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2025.0071-2025.0463.PR0003 02 - Panda Express Yelm Ave - Geotechnical Engineering Report (133)Report Cover Page Panda Express D37983 Geotechnical Engineering Report April 21, 2025 | Terracon Project No. 81255065 Prepared for: Panda Restaurant Group, Inc. 1683 Walnut Grove Ave Ste 301 Rosemead, CA 91770 6949 S. High Tech Drive Midvale, UT 84047 P (801) 545-8500 Terracon.com Facilities | Environmental |Geotechnical |Materials Report Cover Letter to Sign April 21, 2025 Panda Restaurant Group, Inc. 1683 Walnut Grove Ave Ste 301 Rosemead, CA 91770 Attn: Brian Kan P:(626) 799-9898 E:Brian.Kan@pandarg.com Re: Geotechnical Engineering Report Panda Express D37983 1104 Yelm Ave E Yelm, WA Terracon Project No. 81255065 Dear Mr. Kan: We have completed the scope of Geotechnical Engineering services for the above- referenced project in general accordance with Terracon Proposal delivered via email on March 19, 2025. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations, floor slabs, and pavements for the proposed project. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report or if we may be of further service, please contact us. Sincerely, Terracon Jennifer K. Diercksen P.E. (Utah)Zachary L. Koehn, P.E. Project Manager Geotechnical Department Manager Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials i Table of Contents Introduction .................................................................................................... 1 Project Description .......................................................................................... 1 Site Conditions ................................................................................................ 2 Geotechnical Characterization ......................................................................... 3 Seismic Site Class ............................................................................................ 4 Corrosivity ...................................................................................................... 5 Geotechnical Overview .................................................................................... 6 Earthwork ....................................................................................................... 7 Shallow Foundations ..................................................................................... 13 Floor Slabs .................................................................................................... 15 Stormwater Management............................................................................... 17 Pavements .................................................................................................... 19 General Comments ........................................................................................ 22 Attachments Exploration and Testing Procedures Site Location and Exploration Plans Exploration and Laboratory Results Supporting Information Note: This report was originally delivered in a web-based format.Blue Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks that direct the reader to that section and clicking on the logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com. Refer to each individual Attachment for a listing of contents. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 1 Introduction This report presents the results of our subsurface exploration and Geotechnical Engineering services performed for the proposed restaurant to be located at 1104 Yelm Ave E in Yelm, WA. The purpose of these services is to provide information and geotechnical engineering recommendations relative to: ■Subsurface soil conditions ■Groundwater conditions ■Seismic site class per IBC ■Site preparation and earthwork ■Foundation design and construction ■Floor slab design and construction ■Stormwater management ■Pavement design and construction The geotechnical engineering scope of services for this project included the advancement of test borings, laboratory testing, engineering analysis, and preparation of this report. Drawings showing the site and boring locations are shown in the Site Location and Exploration Plan, respectively. The results of the laboratory testing performed on soil samples obtained from the site during our field exploration are included on the boring logs and/or as separate graphs in the Exploration Results section. Project Description Item Description Information Provided MSA Task Order dated 3/19/2025 requesting geotechnical services for new Panda Express Restaurant. Site Plan drawing C-03.0 and ALTA Survey were provided via e- mail on 3/18/2025. Project Description Proposed new Panda Express Restaurant and associated drive thru, drive lanes, and parking lot. Proposed Structure Single-story building with footprint of approximately 2,890 square feet. Building Construction Light commercial construction consisting of wood or metal framed building on shallow foundations with slab on grade (no basement). Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 2 Item Description Finished Floor Elevation At or near existing grade. Maximum Loads (assumed) Columns: 125 kips Walls: 6 kips per linear foot (klf) Slabs: 150 pounds per square foot (psf) Grading/Slopes No grading is anticipated to achieve final grade. Pavements We assume both rigid (concrete) and flexible (asphalt) pavement sections will be considered. Anticipated traffic is as follows: ■Autos/light trucks: 1,000 vehicles per day ■Light delivery and trash collection vehicles: 10 vehicles per week ■Tractor-trailer trucks: 1 vehicle per week The pavement design period is 20 years. Design ESALs are assumed. Building Code 2021 International Building Code (2021 IBC) 2016 ASCE Standard ASCE/SEI 7-16 (ASCE 7-16) Terracon should be notified if any of the above information is inconsistent with the planned construction, especially the grading limits, as modifications to our recommendations may be necessary. Site Conditions The following description of site conditions is derived from our site visit in association with the field exploration and our review of publicly available geologic and topographic maps. Item Description Parcel Information The project is located at 1104 Yelm Ave E, Yelm, WA. Lot size: 1.1 acres. Site coordinates are Latitude 46.9352° N, Longitude 122.5934° W (approximate). Parcel Number 22730110208. Section 30 Township 17 Range 2E See Site Location Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 3 Item Description Existing Improvements Underground utilities Current Ground Cover Grass and weeds, bare soil Existing Topography Relatively flat Geotechnical Characterization Subsurface Conditions We have developed a general characterization of the subsurface conditions based on our review of the subsurface exploration, laboratory data, geologic setting, and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of the site. Conditions observed at each exploration point are indicated in the individual logs. The individual logs can be found in the Exploration Results and the GeoModel can be found in the attachments of this report. As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each boring location, refer to the GeoModel. Model Layer Layer Name General Description 1 Outwash Deposits/Possible Fill Loose to medium dense, well-graded GRAVEL with silt and sand 2 Glacially Consolidated Deposits Medium dense to very dense, GRAVEL with silt and sand or SAND with silt and gravel Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 4 Groundwater Groundwater was encountered during the subsurface exploration at approximately 18 feet below ground surface. Groundwater observations represent groundwater conditions at the time of the field exploration and may not be indicative of other times or at other locations. Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff, and other factors not evident at the time the borings were performed. Groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the boring logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project. Long-term groundwater monitoring was not included in the scope of services for this project. However, it may be performed in the future as an additional service. Seismic Site Class The seismic design requirements for buildings and other structures are based on Seismic Design Category. Site Classification is required to determine the Seismic Design Category for a structure. The Site Classification is based on the upper 100 feet of the site profile defined by a weighted average value of either shear wave velocity, standard penetration resistance, or undrained shear strength in accordance with Section 20.4 of ASCE 7 and the International Building Code (IBC). Based on the soil properties observed at the site and as described in the exploration logs and results, our professional opinion is that a Seismic Site Classification of D – Stiff Soil be considered for the project. Subsurface explorations at this site were extended to a maximum depth of 26.5 feet. The site soil properties below the boring depth to 100 feet were estimated based on our experience and knowledge of geologic conditions of the general area. Additional deeper borings or geophysical testing may be performed to confirm the conditions below the current boring depth. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 5 Description Value 1 ASCE 7-16 Site Classification D Site Latitude 46.9353° North Site Longitude 122.5934° West SS – Short Period Spectral Acceleration 1.281 g S1 – 1-Second Period Spectral Acceleration 0.463 g SMS – Short Period Spectral Acceleration Adjusted for Site Class 1.281 g SM1 – 1-Second Spectral Acceleration Adjusted for Site Class 0.851 g SDS – Design Short Period Spectral Acceleration 0.854 g SD1 – Design 1-Second Spectral Acceleration 0.567 g PGAM - ASCE 7, PGA Adjusted for Site Class 0.554 g 1.The IBC requires a site profile extending to a depth of 100 feet for seismic site classification. Borings were extended to a maximum depth of 26.5 feet. The site properties below the boring depth to 100 feet were estimated based on our experience and knowledge of geologic conditions of the general area. Surface-Fault Rupture The hazard of damage from onsite fault rupture appears to be low based on review of the USGS Earthquake Hazards Program Quaternary Faults and Folds Database available online (https://usgs.maps.arcgis.com/apps/webappviewer/index.html?id=5a6038b3a168456 1a9b0aadf88412fcf) accessed on April 15, 2025. The closest mapped fault is the Olympia Structure fault zone, which lies approximately 4 miles to the southwest. Liquefaction Liquefaction is the phenomenon where saturated soils develop high pore water pressures during seismic shaking and lose their strength characteristics. This phenomenon generally occurs in areas of high seismicity, where groundwater is shallow and loose granular soils or relatively non-plastic fine-grained soils are present. Based on the site geology and subsurface groundwater conditions, the hazard of liquefaction of the site soils is low. Corrosivity The table below lists the results of laboratory soluble sulfate, soluble chloride, electrical resistivity, and pH testing. The values should be provided to the utility Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 6 supplier/manufacturer to aid in their estimate of potential corrosive characteristics of the on-site soils. Corrosivity Test Results Summary Boring Sample Depth (feet) Soil Description Soluble Sulfate (%) Soluble Chloride (%) Electrical Resistivity (Ω-cm) pH B-02 2.5 Poorly-graded GRAVEL with silt and sand 0.02 0.01 5335 6.98 Results of soluble sulfate testing can be classified in accordance with ACI 318 — Building Code Requirements for Structural Concrete. Numerous sources are available to characterize the corrosion potential to buried metals using the parameters above. ANSI/AWWA is commonly used for ductile iron, while threshold values for evaluating the effect on steel can be specific to the buried feature (e.g., piling, culverts, or welded wire reinforcement) or agency for which the work is performed. Imported fill materials may have significantly different properties than the site materials noted above and should be evaluated if expected to be in contact with metals used for construction. Consultation with a NACE-certified corrosion professional is recommended for buried metals on the site. Geotechnical Overview The glacial outwash deposits commonly include large, coarse-granular particles such as cobbles and boulders. The presence of cobbles and boulders immediately below the foundations could lead to cracking and influence long-term performance. Partial overexcavation of the subgrades to reduce the risk of stress-concentration from cobbles and boulders is recommended. The Earthwork and Shallow Foundations section addresses support of the building bearing on native and compacted structural fill. The Floor Slabs section addresses slab-on-grade support of the building. The site is relatively level; therefore, we do not anticipate significant quantities of cutting and filling to produce level building pads and paving areas. Effective drainage should be completed early in the construction sequence and maintained after construction to avoid potential issues. If possible, earthwork should be performed during the warmer and dryer times of the year. If grading is performed during the winter months, fill placement and compaction may be more difficult. Additional site preparation recommendations are provided in the Earthwork section. Based on the conditions encountered in the borings, the proposed structures can be supported on conventional spread footings bearing on structural fill over native soils. Foundation areas should be prepared per the Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 7 recommendations provided in the Earthwork section. The Floor Slabs section addresses slab-on-grade support of the building. Our opinion of pavement section thickness design has been developed based on our understanding of the intended use, assumed traffic, and subgrade preparation recommended herein. The Pavements section includes minimum pavement component thickness. The recommendations contained in this report are based on the results of field and laboratory testing (presented in the Exploration Results), engineering analyses, and our current understanding of the proposed project. The General Comments section provides an understanding of the report’s limitations. Earthwork Earthwork is anticipated to include clearing and grubbing, excavations, and engineered fill placement. The following sections provide recommendations for use in the preparation of specifications for the work. Recommendations include critical quality criteria, as necessary, to render the site in the state considered in our geotechnical engineering evaluation for foundations, floor slabs, and pavements. Site Preparation Prior to placing fill, any existing vegetation, topsoil, and root mats should be removed. Complete stripping of the topsoil should be performed in the proposed building and parking/driveway areas. Although no evidence of fill or underground facilities (such as septic tanks, cesspools, or basements) was observed during the exploration and site reconnaissance, such features could be encountered during construction. If unexpected fills or underground facilities are encountered, such features should be removed, and the excavation thoroughly cleaned prior to backfill placement and/or construction. Subgrade Preparation We recommend that the soils beneath the footings of the proposed structure be removed to a minimum depth of 2 feet below existing grades, or as necessary to reach the dense granular native soil. Structural Fill placed beneath foundations should extend horizontally as shown in the figure in the Foundation Construction Considerations Section. Large-area subgrades should be proofrolled with an adequately loaded vehicle such as a fully loaded tandem-axle dump truck. The proofrolling should be performed under the Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 8 observation of the Geotechnical Engineer or their representative. Areas excessively deflecting under the proofroll should be delineated and subsequently addressed by the Geotechnical Engineer. Such areas should either be removed or modified by scarifying and recompacting. Excessively wet or dry material should either be removed or moisture conditioned and recompacted. Based on the subsurface conditions determined from the geotechnical explorations, subgrade soils exposed during construction are anticipated to be relatively workable; however, the workability of the subgrade may be affected by precipitation, repetitive construction traffic, or other factors. If unworkable conditions develop, workability may be improved by scarifying and drying. Fill Material Types Fill required to achieve design grade should be classified as Structural Fill and Common Fill. Structural Fill is material used below, or within 10 feet of structures and apertures, pavements, and constructed slopes. Common Fill is material used to achieve grades outside of these areas. Import and On-Site Soil: Excavated on-site soil from Soil Layer 1 and 2 may be selectively reused as structural fill with some handling to remove particles over 3-inches in diameter. Imported fill materials should meet the following material property requirements. Regardless of its source, compacted fill should consist of approved materials that are free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade. Material property requirements for on-site soil for use as general fill and structural fill are noted in the table below: Fill Type Recommended Materials Acceptable Location for Placement Structural Fill 9-03.9(3)Crushed Surfacing Base Course 1 9-03.12(1)A Gravel Backfill for Foundations Class A 1 9-03.14(1)Gravel Borrow 1 On-site Native Soils (Soil Layer 2)2, 3 Beneath and adjacent to structural slabs, foundations, building appurtenances, and pavement subgrades Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 9 Fill Type Recommended Materials Acceptable Location for Placement Common Fill Section 9-03.14(3)Common Borrow 1 On-site Native Soils (GeoModel Layers 1 and 2)2, 3 Grade filling, utility trench backfill outside the building foundation, and appurtenances Free-Draining Granular Fill Structural Fill 4 9-03.12(2)Gravel Backfill for Walls 1 9-03.12(4)Gravel Backfill for Drains 1 Backfilling in wet weather, drainage layers for walls, sump drains, footing drains 5 1.WSDOT Standard Specifications 2.Structural and common fill should consist of approved materials free of organic matter and debris. After removing the organic materials, native soils may be reused as Common Fill and as backfill within the pavement subgrade areas in accordance with the Fill Material Types section. Frozen material should not be used, and fill should not be placed on a frozen subgrade. A sample of each material type should be submitted to the Geotechnical Engineer for evaluation prior to use on this site. 3.High fines content in the on-site soils could make this material moisture sensitive and may be difficult to achieve compaction when the moisture content is more than about 2 percentage points above or below the optimum. Particles with a nominal diameter greater than about 3 inches should be removed. 4.Material provided must be specified to be less than 5-percent passing the #200 sieve for the portion of material passing the #4 sieve. 5.Minimum particle size must be greater than drainpipe perforations. Other earthen materials may be suitable for use in addition to the options presented in the table above. All materials should be approved by the Geotechnical Engineer prior to use. Fill Placement and Compaction Requirements Structural Fill and Common Fill should meet the following compaction requirements. Item Structural Fill Common Fill Maximum Lift Thickness 8 inches or less in loose thickness when heavy, self-propelled compaction equipment is used 4 to 6 inches in loose thickness when hand- guided equipment (i.e., jumping jack or plate compactor) is used Same as Structural Fill Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 10 Item Structural Fill Common Fill Minimum Compaction Requirements1 95% of maximum below foundations and floor slabs and within 1-foot of pavement subgrades 92% of maximum above foundations, and below the upper 1-foot of pavement subgrade 92% of maximum dry density Water Content Range1 Typically, within 2% of optimum As required to achieve min. compaction requirements 1.Maximum density and optimum water content as determined by the Modified Proctor test (ASTM D 1557). Utility Trench Backfill Any soft or unsuitable materials encountered at the bottom of utility trench excavations should be removed and replaced with structural fill or bedding material in accordance with public works specifications for the utility be supported. This recommendation is particularly applicable to utility work requiring grade control and/or in areas where subsequent grade raising could cause settlement in the subgrade supporting the utility. Trench excavation should not be conducted below a downward 1:1 projection from existing foundations without engineering review of shoring requirements and geotechnical observation during construction. On-site materials are considered suitable for backfill of utility and pipe trenches from 1 foot above the top of the pipe to the final ground surface, provided the material is free of organic matter and deleterious substances. All trenches should be wide enough to allow for compaction around the haunches of the pipe. If water is encountered in the excavations, it should be removed prior to fill placement. The presence of cobbles and boulders may present challenges with respect to trench stability. Nested cobbles and boulders in trench side walls may become loosened during trench that could influence trench stability. The utility contractor should be prepared to contend with the likely presence of cobbles and boulders in utility trench alignments. Trench backfill should be mechanically placed and compacted as discussed earlier in this report. Compaction of initial lifts should be accomplished with hand-operated tampers or other lightweight compactors. Where trenches are placed beneath slabs or footings, the backfill should satisfy the gradation and expansion index requirements of engineered fill discussed in this report. Flooding or jetting for placement and compaction of backfill is not recommended. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 11 Grading and Drainage All grades must provide effective drainage away from the building during and after construction and should be maintained throughout the life of the structure. Effective drainage will be essential during construction to limit the extent of soil disturbance during the wet season. Water retained next to the building can result in soil movements greater than those discussed in this report. Greater movements can result in unacceptable differential floor slab and/or foundation movements, cracked slabs and walls, and roof leaks. Gutters and downspouts should be routed into tightline pipes that discharge either directly into a municipal storm drain or to an alternative drainage facility. Splash-blocks should also be considered below hose bibs and water spigots. Site grades should be established such that surface water is directed away from foundation and pavement subgrades to prevent an increase in the water content of the soils. Adequate positive drainage which diverts water from structures, open cuts, and slopes should be established to prevent erosion, ground loss, and instability. Locally, flatter grades may be necessary to transition ADA access requirements for flatwork. After building construction and landscaping, final grades should be verified to document that effective drainage has been achieved. Where paving or flatwork abuts the structure a maintenance program should be established to effectively seal and maintain joints to prevent surface water infiltration. Earthwork Construction Considerations Shallow excavations for the proposed structure are anticipated to be accomplished with conventional construction equipment; however, removal of large boulders or zones of cobbles and boulders may require specialty equipment for removal. Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of grade-supported improvements such as floor slabs and pavements. Construction traffic over the completed subgrades should be avoided. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Water collecting over or adjacent to construction areas should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the affected material should be removed, or the materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction. As a minimum, excavations should be performed in accordance with WAC Chapter 296- 155 Part N “Excavation, Trenching, and Shoring”, OSHA 29 CFR, Part 1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local regulations. Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 12 information provided herein be interpreted to mean Terracon is assuming responsibility for construction site safety or the contractor's activities; such responsibility shall neither be implied nor inferred. Construction Observation and Testing The earthwork efforts should be observed by Terracon. Observation should include documentation of adequate removal of vegetation, deleterious materials, and soils, as well as proofrolling and mitigation of unsuitable areas delineated by the proofroll. Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, as recommended by Terracon prior to placement of additional lifts. Each lift of fill should be tested for density and water content. In areas of foundation excavations, the bearing subgrade should be evaluated by Terracon. If unanticipated conditions are observed, Terracon may recommend mitigation options. In addition to the documentation of the essential parameters necessary for construction, the continuation of Terracon as the Geotechnical Engineer into the construction phase of the project provides the continuity to maintain our evaluation of subsurface conditions, including assessing variations and associated design changes. Wet Weather Earthwork The suitability of soils used for Structural Fill depends primarily on their grain-size distribution and moisture content when they are placed. As the fines content (the soil fraction passing the U.S. No. 200 Sieve) increases, soils become more sensitive to small changes in moisture content. Soils containing more than about 5 percent fines (by weight) cannot be consistently compacted to a firm, unyielding condition when the moisture content is more than 2 percentage points above or below optimum. Optimum moisture content is the moisture content at which the maximum dry density for the material is achieved in the laboratory by the ASTM D1557 test procedure. Due to the presence of fines, on-site soils may be sensitive to disturbance from construction activity and increased moisture. Drainage ditches installed early in construction will aid in reducing the amount of free water in the soil. If precipitation occurs prior to or during construction, the near-surface soil could increase in moisture content and become more susceptible to disturbance. If inclement weather or in situ soil moisture content prevent the use of on-site material as structural fill, we recommend the use of materials specified in Fill Material Types for free-draining granular fill. Stockpiled soils should be protected with polyethylene sheeting anchored to withstand local wind conditions and to preserve the soil’s moisture content. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 13 Shallow Foundations If the site has been prepared in accordance with the requirements noted in Earthwork, the following design parameters are applicable for shallow foundations. Design Parameters — Compressive Loads Item Description Maximum Net Allowable Bearing Pressure1, 2 2-feet overexcavation and replacement with structural fill as described in Earthwork 3,000 psf Required Bearing Stratum3 Undisturbed native granular soils (Soil Layer 2) under 2-feet structural fill Minimum Foundation Dimensions 24 inches for Spread Footing 18 inches for Wall Footing Ultimate Passive Resistance4 (equivalent fluid unit weight) 440 pcf (compacted granular backfill) Sliding Resistance5 0.4 allowable coefficient of friction — granular material Minimum Embedment Below Finished Grade6 18 inches Estimated Total Settlement from Structural Loads2 < 1 inch Estimated Differential Settlement2, 7 About 2/3 of total settlement 1.The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. 2.Values provided are for maximum loads noted in Project Description. Additional geotechnical consultation will be necessary if higher loads are anticipated. 3.Unsuitable, loose, or soft soils should be overexcavated and replaced per the recommendations presented in Earthwork. 4.Use of passive earth pressures requires the sides of the excavation for the spread footing foundation to be nearly vertical and the concrete placed neat against these vertical faces or that the footing forms be removed and compacted Structural Fill be placed against the vertical footing face. Assumes no hydrostatic pressure. Passive resistance in the upper 2 feet should be neglected. 5.Can be used to compute sliding resistance where foundations are placed on suitable soil/materials. Frictional resistance for granular materials is dependent on the bearing pressure which may vary due to load combinations. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 14 Item Description 6.Embedment necessary to reduce the effects of frost and/or seasonal water content variations. For sloping ground, maintain depth below the lowest adjacent exterior grade within 5 horizontal feet of the structure. 7.Differential settlements are noted for equivalent-loaded foundations and bearing elevation as measured over a span of 40 feet. Foundation Construction Considerations As noted in Earthwork, the footing excavations should be evaluated under Terracon’s observation. The base of all foundation excavations should be free of water and loose soil, prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care should be taken to prevent wetting or drying of the bearing materials during construction. Excessively wet or dry material or any loose/disturbed material in the bottom of the footing excavations should be removed/reconditioned before foundation concrete is placed. Overexcavation for Structural Fill placement below footings should be conducted as shown below. The overexcavation should be backfilled up to the footing base elevation, with Structural Fill placed, as recommended in the Earthwork section. If prepared foundation subgrades become disturbed prior to casting the foundation, the disturbed materials should be removed and replaced with compacted structural fill. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 15 Foundation Drains We recommend the building be encircled with a perimeter foundation drain to collect exterior seepage water. This drain should consist of a 4-inch diameter perforated pipe within an envelope of washed rock, extending at least 6 inches on all sides of the pipe. The washed rock should conform to WSDOT Section 9-03.12(4), Gravel Backfill for Drains or 9-03.12(5), Gravel Backfill for Drywells. The washed rock envelope should be wrapped with filter fabric (such as Mirafi 140N, or equal) to reduce the migration of fines from the surrounding soil. Ideally, the drain invert would be installed no more than 8 inches above or below the base of the perimeter footings. The perimeter foundation drain should not be connected to roof downspout drains and should be constructed to discharge into the site stormwater system or other appropriate outlets. These recommendations are summarized in the figure below. Floor Slabs Design parameters for floor slabs assume the requirements for Earthwork have been followed. Specific attention should be given to positive drainage away from the structure and positive drainage of the aggregate base beneath the floor slab. Depending on the finished floor elevation, loose soils may be observed at the floor slab subgrade level. These soils should be scarified and recompacted under the observation of the geotechnical engineer. Removal and replacement with properly compacted Structural Fill be necessary. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 16 Floor Slab Design Parameters Design parameters for floor slabs assume the requirements for Earthwork have been followed. Specific attention should be given to have positive drainage away from the structure along with positive drainage of the aggregate base beneath the floor slab. Floor Slab Design Parameters Item Description Floor Slab Support 1 Minimum 6 inches of free-draining of either of the following: ■Washed drain rock ■9-03.12(1)A Gravel Backfill for Foundations Class A (compacted to at least 95% of ASTM D 1557)2, 3 Estimated Modulus of Subgrade Reaction 4 150 pounds per square inch per inch (psi/in) for point loads 80 psi/in for distributed loads 1.Floor slabs should be structurally independent of building footings or walls to reduce the possibility of floor slab cracking caused by differential movements between the slab and foundation. 2.WSDOT Standard Specification. 3.Values of modulus of subgrade reaction are estimated for the subgrade conditions stated. 4.The floor slab design should include a capillary break, comprised of compacted material with less than 12% passing the No. 40 sieve and less than 5% fines (material passing the No. 200 sieve). The use of a vapor retarder should be considered beneath concrete slabs on grade covered with wood, tile, carpet, or other moisture sensitive or impervious coverings, when the project includes humidity-controlled areas, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer should refer to ACI 302 and/or ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder. Saw-cut contraction joints should be placed in the slab to help control the location and extent of cracking. For additional recommendations, refer to the ACI Design Manual. Joints or cracks should be sealed with a waterproof, non-extruding compressible compound specifically recommended for heavy duty concrete pavement and wet environments. Where floor slabs are tied to perimeter walls or turn-down slabs to meet structural or other construction objectives, our experience indicates differential movement between the walls and slabs will likely be observed in adjacent slab expansion joints or floor slab cracks Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 17 beyond the length of the structural dowels. The Structural Engineer should account for potential differential settlement through the use of sufficient control joints, appropriate reinforcing, or other means. Floor Slab Construction Considerations Finished subgrade, within and for at least 10 feet beyond the floor slab, should be protected from traffic, rutting, or other disturbance and maintained in a relatively moist condition until floor slabs are constructed. If the subgrade should become damaged or desiccated prior to construction of floor slabs, the affected material should be removed, and structural fill should be added to replace the resulting excavation. Final conditioning of the finished subgrade should be performed immediately prior to placement of the floor slab support course. Terracon should observe the condition of the floor slab subgrades immediately prior to placement of the floor slab support course, reinforcing steel, and concrete. Attention should be paid to high traffic areas that were rutted and disturbed earlier, and to areas where backfilled trenches are located. Stormwater Management The subsurface conditions generally appear appropriate for stormwater management via infiltration. Infiltration rates were estimated using two methodologies: percolation testing and grain-size analysis. Percolation Testing Terracon completed two percolation tests to estimate the infiltration rates for the management of stormwater runoff via pervious pavements. Percolation tests were conducted in general accordance with the methodology for the Falling Head Percolation Test Procedure (U.S. EPA, On-site Wastewater Treatment and Disposal Systems, 1980). Tests were conducted adjacent to explorations which were advanced to approximately 11½ feet below ground surface to determine the presence of groundwater. The results of the field percolation tests are summarized in the following table. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 18 Infiltration Rate from Grain-Size Analysis Currently, the stormwater management testing requirements are unknown. For planning purposes, we evaluated infiltration potential based on grain size analysis. These should be used for preliminary sizing of the infiltration facility only. In situ testing via pilot infiltration testing (PIT) may be required by local jurisdictions to confirm the values herein. Using the grain-size correlation presented in the Department of Ecology Manual for Western Washington, a unfactored infiltration rate of 15 inches per hour is estimated. Applying the reduction factors of 1.0, 0.4, and 0.9 for site variability, test method, and siltation/bio-buildup, respectively, estimated design infiltration rate is 5½ inches per hour. The civil engineer should review the reduction factors assumed and revise the estimated result, as needed, if lower reduction factors are realized. Preliminary Stormwater Management Design Recommendations The estimated design infiltration rate of 5½ in/hr is valid under the following recommendations: ■If soil units of lower permeability are observed, perform over-excavation as needed to hydraulically connect the infiltration system with an infiltrating soil unit. ■If over-excavation is necessary, backfilling should use granular fill with a fines content less than 5% (i.e. percent passing the #200 sieve). ■Retain Terracon to observe the base of the infiltration system, once excavated, to help identify soils units that may be of lower permeability than the soil unit of which infiltration testing was performed. ■Earthwork is performed using low to moderate ground pressure excavation equipment for leveling and grading soils beneath the base of the infiltration facility. Compacting within the infiltration area will reduce the infiltration rate. Boring ID Approximate Depth (ft) USCS Classification Percolation Rate (in/min)1 Measured Rate (in/hr)1 B-03 2.5 GW-GM 0.25 15 B-06 2.5 SW-SM 0.52 31 1.Unfactored, measured infiltration rate. We recommend multiplying the measured rates by at least 0.5 to estimate the design infiltration rate. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 19 Pavements General Pavement Comments Pavement designs are provided for the traffic conditions and pavement life conditions as noted herein. A critical aspect of pavement performance is site preparation. Pavement designs noted in this section must be applied to the site which has been prepared as recommended in the Earthwork section. Pavement loading was not provided to us. We have assumed the following traffic volume for estimating the minimum pavement thickness. If traffic volume will exceed the assumed values, Terracon should be notified in order to provide pavement sections designed for higher levels of traffic. ■1,000 passenger cars/pick-up trucks and vans/recreational vehicles per day ■10 delivery trucks and garbage/dumpster trucks per week ■1 tractor-trailer truck per day (for heavy duty areas only) For design purposes, we have assumed a CBR value of at least 10. Any imported or borrow source fill placed below the proposed pavements should have a CBR value of at least 10. A modulus of subgrade reaction of 200 lbs. per cubic inch (pci) was assumed for compacted subgrade for concrete pavement design. Pavement Section Thicknesses Design of Asphaltic Concrete (AC) pavements is based on the 1993 AASHTO guidelines. Minimum recommended pavement section thicknesses are presented below: Asphaltic Concrete (AC) Design Layer Light Duty AC Thickness (inches) Heavy Duty AC Thickness (inches) Compacted Subgrade 1 12 12 Crushed Aggregate Base 2 6 6 Asphalt Thickness 3, 4 3 4 1.May vary based on observations following proof-rolling and the requirements specified in the Earthwork section. 2.Aggregate base meeting WSDOT:9-03.9(3) Base Course specifications. 3.Aggregates for asphalt surface meeting WSDOT: 9-03.8(2) ½-inch HMA. 4.PG58H-22 asphalt binder. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 20 Portland Cement Concrete (PCC) Design Layer Light Duty PCC Thickness (inches) Heavy Duty PCC Thickness (inches) Compacted Subgrade 1 12 12 Crushed Aggregate Base 2 6 6 Portland Cement Concrete Thickness 5 6 1.May vary based on observations following proof-rolling and the requirements specified in the Earthwork section. 2.Aggregate base meeting WSDOT:9-03.9(3) Base Course specifications. We recommend that Portland cement concrete (PCC, rigid) pavement be used where rigid pavements are appropriate. These areas include but are not limited to entrance and exit sections, dumpster pads, or any areas where extensive wheel maneuvering or repeated loading is expected. The rigid pavement pads should be large enough to support the wheels of the truck which will be bearing the haul load. Adequate reinforcement and number of longitudinal and transverse control joints should be placed in the rigid pavement in accordance with ACI requirements. Although not required for structural support, the base course layer is recommended to help reduce the potential for slab curl, shrinkage cracking, subgrade “pumping” through joints, and to provide a workable surface. These thicknesses assume the subgrade is properly prepared and compacted as noted above. Proper joint spacing will also be required to prevent excessive slab curling and shrinkage cracking. All joints should be sealed to prevent entry of foreign material and dowelled where necessary for load transfer. The minimum pavement sections outlined above were determined based on post- construction traffic loading conditions. These pavement sections do not account for heavy construction traffic during development. A partially constructed structural section that is subjected to heavy construction traffic can result in pavement deterioration and premature distress or failure. Our experience indicates that this pavement construction practice can result in pavements that will not perform as intended. Considering this information, several alternatives are available to mitigate the impact of heavy construction traffic prior to pavement construction. These include using thicker sections to account for the construction traffic after paving; using some method of soil stabilization to improve the support characteristics of the pavement subgrade; routing heavy construction traffic Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 21 around paved areas; or delaying paving operations until as near the end of construction as is feasible. Pavement Drainage Pavements should be sloped to provide rapid drainage of surface water. Water allowed to pond on or adjacent to the pavements could saturate the subgrade and contribute to premature pavement deterioration. In addition, the pavement subgrade should be graded to provide positive drainage within the granular base section. Appropriate sub-drainage or connection to a suitable daylight outlet should be provided to remove water from the granular subbase. We recommend drainage be included at the bottom of the crushed aggregate base (when used) at the storm structures to aid in removing water that may enter this layer. Drainage could consist of small diameter weep holes excavated around the perimeter of the storm structures. The weep holes should be excavated at the elevation of the crushed aggregate base and soil interface. The excavation should be covered with crushed aggregate encompassed in Mirafi 140NL, or an approved equivalent, which will aid in reducing the amount of fines that enter the storm system. Pavement Maintenance The pavement sections represent minimum recommended thicknesses and, as such, periodic maintenance should be anticipated. Therefore, preventive maintenance should be planned and provided for through an ongoing pavement management program. Maintenance activities are intended to slow the rate of pavement deterioration and to preserve the pavement investment. Maintenance consists of both localized maintenance (e.g. crack and joint sealing and patching) and global maintenance (e.g. surface sealing). Preventive maintenance is usually the priority when implementing a pavement maintenance program. Additional engineering observation is recommended to determine the type and extent of a cost-effective program. Even with periodic maintenance, some movements and related cracking may still occur, and repairs may be required. A pavement’s performance is affected by its surroundings. In addition to providing preventive maintenance, the civil engineer should consider the following recommendations in the design and layout of pavements: ■Final grade adjacent to paved areas should slope down from the edges at a minimum 2%. ■Subgrade and pavement surfaces should have a minimum 2% slope to promote proper surface drainage. ■Install joint sealant and seal cracks immediately. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 22 ■Seal all landscaped areas in or adjacent to pavements to reduce moisture migration to subgrade soils. General Comments Our analysis and opinions are based on our understanding of the project, the geotechnical conditions in the area, and the data obtained from our site exploration. Variations will occur between exploration point locations or due to the modifying effects of construction or weather. The nature and extent of such variations may not become evident until during or after construction. Terracon should be retained as the Geotechnical Engineer, where noted in this report, to provide observation and testing services during pertinent construction phases. If variations appear, we can provide further evaluation and supplemental recommendations. If variations are noted in the absence of our observation and testing services on-site, we should be immediately notified so that we can provide evaluation and supplemental recommendations. Our Scope of Services does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, or bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials, or hazardous conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken. Our services and any correspondence are intended for the sole benefit and exclusive use of our client for specific application to the project discussed and are accomplished in accordance with generally accepted geotechnical engineering practices with no third-party beneficiaries intended. Any third-party access to services or correspondence is solely for information purposes to support the services provided by Terracon to our client. Reliance upon the services and any work product is limited to our client and is not intended for third parties. Any use or reliance of the provided information by third parties is done solely at their own risk. No warranties, either express or implied, are intended or made. Site characteristics as provided are for design purposes and not to estimate excavation cost. Any use of our report in that regard is done at the sole risk of the excavating cost estimator as there may be variations on the site that are not apparent in the data that could significantly affect excavation cost. Any parties charged with estimating excavation costs should seek their own site characterization for specific purposes to obtain the specific level of detail necessary for costing. Site safety and cost estimating including excavation support and dewatering requirements/design are the responsibility of others. Construction and site development have the potential to affect adjacent properties. Such impacts can include damage due to vibration, modification of groundwater/surface water flow during construction, foundation movement due to undermining or subsidence from excavation, and noise or air quality concerns. Evaluation of these items on nearby Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials 23 properties is commonly associated with contractor means and methods and is not addressed in this report. The owner and contractor should consider a preconstruction/precondition survey of the surrounding development. If changes in the nature, design, or location of the project are planned, our conclusions and recommendations shall not be considered valid unless we review the changes and either verify or modify our conclusions in writing. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials Attachments Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials Exploration and Testing Procedures Field Exploration Number of Borings Approximate Boring Depth (feet)Location 2 21.5 building 1 (with monitoring well)26.5 pavement / utilities 3 11.5 pavement / utilities Boring Layout and Elevations: Terracon personnel provided the boring layout using handheld GPS equipment (estimated horizontal accuracy of about ±10 feet) with reference to existing site features. Approximate ground surface elevations were estimated using Google Earth. If elevations and a more precise boring layout are desired, we recommend borings be surveyed. Subsurface Exploration Procedures: We advanced the borings with a track-mounted drill rig using a continuous flight hollow stem auger. Four samples were obtained in the upper 10 feet of each boring and at intervals of 5 feet thereafter. In the split-barrel sampling procedure, a standard 2-inch outer diameter split-barrel sampling spoon was driven into the ground by a 140-pound hammer falling a distance of 30 inches. The number of blows required to advance the sampling spoon the last 12 inches of a normal 18-inch penetration is recorded as the Standard Penetration Test (SPT) resistance value. The SPT resistance values, also referred to as N-values, are indicated in the boring logs at the test depths. We observed and recorded groundwater levels during drilling and sampling. For safety purposes, all borings were backfilled with bentonite after completion, with the exception of B-03, which was completed as a monitoring well with a protective steel cover. We also observed the boreholes at the completion of drilling for the presence of groundwater. The groundwater levels are shown in the attached boring logs. The sampling depths, penetration distances, and other sampling information were recorded on the field boring logs. The samples were placed in appropriate containers and taken to our soil laboratory for testing and classification by a Geotechnical Engineer. Our exploration team prepared field boring logs as part of the drilling operations. These field logs included visual classifications of the materials observed during drilling and our interpretation of the subsurface conditions between samples. Final boring logs were prepared from the field logs. The final boring logs represent the Geotechnical Engineer's interpretation of the field logs and include modifications based on observations and tests of the samples in our laboratory. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials Percolation Testing: A 6.75-inch OD soil boring was drilled to approximately 2.5 feet below the existing site grade. A four-inch-diameter solid PVC pipe was inserted, and the hole was backfilled with 6 inches of gravel and sand to keep the pipe in place. The pipe was then filled with water and the soil allowed to saturate. The time required for the water level to drop incrementally was measured over the course of the field exploration (approximately 6 hours). Laboratory Testing The project engineer reviewed the field data and assigned laboratory tests. The laboratory testing program included the following types of tests: ■Moisture Content ■Atterberg Limits ■Grain Size Distribution ■Corrosivity Testing The laboratory testing program often includes examination of soil samples by an engineer. Based on the results of our field and laboratory programs, we described and classified the soil samples in accordance with the Unified Soil Classification System. Geotechnical Engineering Report Panda Express D37983 | Yelm, WA April 21, 2025 | Terracon Project No. 81255065 Facilities |Environmental |Geotechnical | Materials Site Location and Exploration Plans Contents: Site Location Plan Exploration Plan Note: All attachments are one page unless noted above.