A Revetment is a facing (such as of stone or concrete) to sustain an embankment. Each autumn the Mat Sinking Unit, with over 350 employees, begins several months of work on the Mississippi River for the annual construction program of establishing permanent locations for the constantly moving river banks using flexible concrete blankets. The designers allow the river to eat away at the banks until they arrive at the desired position and at that point, they are fixed in place. Fixing the banks in a permanent location stops the river from meandering and provides both levee protection and safe navigation channels.
Mat sinking is not an 8-to-5 job, but rather, seasonal work conducted during the traditional low water months of August, September, October and November. When the workers leave Vicksburg on the quarter boats, compared by some to a large, floating hotel, their work season consists of 10-hour shifts for 12 consecutive days with two days off. This mat sinking operation is a unique river operation and is the only one of its kind in the world.
The articulated concrete mattress (mat) arrives on location by barge from one of the mat-casting fields along the river in Tennessee, Arkansas, Mississippi and Louisiana. A fleet of 50 mat supply barges, some loaded and on location and some empty and awaiting loading by the mat-loading crew at the casting field, are towed up and down the river by Corps or contract boats.
On location, the mooring barge and spar barge are perpendicular to the shore and the work barge (mat boat) is parallel to shore and tied off to the mooring barge. The work boat positions a supply barge to be tied off to the back of the mat boat and the mat-laying operation is ready to begin.
The four overhead cranes move the 16-block sections of mat from the supply barge across to the mat boat where workers, using a pneumatic "mat-tying" tools, wire the sections together and connect to 3/8-inch launching cables running from the mat boat to the bank. The 4- by 25-foot sections (squares) are tied together with 35 other squares to form one launch. A typical blanket of mat will consist of from 12 to 24 launches. Each supply barge holds 585 squares of mat, consisting of 950 tons of concrete.
In order to get the mat anchored firmly on the bank, anchors are driven in the ground. The crew will hook the mat cables to dozers (tractors) waiting on shore that serve at temporary anchors. The mat boat will then move away from the bank launching the concrete mattress in the process. The mat boat can move riverward 315' along the 400' mooring barge and then spar barges are utilized to allow the mat boat to continue out for the remainder of the channel mat length. The entire plant moves upstream 140 feet and begins the first launch of a new channel mat. The mat forms a protective overcoat to shield the riverbank from erosion and sloughing caused by channel currents and turbulent water associated with river flood stages.
The mat-sinking crew lives and dines on the quarter boats that tie off to the bank near the work area. In fact, many of the crew members love the river life so much they work season after season laying mat on the mighty Mississippi. Although its hard work, the galley cooks provide four exceptional meals a day. The two large dining rooms are designed to feed a crew of over 200, who must eat and be back at work within an hour.
Some of the seasonal professions represented on the mat-sinking crew include clerks, deck hands, drag line operators, electricians, mechanics, quarters boat utility operators, stewards, surveyors, tying tool operators and repairers, tractor drivers, truck drivers and winchmen. These men and women perform one of the most important jobs in the Corps of Engineers river stabilization program. Low water on the river, primarily, determines when the mat season will begin. However, once mat season starts, the operation is ongoing until finished several months later.