Mine Pool Mapping The Pittsburgh Seam

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

2. Acknowledgements Joe Donovan, Ph.D. Eberhard Werner Brenden DuffyHydrology Research CenterWV Water Research InstituteWest Virginia University

3. PittsburghCoal Basin

4. 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

6. Three Hydrologic Settings

7. 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

8. Mining Facts • 4,991 square miles mined • 1,941 square miles flooded • 1.36 trillion gallons in storage • 27.19 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

9. Geochemistry in flooded mines

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

11. Montour Mine • 14,000 Acres • Maximum overburden 850 feet • Closed in 1980 • 56 % flooded • Flooded to 125 feet from surface • Pumped at 3,500 gallons per minute • Residence time 5 to 6 years

14. Post-flooding chemistry of water pumped from the Montour mine

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

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

17. Geochemistry of Free Draining Mines

18. Maiden #1 MineDunkard Creek • pH 3.1 • Acidity 219 mg/l • Iron 25 mg/l • Aluminum 23 mg/l

20. current metals fluxes,flooded mine dischargesyear 2002 green=iron yellow=aluminum manganese=purple

21. Minedischargesthat duenot requiretreatment. Canonsburg Adah Palmer Gates

23. 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.

24. 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. • 1.36 trillion gallons available in storage. • Mapping of the extent of mine flooding can promote mine water utilization, and watershed restoration.