AMEX Gold Company, Lassen Gold Mine, Wetland Mitigation Project

During the development of Lassen Gold Mine, 9.4 acres of wetlands were filled. The Corps Section 404 Permit required the creation of 18.5 acres of wetlands as mitigation. H&C, Inc. developed a watershed model to assess stormwater runoff for the design of snow fences* to capture water to maintain the mitigation wetlands. The wetlands were constructed in 1992. The Corps released Amex and Lassen Gold after only three years of monitoring because the site exceeded the success criteria. As a result of our work, a total of 31 acres of seasonal palustrine persistent emergent wetlands were created.

*Snow fences are often used to make more water available for livestock and irrigation and to improve wildlife habitat. A snow fence acts to trap blowing snow and it was thought that some snow harvesting may occur. In addition to snow harvesting, water from the upgradient watershed and from mine site roadway runoff was diverted into the mitigated wetland. The water harvesting methods are mentioned here because these methods are an opportunity to increase water supplies for future wetland mitigation sites and wildlife management areas and are an example of H&C's ingenuity.