The Colorado Department of Public Health and the Environment required additional monitoring activities after 1,4 dioxane was found in a monitoring well…
According to County Administration Officer Tom Eisenman, CDPHE is requiring one more groundwater monitoring well in addition to the four currently on site.
A revised monitoring plan is due to CDPHE by the end of March.
Neighboring residents were notified last December by BLM that dioxane was found in one monitoring well.
The BLM stated in a memo to the county that CDPHE said the level found at the landfill was too low to cause health problems.
Eisenman said the surrounding groundwater wells on 12 private properties were tested.
One tested positive for dioxane, so a second sample was pulled as well as on an adjacent property’s well. Those results haven’t been received.
Eisenman said the county is providing water to the residents whose well was positive and currently working on a cost analysis of various options to provide a permanent solution for these residents’ well, at the county’s cost.
According to BLM, the landfill was operated from 1967 to Oct. 1993.
According to CDPHE, the closure plan met state requirements at the time it was approved. Since then state regulations have changed.
Waste was deposited into unlined trenches that were about 20 feet deep and regularly burned, according to Doty and Associates, the county’s consultant for the landfill post-closure requirements.
Located in Golden, Doty is an environmental, groundwater and waste management engineering firm.
Eisenman told The Flume that two groundwater monitoring wells were installed in 1991, both several hundred feet from the landfill trenches. They are LF-1 and LF-2 on the adjacent map.
The following history was taken from a 2014 Doty report.
A compliance advisory from CDPHE in 2004, stated the county needed to report groundwater monitoring. In 2006, one sample was tested and contained several volatile organic compounds.
Another advisory sent in 2007, stating groundwater monitoring needed to be implemented and based on the 2006 sampling, explosive gases needed to be identified.
When the state didn’t receive a response from the county, CDPHE conducted a site visit in 2013 and sent a third memo in 2014.
That led to digging excavation test pits both in the landfill and adjacent to it in 2015.
Because gas measurements at the pits showed the landfill is still generating gases, the state is now requiring the installation of gas probes.
The state also required more groundwater monitoring wells in the 2014 memo and implementation of a groundwater monitoring plan.
Doty developed a monitoring plan and two additional wells, LF-3 and LF-4R, were installed by BLM in early 2016.
All four wells were sampled three times in 2016, starting with the second quarter of the year and dioxane was detected in LF-2 and LF-3 in the fourth quarter, according to documentation from CDPHE.
The Flume’s request for copies of the landfill laboratory results was denied by the county.
Eisenman said the county is financially responsible for installing the gas probes and another groundwater monitoring well plus any remediation that is necessary.
According to an online article by Geosyntec Consultants, a world-wide company with two Colorado offices, dioxane removal is very complex and most treatments don’t remove it.
The article stated the process used at one site in Colorado is an advanced oxidation process.
“It has the capability to reduce the dioxane concentration to non-detect levels under the right conditions, but this is likely not achievable for many groundwater matrices,” the article stated.
Advanced oxidation process can include processes using ozone, hydrogen peroxide and/or ultraviolet light to break dioxin into other benign substances.
Research is ongoing regarding the best way to remove dioxane.
The good news
According to the Doty report, the geology in the area indicates that the groundwater found in the monitoring wells are in moraine deposits that were left after glaciers retreated.
These deposits have varying sizes of boulders, cobbles, gravel, sand and silt, usually without any cementing as found in other formations such as sandstone, shale or limestone.
Water can travel through moraine deposits easily.
The report states that the groundwater appears to be a perched aquifer underlain with a reddish clay, probably from a weathered Minturn formation which is a red siltstone.
The clay keeps the groundwater from moving downward, confining it to the depths of the moraine deposits. In the area, the moraine deposits range from 80 to 134 feet.
Aquifers below that may not be contaminated.
Eisenman said the monitoring wells are about 150 feet deep and most private wells in the area use an aquifer at around 250 feet.
The following two sections were obtained the Environmental Protection Agency and National Library of Medicine websites.
What is dioxane?
Dioxane is a synthetic heterocyclic organic compound. This means it is a manmade chemical that contains carbon, hydrogen and oxygen molecules that are connected in a circular pattern.
Dioxane is classified as an ether. It is a colorless liquid with a faint sweet odor. It is flammable; it mixes with and migrates quickly through groundwater.
Dioxane can degrade in the atmosphere into other harmless substances through photosynthesis. But that takes several days.
Health effects of a short term, high dose exposure include nausea, drowsiness, headache, and irritation of the eyes, nose and throat.
Chronic exposure can cause dermatitis and damage to the liver and kidneys. It is considered a possible carcinogen.
The BLM press release stated that according to CDPHE, the amount found in the Park County landfill monitoring well was not high enough to cause health hazards.
Currently, there is no EPA drinking water standard for dioxane. In 2012, EPA established a lifetime health advisory of 0.2 milligrams per liter in drinking water.
Colorado has adopted an interim groundwater quality cleanup standard of .35 micrograms per liter…
Dioxane is used as a solvent in paint and varnish removers, a corrosion inhibitor in chlorinated solvents, a purifying agent in the manufacture of pharmaceuticals and is a by-product in the manufacture of polyethylene terephthalate plastic.
It is used as a wetting and dispersing agent in the textile industry.
Traces may exist in food supplements and food containing residues from packaging adhesives or on food crops treated with certain pesticides.
Dioxane can be an impurity in antifreeze and aircraft deicing fluids and in some consumer products, such as deodorants, shampoos and cosmetics.