Farmers Transport Limited and Dynes Transport Limited were fined $20,000 and $17,000 respectively by Judge Dickey in Hastings District Court on Wednesday for breaching the Resource Management Act 1991.
Hawke's Bay Regional Council (HBRC) says the court's decision to fine the two local companies sends a strong signal to businesses that polluting water in the region will not be tolerated.
HBRC group manager policy and regulation Katrina Brunton said the council is committed to "rigorously enforcing the rules that protect the health of both our environment and community".
It is the third successful prosecution for Hawke's Bay Regional Council this year, after two other companies were fined $11,900 and $12,555 for illegal burning.
"We are committed to pursuing these activities through the court if necessary. It's one of the strongest signals we can send to discourage others," Brunton said.
If any member of the public has information regarding unauthorised discharges to land, air or water they should contact the HRC 24/7 Pollution Hotline on 0800 108 838.