Sanitary landfills--Linings

Landfilling, by all indications, will continue to be the predominant method of solid waste disposal. Traditional civil engineering drainage medium (i.e. sand or gravel) are being replaced by geosynthetics which are much thinner in an effort to create more usable volume for waste. This study examines the effect of compressive creep of geonets as used in leachate collection and detection systems, and how it affects in-plane drainage. HDPE geonet was subjected to a compressive load of 110 psi. The in plane flow rate of municipal solid waste leachate was measured, as well as the change in thickness, for 120 days. In addition, geonet samples were placed between two pieces of HDPE geomembrane. These samples were subjected to a normal load of 140 psi for 120 days. The samples were then inspected for sign of geonet imprint into the geonet, or for strand layover.

Many modern landfills are constructed with double liner systems. Leachate leakage rates through double liner systems are calculated using recently developed formulations which are theoretically correct for leakage detection system (LDS) materials that have unrestricted lateral flow properties. But their applicability to geonets, the most commonly used LDS material, has yet to be determined. In double liner systems, the leakage through the primary liner, the properties of the LDS material, and the slope of the LDS determine the flow patterns in the LDS. These flow patterns are then used to determine the amount of leachate, if any, which leaks through the bottom liner into the ground. This thesis describes the experimental determination of the flow patterns in the geonets and their relationships to established design formulations.

Modem technology has led to a new generation of landfill liner systems that are
highly efficient at intercepting and removing leachate. Many of the modem liner systems
are so effective that little or no leakage occurs through the liner systems. What leakage
may occur is so minimal that, although it can be theoretically predicted, it cannot be
measured, i.e., the resulting groundwater concentrations are well beneath minimum
detection levels of available monitoring well technology. In addition to being highly
effective, some modem liner systems are constructed with two liners separated by a
drainage medium which detects and removes any leakage through the top liner.
These significant improvements in liner system technology have led many landfill
designers, operators, and regulators to question the necessity for current monitoring well
practices. Currently, landfills are required to have a large number of monitoring wells,
and the associated large installation, sampling, and testing costs are inevitably reflected
in higher tipping fees or higher taxes. In either case, the costs are borne by the public.
If the number and frequency of sampling of monitoring wells could be reduced,
significant cost savings could be realized, and the money saved could perhaps be better
spent elsewhere.
This thesis reports the results of research conducted at eleven landfills constructed
with modem landfill liner systems to determine the actual and probable efficacy of the
role o: monitoring wells, and conducts a cost-saving analysis to evaluate whether funds
would have been better spent elsewhere.