Water Reuse and Education - Nursery and Parks Depot

Hornsby Shire Council New South Wales

: Cut platform for water tank.

Synopsis

Hornsby Shire Council wanted to implement water conservation practices at its Pennant Hill’s nursery depot site. Council upgraded the current irrigation system and installed a functional water treatment and reuse facility.

About the Project

This project originated with members of the Water Catchments Team within the Environment Division of Hornsby Shire Council. The project demonstrates elements of Council’s Sustainable Water Development Control Plan (DCP), which has been in place since 1998.

Two 2200-litre poly rainwater tanks are proposed to capture roof water from the existing cottage and amenity buildings. In addition the stormwater run-off reuse tanks include two 105,000-litre concrete tanks and one 27,000-litre tank filled with a special Grodan filtration media. The Grodan media allows slow filtration and disinfection through its special rock wool composition colonised by biological media.

The tank operates 24hrs a day, 7 days a week allowing an aerated flow rate of 0.9 litre/second.

Motivation for Rainwater Reuse

Rainwater is a valuable resource that could be used more fully to benefit Council and the community. Too often it is wasted and can cause environmental damage through erosion of waterways and water quality degradation.

The nursery and parks depot had a number of issues requiring attention:

Run-off with high nutrient and sediment loads flowing into significant neighbouring bushland;
Stabilisation of pathways and driveways to prevent erosion and reduce overland water flows; and
Rainwater capture, treatment and reuse.

Objectives of the Project

Use the nursery/depot site as an example of best practice in the nursery industry and promote this technology to appropriate commercial and domestic applications;
Demonstrate cost savings through stormwater reuse to other local governments;
Significantly reduce the volume of stormwater/irrigation water leaving the site and highlight stormwater quality performance through sampling and analysis;
Reduce weed proliferation and germination downstream of the site through sustained bush regeneration techniques; and
Record community, academic and governmental visitors using the site for educational and training purposes.

Main Components of the Project:

Upgrading of the existing irrigation system for nursery operations;
Placement of rainwater tanks at existing building sites for reuse in toilet flushing;
Re-grading of the site and the construction of a vegetated swale (an open channel) cut-off trench, sedimentation pit and on line wetland;
Installation of stormwater tanks and pumps for water treatment, storage and re-use for irrigation;
Construction of a stormwater overflow channel lined with sandstone rocks and access track;
Sampling and analysis of system performance; and
Community education and training in water conservation.

If the project is successful it will achieve long-term benefits of pollutant reduction and potable water usage reduction.

: Construction of swale.

Benefits and Savings

Social benefits:

The project has educational benefits for the entire community,but in particular focuses on educating the horticultural industry and local government depot operations in best water management practices.

Environmental benefits:

The capture and reuse of stormwater reduces potable water consumption, erosion of waterways, transportation of pollutants and expenditure on downstream weed eradication.

Financial savings for council:

Approximately $4000 per year is saved in reduced potable water consumption.

Costs

Project funding:

NSW Stormwater Trust Grant: $200,000
Council’s Catchments Remediation Special Rate: $150,000
Total project cost: $350.000*

A cost benefit assessment is planned in October 2003 after the initial trial operation period (3 months).

* Variations (specified in Issues and Lessons Learnt) have taken the project over budget by an estimated 10%.

Issues and Lessons Learnt

Unforseen rock excavation resulted in delays and increase in cost.
It was assumed that there would be a balance between material cut and areas to be filled, however this was not the case. Increased costs resulted from additional removal and disposal charges of the unsuitable fill and purchase of additional suitable ripped sandstone material. This could have been assessed prior to commencement by conducting a boring and geo-technical study to identify material quality and depth, to support budget variations.

Water Savings

Community Nursery Site Maximum capacity ~ 45 000L holding tank.
Average yearly rainfall for Frankston 680 mm
Catchment area 520m2
Estimated runoff generation (savings)
350 – 400 Kl per annum.
Estimated storage 280 – 300 days at maximum volume.
Based on 1mm of rainfall on 1m2 will generate 1 litre of runoff.

Acknowledgments

This case study was prepared with assistance from Hornsby Shire Council.

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