ST. PETER WELLHEAD PROTECTION PROGRAM

Publications
Overview of the Wellhead Protection Program (Powerpoint presentation 19,439 k)
St. Peter Wellhead Nitrogen Rate Results, October 2003 (pdf 730 k)
Nitrogen Rate Study Article - May 2004 (pdf 33 k)
South Central Minnesota On Farm Nitrogen Rate Studies (pdf 83 k)
Iowa On Farm Nitrogen Rate Studies (pdf 53 k)
Nitrogen Rate Demonstrationsf(website)

Maps
St. Peter Wellhead Protection Area
St. Peter Wellhead Protection - Progress 2002
St. Peter Wellhead Protection - Progress 2003

Website
2002 Watershed Heroes Conference, St. Peter
http://www.fb.org/programs/waterheroes/conf_6_02/

Project Overview
Throughout the 1980s, nitrate concentrations had been rising, slowly but steadily, in two of the Jordan aquifer wells that supplied drinking to the City of St. Peter, in south-central Minnesota. (The Jordan aquifer is contaminated with nitrates at a level of 10 or more parts per million; the federal drinking water standard is 10 ppm.)

As part of a 1993-1998 Clean Water Partnership project in east Nicollet County, development of a wellhead protection plan was seen by many as a logical step toward protection of the city’s water against future degradation. Wellhead protection was seen as more than a mandated exercise for the distant future; it was critical for providing safe, cost-efficient water right then and for the next few years.

Because St. Peter was one of the first communities in the state to voluntarily develop a wellhead protection plan, the program was able to secure a significant amount of technical assistance from the Minnesota Department of Health (MDH), the Minnesota Department of Agriculture, and the Minnesota Pollution Control Agency.

Delineation of the Drinking Water Supply Management Area
Combining information about geologic formations in the area with well boring and pumping-rate data from private wells of various depths, MDH created a single-layer analytic element computer model. The model was able to define groundwater flow boundaries in the area and determine the location of the groundwater recharge area. Both flow boundary and recharge area are important factors because the Jordan aquifer is cut by the Minnesota River in this area and is subject to variable groundwater flow conditions based on the amount of local precipitation. (For example, relatively flat hydraulic gradients have been measured in years of relatively dry to normal precipitation, whereas a ten-fold increase in gradients was noted during the flood season of 1993.)

These precipitation-dependent variations in groundwater flow occur around St. Peter because a sand terrace overlies the Jordan aquifer in this area. Because no confining layer is present between the sand terrace and the aquifer, recharge is relatively rapid. (Age-dating studies, using chloro-fluoro-carbon, show only an average of 10 to 20 years in age for waters drawn from different levels of the Jordan.)

Agricultural ditches west of the city flow eastward—draining clay-rich, glacial-drift cropland and infiltrating the sand terrace. This infiltration provides a significant source of nitrate-contaminated recharge to the Jordan aquifer.

With that perspective, the city entered into the wellhead protection process by delineating a Drinking Water Supply Management Area (DWSMA) that includes the minor watershed west of the city, where crop production is the dominant land use.

Protection of the Drinking Water Supply Management Area
Since reduction of nitrates is the primary focus of the final wellhead protection plan, the Clean Water Partnership, from 1993 through 1998, educated farmers in the DWSMA about nitrate-reduction, emphasizing the agricultural perspective. City residents were educated from a lawn-care perspective. In the late 1990's, a coalition of local and state agencies, crop consultants, and agri-business cooperatives began working to accelerate changes in the fertilizer practices of the agricultural producers. Learn more about nitrogen rate demonstrations.