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21 March 2005 AGE-NC Project No. 95-0103 Page 3 of 4 Concentrations of hydrocarbons have remained relatively stable in monitoring wells at the site over time; continued ground water monitoring would be required to show decreasing hydrocarbon concentrations. Costs for natural attenuation are generally lower than most active remediation options; however, costs can be highly variable depending on the duration and type of monitoring required. MONITORED NATURAL ATTENUATION-MONITORING Based on recommendations presented in the United States Environmental Protection Agency's How to Evaluate Alternative Cleanup Technologies For Underground Storage Tank Sites-A Guide For Corrective Action Plan Reviewers,ground water monitoring and sampling will be conducted on a quarterly basis for the one year.Ground water monitoring activities will include measuring depth to water and collection of ground water samples from all wells.Ground water monitoring well casing elevations will be re-surveyed to gain an updated ground water table surface.Ground water sample collection procedures previously described work plans and quarterly reports. Site conditions and factors that affect the natural attenuation process are:direction of ground water flow; hydraulic conductivity; lithology/stratigraphy; depth to ground water and fluctuations; disposition of contaminates; status of contaminants (steady state, decreasing and migration); dissolved oxygen levels;geo-chemical indicators(redox);if necessary bio-enumeration and CFU of bio-degrading CFU and ground water recharge or use. Ground water samples will be analyzed by a DHS-certified laboratory for the following constituents: • TPH-g in accordance with EPA Method 8015 Modified;BTEX and the fuel additives methyl tertiary-butyl ether(MTBE), tertiary butanol (TBA), di-isopropyl ether(DIPE), ethyl tert- butyl ether (ETBE), tert-amyl methyl ether (TAME), ethylene dibromide (EDB) and 1,2- dichloroethane(1,2-DCA)in accordance with EPA Method 8260B. • Dissolved oxygen,carbon dioxide,pH,alkalinity,hardness,soluble iron and redox potential, methane/ethane, nitrate/nitrite, sulfate, manganese, ferrous iron, chloride, phosphate, calcium, sodium and potassium. Total organic content and chemical oxidation demand in accordance with EPA Methods.Bio-enumeration of bacteria colonies(CFU-bio-degrading CFU). Filed measurements will include oxidation reduction potential (OPR), dissolved oxygen (DO)content,pH, conductivity and water temperature during sampling. Laboratory reports for ground water analyses,testing methods,laboratory quality assurance/quality control(QA/QC)reports,and sample chain of custody documentation will be presented in a quarterly report with the findings and recommendations. Advanced GeoEnvironmental,Inc.