Sewer Superhighway: Fast Track for Large Diameter Consent Decree Pipeline: Fid-Bau Portal

Sewer Superhighway: Fast Track for Large Diameter Consent Decree Pipeline

Farnsworth, Jeff / Bennett, David

The San Antonio Metropolitan area has experienced sustained growth for decades, putting increased pressure on existing wastewater infrastructure. In June 2013, the San Antonio Water System (SAWS) approved a settlement agreement with the U.S. EPA that requires significant improvements to the SAWS wastewater system over a 10-year period to reduce sanitary sewer overflows (SSOs). This work includes the targeted replacement and rehabilitation of an aging infrastructure system that consists of over 5,200 miles of sewer pipe. One such pipeline is an existing 48-inch concrete trunk sewer, which operates at capacity during dry periods, but and experiences SSOs of 50,000-100,000 gallons or more during periods of minimal rain. SAWS has identified the replacement of this critical sewer pipe as one of its highest priorities, initiating design of a six-mile segment of 60- to 78-inch sewer pipe to increase the current capacity. The project is to be delivered on an expedited schedule, and there are several challenges including an alignment through a U.S. Military Installation and two major hospital complexes, extensive tunneling, and close proximity to a major creek. This paper will focus on design approaches used to expedite project delivery. In all decisions, delivery time and reduction of SSOs were key considerations. Examples of schedule cutting strategies include dividing project into two segments, use of existing right-of-way and easements to eliminate need for condemnation, constructing the new 78-inch line parallel to the existing 48-inch line to nearly eliminate the need for by-pass pumping, and a radical shift in the standard plan review/approval process at SAWS. In summary, the project has been delivered on schedule and is presently under construction.