Mosman Municipal Council

Environment

• Environmental management
• CEC
  • Integrated Projects
  • Bushland
  • Stormwater
  • Seawalls
• Trees
• Bushland and Biodiversity
• Pests and Weeds
• Gardening
• Coastal and Marine
• Water Management
• Ecologically Sustainable Living
• Atmospheric Environment
• Food Safety
• Public Health
• Noise

All of Mosman’s 28 catchments drain directly into the waters of Port Jackson or Middle Harbour, so improving stormwater quality to protect the health of these harbour waterways is a priority for Mosman Council.

Stormwater flowing from urban areas can carry a range of pollutants harmful to marine environments including litter, sediments, organic matter, nutrients, garden chemicals, oils and greases.

CEC Stormwater Projects involve the installation of Stormwater Quality Improvement Devices (SQIDs) to trap pollutants, and education campaigns to alert the community to the causes, effects and solutions to stormwater pollution.

CEC Stormwater Projects that have been implemented include:

• Balmoral Oval Stormwater Reuse Project
• Quakers Hat Bay Stormwater Project
• Little Sirius Cove Stormwater Project
• Mosman Bay
• Water Quality Monitoring Program

Balmoral Oval Stormwater Reuse Project

The Balmoral Oval Stormwater Reuse Project will result in millions of litres of potable water being saved each year, plus the removal of tonnes of pollutants that would otherwise end up at the popular Balmoral Beach.

The project consists of a Stormwater Quality Improvement Device (SQID) in Botanic Road and an underground stormwater storage tank in Lawry Plunkett Reserve.

The SQID has been designed to screen and catch rubbish within the stormwater system, enhancing Harbour water quality at Balmoral.

As Balmoral south is one of Mosman’s largest stormwater catchments, this created a great opportunity to capture and reuse the stormwater that would have simply runoff into the ocean.
Council is using the stormwater to replace the potable water currently used to irrigate Balmoral Oval. The water is treated so it is suitable for irrigation, although not for drinking.

To assist with the construction of this project, Council secured a grant of $250 000 from the Commonwealth Government’s Community Water Grants Scheme, with a further $140 000 from the NSW Water Saving Fund.

Benefits

• Support national initiative of water saving efforts;
• Stormwater runoff will be fi ltered of litter and pollutants before it reaches Balmoral Beach;
• Mitigation of possible fl ood events;
• The quality of coastal waters will be enhanced;
• Council’s expenditure on water for irrigation will be reduced;
• Council’s reliance on Sydney Water’s potable water supply to irrigate will be reduced;
• Irrigation will no longer be under Sydney Water’s water restriction policy;
• Sustainability objectives in Council’s projects will be met; and
• Balmoral Oval and foreshore can be maintained at satisfactory levels thereby reducing the need for returfing.

Please do not drink the recycled irrigation water
Please note that although the water used to irrigate Balmoral Oval and foreshore areas has been treated it is not suitable for drinking.

Quakers Hat Bay Stormwater Project

Quakers Hat Bay is in the north west of Mosman, and forms part of Middle Harbour. The sheltered waters and rocky shores of the Bay provide habitat for marine life while the long bushland reserve on the eastern side of Quakers Hat Bay contains a diverse range of flora and fauna. The bay and its foreshore are very popular for recreational activities including fishing, sailing, walking and nature appreciation.

Water quality in the bay has been affected by both polluted stormwater flowing from the bay’s urban catchment, and sewage overflows from Sydney Water’s major overflow point.

Mosman Council implemented the Quakers Hat Bay Stormwater Project in order to reduce the amount of polluted stormwater entering the bay. Council has improved stormwater quality by installing SQIDs, in Bullecourt Avenue, Killarney Street and Julian Street, to remove large pollutants. The Julian Street SQID is currently being monitored to evaluate its effectiveness in capturing pollutants and improving water quality.

Education

The education program for Quakers Hat Bay included general stormwater awareness materials for residents in the catchment, as well as a program for boatsheds and marinas. The residential campaign has informed people of the ways activities such as washing cars in the gutter, dumping garden vegetation, and hosing leaves down stormwater drains can affect harbour water quality.

Several of the boatsheds and marinas in Mosman have been part of an industry stormwater program that has combined education and regulation.

Little Sirius Cove Stormwater Project

Little Sirius Cove is a bay on the southern side of Mosman, in Port Jackson. The Cove was named after the Sirius, a First Fleet supply ship which was careened in nearby Mosman Bay after circumnavigating the world in 1789.

Like most other areas in Mosman, the Little Sirius Cove catchment is primarily residential. Pollutants in stormwater flowing from the catchment, including litter, organic matter, sediments, nutrients and chemicals, have affected water quality in the Cove. During the Little Sirius Cove Stormwater Project, Mosman Council used a combination of structural and non-structural interventions to improve the quality of stormwater.

Three SQIDs were installed to treat stormwater from the Little Sirius Cove East and Little Sirius Cove West sub-catchments, at Sirius Park, Sirius Cove Rd and Lennox St. To help determine what effect SQIDs have on aspects of water quality, including pollutants such as metals, nutrients, and other parameters including oxygen demand, this report presents the data and results of the monitoring program: Little Sirius Cove SQID - Monitoring and Analysis, 2002 (PDF 1MB).

Gardeners’ Education Campaign

Nearly half of Mosman residents use a commercial gardening service, and inappropriate gardening practices can introduce a range of pollutants, including garden organics, sediment, pesticides and fertilisers, into the stormwater system.

As gardening activities can have a significant effect on stormwater quality in a residential catchment, materials about stormwater safe gardening including letters, fact sheets and postcards, were sent to commercial gardeners who operate in Mosman, and an advertising campaign was run in the local media. This was followed up with a workshop on stormwater with a focus group of commercial gardeners.

Water Quality Monitoring Program

A Water Quality Monitoring Program is currently being implemented as a component of the Community Environmental Contract.

Receiving Water Quality

The first component of the program involved sampling of eight Mosman receiving waters, namely, Balmoral Beach, Edwards Beach, Chinamans Beach, Clifton Gardens-Chowder Bay, Taylors Bay, Little Sirius Cove, Pearl Bay and Quakers Hat Bay.

Sampling was undertaken during mid 2003 to gain an understanding of the quality of Mosman’s waterways compared to national water quality guidelines. Water samples were analysed for chemical, physical and biological indicators of water quality, including temperature, total suspended solids, turbidity, total phosphorus, total nitrogen, pH, dissolved oxygen, electrical conductivity, oils and grease, hydrocarbons, heavy metals and faecal coliforms. Results showed each of the eight beaches/bays within Mosman complied with recommended pollution levels for the majority of water quality parameters analysed.

The main exceptions for non-compliance were for the nutrients phosphorus and nitrogen, which were found to be slightly elevated above recommended levels. Nitrogen levels exceeded acceptable limits for Chinamans Beach, Taylors Bay, Pearl Bay and Quakers Hat Bay, whilst phosphorus levels were above recommended limits at Balmoral Beach, Chinamans Beach and Clifton Gardens. Sources of these pollutants can include fertilisers, detergents, and animal wastes.

Only three sites, Taylors Bay, Pearl Bay and Quakers Hat Bay recorded concentrations of oils and grease, with Quakers Hat Bay being the only site to register levels of hydrocarbons. The use of these waters as a transport route and mooring location for boats was determined to be the most likely cause for the presence of these pollutants.

Although some receiving waters exceeded recommended guideline levels for particular parameters the results obtained from the monitoring of receiving waters indicated that overall the receiving waters of Mosman are in good environmental condition with respect to aquatic ecosystem health.

The receiving water ranked as the best quality was Edwards Beach with Balmoral Beach ranked second.

Monitoring SQID Performance

The second part of the program involved sampling before and after the installation of SQIDs in seven sub-catchments of Mosman.

These sub-catchments (and sites) are: Balmoral Beach Sth (Botanic Rd), Edwards Beach Nth (Stanton Rd), Taylors Bay (Buena Vista Ave), Clifton Gardens-Chowder Bay (Morella Rd), Pearl Bay (Pearl Bay Ave), Shell Cove (Cyprian St), and Chinamans Beach (Rosherville Reserve).

This component of the monitoring program enabled Council to measure the performance of the SQIDs that have been installed. In particular, the program evaluates the effectiveness of the SQIDs in the removal of pollutants from stormwater entering the device, and subsequent improvement in water quality downstream of the device.

The five week sampling period for Pre-SQID Installation was completed in mid-February 2004. Water quality parameters analysed were the same as those analysed for the monitoring of Receiving Waters. Nitrogen and Phosphorus levels were above recommended guidelines at all sample sites and Faecal Coliform counts were also high at all sites. All other parameters were within guideline levels.

Once the respective SQIDs have been installed, post SQID water quality sampling will commence. Sampling will be undertaken over a longer time period so that results can reflect any seasonal variation.

Wet weather sampling of two SQIDs has been completed at Ashton Park, Taylors Bay and Rosherville Reserve, Chinamans Beach. Sampling is currently being conducted at Julian Street.