Boulder County through its Parks and Open Space Department (BCPOS) owns and manages the subject project area (also referred to as Hall Ranch II). The South St. Vrain Creek experienced damage to its stream course, banks, riparian and upland areas, as well as ditches, bridges, roads and private homes from the 2013 flood. The very severe damage in this project area was due to the volume and velocity of water and amount of sediment and other debris immediately exiting the canyon and entering the valley. High stream forces due to sediment laden flows stripped sections of the gravel road surface, eroded gullies through the road surface and sub-base, damaged culverts, caused debris flows across the road and clogged roadside ditches. Most significantly, the hydrodynamic forces completely eroded a 240 foot section of the access road where the South St. Vrain Creek shifted its channel into the road alignment. A temporary low water crossing was put in place during the implementation of the Hall Meadows South St. Vrain Stream Restoration project in order to transport excess materials to the old quarry site located on Hall Ranch II. This temporary low water crossing has been approved by United States Army Corps of Engineers (USACE) and Boulder County to remain in place and will be used as the initial base for the new road reconstruction.
The purpose of the project is to restore the only access road into the Hall Ranch II property to its pre-flood alignment and grade, and to secure mitigation measures that provide protection from subsequent events. The Project site is located at 1450 Old St. Vrain Road, Lyons, CO 80540.
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