Portage County Well Water Quality Project

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Well Water Quality Project Study

Background of Well Water Quality Project 
In the summer of 2017, Portage County conducted a water quality sampling project of 229 drinking water wells throughout the County to evaluate the current status of drinking water.  Portage County partnered with the Center for Watershed Science and Education at the University of Wisconsin-Stevens Point to provide logistical support, water sampling, and data analysis.

The purpose of this project was to generate baseline data on the current status of groundwater quality throughout Portage County.  This information will be used to help identify groundwater quality concerns, inform groundwater management decisions, provide focus for outreach efforts, and aid in the understanding of future changes in groundwater quality in Portage County

 To view a copy of the Well Water Quality Final Report please click here.

How were participants chosen?
Project organizers placed a 4-square mile grid over the entire County.  One well was randomly chosen from each area, creating a grid of 229 random well samples over the County (please see graphic below for approximate locations of chosen wells).  Chosen homeowners received a letter in the mail that detailed the project, as well as postcard that they could fill out indicating whether they wanted to participate in the project.  If a homeowner declined to participate a well closest to the selected one was contacted to see if they wanted to participate.

 Map of Randomized Initial Well Selection

Executive Summary

Groundwater is the principal water supply for Portage County municipalities, industries, and rural residents. While municipal water supplies are regularly monitored and required to meet drinking water standards, private well owners must make decisions regarding when and what to test for and what to do if there is a problem. In an effort to effectively target management and public health outreach efforts related to groundwater and private well owners, Portage County undertook steps to investigate well water quality across the county.

In the summer of 2017, Portage County collaborated with the UW-Stevens Point (UWSP) Center for Watershed Science to sample private wells for nitrate-nitrogen, chloride, pH, alkalinity, total hardness and conductivity. In the interest of ensuring representation from across the county, the county was divided into grid cells each measuring 2 mi. x 2 mi. One well from each grid cell was randomly selected for sampling. Participation was voluntary. For those households that agreed to participate, UWSP staff traveled to each property to collect the sample. Samples were analyzed at the state-certified Water and Environmental Analysis Lab. In total, 214 samples were collected and analyzed, from 202 of the grid’s 229 total cells (88%).

Portage County’s groundwater can generally be characterized as slightly basic (mean pH = 7.41), moderate to hard water (mean total hardness = 208 mg/L as CaCO3), and as having moderate alkalinity (mean = 154 mg/L as CaCO3). Overall, the water on average is well balanced and aesthetically pleasing.

The aesthetic characteristics of the water are largely influenced by the geologic materials groundwater is stored and transported in; with two fairly distinct regions of groundwater quality in Portage County. Groundwater in eastern Portage County tends to be harder, and have higher pH and alkalinity. In western Portage County, low pH, total hardness and alkalinity are more prevalent, conditions likely to produce water that is corrosive. Corrosive water can be problematic for households with metal plumbing; potentially resulting in elevated lead levels, pinhole leaks or corrosion of hot water heaters.

Nitrate is a common health-related contaminant found in Portage County’s groundwater (mean = 6.5 mg/L nitrate-nitrogen). Twenty-four percent of wells tested greater than the 10 mg/L drinking water standard; nearly 2.5 times the statewide average. Approximately 52% of wells tested measured greater than 2 mg/L, which provides evidence that land-use activities are having an effect on water quality in about half of wells tested. Soil drainage properties combined with areas of concentrated agricultural land cover help to explain both the extent and magnitude of nitrate concentrations in Portage County.

Chloride provides additional insight into the effects of land-use on water quality; background levels of chloride in groundwater are typically less than 10 mg/L. The mean in Portage County was 22.0 mg/L. There was evidence that increases in chloride concentrations were related to various agricultural land covers and development density (i.e. roads and septic systems).

This study provides an important benchmark of well water quality in Portage County. These results highlight the main factors affecting well water quality and provide a foundation for future investigations to investigate how or if groundwater is changing over time.

Lastly, it is important to acknowledge the many Portage County residents that agreed to have their wells sampled. Without their participation, this information would not have been possible.

 To view a copy of the Well Water Quality Final Report please click here.

If you have any questions regarding the project, you can contact Jen McNelly, Portage County Water Resource Specialist, at 715-346-1334 or mcnellyj@co.portage.wi.us or Amy Nitka, project manager, at the Center for Watershed Science and Education at 715-346-4078, or amy.nitka@uwsp.edu