By Peter Kenter
Dewatering a project site in Toronto became a whole lot more complicated in 2016. Hoelscher Dewatering has developed a system that dewaters excavations, treats the water and then puts the water back into the ground in a series of injection wells away from the construction site. This helps maintain groundwater levels. In May, the city amended its Sewers Bylaw (Municipal Code Chapter 681). In October, it issued a revamped Private Water Discharge Approval Application that demands significantly more information upfront than its predecessor.
The biggest change to the sewers bylaw concerns the definition of private water — any water not purchased from the city, but requiring discharge into a city sewer. That category now includes all “stormwater and/or groundwater collected on private lands.”
“There was a big transition period for the new application forms with a lot of our clients,” says Laura Maharaj, a hydrogeologist with Groundwater Environmental Management Services, Inc. (GEMS). “Before, you could apply for a short-term construction dewatering permit and at a later date apply for a long-term permit for continuous discharge after the building is completed. Now you have to apply for both at the same time, and much more information is required. No partial applications will be accepted.”
Of particular importance is an accurate tally of the estimated private water to be discharged to city sewers. Maharaj notes that shoring and foundation permits have been withheld until that information has been nailed down.
“You need to choose between fully waterproofing the building, paying to discharge water to the sanitary sewer or creating a permanent treatment system and discharging to the storm sewer for free. Getting the application right is essential to project scheduling,” she says. “We’ve had contractors who used to submit the applications themselves and they’re now asking us to help them complete the new applications.”
Maharaj notes, for example, that the new application requires full mechanical and civil drawings of the permanent private discharge system before any work begins. The new application also devotes an entire page to information on short-term flow meters used to measure water discharge, requiring manufacturers’ specifications, equipment serial numbers and calibration certificates.
While some of this information may have been requested in the past, it’s now part of the formal application. The city recommends that applications be submitted eight to 12 weeks in advance of project initiation. However, Maharaj cautions that in her experience, 12 weeks is more likely than eight. Major errors or omissions can derail the application, while minor ones can cause delays as applicants are instructed to fill in the blanks, then move their applications back into line.
Last fall, German dewatering specialist Hoelscher Dewatering entered the Ontario market as its first foray into North America. One reason is that the province’s complex dewatering regulations, such as those seen in Toronto, largely mirror the European regulatory framework. The other is the large volume of construction spending on transit infrastructure, high-rise buildings and pipelines.
The contractor specializes in completing permit applications, engineering dewatering systems operating during construction projects, and designing permanent dewatering systems left in place after projects are commissioned.
The company is currently at work in Copenhagen on the seventh year of a long-term dewatering contract for the city’s Cityringen (City Circle) transit system.
“Historic buildings in the city are built on wooden piles, and once they’re soaked with water you can’t easily dry them out,” says Patrick Maher, business development manager for Hoelscher Dewatering. “We’ve developed an extremely elaborate system that dewaters the excavations, treats the water to standards close to drinking water quality, then puts the water back into the ground in a series of injection wells away from the site. That recharges the aquifer and helps maintain groundwater levels.”
Maher notes that developers can avoid private water discharge fees by designing high-rise buildings in “bathtub” style, making them fully waterproof, and deflecting water away from the foundation. It’s typically an expensive option. They can also build a drainage layer into the bottom of the building and use a sump to pump the water into either the storm sewer system or the sanitary sewer system.
There is currently no fee to discharge private water to the storm sewer system if capacity exists downstream. However, before developers can enter into a Storm Discharge Agreement with Toronto Water, they must design a system that discharges water treated to the quality standards set by the sewers bylaw. The bylaw sets limits for metals, such as chromium, lead and manganese, and for chemicals, such as xylenes, toluene and trichloroethylene.
The rate for discharging private water to the sanitary sewer is $2.065 per cubic metre as of Jan. 1, 2017.
“You need to choose between fully waterproofing the building, paying to discharge water to the sanitary sewer or creating a permanent treatment system and discharging to the storm sewer for free,” says Maher. “It’s up to the developer to do the calculation.”
Maher notes that re-injecting treated water into the aquifer as the company is doing in Copenhagen could also eliminate discharge fees. However, Toronto Water notes that a wet well would first require approval from the Ontario Ministry of the Environment and Climate Change. The city would then evaluate the wet well to ensure there was no indirect discharge to the sewer system.
“It’s not yet very common here,” says Maher. “It will still require some convincing to the Ministry of Environment that it’s a safe and effective approach.”
This article was reprinted with permission by author Peter Kenter