Ecological effects of sewage and silt in Christchurch's streams and rivers

Environment Canterbury has carried out a number of surveys and studies into the effects on streams and waterways of wastewater inflows and silt deposits, and have released reports on their findings.

ECan’s media release on the effects of untreated sewage being discharged into the lower parts of the Avon and Heathcote rivers and the estuary is here. According to ECan’s map (here), the lower Avon is the part of the river downstream from the Fitzgerald Avenue bridge.

Also available are the following reports:

  • Ecological effects of the Christchurch February earthquake on our city rivers
  • Ecological effects of the Christchurch February earthquake on our city estuary
  • Effects of wastewater overflows on oxygen and ammonia in the Avon and Heathcote rivers
  • Christchurch February Earthquake: Effect on aquatic invertebrates
  • Christchurch February Earthquake: Effect on freshwater fish of the upper Avon River
  • Christchurch February Earthquake: Effect on invertebrates of the lower rivers
  • Effects of seismic activity on inaka spawning grounds on city rivers
  • Mapping earthquake induced topographical change and liquefaction in the Avon-Heathcote Estuary
  • Effects of the Canterbury earthquakes on Avon-Heathcote Estuary/Ihutai ecology

The reports and map are here.

Avonside during the heavy rain

The photographs below were taken yesterday afternoon along River Road and Avonside Drive.

River Road, near Swanns Bridge, with Cowlishaw Street on the far side of the river.

River Road near Dallington Terrace. The road has flooded and a breach is being made in the stop bank to allow the water to run into the Avon.

Avonside Drive near Galbraith Street, from  Dallington Terrace. The green willow trees in the middle-right mark the approximate edge of the bank on Avonside Drive. Behind the stop bank can be seen patches of flooding on Avonside Drive.

Taken from on top of the stop bank on Avonside Drive, a few metres downstream of Galbraith Street. The river surface is about half a metre higher than the road.


Earthquake Royal Commission – submissions added to the on-line document library

The Earthquake Royal Commission has been adding a number of institutional and personal submissions to its on-line document library in recent days.

Today submissions primarily cover aspects of seismicity and soils, with some on engineering. Two historical documents were also loaded.

The book Christchurch – Swamp to City – A Short History of the Christchurch Drainage Board 1875-1989 has been uploaded in PDF format. It contains the full text which is a detailed history of how the city’s storm water and sewage systems were developed. The PDF file contains all the maps including a copy of the “Back Maps”. It is here.

Also added is a copy of the booklet,  Drainage Scheme – Christchurch and the Suburbs, written by William Clark and published in 1878. The author paints an interesting picture of the damp and less than sanitary state of Christchurch at the time and describes how he thinks storm water and sewage should be disposed of. There is an amazing amount of technical detail. The last page is a plan of a water privy showing the arrangement for cleansing by waste water from an artesian well. You can find it here.

CCC – Infrastructure rebuild

The following is an extract from the mayor’s earthquake update released on Friday. It covers, in full, what has been done, and what is intended to be done shortly. Like us, the council is awaiting the third Tonkin & Taylor geotechnical report to know what needs to be done in various suburbs. The full update can be found here.

An important development is the desire of the council to be in charge of the overall land remediation process. It is not clear whether this desire extends to wanting to be involved in land remediation on private property.


The Council is eagerly awaiting EQC’s land remediation plans and has put up its hand to co-ordinate the process within the Christchurch City Council area.

“Logically the Council is best placed to oversee the remediation,” Mr Parker said.

This would enable the Council to closely co-ordinate land remediation with rebuilding of its own infrastructure.

The Council has established an Infrastructure Rebuild Management Office, headed by Rod Cameron. Contractors have been appointed to manage the rebuilding of the Council infrastructure, and design work is already underway.

Temporary and permanent repairs have already been completed in some areas. These include:

  • 4 siphons that go under the Avon River have been repaired
  • repairs have been done to half of the roof of the Denton reservoir tank
  • to reservoir tanks at Cracroft have had repairs to roof structures
  • 4.7 km of water mains has been replaced – mainly in the Avonside/Dallington area
  • 1.8 km of sub mains has been replaced – mainly in the Avonside/Dallington area

Other work underway now includes:

  • harbour and marine structure repairs
  • boat ramp repairs
  • irrigation repairs (Bexley and Halswell)
  • structures repairs – fences and retaining walls
  • bank repairs – Roto Kohatu
  • rock fall repairs – at Castle Rock and Naval Point
  • track repairs – Spencer Park, the Groynes, Halswell Quarry, Coastal Cliff Reserve, Corsair Bay, Cracroft, Castle Rock
  • car parks/driveway repairs

Work about to start includes:

  • Heyders Road, Spencerville, replacement of sewer pipes
  • Halswell Junction Road, replacement of sewer pipes

Road renewal and pothole fixing

The CCC has added more to its webpage Answers to questions raised at recent Council community meetings. This time it covers the planning and timetabling of renewing and repairing roads. The full text is below. The basic points to be taken the new information is:

  • Road renewal will not occur until after sewer and storm water drains are renewed.
  • Road renewal will not start until land remediation has been finished.
  • Resident participation in renewal planning will not occur, roading will be reinstated to the way it was (i.e retain the same street layout). Reinstatement will invariably mean that upgrades or improvements (e.g. speed restricting road designs) are unlikely to be made.
  • Where choices need to be made Council will make these and inform residents about the selected option.
  • Potholes will continue to be repaired as before the earthquake – notify the council of a problem and they will fix it.
  • Child safety issues associated with paths and parks that have been damaged will be done by contractors as part of the Council’s infrastructure rebuilding programme.

What is the road renewal timeframe?  Road renewal will follow pipe renewal works.

Are they going to wait for land remediation to occur before roads are replaced?   Yes.

Will the Council repair the roads and underlying ground to prevent vibration damage in the future?  All repairs will have road shape designs and requirements to minimise traffic-induced vibration.

What say will we have in selecting or advocating for a permanent solution and can there be improvements to parking etc?  Asset renewals will generally replicate assets that existed prior to 4 September 2010 using good practice methodologies. Asset renewals will include optimised decision-making and the installation of “modern equivalent” assets, e.g. new style flat street channels as appropriate. Residents will be informed about the selected option.

Can the Council seal the potholes as they appear?   Yes, please report them to the Council on Ph 941 8999.

When infrastructure is done will they upgrade at the same time?  Designs will generally replicate what existed prior to September 2010. Some “modern equivalent” assets will be installed, e.g. new style flat street channels as appropriate. Each site will be considered separately.

Can we get some interim repairs done to the roads in the meantime as they are dangerous?  All emergency work has been completed and all roads should now be safe for the posted speed limits. Final solutions/ timing will be determined by the contractors repairing the Council’s infrastructure in each area.

Will streets be redesigned to stop speeding when they are reconstructed?  The street layout will be a renewal of the original layout. Speeds will be monitored following all works and action taken if speed is an issue in the future.

Why is the Council not telling people when the water will be turned off?   There are two reasons for turning the water off: for reactive repairs when there is a burst pipe for instance or for planned work, for instance for the connection of re-laid mains. For reactive work when the Council’s contractor turns the water off they ring the Council call centre to let them know so if anyone calls in in there should be a record that the water is off and for how long it is expected to be off. It is not possible or practical to send notices, or inform everyone, every time the water has to be turned off for reactive purposes. For planned shutdowns the contractor doing the work should deliver notices to each household at least 24 hours in advance to notify the residents of the upcoming shut-off.

Can something be done about paths, and safety for kids in parks? Facilities are broken and paths muddy, creating a health and safety issue.   This will be addressed by the contractors rebuilding the Council’s infrastructure.

Will street design stay the same?   Yes, the street layout will be a renewal of the original layout.