Muggli, D. L.. Rescan Environmental Services Ltd., dmuggli@rescan.com
Mastrangelo, L. L.. Rescan Environmental Services Ltd.,
Pelletier, P. Minera Escondida Ltda.,

 
PERFORMANCE VERIFICATION OF THE OUTFALL/DIFFUSER SYSTEM AT COLOSO IN CHILE VIA AN OCEANOGRAPHIC DYE SURVEY: AN EXAMPLE OF ENVIRONMENTALLY SOUND WASTE MANAGEMENT
 
Minera Escondida Limitada transports effluent water from its Coloso Cathode Copper Plant de-watering facility via a 1.3 km outfall pipe to 60 m depth in the marine environment. A multi-port diffuser at the end of the outfall pipe provides rapid mixing of effluent with seawater providing sufficient dilution to ensure copper levels remain below US EPA guidelines. In 1995, the diffuser system was expanded to accommodate increased flow rates up to 50 L/s. On November 16, 1996, the performance of the diffuser was evaluated by measuring dilution factors achieved with the new expanded diffuser system. The fluorescent dye Rhodamine WT was injected into the outfall pipe, and an in situ fluorometer was used to measure dye concentrations in the vicinity of the diffuser system. During the dye survey, the predominant current direction was southwest, with the average current speed being 8 cm/s. The lowest dilution factor measured during the dye survey was 370, which occurred at a depth of 53 meters directly above the diffuser. At a distance approximately 0.5 km downstream (southwest) from the diffuser, the minimum dilution factor measured was 3,000. A dilution factor of 20,000 was measured 1.5 km downstream of the diffuser. The Coloso multi-post diffuser was designed to achieve dilutions of at least 376 to 1 under unfavorable oceanic conditions. This dilution would reduce copper concentrations to below US EPA water quality criterion of 2.9 mg/L total copper within 100 m of the diffuser. During the week of the dye survey, the dissolved copper concentration measured in the effluent was 170 mg/L, which would require dilution factors of only 67 to 103 to meet the most conservative criterion. These dilution factors are easily met within 10m of the diffuser system.
 
Day: Wednesday, Feb. 3
Time: 11:45 - 12:00pm
Location: Sweeney Center
 
Code: SS08WE1145S