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Groundwater and Surface Water Sampling at the ASARCO site, El Paso, Texas

This page contains information regarding groundwater and surface water sampling and results from the ASARCO site in El Paso, Texas.

Groundwater and Surface Water Data 2005 - 2009

ASARCO performed semi-annual groundwater and surface water sampling from 2005 to 2009. The spreadsheet of groundwater data sets forth groundwater data from 2005 to 2008. This includes the original data provided by ASARCO on one sheet as well as the same data rearranged by the TCEQ into two separate sheets for groundwater & surface water results. The TCEQ also divided the groundwater wells into four separate areas for easy identification. The surface water sampling locations are identified in Figure 5 of ASARCO Expert Report.

Split Sampling Event August 2009

The TCEQ region staff collected split samples with the ASARCO facility during the August 2009 semi-annual groundwater sampling event. The rationale for selecting the 19 groundwater wells and five surface water locations is set forth in the Sampling Rationale Document. The EPA-approved SW-846 methods 8260, 8270, 6020, 7470, and 7196 were used to analyze the samples of volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), metals, mercury, and chromium VI, respectively. In addition, the TCEQ requested the lab to report tentatively identified compounds (TICs) in conjunction with analyses using methods 8260 and 8270. The request was made for the laboratory to report TICs to take advantage of a powerful and cost-effective analytical tool that can analyze for compounds potentially present in the sample but not included in the laboratory’s target compounds list for SW-846 methods 8260 and 8270. The XENCO Laboratories performed the analyses for all of the VOCs and SVOCs, including TICs, as well as metals, and mercury. The TraceAnalysis Laboratory in El Paso performed the chromium VI analysis due to the short (24-hour) holding time requirement. Holding times are the length of time a sample can be stored after collection before it needs to be analyzed by a laboratory.

No sample was collected from the EP-96 location (upgradient from the site), because the well was dry. Shaw Environmental & Infrastructure, Inc. (Shaw E&I), a contractor hired by the TCEQ, reviewed all of the sample results as specified in the technical and quality control criteria, established in the scope of work, to document the usability of the data. TraceAnalysis was NELAC-accredited for the chromium VI analysis in groundwater. The XENCO Laboratories were NELAC-accredited for most of the VOCs, SVOCs, metals, and mercury reported, and XENCO flagged the results for which the laboratory did not hold NELAC accreditation. The National Environmental Laboratory Accreditation Conference (NELAC) is an association of states and federal agencies formed to establish mutually acceptable performance standards for the operation of environmental laboratories.

The sampling results are listed in the following files:

General Observations regarding the Sampling Results

  • In the upgradient onsite well EP-129, arsenic and thallium are the only chemicals detected above the drinking water standards.
  • Various metals were detected in the groundwater within the facility boundaries.
  • Arsenic and antimony are the two primary chemical of concerns in the surface water. Arsenic was detected in all five surface water sample locations. Antimony was detected in the most down stream location in the American Canal.
  • With the exception of EP-49 and EP-126, the detected VOCs and SVOCs are near to, or at, the method detection limit. The lab did not identify any reportable TICs. It appears from this round of sampling results that VOCs and SVOCs did not impact the groundwater or surface water except in the locations of EP-49 and EP-126.
  • Bis(2-ethylhexyl) phthalate (BEHP) was detected in wells EP-49 and EP-126. However, BEHP is a common chemical added to PVC and other plastics to increase flexibility. The presence of BEHP observed in these wells is likely due to leaching of BEHP from some plastic components associated with the well construction or used during the collection or analysis of these samples.
  • The EP-49 well is one of the most contaminated wells in the facility and is located inside the metal and diesel plume. The only detection of benzene found during this sampling event was in this well, and the concentration of benzene exceeded the drinking water standard.
  • No vinyl chloride was detected in the groundwater samples. However, Vinyl chloride was detected in the three field blanks samples. These data indicate vinyl chloride was inadvertently introduced into the field blank samples during preparation, handling, collection, shipment, or analysis of the blank samples. The TCEQ has ruled out vinyl chloride as a chemical of concern in the groundwater and is currently conducting further evaluation to determine the potential source(s) of the vinyl chloride found in the field blanks.