The construction of the new dam requires a Works Approval from the Department of Water and Environmental Regulation (DWER), therefore this Environmental Assessment and Management Plan (EAMP) has been prepared to support the Works Approval application. During the 2019 tourist season in the Shire, the new LWF was determined to be inadequate to meet the demands of current tourism development and had no contingency to treat any future waste generation. Therefore, the Shire requested an assessment of the LWF infrastructure and options for expanding the facility to meet current and future demand within the region.
The assessment determined that a new evaporation pond was needed along with rehabilitation of the existing decommissioned ponds. The site is located approximately 11 km south of Exmouth town center and is accessible from the Minilya-Exmouth Road (Figure 1). The LWF is located directly south of the main access road which runs along the northern boundary of the site.
The location and general arrangement of the existing facility is shown in Drawing C-101 contained in Appendix A. Under Schedule 1 of Part V of the Environmental Protection Regulations 1987 (as amended) a Prescribed Premises is an 'industrial premises with the potential to cause emissions and exhaust gases to air, land or water'. Under the Shire's Local Planning Scheme No 4, the Site is located within an area zoned 'Public Purpose – Infrastructure Services'.
The bushland immediately surrounding the site to the north, west and south is zoned 'Rural' and the bush immediately to the east is zoned 'Recreational'.
Topography
Geology
Groundwater
Surface water
4 Proposed Works
Current LWF System
New Evaporation Pond
- Water Balance Assessment
- System Inputs
- System Outputs
It is critical that the LWF has the capacity to manage significant rainfall as the site is located in a cyclonic zone. An average rainfall year is taken into account for the cyclone season and to ensure that there are no old problems with the ponds used on site. An additional single 1:20, 24-hour storm event will be used as a check to ensure that there is no overtopping of the LWF at any time during the year and that the ponds maintain adequate freeboard following a storm event.
An important input into the dam system is the liquid waste that will be processed by the LWF. These input volumes are continued for all the years presented in the water balance model and will be divided equally between the two catchment dams. The input volumes within the two catchment dams for a given month include the remaining liquid waste from the previous month (if any), the liquid waste input for the month and the rainfall within the dam's catchment, based on the selected rainfall scenario.
The input volumes into the existing evaporation pond for a given month include the overflow of liquid waste from one of the receiving ponds for the month, the remaining liquid waste in the pond from the previous month (if any), and the rainfall in the basin of the pond. area based on the selected precipitation scenario. Finally, the input volumes into the new evaporation pond for a given month include the overflow of liquid waste from the existing evaporation pond for the month, the remaining liquid waste in the pond from the previous month (if any), and the rainfall in the pond. catchment area based on the selected precipitation scenario. The freeboard was set at 0.3 m in the existing collection and evaporation ponds and at 0.5 m in the new evaporation pond to determine the available operational volume of each pond.
For the purpose of the calculations, the evaporation area at half the pond depth was set to a minimum. Once the excess liquid waste has evaporated, the evaporation pond should be designed to theoretically be empty by the end of summer to allow for inspection, maintenance, and cleanup as needed.
5 Environmental Aspects and Management
Odour
- Noise
- Dust
- Stormwater
- Liquid Waste and Sludge
Appropriate dust management measures will be implemented during construction works and as necessary during operation (eg use of a mobile water truck). It is anticipated that implementation of the engineering and management measures listed above will be sufficient to manage the dust. There is a potential for stormwater to become contaminated when it contacts the liquid waste in the new evaporation pond.
The existing surface water management system will continue to protect the liquid waste facility from surface water influences. The top of the new pond is designed to slope away from the edge of the pond at a drop of 1:100 (V:H) to prevent rainwater from entering; And. It is expected that the implementation of the above technical and management measures will be sufficient to manage the surface water within the footprint of the proposed works.
There is a possibility of leakage/seepage of liquid waste under the bottom of the pond and a risk of spillage during handling. The new pond will be lined with GCL and an impermeable HDPE geomembrane, which will be installed by a properly trained technician. The cladding will undergo systematic qualitative and quantitative testing to ensure correct fit.
Liquid waste that must be evaporated prior to pond deactivation to reduce volume and increase viscosity to reduce material handling hazards. By implementing these management measures in conjunction with the License's regulatory controls, it is anticipated that the Shire will mitigate the risks of leachate from the evaporation pond and spills from poor material handling.
7 Conclusion
