New Contaminated Water Pond Nº 2 (BAC2) and Industrial Area Drainage System

The expansion of the zinc facilities will occupy the existing BAC2 (contaminated water pond), resulting in the construction of a new contaminated water pond. Furthermore, the dimension of the new BAC must assure the storage capacity to cope with a rainfall event with an adequate return period (T=100 years).

The layout of the new BAC2 foresees its division in two basins, in order to assure a permanent storage pond. The required capacity for this solution is 41 600 m3, of which 7 000 m3 are for sludge storage. The BAC2 was designed assuming that the cleaning operations will be carried out with a sludge pump assembled in a raft. The sludge is pumped to geotubes, where the solids will be retained, and the water will return to the BAC2. 

Since the water and sludge collected into BAC2 are chemically active, it was necessary to guarantee its imperviousness. For that purpose, the basins will be delimited by reinforced concrete structures, with a suited exposure class, and its bottom will be waterproofed with a HDPE geomembrane. The concrete structures will consist in conventional gravity retaining walls, 5,90 m high, counterfort walls, 8,40 m high and composite walls, with total heights between 5,80 m and 8,30 m.

The everyday management of the water level in the basin will be done using a pumping system (the same of the existing BAC), and the water will be pumped to the tailings tank and from there to the IRCL. However, a spillway was also designed to cope with emergency situations. 

The BAC2 substitution also requires the reformulation of the existing drainage system of the industrial area.