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Perchlorate Risk Overstated?
<br />In January, the Los Angeles Times reported
<br />a National Research Council panel finding
<br />that perchlorate does not appear to be as
<br />much of a health risk as originally thought.
<br />While the panel did not recommend a
<br />specific drinking water limit, said the
<br />Times, it did issue a reference dose in
<br />milligrams per kilogram of body weight
<br />that translates to about 20 times the
<br />preliminary dose proposed two years ago
<br />by U.S. Environmental Protection Agency
<br />of 1 part per billion in drinking water.
<br />The National Resources Defense Council
<br />disclaimed the findings and accused the
<br />panel of being influenced by the Pentagon
<br />and the Defense Department, according to
<br />the newspaper. Undoubtedly, the debate
<br />will continue.
<br />NRC's report is scheduled to be available soot at
<br />national - academies.org. NRDC's response is at
<br />www nrdc. orgl medialpressreleasesl050110.asp.
<br />Minimal Perchlorate
<br />in AZ Waters
<br />Last year, the Arizona Department
<br />of Environmental Quality, Arizona
<br />Department of Health Services (ADHS),
<br />Arizona Department of Water Resources,
<br />and Arizona Department of Agriculture
<br />jointly evaluated the extent and impact of
<br />perchlorate contamination in water sources
<br />in Arizona, including the Colorado River.
<br />Perchlorate is currently considered by the
<br />EPA to be an unregulated contaminant,
<br />but ADHS has established an Arizona
<br />Health Based Guidance Level of 14
<br />parts per billion (ppb) as the maximum
<br />concentration of perchlorate in drinking
<br />water that can be consumed without
<br />resulting in adverse health effects.
<br />Most perchlorate in the Colorado River
<br />migrated into Las Vegas Wash, Lake Mead
<br />and, ultimately, the Colorado River from
<br />manufacturing operations near Henderson,
<br />Nevada. Active remediation at the source
<br />has reduced the contaminant load to the
<br />Las Vegas Wash to less than 200 lbs /day.
<br />More than 100 water samples were
<br />36 • March /April 2005 • Southwest Hydrology
<br />collected and analyzed, together with
<br />existing perchlorate data, to determine
<br />the impact of perchlorate on Arizona's
<br />water resources. Sampling locations
<br />included surface waters, groundwater,
<br />agriculture irrigation water, groundwater
<br />recharge facilities, wastewater treatment
<br />plant effluent, and manmade water
<br />impoundments. The results, presented in
<br />the task force's December 2004 report,
<br />show most perchlorate concentrations
<br />ranging from non - detection to
<br />7.4 ppb, with the maximum of 15 ppb in a
<br />groundwater monitoring well in Yuma.
<br />The 79 -page perchlorate report is available at www.
<br />azdeq.govl function laboutldownloadlperch1201.pdf.
<br />$10M for Water Innovation
<br />Projects Awarded in NM
<br />In November, New Mexico Gov. Bill
<br />Richardson announced funding of
<br />25 projects chosen to lead the way in
<br />providing innovative solutions to New
<br />Mexico's water crisis. Once in place, the
<br />pilot projects under the Governor's Water
<br />Innovation Fund could save the state
<br />an estimated 32 billion gallons of water
<br />per year.
<br />The fund awarded a total of $10 million
<br />to projects in four categories: water
<br />recycling, water production, water
<br />conservation, and communities in crisis.
<br />Awards were made to public and private
<br />entities and nonprofit agencies. Funded
<br />projects were judged to be based on good
<br />science and economics, were deemed
<br />ready for testing and deployment, and are
<br />expected to produce results by 2006.
<br />Projects were chosen for their ability
<br />to conserve or deliver useable water
<br />through innovative technologies that
<br />can eventually be applied statewide.
<br />The Finance Council and Department of
<br />Financial Administration will oversee
<br />capital efforts of the Water Innovation
<br />Fund, while drawing on technical expertise
<br />from the State Engineer's office, the New
<br />Mexico Environment Department, the
<br />New Mexico Finance Authority, and the
<br />State Agriculture Department.
<br />Awards ranged from $65,000 for a water
<br />conservation demonstration project to
<br />nearly $750,000 for an aquifer recharge
<br />pilot study. Other funded projects include
<br />automated leak detection systems,
<br />laundry water recycling, solar distillation,
<br />reclamation of produced water, and soil
<br />moisture monitoring systems.
<br />Visit www.governorstate.nm.usl2004 /news/
<br />nov1113004_l.pdf.
<br />Study Urges Caution in
<br />Contaminant Source Tracking
<br />From the U.S. Geological Survey
<br />When a community finds that drinking
<br />or recreational water contains E. coli,
<br />residents and officials naturally want to
<br />find the cause and fix it —quickly. But
<br />several testing methods using E. coli to
<br />identify the sources of fecal contamination
<br />are less accurate in field application than
<br />previously reported, according to a recent
<br />U.S. Geological Survey (USGS) report
<br />published in Environmental Science
<br />and Technology.
<br />The USGS -led study was among the first
<br />to test the accuracy of microbial source
<br />tracking methods against samples of
<br />known origin, called "challenge isolates."
<br />Scientists compared the accuracy of
<br />several source - tracking tools in classifying
<br />E. coli strains to various sources (humans,
<br />dogs, geese, deer, horses, pigs, cows,
<br />and chickens).
<br />When researchers sent E. coli challenge
<br />isolates (the sources of which were
<br />unknown to those conducting the tests)
<br />for testing, many isolates either remained
<br />unclassified or were classified to incorrect
<br />sources. In all, fewer than 30 percent
<br />of challenge isolates were classified to
<br />the correct source - animal species by
<br />any method.
<br />Within the last five years, state
<br />governments have begun using microbial
<br />source tracking methods with E. coli
<br />bacteria to help manage bacteria loads to
<br />streams. Various commercial firms offer
<br />source tracking services to clients around
<br />
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