Raw sewage in Thames enough to fill 700 pools

London Free Press Fri, February 20, 2009

By RANDY RICHMOND

Enough raw sewage to fill about 700 backyard swimming pools flowed untreated into the Thames River from London during last week's heavy rainfall and flooding. Another 3,300 pool-fulls of sewage that received only basic treatment also entered the Thames -- a Canadian Heritage River -- according to figures obtained from the city yesterday. It's the second time in three months that much sewage has entered the river, prompting the city's director of wastewater and treatment to call on Londoners to help. "I can definitely say over the past 10 years we are seeing an increase in the frequency and severity of storms," Ron Standish said. Even as the city spends $100 million over 20 years to attack one cause of the problem, many homeowners are creating a bigger headache, he said. "Most of the flow is coming from homeowners' weeping tiles." In a perfect system, rainwater flows through storm drains into the river and sewage goes through sanitary drains to wastewater treatment plants before reaching the river. But in London, rainwater can fill the sewage lines in three ways: through the ground into old crumbling pipes, through about 6,700 metres of combined sewer and storm water pipes, and through the weeping tiles in people's yards. During storms, the combined rain and sewage water can overwhelm the city's six treatment plants. Most of that wastewater will get at least primary treatment, basically the removal of solids, but not bacterial or chemical treatment. But some of the wastewater will get no treatment at all. The city will spend about $3 million this year, as part of its 20-year plan, to separate the combined sewer/storm water pipes, Standish said. But fixing the weeping tiles presents a tougher challenge, he said. "That has turned out to be very difficult because the weeping tiles are on private property." The city has resisted legislating homeowners to fix the problem, but it does offer a 50 per cent subsidy for homeowners to install sump pumps that divert ground water from weeping tiles and into the storm drain system. "We are encouraging people being flooded to take advantage of this program," Standish said. From Feb. 7 to Feb. 11, about 77,000 cubic metres of raw effluent and 366,000 cubic metres of effluent with basic treatment entered the Thames. During heavy rain and flooding from Dec. 9 to Dec. 28 last year, about 92,000 cubic metres of raw wastewater and 347,000 cubic metres of wastewater with basic treatment entered the river. During the spring melt last April, about 13,000 cubic metres of raw wastewater and 244,000 cubic metres of wastewater with basic treatment entered the river. A 20-foot by 40-foot backyard pool with an average depth of five feet contains about 110 cubic metres of water. Fortunately for the health of the river, the sewage was diluted by the same heavy rains and melt that caused the problem, Standish said.

Randy Richmond is a Free Press reporter.

RANDY.RICHMOND@SUNMEDIA.CA