Erosion and sedimentation
Building and development in urban areas can negatively affect the environment because soil disturbed by these activities can be washed or blown as sediment into the stormwater system and waterways. Sedimentation can:
- block stormwater drains and gully pits, reducing stream capacity and potentially increasing flooding;
- cause turbidity in waterways, reducing the amount of light penetration; and
- smother aquatic life.
The Protection of the Environment Operations Act 1997 has given local government regulatory powers in relation to local environmental management. The Act has strict provisions which require builders, owner-builders, landscapers and individuals working on building sites to assume responsibility for preventing erosion of soil on the site and any consequent sedimentation off site.
Individuals and corporations are now liable for fines for engaging in activities which have the potential to pollute waterways. Local government can also issue Clean Up Notices, which require pollution incidents to be cleaned up, and Prevention Notices to address systemic pollution problems. Each of these Notices require the recipient to pay an administration fee.
An erosion and sediment control plan is required for all new building work, alterations or additions that involve changes to stormwater drainage within Mosman. The plan should be prepared by a qualified engineer and include information on:
- the extent of earthworks, stockpiles, access roads, impervious surfaces, construction entrances and drainage lines;
- proposed run-off diversion measures and sediment trapping devices; and
- proposed re-vegetation and stabilisation measures.
It is imperative that appropriate soil and water sediment and erosion control devices are implemented and maintained during construction and until the site is fully established. On-going monitoring is particularly important on steep sites, where landforms may change as the site develops.