Water Quality Analysis of Eutrophication for the Wills Creek Basin in Allegany and Garrett Counties, Maryland

Water Quality Analyses (WQA) with EPA Concurrence of MDE's Findings:
Wills Creek

Wills Creek is located in Allegany County and flows south from its headwaters in Pennsylvania to its confluence with the North Branch Potomac River at Cumberland, MD.  Jennings Run and Braddock Run are the two main tributaries to Wills Creek, draining western Allegany County and a small portion of northeastern Garrett County.  The drainage area of Wills Creek totals 160,500 acres, with 38,500 acres in Maryland and 122,000 acres in Pennsylvania. Additionally, there are no “high quality”, or Tier II, stream segments (Benthic Index of Biotic Integrity (BIB)/Fish Index of Biotic Integrity (FIBI) aquatic health scores > 4 (scale 1 – 5)) located within the watershed requiring the implementation of Maryland’s antidegradation policy. Lastly, the total population in the Wills Creek watershed is approximately 33,000.

The Wills Creek watershed (basin code 02141003) (2008 Integrated Report Assessment Unit ID: MD-02141003) was identified in Maryland’s 2008 Integrated Report as impaired by cyanide (1996 listing), nutrients (1996 listing), sediment (1996 listing), pH (1998, 2002, 2004 and 2006 listings), fecal bacteria (2002 listing), and impacts to biological communities (2002 listing).  The listing for cyanide and the 1998 and 2004 pH listings have been addressed by Water Quality Analyses (WQAs) completed in 2005 and 2006, respectively, showing no impairment.  The listings for sediment and fecal bacteria have been addressed via TMDLs completed in 2006, and the 2002 and 2006 pH listings were addressed via TMDLs completed in 2008.  The 1996 nutrients listing was refined in the 2008 Integrated Report by identifying phosphorus as the specific impairing substance.  Consequently, for the purpose of this report, the terms nutrients and phosphorus will be used interchangeably.  The listings for impacts to biological communities will be addressed separately at a future date.

A data solicitation for information pertaining to pollutants, including nutrients, in the Wills Creek basin was conducted by Maryland Department of the Environment (MDE) in September 2005, and all readily available data from the past five years have been considered.  Currently, Maryland’s water quality standards do not contain specific numeric criteria for nutrients.  Nutrients typically do not have a direct impact on aquatic life; rather, they mediate impacts through excessive algal growth leading to low dissolved oxygen.  Therefore, the evaluation of potentially eutrophic conditions due to nutrient over-enrichment will be based on whether nutrient-related parameters (i.e., dissolved oxygen levels and chlorophyll a concentrations) are found to impair designated uses in the Wills Creek watershed (in this case, protection of aquatic life and wildlife, fishing, and swimming).

Recently, MDE developed a biological stressor identification (BSID) methodology to identify the most probable cause(s) of the existing biological impairments in Maryland 8-digit watersheds based on the suite of available physical, chemical, and land use data.  The BSID analysis for the Wills Creek watershed indicates inorganic pollutants and flow/sediment stressors are associated with impacts to biological communities; these findings will be addressed separately.  The BSID analysis did not identify any nutrient stressors present and/or nutrient stressors showing a significant association with degraded biological conditions.  The results of the BSID study, combined with the analysis of recent water quality data presented in the report below, indicate that the Wills Creek watershed is not being impaired by nutrients.

The analysis available below supports the conclusion that a TMDL for nutrients is not necessary to achieve water quality standards in the Wills Creek watershed.  Although the waters of the Wills Creek watershed do not display signs of eutrophication, the State reserves the right to require future controls in the watershed if evidence suggests that nutrients from the basin are contributing to downstream water quality problems.  For instance, reductions may be required by the forthcoming Chesapeake Bay TMDL, which is currently under development and was completed by EPA at the end of 2010.

Barring the receipt of contradictory data, the report will be used to support a revision of the nutrients (i.e., phosphorus) listing for the Wills Creek watershed, from Category 5 (“waterbody is impaired, does not attain the water quality standard, and a TMDL is required”) to Category 2 (“waterbodies meeting some [in this case nutrients-related] water quality standards, but with insufficient data to assess all impairments”) when MDE proposes the revision of the Integrated Report.

 

Water Quality Analysis of Eutrophication for the Wills Creek Basin in Allegany and Garrett Counties, Maryland

(Concurrence March 15, 2010)

EPA's Decision Letter

EPA's Decision Letter

Main Report

WQA_Wills_Creek_eutro.pdf (744KB)

Comment Response Document

CRD_Wills_Creek_eutro.pdf (7KB)

Additional Supporting Information

Biological Stressor Identification Wills Creek Watershed Report

BSID Wills_Creek.pdf (600KB)

Biological Stressor Identification Methodology Report

BSID Methodology.pdf (459KB)

 

Contact Information

Please direct questions or comments concerning this project to Maryland's TMDL Program at (410) 537-3572.


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