Charges have been laid after silt from a storm-damaged dam clogged Wairoa waterways over the summer.
The sluice gate at the Waihi dam, which belongs to Eastland Group, was damaged last September and not fixed until March, letting silt pour into three waterways for months.
It has cost Wairoa District Council more than $100,000 to clean up the drinking water, and locals have said the dam's failure "destroyed" their summer.
Hawke's Bay Regional councillor Rex Graham said he is relieved that charges had been laid.
He said contamination from the dam had had a devastating impact on Wairoa.
"The farmers' ... pumps were ruined, weren't able to operate, we were fortunate we didn't have a big drought. It had a widescale effect on the community.
"So I'm pleased at least there seems to be a prosecution."
Mr Graham said elected councillors have been kept in the dark over the investigation by council official.
The council is refusing to name the parties facing charges.
However, the dam's owner, Eastland Group, said it was made aware of the charges yesterday.
Earlier this month RNZ News revealed Eastland Group had been breaching its consent for years and the enforcer - the regional council - knew this since 2013, but no penalties were issued.