Timeline
1900	Reversal of Chicago River completed, improving saftey of Lake Michigan's drinking water supply
1913	Los Angeles city engineer William Mulholland opens the Owens River Aqueduct.
1915	Abel Wolman joins the Maryland Department of Health, where he later perfects a formula for purifying water with chlorine.
1915	Boston engineers Leonard Metcalf and Harrison P. Eddy publish American Sewerage Practice, a standard reference for decades
1915	A. B. Wood invents low-lift screw pump to rid New Orleans of drainage problems
1918	Catskill Aqueduct completed; supplies water for New York City.
1918	First large-scale wastewater treatment plant to use activated sludge method built in Houston.
1935	Hoover Dam construction completed.
1937	Construction begins on Delaware Acqueduct to supply New York City; completed in 1962.
1954	James S. Robbins built first tunnel-boring machine.
1962	Mechanical raise-borer enabled engineers to significantly decrease the amount of time to bore through 200 feet of earth.