The two companies charged in relation to works carried out on the Waihi Dam, and the subsequent discharge of silt into the Waihi and Waiau Rivers, can now be named.
They are Eastland Networks Ltd and Abyss Ltd.
The dam, owned by Eastland Group, began discharging silt into Wairoa waterways in December after a sluice gate was damaged in a storm. It was repaired only in March.
The companies have been charged with four offences arising out of contamination of the Waihi River between December last year and February this year.
Each party will face charges under the Resource Management Act for disturbance of a bed of a lake or river and discharge of contaminants into water.