The 1998 outbreak was caused by contaminated surface water leaking through a loose cable gland on Brookvale Bore 2.
Seventeen recommendations were made to prevent further incidents, such as sealing off leaks and bore casings, but not all recommendations were actioned, the inquiry heard.
Dry wells that leaked in 1998 were still leaking in 2016.
Questions were asked about the fact that the Brookvale boreheads 1 and 2 were not raised above ground after the 1998 outbreak to prevent contaminated water going over the top of the borehead.
"Had the Hastings District Council been looking after the bores enough?" barrister Nathan Gedye asked.
Mr Chapman, who started working for the Hastings District Council in 2006 and at that time had not been told about the 1998 incident, responded that there had been a work programme outlining that the boreheads should be lifted.
He suggested that maybe with only a 10-year consent granted in 2008, the council didn't want to invest in the infrastructure before the consent expired in 2018.
"Had I been aware of the 1998 incident I may have been more concerned. At the time I thought the bores had operated without issues."
The need for more co-operation between the Hastings District Council and the Hawke's Bay Regional Council was also highlighted in terms of both historic events and last year's outbreak.
Mr Chapman confirmed that co-operation and partnership with the regional council was preferred and said that in the past the two agencies had had informal meetings on a regular basis to discuss water issues.
That knowledge sharing fell short, however, due to the focus being more on waste and stormwater issues, he said.
"Issues on water supply were about take and allocation as opposed to water quality."
In terms of the current inquiry Mr Gedye asked Mr Chapman if the fact that the regional council had said the district council was at fault, proceeding with a subsequently dropped prosecution, undermined the inter-agency co-operation.
Mr Chapman confirmed it did make things difficult, and said it was not about fault but rather finding out what happened, and looking to make the water supply safe in the future.
The inquiry also raised when Brookvale bore 3 was shut down in October 2015 after another contamination event, the source of which was the subject of a Tonkin and Taylor investigation, but had potentially been linked to activities at Te Mata Mushrooms.
This link, or lack thereof, was the subject of discussion for the last part of the afternoon.
The hearings continue today, and are expected to continue for the next two to three weeks.