NOAA Teacher at Sea
Aboard R/V Bellows
August 9-18, 2011
Mission: Exploring the Submerged New World Part III
Geographical Area: Florida Middle Grounds off the West Coast of Florida
Date: August 14, 2011
Science and Technology Log
Early morning, August 13, 2011, the weather is cooperating with calm waters. Members of the archaeological research crew and the R/V Bellows crew clear off the stern deck, so the floating screen could be pulled back up and the pump motor for the induction dredge could be mounted on it. This modified design made it more stable and easier to use. The floating screen and induction dredge were then towed into place by the Bellow’s Boston Whaler to the position marked after yesterday’s dives. At the buoy it was anchored and the snorkel for the pump (a long tube that draws in the water) was primed for suction.
The floating screen and induction dredge is being towed into place. At the buoy, it will be anchored and the pump will be primed. When the divers descend at the location, the pump motor will be turned on and the dredging will begin with the removal of the top layer of sediment flowing onto the screen.
According to dive plan protocol, each dive has an assigned Safety Diver who records dive times, tank numbers and PSI on all tanks, both before and after the dive. The Safety Diver with all of their dive gear is on standby. The divers below have the arduous task of moving and then working the large (100’ long) and 6” diameter induction dredge into spots where the rock outcroppings and the sand meet. These features indicate the presence of a possible river channel.
Two members of the Mercyhurst Archaeological Institute research team, Holly and Kim, ready their dive gear for the first dive of the day. Since a number of the divers have not dove with each other before, the dive will serve to orient themselves with each other and the site.
With the assigned Safety Diver and I positioned on the floating screen, the divers swam into position for their descent and dive. The time in on the first dive was 15:19. After allowing for the divers to descend, the pump motor was started. The dredge works on the “Venturi” system. As the pump suctions water from the snorkel into the main 6” line via a tapered 4″ line, this induces a vacuum in the 6” tube which the divers use to remove sediment from the bottom. The time out on the first dive was 15:54 with an actual bottom time (ABT) of 35 minutes and the maximum depth was 38 feet. On the screen a quantity of sedimentary shells, sand dollars and old pieces of coral were raised. The hope is to get through the top layer of marine sediment then through a layer of fresh water sediment to uncover the remains of a terrestrial landscape.
Teacher at Sea, Steven Allen, manning the floating screen and pump motor for the induction dredge. Communication between the divers and the floating screen is done by divers sending up (through the tube) flagged messages such as “throttle down,” “new level,” or “off.”
After an appropriate surface interval (determined by dive charts) and since the weather was still cooperating, a second dive was planned for after dinner. Again, a safety diver and I were positioned on the floating screen and dredge, while the divers entered off the port side of the Bellows and surface swam over to the screen platform. Time In on the second dive was 19:36. As the divers descended, the pump motor was started and the divers below began to remove more top layer sediment and continue to survey the sub-surface features. Two divers also repositioned the floating screen platform anchors. With the sun dipping lower in the western horizon, the floating screen began filling up with sediment. Time out for the dive was 20:05. With a ABT of 29 minutes for the second dive, Principal Investigator, Dr. Andy Hemmings, reported that the divers had excavated a hole roughly one meter deep.
Following the dive, everyone worked to get the divers and their gear out of the water, which was no small task because the Bellows had to leave behind their dive platform that made for easier access in and out of the water for divers. This meant handing up the tanks, buoyancy compensators (BCs), weight belt and fins to the stern deck. Members of the research mission then held a debriefing meeting. Everyone was excited because of how the equipment was working and looked forward to the next day’s dive and continuing to go deeper through the top marine layer of sediment. With a full moon rising, the team filled the air tanks so the mission could get an early start on Sunday.
Dr. Adovasio readies the Nikon D90s underwater camera with Ikelite case for the divers. Extensive photo-documentation is part of the process of documenting both underwater and terrestrial archaeological sites, because the process of excavation inevitably destroys the site.
August 14, Sunday morning—2-4 foot swells and the wind has picked up (12 to 16 knots) out of the west by northwest. Today, we are on a wait and see plan until 11 am. The weather poses a safety hazard for the divers coming back onboard the Bellows without a dive platform and for the team members on the floating screen and induction dredge. By noon the swells had partially subsided and the decision was made to continue diving. Dive #5 went in the water at 3:08 and came up at 3:36. The induction dredge worked fine and more marine sediment was removed. However, due to the waves, the divers below had lost the location of the excavation hole dug on the previous day.
Dive #5 at site 1121. The average depth at this site was approximately 38 feet. During the late Pleistocene (end of the Ice Age 15,000 to 20,000 years ago), this area was part of the terrestrial landscape.
With the swells increasing, Dive #6, a two person dive, went in at 16:59 and came out at 17:08. The original excavation hole was located and marked with a buoy. However, with this dive, the pump motor received a direct hit by a large wave and the pump became inoperable. With the swells increasing and weather reports showing an encroaching front, the decision was made to pull the floating screen and pump out of the water and onto the stern deck of the R/V Bellows.
Thus far on the mission, between modifying the dredging equipment at the dock and out at sea, loading and storing the gear, as well as with assisting the divers and the Bellows crew, I can honestly say that the nature of the work has been much more physically strenuous than I imagined it would be. For the past three days, the work days have been in excess of 12 hours per day and this is in high temperatures and humidity. I have found myself relying quite heavily on my past experiences in construction. But, as the captain remarked, it is very rewarding to see how everyone pulled together as a team, especially when things get a little rough, or as he put it, “on a pitching, heaving, rolling deck.”
This was especially the case when we were raising the floating screen/dredge out of the water and onto the stern of the Bellows in 3-5 foot swells this afternoon. It took two divers in the water to secure the hoses, a man on the platform and a number of hands on the stern deck working together. At one point, as the main wire hoist was raising the floating platform, the main wire steel braided cable snapped, sending the floating screen and dredge back into the ocean from a height of five feet.
With the swells increasing, the captain and the first mate quickly repair the steel cable of the main wire hoist that snapped while lifting the floating screen and dredge onto the stern of the Bellows.
At the end of a somewhat tense forty-five minutes or so, we not only had the floating screen/dredge secured, but also the Bellow’s Boston Whaler was returned to the 01 top deck. As a testament to the expertise of the Bellows crew (not to mention the Mercyhurst team), this was all done safely with only a few minor scrapes and bruises; one of which included a small bump on my head where the steel cable had bounced off my head when it had snapped. Moreover, a most delicious dinner of salmon, sweet potatoes and salad was served afterward as if this were all just routine for them.