Swept Under the Carpet? Road Derived Sediments: Friend Or Foe?
SWEPT UNDER THE CARPET? ROAD DERIVED SEDIMENTS: FRIEND OR FOE? Peter Mortimer Technical Services Manager, Downer NZ Ltd, Dunedin, New Zealand Kirsty Marlow Divisional Manager, Downer NZ Ltd, Queenstown, New Zealand Abstract It is common practice to dispose in landfill the material removed from road surfaces and transported into sumps as part of rain runoff. The material contains contaminants including heavy metals, especially Lead, Copper and Zinc, which has detrimental effects to the receiving environments from landfill leachate. However, a landfill tends to be acidic, and this environment encourages the heavy metals (especially Zinc) to go into solution forming a neutral salt, and leach into the surrounds. Better, if possible to encapsulate the heavy metals elsewhere in a useful product and avoid adding to landfills. Downer undertook research and commissioned laboratory testing as part of a project development for Queenstown Lakes District Council in order to investigate this possibility. This paper will describe the development of a sampling method, and results of testing compared with industry solid waste management limits. Uses to date in the Queenstown Lakes District are discussed, as well as the potential for further use as an economic commodity. Key Words Road Sump Waste, Street sweepings, Road Derived Sediments, Hazardous waste, Landfill, recycling Introduction Road maintenance contracts with an urban component commonly have a requirement to remove the build up of detritus from the road surface and kerb and channel and the sediments and deposits within surface drainage sumps. It is usually the contractors responsibility to dispose of this material in a responsible manner. The cost of this disposal (and thus the price allowed for in tenders) is directly related to the disposal method which is obviously dependant on the definition of the materials being disposed.
[Show full text]