FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

ASSOCIATES(Vv:ATC I "N-C were detected in the influent samples. Approximately 0.16 pounds of TPHg;was removed during the pilot test. Laboratory results of the effluent vapor sample indicated a destruction efficiency of over 98 percent for all constituents analyzed. On June 30, 1999, ATC performed a short-term aur sparge test; The purpose of the test was to determine if the lack of airflow during the previous pilot test was due to subsurface stratigraphy and/or equipment size. Well MW-1 was used as the air injection point. Prior to the test, a grab groundwater sample was collected from well MVS-1. Two air compressors capable of producing flaws up to 10 cfm were connected in series and used to pressurize the well casing to 10 psi. Airflow was initiated at a flowrate of 2 cfm and gradually increased to 4 cf . Helium was then injected at a flowrate of 2 cfm in addition to the air for a total flowrate of 6 cfrn. After 80:minutes of operation, helium was detected in wellVW-5d but no helium was detected in well V -4, seven feet away. It was determined that the injected air and helium were channeling through the subsurface to well VW-5d, At the direction of PHSIEHD, the air sparge test was:terminated to prevent the migration of the plume to the north. Results and field readings from the short-term air sparge test performed on June 30, 1999 are summarized in Table 7; Laboratory results of the groundwater samples collected from W-1 before and after the test indicated that petroleum hydrocarbons increased during the test. An injection rate of 4 cfm was attainable using two small air compressors. Positive pressure was observed approximately 20 feet away from the injection point, with the highest measurements in well VW-5d. Helium was also detected in this well at 18%. 4.0 SUMMARY OF SOIL AND GROUNDWATER CONUTITONS 4.1, Extent of Hydrocarbon-Impacted Sial The lateral extent of gasoline hydrocarbons in soil is delineated by borings B-6 and B-7 to the gest, boring B-5 to the south, boring B-4 to the east, and boring B-15 to the north. The highest concentrations of residual ;gasoline hydrocarbons appear to be north and west of tank T3, from approximately 15 feet bsg to the top of the groundwater surface at the time of the investigation{42 feet WA62524:01tcAr report.doc 7