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HomeMy WebLinkAboutRS_Geotechnical_Report_180309_v1Revised Geotechnical Report King County South Treatment Plant Biogas and Heat Systems Improvements Renton, Washington January 6, 2017 Submitted To: Mr. Ian McKelvey Brown and Caldwell 701 Pike Street, Suite 1200 Seattle, Washington 98101 By: Shannon & Wilson, Inc. 400 N 34th Street, Suite 100 Seattle, W ashington 98103 21-1-22210-001 21-1-22210-001-R1f/wp/lk 21-1-22210-001 i TABLE OF CONTENTS Page 1.0 INTRODUCTION ..................................................................................................................1 2.0 PROJECT AND SITE DESCRIPTION .................................................................................1 3.0 PROJECT SITE GEOLOGY .................................................................................................2 3.1 Puget Rock Group (Renton Formation) .....................................................................2 3.2 Alluvial Fan Deposits .................................................................................................2 3.3 Organic Deposits ........................................................................................................2 3.4 Floodplain Deposits ....................................................................................................2 3.5 Fill ..............................................................................................................................2 4.0 EXISTING SUBSURFACE EXPLORATIONS ...................................................................3 5.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING .................................3 6.0 SUBSURFACE CONDITIONS .............................................................................................4 7.0 CONCLUSIONS AND RECOMMENDATIONS .................................................................5 7.1 Seismic Design Considerations ..................................................................................5 7.1.1 Site Class ......................................................................................................5 7.1.2 Seismic Design Parameters ..........................................................................5 7.1.3 Earthquake-induced Geologic Hazards........................................................6 7.2 Foundations ................................................................................................................7 7.2.1 Spread Footings ...........................................................................................7 7.2.2 Mat Foundation ............................................................................................7 7.2.3 Stone Column Ground Improvement ...........................................................8 7.2.4 Driven Steel Piles .........................................................................................8 7.2.5 Augercast Piles.............................................................................................8 7.3 Lateral Load Resistance .............................................................................................9 7.4 Site Grading and Excavation ....................................................................................10 7.5 Fill Placement and Compaction ...............................................................................10 7.6 Wet Weather Earthwork ...........................................................................................10 7.7 Construction Monitoring ..........................................................................................11 8.0 LIMITATIONS ....................................................................................................................11 9.0 REFERENCES .....................................................................................................................13 TABLE OF CONTENTS (cont.) Page 21-1-22210-001-R1f/wp/lk 21-1-22210-001 ii TABLE 1 Seismic Design Parameters ......................................................................................5 FIGURES 1 Vicinity Map 2 Site and Exploration Plan 3 Generalized Subsurface Profile A-A’ 4 Generalized Subsurface Profile B-B’ 5 Estimated Axial Augercast Pile Resistance 12-inch Diameter – Post-Seismic 6 Estimated Axial Augercast Pile Resistance 24-inch Diameter – Post-Seismic APPENDICES A Subsurface Explorations B Geotechnical Laboratory Results C Important Information About Your Geotechnical/Environmental Report 21-1-22210-001-R1f/wp/lk 21-1-22210-001 1 REVISED GEOTECHNICAL REPORT KING COUNTY SOUTH TREATMENT PLANT BIOGAS AND HEAT SYSTEMS IMPROVEMENTS RENTON, WASHINGTON 1.0 INTRODUCTION This revised report presents the results of our subsurface explorations and geotechnical assessment for the proposed design and construction of new biogas and heat exchange facilities (Facility) at the King County Wastewater Treatment Division’s South Plant, located as shown in the Vicinity Map, Figure 1. This report is revised to clarify our recommendations for foundation design following review comments received from the Owner’s technical review staff. The project will consist of a gas upgrading room and a boiler or HXT building. The new facility is expected to replace the existing scrubbers in phases while existing facilities maintain the ability to deliver biogas. Our services have been performed in general accordance with our Professional Services Subcontract 24825, Standard Subcontract for Geotechnical Services, King County – South Plant Biogas and Heat Systems Improvements. Our services included review of existing subsurface data, performing two subsurface explorations, and performing engineering analyses to develop recommendations for foundation design and associated earthwork for the project. 2.0 PROJECT AND SITE DESCRIPTION The proposed Facility will be located in a vacant field at the north side of the King County South Plant. It will be constructed directly west of the existing digesters and Solids MCC Building. The Facility will be placed between Road “N” and Road “X.” The majority of the proposed Facility site is located at a topographically high point within the plant area on a mound of fill that slopes up from surrounding ground surface by approximately 10 feet. We understand that this mound is to be removed and the project site is to be graded to surrounding surface elevation. According to drawing G3142, provided by Brown and Caldwell, the gas upgrading room will be 88 feet long by 65 feet wide, and the HXT building will be 58 feet long by 40 feet wide. We understand that maximum loads applied by the Facility are expected to not exceed 1,500 pounds per square foot. At this time, we do not know the magnitude of individual column loads. 21-1-22210-001-R1f/wp/lk 21-1-22210-001 2 3.0 PROJECT SITE GEOLOGY Our experience with projects at this location and our recent subsurface exploration indicates that the following geologic units (as encountered from lower to higher elevation) are present at the project site: 3.1 Puget Rock Group (Renton Formation) The site is underlain by rock consisting of the Renton Formation, which is part of the Puget Rock Group. It consists of dark brown to grayish-brown, fine- to coarse-grained, iron-oxide-stained sandstone exhibiting a varying degree of weathering, with beds of coal, carbonaceous siltstone, and claystone. Existing rock outcroppings and the results of subsurface explorations indicate that the bedrock contact dips sharply to the south and the east. The Renton Formation is typically encountered during subsurface explorations around the north and west sides of the South Plant. 3.2 Alluvial Fan Deposits Alluvial fan deposits consist of varying thickness of loose to dense, gray to dark gray sand and sand with gravel. Silty sand containing shells and wood fragments also occur within this formation. Alluvial fan deposits generally possess a relatively high shear strength and low compressibility. 3.3 Organic Deposits The sediments comprising this formation consist of peat; soft, organic silts; and clayey silts. Their thickness appears to decrease from west to east at the South Plant. These deposits exhibit low shear strength and high compressibility. 3.4 Floodplain Deposits The floodplain deposits consist of very loose to medium dense sand and silt layers. They exhibit considerable variation in their engineering properties due to their depositional nature. 3.5 Fill Fill at the project site consists of a silty sand layer of variable thickness. Our subsurface explorations indicate that fill is present to depths of about eight to 25 feet below ground surface (bgs) at the location of the proposed Facility. The thickness of this layer is greatest below the center of the fill mound. 21-1-22210-001-R1f/wp/lk 21-1-22210-001 3 4.0 EXISTING SUBSURFACE EXPLORATIONS The logs of soil borings and test pits performed near the site since 1982 are presented in Appendix A, Subsurface Explorations. The locations of the explorations are shown in the Site and Exploration Plan, Figure 2. We reviewed the explorations to estimate the approximate elevation of bedrock at the project site. As shown in the Cross Sections provided in Figures 3 and 4, only two of these explorations, Boring B-301 and Test Pit 2, encountered sandstone at relatively high elevations. These explorations were performed to the west and the southwest of the proposed Facility site, and their results reinforce the assessment that Renton Formation sandstone dips to the east across the South Plant grounds. The remaining previous explorations generally encountered alluvial sand and silty sand, as well as floodplain deposits, but did not encounter bedrock. 5.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING Our recent explorations consisted of two borings performed at the approximate locations shown in the Site and Exploration Plan, Figure 2. The borings were performed on the southeast and northwest sides of the proposed Facility site. The borings, designated B-1 and B-2, were drilled on July 15 and 22 by Holocene Drilling, Inc. (Holocene) of Puyallup, Washington, under subcontract to Shannon & Wilson, Inc. Holocene used hollow-stem auger techniques to drill boring B-1 and mud rotary techniques to drill boring B-2. Boring B-1 was drilled to a depth of approximately 91.5 feet and boring B-2 was drilled to a depth of approximately 121.5 feet. Both borings were observed by a geologist or engineer from our firm who visually identified the retrieved soils, obtained representative soil samples, and compiled logs of the explorations. A Soil Classification and Log Key is presented in Figure A-1 of Appendix A, and logs of the borings are presented in Figures A-2 and A-3. We detected a hydrocarbon odor at a depth of about 25 feet while drilling boring B-1. A sample from this depth was collected and delivered to Fremont Analytical, Inc. of Seattle, Washington, for environmental testing to assist with disposal characterization of exploration-derived waste. Lab analysis did not detect petroleum hydrocarbons within the sample. The geotechnical laboratory testing program was directed towards determining index properties of the native soils. The tests performed in our Seattle laboratory included water content analysis and analysis of grain size distribution. The water content tests were conducted in accordance with ASTM International (ASTM) Designation: D2216, Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass. The grain size 21-1-22210-001-R1f/wp/lk 21-1-22210-001 4 distribution tests were conducted in accordance with ASTM Designation: D422, Standard Test Method for Particle-Size Analysis of Soils. The results of the water content tests are shown in the boring logs, Figures A-2 and A-3, and the results of the grain size distribution tests are shown in Appendix B. 6.0 SUBSURFACE CONDITIONS The results of borings B-1 and B-2 indicated that the subsurface soils below the proposed Facility location are comprised of the following layers:  Holocene Fill, consisting primarily of very loose to medium dense, brown, silty sand with gravel. Fill was encountered from the surface to a depth of about 25 feet bgs at boring B-1 and about 8 feet bgs at boring B-2.  Holocene Alluvium, consisting primarily of medium dense to very dense, gray to dark gray, poorly graded sand and poorly graded sand with gravel. This layer extended to about 80 feet bgs at boring B-1 and 85 feet bgs at boring B-2.  Layers of floodplain and organic deposits, such as Holocene Lacustrine and Holocene Estuarine. These soils consisted primarily of medium stiff to hard silt and peat, and were found scattered within the Holocene Alluvium material. Layers ranged in thickness from about 2 to 22 feet. A layer of soft to stiff, gray silt was encountered from 8 to 30 feet bgs, and a layer of very soft to soft, gray silt was encountered from about 40 to 60 feet bgs at boring B-2.  Decomposed sandstone, representative of Renton Formation rock. This material was very low strength and completely to highly weathered. Coal was found interbedded within the layer, and coal clasts were observed throughout the layer. The sandstone was encountered at a depth of about 80 feet bgs at boring B-1 and 111 feet bgs at boring B-2, indicating that its elevation at the proposed Facility site is highly variable depending on location, and dips down to the east. Groundwater was observed at about 30 feet bgs (elevation 106 feet) at boring B-1. Mud rotary drilling at boring B-2 prevented accurate measurement of the groundwater level. Previous explorations near the site of the proposed Facility found groundwater at higher elevations than boring B-1. For example, Boring 202, located as shown in Figure 1 and presented in Appendix A, encountered groundwater at a depth of 2 feet (elevation 111 feet). However, groundwater levels at this boring were recorded in April. Groundwater elevation at the South Plant grounds is likely dependent on seasonal weather patterns, and excavation during the winter months may encounter groundwater at much higher elevations than 106 feet. Wet weather earthwork is discussed further in Section 7.6. 21-1-22210-001-R1f/wp/lk 21-1-22210-001 5 7.0 CONCLUSIONS AND RECOMMENDATIONS 7.1 Seismic Design Considerations 7.1.1 Site Class The proposed Facility site is underlain primarily by loose to medium dense sands and silts to a depth of about 50 to 60 feet. Given the nature of these sediments and their susceptibility to liquefaction discussed in Section 7.1.2, we have identified the site classification as Site Class E. 7.1.2 Seismic Design Parameters Seismic design of the Facility will be based on levels of ground motion anticipated for events with different return periods. The 2015 International Building Code (IBC) design code is based on levels of ground motion anticipated for an event with a 2,500-year recurrence interval, while the Basic Safety Earthquake-1 (BSE-1) hazard level is based on levels of ground motion anticipated for an event with a 475-year recurrence interval (International Code Council, 2015). We estimated seismic design parameters for the 2,475-year earthquake using the mapped spectral accelerations provided by the U.S. Geological Survey (USGS) and the site classification procedures outlined in IBC 2015 1615. We estimated seismic design parameters for the 475-year earthquake using the USGS probabilistic seismic hazard deaggregation tool and the conversion factors given in ASCE/SEI 7.11 (2010). The maximum considered spectral accelerations for short periods and the 1-second period are shown in Table 1, as well as the mapped SS and S1 values in the vicinity of the site and the soil response coefficients FA and FV corresponding to Site Class E. TABLE 1 SEISMIC DESIGN PARAMETERS Return Period (years) SS (g’s) S1 (g’s) FA FV SMS (g’s) SM1 (g’s) SDS (g’s) SD1 (g’s) 2,475 1.46 0.54 0.9 2.4 1.31 1.30 0.87 0.87 475 0.67 0.22 1.2 3.2 0.81 0.70 0.81 0.70 21-1-22210-001-R1f/wp/lk 21-1-22210-001 6 We estimated that the site-class adjusted peak ground acceleration is 0.55g for the 2,475-year return period and 0.36g for the 475-year return period. 7.1.3 Earthquake-induced Geologic Hazards Earthquake-induced geologic hazards that may affect a given site include ground surface fault rupture; liquefaction and its associated effects (e.g., loss of shear strength, bearing capacity failure, loss of lateral support, ground oscillation, slumping, lateral spreading, and settlement); and slope instability. The following provides a brief discussion of these hazards. The project site is located about 5 to 6 miles south to southwest of the Seattle Fault Zone. This is considered to be an active fault structure by the USGS. However, the potential for ground surface rupture is not a design issue at the subject site due to its distance to the fault zone and the relatively long repeat times for fault movement. Soil liquefaction is a phenomenon in which pore pressure in loose, saturated, granular soils increases during ground shaking to a level near the initial effective stress, resulting in a reduction of shear strength of the soil (quicksand-like condition). As a result of this reduction in shear strength, ground settlement and lateral spreading (ground movement on very gentle slopes) can occur. Results from boring B-1 indicate that liquefaction may occur at the proposed Facility site within soil layers between about 30 to 60 feet bgs during an earthquake with a 2,475-year or 475-year recurrence interval. This is due to the relatively loose nature of the soils below the groundwater level. Differential settlement of the ground surface should be expected under these conditions. For planning purposes, we recommend assuming that differential settlement could be about 50 percent of the total settlement across the length of any given structure. The actual amount of differential settlement will depend on the load distribution and soil-structure interaction. In our opinion, shallow spread footings bearing in soils at the proposed Facility site will be susceptible to liquefaction-induced settlements, while mat foundations or deep-foundation elements such as piles or shafts bearing in denser soils below approximately 60 feet bgs will mitigate structural settlement due to liquefaction. Section 7.2 discusses foundation considerations. Current plans call for the existing mound to be removed and the proposed Facility to be constructed on a relatively flat site. Slope instability due to ground shaking is therefore low and not considered a design issue for this project. 21-1-22210-001-R1f/wp/lk 21-1-22210-001 7 7.2 Foundations We understand that various factors will influence the selection of a foundation for the proposed Facility. Among these are cost considerations, competency of load-bearing subsurface soils, and allowance for building settlement under static and dynamic conditions. We understand that the Facility may have a basement, which would affect total depth of excavation and condition of bearing soils at the mat foundation bearing elevation. Based on our additional analyses of liquefaction-induced settlements and discussions with the project structural engineer, we recommend that the facility be supported on a mat foundation. We assume that the mat foundation will bear at or below elevation 123 feet where medium dense silty sand is present as the subgrade soil. Five foundation systems that have been considered for this project are discussed below: 7.2.1 Spread Footings Spread footings are the most common type of foundation due to their ease of installation and relatively low cost. On dense, competent soils, spread footings would typically provide adequate resistance to loads comparable to those proposed for the Facility. The existing mound has likely compressed (preloaded) the underlying fill; however, the fill layer extends to 25.5 feet below the top of the mound. Therefore, variable fill materials will be present below the base of the proposed Facility and the preloading effects cannot be relied upon for isolated spread footings. Spread footings are susceptible to differential settlement when constructed on variable fill materials and potentially liquefiable soils. We do not recommend the use of spread footings due to the risk of static differential settlement and the risk of differential settlement due to liquefaction following an earthquake. 7.2.2 Mat Foundation Although more expensive than traditional spread footings, a mat foundation would reduce the potential for differential settlement by evenly distributing structural loads. This foundation type offers more structural continuity and flexural strength than a system of spread footings, and would provide better stability on loose soils and soils that may liquefy. A mat foundation would limit overall settlement at the proposed Facility, including settlement brought on by seismic conditions. A mat foundation may be designed for a maximum allowable bearing pressure of 1,000 pounds per square foot, which is intended to not exceed the preload stress that the bearing 21-1-22210-001-R1f/wp/lk 21-1-22210-001 8 soils have experienced in the past due to the mound of fill that currently exists on the building site. We understand that the structural engineer will perform finite element modelling of the building and mat foundation. For finite element modelling we recommend assuming a modulus of subgrade reaction, k, of 200 pounds per square inch per inch. 7.2.3 Stone Column Ground Improvement Stone column installation uses a vibrator to create a shaft of densely compacted crushed rock. This type of foundation would improve the stability of subsurface soils at the proposed Facility site, and may be installed through layers of silt, such as those found at depths of about 10 to 20 feet bgs. If stone columns are selected, we would recommend they extend down to the dense soil layer encountered at 65 and 60 feet deep in borings B-1 and B-2, respectively. This foundation method could significantly reduce the risk of static and dynamic settlement. Stone column installation is relatively expensive and may cause localized vibration during installation that may affect nearby buildings and buried utilities. 7.2.4 Driven Steel Piles Driven steel piles would significantly reduce settlement by transferring structural loads to deeper, competent sands and gravels. Driven piles also reduce soil export volumes and provide an instant field verification of pile capacity. Pile driving produces significant noise, and we understand that this may prohibit its use at the proposed Facility site. 7.2.5 Augercast Piles Augercast pile installation consists of drilling a hollow-stem auger to the required depth, then injecting grout as the auger is removed. Reinforcing steel is then lowered into the hole. Installation costs are typically lower than those of cast-in-place piers and driven piles, and noise and vibration levels are much lower than those with driven piles. Augercast piles can be installed to depths of 80 to 90 feet, which would provide embedment into dense alluvial material at the proposed Facility site. Transferring loads to this layer would mitigate the risk of both static and dynamic settlement, as the majority of structural loads would bear in non-liquefying soils. Based on our subsurface explorations and engineering analyses, we recommend that the proposed Facility be supported on this type of foundation if a pile foundation is selected. We performed a preliminary analysis of augercast pile capacity at the project site using an in-house computer program. The analysis used a single-pile case and did not consider group effects. It is 21-1-22210-001-R1f/wp/lk 21-1-22210-001 9 our opinion that seismic loading conditions control deep foundation design based on the results of our analysis. Post-earthquake settlements in liquefied soils could induce downdrag loads on augercast piles on the order of 95 kips or 190 kips for 12-inch- and 24-inch-diameter piles, respectively. The short-term downdrag loading caused by liquefaction can typically be accommodated by the piles’ ultimate capacity, with the net result being a temporary reduction to the factor of safety used in the design of the piles. Depth versus allowable pile bearing capacity for the seismic case is shown in Figures 5 and 6. Although we anticipate that the end-bearing depth for augercast piles will be about 75 to 80 feet bgs, pile lengths may differ across the site due to variable elevation of the alluvial layer. Unit cost pricing for augercast piles should be included in the project budget. A contingency for extra pile costs should be included in the project budget. Our analysis considered 12-inch- and 24-inch-diamater augercast piles and assumed that the top 10 feet of fill near boring B-1 will be excavated before pile installation. Other pile diameters may be appropriate and should be evaluated after the project structural engineer has determined vertical and lateral foundation loads. We should be retained to assist the structural engineer in determining the optimum pile type, size, and depth for the anticipated column loads. It is our opinion that augercast pile foundations would experience relatively minor settlements during loading. We estimate total augercast pile settlements would be less than ½ inch. Because of the granular nature of the end-bearing soils, these settlements would be primarily elastic and would occur as the load is applied. No long-term static settlements of earthquake-induced settlements are anticipated. 7.3 Lateral Load Resistance Lateral loads may be resisted by pile foundations, friction along buried walls, and by passive soil resistance against buried portions of a foundation. Footings or mat foundations (if used) that bear in the existing fill may be designed using a coefficient of base friction of 0.4. Passive soil resistance against the buried portions of foundations may be calculated based on an equivalent fluid density of 300 pounds per cubic foot. This value for passive soil resistance includes a factor of safety of 1.5 on the ultimate soil strength in order to limit allowable lateral deformations. This value is based on the assumption of a horizontal surface extending beyond the footing for a distance of at least two times the depth of embedment. Passive resistance should be ignored in the upper 12 inches unless it is specifically required for lateral stability and the backfill in this zone is densely compacted structural fill. It should be ignored entirely if future development could result in removal of the soils providing lateral resistance. 21-1-22210-001-R1f/wp/lk 21-1-22210-001 10 7.4 Site Grading and Excavation Excavations can be accomplished with conventional excavating equipment, such as a dozer, front-end loader, or backhoe. For planning purposes, we recommend that temporary unsupported open-cut slopes in the very loose to medium dense fill be no steeper than 1.5 Horizontal to 1 Vertical. We recommend that all exposed cut slopes be protected with a waterproof covering during periods of wet weather to reduce sloughing and erosion. Final grades should slope away from the Facility to prevent ponding of water next to the structure. 7.5 Fill Placement and Compaction Some backfill may be required for locations around and under Facility foundations and over subsurface pipe trenches. In our opinion, the on-site fill that was observed in the upper 24 feet of boring B-1 and upper 8 feet of boring B-2 is acceptable for use as trench backfill and backfill around structures. Any fill placed beneath structures should consist of imported structural fill. Structural fill should consist of relatively well-graded sand or sand and gravel having a maximum particle size of about 3 inches. It should contain less than 20 percent fines (material passing the No. 200 sieve, based on the ¾-inch minus fraction) and, during wet weather or wet conditions, it should contain no more than 5 percent fines. Structural fill should not contain organics or deleterious material. All fill should be placed in horizontal lifts and compacted to at least 95 percent of its Modified Proctor maximum density (ASTM D1557), and should be verified to be in a dense and unyielding condition. The thickness of loose lifts should not exceed 10 inches for heavy equipment compactors and 6 inches for hand-operated compactors. 7.6 Wet Weather Earthwork Earthwork would most easily be accomplished during the normally drier months of June through mid-October. It is our opinion that earthwork performed during the wet-weather months will prove more costly. The condition of silty sand will deteriorate rapidly when exposed to moisture and construction activity. If shallow foundations are used, this could lead to deeper footing excavations than anticipated. The following recommendations are applicable if earthwork is to be accomplished in wet weather or in wet conditions:  Fill material should consist of clean, granular soil, of which not more than 5 percent by dry weight passes the No. 200 mesh sieve, based on wet-sieving the fraction passing the ¾-inch sieve. The fines should be non-plastic. Such soil would need to 21-1-22210-001-R1f/wp/lk 21-1-22210-001 11 be imported to the site. The identification of suitable wet-weather backfilling material should be made by a geotechnical engineer from our firm experienced in wet-weather construction.  The ground surface in the construction area should be sloped and sealed with a smooth-drum, vibratory roller or equivalent to promote the rapid runoff of precipitation, to prevent surface water from flowing into excavations, and to prevent ponding of water. Soils that become too wet for compaction should be removed and replaced with clean granular soil.  Excavation and placement of structural fill material should be observed on a full-time basis by a geotechnical engineer or technician experienced in wet-weather earthwork to determine that all unsuitable materials are removed and suitable compaction and site drainage is achieved.  Covering work areas, soil stockpiles, or slopes with plastic; sloping, ditching, sumps, dewatering, and other measures should be employed as necessary to permit proper completion of the work. Bales of straw and/or geotextile silt fences should be strategically located to control soil movement and erosion. The above recommendations for wet weather earthwork should be incorporated into the contract specifications. 7.7 Construction Monitoring We recommend that Shannon & Wilson, Inc. be retained to monitor the geotechnical aspects of construction activities at the site including the preparation of subgrades for the structure (if shallow foundations or slab-on-grade floors are utilized), installation of piles, augercast piles, or stone columns (if deep foundations are utilized), and compaction of structural fill or backfill. If driven steel piles or augercast piles are installed, we recommend that a Shannon & Wilson, Inc. representative be on site for the entire installation. Unanticipated soil conditions are commonly encountered and cannot be fully determined by merely taking soil samples or test borings. Such unexpected conditions may require the Contractor to make adjustments in his procedures to attain a properly constructed project. Some contingency fund is recommended to accommodate potential extra costs related to unexpected conditions. 8.0 LIMITATIONS The analyses, conclusions, and recommendations presented in this report are based on the site conditions as they presently exist and assume that the explorations are representative of the 21-1-22210-001-R1f/wp/lk 21-1-22210-001 13 9.0 REFERENCES American Society of Civil Engineers, 2010, Minimum design loads for buildings and other structures (3rd printing): Reston, Va., American Society of Civil Engineers, ASCE Standard ASCE/SEI 7-10. International Code Council, Inc., 2015, International building code: Country Club Hills, Ill., International Code Council, Inc., 690 p. 5 405 167 Renton Lake Washington Tukwila dale Seattle PROJECT LOCATION SW Oa k es Ave VICINITY MAP FIG. 1 Map adapted from aerial imagery provided by Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service. NOTE Fi l e n a m e : J: \ 2 1 1 \ 2 2 2 1 0 \ 0 0 1 \ 2 1 - 1 - 2 2 2 1 0 - 0 0 1 V i c M a p . d w g D a t e : 01 - 0 5 - 2 0 1 7 L o g i n : mj m Seattle Washington Project Location 90 5 97 MT 21-1-22210-001 King County South Biogas Plant Renton, Washington January 2017 0 3,000 6,000 Approximate Scale in Feet A A ' B - 4 0 3 B - 2 0 2 B-301 B B ' B - 5 0 1 TP-2 B - 1 B - 2 2 1 - 1 - 2 2 2 1 0 - 0 0 1 F I G . 2 G e o t e c h n i c a l a n d E n v i r o n m e n t a l C o n s u l t a n t s S H A N N O N & W I L S O N , I N C . S I T E A N D E X P L O R A T I O N P L A N K i n g C o u n t y S o u t h B i o g a s P l a n t R e n t o n , W a s h i n g t o n J a n u a r y 2 0 1 7 Filename: J:\211\22210\001\21-1-22210-001 Plan & Profile.dwg Layout: Site Plan Date: 01-05-2017 Login: mjm B - 1 A B o r i n g D e s i g n a t i o n a n d A p p r o x i m a t e L o c a t i o n T e s t P i t D e s i g n a t i o n a n d A p p r o x i m a t e L o c a t i o n G e n e r a l i z e d S u b s u r f a c e P r o f i l e ( S e e F i g u r e s 3 a n d 4 ) L E G E N D Approximate Facil i t y L o c a t i o n M a p a d a p t e d f r o m a e r i a l i m a g e r y p r o v i d e d b y G o o g l e E a r t h P r o , r e p r o d u c e d b y p e r m i s s i o n g r a n t e d b y G o o g l e E a r t h ™ M a p p i n g S e r v i c e . N O T E M T T P - 2 0 1 0 0 2 0 0 A p p r o x i m a t e S c a l e i n F e e t 7 - 2 2 - 2 0 1 6 ? Approximate Elevation in Feet 150 Southwest A N o r t h e a s t A ' B - 4 0 3 B - 2 B - 2 0 2 B-301500 ( P r o j . 1 5 ' N W ) ( P r o j . 3 6 ' N W ) ( P r o j . 8 1 ' N W ) (Proj. 17' NW)10010-15-1982 4 - 6 - 1 9 8 2 3 - 1 6 - 1 9 8 3 ? ? ? S A N D S T O N E ( R e n t o n F o r m a t i o n ) S a n d a n d S i l t ( H o l o c e n e A l l u v i u a l a n d L a c u s t r i n e ) S A N D S T O N E ( R e n t o n F o r m a t i o n ) D e n s e t o v e r y d e n s e S a n d a n d G r a v e l S a n d a n d S i l t ( H o l o c e n e A l l u v i u a l a n d L a c u s t r i n e ) S a n d a n d S i l t ( H o l o c e n e A l l u v i u a l a n d L a c u s t r i n e ) ? ? ? ? ? ? Approximate Elevation in Feet 1 5 0 5 0 0 1 0 0 B - B ' A p p r o x i m a t e E x i s t i n g G r o u n d S u r f a c e a t T i m e o f B o r i n g 2 1 - 1 - 2 2 2 1 0 - 0 0 1 F I G . 3 G e o t e c h n i c a l a n d E n v i r o n m e n t a l C o n s u l t a n t s S H A N N O N & W I L S O N , I N C . G E N E R A L I Z E D S U B S U R F A C E P R O F I L E A - A ' K i n g C o u n t y S o u t h B i o g a s P l a n t R e n t o n , W a s h i n g t o n J a n u a r y 2 0 1 7 Filename: J:\211\22210\001\21-1-22210-001 Plan & Profile.dwg Layout: A-A' Date: 01-05-2017 Login: mjm 0 5 0 1 0 0 V e r t i c a l S c a l e i n F e e t V e r t i c a l E x a g g e r a t i o n = 2 X Boring DesignationProjected Distance and DirectionApproximate Elevation in FeetApproximate Geologic ContactBottom of BoringDate of Completion (Proj. 17' NW)??10-15-1982 LEGENDB-301 0 1 0 0 2 0 0 H o r i z o n t a l S c a l e i n F e e t (Elev. ~29')(Elev. ~118') ( E l e v . ~ 1 1 3 ' ) ( E l e v . ~ 1 2 7 ' ) ( E l e v . ~ 1 1 4 ' ) 7 - 2 2 - 2 0 1 6 Approximate Elevation in Feet 150 West B E a s t B ' B - 2 500 ( P r o j . 8 2 ' S ) 100 ? ? S A N D S T O N E ( R e n t o n F o r m a t i o n ) D e n s e t o v e r y d e n s e S a n d a n d G r a v e l S a n d a n d S i l t ( H o l o c e n e A l l u v i u a l a n d L a c u s t r i n e ) Approximate Elevation in Feet 1 5 0 5 0 0 1 0 0 A - A ' TP-2(Proj. 0')200 2 0 0 B - 1 ( P r o j . 0 ' ) B - 5 0 1 ( P r o j . 0 ' ) S A N D S T O N E ( R e n t o n F o r m a t i o n ) S a n d a n d S i l t ( H o l o c e n e A l l u v i u a l a n d L a c u s t r i n e ) ? ? ? ? ? ? ? ?? A p p r o x i m a t e E x i s t i n g G r o u n d S u r f a c e a t T i m e o f B o r i n g / T e s t P i t 7 - 1 5 - 2 0 1 6 1 1 - 2 1 - 1 9 8 3 6-26-1981 (Elev. ~182') ( E l e v . ~ 1 3 6 ' ) ( E l e v . ~ 1 2 7 ' ) ( E l e v . ~ 1 3 5 ' ) 2 1 - 1 - 2 2 2 1 0 - 0 0 1 F I G . 4 G e o t e c h n i c a l a n d E n v i r o n m e n t a l C o n s u l t a n t s S H A N N O N & W I L S O N , I N C . G E N E R A L I Z E D S U B S U R F A C E P R O F I L E B - B ' K i n g C o u n t y S o u t h B i o g a s P l a n t R e n t o n , W a s h i n g t o n J a n u a r y 2 0 1 7 Filename: J:\211\22210\001\21-1-22210-001 Plan & Profile.dwg Layout: B-B' Date: 01-05-2017 Login: mjm 0 5 0 1 0 0 V e r t i c a l S c a l e i n F e e t V e r t i c a l E x a g g e r a t i o n = 2 X B o r i n g o r T e s t P i t D e s i g n a t i o n P r o j e c t e d D i s t a n c e a n d D i r e c t i o n A p p r o x i m a t e E l e v a t i o n i n F e e t G r o u n d w a t e r L e v e l D u r i n g D r i l l i n g A p p r o x i m a t e G e o l o g i c C o n t a c t B o t t o m o f B o r i n g o r T e s t P i t D a t e o f C o m p l e t i o n ( P r o j . 8 2 ' S ) ? ? 1 0 - 1 5 - 1 9 8 2 L E G E N D B - 2 ( E l e v . ~ 2 9 ' ) 0 1 0 0 2 0 0 H o r i z o n t a l S c a l e i n F e e t GENERAL NOTES 1. The analyses are based on a single augercast pile and do not consider group action of closely spaced augercast piles (closer than 2.5 diameters, center to center). Once final pile group sizes and spacings are determined, the axial capacity of the pile group should be re-evaluated. 2. Total augercast pile capacity is a summation of its side and base resistances. Ultimate resistances shown on the plot above do not include a factor of safety (FS). ASSUMED SUBSURFACE PROFILE Based on Nearby Exploration: B-1 0 10 20 30 40 50 60 70 80 0 50 100 150 200 DE P T H ( f e e t ) ULTIMATE RESISTANCE (kips) Side Resistance (Seismic) Base Resistance (Seismic) Total Resistance Estimated Liquefied Zone Estimated Liquefied Zone Add Downdrag Loads to Other Foundation Loads Loose to medium dense, gray, Silty Sand with Gravel (SM) 0' Medium stiff to stiff, OL/ML 14' Medium dense, dark gray, Poorly Graded Sand (SP) 18' Hard, brown Silt (ML)28' Medium dense to dense, dark gray, Poorly Graded Sand (SP) 31' Loose to medium dense, gray-brown, Silty Sand (SM) 38' Dense, dark gray, Poorly Graded Sand with Gravel (SP) 54' Decomposed Sandstone 70' Subsurface profile assumes ~10 feet of excavation to remove fill mound King County South Biogas Plant Renton, Washington Geotechnical and Environmental ConsultantsSHANNON & WILSON, INC.FIG.5 ESTIMATED AXIAL AUGERCAST PILE RESISTANCE 12-INCH DIAMATER -POST -SEISMIC January 2017 21-1-22210-001 GENERAL NOTES 1. The analyses are based on a single augercast pile and do not consider group action of closely spaced augercast piles (closer than 2.5 diameters, center to center). Once final pile group sizes and spacings are determined, the axial capacity of the pile group should be re-evaluated. 2. Total augercast pile capacity is a summation of its side and base resistances. Ultimate resistances shown on the plot above do not include a factor of safety (FS). ASSUMED SUBSURFACE PROFILE Based on Nearby Exploration: B-1 0 10 20 30 40 50 60 70 80 0 100 200 300 400 500 DE P T H ( f e e t ) ULTIMATE RESISTANCE (kips) Side Resistance (Seismic) Base Resistance (Seismic) Total Resistance Estimated Liquefied Zone Estimated Liquefied Zone Add Downdrag Loads to Other Foundation Loads Loose to medium dense, gray, Silty Sand with Gravel (SM) 0' Medium stiff to stiff, OL/ML 14' Medium dense, dark gray, Poorly Graded Sand (SP) 18' Hard, brown Silt (ML)28' Medium dense to dense, dark gray, Poorly Graded Sand (SP) 31' Loose to medium dense, gray-brown, Silty Sand (SM) 38' Dense, dark gray, Poorly Graded Sand with Gravel (SP) 54' Decomposed Sandstone 70' Subsurface profile assumes ~10 feet of excavation to remove fill mound King County South Biogas Plant Renton, Washington Geotechnical and Environmental ConsultantsSHANNON & WILSON, INC.FIG.6 ESTIMATED AXIAL AUGERCAST PILE RESISTANCE 24-INCH DIAMATER -POST -SEISMIC January 2017 21-1-22210-001 21-1-22210-001 APPENDIX A SUBSURFACE EXPLORATIONS 21-1-22210-001-R1f-AA/wp/lkn 21-1-22210-001 A-i APPENDIX A SUBSURFACE EXPLORATIONS TABLE OF CONTENTS FIGURES A-1 Soil Description and Log Key (3 sheets) A-2 Log of Boring B-1 (2 sheets) A-3 Log of Boring B-2 (3 sheets) A-4 Boring No. B-403 (Converse Consultants) (2 sheets) A-5 Log of Test Pit No. 2 (Converse Ward Davis Dixon A-6 Boring No. B-301 (Converse Consultants) A-7 Boring No. 202 (Converse Consultants) (2 sheets) A-8 Boring No. B-501 (Converse Consultants) 21-1-22210-001 APPENDIX B GEOTECHNICAL LABORATORY RESULTS 21-1-22210-001-R1f-AB/wp/lkn 21-1-22210-001 B-i APPENDIX B GEOTECHNICAL LABORATORY RESULTS TABLE OF CONTENTS FIGURES B-1 Grain Size Distribution Plot, B-1 B-2 Grain Size Distribution Plot B-2 21-1-22210-001 APPENDIX C IMPORTANT INFORMATION ABOUT YOUR GEOTECHNICAL/ENVIRONMENTAL REPORT Page 1 of 2 1/2017 SHANNON & WILSON, INC. Geotechnical and Environmental Consultants Dated: Attachment to and part of Report 21-1-22210-001 Date: January 6, 2017 To: Mr. Ian McKelvey Brown and Caldwell IMPORTANT INFORMATION ABOUT YOUR GEOTECHNICAL/ENVIRONMENTAL REPORT CONSULTING SERVICES ARE PERFORMED FOR SPECIFIC PURPOSES AND FOR SPECIFIC CLIENTS. Consultants prepare reports to meet the specific needs of specific individuals. A report prepared for a civil engineer may not be adequate for a construction contractor or even another civil engineer. Unless indicated otherwise, your consultant prepared your report expressly for you and expressly for the purposes you indicated. No one other than you should apply this report for its intended purpose without first conferring with the consultant. No party should apply this report for any purpose other than that originally contemplated without first conferring with the consultant. THE CONSULTANT'S REPORT IS BASED ON PROJECT-SPECIFIC FACTORS. A geotechnical/environmental report is based on a subsurface exploration plan designed to consider a unique set of project-specific factors. Depending on the project, these may include: the general nature of the structure and property involved; its size and configuration; its historical use and practice; the location of the structure on the site and its orientation; other improvements such as access roads, parking lots, and underground utilities; and the additional risk created by scope-of-service limitations imposed by the client. To help avoid costly problems, ask the consultant to evaluate how any factors that change subsequent to the date of the report may affect the recommendations. Unless your consultant indicates otherwise, your report should not be used: (1) when the nature of the proposed project is changed (for example, if an office building will be erected instead of a parking garage, or if a refrigerated warehouse will be built instead of an unrefrigerated one, or chemicals are discovered on or near the site); (2) when the size, elevation, or configuration of the proposed project is altered; (3) when the location or orientation of the proposed project is modified; (4) when there is a change of ownership; or (5) for application to an adjacent site. Consultants cannot accept responsibility for problems that may occur if they are not consulted after factors which were considered in the development of the report have changed. SUBSURFACE CONDITIONS CAN CHANGE. Subsurface conditions may be affected as a result of natural processes or human activity. Because a geotechnical/environmental report is based on conditions that existed at the time of subsurface exploration, construction decisions should not be based on a report whose adequacy may have been affected by time. Ask the consultant to advise if additional tests are desirable before construction starts; for example, groundwater conditions commonly vary seasonally. Construction operations at or adjacent to the site and natural events such as floods, earthquakes, or groundwater fluctuations may also affect subsurface conditions and, thus, the continuing adequacy of a geotechnical/environmental report. The consultant should be kept apprised of any such events, and should be consulted to determine if additional tests are necessary. MOST RECOMMENDATIONS ARE PROFESSIONAL JUDGMENTS. Site exploration and testing identifies actual surface and subsurface conditions only at those points where samples are taken. The data were extrapolated by your consultant, who then applied judgment to render an opinion about overall subsurface conditions. The actual interface between materials may be far more gradual or abrupt than your report indicates. Actual conditions in areas not sampled may differ from those predicted in your report. While nothing can be done to prevent such situations, you and your consultant can work together to help reduce their impacts. Retaining your consultant to observe subsurface construction operations can be particularly beneficial in this respect. Page 2 of 2 1/2017 A REPORT'S CONCLUSIONS ARE PRELIMINARY. The conclusions contained in your consultant's report are preliminary because they must be based on the assumption that conditions revealed through selective exploratory sampling are indicative of actual conditions throughout a site. Actual subsurface conditions can be discerned only during earthwork; therefore, you should retain your consultant to observe actual conditions and to provide conclusions. Only the consultant who prepared the report is fully familiar with the background information needed to determine whether or not the report's recommendations based on those conclusions are valid and whether or not the contractor is abiding by applicable recommendations. The consultant who developed your report cannot assume responsibility or liability for the adequacy of the report's recommendations if another party is retained to observe construction. THE CONSULTANT'S REPORT IS SUBJECT TO MISINTERPRETATION. Costly problems can occur when other design professionals develop their plans based on misinterpretation of a geotechnical/environmental report. To help avoid these problems, the consultant should be retained to work with other project design professionals to explain relevant geotechnical, geological, hydrogeological, and environmental findings, and to review the adequacy of their plans and specifications relative to these issues. BORING LOGS AND/OR MONITORING WELL DATA SHOULD NOT BE SEPARATED FROM THE REPORT. Final boring logs developed by the consultant are based upon interpretation of field logs (assembled by site personnel), field test results, and laboratory and/or office evaluation of field samples and data. Only final boring logs and data are customarily included in geotechnical/environmental reports. These final logs should not, under any circumstances, be redrawn for inclusion in architectural or other design drawings, because drafters may commit errors or omissions in the transfer process. To reduce the likelihood of boring log or monitoring well misinterpretation, contractors should be given ready access to the complete geotechnical engineering/environmental report prepared or authorized for their use. If access is provided only to the report prepared for you, you should advise contractors of the report's limitations, assuming that a contractor was not one of the specific persons for whom the report was prepared, and that developing construction cost estimates was not one of the specific purposes for which it was prepared. While a contractor may gain important knowledge from a report prepared for another party, the contractor should discuss the report with your consultant and perform the additional or alternative work believed necessary to obtain the data specifically appropriate for construction cost estimating purposes. Some clients hold the mistaken impression that simply disclaiming responsibility for the accuracy of subsurface information always insulates them from attendant liability. Providing the best available information to contractors helps prevent costly construction problems and the adversarial attitudes that aggravate them to a disproportionate scale. READ RESPONSIBILITY CLAUSES CLOSELY. Because geotechnical/environmental engineering is based extensively on judgment and opinion, it is far less exact than other design disciplines. This situation has resulted in wholly unwarranted claims being lodged against consultants. To help prevent this problem, consultants have developed a number of clauses for use in their contracts, reports, and other documents. These responsibility clauses are not exculpatory clauses designed to transfer the consultant's liabilities to other parties; rather, they are definitive clauses that identify where the consultant's responsibilities begin and end. Their use helps all parties involved recognize their individual responsibilities and take appropriate action. Some of these definitive clauses are likely to appear in your report, and you are encouraged to read them closely. Your consultant will be pleased to give full and frank answers to your questions. The preceding paragraphs are based on information provided by the ASFE/Association of Engineering Firms Practicing in the Geosciences, Silver Spring, Maryland