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HomeMy WebLinkAboutCC - Geotech Report "F p,r I, • i �r 1 � e k ' t GEOTECHNICAL INVESTIGATION LAKE HAZEL ROADWAY WIDENING Lake Hazel Road from Meridian Road to Apex Subdivision Meridian, ID PREPARED FOR: Mr Daniel Frisby Brighton Corporation 2929 West Navigator Drive Meridian, ID 83642 PREPARED BY: Atlas Technical Consultants, LLC September 2, 2022 2791 South Victory View Way B221077g Boise, ID 83709 �TrT—G7T�11 2791 South Victory View Way Boise, ID 83709 (208)376-4748 1 oneatlas.com September 2, 2022 Atlas No. B221077g Mr Daniel Frisby Brighton Corporation 2929 West Navigator Drive Meridian, ID 83642 Subject: Geotechnical Investigation Lake Hazel Roadway Widening Lake Hazel Road from Meridian Road to Apex Subdivision Meridian, ID Dear Mr Frisby: 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 July 14 and 15, 2022. 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. Respectfully submitted, Jacob Schlador, PE Elizabeth Brown, PE Geotechnical Engineer Geotechnical Services Manager Distribution: Zach Meyers, Brighton Corporation (PDF Copy); Lachlin Kinsella, KM Engineering (PDF Copy) Page 1 �TrT-G7T�1 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....................................................................................... 3 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....................................................................................... 5 4.3 Soil and Sediment Profile........................................................................................... 5 4.4 Volatile Organic Scan................................................................................................. 6 5. SITE HYDROLOGY............................................................................................................ 6 5.1 Groundwater.............................................................................................................. 6 5.2 Soil Infiltration Rates .................................................................................................. 7 6. SLOPES AND SETBACKS ................................................................................................ 7 7. LATERAL EARTH PRESSURES ....................................................................................... 7 7.1 Retaining Wall Backfill Materials................................................................................. 8 7.2 Retaining Wall Drainage............................................................................................. 9 8. FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS...........................10 8.1 Canal Crossing Foundation Design Recommendations.............................................10 9. PAVEMENT DISCUSSION AND RECOMMENDATIONS..................................................11 9.1 Flexible Pavement Section........................................................................................11 9.2 Pavement Subgrade Preparation ..............................................................................12 9.3 Common Pavement Section Construction Issues......................................................12 10. CONSTRUCTION CONSIDERATIONS ...........................................................................13 10.1 Earthwork................................................................................................................13 10.2 Dry Weather............................................................................................................13 10.3 Wet Weather...........................................................................................................14 10.4 Soft Subgrade Soils.................................................................................................14 10.5 Frozen Subgrade Soils............................................................................................14 10.6 Structural Fill ...........................................................................................................15 Atlas No. B221077g Page I i Copyright©2022 Atlas Technical Consultants �/��M" ■ p �TrT-G7T-Zr-_. 10.7 Backfill of Walls.......................................................................................................16 10.8 Excavations.............................................................................................................16 10.9 Groundwater Control...............................................................................................17 11. GENERAL COMMENTS..................................................................................................17 12. REFERENCES.................................................................................................................18 TABLES Table 1 — Seismic Design Values................................................................................................4 Table 2 — Groundwater Data.......................................................................................................6 Table 3 — Lateral Earth Pressure Values for Native Soil..............................................................8 Table 4 — Lateral Earth Pressure Values for Fill Materials...........................................................9 Table 5 — Soil Bearing Capacity................................................................................................10 Table 6 — Gravel Equivalent Method Flexible Pavement Specifications ....................................12 APPENDICES Appendix I Warranty and Limiting Conditions Appendix II Vicinity Map Appendix III Site Map Appendix IV Geotechnical Investigation Boring Log Appendix V Geotechnical General Notes Appendix VI Rock Classification System Appendix VI I Gravel Equivalent Method Pavement Design Appendix VIII R-value Laboratory Test Data Appendix IX Important Information About This Geotechnical Engineering Report Atlas No. B221077g Page I ii Copyright©2022 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 2020 AASHTO LRFD Bridge Design Manual. 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 and pavements 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 project is in the southeastern portion of the City of Meridian, Ada County, ID. This project will consist of widening Lake Hazel Road to a 5-lane roadway. It is anticipated that there will be two lanes of traffic for each direction of travel and a center turn lane. This project will also consist of the reconstruction of the Rawson Canal crossing and an unnamed drainage crossing on the east end of the project. Total settlements are limited to 1 inch. Loads of up to 6,000 pounds per lineal foot for wall footings were assumed for settlement calculations. Retaining walls in the form of wing walls are anticipated as part of the project. Atlas has not been provided traffic loading for Lake Hazel Road. However, Atlas was informed by Mr. Zach Meyers with Brighton Corporation that Ada County Highway District (ACHD) requested a Traffic Index (TI) of 10 should be used for Lake Hazel Road from Eagle Road to Locust Grove Road. Therefore, Atlas used a TI of 10 for Lake Hazel Road from Locust Grove Road to Meridian Road. 1.2 Authorization Authorization to perform this exploration and analysis was given in the form of a written authorization to proceed from Mr Daniel Frisby of Brighton Corporation to Jacob Schlador of Atlas Technical Consultants (Atlas), on May 3, 2022. Said authorization is subject to terms, conditions, and limitations described in the Professional Services Contract entered into between Brighton Corporation and Atlas. Our scope of services for the proposed development has been provided in our proposal dated May 3, 2022 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 and pavement materials. Atlas No. B221077g Page11 Copyright©2022 Atlas Technical Consultants 2. SITE DESCRIPTION I Site Access Access to the site may be gained via Interstate 84 to the Meridian Road exit. Proceed south on Meridian Road approximately 3.3 miles to its intersection with Lake Hazel Road. The site consists of Lake Hazel Road from Meridian Road east 0.7 mile. 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 western half of the project site is underlain by "Basalt Flows of Indian Creek, Undivided" as mapped by Othberg and Stanford (1993). This volcanic deposit is composed of multiple flows of medium to dark gray olivine basalt. These flows erupted from numerous vents found south of the Boise River and north of the Snake River, southeast of the City of Boise, Idaho. At the time of eruption lavas flowed into and down ancestral Indian Creek and Boise River valleys. Northwest- trending, gently sloping escarpments suggest faulting of the basalt. These basalts are mantled with loess 2-12 feet thick that contains about 35% pedogenic clay and a duripan that can be 3 feet thick. The eastern half of the project site is underlain by "Gravel of Amity Terrace" as mapped by Othberg and Stanford (1993). The Amity terrace is the fifth terrace above the modern Boise River and represents the first level of Quaternary incision by the Boise River. The terrace, which has been correlated with Deer Flat terrace deposits to the west, is modified extensively by erosion and faulting. Where little erosion has taken place the terrace is mantled with loess 1.6-7 feet thick. Atlas No. B221077g Page12 Copyright©2022 Atlas Technical Consultants �TrT-G7T�__1 2.3 General Site Characteristics The project consists of a 0.7 mile stretch of Lake Hazel Road. The road consists of a two-lane crowned roadway. The site is surrounded on all sides by agricultural fields and residential developments. No vegetation was noted on the project site. However, agricultural crops, weeds, and grasses were observed adjacent to Lake Hazel Road. The site is relatively flat and level with a 3 to 5 feet rise in elevation where Lake Hazel Road crosses the Rawson Canal. Slopes along Rawson Canal were unable to be measured at the time of the investigation because of the presence of flowing water within the canal. However, slopes along the canal banks are assumed to range from roughly 4 feet horizontal to 1 foot vertical (4:1) to 2:1. Regional drainage is north and west toward the Boise River. Stormwater drainage for the site is achieved by sheet runoff across asphaltic concrete. 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 were not noted within the vicinity of Lake Hazel Road. ..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 -250F 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 AASHTO LRFD Bridge Design Manual 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. Seismic Design Parameter Value: 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 0.194 is appropriate for the project site based on a Site Class D. Atlas No. B221077g Page 13 Copyright©2022 Atlas Technical Consultants �r'Irr-c��1 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 2020 AASHTO LRFD Bridge Design Manual. Design spectral response acceleration parameters as presented in the 2020 AASHTO LRFD Bridge Design Manual are defined as a 5% damped design spectral response acceleration at short periods, SDs, 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). Table 1 — Seismic Design Values Site Class D "Default" Ss 0.283 (g) SI 0.103 (g) Fa 1.574 F 2.393 SMs 0.445 SMi 0.247 Sos 0.394 Sol 0.165 4. SOILS EXPLORATION 1.1 Exploration and Sampling Procedures Field exploration conducted to determine engineering characteristics of subsurface materials included a reconnaissance of the project site and investigation by soil boring. Borings were located in the field by means of a Global Positioning System (GPS) device and are reportedly accurate to within ten feet. Borings were advanced by means of a truck-mounted drilling rig equipped with continuous flight hollow-stem augers. At specified depths, samples were obtained using a standard split-spoon sampler and Standard Penetration Test (SPT) blow counts were recorded. Uncorrected SPT blow counts are provided on logs, which can be found in the Appendix. Delayed water level observations were made in open borings to evaluate groundwater levels. At completion of exploration, borings were backfilled with both loose excavated materials and bentonite holeplug. Atlas No. B221077g Page14 Copyright©2022 Atlas Technical Consultants rrN+O= 'T�� __1 Samples have been visually classified in the field by professional staff, identified according to boring 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. 4.2 Laboratory 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, Grain Size Analysis — ASTM C117/C136, and Resistance Value (R-value) and Expansion Pressure of Compacted Soils — Idaho T-8. 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 boring locations, may vary from the individual soil profiles presented in the logs, which can be found in the Appendix. Asphaltic concrete underlain with aggregate base material was encountered at ground surface throughout the site. In borings 4, 5, 6, 7, and 9, poorly graded gravel with sand and varying silt content fill materials were encountered below the aggregate base fills. These fill materials were brown to light brown, dry to slightly moist, medium dense to very dense, and contained fine to coarse-grained sand and fine to coarse gravel. Underlying the surficial fills were typically clay soils with varying amounts of sand content. Clay soils were brown to light brown, slightly moist, medium stiff to hard, and contained fine-grained sand. Typically underlying the clay soils were sandy silt soils and silty sand sediments, with the exception of borings 5 and 6. In borings 5 through 9, sandy silts were encountered below the fill materials. Sandy silts and silty sands were brown to light brown, dry to slightly moist, soft to hard/medium dense to very dense, and contained fine to coarse-grained sand and varying degrees of calcium carbonate cementation. At depth in boring 1 and 6 were silty gravel with sand sediments. Silty gravels with sand were brown to light brown, dry to slightly moist, dense to very dense, and contained fine to coarse-grained sand and fine to coarse gravel. During excavation, boring sidewalls were generally stable. However, moisture contents will affect wall competency with saturated soils having a tendency to readily slough when under load and unsupported. Atlas No. B221077g Page 15 Copyright©2022 Atlas Technical Consultants �TrT-G7T_�. 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. No groundwater was encountered. 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. 5.1 Groundwater During this field investigation, groundwater was not encountered in test pits advanced to a maximum depth of 21.5 feet bgs. Soil moistures in the borings were generally dry to slightly moist throughout. In the vicinity of the project site, groundwater levels are controlled in large part by residential and agricultural 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 Approximate Distance Direction from Site . . from Site (mile) . . April 2008 0.16 West Not Encountered to 17.2 March 2020 0.11 North Not Encountered to 10.1 January 2021 0.13 South Not Encountered to 16.5 January 2021 0.23 Northeast Not Encountered to 14.6 January 2022 0.13 North Not Encountered to 16.2 For construction purposes, groundwater depth can be assumed to remain greater than 20 feet bgs throughout the year. Atlas No. B221077g Page 16 Copyright©2022 Atlas Technical Consultants 5.2 Soil Infiltration Rates Soil permeability, which is a measure of the ability of a soil to transmit a fluid, was not tested in the field. Given the absence of direct measurements, for this report an estimation of infiltration is presented using generally recognized values for each soil type and gradation. Of soils comprising the generalized soil profile for this study, lean clay and fat 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 and silty sand and silty gravel with sand sediments usually display rates of 4 to 8 inches per hour; though calcium carbonate cementation may reduce these values to near zero. Clayey sand and clayey gravel sediments typically have infiltration rates ranging from 2 to 6 inches per hour. Infiltration rates through basalt rock can be highly variable, ranging from nearly zero to greater than 6 inches per hour in some cases. Movement of water through the basalt may be more characteristic of fracture flow. Infiltration testing is required to determine site-specific infiltration rates for drainage design once proposed locations of infiltration facilities are determined. Ada County Highway District (ACHD) will require onsite percolation testing once the proposed locations of infiltration facilities are determined. The quantity of testing will be dependent on the size and number of infiltration facilities planned, and can be determined from Section 8000 of the ACHD Policy Manual. The estimated infiltration rates listed above are to be considered preliminary and are only provided to determine feasibility for onsite infiltration. 6. SLOPES AND SETBACKS Canal slopes were unable to be measured at the time of the investigation due to the presence of water. However, slopes of approximately 4 feet horizontal to 1 foot vertical (4:1) to 2:1 were assumed based on experiences with canals in this area. Foundations are anticipated to reside below the base of the slope. 7. LATERAL EARTH PRESSURES Retaining, below-grade, or basement walls will be subject to lateral earth pressures. The magnitude of earth pressure is a function of both type and compaction of backfill behind walls within the "active" zone, and allowable rotation of the top of the wall. The active zone is defined as the wedge of soil between the surface of the wall and a plane inclined 31 degrees from vertical passing through the base of the wall. All clayey soils must be completely removed from within the active zone. The following recommendations should be used when dealing with lateral earth pressures on a gravity block: 1) a sliding frictional coefficient of 0.35 is appropriate considering native silty sand/sandy silt soils, and 2) a sliding frictional coefficient of 0.45 is appropriate considering granular structural fill under typical conditions. Atlas No. B221077g Page 17 Copyright©2022 Atlas Technical Consultants A state of plastic equilibrium is when the subject material is considered to be 1) homogeneous and unbounded and 2) at the point of incipient instability. This state is evaluated on the basis of unit weight, mechanical properties, and the definition of instability. For the purpose of this report, it is assumed that native relatively free draining soils and imported granular fill material will be the materials of concern regarding lateral earth pressures. If other materials are considered for use, Atlas must be contacted to provide alternate lateral earth pressure information. Furthermore, changes in natural soil moisture, such as can be imposed by site stormwater systems, can change the values listed below. Below-grade restrained walls, such as basement walls, should be designed based on at-rest pressures. Active pressures are appropriate under conditions where the wall moves or rotates away from the soil mass at failure. Passive pressures are used for conditions where the wall moves toward the soil mass at failure. Rotation, or lateral movement, of the top of the wall equal to 0.002 times the height of the wall will be necessary for on-site soil backfill to achieve an "active" loading condition. Lateral movement of the top of the wall equal to 0.001 times the height of the wall will be necessary for the "active" pressure condition for imported granular structural backfill. 7.1 Retaining Wall Backfill Materials For lateral earth pressure analysis, Atlas anticipates that the soils of interest will be the onsite native sandy silt soils and silty sand soils. Clayey soils are not suitable for use as backfill on the soil side of walls. Seismic lateral earth pressures have also been provided in the following tables, and were calculated per the Whitman method. For sandy silt and silty sand soils, the following values are applicable under non-surcharged, drained conditions. Table 3 — Lateral Earth Pressure Values for Native Soil Soil Type: Sandy Silt/Silty Sand Internal Friction Angle: 28 ° Dry Unit Weight: 112 pcf Cohesion: 100 psf Bouyant Unit Weight: 75 pcf Natural Void Ratio: 0.7 Natural Moisture: 14 % Ground Acceleration2: 0.194 Backfill Slope: 0 ° At rest lateral earth pressure: 68 pcf' Ko= 0.53 Active lateral earth pressure: 46 pcf Ka= 0.36 Passive lateral earth pressure: 354 pcf' Kp= 2.77 Seismic active lateral earth pressure: 65 pcf' Kae= 0.51 Seismic passive lateral earth pressure: 285 pcf' Kpe= 2.23 'Lateral earth pressure values are in pounds per square foot,per foot of wall(psf/ft). Alternately,the values presented may also be considered as equivalent fluid with units of pounds per cubic foot(pcf). ZGround acceleration obtained from the USGS Seismic Design Maps. Imported, compacted, structural material, which is used to backfill the soil side of walls, must demonstrate the following characteristics: Atlas No. 6221077g Page 18 Copyright©2022 Atlas Technical Consultants Table 4— Lateral Earth Pressure Values for Fill Materials Soil Type: Compacted Sandy Gravel Fill Internal Friction Angle: 35 ° Dry Unit Weight: 128 pcf Cohesion: N/A Bouyant Unit Weight: 83 pcf Natural Void Ratio: 0.4 Natural Moisture: 5 % Ground Acceleration2: 0.194 Backfill Slope: 0 ° At rest lateral earth pressure: 57 pcf' Ko= 0.43 Active lateral earth pressure: 36 pcf' Ka= 0.27 Passive lateral earth pressure: 496 pcf' Kp= 3.69 Seismic active lateral earth pressure: 56 pcf' Kae= 0.42 Seismic passive lateral earth pressure: 400 pcf' Kpe= 2.97 'Lateral earth pressure values are in pounds per square foot,per foot of wall(psf/ft). Alternately,the values presented may also be considered as equivalent fluid with units of pounds per cubic foot(pcf). ZGround acceleration obtained from the USGS Seismic Design Maps. Please note that the values for seismic lateral earth pressures are calculated using both the static and seismic coefficients. The effect of seismic conditions alone is the difference between the static and seismic lateral earth pressures presented above. In the case that another material is used for backfill, Atlas should be consulted for alternate lateral earth pressure values. Granular structural fill should consist of 4-inch-minus select, clean, granular soil with no more than 30 percent oversize (greater than 3/4-inch) material and no more than 5 percent non-plastic fines (passing the No. 200 sieve). Retaining wall and basement backfill must be placed in accordance with recommendations in the Structural Fill section of this report and must be properly compacted and tested. Lateral earth pressure values do not incorporate specific factors of safety, and are only applicable for non-surcharged, drained conditions. Factors of safety, if applicable, should be integrated into the structural design of the wall. The preceding values are presented for idealized conditions relating to simple shallow structures. For complex structures, deep structures, or structures with significant perimeter landscaping, a soils engineer should be retained as part of the design team in developing appropriate project design parameters and construction specifications. 7.2 Retaining Wall Drainage Atlas recommends that a drainage system be incorporated into the retained soil mass. This can be accomplished by installing wall and toe drains as a part of each soil-supporting wall system. In areas where there is potential for significantly high soil moistures within the supported soil mass, installation of drains within the soil mass is recommended. Particular consideration of roof drain effluent and irrigation water must be made. Further, these drainage systems must be separate from other retaining wall/foundation systems. If the granular structural fill option to reduce lateral pressures is used, a compacted low permeability soil cap is recommended within the upper 2 feet of the surface to limit surface water infiltration behind the walls. Atlas No. B221077g Page 19 Copyright©2022 Atlas Technical Consultants �TrT-G7T��. 8. FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS Various foundation types have been considered for support of the proposed structure. 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 structure 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. 8.1 Canal Crossing Foundation Design Recommendations It has been assumed that foundations for the Rawson Canal Crossing will be approximately 8 to 10 feet below existing ground surface and the foundations for the unnamed canal crossing will be approximately 5 feet below existing ground surface. Rawson Canal was in the vicinity of borings 5 and 6 and the unnamed canal was located in the vicinity of borings 1 and 2. However, if foundation depths vary from those anticipated in this report, Atlas must be contacted to review foundation recommendations and provide updated foundation recommendations, if required. 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: Table 5 — Soil Bearing Capacity Subgrade Compaction . . Footings must bear on competent, undisturbed, native sandy silt soils, silty sand sediments, or Not Required for Native compacted structural fill. Existing lean clay soils and Soil fill materials must be completely removed from 2,5001bs/ft2 below foundation elements.' Excavation depths 95% for Structural Fill ranging from roughly 4.5 to 7 feet bgs should be anticipated to expose proper bearing soils.2 'It will be required for Atlas personnel to verify the bearing soil suitability for each structure at the time of construction. ZDepending 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 sandy silt soils and silty sand sediments and 2) 0.45 for footings bearing on granular structural fill. A passive lateral earth pressure of 354 pounds per square foot per foot (psf/ft) should be used for sandy silt soils and silty sand sediments. For compacted sandy gravel fill, a passive lateral earth pressure of 496 psf/ft should be used. Atlas No. B221077g Page110 Copyright©2022 Atlas Technical Consultants Footings should be proportioned to meet either the stated soil bearing capacity or the 2020 AASHTO LRFD Bridge Design Manual 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. 9. PAVEMENT DISCUSSION AND RECOMMENDATIONS Atlas was not provided traffic loading information for the project. However, Atlas assumed a traffic index of 10 to determine the necessary pavement cross-section for the site based on a past project for Lake Hazel Road. 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. Atlas collected a sample of near-surface soils for Resistance Value (R-value) testing representative of soils to depths of 2 feet below existing ground surface. This sample, consisting of sandy silt soils collected from boring 8, yielded a R-value of 11. 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. Results of the test are graphically depicted in the Appendix. 9.1 Flexible Pavement Section 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. A calculation sheet provided in the Appendix indicates the soils constants, 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. B221077g Page 111 Copyright©2022 Atlas Technical Consultants �TrT-G7Tdr-W� Table 6 — Gravel Equivalent Method Flexible Pavement Specifications ComponentPavement Section - . . . Asphaltic Concrete 4.0 Inches Crushed Aggregate Base 4.0 Inches Structural Subbase 22.0 Inches Compacted Subgrade 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. 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. Pavement Subgrade Preparation Fill materials, associated with the existing asphalt pavement section, were encountered throughout the site. Atlas recommends that these fill materials be compacted in place. Fill must be compacted to at least 95 percent of the maximum dry density as determined by ASTM D698. Once final grades have been determined, Atlas is available to provide additional recommendations. 9.3 Common Pavement Section Construction Issues The subgrade upon which above pavement sections are to be constructed must be properly stripped, compacted, 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. Subgrade clayey and silty soils near and above optimum moisture contents may pump during compaction. Pumping or soft areas must be removed and replaced with structural fill. 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 No. B221077g Page112 Copyright©2022 Atlas Technical Consultants 10. CONSTRUCTION CONSIDERATIONS Recommendations in this report are based upon structural elements of the project being founded on competent, native sandy silt soils, silty sand sediments, or compacted structural fill. Structural areas should be stripped to an elevation that exposes these soil types. 10.1 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. No vegetation was noted on the site at the time of our investigation. However, agricultural crops, weeds, and grasses were noted adjacent to the project site at the time of our investigation. 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. 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 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. 10.2 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. Atlas No. B221077g Page113 Copyright©2022 Atlas Technical Consultants �TrT-G7T��. 10.3 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. 10.4 Soft Subgrade Soils Shallow fine-grained subgrade soils that are high in moisture content should be expected to pump and rut under construction traffic. Throughout construction, soft areas may develop after the existing asphalt is removed and heavy rubber tired equipment drives over the site. In addition, areas where significant cracking has occurred will likely have soft subgrade soils because of moisture infiltration and will be prone to pumping and rutting. 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, other deleterious debris, and used to remove the existing asphalt and to perform any other necessary excavations. 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. 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'/2 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. 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. Atlas No. B221077g Page 114 Copyright©2022 Atlas Technical Consultants 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. 10.6 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. 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 %-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. Atlas No. B221077g Page115 Copyright©2022 Atlas Technical Consultants The ASTM D1557 test method must be used for samples containing up to 40 percent oversize (greater than%-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. 10.7 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. 10.8 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 1'/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 long-term conditions. During the subsurface exploration, boring sidewalls generally exhibited little indication of collapse. 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. Atlas No. B221077g Page116 Copyright©2022 Atlas Technical Consultants 10.9 Groundwater Control Groundwater was not encountered during the investigation and 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. i 1. GENERAL COMMENTS Based on the subsurface conditions encountered during this investigation and available information regarding the proposed project, the site is adequate for the planned construction. When plans and specifications are complete, 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. B221077g Page117 Copyright©2022 Atlas Technical Consultants 12. 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 Association of State Highway and Transportation Officials (AASHTO) (2017). LRFD Bridge Design Specifications. Washington D.C>: AASHTO American Society of Civil Engineers (2021). ASCE 7 Hazards Tool: Web Interface [Online] Available: <https://asce7hazardtool.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) (2013). Standard Test Methods for Resistance Value (R-Value) and Expansion Pressure of Compacted Soils: ASTM D2844. 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. Desert Research Institute.Western Regional Climate Center. [Online]Available: <http://www.wrcc.dri.edu/> (2021). Local Highway Technical Assistance Council (LHTAC) (2017). Idaho Standards for Public Works Construction, 2017. Boise, ID: Author. 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. B221077g Page118 Copyright©2022 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. 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 Atlas No. B221077g Page119 Copyright©2022 Atlas Technical Consultants 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. B221077g Page120 Copyright©2022 Atlas Technical Consultants Vicinity Map Figure 1 LV, I RRY E FAIRVIEW AVE S=-1 55 HVVY 5R 55 IiWY ur trlatierdaie MAP NOTES: .W4, N •Delorme Street Atlas f - W -1 J _� -Not to Scale rk ice- w a.._.,_.__............. .....,_. Beatty LL -•-� -..__,...�.__..- � W FRANKLIN RD E112AN' E FRAM{LI�J Rp-Li RD n , � r � Approximate Site .- Location 46 m7� °E OVERIAND Rb U, Ln. T7 '. -% m -W 4. 4 rn E VICrORY'RD Site Location m TF LA p u7 ti m �n 71' ;�� r m C7 LAKE HAZEL RD Lake Hazel Roadway Widening Lake Hazel Road from ❑ Meridian Road to Apex Subdivision v M. Meridian,ID J COLUMBIA RD Modified from DeLorme by:JBS �. August 25,2022 Drawing:B221077g �• +J7 a. �•N NIP . c 2791 S.Victory View Way Phone: (208)376-4748 Boise,ID 83709 Fax: (208)322-6515 Web: oneatlas.com Site Map Figure 2 I I ® NOTES: I I � N •Not to Scale II II � II II \ II 11 II LEGEND II I I Approximate Site — — I I Boundary II Approximate Atlas I I (iiyNgM Boring Location I I F�cgiyq( Approximate Location — — I of Canal 44 II II � —_ _ _——_� LAKE HAZEL ROAD—� � --- -- — --_ — —� — — -- —�S -- -- -- -- II � II ' � Q \0 ry z 1 Q o LU Lake Hazel Roadway Widening Lake Hazel Road from I I \ Meridian Road to Apex Subdivision I I Meridian,ID II Drawn by:JBS I I August 25,2022 I I Drawing:B221077g II II II /r T • IL —C� II I I 2791 S.Victory View Way Phone: (208)376-4748 I I Boise,ID 83709 Fax: (208)322-6515 Web: oneatlas.com � BORING NO.: B-1 TOTAL DEPTH: 16.5' FIELD BORING LOG GROUNDWATER DEPTH: None PROJECT INFORMATION DRILLING INFORMATION PROJECT: Lake Hazel Roadway Widening DRILLING CO.: Haztech Drilling, Inc. LOCATION: Lake Hazel Rd. East of Meridian Rd. METHOD OF DRILLING: 6" Hollow Stem Auger Meridian, ID SAMPLING METHODS: Split Spoon JOB NO.: B221077g DATES DRILLED: July 15, 2022 LOGGED BY: Colby Meyer, GIT LATITUDE/LONGITUDE: 43.546435, -116.381006 Water level during drilling ® Standard Split Spoon Auger Sample Shelby Tube w W o w C0 aIt CD z w J DESCRIPTION v p p 0 p c) J o o Q in O O U) Q c J LL � m 0 ASPHALTIC CONCRETE: 6 inches thick. o.:: 8,5,4 AGGREGATE BASE (GP-FILL): Brown, �x slightly moist, loose, with fine to coarse- grained sand and fine crushed gravel. 1,2,3 LEAN CLAY WITH SAND (CL): Brown, slightly moist, medium stiff, with fine-grained sand. 5 24.8 NP 93 35.4 9,24,23 0. 30 6 SILTY SAND (SM): Light brown, slightly = moist, medium dense to dense, with fine to coarse-grained sand. --Weak to moderate calcium carbonate ::- cementation from 6.0 to 6.5 feet bgs. 6,10,14 10 6,16,19 0 3 6 15 SILTY GRAVEL WITH SAND (GM): Brown, 7,18,30 0 30 6 slightly moist, dense, with fine to coarse- 0== grained sand and fine to coarse gravel. 2791 S.Victory View Way • Boise, ID 83709 . (208)376-4748 . Fax(208)322-6515 oneatlas.com � BORING NO.: B-2 TOTAL DEPTH: 15.5' FIELD BORING LOG GROUNDWATER DEPTH: None PROJECT INFORMATION DRILLING INFORMATION PROJECT: Lake Hazel Roadway Widening DRILLING CO.: Haztech Drilling, Inc. LOCATION: Lake Hazel Rd. East of Meridian Rd. METHOD OF DRILLING: 6" Hollow Stem Auger Meridian, ID SAMPLING METHODS: Split Spoon JOB NO.: B221077g DATES DRILLED: July 14, 2022 LOGGED BY: Colby Meyer, GIT LATITUDE/LONGITUDE: 43.546435, -116.381452 Water level during drilling ® Standard Split Spoon Auger Sample Shelby Tube w W o w C0 aIt CD z w J DESCRIPTION v p p 0 p c) J o o Q in O O U) Q c J LL � m 0 �.. ASPHALTIC CONCRETE: 5 inches thick. 6,7,4 AGGREGATE BASE (GP-FILL): Brown, dry to slightly moist, medium dense, with fine to coarse-grained sand and fine crushed gravel. 2 2 2 LEAN CLAY WITH SAND (CL): Brown, slightly moist, medium stiff to stiff, with fine- grained sand. 5 _=__ SANDY SILT(ML): Brown to light brown, 19,40,37 0 30 _ = dry to slightly moist, very stiff to hard, with fine-grained sand. _ = --Moderate to strong calcium carbonate _= cementation from 5.0 to 6.5 feet bgs. 7,12,10 10 = 18,36,50 0 30 6 for 6" 15 --- 50 for 5.5" 2791 S.Victory View Way • Boise, ID 83709 . (208)376-4748 . Fax(208)322-6515 oneatlas.com � BORING NO.: B-3 TOTAL DEPTH: 6.5' FIELD BORING LOG GROUNDWATER DEPTH: None PROJECT INFORMATION DRILLING INFORMATION PROJECT: Lake Hazel Roadway Widening DRILLING CO.: Haztech Drilling, Inc. LOCATION: Lake Hazel Rd. East of Meridian Rd. METHOD OF DRILLING: 6" Hollow Stem Auger Meridian, ID SAMPLING METHODS: Split Spoon JOB NO.: B221077g DATES DRILLED: July 14, 2022 LOGGED BY: Colby Meyer, GIT LATITUDE/LONGITUDE: 43.546435, -116.383734 Water level during drilling ® Standard Split Spoon Auger Sample Shelby Tube w W o w C0 aIt CD z w J DESCRIPTION v p � p 0 p c) J o o Q m O O U) Q c J LL � m 0 ASPHALTIC CONCRETE: 7 inches thick. • • AGGREGATE BASE (GP-FILL): Brown, dry �x to slightly moist, medium dense, with fine to 8,9,8 coarse-grained sand and fine crushed gravel. LEAN CLAY WITH SAND (CL): Brown, slightly moist, very stiff, with fine-grained sand. __- SANDY SILT (ML): Light brown, dry, soft to _== very stiff, with fine-grained sand. 9,9,11 5 — 8,2,1 30 2791 S.Victory View Way • Boise, ID 83709 . (208)376-4748 . Fax(208)322-6515 oneatlas.com � BORING NO.: B-4 TOTAL DEPTH: 6.5' FIELD BORING LOG GROUNDWATER DEPTH: None PROJECT INFORMATION DRILLING INFORMATION PROJECT: Lake Hazel Roadway Widening DRILLING CO.: Haztech Drilling, Inc. LOCATION: Lake Hazel Rd. East of Meridian Rd. METHOD OF DRILLING: 6" Hollow Stem Auger Meridian, ID SAMPLING METHODS: Split Spoon JOB NO.: B221077g DATES DRILLED: July 14, 2022 LOGGED BY: Colby Meyer, GIT LATITUDE/LONGITUDE: 43.546427, -116.385705 Water level during drilling ® Standard Split Spoon Auger Sample Shelby Tube w W o w C0 aIt CD z w J DESCRIPTION � v p p 0 p c) J o o Q in O O U) Q c J LL � m 0 ASPHALTIC CONCRETE: 5 inches thick. QOQ AGGREGATE BASE (GP-FILL): Brown, dry 11,21,7 px p to slightly moist, medium dense, with fine to x ; coarse-grained sand and fine crushed gravel. p POORLY GRADED GRAVEL WITH SAND FILL (GP-FILL): Light brown, dry to slightly moist, medium dense, with fine to coarse- grained sand and fine to coarse rounded gravel. SANDY FAT CLAY (CH): Brown, slightly 29.9 56/29 98 61.9 4,8,21 moist, very stiff, with fine-grained sand. SANDY SILT (ML): Brown to light brown, _ = dry to slightly moist, hard, with fine to 5 ==_ medium-grained sand. 11,27,32 0 30 6 __ __ —_ --Moderate calcium carbonate cementation =- throughout. 2791 S.Victory View Way • Boise, ID 83709 . (208)376-4748 . Fax(208)322-6515 oneatlas.com BORING NO.: B-5 IR In Pr TOTAL DEPTH: 21.5' FIELD BORING LOG GROUNDWATER DEPTH: None PROJECT INFORMATION DRILLING INFORMATION PROJECT: Lake Hazel Roadway Widening DRILLING CO.: Haztech Drilling, Inc. LOCATION: Lake Hazel Rd. East of Meridian Rd. METHOD OF DRILLING: 6" Hollow Stem Auger Meridian, ID SAMPLING METHODS: Split Spoon JOB NO.: 8221077g DATES DRILLED: July 14, 2022 LOGGED BY: Colby Meyer, GIT LATITUDE/LONGITUDE: 43.546411, -116.387370 70 in s Water level during drilling Standard Split Spoon Z A Auger Sample I M Shelby Tube w UJ = 0_ u.l o W U) Z o_ ~ DESCRIPTION ? g 0 p o p c) J � o < m 0 0 � m 0 ASPHALTIC CONCRETE: 5 inches thick. 16,34,39 AGGREGATE BASE (GP-FILL): Brown dry to slightly moist, very dense, with fine to p coarse-grained sand and fine crushed 16,25,26 gravel. 5 V POORLY GRADED GRAVEL WITH SAND FILL (GP-FILL): Light brown, dry to slightly 7,19,10 0 0 6 p moist, medium dense to very dense, with fine to coarse-grained sand and fine to coarse rounded gravel. 354 SANDY SILT (ML): Brown to light brown, _— slightly moist, stiff to hard, with fine-grained sand. 10 --Moderate calcium carbonate cementation 5,9,13 0 30 6 from 10.0 to 11.5 feet bgs. — — --Basalt gravels noted from 15.0 to 21.5 feet bgs. 15 = = 6,4,6 0 30 6 20 == 7,18,26 0 30 6 2791 S.Victory View Way • Boise, ID 83709 . (208)376-4748 . Fax(208)322-6515 oneatlas.com BORING NO.: B-6 IR In Pr TOTAL DEPTH: 16.3' FIELD BORING LOG GROUNDWATER DEPTH: None PROJECT INFORMATION DRILLING INFORMATION PROJECT: Lake Hazel Roadway Widening DRILLING CO.: Haztech Drilling, Inc. LOCATION: Lake Hazel Rd. East of Meridian Rd. METHOD OF DRILLING: 6" Hollow Stem Auger Meridian, ID SAMPLING METHODS: Split Spoon JOB NO.: 8221077g DATES DRILLED: July 14, 2022 LOGGED BY: Colby Meyer, GIT LATITUDE/LONGITUDE: 43.546406, -116.388558 in s Water level during drilling Standard Split Spoon Z A Auger Sample I m Shelby Tube w W 2 W C) J (� Z w J DESCRIPTION ? v 4t g O U p o p c) J o o < m 0 0 � m 0 ASPHALTIC CONCRETE: 5 inches thick. 20,25,44 POORLY GRADED GRAVEL WITH SAND FILL (GP-FILL): Light brown, dry to slightly moist, dense to very dense, with fine to coarse-grained sand and fine to coarse 15,22,13 rounded gravel. SANDY SILT (ML): Brown to light brown, 5 = _ dry to slightly moist, soft to very stiff, with 2,2,1 30 6 _ fine-grained sand. --Weak to moderate calcium carbonate cementation from 10.0 to 11.5 feet bgs. 31.7 NP 99 52.1 12,5,4 10 = - 10,11,11 0 30 6 SILTY GRAVEL WITH SAND (GM): Light brown, dry to slightly moist, very dense, with fine to medium-grained sand and fine to — -- coarse gravel. 0— - --Basalt cobbles and boulders encountered 15 — throughout. O— - --Refusal at 16.3 feet bgs on basalt 19,37,50 0 30 6 00..- bedrock. for 4" 2791 S.Victory View Way • Boise, ID 83709 . (208)376-4748 . Fax(208)322-6515 oneatlas.com � BORING NO.: B-7 TOTAL DEPTH: 6.5' FIELD BORING LOG GROUNDWATER DEPTH: None PROJECT INFORMATION DRILLING INFORMATION PROJECT: Lake Hazel Roadway Widening DRILLING CO.: Haztech Drilling, Inc. LOCATION: Lake Hazel Rd. East of Meridian Rd. METHOD OF DRILLING: 6" Hollow Stem Auger Meridian, ID SAMPLING METHODS: Split Spoon JOB NO.: B221077g DATES DRILLED: July 14, 2022 LOGGED BY: Colby Meyer, GIT LATITUDE/LONGITUDE: 43.546402, -116.390026 Water level during drilling ® Standard Split Spoon Auger Sample Shelby Tube w W o w C0 aIt CD z w J DESCRIPTION � v p p 0 p c) J o o Q m O O U) Q c J LL � m 0 _ _ ASPHALTIC CONCRETE: 4 inches thick. X 6,18,12 � � AGGREGATE BASE (GP-FILL): Brown, dry �x to slightly moist, medium dense to dense, with fine to coarse-grained sand and fine 7 crushed gravel. x POORLY GRADED GRAVEL WITH SILT AND SAND FILL (GP-GM-FILL): Light x brown, dry to slightly moist, medium dense to dense, with fine to coarse-grained sand =- and fine to coarse rounded gravel. __ SANDY SILT (ML): Brown, slightly moist, 4,15,19 very stiff to hard, with fine-grained sand. __ __ — --Weak to moderate calcium carbonate cementation from 5.5 to 6.0 feet bgs. 5 —-- 7,12,13 0 30 6 2791 S.Victory View Way • Boise, ID 83709 . (208)376-4748 . Fax(208)322-6515 oneatlas.com � BORING NO.: B-8 TOTAL DEPTH: 6.5' FIELD BORING LOG GROUNDWATER DEPTH: None PROJECT INFORMATION DRILLING INFORMATION PROJECT: Lake Hazel Roadway Widening DRILLING CO.: Haztech Drilling, Inc. LOCATION: Lake Hazel Rd. East of Meridian Rd. METHOD OF DRILLING: 6" Hollow Stem Auger Meridian, ID SAMPLING METHODS: Split Spoon JOB NO.: B221077g DATES DRILLED: July 14, 2022 LOGGED BY: Colby Meyer, GIT LATITUDE/LONGITUDE: 43.546402, -116.391295 Water level during drilling ® Standard Split Spoon Auger Sample Shelby Tube w W o w C0 aIt CD z w J DESCRIPTION v p � p 0 p c) J o o Q in O O U) Q c J LL � m 0 _ _ ASPHALTIC CONCRETE: 6 inches thick. QOQ AGGREGATE BASE (GP-FILL): Brown, 7,4,5 dry, loose, with fine to coarse-grained sand Q Q and fine crushed gravel. --= SANDY SILT (ML): Brown to light brown, --= dry to slightly moist, stiff to hard, with fine- --= grained sand. --Moderate calcium carbonate cementation --= from 5.0 to 5.5 feet bgs. -- 25.6 31/7 100 67.8 4,4,6 5 --- 13,17,22 0 30 6 2791 S.Victory View Way • Boise, ID 83709 . (208)376-4748 . Fax(208)322-6515 oneatlas.com � BORING NO.: B-9 TOTAL DEPTH: 6.5' FIELD BORING LOG GROUNDWATER DEPTH: None PROJECT INFORMATION DRILLING INFORMATION PROJECT: Lake Hazel Roadway Widening DRILLING CO.: Haztech Drilling, Inc. LOCATION: Lake Hazel Rd. East of Meridian Rd. METHOD OF DRILLING: 6" Hollow Stem Auger Meridian, ID SAMPLING METHODS: Split Spoon JOB NO.: B221077g DATES DRILLED: July 14, 2022 LOGGED BY: Colby Meyer, GIT LATITUDE/LONGITUDE: 43.546382, -116.393013 Water level during drilling ® Standard Split Spoon Auger Sample Shelby Tube w W o w C0 aIt CD z w J DESCRIPTION v p � p 0 p c) J o o Q m O O U) Q c J LL � m 0 ASPHALTIC CONCRETE: 5 inches thick. AGGREGATE BASE (GP-FILL): Brown, 10,19,22 px p dry, dense, with fine to coarse-grained sand and fine crushed gravel. Q" Q. ,p p POORLY GRADED GRAVEL WITH SAND p FILL (GP-FILL): Light brown, dry to slightly p moist, dense, with fine to coarse-grained sand and fine to coarse angular gravel. --= SANDY SILT(ML): Brown to light brown, 7,10,12 --= dry to slightly moist, very stiff to hard, with -= fine-grained sand. -_ --Moderate to strong calcium carbonate --= cementation from 5.0 to 5.5 feet bgs. 5 --= 27,44,29 0 30 0 2791 S.Victory View Way • Boise, ID 83709 . (208)376-4748 . Fax(208)322-6515 oneatlas.com �TrT-G7Tdr-W1 Appendix V GEOTECHNICAL GENERAL NOTES Unified Soil Classification System Major Divisions Symbol Soil Descriptions Gravel & GW Well-graded ravels; ravel/sand mixtures with little or no fines Coarse- Gravelly Soils GP Poorl - raded ravels; ravel/sand mixtures with little or no fines Grained < 50% GM Silty gravels; poorly-graded ravel/sand/silt mixtures Soils < coarse GC Clayey gravels; poorly-graded gravel/sand/clay mixtures 50% Sand & Sandy SW Well-graded sands; gravelly sands with little or no fines passes Soils > 50% SP Poorl - raded sands; gravelly sands with little or no fines No.200 coarse SM Silty sands; poorly-graded sand/gravel/silt mixtures sieve fraction Sc Clayey sands; poorly-graded sand/gravel/clay mixtures Fine- ML Inorganic silts; sandy, gravellyor clayey silts Grained Silts & Clays CL Lean clays; inorganic, gravelly, sandy, or silty, low to medium- Soils > LL < 50 plasticity clays 50% OL Organic, low-plasticity clays and silts passes MH Inorganic, elastic silts; sand ravel) or clayey elastic silts No.200 Silts &Clays CH Fat clays high-plasticity, inorganic clays sieve LL > 50 OH Organic, medium to high-plasticity clays and silts Highly Organic Soils PT Peat, humus, h dric soils with high organic content Relative Density • Consistency oisture Contentand Cementation • Class ificatlorh� Coarse-Grained Soils SPT Blow Counts N Description Field Test Very Loose: <4 Dry Absence of moisture, dry to touch Loose: 4-10 Slightly Moist Damp, but no visible moisture Medium Dense: 10-30 Moist Visible moisture Dense: 30-50 Wet Visible free water Very Dense: >50 Saturated Soil is usually below water table Fine-Grained Soils SPT Blow Counts N Description Field Test Very Soft: <2 Weak Crumbles or breaks with handling or Soft: 2-4 slight finger pressure Medium Stiff: 4-8 Moderate Crumbles or breaks with Stiff: 8-15 considerable finger pressure Very Stiff: 15-30 Strong Will not crumble or break with finger Hard: >30 pressure Particle Size M I ]�� Acronym List Boulders: > 12 in. GS grab sample Cobbles: 12 to 3 in. LL Liquid Limit Gravel: 3 in. to 5 mm M moisture content Coarse-Grained Sand: 5 to 0.6 mm NP non-plastic Medium-Grained Sand: 0.6 to 0.2 mm PI Plasticity Index Fine-Grained Sand: 0.2 to 0.075 mm Qp penetrometer value, unconfined compressive Silts: 0.075 to 0.005 mm strength, tsf Clays: < 0.005 mm V vane value, ultimate shearing strength, tsf Atlas No. B221077g Page 132 Copyright©2022 Atlas Technical Consultants �TrT-G7Tdr-W� Appendix VI ROCK CLASSIFICATION SYSTEM Weathering 1=1 Weathering Field Test Fresh No sign of decomposition or discoloration. Rings under hammer impact. Slightly Weathered Slight discoloration inwards from open fractures, otherwise similar to Fresh. Moderately Discoloration throughout. Weaker minerals such as feldspar decomposed. Weathered Strength somewhat less than fresh rock but cores cannot be broken by hand or scraped with a knife. Texture preserved. Most minerals somewhat decomposed. Specimens can be broken by hand with Highly Weathered effort or shaved with knife. Core stones present in rock mass. Texture becoming indistinct but fabric preserved. Completely Minerals decomposed to soil but fabric and structure preserved. Specimens Weathered easily crumbled or penetrated. Fracturing 1,11 F I traTiTUP2 Spacing Description RQD % Rock Quality 6 ft. Very widely 90— 100 Excellent 2 to 6 ft. Widely 75 to 90 Good 8 to 24 in. Moderately 50 to 75 Fair 2 %2 to 8 in. Closel 25 to 50 Poor %to 2 %2 in. Very Close) 0 to 25 Very Poor Competency Approximate Range of Strength Class Field Test Unconfined Compressive Strength (tsf) Extremely I Many blows with geologic hammer required to > 2000 Strong break intact specimen. Very II Hand-held specimen breaks with pick end of 2000 - 1000 Strong hammer under more than one blow. Cannot be scraped or peeled with knife, hand-held Strong III specimen can be broken with single moderate 1000 - 500 blow with pick end of hammer. Moderately Can just be scraped or peeled with knife. Strong IV Indentations 1 mm to 3 mm show in specimen with 500 - 250 moderate blow with pick end of hammer. Material crumbles under moderate blow with pick Weak V end of hammer and can be peeled with a knife, but 250 - 10 is hard to hand-trim for tri-axial test specimen. Friable VI Material crumbles in hand. N/A Atlas No. B221077g Page 133 Copyright©2022 Atlas Technical Consultants �TrT-G7T��. Appendix VII GRAVEL EQUIVALENT METHOD PAVEMENT DESIGN Pavement Section Design Location: Lake Hazel Road Widening, Lake Hazel Road Average Daily Traffic Count: 1,500 All Lanes&Both Directions Design Life: 20 Years Traffic Index: 10.00 Climate Factor: 1 R-Value of Subgrade: 11.00 Subgrade CBR Value: 5 Subgrade Mr: 7,500 R-Value of Aggregate Base: 80 R-Value of Granular Borrow: 60 Subgrade R-Value: 11 Expansion Pressure of Subgrade: 0.00 Unit Weight of Base Materials: 130 Total Design Life 18 kip ESAL's: 2,423,921 ASPHALTIC CONCRETE: Gravel Equivalent,Calculated: 0.640 Thickness: 0.328205128 Use= 4 Inches Gravel Equivalent,ACTUAL: 0.65 CRUSHED AGGREGATE BASE: Gravel Equivalent(Ballast): 1.280 Thickness: 0.573 Use= 4 Inches Gravel Equivalent,ACTUAL: 1.017 SUBBASE: Gravel Equivalent(Ballast): 2.848 Thickness: 1.831 Use= 22 Inches Gravel Equivalent,ACTUAL: 2.850 TOTAL Thickness: 2.500 Thickness Required by Exp. Pressure: 0.000 Design ACHD Depth Substitution Inches Ratios Asphaltic Concrete (at least 2.5): 4.00 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): 22.00 1.00 Atlas No. B221077g Page 134 Copyright©2022 Atlas Technical Consultants Appendix VIII R-VALUE LABORATORY TEST DATA Source and Description: B-8: 1.5'-25, Sandy Silt Date Obtained: Jul 19', 2022 Sample ID: 22-0899 (B221077g) Sampling and Preparation: ASTM D75: AASHTO T2: X ASTM AASHTO X D421: T87: Test Standard: ASTM AASHTO Idaho T8: X D2844: T190: Sample A B C Dry Density Ib/ft3 99.3 98.9 93.9 Moisture Content % 24.2 23.7 23.3 Expansion Pressure (psi) 0.00 0.00 0.00 Exudation Pressure (psi) 316 257 155 R-Value 16 15 7 R-Value @ 200 psi Exudation Pressure = 11 R-Value @ Exudation Pressure 17.0 15.0 13.0 d 11.0 9.0 7.0 5.0 350 300 250 200 150 Exudation Pressure (psi) Atlas No. B221077g Page 135 Copyright©2022 Atlas Technical Consultants IMPOPIOnt InfOPM81100 Rhout ■ GeolechnicalmEngineeping Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes. While you cannot eliminate all such risks, you can manage them. The following information is provided to help. The Geoprofessional Business Association (GBA) will not likely meet the needs of a civil-works constructor or even a has prepared this advisory to help you—assumedly different civil engineer.Because each geotechnical-engineering study a client representative—interpret and apply this is unique,each geotechnical-engineering report is unique,prepared geotechnical-engineering report as effectively as solely for the client. possible. In that way, you can benefit from a lowered Likewise,geotechnical-engineering services are performed for a specific exposure to problems associated with subsurface project and purpose.For example,it is unlikely that a geotechnical- conditions at project sites and development of engineering study for a refrigerated warehouse will be the same as them that,for decades, have been a principal cause one prepared for a parking garage;and a few borings drilled during of construction delays, cost overruns, claims, a preliminary study to evaluate site feasibility will not be adequate to and disputes. If you have questions or want more develop geotechnical design recommendations for the project. information about any of the issues discussed herein, contact your GBA-member geotechnical engineer. Do not rely on this report if your geotechnical engineer prepared it: Active engagement in GBA exposes geotechnical • for a different client; engineers to a wide array of risk-confrontation • for a different project or purpose; techniques that can be of genuine benefit for • for a different site(that may or may not include all or a portion of everyone involved with a construction project. the original site);or before important events occurred at the site or adjacent to it; e.g.,man-made events like construction or environmental Understand the Geotechnical-Engineering Services remediation,or natural events like floods,droughts,earthquakes, Provided for this Report or groundwater fluctuations. Geotechnical-engineering services typically include the planning, collection,interpretation,and analysis of exploratory data from Note,too,the reliability of a geotechnical-engineering report can widely spaced borings and/or test pits.Field data are combined be affected by the passage of time,because of factors like changed with results from laboratory tests of soil and rock samples obtained subsurface conditions;new or modified codes,standards,or from field exploration(if applicable),observations made during site regulations;or new techniques or tools.If you are the least bit uncertain reconnaissance,and historical information to form one or more models about the continued reliability of this report,contact your geotechnical of the expected subsurface conditions beneath the site.Local geology engineer before applying the recommendations in it.A minor amount and alterations of the site surface and subsurface by previous and of additional testing or analysis after the passage of time-if any is proposed construction are also important considerations.Geotechnical required at all-could prevent major problems. engineers apply their engineering training,experience,and judgment to adapt the requirements of the prospective project to the subsurface Read this Report in Full model(s). Estimates are made of the subsurface conditions that Costly problems have occurred because those relying on a geotechnical- will likely be exposed during construction as well as the expected engineering report did not read the report in its entirety.Do not rely on performance of foundations and other structures being planned and/or an executive summary.Do not read selective elements only.Read and affected by construction activities. refer to the report in full. The culmination of these geotechnical-engineering services is typically a You Need to Inform Your Geotechnical Engineer geotechnical-engineering report providing the data obtained,a discussion About Change of the subsurface model(s),the engineering and geologic engineering Your geotechnical engineer considered unique,project-specific factors assessments and analyses made,and the recommendations developed when developing the scope of study behind this report and developing to satisfy the given requirements of the project.These reports may be the confirmation-dependent recommendations the report conveys. titled investigations,explorations,studies,assessments,or evaluations. Typical changes that could erode the reliability of this report include Regardless of the title used,the geotechnical-engineering report is an those that affect: engineering interpretation of the subsurface conditions within the context - the site's size or shape; of the project and does not represent a close examination,systematic inquiry,or thorough investigation of all site and subsurface conditions. the elevation,configuration,location,orientation, function or weight of the proposed structure and Geotechnical-Engineering Services are Performed the desired performance criteria; the composition of the design team;or for Specific Purposes, Persons, and Projects, . project ownership. and At Specific Times Geotechnical engineers structure their services to meet the specific As a general rule,always inform your geotechnical engineer of project needs,goals,and risk management preferences of their clients.A or site changes-even minor ones-and request an assessment of their geotechnical-engineering study conducted for a given civil engineer impact.The geotechnical engineer who prepared this report cannot accept responsibility or liability for problems that arise because the geotechnical conspicuously that you've included the material for information purposes engineer was not informed about developments the engineer otherwise only.To avoid misunderstanding,you may also want to note that would have considered. "informational purposes"means constructors have no right to rely on the interpretations,opinions,conclusions,or recommendations in the Most Of the "Findings" Related in This Report report.Be certain that constructors know they may learn about specific Are Professional Opinions project requirements,including options selected from the report,only Before construction begins,geotechnical engineers explore a site's from the design drawings and specifications.Remind constructors subsurface using various sampling and testing procedures.Geotechnical that they may perform their own studies if they want to,and be sure to engineers can observe actual subsurface conditions only at those specific allow enough time to permit them to do so.Only then might you be in locations where sampling and testing is performed.The data derived from a position to give constructors the information available to you,while that sampling and testing were reviewed by your geotechnical engineer, requiring them to at least share some of the financial responsibilities who then applied professional judgement to form opinions about stemming from unanticipated conditions.Conducting prebid and subsurface conditions throughout the site.Actual sitewide-subsurface preconstruction conferences can also be valuable in this respect. conditions may differ-maybe significantly-from those indicated in this report.Confront that risk by retaining your geotechnical engineer Read Responsibility Provisions Closely to serve on the design team through project completion to obtain Some client representatives,design professionals,and constructors do informed guidance quickly,whenever needed. not realize that geotechnical engineering is far less exact than other engineering disciplines.This happens in part because soil and rock on This Report's Recommendations Are project sites are typically heterogeneous and not manufactured materials Confirmation-Dependent with well-defined engineering properties like steel and concrete.That The recommendations included in this report-including any options or lack of understanding has nurtured unrealistic expectations that have alternatives-are confirmation-dependent.In other words,they are not resulted in disappointments,delays,cost overruns,claims,and disputes. final,because the geotechnical engineer who developed them relied heavily TO confront that risk,geotechnical engineers commonly include on judgement and opinion to do so.Your geotechnical engineer can finalize explanatory provisions in their reports.Sometimes labeled"limitations,' the recommendations only after observing actual subsurface conditions many of these provisions indicate where geotechnical engineers' exposed during construction.If through observation your geotechnical responsibilities begin and end,to help others recognize their own engineer confirms that the conditions assumed to exist actually do exist, responsibilities and risks.Read these provisions closely.Ask questions. the recommendations can be relied upon,assuming no other changes have Your geotechnical engineer should respond fully and frankly. occurred.The geotechnical engineer who prepared this report cannot assume responsibility or liabilityfor confirmation-dependent recommendations fyou Geoenvironmental Concerns Are Not Covered fail to retain that engineer to perform construction observation. The personnel,equipment,and techniques used to perform an environmental study-e.g.,a"phase-one"or"phase-two"enviromnental This Report Could Be Misinterpreted site assessment-differ significantly from those used to perform a Other design professionals'misinterpretation of geotechnical- geotechnical-engineering study.For that reason,a geotechnical-engineering engineering reports has resulted in costly problems.Confront that risk report does not usually provide environmental findings,conclusions,or by having your geotechnical engineer serve as a continuing member of recommendations;e.g.,about the likelihood of encountering underground the design team,to: storage tanks or regulated contaminants.Unanticipated subsurface • confer with other design-team members; environmental problems have led to project failures.If you have not • help develop specifications; obtained your own environmental information about the project site, review pertinent elements of other design professionals'plans and ask your geotechnical consultant for a recommendation on how to find specifications;and environmental risk-management guidance. • be available whenever geotechnical-engineering guidance is needed. Obtain Professional Assistance to Deal with You should also confront the risk of constructors misinterpreting this Moisture Infiltration and Mold report.Do so by retaining your geotechnical engineer to participate in While your geotechnical engineer may have addressed groundwater, prebid and preconstruction conferences and to perform construction- water infiltration,or similar issues in this report,the engineer's phase observations. services were not designed,conducted,or intended to prevent migration of moisture-including water vapor-from the soil Give Constructors a Complete Report and Guidance through building slabs and walls and into the building interior,where Some owners and design professionals mistakenly believe they can shift it can cause mold growth and material-performance deficiencies. unanticipated-subsurface-conditions liability to constructors by limiting Accordingly,proper implementation of the geotechnical engineer's the information they provide for bid preparation.To help prevent recommendations will not of itself be sufficient to prevent the costly,contentious problems this practice has caused,include the moisture infiltration.Confront the risk of moisture infiltration by complete geotechnical-engineering report,along with any attachments including building-envelope or mold specialists on the design team. or appendices,with your contract documents,but be certain to note Geotechnical engineers are not building-envelope or mold specialists. GEOPROFESSIONAL BUSINESS SEA ASSOCIATION Telephone:301/565-2733 e-mail:info@geoprofessional.org www.geoprofessional.org Copyright 2019 by Geoprofessional Business Association(GBA).Duplication,reproduction,or copying of this document,in whole or in part,by any means whatsoever,is strictly prohibited,except with GBAs specific written permission.Excerpting,quoting,or otherwise extracting wording from this document is permitted only with the express written permission of GBA,and only for purposes of scholarly research or book review.Only members of GBA may use this document or its wording as a complement to or as an element of a report of any kind. Any other firm,individual,or other entity that so uses this document without being a GBA member could be committing negligent or intentional(fraudulent)misrepresentation.