Overview of the Delaware Department of Agriculture's Ground Water
Monitoring Program for Pesticides

Delaware's Reliance on Healthy Ground Water
In Delaware, approximately 65 percent of the population obtains its drinking water from ground water. For residents of southern New Castle County, Kent, and Sussex counties, ground water is the sole source of drinking water. Much of the drinking water in these areas is provided by shallow private wells of less than 75 feet, drawing from the water-table aquifer.

How Pesticides Can Reach Ground Water
A pesticide can be defined as any chemical used to control pests; this includes herbicides, insecticides, and fungicides. Pesticides are used to control nuisance organisms and to increase crop yields; therefore pesticides are a beneficial component of Delaware's agricultural industry. However, the potential exists of adversely affecting the environment and human health. When pesticides are applied, whether it is on a farmer's field or around a residential home, there is a chance that some of the product may run off the soil's surface or leach down through the soil to eventually reach the water held in the ground. In Delaware, the water table is very high; this means that the distance from the soil surface to the ground water is relatively small. The high water table and the characterizations of the subsurface soil are factors conducive for contaminant migration into ground water. So monitoring the ground water for the presence of pesticides is particularly important for the state.

Ground Water Monitoring
The Delaware Department of Agriculture's Pesticide Section began monitoring the state's shallow ground water for pesticides in 1995. Since then, the Department has collected more than 600 individual ground water samples from over 220 domestic, agricultural, and monitoring wells. Individual samples have been screened for up to nine different pesticides that are commonly used in agriculture. These include Alachlor, Atrazine, Carbofuran, Chlorpyrifos, Cyanazine, Metolachlor, Metribuzin, Simazine and the compound 2, 4-D. The majority of the wells tested negative. The small number of wells with detections did not exceed the EPA's Maximum Contaminant Levels (MCLs), which are set as thresholds for safe drinking water under the Safe Drinking Water Act. Much of this data is presented in a report of investigations coauthored by the Delaware Geological Survey (DGS) and the Department of Agriculture. Report of Investigations No. 61 entitled "The Occurrence and Distribution of Several Agricultural Pesticides in Delaware's Shallow Ground Water" can be found at the DGS's website http://www.udel.edu/dgs/index.html under publications. More recent data can be found on the DDA's GIS website at http://www.smartmap.com/ag_website/.

You can also find out more about EPA registration of some of these pesticides from the following links:

Atrazine: http://www.epa.gov/pesticides/reregistration/atrazine/

Alachlor: http://www.epa.gov/REDs/factsheets/0063fact.pdf

Metolachlor: http://www.epa.gov/REDs/0001.pdf

Having an active monitoring program is the best way to evaluate the health of the state's ground water. Collecting and analyzing ground water data allows the DDA to detect contaminants before they become significant, as well as measure its progress in its efforts to protect the state's ground water.