HII Projects

DD3 COFFERDAM – Newport News, VA

PROJECT DETAILS

The primary goal of the Newport News Shipyard Dry Dock 3 Cofferdam project was to construct a robust cofferdam system to facilitate underwater construction and maintenance activities at Dry Dock 3.

Precon has completed all requisite work activities, which included the demolition of existing underwater obstructions and utilities, as well as conducting a dive survey to ensure the removal of all obstructions. The team transported, stored, and installed owner-supplied PZC27 sheet piles, each measuring 90 feet in length, utilizing a 300-ton crane barge to construct 11 square coffer cells. Additionally, Precon continued the installation of sheet piles on the southern side to encompass an additional 50 feet of the existing bulkhead. The company also installed structural steel water stops with the assistance of divers and poured reinforced concrete using tremie methods. Precon also formed and placed pile caps and the deck slab to connect the northern and southern banks. Coffer cells were filled with VDOT #57 stone in five-foot layers up to the top. Furthermore, underwater dredging and cleaning of the dry dock apron and sill were conducted using a clamshell, while additional sediment and debris were cleared through the utilization of divers and hydraulic dredge pumps. An apron drainage system was established utilizing filter fabric, sand, and perforated pipes, along with a secondary filtration layer comprised of filter fabric and #78 stone. To construct a stability berm standing 27 feet tall, approximately 4,500 tons of VDOT #57 stone were placed. For cleaning and filling, the dry dock was dewatered, with asphalt subsequently placed to create access ramps from the land to the deck. Lastly, Precon installed handrails and cleats on the deck for stability.

The completion of this project was critical for ensuring structural integrity and stability, allowing for future dewatering activities at Dry Dock 3.

HII Projects

DD11 STAIR TOWER

PROJECT DETAILS

This project consisted of a design-build stair tower for personnel access into Dry Dock 11. PMI provided engineered drawings and assembly/installation of a new 56’ stair tower.

HII Projects

PORT SECURITY BARRIERS & WATERBORNE SECURITY – Newport News, VA

PROJECT DETAILS

Precon provides personnel, equipment, and materials to install, inspect, repair, and remove PSB systems from the NNS waterfront. PMI also completes maintenance projects on these PSB systems to prolong their service life. These projects include removal of the system in its entirety, a complete out-of-water inspection of the system components (moorings and modules), providing a recommended repair scope, and completing the repairs to put the system back into service.

HII Projects

DD11 CLEAT PROTECT

PROJECT DETAILS

This project consisted of raising 11 cleats around Dry Dock 11 by 1.5 to 2 feet by drilling and installing rebar, extending existing hardware, forming and pouring pedestals, and reinstalling cleats.

HII Projects

Marine Pile Jackets North/South Crane Rails 301T

PROJECT DETAILS

Precon completed the installation of 93 epoxy grout-filled nonstructural fiberglass jackets and 6 fiberglass structural jackets filled with cementitious grout. The nonstructural jackets measured 25.5 inches by 25.5 inches and ranged in length from 12 to 33 feet, while the structural jackets were 34 inches square and ranged from 2 to 4 feet in length. All structural jackets were located above mean low water, whereas all nonstructural jackets were underwater. The installation of all jackets was carried out using divers.