Cut-Off Walls and Dewatering Systems as an Effective Method of Contaminated Sites Reclamation Processes

Abstract

There are several engineering disciplines, where construction of cut-off walls is commonly used, these are mainly, foundations engineering, hydroengineering structures, deep dewatered excavation, land reclamation or landfill containment systems. The construction of vertical barriers is mainly based on cut-off wall mono or two-phase technology with the use of bentonite and cement mixture as a filling material. The paper considers two case studies where vertical bentonite barriers were applied to prevent further pollution of the soil-water environment deriving from municipal landfills. The remedial works on site consisted of additional solutions like leachate collecting drainage, ditches restoration, as well as landfill’s body engineering and bioengineering of landfill slopes. On the examples of two restored landfills, it is proved that appropriate investigation of ground conditions and comprehensive earthworks design are crucial for effective soil-water environment quality improvement. The construction and working condition of the proposed system is presented and analyzed. The influence of proposed engineering methods on environment conditions was conducted on the piezometric recording basis, laboratory tests and site investigation, which gave information on contamination level and direction of pollutants migration. Based on the groundwater monitoring results several maps of groundwater level changes were created. The monitoring data revealed improvement of water quality in almost every piezometer after only a few years since the soil and groundwater protection system has been installed at the site. The system’s effectiveness results are confirmed by long term monitoring of groundwater samples of which such indicators as organic, nitrate and heavy metals concentration has decreased significantly over time. It is shown how combined civil and environmental engineering works can play a significant role in reclamation processes.