Construction Sand production is done mostly by small mining companies and, because its price is distance dependent, it must be mined as near as possible to its final use, the cities, causing locational and environmental conflicts with economic and socio-environmental impacts. The Piranema Sand District is no exception. Located at 70 km from downtown Rio de Janeiro city, Brazil, its 70 small mining companies are the main suppliers of the Rio's Metropolitan Area, with 90% of its demand: a critical success factor for major projects like the World's Soccer Cup in 2014 and the Olympic Games in 2016, among others. Piranema's sand mining consists of dredging in submerged open-pits, causing a drastic landscape change and exposure of the aquifer, reason of most conflicts with government agencies. This research project was set with the purpose of improving environmental performance of these mining companies. It consisted of an environmental assessment based on ISO 19011:2002. The results were used to develop a Training Program ministered to the miners and their employees by Geosciences Institute professors. This Training Program had its effectiveness verified by another environmental assessment., The final results were very expressive and showed the improvement of Piranema's mining companies' environmental performances due to the Training Program. They also showed that the environmental assessment of mining activities based on ISO 19011 was effective on pointing out the subjects to be included in the courses, and the Training Program evaluation as well.