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.

REPAIR

Naval Station Norfolk, VA (off-site repair)

PROJECT DETAILS

Precon Marine is providing personnel, equipment and materials to remove port security barrier systems from Naval Station Norfolk and transport to our facility for all necessary repairs and coating. PSBs are then transported back for re-installation.

UNDERWATER CONSTRUCTION

York River, VA

PROJECT DETAILS

Transportation and deployment of approximately 8,500 tons of R4 rip rap stone and 30,000 tons of VDOT #1 crushed stone in the York River, Chesapeake Bay, Virginia, to facilitate oyster reef construction.

UNDERWATER CONSTRUCTION

Norfolk, VA

PROJECT DETAILS

Within specified zones to allocated dredge depths, Precon’s dive team hand dredged underneath the USS Wisconsin Battleship located in Norfolk, VA, utilizing hydraulic dredge pumps with suction hoses and diver hand nozzles.

MARINE CONSTRUCTION

Chesapeake Bay Bridge Tunnel, VA

PROJECT DETAILS

This project focused on replacing the fender system at the North Channel Bridge, part of the Chesapeake Bay Bridge Tunnel. The goal was to enhance the structural integrity and functionality of the fender system, thereby ensuring the safety and navigability of the bridge. Key tasks involved in the project included the removal of existing collars, which were disconnected and removed by divers from the partially submerged stainless steel friction collars on the 12-inch diameter cylinder piles. The removed friction collars were then retrieved and disposed of off-site. Additionally, the project required the demolition of the existing, decayed, and dilapidated creosote-treated timber fender system. New 12-inch by 24-inch diameter, 1.5-inch thick stainless steel friction collars were procured and fabricated. These new collars were installed at the correct elevation using a 300-ton crane barge and divers, ensuring that all bolts were tightened to the specified torque. Creosote-treated dimensional lumber was sourced for the new fender system, and modular sections of the timber fender system were prefabricated to expedite installation. Once the modular fender system was transported to the site, it was secured to the existing fender piles and friction collars. As part of the project, an access ladder, navigation lights, and a tide gauge were also installed.

MARINE CONSTRUCTION

VIRGINIA

PROJECT DETAILS

Precon Marine installed the superstructure steel, the pile cap single & double supports, support stiffener plates, end platform, and fender steel mounting plates. Previously driven 36” x ½” piles (12 each) were cut to grade and 20 pad eyes were welded.

FI & Power & Underwater Construction

MSF RANGE NORFOLK R6 UPGRADES (EMT REPLACEMENTS)

PROJECT DETAILS

PMI conducted a dive survey of the underwater array to gain familiarization with the existing conditions, which were 800′ long and 40′ wide, located within the Entrance Reach Channel West of the Hampton Roads Bridge Tunnel. Water depth ranged from 40 to 60 feet deep. The damaged underwater electromagnetic triaxial (EMT) sensors and associated cable were removed, and new EMT sensors, magnetometer instruments, and associated cables were installed to reach the data concentrator shed. 3,000 cubic yards of non-magnetic gravel were placed over the instrument array, followed by the placement of 9″ thick 8’x20′ articulated concrete matting over the newly laid and existing cables from the array to the data concentrator approximately 2,180 feet away. Upon completion, approximately 56,000 feet of cable were installed.