A number of methods have been implemented to protect the public. These include remediation, containment, collection, treatment, and monitoring of contamination in the soil, air and water.
Containment methods – capping the landfill with clay, underground barrier walls to prevent groundwater flow from the site, an onsite water treatment plant and an innovative system that converts landfill gases into energy – protects the surrounding environment and human health.
Overseen by state and federal regulators, the site’s remediation and containment plan has been in place and operating for decades and is “protective of human health and the environment,” according to the EPA. Every five years, the EPA evaluates the remedy at the Superfund site to ensure it is now and in the future protective of human health and the environment. The agency’s fourth five-year review is scheduled for release later this year.
The landfill gas treatment system collects gas that is naturally generated from the decomposition of the landfill wastes and prevents its release, ensuring that the public is not exposed to hazardous waste through the air or subsurface migration. Additionally, all of the surrounding businesses and residential areas receive drinking water from the City of Aurora and East Cherry Creek Valley Water and Sanitation District, with the exception of a few properties served by private wells that have tested clean.
The EPA has concluded in its last two successive reviews that the site has effectively protected humans and the environment from any type of potential exposure.
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More than 500 monitoring wells extending into both shallow and deep aquifers have been installed within and outside the site to ensure the community is protected. A groundwater monitoring system at the site tracks the movement and direction of the water, and an onsite water treatment plant operates 7 days a week, 24 hours a day, 365 days a year to treat contaminated water. Underground barrier walls extending to the bedrock prevent contaminated water from leaving the site and uncontaminated groundwater from entering the site.
The City of Aurora and the East Cherry Creek Valley Water and Sanitation District provide water to all of the residents and businesses in the area, with the exception of a few properties served by private wells that have tested clean. As a result, the public is never ingesting or bathing in contaminated water. Anyone who may wade or play in nearby Murphy Creek or incidentally ingest some water are not in any danger, according to the EPA.
Through its groundwater monitoring system, data is meticulously evaluated to respond to any potential changes in the movement and direction of groundwater. To date, these evaluations show that the groundwater remedy initiated nearly two decades ago continues to effectively protect the public and the environment.
North End Monitoring
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).
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.
Click to view an animated image of 1,4-dioxane concentrations 2005-16
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 could be residual contamination from the site before cleanup and containment began and before 1,4-dioxane was a known or detected contaminant of concern.
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 right to view the concentration decreases from 2005-2016. The magenta dots represent the groundwater extraction wells.
Since 2005, Colorado has decreased the groundwater standard ten-fold, going from 6.1 ppb to .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 measured. The dark blue shade on the map illustrates the extent of 1.4 dioxane contamination at a concentration level of 0.9 ppb.
Innovative and Environmentally Responsible
The Lowry team is constantly looking for ways to continue protecting the community and environment with the most-advanced technology that produces the least amount of environmental impact.
Water Treatment Plant
A treatment plant onsite not only removes 1,4-dioxane, but leaves a minimal environmental footprint by using a natural biological process.
The waste – in this case 1,4-dioxane and Tetrahydrofuran (known as THF and found in industrial solvents) – is diluted through a water pre-treatment process and piped into an industrial container. Also within the waste are naturally-occurring bacteria (often called “bugs”).
Then oxygen and heat are added to the mix. This creates the perfect meal for the bugs, which go into a feeding frenzy and gobble up the 1,4-dioxane and THF. In fact, this process degrades an average of 97 percent of the waste. The leftovers are discharged to a sanitary sewer system for additional treatment at the Metro and Aurora municipal wastewater treatment plants.
Landfill gas—made up of methane, carbon dioxide, nitrogen and other gases—is created naturally by the biological decomposition of organic matter in landfills under low-oxygen conditions.
The gas-to-energy plant at Lowry Landfill and the adjoining Denver Arapahoe Disposal Site removes roughly 5,000 tons of methane annually, which is the equivalent in greenhouse gas terms of removing 22,000 cars from the road each year. The plant, the first one of its kind in Colorado, beneficially uses waste gas from both sites, providing electricity for about 3,000 homes.
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The key components of Lowry Landfill’s cleanup and containment plan—which have proven themselves to be “protective of human health and the environment,” according to the EPA—are:
Underground Barrier Walls: A system of subterranean walls constructed to bedrock protects fresh groundwater from entering the site and prevents contaminated groundwater from leaving the site.
Onsite Water Treatment Plant: A treatment plant onsite removes all site chemicals to safe standards and also leaves a minimal environmental footprint by using a natural biological process. It treats approximately 1.5 million gallons of contaminated groundwater every month.
North Toe Extraction System: Trenches and wells around the perimeter of the landfill, and at two location north of the landfill, collect contaminated groundwater. The extracted water is pumped to the site’s water treatment plant.
Gas-to-Energy System: Landfill gases—mostly methane and carbon dioxide—are the natural byproduct of decomposing waste that was buried underground at the landfill. The site’s gas-to-energy system extracts the gases, burns them and converts them into electricity for a local utility company.
Landfill Cover: The former landfill area is covered by 4 to 12 feet of compacted clay and soil. The “cap” reduces infiltration of rain and snow into the soil, which minimizes further groundwater contamination.
Groundwater Monitoring Wells and Compliance Program: More than 500 monitoring wells within and outside the site are routinely monitored to ensure the community is protected.
Surface Water Removal Action: An unnamed creek flows through the Lowry Landfill site. Contaminated groundwater is kept separate from clean surface water within the creek stream bed by a channel of permeable material installed beneath the stream bed and covered by a clay barrier. This provides a pathway for groundwater to flow north without contacting surface water. Clean surface water flows above the permeable channel without coming into contact with contaminated groundwater flowing underneath the clay barrier.
Extra Measures: Although not part of the EPA’s ’s formal cleanup plan, property was purchased around the former landfill as a precautionary measure. These properties are deed restricted to prohibit future groundwater use and to control future development around the site so land uses are compatible with cleanup and containment objectives and are in the public interest. The properties are one-half mile wide on the west and south sides of the site and one-quarter mile on the east. No such zone was purchased to the north because the active Denver Arapahoe Disposal Site facility adjoins the Lowry Landfill site at the north end. To see what is happening with buffer areas in the public interest go here.