Wednesday, June 2, 2010

Maritime Field School Week 2

May 24 - May 26
By:  Joe Grinnan

               Monday was a very eventful day. On the B-Street Schooner wreck site divers completed an orientation dive, becoming familiar with the site and its layout. They also replaced the measuring tape on the baseline, securing it in regular intervals with zip ties. In addition, students filled 20 sandbags with sterile sand found offsite in preparation for future unit dredging. Teams also practiced baseline offsets and mapped out the stern of the vessel.

               The teams working on the Emanuel Point II shipwreck also accomplished much on Monday. In the amidships unit (97N 491E), divers dredged about 25 centimeters of sediment from the overburden and ballast strata, ending the day at a depth of 45cm. They recovered numerous objects from the dredge spoil including faunal remains and lead sheathing. Divers working in the stern unit (83N 501E) excavated about 30 centimeters of sediment, ending the day at a depth of approximately 60 cm. The dredge spoil was full of artifacts including faunal remains, flora remains such as a nutshell, a single piece of earthenware ceramics, a brass straight pin, and even a wooden comb!
(Wooden comb and brass straight pin.)
               Tuesday turned out to be an interesting day. We prepared for the day just as we had done on Monday, but on our arrival to the barge there were approximately 2’ seas in the bay with a stiff breeze blowing out of the southeast. The waves unfortunately inhibited our work on the water and the excavations were cancelled. The students instead took a fieldtrip to the T.T. Wentworth museum to look at the artifacts excavated from the Emanuel Point I shipwreck. We also looked at the other exhibits in the museum including colonial era British and Spanish artifacts and objects from Mr. Wentworth’s travels. The field trip was very interesting and informative.

               Wednesday was a very beautiful day and we were able to accomplish a significant amount of work. The visibility on site was the best it has been all summer about 3 meters. One of the dredge heads developed a dime-sized hole in the induction nozzle and thus was left useless, however we were able to dredge in the stern unit (83N 501E). In the dredge spoil from this unit we were able to identify some faunal remains and resin. During excavation a single piece of lead sheathing was piece plotted and some hemp was collected. Although no dredging was completed in the amidships unit (97N 491E), the visibility permitted drawing of a detailed map of the exposed timbers and pieces of lead sheathing. Two of the pieces of lead sheathing were piece plotted and collected.

                On the B-Street Schooner divers completed an orientation dive, becoming familiar with the site and its layout. The teams practiced baseline offsets by mapping the remaining sections of the map left by the divers from Monday, focusing on the bow section. During the dive orientation divers observed metal tacks in the bow, but they were left in place, they also observed a glass bottle near the bow, which was also left in place.
May 27-28, 2010
By:  Brett Briggs

                During the second week of maritime field school, the students really started to demonstrate how well we had adjusted to our daily routines in the field. Daily preparations on the project barge have become very time efficient and smoothly executed. We have all had the opportunity to use the dredge on the Emanuel Point II site and have adjusted to poor visibility underwater. After a nice relaxing day at T. T. Wentworth Museum on Wednesday, due to bad weather, we began our first target dive rotations.

           Target dives are the second phase of remote sensing by sidescan sonar or magnetometer. When an anomaly is detected by either instrument, its GPS coordinates are recorded for further investigation. After interpreting the remote sensing data, divers may be sent into the water to determine the anomaly’s identity. Using a technique called circle searching, divers can systematically do a search of the area where the anomaly was detected. This is accomplished by dropping an anchor with a buoy attached to it on the estimated location of the anomaly. Divers can then descend the buoy anchor line through near zero visibility until they reach the bottom. Beginning on the bottom at the buoy anchor, one diver holds a role of measuring tape while another diver swims away from the buoy anchor with the end of the measuring tape and a probe in his hands. The diver with the probe begins swimming a circle pattern while probing the sand for objects. Using a communication system based on measuring tape tugs, the diver probing the sand can notify the diver at the buoy anchor that he has found something or needs more slack. The diver on the buoy anchor will, in turn, notify the circling diver when he has completed a circle and can widen the search by releasing more measuring tape. If something important is located, the diver on the buoy anchor can simply bring the buoy anchor with him by following the measuring tape to the new discovery and place it next to it for further investigation.
            On Thursday, one group of students performed target dives around Pensacola Bay, while another group carried out dredging operations on a unit in the amidships of EPII. Matt Gifford, David Hodo, and I were the first dive team in the water at EPII and were responsible for setting up the dredge for the day. Unfortunately, very low visibility made communication slower and more difficult than usual between us as we made our preparations. After making our beginning measurements of the excavation unit below baseline, we began setting up the dredge. After that was complete, we gave the signal to start the dredge. However, we soon realized that the dredge was not getting suction and bad visibility made it difficult to communicate this fact to my supervisor. As soon as communication was established, I was able to swim off along the exhaust hose to identify the problem, which turned out to be a kinked hose. As soon as I corrected the problem and made my way to the dredge head to begin dredging, it was time to end the dive. Sometimes bad conditions can really slow operations down.

              Friday, on the other hand, proved to be a very productive day for me. While one group remained at EPII to continue dredging on the amidships unit and metal detecting on the stern for possibly and anchor or rudder hardware, my group performed target dives. I would say that target dives may not be for everyone due to their super low visibility conditions I experienced and the relentless fear of the unknown lurking just outside of sight. However, I had been looking forward to this all week and I loved it. I am excited to report that I even found something on my very first circle search. Besides recovering two lost probes on the bottom of the bay today, I found some potentially very old wooden beams ranging from 4” to as much as almost 3’ below the sand. It was very spongy to the touch and felt riddled with teredo worm holes. I would say that the wood beam found under the 4” of sand was about 10” wide and seemed quite long, although it was hard to identify the extent of it due to bad visibility. Solid objects were detected by probe deep in the sand as much as 3 meters away from the beams closest to the bottom surface and probably goes further out, although that is as far away as we test probed. I am very excited about this find and I hope it turns out to be something important after we perform some further investigations of this site next week.*

*Editor’s note: Unfortunately, this target turned out to be modern material. The search continues for potential sites, however!

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