Project Tag: Diving Services

Capitol Lake Targeted Dredging

While attempting to steal copper, vagrants damaged a disused electrical transformer located within a former brewery building. This caused the release of more than 700 gallons of electrical insulating oil containing polychlorinated biphenyls (PCBs) into the adjacent Deschutes River. The oil traveled downstream into the 260-acre Capitol Lake in Olympia, contaminating the bottom sediment and …

Anode Installation for Juneau, Alaska Cruise Ship Terminals

As the cruise service between the Pacific Northwest and Alaska increases so does the need for additional berthing and dock space. To accommodate this growth,Manson Construction was awarded the contract to fabricate and install two new cruise ship terminals in Juneau,Alaska.

The terminals are comprised of 2,331 new steel pilings,after being driven into place each requiring a sacrificial anode welded to the piling. Global was subcontracted to perform this challenging and critical aspect of the project. The anodes,ranging in weight from 216 to 260 pounds,had to be installed in accordance with AWS D3.6 welding standards at various depths,up to 105 feet below the water line.

Global personnel worked hand in hand with Manson’s project staff to minimize the impact on the project schedule. The crew successfully installed all anodes on a complex array of piles,in adverse conditions,without injury while maintaining the tight schedule set by the client.

El Segundo PLEM Buoy Repairs

Chevron has two product transfer moorings (PLEM),approximately 2 miles offshore of El Segundo. Global provided diving services and topside support for the replacement of hoses,buoys,and connecting components.

Cresta & Rock Creek Dam Survey

PG& E contracted Global to perform surveys of four concrete chambers at two separate Dams; Rock Creek Dam and Cresta Dam both located on the North Fork of the Feather River in Northern California. The concrete basins are approximately 25 feet wide by 124 feet long. Global divers accessed the structures through a trash rack and 48-inch inlet; which added an additional obstacle. The total penetration through the pipe and into the deeper area was approximately 35 feet,plus the additional 124 feet to the end of the chamber,necessitated an in-water tender for every dive.

A probe and a scanning sonar were utilized to conduct the surveys and determine the depths of the built up sediment. At Rock Creek,a Steel Wire Rope was established inside one of the chambers approximately 5 feet off bottom. This enabled an MS 1000 sonar to be suspended in order to scan images of the chamber every 5 feet for the entire length.

Inside the same trash rack a 24” pipe was inspected utilizing an ROV; two gate valves had been previously discovered by PG & E engineers to be non-functioning. These 24-inch pipes bifurcated about 25 feet inside the center pier and split off to both chambers supplying water to keep the gates afloat. It was suspected that the pipes and the valves were full of sediment deposited from upstream.

A thorough report providing the data obtained from the sonar images and the probe measurement was provided to the client upon completion of the project.

Inland Drilling Shaft Extraction

The contractor was digging multiple vertical shafts to a depth of 250′ in a vacant city lot in downtown San Francisco. These shafts are to form a ‘bulkhead’ to prevent soil movement,while excavation for a subway station and California’s future ‘high speed rail line’ is completed on the work site. The casings are filled with water during the excavation to resist surrounding ground pressure. During the extraction of a casing,the sections separated at three locations,120,145,and 170 feet.

Divers were lowered down the 84 inch diameter excavated casing in a man basket to a water depth of 170 feet. Repair options included welding the casing sections together or drilling through the section overlap and installing steel ‘plugs’ to lock the sections together.

The repair was successful and the casing was removed.

Poe Dam Inspection

Divers set up templates and created an as-built drawing of the dam so that PG&E contracted engineers could fabricate a truss type stop log. This installation would support the work and repair of radial gates and additional work. A shallow air surface supplied dive spread was used to take many measurements using a custom designed aluminum jig.

Line 400 Depth of Burial Survey

The purpose of this survey was to determine the elevation of the two 26″ pipelines that comprise the Line 400 Sacramento River pipeline crossing,and the 22kV cable river crossing at the Rio Vista Bridge. After being uncovered by the Derrick Barge,which utilized a 12″ Air-Lift,Global was contracted to take pneumofathometer readings at the top of the pipes. This was necessary in order to identify the cable and pipeline depth for upcoming navigation channel dredge work. If pipelines were established to be at too shallow a depth,the pipeline and cables will subsequently need to be relocated.

Pile Cutoff at Hunters Point

We were contracted to survey,locate,and burn off an assortment of 20 inch diameter steel pilings,during the demolition phase of a pier at an old US Navy Base at Hunters Point in the San Francsico Bay; a ‘superfund’ site clean up. A four-man crew was dispatched and spent 2 long days searching in zero visibilty conditions,marking targets with buoys,and eventually cutting off and retrieving the piles,which ranged from 10′ to 38′ feet long.

Olive Ranch Valve Replacement

We were hired to perform a 12″ valve replacement located in a briney pond at an olive ranch. The first task was to remove a trash screen so that one of our divers could entered a vault,burn off 12 bolts,and replace an existing 12″ slide gate valves with a blind flange until the new valve could arrive.

Upon delivery the two new valves,the dive crew will return,take off the blind flange and replace it with a new valve. In addition,a second old valve will be removed and replaced.

Alaska Bridge Inspections

Our divers traveled throughout Southeast Alaska performing underwater inspections on marine and fresh water structures. Divers inspected for timber decay,missing sections of the structures,scour,and any damage.