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Preliminary Geo Engineering Report Belfair Safeway Addition - COM Engineering / Geo-Tech Reports - 9/5/2008
f.ro •`is y f.. Geotechnical Engineering Associated Earth Sciences, Inc. Subsurface Exploration, Geologic Hazard, and Water Resources Preliminary Geotechnical Engineering Report BELFAIR SAFEWAY (#1571) ADDITION Mason County, Washington Environmental Assessments and Remediation Prepared for .. � Safeway, Inc. c/o Mulvanny G2 Architecture Project No. KE080509A Sustainable Development Services September 5, 2008 Geologic Assessments Associated Earth Sciences, Inc. 0 U W] 0 Cefe6m rq O er25 Veaty ofYen ce September 5, 2008 Project No. KE080509A Safeway, Inc. c/o Mulvanny G2 Architecture 601 SW Second Avenue, Suite 1200 Portland, Oregon 97204 Attention: Ms. Lu Wei Hioe Subject: Subsurface Exploration, Geologic Hazard, and Preliminary Geotechnical Engineering Report Belfair Safeway (#1571) Addition Mason County, Washington Dear Ms. Hioe: We are pleased to present the enclosed copies of the above-referenced report. This report summarizes the results of our subsurface exploration, geologic hazard, and geotechnical engineering studies, and offers recommendations for the preliminary design and development of the proposed project. Our recommendations are preliminary in that definite building locations and construction details have not been finalized at the time of this report. We have enjoyed working with you on this study and are confident that the recommendations presented in this report will aid in the successful completion of your project. If you should have any questions or if we can be of additional help to you, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington Bruce L. Blyton, . Principal Engineer BLB/Id KE080509A3 Projects\20080509\KE\W P Kirkland Everett Tacoma 425-827-7701 425-259-0522 253-722-2992 www.aesgeo.com SUBSURFACE EXPLORATION, GEOLOGIC HAZARD, AND PRELIMINARY GEOTECHNICAL ENGINEERING REPORT BELFAIR SAFEWAY (#1571) ADDITION Mason County, Washington Prepared for: Safeway, Inc. c/o Mulvanny G2 Architecture 601 SW Second Avenue, Suite 1200 Portland, Oregon 97204 Prepared by: Associated Earth Sciences, Inc. 911 5`h Avenue, Suite 100 Kirkland, Washington 98033 425-827-7701 Fax: 425-827-5424 September 5, 2008 Project No. KE080509A Subsurface Exploration, Geologic Hazard, and Belfair Safeway (#1571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Project and Site Conditions I. PROJECT AND SITE CONDITIONS 1.0 INTRODUCTION This report presents the results of Associated Earth Sciences, Inc.'s (AESI's) subsurface exploration, geologic hazard, and preliminary geotechnical engineering study for the proposed addition to the existing Safeway (#1571) store, located at the north corner of State Route 3 and Clifton Lane in the Belfair area of Mason County, Washington (Figure 1). The approximate locations of the explorations accomplished for this study are presented on the "Site and Exploration Plan," Figure 2. If any changes in the nature, design, or locations of the site development improvements are planned, the conclusions and recommendations in this report should be reviewed and modified, or verified. The recommendations in this report are preliminary because grading plans and construction details were not finalized at the time of this report. Once development plans are substantially complete, the conclusions and recommendations in this report should be reviewed and modified, or verified, as appropriate. 1.1 Purpose and Scope The purpose of this study was to provide subsurface data and design recommendations for preliminary design and development of the subject project. This study included a review of available geologic literature, drilling three exploration borings, and performing geologic studies to assess the type, thickness, distribution, and physical properties of the subsurface sediments and shallow ground water conditions. Geologic studies were completed to identify geologic hazards associated with the site. Where warranted, geologic hazard mitigations are recommended. Geotechnical engineering studies were also conducted to recommend the type of suitable foundation, allowable foundation soil bearing pressure, anticipated foundation settlements, basement/retaining wall lateral pressures, floor support recommendations, drainage considerations, including storm water infiltration testing, and erosion mitigation recommendations. This report summarizes our current fieldwork and offers development recommendations, based on our present understanding of the project. 1.2 Authorization Written authorization to proceed with this study was granted by Safeway, Inc. Our study was accomplished in general accordance with our proposal dated August 8, 2008. This report has been prepared for the exclusive use of Safeway, Inc. and its agents for specific application to this project. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering and engineering September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. JPG/ld-KE080509A3-Projects 120080509 WE I WP Page 1 Subsurface Exploration, Geologic Hazard, and Belfair Safeway (#1571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Project and Site Conditions geology practices in effect in this area at the time our report was prepared. No other warranty, express or implied, is made. 2.0 PROJECT AND SITE DESCRIPTION 2.1 Site Description The subject site consists of an existing commercial parcel at the north corner of State Route 3 and Clifton Lane in the Belfair area of Mason County, Washington (Figure 1). The site includes "strip mall"-style retail stores, along with an existing Safeway grocery store. The existing grocery store is a one-story concrete masonry unit (CMU) structure. The area surrounding the existing structures is predominantly paved, with a few landscaped areas. A rockery, ranging in height up to roughly 12 feet, leads up to the adjacent property to the east of the existing Safeway store. 2.2 Project Description Our understanding of the project is based on preliminary project plans provided by Bush, Roed, and Hitchings, Inc. The project consists of the construction of a new addition to the south side of the existing Safeway store. We understand that the current plan includes the infiltration of storm water from the rooftop of the addition into a system located to the east of the existing structure. 3.0 SITE EXPLORATION The site exploration was conducted on August 18, 2008, and consisted of three exploration borings and a geologic and geologic hazard reconnaissance to gain information about the site. The various types of materials and sediments encountered in the explorations, as well as the depths where characteristics of these materials changed, are indicated on the exploration boring logs presented in the Appendix. The depths indicated on the logs where conditions changed may represent gradational variations between sediment types in the field. If changes occurred between sample intervals in our borings, they were interpreted. The locations of the exploration borings are shown on the "Site and Exploration Plan," Figure 2. The conclusions and recommendations presented in this report are based on the exploration borings completed for this study. The number, locations, and depths of the explorations were completed within site and budgetary constraints. Because of the nature of exploratory work below ground, interpolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may sometimes be present due to the random nature of deposition and the alteration of topography by past grading and/or filling. September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. JPL/ld-KE080509A3-Projects M080509WEI WP Page 2 Subsurface Exploration, Geologic Hazard, and Belfair Safeway (#11571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Project and Site Conditions The nature and extent of any variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this report and make appropriate changes. 3.1 Exploration Borings The three borings were completed on the property using a truck-mounted drill rig advancing a 3.75-inch, inside-diameter, hollow-stem auger. During the drilling process, samples were obtained at generally 2.5-foot intervals. The borings were continuously observed and logged by an engineering geologist from our firm. The exploration logs presented in the Appendix are based on the field logs, drilling action, and inspection of the samples secured. Disturbed but representative samples were obtained by using the Standard Penetration Test (SPT) procedure in accordance with American Society for Testing and Materials (ASTM):D 1586. 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 distance 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 are recorded at or before the end of 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 plotted on the attached boring logs. The samples obtained from the split-barrel sampler were classified in the field and representative portions placed in watertight containers. The samples were then transported to our laboratory for further visual classification and geotechnical laboratory testing, as necessary. The various types of soil and ground water elevations, as well as the depths where soil and ground water characteristics changed, are indicated on the exploration boring logs presented in the Appendix of this report. Our explorations and reconnaissance were approximately located by measuring from known site features. Observation Well Installation An observation well was placed in exploration boring EB-3 at the time of drilling to determine if a static ground water level was.present and to measure its depth. On August 20, 2008, a static water level was measured at a depth of 10.3 feet below the ground surface. September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. JPLgd-KE080509A3-Projects1200805091KEMP Page 3 Subsurface Exploration, Geologic Hazard, and Belfair Safeway (#f1571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Project and Site Conditions 4.0 SUBSURFACE CONDITIONS Subsurface conditions at the project site were inferred from the exploration borings accomplished for this study, visual reconnaissance of the site, and review of topography provided on the topographic site plan. As shown on the exploration logs, the exploration borings generally encountered consolidated, granular, glacial sediments. The following section presents more detailed subsurface information organized from the youngest to the oldest sediment types. 4.1 Stratigraphy Vashon Recessional Outwash Below the asphalt, Vashon recessional outwash sediments were encountered in all three exploration borings to the depths explored. The outwash sediments were deposited by meltwater streams flowing from the receding Vashon glacier approximately 10,000 years ago. The outwash material consisted primarily of medium dense to dense, moist to wet, brown, fine to coarse sand, with some gravel, overlying a gravel layer encountered roughly 10 feet below the ground surface. This gravel extended beyond the depths explored. This unit is generally suitable for support of light to moderately loaded foundations and for pavement subbase when properly compacted as discussed in this report. 4.2 Geologic Mapping Review of the regional geologic map titled Geologic Map and Diagrammatic Sections of the Kitsap Peninsula (D. Molenaar, 1962, State of Washington Department of Conservation, Division of Water Resources) indicates that the area of the subject site is underlain by Vashon recessional outwash (Qvr). Our interpretation of the sediments encountered at the subject site is in general agreement with the regional geologic map. 4.3 Hydrology A ground water level was measured in exploration boring EB-3 at a depth of 10.3 feet below the ground surface. It should be noted that the occurrence and level of ground water seepage at the site may vary in response to such factors as changes in season, precipitation, and site use. Exploration for this study was conducted during the month of August when ground water levels are typically lower than their seasonal high. Additional ground water level measurements will be needed to monitor these seasonal influences. September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. !PL/!d-KE080509A3-Projeas1200805091KEMP Page 4 Subsurface Exploration, Geologic Hazard, and Belfair Safeway (#1571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Geologic Hazards and Mitigations II. GEOLOGIC HAZARDS AND MITIGATIONS The following discussion of potential geologic hazards is based on the geologic, topographic, and shallow ground water conditions, as observed and discussed herein. 5.0 SEISMIC HAZARDS AND MITIGATION Earthquakes occur in the Puget Lowland with great regularity. The vast majority of these events are small and are usually not felt by people. However, large earthquakes do occur, as evidenced by the 1949, 7.2-magnitude event; the 2001, 6.8-magnitude event; and the 1965, 6.5-magnitude event. The 1949 earthquake appears to have been the largest in this region during recorded history and was centered in the Olympia area. Evaluation of earthquake return rates indicates that an earthquake of the magnitude between 5.5 and 6.0 is likely within a given 20-year period. Generally, there are four types of potential geologic hazards associated with large seismic events: 1) surficial ground rupture, 2) seismically induced landslides, 3) liquefaction, and 4) ground motion. The potential for each of these hazards to adversely impact the proposed project is discussed below. 5.1 Surficial Ground Rupture The nearest known fault system to the project is the Tacoma Fault. The recurrence interval of movement along this fault system is still unknown, although it is hypothesized to be in excess of several thousand years. No surficial expressions of this fault system have been documented in the vicinity of the site. Due to the suspected long recurrence interval and the lack of surface expressions in the vicinity, the potential for surficial ground rupture is considered to be low during the expected life of the proposed addition, and no mitigation efforts beyond complying with the 2006 International Building Code (IBC) are recommended. 5.2 Seismically Induced Landslides The risk of damage to the proposed project by seismically induced landsliding is low due to the lack of steep slopes in the project area. No mitigation of landslide hazards is warranted. 5.3 Liquefaction The encountered stratigraphy has a low potential for liquefaction due to its medium dense to dense state. No mitigation of liquefaction hazards is warranted. September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. JPL/ld-YE080509A3-Projects120080509iUMP Page 5 Subsurface Exploration, Geologic Hazard, and Belfair Safeway (f11571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Geologic Hazards and Mitigations 5.4 Ground Motion It is our opinion that any earthquake damage to the proposed addition, when founded on suitable bearing strata in accordance with the recommendations contained herein, will be caused by the intensity and acceleration associated with the event and not any of the above- discussed impacts. Structural design of the proposed addition should follow the 2006 IBC. Information presented by the United States Geological Survey (USGS) Earthquake Hazards Program indicates a spectral acceleration for the project area for short periods (0.2 seconds) of Ss = 1.33 and for a 1-second period of Si = 0.49. , Based on the results of subsurface exploration and on an estimation of soil properties at depth utilizing available geologic data, Site Class "C", in conformance with Table 1613.5.2 of the IBC, may be used. 6.0 EROSION HAZARDS AND MITIGATION 6.1 Erosion Hazard Mitigation To mitigate the erosion hazards and potential for off-site sediment transport, we recommend the following: 1. All Temporary Erosion and Sedimentation Control (TESC) measures for a given area to be graded or otherwise worked should be installed prior to any construction activity. 2. Construction access should be provided usirig existing pavement surfacing or rock- covered, temporary access driveways to limit tracking of sediment onto adjacent streets. 3. During the wetter months of the year, or when large storm events are predicted during the summer months, work areas should be stabilized so that if showers occur, the work area can receive the rainfall without excessive erosion or sediment transport. The required measures for an area to be "buttoned-up" will depend on the time of year and the duration the area will be left unworked. During the winter months, areas that are to be left unworked for more than 2 days should be covered with plastic. During the summer months, stabilization will usually consist of seal-rolling the subgrade. 4. Disturbed areas should be revegetated or paved as soon as possible. Outside of the growing season, the disturbed areas should be covered with mulch or plastic sheeting. 5. Surface runoff should be controlled during and following development. Uncontrolled discharge may promote erosion and sediment transport. Collected water should be directed to a County-approved storm drain system. September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. JPL/Id-KE080509A3-Projects1200805091KEIWP Page 6 Subsurface Exploration, Geologic Hazard, and Belfair Safeway (##1571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Geologic Hazards and Mitigations 6. Soils that are to be reused around the site should be stored in such a manner as to reduce erosion from the stockpile. Protective measures may include, but are not limited to, covering with plastic sheeting. 7. Erosion control elements should be maintained and improved, as necessary, until permanent ground cover/pavement is completed. September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. !PL/!d-KE080509A3-Projects1200805091KEWP Page 7 Subsurface Exploration, Geologic Hazard, and Belfair Safeway (111571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Preliminary Design Recommendations III. PRELIMINARY DESIGN RECOMMENDATIONS 7.0 INTRODUCTION Our exploration indicates that, from a geotechnical standpoint, the parcel is suitable for the proposed building addition, provided the recommendations contained herein are properly followed. The foundation bearing stratum is relatively shallow, and conventional spread footing foundations may be utilized for the structure. Consequently, foundations bearing on either the medium dense to very dense, natural sediments, or on structural fill placed over these sediments, are capable of providing suitable building support. 8.0 SITE PREPARATION 8.1 Clearing and Stripping Site preparation of the planned building and pavement areas should include removal of vegetation debris and any other deleterious materials. These unsuitable materials should be properly disposed of off-site. Additionally, any areas of organic topsoil, if present, should be removed and the remaining roots grubbed. Areas where loose surficial soils exist due to grubbing operations should be considered as fill to the depth of disturbance and treated as subsequently recommended for structural fill placement. Any existing septic systems, whether in service or not, should be decommissioned in accordance with King County Public Health requirements and removed from beneath any areas where structures or paving are planned. If any water wells will be removed, they should be decommissioned by a licensed well driller in accordance with Washington Administrative Code (WAC), Section 173-160. Any buried utilities should be removed or relocated if they are under building foundation areas. The resulting depressions should be backfilled with structural fill, as discussed under the "Structural Fill" section of this report. After stripping of the existing pavement, we recommend that the soil exposed in the proposed building or pavement areas be recompacted to a firm and unyielding condition. Any soft or yielding areas identified during or subsequent to recompaction should be overexcavated and backfilled with structural fill. 8.2 Temporary Cut Slopes In our opinion, stable construction slopes should be the responsibility of the contractor and should be determined during construction based on the local conditions encountered at that time. For planning purposes, we anticipate that temporary, unsupported cut slopes in the medium dense, natural sediments can be planned at a maximum slope of 1.5H:1V September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. !PL/1d-KE080509A3-Projects1200805091KEMP Page 8 Subsurface Exploration, Geologic Hazard, and Belfair Safeway (#1571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Preliminary Design Recommendations (Horizontal:Vertical). For temporary cut slopes within the dense to very dense, unweathered natural sediments, up to a 1H:1V inclination may be planned. As is typical with earthwork operations, some sloughing and raveling may occur, and cut slopes may have to be adjusted in the field. Flatter, temporary cut slopes should be anticipated in areas of ground water seepage. In addition, WISHA/OSHA regulations should be followed at all times. 8.3 Site Disturbance The soils encountered in our exploration borings contained varying amounts of fine-grained material. The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened. If disturbance occurs, the softened soils should be removed and the area brought to grade with structural fill. If crushed rock is considered for the access and staging areas, it should be underlain by stabilization fabric (such as Mirafi 50OX or approved equivalent) to reduce the potential of fine-grained materials pumping up through the rock and turning the area to mud. The fabric will also aid in supporting construction equipment, thus reducing the amount of crushed rock required. We recommend that at least 10 inches of rock be placed over the fabric; however, due to the variable nature of the near- surface soils and differences in wheel loads, this thickness may have to be adjusted by the contractor in the field. 9.0 STRUCTURAL FILL Structural fill may be necessary to establish desired grades in some areas, to backfill around foundations and utilities, and to re-establish grade after unsuitable soils are removed. All references to structural fill in this report refer to subgrade preparation, fill type, and placement and compaction of materials, as discussed in this section. If a percentage of compaction is specified under another section of this report, the value given in that section should be used. 9.1 Subgrade Compaction After overexcavation/stripping have been performed to the satisfaction of the geotechnical engineer/engineering geologist, the upper 12 inches of exposed ground should be compacted to a firm and unyielding condition. If the subgrade contains too much moisture, suitable compaction may be difficult or impossible to obtain, and should probably not be attempted. In lieu of compaction of the subgrade surface, the area to receive fill should be blanketed with washed rock or quarry spalls to act as a capillary break between the new fill and the wet subgrade. Where the exposed ground remains soft and further overexcavation is impractical, placement of an engineering stabilization fabric may be necessary to prevent contamination of the free-draining layer by silt migration from below. September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. JPLgd-KE080509A3-ProjeasI20080509WEMP Page 9 i Subsurface Exploration, Geologic Hazard, and Belfair Safeway (#1571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Preliminary Design Recommendations After compaction of the exposed ground is tested and approved, or a free-draining rock course is laid, structural fill may be placed to attain desired grades. 9.2 Structural Fill Compaction Structural fill is defined as non-organic soil, acceptable to the geotechnical engineer, placed in maximum 8-inch loose lifts, with each lift being compacted to at least 95 percent of the modified Proctor maximum dry density using ASTM:D 1557 as the standard. Roadway and utility trench backfill should be placed and compacted in accordance with applicable municipal codes and standards. The top of the compacted fill should extend horizontally a minimum distance of 3 feet beyond the perimeter footings or pavement edges before sloping down at an angle no steeper than 2H:IV. Fill slopes should either be overbuilt and trimmed back to final grade or surface-compacted to the specified density. 9.3 Moisture-Sensitive Fill Soils in which the amount of fine-grained material (smaller than the No. 200 sieve) is greater than approximately 5 percent (measured on the minus No. 4 sieve size) should be considered moisture-sensitive. Use of moisture-sensitive soil in structural fills should be limited to favorable dry weather conditions and near-optimum subgrade moisture. The on-site recessional outwash sediments are generally suitable for use as structural fill, but portions of this soil may contain a moderate amount of silt and be considered moisture-sensitive. In addition, construction equipment traversing the site when the soils are wet can cause considerable disturbance. If fill is placed during wet weather or if proper compaction cannot be obtained, a select import material consisting of a clean, free-draining gravel and/or sand should be used. Free-draining fill consists of non-organic soil with the amount of fine-grained material limited to 5 percent by weight when measured on the minus No. 4 sieve fraction. 9.4 Structural Fill Testing The contractor should note that any proposed fill soils must be evaluated by AESI prior to their use in fills. This would require that we have a sample of the material at least 3 business days in advance to perform a Proctor test and determine its field compaction standard. A representative from our firm should inspect the stripped subgrade and be present during placement of structural fill to observe the work and perform a representative number of in- place density tests. In this way, the adequacy of the earthwork may be evaluated as filling progresses and any problem areas may be corrected at that time. It is important to understand that taking random compaction tests on a part-time basis will not assure L acceptable performance of a fill. As such, we are available to aid the owner in suitable monitoring and testing frequency. September 5, 2008 ASSOCIATED EARTH S JPUId-KE080509A3-Projeas1200805091KEMP joil Subsurface Exploration, Geologic Hazard, and Belfair Safeway (#t1571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Preliminary Design Recommendations 10.0 FOUNDATIONS 10.1 Allowable Soil Bearing Pressure Conventional footings may be used for building support when founded either directly on the medium dense to very dense, natural glacial sediments, or on structural fill placed over these materials, as described under the "Site Preparation" and "Structural Fill" sections of this report. For footings founded either directly upon the medium dense to very dense natural sediments, or on structural fill as described above, we recommend that an allowable bearing pressure of 3,000 pounds per square foot (psf) be used for design purposes, including both dead and live loads. An increase of one-third may be used for short-term wind or seismic loading. 10.2 Footing Widths and Depths Perimeter footings for the proposed building should be buried a minimum of 18 inches into the surrounding soil for frost protection. No minimum burial depth is required for interior footings; however, all footings must penetrate to the prescribed strata, and no footings should be founded in or above loose, organic, or existing fill soils. 10.3 Footings Adjacent to Cuts The area bounded by lines extending downward at 111:1V from any footing must not intersect another footing or intersect a filled area that has not been compacted to at least 95 percent of ASTM:D 1557. In addition, a 1.5H:1V line extending down from any footing must not daylight because sloughing or raveling may eventually undermine the footing. Thus footings should not be placed near the edges of steps or cuts in the bearing soils. 10.4 Footing Settlement Anticipated settlement of footings founded as described above should be on the order of 1 inch or less. However, disturbed soil not removed from footing excavations prior to footing placement could result in increased settlements. 10.5 Footing Subgrade Bearing Verification All footing areas should be observed by AESI prior to placing concrete to verify that the exposed soils can support the design foundation bearing capacity and that construction conforms with the recommendations in this report. Foundation bearing verification may also be required by the governing municipality. September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. !PL/ld-KE080509A3-Projects 120080509WEIWP Page 11 Subsurface Exploration, Geologic Hazard, and Belfair Safeway (#1571)Addition Preliminary Geotechnical Engineering Report Mason County Washington Preliminary Design Recommendations 10.6 Foundation Drainage Perimeter footing drains should be provided, as discussed under the "Drainage Considerations" section of this report. If gravity drainage is not possible, the portion of the structure below the drain level must be designed for combined soil and hydrostatic/buoyant forces. 11.0 LATERAL WALL PRESSURES All backfill behind walls or around foundations should be placed following our recommendations for structural fill and as described in this section of the report. Horizontally backfilled walls, which are free to yield laterally at least 0.1 percent of their height, may be designed using an equivalent fluid equal to 35 pounds per cubic foot (pcf). Fully restrained, horizontally backfilled, rigid walls that cannot yield should be designed for an equivalent fluid of 50 pcf. Walls that retain sloping backfill at a maximum angle of 2H:1V should be designed for 55 pcf for yielding conditions and 75 pcf for restrained conditions. If parking areas are adjacent to walls, a surcharge equivalent to 2 feet of soil should be added to the wall height in determining lateral design forces. Undrained walls/structures must be designed for combined soil and hydrostatic pressures (85 pcf for yielding walls, 100 pcf for unyielding walls with horizontal backfill) and for buoyant/uplift forces. 11.1 Wall Backfill The lateral pressures presented above are based on the conditions of a uniform backfill consisting of either the on-site glacial sediments, or imported sand and gravel compacted to 92 percent of ASTM:D 1557. A higher degree of compaction is not recommended, as this will increase the pressure acting on the walls. A lower compaction may result in unacceptable settlement behind the walls. Thus, the compaction level is critical and must be tested by our firm during placement. The recommended compaction of 92 percent of ASTM:D 1557 applies to any structural fill placed behind the wall within a distance equal to the wall height and up to the elevation of the top of the wall. Structural fill used to construct slopes behind retaining walls should be compacted to at least 95 percent of ASTM:D 1557 if the fill is placed above the elevation of the top of the wall. Surcharges from adjacent footings, heavy construction equipment, or sloping ground must be added to the above-recommended lateral pressures. Footing drains should be provided for all retaining walls, as discussed under the "Drainage Considerations" section of this report. 11.2 Wall Drainage It is imperative that proper drainage be provided so that hydrostatic pressures do not develop against the walls. This would involve installation of a minimum, 1-foot-wide, blanket drain September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. JPL/!d-KE080509A3-Projeas1200805091KEMP Page 12 Subsurface Exploration, Geologic Hazard, and Belfair Safeway (#1571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Preliminary Design Recommendations for the full wall height (excluding the uppermost 1 foot of backfill) using imported washed gravel against the walls. The wall drain material must be hydraulically connected to the footing drainpipe. Wall foundation drains are discussed in Section 13.0 of this report. 11.3 Passive Resistance and Friction Factor Lateral loads can be resisted by friction between the foundation and the natural, medium dense to dense, glacial sediments or supporting structural fill soils, or by "passive" earth pressure acting on the buried portions of the foundations. The foundations must be backfilled with compacted structural fill to achieve the passive resistance provided below. We recommend the following allowable design parameters: • Passive equivalent fluid = 250 pcf • Coefficient of friction = 0.30 Both of these values include a factor of safety of 1.5. 12.0 FLOOR SUPPORT Slab-on-grade floors may be constructed either directly on the medium dense to very dense, natural sediments, or on structural fill placed over these materials. Areas of the slab subgrade that are disturbed (loosened) during construction should be recompacted to an unyielding condition prior to placing the capillary break material, as described below. If moisture intrusion through slab-on-grade floors is to be limited, the floors should be constructed atop a capillary break consisting of a minimum thickness of 4 inches of washed pea gravel or washed, 1/2-inch to 3/a-inch, crushed rock with no fines. The capillary break material should be overlain by a 10-mil (minimum thickness) plastic vapor retarder. 13.0 DRAINAGE CONSIDERATIONS All retaining and perimeter footing walls should be provided with a drain at the footing elevation. The drains should consist of rigid, perforated, polyvinyl chloride (PVC) pipe surrounded by washed pea gravel. The level of the perforations in the pipe should be set approximately 2 inches below the bottom of the footing, and the drains should be constructed with sufficient gradient to allow gravity discharge away from the buildings. All retaining walls should be lined with a minimum, 12-inch-thick, washed gravel blanket provided to within 1 foot of finish grade, and which ties into the footing drain. Roof and surface runoff should September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. JPL11d-KE080509A3-Projects1200805091KE1 wP Page 13 Subsurface Exploration, Geologic Hazard, and ! Belfair Safeway (##1571)Addition Preliminary Geotechnical Engineering Report Mason County Washington Preliminary Design Recommendations not discharge into the footing drain system, but should be handled by a separate, rigid, tightline drain. Exterior grades adjacent to walls should be sloped downward away from the structures to achieve surface drainage. Final exterior grades should promote free and positive drainage away from the buildings at all times. Water must not be allowed to pond or to collect adjacent to foundations or within the immediate building areas. It is recommended that a gradient of at least 3 percent for a minimum distance of 10 feet from the building perimeters be provided, except in paved locations. In paved locations, a minimum gradient of 1 percent should be provided unless provisions are included for collection and disposal of surface water adjacent to the structures. Additionally, pavement subgrades should be crowned to provide drainage toward catch basins and pavement edges. Any crawl-space areas should be provided with drains at low points to prevent water from accumulating. 14.0 INFILTRATION TESTING We completed our infiltration tests at the locations shown on Figure 2 to provide infiltration rate data to the project team. The area and depth targeted for infiltration testing were selected by Bush, Roed, and Hitchings, Inc. Both test locations were within the existing paved parking area. Therefore, to reduce the impact to the existing pavement, we modified the Washington State Department of Ecology Pilot Infiltration Test (PIT) by drilling a 15-inch-diameter boring to the target depth with a truck-mounted drill rig. This modification reduced the disturbance to the existing pavement and resulted in a reduction in the scale of the test. The boring was then filled with clean pea gravel of a significantly larger grain-size distribution than the sand to be tested. Each gravel-filled boring was outfitted with a 4-inch-diameter perforated fill pipe and a 2-inch-diameter observation port. The test results from each location yielded the uncorrected or short-term field infiltration rates shown in Table 1. Table 1 Infiltration Rate Summary Recommended Calculated Field Allowable Test Depth Infiltration Rate Infiltration Rate Exploration No. (feet) (in/hr) (in/hr) INF-1 6 99 11 INF-2 6 88 9.8 in/hr = inches per hour September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. JPL/!d-KE080509A3-Projects 1200805091KEIWP Page 14 Subsurface Exploration, Geologic Hazard, and Belfair Safeway (##1571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Preliminary Design Recommendations Since the scale of the infiltration testing was reduced, a correction factor must be applied to the short-term field infiltration rate. The King County Land Use Inspection Section has presented calibration factors to be used for various types of small-scale tests. Based on these factors, we recommend that a calibration factor of at least 9 be applied to the uncorrected or short-term infiltration rates listed in Table 1. Based on our testing and field conditions observed in our infiltration tests and geotechnical exploration borings performed on this site, it is our opinion that infiltration systems that are designed to be 6 feet deep or less should be designed using an allowable infiltration rate of 9.8 inches per hour. It is our opinion that this design rate has a suitable factor of safety, and the actual rate at which the water will infiltrate from the facility will likely be between the recommended allowable rate and the measured field rates. The infiltration gallery aggregate should be covered by a geotextile filter fabric (Mirafi 180N or equivalent) to separate the aggregate from the pavement base materials. The contractor must protect the system from untreated/turbid water to prevent plugging or blinding of the infiltration surfaces by suspended fines. AESI should be allowed to review the design and observe construction of the infiltration system to verify that subsurface conditions are as anticipated and that the construction conforms to AESI's recommendations. 15.0 PROJECT DESIGN AND CONSTRUCTION MONITORING The recommendations in this report are preliminary because grading plans and construction details were not finalized at the time of this report. We are available to provide additional geotechnical consultation as the project design develops and possibly changes from that upon which this report is based. If significant changes in grading are made, we recommend that AESI perform a geotechnical review of the plans prior to final design completion. In this way, our earthwork and foundation recommendations may be properly interpreted and implemented in the design. We are also available to provide geotechnical engineering and monitoring services during construction. The integrity of the foundations depends on proper site preparation and construction procedures. In addition, engineering decisions may have to be made in the field in the event that variations in subsurface conditions become apparent. Construction monitoring services are not part of this current scope of work. If these services are desired, please let us know, and we will prepare a proposal. September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. rPL11d-KE080509A3-Projecu120080s09UMV& Page 15 Subsurface Exploration, Geologic Hazard, and Belfair Safeway (##1571)Addition Preliminary Geotechnical Engineering Report Mason County, Washington Preliminary Design Recommendations We have enjoyed working with you on this study and are confident that these recommendations will aid in the successful completion of your project. If you should have any questions or require further assistance, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington 84 Y �0 t � col � GO z C 2527 T q 26890 lv� � sed Geb`"o ASS,%G/STEF� �--- -=�/ 0 AL EN 5 o Jeffrey P. Laub, P.G., P.E.G. Bruce L. Blyton, P.E. Project Engineering Geologist Principal Engineer Attachments: Figure 1: Vicinity Map Figure 2: Site and Exploration Plan Appendix: Exploration Logs September 5, 2008 ASSOCIATED EARTH SCIENCES, INC. JPL,/id-KE080509A3-Projects12008050911MWP Page 16 u L w �. tw t—Kt'1,r.3HT RQ ct LD 4,i LU LL s. 2 (=4 1 -'-'.. uj m m u 1 1 i I, I Ld 1, • LFT rh -r, .:. t1 O EEL� S, NE FAIR-S. SITE r� .300 Sr'q fl�$Iq Slq Slgf✓.SJq�•'<�'t Z'<� +r- � �}� .K. i r f �jj� f 5✓t:lt t✓e�•t` tl�S.•.SJ�Jrt S✓::: - ,�'• N p NO SCALE NE BYIERLY DR 0 v a Q m 3 N Associated Earth Sciences,Inc. VICINITY MAP FIGURE 1 BELFAIR SAFEWAY ADDITION DATE 8/08 v. BELFAIR,WASHINGTON PROJ.NO. KE080509A 0 1 � I -- I ! l ' Il { I APPROXIMATE LOCATION OF INFILTRATION TEST TYP a E E � ! I,. APPROXIMATE LOCATION OF EXPLORATION BORING j TYP , 1 f ; h s � a✓ �f N ul 06. t0 EO e Ft FT Reference: BUSH,ROED&HITCHINGS,INC. FIGURE 2 Associated Earth Sciences, Inc. m IMF] ❑ ulym m DATE 8/0 8 LW PROJECT NO. KE080509A APPENDIX •0'° Well-graded gravel and Terms Describing Relative Density and Consistency o•o• GW gravel with sand, little to DensitySPTI�lblows/foot •°o° no fines Very Loose 0 to 4 ` u_ Coarse Loose 4 to 10 > 0 > e o 0;p o Poorly-graded gravel Grained Soils Medium Dense 10 to 3D > 0 � 'o 0 o Test Symbols U, U rn w o c o o p GP and gravel with sand, Dense 30 to 50 - 0 o c o 0 0 0 o G=Grain Size 0 0 0 little to no fines Very Dense >50 0 0 0 o M=Moisture Content cl o Z 00000 d o o •0,0 Consistency SPT(ziblowsffoot A=Atterberg Limits z a-0 a Silty gravel and silty Very Soft 0 to 2 C=Chemical 0 r a) y GM gravel with sand Fine- Soft 2 to 4 DD=Dry Density d .•.0 Grained Soils Medium Stiff 4 to 8 K=Permeability c m � � e Stiff 8 t0 15 Clayey gravel and Very Stiff 15 to 30 w GC clayey gravel with sand Hard >30 Component Definitions Well-graded sand and Descriptive Term Size Range and Sieve Number ° SW sand with gravel,little Boulders Larger than 12' `� to no fines Cobbles 3'to 12' 2 d ..... o LL Gravel 3'to No.4(4.75 mm) y Poorly-graded sand Coarse Gravel 3'to 3/4• c°p cj in w SP and sand with gravel, Fine Gravel 3/4'to No.4(4.75 mm) `o little to no fines Sand No.4(4.75 mm)to No.200(0.075 mm) c c z Coarse Sand No.4(4.75 mm)to No.10(2.00 mm) Silty sand and Medium Sand No.10(2.00 mm)to No.40(0.425 mm) N o N SM silty sand with Fine Sand No.40(0.425 mm)to No.200(0.075 mm) 0 o a � . .. v CDgravel Silt and Clay Smaller than No.200(0.075 mm) I? _ y N Clayey sand and (3)Estimated Percentage Moisture Content SC clayey sand with ravel D Absence of moisture, @ ^" Y Y g Percentage by �'" Component Weight dusty,dry to the touch Trace <5 Slightly Moist-Perceptible Silt,sandy silt,gravelly silt, Few 5 to 10 moisture � MIL silt with sand or gravel Little 15 to 25 Moist-Damp but no visible 2 y m With Non-primary coarse water C, ' L constituents: >15% VeryMoist-Water visible but C:) Clay of low to medium — N 0 Fines content between not free draining d c �' CL Plasticity; silty,Sandy,or 5%and 15% Wet-Visible free water,usually 10 gravelly E gravelly clay, lean clay from below water table aN = J F_:�: Organic clay or silt of low Symbols ::I OILplasticity Blows/6'or 0 Sampler portion of 6' Cement grout Type / surface seal Elastic silt,clayey silt,silt Sampler Type 2.0"OD with micaceous or n Description t> sealtonite MH Split-Spoon a o 2 diatomaceous fine sand or p - Filler pack wth o Sampler 3.0'OD Split-Spoon Sam ler SP blank casing u, o silt ( 3.25'OD Split-Spoon Ring Sampler c•> g Clay of high plasticity, section a c n CH sand or ravel) clay,fat Bulk sample - Y gravelly Y 3.0'OD Thin-Wall Tube Sampler =Screened casing c E clay with Sand or ravel Includin Shelby tube with Hfilter p m N J y 9 C 9 Y ) ',,with filter pack Grab Sample 0 E5 :2 � � End cap c :3 Organic Organic clay or silt of o Portion not recovered OH medium to high f'I Percentage by dry weight (4) Depth of ground water plasticity P tY (2) (SPT)Standard Penetration Test 1 ATD=At time of drilling (ASTM D-1586) SZ Static water level(date) >,c y Peat,muck and other 13) In General Accordance with or 0� PT highly organic soils Standard Practice for Description (s) Combined USCS symbols used for = p and Identification of Soils(ASTM D-2466) fines between 5%and 15% mClassifications of soils In this report are based on visual field and/or laboratory observations,which include density/consistency,moisture condition,grain size,and plasticity estimates and should not be construed to imply field or laboratory testing unless presented herein.Visual-manual and/or laboratory classification methods of ASTM D-2487 and D-2488 were used as an identification guide for the Unified Soil Classification System. 0 r 5 Associated Earth Sciences, Inc. 0_ 7 _ EXPLORATION LOG KEY FIGURE Al a Associated Earth Sciences,Inc. Exploration Log Project Number Exploration Number Sheet KE080509A EB-1 1 of 1 Project Name Belfair Safeway Addition Ground Surface Elevation(ft) Location Belfair. WA Datum N/A Driller/Equipment EDI B-61 Date Start/Finish R/1 R/n$,R/1 R/nA Hammer Weight/Drop 140#/30" Hole Diameter(in) R" N U p N (O N w a Qa m J y Blows/Foot I— a S E T �Ea? o a� O TCc/0) O N o m t DESCRIPTION U 10 20 30 40 ° 3"asphalt. Vashon Recessional Outwash S-1 Dry,brown,fine to coarse SAND,with gravel. a A28 14 5 Same,moist. 5 S-2 Becomes moist at 8'(1'wet sampler). 9 A23 14 10 Wet,brown,GRAVEL,with sand. 4 S-3 7 A 7 10 15 S 4 No recovery(sampler is wet). 8 12 40 28 20 Bottom of exploration boring at 19 feet 25 30 m 35 8 N lh d E m a d h a c� c Sampler Type(ST): o m 2"OD Split Spoon Sampler(SPT) 0 No Recovery M-Moisture Logged by: JPL o [0 Y OD Split Spoon Sampler(D&M) Ring Sample Q Water Level Q Approved by: W ES Sample © Shelby Tube Sample 1 Water Level at time of drilling(ATD) a Associated Earth Sciences,Inc. Exploration Log Project Number Exploration Number Sheet KE080509A EB-2 1 of 1 Project Name Belfair Safeway Addition Ground Surface Elevation(ft) Location Belfair, WA Datum NIA Driller/Equipment EDI B-61 Date Start/Finish 8/1 RfflR R/18/08 Hammer Weight/Drop 140#/30" Hole Diameter(in) all c 6 iR N a U 0 o °' 6 Blows/Foot a)t O. � N .J in a S E m >. �E g; o ru o T cc 0 c/) p m co t DESCRIPTION " 3 10 20 30 40 ° 2"asphalt. Vashon Recessional Outwash Moist,brown,fine to medium SAND,with gravel. 9 S-1 12 A2 14 5 Moist,brown,fine to coarse SAND,with gravel. 9 S-2 Becomes wet at 8'(1'wet sampler). 16 A33 17 10 Wet, brown,GRAVEL,with sand. 9 S-3 15 A3 21 15 S 4 Same,wet. 14 17 A4 29 20 Bottom of exploration boring at 19 feet Water level measures at 14 1/2'immediate after drilling. 25 30 35 0 N 11 m E n d h a' c� 0 Sampler Type(ST): o m 2"OD Split Spoon Sampler(SPT) No Recovery M-Moisture Logged by: JPL o [D Y OD Split Spoon Sampler(D&M) Ring Sample SZ Water Level() Approved by: w ® Grab Sample ® Shelby Tube Sample 1 Water Level at time of drilling(ATD) a Associated Earth Sciences,Inc. Geologic & Monitoring Well Construction Log �, . Project Number Well Number Sheet f NJ a 0 KE080509A EB-3 1 of 1 Project Name Belfair Safeway Addition Location Belfair. WA Elevation(Top of Well Casing) Surface Elevation(ft) Water Level Elevation Date Start/Finish R/1 sms R/1 R/OR Drilling/Equipment EDI B-61 Hole Diameter(in) 8" Hammer Weight/Drop 140#1 30" t > U 75 E WELL CONSTRUCTION T m DESCRIPTION Flush monument 4"asphalt. Concrete seal from ground Vashon Recessional Outwash surface to 1' r . Bentonite seal 1'to 3' Brown sand with gravel in cuttings. 5 2"ID Schedule 40 PVC casing 0.2'to 9.2' Moist, brown,fine to medium SAND,with gravel. 9 12 20 Same,moist. Native sand pack T to 14.2' 12 14 12 Moist to wet,slightly rust-stained brown,fine to medium SAND,with s gravel and silty sand zones. 10 9 8 2"ID Schedule 40 PVC 12 Wet,brown,GRAVEL,with sand. 14 0.020"slot width screen 9.2' 17 to 14.2' 5 Same,wet. 20 11 Same,wet. 30 50/5" 15 Threaded end cap Boring terminated at 14.9 feet on 8/18/08 2"well installed to 14.2'. o m 0 c� c� z rX 0 m IL IL 9 o Sampler Type(ST): g m 2"OD Split Spoon Sampler(SPT) O No Recovery M - Moisture Logged by: JPL m 3"OD Split Spoon Sampler(D&M) Ring Sample Water Level(8/20/08) Approved by: z ® Grab Sample Shelby Tube Sample 1 Water Level at time of drilling(ATD) r � _ r • i 1 Pj E C 1 5 "" Mason County Department of Community Development Submittal Checklist For a Geotechnical Report Instructions: This checklist must be submitted with a Geotechnical Report and completed, signed, and stamped by the licensed professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to the Mason County Resource Ordinance. If an item found to be not applicable, the report should explain the basis for the conclusion. Applicant/Owner §IWMW Parcel# _A 4f1)0010 # Site Address 23961 NE State Route 3.Seelfair v- (1) (a)A discussion of general geologic conditions in the vicinity of the proposed developme Located on page(s) 4 �, u. (b) A discussion of specific soil types Located on page(s) 4 =,a; - ' (c) A discussion of ground water conditions Located on page(s) 3,4 ` (d) A discussion of the upslope geomorphology - '- Located on page(s) 2 """" (e) A discussion of the location of upland waterbodies and wetlands Located on page(s) N/A (f) A discussion of history of landslide activity in the activity in the vicinity, as available ln- referenced maps and recordse iG Fia, Located on page(s) N/A (2) A site plan which identifies the important development and geologic features. Located on Map(s) Figure 2 (3) Locations and logs of exploratory holes or probes. Located on Map(s) Figure 2 (4) The area of the proposed development, the boundaries of the hazard, and associated buffers and setbacks shall be delineated (top, both sides, and toe) on a geologic map of the site. Located on Map(s) N/A (5) A minimum of one cross section at a scale which adequately depicts the subsurface profile, and which incorporates the details of proposed grade changes. Located on Map(s) No proposed Grade Changes (6) A description and results of slope stability analyses performed for both static and seismic loading conditions. Analysis should examine worst case failures. The analysis should include the Simplified Bishop's Method of Circles. The minimum static safety factor is 1.5, the minimum seismic safety factor is 1.1. and the quasi-static analysis coeffients should be a value of 0.15. Located on page(s) N/A(see page 5) (7) (a)Appropriate restrictions on placement of drainage features Located on page(s) 13-14 (b) Appropriate restrictions on placement of septic drain fields Located on page(s) N/A (c) Appropriate restrictions on placement of compacted fills and footings Located on page(s) 9-11 Page 1 of 2 Form Effective June 2008 Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report. (d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Located on page(s) N/A (e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Located on page(s) N/A (8) Recommendations for the preparation of a detailed clearing and grading plan which specifically identifies vegetation to be removed, a schedule for vegetation removal and replanting, and the method of vegetation removal. Located on page(s) N/A(paved) (9) Recommendations for the preparation of a detailed temporary erosion control plan which identifies the specific mitigating measures to be implemented during construction to protect the slope from erosion, landslides and harmful construction methods. Located on page(s) 6-7 (10) An analysis of both on-site and off-site impacts of the proposed development. Located on page(s) N/A(project includes expansion of existing building and on-site infiltration of stormwater, see p.2) (11) Specifications of final development conditions such as, vegetative management, drainage, erosion control, and buffer widths. Located on page(s) 6-7 (erosion control); 13-14 (drainage) (12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation. Located on page(s) N/A(general design recommendations can be found on pp.8-15) (13) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location and nature of existing and proposed development on the site. Located on Map(s) Figure 2 I, Bruce L. Blyton hereby certify under penalty of perjury that 1 am a civil engineer licensed in the State of Washington with specialized knowledge of geotechnical/geological engineering or a geologist or engineering geologist licensed in the State of Washington with special knowledge of the local conditions. I certify that it is my opinion that the Geotechnical Report, dated September 5, 2008 , and entitled Subsurface Exploration, Geologic Hazard, and Preliminary Geotechnical Engineering Report, is complete and true, that the assessment demonstrates conclusively that the risks posed by the landslide hazard can be mitigated through the included geotechnical design recommendations, and that the landslide hazard is mitigated in such a manner as to prevent harm to property and public health and safety. (Signature and Stamp) Q`\)GE L. B 1- 0 F w �tiTG2 0 890 z v F G�STOk -"()NAL Page 2 of 2 Form Effective June 2008 Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report. Associated Earth Sciences, Inc. RECEIVED Cel��atnJc 2� ZJea�sofs'er�;'ce NOV 13 2008 L"ASON CO. Fi1�NNIP�u DEFT. Technical Memorandum Date: October 31, 2008 To: Safeway, Inc. Project Name: Belfair Safeway c/o Mulvanny G2 Architecture (#1571) Addition 601 SW Second Avenue, Suite 1200 Portland, Oregon 97204 Attn: Ms. Lu Wei Hioe From: Jeffrey P. Laub, P.G., P E Project No: KE080509A Bruce L. Blyton, P.E. Subject: Mason County Geotechnical Report Checklist This memorandum presents our response to the "Submittal Checklist for a Geotechnical Report" form, issued by Mason County. We have previously prepared a "Subsurface Exploration, Geologic Hazard, and Preliminary Geotechnical Engineering Report," dated September 5, 2008, for the proposed project. The form issued by the County includes a checklist that asks for the pages where various topics, if applicable, are covered by the geotechnical report for the proposed project. A statement is located at the bottom of the checklist which requires the geotechnical engineer to "certify" that the report "meets all the requirements of the Mason County Resource Ordinance, Landslide Hazard Section, is complete and true, that the assessment demonstrates conclusively that the risks posed by the landslide hazard can be mitigated through the included geotechnical design recommendations, and that all hazards are mitigated in such a manner as to prevent harm to property and public health and safety. " The Mason County certification request is very unusual and outside the standards of practice for geotechnical engineering in this area; further, the "certification" language requested by the County is not insurable. Per our conversation with Mr. Robert Fink with Mason County, we present the attached completed, signed, and stamped checklist, including alternate language. We anticipate that our report will meet County requirements, as there are no steep slopes at the locations of the proposed site improvements. AESI can provide additional recommendations as the design progresses. We trust that this memorandum will meet your current project needs. If you should have any questions or if we can be of additional help to you, please do not hesitate to call. JPL/dr-KE080509A4-Projects\2008050MEMP 1,(iMand Office•911 FKfth Avenue,Suite 100•KGrktand,WA 98033•P(425)827-7701 •F(425)827-5424 Everett Office•2911 1/2 Hewitt Avenue,Suite 2•Everett,WA 98201•P(425)2590522•F(425)252-3408 Tacoma Office•805 Martin Luther King Jr.Way•Tacoma,WA•P(253)722 2992•F(253)722-2993 www.aesgeo.com Mason County Department of Community Development Submittal Checklist For a Geotechnical Report Instructions: This checklist must be submitted with a Geotechnical Report and completed,signed,and stamped by the licensed professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to the Mason County Resource Ordinance. If an item found to be not applicable,the report should explain the basis for the conclusion. Applicant/Owner Safeway Parcel# 123294100010 Site Address 23961 NE State Route 3, Belfair (1) (a)A discussion of general geologic conditions in the vicinity of the proposed development, Located on page(s) 4 (b) A discussion of specific soil types Located on page(s) 4 (c) A discussion of ground water conditions Located on page(s) 3A (d) A discussion of the upslope geomorphology Located on page(s) 2 (e) A discussion of the location of upland waterbodies and wetlands Located on page(s) N/A (f) A discussion of history of landslide activity in the activity in the vicinity,as available in the referenced maps and records Located on page(s) N/A (2) A site plan which identifies the important development and geologic features. Located on Map(s) Figure 2 (3) Locations and logs of exploratory holes or probes. Located on Map(s) Figure 2 (4) The area of the proposed development,the boundaries of the hazard,and associated buffers and setbacks shall be delineated(top,both sides, and toe)on a geologic map of the site. Located on Map(s) N/A (5) A minimum of one cross section at a scale which adequately depicts the subsurface profile,and which incorporates the details of proposed grade changes. Located on Map(s) No proposed Grade Changes (6) A description and results of slope stability analyses performed for both static and seismic loading conditions.Analysis should examine worst case failures.The analysis should include the Simplified Bishop's Method of Circles.The minimum static safety factor is 1.5, the minimum seismic safety factor is 1.1. and the quasi-static analysis coeffients should be a value of 0.15. Located on page(s) N/A(see page 5) (7) (a)Appropriate restrictions on placement of drainage features Located on page(s) 13-14 (b) Appropriate restrictions on placement of septic drain fields Located on page(s) N/A (c) Appropriate restrictions on placement of compacted fills and footings Located on page(s) 9-11 Page 1 of 2 Form Effective June 2008 Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report. (d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Located on page(s) N/A (e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Located on page(s) N/A (8) Recommendations for the preparation of a detailed clearing and grading plan which specifically identifies vegetation to be removed,a schedule for vegetation removal and replanting,and the method of vegetation removal. Located on page(s) N/A(paved) (9) Recommendations for the preparation of a detailed temporary erosion control plan which identifies the specific mitigating measures to be implemented during construction to protect the slope from erosion, landslides and harmful construction methods. Located on page(s) 6-7 (10) An analysis of both on-site and off-site impacts of the proposed development. Located on page(s) N/A(proiect includes expansion of existing building and on-site infiltration of stormwater,see p.2) (11) Specifications of final development conditions such as,vegetative management,drainage, erosion control,and buffer widths. Located on page(s) 6_-7(erosion control); 13-14(drainage) (12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation. Located on page(s) N/A(general design recommendations can be found on pp.8-15) (13) A site map drawn to scale showing the property boundaries,scale, north arrow, and the location and nature of existing and proposed development on the site. Located on Map(s) Figure 2 I, Bruce L. Blyton hereby certify under penalty of perjury that I am a civil engineer licensed in the State of Washington with specialized knowledge of geotechnical/geological engineering or a geologist or engineering geologist licensed in the State of _ Washington with special knowledge of the local conditions.Jt is my opinion that the Geotechnical Deleted:I also certify j Report,dated September 5.2008 ,and entitled Subsurface Exploration, Geologic Hazard and Preliminary Geotechnical Engineerinq Report is complete and true,that the assessment demonstrates Deleted: meets all the requirements conclusively that the risks posed by the landslide hazard can be mitigated through the included of the Mason county Resource geotechnical design recommendations,and that jhe landslide hazard is mitigated in such a manner as to ordinance,Landslide Hazard Section prevent harm to property and public health and safety.(Signature and Stamp) Deleted:all hazards are PUCE L, 84 T pF WAS O o �Q 6 �STEFk /ANAL Page 2 of 2 Form Effective June 2008 Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report. Hi Grace, Here is an updated version of my Current Active Cases that are on Hold. I received the necessary information on two of them and have completed and signed off on them. I received a Geo-Report Submittal Checklist for a third(the Safeway Addition in Belfair) but did not review the Geo-Report;the company that did the Geo had some issues with the wording on our submittal checklist so th,,e�sent��in their own version (Bob knows _about this as I discussed it with him). )Woe7er does the Geo-Review may want to talk with Bob about it. The letter/submittal checklist for the Geo-report is attached to the Geo- Report. Hope this helps, Jim Meow LI I �l F3ate°' �;t to Rio: