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  Evaluation of a Former Landfill Site in Fort Collins, Colorado, Using Ground-Based Optical Remote Sensing Technology (EPA/600/R-05/042) April 2005

A former landfill site in Fort Collins, Colorado, was assessed for landfill gas emissions in support of reuse options for the property. Before initiating any additional development at the property, the city requested assistance from EPA in performing a site assessment to search for the presence of any fugitive gas emissions from the site. This assessment was necessary because of the potential adverse health effects associated with exposure to landfill gas.

The focus of this study was to evaluate fugitive emissions of methane and volatile organic compounds at the site in support of the reuse objectives, using a scanning open-path Fourier transform infrared spectrometer, open-path tunable diode laser absorption spectroscopy, and an ultraviolet differential optical absorption spectrometer. The study involved a technique developed through research funded by the EPA. The technique uses ground-based optical remote sensing technology, known as optical remote sensing-radial plume mapping.

The horizontal radial plume mapping method was used to map surface concentrations, and the vertical radial plume mapping (VRPM) method was used to measure emissions fluxes downwind of the site.

The study did not detect the presence of any surface methane hot spots at the site. The highest methane concentrations detected at the site were only slightly above ambient background levels. However, the survey detected the presence of a gasoline hot spot located in the vicinity of a recreational building. Gasoline concentrations averaged over 81 parts per billion [ppb], with a maximum concentration of about 100 ppb.

The VRPM survey of the site detected methane, ammonia, and gasoline along a downwind configuration at the site. The average calculated gasoline flux from the VRPM survey was 0.87 g/s. The measured methane and ammonia concentrations were well correlated, indicating that the measured concentrations probably came from the same source. Wind data indicated that the source of the methane and ammonia was across a river adjacent to the site.


Susan Thorneloe

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