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Following installation of the four monitor wells and the submittal of a Monitor Well Installation <br /> Report(as described in Section 4.7 of the Work Plan),a quarterly monitoring program is <br /> proposed. The proposed scope of work for the quarterly monitoring program is as follows: <br /> • A water level survey at the four monitor wells will be conducted prior to any monitor <br /> well purge activities. The depth-to-water will be measured at all four wells in accordance <br /> with Section 4.5 (Groundwater Sampling)of the Work Plan. In addition, the floating <br /> product thickness will be determined in MW-4 to 0.01 foot with a standard,battery- <br /> operated, free product/water interface probe. <br /> • Following the water level and free product thickness survey,MW-1,MW-2 and MW-3 <br /> will be purged and sampled in accordance with the approved Work Plan. Groundwater <br /> samples collected from the wells will be analyzed in accordance with Section 4.6 <br /> (Laboratory Analysis)of the approved Work Plan. <br /> • During the initial groundwater sampling event conducted as part of the monitor well <br /> installation(as described in the Work Plan)and on an annual basis thereafter,parameters <br /> will be analyzed in the field and at the laboratory to evaluate the potential for intrinsic <br /> bioremediation at the site. The intrinsic bioremediation parameters may assist in the <br /> evaluation of the natural attenuation of the diesel contamination(if it is occurring)as a <br /> result of aerobic and/or anaerobic metabolism of the petroleum hydrocarbons by naturally <br /> occurring microbes. At all four monitor wells, samples will be collected by Condor and <br /> analyzed by the laboratory for nitrate, sulfate,ferrous iron, and total alkalinity(laboratory <br /> measured intrinsic bioremediation parameters). Field measured intrinsic bioremediation <br /> parameters include dissolved oxygen, oxidation-reduction potential,pH, electrical <br /> conductivity,and temperature. The field measured intrinsic bioremediation parameters <br /> are determined with instrumentation calibrated daily, or more frequently when necessary, <br /> using the manufacturer's recommended procedures. <br /> Comparing intrinsic bioremdiation data for up-gradient groundwater,down-gradient <br /> groundwater, and groundwater in the approximate center of the contaminant plume is <br /> necessary to evaluate if intrinsic bioremediation is occurring at a site. Therefore, <br /> collecting intrinsic bioremediation parameter measurements at MW-4,which will be <br /> installed in the center of the contaminant plume,is vital. Intrinsic bioremediation <br /> parameters will be measured at MW-4 by first bailing off the free-phase diesel, if present, <br /> and collecting the groundwater sample from below it. <br /> Following four consecutive quarters of groundwater and free-phase diesel monitoring at the site, <br /> LOF may propose a reduction of the monitoring program to semi-annual monitoring or annual <br /> monitoring. The results of the quarterly monitoring may indicate that the diesel plume is stable <br /> and/or gradually attenuating and may be effectively monitored on a reduced basis. <br /> Project Schedule <br /> The four monitor wells can be installed within 30 days of the approval of the proposed <br /> modifications to the previously approved scope of work described in this letter. Monitor well <br /> development, surveying, and sampling can be conducted within 5 days of the well installation. <br /> Turn-around-time for laboratory analyses of the initial monitor well sampling is 10 days. A <br /> Monitor Well Installation Report can be submitted 20 days following receipt of the laboratory <br /> analyses. <br /> N� <br /> iJ CONDOR <br />