| Abstract/Description or Keywords |
In general, groundwater flow in the Fish Creek valley system is driven by recharge in upland areas to discharge in the network of streams and lakes that occupy the valley floor. Although review of groundwater data was limited to wells installed within the Fish Creek valley, similar flow systems are expected in the peripheral catchments for Wasp Lake and Big Onion Lake. Groundwater flow divides in general appear to coincide with topographic highs and indicate that, under baseline conditions, the Fish Creek valley is hydraulically separate from the adjacent Taseko River valley. Annual net infiltration is estimated to be in the range from 39 to 77 mm (12 to 15% of average annual precipitation) in the project area and supplies an annual average baseflow in the range from 115 to 228 L/s (estimated for the confluence of Fish Creek and the Taseko River). Refinement of this estimate using available site specific meterological data and calibration against streamflow records should be possible as part of detailed life of mine and closure water balance modeling for the project. Hydraulic conductivities for saturated soil and rock materials in the shallow (~100 mbg) groundwater system are generally on the order of 10-6 cm/s. Geometric mean saturated hydraulic conductivities were estimated from available data for individual material types as summarized in Table C7. The accuracy of these estimates range from approximately Ī 0.5 to Ī 1 order of magnitude depending on material type. However, assessment of potential effects due to seepage from or into individual mine facilities should proceed based on a more detailed review of the available database, as borehole logs, well logs and test records were not available in all cases for detailed review. Groundwater quality within the Fish Creek valley is generally fresh (TDS <1000 mg/L), with dissolved concentrations of major ions increasing with depth and proximity to the mineralized area. pH of the groundwater is on average slightly alkaline (average pH of 8.5) and groundwater temperatures range from 2.2 to 11.2°C. Potable use of groundwater within the Fish Creek catchment area near the mineralized zone should proceed with caution and should consider baseline groundwater quality presented in KP 2007b. |
