There were pointed questions, but also plaudits, for Dunedin City Council staff as they presented a report yesterday concerning the contamination of the city's water supply last year.
Both came at yesterday's council infrastructure services and networks committee meeting, as councillors questioned 3 Waters group manager Tom Dyer on the report's findings.
The report pointed to a vague, handwritten note and an unapproved system for lowering the Ross Creek reservoir as two key issues leading to the contamination scare.
More than 2500 homes and businesses were affected when untreated water from the reservoir entered the city's drinking network through an old, decommissioned pipe on August 14, prompting a three-day boil-water notice covering much of the central city.
Mr Dyer was questioned in detail by Cr Jim O'Malley, who wanted to know more about delays to the Ross Creek Reservoir upgrade and the subse-
quent decisions that led to the contamination scare.
The report showed Opus, overseeing the $6.6million refurbishment, had asked in June for the council to arrange for the level of the reservoir to be lowered by 2.5m, so work could continue on the project.
Cr O'Malley suggested Opus had experienced ``compounding'' delays to the project, and faced a tight timeline to have the water level lowered by August 14 and avoid further delays.
Mr Dyer said delays had been occurring, and if the trend continued, could have put the project six to 12 months behind schedule.
An automated process to lower the reservoir did not begin until August 1, by which time it was unable to remove enough water in the required timeframe.
The usual manual discharge system could not be used, but delays agreeing on an alternative prompted Opus, in an email on August 11, to warn the ``window of opportunity is closing quickly'' and asking for a ``quick decision''.
Portable pumps were considered, but ruled out as they would take too long, and it was decided to use a branch line off the automated dewatering pipeline.
It was not realised at the time another branch of the pipeline, thought to be decommissioned, was still connected to the city's treated water network.
Mr Dyer said the decision to use the old pipe was based on an interpretation of old plans that was deemed ``low-risk'' at the time, but would be handled differently in future.
Staff had thought the old pipe's valve had been removed, and steel plates added to block water, based on an old, handwritten note affixed to the plans, but that had proven not to be the case, he said.
A ``much more thorough'' approach would be taken in future, including digging holes where needed to confirm the accuracy of old plans, Mr Dyer said.
The report also identified other issues which contributed to the contamination scare, none of which by themselves would have caused the problems, as well as a range of improvements to avoid any repeat.
Cr Lee Vandervis congratulated Mr Dyer for the comprehensive nature of the staff report.
Cr O'Malley agreed.
