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BY DAVID J. MITCHELL
River Parishes bureau
April 28, 2013
Texas Brine Co. is building a westward extension of a 1.5-mile containment berm encircling the Assumption Parish sinkhole because a 200-foot stretch of the earthen wall is sinking, authorities said Friday.
John Boudreaux, director of the parish Office of Homeland Security and Emergency Preparedness, said Texas Brine contractors began work on the berm expansion Friday. The V-shaped “reroute” is shown on a company map jutting out from the western part of the berm.
Before the latest developments, Texas Brine officials had said the berm, which is being designed to last at least 20 years, is due for completion by July 1.
Conservation officials have said the berm was designed to hold the sinkhole even at the worst-case size predicted by scientists, about 1,400 feet in diameter. The sinkhole now measures about 1,000 feet across.
Sonny Cranch, spokesman for Texas Brine, said Friday that because of the subsidence, the company is playing it safe and building the new berm.
In addition to the sinkhole, the shift in earth left behind a zone of fractured rock running up outside the cavern and alongside the Napoleonville Dome, scientists have said.
Hecox said that sands from the Mississippi River Alluvial Aquifer, which runs in a band about 120 feet to as much as 600 feet deep, are flowing down into the zone of broken rock under the sinkhole.
Also, the sinkhole’s volume has more than doubled since it was calculated in October, rising from 550,000 cubic yards to 1.2 million cubic yards, Hecox said then.
“The material is flowing out of the bottom (of the sinkhole) down the disturbed rock zone,” Hecox said.
“The material is flowing out of the bottom (of the sinkhole) down the disturbed rock zone,” Hecox said.
Originally posted by qmantoo
Snip
last measured in 1989 and there are quite a few salt domes down there all technically connected (by an area of salt?) I seem to remember.
Snip
Originally posted by jadedANDcynical
reply to post by Honor93
This image shows the dimensions of the salt dome:
Source
If you zoom in, you will see a few of the seismic monitors (the blue triangles) that have been installed to monitor ground motion.
The dashed red line shows the approximate upper edge of the dome. We've learned that the area with the collapsed cavern is had an overhang, creating a false idea of the thickness of the wall.
2 - If you go back through this thread you will see that some of the early admissions by Texas Brine and some government agencies showed that a test bore that was too close to the edge of the salt dome allowed a blowout of the side of the #3 cavern. This allowed the sinkhole to form just off to the side of the salt dome. Then material in the form of land and vegetation started sinking into the cavern that was breached. The original depth of the cavern was a couple of thousand feet, but as material started filling it through the sinkhole it became shallower until the bottom was only a few hundred feet deep. One of the graphics showed that the salt dome was somewhat mushroom shaped. The graphic showed that the actual wall thickness below the "mushroom cap" was less than what was allowed. But when the well that was used to form the cavern was drilled they didn't know about the "mushroom" shape of the salt dome and were taking their wall thickness readings from the "apparent" full size of the dome, not the actual thickness at the depth of the cavern.edit on 30-4-2013 by happykat39 because: (no reason given)
The Louisiana House backed two bills Thursday (May 2) aimed at tightening restrictions around the state's salt domes and solution-mined caverns used to store hydrocarbons or hewn for salt in brine production.
House Bills 493 and 494 by Rep. Karen Gaudet St. Germain, D-Pierre Part, were written in response to a 13-acre sinkhole that first appeared in the swamplands of Assumption Parish last August.
The bills would control the drilling, operations and plugging of the brine and storage caverns that have been drilled into the state's salt domes.
May 02, 2013 - UNITED STATES - According to Gary Hecox, the CB&I hydrogeologist, the seismic array has been updated at the giant Louisiana sinkhole. "The initial seismic data, what we’re finding — the locations of all the micro-earthquakes have been recorded — as you can expect, most of the micro-earthquakes have been located around the Oxy 3 cavern and in the salt. We do have some minor earthquakes out away from that in the vicinity of the other caverns."
Hecox made these revelations at a public briefing on the sinkhole on Wednesday, May 1st, at the Assumption Parish Community Centre.
Expert: Unfortunately what we warned about appears to be happening — Methane from deep below giant sinkhole is now surfacing in community
Gary Hecox, CB&I hydrogeologist: The thermogenic gas from depth has moved upward and has displaced the shallow swamp gas.
So what we talked to you about last November as one of the concerns we had was the deep gas in the MRAA [Mississippi River Alluvial Aquifer] coming up and displacing the shallow gas […]
So unfortunately what we told you several months ago that may be happening in terms of the deep gas displacing the shallow swamp gas appears to be occurring. […]
At least some of the methane in the community that is being detected has moved its way up from depth and is now coming up in the shallow part of the system […]
Now we know at least one of the bubble sites has a direct connection to gas coming up through the disturbed rock zone into the aquifer and is coming up through the other bubble sites.
Now we know at least one of the bubble sites has a direct connection to gas coming up through the disturbed rock zone into the aquifer and is coming up through the other bubble sites.
Is there any data on the amount this thing is rising or falling because it might give us some information about which areas are going to collapse or which areas have more stresses?
The Office of Conservation, in consultation with Assumption Parish Incident Command, is advising the public that the Oxy 3/sinkhole monitoring alert status has been raised to Code 2 – requiring all work directly on the sinkhole to cease until further notice. Seismic monitoring has detected an increasing trend of micro-earthquake (MEQ) activity in the area around the sinkhole and Oxy 3 over the past few days.
Such activity has previously been noted as a likely indication of shifting and sloughing in the sinkhole and the area below it. The seismic activity is limited to the Oxy 3/sinkhole area, showing no indication of impact to the Oxy 1 area. Monitoring is constantly ongoing in the area and Conservation will advise the public of significant changes in subsurface conditions.
Q, there is one dome down there beneath a good part of the western edge of the city and outskirts, in which there are multiple caverns.