WASTE SETTLEMENT MONITORING AND PRE-SETTLEMENT GRADING PLANS
Modern Landfill, Inc.
Lewiston, New York
Short term and long term waste settlement reduces the fill elevation and flattens slopes at landfills. Modern Landfill, Inc. (Modern) retained DE to prepare Pre-Settlement Top of Waste Grading Plans that would result in settling of the slope to 3H:1V over a specified time period to regain lost airspace without re-filling outside slopes post settlement. A preliminary settlement model and pre-settlement grading plan was presented to the New York State Department of Environmental Conservation (NYSDEC). The NYSDEC concurred with the settlement model and allowed for the use of pre-settlement grading plans.
The model considers primary consolidation and secondary settlement due to biological decay. Primary settlement is estimated using Terzaghi’s one dimensional consolidation theory while secondary settlement is estimated using a hyperbolic function developed by analyzing historic topographic mapping at site specific control sections on the landfill spanning more than fifteen years.
Seven years after initiating the pre-settlement grading strategy, DE revisited and checked the average degradation strain parameters in the secondary settlement function for two specific sections at the landfill. DE found the degradation model parameters closely predicted secondary settlement when compared with the field measured values, validating the decomposition function.