The EPA has established safe levels for over one hundred substances that may be in public drinking water sources. There is no EPA or State of Colorado drinking water standard for 1,4-dioxane. The EPA has set a health advisory level of 35 parts per billion for 1,4-dioxane. The average concentration in the District’s drinking water is 1.3 parts per billion which is well below this EPA health advisory level. EPA health advisories are informal guidance levels for unregulated substances in drinking water, issued by the federal government to help states, local health officials, and community water systems in protecting public health.
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Your water continues to be safe to drink and use based on the EPA health advisory level. Water from your tap meets every federal and state standard for safe drinking water. There have been no exceedances of state or federal regulations for 1,4-dioxane or any other drinking water contaminant. Levels of 1,4-dioxane detected in District wells and drinking water reservoirs are consistently below the EPA health advisory level. A health advisory is a guideline that represents an estimated acceptable level for a substance in drinking water based on health effects information. For more information, see the Agency for Toxic Substance & Disease Registry website https://www.atsdr.cdc.gov/substances/toxcommunity.asp
The testing that the District has conducted for the presence of 1,4-dioxane has confirmed that this substance is present in some of the District’s groundwater supplies. Tests on treated drinking water confirm the presence of this substance at an average concentration of 1.3 parts per billion in District water supplies in 2016.
Substances found at very low levels in water are often measured at the level of parts per billion (ppb). A part per billion is the same as one microgram per liter (ug/L). One part per billion is equivalent to one second in 32 years or a single penny in ten million dollars.
In 2011, the EPA identified 1,4-dioxane as an emerging substance of concern as part of a periodic Superfund review. In response to the review, the District began testing for the presence of 1,4-dioxane in groundwater supplies. This is an unregulated substance, meaning there is no drinking water standard for this substance. The District’s water quality chemists conducted sampling to determine if this compound was present. Samples were collected and sent to an independent, certified laboratory. Test reports confirmed that 1,4-dioxane was detected in some samples. The District shared results with the Colorado Department of Public Health and Environment and Tri-County Health Department. Since the presence of 1,4-dioxane was found, the District completed additional sampling using EPA-approved methods.
The District has taken many proactive steps in response to the detection of 1,4-dioxane in its water supply. • In 2013, the District expanded the water laboratory at the Klein Water Treatment Facility to be able to accurately analyze for this substance.• The District continues to monitor 1,4-dioxane concentrations in its water supply • The District has blended its water sources to minimize concentrations to the extent practical and assure that concentrations are well below the EPA health advisory. • The District has also engaged water treatment and engineering consultants to help us examine ways to minimize the presence of this substance. This includes pilot study testing of a process to remove the substance as well as cost estimates for construction of treatment capacity.
The Chemical Sales Co. Superfund site is the apparent source of much of the 1,4-Dioxane loading to groundwater. Remediation of this site, located near 46th and Monaco in Denver, is managed by the CDPHE with oversight from the EPA. The District continues to work with these agencies regarding source control of the substance. More information on EPA's and CDPHE's activities can be found at the following websites: https://cumulis.epa.gov/supercpad/cursites/csitinfo.cfm?id=0800866, https://www.colorado.gov/pacific/cdphe/chemical-sales-company. More detailed information on the cleanup can also be found at https://semspub.epa.gov/work/08/100001630.pdf.
If you would like a copy of the District’s current Water Quality Report, you can read and download the report from a link on the District’s website home page or by direct link at www.sacwsd.org/WQR. For additional information, please contact the District’s Water Quality Information Line: Phone: 303.287.6454; Email: firstname.lastname@example.org; Website: www.sacwsd.org