The Trinity River Authority (TRA) of Texas established its Central Regional Wastewater System (CRWS) in 1957 and began operations in December 1959. The original treatment plant served Irving, Grand Prairie, Farmers Branch, and a portion of western Dallas. The plant has since expanded and now serves approximately 1.2 million people in the Dallas/Fort Worth area. CRWS processes include a bar screen, grit removal, primary clarifiers, aeration tanks, secondary clarifiers, traveling bridge sand filters, chlorine disinfection, and dechlorination. Thirty (30) traveling bridge sand filters were sized to handle the plant design flow rates for tertiary filtration. After many years of operation, however, several of these filters required full rehabilitation due to mechanical and performance degradation. CRWS also faced the additional challenge of soon needing another 100 MGD (378,000 m3/d) of filter capacity. This prompted an exploration of other filter technologies.