Subsidence damage minimal: Study

A FIVE-year study on the effects of coal mining subsidence has found most undermined structures do not suffer damage, and most water supplies remain viable, the Pennsylvania Department of Environmental Protection (DEP) said yesterday.

Angie Tomlinson

The study by the California University of Pennsylvania detailed the effects of underground bituminous mining on surface features such as water supplies, buildings, streams, wetlands, and infrastructure. The study assessed surface features above nine Pennsylvania longwall mines and 72 room and pillar and full retreat mines undermining 37,456 acres.


The study found more than three quarters of water supplies located within 100m of longwall mining remained viable, and more than half the water supply issues reportedly caused by mining were resolved without DEP involvement.


Researchers found groundwater hydrology was not being destroyed by underground mining, as only a nominal amount of groundwater was captured by mine voids.


The report noted the effects of mining on wells and springs was more prevalent in periods of drought.


The report also found the majority of undermined structures did not appear to suffer damage from subsidence, noting that of the 3656 structures undermined during the period, DEP was notified of only 348 structural problems.


When analysing streams, researchers found there were 22 reports of loss of stream flow or pooling. In many cases, stream flow loss eventually recovered, although efforts to grout streams over large sandstone formations had not proven successful in restoring low-flow conditions.


The report concluded wetlands generally were unaffected by underground mining but recommended all wetlands be included on future six-month mining maps.


Subsidence complaints over the five-year study period increased significantly from 50 in 1999 to almost 250 in 2003.


The University’s recommendations included a standardised terminology for assessing all natural and artificial entities potentially affected by underground mining to improve the ability of DEP and mine operators to assess damage from subsidence. The report also recommended DEP develop standardised methods for reporting and tracking the resolution of subsidence complaints.