The Surface Transportation Board (STB), a unit of the Dept. of Transportation, last week dismissed the "Houston Consensus Plan" developed by a coalition of transportation groups as a solution to the shipping bottlenecks resulting from the merger of the Union Pacific and Southern Pacific railroads. The groups submitted their plan in response to the STB's call last March for long-term proposals to deal with rail problems stemming from the merger, which was approved by the board in 1996. The plan was developed jointly by the Chemical Manufacturers Assn. (CMA), the Society of the Plastics Industry Inc., the Texas Chemical Council, the Railroad Commission of Texas, and the Kansas City Southern Industries Inc. and Tex Mex railroads. "Not only are we disappointed," said Randy Speight, manager of distribution programs at CMA, "but we are amazed that the board dismissed virtually outright a plan designed by shipper groups, rail carriers, and a state government agency to accomplish what we understood the STB had requested."