Navy Channel Deepening Project Requires 50000 Feet of Discharge Line

Norfolk Dredging Company’s 10000 horsepower dredge Charleston is deepening five miles of the Navy channel in the Elizabeth River from Lambert’s Point to the Norfolk Naval Shipyard in Portsmouth Virginia. The 24-inch discharge line which began at 21000 feet long will eventually stretch for 50000 feet from the dredge to the Norfolk District’s Craney Island Dredged Material Management Area in Portsmouth.

When IDR talked to project manager David Smith (pictured on right page) on July 11 the pipeline was 34000 feet long.
To assemble a long pipeline “you start at the disposal area and go to the dredging area” said Smith “with an 11-man crew three workboats two derricks and an air compressor.”

It took them five days to set up the initial 21000 feet he said with pipe lengths that had been assembled at the company’s yard.

To begin with 40- to 60-foot lengths of new steel pipe were welded into 500-foot and 120-foot sections. The 120’s are loaded onto barges 42 to a barge and the 500’s are loaded into racks of 10 and pulled by a tugboat to the job site. The 500’s are used in shallow water and the 120’s in deeper water sunken to allow ship traffic. All are connected by Mobile Pulley ball joints for flexibility.
The derricks are specifically designed to handle the pipeline and the crew is unusually fast in assembling it. Adding line is done at the join of the floating and sunken line in 2500-foot lengths.

A maximum of two booster pumps will be added to the line though only one may be needed said Smith. Relief valves are installed at the pontoons and boosters to release air trapped in the system which would otherwise cause the pipeline to blow apart.