Your well may become bacteriologically contaminated for one of the following reasons:
There is a source of contamination too close to the well or the well casing isn’t deep enough to assure that recharge water receives sufficient filtration to remove bacteria. The well may be constructed using poor sanitary practices. New wells often show contamination because during drilling of the well, the drill hole was contaminated through use of dirty tools, pipe and drilling water. New piping, pump or pressure system components also may cause contamination if they are generally soiled and not disinfected prior to use, assembly or installation. The state well code requires disinfections of new wells, pumping equipment and water systems prior to use.
Contaminated surface water or groundwater enters an improperly constructed well (for example):
- “Dug” wells that are walled up with boards, brick, stone or tile sections allow unfiltered surface water and near-surface water to seep into the well through the cracks.
- Casing improperly sealed into the rock and/or unconsolidated geological formation may permit surface water or contaminated groundwater to move vertically downward, contaminating good aquifers.
- Surface water enters the top of the well because the casing doesn’t extend far enough above the ground or a hand pump base isn’t sealed watertight on the casing.
- The well top ends in a nonconforming well pit subject to flooding or seepage of contaminated groundwater.
- Old well casings may rust through, leaving holes near the ground surface where surface water or near-surface waters can seep in and contaminate deeper groundwater.
- The aquifer supplying the well is fractured rock that has poor water-filtering properties.
