•    Do not plug generators to your home’s electrical circuits if you do not have the appropriate automatic cut-off devices. If a generator is running when the power is restored, it can create a great fire risk and jeopardize workers repairing the power lines.

Hygiene and infectious disease related topics

•    After completing cleaning activities, wash your hands with water and soap. Use water that has boiled for 1 minute (allow water to cool before washing your hands). Or disinfected water can also be used in personal hygiene.
•    If you have cuts or open wounds that have been exposed to flood waters, wash them thoroughly with soap and water and apply antibiotic to control infections.
•    Seek immediate medical attention if you are injured or sick.
•    Wash clothes used during cleaning chores with hot water and detergent. These clothes should be washed separately.

Water related topics

•    If the property is disinfected, it is possible that flood waters carry fecal matter from overflown sewage, as well as agricultural and industrial byproducts. Although skin contact is not a serious health risk, there is a certain risk of disease when eating or drinking anything contaminated with flood waters.
•    If you have
•    If you have cuts or open wounds that have been exposed to flood waters, wash them thoroughly with soap and water and apply antibiotic to control infections.
•    To decrease risks associated with cold temperatures while standing on or working in water under at least 75 degrees F (24 degrees C), wear water resistant clothes and water resistant rubber boots, take breaks outside of the water, and change into dry clothes when possible.

Disinfection of wells after an emergency

If you suspect that a well might be contaminated, get in touch with your local health department to receive specific advice.

IMPORTANT INFORMATION: Fuel and other chemical substance emission and spilling are common during floods. If the water that you consume has a fuel or chemical odor, get in touch with your local health department and request a chemical analysis of the water before using it. Until you are certain that the water is safe, use bottled water or any other drinking water source.

Safety cautions

Any source of danger must be cleared before cleaning and disinfecting a well after a flood or other natural disasters. The following cautions will help you do it safely:

1.    Before doing anything, carefully inspect the area around the well to clear any electrical or physical hazard. Said hazards may be downed power lines in the water or ground, metal objects, glass or wood rubble, uncovered holes and slippery surfaces.
2.    Wear rubber soled boots or shoes for shock protection.
3.    Shut off power in the well area before clearing rubble. Inspect all electrical outlets to detect insulation fails or humidity presence. Restore power only if every outlet is dry and appears undamaged to prevent electrical shock.
4.    Do not activate electrical equipment if a persistent fuel odor, such as gasoline, is present at or near the well. Allow the well to air. If the odor persists, get in touch with your local health department. Do not continue with the disinfection process until its contamination cause has been removed.
5.    Before beginning the task, clear all rubble around the well to avoid waste falling in.
6.    When rubble has been cleared from wells with a large diameter (approx.. 90 cm [36 in] pr more), use hooks, nets or ladles to extract them. Do not enter the well. The well may contain accumulated fumes, which creates hazardous situations.
Follow these additional cautions while preparing for well disinfection;
•    Chlorine solutions may cause physical burns. Wear rubber gloves, protective goggles and aprons or water resistant clothes when working with chlorine solutions.
•    When mixing and handling chlorine solutions, work in well ventilated areas and avoid inhaling fumes. When working in confined spaces, use mechanical fans for fresh air circulation.
•    Warn users about consuming and bathing with this water until all well disinfection procedures have been completed and it has been cleaned thoroughly.
Next you will find general instructions for disinfection of wells that may have been contaminated by dangerous microorganisms during floods and other natural disasters.

Steps for disinfected drilled or excavated wells

Chlorination is a water disinfection process with a chlorine solution used to kill bacteria and other microorganisms. This process is recommended after floods and when test results confirm the presence of bacteria. It is an effective method to remove germ contaminations, but there are problems caused by defective well construction or due to underwater contamination, chlorination is but a temporary solution. If contamination persists, it is possible that further research is required.

The disinfection process may take a few hours to a few days to complete. Make sure enough water is stored to satisfy your home’s need before beginning this process.

Read the safety caution section before beginning the disinfection process.

Disinfection procedure

Step 1:        Rub or hose down any foreign material at the edge of the well or pipe lagging. If the well cover was not sealed properly and a flood occurs, there might be sand and silt deposits in the well, which requires thorough cleaning.

Drilled and excavated wells: Remove the cover and clean the inside thoroughly to extract any waste. Special tools or pumps might be necessary to remove the silt and sand. Heavy silt and sand deposits may cause damage to pumps if they are not removed before using the equipment. If silt and sand is present, remove the pump and clean thoroughly before using it.

Excavated wells: Remove the cover and clean the inside thoroughly to extract any floating waste. If the walls are lagged, scrub them with a brush and strong water and chlorine solution. Use bucket or pumps to empty contaminated water and waste from the well. If silt and sand is present, remove the pump and clean thoroughly before using it. Rinse the walls by pouring water along the edge. Empty the contaminated water that was used to rinse the well and that allow it to refill.

Caution: In areas without power, a portable generator might be necessary to operate pumps and equipment. Read safety instructions before starting the generator or any electrical equipment.

Step 2:        Manually, or with the aid of a pump, extract water from the well until water is clear. If the well is low-yield, empty it slowly. If available, use an external faucet to drain the water from the well. Do not pump contaminated water into an existing pressure tank. Disconnect piping between the pressure tank and the pump to allow the contaminated water to stay away from the well and the tank.

Step 3:        Use the chart below to calculate the amount of chlorine granules (bleach) or odorless liquid should be used. To determine the exact amount, find the corresponding well diameter in the left column. Then match the amount of chlorine needed according to the amount of time for every 3 meters (ten feet) of water in the well.

E.g., a 203 millimeter (8 inches) diameter well requires 3 ½ fluid ounces of odorless chlorine (for a retention time of 8 hours at 50 ppm) for each 3 meters (10 feet) of water.  If the water in the well has an approx. depth of 9 meters (30 feet), multiply 3 ½ fluid ounces times 3 to determine the amount of chlorine required (3½ x 3 = 11.5 fluid ounces). In a clean bucket, add this total amount of chloride to approx. 5 gallons of water (or mix this in 5 gallons of water).

If you are not certain of your well’s depth, check the entrance and lag piping of the well for a label indicating its depth. If there is no such label, talk to your neighbors about their well depth. Usually well depth is similar in neighborhoods. If you are still unable to determine the depth of your well, then increase recommended amounts of chlorine in 50%.

International Unit System (metric): A well with 20.0 cm (8 inches) in diameter requires approximately 103.5 milliliters (mL) of odorless chlorine for each 3 meters of water. If the water is approximately  9.1 meters (30 feet) deep, multiply 103 mL times 3  to determine the amount of chlorine requires (103.5 x 3 = 310.5 mL). In a clean bucket, add this total amount of chlorine to approximately 19 liters of water.

Step 4:        Pour the chlorine solution in the well and use a circular pattern to ensure contact in every side of the well’s inner lagging or its pipe lagging. If the drilled or excavated wells have no lagging, pour the solution in the well’s hollow. If possible, recirculate the water by connecting a garden hose to an outside faucet and place the other end in the well. Allow water to run during 15 minutes to ensure that the chlorine solution is mixed within the well.

Step 5:        In the case of well connected to a plumbing system, open every faucet inside and outside of the house and pump water until you notice a strong chlorine odor at each faucet. If you do not perceive a chlorine odor after running the water in every faucet during 15 minutes, increase the amount of chlorine in half of the original amount and repeat these procedures.

Stop the pump and allow the chlorine solution to remain in the well and plumbing system. See the chart in section “Sampling after disinfection” to match amounts of chlorine solution and disinfection time. It is preferable that the solution remains in the well during 8 hours or overnight, if possible. Do not leave chlorine in wells for more than 24 hours, this may affect some parts of the pump.

Step 6:         After the disinfectant has settled in the well during the recommended amount of time, activate the pump, connect a hose to an outside faucet and aim water to a designated area away from the well. The well water has high chlorine concentrations that may be dangerous for plants, septic tanks and water currents. Empty the water in a place where plants and water currents are not harmed. Continue running the water until the chlorine odor has disappeared, then open the faucets inside the house to drain the chlorine in the plumbing system. In low-yield wells, empty the plumbing system slowly to avoid pumping the water excessively. According to depth and size of the well, this process may last a few hours, a day or more.

Water in wells without plumbing systems can simply be pumped or extracted with buckets until the chlorine odor disappears.

Sampling after disinfection

Until water analysis is performed, all water destined to human consumption must be boiled (it should remain boiling for 1 minute), or an alternate water source should be used. Wait for at least 2 days after disinfection to ensure that the chlorine is completely gone from the system. After that, retrieve a water sample to determine total coliform and fecal presence and confirm if the water is apt for consumption. Get in touch with your local health department for sampling and analysis, or with the official in charge of lab certification in your state to find a local lab that performs this type of certifications.

If the sample analysis results show absence of coliforms, total coliforms and bacteria or E. coli bacteria, the water may be considered apt for drinking from a microbiological point of view. Follow up with two additional samples, one in the following 2 to 4 weeks and another in 3 to 4 months. To verify if the water available is apt in long term, continue monitoring the bacterial quality at least twice a year or more often if a change in water quality is suspected.

If the sample analysis results show the presence of total and fecal coliforms or E. coli, repeat well disinfection process and sample analysis. If the tests continue detecting bacteria presence, get in touch with your local health department for help.
 

Chart. Amount of chloride required for each 3.1 meters (10 feet) of water in the well *
Inner well lagging pipe diameter (Standard/SI)	Amount of  5.25% of sodium hypochlorite (Chlorine/ odorless bleach) Standard/SI			Amount of 65% of calcium hypochlorite (Chlorine granules/bleach) Standard/SI
	Disinfection time per disinfectant concentration
	100 ppm for 2 hours	50 ppm for 8 hours	25 ppm for 24 hours	100 ppm for 2 hours	50 ppm for 8 hours	25 ppm for 24 hours
1¼ inches or 3.18 cm	? fluid ounce or 3.7 mL	¾ tbsp. or 3.7 mL	1/3 tbsp. or 3 mL	It is not practical to use chlorine granules for small diameter pipes.
2 inches or 5.08 cm	½ fluid ounce or 14.79 mL	¼ fluid ounce or 7.39 mL	? fluid ounce or 3.7 mL
3 inches or 7.62 cm	1 fluid ounce or 29.57 mL	½ fluid ounce or 14.79 mL	¼ fluid ounce or 7.39 mL
4 inches or 10.16 cm	1½ fluid ounces or 44.36 mL	¾ fluid ounce or 22.18 mL	? fluid ounce or 11.09 mL
6 inches or 15.24 cm	4 fluid ounces or 118.29 mL	2 fluid ounces or 59.15 mL	1 fluid ounce or 29.57 mL	¼ ounce o 7.09 grams	? ounce or 3.54 grams	1/16 ounce or 1.77 grams
8 inches or 20.32 cm	7 fluid ounces or 118.29 mL	3½ fluid ounces or 103.51 mL	1¾ fluid ounces or 51.75 mL	½ ounce o 14.17 grams	¼ ounce or 7.09 grams	? ounce or 3.54 grams
10 inches or 25.40 cm	10 fluid ounces or 295.74 mL	5 fluid ounces or 146.87 mL	2 fluid ounces or 59.15 mL	¾ ounce or 21.26 grams	? ounce or 10.63 grams	3/16 ounce or 5.32 grams
12 inches or 30.48 cm	2 cups or 473.18 mL	1 cup or 236.59 mL	½ cup or 118.29	1 ounce or 28.35 grams	½ ounce or 14.17 grams	¼ de ounce or 7.09 grams
18 inches or 25.72 cm	4½ cups or 1.06 L	2¼ cups or 532.32 mL	1? cups or 266.16 mL	2½ ounces or 70.87 grams	1¼ ounces or 35.44 grams	¾ de ounce or 21.26 grams
2 feet or 60.96 cm	7½ cups or 1.77 L	3¾ cups or 887.21 mL	1? cups or 443.60 mL	4½ ounces or 127.57 grams	2¼ ounces or 63.79 grams	1? ounces or 31.89 grams
3 feet or 91.44 cm	17½ cups or 4.14 L	8¾ cups or 7.01 L	4? cups or 1.04 L	10 ounces or 283.5 grams	5 ounces or 141.75 grams	2½ ounces or 70.87 grams
Notes: 1 spoonful of 65% powdered chlorine=½ ounce; 8 ounces=1 cup. Cm=centimeter; L=liter; mL=milliliter; ppm=parts per million; SI=International Unit System (metric).

Other issues related to disinfection

Drilled and excavated wells may be difficult to disinfect as a result of their build. Many are shallow and have no inner lagging or lagging pipes, which allows pollutants to enter from the upper ground layers. If contamination problems continue, consider improving the existing well or drilling a new one.

Water softener may be harmed by the disinfection process as a result of large amounts of chlorine used. Follow manufacturer instructions regarding appropriate methods to disinfect your water softener. You may need to overlook that equipment until the disinfection process has been completed.