By the time the crew members of the U.S. Coast Guard cutter Sumac retire at night, they are too tired to notice the roar of the generators just a deck below.

"It's hard work, there's no doubt about that," said Executive Petty Officer Steve Adams, who has manned the helm of the Sumac for three years. "But there's no other work I'd rather be doing."

The Sumac patrols the waters of the Mississippi River between Winfield Lock and Dam No. 25, north of St. Louis, and Cairo, Ill., tending to the buoys and shore markers. In all, it covers 242 miles of the Mississippi River, and the 28 navigable miles of the Kaskaskia River.

The boat

The Sumac is a 115-foot-long boat, permanently affixed to the 136-foot-long barge that carries its buoys, drop weights and supplies. It weighs about 900 tons.

Powered by three engines the size of minivans, the Sumac was commissioned Nov. 1, 1944. The barge is older.

"We're the last vessel of our kind in this region," said Adams. "Everything else is smaller, newer and are named after Western rivers."

Carrying state-of-the-art, depth-finding equipment, the Sumac maps, plots and traces the rises and falls of the floor of the Mississippi River.

"Most people think it's just flat under the water and everything is a uniform depth," said Adams. "The fact is, the river can go from 40-feet to about 3-feet deep in a matter of yards."

The forward deck of the Sumac is its business end. There sits a crane used to move the 1,500-pound buoy-anchoring blocks around and to lift the 480-plus-pound buoys out of a holding area to the main deck.

Bales of half-inch cable lines the front part of the deck. It will be strung between the anchors and the buoys.

The boat also has two generators, a primary and a backup, that keep its air conditioning, lighting and water systems running through the night.

The Sumac carries 24,000 gallons of diesel fuel -- typically burning more than 1,000 gallons per day -- and almost 30,000 gallons of water.

It can cruise at speeds in excess of 20 mph downstream, but as its crew works, a speed of 8-10 knots is maintained.

The crew

Reveille is sounded over the ship's intercom between 5 a.m. and 6 a.m. From breakfast, it's off to work.

A handful of the 21 commissioned crew members will board the small boats moored to the side of the barge and head toward the riverbanks. Their cargo: Weed eaters, lawn mowers, hammers, nails, paint, gasoline and just about anything else they will need to repair shore markers, or to make them visible to passing river traffic.

Others head to the front deck to tend to the buoys.

"Safety always comes first," said Master Chief Bob Hunsaker.

On the boat itself, the cook and her assistant prepare the meals, wash the dishes and do general cleanup. The engineers keep the boat running.

The crew works a shift of roughly three weeks on the river, and one week at their home port in St. Louis. While on board, only the helmsmen work rotating, 6-hour shifts. The rest of the crew work through the day.

At night, unless they are assigned to watch duty, the crew is free to leave the boat.

Officers typically use the evening hours to catch up on paperwork, record daily activities in logs, or to just relax.

"I guess you could say we're like a big family," said Adams. "And rightfully so. We spend more time with each other than we do with our families every year."

The job

"It's about a 12-14 hour a day job, depending on the amount of daylight and the weather," said Adams. "We work about the same hours in bad weather, we just wear more clothes."

As the master chief decides where to drop the buoys in the river, he must think ahead to the next time he will visit the same waters, taking into account weather forecasts and river crest predictions.

Boats pushing barges need a water depth of about 9 feet. The Coast Guard tries to give them at least 15 feet.

"Most of the boat operators know that if they hug close to the buoys, they're going to be in some pretty shallow water from time to time," said Adams.

"And they know when we've been here," he said. "If there's paint scraped off the buoys from where boats have collided with them, or if they're missing altogether, they know we haven't been around for a while."

The buoys sometimes fall prey to the large propellers of the boats. "I've hit three buoys myself in my nine years of doing this kind of work," said Adams. "The last one, there was just no avoiding. I revved up the engines and just shredded it in the propellers. It came out looking like confetti floating on the water."

As the Sumac heads upstream, the crew hails all southbound traffic, informing them of their progress.

"The southbound traffic always has the right of way," said Hunsaker. "It would be much harder for them to stop. Most of the time, they're pushing such a load, it could be nearly impossible for them to back off."

Late in the afternoon, the crew that left for shore work notifies the master chief that it will be returning.

"We cut down a forest today," said the officer in charge of the launch, referring to the clearing of brush and debris from a shore marker. "But you can see the marker all the way from the bend now."

On an average day, the Sumac will travel 30-40 miles, tending to buoys along the way.

The future

The flood of 1993 set the Sumac and its crew back a few notches. It is still working to repair shore markers that were wiped out by the floodwaters.

"After the flood, our work really began," said Adams. "It was like starting from scratch."

In September, the Sumac will be honored for 50 years of service at a ceremony under the St. Louis Arch.

"We don't know exactly what we're going to do yet," said Hunsaker. "If it were up to me, we'd bow our heads, have a moment of silence and get back to work. That's what we do here. We work."