Shoal Bay Developments Pty Ltd & Anor v Port Stephens Council

The site and locality

1. The site comprises Lot 114 DP270468, Lot 50 DP15998 and Lot 1 DP850812 being sites referred to as 43 Lagoons Circuit (private road), 7 Donald Street and 2 Dowling Street Nelson Bay. The site is approximately 8.44ha. The residential development for which the Consent was granted, known as Lagoons Estate, is accessed from Lagoons Circuit which runs through the middle of the developed section of the site, off Dowling Street.
2. The site is located approximately 1km to the east of the Nelson Bay central business district and is separated from Nelson Bay itself to the north by a large dune system. The central part of the site contains a lagoon and some vegetation comprising mainly paperbarks, described by Giles JA (with whom McColl JA and Hunt AJA agreed) in Melaleuca Estate Pty Ltd v Port Stephens Council (2006) 143 LGERA 319 at 324 in the following terms: …its lower 2.2 hectares was a dunal swale supporting a melaleuca paper bark forest and some swamp mahogany trees. This area was described as an ephemeral wetland, meaning that it was from time to time inundated as the water table rose with prolonged rainfall but was dry when the water table fell. There was ponding when the groundwater rose above 8m AHD…
3. Stages 1 and 2 of the residential development have been completed, and Stage 3, on the south-eastern section of the site, is yet to be developed. Stages 1 and 2 comprise a combination of dwellings and semi-detached dwellings and some community facilities. The lagoon, and parts of the wick drainage system, are located on community land, and operation and maintenance of the wick system is the responsibility of the Community Association for DP 270468 (ex 2, p 454).
4. The majority of the site is surrounded by existing residential development on its northern and western boundaries, and on the other side of Dowling Street on its eastern boundary. The land to the east of Dowling Street is known as the Seabreeze Estate. The southern boundary of the site adjoins undeveloped land with frontage to Dowling Street, beyond which Nelson Bay Golf Course extends further to the south.
5. The following aerial photograph (ex 4, fig 1) shows the site and its relationship with Nelson Bay, the golf course, and the Seabreeze Estate; the dwellings in Stages 1 and 2; and the central lagoon and vegetation, and the remainder of the site which is yet to be developed.

Background to the application

1. The site was owned by Mrs Margaret Coventry from about 1950 until purchased by Melaleuca Estate Pty Ltd (Melaleuca) under a contract for sale dated 26 July 2000; the sale was completed in August 2002. In 2002 Melaleuca commenced proceedings in the NSW Supreme Court against the Council in negligence and nuisance alleging that it had caused excess water to come onto its land by reason of drainage works undertaken in the 1970s and 1990s on the Seabreeze Estate (the residential estate to the east of Dowling Street), and on Dowling Street. At first instance the proceedings were dismissed: Melaleuca Estate Pty Ltd v Port Stephens Shire Council [2004] NSWSC 415. An appeal to the Court of Appeal was upheld, and in March 2006 (Melaleuca Estate Pty Ltd v Port Stephens Council (2006) 143 LGERA 319) the Court of Appeal made orders: (a) granting an injunction restraining the respondent from continuing to discharge upon the appellant's land stormwater in excess of the natural flow that would flow upon the land; (b) that the respondent take such measures as may be necessary to preclude the coming onto the land of stormwater containing high levels of nutrients and waster materials; and (c) that the injunction set out in paragraphs (a) and (b) be stayed for eighteen months pending the implementation of a drainage system by the respondent for the Seabreeze Estate which enables the stormwater to be controlled within the catchment or disposed of by a thrust bore drainage line or gravity drainage line, to the next catchment in Port Stephens.
2. After the decision of the Court of Appeal the Council undertook works described by the applicants in their Amended Statement of Facts and Contentions in Reply (ex B, para 16A) in the following terms: a. reducing the catchment area of the Site; b. creating storm water detention and infiltration galleries within road reserves; c. creating detention bunds and subsurface galleries at a nearby golf course site; d. creating detention and/or infiltration systems in a nearby sportsfield; e. installing storm water tanks on nearby private properties.
3. On 3 August 2004 Melaleuca lodged a s 96 modification application, seeking to redesign the individual infiltration units to be installed on dwellings to be erected on the site. That application was determined on 9 May 2005.
4. The wick drainage system was installed during 2004-2005 (ex E, p 6). The Court of Appeal noted in its 2006 judgment that the first stage of the wick drainage system on the site, being installation of wicks for building stages 1 and 2, had been constructed ((2006) 143 LGERA 319 at 344).
5. In August 2010 the applicants became owners of lot 114 in DP 270468, Stage 3 of the original Consent.
6. On 24 November 2010 Coeve Design Pty Ltd (on behalf of the owner) lodged a s 96 application seeking the rotation of units and deletion of access off Dowling Street, provision of additional entry off Dowling Street and adjustment of unit levels. That application was determined on 7 March 2013.
7. On 2 September 2011 Coeve Design Pty Ltd lodged a further modification application, which is the subject of these proceedings, seeking the deletion and modification of a number of conditions of consent relating to the wick drainage system. During 2012 there was correspondence between the Council and Coeve Design Pty Ltd, including requests for additional information. That included a request on 10 August 2012 for supporting technical details including complete monitoring results for installed five boreholes, complete details of testing completed to support the adopted wick permeability rate of 32m/d, and works as executed drawings of the constructed wick system; the applicants responded on 14 August 2012. On 3 July 2014 the Council refused the application, and the applicants lodged the Class 1 appeal on 12 September 2014.
8. The interlocutory processes undertaken before the hearing included production of documents under subpoena from a number of individuals and organisations, and notices to produce for inspection issued by the applicants pursuant to Part 21 of the Uniform Civil Procedure Rules 2005 dated 13 November 2014 and 24 January 2015. The applicants sought production of hydrological and/or hydrogeological reports relating to the modification application; documents concerning the Council's drainage system that controls stormwater within the catchment area; and all data, readings, recordings, measurements and monitorings of water levels from the water sensor that monitors the amount of stormwater entering the Lagoons Estate from 2009 to 2011. The documents the subject of the notices to produce were lodged with the Court, and marked as privileged. The Council objected to access being granted first on the basis of relevance, and secondly on the basis of legal professional privilege. The Registrar determined on 6 February 2015 that the documents were relevant in that they would materially assist on the question of whether the conditions of consent sought to be deleted or modified were made redundant as a result of the work carried out by the Council; that the two reports of 2007 were privileged; and that the other documents relating to monitoring were not; and granted access to those documents. An application to review the Registrar's decision was dismissed: Shoal Bay Developments Pty Ltd v Port Stephens Council (No 2) [2015] NSWLEC 36.
9. As amended during the course of the hearing, the modifications now sought by the applicants are:

Issues

1. The modification application in substance seeks to modify the Consent so that it reflects the works actually carried out on the site and does not require the installation of additional wicks or the other work required by the Consent. The applicants' position is that the extent of drainage works that were determined to be required for the residential development at the time the Consent was granted is no longer necessary, in part because of the reduction in the amount of water entering the site as a result of the works undertaken by the Council to comply with the orders of the Court of Appeal.
2. The hearing of this appeal proceeded on the basis that the Council has complied with the orders of the Court of Appeal.
3. The Council contends (ex 1) that: 1. insufficient information has been provided to enable an appropriate assessment of the application, identifying a requirement for a detailed groundwater report prepared by a suitably qualified hydrologist/hydrogeologist incorporating monitoring results, detailed predictions based on the monitoring data for rainfall events up to a 1 in a 100 year event, a reassessment of the performance of the lagoon level based on the period February 2009-August 2009 and an assessment of the impacts of climate change; and for works as executed documents showing the installed drainage works; 2. insufficient information has been provided to enable an assessment of whether the proposal satisfies the relevant provisions of the Port Stephens Local Environmental Plan 2013 (the 2013 LEP) including the objectives of the R2 zone, and cl 7.3 relating to flood planning; and 3. insufficient information has been provided to enable the consent authority to be satisfied that the proposal will not result in the approved development being impacted by flooding.
4. The applicants contend (ex B) that sufficient information has been provided to allow appropriate assessment of the application; that the installed wick system is compatible with the flood risk of the area; that any development carried out pursuant to the Consent as modified will meet the requirements of cl 7.3 of the 2013 LEP, which in any event does not, on its terms, apply to the site; that sufficient information has been provided to demonstrate that the modifications proposed will not result in the approved development being impacted by flooding; that the catchment area of the site has been reduced and the amount of water entering the site has been reduced by over 66% as compared to the amount expected at the time the Consent was granted; that the filtration rate of the wick drainage system as installed is higher than was assumed during the original design; and that the amendments proposed in the application are required to take account of the reduction in the amount of water entering the site as a result of the measures undertaken by the Council.
5. The Council's contentions included a contention that the consent of the Community Association which owns part of the land over which the Consent extends has not been provided as required by c 115 of the Environmental Planning and Assessment Regulation 2000 (the Regulation). During the course of the hearing additional documentation relating to a Special General Meeting of Community Association DP270468 on 22 May 2015 was tendered (ex T). This contention was no longer pressed.

Planning controls

1. At the time the Consent was granted, and at the time the modification application the subject of this appeal was lodged, the applicable local environmental plan was the Port Stephens Local Environmental Plan 2000 (the 2000 LEP). The site was zoned 2(a) Residential. The objectives of the 2(a) Residential zone were: (a) to encourage a range of residential development providing for a variety of housing types and designs, densities and associated land uses, with adequate levels of privacy, solar access, open space, visual amenity and services, and (b) to ensure that infill development has regard to the character of the area in which it is proposed and does not have an unacceptable effect on adjoining land by way of shading, invasion of privacy, noise and the like, and (c) to provide for non-residential uses that are compatible with the area and service local residents, and (d) to facilitate an ecologically sustainable approach to residential development by minimising fossil fuel use, protecting environmental assets and providing for a more efficient use of existing infrastructure and services, and (e) to ensure that the design of residential areas takes into account environmental constraints including soil erosion, flooding and bushfire risk.
2. Clause 10(2) provided that the consent authority must not grant consent for development of land to which the 2000 LEP applied "unless it is satisfied that the proposed development is consistent with the objectives of the zone in which it is intended to be carried out".
3. The 2013 LEP came into force on 22 February 2014. The site is zoned R2 Low Density Residential. The objectives of the R2 zone are: • To provide for the housing needs of the community within a low density residential environment. • To enable other land uses that provide facilities or services to meet the day to day needs of residents. • To protect and enhance the existing residential amenity and character of the area. • To ensure that development is carried out in a way that is compatible with the flood risk of the area.
4. Clause 2.3(2) provides that the consent authority must have regard to the objectives for development in a zone when determining a development application in respect of land within the zone.
5. Clause 7.3 provides: 7.3 Flood planning (1) The objectives of this clause are as follows: (a) to minimise the flood risk to life and property associated with the use of land, (b) to allow development on land that is compatible with the land's flood hazard, taking into account projected changes as a result of climate change, (c) to avoid significant adverse impacts on flood behaviour and the environment. (2) This clause applies to: (a) land identified as "Flood Planning Area" on the Flood Planning Map, and (b) other land at or below the flood planning level. (3) Development consent must not be granted to development on land to which this clause applies unless the consent authority is satisfied that the development: (a) is compatible with the flood hazard of the land, and (b) will not significantly adversely affect flood behaviour resulting in detrimental increases in the potential flood affectation of other development or properties, and (c) incorporates appropriate measures to manage risk to life from flood, and (d) will not significantly adversely affect the environment or cause avoidable erosion, siltation, destruction of riparian vegetation or a reduction in the stability of river banks or watercourses, and (e) is not likely to result in unsustainable social and economic costs to the community as a consequence of flooding. (4) A word or expression used in this clause has the same meaning as it has in the Floodplain Development Manual (ISBN 0 7347 5476 0) published by the NSW Government in April 2005, unless it is otherwise defined in this clause. (5) In this clause: flood planning level means the level of a 1:100 ARI (average recurrent interval) flood event plus 0.5 metre freeboard.
6. The site is not on land identified as "Flood Planning Area" on the Flood Planning Map referred to in cl 7.3(2)(a) of the 2013 LEP.
7. The 1997 NSW Coastal Policy applies to the site. State Environmental Planning Policy No 71 - Coastal Protection (SEPP 71) applies to the site. Clause 16 of SEPP 71 provides: 16 Stormwater The consent authority must not grant consent to a development application to carry out development on land to which this Policy applies if the consent authority is of the opinion that the development will, or is likely to, discharge untreated stormwater into the sea, a beach, or an estuary, a coastal lake, a coastal creek or other similar body of water, or onto a rock platform.

Evidence

1. The hearing commenced on site, with a view which included the lagoon and the inlet to the wick system on the site, and part of the Council drainage works on Dowling Street. Mr Randall Grayson, Chairman/Secretary of the Community Association, and Mr Mitchell Cronin made submissions on site.
2. The applicants relied on expert hydrological evidence from Mr Mark Stuckey (hydrogeologist) and Mr Peter Graham (hydrogeologist). Mr Stuckey and Mr Graham prepared individual statements of evidence (exhibits D, and E and K respectively). The Council relied on expert evidence from Dr Ian Joliffe (hydrologist). Dr Joliffe prepared a statement of evidence (ex 4). Mr Graham, Mr Stuckey and Dr Joliffe prepared a joint report (ex 6). Mr Graham and Dr Joliffe provided a supplementary joint report (ex V). The experts gave oral evidence.
3. Expert planning evidence was provided on behalf of the applicants by Mr Garry Warnes and on behalf of the Council by Ms Amy Stone. Mr Warnes and Ms Stone prepared individual statements of evidence (exhibits C, 3) and a joint report (ex 5). The planners were not required for cross examination.
4. Mr Charles De Bono is an engineer and director of Coeve Design Pty Ltd, and prepared a statement of environmental effects (SEE) for the modification application (ex A). Mr De Bono gave oral evidence.
5. The evidence included a number of photographs: 1. Exhibit E, Mr Graham's statement of evidence, includes photographs taken during construction of Stages 1 and 2; 2. Exhibit F, three photographs taken on 21 April 2015 at 7.00am by Mr David Vitnell, director of the applicant and principal of the firm of solicitors acting for the applicants; 3. Exhibit H, photographs taken on 19 April, 21 April, and 1 March 2015 by Mr Mitchell Cronin; 4. Exhibit J, photographs taken by Mr Cronin on 19 and 21 April 2015, and Mr Randall Grayson on 22-27 April 2015; and 5. Exhibit Q, Mr Graham's photographs identified in oral evidence on 30 April 2015.
6. Exhibit S is a series of videos taken by Mr Vitnell and by Mr Cronin, relied upon by Mr Graham in his statement of evidence of 23 April 2015 (ex K), and on which he commented in oral evidence.
7. The Council's bundle of documents includes submissions made to the Council in response to notification of the modification application (ex 2, tab 22). Those submissions included submissions from residents in the Lagoons Estate raising concerns as to issues with drainage and storage of water runoff from the current development and Council land, including maintenance. Specific concerns raised by residents of Lagoons Estate included a statement that "… the lagoon is often full to a current safe level", and opposition to "any strategy or process that would allow additional water to flow into the area without the strategies currently approved for this development" (ex 2, p 241); and a statement that "the estate currently suffers from poor water management systems resulting from a combination of poor design, poor implementation of design and poor maintenance" (ex 2, p 249). A submission on behalf of the Community Association DP 270468 dated 6 February 2012 raised concerns as to the information provided by Coeve Design in the application, commenting that "the residents of Lagoons Estate have witnessed the effect of heavy continuous rain, the entry of runoff waters from council's areas and adjacent areas into the Lagoons Catchment area", and noting that "the lagoon has been at its current high mark for over three months" and the level had not dissipated in 35 hours as claimed (ex 2, pp 243, 246). A submission from Tomaree Ratepayers and Residents Association requested that agreement not be given to any variation to the conditions of approval that might expose the neighbouring properties or communal facilities to increased risk of flooding or inundation (ex 2, p237). One of the resident submissions stated that the developer had lined the dam (ex 2, p 259); in a further submission (ex U) that statement was clarified to be that the lining was where a section of the floor of the lagoon had been eroded by water flowing out of council pipes; the material used was not a dam lining material and the material did not last long.

Consideration

1. Section 96AA(1) enables modification of a development consent if the consent authority is satisfied that the development to which the consent as modified relates is substantially the same development as the development for which the consent was originally granted, if it has consulted with any relevant Minister, public authority or approval body, and if the application has been properly notified and any submissions are considered. Section 96AA(1A) provides that in determining an application for modification of a consent, the consent authority must take into consideration such of the matters referred to in s 79C (1) of the Act as are of relevance to the development the subject of the application.
2. Section 79C(1)(a) of the Act refers to the provisions of "(i) any environmental planning instrument". The expert planners differed as to the planning controls required to be taken into consideration (ex 5). Ms Stone was of the opinion that the 2013 LEP applies, on the basis that cl 1.18A of the 2013 LEP, which provides that "if a development application has been made before the commencement of this Plan in relation to land to which this Plan applies and the application has not been finally determined before that commencement, the application must be determined as if this Plan had not commenced" applies to a development application, and not to a modification application. Mr Warnes was of the opinion that as Stages 1 and 2 have been completed the development consent continues lawfully in force and can only be interpreted under the terms under which it was issued, namely the 2000 LEP. Mr Warnes did not consider that cl 2.3 of the 2013 LEP, which requires consideration of the objectives of the R2 Residential zone, applies, as in terms it applies when a consent authority is determining a development application; and in his opinion cl 7.3 of the 2013 LEP does not apply for the same reason. Ms Stone was of the opinion that the land zoning map under the 2013 LEP applies to the site and its relevance is not limited to a "development application"; accordingly consideration must be given to the zone objectives, and relying on the evidence of Dr Joliffe she was of the view that insufficient information has been submitted to provide the consent authority with the certainty that the development can be carried out in a way that is compatible with the flood risk of the area. Ms Stone was of the opinion that, applying cl 7.3(2)(b), cl 7.3 of the 2013 LEP applies to this application as there is no information to demonstrate that the flood planning level for the site of 10.5AHD accepted by the Court in granting consent should be amended. Mr Warnes disagreed, and identified a variety of levels over the site representing the 1:100 year event including 11.0AHD (condition 59), 11.5AHD (condition 76) and 13.5AHD plus 0.3m (condition 76).
3. In submissions the applicants' position was that the approach of Mr Warnes should be adopted: neither cl 2.3(2) nor cl 7.3 of the 2013 LEP applies in terms; and that while s 79C of the Act empowers the Court to consider the 2013 LEP, that does not and cannot override the clear language of the provisions. In any event, the site is not on the Council's flood planning map, and the evidence does not establish that the Council has formally adopted any flood planning level for the site so as to require compliance pursuant to cl 7.3(2)(b); while Ms Stone's evidence was that the Council has adopted the 1 in 100 year flood event for the purposes of this matter that can only be an adoption by staff as a method of calculation rather than a formal adoption of a flood planning level.
4. The Council submits that cl 1.8A of the 2013 LEP applies only to a development application, and that the requirement in s 96AA that the consent authority have regard to the matters referred to in s 79C(1) means that the provisions of the 2013 LEP are relevant to this application. While s 96 is a "free standing provision" (North Sydney Council v Michael Standley & Associates Pty Ltd (1998) 43 NSWLR 468) a consent authority is still required to take into account matters referred to in s 79C which in turn includes the provision of any environmental planning instrument. The Land Zoning Map of the 2013 LEP applies to the land and its relevance is not limited to a "development application", and so the Court should give consideration to the zone objectives associated with each of the land use zones as a relevant matter. The development as modified does not satisfy the objectives of the R2 Low Density Residential zone. Clause 7.3 applies as the site is below the flood planning level which is 10.5AHD; that level was accepted in proceedings 10735 of 2000 in which the Consent was granted, and there is no information to demonstrate that that level should be amended; and cl 7.3(3) is not satisfied.
5. In our view it is not necessary to determine whether cl 7.3 of the 2013 LEP applies to the modification application. It makes no difference whether cl 1.8A of the 2013 LEP applies, so that the relevant local environmental plan to which regard is to be had under s 79C(1)(a)(i) is that in force at the date the modification application was lodged, namely the 2000 LEP; or cl 1.8A does not apply (because the present application is not a "development application"), so that the relevant local environmental plan is the 2013 LEP. Whichever is the relevant local environmental plan for the purposes of s 79C(1)(a)(i), the objectives are in any event relevantly the same, as the objectives of the 2(a) Residential zone under the 2000 LEP included "(e) to ensure that the design of residential areas takes into account environmental constraints including soil erosion, flooding and bushfire risk"; and the objectives of the R2 Low Density Residential zone under the 2013 LEP include "to ensure that development is carried out in a way that is compatible with the flood risk of the area". Even if neither provision is a mandatory relevant consideration in assessment of this application, consistent with the oral submissions of the applicants that cl 2.3(3) of the 2013 LEP (which requires consideration of the zone objectives) has no operation for a modification application, s 79C(1) in any event requires the Court to have regard to (b) the likely impacts of the development including environmental impacts on both the natural and built environments; (c) the suitability of the site for the development; (d) any submissions made; and (e) the public interest. In our view, all of those provisions would, in the context of a site where flooding has been an issue in the past, and where the residents report concerns about ongoing drainage issues, require consideration of the flood risk and drainage of the site and the surrounding area.
6. The central issue for the Court is whether the evidence establishes that the modifications proposed to the Consent, so that it reflects the works actually carried out on the site, provide a drainage system that appropriately addresses the potential impacts on the approved development from flooding including those arising from high rainfall events.
7. In summary, the applicants' position is that with the reduced catchment area as a consequence of the Council's drainage works for Seabreeze Estate the system as installed can cope with the expected flows, based on the monitoring data and evidence from storm events in 2009 and mid-April 2015; the wick system as installed has an improvement in performance 300% better than that initially modelled; and the system is serviceable and there is no evidence that it is likely to silt up. No additional wicks are needed, because the extra water is dealt with by including individual systems at each dwelling and the road drainage system.
8. The Council's position is that there is a high level of uncertainty as to the adequacy of the existing drainage system particularly as it is not being maintained, and maintenance is impossible given the infrastructure sitting on top of it; there is a paucity of relevant data as to the effective operation of the system over a prolonged wet period and no data as to the effectiveness of the downstream aquifers to dispose of high flows of water; and there is an acknowledged inability to install additional drainage wicks once Lot 114 is developed.
9. In their joint report (ex 6) Mr Graham, Mr Stuckey and Dr Joliffe addressed the following hydrologic and related issues: 1. Details of the existing installed system; 2. Definition of the catchment area draining to the site; 3. The appropriateness of the system performance assessment based on rainfall and surface runoff events; 4. Whether there is water flowing into the lagoon under pressure from groundwater; and 5. How many wicks would be required to drain the Melaleuca Estate.
10. We agree that a proper understanding of what has been installed; how it has operated; and whether it is adequate to cope with expected flows, based on the catchment area and the features of the system, including both the installed system and the capacity of the lagoon, is required to determine the issues raised in this appeal. We approach our consideration of the evidence on that basis.
11. Before addressing the expert evidence, we note that both Mr Graham and Dr Joliffe came under criticism, the Council pointing to Mr Graham's central role as designer of the wick drainage system, and the applicants submitting that Dr Joliffe was in a position of conflict in relation to the development because of his role as designer of the drainage works undertaken by the Council for the Seabreeze Estate (T 25/5/15, pp219-220). We accept that both Mr Graham and Dr Joliffe have had an ongoing role in the management of drainage issues, both upstream of the site in the case of Dr Joliffe, and on the site, in the case of Mr Graham; however, on our assessment of their evidence there was no indication that either witness lacked the impartiality required of an expert giving evidence on matters within his area of expertise. We would not discount the evidence of either expert simply on the basis of their prior involvement.

The wick drainage system

1. The applicants submit that, based on the evidence of Mr Graham including the photographs taken during construction, the Court can be confident that 554 wicks have been installed; that polypropylene drainage cells have been used for the wicks and inlet cells; that there has been installed three parallel lines of wicks with feeder lines, and inspection points; that the filtration system includes the novel use of oyster shells directly underneath larger rocks, and has been designed to take into account head loss and act as a first flush to water entering the lagoon; and that the wicks are constructed of polypropylene drainage cubes stacked vertically and encased in heavy duty geofabric.
2. In the section of the joint report (ex 6) addressing the details of the installed system, Mr Graham and Mr Stuckey agreed that the existing wick drainage system has 554 installed wicks; and that the filtration system was installed, based on the reports 106019L2 (20 October 2006) and 106019L3 (25 October 2006). Dr Joliffe stated that he had no direct knowledge of the installed system and relied on reports by others. 1. Mr Graham's evidence
3. The wick drainage system required by the Consent was designed by Mr Graham. In addition to his two statements of evidence prepared for these proceedings (ex E, K) and his participation in conferencing and the two joint reports (ex 6, V), the following reports prepared by Mr Graham are in evidence: 1. Aquifer characterisation and stormwater system design, Lagoons Estate, Nelson Bay, New South Wales: July 2003 (Report No 103010, Report to Melaleuca, Environmental & Earth Sciences Pty Ltd) (ex 2, tab 37); 2. Assessment of the disposal capacity of the installed wick drainage system, Melaleuca Estates, Nelson Bay, New South Wales: 29 September 2006 (Environmental & Earth Sciences NSW, report 106019) (ex K, tab 25); 3. Letter dated 20 October 2006 headed Summary of wick drainage system installed at 2 Dowling Street, Nelson Bay, addressed to Melaleuca (ex 2, tab 38); 4. Letter dated 25 October 2006 headed certification of Stage 1 wick drainage system installation, 2 Dowling Street, Nelson Bay, addressed to Melaleuca (ex 2, tab 38); 5. Theoretical Design and Practical Implications of a Large Scale Wick Drainage System for Urban Stormwater Disposal, Nelson Bay, NSW, Australia: project report submitted as partial requirement for the degree of Master of Science, December 2006 (ex 2, tab 24); 6. Letter dated 9 March 2007 to Melaleuca headed Summary of wick drainage system installed at 2 Dowling Street, Nelson Bay, Environmental & Earth Sciences (ex L); and 7. Assessment of Disposal Capacity of the Installed Wick Drainage System, 2 Dowling Street, Nelson Bay, New South Wales, Report No 106019 Environmental & Earth Sciences Pty Ltd, addressed to Melaleuca, July 2007 (ex 2, tab 39).
4. In his December 2006 project report submitted for the Masters of Science (ex 2, tab 24) Mr Graham states that the purpose was to design a suitable urban stormwater drainage system for the site, capable of disposing of stormwater "sourced from a 68ha urban development which is piped into a small ephemeral wetland where the water pools and slowly infiltrates" (p 281). Mr Graham summarised the concept of the drainage design (ex 2, p 276): The drainage design was based on the concept that a highly conductive aquifer was present below the site which is interconnected with Nelson Bay and naturally allows movement of stormwater into the bay. Several semicontinuous layers are present which prevent direct movement of infiltrating stormwater into this aquifer and result in a perched water table. Under natural conditions the rate of infiltration from the perched water table to the lower aquifer combined with high evapotranspiration rates is sufficient to prevent ponding of water at the surface. The development of the site and redirection of stormwater to one location within the catchment resulted in ponding of water and significant variations in the perched water table as the volume of water being fed into the system at one location exceeded the transmissivity of the confining units. The "Wick" drainage system was therefore based on increasing the conductivity of these confining units and allowing the stormwater to feed through into the underlying aquifer, thereby returning the system to a more natural state.
5. In oral evidence (T 30/4/15, p 104) Mr Graham explained the operation of the wick system in the following terms: There's a significant gradient in getting between those locations, and the issue with this site is that we were getting flooding in the lagoon system which meant water was coming from the right hand side of this diagram, moving in and sitting in the lagoon. Our solution to that was to install a wick system. Now, the wick system is placed as far as we could to that higher ground water gradient in as much of the dunal system, the high conductivity sand systems. And what it does is it pumps water from this surcharged area into the area where they've got the high gradient, to flow away from the site, and essentially it's piping the water away from the site through a natural recharge type of system. So we're creating a direct line from the lagoon towards the gradient and towards those sandy materials.
6. Mr Graham summarised (ex 2, p 327) the development of the system through analytical modelling: The project found initially through preliminary analytical modelling that 1900 "wicks" would be required to ensure the drainage system would have the capacity to contain stormwater from a 1 in 100 year storm event. Analytical modelling showed that 673 "wicks" would be sufficient to handle the storm event with a potential disposal volume of 780 m3/hr for this number of wicks. Simulation of 675 "wicks" and the response of the system to the storm event using the calibrated groundwater model showed that the proposed "wick" system would achieve a stable groundwater/wetland system by allowing faster infiltration of the piped stormwater into the lower aquifer thereby reducing the maximum water level in the wetland and also reducing the time frame the system remains saturated.
7. Mr Graham continued: Installation of 558 "wicks" was undertaken and the performance of this number of wicks was monitored. Assessment of these results showed that the average wick disposal rate for 558 wicks is 791 m3/hr. This value is slightly in excess of the potential disposal volume of 780 m3/hr calculated for 673 wicks. The actual performance of the installed system is therefore thought to exceed modelled values and based on data collected to date the current system is considered to have the capacity to contain a 1 in 100 year storm of 2880 min duration in a situation where the wetland level is less than 8.75m AHD at the onset of the storm.
8. At p 42 of his December 2006 report (ex 2, p 322) Mr Graham noted that: Due to time constraints on the development of regions within the catchment a preliminary "wick" drainage system was installed.
9. Mr Graham described the system installed as at December 2006 in the following terms: "-558 11m long wicks installed to upper and lower depths of 8.5m and -2.5m (AHD), constructed of polypropylene drainage cubes encased in heavy duty geofabric. The location of the wicks is shown on (Figure 26); -there are three parallel trenches each seven metres apart, one of these trenches contains 189 wicks, one contains 185 wicks and one contains 180 wicks (Figure 26); -the layout of the wicks within each trench is three rows of between 63 and 60 wicks with 1.5m centres along the row and 2m centres between each of the three rows (Figure 26); -the headers feeding the wicks are also composed of polypropylene drainage cells, the cells are 450mm (wide) x 408mm (high) and are interconnected with the tops of each individual wick; -a feeder line running across the three trenches is also composed of the drainage cells. In this feeder line the cells are 2 high (800mm) and 9 wide (4050mm), reducing to 1 high and 6 wide to feed the last row of wicks (Figure 26); -connecting the feeder lines to the filtration system are two 1200mm concrete pipes; -two inspection points have been installed along the line; one is at the intersection between the concrete pipes and the drainage cells feeding the wicks; the second is immediately after the filtration system.
10. That summary was repeated in the March 2007 report by Mr Graham (ex L) with the exception of the first paragraph, which referred to 554 wicks (not 558), and included as Figure 2 a survey diagram N-37 730 by Southwells Surveyors Pty Ltd, as Figure 3 an "as built" diagram", and as Figure 3 "attached Piling Contractors as-built diagrams". Figure 1 of that report shows "the system installed":
11. Mr Graham identified the changes made to the system as installed in comparison with the requirements of the Consent conditions in a letter to Melaleuca dated 20 October 2006 (ex 2, tab 38). Those changes relevantly included reduction in the size of the wide inlet from along the entire length of the wetland edge (~ 100m) to along the northern edge of the wetland (~ 40m) (condition W6); reduction in the number of wick drains from 1600 in Stages 1 and 2 of the development to 554 during Stage 1 "and potential for installation of an equivalent in Stage 3" (condition WD2); an increase in the upper header for the wicks from 7.5m to 8.5m AHD and an increase in the wick length from 10m to 11m (condition WD3); and an alternative filling to the specified geofabric socks filled with coarse gravel, being polypropylene drainage cells that could be joined end to end in an 11m long wick and encased in heavy duty geofabric.
12. In his statement of evidence dated 10 December 2014 (ex E) Mr Graham explained the alternative construction: The initial wick system was designed to be constructed from a geofabric sock filled with gravel, however the final system utilised polypropylene drainage cells wrapped in geofabric. The initial system was intended to be a 1.0m diameter circular wick, the revised system was a 450 x 480mm cube. As discussed above the perimeter of the wick is the exit point for water discharge and therefore maximising the permeable area of the wick perimeter increases the performance of the wick. The perimeter of the initial gravel filled system was 3.14m of which the permeable area is only 30% (estimate of gravel permeability) giving a permeable area of 0.942m. The perimeter of the polypropylene system was 1.86m with a permeable area of approximately 0.97% [sic] giving a permeable area of 1.800m, making the surface area of the discharge point approximately double that of the initial system. The smaller wicks are also likely to reduce the interference between discharge from individual wicks as the smaller wick diameter allowed for greater spacing between wicks.
13. The letter of 20 October 2006 also describes the filtration treatment, which includes a gross pollutant trap for stormwater moving into the site; direction of the water around the wetland to increase the flow path before entering the wick infiltration system inlet; and passage of water at the mouth of the inlet through a reactive permeable barrier, described in the following terms (ex 2, p 619): At the inlet the stormwater is filtered by rip rap underlain by geofabric at the mouth of the inlet water then passes through a reactive permeable barrier comprising alternate compartments consisting of crushed oyster shells, steel fragments and then a mixture of organic peat and sand before entering the first inspection pit.
14. The filtration system "is designed to remove heavy metals, organic compounds, degradation in the peat and nutrients before they enter the wick infiltration system, thereby preserving the quality of the groundwater contained in the receiving aquifer". Mr Graham states that the filtration system is the only component of the system that will require replacement, at intervals dependent on the stormwater compound (organic and inorganic) loading, expected approximately every 20 years.
15. The letter also noted that in order to further minimise stormwater impacts on wetland water levels, each individual building on site incorporates underground collection tanks (for potential reuse onsite) connected to polypropylene drainage boxes; roadsides have swales containing peat and shell at the base of the spoon drain; and all gardens are to be of natural species with no importation of clayey topsoil allowed; the individual storage and infiltration tanks are located underneath each building, enabling direct access to soil for infiltration (ex 2, p 620). 1. Mr Stuckey's evidence
16. Mr Stuckey is a soil scientist, hydrogeologist, and risk assessor. His statement of evidence dated 10 December 2014 (ex D) was a peer review of the SEE produced by Coeve Design in 2011, and response to the Council's reasons for refusal of the modification application. In undertaking his assessment Mr Stuckey relied (ex D, p 2) on the reports prepared by Mr Graham in 2003 (pre-installation aquifer characterisation report), 2006 (letter report following completion of the design including certifications of structural integrity of the wicks and acceptability of load bearing from overburden), 2007 (letter report detailing final design refinements at installation in particular reduction in wick numbers from 1600 to 554; and report detailing performance of the system following installation of 554 wicks); ongoing monitoring reports of 2009 and 2010 provided by Mr Matthew Rendell; and the Coeve Design 2011 reviews. Mr Stuckey concluded that: 1. the calculations for the system capacity, based on the size of the catchment, storage capacity of the lagoon and 100 year ARI 48 hour storm event values used, were correct; 2. the analytical model for the site had been updated to reflect the final installed system, lagoon and Seabreeze Estate catchment dimensions, as well as potential influences from climate change, and had found that the system was capable of disposing of 100% of the runoff from the Seabreeze Estate if required; 3. the period February to August 2009 demonstrated the effectiveness of the system under very much above average rainfall conditions that were experienced in February, April and May 2009; and 4. the Lagoons Estate receives run-on from Seabreeze Estate for example during a rainfall event of 26mm in 24 hours.
17. Mr Stuckey concluded that the system had been designed to accept all drainage from the Lagoons Estate and also (if required) all drainage from the neighbouring 68ha (reduced to 31.3ha) Seabreeze Estate from a 100 year ARI 48 hour storm event, including any impacts from climate change; and that since commencement the system had been shown to operate efficiently and as per the design predictions including efficient disposal of run-on received from the neighbouring catchment during storm events as small as 26mm in 24 hours and as high as 211mm in 24 hours and over 700mm in three months. (3) Dr Joliffe's evidence
18. Dr Joliffe is an engineer with experience in flooding, urban development and related civil engineering, drainage and stormwater design. In his statement of evidence dated 6 February 2015 (ex 4) Dr Joliffe commented on the design of the wick system, and the adoption of a hydraulic gradient between the lagoon and Nelson Bay of 0.5m/m [sic] and a wick exfiltration area of 15.67m2/wick, which he commented assumed that the wick can discharge through its total perimeter without the consideration of potential impacts of any regional groundwater flow; and the use in the analysis of the value of 32.7m/day for hydraulic connectivity, which he commented was at the higher range of observed values (ex 4, p 13). Dr Joliffe commented on the as built information, stating that the prediction that the lagoon water level would not exceed 11.5m AHD using a system comprising 558 wicks assumed that the wicks could discharge water over their entire perimeter surface without any impact from regional groundwater flow (ex 4, p 16).
19. In addition to the expert hydrological and hydrogeological evidence, Mr De Bono provided reports and gave oral evidence. Mr De Bono is a director of Coeve Design Pty Ltd which prepared the SEE for, and lodged, the modification application. In oral evidence he confirmed that he was involved with the Lagoons Estate during construction, but not following, until his involvement in preparing the modification application (T 29/4/15, p 72). At annexure D to the SEE Mr De Bono provided a summary of works required to accommodate storm water on the Lagoons Estate land, dated 5 August 2011, based on a report provided by Red Earth Geosciences dated 29 September 2007 titled Analysis of Stormwater Mitigation Works and their Hydrogeological Setting - Seabreeze Estate, Nelson Bay, NSW. Included in that document are a statement of the lagoon storage capacity (calculated from the site plan), and the storage capacity of the wicks, pipes and feeder lines; a summary of the installed wick system; and a calculation of the wick system drainage capacity using Darcy's law (Q=KAi) (assuming that 500 wicks will work efficiently). Mr De Bono noted his assumption that the Council's drainage works would cater for between 80-100% of the storm water emanating from the modified catchment (p 137). Mr de Bono concluded that with the reduction in the catchment area, and assuming an 80% effectiveness in the Council's storm water detention and infiltration systems, the volume of water entering the lagoon in a 1 in 100, 48 hour storm event would be 7,140m3 which was marginally above the storage capacity of the lagoon at 9.50m AHD and below the storage capacity at 10.00mAHD and would raise the level of the lagoon less than 1m above the 8.75mAHD (the inlet level of the wick system), and that water would dissipate within 11 hours. Assuming failures of the Council system so that it catered for only 50% of the water emanating from the modified catchment, the additional water would be unlikely to raise the lagoon level more than 10.50m AHD and the water would dissipate within 28 hours; for 30% of the water, the level would be 11.00m AHD, and dissipation would take 39 hours.
20. In a letter to the applicants dated 10 February 2012 (ex 2, tab 23) Mr De Bono responded to a letter from BCS Strata Management to the Council dated 6 February 2012 (ex 2, tab 22) raising concerns about information provided by Coeve Design. In response to concern about the length of time taken to dissipate high water levels in the lagoon, and the statement that the lagoon "has been at its current high mark for over three months", Mr de Bono stated that it "is likely that the filtration system has now clogged up and requires replacement". In oral evidence Mr de Bono stated that he was not aware of any excavation of the filtration system to check whether it was clogged, however verbal advice he had received was that the pH levels are consistent with what is required (T 29/4/15, p 72). In his letter of 10 February 2012 Mr de Bono responded to a concern that a flood level of 10.50m AHD would breach the south and north sewerage pits, spill over the walkway, and engulf the swimming pool, tennis court and community centre, commenting that the conditions of the Consent state that the flood design level is 11.0m AHD, and it "was always envisaged that this level would flood common and private property". In oral evidence Mr De Bono accepted that that was a condition of the Consent, and he confirmed that the tennis court is at 11.0m AHD. On being shown exhibit O, which is a survey dated 28 April 2015 by North Point Surveys (NSW) Pty Ltd, Mr De Bono agreed that it shows the pump station at 10.5m AHD, the south eastern corner of the tennis court at 10.7m, and the land outside the pond on lot 114 at levels below 11m (T 30/4/15, p 90). Mr De Bono's approach is summed up as follows ( T 30/4/15, p 88): You've got more water coming in but the basic principle is, do we need to cater for that - does the lagoon need to cater for that water. If you take into account the injunction, then you should not cater for it. If you take into account the facts, and that was also the letter that the objectors put up, and I think they said somewhere along the line they say, "We're aware of the amount of water that comes into the site", then you have to cater for it. But that's not the intention, the intention is to seek, are the wicks required to cater for the (a) the revised catchment, and (b) the revised catchment with the injunction in place, and that is the basis of the section 96.

Findings

1. It is of concern that Mr Graham, who designed the scheme and who also provided certification to Melaleuca of the Stage 1 wick system installation on 25 October 2006 (ex 2, tab 38), had two different numbers for the actual number of wicks installed. By the time of the hearing he and Mr Stuckey were in agreement that 554 wicks have been installed (ex 6; confirmed in oral evidence). We agree with Dr Joliffe (ex 4, p 24) that while the actual number is not important in respect of the assessment of the system performance, the disparity does provide an uncertainty as to the validity of the provided data. Other inconsistencies in the evidence relate to the dimensions of the cells of the wicks and feeder lines, variously 450mm x 408mm (ex 2, p 322, and ex L); or 450mm x 480mm (ex E p 7). Mr Graham's evidence was that the wicks as installed had a permeability increase to 97%; how that figure was derived is not explained, and is not apparent from consideration of the photographs of the actual wick cubes annexed to exhibit E.
2. It is also of concern that such a complex engineering installation as the grid of wicks and the feeder lines has not, on the evidence before the Court, been recorded on work-as-executed drawings, and that there appear to be no formal construction drawings. The only drawings in evidence purporting to show the arrangement of the wicks, or the feeder or distribution details (including as annexed to the amended proposed modified conditions in ex N), are sketches which appear to be illustrations to demonstrate the concept rather than in a form able to be used as detailed drawings for, or recording, construction. The absence of "as built" drawings was noted by Mr De Bono in his letter to the applicants of 10 February 2012, when he commented (ex 2, tab 23, p 268) that while he understood that the bottom of the pipes near the lagoon entry is set at 8.25mAHD which would set the water level at the top of the pipes at approximately 9.3m AHD, he recommended that the pipe level be checked and confirmed by a surveyor "as no 'as built' drawings are available for confirmation".
3. The most detailed drawing is the plan of proposed wick locations in fig 18 to Mr Graham's report of July 2003 to Melaleuca (ex 2 tab 37), which was in any event not the system later installed. In oral evidence Mr Graham explained that that preliminary wick design system included the required 1600 wicks, and the intention was to do Stage 1 with 857 wicks and then Stage 2 with 743. The system as eventually installed was cut off at a turn on the arrangement of Stage 1, and the non-rectangular arrangement was in response to the excavation conditions on the site (T 30/4/15, pp 16-7). The closest the evidence came to establishing why only 554 wicks were actually installed was in Mr Graham's report of 9 March 2007 (ex L) in which he stated that the refinements to the system as installed in comparison with that required in the consent conditions had the advantage of: "- an increase in the porosity of the wicks and the wide inlet from ~ 30% to ~97% increasing the holding capacity of the wicks and the inflow potential of the inlet by three;" and that "as the revised units had three times the capacity of the original system the number of wicks required was reduced from 1600 to 558". Mr Graham concluded: "Variations to the installed system (compared to the Land and Environment Court approved system) were undertaken based on availability of a more efficient material. Use and implementation of this material has resulted in an increased system performance of 300%".
4. The diagram annexed to the proposed modified conditions as referred to in proposed condition 44 (G1), for which approval is now sought, shows only that the wicks are contained within a tapered elongated rectangular area, and records the drainage system as being "3 rows with 3 insets per row total 880 wicks". In oral evidence Mr Graham stated that the reference to "880" was "a relic of some notation from the Master's assessments", and was one of the numbers of wicks that he trialled, and is not representative of the actual installed number of wicks on the site (T 30/4/15, p 96).
5. The evidence provides no details of the feeder and distribution systems save for descriptions in various reports identified above. In his calculations of the volume of water that can be stored in the polypropylene cell pipelines running to the wick trenches, Mr Graham notes there are approximately 3060 metres of such pipelines. This figure is quoted in the report of July 2003 (ex 2, tab 37), the Project Report submitted in 2006 for Mr Graham's Masters degree (ex 2, tab 24), and the report of July 2007 (ex 3, tab 39). However, it is difficult to see where more than 3 kilometres of drainage cell pipelines to feed the wick trenches are located, given the stated dimensions and arrangement of the trenches and wicks. This figure is also inconsistent with Mr De Bono's statement (ex 2, p 134) that there "approximately 844 liner [sic] metres of feeder lines running to the individual wicks".
6. In the context of these concerns as to the consistency and reliability of the evidence, at best we are able to find that either 554 or 558 wicks have been installed, in the location of Stages 1 and 2 of the development, with the filtration system as described in paragraph [61] above. The gross pollutant trap and wick infiltration system inlet were observed at the site view; and the design of the wicks, and their location and installation, are recorded in the photographs annexed to Mr Graham's statement of evidence of 10 December 2014 (ex E). Whether 554 or 558 wicks were installed is not, on the evidence before us, material. What is material is that the installation of 1600 wicks has not been completed; that the wicks which have been installed are located beneath the infrastructure comprised in Stages 1 and 2 of the development; and, based on the view, that the only accessible parts of the system are the gross pollutant trap at the entrance to the estate and the wick infiltration system inlet at the edge of the lagoon.

The catchment area

1. The applicants submit that the Court can be confident that the Council has reduced the natural flows and volume of surface water entering the site and that what necessarily follows is that there is an actual reduction to the catchment draining into the site; and that the reduction is at least by more than half based on Mr Graham's evidence.
2. In his expert report dated 10 December 2014 (ex E), Mr Graham defined the sources of stormwater that required management as being for Lagoons Estate, to design the site so as to maximise the infiltration of rainfall at the point of ground contact as the site is located on highly permeable dune sands which promote direct rainfall infiltration; and for Seabreeze Estate, the stormwater mitigation programs undertaken by the Council to reduce the catchment area from 68ha to 31ha and installation of infiltration galleries within the catchment to collect detain and infiltrate stormwater. On that basis the required capacity of the wick system only needs to be assessed against the potential stormwater produced by Lagoons Estate.
3. There is some uncertainty in the various reports relied upon by the applicants as to the catchment area. In his report of 23 April 2015 (ex K) Mr Graham states that the catchment is "31.3ha of which 8.379 ha is the subject site and 22.9ha is within Seabreeze Estate". The Red Earth Geosciences draft report of September 2007 (ex 2, p96) states that the Council's drainage works limit the catchment area which can directly impact on the Lagoons Estate, and that: "this has been, or will be, done by redirecting surface or surface-collected flows into other catchment or drainage systems controlled by PSC. Consequently the area of direct impact is now referred to as the 'modified catchment' of area 31.304ha. The original catchment which had previously impacted on Lagoons Estate and particularly the wetland thereon was about 68ha."
4. The Red Earth Geosciences report makes it clear that the area intended to be drained into the Council's underground infiltration galleries in the Seabreeze Estate is 31.304ha, and it does not mention the golf course specifically. However, in its discussion of the "permanent regional water table in this setting" it states: "the groundwater responds to all the aquifer beyond the Lagoons Estate. Thus underground, the artificial separation of the modified catchment (a surface concept) does not apply. It is to be expected that the infiltrated area of influence on the water table will be much greater than just 31.304ha. As figures 2 and 3 show, the groundwater will generally flow towards the Lagoons Estate."
5. Dr Joliffe was involved in the design of the drainage works undertaken by the Council as a consequence of the orders of the Court of Appeal. He described those works (ex 4, p 19, paragraph 88) in the following terms: ♦ Maximise infiltration of surface runoff from the Seabreeze Estate and golf course. This was achieved through the installation of infiltration chambers throughout the area of the Seabreeze estate and the golf course. The chambers, where constructed in the road reserve, were designed to intercept the road pavement runoff and infiltrate that water. ♦ Divert a small catchment area of road pavement near the Armidale Avenue/Grafton Street intersection to the east. ♦ Divert the paved area runoff (road runoff) from the catchment area draining to Austral Street/Fingal Street detention basin to the north. ♦ Diverted a small catchment near the southern end of Armidale Avenue to small detention storages on the golf course. ♦ Made modifications to the drainage system in Dowling Street to permit the monitoring of flow that could enter the Subject Site. ♦ Constructed detention and infiltration facilities on the golf course. ♦ Installed a very limited number of rainwater tanks within the Seabreeze catchment area.
6. Dr Joliffe noted: 89. The above works are understood to have significantly reduced the volume of surface runoff from the Seabreeze Estate and direct the surface runoff into the groundwater through, primarily, infiltration at the infiltration chambers. 90. Discharge of the water to groundwater would increase the volume of groundwater flow, as to that which has occurred since the construction of the Seabreeze Estate and prior to the infiltration system, in the general direction toward the Subject Site.
7. In the joint report (ex 6) Dr Joliffe, Mr Stuckey and Mr Graham considered the definition of the catchment area draining to the site on the basis that the Council has met the Court of Appeal requirements. Dr Joliffe considered that there would be no catchment area drainage surface water directly to the Lagoons Estate except in circumstances of an extreme rainfall with an elevated groundwater level which prevent full infiltration of the rainfall. Mr Stuckey was of the opinion that there would be no surface water draining to the site (8.379ha), "however such drainage has been observed", and the modified catchment area draining to the site is in the order of 22.9ha (31.3- 8.379ha). Mr Graham considered that there should be no surface water flow on to the site, therefore the catchment area is limited to the Lagoons Estate (8.379ha); and the site is located in sandy soils and developed to enhance infiltration at source.
8. Dr Joliffe and Mr Graham provided an additional joint report dated 25 May 2015 addressing the catchment issue (ex V). They stated that they agreed: The areas of 8.379ha (Lagoons Estate), 1.102ha (between Magnus Street and north end of Lagoons Estate), 1.107ha (north east corner of map), 5.909ha (oval and residences north of Fingal Street), 31.304ha (Seabreeze Estate) and 18.778ha (golf course and residences) as shown on Port Stephens Council drawing titled 'Dowling Street Catchment - Nelson Bay' closely define the installed drainage system. Area of 31.304ha identified as Seabreeze Estate assumes that the Council installed system capacity does not meet the Supreme Court of NSW injunction. Should the installed Council system meet the injunction requirements then this area would not contribute surface runoff to Lagoons Estate.
9. There remained areas of disagreement, essentially relating to the golf course. Mr Graham referred to incorporation of bunds on the golf course and subsurface infiltration units, which he interpreted to mean that the Council undertook works to contain surface runoff from the golf course so that it does not flow into the residential area of Seabreeze Estate with the intent being to reduce the surface water catchment area draining to the subject site; Dr Joliffe agreed that works were undertaken on the golf course, not specifically designed and sized to cater for flows up to the 100 year event. Mr Graham considered that the golf course represents an undeveloped area and so surface flow would more closely, in comparison with Seabreeze Estate, be similar to natural overland flows; Dr Joliffe agreed that the golf course is more permeable than the Seabreeze Estate however he could not determine how closely the surface runoff from the golf course replicates the natural regime. Mr Graham considered that the effective catchment area draining towards Lagoons estate consists of Seabreeze Estate (31.304ha); Dr Joliffe stated that he did not know the catchment area as the golf course could contribute both surface runoff and groundwater flow. If the Council works meet the Supreme Court requirements no surface runoff would occur from Seabreeze Estate however groundwater would still occur.

Findings

1. On the assumption the Court is being asked to make, namely that the works undertaken by the Council comply with the orders made by the Court of Appeal, the agreed expert evidence is that there would be no surface runoff from the 31.304ha area of the Seabreeze Estate. We accept that evidence. There remained a disagreement between the experts first, as to whether there is any contribution from surface runoff from the golf course; and secondly, Dr Joliffe's concern as to the groundwater flows. We are not in a position on the available evidence to determine the first concern. As to the second, Dr Joliffe's evidence that as a consequence of the construction of the Council's drainage works surface runoff from the Seabreeze Estate has been directed to the groundwater, primarily through infiltration at the infiltration chambers, was not disputed. That evidence is also supported by the Red Earth Geosciences report of 29 September 2007 (ex 2, p 97) which makes it clear that the infiltration galleries under the Seabreeze Estate were designed to handle rainfall on a modified catchment of 31.304ha, that is, the catchment remaining after the Council modified the original 68ha catchment to reduce the area needing to be drained by the infiltration galleries. The evidence before the Court supports the proposition that groundwater flows are contributing to the lagoon levels on the site (discussed below). As a consequence, we are satisfied that the applicant's proposition that the catchment area has reduced must be understood as limited to surface runoff. The actual flows of water on to the site are addressed below in consideration of the performance of the drainage system.

Whether water flows into the lagoon under pressure from groundwater

1. As noted above, Dr Joliffe was of the opinion that water is flowing into the lagoon under pressure from groundwater. That opinion was based in part on the letter Ongoing Monitoring at Lagoon Estate, Dowling Street Nelson Bay dated 3 February 2010 (Rendell), which in section 6.0 provided interpolated groundwater levels at 11m AHD near the south east corner of the lagoon and 10m AHD near the outlet of the lagoon, and noted that it was likely that the elevated lagoon level observed on 15 July 2009 "is being caused by the high regional groundwater levels feeding back through the WDS" (ex 4, p 17; ex 6, p 3).
2. Mr Graham and Mr Stuckey disagreed. Mr Graham (ex 6, p 3-4) was of the opinion, based on his experience with the site and the site hydrogeology, that the interpretations of the groundwater contours by Rendell in the 2009 and 2010 reports were not accurate. In his opinion they did not take into account the influence of surface water flowing into the lagoon, which causes mounding in the groundwater system, so that rather than the elevated groundwater levels resulting from water moving up from the ground the elevated levels are caused by surface water inflow into the lagoon resulting in localised elevated groundwater levels. The presence of artesian flow observed by Rendell in one well demonstrated that the aquifer system on the eastern side of the Lagoons Estate and within Seabreeze Estate is complex with clay lenses resulting in isolated discontinuous aquifers which have no outlet point. The presence of the clay layers was identified in initial investigations, and was considered in the wick design.
3. In oral evidence (T 30/4/15, p 101) Mr Graham stated that water has two ways of entering the lagoon from upgradient in Seabreeze Estate: from surface runoff, or from a very slow movement of water through the groundwater caused by that water which is infiltrated at point up in the Seabreeze Estate catchment area moving through the water table system in the groundwater system and then moving up through the base of the lagoon and forming a window on the aquifer system itself. Mr Graham later agreed that potentially water from upgradient in the Seabreeze Estate is moving into the lagoon, and the level in the lagoon will always fluctuate based on the surcharged water that is in the upgradient system; what the wicks attempt to do is to move that water away much faster so it does not get trapped and the lagoon level does not rise and flood the site (T 30/4/15, p 152).
4. In his contribution to the joint report (ex 6) Mr Stuckey considered (ex 6, pp 3-4) that water does not feed-back from the wick drainage system to the wetland and water does not flow into the wetland from groundwater discharging at the surface; rather, surface flows from Seabreeze Estate cause ponding in the wetland which is recharged to groundwater via the wick system (direct pathway) and to a much lesser extent by leakage through the base a walls of the wetland (diffuse pathway). Diffuse recharge can only occur when the regional water table is below the wetland water level; and even during very wet periods some level of diffuse recharge is occurring.
5. The applicants submit that while there is evidence of water flowing into the lagoon under pressure from groundwater, that is the nature of the aquifer system and the perched aquifer. On that basis, the question of groundwater is not an issue of importance, as Dr Joliffe has not tried to compute it, and neither of the other experts considered it to be relevant to the question of computing the operation or determining the effectiveness of the system.

Findings

1. Groundwater flow from the wick area to the sea is the theory underlying the functioning of the wick system. On our understanding of the expert evidence, the drainage system incorporating infiltration galleries installed by Council under the Seabreeze Estate is designed to convey water from the surface of the ground to the water table below. Potentially, some of this groundwater from the Seabreeze Estate will reach the Lagoons Estate. As noted above, in his oral evidence Mr Graham acknowledged entry of water into the lagoon through groundwater caused by water infiltrated at points up in the Seabreeze Estate catchment area moving through the water table system. The wick system design, in adopting a modified catchment area of 31.4 ha, assumes the rainwater falling on the Seabreeze Estate reaches Lagoons Estate in the form of groundwater, because no surface flow is assumed to occur from Seabreeze Estate. The evidence of the applicants' experts does not establish, however, given all the water falling on the Seabreeze Estate is collected and infiltrated into the groundwater, where that groundwater flows to. In the end, the evidence appears to support a finding that the modified catchment, comprising Seabreeze Estate, is contributing water to the lagoon in the Lagoons Estate either by groundwater flow, or some surface flow, or a combination of both. That there is some contribution of groundwater is supported by the observations that water has remained in the lagoon for extended periods, and the diagram in Mr Graham's report of July 2003 (ex 2, tab 37, p 536) showing the water table intersecting the lagoon (or "swamp" as described in the drawing). We agree with Dr Joliffe that groundwater contributes to water in the lagoon.

The performance of the wick drainage system

1. The applicants submit that the evidence shows that the system has been able to cope with very significant inflows and very significant storm events, including one in early 2009, and has been able to drain away. The applicants rely in particular on data as to water levels and rainfall in monitoring reports prepared by Matthew Rendell of Environmental Earth Sciences (ex 2, tab 40; ex R) as sufficient to ground the idea that the system operates effectively and no further monitoring is required to prove it. It must be assumed that the Council drainage works upstream have been effective, and if that is so it has removed entirely the surface drainage from Seabreeze Estate and it then follows that the system that was put on the Lagoons Estate to deal with surface flows onto the estate from Seabreeze becomes redundant. The question then becomes what should be done about it, and as identified by Giles JA there is the unnecessary construction cost in constructing something no longer needed.
2. The applicants submit that the relevant matters to consider are regional effects, groundwater gradients, hydraulic conductivity, the draining capacity of the wick system, and monitoring and observations: 1. the regional effects to the site can be assessed by an analysis of ground water offsite and upstream effects, and in that regard the evidence of Mr Graham and Mr Stuckey that groundwater from upstream property has no effect on the lagoon level or draining performance of the wicks is to be preferred to that of Dr Joliffe; 2. on groundwater gradients, Dr Joliffe largely agreed, in principle, with Mr Graham's evidence that groundwater gradient levels could be at different heights under the ground and that because of the groundwater level, soil profile and hydraulic conductivity, "where the lagoon is there's sort of a squeeze or a bottleneck on the groundwater flowing across the area, and once it gets to the other side lagoon it flows away quite quickly" (T 30/4/15, p 101); 3. on hydraulic conductivity, there was no dispute regarding Mr Graham's statement that the rate of conductivity was 32 or 32.5, or his statement in oral evidence that such high conductivity demonstrated the suitability of the area to install the wick system; 4. in relation to the draining capacity of the wick system, Mr Stuckey's evidence was that by his calculations the area of each wick would be equivalent to about 19m2 discharging to an aquifer and that taking into account the soil conductivity the capacity is 30m2, so the total capacity is 554 x 30. Mr Joliffe differed not on the calculation model based on Darcy's law, but on the proposition that it was appropriate to multiply a single wick to arrive at a total, as in his opinion that assumed that each and every wick could discharge at the rate calculated through Darcy's law and there was no consideration of wicks interacting which would reduce the discharge rate. Mr Graham agreed with Dr Joliffe that there would be an effect between each wick, however in his opinion the numerical model took into account the interference that while present was not sufficient to alter the capacity of the wicks; and 5. in relation to monitoring and observations, the applicants rely on Mr Graham's observation in oral evidence based on his visit to the site that the lagoon had maintained a certain level after a 300mm two day rainfall event and where remnant detritus around the edge of the lagoon indicated that the level had been higher. While Mr Graham considered, based on the photographs in exhibit H, that water is not being contained in the Council system and that a significant portion of the water is reaching the lagoon, in his opinion, based on the report of monitoring on 15 July 2009 (ex M), the system had managed to recover from a high rainfall event and everything had responded as would be expected.
3. The applicants submit that it follows that the wick drainage system as installed exceeds expectations and there is no need to alter its construction or operation.
4. The Council submits that despite the wick drainage system being in operation for nearly 9 years, very little actual monitoring has been provided. While emphasis has been placed on monitoring of the Council's upstream system, no emphasis has been placed on monitoring of the applicants' system either within the Lagoons Estate or downstream to show the efficiency of the wick system. It is not merely a matter of how much water is coming down the hill from Seabreeze Estate or into the lagoon from the golf course via the easement, but it is a matter of how efficient the wicks are at disposing of that water. There will always be occasions when water flows from the Seabreeze Estate, and the Court of Appeal orders allow for natural flow; there is an easement in favour of the Council to drain water from the direction of the golf course; and the applicants have not given consideration to groundwater flows into the site, merely surface flows.
5. The experts disagreed as to whether it has been established that the wick drainage system as installed performs to, or exceeds, expectations.
6. Mr Graham was of the opinion that the system has demonstrated its capacity and suitability of design. He considered that stormwater, and not groundwater, is the driver for the system as ongoing overland flow results in contemporaneous inflow of stormwater into the lagoon during rainfall events, as demonstrated by the instantaneous response of water level in the lagoon to rainfall events. If the infiltration systems installed by the Council were working the hydraulic conductivity of the soils would limit the movement of water from the infiltration point to the lagoon to a maximum of 40m/day, and water would gradually move through the system and the natural groundwater system would slowly discharge into Nelson Bay. Current monitoring suggests a rapid rise in the lagoon level following a storm event which is the result of overland flow. In his opinion as the development on Lagoons Estate has not changed the natural groundwater flow system other than to increase the discharge potential, the installed system should be more than adequate to prevent flooding of the site due to surface water flow from the 8.379ha catchment.
7. Mr Stuckey was of the opinion that the success and appropriateness of the system is beyond dispute, particularly as significant runoff from Seabreeze Estate surface flows continue. He considered that the numerical models should be used in preference to the analytical models, as the regional groundwater climatic response requires a numerical model to accurately predict water table levels. When the regional water table is elevated due to significant and prolonged rainfall such as between February and August 2009, recharge to the regional aquifer will be slower due to the decreased gradient, and that merely confirms that the system is behaving in response to natural aquifer levels and disposes of large volumes of surface water from Seabreeze Estate. In his opinion groundwater levels only influence wetland water levels after standing water has collected in the wetland via surface runoff from Seabreeze.
8. In the joint report (ex 6) Dr Joliffe considered that the system performance should be based around groundwater being the driver for the performance assessment as there should be no surface runoff. The observations in the monitoring reports indicate a correlation between the adjacent groundwater level and the lagoon level; the documented analysis appears to be based on exfiltration from the wicks over their entire external surface, the hydraulic gradient being based on them being full of water and the storage volume within the system having them empty; and Mr Stuckey's data shows the recorded water level at the inlet location to have remained near 10m AHD for a period of 4 months in 2009.
9. In considering the expert evidence as to how the wick drainage system has performed, we address three issues: 1. the capacity of the lagoon; 2. what the monitoring data shows; and 3. whether maintenance of the system impacts on performance.

(1)The capacity of the lagoon

1. On our understanding of the expert evidence, the lagoon stores water before it flows from the lagoon outlet into the wicks and surrounding ground. As water flows into the Lagoons Estate, whether as surface flow or as groundwater flow, the lagoon has a finite capacity, depending on its initial water level, to store the earliest inflowing water volume before its water level reaches the level at which water commences to overflow into the wick drainage system. Once the lagoon water level rises above the overflow level, the wick outflow drainage rate will control the rate at which water leaves the lagoon. The wick outflow drainage rate will also control the rate at which the lagoon level continues to rise while ever the wick drainage rate is exceeded by the rate at which surface water or groundwater flows into the lagoon. If the lagoon had no spare capacity at the commencement of inflow (with the water level being already at the overflow level of 8.75 m AHD), the wick drains would have to cope with all the inflow of water to the lagoon until such time that water ceases to flow into the lagoon. However, whenever the lagoon, at the commencement of inflow, has some spare capacity (the water level is below the overflow level to the wick drains) the wick drains would not have to start to operate until such time as the lagoon fills sufficiently to commence overflowing into the wick drainage system.
2. The take up capacity of the lagoon is important for an understanding of the storage area available to control the entry of water into the wicks, and thus for an understanding of the actual performance of the system as modelled, and as revealed in the monitoring data. However, the expert evidence as to the actual capacity of the lagoon was unclear, and inconsistent. Mr Stuckey in his report of 10 December 2014 (ex D) states in his Executive Summary that "The calculations made for wick drainage system capacity in the SOEE report, based on the size of catchment, storage capacity of the lagoon and 100 year 48 hour storm event values used, are correct". However, in his summary of review findings Mr Stuckey states (ex D, p 12) "The only data that Environmental Earth Sciences has been unable to verify is the final storage capacity of the lagoon at various RLs". However, the Tables to his report for stormwater balance on a range of scenarios show a calculation of 42,500m3 for remaining pond storage capacity to 11m and net pond volume; in oral evidence (T 30/4/15 p 131) Mr Stuckey stated that this was an assessment of pond volume including wick capacity.
3. Mr De Bono in Annexure D to the SEE states (ex 2, tab 2, p 134) that the lagoon storage capacity calculated from site plan ranges from 2,140m3 to 8.75m AHD (level of inlet system into wick drains) to 25,819m3 at 11.0m AHD and 35,405m3 at 11.5mAHD. Mr Stuckey commented (ex D, p 4) that the 11.0m AHD figure given by Mr De Bono is less than Environmental Earth Sciences 2007 report (ex 2 tab 39) which had it at 37,600m3 at 11.0m AHD; and noted that "… a lesser volume estimate is more conservative, and is assumed to be based on updated assessment of the lagoon area".
4. Mr Graham also addressed the question of the lagoon capacity, first in his 2003 report (ex 2, tab 37) in which he nominated the lagoon capacity as 37800m3 to RL 11.0AHD. His 2006 thesis report (ex 2, tab 24) states the capacity to be (at p 305) 37800 m3 to RL 11.0, and (at 306), at 43257.5m3; that report conducts hydrological modelling assuming a 68ha catchment (p 281).
5. In his report dated 29 September 2006 (ex K tab 25) Mr Graham notes (p7): The pond is considered to be a major source of storage and it is estimated by Environmental & Earth Sciences that the storage potential of the pond is as follows: - to 8.75m AHD storage capacity is 7,050m3; - from 8.75m AHD to 9.5m AHD storage capacity is 6,900m3; - from 8.75m AHD to 9.6m AHD storage capacity is 8,067m3; - from 8.75m AHD to 10.4m AHD storage capacity is 19,400m3.
6. The 2007 report (ex 2, tab 39) states that the storage capacity has been calculated at 37600 m3 to RL 11.0; while that report does not specify a catchment size, the adoption of identical stormwater inflow quantities to those in the 2006 thesis report would suggest a catchment size of 68ha. In that report Mr Graham added to the storage capacity of the pond at 37,600m3 to 11.0m AHD, the wick storage (157m3), the trench storage (3,706m3) and the pipeline storage (430.5m3), giving a total available storage of 41,893m3 (p 645). The Table 2 Stormwater Balance 558 Wicks provision in that report notes "storage capacity calculated assuming maximum pond level is 11.0 metres and available volume is 37,600m3" (pp 645, 646). At p 652 Graham says that between 11.0-8.75m AHD the volume of water possibly stored is 36,207m3.
7. In oral evidence Mr Graham stated that the pond capacity was the sum of the layers specified in the 29 September 2006 report, which add up to about 40,000m3. At p 6 of that report, in Table 2 Stormwater Balance 558 Wicks, Mr Graham notes "storage capacity calculated assuming maximum pond level is 11.01 metres and available volume is 32,000m3". In oral evidence (T 30/4/15, p 114) Mr Graham stated that the volume of the lagoon at 11m AHD had been calculated as 37,800m3, referring to his July 2003 report (ex 2, tab 37, p 560). Mr Graham subsequently clarified that response, stating that the actual volume in the pond alone is 32,000m3, and 37,800m3 includes the storage capacity within the wick system itself (T 30/4/15 p 130). When asked about the earlier evidence that the pond capacity totalled 40,000m3, Mr Graham acknowledged a variation between the two figures, and stated that the figure of 32,000 "was a conservative one which shows there's even more excess capacity within the system" (T 30/4/15, p 130). In his statement of evidence of 10 December 2014 (ex E) Mr Graham states (at p 6) that the system is able to contain a significant rainfall event "with remaining storage capacity of over 24,000m3 (available capacity in the lagoon between 10m AHD and 11.5m AHD) within the lagoon during the peak intensity of the event".
8. The evidence before the Court does not include a detailed flood contour plan for the Lagoons Estate, and so it is not possible to determine the parameters by which the pond volume has been calculated by the various experts. One site drawing (ex P), discussed during the hearing (T 30/4/15, p 95, L14-29), is confirmed by Mr Graham, who drew the diagram, as showing the "lagoon outline is actually at 11 metres AHD, so that's to an upper water level". That is the only document available to the Court that purports to show the lagoon outline when the water level is at RL 11.0; and based on that diagram, the lagoon outline shown occupies a significant portion of the total area of 8.44 ha for the Lagoons Estate (ex 2, p 59).
9. A further issue is the recommendation by Mr Graham in his July 2007 report (ex 2, tab 39, p 653) that the current system has capacity to deal with 1 in 100 year storm event "with only minor earthworks required to enlarge the pond by approximately 10,000m3"; Mr Graham recommended that the pond be enlarged by that much "to allow a safety margin to ensure residents of Lagoons Estate are not affected". On the evidence before the Court, no such works have been undertaken.
10. The applicants submit that that comment should be understood in the context in which the various storm events had not been assayed, and the assessment was done as a theoretical adjustment. However, in oral evidence (T 30/4/15, p 125) Mr Graham was not able to explain why he was making that recommendation in 2007, after the judgment of the Court of Appeal on 1 March 2006 and well into the 18 month period for Council to carry out the drainage works and when the wicks were in situ and monitoring could have taken place, responding (T 30/4/15, p 125 line 26): I think this was just an experiment into what the current capacity of the system would be assuming that 1600 wicks and the initial court proceedings had stuck firm.
11. We are not persuaded that the actual capacity of the lagoon has been established on the evidence. As noted above, that is an important aspect of understanding the actual performance of the wick drainage system, in particular in understanding how it responds to rainfall events when the lagoon is already at or close to the wick inlet level.

(2)The monitoring data

1. In our view the critical issue in determining whether the drainage system as installed is adequate is whether the applicants' position that it is, is supported by data as to the actual performance of the system. In support of his opinion that the wick drainage system has been demonstrated to cope, Mr Graham relies on the evidence of rainfall events in 2009, and on the storm event of 20-21 April 2015. In his statement of evidence (ex E) he referred to the report of 2007 (ex L) as a summary of what is installed, and the reports of ongoing monitoring of February and August 2010, including a summary of groundwater and lagoon levels during period 19 December 2006 to 17 July 2010, and commented (at p 6): Although the system was designed using detailed analytical and numerical modelling (EES 2007b and Graham 2006), the performance and suitability of the current system is best confirmed through field testing.
2. Mr Graham, Mr Stuckey and Dr Joliffe agreed in oral evidence that with 9 years since installation of the system, actual monitoring is more informative than theoretical modelling. In Mr Stuckey's opinion the kind of monitoring data that would be of use in forming a view as to the effectiveness of the system would be a combination of measurement of groundwater, static water levels and rainfall (T 30/4/15, p 111). Mr Graham agreed that real life measurements are more accurate and useful; and his review of data in his report of 23 April 2015 was referring to actual visual observations in regards to the response of the system to a large influx of water and a high volume rainfall event. Mr Graham accepted that he had never been onsite when a high rainfall event occurred (T 30/4/15, pp 111-112).
3. We agree with the experts that actual monitoring of the system, as opposed to the theoretical modelling, is central to understanding the performance of the wick drainage system.
4. The monitoring reports for the Lagoons Estate in evidence are: 1. 19 May 2009: report by Environmental Earth Sciences NSW (Mr Matthew Rendell) to the Community Association DP 270468 headed Ongoing Monitoring at Lagoon Estate, Dowling Street Nelson Bay (ex 2, tab 40); 2. 3 February 2010: report by Environmental Earth Sciences NSW (Mr Matthew Rendell) to Body Corporate Services, headed Ongoing Monitoring at Lagoon Estate, Dowling Street Nelson Bay (ex M); and 3. 26 August 2010: report by Environmental Earth Sciences NSW (Mr Matthew Rendell) to Body Corporate Services, headed Ongoing Monitoring at Lagoons Estate, Dowling Street Nelson Bay (ex 2, tab 12).
5. Each of those reports involved groundwater monitoring at 5 locations (BHe 1, BHe 2, BHe 3, BHe 4, BHe 5) and surface water monitoring at 2 locations (lagoon, inlet). The sample dates for field data included in the report of 26 August 2010 (Table 4) are 31 October 2006, 29 January 2007, 27 November 2007, 21 January 2009, 15 July 2009 and 15 July 2010; we note that there are gaps in the data, between January 2007- November 2007 and July 2009-July 2010. Figure 4 of each report shows water levels and rainfall in a graph form: the 19 May 2009 report covers the period November 2006 to February 2009; the 3 February 2010 report covers the period December 2006 to June 2009; and the 26 September 2010 report covers the period January 2008 to July 2010.
6. In his report to the Council of 15 January 2013 (ex 2, tab 15) Dr Joliffe states based on monitored groundwater levels and daily rainfall at 6 locations from near the intersection of Dowling St/Parkes St (BHe1) to Magnus Street (BHe5) for periods from 1/1/06-15/7/10 and 1/1/08-1/7/10 (p 202), his observations were that between 2009 to early 2011 was quite dry, with average rainfall observed during the monitoring period at 100mm as compared to long term average of approximately 115mm for January 2009 to June 2011. Dr Joliffe observed that the groundwater level in the lagoon was at a level in excess of 10mAHD for nearly 7 months during 2009. That latter comment was disputed by Mr Stuckey (ex D, p 7), relying on charts of relative water levels and rainfall for February 2009-July 2010 and February 2009-end August 2009 (ex D, p 9, 10) which we note are similar to the charts in the reports noted at [114] above, but which differ slightly as to the recorded dates.
7. We accept, based on the charts relied upon by Mr Stuckey, that in fact the lagoon level was close to 10m AHD after a significant rainfall event in February 2009 (343mm), until early April 2009 when it was 9.5m; water levels in the lagoon were maintained at close to 10m in April and May 2009, when 372mm of rainfall was experienced; and water levels were close to 10m for the duration of June and July, dropping from late July so that at the end of August the lagoon level was at 9.5m AHD. Having regard to the later data in fig 4 of the report of 26 August 2010 (ex 2, p 180), the water level in the lagoon did not drop below 8m AHD until early 2010.
8. Mr Graham's evidence on the rainfall event of February 2009 (ex E p 6) was that the highest intensity event was 15 February 2009 when 210.6mm fell within a 24 hour period (equivalent to a 1 in 50 year event): he relied on the Environment Earth Sciences monitoring reports of February and August 2010 as establishing that the response of the system was an increase in groundwater and lagoon level of between 1- 1.5m (with the lagoon remaining below 10m at all times); and that following this event, groundwater wells in the vicinity of the wick system (BHe3 and BHe4) and the lagoon recovered to pre-event levels within 2 weeks (although ongoing rain prevented full recovery). In his opinion this establishes that the system can contain a significant rainfall event with remaining storage capacity of over 24,000m3 (available capacity in the lagoon between 10m AHD and 11.5m AHD) within the lagoon during the peak intensity of the event.
9. We accept, based on the monitoring data, that there was a significant rainfall event (1 in 50 year) in February 2009, which resulted in significant elevations of water level in the lagoon, inlet and wick system. That recorded data establishes that for that period, which included some subsequent, and lesser, rainfall events, levels in the lagoon remained above the lagoon outlet level of 8.75m AHD for a period of around or exceeding five months (ex 2, p 683; ex D, p 10). That is an indication that water was not being sufficiently drained by the wick drainage system and natural seepage to counter the rate of inflow to the lagoon. We do not accept that it has been established that the wick drainage system can be relied upon to drain, within a few days, inflow to the lagoon that might raise its level above 8.75m AHD. We are not persuaded that Mr Stuckey's analysis supports a counter position.
10. In Table 1 of his report (ex D) Mr Stuckey re-presents Mr Graham's stormwater balance figures, based on a 68 ha catchment with a "100% run-on" and 558 wicks. It can be seen that the water level in the pond rises to a maximum level of RL 11.5, which is the level Mr Graham suggests the pond would rise to in his 2007 report (ex 2, p 645). However, Mr Stuckey has a pond level of RL 3.92 at the onset of the storm, some 4.83 metres below the inlet level to the wicks. Mr Graham states in his report (ex 2, p 651) that "The current system should therefore have sufficient capacity to contain a 1 in 100 year storm of 2880 min duration with an excess volume of 5000m3 of water. This is assuming a situation where the wetland level is less than 8.75m AHD at the onset of the storm". Mr Stuckey appears to have justified Mr Graham's maximum pond level of 11.5m AHD by adopting a starting wetland level 4.83 metres below 8.75m AHD. Mr Stuckey then proceeds to present stormwater balance figures for the "modified" catchment of 31.3 ha, just 500 wicks, and 100% run-on for three further scenarios, being (1) present conditions (Table 2); increased sea level (Table 3); and increased sea level and rainfall (Table 4).
11. In the first scenario, the pond water level is predicted to rise to 10.52m AHD before beginning to drop. This agrees very closely with Mr De Bono's conclusion in his report (ex 2, p138) that "assuming a catastrophic failure in Council's storm water detention and infiltration systems… is unlikely to raise the lagoon level more than 10.5m AHD". Mr De Bono also assumes "a reduction in effectiveness (of the Council's system) to cater for only 50% of the water emanating from the amended catchment". However, Mr Stuckey is catering for 100% run-on, and has a water level in the pond at the onset of the storm of 6.74m AHD, some 2.01m below the wick inlet level. The pond level, under the predicted draining action of the wicks, would drop back to the wick inlet level by about hour 56 of the storm. Curiously, the pond level then continues to drop at a similar rate when it is below the wick inlet level; how this occurs is not explained. In the second and third scenarios, the pond level reaches 10.57m and 10.75m AHD respectively, while the starting level in the pond is 6.74m and 6.81m AHD respectively; and the pond level continues to fall even when overflow to the wicks cannot occur.
12. On our reading of Mr Stuckey's report, none of the scenarios have a lagoon level at 8.75m at the onset of the storm. That would have better represented a more severe, and realistic, scenario on which to test the effectiveness of the system; it was also the situation that in fact occurred for each the rainfall events after the February 2009 rainfall event as recorded in the monitoring data, until late in 2009.
13. The applicants relied on the storm event of 20-21 April 2015, which was shortly before the site view. As noted above, the evidence includes photographs and videos of water flowing into the Lagoons Estate, and at Seabreeze Estate. Mr Graham's evidence was that between 9am 20 April to 9am 21 April 155mm of rainfall was recorded by BOM weather station at Williamstown; there was ongoing rain on 21 April with an additional 147mm recorded at Williamstown up to 3am on 22 April 2015. That equates to a 1 in 10 and 1 in 20 year 48 hour event (ex K, pp 6-7). In oral evidence Mr Graham commented that the water level in the lagoon had dropped by the time of the site view; however the evidence before the Court does not establish what the water level was at the height of the storm event, or its level at the time of the view. While the photographs and video show volumes of water flowing, in the absence of quantification we are unable to draw any conclusions as to the April 2015 storm event.
14. In substance, the applicants' position that the wick drainage system has been demonstrated to cope is based in part on data from a 1 in 50 year event (February 2009) and a 1 in 10 to 1 in 20 year event (April 2015), and on conclusions primarily derived from modelling. In our view the modelling does not provide a reliable basis on which to draw the conclusions sought by the applicants. We have noted above the assumptions on which Mr Stuckey based his conclusions, in particular his starting point of a lagoon level of between 3.92m to 6.81m AHD at the onset of a storm; we also note Mr Graham's report of July 2007 (ex 2, tab 39, p 651) in which he concludes that the system has sufficient capacity to contain a 1 in 100 year storm of 2880 minutes duration with an excess volume of 5000m3 of water, assuming that the wetland level is less than 8.75m AHD at the onset of the storm. Further, we are not persuaded that the data obtained from the monitoring that has been undertaken in fact establishes the performance of the system in the terms put by the applicants.

(3)Maintenance

1. A further factor in our assessment of the performance and adequacy of the wick drainage system is the issue of maintenance. As noted above, the resident submissions referred to a lack of maintenance, and the evidence before the Court does not counter that position.
2. Based on the evidence as to the location of the wicks, and the site view, we find that the installed wicks, being underneath existing dwellings and other infrastructure, will not be able to be inspected and/or maintained. On the evidence before the Court, there is a possibility that fine-grained material entering the wicks at times when the filtration system is being bypassed could commence to clog the wicks and reduce their efficiency. For example, Mr Stuckey's report of 10 December 2014 (ex D, p 12) notes that "the extreme event drainage system is designed to bypass the filter, if the pond water level ever reaches the extreme event level (1 metre below floor level)". We accept that the filtration system has been designed, and is important, to prevent or reduce silt and other fine matter entering the wicks. Mr De Bono was not aware of any steps having been taken to maintain the filtration system in accordance with his recommendation (T 29/4/15, pp 71-72), or that the lagoon has ever been cleaned of silt (T 29/4/15, pp73-74). The Environmental Earth Sciences monitoring report of 19 May 2009 (ex 2, tab 40), states that "observations of the water level in the lagoon indicated that it was higher than the recent rainfall would indicate, this may be due to the inlet being blocked by sediment or algal growth" (p669), and concludes "the water level in the lagoon was observed to be higher than anticipated indicating potential issues with blocking of the wick systems drainage inlet" (p671). The report goes on to recommend "monitoring of water levels in the lagoon be undertaken visually to assess whether the inlet blockage is preventing flows during rainfall events, if this is the case, maintenance work may be required to prevent flooding" (p 673). There is no evidence that any of these maintenance steps have been undertaken.

Conclusion

1. For the reasons above, we have concerns as to the consistency and reliability of the evidence relating to the installation of the wick drainage system. However, we are satisfied that either 554 or 558 wicks have been installed, in the location of Stages 1 and 2 of the development, with the filtration system as described in paragraph [61] above. The wicks which have been installed are located beneath the infrastructure comprised in Stages 1 and 2 of the residential development at Lagoons Estate; the only accessible parts of the system are the gross pollutant trap at the entrance to the estate and the wick infiltration system inlet at the edge of the lagoon; and there is no evidence that any routine maintenance steps as recommended by Mr De Bono or Mr Rendell have been undertaken.
2. Much of the expert evidence on which the applicants sought to rely to support their position that it is unnecessary to install the 1600 wicks required in the Consent, is based on modelling undertaken both before the installation of the system and since. There is some limited monitoring data as to the actual performance of the system. However, we are not persuaded that that evidence supports the proposition that the system as installed can cope with expected flows.
3. We are not persuaded that groundwater flows are irrelevant, or that their effects have been adequately taken into account (and so do not accept the applicants' submission at paragraph 92 above). We accept that there was no dispute as to the rate of conductivity (paragraph 92 above); however we do not understand that to be critical for our findings. In the context of the inconsistencies and uncertainties in the numerical modelling for the wicks, in particular what is the influence on wick discharge when groundwater is at a high level surrounding the wicks, we are not persuaded that the draining capacity of the wicks has been established, as submitted by the applicants (paragraph [92[(d) above). The evidence before the Court does not establish to any degree of satisfaction what the capacity of the lagoon is, and the modelling undertaken, in particular by Mr Stuckey, does not assist in an understanding of the consequences of a major rainfall event occurring at a time the water in the lagoon is at an elevated level. The monitoring data provided by Environment Earth Sciences, showing actual performance, covering the period from October 2006 to July 2010 (with some gaps as noted above), confirms the evidence of the residents that there have been periods when the lagoon level has remained high for extended periods.
4. We are not persuaded that the evidence establishes that the modifications proposed to the Consent so that it reflects the works actually carried out provide a drainage system that appropriately addresses the potential impacts on the approved development from flooding including those arising from high rainfall events. On that basis, the modification application cannot be approved.
5. The Orders of the Court are:
6. The appeal is dismissed.
7. The application to modify Development Consent (Application No 16-1999-2013-1) for an urban housing development at 2 Dowling Street and 7 Donald Street Nelson Bay is refused.
8. The exhibits, except for Exhibits 1, 4, A, B, D, L, M and N, are returned. Linda Pearson Commissioner of the Court Ross Speers Acting Commissioner of the Court

DISCLAIMER - Every effort has been made to comply with suppression orders or statutory provisions prohibiting publication that may apply to this judgment or decision. The onus remains on any person using material in the judgment or decision to ensure that the intended use of that material does not breach any such order or provision. Further enquiries may be directed to the Registry of the Court or Tribunal in which it was generated. Decision last updated: 30 September 2015