Galamsey Mining In Obuasi evertseadvies . Mining activities in Obuasi, Tarkwa pollute 262 rivers . Aug 15, 2011 · A baseline study conducted by the Centre for Environmental Impact Assessment (CEIA), Ghana and WACAM in 2008, has revealed that out of the 160 streams and rivers in the Obuasi mining area, 145 are perceived by residents to be polluted by the operations of mining companies and ...