Dutchman Canyon Wetland Improvement Project: Assessment & Concept Design

Dutchman Canyon Wetland Improvement Project: Assessment & Concept Design

The New Mexico Abandoned Mine Land (AML) program, in partnership with Vermejo Park Ranch, is working to mitigate the effects of legacy coal mining on water resources at the Dutchman Canyon reclamation site by managing mine seepage and improving the quality of water reaching the Dutchman Canyon stream channel. As part of this effort, AML completed work in 2012 to stabilize the existing pond system that collects mine seepage from adjacent adits, including adding freeboard to the pond embankments and constructing a spillway that diverts mine seepage to a new wetland site located just east of the pond system. AML also completed access road and drainage improvements, including a low water crossing and rock chute to control erosion and convey runoff from the new wetland system to the Dutchman Canyon stream channel.

The Dutchman Canyon Wetland Improvement Project was  a continuation of previous mitigation efforts by AML with the goals of:

• Maximizing potential wetland habitat acreage on the site while minimizing excavation and site disturbance
• Addressing erosion issues caused by recent storms, including rill and gully formation within site and damaged erosion control measures at the outlet of the site
• Minimizing operations and maintenance requirements while maximizing habitat management flexibility

Oxbow Ecological Engineering was contracted to complete the assessment and design and as part of the work OEE collected detailed supplemental engineering survey information and geo-referenced photos. OEE collaborated with Fred Phillips Consulting to develop a holistic strategy for improving and increasing wetland habitat and regenerative erosion control design to stabilize eroded upland landforms. OEE completed all analysis, including hydrologic and hydraulic modeling, design, and advanced concept documents for the new wetland complex. Design elements included:

• Earthwork – create a series of three managed wetland cells, delineated by compacted earthen dikes. Dikes are placed and sized to encourage the growth of emergent wetland habitat within the cells and aligned to minimize disturbance to existing wetlands, trees, archeological avoidance areas, roadside drainage ditches, and current drainage patterns from the surrounding watershed.
• Wetland water control – install stop-log water control structures in each cell to allow adaptive management and control of water levels in the cells and allow for complete drainage of the cells for maintenance purposes. Also install auxiliary rock spillway structures at each dike to pass stormwater flows from the surrounding watershed.
• Erosion control – construct rock media lunas at the transition from steep canyon slopes to the flatter valley bottom to encourage dispersed flow and stormwater infiltration and prevent further rill and gully formation. Also repair the damaged rock chute at the outlet of the project including the removal of dislocated rip-rap from dillon canyon stream channel.
• Revegetation: revegetate the wetland site and any disturbed areas with appropriate native plants and/or seed based on anticipated hydrologic zones.