THE LOWER LEVEL
The lower level of the dredge is divided into four major areas:
#1 The Open Dredge Intake and Derrick Area;
#2 The Engine Room;
#3 The Boiler Flat;
#4 The Machine Shop.
#1 The Open Dredge Intake and Derrick Area
This area in the bow includes the dredge suction head (or "dust pan"), a hoisting winch (for the dredge head and spud), a tripod derrick and A-frames, two anchor winches and two capstans. The two hauling winches were manufactured by the American Hoist and Derrick Company of Saint Paul, MN.
To dredge, the Lewis would set two hollow steel piles into the river bottom by jetting water through them. Once the piles were set, the vessel would back down along the line of the channel to be dredged until the full 3600 foot length of 1 1/8 inch steel cable was unwound.
Using two massive winches at the port and starboard sides of the bow, Lewis would slowly move forward, cutting a 50 foot wide, 18-20 foot deep channel. The vessel was capable of dredging an average of 80,000 cubic yards of spoil. The derrick was used to set and pull the steel piles. To anchor, two 20 inch square steel spuds, 38 and 42 feet long, were dropped to the bottom of the river to hold the vessel fast in the swift river current.
Drawing river water from the Missouri, a 250 horsepower steam turbine drove a centrifugal pump that supplied high-pressure water jetted trough 38 nozzles. This water pressure cut loose the sand and silts of the river bed.
As the face of the cut collapsed, the large 36 inch diameter intake pumped the nearly liquid mud at 40,000 g.p.m. out into the 34 inch diameter discharge pipe, which attached aft and ran out on floating pontoons for a distance of 500 to 1000 feet. The pipe was set on a center-pivoting mount on each pontoon to make a snaking line. The last section of pipe on its pontoon was steered by a member of the crew in a small "dog house." The discharge pontoon line was steered by directing the force of the discharged water and mud with a baffle plate.
Two sections of the pontoon-supported discharge line are displayed off the aft port quarter, one of which is the last section with the dog house and baffle plate for steering the line.
#2 The Engine Room
The engine room contains two 800 horse power horizontal compound condensing engines 20 x 40 inches, with a seven-foot stroke built in 1932 by the vessel's builders, the Marietta Manufacturing Company of Mount Pleasant, WV. The engines drove Lewis' two steel and white oak sidewheels, each 25 feet wide. The pumping engine is a single 1300 horsepower, triple-expansion marine steam engine manufactured in 1931 as engine no. 1507 by the American Shipbuilding Company of Lorain, OH.
#3 The Boiler Flat
The Boiler Flat, located aft of the engine room. Steam was proved through two diesel-fired water-tube boilers built by the Foster-Wheeler Corporation of New York
#4 The Machine Shop
The Machine Shop, aft of the boiler room, is filled with spare parts, drills, presses, lathes, a shaper and an anvil--indicative of the Lewis' self-sufficiency on the river.
Captain Meriwether Lewis Foundation, P.O. Box 145, Brownville, Nebraska , 68321
(402) 825-6001 Ф LewisDredgeFoundation@gmail.com