ARCHIVED REPORTS_XR0006203 - Laserfiche WebLink

Home Browse Search

The analytical results for the samples are presented in boldface type in Table 1, along with previous data The laboratory analytical report and chain-of-custody documentation are included as Appendix B Detectable concentrations of TPH-g in the samples ranged from 120�cg/L (MW 1) to 130,000µg/L (V2) The concentration of TPH-g in the sample collected from MW8, located adjacent to the Shell service station and upgradient of the site, was 48,000 ,ug/L Detectable benzene concentrations ranged from 25 /,4g/l- (MW2) to 13,000,ug/L (V2) MTBE was detected in samples at concentrations ranging from 15 µg/L(MW4) to 900µg/L (RW 1) Groundwater sample analytical results are shown in Figure 1 3. SOIL VAPOR EXTRACTION AND TREATMENT SYSTEM A vapor extraction system (VES) has been operating at the site since May 1994 The system P g Y Y extracts soil vapor from the vadose zone through seven wells (V I, V2, V4, MW2, MW3, MW5, and MW6) and destroys hydrocarbons with a catalytic oxidizer The system is augmented with air sparging equipment that injects air below the water table through sparging wells SW 1 and SW2 The oxidizer was converted from thermal to catalytic operation in May 1995, following a Isteady decline in extracted soil vapor concentrations, as shown in Tables 2 and 3 The decline in extracted soil vapor concentrations has continued since the conversion to catalytic operation During the fourth quarter, oxidizer influent samples contained TPH-g concentrations from 42 ,ug/L to below the method detection limit (mdI) of 5 ,ug/L, and benzene was detected from ' 0 78 4g/L to below the mdl of 0 050 ,ug/L In November and December, construction of a groundwater remediation system (UVB) was ' completed The VES system was shut down in December to allow the modification of the system manifold for the UVB system The UVB system consists of an in-situ air stripper groundwater recirculation well Recovery well RW3 was destroyed, and the groundwater ' recirculation well was installed in its place The recirculation well extracts groundwater at a maximum rate of 10 gpm from a 4-foot screen at the base of the well, and the water is pulled to the upper chamber where air is infected to volatilize petroleum hydrocarbons After the groundwater undergoes this treatment it is reinfected through the upper well screen into the formation ' 4. WORK PROPOSED FOR NEXTQ UARTER Groundwater elevations will be measured and groundwater samples will be collected in February 1997 The samples will be analyzed for TPH-g, BTEX, and MTBE ' Because of the proximity of wells IW 1 and MW4, well P 1 is sampled only twice a year Similarly, because of the proximity of wells 1W 1 and RW2, well MW2 is sampled only twice a year On the same basis, well MW I is sampled only twice a year, because of its proximity to well P2 Because concentrations of petroleum hydrocarbons in wells MW 12 and MW 13 have ' wP61 73942Q 1196 TX 4 2