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Scientific Investigations Report 2013–5215

Prepared in cooperation with the Eugene Water & Electric Board

Time-Integrated Passive Sampling as a Complement to Conventional Point-in-Time Sampling for Investigating Drinking-Water Quality, McKenzie River Basin, Oregon, 2007 and 2010–11

By Kathleen A. McCarthy and David A. Alvarez


The Eugene Water & Electric Board (EWEB) supplies drinking water to approximately 200,000 people in Eugene, Oregon. The sole source of this water is the McKenzie River, which has consistently excellent water quality relative to established drinking-water standards. To ensure that this quality is maintained as land use in the source basin changes and water demands increase, EWEB has developed a proactive management strategy that includes a combination of conventional point-in-time discrete water sampling and time‑integrated passive sampling with a combination of chemical analyses and bioassays to explore water quality and identify where vulnerabilities may lie.

In this report, we present the results from six passive‑sampling deployments at six sites in the basin, including the intake and outflow from the EWEB drinking‑water treatment plant (DWTP). This is the first known use of passive samplers to investigate both the source and finished water of a municipal DWTP. Results indicate that low concentrations of several polycyclic aromatic hydrocarbons and organohalogen compounds are consistently present in source waters, and that many of these compounds are also present in finished drinking water. The nature and patterns of compounds detected suggest that land-surface runoff and atmospheric deposition act as ongoing sources of polycyclic aromatic hydrocarbons, some currently used pesticides, and several legacy organochlorine pesticides. Comparison of results from point-in-time and time-integrated sampling indicate that these two methods are complementary and, when used together, provide a clearer understanding of contaminant sources than either method alone.

First posted March 24, 2014

For additional information, contact:
Director, Oregon Water Science Center
U.S. Geological Survey
2130 SW 5th Avenue
Portland, Oregon 97201

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Suggested citation:

McCarthy, K.A., and Alvarez, D.A., 2014, Time-integrated passive sampling as a complement to conventional point-in-time sampling for investigating drinking-water quality, McKenzie River Basin, Oregon, 2007 and 2010–11: U.S. Geological Survey Scientific Investigations Report 2013–5215, 14 p.,

ISSN -2328-0328 (online)




Study Area

Sampling Strategy

Study Methods



Summary and Conclusions


References Cited

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