Loading...
HomeMy WebLinkAboutTract 7325 Soils Report - Drainage Basin InvestigationSoils Engineering Inc . January 27, 2020 Auburn Oaks Developers, LLC 2228 Brundage Lane Bakersfield, CA 93304 Attention: Mr. Victor Baldivia Subject: Addendum No. 1: Drainage Basin Investigation Project: Tract 7325 Development SEI File No. 19-17008 Location: APN's: 437-010-36, 437-010-68 & 437-010-71, Bakersfield, Kern County, CA Reference [1 ]: Geotechnical Investigation Report Project: Tract 7325 Development Location: APN's: 437-010-36, 437-010-68 & 437-010-71, Bakersfield, Kern County, CA SEI File No. 19-17008, Dated, April 22, 2019 Dear Mr. Baldivia: Our scope of work consisted of performing an investigation for the existing drainage basin for Tract 7325 to address the drainage and slope stability. FIELD INVESTIGATION Our field work consisted of drilling two (2) borings in the existing basin area beginning at the finished grade on one bore and ~10 feet due to being in the bottom of the basin on another, finishing at a maximum depth of 31.5 feet below the existing ground surface. A continuous log of the various soils encountered was recorded and classified in accordance with the Unified Soils Classification System (USCS) (Figures 10 and 11 ). LABORATORY TESTING Direct Shear, Permeability, In-place-density, and moisture-content tests were performed on soil samples obtained during our field investigation. Standard Penetration Tests (SPT) were conducted during soil-sampling operations. Samples of earth-materials were taken at intervals varying from three (3)feet to 10 feet and were subjected to laboratory tests to evaluate basin drainage and slope stability.In-place density and moisture-content tests (ASTM D2216), permeability tests (ASTM D2434), anddirect shear tests (ASTM D3080) were performed on samples selected as representative of thepredominant earth materials below existing grade and below the invert of the basin. Test results areattached on the Laboratory Testing Summary, Table 1. SUMP DRAINAGE The subsurface soils, below the proposed invert level of the sump, consisted predominantly of interbedded layers of varying thickness of Silty Sand (SM) and Poorly-Graded Sand (SP) in accordance with the Unified Soils Classification System (USCS). 4400 YEAGER WAY BAKERSFIELD, CA 93313-2019 Phone: 661 831 5100 Fax: 661 831 2111 © 2020 SOILS ENGINEERING, INC. info@sollsengineerlng.com www.sollsenglneerlng.com Auburn Oaks Developers, LLC Project: Tract 7325 Drainage Basin Study Location: APN's 437-010-36, 68 & 71, Bakersfield, CA SOILS ENGINEERING, INC. SE/ File No. 19-17008 January 27, 2020 Page2 Most of these subsurface soils encountered at the anticipated invert level of the existing sump during our field investigation predominantly consist of Silty Sand and Poorly-Graded sand with permeability in the range of 1.58 x 10-3 to 4.14 x 1 o-4, as shown in our boring logs and laboratory test results. Soil permeability indicates that the proposed basin should drain in seven (7) days or less. Maintenance of the existing sump should include removing silt and clay accumulations, including vegetation, from the bottom at regular intervals. SLOPE STABILITY Slope stability for the subject site was assessed using the Price-Morgenstern method using the half­sign procedure and utilizing three different methods to search for the critical-failure surface: The Entry and Exit procedure assuming a circular failure-surface; the Grid-Centers and Radius method also employing a circular failure-surface; and the Block-Failure or Non-Circular failure-surface method. Strength values were obtained from the results of Direct Shear tests, Figures B-1 and B-2, on saturated samples of earth materials obtained from the upper twelve feet below the existing ground surface. Slip-surfaces for the Entry and Exit, Grid and Radius, and Block-Failure methods are shown on Figures A & B. These methods yielded safety-factors ranging from 1.960 to 3.781. We hope this provides the information you require. If you have any questions or need further assistance, please contact Respectfully Submitted, SOILS ENGINEERING, ;;!� L Thomas Bayn . President Attachments: Boring Location Map, Figure 1 Boring Profile Detail: Figure 2 Logs of Borings, Figures 10 & 11 Laboratory Testing, Table 1 Sieve Analysis, Figures A-10 through A-12 Direct Shear, Figure C-2 Stab if ity Charts, Figures A & B 4400 YEAGER WAY BAKERSFIELD, CA 93313-2019 Phone:6618315100 Fax: 661 831 2111 © 2020 SOILS ENGINEERING, INC. info@sollsengineerlng.com www.soilsengineerlng.com