Assumption Parish Incident Command and the Office of Conservation are providing initial results of Itasca’s study on potential future ground-level subsidence in the Bayou Corne area. The findings are preliminary and conservative, pending further refinement of data from survey points to date and information to be gathered in future surveys – but are being made available to ensure that residents of the Bayou Corne community have the best and most up-to-date information that has been developed thus far.
Louisiana DOTD indicates that the subsidence projected for La. 70 in this initial study is within a range that can be managed with standard practices for road maintenance and overlay over the 30-year period modeled. However, out of an abundance of caution, DOTD continues to evaluate possible detour routes in case a need for one should arise.
The study found that normal subsidence levels are projected to be present in the area over the next 30 years. The charts summarizing the initial estimates of potential future subsidence are all based on total cumulative subsidence from the present time to different points in the future – 1.5 years, 5 years, 10 years and 30 years out – and do not distinguish between historical subsidence driven by Louisiana’s normal geologic processes and increases in expected subsidence due to the failure of the Oxy Geismar 3 cavern and subsequent development of the disturbed rock zone and sinkhole. For reference, Itasca has used available historic survey data to estimate that normal rates of subsidence in the Bayou Corne area west of the Napoleonville Salt Dome are in a range of .2 to .4 inches per year, or 2 to 4 inches every 10 years.
Follow this link for initial Itasca subsidence estimates: http://dnr.louisiana.gov/index.cfm?md=pagebuilder&tmp=home&pid=1150