IMPACT OF COAL SURFACE MINING AND RECLAMATION ON SUSPENDED SEDIMENT IN THREE OHIO WATERSHEDS¹

Abstract

Prior to PL95–87 little research had been conducted to determine the impacts of mining and reclamation practices on sediment concentrations and yields on a watershed scale. Furthermore, it was unknown whether sediment yield and other variables would return to undisturbed levels after reclamation. Therefore, three small watersheds, with differing lithologies and soils, were monitored for runoff and suspended sediment concentrations during three phases of watershed disturbances: undisturbed watershed condition, mining and reclamation disturbances, and post‐reclaimed condition. Profound increases in suspended‐sediment concentrations, load rates, and yields due to mining and reclamation activities, and subsequent drastic decreases after reclamation were documented. Even with increases in runoff potential, reductions in suspended‐sediment concentrations and load rates to below or near undisturbed‐watershed levels is possible by using the mulch‐crimping technique and by removing diversions. Maximum concentrations and load rates occurred during times of active disturbances that exposed loose soil and spoil to high‐intensity rains. Sediment concentrations remained elevated compared with the undisturbed watershed when diversions were not well maintained and overtopped, and when they were not removed for final reclamation. Diversions are useful for vegetation establishment, but should be maintained until they are removed for final reclamation after good vegetative cover is established.

Mountaintop Removal Mining and Catchment Hydrology

“…The dominance of surface pathways in runoff generation in mined catchments is further evidenced by the increase in total suspended solids downstream of mining activities [87] that originate from the mine surface during the period immediately following reclamation [88]. However, Ritter and Gardner [57] observed variability in the infiltration rate of mine soils through time; some minesoils maintain low infiltration rates with minimal recovery, while other minesoils return to near pre-mining rates in as little as four years.…”

“…However, this conceptualization of minespoil as a storage reservoir may not capture the complexity of water movement in valley fills. Caruccio et al [58] and Caruccio and Geidel [10] described flow through minespoil as pseudokarst [87], a term more often associated with glacial or pyroclastic sediments that have multiple, rapid responding flow paths [88]. Hawkins and Aljoe [95] showed that pseudokarst was a dominant flow path in minespoil during transient, unsteady conditions but during steady state conditions, flow was dominated by matrix flow.…”

Changes in concentration–discharge regression parameters due to coal mining and reclamation activities / Changements dans les paramètres de régression entre concentration et débit, causés par l’exploitation minière de charbon et des activités de reconversion

“…In the contour-area method, coal is extracted starting at the coal outcrop and successive cuts along the contour are made into the hillside. The spoil from the (Bonta et al, 1997). first cut is thrown down slope and generally forms a much smaller probable drainage basin area for most of Phase 2 (Table 1; Bonta, 2000). After that, the spoil from each cut is placed on the underclay exposed by the previous cut as mining progresses toward the centre of the hilltop.…”

“…Details on physical conditions and weather at the three drainage basins during the study were described previously by Bonta (2000) and Bonta et al (1992a) and only brief descriptions are given here. Three small drainage basins in East-Central Ohio (drainage basins C06, M09 and J11) were instrumented for runoff measurement and water sampling in undisturbed areas.…”

“…The project was funded by the US Bureau of Mines (USBM) and later by the ARS, for a total of about nine years. Different aspects of this large study have been documented in numerous publications (USBM, 1978(USBM, , 1983aBonta et al, 1992aBonta et al, ,b, 1997Bonta & Hamon, 1980;Amerman et al, 1982;Bonta & Sutton, 1983;Dick et al, 1983Dick et al, , 1986Bonta, 2000Bonta, , 2004Bonta & Dick, 2003). Prior to the Ohio study, few investigations were available before enactment of regulations of the Surface Mining and Reclamation Act (Public Law 95-87) in the USA that documented the impacts of mining and reclamation on hydrology, water quality and chemical yields (Curtis, 1971(Curtis, , 1974Grubb & Ryder, 1972;Upham, 1975;Dyer & Curtis, 1977) and fewer were comprehensive (Musser, 1963;Collier et al, 1964Collier et al, , 1970.…”