Thornton cleanup deadline passes as 88th Avenue developer search continues
Thornton’s former shopping center was scheduled to complete active excavation and remediation by the end of July 2026, but the city’s reviewed materials do not confirm that the work finished by Sunday, Aug. 2. At the same time, the city’s search for a mixed-use development partner remains active, with qualifications due Thursday, Aug. 6.
The two-track transition involves the approximately 15.6-acre former Thornton Shopping Center, now called The Market at 88th, at 8800 Washington Street on the northeast corner of East 88th Avenue and Washington Street.
July date was a scheduled cleanup milestone
Thornton’s redevelopment page says excavation activities were expected to begin in February 2026 and conclude by the end of July, with the schedule subject to change. The page does not provide a final completion notice, inspection record or environmental filing confirming that active remediation was completed by July 31.
The March 3, 2026 excavation plan breaks the work into February design, permitting and pre-mobilization; March through May implementation; and a June/July completion-report submittal period. Those documents establish the planned work and reporting schedule, not proof that all field activities were finished on time.
What the cleanup involves
The city’s stated remediation scope includes removing and properly disposing of contaminated soil and bedrock to depths of up to 24 feet, handling and treating contaminated groundwater, removing asbestos water lines and sanitary sewer infrastructure, placing a remediation amendment, and backfilling with clean overburden and engineered fill.
The excavation plan also calls for a carbon-substrate treatment amendment at the base of the main excavation. It provides for an in-situ treatment gallery that could be used to treat deeper groundwater and bedrock beneath the excavation if warranted.
State order identifies PCE contamination and off-site migration
The Colorado Department of Public Health and Environment’s Compliance Order on Consent identifies the facility as a 15.86-acre property at the northeast corner of East 88th Avenue and Washington Street. The order says groundwater beneath the shopping center and neighboring properties is contaminated with tetrachloroethylene, also known as perchloroethylene, PCE or perc, along with related chemicals including trichloroethylene.
The order identifies the primary PCE source beneath a vacant unit at 8866 Washington Street and says contamination from former dry-cleaning operations migrated off-site. It requires the Thornton Development Authority to carry out corrective-action obligations under state environmental oversight.
Active excavation is only one stage of that response. Thornton says remaining on-site groundwater contamination and contamination that migrated southeast will require long-term treatment and monitoring after the active-remediation phase. Vapor-intrusion mitigation may also be required if monitoring identifies a need; the reviewed materials do not establish a current vapor-intrusion condition.
Developer qualifications due Aug. 6
While the cleanup schedule moved to its end-of-July milestone, Thornton’s redevelopment procurement process remained open. City Solicitation 228-26, titled “The Market at 88th Mixed Use Development Opportunity,” was listed as active with responses due at 4 p.m. Thursday, Aug. 6, 2026.
The solicitation seeks developer qualifications for the site. Thornton’s published schedule anticipates a later request-for-proposals phase from September through December 2026.
The process is not final approval of a development plan. The reviewed records do not show that Thornton has selected a development partner, and the eventual mix of retail, housing, dining, jobs, traffic changes or other uses remains undecided.
What happens next
The next near-term checkpoints are any official confirmation or reporting tied to the environmental work and the Aug. 6 qualification deadline. Selection of a development team, later approvals and a construction schedule remain future steps.
For residents and businesses near 88th Avenue and Washington Street, the practical takeaway is that the property is moving from large-scale source-area cleanup toward redevelopment procurement, but it should not yet be treated as a finished development site. Groundwater treatment and monitoring will continue even after active excavation ends.
Sources
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