Water Quality Analysis of Eutrophication for the Evitts Creek Basin in Allegany County, Maryland

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

The Evitts Creek watershed is located in the North Branch Potomac River Sub-basin of the Chesapeake Bay watershed.  The watershed area covers 19,600 acres in Allegany County, Maryland and 39,800 acres in Bedford County, Pennsylvania.  The watershed drains from Bedford County, Pennsylvania, in a southwesterly direction into Allegany County, Maryland, where it empties into the North Branch Potomac River just southeast of Cumberland, Maryland.  Due to the steep terrain, geologic structure, and rock units, the drainage patterns of the sub-watersheds have headwaters on steep slopes (ACPD 2007).  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 Evitts Creek watershed is approximately 18,000.

The Evitts Creek watershed (basin code 02141002) (2008 Integrated Report Assessment Unit ID: MD-02141002) was identified in Maryland’s 2008 Integrated Report as impaired by nutrients (1996 listing, Lake Habeeb – 1998 listing), sediment (1996 listing), pH (1996 listing, Rocky Gap Run – 2006 listing), and impacts to biological communities (2006 listing).  A Water Quality Analysis (WQA) for low pH was completed in 2005 to address the 1996 listing.  A TMDL for nutrients to address the 1998 Lake Habeeb listing was completed in 1999, and a TMDL for sediments was completed in 2006.  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 and the 2006 Rocky Gap Run pH listing will be addressed separately at a future date.

A data solicitation for information pertaining to pollutants, including nutrients, in the Evitts 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 Evitts 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 Evitts 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 for the Evitts Creek watershed 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 Evitts 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 Evitts Creek watershed.  Although the waters of the Evitts 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 scheduled to be completed by the 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 Evitts 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 Evitts Creek Basin in Allegany County, Maryland

(Concurrence March 15, 2010)

EPA's Decision Letter

EPA's Decision Letter

Main  Report

WQA_Evitts_Creek_eutro.pdf (610KB)

Comment Response Document

CRD_Evitts_Creek_eutro.pdf (7KB)

Additional Supporting Information

Biological Stressor Identification Evitts Creek
Watershed Report

BSID Evitts_Creek.pdf (1587KB)

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.


Acrobat® Reader is required to view and print the PDF files. If you do not have it click on the icon to the right. Get Acrobat Reader (its Free!)