Seismic Search for Oil and Gas Impacts Bay and Wildlife Refuge

More than 8,000 explosive charges are being set throughout the southern end of the Lower Laguna Madre, and 14,000 plus are scheduled for detonation on nearby refuge property and private land. The charges are part of an extensive 3D seismic survey for oil and gas covering 238 square miles of Cameron County or some 152,000 acres. The first blasts are scheduled in approximately a week.

"You can expect to see a fish kill," said Winston Denton, regional biologist with Texas Parks and Wildlife, TPW, Coastal Fisheries. "The magnitude of the fish kill is highly variable. Any time there are seismic surveys there are usually some type of fish kill. It is just the magnitude that varies."

According to TPW records a July, 1999 seismic survey in East Matagorda Bay and Matagorda Bay killed an estimated 444,742 fish resulting in a restitution assessment of $74,141.70. A 2006 seismic survey in Trinity and Galveston Bay killed an estimated 14,080 fish and resulted in a fine of $5,474.46.

The current Lower Laguna Madre survey began after Christmas and is scheduled to be completed by May. PGS Onshore of Houston is conducting the seismic work, and environmental monitoring is under the supervision of Blanton and Associates, Inc. of Austin.

"Any exploration of state submerged land requires a permit from the General Land Office," said Jim Suydam, press secretary for the General Land Office or GLO. The survey company has paid the state $299,495 to access 59,899 acres of the Lower Laguna Madre according to Suydam.

"They are drilling holes for a 3D seismic survey." said Rick Hanson, Wildlife Biologist with the United State Fish and Wildlife Service, USFWS. Hanson, a Gas and Oil Specialist, watched as a 80 foot deep hole bored into federal land near Boca Chica Beach. "They are drilling across about 40,000 acres of Lower Rio Grande Valley National Wildlife Refuge."

The USFWS, does not own the mineral rights on the Boca Chica tract or nearby lands being surveyed and consequently the lands are available for exploration and drilling. However, companies are required to follow specific guidelines including having environmental monitors on site.

The USFWS owns approximately 180,000 acres in the Rio Grande Valley, and about half of that includes mineral rights. The majority of the mineral rights are on Santa Ana and Laguna Atascosa Wildlife Refuges, which were the first properties acquired more than 50 years ago. There are 65 producing oil and gas wells on various tracts owned by Fish and Wildlife primarily on land in the upper Valley.

There are no active oil or gas wells in the Lower Laguna Madre, but in past years there have been more than two dozen producing gas wells. According to the GLO, the last gas well was shut down in 2001.

Exploration for new petroleum deposits in the bay is being done by a flotilla of 27 boats, twenty four of which are airboats. Each morning, weather permitting, they head out from the beach on the bayside north of the town of South Padre Island. The airboats are being used to comply with TPW recommendations to protect shallow sea grass beds from prop damage that could occur with conventional boats.

However, the airboats are very loud and because of complaints from residents, noise reduction tactics have been adopted. "When they are within a quarter mile of the Island they will only idle," said Michael Green a project manager with Blanton and Associates, as he watched several of the workboats slowly move out into a channel east of the Franke development.

A dozen of the airboats are equipped with drills that bore into the sediment 8 0 feet, and then a charge is placed in the hole. When the job is finished, a tall bamboo pole and white float mark the spot. There are virtual picket lines of cane poles and buoys every 220 feet or so stretching across much of the bay between the Arroyo Colorado and the entrance to South Bay. There is no seismic survey work being done in South Bay or north of the Arroyo.

A similar technique is used on land, but instead of airboats marsh buggies with huge tires access coastal property for drilling and placement of charges. On a good day a three man crew can drill and set some 20 charges.

"There is no way there can be no impact, but we want them to create as little impact as possible," said Hanson. "Mainly they try and use existing roads and existing open areas. We are allowing them to do a minimal amount of hand trimming in the brush, but no mechanical clearing whatsoever." Access to the thickly wooded brushy lomas or hills is forbidden.

Each of the 14,020 holes on land and 8,871 holes in the bay will be packed with five and a half pounds of geo prime charge similar to dynamite. The detonations are not expected to do any surface damage or cause serious environmental harm. "We have done a lot of projects like this involving seismic work, and it can be done with minimal environmental impact," said Don Blanton, president of Blanton and Associates.

Seismic surveys involve measuring the time it takes sound to travel form a source such as an earthquake or man made explosion. The shock waves, or seismic waves, reflect off the various sub-surface strata in different ways and enable geologists to create computer images of the area to detect where petroleum deposits may be found.

"We feel like the impacts are less if they use two to two and a half pounds so that is what we recommend, Denton said. "But, they can use more if they get a variance from the GLO. The average shoot we see now uses five and a half pounds. They get a better picture and more precise information."

The blasts are designed to explode downward, and only a small percentage creates a blowout. "There is always a chance, but we do not anticipate a problem," said Blanton. "That is one reason we are out there. The GLO requires that we be on site to document any fish kills. It has not been a problem on projects we have monitored." Also, before charges are exploded for recording crews to monitor, work boats nosily circle each site to scare fish away from the imminent blast.

Bill Balboa, Matagorda Bay Ecosystem Leader for TPW, has monitored several seismic operations in his area. "The majority of fish were silversides and mullet, croaker and a few black drum and a few game fish, spotted sea trout and red drum."

Balboa said that if you are on the water you will hear a loud thump or clap when the charge is detonated. "When they were shooting near my home on the bay it was a very distinct whack, and sometimes it actually rattled things." The nearest blasts were some 750 feet from his house.

A similar survey was conducted several yeas ago north of Port Mansfield between the town and the Land Cut, and no serious fish kill was documented. There was also a seismic survey in South Bay some 17 years ago, and no extensive fish kill was noted. If a fish kill occurs, as has resulted in other bay systems, restitution fees would be assessed by TPW for restocking.

Recording crews are expected to begin arriving this week and initial blasts could begin soon. Required notification of imminent detonation will be transmitted to state agencies. While recreational anglers may not be aware of actual blast times, no danger to wade fishermen or boaters is anticipated. "They are not remotely set," Blanton explained. "There will be people right next to them. Typically the recorders are positioned right by where the charges are set."

At least three more months of noisy airboats, drilling and detonations will prevail throughout the southern end of the Lower Laguna Madre and on refuge property. However, if oil and gas deposits are located, then even more activity can be anticipated.


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Copyright 2007 Richard Moore