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GEOTECHNICAL REPORT - 23-00605 - Dutch Bros - New Commercial Bldg
GEOTECHNICAL INVESTIGATION DUTCH BROS REXBURG 855 West Main Street Rexburg, ID PREPARED FOR: Dan Richardson Milk Crate Development LLC 4828 East 1250 South Heber City, UT 84032 PREPARED BY: Atlas Technical Consultants, LLC 484 Eastland Drive South, Suite 103 Twin Falls, ID 83301 August 7, 2023 E231180g Page | 1 484 Eastland Drive South, Suite 103 Twin Falls, ID 83301 (208) 733-5323 | oneatlas.com August 7, 2023 Atlas No. E231180g Dan Richardson Milk Crate Development LLC 4828 East 1250 South Heber City, UT 84032 Subject: Geotechnical Investigation Dutch Bros Rexburg 855 West Main Street Rexburg, ID Dear Dan Richardson: In compliance with your instructions, Atlas has conducted a soils exploration and foundation evaluation for the above referenced development. Fieldwork for this investigation was conducted on July 24, 2023. Data have been analyzed to evaluate pertinent geotechnical conditions. Results of this investigation, together with our recommendations, are to be found in the following report. We have provided a PDF copy for your review and distribution. Often, questions arise concerning soil conditions because of design and construction details that occur on a project. Atlas would be pleased to continue our role as geotechnical engineers during project implementation. If you have any questions, please call us at (208) 733-5323. Respectfully submitted, Robert Jenson, EI Ethan Salove, PE Staff Engineer Geotechnical Engineer Monica Saculles, PE Senior Geotechnical Engineer Atlas No. E231180g Page | i Copyright © 2023 Atlas Technical Consultants CONTENTS 1. INTRODUCTION ................................................................................................................. 2 1.1 Project Description ..................................................................................................... 2 1.2 Scope of Investigation ................................................................................................ 2 2. SITE DESCRIPTION ........................................................................................................... 3 2.1 Regional Geology ....................................................................................................... 3 2.2 General Site Characteristics ....................................................................................... 3 3. SEISMIC SITE EVALUATION ............................................................................................ 3 3.1 Geoseismic Setting .................................................................................................... 3 3.2 Seismic Design Parameter Values ............................................................................. 4 4. SOILS EXPLORATION ....................................................................................................... 4 4.1 Exploration and Sampling Procedures........................................................................ 4 4.2 Laboratory Testing Program ....................................................................................... 5 4.3 Soil and Sediment Profile ........................................................................................... 5 4.4 Volatile Organic Scan ................................................................................................. 5 5. SITE HYDROLOGY ............................................................................................................ 5 5.1 Groundwater .............................................................................................................. 6 5.2 Soil Infiltration Rates .................................................................................................. 6 6. LATERAL EARTH PRESSURES ....................................................................................... 7 6.1 Retaining Wall Backfill Materials................................................................................. 7 6.2 Retaining Wall Drainage ............................................................................................. 9 7. FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS............................ 9 7.1 Foundation Loading Information ................................................................................. 9 7.2 Foundation Design Recommendations ....................................................................... 9 7.3 Floor Slab-on-Grade ..................................................................................................10 8. PAVEMENT DISCUSSION AND RECOMMENDATIONS ..................................................11 8.1 Pavement Design Parameters ...................................................................................11 8.2 Flexible Pavement Sections ......................................................................................11 8.3 Rigid Pavement Sections ..........................................................................................12 8.4 Common Pavement Section Construction Issues ......................................................13 9. CONSTRUCTION CONSIDERATIONS .............................................................................13 9.1 Earthwork ..................................................................................................................13 9.2 Grading .....................................................................................................................14 9.3 Dry Weather ..............................................................................................................14 9.4 Wet Weather .............................................................................................................14 9.5 Soft Subgrade Soils...................................................................................................15 9.6 Frozen Subgrade Soils ..............................................................................................15 9.7 Structural Fill .............................................................................................................16 Atlas No. E231180g Page | ii Copyright © 2023 Atlas Technical Consultants 9.8 Fill Placement and Compaction .................................................................................16 9.9 Backfill of Walls .........................................................................................................18 9.10 Excavations .............................................................................................................18 9.11 Groundwater Control ...............................................................................................18 10. GENERAL COMMENTS ..................................................................................................19 11. REFERENCES.................................................................................................................20 TABLES Table 1 – Seismic Design Values ................................................................................................ 4 Table 2 – Typical Soil Profiles ..................................................................................................... 5 Table 3 – Groundwater Data ....................................................................................................... 6 Table 4 – Generalized Soil Infiltration Rates ............................................................................... 6 Table 5 – Lateral Earth Pressure Values ..................................................................................... 8 Table 6 – Soil Bearing Capacity ................................................................................................ 10 Table 7 – AASHTO Flexible Pavement Specifications............................................................... 12 Table 8 – AASHTO Rigid Pavement Specifications ................................................................... 12 Table 9 – Fill Material Criteria ................................................................................................... 16 Table 10 – Fill Placement and Compaction Requirements ........................................................ 16 APPENDICES Appendix I Warranty and Limiting Conditions Appendix II Vicinity Map Appendix III Site Map Appendix IV Geotechnical Investigation Test Pit Log Appendix V Geotechnical General Notes Appendix VI Important Information About This Geotechnical Engineering Report Atlas No. E231180g Page | 2 Copyright © 2023 Atlas Technical Consultants 1. INTRODUCTION This report presents results of a geotechnical investigation and analysis in support of data utilized in design of structures as defined in the 2018 International Building Code (IBC). Information in support of groundwater and stormwater issues pertinent to the practice of Civil Engineering is included. Observations and recommendations relevant to the earthwork phase of the project are also presented. Revisions in plans or drawings for the proposed structures from those enumerated in this report should be brought to the attention of the soils engineer to determine whether changes in the provided recommendations are required. Deviations from noted subsurface conditions, if encountered during construction, should also be brought to the attention of the soils engineer. 1.1 Project Description The proposed development is in the City of Rexburg, Madison County, ID, and occupies a portion of the NE¼NW¼ of Section 25, Township 6 North, Range 39 East, Boise Meridian. The site to be developed is approximately 0.8 acre. Site maps included in the Appendix show the project location. This project will consist of construction of a single-story drive-through commercial structure that is approximately 950 square-feet in size. Paved areas will developed for the project. Drainage is expected to be directed to onsite infiltration facilities. Location of the infiltration facilities were provided by Barghausen Consulting Engineers. The site is to be brought up 1 to 2 feet above existing grade. 1.2 Scope of Investigation Our scope of work was completed in general accordance with our proposal dated April 11, 2023 and authorized on July 7, 2023. Said authorization is subject to terms, conditions, and limitations described in the Professional Services Contract entered into between Milk Crate Development LLC and Atlas. Atlas’ scope of services included the following: • Subsurface exploration via test pits. • Infiltration testing for stormwater management planning. • Field and laboratory testing of materials encountered and collected. • Preparation of this report, which includes project description, site conditions, and our engineering analysis and evaluation for the project. Atlas No. E231180g Page | 3 Copyright © 2023 Atlas Technical Consultants 2. SITE DESCRIPTION 2.1 Regional Geology The site is located in the city of Rexburg in an area known as the Eastern Snake River Plain. Sediments deposited here are derived from Middle Pleistocene Granites and Upper Pleistocene Rhyolitic Volcanics (Alt and Hyndman, 1998), which outcrop immediately south-southeast of Rexburg, and compose the bedrock throughout the region. Sediments were deposited during the Pleistocene Period (0.6 to 1.8 million years ago) and have been mapped as outwash fanglomerate and terrace gravels, and consist of medium to coarse-grained river deposits (Bond, 1978). These sediments were deposited in a variety of geologic environments, which existed along the northeastern margin of the ancestral Eastern Snake River Plain. Since their deposition, these formations have gradually been eroded away from the Rexburg Foothills. 2.2 General Site Characteristics The following details regarding site conditions are based on visual observations and review of available geologic and topographic maps and imagery: • Current Site Conditions: The site is approximately 0.8 acre. The site currently consists of an undeveloped lot. To the east and north of the property are existing commercial developments. The site is bounded to the west by US 20 and to the north by US 33. To the south is further undeveloped property. • Vegetation: Vegetation on the site consists of bunchgrass and other native weeds and grasses. A small strip of landscaping vegetation can be found along the eastern portion of the project site, including grasses and small trees. • Topography: The site is relatively flat and level. • Drainage: Stormwater drainage for the site is achieved by percolation through surficial soils. The site is situated so that it is unlikely that it will receive any drainage from off-site sources. 3. SEISMIC SITE EVALUATION 3.1 Geoseismic Setting Soils on site are classed as Site Class D in accordance with Chapter 20 of the American Society of Civil Engineers (ASCE) publication ASCE/SEI 7-16. Structures constructed on this site should be designed per IBC requirements for such a seismic classification. Our investigation revealed low hazard potential resulting from potential earthquake motions including: slope instability, liquefaction, and surface rupture caused by faulting or lateral spreading. Atlas No. E231180g Page | 4 Copyright © 2023 Atlas Technical Consultants 3.2 Seismic Design Parameter Values The ASCE 7-16 seismic design parameter values have been provided below. Table 1 – Seismic Design Values Seismic Design Parameter Design Value Site Class D “Default” Site Modified Peak Ground Acceleration, PGAM 0.229 Ss 0.361 (g) S1 0.141 (g) Fa 1.512 Fv 2.318 SMS 0.545 SM1 0.327 SDS 0.363 SD1 0.218 4. SOILS EXPLORATION 4.1 Exploration and Sampling Procedures Field exploration conducted to determine engineering characteristics of subsurface materials included a reconnaissance of the project site and investigation by test pit. Test pit sites were located in the field by means of a Global Positioning System (GPS) device and are reportedly accurate to within ten feet. Upon completion of investigation, each test pit was backfilled with loose excavated materials. Re-excavation and compaction of these test pit areas are required prior to construction. Samples obtained have been visually classified in the field, identified according to test pit number and depth, placed in sealed containers, and transported to our laboratory for additional testing. Subsurface materials have been described in detail on logs provided in the Appendix. Results of field and laboratory tests are also presented in the Appendix. Atlas recommends that these logs not be used to estimate fill material quantities. Atlas No. E231180g Page | 5 Copyright © 2023 Atlas Technical Consultants 4.2 Laboratory Testing Program Along with our field investigation, a supplemental laboratory testing program was conducted to determine additional pertinent engineering characteristics of subsurface materials. Laboratory tests were conducted in accordance with current specifications. The laboratory testing program for this report included: • Atterberg Limits Testing – ASTM D4318 • Grain Size Analysis – ASTM C117/C136 4.3 Soil and Sediment Profile The profile below represents a generalized interpretation for the project site. Note that on site soils strata, encountered between test pit locations, may vary from the individual soil profiles presented in the logs. Table 2 – Typical Soil Profiles Soil Horizons Approximate Depths Soil Types Consistency/Relative Density Surficial Soils1 0 to 3 feet Sandy Lean Clay Hard Intermediate Soils 2 to 6.5 feet Poorly Graded Sand with Gravel Medium Dense to Dense Deeper Soils 3 to 12.5 feet Poorly Graded Gravel with Sand Medium Dense to Dense 1Calcium carbonate cementation noted within portions of these horizons. During excavation, test pit sidewalls were generally stable. However, moisture contents will affect wall competency with saturated soils having a tendency to readily slough when under load and unsupported. 4.4 Volatile Organic Scan Soils obtained during on-site activities were not assessed for volatile organic compounds by portable photoionization detector. Samples obtained during our exploration activities exhibited no apparent odors or discoloration typically associated with this type of contamination. No groundwater was encountered. 5. SITE HYDROLOGY Existing surface drainage conditions are defined in the General Site Characteristics section. Information provided in this section is limited to observations made at the time of the investigation. Either regional or local ordinances may require information beyond the scope of this report. Atlas No. E231180g Page | 6 Copyright © 2023 Atlas Technical Consultants 5.1 Groundwater During this field investigation, groundwater was not encountered in test pits advanced to a maximum depth of 12.5 feet bgs. Atlas has previously performed 4 geotechnical investigations within 0.50 mile of the project site. Information from these investigations has been provided in the table below. Table 3 – Groundwater Data Date Approximate Distance from Site (mile) Direction from Site Groundwater Depth (feet bgs) June 2012 0.33 West 21.0 August 2000 0.17 West Not Encountered to 18.0 April 2014 0.07 East Not Encountered to 17.5 December 2007 0.48 North 13.4 Furthermore, according to Idaho Department of Water Resources (IDWR) monitoring well data within approximately ½-mile of the project site, groundwater was measured at depths ranging between 10 and 33 feet bgs. Based on evidence of this investigation and background knowledge of the area, Atlas has determined that the typical seasonal high groundwater should remain greater than approximately 10 feet bgs. This depth can be confirmed through long-term groundwater monitoring. 5.2 Soil Infiltration Rates Soil permeability, which is a measure of the ability of a soil to transmit a fluid, was tested in the field. For this report, an estimation of infiltration is also presented using generally recognized values. Typical infiltration rates comprising the generalized soil profile for this study have been provided in the table below. Table 4 – Generalized Soil Infiltration Rates Soil Type Typical Infiltration Rate (inches per hour) Sandy Lean Clay* <2 Poorly Graded Sand with Gravel >12 Poorly Graded Gravel with Sand *The presence of cementation/induration may reduce infiltration rates to near zero. Water was added to test pits 4 and 5 at depths of 5.5 and 4.0 feet bgs, respectively, and drained in excess of 8 inches per hour within the poorly graded gravel with sand sediments. The test pits were advanced to their termination depths of 11.0 and 11.5 feet bgs, after water was added. Atlas No. E231180g Page | 7 Copyright © 2023 Atlas Technical Consultants It is recommended that infiltration facilities constructed on the site be extended into native poorly graded gravel with sand sediments. Excavation depths of approximately 3 feet bgs should be anticipated to expose these poorly graded gravel with sand sediments. An infiltration rate of 8 inches per hour should be used in design. Actual infiltration rates should be confirmed at the time of construction. Atlas recommends that all infiltration facilities be constructed in accordance with the local municipality requirements. 6. LATERAL EARTH PRESSURES Retaining walls will be subject to lateral earth pressures. The magnitude of earth pressure is a function of both type and compaction of backfill behind walls within the “active” zone, and allowable rotation of the top of the wall. The active zone is defined as the wedge of soil between the surface of the wall and a plane inclined 29 degrees from vertical passing through the base of the wall. All clayey soils must be completely removed from within the active zone. When dealing with lateral earth pressures on a gravity block the following sliding frictional coefficients should be used: • For native poorly graded sand with gravel use 0.40. • For native poorly graded gravel with sand sediments and imported granular structural fill use 0.45. Restrained walls, such as basement walls, should be designed based on at-rest pressures. Active pressures are appropriate under conditions where the wall moves or rotates away from the soil mass at failure. Passive pressures are used for conditions where the wall moves toward the soil mass at failure. Rotation, or lateral movement, of the top of the wall equal to 0.002 times the height of the wall will be necessary for on-site sandy soil backfill to achieve an “active” loading condition. Lateral movement of the top of the wall equal to 0.001 times the height of the wall will be necessary for the “active” pressure condition for native poorly graded gravels and imported granular structural backfill. 6.1 Retaining Wall Backfill Materials Atlas anticipates that backfill materials will consist of the onsite poorly graded sand with gravel sediments and poorly graded gravel with sand sediments. Clayey soils are not suitable for use as backfill on the soil side of walls. The following values are applicable under non-surcharged, drained conditions. Atlas No. E231180g Page | 8 Copyright © 2023 Atlas Technical Consultants Table 5 – Lateral Earth Pressure Values Soil Type:Poorly Graded Sand with Gravel 32 °Dry Unit Weight:120 pcf 0 psf Bouyant Unit Weight:78 pcf 0.5 Moisture Content:8 % 0.229 Backfill Slope:0 ° 61 pcf1 K0=0.47 40 pcf1 Ka=0.31 422 pcf1 Kp=3.25 62 pcf1 Kae=0.48 325 pcf1 Kpe=2.51 Soil Type:Compacted Sandy Gravel Fill and Native Poorly Graded Gravel with Sand 35 °Dry Unit Weight:128 pcf N/A Bouyant Unit Weight:83 pcf 0.4 Moisture Content:5 % 0.229 Backfill Slope:0 ° 57 pcf1 K0=0.43 36 pcf1 Ka=0.27 496 pcf1 Kp=3.69 60 pcf1 Kae=0.44 382 pcf1 Kpe=2.85 Internal Friction Angle: Cohesion: Natural Void Ratio: Ground Acceleration2: At rest lateral earth pressure: Active lateral earth pressure: Passive lateral earth pressure: Seismic active lateral earth pressure: Seismic passive lateral earth pressure: Internal Friction Angle: Cohesion: Seismic active lateral earth pressure: Seismic passive lateral earth pressure: Natural Void Ratio: Ground Acceleration2: At rest lateral earth pressure: Active lateral earth pressure: Passive lateral earth pressure: 1Lateral earth pressure values are in pounds per square foot, per foot of wall (psf/ft). Alternately, the values presented may also be considered as equivalent fluid with units of pounds per cubic foot (pcf). 2Ground acceleration obtained from the USGS Seismic Design Maps. Note that the values for seismic lateral earth pressures are calculated using both the static and seismic coefficients. The effect of seismic conditions alone is the difference between the static and seismic lateral earth pressures presented above. In the case that another material is used for backfill, Atlas should be consulted for alternate lateral earth pressure values. Granular structural fill should consist of 4-inch-minus select, clean, granular soil with no more than 30 percent oversize (greater than ¾-inch) material and no more than 5 percent non-plastic fines (passing the No. 200 sieve). Retaining wall backfill must be placed in accordance with recommendations in the Fill Placement and Compaction section of this report and must be properly compacted and tested. Lateral earth pressure values do not incorporate specific factors of safety, and are only applicable for non-surcharged, drained conditions. Factors of safety, if applicable, should be integrated into the structural design of the wall. Furthermore, changes in soil moisture, such as can be imposed by site stormwater systems, can change the values listed above. The preceding values are presented for idealized conditions relating to simple shallow structures. For complex structures, deep structures, or structures with significant perimeter landscaping, a soils engineer should be retained as part of the design team in developing appropriate project design parameters and construction specifications. Atlas No. E231180g Page | 9 Copyright © 2023 Atlas Technical Consultants 6.2 Retaining Wall Drainage Atlas recommends that a drainage system be incorporated into the retained soil mass. This can be accomplished by installing wall and toe drains as a part of each soil-supporting wall system. The drainage system should consist of the following: • A 2-foot wide section of drain rock should be placed immediately behind the wall. A compacted, low-permeability soil cap is recommended within the upper 2 feet of the surface to limit surface water infiltration behind the walls. If hardscaping is present, the low-permeability soil cap can be eliminated. • A 4-inch diameter perforated drain pipe should be installed at the footing elevation of each wall. This pipe must slope at least 1 percent to a suitable discharge point away from the wall. These drainage systems must be separate from other retaining wall/foundation systems, such as roof drain effluent and irrigation water systems. 7. FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS Various foundation types have been considered for support of the proposed structure. Two requirements must be met in the design of foundations. First, the applied bearing stress must be less than the ultimate bearing capacity of foundation soils to maintain stability. Second, total and differential settlement must not exceed an amount that will produce an adverse behavior of the superstructure. Allowable settlement is usually exceeded before bearing capacity considerations become important; thus, allowable bearing pressure is normally controlled by settlement considerations. 7.1 Foundation Loading Information Loads of up to 4,000 pounds per lineal foot for wall footings, and column loads of up to 50,000 pounds were assumed for settlement calculations. Total settlement should be limited to approximately 1 inch and differential settlement should be limited to approximately ½ inch, provided the following design and construction recommendations are observed. 7.2 Foundation Design Recommendations Considering subsurface conditions and the proposed construction, it is recommended that the structure be founded upon conventional spread footings and continuous wall footings. The following recommendations are not specific to the individual structures, but rather should be viewed as guidelines for the subdivision-wide development. Based on data obtained from the site and test results from various laboratory tests performed, Atlas recommends the following guidelines for the net allowable soil bearing capacity: Atlas No. E231180g Page | 10 Copyright © 2023 Atlas Technical Consultants Table 6 – Soil Bearing Capacity Footing Depth ASTM D1557 Subgrade Compaction Net Allowable Soil Bearing Capacity Footings must bear on competent, undisturbed, native sandy lean clay soils, poorly graded sand sediments, poorly graded gravel with sand sediments, or compacted structural fill. Existing organic materials or fill materials (if encountered) must be completely removed from below foundation elements.1 An excavation depth of roughly 1.0 foot bgs should be anticipated to expose proper bearing soils.2 Not Required for Native Soil 95% for Structural Fill 2,000 lbs/ft2 1It will be required for Atlas personnel to verify the bearing soil suitability for each structure at the time of construction. 2Depending on the time of year construction takes place, the subgrade soils may be unstable because of high moisture contents. If unstable conditions are encountered, over-excavation and replacement with granular structural fill and/or use of geotextiles may be required. The following sliding frictional coefficient values should be used: 1) 0.35 for footings bearing on native sandy lean clay soils, 2) 0.40 for footings bearing on poorly graded sand with gravel sediments and 2) 0.45 for footings bearing on native poorly graded gravel with sand sediments or granular structural fill. A passive lateral earth pressure of 356 pounds per square foot per foot (psf/ft) should be used for sandy lean clay soils and 422 psf/ft should be used for poorly graded sand with gravel sediments. For compacted sandy gravel fill and native poorly graded gravel with sand sediments, a passive lateral earth pressure of 496 psf/ft should be used. Footings should be proportioned to meet either the stated soil bearing capacity or the 2018 IBC minimum requirements. Objectionable soil types encountered at the bottom of footing excavations should be removed and replaced with structural fill. Excessively loose or soft areas that are encountered in the footings subgrade will require over-excavation and backfilling with structural fill. To minimize the effects of slight differential movement that may occur because of variations in the character of supporting soils and seasonal moisture content, Atlas recommends continuous footings be suitably reinforced to make them as rigid as possible. For frost protection, the bottom of external footings should be 36 inches below finished grade. Foundations must be backfilled in accordance with the Backfill of Walls section 7.3 Floor Slab-on-Grade Organic, loose, or obviously compressive materials must be removed prior to placement of concrete floors or floor-supporting fill. In addition, the remaining subgrade should be treated in accordance with guidelines presented in the Earthwork section. Areas of excessive yielding should be excavated and backfilled with structural fill. Fill used to increase the elevation of the floor slab should meet requirements detailed in the Structural Fill section. Fill materials must be compacted to a minimum 95 percent of the maximum dry density as determined by ASTM D1557. Atlas No. E231180g Page | 11 Copyright © 2023 Atlas Technical Consultants A free-draining granular mat should be provided below slabs-on-grade to provide drainage and a uniform and stable bearing surface. This should be a minimum of 4 inches in thickness and properly compacted. The mat should consist of a sand and gravel mixture, complying with Idaho Standards for Public Works Construction (ISPWC) specifications for ¾-inch (Type 1) crushed aggregate. The granular mat should be compacted to no less than 95 percent of the maximum dry density as determined by ASTM D1557. A moisture-retarder should be placed beneath floor slabs to minimize potential ground moisture effects on moisture-sensitive floor coverings. The moisture-retarder should be at least 15-mil in thickness and have a permeance of less than 0.01 US perms as determined by ASTM E96. Placement of the moisture-retarder will require special consideration with regard to effects on the slab-on-grade and should adhere to recommendations outlined in the ACI 302.1R and ASTM E1745 publications. Upon request, Atlas can provide further consultation regarding installation. 8. PAVEMENT DISCUSSION AND RECOMMENDATIONS 8.1 Pavement Design Parameters Project specific traffic loading information has not been provided. Based on the character of the proposed construction, Atlas has assumed a traffic loading of 52,000 equivalent single axle loads (ESALs) for light duty pavement areas and 100,000 ESALs for moderate duty pavement areas. Light duty pavement should be used for parking lots and moderate duty pavement is to be used for access routes and loading/unloading areas. Atlas can provide a project specific pavement design upon request. Based on experience with soils in the region, a subgrade California Bearing Ratio (CBR) value of 4 has been assumed for near-surface sandy lean clay soils on site. The recommended pavement sections provided below are based on a 20-year design life. To achieve this design life a routine maintenance program that includes crack sealing on a regular basis and possible seal coating will be required. The following are minimum thickness requirements for assured pavement function. Depending on site conditions, additional work, e.g. soil preparation, may be required to support construction equipment. These have been listed within the Soft Subgrade Soils section. 8.2 Flexible Pavement Sections The American Association of State Highway and Transportation Officials (AASHTO) design method has been used to calculate the following pavement sections. Atlas recommends that materials used in the construction of asphaltic concrete pavements meet requirements of the ISPWC Standard Specification for Highway Construction. Construction of the pavement section should be in accordance with these specifications. Atlas No. E231180g Page | 12 Copyright © 2023 Atlas Technical Consultants Table 7 – AASHTO Flexible Pavement Specifications Pavement Section Component Light Duty Moderate Duty Asphaltic Concrete 2.5 Inches 3.0 Inches Crushed Aggregate Base 4.0 Inches 4.0 Inches Structural Subbase 10.0 Inches 10.0 Inches Compacted Subgrade1 Not Required Not Required 1It will be required for Atlas personnel to verify subgrade competency at the time of construction. • Asphaltic Concrete: Asphalt mix design shall meet the requirements of ISPWC Section 810. Materials shall be placed in accordance with ISPWC Standard Specifications for Highway Construction. • Aggregate Base: Material complying with ISPWC Standards for Type 1 Crushed Aggregate Materials. • Structural Subbase: Material complying with ISPWC Section 801 for 3-inch or 6-inch Uncrushed Aggregate Materials. The maximum material diameter cannot exceed 2/3 the component thickness. 8.3 Rigid Pavement Sections The AASHTO pavement design method was used to develop the following rigid concrete pavement sections. Concrete pavement shall be batched and constructed in accordance with the most current American Concrete Institute Standards and in accordance with ISPWC Standard Drawings SD-714, SD-714A, and SD-714B. Native subgrade soils on the site are not frost susceptible, and therefore, do not require joint sealers or under-drains. Table 8 – AASHTO Rigid Pavement Specifications Pavement Section Component Light Duty Moderate Duty Portland Cement Concrete 5.0 Inches 6.0 Inches Crushed Aggregate Base 6.0 Inches 6.0 Inches Structural Subbase Not Required Not Required Compacted Subgrade1 Not Required Not Required 1It will be required for Atlas personnel to verify subgrade competency at the time of construction. • Portland Cement Concrete: 4,000 psi concrete with a modulus of rupture greater than 650 psi generally complying with ISPWC requirement for Portland Cement Concrete per Section 705. • Aggregate Base: Material complying with ISPWC Standards for Type 1 Crushed Aggregate Materials. • Structural Subbase: Material complying with ISPWC Section 801 for 3-inch or 6-inch Uncrushed Aggregate Materials. The maximum material diameter cannot exceed 2/3 the component thickness. Atlas No. E231180g Page | 13 Copyright © 2023 Atlas Technical Consultants 8.4 Common Pavement Section Construction Issues The subgrade upon which above pavement sections are to be constructed must be properly stripped, inspected, and proof-rolled. Proof rolling of subgrade soils should be accomplished using a heavy rubber-tired, fully loaded, tandem-axle dump truck or equivalent. Verification of subgrade competence by Atlas personnel at the time of construction is required. Fill materials on the site must demonstrate the indicated compaction prior to placing material in support of the pavement section. Atlas anticipated that pavement areas will be subjected to moderate traffic. Subgrade clayey and silty soils near and above optimum moisture contents may pump during compaction. Pumping or soft areas must be removed and replaced with structural fill. Fill material and aggregates in support of the pavement section must be compacted to no less than 95 percent of the maximum dry density as determined by ASTM D698 for flexible pavements and by ASTM D1557 for rigid pavements. If a material placed as a pavement section component cannot be tested by usual compaction testing methods, then compaction of that material must be approved by observed proof rolling. Minor deflections from proof rolling for flexible pavements are allowable. Deflections from proof rolling of rigid pavement support courses should not be visually detectable. Atlas recommends that rigid concrete pavement be provided for heavy garbage receptacles. This will eliminate damage caused by the considerable loading transferred through the small steel wheels onto asphaltic concrete. Rigid concrete pavement should consist of Portland Cement Concrete Pavement (PCCP) generally adhering to ISPWC requirement for Portland Cement Concrete. PCCP should be 6 inches thick on a 4-inch drainage fill course (see Floor Slab-on- Grade section), and should be reinforced with welded wire fabric. Control joints must be on 12- foot centers or less. 9. CONSTRUCTION CONSIDERATIONS 9.1 Earthwork Excessively organic soils, deleterious materials, or disturbed soils generally undergo high volume changes when subjected to loads, which is detrimental to subgrade behavior in the area of pavements, floor slabs, structural fills, and foundations. Thick grasses with associated root systems were noted at the time of our investigation. It is recommended that organic or disturbed soils, if encountered, be removed to depths of ½ foot (minimum), and wasted or stockpiled for later use. Stripping depths should be adjusted in the field to assure that the entire root zone or disturbed zone or topsoil are removed prior to placement and compaction of structural fill materials. Exact removal depths should be determined during grading operations by Atlas personnel, and should be based upon subgrade soil type, composition, and firmness or soil stability. If underground storage tanks, underground utilities, wells, or septic systems are discovered during construction activities, they must be decommissioned then removed or abandoned in accordance with governing Federal, State, and local agencies. Excavations developed as the result of such removal must be backfilled with structural fill materials as defined in the Structural Fill section. Atlas No. E231180g Page | 14 Copyright © 2023 Atlas Technical Consultants Atlas should oversee subgrade conditions (i.e., moisture content) as well as placement and compaction of new fill (if required) after native soils are excavated to design grade. Recommendations for structural fill presented in this report can be used to minimize volume changes and differential settlements that are detrimental to the behavior of footings, pavements, and floor slabs. Sufficient density tests should be performed to properly monitor compaction. 9.2 Grading Positive grades must be maintained surrounding structures and pavements, including exterior slabs. The interface of plant bedding materials and underlying soils should be graded to provide drainage away from site elements. Otherwise, bedding materials may direct water to underlying fine-grained soils, which increases the potential for localized heave. Excessive watering of landscaping should be avoided. If structures are to be tightly clustered, limiting space between two adjacent foundation systems, subsurface drains may be required to alleviate water ponding during short, intense storm events. 9.3 Dry Weather If construction is to be conducted during dry seasonal conditions, many problems associated with soft soils may be avoided. However, some rutting of subgrade soils may be induced by shallow groundwater conditions related to springtime runoff or irrigation activities during late summer through early fall. Solutions to problems associated with soft subgrade soils are outlined in the Soft Subgrade Soils section. Problems may also arise because of lack of moisture in native and fill soils at time of placement. This will require the addition of water to achieve near-optimum moisture levels. Low-cohesion soils exposed in excavations may become friable, increasing chances of sloughing or caving. Measures to control excessive dust should be considered as part of the overall health and safety management plan. 9.4 Wet Weather If construction is to be conducted during wet seasonal conditions (commonly from mid-November through May), problems associated with soft soils must be considered as part of the construction plan. During this time of year, fine-grained soils such as silts and clays will become unstable with increased moisture content, and eventually deform or rut. Additionally, constant low temperatures reduce the possibility of drying soils to near optimum conditions. Atlas No. E231180g Page | 15 Copyright © 2023 Atlas Technical Consultants 9.5 Soft Subgrade Soils Shallow fine-grained subgrade soils that are high in moisture content should be expected to pump and rut under construction traffic. During periods of wet weather, construction may become very difficult if not impossible. The following recommendations and options have been included for dealing with soft subgrade conditions: • Track-mounted vehicles should be used to strip the subgrade of root matter and other deleterious debris. Heavy rubber-tired equipment should be prohibited from operating directly on the native subgrade and areas in which structural fill materials have been placed. Construction traffic should be restricted to designated roadways that do not cross, or cross on a limited basis, proposed roadway or parking areas. • Soft areas can be over-excavated and replaced with granular structural fill. • Construction roadways on soft subgrade soils should consist of a minimum 2-foot thickness of large cobbles of 4 to 6 inches in diameter with sufficient sand and fines to fill voids. Construction entrances should consist of a 6-inch thickness of clean, 2-inch minimum, angular drain-rock and must be a minimum of 10 feet wide and 30 to 50 feet long. During the construction process, top dressing of the entrance may be required for maintenance. • Scarification and aeration of subgrade soils can be employed to reduce the moisture content of wet subgrade soils. After stripping is complete, the exposed subgrade should be ripped or disked to a depth of 1½ feet and allowed to air dry for 2 to 4 weeks. Further disking should be performed on a weekly basis to aid the aeration process. • Alternative soil stabilization methods include use of geotextiles, lime, and cement stabilization. Atlas is available to provide recommendations and guidelines at your request. 9.6 Frozen Subgrade Soils Prior to placement of structural fill materials or foundation elements, frozen subgrade soils must either be allowed to thaw or be stripped to depths that expose non-frozen soils and wasted or stockpiled for later use. Stockpiled materials must be allowed to thaw and return to near-optimal conditions prior to use as structural fill. The onsite, shallow clayey soils are susceptible to frost heave during freezing temperatures. For exterior flatwork and other structural elements, adequate drainage away from subgrades is critical. Compaction and use of structural fill will also help to mitigate the potential for frost heave. Complete removal of frost susceptible soils for the full frost depth, followed by replacement with a non-frost susceptible structural fill, can also be used to mitigate the potential for frost heave. Atlas is available to provide further guidance/assistance upon request. Atlas No. E231180g Page | 16 Copyright © 2023 Atlas Technical Consultants 9.7 Structural Fill The following table defines the types of fill material that is suitable for use on the project. Refer to the Fill Placement and Compaction section for recommended placement locations for each fill type listed below. Table 9 – Fill Material Criteria Fill Type Material Lift Thickness* Granular Structural Fill ISPWC Section 801 for 1-inch, 3-inch, or 6-inch Uncrushed Aggregate and ISPWC Section 802 Aggregate Base 12 inches Aggregate Base Material ISPWC Section 802 for Type 1 Crushed Aggregate Base 12 inches Subbase Material ISPWC Section 801 for 3-inch or 6-inch Uncrushed Aggregate 12 inches Suitable Structural Fill Imported SM and GM soils that are free of organics and debris 6 inches Suitable Soil Onsite/imported CL, SM, and GM soils that are free of organics and debris 6 inches *Initial loose thickness, prior to compaction. 9.8 Fill Placement and Compaction Requirements for fill material type and compaction effort are dependent on the planned use of the material. The following table specifies material type and compaction requirements based on the placement location of the fill material. Table 10 – Fill Placement and Compaction Requirements Fill Location Material Type Compaction Foundations Granular Structural Fill 95% of ASTM D1557 Interior Slab-on-Grade and Below Rigid Pavement Subgrade Granular Structural Fill or Suitable Structural Fill 95% of ASTM D1557 Top 4 Inches of Interior and Exterior Slab-on-Grade Aggregate Base Material 95% of ASTM D1557 Below Flexible Pavement Subgrade and Exterior Flatwork Areas Granular Structural Fill or Suitable Structural Fill 95% of ASTM D698 or 92% of ASTM D1557 Foundation and Retaining Wall Backfill Granular Structural Fill or Suitable Structural Fill 95% of ASTM D1557 Utility Trench Backfill Granular Structural Fill or Suitable Soil Per ISPWC Section 306 Landscape Areas Granular Structural Fill or Suitable Soil 92% of ASTM D698 or 90% of ASTM D1557 Atlas No. E231180g Page | 17 Copyright © 2023 Atlas Technical Consultants Prior to placement of structural fill materials, surfaces must be prepared as outlined in the Earthwork section. Structural fill material must be placed in horizontal lifts not exceeding 6- inches in thickness for fine-grained soils and 12-inches in thickness for granular structural fill, aggregate base material, and subbase material. All fill material must be moisture-conditioned to achieve optimum moisture content prior to compaction. During placement all fill materials must be monitored and tested to confirm compaction requirements have been achieved, as specified above, prior to placement of subsequent lifts. In addition, compacted surfaces must be in a firm and unyielding condition. Atlas personnel should be onsite to verify suitability of subgrade soil conditions, identify whether further work is necessary, and perform in-place moisture density testing. Sufficient density tests should be performed to properly monitor compaction. At a minimum, Atlas recommends one test per lift as follows: • Structures – 1 test every 5,000 square feet • Pavement and Exterior Flatwork Areas – 1 test every 10,000 square feet • Foundation and Retaining Wall Backfill – 1 test every 500 square feet • Utility Trench Backfill – 1 test every 100 linear feet • Landscape Areas – 1 test every 15,000 square feet Silty soils require very high moisture contents for compaction, require a long time to dry out if natural moisture contents are too high, and may also be susceptible to frost heave under certain conditions. Therefore, these materials can be quite difficult to work with as moisture content, lift thickness, and compactive effort becomes difficult to control. If silty soil is used for structural fill, lift thicknesses should not exceed 6 inches (loose), and fill material moisture must be closely monitored at both the working elevation and the elevations of materials already placed. Following placement, the exposed surface must be protected from degradation resulting from construction traffic or subsequent construction. It is anticipated that fine-grained soils will not be suitable for reuse during the wet season. Use of silty soils (GM, SM, and ML) as structural fill below footings is prohibited. For structural fill below footings, areas of compacted backfill must extend outside the perimeter of the footings for a distance equal to the thickness of fill between the bottom of foundation and underlying soils, or 5 feet, whichever is less. If material contains more than 40 percent but less than 50 percent oversize (greater than ¾-inch) particles, compaction of fill must be confirmed per ISPWC Section 202.3.8.D.3. Material should contain sufficient fines to fill void spaces and must not contain more than 50 percent oversize particles. Atlas No. E231180g Page | 18 Copyright © 2023 Atlas Technical Consultants 9.9 Backfill of Walls Backfill materials must conform to the requirements of structural fill, as defined in this report. For wall heights greater than 2.5 feet, the maximum material size should not exceed 4 inches in diameter. Placing oversized material against rigid surfaces interferes with proper compaction and can induce excessive point loads on walls. Backfill shall not commence until the wall has gained sufficient strength to resist placement and compaction forces. Further, retaining walls above 2.5 feet in height shall be backfilled in a manner that will limit the potential for damage from compaction methods and/or equipment. It is recommended that only small hand-operated compaction equipment be used for compaction of backfill within a horizontal distance equal to the height of the wall, measured from the back face of the wall. Backfill should be compacted in accordance with the specifications for structural fill, except in those areas where it is determined that future settlement is not a concern, such as planter areas. In nonstructural areas, backfill must be compacted to a firm and unyielding condition. Atlas recommends in these areas that the top 12 inches must consist of a low permeability (clay or silt) soil to limit surface water infiltration. Proper grading away from structures is critical. The surface must be graded away from the structure. In addition, Atlas recommends that roof drains carry stormwater at least 10 feet away from the structure. 9.10 Excavations Shallow excavations that do not exceed 4 feet in depth may be constructed with side slopes approaching vertical. Below this depth, it is recommended that slopes be constructed in accordance with Occupational Safety and Health Administration (OSHA) regulations, Section 1926, Subpart P. Based on these regulations, on-site soils are classified as type “C” soil, and as such, excavations within these soils should be constructed at a maximum slope of 1½ feet horizontal to 1 foot vertical (1½:1) for excavations up to 20 feet in height. Excavations in excess of 20 feet will require additional analysis. Note that these slope angles are considered stable for short-term conditions only, and will not be stable for long-term conditions. During the subsurface exploration, test pit sidewalls generally exhibited little indication of collapse. For deep excavations, native granular sediments cannot be expected to remain in position. These materials are prone to failure and may collapse, thereby undermining upper soil layers. This is especially true when excavations approach depths near the water table. Care must be taken to ensure that excavations are properly backfilled in accordance with procedures outlined in this report. 9.11 Groundwater Control Groundwater was not encountered during the investigation and is anticipated to be below the depth of most construction. Should the scope of the proposed project change, Atlas should be contacted to provide more detailed groundwater control measures. Atlas No. E231180g Page | 19 Copyright © 2023 Atlas Technical Consultants Special precautions may be required for control of surface runoff and subsurface seepage. It is recommended that runoff be directed away from open excavations. Silty and clayey soils may become soft and pump if subjected to excessive traffic during time of surface runoff. Ponded water in construction areas should be drained through methods such as trenching, sloping, crowning grades, nightly smooth drum rolling, or installing a French drain system. Additionally, temporary or permanent driveway sections should be constructed if extended wet weather is forecasted. 10. GENERAL COMMENTS Based on the subsurface conditions encountered during this investigation and available information regarding the proposed structures, the site is adequate for the planned construction. When plans and specifications are complete, and if significant changes are made in the character or location of the proposed structure, consultation with Atlas must be arranged as supplementary recommendations may be required. Suitability of subgrade soils and compaction of structural fill materials must be verified by Atlas personnel prior to placement of structural elements. Additionally, monitoring and testing should be performed to verify that suitable materials are used for structural fill and that proper placement and compaction techniques are utilized. Atlas No. E231180g Page | 20 Copyright © 2023 Atlas Technical Consultants 11. REFERENCES Alt, D.D. and Hyndman, D.W., (1998). Roadside Geology of Idaho. Missoula, MT: Mountain Press Publishing Company. American Association of State Highway and Transportation Officials (AASHTO) (1993). AASHTO Guide for Design of Pavement Structures 1993. Washington D.C.: AASHTO. American Concrete Institute (ACI) (2015). Guide for Concrete Floor and Slab Construction: ACI 302.1R. Farmington Hills, MI: ACI. American Society of Civil Engineers (2021). ASCE 7 Hazards Tool: Web Interface. [Online] Available: <https://asce7hazardtool.online/> (2023). American Society of Civil Engineers (ASCE) (2017). Minimum Design Loads for Buildings and Other Structures: ASCE/SEI 7-16. Reston, VA: ASCE. American Society for Testing and Materials (ASTM) (2017). Standard Test Method for Materials Finer than 75-μm (No. 200) Sieve in Mineral Aggregates by Washing: ASTM C117. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2019). Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates: ASTM C136. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2021). Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort: ASTM D698. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2021). Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort: ASTM D1557. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2017). Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System): ASTM D2487. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2017). Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils: ASTM D4318. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2017). Standard Specification for Plastic Water Vapor Retarders Used in Contact with Soil or Granular Fill Under Concrete Slabs: ASTM E1745. West Conshohocken, PA: ASTM. Bond, J.G., (1978). Geologic Map of Idaho: Idaho Department of Lands, Bureau of Mines and Geology with Contributions from United States Geological Survey, scale 1: 500,000. Moscow, ID. Idaho Department of Water Resources. Well Construction & Drilling, Find a Well Mapping Tool. [Online] Available: <https://idwr.idaho.gov/wells/find-a-well-map/> (2023). Idaho Geological Survey. Geologic Map of Idaho: Web Interface. [Online] Available: <https://www.idahogeology.org/WebMap/?show=geology> (2023). International Building Code Council (2018). International Building Code. Country Club Hills, IL: Author. Local Highway Technical Assistance Council (LHTAC) (2020). Idaho Standards for Public Works Construction. Boise, ID: Author. U.S. Department of Labor, Occupational Safety and Health Administration (2020). CFR 29, Part 1926, Subpart P Appendix A: Safety and Health Regulations for Construction, Excavations. Washington D.C.: OSHA. Atlas No. E231180g Page | 21 Copyright © 2023 Atlas Technical Consultants APPENDIX I WARRANTY AND LIMITING CONDITIONS Atlas warrants that findings and conclusions contained herein have been formulated in accordance with generally accepted professional engineering practice in the fields of foundation engineering, soil mechanics, and engineering geology only for the site and project described in this report. These engineering methods have been developed to provide the client with information regarding apparent or potential engineering conditions relating to the site within the scope cited above and are necessarily limited to conditions observed at the time of the site visit and research. Field observations and research reported herein are considered sufficient in detail and scope to form a reasonable basis for the purposes cited above. Exclusive Use This report was prepared for exclusive use of the property owner(s), at the time of the report, and their retained design consultants (“Client”). Conclusions and recommendations presented in this report are based on the agreed-upon scope of work outlined in this report together with the Contract for Professional Services between the Client and Atlas Technical Consultants (“Consultant”). Use or misuse of this report, or reliance upon findings hereof, by parties other than the Client is at their own risk. Neither Client nor Consultant make representation of warranty to such other parties as to accuracy or completeness of this report or suitability of its use by such other parties for purposes whatsoever, known or unknown, to Client nor Consultant. Neither Client nor Consultant shall have liability to indemnify or hold harmless third parties for losses incurred by actual or purported use or misuse of this report. No other warranties are implied or expressed. Report Recommendations are Limited and Subject to Misinterpretation There is a distinct possibility that conditions may exist that could not be identified within the scope of the investigation or that were not apparent during our site investigation. Findings of this report are limited to data collected from noted explorations advanced and do not account for unidentified fill zones, unsuitable soil types or conditions, and variability in soil moisture and groundwater conditions. To avoid possible misinterpretations of findings, conclusions, and implications of this report, Atlas should be retained to explain the report contents to other design professionals as well as construction professionals. Since actual subsurface conditions on the site can only be verified by earthwork, note that construction recommendations are based on general assumptions from selective observations and selective field exploratory sampling. Upon commencement of construction, such conditions may be identified that require corrective actions, and these required corrective actions may impact the project budget. Therefore, construction recommendations in this report should be considered preliminary, and Atlas should be retained to observe actual subsurface conditions during earthwork construction activities to provide additional construction recommendations as needed. Atlas No. E231180g Page | 22 Copyright © 2023 Atlas Technical Consultants Since geotechnical reports are subject to misinterpretation, do not separate the soil logs from the report. Rather, provide a copy of, or authorize for their use, the complete report to other design professionals or contractors. Locations of exploratory sites referenced within this report should be considered approximate locations only. For more accurate locations, services of a professional land surveyor are recommended. This report is also limited to information available at the time it was prepared. In the event additional information is provided to Atlas following publication of our report, it will be forwarded to the client for evaluation in the form received. Environmental Concerns Comments in this report concerning either onsite conditions or observations, including soil appearances and odors, are provided as general information. These comments are not intended to describe, quantify, or evaluate environmental concerns or situations. Since personnel, skills, procedures, standards, and equipment differ, a geotechnical investigation report is not intended to substitute for a geoenvironmental investigation or a Phase II/III Environmental Site Assessment. If environmental services are needed, Atlas can provide, via a separate contract, those personnel who are trained to investigate and delineate soil and water contamination. © 2023 Microsoft Corporation © 2023 TomTom Vicinity Map Figure 1 MAP NOTES: LEGEND Approximate Site Location Not to Scale Site Location Phone: (208) 529-8242 Fax: (208) 529-6911 Web: oneatlas.com 1753 East Precision Drive Idaho Falls, ID 83401 Dutch Bros 855 West Main Street Rexburg, ID Modified by: EJS August 2, 2023 Drawing: E231180g N © 2023 Microsoft Corporation © 2023 Maxar ©CNES (2023) Distribution Airbus DS Site Map NOTES: LEGEND Approximate Site Boundary Approximate Atlas Test Pit Location Not to ScaleN Dutch Bros 855 West Main Street Rexburg, ID Modified by: EJS August 2, 2023 Drawing: E231180g Figure 2 Phone: (208) 529-8242 Fax: (208) 529-6911 Web: oneatlas.com 1753 East Precision Drive Idaho Falls, ID 83401 TP-1 TP-2 TP-3 TP-4 TP-5 WEST MAIN STREET/STATE HIGHWAY 33 US 20 NORTHBOUND EXIT RAMP Atlas No. E231180g Page | 25 Copyright © 2023 Atlas Technical Consultants APPENDIX IV GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-1 Date Advanced: July 24, 2023 Excavated by: Cardinal Excavation Logged by: Robert Jenson, EI Latitude: 43.825685 Longitude: -111.809410 Depth to Water Table: Not Encountered Total Depth: 11.3 feet bgs Depth (feet bgs) Field Description and USCS Soil and Sediment Classification Sample Type Sample Depth (feet bgs) Qp Lab Test ID 0.0-3.0 Sandy Lean Clay (CL): Brown to dark brown, dry to slightly moist, hard, with fine-grained sand. --Organic material to a depth of 6 inches. --Weak calcium carbonate cementation throughout. 4.5+ 3.0-11.3 Poorly Graded Gravel with Sand (GP): Light grayish-brown to gray, slightly moist to moist, medium dense to dense, with fine to coarse-grained sand, fine to coarse gravel, and 5-inch-minus cobbles. Notes: See Site Map for test pit location. Atlas No. E231180g Page | 26 Copyright © 2023 Atlas Technical Consultants GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-2 Date Advanced: July 24, 2023 Excavated by: Cardinal Excavation Logged by: Robert Jenson, EI Latitude: 43.825830 Longitude: -111.809715 Depth to Water Table: Not Encountered Total Depth: 10.5 feet bgs Depth (feet bgs) Field Description and USCS Soil and Sediment Classification Sample Type Sample Depth (feet bgs) Qp Lab Test ID 0.0-2.5 Sandy Lean Clay (CL): Brown to dark brown, dry to slightly moist, hard, with fine-grained sand. --Organic material to a depth of 6 inches. --Weak calcium carbonate cementation throughout. 4.5+ 2.5-5.0 Poorly Graded Sand with Gravel (SP): Gray to black, slightly moist medium dense to dense, with fine to coarse-grained sand and fine gravel. 5.0-10.5 Poorly Graded Gravel with Sand (GP): Light grayish-brown to gray, slightly moist to moist, medium dense to dense, with fine to coarse-grained sand, fine to coarse gravel, and 5-inch-minus cobbles. GS 5.0-6.0 A Notes: See Site Map for test pit location. Lab Test ID Moisture (%) LL PI Sieve Analysis (% Passing) 3” 1” ½” #4 #10 #40 #100 #200 A 2.3 NP NP 100 82 65 33 25 7 1 0.9 Atlas No. E231180g Page | 27 Copyright © 2023 Atlas Technical Consultants GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-3 Date Advanced: July 24, 2023 Excavated by: Cardinal Excavation Logged by: Robert Jenson, EI Latitude: 43.825648 Longitude: -116.810074 Depth to Water Table: Not Encountered Total Depth: 12.5 feet bgs Depth (feet bgs) Field Description and USCS Soil and Sediment Classification Sample Type Sample Depth (feet bgs) Qp Lab Test ID 0.0-1.9 Sandy Lean Clay (CL): Brown to dark brown, dry to slightly moist, hard, with fine-grained sand. --Organic material to a depth of 6 inches. --Weak calcium carbonate cementation throughout. GS 1.0-1.7 4.5+ B 1.9-6.3 Poorly Graded Sand with Gravel (SP): Gray to black, slightly moist, medium dense to dense, with fine to coarse-grained sand and fine to coarse gravel. 6.3-12.5 Poorly Graded Gravel with Sand (GP): Light grayish-brown to gray, slightly moist to moist, medium dense to dense, with fine to coarse-grained sand, fine to coarse gravel, and 5-inch-minus cobbles. Notes: See Site Map for test pit location. Lab Test ID Moisture (%) LL PI Sieve Analysis (% Passing) #4 #10 #40 #100 #200 B 5.3 23 8 96 95 80 64 50.2 Note: Sieve analysis slightly skewed because of the presence of calcium carbonate cementation. Atlas No. E231180g Page | 28 Copyright © 2023 Atlas Technical Consultants GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-4 Date Advanced: July 24, 2023 Excavated by: Cardinal Excavation Logged by: Robert Jenson, EI Latitude: 43.825933 Longitude: -116.810075 Depth to Water Table: Not Encountered Total Depth: 11.0 feet bgs Depth (feet bgs) Field Description and USCS Soil and Sediment Classification Sample Type Sample Depth (feet bgs) Qp Lab Test ID 0.0-2.7 Sandy Lean Clay (CL): Brown to dark brown, dry to slightly moist, hard, with fine-grained sand. --Organic material to a depth of 6 inches. --Weak calcium carbonate cementation throughout. 4.5+ 2.7-5.2 Poorly Graded Sand with Gravel (SP): Gray to black, slightly moist, medium dense, with fine to coarse-grained sand and fine to coarse gravel. 5.2-11.0 Poorly Graded Gravel with Sand (GP): Light grayish-brown to gray, slightly moist to moist, medium dense to dense, with fine to coarse-grained sand, fine to coarse gravel, and 5- inch-minus cobbles. Notes: See Site Map for test pit location. Infiltration testing conducted at a depth of 5.5 feet bgs. Atlas No. E231180g Page | 29 Copyright © 2023 Atlas Technical Consultants GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-5 Date Advanced: July 24, 2023 Excavated by: Cardinal Excavation Logged by: Robert Jenson, EI Latitude: 43.825883 Longitude: -116.809346 Depth to Water Table: Not Encountered Total Depth: 11.5 feet bgs Depth (feet bgs) Field Description and USCS Soil and Sediment Classification Sample Type Sample Depth (feet bgs) Qp Lab Test ID 0.0-3.0 Sandy Lean Clay (CL): Brown to dark brown, dry to slightly moist, hard, with fine-grained sand. --Organic material to a depth of 6 inches. --Weak calcium carbonate cementation throughout. 4.5+ 3.0-11.5 Poorly Graded Gravel with Sand (GP): Light grayish-brown to gray, slightly moist to moist, medium dense to dense, with fine to coarse-grained sand, fine to coarse gravel, and 5-inch-minus cobbles. Notes: See Site Map for test pit location. Infiltration testing conducted at a depth of 4.0 feet bgs. Atlas No. E231180g Page | 30 Copyright © 2023 Atlas Technical Consultants APPENDIX V GEOTECHNICAL GENERAL NOTES Unified Soil Classification System Major Divisions Symbol Soil Descriptions Coarse-Grained Soils < 50% passes No.200 sieve Gravel & Gravelly Soils < 50% coarse f ti GW Well-graded gravels; gravel/sand mixtures with little or no fines GP Poorly-graded gravels; gravel/sand mixtures with little or no fines GM Silty gravels; poorly-graded gravel/sand/silt mixtures GC Clayey gravels; poorly-graded gravel/sand/clay mixtures Sand & Sandy Soils > 50% coarse fraction SW Well-graded sands; gravelly sands with little or no fines SP Poorly-graded sands; gravelly sands with little or no fines SM Silty sands; poorly-graded sand/gravel/silt mixtures SC Clayey sands; poorly-graded sand/gravel/clay mixtures Fine-Grained Soils > 50% passes No.200 sieve Silts & Clays LL < 50 ML Inorganic silts; sandy, gravelly or clayey silts CL Lean clays; inorganic, gravelly, sandy, or silty, low to medium-plasticity clays OL Organic, low-plasticity clays and silts Silts & Clays LL > 50 MH Inorganic, elastic silts; sandy, gravelly or clayey elastic silts CH Fat clays; high-plasticity, inorganic clays OH Organic, medium to high-plasticity clays and silts Highly Organic Soils PT Peat, humus, hydric soils with high organic content Relative Density and Consistency Classification Moisture Content and Cementation Classification Coarse-Grained Soils SPT Blow Counts (N) Description Field Test Very Loose: < 4 Dry Absence of moisture, dry to touch Loose: 4-10 Slightly Moist Damp, but no visible moisture Medium Dense: 10-30 Moist Visible moisture Dense: 30-50 Wet Visible free water Very Dense: > 50 Saturated Soil is usually below water table Fine-Grained Soils SPT Blow Counts (N) Description Field Test Very Soft: < 2 Weak Crumbles or breaks with handling or slight finger pressure Soft: 2-4 Medium Stiff: 4-8 Moderate Crumbles or breaks with considerable finger pressure Stiff: 8-15 Very Stiff: 15-30 Strong Will not crumble or break with finger pressure Hard: > 30 Particle Size Acronym List Boulders: > 12 in. GS grab sample Cobbles: 12 to 3 in. LL Liquid Limit Gravel: 3 in. to 5 mm M moisture content Coarse-Grained Sand: 5 to 0.6 mm NP non-plastic Medium-Grained Sand: 0.6 to 0.2 mm PI Plasticity Index Fine-Grained Sand: 0.2 to 0.075 mm Qp penetrometer value, unconfined compressive strength, tsf Silts: 0.075 to 0.005 mm Clays: < 0.005 mm V vane value, ultimate shearing strength, tsf Geotechnical-Engineering Report Important Information about This Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes. While you cannot eliminate all such risks, you can manage them. The following information is provided to help. The Geoprofessional Business Association (GBA) has prepared this advisory to help you – assumedly a client representative – interpret and apply this geotechnical-engineering report as effectively as SRVVLEOH,QWKDWZD\\RXFDQEHQH¿WIURPDORZHUHGexposure to problems associated with subsurface conditions at project sites and development of them that, for decades, have been a principal cause of construction delays, cost overruns, claims, and disputes. If you have questions or want more information about any of the issues discussed herein, contact your GBA-member geotechnical engineer. Active engagement in GBA exposes geotechnical engineers to a wide array of risk-confrontation WHFKQLTXHVWKDWFDQEHRIJHQXLQHEHQH¿WIRUeveryone involved with a construction project. Understand the Geotechnical-Engineering Services Provided for this Report Geotechnical-engineering services typically include the planning, collection, interpretation, and analysis of exploratory data from widely spaced borings and/or test pits. Field data are combined with results from laboratory tests of soil and rock samples obtained from field exploration (if applicable), observations made during site reconnaissance, and historical information to form one or more models of the expected subsurface conditions beneath the site. Local geology and alterations of the site surface and subsurface by previous and proposed construction are also important considerations. Geotechnical engineers apply their engineering training, experience, and judgment to adapt the requirements of the prospective project to the subsurface model(s). Estimates are made of the subsurface conditions that will likely be exposed during construction as well as the expected performance of foundations and other structures being planned and/or affected by construction activities. The culmination of these geotechnical-engineering services is typically a geotechnical-engineering report providing the data obtained, a discussion of the subsurface model(s), the engineering and geologic engineering assessments and analyses made, and the recommendations developed to satisfy the given requirements of the project. These reports may be titled investigations, explorations, studies, assessments, or evaluations. Regardless of the title used, the geotechnical-engineering report is an engineering interpretation of the subsurface conditions within the context of the project and does not represent a close examination, systematic inquiry, or thorough investigation of all site and subsurface conditions. Geotechnical-Engineering Services are Performed IRU6SHFL¿F3XUSRVHV3HUVRQVDQG3URMHFWV DQG$W6SHFL¿F7LPHV Geotechnical engineers structure their services to meet the specific needs, goals, and risk management preferences of their clients. A geotechnical-engineering study conducted for a given civil engineer will not likely meet the needs of a civil-works constructor or even a different civil engineer. Because each geotechnical-engineering study is unique, each geotechnical-engineering report is unique, prepared solely for the client. Likewise, geotechnical-engineering services are performed for a specific project and purpose. For example, it is unlikely that a geotechnical- engineering study for a refrigerated warehouse will be the same as one prepared for a parking garage; and a few borings drilled during a preliminary study to evaluate site feasibility will not be adequate to develop geotechnical design recommendations for the project. Do not rely on this report if your geotechnical engineer prepared it: • for a different client; • for a different project or purpose; • for a different site (that may or may not include all or a portion of the original site); or • before important events occurred at the site or adjacent to it; e.g., man-made events like construction or environmental remediation, or natural events like floods, droughts, earthquakes, or groundwater fluctuations. Note, too, the reliability of a geotechnical-engineering report can be affected by the passage of time, because of factors like changed subsurface conditions; new or modified codes, standards, or regulations; or new techniques or tools. If you are the least bit uncertain about the continued reliability of this report, contact your geotechnical engineer before applying the recommendations in it. A minor amount of additional testing or analysis after the passage of time – if any is required at all – could prevent major problems. Read this Report in Full Costly problems have occurred because those relying on a geotechnical- engineering report did not read the report in its entirety. Do not rely on an executive summary. Do not read selective elements only. Read and refer to the report in full. You Need to Inform Your Geotechnical Engineer About Change Your geotechnical engineer considered unique, project-specific factors when developing the scope of study behind this report and developing the confirmation-dependent recommendations the report conveys. Typical changes that could erode the reliability of this report include those that affect: • the site’s size or shape; • the elevation, configuration, location, orientation, function or weight of the proposed structure and the desired performance criteria; • the composition of the design team; or • project ownership. As a general rule, always inform your geotechnical engineer of project or site changes – even minor ones – and request an assessment of their impact. The geotechnical engineer who prepared this report cannot accept responsibility or liability for problems that arise because the geotechnical engineer was not informed about developments the engineer otherwise would have considered. Most of the “Findings” Related in This Report Are Professional Opinions Before construction begins, geotechnical engineers explore a site’s subsurface using various sampling and testing procedures. Geotechnical engineers can observe actual subsurface conditions only at those specific locations where sampling and testing is performed. The data derived from that sampling and testing were reviewed by your geotechnical engineer, who then applied professional judgement to form opinions about subsurface conditions throughout the site. Actual sitewide-subsurface conditions may differ – maybe significantly – from those indicated in this report. Confront that risk by retaining your geotechnical engineer to serve on the design team through project completion to obtain informed guidance quickly, whenever needed. This Report’s Recommendations Are &RQ¿UPDWLRQ'HSHQGHQW The recommendations included in this report – including any options or alternatives – are confirmation-dependent. In other words, they are not final, because the geotechnical engineer who developed them relied heavily on judgement and opinion to do so. Your geotechnical engineer can finalize the recommendations only after observing actual subsurface conditions exposed during construction. If through observation your geotechnical engineer confirms that the conditions assumed to exist actually do exist, the recommendations can be relied upon, assuming no other changes have occurred. The geotechnical engineer who prepared this report cannot assume responsibility or liability for confirmation-dependent recommendations if you fail to retain that engineer to perform construction observation. This Report Could Be Misinterpreted Other design professionals’ misinterpretation of geotechnical- engineering reports has resulted in costly problems. Confront that risk by having your geotechnical engineer serve as a continuing member of the design team, to: • confer with other design-team members; • help develop specifications; • review pertinent elements of other design professionals’ plans and specifications; and • be available whenever geotechnical-engineering guidance is needed. You should also confront the risk of constructors misinterpreting this report. Do so by retaining your geotechnical engineer to participate in prebid and preconstruction conferences and to perform construction- phase observations. Give Constructors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can shift unanticipated-subsurface-conditions liability to constructors by limiting the information they provide for bid preparation. To help prevent the costly, contentious problems this practice has caused, include the complete geotechnical-engineering report, along with any attachments or appendices, with your contract documents, but be certain to note conspicuously that you’ve included the material for information purposes only. To avoid misunderstanding, you may also want to note that “informational purposes” means constructors have no right to rely on the interpretations, opinions, conclusions, or recommendations in the report. Be certain that constructors know they may learn about specific project requirements, including options selected from the report, only from the design drawings and specifications. Remind constructors that they may perform their own studies if they want to, and be sure to allow enough time to permit them to do so. Only then might you be in a position to give constructors the information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Conducting prebid and preconstruction conferences can also be valuable in this respect. Read Responsibility Provisions Closely Some client representatives, design professionals, and constructors do not realize that geotechnical engineering is far less exact than other engineering disciplines. This happens in part because soil and rock on project sites are typically heterogeneous and not manufactured materials with well-defined engineering properties like steel and concrete. That lack of understanding has nurtured unrealistic expectations that have resulted in disappointments, delays, cost overruns, claims, and disputes. To confront that risk, geotechnical engineers commonly include explanatory provisions in their reports. Sometimes labeled “limitations,” many of these provisions indicate where geotechnical engineers’ responsibilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask questions. Your geotechnical engineer should respond fully and frankly. Geoenvironmental Concerns Are Not Covered The personnel, equipment, and techniques used to perform an environmental study – e.g., a “phase-one” or “phase-two” environmental site assessment – differ significantly from those used to perform a geotechnical-engineering study. For that reason, a geotechnical-engineering report does not usually provide environmental findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated subsurface environmental problems have led to project failures. If you have not obtained your own environmental information about the project site, ask your geotechnical consultant for a recommendation on how to find environmental risk-management guidance. 2EWDLQ3URIHVVLRQDO$VVLVWDQFHWR'HDOZLWK 0RLVWXUH,Q¿OWUDWLRQDQG0ROG While your geotechnical engineer may have addressed groundwater, water infiltration, or similar issues in this report, the engineer’s services were not designed, conducted, or intended to prevent migration of moisture – including water vapor – from the soil through building slabs and walls and into the building interior, where it can cause mold growth and material-performance deficiencies. Accordingly, proper implementation of the geotechnical engineer’s recommendations will not of itself be sufficient to prevent moisture infiltration. Confront the risk of moisture infiltration by including building-envelope or mold specialists on the design team. Geotechnical engineers are not building-envelope or mold specialists. 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