Report outlines overpass feasibility

Engineering firm looks at five locations: Jim Smith Lake Road; King Street; 6 Street North; Theatre Road; and McPhee Road

  • Jan. 20, 2014 4:00 p.m.

Included in Monday night’s council agenda was a report about the feasibility of an overpass over one of Cranbrook’s railroad crossings. In the report Urban Systems details the feasibility of an overpass in five locations based on the current clearance requirements for a railway crossing and maximum allowable gradients for roadways identified by the Transportation Association of Canada (TAC).

The minimum clearance for an overpass over the rail grade is 6.858 metres under the TAC guidelines, while the maximum road grade is eight per cent. Urban Systems notes that with those figures, the overpass requires a minimum distance of 108 metres.

The engineering firm looked at these locations for the potential overpass: Jim Smith Lake Road; King Street; 6 Street North; Theatre Road; and McPhee Road.

“Of the five potential overpass locations we have reviewed, most clearly do not pass the most basic geometric parameters required to even consider the location feasible,” Urban Systems noted in the report.

Only the Theatre Road crossing met those basic requirements, though the report noted that there are several businesses and properties that are currently accessed from the location which would be significantly impacted and potentially also cut off due to the approach grades and road fills needed to accommodate the overpass.

The conclusion also assumes that Theatre Road’s north leg could be connected near the overpass location. Urban Systems said that could only be determined with a more detailed site survey.

The report also notes that overpass structures are an expensive alternative to crossings, and that the overpass would likely have to span the entire railway right of way width to accommodate all rail structures, access roads and future expansion potential.

Urban Systems also analyzed the potential costs of a Theatre Road overpass, coming up with an estimated $10.8 million figure. The majority of that figure is the 75 metre by 11.2 metre overpass structure itself, at $5.25 million, the cost of retaining walls at $1 million and the 30 per cent contingency and engineering fund of $2.5 million. The rest is made up of materials, traffic management and mobilization.

The firm estimates that the overpass structure itself would have an expected service life of 75 years, the retaining walls 40 years and the approach roads 20 years. In the review Scott Shepherd, asset management consultant, notes that together the assets will last an average of 53 years.

“Based on current replacement values, approximately $203,000 should be set aside annually to ensure sufficient funds are available for replacement when this infrastructure reaches the end of its expected service life,” Shepherd said in the report.

The report is part of today’s council meeting agenda under the administration updates.