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20-104021_14 Supplemental Geotechnical Report_12-03-2019-V1 Geotechnical Engineering Report The Commons, Supplemental Merlone Geier Partners 457 SW 148th Street, Suite 202 Burien, Washington 98166 Attn: Mr. Glenn Goodman Prepared For: December 3, 2019 Project No. 19-0193 Merlone Geier Partners 457 SW 148th Street, Suite 202 Burien, Washington 98166 Attention: Mr. Glenn Goodman Regarding: Supplemental Geotechnical Report The Commons 32000 Block of Pacific Highway South Federal Way, Washington, 98003 Dear Mr. Goodman, As requested, GeoTest Services, Inc. (GTS) is pleased to submit the following report summarizing the results of our supplemental evaluation for the proposed development located on the 32000 Block of Pacific Highway South in Federal Way, Washington (Vicinity Map, Figure 1). This report has been prepared in general accordance with the terms and conditions established in the services agreement authorized by Merlone Geier. We appreciate the opportunity to provide geotechnical services on this project and look forward to assisting you during the construction phase. Should you have any further questions regarding the information contained within the report, or if we may be of service in other regards, please contact the undersigned. Respectfully, GeoTest Services, Inc. Zach Click Staff Geologist Edwardo Garcia, P.E. Geotechnical Department Manager Enclosure: Supplemental Geotechnical Report TABLE OF CONTENTS PURPOSE AND SCOPE OF SERVICES ...................................................................................................... 1 PROJECT DESCRIPTION ......................................................................................................................... 1 SITE CONDITIONS ................................................................................................................................. 2 Surface Conditions ................................................................................................................................... 2 Subsurface Soil Conditions ....................................................................................................................... 2 General Geologic Conditions .................................................................................................................... 4 Groundwater ............................................................................................................................................ 4 GEOLOGIC HAZARDS ............................................................................................................................ 5 Landslide Hazard ...................................................................................................................................... 5 Erosion Hazard ......................................................................................................................................... 5 Seismic Hazard ......................................................................................................................................... 6 Volcanic Hazard ........................................................................................................................................ 6 CONCLUSIONS AND RECOMMENDATIONS ........................................................................................... 7 Site Preparation and Earthwork ............................................................................................................... 8 Fill and Compaction .................................................................................................................................. 8 Reuse of Existing Fill Soil ...................................................................................................................... 9 Reuse of Native Till Soil ........................................................................................................................ 9 Structural Fill ........................................................................................................................................ 9 Compaction of Structural Fill ............................................................................................................. 10 Wet Weather Earthwork ........................................................................................................................ 10 Seismic Design Considerations ............................................................................................................... 10 Foundation Support ............................................................................................................................... 11 Allowable Bearing Capacity ............................................................................................................... 12 Foundation Settlement ...................................................................................................................... 12 Deep Foundation Alternatives ............................................................................................................... 12 Floor Support ......................................................................................................................................... 13 Foundation and Site Drainage ................................................................................................................ 13 Resistance to Lateral Loads .................................................................................................................... 14 Temporary and Permanent Slopes ........................................................................................................ 15 Utilities ................................................................................................................................................... 16 Pavement Subgrade Preparation ........................................................................................................... 17 Flexible Pavement Sections – Light Duty ........................................................................................... 17 Flexible Pavement Sections – Heavy Duty ......................................................................................... 17 Concrete Pavement Sections ............................................................................................................. 17 Stormwater Infiltration Potential ........................................................................................................... 18 Stormwater Treatment ...................................................................................................................... 18 Geotechnical Consultation and Construction Monitoring ..................................................................... 19 USE OF THIS REPORT .......................................................................................................................... 19 REFERENCES ....................................................................................................................................... 20 GeoTest Services, Inc. The Commons – Federal Way, WA 1 December 3, 2019 Project Number 19-0193 PURPOSE AND SCOPE OF SERVICES The purpose of this evaluation is to establish general subsurface conditions beneath the site from which conclusions and recommendations pertaining to project design can be formulated. Our scope of services includes the following tasks: • Exploration of soil and groundwater conditions underlying the site by advancing 6 hollow stem auger borings with a subcontracted drilling service to evaluate subsurface conditions. • Laboratory testing on representative samples to classify and evaluate the engineering characteristics of the soils encountered. • To provide a written report containing a description of subsurface conditions, exploration logs, findings and recommendations pertaining to site preparation and earthwork, fill and compaction, seismic design, foundation recommendations, concrete slab-on-grade construction, foundation and site drainage, utilities, temporary and permanent slopes, utilities, pavement, stormwater infiltration feasibility, geotechnical consultation and construction monitoring. PROJECT DESCRIPTION GeoTest understands that there are plans to construct one or more single-story retail buildings at the above location. The project is in the western portion of the retail development referred to as “The Commons”. The proposed areas of improvement are largely expected to occur around the now-vacant Sears building. Preliminary construction plans suggest that either one or two new buildings will be constructed that will occupy between 4,300 and 8,500 square feet along with parking stall and drive access. GeoTest was not provided with a formal design plan, but we generally anticipate that new construction will be one story in height and that new construction will utilize shallow conventional foundations. It is possible that additional stories could be present in the final design, but GeoTest expects that structural loads will be relatively light. GeoTest previously provided a geotechnical report titled Geotechnical Engineering Report – Revised, The Commons, 32000 Block of Pacific Highway South, Federal Way, Washington 98003, dated July 23, 2019. This report largely identified subsurface soil conditions to the north of existing buildings and infrastructure. Our current scope of services is intended to provide similar subsurface soil information for areas located to the west of the existing Sears buildings. GeoTest Services, Inc. The Commons – Federal Way, WA 2 December 3, 2019 Project Number 19-0193 SITE CONDITIONS This section includes a description of the general surface and subsurface conditions observed at the project site during the time of our field investigation. Interpretations of site conditions are based on the results and review of available information, site reconnaissance, subsurface explorations, laboratory testing, and previous experience in the project vicinity. Surface Conditions The subject area is presently surfaced with asphalt and contains established drive lanes and parking. The project site and vicinity are generally level in all directions and contain retail businesses in an urban environment. The project site is bordered to the west by Pacific Highway South, to the north and south by asphalt parking and drive lanes, and The Commons retail shopping mall to the east. The area is sparsely vegetated with landscape plantings that include various grass lawns, shrubs, hedges and deciduous trees. There was no observed surface water noted at the time of our exploration. Image 1. Site surface conditions taken from the vicinity of B-4 in the southwest area of the project near Pacific Highway South and South 324th Street. View looking northeast. Subsurface Soil Conditions Subsurface conditions were explored by advancing 6 soil borings (B-9 through B-14) on November 14, 2019. The explorations were advanced to depths of between 21.5 and 31.5 feet below ground surface (BGS) using a 6-inch diameter, hollow-stem auger soil drill on a rubber-tracked drill rig GeoTest Services, Inc. The Commons – Federal Way, WA 3 December 3, 2019 Project Number 19-0193 machine. Samples were generally taken at 2.5-foot and 5-foot intervals. A GeoTest Staff Geologist observed drilling operations and logged the soils encountered. Upon completion, all of the boring locations were backfilled with soil tailings and bentonite, and the upper approximately 6 inches of the boring were capped with compacted cold patch asphalt. Please refer to the attached Site and Exploration Plan, Figure 2, for approximate boring locations. The borehole logs can be found in Figures 5 through 10 of this report, with laboratory results presented in Figures 11 and 12. Disturbed but representative samples were obtained during drilling by using the Standard Penetration Test (SPT) procedure in accordance with American Society for Testing and Materials ASTM D1586 during the explorations. This test and sampling method consists of driving a standard 2-inch outside-diameter, split-barrel sampler a distance of 18 inches into the soil with a 140-pound hammer free-falling a height of 30 inches. The number of blows for each 6-inch interval is recorded and the number of blows required to drive the sampler the final 12 inches is known as the Standard Penetration Resistance (“N”) or blow count. If a total of 50 blows is recorded within one 6-inch interval, the blow count is recorded as the number of blows for the corresponding number of inches of penetration. The resistance, or N-value, provides a measure of the relative density of granular soils or the relative consistency of cohesive soils; these values are reported on the attached boring logs. The subject site was generally surfaced by 2 to 4 inches of asphalt pavement in locations tested. Below the pavement, an imported, compacted fill material was observed to a depth of about 2.5 feet below ground surface (BGS) before transitioning to previously placed fill soils that appeared to consist of native borrow material. Native borrow material typically consists of on-site or regionally available materials that were cut from one end of a project site and used as fill materials in other areas of the same project site. The native borrow fill soils were observed in all locations, in varying thicknesses, and were overlying dense to very dense, undisturbed, native soil. Native borrow fill soils were encountered to depths of between 10 and 20 feet BGS. These soils ranged from very loose to dense, had variable moisture contents, were of variable color, and were primarily silty, gravelly sands with occasional organic debris. Native soils were interpreted to be glacial Till. In majority, the underlying native soils were dense to very dense, light brown to gray, silty, gravelly sand. The native soils extended to the full depth of all explorations. The drill rig generally had difficultly advancing through the Till horizon and blow counts or N-Values were commonly over 50 for a one-foot interval. GeoTest Services, Inc. The Commons – Federal Way, WA 4 December 3, 2019 Project Number 19-0193 Photo 2. Drilling in progress at borehole B-1 in the northeast area of the site, adjacent to Sears and Daiso. View looking southeast. General Geologic Conditions General geologic conditions at the site are mapped as glacial Till of the Vashon Stade of the Fraser Glaciation, specifically known as Vashon Till (Booth, 2004). Glacial Till refers to heterogeneous soils mixed, transported, and deposited directly by a glacier. Glacial Till is generally compact diamicton containing subrounded to well-rounded clasts in a massive, silt- or sand-rich matrix. Generally, the glacial Till is a few meters to a few tens of meters thick, forming undulatory surfaces. Till typically exhibits excellent bearing characteristics and low permeability due to its poor grain size sorting and high density. Areas within this mapped deposit may locally contain peat, non-glacial sediments, artificial fill and modified lands. Our on-site explorations indicate that the encountered native subsurface soil conditions at depth are in accordance with the mapped soil units. It should be noted, however, that extensive amounts of fill are present at the project site. Groundwater Subsurface water was observed in borings B-10 through B-14 at depths of approximately 10.5 to 19.5 feet below the existing ground surface at the time of our explorations. We interpret the encountered water to be perched horizons or transient water conditions that fluctuate seasonally and with storm events. The observed water is not representative of a regional groundwater condition. The Washington State Department of Ecology Well Report Viewer indicates that nearby resource protection wells reported for The Commons shopping mall were in a dry condition at depths of 11 to 16 feet below existing site grades as of 2016. GeoTest Services, Inc. The Commons – Federal Way, WA 5 December 3, 2019 Project Number 19-0193 The groundwater conditions reported on the exploration logs are for the specific locations and dates indicated, and therefore may not be indicative of other locations and/or times. Groundwater levels are variable, and conditions will fluctuate depending on local subsurface conditions, precipitation, and changes in on-site and off-site use. GEOLOGIC HAZARDS GeoTest reviewed Section 19.05 of the Federal Way Revised Code (FWRC) to determine how Geologically Hazardous Areas were defined. Geologically Hazardous areas that exist in the region are typically limited to Landslide, Erosion, and Seismic hazard areas. Based on the proximity to Mount Baker, GeoTest has also included a brief discussion on Volcanic Hazards with respect to the planned construction. Landslide Hazard Landslide hazard areas are those locations potentially subject to episodic downslope movement of a mass of soil or rock. The project site is flat and there are no steep slopes mapped on or in close proximity to the proposed areas of improvement. As such, no slope landslide hazard areas exist on the site per the Federal Way Revised Code (FWRC 19.05.070). Thus, no mitigation is recommended for this type of geologic hazard. Erosion Hazard Section 19.05.070 of the FWRC defines an erosion hazard area as those areas identified by the U.S. Department of Agriculture’s Natural Resource Conservation Service as having a moderate to severe or severe to very severe rill and inter-rill erosion hazard due to natural agents such as wind, rain, splash, frost action or stream flow; those areas containing the following group of soils when they occur on slopes of 15 percent or greater: Alderwood-Kitsap (“AkF”), Alderwood gravelly sandy loam (“AgD”), Kitsap silt loam (“KpD”), Everett (“EvD”), and Indianola (“InD”); and those areas impacted by shoreline and/or stream bank erosion. The site is generally level and does not contain slopes greater than 15 percent with the above- mentioned soil types. The topography within and adjacent to the areas of improvement are not considered to be susceptible to rill and inter-rill erosion. Site development is expected to mitigate for both short-term and long-term erosion through the use of paving, landscaping, and vegetation management. It is GeoTest’s opinion that an Erosion Hazard, as defined by FWRC 19.05.070, is not present on the site. Thus, no specific mitigation to ad dress Erosion Hazards is required. GeoTest Services, Inc. The Commons – Federal Way, WA 6 December 3, 2019 Project Number 19-0193 Seismic Hazard Section 19.05.070 of the FWRC defines seismic hazard areas as those areas that are subject to severe risk of earthquake damage as a result of seismically induced ground shaking, slope failure, settlement or soil liquefaction, or surface faulting. The FWRC states that seismic hazard areas typically occur in areas underlain by cohesionless soils of low density, usually in association with a shallow groundwater table. GeoTest found native soil at depth neither “low density” soil or to have a shallow groundwater table. The near-surface fill soils were generally medium dense and the underlying native soils were significantly denser. A review of the proposed area of improvement mapped by Palmer et al., in the Liquefaction Susceptibility Map of King County, Washington (2004) indicated a “very low” liquefaction susceptibility for native soils. Thus, it is GeoTest’s opinion that the site is not susceptible to seismic induced settlement, shaking, lateral spreading, surface faulting or slope failure because of the flat topography and the dense to very dense native soil that underlies the project site. Thus, a Seismic Hazard, as defined by FWRC 19.05.070, in not present at the site and no specific mitigation to address Seismic Hazards are required. Volcanic Hazard The City of Federal Way and vicinity are in proximity to potential volcanic hazards of the Mount Rainier stratovolcano. According to the DNR Geologic Hazards Maps webpage, Volcanic Hazards in close proximity to Federal Way include lahars (volcanic mudflows) and tephra (ash fall). Lahars are generally described as volcanic mudflows that can travel long distances from their source volcano. A review of the DNR map suggests that the project area is outside of mapped lahar flow areas. Thus, no mitigation to address lahar flows are required as part of the project design. Tephra related hazards exist at the subject site, as they do for the entire Pacific Northwest region. An eruption of Mount Rainier or other Cascade Range volcanoes could be of sufficient size and magnitude to cause an ashfall event. Given the infrequency and size of such eruptions, it is unlikely that any significant mitigation can be provided for this type of volcanic hazard. It is, however, prudent to make the Owner aware that volcanic ash “can pose significant disruption and damage to buildings, transportation, water and wastewater, power supply, communications equipment, and agriculture, leading to potentially substantial societal impacts and costs, even at thicknesses of only a few millimeters or inches” per DNR sources. Thus, no specific mitigation to address volcanic ashfall is considered necessary as part of the project design. GeoTest Services, Inc. The Commons – Federal Way, WA 7 December 3, 2019 Project Number 19-0193 CONCLUSIONS AND RECOMMENDATIONS Based on the evaluation of the data collected during this investigation, it is our opinion that the subsurface conditions at the site are suitable for the proposed development, provided the recommendations contained herein are incorporated into the project design. The subsurface soil explorations encountered similar conditions as in our previous geotechnical report, although the fill depths were approximately 5 vertical feet deeper than our original investigations. Our explorations generically encountered between 15 and 20 feet of historically placed, loose to medium dense fill material overlying dense to very dense, glacially consolidated Till. At the time of this report, GeoTest does not have a formalized design plan. It is, however, assumed that new construction will be either one or two retail buildings between 4,300 to 8,500 square feet in size with relatively light loading conditions. The presence of existing fill under the proposed building footprint will require some overexcavation and replacement of existing fill soil with structural fill, as defined in this report. GeoTest recommends that 2 vertical feet of existing fill be removed and replaced with structural fill below the planned foundations. GeoTest also recommends the use of a woven geotextile fabric such as TenCate® Mirafi® RS280i (or industry equivalent) be placed at the interface between the existing fill soil and the new imported structural fill for uniform support across the foundation alignments. Unless there are basements or extensive grading operations that are planned for the site, it is unlikely that new foundations will be placed on undisturbed native soils. GeoTest generally encountered native soils at depths ranging from about 15 feet to more than 21 feet below existing site grades. Furthermore, the quality of the existing fill was somewhat variable, but generally less dense, at depths between 10 to 20 feet below existing site grades. Thus, moderately- to heavily-loaded foundations, foundations placed more than about 4 feet below existing site grades, or foundations that will support mixed-use or residential structures should consider deep foundation alternatives in order to mitigate the presence of the variably compacted existing fill that exists between 10 and 20 feet below existing site grades. GeoTest is not currently anticipating the use of a deep foundation system, but we can provide recommendations for such a system upon request. The majority of on-site, near surface soils contain elevated fines content ranging from 20 to 40 percent. We consider the reuse of existing fill soils to be feasible across the site if the soils are approved for use within the plans and specifications prepared for this pro ject, placed and compacted at or near optimum moisture content, and are compacted to the requirements of structural fill per this report. Soils with silt and clay contents greater than 5 to 10 percent can be difficult or impossible to compact to industry standards when they are over optimum moisture levels. We recommend that soils with elevated silt contents be reused during the dry season (April through October). GeoTest Services, Inc. The Commons – Federal Way, WA 8 December 3, 2019 Project Number 19-0193 Based on the presence of the variable density, high silt content, existing fill soils that are present on the project site, GeoTest does not recommend that shallow infiltration concepts be incorporated as part of stormwater design for the proposed development. Furthermore, the near-surface existing fill soils are underlain by dense to very dense Till that is generally considered a low-permeability to non-permeable soil. Thus, infiltration concepts that include deeper facilities extending into the undisturbed Till should be considered infeasible. Low Impact Development stormwater management concepts that include the use of raingardens or bioswales, paired with a drain for removing treated stormwater for the facility, appear to be the most likely concepts that will be considered by the designer. Site Preparation and Earthwork The portions of the site proposed for new foundation(s), floor slabs, pavement and/or sidewalk development should be prepared by removing existing pavements, topsoil, deleterious material and significant accumulations of organics. We recommend that new foundations be supported by a minimum of 2 feet of structural fill with TenCate® Mirafi® RS280i (or industry equivalent) geotextile fabric placed at the existing fill interface before placing new imported fill. Areas planned for floor slabs, pavement and walkways may be prepared by removing at least 1 foot of material and replacing with structural fill, or remedially compacting existing fill, to provide firm and unyielding soil conditions for the support of hardscapes. Prior to placement of any foundation elements or structural fill, the exposed subgrade under all areas to be occupied by soil-supported floor slabs, spread, or continuous foundations should be recompacted to a firm and unyielding condition. Verification of compaction can be accomplished through proof rolling with a loaded dump truck, large self-propelled vibrating roller, or similar equipment applicable to the size of the excavation. The purpose of this effort is to identify loose or soft soil deposits so that soil disturbed during site work can be recompacted. Proof rolling should be carefully observed by qualified geotechnical personnel. Areas exhibiting significant deflection, pumping, or over-saturation that cannot be readily compacted should be overexcavated to firm soil. Overexcavated areas should be backfilled with compacted granular material placed in accordance with subsequent recommendations for structural fill. During periods of wet weather, proof rolling could damage the exposed subgrade. Under these conditions, qualified geotechnical personnel should observe subgrade conditions to determine if proof rolling is feasible. Fill and Compaction Structural fill used to obtain final elevations for footings and soil-supported floor slabs must be properly placed and compacted. In most cases, suitable, non-organic, predominantly granular soil may be used for fill material provided the material is properly moisture conditioned prior to GeoTest Services, Inc. The Commons – Federal Way, WA 9 December 3, 2019 Project Number 19-0193 placement and compaction, and the specified degree of compaction is obtained. Material containing topsoil, wood, trash, organic material, or construction debris is not suitable for reuse as structural fill and should be properly disposed offsite or placed in nonstructural areas. Soils containing more than approximately 5 percent fines are considered moisture sensitive, and are difficult to compact to a firm and unyielding condition when over the optimum moisture content by more than approximately 2 percent. The optimum moisture content is that which allows the greatest dry density to be achieved at a given level of compactive effort. Reuse of Existing Fill Soil The existing fill soils are considered suitable for reuse as structural fill if they are free of organics and construction debris, approved for use in the plans and specifications prepared for this project, are placed at or near optimum moisture content, and are compacted to the requirements of structural fill per this report. Existing fill soils, however, have elevated silt contents and will be moisture sensitive. As such, we recommend that grading activities that include these soils only occur during the dry season (April through October). During the winter wet season, it may be difficult or impossible to reuse the existing fill soil as structural fill due to the moisture sensitivity of the soil. Reuse of Native Till Soil The undisturbed, native Till soil at depth is suitable for reuse as structural fill provided it is free of organics, approved for use in the plans and specifications, are placed at or near optimum moisture contents, and are compacted to the requirements of structural fill in this report. It is also notable that the Till is buried by more than 10 vertical feet of existing fill soils across the proposed areas of development. Thus, Till would have to be exposed by the removal of the existing fill for it to be used. At the time of this report, GeoTest is not aware of grading or development plans that include the complete removal of existing fill soils. Structural Fill GTS recommends that imported structural fill consist of clean, well-graded sandy gravel, gravelly sand, or other approved naturally occurring granular material (pit run) with at least 30 percent retained on the No. 4 sieve, or a well-graded crushed rock. Structural fill for dry weather construction may contain up to 10 percent fines (that portion passing the U.S. No. 200 sieve) based on the portion passing the U.S. No. 4 sieve. The use of an imported fill having more than 10 percent fines may be feasible, but the use of these soils should generally be reviewed by the design team prior to the start of construction. Imported structural fill with less than 5 percent fines should be used during wet weather conditions. Due to wet site conditions, soil moisture contents could be high enough that it may GeoTest Services, Inc. The Commons – Federal Way, WA 10 December 3, 2019 Project Number 19-0193 be difficult to compact even clean imported select granular fill to a firm and unyielding condition. Soils with an over-optimum moisture content should be scarified and dried back to a suitable moisture content during periods of dry weather or removed and replaced with drier structural fill. Compaction of Structural Fill Structural fill should be placed in horizontal lifts. The structural fill must measure 8 to 10 inches in loose thickness and be thoroughly compacted. All structural fill placed under load bearing areas should be compacted to at least 95 percent of the maximum dry density, as determined using test method ASTM D1557. The top of the compacted structural fill should extend outside all foundations and other structural improvements a minimum distance equal to the thickness of the fill. We recommend that compaction be tested after placement of each lift in the fill pad. Wet Weather Earthwork The existing fill and native soils are particularly susceptible to degradation during wet weather. As a result, it may be difficult to control the moisture content of site soils during the wet season. If construction takes place during wet weather, GTS recommends that structural fill consist of imported, clean, well-graded sand or sand and gravel as described above. If fill is to be placed or earthwork is to be performed in wet conditions, the contractor may reduce soil disturbance by: • Limiting the size of areas that are stripped of topsoil and left exposed • Accomplishing earthwork in small sections • Limiting construction traffic over unprotected soil • Sloping excavated surfaces to promote runoff • Limiting the size and type of construction equipment used • Providing gravel ‘working mats’ over areas of prepared subgrade • Removing wet surficial soil prior to commencing fill placement each day • Sealing the exposed ground surface by rolling with a smooth drum compactor or rubber- tired roller at the end of each working day • Providing up-gradient perimeter ditches or low earthen berms and using temporary sumps to collect runoff and prevent water from ponding and damaging exposed subgrades Seismic Design Considerations The Pacific Northwest is seismically active and the site could be subject to movement from a moderate or major earthquake. Consequently, moderate levels of seismic shaking should be accounted for during the design life of the project, and the proposed structure should be designed to resist earthquake loading using appropriate design methodology. GeoTest Services, Inc. The Commons – Federal Way, WA 11 December 3, 2019 Project Number 19-0193 For structures designed using the seismic design provisions of the 2015 International Building Code, the existing fill and glacial Till soils underlying the site within the 100 feet is classified as Site Class D, according to 2010 ASCE -7 Standard – Table 20.3-1, Site Class Definitions. The corresponding values for calculating a design response spectrum for the soil profile type is considered appropriate for the site. Please reference the following values for seismic structural design purposes: Conterminous 48 States – 2015 International Building Code Zip Code 98003 Central Latitude = 47.3134, Central Longitude = -122.3126 Short Period (0.2 sec) Spectral Acceleration Maximum Considered Earthquake (MCE) Value of Ss = 1.294 (g) Site Response Coefficient, Fa = 1.0 (Site Class D) Adjusted spectral response acceleration for Site Class D, SMS = Ss x Fa = 1.294 (g) Design spectral response acceleration for Site Class D, SDS = 2/3 x SMs = 0.862 (g) One Second Period (1 sec) Spectral Acceleration Maximum Considered Earthquake (MCE) Value of S1 = 0.496 (g) Site Response Coefficient, Fv = 1.504 (Site Class D) Adjusted spectral response acceleration for Site Class D, SM1 = S1 x Fv = 0.746 (g) Design spectral response acceleration for Site Class D, SD1 = 2/3 x SM1 = 0.497 (g) Foundation Support Continuous or isolated spread footings founded on two feet of overexcavated and replaced, properly compacted structural fill overlying firm and unyielding native borrow fill soils can provide foundation support for the proposed improvements. We recommend that a woven geotextile fabric, such as Tencate® Mirafi® RS280i (or industry equivalent), be placed directly on native borrow fill soils prior to the placement of structural fill. GeoTest recommends that the existing fill be recompacted prior to the placement of geotextile fabric. We recommend that qualified geotechnical personnel confirm that suitable bearing conditions have been reached prior to placement of geotextile fabric, structural fill or foundation formwork. To provide proper support, GeoTest recommends that any pavement, construction debris, deleterious material or soil with organic content greater than 3 percent be removed from beneath the building foundation area(s) and be replaced with properly compacted structural fill as described in the Fill and Compaction section of this report. Localized overexcavation, if necessary, can be backfilled to the design footing elevation with structural fill or lean concrete. GeoTest Services, Inc. The Commons – Federal Way, WA 12 December 3, 2019 Project Number 19-0193 The limits of the overexcavation below foundation areas should extend laterally beyond the edge of each side of the footing a distance equal to the depth of the excavation below the base of the footing. If lean concrete is used to backfill the excavation, the limits of the excavation need only extend a nominal distance beyond the width of the footing. In addition, GeoTest recommends that foundation elements for the proposed structure(s) bear entirely on similar soil conditions to help prevent differential settlement from occurring. Continuous and isolated spread footings should be founded 18 inches, minimum, below the lowest adjacent final grade for freeze/thaw protection. The footings should be sized in accordance with the structural engineer’s prescribed design criteria and seismic considerations. Allowable Bearing Capacity Assuming the above foundation support criteria are satisfied, continuous or isolated spread footings founded at least 2 feet of overexcavated and replaced, compacted structural fill placed over a geogrid and existing, remedially compacted fill soils may be proportioned using a net allowable soil bearing pressure of up to 2,000 pounds per square foot (psf). The "net allowable bearing pressure" refers to the pressure that can be imposed on the soil at foundation level. This pressure includes all dead loads, live loads, the weight of the footing, and any backfill placed above the footing. The net allowable bearing pressure may be increased by one-third for transient wind or seismic loads. Foundation Settlement Settlement of shallow foundations depends on foundation size and bearing pressure, as well as the strength and compressibility characteristics of the underlying soil. If construction is accomplished as recommended and at the maximum allowable soil bearing pressure, GTS estimates the total settlement of building foundations to be less than one inch. Differential settlement between two adjacent load-bearing components supported on competent soil is estimated to be less than one half the total settlement. Deep Foundation Alternatives Foundations that require more than a 2,000 psf bearing capacity, foundations that extend more than about 4 feet below existing site grades, or foundations that support residential structures should consider the use of a deep foundation that extends through the existing fill soils and several feet into the dense to very dense Till at depth. Existing fill soils to the west of the existing Sears building were generally encountered between 15 and 21 feet below existing site grades. Thus, GeoTest is assuming that deep foundations, if required, will be installed at least 5 to 10 feet into competent native soil at depth, resulting in a total deep foundation installation depth of about 25 to 35 feet below existing site grades. GeoTest Services, Inc. The Commons – Federal Way, WA 13 December 3, 2019 Project Number 19-0193 This report is not intended to provide design-level recommendations for deep foundations. This report is, however, stating that large foundation loads or specific building uses may require that deep foundations be utilized due to the existing fill that is present on the site. If requested, GeoTest can provide geotechnical recommendations for a specified deep foundation type as part of an expanded scope of work. Floor Support Conventional slab-on-grade floor construction is feasible for the planned site improvements. Floor slabs may be supported on properly placed and compacted structural fill placed over firm and unyielding existing fill soil. We recommend that floor slabs be supported by at least 1 foot of imported structural fill, which may include a capillary break material. Prior to placement of structural fill, the native borrow fill soil should be recompacted and proof-rolled or otherwise verified as firm and unyielding as recommended in the Site Preparation and Earthwork section of this report. GeoTest recommends that interior concrete slab-on-grade floors be underlain with at least 6 inches of clean, compacted, angular free-draining gravel. The gravel should contain less than 3 percent passing the U.S. Standard No. 200 sieve (based on a wet sieve analysis of that portio n passing the U.S. Standard No. 4 sieve). The purpose of this gravel layer is to provide uniform support for the slab, provide a capillary break, and act as a drainage layer. To help reduce the potential for water vapor migration through floor slabs, a continuous 10 to 15-mil minimum thickness polyethylene sheet with tape-sealed joints should be installed below the slab to serve as an impermeable vapor barrier. The vapor barrier should be installed and sealed in accordance with the manufacturer’s instructions. Exterior concrete slabs-on-grade, such as sidewalks, may be supported directly on properly placed and compacted structural fill or existing fill; however, long-term performance will be enhanced if exterior slabs are placed on a layer of clean, durable, well-draining granular material. Foundation and Site Drainage GeoTest understands that new construction will likely utilize the existing drainage system in part and incorporate additional stormwater controls, as necessary, on completion of the final design and site layout. Positive surface gradients should be provided adjacent to the proposed building(s) to direct surface water away from the structure and toward suitable drainage facilities. Roof drainage should not be introduced into the perimeter footing drains but should be separately discharged directly to the stormwater collection system or similar municipality- approved outlet. GeoTest Services, Inc. The Commons – Federal Way, WA 14 December 3, 2019 Project Number 19-0193 Pavement and sidewalk areas should be sloped, and drainage gradients should be maintained to carry surface water away from the buildings toward an approved stormwater collection system. Surface water should not be allowed to pond and soak into the ground surface near buildings or paved areas during or after construction. Construction excavations should be sloped to dr ain to sumps where water from seepage, rainfall, and runoff can be collected and pumped to a suitable discharge facility. To reduce the potential for groundwater and surface water to seep into interior spaces, GeoTest recommends that an exterior footing drain system be constructed around the perimeter of new building foundations as shown in the Typical Footing Drain Section (Figure 3) of this report. The drain should consist of a perforated pipe measuring 4 inches in diameter at minimum, surrounded by at least 12 inches of filtering media. The pipe should be sloped to carry water to an approved collection system. The filtering media may consist of open-graded drain rock wrapped in a nonwoven geotextile fabric such as Mirafi 140N (or industry equivalent). For foundations supporting retaining walls, drainage backfill should be carried up the back of the wall and be at least 12 inches wide. The drainage backfill should extend from the foundation drain to within approximately 1 foot of the finished grade and consist of open-graded drain rock containing less than 3 percent fines by weight passing the U.S. Standard No. 200 sieve. The invert of the footing drain pipe should be placed at approximately the same elevation as the bottom of the footing or 12 inches below the adjacent floor slab grade, whichever is deeper, so that water will be contained. This process prevents water from seeping through walls or floor slabs. The drain system should include cleanouts to allow for periodic maintenance and inspection. Resistance to Lateral Loads The lateral earth pressures that develop against foundation walls will depend on the method of backfill placement, degree of compaction, slope of backfill, type of backfill material, provisions for drainage, magnitude and location of any adjacent surcharge loads, and the degree to which the wall can yield laterally during or after placement of backfill. If the wall is allowed to rotate or yield so the top of the wall moves an amount equal to or greater than about 0.001 to 0.002 times its height (a yielding wall), the soil pressure exerted comprises the active soil pressure. When a wall is restrained against lateral movement or tilting (a nonyielding wall), the soil pressure exerted comprises the at rest soil pressure. Wall restraint may develop if a rigid structural network is constructed prior to backfilling or if the wall is inherently stiff. GeoTest recommends that yielding walls under drained conditions be designed for an equivalent fluid density of 35 pounds per cubic ft (pcf) for structural fill and 40 pcf for existing fill or native material in active soil conditions. Nonyielding walls under drained conditions should be designed for an equivalent fluid density of 55 pcf for structural fill and 60 pcf for existing fill or native material in at-rest conditions. Design of walls should include appropriate lateral pressures GeoTest Services, Inc. The Commons – Federal Way, WA 15 December 3, 2019 Project Number 19-0193 caused by surcharge loads located within a horizontal distance equal to or less than the height of the wall. For uniform surcharge pressures, a uniformly distributed lateral pressure equal to 35 percent and 50 percent of the vertical surcharge pressure should be added to the lateral soil pressures for yielding and nonyielding walls, respectively. Passive earth pressures developed against the sides of building foundations, in conjunction with friction developed between the base of the footings and the supporting subgrade, will resist lateral loads transmitted from the structure to its foundation. For design purposes, the passive resistance of well-compacted structural fill placed against the sides of foundations is equivalent to a fluid with a density of 250 pounds per cubic foot. If utilizing native soil as backfill, the passive resistance of well-compacted existing or native fill placed against the sides of foundations is equivalent to a fluid with a density of 250 pounds per cubic foot. The recommended value includes a safety factor of about 1.5 and is based on the assumption that the ground surface adjacent to the structure is level in the direction of movement for a distance equal to or greater than twice the embedment depth. The recommended value also assumes drained conditions that will prevent the buildup of hydrostatic pressure in the compacted fill. Foundation walls should include a drain system constructed in general accordance with the recommendations presented in the Foundation and Site Drainage section of this report. In design computations, the upper 12 inches of passive resistance should be neglected if the soil is not covered by floor slabs or pavement. If future plans call for the removal of the soil providing resistance, the passive resistance should not be considered. An allowable coefficient of base friction of 0.35, applied to vertical dead loads only, may be used between the underlying imported granular structural fill and the base of the footing. We recommend an allowable coefficient of friction of 0.30 for native soil or existing fill. If passive and frictional resistance are considered together, one half the recommended passive soil resistance value should be used since larger strains are required to mobilize the passive soil resistance as compared to frictional resistance. A safety factor of about 1.5 is included in the base friction design value. GeoTest does not recommend increasing the coefficient of friction to resist seismic or wind loads. Temporary and Permanent Slopes Actual construction slope configurations and maintenance of safe working conditions, including temporary excavation stability, should be the responsibility of the contractor, who is able to monitor the construction activities and has direct control over the means and methods of construction. All applicable local, state, and federal safety codes should be followed. All open cuts should be monitored during and after excavation for any evidence of instability. If instability is detected, the contractor should flatten the side slopes or install temporary shoring. GeoTest Services, Inc. The Commons – Federal Way, WA 16 December 3, 2019 Project Number 19-0193 Temporary excavations in excess of 4 ft should be shored or sloped in accordance with Safety Standards for Construction Work Part N, WAC 296-155-66403. Temporary unsupported excavations in the fill and native soil encountered at the project site are classified as a Type B soil according to WAC 296-155-66401 and may be sloped as steep as 1:1 (Horizontal: Vertical). All soils encountered are classified as Type C soil in the presence of groundwater seepage and sha ll be sloped at 1.5:1 (H:V). Flatter slopes or temporary shoring may be required in areas where groundwater flow is present and unstable conditions develop. Temporary slopes and excavations should be protected as soon as possible using appropriate methods to prevent erosion during periods of wet weather. We recommend that permanent cut or fill slopes be designed for inclinations of 2H:1V or flatter. Sloped areas that contain ponds, reservoirs or other water retaining/detaining structures shall be designed for inclinations of 3H:1V or flatter geometry. All permanent slopes should be vegetated or otherwise protected to limit the potential for erosion as soon as practical after construction. Utilities Utility trenches must be properly backfilled and compacted to reduce cracking or localized loss of foundation, slab, or pavement support. Excavations for new shallow underground utilities are expected to be placed within loose to medium dense existing fill or undisturbed Till at depth. Trench backfill in improved areas (beneath structures, pavements, sidewalks, etc.) should consist of structural fill as defined in the Fill and Compaction section of this report and may consist of imported, existing or native soils. The selection of soil material for trench backfill will depend on moisture contents and general seasonal conditions. Outside of improved areas, trench backfill may consist of reused native material or existing fill provided the backfill can be compacted to the project specifications. Trench backfill should be placed and compacted in general accordance with the recommendations presented in the Fill and Compaction section of this report. Surcharge loads on trench support systems due to construction equipment, stockpiled material, and vehicle traffic should be included in the design of any anticipated shoring system. The contractor should implement measures to prevent surface water runoff from entering trenches and excavations. In addition, vibration as a result of construction activity and traffic may cause caving of the trench walls. The contractor is responsible for trench configurations. All applicable local, state, and federal safety codes should be followed. All open cuts should be monitored by the contractor during excavation for any evidence of instability. If instability is detected, the contractor should flatten the side slopes or install temporary shoring. If groundwater or groundwater seepage is present, and the trench is not properly dewatered, the soil within the trench zone may be prone to caving, GeoTest Services, Inc. The Commons – Federal Way, WA 17 December 3, 2019 Project Number 19-0193 channeling, and running. Trench widths may be substantially wider than under dewatered conditions. Pavement Subgrade Preparation The final design and lateral extent of new pavements at the project site is unknown at present. We assume that some areas of the project site will be designed for new pavements, while other locations may be designated for resurfacing by crack/chip seal, grind and overlay or other similar methods. The following recommendations are meant as a guideline for the design engineer to develop new pavement sections support by prepared subgrades. Flexible Pavement Sections – Light Duty If utilized within light vehicle parking and lower traffic roadway areas, we recommend a standard, or “light duty”, pavement section consist of 2 inches of Class ½-inch HMA asphalt above 2 inches of Crushed Surfacing Top Course (CSTC) meeting criteria set forth in the Washington State Department of Transportation (WSDOT) Standard Specification 9-03.9(3). The base material for the road section should consist of “gravel base” which may include 8 inches of gravel borrow (with 100% passing the 2-inch sieve) or 6 inches of Crushed Surfacing Base Bourse (CSBC) as classified by WSDOT 9-03.9(3) Standards and Specifications. Flexible Pavement Sections – Heavy Duty New driveways, parking or and any other areas that will be accessed by heavy vehicle traffic or higher volumes, such as trucking or delivery lanes, will require a thicker section and should be designed using a paving section consisting 4 inches of Class ½-inch HMA asphalt above 2 inches of Crushed Surfacing Top Course (CSTC) meeting criteria set forth in the WSDOT Standard Specification 9-03.9(3), overlying gravel base. The base material for the road section should consist of “gravel base” which may include 10 inches of gravel borrow (with 100% passing the 2- inch sieve) or 8 inches of Crushed Surfacing Base Bourse (CSBC) as classified by WSDOT 9-03.9(3) Standards and Specifications. Concrete Pavement Sections Concrete pavements could be used for access drives, parking areas, sidewalks, aprons and other features such as garbage enclosures. Design of concrete pavements is a function of concrete strength, reinforcement steel, and the anticipated loading conditions for the roads. For design purposes, a vertical modulus of subgrade reaction of 200 pounds per cubic inch (pci) should be expected for concrete elements constructed over properly placed and compacted structural fill. GeoTest expects that concrete pavement sections, if utilized, will be at least 8 inches thick and be founded on a minimum of 6 inches of compacted gravel base. The design of concrete access and parking areas will need to be performed by a structural engineer. GeoTest recommends that GeoTest Services, Inc. The Commons – Federal Way, WA 18 December 3, 2019 Project Number 19-0193 subgrade soils supporting concrete pavement sections include minor grade changes to allow for passive drainage away from the pavement. GeoTest is available to further consult, review and/or modify our pavement section recommendations based on further discussion and/or analysis with the project team/owner. The above pavement sections are initial recommendations and may be accepted and/or modified by the site civil engineer based on the actual finished site grading elevations and/or the owner’s preferences. Stormwater Infiltration Potential Based on the presence of the uncontrolled and variable density existing fill soils overlying dense to very dense native conditions, GeoTest does not recommend that on-site stormwater infiltration be incorporated as part of the design for the proposed development. Furthermore, the Stormwater Management Manual for Western Washington does not allow for the infiltration of stormwater into uncontrolled fill. The designer may consider Low Impact Development (LID) design such as raingardens or bioswales be incorporated in combination with detention facilities. Stormwater Treatment The stormwater facilities on-site may require some form of pollutant pretreatment with an amended soil prior to on-site infiltration or offsite discharge. The reuse of on-site soil is often the most sustainable and cost-effective method for pollutant treatment purposes. Cation exchange capacities, organic contents, and pH of site subsurface soils were also tested to determine possible pollutant treatment suitability. Cation exchange capacity, organic content, and pH tests were performed by Northwest Agricultural Consultants on four soil samples collected from the explorations shown in Table 1. A summary of the laboratory test results is presented below. TABLE 1 Cation Exchange Capacity, Organic Content, and pH Laboratory Test Results Test Pit ID Sample Depth (ft) Geologic Unit Cation Exchange Capacity (meq/100 grams) Organic Content (%) pH B-1 2.5 Existing Fill 9.1 2.75 6.4 B-2 0.17 Existing Fill 7.8 1.19 6.5 B-3 5.0 Existing Fill 6.7 1.12 6.9 B-4 2.5 Existing Fill 6.4 1.77 6.8 B-5 5.0 Existing Fill 6.5 0.83 6.9 B-6 2.5 Existing Fill 5.8 0.79 7.0 GeoTest Services, Inc. The Commons – Federal Way, WA 19 December 3, 2019 Project Number 19-0193 Suitability for onsite pollutant treatment is determined in accordance with SSC-6 of the 2012 Washington State Department of Ecology Stormwater Management Manual for Western Washington. Soils with an organic content of greater than or equal to 1 percent and a cation exchange capacity of greater than or equal to 5 meq/100 grams are characterized as suitable for stormwater treatment. Based on the results shown in Table 1, soils within the upper 5 feet are suitable for stormwater treatment. However, due to the elevated fines content, variable construction debris volume and potential for low to negligible infiltration, the owner may elect to import amended soils with the desired properties for planned treatment facilities. GeoTest is available to perform additional laboratory testing as part of an expanded scope of services. Geotechnical Consultation and Construction Monitoring GTS recommends that we be involved in the project design review process. The purpose of the review is to verify that the recommendations presented in this report are understood and incorporated in the design and specifications. We also recommend that geotechnical construction monitoring services be provided. These services should include observation by GTS personnel during structural fill placement, compaction activities and subgrade preparation operations to confirm that design subgrade conditions are obtained beneath the areas of improvement. Periodic field density testing should be performed to verify that the appropriate degree of compaction is obtained. The purpose of these services is to observe compliance with the design concepts, specifications, and recommendations of this report. In the event that subsurface conditions differ from those anticipated before the start of construction, GeoTest Services would be pleased to provide revised recommendations appropriate to the conditions revealed during construction. GeoTest is available to provide a full range of materials testing and special inspection during construction as required by the local building department and the International Building Code. This may include specific construction inspections on materials such as reinforced concrete, reinforced masonry, wood framing and structural steel. These services are supported by our fully accredited materials testing laboratory. USE OF THIS REPORT GeoTest Services has prepared this report for the exclusive use of Merlone Geier Partners and their design consultants for specific application to the design of the proposed The Commons development located at the 32000 Block of Pacific Highway South in Federal Way, Washington. Use of this report by others is at the user’s sole risk. This report is not applicable to other site GeoTest Services, Inc. The Commons – Federal Way, WA 20 December 3, 2019 Project Number 19-0193 locations. Our services are conducted in accordance with accepted practices of the geotechnical engineering profession; no other warranty, express or implied, is made as to the professional advice included in this report. Our site explorations indicate subsurface conditions at the dates and locations indicated. It is not warranted that these conditions are representative of conditions at other locations and times. The analyses, conclusions, and recommendations contained in this report are based on site conditions to the limited depth and time of our explorations, a geological reconnaissance of the area, and a review of previously published USGS geological information for the site. If variations in subsurface conditions are encountered during construction that differs from those contained within this report, GeoTest should be allowed to review the recommendations and, if necessary, make revisions. If there is a substantial lapse of time between submission of this report and the start of construction, or if conditions change due to construction operations at or adjacent to the project site, we recommend that we review this report to determine the applicability of the conclusions and recommendations contained herein. The earthwork contractor is responsible to perform all work in conformance with all applicable WISHA/OSHA regulations. GeoTest Services, Inc. is not responsible for job site safety on this project, and this responsibility is specifically disclaimed. Attachments: Figure 1 Vicinity Map Figure 2 Site and Exploration Plan Figure 3 Typical Footing and Wall Drain Section Figure 4 Soil Classification System and Key Figures 5-10 Field Exploration Logs Figures 11-12 Laboratory Testing Attached NW Agricultural Consultants Results Attached Limitations and Use of This Report REFERENCES Bakeman, S., Dan, G., Howie, D., Killelea, J., Labib, F., & Ed, O. (n.d.). 2012 Stormwater Management Manual for Western Washington, as Amended in December 2014 (The 2014 SWMMWW) (pp. 1-1042) (United States, Washington State Department of Ecology). Booth, D. B.; Waldron, H. H.; Troost, K. G., 2004, Geologic map of the Poverty Bay 7.5' quadrangle, King and Pierce Counties, Washington: U.S. Geological Survey Scientific Investigations Map 2854, 1 sheet, scale 1:24,000. Federal Way Revised Code – Zoning and Development Code - Definitions, §§ 19.05 (2019). Palmer et al., 2004. Liquefaction Susceptibility Map of King County, Washington [Map]. Washington State Department of Natural Resources, Division of Geology and Earth Resources, Open File Report 2004-20 Structural Engineers Association of California/ Office of Statewide Health, Planning and Development (SEAOC/OSHPD) Seismic Design Maps Tool, Retrieved May 2019 from https://seismicmaps.org GeoTest Services, Inc. The Commons – Federal Way, WA 21 December 3, 2019 Project Number 19-0193 United States Geological Survey, Department of the Interior, 7.5-Minute Topographic Map of Poverty Bay, Washington (1949-2017) Retrieved May 2019 from https://store.usgs.gov/map-locator Washington Geologic Information Portal. (n.d.). Retrieved May 2019, from https://geologyportal.dnr.wa.gov/ Washington State Department of Ecology. (n.d.). Well Report Viewer, Retrieved May 2019 from https://fortress.wa.goc/ecy/wellconstruction/map Date:Scale: GGEEOOTTEESSTT SSEERRVVIICCEESS,,IINNCC.. 741 Marine Drive Bellingham,W A 98225 phone:(360)733-7318 fax:(360)733-7418 Figure By:Project THE COMMONS ADDITIONAL BORINGS PACIFIC HIGHWAY SOUTH FEDERAL WAY,WA 98406 19-0767 1 11-21-19 ZC As Shown VICINITY MAP 2 Miles PROJECT LOCATION MMAAPP RREEFFEERREENNCCEEDD FFRROOMM EEssrrii TTooppooggrraapphhiicc Date:Scale: GGEEOOTTEESSTT SSEERRVVIICCEESS,,IINNCC.. 741 Marine Drive Bellingham,W A 98225 phone:(360)733-7318 fax:(360)733-7418 Figure By:Project THE COMMONS ADDITIONAL BORINGS PACIFIC HIGHWAY SOUTH FEDERAL WAY,WASHINGTON 19-0767 2 11-21-19 ZC As Shown SITE AND EXPLORATION PLAN N SATELLITE IMAGE BY GOOGLE MAPS B-#=Approximate Boring Location B-6 B-5 B-3 B-4 B-2 B-1 100 Feet Date:Scale: GGEEOOTTEESSTT SSEERRVVIICCEESS,,IINNCC.. 741 Marine Drive Bellingham,W A 98225 phone:(360)733-7318 fax:(360)733-7418 Figure By:Project THE COMMONS ADDITIONAL BORINGS PACIFIC HIGHWAY SOUTH FEDERAL WAY,WA 19-0767 3 11-21-19 ZC None TYPICAL FOOTING &WALL DRAIN SECTION Notes: Footings Should be properly buried for frost protection in accordance with International Building Code or local building codes (Typically 18 inches below exterior finished grades) The footing drain will need to be modified from this typical drawing to fit the dimensions of the planned footing and slab configuration SHALLOW FOOTINGS WITH INTERIOR SLAB-ON-GRADE Slope to drain away from structure. Floor Slab Suitable Soil Suitable Soil Free Draining Sand and Gravel Fill Coarse Gravel Capillary Break (6 inch minimum typically clear crushed) Four Inch Diameter,Perforated,Rigid PVC Pipe (Perforations oriented down,wrapped in non-woven geotextile filter fabric,directed to suitable discharge) Drainage Material (Drain Rock or Clear Crushed Rock w/no fines) Approved Non-woven Geotextile Filter Fabric (18 inch minimum fabric lap) Compacted Impervious Soil (12 inch minimum) or Pavement (2 inch minimum) Appropriate Waterproofing Applied to Exterior of Wall Vapor Barrier Typical Framing 4 The Commons Additional Borings Pacific Highway South Federal Way, WA 1 Silty gravel; gravel/sand/silt mixture(s) Clayey gravel; gravel/sand/clay mixture(s)GC 1. Soil descriptions are based on the general approach presented in the Standard Practice for Description and Identification of Soils (Visual-Manual Procedure), as outlined in ASTM D 2488. Where laboratory index testing has been conducted, soil classifications are based on the Standard Test Method for Classification of Soils for Engineering Purposes, as outlined in ASTM D 2487. 2. Soil description terminology is based on visual estimates (in the absence of laboratory test data) of the percentages of each soil type and is defined as follows: SW ROCK ML Field and Lab Test DataDrilling and Sampling Key Portion of Sample Retained for Archive or Analysis Sample Depth Interval Recovery Depth Interval Code Description Code Sample Identification Number ATD Groundwater Approximate water elevation at time of drilling (ATD) or on date noted. Groundwater levels can fluctuate due to precipitation, seasonal conditions, and other factors. a b c d e 1 2 3 4 HIGHLY ORGANIC SOIL CLEAN GRAVEL Inorganic clay of low to medium plasticity; gravelly clay; sandy clay; silty clay; lean clay Soil Classification System Organic silt; organic, silty clay of low plasticity 50% - "GRAVEL," "SAND," "SILT," "CLAY," etc. 50% - "very gravelly," "very sandy," "very silty," etc. 30% - "gravelly," "sandy," "silty," etc. 12% - "slightly gravelly," "slightly sandy," "slightly silty," etc. 5% - "trace gravel," "trace sand," "trace silt," etc., or not noted. Inorganic clay of high plasticity; fat clay Peat; humus; swamp soil with high organic content OLCOARSE-GRAINED SOIL(More than 50% of material islarger than No. 200 sieve size)Poorly graded gravel; gravel/sand mixture(s); little or no fines > 30% and < > 12% and < > 5% and < < Primary Constituent: Secondary Constituents: Additional Constituents: (Liquid limit less than 50) Asphalt concrete pavement or Portland cement pavement Well-graded gravel; gravel/sand mixture(s); little or no fines (More than 50% of materialis smaller than No. 200 sievesize)FINE-GRAINED SOILInorganic silt and very fine sand; rock flour; silty or clayey fine sand or clayey silt with slight plasticity PT OH SAND AND SANDY SOIL GRAVEL AND GRAVELLY SOIL SP MH (Liquid limit greater than 50) Notes: > _ _ _ _ (Little or no fines) GRAVEL WITH FINES (Appreciable amount of fines) (Little or no fines) CLEAN SAND SAND WITH FINES GRAPHIC SYMBOL LETTER SYMBOL GP GM Organic clay of medium to high plasticity; organic silt Inorganic silt; micaceous or diatomaceous fine sand Well-graded sand; gravelly sand; little or no fines GRAPHIC SYMBOL (Appreciable amount of fines) DB AC or PC SM SC RK Description SAMPLER TYPESAMPLE NUMBER & INTERVAL CL GW CH SILT AND CLAY 3.25-inch O.D., 2.42-inch I.D. Split Spoon 2.00-inch O.D., 1.50-inch I.D. Split Spoon Shelby Tube Grab Sample Other - See text if applicable 300-lb Hammer, 30-inch Drop 140-lb Hammer, 30-inch Drop Pushed Other - See text if applicable PP = 1.0 TV = 0.5 PID = 100 W = 10 D = 120 -200 = 60 GS AL GT CA (More than 50% of coarse fraction retained on No. 4 sieve) (More than 50% of coarse fraction passed through No. 4 sieve) Pocket Penetrometer, tsf Torvane, tsf Photoionization Detector VOC screening, ppm Moisture Content, % Dry Density, pcf Material smaller than No. 200 sieve, % Grain Size - See separate figure for data Atterberg Limits - See separate figure for data Other Geotechnical Testing Chemical Analysis SILT AND CLAY WOOD DEBRIS Rock (See Rock Classification) Wood, lumber, wood chips Construction debris, garbage Poorly graded sand; gravelly sand; little or no fines USCS LETTER SYMBOL Silty sand; sand/silt mixture(s) Clayey sand; sand/clay mixture(s) PAVEMENT WD OTHER MATERIALS TYPICAL DESCRIPTIONS MAJOR DIVISIONS TYPICAL DESCRIPTIONS(1)(2) Soil Classification System and Key Figure 29 37 21 16 16 25 b2 b2 b2 b2 b2 b2 Boring Completed 11/14/19 Total Depth of Boring = 21.5 ft. SM/ OL SM1 2 3 4 5 6 W = 9 GS Loose, brown, damp, silty SAND with mixed organics (Topsoils and Planter Bed Organics) - This exploration was performed in a landscape planter area Medium dense, tan and brown, damp, very gravelly, very silty SAND (Native Borrow Fill) - Color is generally variegated throughout the Native Borrow Fill - Relative density changes to dense - Relative density changes to medium dense - Color grades to gray - Color alternates between light brown and gray - Color grades to gray 0 5 10 15 20 25 30 Groundwater not encountered.Graphic Symbol1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Bortec1 Inc./Zach Click B-1 Drilling Method: SAMPLE DATA Ground Elevation (ft): Drilled By:19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ SOIL BORING LOGGROUNDWATER Sampler TypeNotes: SOIL PROFILE Blows/FootUSCS SymbolDepth (ft)Sample Number& IntervalNot Determined Hollow-stem Auger Test DataFigure19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ SOIL BORING LOGThe Commons Additional Borings Pacific Highway South Federal Way, WA 5Log of Boring B-1 Perched Conditions, ATD 54 34 37 31 35 36 50/ 6" 50/ 4" 50/ 4" b2 b2 b2 b2 b2 b2 b2 b2 b2 Boring Completed 11/14/19 Total Depth of Boring = 31.5 ft. AC SM SM SM 7 9 10 11 12 13 14 15 16 W = 12 GS W = 10 GS 2" of Asphalt Pavement (Asphalt) Very dense, light brown, damp, gravelly, silty SAND (Fill) Dense, gray, very gravelly, silty SAND (Native Borrow Fill) - Color is generally variegated throughout the Native Borrow Fill - Color grades to brown to dark brown with streaks of gray - Small wood debris observed in sampler - Color grades to blue to gray Dense, tan to light brown, wet, very gravelly, silty SAND (Glacial Till) - Relative density changes to very dense - Boring spoils were observed to be very loose, saturated and semi-fluid 0 5 10 15 20 25 30 Graphic Symbol1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Bortec1 Inc./Zach Click B-2 Drilling Method: SAMPLE DATA Ground Elevation (ft): Drilled By:19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ SOIL BORING LOGGROUNDWATER Sampler TypeNotes: SOIL PROFILE Blows/FootWater LevelUSCS SymbolDepth (ft)Sample Number& IntervalNot Determined Hollow-stem Auger Test DataFigure19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ SOIL BORING LOGThe Commons Additional Borings Pacific Highway South Federal Way, WA 6Log of Boring B-2 Perched Conditions, ATD 20 21 15 2 10 41 b2 b2 b2 b2 b2 b2 Boring Completed 11/14/19 Total Depth of Boring = 21.5 ft. AC SM SM SM 17 18 19 20 21 22 W = 13 GS 2" of Asphalt Pavement (Asphalt) Medium dense, light brown, damp, gravelly, silty SAND (Fill) Medium dense, gray, damp, gravelly, very silty SAND (Native Borrow Fill) - Color is generally variegated throughout the Native Borrow Fill - Color grades to light brown and tan with little gray - Color grades to gray - Relative density changes to very loose - Soil in the sampler is saturated Medium dense, light brown, gravelly, silty SAND (Glacial Till) 0 5 10 15 20 25 30 Graphic Symbol1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Bortec1 Inc./Zach Click B-3 Drilling Method: SAMPLE DATA Ground Elevation (ft): Drilled By:19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ SOIL BORING LOGGROUNDWATER Sampler TypeNotes: SOIL PROFILE Blows/FootWater LevelUSCS SymbolDepth (ft)Sample Number& IntervalNot Determined Hollow-stem Auger Test DataFigure19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ SOIL BORING LOGThe Commons Additional Borings Pacific Highway South Federal Way, WA 7Log of Boring B-3 Perched Conditions, ATD 30 30 10 15 15 44 31 88 b2 b2 b2 b2 b2 b2 b2 b2 Boring Completed 11/14/19 Total Depth of Boring = 31.5 ft. AC SM SM SM 23 24 25 26 27 28 29 30 W = 10 GS W = 10 GS 2" of Asphalt Pavement (Asphalt) Medium dense, light brown, damp, gravelly, silty SAND (Fill) Medium dense, gray with occasional brown, damp, gravelly, very silty SAND (Native Borrow Fill) - Color is generally variegated throughout the Native Borrow Fill Dense, light brown to gray, very gravelly, silty SAND (Glacial Till) - Relative density changes to very dense 0 5 10 15 20 25 30 Graphic Symbol1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Bortec1 Inc./Zach Click B-4 Drilling Method: SAMPLE DATA Ground Elevation (ft): Drilled By:19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ SOIL BORING LOGGROUNDWATER Sampler TypeNotes: SOIL PROFILE Blows/FootWater LevelUSCS SymbolDepth (ft)Sample Number& IntervalNot Determined Hollow-stem Auger Test DataFigure19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ SOIL BORING LOGThe Commons Additional Borings Pacific Highway South Federal Way, WA 8Log of Boring B-4 Perched Conditions, ATD 16 20 40 20 3 50/ 6" b2 b2 b2 b2 b2 b2 Boring Completed 11/14/19 Total Depth of Boring = 21.5 ft. AC SM SM SM 32 33 34 35 36 37 W = 9 GS 4" of Asphalt Pavement (Asphalt) Medium dense, light brown, damp, gravelly, silty SAND (Fill) Medium dense, gray with occasional brown, damp, gravelly, very silty SAND (Native Borrow Fill) - Color is generally variegated throughout the Native Borrow Fill - Relative density changes to dense - Relative density changes to medium dense - Rock obstruction at the tip of the sampler - Relative moisture increases to wet to saturated - Relative density changes to very loose Very dense, light brown, moist to wet, gravelly, silty SAND (Glacial Till) - Rock obstruction at the tip of the sampler 0 5 10 15 20 25 30 Graphic Symbol1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Bortec1 Inc./Zach Click B-5 Drilling Method: SAMPLE DATA Ground Elevation (ft): Drilled By:19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ SOIL BORING LOGGROUNDWATER Sampler TypeNotes: SOIL PROFILE Blows/FootWater LevelUSCS SymbolDepth (ft)Sample Number& IntervalNot Determined Hollow-stem Auger Test DataFigure19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ SOIL BORING LOGThe Commons Additional Borings Pacific Highway South Federal Way, WA 9Log of Boring B-5 Perched Conditions, ATD 48 29 23 11 25 6 b2 b2 b2 b2 b2 b2 Boring Completed 11/14/19 Total Depth of Boring = 21.5 ft. AC SM SM38 39 40 41 42 43 W = 8 GS 1.5" of Asphalt Pavement (Asphalt) Dense, light brown, very gravelly, silty SAND (Fill) Medium dense, light brown and tan with occasional gray, damp, very gravelly, silty SAND (Native Borrow Fill) - Color is generally variegated throughout the Native Borrow Fill - Relative density changes to loose - Relative moisture increases to wet 0 5 10 15 20 25 30 Graphic Symbol1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Bortec1 Inc./Zach Click B-6 Drilling Method: SAMPLE DATA Ground Elevation (ft): Drilled By:19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ SOIL BORING LOGGROUNDWATER Sampler TypeNotes: SOIL PROFILE Blows/FootWater LevelUSCS SymbolDepth (ft)Sample Number& IntervalNot Determined Hollow-stem Auger Test DataFigure19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ SOIL BORING LOGThe Commons Additional Borings Pacific Highway South Federal Way, WA 10Log of Boring B-6 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 Grain Size Test Data 6 103 Depth U.S. SIEVE NUMBERS 8 %Coarse Gravel 2 143/4 2006 Cc = D30 2/(D60* D10) Cu = D60/D10 1 medium % Coarse Sand finecoarse 4 404 20 D10D30 % Fine Sand PointPercent Finer by Weight140 PI % FinesD60 fine D50 Cc 100 Silt or ClaySand coarse 60 Grain Size in Millimeters GravelCobbles 3 U.S. SIEVE OPENING IN INCHES 1.5 % Fine Gravel 1/2 ClassificationDepth 3/8 Cu 50 To be well graded: 1 < Cc < 3 and Cu > 4 for GW or Cu > 6 for SW LL PL % Medium Sand 16 Point 30 HYDROMETER D90 31.0 17.4 21.6 32.1 6.6 8.6 12.7 7.1 21.2 22.1 14.3 21.1 10.1 14.9 20.7 11.4 9.0 15.3 1.9 5.0 22.2 21.8 21.5 23.3 0.355 1.233 1.282 0.324 0.219 0.264 VERY GRAVELLY, VERY SILTY SAND (SM) VERY GRAVELLY, SILTY SAND (SM) GRAVELLY, SILTY SAND (SM) GRAVELLY, VERY SILTY SAND (SM) 7.5 5.0 25.0 10.0 7.5 5.0 25.0 10.0 B-1 B-2 B-2 B-3 B-1 B-2 B-2 B-3 1.371 3.537 2.516 1.049 18.153 20.888 17.884 15.283 Figure19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ GRAIN SIZE W/STATSThe Commons Additional Borings Pacific Highway South Federal Way, WA 11 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 Grain Size Test Data 6 103 Depth U.S. SIEVE NUMBERS 8 %Coarse Gravel 2 143/4 2006 Cc = D30 2/(D60* D10) Cu = D60/D10 1 medium % Coarse Sand finecoarse 4 404 20 D10D30 % Fine Sand PointPercent Finer by Weight140 PI % FinesD60 fine D50 Cc 100 Silt or ClaySand coarse 60 Grain Size in Millimeters GravelCobbles 3 U.S. SIEVE OPENING IN INCHES 1.5 % Fine Gravel 1/2 ClassificationDepth 3/8 Cu 50 To be well graded: 1 < Cc < 3 and Cu > 4 for GW or Cu > 6 for SW LL PL % Medium Sand 16 Point 30 HYDROMETER D90 17.1 2.4 29.8 28.2 7.5 12.6 10.0 5.7 21.3 25.6 22.1 18.4 15.2 19.1 14.9 9.1 19.9 1.4 0.0 21.2 19.0 38.9 23.2 17.5 1.359 2.44 0.37 0.749 0.239 0.5 0.077 0.088 0.132 VERY GRAVELLY, SILTY SAND (SM) POORLY GRADED SAND with GRAVEL (SP) GRAVELLY, SILTY SAND (SM) VERY GRAVELLY, SILTY SAND (SM) 20.0 30.0 2.5 15.0 20.0 30.0 2.5 15.0 B-4 B-4 B-5 B-6 B-4 B-4 B-5 B-6 0.39 36.32 4.166 4.799 0.98 3.858 29.399 14.471 9.011 24.367 Figure19-0767 11/25/19 X:\0-PROJECTS GEO\00000-PROJECTS 2019-GEO\FULL GEO EVALUATIONS\MERLONE GEIER - 19-0767 - THE COMMONS ADDITIONAL BORINGS\GINT\THE COMMONS ADDITIONAL BORINGS.GPJ GRAIN SIZE W/STATSThe Commons Additional Borings Pacific Highway South Federal Way, WA 12 1 1Information in this document is based upon material developed by ASFE, Professional Firms Practicing in the Geosciences(asfe.org) REPORT LIMITATIONS AND GUIDELINES FOR ITS USE1 Subsurface issues may cause construction delays, cost overruns, claims, and disputes. While you cannot eliminate all such risks, you can manage them. The following information is provided to help: Geotechnical Services are Performed for Specific Purposes, Persons, and Projects At GeoTest our geotechnical engineers and geologists structure their services to meet specific needs of our clients. A geotechnical engineering study conducted for a civil engineer may not fulfill the needs of an owner, a construction contractor or even another civil engineer. Because each geotechnical engineering study is unique, each geotechnical engineering report is unique, prepared solely for the client. No one except you should rely on your geotechnical engineer who prepared it. And no one – not even you – should apply the report for any purpose or project except the one originally contemplated. Read the Full Report Serious problems have occurred because those relying on a geotechnical engineering report did not read it all. Do not rely on an executive summary. Do not read selected elements only. A Geotechnical Engineering Report is Based on a Unique Set of Project-Specific Factors GeoTest’s geotechnical engineers consider a number of unique, project-specific factors when establishing the scope of a study. Typical factors include: the clients goals, objectives, and risk management preferences; the general nature of the structure involved its size, and configuration; the location of the structure on the site; and other planned or existing site improvements, such as access roads, parking lots, and underground utilities. Unless GeoTest, who conducted the study specifically states otherwise, do not rely on a geotechnical engineering report that was: • not prepared for you, • not prepared for your project, • not prepared for the specific site explored, or • completed before important project changes were made. 2 1Information in this document is based upon material developed by ASFE, Professional Firms Practicing in the Geosciences(asfe.org) Typical changes that can erode the reliability of an existing geotechnical engineering report include those that affect: • the function of the proposed structure, as when it’s changed, for example, from a parking garage to an office building, or from a light industrial plant to a refrigerated warehouse, • elevation, configuration, location, orientation, or weight of the proposed construction, • alterations in drainage designs; or • composition of the design team; the passage of time; man-made alterations and construction whether on or adjacent to the site; or by natural alterations and events, such as floods, earthquakes or groundwater fluctuations; or project ownership. Always inform GeoTest’s geotechnical engineer of project changes – even minor ones – and request an assessment of their impact. Geotechnical engineers cannot accept responsibility or liability for problems that occur because their reports do not consider developments of which they were not informed. Subsurface Conditions Can Change This geotechnical or geologic report is based on conditions that existed at the time the study was performed. Do not rely on the findings and conclusions of this report, whose adequacy may have been affected by: the passage of time; by man-made events, such as construction on or adjacent to the site; or by natural events, such as floods, earthquakes, or groundwater fluctuations. Always contact GeoTest before applying the report to determine if it is still relevant. A minor amount of additional testing or analysis will help determine if the report remains applicable. Most Geotechnical and Geologic Findings are Professional Opinions Our site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. GeoTest’s engineers and geologists review field and laboratory data and then apply their professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ – sometimes significantly – from those indicated in your report. Retaining GeoTest who developed this report to provide construction observation is the most effective method of managing the risks associated with anticipated or unanticipated conditions. 3 1Information in this document is based upon material developed by ASFE, Professional Firms Practicing in the Geosciences(asfe.org) A Report’s Recommendations are Not Final Do not over-rely on the construction recommendations included in this report. Those recommendations are not final, because geotechnical engineers or geologists develop them principally from judgment and opinion. GeoTest’s geotechnical engineers or geologists can finalize their recommendations only by observing actual subsurface conditions revealed during construction. GeoTest cannot assume responsibility or liability for the report’s recommendations if our firm does not perform the construction observation. A Geotechnical Engineering or Geologic Report may be Subject to Misinterpretation Misinterpretation of this report by other design team members can result in costly problems. Lower that risk by having GeoTest confer with appropriate members of the design team after submitting the report. Also, we suggest retaining GeoTest to review pertinent elements of the design teams plans and specifications. Contractors can also misinterpret a geotechnical engineering report. Reduce that risk by having GeoTest participate in pre-bid and preconstruction conferences, and by providing construction observation. Do not Redraw the Exploration Logs Our geotechnical engineers and geologists prepare final boring and testing logs based upon their interpretation of field logs and laboratory data. To prevent errors of omissions, the logs included in this report should never be redrawn for inclusion in architectural or other design drawings. Only photographic or electronic reproduction is acceptable; but recognizes that separating logs from the report can elevate risk. Give Contractors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can make contractors liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give contractors the complete geotechnical engineering report, but preface it with a clearly written letter of transmittal. In that letter, consider advising the contractors that the report was not prepared for purposes of bid development and that the report’s accuracy is limited; encourage them to confer with GeoTest and/or to conduct additional study to obtain the specific types of information they need or prefer. A pre-bid conference can also be valuable. Be sure contractors have sufficient time to perform additional study. Only then might you be in a position to give contractors the best information available, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. 4 1Information in this document is based upon material developed by ASFE, Professional Firms Practicing in the Geosciences(asfe.org) In addition, it is recommended that a contingency for unanticipated conditions be included in your project budget and schedule. Read Responsibility Provisions Closely Some clients, design professionals, and contractors do not recognize that geotechnical engineering or geology is far less exact than other engineering disciplines. This lack of understanding can create unrealistic expectations that can lead to disappointments, claims, and disputes. To help reduce risk, GeoTest includes an explanatory limitations section in our reports. Read these provisions closely. Ask questions and we encourage our clients or their representative to contact our office if you are unclear as to how these provisions apply to your project. Environmental Concerns Are Not Covered in this Geotechnical or Geologic Report The equipment, techniques, and personnel used to perform an environmental study differ significantly from those used to perform a geotechnical or geologic study. For that reason, a geotechnical engineering or geologic report does not usually relate any environmental findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated containments, etc. If you have not yet obtained your own environmental information, ask your geotechnical consultant for risk management guidance. Do not rely on environmental report prepared for some one else. Obtain Professional Assistance to Deal with Biological Pollutants Diverse strategies can be applied during building design, construction, operation, and maintenance to prevent significant amounts biological pollutants from growing on indoor surfaces. Biological pollutants includes but is not limited to molds, fungi, spores, bacteria and viruses. To be effective, all such strategies should be devised for the express purpose of prevention, integrated into a comprehensive plan, and executed with diligent oversight by a professional biological pollutant prevention consultant. Because just a small amount of water or moisture can lead to the development of severe biological infestations, a number of prevention strategies focus on keeping building surfaces dry. While groundwater, water infiltration, and similar issues may have been addressed as part of this study, the geotechnical engineer or geologist in charge of this project is not a biological pollutant prevention consultant; none of the services preformed in connection with this geotechnical engineering or geological study were designed or conducted for the purpose of preventing biological infestations.