A Case Study on Design, Testing, and Installation of Two Large Diameter Tunnel Liner Projects for the City of Los Angeles

The 12.3-mile long 132-inch diameter and 5.5-mile long 96-inch diameter tunnel liners for the East Central Interceptor Sewer (ECIS) and the North East Interceptor Sewer (NEIS), respectively, consisted of an initial liner and a prestressed concrete cylinder pipe (PCCP) primary liner. The primary liner for ECIS was stiffened steel at the future 13 lateral locations; the lateral connections to the 132 inch stiffened steel tunnel liners varied from 48 inch up to 96 inches in diameter. The 132-inch diameter PCCP primary liner, had a deep single gasketed joint and the 96-inch diameter liner had a double-gasketed testable joint since it runs parallel to the Los Angeles River and is subjected to 100 ft. external water head. Qualification testing prior to pipe manufacture included testing the joint to 120 ft. of external head. The tunnel design loading and handling conditions and design procedures utilized for the PCCP and stiffened steel tunnel liners will be presented in this paper. The liners were installed, with a specially designed laying machine with wheels and lifting hydraulics in 24 ft. long lengths, except at one seismically sensitive area in 4 ft. long lengths. Both tunnel liners were installed with a PVC liner in the concrete lining for corrosion protection.