The Role of Soil Components Such as Charge Characteristics on the Mobility of Contaminants Leached down Gradient of the Ordot Landfill Area In Central Guam

Guam's only municipal solid waste disposal site is located in the village of Ordot in central Guam and has been in use for over fifty years. The site is essentially an open dump covering ~20 acres of the upper Lonfit River valley. Leachate streams occur in several places around the perimeter of the dump and course their way down gradient into the Lonfit River and out into Pago Bay. Their chemical composition is largely unknown and their impact on the local environment remains to be investigated.

As a first step in our investigation from Ordot Dump, surface (runoff) leachate samples were collected to characterize the primary biological and chemical contaminants in leachate water emanating from the Ordot Dump and trace their respective movements down the watershed out into the ocean. The subsurface samples were also collected by lysimeter at 0.7-2.0 meter depths.

A time-series analysis of aqueous and soil samples with emphasis on solute transport through the soil was made in this part of the study. Lysimeters were used to extract interstitial waters from soil inundated by the leachate streams down gradient from the dump, and downstream in the Lonfit-Pago River system. Soil samples from adjacent to lysimeters and water samples from the streams surrounding the dump and the ocean water at the Pago Bay were obtained for these purposes.

Differential mobilization rates of primary contaminants were evaluated by comparing their surface and subsurface distributions and abundances. Finally, their potential impact on the receiving waters will be assessed from an ecological and public health standpoint in future studies. This paper will describe the methodology and the result of the investigation thus far.

Keywords: Soil charges, Contaminants Transport, Leachate, lysimeter, Landfills, Island of Guam