Gravity Driven Dewatering Systems For Landfill Expansion
Free (open access)
183 - 191
S. A. Smith. & J. A. Smyth
A landfill site near the east coast of the United States in North Carolina has utilized a permanent gravity driven ground water dewatering system to construct lower liner grades, decrease a soil deficit at the site and increase landfill capacity. A variety of methods based on published data and field investigations were used to determine the design and impact of the dewatering system for the site. The design of such systems is highly dependant on the hydraulic conductivity of the aquifer and should be scrutinized based on the extent and impact of the proposed dewatering system. The final design of the dewatering system should include a judgement of the collective aquifer testing results to adequately size the system and to evaluate the schedule of implementation based on the time required for full drawdown. Keywords: aquifer dewatering, landfill construction. 1 Introduction The protection of ground water is an integral part of the design of a solid waste landfill. One of the fundamental concepts of modern landfill design has been to prevent the migration of leachate (stormwater that has been in contact with the waste) into the ground water below the landfill. U.S. Federal regulations (40CFR258.40) require that modern landfills include a low permeability soil liner and a flexible membrane liner to prevent leachate migration into the ground water below. In certain states, this concept is enhanced by an additional separation requirement between the seasonal high ground water table and the bottom of the landfill liner system. In North Carolina, state regulations require a separation of four (4) feet between the uppermost aquifer and the liner subgrade. In shallow aquifer systems, this requirement results in construction of the landfill
aquifer dewatering, landfill construction.