What Makes a Stream Impaired?
A closer look at Montour Run Watershed


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After four years of collecting, organizing and analyzing data, ACCD has completed the Montour Run Watershed Assessment and Implementation Plan. This plan outlines data previously collected over the years by a number of watershed stakeholders, pollutants affecting the stream and ways to improve water quality. ACCD and Ethos Collaborative used a combination of field visual assessments and GIS modeling to get a complete look at the watershed.

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About Montour Run Watershed
The Montour Run Watershed includes about 37 square miles located in western Allegheny County and consists of parts of Findlay Township, North Fayette Township, Robinson Township, Moon Township and Coraopolis Borough. The main stem of Montour Run is approximately 12.9 miles in length and empties into the Ohio River.

The Status of Montour Run’s Streams
Most of the streams within the Montour Run Watershed are listed by the PA Department of Environmental Protection (DEP) as “impaired.” However, a few tributaries are listed as “unimpaired” or attaining their designated uses.

What is an impaired stream? DEP uses water quality standards to assess whether Pennsylvania's rivers and lakes are clean and pure enough for specific uses including support of fish and other aquatic life, recreation, water supply for drinking, agriculture, industry and other protected uses. These standards are used to determine the status of each of the state's streams.

According to DEP, 16 miles of streams within the watershed can meet these uses, primarily the Meeks Run and Trout Run Tributaries to the main stem of Montour Run. On the other hand, 48 stream miles are considered impaired, meaning they fail to support one or more of these uses.


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This map outlines the watershed areas in black with streams that are not impaired (blue lines) vs. those that are impaired (tan lines) in the Montour Run Watershed.

Where’s the Pollution Coming From?
Water quality standards are also used to determine what pollutant is specifically causing issues within the streams. These pollutants are listed as impairments.

For example in Montour Run, impairments result from metals, nutrients and sediment related to both past mining activities and stormwater runoff. Mining related impairments include sections of the stream that are affected by Abandoned Mine Drainage (AMD) and strip mine spoil piles.

Runoff from stormwater causes erosion, siltation and sedimentation in Montour Run, and the associated water quality effects are identified as widespread issues affecting stream water quality. Sources of erosion and sediment are numerous, and include runoff from urban or paved areas, construction sites, agricultural areas and barren land. Nutrient impairments and the associated problems of low Dissolved Oxygen (DO) in stream water frequently co-exist with sedimentation and erosion.

By identifying healthy and impaired streams, and mapping out where these pollutants enter waterways, the Montour Run Watershed Assessment and Implementation Plan will help direct targeted conservation efforts. This builds on previous ACCD projects in the watershed including the Milk Run AMD treatment system, stream buffer plantings in North Fayette and restoration efforts at the Montour Woods Conservation Area.