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t ► October 17, 1996 Page 2 Please note that an amended work plan should be submitted within 14 days of the date of this letter(October 4, 1996) that proposes a scope of work that will complete the groundwater and.soil contamination work plan. Groundwater flow has consistently been to the south-southeast. In the subject Work Plan, Well MW-8 was proposed approximately 90 feet south of MW-7. In order to define the extent of hydrocarbons to the south and southeast(downgradient of both Wells MW-7 and MW-5) and to reduce the number of wells necessary to obtain adequate plume definition for risk evaluation, PACIFIC proposes to revise the placement of Well MW-8 to a location approximately 140 feet further to the southeast. The revised location for MW-8 is within the parking area under Highway 4 near the northeast corner of South Center and Lafayette Streets. It is anticipated that MW-8 will define the downgradient extent of petroleum hydrocarbons in groundwater at the site, and allow for subsequent evaluation of risk. In addition to offsite well MW-8, one onsite soil boring(SB-10) is proposed. Selected soil samples collected from boring SB-10 will be tested for water content, bulk density, porosity, and fractional organic carbon content. This site specific data will be used to enhance any future contaminant transport modeling that may be necessary. Additionally, groundwater samples collected from all monitoring wells during the next two quarterly sampling events will be tested for conductivity, pH,temperature, nitrates, sulfates, ferrous iron, dissolved oxygen, and oxidation-reduction potential. These parameters are indicators for biodegradation of hydrocarbons. The results of this additional work will be reported in the well installation report documenting installation of Well MW-8. The amended work plan should include any remediation wells necessary to perform feasibility analysis so that a corrective action plan can be prepared to reduce the concentrations of groundwater and soil contamination. The need for and type of corrective action at this site will be evaluated upon receipt of the results from the work proposed above and from the proposed evaluation of potential sensitive receptors and offsite sources in the vicinity of the site. At that time, if it is determined that a potential risk to human health and/or the environment exists, preparation of a corrective action plan will be initiated. 920-078.1 A/WPLANADD.DOC