Blogs > Water Quality > Data analysis: Utica’s CSOs and the Mohawk River

Data analysis: Utica’s CSOs and the Mohawk River

Mohawk - utica cso sampling map

Riverkeeper sampling sites and the locations of CSOs in Utica.
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Riverkeeper’s Mohawk River water quality monitoring program, in partnership with SUNY Cobleskill, SUNY Poly and community scientists from the region, is in its fourth year. With that data in hand, we’ve analyzed how Utica’s Combined Sewage Overflows (CSOs) affect water quality in the Mohawk River. The City of Utica, like many other river cities on the Hudson River and its largest tributary, the Mohawk River, relies on old infrastructure that is designed to overflow when it rains. Raw sewage is discharged along with polluted street water because the same pipes that carry sewage carry stormwater. Here’s a look at what we can learn from four sampling sites, of the more than 40 sampled monthly in the Mohawk River Watershed.

Utica has eliminated 12 CSOs so far as it completes the Long Term Control Plan required by the Department of Environmental Conservation to comply with the Clean Water Act. However, 36 CSOs remain. Five of these CSOs discharge directly to the Mohawk, while the others discharge to creeks – long ago buried, in most cases – that discharge to the Mohawk. Nail Creek, Ballou Creek and Starch Factory Creek are the three main tributaries that receive CSO discharge and carry it to the Mohawk River.

Riverkeeper primarily measures Enterococci (Entero), a fecal indicator bacteria. While not harmful itself, Entero indicates that pathogens associated with untreated sewage or other fecal contamination is likely to be present. The influence of Utica’s CSOs can be seen clearly in our data from the the two most directly influenced by Utica CSOs, and those immediately up and downstream. This map shows the location of our sampling sites, relative to the Mohawk CSOs and the confluence of the three creeks.

These CSOs have a clear negative influence on water quality, causing a dramatic increase in contamination compared to the upstream sampling location. The concentration of bacteria found through Utica is 4.4-7.7 times the threshold set by the U.S. Environmental Protection Agency for safe swimming.

Entero (cells per 100 mL) geometric mean, by site, in the Utica area. A geometric mean is a weighted average.

The effect of rain, which triggers overflows because of the antiquated infrastructure the city relies on, is clear as well:

Entero (cells per 100 mL) geometric mean, by site, in the Utica area. A geometric mean is a weighted average. Wet weather is defined as 0.25-inch or greater rainfall, cumulative, over three days prior to sampling.

Interestingly, though, rain is not the area’s only influence on water quality. We found an unexpected and concerning pattern showing a steady increase in contamination moving downstream, considering only dry weather samples.

Entero (cells per 100 mL) geometric mean, by site, in the Utica area. A geometric mean is a weighted average. If cumulative rainfall over three days prior to sampling is less than 0.25 inches, samples are considered to be dry weather samples.

Riverkeeper shared these findings with the DEC and made two requests: analyze the feasibility of accelerating the implementation of Utica’s Long Term Control Plan, based on the availability of new state funding like the history $2.5 billion Clean Water Infrastructure Act; and investigate illicit discharges or other potential sources of dry weather sewage releases.

It’s worth noting that, as serious as are the water quality problems near Utica, water quality at the mouth of the Mohawk in the Capital District is worse by a significant degree. The concentration of bacteria found through the Capital District communities of Cohoes, Green Island and Waterford is 7.1-12.6 times the threshold set by the U.S. Environmental Protection Agency for safe swimming. Look for data analysis and next steps for this part of the river soon. (Herkimer also shows a troubling spike in contamination, which we haven’t yet investigated.)

Geometric mean of Entero counts by sample site on the Mohawk River main stem.

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