The earthquakes of 22 February and 13 June 2011 caused major damage to sewer pipes and pump stations in and around Christchurch. As a result, untreated human sewage was discharged into the Avon River/Ōtākaro, the Heathcote River/Ōpāwaho, the Avon-Heathcote Estuary/Ihutai and sea.
(Last updated 16 January 2013)
Post-earthquake Christchurch city waterways update 14/01/2013: There is currently an issue with a sewer main in Richmond that is resulting in a discharge of untreated wastewater to the Avon River/Ōtākaro in the vicinity of the Swanns Road bridge. Water quality is therefore particularly contaminated downstream of Swanns Road. Contact with water in the river should be avoided. Read the CDHB media release.
All continuous pumped sewage discharges to surface water have now stopped due to the repairs made to major sewerage pipes by the Christchurch City Council (CCC).
On 10 November 2011, CCC and the Canterbury District Health Board issued a media release regarding water recreation around Christchurch – read the media release.
Water at all waterways and beaches is now suitable for recreational use as usual. However, there is likely to be bacteria and viruses in sediments of the rivers and estuary.
Recreational users are advised to avoid contact with water containing sediment they have stirred up. People should also avoid contact with all these waterways for 48 hours after heavy rainfall.
The Institute of Environmental Science and Research Limited (ESR) completed a study in July 2012, which investigated the effects of untreated sewage discharges on the quality of the water and sediments in the Avon River/Ōtākaro and in the Avon-Heathcote Estuary/Ihutai. Key findings were:
- During the discharge of large volumes of untreated sewage, all target micro-organisms tested for (including Campylobacter, Cryptosporidium, Giardia and viruses) were present in the water samples and the river and estuarine sediments.
- As sewage discharges decreased, the concentration of the target micro-organisms decreased in the water.
- The sediments appeared to accumulate most of the target micro-organisms and these remained present in the sediments after the discharges had stopped. This was most apparent in non-tidally influenced locations and for larger and environmentally robust organisms such as Cryptosporidium and Giardia.
- Contamination of sediment can remain long after the water quality has returned to “pre-event” status. Due to sewage-impacted river sediments retaining pathogens, people may become exposed to pathogens when sediments are resuspended.
Read the ESR report via the ESR website.
The Medical Officer of Health, Alistair Humphrey, recommends the following cleaning/washing procedure after water-based recreational activity following the removal of warnings for Christchurch beaches and rivers.
- Direct contact with the Avon/Ōtākaro and Heathcote/Ōpāwaho rivers is not encouraged – microbiological monitoring shows that results are back to pre-earthquake levels. These rivers are graded very poor and direct contact should be avoided.
- People should avoid stirring up the sediments in the Avon-Heathcote Estuary/Ihutai as part of their recreational activity as it could contain high loads of bacteria, Giardia and Cryptosporidium. Contact with these micro-organisms can cause infection which may last for many months.
- People who are kite sailing in the estuary should clean themselves off asap when they get home and we would encourage the use of hand sanitiser on site to clean hands after getting out.
- Sailors in the estuary should be ok if they stay within their craft but, if they have come out and stirred up the sediment, they should follow the advice for kite sailors.
- Recreational water activity at beaches is not currently a problem.
There may still be occasional, short duration discharges of untreated sewage into waterways as a result of problems encountered during further repairs to sewerage infrastructure. When such events occur the public will be kept informed through warning signs that will be erected at the location, warnings on this webpage, the Environment Canterbury Facebook page and public warnings through the media.
Routine monitoring at popular freshwater and coastal sites in Canterbury will be undertaken over the 2012-13 summer and this monitoring will begin on 19 November 2012. Read more about the water quality at swimming sites in Canterbury.
Monitoring results
Environment Canterbury and CCC monitored microbiological water quality at a range of sites in and around Christchurch, Kaiapoi and Lyttelton Harbour/Whakaraupō following the 22 February 2011 earthquake. This sampling has now stopped with the cessation of discharges.
The results from post-earthquake sampling are below. Note that microbiological results can be highly variable over time due to changing tides, river flows, inputs from damaged sewerage infrastructure and other faecal contamination sources (e.g. birds and other animals). The spreadsheet has multiple tabs for each of the areas that were sampled.
Monitoring results updated 10th November 2011 (xls 43 kB)
Monitoring results updated 10th November 2011 (pdf 82 kB)