REHABILITATION OF THE PENRITH LAKES SCHEME

Transcription

1 REHABILITATION OF THE PENRITH LAKES SCHEME Mr Robert Golaszewski Construction & Quarry Operations Manager/ Penrith Lakes Development Corporation EXECUTIVE SUMMARY This paper has been prepared to respond to the Institute of Quarrying Australia 2014 nomination for The Volvo Travel Award for the author s contribution toward the advancement of environmental management in the industry through exceptional rehabilitation of the Penrith Lakes Quarry. The Penrith Lakes Scheme is a quarry rehabilitation process which has set world best practice in all levels of the extraction, remediation and completion phases in the life of its quarry. The project near completion has been a previous winner of the prestigious golden hat award, recognised as a NSW State Significant project and been a substantial contributor to the environmental industry through a long term research partnership with the Australian Research Council. Over a 10 year period the applicant has been instrumental in leading on and developing the systems and process to enable Penrith Lakes Development Corporation and its staff to achieve an outcome which benefits its commercial, community and environmental interests. INTRODUCTION PENRITH LAKES DEVELOPMENT CORPORATION AND THE PENRITH LAKES SCHEME In 1981 the Shareholders (Boral, Holcim and Hanson (Heidelberg)) entered into an agreement to form Penrith Lakes Development Corporation (PLDC) for the purpose of securing access to the estimated 150 million tonnes of sand and gravel resources within the Scheme area. Securing access to these resources was a long term strategy to consistently supply the majority of the Sydney metropolitan sand and gravel market over a 30 to 35 year period. Over the years, quarry production from the Penrith Lakes Scheme peaked with volumes between 7 to 8 million tonnes per annum and continues to supply over 50% of the Sydney sand and gravel market. The Penrith Lakes Scheme occupies 1935 hectares of floodplain adjoining the Blue Mountains World Heritage Area and runs adjacent to Sydney s iconic Hawkesbury / Nepean river system, north of Penrith, NSW. The Penrith Lakes Scheme has been considered the largest sand and gravel quarry in the Southern Hemisphere with a robust vision for the future rehabilitation of this extensive quarry operation. The project is a joint venture between three Shareholders and the NSW State Government to adaptively reuse the near exhausted quarry as a major recreational facility for the people of western Sydney. PLDC manages the orderly quarry extraction, design of the Scheme and rehabilitation processes which have evolved over a 30 year period. Dedication of nominated parklands and lakes to the State Government and retention of the remainder of Scheme lands for urban purposes by the joint venture partners is administered through a Deed of Agreement. Rehabilitation of the Penrith Lakes Scheme Page 1

2 The Deed was conceptualised and signed in 1987 to assist with the delivery mechanisms of a range of recreation, state significant conservation outcomes and land for urban development. The conceptual genesis of this Agreement arose from extensive work carried out by PLDC and the Department of Planning and encapsulated in the Regional Environment Study (RES) 1984 which in large part guides the work of PLDC in its rehabilitation of the site. The Scheme is unique in its natural and cultural heritage assets. It contains a number of the Australia s oldest elements of European and contact settlement outside of the Sydney colony in addition to the significant Aboriginal connection and cultural heritage dating back for thousands of years. When completed, the Lakes Scheme will encompass some 770 ha of created lakes and 1200 ha of re establishing ecological communities on newly constructed landforms and water sensitive urban development. These landforms will have the foundations for a diversity of environments, varying from core conservation, wildlife corridors linking surrounding regional vegetation remnants to the Scheme, parklands that deliver areas for active recreational activities, as well as supporting the interface of the Scheme lands with the surrounding developing urban environments. A Natural Heritage and Biodiversity Conservation Master Plan has been developed by PLDC to guide the long term ecological establishment of the Scheme. It draws upon science, best practice and advice from leading experts in relevant fields to re establish and sustain endangered ecological communities and in lake biology in a cost effective manner. Under this Master Plan, these former riparian and terrestrial vegetation communities with their representative plant and animal populations have been re instated. In line with NSW State Government policy some of the significant species from Western Sydney that have largely disappeared from the area have been reintroduced or encouraged to re establish. Rarely does an opportunity present itself on this scale to re instate endangered ecological communities, support unique local wildlife, and make a considerable contribution to both local and regional biodiversity conservation, while incorporating the objectives of providing recreation and local community facilities. In seeking to sustain natural heritage and minimise long term maintenance costs, when adaptively implemented, the innovative Masterplan will provide significant data and direction for future land managers of the Penrith Lakes Scheme and inform the future directions taken by mine rehabilitation professionals both nationally and internationally. The Natural Heritage and Biodiversity Concept Master Plan, and an artist s impression of the finalised scheme are provided in Figure 1 below. Figure 1: Left: Natural Heritage and Biodiversity Concept Master Plan. Right: Artist s Impression of the Completed Scheme Rehabilitation of the Penrith Lakes Scheme Page 2

3 STORMWATER MANAGEMENT A key challenge to achieving the conservation outcomes of the Scheme is that its lakes and associated water bodies will also act as a significant local catchment treatment and flood mitigation facility. The lakes and detention basins will accept storm water from an urban catchment of some 2065 ha and protect urban precincts both within the Scheme and in the surrounding area from 100yr ARI events. To achieve the Scheme delivery PLDC developed the 2012 Water Management Plan (WMP) which was subsequently approved by the NSW Department of Planning. The 2012 Scheme has been designed to respect the hydrology of the Nepean River floodplain and to adopt a landscape context which reflects the natural processes and ecosystems. The extent to which this can be achieved is in a large part dictated by the primary objective of quarrying and its impact on the floodplain s prior natural landscape and hydrology. The 2012 Scheme also strives to achieve diverse landforms and landscapes surrounding the series of interconnected lakes in order to deliver a fundamentally natural outcome. This has represented a significant challenge to PLDC over the years and the 2012 WMP does this as far as is practicable within the constraints of managing a major operating quarry. To achieve the Scheme delivery PLDC has adopted the following approach in arriving at the 2012 WMP: Landform and Lake Construction Principles Design and deliver a series of interconnected lakes flowing naturally from south to the north and discharging into the Nepean River in the north of the site in the same way that the floodplain operated prior to quarrying; Design the flow of water through the lakes by a gravity fed system which as far as practicable replicates the natural path of water across the floodplain prior to quarrying (refer to Figure 2: Scheme Water Flow and Figure 3: Gravity Flow Sections); Design a system that as far as practicable returns pre quarry flows to the Nepean River; Create a number of associated water bodies and wetlands to optimise water quality and establish diverse ecosystems that will attract wildlife and plant species that may have flourished in a floodplain environment prior to European settlement; Design and deliver the lakes and landforms to accommodate the end uses prescribed in the Deed or as otherwise agreed to optimise the social and recreational objectives of the Scheme; Design and deliver a Scheme that not only respects but preserves as much of the Aboriginal, European and natural heritage values of the site as is practicable. Landscape Principles Establish aquatic habitats within the lakes themselves to enable fish, macroinvertebrates and macrophytes to prosper and create a healthy ecosystem for the lakes and ultimately the Nepean River system; Design and deliver a terrestrial landscape that complements the aquatic ecosystems and assists in the treatment of water that enters the lakes from rainfall run off; Design a series of detention basins, wetlands and water quality devices to manage the stormwater inflows from the external catchment before they enter the lakes system to optimise water quality and the opportunities for safe recreational uses by the public as envisaged in the Regional Environmental Study 1984 (RES) and the Deed; Rehabilitation of the Penrith Lakes Scheme Page 3

4 Structural Infrastructure Principles Minimise the number of man made structures to manage this water transfer and where possible build these structures from natural materials to more faithfully replicate a natural landscape (see Figure 5 Flood Water Flow 100yr ARI); Design and deliver a flood protection network which achieves an equivalent or improved flood impact on the Nepean River and surrounding areas in the 100yr ARI event; Design and deliver a flood protection network which equalises the water levels between the Nepean River and the Scheme in a 100yr ARI event and allows floodwaters to recede at a rate that minimises the risk of scouring and damage to the riverbank and Scheme landforms; Design and deliver a water supply system from the Nepean River to enable filling and topping up of the lakes for operational purposes as envisaged in the RES. The 2012 WMP was approved by the NSW Department of Planning in November 2013 and implementation by PLDC is well advanced. PLDC undertakes the design of all the required infrastructure, lakes, landforms and landscapes to deliver the approved 2012 WMP of which the above listed design principles form an integral part. The primary objective of the flood protection works is to fill the lakes with water during the early stages of a flood and should there be any overtopping of the river banks, then the water level in the lakes are designed to equalise with the water level in the river. This provides a superior environmental outcome by limiting the area of river bank that would be exposed to scouring flows. Control weirs interconnecting the lakes with the river and to each other are required to achieve this objective. The control weirs are shown in Figure 5. The 2012 WMP also includes a gravity fed water reticulation system designed to maintain operating levels of the lakes whilst also preventing levels reaching a height which may cause damage to the surrounding parkland landscapes and infrastructure. Pipelines, flowpaths and open channels large enough to move the water caught in each lake s catchment area in storm events are required to achieve this objective. The gravity system and direction of flow as well as locations of water reticulation infrastructure are shown in Figures 2, 4 and 5. Rehabilitation of the Penrith Lakes Scheme Page 4

5 Figure 2: Scheme Water Flow (Normal Operation) Figure 3: Scheme Flooding Response Rehabilitation of the Penrith Lakes Scheme Page 5

6 Figure 4: Gravity Flow Sections IMPLEMENTATION OF THE 2012 WATER MANAGEMENT PLAN Implementation of the Landform, Lake Construction, Landscape and Structural Infrastructure Principles is well progressed. To date, PLDC has successfully completed the Wildlife Lake and Lake B Precincts, (refer figure 5) delivering approximately 490ha of lakes and parkland for handover to the NSW State Government, with approximately 230ha of lakes and landforms dedicated including the Sydney International Regatta Centre (SIRC) and Eastern Lakes Precincts. The completion of these parkland areas has also included numerous items of significant flood and stormwater infrastructure some of which can be seen in Figure 5. Rehabilitation of the Penrith Lakes Scheme Page 6

7 Figure 5: Scheme Water Infrastructure, Landforms, Landscaping and Lake Construction Rehabilitation of the Penrith Lakes Scheme Page 7

8 Dissipation structure for Wildlife Lake Flood Outlet Completed Wildlife Lake Weir Completed Wetland Completed Lake and Landform Native Grass Planting at Wildlife Lake Figure 6: Various Photos Showing Works to Date Wildlife Lake Weir Construction Construction of Wildlife Lake Bird Refuge and surrounding Landform and lake embankment Rehabilitation of the Penrith Lakes Scheme Page 8

9 THE MASTER PLAN NATURAL HERITAGE AND BIODIVERSITY The 2012 Scheme is supported by a detailed Natural Heritage and Biodiversity Conservation Master Plan. The Master Plan integrates ecologically sustainable development and natural resource management principles with NSW planning legislation, development requirements and subsequent end use management of lands across the site. It identifies the native vegetation communities most relevant for re instatement as the basis for establishing conversation outcomes and seeks to address the challenges and ecological principles needed to establish healthy, self sustaining vegetation communities and animal populations, as well as key outcomes, including benchmarks for land use. The Master Plan provides detailed policy and strategic direction for: Rehabilitation of the soils on the newly developed landforms to ensure they are stable and will support the growth of local native plants; Re establishment of relevant Cumberland Plain vegetation communities and grasslands on the landforms to provide resilient ecosystems, habitat for local native animals and vegetative cover appropriate to end uses; Assisting the re introduction of appropriate native animal populations; and Conservation and enhancement of the unquarried lands and their vegetative cover, including the remnant riverbank forests and alluvial woodlands, the cultural heritage plantings and remnant forests and woodlands. KEY CHALLENGES AND ARISING PRINCIPLES To meet identified key challenges, a number of ecological principles have been applied to the development of Scheme wide and precinct plans. These include establishment of natural plant communities that reflect former vegetation types. The main principles to be followed in order to establish and mimic, as far as possible, the former natural vegetation communities include: Use local provenance plant species; Reflect naturally occurring community composition, floristic diversity and abundance; Distribute plant species on the basis of ecological preferences within natural communities; and Develop full structural complexity, integrity and functionality. Establishing ecosystem services and resilience in vegetation communities, and animal populations across the landscape. For resilience to develop and be sustained in vegetation communities that support viable animal populations it is essential to: Develop effectively functioning and viable soil ecosystems; Develop and maintain full natural structural complexity and floristic diversity in the vegetation community; Encourage the establishment of plant animal interactions; Develop and maintain corridors and stepping stones where necessary to establish connectivity across the landscape; and Create buffers around sensitive areas to manage threats. s:\ews\iqa environment award\140724_rg_rehabilitation of the penrith lakes scheme.docx 24 July 2014

10 KEY OUTCOMES Based on scientific research and best practice information, the Natural Heritage & Biodiversity Management Plan conservation outcomes include: Core Conservation Areas to protect biodiversity values; Corridors to link the Core Conservation Areas; Remnant riverbank and escarpment vegetation communities are enhanced and extended; The pre European vegetation linkage between the Escarpment and the Nepean River is re established; The Scheme itself is a key local and regional bridge for wildlife; Urban areas play a key role in supporting biodiversity conservation; Urban creek lines and swales integrate biodiversity to enhance water quality and recreational amenity and provide stepping stones for wildlife; Mosaics of different vegetation communities across the foreshore recreational areas enrich fauna habitats, assist in sustaining biodiversity and provide other useful management functions; Buffer zones around sensitive areas and infrastructure assist in protection of wildlife and are used for fire and infrastructure management; and Incursion of invasive species from other sites is prevented. BENCHMARKS While the above principles are well documented, their translation into quantitative terms that can be used in practice at the landscape and site levels is less well established. Recent scientific research and best practice information on designing urban developments for sustainability (Barnett et al, 2000; Chicago Wilderness Consortium, 2004) and for protection of vegetation communities and wildlife (Bennett et al, 2000; McIntyre et al, 2004; DEC 2005) suggests that for healthy native grassy woodland communities (such as those to be reinstated at Penrith Lakes) to be established and sustained the following whole site minima need to be achieved: At least 30% of the land area should be in woodland; At least 10% (and preferably 20%) of the land area should be set aside as core conservation and be connected to others on the site or within the district; Core conservation areas should be more than hectares in size; Intensive land use should be no more than 30%; Riparian corridor (continuous) along the Nepean River should be at least 100m wide measured from top of bank not including edge buffers and wider where possible; Corridors (continuous strips) across the landscape need to be at least 100 m wide to allow for buffers (5 50m wide); Corridors along drainage lines/gullies should be at least 50m wide and preferably 100m wide; and Patches of vegetation across the landscape should be hectares in size. s:\ews\iqa environment award\140724_rg_rehabilitation of the penrith lakes scheme.docx 24 July 2014

11 ACHIEVEMENTS TO DATE Although still in the development phase, the Penrith Lakes Scheme and the principles in the Master Plan have already been shown to effectively achieve the envisaged whole of site goals. An integrated monitoring program has been established across the scheme, forming a key role in assisting PLDC to adaptively design and implement various emerging elements throughout the Scheme, allowing for continuous improvements in the various land forming and ecological establishment procedures. To date the monitoring tools used to assess the overall success of the Master Plan include landscape function analysis, key ecological or signature indicators and overall water quality achievements of the scheme. Landscape Function Analysis is a process by which the stability of soils and movement of nutrients is assigned a numerical value, and has been conducted on several of the completed landforms around the Penrith Lakes Site. This analysis has been carried out at the various intervals of landform establishment and compared to the previous results as well as to an external, undisturbed analogue site. The results have concluded that the current land forming practices produce a landscape that mimics external undisturbed regions. Ecological Key Performance Indicators that can be drawn from the Integrated Monitoring Program include: Effective noxious weed management including the control and eradication of Salvinia and Water Hyacinth from several water bodies. Nine native frog species have been found around the re established fringe communities of the Scheme with several more species expected to be established including the endangered green and gold bell frog. 165 bird species are regularly recorded on site, 94% of which are native and includes the Baillion s Crake that was last officially sighted in the scheme over 20 years ago. 23 mammals and 15 reptile species have been recorded on site including a native species of Tortoise. 35 hectares of native grass farms producing seven different species have been successfully established and harvested on the site. Establishment of several ecologically significant freshwater wetland sites around the fringes of the scheme, containing 61 families of macroinverterbrates A water management system that currently reduces 91% of Total Phosphorus and 73% of Total Nitrogen loads entering from the surrounding peri urban catchment The Sydney International Regatta Centre has achieved Primary Contact Water Quality 95% of the time since its establishment in 1996 The Integrated Monitoring Program and the Landscape Functional Analysis have been used to measure the performance, track sustainability and enable constant improvement to ensure the desired outcomes are adaptively achieved. Although still in the development stages, the sustainable development approach detailed in the Master Plan shows that the Penrith Lakes Scheme has successfully integrated both economic and social activities with ecological principles so that, to the extent possible natural biodiversity elements can successfully co exist in perpetuity, while the site continues to deliver in its original water based recreational requirements. LEGACY OF THE SCHEME The diverse and unique nature of the Scheme demands that new and integrated approaches to its future management are adopted to ensure the long term viability post shareholder management. It is a key vale of PLDC and its Shareholder Companies to ensure it leaves a highly valuable legacy for the residents of western Sydney, ensuring the parklands and future developments are managed in a way that will not be detrimental to the original goals of the Scheme. s:\ews\iqa environment award\140724_rg_rehabilitation of the penrith lakes scheme.docx 24 July 2014

12 To achieve this bold goal, PLDC are developing a Scheme wide water quality model which will allow highly detailed assessments on the performance of the recreational lakes currently under development. This model has been created using the extensive ecological and physiochemical analysis carried out by PLDC since the Scheme inception and calibrated to these proven performance outcomes to project the future viability and performance of the completed Scheme. When complete, the model will allow for an informed decision on the likely impacts of future management approaches on the long term performance of the Scheme. This assessment will also take into account the surrounding environmental variables such as changes to the Nepean River and the surrounding catchment under various scenarios of developments and climate patterns. The model will allow the future developments on the Scheme to be assessed and identify any potential impacts on the Scheme, as well as set water quality targets for the surrounding developments within the catchment. The model will also provide a mechanism for assessing the likely impacts additional water infrastructure will have on the Scheme, allowing future land managers and shareholders to make sound investments based on a rigorous cost benefit analysis. The outcomes of the water quality modelling process as well as comprehensive management plans for rehabilitated lands and lakes will be provided to the future land managers to ensure the longevity and future value of this unique and bold quarry reclamation project lives on post PLDC management. CONCLUSION The 2012 Scheme Plan is designed to deliver superior environmental outcomes for the rehabilitation of the Penrith Lakes Scheme whilst implementing the requirements of the Deed and relevant planning instruments. The Scheme rehabilitation is being successfully implemented by PLDC with recent milestones being the completion of the Wildlife Lake and Lake B Precincts. The success of these works is already becoming evident through the progressive increases in native flora and fauna re establishing a presence on the site. The design and implementation of the Penrith Lakes Scheme presents a world class environmental solution to the rehabilitation of one of the largest quarries in Australia by providing: 1. A robust solution to manage stormwater from in and around the scheme ranging from regular rainfall events up to the 100 year ARI flood event; 2. Optimises the flood, reticulation and water supply infrastructure to meet long term operational requirements; 3. Provides management options for a range of climatic conditions from prolonged dry periods through to wet periods; 4. Establishes the hierarchy of lakes which optimises the recreational and end usage outcomes for future patrons of Penrith Lakes; 5. Delivers the best opportunity and management strategies to achieve desired water quality targets in the individual lakes; 6. Minimises ongoing maintenance and operation costs; 7. Minimises disturbance to the riverbank zone thereby preserving the natural integrity of the riverbank, and 8. Optimises the use of landscaped and aesthetically pleasing structures in keeping with a recreational and parkland setting. The Scheme will also have a solid management plan post quarry, applying the sound ecological principles that were used to establish the Scheme as well as integrating state of the art modelling tools to ensure the legacy of the quarry be of high quality to the community and flagship of world class quarry rehabilitation for its shareholders. s:\ews\iqa environment award\140724_rg_rehabilitation of the penrith lakes scheme.docx 24 July 2014

13 REFERENCES Barnett, G., Baker, B. and Kearns, A. (2000). Design Principles for Urban Sustainability. Report prepared for PLDC by CSIRO Wildlife and Ecology. Bennett, A.F., Kimber, S.L. and Ryan, P.A. (2000). Revegetation and Wildlife a guide to enhancing revegetated habitats for wildlife conservation in rural environments. Bushcare National Research and Development Program Research Report 2/00. Chicago Wilderness Consortium (2004). Sustainable Development Principles for Protecting Nature in the Chicago Wilderness Region. Design Principles 1. DEC (2005). Recovering Bushland on the Cumberland Plain: Best practice guidelines for the management and restoration of bushland. Sydney: DEC (NSW). McIntyre S., MeIvor, J.G. and Heard, K.M. (Eds) (2004). Managing and Conserving Grassy Woodlands. Canberra: CSIRO Publishing. s:\ews\iqa environment award\140724_rg_rehabilitation of the penrith lakes scheme.docx 24 July 2014