The Numerical Simulation Of Impact On The Groundwater Environment By A Power Plant In Tianjin

In the process of engineering construction and production, carrying out groundwater environment impact assessment and prediction will help the protection of the groundwater environment. The thesis is based on a job of environmental impact assessment on groundwater in a thermal power plant in Tianjin and the job is undertaken by Environmental Geology Research Institute of Tianjin. In the paper the method of numerical simulation of groundwater is adopted to simulate and forecast the environmental impact of groundwater flow and water quality in the process of project construction and operation.The main layers of groundwater exploitation in the evaluation area are the deep fresh water underlain the shallow saline water. The evaluated project neither exploits groundwater in the process of construction and operation or discharges wastewater and domestic sewage, so it shall have a little impact on the local groundwater environment under normal circumstances. But on the condition of abnormal operation the power plant may cause groundwater pollution in case of leakage of an ammonia tank or a waste water pool.The thesis is conducted on the base of some field hydrogeology surveys, including hydrogeology survey, hydrogeology drilling pumping test, water seepage test and so on. By the analysis of the hydro geological conditions in the study area and the characteristics of the evaluated project,the author established the corresponding hydro geological conceptual model and groundwater flow numerical model, and conducted the groundwater seepage field numerical simulation using MODFLOW module of GMS software. The verificated flow model preferably reflects the movement characteristics of the groundwater system. Based on the flow model, the authored established a solute transport model with some tracer simulating factors of pollutants, and solved the water quality model using MT3 DMS module of GMS software, and then forecasted the migration of pollutants in the study area according to three different kinds of simulation conditions, analyzing and predicting the pollution risk.The research results shows that in an abnormal operating or accident condition, if a liquid ammonia tank leaks, the pollution halo scope will continue expanding to the maximum t migration distance of 146 m, and the pollutant concentration will badly exceeds the limit indexes of the Quality Standard for Ground, with the maximum scope of 11016 m2, which will have a big risk of polluting groundwater. In an abnormal operating condition, if the pollutants in the industrial wastewater treatment station leaks, the pollution halo scope will continue expanding to the maximum migration distance of 105 m, but the pollutant concentration will be below the limit indexes, and the risk of groundwater pollution can be acceptable. In case of pollutants leakage, only the unconfined aquifer can be polluted obviously, and the scope will not exceed the factory ranges in 30 years.This paper is helpful to the groundwater environment protection.