Abstarct: Mining sector has a significant role in economy of any country. Moreover, mining operations can cause the various environmental problems such as the contamination of surface and groundwater, soil pollution, the death of creatures and the detrimental impacts on human life. Whenever, the mining operations are carried out below the groundwater table, the large amount of groundwater from the surrounding strata will flow towards the mining excavation. This effect can create a number of water related problems affecting in design, safety, erosion of mining equipments, and economic viability of the mining operations. Prediction of groundwater inflow into open mines and the establishment of an appropriate dewatering system is one of the main problems for designing and development of mining operation. Once pumping has stopped and the mine has been completed, the water level will return to its equilibrium position or original level prior to mining operations. Where the groundwater covers the materials containing pyrite, it becomes contaminated. As a result of the mining operations, the huge volume of the waste are produced that the appropriate management of these wastes is one of the major problems in environmental point of view. These wastes include the overburden waste, dump, mineral processing wastes, tailing and waste dumps. The oxidation of the sulfide minerals, mainly pyrite, in waste dumps of iron mines is an essential environmental problem. In the presence of oxygen and water, the pyrite is oxidized and the acid mine drainage (AMD) is generated. The discharge of the AMD into surface and groundwater resources can make some harmful environmental problems. The main characteristics of the AMD are high concentrations of sulfate and heavy mextals, concentration of Fe+2 and low pH. Since the comprehensive environmental studies have not been done in Iranian mines, therefore such studies in an iron mine are the main objective of this research. Sangan Iron Mine which is known as the second largest iron mine in Iran; is located at 300 km in southeast of Mashhad. The most important objectives of this research in the study area have been formulated as follows: • Modeling of the groundwater inflow into pit of the North C anomaly • Modeling of the groundwater rebound in pit of the North C anomaly • Modeling of the pyrite oxidation, acid generation and transportation of the oxidation product's from the waste dump of the North C anomaly. To achieve the goals, the performed studies at the present research have been presented as bellow: after performance the literature review in the field of environmental hydrogeology in Chapter 1, in consequence, Sangan iron mine has been introduced in chapter 2. The modeling of the pumpage data has been performed in order to recognize the potentiometric surface prior to opening mine and calibration of model as well in chapter 3. In chapter 4, the prediction of groundwater inflow rate into pit of the north C anomaly and the modeling of groundwater recovery process have been done. The modeling of the pyrite oxidation and generation of AMD have been studied in chapter 5. Finally, the obtained results and suggestions have been brought in chapter 6.