VIRTUAL FIELD TRIP # 8

Cote Blanche Salt Dome, North American Salt Company
St. Mary Parish, Louisiana

Lafayette & Shreveport Geological Societies - Field Trip - September 28, 2004


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This was an 'historic' event in that it is the first combined LGS-SGS field trip.

LEADER: DR. BRIAN LOCK,
DEPARTMENT OF GEOLOGY, UNIVERSITY OF LOUISIANA AT LAFAYETTE


Click for larger view.

Group photo - left to right:
Row 1 (back) Gary Hanson [SGS], Nolan Shaw [SGS], Stephanie Synsatayakul, "Skip" Forsthoff, David Williamson [SGS]
Row 2 (front) Dennis Sullivan (seated), Barry Wawak, David Benscoter [SGS],Dr. Brian Lock.


Virtual  Fieldtrip  Stops

dot  Above Ground Photos.

dot  1,500' Level.

dot  1,300' Level.

dot  Mineral Samples - Salt.


 

Barry Wawak's Summary of Cote Blanche Salt Dome Fieldtrip, St. Mary Parish, Louisiana

Tuesday, September 28, nine LGS and SGS (Shreveport Geological Society) members had the opportunity to visit the North American Salt Company Cote Blanche Mine in St. Mary Parish. We received our guidebooks (Salt Mines of South Louisiana, 2003, B.E. Lock and D. H. Kupfer, Louisiana Geological Survey, Guidebook Series #7) and headed to the mine about 8:30 A.M.

The Cote Blanche Salt Mine is located on Cote Blanche Island and is one of the 'Five Islands.' These 'islands' are elevated mounds rising 75 feet or more above the surrounding Holocene coastal marshes. The four northernmost of the islands (Cote Blanche is the most southerly occurring of these four) are roughly evenly spaced (about 7.5 miles apart), with the southernmost island (Belle Isle) located about 22 miles southeast of Cote Blanche (map). Two oil-field-associated structures occur where domes would be expected in this trend (Bayou Carlin, Bayou Sale - both of which are likely salt-related structures). The Cote Blanche Island mine is the youngest of the salt mines associated with these island-domes. The salt under Cote Blanche also extends to the south, under Vermilion Bay.

After a short drive from Lafayette, we arrived at the mine at 9:30, were briefed on safety procedures, and viewed a short film about the mine. Then we were decked out in safety helmets, self-rescuers (converts poisonous CO into less toxic CO2), lights, and steel-toed boots. We picked up our brass ID tags entered the mine.

The Cote Blanche mine produces about 18 tons of salt every two minutes. All of the salt is moved by barge to its end users. Most of the salt is used for animal feed and for winter highway maintenance in the northern states. The mine competes with twelve other American producers and several additional international producers.

The top of the salt is approximately 450 feet below the surface at the 16-foot hoist. The temperature is about 93 F at the working face of the mine. The salt is mined and processed underground. Only product ready for the end-user is lifted to the surface. At the working face, the salt is blasted using a sequenced blast of ANFO, which brings down about 1,000 tons of salt per blast. The 'muck' (blast salt) is hauled in 35 ton dump trucks to a primary crusher that reduces the salt to a size less than 8" in diameter. It is subsequently moved by conveyor to the secondary crusher where the size is further reduced to less than a 2" diameter. After passing through the secondary crusher, the salt is classified by the amount and type of impurity. Then it is stockpiled. The various stocks are blended to make products which meet various customer specifications. A final crusher mixes different grades of salt with certain additives to make the final product. This final product is hoisted to the surface in eighteen ton skips. There are three hoists at the mine. The 16-foot hoist is used for product removal and for air intake. The 14-foot hoist is used as a lift for man and materials. It also serves as an air exhaust. The 8-foot hoist is used for air exhaust and as the secondary man and materials lift.

We entered the mine via the 14-foot hoist. A two minute trip brought us from the surface to the 1,500-foot level, where the salt is currently mined. We visited a number of features on two levels, one at 1,300 feet and the other at 1,500 feet. On the 1,300-foot level we saw an area of significant brine seepage (waterfalls in salt!), an area of 'pegmatite salt' (salt crystal cleavages on the order of inches), small 'onionskins' and larger 'blowouts' (areas where salt is blown out from the main mass of salt because of the expansion of methane gas at the time of blasting). We were also impressed with the immense scale of the room-and-pillar method of mining, which leaves sheer walls of salt 50 - 60 feet high after the mining is completed. On the return to the 1,500-foot level, we encountered 'pink salt' (salt with a small amount of sylvite [KCl] - identified by the 'taste' test), and an area of oil-saturated salt. On this level we stopped at the most recently blasted face (blasted a few hours before we arrived). We saw some of the distinctly-banded salt (photo) that is characteristic of salt dome mines. We were shown specialized salt mining equipment such as the scaler, the undercutter, and the drill truck.

When we left the mine, we turned in our brass ID tags. We had lunch before returning to Lafayette.

We are happy some of our colleagues from the Shreveport Geological Society were able to join us on this trip. LGS members included Dr. Brian Lock, Dennis Sullivan, Stephanie Synsatayakul, Barry Wawak, and 'Skip' Forsthoff. SGS members included David Ray Williamson, Nolan Shaw, Jr., David Benscoter, and Gary Hanson.

The LGS thanks Dr. Lock for making arrangements to visit the mine. We also thank the mine management for allowing occasional visits by interested earth scientists. And many thanks go to our guide, Kevin, for driving us around in the mine and providing commentary.

Barry Wawak


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Location map, the Five Islands (Kupfer, 1998). Note the open circles indicating additional salt features. Also note the changes in the Atchafalaya River.
[from Brian E. Lock and Don H. Kupfer, "Salt Mines of South Louisiana," Guidebook Series # 7, copyright 2003 by The Louisiana Geological Survey.]



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Physiographic map of central coastal Louisiana, showing the Five Islands. Modified by the Federal Energy Administration (1976) from Van Lopik (1955).
[from Brian E. Lock and Don H. Kupfer, "Salt Mines of South Louisiana," Guidebook Series # 7, copyright 2003 by The Louisiana Geological Survey.]


 
This virtual fieldtrip owes a great deal to BARRY WAWAK, who took the excellent photographs, and to SKIP FORSTOFF, who was most generous with his resources.
Many thanks to BARRY WAWAK for his help with photo sequencing and captions.

LINKS

Shaded Relief Map of Louisiana
North American Salt Company, Locations
Fonville Gallery, excellent photo of room and pillar mine structure, Avery Island.
Louisiana Salt Domes.
Summary of Louisiana Geology--Generalized.
Slackpacker.com, brief description of Salt Domes.
LUCEC, brief description of Salt Domes.

 

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Web Author: Karen W. Broussard