Diving and Salvage
October 1, 2018
Underwater construction and salvage jobs require a lot of planning and mustering of highly-experienced teams to complete work and keep business going. One company that has the capability of corralling all the necessary talent and equipment is Seattle-headquartered Global Diving & Salvage, Inc., which has been working on a flurry of projects around the Pacific Northwest and California. Following are two examples of their most recent jobs.
Working with Trinity Construction for the Lake Arrowhead Community Service District, Global provided all diving and underwater construction support for the replacement of the community's aging freshwater intake system. Dive crews performed the sinking and installation of more than 500 feet of new HDPE conduit PLEM (pipeline end manifold) that open into three underwater concrete vaults; the vaults house new 34.5-hp HOMA intake pumps.
Operating from a dive barge at the location, the divers closely worked with the crane operator to assist in the sinking and placement of the pipeline and concrete vaults. Once the three 45,000-lb concrete vaults were carefully lowered into position under the direction of the dive team, the divers installed the spool pieces tying the system together. Clear communication was crucial between the divers in the water and the topside crane team in order to place the large vaults on the lake bottom without damaging them or injuring the divers. After the intake pumps were installed, the system was tested and brought online.
The project site presents several logistical challenges; Lake Arrowhead is a remote lake situated in the San Bernardino Mountains in California and required trucking several oversized loads up narrow mountain roads. Because of the lake's 5,100-foot elevation, the divers' maximum bottom time was restricted to 70-90 minutes and surface decompression was used. Working a 10-hour shift Monday through Friday, Global safely logged more than 80 dives to perform the required installations.
Another interesting Global project involved the salvaging of a 1929 luxury yacht. The R/V Acania was taken over as a US Coast Guard vessel during World War II, then used by NOAA and the US Navy as a research vessel until the 1980s. The 126-foot long, 195-ton vessel sank at her dock in Everett, Washington's Steamboat Slough three days after being purchased by new owners, who contacted Global regarding salvaging the vessel.
A team from Global performed an initial defuel response and inspection. Boom was placed around the vessel to contain any fuel released but the crew was unable to gain access to the tanks due to the vessel's 90-degree starboard list and the strong currents in the slough.
The vessel's location in the slough made the site extremely difficult to access; along with the large tidal exchange and high currents, the narrow channel offered limited maneuverability, shallow depths onsite and at the slough entrance, and low bridge clearance. Limited land access prevented the use of a land-based crane, so the derrick barge Los Angeles was selected as the best tool for performing the parbuckle operation.
Waiting until the tides were suitable, the crews rigged the Acania for parbuckle and the D/B Los Angeles righted the vessel. Six-inch pumps were used to dewater during a tide low enough for her deck to become awash; as water was removed Acania began floating with the incoming tide. Dive teams patched two holes in the hull – the largest approximately 2 inches by 10 inches – and 12-hour watch shifts were established, with the salvage crew checking the pumps and patches every 15 minutes.
Sediment and hazardous materials were cleared from the vessel and she was prepared for towing. A dead ship tow plan was submitted to the US Coast Guard, utilizing the tug Mudcat, an escort barge/dive station and a salvage crew on board the Acania to operate pumps if needed. The Acania was towed 43 nautical miles to Delta Marine Shipyard in Seattle where she underwent a full restoration.
"This was an extremely challenging salvage because of location, current and accessibility," said Global Project Manager Katy Stewart. "We succeeded, in part, because the customer was actively involved and willing to give us the trust and freedom to move ahead and adapt our salvage plan as needed in a fluid situation. We also worked with highly-engaged subcontractors who know Global and are willing to take on a risky project because of our clear communication and our reputation for successful operations."
AUS Diving, with offices in Spokane and Seattle Washington, recently completed a municipal wastewater outfall project for the City of Wilsonville in the Willamette River. The general contractor was North Bank Civil. The work scope included installing a 42-inch steel lined concrete coated pipe.
The first task was to demolish and remove the old 24-inch pipeline. Excavating a 10-foot-deep trench to install the new pipe was necessary as well as the installation of bedding rock. The new pipe was installed in the trench, then it was back filled with rock, and capped with native soil. Large riprap was placed along the bank.
A dredge barge with a two-yard bucket was provided by Marine Industrial Construction, the company that performed the excavation and bedding rock installation. AUS worked from a pipelay barge that was custom built for the job. The barge was outfitted with an A-frame and two winches to handle pipe sections that were sent down on different angles to match the slope. AUS also had a dive boat on site. Divers worked in the water to a maximum of 42 feet during the project. This summertime project had no weather or water conditions that impeded the work.
However, an unexpected delay occurred as the project got underway: a huge amount of construction debris left over from the demolition of a nearby highway bridge replacement project that was completed more than 50 years ago had been dumped in the area. The removal work involved removing large concrete debris. Some of the pieces weighed up to 25,000 pounds each. The concrete debris was removed from the jobsite so that it was not a hazard to navigation and to ensure it wouldn't interfere with any future projects.
Another project now underway for AUS is taking place at Noxon Rapids Dam in Montana located on the Clark Fork River. The dam is owned by the Avista Corporation, and the general contractor is Knight Construction.
The project involves a stoplog replacement – the stoplogs are used to dry out and perform maintenance on spillway gates. There are eight spillways in total on this dam. "Due to the unusual geometry of the dam, a detailed survey was required to fabricate the new stoplogs. We used a custom-built survey frame to accurately measure the angles of the ogee (the curved slope of the dam) in relation to the spillway face to allow Knight Construction to properly fabricate the stoplogs," explains Kirk Neumann, AUS' General Manager.
This is a two-phase project for AUS, with the next phase expected to be carried out in March of 2019. During Phase 2, the new stoplogs will be installed and a proper fit will be confirmed so that maintenance can be performed in the dry on each of the spillway gates.
California-based Underwater Resources, Inc. (URI) recently conducted USCG hull exam and structural steel inspections on the 96-foot, steel-hulled Desert Princess, a passenger cruise vessel that has been operating on Lake Mead for the past 20 years.
Desert Princess was built in 1991 by Skipperliner in La Crosse, Wisconsin. Recently, a small crack that appeared along the bottom steel shell underbody with water leakage in the void #3 compartment. With scheduled outage planned in July 2018, URI conducted another UT thickness exam of the bottom shell plating adjacent to the crack and included URI's Naval Architect, Andy Toro, to attend the inspection in May 2018.
The original design/construction DWGs were reviewed and, after performing additional UT thickness gauging around the area of the crack, a full-scale "mock-up" of the localized compartment including frames was constructed by Toro. Alliance Marine, URI's ship repair/welding and repair partner, was called in to attend a meeting with ship husbandry diving personnel and the Naval Architect at URI's office in San Leandro.
An underwater hull plating repair plan was devised to include fabrication and installation of an aluminum cofferdam that would encompass the entire bottom/side shell plating repair area and allow dewatering of a 16 square-foot area that traversed across the chine.
The repair plan included installation of the cofferdam, sealing and dewatering the area of the crack and the original ¼-inch plating that had corroded, cutting/cropping out an underwater section of shell plating area comprise of just less than 4 square feet and fabricating and inserting a new section of ¼-inch plate with lap seam, a partial section of the frame and gusset plate.
The UT results of the steel inspection and proposed work plan were submitted to Sector San Diego and USCG approval was given to conduct the field repairs that were scheduled for mid-July 2018, the warmest month of the year in the Las Vegas area. Capt. Bridger Christiansen represented the owner of the vessel as Project Manager, as well as serving as liaison with the USCG and the other coordination efforts for the many scheduling and logistical details required to facilitate both the welding and diving work.
During the "wet layup", the shell plating repairs included repowering and replacement of the vessel's two primary generators. "Because of extreme heat exposure concerns for personnel working below deck during the anticipated 110-degree work days, additional consideration needed to be made to provide shade, fan ventilation and AC for crew safety," says Tom Belcher, President of URI.
The large aluminum cofferdam and some of the large bottom/side shell plate components were prefabricated offsite at the Alliance Marine facility in Antioch, California. URI also plumbed valves, added flotation and performed "neutral buoyant" testing of the cofferdam in a fresh water test tank.
Alliance Marine and URI personnel mobilized welding and diving equipment and the aluminum cofferdam and traveled to Boulder City, Nevada over a mid-July 2018 weekend. With the vessel berthed alongside a shallow water floating dock, URI divers cleaned the starboard area around the crack, positioned/installed the cofferdam and dewatered underbody side/bottom shell areas.
The welders initially cut through the corroded plating before removing and trimming the plate in accordance to USCG and ABS guidelines. The welders worked a total of five shifts to cut, crop and insert the new 1/4-inch plating while the divers performed an Alternative Hull Examination (AHE) for the USCG. The cofferdam was flooded, and the area leak tested on the fifth day and removed on the sixth day just prior to performing the final underwater video inspection. The vessel was returned to full service just four days later.