Stream impacts associated with underground mining can include diminished stream flow, a complete loss of flow or pooling within various areas of a stream as well as streambed fracturing and heaving. All three effects can result in a varying degree of habitat loss for aquatic fauna, while a complete flow loss can also result in impacts (i.e., loss of water supply) to terrestrial flora and fauna.
The following tables show existing claims data for streams experiencing flow loss, pooling, and/or fracture and heaving impacts. Data is collected and stored in the Bituminous Underground Mine Information System (BUMIS). Spreadsheets containing the mine name, stream identification, impact length, latitude and longitude locations, and other pertinent data were created to calculate the total length of stream impacts by mine and year.
Any affected stream may contain one impact or a combination of flow loss, pooling and heaving/fracture impacts.
Flow loss
Diminished flow and complete flow loss related to underground mining is usually caused by the development of new fractures, or the expansion of pre-existing factures, under and within the stream bed. These fractures result from land subsidence/land movement in areas that have been directly undermined or areas that are located within the underground mine’s angle of draw. Once a partial or total flow loss has been identified, the mine operator is required to augment the stream until the fractures in the stream bed can be sealed through grouting. Grouting consists of pumping grout (either a cement like material or polyurethane) under the stream bed to create an impervious layer which seals off fractures.
The data tables show all the flow losses that are actively being investigated by the Department from 2018 onward by year, based on the year in which the stream loss was first identified. Within each year, flow losses associated with each mine are broken out and separated based on the stream segment that has been impacted. Within each entry, the panel and panel ID associated with each stream loss is recorded, as well as when the stream loss was first reported and the length of the observed impact. A total length of stream impacts is provided at the end of each mine’s tabular summary of impacts.
Last updated 5/10/2023
Pooling
Pooling is a type of stream impact that can result from subsidence. Pooling develops when the stream section over a panel subsides, but the part of the stream located above the gate (entries) does not subside as significantly. This unsubsided gate acts like a dam, raising the water level on the upstream side of the gate. The result is a reduction of the stream’s flow velocity to near zero at this location. This standstill results in sediment particles settling out and depositing on the stream bed, potentially affecting the habitat used by macroinvertebrates. Additionally, pooling results in a loss of oxygen, a general warming of the water in the pool location and can prevent fish and other organisms from freely navigating the stream. Most pooling occurs in streams with a gradient of less than 2%. To alleviate pooling, mine operators use a technique known as a “gate-cut”. A gate-cut consists of excavating the section of the stream bed that did not subside (the pooled area) until it is at the same elevation as the rest of the stream bed. To determine if a gate-cut has successfully removed the pooling from an impacted stream, the gate-cut is required to be monitored for five years.
The data tables show all the reported stream pooling locations that are actively being investigated by the Department from 2018 onward by year, based on the year in which the pooling was first identified. Within each year, pooling associated with each mine is broken out and separated based on the stream segment. Within each entry, the panel and panel ID associated with each occurrence of pooling is recorded, as well as the length of the impacted stream segment. A total length of pooling is provided for each mine.
Last updated 5/10/2023
Heaving
A heave is where the ground in or crossing the stream bed is raised from its original position in response to extension and compression of rock layers resulting from subsidence. Heaving can disrupt stream flow by halting or redirecting flow.
The data tables show all the reported heaving locations that are actively being investigated by the Department from 2018 onward by year, based on the year in which the heave was first identified. Within each year, heaves associated with each mine are broken out and separated based on the stream segment. Within each entry, the panel and panel ID associated with each occurrence of heaving is recorded.