Geomembrane for effluent pond in New Zealand
New regulation – Geomembranes in dairy farm
Project name: Dairy farm New Zealand
Project date: 2014
Products: 1 650 m² smooth HDPE geomembranes 1.5 mm thickness
Introduction
With the number of dairy cows continuously increasing in the past decades, milk products became New Zealand’s largest export earner. In 2009 dairy products accounted for 21 % of the total merchandise exports.
Cows are outdoors year round. Twice a day they are brought into the milking shed. Regularly the milking shed and the yard around it have be to cleaned. This leads to approximately 70 litres of water contaminated with effluent per cow each day.
During the dryer summer time the water is used for irrigation. However during the wet winter time irrigation has a detrimental effect on the farm land and the environment. The ground is already saturated, thus the effluent runs off into creeks and streams causing pollution.
Effluent ponds
In 2013 a new regulation was passed in New Zealand to protect the environment. Depending on the size and on the location of the farm effluent ponds have to be built. This enables the farms to collect the waste water during winter time and use the additional water during summer for irrigation. The ponds must have at least the size to store the water generated in 90 days. Typically the effluent ponds have a surface size between 1 500 m² and 5 000 m².
To build effluent ponds, first the subsoil has to be prepared and a drainage system has to be installed below the pond. It is topped off with a layer of stone free, fine material (e.g. earth, clay, sand). Then a nonwoven geotextile and finally the geomembrane (1.5 mm HD-PE) is installed. The stone free layer and the geotextile is essential to protect the geomembrane and ensure a long life-time.
HDPE geomembranes
To effectively protect the environment it is essential to have absolutely leak tight effluent ponds. Due to the excellent properties HDPE geomembranes supplied by AGRU have proven most suitable for this application. Among others the most important advantages are the high toughness and the excellent strength which lead to a robust effluent pond. Also important is the ease of installation and excellent weldability. The installation is carried out in a professional way by AGRU New Zealand and Agruline Ltd.
The first figure shows the effluent pond at Walters farm in Otaua during construction in February 2014. Up to date many effluent ponds have been successfully finished using HDPE geomembranes from AGRU. All of them are operating to the satisfaction of the owner and are expected to do so for many years to come.