In-Well Stripping Installation at the Colorado Avenue Site

Setting

• Hastings, Nebraska
• Four wells in two full-scale installations. One 1-well system and one 3-well system.
• TCE and other chlorinated hydrocarbon contamination in one unconfined aquifer
  

Hydrogeology

• Hydraulic conductivity: 252 ft/day
• Plume thickness: 60 ft
• Depth to groundwater: 115 ft
  

Contamination

• TCE, PCE, DCE, TCA, cis-1,2-DCE, and 1,2-DCA
• TCE concentrations entering treatment zones of the wells as high as 500 mg/L.
  

Inorganic Chemistry

• Groundwater is in equilibrium with calcite, indicating potential for calcite scale formation.

Operation Details

• One 20 hp positive displacement pressure blower (one-well system) and one 60-hp positive displacement pressure blower (three-well system)
• Closed-loop systems. Carbon treatment of air before return to wells.
• Two piezometers for each well and two monitoring wells to measure performance.
• Pumping rates: 91 to 147 gpm. Total 21 million gallons per month. Air/water ratios: 20.5:1 to 12.7:1.
• System operation: In service since October 2002 with routine inspection and maintenance of the mechanical systems. Three-well system operated over 2,600 hours non-stop on initial startup. Scheduled re-development of wells performed after four months of operation; no calcite fouling.