Dalquharran Mine Water Treatment Scheme

Site History - The initial outbreak of minewater from the Dalquharran drift mine occurred in 1979 and caused a large scale pollution incident on the River Girvan, a prime salmon river. Initially the minewater had a pH between 3 and 4, an iron concentration of 1300mg/l and a flow rate of 26 l/sec. Sealing of the up dip shallow workings was also carried out by the National Coal Board in an attempt to reduce the water inflow which was partially successful.

Water Chemistry -The mine water at Dalquharran is acidic and highly ferruginous. The current system in use is the ‘dilute and disperse’ principle, whereby minewater is retained within the mine workings in a holding tank. Where the Fe concentrations are 147mg/l and the pH is 5.9. It is estimated that there is approximately 30 days worth of water storage capacity in the mine workings. This system is used instead of a treatment system. The water is only released when the flow in the burn and the receiving river is high enough so that the minewater can be diluted to an acceptable level. At present the Fe concentrations can not exceed 350mg/l (av. range 38-342mg/l) and cannot have a pH outside 5 and 9 (av. 5.9).

Some reeds have been established on site, these can take any excess flow from the drift discharge and control it before release into the watercourse.

Site Design -The fresher cleaner minewater was intercepted by a horizontal borehole, which further reduces flow to the adit. This substantially decreased flows from the adit, and the deeper, more polluted mine water was allowed to issue from the adit mouth.

River and Burn levels are monitored continuously, and the release of minewater from the holding tanks is carried out automatically when water levels in the river are sufficiently high to give adequate dilution.