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HomeMy WebLinkAboutCC - Geotech Report LIMITED GEOTECHNICAL INVESTIGATION 4-LOT SUBDIVISION 4853 North Chimney Peak Drive Meridian, ID PREPARED FOR: Mr. Colton Yasinski 4853 North Chimney Peak Drive Meridian, ID 83646 PREPARED BY: Atlas Technical Consultants, LLC J uar 17 2023 2791 South Victory View Way B222 01 g Boise, ID 83709 2791 South Victory View Way Boise, ID 83709 (208)376-4748 1 oneatlas.com January 17, 2023 Atlas No. 13222701 g Mr. Colton Yasinski 4853 North Chimney Peak Drive Meridian, ID 83646 Subject: Limited Geotechnical Investigation 4-Lot Subdivision 4853 North Chimney Peak Drive Meridian, ID Dear Mr. Yasinski: In compliance with your instructions,Atlas has conducted a limited soils exploration and pavement evaluation for the above referenced development. Fieldwork for this investigation was conducted from December 29 and 30 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, Gavin Marron Jacob Schlador, PE SSp� NAL FN Staff Engineer Geotechnical Engi �o �\CENSF10 C Q 14919 1-17-23 kP Monica Saculles, �91F of Senior Geotechnica r Distribution: David Crawford, Centurion Engineers (PDF Copy) Page 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.........................................................................................2 2.4 Regional Site Climatology and Geochemistry...............................................................3 3. SOILS EXPLORATION .........................................................................................................3 3.1 Exploration and Sampling Procedures..........................................................................3 3.2 Laboratory Testing Program.........................................................................................3 3.3 Soil and Sediment Profile..............................................................................................3 3.4 Volatile Organic Scan ...................................................................................................4 4. SITE HYDROLOGY...............................................................................................................4 4.1 Groundwater.................................................................................................................4 4.2 Soil Infiltration Rates.....................................................................................................5 4.3 Infiltration Testing..........................................................................................................5 5. PAVEMENT DISCUSSION AND RECOMMENDATIONS ....................................................6 5.1 Flexible Pavement Section ...........................................................................................6 5.2 Common Pavement Section Construction Issues.........................................................7 6. CONSTRUCTION CONSIDERATIONS ................................................................................7 6.1 Earthwork......................................................................................................................7 6.2 Dry Weather..................................................................................................................8 6.3 Wet Weather.................................................................................................................8 6.4 Soft Subgrade Soils......................................................................................................8 6.5 Frozen Subgrade Soils .................................................................................................9 6.6 Structural Fill.................................................................................................................9 6.7 Backfill of Walls...........................................................................................................10 6.8 Excavations.................................................................................................................10 6.9 Groundwater Control...................................................................................................11 7. GENERAL COMMENTS .....................................................................................................11 8. REFERENCES ....................................................................................................................12 TABLES Table 1 - Groundwater Data.........................................................................................................5 Table 2 - Infiltration Test Results .................................................................................................5 Atlas No. 6222701 g Page i Copyright©2023 Atlas Technical Consultants Table 3—AASHTO Flexible Pavement Specifications .................................................................6 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 AASHTO Pavement Design Appendix VII Important Information About This Geotechnical Engineering Report Atlas No. B222701g Page 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 pavements. 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 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 proposed development is in the northwestern portion of the City of Meridian, Ada County, ID, and occupies a portion of the S'/2SE'/4 of Section 26, Township 4 North, Range 1 West, Boise Meridian. This project will consist of splitting an existing residential lot to create a 4-lot subdivision. It is anticipated that the existing residential structure will remain as one of the four lots. Additionally, a private drive will be constructed to access the site. The proposed development is approximately 1.5 acres in size. Assumptions have been made for traffic loading of pavements. Retaining walls are not anticipated as part of the project. Atlas has not been informed of the proposed grading plan. 1.2 Authorization Authorization to perform this exploration and analysis was given in the form of a verbal authorization to proceed from Mr. Colton Yasinski to Tyra Hall of Atlas Technical Consultants (Atlas), on December 9, 2022. Said authorization is subject to terms, conditions, and limitations described in the Professional Services Contract entered into between and Atlas. Our scope of services for the proposed development has been provided in our proposal dated November 30, 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 pavement materials. Our scope of work did not include foundation design recommendations. Atlas No. 13222701 g Page 11 Copyright©2023 Atlas Technical Consultants It 2. SITE DESCRIPTION 2.1 Site Access Access to the site may be gained via Interstate 84 to the Ten Mile Road exit. Proceed north on Ten Mile Road approximately 3.8 miles to its intersection with McMillan Road. From this intersection, proceed east on McMillan Road 0.70 mile to Wild Goose Way. Continue north on Wild Goose Way for approximately 0.10 mile to its intersection with Apgar Creek Drive. Proceed east from this intersection roughly 430 feet to Chimney Peak Avenue. Travel south on Chimney Peak Avenue approximately 350 feet to where Chimney Peak Avenue turns to the east. The site is located to west of Chimney Peak Avenue. The location is depicted on site maps included in the Appendix. 2.2 Regional Geology The project site is located within the western Snake River Plain of southwestern Idaho and eastern Oregon. The plain is a northwest trending rift basin, about 45 miles wide and 200 miles long, that developed about 14 million years ago (Ma) and has since been occupied sporadically by large inland lakes. Geologic materials found within and along the plain's margins reflect volcanic and fluvial/lacustrine sedimentary processes that have led to an accumulation of approximately 1 to 2 km of interbedded volcanic and sedimentary deposits within the plain. Along the margins of the plain, streams that drained the highlands to the north and south provided coarse to fine-grained sediments eroded from granitic and volcanic rocks, respectively. About 2 million years ago the last of the lakes was drained and since that time fluvial erosion and deposition has dominated the evolution of the landscape. The project site is underlain by the "Gravel of Whitney Terrace" as mapped by Othberg and Stanford (1993). Sediments of the Whitney terrace consist of sandy pebble and cobble gravel. The Whitney terrace is the second terrace above modern Boise River floodplain, is thickest toward its eastern extent, and is mantled with 2-6 feet of loess. 2.3 General Site Characteristics The site to be developed is approximately 1.5 acres in size and is relatively flat and level. Currently, a residential structure is present in the central portion of the site. The remainder of the site consists of landscaped land. McMillan Road runs along the southern property boundary. The remainder of the site is surrounded by a residential subdivision. Vegetation on the site consists primarily of mature trees and landscape grasses. Regional drainage is north and west toward the Boise River. Stormwater drainage for the site is achieved by percolation through surficial soils. The site is situated so that it is unlikely that it will receive any drainage from off-site sources. Stormwater drainage collection and retention systems are not in place on the project site, but were noted on Chimney Peak Avenue in the form of curbs, gutters, and drop inlets. Atlas No. B222701 g Page 1 2 Copyright©2023 Atlas Technical Consultants 2.4 Regional Site Climatology and Geochemistry According to the Western Regional Climate Center, the average precipitation for the Treasure Valley is on the order of 10 to 12 inches per year, with an annual snowfall of approximately 20 inches and a range from 3 to 49 inches. The monthly mean daily temperatures range from 21 OF 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. SOILS EXPLORATION 3.1 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 of overlying structures. In addition, samples were obtained from representative soil strata encountered. Samples obtained have been visually classified in the field by professional staff, identified according to test pit number and depth, placed in sealed containers, and transported to our laboratory for additional testing. Subsurface materials have been described in detail on logs provided in the Appendix. Results of field and laboratory tests are also presented in the Appendix. Atlas recommends that these logs not be used to estimate fill material quantities. 3.2 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 and Grain Size Analysis —ASTM C117/C136. 3.3 Soil and Sediment Profile The profile below represents a generalized interpretation for the project site. Note that on site soils strata, encountered between test pit locations, may vary from the individual soil profiles presented in the logs, which can be found in the Appendix. Atlas No. 6222701g Page 13 Copyright©2023 Atlas Technical Consultants Lean clay soils were encountered at ground surface. These soils were brown, dry to slightly moist, and medium stiff to stiff, with fine-grained sand. Organic materials were measured to depths of roughly 0.2 foot. Silty sand sediments were observed below the fine-grained clay soils. Silty sands were classified as light brown, dry, and medium dense to dense, with fine to medium- grained sand. Weak to moderate cementation was encountered in portions of this horizon. At depth, poorly graded gravel with sand sediments were exposed. Poorly graded gravels were light brown, dry to saturated, and medium dense to dense, with fine to coarse-grained sand, fine to coarse gravel, and 4-inch minus cobbles.. Competency of test pit sidewalls varied little across the site. In general, fine grained soils remained stable while more granular sediments readily sloughed. However, moisture contents will also affect wall competency with saturated soils having a tendency to readily slough when under load and unsupported. 3.4 Volatile Organic Scan No environmental concerns were identified prior to commencement of the investigation. Therefore, soils obtained during on-site activities were not assessed for volatile organic compounds by portable photoionization detector. Samples obtained during our exploration activities exhibited no odors or discoloration typically associated with this type of contamination. Groundwater encountered did not exhibit obvious signs of contamination. 4. 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. A.1 Groundwater During this field investigation, groundwater was encountered in test pit 1 at a depth of 12.4 feet bgs. Soil moistures in the test pits were generally dry to slightly moist within surficial soils. Within the poorly graded gravel with sand, soil moistures graded from dry to saturated as the water table was approached and penetrated. In the vicinity of the project site, groundwater levels are controlled in large part by residential and commercial irrigation activity and leakage from nearby canals. Maximum groundwater elevations likely occur during the later portion of the irrigation season. Atlas has previously performed 7 geotechnical investigations within 0.40 mile of the project site. Information from these investigations has been provided in the table below. Atlas No, B222701g Page 4 Copyright©2023 Atlas Technical Consultants Table 1 —Groundwater Data Date Approximate Distance Direction from Site Groundwater Depth from •• April 2017 0.12 East 13.6 to 13.9 June 2013 0.18 East 14.2 to 14.4 April 2007 0.25 East 15.0 to 16.0 August 2013 0.31 Northeast 11.8 to 12.3 July 2013 0.32 East 9.8 to 10.9 February 2005 0.32 Northeast 13.9 to 17.4 February 2010 0.33 Northeast Not Encountered to 14.5 For construction purposes, groundwater depth can be assumed to remain greater than 9 feet bgs throughout the year. Since this is an estimated depth and seasonal groundwater levels fluctuate, actual levels should be confirmed by periodic groundwater data collected from a piezometer installed in test pit 1. If desired, Atlas is available to perform this monitoring. 4.2 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 for each soil type and gradation. Of soils comprising the generalized soil profile for this study, lean clay soils generally offer little permeability, with typical hydraulic infiltration rates of less than 2 inches per hour. Silty sand sediments usually display rates of 4 to 8 inches per hour; though calcium carbonate cementation may reduce this value to near zero. Poorly graded sand and gravel sediments typically exhibit infiltration values in excess of 12 inches per hour. 4.3 Infiltration Testing Infiltration testing was conducted using an open test pit method. The test pit area will need to be re-excavated and compacted prior to construction of structures that will be sensitive to settlement. The test location was presoaked prior to testing. Pre-soaking increases soil moistures, which allows the tested soils to reach a saturated condition more readily during testing. Saturation of the tested soils is desirable in order to isolate the vertical component of infiltration by inhibiting horizontal seepage during testing. Testing was conducted on December 30, 2022. Details and results of testing are as follows: Table 2— Infiltration Test Results Test Test Depth Stabilized Infiltration DesignInfiltration Location (feet bgs) Soil Type • per • TP-2 5.7 Silty Sand 1.20 0.60 TP-2 8.6 Poorly Graded Gravels with Sand >16.00 8.00 Atlas No. B222701 g Page 15 Copyright©2023 Atlas Technical Consultants Appropriate factors of safety have been applied to the stabilized infiltration rates achieved during testing to obtain the design infiltration rates listed above. 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. 5. PAVEMENT DISCUSSION AND RECOMMENDATIONS Atlas has made assumptions for traffic loading variables based on the character of the proposed construction. The Client shall review and understand these assumptions to make sure they reflect intended use and loading of pavements both now and in the future. Based on experience with soils in the region, a subgrade California Bearing Ratio (CBR) value of 4 has been assumed for near-surface lean clay soils on site. The following are minimum thickness requirements for assured pavement function. Depending on site conditions, additional work, e.g. soil preparation, may be required to support construction equipment. These have been listed within the Soft Subgrade Soils section. 5.1 Flexible Pavemment Section The American Association of State Highway and Transportation Officials (AASHTO) design method has been used to calculate the following pavement section. A calculation sheet provided in the Appendix indicates the soils constant, traffic loading, traffic projections, and material constants used to calculate the 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 and should adhere to guidelines recommended in the section on Construction Considerations. Table 3—AASHTO Flexible Pavement Specifications SectionPavement • •. _ Private Drive Asphaltic Concrete 2.5 Inches Crushed Aggregate Base 4.0 Inches Structural Subbase 8.0 Inches Compacted Subgrade Not Required 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. Atlas No. B222701g Page 6 Copyright©2023 Atlas Technical Consultants • 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. 5.2 Common Pavement Section Construction Issues The subgrade upon which above pavement sections are to be constructed must be properly stripped, inspected, and proof-rolled. Proof rolling of subgrade soils should be accomplished using a heavy rubber-tired, fully loaded, tandem-axle dump truck or equivalent. Verification of subgrade competence by Atlas personnel at the time of construction is required. Fill materials on the site must demonstrate the indicated compaction prior to placing material in support of the pavement section. Atlas anticipated that pavement areas will be subjected to light 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. 6. CONSTRUCTION CONSIDERATIONS 6.1 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. Mature trees 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. 6222701 g Page 17 Copyright©2023 Atlas Technical Consultants Atlas should oversee subgrade conditions (i.e., moisture content) as well as placement and compaction of new fill (if required) after native soils are excavated to design grade. Recommendations for structural fill presented in this report can be used to minimize volume changes and differential settlements that are detrimental to the behavior of footings, pavements, and floor slabs. Sufficient density tests should be performed to properly monitor compaction. For structural fill beneath parking and driveways, one in-place density test per lift for every 10,000 square feet is recommended. 6.2 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. 6.3 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. .4 Soft Subgrade Sails 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: a Track-mounted vehicles should be used to strip the subgrade of root matter and 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. Atlas No. B222701 g Page , 8 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. 6.5 Frozen Subgrade Soils Prior to placement of structural fill materials or foundation elements, frozen subgrade soils must either be allowed to thaw or be stripped to depths that expose non-frozen soils and wasted or stockpiled for later use. Stockpiled materials must be allowed to thaw and return to near-optimal conditions prior to use as structural fill. The onsite, shallow clayey and silty soils are susceptible to frost heave during freezing temperatures. For exterior flatwork and other structural elements, adequate drainage away from subgrades is critical. Compaction and use of structural fill will also help to mitigate the potential for frost heave. Complete removal of frost susceptible soils for the full frost depth, followed by replacement with a non-frost susceptible structural fill, can also be used to mitigate the potential for frost heave. Atlas is available to provide further guidance/assistance upon request. 6.6 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. 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 3/4-inch) material and no more than 12 percent fines(passing No. 200 sieve). These fill materials should be placed in layers not to exceed 12 inches in loose thickness. Prior to placement of structural fill materials, surfaces must be prepared as outlined in the Construction Considerations section. Structural fill material should be moisture-conditioned to achieve optimum moisture content prior to compaction. All fill materials must be monitored during placement and tested to confirm compaction requirements, outlined below, have been achieved. Atlas No, B222701g Page 19 Copyright©2023 Atlas Technical Consultants Each layer of structural fill must be compacted, as outlined below: o Below Rigid Pavements: A minimum of 95 percent of the maximum dry density as determined by ASTM D1557. Below Flexible Pavements: A minimum of 92 percent of the maximum dry density as determined by ASTM D1557 or 95 percent of the maximum dry density as determined by ASTM D698. The ASTM D1557 test method must be used for samples containing up to 40 percent oversize (greater than 3/-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. 6.7 Dackfill 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. 6.8 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'h 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. Atlas No. 13222701 g Page 10 Copyright©2023 Atlas Technical Consultants ilk -----9-ItT � During the subsurface exploration,test pit sidewalls generally exhibited little indication of collapse; however, sloughing of native granular sediments from test pit sidewalls was observed, particularly after penetration of the water table. For deep excavations, native granular sediments cannot be expected to remain in position. These materials are prone to failure and may collapse, thereby undermining upper soil layers. This is especially true when excavations approach depths near the water table. Care must be taken to ensure that excavations are properly backfilled in accordance with procedures outlined in this report. 6.9 Groundwater Control Groundwater was encountered during the investigation but is anticipated to be below the depth of most construction. Excavations below the water table will require a dewatering program. Dewatering will be required prior to placement of fill materials. Placement of concrete can be accomplished through water by the use of a tremie. 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. 7. 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 pavement, 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. B222701 g Page 1 11 Copyright©2023 Atlas Technical Consultants ilk �—T T � Tom,_ 8. REFERENCES American Association of State Highway and Transportation Officials(AASHTO)(1993).AASHTO Guide for Design of Pavement Structures 1993. Washington D.C.: AASHTO. 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) (2014). 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. 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. Othberg, K. L. and Stanford, L. A., Idaho Geologic Society (1993). Geologic Map of the Boise Valley and Ad oining Area, Western Snake River Plain, Idaho. (scale 1:100,000). Boise, ID: Joslyn and Morris. U.S. Department of Labor, Occupational Safety and Health Administration. CFR 29, Part 1926, Subpart P: Safety and Health Regulations for Construction, Excavations (1986). [Online]Available: <www.osha.gov> (2021). Atlas No. B222701g Page i 12 Copyright©2023 Atlas Technical Consultants Appendix I WARRANTY AND LIMITING CONDITIONS Atlas warrants that findings and conclusions contained herein have been formulated in accordance with generally accepted professional engineering practice in the fields of foundation engineering, soil mechanics, and engineering geology only for the site and project described in this report. These engineering methods have been developed to provide the client with information regarding apparent or potential engineering conditions relating to the site within the scope cited above and are necessarily limited to conditions observed at the time of the site visit and research. Field observations and research reported herein are considered sufficient in detail and scope to form a reasonable basis for the purposes cited above. Exclusive Use This report was prepared for exclusive use of the property owner(s), at the time of the report, and their retained design consultants ("Client"). Conclusions and recommendations presented in this report are based on the agreed-upon scope of work outlined in this report together with the Contract for Professional Services between the Client and Atlas Technical Consultants ("Consultant'). Use or misuse of this report, or reliance upon findings hereof, by parties other than the Client is at their own risk. Neither Client nor Consultant make representation of warranty to such other parties as to accuracy or completeness of this report or suitability of its use by such other parties for purposes whatsoever, known or unknown, to Client or Consultant. Neither Client nor Consultant shall have liability to indemnify or hold harmless third parties for losses incurred by actual or purported use or misuse of this report. No other warranties are implied or expressed. Report Recommendations are Limited and Subject to Misinterpretation There is a distinct possibility that conditions may exist that could not be identified within the scope of the investigation or that were not apparent during our site investigation. Findings of this report are limited to data collected from noted explorations advanced and do not account for unidentified fill zones, unsuitable soil types or conditions, and variability in soil moisture and groundwater conditions. To avoid possible misinterpretations of findings, conclusions, and implications of this report, Atlas should be retained to explain the report contents to other design professionals as well as construction professionals. Since actual subsurface conditions on the site can only be verified by earthwork, note that construction recommendations are based on general assumptions from selective observations and selective field exploratory sampling. Upon commencement of construction, such conditions may be identified that require corrective actions, and these required corrective actions may impact the project budget. Therefore, construction recommendations in this report should be considered preliminary, and Atlas should be retained to observe actual subsurface conditions during earthwork construction activities to provide additional construction recommendations as needed. Atlas No. B222701 g Page 13 Copyright©2023 Atlas Technical Consultants Since geotechnical reports are subject to misinterpretation, do not separate the soil logs from the report. Rather, provide a copy of, or authorize for their use, the complete report to other design professionals or contractors. Locations of exploratory sites referenced within this report should be considered approximate locations only. For more accurate locations, services of a professional land surveyor are recommended. This report is also limited to information available at the time it was prepared. In the event additional information is provided to Atlas following publication of our report, it will be forwarded to the client for evaluation in the form received. Environmental Concerns Comments in this report concerning either onsite conditions or observations, including soil appearances and odors, are provided as general information. These comments are not intended to describe, quantify, or evaluate environmental concerns or situations. Since personnel, skills, procedures, standards, and equipment differ, a geotechnical investigation report is not intended to substitute for a geoenviron mental 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. B222701g Page 14 Copyright©2023 Atlas Technical Consultants Vicinity Map Figure 1 MAP NOTES: BAR Q4E f�, _ N •Deionne Street Atlas rr� Q DUCK ALLEY RD O� Not to Scale ILLOCUST GROVE RD RISIER DR a y' 0 p ? y� LEGEND O p ff N_.___._�_ < 'a a' A 4P {•z '� —_ — a 3 Approximate Site Location 2 cb pC < N �5 ytin m 2 m _. + T3rm vs ut 2a — 2 z '< < m r4 a � pO O f 10l/ �410 00 Lu w Q > u z Z Z z m z Q Site Locatio o Z 3 l 2 4-Lot Subdivision yo v 4853 North Chimney Peak Drive CM[IIAN RD Meridian,ID CMk N RD MCMIIIAN RD ,...r- ._._? M �_ ,. _ Modified from DeLorme by:GJM w December 28,2022 a Drawing:B222701g g 44, E STAR LN Do Y 4 z (u;aZ „_,_ --_ 2791 S.Victory Yew Way Phone:(208)376-4748 m ---n Bose,ID 83709 Fax:(208)3224515 s� Web'.oneatlas.mm Site Map Figure 2 x NOTES: �t N •Not to Scale _ w z i w `• LEGEND w Approximate Site z Boundary I Ct U •'� J Approximate Atlas Test Pit Location Approximate Atlas Test Pit Location with Piezometer m - �TP 2 TP-1 8 1 4-Lot Subdivision 4853 North Chimney Peak Drive Meridian,ID Modified by:GJM January 3,2023 Drawing:B222701g McMILLAN ROAD 2791 S.Victory View Way Phone:(208)376A748 Boise,ID 83709 Fax:(208)322.6515 Web:onea8as.com Appendix IV GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log#: TP-1 Latitude: 43.648735 Date Advanced: December 29, 2022 Longitude: -116.418679 Excavated by: Turn of the Century Homes Depth to Water Table: 12.4 feet bgs Logged by: Wyatt Wolfe Total Depth: 13.2 feet bgs Depth Field Description and USCS Soil and Sample Sample Depth QP Lab (feet bgs) Sediment Classification Type (feet bgs) Test ID Lean Clay (CL): Brown, dry to slightly moist, 0.0-2.5 medium stiff to stiff, with fine-grained sand. GS 1.0-2.0 1.0-1.5 A --Organic material noted to 0.2 foot bgs. Silty Sand (SM): Light brown, dry, medium dense to dense, with fine to medium-grained 2.5-7.9 sand. --Weak to moderate cementation encountered from 3.4 to 6.0 feet bgs. Poorly Graded Gravel with Sand (GP): Light 7.9-13.2 brown, dry to saturated, medium dense to dense, with fine to coarse-grained sand, fine to coarse gravel, and 4-inch minus cobbles. Notes:See Site Map for test pit location. Piezometer installed to a depth of 13.2 feet bgs. • Test ID Moisture 1 #40 #100 #200 A 25.8 33 17 100 1 100 98 95 89.8 Atlas No. 6222701 g Page 17 Copyright©2023 Atlas Technical Consultants own A GEOTECHNICAL INVESTIGATION TEST POT LOG Test Pit Log#: TP-2 Latitude: 43.648789 Date Advanced: December 29, 2022 Longitude: -116.418305 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Wyatt Wolfe Total Depth: 8.6 feet bgs Depth Field Description and USCS Soil and Sample Sample be­p`thilb­� Qp Lab ••s) Sediment Classification •- bgs) Test ID Lean Clay (CL): Brown, dry to slightly moist, 0.0-2.5 medium stiff to stiff,with fine-grained sand. 1.0-1.75 --Organics noted to 0.2 foot bgs. Silty Sand (SM): Light brown, dry, medium dense to dense, with fine to medium-grained 2.5-7.2 sand. --Intermittent weak to moderate cementation encountered throughout. Poorly Graded Gravel with Sand (GP): Light 7 2 8 6 brown, dry, medium dense to dense, with fine to coarse-grained sand, fine to coarse gravel, and 4-inch minus cobbles. Notes:See Site Map for test pit location. Infiltration testing conducted at depths of 5.7 and 8.6 feet bgs. Atlas No. 13222701 g Page 18 Copyright©2023 Atlas Technical Consultants �•-')' I � Appendix V GEOTECHNICAL GENERAL NOTES Unified Soil Classification System Ma-or Divisions Symbol Soil Descriptions Gravel & GW Well- raded ravels; ravel/sand mixtures with little or no fines Coarse- Gravelly Soils GP Poorly-grad d 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 Poorly-graded sands; ravel) sands with little or no fines sieve coarse SM Silt sands; poorly-graded sand/ ravel/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; sandy, 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 and Consistency Moisture Content and Cementation Classification Classification Coarse-Grained Soils SPT Blow Counts N Descri tion 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 Acronym List Boulders: > 12 in. GS 7rab sam le 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. 13222701 g Page 19 Copyright©2023 Atlas Technical Consultants Appendix VI AASHTO PAVEMENT DESIGN Pavement Section Design Location:4-Lot Subdivision,Private Drive Average Daily Traffic Count: 40 All Lanes&Both Directions Design Life: 20 Years Percent of Traffic in Design Lane: 50% Terminal Seviceability Index(Pt): 2.5 Level of Reliability: 95 Subgrade CBRValue: 4 Subgrade Mr: 6,000 Calculation of Design-18 kip ESALs Daily Growth Load Design Traffic Rate Factors ESALs Passenger Cars: 15 2.0% 0.0008 106 Buses: 0 2.0% 0.6806 0 Panel&Pickup Trucks: 3 2.0% 0.0122 325 2-Axle,6-Tire Trucks: 1 2.0% 0.1890 1,676 Emergency Vehicles: 1.0 2.0% 4.4800 39,731 Dump Trucks: 0 2.0% 3.6300 0 Tractor Semi Trailer Trucks: 0 2.0% 2.3719 0 Double Trailer Trucks 0 2.0% 2.3187 0 Heavy Tractor Trailer Combo Trucks: 0 2.0% 2.9760 0 Average Daily Traffic in Design Lane: 20 Total Design Life 18-kip ESALs: 41,838 Actual Log(ESALs): 4.622 Trial SN: 2.40 Trial Log(ESALs): 4.643 Pavement Section Design SN: 2.41 Design Depth Structural Drainage Inches Coefficient Coefficient Asphaltic Concrete: 2.50 0.42 nla Asphalt-Treated Base: 0.00 0.25 nla Cement-Treated Base: 0.00 0.17 nla Crushed Aggregate Base: 4.00 0.14 1.0 Subbase: 8.00 0.10 1.0 Special Aggregate Subgrade: 0.00 0.09 0.9 Atlas No. 6222701 g Page 120 Copyright©2023 Atlas Technical Consultants IMPOPIOnt Infopmation about Geolechnicol-Engineeping I 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. "I he 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 engineering interpretation of the subsurface conditions within the context those that affect: of the project and does not represent a close examination,systematic the site's size,c shape; the elevation,c inquiry,or thorough investigation of all site and subsurface conditions. configuration,location,orientation, function or weight of the proposed structure and Geotechnical-Engineering Services are Performed the desired performance criteria; for Specific Purposes, Persons,and Projects, the composition of the design team;or and At Specific Times project ownership. 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.7hegeotechnical engineer who prepared this report cannot assume responsibility orliabilityforconfiirmation-dependentrecommendations 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"environmental 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 SEA BUSINESS 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 GBA's 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.