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

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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. Apart from the obvious benefits of a central wastewater treatment plant, the Environmental Protection Authority have indicated strongly that they will not accept discharge of raw effluent to the sea in the future. It is proposed to locate the new wastewater treatment plant site in an area to the south of the airport, and to the north of Barnetts Gully. The site is secluded and being located some 2km from the Settlement, there is little risk of offensive odours being blown over the settlement areas. It would not be visually obtrusive. The site would be relatively close to areas proposed for reaf forestation without being adjacent to any of the lakes or groundwater mounds. Alternative sites are presented in this Report. Site (3) near the rubbish tip at Forbes Hill was preferred on economic grounds but was rejected for environmental reasons - proximity to Lakes Herschel and Baghdad and to sites of geological significance. The chosen site, whilst more expensive, is preferred from an environmental viewpoint. Various effluent disposal options have been examined and costed. Options include trickle irrigation of native species, trickle irrigation after nutrient removal, injection into the saline aquifer below the freshwater lens or an ocean outlet at Pt dune. Nutrient removal would be possible, but expensive. Secondary treatment followed by filtration would be required for deep injection to avoid the blockage of injection bores. Injection into the fresh groundwater would be possible after extensive tertiary treatment. Additional activated carbon, and reverse osmosis or microfiltration would all be assumed necessary. There would be considerable potential public health risks associated with this proposal. The proposal would be likely to be unacceptable to the community until substantial scientific evidence is accumulated and the option has not been considered further.

Offshore effluent disposal has been examined. Due to the lack of deep water, lack of effective current8 and the location of important coral areas south of the island, any offshore pipeline would have to be located to the north. Pt dune would be acceptable, but would require effluent to be pumped back from the proposed treatment plant. The cost of an 800m ocean outlet with pump station (an' including environmental studies) would be approximately an aeditional $1.1 million. Options have been examined in order to establish which alternative strikes a balance between cost effectiveness and environmental acceptability. It has been recommended that the most cost effective of the environmentally acceptable alternatives, would suggest that a wastewater treatment plant be established at Site 2 (Figure 1) with disposal of effluent to be via trickle irrigation of local native vegetation over 50-70 ha of land in the Barnetts Gully area. An extensive and ongoing monitoring programme is proposed as part of a water resources management plan. The programme will be formulated to incorporate the following major environmental and operational control features: monitoring of nutrient levels and movement in groundwater and island lake systems. Monitoring of fresh groundwater reserve recharge. Routine operational review of functional efficiency. (3) iv. Review of effluent end-use options, subsequent to monitoring.

V. Review of parallel studies conducted elsewhere. Extensive monitoring of effluent concentrations and spread will be carried out. This monitoring will identify any subsequent problem with nutrients which might cause adverse effects should they migrate towards the islands lake systems in quantity. The preferred location of a wastewater treatment plant at Site 2 with trickle irrigation of effluent to local species will then allow for a cost effective disposal solution with the potential for the addition of nutrient removal processes or ocean outfall options should circumstances change. Independant studies also currently being conducted on the mainland at the Beenyup ocean outfall. This effluent disposal, although many orders of magnitude greater than that of Rottnest, discharges into a Marine Park. Results of this study plus others into land disposal options on the mainland, will be reviewed. It is not an option to "do nothing" about upgrading the provision of fresh water and effluent treatment facilities at Rottnest Island. Such a course would allow continued deterioration within buildings, leakage from aged plumbing systems, inefficient and offensive treatment of wastewater in the settlement area and pumping of untreated sewage to sea. This Report addresses environmental, economic, management and social factors in requesting approval from the EPA to proceed to this upgrade as a matter of some urgency.

[4]

2.0 INTRODUCTION

The proposed upgrading of the water supply and wastewater treatment system for Rottnest Island is a Project of the Rottnest Island Authority (RIA) which has the responsibility to the Minister for Tourism for the administration and operation of Rottnest Island, under the terms of the Rottnest Island Authority Act (1987) and its attendant regulations. This project will be undertaken by the Water Authority of Western Australia (WAWA) in conjunction with the RIA. Project Management during the implementation phase will be provided by WAWA with ongoing operational management being the responsibility of the RIA. During the preparation of the PER, the Executive Officer of the Rottnest Island Authority sought the assistance of CALM. The Executive Director of CALM agreed to this, as the PER had reached a critical stage of development. Various individuals and Branches of CALM were involved, particularly Mr M Waite (Coordinator, liaison with WAWA, Geological Survey and consultants, McArthur and Associates and Amdel Environmental Services), Dr G Keighery (flora), Mr J Bartle (species selection and transpiration) and Dr S Halee (waterfowl and lakes). Various options were considered and evaluated. While CALM staff provided assistance and technical expertise, the choice of the preferred options and justifications for these are the sole responsibility of the Rottnest Island Authority. It is thus the Authority who will defend these choices in the public arena. 2.1 Present Water Managent System 2.1.1 Water Supply Two classes of water are presently provided throughout the visitor accommodation on Rottnest. There is first class (potable or fresh) water supplied to kitchen and laundry/bathroom sinks. Second class (brackish) water is produced from shallow wells on the Island to supply water to toilet cisterns, bathroom showers and outdoor taps. First class water is produced by rainwater harvesting from bitumen catchmenta adjacent to Mt Herschel and augmented with production from fresh water borefields located in the centre of the Island. Typically, the salinity (TDS) of the first class water ranges annually from 400 milligrams per litre (mg/L) to 800 mg/L. Second class water, however, ranges from 7000 mg/L to 25000 mg/L with a median salinity of approximately 19000 mg/L. 2.1.2 Wastewater Treat*ent Wastewater treatment is undertaken on an area serviced basis as follows: * Thomson Bay settlement * Geordie - Longreach settlement * Kingetown Environmental Education Centre * Remote area septage

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The Thomson Bay effluent is treated using an Imhoff Tank as primary treatment with evaporative aerobic ponds providing final treatment. This is located between the Basin and Pinky's Beach in the Thomson Bay Settlement. Geordie - Longreach effluent is macerated and pumped in the untreated form via an ocean outfall at Pt dune to the sea. Kingstown Environmental Education Centre has a sealed septic tank system whose effluent is treated using a recirculating sand filter plant. Effluent from Kingatown is treatable in this fashion because the water supply is entirely first class.

There is limited use of septage systems for remote and infrequent use facilities. 2.2 Proposed Water Manageent System 2.2.1 Water Supply The objective of this water related services project is primarily to establish an adequate single supply of fresh water to each dwelling on Rottnest. This will eliminate the need to reticulate second class water. In 80 doing, upgrade of the existing support services of wastewater treatment, reticulation systems, power supply and environmental services needs to occur in conjunction, tc ensure that the environmental impact is optimized and is in sympathy with the established Island amenity. 2.2.2 Wastewater Treatnt

It is proposed to re-locate the wastewater treatment plant to a site south of the Airport and to accept effluent from the Geordie - Longreach settlements into the main wastewater collection and treatment system. This will enable the discontinuation of the present undesirable practice of discharging untreated effluent to the sea. The additional benefit of removing the existing treatment plant, and the offence to both eye and nose which it frequently causes, will be achieved. 2.2.3 Reticulation Systems Both water supply and sewage reticulation systems will be upgraded to meet the new demands placed upon them. This will rationalise alignments and pipe materials in many of the older areas and will generally provide a sound basis for efficient ongoing operational management practices. 2.2.4 Septage Where practicable, all aeptage systems will be connected to the central wastewater system. The only systems not proposed to be connected, are those of Kingatown Environmental Education Centre which has its own sealed system and isolated septic tank systems at outlying toilet blocks such as those at the extreme west end of the island. [6]

2.3 Proposed Program of Ipleentation

Given favourable response following Public consultation and investigation by the Environmental Protection Authority (EPA), the following tinielines are suggested as a guide to perceived achievable progress: * The dwellings in the Geordie - Longreach settlements will be converted to single class water by July 1991. * Thomson Bay settlement to be single class supply by July 1992. * The new wastewater treatment plant will be developed concurrently and available to receive effluent for treatment by July 1992. Linking of the Geordie - Longreach settlements will have occurred by this time, with the consequent abandonment of the ocean outfall. Implementation is sequential, with the existing unacceptable effluent disposal practices ceasing at the time of commissioning of the proposed new wastewater treatment plant.

It is proposed that the Project will be completed within three years of conunencement. It is a requirement of the Rottnest Island Authority Act (1987) that the EPA gives its consent before the Project is operational. This PER forms part of the requirement under the investigative process of the EPA. Its purpose is to: * Clearly outline the structure of the intended project. * Identify the likely environmental impact on aspects of the Island's geology and ecology. * State management processes and safeguards which are to be enacted and maintained to ensure that all requirements are met. * Provide adequate information for the EPA officers to evaluate the Project.

* Provide a document for study by members of the Public as part of the process of Public consultation. (7)

3.0 NEED FOR THE PROJECT 3.1 General

The need for the Project can be justified using a combination of a number of valid criteria. Generally, these criteria can be categorised under several inter-. related topics - ie: Statutory Geographic (C) Demographic Developmental Economic Environmental The project will be identified with each of these topics to demonstrate its relationship with them. 3.2 Statutory Provisions

The RIA has been created under the Rottnest Island Authority Act (1987) and, specifically, Section 11 - Functions of the Authority and Sections 17 and 18 - Management Plans (Appendix 1), are the legal validation for the Project.

In tandem with the Act, the Rottnest Island Management Plan (RIM?) 1985 provides for Guidelines for Future Development on Rottnest Island under Reconmtendatjon 10.109 and Section 10.5.3 (Appendix 2). In so far as these Guidelines relate specifically to the Project, compliance with them in all relevant aspects can be demonstrated. 3.3 Geographic Considerations Rottnest is located in a semi-arid, temperate zone with virtually no naturally occurring potable water resources. Limited subsurface resources mean that additional water will require treatment of saline feedwaters. Rainfall has proven relatively unreliable, and, while production from alternative sources is necessary, it must be clearly understood that the proposed water related services project must not alter the intrinsic landscape and social character of the Island. 3.4 Dgraphy

Visitors to Rottnest can be broadly categorised as either long or short term Over Night Visitors (ONV) or Day Only Visitors (DOV). Both types of visitor, in the majority, live in Perth and enjoy a high standard of living. Visitors expect the Island's amenities to be equivalent to acconmodation facilities and public utilities in equivalent holiday destinations. Adverse impressions can be expected where any facility unfavourably compares with this benchmark.

It is essential that visitor expectations are maintained, for Rottnest to maintain its popularity as one of Western Australia's premier holiday destinations. In broad terms, Rottnest caters for the equivalent of approximately one third of Perth's population in one year. [ 8 ]

Although many visitors will appreciate the different social character and intrinsic water scarcity of Rottnest Island, it is the reasonable perception that visitors might expect at least the equivalent of Health Department standards of water quality if not the quantity enjoyed on the mainland. 3.5 Developenta1

The RIMP states that development outside the present recognised settlement areas should not occur. The concept of "status quo" development is therefore ventured as being one of a policy of upgrading of existing facilities. The proposed Project is considered consistent with this concept. 3.5.1 Need for more First Class Water Rottnest Island is a key tourist attraction for both Western Australians and for people visiting Perth. A single class of (potable) water would facilitate a more efficient wastewater treatment system and provide for the re-use of treated effluent, rather than discharge a scarce water resource to the sea. Fresh water would also extend the life of the Island's sewerage and plumbing system and reduce the considerable expenditure caused by high maintenance of wet areas (such as showers etc) due to reticulation of salty waters. Hence, it is proposed to convert the dual class system to a single first class system. The average number of visitors to the Island per year over the last few years has been approximately 320,000. it is estimated that the presentannual water consumption on the Island is l50,000m' of which only 70,000m3 is first class water. With tourist growth, the proposed single first class water scheme has been designed for 380,000 visitors annually by 1994/95. To make up the additional quantity of first class water required, the existing sources of water would need to be developed to their full potential. The borefield is and will continue to be closely monitored to ensure the quality of water is not affected by pumping. However it has been decided not to expand the bitumen catchment for environmental reasons. In the past, a dual class water supply with saline water showers, has served to remind Rottnest visitors of the inherent scarcity of fresh water on the island. As it is expected that with a single first class water scheme, water consumption would increase, a consumption awareness prograe will be initiated by the Rottnest Island Authority (RIA) and will include such measures as limited use notices beside taps, automatic metered taps, duof lush cisterns, low volume shower roses and educational articles in visitor information literature. [91

3.5.2 Need for New Waetewater System At present the wastewater system is an outdated treatment process at the Basin involvinc the environmentally unacceptable practice of ir".rg untreated sewage from the Geordie/Longreach Settlement into the ocean. There is a need to upgrade the existing system with an acceptable low maintenance system.

The supply of a single class (potable) water would facilitate a more efficient wastewater treatment plant, and allow for re-use of this scarce water resource for the much needed refforestation of the Island. 3.6 Econoic

The RIMP requires that the Island be managed in an efficient economic manner with any development contributing to the management of the physical and biological environment. This Project contains provisions consistent with this requirement. Once in place, economies of cost and effort in other areas will be realised. 3.7 Environental The RIMP stresses the need for the Authority to continually strive for repair of the natural resources of Rottnest. The benefits of this Project will directly support the effort to reef forest Rottnest, thereby enhancing the animal and plant amenity.

3.8 Snry of Need This Project benefits the Island by providing quality water related services for the user public, thu8 ensuring a reasonable quality of public utilities for visitors, while extending the life of island amenities. The project also has the potential to give valuable assistance in preserving the natural environment of the island while maintaining its inherent social and landscape character. [10)

4.0 ALTERNATIVEs TO THE PROPOSAL: 4.1 Rain the Saw: With no increase in demand: To continue and retain a dual class supply would mean the retention of an unacceptably low 2m pressure head and no improvement in the standard of water supply. If the inadequate and unsatisfactory sewerage treatment and disposal system is retained, health, safety and environmental problems will remain. In addition, if saline second class water is retained, there are increased maintenance costs of existing plumbing and fixtures and no possibility of treated was tewater re-use. with an increase in demand: Further development of the potable water borefield and bitumen catchment would still be required. Health, safety and environmental problems associated with the present wastewater system would remain but further upgrading of the treatment facilities would still be required to accept increased flows. 4.2 Retain two classes of water, but increase capacity and upgrade effluent treatment facilities: The option would provide no improvement in the standard of water supply and would require capital expenditure of borefield, bitumen catchment, storage tanks and reticulation. Because of the saline effluent from a two class system, maintenance requirements of existing plumbing and fixtures are extensive. In addition, the system would not allow re- use of effluent and hence would have to either retain the Point dune ocean outlet and the Basin treatment plant, upgrade the treatment plant to allow sufficient treatment for effluent disposal by on-site soakage, or install an ocean outlet for disposal. with all the options discussed, the Rottnest Island Authority would investigate water conservation strategies such as * Duof lush cisterns * Low volume shower roses * Accommodation limits * Visitor and resident education/ inf ormat ion on limited water resources If the island is to retain its natural character associated with an arid environment, while at the same time providing visitors with a reasonable level of amenity, then it is appropriate to focus awareness on the scarcity of water utilising the strategies listed above. 4.3 Convert to Potable Water Only: There are five sources of potable water supply in order of increasing cost.

Welifield : Bitumen catchment : Desalination : Pipeline Barging. 4.3.1 Wellfield: The groundwater profile at Rottnest Island conu - se a thin layer of freshwater, overlying saltwater The interface between the fresh and salt water is iif fuse with salinities ranging from 1,000 mg/L TDS to 30,000 mg/L TDS over a depth of some 5 to 15 metres. Recharge is from direct infiltration of rainfall. Usable quantities of potable groundwater are restricted to an area located in the western half of the island, where a wellfield has been established. The water resources of this part of the island have been well documented and monitored since 1976. The safe sustainable yield of the potable groundwater wellfield was originally assessed to be 96,000 kL per year. However, an assessment of recent drilling has indicated that the freshwater lens is more extensive than was originally assessed. A more accurate estimate of the maximum safe yield is given in chapter 6.1.3. This limited resource is in delicate balance with the underlying saltwater and is surrounded by regions of high salinity at shallow depths. The seasonal variation in the freshwater lens thickness in the wellfield area is influenced by slow diffusion of winter rainfall with the underlying saltwater and by groundwater abstraction. Excessive localised abstraction of the groundwater may result in the depletion of the freshwater lens and cause upconing of the saltwater. Inland movement of the interface may also occur if excessive abstraction from the wellfield causes a significant reduction in throughf low away from the wellfield to discharge areas around the edge of the lens. Salinity throughout the wellfield fluctuates seasonally in response to groundwater abstraction and rainfall recharge. The average salinity of groundwater abstracted from the wellfield ranges from approximately 600 mg/L TDS at the commencement of the pumping season in October, to 1,100 mg/L TDS at the end of the pumping season in April. Currently the wellfield consists of 11 production wells and a network of 23 salinity profile wells which are used for monitoring purposes. Maximum recommended annual abstraction from the 11 production wells is 49,500 kL per year. in November 1990 the Department of Mines in conjunction with the Water Authority of Western Australia assessed the long term safe yield from the potable wellfield an 190,000 kL per year. For environmental and economic reasons a maximum abstraction of 120,000 kL per year has been recommended. The cheapest option to augment the potable water supply was to develop the wellfield to its full potential. A prograe which was recently completed, involved the drilling of additional production wells to increase the yield from the wellfield, to a level not exceeding 96,000 kL. (12]

The bores will be equipped with suitably rated pumps and to ensure no over-pumping, the borefield will be automated with flow control of the bores. Monitoring of drawdown and salinity of the bores is being and will continue to be implemented. 4.3.2 Bitun Catchment: An extension to the bitumen catchxnent area was considered in the original WAWA report. The RIA Environmental Committee has subsequently recommended against such an extension and the catchment will be retained at its present size. The extensive use of other more expensive but environmentally acceptable methods of water supply will be used. 4.3.3 Desalination: The limited resource of potable water on the island is insufficient to meet the islands water requirements. However, requirements may be met by a number of methods including desalinisation of saline water. Once the fresh water borefield has been fully developed the lowest cost option for the provision of additional freshwater is desalination. The operating costs of the desalination plant and the quantity of hypersaline waste water increases as the salinity of the feed water increases. Therefore it is preferable to desalinate relatively low salinity water. The feed water qxantity required is estimated to amount to 54,000m per annum and could be derived from shallow bores (existing) which currently supply second class water to Tourist accommodation Leederville or Yarragadee aquifer bores (quality not known with certainty on Rottnest) sea water Groundwater with salinity of around 10,000 mg/L TDS may be provided from shallow wells. However, to maintain this level of salinity and avoid upconing of more saline water, pumping yields must be kept low. This in turn requires a large number of shallow wells to be drilled with associated power and pipe-lines requirements, to supply the desalination plant. Seawater could be used to supply the desalination plant. However, as the salinity of seawater is approximately 35,000 mg/L TDS, operating costs of the plant can be reduced by supplying water from a number of deeper second class saline water bores pumping at relatively high rates. [13]

(C) Available data indicates that a deep well drilled into the Leederville or Yarragadee aquifers (about 1,500 metres) may provide feed water to the desalination plant of leas than 10,000 mg/L TDS. There is a remote possibility that groundwater of less than 2,000 mgL TDS may be intersected. In terms of operating costs this is the preferred option. However, the cost of drilling a Yarragadee aquifer well is high. Accurate costs of the different options providing feed water to the desalination plant depend on the quantity of water to be desalinated. When this has been accurately estimated an assessment of the costs of each option will be made and the most prospective option will be adopted.

The Nett Present Value (NPV) (see footnote) associated with the desalination option is estimated to be of the order of $3M in perpetuity. From an environmental point of view attention needs to be given to the disposal of hypersaline waste. It is proposed that the waste be discharged into the sea. The salinity of the waste will depend on the salinity of the feed water. However, if the shallow bores or the Yarragadee bore are utilised, the waste is unlikely to have a salinity significantly different to seawater and the anticipated effect on the environment would therefore be minimal. The power required for the reverse osmosis desalination plant would necessitate upgrading of the generating plant on Rottnest Island and provision has been xade in the costing for purchase of electricity in perpetuity. The final location of the desalination plant has not yet been decided. However, regardless of the location, the saline waste water will be discharged to the ocean. 4.3.4 Pipeline fro. the Mainland: The laying of a pipeline from the mainland has been investigated. The cost of this option is very dependent upon whether it is necessary to bury the pipeline. An NPV of $9M to $1214 would apply, depending on the buried depth of the pipeline. The pipeline is considered unacceptable for a number of reasons: the risk of being ruptured by dragging of ships anchors. the high cost of modifying plumbing to all dwellings on Rottnest caused by water pressure differences.

Footnote: A discussion of Nett Present Value is provided at Appendix 3. [14]

the attendant cost of purchasing water consumed.

competition for supply from an already limited mainland catchinent. 4.3.5 Barging:

The barging of water from the mainland was costed and resulted in an NPV of the order of $12M. This was previously undertaken before the freshwater bore fields were utilized and found to be unsatisfactory. 4.4 Location Of Waatewater Treatment Plant Site: of major concern for any wastewater system is the location of the treatment facilities. For Rottnest Island there are many constraints, both physical and environmental, which limit the number of potential sites. Some of these constraints are listed below: * The plant must not be visible from strategic public observation points. * It must not be located near the fresh groundwater rsource.

* Effluent must not be discharged near the salt lakes. * The site should be as close as possible to the raw wastewater source and to the effluent re-use or disposal areas. * Proximity to power supplies. * Potential pressure-main routes for raw wastewater and effluent.

* Sites located near the airport need to consider the possibility of increased aviation hazard due to bird migration. * It must take into consideration sites of Aboriginal significance and Development Hazard Areas. * A relatively flat area of approximately 3.5ha is required to allow construction of reliable, low maintenance systems, such as aerated lagoons. Figure 1 shows the location of alternative sites identified for consideration. These are discussed below: Site 1: This site was identified in earlier reports as the location of the new plant. However, the topography in this area restricts the type of facility that can be accoodated to a more compact type of treatment, such as an activated sludge plant (with associated high capital and operating coats). The site was considered too close to the coastline and inadequate from a space point of view. [15]

Site 3: This site was considered mainly because of its proximity to power supplies. However, earthworks would be extensive and due to the nearby lakes, emergency overflow would not be permitted. To provide for the unlikely case of power failure at the plant, but not at the main raw wastewater pumping station, a callout alarm system would be provided. In such a situation, either power to the influent pumping station would be cut, while power to the treatment plant is restored, or the secondary pond outlet would be plugged thus providing up to 2 days extra storage at the plant. This effluent would have to be released gradually when normal operation resumed. Site 3 then, had some significant advantages being centrally located between the Geordie and Longreach and Thomson Bay settlements. However, its proximity to Lakes Baghdad and Herschel and the fact that sewerage pipes would have to be laid along the causeway between Herschel and Government House Lakes made this an unattractive site from an environmental viewpoint. In economic terms, however, site 3 was the best option. Site 4: This site (existing plant site at the Basin) has been included for completeness. The existing fenced area is approximately iha (128x76m). The site has certain economic advantages but these are outweighed by the undesirable location of a wastewater treatment plant in the middle of the populated area of the settlement. Furthermore the site is inadequate from a spacing view point for the location of this facility. Site 2: This site was identified as the most desirable site with respect to minimising earthworks if large areas were required to establish an aerated lagoon system. It is a secluded site with extensive ridges to the east and is close to potential areas of reaf forestation. Disadvantages include the proximity to the airport, the distance to the raw wastewater sources and the distance to the power supplies. Site 2 is the preferred site of the Environmental Advisory Committee to the Rottnest Island Authority and the Authority has accepted this advice. The location is to the west of Look-out Hill and the north of Barnetto Gully. There are several significant advantages of this location. The site is not adjacent to any of the lakes and therefore minimises any risk of seepage into the salt lakes. The location is well away from settled areas and there is not a risk of offensive odours being blown over the settlement areas from the site, some 1.5 kilometres from Thomson Bay. The site is relatively close to areas proposed for reaf forestation. [161

with the exception of some 200 metres, the laying of pipes and attendant service cabling to the site will be along the previously disturbed sites of roads and/or the Bickley to Oliver Hill railway line. Therefore there will be minimal disturbance to any ground which has not been previously disturbed. The site is not a public access area and therefore will not be visually obtrusive to cyclists or pedestrians. The route of the pipeline to this proposed site is approximate to the Kingstown Environmental Education Centre. Should the Kingstown effluent treatment plant be inoperable for any reason, it would be a relatively simple exercise to link Kingstown to the main waste water treatment system. The disadvantage of site 2 compared with site 3 is an added estimated cost of 0.27 million dollars for the provision of services to this location compared to the other. The project team and the Rottnest Island Authority members believe that this added cost burden is justifiable on environmental grounds. The proposed route of the service lines to site 2 is shown on figure 1. It is not known to be associated with any sites of Aboriginal significance nor any potential hazard areas. Being located largely along the road and railway lines, there will be minimal environmental impact in installing and maintaining these services. 4.5 Effluent Disposal. Optiona: 4.5.1 Marine Diaposal: Generally marine disposal of treated wastewater is the most common form of disposal for larger coastal communities. The environmental effects can be reduced to acceptable levels providing the following practice is adopted: * Grease, gross solids and other objectional matter must be removed. * Further treatment is required, the extent of which is generally governed by the assimilative capacity of the receiving waters to absorb the wastewater without adverse effects. Disposal of sewage into the marine environment may cause a variety of impacts depending on the pre- discharge level of sewage treatment, volume of waste and the biological and oceanographic characteristics of the discharge site. If the rate of discharge exceeds the assimilative capacity of the environment and the sewage is untreated, then in the extreme case, chronic pollution may manifest as: health problems in humans and marine animals through direct contact with elevated levels of pathogena, primarily faecal bacteria; contamination of edible seafood by pathogens or noxious discharges such as pesticides or heavy metals; [17]

(C) a shift in the ecological balance towards an algal or phytoplankton dominated community due to increased nutrient loadings; deterioration in environmental components due to lethal or sublethal effects of discharges; decrease in aesthetic appeal resulting from floating solids or discolouration of beaches. Effluent from the proposed Rottnest Island system would undergo primary and secondary treatment before disposal, causing a reduction in suspended solids, bacteria, biological oxygen demand and nutrient concentrations. As the origin of sewage is almost entirely domestic, there should be little or no contamination from heavy metals or pesticides. Effluent characteristics would be similar to those of the Beenyup outlet at Ocean Reef, although with a reduction in volume of several orders of magnitude. Environmental impacts at that site presently appear to be limited to an enrichment of algal growth and filter feeders around the end of the outlet. The construction of a properly designed ocean outlet would be difficult on Rottnest, due to the extensive inshore reef system which would need to be traversed. Any future proposal for such an outlet would require extensive further investigation to ensure environmental acceptability. Waters around Rottneat provide an important resource for recreational and commercial activities, including both passive and extractive components. A sutary of uses is given in Figure 9.2 of the Rottnest Island Management Plan (RIMP, 1985). Some significant activities which could be adversely affected through sewage disposal include: gnvi.ronaental appreciation All visitors to the Island are exposed to the beauty of the nearshore shallows which, even to the casual visitor, reflect the water clarity and obvious health of the ecosystem; the majority of visitors spend some time engaged in water-based activities such as swimming, reef walking or snorkelling; the diversity of the nearshore ecosystem and its tropical component add markedly to the aesthetic appeal. Water sporte Under any weather conditions, the Island's bays present a variety of combinations of exposure to wind and swell, ensuring that requirements for a range of water sports can be met, ie: sheltered bays for swimming or boating, exposed point with swell for surfing, windy bays for sailing etc; (18)

C) Underwater diving Snorkelling and SCUBA diving are especially popular in the relatively safe waters surrounding the Island, which offer an enormous range of attractions and diving conditions; several commercial operations rely on this area for dive tours or instruction courses. Fishing Recreational fishing from boats or the shoreline is a major activity around the Island - southern bays are popula.r for salmon, taylor and herring fishing; eastern and northern bays for herring and whiting; offshore of West End for large reef species such as dhufish; potting or diving for Western Rock Lobster is a cherished seasonal activity all round the Island - fishing pressure and safety considerations have necessitated strict management by the Fisheries Department prohibiting spearfishing and nets from much of the nearshore environment. Commercial fishing around the Island occurs at a low level; rock lobster boats work pots to within 1.6km of the Island during the rock lobster season (to within 800m in an area west of Parker Point and Pt dune at the beginning of the season); some shark netting occurs offshore to the west or south outside the netting prohibition; purse-seine fishermen catch small schooling species between the Island and the mainland but rarely venture close to Island waters. Education and Research Nearahore reef environments provide a major focus for education and research activities; the mixture of tropical and temperate fauna and flora provides a valuable resource for ecological research, while the wide reef flats provide a safe and easily accessible natural classroom. A field research station with a major marine research and teaching emphasis exists at Wadjeinup Hill under the control of a Research Committee which reports to the RIA. 4.5.2 Land Disposal: Land disposal of treated wastewater generally requires treatment to at least secondary standard to produce effluent that is low in suspended solids. Additional treatment, such as nutrient removal, to protect sensitive waterways or groundwater, may be required in some circumstances. On Rottnest Island, treated wastewater is seen as a resource that should be utilized for vegetation or reaf forestation purposes. The reaf forestation areas have been selected to minimise the possibility of migration of nutrients, bacteria or other contaminants to water supply areas or to the inland lakes and treatment to secondary standard will be adequate. (19]

4.5.3 Effluent Re-Use:

Effluent re-use to the potable groundwater supply area is not seen as appropriate for Rottnest Is land because of the high level of treatment required and the potential risk to public health. However, there is evidence to suggest that the reverse osmosis process used for desalination of water supplies virtually eliminates bacteria, so that there could be scope for recharge with tertiary treated wastewater (to remove nutrients) some time in the future. This is likely to be unacceptable to the community until substantial scientific evidence is accumulated and therefore shall not be considered further. 4.5.4 sludge Disposal: Because of the low volume of stabilised sludge produced from the proposed treatment system, sludge should be disposed to approved landfill or used as a soil conditioner. Transport to the mainland or incineration could also be considered, but at a much higher cost. The method of sludge disposal will be common to all treatment alternatives. 4.5.5 Deep Effluent Injection: Deep injection of effluent into the saline aquifer below the fresh groundwater lens is possible but relatively expensive. The major problem is the likelihood of the bore hole(s) blocking up. To avoid this problem, the secondary effluent would required additional treatment to reduce suspended solids to very low levels.

TABLE 1: SUMMARY OF ALTERNATIVE EFFLUENT DISPOSAL COSTS.

1. Proposed Plant (At No 2 site) - Disposal to 32ha, trickle irrigated

The plant proposed in the PER is an aerated lagoon plant with the option of sand filters for algae removal if disinfection is required.

CAPITAL 0 & N

Cost of plant including 8and filters - $1.083m $20,000pa

Cost of disposal including pump station, pressure main, irrigation, fencing, bores $0.270m $10,000pa

TOTAL $1.353m $30,000

Footnote: 0 & N = Operation & Maintenance Costs. (20]

Nutrient removal plant (At No 2 site) - Disposal as above

Nutrient removal by an activated sludge plant with nitrification/ denitrification capability, and filtration to reduce P by chemical precipitation to 0.5 mg/hr and effluent disinfection by chlorination.

Oxidation ditch with N & P CAPITAL 0 & K reduction to lOmg/L N and 0.5 mg/L P effluent chlorination $3.311m $110,000pa

Effluent disposal $0.270m $ 10,000pa

Cost of extra power supply to site (length) $0.240m

TOTAL $3.821m $120,000pa

As per (2) but extra treatment so that effluent can be iniected into the groundwater supply mound. (3km from plant).

Overseas practice appears very cautious with incorporation of activated carbon and reverse osmosis. In this case, microfiltration and activated carbon are assumed.

CAPITAL 0 & H

Cost as per (2) but less $ 3.520m $ 110,000pa Chlorination and effluent disposal Add for microfiltration (NP) $ 0.550m $ 50,000pa Add for activated carbon $ 0.660m $ 40,000pa Effluent disposal $ 0.340m $ 10,000pa

$ 5.070m $210,000pa

NOTE: If reverse osmosis is required, add in lieu of $0.9300m +$170,000pa microfiltration (RO $1.47m)

TOTAL $ 6.000m $380.000pa [21]

Proposed Plant (at No 2 site) - disposal to ocean outlet at Pt dune

CAPITAL 0 & M

Cost of plant excluding sand filters $1.022m $20,000pa

Effluent PS and PM (150p) to Pt dune $0.420m $10,000pa

Outlet PS and ocean outlet (800m) including environmental studies $1.100m $10,000pa

TOTAL $2.542m $40,000pa

As per (2) but with nutrient removal and chlorination so that effluent can be injected deep into the saline aquifer below the freshwater lens

CAPITAL 0 & 11

Treatment $ 3.4m Bores $ 0.2m $100..000pa

TOTAL $3.6 $100,000pa

SUMMARY OF COSTS:

CAPITAL 0 & 14

Proposed plant --> trickle irrigate $1.4m $ 30,000pa

Proposed Plant --> nutrient removal -.-> trickle irrigate $3.8m $120,000pa

Proposed Plant --> nutrient removal --> Advanced treatment .--> groundwater supply $5.1 to $210,00 to $6.Om $380..000pa

Proposed plant --> ocean outlet at Pt dune $2.5m $ 40,000pa

Proposed plant --> nutrient removal--> chlorination --> deep injection $3.6m $100,000pa with filtration

Footnote: 0 & 14 = Operation & Maintenance Costs. [22]

5.0 DESCRIPTION OF PROPOSAL: 5.1 Potable Water Upgrade:

The proposed upgrade of the island water supply will include * Single class water to all sites. * Development of the potable water borefield to its sustainable level. * Continued use of the bitumen catchment. * The drilling of a deep bore into the Yarragadee formation to supply the remaining water required in a manner as determined by the salinity level. * The most probable result would be that desalination is required.

* The deep bore would be drilled near Kingstown and the desalination plant sited at this location or adjacent to tanks near the bitumen catchment. 5.2 Waatewater Upgrade: It is proposed to construct a new wastewater treatment plant, located at Site 2. The most economical type of plant for this site is an aerated lagoon system. This system would have the following features. * Two aerated lagoons in series (detention of 1-2 days each at peak flow), followed by a secondary lagoon of 5-10 days detention. * Provision to bypass the first aerated lagoon during extended periods of low flow. * Two 2,000 m2 sand filters to polish and remove algae from the effluent (these sand filters would be constructed if it was determined that effluent disinfection was required). * All lagoons and filters would be sealed with a 1mm high density polythylene plastic (HDPE) liner. * An effluent pumping station with provision to pump unchlorinated lagoon effluent to reafforestation areas. * Emergency on-site soakage area. * Suspended wire grid for bird control. * The plant would be fenced. * Groundwater monitoring bores located immediately to the west and north of the plant. The earthworks for the plant would be constructed with in- situ materials using conventional earthinoving equipment. Surplus spoil would be disposed on site. Time for construction is estimated at 10 weeks. Details of the plant are shown in Figure 2. [23]

Effluent would be pumped to reafforestation areas and trickle irrigated. All reafforestation areas would be sign posted. A system of monitoring bores would be established for early detection of any groundwater contamination. Approximately 160,000 m3 of effluent would need to be disposed of each year. Table 2 below su.nnnarises the monthly effluent quantities expected, neglecting evaporation which averages approximately ten percent.

TABLE 2: Monthly Effluent Q1antitiee Expected, 1992/93 July 9141 m3 August 8821 September 11300 October 13098 November 13828 December 18537 January 24815 February 16845 March 13709 April 12356 May 9586 June 8470 Being essentially domestic, the effluent is not expected to contain significant levels of toxic materials. However, it would contain approximately 7,000kg of nitrogen (40mg/L) and 2,600kg of phosphorus (15mg/L) per year. It would also contain high levels of bacteria (the estimated number of faecal coliforms is expected to be in the range 10,000- 100,000 organisms/lOOmL). Other factors associated with the proposed wastewater treatment plant construction include: * abandoning the Point dune ocean disposal system. * abandoning the existing treatment facilities adjacent to the Basin. * undertaking a monitoring progrannne to ascertain whether effluent re-use can be expanded into other areas of the island (for example, for revegetation establishment). * the laying of new mains and power cables in existing disturbed areas wherever possible (refer to Figure 1) and under existing RIA guidelines. [241

6.0 EXISTING ENVIRONMENT: 6.1 Physical: 6.1.1 Climate: Rottnest Island has a Mediterranean climate with short wet winters and very dry summers. Mean annual rainfall is 718mm with 93% of annual rainfall occurring in the period April to October. The average number of rain days per year is 122. Winds are predominantly southerlies and south-westerlies with occasional north-westerly storm winds. (See Table 3 page 25).

The mean maximum temperatures range from 26.50C in February to 17.10C in July and the mean minimum temperatures range from 18.60C in February to 11.40C in August. The annual evaporation rate is 1500mm. 6.1.2 Geology :

(i) Surface Geology Rottnest Island is built of late Pleistocene to early Holocene dune limestone (Tamala Limestone), with a thin intercalation of late Pleistocene coral-reef limestone (Rottnest Limestone), dune sand, beach sand, swamp deposits and lake deposits. The oldest rocks exposed on the island, belonging to the earlier part of the Tamala Limestone, are probably not more than about 140,000 years old. The most recent review of the geology is by Playford (1988) from which these notes are taken. The Tamala Limestone is a unit of eolian calcarenite, composed of wind-blown shell fragments with variable amounts of quartz sand and is characterized by large- scale eolian cross-bedding, marking successive dune slopes. Over most of Rottnest Island the unit is mantled by residual quartz sand derived by weathering of the sandy limestone. Hard calcrete horizons occur in places, and these are normally underlain by softer limestone with abundant fossil root structures and may be overlain by grey to brown fossil soils. The fossil soils, calcretes, and rootlet horizons mark periods of local interruption in dune building, which allowed time for soils to develop and vegetation to become established, before being overwhelmed again by a new advancing dune. The thickness of the Tamala Limestone in the Rottnest area is probably up to about 115m, including some 70m of section below sea-level, overlying older Pleistocene or Tertiary sands. Most of the exposed formation is believed to be younger than the Rottnest Limestone coral reef, which is about 130,000 years old. However, part of the Tamala Limestone is of Holocene age, laid down during the Flandrian transgression. The contact with overlying modern dune sands is transitional, as cementation of those sands is progressing gradually below the surface.

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The Rottnest Limestone is a late Pleistocene unit of coral-reef limestone and associated shelly limestone exposed at Fairbridge Bluff in Salmon Bay. The formation is overlain and underlain by Tamala Limestone, and is believed to represent a marine tongue intercalated in that formation. The total outcropping thickness of the Rottnest Limestone is 3m, but the lowest part is not exposed as it extends below sea-level on the erosional contact with the underlying Tamala Limestone. The corals include branching and platy species of Acropora and colonies of Goniastrea, Pocillopara and cf. Monomyces. coralline algae encrust most of the corals and contribute significantly as binding organisms in the reef framework. Shelly calcarenites are associated with the reef and some shells are heavily encrusted and bound into the reef framework by coraline algae. The Rottnest Limestone has been dated by uraniu,mthorium methods as 132,000 ± 5,000 years B P. The Herschell Limestone is a unit of Holocene marine shell beds with interbedded lime sand ranging from friable to strongly cemented, which is exposed around margins of the salt lakes on Rottnest Island. The formation consists of two members: the lower Vincent Member and upper Baghdad Member. It overlies and abuts the Tamale Limestone and is overlain by superficial Holocene deposits. The unit is at least 2.5m thick, and is believed to have been deposited in subtidal to intertidal environments when the salt lakes formed lagoonal arms of the sea, and sea-level was up to about 2.4m higher than today. The Herechell Limestone has a very rich fauna of gastropods, bivalves, chitons, scaphopods, arthropods, echinoderms, fish, foraminifers, corals and polychaetes. One hundred and forty two species have been recorded from the Vincent Member, 99 from the Baghdad Member and a further 66 species collected in the past from the formations that have not yet been assigned to individual members. Radiocarbon dating indicates that the two members of the Harachell Limestone have distinct groupings of dates: the Vincent member is 4,800 to 5,900 years old, and the Baghdad Member is 2,200 to 3,100 years old. Thus the dated parts of the two members were deposited over intervals of some 1,100 and 900 years respectively and the time break between them is about 1,700 years. Late Holocene and modern dune sand occurs in various parts of the island, the main developments being in the vicinity of Salmon Bay, Porpoise Bay, Paterson Beach, Thomson Bay, Stark Bay and Narrow Neck. The dunes consist of lime sand composed of fragmentary mol].uecan material, foraminifere and small amount of quartz sand. The maximum thichness of dune sand is probably about 20m, at Oliver Hill. Modern beach sand at Rottnest has essentially the same composition as the dune sand. Most consists of skeletal-fragment lime sand, although quartz sand dominates in a few areas. [27]

Holocene swamp deposits on the island consist of thin layers of lime sand, marl, peat and algal sediments. The maximum thickness ranges from 2.6m in Salmon and Parakeet Swamps to 4.4m in Barker Swamp. Modern salt-lake deposits, consisting of ...al. cyanobacterjal and evaporitic sediments, form veneers on the floors of the salt lakes and around their margins, overlying the Herschell and Taxnala Limes tones (ii) Subsurface Geology:

Knowledge of the subsurface geology of Rottnest Island is based on the old Rottnest Bore, and on geophysical and well data obtained from petroleum exploration activities in the offshore Perth Basin. The total sedimentary section below Rottnest is believed to be about 10,000 to 12,000m thick, and is Tertiary, Cretaceous, Jurassic, Triassic, Permian, and possibly older Palaeozoic in age. Rottnest overlies the eastern edge of the Vlaming Sub-basin of the Perth Basin and is characterized by a thick Tertiary and Cretaceous sequence. Seismic surveys have shown that the Early Cretaceous and older rocks are exten8ively faulted. Movement is believed to have been normal and most fault activity ceased during the Neocomi.an, following the break-up of Gondawana. Rottnest Island is elongated approximately west-southwest, nearly at right angles to the usual north-south coastal trends in this part of the Perth basin. This suggests the possibility of underlying structural control, although there is nothing in the known subsurface structure of the area to confirm this. 6.1.3 Hydrogeo].ogy (ii) Groundwater Three major aquifers occur beneath Rottnest Island. Each has been assigned the name of the major contributing formation. In descending order they are: Tamale aquifer (an unconfined aquifer comprising the Quaternary Tamala Limestone and overlying sands.

Leederville aquifer (a confined aquifer comprising the Cretaceous Leederville Formation)

Yarragadee aquifer (a confined aquifer comprising the Cretaceous Gage and Parmelia Formations and the Jurassic Yarragadee and Cockleshell Gully Formations). [28

The following summary is based on Davidson and Mory (1990) The hydrogeology of the Ta.ala aquifer has been well documented (Playford and Leech, 1977). The upper surface of groundwater in the aquifer is the water table, and the aquifer is unconfined. Groundwater originates from direct rainfall infiltration and forms two thin fresh-water lenses (at Wadjemup Hill and Oliver Hill) resting on saline water with an intervening brackish-water mixing zone. After recharge the groundwater moves slowly under gravity through the aquifer to the coast and discharges into the sea. Substantial depletion by evaporation, transpiration from vegetation and pumping from boreholes occurs during discharge. The fresh-water supply on Rottnest Island is currently obtained from the Wadjemup Hill lens in the west-central part of the island. Production is from 11 bores, which are capable of producing 49,500 cubic metres/year of fresh water (less than 1,000mg/LTDS). An additional 11 production bores have been successfully drilled (June 1990) by the Water Authority of Western Australia, and these, together with the existing bores, should be capable of yielding about 96,000 cubic metres/year. This total is equivalent to about 25% of the annual recharge, which is estimated to be about 380,000 cubic metres per year. The long-term safe yield of fresh groundwater from the Wadjemup Hill lens is estimated to be half of that amount, or 190,000 cubic metres per year and abstraction greater than 96,000 cubic metres per year is therefore feasible. Brackish water of salinity less than 10,000mg/LTDS required for desalination may be obtainable from the fresh-water/salt-water mixing zone below the fresh- water in the Wadjemup Hill lens, or from the Oliver Hill lens south of the salt lakes. However, the mixing zone beneath the Wadjemup Hill lens is less than lOm thick and is considered too thin to be utilized as a groundwater source for the desalination supply. The mixing zone beneath Oliver Hill lens is also thin but if utilized with the fresh-groundwater section in this lens, could provide source water for desalination. This would require a borefield of 10 to 20 bores if the salinity of the source water for desalination is to be maintained at less than 10,000mg/L TDS. The Leederville aquifer is a major confined aquifer which extends under the Perth Metropolitan Area across to Rottnest. It is multi-layered, consisting of interbedded lenses of sandstone, siltstone and shale. In the Leederville aquifer groundwater of salinity less than 10,000mg/L TDS extends to at least 30km of f shore as calculated from the wire-line logs in petroleum exploration wells. On Rottnest Island, water from the old Rottnest bore drilled in 1911-13, which tapped the Leederville aquifer, was reported to be "as salty as the sea" (approximately 35,000mg/L TDS) although it was not analysed and may have been fresher than this. [29]

The Rottnest bore flowed with a pressure head of about 4m A1. Any other deep bore on the island can also be expected to flow if it is drilled at a similar elevation. The Yarragadee aquifer is a deeper confined aquifer that extends west from under the Perth Metropolitan Area to below Rottnest Island. It is also a multi- layered aquifer of sandstone, siltetone and shale and was not reached in the old Rottnest bore. The aquifer contains groundwater under pressure and although the hydraulic continuity through the aquifer is probably impeded by north-south trending faults, artesian flows can be expected from a bore drilled into the aquifer on Rottnest Island. Groundwater in the Yarragadee aquifer ranges in salinity from about 120 to 14,000mg/L TDS onshore, and from 5,000 to greater than 50,000mgIL TDS in offshore wells near Rottnest and beneath the island it could conceivably be less than 6,000mg/L TDS. 6.1.4 The Marine Environent: Nearahore Environaerit: The nearshore marine ecosystem of Rottnest contains a rich mixture of temperate and tropical species. The presence of many tropical species results from the action of the Leeuwin Current in delivering larvae from tropical and subtropical regions and maintaining an elevated water temperature through winter. Water temperature does not reach the same winter lows experienced on metropolitan beaches, as the Island is surrounded by a water mass which is less affected by air temperature. As a result of this tropical component, Rottnest marine communities are generally richer and more diverse than those of similar habitats on the adjacent mainland. Onshore reef flats and shallow nearshore reefs have a particularly abundant fauna of molluscs, corals (hard and soft), echinoderms and other marine invertebrates (Black 1984; Marsh 1984). These areas, especially sections with better-developed coral growths, also contain numerous species of reef-dwelling tropical fish (Hutchins, 1984) which add to their aesthetic appeal. The reef habitats of the western and southern regions of the Island generally contain a richer and more abundant fauna than the more algal- dominated reefs of the northern and eastern bays. Marsh (1984) designates two stretches of southern reefs, Parker Point - Salmon Bay and Nancy Cove- Kitson Point, as containing the most diverse coral communities at Rottnest. In contrasting the affinities of molluscs from western and eastern ends of the Island, Wells (1984) shows that communities from the western reefs have almost double the number of tropical species than eastern reefs; eastern reefs have similar molluac assemblages to more inshore sites. (30]

The Islands marine flora shows a mixture of tropical and temperate species similar to the fauna. This results in a very diverse algal flora with the high species richness of the southern component accentuated with tropical elements. Walker (1984) estimates that this flora may contain more than 400 species. Isolated patches of seagrass communities are found in most shallow exnbayments, but are extensive only in the large eastern enibayments (Walker, 1984). Nine species of seagrass have been recorded.

Although the dynamics of the interaction between tropical and temperate components of the system are largely unknown, substantial seasonal variation in the cover of temperate macroalgae occurs on the nearshore reefs. Altering the nutrient levels of these waters has the potential to enhance the temperate macroalgal component, most likely at the expense of the tropical benthic component. Natural variation in climatic factors causes periodic devastation of these communities (Hodgkin 1959; Black and Johnson 1983; Black 1984). As Black (1984) points out, these communities can recover from such events, largely as a result of their planktonic mode of recruitment. However, past perturbations have been short-lived and a chronic impact such as sewage pollution may lead to an ecological state from which recovery is more difficult. The oceanographic properties of the highly structured embayments around the Island are likely to be complex, responding to wind, swell and tidal height. Most bays are likely to be well flushed over periods of days to weeks but will experience static conditions under some circumstances for shorter periods, usually within a tidal cycle. Bays and reef platforms facing west or south are exposed to higher energy waves than those facing north or east, most waves energy being dissipated on nearshore reefs (RIMP, 1985). Offshore environment: Much less is known about the offshore environment of Rottnest Island than about its well-studied nearshore neighbour. Restricting consideration to a radius of 5km, it is apparent that bathyxnetry provides a major forcing function on conununity structure. West and south of the Island (seaward), depth and wave energy are greater than in areas to the north and east (landward). Animal communities of seaward areas are cha.racterised by an epibenthic suite of filter feeders, such as sponges and ascidians, and support substantial populations of large fish. These include many species popular as targets of anglers or epearfishers, such as blue groper, Achoerodus gouldii, and Western Australian dhufish, Glaucosoma hebraicum. Plants in these areas are predominantly macroalgae, including extensive beds of the brown kelp, Echlonia radiata. Surge from high wave energies provides a scouring influence on substrata, which are primarily hard limestone reef. [ 3 1 ]

Landward communities are likely to be similar to those of reefs, seagrass beds and sandy bottoms closer to the mainland and support populations of smaller fish. These populations include species such as Australian herring, Arripis georgianus, and various whiting, Sillago spp., which are of great significance to anglers. Oceanographically, these waters will still respond to some of the tidal and wind driven features of importance to nearshore circulation. The further from the Island, the less influence these features will have and circulation becomes driven primarily by the Leeuwin Current.

6.2 Biological:

6.2.1 Flora: The vegetation of Rottnest has been mapped by White and Edmiston (1974, 1988) and Penn and Green (1983). These authors have distinguished eleven vegetation communities, all of which have been subject to varying degrees of disturbance during the 160 years of European settlement on the island. The major change has been the conversion of low closed forest and closed scrub to heath. The continued loss of this woodland will cause local extinctions in the flora and fauna (some of which are endemic forms, eg: the Red capped Robin). This problem has been addressed in the management plan. The other unusual vegetation type (for an offshore island) is the saltlake vegetation, which has been little disturbed. 6.2.2 Fauna: The vertebrate fauna of Rottnest Island is dominated by birds. One hundred and seven species have been recorded, three of which no longer occur on the island. of the 104 species that still occur 31 are resident, 16 are regular migrants and 57 have a sporadic occurrence. Four of the residents, one vagrant and one species that no longer occurs are exot' species (Halse, persoral communication). Rottnest is an important habitat for migratory waders. It is estimated that almost 10% of the Ruddy Thrastonea that visit Australia use the island and are concentrated on the salt lakes. Many of the wader species use the beaches and salt lakes of the island are listed in the Japanese and Chinese-. Australia Migratory Bird Agreement, which required the protection of listed species and their habitats. Rottnest is also an important sUmmer habitat for Banded Stilts (which often used to be called Rottnest Island Snipe) with more than 3,000 birde being recorded frequently (Halse, personal communication). Other bird species that are important from a conservation viewpoint are the Red capped Robin, Singing Honeyeater and Rock Parrot. The Singing Honeyeater has diverged markedly from the mainland population during the 6,500 years since Rottnest separated from

Footnote: Dr S A Halse, Conservation and Land Management Wildlife Research Càntre Woodvale. [32]

the mainland and is now regarded as a endemic sub- species. The Rock Parrots on Rottnest are an isolated population (they do not occur on the adjacent mainland). The Quokka is the only indigenous marsupial on Rottnest. The species occurs throughout the island, has been the subject of much research and has a population size of 8,000-12,000, making it the largest population of Quokkas anywhere. Sixteen species of reptile have been recorded on Rottnest. From a conservation viewpoint, the most important species are the Dugite and Bob-tailed Goanna, both of which are endemic sub-species as a result of long isolation from the mainland populations (Halse, personal coxTununication). Three species of frog occur on the island. only a small proportion of the invertebrate fauna of Rottnest has been studied and is poorly known. The aquatic invertebrate fauna of the wetlands of Rottnest consists of 58 species (Edward 1983). Twenty-one of these have been recorded from the salt lakes; they are salt-tolerant insects, crustaceans, worms and molluscs. The remaining species were recorded in the swamps and ephemeral freshwater pools. The ephemeral pool near the airport is the only area where conchostracans (a group of freshwater Crustacea) occur. 6.2.3 Salt Lakes: The salt lakes occupy about 10% of the area of Rottnest Island. There has been little study of their relationship with the unconfined aquifer although it is known they are connected. There are eight permanent salt lakes (Baghdad, Herschel, Government House, Serpentine, Garden, Vincent, Timperley and Pink Lakes). There are two seasonal salt lakes (Negri and Sirius Lakes). Benthic microbial mats composed of blue-green algae and diatoms occur in the three deeper salt lakes (Government House, Serpentine and Herschel Lakes). These lakes become meromictic in winter and spring. Meromictic" conditions exist when rainfall and inflow from seepages form layers of less saline water over the hyper saline water in the lakes. This causes heat to be trapped in the deeper saline water (Halse, personal communication). Meromictic lakes are unusual in Australia and the rest of the world. Stromatolites also occur in these lakes as a result of carbonate precipitating out of fresh water entering the lakes in seepage areas. They are of considerable conservation importance. The salt lakes on Rottnest comprise a unique habitat. No other island off the Western Australian coast contains a network of permanent and seasonal saline lakes. [33]

6.2.4 Seepage Areas: There are extensive seepages around nearly all the salt lakes. These are areas where fresh or brackish water from the unconfined aquifer enters the lakes. Seepage inflow is greater in winter and spring than in summer. The seepage areas have a pivotal role in the ecology of the salt lakes and the whole island. Apart from their influence on the physiochemical properties and biology of the lakes themselves, the seepages affect the vegetation of the shoreline, provide free water and are important for the breeding of bird species such as the Australian Shelduck, Rock Parrots, White Fronted Chats and for a number of other bird and reptile species. 6.2.5 Swamps and Ephemaral Pools: There are eight swamps on the island that used to be seasonal (Lighthouse, Salmon, Bickley, Barkers, Parakeet, Bulldozer, Rifle Range and Aerodrome Swamps). Only Barkers Swamp is now in an undisturbed state; Rifle Range is eutrophic (Halse, personal communication), Aerodrome was created by the building of the airstrip, and the other swamps were excavated for marl and now contain permanent, saline water. Even in their present condition the swamps are used by a ntmber of bird species and constitute an important avian habitat. Barkers Swamp is particularly important because it is representative of the undisturbed condition of many of the swamps. Rottnest Island Management Planning Group (1985) suggested the other swamps could be rehabilitated. Five ephemeral pools (or groups of pools) occur on the island. Garden Pool has been modified by landscaping the eastern shore of Garden Lake, Gull Wash and Frog Pools have been created as a result of road construction (Edward 1983). Corio Pool and the group of small pools east of the airport terminal are relatively undisturbed. 6.3 Human Envi.ronaent:

6.3.1 Historical Background: The first recorded visit by a European to Rottnest was in 1658 when the seaman Abraham Leeman put ashore from the Dutch essel Waeckende Boey under the coand of Volkerson. on 30 December 1696 the Dutch navigator Conunander Willem de Vlainingh landed in Porpoise Bay. Mistaking the quokkas for rate, he gave the island the name ROTTENEST. Possible evidence exists, in some locations near the West End, of an aboriginal presence on the island dating to the time when Rottnest was part of the mainland. [34]

The island has been inhabited since 1830 and has been used for farming, as an Aboriginal prison, boys reformatory, summer residence of early Governors, and since early this century, a holiday destination for Western Australians.

Many references detail aspects of the history and heritage of Rottnest Island. For example:- Rottnest Island, History and Architecture R J Ferguson Rottnest, Links in History J A Henderson Marooned 3 A Henderson Rottnest, History and Legend W Somerville, LL.D. 6.3.2 Aboriginal Sites: The Department of Aboriginal Sites of the Western Australian Museum, in association with interested Aboriginal groups and the Rottnest Island Authority have commenced a programme to identify the known Aboriginal burial sites in Thomson Bay. This is being undertaken in conjunction with Curtin University academic personnel using ground probing radar technology. If successful, this technique should confirm the location of the known burial site and provide further information on the possibility of any further site. Some of the existing sewerage lines are in a location adjacent or within areas of possible sensitivity. The project calls for the presence of a consultant archeologist when any ground disturbance is undertaken in an area of known or suspected Aboriginal significance. Clear guidelines are in existance should any artefacts be found which are of significance to Aboriginal interests. Should the ground probing radar technology prove effective and economic in this environment, the opportunity exists to utilise this technology in areas of likely significance before ground disturbance is undertaken. Input has been sought from the Department of Aboriginal Sites of the Western Australian Museum for advice on an appropriate process for consultation with interested groups. Work to be undertaken should confirm the likely application of this technology and test the preliminary conBultative process which has been put into place. 6.3.3 Current Land Uses: The attached map (figure 3) defines the settlement areas of Rottnest Island together with existing roads, firebreaks and services. [35]

Also outlined is the area of ocean surrounding the island under the direct control of the Rottnest Island Authority. Under the Rottnest Island Authority Act (1987), the definition of the Rottnest Island Reserve is as follows:

the land containing 1,859 hectares comprising Swan Location 10976 as shown and bordered pink, at the commencement of this Act, on Department of Land Administration Plan No. 16860; and the waters comprising Swan Location 11022 as shown, at the commencement of this Act, on Department of Land Administration Plan No. 16932, including the sea-bed and subsoil beneath such waters, being Reserve No. 16713 in the records of the Department of Land Administration. Outlined also is the proposed site of the wastewater treatment plant (site 2). (Figure 1) 6.3.4 Management Plan:

The Rottnest Island Authority is currently implementing those recoimuendations of the Rottnest Island Management Plan (1985) which were endorsed by Cabinet in 1987. The progress of this implementation is currently the subject of review by the Department of Conservation and Land Management. Attached is a copy of the status of progress as at September 1989. (See Table 4 page 36) Implementation is due for completion by the end of fiscal year 1992/93. Many of the recommendations within the RIMP impact on the proposed Water Related Services Project; the current statue report will be available through the offices of CALM in the near future and interested persons should refer directly to this source for further reference. [361

TABLE 4 - SUMMARY OF RIMP RECOMMENDATION STATUS BY TOPIC SEPTEMBER 1989

Not iaple- Eented Ip1eaent-Iap1e- for I2p1een- Iple- ion in aented special tation to aented progress in part reasons be done ------Principles of Develop- 4 2 Development Conservation of Lakes 4 1 3 Rehabilitation 11 13 2 2 4 Bird Breeding Sites 1 2 1 3 Cats, Doqs 3 Rodents 1 3 Exotic + Caged Birds 3 1 2 Nuisance Insects 2 Water Resources 12 1 4 2 5 Sewage Treatment 4 6 Power/Lighting/Gas 3 4 1 1 Roads 2 2 1 Extractive Industries i Rubbish/Quokkas 5 3 0 0 1 Fire + Emergencies 9 1 2 1 1 Boating Facilities! Swimming 6 2 2 0 Paths, Cycleways 4 4 1 1 2 Information 6 6 1 1 4 Intertidal + Subtida]. Biota 1 1 1 2 Settlement 16 2 2 2 0 Historic Sites 6 2 2 Kingstown 14 1 1 Lookouts/Shelters 1 2 Cleanup 5 1 1 2 Wood Scavenging 1 Abriginal Sites 1 2 1 Luggage/Goods Handling 5 3 2 2 2 Airport 3 Vehicles 8 2 0 3 1 Bicycles 6 3 2 3 2 Organised Tours 1 3 1 0 0 Education/Research 1 5 1 Behaviour 1 Residents/Business Associations 1 1 0 1 Legislation 7 Land Tenure 3 1 1 Staff 21 2 0 3 0 Reporting 5 0 Finance 27 5 5 1 6 Resort Management 1 ------Total 52.5% 18% 9.5% 7% 13% [ 3 7 ]

7.0 ENVIRONMENTAL IMPACTS: 7.1 Island Biota: 7.1.1 Borefield:

The effect of installation of bores and maintenance tracks on island biota is not believed to be significant. 7.1.2 Water Pipes and Sewerage Pipes: All pipes, except those south of the airport running to the sewerage treatment plant, will be laid beside existing pipes or roads and will be adjacent to the old railway line to Oliver Hill. The work should not increase the existing level of disturbance to any habitat. The pipeline on the south side of the airport will be aligned as far south as possible to minimise any impact on the small swamp on the south side of the aerodrome, created some years ago when the aerodrome was built on the edge of Government House Lake. 7.1.3 Waatewater Treatnent Plant: The proposed site for the sewerage treatment plant is considered to be a biologically unimportant area and there would be no adverse impacts resulting from locating the plant in that site. 7.2 Waatewater Treatnt:

An impact would be the destruction of the existing vegetation in the immediate site location during construction of the plant. Standard practice of removing and stockpiling of topsoil for later regeneration will be employed.

As aerobic methods of treatment would be employed, odour generation is expected to be minimal during normal operation.

The type of treatment method proposed requires little operator attendance, typically one visit per week. Vehicular traffic would not be significant once the plant was cOmmissioned. The possibility of lagoon liner failure has been examined. It is considered that once installed, any penetration of the liner would most likely be confined to a very small area and would quickly self seal because of the organic content of the wastewater. Being a source of freshwater, it is likely that the lagoons will attract birds. This would be overcome by careful design and the use of bird netting where appropriate. The plant would be clearly visible from the air.

[38]

7.3 Effluent Disposal: Reaf forestation The proposed method of disposal of wastewater from the effluent is to use it to reticulate tree reaf forestation, using species indigenous to Rottnest Island and enclosed within protective fencing. This will provide a new environmental opportunity for the rapid establishment of reaf forested areas on the Island. The objective would be complete uptake of water and nutrients by the plantation. There are considerable implications for the wetland ecosystem of the island and the biota depending on the local topography and hydrology of the area(s) chosen for reticulation. The quantities of pollutant loading have been estimated in Section 5.0 of major concern is the possibility of nutrients leaching through the soil profile to the groundwater, and migrating towards the groundwater supply area or the lakes. For this migration to occur, a potential for groundwater to flow in these directions must be generated. The design application rate is very low and most effluent is expected to flow away from the lakes. However, theoretical modelling has predicted that there may be some movement in this direction over time. It is extremely difficult to determine just how much effluent and with what concentration of nutrients would eventually flow in this direction. Consequently, an extensive monitoring programme will be instigated to allow the implementation of further options as circumstances change. A proposed wastewater treatment plant to the south of the airstrip will dispose of 400 to 800m3/d of treated effluent by irrigating a proposed reaf forestation area located near the treatment plant. Preliminary modelling suggests that a groundwater mound with an elevation of 1 to 2m AND would form beneath the irrigated area, the majority of that groundwater would flow towards the coast with a minority towards Serpentine and Government House Lakes located about 1.5km to the north. Further work will be carried out to assess the impact of the land disposal of effluent on water quality in the Rottnest salt lakes. This work will be carried out by a competent hydrogeological consultant. Monitoring bores will be established and remedial action taken, if required (see also 8.2.1). 7.4 Effluent Disposal: Ocean Outlet Option The potential for impact of sewage disposal varies enormously with the location of the outlet and the distance offshore of the diffuser. An outlet with the diffuser sited well offshore in an area with a dynamic circulation should avoid the majority of adverse impacts on the Island's marine environment. Disposal of effluent in the nearshore environment, especially into an embayment in which onshore winds may temporarily occlude circulation, would cause substantial health and conservation impacts. [391

The deleterious effects of nutrient enrichment of nearshore waters, particularly those adjacent to reef flats, are apparent on reefs close to the present outlet. Occasional records of discoloration of waters and sand and levels of faecal bacteria above those recommended for direct contact exist. While the increased level of pre-discharge treatment proposed for the redevelopment of the sewage disposal system would alleviate some of the bacterial impacts, any proposed ocean outlet should be sited to ensure rapid dilution of effluent and advection away from the island and mainland under most weather conditions. Outlets to the south or west of the Island would meet dilution criteria but would need to be well offshore to avoid return of effluent, especially surfactants, in wind driven currents emanating from the prevailing south westerly winds. Discharges meeting the above criteria would pose little threat to the marine ecology through nutrient additions at the predicted rate of discharge. Physical construction of the outlet would cause extensive damage in some areas. Much of the Rottnest coastline contains steep dunes or rocky cliffs leading to nearshore reef platforms. Pipeline construction across such areas would cause temporary destruction of flora and fauna. Construction of an outlet across a sandy beach would be a lesser impact on the habitat; burying the pipe would ameliorate aesthetic objections. Sandy beaches, however, usually adjoin areas of shallow water and the overall distance from shore to deep, well-mixed, water would be greater than that from a rocky shore. It is not proposed to construct an ocean outlet at this stage. If this option is to be considered in the future, a separate environmental impact study will be undertaken, which will address the issues raised above. 7.5 Effluent Disposal: Land Disposal Option Concentrated Soakage The primary threat to marine environments posed through the soakage of wastewater relates to seepage of effluent or groundwater enriched by effluent into the nearshore zone. Submarine discharge of groundwater into the sea on the nearby metropolitan coastline has been shown to provide a substantial amount of nutrient to the Marmion coastal lagoon (Johannes and Beam, 1985). The existing level of submarine discharge of groundwater for Rottnest is not known. Similarly, the potential for existing flows to be modified through the surface addition of fluids at the proposed disposal sites is unknown. The Parker Point and Salmon Bay areas contain habitats with the highest conservation significance for Rottnest's marine environment. Marsh (1984) lists the Parker Point-Salmon Bay area as one of the two most significant areas for conservation of the Island's coral community. This community supports most of the tropical component of the Island's marine fauna and contributes much of the biodiversity and aesthetic appeal of Rottnest's marine ecosystem. (40)

Pocillopora Reef at Parker Point is the only truly dense stand of coral colonies in Island waters and supports a unique microcosm; the only comparable high-latitude habitat in Australia is at Lord Howe Island. The reef was designated a special appreciation area' in the Island's management plan (RIMP, 1985) and its susceptibility to human impacts has recently been acknowledged by a closure to fishing and boating. The tropical benthic component of the nearshore environment is especially susceptible to impacts from elevated nutrient loadings. Corals usually occupy nutrient poor waters and raised levels of nitrogen (Morrisey, 1987) and phosphorus (Rusmussen, 1987) have been associated with mortality and growth inhibition of corals. Nutrient elevation would also promote growth in the area's algal community, phytoplankton and macroalgae, which would cause further reductions in the tropical fauna. To reach the marine environment, effluent would need to pass through a considerable distance of groundwater and interstitial seawater. Under such conditions levels of faecal bacteria in water used for direct contact are likely to be very low and the prospect of public health implications remote. Salmon Bay is a popular fishing area and public perceptions of fishing in a polluted area may decrease recreational angling. In practice, most species caught are pelagic and bacterial levels are unlikely to render such transients inedible. Rock lobsters and edible shellfish might become contaminated were these living close to the seawater- groundwater interface. Parker Point provides a choice anchorage for boat-based visitors, organic enrichment of sand in the beach or littoral would cause a loss of aesthetic appeal through discoloration and odour. The offshore area between Parker and Salmon Points is unlikely to be affected. This is not a preferred option. (41)

8.0 EW1IROIONT MANAGEMgWr: 8.1 Was tewater Treatment: Revegetation of spoil disposal areas will be undertaken as part of the construction program for the treatment plant. Regular maintenance of mechanical aerators (duty standby is provided) will ensure reliable operation and maintenance of aerobic conditions. However, even with a power failure lasting several hours, the treatment system is adequately robust and will partially treat the incoming wastewater without significant deterioration of effluent quality. In the case of effluent pump station failure, effluent could be stored for up to 2 days, or, alternatively discharged by gravity to the emergency soakage area. 8.2 Effluent Disposal: 8.2.1 Land Disposal: A system of monitoring bores will be established near the reaf forestation area to monitor the impact of wastewater irrigation on groundwater quality and to detect any contamination of groundwater entering the ocean and lake environment. Bacterial and nutrient levels of groundwater will be monitored for at least 5 years after conunencement of disposal. Any submarine discharges of groundwater into the Parker Point - Salmon Bay area would be similarly monitored. These bores would be sampled on a regular basis, 80 that remedial action could be taken well before impacts become unacceptable. Monitoring could cease if no changes were detected within the 5 year period. However, reintroduction of monitoring would occur if disposal volume exceeded 150% of the last monitoring period. If this proposal was approved, a process would coence to evaluate further alternatives. A monitoring system would also be initiated to identify the first signs of any adverse effects. If it was found that nutrients were migrating towards sensitive areas in significant concentrations, modification to the approved system would then be required, for example: * Relocation of the reaf forestation area, or an increase in the irrigated area to reduce mounding effects. Installation of nutrient removal facilities at the treatment plant. * Installation of an ocean outlet. If unacceptable bacterial levels occurred in the groundwater, then the effluent could be filtered and disinfected. As a precaution, the use of effluent for reaf forestation will not be undertaken within 1km of a water supply extraction bore, or within 0.5km of the central lake system. [421

Should elevated groundwater nutrient or bacterial levels become apparent, a marine monitoring program, as described for the ocean Disposal Section will be commenced. 8.2.2 ocean Disposal

A combination of water quality and benthic community monitoring would be required to detect impacts. The study design would incorporate replicated samples at varying distances from the outlet, including distant control replicates. Preliminary sampling would be carried out to quantitatively describe community type and to determine natural spatial variability in the parameters to be recorded. The degree of replication would account for the power of statistical tests to detect changes at sites monitored at the assessed level of natural variability. 9.0 CONCLUSION:

It is proposed to establish an adequate supply of fresh water to each dwelling on Rottnest. The necessary safeguards will be incorporated into plumbing, related fittings and visitor information to ensure that water is conserved and that people generally are aware of its scarcity as a resource on Rottnest Island. The potable groundwater boreuield will be developed to its fullest potential, the existing bitumen catchment will be maintained and desalination of saline water will be provided, if the limited source of potable water on the island is insufficient to meet demand. Based on present estimates, feed water for a desalination plant would be provided from a well drilled into the Yarragadee formation. It is proposed to construct a central wastewater treatment plant south of the airport, to remove the objectionable existing wastewater treatment plant with its objectionable odours, and to discontinue the present undesirable ocean discharge of raw sewage at Pt dune. The new wastewater treatment plant site would be located in an area to the south of the airport and to the north of Barnetts Gully. The site is secluded and being located some 2km from the Settlement, there is little risk of offensive odours being blown over settlement areas. Various effluent disposal options have been examined and costed. Environmentally acceptable options include trickle irrigation of native tree species, trickle irrigation after nutrient removal, injection into the saline aquifer or an ocean outlet at Pt dune. It is proposed that disposal of effluent from the wastewater treatment plant established at site 2 will be via trickle irrigation of local native vegetation over 50-70ha of land in the Barnett°s Gully area. An extensive and ongoing prograe is proposed to monitor the movement of nutrients within the groundwater. If it is subsequently established that nutrients of sufficient quantity to cause adverse effects, are migrating towards the Islands lake systems, then further alternative effluent disposal options will be examined and implemented. [43]

10.0 SUMMARY OF CO*4MI4ENTS:

The Rottnest Island Authority undertakes to provide an integrated water supply and wastewater treatment system to Rottnest Island. Water supply An adequate single supply of fresh water will be established to each dwelling on Rottnest. The potable water borefield will be developed to its sustainable level. Potable groundwater abstraction bores will be equipped with suitably rated pumps to ensure no overpumping and the borefield will be automated with flow control of the bores. Monitoring of drawdown and salinity of the bores is being and will continue to be implemented. the bitumen rainfall catchment will continue to be utilized.

If desalination is required to supplement the available potable water resource, a deep bore will be drilled into the Yarragadee formation in a manner as determined by the salinity level. The bore would be drilled near Kingstown and the desalination plant sited at this location or adjacent to tanks near the bitumen catchmeat. A water consumption awareness programme will be initiated by the Rottnest Island Authority and will include such measures as limited use notices beside taps, automatic metered taps, duoflush cisterns, low volume shower roses and educational articles in visitor information literature. Both water supply and sewage reticulation systems will be upgraded to meet the new demands placed upon them. WaBtewater Treataent: The Rottnest Island Authority undertakes to discontinue the present undesirable practice of discharging untreated effluent to the sea. A central wastewater treatment plant will be relocated to a site south of the airport and north of Barnett's Gully. All septage systems, with the exception of those of Kingstow-n Environmental Education Centre and isolated outlying toilet blocks, will be connected to the central wastewater system. All lagoons and filters will be sealed with a 1mm thick density polyethylene (HDPE) plastic liner. A suspended wire grid will be incorporated for bird control. The plant will be fenced. With the exception of the final 200m, the laying of pipes and attendant service cabling to the site of the proposed wastewater treatment plant will be along the previously disturbed sites of roads and for the Bickley to Oliver Hill railway line. [44]

Groundwater monitoring bores will be located ixtunediately to the west and north of the plant. The present Point dune ocean disposal system and the existing treatment facilities adjacent to the Basin will be abandoned. Reafforestatjon: Effluent will be pumped to a reafforestation area at Barnetts Gully, adjacent to the wastewater treatment plant. 1. Effluent will be utilized to trickle irrigate a 50 - 70ha area of native vegetation. All reafforestation areas will be signposted. As a precaution, the use of effluent for reafforestation will not be undertaken within 1km of a water extraction bore, or within 0.5m of the central lake system. monitoring: Further work will be carried out to assess the impact of the land disposal of effluent on water quality in the Rottnest salt lakes. This work will be carried out by a competent hydrogeological consultant. Monitoring systems will be initiated to identify the first sign of any adverse effects. if it was found that nutrients were migrating towards sensitive areas in significant concentrations, modification to the approved disposal system will then be required, for example: * relocation of the reafforestation area, or an increase in the irrigated area to reduce mounding effects. * installation of nutrient removal facilities at the treatment plant. * installation of an ocean outlet. A monitoring programme will be established to ascertain whether effluent re-use can be expanded into other areas of the island (for example, for revegetation establishment). Bacterial and nutrient levels of groundwater will be monitored for at least 5 years after commencement of disposal. Monitoring could cease if no changes were detected within the 5 year period. Rowever, reintroduction of monitoring would occur if disposal volume exceeded 150% of the last monitoring period. Should elevated groundwater nutrient or bacterial levels become apparent, a marine monitoring prOgramme, an described in the ocean Disposal section, will be commenced. [45]

11.0 REFERENCES:

ANNON (1984). National Estate Survey of Rottnest. National Trust, Perth. BLACK, R. (1984). The intertidal zone: vulnerability or resilience to real or potential stress. Proceedings of the Rottnest Island Marine Management Workshop, Rottnest Island Management Planning Group, pp.10-12. BLACK, R. and M.S. JOHNSON (1983). Marine biological studies on Rottnest Island. Proc. Roy. Soc. WA 66;24-28. BRADSHAW, S.D. (1985). Management of Quokkas on Rottnest Island in Rottnest Island Management Plan, vol.2, pp. 16-20 BURN, S.E. and Edward, D H. D. (1984). Seasonal meromiseis in three hypersaline lakes on Rottnest Island, Western Australia. Aust. J. Mw. Freshwat. Res. 35 : 261 - 265.

DAVIDSON, W.A. and A.J. MORY (1990). Prospects of obtaining additional groundwater supplies on Rottnest Island. Geological Survey of Western Australia, Hydrogeology Report 1990/3 (unpublished). DEAN, K. R. (1985). Notes on some introduced animals and plants on Rottnest Island in Rottnest Island Management Plan, vol 2, pp. 36 - 37. Unpublished report, Rottnest Island Management Planning Group.

EDWARD, D.H.D. (1983). Inland Waters of Rottnest Island in RESEARCH on ROTrNEST ISLAND. ml. Roy. Soc. WA Vol. 66. EDWARD, D. (1985) Inland waters of Rottnest Island in Rottnest Island Management Plan, vol. 2, pp. 18 - 26. Unpublished report, rottnest Island Management Planning Group.

HODGKIN, E.P. (1959). Catastrophic destruction of the litoral fauna and flora near Fremantle, January 1959. West. Aust. Nat. 7;6-11.

HODGKIN, H. P. and Sheard, K. L. (eds) (1959). Rottnest Island: the rottnest Biological Station and recent scientific research. J. Roy. Sec. W. Aust. 42 : 65 - 88. HUMPHRIES, R. B. and Starr, G. M. (1985). Reptiles and amphibians of Rottnest Island in Rottnest Island Management Plan, vol. 2, pp. 12 - 15. HUTCHINS, B. (1984). Marine fish of Rottnest Island waters. Proceedings of the Rottnest Island Marine Management Workshop, Rottnest Island Management Planning Group, pp.13- 14.

JOHANNES, R.E. and C.J. HEARN (1985). The effect of submarine grounwater discharge on nutrient and salinity regimes in a coastal lagoon off Perth, Western Australia. Eatuarine, Coastal and Shelf Science 21:780-800. KEIGHERY, G.T. (1986). Garden Escapes on Rottnest Island - An Annotated Checklist. Landnote 3/86. [46]

MAIN, A. R. (1961). Crinia insignifera Moore (Anura: Leptodactylidae) on Rottnest Island. J. Roy. Sec. W. Aust. 44: 10 - 13. MARSH, H. (1984). Marine invertebrates of Rottnest Island. Proceedings of the Rottnest Island Marine Management Workshop, Rottnest Island Management Planning Group, pp.15- 18. MORRISEY, J. (1987). Nutrient history of the Great Barrier Reef Aquarium. Nutrient Workshop 1987, Great Barrier Reef Marine Park Authority, Townaville, Qid, pp.91-96. PENN, L.G. and J.W. GREEN (1983). Botanical Exploration and vegetational changes on Rottnest Island. J. Roy. Soc. West. Aust. 66 : 20-24. PLAYFORD, P.E. (1988). Guidebook to the geology of Rottnest Island. Geological Society of Australia, Western Australian Division, Excursion Guidebook No. 2. PLAYFORD, P.E. and R.E.J. LEECH (1977). Geology and hydrology of Rottnest Island. Geological Survey of Western Australia Report 6. PLAYFORD, P.E. (1977) Geology and hydrology of Rottnest Island. Part I. Geol. Sur. W.Aust. Rep. 6: 1 - 53. RASMUSSEN, C. (1987). Effects of nutrients carried by mainland runoff on reefs of the Cairns area. A research plan and preliminary results. Nutrient Workshop 1987, Great Barrier Reef Marine Park Authority, Townsville, Qld, pp.66.-91. RIGGERT, T. L. (1969). The bioLgy of the Mountain Duck (Tadorna tadornoides) on Rottnest Island. Unpublished Ph. D. thesis, University of Western Australia. RIMPG (1985). Rottnest Island Management Plan. Vo. 1 The Plan. August 1985. Rottnest Island Management Planning Group. Perth, WA. ROTI'NEST Island Management Planning Group (1985). Rottnest Island Management Plan, vol. 1. Unpublished report, Rottnest Management Planning Group.

SAUNDERS, D. and de Rebeira, 0,. (1985). The Birdlife of Rottnest Island. Saunders and de Rebeira, Perth. STORR, G.M. (1962). Annotated Flora of Rottnest Island, Western Australia. WA Naturalist. 8 109-124. STORR, G.M. (1965). The avifauna of Rottnest Island, Western Australia. II. Lake and littoral birds. Emu 64 105 - 113. WALKER, D. (1984). The marine flora of Rottnest Island. Proceedings of the Rottnest Island Marine Management Workshop, Rottnest Island Management Planning Group, pp.20- 24. WHITE, B.J. and R. EDMISTON (1975). vegetation of Rottnest Island, Perth, Forests Department. 30pp. WHITE, B.J. and R. EDMISTON (1984). Vegetation in Rottnest Island Management Planning Group. Rottnest Island Wildlife Management Workshop. Nedlands: Rottnest Island Management Plan. Vol. 2. (45] [47]

G U I D E L I N E S

GUIDELINES FOR THE PUBLIC ENVIRONMENTAL REPORT (PER) FOR THE PROVISION OF INTEGRATED WATER SUPPLY AND WASTE WATER TREATMENT SYSTEM, ROTTNEST ISLAND AUTHORITY

These guidelines have been prepared following submission of a proposed integrated water supply and waste water treatment system for Rotinest Island received on the 7 February 1990.

These guidelines are intended to identify issues that should be addressed within the Public Environmental Report (PER). They are not intended to be exhaustive and the proponent may consider that other issues should also be included in the document.

The PER should be concise and accurate as well as being readily understood by interested members of the public. Specialist information and technical description should be included where it assists in the understanding of the proposal. It may be appropriate to include ancillary or lengthy information in technical appendices. Particularly voluminous, additional, technical information could be made available at convenient designated locations, such as local libraries, and at appropriate government departments and local authorities.

SUMMARY

The PER should contain a brief summary of:

salient features of the proposal; alternatives considered; description of receiving environment and analysis of potential impacts and their significance; environmental monitoring and management programmes and comrrtments; and conclusions.

2 INTRODUCTION

The PER should include:

identification of proponent and responsible authorities; background and objectives of the proposal; brief details, and timing, of the proposal; relevant statutory requirements and approvals; and purpose and structure of the PER.

3 NEED FOR THE DEVELOPMENT

The PER should outline the justification of the project, ie the need for an integrated water supply and waste water treatment system, the environmental as well as social benefits that will result, and projected costs (in the broad sense). Discussion should make reference to the anticipated surplus volumes of treated effluent that will have to be disposed of appropriately. This should also address the philosophy of creating an additional supply of available fresh water on the island, and the implications this may present in managing the essential character of the island's cultural as well as natural landscapes.

4 EVALUATION OF ALTERNATIVE

The evaluation of alternatives to meeting the proposal's basic objectives, is one of the more important parts of a PER. A discussion of alternatives to the proposal including alternative technology, solutions and sites for various plant and equipment as well as the "do nothing" option should be given. A comparison of these in the context of the stated objectives should be included as well as costs and benefits at both construction and operational stages. In this way the rationale for not choosing certain alternatives should be clear as will the basis for choosing the preferred option. 5 DESCRIPTION OF PROPOSAL

The PER should contain a descnption of the proposal, including:

overall concept; location and layout in site spedhic and general context, and in relation to existing and proposed developments of relevance on the island; construction schedule and methods of construction including source of materials and disposal of wastes; infrastructure including power sources, linear services (underground and above ground), access roads, above and below ground structures etc; control and staging of project; operation during and after construction including decommissioning of existing plant and equipment; rehabilitation of decommissioned sites (if applicable); and projected lifetime; emergency provisions.

6 EXISTING ENVIRONMENT

The PER should provide an overall description of the environment and an appraisal of physical and ecological systems likely to be affected by it.

It should then concentrate on the significant aspects of the environment likely to be impacted by the development (ie in particular, the processes sustaining the system). Only the processes, habitats, resources and potential resources which could be influenced should be defined.

Wherever possible in the discussion of physical and biological processes that are essential deterrrnants in the maintenance of habitats and resources, conceptual models or diagrams should illustrate and synthesise the interactions between the processes.

This discussion should include:

6.1 PhysIcal

offshore and onshore geology; island and immediate coastal geomorphology; drainage; island hydrogeology including water quality, location of groundwater and direction of groundwater movement; water quality; salt lakes and their relationship to the island hydrogeology and ecology; and climatic conditions (eg prevailing winds, frequency of storm events including duration and wind velocity); soil type at recharge sites; condition of existing sites to be made redundant.

6.2 BiologIcal

Island biota and their ecosystems, and should include the immediate coastal and shoreline biota if they are to be affected by the proposals. Speaal attention should be given to the conditions of the salt lakes, nearshore reef systems (eg Point Klune) if relevant, and areas of remnant vegetation and associated fauna. All conservation values of significance should be mapped.

6.3 Human

land use, land tenure and zoning (existing and future as deterrrNned by the Rottnest Island Management Plan and subsequent policy) including conservation and recreational aspects; fishing activities (if relevant); road access; [49]

general public access including tracks, cycleways, as well as other passive recreation areas: landscape including all usually accessible portions of the island; and main areas and faalities to be directly serviced by the proposed water supply and waste water treatment system.

7 ENVIRONMENTAL IMPACTS

This is the most important part of the PER and the result should show the overall effect on the total ecosystem and social surroundings of the location dunng and after construction, and installation of the proposal.

The objective of this section is to synthesise all information and predict potential impacts upon the environment. This should include an assessment of the resilience of the systems identified in Section 6 to natural and humanly-induced pressures. Discussions should include justification as to how aspects of the development can be located in areas of conservation value. Impacts should be quantified where possible. Criteria for making assessments of their significance should be outlined. Compliance with existing environmental and policy recommendations and guidelines (ie Rottnest Island Management Plan) should be demonstrated. In some cases there will be advantage in discussing construction and operation impacts separately.

It will be necessary to deternne impacts on individual components of the environment before a final overall synthesis of potential impacts is made.

The following potential impacts should be included:

island blota, at the various installation sites, including linear installations, and over extensive areas to be used for effluent disposal and groundwater recharge in 8; approximate quantification of total cumulative pollutant loadings into the groundwater as a result of selected effluent disposal method; projected groundwater impact on the affect of both abstraction and recharge as a result of effluent disposal; impacts on the salt lake system and remnant vegetation as a result of abstraction and recharge in both the medium and long-term; projected impact on nearshore reef and marine ecology as a result of effluent disposal direct into the marine environment; landscape; any histoncal, archaeological and ethnographic sites; noise and dust (wind blown sand) associated with the construction and subsequent maintenance phases; land use, including conservation and recreation aspects; traffic and parking associated with operation the wastewater treatment plant, desalination plant and borefields; odour impacts associated with the wastewater treatment plant; community costs of construction and operatior, both during and post construction: and aesthetic impact, ie the effects on the visual and cultural qualities of the island as a result of the proposal being implemented.

The final synthesis should include an assessment of the significance and timing of the various potential impacts identified.

8 ENVIRONMENTAL MANAGEMENT

An environmental management programme should be described on the basis of (and cross- ref erenced to) the synthesis of potential environmental impacts described in 7.

The purpose of the management programme is to demonstrate the manner in which conservation values are protected, and also how potential adverse environmental impacts can be ameliorated in the short and long term, including the terrestrial, salt lake and marine environments, as appropriate.

Responsible authorities for management should be clearly identified as should management administration and funding. [501

Emphasis should be placed on the manner in which monitoring results will result, where appropriate, in amendments to the management programme.

Specific environmental safeguards should be described.

Procedures for reporting the results of monitoring and management to appropriate authorities should be given.

Elements of monitoring and the environmental management programmes should include:

groundwater quality, in particular adjacent to salt lakes and the various saltwater/freshwater interfaces; contingency planning; discharges to land, water, including assidents and emergencies, of waste and sewage disposal; landscaping in terms of use and retention of native endemic species as opposed to exotic species, in utilisation of the treated effluent as part of the possible disposal programme; rehabilitation of works areas and decommissioned sites; noise and odour; public access; operational safety; management costs; strategy for nutrient control where treated effluent is to be used for irrigation purposes; strategy for decontanination of groundwater or soils should this occur, or be required; and monitoring of reef system and marine water quality where any ocean outfall is to occur.

It is important that specific comrrxtments are given to all components and procedures of the management programme, as indicated in Section 9.

9 COMMITMENTS

Where an environmental problem has the potential to occur, the proponent should cover this potential problem with a comrrtment to rectify it. Where appropriate, the commitment should include: a who will do the work; b what the work is; c when the work will be carried out; and d to whose satisfaction the work will be carried out.

A summary of all commitments in numbered form should be given

10 CONCLUSION

An assessment of the environmental acceptability of the project in terms of its overall environmental impact and in the context of the proposed management programme should be given.

11 REFERENCES

All references used in the PER should be listed.

12 APPENDICES

The appendices should include:

Glossary - definitions of technical terms, abbreviations should be included; PER Guideknes - a copy of these Guidenes should be included in the document; Ancillary or lengthy technical information related to discussion in the text of the report. 115000s tfi Potable water (<1000 mg/L)

Brackish water (1000 - 2000 mg/L rM If: Built-up area (settlement) —500— Groundwater salinity (mg/L.) S LONOREACH% o Production bore

- ::•:•:•\ THOMSON 0 BAY 0 32°OO' Pipeline ::j:: cs 32 00'

STARK •<' I.' h'U(CTtwN SAY WA JEMUP HIL

SALMON . 0 BAY 00

0 2km I I

115°O0'

)1 Hydrogeological map of RottneSt Island

Including 1990 Production and Investigation Bores. [52]

Li Ui Li Li IJJ Li 0 0 0 0 0 0 0• o s 0 0 (C) (0 (0 (0 (0 - 6,460,000 N EXISTING RA\ WASTEWATER EXISTING RAW WASTEWATER PUMP STATIONS & OCEAN OUTLET TO BE NEW COMBINED PRESSURE MAIN TO THOMSON BAY. ONED Longrecch EXISTING WASTEWATER Ceordie TREATMENT PLANT, Boy (TO BE REMOVED).

Golf ourse EXISTING RAW WASTEWATER PUMP SAT1ON & NEW PRESSURE MAIN TO TREATMENT PLANT. 6,459,000 N THOMSON LAKE B GHDAD HERSCHE LAKE BAY

SITE 3 '- POWER -T:c & NEW UNERGFCLND C E Kingstown Centre - GOVERNMENT HO JSE LAKE 6,458,000 N .. EXISTING W ASTEWATER ) AERODR0 E . I TREATMENT PLANT U VOW 0

I SITE 1. I 6,457,000 N

"E 2 Reafforesta ion NEW WASTEWATER TREATMENT PLANT EFFLUENT PUMP STATION & PRESSURE MAIN

6,456,000 N

PLAN ROTTNEST ISLAND WASTEWATER SCALE 1:20,000 LOCATION OF EXISTING WORKS

I I PROPOSED TREATMENT PLANT & PRESSURE MAIN 500 0 500 1000 m FIG. WW\R6\ROT1.DWG 11/Ui /Y1 [53]

LU LU LU LU LU STAGE 2 PONDS STAGE 1 PONDS 0 0 0 0 (FUTURE) 3 ROAD NET 2850m3 CUT 0 0 0 0 I I 50 50 3 ROAD 1 3 ROAD (0 (0 r) n 6-457400 N L . RAW WASTEWATER PRESSURE MAIN 7 1133 (/ :1 I/u TOB RL5. 1 5 I I1I TWI RI 4 , RL5.00 FILL 2350m3 I tD 111/I

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2

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SAND FILTER I I 1050 10 20 30 40 50 60 70m < EFFLUENT 2. ______6,457,100N PUMP STATION Ljg E PRESSURE MAINS' / ED 0I I .6 I I I 5 0 5 10 15 20 25 30 35m ED

6,457,000N

STAGE ONE PONDS SHOWN PLAN STAGE TWO PONDS SHOWN SCALE 0 [54(i) ii

0 1 2 Kitomerres

I I I

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Tracks & Firebreaks

11 ReIf1ore5tati0ri Area

Figure 3(i)

Roads & Firebreaks (Settlement Areas)

KI

ESRI-AUSTRALA PTY. LTD. 25 OURW000 ROAO, HAWTHORN. VICTORIA 3122 m Phon. (03) 616 7957 r-i IS PROWSE STREET. [54(ii )]

I

u Reafforestation boundary:

- -- Area underLain by expLotabte groundwater. F __] Temptetonia / Pittosporun reafforestation sites. r 4] Melateuca conservation zones. [_s_J Acacia rostettifera conservation zones. Acacia Littorea conservation zone. Figure 3(tt) Temptetonia conservation zones. VEGETATION CONSERVATION J Pittosporum conservation zones. AND REAFFORESTATION 1 9 1 Ha!ophytic conservation zone ESRI.AUSTRALIA PlY. LTD 25 RURW000 ROAD. 10 Gasoul crystatinum cons-vatin zone. HAWTHORN VICTORIA 1122 ] P00 n. (03) III ?157 El 19 Forests Dept 5 year plan area. W(3T PERTH WA 6000 EI1 Pke.e (09) 322 495 [54(iii)]

I - - Plentations I 2_J Stèbte dune association. r iL] Oevtoptd area. T I Acanthocarpus-Stipa asoc Blowout Ii!!i Melaleuca lanceotata assoc [11I Beach and lake flats T I Ac.acia rosteltifera assoc ______Swamp M.Ialsuca lancriata] ______Aciaac r*tslIl Lake r I Acacu Iittorea association [iiiiL.J Cliff assoc ______[ 8 j Temptetonia retusa Figure 3(iii) Pittosporum association VEGETATION /9 (unpiô); i, lfl £S1-AtJSTRALIA PTY. LTD. 9 Hatophytic association SeuresS: Whils #j-W EdmisIon, 1974, L. P, II I ibuwoOo Moao and /983. Cl/#d by P. I*SP. 1172 ! ,*sp, r . a I I])) W. PIATH *A SOO$ (e) 323 4t5

1

BoThirst INDIAN OCEAN Geordie Point

WSW - THOMSON 0 BAY EN

0

- 0 0 C 0 C 0 0

0 0 0 0 0

SALMON BAY

LEGEND

S INDIAN OCEAN

SCHEME AREA

- ROADS

O PROPOSED BORES

0 EXISTNC BORES

SITE PLAN FIGURE 3(iv) Site of Known Aboriginal significance [ 5 4 ( v ) ]

B Beach _____ and, ridges shefl dominated. H2 Upper terraces flats Lake Foredune and associated blowouts. T k....J Ola with shallow sandy clay cover H2a Predominantly shelL beds, [IiiiIII Swamp Dib Stable foredunes PIL] H2b Moderate - deep sand over shell beds. active blowouts sand sheet [3 ] 02 Discrete / limesand. H2c Cemented to weakly lithified L[J n3 Parabolic sand dunes rLEISTOCENE COASTAL SAND OUNES 04 Relict foredunes limestone 1 [Jj 11 dested. high relief parabolic dune sand dunes Dune flats and low undulating parabolic low relief dune limestone. 05 12 Irregular undulating Egure 3(v)

Interdune swales within 03 dunes. and swales within 11. 12 .[L] 136 j3 Interdune depressions L AND F OR M

Interdune swales within 05 dunes flats Source HESP et a!, 198 06b 14 Hind dune limestone T ESRI.ALJSTRAUA PTY. LTD 25 euw000 ROAD. _____J 4AWTP1OR. vC10RIA 3122 MF P1on. (03) •l I 77 IS PROWSO STRUT. WISI PCRTM W A *005 Li[] (0) 322 S55 [54(vi)]

tJento'7 Ho1m tfacedon 1 2 3 Kitometres J.net 0 Gem

es

E1111 Classified Lillil Recorded LIIiIIII1 ot recorded

Figure 3(vi) SHIPWRECKS ESRI-AUSTRALIA PT?. LTD. AND 25 RURW000 ROAD, HAWTHORN. VICTORIA 3122 PP,on• (03) $t$ 7157 S HISTORICAL SITES 1 PROWSE STREET. WSTE PERTH. W.A. 100% PNo. (01) 322 415% (55

APPENDIX 1

ROTTNEST ISLAND AUTHORITY ACT NO 91 1987

PART III - FUNCTIONS AND POWERS

Functions of Authority

11. (1) The Authority has the control and management of the island for the purposes set out in subsection (2).

(2) The control and management of the Island is vested in the Authority for the purpose of enabling it -

to provide and operate recreational and holiday facilities on the Island;

to maintain and protect the natural environment and the man made resources of the Island and, to the extent that the Authoritys resources allow, repair its natural environment.

PART IV - MANAGEMENT PLANS

Management plan

(1) The Authority shall control and manage the Island in accordance with the management plan for the time being applicable to the Island.

(2) A copy of the management plan referred to in subsection (1) shall be kept in the offices of the Authority and shall be available for inspection by the public during office hours free of charge.

Existing Management Plan

(1) The management plan applicable to the island at the commencement of this Act is the Rottnest Island Management Plan dated 30 August 1985 prepared by the Rottnest Island Management Planning Group and presented to the Minister.

The plan referred to in subsection (1) has effect, subject to this section, until a revised plan is approved under this Part.

The Minister may by notice in writing given to the Authority modify or add to any provision in the management plan referred to in subsection (1), and may vary or revoke a notice so given.

Section 17 (1) has effect subject to any notice given by the Minister under subsection (3) for the time being in force. [561

APPENDIX 1 (Continued)

(5) A copy of any notice given by the Minister under subsection (3) shall be attached to the copy of the management plan kept by the Authority under section 17 (2). (571

APPENDIX 2

ROTINEST ISLAND MAN?tGFJIENT PLAN

10.109 Rec 10.109 The R.I.B. should endorse the Approved in principle for Guidelines for Future Development operatiqnal activities on Rottnest island as a framework within which future land uses on the island can be considered.

10.53 Rec 10.53 Rottnest Island should be declared an Implemented (1989) area to which the Health Act applies. This action can be taken under Section 143 of the Health Act 1911 as amended. 58]

APPENDIX 3: NETT PRESENT VALUE (NPV)

Nett Present Value (NPV) is a technical term routinely used by the Water authority of W A (WAWA). The following is extracted from the WAWA Finance Manual.

NPV is the sum of the present value of the nett cash flow for a particular evaluation period. When a choice needs to be made among different projects then that alternative with the highest NPV should be selected in preference to options with lowest NPV. The following NPV formula assumes that all cash flows occur at the end of the time period, normally one year.

CF CF1 CF2 CF3 npv=Suinof (+i)t (1+i) (l+i)=2 (l+i 3 where K = initial capital outlayed CF = cash flow in a given time period i = discount rate t = the year in which the cash flow CF occurs n = time period for a given cash flow Note: Tables detailing discount rates are provided in Appendix 1 to simplify the use of this formula. If the NPV of a proposal is positive then not only the investment in the project will be recovered with interest but the project would also add value to the Authority.

If the NPV is negative then an insufficient interest on the investment in the propo8al will be recovered and a deficit will result.

Use of NPV Criteria If: NPV greater than 0, Project is economically viable where benefits are greater than costs. NPV equals 0, Project is economically vaible where benefits equal copsts. NPV less than 0, Project is not economically viable where benefits are less than costs. 5.1 NETT PRESENT VALUE (NPV): The most important evaluation criteria is the Nett Present Value (NPV). this is the sum of the PV of the nett cash flows of a project. [59]

EXAMPLE 3 - CALCULATION OF NPV Using the DCF of examples 1 and 2.

Year 0 1 2 3 PV as

discounted = -20 9.091 8.264 7.513 NPV = -20 +9.091 + 8.264 + 7.513 = 4.868 The NPV of the project to the Water Authority is $4.87. From Example 1, the return on the above project was calculated to be $10 (sum of the nett cash flows) over the three year period. Comparing this to the NPV ie. after discounting, the return is $4.87. It is evident that the $10 received over the 3 year period would be worth $4.87 to the Water Authority in today's money values after having provided the required real return of 10% on the $20 capital invested. By determining the NPV of different capital project proposals it becomes possible to select the best combination of projects given the constraints of the capital Works Programme budget.

UBRAflV ENVIRWA, MUTAL PTyjj !J7Hog fTy I MOUflhi STREET P2TH

MW(2)\Envrepl&2