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HomeMy WebLinkAboutRS_TIR_Logan Six_230807_v2.pdf P.O Box 1478 ⬧ Everett, WA 98206 ⬧ P: 425.303.9363 info@insightengineering.net TECHNICAL INFORMATION REPORT For Logan Tower Mixed Use Prepared for City of Renton Renton City Hall - 6th Floor 1055 South Grady Way Renton, WA 98057 Project Site Location: 302 Logan Ave N Renton, WA 98057 Tax Id: 1823059264 IECO Project: 21-1157 Certified Erosion and Sedimentation Control Lead: To be named by contractor Stormwater Site Plan Prepared By: Ryan J. Korte TIR Preparation Date: November 11, 2021 Date revised: February 7, 2023 Approximate Construction Date: September 1, 2023 Applicant: Andrew Kovach 2115 Colby Ave Everett, WA 98201 425-259-0609 Contact: IECO P.O. Box 1478 Everett, WA 98206 425-303-9363 02/09/2023 Insight Engineering Co. – Technical Information Report 2/7/23 - 1 - TABLE OF CONTENTS 1.0 Project Overview ....................................................................................................................3 2.0 Conditions and Requirements Summary ............................................................................7 2.1 Conditions ....................................................................................................................................7 2.2 Requirements Summary ...............................................................................................................8 3.0 Offsite Analysis ....................................................................................................................13 4.0 Flow Control and Water Quality Analysis and Design ......................................................15 4.1 Existing Basin Summary ............................................................................................................15 4.2 Developed Basin Summary ........................................................................................................15 4.3 Water Quality .............................................................................................................................16 5.0 Conveyance Analysis and Design .......................................................................................17 6.0 Special Report and Studies .................................................................................................18 7.0 Other Permits .......................................................................................................................19 8.0 CSWPPP Analysis and Design ...........................................................................................24 9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant .............................28 10.0 Operations and Maintenance Manual ..............................................................................29 Figures Figure 1 - Vicinity Map .................................................................................................................6 Figure 2 - Soil Map .....................................................................................................................11 Figure 3 - Downstream Analysis Map .......................................................................................14 Insight Engineering Co. – Technical Information Report 2/7/23 - 2 - Acronyms and Abbreviations _________________________________________ BMP Best Management Practices RSWDM Renton Surface Water Drainage Manual DOE Department of Ecology ESC Erosion and Sediment Control IECO Insight Engineering Company MR Minimum Requirement NCSS National Cooperative Soil Survey KCRS King County Road Standards KCSWDM King County Surface water Drainage Manual SWPPP Stormwater Pollution Prevention Plan SWMMWW Stormwater Management Manual for Western Washington TESC Temporary Erosion and Sediment Control WWHM Western Washington Hydrology Model Insight Engineering Co. – Technical Information Report 2/7/23 - 3 - 1.0 Project Overview The proposed project “Logan Tower Mixed Use” is located at 302 Logan Ave N in Renton, Washington. More generally, the project site is in Section 36, Township 28 North, and Range 4 East of the Willamette Meridian in King County, Washington. Please refer to the Vicinity Map attached later in the section. This report will follow the Technical Information Report requirements, per the 2022 Renton Surface Water Design Manual. The site is currently undeveloped with lawn. The site contains one drainage basin that slopes to the north side of the site. Please refer to the downstream analysis map for more details. As per the Geotech report attached under Section 6.0 the site contains poorly graded sands with gravel. The site contains 1.08 acres and is zoned as UC (Urban Center). The proposal is to construct a ten-story mixed-use building with three levels of underground parking. The access to the site will be from driveway entrances located on N 4th St and N 3rd St. Sewer and water utilities will be provided by City of Renton. The water will be provided by City of Renton Water District. The project is located within the Lower Cedar River drainage basin. The project is subjected to the peak flow rate flow control standard matching existing conditions. The site is located within the City’s Aquifer Protection Area (APA). The north half of the site is within Zone 1 of the APA and the south half falls in Zone 2. The project is subject to a full drainage review per Figure 1.1.2.A (Flow Chart for Determining Type of Drainage Review Required) according to section 1.1.2.4 (Full Drainage Review). The project is exempt from flow control per section 1.2.3 of the RSWDM the direct discharge exemption may be applied. The project meets the following required criteria #1-5 as outlined on page 1-39 of the RSWDM. Criteria #1: “The flowpath from the project site discharge point to the edge of the 100 - year floodplain of the major receiving water will be no longer than a half mile, except for discharges to Lake Washington.” Insight Engineering Co. – Technical Information Report 2/7/23 - 4 - The site discharge point is about 1,000-feet (0.19 miles) from the discharge point into the lower Cedar River which is less then the maximum distance of 0.5 miles. Criteria #2: “The conveyance system between the project site and the major receiving water will extend to the ordinary high water mark, and will be comprised of manmade conveyance elements (pipes, ditches, etc.) and will be within public right-of-way or a public or private drainage easement.” The downstream conveyance system will be comprised entirely of manmade conveyance elements with most of the run within the public right-of-way crossing through one drainage easement prior to discharging (at the ordinary high-water mark) to the lower Cedar River. See downstream analysis in section 3.2 for a detailed description of the downstream flow. Criteria #3: “The conveyance system will have adequate capacity24 to convey the 25-year peak flow (per Core Requirement #4, Conveyance System), for the entire contributing drainage area, assuming build-out conditions to current zoning for the equivalent area portion (the area that is contained within an arc formed by the shortest, straight line distance from the conveyance system discharge point to the furthermost point of the proposed project) and existing conditions for the remaining area.” The project will generate a peak discharge of 0.23 CFS in the 25-year developed storm. This is very minimal and is not expected to aggravate any downstream problems. Therefore, the proposal will not have any effect on the downstream corridor. A detailed conveyance analysis will be performed for the construction submittal. Criteria #4: The conveyance system will be adequately stabilized to prevent erosion, assuming the same basin conditions as assumed in Criteria (c) above.” The conveyance system will be adequately stabilized as it is an entirely a closed piped system. Criteria #5: “The direct discharge proposal will not divert flows from or increase flows to an existing wetland or stream sufficient to cause a significant adverse impact.” The site will continue to flow to its natural discharge point and will not divert any flows from wetlands. No wetlands are present on or downstream of the site. Insight Engineering Co. – Technical Information Report 2/7/23 - 5 - The project is proposing to direct discharge to the existing drainage system along N 4th Street that is maintained by the city. Water quality is exempt because the total PGIS is only 2,165 SF which is less than the threshold limit of 5,000 SF. For on-site BMPs, as outlined in Appendix C Section C 2.1, full dispersion must be considered first, however the required native vegetated cannot be achieved for this UC zoned project. Full dispersion for the site is not feasible. Full infiltration was considered next, however due to the large footprint of the proposed building and part of the site falling under APA Zone 2 full infiltration is infeasible as the required setbacks could not be met. Limited infiltration, bioretention, and permeable pavement were also considered infeasible due to the Aquifer Protection Area. The roof drains will be connected via a tight line connection to an existing catch basin near the northwest corner of the lot along N 4th Street. Underground parking areas will be connected to the sanitary sewer. Insight Engineering Co. – Technical Information Report 2/7/23 - 6 - FIGURE 1. VICINITY MAP Taken from City of Renton GIS P.O. Box 1478 Everett, WA 98206 425-303-9363 Info@insightengineering.net Figure 1 -Vicinity Map Logan Tower Mixed Use Renton, Washington SCALE: NTS DATE : 2/9/23 JOB #: 21-1157 BY : RJK FILE NAME: 21-1157/doc/drainage report SITE Insight Engineering Co. – Technical Information Report 2/7/23 - 7 - 2.0 Conditions and Requirements Summary 2.1 Conditions There are no conditions to date. Insight Engineering Co. – Technical Information Report 2/7/23 - 8 - 2.2 Requirements Summary 1.2.1 Core Requirement #1: Discharge at the Natural Location The project is proposing to direct discharge to the existing drainage system along N 4th Street that is maintained by the city. Discharge from the developed site will continue to flow to the site’s natural discharge location. 1.2.2 Core Requirement #2: Off-site Analysis Refer to Section 3 for the level two downstream analysis. 1.2.3 Core Requirement #3: Flow Control The project is exempt from flow control per section 1.2.3 of the RSWDM the direct discharge exemption may be applied. 1.2.4 Core Requirement #4: Conveyance System The roof drains will be connected via a tight line connection to an existing catch basin near the northwest corner of the lot along N 4th Street. Underground parking areas will be connected to the sanitary sewer. 1.2.5 Core Requirement #5: Construction Stormwater Pollution Prevention During construction of the infrastructure for the project, temporary erosion control methods will be implemented to prevent sedimentation and erosion using the methods outlined in section 1.2.5.1 of the 2017 RSWDM. Refer to the Grading and SWPPP Plan. 1.2.6 Core Requirement #6: Maintenance and Operations An Operations and Maintenance Manual shall be provided for the construction submittal. 1.2.7 Core Requirement #7: Financial Guarantees and Liability Bond and insurance in accordance with City of Renton’s requirements will be provided upon request or at the behest of the owner during site construction. 1.2.8 Core Requirement #8: Water Quality Water quality is exempt because the total PGIS is only 2,165 SF which is less than the threshold limit of 5,000 SF. Insight Engineering Co. – Technical Information Report 2/7/23 - 9 - 1.2.9 Core Requirement #9: On-Site BMPs For on-site BMPs, as outlined in Appendix C Section C 2.1, full dispersion must be considered first, however the required native vegetated cannot be achieved for this UC zoned project. Full dispersion for the site is not feasible. Full infiltration was considered next, however due to the large footprint of the proposed building and part of the site falling under APA Zone 2 full infiltration is infeasible as the required setbacks could not be met. Limited infiltration, bioretention, and permeable pavement were also considered infeasible due to the Aquifer Protection Area. The roof drains will be connected via a tight line connection to an existing catch basin near the northwest corner of the lot along N 4th Street. Underground parking areas will be connected to the sanitary sewer. Special Requirements – Section 1.3 of KCSWDM 1.3.1 Special Requirement #1: Other Adopted Area Specific Requirements This project is not located in the “other adopted area” that require any area specific requirements. 1.3.2 Special Requirement #2: Flood Plain / Floodway Delineation The project is not located within the 100-yr floodplain. 1.3.3 Special Requirement #3: Flood Protection Facilities Stringent control for the site is not required. 1.3.4 Special Requirement #4: Source Controls A SWPPP will be prepared and kept on site to meet DOE requirements upon construction plan approval. 1.3.5 Special Requirement #5: Oil Control This project is not considered as a high use development. 1.3.6 Special Requirement #6: Aquifer Protection Area The project is located within Zones 1 & 2 of the Aquifer Protection Area. All proposed drainage facilities and conveyance systems are closed systems. No open systems are proposed, therefore Insight Engineering Co. – Technical Information Report 2/7/23 - 10 - the project should not impose any negative impacts to the Aquifer Protection Area. Refer to the appendix for the Groundwater Protection Areas map. Insight Engineering Co. – Technical Information Report 2/7/23 - 11 - FIGURE 2. SOIL MAP P.O. Box 1478 Everett, WA 98206 425-303-9363 Info@insightengineering.net Figure 2 - Soil Map Logan Tower Mixed Use Renton, Washington SCALE: NONE DATE: 2/9/23 JOB #: 21-1157 BY: RJK FILE NAME: 21-1157\docs\drainage report SITE SOILS LEGEND Ur—Urban land Insight Engineering Co. – Technical Information Report 2/7/23 - 12 - King County Area, Washington Ur—Urban land Map Unit Composition • Urban land: 100 percent • Estimates are based on observations, descriptions, and transects of the mapunit. Description of Urban Land Interpretive groups • Land capability classification (irrigated): None specified • Land capability classification (nonirrigated): 8 • Hydric soil rating: No \ Insight Engineering Co. – Technical Information Report 2/7/23 - 13 - 3.0 Offsite Analysis LEVEL 1 DOWNSTREAM ANALYSIS A site reconnaissance was performed by Brian R. Kalab of Insight Engineering on October 22, 2021 to verify the downstream flow paths and observe any drainage problems downstream of the site. The sky was overcast with a temperature of 45 degrees. The site is currently undeveloped with lawn. The site contains one drainage basin that slopes to the north side of the site. 3.1 Upstream Analysis Based on the site reconnaissance and the topographic survey of the site, the upstream flows appear to be minimal. Refer to the Downstream Analysis Map attached in the next page for more details. 3.2 Downstream Analysis Refer to the Downstream Analysis Map attached to the next pages for a visual description of the downstream flow. The outlet from the roof drain will be connected to the existing catch basin along the south side of N 4th St. The flow travels east about 45-feet through 12-inch corrugated polyethylene pipe (CPP) pipe to a CB on the east side of Logan Ave N. The flow then heads south for approximately 700-feet through 12-inch CPP to a CB. The pipe then upsizes to 24-inch CPP and continues south for 70 more feet. The flow crosses to a CB on the west side of Logan Ave N via a 24-inch CPP. The flow then travels southwest under the sidewalk and landscaping for approximately 180-feet through corrugated metal pipe (CMP) to outlet into the Cedar River. This is where the downstream observation was stopped. There did not appear to be any restrictions or erosion problems within 1 mile of the site. Insight Engineering Co. – Technical Information Report 2/7/23 - 14 - FIGURE 3. DOWNSTREAM ANALYSIS MAP P.O. Box 1478 Everett, WA 98206 425-303-9363 Info@insightengineering.net Figure 3 - Downstream Analysis Map Logan Tower Mixed Use Renton, Washington SCALE: NONE DATE: 2/9/23 JOB #: 21-1157 BY: RJK FILE NAME: 21-1157\docs\drainage report Existing Flow path N SITE Insight Engineering Co. – Technical Information Report 2/7/23 - 15 - 4.0 Flow Control and Water Quality Analysis and Design Total Site Area = 1.08 Acres Clearing Limit = 1.11 Acres Total Area Included in the Analysis = 1.11 Acres 4.1 Existing Basin Summary Total Area Included in the Analysis = 1.11 Acres Total Existing Impervious: Existing Sidewalk = 0.01 Acres ( 590 SF) Existing Road = 0.01 Acres ( 428 SF) Total Impervious = 0.02 Acres (1,018 SF) Pervious Areas = 1.09 Acres Refer to the Existing Basin Map attached later in this section for more details. 4.2 Developed Summary Total Area Included in the Analysis = 1.11 Acres Total Developed Impervious: Roof Area = 0.66 Acres (28,580 SF) Driveway = 0.05 Acres ( 2,165 SF) Sidewalk = 0.08 Acres ( 3,555 SF) Existing Sidewalk = 0.01 Acres ( 590 SF) Existing Road = 0.01 Acres ( 428 SF) Total Impervious = 0.81 Acres (35,318 SF) Pervious Areas = 0.30 Acres Refer to the Developed Basin Map attached later in this section for more details. LOGAN AVE NN. 3RD ST. BURNETT ST. N.N. 4TH ST.EXISTING BASIN MAPIECSCALE: 1" = 0502550' LOGAN AVE NN. 3RD ST. BURNETT ST. N.N. 4TH ST.DEVELOPED BASIN MAPIECSCALE: 1" = 0502550' Insight Engineering Co. – Technical Information Report 2/7/23 - 16 - 4.3 Water Quality Water quality is exempt because the total PGIS is only 2,165 SF which is less than the threshold limit of 5,000 SF. Insight Engineering Co. – Technical Information Report 2/7/23 - 17 - 5.0 Conveyance Analysis and Design A detailed conveyance analysis will be included with the construction submittal. Insight Engineering Co. – Technical Information Report 2/7/23 - 18 - 6.0 Special Reports and Studies A. Geotechnical Report B. Sensitive Areas Map C. Watershed Map D. Soil Amendment Calculations Insight Engineering Co. – Technical Information Report 2/7/23 - 19 - A. Geotechnical Report Preliminary Geotechnical Investigation Proposed Mixed Use Building 3xx Logan Avenue North Renton, Washington January 8, 2021 PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON i Table of Contents 1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2.0 PROJECT DESCRIPTION .............................................................................................. 1 3.0 SITE DESCRIPTION ....................................................................................................... 1 4.0 FIELD INVESTIGATION ............................................................................................... 1 4.1.1 Site Investigation Program ................................................................................... 1 5.0 SOIL AND GROUNDWATER CONDITIONS .............................................................. 2 5.1.1 Area Geology ........................................................................................................ 2 5.1.2 Groundwater ........................................................................................................ 3 6.0 GEOLOGIC HAZARDS ................................................................................................... 3 6.1 Erosion Hazard .................................................................................................... 3 6.2 Seismic Hazard .................................................................................................... 3 7.0 DISCUSSION ................................................................................................................... 4 7.1.1 General................................................................................................................. 4 8.0 RECOMMENDATIONS .................................................................................................. 5 8.1.1 Site Preparation ................................................................................................... 5 8.1.2 Temporary Excavations and Shoring .................................................................... 5 8.1.3 Erosion and Sediment Control.............................................................................. 7 8.1.4 Foundation Design ............................................................................................... 7 8.1.5 Concrete Retaining Walls ..................................................................................... 8 8.1.6 Slab on Grade ......................................................................................................10 8.1.7 Stormwater Management ....................................................................................11 8.1.8 Groundwater Influence on Construction .............................................................11 8.1.9 Utilities ...............................................................................................................11 8.1.10 Pavements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.0 CONSTRUCTION FIELD REVIEWS ...........................................................................13 10.0 CLOSURE ...................................................................................................................13 LIST OF APPENDICES Appendix A — Statement of General Conditions Appendix B — Figures Appendix C — Boring Logs Appendix D — Liquefaction Analyses PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 1 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 1.0 Introduction In accordance with your authorization, Cobalt Geosciences, LLC (Cobalt) has completed a preliminary geotechnical investigation for the proposed mixed-use building located at 3xx Logan Avenue North in Renton, Washington (Figure 1). The purpose of the geotechnical investigation was to identify subsurface conditions and to provide geotechnical recommendations for foundation design, stormwater management, earthwork, soil compaction, and suitability of the on-site soils for use as fill. The scope of work for the geotechnical evaluation consisted of a site investigation followed by engineering analyses to prepare this report. Preliminary recommendations presented herein pertain to various geotechnical aspects of the proposed development, including foundation support of the building along with liquefaction analyses. 2.0 Project Description The project includes construction of a multi-story building with at grade retail space and potentially, below grade parking. The building location and elevations have not been finalized. One option includes three stories of below grade parking with cuts of about 37 feet. This report provides preliminary recommendations for estimating and scoping purposes. We should be notified if the planned construction changes and we should be provided with the final plans when they become available so that we may update our recommendations and provide additional analyses/reporting under a separate proposal, if necessary. 3.0 Site Description The site is located at 3xx Logan Avenue North in Renton, Washington (Figure 1). The property consists of one irregularly shaped parcel (No. 1823059264) with a total area of 47,081 square feet. The property is undeveloped and surfaced with gravel and grasses. The site is nearly level to very slightly sloping in multiple directions. The site is bordered to the east by commercial buildings, to the north by N. 4th Street, to the west by Logan Avenue N. and to the south by N. 3rd Street. 4.0 Field Investigation 4.1.1 Site Investigation Program The geotechnical field investigation program was completed on December 23, 2020 and included drilling and sampling two hollow stem auger borings with a truck mounted drill rig. PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 2 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 Disturbed soil samples were obtained during drilling by using the Standard Penetration Test (SPT) as described in ASTM D-1586. The Standard Penetration Test and sampling method consists of driving a standard 2-inch outside-diameter, split barrel sampler into the subsoil with a 140-pound hammer free falling a vertical distance of 30 inches. The summation of hammer-blows required to drive the sampler the final 12-inches of an 18-inch sample interval is defined as the Standard Penetration Resistance, or N- value. The blow count is presented graphically on the boring logs in this appendix. The resistance, or “N” value, provides a measure of the relative density of granular soils or of the relative consistency of cohesive soils. The soils encountered were logged in the field and are described in accordance with the Unified Soil Classification System (USCS). A Cobalt Geosciences field representative conducted the explorations, collected disturbed soil samples, classified the encountered soils, kept a detailed log of the explorations, and observed and recorded pertinent site features. The results of the boring sampling are presented in Appendix C. 5.0 Soil and Groundwater Conditions 5.1.1 Area Geology The site lies within the Puget Lowland. The lowland is part of a regional north-south trending trough that extends from southwestern British Columbia to near Eugene, Oregon. North of Olympia, Washington, this lowland is glacially carved, with a depositional and erosional history including at least four separate glacial advances/retreats. The Puget Lowland is bounded to the west by the Olympic Mountains and to the east by the Cascade Range. The lowland is filled with glacial and non-glacial sediments consisting of interbedded gravel, sand, silt, till, and peat lenses. The Geologic Map of King County indicates that the site is underlain by Quaternary Alluvium In this area, alluvium usually includes variable thicknesses of fine-grained materials overlying a relatively thick sequence of poorly graded sands with gravel. These materials vary in density and composition with depth and can include areas of organic debris, peat, and silt/clay. Explorations Boring B-1 encountered approximately 10 feet of loose to medium dense, silty-fine to fine grained sand (Possible Fill over Alluvium). This layer was underlain by loose to very dense, fine to medium grained sand trace to some gravel (Alluvium), which continued to the termination depth of the boring. It must be noted that there were local interbeds and layers of organic material (some peat), silt and silty-sands, and areas with coarser gravel at multiple depths below grade. Boring B-2 encountered approximately 9 feet of loose to medium dense, silty-fine to fine grained sand (Possible Fill over Alluvium). This layer was underlain by loose to very dense, fine to medium grained sand trace to some gravel (Alluvium), which continued to the termination depth of the boring. This boring also encountered interbeds as discussed above. PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 3 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 5.1.2 Groundwater Groundwater was encountered approximately 10.5 to 12 feet below existing site elevations in B-1 and B-2 respoectively, during our investigation. We anticipate that this represents the regional groundwater table in this area. Groundwater likely fluctuates between about 8 and 16 feet below site elevations during a typical year. Water table elevations often fluctuate over time. The groundwater level will depend on a variety of factors that may include seasonal precipitation, irrigation, land use, climatic conditions and soil permeability. Water levels at the time of the field investigation may be different from those encountered during the construction phase of the project. 6.0 Geologic Hazards 6.1 Erosion Hazard The Natural Resources Conservation Services (NRCS) maps for King County indicate that the site is underlain by Urban Land. These soils generally have a slight to moderate erosion potential in a disturbed state. It is our opinion that soil erosion potential at this project site can be reduced through landscaping and surface water runoff control. Typically, erosion of exposed soils will be most noticeable during periods of rainfall and may be controlled by the use of normal temporary erosion control measures, such as silt fences, hay bales, mulching, control ditches and diversion trenches. The typical wet weather season, with regard to site grading, is from October 31st to April 1st. Erosion control measures should be in place before the onset of wet weather. 6.2 Seismic Hazard The overall subsurface profile corresponds to a Site Class E as defined by Table 1613.5.2 of the 2015 International Building Code (2015 IBC). A Site Class E applies to a soil profile that includes at least 10 feet of loose soils. We referenced the U.S. Geological Survey (USGS) Earthquake Hazards Program Website to obtain values for SS, S1, Fa, and Fv. The USGS website includes the most updated published data on seismic conditions. The site-specific seismic design parameters and adjusted maximum spectral response acceleration parameters are as follows: PGA (Peak Ground Acceleration, in percent of g) SS 144.30% of g S1 54.00% of g FA 0.9 FV 2.4 PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 4 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 Additional seismic considerations include liquefaction potential and amplification of ground motions by soft/loose soil deposits. The liquefaction potential is highest for loose sand with a high groundwater table. Soil liquefaction is a state where soil particles lose contact with each other and become suspended in a viscous fluid. This suspension of the soil grains results in a complete loss of strength as the effective stress drops to zero as a result of increased pore pressures. Liquefaction normally occurs under saturated conditions in soils such as sand in which the strength is purely frictional. However, liquefaction has occurred in soils other than clean sand, such as low plasticity silt. Liquefaction usually occurs under vibratory conditions such as those induced by seismic events. To evaluate the liquefaction potential of the site, we analyzed the following factors: 1) Soil type and plasticity 2) Groundwater depth 3) Relative soil density 4) Initial confining pressure 5) Maximum anticipated intensity and duration of ground shaking The commercially available liquefaction analysis software, LiqSVS was used to evaluate the liquefaction potential and the possible liquefaction induced settlement for the existing site soil conditions. Maximum Considered Earthquake (MCE) was selected in accordance with the 2012 ASCE, 2015 International Building Code (2015 IBC) and the U.S. Geological Survey (USGS) Earthquake Hazards Program website. For this site, we used a peak ground acceleration of 0.535g and a 7.0M earthquake in the liquefaction analyses. The analyses yielded total settlement on the order of 12.7 inches with corresponding differential settlement of about 6.35 inches. From the analyses, the depth of the liquefiable zone was identified as about 12 to 40 feet below grade in the area of B-1. 7.0 DISCUSSION 7.1.1 General The site is underlain by likely areas of fill and at depth by variable composition alluvium which is locally loose. The subsurface soils are locally liquefiable during/after certain seismic events between about 12 and 40 feet below grade. Depending on the final building location, elevations, and loading, the structure may be supported on several types of foundation systems. These include but are not limited to a mat/raft system, auger-cast piles with grade beams, and compacted rock columns or geopiers. Depending on the proposed cuts, temporary or permanent shoring could include soldier pile walls with tieback anchors and potentially walers. PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 5 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 Significant de-watering systems will be required if excavations below the water table are proposed. The groundwater table in this area is relatively shallow and continuous with depth. In other words, groundwater is not perched and localized; therefore, continuous pumping of de-watering wells will be required to construct the building. Water-tight shoring would be necessary to allow this type of system to be effective. 8.0 Recommendations 8.1.1 Site Preparation Based on our understating of the project, clearing and removal of near-surface soils will be necessary. We recommend removal of all organic laden materials and any fill. Based on observations from the site investigation program, it is anticipated that the stripping depth will be 6 to 12 inches. Deeper excavations will be necessary below utilities, existing foundation elements (if present), and in any areas underlain by undocumented fill materials. The near-surface soils consist of silty-sand with gravel and poorly graded sands with silt. Soils with less than 35 percent fines (passing the No. 200 sieve) may be used as structural fill provided they achieve compaction requirements and are within 3 percent of the optimum moisture. These soils may only be suitable for use as fill during the summer months, as they will be above the optimum moisture levels in their natural state. These soils are variably moisture sensitive and may degrade during periods of wet weather and under equipment traffic. Imported structural fill should consist of a sand and gravel mixture with a maximum grain size of 3 inches and less than 5 percent fines (material passing the U.S. Standard No. 200 Sieve). Structural fill should be placed in maximum lift thicknesses of 12 inches and should be compacted to a minimum of 95 percent of the modified proctor maximum dry density, as determined by the ASTM D 1557 test method. 8.1.2 Temporary Excavations Based on our understanding of the project, we anticipate that the near surface grading could include local cuts on the order of approximately 8 feet or less for utility placement. We anticipate that shoring will be required for building foundations. Excavations up to 8 feet in height, if required, should be sloped no steeper than 1.5H:1V (Horizontal:Vertical) in loose fill and/or native soils. If an excavation is subject to heavy vibration or surcharge loads, we recommend that the excavations be sloped no steeper than 2H:1V, where room permits. Any deeper excavations will require shoring. Temporary cuts should be in accordance with the Washington Administrative Code (WAC) Part N, Excavation, Trenching, and Shoring. Temporary slopes should be visually inspected daily by a qualified person during construction activities and the inspections should be documented in daily reports. The contractor is responsible for maintaining the stability of the temporary cut slopes and reducing slope erosion during construction. PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 6 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 Temporary cut slopes should be covered with visqueen to help reduce erosion during wet weather, and the slopes should be closely monitored until the permanent retaining systems or slope configurations are complete. Materials should not be stored or equipment operated within 10 feet of the top of any temporary cut slope. Soil conditions may not be completely known from the geotechnical investigation. In the case of temporary cuts, the existing soil conditions may not be completely revealed until the excavation work exposes the soil. Typically, as excavation work progresses the maximum inclination of temporary slopes will need to be re-evaluated by the geotechnical engineer so that supplemental recommendations can be made. Soil and groundwater conditions can be highly variable. Scheduling for soil work will need to be adjustable, to deal with unanticipated conditions, so that the project can proceed and required deadlines can be met. If any variations or undesirable conditions are encountered during construction, we should be notified so that supplemental recommendations can be made. If room constraints or groundwater conditions do not permit temporary slopes to be cut to the maximum angles allowed by the WAC, temporary shoring systems may be required. The contractor should be responsible for developing temporary shoring systems, if needed. We recommend that Cobalt Geosciences and the project structural engineer review temporary shoring designs prior to installation, to verify the suitability of the proposed systems. Shoring Depending on the depth of planned cuts and final building elevations, temporary and/or permanent shoring will be required. For a single-story depth basement level, we anticipate that cantilever soldier piles with timber lagging will be adequate. At this depth, groundwater may be present near the base of the excavation. Any deeper excavations will likely require water-tight shoring, de-watering wells, and walls capable of resisting high lateral loads. These may include secant pile walls, sheet piles, soldier pile walls with tiebacks, and/or combinations of these systems. The following section includes preliminary recommendations for a typical soldier pile wall for a single- story depth basement level. Soldier piles typically consist of steel W or H-beams inserted into oversized drilled shafts, which are backfilled with structural concrete, lean mix {Controlled Density Fill (CDF)}, or a combination of lean mix to the base of the excavation and structural concrete below the excavation to anchor the soldier piles. Due to the potential for local caving during drilling operations for the soldier pile holes due to soft soil conditions and shallow groundwater, consideration should be given to using slurry or drilling fluid to reduce the risk of caving of the pile holes during installation. If water is present within the pile hole at the time of soldier pile concrete placement, the concrete should be placed starting at the bottom of the hole with a tremie pipe and the column of concrete should be raised slowly to displace the water. Water will be present along with caving soil conditions. We recommend that soldier piles have a maximum spacing of eight feet on center. To account for arching effects, lateral loading on the lagging can be reduced by 50 percent. Unlagged excavation heights should not exceed three feet. No portion of the excavation should remain unsupported overnight. Lagging sections may be up to 6 feet in height depending on stability. PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 7 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 Cantilever soldier pile walls for this site may be designed based on an active lateral earth pressure of 40 pcf for a level backslope, provided the wall is unrestrained (not fixed; permitted to move at least 0.2 percent of the wall height). The pressure will act on the soldier pile width below the base of the excavation as well. All applicable surcharge pressures should be included. A lateral uniform seismic pressure of 8H is recommended for seismic conditions (active). In front of the soldier piles, resistive pressure can be estimated using an allowable passive earth pressure of 250 pcf acting over 2 times the soldier pile diameter, neglecting the upper 2 feet below the base of the excavation. A factor of safety of 1.5 has been incorporated into the passive pressure value. A lateral pressure reduction of 50 percent may be used for design of the lagging for a pile spacing of three diameters. Lagging should be backfilled with 5/8 inch clean angular rock to minimize void spaces. 8.1.3 Erosion and Sediment Control Erosion and sediment control (ESC) is used to reduce the transportation of eroded sediment to wetlands, streams, lakes, drainage systems, and adjacent properties. Erosion and sediment control measures should be implemented and these measures should be in general accordance with local regulations. At a minimum, the following basic recommendations should be incorporated into the design of the erosion and sediment control features for the site: x Schedule the soil, foundation, utility, and other work requiring excavation or the disturbance of the site soils, to take place during the dry season (generally May through September). However, provided precautions are taken using Best Management Practices (BMP’s), grading activities can be completed during the wet season (generally October through April). x All site work should be completed and stabilized as quickly as possible. x Additional perimeter erosion and sediment control features may be required to reduce the possibility of sediment entering the surface water. This may include additional silt fences, silt fences with a higher Apparent Opening Size (AOS), construction of a berm, or other filtration systems. x Any runoff generated by dewatering discharge should be treated through construction of a sediment trap if there is sufficient space. If space is limited other filtration methods will need to be incorporated. 8.1.4 Preliminary Foundation Design Options Due to the presence of liquefiable soils to variable depths below the property, it will be necessary to support the building on a deep foundation system, rock columns, or on a mat/raft grade beam system. Foundation options include auger-cast piles with grade beams, compacted rock columns, or a grade beam raft/mat system. The following sections include preliminary recommendations for several of the foundation support options. Mat Foundations It is our opinion that a rigid or flexible mat foundation system with interconnecting grade beams or structural slab may be used to support the proposed building. PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 8 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 A net allowable bearing pressure of 2,000 pounds per square foot (psf) may be used for design of the mat/raft foundation at a depth of at least 3 feet below grade and on native soils. Local overexcavation may be required. Any fill should be replaced with angular crushed rock. This bearing pressure may be increased if deep cuts are proposed. These recommendations are preliminary only since the recommendations are elevation specific. Resistance to lateral footing displacement can be determined using an allowable friction factor of 0.40 acting between the base of foundations and the supporting subgrades. Lateral resistance for footings can also be developed using an allowable equivalent fluid passive pressure of 250 pounds per cubic foot (pcf) acting against the appropriate vertical footing faces (neglect the upper 12 inches below grade in exterior areas). The allowable friction factor and allowable equivalent fluid passive pressure values include a factor of safety of 1.5. The frictional and passive resistance of the soil may be combined without reduction in determining the total lateral resistance. Foundation excavations should be inspected to verify that the elements will bear on suitable material. It should be noted that tipping may occur during/after certain seismic events, which could result in some structural distress. Exterior footings should have a minimum depth of 18 inches below pad subgrade (soil grade) or adjacent exterior grade, whichever is lower. Once the final design plans have been determined, we should be allowed to review the plans for conformance with our recommendations. Rock Columns Shallow perimeter and column footings supported on compacted rock columns or geopiers. We anticipate that compacted rock columns/aggregate piers will need to extend about 35 feet below current site elevations. Even with ground improvement, some structural damage and distress may occur following certain seismic events (liquefaction). If structural damage is of primary concern, we recommend supporting the building on auger-cast piles. We can provide auger-cast pile recommendations and parameters upon request. If deep cuts are planned and executed, the depth of aggregate piers will likely decrease. We can provide additional input once the overall construction plan with elevations has been prepared. Provided that the concrete grade beam footings are supported on a system of compacted rock columns, a net allowable bearing pressure of 4,000 pounds per square foot (psf) may be used for design. Final structural design should be prepared by a structural engineer experienced with aggregate piers. We recommend that at least one load test be performed to verify adequate bearing capacity. Resistance to lateral footing displacement can be determined using an allowable friction factor of 0.40 acting between the base of foundations and the supporting subgrades. Lateral resistance for footings can also be developed using an allowable equivalent fluid passive pressure of 250 pounds per cubic foot (pcf) acting against the appropriate vertical footing faces (neglect the upper 12 inches below grade in exterior areas). The allowable friction factor and allowable equivalent fluid passive pressure values include a factor of safety of 1.5. The frictional and passive resistance of the soil may be combined without reduction in determining the total lateral resistance. A representative of Cobalt should be present at the site during the installation to verify general conformance with our recommendations. PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 9 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 8.1.5 Reinforced Concrete Retaining Walls The following table, titled Wall Design Criteria, presents the recommended soil related design parameters for single story basement retaining walls with a level backslope. Contact Cobalt if an alternate retaining wall system is used. Wall Design Criteria “At-rest” Conditions (Lateral Earth Pressure – EFD+) 60 pcf (Equivalent Fluid Density) “Active” Conditions (Lateral Earth Pressure – EFD+) 40 pcf (Equivalent Fluid Density) Seismic Increase for “At-rest” Conditions (Lateral Earth Pressure) 25H* (Uniform Distribution) 1 in 2,500 year event Seismic Increase for “At-rest” Conditions (Lateral Earth Pressure) 15H* (Uniform Distribution) 1 in 500 year event Seismic Increase for “Active” Conditions (Lateral Earth Pressure) 8H* (Uniform Distribution) Passive Earth Pressure on Low Side of Wall (Allowable, includes F.S. = 1.5) Neglect upper 12 inches, then 250 pcf EFD+ Soil-Footing Coefficient of Sliding Friction (Allowable; includes F.S. = 1.5) 0.40 *H is the height of the wall; Increase based on one in 500 year seismic event (10 percent probability of being exceeded in 50 years), + EFD – Equivalent Fluid Density The stated lateral earth pressures do not include the effects of hydrostatic pressure generated by water accumulation behind the retaining walls. Uniform horizontal lateral active and at-rest pressures on the retaining walls from vertical surcharges behind the wall may be calculated using active and at-rest lateral earth pressure coefficients of 0.3 and 0.5, respectively. The soil unit weight of 125 pcf may be used to calculate vertical earth surcharges. To reduce the potential for the buildup of water pressure against the walls, continuous footing drains (with cleanouts) should be provided at the bases of the walls. The footing drains should consist of a minimum 4-inch diameter perforated pipe, sloped to drain, with perforations placed down and enveloped by a minimum 6 inches of pea gravel in all directions. The backfill adjacent to and extending a lateral distance behind the walls at least 2 feet should consist of free-draining granular material. All free draining backfill should contain less than 3 percent fines (passing the U.S. Standard No. 200 Sieve) based upon the fraction passing the U.S. Standard No. 4 Sieve with at least 30 percent of the material being retained on the U.S. Standard No. 4 Sieve. The primary purpose of the free-draining material is the reduction of hydrostatic pressure. Some potential for the PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 10 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 moisture to contact the back face of the wall may exist, even with treatment, which may require that more extensive waterproofing be specified for walls, which require interior moisture sensitive finishes. We recommend that the backfill be compacted to at least 90 percent of the maximum dry density based on ASTM Test Method D1557. In place density tests should be performed to verify adequate compaction. Soil compactors place transient surcharges on the backfill. Consequently, only light hand operated equipment is recommended within 3 feet of walls so that excessive stress is not imposed on the walls. Due to the likely presence of regional groundwater at shallow depths, permanent pump systems may be required around the perimeter of the basement level. 8.1.6 Slab-on-Grade We recommend that the upper 18 inches of the existing native soils within slab areas be re-compacted to at least 95 percent of the modified proctor (ASTM D1557 Test Method). The type and depth of soil re- compaction or removal and replacement is highly dependent on the elevation of any slabs. We can update these recommendations once planned floor elevations have been determined. Note that these recommendations may not be applicable for mat or raft foundation systems since they are essentially large slabs. Often, a vapor barrier is considered below concrete slab areas. However, the usage of a vapor barrier could result in curling of the concrete slab at joints. Floor covers sensitive to moisture typically requires the usage of a vapor barrier. A materials or structural engineer should be consulted regarding the detailing of the vapor barrier below concrete slabs. Exterior slabs typically do not utilize vapor barriers. The American Concrete Institutes ACI 360R-06 Design of Slabs on Grade and ACI 302.1R-04 Guide for Concrete Floor and Slab Construction are recommended references for vapor barrier selection and floor slab detailing. Slabs on grade may be designed using a coefficient of subgrade reaction of 180 pounds per cubic inch (pci) assuming the slab-on-grade base course is underlain by structural fill placed and compacted as outlined in Section 8.1. A 4-6 inch thick capillary break material should be placed on the subgrade soils. This may consist of pea gravel or 5/8 inch clean angular rock. A perimeter drainage system is recommended around the residence and potentially within the slab subgrade depending on the finish floor elevations. A perimeter drainage system should consist of 4 inch diameter perforated drain pipes surrounded by a minimum 6 inches of drain rock wrapped in a non- woven geosynthetic filter fabric to reduce migration of soil particles into the drainage system. The perimeter drainage system should discharge by gravity flow to a suitable stormwater system. Exterior grades surrounding buildings should be sloped at a minimum of one percent to facilitate surface water flow away from the building and preferably with a relatively impermeable surface cover immediately adjacent to the building. PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 11 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 8.1.7 Stormwater Management The site is underlain by local fill and at depth by saturated alluvium. While infiltration could be considered, we anticipate that the site development will fully encompass the property limits, thereby making infiltration infeasible. We recommend detention (if required) with direct connection to City stormwater infrastructure. We can provide additional recommendations upon request. 8.1.8 Groundwater Influence on Construction Groundwater was encountered at about 10.5 feet below grade in B-1 and 12 feet in B-2. Regional groundwater will be encountered below about 8 to 12 feet during certain years/seasons. If excavations extend into the groundwater, water-tight shoring and de-watering wells may be required. We can provide additional recommendations upon request; however, any de-watering system utilizing pumping wells will require design by a hydrogeologist. 8.1.9 Utilities Utility trenches should be excavated according to accepted engineering practices following OSHA (Occupational Safety and Health Administration) standards, by a contractor experienced in such work. The contractor is responsible for the safety of open trenches. Traffic and vibration adjacent to trench walls should be reduced; cyclic wetting and drying of excavation side slopes should be avoided. Depending upon the location and depth of some utility trenches, groundwater flow into open excavations could be experienced, especially during or shortly following periods of precipitation. In general, sandy and gravelly soils were encountered at shallow depths in the explorations at this site. These soils have variable cohesion and low density and will have a tendency to cave or slough in excavations. Shoring or sloping back trench sidewalls is required within these soils in excavations greater than 4 feet deep. All utility trench backfill should consist of imported structural fill or suitable on site soils. Utility trench backfill placed in or adjacent to buildings and exterior slabs should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method D1557. The upper 5 feet of utility trench backfill placed in pavement areas should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method D1557. Below 5 feet, utility trench backfill in pavement areas should be compacted to at least 90 percent of the maximum dry density based on ASTM Test Method D1557. Pipe bedding should be in accordance with the pipe manufacturer's recommendations. The contractor is responsible for removing all water-sensitive soils from the trenches regardless of the backfill location and compaction requirements. Depending on the depth and location of the proposed utilities, we anticipate the need to re-compact existing fill soils below the utility structures and pipes. The contractor should use appropriate equipment and methods to avoid damage to the utilities and/or structures during fill placement and compaction procedures. PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 12 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 8.1.10 Pavement Recommendations The near surface subgrade native soils generally consist of silty-sand with gravel. These soils are rated as good for pavement subgrade material (depending on silt content and moisture conditions). We estimate that the subgrade will have a California Bearing Ratio (CBR) value of 10 and a modulus of subgrade reaction value of k = 180 pci, provided the subgrade is prepared in general accordance with our recommendations. These recommendations are for at grade conditions. Recommendations for pavements at basement levels may differ somewhat. We can update these recommendations once plans have been prepared. We recommend that at a minimum, 18 inches of the existing subgrade material be moisture conditioned (as necessary) and re-compacted to prepare for the construction of pavement sections. Deeper levels of recompaction or overexcavation and replacement may be necessary in areas where fill and/or very poor (soft/loose) soils are present. If dense soils are encountered, overexcavation may not be required. Any soils that cannot be compacted to required levels should be removed and replaced with imported structural fill. We anticipate the need for at least 6 inches of new structural fill over medium dense native soils if the work occurs outside of the summer months when drying can occur. The subgrade should be compacted to at least 95 percent of the maximum dry density as determined by ASTM Test Method D1557. In place density tests should be performed to verify proper moisture content and adequate compaction. The recommended flexible and rigid pavement sections are based on design CBR and modulus of subgrade reaction (k) values that are achieved, only following proper subgrade preparation. It should be noted that subgrade soils that have relatively high silt contents will likely be highly sensitive to moisture conditions. The subgrade strength and performance characteristics of a silty subgrade material may be dramatically reduced if this material becomes wet. Based on our knowledge of the proposed project, we expect the traffic to range from light duty (passenger automobiles) to heavy duty (delivery trucks). The following tables show the recommended pavement sections for light duty and heavy duty use. ASPHALTIC CONCRETE (FLEXIBLE) PAVEMENT LIGHT DUTY Asphaltic Concrete Aggregate Base* Compacted Subgrade* ** 2.5 in. 6.0 in. 12.0 in. HEAVY DUTY Asphaltic Concrete Aggregate Base* Compacted Subgrade* ** 4.5 in. 8.0 in. 12.0 in. PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 13 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 PORTLAND CEMENT CONCRETE (RIGID) PAVEMENT Min. PCC Depth Aggregate Base* Compacted Subgrade* ** 6.0 in. 6.0 in. 12.0 in. * 95% compaction based on ASTM Test Method D1557 ** A proof roll may be performed in lieu of in place density tests The asphaltic concrete depth in the flexible pavement tables should be a surface course type asphalt, such as Washington Department of Transportation (WSDOT) ½ inch HMA. The rigid pavement design is based on a Portland Cement Concrete (PCC) mix that has a 28 day compressive strength of 4,000 pounds per square inch (psi). The design is also based on a concrete flexural strength or modulus of rupture of 550 psi. 9.0 Construction Field Reviews Cobalt Geosciences should be retained to provide part time field review during construction in order to verify that the soil conditions encountered are consistent with our design assumptions and that the intent of our recommendations is being met. This will require field and engineering review to: ƒMonitor and test structural fill placement and soil compaction ƒObserve deep foundation installation and testing ƒObserve slab-on-grade preparation Geotechnical design services should also be anticipated during the subsequent final design phase to support the structural design and address specific issues arising during this phase. Field and engineering review services will also be required during the construction phase in order to provide a Final Letter for the project. 10.0 Closure This report was prepared for the exclusive use of Ambili Sukesa and their appointed consultants. Any use of this report or the material contained herein by third parties, or for other than the intended purpose, should first be approved in writing by Cobalt Geosciences, LLC. The recommendations contained in this report are based on assumed continuity of soils with those of our test holes, and assumed structural loads. Cobalt Geosciences should be provided with final architectural and civil drawings when they become available in order that we may review our design recommendations and advise of any revisions, if necessary. PRELIMINARY GEOTECHNICAL INVESTIGATION RENTON, WASHINGTON January 8, 2021 14 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 Use of this report is subject to the Statement of General Conditions provided in Appendix A. It is the responsibility of Ambili Sukesa who is identified as “the Client” within the Statement of General Conditions, and its agents to review the conditions and to notify Cobalt Geosciences should any of these not be satisfied. Respectfully submitted, Cobalt Geosciences, LLC Original signed by: DRAFT ONLY Phil Haberman, PE, LG, LEG Principal PH/sc APPENDIX A Statement of General Conditions Statement of General Conditions USE OF THIS REPORT: This report has been prepared for the sole benefit of the Client or its agent and may not be used by any third party without the express written consent of Cobalt Geosciences and the Client. Any use which a third party makes of this report is the responsibility of such third party. BASIS OF THE REPORT: The information, opinions, and/or recommendations made in this report are in accordance with Cobalt Geosciences present understanding of the site specific project as described by the Client. The applicability of these is restricted to the site conditions encountered at the time of the investigation or study. If the proposed site specific project differs or is modified from what is described in this report or if the site conditions are altered, this report is no longer valid unless Cobalt Geosciences is requested by the Client to review and revise the report to reflect the differing or modified project specifics and/or the altered site conditions. STANDARD OF CARE: Preparation of this report, and all associated work, was carried out in accordance with the normally accepted standard of care in the state of execution for the specific professional service provided to the Client. No other warranty is made. INTERPRETATION OF SITE CONDITIONS: Soil, rock, or other material descriptions, and statements regarding their condition, made in this report are based on site conditions encountered by Cobalt Geosciences at the time of the work and at the specific testing and/or sampling locations. Classifications and statements of condition have been made in accordance with normally accepted practices which are judgmental in nature; no specific description should be considered exact, but rather reflective of the anticipated material behavior. Extrapolation of in situ conditions can only be made to some limited extent beyond the sampling or test points. The extent depends on variability of the soil, rock and groundwater conditions as influenced by geological processes, construction activity, and site use. VARYING OR UNEXPECTED CONDITIONS: Should any site or subsurface conditions be encountered that are different from those described in this report or encountered at the test locations, Cobalt Geosciences must be notified immediately to assess if the varying or unexpected conditions are substantial and if reassessments of the report conclusions or recommendations are required. Cobalt Geosciences will not be responsible to any party for damages incurred as a result of failing to notify Cobalt Geosciences that differing site or sub-surface conditions are present upon becoming aware of such conditions. PLANNING, DESIGN, OR CONSTRUCTION: Development or design plans and specifications should be reviewed by Cobalt Geosciences, sufficiently ahead of initiating the next project stage (property acquisition, tender, construction, etc), to confirm that this report completely addresses the elaborated project specifics and that the contents of this report have been properly interpreted. Specialty quality assurance services (field observations and testing) during construction are a necessary part of the evaluation of sub-subsurface conditions and site preparation works. Site work relating to the recommendations included in this report should only be carried out in the presence of a qualified geotechnical engineer; Cobalt Geosciences cannot be responsible for site work carried out without being present. 10.2 PO Box 82243 Kenmore, WA 98028 cobaltgeo@gmail.com 206-331-1097 APPENDIX B Figures: Vicinity Map, Site Plan N Project Location Renton WASHINGTON VICINITY MAP FIGURE 1 Cobalt Geosciences, LLC P.O. Box 82243 Kenmore, WA 98028 (206) 331-1097 www.cobaltgeo.com cobaltgeo@gmail.com SITE Proposed Mixed Use Building 3xx Logan Avenue North Renton, Washington Cobalt Geosciences, LLC P.O. Box 82243 Kenmore, WA 98028 (206) 331-1097 www.cobaltgeo.com cobaltgeo@gmail.com SITE PLAN FIGURE 2 N Proposed Mixed Use Building 3xx Logan Avenue North Renton, Washington APPENDIX C Boring Logs & Laboratory Analyses PT Well-graded gravels, gravels, gravel-sand mixtures, little or no fines Poorly graded gravels, gravel-sand mixtures, little or no fines Silty gravels, gravel-sand-silt mixtures Clayey gravels, gravel-sand-clay mixtures Well-graded sands, gravelly sands, little or no fines COARSE GRAINED SOILS (more than 50% retained on No. 200 sieve) Primarily organic matter, dark in color, and organic odor Peat, humus, swamp soils with high organic content (ASTM D4427)HIGHLY ORGANIC SOILS FINE GRAINED SOILS (50% or more passes the No. 200 sieve) MAJOR DIVISIONS SYMBOL TYPICAL DESCRIPTION Gravels (more than 50% of coarse fraction retained on No. 4 sieve) Sands (50% or more of coarse fraction passes the No. 4 sieve) Silts and Clays (liquid limit less than 50) Silts and Clays (liquid limit 50 or more) Organic Inorganic Organic Inorganic Sands with Fines (more than 12% fines) Clean Sands (less than 5% fines) Gravels with Fines (more than 12% fines) Clean Gravels (less than 5% fines) Unified Soil Classification System (USCS) Poorly graded sand, gravelly sands, little or no fines Silty sands, sand-silt mixtures Clayey sands, sand-clay mixtures Inorganic silts of low to medium plasticity, sandy silts, gravelly silts, or clayey silts with slight plasticity Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays Organic silts and organic silty clays of low plasticity Inorganic silts, micaceous or diatomaceous fine sands or silty soils, elastic silt Inorganic clays of medium to high plasticity, sandy fat clay, or gravelly fat clay Organic clays of medium to high plasticity, organic silts Moisture Content Definitions Grain Size Definitions Dry Absence of moisture, dusty, dry to the touch Moist Damp but no visible water Wet Visible free water, from below water table Grain Size Definitions Description Sieve Number and/or Size Fines <#200 (0.08 mm) Sand -Fine -Medium -Coarse Gravel -Fine -Coarse Cobbles Boulders #200 to #40 (0.08 to 0.4 mm) #40 to #10 (0.4 to 2 mm) #10 to #4 (2 to 5 mm) #4 to 3/4 inch (5 to 19 mm) 3/4 to 3 inches (19 to 76 mm) 3 to 12 inches (75 to 305 mm) >12 inches (305 mm) Classification of Soil Constituents MAJOR constituents compose more than 50 percent, by weight, of the soil. Major constituents are capitalized (i.e., SAND). Minor constituents compose 12 to 50 percent of the soil and precede the major constituents (i.e., silty SAND). Minor constituents preceded by “slightly” compose 5 to 12 percent of the soil (i.e., slightly silty SAND). Trace constituents compose 0 to 5 percent of the soil (i.e., slightly silty SAND, trace gravel). Relative Density Consistency (Coarse Grained Soils) (Fine Grained Soils) N, SPT, Relative Blows/FT Density 0 - 4 Very loose 4 - 10 Loose 10 - 30 Medium dense 30 - 50 Dense Over 50 Very dense N, SPT, Relative Blows/FT Consistency Under 2 Very soft 2 - 4 Soft 4 - 8 Medium stiff 8 - 15 Stiff 15 - 30 Very stiff Over 30 Hard Cobalt Geosciences, LLC P.O. Box 82243 Kenmore, WA 98028 (206) 331-1097 www.cobaltgeo.com cobaltgeo@gmail.com Soil Classification Chart Figure C1 Log of Boring B-1 Date: December 23, 2020 Contractor: EDI Method: Hollow Stem Auger Depth: 50.2’ Elevation: N/A Logged By: PH Checked By: SC Initial Groundwater: 10.5’ Sample Type: Split Spoon Final Groundwater: Material Description SPT N-Value Moisture Content (%)Plastic Limit Liquid Limit 10 20 30 400 50 4 8 12 16 20 24 28 32 36 40 End of Boring 50.2’ SM/ ML Cobalt Geosciences, LLC P.O. Box 82243 Kenmore, WA 98028 (206) 331-1097 www.cobaltgeo.com cobaltgeo@gmail.com Proposed Mixed Use Building 3xx Logan Avenue North Renton, Washington Boring Log 44 3 4 7 6 20 27 2 3 3 3 4 12 15 25 28 3 5 8 7 11 19 SP Silt trace clay interbed at 23.25’ Organic materials present at 33’ Likely interbeds of silt and silty sand at multiple depths 48 52 5 5 4 Loose, silty-fine to fine grained sand with layers of silty-sand, mottled yellowish brown to grayish brown, moist. (Fill and Alluvium) Loose to very dense, fine to medium grained sand local organics trace to some gravel locally with silt, grayish brown, moist to wet. (Alluvium) 4 3 5 50/2 Log of Boring B-2 Date: December 23, 2020 Contractor: EDI Method: Hollow Stem Auger Depth: 34’ Elevation: N/A Logged By: PH Checked By: SC Initial Groundwater: 12’ Sample Type: Split Spoon Final Groundwater: Material Description SPT N-Value Moisture Content (%)Plastic Limit Liquid Limit 10 20 30 400 50 4 8 12 16 20 24 28 32 36 40 End of Boring 34’ SM/ ML Cobalt Geosciences, LLC P.O. Box 82243 Kenmore, WA 98028 (206) 331-1097 www.cobaltgeo.com cobaltgeo@gmail.com Proposed Mixed Use Building 3xx Logan Avenue North Renton, Washington Boring Log 44 1 4 6 1 4 3 2 1 2 5 12 15 5 9 10 SP Organic materials present at 24’ Likely interbeds of silt and silty sand at multiple depths 48 52 3 13 12 Loose, silty-fine to fine grained sand with layers of silty-sand, mottled yellowish brown to grayish brown, moist. (Fill and Alluvium) Loose to very dense, fine to medium grained sand local organics trace to some gravel locally with silt, grayish brown, moist to wet. (Alluvium) 1 4 6 APPENDIX D Liquefaction Analyses SPT BASED LIQUEFACTION ANALYSIS REPORT :: Input parameters and analysis properties :: Analysis method: Fines correction method: Sampling method: Borehole diameter: Rod length: Hammer energy ratio: NCEER 1998 NCEER 1998 Standard Sampler 65mm to 115mm 3.28 ft 1.00 G.W.T. (in-situ): G.W.T. (earthq.): Earthquake magnitude M w: Peak ground acceleration: Eq. external load: Project title : Location : SPT Name: SPT #1 10.50 ft 8.00 ft 7.00 0.54 g 0.00 tsf Raw SPT Data SPT Count (blows/ft) 50403020100Depth (ft)52 50 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 Raw SPT Data Insitu CSR - CRR Plot CSR - CRR 10. 80. 60. 40. 20Depth (ft)50 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 CSR - CRR Plot During earthq. FS Plot Factor of Safety 21. 510. 50Depth (ft)50 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 FS Plot During earthq. LPI Liquefaction potential 3020100Depth (ft)50 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 LPI During earthq. CRR 7.50 clean sand curve Corrected Blow Count N1(60),cs 50454035302520151050Cyclic Stress Ratio*0. 8 0. 7 0. 6 0. 5 0. 4 0. 3 0. 2 0. 1 0. 0 CRR 7.50 clean sand curve Liquefaction No Liquefaction F.S. color scheme Almost certain it will liquefy Very likely to liquefy Liquefaction and no liq. are equally likely Unlike to liquefy Almost certain it will not liquefy LPI color scheme Very high risk High risk Low risk Project File: Page: 1LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software This software is registered to: Cobalt Geosciences Raw SPT Data SPT Count (blows/ft) 50403020100Depth (ft)52 50 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 Raw SPT Data Insitu CSR - CRR Plot CSR - CRR 10. 80. 60. 40. 20Depth (ft)50 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 CSR - CRR Plot During earthq. FS Plot Factor of Safety 21. 510. 50Depth (ft)50 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 FS Plot During earthq. Vertical Liq. Settlements Cuml. Settlement (in) 1050Depth (ft)50 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 Vertical Liq. Settlements During earthq. Lateral Liq. Displacements Cuml. Displacement (ft) 0Depth (ft)50 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 Lateral Liq. Displacements During earthq. :: Overall Liquefaction Assessment Analysis Plots :: Project File: Page: 2LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software This software is registered to: Cobalt Geosciences Test Depth (ft) :: Field input data :: SPT Field Value (blows) Fines Content (%) Unit Weight (pcf) Infl. Thickness (ft) Can Liquefy 4.00 6 50.00 115.00 5.00 No 8.00 11 25.00 115.00 5.00 No 14.00 9 5.00 115.00 5.00 Yes 18.00 47 5.00 120.00 5.00 Yes 23.00 8 5.00 115.00 5.00 Yes 28.00 30 5.00 120.00 5.00 Yes 33.00 16 5.00 120.00 5.00 Yes 38.00 13 5.00 120.00 5.00 Yes 43.00 50 5.00 125.00 5.00 Yes 50.00 50 5.00 125.00 5.00 Yes Abbreviations Depth: SPT Field Value: Fines Content: Unit Weight: Infl. Thickness: Can Liquefy: Depth at which test was performed (ft) Number of blows per foot Fines content at test depth (%) Unit weight at test depth (pcf) Thickness of the soil layer to be considered in settlements analysis (ft) User defined switch for excluding/including test depth from the analysis procedure :: Cyclic Resistance Ratio (CRR) calculation data :: CRR 7.5Depth (ft) SPT Field Value CN CE CB CR C S (N 1)60 (N 1)60csαβFines Content (%) σ v(tsf) u o(tsf) σ'vo(tsf)Unit Weight (pcf) 4.00 6 1.55 1.00 1.00 0.75 1.00 7 5.00 1.20 13 4.00050.00115.00 0.23 0.00 0.23 8.00 11 1.35 1.00 1.00 0.75 1.00 11 4.29 1.12 17 4.00025.00115.00 0.46 0.00 0.46 14.00 9 1.18 1.00 1.00 0.85 1.00 9 0.00 1.00 9 0.0995.00115.00 0.81 0.11 0.70 18.00 47 1.12 1.00 1.00 0.95 1.00 50 0.00 1.00 50 4.0005.00120.00 1.05 0.23 0.81 23.00 8 1.05 1.00 1.00 0.95 1.00 8 0.00 1.00 8 0.0905.00115.00 1.33 0.39 0.94 28.00 30 0.99 1.00 1.00 0.95 1.00 28 0.00 1.00 28 0.3485.00120.00 1.63 0.55 1.09 33.00 16 0.93 1.00 1.00 1.00 1.00 15 0.00 1.00 15 0.1635.00120.00 1.93 0.70 1.23 38.00 13 0.88 1.00 1.00 1.00 1.00 11 0.00 1.00 11 0.1205.00120.00 2.23 0.86 1.37 43.00 50 0.83 1.00 1.00 1.00 1.00 42 0.00 1.00 42 4.0005.00125.00 2.55 1.01 1.53 50.00 50 0.77 1.00 1.00 1.00 1.00 39 0.00 1.00 39 4.0005.00125.00 2.98 1.23 1.75 σ v: u o: σ'vo: CN: CE: CB: CR: CS: N1(60): α, β: N1(60)cs: CRR7.5: Total stress during SPT test (tsf) Water pore pressure during SPT test (tsf) Effective overburden pressure during SPT test (tsf) Overburden corretion factor Energy correction factor Borehole diameter correction factor Rod length correction factor Liner correction factor Corrected N SPT to a 60% energy ratio Clean sand equivalent clean sand formula coefficients Corected N1(60) value for fines content Cyclic resistance ratio for M=7.5 Abbreviations σ v, e q(tsf) r d CSR MSF CSR eq,M=7.5 K si g m a CSR * :: Cyclic Stress Ratio calculation (CSR fully adjusted and normalized) :: Depth (ft) Unit Weight (pcf) u o, e q(tsf) σ'vo,eq(tsf) FSα 4.00 115.00 0.23 0.00 0.23 0.99 0.348 1.19 0.292 1.00 0.292 2.0001.00 8.00 115.00 0.46 0.00 0.46 0.98 0.345 1.19 0.289 1.00 0.289 2.0001.00 Project File: Page: 3LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software This software is registered to: Cobalt Geosciences σ v, e q(tsf) r d CSR MSF CSR eq,M=7.5 K si g m a CSR * :: Cyclic Stress Ratio calculation (CSR fully adjusted and normalized) :: Depth (ft) Unit Weight (pcf) u o, e q(tsf) σ'vo,eq(tsf) FSα 14.00 115.00 0.81 0.19 0.62 0.97 0.444 1.19 0.372 1.00 0.372 0.2671.00 18.00 120.00 1.05 0.31 0.73 0.96 0.481 1.19 0.404 1.00 0.404 2.0001.00 23.00 115.00 1.33 0.47 0.86 0.95 0.513 1.19 0.430 1.00 0.430 0.2081.00 28.00 120.00 1.63 0.62 1.01 0.93 0.529 1.19 0.443 1.00 0.443 0.7851.00 33.00 120.00 1.93 0.78 1.15 0.90 0.532 1.19 0.446 0.98 0.454 0.3601.00 38.00 120.00 2.23 0.94 1.30 0.87 0.525 1.19 0.440 0.96 0.458 0.2621.00 43.00 125.00 2.55 1.09 1.45 0.82 0.506 1.19 0.425 0.94 0.452 2.0001.00 50.00 125.00 2.98 1.31 1.67 0.75 0.471 1.19 0.395 0.91 0.433 2.0001.00 σv,eq: uo,eq: σ'vo,eq: rd : α: CSR : MSF : CSR eq,M=7.5: Ksigma: CSR *: FS: Total overburden pressure at test point, during earthquake (tsf) Water pressure at test point, during earthquake (tsf) Effective overburden pressure, during earthquake (tsf) Nonlinear shear mass factor Improvement factor due to stone columns Cyclic Stress Ratio (adjusted for improvement) Magnitude Scaling Factor CSR adjusted for M=7.5 Effective overburden stress factor CSR fully adjusted (user FS applied)*** Calculated factor of safety against soi l l iquefaction Abbreviations 1.00*** User FS: :: Liquefaction potential according to Iwasaki :: Depth (ft) FS F Thickness (ft) wz IL 4.00 2.000 0.00 9.39 0.004.00 8.00 2.000 0.00 8.78 0.004.00 14.00 0.267 0.73 7.87 10.556.00 18.00 2.000 0.00 7.26 0.004.00 23.00 0.208 0.79 6.49 7.845.00 28.00 0.785 0.21 5.73 1.885.00 33.00 0.360 0.64 4.97 4.855.00 38.00 0.262 0.74 4.21 4.735.00 43.00 2.000 0.00 3.45 0.005.00 50.00 2.000 0.00 2.38 0.007.00 29.84 IL = 0.00 - No liquefaction IL between 0.00 and 5 - Liquefaction not probable IL between 5 and 15 - Liquefaction probable IL > 15 - Liquefaction certain Overall potential I L : :: Vertical settlements estimation for dry sands :: Depth (ft) (N 1)60 τav p Gmax(tsf) α b γ ε 15 Nc εNc(%)ΔS (in) Δh (ft) 4.00 7 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.0005.00 Project File: Page: 4LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software This software is registered to: Cobalt Geosciences :: Vertical settlements estimation for dry sands :: Depth (ft) (N 1)60 τav p Gmax(tsf) α b γ ε 15 Nc εNc(%)ΔS (in) Δh (ft) Abbreviations τav: p: Gmax: α, b: γ: ε15: Nc: εNc: Δh: ΔS: Average cyclic shear stress Average stress Maximum shear modulus (tsf) Shear strain formula variables Average shear strain Volumetric strain after 15 cycles Number of cycles Volumetric strain for number of cycles Nc (%) Thickness of soil layer (in) Settlement of soil layer (in) 0.000Cumulative settlemetns: :: Vertical settlements estimation for saturated sands :: Depth (ft) D 50(in) q c/N e v(%)Δh (ft) s (in) 8.00 0.01 2.10 0.00 5.00 0.000 14.00 0.10 4.04 5.36 5.00 3.216 18.00 0.10 4.04 0.00 5.00 0.000 23.00 0.10 4.04 5.80 5.00 3.480 28.00 0.10 4.04 1.70 5.00 1.019 33.00 0.10 4.04 3.53 5.00 2.115 38.00 0.10 4.04 4.55 5.00 2.728 43.00 0.10 4.04 0.00 5.00 0.000 50.00 0.10 4.04 0.00 5.00 0.000 Abbreviations 12.559Cumulative settlements: D50: qc/N: ev: Δh: s: Median grain size (in) Ratio of cone resistance to SPT Post liquefaction volumetric strain (%) Thickness of soil layer to be considered (ft) Estimated settlement (in) :: Lateral displacements estimation for saturated sands :: Depth (ft) (N 1)60 Dr(%) γ max(%) dz(ft) LDI LD (ft) 4.00 7 37.04 0.00 5.00 0.000 0.00 8.00 11 46.43 0.00 5.00 0.000 0.00 14.00 9 42.00 51.20 5.00 0.000 0.00 18.00 50 100.00 0.00 5.00 0.000 0.00 23.00 8 39.60 51.20 5.00 0.000 0.00 28.00 28 74.08 6.43 5.00 0.000 0.00 33.00 15 54.22 34.10 5.00 0.000 0.00 38.00 11 46.43 34.10 5.00 0.000 0.00 43.00 42 90.73 0.00 5.00 0.000 0.00 50.00 39 87.43 0.00 5.00 0.000 0.00 Project File: Page: 5LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software This software is registered to: Cobalt Geosciences :: Lateral displacements estimation for saturated sands :: Depth (ft) (N 1)60 Dr(%) γ max(%) dz(ft) LDI LD (ft) 0.00 Abbreviations Cumulative lateral displacements: Dr: γmax: dz: LDI: LD: Relative density (%) Maximum amplitude of cyclic shear strain (%) Soil layer thickness (ft) Lateral displacement index (ft) Actual estimated displacement (ft) Project File: Page: 6LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software References ⦁ Ronald D. Andrus, Hossein Hayati, Nisha P. Mohanan, 2009. Correcting Liquefaction Resistance for Aged Sands Using Measured to Estimated Velocity Ratio, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 135, No. 6, June 1 ⦁ Boulanger, R.W. and Idriss, I. M., 2014. CPT AND SPT BASED LIQUEFACTION TRIGGERING PROCEDURES. DEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERING COLLEGE OF ENGINEERING UNIVERSITY OF CALIFORNIA AT DAVIS ⦁ Dipl.-Ing. Heinz J. Priebe, Vibro Replacement to Prevent Earthquake Induced Liquefaction, Proceedings of the Geotechnique- Colloquium at Darmstadt, Germany, on March 19th, 1998 (also published in Ground Engineering, September 1998), Technical paper 12-57E ⦁ Robertson, P.K. and Cabal, K.L., 2007,Guide to Cone Penetration Testing for Geotechnical Engineering. Available at no cost at http://www.geologismiki.gr/ ⦁ Youd, T.L., Idriss, I.M., Andrus, R.D., Arango, I., Castro, G., Christian, J.T., Dobry, R., Finn, W.D.L., Harder, L.F., Hynes , M.E., Ishihara, K., Koester, J., Liao, S., Marcuson III, W.F., Martin, G.R., Mitchell, J.K., Moriwaki, Y., Power, M.S., Robertson, P.K., Seed, R., and Stokoe, K.H., Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF Workshop on Evaluation of Liquefaction Resistance of Soils, ASCE, Journal of Geotechnical & Geoenvironmental Engineering, Vol. 127, October, pp 817-833 ⦁ Zhang, G., Robertson. P.K., Brachman, R., 2002, Estimating Liquefaction Induced Ground Settlements from the CPT, Canadian Geotechnical Journal, 39: pp 1168-1180 ⦁ Zhang, G., Robertson. P.K., Brachman, R., 2004, Estimating Liquefaction Induced Lateral Displacements using the SPT and CPT, ASCE, Journal of Geotechnical & Geoenvironmental Engineering, Vol. 130, No. 8, 861 -871 ⦁ Pradel, D., 1998, Procedure to Evaluate Earthquake-Induced Settlements in Dry Sandy Soils, ASCE, Journal of Geotechnical & Geoenvironmental Engineering, Vol. 124, No. 4, 364-368 ⦁ R. Kayen, R. E. S. Moss, E. M. Thompson, R. B. Seed, K. O. Cetin, A. Der Kiureghian, Y. Tanaka, K. Tokimatsu, 2013. Shear- Wave Velocity–Based Probabilistic and Deterministic Assessment of Seismic Soil Liquefaction Potential, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 139, No. 3, March 1 LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software SPT BASED LIQUEFACTION ANALYSIS REPORT :: Input parameters and analysis properties :: Analysis method: Fines correction method: Sampling method: Borehole diameter: Rod length: Hammer energy ratio: NCEER 1998 NCEER 1998 Standard Sampler 65mm to 115mm 3.28 ft 1.00 G.W.T. (in-situ): G.W.T. (earthq.): Earthquake magnitude M w: Peak ground acceleration: Eq. external load: Project title : Location : SPT Name: SPT #1 10.50 ft 8.00 ft 7.00 0.54 g 0.00 tsf Raw SPT Data SPT Count (blows/ft) 50403020100Depth (ft)34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 Raw SPT Data Insitu CSR - CRR Plot CSR - CRR 10. 80. 60. 40. 20Depth (ft)33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 CSR - CRR Plot During earthq. FS Plot Factor of Safety 21. 510. 50Depth (ft)33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 FS Plot During earthq. LPI Liquefaction potential 20100Depth (ft)33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 LPI During earthq. CRR 7.50 clean sand curve Corrected Blow Count N1(60),cs 50454035302520151050Cyclic Stress Ratio*0. 8 0. 7 0. 6 0. 5 0. 4 0. 3 0. 2 0. 1 0. 0 CRR 7.50 clean sand curve Liquefaction No Liquefaction F.S. color scheme Almost certain it will liquefy Very likely to liquefy Liquefaction and no liq. are equally likely Unlike to liquefy Almost certain it will not liquefy LPI color scheme Very high risk High risk Low risk Project File: Page: 1LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software This software is registered to: Cobalt Geosciences Raw SPT Data SPT Count (blows/ft) 50403020100Depth (ft)35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 Raw SPT Data Insitu CSR - CRR Plot CSR - CRR 10. 80. 60. 40. 20Depth (ft)33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 CSR - CRR Plot During earthq. FS Plot Factor of Safety 210Depth (ft)33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 FS Plot During earthq. Vertical Liq. Settlements Cuml. Settlement (in) 8642Depth (ft)33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 Vertical Liq. Settlements During earthq. Lateral Liq. Displacements Cuml. Displacement (ft) 0Depth (ft)33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 Lateral Liq. Displacements During earthq. :: Overall Liquefaction Assessment Analysis Plots :: Project File: Page: 2LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software This software is registered to: Cobalt Geosciences Test Depth (ft) :: Field input data :: SPT Field Value (blows) Fines Content (%) Unit Weight (pcf) Infl. Thickness (ft) Can Liquefy 4.00 3 50.00 115.00 5.00 No 8.00 10 25.00 115.00 5.00 No 14.00 25 5.00 115.00 5.00 Yes 18.00 7 25.00 115.00 5.00 Yes 23.00 10 35.00 115.00 5.00 Yes 28.00 19 5.00 120.00 5.00 Yes 33.00 20 5.00 120.00 5.00 Yes Abbreviations Depth: SPT Field Value: Fines Content: Unit Weight: Infl. Thickness: Can Liquefy: Depth at which test was performed (ft) Number of blows per foot Fines content at test depth (%) Unit weight at test depth (pcf) Thickness of the soil layer to be considered in settlements analysis (ft) User defined switch for excluding/including test depth from the analysis procedure :: Cyclic Resistance Ratio (CRR) calculation data :: CRR 7.5Depth (ft) SPT Field Value CN CE CB CR C S (N 1)60 (N 1)60csαβFines Content (%) σ v(tsf) u o(tsf) σ'vo(tsf)Unit Weight (pcf) 4.00 3 1.55 1.00 1.00 0.75 1.00 3 5.00 1.20 9 4.00050.00115.00 0.23 0.00 0.23 8.00 10 1.35 1.00 1.00 0.75 1.00 10 4.29 1.12 15 4.00025.00115.00 0.46 0.00 0.46 14.00 25 1.18 1.00 1.00 0.85 1.00 25 0.00 1.00 25 0.2855.00115.00 0.81 0.11 0.70 18.00 7 1.12 1.00 1.00 0.95 1.00 7 4.29 1.12 12 0.13125.00115.00 1.04 0.23 0.80 23.00 10 1.06 1.00 1.00 0.95 1.00 10 5.00 1.20 17 0.18535.00115.00 1.32 0.39 0.93 28.00 19 0.99 1.00 1.00 0.95 1.00 18 0.00 1.00 18 0.1965.00120.00 1.62 0.55 1.08 33.00 20 0.93 1.00 1.00 1.00 1.00 19 0.00 1.00 19 0.2065.00120.00 1.92 0.70 1.22 σ v: u o: σ'vo: CN: CE: CB: CR: CS: N1(60): α, β: N1(60)cs: CRR7.5: Total stress during SPT test (tsf) Water pore pressure during SPT test (tsf) Effective overburden pressure during SPT test (tsf) Overburden corretion factor Energy correction factor Borehole diameter correction factor Rod length correction factor Liner correction factor Corrected N SPT to a 60% energy ratio Clean sand equivalent clean sand formula coefficients Corected N1(60) value for fines content Cyclic resistance ratio for M=7.5 Abbreviations σ v, e q(tsf) r d CSR MSF CSR eq,M=7.5 K si g m a CSR * :: Cyclic Stress Ratio calculation (CSR fully adjusted and normalized) :: Depth (ft) Unit Weight (pcf) u o, e q(tsf) σ'vo,eq(tsf) FSα 4.00 115.00 0.23 0.00 0.23 0.99 0.348 1.19 0.292 1.00 0.292 2.0001.00 8.00 115.00 0.46 0.00 0.46 0.98 0.345 1.19 0.289 1.00 0.289 2.0001.00 14.00 115.00 0.81 0.19 0.62 0.97 0.444 1.19 0.372 1.00 0.372 0.7661.00 18.00 115.00 1.04 0.31 0.72 0.96 0.483 1.19 0.405 1.00 0.405 0.3231.00 23.00 115.00 1.32 0.47 0.85 0.95 0.515 1.19 0.432 1.00 0.432 0.4281.00 28.00 120.00 1.62 0.62 1.00 0.93 0.531 1.19 0.445 1.00 0.445 0.4391.00 33.00 120.00 1.92 0.78 1.14 0.90 0.534 1.19 0.448 0.98 0.455 0.4541.00 Project File: Page: 3LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software This software is registered to: Cobalt Geosciences σ v, e q(tsf) r d CSR MSF CSR eq,M=7.5 K si g m a CSR * :: Cyclic Stress Ratio calculation (CSR fully adjusted and normalized) :: Depth (ft) Unit Weight (pcf) u o, e q(tsf) σ'vo,eq(tsf) FSα σv,eq: uo,eq: σ'vo,eq: rd : α: CSR : MSF : CSR eq,M=7.5: Ksigma: CSR *: FS: Total overburden pressure at test point, during earthquake (tsf) Water pressure at test point, during earthquake (tsf) Effective overburden pressure, during earthquake (tsf) Nonlinear shear mass factor Improvement factor due to stone columns Cyclic Stress Ratio (adjusted for improvement) Magnitude Scaling Factor CSR adjusted for M=7.5 Effective overburden stress factor CSR fully adjusted (user FS applied)*** Calculated factor of safety against soi l l iquefaction Abbreviations 1.00*** User FS: :: Liquefaction potential according to Iwasaki :: Depth (ft) FS F Thickness (ft) wz IL 4.00 2.000 0.00 9.39 0.004.00 8.00 2.000 0.00 8.78 0.004.00 14.00 0.766 0.23 7.87 3.376.00 18.00 0.323 0.68 7.26 5.994.00 23.00 0.428 0.57 6.49 5.675.00 28.00 0.439 0.56 5.73 4.905.00 33.00 0.454 0.55 4.97 4.145.00 24.06 IL = 0.00 - No liquefaction IL between 0.00 and 5 - Liquefaction not probable IL between 5 and 15 - Liquefaction probable IL > 15 - Liquefaction certain Overall potential I L : :: Vertical settlements estimation for dry sands :: Depth (ft) (N 1)60 τav p Gmax(tsf) α b γ ε 15 Nc εNc(%)ΔS (in) Δh (ft) 4.00 3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.0005.00 Abbreviations τav: p: Gmax: α, b: γ: ε15: Nc: εNc: Δh: ΔS: Average cyclic shear stress Average stress Maximum shear modulus (tsf) Shear strain formula variables Average shear strain Volumetric strain after 15 cycles Number of cycles Volumetric strain for number of cycles Nc (%) Thickness of soil layer (in) Settlement of soil layer (in) 0.000Cumulative settlemetns: :: Vertical settlements estimation for saturated sands :: Depth (ft) D 50(in) q c/N e v(%)Δh (ft) s (in) Project File: Page: 4LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software This software is registered to: Cobalt Geosciences :: Vertical settlements estimation for saturated sands :: Depth (ft) D 50(in) q c/N e v(%)Δh (ft) s (in) 8.00 0.01 2.10 0.00 5.00 0.000 14.00 0.10 4.04 2.00 5.00 1.203 18.00 0.10 4.04 4.23 5.00 2.540 23.00 0.10 4.04 3.18 5.00 1.909 28.00 0.10 4.04 3.04 5.00 1.822 33.00 0.10 4.04 2.90 5.00 1.743 Abbreviations 9.217Cumulative settlements: D50: qc/N: ev: Δh: s: Median grain size (in) Ratio of cone resistance to SPT Post liquefaction volumetric strain (%) Thickness of soil layer to be considered (ft) Estimated settlement (in) :: Lateral displacements estimation for saturated sands :: Depth (ft) (N 1)60 Dr(%) γ max(%) dz(ft) LDI LD (ft) 4.00 3 24.25 0.00 5.00 0.000 0.00 8.00 10 44.27 0.00 5.00 0.000 0.00 14.00 25 70.00 6.92 5.00 0.000 0.00 18.00 7 37.04 51.20 5.00 0.000 0.00 23.00 10 44.27 51.20 5.00 0.000 0.00 28.00 18 59.40 22.70 5.00 0.000 0.00 33.00 19 61.02 22.70 5.00 0.000 0.00 0.00 Abbreviations Cumulative lateral displacements: Dr: γmax: dz: LDI: LD: Relative density (%) Maximum amplitude of cyclic shear strain (%) Soil layer thickness (ft) Lateral displacement index (ft) Actual estimated displacement (ft) Project File: Page: 5LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software References ⦁ Ronald D. Andrus, Hossein Hayati, Nisha P. Mohanan, 2009. Correcting Liquefaction Resistance for Aged Sands Using Measured to Estimated Velocity Ratio, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 135, No. 6, June 1 ⦁ Boulanger, R.W. and Idriss, I. M., 2014. CPT AND SPT BASED LIQUEFACTION TRIGGERING PROCEDURES. DEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERING COLLEGE OF ENGINEERING UNIVERSITY OF CALIFORNIA AT DAVIS ⦁ Dipl.-Ing. Heinz J. Priebe, Vibro Replacement to Prevent Earthquake Induced Liquefaction, Proceedings of the Geotechnique- Colloquium at Darmstadt, Germany, on March 19th, 1998 (also published in Ground Engineering, September 1998), Technical paper 12-57E ⦁ Robertson, P.K. and Cabal, K.L., 2007,Guide to Cone Penetration Testing for Geotechnical Engineering. Available at no cost at http://www.geologismiki.gr/ ⦁ Youd, T.L., Idriss, I.M., Andrus, R.D., Arango, I., Castro, G., Christian, J.T., Dobry, R., Finn, W.D.L., Harder, L.F., Hynes , M.E., Ishihara, K., Koester, J., Liao, S., Marcuson III, W.F., Martin, G.R., Mitchell, J.K., Moriwaki, Y., Power, M.S., Robertson, P.K., Seed, R., and Stokoe, K.H., Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF Workshop on Evaluation of Liquefaction Resistance of Soils, ASCE, Journal of Geotechnical & Geoenvironmental Engineering, Vol. 127, October, pp 817-833 ⦁ Zhang, G., Robertson. P.K., Brachman, R., 2002, Estimating Liquefaction Induced Ground Settlements from the CPT, Canadian Geotechnical Journal, 39: pp 1168-1180 ⦁ Zhang, G., Robertson. P.K., Brachman, R., 2004, Estimating Liquefaction Induced Lateral Displacements using the SPT and CPT, ASCE, Journal of Geotechnical & Geoenvironmental Engineering, Vol. 130, No. 8, 861 -871 ⦁ Pradel, D., 1998, Procedure to Evaluate Earthquake-Induced Settlements in Dry Sandy Soils, ASCE, Journal of Geotechnical & Geoenvironmental Engineering, Vol. 124, No. 4, 364-368 ⦁ R. Kayen, R. E. S. Moss, E. M. Thompson, R. B. Seed, K. O. Cetin, A. Der Kiureghian, Y. Tanaka, K. Tokimatsu, 2013. Shear- Wave Velocity–Based Probabilistic and Deterministic Assessment of Seismic Soil Liquefaction Potential, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 139, No. 3, March 1 LiqSVs 1.3.3.1 - SPT & Vs Liquefaction Assessment Software Insight Engineering Co. – Technical Information Report 2/7/23 - 20 - B. Sensitive Areas Map 2,257 188 WGS_1984_Web_Mercator_Auxiliary_Sphere Critical Areas Map This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. THIS MAP IS NOT TO BE USED FOR NAVIGATION Notes Legend 128 0 64 128 Feet 11/09/2021 City and County Labels Addresses Parcels City and County Boundary <all other values> Renton Erosion Hazard - High Floodway Special Flood Hazard Areas (100 year flood) Landslide Very High High Moderate Unclassified Slope City of Renton >15% & <=25% >25% & <=40% (Sensitive) >40% & <=90% (Protected) >90% (Protected) Environment Designations Natural Shoreline High Intensity Shoreline Isolated High Intensity Shoreline Residential Urban Conservancy Jurisdictions Streams (Classified) <all other values> Type S Shoreline Type F Fish Type Np Non-Fish Type Ns Non-Fish Seasonal Unclassified Not Visited Wetlands Streets Points of Interest Parks Waterbodies 2019.sid Red: Band_1 Green: Band_2 Blue: Band_3 Insight Engineering Co. – Technical Information Report 2/7/23 - 21 - C. Watershed Map Thorton Cree k R o c k Cr eekR e x Ri verCe d a r R i v er C edar River BearCreek K e l sey CreekMay Creek T aylor Creek N o r t h F o r k C e d a r R i v e r T rou blesome C reekCoal Creek ELW ELW EastLakeWashington ELW EastLakeWashington ForbesCreek JuanitaCreek Kelsey Creek Lake Union Lower Cedar River LyonCreek May Creek McaleerCreek Mercer Island Mercer Slough Thornton Creek Upper Cedar River West Lake Washington West LakeWashington West LakeWashingtonLake WashingtonLake Ballinger Green Lake Lake Union LakeDesire Walsh Lake ShadyLake LakeTwelve SpringLake RetreatLake ChesterMorseLake Ce d a r R i v e rCedarRiverCedarRiver ALGONA AUBURN BEAUX ARTS BELLEVUE BLAC K DIAM ON D BLAC K DIA M ON D BOTHELL BRIER BURIEN CARNATION CAR N AT ION CARNATION CLYDE HILL COV ING TO N DES M OIN ES DUVALL DUVALL EDMONDS FEDE RA L WAY HUNTS POINT I N D EX ISSAQUAH KENT KENT KENT KEN T KENT KEN T KEN T KEN T KIRKLAND KIRKLAND MA PL E VA LL EY MEDINA ME R C ER I S LA N D MO U N T L A KE EDMONDS LYNNWOOD TER RA CE NEWCASTLE N ORM A N DY PAR K NORTHBEND REDMOND REDM ON D REDM ON D RENTON SAM M AM ISH SEATAC SEATTLE SNOQUALMIESNOQUALMIE SNOQUALMIE TUKW ILA W OO D I N V IL LE WOODW AY YA RR OWPOINT P ACIF IC LAKE FOREST PARK KENMORE SHOR ELI N E SEATTLE SEATTLE BELLEVUE Department of Natural Resources and Parks Water and Land Resources Division N Watershed Boundary Basin Boundary River Stream Major Road Incorporated Area Lake Produced by: King County IT Services, GIS, Visual Communications and Web Section File Name: 1211_2650_CedarLkWashMap.ai skrau November 2012 0 1 2 4 Miles The Lake Washington/Cedar River Watershed Insight Engineering Co. – Technical Information Report 2/7/23 - 22 - D. Soil Amendment Calculations 11/9/21, 10:30 AM Achieving the Post-construction Soil Standard - King County https://kingcounty.gov/depts/dnrp/solid-waste/compost-calculator.aspx 2/3 Compost and topsoil calculator for meeting post- construction soil standards (King County Code 16.82) Results You have selected the Pre-Approved Compost Amendment Rate, which is 1.75 inches for turf applications. Stockpile these quantities of site soil: 251.7 cubic yards of stockpiled site soil. Order these quantities of compost and/or topsoil: 70.5 cubic yards of compost. 0.0 cubic yards of topsoil. Amount of soil to stockpile Amount compost needed Amount topsoil needed Option 1: Leave native soil undisturbed N/A N/A N/A Option 2: Amend existing soil in- place Areas: Square footage in thousands = *** Option 3: Import topsoil mix Areas: Square footage in thousands = *** Option 4: Disturbed Soil - stockpile, reapply and amend Areas: Square footage in thousands = 13068 251.7 cubic yards 70.5 cubic yards * Totals 251.7 cubic yards stockpiled soil 70.5 cubic yards * Print Return Step 4: Enter the results of the calculations for compost and/or topsoil needed from the table above on the Soil Management Plan  1 MB, and attach a print-out of the calculation results to the Plan. Submit to Department of Local Services, Permitting Division as part of the permitting process. Department of Local Services, Permitting Division reviewers will also use the calculator to verify the compost and/or soil quantities that permit applicant must enter in the Soil Management Plan. Note that separate calculation sheets are needed for turf and planting beds. Insight Engineering Co. – Technical Information Report 2/7/23 - 23 - 7.0 Other Permits Insight Engineering Co. – Technical Information Report 2/7/23 - 24 - 8.0 CSWPPP Analysis and Design This Stormwater Pollution Prevention Plan (SWPPP) has been prepared as part of the construction stormwater permit requirements for Logan Tower Mixed Use located at 15525 Lake Shore Blvd NE in Lake Forest Park, Washington. More generally, the project site is in Section 36, Township 28 North, and Range 4 East of the Willamette Meridian in King County, Washington. The site contains 1.08 acres and is zoned as UC (Urban Center). The proposal is to construct a ten- story mixed-use building with three levels of underground parking. The access to the site will be from driveway entrances located on N 4th St and N 3rd St. The project is exempt from flow control as section 1.2.3 of the RSWDM the direct discharge exemption may be applied to the project because it meets all the required criteria outlined on page 1-39 of the RSWDM. The project is proposing to direct discharge to the existing drainage system along N 4th Street that is maintained by the city. Water quality is exempt because the total PGIS is only 2,165 SF which is less than the threshold limit of 5,000 SF. The purpose of this SWPPP is to describe the proposed construction activities and all temporary and permanent erosion and sediment control (TESC) measures, pollution prevention measures, inspection/monitoring activities, and recordkeeping that will be implemented during the proposed construction project. The objectives of the SWPPP are to: 1. Implement Best Management Practices (BMPs) to prevent erosion and sedimentation, and to identify, reduce, eliminate or prevent stormwater contamination and water pollution from construction activity. 2. Prevent violations of surface water quality, ground water quality, or sediment management standards. 3. Prevent, during the construction phase, adverse water quality impacts including impacts on beneficial uses of the receiving water by controlling peak flow rates and volumes of stormwater runoff at the Permittee’s outfalls and downstream of the outfalls. This SWPPP was prepared using the Ecology SWPPP Template. This SWPPP was prepared based on the requirements set forth in the Construction Stormwater General Permit and in the Stormwater Management Manual for Western Washington (SWMMWW 2014). Insight Engineering Co. – Technical Information Report 2/7/23 - 25 - The 13 BMP Elements Element #1 – Mark Clearing Limits To protect adjacent properties and to reduce the area of soil exposed to construction, the limits of construction will be clearly marked before land-disturbing activities begin. Element #2 – Establish Construction Access Construction access or activities occurring on unpaved areas shall be minimized, yet where necessary, access points shall be stabilized to minimize the tracking of sediment onto public roads, and wheel washing, street sweeping, and street cleaning shall be employed to prevent sediment from entering state waters. Install the temporary construction entrance, according to the approved construction plans, prior to any clearing or grading activities. Maintain until the access road is paved. Element #3 – Control Flow Rates In order to protect the properties and waterways downstream of the project site, stormwater discharges from the site will be controlled. In general, discharge rates of stormwater from the site will be controlled where increases in impervious area or soil compaction during construction could lead to downstream erosion, or where necessary to meet local agency stormwater discharge requirements. pond is proposed to control flow rates during grading activity. Element #4 – Install Sediment Controls Install silt fencing, according to the approved plans, prior to any clearing or grading activities. Maintain until all construction activities are completed. Element #5 – Stabilize Soils Exposed and un-worked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. Apply temporary hydro-seed to exposed and un-worked soils, according to the approved construction plans, as needed to prevent erosion during site grading. Apply permanent hydro-seed to areas at final grade as site grading is completed. Apply mulching to exposed and un-worked soils, according to the approved construction plans, as needed to prevent erosion during site grading. Maintain until site grading is completed and permanent hydro-seed is applied. Cover stockpiles with plastic sheeting, according to the approved construction plans, as needed to prevent erosion during site grading. Maintain until stockpiles are removed from site. Element #6 – Protect Slopes All cut and fill slopes will be designed, constructed, and protected in a manner than minimizes erosion. The following specific BMPs will be used to protect slopes for this project. Element #7 – Protect Drain Inlets All storm drain inlets and culverts made operable during construction shall be protected to prevent unfiltered or untreated water from entering the drainage conveyance system. However, the first Insight Engineering Co. – Technical Information Report 2/7/23 - 26 - priority is to keep all access roads clean of sediment and keep street wash water separate from entering storm drains until treatment can be provided. Element #8 – Stabilize Channels and Outlets Where site runoff is to be conveyed in channels,or discharged to a stream or some other natural drainage point, efforts will be taken to prevent downstream erosion. Element #9 – Control Pollutants All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and preventative measures will be taken to ensure that the site will be kept clean, well-organized, and free of debris. Element #10 – Control Dewatering There will be no dewatering expected as part of this proposal. If it occurs, Baker tanks will be used for dewatering. Element #11 – Maintain BMPs All temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to assure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with each particular BMP’s specifications. Visual monitoring of the BMPs will be conducted at least once every calendar week and within 24 hours of any rainfall event that causes a discharge from the site. If the site becomes inactive, and is temporarily stabilized, the inspection frequency will be reduced to once every month. All temporary erosion and sediment control BMPs shall be removed within 30 days after the final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be removed or stabilized on site. Disturbed soil resulting from removal of BMPs or vegetation shall be permanently stabilized. Element #12 – Manage the Project Erosion and sediment control BMPs for this project have been designed based on the following principles: Design the project to fit the existing topography, soils, and drainage patterns; Emphasize erosion control rather than sediment control; Minimize the extent and duration of the area exposed; Keep runoff velocities low; Retain sediment on site; Thoroughly monitor site and maintain all ESC measures and Schedule major earthwork during the dry season. The SWPPP shall be modified as necessary to include additional or modified BMPs designed to correct problems identified. Insight Engineering Co. – Technical Information Report 2/7/23 - 27 - Revisions to the SWPPP shall be completed within seven (7) days following the inspection. Element #13 – Protect On-site Stormwater Management BMPs for Runoff from Roofs and Other Hard Surfaces On-site stormwater management BMPs used for runoff from roofs and other hard surfaces include: full dispersion, roof downspout full infiltration or dispersion systems, perforated stub-out connections, rain gardens, bioretention systems, permeable pavement, sheetflow dispersion, and concentrated flow dispersion. The areas on the site to be used for these BMPs shall be protected from siltation and compaction during construction by sequencing the construction in a fashion to install these BMPs at the latter part of the construction grading operations, by excluding equipment from the BMPS and the associated areas, and by using the erosion and sedimentation control BMPs listed below. Additional requirements for protecting these BMPs during the construction process, testing functionality, and restoring functionality are needed at the final stage of the construction process. Relevant BMPs BMP C102: Buffer Zone BMP C103: High Visibility Fence BMP C200: Interceptor Dike and Swale BMP C201: Grass-lined Channels BMP C207: Check Dams BMP C208: Triangular Silt Dike BMP C231: Brush Barrier BMP C233: Silt Fence BMP C234: Vegetated Strip Insight Engineering Co. – Technical Information Report 2/7/23 - 28 - 9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant Bond and insurance in accordance with City of Renton’s requirements will be provided upon request or at the behest of the owner during site construction. Insight Engineering Co. – Technical Information Report 2/7/23 - 29 - 10.0 Operations and Maintenance Manual The Operations and Maintenance Manual will be included with the construction submittal.