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Sliplining Under San Francisco’s Hectic Embarcadero Area
Due to the strict environmental regulations for California and the city, precautions were required in case suspected hazardous or contaminated material was encountered. These precautions extended to the handling and disposal of the excavated material and the waste material encountered within the existing force main.
Sliplining operations were conducted over a period of several months due to various delays in access to the site. Pipe installation was done in two pulls. Pits were constructed at the starting (tie-in) point, the existing double 45-degree location and at the exit (tie-in).
Because of tight site constraints, the lay down area for stringing fused HDPE pipe sections and pulling the pipe into the steel host pipe left limited construction options.
A key component of the pipe insertion planning effort was determining which locations were feasible for stringing the fused pipe together. To accomplish this and also allow for continued pedestrian access to the shops located along the Bay, the size of the insertion pits was made as short as possible. Nevertheless, the HDPE pipe material’s bending radius controlled the pit lengths and consequently, rollers were used for deflecting the HDPE pipe while inserting it from the ground surface into the excavation and host pipe. These rollers were aligned to comply with the material’s bending radii and the pull forces required to insert the HDPE.
Two issues occurred while fusing the pipe sections. First, the cold temperatures extended the duration of the fusing operations by almost twice the originally anticipated time.
Second, pulling the fused 1,100-feet of 28-inch HDPE pipe in place prior to the sliplining process required extensive planning efforts. In order to string the pipe, some major intersections had to be closed to pedestrian traffic, requiring very extensive pedestrian control, assisted by the police.
Sylvia Hartonto, P.E., Shimmick Construction, and Rafael Ortega, P.E., Lockwood, Andrews & Newnam, who worked closely on this job, agreed that planning was critical.