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' 105 October 2000 <br /> AGE-NC Project No: 95-0197 <br /> Page 2 of 6 <br /> On 08&09 April 1999 four borings were advanced at the site to maximum depths„of 35 feet <br /> ' . bsg. Borings MW-1 through MW-4 were converted into 2-inch diameter PVC groundwater <br /> monitoring wells. The soil and ground water samples were anal y2ed'for TPH=g,.TPH-d, Y <br /> BTEX compounds,methyl tertiary butyl ether(MTBE),and the suite of five fuel oxygenated <br /> compounds. No target analytes were detected above laboratory reporting limits in any of the <br /> ' p g <br /> soil samples selected for analysis: Ground water samples were collected on 12 April'1999, <br /> TPH-d was detected in the ground water sample collected from MW-1 at'a concentration bf: <br /> w samples,collected from MW-2 and <br /> „ 130 µg/1 and MTBE was detected m the ground water p <br /> MW-3 at concentrations of'2.5 µg/1 and 0.71 µg/l.., „ <br /> 2.2, ;REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING <br /> The site is located within the'northern San Joaquin Valley which comprises part of the Great Valley <br /> geomorphic province of California. The San Joaquin Valley is a large, elongate, northwest-trending <br /> asymmetrical structural.trough(basin). It is bordered by-the Coast Ranges to the west, the Klamath <br /> Mountains'andrCascade Range to the north,'and the Sierra Nevada to.the'east. This trough has been <br /> filled with' sediments derived from both marine and continental.'sources. Thickness of the, <br /> ' -sedimentary fill ranges from thin veneers'along the'valk edges to more than'20,000 feet in the south <br /> central portion of the valley. The'sedimentary formations range m age with the older deposits being <br /> primarily marine in origin•;and the .younger' deposits being primarily continental. The younger <br /> continental-derived sediments' were .,primarily deposited in, lacustrine; fluvial,• arid' alluvial <br /> environments with sediment'solaces tieing the mountain ranges surrounding the Valley{Olmsted and' ; <br /> Davis, 1961).The site is located on unconsolidated and semi-consolidated alluvium, lake; playa and <br /> terrace deposlfs.of Quafernary'age (California Division of`Mines and Geo logy;1. 1 ' <br /> 977).:-, <br /> The-Modesto','Riverbank and Turlock.Lake Formations and overlying Recent alluvium-are the' ” <br /> principal sources of domestic ground water in the 13,SOfl-s'quaie"mile San"Joaquin Valley Ground <br /> Water Basin (Basin 5-22). <br /> 2.3.. 'GROUND WATERDEPTH AND FLOW DIRECTION a ; <br /> Based ori tl a San Joaquin County Flood Control District and Water Conservation District Lines of, <br /> Equal Depth:of-•Water Wells F.all°I998'rnap;'•ahe estimated depth to ground water:in the .vicinity of <br /> the site is 15 to 25 feet below surface'grade s Based on Quarterly Report- Second Quarter <br /> 2000, dated 02'August 2000 prepared by AGE, the.approximate depth to ground Ovate is 13.50'feet <br /> ' as,of 26 June 2000. <br /> • ' :' Based upon data obtained from,previous'monitoring events, the prevailing ground-water flow <br /> Advanced GeoEnvironniental,Inca <br />