Seepage from older tailing ponds, Chino Mines Company, New Mexico: Part I

Transport of acidic tailing pore water through Chino Mine Company’s older inactive tailing ponds is limited by the relatively low infiltration rate into and low rate of drainage from the ponds. Monitoring instruments were installed in the tailing as part of a comprehensive hydrogeologic characterization program to assess the quantity and quality of seepage in the tailing. Preliminary monitoring of hydraulic parameters related to water drainage from the tailing indicates no consistent wetting or drying trends; ponding may be necessary to generate infiltration pulses in the tailing; estimated annual vertical fluxes are between 0.1 and 1.5 in/yr (0.25 and 3.8 cm/yr). Neither the field nor laboratory chemical analyses showed temporal trends. Percolation presently recharging the underlying groundwater is alkaline and similar to tailing slurry water. Pyrite oxidization occurs in the upper 10 to 15 ft (3 to 4 m) of tailing and acidic pore waters have migrated to depths of about 40 ft (12 m) in the oldest tailing ponds.