VESSEL REVIEW | US Army Corps of Engineers’ newest dam maintenance and debris-clearing workboat

The Walla Walla District of the US Army Corps of Engineers (USACE) recently took delivery of a new tug intended to support activities at the Little Goose Dam on the stretch of the Snake River that passes through eastern Washington State.

Built by WCT Marine and Construction of Astoria, Oregon, to a workboat design that was developed by local naval architects Crescere Marine, the all-steel vessel is tasked primarily with preventing debris from floating into and clogging up the dam, which has been supplying hydroelectric power to Washington's Columbia and Whitman Counties for over 50 years.

The tug has a length of 26 feet (7.92 metres), a beam of 13.5 feet (4.1 metres), and a draught of only five feet (1.5 metres) even at full load. The small size not only enables it to easily sail in the waters in and around the highly important dam, it also allows it to be loaded onto and transported via truck as an alternative option for deployment. The vessel is thus also fitted with four heavy lifting eyes to allow it be lifted and lowered via crane.

The pilothouse was kept as low as possible to make the vessel compact enough for road transport. However, it still offers an elevated cabin height to provide the operator with an improved all-around view.

The tug has a relatively wide beam considering its small size to provide enough space in the engine compartment for a pair of Cummins QSB6.7 six-cylinder, four-stroke diesels that each have a rated output of 301 hp (224 kW). The engines, which are EPA Tier III-compliant, turn two Workhorse open, four-bladed 32- by 20-inch (812- by 508-millimetre) propellers via horizontal driveshafts and ZF 325-I gearboxes with 2.957:1 reduction to deliver a bollard pull of 5.5 tons (4.5 tonnes).

The tug is also fitted with two full-size push knees, tankage for up to 350 gallons (1,324 litres) of fuel, jog stick steering, and R.W. Fernstrum and Company keel coolers for the engines installed in hull side recesses.

The vessel complies with the American Bureau of Shipping's 2020 Marine Vessel Rules for structures, as well as US Coast Guard CFR rules for towing stability at full power.

The new tug entered service with the USACE Walla Walla District in the second quarter of 2021 following construction that took place over the previous winter. It replaced an older vessel that had been utilised in the same debris-clearing role at the Little Goose Dam. Other duties include the transport of maintenance equipment and the placement of barriers at key points to enable USACE technicians to safely inspect and repair dam infrastructure.

See more stories from this month's Tug and Salvage Week here.