Fracturing Emplaced Vegetable Oil Emulsionand Bioaugmentation in a Bedrock Aquifer

摘要

A former manufacturing facility in northern New Jersey is undergoingremedial activities to address historic releases from a former dry well. Groundwater in theunderlying Brunswick Shale formation had been impacted with tetrachloroethene (PCE)at concentrations ranging from 1.0 to 4.0 mg/L in the shallow bedrock over the last fiveyears. The bedrock formation has an average of 2 fractures per 10 vertical feet whichwere filled or partially filled with calcite or open, but tightly spaced. The maximumachievable liquid injection rate without significant back pressure was only 7.5 gallons perminute. A microcosm study concluded biostimulation with bioaugmentation could beused to remediate the groundwater. Terra Systems, Inc., Slow Release Substrate (SRSTM),a patented emulsified vegetable oil, was chosen over substrates requiring multiple injectionsor recirculation systems.A pilot-test consisting of three bedrock injection wells and one existing monitoringwell was implemented in the vicinity of the former dry well. Down-hole geophysicaltesting was used to identify and select fractured zones within the open boreholes for targetedinjections. Packers were used to isolate 4 to 5 fractured zones within each wellduring the injections to facilitate lateral substrate distribution. ARS Technologies’ patentedPneumatic Fracturing and Liquid Atomized Injection technology was then used todilate the targeted tightly spaced (or filled/partially filled) fractures to enhance the horizontalsubstrate distribution. Approximately 60 to 75 gallons (or 160 to 200 pounds ofemulsified vegetable oil) of dilute SRSTM Was injected into each fracture zone. Substrateinjections were immediately followed with an injection of an equal volume of atomizedchase water. Real-time data coupled with postinjection measurements confirmed an approximatea 35 foot injection radius of influence. In addition, DO and ORP reductionsinto anaerobic conditions were measured 90 feet in the downgradient groundwater andbedrock strike direction. Bioaugmentation was performed three months after SRSTM injectionusing the same injection technique.Groundwater data 60 days after the SRSTM injection indicated anaerobic groundwaterconditions favorable for reductive dehalogenation in a 30,000 square foot area around theinjection wells in the upper 40 feet of the aquifer. Shallow bedrock monitoring wells (I.e.,upper 20 feet) within the injection zone experienced a 90% or greater reduction in PCE,minimal generation of trichloroethene (TCE), cis-1,2-dichloroethene (cis-DCE) and vinylchloride (VC) and significant (I.e., 150% to 200%) increases in hydrogen concentrations.The deep wells in the same area have also seen similar groundwater chemistryimprovements.