Hamby Wastewater Treatment Outfall Pipeline, City of Abilene, Texas

Plummer designed a five mile-24-inch pipeline and outfall for a water reuse project in Abilene.  The outfall was designed for a maximum flow of 9 million gallons per day (MGD) and constructed of articulated concrete blocks (ACB) to control erosion.  ACBs were selected based on ease of installation and capability to be installed in submerged areas. Plummer included a plunge pool at the outlet and flattened the last few hundred feet of the outfall pipeline to dissipate energy and minimize erosion during times of low lake levels.  As the outfall pipeline reached its point of termination, it gradually became exposed.  Articulated concrete blocks were extended to cover the exposed pipe to prevent erosion from wave action.  The outfall pipeline was installed in a reinforced concrete pipe to  prevent collapse of the pipeline from the weight of the ACBs.  An upstream vent pipe was added to allow air to freely move in and out of the pipeline without relying on mechanical devices.