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Water Quality across an active inter-provincial 24-inch crude oil pipeline and an inactive 18inch pipeline. All necessary approvals and engineering were needed to ensure construction activities did not affect the pipelines. Staging of the entire construction effort had to be closely coordinated as site access was only available via the south end of the ravine. This, combined with the soft soil conditions, required the use of geosynthetics and temporary access road construction to allow heavy equipment to operate on the soft organic soils. A 90 m temporary access road underlain by a non-woven geotextile was constructed throughout the length of the ravine. Heavy equipment worked off the end of the road, and as construction progressed, the road was removed to make way for the SSF wetland treatment system. Specialized, six-wheel-drive articulated haul trucks were needed to transport excavated soils out of the valley and treatment media back in for use in the wetland cells. Following design and approvals, the SSF wetland was fully constructed
within two months in late 2005 at a cost of $200,000, including design, approvals and construction. It was commissioned in February 2006. Operations and performance The certificate of approval (CofA) issued by the Ministry of Environment set discharge limits on biochemical oxygen demand (BOD5), total suspended solids, un-ionized ammonia, total phosphorus, dissolved oxygen and pH. These parameters are sampled every second week in the raw influent, primary effluent and treated effluent for compliance purposes. The CofA initially required weekly sampling of these parameters, but due to consistently good performance, the MOE has authorized a reduced sampling frequency. These same locations, plus the system bypass, are also sampled every second month for a longer parameter set that includes additional conventional parameters and metals. Iron, a common landfill-related metal, is reduced from influent concentrations of 20 mg/L to typically less than 0.03 mg/L in the treated effluent. This is well below the
provincial water quality objective for surface waters of 0.3 mg/L. In addition to water quality sampling, influent flow, effluent flow and bypass flow are continuously monitored at the site using battery-powered level meters. Operation and maintenance includes winterization with a 0.5 m straw thatch blanket over the upstream 30% of each cell, periodic removal of invasive species, flushing and cleaning of the weir and sediment chambers as required, twice-yearly exercising of valves, and flow-meter maintenance. Since 2009, Integrated Municipal Services and the City of Thorold have utilized the wetland treatment system as an outdoor learning opportunity. Students from Niagara College’s Ecosystem Restoration and Environmental Technician programs have been onsite to learn how the wetland functions and to exercise their newly acquired skills and education in a practical setting. Most recently, the students have assisted with the winterization of the wetland, conducted plant inventories, and helped with the management of invasive species and the improvement of habitat features. In the future, the wetland will feature signage for future student education and overall public awareness about the importance of the wetland treatment system and all its features. Following a brief startup period, the treatment wetland at the closed Rice Road Landfill has provided consistent removal of ammonia, phosphorus and other parameters listed in the site CofA. This includes excellent cold-weather performance. A new investigation has begun at the site to examine the feasibility of increasing the peak flow rate through the treatment system, to reduce the frequency of wet-weather bypass events. Bruce Gall is with Urban & Environmental Management Inc. E-mail: bgall@uemconsulting.com. Kyle Monteith is with Integrated Municipal Services. E-mail: kmonteith@walkerind.com
Environmental Food Mineral Petroleum www.cala.ca
52 | Summer 2012
Environmental Science & Engineering Magazine