Link to USGS home page.
Texas Water Science Center

In cooperation with the U.S. Air Force, Aeronautical Systems Center,
Environmental Management Directorate, Wright-Patterson Air Force Base, Ohio

Subsurface Occurrence and Potential Source Areas of Chlorinated Ethenes Identified Using Concentrations and Concentration Ratios, Air Force Plant 4 and Naval Air Station-Joint Reserve Base Carswell Field, Fort Worth, Texas

By C. Amanda Garcia

U.S. Geological Survey
Scientific Investigations Report 2005–5176

This report is available as a pdf. (6.49 MB)


Abstract

The U.S. Geological Survey, in cooperation with the U.S. Air Force Aeronautical Systems Center, Environmental Management Directorate, conducted a study during 2003–05 to characterize the subsurface occurrence and identify potential source areas of the volatile organic compounds classified as chlorinated ethenes at U.S. Air Force Plant 4 (AFP4) and adjacent Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) at Fort Worth, Texas. The solubilized chlorinated ethenes detected in the alluvial aquifer originated as either released solvents (tetrachloroethene [PCE], trichloroethene [TCE], and trans-1,2-dichloroethene [trans-DCE]) or degradation products of the released solvents (TCE, cis-1,2-dichloroethene [cis-DCE], and trans-DCE). The combined influences of topographic- and bedrock-surface configurations result in a water table that generally slopes away from a ground-water divide approximately coincident with bedrock highs and the 1-mile-long aircraft assembly building at AFP4.

Highest TCE concentrations (10,000 to 920,000 micrograms per liter) occur near Building 181, west of Building 12, and at landfill 3. Highest PCE concentrations (500 to 920 micrograms per liter) occur near Buildings 4 and 5. Highest cis-DCE concentrations (5,000 to 710,000 micrograms per liter) occur at landfill 3. Highest trans-DCE concentrations (1,000 to 1,700 micrograms per liter) occur just south of Building 181 and at landfill 3.

Ratios of parent-compound to daughter-product concentrations that increase in relatively short distances (tens to 100s of feet) along downgradient ground-water flow paths can indicate a contributing source in the vicinity of the increase. Largest increases in ratio of PCE to TCE concentrations are three orders of magnitude from 0.01 to 2.7 and 7.1 between nearby wells in the northeastern part of NAS–JRB. In the northern part of NAS–JRB, the largest increases in TCE to total DCE concentration ratios relative to ratios at upgradient wells are from 17 to 240 or from 17 to 260. In the southern part of NAS–JRB, the largest ratio increases with respect to those at upgradient wells are from 22 and 24 to 130, and from 0 and 7.2 to 71. Numerous maximum historical ratios of trans-DCE to cis-DCE are greater than 1, which can indicate that trans-DCE likely was released as a solvent and does not occur only as a result of degradation of TCE.

High concentrations of TCE, PCE, cis-DCE, and trans-DCE, abrupt increases in ratios of PCE to TCE and TCE to total DCE, and ratios of trans-DCE to cis-DCE greater than 1 were used to identify 16 potential source areas of chlorinated ethenes at NAS–JRB. The evidence for some of the potential source areas is stronger than for others, but each area reflects one or more of the conditions indicative of chlorinated ethenes entering the aquifer. Potential source areas supported by the strongest evidence are Building 181, between buildings 4 and 5, just west of Building 12, and landfills 1 and 3. The highest historical TCE concentration in the study area, 920,000 micrograms per liter, is near Building 181. The potential source area between Buildings 4 and 5 primarily is identified by notably high PCE concentrations (to 920 micrograms per liter). Primary evidence for the potential source are just west of Building 12 is the notably high TCE concentrations (for example, 160,000 micrograms per liter) that appear to originate in the area. Primary evidence for the potential source area at landfills 1 and (primarily) 3 is the magnitudes of TCE concentrations (for example, two in the 100,000-to-920,000-microgram-per-liter range), cis-DCE concentrations (several in the 5,000-to-710,000-microgram-per-liter range), and trans-DCE concentrations (several in the 500-to-1,700-microgram-per-liter range). The ratio of trans-DCE to cis-DCE at one well in landfill 3 (6.7) is appreciably above the threshold that can indicate likely solvent release as opposed to TCE degradation alone.

Table of Contents

Abstract

Introduction

Study Area Setting and Remediation of Chlorinated Ethenes

Indicators of Subsurface Occurrence and Potential Source Areas of Chlorinated Ethenes

Acknowledgments

Hydrogeology and Directions of Ground-Water Flow in the Alluvial Aquifer

Subsurface Occurrence of Chlorinated Ethenes

Concentrations

Ratios of Concentrations

Potential Source Areas of Chlorinated Ethenes

Summary

References

Appendix—Alluvial aquifer data pertinent to this report, Air Force Plant 4 and Naval Air Station-Joint Reserve Base Carswell Field, Fort Worth, Texas
Table A1.   Maximum historical tetrachloroethene (PCE) concentrations in the alluvial aquifer, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1984–2003
Table A2.   Maximum historical trichloroethene (TCE) concentrations in the alluvial aquifer, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1983–2003
Table A3.   Maximum historical cis-1,2-dichloroethene (cis-DCE) concentrations in the alluvial aquifer, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1991–2003
Table A4.   Maximum historical trans-1,2-dichloroethene (trans-DCE) concentrations in the alluvial aquifer, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1983–2003
Table A5.   Maximum historical tetrachloroethene (PCE) and trichloroethene (TCE) concentrations in the alluvial aquifer, used to compute parent-compound to daughter-product concentration ratios, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1983–2003
Table A6.   Maximum historical trichloroethene (TCE) and total 1,2-dichloroethene (total DCE) concentrations in the alluvial aquifer, used to compute parent-compound to daughter-product concentration ratios, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1991–2003
Table A7.   Maximum historical trans-1,2-dichloroethene (trans-DCE) and cis-1,2-dichloroethene (cis-DCE) concentrations in the alluvial aquifer, used to compute concentration ratios, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1991–2003

Figures

1–3.   Maps showing:
  1.   Location of Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas
  2.   Altitude of the top of the Goodland-Walnut confining unit, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas
  3.   Water table and direction of ground-water flow in the alluvial aquifer, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1995
4–7.   Maps showing maximum historical:
  4.   Trichloroethene (TCE) concentrations in the alluvial aquifer, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field NAS–JRB) (study area, Fort Worth, Texas, 1984–2003
  5.   Tetrachloroethene (PCE) concentrations in the alluvial aquifer, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1983–2003
  6.   cis-1,2-Dichloroethene (cis-DCE) concentrations in the alluvial aquifer, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1991–2003
  7.   trans-1,2-Dichloroethene (trans-DCE) concentrations in the alluvial aquifer, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1983–2003
8–13.   Graphs showing molar concentrations of:
  8.   Trichloroethene (TCE), tetrachloroethene (PCE), and total 1,2-dichloroethene (total DCE) with distance downgradient along a generalized ground-water flow path beginning at well HM–64 (for simplicity, projected straight-line distance), Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1995
  9.   Trichloroethene (TCE), tetrachloroethene (PCE), and total 1,2-dichloroethene (total DCE) with distance downgradient along a generalized ground-water flow path beginning at well HM–59 (for simplicity, projected straight-line distance), Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 2003
  10.   Trichloroethene (TCE), tetrachloroethene (PCE), and total 1,2-dichloroethene (total DCE) with distance downgradient along a generalized ground-water flow path beginning at well HM–123 (for simplicity, projected straight-line distance), Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 2003
  11.   Trichloroethene (TCE) with time for alluvial wells in the southern part of Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas
  12.   Tetrachloroethene (PCE) with time for alluvial wells in the southern part of Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas
  13.   Total 1,2-dichloroethene (total DCE) with time for alluvial wells in the southern part of Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas
14–16.   Maps showing maximum historical concentration ratios of :
  14.   Tetrachloroethene (PCE) to trichloroethene (TCE) in the alluvial aquifer, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1983–2003
  15.   Trichloroethene (TCE) to total 1,2-dichloroethene (total DCE) in the alluvial aquifer, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1991–2003
  16.   trans-1,2-Dichloroethene (trans-DCE) to cis-1,2-dichloroethene (cis-DCE) in the alluvial aquifer, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas, 1991–2003
17.   Potential source areas of chlorinated ethenes, Air Force Plant 4 (AFP4) and Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) study area, Fort Worth, Texas

To view this document, you need the Adobe Acrobat® Reader installed on your computer.
(A free copy of the Acrobat® Reader may be downloaded from Adobe Systems Incorporated.)

 

FirstGov button  Take Pride in America button