Trenchless Technology

Fall Canada 2018

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W W W.T R E N C H L E S S T EC H N O LO GY.C O M/C A N A DA 33 Jennifer Leno, Environmental Tech- nician with the Town of Cobourg , stated that the amount of wastewater that is treated on any given day can vary dramatically depending on the environment and weather conditions — anywhere from 9,000 cubic metres per day on average up to 40,000 per day during a significant rain event . Losing this much sewer capacity can be very expensive for a municipality and affect future development . Old Adage Needs an Update Various water treatment methods, such as heating water to purify it, date as far back as the ancient Greeks in 2000 BC. There is an old adage dating back to the 1950s, however, which is more relevant to our situation today: The solution to pollution is dilution. The thought process back then was that the best way to handle sewage (as well as other forms of pollution such as air) was to dilute it some- how. In the case of sewage, this was often done by running the sanitary sewer lines into the clean waterways within any given municipality. That 's one of the reasons there are so many manhole frames and covers located next to waterways. It was determined over time, and with the exponential growth of communities, that this was not an effective solution. Municipali- ties then began directing these sewer lines to the water treatment plants in- stead of directly into the waterways. Although water treatment plants date as far back as the 1800s, the thought process was not the same as it is today with regards to keeping our waterways free of sewage and other harmful substances. These manhole locations next to waterways oftentimes become covered in water as the water level rises due to excessive rainfall and meltwater. Cobourg 's leaders realized that something needed to be done to prevent these inflow and infiltration compromised locations from generat- ing an excessive treatment cost. The Solution The types of inflow and infiltration sensitive areas described above can be addressed through the use of wa- tertight manhole frame and covers. The Lifespan System from Hamilton Kent was one of the solutions that the town of Cobourg used to stop surface level inflow in these areas. The Lifespan System is a watertight, corrosion-proof, non-conductive lock- ing rubber manhole frame and cover system that prevents rain-derived in- flow from entering sanitary sewers through the top of the manhole. Aside from robbing a sanitary sys- tem of its capacity, infiltration can also cause erosion of fine materi- als from the soil envelope, which in turn leads to voids in the surround- ing backfill and possible pavement degradation. A key advantage of a watertight manhole system is that it dramatically lessens the effects of pavement pancaking and deteriora- tion since infiltration is drastically reduced around the frame and cover. " The pavement is still pristine around the Lifespan System locations installed in-road after nearly 5 years," says Leno. The Town of Cobourg is planning to install 25 watertight manhole so - lutions each year over the next sev- eral years until they have finished re- placing approximately 150 manholes that are in the Town's floodplain ar- eas and near the town's four creeks. Because Cobourg officials found a way to reduce the amount of inflow and infiltration coming through man- holes, lost sewer capacity has been restored, development has progressed and the underground rehabilitation of the wastewater collection system can be addressed at a more reasonable and financially feasible rate. Construction or expansion of wastewater collection systems could be done years — and po- tentially decades — in the future. Jason Clowater is business development manager at Hamilton Kent. The Public Works Department for the Town of Cobourg, Ontario, is in the process of replacing 150 manholes in its floodplain area.

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