INNOVATION November-December 2012

f ea t u r e s

A completed Pond 3, ready to store reclaimed water.

Inset: Pond 3 under construction.

wastewater group within the project, now with the City of Calgary. The new aeration system in storage pond No. 2 allows the City to increase or decrease the needed surface water level as required. A third, man-made storage pond (No. 3) was built at the southerly end of the spray irrigation property, approximately six kilometres from the other storage ponds and near the irrigation area. It exists as an additional holding pond as it can take water through the pipeline from pond No. 2. Water stored in this third pond can be released into the Kootenay River via a 3.7 kilometre pipeline, but not before it goes through a new ultraviolet disinfec- tion system. This treated water may also one day be used to provide high quality effluent to recharge a large wetlands area situated adjacent the outfall pipeline route. The outfall pipeline to the Kootenay River runs past wet- lands created by Ducks Unlimited in an oxbow area of the river in the early 1970s. The City and Ducks Unlimited have talked about bringing treated water into the wetlands from storage pond No. 3. “It is only a 100-metre pipeline that is needed to be built [from the City outfall line to the wetlands area],” says Joe McGowan, in charge of public works for Cranbrook. Potentially, the wetlands could take up to a million cubic metres of water per year. Vargas calls storage pond No. 3 “one of the most beautiful in the world as it is sculpted to follow the landscape and perfectly shaped.” The storage pond, which has a liner, is able to hold one million cubic metres of water. The pipeline taking treated effluent water from the third stor- age pond to the Kootenay River presented its own challenges. Consulting environmental engineer Julia O’Shannassy PEng, for the City said that the ability to use horizontal directional drilling on approximately 100 metres near the river preserved the eco- system around the water body. The riverbanks are a very fine silt and easily eroded and hard to compact when construction occurs. There was also the the potential for material to slide into the river. The river also had a green belt of trees that had to be preserved.

criteria. “We couldn’t make the 824 criteria,” says Hodge. Things got worse. Starting in early 2000 and culminating in 2007, wetter years were sending more runoff into storage ponds. “It was the straw that broke the camel’s back,” he observes. “The only real alternative was to build capability so that our levels would not exceed 824 and if we had to, then discharge into the Kootenay River,” Hodge tells. That brought new concerns. “Requirements set by the Federal Government for discharge of efflu- ent to both land and surface waters were getting tighter and tighter.” AECOM was retained in the fall of 2009 and over an eight- month period, an assessment was made of the overall system, which involved two pumping stations, a three-cell facultative lagoon treatment system that used oxygen to promote bacteria in the lagoons (one cell had an outdated mechanical surface aera- tion system), a total of 9.4 kilometres of transfer pipeline carrying partially treated wastewater to the spraying system at the northeast side of the city and the irrigation system itself. During this period, environmental impact statements were detailed, consultation with First Nations took place and regulatory approvals were sought. The scope of the work needed was broad; virtually every aspect of the system required enhancement ranging from more modern computerization of controls to replacing sections of the transfer pipeline (remaining sections having an estimated life of five to 10 years). It became evident that a new storage pond, located near the irrigation area, was needed. The irrigation system also needed upgrading with more efficient spraying system. Today, all three lagoon cells have been fitted with high-effi- ciency fine bubble aeration systems. Storage pond No. 2, which received primary treated sewage, was upgraded with a new coarse bubble aeration system. It is now a variable level treatment and storage lagoon. “This is the first time in my career that I have seen an aera- tion system in a pond with such surface level variation,” says Carlos Vargas PEng, formerly AECOM’s leader for the water and

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