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4 <br /> pond was begun. With a design capacity of 500 million tons, this pond would increase the area <br /> impounded for tailing deposition from approximately 600 ha to more than 1200 ha. Land acquisition was <br /> begun in the mid-1960's, and since this pond was to be located in the Ten Mile mining district, where <br /> there were a number of old mines with existing poor quality discharges. The interceptor canals were <br /> extended around all of the land we were purchasing for our tailing pond and the Company accepted <br /> responsibility for any poor quality mine drainages that were within that boundary. In addition, it also <br /> voluntarily accepted responsibility for poor quality drainage from inactive mines that were above the <br /> property, but that were not owned by the Company. The Company felt that the larger volume of water in <br /> the tailing ponds would allow assimilation of these drainages with relative ease, and thereby reduce the <br /> loading to Ten Mile Creek. One of these was more significant than the others. The Wilfley Mine, located <br /> on Searle Creek, was one of the extremely bad actors draining into Ten Mile Creek and it had been doing <br /> so for approximately 100 years. When it was brought into the system in 1967, the water quality of Ten <br /> Mile Creek began to improve almost immediately. <br /> Calculation of Discharge Flow Rate <br /> Concurrent with development of this new tailing pond, the Company was applying.for its first <br /> NPDES permit under the new Clean Water Act (1974). That permit, required the removal of dissolved <br /> molybdenum from any water discharged to Ten Mile Creek. At the time, there was considerable <br /> uncertainty of the best method to perform Mo removal, so a research program was begun. Many schemes <br /> were tested, but the one that was finally agreed upon, was one of ion exchange and at the time, it was <br /> determined that we would need a flow rate of approximately 63 I/s to keep the system in balance. <br /> In retrospect, this volume calculation was the single most critical calculation in the permitting <br /> process. This paper will return to it many times. It is significant to recall that Climax was never able to <br /> shut down, due to demand for molybdenum. Being an old mine with no pre-existing data, no one was <br /> certain what amount of water was generated in the historic mining district, nor for that matter, what <br />