Optimal location of cutoff walls for seawater intrusion

In this paper, the simulation–optimization method is used to study the optimal location of cutoff walls for seawater intrusion. The optimization model is based on minimizing the chlorine concentration of two water sources after 50 years. In order to reduce the computational complexity, a Kriging surrogate model simulation is coupled with the optimization model. Finally, a hypothetical case is used to evaluate the accuracy of the surrogate model and the performance of the optimization model. The results show that the outputs of the Kriging surrogate model and the variable density groundwater simulation model for the same cutoff wall design fit well, and the average relative error of the two outputs is only 2.2% which proves that it is feasible to apply the Kriging surrogate model to this problem. By solving the optimization model, the location of the cutoff wall which minimizes the sum of chlorine concentration of the two water sources after 50 years is obtained. This provides a stable and reliable method for the site selection of cutoff walls for future projects intended to prevent and control seawater intrusion.

A change model of the hydraulic characteristics of the territory occupied by the landfill of solid industrial and domestic waste

Introduction. A landfill of solid industrial and domestic waste (LSIDW) is a source of negative impact on the environment. Although landfills have coverings, and they are equipped with engineering systems designated for the capturing and treatment of the biogas, LSIDW landfills still have a negative impact on subsurface and surface waters due to the spread of leachate. The purpose of this work is to obtain predictive data on changes in the hydrogeological characteristics of the territory of Salaryevo landfill, and to develop a simulation model to assess the application of technical solutions in the course of the landfill reclamation. Materials and methods. Processing Modflow is the software designated for the 3D modeling of filtration and transportation of pollutants. An engineering report based on the engineering and environmental surveys, performed by JSC MosvodokanalNIIproekt in the Salaryevo landfill and its environs in 2017, served as the input data designated for a simulation model. Results. Processing Modflow software allowed to consider three options of cutoff walls, tailored to this landfill. The installation of cutoff walls on the east and west sides of the landfill, to be performed with regard for the sorption function of the cutoff walls, is the most effective solution. The results have shown that the cutoff walls, installed to prevent the leachate from seeping, can potentially reduce the area, exposed to the impact, by 500 m. Conclusions. It is recommended to install a cutoff wall in the west and a sorption curtain in the east in the course of recultivating Salaryevo landfill; this solution will ensure the containment of the leachate inside the landfill and prevent its spreading.