Contaminants:

Reactive Media:

Cost:
$195,000

Construction:

Point of Contact:
Leo G. Henning
Kansas Department of Health and Environment
Tel: 785-296-1914
Fax: 785-296-4823
Email: lhenning@
kdhe.state.ks.us
Bldg 740 at Forbes Field
Topeka , KS 66620

A pilot test using two different in-well stripping processes for remediation of perchloroethylene (PCE) in ground water was conducted in Hutchinson, Kansas, in 1997. This pilot was part of a test involving three similar locations within the city to evaluate three different technologies: air sparging with soil vapor extraction (AAS/SVE), ozone and air injection with vertical circulation of ground water (C-Sparge™), and in-well stripping (NoVOCs™). All three test sites were located near former or existing dry-cleaning facilities.

This field demonstration cost approximately $195,000, of which $95,000 was for the NoVOCs™ test and $52,000 was for the C-Sparge™ test. A cost comparison indicated that the AAS/SVE system was the least expensive to install and the C-Sparge™ most economical to operate. The NoVOCs™ was the most expensive to install and operate. Dissolved-phase PCE appeared limited to the top 15 ft of the aquifer with maximum concentrations ranging from 30-600 µg/L.

Underlying sediments consist of unconsolidated stream and terrace deposits (sand, silt, and clay). The water table is from 14-16 ft below ground surface (bgs). The hydraulic conductivity value calculated at one location was estimated at 500-770 ft/d with a general hydraulic gradient of 0.001.

Each test configuration consisted of an above-ground remediation system in a temporary enclosure or trailer, a single or combination remediation well configuration, above-grade and below-grade piping, and ground-water monitoring wells. The placement of monitoring wells varied for each site to accommodate the technology-specific data collection requirements.

The NoVOCs™ system included an 8-in diameter PVC remediation well installed to a depth of 38 ft with one stainless steel screen bracketing the water table and one fully in the saturated zone. The system was also equipped with an air diffuser and an infiltration gallery. Four monitoring wells were constructed to a total depth of 35 ft bgs at distances of 30-80 ft from the remediation well. Air was injected into the remediation well at a rate of approximately 70-95 standard cubic feet per minute (scfm) and the flow rate through the well was approximately 40 gpm.

The C-Sparge™ system involved a 4-in diameter PVC remediation well installed to 35 ft bgs with a micro-porous sparge point placed in the lower part of the borehole. The well was screened in the vadose and saturated zones. A self-contained down-hole unit, including a second sparge point and fluid pump, was installed in the casing. Ground-water information was collected from a cluster of five monitoring wells. The average rate of injection was 3 scfm. This technology is enhanced by the addition of ozone to oxidize the contaminants. It further differs from NoVOCs™ treatment in that the reaction takes place in the formation instead of in the well, thereby treating PCE in both the saturated soil and ground water as opposed to only treating the ground water.

Pilot test activities for all sites were conducted over a 5-month period and included monitoring well and system installation, pre-test ground-water sampling, a 6-day system start-up period, on-going data collection and operation and maintenance, and post-test ground-water sampling.

Monitoring wells 30 ft from the remediation well using NoVOCs™ indicate an 87% reduction in concentration of PCE, from 39 to 5 µg/L. C-Sparge™ resulted in a 91% reduction from 34 to 3 µg/L, and AAS/SVE resulted in a 66% reduction from 489 to 168 g/L.