Langvatnet Lake is situated in Fauske Municipality in Nordland County, northern Norway. It measures approximately 10.7 km in length and 0.9 km in width, extending in a northwest-southeast direction, and covers an area of 5.63 km².

The entire mining area drains into Lake Langvann, part of the Sjønstå River system, posing significant ecological risks, primarily from acidic water runoff (acid mine drainage, AMD) and metal pollution. AMD occurs due to the oxidation of sulfide-rich rocks, with water passing through and exiting old mine shafts, adits, smelters, and waste rock piles, affecting both surface and groundwater.

Historical data spanning recent decades is available, and various remediation efforts have been made to mitigate the impact of mining activities. To prevent further oxidation of sulfide minerals, underground mines in the northern part of the mining district were flooded, and entrances were sealed with concrete plugs. Despite these efforts, heavy metal concentrations did not decrease. Measurements were taken from 2001 to 2005 to monitor mine outlets.

For decades, Langvatnet Lake has been an environmental disaster for Nordland County due to continuous heavy metal leaching from historical mining activities. This pollution has prevented the area from being properly utilized for fishing, reindeer farming, agriculture, and recreational activities by the local community.

To reduce pollutant levels, it is suggested to establish vegetation buffer strips with diverse layers and types of vegetation around the lake or in specific sections. Additionally, floating wetlands are proposed as a potential solution.