Coal fly ash in the Mohawk
Hotspots a legacy of coal power plants
Fly ash from burning coal is almost everywhere in the Mohawk River and a hotspot between Amsterdam and Schenectady may indicate that the river is cutting into spoils dumped long ago. I recently wrote about microplastics in the River, and that work resulted in a parallel study on the discovery of fly ash in the same samples caught in a manta trawl pulled through the water. This recent finding is concerning because fly ash contains a number of heavy metals and toxins. When we started this investigation, we weren’t looking for fly ash; we were looking for microplastics but stumbled upon this interesting issue related to burning coal from long ago.
Coal fly ash is produced from the combustion of coal in power plants. Fly ash and coal ash are the less dense waste byproducts of coal-burning furnaces, but together they make up the bulk of the Coal Combustion Residuals (CCR). Both have a basic chemistry dominated by (Si+Al+O±Fe) with or without additional elements (e.g., Zn, Ti) - and also a number of heavy metals, especially arsenic.
The 2008 Kingston spill of coal fly ash slurry in Tennessee was so large it could be imaged from space. The Environmental Integrity Project reported a year later that the Kingston spill released 2.66 million pounds of 10 toxic pollutants – arsenic, barium, chromium, copper, lead, manganese, mercury, nickel, vanadium and zinc - into the Emory River, more than was released annually by all US power plants at the time.
Fly ash cenospheres (hollow round silicate fragments) and coal ash (brown irregular pieces) from trawls in the Mohawk River (these from below Lock 9 in Glenville/Rotterdam Junction). They are a byproduct of coal combustion, and a major waste product from coal-fired power plants. They are remarkably common in the River between Amsterdam and Schenectady. Some of the silicate particles contain enough trapped air to float in water (Photos: JA Smith, Union College).
Under the microscope, fly ash is distinguished by a relatively smooth glassy surface on a droplet or sub-spherical shape, whereas coal ash has a rough and porous surface that is dark. But both include bubbles made of silicate (rock), and they are buoyant in water when the bubbles are intact. The distribution of fly ash and coal ash in the Mohawk River is interesting and concerning.
Two fly ash particles as seen under a reflecting-light microscope. The air bubble (dark center) is surrounded by a thin delicate wall of silicate (bright) and burned coal fragments (in the wall, not visible at this scale). The particles were placed on sticky tape, the area around the particles was flooded with epoxy, and then the sample was polished. We did compositional analysis on these and other particles (Photos: JI Garver).
Total fly ash and coal ash particle counts in 63 trawl samples from the entire length of the Mohawk River (left side is Rome, right side is Cohoes - see map below). The most significant hotspot for fly ash and coal ash particles is between Amsterdam and Schenectady. This concentration of particles may be related to a historic Adirondack Power and Light coal-fired power plant (just upstream from Lock 10).
Map of the main stem of the Mohawk River showing location of individual trawl samples analyzed for fly ash and coal ash. This sampling was done in 2016 and is detailed in Smith et al., 2017. Trawl sample numbers correspond to those of the graph above - this was the first systematic collection of microplastics and ash along the entire river.
Spoils from Adirondack Power and Light?
One distinct hotspot of fly ash occurs in the Amsterdam-Glenville area. This stretch of the Mohawk River includes the former coal-burning Adirondack Power and Light plant, located between Lock 10 and Amsterdam. This plant burned tons and tons of coal nearly 100 years ago. The sample with the second-highest fly/coal ash particle count (96 particles), was collected adjacent to the now-defunct power plant. The sample with the highest concentration of particles was collected immediately downriver of Lock 9.
The history of the Adirondack Power and Light plant was reviewed recently by Bob Cudmore. Construction of the plant started in 1920 and it was completed in 15 months. It burned high-grade anthracite coal brought in by rail from Pennsylvania. An expansion of the plant was completed in 1925. Newspaper accounts at the time suggested it would burn an astounding 200,000 tons of coal annually to generate electricity. Plant production slowed in 1926 (soon after expansion) due to the emergence of hydropower, and the plant eventually stopped generating electricity in 1950.
The Adirondack Power and Light plant on the Mohawk River just upstream from Lock E10 (Cranesville) near Amsterdam NY. A working hypothesis is that some of the fly ash in the River is from material discarded from this plant - somewhere along the River - because the highest occurrence of fly ash is in this section of the River (Photo: JI Garver).
It seems likely that the fly ash and coal ash particles are present in soil along the river banks where they can be eroded by normal flow conditions and by extreme events such as the channel migration and sediment remobilization that occurred during Hurricane Irene and Tropical Storm Lee in 2011.
Toxic legacy of the past
Coal fly ash in the River is an unfortunate legacy of the past. One hypothesis is that the ash in the Mohawk is related to dumps of spoils along the river banks, but at this point the location of these spoils in not known. This occurrence of fly ash is important because this waste may have a considerable number of toxic elements. Today the EPA is considering changes to State Coal Combustion Residuals Permit Programs, which would affect disposal today, but not legacy dumps. In August 2017 the Physicians for Social Responsibility wrote the EPA and noted:
Coal combustion residuals (CCR) are one of the largest toxic waste streams in the United States. U.S. coal-fired power plants burn more than 800 million tons of coal every year, producing more than 110 million tons of industrial solid waste in the form of fly ash, bottom ash, scrubber sludge and boiler slag (collectively known as CCR or coal ash). Coal ash is a deadly brew of carcinogens, neurotoxins, and poisons—including arsenic, boron, cadmium, hexavalent chromium, lead, mercury, selenium and thallium. When this dangerous waste is dumped without proper safeguards, hazardous chemicals are released to air, groundwater, surface water and soil, and nearby communities are harmed.
The detection of fly ash in the Mohawk was a serendipitous discovery that has important implications, and this intriguing result has produced more questions than answers. Where are the spoils of fly ash along the river? Are there dumps of fly ash all along the river? What is the environmental hazard of these spoils in place and also once they are liberated and continue their journey down the Mohawk and into the Hudson?
We are reminded that sometimes the best science produces great questions as opposed to definitive answers. Investigation of the fly ash/coal ash legacy in the Mohawk Watershed would be a fascinating research project for an ambitious scientist. An interesting first step would involve historical forensic work on where disposal sites are located.
This and other Notes from a Watershed are available at: https://mohawk.substack.com/
Discovery paper is: Smith, J.A., Garver, J.I., Hodge, J.L., and Kurtz, B.H., 2017. Fly ash and coal ash in the Mohawk River, in Cockburn, J.M.H. and Garver, J.I. (ed.), 2017. Proceedings of the 2016 Mohawk Watershed Symposium, Union College, Schenectady, NY, March 18, 2016, v.9, 75 pg. p. 63-66.