Laserfiche WebLink
u 0 <br /> FRI 205513 MRS Tosco 76 Service Staiion.StoQjMa.CA <br /> April 28. 1499 <br /> • Report To date, Tosco has not received a response and/or approval of the Work Plan addendum from <br /> the County <br /> Tosco performed a well survey to Identify registered wells within a 114 mile radius of the site The <br /> purpose of this survey was to identify wells that may provide conduits for potential vertical migration <br /> of dissolved hydrocarbons and oxygenated compounds and to provide information regarding sensitive <br /> receptors in the area The data indicates ten registered wells within 114-mile of the site, seven of these <br /> wells are cathodic protection wells and three are water supply wells The closest water supply well is <br /> approximately 1,000 feet northeast of the site in the generally upgradient direction of interpreted <br /> historical groundwater flow <br /> In July 1997, Triangle Environmental, Inc performed a tightness test to evaluate the integrity of the <br /> existing fuel distribution system The results indicate the system passed within allowable tolerances <br /> During third quarter 1997, Tosco performed an underground utility search to identify locations and <br /> orientations of utility trenches and to evaluate whether these facilities may provide conduits for the <br /> potential lateral off-site migration of dissolved hydrocarbons and oxygenated compounds The results <br /> of this utility search indicated that utilities are primarily located within the March Lane right-of-way <br /> and are oriented east to west Lateral utility trench lines servicing specific sites are oriented <br /> perpendicular to the main utility lines The deepest utility trench (approximately 10 5 feet bgs) <br /> identified near this site appears to be a 21-inch sewer line located approximately 70 feet south of the <br /> southern property boundary of this site Research indicated that this sewer line is a gravity drain <br /> system draining towards the west The locations of the underground utilities are shown on Plate 2 <br /> On January 28, 1998, Tosco submitted the fourth quarter 1997 Quarterly Summary Report which <br /> included proposed off-site cone penetrometer (CPT) locations to further evaluate the extent of dissolved <br /> MTBE detected in groundwater during ongoing quarterly groundwater monitoring and sampling Tosca <br /> received approval for implementation of the amended Work Plan (August 8, 1997) and the proposed <br /> CPT locations (provided in ERI's January 28, 1998, Quarterly Summary Report) in a letter dated <br /> January 14, 1999 <br /> FIRST QUARTER ACTIVITIES <br /> Based upon previous work completed at the site and in accordance with the correspondence and request <br /> from the County, Tosco performed the following tasks during the first quarter 1999 <br /> • Gettler-Ryan, Inc (GRI) of Dublin, California performed groundwater monitoring and <br /> sampling at the site on March 1, 1999 The GRI First Quarter 1999 Groundwater Monitoring <br /> and Sampling Report is attached The results of the quarterly monitoring and sampling event <br /> indicate the following <br /> - Groundwater was measured at approximately 5 2 to 8 0 feet bgs (an elevation <br /> Increase of approximately 0 7 to 1 2 feet since the fourth quarter 1998 groundwater <br /> monitoring and sampling event) in the groundwater monitoring wells During March <br /> 1999, groundwater flow direction was towards the southwest at a calculated hydraulic <br /> gradient ranging from approximately 0 005 to 0 006 Historical groundwater flow <br /> •' 3 <br />