Project Tag: Dive Control Vans

Bradford Island Contaminated Sediment Removal

In 2000 and 2002,the US Army Corps of Engineers (USCOE) removed discarded pieces of electrical equipment adjacent to the upstream side of Bradford Island,part of the Bonneville Dam complex. These pieces of equipment contained PCBs that had leached out and were found in the surrounding sediment.

After the equipment was removed,a survey was performed to identify areas were the PCB concentration was above allowable limits. In 2007,a proposal was put out by USCOE to remove this PCB contaminated sediment.

We supplied the floating platforms on which the filtration system was assembled,and conducted all maneuvering and handling of the platforms. We also provide all the diving services required to perform the removal of the PCB-contaminated sediment.

Three areas were identified as “hot spots.” These areas totaled over 41,000 square feet. All three areas were dredged with a 6-inch diver-operated dredge. Dredging operations were completed in 23 days.

Working in sediment that contained high levels of PCBs required the implementation of contaminated-diving procedures. Divers wore vulcanized rubber dive suits with special neck seals that are integral to the dive hat,and connected boots and sealed gloves which totally isolate the diver from the surrounding water. When the diver surfaced,tenders wore rain suits and face shields to protect themselves from contaminated sediment that may have attached itself to the diver’s suit.

Historical Tug USS Wenonah

When the vintage 100-foot World War II Tug,USS Wenonah,took on water and sank at her berth August 17,2009 on Treasure Island,she created an oil spill and a continued threat to the environment due to remaining hydrocarbons and other hazardous materials on board. Thanks to our collaboration with the U.S. Coast Guard – Sector San Francisco,and the California Department of Fish and Game (Office of Spill Prevention and Response),the vessel was quickly recovered to mitigate further environmental damage.

We were contracted by the US Coast Guard – Sector San Francisco and quickly dispatched a team from our office in Rio Vista,CA. Salvage specialists,divers and heavy rigging equipment arrived at the scene while naval architects calculated weights and analyzed the vessels strengths and lifting characteristics.

Working in 30 feet of water,our divers dug trenches in the thick mud and debris beneath the wreck and maneuvered heavy chains underneath it in preparation for lifting. We contracted with American Bridge/Fluor to acquire the services of the “Left Coast Lifter,” a shear-leg crane working in San Francisco Bay,to assist in re-floating the vessel. With a lifting capacity of 1,700 metric tons,the “Left Coast Lifter” is one of the largest floating cranes operating in the continental United States.

Our crews attached the chains to the crane and quickly commenced lifting operations of the 440-metric ton vessel. US Coast Guard – Pacific Strike Team recognized a unique opportunity for training and boarded the vessel to de-water the hull under our oversight while divers surveyed and patched the vessel.

On August 31,with the vessel back in her berth and safely afloat,we delivered the vessel to the US Coast Guard – Sector San Francisco,which is working with other agencies to determine the vessel’s future.

“Synergy between state and local agencies ensured the unified command was able to focus resources in an efficient and timely manner,” said LCDR Agustus Bannan,U.S. Coast Guard – Sector San Francisco. “Serving the general public and our stakeholders,we capitalized on the cooperation and good will of Global Diving and American Bridge that brought us the needed resource to complete the job.”

Robson Bight Salvage

Global Diving & Salvage,Inc. and Mammoet Salvage of Holland performed a highly technical deep-water recovery of a fuel-laden tanker trunk in the sensitive waters of the Robson Bight Ecological Reserve at the northern end of Vancouver Island,British Columbia. The reserve is considered critical habitat for the resident Orca (Killer Whale) populations along Canada’s west coast. The work was performed directly for the Ministry of Environment,British Columbia.

Working at a depth of 1,165ft using Global’s Cougar Work Class ROV,divers,and a specially engineered Deep Water Recovery Casing (DWRC),the team carefully and successfully recovered the sunken tanker truck laden with diesel fuel as well as a container containing assorted oils and hazardous materials from the sea floor. The operation was completed safely and with no additional impact to the environment. How it happened.

Hood Canal Bridge Replacement

We were contracted by Kiewit to provide diving and ROV services to route the 3-inch galvanized steel anchor wires through the new concrete anchor blocks that support the new east half of the bridge. The anchors are located in 60 to 380 feet of water. The new anchor wire was pulled through an anchor and connected to the bridge where the proper tension was achieved. Each leg of the two wires that attach to the anchor block has a tensile strength of over 1 million pounds. The anchors themselves weigh over 2 million pounds each. The project required the placement and connection of 20 anchors to secure the bridge in place.

Our divers connected the new anchor lines to the messenger lines that were in place and observed that the new wire,as it was pulled through,did not kink or get bound up. On the deeper anchors,the Cougar XT ROV was used. This vehicle,equipped with two five-function manipulators,was able to make the required connections and had enough power to stay on station during all but the heaviest currents.

Boat Ramp Upgrade

The project required replacement of an existing woodpile-supported boat launch. The ramp was located along side the causeway and adjacent to the product lines used to move products to and from tankers and barges moored at the end of the pier. Lifting and removing the existing materials,driving the new steel pile,and setting the new ramp structure all had to be done from the water. We hired Culbertson Marine of Anacortes,WA to provide crane support from their barge,which was moored just offshore of the ramp.

The ramp was removed in several pieces and set aboard the barge for further disassembly. The pilings were obstructed by riprap that was placed as armor along the shore. Rocks had to be individually rigged and set aside with the crane. Once the pilings were exposed,they were cut off at the mud line. New steel piles were driven adjacent to the old piling locations. The steel pilings were cut off at the proper grade,the new ramp was assembled in sections,and then lowered over the new pilings and secured in place. Once all pieces were in place,the track was installed. An alignment fixture was used for proper spacing of the tracks to allow the cart supporting the boat to move freely.

The work was done in an intertidal zone,with divers working above and below the water as the tide came in and out and the work progressed either in- or offshore.

The Dalles Bay 8/9 Spillwall

We were contracted by Kiewit to provide diving services to assist with the installation of a wall between Bays 8 and 9 of The Dalles Dam on the Columbia River. The wall is intended to redirect the salmonids that are migrating downstream and increase their survival rate.

The wall is 10 feet wide and over 800 feet long,the last 150 feet of which is at an angle to direct the water flow into a deeper portion of the river. It is constructed of precast concrete segments that were installed in the spillway and onto a leveling slab built on the river bottom. The segments were set in place and leveled using jacking rods. Once level and in place,the next segment was brought in and the process repeated. After several of them were in place,divers tied the segments together with rebar dowels. Forms were then installed on the joints between and around the bottoms. Concrete was then tremied into the segments. This process was repeated across the stilling basin.

Where the wall extends beyond the stilling basin,a 15-foot-wide leveling slab was installed. The river bottom was cleaned of loose debris. An area that ran across the path of the wall was excavated,because the underlying rock was fractured and non-competent. Form work was lowered from the surface and fit to the bottom contour. Rebar doweling was drilled and epoxied into the river bottom where needed. Rebar mats were installed inside the form work. Concrete was again tremied in place.

The wall has been carried over onto the leveling slab in the same manner as on the stilling basin.