Phytocap Trial – Lakes Creek Road Landfill

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Phytocap Trial – Lakes Creek Road Landfill

PDF] Phytocap Trial – Lakes Creek Road Landfill

Rockhampton City Council in conjunction with Phytolink Australia (Mr Richard Yeates) and

the Central Queensland University (Primary Industries Research Centre - School of

Biological and Environmental Sciences - Dr Nanjappa Ashwath, Kartik Venkatraman & Dr

Ninghu Su) has been trialling a new capping system for Landfills.

Rockhampton City Council resolved to trial a Phytocap cap at its Landfill for the following

reasons:

• Council was going to have to cap 42 ha of the Landfill in a short period of time.

• The cost in dollars and difficulty in finding suitable clays was going to be a large

burden upon Council and the community/environment.

• Phytocapping would greatly reduce the costs involved in capping the Landfill and

reduce the demand for suitable clay.

• Council had an opportunity to produce some of the required soils for the Phytocap

from products currently being deposited at the Landfill for disposal and or

treatment (i.e. soils, sewage and water treatment sludges and greenwaste

(mulched), and therefore have the opportunity to make significant savings in

dollars and Landfill airspace by diverting these products to the cap manufacture.

• Recent data from America showed that standard clay caps failed particularly after

a drought event. Rockhampton is in a dry climate and therefore any caps placed

at the local Landfill would more than likely fail.

The Project Aims and Objectives are as follows:

• Compare the suitability and effectiveness of Evaporation/Transpiration (ET) capping

and soil-less (i.e. planted into the interim cover) phytocapping techniques;

• Establish a range of selected plant species on both the ET cap (Phytocap) trials

established at the Lakes Creek Rd Landfill site to act as biopumps to remove excess

rainwater;

• Monitor the growth, root distribution and transpiration rates of the established

species with the view to identifying plant species that are highly effective as

biopumps in landfill remediation and leachate control;

• Monitor both experimental plots for methane emissions and water movement

through the substrates; and

• Model the water balance for the experimental plots, taking into consideration the

amount of water (i.e. rainfall plus irrigation) received by the system, the quantities

being transpired by the plants, the amount that is evaporated from the soil and the

amount that infiltrates into the landfill system.

The trial was established three years ago and formally ceased operation on June 30, 2006.

Though data will be recorded from the trial plots until December 30, 2006.

The trial consisted of three plots, two duplicated plots approximately 25m by 50m (five

plots in total). One plot consisted of trees planted directly in the final day cover (400mm)

of the Landfill and the other two involved the addition of soil to the day cover. One pair

of these plots had 700mm of additional specially selected local soils added and the other

had 1,400mm of additional specially selected local soils added. A variety of soil types

were used from sandy loam through to light clays, placed in distinct layers and not

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compacted. Into all plots were planted 21 species of selected tree seedlings. The plots

were also irrigated as needed.

A variety of measuring equipment was also installed into the plots to measure water

movement into and out of the plots’ soil and trees.

The plots were then monitored throughout approximately three seasons.

The preliminary results reveal that a number of the selected tree species in combination

with their associated soils could indeed manage the flow of water into the plot to the

extent that very little if any water would pass through the capping layer into the

underlying waste in a average year for the locality of Rockhampton.

The results from the monitoring are now being assessed against past rain events to

determine the likelihood of this capping systems meeting the long-term demands of this

locality. Early indications are that a Phytocap at the Rockhampton locality will be

successful based on the historical data and it should be noted that with the greenhouse

effect we are expecting a drier climate, which will only enhance the Phytocap