SAME ECOI Webinar: Controlled Hydraulic Fracturing for Delivery of mZVI in Low Permeability Settings
Zero-valent iron (ZVI) is a proven amendment for in-situ chemical reduction of chlorinated solvents, and hydraulic fracturing is particularly well-suited for delivering high mass loadings of microscale ZVI (mZVI) into low-permeability and heterogeneous formations.
This webinar presents two full-scale case studies where ZVI-filled fractures facilitated treatment of target compounds for at least ten years. At a site in Denmark, a source zone treatment was implemented to address TCE impacts in soil and groundwater using hydraulic fracturing to deliver mZVI into glacial clay till. After six years, the total contaminant mass in soil decreased by approximately 85%, and mass discharge of TCE in groundwater downgradient of the treatment zone decreased by more than 98%.
More recently, 10-year post-injection groundwater sampling showed further reductions in mass flux through the treatment zone and continued production of the complete degradation products ethene and ethane within and downgradient of the treatment zone. At a second site, located in South Carolina, a 17-acre TCE plume was treated using linear arrays of injection locations to create injected PRBs with fractures spanning three geologic units: saprolite, weathered bedrock, and fractured crystalline bedrock. ORP measurements in groundwater showed persistent reducing conditions immediately downgradient of the treatment zone over the five years these data were collected. After ten years of persistent treatment, TCE concentrations in offsite wells decreased by 98% from an average of 5,300 ug/L to 90 ug/L, and the areal extent of the 100 ug/L plume decreased from 11 acres at baseline to 0.9 acres.
