Idaho Wellhead Sampling Program Nitrate Sampling WASHINGTON COUNTY APRIL 1995

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 member relation representative for district 4, in conjunction with the Washington County Farm Bureau, collected 89 private wellhead samples from farmers and rural residents on April 5, 1995.

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) 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 Division of Environmental Quality (DEQ) designed the quality assurance plan for the field effort, the questionnaire, and sampling procedures for the public. The United States Geological Survey (USGS) and the Natural Resource Conservation Service (NRCS) assisted with the collection of samples for quality assurance.

Why Conduct This Program in Washington County?
Groundwater monitoring surveys across the U.S. have shown that agrichemicals such as nitrogen fertilizers are contaminating many sources of groundwater. Surveys in Idaho show that nitrates are being found in several major aquifers. Over 90 percent of the rural residents of Washington 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 Washington County encouraged this wellhead sampling program for nitrates because:

• Observations that some wellheads are not constructed properly--causing a danger of contaminants being directly transferred into the groundwater.
• Shallow 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 of surrounding counties with similar topographic characteristics.
• Intensive animal operations exist over shallow groundwater.

The Sampling

Date: April 5, 1995
	Samples collected:
Rural residents	89
Blind/controls	40
Total	129

Sampling Results
Thirty percent of the sampled wells in Washington County contained nitrate-N levels greater than 10 ppm, which is the U.S. Public Health Service drinking water standard. Thirty percent of the sampled wells contained less than 2.0 ppm nitrate-N.

Compared to the EPA's National Survey for Nitrates conducted in 1988, a higher percentage of wells in Washington 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 30 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:

• 30 percent of sampled wells do contain excessive levels of nitrate based on U.S. Public Health Service drinking water standards.
• 30 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 fact that 70 percent of the wells sampled in this study exceeded 2.0 ppm NO₃-N suggests that nitrate contamination of groundwater in Washington County is a serious problem that warrants the immediate implementation of BMPs to prevent further deterioration of water quality. Best management practices (BMPs) are management strategies that can be used by growers and/or well owners to reduce or eliminate further introductions of nitrate into groundwater.

The wells containing less than 2.0 ppm NO₃-N are in very good shape. There is no reason to believe that man-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.

The 40 percent of sampled wells that contained between 2 and 10 ppm NO₃-N should be checked again in 2 to 3 years. Although these wells meet federal nitrate drinking water standards, it is probable that human activity has introduced nitrate into water in the vicinity of these wells since detected NO₃-N levels are greater than normal, natural nitrate values in aquifers. Nitrogen fertilizer is the likely source of the elevated nitrogen levels in the groundwater; however, animal wastes, septic systems, and plant residues may also be responsible for the elevated nitrate-N values. Changes in the management of nitrogen fertilization may be warranted in certain situations.

Even though this data suggested that nitrate levels in groundwater are higher in Washington County than in other areas of the Treasure Valley (Ada, Canyon, Gem, Owyhee, and Payette counties), farming practices in Washington county may not be that different than in the rest of the region. Rather, groundwater in Washington County happens to be more vulnerable due to shallower water tables and sandier textured soils.

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. Forty 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-32, was prepared by R. L. Mahler, T. D. Stieber, and K. A. Loeffelman, Soil Science Division, University of Idaho, Moscow, Idaho 83844. Stieber is a water quality extension agent located at Payette, ID.
1,000, 5-95

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