The Environment Agency has said it is satisfied with fines handed out to Wrexham woodchip giant Kronospan after it polluted local water courses.
Kronospan said it was working with experts to prevent further pollution
The Chirk-based firm was ordered to pay £60,000 after pleading guilty to a number of offences on Thursday.
Four of them related to an incident in July last year when oil leaked into the River Dee via a tributary.
Kronospan said it regretted the incident and had expert help to advise on preventing further pollution.
The company faced eight counts, including those relating to the River Dee spill in 2003.
No flora or fauna was damaged, but Dee Valley Water closed its water treatment works as a precaution.
Routine testing revealed there had been oil in the water which potentially could have been harmful to human health.
Wrexham magistrates heard that heat transfer oil had been in Kronospan's surface water lagoons which had overflowed due to heavy rainfall.
The company also faced four charges relating to accidentally releasing non-treated effluent into the Afon Bradley between 5 Dec 2002 and 17 July 2003.
Kronospan pleaded guilty to all the charges and was ordered to pay costs of £7,315.
Firm regrets incident
An Environment Agency spokesman said afterwards that the fines reflected the seriousness of the potential harm to the environment.
A Kronospan spokesman said: "Kronospan regrets very much any environmental incidents that occurred at the Chirk site.
"These have arisen when there is excessive rainfall and the volume of water cannot be contained within the existing surface water storage lagoons."
The firm said it was working with consultants to look at alternatives to try to prevent further pollution incidents in the future.