Nebraska Water Science Center
Nebraska Water Science Center Podcast Series
Episode 3: Contamination in domestic wells transcript: May 5, 2009
Subject: Contamination in domestic wells
Rachael McLeod Welcome to the fourth episode of Nebraskast where we talk to real USGS scientists about the important water resources work they're doing all over Nebraska. My name is Rachael McLeod and I'm here with Jill Frankforter who is a hydrologist with the USGS Nebraska Water Science Center. Jill, we're talking today about a report that was recently released about contamination in domestic wells. The study was conducted by the National Water-Quality Assessment Program also known as NAWQA. What is NAWQA? And tell us a little bit about the scope of this study.
Jill Frankforter The National Water-Quality Assessment Program or NAWQA program was started in mid-1990s and is general assessment of the quality of the nations water resources - specifically surface and groundwater. The study that we're talking about specifically today was a study of water quality in domestic wells across the nation. The lead scientist on the report was Leslie DeSimone who is with Massachusetts Water Science Center and the report that she put together summarizes water quality in domestic wells approximately 2,100 domestic wells across the nation. They're located in 30 different aquifers within the nation and then I want to talk a little bit more specifically about the results as they relate to the sites that they sampled in Nebraska. This report includes data from 136 wells that were sampled in Nebraska. They were primarily from the High Plains aquifer as well as from the Platte River or alluvial aquifer. So we'll talk about those.
Rachael McLeod What kinds of contaminants were researchers looking for in this study?
Jill Frankforter It was a very broad suite of contaminants. There are about 219 total contaminants and they included things like physical properties, chemical constituents. They're looking at pH, major ions, trace metals, radio nucleotides, nutrients that might be in the water as well as the presence of pesticides or volatile organic compounds. And then on some of the wells -- approximately 400 of the wells that they sampled -- they also looked at microbial contaminants, specifically bacteria.
Rachael McLeod Where did the contaminants come from? How are they getting in the water?
Jill Frankforter IThere's two different potential sources. A lot of the compounds are actually naturally occurring, so they're coming out of the geologic formations that the well exists in or in the soil the well is finished in. Some of the compounds are also or could be manmade or result of activities in the area of the well.
Rachael McLeod What about some of the safety limits for the contaminants? How did the researchers go about deciding what limits to use?
Jill Frankforter The levels that they compared to are based on potential human health concerns. Some of the human health benchmark levels that they used are actually based on enforceable levels that were set by the US Environmental Protection Agency and these are maximum contaminant levels or MCLs that are established for public water supply systems. There are also some levels that are based on health-based screening levels and these are levels that were established by the USGS in cooperation with the US Environmental Protection Agency. Basically, these health-based screening levels were established for compounds or constituents that don't have MCLs but may have human health concerns. They were established using some of the same methodologies that they use to establish MCLs.
Rachael McLeod So what were the nationwide findings for the study?
Jill Frankforter Nationwide, they found that about 23% of the wells or the 2,100 wells that they sampled had at least one contaminant that was present at a level that exceeded one of the health-based screening levels. Some of the compounds that they found at these levels pretty consistently, pretty frequently were uranium, nitrate, arsenic and radon. In 60% of the wells, they also found pesticides or volatile organic compounds. These weren't at high levels, they weren't at levels that exceeded the human health base levels, but were present in concentrations that were detectable.
Rachael McLeod How did those findings compare to findings in Nebraska?
Jill Frankforter Within Nebraska, we had some fairly similar results as far as what was found in our wells and concentrations that exceeded the health-based screening levels. Approximately 18% or 25 of the 136 wells had at least one compound that was present at a concentration that exceeded a health-based screening level. Some of these compounds were uranium again, arsenic, nitrate. We also found bacteria in some of the wells. There were seven wells that had a detectable concentration or a colony of total coliform and two that had E. coli.
If you add in the constituent of radon, which is a little bit more complicated, then these values - these numbers for Nebraska go up a little bit. There are actually two US Environmental Protection Agency MCL levels for radon. The level that's applied to a public water supply system varies depending upon whether they have a mitigation plan in place.
Now if you compare our results to the upper level, which is 4,000 picocuries per liter, then none of the wells that we had in Nebraska had concentrations of radon that exceeded that criteria level for that concentration level. If you look at the lower proposed MCL level for radon, which is 300 picocuries per liter, then we had 55 of a 136 wells that had concentrations above 300 picocuries per liter.
Rachael McLeod In Nebraska, how many people get their water from private wells?
Jill Frankforter Probably 17% of the population within the state or about 300,000 people get their water from domestic wells. When you compare that to the national values, it's a little higher than the national level. The national level I think is 15% of the people get their water from domestic supplies. So we're a little bit higher than the national average.
Rachael McLeod Are these folks required to test their wells for the contaminants that were analyzed for in the study?
Jill Frankforter Requirements for sampling and testing the wells are at the time that the well is installed or if there's a transfer in ownership. Other than that, there are no regulatory requirements to test domestic wells. It's the responsibility of the homeowner to test their own domestic water supply.
Rachael McLeod And who should the domestic well water users contact if they'd like to have their water tested?
Jill Frankforter The primary contact, if anybody has any concerns or interest in the quality of the domestic well water, it's probably the Nebraska Department of Health and Human Services. They have a website that we will have a link to on our webpage. That is www.hhs.state.ne.us and you'll be able to get to their website from that location. But the Nebraska Department of Health and Human Services lab is responsible for administering the US Environmental Protection Agencies Federal Safe Drinking Water Act. So they are required to either be able to analyze water for all these constituents that are regulated under the Safe Drinking Water Act or have contacts with labs that can provide that analytical capability so they'd be a great resource to contact for testing for any of these constituents.
Rachael McLeod And what if somebody has questions about the study or would like more details about the findings? Where can they go to find that information?
Jill Frankforter We will have a link established on our webpage that you'll be able to get to the National Quality Assessment Programs link for the report. They've established a link that has access to reports, some of the data and as well as contact information for the lead author on the report who's Leslie DeSimone and then we'll have a link to that from our website which is at http://ne.water.usgs.gov.
Rachael McLeod Jill, I'd like to thank you for taking the time to talk to us today.
Jill Frankforter Well, thank you.