The Greater Wellington Regional Council (GWRC) engaged NIWA to prepare and process estuarine sediment samples collected from Porirua Harbour in late 2010 and manage the analyses of both organic and metal contaminants for comparison with ANZECC sediment quality guidelines. Metal contaminants were analysed by Hill Laboratories and reported elsewhere. NIWA provided analytical data for organochlorine pesticides (OCs), polycyclic aromatic hydrocarbons (PAHs) and particle size distributions (0-300 μm). This report describes methodology and presents results [including quality assurance (QA) data] for the analyses of OCs, PAHs and particle size distributions for estuarine sediment samples collected from Porirua Harbour in 2010.

Wellington International Airport Limited (WIAL) propose to lengthen the existing runway from approximately 1950 m to at least 2300 m. This would be achieved by extending the current runway area into Lyall Bay, Wellington. Sediment sampling and chemical analyses were performed. All contaminant levels were well below ANZECC sediment quality guidelines. Contaminant concentrations in Lyall Bay surficial sediments were very low and uniformly distributed across the study area, including at sites most likely to be disturbed by construction activities. Mobilisation of sediment from 0-0.2 m depths from within the area of the proposed runway extension is not expected to result in any significant increase in sediment contaminant concentrations in surrounding areas. From a contaminant perspective, the risk of adverse effects on the water column from transient sediment suspension/disturbance events during construction is very low given that water column concentrations, even after allowing for reasonable mixing, are estimated to be at least two orders of magnitude lower than default ANZECC water quality trigger values.

This report briefly describes methodology and presents results [including quality assurance (QA) data] for the analyses of Wellington Harbour marine sediments for sediment contaminants. Results reported for total organic carbon (TOC), total petroleum hydrocarbons (TPH), organochlorine pesticides, Polycyclic aromatic hydrocarbons (PAH), PAH chemical markers, heavy metals and sediment particle size distributions. TPH, TOC and heavy metal results were produced by Hill Laboratories. Organochlorine pesticides, PAH and PAH chemical marker compound results were produced by NIWA.