The EPA has established acceptable levels for over one hundred substances that may be in public drinking water sources. There is no federal or State of Colorado drinking water standard for 1,4-dioxane. SACWSD will follow EPA guidance in the absence of state-specific requirements. The EPA has set a health advisory level of 35 parts per billion for 1,4-dioxane. (A health advisory is a guideline that represents an estimated acceptable level for a substance in drinking water based on health effects information.) The average 1,4-dioxane concentration in the districts drinking water (1.3 parts per billion average for 2016) is much lower than the EPA health advisory level.
The District has taken a proactive approach to dealing with 1,4-dioxane. This started with initial voluntary sampling efforts along with expansion and upgrade of the drinking water laboratory to allow for testing of this substance. Since detecting the presence of 1,4-dioxane in some of the Districts groundwater wells, the District has discontinued the use of the well with the highest concentration of the substance. The District has investigated the source of the substance and determined the main source to be the Chemical Sales Co. Superfund site. Remediation of this site, located near 46th and Monaco in Denver, is managed by the CDPHE with oversight from the EPA. For more information, see CDPHE's and EPA's webpages on the Chemical Sales Superfund Site.
The District continues to work with these agencies regarding source control of the substance. The District has also completed pilot testing of treatment technologies capable of treating the substance, as well as an engineering study to get a cost estimate of full-scale treatment.
The District will continue to keep its customers informed as information becomes available. The District publishes an annual Water Quality Report in June that is available to all customers electronically or by direct link at www.sacwsd.org/wqr. For additional information, please contact the District’s Water quality Information line at 303-287-6454 or via email at wqinfo@sacwsd.org.