Automated Monitoring for the Cape Cod Toxic Substances Hydrology Research Site Cessation Experiment.

by Denis R. LeBlanc, Chief Research Scientist

A plume of sewage-contaminated groundwater was formed in the shallow, Cape Cod sand and gravel aquifer by more than 60 years of land disposal of treated sewage at the Massachusetts Military Reservation.

In December 1995, after the disposal site was moved to another location, the U.S. Geological Survey began collecting groundwater samples to observe the natural cleanup of the aquifer. Because it was not known in advance how rapidly geochemical microbiological changes would occur, frequent collection and analysis of water samples from a network of observation wells and multilevel samplers was required. A prototype automated device to collect water samples and measure field parameters, such as specific conductance, dissolved oxygen, and pH, was installed to determine the water-quality characteristics at three sampling points at a frequent sampling interval. Three months of data from this device showed that the changes were gradual and could be characterized by fewer sampling rounds than had been originally planned. The scaled-back sampling resulted in significant savings of money and time with no loss of information about the natural restoration process. See Hess and others (1996) for more information on the source cessation study. Hess, K.M., LeBlanc, D.R., Kent, D.B., and Smith, R.L., 1996, Natural restoration of a sewage-contaminated aquifer, Cape Cod, Massachusetts, in Hydrology and Hydrogeology of Urban and Urbanizing Areas--Proceedings of the conference, Boston, Mass., April 21-24, 1996: Minneapolis, Minnesota, American Institute of Hydrology, p. WQE13-WQE25.
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