indicated that the pressure had been reduced by equal amounts, which indicated to Calnev personnel that the check valves still had not seated. The 200-psig reduction also indicated that the remaining pressure on the line was due to the weight of the liquid and, as the maintenance superintendent stated, "that additional efforts would be only minimally successful in reducing the pressure at the Highland Avenue location [derailment site]," because backflow sufficient to seat a 14-inch check valve clapper could not be induced by withdrawing product through a 1¼-inch opening. As a result, Calnev suspended activities to reduce further the pressure on the pipeline, which at 10:00 a.m. on May 12, was 800 psig at Colton, or about 50 percent of the maximum operating pressure established by Calnev. According to Calnev’s manager of operations, Calnev did not at that time consider the possibility that the check valves were malfunctioning, but believed that the check valves did not close because of the inadequacy of the method used to induce backflow.
Meanwhile, SP’s division mechanical officer and other SP personnel had arrived on site and in consultation with Calnev and the incident commander began discussing plans for removal of the railroad equipment. According to the division mechanical officer, "the plan was to remove the cars and in no way affect the pipeline." The plan included cutting a breach (road) in the railroad levee through which the railroad equipment would be moved to the other side of the track. According to the San Bernardino Fire Department and Calnev, SP was advised that when the cars were to be removed, all cars were to be lifted and not dragged over the pipeline. Calnev’s manager of operations testified that he was aware of an accident in Montclair, California, in the latter part of 1988, during which wreckage removal operations possibly caused damage to a pipeline and that he wanted to avoid a repeat of such an incident. According to Calnev’s manager of operations, he did not discuss with the Fire Department or SP at that time what actions Calnev would take to inspect its pipeline after the cars were removed. Search and rescue operations continued until late in the evening on May 12, and efforts to begin removal of the wreckage were delayed until the following day.
May 13, 1989.—On the morning of May 13, SP removed 50 to 75 feet of track in preparation for making the breach (road) through the railroad levee that would be used for removing the railroad wreckage from the east side of the track to the west side. According to SP’s division mechanical officer, the site of the breach was determined by a break in the distribution of wrecked cars on the east side of the track (figure 4). Once the breach had been made, two 225-ton cranes and several bulldozers and front-end loaders came through the breach from the west side of the track, crossed over the pipeline, and were positioned at various points around the wreckage (figures 6 and 7). SP’s division mechanical officer testified that a lot of the trona that had spilled from the train was used to cover the ground and that with the the trona and the fill removed from the levee, there was about 6 to 7 feet of cover over the normal level of the ground in the area through which the equipment was moved. At the time the breach in the levee was made, the exact depth of the pipeline below natural grade had not been determined. During the morning of May 12, Calnev personnel used a line locator and yellow paint to mark the location of the pipeline throughout the derailment area. Later