# Presentation: 466679

- Potential Pathways
- for
- Coliform Contamination

## Fixing Positive Coliform Results

## Fixing Positive Coliform Results

- Adopt the mentality that every positive coliform result has a source.
- Thoroughly investigate to determine potential sources.
- Do not flush and disinfect the entire       system following a positive routine       result.

## Fixing Positive Coliform Results

- Understand that repeat samples are intended to determine whether coliform contamination is widespread or isolated.
- Take repeat samples at the correct locations.
- Review past monitoring results to see if there are any trends.

## Fixing Positive Coliform Results

- If the system uses sodium hypochlorite for disinfection, review:
- procedures for replacing or freshening-up the hypochlorite feed solution
- chlorine residual monitoring frequency in the distribution system
- locations for chlorine residual monitoring
- expiration date of test kit chemicals
- water usage records, particularly peak usage vs. chlorine feed and contact time

## Investigative Sampling

- If after thoroughly inspecting the system for potential pathways for the coliform contamination you still have not identified a source, take investigative samples of the:
- water source
- storage tank
- each section of the distribution system
- Check the box on the the bacteriological sampling form that the samples are “special” or “investigative”.

## Slide 7

## Slide 8

## If Potential Coliform Source Cannot Be Identified

- Shutdown the system if a source cannot be found.
- Flush and disinfect the storage tank and distribution system completely if a source cannot be identified.
- If the source is determined to be contaminated, disinfect it obtaining a free chlorine residual of 100 mg/L.

## If Potential Coliform Source Cannot Be Identified

- Premix your chlorine solution in a container.
- Pour the solution into the well through a hose which the hose is being raised and lowered through the water.
- Hold the chlorine in the source for at least 24-hours.
- Pump the well or flush out the spring box until the chlorine residual is 1 mg/l or less.

## Slide 11

## Slide 12

## Slide 13

## Disinfection of the Distribution System

- To disinfect the distribution system chlorinate the source and pump or feed the water into the system.
- Let the water run out of each tap until a chlorine odor is detected.
- Hold the chlorinated water in the distribution system for at least 24-hours.
- Keep the chlorinated water out of nearby surface water.

- Start your search at the well house.

## Check the well casing to see if its properly sealed

## An incomplete repair may be a source

## Can surface water runoff infiltrate around the well casing?

- Seal any cracks in the concrete pad around the casing.
- Pad should extend above grade and slope away from the casing.
- Hand pump pad should have a drain that discharges to grade at least 100 feet away.

## Surface water runoff into vaults associated with the water system is another potential pathway for contaminates   

- <date/time>

- Surface water runoff into vaults associated with the water system is another potential pathway for contaminates

## Surface water runoff and sediment has potentially contaminated the filter

- <date/time>

- Avoid putting anything that must be maintained in a vault.

## Can surface water pond about the well casing?

## Is the casing sealed to prevent dirt and runoff from entering?

## Is the well subject to flooding or is it under the direct influence of surface water?

## Is there a septic system or other source of coliforms within 100 feet of the well?

- <date/time>

## Is there a vault toilet within 100 feet of the well?

- A vault toilet you would be proud to take Mom to.

## Storage tanks are common source of contamination.  If sediment accumulates in the tank, periodic cleaning and disinfecting is necessary.

- An overflow that is not properly screened provides a pathway for rodents and other small animals.
- At least a #4 mesh screen sandwiched between flanges should be installed.

- If possible, overflow should terminate 12 to 24 inches above grade to make it more for rodents to tamper with the screen.

## Divert surface water runoff away from storage tank access hatches

- <date/time>

## Keep access hatch locked or otherwise secured

## Keep hatch covers well above grade and ensure their covers are sealed with a gasket

## Remove tall vegetation around the well that your sample containers may brush against

- Debris accumulated in the well house may be a source of contamination
- Maintain the structure to prevent rodents from living in it

## Properly seal all abandoned wells

## Slide 41

## Slide 42

- Stagnant water due to  excessive storage volume may cause grown of heterotrophic (noncoliform) bacteria.

## Corrosion inside very old tanks will affect the quality of the water

## Provide a separate water line with  backflow prevention on it to meet fire demands

## Cross Connections

- Has the water system pressure dropped below 20 psi shortly before the positive coliform result due to:
- water line break
- high water demand (e.g., opening of a hydrant to fill fire engines)
- Are backflow preventors installed on all potential cross connections?

## A reduced pressure backflow preventor should be installed on lawn irrigation lines

- Backflow preventors should be tested annually to ensure they are functioning properly

- Are vacuum breakers installed on all hose bibs?

## Install vacuum breakers with manual drains to prevent the tap from freezing

## Slide 50

## Slide 51

## Slide 52

## Do shop sink faucets have built in backflow preventors?

## Springs

## Check isolation and air relief valves on the line from the spring to the site to determine whether they are impacted by runoff or soil erosion

- <date/time>

## Ensure storage tank hatch is not subject to surface water runoff

- <date/time>

## Check that the access hatch is bolted closed and sealed with a gasket

- <date/time>

## The vent must be screened to keep insects out

- <date/time>

## Does the spring also supply wildlife or cattle troughs?

- <date/time>

## Are total separate water lines run for drinking vs. wildlife/cattle?

## Slide 61