INNOVATION November-December 2012

original system but also have strong and consistent sustainability features throughout each portion of the upgrade and expansion. In order to achieve that objective, guidelines were established. “We set up a project plan and all the staff had to think along those lines when starting to design anything. It was the very basis, right from the conceptual stage through to the commissioning. It takes a lot of effort but if there is that concern at the early stage, it will carry through,” tells Pillai. Also, sustainability projects often carry an increased cost. According to Pillai, the challenge here was again to find a way to keep the cost affordable for a municipality with a population of 20,000. “We had to think outside the box as well,” he says. The project consisted of approximately 14 different contracts. AECOM assumed the role of representing the client with contrac- tors as well as providing engineering as a cost-cutting effort. On each of the segments, senior personnel met with team members to brainstorm ideas fitting within the original sustainability guide- lines and at the best cost. The city’s innovative approach to sewage treatment and disposal started in 1978, when the BC Ministry of Environment withdrew a permit to continue discharging treated effluent water, from treat- ment lagoons, into a nearby creek. The city looked at the cost of a full-scale mechanical treatment plant and balked. “We decided to acquire some crown land and dispose of treated sewage by using it as a source for irrigating cattle grazing and crop lands” says Jamie Hodge PEng, director of the City’s Engineering Services Department. Treated effluent water is sprayed on 60% of the 2,500 acres of crown land now under the city’s jurisdiction. Spraying occurs from May into October when the first frost hits, shutting down the spray system. “In order for the system to work,” explains Hodge, “we had to graze those lands.” Otherwise, the grass would grow and stagnate. That led to crops, with alfalfa harvested twice a year, and provided large grazing tracts that now feed 3,500 cattle and sustain six farms in the area. Environmental and Regulatory Challenges The city’s system ran smoothly for two decades, before encoun- tering issues. The first was a burgeoning population that placed greater pressure on the system. Originally the city’s two storage ponds were licensed at a holding capacity based on a maximum surface operating level of 827 feet above sea level; however, to accommodate the increased wastewater flow plus higher than normal snow pack run-off, the ponds were rising to as high as 830 feet above sea level in the late l990s. At the same time, the CPR rail line, approximately six kilome- tres away, experienced some slope instability and a derailment. CPR’s consultants determined that it was caused by leakage from the city’s ponds which had migrated through sub-surface soils to the CPR lands and weakened cut slopes along the trackage, causing the slope instability issues CPR was experiencing. “The Ministry of Environment, without any other science, accepted that as plausible,” Opposite page top: Aerial view of spray irrigation lands. Inset left: Cattle grazing in irrigated pasture. The City of Cranbrook uses treated sewage water for irrigation of crop and pasture fields. Inset right: Sewage treatment lagoon from Cranbrook’s existing sewage treatment system in 2010.

tells Hodge, whereas the City’s position was that to erode the rail line leaking water would have to run uphill some four to five kilo- metres. Regardless, Cranbrook saw its permit for storage capacity reduced to 824 feet above sea level in Pond 2, resulting in an overall 40% loss of storage volume for winter storage purposes. What then ensued was a battle between the City, CPR and BC regulators. Each party was entrenched in a position and cordial relations plummeted as Cranbrook continued to violate its permit

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