By Brian Hoop
ODOT has received approval from the City on an Environmental Review to complete additional rock wall stabilization work along Bridge Avenue where landslides occurred in April 2022. The proposed work will affect 39,556 square feet of temporary and permanent disturbance area and include the removal of 67 native trees; emergency work last year affected 12,203 square feet of disturbance area and the removal of 26 native trees.
The approval requires $283,500 for mitigation to take place in the Central Management Unit of Forest Park, restoring between 81 and 95 acres and planting of 32,400 to 38,000 native trees and shrubs. This will result in invasive plant coverage of less than 20% of surface area including English Ivy, clematis, and Himalayan blackberry. English laurel and holly will be cut and treated within the project area.
Parks and Recreation will install an average of 400 native plants per acre in impacted areas. This will provide lasting improvements to the forest ecosystem by decreasing the presence of invasives to the point that they no longer impact the health of the forest while restoring a diverse native plant community that enhances wildlife habitat. This will also help reduce erosion and contribute to the long-term sustainability of the forest.
The rock wall work will complete hazardous vegetation clearing, loose rock removal, and installation of additional pinned mesh containment on the rock face along NW Bridge Avenue, preventing future rockfall events and adequately mitigating those that do occur.
ODOT was required to seek approval since most of the affected area is within Environmental Conservation and Environmental Protection overlay zones, the majority occurring within the City’s Forest Park Natural Resource Management Plan (NRMP) boundary. ODOT geotechnical engineers determined that the recent rockfall events were caused by root wedging, a process in which plants and their roots wedge into existing cracks within the rockface, widening the cracks, and eventually loosening larger rocks and boulders until they break free from the rockface.
For more information on this case – LU 22-205565 EN – go to: https://tinyurl.com/5dmpxs2f