OVERCOMING ACCESS ISSUES AT A REMOTE PASSIVE TREATMENT SITE NEAR LAKE SHASTA, CA

摘要

Constructing bench scale and pilot scale sulfate reducing bioreactors (SRBRs) at abandoned mine sites can become routine until the site is accessible only by boat. The Golinsky site is a small underground copper mine complex consisting of abandoned mine workings and remnants of smelter operations located on a steep hillside above Little Backbone Creek, a tributary to Lake Shasta. The mine pool (impounded behind bulkheads) is typical acid rock drainage with a pH of 2.5 to 4 containing heavy metals including iron, aluminum, copper, zinc, cadmium, and manganese. The US Forest Service committed to a bench and pilot scale testing program to demonstrate that the SRBR technology would work at the remote site and reduce metal loading on Lake Shasta. However, accessing the site requires a three-mile boat trip across the lake and a two-mile hike along a narrow abandoned railroad grade from the beach head to the mine. The windows of construction access were controlled by the weather but also by changing lake levels. Bench and pilot SRBR test systems were constructed in 2004. For the pilot system, all the materials (about 45 tons) and construction equipment were hauled across Lake Shasta in a WWII vintage landing craft. Efficiently off-loading this quantity of material was a challenge that was met with an innovative cable tramway system strung between the landing craft and a shore-based tower consisting of two large pine trees. Implementing the amphibious "assault" on "D-Day" with just one landing craft was complicated enough; indeed, the experience invoked a greater respect for the Allied soldiers and commanders in Normandy almost 60 years to the day earlier.