The study area is underlain by glacial materials deposited during the passage of ice sheets of the Pleistocene epoch. a till drumlin lies just to the west of the valley site, and to the east is the Johnson Creek Stream Valley. Overburden materials indicate that a transition from glaciofluvial (ice contact and outwash) deposits to till underlie the site. The thickness of unconsolidated deposits under the site is on the order of thirty-two to fifty feet.

A dense basal or lodgement till, composed of dense, unsorted and unstratified silty sands and some gravel, ranges from two to five feet thick over the bedrock at the site. a compacted outwash sand and gravel strata of eight to ten foot thickness overlies this basal till. An ablation till, which is coarser grained than the lodgement till, ranges from four to eight feet thick above the outwash. This till is overlain by a layer of medium to fine sands and gravel located at or near the surface north and east of the site. A thin irregular clay layer two to ten feet thick lying at a depth of six to twelve feet below the ground surface was found primarily under the southern end of the valley site overlying the outwash sand.

Bedrock beneath the valley site has been described as the Merrimack Quartzite Formation. The bedrock has a schistose texture and is composed of mostly fine grained phyllites and mica shist. The depth of bedrock ranges from thirty-two to fifty feet within the study area. The upper five to ten feet is composed of soft phyllite. The phyllite is gneissic with the foliation dipping between 30 degrees and 50 degrees. Joints for the most part are parallel to the foliation but occasional vertical and horizontal joints were also observed. The bedrock becomes quartzitic with depth but maintains similar structural attitudes. The bedrock surface dips to the south toward center street and to the east toward Johnson Creek Valley.

The aquifer in the study area is a relatively thin phreatic aquifer which occurs in the overburden soils and shallow weathered bedrock. The depth to the water table is twenty-five to thirty feet below the ground surface. The aquifer material are granular soils of glacial origin which fill a relatively narrow north/south winding valley.

• Dense Non-aqueous Phase Liquids (DNAPLs)
• Fractured Bedrock

The plume in 1990 was approximately 3,900 feet long and 1,000 feet wide at its widest.

• Tetrachloroethene (1,600 µg/L)
• Trichloroethene (150,000 µg/L)
• 1,2-Dichloroethene (7,900 µg/L)
• Arsenic (230 µg/L)
• Chromium (70 µg/L)
• Copper (1,100 µg/L)
• Lead (130 µg/L)

• Pump and Treat

Cleanup goals are MCLs.

The pump and treat system continues to operate and concentrations are trending downward.

http://cfpub.epa.gov/supercpad/cursites/csitinfo.cfm?id=0100750