NDRRA Flood Restoration Guideline for Queensland Local Governments

Transcription

1 NDRRA Flood Restoration Guideline for Queensland Local Governments Prepared by: IPWEAQ Page 1 of 34 Revision No.2.0

2 Quality Information Document Ref NDRRA Flood Restoration Guideline for Queensland Local Governments IPWEAQ - NDRRA Date 3 September 2012 Prepared by Reviewed by Michael Kahler Suzanna Barnes-Gillard Revision History Revision Revision Date September January 2013 Details Issued to Qld Members Issued to Qld Members Name/Position Suzanna Barnes- Gillard Suzanna Barnes- Gillard Authorised Signature DISCLAIMER Every effort and care has been taken by IPWEAQ to verify that the methods and recommendations contained in these Guidelines are appropriate for Queensland. Notwithstanding these efforts, no warranty or guarantee, express, implied, or statutory is made as to the accuracy, reliability, suitability or results of the methods or recommendations. The authors shall have no liability or responsibility to the user or any other person or entity with respect to any liability, loss or damage caused or alleged to be caused, directly or indirectly, by the adoption and use of the methods and recommendations of the Guidelines, anticipatory profits, or consequential damages resulting from the use of the Guidelines. Use of the Guidelines requires professional interpretation and judgement. Appropriate procedures and assessment must be applied to suit the particular circumstances under consideration. IPWEAQ Page 2 of 34 Revision No.2.0

3 TABLE OF CONTENTS 1 Introduction Purpose Funding Eligibility NDRRA Funding Categories Complementary Works (ineligible for NDRRA funding) Fitness for Purpose Design General Safety Reuse of Existing Materials and Infrastructure Pavement Structural Design Life Pavement Drainage...Error! Bookmark not defined. 4 Drainage Infrastructure Key Drainage Requirements Safety in Design Road Essential Public Assets - Work Types & Funding Eligibility Pavements Bridges, Drainage Structures and Embankments Road Geometry Roadside Furniture and Delineation Improving Resilience and VfM Outcomes Introduction Pavements Existing Moisture Conditions Design Approach Non-flooded Pavements (Saturation Damage) Flooded Pavements Surfacing of Unsealed Roads Drainage Infrastructure Design Approach Bridge Approaches, Abutments and Piers a) Pavements b) Bridges, Drainage Structures and Embankments c) Road Geometry d) Roadside Furniture and Delineation IPWEAQ Page 3 of 34 Revision No.2.0

4 Overview 1 Introduction 1.1 Purpose Based on feedback from IPWEAQ members and senior Queensland Reconstruction Authority (QldRA) officers, there is a need to provide additional information to assist local government practitioners in determining eligible flood restoration works and fit for purpose design treatments. As a result, IPWEAQ has prepared this guideline to assist its members and improve the level of confidence and consistency around flood restoration submissions. The guideline provides a general approach only and does not attempt to define specific design treatments. The guidelines apply to road and drainage restoration works and focus on eligibility considerations and determination of a fit for purpose design treatment. Whilst the guidelines have been based on previous flood restoration experience and engagement with QldRA during their preparation, they are not a QldRA document. This guideline is to be read in conjunction with the QldRA Submission Guide V3 for NDRRA Applicants (currently under review by QldRA) and focuses on NDRRA Category B funding. This guideline also provides additional information on the selection of design treatments for restoration works which are likely to be deemed fit for purpose and considered an appropriate level of response treatment for flood damage. 2 Funding Eligibility 2.1 NDRRA Funding Categories There are two funding categories under NDRRA for local government flood restoration works: Restoration This funding is for the restoration of essential public assets, following an eligible disaster event, to pre-disaster standard/level of service, in accordance with current engineering standards and requirements and building codes and guidelines, while maintaining the same asset class and/or immunity level. Betterment - In rare cases betterment of an asset can be eligible for NDRRA funding. Relatively few local government assets will meet the eligibility criteria under the Federal NDRRA guidelines as detailed below. The level of effort to prepare the business case and approval process (which requires consideration by State Cabinet, approval and referral to the Federal Secretary for consideration) is very onerous. The following criteria must be met for proposed betterment works IPWEAQ Page 4 of 34 Revision No.2.0

5 to be eligible for NDRRA funding: o the asset is an essential public asset; and o the State Cabinet informs the Federal Secretary of its decision to restore the asset to a more disaster-resilient standard, and of its reasons for doing so; and o the Federal Secretary is satisfied with the cost effectiveness of the proposal; and o the Federal Secretary is satisfied that the increased disaster-resilience of the asset will mitigate the impact of future natural disasters. 2.2 Complementary Works (ineligible for NDRRA funding) This work is the component of work which is additional to the work required to reinstate an essential public asset to its pre-event standard. Typically it involves additional works which will increase the service standard of an essential public asset to that which existed preevent. Examples include constructing a two lane road where the flood damaged section was single lane, increasing seal widths, significantly increasing pavement depth, increasing pavement width, extending the extent of works beyond the flood damaged area, increasing flood immunity through changing vertical alignment, increasing culvert capacity. Complementary Works may also apply where the extent of restoration works is increased beyond the minimum required to reinstate the flood damaged asset to pre-event standard. A common example is the use of half or full pavement width treatments rather than isolated failure repair to rectify flood damage. Where half or full width treatments can be undertaken at a cost equal to or lesser than isolated failure repairs the works will typically be fully recoverable under NDRRA and provide a superior VfM outcome. Where the costs of this approach are above the costs to reinstate the isolated failures resulting from flood damage the difference in the cost of the two treatments will likely be determined as complementary works by QldRA. When undertaking NDRRA works there may be opportunities to combine and coordinate the works with the ordinary capital works program to provide increased efficiencies and economies of scale. Cost control and reporting systems need to be established to ensure a clear demarcation between the scope and cost of NDRRA and non-ndrra works where this occurs. Reactive and scheduled maintenance program activities need to be coordinated and recorded where works occur on assets where planned NDRRA works are proposed. In some instances, early works can be undertaken to make sections safe and these works incorporated into the permanent restoration works. Where the time period between the interim works and final reconstruction works is not excessive and the interim works can be IPWEAQ Page 5 of 34 Revision No.2.0

6 demonstrated to reduce the cost of the final restoration works the costs of interim works may be recoverable under NDRRA. A good example of this approach is the undertaking of isolated failure repair on pavements where the interim failure repairs are incorporated into the pavement of the permanent restoration works. Opportunities to collaborate with neighboring local governments also undertaking NDRRA works should be investigated as the efficiencies and benefits can sometimes be achieved through the pooling of in-house resources and knowledge, and through economies of scale by increasing the scope of restoration works tendered and increasing the level of market interest and contractor capability. 3 Fitness for Purpose Design 3.1 General When designing flood restoration works engineers are faced with a number of challenges. These include but are not limited to:- The pre-event design standards of damaged essential public assets do not align with current engineering standards. Saturated subgrades and associated low subgrade strength require additional design treatments (in excess of the pre-event standard) such as subgrade stabilization, subsoil drainage, placement of geo-fabric and increased pavement depth. Changing traffic conditions such as increased traffic volume and increased percentage of heavy vehicles. In some instances this may result in a change in the road function and design cross section for proposed restoration works. Inadequate surface water drainage due to deficiencies in existing longitudinal drainage and cross drainage on damaged road sections Constraints on using cost effective treatments such as in-situ stabilization due to deficiencies in the existing pavement materials and/or lack of availability of cost effective new pavement materials which meet current engineering specifications. An absence of a consistent and clearly defined road hierarchy and associated design standards for all road types within the LG region. The absence of hydrographic studies to define the catchment characteristics and define design flow for culverts and floodways. The need for additional design elements to improve asset resilience which may be considered complementary works by QldRA if they were not present prior to the event. Typical examples of treatment to improve resilience and VfM include raising IPWEAQ Page 6 of 34 Revision No.2.0

7 the vertical alignment of roads, addition of subsoil drainage, and construction of cutoff walls, wingwalls and scour protection on drainage structures. When considering proposed design treatments for restoration works QldRA have a strong focus on scope, VfM and the appropriateness of the proposed design treatment. As the costs of eligible works for Councils are fully recoverable under NDRRA guidelines the physical footprint of the damage identified in the submission compared to that of the final restoration works is closely monitored by QldRA. Similarly the pre-event condition and service standard of the asset are considered and compared to the proposed restoration treatment by QldRA to determine whether the proposed treatment is an appropriate level of response and fit for purpose. All design is a compromise between the ideal and what is fit for purpose and affordable. Relevant engineering experience, professional judgment, and an understanding of the technical fundamentals, principles and safety aspects of design criteria and practices is necessary when making tradeoffs between competing priorities. Importantly, restoration solutions must not create any increase in safety risk than existed prior to the declared natural disaster events. In reality, with constrained budgets, application of the guidelines to the extensively damaged and aged network requires compromises and some residual performance risks will remain. It is expected that experienced practitioners will apply the guidelines to deliver fit for purpose outcomes within approved QldRA funding and Council budget allocations for complementary works. 3.2 Safety As a minimum, the existing level of safety prior to the flood event is to be maintained. Restoration works on essential public assets to achieve the pre event safety conditions are eligible for NDRRA funding. Where current engineering standards require additional safety measures to be incorporated in the design, LG s may be required to contribute funding for the costs over and above reinstatement costs to pre-event standard. Alternate safety treatments which comply with current engineering standards and enable and improvement in safety levels to the pre-event standard for a similar cost will generally be eligible for full NDRRA funding. In some instances a road safety audit may be warranted. If a road safety audit identifies a more costly and extensive design solution than the pre-event conditions a complementary works funding contribution from the Council will likely be required for the additional cost component. If complementary works funding is not available, the design solution may IPWEAQ Page 7 of 34 Revision No.2.0

8 warrant consideration by Council in future capital program budgets. Where the works cannot be implemented due to budget constraints, interim safety treatments should be considered such as speed management measures. 3.3 Reuse of Existing Materials and Infrastructure Reuse of existing materials and infrastructure is actively encouraged in the program (e.g. paving materials, traffic signs, guardrails, stormwater pipes and culverts etc). The decision to reuse materials and infrastructure is to be made by an experienced practitioner by considering factors such as likely residual life, risk of failure and compliance with current day standards etc. 3.4 Pavement Structural Design Life When selecting a pavement design life Council staff must be cognizant of the pre-event condition of the asset and the design standard. In many cases the asset condition prior to the flood event will have deteriorated significantly from the time of its creation. This is clearly evident on road sections where the extent of road immediately adjacent to flood damage sections is poor and approaching the end of its useful life. Where flood damaged assets exhibited significant deterioration prior to the flood event and/or where the design standard of the asset did not closely align with current engineering standards, QldRA may not fund the cost of renewal of the asset to current engineering design standards. To be fully eligible for NDRRA funding the pavement design adopted must take into consideration the pre-event condition and design standard of the asset. For example, the design for a pavement under current engineering standards may require a 20 year design life to be used. The restoration of the asset to this standard will often result in a pavement significantly deeper than the adjacent undamaged pavement sections and a significant improvement of the asset useful life when compared to the pre-event condition. A compromise approach needs to be adopted to ensure the pavement design life adopted achieves a reasonable engineering and VfM solution. For example in lieu of a 20 year design life a 10 year design life may be adopted on sealed roads which recognizes pre-event deterioration of the asset and results in a more proportional design treatment being selected and pavement depths which more closely match the pre-event pavement depth. QldRA has recently advised that, based on submission data received from across the State, pavement depths up to 300mm are considered typical. In some instances QldRA will only approve the value of the proposed new pavement up to the same depth as the pre-event pavement. In some instances a restoration treatment which results in a pavement depth in the order of 300mm can be achieved through treatments such as insitu stabilization and on lower order roads with IPWEAQ Page 8 of 34 Revision No.2.0

9 reasonable subgrade strength and low traffic volumes where unbound granular pavement depths of 300mm are suitable. There are significant advantages in terms of risk exposure to weather, cost, time of construction and material reuse when box out and replacement of materials can be avoided by using an effective design treatment using in-situ materials. On roads with poor subgrade strength and/or high traffic volumes pavement depths in excess of 300mm will likely be required even when adopting a 10 year pavement design life. Subsequently the maximum 300mm pavement depth requirement should be used as a guide. Individual sealed pavement design depths will likely fall above or below this depth depending on the road function, subgrade properties, local design factors, traffic loading etc. The treatment adopted should reflect that of Council s standard practice for reconstruction on the same standard of road in non flood-affected areas. For higher order roads in the network which were in good condition prior to the event and exhibit pavements that reflect current engineering standards, the same design standard should be adopted for any restoration work (for example 20 year pavement design life) as this will reflect the pre-event asset standard. Typically the pre-event pavement depth of these roads will be closely aligned with the proposed restoration design. Where a design life is adopted that provides a significantly greater pavement depth and residual life to that exhibited by the asset prior to the flood event, a complementary works funding contribution will likely be required from the Council. The complementary funding component will apply the portion of the works which QldRA deems to be of a higher standard to the pre-event standard. QldRA require the proposed pavement design depth to align closely with the pre-event pavement depth. Subsequently a pavement design life should be adopted which achieves this outcome if Council requires all costs to be eligible for NDRRA funding. In some circumstances Council will adopt a higher pavement design standard than the preevent standard to provide the best whole of life and VfM outcome. This approach may require a complimentary works funding allocation by Council for the portion of the pavement depth above the pre-event depth. 4 Drainage Infrastructure 4.1 Key Drainage Requirements IPWEAQ Page 9 of 34 Revision No.2.0

10 Where drainage assets have been destroyed or suffered damage from the declared flood event, proposed NDRRA restoration works should aim to reinstate the drainage system to its pre-event immunity level using current engineering standards. With respect to road drainage, this pre-event standard is the original design standard (e.g. 1 in 10 year immunity) or service level of the drainage system. Simply replacing culverts with like for like may not give the same hydraulic performance / capability as originally designed. This can be a result of changes in design standards since the asset was created (e.g. QUDM vs. AR&R), changes to the catchment characteristics, and/or alteration of the catchment and terrain by the flooding. These factors should be considered when determining if like for like replacement is appropriate. It is recommended that the original design and its intent be reviewed and understood to ensure that design work properly reinstates the drainage system to at least match original performance criteria. Council may wish to improve the flood immunity of drainage structures to the pre-event standard in some instances due to current or future road function or service level requirements. Where this is warranted Council will need to allocate complementary funds to cover the additional cost component of the design which is over and above the costs to reinstate to the pre-event service standard. 5 Safety in Design Where detailed design is required for NDRRA restoration works, Councils need to consider the new legal obligations for designers of road infrastructure introduced in Queensland on 1July 2007 under amendments to the Workplace Health and Safety Act 1995 (the "Act"). Since 2003, designers have had an obligation to design a structure that is intended to be used as a workplace that is without risk to the persons when it is being used for the purpose for which it was designed (s34b). The Act has been amended to include designers as one of the several duty holders responsible for health and safety in the workplace. Workplace Health and Safety should be considered for three groups of people: Those who use the road system for their livelihood (truck drivers, taxi drivers, bus drivers, tourist operators) and the safety of this group cannot be separated from that of the driving population as a whole; Enforcement - Police, Transport Inspectors; and Those who build maintain and operate: construction workers, maintenance workers, traffic response crews, emergency services and their supervisors IPWEAQ Page 10 of 34 Revision No.2.0

11 Some significant hazards faced by the third group include: Working close to moving traffic Working at height Working on slopes Working in confined spaces Working with specialist materials Safety in Design requires a more rigorous and documented design processes that uses a risk management approach in consideration of construction, operation, and maintenance requirements and should be applied to the design of all public infrastructure assets. IPWEAQ Page 11 of 34 Revision No.2.0

12 6 Road Essential Public Assets - Work Types & Funding Eligibility 6.1 Pavements Table 1 Pavement Work Types and Funding Eligibility Type Pavement Work Type Gravel Resheets 1 Pavement patching (Case example 3) 2 Part-width pavement rehabilitation Eligible NDRRA Works Where gravel material has been removed as a result of concentrated surface runoff or sheet flow; or where gravel has been saturated as a result of inundation or prolonged rainfall associated with the declared event and gravel strength significantly reduced causing rutting and poor road formation. Reform or resheet in accordance with Council s design standard. The works should be representative of the Council's usual practice. Typically a 100mm to 150mm compacted gravel resheet depth is supported by QldRA. The adopted depth of gravel resheets will be dependent on gravel properties and the standard practice/design standard applied by the Council for resheets works. Where isolated pavement failures occur as a result of the declared flood event. The design treatment adopted for the failure options analysis to identify the most cost effective and suitable treatment type. Failure repair depths and materials are consistent with an adjacent pavement (pre-event pavement depth) and LG practice. Design life of failure repairs treatment is representative of pre-event remaining useful life. Where there is consistent damage along a segment/s of the pavement cross section. The pavement design selected takes into account the preevent pavement depth and type and provides a similar performance outcome. The pavement depth proposed is not greater than the preevent pavement depth. A pavement design life is adopted which takes into account the pre-event asset Complementary Works Improvement works component where the road formation is significantly improved through widening or raising of vertical alignment. Additional resheet depth where resheet depth is greater than the pre-existing standard and/or current standard practice of the Council. If a higher-order treatment type is chosen, e.g. half road width or full width repairs the additional cost of the treatment will be complementary works, unless the cost of the higher-order treatment can be demonstrated to be equal to or lesser than the isolated pavement repair costs and thus achieves a superior VfM outcome. If full-width pavement rehabilitation is chosen, the additional cost above the part width repair will be complementary funding. The additional cost of a stronger pavement (e.g. one with a higher design life than the original asset or adjacent undamaged road sections) IPWEAQ Page 12 of 34 Revision No. 2.0

13 Type Pavement Work Type 3 Full-width pavement rehabilitation (Case example 2) Eligible NDRRA Works deterioration. If the pavement depth required is greater than the preexisting depth as a result of very poor subgrade strength resulting from saturation all measures have been implemented to reduce costs and provide a cost effective design treatment which aligns with the preevent pavement design standard. Where there is damage across the full width of the carriageway as a result of the declared flood event and an appropriate pavement design is adopted. The pavement design selected takes into account the preevent pavement depth and type and provides a similar performance outcome. The pavement depth proposed is not greater than the preevent pavement depth. A pavement design life is adopted which takes into account the pre-event asset deterioration. If the pavement depth required is greater than the preexisting depth as a result of very poor subgrade strength resulting from saturation all measures have been implemented to reduce costs and provide a cost effective design treatment which aligns with the preevent design standard. Complementary Works will be complementary funding. The additional cost of a stronger pavement (e.g. one with a higher design life than the pre event asset). 6.2 Bridges, Drainage Structures and Embankments Table 2 Bridge, Culvert and Embankment Damage Types and Funding Eligibility Bridge or Drainage Type Structure Damage Type 1 Bridges or culverts destroyed as a result of the declared event Eligible NDRRA works Full replacement of structure and damaged approaches and pavement based on current hydraulic conditions using preevent performance criteria (ARI). The proposed design and cost estimate must take into consideration the pre-event condition of the asset. Complementary Works Providing increased width to match a final vision carriage-way width of the approach roadways (if these widths are greater). Increasing immunity e.g. upgrading drainage to cater for a higher ARI to meet the desired current or future service standard. Replacing a significantly deteriorated IPWEAQ Page 13 of 34 Revision No. 2.0

14 Type Bridge or Drainage Structure Damage Type 2 Abutment protection destroyed or damaged 3 Pier that has sunk or lost load capacity due to scour 4 Damaged bridge barrier Eligible NDRRA works Replacement with similar or more resilient materials to current design criteria Underpinning and/or reinstatement of axial and/or moment load capacity pier Replacement to existing or current engineering standards Complementary Works asset near the end of its remaining useful life with a new asset may necessitate the allocation of Council complementary works funds for a portion of the project costs. Detailed discussions with QldRA to determine eligibility and scope are recommended prior to finalization of design in these instances. The additional cost of providing materials more expensive than specified by current design criteria Extra cost of bridge deck strengthening 5 Damaged batters including damaged floodway protection 6 Damaged pavements on Floodways Reinstatement of existing where damage is minor Provision of additional resilience where damage is significant including flattening batters where appropriate if the works can demonstrate a VfM outcome. Reinstatement to pre-event standard. Reinstatement using more resilient materials to current engineering standards provided a VfM outcome can be demonstrated (i.e. improved resilience for relatively low additional cost of like for like replacement). 7 Cross Drainage Reinstatement using existing materials where pipes or culverts are not damaged. Replacement with new pipes or culverts to current engineering standards. The design standard/serviceability standard of cross drainage is the Cost of realignment of bridge approach barriers to current engineering requirements Cost of resumptions or environmental offsets Increased cross drainage/ under drainage beneath floodway. Increased cost component of replacing sealed granular pavement through floodway with reinforced concrete structure. Costs associated with increasing the hydraulic capacity and service standard (e.g. 1 in 10 year design storm, where preevent serviceability 1 in 5 year design storm). Costs IPWEAQ Page 14 of 34 Revision No. 2.0

15 Type Bridge or Drainage Structure Damage Type 8 Large culvert damaged 9 Scoured longitudinal drains 10 Damage to end walls and scour around structurally unsuitable culvert (does not satisfy current engineering standards) Eligible NDRRA works same as the pre-event level (e.g. remains at a 1 in 5 year design ARI for serviceability). Replacement with new bridge structure at a similar cost to reinstatement of like with like. Reinstatement with alternate design solution which provides improved value-for-money and increased resilience for no increase or minor increase in cost than like for like replacement. Reinstatement of existing V- drain. Replacement with trapezoidal drain if costs are equivalent to reinstatement of existing V- drain. Reinstatement of end walls and scour protection Complementary Works associated with the extension of culverts to enable road widening or future widening. Where an alternate and higher order design solution is adopted the cost on and above like with like reinstatement will require complementary funding. Additional cost of trapezoidal drain over the reinstatement of V-drain Supply and installation of new (structurally adequate) culvert components IPWEAQ Page 15 of 34 Revision No. 2.0

16 6.3 Road Geometry Table 3 Geometric Issues and Funding Eligibility Type Geometric Issue Eligible NDRRA works Complementary Works 1 Seal width of two-lane, two-way rural road 5 Opportunities to facilitate future link development stages, e.g. provision for cycle paths 6 Opportunities to upgrade single lane roads to two lane roads Formation widening and provision of seal widths in accordance with current engineering standard for the same service standard. None, unless no additional cost is involved. None, unless no additional cost is involved. Formation widening to achieve a width greater than the current engineering standard for the pre-event service standard. Additional width to provide future cycle paths / wider shoulders. Works to extend the width of seal and any necessary pavement upgrades 7 Geometric elements not listed above that do not meet the current design standards e.g. clear zone widths, horizontal and vertical alignments, sight distance, intersection turn treatments None, unless work can be completed for no extra cost Any work undertaken to improve the substandard geometric parameter 8 Improvements to an identified crash history Low cost mitigating treatments Higher cost Improvements 9 Missing links - road sections less than 1km in length remaining between two NDRRA funded sections that require significant pavement works. None Any improvements to undamaged sections. 10 Undertake road survey including Mobile Laser Scanning None IPWEAQ Page 16 of 34 Revision No. 2.0

17 6.4 Roadside Furniture and Delineation Table 4 Roadside Furniture and Delineation Funding Eligibility Type Damage sustained Eligible NDRRA works Complementary Works 1 Flood damaged roadside safety barrier 2 Pavement damage requiring new seals and line-marking Reinstate to current standards up to the existing length A line-marking design that is compliant with the TMR Manual of Uniform Traffic Control Devices (MUTCD). Extensions required to satisfy current engineering requirements Additional line-marking above that required by the TMR MUTCD. 3 Flood damaged signs Flood damaged signs to be replaced with new signs as per the TMR MUTCD. Additional low cost devices to manage road safety risks can be implemented. Required signs that did not exist pre-event. Implementation of higher cost safety treatments to mitigate risks identified in recent or existing road safety audits. IPWEAQ Page 17 of 34 Revision No. 2.0

18 7 Improving Resilience and VfM Outcomes 7.1 Introduction Resilience is the ability to absorb a disaster event and return the community to acceptable operating conditions. A major objective of Councils and QldRA is to improve the resilience of Queensland s road and transport infrastructure so that it will not suffer the same magnitude of damage as that experienced in recent events. Works likely to contribute to network resilience are those that: improve the network s ability to survive future similar flooding events by reducing the extent of damage reduce the work and/or time required for the network to be recovered to unrestricted usage following a future event without improving its flood immunity Examples are pavement structural improvement, shoulder sealing, resurfacing, slope stability work, floodway improvements, drainage and structures scour protection, and drainage scour protection. Designers must consider improving the resilience of their projects by: identifying all infrastructure that has been damaged unless unaffordable, designing infrastructure at all damaged sites with an improved tolerance to damage. Whole-of-life cost considerations can be used to support what improvements to resilience should be incorporated into proposed designs however detailed early discussions with QldRA are recommended. Depending on the demonstrated need, scope and costs of the proposed works to provide improved resilience may be funded or part funded under NDRRA or need to be fully funded by Council as complementary works. This section provides information on improving the resilience of road and transport infrastructure. 7.2 Pavements Existing Moisture Conditions Reconstruction works will have to contend with above average, wet ground conditions for some time following any flood event. Feedback from local government engineers across the State have shown that a significant number of bridges and culverts still had water flowing through them or ponding beneath them at the time restoration works commenced. Similarly, a significant number of table drains were holding water and seepages were still active in cut IPWEAQ Page 18 of 34 Revision No. 2.0

19 faces and adjacent gullies. Evidence suggests that six months after the declared event water tables were still high and adjacent pavements vulnerable with areas of distress continuing to grow at an accelerated rate under traffic. It is difficult to forecast how long the high water tables remain. Even average rainfall over the six to nine months after an event may continue to top-up aquifers and sustain high water tables in some areas. The pavement design solutions developed will need to allow for these existing moisture conditions. Detailed early discussions with QldRA are recommended around the proposed design treatment where pavement saturation is the primary cause of failure. Pavement saturation damage continues to be a complex and somewhat controversial issue for Councils, QldRA and EMA Design Approach The design of pavement repair solutions needs to address contributory causes. To simply reinstate or replace proven vulnerable pavement materials with the same quality or characteristics will not improve resilience. Contributory causes are identified through relevant testing and investigatory techniques. The best pavement solution will be the one that meets the required service standard at the lowest whole-of-life cost when taking into account factors such as initial construction cost, on-going maintenance costs, repair and/or rehabilitation costs and frequency and period of inundation to be expected. In the selection of appropriate solutions, designers should carefully consider whether increased resilience can be economically achieved without changing the service standard of the asset. Where improved resilience can only be achieved through a change of service standard of the asset a complementary works funding contribution from the Council will likely be required. In many instances Councils will not have the available funding to improve the resilience of the asset and a reinstatement to preevent standard and resilience levels will be the only option. In determining a design treatment it is important to address contributory cause/s of failure. For example, it may be a better outcome to obtain NDRRA funding for improving pavement drainage along with the provision of a new seal, rather than to provide a completely new pavement without addressing contributory causes and no improvement of resilience Non-flooded Pavements (Saturation Damage) The guidance in this section applies to pavements that are not inundated for significant periods of time but have suffered saturation damage due to moisture ingress as a result of IPWEAQ Page 19 of 34 Revision No. 2.0

20 the abnormally prolonged rainfall periods associated with the declared event. These pavements are often on grade/s with adjacent longitudinal drains. Examples of improved resilience for non-flooded pavements are as follows: Reducing the pavement s moisture susceptibility Providing sealed shoulders to provide extra distance between the outer wheel path and the zone of influence of inundation i.e. eliminate unsealed shoulders Modifying/stabilising pavements utilising cementitious or bituminous stabilising agents to reduce the moisture sensitivity of the in-situ pavement materials Overlay or substitution of existing pavement materials with new bound materials e.g. asphalt or bitumen bound base materials Improving pavement drainage (where damage has occurred) Reinstating table drains Cleaning subsoil drains and culverts Repairing surface cracks (not eligible for NDRRA funding) Adding a geotextile seal Adding a drainage blanket If there is evidence of pavement distress from water infiltrating from below the pavement in cuttings, or there is evidence that the water table is sometimes within or above the pavement, consideration should be given to the installation of deep longitudinal cut-off drains or use of drainage blankets on top of the subgrade in cuttings. Designers will need to be conscious of any risks in providing for the increased resilience. For example, stabilised pavements are more prone to fatigue, unless there is adequate depth of pavement to resist this. 7.3 Flooded Pavements The guidance in this section applies to pavements that are inundated for a significant period of time. These pavements are often at low points located around major cross drains or in flat terrain. Pavements are at their most vulnerable when subjected to traffic loading at high moisture conditions. The longer a pavement is flooded the more likely it is that its moisture content will increase. Pavements do not dry out quickly, so the longer the combination of traffic loading and high moisture content continues the larger the loss of service life is likely to be. IPWEAQ Page 20 of 34 Revision No. 2.0

21 This is particularly the case for unbound granular pavements. With the probable exception of concrete pavements, all pavements will suffer loss of service life if the pavement structure, including the subgrade, is trafficked when above its designed operating moisture range. Non-concrete pavements may provide an acceptable level of resilience (or performance) if restrictions on traffic loading are applied over several weeks and months after periods of inundation. However, this may not meet community expectations and will be very difficult to administer. It is recommended that priority be given to providing a high level of resilience on the higherorder roads. This may be more easily justified on higher-order roads with higher traffic volumes, particularly if shorter lengths of inundation and stable subgrades apply. Where, due to whole-of-life cost considerations and/or budget and/or resource constraints, non-concrete pavements, particularly unbound granular are considered in areas subject to inundation, local knowledge and experience is required to determine how long a particular pavement material could be inundated without significant loss of service. Load restrictions may have to be applied until deflection analysis indicates there are no signs of weakness, particularly in the outer wheel path. Examples of improved resilience for pavements subject to flooding are as follows. Please note that the level of improvement gained under some of these treatments is not certain. In these cases, local knowledge and experience is required to determine their suitability. Reducing the pavement s moisture susceptibility Providing increased flood protection on the downstream side of floodways to resist embankment batter erosion that if left unprotected will result in damage to pavement seals and materials Providing more under-drainage for waterways (including floodways), where there is a history of recurrent damage to seals and pavement materials when over-topped due to high velocity flows or long period of inundation Installing concrete pavements on floodways (including approaches) Installing concrete pavements on approaches to low-level bridges IPWEAQ Page 21 of 34 Revision No. 2.0

22 7.4 Surfacing of Unsealed Roads For unsealed roads, there may be economic benefits of sealing: road sections that flood (e.g. floodways) steeper sections of roadway that are prone to scour sections where there is a loss of traction and damage under traffic when wet. Sealing these sections of roadway could be done in association with sealing of other sections to improve factors such as safety (e.g. sealing sections comprising tighter horizontal curves). The latter is funded under Complementary Works. 7.5 Drainage Infrastructure Design Approach Consideration should be given to providing more resilient drainage solutions where damage has occurred, particularly if the damage has occurred often. Whole of life cost considerations can be used to determine whether a more resilient drainage solution is justified. Increased resilience to overtopping can be provided through three broad strategies: - increased capacity, reduced difference in head, and scour protection. The risk of scour to drainage structures, embankments and pavements is reduced as more floodwater is channeled under the road. There are also direct safety and economic benefits from minimising the time during which water lies across road carriageways. In many cases a nominal increase in pipe size can be achieved at a low incremental cost to greatly improve under-road capacity/performance. On some floodways, the risk of scour is reduced if the road surface is at the same level as the ground / base channel minimising damming effects, and resulting in less armouring protection being required. However, there will still be some uplift pressure on the pavement and possible scouring from pooling if there is a high upstream velocity. Obviously this solution requires a full or partially boxed pavement below the natural surface that needs to be specifically designed to operate in saturated conditions, at least during normal wet seasons. This strategy will not be possible if the pavement is to be raised or high embankments already exist. IPWEAQ Page 22 of 34 Revision No. 2.0

23 If it is not possible to improve resilience through the previous strategies, then armament protection against scouring should be considered. In many instances, protection from scouring will be the only practical option. For example, if a road is on a floodplain and provision of increased culvert capacity (i.e. under-flow capacity) is too costly then designing for overtopping will be required. In this case, protection against scouring of the embankment may be the only practical treatment that will improve the resilience of that section. Downstream embankments at culverts and bridges are more likely to scour from overtopping than upstream embankments and will usually require scour protection. However, upstream embankment protection should also be considered on a case-by-case basis. At bridge sites, spill-though abutments may be undermined. Similarly at culvert locations, overtopping can result in removal of material supporting the culvert. 7.6 Bridge Approaches, Abutments and Piers Addressing contributory causes of damage to bridge approaches, abutments and piers requires an investigation to establish factors such as: the magnitude of the event whether the original assumed design immunity for that bridge was meant to cope with such an event how well the bridge has performed what is now required for the bridge to perform as originally intended whether complementary works are required to improve on the bridge s original design immunity. It is recommended heavy duty scour protection is incorporated in all instances where scouring has occurred at abutments and piers. For bridges, batter protection on the downstream side of the road embankment shall extend along each carriageway past the abutment (in both directions) for a distance three times the height of the road embankment, but not less than 10 metres. IPWEAQ Page 23 of 34 Revision No. 2.0

24 Attachment A Examples of Typical Food Damage Road Assets Figure 1 Pavement Breakouts Figure 2 Pavement Crocodile Cracking Figure 3 Pavement Potholing Figure 4 Pavement Rutting IPWEAQ Page 24 of 34 Revision No. 2.0

25 Figure 5 Pavement Stress Cracking Figure 6 Lifting / Loss of Bitumen Seal Figure 7 Flushing of Bitumen Seal in Wheel Paths Figure 8 Unsealed Shoulder Scouring Figure 9 Flood Debris to be Removed Figure 10 Scouring of Bridge Structures IPWEAQ Page 25 of 34 Revision No. 2.0

26 Figure 11 Scouring / Loss of Culvert Inlet / Outlet Structures and Protection Works Figure 12 Scouring / Loss of Gravel Sheeting Material Figure 13 Damage to Floodway Structures Figure 14 Slope Failure & Instability Figure 15 Embankment Slump IPWEAQ Page 26 of 34 Revision No. 2.0

27 Attachment B Case Examples Road Drainage & Bridge Assets a) Pavements The inner and outer wheel paths in both traffic lanes of a section of two-lane carriageway has been damaged over the full length of a road section by the declared rainfall / flooding event. The reconstruction of the full carriageway width to pre-event service standard (i.e. using full-width pavement rehabilitation) for that section is ELIGIBLE for NDRRA funding. There are isolated patches / areas of a road that have been damaged by the declared flood event. The reconstruction of the patches and the seal required (initial primer seal and follow-up overlapping seal) for those areas are ELIGIBLE for NDRRA funding. Any additional seal provided to the remainder of the undamaged pavement is INELIGIBLE for NDRRA funding. (Note: seal texture differences and age and condition of remaining seal need to be taken into account when considering the need for a full-width seal). A review of the treatment options for restoration works over a section of damaged pavement identifies full-width reconstruction of the pavement can be completed at a similar cost of isolated failure repairs due to economies of scale, more cost effective treatment type (e.g. in situ stabilization) improved constructability etc. The full-width restoration is adopted in lieu of the isolated failure repair (patch work) approach for the road section. The costs of full width restoration of the road section will be ELIGIBLE for NDRRA funding provided that the Council can demonstrate the cost of full-width restoration is less than or equal to the cost of isolated failure repairs over the subject road section. The adopted approach will result in a higher VfM outcome and improved resilience. IPWEAQ Page 27 of 34 Revision No. 2.0

28 If the costs of the full-width restoration of the section are significantly higher than the cost of repair of the individual flood damage failures, the additional cost of full width treatment is INELIGIBLE for NDRRA funding and a complementary funding contribution will be required. The current engineering standard for a damaged pavement requires a 20 year design life to be adopted. A full depth reconstruction of the pavement will be required as alternate treatments such as insitu stabilsation have been deemed inappropriate due to factors such as loss of original pavement material, unsuitable material type, low subgrade strength etc. The use of a 20 year design life will result in a pavement depth significantly deeper than the pre-event pavement and adjacent pavement. The pavement damaged as a result of the flood event was approximately 50% through its useful life at the time of the event. In recognition of the adjacent pavement depth and condition, a 10 year design life is adopted in lieu of 20 year by the Council. A design option analysis is carried out to confirm that the pavement design adopted is the most cost effective treatment type. The costs of the full depth reconstruction to the lesser pavement design life of 10 years will be ELIGIBLE for NDRRA funding provided the Council demonstrates this reflects the preevent service standard, pre-event pavement depth, remaining useful life the road function and the treatment option adopted provides the best VfM outcome. If a 20 year design life is adopted by the Council, the additional costs above a 10 year design treatment will be INELIGIBLE for NDRRA funding and a complementary funding contribution will be required. IPWEAQ Page 28 of 34 Revision No. 2.0

29 b) Bridges, Drainage Structures and Embankments The end pipe of a 450mm diameter culvert along with the end wall has been separated from the remainder of the culvert as a result of the flood waters. This has resulted in the exposure of the remainder of the culvert as well as scour to the embankment. The remainder of the culvert is structurally unsuitable as a result of the age of the culvert. As the end cell/pipe, headwall and embankment was impacted by the flood event then only this work (reinstatement of the existing pipe, headwall, embankment and pavement) is ELIGIBLE for reconstruction. But the unsuitable culvert has to be replaced. The cost of supply and installation of the new culvert components to the site is INELIGIBLE for funding under NDDRA and must be replaced under complementary works funding. The entire length of a 2 cell 375mm diameter culvert has been damaged as a result of flood waters. The original 2 cell 375mm diameter culvert was designed to Q20 flood immunity. A hydraulic assessment has been undertaken subsequent to the flood event and as a result of a change in the local catchment (not caused by the flood event) the assessment finds that to provide the same Q20 flood immunity an additional cell (3 cells in total) is required to be constructed to comply with the current engineering standards. As the 3 cell culvert provides the pre-disaster standard / flood immunity and is proposed to be constructed in accordance with the current engineering standards then the replacement of all 3 x cells of the culvert is ELIGIBLE for funding. The entire length of a 2 cell 450mm diameter culvert has been damaged as a result of flood waters. The original 2 cell 450mm diameter culvert was designed to Q5 flood immunity. The current engineering standard for this location stipulates that Q10 flood immunity shall be provided. This flood immunity increase results in an additional cell (3 cells in total) is required to be constructed to comply with the current engineering standards. As the 3 cell culvert provides improved pre-disaster standard flood immunity and is proposed to be constructed in accordance with the current engineering standards then only the replacement of 2 cells of the culvert is ELIGIBLE for funding. If 3 cells are to be installed the additional 1 cell is INELIGIBLE for NDRRA funding. IPWEAQ Page 29 of 34 Revision No. 2.0