There are two ISR Au projects that have been running for many years, one of them on the outskirts of Ekaterinburg. The key factors in appraising a mineral deposit for in situ recovery (ISR) are the hydrogeological characteristics of the deposit, for if the ISR system cannot be confined it is not going to be viable environmentally. However for the right deposits it is a low cost solution to mining, while cutting out all the infrastructure and costs involved in conventional mining, which also itself has (better known) environmental issues.

You could contact Nikolai Savenya at Urals Geotechnical Company who have worked on many ISR projects.

The technology is used in Russia with already 4 deposits in weathering crusts.  Word is the main advantages of Underground leaching are:

• leaching with a cyanide free solution;
• development of poor and off-balance ores with a content of from 0.5 g/t;
• development of fields with complex geological conditions or confined to very wet rocks or for areas with water scarcity;
• increase the degree of extraction at the expense of small and fine gold;
• small (1-2 months) the timing of input fields in operation;
• depth of the ore bodies is not important (the depth from 10 to 100 m);
• In situ leaching is a more environmentally friendly method than traditional methods of mining gold;
• improvement of technical and economic indicators of mining;
• a cheaper way of gold mining than heap leaching.

You make some broad statements that you do not support, and may not be true.

• leaching with a cyanide free solution; You can use cyanide for ISR, but as mentioned by others it needs to be determined by the specific deposit and ore body.
• development of poor and off-balance ores with a content of from 0.5 g/t; again this needs to be determined by the specific ore body and is not a global truth.
• development of fields with complex geological conditions or confined to very wet rocks or for areas with water scarcity; This actually maybe a reason ISR does NOT work.
• increase the degree of extraction at the expense of small and fine gold; Actually small and fine gold would be the first to be extracted as all leaching is a particle surface action and leaching can contaminate the surface of large particles preventing further leaching.
• small (1-2 months) the timing of input fields in operation; again this is a specific ore body issue and can be false, especially as you need to know a whole lot more about the ore body before you start.
• depth of the ore bodies is not important (the depth from 10 to 100 m); Depth can be a very critical factor as to pumping out the lixiviant is a hydraulic head issue. Also depths greater than 100m may be more accessible to ISR, while shallower deposits more amendable to conventional mining.
• In situ leaching is a more environmentally friendly method than traditional methods of mining gold; Again a very ore body specific issue, this has been one of the big issue in enhanced oil recovery processes which some have complained are doing significant environmental damage.
• improvement of technical and economic indicators of mining; ore body dependent again.
• a cheaper way of gold mining than heap leaching; ore body dependent again.

ISR has a great potential, but it needs to be evaluated for each ore body and can not be assumed to be the best overall.

I can use cyianide and i can use hypochlorite - it is not so toxic. Some place in Ghana doesn't has body just a scattering of fine gold - washing is not caught it.  It needs to understood where (of course not everywhere) to use it (using mineralogy as the smaller the gold pieces/grain the better it leaches.

Sometimes, in the field, it is not possible to know exectly what is the place in front of you. Very often geologist spend money and time and give incorrect forecast. You can understand it when you open pit and start to wash (before you spend money on more classic prospecting.

Leaching does no have to be with cyanide. After the extraction process is a process of regeneration.