The Mine Waste Management Facility of Perama Hill goldmine has been designed according to the highest environmental performance standards & regulations, as laid out by the European Union and Greek legislation. Notably, EU/21/2006 describes in detail every step of the process of the mine’s operation.
Specifically for the management of the mine waste, the procedure is as follows:
After the leaching of the excavated ore with sodium cyanide solution and with carbon presence for the recovery of gold and silver, the remaining slurry goes through the stage of cyanides destruction according to “INCO” method (SO2+O2). After this process the total cyanides content within the liquid phase of the slurry will be less than 1ppm (at least ten times less than the safety limit set by the aforementioned EU directive). From the cyanide destruction tank the waste sludge goes through a condensation and dewatering process via filter press units, before it is then transported and deposited in the specially designed area of the MWMF, complete with composite lining system bedding and under drainage systems to manage and direct upstream flow as well as seepage into the downstream collector sump.
The design of the MWMF has been completed under the “zero discharge to the environment” principle, in full compliance with the European Union directive for Best Available Techniques (2006).
Filter Press Unit
The filter press is a mechanical unit that compresses the processed slurry after the stage of cyanides destruction. In the Perama Hill Process Plant, there will be a series of filter presses connected to account for the daily production needs, as well as the needs for recycled water from the filter presses.
Mine Waste Management Facility – Main Design Characteristics
The area is limited by four embankments, which will be constructed around it (east, west, upstream and downstream), and will ensure the permanent and environmentally safe disposal of the mine processing waste material.
The main embankment (downstream) will be a typical stonewall construction, and for its erection as with the rest of the embankments, material coming from the same area.
Design to withstand earthquake of magnitude 8,1 Richter.
Total height will be 40m and elevation of 195m.
For the water management a surface water collection pond will be constructed downstream of the construction. Surface runoffs of the greater catchment area will be collected by the upstream embankment and through peripheral channels they will be collected downstream.
Sealing – Area’s lining system
The sealing of the MWMF area will be achieved by a combination of sealing materials covering the inside surface of the area as well as the upstream surface of the embankments, which includes: GCL (Geo Synthetic Liner) of very low permeability (1x 10-10 m/sec) topped by HDPE geomembrane, 1,5mm thick and with total permeability of 1x 10-10 m/sec.
An over drainage system will be placed above the geomembrane in the MWMF basin area so as to reduce the head across the composite lining which reduces seepage through any defects in the composite lining system and assists in the rate of consolidation of the filter cake.
The surface drainage of the greater catchment area will be collected by an embankment upstream of the MWMF basin and through peripheral water channels around the basin as well as diversion embankments downstream of the construction, surface waters will be directed into the collection pond or downstream of the area, depending on the weather conditions.
After the cyanides destruction process INCO (SO2+O2), the dewatered filter cake will be transported by trucks into the modified basin area of overall net volume capacity of 6.9 Mm3.
After the end of the mining activity the rehabilitation works of the MWMF will begin, covering it with oxidised waste rock, geomembrane and finally with fertile cap soil. On the vegetation cap soil various endemic plants will be planted.
After a period of at least 5 years of environmental monitoring, the project area will be returned to the previously agreed land use.