Appledore Engineering
Industrial marine terminals are an essential part of today's economy, so maintaining and repairing waterfront infrastructure is of extreme importance. This work requires specialized underwater inspection know-how and an in-depth knowledge of structural engineering practice. The underwater inspection field is where commercial engineer-divers do their most important work. The following example shows how underwater inspection teams help keep these facilities in safe working condition.

An inspection team of commercial engineer-divers from ADC member Appledore Engineering, Inc. (AEI) performed a routine inspection of a New Hampshire industrial marine terminal in October and November of 2003. The terminal consisted of a main wharf, associated walkways, auxiliary pier, and mooring structures, predominately along the shoreline.

The main wharf (circa 1948) consists of a 407-foot-long by 38-foot-wide reinforced concrete work platform on a steel superstructure supported by steel caissons. The auxiliary pier is an 18-foot-long by 20-foot-wide timber pier. This structure is used to support oil response operations on the Piscataqua River. The facility services coal and oil vessels or barges.

This inspection was to assess the general overall condition and identify repairs for the facility. It was broken down into three levels to best focus the team's efforts.

The level I inspection relied primarily on visual and/or tactile observations to identify gross deficiencies. The level II inspection consisted of removing marine growth at discrete locations to better assess the condition of the structures. The level III inspection used specialized equipment to assess the remaining structural capacity of key structural elements. The dive operations were staged out of AEI's portable dive locker.

Level I inspection of the terminal's main wharf identified scour at nine of 22 steel caissons. This scour exposed uncoated steel HP14x102 foundation piles within the steel caisson shells. There are five piles within each steel caisson shell that are driven to bedrock and are responsible for transferring crane and vessel loads into the underlying bedrock. These piles have no corrosion allowance, as they were never intended to be exposed to the environment.

AEI engineer-divers used an underwater ultrasonic thickness meter to determine that the piles had corrosion losses on average of six percent from their original section. AEI engineer-divers recommended repair methods to fix this deterioration that will be carried out by a marine contractor at a future date. This was the first inspection that had identified the significance of the exposed foundation piles. Level I inspection of the auxiliary pier indicated approximately 50 percent of the timber-bearing piles had advanced deterioration due to marine borer attack. This deterioration progressed from the interior of the piles and was not visible until it had progressed to a critical stage.

AEI engineer-divers performed Level III increment cores to assess this hidden deterioration on the piles, still retaining the outer shell and caliper diameter measurements on piles that had lost the outer shell. AEI recommended the auxiliary pier be reconstructed, which will also be carried out by a marine contractor.

The previous inspection did not take cores and rated the pier in good overall condition, failing to detect the hidden deterioration, thus underscoring the importance of specialized level III testing.

AEI engineer-divers were able to efficiently evaluate the underwater structures at this site having the knowledge, experience and training required for this specialized discipline. The most common mode of failure for waterfront structures occurs from problems with the underwater support system and it is imperative that the divers have an expert understanding of what is and what is not important when performing such a task.

Appledore Engineering has a crew of 17 engineer-divers on staff, most holding advanced degrees in the specialty fields of civil, structural, and ocean engineering. AEI has performed over 500 underwater facility assessment inspections around the world for the US Navy and US Coast Guard.

AEI's President, Lawrence J. Wagner, PE, and Vice President, Robert M. Snover, PE, are ADC-certified commercial divers. Each has more than 35 years of diving experience and are actively engaged in all the company's waterfront assessment projects.

WJ Castle & Associates
In February 2003, WJ Castle, PE & Associates was retained by the Burlington County Bridge Commission to perform an emergency underwater inspection of the timber fender system at the Tacony-Palmyra Bridge, which crosses the Delaware River and connects Pennsylvania and New Jersey.

The fender was located at Pier E on the west side of the main shipping channel. Heavy ice flows and build-up caused serious damage and resulted in the loss of the upstream fender section. This end section was constructed of extensive timber pilings and heavy cross-bracing with concrete encasement, weighing approximately 175 tons.

WJ Castle's inspection found that the nose of the fender had totally separated from the rest of the fender and was lying along the bottom in the main channel, a potential hazard for boat traffic. Due to the location, the US Coast Guard partially closed the main channel, which limited the size of cargo vessels that were able to travel upstream. Therefore, the complete removal of this fender section was required as soon as possible.

Castle provided the engineering necessary to analyze the procedure needed to remove the nose section and the construction management for the entire project. Castle affiliate, Hydro-Marine Construction, provided all the underwater construction and dive work.

Since the debris was too large and heavy to pick up in one piece, several smaller sections were cut with the use of hydraulic equipment such as chainsaws and concrete chipping hammers. Timber piles and walers were also cut off to free the fender from the channel bottom. Castle then had to analyze the position and weight of the remaining sections to be lifted. The smaller sections, with weights up to 15 tons, were wrapped and lifted by cable slings and shackles onto a debris scow by use of a 120-ton crane mounted on a barge.

The remaining section, weighing approximately 148 tons, was lifted by use of a special 300-ton barge-mounted crane. All 35 timber pilings that had been either cut off or snapped off were removed from the channel bottom.

The maximum depth of the water was 55 feet (17m), with strong tidal currents and no visibility. The US Army Corp of Engineers performed a sidescan sonar survey upon completion of the work to verify the removal of the entire section and debris.

For more, visit www.wjcastlegroup.com.

Moscow Dive Center
Russian ADC member Moscow Dive Center (MDC) has worked as an inspection and diving contractor on the building of a gas pipeline across Russia's Enisey River for the past three years. The unique project featured very severe weather and work conditions.

The pipeline was to be constructed at the Enisey's estuary arctic oceanfront, in the northern part of Siberia. The estuary was more than 7,200 feet wide. Water velocity reached five-feet-per second at depths to 197 feet (60m), with high winds and 10-foot waves. The MDC crew had to work through the winters, in extremely low temperatures. And on top of all that, there is shipping route of atomic ice-boats through that part of the river, with year-round navigation.

This pipeline crossing involved the open trench method, with two trenches, each 23 feet wide and 16 feet deep. The work plan was created in November 2000, and the MDC fleet was mobilized for the job in June 2001. MDC used an 800Hp towboat, a derrick barge, and two diving vessels with 150-ton winches.

For digging the trenches, MDC used a hydromechanical scraper made specifically for this project. It was a challenge to dig into the bed of the river because of the permafrost. Also, underwater inspections of the loamy river bottom by the MDC divers showed that it was covered with boulders and pebbles.

MDC's crew ran the scraper 24 hours a day. The scraper was pulled with two winch cables, which stood on different sides of the river. Despite the large diameter of the cables, the harsh conditions broke them repeatedly. Each time, divers were sent out in search of the cables, and they were recovered for splicing.

The scraper also had to be lifted up to a barge for repair work, which was especially difficult because of frequent storms. The next phase was laying the gas pipeline. Unfortunately, this portion of the job came during the period of freezing over the river. However, with an organized plan and staff, MDC succeeded in finishing the pipelay operations just one day before the ice came.

But this was not the end of the first phase.

Because of a technical mistake, divers had to manually aid in the unloading of pontoons. The air temperature varied from minus-40 to minus-10 degrees centigrade, and the ice thickness was six feet (2m). This part of project had to be completed before the flood waters came, so from late March until mid-May 2002, divers corrected a total of 64 pontoons.

The second phase began in July 2002. Because of an early fall and winter, the MDC had to work through the winter using heavy machines on the ice. MDC finally completed this incredibly difficult inspection, diving, and construction job in May of this year.

Subsea Technology Ltd.
Third-party inspections have long been part of a sound management plan for managing underwater infrastructure. In May 2003, BP China contracted Subsea Technology Application, sister company of ADC member Asia Divers, for inspection services on the Liuhua 11-1 Project in the South China Sea.

Subsea Tech is tasked with ensuring that diving contractors hired by BP China adhere to the correct diving and safety standards. Subsea Tech has developed an auditing system made based on the ADC Consensus Standards.

During the tendering stage of the project, Subsea Tech was asked to assist BP China to assess the proposed methods and equipment to be deployed by bidding diving contractors. Subsea Tech ensured that the quality and safety documentation submitted by the selected candidates complied with the ADC Standards. In performing this auditing service, Subsea Tech examined each bidder's diver qualifications and physical fitness, diving equipment condition and quality, diving plans, safety manuals, and emergency plans.

After the appropriate diving contractors were selected and approved by BP China, Subsea Tech continued the audit process, ensuring ADC compliance prior to the loading of diving equipment to BP China's worksite. Daily audits are carried out to make sure the diving contractor is complying with the approved procedures, diving plan, safety manuals, emergency plans and equipment.

BP China's goal in this ongoing inspection process is to ensure the safety and efficiency of the commercial diving contractors it hires on the Liuhua 11-1 Project.

Spain's STS
Spanish ADC member STS (Servicios Tecnicos Subacuaticos) was established in August 1993 by qualified professionals with more than 20 years of experience in the commercial diving industry. Their goal is to serve a growing market in the straight of Gibraltar, as well as other Spanish or foreign ports.

STS applies the most up-to-date and advanced techniques on underwater inspections and repairs.

On a recent emergency job, STS inspected a super-tanker vessel anchored at Algeciras Bay, south of Spain, in may 2003. Several permanent underwater DNV-approved repairs were carried out due to cavitational corroded pitting holes located on the vessel's flat bottom stern area.

Divers secured one steel cofferdam to repair the damaged area internally. Coded diver/welders cropped one section of flat bottom shell plating and welded one 400mm x 400mm x 22mm certified "insert" plate. NDT methods to inspect the welding seams step-by-step for surface welding indications were used.

Follwing the internal work, STS divers removed the steel cofferdam and inspected full penetration close-up with a closed-circuit TV system in order to get class approval.

On another Algeciras Bay project, STS inspected an FPSO in January 2003. Underwater video inspection was used in lieu of dry docking. Repairs included underwater propeller polishing and replacement of two 62-ton azimuthal thrusters.

SeaView Systems
SeaView Systems, based in Dexter, Michigan, considers itself the new kid on the block in the world of inland ROV operations. After many years of offshore ROV experience, SeaView is looking to establish itself as a leader in long distance pipeline inspection.

As part of its pipeline inspection capabilities, with penetrations up to 5,000 feet, SeaView Systems operates a SeaBotix LBV150 ROV. The LBV provides the ability to take video in confined locations and in environments that would not be safe for a diver.

Ohio's Underwater Marine Contractors recently approached SeaView Systems to perform an inspection of the water inlet cribs and risers of a nuclear power station. This was the first phase of a 3,000-foot inspection project performed for the nuclear facility.

The work required a thorough visual inspection of two vertical risers and a connection tunnel, as well as a 300-foot penetration into the main water inlet tunnel to shore. SeaView was to check on the degree of zebra mussel infestation and monitor any possible resulting restriction, as well as assessing the general structural condition of the crib, risers, and horizontal tunnels.

Being mid-summer, the powerplant was operating near full capacity and drawing in water at a rate well in excess of two knots. This presented a challenge to control the ROV in a manner that would still provide a steady platform for the required visual inspection.

In order to counter the water current, an Underwater Marine diver entered the inlet crib and rigged a fairlead over the center of the submerged vertical riser. The ROV's umbilical was led through this. A 3-point bridle was fitted to the vehicle so it could be maneuvered in the horizontal plane, while the diver handled the umbilical to control the vertical component. Both of the risers were thoroughly inspected by performing overlapping runs.

In addition to the vertical risers, SeaView was required to inspect a horizontal connection tunnel and 300 feet of the main run to shore. For this portion of the inspection, the vehicle penetration depth was controlled by the diver tailing the umbilical as it passed through the fairlead rigged at the top of the riser.

Once again, each tunnel was thoroughly inspected by performing multiple passes at three-, six-, nine-, and 12-o'clock positions. The entire water inlet construction was visually inspected with the facility running at near full capacity.

This inspection illustrated the way in which ROV and diver can form a synergy and achieve tasks that would not be possible by either one alone. The ROV umbilical could not be adequately controlled from the surface, but required a diver to control it from within the inlet crib. Likewise, the diver could not safely work in the current at that depth, but required an ROV to perform the actual penetration and inspection tasks.

There is some irony to this case. Once the inspection was complete and UMC's vessel was returning to shore, one of the power plant engineers onboard excitedly pointed toward the facilities exhaust stack, noting that there was no steam being issued.

It just so happened that the inspection fell on August 14, 2003 - the day the northeastern United States and parts of Canada went dark. Had the team waited a few hours later to start the inspection, we could have performed the inspection in an almost zero current - a very rare situation for a nuclear power plant.

Commercial Dive Services NZ
New Zealand ADC member Commercial Dive Services NZ (CDSNZ) was contracted to design, install, and inspect a waste product distribution system to meet government regulations. The client required a relatively quick installation time for the outfall pipeline, and also wanted a design that could be modified at a later date.

Situated on the west coast of the New Zealand's North Island, the job site's long shore currents and drift are sometimes extreme. Another problem was that no drilling could take place due to the pipeline being cable-strained.

This left CDSNZ the option of a quick-to-fit flange, and the design experiments began. After a few attempts, a prototype flange was designed using three different angles of pipe. The CDSNZ team installed these and let nature take its course.

The first inspection of the newly installed flanges took place after a week-long 40-knot southerly tide had pounded the pipeline. The design had a 22.5-degree bend and a foot leg securing it. The divers found the leg system tightened well and, after a settling period, the upturned stick pins on the legs had bitten into the internal concrete lining on the pipe. They were then secured with a lock nut and were there to stay.

An important feature of the flange design was to have a rubberized gasket at the base. From closed-circuit video inspections, the CDSNZ crew was able to determine that the gasket provided a small cushioning effect and did not allow structure crack on the base of the flange. Also, the flanges can be easily altered, as requested by the client. The next step will be a cold cut and Duct-bills to be fitted. This will be done without upsetting the placement of the system.

Since that particular job, Commercial Dive Services New Zealand has been contracted to install the same type system in other areas. The team reports that it seems easier each time they perform the operation.

MagnaPatch Gulf
"If a picture says a thousand words, then Tapetum just wrote a novel," said one engineer when viewing the results of Tapetum zero-visibility imaging.

MagnaPatch Gulf has been using its Tapetum sonar for several months, inspecting dams, bridges, sunken vessels, and wooden wharves. Most recently, the Tapetum sonar system was used to inspect a broken piling for the Port of Houston Authority.

Like most ports, the Port of Houston Authority experiences zero or near-zero visibility conditions most of the time. On most imaging projects, the Tapetum system is handled by divers. For this project, the MagnaPatch Gulf response vessel Triton and an ROV were outfitted to guide the sonar and recover the images.

Above water, the damaged piling could be easily seen. However, its condition below the water was unknown.

The resulting Tapetum inspection showed damage that was unsuspected by the Port Authority, was not part of the job description, and would have been difficult for even a diver to discern.

Behind each frontal pile cap existed four support piles. Three of these were shown to have received considerable damage, thus confirming the extent of the repairs that were required.