Laserfiche WebLink
Californi egional Water Quality Corol Board <br /> Central Valley Region <br /> Karl E.Longley,ScD,P.E.,Chair <br /> Linda S.Adams Arnold <br /> 11020 Sun Center Drive#200,Rancho Cordova,California 9567o-6114 <br /> Secretaryfor __ D Schwarzenegger <br /> Environmental Phone(916)464-3291•FAX(916)464-4645 { �1 r ' <br /> http://www.mterboards.ca.gov/centralvalley 1..1 '� \uUUI I Governor <br /> Protection �E <br /> 5 November 2009 RUyi 10 2009 <br /> ENVjR0tjh ENT HEALTH <br /> Mr. Joe Lentini pymmSERVECES <br /> Shell Oil Products US <br /> 20945 S. Wilmington Avenue <br /> Carson, CA 90810 <br /> REVIEW OF MONITORING WELL INSTALLATION WORK PLAN, FORMER SHELL CRUDE <br /> OIL PIPELINES, HANSEN ROAD NEAR SCHULTE ROAD, TRACY, SAN JOAQUIN <br /> COUNTY <br /> Staff of the California Regional Water Quality Control Board, Central Valley Region (Central <br /> Valley Water Board) has reviewed the 15 October 2009 Monitoring Well Installation Work <br /> Plan, Former Shell Central Valley Crude Oil Pipeline, Hansen Road Near Schulte Road, <br /> Cordes Ranch, Tracy, San Joaquin County, California (Work Plan) submitted by Conestoga- <br /> Rovers & Associates (CRA) on behalf of Equilon Enterprises LLC doing business as Shell Oil <br /> Products US (Shell). The purpose of the proposed monitoring wells is to determine <br /> groundwater flow direction, gradient, verify concentrations previously detected in grab <br /> groundwater samples, as well as monitor plume stability and concentration trends. The <br /> proposed scope of work is the first phase of a phased approach for assessing the groundwater <br /> plume using monitoring wells. <br /> In 2001 , Shell removed a pipeline from the Cordes Ranch property in anticipation of <br /> development. During the removal, six areas referred to as Trenches 1 through 6 were <br /> observed to be impacted by petroleum hydrocarbons. Two of the areas were over-excavated <br /> to a maximum depth of 20 feet. Several subsequent investigations showed the areas of <br /> concern to correspond to Trenches 2, 3, and 4 with total petroleum hydrocarbons as crude oil <br /> (TPHc) up to 31,780 milligrams per kilogram in soil and 730,000 micrograms per liter (Ng/L) in <br /> groundwater. Benzene concentrations up to 620 pg/L have been detected in shallow <br /> groundwater. Dissolved phase petroleum hydrocarbons have also been identified extending <br /> significantly below first encountered groundwater in multiple borings. Groundwater is first <br /> encountered at approximately 30 feet below ground surface. Near Trench 3, the highest TPHc <br /> detected at the site of 730,000 pg/L was found at 110 feet in boring B-69. <br /> In 2008, a sensitive receptor survey identified three domestic wells northwest of the <br /> investigation area in close proximity to the former pipeline alignment. This section of the <br /> pipeline near the water supply wells has not been removed or investigated for potential <br /> releases. Given the nature and extent of pollution discovered at locations where the pipeline <br /> has been removed and the possibility that similar subsurface pollution could exist closer to the <br /> water supply wells, Central Valley Water Board staff requested in letter dated 29 September <br /> 2009 that Shell sample these wells by 30 November 2009. The well sampling is being <br /> addressed separately from the Work Plan reviewed in this letter. <br /> California Environmental Protection Agency <br /> �a Recycled Paper <br />