SILT REMOVAL FROM A RESERVOIR IN HEEL, THE NETHERLANDS

摘要

A former gravel pit is used as a reservoir for a nearby water treatment plant. A layer of fine silt has been deposited over the gravel that remained in the pit and this significantly reduces the permeability of the gravel. For properly operating the plant, this silt had to be removed with as less impact on the environment as possible. To investigate the impact of dredging this material, a trial project was executed first. A wheel dredger with a specially designed hood around the wheel was put to use. The hood functioned extremely well; no turbidity was observed outside the hood. The silt needed to be dumped back in the reservoir at 30 m depth, and in order to avoid too much contamination of the reservoir and spreading during dumping, a silt screen was utilized. Especially the use of the screen was innovative since no experience with such a function and length existed. The silt screen caused initially some operational problems, but by making adaptations to the screen it functioned very satisfactory. After successfully completing the trial test, the permeability of the gravel layer was found to be increased by 40%.