GA003 – Pneumatic Fracturing, Chemical Oxidation
Marine Corps Logistics Base – Albany, Georgia
Figure 1: KMnO4 Mixing Area
The purpose of the project was to evaluate the performance of in situ chemical oxidation to destroy chlorinated volatile organic compounds (CVOC’s). The test was performed in an area at the Navy’s MCLB located in Albany, Georgia. The specific area contained CVOCs within the upper water bearing zone (UWBZ) of the Ocala limestone. Monitoring data from the site indicated that groundwater was impacted by TCE and DCE at levels that exceeded 10,000 ug/l. The depth to groundwater is 55 ft. bgs. During the field application, 5,225 lbs. of KMnO4 was emplaced within two (2) boreholes at the site and targeted an injection depth interval of approximately 60-80 ft. bgs.
Based on soil borings, laboratory analysis and field observations, the geology of the test area was very cohesive allowing for the boreholes to remain open for extended periods of time without collapsing.
Injection pressures varied throughout the test with most of the initiation pressures between 75 and 140 psig.
During the fracturing and injection, pressure response measurements in surrounding monitoring wells indicated that significant radial influence was achieved by the injection technique. These measurements suggested that fracture/gas propagation occurred in multiple injections and was confirmed by the presence of KMnO4 (purple color) present in the surrounding monitoring wells.
Figure 2: Well Sampling
At the completion of the project, groundwater monitoring indicated that the fracturing and atomization process distributed the permanganate horizontally within the target water bearing zone. Six months after the injection, purple color (evidence of permanganate ion) and high oxygen reduction potential (ORP) readings were observed in a monitoring well 70 ft. from the injection wells. There also was distribution vertically upward as evidenced by the presence of purple color in monitoring wells screened above the injection zone. In all monitoring wells, the TCE was reduced to non-detect levels within 1 month of injection and no rebound was observed to date.
After 12 months of groundwater monitoring, permanganate continued to be observed along with very high ORP in the surrounding monitoring wells. This data was very encouraging because it demonstrated the long-term stability of permanganate in this aquifer. TCE remained below MCL and total CVOCs did not increase.
Measurement of Cr+6 exceeding MCL (0.1 mg/l) was not detected in any of the monitoring wells. This indicated that there were no induced metal solubility issues within the pilot test area. Downgradient monitoring wells were consistent with pre-injection background levels, thereby demonstrating no inorganic plume was induced by the oxidant injections.
Figure 3: TCE Concentration Trend After Potassium Permanganate Injection