Document Redmond_doc_55a4810d67

Geotechnical & Earthquake Engineering Consultants REVISED GEOTECHNICAL REPORT PROPOSED REDMOND WAY FLATS 16760 Redmond Way Redmond, Washington PROJECT NO. 17-311.200 May 2018 Prepared for: Boxspring Redmond, LLC ---PAGE BREAK--- 3213 Eastlake Avenue East, Suite B Seattle, WA 98102 T. (206) 262-0370 F. (206) 262-0374 Geotechnical & Earthquake Engineering Consultants May 17, 2018 PanGEO Project No. 17-311.200 Ms. Tejal Pastakia Boxspring Redmond, LLC 94 Pike Street Seattle, Washington 98101 Subject: Geotechnical Report - Revised Proposed Redmond Way Flats 16760 Redmond Way, Redmond, Washington Dear Ms. Pastakia: As requested, PanGEO, Inc. is pleased to present this geotechnical report to assist the project team with the planning and design of the proposed Redmond Way Flats, 16760 Redmond Way in Redmond, Washington. In preparing this report, we drilled three test borings at the site, reviewed geotechnical and groundwater data for the site vicinity, and conducted our engineering analyses. In our opinion, the site may be developed generally as planned. Building support can be provided using a conventional spread and continuous footing foundation system for foundation elements at least two feet above the seasonal high groundwater table. Where construction will extend to within two feet of the seasonal high groundwater table or below the seasonal high groundwater table, it is our opinion that a mat foundation and watertight construction methods should be used. Should you have any questions, please do not hesitate to call. Sincerely, Scott D. Dinkelman, LEG, LHG Senior Hydrogeologist ---PAGE BREAK--- 17-311.200 16760 Redmond Way, REV1 Page i PanGEO, Inc. TABLE OF CONTENTS Section Page 1.0 GENERAL 2.0 SITE AND PROJECT DESCRIPTION 3.0 SUBSURFACE EXPLORATION AND SOIL CONDITIONS 3.1 SITE GEOLOGY 3.2 SUBSURFACE EXPLORATION 3.3 SOIL 3.4 PREVIOUS SUBSURFACE EXPLORATION REVIEW 3.5 GROUNDWATER 3.6 LABORATORY TESTING 4.0 CRITICAL AQUIFER RECHARGE AREA CONSIDERATIONS 4.1 CRITICAL AQUIFER RECHARGE AREAS 4.2 SEASONAL GROUNDWATER ELEVATION DATA 4.3 ENVIRONMENTAL REVIEW 4.4 POTENTIAL CONSTRUCTION GROUNDWATER QUALITY IMPACTS 4.5 POTENTIAL LONG-TERM GROUNDWATER IMPACTS 4.5.1 Stormwater Infiltration Impacts 4.6 CRITICAL AQUIFER RECHARGE AREA 5.0 DEWATERING 6.0 PRELIMINARY INFILTRATION ASSESSMENT 7.0 GEOTECHNICAL RECOMMENDATIONS 7.1 SEISMIC DESIGN PARAMETERS 7.2 BUILDING FOUNDATIONS 7.2.1 General 7.2.2 Spread Footing Foundations 7.2.3 Mat Foundations 7.2.4 Lateral Resistance 7.2.5 Foundation Subgrade Preparation 7.2.6 Perimeter Footing Drains 7.3 FLOORS SLABS 7.4 HYDROSTATIC UPLIFT 7.5 RETAINING WALL DESIGN PARAMETERS 7.5.1 Surcharge Loads 7.5.2 Lateral Resistance 7.5.3 Wall Drainage 7.5.4 Wall 7.6 PERMANENT CUT AND FILL SLOPES 8.0 TEMPORARY EXCAVATIONS AND SHORING 8.1 TEMPORARY EXCAVATIONS 8.2 TEMPORARY SHORING 8.2.1 Temporary Soldier Pile Shoring Design Parameters 8.2.2 Wall Design Parameters 8.2.3 Lagging 8.2.4 Baseline Survey and Monitoring 9.0 EARTHWORK CONSIDERATIONS 9.1 DEMOLITION AND CLEARING 9.2 STRUCTURAL FILL AND COMPACTION 9.3 MATERIAL REUSE ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page ii PanGEO, Inc. 9.4 WET WEATHER CONSTRUCTION 9.5 EROSION CONSIDERATIONS 10.0 ADDITIONAL SERVICES 11.0 CLOSURE 12.0 REFERENCES ATTACHMENTS: Figure 1 Vicinity Map Figure 2 Site and Exploration Plan Figure 3 City of Redmond Groundwater Monitoring Well Locations and Groundwater Flow Direction Figure 4 Groundwater Elevations and Precipitation, City of Redmond Monitoring Wells Figure 5 Design Lateral Pressures, Soldier Pile Wall, Cantilevered Appendix A Boring Logs Figure A-1 Terms and Symbols for Boring and Test Pit Logs Figures A-2 through A-4 Logs of Borings PG-1 through PG-3 Appendix B Laboratory Test Results Figure B-1 through B-4 Grain Size Distribution Test Results Appendix C Creative Engineering Options, Inc. Test Pit Logs TP-3 and TP-4 Appendix D Converse Consultants NW Summary Monitoring Well Logs Appendix E General Construction Practices for Critical Aquifer Recharge Areas Appendix F General Best Management Practices for Critical Aquifer Recharge Areas ---PAGE BREAK--- 17-311.200 16760 Redmond Way, REV1 Page 1 PanGEO, Inc. GEOTECHNICAL REPORT - REVISED PROPOSED REDMOND WAY FLATS 16760 REDMOND WAY REDMOND, WASHINGTON 1.0 GENERAL As requested, PanGEO, Inc. is pleased to present this revised geotechnical report to assist the project team with the planning and design of the proposed Redmond Way Flats at 16760 Redmond Way in Redmond, Washington. This study was performed in general accordance with our mutually agreed scope of services outlined in our agreement dated January 11, 2018. Our scope of services included reviewing readily available geologic, groundwater, and geotechnical data, drilling three borings, conducting a site reconnaissance, and evaluating the feasibility of developing the site as planned. 2.0 SITE AND PROJECT DESCRIPTION The subject property is located at 16760 Redmond Way in Redmond, Washington. The approximate location of the site is shown on the attached Figure 1, Vicinity Map. The approximately rectangular-shaped lot comprises an area of about 25,500 square feet and is bordered to the north and west by single-story retail buildings, to the south by Redmond Way, and to the west by 168th Avenue Northeast and Anderson Park on the east side of 168th Avenue Northeast. In the central portion of the site is a one-story retail building that is surrounded by asphalt paved parking and drive areas. The existing building was constructed in 1996. Plates 1 and 2, on the next page and the attached Figure 2, Site and Exploration Plan show the configuration of the site and general site conditions. The site and the immediate surrounding area is generally flat, with about three feet of elevation change across the length of the site. Based on review of the topographic survey, site grades range from elevation 46 to 49 feet (NAVD88). We understand it is planned to demolish the existing building and construct a new mixed- use building at the site. The proposed building will consist of five levels of living space over a ground level of retail space. One level of below grade parking is planned. It is also planned to construct a partial second below grade level to accommodate a car stacker pit. The below grade parking level will have a finished floor elevation of 38½ feet, or about 10 feet below grade. We estimate the foundation subgrade elevation for the below grade parking level will extend to elevation 36½ feet. The car stacker pits will have a finished ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 2 PanGEO, Inc. floor elevation of 32 feet with a construction subgrade elevation of about 30½ feet. Plate 3, on the following page shows a section through the site, illustrating the configuration of the below grade portions of the building. The project will include an elevator pit located in the south central portion of the building. The construction subgrade for the elevator pit will be elevation 28.2 feet. The project will also use a tower crane during construction. The location of the tower crane has not been determined, but will likely be located near the elevator in the south-central portion of the building footprint. The tower crane will also have a construction subgrade elevation of 28.2 feet, the same as the elevator pit. The approximate location of the elevator pit is shown on Figure 2. A portion of the building section showing the elevator pit is provided as Plate 4, below. Plate 1: Bird’s Eye view of site looking from south to north. The approximate limits of the site are outlined in yellow dashed line. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 3 PanGEO, Inc. Plate 2: View from the southwest corner of the site looking to the north-northwest. Plate 3: East-west section through proposed building. The lower parking level will have a finished floor elevation of 38.5 feet. The car stacker pits will have a finished floor elevation of 32 feet. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 4 PanGEO, Inc. Plate 4: Building section through elevator pit. The excavation for the below grade parking will extend up to the property boundaries as a zero-lot line excavation with vertical sides supported by temporary shoring. We estimate the shored excavation depth will be about 10 to 12 feet. The conclusions and recommendations in this report are based on our understanding of the proposed development, which is in turn based on the project information provided. If the above project description is incorrect, or the project information changes, we should be consulted to review the recommendations contained in this study and make modifications, if needed. In any case PanGEO should be retained to provide a review of the final design to confirm that our geotechnical recommendations have been correctly interpreted and adequately implemented in the construction documents. 3.0 SUBSURFACE EXPLORATION AND SOIL CONDITIONS 3.1 SITE GEOLOGY Based on review of the Geologic Map of the Redmond Quadrangle, King County, Washington (Minard 1988), the project site is underlain by Younger Alluvium – Geologic ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 5 PanGEO, Inc. Map Unit Qyal. Younger Alluvium consists of stratified sand, silt and clay derived from glacial outwash deposited in the upper Bear Creek drainage. 3.2 SUBSURFACE EXPLORATION Three borings, PG-1 through PG-3 were drilled at the site on February 20, 2018. The borings were drilled using an RCT 60 track-mounted drill rig operated by Boretec, Inc. under a subcontract to PanGEO and were logged by a geologist with our firm. The borings were drilled to a maximum depth of 36.5 feet below grade. The approximate boring locations were identified in the field by measuring from property corners and site features and are shown on Figure 2, Site and Exploration Plan. Standard Penetration Tests (SPT) were performed at 2½- to 5-foot depth intervals using a standard, 2-inch diameter split-spoon sampler. The sampler was advanced with a 140- pound drop hammer falling a distance of 30 inches for each strike, in general accordance with ASTM D-1586, Standard Test Method for Penetration Test and Split Barrel Sampling of Soils. The soils were logged in general accordance with ASTM D-2487 Standard Practice for Classification of Soils for Engineering Purposes and the system summarized on Figure A- 1, Terms and Symbols for Boring and Test Pit Logs. 3.3 SOIL CONDITIONS For a detailed description of the subsurface conditions encountered at each exploration location, please refer to our boring logs provided in Appendix A. The stratigraphic contacts indicated on the boring logs represent the approximate depth to boundaries between soil units. Actual transitions between soil units may be more gradual or occur at different elevations. The descriptions of groundwater conditions and depths are likewise approximate. The following is a generalized description of the soils encountered in the borings. Asphalt Pavement: All of our borings were located in asphalt paved parking and drive areas. The asphalt pavement layer ranges from 2 to 2½ inches thick. Quaternary Younger Alluvium (Qyal): Below the pavement, we encountered poorly graded gravel with sand and poorly graded sand with varying amounts of gravel ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 6 PanGEO, Inc. and cobbles. The soil was typically medium dense to a depth of 20 to 25 feet below grade, grading to dense to very dense below 20 to 25 feet below grade. Our subsurface descriptions are based on the conditions encountered at the time of our exploration. Soil conditions between our exploration locations may vary from those encountered. The nature and extent of variations between our exploratory locations may not become evident until construction. If variations do appear, PanGEO should be requested to reevaluate the recommendations in this report and to modify or verify them in writing prior to proceeding with earthwork and construction. 3.4 PREVIOUS SUBSURFACE EXPLORATION REVIEW As part of our study we reviewed summary logs of previous subsurface investigations in the vicinity of the site. The logs were obtained from the Washington Department of Natural Resources Geologic Information Portal. Specifically, we reviewed two test pit logs (Test Pits TP-3 and TP-4) from a geotechnical report by Creative Engineering Options, Inc. dated July 12, 1994 prepared for the current building at the site. We also reviewed the logs from one boring and four monitoring wells installed as part of an Environmental Site Assessment (ESA) prepared by Converse Consultants NW dated February 8, 1993 to assess the environmental impacts from a Chevron fueling station that formerly occupied the property. The reviewed test pit, boring, and monitoring well logs were located in the south half of the site and are approximately shown on the attached Figure 2. Summary logs for the geotechnical report and ESA are included in Appendix C and D, respectively. The soils encountered in the reviewed test pit and monitoring well logs consisted of Quaternary Younger Alluvium and are consistent with the conditions encountered in our borings. 3.5 GROUNDWATER We encountered groundwater in our test borings (PG-1 through PG-3) during drilling at about 24 feet below grade. A standpipe piezometer was installed in Boring PG-1 to allow for monitoring of groundwater levels after completion of drilling. A measurement obtained on February 23, 2018 yielded a groundwater level of 22 feet below grade. An electronic pressure transducer (data logger) was installed in the standpipe piezometer in Boring PG- 1 to allow for automatic recording of groundwater levels. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 7 PanGEO, Inc. Groundwater levels in the alluvial soils below Redmond fluctuate seasonally due to changes in precipitation, land use and groundwater withdrawals. As part of their wellhead protection program, the City of Redmond monitors groundwater levels using a network of more than 100 monitoring wells. The locations of the City of Redmond monitoring wells closest to the subject site are shown on Figure 3, City of Redmond Groundwater Monitoring Well Locations and Groundwater Flow Direction. The closest well to the site is MW009, which is located about 100 feet east of the site and is approximately shown on Figure 2. Other wells near the site include MW010, MW011, MW012, and MW008. The other well locations are also shown on Figure 3. Groundwater levels in MW009 have been monitored by the City using pressure transducers and by hand gauging from 2012 through the present and provides a good historical record of groundwater fluctuations. Groundwater levels in MW013 have been hand gauged from 2012 to 2016 and automatically recorded using pressure transducers from 2016 to the present. MW010, MW011, and MW012 have been manually gauged twice a year, once during the wet season and once during the dry season, from 2007 through 2016. Two construction projects located about 600 feet west of the site were actively dewatering from the summer of 2016 through the spring of 2017, as such groundwater levels during that period are likely depressed and do not reflect actual groundwater conditions. We understand another project started dewatering near the subject site in October 2017, which would also be depressing water levels in the vicinity of the site. Based on a review of the City’s groundwater records from MW009, groundwater levels in this area fluctuate by more than ten feet between the seasonal high and low of elevation 32.4 feet and elevation 22.25 feet, respectively, based on the NAVD88 datum. For design purposes, we recommend using a seasonal high groundwater table elevation of 32.4 feet. This value may need to be revised based on additional groundwater level monitoring at the site. 3.6 LABORATORY TESTING Laboratory tests were conducted on representative soil samples to verify or modify the field soil classification and to evaluate the general physical properties and engineering characteristics of the soil encountered. Visual field classifications were supplemented by grain size analyses on representative soil samples. The results of laboratory tests performed on specific samples are provided either at the appropriate sample depth on the individual boring logs or on a separate data sheet contained in Appendix B. It is important to note that ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 8 PanGEO, Inc. these test results may not accurately represent the overall in-situ soil conditions. Our geotechnical recommendations are based on our interpretation of these test results and their use in guiding our engineering judgment. 4.0 CRITICAL AQUIFER RECHARGE AREA CONSIDERATIONS 4.1 CRITICAL AQUIFER RECHARGE AREAS The subject site is located within a Critical Aquifer Recharge Area (CARA) Environmentally Critical Area (ECA) as defined in City of Redmond Zoning Code (RZC) 20D.140.50. Sensitive areas maps prepared by the City of Redmond indicate the site is located within a Wellhead Protection Zone 1, which represents the land area overlying portions of the aquifer with a six-month or less time-of-travel to any public water source well. The CARA designation is assigned based on the presence of the Redmond Alluvial Aquifer which is an unconfined aquifer that is the primary water source for the City of Redmond. An unconfined aquifer is defined as an aquifer in which the upper boundary is the water table and it is therefore not separated from the ground surface by a restrictive or confining soil layer. Unconfined aquifers have a risk of contamination and water quality degradation from contaminants released to the ground surface and infiltrating surface water. The closest City of Redmond water supply wells to the subject site are Wells 1 and 2 located about 200 to 300 feet northeast of the site. 4.2 SEASONAL GROUNDWATER ELEVATION DATA The City of Redmond monitors more than 100 wells in the Redmond Alluvial Aquifer as part of their wellhead protection program. Water levels in the wells are manually gauged at least twice a year, once during wet season and again during the dry season, and several of the wells have been periodically instrumented with pressure transducers to provide monitoring of groundwater levels at regular intervals. We reviewed the City of Redmond groundwater elevation data for six monitoring wells located within a 1,300-foot radius of the site. The approximate locations of the City of Redmond monitoring wells in the vicinity of the site are shown on Figure 3, City of Redmond Groundwater Monitoring Well Locations and Groundwater Flow Direction. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 9 PanGEO, Inc. The monitoring well water level data provided by the City was plotted along with historical precipitation records and are presented as Figure 4, Groundwater Elevations and Precipitation, City of Redmond Monitoring Wells. The graphs show the seasonal response of the wells to seasonal fluctuations in precipitation. Based on review of the data, groundwater levels typically rise in October, peaking in mid to late December with a seasonal high groundwater elevation near the site of 32.4 feet. The groundwater levels decrease in the late spring and throughout the summer with a seasonal low groundwater elevation of 22.25 feet. Elevations are based on the NAVD88 datum. The water level data provided for the August 2015 monitoring period were used to infer the groundwater flow direction. Based on our review, groundwater flow in the vicinity of the site is generally from the east to west-northwest with an estimated groundwater gradient of 0.2 percent. The closest surface water body in the vicinity of the site is Bear Creek, located about 1,800 feet east of the site. 4.3 ENVIRONMENTAL REVIEW The project environmental consultant, G-Logics prepared a Phase I environmental site assessment (ESA) for the subject site (G-Logics, 2017) and reviewed environmental studies and historical water quality data available for the subject site and surrounding area. Based on review of the ESA, the following is a summary of the previous environmentally significant uses of the site: • The site was originally developed as a gas station in 1948. The gas station had at least five underground storage tanks and one hydraulic lift. • In 1966 the original gas station was demolished and a new station constructed. The new station had six underground storage tanks and three hydraulic hoists. • In 1993, the former gas station equipment tanks, piping, hoists) was removed from the property. • Contaminated soils were excavated and either treated on site then used as backfill or disposed off-site. Quarterly groundwater monitoring-was conducted from 1995 to 1998. • A site assessment in 1995 identified that some petroleum-impacted soils remained on the property. These soils contained diesel, but were below MTCA Method A Cleanup Levels. • In 2000 the property received a No Further Action Determination from the Washington Department of Ecology. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 10 PanGEO, Inc. • In the mid-1990’s, the site was redeveloped with a Boston Market Restaurant. • In 1998, the Boston Market Restaurant closed and the building use was changed to its current use as a mattress retail store. 4.4 POTENTIAL CONSTRUCTION GROUNDWATER QUALITY IMPACTS Because the site is located within a Wellhead Protection Zone 1, the City requires an assessment of potential impacts to groundwater quality due to construction activities. At the time this report was prepared, details regarding the proposed construction sequencing or methods were not available. When this information is available from the contractor or civil engineer, a more detailed discussion of potential construction related groundwater impacts can be provided. For planning purposes, we are including general best construction practices for CARA areas in Appendix E of this report. The construction should also conform to Redmond Zoning Code (RZC) 21.64.050.D.3.f, Protection Standards During Construction. 4.5 POTENTIAL LONG-TERM GROUNDWATER IMPACTS The proposed development will primarily consist of residential space with ground level retail and parking and below grade parking. We anticipate potential contaminants from the proposed development could consist of leaks or discharges from vehicles in the parking garage and household chemicals. All drainage within the building, such as surface water from below grade parking, the trash room and wash water, should pass through an oil/water separator and be discharged to the sanitary sewer. Locations where significant spills and leaks could potentially occur at the facility and that could contribute pollutants to stormwater, surface water and groundwater include: • Vehicle Storage Areas • Liquid Storage Areas For planning purposes, we are including general best management practices (BMP’s) for CARA areas in Appendix F of this report. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 11 PanGEO, Inc. 4.5.1 Stormwater Infiltration Impacts Surface water from the building roof will be infiltrated using five dry wells along the south side of the site. The project environmental consultant, g-logics reviewed the potential for the stormwater system to mobilize contaminants related to the former site use as a gas station due to the infiltration of low pH runoff (gLogics, 2018). Based on review of their evaluation, environmental studies and an environmental clean-up were conducted at the site in the 1990’s. The site received a No Further Action Determination from the Washington Department of Ecology in a letter dated September 11, 2000. As such, there should be limited remaining contaminants on the property that could be directed to the City’s water supply wells. Groundwater flow is also to the west, northwest, away from the City’s wells. The planned improvements will include an excavation to elevation 28.2 feet. If contaminated or impacted soils are encountered they would need to be removed and disposed of in accordance with environmental regulations. 4.6 CRITICAL AQUIFER RECHARGE AREA CONCLUSIONS The site is underlain by the Redmond Alluvial Aquifer. Based on the current development plan with one level of below grade parking and the planned construction start in June 2019 it is not expected that the building excavation will intercept the groundwater table. The proposed development will include residential and retail space. These tenants are not expected to generate hazardous materials. Drainage collected within the building should pass through an oil/water separator and be pumped to the sanitary sewer. Based on our experience with similar projects and the subsurface conditions encountered, surface water from the development can be infiltrated or allowed to sheet flow to the existing storm drain system, similar to the predevelopment condition. Based on our review, in our opinion, impacts to the Redmond Alluvium Aquifer from the development can be designed to be minimized. 5.0 DEWATERING A dewatering approach has been prepared by Bender Consulting, LLC (Bender, 2018). Based on review of the approach it is planned to start construction in June 2019. The ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 12 PanGEO, Inc. excavation will extend to a depth of 28.2 feet below grade. The Bender report indicates the groundwater table is typically below elevation 28 feet for 4 to 6 months during the drier portion of the year, which we understand is enough time to complete the excavation and two provide for building construction to extend above the seasonal high groundwater table. With this approach, it appears dewatering should not be necessary. The dewatering approach also recommends allowing the excavation to flood during the wet season, if necessary. We recommend continuing to monitor groundwater levels for a least a year to develop a better understanding of seasonal groundwater fluctuations. As the development plan is finalized, PanGEO can assist with providing additional testing and analysis and refining the dewatering needs, if required. 6.0 PRELIMINARY INFILTRATION ASSESSMENT To provide a preliminary assessment of the feasibility of infiltrating stormwater, we reviewed the results of our grain size distribution testing performed on representative soil samples collected from our borings and considered our experience with infiltration on other projects near the site. Based on our review infiltration of stormwater should be feasible. For preliminary planning purposes, the sandy soils underlying the site should be capable of achieving an ultimate infiltration rate of at least 10 inches per hour. The infiltration capability of the soil should be confirmed based on the results of field infiltration tests conducted after the conceptual storm drainage system design has been completed and it is known where the infiltration galleries will be located. 7.0 GEOTECHNICAL RECOMMENDATIONS 7.1 SEISMIC DESIGN PARAMETERS The 2015 International Building Code (IBC) seismic design section provides a basis for seismic design of structures. Table 1 below provides seismic design parameters for the site that are in conformance with the 2015 IBC, which specifies a design earthquake having a 2% probability of occurrence in 50 years (return interval of 2,475 years), and the 2008 USGS seismic hazard maps. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 13 PanGEO, Inc. Table 1 – Seismic Design Parameters The spectral response accelerations were obtained from the USGS Earthquake Hazards Program Interpolated Probabilistic Ground Motion website (2008 data) for the project latitude and longitude. Liquefaction Potential - Liquefaction is a process that can occur when soils lose shear strength for short periods of time during a seismic event. Ground shaking of sufficient strength and duration results in the loss of grain-to-grain contact and an increase in pore water pressure, causing the soil to behave as a fluid. Soils with a potential for liquefaction are typically cohesionless, predominately silt and sand sized, must be loose, and be below the groundwater table. The site is predominantly underlain by medium dense to dense poorly graded sand and gravel. Based on these conditions, in our opinion the liquefaction potential at the site is low and design considerations related to soil liquefaction are not necessary for this project. 7.2 BUILDING FOUNDATIONS 7.2.1 General Based on the subsurface conditions and our understanding of the planned development, and assuming the bottom of the footings will be located at least two feet above the seasonal high groundwater elevation of 32.4 feet it is our opinion the proposed building may be supported on a spread footing foundation. If portions of the building will extend to within two feet of the seasonal high groundwater table elevation or will extend below the seasonal high groundwater table, a mat foundation should be used to support those portions of the building and those portions of the building should be designed as watertight structures designed to withstand hydrostatic pressures. Site Class Spectral Acceleration at 0.2 sec. SS Spectral Acceleration at 1.0 sec. S1 Site Coefficients Design Spectral Response Parameters Control Periods [sec.] Fa Fv SDS SD1 TO TS D 1.254 0.480 1.000 1.500 0.836 0.487 0.117 0.583 ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 14 PanGEO, Inc. PanGEO should be contacted to provide additional recommendations if foundations will be located within two feet of the seasonal high groundwater elevation. 7.2.2 Spread Footing Foundations Portions of the proposed development located least two feet above the season high groundwater elevation of 32.4 feet should be supported on spread footings bearing on the medium dense to dense, undisturbed native soil underlying the site, or on properly compacted structural fill placed on undisturbed native soil. For frost protection considerations, exterior foundation elements should be placed at a minimum depth of 18 inches below final exterior grade. Interior spread foundations should be placed at a minimum depth of 12 inches below the top of concrete slabs. We recommend a maximum allowable soil bearing pressure of 4,000 pounds per square foot (psf) be used for sizing foundation elements. The recommended allowable bearing pressure is for dead plus live loads. For allowable stress design, the recommended bearing pressure may be increased by one-third for transient loading, such as wind or seismic forces. Continuous and individual spread footings should have minimum widths of 18 and 24 inches, respectively. Footings designed and constructed in accordance with the above recommendations should experience total settlement of less than one inch and differential settlement of less than ½ inch. Most of the anticipated settlement should occur during construction as dead loads are applied. 7.2.3 Mat Foundations Where portions of the building will extend within two feet of the seasonal high groundwater table or below the seasonal high groundwater table, such as the elevator pits and car stacker pits, we recommend these elements be designed as watertight structures to withstand hydrostatic pressures. A concrete mat foundation should be used to support these portions of the building. The mat slab should bear on the medium dense to dense soils that should be encountered at the construction subgrade elevation. The mat foundation should be designed so that is sufficiently stiff to spread the concentrated column loads out over a wide area. A structural mat foundation can be evaluating using a modulus of subgrade reaction of 200 pounds per cubic inch (pci). Local ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 15 PanGEO, Inc. bearing pressures below concentrated loads can be evaluated using an allowable soil bearing pressure of 5,000 psf. The allowable bearing pressure may be increased by 1/3 for transient loading such as wind or seismic loads. Reinforcing steel and post tensioning requirements for the mat foundations should be designed by the project structural engineer to withstand hydrostatic uplift. 7.2.4 Lateral Resistance Lateral loads on the structure may be resisted by passive earth pressure developed against the embedded portion of the foundation system and by frictional resistance between the bottom of the foundation and the supporting subgrade soils. A frictional coefficient of 0.35 may be used to evaluate sliding resistance developed between the foundation and the compacted subgrade soil. Passive soil resistance may be calculated using an equivalent fluid weight of 175 below the seasonal high water table (assume elevation 32.4 feet for design) and 350 pcf above the water table, assuming foundations are backfilled with structural fill. The above values include a factor of safety of 1.5. Unless covered by pavements or slabs, the passive resistance in the upper 12 inches of soil should be neglected. 7.2.5 Foundation Subgrade Preparation Foundation excavations should be observed by PanGEO. The foundation subgrade should be properly prepared and in a dense condition prior to setting forms and rebar. Loose or softened soil exposed in the excavation subgrade should be overexcavated and replaced with structural fill. 7.2.6 Perimeter Footing Drains Due to the presence of highly permeable soils below the site, it is our opinion a footing drain with a discharge is not necessary. In our opinion, the relatively permeable soils underlying the site will provide suitable drainage around the building without the use of a footing drain. Exterior grades around the building perimeter should be sloped to drain at a minimum 2 percent slope for a horizontal distance of at least 10 feet. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 16 PanGEO, Inc. 7.3 FLOORS SLABS The floor slab for the footing supported parts of the building may be constructed using conventional concrete slab-on-grade floor construction. The floor slab should be supported on competent native soil or on structural fill. Any over-excavations, if needed, should be backfilled with structural fill. Interior concrete slab-on-grade floors should be underlain by a capillary break consisting of at least of 4 inches of pea gravel or compacted ¾-inch, clean crushed rock (less than 3 percent fines), placed on top of the one foot of newly placed structural fill. The capillary break material should meet the gradational requirements provided in Table 2, below. Table 2 – Capillary Break Gradation The capillary break should be placed on the subgrade that has been compacted to a dense and unyielding condition. A 10-mil polyethylene vapor barrier should also be placed directly below the slab. Construction joints should be incorporated into the floor slab to control cracking. Where a mat foundation is used in conjunction with watertight construction, a capillary break and vapor barrier are not necessary. 7.4 HYDROSTATIC UPLIFT The watertight below grade portion of the building will be subjected to hydrostatic uplift forces when the groundwater level outside the structures is higher than the base of the mat slab. For design against hydrostatic uplift, structural elements within two feet of the seasonal high groundwater elevation of 32.4 feet should be designed to resist this upward force and to prevent possible heave and cracking of foundations and slabs. The weight of the structure and the uplift capacity of the shoring system around the basement perimeter may be used to resist uplift forces. Sieve Size Percent Passing ¾-inch 100 No. 4 0 – 10 No. 100 0 – 5 No. 200 0 – 3 ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 17 PanGEO, Inc. 7.5 RETAINING WALL DESIGN PARAMETERS Cast-in-place concrete retaining and basement walls should be designed to resist the lateral earth pressures exerted by the soils behind the wall. Proper drainage provisions should also be provided to intercept and remove groundwater and infiltrating surface water that may collect behind the walls. Cantilever walls should be designed for an equivalent fluid pressure of 35 pcf for a level backfill condition and assuming the walls are free to rotate. If the walls are restrained at the top from free movement, such as basement walls with a floor diaphragm, an equivalent fluid pressure of 45 pcf should be used for a level backfill condition at least two feet above the seasonal high groundwater elevation of 32.4 feet. Walls within two feet or below the seasonal high groundwater elevation of 32.4 feet should designed for an equivalent fluid weight of 85 pcf. Permanent walls should be designed for an additional uniform lateral pressure of 7H psf for seismic loading, where H corresponds to the height of the buried depth of the wall. The recommended lateral pressures assume the backfill behind the walls consists of a free draining and properly compacted fill with adequate drainage provisions. 7.5.1 Surcharge Loads Surcharge loads, where present, should also be included in the design of retaining walls. We recommend a lateral load coefficient of 0.4 be used to compute the lateral pressure on the wall face resulting from surcharge loads located within a horizontal distance of one- half the wall height. 7.5.2 Lateral Resistance Lateral forces from seismic loading and unbalanced lateral earth pressures may be resisted by a combination of passive earth pressures acting against the embedded portions of the foundations and by friction acting on the base of the wall foundation. Passive soil resistance may be calculated using an equivalent fluid weight of 175 pcf within two feet or below the seasonal high water table (assume elevation 32.4 feet for design) and 350 pcf at least two feet above the seasonal high water table. This value includes a factor of safety of 1.5, assuming the footing is backfilled with structural fill. A friction coefficient of 0.35 may be used to determine the frictional resistance at the base of the footings. The coefficient includes a factor of safety of 1.5. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 18 PanGEO, Inc. 7.5.3 Wall Drainage Provisions for wall drainage should consist of a minimum 18-inch wide zone of free draining granular soils (i.e. pea gravel or washed rock) is recommended to be placed adjacent to the wall for the full height of the wall. Alternatively, a composite drainage material, such as Miradrain 6000, may be used in lieu of the clean crushed rock or pea gravel. A 4-inch diameter perforated drainpipe placed behind and at the base of the wall foundation to disperse any intercepted seepage. Where basement walls will be constructed against shoring, a geocomposite drain, such as MiraDrain 6000 or an approved equivalent may be placed between the shoring wall and permanent basement walls. The geocomposite drain should be allowed to drain directly to the relatively permeable native soils. 7.5.4 Wall Backfill Retaining wall backfill should consist of free draining granular material such as a soil meeting the requirements of Gravel Borrow as defined in Section 9-03.14(1) of the WSDOT Standard Specifications for Road, Bridge, and Municipal Construction (WSDOT, 2018). In areas where space is limited between the wall and the face of excavation, pea gravel may be used as backfill without compaction. Wall backfill should be moisture conditioned to within near of optimum moisture content, placed in loose, horizontal lifts less than 8 inches in thickness, and systematically compacted to a dense and relatively unyielding condition and to at least 95 percent of the maximum dry density, as determined using test method ASTM D-1557 (Modified Proctor). Within 5 feet of the wall, the backfill should be compacted with hand-operated equipment to at least 90 percent of the maximum dry density. 7.6 PERMANENT CUT AND FILL SLOPES Based on the anticipated soil that will be exposed in the planned excavation, we recommend permanent cut and fill slopes be constructed no steeper than 2H:1V (Horizontal:Vertical). ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 19 PanGEO, Inc. 8.0 TEMPORARY EXCAVATIONS AND SHORING 8.1 TEMPORARY EXCAVATIONS In order to achieve construction subgrade elevations for the below grade parking, an excavation extending to a depth of 10 to 18 feet below grade is planned. Temporary excavations should be constructed in accordance with Part N of WAC (Washington Administrative Code) 296-155. The contractor is responsible for maintaining safe excavation slopes and/or shoring. Based on the soil conditions encountered in the test borings, it is our opinion temporary excavations may be cut at a maximum 1½H:1V inclination. If sufficient space is not available, temporary excavation shoring will be needed. Temporary excavations should be evaluated in the field during construction based on actual observed soil conditions. If seepage is encountered, excavation slope inclinations may need to be reduced. During wet weather, the cut slopes may need to be flattened to reduce potential erosion or should be covered with plastic sheeting. 8.2 TEMPORARY SHORING We anticipate a combination of conventional open cuts and temporary shoring may be used to accomplish the planned excavation. Given the subsurface conditions at the site, in our opinion temporary shoring consisting of a soldier pile wall is likely the most cost-effective shoring option. The shoring system should be designed to provide adequate protection for the workers, adjacent structures, utilities, and other facilities. Excavations should be performed in accordance with the current requirements of WISHA. Construction should proceed as rapidly as feasible, to limit the time temporary excavations are open. 8.2.1 Temporary Soldier Pile Shoring Design Parameters A soldier pile wall consists of vertical steel beams, typically spaced from 6 to 8 feet apart along the proposed excavation wall, spanned by timber lagging. Prior to the start of excavation, the steel beams are installed into holes drilled to a design depth and then backfilled with lean mix or structural concrete. As the excavation proceeds downward and the steel piles are subsequently exposed, timber lagging is installed between the piles to further stabilize the walls of the excavation. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 20 PanGEO, Inc. 8.2.2 Wall Design Parameters We recommend the earth pressures depicted on Figure 5, Design Lateral Pressures, Soldier Pile Wall, Cantilevered be used for design of soldier pile walls for this project. Our shoring design parameters assume the excavation is fully dewatered and do not include hydrostatic pressures from groundwater. The vertical capacity of the soldier piles should be determined using an allowable skin friction value of 0.5 ksf for the portion of the pile below the bottom of the excavation, and an allowable end soil bearing capacity value of 15 ksf. 8.2.3 Lagging Lagging design recommendations for general conditions are presented on Figure 5. Lagging located within 10 feet of the top of the shoring which may be subjected to surcharge loads from construction equipment or material storage should be designed for an additional uniform lateral surcharge pressure of 200 psf. This pressure approximately corresponds to a vertical uniform surcharge load of 500 psf at the top of the wall for general construction surcharge. Point loads located close to the top of the wall, such as outriggers of heavy cranes, may apply additional loads to the lagging. These loads may need to be individually analyzed. However, lagging designed for a uniform load of 600 psf in the top 10 feet of the wall should be able to accommodate most crane outrigger loads. We recommend voids behind the lagging be backfilled with CDF. Because the site is located over the Redmond Alluvial Aquifer, untreated timber should be used for lagging. 8.2.4 Baseline Survey and Monitoring Ground movements will occur as a result of excavation activities. As such, ground surface elevations of the adjacent properties and city streets should be documented prior to commencing earthwork to provide baseline data. As a minimum, optical survey points should be established at the following locations: • The top of every other soldier pile. These monitoring points should be monitored twice a week. The monitoring frequency may be reduced based on the monitoring results. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 21 PanGEO, Inc. • Adjacent structures located within 25 feet of the shoring walls. • The curbs and the centerlines of adjacent streets should be monitored by establishing a set of baseline point spaced no more than 20 feet apart. These monitoring points should not need to be regularly surveyed after the baseline is established unless the soldier pile wall monitoring indicates deflections exceeding one inch. The monitoring program should include monitoring for changes in both the horizontal (x and y directions) and vertical deformations. The monitoring should be performed by the contractor or the project surveyor, and the results should be submitted to PanGEO for review. The results of the monitoring will allow the design team to confirm design parameters, and for the contractor to make adjustments if necessary. We also recommend the existing conditions along the public right of way and the adjacent private properties be photo-documented prior to commencing earthwork at the site. 9.0 EARTHWORK CONSIDERATIONS 9.1 DEMOLITION AND CLEARING Building, pavement and areas to receive structural fill should be stripped and cleared of existing structures, surface vegetation, organic matter, and other deleterious material. Existing utility pipes to be abandoned should be plugged or removed so they do not provide a conduit for water and cause soil saturation and stability problems. In no case should the demolition materials be used as structural fill or mixed with material to be used as structural fill. Following the stripping operation and excavations necessary to achieve construction subgrade elevations, the ground surface where structural fill, foundations, slabs, or pavements are to be placed should be observed by a representative of PanGEO. Soil in loose or soft areas, if re-compacted and still yielding, should be overexcavated and replaced with structural fill to a depth that will provide a stable base beneath the general structural fill. The optional use of a geotextile fabric placed directly on the overexcavated surface may also help to bridge unstable areas. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 22 PanGEO, Inc. 9.2 STRUCTURAL FILL AND COMPACTION Structural fill, if needed, should be free of or organic and inorganic debris, be near its optimum moisture content, and be capable of being compacted to the requirements of structural fill. The native soils underlying the site are relatively granular and can be used as structural fill during dry weather. If an imported granular fill is to be used, it should consist of clean fill from a commercial source that complies with Redmond Municipal Code (RMC) Chapter 15.24.080 and 15.24.095. The fill should comprise a well graded material containing less than five percent fines (silt and clay sized particles) passing the US No. 200 Sieve based on the percent passing the ¾-inch sieve. Structural fill should be moisture conditioned to within about 3 percent of optimum moisture content, placed in loose, horizontal lifts less than 8 inches in thickness, and compacted to at least 95 percent maximum density, determined using ASTM D 1557 (Modified Proctor). The procedure to achieve proper density of a compacted fill depends on the size and type of compacting equipment, the number of passes, thickness of the lifts being compacted, and certain soil properties. If the excavation to be backfilled is constricted and limits the use of heavy equipment, smaller equipment can be used, but the lift thickness will need to be reduced to achieve the required relative compaction. Generally, loosely compacted soils are a result of poor construction technique or improper moisture content. Soils with high fines contents are particularly susceptible to becoming too wet and coarse-grained materials easily become too dry, for proper compaction. Silty or clayey soils with a moisture content too high for adequate compaction should be dried as necessary, or moisture conditioned by mixing with drier materials, or other methods. 9.3 MATERIAL REUSE The native soils underlying the site are suitable for use as structural fill. If it is planned to use the native soil as structural fill, the excavated soil should be stockpiled and protected with plastic sheeting to prevent it from becoming saturated by precipitation or runoff. 9.4 WET WEATHER CONSTRUCTION General recommendations relative to earthwork performed in wet weather or in wet conditions are presented below. The following procedures are best management practices recommended for use in wet weather construction: ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 23 PanGEO, Inc. • Earthwork should be performed in small areas to minimize subgrade exposure to wet weather. Excavation or the removal of unsuitable soil should be followed by the placement and compaction of clean structural fill. The size and type of construction equipment used may have to be limited to prevent soil disturbance. • During wet weather, the allowable fines content of the structural fill should be reduced to no more than 5 percent by weight based on the portion passing the 0.75-inch sieve. The fines should be non-plastic. • The ground surface within the construction area should be graded to promote run-off of surface water and to prevent the ponding of water. • Geotextile silt fences should be installed at strategic locations around the site to control erosion and the movement of soil. • Excavation slopes and soils stockpiled on site should be covered with plastic sheeting. 9.5 EROSION CONSIDERATIONS Surface runoff can be controlled during construction by careful grading practices. Typically, this includes the construction of shallow, upgrade perimeter ditches or low earthen berms in conjunction with silt fences to collect runoff and prevent water from entering excavations or to prevent runoff from the construction area leaving the immediate work site. Temporary erosion control may require the use of hay bales on the downhill side of the project to prevent water from leaving the site and potential storm water detention to trap sand and silt before the water is discharged to a suitable outlet. All collected water should be directed under control to a positive and permanent discharge system. Permanent control of surface water should be incorporated in the final grading design. Adequate surface gradients and drainage systems should be incorporated into the design such that surface runoff is collected and directed away from the structure to a suitable outlet. Potential issues associated with erosion may also be reduced by establishing vegetation within disturbed areas immediately following grading operations. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 24 PanGEO, Inc. 10.0 ADDITIONAL SERVICES To confirm that our recommendations are properly incorporated into the design and construction of the proposed addition, PanGEO should be retained to conduct a review of the final project plans and specifications, and to monitor the construction of geotechnical elements. The City of Redmond, as part of the permitting process, will also require geotechnical construction inspection services. PanGEO can provide you a cost estimate for construction monitoring services at a later date. ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 25 PanGEO, Inc. 11.0 CLOSURE We have prepared this report for Boxspring Redmond, LLC and the project design team. Recommendations contained in this report are based on a site reconnaissance, a subsurface exploration program, review of pertinent subsurface information, and our understanding of the project. The study was performed using a mutually agreed-upon scope of work. Variations in soil conditions may exist between the locations of the explorations and the actual conditions underlying the site. The nature and extent of soil variations may not be evident until construction occurs. If any soil conditions are encountered at the site that are different from those described in this report, we should be notified immediately to review the applicability of our recommendations. Additionally, we should also be notified to review the applicability of our recommendations if there are any changes in the project scope. Our scope of services does not include services related to construction safety precautions. Our recommendations are not intended to direct the contractors’ methods, techniques, sequences or procedures, except as specifically described in our report for consideration in design. Additionally, the scope of our services specifically excludes the assessment of environmental characteristics, particularly those involving hazardous substances. We are not mold consultants nor are our recommendations to be interpreted as being preventative of mold development. A mold specialist should be consulted for all mold-related issues. This report has been prepared for planning and design purposes for specific application to the proposed project in accordance with the generally accepted standards of local practice at the time this report was written. No warranty, express or implied, is made. This report may be used only by the client and for the purposes stated, within a reasonable time from its issuance. Land use, site conditions (both off and on-site), or other factors including advances in our understanding of applied science, may change over time and could materially affect our findings. Therefore, this report should not be relied upon after 24 months from its issuance. PanGEO should be notified if the project is delayed by more than 24 months from the date of this report so that we may review the applicability of our conclusions considering the time lapse. It is the client’s responsibility to see that all parties to this project, including the designer, contractor, subcontractors, etc., are made aware of this report in its entirety. The use of information contained in this report for bidding purposes should be done at the contractor’s option and risk. Any party other than the client who wishes to use this report shall notify ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 26 PanGEO, Inc. PanGEO of such intended use and for permission to copy this report. Based on the intended use of the report, PanGEO may require that additional work be performed and that an updated report be reissued. Noncompliance with any of these requirements will release PanGEO from any liability resulting from the use this report. Sincerely, PanGEO, Inc. Scott D. Dinkelman, LEG, LHG Siew L Tan, P.E. Senior Hydrogeologist Principal Geotechnical Engineer ---PAGE BREAK--- Geotechnical Report - Revised Proposed Redmond Way Flats: 16760 Redmond Way, Redmond, Washington May 17, 2018 17-311.200 16760 Redmond Way, REV1 Page 27 PanGEO, Inc. 12.0 REFERENCES City of Redmond, 2011, Map 64.6 Wellhead Protection Zones, City of Redmond Public Works. International Code Council, 2015, International Building Code (IBC), 2015. Minard, J. Booth, D. 1988, The Geologic Map of the Redmond Quadrangle, King County, Washington – U. S. Geological Survey Miscellaneous Field Studies, Map MF- 2016, scale 1:24,000. United States Geological Survey, Earthquake Hazards Program, Interpolated Probabalisitic Ground Motion for the Conterminous 48 States by Latitude and Longitude, 2008 Data, accessed via: http://earthquake.usgs.gov/designmaps/us/application.php WSDOT, 2018, Standard Specifications for Road, Bridge and Municipal Construction, M 41-10. ---PAGE BREAK--- Figure No. Project No. 17-311.200 Proposed Redmond Way Flats 16760 Redmond Way Redmond, WA 1 file.grf w/ file.dat 3/6/18 (15:18) SDD VICINITY MAP Not-To-Scale Base Map: WSDOT GeoPortal ---PAGE BREAK--- Project No. Figure No. SITE AND EXPLORATION PLAN 17-311.200 2 13-011_Fig 2 Site & Exploration Plan.grf 3/6/18 JCR Approximate Boring Location, PanGEO, Inc., February 2018 (Circle around symbol indicates standpipe piezometer installation) LEGEND: Approx. Scale (feet) Note: Site plan modified from Boundary/Topographic Survey, Bush Roed & Hitchings, Inc., dated March 5, 2018. Redmond Way Flats 16760 Redmond Way RedmondIssaquah, WA Subject Site REDMOND WAY 168TH AVENUE NORTHEAST Approximate Monitoring Well Location, Converse Consultants NW, December 1992 Approximate Test Pit Location, Creative Engineering Options, Inc., July 1994 Approximate Monitoring Well Location, City of Redmond ---PAGE BREAK--- Project No. Figure No. CITY OF REDMOND GROUNDWATER MONITORING WELL LOCATIONS AND GROUNDWATER FLOW DIRECTION 17-311 3 13-011_Fig 2 Site & Exploration Plan.grf 5/17/18 JCR LEGEND: Approx. Scale (feet) Subject Site Redmond Way Flats 16760 Redmond Way Redmond, WA ---PAGE BREAK--- Project No. 17-311.200 Figure No. Redmond Way Flats 16760 Redmond Way Redmond, WA Groundwater Elevations and Precipitation City of Redmond Monitoring Wells 4 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 20 25 30 35 40 45 50 12/23/11 7/10/12 1/26/13 8/14/13 3/2/14 9/18/14 4/6/15 10/23/15 5/10/16 11/26/16 Elevation (Feet) Date MW008 MW009 MW010 MW011 MW012 MW013 Precipitation ---PAGE BREAK--- Project No. Figure No. DESIGN LATERAL PRESSURES SOLDIER PILE WALL CANTILEVERED 17-311.200 5 file.grf w/ file.dat 3/7/18 (07:56) TEA2 Notes: 1. Active earth pressures assume shoring is fully drained and hydrostatic pressures are not allowed to develop behind the shoring. 2. Minumum embedment should be at least 10 feet below bottom of excavation. 3. A factor of safety of 1.5 has been applied to the recommended passive pressure values. No factor of safety has been applied to the recommended active earth pressure values. 4. Active pressures should be applied over the full width of the pile spacing above the base of the excavation, and over one pile diameter below the base of the excavation. 5. Surcharge pressures should be applied over the entire length of the loaded area. 6. Passive pressure should be applied to two times the diameter of the soldier piles. 7. Use 50% of the active and surcharge pressures for lagging design with soldier piles spaced at 8' or less. 8. Refer to report text for additional discussions. Base of Excavation Soldier Pile Wall with Timber Lagging H Passive Pressure Active Pressure Footing Surcharge = q 350 pcf above elevation 37.6 feet 175 pcf below elevation 37.6 feet 1 45 pcf (1H:1V backslope) 35 pcf (level backslope) 1 Bf 1 1 1H:1V Temporary Cut (if applicable) Level Backslope X Apply only to above bottom of excavation 0.4(1 - X/H) q Street Traffic Surcharge: 80 psf uniform pressure x Apply only to above bottom of excavation H/4, but > 5ft 15 feet max Footing Surcharge Proposed Redmond Way Flats 16760 Redmond Way Redmond, Washington ---PAGE BREAK--- APPENDIX A BORING LOGS ---PAGE BREAK--- 2 1/2" Asphalt Parking Lot. Medium dense, brown, sandy GRAVEL trace silt; moist; poorly graded, trace iron oxide staining [Quaternary Alluvium]. --poor recovery: blow count inflated by gravel. --broken cobble in tip; blow count inflated by gravel. Medium dense to dense, grey-brown, gravelly, fine to medium SAND trace silt; moist to water-bearing; poorly graded, occasional sandy silt interlayers [Quaternary Alluvium]. --broken cobble in tip; blow count inflated by gravel. sandy silt interlayer. sandy silt interlayer. --broken cobble in tip; blow count inflated by gravel. --groundwater encountered at about 24' based on water on drilling tools. sandy silt interlayer. Dense to very dense, grey, fine gravelly, fine to coarse SAND; water-bearing; poorly graded [Quaternary Alluvium]. --drillers encountered ~1 foot heave, sampled and removed. --becomes very dense. --interlayered coarse sand and fine to medium sand. --becomes dense. --decreasing gravel content (trace fine gravel). Boring terminated at about 36.5 feet below grade. Groundwater encountered at about 24 feet during drilling. S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8 S-9 50/3 34 12 9 13 12 50/5 17 27 41 14 15 14 23 25 38 18 19 38 14 23 30 12 15 15 Remarks: Drilling was performed using an RCT 60 Track Drill. Standard Penetration Test (SPT) sampler driven with a 140 lb hammer using a rope and cathead dropping 30 inches per stroke. Elevations estimated based on Google Earth . 0 5 10 15 20 25 30 35 40 The stratification lines represent approximate boundaries. The transition may be gradual. MATERIAL DESCRIPTION Figure A-2 Other Tests Sample No. Completion Depth: Date Borehole Started: Date Borehole Completed: Logged By: Drilling Company: Depth, (ft) Proposed Mixed-Use Development 17-311 16760 Redmond Way, Redmond, WA Northing: 47.67276, Easting: -122.11678 36.5ft 2/21/18 2/21/18 B. Weitering Boretec Sheet 1 of 1 Project: Job Number: Location: Coordinates: Symbol Sample Type Blows / 6 in. 49.0ft Not surveyed HSA SPT Surface Elevation: Top of Casing Elev.: Drilling Method: Sampling Method: LOG OF TEST BORING PG-1 N-Value 0 Moisture LL 50 PL RQD Recovery 100 Instrument ---PAGE BREAK--- 2" Asphalt Parking Lot. Medium dense, grey-brown, sandy GRAVEL trace silt; moist; poorly graded [Quaternary Alluvium]. --broken cobble in tip; blow count inflated by gravel. --poor recovery - tip only. --minor perched moisture. --iron oxide staining. --trace iron oxide staining. Dense to very dense, grey, gravelly fine to coarse SAND; moist to water-bearing; poorly graded [Quaternary Alluvium]. --groundwater encountered at about 24' based on water on drilling tools. --blow count may be inflated. --fine sand to fine gravelly coarse sand (fining upward). --becomes medium dense. silt interlayer. Boring terminated at about 36.5 feet below grade. Groundwater encountered at about 24 feet during drilling. S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8 S-9 7 5 5 8 33 50/3 13 9 15 28 21 18 10 11 12 14 17 12 15 50/4 30 22 13 9 11 15 Remarks: Drilling was performed using an RCT 60 Track Drill. Standard Penetration Test (SPT) sampler driven with a 140 lb hammer using a rope and cathead dropping 30 inches per stroke. Elevations estimated based on Google Earth . 0 5 10 15 20 25 30 35 40 The stratification lines represent approximate boundaries. The transition may be gradual. MATERIAL DESCRIPTION Figure A-3 Other Tests Sample No. Completion Depth: Date Borehole Started: Date Borehole Completed: Logged By: Drilling Company: Depth, (ft) Proposed Mixed-Use Development 17-311 16760 Redmond Way, Redmond, WA Northing: 47.67308, Easting: -122.11673 36.5ft 2/21/18 2/21/18 B. Weitering Boretec Sheet 1 of 1 Project: Job Number: Location: Coordinates: Symbol Sample Type Blows / 6 in. 49.0ft HSA SPT Surface Elevation: Top of Casing Elev.: Drilling Method: Sampling Method: LOG OF TEST BORING PG-2 N-Value 0 Moisture LL 50 PL RQD Recovery 100 ---PAGE BREAK--- 2 1/2" Asphalt Parking Lot. Medium dense to dense, grey-brown, sandy GRAVEL trace silt; moist; poorly graded, trace iron oxide staining [Quaternary Alluvium]. --no recovery: broken cobble in tip. --broken cobble in tip; blow count inflated by gravel. --becomes dense. --blow count may be inflated by gravel. --becomes medium dense, grey. Dense to very dense, grey, gravelly medium to coarse SAND; moist to water-bearing; poorly graded [Quaternary Alluvium]. --groundwater encountered at about 24' based on water on drilling tools. --blow count may be inflated. --decreasing gravel content gravelly). --decreasing gravel content (trace fine gravel). Boring terminated at about 36.5 feet below grade. Groundwater encountered at about 24 feet during drilling. S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8 S-9 17 11 11 8 9 12 24 32 17 16 21 20 50/6 7 13 14 19 21 29 12 24 19 17 18 16 Remarks: Drilling was performed using an RCT 60 Track Drill. Standard Penetration Test (SPT) sampler driven with a 140 lb hammer using a rope and cathead dropping 30 inches per stroke. Elevations estimated based on Google Earth . 0 5 10 15 20 25 30 35 40 The stratification lines represent approximate boundaries. The transition may be gradual. MATERIAL DESCRIPTION Figure A-4 Other Tests Sample No. Completion Depth: Date Borehole Started: Date Borehole Completed: Logged By: Drilling Company: Depth, (ft) Proposed Mixed-Use Development 17-311 16760 Redmond Way, Redmond, WA Northing: 47.67308, Easting: -122.11647 36.5ft 2/21/18 2/21/18 B. Weitering Boretec Sheet 1 of 1 Project: Job Number: Location: Coordinates: Symbol Sample Type Blows / 6 in. 49.0ft HSA SPT Surface Elevation: Top of Casing Elev.: Drilling Method: Sampling Method: LOG OF TEST BORING PG-3 N-Value 0 Moisture LL 50 PL RQD Recovery 100 ---PAGE BREAK--- APPENDIX B LABORATORY TEST RESULTS ---PAGE BREAK--- THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE PanGeo Redmond Flats SAMPLE ID/TYPE PG-1 S8 PROJECT NO. 17-311.200 SAMPLE DEPTH 30' TECH/TEST DATE SPT 3/6/2018 DATE RECEIVED 3/1/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1) 1277.1 Weight Of Sample (gm) 1125.7 Wt Dry Soil & Tare (gm) (w2) 1125.7 Tare Weight (gm) 15.4 Weight of Tare (gm) (w3) 15.4 (W6) Total Dry Weight (gm) 1110.3 Weight of Water (gm) (w4=w1-w2) 151.4 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 1110.3 Cumulative Moisture Content (w4/w5)*100 14 Wt Ret (Wt-Tare) (%Retained) % PASS +Tare {(wt ret/w6)*100} (100-%ret) % COBBLES 0.0 12.0" 15.4 0.00 0.00 100.00 cobbles % C GRAVEL 0.0 3.0" 15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 4.1 2.5" coarse gravel % C SAND 5.8 2.0" coarse gravel % M SAND 64.7 1.5" 15.4 0.00 0.00 100.00 coarse gravel % F SAND 21.7 1.0" coarse gravel % FINES 3.7 0.75" 15.4 0.00 0.00 100.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375" 39.4 24.00 2.16 97.84 fine gravel D10 (mm) 0.19 #4 60.5 45.10 4.06 95.94 coarse sand D30 (mm) 0.48 #10 125.4 110.00 9.91 90.09 medium sand D60 (mm) 0.9 #20 medium sand Cu 4.7 #40 844.1 828.70 74.64 25.36 fine sand Cc 1.3 #60 fine sand #100 1059.7 1044.30 94.06 5.94 fine sand #200 1084.8 1069.40 96.32 3.68 fines PAN silt/clay 322 DESCRIPTION poorly graded SAND with trace silt USCS SP Prepared For: Reviewed By: KW PanGeo 0 10 20 30 40 50 60 70 80 90 100 0.001 0.01 0.1 1 10 100 1000 % P A S S I N G Grain size in millimeters 12" 3" 2" 1" .75" .375" #4 #10 #20 #40 #60 #100 #200 ---PAGE BREAK--- THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE PanGeo Redmond Flats SAMPLE ID/TYPE PG-2 S7 PROJECT NO. 17-311.200 SAMPLE DEPTH 25' TECH/TEST DATE SPT 3/6/2018 DATE RECEIVED 3/1/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1) 937.4 Weight Of Sample (gm) 860.8 Wt Dry Soil & Tare (gm) (w2) 860.8 Tare Weight (gm) 15.4 Weight of Tare (gm) (w3) 15.4 (W6) Total Dry Weight (gm) 845.4 Weight of Water (gm) (w4=w1-w2) 76.6 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 845.4 Cumulative Moisture Content (w4/w5)*100 9 Wt Ret (Wt-Tare) (%Retained) % PASS +Tare {(wt ret/w6)*100} (100-%ret) % COBBLES 0.0 12.0" 15.4 0.00 0.00 100.00 cobbles % C GRAVEL 11.7 3.0" 15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 26.2 2.5" coarse gravel % C SAND 21.9 2.0" coarse gravel % M SAND 24.1 1.5" 15.4 0.00 0.00 100.00 coarse gravel % F SAND 10.6 1.0" coarse gravel % FINES 5.5 0.75" 114.2 98.80 11.69 88.31 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375" 201.6 186.20 22.03 77.97 fine gravel D10 (mm) 0.2 #4 335.7 320.29 37.89 62.11 coarse sand D30 (mm) 1 #10 520.7 505.30 59.77 40.23 medium sand D60 (mm) 4.5 #20 medium sand Cu 22.5 #40 724.8 709.40 83.91 16.09 fine sand Cc 1.1 #60 fine sand #100 795.3 779.90 92.25 7.75 fine sand #200 814.0 798.60 94.46 5.54 fines PAN silt/clay 322 DESCRIPTION Gravelly well-graded sand with some silt USCS SW-SM Prepared For: Reviewed By: KW PanGeo 0 10 20 30 40 50 60 70 80 90 100 0.001 0.01 0.1 1 10 100 1000 % P A S S I N G Grain size in millimeters 12" 3" 2" 1" .75" .375" #4 #10 #20 #40 #60 #100 #200 ---PAGE BREAK--- THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE PanGeo Redmond Flats SAMPLE ID/TYPE PG-2 S9 PROJECT NO. 17-311.200 SAMPLE DEPTH 35' TECH/TEST DATE SPT 3/6/2018 DATE RECEIVED 3/1/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1) 489.3 Weight Of Sample (gm) 431.2 Wt Dry Soil & Tare (gm) (w2) 431.2 Tare Weight (gm) 15.4 Weight of Tare (gm) (w3) 15.4 (W6) Total Dry Weight (gm) 415.8 Weight of Water (gm) (w4=w1-w2) 58.1 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 415.8 Cumulative Moisture Content (w4/w5)*100 14 Wt Ret (Wt-Tare) (%Retained) % PASS +Tare {(wt ret/w6)*100} (100-%ret) % COBBLES 0.0 12.0" 15.4 0.00 0.00 100.00 cobbles % C GRAVEL 7.3 3.0" 15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 37.5 2.5" coarse gravel % C SAND 19.8 2.0" coarse gravel % M SAND 21.3 1.5" 15.4 0.00 0.00 100.00 coarse gravel % F SAND 8.8 1.0" coarse gravel % FINES 5.4 0.75" 45.7 30.30 7.29 92.71 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375" 110.0 94.60 22.75 77.25 fine gravel D10 (mm) 0.25 #4 201.6 186.20 44.78 55.22 coarse sand D30 (mm) 1.5 #10 283.9 268.50 64.57 35.43 medium sand D60 (mm) 5.5 #20 medium sand Cu 22.0 #40 372.3 356.90 85.83 14.17 fine sand Cc 1.6 #60 fine sand #100 402.6 387.20 93.12 6.88 fine sand #200 408.7 393.30 94.59 5.41 fines PAN silt/clay 322 DESCRIPTION Gravelly well graded sand with some silt USCS SW-SM Prepared For: Reviewed By: KW PanGeo 0 10 20 30 40 50 60 70 80 90 100 0.001 0.01 0.1 1 10 100 1000 % P A S S I N G Grain size in millimeters 12" 3" 2" 1" .75" .375" #4 #10 #20 #40 #60 #100 #200 ---PAGE BREAK--- THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE PanGeo Redmond Flats SAMPLE ID/TYPE PG-3 S8 PROJECT NO. 17-311.200 SAMPLE DEPTH 30' TECH/TEST DATE SPT 3/6/2018 DATE RECEIVED 3/1/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1) 732.7 Weight Of Sample (gm) 658.3 Wt Dry Soil & Tare (gm) (w2) 658.3 Tare Weight (gm) 15.4 Weight of Tare (gm) (w3) 15.4 (W6) Total Dry Weight (gm) 642.9 Weight of Water (gm) (w4=w1-w2) 74.4 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 642.9 Cumulative Moisture Content (w4/w5)*100 12 Wt Ret (Wt-Tare) (%Retained) % PASS +Tare {(wt ret/w6)*100} (100-%ret) % COBBLES 0.0 12.0" 15.4 0.00 0.00 100.00 cobbles % C GRAVEL 5.5 3.0" 15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 25.5 2.5" coarse gravel % C SAND 22.2 2.0" coarse gravel % M SAND 35.5 1.5" 15.4 0.00 0.00 100.00 coarse gravel % F SAND 7.1 1.0" coarse gravel % FINES 4.1 0.75" 51.0 35.60 5.54 94.46 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375" 117.2 101.80 15.83 84.17 fine gravel D10 (mm) 0.35 #4 215.1 199.70 31.06 68.94 coarse sand D30 (mm) 0.95 #10 357.8 342.40 53.26 46.74 medium sand D60 (mm) 3.4 #20 medium sand Cu 9.7 #40 586.3 570.90 88.80 11.20 fine sand Cc 0.8 #60 fine sand #100 624.2 608.80 94.70 5.30 fine sand #200 631.8 616.40 95.88 4.12 fines PAN silt/clay 322 DESCRIPTION Gravelly poorly graded SAND wth trace silt USCS SP Prepared For: Reviewed By: KW PanGeo 0 10 20 30 40 50 60 70 80 90 100 0.001 0.01 0.1 1 10 100 1000 % P A S S I N G Grain size in millimeters 12" 3" 2" 1" .75" .375" #4 #10 #20 #40 #60 #100 #200 ---PAGE BREAK--- APPENDIX C CREATIVE ENGINEERING OPTIONS, INC. TEST PIT LOGS TP-3 AND TP-4 ---PAGE BREAK--- ~ g C ~ ~ 0 5 10 15 Logged by: DA Date: 612.7/94 Symbols - - - - - GP - - - . - - BOH - - Test Pit No. 3 Soll Description 1-1/4 inch minus crushed rock Dark brown, sandy, fine to coarse GRAVEL, moist, dense, little silt cobbles to 12 inch size - caving from south side of pit lest Pit terminated at 11.5 feet below existing grade. No groundwater encountered during excavation. Logged by: DA Date: 6/27/94 Test Pit No. 4 Soll Description Elevation: 101 feet 6.6 Elevation: 101 feet O GP 5 SP 10 BOH Brown, gravelly fine to coarse SAND, moist, mediumd ense, (possible fill) encountered tank at 3 feet - excavation caving bottom of tank at 6-1/2 feet - hydrocarbon odor Test Pit terminated at 9.5 feet below existing grade. No groundwater seepage encountered during excavation. 4.3 Creative Engineering Options 1NC • A Firm Praak:ng n lhe Geosclences TEST PIT LOG Boston Chicken - Redmond Plate 8 ---PAGE BREAK--- APPENDIX D CONVERSE CONSULTANTS NW SUMMARY MONITORING WELL LOGS ---PAGE BREAK--- I i i I 8 Converse NW Geoloeic & Monitorine Well Construction Loe of 2 Project Number 92-35559-01 I Well Number l MW-1 Sheet 1 Project Redmond Chevron Station #60096388 Location Redmond, Washington Elevation (Top of Well Casing) ) 00 44 Water Level Elev. Hayes Drilling Surface Elevation 5 9 , _ Start Date December 7, 1992 Finish Date December 7, 1992 Drilling Contractor Drilling Method HSA 4 25" TD, 8" OD Depth feet - 5 1-IQ Well Construction flush steel monument concrete surface seal bentonite annular seal riser, 2" ID schedule 40 PVC r- ST - Sampler Type: I 2" OD Split Spoon Sampler (SPT) D Grab Sample 3" OD Ring Lined Sampler (RS) Lab S Blows/ OVM Tests r 6" Readin~ Description C C / / / / / v v / I/ v v 17 v v v 5 13 15 36 26 26 9 15 15 10 17 11 (ppm) 0 0 0 0 asphaltic concrete, 3-inches thick crushed rock, 6-inches thick SANDY GRAVEL; dark brown, gravel fine to coarse, sand fine to coarse, few cobbles; moist no sample recovered, medium dense drilling on large boulder SANDY GRAVEL; brown, gravel fine to coarse, sand fine to coarse, trace to little silt; dense, dry SANDY GRAVEL; dark brown, gravel fine to coarse, sand fine to coarse, trace to little silt; medium dense, dry no sample recovered, medium dense Lab Tests: Logged by: CSB C - Chemical Properties Approved by: DAY (Sample I.D. Number) ~ Water Level (Date of Measurement) Figure No. A-3 ---PAGE BREAK--- I I Project Number I Well Number I MW-1 Sheet 2 of Geoloidc Monitorin2 Well Construction Lo2 Converse NW 92-35559-01 2 Project Redmond Chevron Station #60096388 Location Redmond, Washington Elevation (Top of Well Casing) JOO 44 Surface Elevation Water Level Elev. 81.36 Start Date December 7, 1992 Hayes Drilling Finish Date December 7, 1992 Drilling Contractor Drilling Method HSA 4 25" TD, 8" QD Depth feet ,-20 -25 ~ : Il ~ ~ r:~r: • : : Well Construction filter pack, 10/20 Colorado silica sand well screen, 2" ID schedule 40 PVC, 0.020" slot size 12/17 /92 (19.23') 12/7/92 ATD riveted PVC end cap ST - Sampler Type: I 2" OD Split Spoon Sampler (SPT) 8 Grab Sample 3" OD Ring Lined Sampler (RS) Lab S Blows/ OVM Tests I 6" ~eading Description C ; 50/5" 0 cobble stuck in sampler shoe, no sample recovered / 50/4" no sample recovered, very dense v v v / / / / / / / / 14 14 14 10 14 10 8 10 15 0 0 0 difficult drilling, large boulder no sample recovered, medium dense SANDY GRAVEL; gray-brown, gravel fine to coarse, sand medium to coarse, trace silt; dense, wet SAND; gray-brown, fine to medium, few fine gravel; medium dense, wet / / Bottom of boring at depth 25.5 feet Monitoring well installed to depth 25.0 feet Soil sampler driven using 300-pound hammer falling 30-inches Lab Tests: Logged by: CSB C - Chemical Properties Approved by: DAY (Sample I.D. Number) sz Water Level (Date of Measurement) Figure No. A-3 ---PAGE BREAK--- I I I l , ~ l Converse NW Geolo1?ic Monitorine: Well Construction Loe: Project Number 92-35559-01 I Well Number I MW-2 Sheet 1 of 2 Project Redmond Chevron Station #60096388 Location Redmond, Washington Elevation (Top of Well Casing) 98 37 Surface Elevation _ Water Level Elev. 81.39 Start Date December 7, 1992 Hayes Drilling Drilling Contractor Drilling Method HSA 4 25" TD, 8" OD Depth feet 5 t Well Construction flush steel monument concrete surface seal bentonite annular seal riser, 2" ID schedule 40 PVC ST - Sampler Type: I 2" OD Split Spoon Sampler (SPT) ~ Grab Sample 3" OD Ring Lined Sampler (RS) Lab Tests C Finish Date December 7, 1992 !Blows/ OVM 6" R.eadini Description 7 / / / I / / / ii / / / 2 3 4 9 6 11 7 4 / / 50/0" ii ii ii ii V V V 8 13 23 P- 17 ~ 20/5" / / (ppm) asphaltic concrete, 3-inches thick crushed rock, 3-inches thick 0 0 0 no analytical sample recovered GRAVEL WITH SAND; brown, gravel fine, some sand medium to coarse; loose, moist no analytical sample recovered SANDY GRAVEL; brown, gravel fine to coarse, sand fine to coarse; medium dense, moist no analytical sample recovered SANDY GRAVEL; brown, gravel fine to coarse, sand fine to coarse, trace silt; very dense, moist SANDY GRAVEL; brown, gravel fine to coarse, sand medium to coarse, little silt, few cobble fragments; dense, dry no sample recovered, very dense Lab Tests: Logged by: CSB C - Chemical Properties Approved by: DAY (Sample I.D. Number) ~ Water Level (Date of Measurement) Figure No. A-4 ---PAGE BREAK--- I i Geoloe:ic Monitorine Well Construction Loe: Converse NW Project Number 92-35559-01 Project Redmond Chevron Station #60096388 Elevation (Top of Well Casing) 98 37 Water Level Elev. 81,39 Hayes Drilling Drilling Contractor Drilling Method RSA 4 25" TD, 8" OD Depth feet '""20 >-25 Well Construction filter pack, 10/20 Colorado silica sand 12/17/92 (17.41') 12/7/92 ATD well screen, 2" ID schedule 40 PVC, 0.020" slot size riveted PVC end cap ST - Sampler Type: Lab S Blows/ OVM Tests 6" Readin~ / / / / / / / 17 / I/ I/ I/ I/ ll I/ / 9 24 19 9 18 17 7 50 30 0 0 Lab Tests: I Well Number I MW-2 Sheet 2 of 2 Location Redmond, Washington Surface Elevation _ Start Date December 7, 1992 Finish Date December 7, 1992 Description SANDY GRAVEL; gray-brown, gravel fine to coarse, sand fine to medium, little silt; dense, dry as above, wet SANDY GRAVEL; brown-gray, trace silt; very dense, wet Bottom of boring at depth 24.5 feet Monitoring well installed to depth 24.0 feet Soil sampler driven using 300-pound hammer falling 30-inches Logged by: CSB I 2" OD Split Spoon Sampler (SPT) D Grab Sample C - Chemical Properties Approved by: DAY (Sample I.D. Number) 3" OD Ring Lined Sampler (RS) sz Wate~ Level (Date of Measurement) Figure No. A-4 ---PAGE BREAK--- I i I Converse NW Geoloe:ic Monitorine: Well Construction Loe: Project Number 92-35559-01 I Well Number I MW-3 Sheet 1 of 2 Project Redmond Chevron Station #60096388 Location Redmond, Washington Elevation (Top of Well Casing) 99 04 Surface Elevation _ Water Level Elev. 81.34 Start Date December 8, 1992 Hayes Drilling Drilling Contractor Drilling Method BSA 4 25" TD, 8 11 OD Depth feet - 5 -10 Well Construction flush steel monument concrete surface seal bentonite annular seal 2" ID schedule 40 ST - Sampler Type: I 2" OD Split Spoon Sampler (SPT) 0 Grab Sample kJ 3" OD Ring Lined Sampler (RS) Lab Tests Finish Date December 8, 1992 a1ows/ OVM 6" R.eadin~ Description 7 3 6 v 7 v v 1,1 1,1 / 5 / 50/4" / / / 24 29 30 / 50/6" / / / v / / 18 25 26 (ppm) asphaltic concrete, 4-inches thick crushed rock, 3-inches thick 0 0 large cobbles no analytical sample recovered SANDY GRAVEL; brown, gravel fine to coarse, sand fine to coarse; medium dense, moist GRAVELLY SAND; brown, medium to coarse, gravel fine to coarse, trace fine sand, trace silt; medium dense, moist GRAVELLY SAND; brown, fine to coarse, gravel fine to coarse; very dense, moist no sample recovered, very dense no sample recovered, very dense no sample recovered, dense Lab Tests: Logged by: CSB C - Chemical Properties Approved by: DAY (Sample I.D. Number) ¥ Water Level (Date of Measurement) Figure No. A-5 ---PAGE BREAK--- Geolot?ic Monitorint? Well Construction Lot? Converse NW Project Number 92-35559-01 Project Redmond Chevron Station #60096388 Elevation (Top of Well Casing) 99 04 Water Level Elev. 81.34 Hayes Drilling Drilling Contractor Drilling Method HSA 4 25" TD, 8" on Depth feet -20 ~25 Well Construction filter pack, 10/20 Colorado silica sand 12/17 /92 (17.89') 12/8/92 ATD well screen, 2" ID schedule 40 PVC, 0.020" slot size riveted PVC end cap ST - Sampler Type: Lab S Blows/ OVM Tests r 6" lleading C / 13 / 50/5" / / / 7 50/1" I/ I/ / I/ / / / T / / / / / I/ I/ 37 18 25 28 25 29 0 0 1 Lab Tests: I Well Number I MW-3 Sheet 2 of 2 Location Redmond, Washington Surface Elevation _ Start Date December 8, 1992 Finish Date December 8, 1992 Description GRAVELLY SILTY SAND; brown, fine to coarse, gravel fine to coarse; very dense, moist difficult drilling no sample recovered, very dense SAND; gray, fine to coarse, trace silt; dense, wet as above, increasing silt Bottom of boring at depth 24.5 feet Monitoring well installed to depth 24.0 feet Soil sampler driven using 300-pound hammer falling 30-inches Logged by: CSB I 2" OD Split Spoon Sampler (SPT) C - Chemical Properties Approved by: DAY (Sample I.D. Number) sz Water Level (Date of Measurement) Figure No. A-5 D Grab Sample [2 3" OD Ring Lined Sampler (RS) ---PAGE BREAK--- Converse NW Geoloeic & Monitorine Well Construction Loe Project Number 92-35559-01 Project Redmond Chevron Station #60096388 Elevation (Top of Well Casing) 99 29 Water Level Elev. 81.48 Hayes Drilling Drilling Contractor Drilling Method HSA 4 25" TD, 8" OD Depth feet - 5 -10 ~ Well Construction flush steel monument concrete surface seal bentonite annular seal riser, 2" ID schedule 40 PVC ST - Sampler Type: Lab S Blows/ OVM Tests r 6 11 Readin~ C C / 12 / 16 50/0" ~ / V V / / / / I/ I/ I/ I/ V V V V V V V V V V 7 5 15 19 7 17 21 12 15 15 / 9 / 28 / 50/0" / (ppm) 0 1 Lab Tests: I Well Number I MW-4 Sheet 1 of Location Redmond, Washington Surface Elevation ~9-9-5-6 _ Start Date December 8, 1992 Finish Date December 8, 1992 Description asphaltic concrete, 3-inches thick crushed rock, 2-inches thick no sample recovered, very dense no sample recovered, dense GRAVELLY SAND; dark brown, sand fine to coarse, gravel fine to coarse, trace silt; dense, moist no sample recovered, medium dense SAND WITH GRAVEL; yellow-brown, fine to coarse, gravel fine to coarse, little silt, 2" diameter rock caught in sampler shoe; very dense, moist Logged by: CSB I 2" OD Split Spoon Sampler (SPT) C - Chemical Properties Approved by: DAY ~ Grab Sample (Sample I.D. Number) 3" OD Ring Lined Sampler (RS) Water Level (Date of Measurement) Figure No. A-6 ---PAGE BREAK--- I I Geoloe-ic Monitorine- Well Construction Loe Converse NW Project Number 92-35559-01 Project Redmond Chevron Station #60096388 Elevation (Top of Well Casing) 99 29 Water Level Elev. 81.48 Hayes Drilling Drilling Contractor Drilling Method HSA 4 25" TD, 8" OD Depth feet -20 -25 - i:l . ~Il ~ ?ii . ~ . : . ;JI Well Construction filter pack, 10/20 Colorado silica sand 12/17 /92 (18.08') 12/8/92 ATD well screen, 2" ID schedule 40 PVC, 0.020" slot size riveted PVC end cap ST - Sampler Type: Lab S ~3lows/ OVM Tests I 6" R.eadin~ C I/ 8 V 10 V 18 V V y / 7 / I/ I/ I/ I/ I/ / / / / / / / / / 8 10 15 4 13 15 8 12 20 0 Lab Tests: I Well Number I MW-4 Sheet 2 of 2 Location Redmond, Washington Surface Elevation ~9_9~5_6 _ Start Date December 8, 1992 Finish Date December 8, 1992 Description GRAVELLY SAND; brown, fine to coarse, gravel fine to coarse, little silt; medium dense, moist SANDY GRAVEL WITH SMALL COBBLES; yellow-brown, gravel fine to coarse, sand fine to coarse, 2.5" diameter cobbles, few silt; medium dense, wet no sample recovered, medium dense GRAVELLY SAND; gray, fine to coarse sand, fine to coarse gravel, trace silt; medium dense, wet Bottom of boring at depth 24.5 feet Monitoring well installed to depth 24.0 feet Soil sampler driven using 300-pound hammer falling 30-inches Logged by: CSB I 2" OD Split Spoon Sampler (SPT) C - Chemical Properties Approved by: DAY 8 Grab Sample (Sample I.D. Number) 3" OD Ring Lined Sampler (RS) Water Level (Date of Measurement) Figure No. A-6 ---PAGE BREAK--- I I I I LOG OF BORING NO. B-4 Sheet 1 of 1 Date drilled 12/8/92 V i Driving Weight and Drop 3001h./ 30" drop Elevation (ft) 101 C 0 Ill QJ + .c Ill a. > E a. QJ Ill QJ - Cl lJ.J 100 I 5 95 co " Ill 3 0 IO 4 7 9 o_ .C..c O.e Ill !§en This log is part of the report prepared by: Converse Consultants NW for the named project and should be reaa together with that report for complete interpretation. This summary applies only at the location of this boring and at the time of drilling. Subsurface conditions may differ at other locations and may change at this location with the passage of time. The data presented are a simplification of actual conditions encountered. DESCRIPTION Asphaltic Concrete 3" thick Crushed Rock 2" thick SANDY GRAVEL with some cobbles no analytical sample recovered SANDY GRAVEL; brown, fine to coarse, sand medium to coarse, some cobbles; medium dense, moist Refusal at depth 6.0 feet Hole backfilled with soil cuttings and bentonite chip mixture Soil sampler driven using 300-pound hammer falling 30-inches Redmond Chevron Station #60096388 Redmond, Washington Chevron U.S.A. Products Co. @ Converse Consultants NW Geotechnical Engineering and Applied Earth Sciences C 0 "!ii- Ill QJ 0 QJ "CJ Q. QJ3 Ill .a 0 Cl ~ Ill QJ Ill QJ Ill QJ oc QJ :c 0 u 0 Project No. 92-35559-01 Figure No. A-7 ---PAGE BREAK--- APPENDIX E GENERAL CONSTRUCTION PRACTICES FOR CRITICAL AQUIFER RECHARGE AREAS ---PAGE BREAK--- GENERAL In general, based on our understanding of the planned development, we anticipate potential construction related contaminants may consist of, but not limited to the following: • Fuel, lubricants, hydraulic fluid and coolants, etc., from equipment; • Construction materials, including imported fill, pressure treated wood, concrete washwater and water generated by concrete treatment processes; and • Solvents, paints, and degreasers used during construction. The contractor should maintain best management practices (BMP) in the storage, transfer and use of these materials. The contractor should also be prepared to contain and control a release of these materials if they are spilled on-site. The General Contractor should prepare a Spill Prevention Control and Countermeasure (SPCC) plan to address the potential for a spill. The General Contractor should also designate a person on- site that has appropriate knowledge to be responsible for supervising activities dealing with hazardous materials and who has adequate training to take mitigating actions necessary in the event of a fire or spill. construction should also conform to Redmond Zoning Code (RZC) 21.64.050.D.3.f, Protection Standards During Construction. The following sections of this portion of our study discuss the control of potential construction related contaminants. This information is general in nature and primarily provided for informational purposes. The contractor should be responsible for developing their own spill prevention and response plan based on the planned construction and the actual equipment and materials to be used on-site. Equipment Fuel, Hydraulic Fluids, Lubricants, and Coolants Hazardous materials shall not be accessible to the public while unsupervised (locked storage sheds, locked fencing, locked fuel tanks etc.); Prior to moving equipment onto the site, the contractor should visually inspect their equipment for cracks, excessive corrosion, or other damage that may compromise the integrity of the fuel, hydraulic fluid, or cooling systems. Construction vehicles and stationary equipment leaking hazardous materials should be repaired or removed immediately after a leak is detected. Construction vehicles and stationary equipment leaking hazardous materials need to be removed and repaired immediately. ---PAGE BREAK--- Fuel nozzles should be equipped with automatic shut off valves. Prior to the arrival on-site of any fuel tank truck, all outlets on the vehicle should be examined by the driver for leakage and be tightened, adjusted, or replaced to prevent discharges on-site. Routine maintenance of construction equipment, such as oil changes should be accomplished off- site. If maintenance is conducted on-site, it should be conducted in a manner to gather all discharges such that they can be removed from the site to a suitable disposal location. Refueling of dewatering pumps, generators, and other small portable equipment should be performed using approved containers. If a pickup truck-mounted tank is used to fill equipment fuel tanks, the pump hose should have an automatic shut off valve and the person conducting the refueling should be present during the filling operations. The provisions in the Washington Department of Ecology (WDOE) Stormwater Management Manual for Western Washington BMP S419 Mobile Fueling of Vehicles and Heavy Equipment (WDOE 2012) should also be followed for refueling construction equipment. Construction Materials Concrete Washwater – Concrete washwater is high in suspended solids and has a high pH. Washwater from concrete trucks should not be discharged to the ground. Concrete washwater from the cleanout of trucks, chutes, pumps and hoses should ideally be returned with the concrete trucks for disposal at the batch plant. Alternatively, concrete washwater can be collected on-site using washout tubs or a concrete washout structure constructed on-site. Concrete washwater should be managed in accordance with WDOE BMP C154 Concrete Washout Area of the WDOE Manual (WDOE 2012). Concrete saw cutting and surface preparation processes can generate leachate that contains fine particles and high pH. Runoff or leachate from wet or curing concrete as well as concrete grinding, saw cutting, or exposed aggregate surfacing processes should be collected and disposed of in accordance with WDOE BMP C152 Sawcutting and Surfacing Pollution Prevention (WDOE 2012). Imported Fill – Where imported fill materials are to be used on-site, such as structural fill, gravel backfill around dewatering wells, pipe bedding, or other natural aggregate materials, the fill should consist of clean fill from a commercial source. ---PAGE BREAK--- Storage of Materials The contractor should store fuel, petroleum products and other hazardous materials in a safe location and within a secondary containment structure or bund. Secondary containment systems should consist of a manufactured containment system or site constructed bermed area lined with an impervious material to provide a minimum containment volume of 110 percent of the largest storage container within the storage area. Flammable and combustible liquid transferred from tanks to construction vehicles and stationary equipment should be performed in compliance with the Redmond Fire Code (Chapter 15.06 RMC). If a spill occurs in the containment structure, the accumulated wastewater should be drawn off and pumped to a storage container for proper disposal. The contractor should visually inspect hazardous material storage containers on a daily basis and whenever the storage tanks are refilled. Visible leaks in tanks or barrels should be repaired as soon as possible. If concrete or cement will be stored on-site in bulk, it should be stored on pallets and within a secondary containment structure. Storage and containment of material should be performed in accordance with the WDOE Manual BMP C153 Delivery, Storage and Containment (WDOE 2012). Construction Spill Kit In the event of a spill, the release should be contained and cleaned up as soon as possible. The contractor should have a spill kit on-site with a sufficient quantity of absorbent and barrier materials to adequately contain and recover spills of fuel and lubricants for the piece of equipment with the largest volume of fuel along with any associated lubricants and coolants. These materials may include but are not limited to the following: • Drip pans; • Buckets; • Straw bales; • Oil absorbent socks and pads; • Absorbent clay; • Sawdust; • Drying agents; • Plastic sheeting; and • Other materials as needed. ---PAGE BREAK--- The contractor also should have available on-site an assortment of hand tools to aid in the placement of absorbent materials and the containment and collection of a spill. ---PAGE BREAK--- APPENDIX F GENERAL BEST MANAGEMENT PRACTICES FOR CRITICAL AQUIFER RECHARGE AREAS ---PAGE BREAK--- GENERAL The site will be developed with a mixed-use development consisting of retail and residential uses. These tenants are not expected to generate hazardous materials. We anticipate potential building use contaminants may consist of, but not limited to the following: • Fuel, lubricants, hydraulic fluid, batteries and coolants from vehicles. • Household cleaning products. Locations where significant spills and leaks could potentially occur at the facility and that could contribute pollutants to stormwater, surface water and groundwater include: • Vehicle storage areas • Liquid storage area The building users should maintain best management practices (BMP) in the storage, transfer and use of these materials. The BMP’s should be implemented in recognition that preventing pollutants from coming into contact with stormwater and groundwater is generally more effective, and less costly than trying to remove pollutants from stormwater and that using control measures in combination is more effective than using control measures in isolation for minimizing pollutants. BMP’s for Good Housekeeping Description of Pollutant Sources Pollutant sources include cleaning supplies, vehicle fluids, lubricants stored in containers, and hydraulic fluids for vehicle lifts. Source Control BMP’s • Unloading of materials, cleaning supplies, and products should be confined to designated areas. • Materials, cleaning supplies and products should be moved inside or to a covered storage area on the same day as they are received at the facility. • Unless essential for use, materials should not be transferred to containers other than those supplied by the manufacturer. • Approved mixing or transfer of material should be performed inside a building or under a covered area. • Containers should store indoors or an appropriate cabinet. ---PAGE BREAK--- • Used oil, antifreeze, and hazardous waste (if any) should be collected and placed in appropriately labeled bulk storage containers. These containers should be emptied and their contents shipped off site for disposal or recycling on a regular basis. • The condition of drums and tanks containing waste and virgin products should be inspected regularly and the results documented. • All storage and shop areas should be inspected and cleaned on a weekly basis and the maintenance supervisor notified if issues are found and that need to be taken care of immediately. • Structural BMPs (curbs, gutters, retention basin, etc.) should inspected on an annual basis and after each major storm event. • Provide signage clearly designating storage areas and listing the maximum container volume to be stored in the area. • Dumpster(s) should be placed in a designated area with curbs. • Dumpster lids should remain closed when not in use. • Spills should be cleaned up using dry cleanup methods. • Drip pans should be placed under vehicles or equipment needing service. Materials and equipment necessary for spill cleanup should be kept on-site. The spill kit should include at least the following: • Broom • Dust pan • Mop bucket • Gloves • Goggles • Dust masks • Absorbent clay • Labeled bags • Absorbent socks • Plastic and metal containers Spill kits should be inspected and restocked on a quarterly basis. The procedures for preventing and responding to spills and leaks are evaluated annually and updated as necessary and appropriate. BMP’s for Vehicles and Equipment Description of Pollutant Sources ---PAGE BREAK--- Pollutant sources include parts/vehicle cleaning, spills/leaks of fuel and other liquids, replacement of liquids, outdoor storage of vehicle parts, batteries and liquids, and vehicle parking. Source Control BMPs • Inspect all incoming vehicles, parts, and equipment for leaks. • Use drip pans or containers under parts or vehicles or hydraulic lifts that drip or that are likely to drip liquids. • Drip pans should be inspected regularly and emptied as needed. • Remove batteries and liquids from vehicles and equipment in designated areas designed to contain spills and leaks. • Store used or damaged batteries in a designated area with covered secondary containment designed to prevent run-on and runoff. • Empty oil and fuel filters before disposal. Provide for proper disposal of waste oil and fuel. • Do not pour/convey washwater, liquid waste, or other pollutants into storm drains or to surface water. Check with the local sanitary sewer authority for approval to discharge to a sanitary sewer. • Building floor drains should not be connected to storm drains, surface water sources, or areas where surface water can infiltrate. • Vehicle fluids, cleaning supplies, and chemicals should be properly stored in accordance with the appropriate material safety data sheets (MSDS). • Inspect all BMPs regularly, particularly after a significant storm event. Identify and correct deficiencies to confirm that the BMPs are functioning as intended. BMPs for Washing Vehicles Description of Pollutant Sources ---PAGE BREAK--- Vehicles that may be cleaned using low or high pressure water or steam. Washwater from cleaning activities can contain oil and grease, suspended solids, heavy metals, soluble organics, soaps, and detergents that can contaminate stormwater and surface water. Source Control BMPs: • Washing of vehicles, parts, and equipment should be performed in a designated area. BMPs for Parking Lots Description of Pollutant Sources Parking lots can be sources of toxic hydrocarbons and other organic compounds, oils and greases, metals, and suspended solids caused by the parked vehicles. Source control BMPs: • If washing of a parking lot is conducted, discharge the washwater to a sanitary sewer, if allowed by the local sewer authority, or other approved wastewater treatment system, or collect the washwater for off-site disposal. • Do not hose down parking lots to a storm drain, surface water sources, or areas where surface water can infiltrate. • Outdoor parking lots, storage areas, and driveways, should be dry swept or vacuum swept regularly to collect dirt, waste, and debris.