Mercury Removal and Biotechnical Bank Stabilization in an Urban, Steelhead Stream

摘要

Topic: Mercury (calsine) removal from a steelhead trout stream in San Jose, California and restoration of excavated creek banks using biotechnical techniques. Alamitos Creek, located in San Jose California, flows to San Francisco Bay and has been designated an impaired water bodies under the Federal Clean Water Act due to mercury contamination. . Historic mercury mining operations in the Guadalupe Mining District from the 1850s to 1930s created piles of mine tailings and kiln slag called calcines. These piles were located on hillsides, often near creeks, at the upper end of the Alamitos Creek Watershed. Seasonal flooding created mud flows which transported the calcines down the watershed, resulting in mercury deposits in the Alamitos Creek. Removal of the calsine deposits is a successful method of reducing mercury concentrations in Alamitos Creek and eventually San Francisco Bay. The calsine deposit removal must include stabilization of the creek bank to avoid inducing new erosion and destabilizing reaches of the creek. Alamitos Creek is also listed by U.S Fish and Wildlife Service as habitat for threatened Central Coast Steelhead Trout. Santa Clara Valley Water District staff conducted projects in 2003 and 2004 which removed calcines and stabilized the creek banks at 4 sites. Biotechnical techniques such as log, toe revetment, brush layering and live siltation were used for these projects. These techniques provided the habitat needs for the fisheries resources and the erosion stabilization needed for slope protection. The bank stabilization projects were also an opportunity to have a 4 day workshop to train staff on designing and installing biotechnical techniques. This workshop will provide those attending with the experience gained from the various agencies, permit requirements for these projects, the BMPs, and the techniques used to construct them.