ROTTNEST iSLAND AUTHORITY 628.1:628.314(9 41) 1$ ~ 1~ $ WES 910294/1 Copy A Department of Environmental Protection Library - -, ROTTNEST ISLAND AUTHORITY UBkM' INVIETAL PMOTt STLEET PERTH PROVISION OP AN INTEGRATED WATER SUPPLY AND WASTEWATER TREATMENT SYSTEM PUBLIC ENVIRONMENTAL REPORT ML oTcr inJmoRrrY JANUARY 1991 PROPOSED RONEST ISLAND INTEGRATED WATER SUPPLY AND WASTEWATER TREATMENT SYSTEM PUBLIC ENVIRONMENTAL REPORT The Environmental Protection Authority (EPA) invites persons and organisations to make a submission on this proposal. This Public Environmental Report (PER) for the proposed integrated water supply and wastewater treatment system for Rottnest Island has been co-ordinated by the Environmental Protection Branch of the Department of Conservation and Land Management (CALM) with technical input from the Water Authority of Western Australia (WAWA), Geological Surveys of Western Australia, CALM Research Branches at Como, Woodvale and Marmion, AMDAL Consultants and Geoff McArthur and Associates on behalf of the Rottnest Island Authority. The PER will be available for comment for 8 weeks, beginning 2nd February 1991, and finishing 30th March 1991. Comments from Government agencies and from the public will assist th EPA in preparing an Assessment Report, in which it will make a recommendation to Government. WHY WRITE A SUBMISSION? A submission is a way to provide information, express your opinion and put forward your suggested course of action including any alternative approach. It is useful if you indicate any suggestions you have to improve the proposal. All Submissions received will be acknowledged. DEVELOPING A SUBMISSION: You may agree or disagree, or comment on, the general issues discussed in the PER or with specific proposals. It helps if you give reasons for your conclusions, supported by relevant data. You may make an important contribution by suggesting ways to make the proposal environmentally more acceptable. When making comments on specific proposals in the PER * clearly state your point of view * indicate the source of your information or argument if this is applicable, and * suggest recommendations, safeguards or alternatives. POINTS TO KEEP IN MIND: It will be easier to analyse your submission if you keep in mind the following points * attempt to list points so that the issues raised are clear. A summary of your submission is helpful; * refer each point to the appropriate section of the PER; * if you discuss different sections of the PER, keep them distinct and separate, so there is no confusion as to which section you are considering; * attach any factual information you wish to provide and give details of the source. Make sure your information is accurate; * please indicate whether your submission can be quoted, in part or in full, by the EPA in its Assessment Report. Rlher to include * your name, * your address, and * date. The closing date for submission is 3rd April 1991 Submissions should be addressed to The Chairman Environmental Protection Authority 1 Mount Street PERTH WA 6000 Attention : Mr Cohn Murray (I) TABLE OF CONTENTS Page 1.0 SUMMARY 1 2.0 INTRODUCTION 4 2.1 Present Water Management System 4 2.1.1 Water Supply 4 2.1.2 Wastewater Treatment 4 2.2 Proposed Water Management System 5 2.2.1 Water Supply 5 2.2.2 Wastewater Treatment 5 2.2.3 Reticulation Systems 5 2.2.4 Septage 5 2.3 Proposed Program of Implementation 6 3.0 NEED FOR THE PROJECT 7 3.1 General 7 3.2 Statutory Provisions 7 3.3 Geographic Consideration 7 3.4 Demography 7 3.5 Developmental 8 3.5.1 Need for more first class water 8 3.5.2 Need for a new wastewater system 9 3.6 Economic 3.7 Environmental 9 3.8 SummAry of the Need 9 4.0 ALTERNATIVES TO THE PROPOSAL 10 4.1 Remain the same 10 4.2 Retain two classes of water but increase capacity and upgrade effluent treatment facilities. 10 4.3 Convert to potable water only 10 4.3.1 Weilfield 11 4.3.2 Catchment 12 4.3.3 Desalination 12 4.3.4 Mainland Pipeline 13 4.3.5 Barging 14 4.4 Location of wastewater treatment plant site 14 4.5 Effluent disposal options 16 4.5.1 Marine disposal 16 4.5.2 Land disposal 18 4.5.3 Effluent re-use 18 4.5.4 sludge Disposal 19 4.5.5 Deep Effluent Injection 19 TABLE OF CONTENTS (continued) Page 5.0 DESCRIPTION OF PROPOSAL 22 5.1 Potable water upgrade 22 5.2 Wastewater upgrade 22 6.0 EXISTING ENVIRONMENT 24 6.1 Physical 24 6.1.1 Climate 24 6.1.2 Geology and Geomorphology 24 6.1.3 Hydrology 27 6.1.4 Marine Environment 29 6.2 Biological 31 6.2.1 Flora 31 6.2.2 Fauna 31 6.2.3 Salt Lakes 32 6.2.4 Seepage Areas 33 6.2.5 Swamps and Ephemeral Areas 33 6.3 Human Environment 33 6.3.1 Historical Background 33 6.3.2 Aboriginal Sites 34 6.3.3 Current Land Uses 34 6.3.4 Management Plan 35 7.0 iips 37 7.1 Island Biota 37 7.1.1 Borefield 37 7.1.2 Water Sewerage Pipes 37 7.1.3 Sewerage Treatment Plant 37 7.2 Wastewater Treatment 37 7.3 Effluent Disposal: Reaf forestation 38 7.4 Effluent Disposal: Ocean Outlet Option 38 7.5 Effluent Disposal: Land Disposal Option Concentrated Soakage 39 8.0 EM XONMZNTAL MMMAGENENT 41 8.1 Wastewater Treatment 41 8.2 Effluent Disposal 41 8.2.1 Land Disposal 41 8.2.2 Ocean Disposal 42 9.0 CONLUS ION 42 10.0 swuim or coioiirs 43 11.0 REFERENCES 47 TABLE OF CONTENTS (continued) Page 12.0 ENVIRONMENTAL PROTECTION AUTHORITY - GUIDELINES FOR THE PUBLIC ENVIRONMENTAL REPORT (PER) 47 LIST OF FIGURES: Figure 1: Location of alternative wastewater treatment plant sites. 52 Figure 2: Layout of aerated pond plant. 53 Figure 3(i) : Roads and Firebreaks (Settlement Areas). 54(i) Figure 30): Vegetation, Conservation and Re—afforestation. Figure 3(iii): Vegetation. 54(iii) Figure 3(iv) : Sites of Known Aboriginal Significance. 54(iv) Figure 3(v) Landform. Figure 3(vi) : Shipwrecks and Historical Sites. 54(vi) LIST OF TABLES: Table Summary of alternative effluent disposal cost. 19 Table Monthly effluent quantities, 1992/93. 23 Table Rottnest Island Surface Wind Analysis. 25 Table Summary of RIMP recommendation status by topic. 36 LIST OF APPENDICES: Appendix 1: Rottnest Island Authority Act, Sections 11, 17 and 18. Appendix 2: Rottnest Island Management Plan Recommendations 10.109 and 10.53. Appendix 3: Nett Present Value. [1] 1.0 SUMMARY: Rottnest Island enjoys a mediterranean region climate, and is situated in an arid zone adjacent to metropolitan Perth. The proposed Water Related Services project has the following objectives: To substantially upgrade an outdated wastewater treatment process and to replace the environmentally unacceptable practice of pumping untreated sewage from the Geordie/Longreach settlement into the ocean; To replace the provision of dual fresh and saline water into tourist accoimnodation with a single class of fresh water. The provision of fresh water into the effluent treatment system will dramatically improve the efficiency of handling wastewater on the Island. This will greatly reduce deterioration of wet areas, (such as bathrooms, toilets etc) reduce maintenance and leakage and generally improve the appearance of dwellings for visitors; To ensure that the essential character of Rottnest is not adversely affected for the large number of Western Australians who visit the Island. Two classes of water are presently provided throughout the visitor accommodation on Rottnest Island. Fresh (potable) water is provided to kitchen and laundry/bathroom sinks with brackish water supplied to toilets, showers and outdoor taps. Wastewater treatment is via primary treatment and evaporative aerobic ponds near the Basin in Thomson Bay, an ocean outfall of untreated effluent from Geordie-Longreach to Pt dune and to the sea and a sealed septic system at Kingstown Environmental Education Centre. The provision of a single class of fresh water would facilitate a more efficient wastewater treatment system, provide for the re- use of treated effluent and cease the universally unacceptable discharge of untreated wastewater to the sea. Fresh water would also extend the life of the Ialands sewerage and plumbing system and reduce the considerable expenditure caused by high maintenance of wet areas due to the use of saline waters. It is proposed to establish an adequate supply of fresh water to each dwelling on Rottnest. The necessary safeguards will be built into plumbing, related fittings and visitor information to ensure water is conserved and that people generally are aware of its scarcity as a resource on Rottnest Island. Alternative proposals are presented for the supply of potable water. The most economic of the options to augment the potable water supply which are seen as environmentally acceptable, is to develop the borefie].d to its fullest potential, maintain the existing bitumen catchment and provide desalination of saline water, if the limited source of potable water on the island is insufficient to meet demand. There are two freshwater mounds, one at Oliver Hill and one at the West End of the Island. Although the precise amount is unknown, current estimates as presented (1990) are conservative and quantities are expected to be greater, rather than less. Based on present estimates, it is proposed to drill a well into the Yarragadee formation to provide feed water for desalination. If the freshwater resource is subsequently found to be greater than estimated, the need for a well or for desalination will be re-evaluated. (2] It is proposed to construct a central wastewater treatment plant south of the airport. This will remove the objectionable existing treatment plant with its associated odours and discontinue the present undesirable ocean discharge of raw sewage at Pt dune.