Water Sensitive Urban Design (WSUD) application auditing

摘要

BackgroundudWSUD implementation in the Gold Coast City Council area commenced more than a decade ago. As a result, Council is expected to be in possession of WSUD assets valued at over tens of million dollars. The Gold Coast City Council is responsible for the maintenance and long-term management of these WSUD assets. Any shortcoming in implementation of best WSUD practices can potentially result in substantial liabilities and ineffective expenditure for the Council in addition to reduced efficiencies and outcomes. This highlights the importance of periodic auditing of WSUD implementation.ududProject scope udThe overall study entailed the following tasks:ud* A state-of-the-art literature review of the conceptual hydraulic and water quality treatment principles, current state of knowledge in relation to industry standards, best practice and identification of knowledge gaps in relation to maintenance and management practices and potential barriers to the implementation of WSUD.udud* Council stakeholder interviews to understand current practical issues in relation to the implementation of WSUD and the process of WSUD application from development application approval to asset management.udud* Field auditing of selected WSUD systems for condition assessment and identification of possible strengths and weaknesses in implementation. udud* Review of the Land Development Guidelines in order to identify any gaps and to propose recommendations for improvement.ududConclusionsudGiven below is a consolidated summary of the findings of the study undertaken.ududState-of-the-art literature reviewudThough the conceptual framework for WSUD implementation is well established, the underlying theoretical knowledge underpinning the treatment processes and maintenance regimes and life cycle costing are still not well understood. Essentially, these are the recurring themes in the literature, namely, the inadequate understanding of treatment processes and lack of guidance to ensure specificity of maintenance regimes and life cycle costing of WSUDs.udThe fundamental barriers to successful WSUD implementation are:ud* Lack of knowledge transfer – This essentially relates to the lack of appropriate dissemination of research outcomes and the common absence of protocols for knowledge transfer within the same organisation.udud* Cultural barriers – These relate to social and institutional factors, including institutional inertia and the lack of clear understanding of the benefits.udud* Fragmented responsibilities – This results from poor administrative integration within local councils in relation to WSUDs.udud* Technical barriers – These relate to lack of knowledge on operational and maintenance practices which is compounded by model limitations and the lack of long-term quantitative performance evaluation data.udud* Lack of engineering standards – Despite the availability of numerous guidelines which are non-enforceable and can sometimes be confusing, there is a need for stringent engineering standards.ududThe knowledge gaps in relation to WSUDs are only closing very slowly. Some of the common knowledge gaps identified in recent publications have been recognised almost a decade ago. The key knowledge gaps identified in the published literature are:ud* lack of knowledge on operational and maintenance practices;ud* lack of reliable methodology for identifying life cycle issues including costs;ud* lack of technical knowledge on system performance;ud* lack of guidance on retrofitting in existing developments.ududBased on the review of barriers to WSUD implementation and current knowledge gaps, the following were identified as core areas for further investigation:ud* performance evaluation of WSUD devices to enhance model development and to assess their viability in the context of environmental, economic and social drivers;udestablishing realistic life cycle costs to strengthen maintenance and asset management practices;udud* development of guidelines specific to retrofitting in view of the unique challenges posed by existing urban precincts together with guidance to ensure site specificity;udestablishment of a process for knowledge translation for enhancing currently available best practice guidelines;udud* identification of drivers and overcoming of barriers in the areas of institutional fragmentation, knowledge gaps and awareness of WSUD practices. ududGCCC stakeholder interviewsudFourteen staff members involved in WSUD systems management in the Gold Coast City Council, representing four Directorates were interviewed using a standard questionnaire. The primary issues identified by the stakeholders were:ud* standardisation of WSUD terminology;udud* clear protocols for safeguarding devices during the construction phase;udud* engagement of all council stakeholders in the WSUD process from the initial phase;udud* limitations in the Land Development Guidelines;udud* ensuring public safety through design;udud* system siting to avoid conflicts with environmental and public use of open space;udud* provision of adequate access for maintenance;udud* integration of social and ecosystem issues to ensure long-term viability of systems in relation to both, vandalism and visual recreation;udud* lack of performance monitoring and inadequacy of the maintenance budget;udud* lack of technical training for staff involved in WSUD design approvals and maintenance;udincentives for developers for acting responsibly in stormwater management.ududField auditing of WSUD systemsudA representative cross section of WSUD systems in the Gold Coast were audited in the field. The following strengths and weaknesses in WSUD implementation were noted:ud* The implementation of WSUD systems in the field is not consistent.udud* The concerns raised by the stakeholders during the interviews in relation to WSUD implementation was validated from the observations from the field auditing, particularly in relation to the following:ud * safeguarding of devices during the construction phaseud * public safetyud * accessibility for maintenanceud * lack of performance monitoring by Council to assess system performanceud * inadequate maintenance of existing systems to suit site specific requirements.udud* A treatment train approach is not being consistently adopted. udud* Most of the systems audited have satisfactorily catered for public safety.udAccessibility for maintenance has been satisfactorily catered for in most of the systems that were audited.udud* Systems are being commissioned prior to construction activities being substantially completed.udud* The hydraulic design of most systems appears to be satisfactory. udud* The design intent of the systems is not always clear.ududReview of Land Development GuidelinesudThe Land Development Guidelines (TDG) was extensively reviewed and the following primary issues were noted in relation to WSUD implementation: ud* the LDG appears to have been prepared primarily to provide guidance to developers. It is not clear to what extent the guidelines are applicable to Council staff involved in WSUD maintenance and management; udud* Section 13 is very voluminous and appears to be a compilation of a series of individual documents resulting in difficulties in locating specific information, a lack of integration and duplication of information;udud* the LDG has been developed with a primary focus on new urban precinct development and the retrofitting of systems in existing developments has not been specifically discussed; udud* WSUDs are discussed in two different sections in the LDG and it is not clear which section takes precedence as there are inconsistencies between the two sections;udthere is inconsistent terminology being used;udud* there is a need for consolidation of information provided in different sections in the LDG;udud* there are inconsistencies in the design criteria provided;udud* there is a need for regular updating of the LDG to ensure that the information provided encompasses the state-of-the-art;udud* there is limited guidance provided for the preparation of maintenance plans and life cycle costing to assist developers in asset handover and to assist Council staff in assessment.udud* Based on these observations, eleven recommendations have been provided which are discussed below.ududAdditionally, the stakeholder provided the following specific comments during the interviews in relation to the LDG:ud* lack of flexibility to cover the different stages of the life cycle of the systems;udud* no differentiation in projects undertaken by developers and Council;udud* inadequate information with regards to safety issues such as maximum standing water depth, fencing and safety barriers and public access;udud* lack of detailed design criteria in relation to Crime Prevention through Environmental Design, safety, amenity, environment, surrounding uses and impacts on surroundings;udud* inadequate information regarding maintenance requirements specific to the assessment and compliance phases;udud* recommendations for plantings are based primarily on landscape requirements rather than pollutant uptake capability.ududRecommendationsudWith regards to the Land Development Guidelines, the following specific recommendations are provided:ud1. the relevant sections and their extent of applicability to Council should be clearly identified;udud2. integration of the different subsections within Section 13 and re-formatting the document for easy reference;udud3. the maintenance guidelines provided in Section 13 should be translated to a maintenance manual for guidance of Council staff;udud4. should consider extending the Guidelines to specifically encompass retrofitting of WSUD systems to existing urban precincts;udud5. Section 3 needs to be revised to be made consistent with Section 13, to ensure priority for WSUD practices in urban precincts and to move away from conventional stormwater drainage design such as kerb and channelling;udud6. it would also be good to specify as to which Section takes predominance in relation to stormwater drainage. It is expected that Section 13 would take predominance over the other sections in the LDG;udud7. terminology needs to be made consistent to avoid confusion among developers and Council staff. Water Sensitive Urban Design is the term commonly used in Australia for stormwater quality treatment, rather than Stormwater Quality Improvement Devices. This once again underlines the need for ensuring consistency between Section 3 and Section 13;udud8. it would also be good if there is a glossary of commonly used terms in relation to WSUD for use by all stakeholders and which should also be reflected in the LDG;udud9. consolidation of all WSUD information into one section should be considered together with appropriate indicators in other LDG Sections regarding the availability of WSUD information. Ensuring consistency in the information provided is implied;udud10. Section 13 should be updated at regular intervals to ensure the incorporation of the latest in research outcomes and incorporating criteria and guidance based on the state-of-the-art knowledge. The updating could be undertaken, say, in five year cycles. This would help to overcome the current lack of knowledge transfer;udud11. the Council should consider commissioning specialised studies to extend the current knowledge base in relation to WSUD maintenance and life cycle costing. Additionally, Recommendation 10 is also applicable in this instance.ududThe following additional recommendations are made based on the state-of-the-art literature review, stakeholder interviews and field auditing of WSUD systems:ud1. Performance monitoring of existing systems to assess improvements to water quality, identify modifications and enhancements to improve performance;udud2. Appropriate and monitored maintenance during different phases of development of built assets over time is needed to investigate the most appropriate time/phase of development to commission the final WSUD asset.udud3. Undertake focussed investigations in the areas of WSUD maintenance and asset management in order to establish more realistic life cycle costs of systems and maintenance schedules;udud4. the engagement of all relevant Council stakeholders from the initial stage of concept planning through to asset handover, and ongoing monitoring. This close engagement of internal stakeholders will assist in building a greater understanding of responsibilities and contribute to overcoming constraints imposed by fragmented responsibilities;udud5. the undertaking of a public education program to inform the community of the benefits and ecosystem functions of WSUD systems;udud6. technical training to impart state-of-the-art knowledge to staff involved in the approval of designs and maintenance and management of WSUD projects;udud7. during the construction phase, it is important to ensure that appropriate measures to safeguard WSUD devices are implemented;udud8. risks associated with potential public access to open water zones should be minimised with the application of appropriate safety measures;udud9. system siting should ensure that potential conflicts are avoided with respect to public and ecosystem needs;udud10. integration of social and ecosystem issues to ensure long-term viability of systems;udprovide incentives to developers who are proactive and responsible in the area of stormwater management.