No preview available
HomeMy WebLinkAboutRS_Geotch Report_Earlington_Shoring_171013_v1associated earth sciences incorporated Associated Earth Sciences, Inc. 911 5th Avenue Kirkland, WA 98033 P (425) 827 7701 F (425) 827 5424 Geotechnical Engineering Feasibility Report MINTER PROPERTY Renton, Washington Prepared For: BLUE FERN DEVELOPMENT January 18, 2017 Project No. KE160641A January 18, 2017 Project No. KE160641A Blue Fern Development 11232 120th Avenue NE Kirkland, Washington 98033 Attention: Mr. John Groves associa ted earth sciences incorporate d Subject: Geotechnical Engineering Feasibility Report Minter Property South 132nd Street and Renton Avenue South Renton, Washington Dear Mr. Groves: We are pleased to present the enclosed copies of the referenced report. This report summarizes the results of our geotechnical engineering feasibility study and offers preliminary recommendations for the design and development of the proposed project. This report is based on two site concept sketches you provided, and our knowledge of the site gained through completion of a preliminary geotechnical engineering study of the site for another client in 2007. The recommendations presented in this report are based on subsurface explorations completed onsite by Associated Earth Sciences, Inc. in 2007. We recommend that we be allowed to review project plans when they are developed and update our recommendations as needed. We have enjoyed working with you on this study and are confident that the recommendations presented in this report will aid in the successful completion of your project. If you should have any questions or if we can be of additional help to you, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington �4N __ \ __ _ Kurt D. Merriman, P.E. Senior Principal Engineer KDM/ld -KE160641A3 -Projects\20160641\KE\WP Kirkland Office I 911 Fifth Avenue I Kirkland, WA 98033 P I 425.827.7701 FI 425.827.5424 Everett Office I 2911 ½ Hewitt Avenue, Suite 2 I Everett, WA 98201 P I 425.259.0522 F I 425.827.5424 Tacoma Office I 1552 Commerce Street, Suite 102 I Tacoma, WA 98402 P I 253.722.2992 F I 253.722.2993 www.aesgeo.com GEOTECHNICAL ENGINEERING FEASIBILITY REPORT MINTER PROPERTY Renton, Washington Prepared for: Blue Fern Development 11232 120th Avenue NE Kirkland, Washington 98033 Prepared by: Associated Earth Sciences, Inc. 911 5th Avenue Kirkland, Washington 98033 425-827-7701 Fax: 425-827-5424 January 18, 2017 Project No. KE160641A Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Project and Site Conditions January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 1 I. PROJECT AND SITE CONDITIONS 1.0 INTRODUCTION This report presents the results of our geotechnical engineering feasibility study for the proposed new residential development. The site location is shown on the “Vicinity Map,” Figure 1. The approximate locations of explorations completed for our 2007 study are shown on the “Site and Exploration Plan,” Figure 2. This report is based on two previously referenced site concept drawings, and our knowledge of the site gained through completion of a preliminary geotechnical engineering study of the site for another client in 2007. Interpretive exploration logs and associated laboratory test results completed for our 2007 study are included in the Appendix. The conclusions and recommendations contained in this report should be reviewed and modified, or verified, to reflect final plans when they are developed. When our 2007 geotechnical engineering report for the site was prepared, the site was under King County jurisdiction. The site was annexed by Renton in 2009, and this annexation means that geotechnical critical areas considerations for the project are substantially different than in 2007. Geotechnical critical areas are discussed in further detail later in this report. 1.1 Purpose and Scope The purpose of this study was to provide subsurface data to be used in the preliminary design of the project. Our study included a review of selected geologic literature, a review of subsurface data from our 2007 exploration, and performing geologic studies to assess the type, thickness, distribution, and physical properties of the subsurface sediments and shallow ground water. Geotechnical engineering studies were completed to formulate preliminary recommendations for site preparation, site grading, construction, and drainage. Storm water infiltration feasibility recommendations were also formulated for the proposed project. This report summarizes our previous fieldwork completed for our 2007 study and offers recommendations for development based on our present understanding of the project. We recommend that we be allowed to review project plans prior to construction to verify that our geotechnical engineering recommendations have been correctly interpreted and incorporated into the design. 1.2 Authorization This report has been prepared for the exclusive use of Blue Fern Development and its agents for specific application to this project. Our work was performed in accordance with our scope of work and cost proposal dated December 1, 2016. We were authorized to proceed by means of a signed proposal. Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Project and Site Conditions January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 2 Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering and engineering geology practices in effect in this area at the time our report was prepared. No other warranty, express or implied, is made. 2.0 PROJECT AND SITE DESCRIPTION This report was completed with an understanding of the project based on two previously referenced site concept sketches prepared by Contour Engineering LLC, and our knowledge of the site gained through completion of a preliminary geotechnical engineering study of the site for another client in 2007. The project site is irregularly shaped in plan view, and includes several parcels with a total area of approximately 4 acres. The site slopes down to the south with moderate inclinations and overall vertical relief of approximately 70 feet. At the time of our subsurface exploration program, the site was developed with a commercial plant nursery that included a sales building, several greenhouses, and a detached home. We understand that a home previously existed on the east part of the site, and the remnants of that home were demolished after it burned. Gravel driveway and parking areas provided access to various parts of the site, and mature trees were present in an area on the east part of the site. The site appeared to have been graded to its current configuration that generally includes relatively flatter terraces separated by slopes. We anticipate that these flatter terraces were created by cutting on the upslope side and filling on the downslope side. This theory is supported by the subsurface conditions observed in our exploration pits completed as part of our 2007 study of the site. The site includes slopes that meet geometric criteria for treatment as Sensitive Slopes as defined in Renton Municipal Code (RMC) 4-3-050. To support any development proposal, a topographic survey which explicitly depicts Sensitive Slopes will be required. The critical slope plan should be prepared by the project surveyor. The development proposal will also require a detailed geotechnical engineering report that is specific to the proposed site grading plan and critical areas plan. It should be noted that RMC requires a 15-foot buffer around Protected Slopes. RMC provides a mechanism for reducing or eliminating the Protected Slope buffer. Such reductions require a detailed geotechnical report. The City will also hire a third party geotechnical consultant at Blue Fern Development’s expense to review our work. Current site concept drawings call for construction of 65 new single-family residential lots, new paved access roads, and a storm water management area identified on the east part of the site. No site grading or retaining walls are depicted on the concept drawings. We understand that storm water infiltration is desired on this site if feasible. This report contains a feasibility level infiltration discussion. Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Project and Site Conditions January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 3 3.0 SUBSURFACE EXPLORATION Our previous 2007 field study of the site included excavation of nine exploration pits. The exploration locations were measured in the field from known site features, and the locations depicted on Figure 2 are taken from a site concept sketch provided to us by Blue Fern Development. Interpretive exploration logs from our 2007 study are presented in the Appendix. The various types of sediments, as well as the depths where characteristics of the sediments changed, are indicated on the exploration logs presented in the Appendix. The depths indicated on the logs where conditions changed may represent gradational variations between sediment types in the field. The conclusions and recommendations presented in this report are based on the explorations completed for our 2007 study of the site. Because of the nature of exploratory work below ground, extrapolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may sometimes be present due to the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of any variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this report and make appropriate changes. 3.1 Exploration Pits The exploration pits were excavated using a track-mounted excavator. The pits permitted direct, visual observation of subsurface conditions. Materials encountered in the exploration pits were studied and classified in the field by an engineering geologist from our firm. All exploration pits were backfilled immediately after examination and logging. Selected samples were then transported to our laboratory for further visual classification and testing, as necessary. 4.0 SUBSURFACE CONDITIONS Subsurface conditions at the project site were inferred from the field explorations accomplished for our 2007 study, visual reconnaissance of the site, and review of selected geologic literature. The general distribution of geologic units is shown on the field logs. The explorations generally encountered medium dense silty to clean sand, interpreted as recessional outwash, overlying medium dense grading to very dense silty sand with gravel and cobbles, interpreted as lodgement till. Existing fill was observed in six exploration pits to depths of up to approximately 9 feet. We reviewed published geologic mapping on Pacific Northwest Center for Geologic Mapping Studies, 2006, Geologic Map of King County, Washington, D.B. Booth and A.P. Wisher, compilers, scale 1:100,000. Our interpretation of Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Project and Site Conditions January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 4 geologic conditions at the site closely corresponds to those shown on the referenced geologic map. The project vicinity has outcrops of sandstone bedrock of the Tukwila Formation. Although no bedrock was encountered in our explorations, it is possible that bedrock may be encountered below the lodgement till in deeper site utility excavations. Typically, the upper portion of the bedrock is weathered and can be removed with typical earthwork excavation equipment. 4.1 Stratigraphy Topsoil/Gravel Surfacing We observed a surficial layer of topsoil or gravel surfacing at several of the exploration pit locations. The observed surface materials and thicknesses are noted on the attached exploration logs. Fill Fill soils (those not naturally placed) were encountered in six exploration pits to depths of up to approximately 9 feet below the existing ground surface. Most of the existing fill appeared to consist of sand with silt and gravel that was similar in gradation to the native site soils, and likely originated from excavations onsite. Most of the fill contained little or no debris or other deleterious materials that would prevent its reuse in structural fill applications. One notable exception was exploration pit EP-6, which contained existing fill that included asphalt, concrete rubble, and wood waste. Existing fill is expected to be silty, moisture-sensitive, and above optimum moisture content for compaction purposes. It appears that with the exception of fill observed in EP-6, existing fill materials would be available for reuse in structural fill applications if they are moisture-conditioned during dry site and weather conditions and are free of excessively organic material. Existing fill is not recommended for support of foundations, and will require remedial preparation in areas that will support paving and utilities. Vashon Recessional Outwash Deposits Sediments interpreted to be representative of Vashon recessional outwash were encountered in three of the exploration pits. The Vashon recessional outwash sediments generally consisted of loose grading to medium dense, fine to medium sand with variable silt and gravel content. Recessional outwash was deposited by rivers flowing from the base of northward- retreating continental glaciers near the end of the Vashon Stade of the Fraser Glaciation, approximately 13,000 years ago. Recessional outwash deposits are typically somewhat loose, but are suitable for support of foundations, floor slabs, and paving, with proper preparation. Excavated recessional outwash sediments are expected to be moisture-sensitive and above optimum moisture content for reuse in structural fill applications. Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Project and Site Conditions January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 5 Vashon Lodgement Till Six of our exploration pits encountered medium dense grading to very dense silty sand with gravel and cobbles, interpreted as Vashon lodgement till. The lodgement till observed in our explorations graded from medium dense and brown in the weathered zone near the surface to dense to very dense and gray at depth. Lodgement till was deposited at the base of an active continental glacier and was subsequently compacted by the weight of the overlying glacial ice. Lodgement till typically possesses high-strength and low-compressibility attributes that are favorable for support of foundations, floor slabs, and paving, with proper preparation. Lodgement till is silty and highly moisture-sensitive. In the presence of moisture contents above the optimum moisture content for compaction purposes, lodgement till can be easily disturbed by vehicles and earthwork equipment. Careful management of moisture-sensitive soils, as recommended in this report, will be needed to reduce the potential for disturbance of wet lodgement till soils and costs associated with repairing disturbed soils. 4.2 Hydrology Ground water seepage was encountered in six of our exploration pits. The observed seepage occurred in recessional outwash and fill sediments, and within more-permeable granular layers within the lodgement till. Actual depths of ground water observed in each exploration pit are depicted on the logs in the Appendix. Observed ground water seepage was interpreted to represent perched ground water. Perched ground water occurs where downward infiltration of surface water is impeded by low-permeability soil layers such as lodgement till, and the ground water migrates laterally and generally downslope. Ground water conditions should be expected to vary in response to changes in season, weather, on- and off-site land use, and other factors. 4.3 Laboratory Test Results Laboratory testing was completed on selected soil samples from our 2007 explorations. Laboratory testing results are included in the Appendix. Moisture content was tested in accordance with American Society for Testing and Materials (ASTM) D-2216. Table 1 summarizes the moisture content laboratory results. Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Project and Site Conditions January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 6 Table 1 Exploration Pit Approximate Ground Surface Elevation (feet) Depth to Bearing Soil (feet) Approximate Bearing Soil Elevation (feet) Depth Tested (feet) Existing Moisture Content (percent) EP-1 242 8.5 233.5 8.5 17.8* EP-1 14 18.0 * EP-2 246 0.5 245.5 3 15.6* EP-2 7 13.2* EP-3 255 8 247 3 12.5* EP-3 5 13.5* EP-3 9 11.0* EP-4 264 5 259 8 11.2* EP-4 12 17.5* EP-5 264 6 258 10 12.7* EP-6 295 9 286 EP-7 275 0 275 5 17.0* EP-8 247 4.5 242.5 8 14.6* EP-9 241 2 239 4 20.6* EP-9 7 24.9* * Samples above optimum moisture content. The maximum dry density of one soil sample was determined using the modified Proctor test procedure (ASTM D-1557). The results are as follows in Table 2. Table 2 Sample Location Maximum Dry Density (pcf)(1) Optimum Moisture Content (percent)(2) EP-2 @ 4’ 132.0 8.0 (1) pcf = pounds per cubic foot. (2) Reported results are not corrected for gravel content. 4.4 Infiltration Feasibility Most of the shallow site soils are either dense and impermeable or saturated, and therefore storm water infiltration using shallow strategies does not appear feasible. One exploration pit previously completed near the southeast site corner (EP-1) encountered unsaturated recessional outwash that could potentially serve as an infiltration receptor if it is laterally and vertically extensive and unsaturated, which has not been proven by existing exploration data. Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Project and Site Conditions January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 7 The concern for shallow infiltration at this site is not limited to whether or not ground water is able to infiltrate into the subsurface soils, but also the potential adverse effects that additional ground water would have on slope stability of site slopes. Another adverse effect that must be considered is the potential emergence of infiltrated ground water onto neighboring properties. It appears unlikely, in our opinion, that further geotechnical work would support the use of storm water infiltration for the project using conventional shallow infiltration strategies. We are available to discuss the potential for infiltration strategies further upon request. Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Geologic Hazards and Mitigations January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 8 II. GEOLOGIC HAZARDS AND MITIGATIONS The following discussion of potential geologic hazards is based on the geologic, slope, and shallow ground water conditions, as observed and discussed herein. 5.0 LANDSLIDE HAZARDS AND MITIGATIONS Geotechnical critical areas are discussed in RMC Section 4.3.050. Based on site geometry and City maps, it appears likely that the site contains slopes that meet geometric criteria for treatment as Sensitive Slopes, and Low, Medium, and High Landslide Hazard Areas. Most of these designations impose additional analysis requirements to be met in support of any development proposal but do not automatically impose limitations that would affect project layout. 6.0 SEISMIC HAZARDS AND MITIGATIONS Earthquakes occur regularly in the Puget Lowland. Most of these events are small and are usually not felt by humans. However, large earthquakes do occur, as evidenced by the 2001, 6.8-magnitude event; the 1965, 6.5-magnitude event; and the 1949, 7.2-magnitude event. The 1949 earthquake appears to have been the largest in this region during recorded history and was centered in the Olympia area. Evaluation of earthquake return rates indicates that an earthquake of the magnitude between 5.5 and 6.0 is likely within a given 20-year period. Generally, there are four types of potential geologic hazards associated with large seismic events: 1) surficial ground rupture, 2) seismically induced landslides, 3) liquefaction, and 4) ground motion. The potential for each of these hazards to adversely impact the proposed project is discussed below. 6.1 Surficial Ground Rupture The nearest known fault zone to the project site is the Seattle Fault Zone, located approximately one mile north of the site. Studies by the United States Geological Survey (USGS) (e.g., Johnson et al., 1994, Origin and Evolution of the Seattle Fault and Seattle Basin, Washington, Geology, v. 22, p.71-74 and Johnson et al., 1999, Active Tectonics of the Seattle Fault and Central Puget Sound Washington - Implications for Earthquake Hazards, Geological Society of America Bulletin, July 1999, v. 111, n. 7, p. 1042-1053) have provided evidence of surficial ground rupture along a northern splay of the Seattle Fault. According to the USGS studies, the latest movement of this fault was about 1,100 years ago when about 20 feet of surficial displacement took place. This displacement can presently be seen in the form of raised, wave-cut beach terraces along Alki Point in West Seattle and Restoration Point at the Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Geologic Hazards and Mitigations January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 9 south end of Bainbridge Island. The recurrence interval of movement along this fault system is unknown, although it is hypothesized to be several thousand years. Due to the suspected long recurrence interval and the distance from the site to the currently recognized limits of the Seattle Fault Zone, the potential for surficial ground rupture is considered to be low during the expected life of the structures. 6.2 Seismically Induced Landslides A final geotechnical report for the project will include slope stability analyses completed under static and design level seismic conditions. Seismic slope stability modeling has not been completed at this time. 6.3 Liquefaction Liquefaction is a temporary loss in soil shear strength that can occur when loose granular soils below the ground water table are exposed to cyclic accelerations, such as those that occur during earthquakes. Our explorations suggest that the potential risk of damage to the proposed development by liquefaction is low, due to the dense glacially consolidated lodgement till sediments observed at shallow depths in most areas. 6.4 Ground Motion/Seismic Site Class (2015 International Building Code) Structural design of the buildings should follow 2015 International Building Code (IBC) standards. We recommend that the project be designed in accordance with Site Class “D” as defined in IBC Table 20.3-1 of American Society of Civil Engineers (ASCE) 7 – Minimum Design Loads for Buildings and Other Structures. 6.5 Erosion Control The site contains areas that meet City of Renton criteria for treatment as Erosion Hazard Areas. Project plans should include implementation of temporary erosion controls in accordance with local standards of practice. Control methods should include limiting earthwork to seasonally drier periods, typically April 1 to October 31, use of perimeter silt fences, and straw mulch in exposed areas. Removal of existing vegetation should be limited to those areas that are required to construct the project, and new landscaping and vegetation with equivalent erosion mitigation potential should be established as soon as possible after grading is complete. During construction, surface water should be collected as close as possible to the source to minimize silt entrainment that could require treatment or detention prior to discharge. Timely implementation of permanent drainage control measures should also be a part of the project plans, and will help reduce erosion and generation of silty surface water onsite. Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Preliminary Design Recommendations January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 10 III. PRELIMINARY DESIGN RECOMMENDATIONS 7.0 INTRODUCTION Our exploration indicates that, from a geotechnical standpoint, the proposed project is feasible provided the recommendations contained herein are properly followed. The bearing stratum is sufficiently shallow that conventional shallow foundations should perform well with proper subgrade preparation. Existing fill was observed in existing terraces onsite, and will require special preparation for construction of new structures. Ground water seepage was encountered in several of our explorations and is expected to be encountered during construction in significant excavations. Ground water was observed in our exploration pits on the south part of the site at lower elevations, and therefore may be a factor in design of the storm water management system. 8.0 SITE PREPARATION Site preparation should include removal of all grass, trees, brush, debris, and any other deleterious materials from structural areas. All existing fill around structures that have been demolished should be removed. If any heating oil storage tanks or other similar structures are discovered, they should be decommissioned and removed in accordance with applicable Washington State Department of Ecology regulations. Existing septic systems should be decommissioned in accordance with King County Health Department regulations and removed from below planned structures. Any depressions below planned final grades caused by demolition activities should be backfilled with structural fill, as discussed under the “Structural Fill” section of this report. The existing topsoil, grass, and shrubs should be removed from areas where new buildings, paving, or other structures are planned. The actual observed in-place depth of topsoil and sod at the exploration locations is presented on the exploration logs in the Appendix. After stripping, remaining roots and stumps should be removed from structural areas. All soils disturbed by stripping and grubbing operations should be recompacted as described below for structural fill. Once excavation to subgrade elevation is complete, existing fill should be addressed. Below building foundation areas, we recommend that existing fill be removed to expose underlying undisturbed native materials that are suitable for structural support. The resulting surface should be proof-rolled with a loaded dump truck or other suitable equipment. Any soft, loose, yielding areas or areas exposing existing fill should be excavated to expose suitable bearing soils. The subgrade should then be compacted to at least 95 percent of the modified Proctor maximum dry density, as determined by the ASTM D-1557 test procedure. Structural fill can then be placed to achieve desired grades, if needed. In areas of planned paving, similar Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Preliminary Design Recommendations January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 11 preparation methods should be used; however, excavation need only extend 2 feet below planned paving subgrade elevation. We recommend that where existing fills underlie planned grade-sensitive utilities, such as gravity sewer lines, that the upper 2 feet of material below the pipe be prepared as described above for paving subgrades. 8.1 Cutoff Drains Grading challenges caused by ground water seepage would be significantly reduced if a cutoff drain was installed on the upslope side of the project prior to starting other earthwork. Ideally, the cutoff drain would be installed as early as possible and would cover the entire northern site boundary. It may be beneficial if the drain also extended along the west property boundary as far south as any planned substantial excavations in that area. Drains should consist of trenches at least 18 inches wide, excavated to a depth of at least 1 foot into dense silty soils underlying any recessional outwash or fill. The trenches should be provided with a 6-inch, perforated drainpipe, graded to drain to a suitable discharge, and backfilled to within 1 foot of the ground surface by washed drain rock. We recommend that cleanouts be provided at appropriate intervals to allow future maintenance. 8.2 Temporary Cut Slopes In our opinion, stable construction slopes should be the responsibility of the contractor and should be determined during construction. For estimating purposes, however, temporary, unsupported cut slopes can be planned at 1.5H:1V (Horizontal:Vertical) in the weathered till, fill, and recessional outwash deposits and at 1H:1V in dense, unweathered lodgement till. These slope angles are for areas where ground water seepage is not encountered, and assume that surface water is not allowed to flow across the temporary slope faces. If ground or surface water is present when the temporary excavation slopes are exposed, flatter slope angles or temporary shoring will be required. As is typical with earthwork operations, some sloughing and raveling may occur, and cut slopes may have to be adjusted in the field. In addition, WISHA/OSHA regulations should be followed at all times. 8.3 Site Disturbance Most of the on-site soils contain fine-grained material, which makes them moisture-sensitive and subject to disturbance when wet. The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened. If disturbance occurs, the softened soils should be removed and the area brought to grade with structural fill. 8.4 Winter Construction Due to the silt content and existing moisture content of the site soils, it will be nearly impossible to use the existing soil as structural fill unless the fill can be placed during favorable Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Preliminary Design Recommendations January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 12 dry weather conditions. If construction takes place in winter, drying is not expected to be feasible, and we anticipate that all of the excavated on-site materials will be unsuitable for structural fill applications. Even during dry weather, site soils excavated for installation of buried utilities might not be suitable for utility backfill under paving or other structures. We recommend budgeting for backfill of buried utility trenches in structural areas with imported select structural fill. For summer construction, significant, but unavoidable effort may be needed to scarify, aerate, and dry site soils that are above optimum moisture content to reduce moisture content prior to compaction in structural fill applications. The effort required to dry site soils would be reduced (but not eliminated) if the cutoff drain is installed, as recommended above. Care should be taken to seal all earthwork areas during mass grading at the end of each workday by grading all surfaces to drain and sealing them with a smooth-drum roller. Stockpiled soils that will be reused in structural fill applications should be covered whenever rain is possible. If winter construction is expected, crushed rock fill could be used to provide construction staging areas. The stripped subgrade should be observed by the geotechnical engineer, and should then be covered with a geotextile fabric, such as Mirafi 500X or equivalent. Once the fabric is placed, we recommend using a crushed rock fill layer at least 10 inches thick in areas where construction equipment will be used. 9.0 STRUCTURAL FILL All references to structural fill in this report refer to subgrade preparation, fill type, placement, and compaction of materials, as discussed in this section. If a percentage of compaction is specified under another section of this report, the value given in that section should be used. For backfill of buried utilities in the right-of-way, the backfill should be placed and compacted in accordance with the City of Renton codes and standards. After stripping, planned excavation, and any required overexcavation have been performed to the satisfaction of the geotechnical engineer/engineering geologist, the surface of the exposed ground should be recompacted to a firm and unyielding condition. If the subgrade contains too much moisture, adequate recompaction may be difficult or impossible to obtain, and should probably not be attempted. In lieu of recompaction, the area to receive fill should be blanketed with washed rock or quarry spalls to act as a capillary break between the new fill and the wet subgrade. Where the exposed ground remains soft and further overexcavation is impractical, placement of an engineering stabilization fabric may be necessary to prevent contamination of the free-draining layer by silt migration from below. After recompaction of the exposed ground is tested and approved, or a free-draining rock course is laid, structural fill may be placed to attain desired grades. Structural fill is defined as non-organic soil, acceptable to the geotechnical engineer, placed in maximum 8-inch loose lifts, with each lift being compacted to 95 percent of ASTM D-1557. The top of the compacted fill Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Preliminary Design Recommendations January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 13 should extend horizontally outward a minimum distance of 3 feet beyond the locations of the perimeter footings or roadway edges before sloping down at a maximum angle of 2H:1V. The contractor should note that any proposed fill soils must be evaluated by AESI prior to their use in fills. This would require that we have a sample of the material at least 72 hours in advance to perform a Proctor test and determine its field compaction standard. Soils in which the amount of fine-grained material (smaller than the No. 200 sieve) is greater than approximately 5 percent (measured on the minus No. 4 sieve size) should be considered moisture-sensitive. The existing fill and lodgement till soils are estimated to contain substantially more than 5 percent fine-grained material. Use of moisture-sensitive soil in structural fills should be limited to favorable dry weather and dry subgrade conditions. Construction equipment traversing the site when the soils are wet can cause considerable disturbance. If fill is placed during wet weather or if proper compaction cannot be obtained, a select, import material consisting of a clean, free-draining gravel and/or sand should be used. Free-draining fill consists of non-organic soil, with the amount of fine-grained material limited to 5 percent by weight when measured on the minus No. 4 sieve fraction, and at least 25 percent retained on the No. 4 sieve. In order to reuse excavated on-site soils in structural fill applications, it will be necessary to moisture-condition wet site soils by aeration and drying during favorable dry weather conditions. Alternatives to drying site soils include using imported granular soils suitable for use in structural fill, or treating wet soils with Portland cement. 10.0 FOUNDATIONS Spread footings may be used for building support when they are founded on approved structural fill placed as described above, or on the glacial soils that are prepared as recommended in this report. Based on our observations, suitable foundation bearing soils are expected approximately up to 9 feet below the existing ground surface within the building lots. Existing fill should be removed and replaced with structural fill, as described in the “Site Preparation” section of this report. For residential structures, footings may be designed for an allowable foundation soil bearing pressure of 3,000 pounds per square foot (psf), including both dead and live loads. An increase of one-third may be used for short-term wind or seismic loading. Perimeter footings should be buried at least 18 inches into the surrounding soil for frost protection. However, all foundations must penetrate to the prescribed bearing strata, and no foundations should be constructed in or above loose, organic, or existing fill soils. Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Preliminary Design Recommendations January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 14 If a concrete storm water detention vault is proposed, it may be feasible to design vault foundations using higher foundation soil bearing pressures than those presented above for new homes. If a storm water vault is planned we should be allowed to offer situation-specific geotechnical engineering design recommendations. Anticipated settlement of footings founded, as recommended, should be on the order of ¾ inch or less, with differential settlement of ½ inch or less. However, disturbed material not removed from footing trenches prior to footing placement could result in increased settlements. All footing areas should be inspected by AESI prior to placing concrete to verify that the foundation subgrades are undisturbed and construction conforms to the recommendations contained in this report. Such inspections may be required by the City of Renton. Perimeter footing drains should be provided, as discussed under the “Drainage Considerations” section of this report. It should be noted that the area bounded by lines extending downward at 1H:1V from any footing must not intersect another footing or intersect a filled area that has not been compacted to at least 95 percent of ASTM D-1557. In addition, a 1.5H:1V line extending down and away from any footing must not daylight because sloughing or raveling may eventually undermine the footing. Thus, footings should not be placed near the edges of steps or cuts in the bearing soils. 11.0 FLOOR SUPPORT If crawl-space floors are used, an impervious moisture barrier should be provided above the soil surface within the crawl space. Slab-on-grade floors may be used over medium dense to very dense native soils, or over structural fill placed as recommended in the “Site Preparation” and “Structural Fill” sections of this report. Slab-on-grade floors should be cast atop a minimum of 4 inches of washed pea gravel or washed crushed “chip” rock with less than 3 percent passing the U.S. No. 200 sieve to act as a capillary break. The floors should also be protected from dampness by covering the capillary break layer with an impervious moisture barrier at least 10 mils in thickness. 12.0 DRAINAGE CONSIDERATIONS All footings, basement walls, and retaining walls should be provided with a drain at the footing elevation. Drains should consist of rigid, perforated, polyvinyl chloride (PVC) pipe surrounded by washed pea gravel. The level of the perforations in the pipe should be set downward and at the bottom of the footing at all locations, and the drain collectors should be constructed with sufficient gradient to allow gravity discharge away from the buildings. In addition, all foundation walls taller than 3 feet should be lined with a minimum, 12-inch-thick, washed gravel blanket drain provided to within 1 foot of finish grade that ties into the footing drain. Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Preliminary Design Recommendations January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 15 A prefabricated drainage mat is not an acceptable alternative to the gravel blanket drain unless the entire excavation backfill consists of free-draining structural fill. Roof and surface runoff should not discharge into the footing drain system, but should be handled by a separate, rigid, tightline drain. In planning, exterior grades adjacent to foundations should be sloped downward away from the structures to achieve surface drainage. These recommendations apply to conventional shallow foundation walls and landscape walls less than about 4 feet tall. One should refer to the following section for walls up to 10 feet tall. 13.0 CAST-IN-PLACE RETAINING WALLS AND BASEMENT WALLS All backfill behind foundation walls or around foundation units should be placed as per our recommendations for structural fill and as described in this section of the report. Horizontally backfilled walls that are free to yield laterally at least 0.1 percent of their height may be designed to resist active lateral earth pressure represented by an equivalent fluid equal to 35 pounds per cubic foot (pcf). Fully restrained, horizontally backfilled, rigid walls that cannot yield should be designed for at-rest conditions and an equivalent fluid of 50 pcf. Walls with sloping backfill up to a maximum gradient of 2H:1V should be designed using an equivalent fluid of 55 pcf for yielding conditions or 75 pcf for fully restrained conditions. If parking areas are adjacent to walls, a surcharge equivalent to 2 feet of soil should be added to the wall height in determining lateral design forces. As required by the 2015 IBC, retaining wall design should include a seismic surcharge pressure in addition to the equivalent fluid pressures presented above. Considering the site soils and the recommended wall backfill materials, we recommend a seismic surcharge pressure of 5H and 10H psf, where H is the wall height in feet for the “active” and “at-rest” loading conditions, respectively. The seismic surcharge should be modeled as a rectangular distribution with the resultant applied at the midpoint of the walls. The lateral pressures presented above are based on the conditions of a uniform backfill consisting of excavated on-site soils, or imported structural fill compacted to 90 percent of ASTM D-1557. A higher degree of compaction is not recommended, as this will increase the pressure acting on the walls. A lower compaction may result in settlement of the slab-on-grade or other structures supported above the walls. Thus, the compaction level is critical and must be tested by our firm during placement. Surcharges from adjacent footings or heavy construction equipment must be added to the above values. Perimeter footing drains should be provided for all retaining walls, as discussed under the “Drainage Considerations” section of this report. It is imperative that proper drainage be provided so that hydrostatic pressures do not develop against the walls. This would involve installation of a minimum 1-foot-wide blanket drain to Minter Property Geotechnical Engineering Feasibility Report Renton, Washington Preliminary Design Recommendations January 18, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/ld - KE160641A3 - Projects\20160641\KE\WP Page 16 within 1 foot of finish grade for the full wall height using imported, washed gravel against the walls. If situations exist where a footing drain is not feasible for a foundation wall or retaining wall, the wall should be designed for saturated lateral earth pressures and a hydrostatic surcharge. We should be allowed to offer situation-specific recommendations if this situation arises. The use of drainage improvements as recommended herein does not alleviate the need for waterproofing where finished spaces are planned on the interior side of basement walls. Backfilled walls with finished interior space should be waterproofed in accordance with recommendations of the building designer. 13.1 Passive Resistance and Friction Factors Lateral loads can be resisted by friction between the foundation and the natural glacial soils or supporting structural fill soils, or by passive earth pressure acting on the buried portions of the foundations. The foundations must be backfilled with structural fill and compacted to at least 95 percent of the maximum dry density to achieve the passive resistance provided below. We recommend the following allowable design parameters: • Passive equivalent fluid = 250 pcf • Coefficient of friction = 0.30 14.0 PAVEMENT RECOMMENDATIONS The pavement for this project is expected to be supported by lodgement till sediments, recessional outwash, or structural fill soils. These soils should be suitable, with proper preparation, to allow the use of standard paving sections. The City of Renton minimum paving section for residential access streets is summarized in RMC 4-6-060 and is 4 inches of asphalt concrete paving (ACP) above 6 inches of crushed rock base. All depths given are compacted depths. All paving materials, base course materials, and placement procedures should comply with suitable standard specifications, such as the Washington State Department of Transportation (WSDOT) Standard Specifications for Road, Bridge, and Municipal Construction or other suitable specifications. All structural fill and all native subgrades less than 4 feet below finished grade for a planned roadway should be compacted to 95 percent of the modified Proctor maximum dry density, as determined by ASTM D-1557. Prior to structural fill placement or to placement of base course materials over native subgrades, the area should be proof-rolled under the observation of AESI with a loaded dump truck or other suitable equipment to identify any soft or yielding areas. Any soft or yielding areas should be repaired prior to continuing work. RENTON SEATTLE TUKWIL A KING COUNTY Copyright:© 2013 National Geographic Society, i-cubed 0 20001000 FEET ± NOTE: BLACK AND WHITEREPRODUCTION OF THIS COLORORIGINAL MAY REDUCE ITSEFFECTIVENESS AND LEAD TOINCORRECT INTERPRETATION VICINITY MAP PROJ NO. DATE: FIGURE:KE160641A 12/16 1 Document Path: G:\GIS_Projects\aTemplates\aVM_Template\VM_MXD\160641 Fig1 VM_Minter.mxdDATA SOURCES / REFERENCES:USGS: 24K SERIES TOPOGRAPHIC MAPSKING CO: STREETS, CITY LIMITS, PARCELS 2016 LOCATIONS AND DISTANCES SHOWN ARE APPROXIMATE KitsapCounty Snohomish County Pierce County King County RentonAveS S 130th St S 132nd St 84thAveS!( SITE ¬«167 ¥405 MINTER PROPERTYRENTON, WASHINGTON NOTES: 1. BASE MAP REFERENCE: CONTOUR ENGINEERING LLC, MINTER PROPERTY, BOUNDARY AND TOPOGRAPHIC SURVEY, 5/17/13.160641 Minter \ 160641 F2 Site-Explr.cdrMINTER PROPERTY RENTON, WASHINGTON SITE AND EXPLORATION PLAN PROJ NO.DATE:FIGURE: KE160641A 12/16 2 BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAY REDUCE ITS EFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION. a s s o c i a t e d e a r t h s c i e n c e s i n c o r p o r a t e d FEET 40 800 N CONTOUR INTERVAL = 2’ LEGEND: EXPLORATION PITEP NOTE: LOCATION AND DISTANCES SHOWN ARE APPROXIMATE. EP-6 EP-7 EP-5 EP-4 EP-1 EP-2 EP-3 EP-9 EP-8 APPENDIX Exploration Logs Laboratory Testing Results Elev. 242 feet Topsoil and Topsoil Fill Fill Loose to medium dense, very moist, yellowish brown, fine to medium SAND, with silt, few fine gravel, trace cobbles, trace debris - wire and plastic (SM). Recessional Outwash Medium dense, very moist, reddish brown, fine to medium SAND, with silt, little fine to coarse gravel (SM). Becomes mottled gray and brown. Bottom of exploration pit at depth 16.5 feetWeak seepage below 11 feet. No caving. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-1 Depth (ft)KCTP3 160641.GPJ December 28, 2016 Elev. 246 feet Topsoil Lodgement Till Medium dense, very moist, mottled gray, fine to coarse SAND, with silt, little fine to coarse gravel, trace cobbles (SM). Becomes dense grading to very dense, gray. Bottom of exploration pit at depth 11 feet Weak seepage zones 4 to 5 feet and 7 feet. No caving. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-2 Depth (ft)KCTP3 160641.GPJ December 28, 2016 Elev. 255 feet Fill Loose, very moist to wet, mixed, brown, gray, and dark gray, fine to coarse SAND, with silt, little to with fine to coarse gravel (SM). Lodgement Till Dense grading to very dense, very moist, gray, fine to coarse SAND, with silt, with fine to coarse gravel (SM). Bottom of exploration pit at depth 11.5 feetWeak seepage zones 3.5 to 8 feet. Slight to moderate caving above 8 feet. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-3 Depth (ft)KCTP3 160641.GPJ December 28, 2016 Elev. 264 feet Fill Loose, very moist, brown, fine SAND, with silt, trace fine gravel. Drain lines bedded in washed rock - 8 feet +/- on center at 4 feet deep. Lodgement Till Dense grading to very dense, very moist, mottled gray to gray, fine to coarse SAND, with silt, little to with fine gravel (SM). Bottom of exploration pit at depth 11 feet No seepage. Slight caving above 5 feet. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-4 Depth (ft)KCTP3 160641.GPJ December 28, 2016 Elev. 264 feet Gravel Fill and Topsoil Fill Loose, very moist, brown, fine SAND, with silt, little fine to coarse gravel, trace concrete rubble and plastic drain pipe bedded in washed rock at ~4 feet (SM). Lodgement Till Dense grading to very dense, very moist, gray, fine to coarse SAND, with silt, trace fine to coarse gravel (SM). Poly pipe in ditch at 7 feet. Bottom of exploration pit at depth 11 feet No seepage or caving. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-5 Depth (ft)KCTP3 160641.GPJ December 28, 2016 Elev. 295 feet Fill Loose, wet, brown, fine to coarse SAND, with silt, concrete and asphalt rubble, wood (logs, roots, sticks) (SM). Recessional Outwash Medium dense, very moist, gray, silty fine to coarse SAND, with silt, trace fine gravel (SM). Bottom of exploration pit at depth 12 feet Weak seepage 0 to 9 feet. Moderate caving 0 to 9 feet. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-6 Depth (ft)KCTP3 160641.GPJ December 28, 2016 Elev. 275 feet Lodgement Till Medium dense grading to dense, mottled gray, fine to coarse SAND, with silt, little fine to coarse gravel (SM). Bottom of exploration pit at depth 4 feetExploration termianted due to space constraints. No seepage or caving. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-7 Depth (ft)KCTP3 160641.GPJ December 28, 2016 Elev. 247 feet Gravel Surface Fill Loose, very moist to wet, brown, fine to coarse SAND, with silt, trace gravel, drainpipe backfilled with washed rock at 4 feet (SM). Recessional Outwash Medium dense to dense, very moist, brown, fine to coarse SAND, few silt, few fine to coarse gravel (SW). Bottom of exploration pit at depth 9 feetWeak seepage 3 to 6 feet. Slight caving 3 to 6 feet. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-8 Depth (ft)KCTP3 160641.GPJ December 28, 2016 Elev. 241 feet Topsoil and Topsoil Fill Lodgement Till Medium dense grading to dense, very moist to wet, mottled gray, fine SAND, with silt (SM). Bottom of exploration pit at depth 11 feet Weak seepage below 3 feet. No caving. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-9 Depth (ft)KCTP3 160641.GPJ December 28, 2016 Proctor Analysis ASTM D1557, D698 Date Sampled Project Project No.Soil Description Minter Property KE160641A Tested By Collected By Location EB/EP No.Depth MS BG Southeast Site EP-2 4' Percent passing 3/4" sieve:97% A Mold Number 1 2 3 B Water Added field wet dry C Wt. of Wet Soil + Mold (lb)23.150 22.955 22.850 D Wt. of Mold (lb)12.405 12.405 12.405 E Wt. of Wet Soil (lb)10.745 10.550 10.445 F Wet Density, (pcf)144.327 141.708 140.297 G Wt. of Pan (lb)0.495 0.490 0.500 H Wt. of Wet Soil + Pan (lb)3.600 2.480 2.460 J Wt. of Dry Soil + Pan (lb)3.330 2.275 2.335 K Wt. of Water (lb)0.270 0.205 0.125 M Wt. of Dry Soil (lb)2.835 1.785 1.835 N Moisture Content (%)9.5 11.5 6.8 O Dry Density (pcf)131.8 127.1 131.3 Z For a 6 inch mold: Z = 0.074449 For a 4" mold: Z = 0.0333 Optimum Moisture Percentage: Maximum Dry Density: Corrected Moisture Percentage: Corrected Maximum Dry Density: Assumed Specific Gravity:2.7 ASSOCIATED EARTH SCIENCES, INC. 911 Fifth Ave., Suite 100 Kirkland, WA 98033 425-827-7701 FAX 425-827-5424 Correction for oversize: ASTM D4718 Remarks N/A 132.0 N/A Test Results: 8.0 3/28/2007 Automatic Tamper SAND trace gravel silt ASTM D1557 Method C 110.0 115.0 120.0 125.0 130.0 135.0 140.0 0.0 5.0 10.0 15.0 20.0dry density.(pcf)moisture content, % Moisture Content ASTM D 2216 Date Sampled Project Project No.Soil Description3/28/2007 Minter Property KE160641A Tested By Location EB/EP No.Depth Various MS Onsite Sample ID EP-1 8.5'EP-1 14'EP-2 3' Wet Weight + Pan 455.0 533.2 388.5 Dry Weight + Pan 401.4 467.1 349.4 Weight of Pan 99.6 100.8 99.8 Weight of Moisture 53.6 66.1 39.1 Dry Weight of Soil 301.8 366.3 249.6 % Moisture 17.8 18.0 15.7 Sample ID EP-2 7'EP-3 3'EP-3 1-5' Wet Weight + Pan 329.5 377.9 362.3 Dry Weight + Pan 302.9 347.0 330.9 Weight of Pan 100.7 101.0 97.9 Weight of Moisture 26.6 30.9 31.4 Dry Weight of Soil 202.2 246.0 233.0 % Moisture 13.2 12.6 13.5 Sample ID EP-3 9'EP-4 8'EP-4 12' Wet Weight + Pan 414.0 458.5 331.0 Dry Weight + Pan 382.9 422.4 296.5 Weight of Pan 101.3 100.5 100.0 Weight of Moisture 31.1 36.1 34.5 Dry Weight of Soil 281.6 321.9 196.5 % Moisture 11.0 11.2 17.6 Sample ID EP-5 10'EP-7 5'EP-8 8' Wet Weight + Pan 327.0 520.5 350.1 Dry Weight + Pan 301.5 459.4 317.6 Weight of Pan 101.4 99.7 95.7 Weight of Moisture 25.5 61.1 32.5 Dry Weight of Soil 200.1 359.7 221.9 % Moisture 12.7 17.0 14.6 ASSOCIATED EARTH SCIENCES, INC. 911 5th Ave., Suite 100 Kirkland, WA 98033 425-827-7701 FAX 425-827-5424 Moisture Content ASTM D 2216 Date Sampled Project Project No.Soil Description3/28/2007 Minter Property KE160641A Tested By Location EB/EP No.Depth Various MS Onsite Sample ID EP-9 4'EP-9 7' Wet Weight + Pan 318.0 394.2 Dry Weight + Pan 280.6 335.5 Weight of Pan 98.8 99.5 Weight of Moisture 37.4 58.7 Dry Weight of Soil 181.8 236.0 % Moisture 20.6 24.9 ASSOCIATED EARTH SCIENCES, INC. 911 5th Ave., Suite 100 Kirkland, WA 98033 425-827-7701 FAX 425-827-5424 Kirkland Office | 911 Fifth Avenue | Kirkland, WA 98033 P | 425.827.7701 F| 425.827.5424 Everett Office | 2911 ½ Hewitt Avenue, Suite 2 | Everett, WA 98201 P | 425.259.0522 F | 425. 827.5424 Tacoma Office | 1552 Commerce Street, Suite 102 | Tacoma, WA 98402 P | 253.722.2992 F | 253.722.2993 www.aesgeo.com May 1, 2017 Project No. 160641E001 Blue Fern Development 11232 120th Avenue NE Kirkland, Washington 98033 Attention: Mr. John Groves Subject: Supplementary Geotechnical Engineering Report Shoring Wall and Detention Vault Recommendations Minter Property South 132nd Street and Renton Avenue South Renton, Washington Reference: Geotechnical Engineering Feasibility Report Minter Property South 132nd Street and Renton Avenue South Renton, Washington Dear Mr. Groves: As requested, this letter-report presents supplemental geotechnical engineering recommendations for support of the planned retaining wall at the north end of the cul-de-sac as well as recommendations for temporary shoring in support of the excavation for the planned detention vault in the southeast part of the property. We are familiar with the project through completion of the referenced geotechnical report, and that report remains in effect except as revised in this letter-report. This supplemental letter-report is based on a plan set by ESM Consulting Engineers LLC (ESM), titled “Minter Townhomes,” dated February 14, 2017. BACKGROUND The referenced geotechnical engineering report summarizes the results of our geotechnical engineering feasibility study and offers preliminary recommendations for the design and development of the proposed project. The referenced report is based on two site concept sketches, provided by Blue Fern Development (Blue Fern), that were current at the time our report DRAFT Minter Property Supplementary Geotechnical Engineering Report Renton, Washington Shoring Wall and Detention Vault recommendations May 1, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/pc – 160641E001-4 – Projects/20160641\KE\WP Page 2 was written, and our knowledge of the site gained through completion of a preliminary geotechnical engineering study of the site for another client in 2007. The recommendations presented in this supplementary letter-report are based on subsurface explorations recently completed onsite by Associated Earth Sciences, Inc. (AESI) on March 14, 2017. INTRODUCTION This supplementary letter-report presents the results of our subsurface exploration and geotechnical engineering study for the proposed shoring walls and planned detention vault at the proposed new residential development. The site location is shown on the “Vicinity Map,” Figure 1. The approximate locations of explorations completed for this study as well as the locations of our explorations completed for our 2007 study are shown on the “Site and Exploration Plan,” Figure 2. This letter-report is based in part on a previously referenced plan set, which was used as a basis for Figure 2. Interpretive exploration logs associated with work completed by AESI for this study and for our 2007 study are included in the Appendix. The conclusions and recommendations contained in this letter-report should be reviewed and modified, or verified, if project plans change substantially. The referenced plan set shows a planned detention vault in the southeast corner of the site. The bottom of vault elevation is 226. We understand that the vault cut will be approximately 20 feet deep at the south end where existing topography is at an elevation of 246 and approximately 36 feet deep at the north end where existing topography is at elevation of 262. We also understand that the east side of the planned vault ranges from approximately 16 to 23 feet from the edge of the right-of-way (Renton Avenue South) and the south side of the vault is approximately 15 feet from the edge of the right-of-way (South 132nd Street). Due to the depth of the planned vault cut and the close proximity of the vault to the right-of-ways, we understand that temporary shoring walls will be required to complete the excavation. Due to the height of the required shoring walls, we recommend temporary shoring using soil nails and vertical elements, as described in this letter-report. The referenced plan depicts a concrete retaining wall with a maximum height of 8 feet planned between the north end of the cul-de-sac and the right-of-way (Renton Avenue South). The wall is shown very close to the right-of-way and a conventional temporary excavation cut slope does not seem feasible. Therefore, we suggest the use of a permanent excavation facing that can be constructed without an open excavation. We have provided recommendations for a conventional cantilever soldier pile wall in this letter-report. We are available to discuss other wall types if desired. DRAFT Minter Property Supplementary Geotechnical Engineering Report Renton, Washington Shoring Wall and Detention Vault recommendations May 1, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/pc – 160641E001-4 – Projects/20160641\KE\WP Page 3 SUBSURFACE EXPLORATION Our field study included advancing three exploration borings. One of the borings was advanced in the location of the planned retaining wall at the north end of the cul-de-sac. Two of the borings were advanced within the footprint of the planned detention vault. The conclusions and recommendations presented in this letter-report are based on the explorations completed for this study. The number, locations, and depths of our explorations were completed within site and budgetary constraints. The locations of the exploration borings were measured in the field from known landmarks, and the locations depicted on Figure 2 are taken from plans provided to us by Blue Fern. Interpretive exploration logs are presented in the Appendix. SUBSURFACE CONDITIONS Exploration borings EB-1 and EB-2, located in the area of the planned detention vault, encountered approximately 10 feet of very loose to loose, very silty sand with variable organic content, interpreted as existing fill. Native materials encountered beneath the fill consisted of medium dense to very dense stratified sand interpreted as recessional outwash deposits underlain by very dense lodgement till sediments. Exploration EB-3, located at the north end of the cul-de-sac, encountered native materials consisting of very dense lodgement till sediments underlain by very dense, tuffaceous sandstone from the Tukwila Formation. Both exploration borings EB-1 and EB-2 encountered ground water seepage at a depth of approximately 17 feet below ground surface. The observed seepage is interpreted to represent perched ground water, where downward infiltration of surface water is impeded by lower-permeability soils at depths. We anticipate that perched ground water will be encountered at the interface between the recessional outwash and the lodgement till at the time of construction. It should be noted that fluctuations in the level of the ground water may occur due to the time of the year, on- and off-site land use, and variations in the amount of rainfall. Project scheduling and budgeting should plan for temporary dewatering of the detention vault excavation, as described in this letter-report. TEMPORARY AND PERMANENT CUT SLOPES In our opinion, stable construction slopes should be the responsibility of the contractor and should be determined during construction. Based on our review of the referenced plans, we anticipate that temporary unsupported cut slopes will be suitable for the excavation of the north and west sides of the planned vault. For estimating purposes, we recommend that temporary, unsupported cut slopes, completed in the unsaturated existing fill and the recessional outwash can be planned at a maximum slope of 1.5H:1V (Horizontal:Vertical) up to a maximum height of 10 feet. Temporary cuts of similar height in the underlying lodgement till and sandstone can be planned at DRAFT Minter Property Supplementary Geotechnical Engineering Report Renton, Washington Shoring Wall and Detention Vault recommendations May 1, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/pc – 160641E001-4 – Projects/20160641\KE\WP Page 4 a maximum slope of 1H:1V. Flatter temporary cut slopes should be planned in areas of ground water seepage. We anticipate that temporary unsupported cut slopes will not be utilized for the east and south sides of the planned vault excavation or for the north end of the excavation for the planned cul-de-sac. During excavation shoring construction, temporary vertical cuts up to 4 to 6 feet are expected for placement of lagging or prior to placing a shotcrete soil nail facing. As is typical with earthwork operations, some sloughing and raveling may occur and cut slopes may have to be adjusted in the field. In addition, WISHA/OSHA regulations should be followed at all times. DEWATERING RECOMMENDATIONS Our subsurface explorations completed for this study revealed ground water seepage interpreted as perched ground water within the detention vault footprint at approximately 17 feet below ground surface at the time of drilling. At the north end of the vault ground water was encountered at an approximate elevation of 243 and an approximate elevation of 231 at the south end of the vault. The seepage was encountered near the contact between the recessional outwash and the underlying impermeable lodgement till. The perched seepage will be encountered during excavation shoring installation. Depending on the volume of seepage present, dewatering may be required to reduce excavation face erosion. Alternately a temporary dewatering system installed early on in the construction phase would control the perched seepage upgradient of the cut face. A temporary dewatering system consisting of a cutoff drain upslope of the vault would catch the water before it reached the face of the cut. The cutoff drain would be installed between the edge of the right-of-way and the north and east sides of the planned vault. The drain should consist of a trench at least 18 inches wide, excavated to a depth of at least 1 foot into the dense silty lodgement till soils underlying any fill and recessional outwash. The depth to dense lodgement till encountered in our explorations in this area ranged from 5 to 20 feet below existing ground level. The depth of the excavation for the cutoff drain should be adjusted in the field at the time of construction. EXCAVATION SHORING Permanent Soldier Pile Walls A permanent retaining wall up to approximately 8 feet tall is anticipated on the north side of the site between the cul-de-sac and the south edge of the right-of-way. Existing off-site structures that might be in close proximity to the shoring wall include street paving and buried utilities. In our opinion, a conventional shoring system consisting of soldier piles and lagging would be well suited for supporting the excavation side wall at this location. The following sections provide design recommendations for cantilever soldier pile walls. The attached “Permanent Soldier Pile DRAFT Minter Property Supplementary Geotechnical Engineering Report Renton, Washington Shoring Wall and Detention Vault recommendations May 1, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/pc – 160641E001-4 – Projects/20160641\KE\WP Page 5 Wall Design Criteria” (Figure 3) in combination with the “Surcharge Pressure on Adjacent Walls” (Figure 4) illustrate our recommendations. We recommend that soldier pile walls be designed to resist lateral soil pressures based on active earth pressure, passive earth pressure, seismic surcharge, and traffic surcharge conditions (where applicable). Shoring walls are not perfectly rigid, and some displacements of supported soils are expected. Typically, displacements are on the order of 1 inch or less, and extend laterally behind the shoring system a distance equal to one to two times the wall height. For that reason we recommend detailed photographic documentation and survey of adjacent structures prior to construction. We also recommend survey monitoring of shoring system performance during and following installation. The City of Renton will likely require such monitoring as a condition of permitting. We are available to assist in design of the monitoring program on request. Cantilever soldier pile walls or walls with a single row of tieback anchors should be designed to resist active lateral earth pressure represented by an equivalent fluid of 35 pounds per square foot (psf) for unrestrained conditions and 50 psf for restrained (at rest) conditions, plus surcharges, structures, construction equipment, material stockpiles, or other loads. Permanent shoring walls should also be designed to resist seismic pressure represented by an equivalent fluid of 5H psf for active conditions and an equivalent fluid of 10H psf for restrained conditions. A lateral earth pressure diagram is presented on Figure 3 of this letter-report. Lagging between soldier piles should be designed to resist one-half of the total computed lateral earth pressure as a result of arching effects. Below the excavation level, the combined pressures may be considered to act over only the diameter of the grouted soldier pile section. In order to preserve lateral resistance, excavation should not be allowed below a line that begins at the foundation elevation level of the planned vault and projects downward and away from the shoring wall at an inclination of 1.5H:1V. From a soil standpoint, the grouted soldier piles must be designed for sufficient vertical capacity in the event that tieback anchors are required for all or part of the wall. For design purposes, the vertical load capacity of soldier piles should be determined based on an allowable adhesion or side friction of 1 kip per square foot (ksf) and an allowable end bearing of 20 ksf. We recommend a minimum depth of embedment be determined by the structural engineer to satisfy moment equilibrium. All soldier piles should be backfilled with concrete or lean mix after drilling and installation. The concrete above the excavation base elevation could consist of lean mix concrete or controlled density fill (CDF) to facilitate installation of lagging. The soldier piles also need to be located a sufficient depth below the base of the excavation to provide adequate lateral or “kick-out” resistance to horizontal loads below the lowest brace or soil nail level. Lateral resistance of soldier piles may be computed on the basis of passive pressure represented by an equivalent fluid of 300 pounds per cubic foot (pcf). Resistance from the uppermost 2 feet of soil below excavation level should be ignored due to potential ground disturbance. This pressure may be considered to be acting against twice the diameter of the grouted soldier pile section. DRAFT Minter Property Supplementary Geotechnical Engineering Report Renton, Washington Shoring Wall and Detention Vault recommendations May 1, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/pc – 160641E001-4 – Projects/20160641\KE\WP Page 6 The contractor should be experienced with the installation of soldier piles. Based on the ground water observed in our exploration borings EB-1 and EB-2, we anticipate that the contractor should be prepared to drill under a fluid head or case the holes for the pile borings if a temporary dewatering system is not installed. Although our borings did not encounter boulders or obstructions, they are possible. If the obstruction cannot be removed or drilled through, the pile boring may need to be moved. Relocated piles may require additional pile(s) to compensate for the relocation. Soldier pile wall construction should begin with installation of all of the soldier piles. When all piles have been installed, pile monitoring points have been set, and the concrete is cured, excavation can begin. Treated-timber lagging should be installed as the excavation progresses. Voids between lagging and the cut face should be minimized by cutting only as much as necessary to install lagging. Void spaces between the lagging and cut face should be backfilled with CDF with a minimum compressive strength of 200 pounds per square inch (psi), with washed pea gravel, or with an alternate material approved by the wall designer and geotechnical engineer. Soil Nail Shoring Walls There is a planned detention vault located in the southeast part of the site. Temporary excavation shoring up to approximately 36 feet tall is anticipated on the north end of the vault and up to approximately 20 feet tall on the south end of the vault. In our opinion, a conventional shoring system consisting of soil nails with vertical elements would be well suited for supporting the excavation sidewalls at this location. The following sections provide design recommendations for soil nail walls. The attached “Temporary Soil Nail Wall Design Criteria” (Figure 5) in combination with the “Surcharge Pressure on Adjacent Walls” (Figure 4) illustrate our recommendations. Soil nail shoring walls typically consist of creating 4- to 6-foot unsupported vertical cuts that are left open until soil nails are installed and shotcrete is applied. Based on our explorations, the subsurface conditions in the area of the vault footprint generally consist of loose to medium dense existing fill and recessional outwash soils to a depth of approximately 20 feet. Underlying the weaker soils our explorations encountered very dense lodgement till and sandstone. Due to the relatively loose soils in the top 20 feet of the planned excavation, we recommend the use of vertical elements along the top of the shoring walls. The vertical elements should be installed prior to making the first cut for the shoring walls. We differ to the structural engineer for the design of the size and spacing of the vertical elements. AESI does not provide soil nailing design drawings. We rely on experienced professional designers and contractors to provide the design drawings and details necessary to obtain permits. AESI can, however, provide the required inspection and monitoring of proof-testing to satisfy City of Renton requirements. The following letter-report sections provide the basic information for the site soils to be used in a soil nail wall design. The final design should satisfy the criteria presented in this DRAFT Minter Property Supplementary Geotechnical Engineering Report Renton, Washington Shoring Wall and Detention Vault recommendations May 1, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/pc – 160641E001-4 – Projects/20160641\KE\WP Page 7 letter-report, and installation and performance criteria required by the City of Renton for temporary soil nail-supported wall construction. Soil nailing consists of installing a grid pattern of grouted rebar tendons (“nails”) into slightly inclined drilled holes spaced on a vertical soil cut face as excavation proceeds. The soil nail tendons are typically shorter in length than conventional tieback anchors. This produces a reinforced zone that is itself stable and supports the unreinforced ground behind it. The nails are passive, in that they are untensioned at the time of installation; over time, they become tensioned as they resist the deformation of the adjacent soil. The nail reinforcement improves stability in two ways. First, soil nails reduce the driving force along potential failure surfaces. Second, in frictional soils, nails increase the normal force and hence the soil shear resistance along potential slip surfaces. Soil nailing reinforcement is conducted by excavating vertically from the top down in stages of approximately 4 to 6 feet. After each stage of excavation, the exposed soils along the limits of the excavation are reinforced prior to proceeding with the next stage of excavation. Construction of a soil nail wall typically involves the following major steps: 1. Drill and install perimeter face stabilization elements, if needed; 2. Excavate soil, typically using a 6-foot lift, leaving a berm in place on the lower half of the lift; 3. Drill nail holes; 4. Install and grout nails; 5. Excavate out berm to form vertical cut face; 6. Place drainage mat against cut soil face and protect with plastic sheeting; 7. Place waterproofing (if specified); 8. Place reinforcements, bearing plates, and studs; 9. Apply shotcrete wall; and 10. Repeat process down to final excavation grade. Consequently, this method requires that the soil withstand short-term, temporary vertical cuts of approximately 6 feet without caving. The lower portion of the recessional outwash deposits that overlie the lodgement till sediments that were encountered in our exploration borings were observed to be saturated. As previously discussed, temporary construction dewatering should be considered in order to lower ground water levels to complete the excavation and the shoring walls. Open cuts should not be allowed to stand unshored for more than 3 days. This time could be less if zones of fractured or slickensided soil or ground water seepage are encountered. Open face cuts should not be left open over weekends or holidays. After applying the first lift of shotcrete, the next lift can be built after 4 days or once the shotcrete has attained 50 percent of its design strength. The project structural engineer should verify this recommended interval between lifts and provide additional or alternative recommendations, if necessary. DRAFT Minter Property Supplementary Geotechnical Engineering Report Renton, Washington Shoring Wall and Detention Vault recommendations May 1, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/pc – 160641E001-4 – Projects/20160641\KE\WP Page 8 A series of load tests must be performed to verify the design and ultimate skin friction or adhesion of the soil nails. Two types of testing should be accomplished for soil nailing. An initial verification test program is performed prior to wall construction to verify that the design adhesion values are correct. Common verification testing programs consist of at least two 200-percent tests of the design or allowable load in the soil for each excavation wall. Verification testing is usually accomplished by loading each nail in 25-percent increments held for 5 minutes up to the final load of 200-percent design load. Creep measurements are recorded during the verification test, where the load is generally held for an hour and any nail movement is measured. The creep measurements are commonly performed at either the 150-percent or the 200-percent point. Verification nails should be constructed exactly as the production nails will be constructed, including the same drilling equipment, driller, inclination, grout, etc. Verification test nails are commonly sacrificial nails that do not become incorporated in the shoring wall. As construction of the wall proceeds, proof-tests are conducted on approximately one of every 20 nails to verify that the soil conditions and installation methods have not changed. Proof-test procedures are similar to the verification procedures except that the final load is less (130 percent) and the creep measurements usually last only 10 minutes. Proof-test nails remain in the wall following testing and are an integral part of the shoring. We recommend that AESI monitor installation and testing of both the verification and proof nails. For design purposes, we recommend the following soil parameters be utilized: Moist Unit Weight: 140 pcf Friction Angle: Existing fill 30 degrees Vashon recessional outwash 30 degrees Vashon lodgement till 35 degrees Tukwila Formation 35 degrees Cohesion: 0 psf For design of soil nail anchors used in the shoring system, the anchor loads are transmitted to the surrounding soil by side friction or adhesion with the soil. For anchors installed with an air-rotary drill or hollow-stem auger in the glacial sediments, an allowable shaft adhesion of 1,250 psf can be assumed. The competence of the glacially overridden soil encountered at the site indicates that it is likely the soil nail anchor holes can generally be drilled and the anchors installed without the use of casing, assuming the construction dewatering system has already been installed. However, caving should be expected in the upper loose fill, in the Vashon recessional outwash, and in areas of ground water seepage. The contractor should be prepared to use casing, where necessary, to maintain open borings. The anchor holes should be drilled without the use of drilling fluids or water so that the optimum allowable adhesion between the grouted anchor and the soil can be developed. The DRAFT Minter Property Supplementary Geotechnical Engineering Report Renton, Washington Shoring Wall and Detention Vault recommendations May 1, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/pc – 160641E001-4 – Projects/20160641\KE\WP Page 9 holes should be grouted immediately after drilling or re-drilled prior to grouting, if left open for a period of more than 2 hours. Anchors should be installed such that they avoid conflict with all underground utilities, and a minimum separation of 10 feet should be maintained between all anchors and any nearby utilities. Surface water should be controlled by means of curbs, gutters, or swales, so that water does not flow over exposed soil cuts or newly constructed walls. Drainage behind the shotcrete wall should be provided by installing Mira-Drain or equivalent drainage mats per the manufacturer’s recommendations. The drainage mats should be installed behind the shotcrete wall for the full wall height, with the 2- up to 4-foot-wide fabric strips placed at a spacing of 8-feet on-center for the full length of all walls. The Mira-Drain mats should freely communicate with the perimeter drain system through a series of weep holes or drain sleeves. Monitoring Program A program should be established to monitor the horizontal and vertical movement of the excavation sidewalls and the installed soil nail shoring wall. This monitoring program may be required by the City of Renton. The monitoring should be performed by a licensed surveyor with monitoring points established on settlement-sensitive structures (buildings, manholes, poles, etc.) around the excavation and at regular intervals along the shoring wall. Monitoring should be performed at least twice a week, and the specifics of the monitoring program should be provided to AESI for review prior to implementation. We recommend the monitoring program be prepared as part of the final shoring wall design. Permanent Soil Nails If any soil nails are to be permanent, they should be constructed with the required corrosion protection. The designer should specify any special construction, materials, and testing requirement for a permanent wall system. DETENTION VAULT CONSIDERATIONS The detention vault foundations are expected to be supported entirely on glacially consolidated very dense sediments or very dense sandstone, and may be designed using an allowable foundation soil bearing pressure of 5,000 psf. The detention vaults may be designed to resist active or at-rest lateral earth pressures as described in Section 13.0 “CAST-IN-PLACE RETAINING WALLS AND BASEMENT WALLS” of the referenced “Geotechnical Engineering Feasibility Report,” assuming drained conditions. If it is not possible to construct the vault with a foundation drain, hydrostatic surcharges must be incorporated and a lateral pressure of 90 pcf (equivalent fluid) should be assumed, representing combined soil and hydrostatic loads, under active conditions. If DRAFT Minter Property Supplementary Geotechnical Engineering Report Renton, Washington Shoring Wall and Detention Vault recommendations May 1, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/pc – 160641E001-4 – Projects/20160641\KE\WP Page 10 paved surfaces are to be constructed above the backfill soils, lateral pressures should include a uniform traffic surcharge of equivalent to 2 additional feet of soil depth. CLOSURE We appreciate the opportunity to be of continued service. If you have any questions, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington ______________________________ Daniel D. Voth Kurt D. Merriman, P.E. Staff Geologist Senior Principal Engineer Attachments: Figure 1: Vicinity Map Figure 2: Site and Exploration Plan Figure 3: Permanent Soldier Pile Wall Design Criteria Figure 4: Surcharge Pressure on Adjacent Walls Figure 5: Temporary Soil Nail Wall Criteria Appendix: Exploration Logs DRAFT RENTON SEATTLE TUKWILA KING COUNTY Copyright:© 2013 National Geographic Society, i-cubed 0 20001000 FEET ± NOTE: BLACK AND WHITEREPRODUCTION OF THIS COLORORIGINAL MAY REDUCE ITSEFFECTIVENESS AND LEAD TOINCORRECT INTERPRETATION VICINITY MAP PROJ NO. DATE: FIGURE:KE160641A 12/16 1 Document Path: G:\GIS_Projects\aTemplates\aVM_Template\VM_MXD\160641 Fig1 VM_Minter.mxdDATA SOURCES / REFERENCES:USGS: 24K SERIES TOPOGRAPHIC MAPSKING CO: STREETS, CITY LIMITS, PARCELS 2016 LOCATIONS AND DISTANCES SHOWN ARE APPROXIMATE KitsapCounty Snohomish County Pierce County King County RentonAveS S 130th St S 132nd St 84thAveS!( SITE ¬«167 ¥405 MINTER PROPERTYRENTON, WASHINGTONDRAFT NOTES: 1. BASE MAP REFERENCE: ESM CONSULTING ENGINEERS LLC, MINTER TOWNHOMES, PRELIMINARY SITE PLAN, GRADING AND UTILITIES, SHEET EN-04, 2/14/17.160641 Minter \ 160641 F2 Site-Explr 4-17.cdrMINTER PROPERTY RENTON, WASHINGTON SITE AND EXPLORATION PLAN PROJ NO.DATE:FIGURE: 160641E001 4/17 2 BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAY REDUCE ITS EFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION. a s s o c i a t e d e a r t h s c i e n c e s i n c o r p o r a t e d FEET 40 800 N CONTOUR INTERVAL = 2’ LEGEND: EXPLORATION PIT EXPLORATION BORING EP NOTE: LOCATION AND DISTANCES SHOWN ARE APPROXIMATE. EB EP-6 EP-7 EP-5 EP-4 EP-1 EP-2 EP-3 EP-9 EP-8 EB-3 EB-2 EB-1DRAFT 35 (H+D) PSF FOR UNRESTRAINED CONDITIONS AND LEVEL BACKSLOPE 50 (H+D) PSF FOR RESTRAINED AT REST ACTIVE PRESSURE ACTS OVER SOLDIER PILE SPACING ABOVE EXCAVATION LEVEL AND ONE PILE DIAMETER BELOW THE EXCAVATION LEVEL HBASE OF EXCAVATION GROUND SURFACE 300 (D) PSF PASSIVE PRESSURE ACTS OVER TWICE PILE DIAMETER PASSIVE PRESSURE BASED ON DEPTH BELOW BASE OF EXCAVATION 250 PSF TRAFFIC SURCHARGE ROAD / SIDEWALK SURCHARGE SEISMIC SURCHARGE 5H PSF ACTIVE 10H PSF AT REST D = VARIES2’ NOTES: 1. SOLDIER PILE EMBEDMENT DEPTH “D” SHOULD CONSIDER NECESSARY VERTICAL CAPACITY, KICKOUT, AND OVERTURNING RESISTANCE. 2. PASSIVE PRESSURE INCLUDES A FACTOR OF SAFETY OF 1.5. 3. DIAGRAM DOES NOT INCLUDE HYDROSTATIC PRESSURES AND ASSUMES WALLS ARE SUITABLY DRAINED TO PREVENT BUILDUP OF HYDROSTATIC PRESSURE. 4. DIAGRAM IS ILLUSTRATIVE AND NOT REFERENCED TO A PARTICULAR LOCATION. 5. LAGGING MAY BE DESIGNED USING 50 PERCENT OF THE ACTIVE EARTH PRESSURE. 6. SLOPE ABOVE SHORING WALL SHALL BE NO STEEPER THAN 1.5H:1V. 7. SURCHARGE SHOULD BE ADDED FOR ANY ROADS, FOUNDATIONS, MATERIAL STOCKPILES, ETC., NOT SHOWN ABOVE, IN ACCORDANCE WITH FIGURE 4. MINTER PROPERTY RENTON, WASHINGTON 160641 Minter \ 160641 F3 Soldier 4-17.cdrPERMANENT SOLDIER PILE WALL DESIGN CRITERIA PROJ NO.DATE:FIGURE: 160641E001 4/17 3 a s s o c i a t e d e a r t h s c i e n c e s i n c o r p o r a t e dDRAFT MINTER PROPERTY RENTON, WASHINGTON 160641 Minter \ 160641 F4 Pressure.cdrSURCHARGE PRESSURE ON ADJACENT WALLS PROJ NO.DATE:FIGURE: 160641E001 4/17 4 a s s o c i a t e d e a r t h s c i e n c e s i n c o r p o r a t e d LEGEND: EXCAVATION DEPTH BELOW FOOTING IN FEET LATERAL SOIL PRESSURE IN PSF UNIT LOADING PRESSURE IN PSF RADIANSb sh D q a b q b/2 sh DGROUND SURFACE BASE OF EXCAVATION ISOLATED FOOTING abbsh= 0.64q ( - SIN COS2 ) sh DGROUND SURFACE BASE OF EXCAVATION X = mDq LINE LOAD PRESSURE z = nDCONTINUOUS FOOTING PARALLEL TO EXCAVATION (FOR m>0.4) sh =1.28q D 2m n 2 2 2(m + n ) sh =q D 0.2 n 2 2(0.16 + n ) (FOR m<0.4) UNIFORM LOAD DISTRIBUTION sh q = VERTICAL PRESSURE IN PSF = 0.4q BASE OF EXCAVATION sh UNIFORM LOAD q DRAFT H0.25HGLACIAL SOILS: APPARENT EARTH PRESSURE 26H PSF + BASE OF EXCAVATION 1.5H:1V M A X SLOPE SURCHARGE: 15 H PSF FOR 2 H:1V 20 H PSF FOR 1.5H:1V SOIL NAIL SOIL NAIL MINTER PROPERTY RENTON, WASHINGTON 160641 Minter \ 160641 F5 Soil Nail.cdrTEMPORARY SOIL NAIL WALL DESIGN CRITERIA PROJ NO.DATE:FIGURE: 160641E001 4/17 5 a s s o c i a t e d e a r t h s c i e n c e s i n c o r p o r a t e d NOTES: 1. DIAGRAM DOES NOT INCLUDE HYDROSTATIC PRESSURES AND ASSUMES WALLS ARE SUITABLY DRAINED TO PREVENT BUILDUP OF HYDROSTATIC PRESSURE. 2. DIAGRAM IS ILLUSTRATIVE AND NOT REFERENCED TO A PARTICULAR LOCATION. 3. BASE OF EXCAVATION SHALL BE DEFINED AS THE FOUNDATION SUBGRADE ELEVATION. 4. SEISMIC SURCHARGE REQUIRED FOR ANY PERMANENT WALLS. 5. ADD SURCHARGES FOR ADJACENT STRUCTURES OR TRAFFIC IN ACCORDANCE WITH FIGURE 4 IF REQUIRED.DRAFT APPENDIX DRAFT DRAFT Grass / Topsoil Fill Very loose, very moist, brown, very silty, fine to medium SAND, somewood debris and organics, trace gravel (SM). Vashon Recessional OutwashMedium dense, very moist, grayish brown, silty, fine to medium SAND,trace gravel; stratified (SM). Hard drilling at 13 feet. Dense, very moist to wet, grayish brown, silty, fine to medium SAND, tracegravel, some silt interbeds; stratified (SM). Perched ground water at 17 feet. Vashon Lodgement TillVery dense, moist, gray, very silty, fine to medium SAND, trace coarsesand, trace gravel; unsorted (SM). As above. No recovery due to rock. No recovery due to rock. 121 257 162325 152544 2250/6" 50/5" 4150/5" S-1 S-2 S-3 S-4 S-5 S-6 S-7 1 of 2 ESM Sheet Depth (ft)Exploration Number160641E001 M - Moisture 6 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Boretec / Track Well5 10 15 20 25 30 35 Water LevelProject Name EB-1 SymbolDV2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 3/14/17,3/14/17 Logged by: Shelby Tube Sample 140# / 30" Ring Sample No Recovery Water Level at time of drilling (ATD) Minter Property 248 Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log AESIBOR 160641.GPJ March 28, 201733 1212 4848 69 5050/6" 5050/5" 5050/5"DRAFT Very dense, moist, gray, very silty, fine SAND, trace medium to coarsesand, trace to some gravel; unsorted (SM).333150/6" S-8 Bottom of exploration boring at 41.5 feetNo ground water encountered. 2 of 2 ESM Sheet Depth (ft)Exploration Number160641E001 M - Moisture 6 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Boretec / Track Well45 50 55 60 65 70 75 Water LevelProject Name EB-1 SymbolDV2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 3/14/17,3/14/17 Logged by: Shelby Tube Sample 140# / 30" Ring Sample No Recovery Water Level at time of drilling (ATD) Minter Property 248 Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log AESIBOR 160641.GPJ March 28, 20175050/6"DRAFT Grass / Topsoil Fill Loose, moist to very moist, dark brown, very silty, organic-rich, fine tomedium SAND, trace gravel (SM). Vashon Recessional OutwashMedium dense, moist, to very moist, brownish gray, silty, fine to mediumSAND, some gravel, trace zones of oxidation; stratified (SM). Driller notes gravels at 12 feet. Very dense, very moist, grayish brown, silty, fine to medium SAND, traceto some gravel, trace coarse sand; stratified (SM). Perched water at 17 feet. Vashon Lodgement TillVery dense, moist, gray, silty, fine SAND, some gravel; unsorted; mildreaction with HCl (SM). Becomes slightly moist. Becomes slightly moist to dry. Tukwila FormationVery dense, dry, gray, poorly stratified, tuffaceous SANDSTONE. 344 61215 212428 2550/6" 152442 242740 50/6" S-1 S-2 S-3 S-4 S-5 S-6 S-7 1 of 2 ESM Sheet Depth (ft)Exploration Number160641E001 M - Moisture 6 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Boretec / Track Well5 10 15 20 25 30 35 Water LevelProject Name EB-2 SymbolDV2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 3/14/17,3/14/17 Logged by: Shelby Tube Sample 140# / 30" Ring Sample No Recovery Water Level at time of drilling (ATD) Minter Property 260 Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log AESIBOR 160641.GPJ March 28, 201788 2727 52 5050/6" 66 67 5050/6"DRAFT As above.50/5"S-8 Bottom of exploration boring at 41.5 feetNo ground water encountered. 2 of 2 ESM Sheet Depth (ft)Exploration Number160641E001 M - Moisture 6 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Boretec / Track Well45 50 55 60 65 70 75 Water LevelProject Name EB-2 SymbolDV2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 3/14/17,3/14/17 Logged by: Shelby Tube Sample 140# / 30" Ring Sample No Recovery Water Level at time of drilling (ATD) Minter Property 260 Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log AESIBOR 160641.GPJ March 28, 20175050/5"DRAFT Crushed Rock Vashon Lodgement Till Very dense, moist, tan, silty, fine SAND, trace gravel; unsorted (SM). Very dense, slightly moist, gray, silty, fine SAND, trace gravel; unsorted(SM). Very dense, dry, gray, silty, fine SAND, some gravel; unsorted (SM). Tukwila FormationVery dense, dry, gray, poorly stratified, tuffaceous SANDSTONE. As above. 3950/5" 50/4" 50/5" 50/5" S-1 S-2 S-3 S-4 Bottom of exploration boring at 21.5 feetNo ground water encountered. 1 of 1 ESM Sheet Depth (ft)Exploration Number160641E001 M - Moisture 6 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Boretec / Track Well5 10 15 20 25 30 35 Water LevelProject Name EB-3 SymbolDV2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 3/14/17,3/14/17 Logged by: Shelby Tube Sample 140# / 30" Ring Sample No Recovery Water Level at time of drilling (ATD) Minter Property 278 Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log AESIBOR 160641.GPJ March 28, 20175050/5" 5050/4" 5050/5" 5050/5"DRAFT Elev. 242 feet Topsoil and Topsoil Fill Fill Loose to medium dense, very moist, yellowish brown, fine to medium SAND, with silt, few fine gravel, trace cobbles, trace debris - wire and plastic (SM). Recessional Outwash Medium dense, very moist, reddish brown, fine to medium SAND, with silt, little fine to coarse gravel (SM). Becomes mottled gray and brown. Bottom of exploration pit at depth 16.5 feetWeak seepage below 11 feet. No caving. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-1 Depth (ft)KCTP3 160641.GPJ December 28, 2016DRAFT Elev. 246 feet Topsoil Lodgement Till Medium dense, very moist, mottled gray, fine to coarse SAND, with silt, little fine to coarse gravel, trace cobbles (SM). Becomes dense grading to very dense, gray. Bottom of exploration pit at depth 11 feet Weak seepage zones 4 to 5 feet and 7 feet. No caving. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-2 Depth (ft)KCTP3 160641.GPJ December 28, 2016DRAFT Elev. 255 feet Fill Loose, very moist to wet, mixed, brown, gray, and dark gray, fine to coarse SAND, with silt, little to with fine to coarse gravel (SM). Lodgement Till Dense grading to very dense, very moist, gray, fine to coarse SAND, with silt, with fine to coarse gravel (SM). Bottom of exploration pit at depth 11.5 feetWeak seepage zones 3.5 to 8 feet. Slight to moderate caving above 8 feet. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-3 Depth (ft)KCTP3 160641.GPJ December 28, 2016DRAFT Elev. 264 feet Fill Loose, very moist, brown, fine SAND, with silt, trace fine gravel. Drain lines bedded in washed rock - 8 feet +/- on center at 4 feet deep. Lodgement Till Dense grading to very dense, very moist, mottled gray to gray, fine to coarse SAND, with silt, little to with fine gravel (SM). Bottom of exploration pit at depth 11 feet No seepage. Slight caving above 5 feet. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-4 Depth (ft)KCTP3 160641.GPJ December 28, 2016DRAFT Elev. 264 feet Gravel Fill and Topsoil Fill Loose, very moist, brown, fine SAND, with silt, little fine to coarse gravel, trace concrete rubble and plastic drain pipe bedded in washed rock at ~4 feet (SM). Lodgement Till Dense grading to very dense, very moist, gray, fine to coarse SAND, with silt, trace fine to coarse gravel (SM). Poly pipe in ditch at 7 feet. Bottom of exploration pit at depth 11 feet No seepage or caving. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-5 Depth (ft)KCTP3 160641.GPJ December 28, 2016DRAFT Elev. 295 feet Fill Loose, wet, brown, fine to coarse SAND, with silt, concrete and asphalt rubble, wood (logs, roots, sticks) (SM). Recessional Outwash Medium dense, very moist, gray, silty fine to coarse SAND, with silt, trace fine gravel (SM). Bottom of exploration pit at depth 12 feet Weak seepage 0 to 9 feet. Moderate caving 0 to 9 feet. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-6 Depth (ft)KCTP3 160641.GPJ December 28, 2016DRAFT Elev. 275 feet Lodgement Till Medium dense grading to dense, mottled gray, fine to coarse SAND, with silt, little fine to coarse gravel (SM). Bottom of exploration pit at depth 4 feetExploration termianted due to space constraints. No seepage or caving. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-7 Depth (ft)KCTP3 160641.GPJ December 28, 2016DRAFT Elev. 247 feet Gravel Surface Fill Loose, very moist to wet, brown, fine to coarse SAND, with silt, trace gravel, drainpipe backfilled with washed rock at 4 feet (SM). Recessional Outwash Medium dense to dense, very moist, brown, fine to coarse SAND, few silt, few fine to coarse gravel (SW). Bottom of exploration pit at depth 9 feetWeak seepage 3 to 6 feet. Slight caving 3 to 6 feet. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-8 Depth (ft)KCTP3 160641.GPJ December 28, 2016DRAFT Elev. 241 feet Topsoil and Topsoil Fill Lodgement Till Medium dense grading to dense, very moist to wet, mottled gray, fine SAND, with silt (SM). Bottom of exploration pit at depth 11 feet Weak seepage below 3 feet. No caving. DESCRIPTION Renton, WA Minter Property 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: BWG Approved by: BWG 3/28/07 Project No. KE160641A LOG OF EXPLORATION PIT NO. EP-9 Depth (ft)KCTP3 160641.GPJ December 28, 2016DRAFT