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.,,~ B. 'Ihe annual overall water balance is shown below, based on the annual „Ux;,mm, precipitation of 33": In: Precipitation 10,550,000 gallons Out: Absorption in Ore Negl. E<+aporation frtiun Ponds, Unsprayed Heaps, and Ditches Negl. Etraporation fr~n Spraying Heaps 18,450,000 gallons Net: Make-up Water Required: 7,900,000 gallons As indicated, under worst-race conditions, an annual water make-up will be required, consistent with zero-discharge operation of the facility. For an average precipitation year of 18.2 inches, the calculated water make-up would total 12,630,000 gallons. Desi~ for Maximum Solution Capacity ZYre ,rux;,mm, solution surge capacity, designed to pmtec-t against discharge under the most severe conditions, is provided by excess capacity in the oversized pregnant pond, fluid volume within the heap, further excess volume up to the back-up dam behind the pregnant pond, aryl the back-up emergency porn at the base of the dam behind the pregnant porn. Zhis is the same max;,m,m solution surge capacity and system maintained during 1988 operations. Design for maxianan solution capacity is based on a 100-year, 24- hour maximum precipitation event of 3.5 inches of water, in addition to other factors required for sizing of surge capacity. nt~x;,m m, solution capacity is designed based on the following sequence of events: Day 1-6: Steady precipitation at 0.1"/day. No evaporation achieved by heap sPraYir~4• Day 7 100-year, 24-hour maxirmmm precipitation event. No evaporation achieved by heap spraying Day 8-X: No precipitation. P,mg~s down - no evaporation achieved. Complete de-saturation of heap modules order spray (10 US gallons/ST rock). It is further acc~mrx; that the pregnant pond will regn;r+~ 200,000 US gallons as working volume. The max;imim asSRmied recovery plant down-time is one operating day arri it is assumed that excess solution will be kept in barren pond inventory to pE+*~++; t spraYirg during down-time. 2