Montour Run Watershed Assessment & Implementation Plan

ii. Water Resources
Precipitation
Pittsburgh averages 38.2 inches of precipitation per
year. However, since 2016, the region has received everincreasing
rainfall amounts each year. In 2016, rainfall
was 2.7 inches above average, in 2017, 8 inches above
average, and in 2018 Pittsburgh received nearly double
the average amount of rainfall, 33.8 inches above
average (Figure 1.2.1). The Pennsylvania Department of
Environmental Protection [DEP] predicts the conditions
will increase flooding in the winter and spring, as we
experience more intense rainfall, and droughts in the
summer and fall, as the snow evaporates earlier due to
warmer temperatures.
Surface Water, Wetlands, Ponds
The main stem of Montour Run trends westerly for
approximately 12.9 miles from where it empties into
the Ohio River. The stream exhibits a dendritic drainage
pattern. The stream runs through a valley with relatively
steep sides, and a small floodplain on either side of the
stream. This relationship between stream and banks
creates a Sinuosity Index of approximately 1.4 along the
length of the stream, classifying this stream as “twisty”.
In all, 48 stream miles in the Montour Run watershed are
listed as “non-attaining” and 16 mile as “attaining” and the
remaining small streams are unclassified.
The region contains no large natural ponds. There are
a number of small man-made reservoirs that were
constructed for specific purposes: recreation, stormwater
detention, AMD treatment. In total, these ponds cover
~90 acres of the watershed. There are a number of small
wetlands scattered throughout the watershed. In all, there
are 92 acres classified as wetlands, range in size from ~ 0.1
acre to 6 acres. The wetlands are located for the most part
in the riparian areas of streams.
iii. Previous Efforts to Identify
and Address Pollution Sources
Areas of the Montour Run Watershed have been the focus
of efforts on the part of conservation groups and the PA
Department of Environmental Protection. Over the years,
these stakeholders have worked to evaluate and improve
water quality in the Montour Run Watershed, successfully
reducing the effects of abandoned mine drainage and
improving aquatic habitat. The extent of previous efforts
discussed below highlights the additional improvement
work needed to continue this trajectory.
Previous Water Quality Studies
Montour Run has long been identified as having impaired
water quality. Stakeholder groups from private, public,
and government sectors examined stream water quality
and submitted studies over the years. These studies
helped to define the water quality issues in Montour Run,
focus restoration efforts, and build community support
for conservation.
The Montour Valley Alliance, a precursor to the
currently existing Montour Run Watershed Association,
commissioned a study in 1997 from the Army Corps of
Engineers detailing the water quality and aquatic life
resources. Identified issues included streambank erosion,
siltation with an accompanying decrease in habitat
quality, flooding, and in particular degraded water quality
from (AMD) and de-icing solutions used at the Pittsburgh
International Airport. Notably, de-icing operations
resulted in high biological oxygen demand and ammonia
concentrations in affected streams (Thorne 2000).
The same de-icing chemicals were cited as cause for
concern in a May 2000 PA Fish and Boat Commission
Figure 1.2.1- Monthly precipitation for the Pittsburgh Region.
Figure 1.3.1-Attaining and non-attaining streams in the Montour Run Watershed.
8 | Background Information & Watershed Overview Montour Run Watershed Assessment & Implementation Plan | 9