Mining waste

Lake deposit

Mining waste deposits, also known as mine tailings or mining waste piles, are the residual materials left after valuable minerals or metals have been extracted from ore. These deposits vary in form, including tailings ponds, waste rock piles, and slag heaps, depending on the mining and processing methods used.

The Knaben molybdenum mines in Norway, operational from 1885 to 1973, left behind significant mining waste deposits, primarily consisting of tailings and waste rock. One of the most prominent remnants is a sand landfill covering approximately 120 acres and reaching up to 20 meters thick, located beneath the former processing plant. This deposit contains elevated levels of metals, including molybdenum, copper, and zinc.

Originally, mine waste was deposited into two lakes—Lille Knabetjødn and Store Knabetjødn—with Lille Knabetjødn now completely filled and Store Knabetjødn partially filled. Over time, infilling between the lakes led to the formation of the extensive sand deposit seen today.

The heavy metal content in these tailings poses environmental risks, primarily leaching into water sources and affecting local ecosystems. The Norwegian Geotechnical Institute (NGI) has conducted assessments and mitigation studies to evaluate the stability of the landfill and recommend measures to reduce contamination and rehabilitate the area.

Knaben’s mining waste remains a complex environmental issue, requiring continuous monitoring, remediation strategies, and resource recovery considerations to mitigate long-term ecological impacts.