09 Apr, 2008
USGS Study Finds Pesticides in the Lower Clackamas River Mainstem and Tributaries, and in Samples of Drinking Water
Posted by: RSS In: Usgs.gov
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.
