Meeting the Standard — Air Release Valve and PCCP Rehabilitation

Abstract

Air Release Valves (ARVs) are critical to the performance of water transmission lines. They provide a means for trapped air to be released and they serve to dissipate transient (surge) events caused by rapid closure of valves or the start up or shut down of pumps. Changes in the Texas Commission on Environmental Quality (TCEQ) rules for Public Water Systems Chapter 290 raised concerns that the air release vent piping in question may not be up to standards. The City of Houston (City) also expressed concerns about the long-term serviceability of the pipeline due to the age and the pipe material. An inventory of the existing air valve data was performed, which included review of record drawings, pipe lay schedules, and the City’s Geographic Information and Mapping System (GIMS) data to determine the location of existing air valves and appurtenances. Direct consultation with City maintenance personnel also assisted in the location effort. The air valves were identified, their operation was tested and their physical condition was evaluated. Transient modeling was also performed by inputting the recorded profile and valve locations along with past, current and future projected plant operation scenarios in The Liquid Transient (LIQT®) software. A design package was then prepared to remove and replace the deficient air valves, including the isolation gate valves. After test-cuts were performed to determine the functionality of isolation valves and determine the shut down sections of pipe. Existing ARVs were replaced in accordance with City and TCEQ standards, and distressed pipe sections replaced or reinforced. The line was able to be fully returned in service.