DRAFT Groundwater Management Plan
Section 4 The County's Groundwater Resources
TOC | Sec 1 | Sec 2 | Sec3 | Sec 4 | Sec 5 | Sec 6 | Apx SR | Apx PS | Apx VG | Apx RE | Apx CE | Apx AD | Apx WA |Apx HC | Apx PH
4.0 THE COUNTY’S GROUNDWATER RESOURCES (pdf file--text only)
4.1 INTRODUCTION
The citizens of Portage County are highly dependent on groundwater for drinking, municipal, industrial, agricultural, and other uses. So too are the County’s streams, lakes, wetlands, and aquatic plant and animal communities. Our groundwater is owned by all of us in a public trust. Along with the rights of ownership go the responsibilities for stewardship, and for passing the resource on to future generations. Three critical groundwater challenges have been identified by the Groundwater Citizens Advisory Committee (GCAC) - groundwater quantity, nitrate pollution, and pesticide pollution – as priorities for future action. The GCAC has also suggested goals and some strategies to address these challenges.
Groundwater quantity conflicts arise when pumping lowers the water table so that all users are unable to get sufficient water for their needs, and when pumping diverts water away from streams, lakes, and wetlands. A critical groundwater quantity concern exists in the Little Plover River basin, where groundwater use may be leading to the demise of the stream and its native brook trout fishery. A goal and strategies have been developed to meet this specific concern, and to identify other severely limited groundwater problem areas.
Nitate pollution affects much of Portage County’s groundwater and most of its wells. About 20% of County wells exceed the standard. A variety of human health concerns regarding nitrate exist, as well as concerns about toxicity to aquatic wildlife. Nitrate concentrations in Portage County groundwater have been increasing for about 30 years, and the increase continues. Reducing nitrate pollution will require tackling agricultural sources, which are responsible for perhaps 95% of nitrate pollution.
Pesticide pollution also affects large numbers of County wells. Atrazine is the largest problem, occurring in 40% of wells. About 3% of wells have been estimated to exceed the atrazine health standard, but this is likely an underestimate caused by a faulty interpretation of the analytical method. Other pesticides are also likely present in groundwater. More information is needed on what pesticides are used in the County, and which pesticide residues leach to groundwater. Further, better information is needed on the toxicology data that exist for these compounds and where toxicology data are lacking.
4.2 GROUNDWATER QUANTITY
Groundwater quantity was never given much attention in Portage County, except by a few very knowledgeable individuals. The presence of practically unlimited groundwater, a few feet below the surface in the sand plain, easily accessible to anyone who wanted it, allowed us to take this precious resource for granted. It also allowed the development of the irrigated agricultural industry that is such a large part of Portage County’s economy and culture.
In most areas of the County, sufficient groundwater exists to serve the needs of most citizens. In bedrock wells in the northwestern part of the County, low flows can severely limit available quantities of water. This is especially challenging for municipalities, such as Junction City, and agricultural operators located in this area.
In areas where high volume users, such as municipalities, industries, and irrigated agriculture, all draw significant quantities of groundwater, they affect each other and the natural environment. This has been observed over the past couple of decades in the Little Plover River basin.
Issues to be considered when looking at groundwater quantity concerns are the natural climatic cycles, and the needs of humans and the environment. According to water level measurements taken since the 1950’s, we are able to see fluctuations in normal water table levels of approximately ten feet on a recurring basis, and of annual fluctuations of about five feet. (See Figures 4.7 through 4.10) Long time residents of the area around Lake Emily will no doubt recognize the groundwater level variations which
correspond with lake level changes. Current groundwater levels in these monitoring wells are the lowest since we began recording. It is primarily during times of low water tables, associated with lower annual precipitation, that the greatest demands are placed on our groundwater for municipal and irrigation uses.
A distinction needs to be drawn between the amount of water pumped out of the ground and the amount actually removed from its natural discharge area. Groundwater pumped from private wells is usually returned to the aquifer after treatment in a POWTS. Only a negligible amount is lost.
However, considering the water pumped for irrigation, industrial, and municipal uses, a good deal of the water is "consumed" rather than returning to its natural discharge zone. For agricultural irrigation, the net effect is that groundwater recharge is reduced about 30 to 40% on each irrigated acre, which reduces discharge to lakes and streams by an equal amount. Pumping for industrial and municipal purposes can have a greater influence because most of this pumping is concentrated in small areas, and groundwater pumped for this purpose is frequently diverted away from the streams where the groundwater would naturally want to discharge. The same would be true for a bottled water or beverage bottling facility. The groundwater is “mined” and none is returned to the aquifer.
For example, the City of Stevens Point pumps water from the Plover River basin (amounting to about 10% of the river’s flow), circulates it through the City, and discharges the water to the Wisconsin River. Similarly, the Village of Plover wells take groundwater from the Little Plover Basin, and discharges it to the Wisconsin River. Groundwater models have shown that flows in the Little Plover could diminish by over 40%, when the well pumping reaches design capacity. This 40%, added to the 10% or so reduction from irrigation, could mean the demise of the Little Plover as a native brook trout fishery. This effect on the Little Plover River may be ameliorated by pumping more of the Villages water from the new well sited south of Lake Pacawa.
By far, the most concentrated withdrawal of groundwater in the County is in the Village of Whiting, where a high density of municipal and industrial wells is located. This wellfield likely has some, though possibly small, influence on surface water. Monitoring wells in the vicinity of this wellfield have shown some declines in water levels.
In 2002, the City of Wisconsin Rapids announced plans to study installation of a municipal well in the Town of Grant in Portage County. Town of Grant residents were concerned about the effects that “mining” the groundwater would have on their private wells and the natural environment. Irrigation well owners and cranberry growers were concerned about declining water levels for their crops. It was determined that under current Wisconsin Statutes, the Town and County can have very little influence over where a municipal well is located, even one exporting groundwater to a municipality in another county.
The Portage County Board, in response to a request by the GCAC, passed a resolution (Appendix HC) opposing any withdrawal of water from the County without a full hydrogeological study of likely impacts, and requesting that the Wisconsin State Legislature enact legislation allowing counties to regulate such removals of groundwater from the County. Draft groundwater quantity legislation is currently being studied by Legislative committees and working groups.
4.1 Pesticide Table PAGE 1
4.1 Pesticide Table PAGE 2
4.3 GROUNDWATER QUALITY
When discussing groundwater quality, it is important to understand the differences between natural groundwater quality (which we can do little about except educate ourselves), individual well problems (which we may be able to do something about as water users), and groundwater pollution from human activities and land uses (which we have an obligation to address). Most of the following information will concentrate on the human activities and land uses, although current and proposed County groundwater programs also address health concerns related to the first two.
4.3.1 Natural Groundwater Quality Concerns
The natural groundwater quality of Portage County is generally good. Where natural water quality problems exist, they include iron, manganese, radionuclides, and corrosive water. Arsenic is not a concern here.
Iron and manganese are two metals that occur naturally in the sediments and bedrock that make up the County’s aquifers. Both are essential to life, but become a nuisance when they are present in water at too high a concentration. This happens under certain chemical conditions when oxygen in the groundwater becomes depleted, and the iron and manganese in aquifer materials undergo a chemical change that makes them soluble in groundwater. The main concern with iron and manganese is not health, but rather taste, odor, and staining of plumbing fixtures and laundry. The US Environmental Protection Agency set a drinking water standard based on aesthetic (not health) concerns of 0.3 parts per million for iron and 0.05 ppm for manganese. Iron and manganese tend to be more of a problem in the shallow rock and marsh provinces, or in sand and gravel wells screened near bedrock. Individual treatment units, and installing a well into a different part of the aquifer, are routinely used to deal with these contaminants. Iron and manganese are found throughout the County, but nuisance levels are most severe in southwestern and western Portage County.
Radionuclides are elements that undergo nuclear decay. Nuclear decay is the process by which atoms split to form other atoms, and in the process emit potentially harmful radiation. A number of radioactive elements - radium, radon, uranium, thorium, and others - occur in the bedrock aquifer, particularly at greater depths. The USEPA is in the process of revising standards for radioactivity in drinking water for public water supplies. The current standards are: "combined radium 226/228 of 5 pCi/L (picocuries per liter); a combined standard of 4 millirems for beta emitters; and a gross alpha standard for all alphas of 15 pCi/1, not including radon and uranium” (http://www.epa.gov/ogwdw000/standard/radionuc.html ). We do not know the number of wells in Portage County with exceedances of radioactivity standards, but radon from well water is a significant contributor of residential radon levels. Radon, when inhaled, is known to contribute to lung cancer, particularly in combination with tobacco smoke.
Since bedrock wells are more common in the northwest part of the County, this is likely where the greatest radioactivity concerns exist. Over 2,000 Portage County wells terminate in the bedrock aquifer (see Figure 4.1). Only a few have been tested for radionuclides. Significant levels of groundwater radioactivity east of Stevens Point have resulted in abandonment of several wells.
Studies by DNR in areas of granite wells have shown dangerous levels of radionuclides in a significant percentage of these wells. Unfortunately, no widespread sampling of bedrock wells, similar to that conducted for atrazine in the mid-90’s, has been conducted in Portage County.
Corrosive water is a term used for naturally soft and acidic water. The water itself is not harmful; however, its chemistry is right for dissolving metal in plumbing. This results in damage to plumbing (e.g., leaks in copper pipe), but more importantly, dissolved copper and lead in drinking water can cause severe health problems, ranging from indigestion and headaches, to brain and liver damage, especially in children. Dissolved lead is more of a problem in older homes (pre-1984) when lead solder was commonly
Figure 4.1 Radioactivity
used, but dissolved copper is a problem in homes that have copper pipes. Corrosive water is most common in the southwestern part of the County (Figure 4.2).
Microorganisms (bacteria, viruses, and others) occur naturally in the environment, including in aquifers and groundwater. Most are harmless or even beneficial, but some can cause disease, and others create nuisance conditions. Coliform bacteria and fecal coliform bacteria are frequently analyzed in well water samples. Coliform bacteria are a broad group that have members who live in soil, water, vegetation, and in the gut of animals. Fecal coliform bacteria are members of the group who specifically live in the gut or in feces. Most members of the coliform group do not cause disease; however, they are good indicators that a breach exists in the sanitary condition of a water system. In Portage County, coliform bacteria are usually not present as a groundwater contaminant, but rather, enter wells via a defect (missing well cap, cracked casing, and poor well construction) or move through groundwater from a substandard septic system into a shallow well. Following well reconstruction or repair, disinfection can usually eliminate bacterial contamination.
Unused wells (see Figure 3.6) that have not been properly abandoned provide ideal routes for bacteria to enter nearby wells, since contaminants can move directly from the surface to groundwater. One of the proposed strategies will address this problem. Even following abandonment of an unused well, nearby wells may be test unsafe for an extended period of time (months), and will probably not respond well to disinfection.
Metals (other than those naturally occurring or corrosivity-related) that are of concern from a drinking water and groundwater perspective, include arsenic, lead, cadmium, mercury, and others. When found in groundwater, these would most likely be found in association with landfills, or electroplating and other industrial sites. Metals pollution of groundwater is rarely widespread. No instances of metals pollution of groundwater, at levels of concern, have been documented in Portage County.
4.3.2 Human Induced Groundwater Quality Concerns
Petroleum-related Organic Pollutants
Common pollutants in this category (excluding pesticides) include benzene, toluene, dichlorethane, trichloroethylene, xylene, and others. Instances of this type pollution are relatively rare, usually cover small areas, and frequently are related to accidental discharges. Most are due to old spills around gas stations, dry cleaners, industrial sites, and pipelines, and may be present near current salvage yards. About 40 wells in the County are believed to contain these pollutants. Most contaminated sites have been addressed by the property owner (with assistance from DNR and PECFA) or have low enough contaminant levels to be candidates for natural attenuation. Excavated soils (from contaminated sites) containing low levels of these contaminants are generally landspread to allow the soil to provide final treatment. According to an analysis done using the County GIS, only an area of cropland in Pine Grove meets the State code criteria for landspreading of petroleum contaminated soils. No sites have been approved in the County for this type of land application.
In addition to these known point sources of contamination, organic chemicals from cleaning and other household chemicals are routinely discharged to groundwater through private onsite wastewater treatment systems (POWTS). Some POWTS, which incorporate pretreatment, will do a better job of treating for these contaminants than standard systems. These contaminants are also present in stormwater runoff from roads, parking lots, and other paved surfaces. Stormwater must be adequately treated by discharging to properly constructed retention-infiltration basins. Percolation of stormwater through topsoil lined basins will trap these organic contaminants, as well as some others that may be present. Discharge of stormwater to drywells or unlined basins, will allow these contaminants to be flushed into our groundwater.
Chlorides
In areas of runoff from paved surfaces (parking lots and highways), chlorides can be found at significant levels. A high percentage of chloride passes into the groundwater since it is not significantly attenuated during infiltration. Chlorides can be an indicator of contamination from septic systems, road salt, or animal waste and fertilizers.
Pesticides
The term "pesticide" includes herbicides, insecticides, nematocides, fungicides, and other compounds used to control organisms. Over 90 different pesticide products were reported as being used in Wisconsin in 1996. About two thirds of these have been reportedly used in Portage County. (See Table 4.1) Pesticide application rates vary substantially among crops; averaging about 0.8 pounds (as active ingredient) per acre for soybeans, 2 to 3 pounds per acre for field corn, and around 28 pounds per acre on potatoes. Source: Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP) 1997.
Pesticides are also used around homes - on lawns and gardens. The most commonly used pesticide around households is the 2,4-D contained in "weed and feed" lawn fertilizer formulations. Also used around households are malathion, carbaryl, and diazinon. At label application rates, 1.75 pounds of 2,4-D can be applied on a home lawn with two applications permissible per year. Actual usage is less. In a survey of two subdivisions with fairly well manicured lawns, only about half of households used a weed and feed formulation on their lawns, and then only once per year
The split between pesticides applied for agricultural compared to nonagricultural purposes is not precisely known, but a perspective may be gained by using the following comparison suggested by a DATCP official (James Vanden Brook, Groundwater Unit Leader) The herbicide 2,4-D is likely the most commonly used, nonagricultural pesticide. In the US, 16 times more 2,4-D is used in agriculture than on turf (Sources: I.C. Munro, 1992. A comprehensive, integrated review and evaluation of the scientific evidence relating to the safety of the herbicide 2,4,D. M.P. Kelty, undated. 2,4-D: a statement of position.). Because 2,4-D makes up only 0.2% of the agricultural pesticides used in Wisconsin, it follows that home and other turf use of 2,4-D is only 1/16 of 0.2% (0.013% or about 1/10,000) of the total agricultural pesticide use. While this analysis is imperfect, and neglects other less commonly used household pesticides, it demonstrates relative magnitudes of pesticide use.
For several reasons, it is currently impossible to determine the amounts of specific pesticide residues ("residues" means the parent pesticide, plus its related breakdown products) present in Portage County groundwater. With the exception of atrazine and aldicarb, very few wells have been sampled for many of the pesticides that can be expected to leach to groundwater. It is reasonable to expect, based on widespread detection of residues of soluble pesticides such as atrazine, alachlor, and aldicarb, that other leachable pesticides have been reaching groundwater where they have been used.
Atrazine residues are widespread, having been detected in over 40% of Portage County wells. About 3% of wells are known to exceed the standard of 3.0 parts per billion. This has led to the establishment of several atrazine moratorium areas (Figure 4.5) in the County, where atrazine cannot presently be used. More wells in which atrazine has been detected, may exceed the atrazine standard. A problem exists that most wells are tested for atrazine using a "triazine screen". This test, though significantly less expensive than the gas chromatograph analysis used for regulatory testing, consistently underestimates the true amount of atrazine residues present in groundwater. It is estimated that over 20% of wells, testing below 1 part per billion on the triazine screen, in reality exceed the groundwater standard of 3 parts per billion. Follow-up gas chromatograph analyses have been provided, by CIBA GEIGY and NOVARTIS (through DNR) in the past, for triazine screen results above 1.0 ppb in Portage County.
Figure 4.2 Corrosivity
Figure 4.3 Nitrate
Figure 4.4 Pesticides
Figure 4.5 Atrazine
Alachlor ESA, one of the degradation products of the pesticide alachlor, is probably a common pollutant. A DATCP study found that 15% of wells tested in central Wisconsin contained this compound (DATCP, 1995, a survey of atrazine in Wisconsin groundwater). Some controversy existed over the level at which alachlor ESA should be regulated. The Wisconsin Division of Health has recommended an interim 20 parts per billion Health Advisory Level.
Metolachlor and metribuzin have been found in groundwater near where they are used, though not necessarily above standards. These have been found in monitoring wells down gradient of vegetable fields, but little is otherwise known about their distribution.
Data on the prevalence and toxicology of potential pesticide residues are not well established. Regarding drinking water standards for pesticides, the United State Geological Survey pointed out (1999, Distribution of Major Herbicides in Ground Water of the United States), "These criteria [drinking water standards], however, may not accurately reflect the overall health risks associated with pesticide detections in water resources because they have been established only for a relatively small number of pesticides and they do not account for the additive or synergistic effects of mixtures, impacts on the health of aquatic ecosystems, or the effects of pesticide metabolites."
Nitrate nitrogen is the most widespread groundwater contaminant (See Figure 4.3) in Portage County. It is not the most serious health concern, but it represents the magnitude of our groundwater contamination problem. It can be effectively used as an indicator of other highly soluble contaminants associated with land use. It changes the way we need to look at our groundwater. Our expectation of clean groundwater pumped from a well, or present in a stream, must be changed to recognize the likelihood that it is contaminated. The recommended goals in Section 6.0 do not accept this notion, calling for nitrate nitrogen levels to (eventually) reach safe levels throughout the County.
Nitrate nitrogen levels continue to rise in some areas of the County, most notably the Village of Whiting wellfield, as predicted by research conducted by Dr. George Kraft in the 1990’s. Though some small areas have shown declining nitrate nitrogen levels, as in the Village of Plover east well field, this is not the norm Countywide. Since nitrate nitrogen is one of the commonly tested groundwater parameters in private water well samples, a continual source of fresh data flows through the UWSP Environmental Task force Lab. Unfortunately, the samples submitted are not representative of all areas of the County.
Efforts made during the 1990’s, by farmers and homeowners in cooperation with the Stevens Point – Whiting – Plover Wellhead Protection project, have had some limited success in reducing nitrate nitrogen loading to the groundwater in the municipal well recharge area. Unfortunately, all of the efforts did not succeed in lowering levels of this contaminant areawide, only keeping levels from increasing quite as fast as they might otherwise.
The areas of the County most affected by high nitrate nitrogen levels are in the areas of agriculture (especially irrigated) on sandy soils, and in areas of small lot residential development. Especially high levels, in excess of 60 parts per million, are found along the groundwater divide northwest of Almond.
Figure 4.6 Nitrate levels in Whiting Municipal Well
Current data not yet incorporated for this draft.
TOC | Sec 1 | Sec 2 | Sec3 | Sec 4 | Sec 5 | Sec 6 | Apx SR | Apx PS | Apx VG | Apx RE | Apx CE | Apx AD | Apx WA |Apx HC | Apx PH
Back to:
Managing the Resource