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Waste Water Treatment Plant
Soil Gas Survey Results, January - February 2001
Introduction
A soil gas survey was performed at the Waste Water Treatment Plant (WWTP) located in the southwestern portion of CSSA. This report contains a summary of the analytical results from the WWTP soil gas survey. A detailed description of the methodology is included behind the Soil Gas Surveys tab in Volume 3-1.1. This work was performed in conjunction with soil gas surveys performed at SWMU B-3, SWMU B-4, AOC 55, AOC 57, AOC 63, and AOC 65 from January 2, 2001 through February 23, 2001.
The distribution and concentrations for the compounds detected are addressed below. Minor amounts of benzene, toluene, and xylene were detected in soil gas samples throughout the soil gas survey. The detection of these compounds is attributed to artifact contamination from the gas generator used to power the vacuum pump and/or the combustion engine of the geoprobe truck. The frequency of detectable BTEX compounds decreased substantially after the gas generator was moved to the front of the geoprobe rig, and the rig was shut down during sample collection. The BTEX concentrations detected during the soil gas survey are presented in the data tables, but are not discussed in the soil gas findings. The complete laboratory results are presented in Appendix A. Sample locations are presented in the WWTP Sample Location Map, Figure WWTP-1.
Determination of Sampling Locations
The wastewater treatment plant area was selected for testing with the remaining grid points because it potentially could have received wastewater containing VOCs. The grid layout for the wastewater treatment plant included 45 grid points and extended approximately 500 feet to the east of the plant. Figure WWTP-1 presents the grid layout relative to the wastewater treatment plant and surrounding topography. The treatment plant is located on the southwestern boundary of CSSA, south of AOC 65 and AOC 57. The grid points were spaced approximately 100 feet from each other. The layout was located down-slope of the plant and in the direction of the buried utility lines that transport wastewater to the facility. The grid layout should provide indications regarding potential releases of VOCs from the plant through surface spills or from buried utility lines.
Soil Gas Survey Results for Waste Water Treatment Plant
A total of 42 samples were collected at the WWTP at locations presented on Figure WWTP-1. Sampling depths ranged from 1 to 4 feet, with depth determined by refusal. Detected constituents at the WWTP survey area included benzene, toluene, ethylbenzene, and xylenes (BTEX). A summary of these BTEX detections is included in Table WWTP-1. No figure is included in this report depicting a contaminant plume in this grid layout because target VOC compounds were not detected from any of the sampled grid points.
Summary of Findings and Recommendations
From the soil gas survey results, it appears that no significant VOC contamination has been released to, or is present in, the soil and groundwater underlying the WWTP. No additional investigation activities are proposed at the WWTP with regard to VOC contamination.
Table WWTP-1 - Waste Water Treatment Plant Detected Constituents