In a mediation agreement last week Delta admitted it had discharged waste waters containing several pollutants into the river feeding into Lithgow and Sydney’s water supply.

The pollutants included copper, boron, zinc, arsenic, aluminium and fluoride.

The case came about after the society discovered the pollutants while stormwater testing in 2007.

They then had independent testing undertaken by Dr Ian Wright from the University of Western Sydney who discovered high levels of metals.

“At that stage we thought the Department of Environment would act, and we wrote to them about the levels but nothing happened.

“It was then we decided to take the case, and that was very exciting on a number of levels,” Blue Mountains Conservation Society vice president Tara Cameron said.

During the mediation to finalise the case the Blue Mountains Conservation Society and Delta Electricity agreed to discontinue legal action based on three points.

The Blue Mountains Conversation Society said they will be watching Delta closely to make sure they comply with the points.

Find out what the points are in today's Lithgow Mercury.