Environmental Snapshot: Selenium in Gravel Pits

Often overlooked but naturally everywhere, selenium can have a big impact on our streams and the species that rely on them. Find out why we track it, who it affects, and how we’re planning for a more sustainable future.

What is selenium, and why does Four Corners Materials test for it?

Selenium is a naturally occurring element in different soils and rock materials. It enters water sources through mining, agricultural activities, and natural geological processes. Although naturally occurring, high concentrations can pose a risk to wildlife and public health, there is little contribution from our industry. The state has established limits on the concentration of selenium in its waterways, requiring dischargers to adhere to specific limits to reduce selenium outputs, even those not directly generated by these dischargers.

What species are affected?

Herbivores can be adversely affected when they consume plants that are rich in selenium, particularly those growing near water sources with high selenium concentrations. Signs of selenium toxicity may include changes in appearance, such as hair and hoof loss, as well as respiratory distress, which can sometimes lead to death. Mule deer, elk, and bighorn sheep are the most commonly affected species. Although the negative effects of selenium are significant, they usually occur only in the presence of high, unnatural concentrations. It is important to note that selenium occurs naturally, and a healthy intake of this micronutrient is beneficial for these animals’ metabolism and immune function.

The Colorado River Cutthroat Trout is another species significantly impacted by selenium. Due to its declining population in Colorado, this fish is listed as a species of special concern. It is often referred to as the “canary in the coal mine” for water sources because of its high sensitivity to changes in pollution, temperature, and habitat fragmentation. By monitoring the population changes of the Colorado River Cutthroat Trout, scientists can gain insights into water quality and the overall health of the ecosystem.

How do I know if selenium is present?

Indicators of selenium presence in an ecosystem may include yellow or orange coloring, metallic or rotten odors, excessive algae growth, dead vegetation, and an abundance of selenium-accumulating plants such as watercress and certain grasses. Additionally, ongoing health issues in wildlife can signal selenium contamination. The concentration of selenium can be measured through water testing. To mitigate selenium levels, strategies may include reducing algae blooms, increasing oxygen content through aeration, and regularly maintaining water sources and filtration systems, such as sand, activated carbon, and reverse osmosis.

How are we moving forward?

Four Corners Materials continues to monitor for selenium and test discharge water for concentration amounts so we can help ensure greater ecosystem health and protect vulnerable species at our locations.

By the Rockies South Environmental Team, with major writing contributions from Jessica Homan, Environmental Intern, and research provided by the team.