Pacific Environment is pleased to announce that one of our senior consultants, Mr. Aidan Marsh, has had three extracts from recent projects accepted for presentation at EcoForum 2014 on 29-31 October on the Gold Coast.

Aidan is our landfill gas monitoring expert and has only recently joined us, along with the other members of the Waste Solutions Australia (WSA) team, in a recent acquisition by Pacific Environment. 

The projects being discussed are to do with the Gold Coast Light Rail, Landfill and Low Calorific Flaring and Phytocaps

Aidan has included brief summaries of the information on the three projects that he will be sharing at EcoForum 2014  below. 

Project 1:

Gold Coast Light Rail

In 2011 we were engaged to assist with the development of the Gold Coast Light Rail Project. A public transport office, depot building and related infrastructure were constructed on a former municipal waste landfill site that was actively producing Landfill Gas (LFG).  A series of investigation programs were undertaken prior, during and after construction. The aims of the programs were characterised the site condition and implement management measures to ensure risks to construction workers and occupants of the site buildings associated with the presence of hazardous LFG were minimised. We also designed an underground gas protection system for the development.

Project 2: 

 Landfill and low calorific flaring

More recently we have worked closely with local councils on investigation and mitigation of risk from landfill gas that was migrating off site. Out of these investigations we worked collaboratively with EHP to develop landfill monitoring guidance that was based on flow measurement as well as gas concentration giving a more appropriate risk based system.  We also designed a gas vent system that was designed to work with a low calorific flare. Pacific Environment’s strategic partner can supply and operate this system that has been validated by Government Regulators and independent consults to sustainably combust methane down to 12 % volume/volume without LPG support.

 Project 3:


Landfill final covers have traditionally been constructed from low permeability materials (eg. compacted clay, geosynthetic clays and geomembranes) that are intended to resist the percolation of water into the waste zone.

 Phytocaps, in contrast, are vegetated soil covers that control percolation through a water balance mechanism. Phytocaps are also known as ‘water balance covers’, ‘evapotranspiration covers’, ‘store and release covers’ and ‘alternative covers’.

 The phytocap’s lightly compacted soil layer stores moisture during rain events and the sun and plants remove the water from the soil by evapotranspiration, returning it to the atmosphere. These water balance mechanisms work with, rather than against nature.

 These different mechanisms are illustrated in the following diagrams:

phytocaps, landfill gas, solid waste
A comparison of both mechanisms.


More than a decade of monitoring at sites in the USA and Australia has demonstrated that phytocaps are resilient and can meet performance requirements under a wide range of climatic, geographic, geological and hydrological conditions. They have produced equivalent or superior hydraulic performance to compacted clay caps in most situations. Moreover their performance improves over time as vegetation matures;

 ·         Phytocaps control fugitive landfill gas emission effectively, and at no additional cost, through oxidation of the gases by the action of enhanced

 ·         Depending on government climate change policy settings, this may translate into an economic benefit for landfill owners.

 ·         Phytocaps work with, rather than against nature and so are not as subject to post-construction failure. Because they are self-sustaining they require low maintenance.

 ·         Where maintenance is required, they can be repaired effectively and relatively easily and cheaply

 ·         Because they are applied in thick and lightly compacted lifts and take advantage of borrow soils available at or near the site, construction costs for phytocaps are typically less than for conventional caps

 ·         Planting costs are relatively minor

 Phytocaps provide an aesthetically pleasing and more biodiverse cover and end use.

 Use of phytocaps is becoming a realistic and feasible option for completion of landfill sites. Not only is methane effectively oxidised in a phytocap the federal government has added phytocaps to the positive list for inclusion into the Carbon Farming Initiative and we have developed a methodology that is designed to measure the amount of methane  that can be mitigated . This means not only can a cost effective borrow source of material be used to cap the site, carbon credits will become available as well.