by Matthew Skarie
|Photo 1: Rawley Mine Before Cleanup
Kerber Creek is a 19-mile-long waterway located in the northeast portion of Saguache County. It starts just above the town of Bonanza and empties into the San Luis Creek just past the town of Villa Grove. These waterways are part of the Rio Grande Basin.
In the 1880s silver ore was discovered in the area. By 1900, more than 1500 prospect hole and mines had opened, the largest being the Rawley Mine. Over the years approximately 476,000 tons of ore were produced from the Rawley mine alone. Mining continued sporadically in the area for the next 80 years with another major boom in the 1920s. Several dams were constructed in order to accommodate the tailings created by the volume of ore being mined. In the 1960s-70s mine waste was washed downstream after dam failures, leaving over 200 acres of mine waste along the stream.
The waste left behind from the decades of mining has impacted both the creek and floodplains surrounding Kerber Creek. In 1994, the American Smelting and Refining Company (ASARCO, Inc.) initiated cleanup of the main stem of Kerber Creek. By 1998 they had completed their riparian restoration and constructed a plug in the Rawley 12 adit in order to eliminate the discharge. Also during this time the Colorado Department of Public Health and Environment (CDPHE) removed three waste piles located within the watershed. Although these cleanups did improve the water and soil quality in the upper watershed, they still left 17 miles of contamination in the lower watershed and impaired stream channel in the entire drainage.
In 2005 a multi-partnered initiative, including the Bureau of Land Management (BLM), Trout Unlimited (TU), the Natural Resources Conservation Service (NRCS) and the stakeholders who formed the Bonanza Stakeholders Group (BSG) began a revitalization effort focusing on the lower part of the Kerber Creek watershed. These groups along with other partners have worked together to restore, maintain, and monitor the watershed. This effort looked at several environmental impacts left from the tailings. The goals of this effort were to reduce metal mobility in soils, increase sinuosity, reduce the channel width, improve depth, increase the density of aquatic life, increase vegetation cover and stabilize the stream banks.
|Photo 2: Tailings pile along Kerber Creek before phytostabilization
In order to prevent metals from entering the creek and to reduce sediment loading during remediation 1.5 miles of wattles were installed along drainages and other areas along the creek. To reduce the mobility of metals in soils phytostabilization followed by revegetation was used for in-place treatment of mine waste. Phytostabilization reduces the risk of further environmental degradation by preventing metals from leaching and dispersing into surface and ground water, being spread by air and from moving through plants and soils. Soil amendments were used to bind metals and reduce their mobility, limiting their availability to plants. For this project lime, limestone and compost were used.
Natural processes will occur to improve stream sinuosity as stream channel stabilization projects are implemented. Rock structures, sedge mats and willow plants are being used to close in the riparian vegetation and narrow the creek. This will improve floodplain recharge, reduce channel width and increase the depth. As this occurs the stream banks will stabilize and eventually be able to facilitate sustainable fate and transport of sediment.
Another project goal is to increase the density of aquatic life in Kerber Creek. In the 1980s sampling showed that there were no fish in the creek. Further sampling in 2008 and 2009 showed that brook trout and long nose dace are now self-sustaining in Kerber Creek. While the quality of water in Kerber Creek improves aquatic life will naturally migrate from tributaries into the stream. Continued monitoring will occur to document macro-invertebrate and fishery densities. The end goal is to closely match the nearest similar natural stream community.
|Photo 3: One Year Later
Work has been done to increase upland vegetation, which will result in decreased overland flow, a reduction in metals loading and slower infiltration of rainfall and snow melts. Phytostabilization was used to accomplish this goal. Sites were seeded with a mix of native plants known for their high metals tolerance. The ultimate goal is to increase the vegetation cover by 50%. Stream banks will be stabilized with vegetation to be able to withstand event flows without extensive erosion. The banks will be pulled back to a 1:3 slope.
Since 2007 60 acres of mine waste along the creek have been phytostabilized, 40 of those acres in the last year. Partners have contributed over $1.2 million in aid for clean-up. Also, these partners have contributed over 3,000 volunteer hours towards the project. Looking ahead we will continue to restore and monitor progress along the lower part of the watershed. Also, the project will expand to include the upper watershed. The areas of the upper watershed will be assessed to see which environmental issues are affecting this area. A watershed plan is being developed by partners and stakeholders. Quarterly meetings are held to discuss project status and watershed plan elements.