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• Concentrations of dissolved-phase hydrocarbons as detected in monitoring wells have . generally decreased through time. • Remedial, excavation efforts have removed petroleum hydrocarbons to the fullest practical extent. • Adsorbed-phase hydrocarbons in the vicinity of the former aboveground storage tanks and underground storage tank are present within the capillary fringe only and extend vertically to below ground water. Remedial excavation operations in 1990 have effectively removed hydrocarbon-affected soil from the vadose zone in the vicinity of the former storage tanks. • The presence of adsorbed-phase hydrocarbons below static water level appears to indicate a smear zone due to water table fluctuations. It can be expected that concentrations attenuate rapidly with depth as in MW-12. • Estimations of hydraulic conductivity (K), transmissivity (T), storativity (S), and average linear velocity were made from data collected during the aquifer pumping test. The K value estimated from aquifer testing is 7.47 x 104 ft/min; this compares favorably with those ranges of values given by Freeze and Cherry for similar soil types. Transmissivity was estimated at a low 1.35 x 10'2 ft2/min. For comparison, Freeze and Cherry indicate that transmissivities greater than 9.6 ft2/min represent good aquifers for water well exploitation. The value estimated for storativity at the site is 1.0 x 1W, and that for linear velocity: 11.2 ft/year. The value of linear velocity given is that for advective flow, and represents the bulk motion of ground water movement. Contaminant velocity, however, is affected by sorption, degradation, and volatilization processes, factors which inhibit contaminant migration. Hydrocarbon contaminant velocity and therefore transport will be lower than the advective movement of ground water. The actual rate of contaminant migration is unknown, and estimates of such can be developed using a fate and transport model. • Data collected from these most recent investigative tasks, coupled with that from past investigations, will be used in the human health risk assessment for petroleum hydrocarbons in ground water. The site assessment activities summarized in this report have been conducted in accordance with current practice and the standard of care exercised by geologists and engineers performing similar tasks in this area. No warranty, expressed or implied, is made regarding the conclusions and recommendations presented in this report. The conclusions and recommr,11datloas are`based W101% upon an r 4-L&M 5i5 01'tl a V�sei iGu �r4LUltlVLO• ii aCia ai:.ouuitiv:n u7iiCi �iau tuv�� described in this report, our office should be notified. i 8