Remediation methods for white phosphorus contamination in a coastal salt marsh

With the closure of many military bases worldwide and a closer scrutiny of practices on remaining bases, the environmental impact of the military is n ow an important consideration in the operation of bases. Many previously-un known environmental problems related to chemicals are surfacing. White phos phorus, a chemical commonly used as an obscurant, is a chemical previously thought to be innocuous after use. In 1990, however, it was linked to the d eaths of thousands of waterfowl at the Eagle River Flats impact area on Ft Richardson near Anchorage, Alaska, USA, and shortly after, a series of reme dial investigations was initiated. This paper describes three of the remedi al methods currently under investigation, namely enhanced in-situ remediati on, pond draining through ditching or pumping, and dredging. These three ap proaches are best applied in different environments, but they can be used t ogether or in conjunction with other strategies. Their impacts on the envir onment will vary as well. Experience with these remediation strategies has proven very useful in dete rmining the direction that the clean-up effort at Eagle River Flats (ERF) s hould take. Dredging, an effective means of removing contaminated sediments for off-site remediation, has been shown to be too slow and expensive at t he ERF because unexploded ordnance is present. Enhanced natural remediation is effective under favourable climatological conditions in areas that expe rience intermittent flooding, but desaturation of the sediments is critical to its effectiveness. Pond draining by blasting a ditch effectively remove s waterfowl feeding habitat, but attenuation of the contaminant is inhibite d because the ditch increases flooding frequency, and the habitat alteratio n is permanent. Pond pumping, where feasible, has shown great potential for the desaturating of wide areas of ERF, enabling the natural attenuation me chanism to progress. Further investigation will be necessary to confirm the se initial conclusions and determine the overall effectiveness of all three methodologies. Methods developed over the course of this work may be appli ed to other remediation projects where in-situ volatilization can occur and limited disturbance of wetlands is critical.