Archived: FAQ About the Bayou Corne Sinkhole Incident

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Categorized | State News

Frequently Asked Questions About Bayou Corne Sinkhole Incident

Posted on 23 August 2012.

The following questions represent the most frequently asked questions and issued submitted to AskGOHSEP ‘at’ la.gov about the Bayou Corne sinkhole incident. This document was compiled using information from the responding local and state agencies.

SINKHOLE

 

Has the bubbling gas been compared with the gas from brine mining caverns adjacent to the one considered breached?

Yes, isotopic analysis of gas samples collected in the area is being conducted to match the gas back to operations occurring in the Bayou. The kind of testing takes several weeks and results are not yet available.

Are measurements being taken? How big is the sinkhole?

Yes, the sinkhole is being monitored regularly. As expected, the surface of the sinkhole that has formed in Bayou Corne has grown over the past few days as the land on the outer edge of the area is sloughing off into the sinkhole. This natural growth of the sinkhole was expected and could continue.

Last week, the sinkhole was 476 feet (from the northeast to the southwest) by 640 feet (from the northwest to the southeast). State and local officials monitoring the situation will continue with regular overflights throughout the duration of the incident.

Is the elevation of the land between highway 70 and the sinkhole being measure to see if there is any change in the land and how fast the change is taken place?

Yes, the size of the sinkhole is being monitored regularly.

Will the sinkhole continue to grow?

Yes, experts expect that the sinkhole will continue to grow. It is still smaller than the maximum size scientists predict it could grow to. Even at that maximum size, it is not to expect homes, which are about a half a mile from the site where the incident is occurring.

BRINE CAVERN / SALT DOME INTEGRITY

Who is responsible for testing and monitoring the salt dome in its entirety? What is being done?

Ensuring the stability of the salt dome and the surface support and studying any potential events that could impact that stability are top concerns for the state’s emergency response effort in the area, and the subject of ongoing monitoring and study by our partners with the U.S. Geological Survey and other member organizations in the science team that has been organized to assist in the response to this ongoing event.

At the same time, staff with DNR/Office of Conservation are reviewing operations records of sites within the dome and maintaining communications with operators as they closely monitor the pressures and other aspects involved in their operations in the salt dome. In addition the operators in the salt dome area have been ordered by DNR/Office of Conservation to take all necessary precautions actions to prevent any threats to human safety or the environment.

RELIEF WELL:

Is the well being drilled really a relief well?

The name “relief well” has been used because it is a term that is often used to get across the concept of drilling a new well to deal with an potential problem in an existing well. A more accurate description would be “investigatory well.”

Why is a new well going to be drilled? What will it do?

The primary initial purpose of the well is to gain direct access to the interior of the abandoned brine cavern so that equipment can be sent down the wellbore to determine the stability, internal pressure and contents of the cavern. The top of the cavern lies about 3,400 feet below the surface, leaving no option but a new well to realistically have any chance to determine the exact condition of the cavern.

Conditions in the cavern may be such that action such as venting natural gas are a part of the plan to deal with the cause of the sinkhole and natural gas bubbling in the area, and the new well would be a critical part of any such plan.

Is the erosion of the salt cavern being monitored?

Ongoing monitoring of cavern pressures and integrity was conducted during the productive period of the cavern’s operations prior to its having been plugged and abandoned, which indicated that the cavern was structurally sound. Part of the purpose of the investigatory well currently being drilled is to determine the current status of the cavern and its contents.

If you relieve pressure on the carven then will the bubbles stop and reverse the other way and drain Bayou Corne?

Generally speaking, surface water under the pressure of simple gravity does not move as easily between underground formations as deep natural gas under the influence of geologic pressure does. However, the scientific team gathered in response to the ongoing situation will be consulted on what surface effects could be

expected from the reduction of any areas of underground pressure if they are found in the ongoing study of the event and its causes.

Once the process for the drilling begins in Bayou Corne for the relief well, will the parish enforce a forced evacuation and/or road closure?

The mandatory evacuation remains in place, but it has not yet been a forced one. Should conditions warrant a forced evacuation, the parish will notify those residents living in the area. Right now, a road closure is not in place, but officials from the Department of Transportation and Development continues to monitor the roads in the area and, at this time, has no concerns related to the integrity of its state roads, specifically La. 70 in Assumption parish. DOTD would like to remind motorists to practice caution while driving on La. 70 in Assumption Parish, as there may be heavy truck traffic entering and exiting the roadway.

BUTANE STORAGE CAVERN

How far from the Texas Brine storage cavern is the underground butane storage cavern operated by Crosstex? How much butane is contained in the cavern?

Crosstex operates storage cavern that contains 940,000 barrels of butane, which is located 1,600 feet from the sinkhole.

What is the company and the state doing to monitor this cavern while the drilling happens?

Crosstex is continuing operations and is continuously monitoring the well pressures, conducting mechanical integrity checks for all piping, performing hourly visual checks at each well and manning its facility 24 hours a day, seven days a week.

The company is already under an emergency order issued by the Department of Natural Resources on August 3, which directs it and other operators to take all necessary steps to protect their operations against damage due to the subsidence event in the Grand Bayou/Bayou Corne area. DNR has also required daily reports from Crosstex and continues to review seismic reports in the area of the Crosstex cavern that are being collected by USGS. These reports are also being sent to a science advisory group who are working closely with DNR to verify and monitor Crosstex’s efforts.

What would the impact area be if one or more of the caverns storing LPG and Natural Gas near the Texas Brine Cavern #180708 were to explode?

After reviewing an updated plan from Crosstex, the state believes that the cavern poses little-to-no threat to the population living in Grand Bayou/Bayou Corne area. Last week, at DEQ’s request, Crosstex Energy Services re-evaluated their worst case scenario analysis. Their initial analysis was based on the concept of a failure of the pipeline at the surface. Based on that analysis, the impact radius calculated was broken windows at 0.3 miles. It was noted that the quantity of butane was doubled for this calculation in order to be more protective of human health. At the state’s request, Crosstex modified their worst-case scenario to consider that their butane-filled cavern was akin to an underground storage tank and calculations should be based on any failure of that system.

An important factor to understand is that the butane in this cavern is stored more than a half-mile below ground surface. At this depth and pressure, the butane is a liquid. The only way to get it to the surface is to pump salt

water, which is heavier than butane, into the cavern in order to displace the butane to the surface. A failure of the cavern or piping would not cause this material to free-flow upward to the surface.

Concerns have been expressed regarding the possibility of the sink hole somehow expanding into the cavern holding the butane. It should be noted that the cavern containing the butane liquid is more than a half-mile underground and deep in the stable salt dome. The sink hole, at the deepest depth known to this point, is several hundred feet.

While it is easy to simply convert the known quantity of butane into a blast scenario, that does not mean this scenario is possible. A blast scenario of the liquid butane stored at the pressure and depth at which it is stored in the absence of oxygen is not possible. If the piping failed, some vapors could come to the top of the well head. If there was an ignition source, there could be slow burn at the wellhead. Lacking pressure or some other driving force to push it rapidly to the surface, it would not be expected to create a violent reaction such as an explosion. If the salt dome were to fracture and cause the casing for the storage of the liquid butane to crack, the liquid butane would flow into the cracks of the salt dome and not come to the surface.

How far will we be impacted if the butane cavern explodes does Napoleonville have anything to worry about or will feel anything or should we evacuate?

The state has reviewed the worst case scenario analysis on the butane cavern done by Crosstex, the company that operates the cavern, and both the departments of Environmental Quality and Natural Resources agree with Crosstex’s calculations that the cavern poses little-to-no threat to the population near where a slurry hole appeared in early August.

Last week, at DEQ’s request, Crosstex Energy Services re-evaluated their worst case scenario analysis. Their initial analysis was based on the concept of a failure of the pipeline at the surface. Based on that analysis, the impact radius calculated was broken windows at 0.3 miles. To see Crosstex’s letter explaining the calculations and the worst case scenario, go to http://www.deq.louisiana.gov.

Will this butane cavern be vacated during the drilling process. If not, why not?

Out of an abundance of caution, Crosstex is moving butane to another cavern 1,000 feet away from the original cavern. The departments of Environmental Quality and Natural Resources have reviewed Crosstex Entergy Services’ updated risk management plan for its storage cavern in Assumption Parish. Both agencies agree with Crosstex’s calculations that the cavern poses little-to-no threat to the population near where a slurry hole appeared in early August.

PUBLIC UTILITIES AND INFRASTRUCTURE

I am concerned about the public utilities which pass thru the area of Bayou Corne/Grand Bayou. Is an alternate plan in the works for rerouting at this time if necessary?

All utility companies that provide services to this area (Grand Bayou/Bayou Corne) have been contacted and all service companies have plans in place should a disruption of any service take place due to the operations currently taking place in Bayou Corne.

At this time, no such disruption is anticipated; however, plans have been developed and local service utility representatives are kept abreast of daily operations of the site.

What kind of monitoring is being done to make sure the roads are safe to drive on?

The Department of Transportation and Development continues to monitor the roads in the area and, at this time, has no concerns related to the integrity of its state roads, specifically La. 70 in Assumption parish. DOTD would like to remind motorists to practice caution while driving on La. 70 in Assumption Parish, as there may be heavy truck traffic entering and exiting the roadway.

Out of an abundance of caution, DOTD engineers are continuously monitoring the state road system in this area — 24 hours a day with roving patrols and frequent surveys. If conditions change, DOTD crews are prepared to close roads immediately to ensure public safety and will announce appropriate detours. DOTD engineers are measuring elevation levels weekly using GPS technology at four locations along La. 70 – one on Highway 70 perpendicular to the site, and at the Bayou Choupique, Grand Bayou and Bayou Corne bridges. So far, no changes in elevation have been found at these locations.

Has DOTD put together a plan to reroute La. 70 if it would be closed? What is the plan for where the detour would occur?

DOTD, at this time, has no concerns related to the integrity of its state roads, specifically La. 70 in Assumption Parish. However, out of an abundance of caution, DOTD engineers are continuously monitoring the state road system in this area — 24 hours a day with roving patrols and frequent surveys. If conditions change, DOTD crews are prepared to close the roads immediately to ensure public safety and will announce appropriate detours. The Department of Transportation and Development is monitoring LA 70 from the Bayou Corne Bridge east to LA 996. The Department is also monitoring a one-half mile stretch of LA 69 from its intersection with LA 70. In the event conditions develop that would make the road network unusable or unsafe, we have planned the detour to be as follow:

♦ Traffic traveling to Pierre Part and points south: Will be directed to LA 1 south to la 398 west, to LA 662 west, to Hwy 90 west to LA 70.

♦ Traffic traveling from Pierre Part and points south: Will be directed to US 90 east to LA 662 east, to LA 398 east, to LA 1 north to LA 70.

♦ Local traffic (passenger vehicles and trucks below the posting of the bayou pigeon bridge (15/25)) will be able to take LA 997 to LA 75 to LA 404 to LA 69.

If the order is given to close the road our crews will install trailblazing signs to notify drivers of the detour. We will also install Variable Message Signs (VMS) at LA 70 at LA 1 and LA 70 at LA 69. We will notify District 03 and they will install a VMS on LA 70 just north of Morgan City.

SCENARIOS

I’m hearing a lot of conflicting information such as the risk of catastrophic explosions, excessive radiation and other alarming scenarios. How do I know what to believe?

The situation is being monitored around the clock by involved state agencies and, so far, extensive testing by the state Department of Environmental Quality has shown no harmful environmental releases. All of DEQ’s data was reviewed by the state Department of Health and Hospitals, which certified in multiple letters to Assumption parish that no public health threats have been present so far.

The agencies participating in monitoring for harmful conditions must meet state and federal laws and regulations to make sure the testing results are of high quality. Official state samples have to meet rigorous checks and balances before they can become official, validated results that the scientists and others studying this incident can use as clues to solve the problem. A team of qualified scientists from state and federal agencies, academia and private industry are working together to make sure that sound science is being used to monitor this situation and to determine if the public is safe.

There are many factors that play a role in collecting the proper water, air and/or soil sample.

All state samples have to have the proper chain of custody and have to meet quality assurance and quality control requirements. To increase transparency, state agencies are publishing their results online. If you want to view the validated samples, are available to the public through a variety of different Websites, including deq.louisiana.gov.

Is it true that wells are releasing gas that isn’t visible to the eye, but shows up on an infrared camera?

The Department of Environmental Quality used its infrared camera in July to assist the Department of Natural Resources to check abandoned wells for possible releases of gasses, which are not visible to the human eye. While in the process of checking the wells, DEQ scientists also used the infrared camera to visually observe the bubbles in Bayou Corne.

There were no gasses visible through the camera coming from the bubbles because any gas that was being emitted was at such low levels it could not be seen. However, we do know there is an industrial supply well on private property that was venting natural gas and that the slurry hole was also venting natural gas.

Isotopic samples, which are highly specialized, were taken at the venting well and the bubbles in the water in an effort to identify that gas to see if it was coming natural or industrial sources. And, if the gas is industrial, this isotopic analysis may help us try to pinpoint the source.

The DEQ also has sampled more than 95 homes looking for flammability as well as a variety of pollutants. None of the samples at any of the private properties have shown any sources of concern. The bubbles in the bayou were also tested for these same parameters. Low levels of methane were detected coming from the bubbling area. However, explosive levels of methane are in the 10,000 parts per million range and the levels DEQ detected were less than 1,000 ppm.

Daily, DEQ scientists conduct at least two air-monitoring runs in the nearby community. This person is conducting roving monitoring with a handheld monitor. If this person smells something, or picks up a hit on the monitor, then a canister is taken for further analysis. Odors and hits on the monitoring equipment do not mean there are pollutants at a level of concern. However, either one may mean additional sampling is needed. Out of

an abundance of caution, DEQ personnel are instructed to take the canister sample. While odors have been detected, there have been no health risk levels of any pollutant. That does not mean the odors will not bother someone. People handle odors differently. Scientifically, it means the pollution levels are below health risk values.

The DEQ Mobile Air Monitoring Laboratory pulls two air canister samples daily between the slurry hole and the community. All samples have been below health risk values.

Is it true that there is excessive radiation coming out of the slurry hole?

Rumors of radiation were addressed when the Department of Environmental Quality went to the slurry hole and used handheld monitors to take continuous readings for naturally occurring radioactive material. Scientists also took water and slurry samples. All surface sampling for NORM came back at background levels.

NORM only poses a risk when it is ingested or inhaled at increased levels over an extended period of time. DEQ scientists did not see NORM as a health risk because the levels were background and there was no identifiable exposure pathway.

I’ve heard the water is incredibly polluted. Is that true?

Water samples in the slurry hole did show high salinity (salt) and elevated levels of pollutants related to diesel. These would pose a health risk if ingested – but only if someone went to the slurry hole and drank the water. However, they do not pose a health risk for the nearby community.

Can you tell me if it is likely that the butane cavern will explode?

The state required a nearby facility, Crosstex, which stores liquid butane, to provide an updated worst-case scenario to the DEQ. This information was studied by DEQ, DNR and others before being made public for everyone’s review. It was deemed that the liquid butane posed no threat at its current location and under the vapor pressure it was being stored. However, Crosstex has said it will move the liquid butane to another storage area further away to allay residents’ fears.

LONG TERM IMPACTS

What kind of ecological impact can we expect if this cavern has collapsed as we feared? Will we be able to contain a hole that is 400 feet deep? Can we expect dead vegetation, dead trees, fish kills, etc?

Natural gas is not toxic, so fish kills or dying trees are not expected. There are Diesel-like fluids in the slurry pool, which has affected some of the smaller vegetation. That impact is very localized to the slurry pool and the Diesel is being contained in the slurry area by oil booms. DEQ scientists have looked for salt water associated with the bubbling in the bayou and not found any. The slurry pool water is slightly elevated salinity (1 part per thousand) but not enough to kill trees or fish. There have been no observed fish kills. All DEQ data is posted online at deq.louisiana.gov.

PUBLIC INFORMATION / MEETINGS

Who is representing Assumption parish residents at the Unified Command Group meetings?

The parish is well represented by the Police Jury President, the Sheriff and the director of the parish Office of Emergency Preparedness. Unified Command Group meetings are conducted to detail future planning and coordinating tasks and responsibilities for the operational period. The attendees are state agencies and local officials with technical responsibilities in controlling the situation.

What is the best Website to find upcoming meeting information?

The parish has been posting updates on its blog, assumptionla.wordpress.com and also online at http://www.assumptionla.com/bayoucorne. Texas Brine is also posting information online: http://www.texasbrine.com/response/

In addition, there are other resources available online from state agencies:

GOHSEP:

http://www.gohsep.la.gov/

Assumption parish:

http://assumptionla.com/bayoucorne

Department of Natural Resources:

http://dnr.louisiana.gov/index.cfm?md=pagebuilder&tmp=home&pid=939&pnid=0&nid=172

Department of Environmental Quality:

http://www.deq.louisiana.gov/portal/bayoucorne.aspx

What is being done to educate people about risks that may be associated with this type of work?

State and local officials involved in the response to this incident have been making regular statements to the public via the press and are sharing a significant amount of information online. In addition, the parish is sharing information about the incident with those most directly affected by using its emergency alert text messaging system.

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