How to save millions over the life of your landfill
Guest blog by Michael White, Discipline Leader of Civil Infrastructure (Australia), Meinhardt Australia
The Victorian EPA’s Best Practice and Environmental Management (BPEM) guidelines released in 2010 requires all new landfill cells (type 2 – municipal solid waste) to have a composite liner system. While it was initially thought that this requirement would only impact the capital cost of construction (typically around $750K, depending on the Cell area and material specification) and not the expected landfill airspace and subsequent projected revenue, in reality, the requirement does significantly compromise the available airspace of a landfill.
Under the BPEM, the composite liner system must comprise a 1,000mm-thick compacted clay liner (CCL), 2mm High Density Polyethylene (HDPE) geomembrane liner and a geotextile cushion protection layer.
Additionally, existing unlined cells that have been temporarily capped may no longer be exempt from the latest BPEM requirements as they could receive additional waste in the future, once an adjacent new cell is in operation.
Given the possibility of this scenario, the EPA requires all new waste filling and leachate generation to be stored, captured and treated in accordance with the latest BPEM. This of course, is to ensure that no additional leachate generation is allowed to permeate into the existing unlined cell, which may cause potential risk to the receiving or surrounding environment.
There are two main options used to mitigate the risk of future waste or leachate entering an existing non-BPEM cell.
These include using a:
1. Vertical separation bund (see figure 1); or
2. Flexible liner across the existing waste face/cover (see figure 2).
The initial opinion that installing composite liners would only impact construction costs was based on the view that the addition of an HDPE geomembrane and geotextile cushion liner would not increase or affect the overall thickness of a liner. However, as shown in both figures, the available airspace is in fact, affected.
Thus, capital costs relating to the installation of the BPEM compliant liners coupled with a loss of airspace will no doubt cause major budget issues and constraints to the landfill operator.
Time and budget savers
With a bit of practical imagination, these potential compromises can be avoided.
Some suggestions include:
1. Maintaining workable batter grades and offsetting between waste operations and construction works to avoid relocation of waste. Cost savings: more than $100,000.
2. In achieving minimum/maximum grades and layer thickness, design layers can be compromised or relaxed to avoid further re-work and placement of additional material. A lot of money and time is lost if a contractor has to meet design levels when working on a landfill surface that is under long-term settlement. Cost savings: more than $100,000.
3. Thorough record keeping (as built data) and reporting by the Geotechnical Inspection and Testing Authority and the Third Party Construction Quality Assurance can shorten authority approvals significantly. This is crucial for the project, minimising delays to on-site waste operations and/or delays to the commencement of subsequent staged works.
As indicated in points 1 to 3 above, the time and dollar factor to manage your landfill can easily creep into the millions given the potential loss of airspace, productivity on-site and need for authority consultation.
Maximising these savings
To save millions over the life of a landfill, there are several steps that a landfill operator and design consultant should take.
1. Review the landfill master plan to identify which non-BPEM cells will interface with the new BPEM cells.
2. Seek expert advice and confirm the required arrangement between booth cells.
3. Avoid overfilling the existing waste face batter – preferably of a maximum grade of 1V:3H – to allow access for future construction works of option two
4. If you’ve chosen option two, monthly surveys to monitor the behavioural trend of waste settlement should be undertaken to assist the landfill design consultant with resolving expected forces on the liner.
5. Again, with option two, test pits should be conducted during construction to verify constructed liner thickness due to the potential ongoing settlement of waste.
6. If option one has been chosen, ensure that there is sufficient buffer distance and coordination between landfill operation and cell construction equipment. It is also worth noting that the staged separation bunds can only progress once landfill waste filling is completed, making this a highly complex construction program.
As closing off old non-BPEM landfill cells can result in significant cost and loss of airspace, it is crucial to understand the EPA requirements, study the options to select one that best fits your site and operations and understand the associated costs and time implications for construction.
Meinhardt will be sponsoring the Innovation Zone and awards at this year’s Australasian Waste and Recycling Expo, which will be held at the Sydney Olympic Park on October 9 and 10.
About the Author:
Michael White is Meinhardt’s Discipline Leader of Civil Infrastructure (Australia). A qualified engineer, White has more than 22 years of technical, commercial and management experience and has been actively involved in the design and project management of many large-scale infrastructure and commercial buildings projects
This article was originally published in Inside Waste Magazine