TWO gaping holes, one of them about five metres deep, developed late on Wednesday at the Dovedale end of Bacon Street as the Clarence River was near the top end of its peak.
Though none of the council officers at the site wished to be officially quoted, several theories abounded as to what the holes were exactly.
What is known is that the holes, which are some 20 metres apart from one another, follow the line of underground stormwater pipes which run east-west along Bacon Street.
Each hole was at least three metres in diametre and council workers filled one of the holes, closest to the river, with truckloads of sand and gravel until 12.30am yesterday.
Additionally – a gully which sits in a low point (north-south) and crosses Bacon Street near Kent Street, had filled with water from the flooding Clarence.
Late night witnesses at the scene and council officers alike agreed there hadn’t been near enough rain in the Grafton area to fill up the gully with rainwater.
Some residents of Kent Street had been warned by the SES to be prepared for flooding of their ground floors if the problem could not be fixed by council.
Intriguing theories included water running along sand which is used to cushion stormwater pipes, or holes in pipes sucking in the ground from above with the tremendous pressure of gushing floodwaters running through stormwater pipes. But the exact diagnosis is still undetermined.