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Aurora outlines remediation plan and grants for Highway 30 landfill contamination
Summary
City staff described contamination at the closed Highway 30 landfill and remediation options including regrading, permeable reactive barriers, soil vapor extraction with combustor, and possible excavation; state grants of about $11.4 million will fund initial work toward an estimated full cost of roughly $35.5 million.
Aurora City staff on Sept. 10 briefed the Planning and Economic Development Policy Committee on contamination and remediation planning for the Highway 30 landfill, a closed municipal landfill owned by the city.
"This landfill is in Ward 2," said Jeffrey Moore, manager of the city's energy and environment division. He said the landfill closed in 1975 and that state regulator CDPHE (Colorado Department of Public Health and Environment) issued a compliance advisory in 2016 and a final compliance order and consent in late 2019 requiring cleanup of groundwater and some soils.
Moore said the investigation phase is complete: contractors drilled more than 100 monitoring points and soil vapor wells to delineate two former waste trenches. He described contaminants identified by state guidance, including 1,4-dioxane (an industrial solvent) concentrated in the west trench and trichloroethylene (TCE) concentrated in the east trench. The trenches are relatively shallow — Moore said the deepest parts are on the order of 25 to 30 feet below the surface — and the affected water is "shallow groundwater, tens of feet deep," not the deeper aquifers the city operates.
Staff presented a set of remediation approaches in the Assessment of Corrective Measures Report (ACMR): regrading waste areas to reduce ponding, installing permeable reactive barriers (PRBs) at two locations to capture and neutralize contaminants, and connecting passive methane vents into a soil vapor extraction system with a blower and combustor. Moore said those three systems have grant funds to begin implementation this year and next. "All of these things that I've just talked about, these 3 systems, we have grant funds to do this work," he said.
Moore said excavation of saturated waste and off‑site disposal is a potential future step if monitoring shows the initial remedies are insufficient, but that excavation is the most expensive option. He estimated an all-in remediation cost of about $35,500,000 if excavation is required.
The city has received substantial state grant support for initial work. Moore said Aurora signed a March contract for $7,900,000 from a state grant program created by the Colorado legislature to help local governments remediate closed landfills. The city applied for an additional approximately $3.5 million in a subsequent grant cycle; Moore said that amount was approved by the advisory committee and by CDPHE earlier that week, bringing the city's approved grant total to about $11,400,000 of the $15,000,000 program appropriation.
Moore said the city has already spent about $2.5 million over the past decade on investigation work (roughly $250,000 per year) from the capital projects fund and has received $81,000 in reimbursements through June under the state grant. He said the ACMR was submitted in December, CDPHE returned comments in the spring that the city addressed over the summer, and CDPHE will post a public comment period tied to the ACMR.
Moore provided a public-notice timeline: he said CDPHE will run a 45-day public comment period, noting a Sentinel posting and an end date of Nov. 9 for comments. Staff said communications work is underway to notify council and the public and that initial grant-funded remediation work has already begun. "This is a long term project...we're going to take it step by step," Moore said, adding monitoring will continue for decades.
Committee members asked for clarity on human-health exposure and potential affected parties. Moore said there were no known direct impacts to individuals at present and that the city's drinking water is supplied by Aurora Water (not private wells), but noted private wells in unincorporated areas north of the landfill could be affected in the future if contamination migrated and that city liability stems from the city's historical ownership and operation of the landfill.
The presentation was for information only; no committee action was requested. Ending
Staff will proceed with the public comment period, grant-funded initial implementation, and ongoing monitoring, with further actions depending on monitoring results and cost-effectiveness of initial remedies.
