Need for tree removal
The Transportation / Utility Corridor (TUC) is land set aside to house the ring road, major power lines, pipelines and linear municipal utilities. Now that the West Calgary Ring Road (WCRR) project is underway, several underground utilities are being installed within the TUC east and west of Valley Ridge Boulevard NW as part of construction: a new stormwater feedermain, re-aligning the existing water feedermain and in the future, The City of Calgary will install a sanitary feedermain. Additionally, this land must also accommodate the ring road itself which includes a retaining wall and bridge structure as part of the upgraded Trans-Canada Highway / Valley Ridge Blvd NW interchange.
The planned construction activities require deep excavations that could damage the tree root systems, potentially resulting in destabilizing the trees or tree deaths. Poplar trees have an expansive root system, typically spreading out two or three times the height of the tree. Both conditions present a high safety risk to construction workers, adjacent properties and residents. To determine which trees needed to be removed, the design-build contractor for the North project, EllisDon Construction Services Inc. (EllisDon), engaged ArborCare Tree Service Ltd. (ArborCare) to perform an Impact Assessment on the trees within the work area.
Arborist’s assessment and recommendations
ArborCare visited the site on August 1 and 12, 2019, to assess approximately 200 existing Poplar and Spruce trees. Based on the size and species of the existing trees, the Arborist calculated the how far away the excavation would need to be minimize risk to the trees. Based on those distance requirements for working safely, the Arborist determined approximately 65% of the existing trees were in direct conflict with the essential construction activities and need to be removed.
At the community’s request, the Arborist evaluated the possibility of transplanting the Spruce trees west of Valley Ridge Blvd NW. For a number of factors, including the relatively small size of the trees and a lack of available space nearby to store them, the Arborist indicated they were likely to die before being replanted.
Design review and outcome
Following the Arborist’s recommendations, EllisDon submitted their tree removal request to the Province. The Province reviewed the request to determine if the design could be revised to save additional trees. After rigorous examination, the end result was about half of the 200 trees in the work area needed to be removed due to the limited space coupled with the size of the root systems.
The trees identified for removal were surveyed by a professional Biologist for wildlife habitats and none were found. Approval to remove these trees was granted and was complete in mid-September.
Tree replacement
The removed trees will be replaced at a 2-to-1 compensation ratio where space is available. The locations will be determined based suitable tree species, size and spacing to encourage healthy growth and full coverage. The trees will be replaced when the work in this area is complete. When the locations have been determined a plan will be shared with the community.
The replacement trees will be a mixture of:
- 40% White spruce (Picea Glauca)
- 40% Lodgepole pine (Pinus contorta var. latifolia)
- 20% Trembling aspen (Pupulus tremuloides)
Approximately 40% of replacement trees will be 2.5 – 3 metres tall and the remaining 60% will be between 1 and 1.5 metres in height.