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PZ - Geotech Report ALLWEST MATERIALS OTESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY September 24, 2021 Don Newell Landmark Pacific Development, Inc. P.O. Box 1939 Eagle, Idaho 83616 RE: Geotechnical Evaluation Woodcrest Townhomes Subdivision 1789 North Hickory Way Meridian, Idaho ALLWEST Project No. 521-095G Mr. Newell: ALLWEST has completed the authorized geotechnical evaluation for the proposed Woodcrest Townhomes Subdivision development planned at the above address in Meridian, Idaho. The purpose of this evaluation was to characterize subsurface soil conditions at the site and provide geotechnical recommendations to assist planning, design, and construction of the proposed development. Based on our evaluation, the site is suitable forthe planned development. The attached report presents the results of ourfield evaluation, laboratory testing, and our recommendations. We appreciate the opportunity to be of service to Landmark Pacific. If you have any questions or need additional information, please contact us at (208) 895-7898. Sincerely, ALLWEST 14253 Adrian Mascorro P.E. AMA Anish Pathak E.I. Area Manager Staff Engineer ~ 255 N. Linder Rd., Suite#100, Meridian, ID 83642 Phone: 208.895.7898• Fax: 208.898.3959 Hayden, ID•Lewiston, ID• Meridian, ID•Spokane Valley,WA• Missoula, MT www.allwesttesting.com GEOTECHNICAL EVALUATION WOODCREST TOWNHOMES SUBDIVISION MERIDIAN, IDAHO ALLWEST PROJECT NO. 521 -095G September 24, 2021 Prepared for: Landmark Pacific Development, Inc. P.O. Box 1939 Eagle, Idaho 83616 Prepared By: ALLWEST 255 North Linder Road, Suite 100 Meridian, Idaho 83642 A LWE T WWW.ALLWESTTESTING.COM TABLE OF CONTENTS ALLWEST Project No. 521-095G Woodcrest Townhomes Subdivision Meridian, Idaho Page 1.0 SCOPE OF SERVICES ........................................................................................2 2.0 PROJECT UNDERSTANDING/ PROPOSED CONSTRUCTION.........................2 3.0 FIELD EVALUATION PROCEDURES.................................................................3 4.0 SITE CONDITIONS ..............................................................................................3 4.1 General Geologic Conditions............................................................................. 3 4.2 General Soil Conditions.....................................................................................4 5.0 EXPLORATION AND SAMPLING .......................................................................4 5.1 Subsurface Soil Conditions ...............................................................................4 5.2 Subsurface Water..............................................................................................4 6.0 LABORATORY TESTING ....................................................................................5 7.0 CONCLUSIONS AND RECOMMENDATIONS ....................................................5 7.1 Grading and Drainage....................................................................................... 5 7.2 Site Preparation................................................................................................. 5 7.3 Subgrade Stabilization ...................................................................................... 6 7.4 Excavation......................................................................................................... 7 7.5 Materials............................................................................................................ 7 7.6 Fill Placement and Compaction......................................................................... 8 7.7 Utility Trenches.................................................................................................. 9 7.8 Wet Weather Construction ................................................................................ 9 7.9 Cold Weather Construction ............................................................................... 9 7.10 Stormwater Disposal ..................................................................................... 10 7.11 Asphalt Pavements ....................................................................................... 10 7.12 Foundation Recommendations...................................................................... 11 7.12.1 Shallow Foundation Design ............................................................... 11 7.12.2 Concrete Slabs-On-Grade ................................................................. 12 8.0 ADDITIONAL RECOMMENDED SERVICES..................................................... 12 9.0 EVALUATION LIMITATIONS............................................................................. 13 Appendix A— Site Vicinity Map, Exploration Location Plan Appendix B —Test Pit Logs, Unified Soil Classification System Appendix C— Laboratory Test Results GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation Woodcrest Townhomes Subdivision Meridian, Idaho ALLWEST has completed the geotechnical evaluation for the proposed Woodcrest Townhomes Subdivision development planned at 1789 North Hickory Way in Meridian, Idaho. The general location of the site is shown on Figure A-1 — Site Vicinity Map in Appendix A of this report. The purpose of this evaluation was to identify subsurface soil conditions at the site, and provide opinions and recommendations for the proposed development, relative to earthwork, stormwater disposal, asphalt pavement section design, and foundation construction. This report details the results of our field evaluation and presents recommendations to assist development. 1.0 SCOPE OF SERVICES Our scope of services for the project included the following: 1) Prior to subsurface exploration, we visited the site to observe site accessibility and to pre-mark exploration locations, as required by Idaho Digline. 2) Notified Idaho Digline to locate on-site utilities, as required by Idaho state law. 3) Subcontracted a backhoe and operator to observe the excavation of 7 test pits throughout the site. 4) Visually described, classified, and logged the soils encountered within test pits and we obtained soil samples within select test pits. 5) Performed seepage tests within select test pits to evaluate subsurface seepage and installed a PVC pipe within 3 test pits for future groundwater monitoring. 6) Performed laboratory tests on select soil samples to assess some of the soil engineering properties and characteristics. 7) Reviewed the results of the field evaluation and laboratory testing, performed engineering analyses, and prepared this report with field and laboratory results, subsurface logs, and geotechnical-related opinions and recommendations. We provided our services for the project in general accordance with our geotechnical proposal (521-095P) dated March 1, 2021. 2.0 PROJECT UNDERSTANDING/ PROPOSED CONSTRUCTION Based on electronic communication with you on February 18, 2021, which included a Site Layout 12 (no date) by Blaine A. Womer and architectural elevation drawings for Fairway Townhomes (4-unit) (dated December 28, 2020) by ogos Architecture, we understand plans consist of developing an approximate 2-acre site with seven two- story townhome buildings, with each building containing either two, three, or four livable units. The development will contain associated infrastructure, stormwater disposal GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 521-095G Woodcrest Townhomes Subdivision Page 3 Meridian, Idaho facilities, and an asphalt-paved roadway and access-lane. We assume the buildings will be supported on conventional shallow foundations, with garages consisting of slab- on-grade construction. Site grading plans are not available at the time of this report, but we anticipate final site grades will remain similar to existing grades, with expected cut and fill for the site to be 2 feet or less for foundation construction. We assume that no below-grade construction (i.e., basements) will occur as part of the development. Note, that by authorizing ALLWEST to provide this geotechnical evaluation for residential townhome construction, you are also authorizing ALLWEST to provide follow-up construction observation and monitoring during earthwork construction. These services will be provided on a time-and-expense basis, and are beyond the scope of services in this evaluation. If we are not retained to provide these follow-up services, we cannot be held responsible for earthwork-related errors or omissions during earthwork construction, or potential subsequent poor concrete performance. 3.0 FIELD EVALUATION PROCEDURES To complete this evaluation, on March 5, 2021, we observed the excavation of 7 test pits to maximum depths of 9 to 13 feet; depths varied due to soil caving within select test pits. We identified subsurface soil conditions, logged the subsurface soil profiles, and obtained soil samples for laboratory testing. We performed field seepage testing within three test pits to help evaluate subsurface soil seepage. At completion of exploration, the test pits were loosely backfilled with excavated soil approximately level with existing ground surfaces. Approximate test pit locations are shown on Figure A-2 — Exploration Location Plan in Appendix A. 4.0 SITE CONDITIONS At the time of exploration, the site consisted of undeveloped land with native vegetation, and trees along the north boundary. The overall site is bordered by North Hickory Way to the north, a mix of residential buildings and undeveloped farmland to the west, and commercial properties to the south and east. 4.1 General Geologic Conditions The geologic conditions at the site are mapped as Gravel of Whitney Terrace (Qwg) on the "Geologic Map of the Boise Valley and Adjoining Area, Western Snake River Plain, Idaho" (by Othberg and Stanford, 1992). Soils consist of sandy pebble and cobble gravel up to 16 to 80 feet thick, mantled by 3 to 6 feet of loess. The soils encountered in test pits are generally consistent with geologic mapping. GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 521-095G Woodcrest Townhomes Subdivision Page 4 Meridian, Idaho 4.2 General Soil Conditions The USDA Natural Resources Conservation Service (NRCS), which represents the upper 5 feet of soil profile, has mapped the soils on the site as Purdam silt loam. The parent materials are mixed alluvium, lacustrine deposits, and/or loess consisting of silt loam, silty clay loam, cemented material, and stratified sand to loam. The soils encountered in test pits are generally consistent with NRCS mapping. 5.0 EXPLORATION AND SAMPLING We observed the excavation of test pits with a Case 580C backhoe with a 3-foot-wide bucket. We visually described the soils encountered within test pits referencing ASTM D 2488, which utilizes the Unified Soil Classification System (USCS), and we obtained soil samples at select depths for further identification and laboratory testing. We performed seepage testing within three test pits on site. The test pit locations were identified on-site with white-flagged stakes or white PVC pipes. We obtained Google Earth latitude and longitude coordinates of test pit locations with a hand-held cellular device. These coordinates can be found on individual test pit logs in Appendix B and should be considered accurate to the degree implied by the method used. 5.1 Subsurface Soil Conditions At the time of exploration, the site contained approximately 3 inches of surficial roots and vegetation at the ground surface. We observed trees along the north boundary of the site; large tree roots may be encountered between 2 and 4 feet below ground. In general, subsurface soils within the observed test pits consisted of surficial native lean clays or sandy silts, underlain by silts or sandy silts with varying amounts and thicknesses of induration and/or cementation, overlying gravels and sands with depth. Detailed soil descriptions, depths, and notes are presented on individual test pit logs in Appendix B. The descriptive soil terms used on the test pit logs in this report, can be referenced by the USCS. A copy of the USCS is included in Appendix B. Subsurface conditions may vary between exploration locations. Such changes in subsurface conditions may not be apparent until construction, and if they change significantly from those observed, then accordingly, construction timing, plans, and costs may change. 5.2 Subsurface Water At the time of exploration, we did not encounter groundwater within test pits down to a maximum depth of 13 feet. Groundwater in the area is typically influenced by local irrigation and nearby canals, drains, and laterals. Groundwater may also be influenced by precipitation, on-site construction, and development to adjacent sites. Subsurface water will fluctuate throughout the different seasons of the year, but will most likely be affected during seasonal snow melt and irrigation seasons (March to October). We GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 521-095G Woodcrest Townhomes Subdivision Page 5 Meridian, Idaho recommend monitoring be accomplished to verify the presence or absence of seasonal high groundwater throughout the site, to assist civil stormwater disposal design. We installed PVC pipes within 3 test pits throughout the site for future groundwater monitoring. ALLWEST can perform monthly groundwater monitoring, if requested. 6.0 LABORATORY TESTING We performed laboratory testing to supplement field classifications and to assess some of the soil engineering properties and parameters. The laboratory tests conducted included moisture content (ASTM D 2216), gradation (ASTM D 1140), Atterberg limits (ASTM D 4318), and California bearing ratio (CBR) (ASTM D 1883). Laboratory test results are summarized in Appendix C, and are also presented on test pit logs in Appendix B, where applicable. 7.0 CONCLUSIONS AND RECOMMENDATIONS Based on our observations, testing, and evaluation, in our opinion the site is suitable for the planned residential development, provided our recommendations are adhered to. The following recommendations are presented to assist with planning, design, and construction of the development, relative to earthwork, infrastructure, stormwater disposal, asphalt pavement section design, and shallow foundation construction. These recommendations are based on our understanding of the proposed development, the conditions observed within exploration locations, laboratory test results, and engineering analysis. If the scope of construction changes, or if conditions are encountered during construction that differ from those described herein, we should be notified so we can review our recommendations and provide revisions, if necessary. 7.1 Grading and Drainage We did not review final grading plans for this development, but we anticipate site grading will consist of cuts and fills of up to 2 feet or less. We should be notified if actual site grading varies significantly from this stated information, as it may affect our recommendations herein. Final site grades should be such that final ground surfaces slope away at 5% for 5 feet from foundations and any other development areas. 7.2 Site Preparation • Prior to conducting site grading, surficial soil containing vegetation, roots and organics should be removed below proposed site grading fill areas, pavement areas, foundation areas, and any other development areas. In general, we anticipate approximately 3 inches of site stripping will be required for majority of the site to remove surficial vegetation and roots. GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 521-095G Woodcrest Townhomes Subdivision Page 6 Meridian, Idaho • Where trees are encountered and will be removed as part of the development, large root systems should be completely over-excavated and replaced with suitable fill soils. Tree roots depths will not fully be known until construction, but we anticipate a minimum of 2 to 4 feet of over-excavation will be required to remove tree roots. • Loose test pit backfill will settle with time, so where any test pits are located below proposed structures or any development areas, the loose test pit backfill soil must be re-excavated its entire depth and replaced with suitably moisture- conditioned and compacted fill soils. Existing over-excavated soils can be reused to backfill the test pits, provided the soils are not overly saturated, and they can achieve the required compaction criteria (as required in section 7.6 Fill Placement and Compaction). Test pit locations are identified in the field with white-flagged stakes or with white PVC pipes. We recommend test pit areas be accurately surveyed so that they may be located and remediated, prior to earthwork construction and development. • After site stripping, over-excavations, loose test pit remediation, and prior to site grading, utility backfill, roadway construction, foundation construction, or any other type of development, the exposed subgrades should be proof-rolled with a minimum of 5-ton vibratory roller, with loaded dump trucks, with loaded front- end loaders, or with a vibratory hoe-pack, to confirm subgrade stability. This will also assist in identifying any soft subgrade areas. If native subgrades are observed to significantly deflect or pump, the subgrades should be over- excavated and replaced with properly compacted fills or stabilized as recommended in section 7.3 Subgrade Stabilization. 7.3 Subgrade Stabilization If the subgrade soils are observed to pump or deflect significantly during grading, the subgrades should be stabilized prior to fill placement. Subgrades may be stabilized using geosynthetic reinforcement in conjunction with imported granular structural fill. The required thicknesses of granular structural fill (used in conjunction with geosynthetic reinforcement)will be dependent on the construction traffic loading, which is unknown at this time. Therefore, a certain degree of trial and error may be required during construction to verify recommended stabilization section thicknesses. Geosynthetic reinforcement should consist of Tensar TX-160 or equivalent. Alternatives to Tensar TX-160 must be approved by the geotechnical engineer prior to use on site. The following recommendations are provided for subgrade stabilization using geosynthetic reinforcement. • Geosynthetic reinforcement materials should be placed on a non-disturbed subgrade with smooth surface. Loose and disturbed soil should be removed prior to placement of geosynthetic reinforcement materials. GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 521-095G Woodcrest Townhomes Subdivision Page 7 Meridian, Idaho • A minimum weight 4-ounce, non-woven filter fabric should be placed on the undisturbed subgrade. The geosynthetic reinforcement should be placed directly on top of the filter fabric. The filter fabric and geosynthetic reinforcement should be unrolled in the primary direction of fill placement and should be over- lapped at least 3 feet, or follow manufacturer's recommendations. • The geosynthetic materials should be pulled taut to remove slack. • Construction equipment should not be operated directly on the geosynthetic materials. Fill should be placed from outside the excavation to create a pad to operate equipment on. We recommend a minimum of 12 to 18 inches of granular structural fill be placed over the geosynthetic reinforcement before operating construction equipment on the fill. Low pressure, track-mounted equipment should be used to place fill over the geosynthetic reinforcement. • Granular structural fill placed directly over geosynthetic reinforcement should be properly moisture-conditioned prior to placement, and once placed, be statically rolled. This section is the "bridge" section over soft subgrades. • After the first "bridge" lift has been placed, the remaining fill material above the "bridge" section should be compacted to structural fill criteria in section 7.6 Fill Placement and Compaction, utilizing vibratory compaction methods. • Vibration should be discontinued if it reduces the subgrade stability. If compaction criterion is not met within the fill lift above the "bridge" section, the "bridge" section thickness is not enough, and subgrade stabilization must be attempted again with a greater "bridge" section. The geotechnical engineer or a representative of the geotechnical engineer must be on-site during subgrade stabilization to verify our recommendations are followed, and to provide additional recommendations, as needed. 7.4 Excavation Excavation of on-site soil can be accomplished with typical excavation equipment. We recommend excavations greater than 4 feet deep be sloped no steeper than 1.5H:1V (horizontal to vertical). Alternatively, deeper excavations may be shored or braced in accordance with Occupational Safety and Health Administration (OSHA) specifications and local codes. Regarding trench wall support, the site soil is considered Type C soil according to OSHA guidelines. Ultimately, the contractor is responsible for site safety, excavation configurations and following OSHA guidelines. 7.5 Materials Stripped soils containing vegetation or debris are only suitable for use in non-structural landscape areas. Existing on-site soils may be reused as site grading fill, provided they are stockpiled separately, they meet the criteria below, and they are moisture- GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 521-095G Woodcrest Townhomes Subdivision Page 8 Meridian, Idaho conditioned and compacted as required in this report. Imported granular soils should be free of organics, debris, and other deleterious material and meet the following criteria. Import materials should be approved by ALLWEST prior to delivery to the site. Fill Type Criteria Site Grading Fill Maximum size 5 6 inches; 0 Retained on /4 Inch sieve < 300 ; Liquid limit < 50/o Maximum size <_ 6 inches; Granular Structural Fill, Retained on 3/4-inch sieve < 30%; Granular Subbase Passing No. 200 sieve <_ 15%; Non-plastic Alternatively, meet ISPWC section 801 6 inches max Maximum size 5 1 inch; Crushed Base Course Retained on 3/4-inch sieve < 10%; Passing No. 200 sieve < 10%; Non-plastic Alternatively, meet ISPWC section 802 (Type 1) Maximum size <_ 2 inches; Utility Trench Backfill Retained on 3/4-inch sieve <030%; Passing No. 200 sieve <_ 10/o; Non-plastic Alternatively, meet ISPWC section 305 (Type 1) 7.6 Fill Placement and Compaction Fill should be placed in lift thicknesses which are appropriate for the compaction equipment used. Typically, 8- to 12-inch-thick loose-lifts are appropriate for typical rubber-tire and steel-drum compaction equipment. Lift thicknesses 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 following percentages of the maximum dry density as determined by ASTM D 1557 (modified Proctor). For roadway and utility trench construction only, the local governing jurisdiction may provide their own method of determining the maximum dry density and compaction requirements (including subgrade). Fill Area Compaction M Subgrade' Proof-rol12 Site Grading Fill / Granular Structural Fill 95 Granular Subbase/ Crushed Base Course 952 Utility Trench Backfill 922 'Subgrade stability must be verified and approved by a representative of the geotechnical engineer prior to any fill placement or construction. 2For roadway and utility trench construction only, the local governing jurisdiction may provide their own method of determining the maximum dry density and compaction requirements (including subgrade). GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 521-095G Woodcrest Townhomes Subdivision Page 9 Meridian, Idaho 7.7 Utility Trenches Support soils for underground utilities will most likely consist of sandy lean clays, sandy silts, and/or gravels with silt and sand. These soils should provide adequate support for utilities, provided utility subgrades are compacted utilizing vibratory methods, such as with a large vibratory hoe-pack. If utility pipe subgrades are soft, yielding, and/or saturated at the time of construction, subgrade over-excavation and replacement with competent structural fill may be required below utilities. If support soils yield and/or are saturated at the time of construction, we should be notified to observe these soils and provide additional recommendations, as necessary. We strongly recommend backfilling trench excavations with fill soils which meet criteria in section 7.5 Materials, as on-site fine-grained soils (silts and clays) may be difficult to moisture-condition and compact in utility trenches. 7.8 Wet Weather Construction We recommend earthwork for this site be scheduled for the drier seasons of the year. 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. If construction occurs during or immediately after excessive precipitation, it may be necessary to over- excavate and replace saturated subgrade soil, which might otherwise be suitable. The on-site soils are sensitive to disturbance when wet. If these soils become wet and unstable, we recommend construction traffic is minimized where these soils are exposed. Low ground-pressure (tracked) equipment should be used to minimize disturbance. Soft and disturbed subgrade areas should be excavated to undisturbed soil and backfilled with structural fill, compacted to requirements stated in this report. In addition, it should be noted the on-site soils tend to have notable adhesion when wet and may be easily transported off-site by construction traffic. 7.9 Cold Weather Construction The on-site soils are frost susceptible. 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 excavated and fill areas prior to additional earthwork or construction. Pavement, flatwork, and foundation portions of the construction should not be placed on frozen ground, nor should the supporting soils be permitted to freeze during or after construction. Frozen soils must not be used as fill. If native subgrades, or suitably moisture-conditioned and compacted fill lifts, will be left exposed to freezing temperatures overnight, those areas should be protected with a minimum of 12 inches of loose soil, or covered with heated construction blankets, so construction subgrades do not freeze. Any frozen soils should be removed prior to additional fill placement or construction of any kind. GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 521-095G Woodcrest Townhomes Subdivision Page 10 Meridian, Idaho Earthwork construction during cold inclement weather will require a higher level of attention and detail to achieve required construction and compaction criteria, and may lead to additional earthwork requirements and extended construction schedules. 7.10 Stormwater Disposal During our field investigation we performed field seepage testing within test pits TP-1, TP-3, and TP-5, where we noted field-measured seepage rates of greater than 15 inches per hour (in/hr) within poorly-graded gravel with silt and sand, and greater than 30 in/hr within poorly-graded gravel with sand. Due to our field observations and the variability of indurated and cemented soils, we do not recommend stormwater disposal occur within or above sandy silt soils, as indurated and cemented soils will exhibit very poor and inconsistent soil seepage. Based on our field evaluation, the following allowable seepage rate should be utilized for on-site stormwater disposal into poorly-graded gravel with silt and sand or poorly- grade gravel with sand. • Poorly-graded gravel with sand (with or without silt) ..................... 8 in/hr Stormwater disposal facilities should be constructed a minimum of 1 foot into the receiving. Seepage beds should be "burrito wrapped" or otherwise maintain a separation/filter fabric between native fine-grained soils and drain rock/filter sand to help prevent fine soil migration into drainable/filtering media. During construction, ALLWEST should observe stormwater disposal facility subgrades to establish if the suitable receiving soil is encountered and to ensure the separation/filter fabric has been properly installed. The proper separation from bottom of stormwater disposal facilities and seasonal high groundwater should be maintained. At the time of exploration, we did not observe groundwater within the test pits. Groundwater monitoring should be accomplished within the installed PVC pipes on-site to verify the presence or absence of groundwater. We installed slotted a PVC pipes within 3 test pits on-site for future groundwater monitoring. These pipes should be monitored monthly or biweekly during seasonal snow melt and irrigation seasons (March to October) to confirm the seasonal high groundwater elevations throughout the site. 7.11 Asphalt Pavements Prior to pavement section construction, the pavement subgrade should be proof-rolled as recommended in section 7.2 Site Preparation (or as recommended by local jurisdictions). Local roadways should be designed for a 20-year Equivalent Single Axle Load (ESAL) of 33,000, which is equivalent to a traffic index (TI) of 6. If actual traffic conditions are different than what is stated, we should be notified so that we may modify our pavement section design. GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 521-095G Woodcrest Townhomes Subdivision Page 11 Meridian, Idaho Based on existing site grades, the roadway subgrade will consist of sandy lean clay or sandy silt soils. We performed CBR testing on a sandy silt soil to evaluate pavement section design, where we obtained a CBR of 24.7. However, based on our experience with lean clays and the variability of subgrade soils, we recommend a CBR of 12 be used for pavement section design, which is equivalent to an R-value of 30. The following flexible asphalt pavement section design is provided adhering to the Idaho Transportation Department (ITD), which utilizes the AASHTO pavement design methodology. Based on subgrade preparation requirements, design assumptions, and frost-depth requirements, we recommend the following pavement section be utilized for subdivision roadway construction for local roadways. Asphalt Crushed Granular Pavement Application Concrete Base Course Subbase inches inches inches Local Roadway 2.5 4 9 Base course and subbase should conform to the material recommendations as noted in this report and should be placed over a properly prepared subgrade. The subgrade, subbase, and base course surfaces should slope at no less than 2% away from the crown of the roadway to help reduce the potential for surface water infiltration into the underlying pavement subgrade. Asphalt concrete pavement should be compacted to minimum of 92% of the Rice density. Crack maintenance on pavements should be performed at a minimum of every 3 years, or when cracking is evident. Crack sealing will help reduce surface water infiltration into the supporting soils. 7.12 Foundation Recommendations The following recommendations should be utilized to design and construct proposed shallow foundations. 7.12.1 Shallow Foundation Design • For frost protection, footings should be embedded at least 24 inches below the lowest adjacent grade. • Spread footings should be supported entirely on a minimum of 1 foot of granular structural fill over existing native subgrades. Granular structural fill should extend a minimum of 6 inches beyond sides of footings. • Prior to placing concrete, ALLWEST should observe all footing excavations to verify that our recommendations are being followed. Foundation subgrade soils should be probed and approved by ALLWEST, prior to placement of granular structural fill. GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 521-095G Woodcrest Townhomes Subdivision Page 12 Meridian, Idaho • After the subgrade has been observed and approved, the placed granular structural fill should be tested for suitable moisture content and compaction (as required in section 7.6 Fill Placement and Compaction) prior to concrete placement. • If the subgrades are approved and granular structural fill meets compaction criteria, footings may be designed for the following bearing pressure: Allowable Bearing Minimum Granular Subgrade Type Pressure Structural Fill Thickness (psf) below Footing (feet) Native Silts or Clays 1 2,500 1 1 The net allowable bearing pressure value may be increased by 1/3 to account for transient loads such as wind and seismic. • If the previous recommendations are implemented, it is our opinion total settlement will be approximately less than 1 inch and differential settlement will be approximately less than '/2 of an inch. • A coefficient of friction of 0.40 may be used for sliding resistance between concrete footings and native soils, and 0.45 may be used for sliding resistance between concrete footings and imported granular structural fill. 7.12.2 Concrete Slabs-On-Grade We recommend placing a minimum of 6 inches of crushed base course immediately below slabs and flatwork. Subgrades within these areas should be prepared as indicated in Section 7.2 Site Preparation of this report. Base course should be compacted as recommended in Section 7.5 Fill Placement and Compaction. We recommend consideration be given to including a moisture vapor retarder beneath concrete slab-on-grade floors to retard moisture migration through the slabs if moisture-sensitive floor coverings are planned. We recommend the moisture retarder be installed per American Concrete Institute (ACI) recommendations and specifications. To protect slabs from moisture migration which may impact flooring performance, it is important to include the moisture vapor retarder as well as directing surface and subsurface water away from the slabs. In addition, concrete should have adequate time to cure prior to placing impermeable flooring. 8.0 ADDITIONAL RECOMMENDED SERVICES By authorizing ALLWEST to provide this evaluation, you are also authorizing us to provide observations and testing throughout construction. As an independent testing company, ALLWEST can document the recommendations included in this report are GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 521-095G Woodcrest Townhomes Subdivision Page 13 Meridian, Idaho properly implemented, provide quality control testing, and observe earthwork for conformance to project specifications. As a minimum, we recommend the following testing and observations be provided by ALLWEST: • Observe site stripping, any over-excavations, compaction of test pit backfill, and any other soil backfills. • Observe subgrade proof-rolling and approve subgrades prior to fill construction, materials placement, and construction of any kind. • Observe removal of disturbed soil and subgrade stabilization, if required. • Conduct compaction testing of fill for general site grading, utilities, pavement areas, and foundation/slab areas. • Observe placement of/test asphalt for compaction, oil content and gradation. If we are not retained to provide the recommended construction observation and testing services, we shall not be responsible for soil engineering-related construction errors or omissions. 9.0 EVALUATION LIMITATIONS This report has been prepared to assist planning, design, and construction of the proposed Woodcrest Townhomes Subdivision in Meridian, Idaho. Our services consist of professional opinions and conclusions made in accordance with generally accepted geotechnical engineering principles and practices in our local area at the time this report was prepared. This acknowledgement is in lieu of all warranties either expressed or implied. The following plates complete this report: Appendix A— Site Vicinity Map, Exploration Location Plan Appendix B — Test Pit Logs, Unified Soil Classification System Appendix C — Laboratory Test Results GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE-OWNED COMPANY Appendix A A-1 — Site Vicinity Map A-2 — Exploration Location Plan ALLWEST i r- E-Ustick-R -E Edgar Ct 8; E-Addeson ° E-Bald tin Sty` Sto � :E Kamaygw E Sedgevd�Ck°5 _ - R.� _ gapCeek D` 1 m• vim, r k E Chlmer e_DrAIAI z .. AI 1A _l.� Meaet sass 5t - ow � 9 � _ -� _�BEue=Heron=St; � ,a .�-- � * � �- •x ^E James CtrDr-LTCD M rn e �• •. 111II +1111 -7 1 ar - ':11 _ E-Fairview-Ave-- J MIRE M Wiso Ln Y 7 i -I T '; F. E-Washington E Carlt Av 1 5 0 y i _I z z— - z— E-Commercial-St- ItiI Er II rm -Ada-St t zI'— 1n E BowS I_ .16 _ rt R. E�W,liila IS Sty Ile 9 . Springwood br.--r�: .t Y ;.. r J , qu , 4000 ftFigure A-1 - Site Vicinity ' . . - Geotechnical Evaluation Woodcrest Townhomes •• • Meridian, •, • Linder255 N. Road, Suite 100 Client: Landmark Pacific Development, NOTION •, • Is, • - • 1• • 1: :• :•: 1: :•: • • �, -• IF 1 JI�IrD. f R .01 I �� t/ :'y l Al'• � � YS A 1 .'1 1 y r'RI I.ASO €Jl / J I CT t r •:ti / \ a 10.Ld LLrMes F1sCVEYI unwq Imo— —. _ ■� I I I 15C3 Legend Figure A-2 - Exploration Location Plan p Approximate location of test pit AL�WEST Geotechnical Evaluation observed by ALLWEST. Woodcrest Townhomes Subdivision Meridian, Idaho Slotted PVC pipe installed in 255 N. Linder Road, Suite 100 Client: Landmark Pacific Development, Inc. test pit. Meridian, Idaho 83642 Project No.: 521-095G Phone: (208) 895-7898 Fax: (208) 898-3959 Date: September 2021 Appendix B Test Pit Logs Unified Soil Classification System (USCS) ALLWEST ALLWEST DATE STARTED: 3/5/2021 TP - 1 DATE FINISHED: 3/5/2021 EXCAVATOR: CASE 580C MERIDIAN,IDAHO OPERATOR:Steve Just GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc. EXCAVATION METHOD:3-ft wide test pit LOGGER:Anish Pathak TEST PIT LOG WEATHER:Sunny PROJECT:521-095G NOTES:See Figure A-2 in Appendix A for approximate test pit location. Woodcrest Townhomes Subdivision LATITUDE(DEGREES):N 43°37'16.068"(43.62113°) U U LONGITUDE(DEGREES):W-116°21'49.7916" (-116.363831°) U u) TOTAL DEPTH: 13' = SAMPLE w Q DESCRIPTION W NOTES Sandy Lean CLAY(Native); brown,stiff, moist Significant roots and vegetation observed o inches. 1 cL 2 SILT; brown, medium dense, moist 3 ML ... moderate induration observed throughout soil profile Passing No.200 sieve=86% BG Moisture content= 12% 4 Sandy SILT;tan,medium dense to very dense, moist 5 ... moderate induration observed from 4 to 6 feet 6 ML 7 ...strong cementation observed from 6 to 8-1/2 feet 8— Poorly-graded GRAVEL with silt,sand and cobbles;tan, medium dense,moist 01 9 0 0 GP-GM 0 1 0 0 1 Poorly-graded GRAVEL with sand;tan,medium dense, moist j 0 0 Q 1 GP o Field seepage test performed at 12 feet. Field seepage rate=>30 in/hr. 0 Q o� 1 Test pit terminated at 13 feet. Slotted PVC pipe installed to 13 feet. 1 WATER LEVELS a WHILE EXCAVATING Y AT COMPLETION 1 AFTER EXCAVATING Sheet 1 of 1 ALLWEST DATE STARTED: 3/5/2021 TP - 2 DATE FINISHED: 3/5/2021 EXCAVATOR: CASE 580C MERIDIAN,IDAHO OPERATOR:Steve Just GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc. EXCAVATION METHOD:3-ft wide test pit LOGGER:Anish Pathak TEST PIT LOG WEATHER:Sunny PROJECT:521-095G NOTES:See Figure A-2 in Appendix A for approximate test pit location. Woodcrest Townhomes Subdivision LATITUDE(DEGREES):N 43°37'15.1608"(43.620878°) U U LONGITUDE(DEGREES):W-116°21'49.1292" (-116.363647°) U u) TOTAL DEPTH: 10' = SAMPLE w Q DESCRIPTION W NOTES Sandy Lean CLAY(Native); brown,stiff, moist Significant roots and vegetation observed o inches. CL 1 Sandy SILT;tan,medium dense to very dense, moist 2 ... moderate induration observed from 1-1/2 to 3 feet 3 ML 4 ...strong cementation observed from 3 to 5 feet 5 Poorly-graded GRAVEL with silt and sand;tan, medium dense, moist ° 6 0 ° O 7 ° GP-GM 8 ° 01 9 01 O 1 Test pit terminated at 10 feet due to caving. 1 1 1 1 WATER LEVELS a WHILE EXCAVATING Y AT COMPLETION 1 AFTER EXCAVATING Sheet 1 of 1 ALLWEST DATE STARTED: 3/5/2021 TP - 3 DATE FINISHED: 3/5/2021 EXCAVATOR: CASE 580C MERIDIAN,IDAHO OPERATOR:Steve Just GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc. EXCAVATION METHOD:3-ft wide test pit LOGGER:Anish Pathak TEST PIT LOG WEATHER:Sunny PROJECT:521-095G NOTES:See Figure A-2 in Appendix A for approximate test pit location. Woodcrest Townhomes Subdivision LATITUDE(DEGREES):N 43°37'15.1104"(43.620864°) U U LONGITUDE(DEGREES):W-116°21'47.6316" (-116.363231°) U u) TOTAL DEPTH: 13' = SAMPLE w Q DESCRIPTION W NOTES Sandy Lean CLAY(Native); brown,stiff, moist bigniTicant roots and vegetation observed o inches. Passing No.200 sieve=66% BG Moisture content=23% 1 cIL LL=33, PL=23,PI= 10 2 Sandy SILT;tan,medium dense to dense, moist 3 ML . moderate induration observed throughout soil profile BG Passing No.200 sieve=66% Moisture content= 15% 4 5 Poorly-graded GRAVEL with silt,sand and cobbles;tan, medium dense,moist 0 6 ° 0 7 ° Field seepage test performed at 7 feet. Field seepage rate=>15 in/hr. ° GP-GM 0 8 ° 0 9 ° 0 0 1 0 Poorly-graded GRAVEL with sand;tan,medium dense, moist 0 1 oO o� GP 0 1 o� 0 Q 1 Test pit terminated at 13 feet. Slotted PVC pipe installed to 13 feet. 1 WATER LEVELS a WHILE EXCAVATING Y AT COMPLETION 1 AFTER EXCAVATING Sheet 1 of 1 ALLWEST DATE STARTED: 3/5/2021 TP - 4 DATE FINISHED: 3/5/2021 EXCAVATOR: CASE 580C MERIDIAN,IDAHO OPERATOR:Steve Just GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc. EXCAVATION METHOD:3-ft wide test pit LOGGER:Anish Pathak TEST PIT LOG WEATHER:Sunny PROJECT:521-095G NOTES:See Figure A-2 in Appendix A for approximate test pit location. Woodcrest Townhomes Subdivision LATITUDE(DEGREES):N 43°37'14.0196"(43.620561°) U U LONGITUDE(DEGREES):W-116°21'47.43" (-116.363175°) U u) TOTAL DEPTH:9' = SAMPLE w Q DESCRIPTION W NOTES Sandy SILT(Native); brown, medium dense to dense,moist 6igniticant roots and vegetation observed o inches. 1 Passing No.200 sieve=65% BK LL=32, PL=28,PI=4 MIL CBR=24.7 2 ... moderate induration observed from 2 to 3-1/2 feet 3 Poorly-graded GRAVEL with silt and sand;tan, medium dense, moist ° 4 0 ° O 5 ° O 6 ° GP-GM O ° 7 0 ° O ° O 9 Test pit terminated at 9 feet due to caving. 1 1 1 1 1 WATER LEVELS a WHILE EXCAVATING Y AT COMPLETION 1 AFTER EXCAVATING Sheet 1 of 1 ALLWEST DATE STARTED: 3/5/2021 TP - 5 DATE FINISHED: 3/5/2021 EXCAVATOR: CASE 580C MERIDIAN,IDAHO OPERATOR:Steve Just GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc. EXCAVATION METHOD:3-ft wide test pit LOGGER:Anish Pathak TEST PIT LOG WEATHER:Sunny PROJECT:521-095G NOTES:See Figure A-2 in Appendix A for approximate test pit location. Woodcrest Townhomes Subdivision LATITUDE(DEGREES):N 43°37'14.3256"(43.620646°) U U LONGITUDE(DEGREES):W-116°21'50.1372" (-116.363927°) U u) TOTAL DEPTH:9' = SAMPLE CL w Q DESCRIPTION W NOTES Sandy SILT(Native); brown to light tan,medium dense to dense, 6igniticant roots and vegetation observed o moist inches. 1 2 BG 3 MIL ... moderate induration observed from 2 to 5 feet 4 5 ... moderate cementation observed from 5 to 6-1/2 feet 6— Poorly-graded GRAVEL with silt and sand;tan, medium dense, moist 7 0 GP-GM 0 0 8 Poorly-graded GRAVEL with sand;tan,medium dense, moist o Field seepage test performed at 8 1/2 feet. GIR o Field seepage rate=>30 in/hr. 9 Test pit terminated at 9 feet due to caving. 1 1 1 1 1 WATER LEVELS a WHILE EXCAVATING Y AT COMPLETION 1 AFTER EXCAVATING Sheet 1 of 1 ALLWEST DATE STARTED: 3/5/2021 TP - 6 DATE FINISHED: 3/5/2021 EXCAVATOR: CASE 580C MERIDIAN,IDAHO OPERATOR:Steve Just GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc. EXCAVATION METHOD:3-ft wide test pit LOGGER:Anish Pathak TEST PIT LOG WEATHER:Sunny PROJECT:521-095G NOTES:See Figure A-2 in Appendix A for approximate test pit location. Woodcrest Townhomes Subdivision LATITUDE(DEGREES):N 43°37'14.4336"(43.620676°) U U LONGITUDE(DEGREES):W-116°21'51.8076" (-116.364391°) U u) TOTAL DEPTH: 10' = SAMPLE w Q DESCRIPTION W NOTES Sandy SILT(Native); brown, medium dense, moist 6igniticant roots and vegetation observed o inches. 1 ML 2 SILT; brown,dense, moist 3 ML ... moderate induration observed throughout soil profile 4 Sandy SILT; light tan,medium dense to dense, moist ... moderate induration observed from 4 to 5-1/2 feet 5 ML 6 ...weak cementation observed from 5-1/2 to 7 feet 7 Poorly-graded GRAVEL with silt and sand;tan, medium dense, moist 0 8— GP-GM 0 9 0 0 O 1 Test pit terminated at 10 feet. 1 1 1 1 WATER LEVELS a WHILE EXCAVATING Y AT COMPLETION 1 AFTER EXCAVATING Sheet 1 of 1 ALLWEST DATE STARTED: 3/5/2021 TP - 7 DATE FINISHED: 3/5/2021 EXCAVATOR: CASE 580C MERIDIAN,IDAHO OPERATOR:Steve Just GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc. EXCAVATION METHOD:3-ft wide test pit LOGGER:Anish Pathak TEST PIT LOG WEATHER:Sunny PROJECT:521-095G NOTES:See Figure A-2 in Appendix A for approximate test pit location. Woodcrest Townhomes Subdivision LATITUDE(DEGREES):N 43°37'13.3428"(43.620373°) U U LONGITUDE(DEGREES):W-116°21'50.688" (-116.36408°) U u) TOTAL DEPTH: 10' = SAMPLE w Q DESCRIPTION W NOTES Sandy SILT(Native); brown to light tan,medium dense, moist 6igniticant roots and vegetation observed o inches. 1 2— ML 3 4 Poorly-graded GRAVEL with silt and sand;tan, medium dense, moist ° 0 5 ° GP-GM O 0 6 0 0 O Poorly-graded GRAVEL with sand and cobbles;tan,medium dense,moist ° 0 Q $ o� O GP Q o� 9 0 Q o� O 1 Test pit terminated at 10 feet due to caving. Slotted PVC pipe installed to 10 feet. 1 1 1 1 WATER LEVELS a WHILE EXCAVATING Y AT COMPLETION 1 AFTER EXCAVATING Sheet 1 of 1 Unified Soil Classification System MAJOR DIVISIONS SYMBOL TYPICAL NAMES Well-Graded Gravel, CLEAN GW Gravel-Sand Mixtures. GRAVELS GP Poorly-Graded Gravel, GRAVELS Gravel-Sand Mixtures. Silty Gravel, COARSE GRAVELS GM Gravel-Sand-Silt Mixtures. GRAINED WITH FINES GC Clayey Gravel, SOILS Gravel-Sand-Clay Mixtures. Well-Graded Sand, CLEAN SW Gravelly Sand. SANDS SP Poorly-Graded Sand, SANDS Gravelly Sand. Silty Sand, SANDS L SM Sand-Silt Mixtures. WITH FINES Sc Clayey Sand, Sand-Clay Mixtures. ML Inorganic Silt, SILTS AND CLAYS Silty or Clayey Fine Sand. Inorganic Clay of Low to LIQUID LIMIT CL Medium Plasticity, LESS THAN 50% Sandy or Silty Clay. FINE OL Organic Silt and Clay of Low GRAINED Plasticity. SOILS Inorganic Silt, Elastic Silt, SILTS AND CLAYS MH Micaceous Silt, Fine Sand or Silt. LIQUID LIMIT CH Inorganic Clay of High Plasticity, GREATER THAN 50% Fat Clay. OH Organic Clay of Medium to High Plasticity. Highly Organic Soils PT Peat, Muck and Other Highly Organic Soils. ALLWEST Appendix C Laboratory Test Results ALLWEST Summary of Laboratory Test Results Moisture Gradation Atterberg Limits Test Pit Depth Content Liquid Plasticity CBR Sample Classification No. (Feet) N Gravel Sand Silt/Clay Limit Index (USCS) M M M M M 1 3'/2-4 12 14 86 SILT (ML) 3 '/2- 1 23 34 66 33 10 Sandy Lean CLAY CL 3 3'/2-4 15 34 66 Sandy SILT (ML) 4 1 - 2 - 35 65 32 4 24.7 Sandy SILT ML Table C-1 255 N. Linder Road, Suite 100 • 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— 0 ; c L-ML �ML or OL MH or OH i 0 0 10 20 30 40 50 60 70 80 90 100 110 LIQUID LIMIT MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS • Sandy Lean Clay 33 23 10 66% CL c■ Sandy Silt 32 28 4 65% ML CD U X O O U 7 O ` Project No. 521-095G Client: Landmark Pacific Development,Inc. Remarks: aD Project: Woodcrest Townhomes Subdivision c *Location: TP-3 Depth: 0.5'-l' ■Location: TP-4 Depth: F-2' 0 cn ALLWEST Figure C-1 Tested By: C. Downes Checked By:J.Varozza California Bearing Ratio ASTM D 1883 Project: Woodcrest Townhomes Subdivision Project No.: 521-095G Client: Landmark Pacific Development, Inc. Location: TP-4 @ 1 - 2 ft Date Tested: 4/12/21 Compaction Method: ASTM D1557 Tested By: C. Downes Classification: Sandy Silt (ML) 500 450 400 350 a 300 c 0 a 250 4A PSI @ 0.1 inch penetration = 247 200 N 150 100 50 0 0 0.1 0.2 0.3 0.4 0.5 Penetration(inches) CBR @ 0.1 Inch Penetration: 24.7 Maximum Dry Unit Weight (pcf): 104.7 Swell (%): 0.5 Optimum Water Content (%): 17 Dry Unit Weight Before Soak(pcf): 94.0 Remold of Max. Dry Unt Wgt(%): 90 Water Content Before Soak (%): 19.3 Water Content After Soak, Top 1 Inch (%): 27.8 Surcharge (psf): 50 Immersion Period (hrs): 96 Reviewed By: James Varozza Figure: C-2 ,ALLI EST 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 ALLWEST.