Thomsons Lake Urban Development Revised South Jandakot Drainage

Thomsons Lake Urban Development Revised South Jandakot Drainage Management Plan Ministerial Condition 2 Report and Recommendations of the Environmental Protection Authority ISSN 1030-0120 ISBN 0 7309 3458 6 Contents Page Summary and recommendations 1 Introduction 2 Environmental assessment of urban development proposal (1987) 3 Environmental assessment of Drainage Management Plan (1989) 4 Revised Drainage Management Plan 4 5 Public and Government submissions 7 6 Independent engineering assessment 8 7 NRMC report on drainage issues 8 8 Environmental assessment of revised Drainage Management Plan 9 9 Conclusion 13 1 0 References 13 Figures 1 Thomsons Lake urban structure study - preferred option 2 2 Proposed Metropolitan Region Scheme amendment 3 3 Cross section along Bartram Road 5 4 Proposed urban drainage system 6 Appendices 1 Ministerial conditions 2 Report and recommendations of the Environmental Protection Authority, May 1989, Bulletin 388- summary 3 Water Authority of Western Australia and the Department of Conservation and Land Management's advice to the Environmental Protection Authority on the revised Drainage Management Plan 4 Review of engineering aspects by Binnie & Partners Pty Ud 5 A report to the Environmental Protection Authority on drainage issues by NRMC Ply Ltd - executive summary 6 CSIRO's advice to the Environmental Protection Authority regarding the use of cyclodiene termiticides Summary Drainage Management Plan, the recommendations contained in this Report and also the results of the The Environmental Protection Authority has investigations into the issues identified in this examined a revised plan to drain land in South Report. Jandakot east of Thomsons Lake to enable housing development to proceed. Preparation of an Acceptability of the Drainage Management Plan in acceptable drainage management plan was a regard to its potential impact on the Beeliar condition of approval for housing development in wetlands is on the basis that there will be no South Jandakot issued by the Minister for the drainage into the southern Beeliar wetlands once Environment in t 988. urban development has commenced, other than by the drainage scheme outlined in the Plan. That is. In May t 989 the Environmental Protection Authority the Authority is opposed to the suggestion in the reported on a previous drainage management plan, Pian that development would commence up to two concluding that the acceptability of the plan had not years before the establish men! of the South been demonstrated. The Authority went on to Jandakot Branch Drain and associated pumping suggest a compromise solution which would allow stations. some houses to be constructed and also ensure that the Jandakot groundwater resource was The Authority supports the commitment to fully protected. investigate options for disposal of the drainage water and believes that, until viable alternatives are The proponent did not support the suggested available, discharge to Cockburn Sound would be compromise solution, and has submitted a revised environmentally acceptable providing there is no drainage management plan, the main features of detrimental effect on the beneficial uses of the which are: waters to which discharae is occurrina. Soecifcallv. a local drainage system within the urban area; discharge to Cockburn -Sound should not result in localised pollution, or a net increase in the nutrient a sub-soil pipe drainage system in the low~ loading to Cockburn Sound. In regard to the lying parts of the urban area; and nutrient loading to Cockburn Sound, the proponent a main drainage pipe front east of Thorn sons must ensure that the nutrient input from an existing Lake to Yangebup Lake, and an outlet pipe source, such as an industrial development, is from Yangebup Lake to Cockburn Sound. reduced by an equivaient amount to that being discharged by ihe drainage scheme. In examining the revised South Jandakot Drainage Management Plan, the Environmental Protection In regard to the Jandakot groundwater resource, Authority considered the environmental impacts of the Environmental Protection Authority considers a the proposed drainage scheme, and also the expert conservative approach must be taken to advice of the Water Authority. Department of development in its catchment to ensure the Conservation and Land Management and technical resource is protected. The current structure plan consultants, and extensive public input. for South Jandakot proposes urban development "upstream" of public water supply bores. Specifically, the main variables which determine the environmental acceptability of the drainage The Authority reiterates its position that management plan are the volume of drainage water, it does not support urban development on the physical impact of the drainage scheme, the land above the Jandakot groundwater impact of drainage water on the Beeliar wetlands, mound between the two lines of public and disposal of the drainage water. water supply bores. The Departmgnt of Conservation and Land Recommendation 1 Management and the Environmental Protection Authority have concluded that the revised Drainage The Environmental Protection Authority Management Plan for South Jandakot is concludes that Ministerial Condition 2 for acceptable, subject to the recommendations the urban development of the South contained in this report. Jandakot area east of Thomsons Lake has been satisfied subiect to the The Water Authority is generally satisfied with the recommendations contain.ed in this revised Drainage Management Pian from a technical Report. viewpoint, bui has not yet resoived financiai aspects of implementation of the drainage scheme. Recommendation 2 The Water Authority is currently investigating this matter with the proponent. and will advise the The Environmental Protection Authority Minister for the Environment directly on the recommends that prior to subdivision outcome of these investigations. approval of the South Jandakot area being granted, an Environmental There are a number of specific technical issues Management Programme should be which require clarification throuah further prepared to accommodate the investigations associated with the detailed pianninq commitments in the revised Drainage and design of the urban development and drainage Management Plan, the recommendations scheme. Accordingly, the Authority considers it contained in this report, and the results appropriate that, prior to subdivision proceeding, an of the further investigations Identified in Environmental Management Programme ls prepared this Report. which accommodates the commitments given in the The Environmental Management Programme should establish reporting and review mechanisms for the drainage scheme, and should be to the satisfaction of the Department of Conservation and Land Management, the Water Authority and Environmental Protection Authority. Recommendation 3 The Environmental Protection Authority recommends that no drainage into the southern Beeliar wetlands be permitted once urban development has commenced other than by the drainage scheme outlined in the Drainage Management Plan. Recommendation 4 The Environmental Protection Authority recommends that, until viable alternatives are aval!ab!e, discharge to Cockburn Sound would be environmentally acceptable providing there is no detrimental effect on the beneficial uses ol the waters to which discharge is occurring. !n part!cu!ar,: the discharge should not result in localised pollution; and the proponent should ensure that the nutrient input to Cockburn Sound from an existing source~ such as one of the Industries currently discharging into Cockburn Sound, is reduced by an equivalent amount to that being discharged by the drainage scheme. Monitoring of both physical and biological parameters of the drainage water and receiving water should be undertaken, and appropriate action taken by the proponent if there is an unacceptable change in water quality which would result in a detrimental effect on the beneficial uses of Cockburn Sound. The monitoring of the outlet to Cockburn Sound, and reporting of results, should be addressed in the Environmental Management Programme. 1. Introduction considered to be generally undesirable within the main catchment of a public water supply area, the In February t990 the Department of Planning and Environmental Protection Authority recognised that Urban Development submitted to the Environmental the Water Authority was prepared to accept the Protection Authority the revised South Jandakot concept because it regarded urban development as Drainage Management Plan for consideration. The potentially more controllable in terms of impacts on Drainage Management Plan seeks to address the the groundwater quality than likely alternative land water management concerns associated with a uses. Given the evidence available which suggests proposal to rezone land in South Jandakot for urban urban development may be a significant source of development (see Figure t ). groundwater pollution, this conclusion is difficult to The Drainage Management Plan must also be explain. acceptable to the Department of Conservation and Land Management and the Water Authority of Drainage management Western Australia, and advice was sought by the The Environmental Protection Authority's second Authority from those agencies. major concern was that there would be an obvious The Drainage Management Plan has been publicly need to drain all or parts of the area, but there was available since 26 February t990, and the Authority no detailed proposal

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