Background

The local water utility, Comisión Estatal de Servicios Públicos de Tijuana (CESPT), regularly conducts video inspections of its wastewater collection infrastructure. This effort can be hampered by manholes that are spaced too far apart and do not allow for adequate line maintenance, which could lead to concrete deterioration from the buildup of hydrogen sulfide (H2S) gas and unpleasant odors. Based on these inspections, CESPT has identified aging and deteriorated sewer lines requiring rehabilitation to prevent failures that could result in raw wastewater discharges to the Tijuana River. During the 2016-2017 winter season, heavy rainfall caused the collapse of several sections of a sewer main, spilling untreated wastewater into the Tijuana River, which eventually flowed into the United States. To address this situation, the state government instructed CESPT to develop a comprehensive wastewater treatment and reuse plan. Immediate actions under the plan included the rehabilitation of critical sewer mains.

Scope

The project consisted of rehabilitating approximately 4,193 linear meters (13,756.6 ft) of the Collector Poniente in three consecutive segments: Segment 1 with 1,086 m (3,563 ft) of 42-inch diameter pipe; Segment 2 with 789 m (2,588.6 ft) of 42-inch diameter pipe; and Segment 3 with 2,318 meters (7,605 ft) of pipe ranging from 18- to 42-inches in diameter. The project also included the replacement of approximately 310 m (1,017 ft) of sewer laterals connected to the Collector Poniente, with diameters ranging from 8 to 12 inches.

Benefits

The project has improved wastewater collection and conveyance infrastructure for up to 23,500 existing residential wastewater connections and reduced the risk of line failures, preventing the potential discharge of approximately 177 liters per second (lps) or 4 million gallons per day (mgd) of wastewater that could affect the Tijuana River, a transboundary water body.