SULFUR CREEK MINING DISTRICT WASTE REMOVAL
- Reconstruction of Lincoln Creek stream channel
- Removal of 20,000 cy of mercury-impacted waste rock from six individual mine sites
- Sensitive location near hot springs attraction with year-round visitors
- Bat breeding season
- Hetch Hetchy tribal considerations
- Rehabilitation/construction of over 3.5 miles of roads in order to reach mine sites
- Mobilization of two rail car bridges over two miles of active BLM utilizing cranes to pioneer crossings to the repository
The Sulphur Creek Mine Waste Removal project required mitigation of the migration of mine waste containing mercury into Sulphur Creek. The site is located on approximately 465 acres within the Sulphur Creek watershed in Colusa County, California where elevations range from 1,400 to 1,640 ft above sea level. Several of the mine sites were located directly adjacent to Sulphur Creek, which flows continuously from October to June. The six mine sites included calcine tailings, waste rock, mercury enriched soils, ore, miscellaneous waste piles, and mining equipment and structures. An active hot spring was located on the north bank of Sulphur Creek about one mile east of the Central Mine. Because of a study conducted in 2000-2001 concerning the potential ecological and human health impacts of mercury in the Cache Creek watershed, it was determined that the mine remediation approach would focused on site erosion control and material isolation.
Great Lakes Environmental & Infrastructure (Great Lakes E&I) was contracted by Homestake Mining Company to excavate, haul, and place 17,000 cy of material in an on-site repository in order to provide permanent containment for the waste material, preventing it from migrating into the active watershed. The nearby active hot spring required an alternate route for equipment mobilization/demobilization. This road was two miles long and required significant improvement to accommodate heavy equipment including a Komatsu PC 400 excavator, 4,000 gallon water trucks, and two rail car bridges that had to be installed using 20 ton cranes. The entrance to the road was located off Highway 20 and required traffic control approved by Caltrans in order to provide access and egress. Because of the narrow one lane road, the project team developed a radio communication plan for successfully managing heavy equipment traffic. A marker system was also developed that allowed drivers to communicate their road locations over the radio, notifying others of oncoming traffic.
Additional project complexities included the bat breeding season and the resort owner’s request to utilize the site for a personal event. Although this resulted in standby for our equipment and personnel, the project team offered minimized mobilization and demobilization of equipment in order to mitigate cost impacts. The project team also provided a more cost-effective sound barrier technique in order to meet the specifications of the ecological impacts on the bats within the mine sites.