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Colorado’s Well Water Risks After a Flood

Assessing the water quality of your private well is a critical step to recovering from a flood. Learn how flooding in Colorado can contaminate private drinking wells.

During a Colorado flood, being overwhelmed by floodwaters is only the first problem. After the floodwater subsides, the cleanup and repairs begin. This includes addressing your drinking water quality.

Private well owners are independently responsible for a well’s safety and quality. Below, we’ll break down the science of how flooding can affect well water, what type of contaminants could be in your water, and what you can do to help your well water be safe to drink. 


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What Type of Contaminants Are in Floodwaters?

The first issue to keep in mind is that floodwaters are a toxic soup. Flooding will pick up the contaminants of whatever it touches. This could be pesticides on nearby farms, industrial waste from manufacturing facilities, car fluids, and more. 

Most floods also contain sewage because of overflowing sewage treatment plants and underground septic systems. That means that floodwaters are usually unsanitary with risks of E.coli, coliform, and other bacteria.

How Does Flooding Contaminate Your Well?

Water easily mixes with itself. During a flood, this means that contaminated water flowing through the streets can mix with the drinking water in your well.

If floodwaters reach your wellhead, your well water will likely be contaminated. Even air-tight seals may not be enough to keep the bacteria and toxins from leaching into your well.

Floodwaters don’t even need to have direct contact with your well for it to affect your home’s water quality. For example, floodwaters that saturate the soil around your well could cause seepage. Floodwaters can also contaminate the groundwater or aquifers below the surface of the soil. In these cases, if your well reaches the groundwater table below, your well could be contaminated. 

To learn more about potential flood contamination, the EPA’s guide to well water quality lets you match potential water contaminants to risk factors or conditions. For example, you may want to test for nitrates if there is agriculture nearby, or if landfills or gas stations are nearby, you may want to test for volatile organic compounds (VOCs). 

How Has Colorado Been Affected by Well Water Contamination?

In Colorado, there have been recent reports of well water contamination. Flooding and rain can cause long-term contamination that can spread through wells in a wide area. 

In recent years, a group of fluorochemicals called PFAS has been especially concerning. These so-called forever chemicals have leached into water systems near Air Force bases and oil refineries. From there, they spread through the groundwater. Nearby neighborhoods have started to report high levels of PFAS in their well water. 

At the U.S. Air Force Academy near Colorado Springs, PFAS contamination in the Monument Creek watershed has been measured at levels 1,000 times higher than the EPA’s recommended levels. Well tests near Colorado Springs have reported well water 20 times higher than the EPA’s health advisory level. 

Other parts of the state are having problems too. Testing a well in the north Denver metro area revealed that PFAS contamination was 147 times higher than the EPA health advisory level.

8 Steps to Protect Your Well Water After a Flood

After a flood, these eight steps can help you discover what is in your well water, stop bacterial growth, and protect your household from safety risks. 

1. Test your well. 

Testing your well water for contaminants is the only way to know exactly what’s in your water. For help, call the EPA’s Safe Drinking Water Hotline at 1-800-426-4791, or use the well water resources from the Colorado Department of Public Health including water testing lab information and tools for interpreting test results. 

2. Run water until clear.

Follow the recommendations from safety experts and plumbers about when it’s safe to begin the process of disinfecting your well. When you’re ready, the first step is to clear out sediment from your lines by running an outside faucet until the water becomes clear. 

3. Shock well with bleach. 

When disinfecting your well, follow the manufacturer’s guidelines about your well and specifics related to your water system such as water treatment devices. This video about shock chlorinating a private well explains the process and calculations for disinfecting your water. The general process involves removing the well cover and pouring the recommended amount of bleach into the system. Then to mix the bleach into the well, use an outdoor hose to add water into the casing unit until you smell chlorine coming from the hose. 

4. Populate the lines, wait, and flush system.

To kill any bacteria lurking in your pipes, go to each faucet in your house and run the cold water until you smell bleach. After doing this for all faucets, both indoor and outdoor, wait six to 24 hours without using the water while the bleach kills the bacteria. Afterward, run the water from an outdoor hose until you no longer smell bleach in the water. 

5.  Re-test water.

About seven to 10 days after disinfection, re-test your water. Waiting will allow any remaining bacteria to repopulate to detectable levels, and testing too soon could give you a false reading that your water is safe. Remember to take a long-range view of water safety. Because of how contaminants can move through groundwater, you may want to retest your well every few months to check that your drinking water is safe. 

6. Don’t use septic systems immediately after a flood.

During a flood, a saturated leach field could cause your septic system to fail. This could cause sewage or wastewater to back up into your basement, bubble up out of the ground, or contaminate your well. Check with your plumber or safety inspector about when your septic system is safe to use. 

7. Drink bottled water until you are certain water is free of contaminants.

Well water contamination can have serious health consequences. Prioritize safety by drinking bottled water until you’re certain your home’s well water is safe. You don’t want to experience health problems when you’re dealing with other aspects of flood recovery such as making foundation repairs, improving drainage, or installing a sump pump.

8. Get a professional foundation inspection to identify hidden damage.

Just as groundwater below the surface can affect your drinking water, the soil below your home could be affecting your foundation. Flooding and runoff can lead to several types of foundation problems, including differential settlement. In these cases, the home is unevenly supported by the soil below, and the building could start to tilt, bow, or crack. This affects the home’s livability and can reduce its market value by up to 30 percent. 

Your home’s foundation may be out of sight, but it shouldn’t be out of mind. Sign up for a free inspection from the foundation and waterproofing experts at Complete Basement Systems.

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