DRAFT Groundwater Management Plan
Section 3 Land Use & Potential Pollution Sources
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SECTION 3.0 LAND USE AND POTENTIAL POLLUTION SOURCES (pdf file--text only)
SECTION 3.1 INTRODUCTION
There are many potential sources of groundwater contamination in Portage County. Some are naturally present in our groundwater, but most are related to our uses of the County land and water resources. The increased residential development in rural areas, in close proximity to agriculture, exposes more of our citizens each year to all of the nutrients and pesticides historically leached to groundwater. The task of inventorying the potential sources is complicated by temporal changes in land uses and the dynamic state of our knowledge of groundwater pollutants. Many sources of pollutants have been present long enough to have established “track records”, either positive or negative. Table 3.1 lists basic groundwater pollution sources that are known to exist in Portage County. The list is divided into aboveground and underground sources. The environmental assessment contained in Section 2 describes the importance of the soil layers for pollution attenuation. Any contaminants buried or discharged below the soil have an inherently greater likelihood of adversely impacting groundwater quality. The list is further divided into point (specific location) and nonpoint (widespread) sources.
Many of the point sources were addressed in the 1988 Plan and are able to be carefully managed and continually monitored. Such facilities include the County landfill, fertilizer and pesticide storage and sales, petroleum product storage tanks, road salt storage, and manufacturing plants. Other point sources, such as private onsite wastewater treatment systems and manure storage facilities, are not as easily managed or strictly regulated, but are constructed to prevent groundwater contamination.
Nonpoint sources, including agricultural nutrients and chemicals used for production, pesticides used along road and utility rights-of-way, and land application of biosolids, are much more difficult to manage without allowing detrimental impacts on our groundwater and surface water resources.
Aboveground Point Discharges
Stormwater infiltration basins
Accidental spills
Aboveground storage tanks
Aboveground Nonpoint Discharges
Urban runoff
Lawn and garden fertilizers and pesticides
Rights of way maintenance pesticides
Road salt
Biosolids land application
Agricultural fertilizers and pesticides
Manure spreading
Private onsite wastewater treatment systems (POWTS)
Sewer leakage
Cemeteries
Unused wells
Backsiphoning
Landfills
Underground storage tanks
Petroleum products pipelines
SECTION 3.2 LAND USE AND POPULATION SUMMARY
Table 3.3 summarizes Portage County land use in the year 2000. Agriculture is the largest individual land use in the County, comprising approximately 55% of the total land area of the County. The amount of irrigated agricultural land in the County is steadily increasing, though currently at a slower rate than in previous decades, due primarily to the conversion of forested sand plain lands to potato and other vegetable crop production. Approximately 40% of all County cropland, or 120,000 acres, is irrigated. This is an increase from 2,802 acres in 1954 and an increase of 70,000 acres (140%) since the 1988 Plan was written.
Forest lands rank second in total area, accounting for about 28% of all lands. This category includes pine plantations, as well as the naturally occurring stands of timber. About 12,000 acres of these forest lands are managed under the State's Forest Crop and Woodland Tax laws. In total, agricultural and forest lands comprise nearly 83% of the County. Swamp and waste lands comprise an additional 5.2%.
Table 3.3. Year 2000 Land Use Summary for Portage County
Land Use Category Acres % of County
Agriculture 283,731 54.7%
Forest 142,799 27.6%
Swamp and Waste 27,323 5.2%
Urban (Incorporated) Areas 18,546 3.6%
Rural Development 15,468 3.0%
Transportation Right‑Of‑Way 12,998 2.5%
Water Bodies 6,604 1.3%
Other 10,931 2.1%
518,400 100.0%
Source: Portage County Planning and Zoning
Urban areas, including the City of Stevens Point and the nine incorporated villages in the County, encompass about 3.6% of the land area. The Stevens Point‑Whiting‑Plover‑Park Ridge urban area itself covers about 30 square miles. Rural development, including residential and commercial developments in unincorporated towns, encompasses about 3% of the land. Taken together, urban and rural development account for nearly 7% of the County's land area.
Transportation right‑of‑way includes those lands used for State, County, and town roads, as well as railroads. The right‑of‑way required for these facilities is larger than the pavement or track width itself. This use comprises about 2.5% of the County's land, not including road rights‑of‑way in the urban areas.
Natural surface water bodies constitute 1.3% of the land area. The DuBay, Stevens Point, and Biron flowages of the Wisconsin River represent the majority of this acreage.
The "other" category includes miscellaneous uses not otherwise identified in this land use summary, such as gravel pits and disturbed lands. Other lands constitute 2.1% of the land area.
The year 2000 population of Portage County is 67,182, and is distributed between: 1 city, 9 villages, and 17 towns (Table 3.4). A majority of the County population (53.5%) is concentrated in the urban area, consisting of the City of Stevens Point and the Villages of Whiting, Park Ridge, and Plover. Approximately 41.6% of the County population is located in the 17 towns, and the remaining 4.9% is located in the 6 "rural villages" outside of the Stevens Point urban area.
The County population has fluctuated from decade to decade, but can be characterized by slow and steady growth that is projected to continue (Table 3.5). The fastest growing communities in recent years were the City of Stevens Point, the Village of Plover, and the Towns of Lanark, Hull, Stockton, and Plover (Table 3.6). Much of the growth in the Stevens Point urban area is in the commercial development along Highway 10 East. Anticipated future growth in the urban area will be within the Sewer Service Area.
Rural home development continues to rise, with more and more individuals who move to the "country" commuting to jobs in the urban areas. In addition to Stevens Point and Plover, rural residents in Portage County increasingly commute to Wausau, Wisconsin Rapids, Marshfield, and the Appleton areas. Nonfarm, rural residents now represent over 80% of the population of the unincorporated towns in Portage County. It is projected that approximately 1,400 additional acres of land will be needed for residential development in the towns over the next 20 years, and roughly 1,000 acres will be needed for new City and village residents.
The County's population is projected to increase by a total of 14,073 people from 2000 to the year 2020. It is anticipated that much of this new growth will continue to take place in urban fringes and in the outlying townships. The Stevens Point – Whiting – Plover urban area can be expected to continue its growth outward into the Towns of Plover and Hull, and to a lesser degree, the Towns of Linwood, Carson, and Stockton.
Presently, approximately 30,000 people, or 45% of the County population, depend on private wells for their water supply. Only Stevens Point, and the Villages of Plover, Whiting, Junction City, and Amherst have municipal water systems. Municipal sewage treatment systems serve residents in Stevens Point and the Villages of Park Ridge, Whiting, Plover, Junction City, Almond, Amherst, and Rosholt. This leaves about 30,000 people, discharging their sewage to POWTS. Due to political and economic factors, municipal services will probably not be available to much of the anticipated population growth in the unincorporated urban fringe and rural development areas.
Table 3.4 Portage County Population (2000)
Municipality Population % of Total County Pop
T Alban 826 1.3
T Almond 642 1.0
T Amherst 1,252 2.0
T Belmont 555 0.9
T Buena Vista 1,097 1.8
T Carson 1,456 2.4
T Dewey 859 1.4
T Eau Pleine 1,002 1.6
T Grant 1,718 2.8
T Hull 5,620 9.2
T Lanark 1,144 1.9
T Linwood 1,095 1.8
T New Hope 661 1.1
T Pine Grove 829 1.4
T Plover 2,430 4.0
T Sharon 1,773 2.9
T Stockton 2,495 4.1
V Almond 553 0.9
V Amherst 780 1.3
V Amherst Junction 302 0.5
V Junction City 612 1.0
V Nelsonville 196 0.3
V Park Ridge 584 1.0
V Plover 7,037 11.5
V Rosholt 559 0.9
V Whiting 1,999 3.3
C Stevens Point 23,180 37.8
Total for County 67,182 100.0
Table 3.5. Portage County Population Trends 1900‑2020
Source Year County Population % Change
Census 1900 29,483 18.9
Census 1910 30,945 5.0
Census 1920 33,649 8.7
Census 1930 33,827 0.5
Census 1940 35,800 5.8
Census 1950 34,858 ‑2.6
Census 1960 36,964 6.0
Census 1970 47,541 28.6
Census 1980 57,410 20.8
Census 1990 61,405 7.0
Census 2000 67,182 9.4
Projected 2010 74,786 11.3
Projected 2020 81,255 8.7
Sources: U.S. Census of Population, Wisconsin Department of Administration Population (WDA) Estimates
Land use maps have been developed for the seventeen Towns in Portage County, presenting detailed information on the current distribution of land uses. In addition to the land use maps previously adopted by the individual municipalities, the County is currently engaged in a Comprehensive Land Use Planning process involving most of the County municipalities. This Comprehensive Planning initiative will be completed in 2005. Several of the major elements of the Countywide Comprehensive Plan involve aspects of groundwater management.
SECTION 3.3 MANURE STORAGE STRUCTURES
There are currently over one hundred manure storage structures in Portage County. (Figure 3.9) The animal waste, often including the barnyard runoff, is stored (for up to six months) in the structure until soil and crop conditions allow proper application to maximize nutrient availability and prevent runoff to streams. Many of these structures are very well constructed, watertight concrete and steel tanks or clay lined manure pits. The threat to groundwater is minimal provided these structures are properly maintained and managed. Other storage structures were built prior to current standards, and groundwater protection is not as certain. The Land Conservation Division encourages farmers with older storage structures to upgrade them, sometimes offering cost sharing to accomplish the goal. Over the past years, several farmers with older systems have closed their operations due to the poor economic conditions.
Innovative manure composting systems, such as that operated by Gordondale Farms of Nelsonville, can greatly decrease the amount of manure that must be stored. The composted manure can be reused as animal bedding. During the composting, methane gas is generated and used to produce electricity. The remaining effluent must still be stored until it can be landspread.
SECTION 3.4 PETROLEUM PRODUCT PIPELINES
Petroleum products can seriously pollute groundwater, posing a threat to health and property. Gasoline is less dense than water and, therefore, floats on the groundwater surface, and may infiltrate into basements and sewers, causing a significant fire and explosion hazard. Drinking water supplies contaminated with petroleum products are objectionable because of the taste, odor, and health concerns. Volatile organic compounds are related to a host of health problems. For example, benzene, a component of common gasoline, is strongly linked to leukemia in humans and can remain above the public health standard of 0.67 parts per billion (micrograms per liter) even after considerable dilution.
Figure 3.9 Manure Storage Structures
Figure 3.4 Pipelines
There is one petroleum product pipeline in Portage County. The Koch Refinery pipeline originates at the Koch Refinery south of Minneapolis‑St. Paul, passes through Carson and Eau Pleine, and terminates at the above‑ground tank storage farm at the junction of Highways 10 and 34, east of Junction City.
Maximum storage capacity of the tank farm is approximately 19 million gallons. The environmental setting for the tank farm area can be generalized as RzB and PoA soils, with a low potential for groundwater contamination.
All storage tanks are diked with materials from the site and have high level alarms. Spills within the storage tank area, such as at the truck loading area, are directed to a separator for recovery. Koch also maintains a contingency plan, personnel, and equipment to respond to and clean up spills. There are no monitoring wells at the site.
The pipeline continues southeast from the tank farm through the Towns of Carson, Linwood, Plover, Buena Vista and Almond. Several leaks in the 1980’s resulted in reconstruction of major portions of the pipeline, and installation of monitoring devices. The 12 inch pipeline is used to transport fuel oil, gasoline, and liquid propane. Length of the pipeline within Portage County is approximately 50 miles (Figure 3.4). The pipeline is maintained with cathodic and internal corrosion inhibitors. Input‑output flows are computer monitored for rapid detection of any breaks in the pipeline.
Biosolids, formerly referred to as sludge, are byproducts of manufacturing (food, paper) and sewage treatment processes. Also included is the septage (see Sec. 3.12) pumped from septic and holding tanks. These materials have variable concentrations of useful soil amendments, which when properly applied and incorporated into the soil, can be utilized by agricultural crops. These materials also contain varying levels of potential groundwater contaminants. Potentially hazardous components of sludge include heavy metals such as cadmium, chromium, lead, and mercury, pathogenic bacteria and viruses, nutrients such as nitrogen and phosphorus, and high salt content. These materials may contaminate groundwater, if applied in excess of the land's ability to seasonally or cumulatively assimilate the materials, or if site conditions exist that encourage leaching of the materials out of the active soil zone, such as in sandy soils under irrigation.
A significant acreage, widely distributed throughout the County (Figure 3.5), has been approved by the Department of Natural Resources (DNR) for land application of over a dozen different types of biosolids. Because the sites are reviewed by DNR staff, based on the information submitted by each individual biosolids applicator, several sites in Portage County have been approved for application of biosolids by several different haulers for the spreading of several different materials on the same site. This situation could result in over application and discharge of contaminants to groundwater. None of the approved sites are presently required to have monitoring wells, although some private wells in the vicinity of municipal sludge spreading sites are tested. The WDNR does have the authority to require whatever groundwater monitoring and plant tissue analysis that is deemed necessary.
Municipal sewage treatment plant sludge, while highly pretreated for removal of pathogens and nutrients, is closely regulated by DNR staff, and tested prior to land application by the licensed sewage treatment plant operator employed by the city or village. Septic and holding tank waste, by contrast, is not tested prior to application even though it may be treated with lime to kill pathogens prior to land application. Biosolids from food processing (whey, vegetable byproducts) and paper production have individualized nutrient and contaminant makeup, and are generally regulated based on the most limiting groundwater contamination standard. Nutrient management plans may be required to provide plant uptake of the available nutrients. Typically sludge loading rates are calculated based on specific sludge nitrogen content, crop nitrogen needs, and site. Sludge can be applied at a maximum loading rate that will meet the total nitrogen requirement of the crop. However, at maximum loading rates, the WDNR requires farmers to track nitrogen loading to prevent leaching. Most sludge loading rates are based on 30% of the total nitrogen need of the crop, because, at this level the WDNR does not require nitrogen tracking.
Figure 3.5 Landspreading
Figure 5.3 On-Site Wastewater
SECTION 3.6 SPRAY IRRIGATION OF WASTEWATER
Spray irrigation of wastewater from food processing operations is a common method of treatment and disposal utilizing vegetation, which is harvested to remove nutrients, and the active soil zone over a wide area. Food processing wastewater has significant levels of nutrients, such as forms of nitrogen, dissolved solids, and oxygen demanding materials. The wastewater may also contain any other materials associated with the agricultural product, though pesticide regulations prohibit applications of chemicals too close to harvest.
There are 3 spray irrigation systems currently under permit by the DNR in Portage County: American Potato, McCain Foods, and Del Monte. Extensive groundwater quality monitoring is required as a provision of the DNR permits. Typical test parameters include groundwater elevation, organic nitrogen, ammonia nitrogen, nitrate‑nitrite nitrogen, total dissolved solids, BOD5, COD, pH, conductivity, and chlorides. Sampling frequency ranges from biweekly to quarterly. Specific testing requirements vary with the WPDES permit.
SECTION 3.7 UNUSED OR UNSAFE WELLS
Unused wells represent a major threat to the groundwater, especially if left open to whatever contaminants may find their way downward. Unused basement wells, fairly common in Portage County, can provide an excellent route to groundwater for sewage, heating fuel, and anything else spilled on a basement floor. During a house fire, significant amounts of contaminated water can be flushed into an unused well in a basement. Even though a well may no longer be useful, whether due to inadequate water production or other reason, it still constitutes a direct connection to the groundwater. It is estimated, based on DNR records of replacement wells, that there are at least two thousand unused, private wells in Portage County. (Figure 3.6) The number is probably significantly higher, since many driven point wells, replaced by property owners, were never recorded with DNR.
Each of the municipalities with a municipal water supply system has an ordinance regulating private wells within its municipal boundaries. The ordinances generally require that an unused well be properly abandoned to prevent contamination of the groundwater, possibly even the groundwater supplying the municipal wells.
Even in a municipality with a public water supply system, a property owner has the option to use his private well, and unless there is a problem with improper plumbing, a well in use is generally not a threat to the groundwater. These private wells are required to be inspected for proper construction and tested to be certain that they are providing safe water.
SECTION 3.8 PETROLEUM PRODUCT STORAGE TANKS
In the 1990’s, many of the petroleum product storage tanks in Portage County were removed. Some were found to be leaking and site cleanups were commenced under DNR regulations. Many of the tanks that were removed were not replaced because they were no longer needed. It is estimated that approximately 100 underground tanks have not yet been addressed, although many of them may have been removed and not reported. Those that were replaced have been provided with either double wall construction or leak monitoring systems or both. In addition, the piping between the tanks and the dispensers (gas station or fuel depot) is generally double wall construction. Owners must maintain product records, and tanks are subject to annual inspections.
The Department of Industry, Labor and Human Relations (DILHR) maintains a registry of petroleum product tanks still in service, as well as records of properly abandoned tanks. Removal of tanks must be supervised by a state certified inspector. Newly installed petroleum product tanks in Portage County require state approval by the inspector from the Village of Plover Fire Department, or the Stevens Point Fire Department (in the City).
Figure 3.6 Unused Wells
Aboveground tanks are routinely installed in secondary containment structures. Secondary containment is required in wellhead protection areas. In the event of a tank leak, the secondary containment will catch the release of the product and prevent it from discharging to the groundwater. Aboveground tanks greater than 60 gallons, and underground tanks greater than 10 gallons, are regulated.
SECTION 3.9 PRIVATE ONSITE WASTEWATER TREATMENT SYSTEMS
In the areas of the County not served by municipal sewerage systems, POWTS have long been used for sewage disposal. Traditional septic systems, whether conventional or mound type systems, are designed to remove pathogenic bacteria. Given a properly designed and maintained system, the soil can do a pretty effective job of removing these disease causing bacteria. Bacteria will generally be attenuated within a few feet. These systems are considerably less effective in removing viruses, organic chemicals, and soluble nutrients such as nitrate nitrogen. Viruses can travel in excess of seven hundred feet, and survive for several months in saturated soils. According to research by Shaw, each person utilizing a POWTS for sewage treatment discharges an average of 10 pounds of nitrate N to groundwater each year. Assuming complete dilution, in order to maintain nitrate N at levels below the health standard of 10 parts per million, a two acre lot is required for a four person family. Given these values, approximately 300,000 pounds of nitrogen would be discharged to the groundwater annually from POWTS in the unsewered areas.
Soil tests to determine the depth to groundwater or bedrock were not required prior to the early 1970’s. Many septic systems were installed without any knowledge of the need for adequate separation (at least 36’’) between seasonally saturated soil and sewage discharges. While many of these older septic systems have failed and been replaced, it is estimated that nearly fifteen hundred (Figure 5.3) still exist, continuing to discharge disease causing bacteria and viruses in or too close to the groundwater. Some of these systems serve restaurants or other public buildings.
The Department of Commerce adopted revisions to several codes regulating the design, installation, and maintenance of private onsite wastewater treatment systems (POWTS) in the summer of 2000 (See Section 5.1) Generally referred to as the COM-83 package, these revisions allow for several types of POWTS not previously approved for use in Wisconsin. These newer types of systems incorporate pretreatment technology, such as filters and aerobic or anaerobic digesters, and as a result of the pretreatment, can discharge a much cleaner effluent to the environment. These newer systems can be sited on properties (with very shallow bedrock or groundwater) previously suitable for only holding tanks, or for mound systems with variances from State codes. Figure 3.2 shows area suitable for POWTS under the new code. Significant lands could be opened to development, including some with very poor soils for building.
These newer POWTS are significantly more expensive than traditional systems, and require much more maintenance than simple septic tank pumping every two or three years. They are also significantly more complex, requiring much more careful design and installation. This complexity increases the plan review and inspection workload of the County Onsite Waste Specialists, and requires even more detailed onsite soil verifications prior to plan review and permit issuance.
In 2000, Portage County placed a moratorium on use of these new technologies within its boundaries. It was one of only a few counties in Wisconsin to do so. This moratorium expired in 2003, allowing property owners to pursue these options. Only if properly sited and maintained, will these systems properly treat sewage before it is discharged to groundwater.
The Villages of Nelsonville, Amherst Junction, and the unincorporated areas of Bancroft, Kellner, and Polonia utilize POWTS for sewage treatment. Small lots in these areas result in very close proximities of POWTS and private wells. Contaminant loading to groundwater is significantly more problematic than on larger lots in more rural settings. Private wells are subject to high nitrate levels.
Figure 3.2 POWTS Suitable
SECTION 3.10 LANDFILLS
Landfills (also formerly known as dumps) have been around as long as people have lived in Portage County. The locations of many of the smaller, private dumps are unknown. The amount of the materials deposited in these was small, and the toxicities of the materials were likely fairly low as compared to current solid waste. The locations (Figure 3.10) of several dozen landfills, including the existing Portage County Landfill and former municipal landfills, are known. All, except the County Landfill, have been closed. Sampling from private wells near these old landfills has not shown widespread deterioration of groundwater, but no systematic sampling has been conducted to date.
Other private landfills in the County are licensed to accept construction demolition waste, or waste from paper processing. In the case of the former, the materials deposited do not have a high potential to leach contaminants to groundwater. For the paper company landfills, extensive testing of the materials, and sampling of nearby monitoring wells, is conducted.
SECTION 3.11 STORAGE AND USE OF ROAD SALT
Because of the winter climate of Portage County, road salting with sodium chloride is, and will probably continue to be, a common activity as long as the public demands snow and ice free roads. Cost effective, safe alternatives do not appear likely in the near future, although significant progress has been made since the first Groundwater Management Plan was published in 1988. High salt concentrations, usually in relation to an uncontrolled point source, can pose a health hazard to some individuals. The public welfare standard for chloride is 250 mg/l, and the preventive action limit is 150 mg/l. Road salt amounting to 8564 tons was used on Portage County roads in the relatively snowy 1985‑1986 winter. Currently road salt use is approximately 7000 tons per year.
All salt is supplied through the County Highway Department except for that used by the City of Stevens Point, and private contractors. The bulk of the salt storage therefore is at two locations in the County; the Stevens Point City Garage and the Portage County Highway Department grounds. Cleanup of City of Stevens Point and Portage County equipment is at sewered facilities.
SECTION 3.12 MUNICIPAL SEWER SYSTEMS
Most of the urban area of the County is served by municipal sewerage services, although several POWTS and sewage holding tanks are located within incorporated municipalities. Municipal sanitary sewers serve the City of Stevens Point, Villages of Park Ridge, Plover, Whiting, Almond, Rosholt, Junction City, and Amherst, as well as a portion of the Town of Plover under a boundary adjustment agreement. The City of Stevens Point provides sewer and water services to the boundary adjustment area of the Town of Plover, with the assurance that the properties in the served area will be annexed to the City within a few years. Park Ridge also contracts with the City of Stevens Point for sewage treatment services. (Figure 5.1)
SECTION 3.13 SEPTAGE
Adequate data is not available to properly identify the fate of much of the septage waste generated in the County. Many of the WDNR legal descriptions and approved acreages in Figure 3.5 were inaccurate, and required correction in order to be mapped. If all of the approved sites cannot be accurately located by legal description, some of the other requirements for landspreading of septage according to NR 113 also may not be met, and may go unnoticed by the WDNR. Minimum distances from houses, wells, and wetlands, could be checked to verify this presumption. As rural residential land use increases (Sec. 3.2), it is more and more difficult to find proper landspreading treatment sites. A site approval for septage spreading is valid for five years, even if homes and wells are subsequently located within the spreading area setbacks.
There are about 200 sewage holding tank systems in Portage County. Assuming 2.71 people per household, and a conservative 20 gallons of waste per person per day, approximately 3.9 million gallons of holding tank waste must be disposed of yearly. The sewage treatment plants receive only a very small
Figure 3.10 Landfills
Figure 5.1 Municipal Sewerage Systems
fraction of this amount. Septic tank waste is estimated at 3.3 million gallons per year in Portage County, assuming a population of about 30000 served by POWTS, 2.71 people per household, an average tank capacity of 1,000 gallons, and a pumping frequency of once every 3 years. These figures do not include septage from commercial or industrial sources. With the large quantities of septage generated in Portage County (7.2 million gallons annually) and little information on its ultimate fate, landspreading of septage is a potential groundwater threat. Portage County may want to consider applying for the authority to regulate septage disposal, if the WDNR is found to be performing the task inadequately. The DNR only has one person to monitor a five county area (including Portage) for all landspreading activities.
SECTION 3.14 AGRICULTURAL CHEMICALS – NITRATE NITROGEN
The drinking water standard (10 parts per million as nitrate-nitrogen) is based on the risk of methemoglobinemia (blue baby disease) to infants. This standard has been unchanged for several decades. Other countries have adopted similar standards. Recent research implicates diarrhea-causing agents, in combination with nitrate nitrogen, in causing methemoglobinemia. Other concerns over health risks associated with nitrate in drinking water have been expressed regarding non-Hodgkins lymphoma, gastric cancer, hypertension, thyroid disorder, birth defects, and miscarriage. Besides human health, concerns about nitrate include toxicity to livestock, fish eggs and fry, amphibian eggs and tadpoles, and the formation of the "Dead Zone" from discharge of nitrogen from the Mississippi River into the Gulf of Mexico.
In some parts of the County, and with some agricultural systems (non-irrigated systems, dairy agriculture, heavier soils), traditional approaches of reducing nitrate loading, by cutting available nitrogen on fields to recommended levels, may substantially improve groundwater. More research is needed.
Based on quantities discharged, nitrate nitrogen leached to groundwater from agricultural operations is the most significant pollutant to Portage County groundwater. Research studies in the 1990’s by Kraft and others showed that well over ninety percent of groundwater nitrate statewide comes from agriculture. In Portage County, the high percentage of land use in agriculture means that a greater portion of groundwater nitrate comes from agriculture. In some areas of the County, nearly 99% of groundwater nitrate comes from agriculture.
The types of crops grown in some parts of the county, especially under irrigation, result in leaching (to groundwater) of up one third of the nitrogen applied to the crop. Continuing to grow current crops, using established rotations, will continue to increase groundwater nitrate levels. This will happen even if University of Wisconsin recommended Best Management Practices are followed. New strategies will be needed in this industry for improvements to be made.
Already, over 20% of County wells exceed the drinking water standard, including two municipal water systems (Villages of Plover and Whiting), which spend thousands of dollars per year to treat their water. (Figure 4.3)
SECTION 3.15 AGRICULTURAL CHEMICALS – PESTICIDES
The term pesticides applies to herbicides, fungicides, insecticides, nematocides, and other chemicals intended to kill (unwanted) pest organisms. Very little of the County’s agricultural land, irrigated or non-irrigated, receives no pesticides. Depending on the crop grown, widely varying amounts and mixtures of pesticides are used. Generally, higher value crops receive more pesticides than lower value crops, with soybeans receiving less than a pound per acre, and potatoes receiving about 28 pounds per acre according to the Wisconsin Department of Agriculture (DATCP) in 1997. Irrigated farmland accounts for approximately 40% of all County cropland.
Given current technologies and practices, it is not possible to grow some of the current crops without pesticides, although significant efforts are underway in Portage County to apply UW research, and to conduct field tests of biological integrated pest management (Bio IPM). This effort is being coordinated through Tim Connell, UW Extension Agriculture Agent.
Groundwater can be contaminated with pesticides due to improper storage, handling, transport, and use. Storage and handling facilities are regulated and routinely inspected by DATCP staff. Currently, very few farms store pesticides on site, according to Portage County Emergency Management, preferring to obtain the products from the suppliers at the time of application. Many of the suppliers do the actual applications to the crops.
Not all pesticides are created equal, although the term pesticides itself stirs anxiety in many people. Pesticides posing the greatest threat to groundwater are those with high solubility, toxicity, persistence, and low soil particle attraction qualities. Newer formulations generally have lower potential to reach groundwater, than longer-used chemicals, such as atrazine and aldicarb. Both of these pesticides have been widely detected in Portage County groundwater; in places at levels considered unsafe for human consumption. (Figure 4.5) Although aldicarb has not been used in the County since 1986, and has not been recently detected in private wells, it is still present in groundwater.
Pesticides are also used around homes, and on turf 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 generally 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 (Source: C. Mechenich, 1991)
The split between pesticides applied for agricultural compared to nonagricultural purposes is not precisely known, but it is estimated that about one ten-thousandth of total agricultural pesticides used are applied to lawns and other turf areas. A perspective may be gained by using the following comparison suggested by a Wisconsin Department of Agriculture, Trade, and Consumer Protection 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 et al., 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 (it neglects other, less commonly used pesticides), it demonstrates relative magnitudes of pesticide use.
Combinations of pesticides can have synergistic, antagonistic, or additive properties. The combined effect of different pesticides has not been addressed in the EPA registration process. When the effectiveness of a pesticide, in combination with other chemicals, is greater than the expected effects of the sum of the individual compounds, it is known as synergism. Antagonism is when the effectiveness of a pesticide, in combination with other chemicals, is less than the anticipated efficacy of the individual compounds. Additive properties are evident when chemicals in combination are no more or less effective than if applied separately.
Recent research by UW Madison Dept. of Zoology Warren Porter has shown evidence of effects on children (hyperactivity and aggression, learning disabilities, and immune function) from very low levels of a mixture of pesticides (including 2,4-D) commonly found around residential lawns and gardens. Similar chemicals are widely applied to cropland in Portage County. Research by Porter and others indicates that mixtures of pesticides, or of pesticides and nitrate nitrogen, are potentially more toxic to humans than individual chemicals. This heightened toxicity may be due to synergistic effects of chemical combinations.
Pesticides in drinking water have been shown to cause a wide variety of health problems for humans, and for non-target organisms in the environment. Due to the mode of action of various pesticides, they can affect human endocrine and immune systems at extremely low levels. Chronic problems can develop at levels much lower than those determined safe in laboratory tests.
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