Bisso introduces second tractor tug with a third on the way

Bisso Towboat, one of three competing ship-assist companies on the lower Mississippi River, is continuing its decade-long new-building program with the introduction this spring of a new 4,400 hp z-drive tractor tug, Alma S.

This tug has been a long time in the building as her construction took place over the last year, which included long delays caused by Hurricane Katrina in 2005, and its effects on shipyards in Louisiana. Alma S. was delivered in April from Main Iron Works, Houma, La. The company signed a contract for her construction in late 2004.

All the Gulf Coast shipyards have had difficulties with labor shortages in the wake of Hurricane Katrina, said Scott Slatten, president of Bisso Towboat. Labor problems were compounded at Main Iron Works that had orders for several ship-assist tugs plus other new vessels when the storm ravaged the area in September 2005.

Alma S., named for Slatten’s mother Alma Slatten, is Bisso’s 6th new tug introduced in less than 10 years, and she is the second z-drive-style tractor tug. Alma S. is closely patterned after the Bisso tractor Cecilia B. Slatten, introduced in 1999. At the time, Cecilia was the first tractor-style tug of any type to be introduced on the lower Mississippi.


Bisso Towing, according to Slatten, is already in the process of signing up for another tractor to be built at Main Iron Works, and it’s possible that the company will never again build a conventional twin or triple-screw tugboat, at least not in the foreseeable future.

“It would not make sense for us to build a conventional tug,” Slatten said. “We’ve learned that these z-drives are the best. Now that I’ve got two of them I can pretty much move anything on the river. If I can get a third, it will be just phenomenal.”

Since the Cecilia B. Slatten was introduced about seven years ago, Crescent Towing, a competing company, has introduced another z-drive tractor, the 5,000 hp Point Clear, for service based in New Orleans.


“The period of experimentation with these tugs was over about three years ago,” said Slatten. “The z-drives have held up just as well as any other propulsion system here in the challenging environment of the lower river.”

Initially, there was concern that z-drive propulsion would not be able to stand up to damage caused by debris floating in the fast-flowing Mississippi.


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But Bisso’s first z-drive tug has performed thousands of dockings and undockings at all times of year without incident, said Slatten.

In addition to its two tractor tugs, Bisso also operates 10 conventional twin- or triple-screw tugs and two pushboats. The company sold off its last single-screw tugs in 2005. The three primary tug companies based in New Orleans, Bisso, Crescent and EN Bisso & Sons, range over a 200-mile territory from the mouth of the river to Baton Rouge. A fourth company, River Parishes Co. (RIVCO), also operates in the area.

Bisso Towboat focuses entirely on ship-assist work in its territory, choosing not to engage in offshore towing.

The Port of New Orleans ranks among America’s leading commercial ports with about 11 million tons of general cargo handled in a typical year (pre-Katrina). More than 5,000 inbound ships arrived at the mouth of the Mississippi River in 2003 and 2004 with destinations spread out along the entire 250-mile route as far north as Baton Rouge — an area that includes about 130 docks that can handle ships. New Orleans itself is situated about 100 miles up the river from the Gulf of Mexico. The immediate New Orleans area, between mile 150 and 180 generates about 30 percent of the work for local tug companies.


The Mississippi, which drains much of the middle of America, is notorious for its brown water carrying everything from fine sediment to massive logs on its march towards the Gulf of Mexico. Historically the river runs highest and fastest in spring as it carries runoff from melted snow and spring storms from America’s heartland. Periods when the river is highest are also peak times for tugboat businesses on the lower river.

“We can’t afford to have any of our tugs, particularly the z-drive tugs, laid up during those times because of underwater gear damage,” said Slatten. “But we’ve been delighted with the way the Cecilia has turned many a log into matchsticks,” he added. “Mostly she just eats up anything that comes her way, but the few times she has gotten stuck with something in the gear, she has just backed down a bit and cleared her gear almost immediately. Another time they blew the obstructing log out of one nozzle by thrusting at it with the other nozzle.”

Bisso’s new tug, Alma S., measures 100 feet in length and is rated at bollard pull of close to 60 tons, according to Slatten. The tug is powered by a pair of EMD 16-645E6 diesel engines producing 2,150 hp each at 900 rpm. The rebuilt engines have been modified with electronic injectors and other improvements to make them EPA compliant. The tug’s light cruising speed is rated at 14 knots, according to specifications.

Other key items of machinery aboard the new tug include a pair of John Deere 100 kw diesel generators and a Markey DYSF-42 hydraulic hawser winch with render-recovery features. The bow-mounted winch is loaded with 500 feet of eight-inch circumference Plasma Line from Puget Sound Rope.

On the aft deck is a set of H-bitts and a 100-ton quick-release tow hook provided by Washington Chain & Supply. A McElroy Manufacturing vertical capstan is also located on the aft deck.

Other on-board items of interest include an alarm system from Engine Monitor, Inc., fenders by M&M and an Owens Kleen Tank waste handling system. Wheelhouse electronics include Furuno radar, Simrad GPS and autopilot, and Furuno AIS system.

The tug has tank capacity for 43,000 gallons of fuel, 11,000 gallons of potable water, and 1,800 gallons of lube and hydraulic oil. She can also store up to 1,500 gallons of waste engine oil.

One change between Cecilia and Alma was a further inboard slant to bulwarks and side bitts in order to provide greater clearance when working under a ship’s counters, according to Slatten. The John Deere generators have also replaced the Detroit Diesel generators installed on Cecilia. “Aside from those and some minor changes here and there, mostly for crew comfort, the Alma is almost exactly the same as the Cecilia,” he said.

Alma S. will likely be employed similarly to Cecilia, in difficult berthing situations where pilots request the advantages of a highly maneuverable z-drive tug, said Slatten.


Cecilia spends much of her time in the Burnside area, about halfway between New Orleans and Baton Rouge. Aside from tanker berths, she is often engaged in docking grain ships at the Zen-Noh grain elevator. This involves a berth where an eddy often runs upriver parallel to the dock.


“She works extremely well at that berth, and the pilots always ask for her,” said Slatten. “She typically makes up to the center chock on the stern while the other tugs are on the side. They use her as a 4,300 hp brake and rudder, so that the ship can keep coming ahead with its propeller, even as she is slowing down. That way the ship’s rudder still has an effect, and the Cecilia just keeps backing harder.”

Slatten said his eagerness to start construction of a third z-drive tractor tug indicates his faith in a complete restoration of maritime business on the lower Mississippi.


“Business is going as well as could be expected,” he said. “Our industry, at least, has bounced back very well. We are pretty much back to where we were before Katrina, with some exceptions.”

By Professional Mariner Staff