DEERFOOT TRAIL EXTENSION-MANAGING RUNOFF TO PROTECT THE BOW RIVER

摘要

The Deerfoot Trail Extension is 11 km of new freeway which was opened to traffic Nov.28th, 2003. The project cost $100M, and extends south from Hwy 22X to the existing Hwy 2 / 2Ainterchange south of Calgary. This completes a previously missing direct link in Hwy 2, which is part ofthe North / South trade corridor through Alberta.This project resulted in new twin bridges across the Bow River. The Bow River is rated as one of the topsix fly fishing rivers in North America. This, along with the design team's desire to "raise the bar" for thisproject resulted in the first Alberta provincial highway project to incorporate a storm drainage system thatcaptures all highway runoff from the bridges, and 2 km of hwy to the south, and carries it to a two stagesedimentation pond. Here, a minimum 85% of sediment is removed from the run-off before flowing to aninfiltration gallery in adjacent granular soils. The system is designed so that overflows (above designstorm event) from the infiltration gallery would enter the intermittent Pine Creek, which meanders for over1 km before entering the Bow River.The sedimentation pond is designed with a central weir which captures the majority of the sediment, andmakes periodic pond cleaning more efficient. The outfall structure is designed to remove water frombottom levels of the pond, thereby allowing any hydrocarbon spills to stay in the pond by floating on thesurface until they can be cleaned up.A similar drainage system was designed by other consultants to capture runoff from Deerfoot Trail north ofthe Bow River.The project also included several other noteworthy environmental mitigations, including:1. Alignment shift 130m west to miss Bow River side channel2. Re-alignment of Pine Creek to restore creek-bed lost under Deerfoot trail embankment3. 4m × 7m × 85m wildlife underpass complete with median sky-light4. 2.4m high wildlife fencing from the Bow River south for 2 km5. "Wildlife Impediments" at ends of fence to prevent animals "end-running"6. Plantings to create new protected wildlife corridors along both sides of Deerfoot Trail embankmentfrom Bow River to south escarpment7. Lengthened Bow River bridges to provide 30m "dry" wildlife corridors along both sides of the Bow river8. Development of first ECO Plans (Environmental Construction Operations) for Alberta Transportationprojects, to manage and minimize sediment escaping into Pine Creek and Bow River during road andbridge construction.