An important ecological aspect of work of all mining enterprises that use drilling-and-blasting mining of rock mass with the application of industrial explosive agents (poremite, granemite, igdanite and others) based on ammonium nitrate is inevitable contamination of drainage waters with nitrogen compounds (ammonium ion NH4+, ion nitrate NO2-and ion nitrate NO3-). These drainage waters that are pumped out during drainage of deposits as a rule are discharged into surface water bodies which leads to their contamination. Execution of stringent requirements of environmental regulation based on protection of water bodies from contamination with nitrogen compounds during discharge of drainage waters dictates the need for selection and development of optimal from the standpoint of eco-economic positions technology of purification. Researching of formation processes of their chemical composition based on contaminated compounds and volume of drainage waters that are subject for cleaning for mining enterprises is necessary for this purpose. This article explores formation processes of chemical contamination of drainage waters with nitrogen compounds that are done in conditions of large pit of construction industry for the purpose of determining possible drainage water purification technologies. Results of research are used by the investigated enterprise during development of drainage water purification technology from nitrogen compounds and optimization of water treatment facilities work depending on the natural and man-caused factors taking into consideration specific conditions of enterprise and its infrastructure (connection of mass of nitrogen compound losses with the seasonality of water inflows, volume of rock mass, types of applied explosive agents).