The owners of the Wensleydale Creamery in Hawes say improvements are being made to the site’s drainage system.
It follows concerns about pollution getting into nearby Gayle Beck.
In June, the Environment Agency investigated after local residents spotted discoloured water in the stream.
Locals said discolouration had been spotted on previous occasions too.
A report into the June incident concluded that the creamery was the most likely source of the pollution, with the business to be charged for the officer’s time investigating the incident.
It stated: “Recharge to be claimed against Wensleydale Creamery as there is nowhere further upstream of the creamery that could have discharged enough white liquid to affect the watercourse to the extent the pictures show.
“There are also known issues with the drains at the Creamery so based upon probability this will most likely be the source.”
Reacting to the report, a spokesperson Saputo, which owns the creamery, said: “We take our environmental commitments very seriously and fully investigate any pollution incidents which are alleged to be attributable to our manufacturing facility.
“The Environmental Agency report is inconclusive as to the source of the pollution and there is no evidence to pinpoint the cause.
“However, the Creamery recognises that improvements to its drainage systems are required and investments are ongoing in that area.”
Andrew Fagg, a member of Hawes and High Abbotside Angling Association’s committee, which has raised concerns about the pollution incidents, welcomed news of the work to the drainage system.
He said: “The Environment Agency incident report has confirmed what local people who saw the beck turn white in June knew straightaway: that once again waste from the dairy, this time milk, had made its way into Gayle Beck.
“It’s great news for people – and for trout – that new owner Saputo seems to be getting to the bottom of what is a decades-long problem and is investing serious money to put it right.”