Tracer Test in the Bowden Close Passive Treatment System (UK) – Preliminary Results

A mine water tracer test with bromide, Na-fluorescein, and NaCl was conducted at the Bowden Close passive treatment system in County Durham, UK. This passive treatment system comprises two RAPS units and one polishing wetland with surface areas of 1511 m, 1124 m, and 990 m, respectively. Mean residence times of 4—5 days and mean effective velocities of 0.01 m h-1 through the active RAPS layer were deduced for the two RAPS units. The maximum mine water flow rates differs between the two RAPS (30—50 L min-1 in RAPS 1 (mainly fed by adit drainage), and 90—110 L min-1 in RAPS II (fed by spoil leachate). With the exception of the NaCl tracer, which was too heavily diluted due to intense rainfall, all tracers where applied successfully in the test