Case Study 3 | Plastic Well Casing and Standard Well Cap


Private Well 1950s Community In Pennsylvania


Plastic Well Casing and Standard Well Cap

Private Well with Standard Well Cap - Failed Bacteria Test and Grass Clippings Under the Well Cap.
BART Test - Positive Iron Bacteria Test Result

Level 1 Observational Testing / Water Issues

1. The water appeared to be turbid and had gas bubbles; the homeowner was concerned about a natural gas leak and natural gas drilling.
2. The water had an intermittent brown to black color with some sediment and staining.
3. The water had a slight odor.
4. There were intermittent odors throughout the home at different fixtures.
5. Bacteria (Specific Case) in well water: The main reason the homeowner called was that the well failed the bacteria test for a real estate mortgage refinance. The well was positive for total coliform and E. coli and he was told to buy a $ 2500 UV disinfection system.
6. Historic Usage: Homeowner reported that the water became intermittently discolored (black and brown); there was some gas when the well was purged for long periods of time, but the well had never run dry.
7. Certified testing showed the raw well water had tested positive for Total Coliform and E. coli, but the laboratory data showed only the presence or absence of these bacteria without an actual enumeration. The system had a whole-house particle filter that was discolored yellow-brown to black with some sediment, there was quartz sand in the filter, and the filter was very slimy. The steel well casing was corroded.
8. There was some evidence of Iron and Manganese staining on various surfaces and in the aeration devices.
9. The toilet tank showed evidence of nuisance bacteria that appeared to be typical of  Slime and Iron Bacteria.

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Neighborhood Environmental Report

Activities in the area: gas drilling, urban landscapes and runoff, pipeline work, excavations, stormwater systems, fertilizers, and road salting.

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Inspection & Assessment
Level 2 and Level 3 Testing

1. Documented well construction and water level.
2. The static water level was just below the base of the PVC casing and the well had a standard well cap.
3. There were grass clippings, spider webs and egg masses, earwigs , and other insects under the well cap.
4. During the purging of the well we monitored the water quality and appearance and field-checked the pH, conductivity, temperature, and methane content of the water. The water had no detectable methane, i.e. Lower Explosion Limit was < 1 %, but the well did produce discolored water and sediment because we removed the inline filter, and the water appeared to have a metallic sheen. We conducted a Level 3 informational water testing for general water quality, nuisance bacteria, and trace organics and we conducted a Level 4 test for total coliform, E. coli., and a standard plate count using an enumeration method. (Note:  An enumeration method gives you the actual colony count for the bacteria, i.e. a number of bacteria per 100 ml of water, and not just presence or absence).
5. The results of the testing:
Level 3 Testing - the well had a slightly elevated level of copper, lead, iron, and manganese with a trace level of arsenic, but the pH, hardness, and other water quality were ok. There was no evidence of contaminants from volatile organics or synthetic organic compounds such as herbicides and pesticides. We tested for nuisance bacteria and found that the slime and iron-reducing bacteria were high and at a nuisance level.

Level 4 Testing - the well had a total coliform count of over 80 colonies per 100 ml with an E. coli count of 43 colonies per 100 ml; the heterotrophic plate count was over 700 colonies per ml. The standards are: total coliform < 1 colony per 100 ml, E. coli negative, and heterotrophic bacteria < 500 colonies per ml).

Treatment Action

1. We shock disinfected the well with a residual of 50 ppm - chlorine. We used an NFS-approved chlorine known as Well Safe. When we conducted this shock disinfection, we recirculated the water (after the particle filter housing with the cartridge was removed) back to the well. After this shock disinfection we retested for bacterial contamination. To our surprise, the bacterial concentration went UP! Hypothesis (science term for guess): Because the well had a lot of grass clippings and other debris in it that could not be removed prior to the shock disinfection, we thought that the debris was washed down into the well and this may have used up the chlorine residual, something that we missed because we did not monitor the chlorine level or the ORP during the recirculation process.
2. We shock disinfected the well at 100 ppm with more recirculation and checked chlorine levels with chlorine test strips and an ORP sensor and added more chlorine if the residual in the water dropped below 50 ppm in the recirculated water or in the water within the plumbing of the home.  We also pasteurized and flushed the water heater and hot water lines. We flushed the system to waste to a point at which there was no chlorine detectable and then after one week we retested the water with the particle filter removed from the system.
3. We changed the well cap to a sanitary well cap.


1. Total Coliform, E.coli, Nuisance Bacteria, and standard plate count were at low levels or not detectable.
2. There were no Iron or Manganese problems and no Total Suspended Solids (TSS).
3. The well yield and specific capacity increased.
4. Recommendation:  Quarterly Monitoring for 1st year and then switch to an annual test. Our primary concern was that the well casing was not grouted and did not have a Drive Shoe. Therefore, it is possible for the well to be vulnerable to the migration of shallow water contamination following major recharge events.
5. After the first year and the first major rainfall event, the bacterial problem returned. Since the well has a PVC casing, we could not repair it, so the homeowner had a certified installer put in a whole-house UV disinfection system with a backwashable particle filter.

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