GROUNDWATER QUALITY PLAN
The first regular session of the Idaho Centennial Legislature (1989) passed an act to create a Groundwater Quality Council composed of 17 voting members and 5 non-voting representatives of the University of Idaho College of Mines, Idaho Water Resources Research Institute (IWRRI), the U.S. Environmental Protection Agency (EPA), the Idaho National Engineering Laboratory (INEL), and the United States Geological Survey (USGS). This body was charged with the development of a groundwater quality plan for Idaho. The document developed by the Groundwater Quality Council was passed in the waning days of the 1992 session of the Idaho Legislature.
The legislature mandated that the plan do the following:
This new plan includes an Agricultural Chemical and Nutrient Management policy which provides for the application of agricultural chemicals or nutrients to crops so that they will not impair beneficial water uses below the crop root zone. This policy emphasizes the need for agrichemical management so that retention is maximized within the crop root zone. Under the new policy, agrichemicals and nutrients (primarily nitrates) found in intermittently saturated soils within the crop root zone will not be considered groundwater contaminants. The document states that proper management of these chemicals is also necessary to prevent contamination of the underlying groundwater and to assure the continued availability of nutrients and registered chemicals which are needed to benefit agricultural production.
Implementation of voluntary best management practices (BMPs) is expected to be the emphasis for protecting groundwater beneath crop root zones. If voluntary BMPs are determined to be inadequate, a mandatory approach may be needed. The basic criteria for determining the need for BMPs is shown in Fig. A:
An agrichemical is evaluated as a potential groundwater contaminant. If the potential for contamination is low an emphasis will be placed on an effective information and education program for the application and use of the specified agrichemical. If the contamination potential is high it will be determined if a BMP is appropriate for its application and use.
If a BMP is not appropriate, application and use will be regulated. If a BMP is deemed appropriate however, the BMP will be developed, implemented, and assessed (see Figs. A and B). The BMP is voluntary at this stage. The agricultural feedback loop (see Fig. B) allows the development, implementation, evaluation, and improvement of BMPs. Based on the potential for a contaminant and suspected cause, a specific time period will be set to determine effectiveness of BMPs in maintaining and improving groundwater quality. If groundwater deteriorates, or if impaired groundwater does not improve, then mandatory participation in applying voluntary BMPs will be required. If after mandatory participation the groundwater quality trend is still not improving, BMPs with more stringent protection must be applied. If after this, there is still no improvement in the groundwater quality trend, regulatory programs will be required.
In summary the Agricultural Chemical and Nutrient Management policy of the state's groudwater plan will emphasize voluntary BMPs and public education. Remember that this document as passed by the legislature is a planning document for directing groundwater quality protection -- not a set of laws.
FROM THE EDITOR
Commercial fertilizers and pesticides are two of the most important technological developments of the twentieth century. During the past 30 years, however, concern has arisen about the threats they may pose to mankind and the environment. Both farmers and the general public desire careful management of nutrients in order to avoid contamination of our surface and groundwaters.
Over 300 people received training in nutrient management at a series of statewide workshops conducted at Lewiston, Nampa, Twin Falls, Pocatello, and Idaho Falls in February. These workshops were co-sponsored by the University of Idaho Cooperative Extension System (UI-CES), the Idaho Soil Conservation Commission (ISCC), the Soil Conservation Service (SCS), the Idaho Division of Environmental Quality (IDEQ), and the U.S. Environmental Protection Agency. In addition to program sponsors, speakers from the Idaho Department of Agriculture and the fertilizer industry were included on the program. Program topics at these workshops included: (1) agrichemicals and water quality in Idaho; (2) agrichemical processes in soil and water; (3) nutrient management using manures and crop rotations; (4) BMPs for nutrient management; (5) regulation -- what does the future hold?; and (6) current agrichemical programs in Idaho. A 168 page workbook was given to all attendees. Additional copies of this workbook can be obtained for $6.00 from R. L. Mahler, Soil Science Division, University of Idaho, Moscow, ID 83844.
This Nutrient Management Workshop was a success because it was an interagency effort and it provided relevant information to targeted user groups.
YOU CAN PROTECT WATER
House and garden chemicals have simplified domestic chores, but they can be dangerous. Be responsible with these products so they don't damage the environment or turn up in our water or foods. Some simple rules of thumb are provided below to protect groundwater.
IFB WELLHEAD SURVEY -- BONNEVILLE
On March 18, 1992, Bonneville County became the 12th county in Idaho to take part in the wellhead survey program coordinated by the Idaho Farm Bureau (IFB). Although this program was coordinated by the IFB it was truly a cooperative effort as five different government agencies and the Idaho Farm Bureau Federation united to make the program a success. The Idaho Department of Agriculture (IDA), Soil Conservation Service (SCS), 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) also participated in this study.
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. Nitrates were determined on water samples by the UI-LAB 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.
In Bonneville County 49 private wellhead samples were collected from farmers and rural residents. None of the sampled wells in Bonneville County contained nitrate-N levels greater than 10 ppm, which is the National Public Health Service drinking water standard. Over 59 percent of the sampled wells contained less than 2.0 ppm nitrate-N.
A total of 1,599 samples from private wells and 1,093 control and quality assurance samples have now been collected from 12 Idaho counties. Over the next 12 months this program will be brought to several more counties. CES has and will continue to prepare county by county brochures that provide the data from each sampling event as they occur. Brochures can be obtained directly from the individual county extension offices.
GROUNDWATER: USES AND POTENTIAL
Idaho ranks among the top five states for volume of groundwater used. In 1985, more than 4.3 billion gallons were withdrawn from Idaho's aquifers daily, representing 22 percent of total water use in the state (the other 78 percent came from surface water). The principal use is for irrigation of more than 1.3 million acres of cropland, primarily in southern Idaho. More than 90 percent of Idaho's groundwater withdrawals are for agriculture, although this represents only 20 percent of all the water used for agriculture in the state.
Other sectors are even more dependent on groundwater, For example, more than 87 percent of Idaho's domestic and commercial water suppplies come from groundwater, including 95 percent of drinking water. In industry and mining 52.4 percent of water comes from groundwater.
Groundwater contamination can occur directly, by injection of contaminants into the groundwater through wells, or indirectly, when the ability of the soil to immobilize or break down contaminants is exceeded. Under the latter condition, contaminants applied at the land's surface move downward and may eventually reach the aquifer.
For example, some wells in Idaho contain excessive levels of nitrates that may come from agricultural fertilizers, septic tanks and/or livestock feeding operations. A recent well survey conducted by the Idaho Farm Bureau in Cassia, Minidoka, and Jerome counties showed that about 4 percent of wells sampled failed to meet the federal drinking water standard for nitrates.
In 1985 the Idaho Department of Water Resources and Idaho Department of Health and Welfare ranked potential sources of groundwater contamination in Idaho (see list below). The ranking was based on two factors. The first was the adequacy of present regulatory programs for land use practices that could be sources of contamination. The second was the relative risk to public health or the environment posed by the potential contamination sources. Petroleum handling and storage was ranked first as posing the greatest risk to groundwater quality in Idaho.
The priority of potential sources of groundwater contamination in Idaho, based on rankings by the Idaho Department of Health and Welfare and the Idaho Department of Water Resources, is as follows:
Idaho's principal aquifers have been evaluated for potential contamination based on population density (as a measure of land use) and intensity of groundwater use. The most vulnerable major aquifers in Idaho are the Boise Valley, Eastern Snake Plain, and Rathdrum Prairie aquifers.
LEAD IN DRINKING
People are constantly exposed to lead from a variety of sources. However, the elevated levels of lead recently found in some drinking water sources in the U.S. is a new public concern. Lead affects human health by reacting with enzymes within the body to slow or stop essential physiological reactions. Exposure to even low levels of lead over an extended period of time can have severe effects, since lead is accumulated and stored in bone. When bone storage is saturated, blood lead levels begin to affect nerve tissue.
Humans are exposed to lead from the air we breathe, the food we eat, and the water we drink. Lead in the atmosphere largely results from automobile and industrial emissions. This atmospheric lead falls back to earth in the form of rain, which affects soil, plants, and water.
Daily intake of lead from various sources are difficult to estimate. Differences in eating habits, location, and water consumption, in addition to the size and age of the individual, need to be considered. The daily quantity of lead absorbed from the air by adults ranges from 6 to 24 micrograms (one-millionth of a gram). The estimated adult daily absorption of lead from food is 10 to 30 micrograms.
Drinking water presents a third source of lead exposure to people. The estimated mean daily absorption of lead from drinking water is 3 to 10 micrograms. The additive exposure from food, air, and water can result in lead absorption surpassing the 50 to 60 micrograms/day limit. This is considered the limit for no observable health effects.
The total lead intake limit of 50 to 60 micrograms of lead/day applies to adults. Children absorb 40 to 50 percent of ingested lead as opposed to only 5 to 10 percent absorption by adults. Contaminated water is also a greater risk to children because of their smaller size and immature nervous system.
The current lead standard for drinking water is 0.05 ppm (50 micrograms/liter). The EPA may reduce this to 0.02 ppm. The natural lead content of surface water is about 0.023 ppm and groundwater has a lead content of approximately 0.01 ppm. The pH of the water between these two sources affects how easily lead dissolves into the system. Municipal supplies of soft, acidic water can dissolve lead from pipes or solder of household water systems.
The initial determination of lead in drinking water begins with the local water supplier who can inform you if the drinking water is soft or acidic, conditions which enhance leaching of lead from pipes. A plumbing inspector can determine if lead has been used in a home. Because lead is soft, it can be easily scraped from a pipe or joint. Water samples can be analyzed for lead content at certified labs. The sample should be taken from the tap after water has been in the pipes for several hours or overnight to evaluate the highest level of lead exposure. A second sample, taken after the water has flowed for 3 to 5 minutes, will determine if flushing the water lines decreases the lead content substantially.
If lead in the drinking water exceeds the 0.05 ppm standard, the potential risk from lead solder or pipes must be reduced. Leaching of lead depends upon the water temperature and its corrosive power as well as its time in contact with the lead source.
Highest concentrations of lead occur in new plumbing installations. Shallow water sources tend to be more corrosive (lower pH) than deep wells. Water consumption should not be the first daily use of water because of the higher lead levels found in water held in pipes overnight. Showering or running the tap for 3 to 5 minutes before drinking or cooking with the water is recommended. Avoid using hot tap water for cooking as lead dissolves more easily and quickly in hot than cold water.
Recommended treatments for removing high or persistent lead levels in water that enter the household are reverse osmosis (RO) or distillation. The RO method forces water through a membrane under pressure. The membrane is designed to reject certain substances and in essence, the contaminant is removed from the water.
Distillation units remove the lead by first boiling the water and then collecting and condensing the steam. This system leaves behind many impurities, and nearly contaminated-free water is produced. Distillation removes approximately 99 percent of the lead from water.
A water treatment salesperson, your local health department, or county Cooperative Extension office has additional information about these treatment methods.
To reduce lead contamination of drinking water, alternative products must be used in the plumbing systems of new homes. Alternative materials to the traditional tin/lead solder are being used. Both tin/antimony or tin/silver solders are considered to be better quality but more expensive, but in a home plumbing system that requires less than 1 pound of solder, the cost of using either substitute material is acceptable.
In summary, lead has no benefit to human health. Rather, high levels of
lead in the blood can contribute to a variety of health problems.
Children are at an increased risk of lead toxicity due to their smaller
size and immature nervous systems. Reducing lead in the environment has
economic as well as health benefits, and elimination of lead in
drinking water has become a national priority. Individuals should
become aware and informed of the problems of high lead levels and take
steps to reduce exposure.
(Adapted from Water Treatment Notes, Cornell Cooperative Extension)
BMPs FOR HANDLING
Over 90 percent of the drinking water consumed in Idaho is supplied by groundwater. This resource is vital to homeowners and industry as well as Idaho's agricultural community. Best management practices (BMPs) for agricultural management have been and are becoming more important.
Groundwater is found in the pores and cracks of underground sand, gravel, and rock deposits. The formation through which it slowly flows is called an aquifer. The top of the water-saturated zone is the water table, and water percolating down to it is called recharge.
Recent surveys by Idaho water quality specialists have found trace amounts of nitrates and, in some cases, pesticides in the drinking water. Nitrates can get into drinking water from many sources, but poor management practices can cause pesticide contamination. Pesticides can get into groundwater through agricultural, industrial, and homeowner uses as well as spills and improper disposal. Contaminated water is difficult and expensive to manage once it becomes dispersed underground.
Careful pesticide application practices will protect the groundwater and help to ensure personal and public safety. Specific types of BMPs for pesticide application that should be used in Idaho include:
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All contents copyright © 1997-2003. College of Agricultural and Life Sciences, University of Idaho. All rights reserved. Revised: January 3, 2003