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' Mr Harlin Knoll <br /> • May 1998 <br /> Pa <br /> Page to <br />' excavation of additional contarrunated soil from the northern and eastern <br /> sidewalls of the UST #1, thereby extending the excavation approximately <br /> 3 feet in those directions No further soil excavation was conducted at <br /> the UST #2 location Confirmatory soil samples were collected from the <br /> northern and eastern sfdewalls of the UST #1 excavation following the <br />' excavation (UST1-8 and UST1-9, respectively) The samples were <br /> analyzed for the same parameters that were analyzed for during the <br /> previous sampling event <br />' TPH-g was detected in the sample collected from the northern sidewall at <br /> a concentration of 32 mg/kg, low concentrations of BTEX compounds <br />' were also detected in this sample The eastern sidewall sample, UST1-9, <br /> did not contain detectable concentrations of TPH-g or BTEX The sample <br /> results are shown on Table 1 <br /> Monitoring Well Installation <br /> Based on the results of the soil and ground water investigation, the <br /> County requested that a monitoring well be placed downgradient of each <br /> excavation to monitor the concentrations of TPH-g and BTEX in the <br /> ground water ERM installed one monitoring well at a location <br /> downgradient (north-northeast) of each of the former UST locations on <br />' 27 April 1998 Monitoring well MW-1 was installed approximately 100 <br /> feet downgradient of former UST #1 as shown on Figure 2 Monitoring <br /> 1 well MW-2 was installed approximately 100 feet downgradient of former <br /> UST#2 as shown on Figure 3 Each of the monitoring wells was <br /> constructed with 2-inch PVC and screened from a depth of <br /> approximately five to fifteen feet bgs The wells were constructed in <br /> accordance with all applicable regulations <br />' Soil cuttings generated during installation of the monitoring wells were <br /> disposed of with the soil generated during the excavation activities <br />' described above Ground water purged during the development and <br /> sampling of the monitoring wells was treated and disposed of with <br /> ground water generated during the final excavation and backfilling <br /> activities at UST #1 (discussed below) Well construction logs for the two <br /> monitoring wells are included as Attachment 4 to this report <br />' Following installation, the wells were developed and sampled on <br /> 1 May 1998 A TPH-g concentration of 74 mg/1 was detected in the <br />' sample collected from MW-1, BTEX compounds were also detected in <br /> this sample at concentrations ranging from 0 053 mg/I (benzene) to <br />