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Home My WebLink AboutPZ - Geotechnical Investigation ENGINEERING •GEOTECHNICAL •ENVIRONMENTAL (ESA I & II) • MATERIALS TESTING •SPECIAL INSPECTIONS • ORGANIC CHEMISTRY • PAVEMENT DESIGN •GEOLOGY PRELIMINARY GEOTECHNICAL ENGINEERING STUDY Maslonka Property NE Corner of Linder Road and Amity Road Boise, Idaho CMT PROJECT NO. 13175 FOR: DevCo, LLC Laren M. Bailey, MCRP, PMP September 12, 2019 ENGINEERING • GEOTECHNICAL • ENVIRONMENTAL (ESA I & II) • MATERIALS TESTING • SPECIAL INSPECTIONS ORGANIC CHEMISTRY • PAVEMENT DESIGN • GEOLOGY www.cmtlaboratories.com September 12, 2019 DevCo LLC Attn: Laren Bailey Subject: Preliminary Geotechnical Engineering Study Maslonka Property NE Corner of Linder and Amity Boise, Idaho CMT Project No. 13175 Mr. Bailey: Submitted herewith is our preliminary geotechnical engineering study for the subject site. This report contains the results of our findings with respect to the available project characteristics. On August 23, 2019, a CMT Engineering Laboratories (CMT) engineer was on-site and supervised the excavation of 4 test pits extending to a depth of about 10 feet below the existing ground surface. Soil samples were obtained during the field operations and subsequently transported to our laboratory for further testing and observation. We appreciate the opportunity to work with you at this stage of the project. CMT offers a full range of Geotechnical Engineering, Geological, Material Testing, Special Inspection services, and Phase I and II Environmental Site Assessments. With 9 offices throughout Utah, Idaho and Arizona, our staff is capable of efficiently serving your project needs. If we can be of further assistance or if you have any questions regarding this project, please do not hesitate to contact us at (208) 912-1868. Sincerely, CMT Engineering Laboratories Reviewed by: Phillip Pack, P.E. Greg Mugavero Senior Geotechnical Engineer Regional Manager TABLE OF CONTENTS 1.0 INTRODUCTION ............................................................................................................................................................3 1.1 General ...................................................................................................................................................................................3 1.2 Objectives, Scope and Authorization ......................................................................................................................................4 2.0 FIELD EXPLORATION .....................................................................................................................................................4 2.1 General ...................................................................................................................................................................................4 3.0 LABORATORY TESTING .................................................................................................................................................5 4.0 SITE CONDITIONS .........................................................................................................................................................5 4.1 Surface Conditions ..................................................................................................................................................................5 4.2 Subsurface Soils ......................................................................................................................................................................5 4.3 Groundwater ..........................................................................................................................................................................6 4.4 Site Subsurface Variations ......................................................................................................................................................6 5.0 LIMITATIONS ...............................................................................................................................................................6 APPENDIX Figure 1: Site Plan Figures 2 -5: Test Pit Logs Figure 6: Key to Symbols Preliminary Geotechnical Engineering Study Page 3 Maslonka Property – Boise, Idaho CMT Project No. 13175 1.0 INTRODUCTION 1.1 General CMT Engineering Laboratories (CMT) was retained to conduct a preliminary geotechnical subsurface study for the proposed development of a residential subdivision. The parcel is situated on the NE corner of Amity Road and Linder Road in Boise, Idaho, as shown in the Vicinity Map below. SITE VICINITY MAP Preliminary Geotechnical Engineering Study Page 4 Maslonka Property – Boise, Idaho CMT Project No. 13175 1.2 Objectives, Scope and Authorization The objectives and scope of our study were planned in discussions between Mr. Laren Bailey of DevCo LLC and Phillip Pack of CMT Engineering Laboratories (CMT). In general, the objectives of this study were to define and evaluate the subsurface soil and groundwater conditions at the site. In accomplishing these objectives, our scope of work has included performing field exploration, which consisted of the excavating/logging/sampling of 4 test pits, and performing laboratory testing on representative samples. This scope of work was authorized by returning a signed copy of our proposal dated August 8, 2019. 2.0 FIELD EXPLORATION 2.1 General In order to define and evaluate the subsurface soil and groundwater conditions at the site, 4 test pits were excavated with a backhoe at the site to a depth of approximately 10 feet below the existing ground surface. Locations of the test pits are shown on Figure 1, Site Plan, included in the Appendix. The field exploration was performed under the supervision of an experienced member of our geotechnical staff. Representative soil samples were collected by obtaining disturbed "grab" samples and cutting re latively undisturbed "block" samples from within each test pit. The samples were placed in sealed plastic bags and containers prior to transport to the laboratory. The subsurface soils encountered in the test pits were logged and described in general acc ordance with ASTM1 D-2488. Soil samples were collected as described above, and were classified in the field based upon visual and textural examination. These field classifications were supplemented by subsequent examination and testing of select samples in our laboratory. Graphical representations of the subsurface conditions encountered are presented on each individual Test Pit Log, Figures 2 through 5, included in the Appendix. A Key to Symbols defining the terms and symbols used on the logs, is provided as Figure 6 in the Appendix. When backfilling the test pits, only minimal effort was made to compact the backfill and no compaction testing was performed. Thus, settlement of the backfill in the test pits over time should be anticipated. 1American Society for Testing and Materials Preliminary Geotechnical Engineering Study Page 5 Maslonka Property – Boise, Idaho CMT Project No. 13175 3.0 LABORATORY TESTING Selected samples of the subsurface soils were subjected to various laboratory tests to assess pertinent engineering properties, as follows: 1. Moisture Content, ASTM D-2216, Percent moisture representative of field conditions 2. Atterberg Limits, ASTM D-4318, Plasticity and workability 3. Gradation Analysis, ASTM D-1140/C-117, Grain Size Analysis Laboratory test results are presented on the test pit logs (Figures 2 through 5) and in the attached Appendix. 4.0 SITE CONDITIONS 4.1 Surface Conditions At the time the test pits were excavated the site consisted of two adjacent fields vegetated with grain and some grasses and weeds. The site grade sloped downward to the south with an overall gradient of about 5 to 10 feet. Based upon aerial photos readily available online dating back to 1993, the site appears to have been fields since that time. The site is bounded on the south by Amity Road and on the west by Linder Road (see Vicinity Map in Section 1.1 above). 4.2 Subsurface Soils At the locations of the test pits we encountered approximately 4 to 6 inches of topsoil at the surface. Natural soils were observed beneath the topsoil/fill soils, consisting of light brown SILT (ML) with caliche extending to depths of about 5 to 6 feet below the surface. Natural, light brown coarse SAND (SP) with gravel and cobbles was encountered extending to the full depth penetrated, 10 feet. The silt soils were slightly moist brown in color, and estimated to be medium stiff in consistency. The natural sand soils were moist, brown in color, and estimated to be medium dense to dense. For a more descriptive interpretation of subsurface conditions, please refer to the test pit logs, Figures 2 through 5, which graphically represent the subsurface conditions encountered. The lines designating the interface between soil types on the logs generally represent approximate boundaries - in situ, the transition between soil types may be gradual. Preliminary Geotechnical Engineering Study Page 6 Maslonka Property – Boise, Idaho CMT Project No. 13175 4.3 Groundwater Groundwater was not encountered at the time of our field explorations within the maximum depth explored of about 10 feet below the existing ground surface. Therefore, groundwater is not anticipated to affect proposed construction. Groundwater levels can fluctuate as much as 1.5 to 2 feet seasonally. Numerous other factors such as heavy precipitation, irrigation of neighboring land, and other unforeseen factors, may also influence ground water elevations at the site. The detailed evaluation of these and other factors, which may be responsible for ground water fluctuations, is beyond the scope of this study. 4.4 Site Subsurface Variations Based on the results of the subsurface explorations and our experience, variations in the continuity and nature of subsurface conditions should be anticipated. Due to the heterogeneous characteristics of natural soils, care should be taken in interpolating or extrapolating subsurface conditions between or beyond the exploratory locations. Also, when logging and sampling of the test pits was completed, the test pits were backfilled with the excavated soils but minimal to no effort was made to compact these soils. Thus, settlement of the backfill in the test pits over time should be anticipated. 5.0 LIMITATIONS The recommendations provided herein were developed by evaluating the information obtained from the subsurface explorations and soils encountered therein . The exploration logs reflect the subsurface conditions only at the specific location at the particular time designated on the logs. Soil and ground water conditions may differ from conditions encountered at the actual exploration locations. The nature and ex tent of any variation in the explorations may not become evident until during the course of construction. If variations do appear, it may become necessary to re-evaluate the recommendations of this report after we have observed the variation. Our professional services have been performed, our findings obtained, and our recommendations prepared in accordance with generally accepted geotechnical engineering principles and practices. This warranty is in lieu of all other warranties, either expressed or imp lied. We appreciate the opportunity to be of service to you on this project. If we can be of further assistance or if you have any questions regarding this project, please do not hesitate to contact us at (208) 912-1868 SUPPORTING DOCUMENTATION APPENDIX Date: Job # Maslonka Property Figure:1Northeast Corner of Linder Road and Amity Road Site Plan 0-Jan-00 13175 N TP-1 TP-2 TP-3 TP-4 TOPSOIL, brown silt with vegetation Light Brown SILT (ML), with caliche grades to cemented caliche hard Light Brown Coarse SAND (SP), with gravel and cobbles END AT 10' Remarks: Excavated By: Logged By: Page: Date: 13175NE Corner Amity & Linder 10' (see Remarks) 8/23/19 Gradation Atterberg Job #: TP-1 Soil Description Surface Elev. (approx): Equipment: Rubber Tire Backhoe Maslonka Property Test Pit Log Total Depth: Water Depth: Lou Watts Inselman Excavation Groundwater not encountered during excavation.Figure: 21 of 1 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28Depth (ft)GRAPHICLOGSample TypeSample #Moisture (%)Dry Density(pcf)Gravel %Sand %Fines %LLPLPI TOPSOIL, brown silty sand with vegetation Light Brown SILT (ML), with caliche Light Brown Coarse SAND (SP), with gravel and cobbles grades with fine to medium sand END AT 11' Remarks: Excavated By: Logged By: Page: Groundwater not encountered during excavation.Figure: 3Inselman Excavation Lou Watts 1 of 1 Soil Description Gradation Atterberg Water Depth:(see Remarks)Job #:Surface Elev. (approx): NE Corner Amity & Linder Equipment: Rubber Tire Backhoe 13175 Total Depth:11'Date:8/23/19 Maslonka Property Test Pit Log TP-2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28Depth (ft)GRAPHICLOGSample TypeSample #Moisture (%)Dry Density(pcf)Gravel %Sand %Fines %LLPLPI Brown Silty SAND (SM) grades with caliche grades to cemented caliche Light Brown Medium to Coarse SAND (SP), with gravel and cobbles END AT 10' Remarks: Excavated By: Logged By: Page: Maslonka Property Test Pit Log TP-3 Surface Elev. (approx): Water Depth:NE Corner Amity & Linder Equipment: Rubber Tire Backhoe Total Depth:10'Date:8/23/19 Soil Description Gradation Atterberg (see Remarks)Job #:13175 Groundwater not encountered during excavation.Figure: 4Inselman Excavation Lou Watts 1 of 1 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28Depth (ft)GRAPHICLOGSample TypeSample #Moisture (%)Dry Density(pcf)Gravel %Sand %Fines %LLPLPI TOPSOIL, brown clayey sand with vegetation Brown Clayey SAND (SC) Brown Medium SAND (SP), with caliche grades with medium to coarse sand grades to cemented caliche REFUSAL AT 6.5' Remarks: Excavated By: Logged By: Page: Maslonka Property Test Pit Log TP-4 Surface Elev. (approx): Water Depth:NE Corner Amity & Linder Equipment: Rubber Tire Backhoe Total Depth:6.5'Date:8/23/19 Soil Description Gradation Atterberg (see Remarks)Job #:13175 Groundwater not encountered during excavation.Figure: 5Inselman Excavation Lou Watts 1 of 1 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28Depth (ft)GRAPHICLOGSample TypeSample #Moisture (%)Dry Density(pcf)Gravel %Sand %Fines %LLPLPI Date: Job #: Gradation ⑧ ① ② ③ ④ ⑤ ⑥ ⑦ MODIFIERS Description Thickness Trace Seam Up to ½ inch <5% Lense Up to 12 inches Some Layer Greater than 12 in.5-12% Occasional 1 or less per foot With Frequent More than 1 per foot > 12% Note: Dual Symbols are used to indicate borderline soil classifications (i.e. GP-GM, SC-SM, etc.). Maslonka Property Key to Symbols (enter location)Farrer Excavation 13175 Soil Description Atterberg ⑨ COLUMN DESCRIPTIONS ①Depth (ft.): Depth (feet) below the ground surface (including groundwater depth - see water symbol below).⑨Atterberg: Individual descriptions of Atterberg Tests are as follows: ②Graphic Log: Graphic depicting type of soil encountered (see ② below). LL = Liquid Limit (%): Water content at which a soil changes from plastic to liquid behavior. ③Soil Description: Description of soils encountered, including Unified Soil Classification Symbol (see below). PL = Plastic Limit (%): Water content at which a soil changes from liquid to plastic behavior. ④Sample Type: Type of soil sample collected at depth interval shown; sampler symbols are explained below-right. PI = Plasticity Index (%): Range of water content at which a soil exhibits plastic properties (= Liquid Limit - Plastic Limit). ⑤Sample #: Consecutive numbering of soil samples collected during field exploration.STRATIFICATION MOISTURE CONTENT ⑥Moisture (%): Water content of soil sample measured in laboratory (percentage of dry weight of sample). Dry: Absence of moisture, dusty, dry to the touch. ⑦Dry Density (pcf): The dry density of a soil measured in laboratory (pounds per cubic foot). Moist: Damp / moist to the touch, but no visible water. ⑧ Gradation: Percentages of Gravel, Sand and Fines (Silt/Clay), obtained from lab test results of soil passing the No. 4 and No. 200 sieves. Saturated: Visible water, usually soil below groundwater. ②TYPICAL DESCRIPTIONS COARSE- GRAINED SOILS More than 50% of material is larger than No. 200 sieve size. GRAVELS The coarse fraction retained on No. 4 sieve. CLEAN GRAVELS GW Well-Graded Gravels, Gravel-Sand Mixtures, Little or No Fines SAMPLER SYMBOLS (< 5% fines)GP Poorly-Graded Gravels, Gravel-Sand Mixtures, Little or No Fines Block SampleGRAVELS WITH FINES GM Silty Gravels, Gravel-Sand-Silt Mixtures Bulk/Bag Sample ( ≥ 12% fines)GC Clayey Gravels, Gravel-Sand-Clay Mixtures Modified California Sampler SANDS The coarse fraction passing through No. 4 sieve. CLEAN SANDS SW Well-Graded Sands, Gravelly Sands, Little or No Fines 3.5" OD, 2.42" ID D&M Sampler(< 5% fines)SP Poorly-Graded Sands, Gravelly Sands, Little or No Fines Rock CoreSANDS WITH FINES SM Silty Sands, Sand-Silt Mixtures Standard Penetration Split Spoon Sampler( ≥ 12% fines)SC Clayey Sands, Sand-Clay Mixtures FINE- GRAINED SOILS More than 50% of material is smaller than No. 200 sieve size. SILTS AND CLAYS Liquid Limit less than 50% ML Inorganic Silts and Sandy Silts with No Plasticity or Clayey Silts with Slight Plasticity Thin Wall (Shelby Tube) CL Inorganic Clays of Low to Medium Plasticity, Gravelly Clays, Sandy Clays, Silty Clays, Lean Clays OL Organic Silts and Organic Silty Clays of Low Plasticity SILTS AND CLAYS Liquid Limit greater than 50% MH Inorganic Silts, Micacious or Diatomacious Fine Sand or Silty Soils WATER SYMBOL CH Inorganic Clays of High Plasticity, Fat Clays Encountered Water LevelOHOrganic Silts and Organic Clays of Medium to High Plasticity Measured Water LevelHIGHLY ORGANIC SOILS PT Peat, Soils with High Organic Contents (see Remarks on Logs) 1. The results of laboratory tests on the samples collected are shown on the logs at the respective sample depths. 2. The subsurface conditions represented on the logs are for the locations specified. Caution should be exercised if interpolating between or extrapolating beyond the exploration locations. 3. The information presented on each log is subject to the limitations, conclusions, and recommendations presented in this report. Figure:6UNIFIED SOIL CLASSIFICATION SYSTEM (USCS)MAJOR DIVISIONS USCS SYMBOLSDepth (ft)GRAPHIC LOGSample TypeSample #Moisture (%)Dry Density(pcf)Gravel %Sand %Fines %LLPLPI