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SECOR May 25, 1999 International Incorporated Mr. Ron Foust William Lyon Homes,Inc. ' 2208 Camino Ramon San Ramon,California 94583 Re: Letter Report-Soil and Groundwater Investigation William Lyon Homes,Inc. Stonebridge Development,Lathrop Dear Mr. Foust: ' Secor International Incorporated(SECOR)is pleased to present this letter report documenting the soil and groundwater investigation at the proposed residential development at the William Lyon Homes,Inc.property in Lathrop,California(WLH development; see Figure 1, Site Location Map).Due to the historic presence of volatile organic compounds, primarily TCE (trichloroethene), Lyon Homes requested that a soil and groundwater survey be conducted prior to site grading.TCE had migrated to the site from the former Sharpe Depot east of Stonebridge.This report describes the methods and procedures used during drilling and soil and groundwater sampling associated with the above mentioned property. ' Scope of Work Task 1: Pre-Field Activities ' Prior to performing any intrusive activities,SECOR submitted a Work Plan to,and obtained drilling permits from, the San Joaquin County Environmental Health Division (SJCEHD). SECOR also prepared a Site- specific Health and Safety Plan (HASP) to address the proposed scope of work prior to initiating field activities. The proposed boring locations were cleared by the land owner and Underground Services Alert (USA)was notified. ' Task 2: Drilling and Sampling Activities ' To investigate the soil beneath the site, ten (10) soil borings were advanced to the water table and continuously cored for lithologic description.Soil encountered was logged by a SECOR geologist according to the Unified Soil Classification System (USCS), and soil samples were screened in the field for the presence of volatile organic compounds (VOCs) using a Photoionization Detector (PID). Boring logs ' describing the soil encountered are presented in Attachment A. Soil samples were selected for chemical analysis based on PID readings and lithologic conditions. t In order to collect soil samples,the borings were advanced utilizing a hydraulically and pneumatically driven direct-push sampler. The direct-push sampler was equipped with a 2-inch outside diameter core barrel.The direct-push sampler advances two nested sampling rods that are driven simultaneously; small diameter inner ' sampling rods are used to obtain and retrieve the soil cores, and larger diameter outer rods serve as a temporary drive casing. The use of a drive casing prevents sloughing of the formation while the inner rods are withdrawn from the borehole. This ensured that the drive sampler was always sampling soil from the desired depth interval, rather than soil that has sloughed in from higher up in the borehole. ' SECOR Job No.70139-004-02 Drill Report 1:\70139\004-02\Drill Report.doc ' 1390 Willow Pass Road, Suite 360, Concord, CA 94520-5250 (925)686-9780 (925)686-3099 FAX www.secor.com