IMPACT OF COAL SURFACE MINING AND RECLAMATION ON SURFACE-WATER-CHEMICAL CONCENTRATIONS AND LOAD RATES IN THREE OHIO WATERSHEDS

Authors: Bonta, James - Jim; DICK, WARREN - OSU-OARDC

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2003
Publication Date: 8/1/2003
Citation: Bonta, J.V., Dick, W.A. Impact of coal surface mining and reclamation on surface water chemical concentrations and load rates in three Ohio watersheds. Journal of the American Water Resources Association. 2003. v. 39(4). p. 793-815.

Interpretive Summary: Coal mining and reclamation can significantly change sediment and chemical loads from watersheds compared to the premining condition. Small watershed studies were conducted to document the change in rate of chemical release (load rates) from the study sites (37 constituents), the total loads, and how often chemical that are regulated exceed their standard. Generally, average load rates increased due to land-surface disturbances and were highly variable. "Minor", "moderate", "substantial" impacts were found on average for 7%, 23%, and 70% of comparisons between different types of disturbances. The combined effect of changing runoff rates and volumes and changes in chemical concentrations as a result of disturbances, impacted the rate of chemical loading to streams. The reclamation practice of installing water-control diversions appears to cause water quality to worsen, but removal of diversions appears to improve water quality. Revegetation of a reclaimed area increased chemical loads at one site even though the concentrations were less after reclamation which was due to increased runoff after reclamation. Some chemicals that are regulated often exceeded standards before mining began, however, maximums were less after some disturbances, but occurred more often. The chemistry of stream water was changing after several years of reclamation. Much variability was observed in the response of the three sites to the near-complete, drastic land disturbances. The results are useful to government regulators, university and government scientists.

Technical Abstract: The effects of mining and reclaiming (M&R) watersheds on stream chemical load rates (LR), yields, and standards were studied on 3 watersheds. Comparisons were made between phases of land disturbances: Phase 1(natural), Phase 2 (mining and reclamation), and Phase 3/3F (incomplete reclamation/final condition). M&R affected flow-duration curves by decreasing or increasing baseflows and increasing high flows. Average LRs increased due to M&R activities and were highly variable. Minor, moderate, substantial impacts were uniform for 7%, 23%, and 70% of phase comparisons. The impact of M&R on average LRs was not necessarily the same as on average concentrations. Evaluations of M&R require incorporation of changing hydrologic conditions and rates of release of chemicals into streams. Average LRs increased across all sites and disturbances for Mn, dissolved solids, and SO4 between Phases 1 and 3F. No constituent was consistently lower at all sites and only trace substances decreased. M09 was the most impacted site in average LRs and the number of constituents, and least impacted in average concentrations. Diversions can sustain large increases in chemical LRs, and removal of diversions can reduce chemical LRs. Revegetation of poorly reclaimed areas can decrease or increase chemical loads. Chemical LRs tracked sediment LRs. LRs are sensitive to M&R methods, diversions, changing hydrology, changing regressions, changing watershed areas, and geology. The impact of mining and reclamation often was to decrease maximum regulated concentrations, but increase the frequency of exceedance compared to Phase 1. Hydrology and water quality were changing at the end of monitoring.