Project Tag: Dive Control Vans

Dix Dam Face Slab Repair

Upon completion in the mid 1920’s,Dix Dam was the largest rock filled dam in the world standing approximately 287 feet above the riverbed. It was built in the private sector by it’s current owner,Kentucky Utilities Company,to create a reservoir for operating a hydroelectric generating station.

Global was selected to perform and manage repair work to an existing earth filled dam. Divers removed debris including cars,trees,and sediment from several areas of the dam and then these areas were surveyed using sonar and tactile methods. Damaged areas of the face slab were covered using sheet membrane secured to the face of the dam. Work took place in up to 140 feet of water.

Seawater Intake Lines – Modification & Cleaning

Global Diving & Salvage,Inc was the prime contractor / project manager responsible for the modification and cleaning of the SeaLife Center’s intake lines. The first phase of the project was to install a pig launcher system; tasks included dewatering the Center’s wet well,installing an isolation valve between the well’s chambers,and saw cutting new access holes in the pump room floor.

The second phase of the project consisted of the dive crew cutting a 24 inch HDPE pipe and lifting it out of the soft bottom material to allow for an ROV inspection of the intake pipe. The inspection was short lived as the pipe was impassable due to marine growth and sediment. In order to clean the lines,several cleaning pigs were launched to remove the blockage. A new intake screen and support structure was installed along with a remotely operated pig catcher.

Dive crews worked off of a barge with a 150 ton crane and four point mooring system that was strategically anchored over the buried intake support functions. A deep gas dive system was utilized to accommodate dive operations in up to 260′ of seawater. The final quality control inspection was performed by an ROV flying over 200′ up the pipe to inspect for marine growth and debris.

South Timbalier 196 B – Platform Removal

We provided surface diving support aboard the D/B Superior Performance to assist,as needed,with the removal of the topside package and platform jacket. Dive work was performed down to 105 fsw using standard surface diving procedures.

The platform was initially cut free from the jacket then the legs were cut 15 feet below mud line using explosives. After all the legs had been severed,the platform toppled onto its side so that the D/B Superior Performance could pick up the structure,approximately 710 metric tons,and set it on the materials barge for transport to shore and proper disposal.

Bay Tunnel – Ravenswood Portal

We have been contracted to assist with the underwater construction of a launch portal for the new Bay Tunnel. Diving is being conducted to depths of 130 fsw in zero visibility. The crews are installing rebar dowels,rebar mats,and assisting with the tremmie pour of a ten foot thick concrete floor. After the tremmie pour is complete the shaft will be de-watered in preparation for the tunnel construction. Upon completion of the shaft the horizontal tunnel under San Francisco Bay will be drilled with a Tunnel Boring Machine.

BART Transbay Tube Support

Global is providing diving assistance in the removal and replacement of anode cable and anode arrays for the BART transbay tube. The work is being performed as part of ongoing maintenance for the tube. The divers are utilize dredges and airlifts with the derrick assistance to remove up to 30’ of bay mud covering the tube to access cable penetrations. Fourteen of the anode arrays are schedule to be replaced in depths down to 130 feet. Project challenges are the bay currents and the water depth.

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.

Cheesman Dam Upstream Control Project – Phase 1

Cheesman Dam,located at 6,842 feet of elevation,is a primary reservoir for Denver Water who provides the potable water to Denver,CO and surrounding areas. Completed in 1905,it was built by Italian Master Masons using finely set and mortared granite blocks. Cheesman was a technological masterpiece and landmark of civil engineering for decades to come.

The Upstream Control Project,Phase 1,encompassed the replacement of three internal gate valves with new hydraulic slide gates located on the upstream face of the dam. The first step was to upgrade the existing Auxiliary,Mid and Low Level outlets,located at 60′,150′,and 200′ deep respectively.

Diver’s worked off of 80-foot by 80-foot sectional barge platform on the reservoir. Due to the depth and the amount of work required a combination of surface and saturation diving was utilized. The Auxiliary level work was done using surface supplied air while the mid and low level outlet work was done using saturation diving.

The original bypass outlets,tunneled through the canyon wall,were enlarged to accept new stainless steel spool pieces,one weighing 29,000 pounds and other two weighing 14,000 pounds each. Divers drilled holes at predetermined location and used underwater explosives to enlarge the openings to accept the new spool pieces. The spools were installed just inside the canyon wall,secured in place with epoxy anchors drilled into the native material,and securely grouted to provide a leak free seal. The new stainless steel slide gates were then mounted to the face of the spool pieces and protected by trash racks to prevent rubble from entering the intake system.

The new valves are operated from a new control structure built on the crest of the dam. This structure houses the hydraulic pump unit and controls which operate the valves. To connect the hydraulic tubing to the valves,holes were drilled from the crest of the dam,exiting into the reservoir next to the gate locations. Hydraulic tubing was installed into the holes and secured in place with grout,connecting the controls on the surface to the individual valves.

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.

Olmsted Lock and Dam

We have been contracted by the Washington Group to provide diving and dive related services as required in the building of Olmsted Dam on the Ohio River. After studying various dam construction methods,the Corps of Engineers (COE) decided to use an innovative method known as “In-the-Dry” for Olmsted Dam. Basically,sections of the dam known as shells are prefabricated on shore in a precast yard and carried out into the river and set in place. The dam consists of two primary areas; the tainter gate section and the navigable pass section.

Mercer Island Sewer Line and Pump Station #4 Replacement

The existing sewer line on the northwest corner of Mercer Island was installed in the mid-1950s,and is constructed of asbestos-cement (AC) material. The line has been suffering ongoing pipeline deterioration,capacity deficiencies,and other operation and maintenance problems. Manson Construction was awarded the contract to replace this portion of the sewer line with cast iron pipe and selected us to provide the diving services. This project will extend over a two-year period and involves the replacement of over 7,000 feet of pipe with 32 side sewer connections.

We are working very closely with Manson during all aspects of the project,including: installing both gravity and force main pipes,aligning and connecting the side sewer piping,assisting with hand dredging under docks and in tight areas where the derrick cannot access,and making the physical transition from the existing line to the new piping.