This guest post was written by Rob Rossi, a graduate student in the department of Geology and Environmental Science at the University of Pittsburgh. He was a graduate summer intern of NMRWA in 2015.
Road salt is a common part of winter for many Pittsburgh residents. In Pennsylvania, more than 840,000 tons of road salt (sodium chloride, or table salt) were applied to roadways between 2009 and 2014. Although it helps keep our roads and sidewalks ice and snow free, road salt has unintended consequences. Many people are familiar with the ever annoying winter problems of salt stained clothing or shoes/boots, but the environmental effects of road salt are less obvious. Road salt can have numerous negative effects on the environment, such as increased fresh water and soil salinity, and less obvious effects, such as increased time necessary for rain to soak into the soil. Additionally, when road salt dissolves in highway runoff, these waters have high total dissolved solids (TDS), which can flush roadside soil metals from clay particles (see animated Figure 1). Metals flushed by these reactions can include plant nutrients (e.g., potassium, calcium, magnesium) or toxic trace metals (e.g., arsenic, lead, cadmium).
Road Salt Study in Nine Mile Run
Rob Rossi, a graduate student in the Department of Geology and Environmental Science at the University of Pittsburgh, has been researching the effects of road salt on roadside soils in Nine Mile Run. Specifically, Rob has been analyzing soil and soil water chemistry in samples collected from three roadside soil water sampler “nests”. Each nest is a group of four lysimeters which behave much like giant straws, sucking up soil water samples when a vacuum is applied to the end of the soil water sampler (see Figure 2). The lysimeters collect soil water at roughly 6, 12, 24, and 36 inch depths along a hill slope perpendicular to I-376.
In the soil samples, soil sodium concentrations are highest in soils collected from near the road. Soil sodium concentrations decrease with distance from the roadway, approaching values observed in the local bedrock (see Figure 3). One theory is that high sodium concentrations can be attributed to the minerals breaking down in the bedrock but because sodium concentrations in roadside soils are much higher than sodium concentrations found in the bedrock, minerals in the bedrock breaking down is likely not what inputs sodium to these soils. Instead, the application of road salt to I-376 is likely causing high sodium concentrations in roadside soils.
Sodium concentrations in sampled soil waters peak at different times throughout the year relative to the location along the hillslope (see Figure 4). In particular, the earliest peaks in soil water sodium concentrations occur in the top hillslope soil waters in late February/early March in the intermediate depth (39 and 61 cm depth) soil waters. Additionally, soil water samples from the deepest top hillslope nest have, in general, the highest sodium concentration. While sodium concentrations spike in soil waters collected from all depths of the top hillslope nest station, soil water sodium concentrations peak only in deeper soil waters of the mid hillslope nest. Moreover, the peak in soil water sodium concentrations at the mid hillslope nest do not peak at the same time as when soil water sodium concentrations peak at the top hillslope nest.
These patterns in soil water sodium concentrations suggest that the way soil water flows in roadside soils influences the movement of sodium through these soils. Specifically, because the deeper top hillslope lysimeters (i.e., 12, 24, and 36 inch) peak before the shallowest (i.e., 6 inch) lysimeter, high TDS waters likely interact with deeper soils first. High TDS runoff from the highway is often observed to enter the soil column via infiltration (i.e., water percolating downwards through the soil), which produces a peak in sodium concentrations in the shallowest soil waters first. However, because this pattern in soil water sodium concentrations is not observed in samples collected from the Nine Mile Run transect, sodium is potentially transported to deeper soils via lateral flow originating from leaking highway drains and water flow between bedrock layers.
Previous scientific studies have observed that sodium loadings to soils persist beyond the period when road salt is applied to roadways, and this relationship is also apparent at this study site. Specifically, sodium persists as slow moving wave, where peaks in top hillslope soil water sodium concentrations occur within a month of when road salting ends, and peaks in soil water sodium concentrations at the mid and bottom hillslope stations occur later in the year. Thus, the distance from the roadside affects when soil water sodium concentrations will peak, suggesting that sodium is relatively slowly released from roadside soils throughout the spring and summer.
How does road salt affect the water quality of Nine Mile Run?
The results of this study suggest that sodium and metals are continually flushed to stream waters throughout the year. When sodium levels are high, the ecosystem cannot physiologically maintain a salt balance, which affects aquatic organisms living in the stream – particularly plants and animals that are not adapted to high concentrations of ions, and therefore cannot regulate the water and salt content within their cells. This stress can change the diversity of species within the ecosystem. The increased metal loading could impair the stream ecosystem, negatively impacting aquatic life such as fish. Some metals may be either beneficial or toxic, depending on their concentration. The primary mechanism for toxicity to organisms that live in streams is by absorption or uptake across the gills. The metals that are most toxic to aquatic organisms are Copper, Iron, Cadmium, Zinc, Mercury, and Lead.
Thus, it is likely that road salt application impacts soils down the hillside of I-376, and that the negative impacts of road salt application are not limited to the winter and early spring.
As you may have seen in our Spring newsletter, since 2013 we have been working with the Pittsburgh Parks Conservancy (PPC) on a grant received from the National Fish and Wildlife Foundation’s Five Star and Urban Waters Restoration Program. One of the goals of our partnership on this grant was to develop a culture of stewardship for the Nine Mile Run watershed by engaging a wide range of ages in citizen science and stewardship activities. One way we approached this was to implement PPC’s Mission Ground Truth (MGT) program at Wilkinsburg Middle School.
MGT is an interdisciplinary ecosystem assessment program mapped to PA state academic standards for 7th and 8th grade students that includes in-class discovery activities as well as a field trip to Frick Park. During the field trip, students get to be ecologists for the day, and have the opportunity to use the same tools and sampling methods that scientists use to evaluate the health of forest and stream ecosystems.
Recently, NMRWA staff worked for two days in Frick Park with Environmental Educators from PPC to help lead the Wilkinsburg Middle School students through the field day programming.
We began each morning by discussing goals for the day, then broke into small groups. During the morning session, the groups each explored a section of the Fern Hollow stream while discussing questions such as “how can ecologists detect and measure pollution in a stream?” and “what benefits do humans and animals get from streams?” Then the students recorded data on physical and chemical water quality characteristics, such as temperature, pH, dissolved oxygen, conductivity, and velocity. Next, we explored the benthic macroinvertebrate populations by carefully overturning rocks and collecting samples using a net. To wrap up, we would discuss how everything tied together by asking questions like “based on the data we collected, is the stream healthy or unhealthy?“and “how does the quality of Fern Hollow affect the health of Nine Mile Run?”
After a break for lunch, the students got to venture into the forest for a deeper look at the complex forest ecology present in Frick Park. We identified different tree and plant species and talked about the various ecosystem services that forests provide to animals, streams, and people. We asked questions like “why is biodiversity important in forests?” and “how is the health of this forest related to the health of Fern Hollow and Nine Mile Run?” Then the students used forestry tools to collect data on the location, size, and type of trees, and we looked for evidence of Asian long-horned beetles. To wrap up, we asked questions similar to the morning session, like “is this section of the forest healthy or unhealthy?”
Over the course of the two days, we had a wonderful & enriching experience working with the students and with the PPC staff. Thank you to Mike, Taiji, Steve, and Chelsea for their expertise & enthusiasm in implementing the MGT programming!
Most of you are aware by now there is an issue of combined sewer overflows (CSOs) polluting Nine Mile Run. During wet weather, our watershed’s aging combined sewer systems do not have the capacity to handle both stormwater and sewage so they overflow into Nine Mile Run, introducing pathogens, trash, and other pollutants to the stream. We have actively worked to correct this issue through green stormwater infrastructure (GSI) interventions in the upper watershed over the last 14 years, including installing rain barrels and rain gardens and planting over 900 street trees.
Despite all of this effort, however, we still have degraded water quality during and after wet weather. When we developed our 2013-15 Strategic Plan there was one main goal: to reduce the flow of stormwater and sewage into Nine Mile Run.
We understood to achieve this goal we would need to install GSI facilities capable of capturing large quantities of stormwater before it enters the combined sewer system. In 2014, we worked with Matt Graham of Landbase Systems to identify areas in the watershed that have high amounts of stormwater flowing into curb inlets and eventually overflowing into Nine Mile Run. Through detailed analysis, he identified an area in the Homewood neighborhood of Pittsburgh, which is actually outside of the watershed, but is part of the Nine Mile Run sewershed, that contributes over 25 million gallons of stormwater and sewerage overflow to the stream annually during wet weather events.
In case you aren’t familiar, a sewershed is simply a drainage area determined by the curbs, storm drains, pipes, and outfalls that all drain to a common outlet (e.g., Nine Mile Run). It doesn’t match perfectly with the Nine Mile Run watershed boundary because sewersheds often cross the boundaries of watersheds that existed before urbanization.
The Rosedale Runoff Reduction Project (RRRP) is a holistic sustainable stormwater project with the goal to remove all 25 million gallons of overflow entering the stream. We will achieve this by constructing 3 large GSI sites, 40 stormwater management tree pits, 200 Hydra rain containers, and 10 rain gardens.
In October 2014, we were awarded $150,000 from PA Department of Community and Economic Development (DCED) Commonwealth Financing Authority (CFA) Watershed Restoration and Protection Program to construct one of the GSI sites. And most recently in January, we received notification that we were awarded $236,175 from the PA Department of Environmental Protection (DEP) Growing Greener Program to construct a second site and install 200 Hydras. Both of these grant awards will allow us to implement the first phase of the RRRP, which proposes to remove 7 million gallons of annual runoff from the combined sewer system.
Stay tuned for proposed plans, details, schedule of implementation, and outreach events related to the RRRP!
People are often surprised to learn that yes, there are fish living in Nine Mile Run and in fact… there are rather a LOT of them!
Led by NMRWA Monitoring Committee members Brady Porter and Michael Koryak, fish sampling is performed on an annual basis, typically in the fall. Since the stream restoration was completed in 2006, their data have shown marked improvement in the number and diversity of fish in the stream.
Immediately post-restoration, the entire stream was electro-fished and only 116 fish comprising seven different species were found. Today, it’s impossible to sample the entire length of the stream in one day due to the number of fish and time it would take to process them all!
For example, last Wednesday, NMRWA Monitoring Committee members and other volunteers sampled for fish in lower Nine Mile Run. Beginning at the mouth of the stream near Duck Hollow in the morning, and traveling upstream to finish just below the pedestrian bridge in the late afternoon, we caught nearly 2,300 fish comprising 17 different species! This is the second highest species count ever found in this section of the stream – 21 species were found in 2011.
Additionally, we found two new species that had never been collected from Nine Mile Run before: Gizzard shad and Silverjaw minnows. The addition of these two species brings the total species count of fish collected from this stretch of Nine Mile Run since 1999 to 30!
This week, barring inclement weather, we will finish our fish sampling for the year when we sample a section of the stream in the main part of Frick Park.
As always, thanks to Brady and Mike and all the volunteers who help make this important sampling effort happen!
Want to learn more about our stream monitoring work? Head on over to our monitoring page for more information and nifty, interactive data maps!
Today’s blog post comes from the Clean Rivers Campaign – an education & advocacy program designed to raise awareness of the stormwater runoff and sewage overflow issues in Allegheny County. NMRWA is one of the CRC’s six founding organizations.
Clean Rivers Campaign Happy Hour
Last Thursday, May 1st, the Clean Rivers Campaign hosted a Happy Hour. This event was an opportunity for the campaign and its supporters to meet, mingle, network and celebrate the success of the campaign over the last two years. Borelli Edwards Gallery on Butler Street in Lawrenceville hosted the Happy Hour. The gallery was simultaneously hosting the art of Cynthia Cooley’s exhibit Pittsburgh Evolves: Looking Back, Looking Forward. Cynthia’s beautiful paintings of Pittsburgh landscapes, scenes and landmarks provided a unique and relevant background for the conversations of the Happy Hour. Old and familiar faces made up the great turnout. Check out a few pictures below of attendees showing their support for the campaign. You can see more pictures on Clean Rivers Campaign’s Facebook page.