Review of information gathered in the CPT/MIHPT with through spring and summer to identify gas extent and gathering points in the subsurface in and around the Bayou Corne/Grand Bayou area has revealed an opportunity to provide a barrier to gas migration to surface and reduce the near-term potential for gas concentration below slabs or within home and other structures in the community. That opportunity has led to development of a three-tiered approach to accelerate the effort to cut off the flow of gas below the community – one that could provide observable results within weeks instead of years.
The three-tier effort – simultaneously attacking gas above the aquifer, within the aquifer and below the aquifer – to be carried out by Texas Brine under the oversight and guidance of Assumption Parish Incident Command the state Department of Natural Resources, and the Blue Ribbon Commission, will include intercepting gas in the shallow soil and sands presenting the closest threat to the community, improving the efficiency of vent wells to remove gas from the aquifer, and evaluating potential deeper source(s) of the gas in the area to identify appropriate response actions.
A key component of the new phase of the response will be the use of Dual Phase Vacuum Extraction (DPVE) pumps to intercept gas in the shallow subsurface between the surface and the gas built up in the aquifer. DPVE draws both liquid and gas from the subsurface, which provides the potential to overcome what has been a significant hurdle in removing gas from water-heavy Bayou Corne/Grand Bayou area. The intent is to use the DPVE approach to stop the flow of gas to surface and remove the potential for gas gathering below slabs or within homes or other structures in the community.
DPVE is a proven technology for remediation of gas in shallow soils, and data from CPT and MIHPT probes has provided information needed to accurately target gas pathways and gathering points. The DPVE has already been successfully tested on the Texas Brine facility near they Oxy Geismar 2 well pad, where two established bubble sites ceased bubbling shortly after pumping began.
The shallow DPVE approach is intended to serve as an interim measure to provide for public safety, even as work continues implementing a similar gas/liquid removal approach for existing and future vent wells into the aquifer.
At the same time, work is ongoing to further identify the deeper source of gas that originally charged the aquifer, drawing upon 3D seismic information and the expertise of the Science Work Group and Blue Ribbon Commission, and determine to what degree gas is still flowing and potential for intercepting it.
Initial steps in implementing the shallow DPVE portion of the overall strategy will be discussed with the public at the Assumption Parish OEP Bayou Corne/Grand Bayou Command Center tomorrow night.