Thomas Well 1 was one of 5 wells targeted for rehabilitation January 2017 utilizing the HCT Well-Klean© Program.
Each rehabilitation project was highly successful with the exception of Thomas Well #1 where a clean Bac T couldn't be obtained.
Thomas Well #1 was constructed in 1956, 61 years prior to this rehabilitation date. The casing is 16 inches diameter, low carbon steel alloy, with louvered perforations from 600 to 1,224 ft. below ground level.
Tool used for brushing and plunging
The program prescribed for the rehabilitation included pre-cleaning (brush and bail with a biocide), bio-remediate (deep cleaning with biocide), descaling, zonal pump and lift with soda water, disinfect and volumetric flushing for NSF 60 requirements.
Because of the age of the well, a CITM scan was performed. The scan showed the most amount of corrosion on the casing occurred at the static water level. This would make sense as it is the vapor phase of water which is the most corrosive. However, though the scan indicated the area of corrosion in the color red, the amount of casing loss appeared to be less than 15%, thereby not of concern to aggressive cleaning by both chemical and physical means.
Plunger disc(s) - two on top and two on bottom.
The amount of product used;
WaterSOLV™ BC - Brush & Bail with Biocide
12,000 ppm - 1% active peroxide
WaterSOLV™ BC - Bio-remediate
100,000 ppm - 2.81 active peroxide
Well-Klean© Pre-blend - Descale
30% - 9.45% active descaler
Sodium Bicarbonate - Neutralize & Passivate
Sodium Hypochlorite 12.5% - Disinfect
Flush - NSF 60 Standard
Unable to pass a Bac T, the well was flushed continually and consistently,. After 3 million gallons of water it still would not pass a Bac T.
We Don't Guess, We Test and the Investigation Begins
With the ultimate goal to get this well back online as soon as possible, the questions are; why is this well different from the other 4? Why is it problematic to pass a Bac T when the others were not? What did we do different, if anything, or what do we need to do different? Is, are there anomalies with this well that we've not taken into consideration or that we've not faced before? Where do we start?
We began by pulling the motor, column pipe and bowls and performed a video. What we saw was a significant amount of soft, fluffy biomatter attached to the steel casing. The matter was only attached to the casing above the anoxic area (anoxic area being where the sulfate reducing bacteria were not prevalent). With the presence of all this matter, the question arose; How could all this still be there when it was chemically treated, wire brushed and plunged?
The tools were inspected and they were in complete compliance with the project; frayed wire brush, 720 degree coverage, double dual disc plungers - V-cut to offer maximum plunging activity yet allow any in-fill to fall through the discs.
What we learned is that prior to videoing the well, the camera had malfunctioned, and the disinfection chemistry sat in the well about 10 days. The chemistry reacted with biomatter still present on the casing wall, even though the casing wall was scarified and plunged with enormous amount of physical and chemical energy.
You can't discount soak times. Soak times are a necessity of chemistry. Also, physical energy, even in a scarifying situation, is not sufficient to move the roots of biomatter.