The Scottish Environment Protection Agency (SEPA) has been monitoring a discharge which has been seeping into Grangemouth’s Grange Burn.
Officers investigating the matter pinpointed Forth Ports’ construction of a new warehouse on the docks at South Shore Road.
A SEPA spokesperson said: “As part of this work, a new outfall has been constructed discharging into the Grange Burn. The outfall construction has now been completed and a non-return flap installed.
“The outfall will take surface water from the site and the discharge from the small septic tank which has been authorised by SEPA.”
Despite concerns from residents, Forth Ports confirmed there was nothing toxic going into the burn.
A spokesperson said: “It is simply surface water from the roof and roads – rain water – from the site being collected in the tank.”