RESULTS OF SOIL GAS AND GROUNDWATER MONITORING AT A CARBON SEQUESTRATION TEST SITE, BLACK WARRIOR BASIN, ALABAMA
At the Deerlick Creek control site, soil gas samples were collected at each monitoring location at four depths from 21 stations. The carbon isotopic ratios of the soil CO2 suggest a bacterial source and that bacterial activity intensifies downward in the soil profile. Wetter gas in the soil profile than in the adjacent well indicates these gases are locally derived.
Soil flux was monitored for 10 months at the control site; at the injection site, soil CO2 flux was monitored for 17 months. Soil flux was highly variable among stations and over time. A seasonal pattern was identified with highest flux during summer and lowest flux during winter. No change in soil CO2 flux was observed during or after injection.
The shallow groundwater aquifer, used by some local residents for drinking water, was sampled monthly from February through January 2011. Samples were analyzed for organic and common inorganic nonmetal and metal constituents. Results indicate no change in groundwater quality.
It is important to document the baseline groundwater quality, soil gas composition and CO2 flux ranges for comparison to any sampling during or post-injection. Continued monitoring of groundwater, soil gas and CO2 flux can augment other monitoring activities, helping confirm containment of the gas. Changes in flux rate, soil gas, or groundwater quality could indicate the need for further investigations. Additionally, soil gas composition can also help determine the origin of the gases and the potential for leakage.