The site is located within the Connecticut Valley Lowland section of the New England physiographic province. The Connecticut Valley Lowland occupies a regional, structural rift basin, which is characterized by block-faulted and tilted bedrock strata. The geology of the region, in general, consists of the Upper Triassic New Haven Arkose, overlain by Wisconsin-age unconsolidated deposits formed when glaciers eroded and smoothed the bedrock hills.

Directly beneath the site, depth to bedrock varies, from approximately 15 to 40 feet below grade at the Operations Area, to approximately 25 to 45 feet below grade on the Cianci property, to approximately 80 to 100 feet below grade at the Town Well Field. Core samples and drilling observations indicate that the upper five feet of the bedrock in the Operations Area and Cianci property is severely weathered and partially decomposed. The degree of weathering generally decreases with depth. In the interval between five and 30feet below the top of bedrock, the bedrock is less weathered but is still highly fractured and permeable.

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

The overburden plume is approximately 2,400 feet long and 960 feet at its widest. The bedrock plume is about 2,160 feet long and 960 feet at its widest. The lateral extent of DNAPL in the bedrock is believed to be over a 720 wide by 1080 foot long area.

• Benzene (610 µg/L)
• Carbon tetrachloride (9,100 µg/L)
• 1,1-Dichloroethene (15,000 µg/L)
• 1,2-Dichloroethene (110,000 µg/L)
• Ethylbenzene (60,000 µg/L)
• Trichloroethene (41,000 µg/L)
• 1,1,1-Trichloroethane (320,000 µg/L)
• Toluene (150,000 µg/L)
• Tetrachloroethene (6,400 µg/L)
• 4-Methyl-2-pentanone (MIBK) (22,000 µg/L)

• Thermal Treatment (In Situ)
  • Conductive Heating
• Pump and Treat
• Other (Monitored Natural Attenuation)

The interim groundwater cleanup levels are based on the Connecticut regulations and for the volatile organics are set for the most part at .5 ug/L.

Overburden pump and treat started in 1995 and continues. There is one bedrock well that is placed just upgradient of the source zone. The conductive heating for the overburden source zone should begin in 2012.