Archaeology of the La Salle Shipwreck Project
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Excavated material, at every level, was placed in labeled buckets and washed through screens. Exceptions include; sediment, next to the cofferdam’s inner walls, that was removed to help drainage, and sediment removed well beneath the excavated hull remains, approximately 60-90 centimeters. Each bucket was labeled with a piece of flagging tape that had the unit, quadrant within that unit, level, date and excavator. This information was included to provide provenience for any artifacts found in the screening process. Supplementary information was included when excavating within a specific feature or as part of an overall cleanup, when no actual grid coordinates were applicable. Working within a feature will be explained in the preceding section.
As archaeologists worked through increasingly lower levels, they switched from shovels to trowels and brushes. The soft wet sand made excavation relatively easy and most of the upper levels were quickly excavated. Soon, however, delicate artifacts began emerging, which required even more precise tools. Trowels proved too harsh to effectively expose organic materials such as leather and rope. After several trials, crewmembers found small rubber spatulas, thin long wood skewers, and curved wood pottery tools to be the most efficient tools.
The most effective excavation method for this project was a combination of a gentle water spray immediately followed with vacuuming. At first, this method was not used as an excavation tool, but rather to clean artifacts in preparation for photographing and drawing. Experience revealed that a gentle water spray cleared sediment without disrupting provenience, and could be used as a reliable excavation method. At its most gentle, the water spray was able to remove sediment around rope and sailcloth with minimal material loss. All other methods proved too harsh to separate the delicate fibers from surrounding soil.
In conjunction with the water spray, it was necessary to use a vacuuming system to prevent water from pooling in lower areas or running into other sections. Wet-dry shop vacuums proved the most useful for this application. They also worked well for general clean up of loose sediment in preparation for drawing or photographing. Unfortunately, the vacuums were not made for constant abuse. Rarely did a vacuum last more than a few weeks before overheating from the constant heavy flow of sediment.
Much of the site was heavily concreted, requiring an aggressive approach to remove the surrounding matrix. The corrosion product formed an almost impenetrable layer that contained no remaining iron artifactual material. The most effective tools for concretion removal were pneumatic air hammers and chisels. Both tools allowed controlled removal of artifacts in and around the concreted areas. Additionally, lower levels throughout the wreck, consisted of heavily concreted ballast. Air hammers and chisels were the only means available to remove the rock ballast. Fortunately, through systematic removal, the hard concretion eventually gave way, most times spalling off of existing artifacts, such as iron cannon balls.
Forms
Three basic forms were utilized to record the shipwreck and associated remains: unit summary forms, drawing forms, and timber recording forms. The unit summary form was an 8 ½ x 11 sheet used to record any notes or observations pertaining to a unit at a certain level. Each form contained descriptive information, detailing location, date, level, whether drawn or photographed, and additional notes. A unit summary often comprised several pages, but many units, when excavating in sterile sediment, have only a paragraph or a couple sentences. The drawing forms were also on 8 ½ x 11 sheets and were used to draw observations within each unit. Again, each form contained descriptive information, locational data, date, level, whether photographed, and a large area to draw the unit. The last form, the timber recording form was used to describe each timber as it was removed. Again all of the same information as the other 2 previous forms was recorded.
Drawing
Once an area was excavated the requisite 10 centimeters, the unit was ready for drawing. To facilitate unit drawings, several PVC grid templates were constructed to give a frame of reference. The grids consisted of four PVC sections of 1/4-inch pipe connected with four PVC elbow joints. Every 10 centimeters was painted in alternating black or white sections. Each section also had a piece of fishing line that ran from one side of the frame to the other, creating a grid within the PVC frame. This PVC grid allowed archaeologist to more accurately draw the unit on the unit drawing form that was a scaled version of the PVC grid with every 10 centimeters marked off as well.
