Water quality

 The public and our committee, are concerned about the water  quality in Middle Harbour after major rainfall; especially due to sewer discharges at Quakers Hat, Long Bay, the north arm of Sugarloaf Bay, Scotts Creek and Roseville Bridge. Sedimentation is a concern in the north and south arms of Sugarloaf Bay; where Flat Rock Creek discharges into Long Bay and in Sandy Bay, Clontarf.  Long Bay was last dredged in 1988 removing sediment so that the water levels at low tide came up to the rock wall. Now at low tide an exposed area of sediment has pushed the water levels back 50 metres from the rock wall - restricting the area for boating and recreational fishing and degrading the environment for fish.

Why water quality deteriorates

 The water quality in Middle Harbour is deteriorating because of:

•  sewer overflows
•  stormwater pollution
•  land degradation.

Stormwater overflows.

Sewer overflows are the source of 98% of the faecal coliforms found in Middle Harbour. Contact with these faecal coliforms or associated organisms can, of course, be a disease risk. There are five major sewer overflow points that cause significant sewage pollution after heavy rain. Such pollution can lead to swimming bans at the beaches and at Northbridge baths. For example, swimming is banned at Northbridge baths for a week or two after heavy rain. In some years there have been up to 12 sewer overflows at Sailors Bay. But not all overflows caused bath closures.

Stormwater pollution.

Water washes into the stormwater drainage system from houses, gardens, roads, playing fields, shopping centres and industrial areas - and ends up in bushland, creeks and waterways. The water is contaminated with soil, road gravel, fertilisers, dog droppings, detergent, oils, metals, litter, seeds, plants and other organic material. These contaminants end up in the main creeks and estuarine systems, often transported from their place of origin by being attached to suspended particles such as clay. In this way, contaminants such as suspended solids (leaves, gravel and silt), nutrients (nitrogen, phosphorus) oils, herbicides and pesticides are washed from roads and other impervious surfaces into streams and bushland next to developed areas. If these contaminants are concentrated, they pollute the water in creeks, waterways and beaches; and they can reduce oxygen in the water to the point that fish and other aquatic life may die.

Land use and degradation.

Activities that disturb the land, such as quarries and road and building works, contaminate the water that runs off from these sites. Contamination also comes from small scale agriculture: horticulture and plant nurseries; and from keeping animals: horse stables and yards, dog and cat boarding and breeding kennels and so on. These activities contribute pesticides, nutrients and sediments to downstream waters and so pollute the waters of Middle Harbour.

The outstanding landscape values of Middle Harbour can be lost or degraded by inappropriate landuse or management.
 
   Solutions

In most situations techniques are available to improve the quality of water leaving or being discharged from a particular site.