Owner/Client
Nyrstar Tennessee Mines
Location
Elmwood, TN
CEC Services
- Aquatic and Terrestrial Habitat Surveys
- Ecosystem Restoration
- Fish and Macroinvertebrate Surveys
- Wetland & Stream Mitigation Design
- Stream Assessments and Restoration
- As-built Surveys
- Construction Surveys
- Horizontal and Vertical Control Surveys
- Topographic Surveys
- Construction Management
- Construction Services
- Design/Build Services
Owner Objective
Nyrstar requested a design/build stream mitigation project for the removal of two obsolete mill ponds and creation/restoration of new stream channel on the unnamed tributary to the Caney Fork River. Nyrstar’s Elmwood tailings impoundment needed greater storage volume that required the need to raise the dam. Construction of the proposed dam stages and subsequent placement of tailings would physically impact a stream. Nyrstar must offset the impacts related to the impoundment modifications by constructing a total of 1,615 linear feet of stream and habitat restoration at two locations. The Elmwood Stream Mitigation project involved 720 linear feet of an unnamed tributary to the Caney Fork River at Nyrstar’s Elmwood mine property in Smith County, Tennessee.
CEC Approach
CEC’s approach to restoration of the unnamed tributary involved the removal of two mill ponds and construction of a natural stream channel in the footprint. The design approach focused on maintaining channel stability and improving instream and riparian habitat. The design entailed the construction a series of boulder step-pools and riffle cascades. The riffle cascade and step pool habitat reduces bed shear stress, and provides for a more self-sustaining stream system. Restoration measures included dam removal, channel and floodplain excavation, boulder structure installation, and tree planting. Riparian restoration activities included sowing a perennial native seed mix, live staking on the newly graded banks, and tree planting within the riparian buffer.
