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HomeMy WebLinkAboutPZ - Geotech Report NMENTAL TECHNICAL ALLWEST MATERIALS OTESTING I SPEC AL IRO PECT ON AN EMPLOYEE-OWNED COMPANY June 4, 2025 BLM Venture, LLC P.O. Box 190804 Bosie, Idaho 83719 Attention: Lynn Carrillo (lynn ccD-ethridgedevelopment.com) RE: Geotechnical Evaluation Blueberry Hills Subdivision 4315 N Ten Mile Road Meridian, Idaho ALLWEST Project No. 524-689G Lynn Carrillo, ALLWEST has completed the authorized geotechnical evaluation for the proposed Blueberry Hills Subdivision to be located at 4315 N Ten Mile Road in Meridian, Idaho. The purpose of this evaluation was to characterize the subsurface conditions at the project site and prepare the attached report with the results of the field evaluation and our geotechnical recommendations to assist with design and construction of the proposed development. We appreciate the opportunity to work with you on this project. Please contact us if you have any questions or need additional information. ZONAL Sincerely, 10ENS� ALLWEST Scott M. Fraser, P.E. fp, �T4 Engineering Services Manager o TE OF 1� 5 �� M yv. 6/4/2025 255 N. Linder Road, Meridian, ID 83642 Phone: 208.895.7898 Hayden, ID• Lewiston, ID •Meridian, ID •Missoula, MT•Spokane Valley, WA•Tri-Cities,WA www.allwesttesting.com GEOTECHNICAL EVALUATION BLUEBERRY HILLS SUBDIVISION 4315 N TEN MILE ROAD MERIDIAN, IDAHO PROJECT NO. 524-689G June 4, 2025 a � fly'` Prepared for: BLM VENTURE, LLC P.O. BOX 190804 BOSIE, IDAHO 83719 Prepared by: ALLWEST 255 N. LINDER ROAD MERIDIAN, IDAHO TABLE OF CONTENTS GEOTECHNICAL EVALUATION BLUEBERRY HILLS SUBDIVISION 4315 N TEN MILE ROAD MERIDIAN, IDAHO Page 1.0 EXECUTIVE SUMMARY................................................................................................ 1 2.0 PROJECT DOCUMENTS............................................................................................... 2 3.0 PROJECT DESCRIPTION ............................................................................................. 2 4.0 SITE CONDITIONS........................................................................................................ 2 4.1 Published Subsurface Conditions..................................................................................... 2 4.2 Subsurface Exploration Program...................................................................................... 2 4.3 Soil Characterization ........................................................................................................ 3 4.4 Groundwater Conditions................................................................................................... 3 5.0 LABORATORY TESTING............................................................................................... 3 6.0 CONCLUSIONS AND RECOMMENDATIONS............................................................... 4 6.1 Site Preparation................................................................................................................ 4 6.2 Temporary Excavation and Trenching .............................................................................. 5 6.3 Materials........................................................................................................................... 6 6.4 Fill Placement and Compaction ........................................................................................ 6 6.5 Wet Weather Construction................................................................................................ 7 6.6 Cold Weather Construction............................................................................................... 7 6.7 Stormwater and Drainage................................................................................................. 8 6.8 Infiltration Recommendations ........................................................................................... 8 6.9 Pavement......................................................................................................................... 9 7.0 ADDITIONAL RECOMMENDED SERVICES.................................................................10 8.0 EVALUATION LIMITATIONS ........................................................................................11 Appendix A—Vicinity Map, Site and Exploration Map Appendix B — Exploration Logs, Soil Classification Chart Appendix C — Laboratory Test Results GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY GEOTECHNICAL EVALUATION BLUEBERRY HILLS SUBDIVISION 4315 N TEN MILE ROAD MERIDIAN, IDAHO 1.0 EXECUTIVE SUMMARY ALLWEST has completed the authorized geotechnical evaluation for the proposed Blueberry Hills Subdivision project located at 4315 N Ten Mile Road in Meridian, Idaho. Our services were provided in accordance with our proposal dated February 10, 2025. The site is suitable for the proposed development provided the recommendations in this report are properly implemented during design and construction. Close monitoring of the construction operations discussed herein will be critical in achieving the design subgrade support and is required by the International Building Code (IBC). If we are not retained to provide required construction observation and materials testing services, we cannot be responsible for soil engineering related construction errors or omissions. The following summarizes select geotechnical information/recommendations from this evaluation: ♦ A stripping depth of approximately 3 to 12 inches is anticipated for most of the site to remove surficial vegetation and roots. Actual stripping depths should be determined based upon visual observations made during construction when soil conditions are exposed. ♦ Varying thicknesses of weak cementation were observed test pits TP-1 through TP-3 and TP-5 within the silty sand soil layers. ♦ Groundwater was observed within all test pit explorations at depths of 5.5 to 7.5 feet below existing ground surface (bgs). ♦ Infiltration rates ranged from approximately 1 to 3 in./hr. in the areas tested. These rates are based on limited field testing without application of a factor of safety. Due to variability in soil conditions, cementation, and groundwater levels, infiltration may be infeasible. If stormwater infiltration is proposed, coordination with ALLWEST and additional testing during construction are recommended to confirm soil conditions and performance. Designs should include appropriate safety factors and account for potential groundwater mounding or submersion. Further recommendations are presented in Section 6.8, Infiltration Recommendations. ♦ Sidewall instability and caving were observed in all test pits at 7.5 to 9.5 feet bgs, suggesting the presence of weak or cohesionless soils and/or potential groundwater influence at those depths. Excavation support or appropriate sloping may be necessary to ensure safe construction conditions in these areas as necessary. ♦ Undocumented fill or excessive organics was not observed during test pit exploration; however, due to existing onsite development, we anticipate that undocumented fill or areas of excessive organics may be present in portions of the site. The absence of fill or excessive organics in our test pits does not rule out their presence elsewhere on the site, particularly in areas not explored. This summary should be used in conjunction with the entire report. It should be recognized that details were not included or fully developed in this section, and the report must be read in its entirety for a comprehensive understanding of the items contained herein. GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-689G Blueberry Hills Subdivision June 4, 2025 Meridian, Idaho Page 2 2.0 PROJECT DOCUMENTS The following documents were provided to ALLWEST to help our understanding of the planned development: ♦ Conceptual Redevelopment Plan, Site Plan, by Marla Carson Architecture, Revision N dated October 18, 2024. 3.0 PROJECT DESCRIPTION Based on communication with the client and review of the project documents, we understand that development will consist of an approximate 8-acre residential subdivision with associated infrastructure, stormwater disposal facilities, and asphalt-paved roadways. The subdivision will include 23 lots for single-family residences, open space, and a pond. The pond will be excavated to generate fill material which will then be used to raise the existing site grades to achieve minimum coverage over sewer utilities. Grading plans were not provided for our review; however, we assume fills up to approximately five feet will be required to achieve final site grades. We assume that residential buildings will consist of typical one- to two-story wood-framed structures supported by continuous perimeter and pier pad foundations with concrete slab-on-grade garage floors. Structural loads were not available at the time of this report; however, based on the proposed structures and construction materials, we assume wall loads of approximately 3 kips per foot for continuous footings and column loads of 20 kips or less 4.0 SITE CONDITIONS Existing onsite development observed consisted of two single family residences and several agricultural outbuildings in the central area of the site, numerous corals and a gravel driveway bordering the northern site boundary. The site is bounded by residential development to the north and south, undeveloped farmland to the west, and Ten Mile Road to the east. The general location of the project site is shown on Figure A-1: Vicinity Map in Appendix A. 4.1 Published Subsurface Conditions The geologic conditions at the site are mapped as Gravel of Whiteny Terrace (map symbol -Qwg) on the "Geologic Map of the Boise Valley and Adjoining Area, Western Snake River Plain, Idaho", by K.L. Othberg, and L.R. Stanford, 1992. This geologic unit is described as sandy pebble and cobble gravel that is 16 to 80 feet thick and is mantled by 2 to 7 feet of loess. The USDA Natural Resources Conservation Service (NRCS) has mapped near surface soil types on the project site as Purdam silt loam. These soil units consist of silt loam, silty clay loam, stratified sand to loam, and cemented material. The Purdam silt loam is described as well drained soil formed from mixed alluvium, lacustrine deposits, and/or loess. The capacity of the most limiting layer to transmit water is very low to moderately low. 4.2 Subsurface Exploration Program ALLWEST observed the excavation of six test pits (TP-1 through TP-6) at the site on April 10, 2025, utilizing a Case 580 Super M backhoe with a 24-inch toothed excavation bucket. Test pits GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-689G Blueberry Hills Subdivision June 4, 2025 Meridian, Idaho Page 3 were advanced to depths of 7.5 to 9.5 feet bgs. Maximum depths varied due to caving conditions encountered within the test pits. The soil conditions observed in the test pits were described and classified in general accordance with ASTM D2488. Representative soil samples were obtained from the test pit side walls or excavation spoil piles for further identification and laboratory testing. The approximate locations of the test pits are shown on Figure A-2: Site and Exploration Map in Appendix A. Infiltration testing was performed within select test pits to assess the rate at which water permeates into the subsurface soil. Infiltration testing was performed using general open pit-falling head methodology. Additional testing should be conducted once stormwater disposal facility locations are determined using methodology accepted by the governing jurisdiction. 4.3 Soil Characterization Detailed descriptions of the observed soil are presented on the exploration logs in Appendix B. The descriptive soil terms used on the exploration logs, and in this report, can be referenced on the Unified Soil Classification System (USCS) included as part of the Soil Classification Chart in Appendix B. The subsurface conditions may vary between exploration locations; such changes in subsurface conditions may not be apparent until construction. General descriptions of the observed soil units follow: Topsoil: Topsoil containing abundant roots and organics was observed in all test pits and was observed to be approximately 3 to 12 inches thick. Native Soil: Native soil consisted of lean clays with varying amounts of silt and sand, silty sands, sands with gravel and silt, and gravels with sand. Gravel with sand soil units included subrounded gravel and cobble clasts up to 12 inches in maximum dimension. The estimated content of oversized material (gravel and cobbles larger than 3 inches) was approximately 10 percent by volume. Varying thicknesses of weak cementation were commonly observed within the silty sand soil layers. 4.4 Groundwater Conditions Groundwater was observed within all test pits at depths of 5.5 to 7.5 feet bgs. Groundwater in the area may be influenced by local irrigation and nearby canals, ditches, and laterals. Changes in precipitation, construction, and other factors may also impact the depth to groundwater on-site. As a result, actual groundwater conditions may be different during development. Groundwater will fluctuate throughout the year and will likely peak during snowmelt and irrigation seasons (typically March to October). Piezometers were installed within some of the test pits for future groundwater monitoring. If requested, ALLWEST can perform monthly groundwater monitoring to help establish seasonal high groundwater on-site. 5.0 LABORATORY TESTING Laboratory testing was performed on select soil samples to supplement field classifications and to assess some of the soil engineering properties. The laboratory testing completed, and the GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-689G Blueberry Hills Subdivision June 4, 2025 Meridian, Idaho Page 4 information acquired, are presented in Table 1. The laboratory test results are included in Appendix C and select results are also presented on the exploration logs in Appendix B. Table 1 - Laboratory Tests Test Performed Information Acquired Natural Water Content Water content representative of soil conditions at the time (ASTM D2216) and location samples were collected. Particle-size Distribution Size distribution of soil particles (i.e., gravel, sand, and (ASTM D6913) silt/clay) of a particular sample. Fines Content Portion of soil passing the No. 200 sieve (silt/clay). (ASTM D1140) Atterberg Limits Effects of varying water content on the consistency of fine- (ASTM D4318) grained soil present in a particular sample. California Bearing Ratio This test method is used to evaluate the strength and load- (ASTM D1883) bearing capacity of subgrade soil and/or materials for pavement design and construction. 6.0 CONCLUSIONS AND RECOMMENDATIONS Based on our understanding of the project and the subsurface conditions presented in the previous sections of this report, the site appears suitable for the proposed development provided the recommendations presented herein are properly implemented during design and construction. If the proposed construction changes or if unforeseen conditions are encountered, we must be given the opportunity to review the current information and update our recommendations. Additionally, we should be given the opportunity to review development plans and specifications to confirm the recommendations presented in this report were properly incorporated. 6.1 Site Preparation Clearing and Stripping: Topsoil containing abundant roots and organics should be removed (i.e., stripped) below proposed development areas. Based on the subsurface conditions observed in our explorations, we anticipate approximately 3 to 12 inches of stripping will be required for most of the site. Stripped materials should be disposed of off-site or only used for topsoil within non- structural landscape areas.Where trees will be removed (i.e., cleared)as part of the development, large root systems should be completely over-excavated to suitable native soil. Demolition: We anticipate existing improvements (structures, utilities, infrastructure, etc.) will be demolished and removed as part of development. Existing improvements should be completely removed and over-excavated to suitable native soil. This also includes basements, septic tanks, and wastewater drain fields. GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-689G Blueberry Hills Subdivision June 4, 2025 Meridian, Idaho Page 5 Test Pit Remediation: Test pit excavations were loosely backfilled with the excavated soil following logging. To reduce the potential for future settlement, we recommend that test pit backfill be entirely over-excavated below development areas. The approximate test pit locations are shown on Figure A-2: Site and Exploration Map in Appendix A and their depths are presented on the exploration logs in Appendix B. Over-Excavations: Depths and lateral limits of over-excavations may not fully be known until earthwork begins. Over-excavations associated with tree removal, demolition, unsuitable soil, and test pit remediation should be backfilled with adequately moisture-conditioned and compacted structural fill in accordance with the following sections of this report. Subgrade Preparation: Subgrade refers to the native soil exposed at the base of any excavation. Subgrades should be evaluated by ALLWEST to determine if they are suitable and that the actual subsurface conditions are consistent with those observed during exploration. Exposed subgrades should be evaluated by proof-rolling using vibratory rollers, fully loaded dump trucks/front-end loaders, vibratory hoe-packs, or other suitable equipment. If native subgrades are observed to significantly deflect or pump during proof-rolling, the subgrades are not suitable, and subgrade stabilization will be needed. ALLWEST should be consulted to provide recommendations to achieve a stable subgrade based on the actual conditions observed during earthwork. 6.2 Temporary Excavation and Trenching Based on the conditions observed during our explorations,we anticipate that excavation of on-site soils can generally be achieved using typical excavation equipment. However, weakly cemented soil layers were encountered in several test pits (TP-1 through TP-3 and TP-5) at depths of approximately 1 to 6.5 feet below existing ground surface. These zones required moderate digging effort using a Case 580 Super M backhoe. Contractors should be aware that smaller equipment (e.g., mini excavators) may have difficulty penetrating these cemented soils. Excavation equipment should be appropriately sized and capable of breaking through these materials, especially in areas requiring deeper cuts or over-excavation. Temporary excavation slope stability is a function of many factors, including groundwater conditions, soil type and density, excavation depth, nearby surcharge loads, and the duration that the excavation remains open. Depending on the depth of excavation and seasonal groundwater levels, dewatering may be required to facilitate utility installation. Groundwater control measures should be planned to maintain stable trench conditions and prevent water-related delays or instability during construction. It is exceedingly difficult under the variable circumstances to pre-establish a safe and "maintenance-free" temporary cut slope angle. Therefore, it is the responsibility of the contractor to maintain safe temporary slope configurations since the contractor is continuously at the job site, able to observe the nature and condition of the cut slopes, and able to monitor the subsurface materials and groundwater conditions encountered. Unsupported vertical slopes or cuts deeper than 4 feet are not recommended if worker access is necessary. The cuts should be adequately sloped, shored, or supported to prevent injury to personnel from local sloughing and spalling. The GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-689G Blueberry Hills Subdivision June 4, 2025 Meridian, Idaho Page 6 excavation should conform to applicable federal, state, and local regulations. Regarding trench wall support, the site soil is considered Type C soil according to OSHA guidelines and therefore should not exceed a 1.5HAV (horizontal to vertical) temporary slope. 6.3 Materials Stripped soil containing abundant roots and organics should be disposed of off-site or only used for topsoil within non-structural landscape areas. Structural fill should have a liquid limit less than 50 and not contain materials greater than 6 inches in maximum dimension. Based on our observations and testing, native soils appear suitable for use as general structural fill during grading. Imported materials should consist of soil that is free of organics, debris, and other deleterious material and meet the following criteria. Imported materials should be approved by ALLWEST prior to delivery to the site. Recommended criteria for imported soil and aggregate types are presented in Table 2. Table 2 - Imported Soil and Aggregate Recommendations. Type Criteria Maximum size <_ 6 inches, Retained on %-inch sieve < 30%, Structural Fill / Granular Subbase Passing No. 200 Sieve <_ 15%, and non-plastic. Alternatively, meet ISPWC section 801 (6-inch maximum) or 802 (Type 11). Maximum size <_ 1 inch, Crushed Aggregate Base Retained on %-inch sieve <010%, Passing No. 200 sieve < 10/o, and Non-plastic. Alternatively, meet ISPWC section 802 (Type 1) Maximum size <_ 3 inches; Utility Trench Backfill Retained on 3/4-inch sieve < 30%; (above pipe bedding) Passing No. 200 sieve <_ 10%; Non-plastic Or meet ISPWC section 801 (3-inch maximum) 6.4 Fill Placement and Compaction Prior to fill placement, exposed subgrades should be observed and approved by ALLWEST. Fill should be placed in loose lift thicknesses which are appropriate for the compaction equipment used. Typically, 8- to 12-inch-thick lifts are appropriate for typical rubber-tire and steel-drum compaction equipment. Lift thickness should be reduced to 4 inches for hand operated compaction equipment. Fill should be moisture conditioned to within 2 percentage points of the optimum moisture content prior to placement to facilitate compaction. Fill should be compacted to the minimum relative compaction of the maximum dry density, as determined by ASTM D1557 (modified Proctor), provided in Table 3. GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-689G Blueberry Hills Subdivision June 4, 2025 Meridian, Idaho Page 7 Table 3 - Compaction Requirements Minimum Relative Type Compaction Structural Fill 95 Granular Subbase 95 Crushed Aggregate Base 95 Utility Trench Backfill 92 For roadway and utility construction, local governing agencies may supersede the criteria presented herein, and may provide their own minimum compaction requirements and methods of determining maximum density. This also includes preparation and approval requirements for exposed subgrades. For materials that are too granular to density test (generally greater than 30 percent retained on a %-inch sieve), an appropriate method-based compaction specification should be used in accordance with local governing jurisdictions or as outlined in Section 202.3.8.C.3 of the Idaho Standards for Public Works Construction (ISPWC). Fine-grained soil (silts and clays) may be difficult to moisture-condition and compact in utility trenches. Therefore, we recommend backfilling trench excavations with soil that meet the criteria presented in Table 2. 6.5 Wet Weather Construction Due to wet weather conditions in this climatic region during late fall, winter, and early spring, we recommend construction (especially site grading)take place during the late spring, summer, and early fall seasons, if possible. If construction occurs during or immediately after excessive precipitation or snowmelt, it may be necessary to over-excavate and replace wet subgrade soil which might otherwise be suitable. If construction is undertaken in wet periods of the year, it will be important to slope the ground surface to provide drainage away from construction. In addition, wet soil tends to have notable adhesion and may be easily transported off-site by construction traffic. Dewatering should be anticipated for excavations exceeding 6 feet in depth, particularly in areas where shallow groundwater was observed. Appropriate groundwater control measures, such as sump pumps or well points, may be necessary to maintain dry and stable excavation conditions and to ensure safe and efficient utility installation. 6.6 Cold Weather Construction If site grading and construction are anticipated during cold weather, we recommend good winter construction practices be observed. Snow and ice should be removed from all fill placement surfaces prior to additional earthwork or construction. Improvements should not be placed on frozen ground, nor should the supporting soil be permitted to freeze during or after construction. Frozen soil should not be used as fill. GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-689G Blueberry Hills Subdivision June 4, 2025 Meridian, Idaho Page 8 Construction subgrades left exposed to freezing temperatures overnight can be protected with a temporary lift of loose soil or covered with heated construction blankets, so subgrades do not freeze. Frozen cover soil should be removed prior to any fill placement or construction. 6.7 Stormwater and Drainage Ground surfaces should be sloped a minimum of 5% within 10 feet of foundations to direct water runoff away from structural foundations and pavement areas. In cases where the recommended grade cannot be achieved due to site constraints, drains should be installed to effectively divert water away from foundations. Impervious surfaces, like concrete or pavers, should slope a minimum of 2% within 10 feet of foundations. Water should not be allowed to infiltrate or pond adjacent to foundations and pavement areas. 6.8 Infiltration Recommendations Surface water runoff is anticipated to be directed to stormwater disposal facilities (detention basins, seepage beds, etc.) for the overall development. Final locations of planned stormwater disposal facilities were not known at the time of this report. The infiltration recommendations provided below are for specific soil types and subsurface conditions observed during our exploration. During exploration, we performed infiltration testing in test pits TP-2, TP-5, and TP-6 within silty sand and silty gravel with sand soil. Varying thicknesses of weak cementation were observed test pits TP-1 through TP-3 and TP-5 within the silty sand soil layers at depths of 1 to 6.5 feet bgs. We do not recommend stormwater disposal be accomplished within cemented soil, as they typically exhibit very poor and inconsistent infiltration. Refer to the test pit logs in Appendix B to verify depths and contacts of soil which is not suitable for stormwater disposal. Stormwater disposal should occur within the native non-cemented silty gravel with sand (GM) soils. Based on infiltration test results and our experience with similar soil types, the design infiltration rates provided in Table 4 may be utilized for on-site stormwater disposal design. Reported infiltration rates reflect raw field measurements and do not include any factor of safety. Appropriate factors of safety should be applied in accordance with applicable codes, regulatory guidance, and project-specific design criteria. Due to variability in soil conditions, localized cementation, and potential groundwater fluctuations, infiltration may not be suitable in all areas. If infiltration is proposed, careful coordination with ALLWEST should be conducted throughout project design and construction. Additional infiltration testing and subgrade observations should be performed once stormwater disposal facility locations are determined and during construction to verify soil conditions are consistent with tested locations and that adequate separation from groundwater is maintained. Design modifications or increased system capacity may be required if groundwater mounding, submersion, or other performance concerns arise. All designs should incorporate appropriate safety factors consistent with applicable codes and project-specific criteria. Refer to the test pit logs in Appendix B for approximate depths and boundaries of these unsuitable materials. GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-689G Blueberry Hills Subdivision June 4, 2025 Meridian, Idaho Page 9 Table 4 - Infiltration Rates Soil Type Field-Measured Infiltration Rate in/hr Silty GRAVEL with Sand, GM 3 Stormwater disposal facilities should be constructed a minimum of 1 foot into the recommended receiving soil. Filter fabric should be properly utilized to separate native soil from stormwater disposal facility drain rock and filter sand materials to help reduce the migration of fine soil into drain rock and filter sand void space. The proper separation from bottom of stormwater disposal facilities and seasonal high groundwater should be maintained in accordance with the governing jurisdiction. ALLWEST recommends groundwater monitoring be performed throughout seasonal snowmelt and irrigation seasons (typically March to October) to help establish a seasonal high groundwater elevation at the site. Upon authorization, ALLWEST can perform monthly groundwater monitoring for the site in accordance with ALLWEST's Proposal for Geotechnical Evaluation dated February 10, 2025. During exploration, groundwater was observed within '/2 to 4 feet of the silty gravel with sand soil layers where infiltration is feasible. Seasonal high groundwater levels may be shallower than the observed silty gravel with sand layers, which may prevent infiltration into the underlying soil. Instead, lateral flow may occur within the overlying silty sand soil, which may be cemented or exhibit very poor infiltration characteristics. Therefore, alternate methods of stormwater management, such as evaporation ponds and/or swales, may be needed. 6.9 Pavement Based on our exploration and understanding of the proposed development, we anticipate that pavement subgrade areas will consist of lean clays with sand, sandy lean clays, sandy silty clays, and/or silty sands. We performed CBR testing on a sandy silty clay soil sample and obtained a value of 17.3 percent. Prior to pavement section construction, subgrades should be proof-rolled as recommended in Section 6.1, Site Preparation or prepared as required by local jurisdictions. Anticipated traffic conditions were not provided for our pavement design. The parameters used in our pavement section design were estimated based on our experience with similar projects. If actual traffic conditions vary from those stated in Table 5, we should be notified so we may redesign the recommended pavement sections. GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-689G Blueberry Hills Subdivision June 4, 2025 Meridian, Idaho Page 10 Table 5 - Pavement Design Parameters Design Parameter Value California Bearing Ratio (CBR) 17.3% Equivalent Single- Local Roadways 33,0001 Axle Loads (ESALs) Collector Roadways 370'0002 Pavement Reliability 90% Pavement Design Life 20- ear Initial Serviceability 4.2 Terminal Serviceability 2.5 'Approximately equivalent to a Traffic Index of 6. 'Approximately equivalent to a Traffic Index of 8. The following sections were designed utilizing ITD gravel equivalent methodology and, our experience with local jurisdictions. Recommended flexible pavement sections are presented in Table 6. Table 6 - Recommended Pavement Sections Flexible Pavement Crushed Base Pavement Area Asphalt in. Course in. Subbase in. Local Roads 2.5 4 9 Collector Roads 3 6 10 Pavements should be sloped to provide suitable 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 crushed base course/subbase subsections. The pavement sections provided in this report represent minimum recommended thicknesses. Preventive maintenance (crack/joint sealing, patching, overlay, etc.) should be planned as part of an on-going pavement management program. Preventive maintenance is intended to slow the rate of pavement deterioration and preserve the integrity of the pavement. 7.0 ADDITIONAL RECOMMENDED SERVICES ALLWEST should review final development plans and specifications to confirm the recommendations presented in this report were properly incorporated. Close monitoring of the construction operations discussed herein will be critical in achieving the design subgrade support and is required by the International Building Code. We recommend ALLWEST be retained to GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-689G Blueberry Hills Subdivision June 4, 2025 Meridian, Idaho Page 11 provide observation and testing services throughout construction. We recommend the following testing and observations be provided by ALLWEST: ♦ Observe site stripping, test pit remediation, and any other soil over-excavations and backfills. ♦ Observe subgrade proof-rolling and approve subgrades prior to fill/materials placement or roadway section/utility construction. ♦ Observe stormwater disposal facility subgrade soil and overall stormwater disposal facility construction. ♦ Conduct compaction testing of any fill soil placed for general site grading, utility backfills, and pavements. ♦ Observe placement of/test asphalt for compaction, oil content, and gradation. If we are not retained to provide the recommended construction observation and materials testing services, we cannot be responsible for errors and omissions related to geotechnical aspects of the project's construction. 8.0 EVALUATION LIMITATIONS This report has been prepared to assist the design and construction for the proposed Blueberry Hills Subdivision project located at 4315 N Ten Mile Road in Meridian, Idaho. Reliance by any other party is prohibited without the written authorization of ALLWEST. Our services consist of professional opinions and conclusions made in accordance with generally accepted geotechnical engineering principles and practices in the local area at the time this report was prepared. This acknowledgement is in lieu of all warranties, express or implied. GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-689G Blueberry Hills Subdivision Meridian, Idaho Appendix A Vicinity Map Site and Exploration Map ALLWEST -ITfm=n'A\. i�iY Ism �{ PIS 2 x i 4 Na P rr>r`- �.. I. Ci 3t.�ii �eAC Base Map:Google Earth Imagery Date 10/03/2024 - 10 � s✓, +�'.�I P�I�r.�' �� """ dt�A ,,s R 1 Q `ILI r _ I t. A 1. GA —F NEAR I It 26 t Writ KAN a illu Pu 1 Igor �� L . W McMillan Rd big, I mr I, . ` �•qvl �PJ1, V��,����., .i rhu �2N �.r^4y y� I 1 7-1 rAAri 111 2s - x Pn WAS ME _ id 701 I ,L,-q�,�•. � � �I t "'P>�a'r �I \ Tls'7 L 6�1 G9+iv SJ k� _ E ..�I";. ..,c, .t � ''�- r \ f!f✓t' .;�_ x��—t - � li �_:`«`I -El-� �g��.+'rtl `-� rcpm.�t��y ,' G�i ^2,6�t'`� 6"". ���\ c�eA. 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FIGURE A-1:VICINITY MAP GEOTECHNICAL EVALUATION ALLWESTBLUEBERRY HILLS SUBDIVISION MERIDIAN, IDAHO 255 N.LINDER ROAD CLIENT: BLM VENTURE,LLC MERIDIAN,IDAHO 83642 PHONE:(208)895-7898 FAX:(208)898-3959 PROJECT NO.:524-689G DATE:JUNE 2025 Base Map:Conceptual Redevelopment Plan,Site Plan,by Marla Carson Architect,Revision N dated October 18,2024. �' ; .o>�►` - i37 —� VJ c;rand llahi-1 ( -_J gn 3 :A 7j1 -R \ 1 I j O Eik Bucife Ln Boundary °a 4 Q TP-1 w 3 / _ TP-2 TP 3 — G;•I C ■ . ii 76 t r .. k TP-4 , , F7o * o I 0 0 0 0 0 0 0 0 0 0 mxlae i m%,oe m'x,�' - 84'X1CB' 80'%1pe 80'%108' SVxi08' 80'%I21' 80 x.>0 ' - ' v LEGEND � . 0 Approximate location of test pit observed by ALLWEST. * Slotted PVC pipe was installed in test pit. FIGURE A-2:EXPLORATION LOCATION MAP N ALLWEST GEOTECHNICAL EVALUATION BLUEBERRY HILLS SUBDIVISION 0 150' 300' MERIDIAN, IDAHO 255 N.LINDER ROAD CLIENT:BLM VENTURE,LLC MERIDIAN,IDAHO 83642 PHONE:(208)895-7898 FAX:(208)898-3959 PROJECT NO.:524-689G DATE:JUNE 2025 Geotechnical Evaluation ALLWEST Project No. 524-689G Blueberry Hills Subdivision Meridian, Idaho Appendix B Exploration Logs Soil Classification Chart ALLWEST Blueberry Hills Subdivision TP-1 ALL1lET Meridian, Idaho Pagel of 1 Project No.: 524-689G Date: 04/10/2025 Groundwater Observations: Water encountered @ 6' Contractor: Just Dig It Hole Depth: 9.0' Equipment: Case 580 Super M V. Datum: - Operator: Steve Just Elevation: N/A Logged By: Parker Norris Coordinates: 43.6437244433983,-116.438203163363 Samples Lab 0 n Soil Description and Remarks Q �� m CU U) ii 2 n o 0 m � J Topsoil,abundant roots and organics;3 inches thick 0.3 Lean CLAY with sand(CL),medium stiff, moist, brown 1 2 2.0 Silty SAND(SM), medium dense,moist to wet, orange brown 3- 4- Weak cementation observed throughout soil layer. 5 6 6.5 Poorly graded SAND with silt and gravel(SP-SM), medium dense,wet,light brown Subrounded gravel up to 3 inches in maximum dimension observed. Bulk as 51 5 8 9 9.0 Test pit terminated due to caving.Slotted pipe installed. Notes: See Figure A-2 for approximate test pit location. Page 1 of 1 Blueberry Hills Subdivision TP-2 ALL1lET Meridian, Idaho Pagel of 1 Project No.: 524-689G Date: 04/10/2025 Groundwater Observations: Water encountered @ 6.5' Contractor: Just Dig It Hole Depth: 8.0' Equipment: Case 580 Super M V. Datum: - Operator: Steve Just Elevation: N/A Logged By: Parker Norris Coordinates: 43.6436006062546,-116.437009862142 Samples Lab 0 o o J Q N d E- Soil Description and Remarks fl Q E o m @ m U CD cn ii C0 E � 8-10 0 com J N O Topsoil,abundant roots and organics;3 inches thick 0.3 Lean CLAY with sand(CL),medium stiff, moist, brown 1 1.5 Silty SAND(SM), medium dense,moist,orange Grab zs 13 2 brown 3 Weak cementation observed throughout soil layer 4 5 5.0 Silty GRAVEL with sand(GM),medium dense,moist to wet,light brown Subrounded gravel and cobbles up to 5 inches in 6 maximum dimension observed. Field infiltration test performed at 5.5 feet;rate= 1 0 in/hr. 7 8 8.0 Test pit terminated due to caving.Slotted pipe installed. Notes: See Figure A-2 for approximate test pit location. Page 1 of 1 Blueberry Hills Subdivision TP-3 ALL1lET Meridian, Idaho Pagel of 1 Project No.: 524-689G Date: 04/10/2025 Groundwater Observations: Water encountered @ 6.5' Contractor: Just Dig It Hole Depth: 7.5' Equipment: Case 580 Super M V. Datum: - Operator: Steve Just Elevation: N/A Logged By: Parker Norris Coordinates: 43.6436331584565,-116.433969651494 Samples Lab 0 _ o 0 J Q E- Soil Description and RemarksCL Q �� 2 n CO (n LL U E o 0CID 0 TOPSOIL,abundant tree roots and organics; 12 inches thick 1 1.0 Silty SAND(SM), medium dense,moist,brown 2- 3- Weak cementation observed throughout soil layer. 4 5 5.5 Silty GRAVEL with sand(GM),medium dense,moist 6 to wet,brown Subrounded gravel and cobbles up to 6 inches in 0 maximum dimension observed. 7 7.5 Test pit terminated due to caving.Slotted pipe installed. Notes: See Figure A-2 for approximate test pit location. Page 1 of 1 Blueberry Hills Subdivision TP-4 ALL1lET Meridian, Idaho Pagel of 1 Project No.: 524-689G Date: 04/10/2025 Groundwater Observations: Water encountered @ 5.5' Contractor: Just Dig It Hole Depth: 8.5' Equipment: Case 580 Super M V. Datum: - Operator: Steve Just Elevation: N/A Logged By: Parker Norris Coordinates: 43.6434202196622,-116.434631199015 Samples Lab 0 p p _ a E^ � Soil Description and Remarks �T o > � fl Q E o m c �J C7 07 ii 0 � v o 0 0 -2 J (0 N 7 2 -J N Q O Topsoil,abundant roots and organics;3 inches thick 0.3 Sandy silty CLAY(CL-ML),medium stiff,moist,brown 1 Bulk 64 26-20-6 2 2.0 Silty SAND(SM), medium dense,moist to wet,brown 3 Grab 30 34 4 5 0 6 6.5 Silty GRAVEL with sand(GM),medium dense,moist to wet,light brown Subrounded gravel and cobbles up to 6 inches in maximum dimension observed. 8 8.5 Test pit terminated due to caving. Notes: See Figure A-2 for approximate test pit location. Page 1 of 1 Blueberry Hills Subdivision TP-5 ALL1lET Meridian, Idaho Pagel of 1 Project No.: 524-689G Date: 04/10/2025 Groundwater Observations: Water encountered @ 6' Contractor: Just Dig It Hole Depth: 7.5' Equipment: Case 580 Super M V. Datum: - Operator: Steve Just Elevation: N/A Logged By: Parker Norris Coordinates: 43.6430254937658,-116.43587145874 Samples Lab 0 o o J Q N d E- Soil Description and Remarks fl Q E o m @ m U CD cn ii C� E � 8-10 0 com J N O Topsoil,abundant roots and organics;3 inches thick 0.3 Lean CLAY with sand(CL),medium stiff, moist, brown 1 1.5 Silty SAND(SM), medium dense,moist,orange 2 brown 3 Weak cementation observed throughout soil layer. 4 Grab 22 1s Field infiltration test performed at 4.5 feet;rate= 1 5 in/hr. 5.5 Silty GRAVEL with sand(GM),medium dense,moist to 0 6 wet,light brown Subrounded gravel and cobbles up to 12 inches in maximum dimension observed. 7 7.5 Test pit terminated due to caving.Slotted pipe installed. Notes: See Figure A-2 for approximate test pit location. Page 1 of 1 Blueberry Hills Subdivision TP-6 ALL1lET Meridian, Idaho Pagel of 1 Project No.: 524-689G Date: 04/10/2025 Groundwater Observations: Water encountered @ 7.5' Contractor: Just Dig It Hole Depth: 9.5' Equipment: Case 580 Super M V. Datum: - Operator: Steve Just Elevation: N/A Logged By: Parker Norris Coordinates: 43.6431166888429, -116.43768153225 Samples Lab 0 p p _ a E^ � Soil Description and Remarks �T o > � fl Q E o m c �J C7 cn ii 0 � v o 0 0 -2 J (0 N 7 2 -J N Q O Topsoil,abundant roots and organics;3 inches thick 0.3 Sandy lean CLAY(CL),medium stiff,moist,light brown Grab 19 69 38-20-18 1 2 3 3.0 Silty GRAVEL with sand(GM),medium dense,moist to wet,light brown •i Subrounded gravel and cobbles up to 5 inches in • Grab 7 11 4 maximum dimension observed. Field infiltration test performed at 4 feet;rate=3 in/hr. 5 • •b 6 •� �. . 7 • V 8 •i �. 9 • 9.5 • Test pit terminated due to caving.Slotted pipe installed. Notes: See Figure A-2 for approximate test pit location. Page 1 of 1 SOIL CLASSIFICATION CHART (ASTM D2487 & D2488) MAJOR GROUP TYPICAL SOIL NAMES TYPICAL SOIL DESCRIPTORS DIVISIONS SYMBOL GW Well-graded gravel,gravel-sand mixtures,little or no fines. Description SPT Blow Counts O Very loose less than 4 Loose 4 to 10 w GP Poorly-graded gravel,gravel-sand mixtures,little or no fines. Medium dense 11 to 29 C3� > O Dense 30 to 50 Very dense greater than 50 0 o O GM Silty gravel,gravel-sand-silt mixtures. o Material Sieve Sizes CC14 Boulders greater than 12" w r GC Clayey gravel,gravel-sand-silt-clay mixtures. Cobbles 3"to<12" z � Q o Coarse gravel 3/4"to<3" Fine gravel #4 to<3/4" SW Well-graded sand,gravelly sand,little or no fines. Coarse sand <#4 to#10 Medium sand <#10 to#40 Q w Fine sand <#40 to#200 oo SP Poorly-graded sand,gravelly sand, little or no fines. Silt or clay less than#200 n ¢ Sieve Number Aperture SM Silty sand,sand-silt mixtures. #4 4.76 mm(0.187 in) #10 2.00 mm(0.0787 in) #40 0.42 mm(0.0165 in) SC Clayey sand,sand-clay mixtures. #200 0.074 mm(0.00291 in) ML Inorganic silt,non-plastic to low plasticity,gravelly silt, Description SPT Blow Counts Q LO sandy silt,clayey silt. v Very soft less than 2 U '= Soft 2 to 3 o E Inorganic clay of low to medium plasticity,gravelly clay, v� o z i CL sandy clay,silty clay(CL-ML),lean clay. Medium stiff 4 to 8 J N Q -0 Stiff 9 to 15 r J J Very stiff 16 to 29 o - r OL Organic silt and organic silty clay of low plasticity. Hard 30 to 50 Lu z =; r Very Hard greater than 50 0 L MH Inorganic silt,micaceous or diatomaceous fine sandy or Plasticity Soil Characteristics C7 Q silty soils,elastic silt. uw °�' A Non-plastic Cannot be rolled at any water content. Qo : Low A thread can barely be rolled while moist. z 1D CH Inorganic clay of high plasticity,fat clay. Medium A thread can be rolled easily but cannot be o rerolled after reaching the plastic limit. J a High A thread can be rolled and re-rolled several F OH:-:: Organic clay of medium to high plasticity. times after reaching the plastic limit. Definitions ORGANIC SOILS W PTy Peat and other highly organic soils. Liquid Limit(LL) Moisture content at which soil changes state from plastic to liquid. Plastic Limit(PL) Moisture content at which soil Dry Absence of moisture in sample. Dusty,dry to the touch. changes state from semi-solid to plastic. Plasticity Index(PI) Range of moisture contents at which Slightly Moisture in sample is below the optimum moisture content. a soil behaves plastically(LL-PL-PI). Moist Grains adhere slightly though surface tension. MOISTURE Moist Moisture in sample is at or near optimum moisture content. PLASTICITY CHART (ASTM D4318) No free water is visible. Moisture in sample is above the optimum moisture content. a 50 Wet Free water is visible in sample. w 0 o G� Weak Crumbles or breaks with handling or slight finger pressure. � CL-ML i CL MH or OH CEMENTATION Moderate Crumbles or breaks with considerable finger pressure. a a ML 0 0 16 50 Strong Will not crumble or break with finger pressure. LIQUID LIMIT(LL) ALLWEST Geotechnical Evaluation ALLWEST Project No. 524-689G Blueberry Hills Subdivision Meridian, Idaho Appendix C Laboratory Test Results ALLWEST Table C-1: Summary of Laboratory Test Results Moisture Gradation Atterberg Limits Test Pit Depth Liquid Plastic Plasticity CBR Sample Classification Content Gravel Sand Silt/Clay ° (Feet) M) ° ° ° Limit Limit Index (�°) (USCS ) TP-1 7-8 44 51 5 Poorly graded sand with silt and gravel (SP-SM) TP-2 1.5-2 28 13 Silty SAND SM TP-4 0.5-1.5 64 26 20 6 17.3 Sandy silty CLAY(CL-ML) TP-4 3-3.5 30 34 Silty SAND SM TP-5 4-4.5 22 18 Silty SAND (SM) TP-6 0.5-1 19 69 38 20 18 Sandy lean CLAY CL TP-6 3.5-4 7 1 11 1 1 Poorly graded gravel with silt and sand (GP-GM) 255 N. Linder Road • Meridian, Idaho 83642 •(208)895-7895• Fax(208)898-3959 www.allwesttesting.com This report may not be reproduced, except in full,without the permission of ALLWEST.