ARCHIVED REPORTS_XR0005603 CASE 1

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URS Mr Mike Infurna Page 4 • San Joaquin County Environmental Health Department ARCO 6020 February 16, 2006 SENSITIVE RECEPTORS In August 2003, URS conducted a well records file review at the Department of Water Resources (DWR) The information requested was as follows general well information, well construction information, and well locations within a radius of 2,000 feet from the site No existing water supply wells were identified within the search area According to the City of Manteca Water Department, there are no municipal wells located within the search area CONCLUSIONS AND RECOMMENDATIONS The following information fulfills the RWQCB Central Valley Region's outstanding requirements for site closure The RWQCB checklist for No Further Action at UST sites is included as Attachment F • All USTs and appurtenances have been upgraded at the site • The extent of petroleum-impacted soil and groundwater has been ascertained from the investigations conducted at the site • 0 Existing gasoline range organics (provides a slightly larger range than TPHg) BTEX, and oxygenates/additives are below the detection limit with the exception of one detection of MtBE (0 70µg/L in MD-13D), which is well below the maximum contaminant limit Total mass of MtBE, in groundwater has been reduced from 0 74 pounds in 2003 to 0 003 pounds in 2006, a reduction of over 99% Based on the review of historical soil and groundwater investigations, URS requests that ARCO Station No 6020 be considered "low risk" and recommends closure and No Further Action A checklist of data required by the RWQCB Central Valley Region for no further action at UST sites is presented as Attachment F This document is based on data, site conditions, and other information that are generally applicable as of the date of the document The conclusions and recommendations herein are therefore applicable only to that time frame K 1Wprocess'J5 BP ARC0106020\0osure Rpts\Text 21606 doc