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Effects of Mining on Aquatic Ecosystems

Environmental Effects of Mining in the Anthracite Region: Problems and Possible Solutions

 

Kenneth M. Klemow, Ph.D.

Effects of Mining on Aquatic Ecosystems

Mining has had a profound impact on aquatic ecosystems like wetlands, creeks, and lakes of northeastern Pennsylvania. Such ecosystems are extremely valuable from both ecological and recreational perspectives. Communities that develop in aquatic ecosystems are typically composed of microscopic species, larger invertebrates like caddisflies and stoneflies, and vertebrates like fish and amphibians. Those organisms interact in complex ways, and play crucial roles in nutrient turnover and energy processing. An important property of aquatic ecosystems is that they are interconnected by the flow of water downstream. Thus, energy and nutrients received by small creeks and wetlands high in the watershed are often used by populations of commercially important finfish and shellfish in downstream rivers and estuaries.

Effects of mining on aquatic resources are both physical and chemical in nature. Most of earthmoving activities of mining occurred well before the enactment of laws designed to protect aquatic resources - particularly the 1977 Federal Water Pollution Control Act. Strip mining and the deposition of culm material occurred without any regard to wetlands, watercourses, and other waterbodies. Thus, miles of stream channel habitat and many hundreds of acres of wetland in the anthracite areas have been destroyed by indiscriminate digging and filling. One prime example of such destruction can be seen in the Nanticoke Creek corridor in central Luzerne County. There, the normal course of water that drains the unmined upper slopes of Wilkes-Barre Mountain is blocked by a huge culm bank complex near Warrior Run. As a result, the headwaters of Nanticoke Creek are completely isolated from the lower reaches of that creek, and ultimately the Susquehanna River. Results from preliminary studies indicate that biological diversity and food chain support are lower than expected in the Nanticoke Creek headwaters, compared to similar creeks that are directly connected to lower reaches of their watershed.

In many places where streams flow through mine impacted areas, the fractured bedrock allows surface streamflow to seep underground. That loss of water is directly opposite to the typical gain in flow as one proceeds to lower positions in watersheds not impacted by mining. As will be noted shortly, that “lost” water is only temporarily hidden from view. Instead, the water resurfaces further down the watershed, often in a highly contaminated form.

Even if not completely obliterated, stream channels are often altered and degraded on mined sites. Studies of stream channel morphology on mined sites show that creeks there have unusually steep banks composed of unstable material. That morphology is highly unfavorable during floods because it causes unacceptably high levels of erosion, and because it often exacerbates downstream flooding. Siltation of creeks lower in the watershed is especially problematic because many valuable stream invertebrate species cannot tolerate sediment deposition.

The loss of wetlands in mined areas is another source of concern. Wetlands have many environmental benefits and enjoy the protection of federal and state laws. Wetland soils are typically porous and absorb water during periods of heavy precipitation, therefore reducing the severity of downstream flooding. Wetlands also act as excellent natural water purifiers because they trap suspended sediments and remove dissolved pollutants like nitrates, phosphates, and heavy metals. Wetlands also provide habitat to plants and animals. In that context, wetlands serve as spawning and rearing sites for fish and amphibians, breeding locations for many birds, and locations for food chain support for dozens of mammal species. The loss of wetlands due to mining activities has led to dirtier water downstream, exacerbated flooding in some cases, and a regional loss of biological diversity and ecological productivity.

Concurrent with the loss of healthy aquatic habitat, mining has created two types of unproductive open-water conditions: stripping-pit pools and sedimentation lagoons. The former are bodies of open water that develop in strip mine operations, where the excavated pit intercepts the prevailing water table. These inadvertent, artificial lakes are characterized by steep walls and depths that exceed 30’. Aside from the inherent danger that they pose, stripping-pit pools have low ecological productivity because they are typically isolated from other aquatic habitats, and because their water often contains pollutants that cannot support life. Sedimentation lagoons are natural or artificial bodies of water that are found near old mining operations. They functioned as settling basins to clarify water used to wash coal. As a result, the substrate of such lagoons is composed of deposits of fine-grained mine-wash. Such deposits are infertile and often contain high concentrations of toxic elements. Therefore, sedimentation lagoons are typically lifeless, save a few very hardy species of low ecological value.

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