The site lies within the Newark Basin which is composed of mostly Triassic Rocks. The stratigraphy at the test site consists of four to six feet of a silty clay overlying the bedrock of the Brunswick Formation. The Brunswick Formation at this site consists primarily of a red, brown siltstone which is slightly weathered to approximately 12 feet. Vugs are found frequently in this zone. Underneath the weathered zone, is a brownish gray siltstone that is approximately one foot thick. Below 13 feet, the formation becomes more competent to a depth of 21 ft.

Significant zones of fractures are present between 14 ft and 21 ft below the surface. In this zone, fractures are between one inch and five inches apart. High angle fractures are more common in the upper intervals (14-19 ft). Below 21 ft are several moderately fractured zones interbedded with unfractured zones. Below 27 ft. the formation becomes more competent, with an Rock Quality Designator approaching 50%.

Ground water occurs mostly in the vertical joints and along the bedding planes. Ground water transmission occurs through the same.

• Fractured Bedrock

• Trichloroethene (690 µg/L)

• Other

Comments:
Site characterization technologies were not available. Tests, to determine the feasibility of pneumatic fracturing included slug tests, rising and falling head tests and pumping tests.

Two types of air permeability testing were performed; air injection and soil vapor extraction. The data collected included applied vacuum/pressure, extraction/injection air flow rate, vacuum/pressure influence at distance and extracted vapor concentrations. The soil vapor extraction tests were completed to obtain an alternative set of data due to the low permeability of the formation.

• Fracturing
• Soil Vapor Extraction
  • In Fractured Bedrock Vadose Zone

None provided

Full scale remediation began in 1995 with pneumatic fracturing and dual phase extraction. Twenty extraction were installed. Area of treatment is 1.5 acres and the depth of treatment is 30 ft. Total capitol costs was $1.1 million.

The DPE was successful in removing the bulk mass of contamination and bringing the dissolved TCE concentrations down to the single diget ppm levels. At this point, the system was considered inefficient and costly as the mass removal had asymptoted.

A second pilot test consisted of applying Ferox technology which is based on a specialty ZVI powder integrated with a gas-based injection method. The ZVI powder was injected into three existing open-rock wells using nitrogen gas as a carrier fluid.

Fractures previously created during the initial application 6 years earlier were redialated prior to the ntroduction of an iron water slurry in conjunction with the nitrogen gas. The volume flow rate and the velocity of the nitrogen gas "atomized" the ZVI slurry and dispersed it uniformly. The iron was injected into depths from 12 ft bgs to approximately 27 ft bgs.

Based on field observation and pressure monitoring, the injection process was a success in dispersing the Ferox powder into the target zone. Results, after four rounds of post injection sampling, significant TCE reduction was observed in most of the monitoring wells. Concentrations decreased from as high as 3,7000 ug/l to non-detect. Subsequent to the injection, the TCE-to-DCE ratio began to change as the cis concentrations increased to approach those of TCE and in some cases, surpass them. This reversal in the TCE and DCE concentrations is indicative of de chlorination of TCE.