Sanitary infrastructure capacity impacting NW development
Rapid population growth in the city’s northwest is creating new challenges for planners on how to best manage the quadrant`s already strained sewage infrastructure system.
The West Memorial Sanitary Trunk – which extends from the communities of Bowness to Rocky Ridge and impacts 24 communities overall – is, and has been for at least two years now, operating at capacity in certain areas.
“There’s a portion of the trunk within Bowness that has a capacity constraint,” said Francois Bouchart manager of infrastructure and planning with City of Calgary Water Resources, noting the area the trunk serves has seen a 30 per cent population increase over the last decade.
Bouchart said the usual flow – including toilet flushes and dishwashers – can currently be accommodated. The problem is in-flow infiltration from small cracks that develop in the trunk, allowing rain and groundwater to enter the pipe, as well as rain and stormwater that enters through small openings in manholes.
Because of the constraints, development in the city’s northwest is now being closely monitored. The City recently introduced new criteria for how planning, development and building applications will be processed in impacted communities, including Bowness, Edgemont, Hawkwood, Citadel, Dalhousie, Varsity, Ranchlands, Arbour Lake, Scenic Acres, Silver Springs, Tuscany, Royal Oak, Rocky Ridge, Valley Ridge and Crestmont.
Homeowners applying for development and building applications – including basement renovations and decks – that do not impact sanitary sewer, as well as homeowners looking to replace a single-family unit with two single-family units, a semi-attached dwelling or a duplex, will not be affected by the new criteria, and will be reviewed as per usual.
However, building permits larger than a proposed subdivision of one to two lots, or one that adds to the net increase of the sanitary system, will not be approved in impacted areas. The City will suggest options – such as trucking sewage off-site, diverting it to another sanitary catchment or utilizing water reuse – but the cost of those methods will be the responsibility of the applicant.
“For developments that haven’t started, what we really need is that to slow down,” said Bouchard.
Other components of the new criteria include:
• Eliminating the need to delay applications with no sanitary impact caused by case-by-case review; • Providing customers further clarity on how their project might be impacted before submitting an application; • Enabling customers to plan, develop or build to the furthest point possible before wastewater upgrades are completed, and; • Delivering a consistent and transparent method of approving, holding or rejecting applications. In communities affected by the trunk constraint, residents are of mixed opinions on the trunk upgrades.
“Tuscany is a nearly-complete community, and a few residential developments have been delayed as a result of the necessary upgrades,” said Kelli Taylor, president of the Tuscany Community Association.
“Some adjacent neighbours are somewhat frustrated, due to the appearance of the undeveloped land, and would like to see these parcels built as soon as possible. Others enjoy the natural look of the land, do not want the areas to ever be developed, and are pleased with the delay. Either way, residents are concerned about the ability to sell their homes, as the timeline for construction seems uncertain.”
Last November, council approved $50 million in trunk upgrades. A tender package is currently being prepared by the City with expectations it will be awarded this fall – at which point a contractor will be awarded the project.
The anticipated completion date for the upgrades is 2017. Until then, and to reduce backflow risk to area residents, Bouchart said the City is lining existing sewers with a structural liner that seals cracks preventing groundwater and rain seepage. Another option is to install back flow prevention valves, but Bouchart said that measure is up to the homeowner.