Walker-Calloway Interceptor Failure and Emergency Repair: A Case Study in Murphy’s Law

The Trinity River Authority of Texas (TRA) supports the City of Fort Worth by operating and maintaining the Walker-Calloway Interceptor system, a 4.7-mi major wastewater conveyance system constructed in 1970 of unlined reinforced concrete pipe (RCP). On June 4, 2022, a brief, intense rain event occurred within the Calloway branch of the collection system and led to a sudden increase in wastewater flow, causing surcharge. The surcharge event caused a portion of the unlined concrete pipe to become dislodged and collapse in the path of flow leading to an SSO immediately upstream from the blockage. Unseen from above grade, the pipe collapse had undermined a 25″ tall drainage channel embankment and the residential driveway above the collapsed pipe. During excavation for the repair of the pipe, a massive cavern was discovered and subsequently repaired. The collapsed pipe was uncovered and replaced along with the downstream section of pipe, which was also deteriorated to the point of collapse. A combination of open cut and pipe bursting was used in the repair, and flow was restored on July 1, 2022.