Agricultural weed killer products found in groundwater
MUNCIE — Agricultural weed-killer breakdown products were found in 68 of 398 groundwater samples collected from private residential water wells and small public water supply wells statewide, the Indiana Department of Environmental Management (IDEM) has announced.
About 1.6 million Hoosiers, or 26 percent of the population, obtain their water from private, domestic wells, which are not required to be tested on a regular basis for quality.
The herbicide degradation products (degradates) were detected in one of the four wells sampled in Delaware County and in one of the eight wells sampled in Henry County.
The state's annual groundwater monitoring program also found detectable levels of nitrates in two of the nine wells sampled in Wayne County, though they were not above the federal government's maximum contaminant level for drinking water.
The major sources of nitrates in drinking water are runoff from fertilizer use, leaking septic tanks and erosion of natural deposits.
It was degradates of acetochlor and alachlor — herbicides commonly used in Indiana to control broadleaf and grassy weeds in corn and soybeans — that were found in Delaware and Henry county wells. No maximum contaminant levels in drinking water have been established for herbicide degradates.
In addition, arsenic was detected in 12 samples from Delaware, Henry, Jay, Randolph and Wayne counties — and at levels that exceeded the maximum contaminant level in Jay, Randolph and Wayne.
Natural events, such as dissolution of minerals from clay and erosion of rocks, can release arsenic into the water.
The samples were collected in 2013-14 from 271 private residential wells and 128 public water supplies like churches, schools and small businesses.
IDEM says well testing, which has been conducted annually since 2008, provides a view of untreated water as it exists in deep, underground aquifers. Private wells are the responsibility of owners and are not regulated by the federal Safe Drinking Water Act.
The latest annual report also found elevated iron concentrations exceeding the secondary maximum contaminant level in 263 samples statewide. Iron is a secondary contaminant and not aesthetically pleasing.
Trace amounts of the weed killers atrazine and 2,4-D, used on row crops, along with the weed killer simazine, are detectable in the drinking water delivered to Muncie's homes and businesses, though at concentrations below the maximum contaminant level.
Hydrogeologic settings in East Central Indiana include stream valleys and floodplains where the water table is quite low (less than five feet); shallow water tables in sluiceways containing abundant sand and gravel deposits at significant depths; tunnel valleys or melt water discharge channels that formed at the base of the ice sheet and carried away melt water and deposits to the front of glaciers; and bedrock aquifers at depths ranging from less than 30 feet to hundreds of feet.
Contact Seth Slabaugh at (765) 213-5834.
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