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. Discussion The dissolved contaminants appeared to have migrated in a northeasterly direction from the former tank pit area from previous study (Wright 1996) This field evidence indicated that the migration in the shallow aquifer had occurred along or fust below the capillary fringe for a limited distance The reconnaissance borings of 1996 clearly showed an easterly contaminant movement It is surmised that seepage from the canal currently influences flow The groundwater monitoring well data shows that only MW-2 revealed dissolved TPHA at 340 ppb These concentrations indicate highly degraded volatile components in the gasoline product This indicates that the residual contaminants are not mobile The concentration differences between these studies are attributed to the drilling action which tends to free absorbed contaminants However since the monitoring wells are located at points further from the reconnaissance borings, the migration and quantity of dissolved contaminants appears minimal Concentrations of BTEX were not detected in any well water sample, indicating that natural biodegradation process have operated on this fuel, and the fuel is highly degraded A relatively flat gradient, together with the clayey sand aquifer strata, appear to have limited migration of the plume . Conclusions and Recommendations Three groundwater monitoring wells were used to further define the extent of petroleum contaminants in the vicinity of a former underground storage tank location Previous exploratory soil borings and reconnaissance groundwater sampling show that highly degraded TPHG and BTEX occurs downgradient of the former tank and dispenser area (Wright, 1996) Contaminant distribution is indicative of a contaminant plume to the east Groundwater flow is currently southwesterly, and is attributed to seepage from the nearby canal influence Local regional groundwater is anticipated to flow easterly given previous work and contaminant dispersal when the canalis empty Cleanup actions of further soil excavation, and soil and groundwater extraction and treatment do not appear to be cost effective for this site's degraded contaminant composition and distribution and pending State guidance Given the degraded BTEX volatile component chemistry of the dissolved plume, Wright feels that natural biologic action will continue to decompose the gasoline However, site groundwater monitoring is warranted We also recommend that monitoring for biologic parameters be added to the monitoring program to estimate biologic activity (i e , dissolved oxygen, pH, ferrous iron, sulfate and nitrate, Buscheck and O'Reilly, 1995) This will establish a baseline to estimate the biologic activity inferred from the data collected Periodic monitoring is proposed quarterly for the next two quarters, with a review of data to ascertain the feasibility of site closure Haley Wells Project No 4111 Page 4