Tailings disposal at a marine placer mining operation by WestGold, Alaska

Abstract

From 1985 to 1990 WestGold managed a marine placer mining operation with substantial documentation concerning its submarine tailings disposal (STD) system. For 5 years the operation involved the use of a floating bucket‐ladder dredge with an integrated, gravity‐based treatment plant to extract free particulate gold from the seabed gravels. Three‐quarters of the throughput was disposed of at 1.5 m below sea level through two pipes, each of 0.51‐m diameter. The system's design resulted from considerable trial and error and modeling studies to achieve regulated seawater conditions. The information is publicly available as a result of a very open permitting and operating process. The mining permit specified waste discharge controls and. environmental impact limits for topics of local concern: the dredge's effluents, the red king crab population (an important fishery resource), seawater turbidity, and bioaccumulation of trace metals, especially mercury (a remnant of prior beach mining). The impact on crab stoc...