Released: May 08, 2007

Flooded Wells May Pose Health Risk

MANHATTAN, Kan. – Wet, spring weather improved Kansas pond levels, recharged groundwater aquifers and aided crop development, but some areas have had too much of a good thing.

“Wells that have been flooded need to be checked, cleaned and disinfected for the safety, health and life of the well and equipment before it’s returned to service,” said Morgan Powell, agricultural engineer with Kansas State University Research and Extension.

In recent weeks, heavy rains in some parts of the state have resulted in flooding of some creeks and rivers. Wells in flood pathways or near flooded areas have been affected.

“In addition to pathogens that can make us sick, flood water carries abrasive sediment, debris, the occasional toxic chemicals, and other contaminants,” he said. “Choosing not to check and clean flooded wells may further damage equipment or lead to health consequences.”

Powell gave these recommendations to minimize damage to the pump, power unit, life of the well and consumer safety:

* Check the well and power unit for damage; the well’s construction, compared with standards; and run-in of flood water.

“Look for damage to the casing and components of the well. Also evaluate the well construction, as compared to KDHE (Kansas Department of Health and Environment) standards for well uses,” he said. “If flood water was above the well casing, some contaminated water will have entered the well, so disinfection is essential.”

* Consult electrical and mechanical service providers and check any submerged electrical or mechanical components, including the motor, gear boxes, controls and internal combustion engine. Taking shortcuts on this can cause shorts in electrical equipment that could injure or kill people or shorten the life of the mechanical components because of moisture, rust or lubrication.

* If the well yields cloudy or turbid water, a run-in of flood water is likely. If it signals that sediment has entered the well, bring in a licensed well driller to remove the pump and clean out the sediment. Water pumps are not designed to handle sediment -- it will wear and may damage the pump. Well drillers have knowledge, skills and equipment to remove sediment.

* After checking the equipment and replacing the pump, the well should be pumped until all traces of turbidity have been removed and the water runs clear.

* Disinfect the well and water system after the well has been fully restored.

The amount of water and chlorine required to treat wells varies for wells used for irrigation and those for domestic household drinking water. It also varies by well size and water volume.

Powell recommends a chlorine dose of at least 500 milligrams per liter (or parts per million) for domestic and 200 mg/L or ppm for irrigation wells.

The water will not be useable for drinking after the disinfection process until the well is flushed and a follow-up test is free of bacteria.

“After a flood, a domestic well should not be used for drinking water without emergency disinfection – a rolling boiling for at least three minutes or two drops of chlorine per quart (8 drops per gallon) of clear water -- until a water test has shown the well is free of total coliform bacteria,” Powell said. “Think of it as cleaning your dishes after they were contaminated.”

* A bacterial water test should be collected a week after the shock chlorination. When the test shows no bacteria, it confirms the well can again be safely used for drinking.

“If the water test is not free of bacteria, repeat the shock chlorination disinfection process,” Powell said. “Wait at least three weeks before doing a third or more shock chlorination.”

More K-State Research and Extension and government agency information about wells and shock chlorination is available at http://www.kswaterwell.org .

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Mary Lou Peter-Blecha,
mlpeter@oznet.ksu.edu
K-State Research& Extension News