CSA Haley & Aldrich 01272025 - Laserfiche WebLink

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Consulting Services Agreement between City of San Leandro and Haley & Aldrich, Inc. for Design Services for Lake Chabot Road Erosion Repairs Last revised 12/2024 Exhibit A - Page 2A of 5 Aldrich will conduct 1-hour meetings via Microsoft Teams every other week to update the City on work status, budget, and upcoming tasks. TASK 2 – GEOTECHNICAL ENGINEERING Task 2.1- Site Reconnaissance and Utility Clearance: During this task, Haley & Aldrich will visit the site to evaluate the site conditions and develop an understanding of the characteristics that may pose challenges. We will utilize the previously completed surveys of the area from LCC and the services of USA North to determine the optimal locations for subsurface exploration. Our time spent and observations on Site A will be recorded in field reports and shared with the City. Task 2.2 - Field Exploration: Haley & Aldrich retains a copy of the boring logs from Treadwell & Rollo (2011). While these logs are useful to understanding the types of material that will be encountered, the depths of strata have changed due to erosion and landslides, and subsurface exploration will need to be conducted again. Subsurface exploration will consist of drilling up to three borings along Lake Chabot Road near the slip-out. The borings will be drilled using a track-mounted drill rig equipped with 6-inch diameter solid flight augers and will extend to depths of up to 40 feet below grade unless drill refusal occurs at a shallower depth. The borings are anticipated to be drilled over the course of two days. A drilling permit will be obtained through Alameda County. It is assumed that an encroachment permit is not required. It is assumed that the City will remove the barriers to provide access for field vehicles to the site. It is assumed that traffic control is not required since a detour is in place. To compare pre and post slide conditions, soil samples will be collected from two of the borings utilizing Standard Penetration Test Split Spoon Sampler and California Modified Sampler methods and obtain blow count data for engineering analysis. Soil samples will generally be taken at 3- to 5- foot intervals. Groundwater levels will be measured in the borings if encountered. Soil cuttings will be collected and discretely scattered on site. Testing and disposal charges will be added to our estimate if contaminated materials are encountered. During the previous subsurface exploration of Site A, serpentinite was encountered and tested for the presence of naturally occurring asbestos (NOA). According to our records, NOA were not present in the samples taken. Task 2.3 - Laboratory Testing: Lab testing will be performed on selected soil and rock samples retrieved from the borings to determine engineering properties and confirm field classifications. Laboratory testing is anticipated to include but is not limited to moisture content, dry soil density, sieve analysis, Atterberg Limits, and shear strength testing. In addition, one sample will be tested following Caltrans corrosion requirements, including Minimum Resistivity, pH, Chloride, and Sulfate. To ensure proper safety precautions are taken later on during the construction phase of the project, testing for presence of NOA may be added to the laboratory testing schedule. Task 2.4 - Engineering and Slope Stability Analysis: We will assess the boring logs and lab results to estimate geotechnical properties and perform a slope stability analysis using Rocscience's Slide software on a representative cross-section. Back-analysis will confirm the recommended design parameters for repair, allowing us to provide an informed opinion on the current slip out and its impact on existing and future retaining structures. This analysis will be integrated into our geotechnical design recommendations. Task 2.5 - Geotechnical Report: The results from the data review, subsurface exploration, laboratory testing, and engineering analysis will be used as the basis for discussing repair alternatives, selecting a recommended repair design concept, and developing geotechnical recommendations to be presented in a Geotechnical Design Report, with supporting graphics and data. If additional comments or edits are required by any County or City review, modifications/ report edits, and resubmittal will be completed on a time-and-expenses basis. Docusign Envelope ID: 5A210297-2C6D-4132-9363-47ABA0868216