2.0 Preparation for Fish Cage and Mooring Deployment

Since the recovery of the North cage and mooring in June 2000 (see Appendix II), work has focused on the cleaning, inspection, and repair of the various components. Where necessary, new lines, chains, parts, and shackles were ordered and assembled. Alterations and improvements to the mooring and crown lines were made to ease deployment as described in section 2.4.

The fish cage rim was disassembled and tested for leaks. Because the fish cage was floating lower than normal, and at an angle it was suspected that there may have been some loss of buoyancy due to flooding in the rim. Each section was pressurized and tested for leaks with soapy water. Two of the sections were found to have small pinholes in the flat plates connecting the sections where holes had been sealed after the sections were hot dip galvanized. The holes were repaired. Although pinhole leaks were found, no water was found in the rim sections. It is believed that these rim sections maintained a certain amount of integrity while deployed because they were pressurized. Once the pinholes were repaired, the rim sections were re-pressurized to approximately 30 psi.

UNH also drilled holes in the deck of the fish cage for mounting tubes for the electronics to be placed on the fish cage at a later date. Environmental sensors were to be deployed in the fish cage. These included pressure (burst sampled for waves and averaged to half hourly values to determine average cage depth), temperature for water properties in the cage for comparison with the nearby monitoring mooring, and an optical backscattering sensor. Also, an acoustic Doppler current meter would determine the water velocity in the cage, again to compare with the ADCP velocity measured on the monitoring mooring. These sensors were mounted on a bracket that bolted to the cage in the through-spar rod holding the old feeding tube in place. UNH also welded two tabs on the cage, so that the sensor clamp could be bolted to the spar. The electrical cables ran up a pipe that bolted to the deck of the spar, and the cables passes through a hole drilled in the deck to reach the electronics to be mounted on top of the deck at a later date.

In addition, two load cells on short mounting bars with electrical cables to the spar were readied and antichafing gear applied for mounting on the fish cage in the Portsmouth Naval Shipyard Dry Dock. Other preparatory activities that occurred just prior to deployment include:

Thursday August 17, 2000 - On board the Galen J., Michael Chambers, Noel Carlson, and Glen Rice dove and inspected the Navy Dry Dock number 3. Submarine bulkheads were marked with buoys prior to cage transfer and construction to prevent any underwater collisions of the spar and bulkheads.

Friday August 18, 2000 - The Sea Station spar with counter weight and rim (see Baldwin, et al., 2000) were deployed into the river at the Port Authority pier and towed by the R/V Gulf Challenger (Captain Paul Pelletier and first mate Ken Houtler) to the Portsmouth Navy Ship Yard Dry Dock No. 3. The cage was moored in the middle of the dry dock over the weekend for early construction for Monday morning August 21.

Saturday August 19,2000 - Alex Walsh from E-Paint delivered the remaining antifouling coated mooring lines and fish cage net to the Port Authority Pier. A final check was made of the fish cage and mooring components.

Due to extensive bio-fouling of the net and mooring lines during the 1999-2000 deployment, an anti-fouling paint was located and applied to all lines and the fish cage net for this deployment. This will test the benefits in reduced cage cleaning effort, and test for any adverse effects to the fish. E-Paint, East Falmouth, MA, was recommended. This company produces and applies a variety of anti-fouling paints. Alex Welsh, technical representative for E-Paint, suggested their No Foul SN-1 anti-fouling paint. This EPA approved paint is copper and tin-free, and utilizes hydrogen peroxide as an active ingredient. The hydrogen peroxide maintains a surface that is inhospitable to fouling organisms for up to 12 months. In addition, No Foul SN-1 has been tested and used on US Coast Guard, Navy and Army Corp of Engineers vessels.

The painting process of the net and mooring components took approximately three weeks to finish. The different components were coated with different colors to aid in their recognition onshore as well as in the ocean. The color schemes of the mooring components are as follows:

To enable data telemetry from the NE grid corner load cells, the Northeast corner lower bridle and cage bridle lines had a _ inch diameter electrical cable with a heavily insulated neoprene jacket added. WHOI received these two lines from E-Paint after the antifouling material had been applied, so that WHOI could add conductors for the telemetry link. Walter Paul and Jim Irish measured the elongation and contraction of these lines under tension to 5,000 lbs. to determine the Poisson Ratio for the rope. This is the ratio of the diameter contraction to axial elongation. From this the proper wrap angle for a conductor cable, spiraled around the rope was determined. At this wrap angle, the electrical cable will allow the rope to stretch under load with close to zero stretch the conductor itself, only stretching of the helical coil geometry (which does not stretch the copper wires). The cable was wrapped around the lower bridle and cage bridle lines with a constant wrap angle of about 45 to 50º. The cable was tied tightly to the riser line with help of heavy nylon braided net twine (see Picture 1). This maintains the coiled geometry in the riser cable that is paramount to its ability to stretch as a coil without stretching the conductor wires to failure, while the riser line is elongated under applied mooring tension.

To deploy the moorings utilizing the capabilities and within the limitations of the Nobska, a methodology was developed by Mat Stommel and Will Ostrom with input from Jim Irish, Dave Fredriksson and Walter Paul that would:

• Simplify and speed up the mooring deployment and recovery operations
• Remove and minimize dangerous mooring operations
• East handling of the heavy components (anchors, steamer chain, etc.)
• Fully utilize the potential of the winch and net reel capability of the FV Nobska for expediency and safety of handling.