Stream restoration is critical for mine reclamation

Benefits of a naturally restored stream

Most people would agree that reclaiming disturbed areas to a natural state is a good thing. It’s better for the environment and biodiversity. There are other benefits, too.

Responsible mining builds support for future projects. How? A mining company that has shown attention, care, and funding focused on environmental remediation is more attractive in the eyes of investors and the public. Plus, a proven record of responsible mining and environmental care also helps gain trust in communities who are often quick to oppose nearby mining activity.

Support and buy-in is a very real component of today’s mining landscape. Environmental stewardship helps our clients achieve many environmental, social, and governance (ESG) goals. Independent reviews can verify these. Mining companies with awards or certifications for their environmental work are less likely to be opposed than those who don’t. Plus, focusing on the “E” of ESG helps with social goals as well—promoting sustainable and healthy communities, environmental justice, and Indigenous relations. Lastly, it supports governance, by demonstrating regulatory compliance and risk management. The more we look at projects through an ESG lens, the easier it becomes to see compounding benefits.

Sometimes, a project supports each component of ESG. For example, the Alamosa River Restoration in Colorado was good for the environment, promoted healthier communities, and achieved regulatory compliance. How? By restoring more than 12,000 linear feet of the river. The project improved the larger watershed beyond the Alamosa River. We saw reduced sediment loading, a stabilized channel, recharged groundwater, and safeguarded infrastructure. 

Another good example in Colorado is Four Mile Creek. It supplies water to a few small towns near Boulder, and the watershed had been impacted by previous mining activity.

When our team started work here, the amount of arsenic in the water was over the drinking water standard. Our work included testing waste rock piles to determine what metals were present and removing waste rock from the channel. We also capped remaining waste rock with an evapotranspiration cover to reduce leaching. Finally, we planted vegetation consistent with the surrounding forest.

After the restoration of the main channel and side tributaries, water quality in Ingram Gulch has greatly improved. Now, arsenic levels are below detection limits. 

Sounds great, but at what cost?

Mining is also a business and needs to make money. But, going above and beyond does not always mean more cost.

Regardless of the channel type, water management is typically a small percentage of the total reclamation costs at a mine. The greatest costs are usually slope grading, topsoiling, and vegetation. In other words, adjusting the channel construction costs from hard armor to a natural system has a small impact on the final cost.

When restoring a stream, hydrogeologists use geometry and vegetation for erosion protection. As such, any additional excavation and vegetation may cost less than buying and placing rocks. Maintenance costs are also generally less. This is because a natural stream is a resilient ecosystem through a balance of erosion and sediment deposition. Flooding is mitigated by building a grassy marsh area rather than riprap armoring.

In both the US and Canada, many mining projects may qualify for state and federal tax incentives and low-interest loans to support reclamation work. This is especially true for historic or abandoned mine sites that don’t have an active supply of funding.

Components of a restored stream

Stream restoration doesn’t require a major effort beyond reclamation and monitoring. Initial water treatment and grading is the same for both nature-based and traditional methods. The main difference lies in re-creating a natural ecosystem using:

• Low-flow channel: It’s key to concentrate seasonal low flows in the low-flow channel to provide a continuous water path. This channel usually meanders through the floodplain to limit channel gradient.
• Riffle-pool sequence: Riffle-pool sequences create aquatic habitats with riffles on straight segments and pools at bends. Both habitat types are necessary for fish and insects to propagate. These structures also provide gradient control on slopes up to 5 percent.
• Floodplains: When there is more water than the stream can hold, it enters the floodplain. Even higher flows may reach overflow areas above the floodplain. This is natural in a resilient riparian ecosystem. The greater flow area and vegetation helps decrease flow velocities and limits erosion.
• Boulder walls or vegetated soil lifts: Sometimes the site topography may need small sections of armoring. But the choices extend beyond riprap. Boulder walls or vegetated soil lifts can provide support and integrate with the natural landscape.
• Vegetation: Choose a diverse seed and plant mixture that mimics the nearby natural stream setting. Riparian plant species thrive where water is present. They flourish on floodplains, tolerate high water tables, and provide erosion resistance. Plants create shade and help control stream temperatures. They also promote biodiversity by providing habitat for both land and aquatic animals and insects.
• Fish passage: Fish ladders are sections of stream built to help fish navigate upstream where there are steep slopes and high velocities. Without help, those fish may not access important breeding habitat. In many parts of the US, new projects include some kind of fish and aquatic life component. These enhancements can take many forms depending on the swimming ability of the native fish. 

Another big benefit: carbon capture

A benefit that’s getting lots of attention lately is the potential for riparian and wetland areas to sequester carbon. Large swaths of land—especially forested riparian ecosystems—can become carbon sinks as part of a carbon offset program. We’re seeing this in many industrial site closure plans. We anticipate it will increase in popularity as more companies look to secure carbon offsets.

It’s the right thing to do

We hope to see natural streams as part of every future mine closure plan. Choosing to restore stream channels as part of your mine reclamation project is the right thing to do.

But it can also make it easier to obtain permits, funding, and community support. It will also help show the mining industry’s commitment to sustainability and our shared water future. If a mine owner is already grading the site to construct a channel, why not go the extra step and create something that mimics a natural stream? It will only benefit us all.