A typical SCS landfill expansion project contains an engineering evaluation and analyses addressing important technical considerations which include the existing hydrogeologic conditions, global slope stability, Landfill base settlement, geomembrane compression and strain, leachate pipe strength, useful life of the existing infrastructure and utility lines, stormwater management, leachate and landfill gas system expansion.
This case study site, it shows that the vertical or piggyback expansion of a landfill is a unique way of solving landfill airspace shortage problem. Its feasibility is always site specific and depending on the existing waste types, slopes, liners, design capacity of leachate and gas collection, and stormwater management systems. In addition, the landfill design needs to be thoroughly investigated, engineered, and operated.
From the results of the global final slope stability and the landfill base settlement analyses, it concluded that a vertical expansion at the case study landfill will not increase the risk to human health or the environment over the existing regulatory approved conditions. A vertical expansion provides the landfill owner with an opportunity to increase the landfill volume and provide the residents with the maximum service life within the existing footprint of the permitted Landfill. This maximization of available resources does not expand the environmental footprint of the site and provides better environmental protection and at the same time creates a sustainable landfill site.
A vertical expansion provides the landfill owner with an opportunity to increase the landfill volume and provide the residents with the maximum service life within the existing footprint of the permitted Landfill. This maximization of available resources does not expand the environmental footprint of the site and provides better environmental protection and at the same time creates a sustainable landfill site.
This case study was presented at ISWA 2016.
Dynamic compaction is a construction technique that increases the density of soil/waste deposits by dropping a heavy weight at regular intervals to consolidate and improve the geotechnical characteristics of the deposit so that it can be suitable for redevelopment. This construction technique can be used to transform otherwise undevelopable property, such as old landfill areas, into developable property.
Most soil types can be improved by dynamic compaction; the method is particularly well suited to non-organic, irregular fill, where variable characteristics such as solid wastes are present. Field conditions and several other parameters are considered when designing and implementing dynamic compaction programs to keep costs in line. The primary considerations include, but are not limited to, waste delineation, distance from the ground surface to ground water, waste thickness, minimum energy, and selection of dynamic compaction parameters.
The following factors and associated costs should be evaluated if dynamic compaction is to be considered:
Major change orders and environmental impacts can be expected if the plan does not address these factors.
If you decide to consider dynamic compaction in your redevelopment project, having onsite construction quality assurance monitoring during the process is important. CQA monitoring will verify that the work is implemented as designed and permitted, and that proper techniques are used to make sure the proper distribution of energy into the ground is taking place. The CQA monitor will also check to see that the final configuration of the fill is achieved, a safe working environment is maintained., and that ground vibrations are monitored near adjacent structures to to prevent structural damage.
For developments involving construction of buildings over a dynamically compacted areas, a combustible gas barrier layer is generally required below the building footprint to safely collect and vent subsurface combustible gases (i.e., typically methane) to the environment. Construction costs associated with a combustible gas barrier layer should include the following:
In summary, dynamic compaction is a proven geotechnical construction engineering method that can be used to improve certain landfill areas to support redevelopment. SCS Engineers has completed many projects of this nature and is ready to serve and help to bring your project in service.
Ali Khatami, PhD, PE, LEP, CGC, is a Project Director and a Vice President of SCS Engineers. He is also our National Expert for Landfill Design and Construction Quality Assurance. He has nearly 40 years of research and professional experience in mechanical, structural, and civil engineering.
Dr. Khatami has acquired extensive experience and knowledge in the areas of geology, hydrogeology, hydrology, hydraulics, construction methods, material science, construction quality assurance (CQA), and stability of earth systems. Dr. Khatami has applied this experience in the siting of numerous landfills and the remediation of hazardous waste contaminated sites.
Dr. Khatami has been involved in the design and permitting of civil/environmental projects such as surface water management systems, drainage structures, municipal solid waste landfills, hazardous solid waste landfills, low-level radioactive waste landfills, leachate and wastewater conveyance and treatment systems. He has also been involved with the design of gas management systems, hazardous waste impoundments, storage tank systems, waste tire processing facilities, composting facilities, material recovery facilities, landfill gas collection and disposal systems, leachate evaporator systems, and liquid impoundment floating covers.