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CC - Geotech report
Street Elevation Sheet The Geotek Report which is attached within this short plat application is referenced in the NINE MILE CREEK BUNGALOWS finish centerline elevation statement which has been attached as a document labeled Centerline Certification. The construction plans, sheet 4 has the elevations as shown. " w � � L N, L I „ r r r GEOTECHNICAL INVESTIGATION NINE MILE CREEK BUNGALOWS 2055 S Locust Grove Road Meridian, ID PREPARED FOR: Robyn Shea Idaho Summit Real Estate 2055 S Locust Grove Rd Meridian, ID 83642 PREPARED BY: Atlas Technical Consultants, LLC September 11, 2023 2791 South Victory View Way B231456g Boise, ID 83709 2791 South Victory View Way Boise, ID 83709 (208)376-4748 1 oneatlas.com September 11, 2023 Atlas No. B231456g Robyn Shea Idaho Summit Real Estate 2055 S Locust Grove Rd Meridian, ID 83642 Subject: Geotechnical Investigation Nine Mile Creek Bungalows 2055 S Locust Grove Road Meridian, ID Dear Robyn Shea: 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 August 25, 2023. 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, Max Kasberger, PE Clinton Wyllie, PG Geotechnical Engineer Staff Geologist Elizabeth Brown, PE National Practice Manager- Geotechnical Page 1 �TrT-G7T-�. CONTENTS 1. INTRODUCTION................................................................................................................. 2 1.1 Project Description ..................................................................................................... 2 1.2 Scope of Investigation................................................................................................ 2 2. SITE DESCRIPTION........................................................................................................... 3 2.1 Regional Geology....................................................................................................... 3 2.2 General Site Characteristics....................................................................................... 3 3. SEISMIC SITE EVALUATION ............................................................................................ 3 3.1 Geoseismic Setting .................................................................................................... 3 3.2 Seismic Design Parameter Values ............................................................................. 4 4. SOILS EXPLORATION....................................................................................................... 4 4.1 Exploration and Sampling Procedures........................................................................ 4 4.2 Laboratory Testing Program....................................................................................... 4 4.3 Soil and Sediment Profile........................................................................................... 5 4.4 Volatile Organic Scan................................................................................................. 5 5. SITE HYDROLOGY... ..................................................................................................... 5 5.1 Groundwater.............................................................................................................. 5 5.2 Soil Infiltration Rates .................................................................................................. 6 5.3 Infiltration Testing....................................................................................................... 6 6. FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS............................ 6 6.1 Foundation Loading Information................................................................................. 7 6.2 Foundation Design Recommendations....................................................................... 7 6.3 Garage, Patio, Floor Slab-on-Grade........................................................................... 8 7. PAVEMENT DISCUSSION AND RECOMMENDATIONS................................................... 8 7.1 Pavement Design Parameters.................................................................................... 8 7.2 Flexible Pavement Section......................................................................................... 9 7.3 Pavement Subgrade Preparation ............................................................................... 9 7.4 Common Pavement Section Construction Issues......................................................10 8. CONSTRUCTION CONSIDERATIONS ............................................................................. 8.1 Earthwork..................................................................................................................10 8.2 Grading .....................................................................................................................11 8.3 Dry Weather..............................................................................................................11 8.4 Wet Weather.............................................................................................................11 8.5 Soft Subgrade Soils...................................................................................................11 8.6 Frozen Subgrade Soils..............................................................................................12 8.7 Structural Fill .............................................................................................................12 8.8 Fill Placement and Compaction.................................................................................13 8.9 Backfill of Walls.........................................................................................................14 Atlas No. B231456g Page I i Copyright©2023 Atlas Technical Consultants �M" ■ �TrT-G7T-Zr-_. 8.10 Excavations.............................................................................................................15 8.11 Groundwater Control...............................................................................................15 9. GENERAL COMMENTS....................................................................................................15 10. REFERENCES.................................................................................................................16 TABLES Table 1 — Seismic Design Values................................................................................................4 Table 2 —Typical Soil Profiles.....................................................................................................5 Table 3 — Groundwater Data.......................................................................................................6 Table 4 — Soil Bearing Capacity..................................................................................................7 Table 5 —AASHTO Flexible Pavement Specifications.................................................................9 Table 6 — Fill Material Criteria ...................................................................................................12 Table 7 — Fill Placement and Compaction Requirements..........................................................13 APPENDICES Appendix I Warranty and Limiting Conditions Appendix II Vicinity Map Appendix III Site Map Appendix IV Geotechnical Investigation Test Pit Log Appendix V Geotechnical General Notes Appendix VI Important Information About This Geotechnical Engineering Report Atlas No. B231456g Page I ii Copyright©2023 Atlas Technical Consultants 1. INTRODUCTION This report presents results of a geotechnical investigation and analysis in support of data utilized in design of structures as defined in the 2018 International Building Code (IBC). Information in support of groundwater and stormwater issues pertinent to the practice of Civil Engineering is included. Observations and recommendations relevant to the earthwork phase of the project are also presented. Revisions in plans or drawings for the proposed development from those enumerated in this report should be brought to the attention of the soils engineer to determine whether changes in the provided recommendations are required. Deviations from noted subsurface conditions, if encountered during construction, should also be brought to the attention of the soils engineer. 1.1 Project Description The proposed development is in the City of Meridian, Ada County, ID, and occupies a portion of the SE'/4NE'/4 of Section 19, Township 3 North, Range 1 East, Boise Meridian. The site to be developed is approximately 1.3 acres. Site maps included in the Appendix show the project location. This project will consist of subdividing the existing lot into 4 lots ranging between 0.24 and 0.36 acre in size. A paved driveway will be constructed to access the lots. The existing house and carport will remain on the site as lot 1, and the other existing structures will be demolished. Retaining walls are not anticipated as part of the project. Drainage is expected to be directed to onsite infiltration facilities. Location of the infiltration facilities are unknown at this time. Atlas has not been informed of the proposed grading plan. icope of Investigation Our scope of work was completed in general accordance with our proposal dated August 4, 2023 and authorized on August 14, 2023. Said authorization is subject to terms, conditions, and limitations described in the Professional Services Contract entered into between Idaho Summit Real Estate and Atlas. Atlas' scope of services included the following: Subsurface exploration via test pits advanced with a client supplied excavator. Infiltration testing for stormwater management planning. Field and laboratory testing of materials encountered and collected. Preparation of this report, which includes project description, site conditions, and our engineering analysis and evaluation for the project. The scope of work did not include design recommendations specific to individual residences. Atlas No. B231456g Page12 Copyright©2023 Atlas Technical Consultants 2. SITE DESCRIPTION 2.1 Regional Geology The project site is located within the western Snake River Plain of southwestern Idaho and eastern Oregon. The plain is a northwest trending rift basin, about 45 miles wide and 200 miles long, that developed about 14 million years ago (Ma) and has since been occupied sporadically by large inland lakes. Geologic materials found within and along the plain's margins reflect volcanic and fluvial/lacustrine sedimentary processes that have led to an accumulation of approximately 1 to 2 km of interbedded volcanic and sedimentary deposits within the plain. Along the margins of the plain, streams that drained the highlands to the north and south provided coarse to fine-grained sediments eroded from granitic and volcanic rocks, respectively. About 2 million years ago the last of the lakes was drained and since that time fluvial erosion and deposition has dominated the evolution of the landscape. The project site is underlain by "Sandy Alluvium of Side-Stream Valleys and Gulches" as mapped by Othberg and Stanford (1993). Locally, these deposits are composed of medium to coarse sand interbedded with silty fine sand and silt and are mostly derived from weathered granite and reworked Tertiary sediments of the Boise Foothills. The thickness of this unit is variable. Because of the relative youthfulness of these deposits they contain only minor pedogenic clay and calcium carbonate. 2.2 General Site Characteristics The following details regarding site conditions are based on visual observations and review of available geologic and topographic maps and imagery: • Current Site Conditions: The site is approximately 1.3 acres and currently consists of a residential property. The residence is located in the southeast quarter of the lot, with associated out buildings to the west and north. The site is bounded to the north/northeast by Ninemile Creek. The northern half of the property consists of a gravel driveway and parking area. The southern portion of the site consists of landscape grass. • Vegetation: Vegetation on the site consists primarily of landscape grasses adjacent to the structure. • Topography: The site is relatively flat and level. • Drainage: Stormwater drainage for the site is achieved by percolation through surficial soils. The site is situated so that it is unlikely that it will receive any drainage from off-site sources. 3. SEISMIC SITE EVALUATION 3.1 Geoseismic Setting Soils on site are classed as Site Class D in accordance with Chapter 20 of the American Society of Civil Engineers (ASCE) publication ASCE/SEI 7-16. Structures constructed on this site should be designed per IBC requirements for such a seismic classification. Our investigation revealed low hazard potential resulting from potential earthquake motions including: slope instability, liquefaction, and surface rupture caused by faulting or lateral spreading. Atlas No. B231456g Page 13 Copyright©2023 Atlas Technical Consultants 3.2 Seismic Design Parameter Values The ASCE 7-16 seismic design parameter values have been provided below. Table 1 — Seismic Design Values Seismic Design Parameter Design Value Site Class D "Default" Site Modified Peak Ground 0.197 Acceleration, PGAM Ss 0.288 (g) S, 0.105 (g) Fa 1.570 Fv 2.390 Sens 0.452 SM, 0.251 Sos 0.301 Sol 0.167 4. SOILS EXPLORATION 4.1 Exploration and Sampling Procedures Field exploration conducted to determine engineering characteristics of subsurface materials included a reconnaissance of the project site and investigation by test pit. Test pit sites were located in the field by means of a Global Positioning System (GPS) device and are reportedly accurate to within ten feet. Upon completion of investigation, each test pit was backfilled with loose excavated materials. Re-excavation and compaction of these test pit areas are required prior to construction. Samples obtained have been visually classified in the field, identified according to test pit number and depth, placed in sealed containers, and transported to our laboratory for additional testing. Subsurface materials have been described in detail on logs provided in the Appendix. Results of field and laboratory tests are also presented in the Appendix. Atlas recommends that these logs not be used to estimate fill material quantities. 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. Laboratory tests were conducted in accordance with current specifications. The laboratory testing program for this report included: • Atterberg Limits Testing —ASTM D4318 • Grain Size Analysis —ASTM C117/C136 Atlas No. B231456g Page14 Copyright©2023 Atlas Technical Consultants 4.3 Soil and Sediment Profile The profile below represents a generalized interpretation for the project site. Note that on site soils strata, encountered between test pit locations, may vary from the individual soil profiles presented in the logs. Table 2 —Typical Soil Profiles ApproximateSoil Horizons . DepthsSoil Types Fill Materials' 0 to 3 feet Sandy Silt Fill, Silty Gravel with Sand Fill Very Stiff/ Medium Dense Deeper Soils 3 to 9 feet Clayey Gravel with Sand, Poorly Graded Medium Dense Gravel with Clay and Sand 'Debris encountered within portions of fill materials. During excavation,test pit 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. 4.4 Volatile Organic Scan 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 apparent 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 9.0 feet bgs. Atlas has previously performed 6 geotechnical investigations within 0.45 mile of the project site. Information from these investigations has been provided in the table below. Atlas No. B231456g Page 15 Copyright©2023 Atlas Technical Consultants �TrT-G7Tdr-W� Table 3— Groundwater Data April 2017 0.16 Northeast Not Encountered to 17.3 July 2004 0.31 North Not Encountered to 14.9 July 2018 0.33 East Not Encountered to 21.5 September 2022 0.35 North Not Encountered to 16.5 November 2020 0.39 East Not Encountered to 15.1 August 2017 0.43 North 26.4 For construction purposes, groundwater depth can be assumed to remain greater than 20 feet bgs throughout the year. Soil Infiltration Rates Soil permeability, which is a measure of the ability of a soil to transmit a fluid, was tested in the field. For this report, an estimation of infiltration is also presented using generally recognized values. Infiltration rates for clayey gravel with sand sediments and poorly graded gravel with clay and sand sediments typically range between less than 2 and 6 inches per hour. 5.3 Infiltration Testing Infiltration testing was conducted using an open test pit method. The test location was presoaked prior to testing. Pre-soaking increases soil moistures, which allows the tested soils to reach a saturated condition more readily during testing. Saturation of the tested soils is desirable in order to isolate the vertical component of infiltration by inhibiting horizontal seepage during testing. On August 25, 2023, testing was conducted within poorly graded gravel with clay and sand sediments at a depth of 5.2 feet bgs in test pit 2. A stabilized infiltration rate of 5.8 inches per hour was achieved during testing. Atlas recommends a design infiltration rate of 2.9 inches per hour. The reason for the decreased infiltration rate is to account for long term saturation of the soils and the potential for less permeable soils to settle into the bottom of the infiltration facilities. Atlas recommends that all infiltration facilities be constructed in accordance with the local municipality requirements. . FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS Various foundation types have been considered for support of the proposed structures. Two requirements must be met in the design of foundations. First, the applied bearing stress must be less than the ultimate bearing capacity of foundation soils to maintain stability. Second, total and differential settlement must not exceed an amount that will produce an adverse behavior of the superstructure. Allowable settlement is usually exceeded before bearing capacity considerations become important; thus, allowable bearing pressure is normally controlled by settlement considerations. Atlas No. B231456g Page 16 Copyright©2023 Atlas Technical Consultants 6.1 Foundation Loading Information Loads of up to 4,000 pounds per lineal foot for wall footings, and column loads of up to 50,000 pounds were assumed for settlement calculations. Total settlement should be limited to approximately 1 inch and differential settlement should be limited to approximately '/2 inch, provided the following design and construction recommendations are observed. 6.2 Foundation Design Recommendations Considering subsurface conditions and the proposed construction, it is recommended that the structures be founded upon conventional spread footings and continuous wall footings. The following recommendations are not specific to the individual structures, but rather should be viewed as guidelines for the subdivision-wide development. 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 4— Soil Bearing Capacity Footings must bear on competent, undisturbed, 3,000Ibs/ft2 native poorly graded gravel with clay and sand Not Required for Native A '/3 increase is sediments or compacted structural fill. Existing fill Soil allowable if the materials must be completely removed from below alternative basic load foundation elements.' Excavation depths ranging 95% for Structural Fill combinations of Section from roughly 2.8 to 3.2 feet bgs should be 1605.3.2 of the 2018 IBC anticipated to expose proper bearing soils.2 are used in design. 'It will be required for Atlas personnel to verify the bearing soil suitability for each structure at the time of construction. 2Depending on the time of year construction takes place,the subgrade soils may be unstable because of high moisture contents. If unstable conditions are encountered,over-excavation and replacement with granular structural fill and/or use of geotextiles may be required. The following sliding frictional coefficient values should be used: 1) 0.35 for footings bearing on native poorly graded gravel with clay and sand sediments and 2) 0.45 for footings bearing on granular structural fill. A passive lateral earth pressure of 415 pounds per square foot per foot (psf/ft) should be used for poorly graded gravel with clay and sand sediments. For compacted sandy gravel fill, a passive lateral earth pressure of 496 psf/ft should be used. Footings should be proportioned to meet either the stated soil bearing capacity or the 2018 IBC minimum requirements. Objectionable soil types encountered at the bottom of footing excavations should be removed and replaced with structural fill. Excessively loose or soft areas that are encountered in the footings subgrade will require over-excavation and backfilling with structural fill. To minimize the effects of slight differential movement that may occur because of variations in the character of supporting soils and seasonal moisture content, Atlas recommends continuous footings be suitably reinforced to make them as rigid as possible. For frost protection, the bottom of external footings should be 24 inches below finished grade. Foundations must be backfilled in accordance with the Backfill of Walls section. Atlas No. B231456g Page 17 Copyright©2023 Atlas Technical Consultants 6.3 Garage, Patio, Floor Slab-on-Grade Uncontrolled fill, which contained debris, was encountered in portions of the site. Atlas recommends that these fill materials be removed to a depth of at least 2 feet below existing grade. If fill materials remain after excavation, all debris must be removed and the exposed subgrade must be compacted to at least 95 percent of the maximum dry density as determined by ASTM D1557. The excavated fill materials can be replaced in accordance with the Fill Placement and Compaction section provided that all organic material and debris is completely removed. Once final grades have been determined, Atlas is available to provide additional recommendations. Additionally, it is assumed that fill materials resulting from demolition activities will be present at the time of construction. Atlas recommends all fill materials resulting from demolition activities be removed below any structures. Organic, loose, or obviously compressive materials must be removed prior to placement of concrete floors or floor-supporting fill. In addition, the remaining subgrade should be treated in accordance with guidelines presented in the Earthwork section. Areas of excessive yielding should be excavated and backfilled with structural fill. Fill used to increase the elevation of the floor slab should meet requirements detailed in the Structural Fill section. Fill materials must be compacted to a minimum 95 percent of the maximum dry density as determined by ASTM D1557. A free-draining granular mat should be provided below slabs-on-grade to provide drainage and a uniform and stable bearing surface. This should be a minimum of 4 inches in thickness and properly compacted. The mat should consist of a sand and gravel mixture, complying with Idaho Standards for Public Works Construction (ISPWC) specifications for %-inch (Type 1) crushed aggregate. The granular mat should be compacted to no less than 95 percent of the maximum dry density as determined by ASTM D1557. A moisture-retarder should be placed beneath floor slabs to minimize potential ground moisture effects on moisture-sensitive floor coverings. The moisture-retarder should be at least 15-mil in thickness and have a permeance of less than 0.01 US perms as determined by ASTM E96. Placement of the moisture-retarder will require special consideration with regard to effects on the slab-on-grade and should adhere to recommendations outlined in the ACI 302.1 R and ASTM E1745 publications. Upon request, Atlas can provide further consultation regarding installation. 7. PAVEMENT DISCUSSION AND RECOMMENDATIONS 7.1 Pavement Design Parameters Project specific traffic loading information has not been provided. Based on the character of the proposed construction, Atlas has assumed a traffic loading of 45,000 equivalent single axle loads (ESALs) for the residential roadway. Atlas can provide a project specific pavement design upon request. Based on experience with soils in the region, a subgrade California Bearing Ratio (CBR) value of 5 has been assumed for near-surface poorly graded gravel with clay and sand sediments and silty gravel with sand fill materials on site. Atlas No. B231456g Page 18 Copyright©2023 Atlas Technical Consultants The recommended pavement section provided below is based on a 20-year design life. To achieve this design life a routine maintenance program that includes crack sealing on a regular basis and possible seal coating will be required. 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 Subqrade Soils section. 7.2 Flexible Pavement Section The American Association of State Highway and Transportation Officials (AASHTO) design method has been used to calculate the following pavement section. Atlas recommends that materials used in the construction of asphaltic concrete pavements meet requirements of the ISPWC Standard Specification for Highway Construction. Construction of the pavement section should be in accordance with these specifications. Table 5—AASHTO Flexible Pavement Specifications ComponentPavement Section Roadway Asphaltic Concrete 2.5 Inches Crushed Aggregate Base 4.0 Inches Structural Subbase 6.0 Inches Compacted Subgrade' See Pavement Subgrade Preparation Section • 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 Type 1 Crushed Aggregate Materials. • Structural Subbase: Material complying with ISPWC Section 801 for 3-inch or 6-inch Uncrushed Aggregate Materials. The maximum material diameter cannot exceed 2/3 the component thickness. 7.3 Pavement Subgrade Preparation Uncontrolled fill, which contained debris, was encountered in portions of the site. Atlas recommends that these fill materials be removed to a depth of at least 2 feet below existing grade. If fill materials remain after excavation, all debris must be removed and the exposed subgrade must be compacted to at least 95 percent of the maximum dry density as determined by ASTM D698 for flexible pavements. The excavated fill materials can be replaced in accordance with the Fill Placement and Compaction section provided that all organic material and debris is completely removed. However, the existing fill materials are not suitable for use as either the base or subbase components of the recommended pavement section. Once final grades have been determined, Atlas is available to provide additional recommendations. Atlas No. B231456g Page 19 Copyright©2023 Atlas Technical Consultants �/��M" ■ p �TrT-G7T-*1. Additionally, it is assumed that fill materials resulting from demolition activities will be present at the time of construction. Atlas recommends all fill materials resulting from demolition activities be removed below any roadways. 7.4 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. 8. CONSTRUCTION CONSIDERATIONS 8.1 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. Brush and thick grasses with associated root systems were noted 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. However, in areas where trees are/were present, deeper excavation depths should be anticipated. Stripping depths should be adjusted in the field to assure that the entire root zone or disturbed zone or topsoil are removed prior to placement and compaction of structural fill materials. Exact removal depths should be determined during grading operations by Atlas personnel, and should be based upon subgrade soil type, composition, and firmness or soil stability. If underground storage tanks, underground utilities, wells, or septic systems are discovered during construction activities, they must be decommissioned then removed or abandoned in accordance with governing Federal, State, and local agencies. Excavations developed as the result of such removal must be backfilled with structural fill materials as defined in the Structural Fill section. Atlas No. B231456g Page110 Copyright©2023 Atlas Technical Consultants �rrN+=0 A�1. 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. 8.2 Grading Positive grades must be maintained surrounding structures and pavements, including exterior slabs. The interface of plant bedding materials and underlying soils should be graded to provide drainage away from site elements. Otherwise, bedding materials may direct water to underlying fine-grained soils, which increases the potential for localized heave. Excessive watering of landscaping should be avoided. 8.3 Dry Weather If construction is to be conducted during dry seasonal conditions, many problems associated with soft soils may be avoided. However, some rutting of subgrade soils may be induced by shallow groundwater conditions related to springtime runoff or irrigation activities during late summer through early fall. Solutions to problems associated with soft subgrade soils are outlined in the Soft Subgrade Soils section. Problems may also arise because of lack of moisture in native and fill soils at time of placement. This will require the addition of water to achieve near-optimum moisture levels. Low-cohesion soils exposed in excavations may become friable, increasing chances of sloughing or caving. Measures to control excessive dust should be considered as part of the overall health and safety management plan. 8.4 Wet Weather If construction is to be conducted during wet seasonal conditions (commonly from mid-November through May), problems associated with soft soils must be considered as part of the construction plan. During this time of year, fine-grained soils such as silts and clays will become unstable with increased moisture content, and eventually deform or rut. Additionally, constant low temperatures reduce the possibility of drying soils to near optimum conditions. 8.5 Soft Subgrade Soils Shallow fine-grained subgrade soils that are high in moisture content should be expected to pump and rut under construction traffic. During periods of wet weather, construction may become very difficult if not impossible. The following recommendations and options have been included for dealing with soft subgrade conditions: • Track-mounted vehicles should be used to strip the subgrade of root matter and other deleterious debris. Heavy rubber-tired equipment should be prohibited from operating directly on the native subgrade and areas in which structural fill materials have been placed. Construction traffic should be restricted to designated roadways that do not cross, or cross on a limited basis, proposed roadway or parking areas. • Soft areas can be over-excavated and replaced with granular structural fill. Atlas No. B231456g Page111 Copyright©2023 Atlas Technical Consultants • Construction roadways on soft subgrade soils should consist of a minimum 2-foot thickness of large cobbles of 4 to 6 inches in diameter with sufficient sand and fines to fill voids. Construction entrances should consist of a 6-inch thickness of clean, 2-inch minimum, angular drain-rock and must be a minimum of 10 feet wide and 30 to 50 feet long. During the construction process, top dressing of the entrance may be required for maintenance. • Scarification and aeration of subgrade soils can be employed to reduce the moisture content of wet subgrade soils. After stripping is complete, the exposed subgrade should be ripped or disked to a depth of 1'/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. 8.6 Frozen Subgrade Soils Prior to placement of structural fill materials or foundation elements, frozen subgrade soils must either be allowed to thaw or be stripped to depths that expose non-frozen soils and wasted or stockpiled for later use. Stockpiled materials must be allowed to thaw and return to near-optimal conditions prior to use as structural fill. The onsite, shallow clayey and silty soils are susceptible to frost heave during freezing temperatures. For exterior flatwork and other structural elements, adequate drainage away from subgrades is critical. Compaction and use of structural fill will also help to mitigate the potential for frost heave. Complete removal of frost susceptible soils for the full frost depth, followed by replacement with a non-frost susceptible structural fill, can also be used to mitigate the potential for frost heave. Atlas is available to provide further guidance/assistance upon request. 8.7 Structural Fill The following table defines the types of fill material that is suitable for use on the project. Refer to the Fill Placement and Compaction section for recommended placement locations for each fill type listed below. Table 6— Fill Material Criteria Fill Type Material Lift Thickness* ISPWC Section 801 for 1-inch, 3-inch, or 6- Granular Structural Fill inch Uncrushed Aggregate and 12 inches ISPWC Section 802 Aggregate Base Aggregate Base Material ISPWC Section 802 for Type 1 Crushed 12 inches Aggregate Base Subbase Material ISPWC Section 801 for 3-inch or 6-inch 12 inches Uncrushed Aggregate Suitable Structural Fill Onsite/imported ML, SM, GM, GC and GP- 6 inches GC soils that are free of organics and debris Initial loose thickness,prior to compaction. Atlas No. B231456g Page112 Copyright©2023 Atlas Technical Consultants �TrT-G7T�1 8.8 Fill Placement and Compaction Requirements for fill material type and compaction effort are dependent on the planned use of the material. The following table specifies material type and compaction requirements based on the placement location of the fill material. Table 7 — Fill Placement and Compaction Requirements Foundations Granular Structural Fill 95% of ASTM D1557 Interior Slab-on-Grade and Below Granular Structural Fill or 95% of ASTM D1557 Rigid Pavement Subgrade Suitable Structural Fill Top 4 Inches of Interior and Exterior Aggregate Base Material 95% of ASTM D1557 Slab-on-Grade Below Flexible Pavement Subgrade Granular Structural Fill or 95% of ASTM D698 or and Exterior Flatwork Areas Suitable Structural Fill 92% of ASTM D1557 Foundation and Retaining Wall Granular Structural Fill or 95% of ASTM D1557 Backfill Suitable Structural Fill Utility Trench Backfill Granular Structural Fill or Per ISPWC Section 306 Suitable Structural Fill Landscape Areas Granular Structural Fill or 92% of ASTM D698 or Suitable Structural Fill 90/o of ASTM D1557 Prior to placement of structural fill materials, surfaces must be prepared as outlined in the Earthwork section. Structural fill material must be placed in horizontal lifts not exceeding 6- inches in thickness for fine-grained soils and 12-inches in thickness for granular structural fill, aggregate base material, and subbase material. All fill material must be moisture-conditioned to achieve optimum moisture content prior to compaction. During placement all fill materials must be monitored and tested to confirm compaction requirements have been achieved, as specified above, prior to placement of subsequent lifts. In addition, compacted surfaces must be in a firm and unyielding condition. Atlas personnel should be onsite to verify suitability of subgrade soil conditions, identify whether further work is necessary, and perform in-place moisture density testing. Sufficient density tests should be performed to properly monitor compaction. At a minimum, Atlas recommends one test per lift as follows: Structures — 1 test every 5,000 square feet Pavement and Exterior Flatwork Areas — 1 test every 10,000 square feet Foundation and Retaining Wall Backfill — 1 test every 500 square feet Utility Trench Backfill — 1 test every 100 linear feet Landscape Areas — 1 test every 15,000 square feet Atlas No. B231456g Pagel13 Copyright©2023 Atlas Technical Consultants Silty and clayey soils require very high moisture contents for compaction, 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 or clayey 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 laced. Following placement, the exposed surface must be protected from degradation resulting from construction traffic or subsequent construction. It is anticipated that fine-grained soils will not be suitable for reuse during the wet season. Use of silty soils (GM, SM, and ML) as structural fill below footings is prohibited. 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. If material contains more than 40 percent but less than 50 percent oversize (greater than 3/4-inch) particles, compaction of fill must be confirmed per ISPWC Section 202.3.8.C.3. Material should contain sufficient fines to fill void spaces and must not contain more than 50 percent oversize particles. 8.9 Backfill of Walls Backfill materials must conform to the requirements of structural fill, as defined in this report. For wall heights greater than 2.5 feet, the maximum material size should not exceed 4 inches in diameter. Placing oversized material against rigid surfaces interferes with proper compaction and can induce excessive point loads on walls. Backfill shall not commence until the wall has gained sufficient strength to resist placement and compaction forces. Further, retaining walls above 2.5 feet in height shall be backfilled in a manner that will limit the potential for damage from compaction methods and/or equipment. It is recommended that only small hand-operated compaction equipment be used for compaction of backfill within a horizontal distance equal to the height of the wall, measured from the back face of the wall. Backfill should be compacted in accordance with the specifications for structural fill, except in those areas where it is determined that future settlement is not a concern, such as planter areas. In nonstructural areas, backfill must be compacted to a firm and unyielding condition. Atlas recommends in these areas that the top 12 inches must consist of a low permeability (clay or silt) soil to limit surface water infiltration. Proper grading away from structures is critical. The surface must be graded away from the structure. In addition, Atlas recommends that roof drains carry stormwater at least 10 feet away from the structure. Atlas No. B231456g Page114 Copyright©2023 Atlas Technical Consultants 8.10 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, test pit sidewalls generally exhibited little indication of collapse; however, for deep excavations, native granular sediments cannot be expected to remain in position. These materials are prone to failure and may collapse, thereby undermining upper soil layers. This is especially true when excavations approach depths near the water table. Care must be taken to ensure that excavations are properly backfilled in accordance with procedures outlined in this report. 8.11 Groundwater Control Groundwater is anticipated to be below the depth of most construction. 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. 9. GENERAL COMMENTS Based on the subsurface conditions encountered during this investigation and available information regarding the proposed development, the site is adequate for the planned construction. When plans and specifications are complete, and if significant changes are made in the character or location of the proposed development, 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. B231456g Page115 Copyright©2023 Atlas Technical Consultants 10. REFERENCES American Association of State Highway and Transportation Officials (AASHTO) (1993). AASHTO Guide for Design of Pavement Structures 1993. Washington D.C.: AASHTO. American Concrete Institute (ACI) (2015). Guide for Concrete Floor and Slab Construction: ACI 302.1 R. Farmington Hills, MI: ACI. American Society of Civil Engineers (2021). ASCE 7 Hazards Tool: Web Interface. [Online] Available: <https://asce7hazardtool.online/> (2023). American Society of Civil Engineers (ASCE) (2017). 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) (2019). Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates: ASTM C136. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2021). 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) (2021). 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) (2021). Standard Test Methods for California Bearing Ratio: ASTM D1883. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2017). Standard Practice for Classification of Soils for Engineering Purposes(Unified Soil Classification System):ASTM D2487.West Conshohocken, PA:ASTM. American Society for Testing and Materials (ASTM) (2017). Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils: ASTM D4318. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2017). Standard Specification for Plastic Water Vapor Retarders Used in Contact with Soil or Granular Fill Under Concrete Slabs: ASTM E1745. West International Building Code Council (2018). International Building Code. Country Club Hills, IL: Author. Local Highway Technical Assistance Council (LHTAC) (2020). Idaho Standards for Public Works Construction. Boise, ID: Author. Othberg, K. L. and Stanford, L. A., Idaho Geologic Society (1993). Geologic Map of the Boise Valley and Adjoining Area, Western Snake River Plain, Idaho. (scale 1:100,000). Boise, ID: Joslyn and Morris. U.S. Department of Labor, Occupational Safety and Health Administration 2( 020). CFR 29, Part 1926, Subpart P Appendix A: Safety and Health Regulations for Construction, Excavations. Washington D.C.: OSHA. Atlas No. B231456g Page116 Copyright©2023 Atlas Technical Consultants �TrT-G7T_�. 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. Limitations Test pits were limited to a maximum depth of 9.0 feet bgs due to excavator limitations. 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 nor 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. Atlas No. B231456g Page117 Copyright©2023 Atlas Technical Consultants 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 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. B231456g Page118 Copyright©2023 Atlas Technical Consultants Vicinity Map Figure 1 MAP NOTES: Not to Scale LEGEND Approximate Site Location Site Location Nine Mile Creek Bungalows 2055 South Locust Grove Road Meridian,ID Modified by:MPK September 5,2023 Drawing:B2301456g 'JI 2791 S.Victory View Way Phone: (208)376-4748 Boise,ID 83709 Fax: (208)322-6515 Web: oneatlas.corn Site Map Figure 2 --------------- -------------- — — - -- NOTES: %I \ N •Not to Scale ————————— — — El ' ❑ �� o LEGEND %/X = \�� w Approximate Site TP-1 � Boundary < �� 2i Approximate Atlas Test ti 8 o F� Pit Location 0 �1 4 i I TP-2 —�-- i --------------------- I n I I °II LU ----------- 70— fj 1 -1 I 0 1 I i I w CO 0 I I I '� I i I Nine Mile Creek Bungalows 2055 South Locust Grove Road Meridian,ID ® � I =vi i i Modified by:MPK September 5,2023 Drawing:B2301456g I I li� I I —G7T�� I 2791 S.Victory View Way Phone: (208)376-4748 Boise,ID 83709 Fax: (208)322-6515 Web: oneatlas.com �TrT-G7T�", APPENDIX IV GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-1 Latitude: 43.586438 Date Advanced: August 25, 2023 Longitude: -116.374150 Excavated by: Client Supplied Excavator Depth to Water Table: Not Encountered Logged by: Colby Meyer, GIT Total Depth: 9.0 feet bgs RL q EE=Eq �� MMME"I Dep eld Description and USCS Soil and Samp re Sample Depth Lab e . . . . . Test ID Silty Gravel with Sand Fill (GM-FILL): Light brown to brown, dry to slightly moist, medium 0.0-3.2 dense, with fine to coarse-grained sand and fine to coarse gravel. --Metal pipe debris encountered at 3.0 feet bgs. Poorly Graded Gravel with Clay and Sand 3.2-5.5 (GP-GC): Light brown, slightly moist, medium dense, with fine to coarse-grained sand and fine to coarse gravel. Clayey Gravel with Sand (GC): Light brown, slightly moist, medium dense, with fine to 5.5-9.0 coarse-grained sand, fine to coarse gravel, and 8-inch minus cobbles. --Increased clay content noted from 7.5 to 9.0 feet bgs. Notes:See Site Map for test pit location. Atlas No. B231456g Page 121 Copyright©2023 Atlas Technical Consultants �TrT-G7T�1 GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-2 Latitude: 43.586396 Date Advanced: August 25, 2023 Longitude: -116.375446 Excavated by: Client Supplied Excavator Depth to Water Table: Not Encountered Logged by: Colby Meyer, GIT Total Depth: 5.2 feet bgs Depth ieldd Description and USCS Soil and Sample Sample Depth Qp Lab ••s) Sediment Classification • •• iw�i _Mim — Silty Gravel with Sand Fill (GM-FILL): Light brown, dry to slightly moist, medium dense, 0.0-0.7 with fine to coarse-grained sand and fine gravel. --Plastic debris encountered at 0.7 foot bgs. Sandy Silt Fill(ML-FILL): Brown,slightly moist, 0.7-2.8 very stiff, with fine to medium-grained sand. 2.5 Poorly Graded Gravel with Clay and Sand 2 8 5 2 (GP-GC): Light brown, slightly moist, medium GS 4.5-5.0 A dense, with fine to coarse-grained sand and fine to coarse gravel. Notes:See Site Map for test pit location. Infiltration testing conducted at a depth of 5.2 feet bgs. • Test MoisturePassing) I #40 #100 #200 A 4.2 NP* NP* 67 53 38 33 18 13 10.6 *Atterberg limits skewed due to sample size. Atlas No. B231456g Page 122 Copyright©2023 Atlas Technical Consultants �TrT-G7Tdr-W� 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 Poorly-graded 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 > ILL < 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 ILL > 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 ificatlorWllllllllllllll, 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 ML Boulders: > 12 in. GS grab ample Cobbles: 12 to 3 in. ILL 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. B231456g Page 123 Copyright©2023 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.