Abstract
Water samples were collected from 21 production and domestic
wells in the Mohawk River Basin in New York in July 2011 to characterize
groundwater quality in the basin. The samples were collected and
processed using standard U.S. Geological Survey procedures and were
analyzed for 148 physiochemical properties and constituents, including
dissolved gases, major ions, nutrients, trace elements, pesticides,
volatile organic compounds (VOCs), radionuclides, and indicator
bacteria.
The Mohawk River Basin covers 3,500 square miles in New York
and is underlain by shale, sandstone, carbonate, and crystalline
bedrock. The bedrock is overlain by till in much of the basin, but
surficial deposits of saturated sand and gravel are present in some
areas. Nine of the wells sampled in the Mohawk River Basin are completed
in sand and gravel deposits, and 12 are completed in bedrock.
Groundwater in the Mohawk River Basin was typically neutral or slightly
basic; the water typically was very hard. Bicarbonate, chloride,
calcium, and sodium were the major ions with the greatest median
concentrations; the dominant nutrient was nitrate. Methane was detected
in 15 samples. Strontium, iron, barium, boron, and manganese were the
trace elements with the highest median concentrations. Four pesticides,
all herbicides or their degradates, were detected in four samples at
trace levels; three VOCs, including chloroform and two solvents, were
detected in four samples. The greatest radon-222 activity, 2,300
picocuries per liter, was measured in a sample from a bedrock well, but
the median radon activity was higher in samples from sand and gravel
wells than in samples from bedrock wells. Coliform bacteria were
detected in five samples with a maximum of 92 colony-forming units per
100 milliliters.
Water quality in the Mohawk River Basin is generally good,
but concentrations of some constituents equaled or exceeded current or
proposed Federal or New York State drinking-water standards. The
standards exceeded are color (1 sample), pH (1 sample), sodium (9
samples), chloride (1 sample), sulfate (2 samples), dissolved solids (7
samples), aluminum (3 samples), iron (8 samples), manganese (6 samples),
radon-222 (10 samples), and bacteria (5 samples). Fecal coliform
bacteria and Escherichia coli (E. coli) were each detected in one
sample. Concentrations of fluoride, nitrate, nitrite, antimony, arsenic,
barium, beryllium, cadmium, chromium, copper, lead, mercury, selenium,
silver, thallium, zinc, and uranium, and gross alpha activities, did not
exceed existing drinking-water standards in any of the samples
collected. Methane concentrations in two samples were greater than 28
milligrams per liter, and the maximum measured concentration was 44.3
milligrams per liter.