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Home My WebLink AboutPZ - Geotech Report TECHNICAL ALLWEST MATERIALS OTESTING I SPECIAL IINOSPECT ON AN EMPLOYEE-OWNED COMPANY September 3, 2024 Trilogy Development 9839 West Cable Car Street, Suite 101 Boise, Idaho 83709 Attention: Shawn Brownlee (shawn(a)-trilogyidaho.com) RE: Geotechnical Evaluation Morgan Grove Lane Development 3050 N Morgan Grove Lane Meridian, Idaho ALLWEST Project No. 524-391 G Shawn Brownlee, ALLWEST has completed the authorized geotechnical evaluation for the proposed Morgan Grove Lane Development located at 3050 N Morgan Grove Lane 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 provide services with you on this project. Please contact us if you have any questions or need additional information. Sincerely, �1E 09/03/202U ALLWEST oQ�pFESSIpNq` cENSp�� tv��C' 9/3/2g Cho 4 KEVIN AN DREW o F c� DYEKMAN N0. 1727 15> rE 0F \oP,�o �RQBER� Kevin Dyekman, P.G. Samuel P. Sommers, P.E. Senior Engineering Geologist Senior Geotechnical Engineer 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 MORGAN GROVE LANE DEVELOPMENT 3050 N MORGAN GROVE LANE MERIDIAN, IDAHO PROJECT NO. 524-391G September 3, 2024 Prepared for: TRILOGY DEVELOPMENT 9839 WEST CABLE CAR STREET, SUITE 101 BOISE, IDAHO 83709 Prepared by: ALLWEST 255 N. LINDER ROAD MERIDIAN, IDAHO TABLE OF CONTENTS GEOTECHNICAL EVALUATION MORGAN GROVE LANE DEVELOPMENT 3050 N MORGAN GROVE LANE 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..............................................................................................................................5 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..........................................................................................10 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 MORGAN GROVE LANE DEVELOPMENT 3050 N MORGAN GROVE LANE MERIDIAN, IDAHO 1.0 EXECUTIVE SUMMARY ALLWEST has completed the authorized geotechnical evaluation for the proposed Morgan Grove Lane Development project located at 3050 N Morgan Grove Lane in Meridian, Idaho. Our services were provided in accordance with our proposal no. 524-391 G dated June 14, 2024. 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: ♦ The observed natural soil consisted of silty clay with sand, silt with sand, silty sand, and poorly graded gravel with sand. Poorly graded gravel with sand soil units included subrounded gravel and cobble clasts up to 6 inches in maximum dimension. ♦ Weak to moderate cementation was observed within the silty sand soil layers in test pits TP-5 and TP-7. ♦ At the time of exploration, we observed groundwater within each test pit at depths of 7 to 11 feet below existing ground surface. ♦ We anticipate approximately 2 to 4 inches of site stripping will be required for most of the site to remove topsoil. ♦ We recommend stormwater disposal occur within non-cemented silty sand and poorly graded gravel with sand soil, as observed during our field exploration. Allowable seepage rates for stormwater disposal are 1.5 inches per hour (in./hr.) into on-site silty sand and 8 in./hr. into on-site poorly graded gravel with sand. ♦ For local roadways we recommend pavement sections of 2.5-inches of asphalt concrete, over 4-inches of crushed aggregate base, over 9-inches of aggregate subbase. ♦ For collector roadways we recommend pavement sections of 3-inches of asphalt concrete, over 6-inches of crushed aggregate base, over 12-inches of aggregate subbase. 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. 524-391 G Morgan Grove Lane Development September 3, 2024 Meridian, Idaho Page 2 2.0 PROJECT DOCUMENTS The following documents were provided to ALLWEST to help our understanding of the planned development: ♦ LandproDATA Parcel Map, Morgan Map, dated June 5, 2024. 3.0 PROJECT DESCRIPTION Based on communication with you and our review of the project documents, we understand the 11.44-acre site will be developed as a residential subdivision with associated infrastructure, stormwater disposal facilities, and asphalt-paved roadways. We did not review grading plans, as they were not available at the time of this evaluation, but we anticipate cuts and fills for general site grading to be 3 feet or less. 4.0 SITE CONDITIONS At the time of exploration, the site was primarily comprised of pastureland with the northern portion of the property occupied by Hawkeye Landscape company. The site is bordered by farmland to the south and east, N Morgan Grove Lane to the west, and Ustick Road to the north. 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 Whitney 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 approximately 16 to 80 feet thick and is mantled by approximately 3 to 7 feet of loess. The USDA Natural Resources Conservation Service (NRCS) has mapped the near surface soil types on the project site as the Power silt loam and Purdam silt loam. These soil units consist of silty clay loam, silt loam, very fine sandy loam, stratified sand to loam, paragravelly silt loam, and cemented material. The Power silt loam is described as well drained soil formed from mixed alluvium and/or loess. The capacity of the most limiting layer to transmit water is moderately high. The Purdam silt loam is described as well drained soil formed form 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 We observed the excavation of 10 test pits (TP-1 through TP-10) at the site on June 26, 2024, utilizing a Case 580c backhoe with a 24-inch toothed excavation bucket. Test pits were advanced to maximum depths of 9 to 12'/z feet below the existing ground surface. Maximum depths varied due to caving conditions encountered within some of the test pits. The soil conditions observed in the test pits were described and classified in general accordance with ASTM D2488. We obtained representative soil samples from the test pit side walls or excavation spoil piles for further GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-391 G Morgan Grove Lane Development September 3, 2024 Meridian, Idaho Page 3 identification and laboratory testing. The approximate locations of the test pits are shown on Figure A-2: Site and Exploration Map in Appendix A. Field 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 infiltration testing should be performed once stormwater disposal facility locations are determined. 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 each test pit.The topsoil layer was observed to be approximately 2 to 4 inches thick. Natural Soil: The observed natural soil consisted of silty clay with sand, silt with sand, silty sand, and poorly graded gravel with sand. Weak to moderate cementation was observed within the silty sand soil layers in test pits TP-5 and TP-7. Poorly graded gravel with sand soil units included subrounded gravel and cobble clasts up to 6 inches in maximum dimension. 4.4 Groundwater Conditions We observed groundwater within each test pit at depths of 7 to 11 feet below existing ground surface. Groundwater in the area may be influenced by local irrigation and on-site or 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). We installed slotted pipes within each test pit for groundwater monitoring. ALLWEST is currently performing monthly groundwater monitoring to help establish seasonal high groundwater on-site. 5.0 LABORATORY TESTING We performed laboratory testing to supplement field classifications and to assess some of the soil engineering properties. The laboratory testing completed, and the information acquired, are presented in Table 1. The laboratory test results are included in Appendix C and some results are also presented on the exploration logs in Appendix B. GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-391 G Morgan Grove Lane Development September 3, 2024 Meridian, Idaho Page 4 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. 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 is 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 new 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 2 to 4 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 natural soil. We anticipate approximately 3 to 4 feet of over-excavation will be required to remove large tree root systems. 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 natural soil. This also includes basements, septic tanks, and wastewater drain fields. 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 GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-391 G Morgan Grove Lane Development September 3, 2024 Meridian, Idaho Page 5 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 demolition and test pit remediation should be backfilled with suitably moisture-conditioned and compacted site grading fill in accordance with the following sections of this report. Subgrade Preparation: Subgrade refers to the natural soil exposed at the base of any excavation. Subgrades should be evaluated by the geotechnical engineer of record, or staff under their supervision, to determine that 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, loaded dump trucks/front-end loaders, vibratory hoe-packs, or other suitable equipment. If natural 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 for subgrade stabilization based on the actual conditions observed during earthwork. 6.2 Temporary Excavation and Trenching Based on the conditions observed within our explorations, we anticipate excavation of the on-site soil can be achieved with typical excavation equipment. Temporary excavation slope stability is a function of many factors, including: ♦ The presence and abundance of groundwater. ♦ The type and density of the various soil strata. ♦ The depth of cut. ♦ Surcharge loadings adjacent to the excavation. ♦ The length of time the excavation remains open. 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 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 1.5H:1V (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. Based on our observations and laboratory GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-391 G Morgan Grove Lane Development September 3, 2024 Meridian, Idaho Page 6 testing, the on-site soil is suitable for use as site grading fill during earthwork. Site grading fill should have a liquid limit less than 50 and not contain materials greater than 6 inches in maximum dimension. Imported materials should consist of granular soil that is free of organics, debris, and other deleterious material and meet the following criteria. Imported materials should be approved by the geotechnical engineer 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, Granular Structural Fill / Retained on %-inch sieve < 30%, 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 3/4-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 %-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 the geotechnical engineer of record, or their representative. Fill should be placed in 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% 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. 524-391 G Morgan Grove Lane Development September 3, 2024 Meridian, Idaho Page 7 Table 3 - Compaction Requirements Minimum Relative Type Compaction Site Grading Fill 95 Granular Structural Fill / 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 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. 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. 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. GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-391 G Morgan Grove Lane Development September 3, 2024 Meridian, Idaho Page 8 6.7 Stormwater and Drainage We recommend ground surfaces be sloped to direct water runoff away from structural foundations and pavement areas. We recommend the ground surface be sloped a minimum of 5% within 10 feet of foundations. 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. Ultimately, water should not be allowed to infiltrate or pond adjacent to foundations and pavement areas. 6.8 Infiltration Recommendations We anticipate surface water runoff will be directed to stormwater disposal facilities (detention basins, seepage beds, etc.) for the overall development. 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-4, -6, -7, and -8 within on-site silty sand and poorly graded gravel with sand soil units. We recommend stormwater disposal occur within non-cemented silty sand and poorly graded gravel with sand soil, as observed during our field exploration. 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. Table 4 - Infiltration Rates Field-Measured Infiltration Rate Design Infiltration Soil Type in./hr. Rate in./hr. Silty sand 3 to 4 1.5 Poorly graded gravel with >15 8 sand Additional infiltration testing may be needed once stormwater disposal facility locations are determined and should be performed using methodology accepted by the governing jurisdiction. Stormwater disposal facilities should be constructed a minimum of 1 foot into the recommended receiving soil. Filter fabric should be properly utilized to separate natural 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. Groundwater monitoring should be performed throughout seasonal snowmelt and irrigation seasons (typically March to October) to help establish a seasonal high groundwater elevation at the site. ALLWEST is currently performing monthly groundwater monitoring for the site. GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-391 G Morgan Grove Lane Development September 3, 2024 Meridian, Idaho Page 9 6.9 Pavement Based on our exploration and understanding of the proposed development, we anticipate that pavement subgrade areas will consist of silty clay with sand, silt with sand, and/or silty sand. We performed CBR testing on a silt with sand soil sample and obtained a value of 12.4 percent. Prior to pavement section construction, subgrades should be proof-rolled as recommended in section 6.1 Site Preparation or 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. Table 5 - Pavement Design Parameters Design Parameter Value California Bearing Ratio (CBR) 12.4% 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. 2Approximately equivalent to a Traffic Index of 8. The following sections were designed utilizing AASHTO 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 12 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. GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION ALLWEST AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 524-391 G Morgan Grove Lane Development September 3, 2024 Meridian, Idaho Page 10 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 IBC. We recommend ALLWEST be retained to 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 removal of disturbed soil and subgrade stabilization, if required. ♦ 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 below foundations, slabs, flatwork, 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 construction. 8.0 EVALUATION LIMITATIONS This report has been prepared to assist the design and construction of the proposed Morgan Grove Lane Development located at 3050 N Morgan Grove Lane 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. 524-391G Morgan Grove Lane Development Meridian, Idaho Appendix A Vicinity Map Site and Exploration Map ALLWEBT Base Map:Google Earth,Imagery Date:04/17/2024-' { Ulu `�srr.,,t� *^ ■` �^� x»I� � �6w; I'' -Awe 44 - 16 Aw 1p MEN t � ►..1. � deg' wM-v�: t.-...4� .y, 3 +•_ yll R 0 V Qum - - Site '�'� �- r r gfi` rfM a .�t� ' '1i 1iuKasy'_A ,• i , �I �Y tAilildki rF -..,k ,I �3, �.�,�'➢ F :�,�, krx.,� a ..�' ! �,tK �r�� ray,.d,,,,� FIR'441 cif luil ^ �. fir. �v■n' f - 7' �I _ A - •� �e � "`" � . �it IR_, {p+7`��_I L I �1�1 �� y� '(� y� i � �. ff rc i✓ `-call 11 I �A4 J J�61�I !i - .1F, �'�■, -. `k:W "� t,w � !ire n +A $.�r 9 it�' _— LA— fil � Y wi •� r'lrY..--;.� �T ib`', ! a{ �- 4M+F.''*:MAlll R 0' 6,000' 12,000' FIGURE A-1:VICINITY MAP GEOTECHNICAL EVALUATION ALLWESTMORGAN GROVE LANE DEVELOPMENT MERIDIAN, IDAHO 255 N.LINDER ROAD CLIENT:TRILOGY DEVELOPMENT MERIDIAN,IDAHO83642 PHONE:(208)895-7898 FAX:(208)898-3959 PROJECT NO.:524-391G DATE:SEPTEMBER 2024 F Base Map:Google Earth,Imagery Date:07/13/2023 1fri r 5-. Y v U Stick Rd,, !' I t 'I f •� '+ �. �'� � �� TAP 2 . I.. r �,�� J 0 - AA O ca TP-4 k TP- C i I ,'yam. � •t� .r 0 TP-7 ■] TP-10 ■ TP-8 TP_9 , p 1► " N I LEGEND 0 Approximate location of test pit observed by ALLWEST. 0 200' 400' FIGURE A-2: SITE AND EXPLORATION MAP GEOTECHNICAL EVALUATION ALLWESTMORGAN GROVE LANE DEVELOPMENT MERIDIAN, IDAHO 255 N.LINDER ROAD CLIENT:TRILOGY DEVELOPMENT MERIDIAN,IDAHO 83642 PHONE:(208)895-7898 FAX:(208)898-3959 PROJECT NO.:524-391 G DATE:SEPTEMBER 2024 Geotechnical Evaluation ALLWEST Project No. 524-391G Morgan Grove Lane Development Meridian, Idaho Appendix B Exploration Logs Soil Classification Chart ALLWEBT Morgan Grove Lane Development TP-1 ALL111ET 3050 Morgan Grove Ln, Meridian, ID 83646, USA Pagel of 1 Project No.: 524-391G Date: 06/26/2024 Comments: Contractor: Just Dig It Hole Depth: 9.5' See Figure A-2 for approximate test pit location. Equipment: Case 580c Initial Water: 7 Operator: Steve Just Logged By: Parker Norris Method: 24-inch toothed bucket Coordinates: 43.633938,-116.464580 Samples Lab a o O J a J d E J a Soil Description and Remarks t U) > C c o a o� C� U) u- U (� E s o 0 0 m M Q 2) U a N 0 Q � TOPSOIL;abundant roots and organics,4 inches thick 0.3 Silty CLAY with sand(CL-ML);medium stiff,moist,dark brown 5 5ft Grab 77 28-21-7 21 6.5 Silty SAND(SM);dense,moist to wet,brown to gray 8.0 Poorly graded GRAVEL with sand(GP);medium dense,wet, 'a. brown `U.• subrounded gravel and cobbles up to 6 inches in maximum dimension 9.5 ! ! Test pit terminated due to caving.Slotted pipe installed. Water Levels 0 Water encountered @ 7' 1 - Morgan Grove Lane Development Tp_2 ALL111ET 3050 Morgan Grove Ln, Meridian, ID 83646, USA Pagel of 1 Project No.: 524-391G Date: 06/26/2024 Comments: Contractor: Just Dig It Hole Depth: 9' See Figure A-2 for approximate test pit location. Equipment: Case 580c Initial Water: 7.5 Operator: Steve Just Logged By: Parker Norris Method: 24-inch toothed bucket Coordinates: 43.633050,-116.464524 Samples Lab a C J a J E J U T a) 'O M a Soil Description and Remarks t m c 2 °n' LL E_ o U C7 E s 8-10 8-1M U) a Q TOPSOIL;abundant roots and organics,4 inches thick 0.3 SILT with sand(ML);medium stiff,moist,brown 1.0 Silty SAND(SM);medium dense,moist,brown 5 6.5 Poorly graded GRAVEL with sand(GP); medium dense,moist to wet,brown ate.• 0 subrounded gravel and cobbles up to 6 inches in maximum dimension 1 b •0.• 9.0 Test pit terminated due to caving.Slotted pipe installed. Water Levels 0 Water encountered @ 7.5' 1 - Morgan Grove Lane Development TP-3 ALL111ET 3050 Morgan Grove Ln, Meridian, ID 83646, USA Pagel of 1 Project No.: 524-391G Date: 06/26/2024 Comments: Contractor: Just Dig It Hole Depth: 9' See Figure A-2 for approximate test pit location. Equipment: Case 580c Initial Water: 7.5 Operator: Steve Just Logged By: Parker Norris Method: 24-inch toothed bucket Coordinates: 43.632821,-116.463893 Samples Lab a o O a. a J d E J a Soil Description and Remarks t � > C c o m a o� CO U) iL U (� E s o 0 0 m M Q 2) U a N 0 Q � TOPSOIL;abundant roots and organics,4 inches thick 0.3 Silty SAND(SM);medium dense,moist,brown 3.5 ft Grab 35 21 5 6.5 Poorly graded GRAVEL with sand(GP);medium dense,moist to wet,brown .• �. �. 0 subrounded gravel up to 3 inches in maximum dimension , '': ' 9.0 Test pit terminated due to caving.Slotted pipe installed. Water Levels 0 Water encountered @ 7.5' 1 - Morgan Grove Lane Development TP-4 ALL111ET 3050 Morgan Grove Ln, Meridian, ID 83646, USA Pagel of 1 Project No.: 524-391G Date: 06/26/2024 Comments: Contractor: Just Dig It Hole Depth: 10, See Figure A-2 for approximate test pit location. Equipment: Case 580c Initial Water: 9 Operator: Steve Just Logged By: Parker Norris Method: 24-inch toothed bucket Coordinates: 43.631589,-116.464660 Samples Lab a o O J a J d E J a Soil Description and Remarks t � > C c o m a o� C� U) iL U (� E s o 0 0 m M Q 2) U a N 0 Q � TOPSOIL;abundant roots and organics,4 inches thick 0.3 SILT with sand(ML);medium stiff,moist,dark brown 1.5 Silty SAND(SM); medium dense, moist,tan 3.5 ft Grab 15 30 Infiltration test performed at 4 feet;rate=3 in/hr 5 7.0 Poorly graded GRAVEL with sand(GP);medium dense,moist to wet,tan ,• subrounded gravel and cobbles up to 6 inches in maximum dimension !,%.! 0 b 10 10.0 Test pit terminated due to caving.Slotted pipe installed. Water Levels 0 Water encountered @ 9' 1 - Morgan Grove Lane Development TP-5 ALL111ET 3050 Morgan Grove Ln, Meridian, ID 83646, USA Pagel of 1 Project No.: 524-391G Date: 06/26/2024 Comments: Contractor: Just Dig It Hole Depth: 10.5' See Figure A-2 for approximate test pit location. Equipment: Case 580c Initial Water: 9 Operator: Steve Just Logged By: Parker Norris Method: 24-inch toothed bucket Coordinates: 43.631606,-116.463688 Samples Lab a C J a J E J U T N 'O M a Soil Description and Remarks t m c 2 °' LL E_ n o U (7 E s CU 8-10 8-1 U) a Q TOPSOIL;abundant roots and organics,4 inches thick 0.3 Silty SAND(SM);medium dense to dense,moist,light brown Weak to moderate cementation throughout 5 6.0 Poorly graded GRAVEL with sand (GP); medium dense,moist to •� wet,tan ��.• subrounded gravel and cobbles up to 6 inches in maximum dimension 10 •� ' 10.5 Test pit terminated due to caving.Slotted pipe installed. Water Levels 0 Water encountered @ 9' 1 - Morgan Grove Lane Development TP-6 ALL111ET 3050 Morgan Grove Ln, Meridian, ID 83646, USA Pagel of 1 Project No.: 524-391G Date: 06/26/2024 Comments: Contractor: Just Dig It Hole Depth: 10, See Figure A-2 for approximate test pit location. Equipment: Case 580c Initial Water: 9 Operator: Steve Just Logged By: Parker Norris Method: 24-inch toothed bucket Coordinates: 43.631560,-116.462752 Samples Lab a C J a J E J U T N 'O M a Soil Description and Remarks t > c 2 - LL E_ n o U (7 E s CU 8-10 8-1 U) a Q TOPSOIL;abundant roots and organics,4 inches thick 0.3 Silty SAND(SM);medium dense,moist,brown 5 5.0 :. Poorly graded GRAVEL with sand(GP);medium dense,moist to wet,tan ��.• subrounded gravel and cobbles up to 6 inches in maximum dimension !,%.! Infiltration test performed at 6 feet; rate> 15 in/hr •o.• 6�b •0.• �S.• 10 10.0 Test pit terminated due to caving.Slotted pipe installed. Water Levels 0 Water encountered @ 9' 1 - Morgan Grove Lane Development Tp_7 LLI E T 3050 Morgan Grove Ln, Meridian, ID 83646, USA Page 1 of 1 Project No.: 524-391 G Date: 06/26/2024 Comments: Contractor: Just Dig It Hole Depth: 12.5' See Figure A-2 for approximate test pit location. Equipment: Case 580c Initial Water: 11 Operator: Steve Just Logged By: Parker Norris Method: 24-inch toothed bucket Coordinates: 43.630651,-116.464672 Samples Lab a O J J d E d E d a Soil Description and Remarks r U o o 0 rn LL E 0 E s 8-1 0 0 CO 0 a 72 TOPSOIL;abundant roots and organics,2 inches thick 0 2 0.5 ft SILT with sand(ML); medium stiff,moist,brown Bulk 71 36-27-9 2.5 Silty SAND(SM); medium dense to dense,moist,brown Weak to moderate cementation throughout soil layer 5 6.0 Poorly graded GRAVEL with sand(GP);dense, moist to wet, brown .• subrounded gravel and cobbles up to 6 inches in maximum dimension Infiltration test performed at 7 feet; rate> 15in/hr ��:�• �.:�. 10 12.5 Test pit terminated.Slotted pipe installed. Water Levels 0 Water encountered @ 11' V Morgan Grove Lane Development Tp_g ALL111ET 3050 Morgan Grove Ln, Meridian, ID 83646, USA Pagel of 1 Project No.: 524-391G Date: 06/26/2024 Comments: Contractor: Just Dig It Hole Depth: 12' See Figure A-2 for approximate test pit location. Equipment: Case 580c Initial Water: 10.5 Operator: Steve Just Logged By: Parker Norris Method: 24-inch toothed bucket Coordinates: 43.630584,-116.463633 Samples Lab a o O J a J d E J a Soil Description and Remarks t CO > C c o a o� C� U) u- U (D E t o 0 0 m M Q 2) U a N 0 Q � TOPSOIL;abundant roots and organics,2 inches thick 0 2 SILT with sand(ML);medium stiff,moist,brown 1.0 Silty SAND(SM);medium dense,moist,light brown 5- 6ft Grab 14 Infiltration test performed at 6.5 feet; rate=4 in/hr Poorly graded GRAVEL with sand(GP);dense,moist to wet,tan subrounded gravel and cobbles up to 6 inches in maximum !.•• 10 dimension 12.0 Test pit terminated.Slotted pipe installed. Water Levels 0 Water encountered @ 10.5' 1 - Morgan Grove Lane Development TP_9 ALL111ET 3050 Morgan Grove Ln, Meridian, ID 83646, USA Pagel of 1 Project No.: 524-391G Date: 06/26/2024 Comments: Contractor: Just Dig It Hole Depth: 10.5' See Figure A-2 for approximate test pit location. Equipment: Case 580c Initial Water: 9 Operator: Steve Just Logged By: Parker Norris Method: 24-inch toothed bucket Coordinates: 43.630569,-116.462726 Samples Lab a C J a J E J U T a) 'O M a Soil Description and Remarks t m c 2 °n' LL E_ o U C7 E s 8-10 8-1M U) a Q TOPSOIL;abundant roots and organics,4 inches thick 0.3 SILT with sand(ML);medium stiff,moist,brown 1.0 Silty SAND(SM);medium dense,moist,light brown 41 6.0 Poorly graded GRAVEL with sand (GP); medium dense,moist to •� wet,tan ��.• subrounded gravel and cobbles up to 6 inches in maximum dimension 10 •� ' 10.5 Test pit terminated.Slotted pipe installed. Water Levels 0 Water encountered @ 9' 1 - Morgan Grove Lane Development TP-10 ALL111ET 3050 Morgan Grove Ln, Meridian, ID 83646, USA Pagel of 1 Project No.: 524-391G Date: 06/26/2024 Comments: Contractor: Just Dig It Hole Depth: 10.5' See Figure A-2 for approximate test pit location. Equipment: Case 580c Initial Water: 9 Operator: Steve Just Logged By: Parker Norris Method: 24-inch toothed bucket Coordinates: 43.630663,-116.461895 Samples Lab a o O J a J d E J a Soil Description and Remarks t � > C c o a o� C� U) u- U (� E s o 0 0 m M Q 2) U a N 0 Q � TOPSOIL;abundant roots and organics,4 inches thick 0.3 SILT with sand(ML);medium stiff,moist,brown 1.0 Silty SAND(SM);medium dense,moist,light brown 2.5 ft Grab 2717 5 6.0 Poorly graded GRAVEL with sand (GP); medium dense,moist to •� wet,light brown .• subrounded gravel and cobbles up to 6 inches in maximum dimension b*. 10 •� ' 10.5 Test pit terminated.Slotted pipe installed. Water Levels 0 Water encountered @ 9' 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. 524-391G Morgan Grove Lane Development Meridian, Idaho Appendix C Laboratory Test Results ALLWEBT Table C-1: Summary of Laboratory Test Results Moisture Gradation Atterberg Limits Test Pit Depth Content Gravel Sand Silt/Clay Liquid Plastic Plasticity CBR Sample Classification (Feet) Limit Limit Index N (USCS) N (%) (%) TP-1 5-5.5 21 77 28 21 7 Silty CLAY with Sand (CL-ML) TP-3 3.5-4 21 35 Silty SAND(SM) TP-4 3.5-4 30 15 Silty SAND (SM) TP-7 0.5- 1.5 71 36 27 9 12.4 SILT with Sand (ML) TP-8 6-6.5 14 20 Silty SAND (SM) TP-10 2.5-3 17 27 Silty SAND(SM) 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. LIQUID AND PLASTIC LIMITS TEST REPORT 60 Dashed line indicates the approximate upper limit boundary for natural soils 50 O �0 ' G 40 U C � X W N— Z_ � v 30 c F- LU C/) ' Q i J / a: 20 H U) LU J / J Q 10 o ■ c L-ML ML or OL MH or OH 0 0 10 20 30 40 50 60 70 80 90 100 110 LIQUID LIMIT 0 MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS • Silty Clay with sand 28 21 7 77% CL-ML c■ Silt with sand 36 27 9 71% ML CD U X U U U 7 O ` Project No. 524-391G Client: Trilogy Development Remarks: aD Project: Morgan Grove Lane Development c *Location: TP-1 Depth: 5'-5.5' ■Location: TP-7 Depth: 0.5'-1.5' 0 En ALLWEST E H Figure C-1 Tested By: C. Downes Checked By:J.Varozza California Bearing Ratio ASTM D 1883 Project: Morgan Grove Lane Development Project No.: 524-391 G Client: Trilogy Development Location: TP-7 @ 0.5 - 1.5 ft Date Tested: 7/9/24 Compaction Method: ASTM D1557 Tested By: C. Downes Classification: Silt with sand (ML) 375 350 325 300 275 250 Q- 225 c �°� 200 a c 175 PSI @ 0.2 inch penetration= 187 L 150 N 125 100 75 50 25 0 0 0.1 0.2 0.3 0.4 0.5 Penetration(inches) CBR @ 0.2 Inch Penetration: 12.4 Maximum Dry Unit Weight (pcf): 108.1 Swell (%): 0.5 Optimum Water Content (%): 16.3 Dry Unit Weight Before Soak (pcf): 96.9 Remold of Max. Dry Unt Wgt(%): 90 Water Content Before Soak (%): 18.9 Water Content After Soak, Top 1 Inch (%): 26.9 Surcharge (psf): 50 Immersion Period (hrs): 96 Reviewed By: Kevin Dyekman, P.G. Figure: C-2 LL E T 255 N Linder Rd,Suite 100•Meridian, ID 83642•(208)895-7898•Fax(208)898-3959 www.allwesttesting.com This report shall not be reproduced except in full without the permission of ALLW EST.