The city of Hamilton, Ontario, is embarking on a $550-million upgrade of its main wastewater-treatment plant. CH2M Hill, with subconsultant AECOM, is performing detailed design and services during construction of the project, which could last five to seven years, says Dan McKinnon, acting director of operations for the Hamilton Dept. of Public Works. The project will replace a 500-megaliter-per-day activated-sludge treatment plant with a 1,000-mld membrane bioreactor, treat a large combined-sewer flow and help to clean up a polluted Lake Ontario harbor. “There is no aspect of the existing wastewater-treatment plant that won’t be touched,” says McKinnon. The planned bioreactor
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.