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GEOTECHNICAL INVESTIGATION ELM GROVE COTTAGES 405 E Fairview Avenue Meridian, ID PREPARED FOR: Mr. Steve Arnold A Team Land Consultants 1785 S. Whisper Cove Boise, ID 83709 PREPARED BY: Atlas Technical Consultants, LLC July 7, 2021 2791 South Victory View Way B211738g Boise, ID 83709 July 7, 2021 Atlas No. B211738g Mr. Steve Arnold A Team Land Consultants 1785 S. Whisper Cove Boise, ID 83709 Subject: GeotechnicalInvestigation Elm Grove Cottages 405 E Fairview Avenue Meridian, ID Dear Mr. Arnold: In compliance with your instructions, Atlas has conducted a soils exploration and foundation evaluation for the above referenced development. Fieldwork for this investigation was conducted on June 22 and 23, 2021. Data have been analyzed to evaluate pertinent geotechnical conditions. Results of this investigation, together with our recommendations, are to be found in the following report. We have provided a PDF copy for your review and distribution. Often, questions arise concerning soil conditions because of design and construction details that occur on a project. Atlas would be pleased to continue our role as geotechnical engineers during project implementation. If you have any questions, please call us at (208) 376-4748. �SSA�NAL FN� Respectfully submitted, �o�\CENS Fo Q � 14898 7/7/2021 0 OF \�PO�� Gavin Marron, El Elizabeth Brown, gSETH 6R Staff Engineer Geotechnical Services er C7 Clinton Wyllie, PG Staff Geologist Atlas No. 13211738g Page I i Copyright © 2021 Atlas Technical Consultants CONTENTS 1. INTRODUCTION...................................................................................................................1 1.1 Project Description........................................................................................................1 1.2 Authorization.................................................................................................................1 1.3 Scope of Investigation...................................................................................................1 2. SITE DESCRIPTION.............................................................................................................2 2.1 Site Access...................................................................................................................2 2.2 Regional Geology.........................................................................................................2 2.3 General Site Characteristics.........................................................................................2 2.4 Regional Site Climatology and Geochemistry...............................................................3 3. SEISMIC SITE EVALUATION...............................................................................................3 3.1 Geoseismic Setting.......................................................................................................3 3.2 Seismic Design Parameter Values...............................................................................3 4. SOILS EXPLORATION.........................................................................................................4 4.1 Exploration and Sampling Procedures..........................................................................4 4.2 Laboratory Testing Program.........................................................................................4 4.3 Soil and Sediment Profile..............................................................................................5 4.4 Volatile Organic Scan...................................................................................................5 5. SITE HYDROLOGY................................................................................................................, 5.1 Groundwater.................................................................................................................6 5.2 Soil Infiltration Rates.....................................................................................................6 5.3 Infiltration Testing..........................................................................................................7 6. FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS .............................7 6.1 Foundation Design Recommendations.........................................................................7 6.2 Floor, Patio, and Garage Slab-on-Grade......................................................................8 7. PAVEMENT DISCUSSION AND RECOMMENDATIONS....................................................9 7.1 Flexible Pavement Sections..........................................................................................9 7.2 Pavement Subgrade Preparation................................................................................10 7.3 Common Pavement Section Construction Issues.......................................................10 8. CONSTRUCTION CONSIDERATIONS..............................................................................11 8.1 Earthwork....................................................................................................................11 8.2 Dry Weather................................................................................................................12 8.3 Wet Weather...............................................................................................................12 8.4 Soft Subgrade Soils....................................................................................................12 8.5 Frozen Subgrade Soils...............................................................................................13 8.6 Structural Fill...............................................................................................................13 8.7 Backfill of Walls...........................................................................................................14 8.8 Excavations.................................................................................................................15 Atlas No. 13211738g Page I ii Copyright © 2021 Atlas Technical Consultants 8.9 Groundwater Control...................................................................................................15 9. GENERAL COMMENTS.....................................................................................................16 10. REFERENCES..................................................................................................................17 TABLES Table 1 — Seismic Design Values................................................................................................. 4 Table 2 — Groundwater Data.........................................................................................................6 Table3 — Soil Bearing Capacity.................................................................................................... 8 Table 4 — Gravel Equivalent Method Flexible Pavement Specifications ..................................... 10 APPENDICES Appendix I Warranty and Limiting Conditions Appendix II Vicinity Map Appendix III Site Map Appendix IV Geotechnical Investigation Test Pit Log Appendix V Geotechnical General Notes Appendix VI Gravel Equivalent Method Pavement Design Appendix VII Important Information About This Geotechnical Engineering Report Atlas No. B211738g Page I iii Copyright © 2021 Atlas Technical Consultants 1. INTRODUCTION This report presents results of a geotechnical investigation and analysis in support of data utilized in design of structures as defined in the 2018 International Building Code (IBC). Information in support of groundwater and stormwater issues pertinent to the practice of Civil Engineering is included. Observations and recommendations relevant to the earthwork phase of the project are also presented. Revisions in plans or drawings for the proposed structures from those enumerated in this report should be brought to the attention of the soils engineer to determine whether changes in the provided recommendations are required. Deviations from noted subsurface conditions, if encountered during construction, should also be brought to the attention of the soils engineer. 1.1 Project Description The proposed development is in the central portion of the City of Meridian, Ada County, ID, and occupies a portion of the NE'/4NW'/4 of Section 7, Township 3 North, Range 1 East, Boise Meridian. This project is expected to consist of 30 residential cottage structures. The site is approximately 7.8 acres in size, though only the southern 3 acres will be developed at this time. Total settlements are limited to 1 inch. Loads of up to 4,000 pounds per lineal foot for wall footings, and column loads of up to 50,000 pounds were assumed for settlement calculations. Additionally, assumptions have been made for traffic loading of pavements. Retaining walls are not anticipated as part of the project. Atlas has not been informed of the proposed grading plan. 1.2 Authorization Authorization to perform this exploration and analysis was given in the form of a written authorization to proceed from Mr. Steve Arnold of A Team Land Consultants to Gavin Marron of Atlas Technical Consultants (Atlas), on May 11, 2021. Said authorization is subject to terms, conditions, and limitations described in the Professional Services Contract entered into between A Team Land Consultants and Atlas. Our scope of services for the proposed development has been provided in our proposal dated April 15, 2021 and repeated below. 1.3 Scope of Investigation The scope of this investigation included review of geologic literature and existing available geotechnical studies of the area, visual site reconnaissance of the immediate site, subsurface exploration of the site, field and laboratory testing of materials collected, and engineering analysis and evaluation of foundation materials. Atlas No. 13211738g Page 11 Copyright © 2021 Atlas Technical Consultants 2. SITE DESCRIPTION 2.1 Site Access Access to the site may be gained via Interstate 84 to the Meridian Road exit. Proceed north on Meridian Road approximately 0.25 mile where the road veers to the northeast and becomes Main Street. Continue north on Main Street roughly 1.15 miles to Carlton Avenue. Head east on Carlton Avenue approximately 600 feet to 2'/2 Street. Proceed north on 2'/2 Street approximately 0.2 mile to Badley Avenue. Proceed east on Badley Avenue roughly 560 feet. The site is located on the north side of Badley Avenue. The location is depicted on site maps included in the Appendix. 2.2 Regional Geology The project site is located within the western Snake River Plain of southwestern Idaho and eastern Oregon. The plain is a northwest trending rift basin, about 45 miles wide and 200 miles long, that developed about 14 million years ago (Ma) and has since been occupied sporadically by large inland lakes. Geologic materials found within and along the plain's margins reflect volcanic and fluvial/lacustrine sedimentary processes that have led to an accumulation of approximately 1 to 2 km of interbedded volcanic and sedimentary deposits within the plain. Along the margins of the plain, streams that drained the highlands to the north and south provided coarse to fine-grained sediments eroded from granitic and volcanic rocks, respectively. About 2 million years ago the last of the lakes was drained and since that time fluvial erosion and deposition has dominated the evolution of the landscape. The project site is underlain by "Sandy Alluvium of Side -Stream Valleys and Gulches" as mapped by Othberg and Stanford (1993). Locally, these deposits are composed of medium to coarse sand interbedded with silty fine sand and silt and are mostly derived from weathered granite and reworked Tertiary sediments of the Boise Foothills. The thickness of this unit is variable. Because of the relative youthfulness of these deposits they contain only minor pedogenic clay and calcium carbonate. 2.3 General Site Characteristics The site to be developed is approximately 3.0 acres in size. Currently, the site exists as an undeveloped lot. Along the northern property boundary, a mobile home development is in place. The remainder of the site is surrounded by existing residential properties and undeveloped land. Based on historical aerial photographs of the site, a ditch used to run across the site from the northwest corner to the southeast corner. Vegetation on the site consists primarily of bunchgrass and other native weeds and grasses. Mature trees are present along the eastern and western property boundaries. The site is relatively flat and level. Regional drainage is north and west toward the Boise River. Stormwater drainage for the site is achieved by percolation through surficial soils. The site is situated so that it is unlikely that it will receive any drainage from off -site sources. Stormwater drainage collection and retention systems are not in place on the project site, but were noted along adjacent roadways in the form of curb, gutter, and drop inlets. Atlas No. 13211738g Page 12 Copyright © 2021 Atlas Technical Consultants 2.4 Regional Site Climatology and Geochemistry According to the Western Regional Climate Center, the average precipitation for the Treasure Valley is on the order of 10 to 12 inches per year, with an annual snowfall of approximately 20 inches and a range from 3 to 49 inches. The monthly mean daily temperatures range from 21 °F to 950F, with daily extremes ranging from roughly -25°F to 111 OF. Winds are generally from the northwest or southeast with an annual average wind speed of approximately 9 miles per hour (mph) and a maximum of 62 mph. Soils and sediments in the area are primarily derived from siliceous materials and exhibit low electro-chemical potential for corrosion of metals or concretes. Local aggregates are generally appropriate for Portland cement and lime cement mixtures. Surface water, groundwater, and soils in the region typically have pH levels ranging from 7.2 to 8.2. 3. SEISMIC SITE EVALUATION 3.1 Geoseismic Setting Soils on site are classed as Site Class D in accordance with Chapter 20 of the American Society of Civil Engineers (ASCE) publication ASCE/SEI 7-16. Structures constructed on this site should be designed per IBC requirements for such a seismic classification. Our investigation did not reveal hazards resulting from potential earthquake motions including: slope instability, liquefaction, and surface rupture caused by faulting or lateral spreading. Incidence and anticipated acceleration of seismic activity in the area is low. 3.2 Seismic Design Parameter Values The United States Geological Survey National Seismic Hazard Maps (2008), includes a peak ground acceleration map. The map for 2% probability of exceedance in 50 years in the Western United States in standard gravity (g) indicates that a peak ground acceleration of 0.198 is appropriate for the project site based on a Site Class D. The following section provides an assessment of the earthquake -induced earthquake loads for the site based on the Risk -Targeted Maximum Considered Earthquake (MCER). The MCER spectral response acceleration for short periods, SMs, and at 1-second period, Smi, are adjusted for site class effects as required by the 2018 IBC. Design spectral response acceleration parameters as presented in the 2018 IBC are defined as a 5% damped design spectral response acceleration at short periods, Sos, and at 1-second period, SDI. The USGS National Seismic Hazards Mapping Project includes a program that provides values for ground motion at a selected site based on the same data that were used to prepare the USGS ground motion maps. The maps were developed using attenuation relationships for soft rock sites; the source model, assumptions, and empirical relationships used in preparation of the maps are described in Petersen and others (1996). Atlas No. B211738g Page 13 Copyright © 2021 Atlas Technical Consultants Table 1 — Seismic Design Values Site Class D "Stiff Soil" Ss 0.291 (g) S1 0.106 (g) Fa 1.567 Fv 2.388 SMs 0.456 SMi 0.253 SDs 0.304 SD1 0.169 4. SOILS EXPLORATION exploration and Sampling Procedures Field exploration conducted to determine engineering characteristics of subsurface materials included a reconnaissance of the project site and investigation by test pit. Test pit sites were located in the field by means of a Global Positioning System (GPS) device and are reportedly accurate to within fifteen feet. Upon completion of investigation, each test pit was backfilled with loose excavated materials. Re -excavation and compaction of these test pit areas are required prior to construction of overlying structures. In addition, samples were obtained from representative soil strata encountered. Samples obtained have been visually classified in the field by professional staff, identified according to test pit number and depth, placed in sealed containers, and transported to our laboratory for additional testing. Subsurface materials have been described in detail on logs provided in the Appendix. Results of field and laboratory tests are also presented in the Appendix. Atlas recommends that these logs not be used to estimate fill material quantities. aboratory Testing Program Along with our field investigation, a supplemental laboratory testing program was conducted to determine additional pertinent engineering characteristics of subsurface materials necessary in an analysis of anticipated behavior of the proposed structures. Laboratory tests were conducted in accordance with current applicable American Society for Testing and Materials (ASTM) specifications, and results of these tests are to be found in the Appendix. The laboratory testing program for this report included: Atterberg Limits Testing — ASTM D4318 and Grain Size Analysis — ASTM C 117/C 136. Atlas No. B211738g Page 14 Copyright © 2021 Atlas Technical Consultants 4.3 Soil and Sediment Profile The profile below represents a generalized interpretation for the project site. Note that on site soils strata, encountered between test pit locations, may vary from the individual soil profiles presented in the logs, which can be found in the Appendix. Silty sand with gravel fill materials were encountered at ground surface within test pit 2. These materials were brown to light brown, dry, and medium dense. Fine to coarse -grained sand, fine to coarse gravel, and 4-inch-minus cobbles were present throughout. Lean clays were encountered beneath surficial fill materials in test pit 2 and at ground surface in test pit 1. These fine-grained soils were brown, dry to slightly moist, and soft to stiff. Fine-grained sand was present throughout. Organic materials were measured to depths of roughly 0.4 foot in test pit 1. Sandy silt soils were observed below lean clay soils in test pit 1. These fine-grained soils were light brown, dry, and hard, with fine-grained sand. Moderate cementation was encountered throughout. At depth, poorly graded gravel with sand sediments were exposed. Poorly graded gravels were light brown to brown, slightly moist to saturated, and medium dense to dense. Fine to coarse - grained sand, fine to coarse gravel, and 8-inch minus cobbles were noted throughout. Trace clay content was noted throughout. Competency of test pit sidewalls varied little across the site. In general, fine grained soils remained stable while more granular sediments readily sloughed. However, moisture contents will also affect wall competency with saturated soils having a tendency to readily slough when under load and unsupported. 4.4 Volatile Organic Scan No environmental concerns were identified prior to commencement of the investigation. Therefore, soils obtained during on -site activities were not assessed for volatile organic compounds by portable photoionization detector. Samples obtained during our exploration activities exhibited no odors or discoloration typically associated with this type of contamination. Groundwater encountered did not exhibit obvious signs of contamination. 5. SITE HYDROLOGY Existing surface drainage conditions are defined in the General Site Characteristics section. Information provided in this section is limited to observations made at the time of the investigation. Either regional or local ordinances may require information beyond the scope of this report. Atlas No. B211738g Page 15 Copyright © 2021 Atlas Technical Consultants 5.1 Groundwater During this field investigation, groundwater was encountered in test pit 1 at a depth of 8.0 feet bgs. Soil moistures in the test pits were generally dry to slightly moist within surficial soils. Within the poorly graded gravels, soil moistures graded from slightly moist to saturated as the water table was approached and penetrated. In the vicinity of the project site, groundwater levels are controlled in large part by residential and commercial irrigation activity and leakage from nearby canals. Maximum groundwater elevations likely occur during the later portion of the irrigation season. Atlas has previously performed 5 geotechnical investigations within 0.25 mile of the project site. Information from these investigations has been provided in the table below. Table 2 — Groundwater Data from Site (7mil7e) 11'I'V (feet .. April 2017 0.10 West 16.3 February 2020 0.21 Northeast Not Encountered to 14.5 July 2015 0.13 Northeast Not Encountered to 7.9 April 2021 0.20 Southwest Not Encountered to 12.0 September 2010 0.26 Southwest 15.6 Furthermore, according to United States Geological Survey (USGS) monitoring well data within approximately'/2-mile of the project site, groundwater was measured at depths ranging between 7 and 13 feet bgs, which equates to groundwater elevations of 2,585 to 2,591 feet above mean sea level (msl). For construction purposes, groundwater depth can be assumed to remain greater than 7 feet bgs throughout the year. Since this is an estimated depth and seasonal groundwater levels fluctuate, actual levels should be confirmed by periodic groundwater data collected from the piezometer installed in test pit 1. If desired, Atlas is available to perform this monitoring. ;oil Infiltration Rates Soil permeability, which is a measure of the ability of a soil to transmit a fluid, was tested in the field. For this report, an estimation of infiltration is also presented using generally recognized values for each soil type and gradation. Of soils comprising the generalized soil profile for this study, lean clay soils generally offer little permeability, with typical hydraulic infiltration rates of less than 2 inches per hour. Sandy silt soils will commonly exhibit infiltration rates from 2 to 4 inches per hour; though calcium carbonate cementation may reduce this value to near zero. Poorly graded sand and gravel sediments typically exhibit infiltration values in excess of 12 inches per hour; though the presence of trace clay content may reduce these values. Atlas No. B211738g Page 16 Copyright © 2021 Atlas Technical Consultants 5.3 Infiltration Testing Infiltration testing was conducted in general accordance with the Ada County Highway District (ACHD) Policy Manual. The test pit area will need to be re -excavated and compacted prior to construction of structures that will be sensitive to settlement. The test location was presoaked prior to testing. Pre-soaking increases soil moistures, which allows the tested soils to reach a saturated condition more readily during testing. Saturation of the tested soils is desirable in order to isolate the vertical component of infiltration by inhibiting horizontal seepage during testing. On June 24, 2021, testing was conducted within poorly graded gravel with sand sediments at a depth of 5.0 feet bgs in test pit 2. A stabilized infiltration rate of 5.64 inches per hour was achieved during testing. Per the ACHD Policy Manual, a safety factor of 2 must be applied to tested infiltration rates less than 8 inches per hour. Atlas recommends that all infiltration facilities be constructed in accordance with the local municipality requirements. FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS Various foundation types have been considered for support of the proposed structures. Two requirements must be met in the design of foundations. First, the applied bearing stress must be less than the ultimate bearing capacity of foundation soils to maintain stability. Second, total and differential settlement must not exceed an amount that will produce an adverse behavior of the superstructure. Allowable settlement is usually exceeded before bearing capacity considerations become important; thus, allowable bearing pressure is normally controlled by settlement considerations. Considering subsurface conditions and the proposed construction, it is recommended that the structures be founded upon conventional spread footings and continuous wall footings. Total settlements should not exceed 1 inch if the following design and construction recommendations are observed. -oundation Design Recommendations Based on data obtained from the site and test results from various laboratory tests performed, Atlas recommends the following guidelines for the net allowable soil bearing capacity: Atlas No. 13211738g Page 17 Copyright © 2021 Atlas Technical Consultants Table 3 — Soil Bearing Capacity •• • • • • Depth Footings must bear on competent, undisturbed, 1,500 Ibs/ft' native lean clay soils or compacted structural fill. Not Required for Native , Existing fill materials and organics must be Soil A /3 increase is allowable completely removed from below foundation for short-term loading, elements.' Excavation depths ranging from roughly 95/o o for Structural Fill which is defined by 0.4 to 1.5 feet bgs should be anticipated to expose seismic events or proper bearing soils.' designed wind speeds. 'It will be required for Atlas personnel to verify the bearing soil suitability for each structure at the time of construction. 2Depending on the time of year construction takes place, the subgrade soils may be unstable because of high moisture contents. If unstable conditions are encountered, over -excavation and replacement with granular structural fill and/or use of geotextiles may be required. The following sliding frictional coefficient values should be used: 1) 0.35 for footings bearing on native lean clay soils and 2) 0.45 for footings bearing on granular structural fill. A passive lateral earth pressure of 300 pounds per square foot per foot (psf/ft) should be used for lean clay soils. For compacted sandy gravel fill, a passive lateral earth pressure of 496 psf/ft should be used. Footings should be proportioned to meet either the stated soil bearing capacity or the 2018 IBC minimum requirements. Total settlement should be limited to approximately 1 inch, and differential settlement should be limited to approximately '/2 inch. Objectionable soil types encountered at the bottom of footing excavations should be removed and replaced with structural fill. Excessively loose or soft areas that are encountered in the footings subgrade will require over -excavation and backfilling with structural fill. To minimize the effects of slight differential movement that may occur because of variations in the character of supporting soils and seasonal moisture content, Atlas recommends continuous footings be suitably reinforced to make them as rigid as possible. For frost protection, the bottom of external footings should be 24 inches below finished grade. 6.2 Floor, Patio, and Garage Slab -on -Grade Uncontrolled fill was encountered in the vicinity of test pit 2. Atlas recommends that these fill materials be completely removed below existing grade. The excavated fill materials can be replaced in accordance with the Structural Fill section provided that all organic material and/or debris is completely removed. Once final grades have been determined, Atlas is available to provide additional recommendations. Organic, loose, or obviously compressive materials must be removed prior to placement of concrete floors or floor -supporting fill. In addition, the remaining subgrade should be treated in accordance with guidelines presented in the Earthwork section. Areas of excessive yielding should be excavated and backfilled with structural fill. Fill used to increase the elevation of the floor slab should meet requirements detailed in the Structural Fill section. Fill materials must be compacted to a minimum 95 percent of the maximum dry density as determined by ASTM D1557. Atlas No. 13211738g Page 18 Copyright © 2021 Atlas Technical Consultants A free -draining granular mat should be provided below slabs -on -grade to provide drainage and a uniform and stable bearing surface. This should be a minimum of 4 inches in thickness and properly compacted. The mat should consist of a sand and gravel mixture, complying with Idaho Standards for Public Works Construction (ISPWC) specifications for 3/4-inch (Type 1) crushed aggregate. The granular mat should be compacted to no less than 95 percent of the maximum dry density as determined by ASTM D1557. A moisture -retarder should be placed beneath floor slabs to minimize potential ground moisture effects on moisture -sensitive floor coverings. The moisture -retarder should be at least 15-mil in thickness and have a permeance of less than 0.01 US perms as determined by ASTM E96. Placement of the moisture -retarder will require special consideration with regard to effects on the slab -on -grade and should adhere to recommendations outlined in the ACI 302.1 R and ASTM E1745 publications. Upon request, Atlas can provide further consultation regarding installation. 7. PAVEMENT DISCUSSION AND RECOMMENDATIONS As required by Ada County Highway District (ACHD), Atlas has used traffic indexes of 6 and 8 to determine the necessary pavement cross-section for the site. Atlas has made assumptions for traffic loading variables based on the character of the proposed construction. The Client should review these assumptions to make sure they reflect intended use and loading of pavements both now and in the future. Based on experience with soils in the region, a subgrade Resistance Value (R-value) of 7 has been assumed for near -surface lean clay soils on site. The following are minimum thickness requirements for assured pavement function. Depending on site conditions, additional work, e.g. soil preparation, may be required to support construction equipment. These have been listed within the Soft Subgrade Soils section. 7.1 Flexible Pavement Sections The Gravel Equivalent Method, as defined in Section 500 of the State of Idaho Department of Transportation (ITD) Materials Manual, was used to develop the pavement sections. ACHD parameters for traffic index and substitution ratios, which were obtained from the ACHD Policy Manual, were also used in the design. Calculation sheets provided in the Appendix indicate the soils constant, traffic loading, traffic projections, and material constants used to calculate the pavement sections. Atlas recommends that materials used in the construction of asphaltic concrete pavements meet the requirements of the ISPWC Standard Specification for Highway Construction. Construction of the pavement section should be in accordance with these specifications and should adhere to guidelines recommended in the section on Construction Considerations. Atlas No. 13211738g Page 19 Copyright © 2021 Atlas Technical Consultants Table 4 - Gravel Equivalent Method Flexible Pavement Specifications Pavement Section Component Asphaltic Concrete Residential Roadway94rw 2.5 Inches Collector Roadways-4 3.5 Inches Crushed Aggregate Base 4.0 Inches 8.0 Inches Structural Subbase 14.0 Inches 14.0 Inches Compacted Subgrade See Pavement Subgrade Preparation Section See Pavement Subgrade Preparation Section 'It will be required for Atlas personnel to verify subgrade competency at the time of construction. Asphaltic Concrete: Asphalt mix design shall meet the requirements of ISPWC, Section 810 Class III plant mix. Materials shall be placed in accordance with ISPWC Standard Specifications for Highway Construction. Aggregate Base: Material complying with ISPWC Standards for Crushed Aggregate Materials. Structural Subbase: Granular structural fill material complying with the requirements detailed in the Structural Fill section of this report except that the maximum material diameter is no more than 2/3 the component thickness. Gradation and suitability requirements shall be per ISPWC Section 801, Table 1. ' 9 Pavement Subgrade Preparation Uncontrolled fill was encountered in the vicinity of test pit 2. Atlas recommends that these fill materials be completely removed below existing grade. The excavated fill materials can be replaced in accordance with the Structural Fill section provided that all organic material and/or debris is completely removed. However, the existing fill materials are not suitable for use as either the base or subbase components of the recommended pavement section. Once final grades have been determined, Atlas is available to provide additional recommendations. '.3 Common Pavement Section Construction Issues The subgrade upon which above pavement sections are to be constructed must be properly stripped, inspected, and proof -rolled. Proof rolling of subgrade soils should be accomplished using a heavy rubber -tired, fully loaded, tandem -axle dump truck or equivalent. Verification of subgrade competence by Atlas personnel at the time of construction is required. Fill materials on the site must demonstrate the indicated compaction prior to placing material in support of the pavement section. Atlas anticipated that pavement areas will be subjected to moderate traffic. Subarade clavev and siltv soils near and above optimum moisture contents may Dumb durina compaction. Pumping or soft areas must be removed and replaced with structural fill. Atlas No. B211738g Page I10 Copyright © 2021 Atlas Technical Consultants Fill material and aggregates in support of the pavement section must be compacted to no less than 95 percent of the maximum dry density as determined by ASTM D698 for flexible pavements and by ASTM D1557 for rigid pavements. If a material placed as a pavement section component cannot be tested by usual compaction testing methods, then compaction of that material must be approved by observed proof rolling. Minor deflections from proof rolling for flexible pavements are allowable. Deflections from proof rolling of rigid pavement support courses should not be visually detectable. Atlas recommends that rigid concrete pavement be provided for heavy garbage receptacles. This will eliminate damage caused by the considerable loading transferred through the small steel wheels onto asphaltic concrete. Rigid concrete pavement should consist of Portland Cement Concrete Pavement (PCCP) generally adhering to ITD specifications for Urban Concrete. PCCP should be 6 inches thick on a 4-inch drainage fill course (see Floor Slab -on -Grade section), and should be reinforced with welded wire fabric. Control joints must be on 12-foot centers or less. CONSTRUCTION CONSIDERATIONS Recommendations in this report are based upon structural elements of the project being founded on competent, native lean clay soils or compacted structural fill. Structural areas should be stripped to an elevation that exposes these soil types. Earthwork Excessively organic soils, deleterious materials, or disturbed soils generally undergo high volume changes when subjected to loads, which is detrimental to subgrade behavior in the area of pavements, floor slabs, structural fills, and foundations. It is recommended that organic or disturbed soils, if encountered, be removed to depths of 1 foot (minimum), and wasted or stockpiled for later use. However, in areas where trees are/were present, deeper excavation depths should be anticipated. Stripping depths should be adjusted in the field to assure that the entire root zone or disturbed zone or topsoil are removed prior to placement and compaction of structural fill materials. Exact removal depths should be determined during grading operations by Atlas personnel, and should be based upon subgrade soil type, composition, and firmness or soil stability. If underground storage tanks, underground utilities, wells, or septic systems are discovered during construction activities, they must be decommissioned then removed or abandoned in accordance with governing Federal, State, and local agencies. Excavations developed as the result of such removal must be backfilled with structural fill materials as defined in the Structural Fill section. Atlas No. B211738g Page 111 Copyright © 2021 Atlas Technical Consultants Atlas should oversee subgrade conditions (i.e., moisture content) as well as placement and compaction of new fill (if required) after native soils are excavated to design grade. Recommendations for structural fill presented in this report can be used to minimize volume changes and differential settlements that are detrimental to the behavior of footings, pavements, and floor slabs. Sufficient density tests should be performed to properly monitor compaction. For structural fill beneath building structures, one in -place density test per lift for every 5,000 square feet is recommended. In parking and driveway areas, this can be decreased to one test per lift for every 10,000 square feet. 8.2 Dry Weather If construction is to be conducted during dry seasonal conditions, many problems associated with soft soils may be avoided. However, some rutting of subgrade soils may be induced by shallow groundwater conditions related to springtime runoff or irrigation activities during late summer through early fall. Solutions to problems associated with soft subgrade soils are outlined in the Soft Subgrade Soils section. Problems may also arise because of lack of moisture in native and fill soils at time of placement. This will require the addition of water to achieve near -optimum moisture levels. Low -cohesion soils exposed in excavations may become friable, increasing chances of sloughing or caving. Measures to control excessive dust should be considered as part of the overall health and safety management plan. 8.3 Wet Weather If construction is to be conducted during wet seasonal conditions (commonly from mid -November through May), problems associated with soft soils must be considered as part of the construction plan. During this time of year, fine-grained soils such as silts and clays will become unstable with increased moisture content, and eventually deform or rut. Additionally, constant low temperatures reduce the possibility of drying soils to near optimum conditions. 8.4 Soft Subgrade Soils Shallow fine-grained subgrade soils that are high in moisture content should be expected to pump and rut under construction traffic. During periods of wet weather, construction may become very difficult if not impossible. The following recommendations and options have been included for dealing with soft subgrade conditions: • Track -mounted vehicles should be used to strip the subgrade of root matter and other deleterious debris. Heavy rubber -tired equipment should be prohibited from operating directly on the native subgrade and areas in which structural fill materials have been placed. Construction traffic should be restricted to designated roadways that do not cross, or cross on a limited basis, proposed roadway or parking areas. • Soft areas can be over -excavated and replaced with granular structural fill. Atlas No. B211738g Page 112 Copyright © 2021 Atlas Technical Consultants • Construction roadways on soft subgrade soils should consist of a minimum 2-foot thickness of large cobbles of 4 to 6 inches in diameter with sufficient sand and fines to fill voids. Construction entrances should consist of a 6-inch thickness of clean, 2-inch minimum, angular drain -rock and must be a minimum of 10 feet wide and 30 to 50 feet long. During the construction process, top dressing of the entrance may be required for maintenance. • Scarification and aeration of subgrade soils can be employed to reduce the moisture content of wet subgrade soils. After stripping is complete, the exposed subgrade should be ripped or disked to a depth of 1'/z feet and allowed to air dry for 2 to 4 weeks. Further disking should be performed on a weekly basis to aid the aeration process. • Alternative soil stabilization methods include use of geotextiles, lime, and cement stabilization. Atlas is available to provide recommendations and guidelines at your request. 8.5 Frozen Subgrade Soils Prior to placement of structural fill materials or foundation elements, frozen subgrade soils must either be allowed to thaw or be stripped to depths that expose non -frozen soils and wasted or stockpiled for later use. Stockpiled materials must be allowed to thaw and return to near -optimal conditions prior to use as structural fill. The onsite, shallow clayey and silty soils are susceptible to frost heave during freezing temperatures. For exterior flatwork and other structural elements, adequate drainage away from subgrades is critical. Compaction and use of structural fill will also help to mitigate the potential for frost heave. Complete removal of frost susceptible soils for the full frost depth, followed by replacement with a non -frost susceptible structural fill, can also be used to mitigate the potential for frost heave. Atlas is available to provide further guidance/assistance upon request. 8.6 Structural Fill Soils recommended for use as structural fill are those classified as GW, GP, SW, and SP in accordance with the Unified Soil Classification System (USCS) (ASTM D2487). Use of silty soils (USCS designation of GM, SM, and ML) as structural fill may be acceptable. However, use of silty soils (GM, SM, and ML) as structural fill below footings is prohibited. These materials require very high moisture contents for compaction and require a long time to dry out if natural moisture contents are too high and may also be susceptible to frost heave under certain conditions. Therefore, these materials can be quite difficult to work with as moisture content, lift thickness, and compactive effort becomes difficult to control. If silty soil is used for structural fill, lift thicknesses should not exceed 6 inches (loose), and fill material moisture must be closely monitored at both the working elevation and the elevations of materials already placed. Following placement, silty soils must be protected from degradation resulting from construction traffic or subsequent construction. Atlas No. B211738g Page113 Copyright © 2021 Atlas Technical Consultants Recommended granular structural fill materials, those classified as GW, GP, SW, and SP, should consist of a 6-inch minus select, clean, granular soil with no more than 50 percent oversize (greater than 3/4-inch) material and no more than 12 percent fines (passing No. 200 sieve). These fill materials should be placed in layers not to exceed 12 inches in loose thickness. Prior to placement of structural fill materials, surfaces must be prepared as outlined in the Construction Considerations section. Structural fill material should be moisture -conditioned to achieve optimum moisture content prior to compaction. For structural fill below footings, areas of compacted backfill must extend outside the perimeter of the footings for a distance equal to the thickness of fill between the bottom of foundation and underlying soils, or 5 feet, whichever is less. All fill materials must be monitored during placement and tested to confirm compaction requirements, outlined below, have been achieved. Each layer of structural fill must be compacted, as outlined below: • Below Structures and Rigid Pavements: A minimum of 95 percent of the maximum dry density as determined by ASTM D1557. • Below Flexible Pavements: A minimum of 92 percent of the maximum dry density as determined by ASTM D1557 or 95 percent of the maximum dry density as determined by ASTM D698. The ASTM D1557 test method must be used for samples containing up to 40 percent oversize (greater than 3/4-inch) particles. If material contains more than 40 percent but less than 50 percent oversize particles, compaction of fill must be confirmed by proof rolling each lift with a 10-ton vibratory roller (or equivalent) until the maximum density has been achieved. Density testing must be performed after each proof rolling pass until the in -place density test results indicate a drop (or no increase) in the dry density, defined as maximum density or "break over" point. The number of required passes should be used as the requirements on the remainder of fill placement. Material should contain sufficient fines to fill void spaces, and must not contain more than 50 percent oversize particles. 8.7 Backfill of Walls Backfill materials must conform to the requirements of structural fill, as defined in this report. For wall heights greater than 2.5 feet, the maximum material size should not exceed 4 inches in diameter. Placing oversized material against rigid surfaces interferes with proper compaction, and can induce excessive point loads on walls. Backfill shall not commence until the wall has gained sufficient strength to resist placement and compaction forces. Further, retaining walls above 2.5 feet in height shall be backfilled in a manner that will limit the potential for damage from compaction methods and/or equipment. It is recommended that only small hand -operated compaction equipment be used for compaction of backfill within a horizontal distance equal to the height of the wall, measured from the back face of the wall. Backfill should be compacted in accordance with the specifications for structural fill, except in those areas where it is determined that future settlement is not a concern, such as planter areas. In nonstructural areas, backfill must be compacted to a firm and unyielding condition. Atlas No. 13211738g Page 114 Copyright © 2021 Atlas Technical Consultants 8.8 Excavations Shallow excavations that do not exceed 4 feet in depth may be constructed with side slopes approaching vertical. Below this depth, it is recommended that slopes be constructed in accordance with Occupational Safety and Health Administration (OSHA) regulations, Section 1926, Subpart P. Based on these regulations, on -site soils are classified as type "C" soil, and as such, excavations within these soils should be constructed at a maximum slope of 11/2 feet horizontal to 1 foot vertical (11/2:1) for excavations up to 20 feet in height. Excavations in excess of 20 feet will require additional analysis. Note that these slope angles are considered stable for short-term conditions only. and will not be stable for Iona -term conditions. During the subsurface exploration, test pit sidewalls generally exhibited little indication of collapse; however, sloughing of fill materials and native granular sediments from test pit sidewalls was observed, particularly after penetration of the water table. For deep excavations, native granular sediments cannot be expected to remain in position. These materials are prone to failure and may collapse, thereby undermining upper soil layers. This is especially true when excavations approach depths near the water table. Care must be taken to ensure that excavations are properly backfilled in accordance with procedures outlined in this report. 8.9 Groundwater Control Groundwater was encountered during the investigation but is anticipated to be below the depth of most construction. Excavations below the water table will require a dewatering program. Dewatering will be required prior to placement of fill materials. Placement of concrete can be accomplished through water by the use of a treme. It may be possible to discharge dewatering effluent to remote portions of the site, to a sump, or to a pit. This will essentially recycle effluent, thus eliminating the need to enter into agreements with local drainage authorities. Should the scope of the proposed project change, Atlas should be contacted to provide more detailed groundwater control measures. Special precautions may be required for control of surface runoff and subsurface seepage. It is recommended that runoff be directed away from open excavations. Silty and clayey soils may become soft and pump if subjected to excessive traffic during time of surface runoff. Ponded water in construction areas should be drained through methods such as trenching, sloping, crowning grades, nightly smooth drum rolling, or installing a French drain system. Additionally, temporary or permanent driveway sections should be constructed if extended wet weather is forecasted. Atlas No. 13211738g Page 115 Copyright © 2021 Atlas Technical Consultants 9. GENERAL COMMENTS Based on the subsurface conditions encountered during this investigation and available information regarding the proposed structures the site is adequate for the planned construction. When plans and specifications are complete, and if significant changes are made in the character or location of the proposed structures, consultation with Atlas must be arranged as supplementary recommendations may be required. Suitability of subgrade soils and compaction of structural fill materials must be verified by Atlas personnel prior to placement of structural elements. Additionally, monitoring and testing should be performed to verify that suitable materials are used for structural fill and that proper placement and compaction techniques are utilized. Atlas No. 13211738g Page 116 Copyright © 2021 Atlas Technical Consultants 10. REFERENCES Ada County Highway District (ACHD) (2017). Ada County Highway District Policy Manual (August 2017). [Online] Available: <http://www.achdidaho.org/AboutACHD/PolicyManual.aspx> (2021). American Concrete Institute (ACI) (2015). Guide for Concrete Floor and Slab Construction: ACI 302.1 R. Farmington Hills, MI: ACI. American Society of Civil Engineers (2021). ASCE 7 Hazards Tool: Web Interface [Online] Available: <https:Hasce7hazardtool.online/> (2021). American Society of Civil Engineers (ASCE) (2013). Minimum Design Loads for Buildings and Other Structures: ASCE/SEI 7-16. Reston, VA: ASCE. American Society for Testing and Materials (ASTM) (2017). Standard Test Method for Materials Finer than 75-um (No. 200) Sieve in Mineral Aggregates by Washing: ASTM C117. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2014). Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates: ASTM C136. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2012). Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort: ASTM D698. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2012). Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort: ASTM D1557. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2017). Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System): ASTM D2487. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2017). Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils: ASTM D4318. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2011). Standard Specification for Plastic Water Vapor Retarders Used in Contact with Soil or Granular Fill Under Concrete Slabs: ASTM E1745. West Conshohocken, PA: ASTM. Desert Research Institute. Western Regional Climate Center. [Online] Available: <http://www.wrcc.dri.edu/> (2021). International Building Code Council (2018). International Building Code, 2018. Country Club Hills, IL: Author. Local Highway Technical Assistance Council (LHTAC) (2017). Idaho Standards for Public Works Construction, 2017. Boise, ID: Author. Othberg, K. L. and Stanford, L. A., Idaho Geologic Society (1993). Geologic Map of the Boise Valley and Adloining Area, Western Snake River Plain, Idaho. (scale 1:100,000). Boise, ID: Joslyn and Morris. U.S. Department of Labor, Occupational Safety and Health Administration. CFR 29, Part 1926, Subpart P: Safety and Health Regulations for Construction, Excavations (1986). [Online] Available: <www.osha.gov> (2021). Atlas No. 13211738g Page 117 Copyright © 2021 Atlas Technical Consultants U.S. Geological Survey (2021). National Water Information System: Web Interface. [Online] Available: <http://waterdata.usgs.gov/nwis> (2021). Atlas No. B211738g Page 118 Copyright © 2021 Atlas Technical Consultants Appendix I WARRANTY AND LIMITING CONDITIONS Atlas warrants that findings and conclusions contained herein have been formulated in accordance with generally accepted professional engineering practice in the fields of foundation engineering, soil mechanics, and engineering geology only for the site and project described in this report. These engineering methods have been developed to provide the client with information regarding apparent or potential engineering conditions relating to the site within the scope cited above and are necessarily limited to conditions observed at the time of the site visit and research. Field observations and research reported herein are considered sufficient in detail and scope to form a reasonable basis for the purposes cited above. Exclusive Use This report was prepared for exclusive use of the property owner(s), at the time of the report, and their retained design consultants ("Client"). Conclusions and recommendations presented in this report are based on the agreed -upon scope of work outlined in this report together with the Contract for Professional Services between the Client and Atlas Technical Consultants ("Consultant"). Use or misuse of this report, or reliance upon findings hereof, by parties other than the Client is at their own risk. Neither Client nor Consultant make representation of warranty to such other parties as to accuracy or completeness of this report or suitability of its use by such other parties for purposes whatsoever, known or unknown, to Client or Consultant. Neither Client nor Consultant shall have liability to indemnify or hold harmless third parties for losses incurred by actual or purported use or misuse of this report. No other warranties are implied or expressed. Report Recommendations are Limited and Subject to Misinterpretation There is a distinct possibility that conditions may exist that could not be identified within the scope of the investigation or that were not apparent during our site investigation. Findings of this report are limited to data collected from noted explorations advanced and do not account for unidentified fill zones, unsuitable soil types or conditions, and variability in soil moisture and groundwater conditions. To avoid possible misinterpretations of findings, conclusions, and implications of this report, Atlas should be retained to explain the report contents to other design professionals as well as construction professionals. Since actual subsurface conditions on the site can only be verified by earthwork, note that construction recommendations are based on general assumptions from selective observations and selective field exploratory sampling. Upon commencement of construction, such conditions may be identified that require corrective actions, and these required corrective actions may impact the project budget. Therefore, construction recommendations in this report should be considered preliminary, and Atlas should be retained to observe actual subsurface conditions during earthwork construction activities to provide additional construction recommendations as needed. Atlas No. B211738g Page 119 Copyright © 2021 Atlas Technical Consultants Since geotechnical reports are subject to misinterpretation, do not separate the soil logs from the report. Rather, provide a copy of, or authorize for their use, the complete report to other design professionals or contractors. Locations of exploratory sites referenced within this report should be considered approximate locations only. For more accurate locations, services of a professional land surveyor are recommended. This report is also limited to information available at the time it was prepared. In the event additional information is provided to Atlas following publication of our report, it will be forwarded to the client for evaluation in the form received. Environmental Concerns Comments in this report concerning either onsite conditions or observations, including soil appearances and odors, are provided as general information. These comments are not intended to describe, quantify, or evaluate environmental concerns or situations. Since personnel, skills, procedures, standards, and equipment differ, a geotechnical investigation report is not intended to substitute for a geoenvironmental investigation or a Phase II/III Environmental Site Assessment. If environmental services are needed, Atlas can provide, via a separate contract, those personnel who are trained to investigate and delineate soil and water contamination. Atlas No. B211738g Page 120 Copyright © 2021 Atlas Technical Consultants Vicinity Map Figure 1 m M "�' c3' z < z Z ^' Un F- z �> O- x z z z � MAP NOTES: A J z At m 3 c oo m =1 a _ v oz I z F �"'/ • Delorme Street Atlas O z = 0D m l�? X 3 3 w @9 O m - { 3 E OAKCREST DR 04,i z • Not to Scale 3� p ¢ 'P� z Z F M- a E CLARENE ST- `rT m z v z 17 mD O n <z 3 N RADIAL CT o z m w OQ m v Q p0 Z Z F w HICKORY ry W YOST CT 3 a C U N r W AY - In�� z m 3 > LEGEND W-CHERRY LN = ' SR 55 HWY SR 55_HWY _ c Q SR 55 HWY ��. a E_FAIRVIEW AVE - - --� —�z Approximate Site T ?_ Site Location' z Location NPf Z. V„ o — _ E.)EW.EL ST w m INU PL = m x Q _ 41 �� 1 U1 N v w i z� -4� v m Q F O Z v to _ a r k1Z G2� z—Ln ¢ G E WASHINGTON AVE m p Z n� N /V M p 2 O —� W CARLTON AVE z ° T �� = FF s m V) w to > W STATE AVE F- N RSB�R - N v 20 < Meridian = w Gpygr im Inn!C w a ~ v .. W > rn LLj �LU t-__F N > W IDAHO AVE ;13in w Z��_ N I BROgpwAraVE E COMMERCIAL AVE �= co=- E COMMERClA� 3 3 a z f E BOWER ST*'+++' .,...-... z - ER .r z E ADA AVE m z O LANARK ST :E r- Un E KING ST D - E KING ST = r 70 .�. v r o)L__ WILLIAMS AVE -4 n U' z_= �^a-� - E-FRANKLIN-RO _ v E FRANKLIN RD E_FRANKLIN-RD_ a� r'' Qp _ F w N, v' y n E SPRINGWOOD DR I = •�il� yW D' Ov V1Un Q I N - - v' n �O 2' < n_ v �° Z to r O h N m A z i 2 I —_ I tP m Un A VI O { z v < _ a PENNWOOD ST r+, E WATERTOWER LN p_ 9 m �' O < r } > m C W 7o m m ut P < p < z Q r `^ 8 v-43 p O�if` L D � Elm Grove Cottages 6' E CORPORATE DR cD C m < m ,4 ,� G w _ ,n< z � n, 405 East Farview Avenue m '^'" m �� > Meridian, ID D Z = WALTMAN LN .i Py D r p min > p m Pc >z �� E CENTRAL DR __ �,, m— Modified from DeLorme by: GJM )r' >0 �� J� p WELLS CIR June 25, 2021 W VERBENA DR M0 z� 1�� eo Drawing: B211738g a 30 30 55 3c 0 55 m 0 O v _ 3 O Q E OVERLAND RD IM p 2791 S. Victory View Way Phone: (208) 376-4748 Z X E_ O_VERLAND RD -Fq - _ �_ -E SHEPHERD ST F Boise, ID 83709 Fax: (208) 322-6515 Web: oneatlas.com z J Site Map Figure 2 - ®NOTES: N •Not to Scale 7 L • M 7 - LEGEND Approximate Area of Work 3 W-1 3:� 13 \ Approximate Atlas Test 8 \ Pit Location --j Approximate Atlas Test Pit Location iy ` with Piezometer ® 24*-0" LIM ■w� P4 �� N1I■ rig w °C f w tr U) P-0 Of M 1 Q ® ® � PO ww� .rr -r• W was n. � wrsw� Elm Grove Cottages .... �... 405 East Farview Avenue Meridian, ID TP-2 Modified by: GJM I M e R+ June 25, 2021 Drawing: B2117389 L-i Er - 2791 S. Victory View Way Phone: (208) 376-4748 U� BADLEY AVENUE— Boise, ID 83709 Fax: (208) 322-6515 Web: oneatlas.com Appendix IV GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-1 Date Advanced: June 22, 2021 Excavated by: Turn of the Century Homes Logged by: Bryar Jensen Latitude: 43.617286 Longitude:-116.387719 Depth to Water Table: 8.0 feet bgs Total Depth: 9.5 feet bgs Depth• •Sample eL(feet• .• • •• Lean Clay (CL): Brown, dry to slightly moist, 0.0-4.2 medium stiff to stiff, with fine-grained sand. 0.75-1.5 --Organics encountered to a depth of 0.4 foot bgs. Sandy Silt (ML): Light brown, dry, hard, with 4.2-7.4 fine to coarse -grained sand. --Moderate cementation encountered throughout. Poorly Graded Gravel with Sand (GP): Light brown, slightly moist to saturated, medium 7.4-9.5 dense, with fine to coarse -grained sand, fine to coarse gravel, and 8-inch-minus cobbles. --Trace clay content noted throughout. Notes: See Site Map for test pit location. Piezometer installed to a depth of 9.5 feet bgs. Atlas No. B211738g Page 123 Copyright © 2021 Atlas Technical Consultants GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-2 Latitude: 43.616796 Date Advanced: June 22, 2021 Longitude:-116.387136 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Bryar Jensen Total Depth: 5.0 feet bgs ep IRIell7dDescription ret and USCS Soil andIM 7 Sample Depth e. Lab bgs) Test ID Silty Sand with Gravel Fill (SM-FILL): Brown to 0.0-1.5 light brown, dry, medium dense, with fine to coarse -grained sand, fine to coarse gravel, and 4-inch-minus cobbles. 1.5-4.5 Lean Clay (CL): Brown, dry to slightly moist, GS 1.5-2.0 0.5-1.0 A soft to stiff, with fine-grained sand. Poorly Graded Gravel with Sand (GP): Light brown to brown, slightly moist, medium dense 4.5-5.0 to dense, with fine to coarse -grained sand, fine to coarse gravel, and 6-inch-minus cobbles. --Trace clay content noted throughout. Notes: See Site Map for test pit location. Infiltration testing conducted at a depth of 5.0 feet bgs. Atlas No. B211738g Page 124 Copyright © 2021 Atlas Technical Consultants Appendix V GEOTECHNICAL GENERAL NOTES Major Divisions Unified Soil Classification Symbol Soil Descriptions Coarse- Grained Soils < Gravel & Gravelly Soils < 50% coarse GW Well -graded gravels; gravel/sand mixtures with little or no fines GP Poorly -graded gravels; gravel/sand mixtures with little or no fines GM Silty gravels; poorly -graded gravel/sand/silt mixtures GC Clayey ravels; poor) raded gravel/sand/clay mixtures Y Y g Y-9 9 Y 50% passes No.200 sieve Sand & Sandy Soils > 50% coarse fraction SW Well -graded sands; gravelly sands with little or no fines SP Poorly -graded sands; gravelly sands with little or no fines SM Silty sands; poorly -graded sand/gravel/silt mixtures SC Clayey sands; poorly -graded sand/gravel/clay mixtures Fine- Grained Soils > 50% Silts & Clays LL < 50 ML Inorganic silts; sandy, gravelly or clayey silts CL Lean clays; inorganic, gravelly, sandy, or silty, low to medium - plasticity clays OL Organic, low -plasticity clays and silts passes No.200 sieve Silts & Clays LL > 50 MH Inorganic, elastic silts; sandy, gravelly or clayey elastic silts CH Fat clays; high -plasticity, inorganic clays OH Organic, medium to high -plasticity clays and silts Highly Organic Soils PT Peat, humus, hydric soils with high organic content tive Density and Consistency Coarse -Grained Soils SPT Blow Counts (N) Very Loose: < 4 Loose: 4-10 Medium Dense: 10-30 Dense: 30-50 Very Dense: > 50 Fine -Grained Soils SPT Blow Counts (N) Very Soft: < 2 Soft: 2-4 Medium Stiff: 4-8 Stiff: 8-15 Very Stiff: 15-30 Hard: > 30 Particle Boulders: Size > 12 in. Cobbles: 12 to 3 in. Gravel: 3 in. to 5 mm Coarse -Grained Sand: 5 to 0.6 mm Medium -Grained Sand: 0.6 to 0.2 mm Fine -Grained Sand: 0.2 to 0.075 mm Silts: 0.075 to 0.005 mm Clays: < 0.005 mm ik Moisture Description Content and Cementation Field Test Dry Absence of moisture, dry to touch Slightly Moist Damp, but no visible moisture Moist Visible moisture Wet Visible free water Saturated Soil is usually below water table Description Field Test Weak Crumbles or breaks with handling or slight finger pressure Moderate Crumbles or breaks with considerable finger pressure Strong Will not crumble or break with finger pressure GS Acronym grab sample LL Liquid Limit M moisture content NP non -plastic PI Plasticity Index Qp penetrometer value, unconfined compressive strength, tsf V vane value, ultimate shearing strength, tsf Atlas No. B211738g Page 125 Copyright © 2021 Atlas Technical Consultants Appendix VI GRAVEL EQUIVALENT METHOD PAVEMENT DESIGN Pavement Section Design Location: Elm Grove Cottages Residential Roadways Average Daily Traffic Count: All Lanes & Both Directions Design Life: 20 Years Traffic Index: 6.00 Climate Factor: 1 R-Value of Subgrade: 7.00 Subgrade CBR Value: 3 Subgrade Mr: 4,500 R-Value of Aggregate Base: 80 R-Value of Granular Borrow: 60 Subgrade R-Value: 7 Expansion Pressure of Subgrade: 1.40 Unit Weight of Base Materials: 130 Total Design Life 18 kip ESAL's: 33,131 ASPHALTIC CONCRETE: Gravel Equivalent, Calculated: 0.384 Thickness: 0.19692308 Gravel Equivalent, ACTUAL: 0.41 CRUSHED AGGREGATE BASE: Gravel Equivalent (Ballast): 0.768 Thickness: 0.329 Gravel Equivalent, ACTUAL: 0.773 SUBBASE: Gravel Equivalent (Ballast): 1.786 Thickness: 1.013 Gravel Equivalent, ACTUAL: 1.940 TOTAL Thickness: 1.708 Thickness Required by Exp. Pressure: 1.551 Design ACHD Depth Substitution Inches Ratios Asphaltic Concrete (at least 2.5): 2.50 1.95 Asphalt Treated Base (at least 4.2): 0.00 Cement Treated Base (at least 4.2): 0.00 Crushed Aggregate Base (at least 4.2): 4.00 1.10 Subbase (at least 4.2): 14.00 1.00 Use = 2.5 Inches Use = 4 Inches Use = 14 Inches Atlas No. B211738g Page 126 Copyright © 2021 Atlas Technical Consultants GRAVEL EQUIVALENT METHOD PAVEMENT DESIGN Pavement Section Design Location: Elm Grove Cottages, Collector Roadways Average Daily Traffic Count: All Lanes & Both Directions Design Life: 20 Years Traffic Index: 8.00 Climate Factor: 1 R-Value of Subgrade: 7.00 Subgrade CBR Value: 3 Subgrade Mr: 4,500 R-Value of Aggregate Base: 80 R-Value of Granular Borrow: 60 Subgrade R-Value: 7 Expansion Pressure of Subgrade: 1.40 Unit Weight of Base Materials: 130 Total Design Life 18 kip ESAL's: 371,659 ASPHALTIC CONCRETE: Gravel Equivalent, Calculated: 0.512 Thickness: 0.2625641 Use = 3.5 Inches Gravel Equivalent, ACTUAL: 0.57 CRUSHED AGGREGATE BASE: Gravel Equivalent (Ballast): 1.024 Thickness: 0.414 Use = 8 Inches Gravel Equivalent, ACTUAL: 1.302 SUBBASE: Gravel Equivalent (Ballast): 2.381 Thickness: 1.079 Use = 14 Inches Gravel Equivalent, ACTUAL: 2.469 TOTAL Thickness: 2.125 Thickness Required by Exp. Pressure: 1.551 Design ACHD Depth Substitution Inches Ratios Asphaltic Concrete (at least 2.5): 3.50 1.95 Asphalt Treated Base (at least 4.2): 0.00 Cement Treated Base (at least 4.2): 0.00 Crushed Aggregate Base (at least 4.2): 8.00 1.10 Subbase (at least 4.2): 14.00 1.00 Atlas No. B211738g Page 127 Copyright © 2021 Atlas Technical Consultants r- Geolechnical-Engineeping Report --, The Geoprofessional Business Association (GBA) has prepared this advisory to help you - assumedly a client representative - interpret and apply this geotechnical-engineering report as effectively as possible. In that way, you can benefit from a lowered exposure to problems associated with subsurface conditions at project sites and development of them that, for decades, have been a principal cause of construction delays, cost overruns, claims, and disputes. If you have questions or want more information about any of the issues discussed herein, contact your GBA-member geotechnical engineer. Active engagement in GBA exposes geotechnical engineers to a wide array of risk -confrontation techniques that can be of genuine benefit for everyone involved with a construction project. Understand the Geotechnical-Engineering Services Provided for this Report Geotechnical-engineering services typically include the planning, collection, interpretation, and analysis of exploratory data from widely spaced borings and/or test pits. Field data are combined with results from laboratory tests of soil and rock samples obtained from field exploration (if applicable), observations made during site reconnaissance, and historical information to form one or more models of the expected subsurface conditions beneath the site. Local geology and alterations of the site surface and subsurface by previous and proposed construction are also important considerations. Geotechnical engineers apply their engineering training, experience, and judgment to adapt the requirements of the prospective project to the subsurface model(s). Estimates are made of the subsurface conditions that will likely be exposed during construction as well as the expected performance of foundations and other structures being planned and/or affected by construction activities. The culmination of these geotechnical-engineering services is typically a geotechnical-engineering report providing the data obtained, a discussion of the subsurface model(s), the engineering and geologic engineering assessments and analyses made, and the recommendations developed to satisfy the given requirements of the project. These reports may be titled investigations, explorations, studies, assessments, or evaluations. Regardless of the title used, the geotechnical-engineering report is an engineering interpretation of the subsurface conditions within the context of the project and does not represent a close examination, systematic inquiry, or thorough investigation of all site and subsurface conditions. Geotechnical-Engineering Services are Performed for Specific Purposes, Persons, and Projects, and At Specific Times Geotechnical engineers structure their services to meet the specific needs, goals, and risk management preferences of their clients. A geotechnical-engineering study conducted for a given civil engineer will not likely meet the needs of a civil -works constructor or even a different civil engineer. Because each geotechnical-engineering study is unique, each geotechnical-engineering report is unique, prepared solely for the client. Likewise, geotechnical-engineering services are performed for a specific project and purpose. For example, it is unlikely that a geotechnical- engineering study for a refrigerated warehouse will be the same as one prepared for a parking garage; and a few borings drilled during a preliminary study to evaluate site feasibility will not be adequate to develop geotechnical design recommendations for the project. Do not rely on this report if your geotechnical engineer prepared it: • for a different client; • for a different project or purpose; • for a different site (that may or may not include all or a portion of the original site); or • before important events occurred at the site or adjacent to it; e.g., man-made events like construction or environmental remediation, or natural events like floods, droughts, earthquakes, or groundwater fluctuations. Note, too, the reliability of a geotechnical-engineering report can be affected by the passage of time, because of factors like changed subsurface conditions; new or modified codes, standards, or regulations; or new techniques or tools. If you are the least bit uncertain about the continued reliability of this report, contact your geotechnical engineer before applying the recommendations in it. A minor amount of additional testing or analysis after the passage of time - if any is required at all - could prevent major problems. Read this Report in Full Costly problems have occurred because those relying on a geotechnical- engineering report did not read the report in its entirety. Do not rely on an executive summary. Do not read selective elements only. Read and refer to the report in full. You Need to Inform Your Geotechnical Engineer About Change Your geotechnical engineer considered unique, project -specific factors when developing the scope of study behind this report and developing the confirmation -dependent recommendations the report conveys. Typical changes that could erode the reliability of this report include those that affect: • the site's size or shape; • the elevation, configuration, location, orientation, function or weight of the proposed structure and the desired performance criteria; • the composition of the design team; or • project ownership. As a general rule, always inform your geotechnical engineer of project or site changes - even minor ones - and request an assessment of their impact. The geotechnical engineer who prepared this report cannot accept responsibility or liability for problems that arise because the geotechnical engineer was not informed about developments the engineer otherwise would have considered. Most of the "Findings" Related in This Report Are Professional Opinions Before construction begins, geotechnical engineers explore a site's subsurface using various sampling and testing procedures. Geotechnical engineers can observe actual subsurface conditions only at those specific locations where sampling and testing is performed. The data derived from that sampling and testing were reviewed by your geotechnical engineer, who then applied professional judgement to form opinions about subsurface conditions throughout the site. Actual sitewide-subsurface conditions may differ - maybe significantly - from those indicated in this report. Confront that risk by retaining your geotechnical engineer to serve on the design team through project completion to obtain informed guidance quickly, whenever needed. This Report's Recommendations Are Confirmation -Dependent The recommendations included in this report - including any options or alternatives - are confirmation -dependent. In other words, they are not final, because the geotechnical engineer who developed them relied heavily on judgement and opinion to do so. Your geotechnical engineer can finalize the recommendations only after observing actual subsurface conditions exposed during construction. If through observation your geotechnical engineer confirms that the conditions assumed to exist actually do exist, the recommendations can be relied upon, assuming no other changes have occurred. The geotechnical engineer who prepared this report cannot assume responsibility or liability for confirmation -dependent recommendations if you fail to retain that engineer to perform construction observation. This Report Could Be Misinterpreted Other design professionals' misinterpretation of geotechnical- engineering reports has resulted in costly problems. Confront that risk by having your geotechnical engineer serve as a continuing member of the design team, to: confer with other design -team members; help develop specifications; • review pertinent elements of other design professionals' plans and specifications; and be available whenever geotechnical-engineering guidance is needed. You should also confront the risk of constructors misinterpreting this report. Do so by retaining your geotechnical engineer to participate in prebid and preconstruction conferences and to perform construction - phase observations. Give Constructors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can shift unanticipated -subsurface -conditions liability to constructors by limiting the information they provide for bid preparation. To help prevent the costly, contentious problems this practice has caused, include the complete geotechnical-engineering report, along with any attachments or appendices, with your contract documents, but be certain to note conspicuously that you've included the material for information purposes only. To avoid misunderstanding, you may also want to note that "informational purposes" means constructors have no right to rely on the interpretations, opinions, conclusions, or recommendations in the report. Be certain that constructors know they may learn about specific project requirements, including options selected from the report, only from the design drawings and specifications. Remind constructors that they may perform their own studies if they want to, and be sure to allow enough time to permit them to do so. Only then might you be in a position to give constructors the information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Conducting prebid and preconstruction conferences can also be valuable in this respect. Read Responsibility Provisions Closely Some client representatives, design professionals, and constructors do not realize that geotechnical engineering is far less exact than other engineering disciplines. This happens in part because soil and rock on project sites are typically heterogeneous and not manufactured materials with well-defined engineering properties like steel and concrete. That lack of understanding has nurtured unrealistic expectations that have resulted in disappointments, delays, cost overruns, claims, and disputes. To confront that risk, geotechnical engineers commonly include explanatory provisions in their reports. Sometimes labeled "limitations;' many of these provisions indicate where geotechnical engineers' responsibilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask questions. Your geotechnical engineer should respond fully and frankly. Geoenvi ron mental Concerns Are Not Covered The personnel, equipment, and techniques used to perform an environmental study - e.g., a "phase -one" or "phase -two" environmental site assessment - differ significantly from those used to perform a geotechnical-engineering study. For that reason, a geotechnical-engineering report does not usually provide environmental findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated subsurface environmental problems have led to project failures. If you have not obtained your own environmental information about the project site, ask your geotechnical consultant for a recommendation on how to find environmental risk -management guidance. Obtain Professional Assistance to Deal with Moisture Infiltration and Mold While your geotechnical engineer may have addressed groundwater, water infiltration, or similar issues in this report, the engineer's services were not designed, conducted, or intended to prevent migration of moisture - including water vapor - from the soil through building slabs and walls and into the building interior, where it can cause mold growth and material -performance deficiencies. Accordingly, proper implementation of the geotechnical engineer's recommendations will not of itself be sufficient to prevent moisture infiltration. Confront the risk of moisture infiltration by including building -envelope or mold specialists on the design team. Geotechnical engineers are not building -envelope or mold specialists. 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