednse, water bearing
Brown sandy GRAVEL, dense, water bearing
Boring terminated at 51' 6"Depth (feet)30
35
40
45
50
55
60 Sample TypeSampling Resistance, blows/ft29
34
23
20
44Elevation (feet)Sheet 2 of 2
Project Name:Dreamliner Mixed Use
Project Number:2020-618-1
Client:Dreamliner LLC
Boring No.: B-4
Date(s) Drilled:1/13/2021
Drilling Method(s):Hollow Stem Auger
Drill Rig Type:Track Rig
Groundwater Level:10'
Borehole Backfill:Bentonite Chips
Logged By:ELW
Drill Bit Size/Type:8" auger
Drilling Contractor:Bortec
Sampling Method(s):SPT
Location:511 Airport Way, Renton, Washington
Surface Conditions:Grass
Total Depth of Borehole:
Approximate
Surface Elevation:N/A
Hammer Data :140 lb, 30" drop, rope and
cathead
USCS SymbolML
ML
SP
ML
ML Moisture (%)36
36
11
36
30Recovery (%)Graphic LogRQD (%)MATERIAL DESCRIPTION
Tan mottled SILT with some sand, very soft to soft, wet
Brown sandy SILT, very stiff, Saturated
Gray coarse SAND with some gravel, medium dense, water bearing
Gray SILT, soft to medium stiff, saturated
Gray sandy SILT, medium stiff, saturatedDepth (feet)0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30 Sample TypeSampling Resistance, blows/ft2
17
16
4
7Elevation (feet)Sheet 1 of 2
Project Name:Dreamliner Mixed Use
Project Number:2020-618-1
Client:Dreamliner LLC
Boring No.: B-4
USCS SymbolSP
GP
GP
ML Moisture (%)19
9
29Recovery (%)Graphic LogRQD (%)MATERIAL DESCRIPTION
Gray gravelly SAND with trace silt, dense, water bearing
Brown GRAVEL, very dense, water bearing
Brown GRAVEL with some sand and trace silt, medium dense, water bearing
Brown to gray SILT with some sand and gravel, medium stiff, saturated
59% fines
Boring terminated at 46' 6"Depth (feet)30
35
40
45
50
55
60 Sample TypeSampling Resistance, blows/ft47
56
17
5Elevation (feet)Sheet 2 of 2
Project Name:Dreamliner Mixed Use
Project Number:2020-618-1
Client:Dreamliner LLC
Key to Log of Boring
USCS SymbolMoisture (%)Recovery (%)Graphic LogRQD (%)MATERIAL DESCRIPTIONDepth (feet)Sample TypeSampling Resistance, blows/ftElevation (feet)1 2 3 4 5 6 7 8 9 10
COLUMN DESCRIPTIONS
1 Elevation (feet): Elevation (MSL, feet).
2 Depth (feet): Depth in feet below the ground surface.
3 Sample Type: Type of soil sample collected at the depth interval
shown.
4 Sampling Resistance, blows/ft: Number of blows to advance driven
sampler one foot (or distance shown) beyond seating interval
using the hammer identified on the boring log.
5 RQD (%): Rock Quality Designation is a relative index of the rock
mass quality calculated by comparing the cumulative length of
intact pieces of core exceeding 100 mm in length to the cored
interval length.
6 Recovery (%): Core Recovery Percentage is determined based on
a ratio of the length of core sample recovered compared to the
cored interval length.
7 USCS Symbol: USCS symbol of the subsurface material.
8 Graphic Log: Graphic depiction of the subsurface material
encountered.
9 MATERIAL DESCRIPTION: Description of material encountered.
May include consistency, moisture, color, and other descriptive
text.
10 Moisture (%): Moisture, expressed as a water content.
FIELD AND LABORATORY TEST ABBREVIATIONS
CHEM: Chemical tests to assess corrosivity
COMP: Compaction test
CONS: One-dimensional consolidation test
LL: Liquid Limit, percent
PI: Plasticity Index, percent
SA: Sieve analysis (percent passing No. 200 Sieve)
UC: Unconfined compressive strength test, Qu, in ksf
WA: Wash sieve (percent passing No. 200 Sieve)
MATERIAL GRAPHIC SYMBOLS
AF
Poorly graded GRAVEL (GP)
SILT, SILT w/SAND, SANDY SILT (ML)
Silty SAND (SM)
Poorly graded SAND (SP)
Poorly graded SAND with Silt (SP-SM)
Well graded SAND (SW)
TYPICAL SAMPLER GRAPHIC SYMBOLS
Auger sampler
Bulk Sample
3-inch-OD California w/
brass rings
CME Sampler
Grab Sample
2.5-inch-OD Modified
California w/ brass liners
Pitcher Sample
2-inch-OD unlined split
spoon (SPT)
Shelby Tube (Thin-walled,
fixed head)
OTHER GRAPHIC SYMBOLS
Water level (at time of drilling, ATD)
Water level (after waiting)
Minor change in material properties within a
stratum
Inferred/gradational contact between strata
?Queried contact between strata
GENERAL NOTES
1: Soil classifications are based on the Unified Soil Classification System. Descriptions and stratum lines are interpretive, and actual lithologic changes may be
gradual. Field descriptions may have been modified to reflect results of lab tests.
2: Descriptions on these logs apply only at the specific boring locations and at the time the borings were advanced. They are not warranted to be representative
of subsurface conditions at other locations or times.
Sheet 1 of 1
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Dreamliner Mixed Use SAMPLE ID/TYPE B-1
PROJECT NO.2020-618 SAMPLE DEPTH 15 feet
TECH/TEST DATE JDH/RT 1/18/2021 DATE RECEIVED 1/18/2021
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)527.9 Weight Of Sample (gm)463.3
Wt Dry Soil & Tare (gm) (w2)463.3 Tare Weight (gm) 16.4
Weight of Tare (gm) (w3)16.4 (W6) Total Dry Weight (gm) 446.9
Weight of Water (gm) (w4=w1-w2) 64.6 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 446.9 Cumulative
Moisture Content (%) (w4/w5)*100 14 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.4 0.00 0.00 100.00 cobbles
% C GRAVEL 0.0 3.0"16.4 0.00 0.00 100.00 coarse gravel
% F GRAVEL 16.3 2.5" coarse gravel
% C SAND 26.4 2.0" coarse gravel
% M SAND 40.2 1.5"16.4 0.00 0.00 100.00 coarse gravel
% F SAND 12.7 1.0" coarse gravel
% FINES 4.4 0.75"16.4 0.00 0.00 100.00 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"24.1 7.70 1.72 98.28 fine gravel
D10 (mm)0.23 #4 89.4 73.00 16.33 83.67 coarse sand
D30 (mm)0.7 #10 207.3 190.90 42.72 57.28 medium sand
D60 (mm)2.2 #20 medium sand
Cu 9.6 #40 387.0 370.60 82.93 17.07 fine sand
Cc 1.0 #60 fine sand
#100 437.6 421.20 94.25 5.75 fine sand
#200 443.7 427.30 95.61 4.39 fines
PAN 463.3 446.90 100.00 0.00 silt/clay
DESCRIPTION SAND with some gravel and trace silt
USCS SW
Prepared For: Dreamliner LLC Reviewed By: ELW
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Dreamliner Mixed Use SAMPLE ID/TYPE B-2
PROJECT NO.2020-618 SAMPLE DEPTH 10 feet
TECH/TEST DATE JDH/RT 1/18/2021 DATE RECEIVED 1/18/2021
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)483.4 Weight Of Sample (gm)418.3
Wt Dry Soil & Tare (gm) (w2)418.3 Tare Weight (gm) 16.2
Weight of Tare (gm) (w3)16.2 (W6) Total Dry Weight (gm) 402.1
Weight of Water (gm) (w4=w1-w2) 65.1 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 402.1 Cumulative
Moisture Content (%) (w4/w5)*100 16 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.2 0.00 0.00 100.00 cobbles
% C GRAVEL 8.5 3.0"16.2 0.00 0.00 100.00 coarse gravel
% F GRAVEL 18.2 2.5" coarse gravel
% C SAND 8.1 2.0" coarse gravel
% M SAND 23.2 1.5"16.2 0.00 0.00 100.00 coarse gravel
% F SAND 35.5 1.0" coarse gravel
% FINES 6.5 0.75"50.2 34.00 8.46 91.54 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"97.2 81.00 20.14 79.86 fine gravel
D10 (mm)0.16 #4 123.4 107.20 26.66 73.34 coarse sand
D30 (mm)0.29 #10 156.1 139.90 34.79 65.21 medium sand
D60 (mm)1.5 #20 medium sand
Cu 9.4 #40 249.3 233.10 57.97 42.03 fine sand
Cc 0.4 #60 fine sand
#100 380.2 364.00 90.52 9.48 fine sand
#200 392.2 376.00 93.51 6.49 fines
PAN 418.3 402.10 100.00 0.00 silt/clay
DESCRIPTION SAND with some silt and gravel
USCS SP-SM
Prepared For: Dreamliner LLC Reviewed By: ELW
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Dreamliner Mixed Use SAMPLE ID/TYPE B-2
PROJECT NO.2020-618 SAMPLE DEPTH 20 feet
TECH/TEST DATE JDH/RT 1/18/2021 DATE RECEIVED 1/18/2021
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)312.7 Weight Of Sample (gm)232.0
Wt Dry Soil & Tare (gm) (w2)232.0 Tare Weight (gm) 16.0
Weight of Tare (gm) (w3)16.0 (W6) Total Dry Weight (gm) 216.0
Weight of Water (gm) (w4=w1-w2) 80.7 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 216.0 Cumulative
Moisture Content (%) (w4/w5)*100 37 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.0 0.00 0.00 100.00 cobbles
% C GRAVEL 0.0 3.0"16.0 0.00 0.00 100.00 coarse gravel
% F GRAVEL 2.3 2.5" coarse gravel
% C SAND 1.9 2.0" coarse gravel
% M SAND 1.9 1.5"16.0 0.00 0.00 100.00 coarse gravel
% F SAND 4.1 1.0" coarse gravel
% FINES 89.9 0.75"16.0 0.00 0.00 100.00 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"17.5 1.50 0.69 99.31 fine gravel
D10 (mm)#4 20.9 4.90 2.27 97.73 coarse sand
D30 (mm)#10 25.1 9.10 4.21 95.79 medium sand
D60 (mm)#20 medium sand
Cu #40 29.1 13.10 6.06 93.94 fine sand
Cc #60 fine sand
#100 32.5 16.50 7.64 92.36 fine sand
#200 37.9 21.90 10.14 89.86 fines
PAN 232.0 216.00 100.00 0.00 silt/clay
DESCRIPTION SILT with trace sand
USCS ML
Prepared For: Dreamliner LLC Reviewed By: ELW
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Dreamliner Mixed Use SAMPLE ID/TYPE B-2
PROJECT NO.2020-618 SAMPLE DEPTH 30 feet
TECH/TEST DATE JDH/RT 1/18/2021 DATE RECEIVED 1/18/2021
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)264.5 Weight Of Sample (gm)209.3
Wt Dry Soil & Tare (gm) (w2)209.3 Tare Weight (gm) 16.1
Weight of Tare (gm) (w3)16.1 (W6) Total Dry Weight (gm) 193.2
Weight of Water (gm) (w4=w1-w2) 55.2 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 193.2 Cumulative
Moisture Content (%) (w4/w5)*100 29 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.1 0.00 0.00 100.00 cobbles
% C GRAVEL 0.0 3.0"16.1 0.00 0.00 100.00 coarse gravel
% F GRAVEL 0.2 2.5" coarse gravel
% C SAND 0.4 2.0" coarse gravel
% M SAND 0.8 1.5"16.1 0.00 0.00 100.00 coarse gravel
% F SAND 56.6 1.0" coarse gravel
% FINES 42.0 0.75"16.1 0.00 0.00 100.00 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"16.1 0.00 0.00 100.00 fine gravel
D10 (mm)#4 16.4 0.30 0.16 99.84 coarse sand
D30 (mm)#10 17.2 1.10 0.57 99.43 medium sand
D60 (mm)#20 medium sand
Cu #40 18.8 2.70 1.40 98.60 fine sand
Cc #60 fine sand
#100 102.2 86.10 44.57 55.43 fine sand
#200 128.1 112.00 57.97 42.03 fines
PAN 209.3 193.20 100.00 0.00 silt/clay
DESCRIPTION Silty SAND
USCS SM
Prepared For: Dreamliner LLC Reviewed By: ELW
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Dreamliner Mixed Use SAMPLE ID/TYPE B-3
PROJECT NO.2020-618 SAMPLE DEPTH 25 feet
TECH/TEST DATE JDH/RT 1/18/2021 DATE RECEIVED 1/18/2021
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)366.7 Weight Of Sample (gm)293.8
Wt Dry Soil & Tare (gm) (w2)293.8 Tare Weight (gm) 32.1
Weight of Tare (gm) (w3)32.1 (W6) Total Dry Weight (gm) 261.7
Weight of Water (gm) (w4=w1-w2) 72.9 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 261.7 Cumulative
Moisture Content (%) (w4/w5)*100 28 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"32.1 0.00 0.00 100.00 cobbles
% C GRAVEL 0.0 3.0"32.1 0.00 0.00 100.00 coarse gravel
% F GRAVEL 7.7 2.5" coarse gravel
% C SAND 1.8 2.0" coarse gravel
% M SAND 13.3 1.5"32.1 0.00 0.00 100.00 coarse gravel
% F SAND 53.7 1.0" coarse gravel
% FINES 23.4 0.75"32.1 0.00 0.00 100.00 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"45.4 13.30 5.08 94.92 fine gravel
D10 (mm)#4 52.3 20.20 7.72 92.28 coarse sand
D30 (mm)#10 57.1 25.00 9.55 90.45 medium sand
D60 (mm)#20 medium sand
Cu #40 92.0 59.90 22.89 77.11 fine sand
Cc #60 fine sand
#100 204.5 172.40 65.88 34.12 fine sand
#200 232.5 200.40 76.58 23.42 fines
PAN 293.8 261.70 100.00 0.00 silt/clay
DESCRIPTION Silty SAND with trace gravel
USCS SM
Prepared For: Dreamliner LLC Reviewed By: ELW
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Dreamliner Mixed Use SAMPLE ID/TYPE B-3
PROJECT NO.2020-618 SAMPLE DEPTH 35 feet
TECH/TEST DATE JDH/RT 1/18/2021 DATE RECEIVED 1/18/2021
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)436.4 Weight Of Sample (gm)387.4
Wt Dry Soil & Tare (gm) (w2)387.4 Tare Weight (gm) 16.3
Weight of Tare (gm) (w3)16.3 (W6) Total Dry Weight (gm) 371.1
Weight of Water (gm) (w4=w1-w2) 49.0 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 371.1 Cumulative
Moisture Content (%) (w4/w5)*100 13 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.3 0.00 0.00 100.00 cobbles
% C GRAVEL 8.8 3.0"16.3 0.00 0.00 100.00 coarse gravel
% F GRAVEL 29.9 2.5" coarse gravel
% C SAND 7.3 2.0" coarse gravel
% M SAND 10.5 1.5"16.3 0.00 0.00 100.00 coarse gravel
% F SAND 31.0 1.0" coarse gravel
% FINES 12.5 0.75"48.9 32.60 8.78 91.22 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"133.3 117.00 31.53 68.47 fine gravel
D10 (mm)#4 159.9 143.60 38.70 61.30 coarse sand
D30 (mm)#10 187.1 170.80 46.03 53.97 medium sand
D60 (mm)#20 medium sand
Cu #40 226.0 209.70 56.51 43.49 fine sand
Cc #60 fine sand
#100 323.4 307.10 82.75 17.25 fine sand
#200 341.1 324.80 87.52 12.48 fines
PAN 387.4 371.10 100.00 0.00 silt/clay
DESCRIPTION Silty gravelly SAND
USCS SM
Prepared For: Dreamliner LLC Reviewed By: ELW
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Dreamliner Mixed Use SAMPLE ID/TYPE B-4
PROJECT NO.2020-618 SAMPLE DEPTH 45 feet
TECH/TEST DATE JDH/RT 1/18/2021 DATE RECEIVED 1/18/2021
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)388.4 Weight Of Sample (gm)305.6
Wt Dry Soil & Tare (gm) (w2)305.6 Tare Weight (gm) 16.4
Weight of Tare (gm) (w3)16.4 (W6) Total Dry Weight (gm) 289.2
Weight of Water (gm) (w4=w1-w2) 82.8 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 289.2 Cumulative
Moisture Content (%) (w4/w5)*100 29 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.4 0.00 0.00 100.00 cobbles
% C GRAVEL 16.8 3.0"16.4 0.00 0.00 100.00 coarse gravel
% F GRAVEL 1.2 2.5" coarse gravel
% C SAND 1.5 2.0" coarse gravel
% M SAND 2.1 1.5"16.4 0.00 0.00 100.00 coarse gravel
% F SAND 19.5 1.0" coarse gravel
% FINES 59.0 0.75"65.0 48.60 16.80 83.20 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"65.0 48.60 16.80 83.20 fine gravel
D10 (mm)#4 68.4 52.00 17.98 82.02 coarse sand
D30 (mm)#10 72.6 56.20 19.43 80.57 medium sand
D60 (mm)#20 medium sand
Cu #40 78.7 62.30 21.54 78.46 fine sand
Cc #60 fine sand
#100 103.7 87.30 30.19 69.81 fine sand
#200 135.0 118.60 41.01 58.99 fines
PAN 305.6 289.20 100.00 0.00 silt/clay
DESCRIPTION SILT with some sand and gravel
USCS ML
Prepared For: Dreamliner LLC Reviewed By: ELW
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200
Geotechnical Engineering Report January 26, 2021
Dreamliner Mixed Use, Renton, Washington RGI Project No. 2020-618-1
APPENDIX B
LIQUEFACTION ANALYSIS
Liquefaction analysis was completed using the LiquefyPro software from CivilTech Software
USA. Soil and groundwater conditions from borings B-1 and B-3 were used and the
printouts are attached.
Silt with some sand
Sandy gravel
Sand with some gravel
Sand with some gravel
Sandy silt
Gravelly sand
Gravel
Sandy gravel
Sand with some gravel
LiquefyPro CivilTech Software USA www.civiltech.comCivilTech Corporation
LIQUEFACTION ANALYSIS
Dreamliner Mixed Use
2020-618-1 Plate A-1
Hole No.=B-1 Water Depth=10 ft Magnitude=7
Acceleration=0.535g
(ft)
0
10
20
30
40
50
60
70
Shear Stress Ratio
CRR CSR fs1
Shaded Zone has Liquefaction Potential
0 1
Soil DescriptionFactor of Safety
0 51
Settlement
Saturated
Unsaturat.
S = 5.94 in.
0 (in.) 10
fs1=1
Sandy gravel
Gravelly sand
Silt with some sand
Silty sand with trace gravel
Sand with some gravel
Silty gravelly sand
Gravelly sand
Sandy gravel
LiquefyPro CivilTech Software USA www.civiltech.comCivilTech Corporation
LIQUEFACTION ANALYSIS
Dreamliner Mixed Use
2020-618-1 Plate A-1
Hole No.=B-3 Water Depth=10 ft Magnitude=7
Acceleration=0.535g
(ft)
0
10
20
30
40
50
60
70
Shear Stress Ratio
CRR CSR fs1
Shaded Zone has Liquefaction Potential
0 1
Soil DescriptionFactor of Safety
0 51
Settlement
Saturated
Unsaturat.
S = 7.84 in.
0 (in.) 10
fs1=1
Appendix B
Operation and Maintenance Manual
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual
A-10
NO. 5 – CATCH BASINS AND MANHOLES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Structure Sediment
accumulation
Sediment exceeds 60% of the depth from
the bottom of the catch basin to the invert
of the lowest pipe into or out of the catch
basin or is within 6 inches of the invert of
the lowest pipe into or out of the catch
basin.
Sump of catch basin contains no sediment.
Trash and debris Trash or debris of more than ½ cubic foot
which is located immediately in front of the
catch basin opening or is blocking capacity
of the catch basin by more than 10%.
No Trash or debris blocking or potentially
blocking entrance to catch basin.
Trash or debris in the catch basin that
exceeds 1/3 the depth from the bottom of
basin to invert the lowest pipe into or out of
the basin.
No trash or debris in the catch basin.
Dead animals or vegetation that could
generate odors that could cause
complaints or dangerous gases (e.g.,
methane).
No dead animals or vegetation present
within catch basin.
Deposits of garbage exceeding 1 cubic
foot in volume.
No condition present which would attract or
support the breeding of insects or rodents.
Damage to frame
and/or top slab
Corner of frame extends more than ¾ inch
past curb face into the street (If
applicable).
Frame is even with curb.
Top slab has holes larger than 2 square
inches or cracks wider than ¼ inch.
Top slab is free of holes and cracks.
Frame not sitting flush on top slab, i.e.,
separation of more than ¾ inch of the
frame from the top slab.
Frame is sitting flush on top slab.
Cracks in walls or
bottom
Cracks wider than ½ inch and longer than
3 feet, any evidence of soil particles
entering catch basin through cracks, or
maintenance person judges that catch
basin is unsound.
Catch basin is sealed and is structurally
sound.
Cracks wider than ½ inch and longer than
1 foot at the joint of any inlet/outlet pipe or
any evidence of soil particles entering
catch basin through cracks.
No cracks more than 1/4 inch wide at the
joint of inlet/outlet pipe.
Settlement/
misalignment
Catch basin has settled more than 1 inch
or has rotated more than 2 inches out of
alignment.
Basin replaced or repaired to design
standards.
Damaged pipe joints Cracks wider than ½-inch at the joint of the
inlet/outlet pipes or any evidence of soil
entering the catch basin at the joint of the
inlet/outlet pipes.
No cracks more than ¼-inch wide at the
joint of inlet/outlet pipes.
Contaminants and
pollution
Any evidence of contaminants or pollution
such as oil, gasoline, concrete slurries or
paint.
Materials removed and disposed of
according to applicable regulations. Source
control BMPs implemented if appropriate.
No contaminants present other than a
surface oil film.
Inlet/Outlet Pipe Sediment
accumulation
Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in
inlet/outlet pipes (includes floatables and
non-floatables).
No trash or debris in pipes.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-11
NO. 5 – CATCH BASINS AND MANHOLES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Inlet/Outlet Pipe
(cont.)
Damaged inlet/outlet
pipe
Cracks wider than ½-inch at the joint of the
inlet/outlet pipes or any evidence of soil
entering at the joints of the inlet/outlet
pipes.
No cracks more than ¼-inch wide at the
joint of the inlet/outlet pipe.
Metal Grates
(Catch Basins)
Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards.
Trash and debris Trash and debris that is blocking more
than 20% of grate surface.
Grate free of trash and debris. footnote to
guidelines for disposal
Damaged or missing
grate
Grate missing or broken member(s) of the
grate. Any open structure requires
urgent maintenance.
Grate is in place and meets design
standards.
Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in
place. Any open structure requires
urgent maintenance.
Cover/lid protects opening to structure.
Locking mechanism
not working
Mechanism cannot be opened by one
maintenance person with proper tools.
Bolts cannot be seated. Self-locking
cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to
remove
One maintenance person cannot remove
cover/lid after applying 80 lbs. of lift.
Cover/lid can be removed and reinstalled
by one maintenance person.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual
A-12
NO. 6 – CONVEYANCE PIPES AND DITCHES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Pipes Sediment & debris
accumulation
Accumulated sediment or debris that
exceeds 20% of the diameter of the pipe.
Water flows freely through pipes.
Vegetation/root
growth in pipe
Vegetation/roots that reduce free
movement of water through pipes.
Water flows freely through pipes.
Contaminants and
pollution
Any evidence of contaminants or pollution
such as oil, gasoline, concrete slurries or
paint.
Materials removed and disposed of
according to applicable regulations. Source
control BMPs implemented if appropriate.
No contaminants present other than a
surface oil film.
Damage to protective
coating or corrosion
Protective coating is damaged; rust or
corrosion is weakening the structural
integrity of any part of pipe.
Pipe repaired or replaced.
Damaged pipes Any dent that decreases the cross section
area of pipe by more than 20% or is
determined to have weakened structural
integrity of the pipe.
Pipe repaired or replaced.
Ditches Trash and debris Trash and debris exceeds 1 cubic foot per
1,000 square feet of ditch and slopes.
Trash and debris cleared from ditches.
Sediment
accumulation
Accumulated sediment that exceeds 20%
of the design depth.
Ditch cleaned/flushed of all sediment and
debris so that it matches design.
Noxious weeds Any noxious or nuisance vegetation which
may constitute a hazard to City personnel
or the public.
Noxious and nuisance vegetation removed
according to applicable regulations. No
danger of noxious vegetation where City
personnel or the public might normally be.
Contaminants and
pollution
Any evidence of contaminants or pollution
such as oil, gasoline, concrete slurries or
paint.
Materials removed and disposed of
according to applicable regulations. Source
control BMPs implemented if appropriate.
No contaminants present other than a
surface oil film.
Excessive vegetation
growth
Vegetation that reduces free movement of
water through ditches.
Water flows freely through ditches.
Erosion damage to
slopes
Any erosion observed on a ditch slope. Slopes are not eroding.
Rock lining out of
place or missing (If
applicable)
One layer or less of rock exists above
native soil area 5 square feet or more, any
exposed native soil.
Replace rocks to design standards.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-17
NO. 11 – GROUNDS (LANDSCAPING)
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Trash and debris Any trash and debris which exceed 1 cubic
foot per 1,000 square feet (this is about
equal to the amount of trash it would take
to fill up one standard size office garbage
can). In general, there should be no visual
evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which
may constitute a hazard to City personnel
or the public.
Noxious and nuisance vegetation removed
according to applicable regulations. No
danger of noxious vegetation where City
personnel or the public might normally be.
Contaminants and
pollution
Any evidence of contaminants or pollution
such as oil, gasoline, concrete slurries or
paint.
Materials removed and disposed of
according to applicable regulations. Source
control BMPs implemented if appropriate.
No contaminants present other than a
surface oil film.
Excessive growth of
grass/groundcover
Grass or groundcover exceeds 18 inches
in height.
Grass or groundcover mowed to a height
no greater than 6 inches.
Trees and Shrubs Hazard tree identified Any tree or limb of a tree identified as
having a potential to fall and cause
property damage or threaten human life. A
hazard tree identified by a qualified
arborist must be removed as soon as
possible.
No hazard trees in facility.
Damaged tree or
shrub identified
Limbs or parts of trees or shrubs that are
split or broken which affect more than 25%
of the total foliage of the tree or shrub.
Trees and shrubs with less than 5% of total
foliage with split or broken limbs.
Trees or shrubs that have been blown
down or knocked over.
No blown down vegetation or knocked over
vegetation. Trees or shrubs free of injury.
Trees or shrubs which are not adequately
supported or are leaning over, causing
exposure of the roots.
Tree or shrub in place and adequately
supported; dead or diseased trees
removed.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-33
NO. 22 – BAFFLE OIL/WATER SEPARATOR
MAINTENANCE
COMPONENT DEFECT
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Trash and debris Any trash or debris which impairs the
function of the facility.
Trash and debris removed from facility.
Contaminants and
pollution
Floating oil in excess of 1 inch in first
chamber, any oil in other chambers or
other contaminants of any type in any
chamber.
No contaminants present other than a
surface oil film.
Vault Treatment
Area
Sediment
accumulation
Sediment accumulates exceeds 6 inches
in the vault.
No sediment in the vault.
Discharge water not
clear
Inspection of discharge water shows
obvious signs of poor water quality-
effluent discharge from vault shows thick
visible sheen.
Effluent discharge is clear.
Trash or debris
accumulation
Any trash and debris accumulation in vault
(floatables and non-floatables).
Vault is clear of trash and debris.
Oil accumulation Oil accumulations that exceed 1 inch, at
the surface of the water in the oil/water
separator chamber.
No visible oil depth on water.
Vault Structure Damage to wall,
frame, bottom, and/or
top slab
Cracks wider than ½-inch or evidence of
soil particles entering the structure through
the cracks, or maintenance/inspection
personnel determines that the vault is not
structurally sound.
Vault replaced or repaired to design
specifications.
Baffles damaged Baffles corroding, cracking, warping and/or
showing signs of failure as determined by
maintenance inspection personnel.
Repair or replace baffles to specifications.
Gravity Drain Inoperable valve Valve will not open and close. Valve opens and closes normally.
Valve won’t seal Valve does not seal completely. Valve completely seals closed.
Inlet/Outlet Pipe Sediment
accumulation
Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in
inlet/outlet pipes (includes floatables and
non-floatables).
No trash or debris in pipes.
Damaged inlet/outlet
pipe
Cracks wider than ½-inch at the joint of the
inlet/outlet pipes or any evidence of soil
entering at the joints of the inlet/outlet
pipes.
No cracks more than ¼-inch wide at the
joint of the inlet/outlet pipe.
Access Manhole Cover/lid not in place Cover/lid is missing or only partially in
place. Any open manhole requires
immediate maintenance.
Manhole access covered.
Locking mechanism
not working
Mechanism cannot be opened by one
maintenance person with proper tools.
Bolts cannot be seated. Self-locking
cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to
remove
One maintenance person cannot remove
cover/lid after applying 80 lbs of lift.
Cover/lid can be removed and reinstalled
by one maintenance person.
Ladder rungs unsafe Missing rungs, misalignment, rust, or
cracks.
Ladder meets design standards. Allows
maintenance person safe access.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual
A-34
NO. 22 – BAFFLE OIL/WATER SEPARATOR
MAINTENANCE
COMPONENT DEFECT
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Large Access
Doors/Plate
Damaged or difficult
to open
Large access doors or plates cannot be
opened/removed using normal equipment.
Replace or repair access door so it can
opened as designed.
Gaps, doesn't cover
completely
Large access doors not flat and/or access
opening not completely covered.
Doors close flat and cover access opening
completely.
Lifting rings missing,
rusted
Lifting rings not capable of lifting weight of
door or cover/lid.
Lifting rings sufficient to lift or remove
cover/lid.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-35
NO. 23 – COALESCING PLATE OIL/WATER SEPARATOR
MAINTENANCE
COMPONENT DEFECT
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Trash and debris Any trash or debris which impairs the
function of the facility.
Trash and debris removed from facility.
Contaminants and
pollution
Floating oil in excess of 1 inch in first
chamber, any oil in other chambers or
other contaminants of any type in any
chamber.
No contaminants present other than a
surface oil film.
Vault Treatment
Area
Sediment
accumulation in the
forebay
Sediment accumulation of 6 inches or
greater in the forebay.
No sediment in the forebay.
Discharge water not
clear
Inspection of discharge water shows
obvious signs of poor water quality –
effluent discharge from vault shows thick
visible sheen.
Repair function of plates so effluent is
clear.
Trash or debris
accumulation
Trash and debris accumulation in vault
(floatables and non-floatables).
Trash and debris removed from vault.
Oil accumulation Oil accumulation that exceeds 1 inch at the
water surface in the in the coalescing plate
chamber.
No visible oil depth on water and
coalescing plates clear of oil.
Coalescing Plates Damaged Plate media broken, deformed, cracked
and/or showing signs of failure.
Replace that portion of media pack or
entire plate pack depending on severity of
failure.
Sediment
accumulation
Any sediment accumulation which
interferes with the operation of the
coalescing plates.
No sediment accumulation interfering with
the coalescing plates.
Vault Structure Damage to wall,
frame, bottom, and/or
top slab
Cracks wider than ½-inch and any
evidence of soil particles entering the
structure through the cracks, or
maintenance inspection personnel
determines that the vault is not structurally
sound.
Vault replaced or repaired to design
specifications.
Baffles damaged Baffles corroding, cracking, warping and/or
showing signs of failure as determined by
maintenance/inspection person.
Repair or replace baffles to specifications.
Ventilation Pipes Plugged ventilation
pipes
Any obstruction to the ventilation pipes. Ventilation pipes are clear.
Shutoff Valve Damaged or
inoperable shutoff
valve
Shutoff valve cannot be opened or closed. Shutoff valve operates normally.
Inlet/Outlet Pipe Sediment
accumulation
Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in
inlet/outlet pipes (includes floatables and
non-floatables).
No trash or debris in pipes.
Damaged inlet/outlet
pipe
Cracks wider than ½-inch at the joint of the
inlet/outlet pipes or any evidence of soil
entering at the joints of the inlet/outlet
pipes.
No cracks more than ¼-inch wide at the
joint of the inlet/outlet pipe.
Access Manhole Cover/lid not in place Cover/lid is missing or only partially in
place. Any open manhole requires
immediate maintenance.
Manhole access covered.
Locking mechanism
not working
Mechanism cannot be opened by one
maintenance person with proper tools.
Bolts cannot be seated. Self-locking
cover/lid does not work.
Mechanism opens with proper tools.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual
A-36
NO. 23 – COALESCING PLATE OIL/WATER SEPARATOR
MAINTENANCE
COMPONENT DEFECT
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Access Manhole
(cont.)
Cover/lid difficult to
remove
One maintenance person cannot remove
cover/lid after applying 80 lbs of lift.
Cover/lid can be removed and reinstalled
by one maintenance person.
Ladder rungs unsafe Missing rungs, misalignment, rust, or
cracks.
Ladder meets design standards. Allows
maintenance person safe access.
Large access
doors/plate
Damaged or difficult
to open
Large access doors or plates cannot be
opened/removed using normal equipment.
Replace or repair access door so it can
opened as designed.
Gaps, doesn't cover
completely
Large access doors not flat and/or access
opening not completely covered.
Doors close flat and cover access opening
completely.
Lifting rings missing,
rusted
Lifting rings not capable of lifting weight of
door or plate.
Lifting rings sufficient to lift or remove door
or plate.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-37
NO. 24 – CATCH BASIN INSERT (NOT ALLOWED IN THE CITY FOR OIL CONTROL)
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-47
NO. 38 – SOIL AMENDMENT BMP
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Soil Media Unhealthy vegetation Vegetation not fully covering ground
surface or vegetation health is poor.
Yellowing: possible Nitrogen (N)
deficiency. Poor growth: possible
Phosphorous (P) deficiency. Poor
flowering, spotting or curled leaves, or
weak roots or stems: possible Potassium
(K) deficiency.
Plants are healthy and appropriate for site
conditions
Inadequate soil
nutrients and
structure
In the fall, return leaf fall and shredded
woody materials from the landscape to the
site when possible
Soil providing plant nutrients and structure
Excessive vegetation
growth
Grass becomes excessively tall (greater
than 10 inches); nuisance weeds and other
vegetation start to take over.
Healthy turf- “grasscycle” (mulch-mow or
leave the clippings) to build turf health
Weeds Preventive maintenance Avoid use of pesticides (bug and weed
killers), like “weed & feed,” which damage
the soil
Fertilizer needed Where fertilization is needed (mainly turf
and annual flower beds), a moderate
fertilization program should be used which
relies on compost, natural fertilizers or
slow-release synthetic balanced fertilizers
Integrated Pest Management (IPM)
protocols for fertilization followed
Bare spots Bare spots on soil No bare spots, area covered with
vegetation or mulch mixed into the
underlying soil.
Compaction Poor infiltration due to soil compaction
• To remediate compaction, aerate
soil, till to at least 8-inch depth, or
further amend soil with compost and
re-till
• If areas are turf, aerate compacted
areas and top dress them with 1/4 to
1/2 inch of compost to renovate them
• If drainage is still slow, consider
investigating alternative causes (e.g.,
high wet season groundwater levels,
low permeability soils)
• Also consider site use and protection
from compacting activities
No soil compaction
Poor infiltration Soils become waterlogged, do not appear
to be infiltrating.
Facility infiltrating properly
Erosion/Scouring Erosion Areas of potential erosion are visible Causes of erosion (e.g., concentrate flow
entering area, channelization of runoff)
identified and damaged area stabilized
(regrade, rock, vegetation, erosion control
matting).For deep channels or cuts (over 3
inches in ponding depth), temporary
erosion control measures in place until
permanent repairs can be made
Grass/Vegetation Unhealthy vegetation Less than 75% of planted vegetation is
healthy with a generally good appearance.
Healthy vegetation. Unhealthy plants
removed/replaced. Appropriate vegetation
planted in terms of exposure, soil and soil
moisture.
Noxious Weeds Noxious weeds Listed noxious vegetation is present (refer
to current County noxious weed list).
No noxious weeds present.