City of Kingston addresses flooding of Gardiners Road underpass

Gardiners Road underpass flooding in July 2021. Photo by Cody Stafford-Arenburg/Kingstonist.

Anyone who has spent any time on Kingston’s west-end roadways will know that every time heavy rain passes through the area, the underpass on Gardiners Road is likely to fill with rainwater.

Over the past few years, the occurrences of flooding in that area have increased, perhaps in relation to increased severe weather events. Kingstonist inquired with the City of Kingston to find out why the flooding occurs and what, if anything, they have planned to alleviate the issue.

The Gardiners Road underpass, which was constructed in 1983, was designed to separate the municipal roadway from the public level crossing of the CN Rail.

“The purpose of the project was to better manage the increased traffic flow along Gardiners Road, which would often back up onto the busy east-west arterial there of Bath Road, to the south,” stated Adam Hardy, Supervising Engineer for the City of Kingston.

Hardy noted that an overpass at that crossing was not considered at the time, as there is insufficient space for the length of approach needed to create a high enough overpass, and keeping a four-lane road with a level CN crossing would not have been in anyone’s best interest.

At the time of construction, and throughout continued development in the area, private property owners, as well as City workers, have been educated on keeping storm sewer channels clear. More recently, the City is requiring that property owners in the area “reduce what we call the peak or the highest stormwater flows leaving their site by at least 20 per cent, using some form of on-site stormwater storage,” Hardy said, noting that this is a condition of approval for new development.

In 2017, after a particularly significant storm and related flooding incidents, the City hired a consultant to look at a number of locations that experienced flooding, the Gardiners Road underpass being one.

“One of the things they did was what [the consultants] call a hydrologic and hydraulic analysis, so looking at what water is captured in the area and heads to the underpass, and how the stormwater system functions,” Hardy shared.

“So, the catch basins, the pipes, the drainage channels, [all were] confirmed that the system… was designed in accordance with the standards at the time. But it meets our current municipal design standards and current provincial regulations, and can manage rainfall for the most significant events you’d expect to see in a typical two- to five-year timeframe.”

According to Hardy, one of the long-term solutions proposed in this study suggests the consideration of a stormwater management pond in the downstream drainage channel (west of the storm sewer outlet). “Since this memo was submitted in 2019, City staff have investigated this option and determined it was not an effective solution because it does not address the need for a clear overland flow path from the underpass to the drainage channel that would prevent the road from flooding during heavy rainfall events,” he said.

Hardy stated that stormwater has become “more front of mind” in recent years, and that the rainfall data which developers use to determine designs for construction rely on past data.

“Certainly there’s been, you know, a change in the climate, let’s say, where we are seeing more frequent, more severe, more intense storm events than we may have at the time [of construction]. So from a stormwater perspective, that may be a different input or consideration, if it were to be constructed today, but again, you know, the options [at the rail crossing] are over, through or under,” he maintained.

Indeed, over the past 148 years, Kingston’s annual precipitation has increased by about 98mm (10 per cent), according to @YGK_Weather. Over that same time frame, of all the wettest Springs on record (ie. those with >300mm of precipitation), five of eight of those have been in the past 11 years.

Graph showing the increasing trend of average precipitation over the years. Source: @YGK_Weather
Table highlighting Kingston’s wettest springs since 1872. Source: @YGK_Weather

In terms of how the City is alerted to localized flooding, such as the occurrences at the Gardiners Road underpass, Hardy said that they mainly rely on public input through their customer relationship management system. “It tracks all those incoming flooding concerns or any concerns in general that we’ve received, and assigns them sort of a tracking number and forwards them directly to an appropriate supervisor,” he shared.

The City then sends the appropriate personnel to investigate and take whatever action is necessary. Hardy also noted that Environment Canada and the Cataraqui Region Conservation Authority will issue notices ahead of weather events or potential instances of flooding in the area. “When special weather statements are issued, the City of Kingston shares flood preparedness and safety messages from Utilities Kingston and the Cataraqui Region Conservation Authority,” he clarified. “If City buses end up on detour, Kingston Transit will usually send information to passengers advising of the temporary detour and bus stops that are out of service.”

According to Hardy, the underpass is on the city’s flood zone monitoring list. “That ensures that the storm sewer system there is inspected, cleared, and determined to be functioning properly before and after heavy rainfall events, and includes increased street cleaning, sweeping, and flushing of the sewers on a regular basis,” he stated. “And these efforts, in particular, have been elevated at the underpass since the very significant flooding experienced in 2017.”

The City also does regular maintenance in that area. “So, we clean the catch basins, we flush and camera the sewers in that area, and clean out the downstream drainage channel if it’s overgrown or there’s debris. It can be a problem spot for that, so we’ve enhanced our frequency of inspections through there,” Hardy said.

When asked if the City has plans to further alleviate the flooding at the underpass, Hardy said, “I don’t think it’s possible to entirely eliminate the flooding in this particular location.”

“It’s possible to reduce the risk, and by that I mean the frequency and the severity, and even the duration of the flooding and the impacts to the public,” he continued. “Really, the most feasible or prudent course of action would be to continue with the current approach, which is advanced warnings to the public, continuing with the proactive monitoring and maintenance, and inspection and cleaning. When the flooding is particularly bad, we assist with traffic control.”

According to Hardy, drivers along Gardiners Road will have to continue to monitor weather forecasts and get their notifications on social media to stay current on any localized flooding in the City of Kingston.

With files from Cris Vilela.

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