SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

Ernesto Renteria, Jr. April 1, 2015 Pimentel Property Page 3 of 4 1650 S. EI Dorado Street Stockton, CA 95219 reports with the QA/QC data were provided, but there are still some information gaps that the EHD will request AGE to complete. Regarding the soil gas results, the CVRWQCB was concerned with the location of the sampling points relative to the former location of the dry cleaning equipment, which would be the more probable location of leaks. As the former location of the equipment was not provided, there is some uncertainty that the one vapor point sampled in the former dry cleaning area was near the point most likely to have been at a release point; the EHD is of the opinion that this uncertainty can be reduced by identifying the location(s) of the former dry cleaning equipment or increasing the number of sampling points in the former dry cleaning facility building footprint. It seems a bit surprising that the one soil gas sample not to contain detectable concentrations of PCE was the one collected within the suspected footprint of the former facility building. The EHD also recommends sampling along the former sewer line if it still exists and its location can be determined; the CVRWQCB also recommends videotaping the sewer line interior to identify potential release points to guide the selection of sampling points. The CVRWQCB thought the sample with a high leak-detector concentration should be resampled, and that a five-foot sample depth may be more appropriate; the EHD agrees. The deeper, standard depth may help minimize the potential compromising of sample integrity by leakage of atmospheric air. Any additional soil gas sampling should incorporate a methodology for quantifying the effects of atmospheric leakage, if detected, on the analytical results. The soil and groundwater data collected from boring B3 shows that there was a release in the area of the possible former UST system and the soil discoloration, odor and analytical data demonstrated that the boring was located in or near a point of release. The lack of detectable BTEX in the B3 soil samples is consistent with an aged, biodegraded petroleum fuel release, as is the lack of benzene and minimal toluene, ethylbenzene and xylenes in the B3 groundwater sample. However, the sample does show that groundwater was impacted by the release. As groundwater has been impacted, current practice is to determine the depth of the impact as well as the lateral extent. The depth, or vertical extent, of impacted groundwater has not been demonstrated, however, if it can be shown that the groundwater samples collected from 131, B2 and/or B7 are downgradient of B3 and are from the sandy interval encountered at 35 feet below surface grade (bsg) in B7, and deeper contamination is not encountered, the EHD will consider the lateral extent of impacted groundwater to be adequately demonstrated at this time. As stated by AGE, the concentrations of contaminants encountered during the investigations described above do not exceed the ESLs and CHHSLs screening levels used to identify a variety of environmental concerns; however the EHD cannot issue a letter stating that the investigation of possible UST and dry cleaning releases is complete and that no additional investigation would be useful or appropriate until the following items have been adequately demonstrated: • All data QA/QC elements have been reported and are satisfactory, • The soil gas sampling density in the former dry cleaning facility building footprint is sufficient for reasonable confidence that any releases from the equipment or plumbing have been detected; • The vertical and lateral extent groundwater impacted by the suspected UST release has been delineated; and