Great Egg Harbor
Method(s) Used: Underwater Cutting
Location: Ocean City, NJ
In September 1999, Kiewit/Tidewater, AJV began constructing a new 3,450-foot-long bridge over Great Egg Harbor in Ocean City, NJ adjacent to an existing bascule bridge. The new structure had battered (angled) piles that required precision cutting underwater to complete the new bents. Kiewit contracted In-Place Machining Company to complete this unusual job.
Precision Underwater Cutting Required In Great Egg Harbor
The job required precision cutting of 82 pre-stressed concrete cylinder piles, which would support the new bridge structure. The hollow piles were 54 inches in diameter and driven deep into the tidal floor at an angle. In order to cut the piles correctly, In-Place Machining needed to find a way to make a precision cut below the surface of the water, severing pre-stressed reinforcing strands and spiral-wrapped rebar, while also preserving the structural integrity of the piles. The elevation of the cut also needed to be closely controlled. Because the piles were located in the harbor, this limited-access job also required a saw that would work consistently in salty underwater conditions.
In-Place Machining conceptualized a modified wall saw on a circular track that would perform in underwater conditions. They contracted with CSDA manufacturer member Diamond Products, Elyria, OH, to create a modified wall saw and track. To facilitate shop fabrication and testing, a 54-inch-diameter, hollow, pre-stressed concrete pile was shipped to Diamond Products’ shop in Ohio. Diamond Products modified a DZ Wall Saw and created an I-beam guide rail circular track customized to fit around the concrete pile. Special guide rollers were needed to hold the saw onto the circular track. They also added additional remote operation capabilities, blade indicators, and hydraulic-actuated stabilizers at the request of Kiewit and In-Place Machining Company.
To begin the cut at each pile, a crane operator lifted the entire support platform and modified wall saw, lined it up with the pile to be cut, and carefully lowered it into the hollow core of the pile. This was somewhat difficult, as the piles were set at an angle in the water. After lining up the saw and setting the actuator pistons for the track, operators began the cut by making a 1-inch-deep, 360-degree pass around the pile. Operators then made a second 360-degree pass, cutting an additional depth of 2 inches. They completed the cut with a third pass, making the total cut 6 inches deep. A total of 82 piles, in groups of four, six, or eight per bent, were cut with this timesaving machine. Typical cuts were made in one hour versus several hours with hand tools and a dive team. Kiewit confirmed that significant time and money were saved with this unique diamond-cutting saw.