Archaeology of the La Salle Shipwreck Project
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Between June 4, 1995 and July 31, 1995 the Texas Historical Commission (THC) undertook a major marine magnetometer survey in Matagorda Bay, along the central Texas coast. The purpose of the project was to record any possible shipwrecks or other archaeological maritime sites. This survey identified 39 anomalies that were considered significant enough for further investigation by divers.
After locating the most promising site, divers were put in the water to investigate the cause of the anomaly. Divers began recovering cast lead shot and wooden remains, suggesting a historic shipwreck. The site began to look particularly significant when divers discovered a brass buckle.
This buckle suggested to archaeologists a date prior to the 19th century. Shortly after this discovery, divers located another much larger object, an 800-pound bronze cannon with ornate decorations. This find along with historic Spanish and French documents strongly suggested the discovery of a very important historic shipwreck in Matagorda Bay, la Belle, lost in 1686.
After locating la Belle, archaeologists at the Texas Historical Commission had to decide the best method to systematically excavate the site while giving the remains the best possible protection. Because the waters of Matagorda Bay are very murky, allowing only 6-8” of visibility, it was decided the only means available to accurately excavate, record and recover the remains of this historic wreck were by utilizing the features provided by a enclosed unit called a cofferdam. This feature is a structure made of steel pilings placed one next to the other all the way around the site. A second wall was also constructed 30 feet outside of the first. Sand was placed in between the walls creating a 30 foot thick wall around the shipwreck site. Once the structure was complete, the water inside the cofferdam was drained revealing the bay floor. In this manner, archaeologists were able to excavate the site in a semi-dry environment.
The process of excavating and recording the remains of la Belle proved an extremely complicated and at times, almost impossible task. Utilizing a drained cofferdam, in conjunction with a semi-dry environment, researchers had to experiment with new types of tools and utilize standard tools in new ways. Although much careful planning was directed at efficiently and accurately excavating the remains, no one could predict or prepare for situations that unfolded throughout the excavation. The methodology combined both terrestrial and underwater archaeological techniques. Although the cofferdam was drained, the soil never completely dried out, and the excavation pit itself often flooded when pumps failed or waves brought in new water. On the upper sediment levels traditional terrestrial tools were used, however, the lower levels exhibited soft sand and mud which, at times, formed a slurry that was unable to hold discreet walls. The waterlogged environment, which increased preservation, required special tools and innovative techniques to minimize damage to delicate artifacts and to work effectively within the saturated conditions.
Cofferdam
Working in a dry cofferdam was one of the project’s most extraordinary features, and one that most effected methodology. In many ways the cofferdam exceeded everyone’s expectations, however, the cofferdam also presented a variety of problems. Indeed, the cofferdam provided archaeologists with a “terrestrial” site and the conveniences associated with working on land. Unfortunately, delicate artifact assemblages suffered from constant exposure to heat and humidity. The cofferdam’s environmental conditions therefore necessitated a full-time task of constantly wetting the hull and its artifacts to prevent undue damage.
Although the cofferdam had several advantages, it encompassed many logistical and methodological disadvantages. Location was one of the cofferdam’s major disadvantages. The site was located in Matagorda Bay, 15 miles south of the crew headquarters, in Palacios, Texas. Transportation to and from the cofferdam averaged 1 hour each way, therefore, supplies and tools had to be thought out and loaded in advance. It was costly and inefficient to return to Palacios for equipment whenever a problem arose. In several instances delicate artifacts were exposed, needing immediate removal. The crew, therefore, had to constantly re-evaluate recovery procedures, shift available resources as necessary to accommodate the fragile artifacts, and to afford all possible protection. Also, as mentioned above, the constant exposure of the sun and heat on the shipwreck and associated remains was another disadvantage. This was a constant battle and one that need continuous attention to keep the remains protected.
All methodology centered around the cofferdam’s application and its effect on working conditions. Activities on the cofferdam were divided into the 2 areas: topside and the excavation pit. Topside operations included screening, office duties, tool storage, pump and generator maintenance, surveying, timber storage and public interaction. The following is a brief overview of the topside layout, including a general description of the various operations.
The office building/ bunkhouse was one of the major centers of operations for topside crew. The office, situated between the screening area and the generators, was used for meetings, briefings, meals, and as sleeping quarters. Crew members met in the office to discuss excavation options and methodology questions. Also, the only phones or radios on the cofferdam were located in the office. At night the office functioned as a bunkhouse for a crew member acting as the night guard.
