landfilldesign.com
Innovative Landfill Cell Design
| In a traditional sawtooth design, leachate collection pipe is installed at the bottom of each lateral, and surrounded by gravel with geotextile wrap. The hydraulic performance of traditional landfill bottom liner systems significantly limits leachate recirculation and full-scale bioreactor operations. In addition, traditional designs require extensive coordination between specialized subcontractors, resulting in long construction schedules and high costs. |
The innovative design features a high flow tri-planar geonet in a configuration that eliminates the leachate collection lateral pipes, and a precast drop inlet that collects leachate from both the leachate collection and leak detection systems. The drop inlet design eliminates the need for pipe penetrations and their accompanying boots associated with more traditional liner penetrations and seaming techniques.
The overall performance benefits of the new bottom liner design over traditional designs include the significant increase in the hydraulic performance of the liner system. The form and properties of the tri-planar geonet used in the leachate collection system greatly improves the hydraulic characteristics of the liner system. The robust collection system can more easily accommodate increased hydraulic loading rates resulting from leachate recirculation associated with bioreactor operations. Another system benefit includes the associated decrease in threat to the environment, due to very low expected maximum head on the liner. Modeling results show that less than a quarter of inches of head are expected on the liner. The potential for leakage has been reduced by having only one liner penetration and by improving the weld quality with the drop inlet design. The orientation and access of the drop inlet results in high quality welds, which greatly minimizes the potential for leachate leakage. Welding the penetrated geomembrane to the drop inlet permits the weld to be tested, which is not possible with traditional pipe.
Replacement of traditional collection laterals with a tri-planar geonet liner system has led to reduced construction complexity, duration, and costs. The elimination of collection laterals greatly simplifies the grading plan, and therefore enabled grading to be accomplished by landfill personnel and reduces construction time. In addition, the simplicity of the bottom liner system allowed owners to perform major elements of the construction without risk of impacting their contractors. Another significant innovation incorporated into the new bottom liner system, which allows a modular construction process, is the development of a composite HDPE/concrete precast drop inlet for leachate conveyance from within the lined cell. The HDPE-lined top surface of the drop inlet easily facilitates the equipment that is necessary to weld the landfill liner directly to the top surfaces of the drop inlet. Significant reductions in project duration (over 60%) and cost (over 25%) over traditional bottom liner designs were achieved for these two projects.
The innovative design features a high flow tri-planar geonet in a configuration that eliminates the leachate collection lateral pipes, and a precast drop inlet that collects leachate from both the leachate collection and leak detection systems. The drop inlet design eliminates the need for pipe penetrations and their accompanying boots associated with more traditional liner penetrations and seaming techniques.
1) Evaluation of creep reduction factor
2) Evaluate the hydraulic conductivity of a triplanar at two construction stages ( double sided | single sided )
Below is a list of papers and reports referred to above. You can download the full text/abstract in *.pdf (Acrobat) format. For more related references on the subject, please visit www.landfilldesign.com.
DeVita, J.L. and Arnold, J.P. (2001), “The design and construction of an innovative landfill bottom liner system”, Proc. of the 8th International waste management and landfill symposium, Sardinia, Italy.
Copyright 2001 Advanced Geotech Systems. All rights reserved.