Swan River

ERC was contracted by Summit County to complete a design/build restoration for an approximately one mile reach of the Upper Swan River. The Upper Swan River project area, a major tributary to the Blue River, had been historically mined using dredging techniques leaving the stream below ground and the valley devoid of natural vegetation and ecological function. ERC’s task was to recreate the stream, riparian, and upland areas in a natural manner to replicate pre-mining activities. Work included creation of a meandering valley river and restoration of approximately 29 acres of riparian and upland habitat. ERC worked closely with project sponsors including Summit County, the Town of Breckenridge, and the Forest Service to define appropriate hydrology, channel morphology, bankfull channel widths, channel planform, substrate liner material, rock sizing, a new aquatic organism passage bridge and stream profile as well as riparian and upland restoration techniques. The plan employed natural channel design including riffle-pool-glide sequences and establishment of native vegetation communities. This complex restoration project illustrates our team’s abilities to incorporate the full gamut of technical, permitting and construction complexities of a large-scale multi-objective restoration project.

Before & After

Photos provide an overview of pre project conditions of the stream channel alignment

Swan River After

Overview

The project objective was to create a natural restoration of the Swan River valley bottom as a public open space amenity. To facilitate this work, the level of the existing groundwater table was determined and a plan that lowered the valley elevations to a point where water could be captured to create a new stream was devised. Regional streams were evaluated to determine an appropriate planform for the new channel. A meandering stream, riparian zone and floodplain were created. Dredge material was excavated, crushed and regraded to form the new landscape while mine tailings were consolidated and capped. Areas adjacent to the stream were designed to recreate a natural riparian corridor and the surrounding landscape was sculpted to replicate an upland valley topography.

Construction

In 2016 the first phase of restoration work was completed on the Swan River near Breckenridge, CO. The work was a demonstration project showing a riverine system that had been lost due to placer mining and subsequently impacted by tailings deposition could be restored to approximate near pre-mining conditions.

Improvements

Objectives achieved by the restoration include:

• Creation a natural, stable channel to convey existing and anticipated flows and sediment loads;
• Establishment of a gaining stream with perennial stream flows;
• Development of instream aquatic habitat including pools, riffles, glides, spawning and rearing areas;
• Removal of a vertical aquatic migration barrier and creation of a bankfull bridge crossing;
• Restoration of floodplain connectivity;
• Reclamation of mine tailings;
• Removal, regrading and capping of remaining dredge material; and
• Creation of riparian and upland function and habitat

Results