+--------------------------------------------------------------------------+ | OCEANUS CRUISE SYNOPSIS | +--------------------------------------------------------------------------+ Voyage - Leg: OC 420 Voyage Dates: 01-02 December 2005 Chief Sci(s): Spahr Webb (Webb) Address: Lamont Doherty Earth Observatory 61 Rte 9W Palisades, NY 10964 Phone: 845-365-8439 Email: scw@ldeo.columbia.edu Cruise Objective: deploy and recovery buried sensor and mooring. Science Activities: Operations Area: south of Martha's Vineyard 100' SSSG Tech: sssg @oceanus.whoi.edu Departure Port: Woods Hole, MA Agent: Master R/V Oceanus Attn: Scientist's Name c/o WHOI 266 Woods Hole Rd. Woods Hole, MA 02543 Contact: John Dyke tel. (508) 289-3770 fax: (508) 457-2185 email: jdyke@whoi.edu Arrival Port: Woods Hole, MA Agent: Same as Above Installed Scientific 12 kHz Equipment: WHOI-Provided Science Tools: Program-Provided Science Tools: Shipboard GPS Navigation Equipment/Nav: Trawl Wire - deploy buried sensor system (~350 lbs) in 1000 ft. water depth Other Requirements: buried sensor will require towing instrument into bottom like a plow anchor Notes: Night Work Anticipated This plan is a first draft with substantial revision likely. The primary purpose of the cruise is to deploy into the sediment south of MV a seismic sensor (the "plow") and collect a few hours of data. The plow weighs about 600 lbs in air. Currently, I am planning to use divers to examine the attitude and depth of penetration of the plow. Will Ostrom has been talking to the WHOI dive office to arrange two divers for the cruise. Diving will be done in roughly 50' of water during daylight hours. Will load on Nov. 30. Gear will be contained in a small truck arriving late on Nov. 29. The site is in 50-60' of water roughly 3 miles off MV (one mile from the tower). It is 26 miles from WHOI. The buried sensor looks a lot like a plow anchor roughly 5' x 3' x 3' except that it has an "X" of pipes extending to the front, sides and back on a post extending roughly 24" above the plow part. The "X" limits the depth and penetration angle of the plow. The side and back pieces are 6' long, the front "shank" used to tow the plow is 12' long. The anchor is made of substantial steel plate and heavy pipe (2" and 3" pipe). I will send a photo of the plow tomorrow. It appears the X will fit narrowly through the A-frame (inside dimension 12.5'). If not, we will deploy the plow with the ship's crane on a release hook off the back of the ship. The plow was tested off San Diego in early November using the R/V Sproul. We have modified the plow since this test by extending the front shank 6' to better limit the angle the plow penetrates the ground. The idea is to have the plow enter the ground at a gentle angle (25 degrees) rather than steeply (45 degrees+) as does a standard anchor (this limits the maximum load). The test off San Diego was into very hard mud with shells. It is expected that the sand off MV will be easier to penetrate, although I understand there may be a peat layer at several meters depth that may limit the depth of penetration. Off San Diego the penetration was limited to about 30" depth with loads reaching briefly 6000 lbs. We would like to push the maximum pulling force to 7000 lbs if necessary with the Oceanus (we were limited by the winch on the Sproul). The deployment consists of first deploying a small buoy floating the retrieval rope attached to the center of the X on the plow. Will Ostrum is arranging to obtain a sufficient length of Spectra line or wire rope for this purpose. The line is attached to the top of the plow to allow pulling the plow vertically out of the ground. As the ship steams slowing into the current, the plow is then lowered to the seabed through the A-frame on the ship's trawl wire. I would then like to hold the ship stationary adjacent to the plow for roughly one hour to collect data with the plow while it is unburied. This would require slackening the trawl wire to avoid tugging on the instrument. To do this on the Sproul, the ship anchored. This may be too tricky an operation for success in bad weather. We would then pull the plow into the bottom. This requires having sufficient scope on the trawl wire (5 to 10 times water depth). If the ship is anchored, we would simply pull against the ship anchors. We need to pull the anchor roughly 100' to insure the plow is fully buried. As noted, maximum loads might reach 8000 lbs, but hopefully will be much less. The "X" limits the depth of penetration to about 40" so the load is expected to increase until the plow is fully buried but then remain roughly constant as the plow is pulled horizontally at fixed depth. It is important that we be able to determine the load on the wire during the deployment to keep loads within safe values. We would then send the divers down to examine the depth of penetration and attitude of the plow. We have a video camera for recording the bottom installation. In theory, the X will be flush to the seabed. The trawl wire would then be disconnected from the plow. This could be done either by having the divers unshackle the wire from the plow, or by cutting the trawl wire at the ship, if it is too dangerous for the divers to work near the trawl wire. Cutting the trawl wire would require the sacrifice of less than 100' of wire. The plow would then be left in the bottom for several hours while seismic data were recorded. At the end of the interval the ship would maneuver to recover the buoy and the retrieval line. The retrieval line (roughly 50') would be shackled to the end of the trawl wire. The ship would back down over the plow and the trawl winch would be used to pull the plow back out of the bottom. There is apparently sufficient distance in the trawl wire path above the deck to pull the plow out of the seabed and most of the way to the sea surface. We may need to stop off the wire and use some other means to get the plow out of the water and onto deck (capstan or crane). It should be possible to accomplish all this work within a 24 hour period, but there are two days available for the work, if necessary. We would unload as convenient, on either the 2nd or 3rd. Navy Clearance Status: Last Modified: 12/13/2006 Check List: Required? Comments US Customs Form No Explosives Clearance No Isotope Use Approval No Diplomatic Clearance No SCUBA Diving No