LeMasters, Gary S.; Doyle, Douglas J. / Grade A dairy farm well water quality survey
Abstract, pp. i-ii PDF (319.7 KB)
ABSTRACT The Wisconsin Department of Agriculture, Trade and Consumer Protection (WDATCP) estimated the proportion of wells on Grade A dairy farms that contain detectable levels of pesticides and nitrate- nitrogen (NO3-N). A random sample of 550 farms was drawn from the population of 23,543 Grade A dairy farms. These farms were chosen because WDATCP has authority to collect water samples as part of its inspection program and because sampling this population should provide a meaningful measure of the presence of pesticides in groundwater in rural Wisconsin. Water samples were actually collected from 534 of the 550 farms and analyzed for 44 compounds including 10 of the herbicides and 4 of the insecticides most commonly used in Wisconsin. One or more herbicides were detected in 71 wells. Sixty-four (64) of these contained atrazine alone, 3 contained alachlor (LassoO) alone, 1 contained metribuzin (Sencor®) alone, 1 contained atrazine and alachlor, 1 contained atrazine and metolachlor (Dual®), and 1 contained alachlor and metribuzin. The maximum concentration of atrazine was 19.4 micrograms per liter (ug/l) with a median of 0.45 ug/1. The Enforcement Standard for atrazine of 3.5 ug/l was exceeded in 3 wells. The maximum alachlor concentration was 5.9 ug/l with a median of 0.7 ug/l. The Enforcement Standard for alachlor of 0.5 ug/l was exceeded in all 5 wells where it was detected. The proportion of wells on Grade A dairy farms that contain detectable levels of pesticides is estimated with 95 percent confidence to be between 10 and 16 percent. The proportion of wells containing detectable (at or above 0.15 ug/l) levels of atrazine is estimated to be between 9 and 15 percent. Between 5 and 9 percent of the wells contain atrazine above the Preventive Action Limit of 0.35 ug/l. There were insufficient data to estimate the proportion of wells containing any pesticide above an Enforcement Standard. The proportion of wells containing NO,- N is estimated to be between 61 and 69 percent. The proportion of wells containing NO3-N above the'Enforcement Standard of 10 mg/l is estimated to be between 7 and 13 percent. The survey was not designed to determine whether the pesticide detections resulted from pesticide application according to label directions or from mishandling. However, many farm operators whose wells contained a pesticide above the Preventive Action Limit were interviewed about the way they handle and apply practices. From these interviews it seems that while most of the farm operators handle these compounds carefully, improper disposal of pesticide rinsate and empty containers may be a problem source. Farm operators also need better information about the construction of their well and the relationship between activities at the surface and groundwater quality. Finally, the regulatory community needs to assist the farm community in understanding the health implications of Wisconsin's groundwater standards.