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Contamination of Ground Water by Perchloroethene (PCE) – A National Perspective. By Michael Moran U.S. Geological Survey. Ground Water Resources Association of California, 13th Symposium Series on Groundwater Contaminants Conference, Newport Beach, California, November 10, 2004 .

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contamination of ground water by perchloroethene pce a national perspective

Contamination of Ground Water by Perchloroethene (PCE) – A National Perspective

By Michael Moran

U.S. Geological Survey

Ground Water Resources Association of California, 13th Symposium Series on Groundwater Contaminants Conference, Newport Beach, California, November 10, 2004

U.S. Department of the Interior

U.S. Geological Survey

slide2

Production and Use of PCE

  • PCE use in dry cleaning began in 1940s
  • Production declined after peak in 1970s
  • As of 2002, PCE was primary solvent for
  • 85% of drycleaners

- this constitutes 25% of PCE production

- remainder is used as industrial solvent

slide4

Physicochemical Properties

of PCE

  • Denser than water
  • High solubility relative to MCL
  • Moderate organic carbon partitioning
  • Relatively high Henry’s coefficient
  • Relatively long half-life in water
slide7

Data on PCE in Ground Water

These data represent a

select subset of all wells

slide8

PCE in Ground Water

3 – ranking of PCE among all

detected VOCs

(assessment level of 0.2 g/L)

slide9

Occurrence Using Uncensored

Concentrations

detection frequency

using no assessment level

slide11

Quantified Concentrations

outlier

(> 1.5  IQR)

75th percentile

median

25th percentile

1.5  IQR

slide12

Concentrations Relative to MCL

Domestic wells

Public wells

Urban land use

Major aquifers

slide13

Occurrence of TCE With PCE

  • Among 4 solvents in ground water,
  • PCE-TCE was most common mixture
  • TCE may be daughter product of
  • reductive dechlorination of PCE
slide14

Occurrence of TCE With PCE

  • PCE occurred more frequently in
  • oxic ground water compared to anoxic
  • Molar concentration ratios of PCE/TCE
  • were 3 times higher in oxic ground water
  • compared to anoxic
slide15

Associations With

PCE Occurrence

Major aquifers:

1. Redox conditions

2. RCRA facilities within 1 km

3. Depth to top of aquifer

slide16

Associations With

PCE Occurrence

Domestic wells:

1. Population density

2. RCRA facilities within 1 km

Public wells:

1. Population density

2. Well depth

3. Proximity to dry-cleaner LUST

slide17

Dry Cleaners as RCRA Facilities

 Most dry cleaners that use PCE are probably

regulated under RCRA

 We estimate that about

30% of RCRA sites are

dry cleaning facilities

  6,000 RCRA-regulated

dry cleaners

slide18

Summary and Conclusions

  • At a national scale, PCE is one of the most
  • frequently detected VOCs in ground water
  • PCE concentrations exceed the MCL more
  • frequently than most other VOCs
  • RCRA facilities and dry cleaners are
  • associated with PCE occurrence