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Rehabilitation of the Public Water Supply borehole in Fair Isle

Published in the March 2012 issue of Water Active by Drilcorp, this case study article details the successful rehabilitation of the public water supply borehole for Fair Isle in Scotland.

Synopsis: The public water supply borehole for Fair Isle was contaminated with manganese and iron deposits which had choked the pump, screen and possibly the rock fissures. The borehole is 200mm in diameter, 73m deep and provides water for 70 inhabitants as well as to a small storage reservoir.

A 6 hour pre-treatment test recorded initial pumping at 36.7lpm down to 14.57 lpm after 3 hours with an average flow of 16.66 lpm, indicating the pump was not running to it’s full potential. Rest water level was recorded at 11.97m bgl. After 6 hours the water level had drawn down to 43.77m bgl.

BoreSaver Ultra C was injected into the well, circulated for 24 hours, the pump removed and the well pumped clean with an air lift eductor. The pump was inspected and cleaned at the surface prior to re-installing.

A CCTV survey confirmed all contamination had been removed. The post-treatment pump test recorded an average flow of 22.22 lpm, a significant increase in well performance. Drawdown levels after 6 hours reduced by 3m, indicating that the water was flowing into the well more freely after cleaning.

To read the full case study in Water Active click here