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� � w Procedure No. Revision Number �"�' ' ERD SOP-2.10 3 I Page 3 of 4 The wells to be sampled for coliform bacteria will be included in the quarterly Sampling Plan provided by the SC. Prior to sample collection, all calculations will be made and appropriate chlorination performed. ' 6.1.3 A 5.25% sodium hypochlorite solution (standard household bleach) is routinely used. The U.S. EPA recommends using a solution with a minimum concentration of 100 mg/L for proper sterilization. The following formula is used to calculate the quantity of sodium hypochlorite to be added to the well: ' Volume hypochlorite (oz.)= (W)(64) (RIP) where ' W=water volume in well (gal), R=required hypochlorite concentration in the well (decimal), and P=Percent available chlorine(decimal). 6.1.4 When using the above' equation, the required hypochlorite concentration and percent available chlorine should be in decimal form. For example: 100 mg/L= 100 ppm = 100/1,000,000 = 0.0001; percent available chlorine of 5.25% = 0.0525. The volume (gal) is the amount of water in the well casing (casing ' volume) and is calculated as per ERD SOP 2.1, "Presample Purging of Wells." These calculations should be documented on the appropriate field forms. 6.1.5 The SC or appropriate personnel should inform the contract analytical laboratory ' ahead of time to allow for preparation when collecting samples on a rush turn- around time or samples having short hold times. 6.1.6 In consultation with the SC and field support personnel, ensure that adequate containment devices are available at the well head for purge water collection. The quantity of purge water to be collected for each well is listed in the Routine Sampling Schedule. 6.1.7 Ensure that an adequate amount of 5.25% sodium hypochlorite (standard t household bleach) is on hand, according to the calculated dosages of the required solution. Use a fresh supply for every sampling event. 6.1.8 Ensure the availability of a pool test kit with the appropriate solution to test for ' chlorine in water which measures in the ppm range. 6.2 Operation ' 6.2.1 Add the calculated amount of 5.25% sodium hypochlorite to the well. Use the pump to recirculate the water to ensure thorough mixing of the disinfectant with the well water. Turn the pump on and off several times during this procedure. 6.2.2 After disinfection, the water in each well will be allowed to stand for 24 hours. After 24 hours the water should be pumped until the presence of chlorine is no ' longer detectable. Test for the presence of chlorine by using a pool test kit according to manufacturers instructions. Once the water is free of residual chlorine, a coliform bacteria sample may be collected in a 100 mL pre-sterilized polyethylene container as described in ERD SOP 4.3, "Sample Containers and ' Preservation."