LANDFILLS: Owners Can Find Benefits Of Building In Phases

Juan Vargas

Today the majority of new and expanding landfill projects are being developed in phases. Typic-ally, one area of the site is filled while the next area undergoes fine grading and liner construction and the subsequent area is being excavated. While this approach offers numerous advantages to landfill owners and operators, the public ultimately benefits most through more competitive tipping fees and superior facilities.

Phased development has ma-tured along with landfill disposal services, evolving from a simple sketch showing the general fill direction to a comprehensive planning and engineering effort. The spotlight of the permitting process has made regulators, owners and designers alike focus not only on the completed project but also on the approach. The overall objective of this approach is to optimize fa-cility operations and provide the lowest possible life cycle cost for the project.

As tipping fees begin to become more price competitive, a comprehensive phased development effort offers the private owners and operators the most efficient opportunity to optimize their profit margins. With all budget allocations and limitations in mind, publicly owned landfills can allow municipalities and various other public entities to plan ahead in scheduling project development and to adjust their collection and disposal rates ac-cordingly.

Not all of the benefits from the phased development procedures are financial, however. New landfills are usually large facilities with longer operating lives. If the post-closure maintenance period is in-cluded in the development stages, some of the facilities will have a total life in excess of 70 years, which is longer than most typical civil engineering structures. Phased development provides a road map to ensure the continuity of design and the operation criteria that are key to the successful completion of a phased development project.

A phased development effort re-hearses, either on paper or on the computer screen, the construction and filling of each proposed landfill phase to identify potential design and operation problems such as steep temporary cuts or waste slopes which will probably be required during the life of the facility. Slopes need to be analyzed for stability. Since some site areas might be unaccessible at different times because of construction or operation procedures, provisions would need to be made to prevent access limitations. Such problems typically are not obvious unless the operators analyze the project phase by phase.

Multiple phased development schemes can be studied more efficiently by using Computer Aided Drafting and Design (CADD) to choose the best alternative available. Computer Aided Drafting and Design optimizes the landfill de-sign, which increases protection for the environment.

CADD provides the user with well-defined limits and other design information for each phase of the landfill. In addition, the construction details are the same for all phases of the project. Augmenting the design data with existing re-cords as each phase is completed produces a combination of data that can tie elements of adjacent phases together and facilitate construction of subsequent phases. The result is sound, cost-efficient construction.

The major impact of phased de-velopment allows the operators to control available disposal capacity. Estimating disposal capacity for landfills is as important as taking inventory in a commercial est-ablishment. Having too much or too little is not good business practice. Since new landfill facilities have a long, useful life, maintaining a constant capacity surplus throughout the life of the facility can be onerous for the landfill op-eration.

To overcome the problem of having too much or not enough disposal capacity, phased development can be expanded beyond a design approach to reach its full potential. By linking the CADD design files with the landfill operation database which might include daily waste tonnage, excavation volumes and daily cover requirements, owners and operators gain valuable information about the entire landfill operation such as remaining ca-pacity, up-to-date project cost on a per ton basis (permitting, construction, operation and closure) and impact on project schedule due to fluctuations on daily waste tonnage.

In this way, phased development achieves its ultimate objective and becomes a site development tool. On-line interaction then allows owners and operators to create and evaluate "what-if" scenarios, and real-time feedback gives them a handle on the life cycle cost over the duration of the project. In to-day's market, phased development in this expanded form offers operators opportunities to efficiently manage their day-to-day activities.