Third Party Oversight

Former Drycleaner Facility
Denver, Colorado

Services Provided


Trihydro provides expert senior technical support to an insurance company on a claim related to groundwater impacts from a former drycleaner in Denver, Colorado. Tetrachloroethene (PCE) concentrations have been detected in groundwater at concentrations greater than 100,000 ug/L.  Site investigations have determined that PCE impacts are primarily the result of a former dry cleaner that operated on an adjacent property.  PCE impacts have migrated through overburden and fractured rock to beneath a large commercial building owned  by the insured.  PCE in groundwater affects the insured because a pre-existing dewatering system required retrofits to treat PCE prior to discharge, and PCE migration from groundwater into indoor air required installation of a sub-slab depressurization (SSD) system.  

Trihydro’s technical support has encompassed a wide range of technical and regulatory issues.  Trihydro has reviewed the conceptual site model (CSM) presented by the former dry cleaner, including drastic revisions to the hydrogeologic relationship between the former dry cleaner and the insured’s building.  In addition, Trihydro evaluated PCE fate and transport to assess both the former dry cleaner as well as other potential sources contributions to PCE observed beneath the insured’s building. Trihydro has suggested optimization methods  for operation of the SSD and dewatering systems. Lastly, Trihydro has provided expert technical advice relative to the proposed in-situ chemical oxidation (ISCO) remediation system proposed by the former dry cleaners. 
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Trihydro met with consulting and legal representatives of the former drycleaner and state regulators and presented risks to concrete integrity that were posed by the proposed ISCO remediation program with sodium persulfate.  A key outcome of this meeting was that the ISCO program was changed to permanganate, which posed much less risk to the insured’s building foundation.