There are no detectable concentrations of natural gas or chemicals and no elevated radiation in the area of a swampy sinkhole in South Louisiana, according to a recent aerial survey, the Environmental Protection Agency (EPA) told Louisiana officials. However, the sinkhole is requiring a natural gas pipeline operator to relocate facilities.
In early August the sinkhole appeared and devoured cypress trees and forced the evacuation of area residents. Facilities of Florida Gas Transmission, Enterprise Products Partners LP's Acadian Gas Pipeline LLC, Crosstex Energy LP and a gas storage facility were affected (see NGI, Aug. 13). The EPA, at the request of the Louisiana Office of Conservation and Department of Environmental Quality (DEQ), late last month deployed to the Bayou Corne area its airborne spectrophotometric environmental collection technology (ASPECT) airplane, equipped to detect natural gas, processed chemicals and radioactive sources in the atmosphere or on the surface of land or water.
"Though DEQ has maintained an ongoing program of air and water quality monitoring in the area since the initial reports of natural gas bubbling around Bayou Corne in early June, we joined with the Office of Conservation asking that the EPA deploy its state-of-the-art ASPECT plane to add an extra layer of observation and monitoring to ensure we are doing everything possible to protect public safety," said DEQ Secretary Peggy Hatch said. The ASPECT plane surveyed the area on Aug. 25, making 17 passes over the Bayou Corne area and nearby Napoleonville Salt Dome to detect and quantify any significant levels of natural gas, chemical or radiological releases to the atmosphere from the sinkhole, from other salt dome operations or from nearby land and waters.
According to the EPA, the ASPECT equipment did not detect concentrations of natural gas or other petrochemical releases anywhere in the survey area, including no chemical signatures or plumes emitted from the sinkhole. Any concentration of those substances great enough to present a hazard to public safety would have been detectable to the ASPECT survey, according to the agencies. Additionally, the survey found no indication of elevated radiation levels linked to or near cavern operations, and that all portions of the survey area were within normal radiation levels.
The ASPECT flight did pick up the diesel sheen that remains on the surface of the slurry area, likely accounting for reports from the area of a continued diesel odor, but showed no detectable emissions from the area in concentrations great enough to represent a public hazard.
"As DEQ has noted in past reports, while natural gas is bubbling from Bayou Corne, Grand Bayou and the slurry area, it is mostly composed of methane and is not toxic. The amount of methane emitted has been measured by laboratory analyses as very slight and diffuses so quickly that it is difficult to capture with visible spectra, such as the infrared technology used by the ASPECT plane," DEQ said. "Not only is natural gas not toxic, but the amount being emitted is so small that the situation could not possibly cause health concerns from air pollution."
Louisiana's Office of Conservation plans to drill an observational water well to test for concentrations of natural gas in the Mississippi River Alluvial Aquifer between the western side of a troubled salt dome and the Bayou Corne Community in the southern part of the state.
The sinkhole continues to cause concern for pipeline operators in the area.
Crosstex Energy previously took a section of its 36-inch diameter gas pipeline located near the sinkhole out of service. Service to certain markets, primarily in the Mississippi River area, has been curtailed or interrupted, and the partnership has worked with its customers to secure alternative gas supplies. Crosstex said recently the impact of the sinkhole is costing it about $250-300,000 per month while the pipeline is out of service. The company said it will relocate the portion of the pipeline affected and certain services will not resume until the relocation has been completed. It is evaluating potential rerouting alternatives, timing and expected costs.
"Based on the current alternatives being considered, the partnership estimates the cost of the relocation to be $20-25 million and expects to complete the relocation by summer 2013," it said. "The partnership is assessing the potential for recovering its losses from responsible parties and insurance coverage. The partnership plans to write off its investment in the section of the impacted existing pipeline and capitalize the costs of the replacement pipeline. The write-off is a non-cash impairment charge and estimated to be less than $0.5 million."
Crosstex also owns and operates the Napoleonville storage facility, which is located off Highway 70 in the Bayou Corne area near the sinkhole. The facility consists of two salt dome natural gas liquids storage caverns. Crosstex said it is currently storing approximately 900,000 bbl of normal butane in the facilities for third parties. "The partnership's management does not believe that the storage facilities have been affected by the slurry," the company said. The DEQ said in mid-August the cavern was not threatened by the sinkhole.
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