Flood Safety and Colliform

Coliform Bacteria and Your Drilled Well

A properly constructed and adequately cased drilled water well usually obtains its water at a depth where coliform bacteria are not present. All water in ponds, streams, and rainwater running over the ground surface contains harmful bacteria, viruses, and other organisms. These organisms die or are filtered out as water moves through the subsurface ground water environment. However, groundwater can be contaminated when there is insufficient filtration or travel time between the land surface and the ground water, such as inadequate separation distances from the well to sewage systems and other pollution sources. Some of the common ways in which bacteria can get into a well are as follows:

  1. The pitless adapter can leak or the well casing can become cracked. Visually inspect the interior of the casing on a regular basis to make sure there are no cracks or leaks present.
  2. Over time well casings may rust through, leaving holes near the ground surface where water can seep in and contaminate deeper ground water.
  3. Surface water could enter the top of the well if the casing does not extend far enough above the ground. Consider extending the casing to at least 24” above the ground surface.
  4. Bacteria can be introduced into a well when it is drilled, or when a pump is installed or serviced. Water wells should be sanitized after any service or installation work. Refer to the TCHD (Tompkins County Health Department) handout for directions on shock disinfecting wells.
  5. Unsealed abandoned water wells can directly channel contaminated surface water into groundwater. Refer to the TCHD handout for more information regarding well abandonment.
  6. Backflow can occur if water systems are not installed with properly functioning backflow prevention devices. Backflow prevention devices are essential to prevent any risk of bacteria being siphoned back into the well. For example, installation of an atmospheric vacuum breaker on each outside faucet will provide backflow protection if the end of a hose is accidentally submerged in material that could contaminate a well, such as lawn fertilizers, herbicides, swimming pools, or puddles.
  7. Surface water and insects can easily enter the well through a poorly constructed or unsecured well cap. Several types of common well covers are not vermin proof. Look to make sure that the electrical conduit (where the wires enter the well) is sealed and the gasket around the well is tight and intact, so that when the cover is bolted down the gasket will be pushing into the well’s casing. The well cover should include a downward facing screened vent that serves to prevent a vacuum forming within the well. Also make sure that bolts or screws are not missing from the well cover.

Homeowners should test their well water annually for coliform bacteria. Although most coliforms are harmless, they are an indication that disease-causing bacteria, viruses, or protozoa may be present in the drinking water. The TCHD maintains listings of certified testing laboratories.

If coliform bacteria are detected in your drinking water, the TCHD recommends making sure that the well is in good condition and shock disinfecting the well before collecting another water sample. Contact the TCHD for assistance and advice.

Flood Safety & Cleanup

Following extensive flooding in some areas of Tompkins County in the wake of the storms of June 14, 2015, the Tompkins County Health Department (TCHD) advises county residents whose private water well supplies have been impacted by the storms to take appropriate precautions to ensure their water is safe.

Private Well Water

If the area around a private well has been flooded or there is any suspicion or risk that the well has been contaminated from flood waters, consumers are advised to stop drinking, cooking, brushing teeth and bathing with the well water and disinfect the well. Wells in flooded areas may be contaminated with waterborne germs that can cause serious illness. Until the well has been properly disinfected and tested, water used for these purposes should be disinfected as mentioned below or bottled water should be used.

Warning signs that a well may be unsafe include: debris, mud or water and mud stains that indicate the well was flooded; erosion or instability in the ground surface around the well; damage to the well casing; a loose well cap; unusual odor, taste or appearance of the well water; or any visible electrical wires or components.

If the well has been or is suspected of being flooded, the well pump should not be turned on until the well has been thoroughly assessed and repaired as needed by a plumber or other well professional. Beware of electrical shock if your basement or electrical system has been flooded. Also, no one should drink, bathe, brush teeth or cook with well water after a flood until the well has been restored by proper disinfection and flushing. Unless there is indication that the well has been impacted by spilled fuels, oil or other chemicals, then it should be safe to continue to use water for flushing toilets.

Until the well is properly disinfected, bottled water should be used for washing, drinking or cooking. Tap water can be used if it has been disinfected by one of the following methods:

  • Disinfection by boiling the water – This method produces the safest water. Bring the water to a rolling boil and maintain a full boil for one minute. After cooling, it is recommended that oxygen be restored to the water by pouring it back and forth between two containers – this will also improve the taste.
  • Disinfection with Iodine or Chlorine tablets – First, check the expiration of the tablets before using and then follow package directions. One tablet is usually sufficient for one quart of water; double the dose if the water is cloudy.

For more information on disinfecting contaminated water, download this PDF document from the NYS Department of Health.

Disinfecting a Well

A New York State Department of Environmental Conservation (DEC) registered well driller can be contacted for information about disinfecting your well and additional treatment if needed. For do-it-your-selfers, information about disinfecting a well, including step-by-step instructions, can be found by downloading this PDF document from the NYS Department of Health.

After a well has been properly disinfected and chlorine has been flushed out of the water system, the water should be tested for bacteriological contamination. A list of labs that have been certified for drinking water testing can be found at the Wadsworth Lab website. Scroll down the page to find Tompkins County listings.

Continue to disinfect any water used for drinking or food preparation, or use bottled water until sampling has shown the water to be safe and free of contamination. You should consider retesting your well several weeks after flooding since groundwater contamination after a flood may impact the well.

Public Drinking Water Supplies

TCHD officials and water suppliers are aware that turbidity levels are significantly higher than normal in some of the County’s municipalities as a result of yesterday’s storm, and that contamination by untreated sewage is present in many of the impacted waterways. Water suppliers are taking appropriate steps to ensure that the water is adequately treated, such as monitoring more frequently, increasing chemical treatment, and ensuring adequate filtration. Drinking water utilities (community water systems) are required to follow specific regulations and procedures to ensure water is safe for consumption and use and these requirements continue to be in full effect during the aftermath of the storm.

Drinking water utilities in Tompkins County are required to monitor water quality levels for a variety of man-made chemicals, naturally-occurring contaminants, physical characteristics and microbial pathogens and immediately report any public health hazards or emergency conditions to TCHD. The utilities will work with TCHD to identify and initiate an appropriate response action, and must notify TCHD of any changes in conditions until the problem is resolved

More Information

The following links to websites provide additional advice for dealing with the aftermath of flooding:

House Cleanup Resources

What to Do with Wells after Floods

Being prepared before the storm hits is also important. Visit Don't Be Left in the Dark: Weathering floods, storms, and power outages on the NYS Department of Health web site. You can also download a PDF booklet there.

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