Rehabilitation in the rocky mountains

Reinstating the 3.5km long Laramie-Poudre irrigation tunnel in Colorado, US, involved a wide variety of rehabilitation methods. Restricted access to the site and tunnel works combined with strict environmental constraints also created major logistical challenges. The 3.5km long Laramie-Poudre Tunnel is located about 87km northwest of Fort Collins in northern Colorado, 72km up the narrow Poudre Canyon. The tunnel was driven from 1909 to 1911 at the narrowest point between the Laramie River in the west and the Cache La Poudre River in the east. The tunnel provides valuable irrigation water for agricultural, domestic, and industrial uses along Colorado's northern Front Range. In May 2000, the centre of the tunnel collapsed, flooding the upstream area and slowing the water to the Poudre River to a trickle.