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11/08/1996 08:57 1209B3­52 WRIGHT ENVIRONF rAL r,Aut na <br /> Cleanup actions of further oil excavation, and soil and groundwater extraction and <br /> treatment do not appear to be cost effective for this site's contaminant composition, and <br /> distribution and pending sale guidance. Given the degraded Benzene, Toluene, <br /> Ethylbenzenc, and total Xylenes (BTEX) volatile component chemistry of the dissolved <br /> plume Wright feels that o*ttral bi6logic action will continue to degrade the gasoline, <br /> however, continued grotar twater monitoring is warranted and the existing groundwater <br /> monitoring array should SAE expanded for this purpose. <br /> Based on the letter request.fivrn the PHS-EHD, date stamped July 26, 1996, and <br /> telephone conversations with their representative, a minimum of three additional wells <br /> will be installed. One wig be placed upgradient, one downgradient, and one at the <br /> northern edge of the c:on*.i bran t plume (see Figure 1). The new and existing wells <br /> will be monitored at gweliYstly intervals to meet the requirements of the PHS-EHD for <br /> underground tank pettoleiak releases. The data collected in this periodic monitoring <br /> program can be used to uuk hydrocarbons in groundwater. <br /> The PHS-EHD indicatedilrst methods for data collection to estimate the rate of <br /> contaminant plume atabitkittion or blo-attenuation should be proposed in this workplan. <br /> Wright recommends'bipiq*parameters be added to the monitoring program to <br /> estimate biologic activity ti.e., dissolved oxygen, oxidation reduction potential, pH, <br /> conductivity, tetnperawre; Adinity, nitrate, ferrous iron, sulfate and biologic <br /> screening (for assumed plmdomonas genera); Wiedemeier and others, 19951. This <br /> will establish baseline dWd onditions regarding biologic activity, and gathers data for <br /> determining indigemewbi�degeadation conditions for natural attenuation. Wright also <br /> recommends penneabil W.,Osdus of soil core samples from within each of the two <br /> prominent aquifer lithof eles identified in previous work. Along with continued <br /> quarterly groundwater maxlwag data, the results can be used to estimate groundwater <br /> flow rates and the rate of of ouninant plume stabilization. <br /> SCOPE OF WORK <br /> TASK ONE: MUAIMIISlIuIG WELL INSTALLATION <br /> Task 1.1 - soil SM1001 <br /> Three borings will be dr"d for conversion to groundwater monitoring wells at the <br /> locations shown on Figuvii 1. Drilling and well installation permits will be secured <br /> from the PHS-EHD. Wr*will prepare a site specific health and safety plan, notify <br /> Underground Service Atert, and perform utility location prior to the start of field work. <br /> Borings for the monit"tuella will be installed by the use of a truck-mounted hollow <br /> stem auger. The sampler'"I be advanced to the desired sampling depth interval, and a <br /> soil sample core collected. The boreholes will be logged using the Unified Soils <br /> c nr&Cor DRAFT, Project No. 4096 DRAFT Page 2 <br />