Opening an Offshore Maritime Site for Continued Excavation

By Hunter Brendel, Master of Maritime Archaeology student

The Lighthouse Archaeological Maritime Program (LAMP) 2014 Field School, in which I am participating, is a continuation of the total excavation of the Storm Wreck, an eighteenth-century American revolutionary war shipwreck off the coast of St. Augustine, Florida. Most field schools I am familiar with are usually shore dives of sites that entail pre-disturbance assessments. This field school is different. Work on site began in 2009 and has already covered five field seasons of surveying, researching, and excavating approximately 30 1×1 square meter units. This field season continues work from previous seasons.

The Storm Wreck lies approximately a kilometer off the coast in about nine meters of water, so access to the site requires the use of a research vessel. The LAMP research vessel, Roper, is moored over the site to provide surface support to archaeological divers and houses two water dredges that are used to excavate the site. There is a catch, however, as mooring directly on site risks disturbing the site and the archaeologists working on it. The vessel also needs to be soundly anchored to protect it from the elements, such as ocean swells, wind, and the risk of suddenly-turning weather (the shipwreck is named the Storm Wreck, after all).

In order to moor Roper over the Storm Wreck so that archaeological work may be safely conducted, the staff at LAMP have devised a three-point mooring system. Three permanent anchors are located north, east, and west of site. These anchors have individual mooring lines attached to them that are located by divers, raised, and tied to a fixed point over the Storm Wreck site. The lines are then attached to a buoy and submerged over site with the buoy acting as a down line for the divers once they commence work.

When I first arrived in St. Augustine a week before the field school started, my initial task was to help locate the mooring lines and open the site for work the next week. A fellow supervisor and I joked that finding the mooring lines was like opening the curtains on the first act of a play—the 2014 LAMP Field School—with the Storm Wreck site being the stage.

Finding the mooring lines in low visibility is not as simple as diving down to the lines and raising them. First, you have to find them by feeling the area. To do so, LAMP developed a method of circle search that allows both divers to swim around the search area. In a traditional circle search, one diver holds down the zero end of a measuring tape in a fixed position while the other diver searches with the other end of the tape on a 360 degree axis. LAMP’s method of a circle search, however, allows both divers to search by holding down the zero end of the tape with a t-probe and mushroom anchor. This frees up the diver (the finder) who would usually hold down the zero end, allowing him or her to search the length of the tape while the other diver (the navigator) rotates around a 360 degree axis on a northern bearing. When the full circle is complete, the navigator extends the length of the tape another five meters while the finder continues to swim the length of the tape (Figure 1).

Using GPS coordinates, Roper placed my dive buddy and me over where one of the anchors was supposed to be. Diving down, we had three principal tools with which to conduct our circle survey: a t-probe, a mushroom anchor, and a measuring tape. Using the mushroom anchor, which also served to hold our down line, we drove the t-probe and measuring tape into the seabed. My dive buddy, who was in the navigator role, extended the tape out to a length of five meters and with a compass conducted a full 360 degree axis sweep on a northern bearing. My role was finder.

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Figure 1. A sketch showing how LAMP conducts circle searches with a pair of divers. The circle displayed is the search area. One diver (the navigator) holds the end of the tape at a distance of five meters and rotates on a northern 360 degree axis. When the circle is completed, the navigator extends the tape five more meters to expand the search area until the objective is found. The other diver (the finder) searches both sides of the tape as the measuring tape is rotated and extended. Sketch by Hunter Brendel.

 

As the navigator rotated around the axis, I searched up and down the measuring tape, which was held in place by the t-probe and mushroom anchor. Usually after the circle is completed, the navigator would extend the tape another five meters and widen our search area. Fortunately, before the first lap was done, I felt a snag in the measuring tape. Tracing the kink in the tape, I felt the mooring line blocking its path. We had found our anchor.

After lifting the mooring lines for all three anchors, we tied them together with a buoy and down line secured by a screw anchor only two meters from the Storm Wreck. The LAMP 2014 Field School was officially opened.

Whenever Roper finds the site by GPS, we locate the buoy that holds the mooring lines, untie them, and fix the three lines to the bow and aft of the stern. To release tension on the lines, LAMP uses pelican hooks for a safer and more secure hold (Figure 2). Then the real work begins!

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Figure 2. One of the three-point mooring lines secured aft of the stern of Roper. To reduce tension on the line, a pelican hook is used. This technique of using a pelican hook was adopted by LAMP from local shrimp trawlers. Photo by Hunter Brendel courtesy of LAMP.

One response to “Opening an Offshore Maritime Site for Continued Excavation

  1. Andrea Leonard

    A good read. Keep up the great posts Hunter.
    Andrea