Lake Rotorua public health warning lifted
Update: 3.30pm 2 November 2021
Following advice from Toi Te Ora Public Health, the health warning for Lake Rotorua near Arnold Street and Waiteti Road in Ngongotahā has been lifted. The warning signs will be removed today.
Now that the warning has been lifted, people can return to activity in that area of Lake Rotorua.
For more information about safe swimming areas in Rotorua visit www.boprc.govt.nz/living-in-the-bay/safe-swimming-areas
Update: 7pm Friday 29 October 2021
Despite initial tests on Wednesday indicating the lake water quality at all sample points was within safe swimming guidelines, further testing on Thursday indicated higher bacteria levels at two points near the mouth of the Waiteti Stream.
Additionally, following the heavy rain on Thursday night and Friday morning, as per the standard public health warning, people should avoid swimming in lakes, rivers, streams and estuaries for a period of 48 hours after heavy or prolonged rain due to potential bacteria contamination from water runoff.
For these reasons the health warning will remain in place over the weekend.
Update: 3pm Thursday 28 October 2021
The latest test results for the site of the wastewater overflow near Arnold Street and Waiteti Road in Ngongotahā were analysed today and all showed reduced bacteria levels to below the recommended safe swimming level.
The test samples of lake water were taken yesterday (Wednesday 27 October) at five points along the lake shore in the vicinity of last week’s overflow.
Despite the favourable test results, Toi Te Ora Public Health has requested that the health warning stay in place as a precaution until a set of secondary results indicate that the water is safe for swimming.
The health warning, and the signage on site will remain in place for at least another 24 hours until further testing can be completed and analysed.
Council officers are keeping in mind that rain over night and further rain forecast for this evening may effect tomorrow’s test results as it’s typical to see elevated levels of bacteria in water after rain.
Further updates will be provided once the next round of testing is complete.
Update: 4pm Tuesday 26 October 2021
Lake water testing continued over the long weekend in the area of the recent wastewater overflow site and other nearby locations in the vicinity of Arnold Street and Waiteti Road in Ngongotahā.
The overflow happened during the evening of Monday 18 October and the health warning has been in place since that night.
Tests over the weekend have confirmed the significant drop in bacteria contamination levels since the overflow, however the levels have not reduced enough to remove the health warning.
Rotorua Lakes Council’s 3 Waters Services Manager Eric Cawte says further investigations into the bacteria contamination levels needs to be carried out before Council is confident in removing the warning.
“The lingering levels of bacteria in the water that our tests are picking up are not consistent with what we would typically see following a limited overflow into a large body of water. Normally, after a few days the contaminants linked to an overflow would disperse and diluted into the lake and the bacteria levels to reduce to below the recommended safe swimming levels.”
“What we are seeing is slightly elevated levels of bacteria around the Waiteti stream mouth, further upstream and in areas that are quite some way from the overflow site. We are considering whether there are other factors contributing towards the elevated levels.”
To help determine the actual reason for these findings, and to help make the appropriate decision regarding the public safety of being in and around the water in this area, Council is communicating with partners Toi Te Ora Public Health and the Bay of Plenty Regional Council to assess and analyse the current test results.
For reasons of public health the warning will remain in place until bacteria contamination levels have reached and stayed consistently below the recommended level for safe swimming.
Update: 2pm Friday 22 October 2021
The health warning in place for Lake Rotorua near Arnold Street and Waiteti Road in Ngongotahā is still in place and will remain until test results show that contaminant levels have dropped to the recommended safe swimming level. Testing will continue over the long weekend.
Council has been receiving daily water testing results and although contaminant levels have reduced significantly since Monday evening, the detected presence of contaminants above the recommended level for safe swimming means further testing will be required to take place before the warning is lifted.
Testing at the Waiteti Stream mouth and further upstream will help to build a better picture of the baseline contaminant levels in the stream unrelated to this event and will enable Council to reach a final decision as to when that area of the lake can reopen again for safe swimming and recreation.
Signage will remain in place to warn people using the area.
Investigations into the cause of the computer fault (the loss of programming code) have continued and it is likely, due to the timing of the fault that it was due to a power cut in the area that afternoon.
To safeguard against similar issues happening at other pump stations, TRILITY will be carrying out a review of the electrical systems at all 80 pump stations in Rotorua.
Update: 4pm Wednesday 20 October 2021
The health warning for Lake Rotorua near Arnold Street and Waiteti Road in Ngongotahā is still in place.
Test results from the evening of overflow and the following morning have been analysed. As expected, the highest levels of contamination were detected at the entry site of the overflow into the lake, and testing shows that the levels of contamination reduced significantly within the first 12 hours. Test analysis takes at least 24 hours and we expect more results to be available tomorrow.
Investigations into the cause of the computer fault (the loss of programming code) is still ongoing.
TRILITY will continue testing to determine when the warning should be lifted, 48 hours in the generally advised minimum time for such warnings to be in place and test results will confirm the warning time frame.
In the meantime, it is safe to enter the water at other locations around the lake. Just keep an eye out for any signage that may indicate a health warning.
Update: 5pm Tuesday 19 October 2021
The fault has been identified as a loss of programming code from the memory of the Programmed Logic Controller. Council and TRILITY are trying to ascertain if the loss of programming code was related to a power cut in the area yesterday, during which a generator was used to supply power. The mains power was restored around the time that the pump station is believed to have stopped operating. Investigations into the cause of the loss of programming code is ongoing.
The Programmable Logic Controller at the pump station has been re-programmed and has been operating satisfactorily, and a level sensor for the backup alarm system has been replaced with a new one as a precaution.
19 October 2021
A public health warning is in place for Lake Rotorua near Arnold Street and Waiteti Road in Ngongotahā.
Yesterday evening Council was alerted by a member of the public about an overflow from a manhole on their property. Wastewater flowed from the manhole across the ground and made its way into the lake.
It is estimated that the overflow was happening for approximately three hours before Council was alerted to the issue. TRILITY staff attended immediately and restarted the nearby pump station to manually stop the overflow.
The cause of the overflow is under investigation however, initial inspections have found a major fault in the on-site computer that controls the pump station. It is unclear, at this stage, what caused the fault.
The affected land was cleaned and disinfected, and signs are now in place along the beach to warn against recreational activity and swimming. The signs will be in place for at least the next 48 hours. Samples of lake water have been taken for testing and further testing will take place over the next several days.
Relevant authorities including Te Arawa Lakes Trust, Bay of Plenty Regional Council and Toi Te Ora Public Health have been notified.
Updates about the health warning will be provided over the next few days.