A 2000-2005 U.S. Geological Survey (USGS) study found a variety of pesticides in water samples from the lower Clackamas River mainstem and tributaries, along with trace-level detections of pesticides in treated drinking-water samples collected from a drinking-water treatment plant that uses the river as a raw-water source, according to a recently released USGS report. All of the detections in drinking water were, however, far below existing USEPA drinking-water standards and other human health benchmarks.
The Clackamas River Water Providers, a coalition of municipal drinking water providers, and the Clackamas County Department of Water Environment Services cooperated with the USGS in the study. The USGS also is working closely with Clackamas County Soil and Water Conservation District and state agencies that include the Departments of Environmental Quality, Human Services, Agriculture, and Forestry on this issue.
A total of 63 pesticide compounds were detected in 119 water samples collected during storm and nonstorm conditions using low-level detection methods. More pesticides were detected in the tributaries than in the Clackamas River mainstem, and the fewest were detected in treated drinking water. One or more of 15 pesticides were detected in nine of 15 samples of drinking water. Most of the compounds analyzed for, however, were not detected-98 percent of the 1,790 individual pesticide analyses of finished drinking water were below laboratory method detection levels.
Pesticides were detected in all eight of the lower-basin tributaries after heavy rainfall, with the largest pesticide contributions coming from Deep and Rock Creeks. The herbicides atrazine and simazine were the most common, detected in half of the samples. High-use herbicides such as glyphosate and triclopyr/2,4-D-the active ingredients in RoundUP™ and Crossbow™, respectively-also were frequently detected.
Concentrations of four insecticides-diazinon, chlorpyrifos, azinphos-methyl, and p,p'-DDE-exceeded USEPA aquatic-life benchmarks during storms in seven streams, and concentrations of several other pesticides exceeded other, non-USEPA benchmarks, including chlorpyrifos in the Clackamas River mainstem. Nearly one-quarter of the tributary samples had at least one pesticide that exceeded an aquatic-life benchmark. Further, "Benchmarks have not been established for many of the pesticides detected, and current regulations do not yet account for multiple compounds that often occur in a single sample," noted Kurt Carpenter, USGS Hydrologist and lead scientist for the study.
Pesticide sources in the Clackamas River basin are difficult to identify because of the diverse land use in the basin and the multiple-use nature of most of the pesticides detected. According to Carpenter, more than 90 percent of the 51 current-use pesticides can be used on nursery or other agricultural crops; about one-half are commonly used on lawns and landscaping in urban areas, on golf courses, or along roads and right-of-ways; and some can be used on forestland. "Because pesticide-use data currently are reported only for the Willamette River basin as a whole, not for individual subbasins, watershed managers could benefit from more detailed reports of which pesticides are being used and where," Carpenter observed.
Kim Swan, Manager of the Clackamas River Water Providers, noted that "Although the current levels of pesticides in our drinking water are well below dangerous thresholds, their presence is a warning sign. Studies such as this provide us with the tools to identify where problems are and give us the opportunity to work with other stakeholders in the watershed to prevent pesticides from getting into the river to begin with."
Andrew Swanson, Water Quality Analyst with Clackamas County Water Environment Services Department (WES) stated that "Even though pesticides were typically detected at low levels during this study, the data collected will prove valuable in increasing public awareness of this important issue. WES is concerned about the numerous pesticides, regardless of the detected level, in water flowing from and through North Clackamas County's urban area. As a result, WES is working in a cooperative manner with other watershed partners to develop and implement a public awareness and educational campaign regarding pesticides. We appreciate the USGS' efforts in bringing this subject to the forefront of the environmental challenges we're all facing today in the Clackamas River watershed."
Results of the lower Clackamas River pesticide study are available in USGS Scientific Investigations Report 2008-5027, "Pesticide Occurrence and Distribution in the Lower Clackamas River Basin, Oregon, 2000-2005." For more questions regarding your drinking water please contact Kim Swan at (503) 723-3510.
USGS provides science for a changing world. For more information, visit www.usgs.gov.
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