Project Tag: California

Pit 5 Instream Flow Release Modifications

Global Diving & Salvage,Inc. was contracted to install nine 18” x 44” outlet gates on the upstream face of four existing wheel gates. The design required that the new gates be installed in a water depth of 20’. To accomplish the work Global provided engineering and cofferdam design of two 25 foot tall cofferdams which had a radius of 4’. The cofferdams were fabricated in the bay area and shipped to site where they were utilized.

To accomplish the work Global certified underwater welders installed pad eyes on the upstream face to attach turnbuckles. Willliams undercut anchors were also installed to provide hold down capabilities. After installing the cofferdams and working under confined space and fall protection regulations Global’s surface welders cut openings and installed bow outlet pipes,gates,and operator platforms on the upstream face. The work progressed and the cofferdams were moved from site to site. All work was tested and installed to clients high expectations. The work was completed on time and within budget.

Pit 4 Cofferdam Installation

Global Diving & Salvage,Inc. provided a dive crew to install and seal a 25’ x 15’ wide cofferdam to the face of Pit 4 Dam. The installation required the removal of 5.5 cubic yards of concrete. To accomplish the removal the divers utilized rivet busters,sinker drills and rock splitters. After removal of the concrete the cofferdam was installed with almost 40 epoxy anchors which were pull tested prior to tightening. The cofferdam is being installed to allow for a new 8 foot diameter penetration and gate through the existing dam. A new intake structure will subsequently be installed.

Natural Gas Pipeline Replacement

As a subcontractor to ARB,Inc.,we performed marine operations on the replacement of 1,000-feet to an existing gas pipeline project. The project was performed to allow for seismic retrofit and replacement of a portion of the Bay Bridge. We headed the marine portion of the project along with a team comprised of Fugro West for navigation,CS Marine for barges and derricks,and Longitude 123 for project management,plans and permitting.

We provided crew boat services for the marine operations and diving support throughout the project. The project required dredging more than 1,000 lineal feet of live gas pipeline with an existing burial of over 10 feet. Dredging was conducted within extremely stringent turbidity control. To meet these demands,we provided a Toyo suction-dredging system and the material was pumped into a sealed barge. The dredge material was transported to an offshore disposal site where it was pumped off. The amount of material was in excess of 43,000 cubic yards.

Other aspects of the project included assisting with the lifting of existing gas lines after ARB directionally drilled out to a casing placed at the exit hole. We provided all offshore handling of the new 1,000-foot segment.

After the new pipeline was installed and tested,the old segment was removed and the new line backfilled.

Point Bonita Vessel Salvage

A sailboat drifted onto a shore losing its mast on the rocky coast line just north of the Golden Gate Bridge and Point Bonita Lighthouse. The stranding happened in an ecologically sensitive area. We were called in to asses the situation. We determined that the most expeditious method to remove the sailboat,before it was broken up by the surf,was to lift it with a helicopter. Once removed from the shoreline,it was set on a truck for transport.

French Meadows Low-Level Outlet Cylinder Replacement

We performed emergency repairs to a leaking hydraulic system. The repairs were completed at a depth of 175 feet at an elevation of 5,400 feet. With altitude corrections,diving depths were equivalent to 200 feet. To accomplish this task,we mobilized all aspects of a mixed-gas diving spread to French Meadows Reservoir in December,2006.

Together with PG&E personnel,we replaced the existing 14″ hydraulic cylinder and portions of the existing lines. After the replacement of the cylinder,the new cylinder and hydraulic required less than 1/3 of the original hydraulic pressure to operate the gate.

The project was conducted over a three-week time frame involving 25 dives without incident. We were responsible for providing cranes,barges,and environmental controls for the operation. The operational considerations included -30 below zero temperatures and extreme snow accumulations. A major concern of all parties was the potential release of hydraulic fluids into the lake.

All diving and operations were conducted safely and without incident in the extremely harsh deep-diving environment. Environmentally,the project was conducted without incident.

Canyon Dam Outlet Tower Stem Replacement

Pacific Gas and Electric contracted us for this stem replacement project. We replaced approximately 80 lineal feet of stem,including stem guides and roller assemblies. The existing stem was attached to the vertical slide gate with rivets that were drilled out,enabling re-utilization of the holes to exacting tolerances.

Canyon Dam Outlet Tower in Lake Almanor,CA stands in approximately 85 feet of fresh water at 4,500 feet of elevation. To perform the project,we mobilized a portable barge system,a surface-supplied dive spread with decompression chambers,and a 20-ton hydraulic crane to the lake. The crane was driven onto the barge to assist with removal and replacement of large stem sections.

To remove the existing stem,divers utilized a hydraulic-driven magnetic drill press. The project was performed safely,efficiently,and within budget. Upon completion of the stem replacement,the stem was tested and performed within tolerances.

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.”