Project Tag: DSV Sand Island (Anchorage)

Christy Lee Oil Platform Fender Repair

In early March of 2012,the north fender on the Christy Lee oil platform,owned and operated by Hilcorp,experienced mechanical failure which caused it to plunge into approximately 80’ of water in the Cook Inlet. The fender structure mechanically raised and lowered with the tide to keep visiting tankers properly fended during calls. The timeline for a prompt solution was critical,as delaying the arrival of tankers to the Christy Lee would subsequently result in substantial monetary loss.

Global used sonar equipment to determine the exact location of the damaged fender and its orientation on the sea floor. It was concluded that there was sufficient water depth above the fender to allow vessels to continue to call at the berth; however,a temporary system would need to be devised in order to keep the platform operational.

Global developed a plan to install a temporary fender,which consisted of assembling a Flexi-float barge system that would encompass both of the north legs of the platform and span the gap left by the missing fender. It was evaluated by our internal engineering staff and was verified by a third party engineering firm. Global successfully mobilized,fabricated,and installed the temporary fender system in just over two weeks,three days prior to the arrival of the next scheduled tanker.

In July,Global remobilized to the platform to recover the sunken fender. Constructed by a steel framework with a timber face and concrete counterweights,the fender is trapezoidal in shape and measures approximately 96’ long,30’ wide,and 8’ tall,and weigh 175 tons. Divers rigged the fender for removal,taking advantage of the short slack tide intervals between 3.5 knot flood and ebb currents. Global subcontracted Pacific Pile & Marine to provide a 500 ton crane,mounted on the barge “Salvation”. The 175.5 ton fender was lifted from the seafloor and loaded onto the deck barge “Mr. Ed”. It was then transported to the ASRC dock in Nikiski,AK where it was offloaded onto the pier,flipped over,and set down for repairs.

Upon completion of repairs,the fender was transported back to the site for reinstallation. Once onsite,the “Salvation” lifted the fender and set it into a ‘stored’ position on the platform,allowing the temporary fender system to be dismantled and removed. The repaired fender,already secured to the platform,was then lowered into its permanent place and the concrete counterweights reattached. The repaired system has been fully operational since mid-October.

“Not an easy feat for a project team to consistently rise and meet numerous challenges over many months. A remarkable project executed remarkably well by remarkable people across the board” said Bo York,Hilcorp Facilities Engineering Manager.

Remote Alaska Tug and Barge Salvage

Global Diving & Salvage,Inc. was called to respond to the grounding of a tug and barge on remote Ukolnoi Island,one of the Pavlof Islands situated within the Alaska Maritime National Wildlife Refuge near Pavlof Bay. Global mobilized two salvage masters,a salvage engineer,and salvage technicians as well as local responders to the site. Three towing vessels,one spill response vessel,a hydrographic survey vessel,two barges,two landing craft,two dive support vessels along with specialized salvage equipment were mobilized and participated in the operation. The exposed area required careful staging of personnel and equipment to be able to take advantage of weather opportunities as they arose.

Working closely with the client’s personnel,the bulk of the 97 containers were removed from the barge to lighten the ground reaction. All frozen containers were kept frozen and all cargo was salved. 14,000 gallons of diesel fuel were removed from the tug before temporary repairs were affected and it was refloated. Compressed air provided by specialized high capacity salvage blowers was used to refloat the barge due to the condition of the bottom plate. Both vessels were taken to safe harbor for final disposition and repair.

Cook Inlet Spartan 151 Jack-up Rig

Operating from Global’s DSV Sand Island,divers performed an underwater survey of the spud cans on the Spartan 151 Jack-Up rig. Divers removed the well cap from the well head stub and then assisted in the installation of a overshot riser.

Work was completed in the Cook Inlet,an area notorious for up to 30-foot tidal swings and zero visibility water. Water velocity was measured using a Doppler Current Profiler and limited bottom times to 30 – 45 minutes per tidal swing.

Lift Bags Raise Sound Developer Derelict

The Sound Developer was an ex-US Navy landing craft that was 132 feet long overall. She had a beam of 29 feet and a normal draft of 5 feet. The US government sold the vessel at auction and the ship passed through several owners before falling into neglect which ultimately ended with the derelict sinking at her moorings in the harbor at Cordova,Alaska in august of 2009.

Shortly after the sinking the US Coast Guard activated Global Diving & Salvage through the established Basic Ordering Agreement (BOA) contract. Global mobilized resources to Cordova where the pollution threat was mitigated through the removal of the copious oil filled containers,batteries and other HAZMAT. The US Coast Guard then worked through a nearly 2 year long process seeking Headquarters approval to refloat the vessel,transport it to shore and deliver it to the City of Cordova for dismantling and disposal.

Upon receipt of approval the US Coast Guard solicited competitive bids to affect the recovery. Through this process Global was contracted by the USCG to remove the pollution and navigation threat from the Harbor,move it to an area onshore outside of the harbor and perform gross decontamination of the vessel.

Due to the remoteness of the location,no heavy lift assets were available. A plan was developed to utilize lift bags to raise the vessel,secure it for the short tow out of the harbor to the designated shore position.

Divers secured a total of 31 lift bags that were used to raise the vessel: 24 – nine ton; 5 – five ton and 2 – twenty two ton bags. The lift bags were strategically placed and secured to the hull.

All the lift bags were connected to a manifold,from which all inflation / deflation operations were carried out under the supervision and at the direction of the salvage master.

Once afloat the bags were further secured to the vessel and made ready for the open water tow to the beaching area outside the harbor. The vessel was placed aground at high tide and was shifted further ashore through subsequent tide cycles.

The operation was timed to coincide with the highest tides of the season to ensure it would be brought on shore as high up the beach as possible. This phase of the operation was complicated by extremely challenging weather conditions that impacted the schedule and the work conditions.

Once the Sound Developer was safely secured on shore,Global conducted further cleaning and gross decontamination. The vessel was inspected and cleared by on scene US Coast Guard personnel and custody of the vessel was transferred to the City of Cordova.

Pipeline Abandonment

Global mobilized a four point mooring system and a deep air diving system onto a landing craft. The vessel was then moored 40ft from the leg of a production platform and directly over a sub sea oil and gas manifold. This required anchor operations to conducted in 3 pipeline corridors and near an active production platform. The project involved installing several hot tap installations and disassembling and re-assembling various spool pieces of the subsea manifold,which aid in the ability to utilitize cleaning pigs in both lines from the platform. All this was done without interrupting flow thought the manifold or operations on the production platform that it is connected to. This project was performed in Cook Inlet that is typical has zero visibility and tidal current in the excess of six knots

Cook Inlet Installation of Anode Sleds

Divers installed 4 impressed current anode sleds on a platform in Cook Inlet,Alaska. The four legged platform sits in 200’ salt water,all failing anode cables were removed from one of the north legs,and replaced with a new anode and cable. Two of the remaining three anode cables were routed through an unused riser tube in the SW Leg,and the remaining anode cable was routed through a unused riser tube in the south east leg. Divers,the DSV Sand Island,and a topside platform rigging crew were utilized to position anode sleds on the seafloor utilizing its on deck anchor winch.

Platform Inspection

Our inspection of the this platform included high pressure cleaning of weld locations for inspections and concurrent black-water photography for the client’s records.

Abandoned Pipeline Decommissioning

A 19-mile AMOCO pipeline was legally abandoned in 1974,but subsequently began leaking in 2001. We were hired to decommission the Cook Inlet pipeline after multiple leaks were detected. The project required installing underwater hot taps,pipeline alignment,excavation of buried sections,and attaching surface suction lines to an anchored barge. Divers using a Broco torch then severed the pipes and fresh headed with a hydraulic guillotine saw.

The divers then installed 400 lb hydraulic clamps at each cut,and a subsea pig launcher was connected. The pumping of a gel train through the 10-inch pipe for internal cleaning was prevented by multiple breaks in the heavy wall pipeline. Instead hot taps were installed to provide a method to vacuum the line contents to vac trucks located on the support barge. The sequence of events was repeated a number of times at the line high points to complete the cleaning of the entire line for accepted abandonment by the ADEC and EPA.

This work was completed in zero visibility during the slack tides in Cook Inlet,known for its extreme tide range of approximately 40 feet difference between high and low tides.

Subsea Pipeline Spool Piece Installation

We were hired to replace a pipeline spool exiting on one leg of the production platform Grayling located in Cook Inlet. The project required taking ultrasonic thickness readings and blackwater video pictures of various components.

The project involved removing pipe sections,measuring replacement pieces,and installing the new surface-fabricated steel pipe replacement pieces. Hydraulic stud stretchers and hydraulic impact wrenches were used to take apart and replace the flange bolts. Re-tightening the flange bolts required following an exact torque sequence.

The two replacements were completed in approximately a working depth of 140 feet of sea water.

Pipeline Riser Conversion

The project required the use of two hydraulic guillotine saws,hydraulic grinders,and impact wrenches. We “fresh headed” the pipeline using a torque connector,then had the associated spool piece measured,manufactured,and installed during a six day period. The subsea portion of the project was completed four days ahead of schedule.