Balbriggan beach has now been declared safe for swimming following a serious pollution incident earlier this week.
Fingal County Council said tests found E coli levels of 100 units per 100 millilitres were well within the 250 unit limit for Blue Flag beaches.
E coli readings were in excess of 10,000 units per 100ml were recorded after raw sewage flowed into the sea for over 24 hours before being discovered by a member of the public on Tuesday.
The council believes that heavy rain caused an electrical fault to both a pumping station and an alarm system.
