Blackstone was tasked by Magellan Pipeline Company to provide an environmental risk evaluation associated with the removal of an abandoned section of pipeline crossing the Cache la Poudre River in Larimer County, Colorado. A 900-foot section of pipeline crossing the river was horizontal directionally drilled below the river channel, resulting in about 900 feet of abandoned, inactive pipeline being left in place. About 130 feet of the abandoned section was exposed on the riverbed. Prior to re-drilling the pipeline, previous efforts to protect the exposed section of pipeline included installation of concrete grout matting around the line to prevent damage from debris such as tree limbs flowing down the channel. Larimer County wanted a review of potential environmental impacts associated with the abandoned section of line to assist in their determination of whether it should remain in-place or be cut, capped and removed from the river channel.
The assessment identified potential impacts associated with both options of leaving the abandoned section of line in-place and removing it. Potential impacts to trout/fish habitat, Cache la Poudre River ecology, riverbank slope stability, water quality, wetlands, riparian zones, and recreational use were evaluated. It was concluded that the abandoned section of pipeline could be removed, but not without impacts to the river and its surroundings.