Volatile organic chemicals (VOCs) are used to make the solvents, cleaners, and degreasers which are found in many industrial and household products. Testing shows that a small percentage of Wisconsin wells are contaminated with VOCs. It can take years for spilled VOCs to show up in a well. The actions we take, or fail to take during the next few decades will directly affect the quality of our drinking water for generations to come.
For a free brochure containing the information on this page, contact the nearest DNR office and request publication number WS-009.
VOC's are a group of commonly used chemicals that evaporate, or volatilize, when exposed to air. Since they dissolve many other substances, VOC's are widely used as cleaning and liquefying agents in fuels, degreasers, solvents, polishes, cosmetics,drugs, and dry cleaning solutions.
VOC's are found at airports and service stations; machine, print and paint shops; electronics and chemical plants; dry cleaning establishments; and in household products.
Some common VOC's are trichloroethylene (TCE),tetrachloroethylene (also called "perchlorethylene," which is dry cleaning fluid), trichloroethane, benzene, toluene, and xylenes.
When VOC's are spilled or dumped, a portion will evaporate, but some usually soaks into the ground. In soil, the VOC's can be carried deeper with percolating rainwater or melting snow. If they reach the water table, they can persist for years because the cool, dark, low-bacteria environment does not promote decomposition. If the VOC's in the groundwater migrate to nearby wells, they can end up in someone's drinking water.
The Department of Natural Resources has been conducting a great deal of VOC testing since 1982. All community wells and surface water sources have now been tested for a wide range of VOC's, as have approximately 1,500 noncommunity public andprivate wells.
Of the 2,230 community wells sampled in Wisconsin, 113 (5.1%) have shown the presence of at least one VOC. Some of these are bare traces, one or two parts per billion. But 28 community wells exceed state health advisory Levels for drinking water. Health advisory levels set limits on water contaminants for which there are no state drinking water standards.
Of the 1,500 private and noncommunity public wells which have been tested, 355 show the presence of at least one VOC. This detection rate should, not be misinterpreted, however. Many of the private wells were selected for sampling because they were especially vulnerable to contamination, were near other contaminated wells, or were delivering water with strange tastes or odors.
Several factors increase a well's vulnerability to VOC contamination.
One factor is the distance between the well and the source or sources of contamination. Many of the VOC-contaminated wells are located near industrial or commercial areas, gas stations, landfills, or railroad tracks.
A second factor is the amount of VOC which has been dumped or spilled. Often VOC contamination is caused by local spills or dumping and is confined to a rather small geographical area (although there may often be more than one suspected source of VOC's in the area). When a large quantity of contaminant is released, as sometimes occurs with industrial spills or leakingunderground storage tanks, a larger geographical area can be affected.
A third factor is the depth of the well casing. Since contaminants are seeping from the ground surface, a shallow well will be affected sooner than a deep well.
A fourth factor is the local geology. Areas with highly porous or "thin" soils and shallow depths to groundwater are most vulnerable. On the other hand, areas with thick layers of certain types of soil can absorb and significantly slow down the movement of some contaminants. This is particularly important because many organic chemicals can be broken down by soil bacteria if they are held near the ground surface long enough for the bacteria to work.
A fifth factor is time. Groundwater typically moves very slowly, and it can sometimes take year for a spilled contaminant to reach nearby wells. The time and distance contaminants must travel are extremely important because many wells which presently show no contamination may eventually become contaminated by spills which have already occurred. In other words, we won't know the full impacts of the contamination we have already caused for many years to come. This is why we cannot be complacent, and must continue to test our water supplies.
Because of their widespread use, VOC's are often also found in food and air. The VOC's which are components of gasoline are quite commonly detected in city air. When products containing VOC's are used indoors without adequate ventilation, concentrations can become quite high.
As a group, VOC's are not among the most toxic environmental pollutants. The most common VOC's have been in widespread use for many years. Health researchers have a considerable amount of health effects information about these compounds from both animal studies and high-dose human occupational exposures.
Health Advisory Levels are based on a "no-effect level." The no-effect level is the maximum VOC dose that does not produce a toxic effect in experiments. This no-effect level is further reduced by a safety factor which ranges from one tenth to one thousandth (depending upon the strength of the scientific evidence). From this number a health advisory level is then established.
Some VOC's are known or suspected carcinogens (cancer causers). Current scientific theory on how cancer starts indicates that even a small level of exposure to a carcinogen may cause an equally small level of risk to some people. State health advisory levels for carcinogens in drinking water are conservatively set so that lifetime consumption of the water will cause no more than 1 to 10 additional cancers for every million persons exposed. This level of risk is comparable to being killed by a lightening strike or tornado.
The preferable methods for reducing VOC's include reconstructing the wells in deeper, uncontaminated water-bearing layers, or drilling new wells in an uncontaminated area. The advantage of finding a new source of uncontaminated groundwater is that it eliminates the maintenance and water testing which is necessary with treatment facilities. These options may not be possible if the existing well cannot be reconstructed or uncontaminated groundwater is not available in the area.
As a second option for reducing VOC's, communities can treat the water using special aeration methods or filtration through activated carbon. These methods effectively remove many VOC's, but equipment costs and operation and maintenance costs can be sizable. Water quality must also be periodically monitored to assure that treatment continues to work. One additional benefitof treating water is that some chemicals are removed from the groundwater by pumping large community wells.
Corrective measures for private water supplies vary, but the preferred solution is to obtain a new uncontaminated water supply. Owners whose wells contain VOC's above health advisory levels can get advice from the DNR on both temporary and long range options for reducing VOC's.
For some VOC's, temporary arrangements may include:
Home water treatment units require approval from the Department of Industry, Labor and HumanRelations (for the make and model), and approval from DNR for the specific installation. Well owners should be wary of high pressure sales claims for some treatment systems.
Regional DNR specialists will help contaminated well owners with the preferable option of acquiring an uncontaminated water supply by reconstructing the existing well, constructing a new well, or connecting to a nearby community water system.
State Well Compensation Grants. Under this program, owners of contaminated, private, residential wells may be eligible for a State Well Compensation grant. These grants will pay up to 80% of costs for testing, obtaining temporary alternate water, constructing a new well or reconstructing your well, or treating water. Eligibility guidelines and applications are available from DNR Regional offices.
Monitoring In addition to working with the owners of VOC contaminated wells, the DNR will continue to periodically monitor all community wells and selected "high risk" private wells for VOC's. Water utilities are asked to inform consumers when VOC's are detected in a well, and the DNR has issued periodic press releases summarizing all VOC detections.
Wisconsin Act 410, which became effective in May, 1984, established Groundwater Protection Standards. It also authorizedstill more stringent preventive action limits, which serve as both a trigger for remedial actions and a goal when designing state-regulated facilities, such as wastewater treatment plants and landfills.
Wisconsin Act 410 also established a new Environmental Repair Fund, which set up state sponsored environmental cleanupactivities. (For more information on Wisconsin Act 410, write for: "Groundwater Reports on WI Act 410," Wisconsin Department of Natural Resources, Bureau of Water Resources Management, P.O. Box 7921, Madison, Wisconsin 53707.)
The most important actions you can take are those which will prevent future contamination. It is important to understand that pouring dirty or spent solvents or paint thinners onto the ground does not really get rid of them - they may be heading straight for your drinking water.
Underground fuel tanks, such as those used by service stations, don't last forever. They must be regularly checked for leaks and removed when their useful life span is over.
Flushing solvents like paint thinners and cleaning fluid into a septic system injects them directly into the ground.
Commercial or industrial spills should be reported immediately, so that rapid measures can be taken to minimize the impacts (the 24-hour emergency hotline is (608) 266(c)3232; collect calls accepted. For more information about Volatile Organic Chemicals
For further information on VOC's and drinking water, contact your nearest DNR statewide office.
For more information, contact: Margie Damgaard, IS Professional, Public Water Section
The Official Internet site for the Wisconsin Department of Natural Resources