Residents learned of the impacts and mitigations from the two-block closure of Riverside Drive between 5 Avenue E and 3 Avenue E for flood mitigation during a virtual information session hosted by the Drumheller Resiliency and Flood Mitigation Office (DRFMO) on Wednesday, March 16; the findings were determined by a Traffic Impact Assessment (TIA) by Sweet Tech Engineering.
One of the primary concerns addressed by residents was the potential increase of emergency response times this closure could create, and the TIA was used to determine any potential impacts and develop mitigation strategies.
“Closing this two-block section we understood this would have impacts to existing traffic patterns and habits,” said Sweet Tech principal engineer Eric Sweet. He added these impacts warranted investigation due to their importance.
Data from a 2007 iTrans study was used, along with traffic counts at two intersections along Riverside Drive from August 2021; traffic counts along the Highway 9 and Highway 56 corridors were also collected from Alberta Transportation and appropriate growth rates were applied to provide a “worst-case scenario” to estimate the impact the road closure would have.
From this data it was determined three intersections-at Railway Avenue and 5 Street, Railway Avenue and Centre Street, and Centre Street and 3 Avenue-could have delays due to greater traffic volume, and changes to these intersections were recommended.
This would convert the four-way stop at Railway Avenue and 5 Street intersection and the Centre Street and 3 Avenue to a two-way stop, prioritizing diverting traffic into the downtown core via Centre Street; a dedicated right-hand turn lane at Railway Avenue and Centre Street was also recommended.
Based on the data from the traffic modelling, it was determined these changes would have no negative impact on emergency response times.
The Drumheller Fire Department received some 155 emergency calls in 2021 and Riverside Drive was used in about half of these calls; this route has an average response time of 130.3 seconds in morning peak hours, and 131.1 seconds during evening peak hours.
Using the preferred diversion route along Centre Street and Railway Avenue would cut this response time down, pre-closure, to about 107.3 seconds and 107.9 seconds during morning and evening peak hours respectively; post-closure this would be further cut down by about seven seconds in the morning and about one second in the evening.
An alternate route using 2 Avenue and Highway 56, both pre- and post-closure, would remain the same at 119.4 seconds due to the emergency traffic light at this intersection.
Mr. Sweet explained the dike along Riverside Drive is one of the most vulnerable sections due to its overall length and the need to build it up to the 1,850 cubic metres per second flow rate.
Although other flood mitigation measures were considered for this area, due to costs or regulatory constraints, these were not deemed feasible. One option, to keep Riverside Drive open, would require a retaining wall about 280 metres long and nearly 10 feet high along this stretch.
Preliminary capital cost estimates, for just the retaining wall, were in the ballpark of $1.2 million; this does not include an estimated $500,000 minimum needed for road work needed following berm construction, or ongoing maintenance, which would be borne by the Town.
Mr. Sweet also noted the retaining wall could face damages in the event of a flood from adaptive fill being placed on top and these repairs would not be covered under the provincial or federal funding for the project.
After the original announcement of the road closure a citizen survey was conducted over a six-week period between December 2021 and January 2022; a total of 387 responses were received, equating to about 4.6 per cent of Drumheller’s population.
Of these responses, 203 respondents use Riverside Drive to commute but are not directly impacted; 167 respondents live in nearby neighbourhoods in the footprint of the dike, and 105 of those are directly impacted residents. Among the respondents were downtown business owners, volunteer firefighters and other emergency responders.
A total of 86.3 per cent of all respondents, both commuters and impacted residents, cited traffic as a primary concern, and 101 of the 105 directly affected residents were concerned about the traffic changes the closure would cause.
The preferred diversion route through the downtown core via Centre Street would provide benefits to businesses in the area and falls in line with the town’s 15-year Downtown Area Revitalization Plan (DARP). It was also noted, by moving the plaza to between Railway Avenue and 3 Avenue it would eliminate the need to close Centre Street for events and festivals, leaving this area unobstructed for emergency and other traffic.
First reading of the Road Closure Bylaw came before council on Monday, March 21 and a public hearing was scheduled for Tuesday, April 19.
The bylaw and information from the public hearing will be forwarded to the Minister of Transportation and, if approved, the bylaw will be brought back to council for second and third reading considerations.
