Thursday’s historically high rains discharged unexpected amounts of raw sewage to the shorelines of Greater Victoria.
Stormwater flows from Thursday’s 48 millimetres of precipitation infiltrated numerous wastewater overflows along the shorelines, particularly in Saanich, Oak Bay, Victoria and Esquimalt.
The region’s main trunk sewer system is not designed to handle 5 centimetres of rain in one day, which is about 10 per cent of Victoria’s anticipated annual rainfall of 58 cm per year (according to Victoria’s website).
The Capital Regional District and Island Health confirmed they’ll sample the beaches for enterococci levels above/below the 70CFU/100mL recreational limit, said Matthew McCrank, senior manager of infrastructure operations with the CRD.
Until the numbers are in (it will take a day or two) it’s best to keep dogs (and humans) out of the water along the beaches of Saanich’s Arbutus Cove, Finnerty Cove, Telegraph Cove and Cadboro Bay, Oak Bay’s McNeill Bay, Victoria’s Clover Point and Ross Bay, and Esquimalt’s Saxe Point, Macaulay Point and McLoughlin Point.
“We’ll post a sign in the affected areas if it remains above the 70CFU/100mL [threshold],” McCrank said.
Sewage overflows are nothing new in the region that still sends untreated waste into the Salish Sea, such as Saanich’s Arbutus Road area, where the smell of fresh rain is commonly replaced by the stench of sewer.
“Infiltration,” as it’s known, is a common problem around the region, not just in Saanich or Oak Bay. And it’s generally in certain areas, McCrank said.
So where does sewer infiltration come from?
It can be as easy as stormwater flooding over the four holes seen in manhole covers along the street surface. But mostly, it’s because municipalities such as Oak Bay’s Rutland pump station are overwhelmed by a system that’s not designed to anticipate heavy rain events.
— Sarah Campden (@scampden) January 4, 2019
Keep in mind, Vancouver’s annual rainfall is nearly three times greater than Victoria’s.
The other reason for infiltration is that the wastewater pipes are not all sealed, meaning there is various entrance points. Some municipalities continue to drain storm water through their wastewater system to this day, and based on the expected amount of rainfall in Victoria, it mostly works.
Greater Victoria’s new $765 million wastewater treatment system will actually minimize some of the common overflows though to what extent, McCrank can’t confirm.
Part of the deal will install a 5,000 metres-cubed attenuation tank along Arbutus Road, known as the Arbutus Attenuation area which currently overwhelms the sewage outflows in that area. Instead, the tank will release into the new wastewater system and flow to McLoughlin Point. Plans for the tank were made in a 2013 deal when Saanich secured 2.8 hectares of Haro Woods with the CRD.
Cadboro Bay is often hit during high rain events for multiple reasons as Rutland and Humber collect sewage only from Oak Bay but overflow with light to moderate rains.