ARCHIVED REPORTS_XR0011036 - Laserfiche WebLink

Home Browse Search

Section 2 Interim AS/SVE Development and Progress ASISVE System Overview The interim ASISVE system was described as a component of the recommended remediation system presented in the RI/FS performed by CH2M HILL in 1991. The former UST site was characterized as having smear zone contamination directly below the location of the old tanks. The ASISVE process was conceived to remediate this smear zone contamination, which is considered the ongoing source of groundwater contamination. It is believed that gasoline trapped in the smear zone continues to migrate from free phase in soils to dissolved phase in the groundwater. The ASISVE system consists of two well pairs, a sparging blower, a vapor extraction blower, and an engine for destroying extracted gasoline vapor. Each well pair consists of a sparging well and a soil vapor extraction well. Sparging wells consist of a 2-foot well screen at a depth of 90 feet bgs. Vapor extraction wells have a 10-foot well screen interval at a depth of 60 to 70 feet bgs. Piezometers were installed to assess the influence of the-AS/SVE system on j groundwater and soil vapor at various depths. Piezometers are in two nested clusters: NP-1 and NP-2. NP-1 piezometers are screened at 90, 80, and 70 feet bgs to monitor groundwater character at various depths. NR-2 piezometers are screened at 45 to 46 feet (NP-2-45') and 64 to 65 feet bgs (NP-2-65') to monitor vacuum influence and soil vapor character at two depths. The arrangement of the ASISVE wells and piezometers is shown in section view in Figure 2-1 and in plan view in Figure 2-4 at the end of the section. Construction of the AS/SVE system began in August 1994 and was completed in February 1995. The system has been operating continuously since late February 1995. Planned Operation and Monitoring The progress monitoring plan for the AS/SVE system consists of the following sampling and testing events. • Weekly measurement of engine intake (i.e., soil vapor plus dilution air) and exhaust, and all flow rates,pressures, and temperatures throughout the system. • Monthly measurement of differential vacuum, total volatile organic compounds ti (VOCs) by photo ionization detector (PID), and percentage oxygen in NP-2 ; piezometers. • Monthly measurement of dissolved oxygen; water level; pH; total petroleum hydrocarbons as gasoline (TPH(g)); and benzene, toluene, ethylbenzene, and total xylenes (STEX) in NP-1 piezometers. • A bimonthly respiration test, where dissolved oxygen change is measured in I NP-1 piezometers over 48 hours while the AS/SVE system is not in operation. 4 f SF010030981.doc 2-1 1