The northern end of Wollongong Harbour has been reopened to swimmers after the results of water testing conducted last Saturday.
The southern end of the harbour remains closed, with high levels of ammonia, faecal coliforms and enterococci recorded in water close to the sewage leak discovered almost two weeks ago.
The harbour was closed to swimmers last Friday after sewage was discovered seeping into the water through a sandstone wall near the Fishermen's Co-op building.
The leak was first detected on January 11.
Last Saturday, Sydney Water collected six water samples from different parts of the harbour beach front (sites 1-6 on the aerial image of the harbour) and one sample from a North Beach site.
The samples were analysed for ammonia, faecal coliforms and enterococci.
Sydney Water released the results of the testing on Wednesday afternoon.
It said high levels of ammonia were recorded at site 1 (the source of the sewage leak) and were negligible at the other six sites.
High levels of ammonia are indicative of the presence of raw sewage.
Very high levels of faecal coliforms - 4,400,000cfu per 100 millilitres - were also recorded at site 1.
The term "cfu" refers to "colony forming units" and is a measure of the number of different types of bacteria in the water samples.
The recommended levels for faecal coliforms in a "primary contact waterway" are less than 150cfu/100ml.
Acceptable levels were found at the other six sites.
Sydney Water said these results indicated the sewage has been diluted from the source at site 1.
The level of enterococci (a measurement used to assess swimming water quality in the NSW Beachwatch program) recorded at site 1 was 40cfu/100ml, which is above the primary contact swimming threshold of 35cfu/100 ml.
Levels at the other sites were below the acceptable limit.
Sydney Water said a private wastewater pipe servicing the Fishermen's Co-op building has been identified as the source of the leak.
Property owner NSW Trade and Investment, Crown Lands is undertaking repairs to the pipe.
A statement issued by Crown Lands said work began on Wednesday on repairing about 50 metres of the private pipe connecting to the co-op building.
"All work on relining the 50-metre section is expected to be completed by Friday," the statement said.
It added that "a contingency plan will be implemented over the weekend to monitor the system and ensure it is working satisfactorily".
The EPA will continue to monitor water quality.