Options for improving Cox's Creek
3 February 2006
Working party identifies options for improving Cox's Creek
Possible options for improving the environment at Cox's Creek were reported to Auckland City Council's Works and Services Committee meeting yesterday.
"Auckland City appreciates that Cox's Creek is a valued natural environment for the community. These options address the issues of odour, aesthetics, bathing water quality and ecology, which are of concern to residents," says, Councillor Neil Abel, chairperson of Auckland City's Works and Service Committee.
A joint working group of representatives from Auckland City, Metrowater and Watercare Services was formed in early 2005 to address the continuing pollution problems at Cox's Creek. The group has focused on finding solutions for the short, medium and long-term.
"A number of projects have already been carried out to alleviate some of the problems," Councillor Abel says. "Metrowater implemented sewer separation through part of the catchment in the late 1990s, Auckland City has completed flood alleviation projects, and Watercare Services completed improvement works in 2005 which have significantly reduced the amount of wastewater escaping from the trunk wastewater network into Cox's Bay.
"However, we know that there's no quick fix, and that we need to do very careful research to make sure that any work to improve the environment of Cox's Creek will actually make a difference.
"It's important to recognise that we're currently going through a process to find solutions for a difficult problem. Any works to improve the environment of Cox's Creek will take time."
The working party commissioned a report to understand the receiving environment and suggest what could be done to improve the environment. The report highlighted a number of factors that contribute to the problem, including: * organic pollutants such as plants (from the stormwater system) and wastewater are being transported into the system by combined sewers, causing an odour through the process on decomposition * the lack of an even gradient from Parawai Crescent outfalls to the West End Road culvert, resulting in the formation of ponds with very limited tidal flushing, causing the ponds to become stagnant with subsequent odour and environmental issues.
The working party found that there was no short-term option that would prevent the need for significant and frequent sewer overflows into Cox's Creek, and therefore focused on options that mitigated the adverse effects of overflows. These options include: * surveying and filling the scour pool* and stream bed from the stormwater outfalls from Richmond Road, Parawai Crescent and Wharf Road, to the West End Road culvert * stream works, including riparian planting.
These options, which are likely to involved council funding, are estimated to cost approximately $1 million, subject to a scoping exercise that is expected to be completed by May 2006. Comment will then be sought from interested parties including the Western Bays Community Board prior to drafting the stormwater works programme in September 2006. All works will require resource consents.
Options have already been approved by Metrowater for solutions to dry-weather overflows in wastewater systems in the contributing Grey Lynn catchment, and have been provisionally programmed for the next two years. These include: * localised wastewater separation * installation of grit traps * installation of screens * automated monitoring of wastewater overflow structures.
These measures are estimated to cost approximately $6.5 million.
Watercare Services is currently investigating long-term regional options for enhanced collection and treatment of the regions' trunk wastewater services. The aim is to eliminate all discharges from the trunk wastewater network throughout the region, with the Auckland city area as the key focus. Further investigations will follow the outcome of the Watercare Services-led regional wastewater master plans. Initial reports are expected by December 2006.
*scour pool - a pool that has formed below stormwater outfalls in the stream bed.