Six private wells out of 50 sampled this year had detectable levels of the chemical 1,4-dioxane, according to a Minnesota Department of Health (MDH) and Minnesota Pollution Control Agency (MPCA) update released Sept. 23.
Concentrations in all six wells were below the MDH health risk limit (HRL) for drinking water of 1 part per billion and are not of health concern. Additional confirmation sampling is recommended.
The source of the 1,4-dioxane is not known, according to the agencies. The chemical was detected in groundwater on Water Gremlin property at concentrations greater than the HRL in December 2019; however, the distribution of the 1,4-dioxane in private wells makes the source unclear, particularly for wells at the south end of the sampling area. Additional data collection and analysis is required to better understand the occurrence and movement of 1,4-dioxane in the area.
In April, MPCA directed Water Gremlin to sample additional private wells within a one-mile radius of its White Bear Township facility. The company's environmental consultant, Wenck, sent letters to 97 residents at priority locations requesting access to collect and test their well water. Forty-four well owners provided access, including some that were sampled in January/February. Three of 11 wells had detectable levels at that time, all significantly less than the HRL of 1 ppb.
MDH staff also collected samples at the same time from eight homes to verify testing results. The public health lab reported the same results as the lab used by Water Gremlin.
MPCA will determine locations of the next round of residential well sampling.
— From press release