Loading...
GEOTECH REPORTS V1d ALLWEST MATERIALS OTESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY February 22, 2021 Joe Perdew Biltmore Company 1580 West Cayuse Creek Drive Meridian, Idaho 83642 0oeCaD-biltmoreco.com RE: Geotechnical Evaluation Ustick Linder Subdivision Meridian, Idaho ALLWEST Project No. 520-507G Mr. Perdew: ALLWEST has completed the geotechnical evaluation for the proposed Ustick Linder Subdivision to be located at the northwest comer of the West Ustick and North Linder Roads intersection in Meridian, Idaho. The purpose of this evaluation was to characterize subsurface soil conditions at the site and provide geotechnical recommendations to assist design and construction of the proposed development. Based on our evaluation, the site is suitable for the planned development. The attached report presents the results of our field evaluation, laboratory testing, and our recommendations. We appreciate the opportunity to be of service to Biltmore Company. If you have any questions or need additional information, please contact us at (208) 895-7898. Sincerely, ALLWEST Adrian Mascorro, P.E. Area Manager 14253 ar�'� Anish Pathak, E.I. 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.allwesftesting.com GEOTECHNICAL EVALUATION USTICK LINDER SUBDIVISION MERIDIAN, IDAHO ALLWEST PROJECT NO. 520-507G February 22, 2021 Prepared for: Biltmore Company 1580 W. Cayuse Creek Drive Meridian, Idaho 83642 Prepared By: ALLWEST 255 North Linder Road, Suite 100 Meridian, Idaho 83642 ALLWEST WWW.ALLWESTTESTING.COM TABLE OF CONTENTS ALLWEST Project No. 520-507G Ustick Linder Subdivision Meridian, Idaho Page 1.0 SCOPE OF SERVICES........................................................................................ 2 2.0 PROJECT UNDERSTANDING.............................................................................2 3.0 FIELD EVALUATION PROCEDURES................................................................. 3 4.0 SITE CONDITIONS.............................................................................................. 3 4.1 General Geologic Conditions............................................................................. 3 4.2 General Soil Conditions.....................................................................................3 5.0 EXPLORATION AND SAMPLING.......................................................................4 5.1 Subsurface Soil Conditions............................................................................... 4 5.2 Subsurface Water..............................................................................................5 6.0 LABORATORY TESTING.................................................................................... 5 7.0 CONCLUSIONS AND RECOMMENDATIONS .................................................... 5 7.1 Grading and Drainage....................................................................................... 6 7.2 Site Preparation................................................................................................. 6 7.3 Subgrade Stabilization...................................................................................... 7 7.4 Excavation.........................................................................................................8 7.5 Materials............................................................................................................8 7.6 Fill Placement and Compaction......................................................................... 8 7.7 Utility Trenches.................................................................................................. 9 7.8 Wet Weather Construction................................................................................ 9 7.9 Cold Weather Construction............................................................................. 10 7.10 Stormwater Disposal..................................................................................... 10 7.11 Asphalt Pavements....................................................................................... 11 7.12 Foundation Recommendations...................................................................... 12 7.12.1 Shallow Foundation Design............................................................... 12 7.12.2 Concrete Slabs-On-Grade................................................................. 12 8.0 ADDITIONAL RECOMMENDED SERVICES.....................................................13 9.0 EVALUATION LIMITATIONS.............................................................................14 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 Ustick Linder Subdivision Meridian, Idaho ALLWEST has completed the geotechnical evaluation for the proposed Ustick Linder Subdivision to be located on the northwest corner of the West Ustick and North Linder Roads intersection 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, pavement section design, and foundation construction. This report details the results of our field evaluation and presents recommendations to assist design and construction. 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 6 test pits throughout the site. 4) Described, classified, and logged the soils encountered within test pits, and obtained soil samples within select test pits. 5) Performed seepage tests within select test pits to evaluate subsurface seepage and installed PVC pipes 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 our field and laboratory evaluation results, subsurface logs, and geotechnical-related opinions and recommendations. We provided our services for the project in general accordance with our geotechnical proposal (520-507P) dated December 23, 2020. 2.0 PROJECT UNDERSTANDING Based on electronic communication with you, and review of the Conceptual Plan for Ustick Linder Subdivision prepared by Bailey Engineering (dated December 15, 2020), we understand the project will consist of an approximate 4'/2-acre residential and commercial development with associated utilities, stormwater disposal facilities, and GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 520-507G Ustick Linder Subdivision Page 3 Meridian, Idaho asphalt -paved roadways and parking. Plans consist of construction of six 4-plex and three 6-plex buildings with a total of 42 livable units, as well as two commercial buildings. We did not review final structural plans at the time of this report, but based on existing developments in the area, we anticipate the proposed buildings will be single- or two-story structures, constructed utilizing shallow foundations and slab -on - grade construction. If proposed structures will be taller than two stories, we should be notified so we can review final structural plans, and provide revised foundation -related recommendations, as the recommendations in this report are based on maximum height of two-story structures. 3.0 FIELD EVALUATION PROCEDURES To complete this evaluation, on January 12, 2021 we observed the excavation of 6 test pits to a maximum depth of 13'/2 feet. We identified subsurface soil conditions and logged the subsurface soil profiles, and obtained soil samples for laboratory testing. We performed field seepage testing within select 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 was undeveloped and covered with surficial vegetation consisting of weeds, bushes, and a tree. The site was bordered by West Ustick Road to the south, North Linder Road to the east, farmland with a private residence to the north, and a residential subdivision to the west. The Creason Lateral borders the site along the southwest corner of the site. 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). Surficial soils consist of 3 to 6 feet of loess underlain by sandy pebble and cobble gravel down 16 to 80 feet deep. The soils encountered within test pits are generally consistent with geologic mapping. 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 Abo silt loam and Aquic Torriorthents. The parent materials are mixed alluvium and/or lacustrine deposits consisting of silt loam, clay loam, loam, fine gravelly coarse sandy loam, sand, and gravel. The soils encountered within test pits are generally consistent with NRCS mapping. GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 520-507G Ustick Linder Subdivision Page 4 Meridian, Idaho 5.0 EXPLORATION AND SAMPLING We observed the excavation of the test pits with a CASE 580C rubber -tired 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 select test pits throughout the site. The test pit locations were identified on -site with 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 the 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. We observed a tree in the southwest corner of the site; large tree roots may be encountered between 2 and 3 feet below ground. In general, the subsurface soils within the observed test pits consisted of surficial silts with sand or lean clays. Occasionally, surficial fill soils consisting of sand and gravel were encountered within the test pits. The subsurface soils underlying the surficial soils generally consisted of sandy silts overlaying poorly -graded gravel with silt and sand. Specific descriptions of soils observed throughout our field exploration follow: Poorly -graded gravel with sand, Silty sand with gravel (Fill) — At the ground surface within test pits TP-2 and TP-6, we observed fill soils consisting of poorly -graded gravel with sand or silty sand with gravel to depths of 1 to 11/2 feet. We described fill soils as tan or brown, loose, and moist. Lean clay with sand, Lean clay (CL) (Native) — Underlying surficial fill in test pit TP-2 and at the ground surface in TP-4, we observed native lean clay down to depths of 2'/2 to 3'/2 feet below ground. We described the clay soils as brown, stiff, and moist. Silt with sand, Sandy silt (ML) (Native) — At the ground surface in test pits TP-1, TP-3, and TP-5, or underlying surficial soils in test pits TP-4 and TP-6, we observed native silt with sand and/or sandy silt down to depths of 3 to 4'/2 feet below ground. We described the silty soils as brown, medium dense, and moist. We observed moderate cementation within the sandy silt in test pits TP-3 and TP-5 at approximately 3 to 4 feet below ground. Poorly -graded gravel with silt and sand (GP -GM) — Underlying sandy silt or lean clay with sand, we observed poorly -graded gravel with silt and sand down to depths of 9 to 13 feet (maximum test pit termination depths). We described poorly -graded gravel with silt and sand as orange -tan, medium dense, and moist to saturated. GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 520-507G Ustick Linder Subdivision Page 5 Meridian, Idaho Clayey gravel with sand (GC) — Underlying the poorly -graded gravel with silt and sand within test pit TP-5, we observed clayey gravel with sand down to the test pit termination depth of 13'/2 feet below ground. We described clayey gravel with sand as brown, medium dense, and moist. 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 encountered groundwater within test pits TP-1 through TP-4 (in the northern half of the site) at depths between 8 and 9 feet below ground surface. Groundwater in the area is typically affected by local irrigation and nearby creeks and laterals, but may also vary due to on -site construction and development to adjacent sites. Groundwater 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 installed PVC pipes within each test pit for future groundwater monitoring. Monthly or biweekly groundwater monitoring should be accomplished throughout snowmelt and irrigation seasons to verify the presence or absence of groundwater within the on -site PVC pipes, to assist civil stormwater disposal design. 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. 7.0 CONCLUSIONS AND RECOMMENDATIONS Based on our observations, testing, and evaluation, in our opinion the site is suitable for the planned development, provided our recommendations are adhered to. The following recommendations are presented to assist with design and construction of the development, relative to earthwork, infrastructure, stormwater disposal, asphalt pavements, and foundation construction. ALLWEST GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 520-507G Ustick Linder Subdivision Page 6 Meridian, Idaho These recommendations are based on our understanding of the proposed development, the subsurface conditions observed within the excavated test pits, 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 grading should be such that surfaces slope away 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, pavements or 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. • If the tree encountered in the southwest corner of the site will be removed as part of the development, or if any large root systems remain in the southern half of the site (based on old aerial images), those root systems must 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 3 feet of over -excavation will be required to remove large tree root systems. • Loose test pit backfill will densify with time, which could lead to undesirable settlements below improved areas. Therefore, if any test pit backfill areas are located below proposed structures or any improvement areas, test pits should be re -excavated their entire depth and replaced with suitably moisture - conditioned and compacted fill. 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. We recommend test pit locations be accurately surveyed so that they may be located and remediated, prior to earthwork construction and development. • After site stripping, any over -excavations, and loose test pit backfill remediation, the exposed subgrade should be proof -rolled with a minimum of 5-ton vibratory roller, with a loaded dump truck, or with a loaded front loader, to confirm subgrade stability. This will assist in identifying soft subgrade areas. If subgrade GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY Geotechnical Evaluation Ustick Linder Subdivision Meridian, Idaho ALLWEST Project No. 520-507G Page 7 soil is observed to significantly deflect or pump, it should be over -excavated and replaced with properly compacted fill 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. • 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 to a firm, non -yielding surface. 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. GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY Geotechnical Evaluation Ustick Linder Subdivision Meridian, Idaho ALLWEST Project No. 520-507G Page 8 • 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:1 V (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 and 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 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 <_ 6 inches; o 0 Retained on /4 inch sieve < 30 /o; 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) Maximum size <_ 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 I Maximum size <_ 2 inches; Utility Trench Backfill Retained on 3/4-inch sieve < 30%; Passing No. 200 sieve <_ 10%; 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 ALLWEST GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 520-507G Ustick Linder Subdivision Page 9 Meridian, Idaho 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 / Pavements 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). 7.7 Utility Trenches Support soils for underground utilities will most likely consist of clays, silts, or gravels with sand soils. 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 even more 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 reduce the ALLWEST GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 520-507G Ustick Linder Subdivision Page 10 Meridian, Idaho potential for 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 and flatwork 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 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. Earthwork construction during cold inclement weather will require a higher level of attention and detail to achieve required earthwork 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-4, and TP-5, where we noted field -measured seepage rates of 5 to 10 inches per hour (in/hr) within the poorly -graded gravel with silt and sand. Due to our field observations and the variability of cemented soils, we do not recommend stormwater disposal occur within or above sandy silt, as cemented soils will exhibit very poor and inconsistent soil seepage. Based on our field evaluation, the following recommended seepage rate, with an appropriate factor of safety, should be utilized for on -site stormwater disposal into poorly -graded gravel with silt and sand. • Poorly -graded gravel with silt and sand ........................... 4 in/hr Stormwater disposal facilities should be constructed a minimum of 1 foot into the gravel with silt and sand layer. 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 GEOTECHNICAL I ENVIRONMENTAL ALLWESTMATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 520-507G Ustick Linder Subdivision Page 11 Meridian, Idaho 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 observed groundwater in test pits TP-1 through TP-4 at depths ranging from approximately 8 and 9 feet below existing ground surfaces. We installed slotted PVC pipes within each test pit for future groundwater monitoring. At a minimum, 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 and collector roadways should be designed for a 20-year Equivalent Single Axle Load (ESAL) of 33,000 and 370,000, respectively, which are equivalent to traffic indexes (TI) of 6 and 8, respectively. If actual traffic conditions are different than what is stated, we should be notified so that we may modify our pavement section design. We anticipate the roadway subgrades will consist of silt and/or clay soils. As such, we performed CBR testing on a lean clay with sand soil to assist pavement section design. Based on laboratory testing, we obtained a CBR of 10 for the lean clay with sand, which correlates to an R-value of 25. 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 considerations, we recommend the following pavement sections be utilized for parking and access lanes, and subdivision roadway construction for local and collector roadways. Asphalt Crushed Granular Pavement Application Concrete Base Course Subbase inches inches inches Local Roadway / Parking / Access Lanes 2.5 4 9 Collector Roadway 3 6 11 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 ALLWEST GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY Geotechnical Evaluation Ustick Linder Subdivision Meridian, Idaho ALLWEST Project No. 520-507G Page 12 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 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 soil should be probed and approved, prior to placement of fill or concrete. • Footings may be designed for the following bearing pressures: Allowable Bearing Minimum Granular Subgrade Type Pressure Structural Fill Thickness (psf) below Footing (feet) Native Silt / Clay 2,500 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 0.45 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. Subgrade within these areas should be prepared as ALLWEST GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 520-507G Ustick Linder Subdivision Page 13 Meridian, Idaho 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 To maintain continuity and efficiency, we recommend ALLWEST be retained to provide observations and testing throughout construction. As an independent testing company, ALLWEST can document the recommendations included in this report are 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, and compaction of test pit backfill, and any other soil backfills. • Observe proof -rolling of the subgrade prior to fill placement. • Observe removal of disturbed soil and subgrade stabilization, if required. • Observe seepage bed subgrades and observe overall construction. • Observe, probe, and approved foundation subgrade soils prior to granular structural fill placement and compaction. • Conduct compaction testing of fill placed for general site grading, utilities, pavement areas, and foundation areas. • Observe placement of and 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. ALLWEST GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY Geotechnical Evaluation ALLWEST Project No. 520-507G Ustick Linder Subdivision Page 14 Meridian, Idaho 9.0 EVALUATION LIMITATIONS This report has been prepared to assist design and construction of the proposed Ustick Linder 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 ALLWEST GEOTECHNICAL I ENVIRONMENTAL MATERIALS TESTING I SPECIAL INSPECTION AN EMPLOYEE -OWNED COMPANY Appendix A A-1 — Site Vicinity Map A-2 — Exploration Location Plan ALLWEST I1' III1111� r .►r� � w- �•yh - _ _ - _ •rw17. AtI• " �.--� • r- Ustick Road ;� •. -.. •F LTP 3 J -�' fin• ♦, � � y goo• `� t +• • ' art � ''� fr u � -� �;-• t �� r Figure A-1 - Site Vicinity .. -. echnical Evaluation Ustick Linder Subdivision Meridian,... 5.8 0 01579 E LI Legend 0 Approximate location of test pit observed by ALLWEST. �t Slotted PVC pipe installed in test pit. ALLWEST 255 N. Linder Road, Suite 100 Meridian, Idaho 83642 Phone- (208) 895-7898 Fax: (208) 898-3959 Figure A-2 - Exploration Location Plan Geotechnical Evaluation Ustick Linder Subdivision Meridian, Idaho Client- Biltmore Company Project No.: 520-507G Date: February 2021 Appendix B Test Pit Logs Unified Soil Classification System (USCS) ALLWEST ALLWEST DATE STARTED: 1/12/2021 TP - 1 MERIDIAN, IDAHO DATE FINISHED: 1/12/2021 EXCAVATOR: CASE 580C OPERATOR: Steve Just EXCAVATION METHOD: 3-ft wide bucket GEOTECHNICAL SECTION COMPANY: Just Dig'It Exc. LOGGER:Anish Pathak TEST PIT LOG WEATHER:Cloudy PROJECT: 520-507G NOTES: See Figure A-2 in Appendix A for approximate test pit location. Ustick Linder Subdivision LATITUDE (DEGREES): N 43°38'8.3868" (43.635663°) OJ LONGITUDE (DEGREES): W-116'24'54.216" (-116.41506°) w a �j U d u) TOTAL DEPTH: 9' a Q DESCRIPTION `� NOTES SILT with sand (Native); brown, medium dense, moist Significant roots and vegetation observed to 3 inches. 1 ML 2 3 Sandy SILT; brown, medium dense, moist ML 4-Poorly-graded GRAVEL with silt and sand; orange -tan, medium dense, moist to saturated 5 j` Field seepage test performed at 5 feet. Field seepage rate = 5 in/hr. �< 6 0 � GP -GM 7 O l _ __ O - 9 0 Test pit terminated at 9 feet. Slotted PVC pipe installed to 9 feet. 1 1 1 1 1 WATER LEVELS 8' v WHILE EXCAVATING Y AT COMPLETION 1 AFTER EXCAVATING Sheet 1 of 1 ALLWEST DATE STARTED: 1/12/2021 TIP - 2 MERIDIAN, IDAHO DATE FINISHED: 1/12/2021 EXCAVATOR: CASE 580C OPERATOR: Steve Just EXCAVATION METHOD: 3-ft wide bucket GEOTECHNICAL SECTION COMPANY: Just Dig'lt Exc. LOGGER:Anish Pathak TEST PIT LOG WEATHER:Cloudy PROJECT: 520-507G NOTES: See Figure A-2 in Appendix A for approximate test pit location. Ustick Linder Subdivision LATITUDE (DEGREES): N 43°38'8.2428" (43.635623°) LONGITUDE (DEGREES): W-116°24'50.3388" (-116.413983°) 0 w a �j U d u) TOTAL DEPTH: 9.5' a Q `o DESCRIPTION Of NOTES Poorly -graded GRAVEL with sand (Fill); tan, loose, moist 1 2 CL 3 4 5 6 GP -GM 7- 8— 9 1 1 Poorly-graded GRAVEL with silt and sand; orange -tan, medium dense, moist to saturated Test pit terminated at 9-1/2 feet. Slotted PVC pipe installed to 9-1/2 feet. WATER LEVELS v WHILE EXCAVATING Y AT COMPLETION 1 AFTER EXCAVATING Passing No. 200 sieve = 82% BK LL = 38, PL = 19, PI = 19 CBR = 10.0 7 Sheet 1 of 1 ALLWEST DATE STARTED: 1/12/2021 TIP - 3 DATE FINISHED: 1/12/2021 EXCAVATOR: CASE 580C MERIDIAN, IDAHO OPERATOR: Steve Just EXCAVATION METHOD: 3-ft wide bucket GEOTECHNICAL SECTION COMPANY: Just Dig'It Exc. LOGGER:Anish Pathak TEST PIT LOG WEATHER:Cloudy PROJECT: 520-507G NOTES: See Figure A-2 in Appendix A for approximate test pit location. Ustick Linder Subdivision LATITUDE (DEGREES): N 43°38'5.6544" (43.634904°) LONGITUDE (DEGREES): W-116°24'53.8776" (-116.414966°) 0 w �j U d a u) TOTAL DEPTH: 12' a Q DESCRIPTION `� NOTES SILT with sand (Native); brown, medium dense, moist Significant roots and vegetation observed to 3 inches. 1 ML 2 Sandy SILT; brown, medium dense, moist 3 ML ... moderate cementation observed from 3 to 3-1/2 feet 4 Poorly -graded GRAVEL with silt and sand; orange -tan, medium dense, moist to saturated 5- 6- 7- 8— ij GP -GM 9 - 1 1 Test pit terminated at 12 feet. Slotted PVC pipe installed to 12 feet. 1 1 WATER LEVELS v WHILE EXCAVATING Y AT COMPLETION T AFTER EXCAVATING Sheet 1 of 1 ALLWEST DATE STARTED: 1/12/2021 TIP - 4 MERIDIAN, IDAHO DATE FINISHED: 1/12/2021 EXCAVATOR: CASE 580C OPERATOR: Steve Just EXCAVATION METHOD: 3-ft wide bucket GEOTECHNICAL SECTION COMPANY: Just Dig'It Exc. LOGGER:Anish Pathak TEST PIT LOG WEATHER:Cloudy PROJECT: 520-507G NOTES: See Figure A-2 in Appendix A for approximate test pit location. Ustick Linder Subdivision LATITUDE (DEGREES): N 43°38'5.6868" (43.634913°) LONGITUDE (DEGREES): W-116'24'50.364" (-116.41399°) 0 w a �j U d u) TOTAL DEPTH: 10' a Q U) DESCRIPTION Of NOTES Lean CLAY (Native), brown, stiff, moist BG Passing No. 200 sieve = 89% Moisture content = 23% 1 LL = 38, PL = 19, PI = 19 CL 2 Sandy SILT; brown, medium dense, moist BG Passing No. 200 sieve = 57% Moisture content = 29% 3 ML 4 Poorly -graded GRAVEL with silt and sand; orange -tan, medium dense, moist to saturated 5- 6— Field seepage test performed at 6 feet. Field seepage rate = 8 in/hr. 7 GP -GM 8- 9 1 Test pit terminated at 10 feet. Slotted PVC pipe installed to 10 feet. 1 1 1 1 WATER LEVELS 9' v WHILE EXCAVATING Y AT COMPLETION 1 AFTER EXCAVATING Sheet 1 of 1 ALLWEST DATE STARTED: 1/12/2021 TIP - 5 MERIDIAN, IDAHO DATE FINISHED: 1/12/2021 EXCAVATOR: CASE 580C OPERATOR: Steve Just EXCAVATION METHOD: 3-ft wide bucket GEOTECHNICAL SECTION COMPANY: Just Dig'It Exc. LOGGER:Anish Pathak TEST PIT LOG WEATHER:Cloudy PROJECT: 520-507G NOTES: See Figure A-2 in Appendix A for approximate test pit location. Ustick Linder Subdivision LATITUDE (DEGREES): N 43°38'3.0156" (43.634171 °) LONGITUDE (DEGREES): W-116°24'53.4276" (-116.414841 °) 0 w a �j U d u) TOTAL DEPTH: 13.5' a Q `� DESCRIPTION NOTES SILT with sand (Native); brown, medium dense, moist Significant roots and vegetation observed to 3 inches. 1 ML 13G Passing No. 200 sieve = 73% Moisture content = 20% 2 Sandy SILT; brown, medium dense, moist 3 13G Passing No. 200 sieve = 51 % ML Moisture content = 22% 4­1 5 6- 7— GP-GM 8 9 1 1 GC 1 1 1 ... moderate cementation observed from 3-1/2 to 4 feet Poorly -graded GRAVEL with silt and sand; orange -tan, medium dense, moist Test pit terminated at 13-1/2 feet. Slotted PVC pipe installed to 13-1/2 feet. WATER LEVELS v WHILE EXCAVATING Y AT COMPLETION 1 AFTER EXCAVATING Field seepage test performed at 6 feet. Field seepage rate = 10 in/hr. Sheet 1 of 1 ALLWEST DATE STARTED: 1/12/2021 TIP - 6 DATE FINISHED: 1/12/2021 EXCAVATOR: CASE 580C MERIDIAN, IDAHO OPERATOR: Steve Just EXCAVATION METHOD: 3-ft wide bucket GEOTECHNICAL SECTION COMPANY: Just Dig'lt Exc. LOGGER:Anish Pathak TEST PIT LOG WEATHER:Cloudy PROJECT: 520-507G NOTES: See Figure A-2 in Appendix A for approximate test pit location. Ustick Linder Subdivision LATITUDE (DEGREES): N 43°38'2.8248" (43.634118°) LONGITUDE (DEGREES): W-116°24'51.0444" (-116.414179°) OJ w �j U d a u) TOTAL DEPTH: 13' a Q DESCRIPTION Of `� NOTES Silty SAND with gravel (Fill); brown, loose, moist Significant roots and vegetation observed to 3 inches. FILL 1 Sandy SILT (Native); brown, medium dense, moist 2—] W 3 Poorly -graded GRAVEL with silt and sand; orange -tan, medium dense, moist 4­1 5-1 6-1 7-1 8--� GP -GM 9-1 10-7 1v-1 12-7 1 Test pit terminated at 13 feet. Slotted PVC pipe installed to 13 feet. 14-7 WATER LEVELS v WHILE EXCAVATING Y AT COMPLETION 1 AFTER EXCAVATING Sheet 1 of 1 Unified Soil Classification System MAJOR DIVISIONS SYMBOL TYPICAL NAMES GW Well -Graded Gravel, CLEAN Gravel -Sand Mixtures. GP Poorly -Graded Gravel, GRAVELS GRAVELS Gravel -Sand Mixtures. GM Silty Gravel, GRAVELS Gravel -Sand -Silt Mixtures. COARSE WITH FINES Clayey Gravel, GRAINED GC Gravel -Sand -Clay Mixtures. SOILS Well -Graded Sand, CLEAN SW Gravelly Sand. SANDS SP Poorly -Graded Sand, SANDS Gravelly Sand. SM Silty Sand, SANDS Sand -Silt Mixtures. WITH FINES SC Clayey Sand, Sand -Clay Mixtures. ML Inorganic Silt, Silty or Clayey Fine Sand. SILTS AND CLAYS Inorganic Clay of Low to LIQUID LIMIT CL Medium Plasticity, LESS THAN 50% Sandy or Silty Clay. OL Organic Silt and Clay of Low FINE Plasticity. GRAINED SOILS Inorganic Silt, Elastic Silt, SILTS AND CLAYS MH Micaceous Silt, Fine Sand or Silt. CH Inorganic Clay of High Plasticity, LIQUID LIMIT 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 Test Pit No. Depth (Feet) Moisture Content M Gradation Atterberg Limits CBR Sample Classification (USCS) Liquid Limit M Plasticity Index M Gravel M Sand M Silt/Clay M 2 1 - 2 - 18 82 38 19 10 Lean CLAY with sand (CL) 4 0.5 - 1 23 11 89 38 19 Lean CLAY (CL) 4 2.5 - 3 29 43 57 Sandy SILT (ML) 5 1 - 1.5 20 27 73 SILT with sand (ML) 5 3 - 3.5 22 49 51 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 50 40 U C X W C � i Z a) r a) U 30 W c U) CL Q O�j J C (D 20 w J J 0 10 c 0 (n o 0 10 20 30 40 50 60 70 80 90 100 110 LIQUID LIMIT 0 MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS • Lean Clay with sand 38 19 19 -- 82% CL Lean Clay 38 19 19 -- 89% CL a) U X a) a) U 7 O Project No. 520-507G Client: Biltmore Company Remarks: a) a) Project: Ustick Linder Subdivision 9Location: TP-2 Depth: F-2' ■Location: TP-4 Depth: 0.5'-1' 1= 0 ALLWEST IEi�. �� Figure C-1 % upper limit boundary for natural soils , , co, i , i , , , 1O , , O i , , `'MILML or OL MH or OH Tested By: C. Downes Checked By: J. Varozza Tested By: C. Downes Checked By: J. Varozza California Bearing Ratio ASTM D 1883 Project: Ustick Linder Subdivision Client: Biltmore Company Date Tested: 2/1/21 Tested By: C. Downes 275 250 225 200 175 a 40 c 150 'a o 125 0 v L n 100 75 50 25 0 0 Project No.: 520-507G Location: TP-2 @ 1 - 2 ft Compaction Method: ASTM D1557 Classification: Lean Clay with sand (CL) 0.1 0.2 0.3 0.4 0.5 Penetration (inches) CBR @ 0.1 Inch Penetration: 10.0 Maximum Dry Unit Weight (pcf): 113.8 Swell (%): 2.8 Optimum Water Content (%): 12.6 Dry Unit Weight Before Soak (pcf): 103.4 Remold of Max. Dry Unt Wgt (%): 91 Water Content Before Soak (%): 13.6 Water Content After Soak, Top 1 Inch (%): 26.4 Surcharge (psf): 50 Immersion Period (hrs): 96 Reviewed By: James Varozza Figure: C-2 ALLWEST 255 N Linder Rd, Suite 100 • Meridian, ID 83642 • (208) 895-7898 • Fax (208) 898-3959 www. a l l westte st i n g. co m This report shall not be reproduced except in full without the permission of ALLWEST.