Environmental Health - Toxic Substances Hydrology Program

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Can a Sewage-Contaminated Aquifer Naturally Clean Itself?

The answer may be yes, but it might take much longer then scientists originally guessed. USGS scientists are studying the natural restoration of an aquifer that was contaminated by 60 years of land disposal of treated sewage. Studies at the abandoned sewage-disposal facility at the Massachusetts Military Reservation on Cape Cod have shown that:

  • The natural cleanup in the aquifer on Cape Cod is taking longer than USGS scientists had expected.
  • Although the natural ground-water flow has flushed away some contaminants in the aquifer under the disposal area, continuing biodegradation of organic materials associated with the aquifer sediments is maintaining low oxygen levels and elevated pH.
  • Some contaminants, such as phosphorus and zinc, are expected to remain at elevated levels in the sewage-contaminated zone for many years because of the persistent low oxygen levels and elevated pH.
  • Geochemical models developed for the studies at the site predict that restoration to pre-contamination conditions may take many decades.

The Department of Defense is using the predictions of the long natural-cleanup time to develop plume-management strategies that protect the environment and drinking-water supplies in the Cape Cod sole source aquifer.

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