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i CGealrgical Technics Inc. Page 5 Groundwater Monitoring Report Project No. 1030.2 May 7,2003 Parameter Source of the Background Plume Plume ' Parameter Behavior Behavior Core Margins Nitrate' e"Acceptor Slightly Enriched Depleted Not Depleted Ferrous Ironz Metabolic Byproduct Slightly Enriched Slightly Enriched Not Enriched Sulfate' e"Acceptor Site Specific Slightly Enriched Mildly Depleted Temperature Metabolic Byproduct Site Specific Elevated Slight Elevated ' pH Metabolic Byproduct Site Specific Slightly Lower Slightly Higher Alkalinity Metabolic Byproduct Site Specific Enriched Mildly Depleted Redox Potential Metabolic Byproduct Negative Value Depleted Slightly Lower Conductivity Metabolic Byproduct Site Specific Elevated Unaffected e =electron Terminal electron accepting process: 1 —denitrification 2=reduction The test results showed the following: • MW-1 has a high level of alkalinity compared to MW-2 and MW-3. Elevated levels of alkalinity are an indicator of benzene biodegradation, either aerobic or anaerobic. • The average nitrate as nitrogen constituent in MW-2, 3 and 4 is 15.7 mg/L. MW-I has 12 mg/L indicating nitrate depletion, which is consistent with biodegradation in an anaerobic environment. ' * Redox potential has been consistently lowest in MW-I suggesting MW-I is near the center of the plume (Table 5). ' ❑ Redox potential measured over three years may suggest the site conditions are in an anaerobic state. ❑ Redox potential measurements from the last two quarters suggest that there is reaction between groundwater and the halo of the plume near MW-2, MW-3 and MW-4. • The groundwater temperature at the site ranges between 65° and 75°F. * The measured pH in the water table wells range between 7.3 and 7.6. The test results showed the following trends when comparing the contaminated zone to ' background conditions. • Alkalinity of the contaminated zone was enriched compared to background. This may ' be secondary evidence of aerobic biodegradation activity. • Nitrate of the contaminated zone was depleted compared to background. • Sulfate and total iron was inconclusive. ' • Oxidation-reduction potential of the contaminated zone is lower compared to background. • The measured pH in the water table wells range between 7.3 and 7.6. This pH range is conducive to maintaining aerobic biodegradation activity. • Temperature was slightly elevated in the impacted area.