AWD 1,4 Dioxane Results for
|*Running Annual Average for last 4 Quarterly Samples Taken
|September 16, 2019||non-detect <0.144 ppb|
|May 14, 2019||non-detect <0.153 ppb|
|March 26, 2019||0.210 ppb|
|December 10, 2018||0.206 ppb|
|September 19, 2018||0.136 ppb|
|June 11, 2018||0.204 ppb|
|March 14, 2018||0.235 ppb|
|December 11, 2017||0.211 ppb|
|August 31, 2017||0.182 ppb|
|May 3, 2017||0.201 ppb|
|February 1, 2017||0.257 ppb|
|November 17, 2016||0.285 ppb|
|September 7, 2016||0.256 ppb|
|June 6, 2016||0.238 ppb|
|February 10, 2016||0.291 ppb|
|November 16, 2015||0.258 ppb|
|August 17, 2015||0.219 ppb|
|June 25, 2015||0.218 ppb|
*Running Annual Average – The highest level of a contaminant as determined by an average of the prior four quarterly samples taken at the South Acton Water Treatment Plant (SAWTP).
MassDEP Guideline for 1,4-dioxane in drinking water is 0.3 ppb
The Acton Water District has been monitoring our sources of supply in South Acton for 1,4-dioxane since 2006, when it was first identified as a potential concern at the WR Grace Superfund site. Since that time we have learned a great deal about 1,4-dioxane, how it may be regulated in drinking water, where we believe it is coming from, and how it may be treated in the future. A few points that are important to understand:
Following the change in the drinking water guideline value for 1,4-dioxane by the Massachusetts Department of Environmental Protection (MassDEP) in 2011, we began our quest to understand what the guideline would mean for us. This was important, as MassDEP has applied guidance values to various other compounds in different ways. More information on how contaminants are evaluated for drinking water suitability can be found at https://www.mass.gov/service-details/dwps-use-of-mcls-office-of-research-and-standards-drinking-water-guidelines-for.
The first step was to determine against which data point(s) the guideline would be measured. It was determined that compliance with the guideline would be based on the treated water concentrations from the SAWTP on a running annual average (four most recent quarterly samples). This data is presented in the graph below. Next, we wanted to know what would happen if we exceed that guideline. Working with our team of advisors, MassDEP informed us that a site specific risk characterization would be completed. At our urging, this assessment was completed proactively, as we felt it was prudent in our planning and resource allocation to understand the longer term impacts of what the guideline would mean. The good news is unacceptable health risks for 1,4-dioxane are associated with much higher levels than those we have historically seen in our treated water.
It is our understanding that when the guideline was set, it was to be protective of non-cancerous and cancerous risks occurring. This takes into consideration excess lifetime cancer risks (ELCRs) at both one in a million and one in one hundred thousand chance of increasing an individual getting cancer if exposed for 70 years to consuming two liters of water daily. What this means is that one person in one million or one hundred thousand could attribute a cancer to the drinking water. Therefore people that do not consume 2 liters per day of drinking water or do not spend 70 years doing so, will be at a lower risk.
The difference between the guideline and the level at which unacceptable risk occurs is due to the risk assessment process itself. The guideline, in effect, is a screening value to determine what, if any, additional steps need to be taken to understand the safety of the water. This includes a safety factor between the two ELCRs noted above. Many of the steps we have been taking would be considered next steps should our concentration of 1,4-dioxane exceed the guideline.
To summarize the findings, MassDEP provided concise guidance that current levels in both the untreated groundwater and treated drinking water do not pose an unacceptable risk to our customers. Given the concentrations of 1,4-dioxane observed in the aquifer surrounding our wells, an unacceptable risk could be present if these elevated concentrations reach our production wells. For perspective, these concentrations would be almost six times the highest concentration currently observed in a single production well. Therefore continued monitoring and reporting of 1,4-dioxane concentrations in our raw and treated water is required. MassDEP also called for effective steps to intercept the plume and/or steps to ensure blending and treatment can maintain acceptable levels of 1,4-dioxane going forward.
Please continue to check this website for new information. This site is updated with the results of our quarterly monitoring data and contains other helpful background information. You can also speak with or email our Environmental Manager if you have questions or concerns. He can be reached at 978-263-9107 or