ElectraNet says it has been managing an incident at its Happy Valley sub-station, which has impacted adjacent SA Water land.
A quantity of oily stormwater was discharged from the sub-station on to neighbouring SA Water land during planned maintenance works.
ElectraNet promptly notified the Environment Protection Authority and SA Water and took immediate steps to contain and rectify the impact.
There has been no impact to drainage lines, the public road or the Happy Valley Reservoir.
ElectraNet says it takes its environmental responsibilities seriously and is taking all actions necessary to promptly address the issue.