U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2005-5042
By Jeffrey J. Chaplin
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More than 100 years of anthracite coal mining has changed surface- and ground-water hydrology and contaminated streams draining the Southern Anthracite Coal Field in east-central Pennsylvania. Bear Creek drains the western prong of the Southern Anthracite Coal Field and is affected by metals in drainage from abandoned mines and streamwater losses. Total Maximum Daily Loads (TMDL) developed for dissolved iron of about 5 lb/d (pounds per day) commonly are exceeded in the reach downstream of mine discharges. Restoration of Bear Creek using aerobic ponds to passively remove iron in abandoned mine drainage is under consideration (2004) by the Dauphin County Conservation District. This report, prepared in cooperation with the Dauphin County Conservation District, evaluates chemical and hydrologic data collected in Bear Creek and its receiving waters prior to implementation of mine-drainage treatment. The data collected represent the type of baseline information needed for documentation of water-quality changes following passive treatment of mine drainage in Pennsylvania and in other similar hydrogeologic settings.
Seven surface-water sites on Bear Creek and two mine discharges were monitored for nearly three years to characterize the chemistry and hydrology of the following: (1) Bear Creek upstream of the mine discharges (BC-UMD), (2) water draining from the Lykens-Williamstown Mine Pool at the Lykens Water-Level Tunnel (LWLT) and Lykens Drift (LD) discharges, (3) Bear Creek after mixing with the mine discharges (BC-DMD), and (4) Bear Creek prior to mixing with Wiconisco Creek (BCM). Two sites on Wiconisco Creek, upstream and downstream of Bear Creek (WC-UBC and WC-DBC, respectively), were selected to evaluate changes in streamflow and water quality upon mixing with Bear Creek.
During periods of below-normal precipitation, streamwater loss was commonly 100 percent upstream of site BC-UMD (streamflow range = 0 to 9.7 ft3/s (cubic feet per second)) but no loss was detected downstream owing to sustained mine water drainage from the Lykens Water-Level Tunnel (range = 0.41 to 3.7 ft3/s), Lykens Drift (range = 0.40 to 6.1 ft3/s), and diffuse zones of seepage. Collectively, mine water inputs contributed about 84 percent of base flow and 53 percent of stormflow measured in the downstream reach.
An option under consideration by the Dauphin County Conservation District for treatment of the discharge from the LWLT requires the source of the discharge to be captured and rerouted downstream, bypassing approximately 1,000 feet of stream channel. Because streamwater loss upstream of the tunnel was commonly 100 percent, rerouting the discharge from the LWLT may extend the reach of Bear Creek that is subject to dryness.
Differences in the chemistry of water discharging from the LWLT compared to the LD suggest that the flow path through the Lykens-Williamstown Mine Pool to each mine discharge is unique. The LWLT is marginally alkaline (median net acid neutralizing capacity (ANC) = 9 mg/L (milligrams per liter) as CaCO3; median pH = 5.9), commonly becomes acidic (minimum net ANC = -74 mg/L as CaCO3) at low flow, and may benefit from alkaline amendments prior to passive treatment. Water discharging from the LD provides excess ANC (median net ANC = 123 mg/L as CaCO3; median pH = 6.5) to the downstream reach and is nearly anoxic at its source (median dissolved oxygen = 0.5 mg/L). Low dissolved oxygen water with relatively high ANC and metals concentrations discharging from the LD is characteristic of a deeper flow path and longer residence time within the mine pool than the more acidic, oxygenated water discharging from the LWLT.
TMDLs for iron have been developed for dissolved species only. Consequently, distinguishing between dissolved and suspended iron in Bear Creek is important for evaluating water-quality improvement through TMDL attainment. Median total iron concentration increased from 550 mg/L (micrograms per liter) at site BC-UMD (mean load of approximately 5 lb/d) to 10,600 mg/L at site BCM (mean load of 540 lb/d) but the TMDL was met at site BCM approximately 10 percent of the time because most of the iron at that site is suspended. Water draining from LWLT (median dissolved iron concentration = 5,170 mg/L) and LD (median dissolved iron concentration = 18,300 mg/L) undergoes oxidation and hydrolysis quickly. As a result, TMDL attainment at site BCM is a consequence of dissolved iron converting to suspended solids but is not indicative of improvement in water quality or benefits to aquatic life. To properly interpret any improvement achieved through attainment of TMDLs developed for dissolved constituents, data for the corresponding suspended fraction are essential.
Abstract
Introduction
Purpose and Scope
Description of Study Area
Geologic Setting
Mining History and Techniques
Origin of Mine Water
Previous Investigations of Mine Drainage in Bear Creek Watershed
Study Design and Methods
Effects of Historical Coal Mining on Streamflow
Effects of Drainage From Abandoned Mines on Water Quality
Net Acid Neutralizing Capacity (ANC)
Specific Conductance
Dissolved Oxygen
pH
Iron
Manganese
Aluminum
Metal Loading Rates
Passive-Treatment Technologies for Iron Removal
Summary and Conclusions
Acknowledgments
References Cited
Figures
1. Map showing locations, sampling sites, historical coal-mining features, geologic cross sections, and proposed treatment within and proximate to Bear Creek watershed, Dauphin County, Pennsylvania
2. Geologic cross section M-M’ showing anthracite coal-bearing strata in Bear Creek watershed, Dauphin County, Pennsylvania
3. Geologic cross section Q-Q’ showing anthracite coal-bearing strata in Bear Creek watershed, Dauphin County, Pennsylvania
4. Photographs showing mine drainage discharging from the Lykens Water-Level Tunnel (LWLT) in Bear Creek watershed, Dauphin County, Pennsylvania
5. Photographs showing mine drainage discharging from the Lykens Drift (LD) discharge in Bear Creek watershed, Dauphin County, Pennsylvania
6. Photographs showing mine drainage from several seeps adjacent to the Lykens Drift discharge in Bear Creek watershed, Dauphin County, Pennsylvania
7. Streamflow hydrograph for Bear Creek downstream of mine inputs (BC-DMD) superimposed on instantaneous streamflow measurements upstream of mine inputs (BC-UMD), and precipitation measured approximately 8.5 miles southwest of Bear Creek at DeHart Reservoir Dam
8. Pie chart showing percent contribution of base flow (A) and stormflow (B) to Bear Creek downstream of mine drainage (BC-DMD) computed as the mean ratio of instantaneous flow at sites Bear Creek upstream of mine drainage (BC-UMD), Lykens Water-Level Tunnel (LWLT), and Lykens Drift (LD) to instantaneous flow at site BC-DMD
9. Ranges of net acid neutralizing capacity measured at seven sites in the Bear Creek study area, Dauphin County, Pennsylvania, from March 1999 to December 2002
10. Relation of net acid neutralizing capacity to flow at seven sites in the Bear Creek study area, Dauphin County, Pennsylvania, from March 1999 to December 2002
11. Ranges of specific conductance measured at seven sites in the Bear Creek study area, Dauphin County, Pennsylvania, from March 1999 to December 2002
12. Relation of specific conductance to flow at seven sites in the Bear Creek study area, Dauphin County, Pennsylvania, from March 1999 to December 2002
13. Ranges of dissolved oxygen measured at seven sites in the Bear Creek study area, Dauphin County, Pennsylvania, from March 1999 to December 2002
14. Relation of dissolved oxygen to flow at seven sites in the Bear Creek study area, Dauphin County, Pennsylvania, from March 1999 to December 2002
15. Ranges of pH measured at seven sites in the Bear Creek study area, Dauphin County, Pennsylvania, from March 1999 to December 2002
16. Relation of pH to flow at seven sites in the Bear Creek study area, Dauphin County, Pennsylvania, from March 1999 to December 2002
17. Ranges of dissolved and total iron measured at seven sites in the Bear Creek study area, Dauphin County, Pennsylvania, from March 1999 to December 2002
18. Relation of dissolved and total iron to flow at seven sites in the Bear Creek study area, Dauphin County Pennsylvania, from March 1999 to December 2002
19. Ranges of dissolved and total manganese measured at seven sites in the Bear Creek study area, Dauphin County, Pennsylvania, from March 1999 to December 2002
20. Relation of dissolved and total manganese to flow at seven sites in the Bear Creek study area, Dauphin County, Pennsylvania, from March 1999 to December 2002
21. Sketch showing mean loading rates of total iron (FE) and manganese (MN) in the Bear Creek study area, Dauphin County, Pennsylvania
22. Flow chart of passive-treatment alternatives adapted from Hedin and others (1994) and Skousen and others (2000)
Tables
1. Water-quality standards and Total Maximum Daily Loads for iron and manganese at the mouth of Bear Creek, Dauphin County, Pennsylvania
2. Sampling sites in the Bear Creek and Wiconisco Creek watersheds, Dauphin County, Pennsylvania
3. Comparison of selected constituents in duplicate samples analyzed separately by the Pennsylvania Department of Environmental Protection Laboratory and the U.S. Geological Survey National Water-Quality Laboratory
4. Summary of instantaneous flow data collected at nine sites on Bear Creek and two sites on Wiconisco Creek, Dauphin County, Pennsylvania, from March 1999 to December 2002
5. Summary statistics for water-quality data collected at nine sites on Bear Creek and two sites on Wiconisco Creek, Dauphin County, Pennsylvania, from March 1999 to December 2002
6. Results of statistical analyses performed on four paired sites in the Bear Creek study area, Dauphin County, Pennsylvania
7. Computed mean loads of dissolved iron and total manganese compared to Total Maximum Daily Loads at selected sites in the Bear Creek watershed, Dauphin County, Pennsylvania
This report is available online in Portable Document Format (PDF). If you do not have the Adobe Acrobat PDF Reader, it is available for free download from Adobe Systems Incorporated.
View the full report in PDF 1,941 KB
For more information about USGS activities in Pennsylvania contact:
Director
USGS Pennsylvania Water Science Center
215 Limekiln Road
New Cumberland, Pennsylvania 17070
Telephone: (717) 730-6960
Fax: (717) 730-6997
or access the USGS Water Resources of Pennsylvania home page at:
http://pa.water.usgs.gov/.
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