Forensic Hydrology: Hydrocarbon Release Investigation
Garfield County, Colorado

Western Water & Land conducted a forensic hydrologic investigation of the source of hydrocarbon products discovered in groundwater near the intersection of a pipeline corridor and Parachute Creek in western Colorado. The investigation was initiated by compiling lithologic and groundwater information obtained during investigation of the apparent release. The information was used to refine the understanding of hydrogeologic conditions at the site, including lithologic character of the underlying aquifer, groundwater levels, groundwater flow, and hydraulic conductivity based on local aquifer tests which were used to estimate average linear velocity of groundwater flow at the site. Western Water & Land characterized the potential source contaminants (natural gas liquids and condensate) to evaluate possible transport and fate behavior and used detailed compositional analytical results for samples of the potential source contaminants to complete an evaluation of geochemical fingerprinting of the suspect hydrocarbons. The nature and extent of contamination was evaluated on the basis of analytical results for surface and groundwater samples collected in the vicinity of the release. Interpretation of the results included consideration of compositional weathering effects where a hydrocarbon product changes in composition due to environmental factors such as evaporation (volatilization), dissolution, and biodegradation. The contaminant data coupled with the hydrogeologic information generated for the study provided the information required to formulate a conceptual hydrogeologic model for the site, identify the likely contaminant source, and project contaminant migration behavior. WWL presented the results of the investigation to the Colorado Oil and Gas Conservation Commission (GOGCC), Colorado Department of Public Health and Environment (CDPHE), and the U.S. Environmental Protection Agency (EPA). The investigation contributed to a formal acknowledgment by the COGCC that the source contamination was not related to the client’s facilities.