McMillan Water Treatment Plant DC: embedding culture in civil engineering

McMillan Water Treatment Plant DC: embedding culture in civil engineering W. M. Kim Roddis George Washington University Abstract Submission The McMillan Water Treatment Plant (WTP) in Washington, DC is a case study in CE 1010 Introduction to Civil and Environmental Engineering. It not only surveys 100 years of urban drinking water technology, but also includes multiple cultural aspects. Washington, DC has historically been plagued by poor drinking water quality. Union troops stationed In Washington during the Civil War suffered from waterborne diseases. Abraham Lincoln's son Willie died at age 11 of typhoid fever. Public health improved with the opening of the original McMillan WTP in 1905. This was a slow sand filter plant, purifying water using physical and biological filtration processes. Such slow sand filters provide potable water without the use of chemicals but are land and labor intensive. The cells for the sand filters covered many acres. Fredrick Law Olmsted designed a 25 acre public park over most of the grid of cells. McMillan Park, opening in 1912, was the only de facto racially integrated park in DC at the time. The park provided a rare opportunity to enjoy this public good for people in the surrounding communities until it was fenced off at the beginning of WWII. In 1986, the WTP was decommissioned with the opening of the adjacent rapid sand filter WTP. This technology uses physical and chemical processes to provide potable water. Potomac River water flows from the Great Falls raw water intake and the Little Falls raw water pumping station. Pre-sedimentation occurs at Dalecarlia Reservoir. Fluoride and the coagulant, alum, are added and the water enters the Georgetown Sedimentation Basins. The water flows underground through the Washington City Tunnel to the McMillan Reservoir. Power actuated carbon and chlorine are added and the water flows through the rapid sand filter. Lime, orthophosphate, and chlorine are added and primary disinfection takes place during dwell time in the clearwell. Ammonia is added and the water passes to the storage clearwell. DC WASA Bryant Street Pump Station drives the water to storage tanks from which the water is distributed to consumers in the District of Columbia, Arlington County, and the City of Falls Church. The McMillan WTP is still in use today. It has been and continues to be upgraded with modern advances in water treatment. One change, made before 2001, had dire unintended consequences. Chemical treatment was changed from chlorine to chloramine. This provided longer term disinfection when water flowed through distribution pipes. Tragically, this also destabilized the pipe chemistry, resulting in harmful lead levels. The problem was fixed in 2004, but thousands of children suffered permanent damage. With the less land intensive rapid sand filter in place, the 25 acre fenced and closed McMillan park was sold to the government of DC. In 2021, this space remains chained off and idle, with the city unable to formulate a development plan acceptable to the neighborhoods. My teaching philosophy is to approach engineering problem-solving in a broader societal context. Civil engineering inherently serves society. Selecting case studies that embed significant cultural content into the civil engineering problem statement allows me to emphasize to my students that solving the right problem is as important as solving the problem right.