Naval Research Laboratory Seawall
Services Applied by VCS Engineering
Project Description
The Naval Research Laboratory in Washington, DC has an existing steel sheet pile bulkhead wall that was built in the 1980’s. The bulkhead consists of 3,200 LF of steel sheet pile with W8x40 battered pile buttresses on the waterside that are welded to a W10x39 wale, which is periodically submerged at high tide. The bulkhead is downstream from the Anacostia River and is mostly fresh water. Salinity fluctuates based on river flow, with the normal water resistivity ranging from 1200 to 3600 ohm-cm. The existing wall was not coated and had begun to perforate at the mudline and near the cap.
Scope
A Design-Build project was awarded to Marine Solutions, Nicholasville, KY to rehabilitate this bulkhead. VCS provided cathodic protection design services, installation training, and quality control services for the CP system. The system included a Portland cement mortar-filled stay-in-place fiberglass pile jackets for the buttress piles from approximately 1 foot into the river bottom up to the wale. Alkali-activated zinc galvanic anodes were incorporated into the jacket system to protect the buttress piles from corrosion. Magnesium galvanic anodes were buried in a shallow trench dug into the riverbed 4 to 5 feet from the bulkhead. Each anode was wired to a bolt in the new bulkhead cap.
Upon completion of the jackets and anode installation, the entire wall was pressure washed and coated with an underwater epoxy paint. This hand-applied coating complements the galvanic anodes and once completed, the galvanic anodes produced a potential shift sufficient to meet NACE criteria along the entire length of wall to provide corrosion mitigation for a minimum of 25 years.