Colorado has some of the strictest groundwater standards in the country. In 2005, the Colorado Water Quality Control Commission established a new groundwater standard for 1,4 dioxane of 6.1 ppb (parts per billion). Today, the Colorado groundwater standard is 0.35 ppb, below even what analytical laboratories can accurately measure.
1,4 dioxane is a man-made substance used as an industrial solvent. It is still used today in paints and varnishes and can be found in some cosmetics, deodorants, toothpastes, cleaning products, and soaps. The EPA has classified it as a “probable human carcinogen.”
New technological advancements capable of detecting and measuring 1,4 dioxane at the new standards found 1,4 dioxane north of the Site which indicates the remedy components are effectively controlling the plume.
Click to view an animated image of 1,4 dioxane concentrations 2005-2020.
The EPA found:
There is no significant health risk associated with the surface water or groundwater.
The water is not a drinking water source and the risk from occasional contact with contaminated groundwater entering Murphy Creek is insignificant. Anyone who comes into contact with creek water or wades in the creek is not in danger.
The 1,4 dioxane is residual contamination from the site before cleanup and containment began and before 1,4 dioxane was a known or detected contaminant of concern and began being removed at the site’s water treatment plant.
The groundwater extraction and treatment response at the site has significantly decreased the 1,4 dioxane concentrations, and they continue to decline. Please see the map at the left to view the concentration decreases from 2005-2020. The magenta dots represent the groundwater extraction wells.
Since 2005, Colorado has decreased the groundwater standard ten-fold, going from 6.1 ppb to 0.35 ppb. Technology has not advanced to a point where 1,4 dioxane can be consistently measured at that low level, so the site must comply with a 0.9 ppb standard, which can be reliably measured. The dark blue shade on the map illustrates the extent of 1,4 dioxane contamination at a concentration level of 0.9 ppb.
For the most up-to-date information on North End Monitoring Results, please go here.