Mine Pool Mapping The Pittsburgh Seam Bruce Leavitt, P.E., P.G. Consulting Hydrogeologist

Acknowledgements Joe Donovan, Ph.D. Eberhard Werner Brenden Duffy Hydrology Research Center WV Water Research Institute West Virginia University

Pittsburgh Coal Basin

Mine water in the Pittsburgh coal basin Mine water in the Pittsburgh coal basin largest and oldest bituminous coal basin in North America currently about 55% of reserves are mined out between 1980 and today, a large number of mine closures have occurred in mines extending to outcrop flooding of these nearly closed mines has created a new set of groundwater conditions and environmental threats the few deep mines (11) still active are deeper in the basin and hydraulically isolated from this mine-flooding risk

Three Hydrologic Settings

major categories of mine flooding major categories of mine flooding free draining: above drainage mines -- many currently- discharging active: pumped dry flooding: water level rising; mine resaturating fully-flooded – with control: water level stabilized by pumping and/or barrier leakage – without control surface discharge occurs

Mining Facts 4,991 square miles mined 1,941 square miles flooded 1.36 trillion gallons in storage billion gallons discharged per year 63.4 % does not go through a treatment plant 37.8 % of the acidity is untreated 40 % of the iron is untreated 97.7 % of the aluminum is untreated

Geochemistry in flooded mines

Effect of Flooding on Mine Water Chemistry Rapid dissolution of acidic salts Exclusion of oxygen from the mine Chemical reaction with recharging ground water.

Montour Mine 14,000 Acres Maximum overburden 850 feet Closed in % flooded Flooded to 125 feet from surface Pumped at 3,500 gallons per minute Residence time 5 to 6 years

Post-flooding chemistry of water pumped from the Montour mine

Post-flooding chemistry of alkalinity, calculated acidity, and pH in water pumped from the Montour mine

Post-flooding chemistry of Al and Mn in water pumped from the Montour mine

Geochemistry of Free Draining Mines

Maiden #1 Mine Dunkard Creek pH 3.1 Acidity219 mg/l Iron 25 mg/l Aluminum 23 mg/l

current metals fluxes, flooded mine discharges year 2002 green=iron yellow=aluminum manganese=purple

Mine discharges that due not require treatment. Gates Palmer Adah Canonsburg

Conclusions Water discharging from Pittsburgh seam underground mines are of two distinct types. Flooded mines ultimately produce net alkaline water with low metals concentrations. Eventually these mines may be suitable for discharge without treatment. Free draining mines generate low pH, aluminum dominated discharges that are expected to persist for decades.

Conclusions continued Underground mining in the Pittsburgh seam has created the most prolific aquifer in Western half of the State. Utilization of this aquifer is in its infancy. More than 27 billion gallons available per year trillion gallons available in storage. Mapping of the extent of mine flooding can promote mine water utilization, and watershed restoration.