The screed is being used by Shea S and M Ball in the construction of 12,500 feet of invert for a subway tunnel that reaches a maximum depth of 100 feet below the Potomac River, part of the 97.7 mile Metro public transportation system being built in Washington, D. C. The invert is formed around two curves with transition spirals at each end, one with a radius of 955.5 feet, the other with a 15,000 foot radius. The screed runs on rails which are attached to structural steel ribs on the sidewall of the excavation. It is pushed from specially designed rail grippers controlled by a 72 inch stroke hydraulic system designed to advance at a uniform rate of speed. A ratchet arrangement in the gripper permits it to be pulled forward easily to the next location of the rail. To accommodate the super elevation, the rail on the inside of the curve is kept at level while the grade rail on the outside of the curve is raised. The procedure permits the necessary adjustments to be made well ahead of the point where concrete is being placed. On one curve the grade rail is gradually raised 10 and one-half inches from level. The screed panels are adjustable to form a drain gutter at the lower elevation of the invert, whether this occurs on center as in tangent selections, or on the left or right as on curves. The drain is shifted to the side abruptly rather than gradually so that only one panel change is necessary rather than several.