Idaho Wellhead Sampling Program Nitrate Sampling ONEIDA COUNTY MAY 1998

Water Quality
Water is the lifeblood of Idaho! Idaho ranks second in the United States in water use, only to California. Our traditional industries such as agriculture, forestry, and mining are all water dependent. And a large portion of tourist revenues in Idaho are tied to attractions with water. In addition to the economy, high quality water is essential to Idaho's recreational opportunities and wildlands. We must protect water quality to maintain our high standard of living and uniquely rich quality of life in Idaho.

Over 90 percent of Idahoans rely on groundwater for their drinking water. Surveys in Idaho have generally shown that groundwater quality is not a widespread problem.

The Program
The Idaho Private Wellhead Sampling Program was initiated and coordinated by the Idaho Farm Bureau Federation (IFB). Coordinator Chuck Garner, Idaho Farm Bureau Federation's Program Director, in conjunction with the Oneida County Farm Bureau, collected 43 private wellhead samples from farmers and rural residents on May 5, 1998.

This program was truly a cooperative effort as six different government agencies and the Idaho Farm Bureau Federation, a private membership-oriented organization, united to make the program a success. The Idaho Department of Agriculture (IDA), the Southeast District Health Department (SEHD), and the University of Idaho Cooperative Extension System (UI CES) assisted with program logistics, sample bottle distribution, and dissemination of information. The University of Idaho College of Agriculture's Analytical Laboratory (UI LAB) had major roles in planning and designing the quality assurance phase of the analytical part of the program and analyzed all samples for nitrates. The Idaho Farm Bureau (IFB) designed the quality assurance plan for the field effort, the questionnaire, and sampling procedures for the public based on an original model designed by the Idaho Division of Environmental Quality (DEQ). The Oneida County Soil and Water Conservation District (SWCD) assisted with the collection of samples for quality assurance and provided the initial publicity for the program.

Why Conduct This Program in Oneida County?
Groundwater monitoring surveys across the U.S. have shown that agrichemicals such as nitrogen fertilizers and manures may be contributing nitrates to groundwater. Surveys in Idaho show that nitrates are being found in several major aquifers. Over 90 percent of the rural residents of Oneida County obtain their drinking water from groundwater. In addition to the high reliance of groundwater for drinking water the combination of intensive agriculture using large quantities of agrichemicals and relatively shallow aquifers may put groundwater quality in jeopardy.

Residents of Oneida County encouraged this wellhead sampling program for nitrates because:

• Aquifers are extensively utilized by local residents for drinking water.
• Intensive and extensive N fertilizer use.
• No baseline wellhead data exists to determine trends or to evaluate the need for BMPs.
• Excessive nitrate levels have been observed in wells in several counties in southern Idaho.

The Sampling

Date: May 5, 1998
	Samples collected:
Rural residents	43
Blind/controls	16
Total	59

Sampling Results
None of the sampled wells in Oneida County contained nitrate-N levels greater than 10 ppm, which is the U.S. Public Health Service drinking water standard. Consequently all sampled wells were considered safe for drinking from a nitrate standpoint. Sixty percent of the sampled wells in Oneida County contained less than 2.0 ppm nitrate-N.

Compared to the EPA's National Survey for Nitrates conducted in 1988, a lower percentage of wells in Oneida County exceed the federal health standard for nitrates than the national average. In the EPA survey 2.4 percent of rural domestic wells contained nitrate levels exceeding federal health standards (10 ppm NO₃-N). Another 40 percent of rural domestic wells contained detectable levels of nitrates. On a national level, EPA estimates that about 250,000 rural wells exceed U.S. Public Health Service standards for NO₃-N.

What Do the Sampling Results Mean?
This study shows that:

• Based on U.S. Public Health Service nitrate drinking water standards, 100 percent of the samples are considered safe.
• 60 percent of sampled wells contain less than 2 ppm NO₃-N.
• 40 percent of sampled wells contain between 2 and 10 ppm NO₃-N.

The wells containing less than 2.0 ppm NO₃-N (60 percent of sampled wells) are in excellent shape. There is no reason to believe that human-induced practices are adding nitrates to groundwater in these areas since low levels of nitrates (1 to 2 ppm) may be natural in some aquifers.

People living in Oneida County should be encouraged that not one sampled well exceeded the federal standard for nitrate. However, 40 percent of the wells contained nitrate-N values of 2.0 ppm or more. Although considered safe for drinking, these wells should be checked again for nitrates in 3 to 5 years. Landowners should consider the implementation of best management practices (BMPs) in areas where NO₃-N values exceed 2.0 ppm to prevent deterioration of water quality. BMPs are management strategies that can be used by landowners (rural residents, farmers, ranchers) to reduce further introductions of nitrate into groundwater.

The 40 percent of the sampled wells that contained between 2 and 10 ppm NO₃-N have probably been impacted by human activity. There are several potential sources of nitrates including: (1) nitrogen fertilizer, (2) animal manure, (3) organic matter decomposition, and (4) poorly maintained septic systems. Consequently, it is impossible to determine the specific source of the nitrates in wells. As rural areas in Idaho continue to grow (more homes in rural areas using septic systems) routine maintenance of septic systems will become increasingly important as septic tanks may leak nitrates into groundwater if they fill. To prevent this, septic tanks should be pumped out every 3 years. Survey data indicates that less than 25 percent of the septic systems in Idaho's rural areas are maintained with a 3 year frequency.

This data suggests that nitrate levels in groundwater in Oneida County are similar to levels found in other areas of southeastern Idaho.

Nitrate and Groundwater
Humans ingest nitrate in food and water. In older children and adults, nitrate is ingested, absorbed from the digestive tract, and excreted rapidly in the urine. Healthy human adults can consume fairly large amounts of nitrate with no short-term adverse effects. The health effects of chronic, long-term consumptions of high levels of nitrate are uncertain.

Infants younger than 6 months are believed to be susceptible to nitrate poisoning. Bacteria present in their digestive systems at birth can change nitrate to toxic nitrite (NO₂). Newborn infants have little acid in their digestive tracts, and they depend on these bacteria to help digest food. Generally, by the time infants reach 6 months, hydrochloric acid levels increase in their stomachs and kill most of the bacteria that convert nitrate to nitrite.

Once formed, the nitrite is absorbed and enters the bloodstream. There it reacts with the oxygen-carrying hemoglobin to form a new compound called "methemoglobin." This compound interferes with the blood's ability to carry oxygen. As oxygen levels decrease, babies may show signs of suffocation. This condition is called "methemoglobinemia." The major symptom of methemoglobinemia is bluish skin color, most noticeably around the eyes and mouth.

Infant deaths from methemoglobinemia, sometimes called "blue baby syndrome," are rare. Some documented deaths have been linked to high levels of nitrate in well water. Doctors now recommend using bottled water to make formula when nitrate levels exceed the U.S. Public Health Service drinking water standard of 10 parts per million (ppm) NO₃-N.

Quality Assurance
Quality control in this sampling project was the top priority. Blind spiked samples and blanks were randomly dispersed with farmer-provided samples to assure top quality. In addition, in some cases, duplicate farm wellhead samples were included. Twenty-one quality control samples were part of this study.

Nitrates were determined on water samples by the University of Idaho College of Agriculture's Analytical Laboratory in Moscow. After collection, a preservative was added to the sample before shipment to Moscow. Samples were run in the laboratory within 72 hours after collection. The most modern analytical techniques and equipment were used in this operation. A high degree of confidence should be placed on the numbers obtained from these samples.

The University of Idaho Cooperative Extension System has over 140 faculty strategically located throughout the state, including 84 agricultural educators stationed in 42 of 44 counties. In addition, faculty (specialists) are located on campus in Moscow and at research and extension centers in Aberdeen, Caldwell, Idaho Falls, Kimberly, Parma, Sandpoint, Tetonia, and Twin Falls.

This brochure, WQ-37, was prepared by R. L. Mahler, K. A. Loeffelman, and K. Anderson, Soil Science Division, University of Idaho, Moscow, Idaho 83844. Anderson is the inorganic group leader in the Department of Food Science and Technology.
500, 6-98

Comments to webmistress: karenl@uidaho.edu

All contents copyright © 1997-2003.
College of Agricultural and Life Sciences, University of Idaho.
All rights reserved.

Revised: January 3, 2003

URL: http://www.uidaho.edu/wq/wqbr/wqbr37.html