Salinity Infrastructure Literature review 080220gd · 1.5 Context for the literature review 10 2...

ENPLAN PARTNERS with

Agricultural Decisions Pty Ltd

MONITORING THE IMPACT OF SALINITY ON

INFRASTRUCTURE IN THE CORANGAMITE CMA

REGION:

LITERATURE REVIEW

CCMA Reference No: WLE 12 0045

22 February 2008

Monitoring the Impact of Salinity on Infrastructure in the Corangamite CMA Region

EXPLANATORY NOTE

EnPlan Partners is the registered business and operating name for projects performed by EnPlan Australia Pty Ltd,

Darrel Brewin and Associates Pty Ltd, Chris Harty Planning and Environmental Management and Alan Thatcher

Planning & NRM. The Directors of EnPlan Partners are Graeme A David, Darrel C Brewin, Christopher Harty, and

Alan C Thatcher. Projects conducted by EnPlan Partners are contracted to one or other of the participating

companies.

DOCUMENT RELEASE INFORMATION

The content of this document is the property of EnPlan Australia Pty Ltd, and is submitted for the use of the

Corangamite CMA and its stakeholder municipalities. The contents of this document are not to be used, copied,

reproduced by or issued in whole or part to other persons or organisations including other applicants, without the

signed written permission of EnPlan Australia Pty Ltd.

EnPlan Australia Pty Ltd and the other parties co-submitters of this document make no representation, undertake no

duty and accept no responsibility to any third party who may use or rely on this document or its information.

Authors: Graeme David, Darrel Brewin, Alan Thatcher

Document clearance

This document is cleared as follows

Person Position Document No Document status Date

Graeme David Director, EnPlan EP080219-1 Final Draft

22.02.2008

Darrel Brewin Director, Darrel Brewin and Associates

Signed:

For and on behalf of EnPlan Partners

Date: 22 February 2008

Distribution: Corangamite Catchment Management Authority

Principal company EnPlan Australia Pty Ltd

ABN (EnPlan Aust Pty Ltd) 21 093 543 536

Company status EnPlan Australia Pty Ltd is a registered company under the Corporations Law of Victoria. The Company is limited by shares, and is a proprietary limited company.

Registration date 29 June 2000

ACN 093 543 536

Registered address 3 Strachan Ave, Geelong West Vic, 3218

Contact information Ph: 03 5229 9278: Mob: 0409 976 002: Fax: 03 5229 9278

Email: [email protected] .Internet: www.enplan.com.au


CONTENTS Executive Summary 4

1 Introduction 8 1.1 Purpose of this report 8 1.2 Project Overview 8 1.3 The study area and project stakeholders 8 1.4 Project Objectives and purpose 9 1.5 Context for the literature review 10

2 What is salinity? 10

3 Salinity and Development 12 3.1 Impact of development on salinity 17 3.2 Impact of Salinity on Development and infrastructure 18

3.2.1 Salt effects on concrete and masonry 22 3.2.2 Salt effects on roads and bridges 24

4 Salinity Cost to Infrastructure 33 4.1 Overview 33 4.2 Cost of salinity to local Government 35

4.2.1 Local Government studies 35

5 CONCLUSIONS 43

6 REFERENCES 44

Tables: Table 1: Salinity costs to built, infrastructure in Western Australia (from

Dames and Moore, 2003). 5 Table 2: Sample cost functions for various stakeholders and levels of salinity

impact (from Wilson and Laurie, 2001) 6 Table 3: Estimated infrastructure life expectancy and annual percentage

increase in maintenance / renewal costs (from SGS, 2000) 7 Table 4: Relationship between salinity and different developments 14 Table 5: Projected estimates for scale of salinity impacts in Australia on rail,

roads and numbers of towns. 19 Table 6: Assets at high risk from salinity from shallow groundwater and

under the worst-case scenario in Victoria 19 Table 7: Projected scale of asset to be impacted by salinity for 2020 and

2050, compared with current estimates. 20 Table 8: Victorian towns with a dryland salinity risk as identified in the

Australian Natural Resources Atlas. 21 Table 9: Key sources of moisture in road pavement sub-grades 27 Table 10: Salinity management approaches for roads. 28 Table 11: Probable reasons for premature failure of a road structure 29 Table 12: Road maintenance and rehabilitation measures 30


EnPlan Partners: October 2007 4

Table 13: Estimated costs for repair and maintenance rural cost on roads in salt affected areas in the Murray Darling Basin. 36

Table 14: Length of urban roads used in Murray Darling Basin study of salinity damage to infrastructure. 37

Table 15: Severity categories for salinity damage to roads 37 Table 16: Example staged maintenance program for roads 39 Table 17: Estimated salinity damage to roads 38 Table 18: Salinity costs to road infrastructure. 38

EXECUTIVE SUMMARY This report provides a literature review of information relating to the cost of salinity damage to built public infrastructure. It forms part of a review of the cost of salinity damage to built public infrastructure of the eight municipalities in the Corangamite CMA Region: City of Greater Geelong, City of Ballarat, Borough of Queenscliffe, and the Shires of Colac Otway, Corangamite, Golden Plains, Moorabool, and Surf Coast.

Salinity has been heavily researched and investigated across Victoria since the mid-1970’s. It has been the subject of the State salinity strategy since 1988, and of evolving Regional strategies and plans since the early to mid 1990s. The Corangamite Regional Salinity Action Plan is a subordinate of the Corangamite Regional Catchment Strategy.

The technical principles of the causes and effects of salinity processes are now well understood, however understanding cause and effect at particular sites often accompanied by uncertainty, as the processes occur underground and are influenced by many geological and environmental variables.

While salinity is often associated primarily with rural and agricultural production areas, it is also a substantial issue in some urban areas. In short, salinity and associated high watertables have the capacity to damage built infrastructure in both rural and urban areas. Considerable science has been devoted to understanding the chemical and physical processes that cause infrastructure deterioration. Also, there are now a quantity of explanatory documents in Australia that identify the impacts of salinity on infrastructure including roads, buildings, pipes, recreational areas and sports grounds. Such documents have been produced in most States and by municipalities that experience urban salinity. A number of these are in New South Wales, including Dubbo, Wagga Wagga, and municipalities in the Western Region of Sydney.

This literature review attends to this matter.

The following tables provide the latest and best condensed contemporary study information on the costs of salinity to built infrastructure.



Table 1: Salinity costs to built, infrastructure in Western Australia (from Dames and Moore, 2003). Item Depth to

groundwater Cost ($) Notes

House: brick on ground

1.5 m Nil

0.5 m $6,000/house in 3rd year after groundwater reaches 0.5m

Construction of perimeter drains around each house block, with slotted pipe and granular fill, to promote discharge of groundwater to surface runoff, such as natural channel, or exiting kerbside drain, with a sump serving the whole street and a pump to surface channel/disposal route if required.

$2,000/house in 1st year after groundwater reaches 0.5m

Repair of fretting brickwork, crumbling mortar; assumed to be a once-off expenditure, due to assumed installation of perimeter drains (see above), which would prevent recurrence.

House on stumps

1.5 m Nil

0.5 m $1,000/house every five years.

Jacking and re-stumping where necessary, starting in the first year the groundwater reaches 0.5 m.

Main road

1.5 m $145,000/km every seven years

Costs apply to 0.3 of the length of road in the zone every seven years.

0.5 m $195,000 / km every three years

Costs apply to 0.3 of the length of road in the zone every three years.

Local road

1.5 m

$70,000/km every seven years

As above, but with lower level of costs due to reduced traffic carried on local roads

0.5 m $100,000/km every three years

Source: Dames & Moore (2001) via NSW Costs of Urban Salinity (refer footnote) (from a study of urban salinity in Western Australia



Table 2: Sample cost functions for various stakeholders and levels of salinity impact (from Wilson and Laurie, 2001) Very

Slight Impact

Slight Impact

Moderate Impact

Severe Impact

Households $/household/year $75 $250 $2,135 Industrial/Commercial / retail buildings

$/building/year $450 $1,500 $3,750 $6,000

Local councils Increased repair and maintenance

Rural minor sealed roads $/km/yr

$100 $300 $700 $1200

Rural non-sealed roads $/km/yr

$75 $200 $500 $800

Urban sealed roads $/km/yr

$150 $375 $1,150 $2,400

Cost of shortened lifespan

Rural minor sealed roads $/km/yr

$296 $1,333

Rural non-sealed roads $/km/yr

$222 $1,000

Urban sealed roads $/km/yr

$407 $1,833

State government agencies and utilities Increased repair and maintenance

National & state highways $/km/yr

$2,000 $6,930 $17,325 $31,105

Major sealed roads $/km/yr

$200 $450 $1,600 $3,600

Railway infrastructure $/km single track/yr

$11,723 $24,971 $59,465

Cost of shortened lifespan

National & state highways $/km/yr

$2,407 $10,833

Major sealed roads $/km/yr

$481 $2,167

Source: Reproduced from Wilson. S, and Laurie (2001)



Table 3: Estimated infrastructure life expectancy and annual percentage increase in maintenance / renewal costs (from SGS, 2000)

Unaffected/low Moderate Severe

Infrastructure Type Life span (yrs)

Increase pa

Life span (yrs)

Increase pa

Life span (yrs)

Increase pa

Roads sealed / unsealed (average)

20 5% 15 8% 10 13%

Bridges timber 50 3% 40 4% 30 5% Bridges steel 60 10% 45 12% 30 15% Bridges concrete (<$100,000)

60 6% 45 9% 30 12%

Bridges concrete (>$100,000)

100 6% 75 9% 50 12%

Drainage pipes 50 10% 35 12% 25 15% Drainage pits 50 10% 25 12% 10 15% Retention basins 50 8% 50 10% 50 12% Swimming pools 50 10% 40 12% 25 15% Buildings 50-100 5% 40-80 10% 25-50 15% Airports 50-100 6% 20-30 10% 10-20 15% Cemeteries 50-100 10% 25-50 20% 0 30% Street trees 10-100 10% 0 100% 0 100% Recreation reserves

10-100 10% 0 100% 0 100%

Open space 10-100 10% 0 100% 0 100%

Source: Reproduced from SGS (2000) via DPNR (2003)

The Tables show similar orders of magnitude for damage to buildings in the order of the low thousands per annum for dwelling type structures. In most cases this could be countered at the design stage of buildings, but the preferred option is of course to avoid building in salt affected or potentially salt affected sites.

The impact of salinity on roads in western Australia and in northern Victoria is generally greater in total than would be expected in south western Victoria. Landscapes are flatter in these areas, and watertables are close to the surface over expansive areas. In south western Victoria impact of salinity on roads is likely to be restricted to short road lengths crossing laterally across the floor of drainage depressions, or crossing sections former lake beds with high saline water tables. However where roads are affected by salinity costs could be expected to be similar per unit distance than in other areas

The severity of salt damage to pipe infrastructure (and hence costs associated with Salt damage to pipe infrastructure will vary in severity due to a range of fact of such damage will depend greatly on the concentration of salts and other local environmental conditions. If pipe and associated infrastructure (eg hot water services) are susceptible to salt damage however, it is clear that the presence of salt will shorten infrastructure life by some extent and thus be associated with costs.



1 INTRODUCTION

1.1 PURPOSE OF THIS REPORT

This report presents a review of Australian literature on the impacts and costs of salinity to built infrastructure. The report is part of the wider project described below.

1.2 PROJECT OVERVIEW

This Project identifies:

• the built assets that are identified as damaged or being at risk of damage in salinity discharge areas in eight municipalities in the Corangamite CMA region; and

• the cost associated with managing and maintaining those assets.

For this purpose, built assets include but are not limited to roads, paths, pipes, culverts, bridges, drains, buildings, parks and gardens, recreation grounds, caravan parks and depots.

Salinity is recognised in the Corangamite Regional Catchment Strategy (RCS) as an important threat to land and water resources, and to built infrastructure including urban infrastructure.

The Corangamite Salinity Action Plan (SAP) is a component document that underpins the RCS. It identifies the integrity of built infrastructure as an area of focus, and it sets Resource Condition Targets to:

• protect roads in target areas where identified as threatened by salinity, and

• reduce urban infrastructure at risk.

1.3 THE STUDY AREA AND PROJECT STAKEHOLDERS

The project applies to the mapped salinity discharge areas in the Cities of Ballarat and Greater Geelong, the Borough of Queenscliffe, and the Colac-Otway, Corangamite, Golden Plains Moorabool, Queenscliffe and Surf Coast Shires as identified in Figure 1 below. The municipalities are the project’s primary stakeholders.



Figure 1: Map of Corangamite Region showing focus areas for salinity damage to built infrastructure.

Source: Project brief

1.4 PROJECT OBJECTIVES AND PURPOSE

The aims of the overall project are to:

Identify the public infrastructure managed by local government in the Corangamite region that is threatened by, or potentially threatened by salinity processes.

Quantify the costs of maintaining and replacing infrastructure managed by local government in saline land areas in the Corangamite CMA region.

(Source: P3 of project brief)

The objectives of the Project are to:

• Gather baseline information on the impacts of salt attack on infrastructure owned and, or managed by local government in the Corangamite Region.

• Understand the costs of maintaining infrastructure managed by local government in the Corangamite Region.

• Model the cost benefits for investment in salinity intervention on infrastructure managed by local government in the Corangamite Region.

• Collect infrastructure spatial and economic data within salinity target areas.

• To develop recommendations to guide infrastructure monitoring in the future.

The project brief identified that in achieving the above aims and objectives the study must provide:

• an inventory of built assets and their spatial location;

• assessment of built assets at risk or damaged by salinity; and

• the costs associated with managing, maintaining and replacing those assets in each salinity discharge area where these assets are owned and/or managed and maintained by local government.



A requirement in achieving the above outputs is to ‘conduct an extensive literature review on the economic costs of salinity impacts and accepted practice in managing salinity impacts on build infrastructure in Australia, in particular assets owned and, or managed by local government’.

1.5 CONTEXT FOR THE LITERATURE REVIEW

Much has been written on salinity over three past three decades, as salinity incidence has increased and as it has become better understood from extensive technical, social and environmental research. Salinity management has also been the focus of national and statewide programming across the Murray Darling Basin and in most states, and knowledge gained from practical experience has increased greatly. In Victoria, dual focus has been applied via the State Salinity Strategy ‘Salt Action Joint Action’ which covers the full state, and the Murray Darling Basin initiative which covers the north of the State.

While most public and media attention on salinity in Victoria has focused on the northern regions (ie in the Murray Darling Basin), it is also a significant issue in parts of the south east and south west of the State. This includes the Corangamite Region. Also, while salinity is often associated primarily with rural and agricultural production areas, it is also a substantial issue in some urban areas. In short, salinity and associated high watertables have the capacity to damage built infrastructure in both rural and urban areas. This literature review attends to this matter.

Interstate, salinity has received much attention in Western Australia and New South Wales, with generally less profile in other States. In South Australia, which draws most of its domestic water supplies from the River Murray, much focus is devoted to the quality of the water in the River, including salinity.

In NSW, considerable attention is paid to salinity and built infrastructure. Urban salinity has received considerable focus in the western Region of Sydney, where problems relate directly to the inherent characteristics of the soils, and in rural cities including Dubbo and Wagga Wagga which have active remedial and community awareness programs to deal with it.

Much of the available literature on investigations into the non-agricultural costs of salinity has been authored or co-authored by Dr Suzanne Wilson. Much of Dr Wilson’s literature is based on a series of studies jointly commissioned by the Murray Darling Basin Commission and Land and Water Australia during the 1990’s. In 2005 Dr Wilson changed professions and is not available for further input on this matter.

2 WHAT IS SALINITY? Salinity occurs on the land surface as a result of processes occurring within the land. The processes are well understood and widely documented, and it is not intended to review this here. However a summary explanation is provided to establish further context for this document.

The hydrologic cycle continually circulates water between the land, the oceans and the atmosphere, via rainfall, evaporation, transpiration (via plants), runoff over the land surface including stream flows, and infiltration into the land.



Figure 2: The natural water cycle

Source: (WA Water and Rivers Commission)

Water stored in the land (ie groundwater) moves slowly towards rivers, wetlands or the sea, but may also rise to, or close to the soil surface. Soil is saturated when the water starts to drain from the pores, and water will fill the hole dug below the saturation point or watertable level. All water reaching the watertable is called recharge.

Watertables have generally risen in Australia since European settlement, mainly resulting from human activities including land clearance for agriculture, and the application of water to the land surface by irrigation of agricultural, recreational and urban lands. Common agricultural crops, ornamental plants or garden lawns, transpire less rainfall, and more water moves past the root zone, increasing groundwater recharge and raising watertables.

Source: Local Government Salinity Management Handbook: A Resource Guide for the Public Works Professional Institute of Public Works Engineering. Australia.(2001)



All water stored in the soil contains dissolved salts including sodium chloride, magnesium and calcium sulphates, and bicarbonates which will move with the water. The mix of salts may vary depending on the nature of the landscape. Salinity becomes an issue when salt concentrations become high enough to damage natural or built environments.

Salt ‘scalds’ are caused where water is drawn to the surface via capillary action driven by evaporation from the soil surface. While water is evaporated, the salts accumulate on and in the upper soils. Soil properties can be altered structurally and chemically, with side effects of diminishing plant growth.

Urban development activities that can impact on the water cycle include drainage, built infrastructure and drawing water for water supplies associated with urban development and expanding human settlement, and surface application (eg garden watering, irrigation of parks and recreation areas, such as golf courses and sports fields, and leakage from water supply and sewerage infrastructure.

3 SALINITY AND DEVELOPMENT The information publication titled ‘Guide to Residential Slabs and Footings in Saline Environments’1 of the Cement Concrete and Aggregates Australia identifies three consideration categories for urban salinity sites:

• Sites with low salinity hazard. Typical are those where there are low levels of salts, good drainage (leaching of salts) or those with stable, deep water tables.

• Sites that have existing salinity hazard. Salt-related problems in urban environments include staining of surfaces (white deposit), fretting brickwork, dying vegetation, bare clay 'scalded' surfaces and rapid corrosion of metallic items. For new developments, soil investigations can readily identify whether there is a problem with salinity.

• Sites that have the potential to develop a salinity hazard. Salts are present, but are well below the surface. Because salinity is a dynamic system involving many variables, over time, change in climate, land use and land cover (urbanisation) may result in rising water tables; also, salts may be imported to the area.

The Western Sydney Salinity Code of Practice2 states that

In urban areas the processes which cause salinity are intensified by the increased volumes of water added to the natural system in urban areas. Additional water comes from the irrigation of gardens, lawns and parks, from leaking underground pipes and pools and from the concentrated infiltration of stormwater. Urban salinity can also be related to sub-surface water flows being impeded by structures such as roads and by poor drainage conditions on a site.

……

1 Guide to Residential Slabs and Footings in Saline Environments. Cement Concrete & Aggregates Australia. May 2005 2 Footnote: In 2003 the Board of the Western Sydney Region Organisation of Councils (WSROC) endorsed the Salinity Code of Practice for adoption by the Councils of Greater Western Sydney as the basis of a coordinated and consistent salinity management response by the councils in the region. While the CoP has not been formally adopted by all Councils, it provides a framework by which they can better consider the implications of the salinity potential in the region, both in relation to their own activities and as an issue for new developments.



Much of the cost of urban salinity will be borne by local authorities in the form of increased infrastructure repair and replacement, decreased useability of assets and environment, increased environmental obligations and a potentially reduced rate base.

……

Approaches to urban salinity management need to be pro-active and precautionary, with efforts focused on avoiding potential salinity problems when development occurs, rather than trying to treat salinity problems once they are identified. This means that some activities will need to be managed on the basis that they may contribute to a salinity problem, without having certainty of how they do contribute.3

The Western Sydney Salinity Code of Practice also provides a comprehensive Table on the relationship between salinity and different developments. The Table is presented here as Table 4 on page 14. This Table has been adapted by EnPlan for reproduction in Applicant Information Kit for use in Corangamite Region municipalities with Salinity Management Overlays. Content in following sections of this report expands on some parts of this Table

It is clear that decisions regarding the planning for and design of developments in some urban growth areas require consideration of potential salinity impacts. Appreciating the fundamental causes of salinity is the first step towards understanding the risk and how the problem can be managed.

It is also important that there are two key aspects of the interaction between salinity and development:

• Impact of development on salinity

• Impact of salinity on development and

These matters are discussed below and summarised in Table 4 on Page 14.

The interface between roads and salinity are a main topic for attention in this review report. This is addressed in subsequent sections of this report.

3 Pages 11-13. Western Sydney Salinity Code of Practice. Western Sydney Region Organisation of Councils. 2002


Table 4: Relationship between salinity and different developments Development/ Activity Type

Potential impact of salinity on development

Potential impact of development on salinity

Management options for considerations

Multi-lot sub-division developments eg Large housing or industrial estate

• If present, salinity may limit the capability of the land to sustain the development proposed.

• Groundwater or soil salinity may damage buildings, infrastructure, (eg roads, underground services), and parks and reserves.

• Waterlogging associated with high watertables or drainage deficiencies may contribute to deterioration of infrastructure.

• Salinity damage may have long term impacts on perceived land/property values and increased maintenance costs to the community.

• Salinity may limit the effectiveness of stormwater or wastewater treatment systems.

• Clearing of native vegetation (trees, shrubs and grasses) may change the rates of evapo-transpiration and therefore the water balance, contributing to increased salinity.

• Increased water inputs associated with urban development eg garden watering, leaking pipes, may increase or expand outbreaks of soil salinity and/or rising groundwater

• Changed flow and drainage patterns may increase water accumulation and associated salinity in areas of impeded flow eg. Drainage lines, retaining walls, footings and roads.

• Use of recycled water or on-site waste-water re-use systems may increase salt loads in soils and waterways over time, and/or contribute to water logging.

• Stormwater management systems involving detention or infiltration may contribute to rising groundwater levels, perched watertables or surface soil salinity if not well designed.

• Exposure of saline soils.

• Need to understand the land capability relating to salinity.

• Undertake site specific salinity investigations, including hydro-geological assessments.

• Prepare management plans, precinct plans, planning scheme policy, and other guidelines for the site in light of salinity investigations.

• Design infrastructure, including roads, pavements, stormwater system, underground services, parks and community facilities to minimise salinity impacts and reduce the long-term maintenance costs. Should also address the impact of the development on salinity processes.

• Avoid or minimise exposure of problem sub-soil material.

Single lot. Developments eg. Typical house, extensions or renovations to existing properties

• Salinity associated with soils or groundwater may result in damage to the property, including driveways, gardens, underground services and paving/ fences.

• Waterlogging associated with poor drainage or groundwater may result in property damage or contribute to salinity problems.

• Building may be directly exposed to saline subsoils through building techniques used.

• Increased water inputs from sites from garden watering, leaking pipes and leaking swimming pools, contributing to increased outbreaks of salinity and/or rising groundwater.

• Changed water flow and drainage may result in areas of water accumulation and associated salinity eg, retaining walls, footings, paving, driveway, landscaping.

• On-site stormwater or wastewater treatment may contribute to localised salinity, raised

• Use salt resistant materials and construction techniques where necessary, eg, for buildings, driveways, underground services etc.

• Design and maintain development to provide good drainage on site and avoid waterlogging.

• Properly install and maintain stormwater drainage and guttering, outdoor taps and irrigation.

• Base landscaping on water-wise gardening,



Development/ Activity Type

Potential impact of salinity on development

Potential impact of development on salinity

Management options for considerations

water-tables and/or increased salt loads. • Development activities may expose saline

sub-soil. •

and do not place gardens against buildings. • Use appropriate plant species. • Avoid or minimise sub-soil exposure.

Irrigation Developments eg intensive agriculture, effluent disposal, sporting fields, major gardens/ landscaping, golf courses.

• Increased salinity may reduce agricultural productivity, or damage growth and aesthetics of sporting fields, landscaping and greens.

• Could result in increased maintenance and production costs.

• Salinity in the soil and associated high watertables may limit the effectiveness of effluent disposal systems in retaining nutrients and disposing of water.

• Increased water inputs may contribute to rising groundwater levels, or the surface expression of soil salinity.

• Fertilizers and effluent may cause increased salt loads in the soil.

• Careful investigation to assess the area’s capability and salinity potential.

• Consider regional recharge/ discharge patterns when siting such developments.

• Use waterwise agriculture/ gardening practices, including suitable species.

• Use ‘smart’ irrigation systems where such systems are permitted.

• Control fertilizer use and consider salt loads in designing effluent disposal system.

Stormwater Management Works

• Salinity or rising groundwater can affect drainage infrastructure, causing damage to pipes, causeways and detention basins.

• Reshaping and excavation may place infrastructure below the water table or in contact with saline sub soils.

• Salinity may limit the effectiveness of infiltration based systems to retain nutrients and dispose of water.

• Salinity related raised water tables and increased water logging may increase flooding.

• Soil and water salinity may affect vegetation in wetlands, channels, swales, creek banks.

• Increased water inputs or system leaks may contribute to rising groundwater levels, or surface soil salinity.

• Changed water flow patterns and rates may increase salinity in areas where water accumulates eg, riparian zones, poor drainage areas, areas of impeded flow.

• Stormwater management systems involving detention or infiltration may add to rising groundwater levels, perched watertables, or surface expressions of soil salinity.

• Interception of saline groundwater can result in saline discharge to creeks.

• Carefully assess and take account of the area’s capability for the development proposed.

• Consider regional recharge/ discharge patterns when planning such developments.

• Limited focus on infiltration and un-lined detention basins in areas with a salinity potential.

• Carefully consider all aspects of proposals associated with an irrigation development.

• Use salt resistant materials and construction techniques.



Road Construction/ maintenance

• Salinity can affect materials in road seals, base and kerbing, causing damage and shortened lifespan.

• Damage to the seal or edge may allow water to get into the road.

• Rising water tables, perched water tables, or accumulating soil water can weaken road bases.

• Cut of the road may: • intercept or impede natural drainage, causing

areas of water accumulation and associated salinity.

• intercept groundwater levels, create a perched watertable, or cause increased recharge to groundwater.

• expose saline soil materials, causing salinity and erosion.

• Road compaction may impede natural drainage, or cause increased pressure and discharge of groundwater.

• Design roads to avoid impeded drainage, interception of flow or groundwater, or recharge.

• Design roads to avoid excessive compaction in areas with raised water-tables.

• Use good soil management practices to minimise post construction exposure of saline sub-soils.

• Use salt resistant concrete and other materials in construction and repairs.

Source: Adapted from Western Sydney Salinity Code of Practice. Western Sydney Regional Organisation of Councils. March 2003 (Amended January 2004): (Refer http://www.wsroc.com.au/downloads/WS_Salinity_Code.pdf


3.1 IMPACT OF DEVELOPMENT ON SALINITY

It is widely documented that large scale developments such as suburban scale residential or urban developments, or irrigated recreational areas such as sports reserves, municipal parks, or golf courses can alter local surface hydrology (ie: surface flow volumes and behaviour) and hydrogeology (sub-surface water characteristics). Excess garden watering and irrigation can cause raise watertables locally or more widely (depending on local environments). Where watertables rise to within around 1.5 metres of the land surface this can cause the onset of salinity problems, depending on local factors including the salinity of groundwaters, soil types, and the extent and type of ground cover. In some cases such raised watertables may be locally perched, or alternatively be part of a regional system – with the latter being more difficult to address. Precise impacts can be difficult to determine in advance, but potentials for such large developments to cause impacts provides solid reason for requiring planning applications associated with them to be accompanied by hydrogeological or geotechnical reports.

EnPlan Partners has used (and continues to use) the following categorisation of salinity incidence to assist with explanations and the development of statutory planning material in its preparation of Salinity Management Overlays

• Category 1: Areas currently affected by secondary salinity. (ie areas affected by salinity as a consequence of European settlement)

• Category 2: Areas of primary salinity regarded as an asset (ie: generally areas affected by salinity prior to European settlement and considered to be part of the natural ecology).

• Category 3: Areas not currently affected by salinity, but with a stated likelihood of experiencing secondary saline groundwater discharge within a given time-frame. (ie: generally areas surrounding existing Category 1 or Category 2 salinity or where water tables are to within around 1.5 metres of the land surface.)

• Category 4: Areas where inappropriate land-use or development may adversely impact on primary salinity assets.

• Category 5: Areas where development or inappropriate land-use may ultimately initiate secondary salinity or exacerbate existing secondary salinity elsewhere in the landscape

Categories 4 and 5 recognise the potential for development to cause or exacerbate salinity and associated matters.

Further to this, the Western Sydney Salinity Code of Practice identifies the following ways that urban development may contribute to salinity problems.

By exposing sodic or saline sub-soils.

When areas are developed the processes of cut and fill, particularly for slab on ground construction, disturbs the upper layers of soils. If the lower soil profile has saline or sodic properties, this can result in the occurrence of salinity problems and erosion. This may also lower the surface closer to the water table.

By increasing the level of regional groundwater and encouraging the development of perched water tables.

Urban development tends to increase the amount of water entering the natural system, eg, the irrigation of parks and gardens, leaking storm water and sewer pipes and changes in storm water flows and concentrations. As well, compaction and fill changes permeability and soil drainage and can contribute to the creation of perched water tables.



By changing soil groundwater flow and creating areas of impeded drainage or forced discharge.

This can result in sub-soil salinity being expressed on the surface at these points, eg, where roads, house slabs, retaining walls or trenches impede or intercept the soil water flow, cause compaction, or create hydraulic pressure that raises groundwater.

By developing or disturbing areas sensitive to salinity.

Some areas exist in a delicate balance that, once disturbed, are difficult to restore and rapidly deteriorate, eg, removing established salt resistant vegetation in riparian corridors could increase erosion and down stream disturbances.

Other forms of categorising salinity and development impacts on it exist, but the above expressions provide a good cover of scenarios relevant to this report.

3.2 IMPACT OF SALINITY ON DEVELOPMENT AND INFRASTRUCTURE

Most attention to salinity focuses on its impact on built, natural, and agricultural assets. The focus of this literature review is on the built assets.

High saline watertables can shorten the expected lifespan of infrastructure. This accelerated rate of deterioration may arise from one or more of various processes including the following:

• concrete cancer in road and rail culverts, building foundations, concrete fence posts, walk ways and cycle paths, bridges, etc;

• corrosion of steel fences, fuel & water tanks, water, sewerage and septic pipes and fixtures, railway lines, steel telephone poles, etc; and

• soil structural decline and the resulting breakdown of railway, road, bridge and building foundations (refer Booth Associates 1996 and others).

For buildings, recommendations or specifications for protecting concrete and associated masonry assets contained in Australian Standards and associated documents including the Guide to Residential Slabs and Footings in Saline Environments are all based on a design life of 40–60 years. This includes the following Building Code of Australia and Australian Standards documents that should be referred to by persons requiring more information on this subject.

• Building Code of Australia.

• AS 2870 Residential Slabs and Footings

• AS 3600 Concrete Structures,

• AS 2159 Piling – Design and Installation,

• AS 3735 Concrete Structures for Retaining Liquids and associated commentary

• AS 3798-2007 Guidelines on earthworks for commercial and residential developments

The Australian Natural Resources Atlas Natural Resource Topics – Salinity Impacts 4 states the following:

Large decreases in the lifespan of road pavement occur when groundwater levels rise to within 2 m of the pavement surface. Salt also destroys the properties of

4 Website: http://www.anra.gov.au/topics/salinity/impacts/index.html#infrastructure



bitumen and concrete structures. Road and bridge damage caused by shallow, saline groundwater is a major cost at all levels of government.

• Estimates are that high watertables potentially affect about 34% of State roads and 21% of national highways in south-west New South Wales, with damage costing $9 m each year for classified roads (Douglas 1997).

• Main Roads Western Australia estimated that in 1997, salinity affected 500 km of main roads and that this was likely to double within 20 years (McRobert et al. 1997).

Structures associated with communication and gas pipelines are subject to a similar fate. Wagga Wagga is one of the worst affected towns in New South Wales, experiencing salinity-induced damage to roads, footpaths, parks, sewage pipes, housing and industry (Bugden 1997). Salinity is also present in other provincial cities and towns in New South Wales and Victoria (e.g. Dubbo, Forbes, Cowra, Booroowa, Bendigo) as well as Western Sydney.

Predictions suggest that approximately 30 rural towns in Western Australia will be threatened by rising saline watertables by 2050, leading to damage to roads, recreation facilities and buildings; and difficulties with public utilities such as water supplies and waste management systems. In Victoria, predictions are that more than 60 towns will be at risk from shallow watertables.

The Atlas summarises the following magnitude impacts on rail, road infrastructure and numbers of affected towns in Australia.

Table 5: Projected estimates for scale of salinity impacts in Australia on rail, roads and numbers of towns.

Asset 2000 2020 2050 Rail (km)1 1 600 2 060 5 100 Roads (km)1 19 900 26 600 67 400 Towns (number)2 68 125 219

1 Data from WA, SA, Vic and NSW, Qld only for 2050. 2 Data from WA, SA, Vic and NSW.

The Atlas also includes coverage on Victorian assets at risk of salinity impact and the scale of assets expected to be affected in the future, as presented in Table 6 and Table 7 below.

Table 6: Assets at high risk from salinity from shallow groundwater and under the worst-case scenario in Victoria

Asset Current 2020 2050 Agricultural land (ha) 555,000 1,170, 000 2,800,000 Perennial vegetation (ha) 6,200 11,830 24,280 Railways (km) 131 303 952 Freeways and major roads (km) 808 1,541 3,597 Other roads (km) 3,088 6,513 17,326 Length of stream or perimeter of 10,121 18,146 34,599 Towns (number) 10 21 63 Ramsar wetlands* (number) 4 5 8

Coastal wetlands are not included in those at risk.

Source: Australian Natural Resources Atlas Natural Resource Topics: Salinity - Impacts & Costs – Victoria



Table 7: Projected scale of asset to be impacted by salinity for 2020 and 2050, compared with current estimates.

Asset Current 2020 2050 Railways (km) 131 303 952 Freeways and major roads (km) 808 1 541 3 597 Other roads (km) 3 088 6 513 17 326 Towns (number) 10 21 63 Ramsar wetlands* (number) 4 5 8

Source: Australian Natural Resources Atlas Natural Resource Topics: Salinity - Impacts & Costs – Victoria

The Atlas document states the following

Potential impacts of shallow water tables and dryland salinity on physical infrastructure in Victoria have been expressed in relation to transportation networks and rural towns. The figure below shows the change in the length of road and rail networks and number and area of rural towns predicted to be located in areas with shallow water tables. The length of road traversing shallow water table areas could increase from almost 4000 km currently to between 11,000 and 21,000 km in 2050. Up to 200 km of freeway and almost 3400 km of major road could be constructed on land that has or may develop shallow water tables. The length of railway could increase between four and seven-fold, from 131 km currently to 500-952 km in 2050. These changes, particularly for the road network, would be expected to greatly increase the maintenance costs incurred by local government and VicRoads.

The number of rural towns (not including provincial centres with populations exceeding 10 000) in Victoria located in areas predicted to have or develop shallow water tables could increase from 5 to between 28 and 63 in 2050.

Victorian towns identified by the natural resources atlas as containing dryland salinity risks are identified in Table 8. Corangamite Region towns are in green text boxes.

(It is noted that the authors of this document consider that the data leading to designation of towns in the above Table is at a high strategic level, and we are not satisfied that the table provides a reasonable outcome on the salinity status of towns in the Corangamite Region. We are not satisfied that a number of the listed towns, for example including Anglesea, Ballan, Clifton Springs, Drysdale, Lorne, and Lara, contain any significant dryland salinity risk.)



Table 8: Victorian towns with a dryland salinity risk as identified in the Australian Natural Resources Atlas.

Towns with 500-1000 people Apollo Bay Avenel Bannockburn Eildon Indented Head Timboon Violet Town Winchelsea Wycheproof Yea Towns With 1000-5000 People Anglesea Ballan Beaufort Broadford Casterton Charlton Cobram Dromana Drysdale Euroa Gisborne Heathcote Koo-Wee-Rup Lancefield Lorne Myrtleford Nagambie Numurkah Paynesville Port Fairy Romsey Rushworth Terang Torquay Yarrawonga Towns with 5000-10000 people Benalla Clifton Springs Hastings Lara Towns with 10-20 000 people Colac Horsham Portland Sale

Author’s note: Towns shaded pale green are in the Corangamite study region.

The document titled ‘Permit Application Requirements for Developments in Salinity Management Overlay Areas’ prepared by EnPlan Partners in November 2007 for the project covering the development of Salinity Management Overlays for the City of Greater Geelong, City of Ballarat, Shire of Moorabool, and Borough of Queenscliffe identifies that building in a saline environment can result in major damage to buildings, roads, urban infrastructure, gardens and the environment.

The document identifies that salts in the soil dissolve in water and can move with water into and around buildings. Unless sealed off, moisture from the ground containing salt can be drawn into building material by capillary action in the same way as it is drawn through blotting paper. It notes that the following symptoms of salinity may occur in built infrastructure and associated assets:

• Water discharge from the ground

• Salt deposits or efflorescence on the ground

• Erosion of bricks, concrete, and mortar joints

• Damage to roads



• Corrosion of pipes

• Damp brickwork

• Bubbling of paint surfaces

• Erosion of concrete drain surfaces

• Poor plant growth.

In particular, and relevant to the current project, high saline watertables may shorten the expected lifespan of infrastructure managed by Local Governments. This accelerated rate of deterioration may be in the form of one or more of the following:

• concrete cancer in road and rail culverts, building foundations, concrete fence posts, walk ways and cycle paths, bridges, etc;

• corrosion of steel fences, fuel & water tanks, water, sewerage and septic pipes & fixtures, railway lines, steel telephone poles, etc; and

• soil structural decline and the resulting breakdown of railway, road, bridge and building foundations (Booth Associates 1996).

The clear inference from the above and from logical thought is that where possible, land known to be affected by soil salinity, should be avoided as sites for buildings, gardens, or other forms of infrastructure development.

3.2.1 Salt effects on concrete and masonry

For buildings, recommendations or specifications for protecting concrete and associated masonry assets contained in Australian Standards and associated documents including the Guide to Residential Slabs and Footings in Saline Environments are all based on a design life of 40–60 years. This includes the following Building Code of Australia and Australian Standards documents that should be referred to by persons requiring more information on this subject.

• Building Code of Australia.

• AS 2870 Residential Slabs and Footings

• AS 3600 Concrete Structures,

• AS 2159 Piling – Design and Installation,

• AS 3735 Concrete Structures for Retaining Liquids and associated commentary

• AS 3798-2007 Guidelines on earthworks for commercial and residential developments

The following text in this section is derived largely from the ‘Guide to Residential Slabs and Footings in Saline Environments’ of Cement Concrete and Aggregates Australia. Similar explanations could be drawn from a range of other readily accessible documents.

Salt attack occurs from the action of soluble salts, and a range of different mechanisms can occur that are commonly referred to as ‘salt damp’. This can be in a low saline environment, and where this is the case, designing and constructing concrete residential slabs and footings for durability can be a straightforward process. The Guide to Residential Slabs and Footings identifies three main mechanisms by which salts in the groundwater can attack reinforced concrete:

• Physical attack



• Chemical attack

• Corrosion of reinforcement.

As each requires water to dissolve and transport the salts to the concrete surface, it follows that concrete can be in contact with a highly saline dry soil with no impact on the concrete.

Physical attack

Soil moisture can enter concrete to cause rising damp and crystallisation of chloride and sulphate salts as the water evaporates. The formed crystals can cause expansion pressures in the concrete, affecting its strength and fragmenting the surface.

With buried concrete elements, fresh surfaces do not generally become exposed to further attack, while the softened layer will typically slow down the rate at which further concrete will be attacked.

Chemical Attack

The various salts in soils can attack concrete including chlorides and various sulphate salts. The severity of attack depends on a range of matters including the types and concentrations of salts, the movement of groundwater, pressure, and temperature.

Reactions between the salt constituents and concrete constituents typically form larger volume products than the original compounds. The swelling caused in the concrete causes cracking, which then allows for further penetration of substances, and further deterioration.

Where concrete is dense, good-quality, and has low-permeability and the rate of salt replenishment from the surrounding soil is slow (ie in dry environments), the rate of formation of reaction products; and subsequent attack will be limited. (Further details is provided in the following references

• Australian Standard AS 3735 and its supplementary documents).

• Stark11 and Harrison12.

• BRE Digest 3639.

Corrosion of Reinforcement

The concrete surrounding reinforcement provides a highly alkaline environment (pH of around 12). This protects the steel surface from corrosion by forming a highly impermeable oxide layer, while the concrete cover over the reinforcement provides a physical barrier against salt ingress. However steel protection can be impaired and corrosion initiated by two main mechanisms:

• Ingress of salts which, if sufficiently concentrated can cause corrosion even in an alkaline environment.

• Carbonation: ie: Reduction in the concrete’s alkalinity, to prevent the formation of the protective oxide layer.

Salt ingress is the main form of corrosion. Soluble chloride ions attack the oxide film around the steel, to initiate corrosion where moisture and oxygen are present. This causes spalling of the concrete when the expansive forces caused by rust exceed the tensile capacity of the concrete. Corrosion of reinforcement can be negligible in continuously submerged environments, due to the lack of oxygen, slow diffusion of salts through the saturated concrete pores and potentially the pores becoming blocked with insoluble products.

In zones that are subjected to repeated wetting and drying, saline water may be drawn through the pores of the concrete by capillary action.



The less common carbonation process requires reaction between calcium hydroxide in the concrete reacting with atmospheric carbon dioxide to form less-alkaline products. It is unlikely to cause corrosion in slabs and footings buried in the ground, particularly if in moist environments, and where water flow through the soil and across the surface of a buried slab or footing is insufficient to remove or 'wash out' any soluble alkalis.

3.2.2 Salt effects on roads and bridges

A comprehensive study of salinity impacts and costs associated with roads was conducted for Austroads Incorporated5 in 2004. Its report is titled Salinity and Rising Water Tables - Risks for Road Assets (Austroads Publication No. AP-R246/04).

The specific objectives of the Austroads project were to:

1. Identify areas of the road asset at risk of being affected by dryland salinity and rising watertables;

2. Provide an indication of the types and extent of damage already occurring to the road asset, using Victoria as a case study;

3. Assess (in broad terms) the potential cost implications of mitigating these impacts; and

4. Outline generic methods of reducing the impact of dryland salinity and rising water-tables on the road asset.

The Report includes four Sections.

• Part A identifies how high water-tables and salinity are presently affecting road assets in Australia

• Part B overviews recent studies of ‘damage cost functions’ that can be used to estimate the economic costs of salinity and rising water-tables on road infrastructure.

• Part C summarises the main salinity management options available to land, water and infrastructure managers in salt-affected catchments

• Part D outlines a program for future research.

The Austroads report concluded in general that it is difficult to be definitive about the extent of salinity damage to roads and makes the following specific conclusions6:

• Salinity damage cost estimates for ‘high risk’ roads only, range between $50-$100 million in year 2000, increasing to $168-$380 million by the year 2050.

• Problems with the highway and main road network (which can be directly attributed to a high watertable and salinity) are only beginning to be recognised and/or experienced in some States.

• Data on increased road rehabilitation and maintenance costs over the life cycle of either pavements or other structures is presently not being collected by road managers, so it is not possible to verify the economic problem that salinity is presenting to road agencies at this point in time.

5 Austroads is the association of Australian and New Zealand road transport and traffic authorities (including VicRoads) whose purpose is to contribute to the achievement of improved Australian and New Zealand transport related outcomes 6 Page ii. Salinity and Rising Water Tables - Risks for Road Assets. Publication No. AP-R246/04) Austroads Incorporated 2004



• The success of possible road based salinity management options has not been conclusively reported because the performance of treatments already adopted has not been well monitored.

• A number of technical issues need to be resolved with respect to attributing damage costs to high watertables and salinity.

The Austroads report also proposes the inclusion of salinity design issues in updated road drainage and construction guidelines

Despite the above the Ausroads report identifies in part that the National Land and Water Resources Audit of 2000 found that the total proportional length of roads at risk from dryland salinity and rising water-tables between states is as follows: Western Australia 70%; Victoria 20%, NSW 5%; SA 5%, and that the total length of roads likely to be affected by 2050 will increase by 3 times.

For Victoria the report identified that the 2000 Victorian Salinity Audit7 determined salinity risk based on water-table depth and trends in water-table change8. Most of the ‘high risk’ areas are located in the Corangamite, Glenelg, Goulburn-Broken and North Central catchment regions. The Victorian audit also used two scenarios (best-case and worst-case) to project changes in road lengths located within high risk salinity areas.

• Under the worst-case scenario, the length of roads at risk are projected to increase from just around 3,800km (in 1998) to around 21,000 km (in the year 2050).

• Under the best-case scenario the length of road at risk is estimated to be around 11,000 km in the year 2050.

Freeways and major roads represented around 17% of the total projected road length at risk under the worst case scenario in year 2050. Table 13 and Table 14 provide a breakdown of road length by road type and catchment region for the two scenarios considered.

Table 9: Road infrastructure by road type within selected catchments (2050, Best Case Scenario)

Catchment Corangamite Glenelg Goulburn North Central

Roads at Risk (km)

Freeway 0 - 132 -

Highway(sealed) 20 33 320 143

Major Road Sealed 84 117 453 267

Major Road Unsealed 0 2 31 230

Other Road sealed 170 335 1,387 349

Other road unsealed 206 257 4,222 1,696

Source: Clifton, 2000 via Austroads 2004

7 Clifton, C. (2000). Final Report Victorian Salinity Audit, Prepared for the National Land and Water Resources Audit by Sinclair Knight Merz and Agriculture Victoria. 8 The Victorian Salinity Audit, classified ‘high risk’ areas as those with watertable depth <2m (with flat or rising watertable trend), and areas where watertable depth with a rising trend was between 2m and 5m.



Table 10: Road infrastructure by road type within selected catchments (2050, Worst Case Scenario)

Catchment Corangamite Glenelg Goulburn North Central

Roads at Risk(km)

Freeway 16 - 132 -

Highway(sealed) 147 329 320 148

Major Road Sealed 716 732 453 283

Major Road Unsealed 7 17 31 244

Other Road sealed 1,373 1,995 1,387 368

Other road unsealed 1,748 1,954 4,223 1,764

Source: Clifton, 2000 via Austroads 2004

No infrastructure cost information was reported in the Victorian Salinity Audit, however, the Austroads report developed estimates of this using cost functions processes to estimate the additional road infrastructure maintenance costs for Victoria in the year 2050 as shown in Table 11.

Table 11: Additional road infrastructure costs

Victoria Best Case Scenario Worst Case Scenario

‘Interim’ cost functions $14.5mpa $28.8mpa

‘Revised’ Cost functions $31.3mpa $60.1mpa

Source: Austroads 2004

The report identifies that prior to any road reconstruction or maintenance programs being developed the causes of problems need to be carefully evaluated as a range of sources of moisture apart from high watertables (and associated salinity), can impact on road foundations. Table 12 below indicates those other sources that need to be considered in determining remedial measures for damaged roads.

Table (Table 13) on approaches for salinity management for roads is also extracted from the Austroads document and provides a useful ‘spot’ overview of consideration matters.



Table 12: Key sources of moisture in road pavement sub-grades Key sources of moisture in pavement subgrades

Description

1 Rainfall entering the surface of the road

Prolonged percolation of water though cracks and other openings in a deteriorated pavement can occur.

2 Pavement shoulders Lateral movement of moisture from pavement materials making up the road shoulder.

3 Seepage from higher ground adjacent to the road

May occur where a layer of permeable soil overlies an impermeable layer, in the form of a local seepage or spring; generally occurs in cuttings.

4 Lateral seepage from roadside median

Transfer of moisture to or from the soil in the roadside median is possible, however an operating surface drainage system would usually minimise this source of moisture.

5 Capillary rise above the water-table

Base and sub-base layers of a road formation may be within the capillary zone, which is the area within the influence of the suction effect of the watertable The amount of moisture transferred through the pores of the soil into the sub-grade by surface tension will depend on soil type – as shown in Table5. pp.7.

6 Water vapour movements

Transfer of moisture though soil as a vapour is associated with differences in vapour pressure caused by differences either in moisture or in temperature in the soil beneath the road formation; generally occurs when the soil is relatively dry.

7 Groundwater hydrology in the vicinity of the road

A high water-table may be relatively static or there may be artesian pressure or head, depending on local site conditions

Source: Adapted from Gerke 1987, Baldwin et al. 1997 via Austroads Pub. No. AP-R246/04


Table 13: Salinity management approaches for roads.

Salinity management approach Comments Performance criteria

Capital cost Ongoing maintenance

Effectiveness

Road maintenance and rehabilitation measures • Road reconstruction – raise pavement to provide capillary

break and reconstruct • pavement raised up to ~1 m above the natural surface level High Low High (immed.

benefit) • Pavement rehabilitation – eg. 200mm granular resheet,

geotextile or aggregate drainage blanket installation • heavily dependent upon long-term subgrade strength (likely

to be weakened in a high water table situation) Moderate Moderate Moderate

• Intensive maintenance – surface drainage works, patching,stabilisation, asphalt regulate, fabric seal etc

• dependent on sub-grade strength and traffic loading Low-Mod. High Low

Additional engineering approaches: • Groundwater pumping – single wells or spear-point systems

with pumps • requires sufficient aquifer permeability, success will very

much depend on local site factors Moderate

High

Low-Mod.

• Sub-surface drainage installation – placed just beneath or deeper (formation drains) below the sub-grade

• performance will be site specific and dependent on sufficient grades, formation permeability

Moderate

Moderate

Moderate

• Surface drainage improvement – for runoff management and water table control (deeper interceptor drains).

• shallow surface drains nearly always achieve benefits providing there is sufficient surface gradients to drain water, deeper drains raise concerns about road safety and stability in longer term

Low

Low

Mod. –High (shallow surface drains only

All 3 options will depend on the presence of a suitable discharge point to environment; surface drainage water will tend to be lower in salinity and hence “safer” to discharge

Revegetation approaches:

• Recharge control – broad-scale revegetation of catchment • requires enormous cooperation and goodwill within each catchment community

High

Low

High (over long term)

• Roadside planting for local discharge control – revegetation of road verge or adjacent landholders properties

• success of vegetation in achieving drawdown in the water table to protect pavements will depend on local site factors

Low Moderate Moderate

Source: Page 42 Austroads Pub. No. AP-R246/04.


The Austroads report contains comprehensive sections on detecting salinity damage and on associated maintenance and reconstruction of roads. The following are some key statements and tabulations from the relevant sections. (These are not presented in the Austroads document as continuous text).

In most cases it will be various road maintenance and rehabilitation measures that will be the most feasible and direct options available to road managers to protect assets from salinity. There may be opportunity for improving surface drainage and introducing some form of sub-surface drainage and/or groundwater pumping options at some sites, depending on the availability of suitable discharge points in the local environment. (p27)

The causes of salinity in a particular location may, in fact, be located many hundreds of kilometres away from the problem location. Therefore, road design needs to be considered within a catchment wide context, recognising that localised road design measures will not have significant influence over the causes of salinity. (p26)

It is not easy to determine the precise impacts of a high water-table and salinity on road assets since there are usually a range of interlinked processes contributing to the base failure of pavements and deterioration of structures. As a general guide, however, topographically low areas within districts with known salinity problems will be the most likely sections of road vulnerable to salinity impacts. (p26)

Excess moisture in the sub grade will lead to a weakening and loss of support to the pavement, resulting in longitudinal rutting in the wheel paths and associated cracking, and ultimately pavement failure (NAASRA 1983). (p26)

Poor construction techniques and incorrect materials usage are factors which would need to be ruled out prior to attributing the cause of a pavement failure to the presence of a high water-table. (p28)

Table 14: Probable reasons for premature failure of a road structure Poor construction techniques

• Wet construction • Inadequate & non uniform compaction • Incorrect layer thickness

Incorrect materials usage

• Insufficient sampling during design and following compaction

• Subgrade quality over-estimated • Long term properties not evaluated • Incorrect design assumptions

Moisture conditions occur that were not originally envisaged

• Intermittent flow from permeable layer in a cutting • Saturation of base • A rising water table • Capillary rise

Source: Adapted from page 27 Austroads Pub. No. AP-R246/04.

The Austroads report also discusses the reconstruction, rehabilitation and staged management approaches identified in Table 15 which are not covered in detail here. (Readers of this report are referred to the Austroads document for additional information). However on the matter of ‘staged management’ it provides the following text and tabulation information

This approach is able to be adopted on lower traffic volume roads where the rate of development of pavement distress allows for maintenance works to be undertaken over a longer period than that of the heavier trafficked pavements. The following works outlined in Table 28 may also apply to the general case and not just to pavements in high water-table zones.



This suite of staged works may be successful in effectively deferring major rehabilitation costs, however, this will depend on the moisture susceptibility of heavier trafficked pavements in particular. Nonetheless, the costs of a staged maintenance program can be substantial, up to $35,000 per km/year over a 4 year period of intensive maintenance (assuming a pavement width of 8m).

Table 15 summarises maintenance and rehabilitation measures for sealed roads, applicable to addressing high water table / salinity damage.

Table 15: Road maintenance and rehabilitation measures

Category of action Action options

Reconstruction • raise onto embankment and

reconstruct • drainage blanket resheet

• Raise pavement level (between ~ 400 – 1000mm) with suitable material to physically separate it from the influence of saturated conditions and reconstruct

• Add sufficient thickness of quality coarse material to provide adequate cover of weakened subgrade - with or without the addition of a geotextile.

Rehabilitation • resheeting • stabilisation and heavy patching

• Re-sheet pavement with 200 mm of new quarried material

• Stabilise foundation and pavement materials to reduce their susceptibility to water

Staged maintenance • traverse shape correction, • minor patching • improve drainage

• Implement an intensive regime of maintenance activities including: • Drainage improvements e.g. reshaping table drains,

cleaning out structures • Shape correction eg. asphalt regulate, 1 or 2 coat

fabric seal


Regarding unsealed roads in high watertable areas, the Austroads publication states the following

Probably the most cost effective way to maintain unsealed roads in areas with a high water-table is to improve the drainage of the pavement itself by restoring the surface shape and maintaining sufficient crossfall (between 4 – 6%) to facilitate the shedding of water off the road. This can be achieved through good grading practice. This will minimise any flat spots in the road surface and prevent water retention on the pavement itself leading to reduced potholing.

It should be noted, however, that the maintenance of sufficient longitudinal drainage in the table drains is sometimes difficult, especially in low lying areas where longitudinal drainage dominates the pavement drainage. If the road is likely to be subject to heavy traffic volumes and/or axle loads, then sealing the section traversing the waterlogged and salt affected zone may be the best option. In general, however, higher maintenance costs would be expected following sealing, because regular shape repair, patching and reinstatement of the surface will be required in areas with a high water-table.

(pp 31-32)

In concluding its discussion, the Austroads report states the following regarding salinity damage to roads.

Road reconstruction in salt affected areas, involving raising the pavement above the influence of the water table, will be likely to give immediate benefits at a high initial cost. The benefits of re-sheeting will depend on the sub-grade strength so will tend to have only moderate and relatively short term effectiveness in areas with a high water table. Intensive maintenance on affected sites is probably the



usual practice taken, however the performance will usually be low because of the number of interventions required over the life of the pavement will tend to be high.

Alternatives to road rehabilitation and maintenance might include road relocation or choosing higher road design standards (and therefore accepting higher maintenance costs) than would normally be introduced, in areas known to be affected by high water tables and salinity.

The extent to which either revegetation or drainage/pumping options will be cost-effective in lowering water-tables and protecting roads is very difficult to predict. Particularly since the results will be site specific and to some extent will remain uncertain even following preliminary site investigations.

Deep drainage or groundwater pumping in discharge zones will be expensive, require high maintenance and, at best, offer only an interim measure to lower water-tables. It may be acceptable in some circumstances where particularly valuable assets are to be protected, or in ‘buying time’ while adjacent landholders adopt more sustainable farming systems which will reduce recharge to groundwater and reverse rising watertable trends.

Further caution arises due to the potential for adverse environmental impacts from saline groundwater disposal. Road agencies must be mindful that farmers and government agencies with water quality and environmental management responsibilities may be intolerant toward receiving additional saline water flows downstream.

Accordingly, permanent tree belts provide an alternative low cost, low maintenance and more sustainable treatment than deep drainage or groundwater pumping. They also have potential to provide both income and ecological value for local communities. Tree planting on private land adjacent main roads would increase the effectiveness of roadside revegetation in protecting pavements. Co-operation with farmers will be the largest factor in determining the success of salinity mitigation techniques to protect roads. Affected roads are situated in the lower parts of the catchment making it unfeasible for Road agencies to work in isolation to achieve good results. Revegetation would provide longer term benefits for road agencies and the broader community.

Work of Dr Suzanne Wilson is quoted and referenced in the above mentioned Austroads report.

The following text is quoted from a report of Dr Wilson titled Understanding and Preventing Impacts of Salinity on Infrastructure in Rural and Urban Landscapes9

Most roads and bridges have been designed for sites with a dry sub-soil and a low frequency / duration of soil saturation. Where groundwater saturates the soil within 2 metres of the surface, the foundation often deteriorates rapidly causing a breakdown of the base and deterioration of the surface (Hamilton 1995).

This deterioration in the road surface occurs because the downward pressure applied to the surfaces, especially those subject to frequent truck use, penetrates to a depth of 1.5 m or more. When the subsoil at this depth is saturated, there can often be considerable movement of the sub-soil, especially if this sub-soil has a high clay content. This sub-soil movement is frequently transmitted upwards through the road base, and eventually results in localized ‘heaving’ of the road surface, followed by cracking of the bitumen surface, complete break-up of the road itself, and further penetration of surface water into the road foundation (ACTEW 1997; Wooldridge 1998). The end result is premature road failure, more frequent and costly maintenance, or a combination of both.

9 Understanding and Preventing Impacts of Salinity on Infrastructure in Rural and Urban Landscapes. Wilson S. Wilson Land Management Services Pty Ltd. (Undated)



However, there are numerous factors that ultimately influence the impact of high saline watertables on roads and bridges, including:

• the intensity of use;

• rainfall;

• groundwater level and salinity concentration;

• soil type;

• method and material used during construction;

• quality of the road drainage;

• elevation of the road above the surrounding area; and

• condition of the bitumen seal (Hill 1999).


4 SALINITY COST TO INFRASTRUCTURE

4.1 OVERVIEW

The costs of salinity to infrastructure are covered in several documents but the topic is generally less well covered than that of the effects physical of salinity on infrastructure (and vice versa). Main documents attending to the costs of salinity on infrastructure include the following

• Various reports of Dr Suzanne Wilson (of Wilson Land Management Services Pty Ltd) and colleagues, mainly jointly to the Murray Darling Basin Commission and to Land and Water Australia

• The 2000 National Land and Water Resource Audit of

• The 2003 NSW Government document titled The Costs of Urban Salinity of

• The 2004 Ausroads document titled Salinity and Rising Water Tables - Risks for Road Assets (Austroads Publication No. AP-R246/04)

The National Land and Water Resource Audit of 2000 used three approaches to estimating actual and potential damage costs incurred on road infrastructure. It shows that salinity damage cost estimates in Australia, for ‘high risk’ roads only, range between $50-$100 million in year 2000, to increase to $168-$380 million by the year 2050.

Part B of the Austroads salinity and road risk10 referred to extensively earlier in this report, also summarises of a survey of asset managers in VicRoads regions to attempt to ‘ground truth’ the road damage costs reported in the National Land and Water Resource Audit. It states that while some of the interviewees were able to directly attribute increased periodic maintenance and reconstruction costs to raised water-tables and salinity, they all reported that they were unable to quantify the increased costs due to this type of damage compared with other sources of damage to the network.

The NSW government’s Urban salinity series booklet Costs of Urban Salinity11 is based on an extensive literature review. It provides various summaries of contemporary information from work of Dr Wilson, the Australian Bureau of Agricultural and Resource Economics (ABARE)12, and the firm Dames and Moore13 (now URS) of Perth. Key summary information is presented in Tables 1, 2, and 3 in the Executive Summary of this document:

• Table 1: Salinity costs to built, infrastructure in Western Australia (from Dames and Moore, 2003).

10 Salinity and Rising Water Tables - Risks for Road Assets. Publication No. AP-R246/04) Austroads Incorporated 2004 11 Costs of Urban Salinity. Local Government Salinity Initiative - Booklet No.10 NSW Department of Primary Industries and Department of Infrastructure, Planning and Natural Resources. First published 2005 12 Oliver, M., Wilson, S., Gombosso, J. and Muller, T. (1996). Costs of Salinity to Government Agencies and Public Utilities in the Murray-Darling Basin, Australian Bureau of Agricultural & Resource Economics Research Report 96.2, Canberra, ACT 13 Dames & Moore (2001) Economic impacts of salinity on townsite infrastructure, report for the Rural Towns Management Committee and Agriculture Western Australia. Prepared by Dames & Moore (now URS), Perth, WA.



• Table 2: Sample cost functions for various stakeholders and levels of salinity impact (from Wilson and Laurie, 2001)

• Table 3: Estimated infrastructure life expectancy and annual percentage increase in maintenance / renewal costs (from SGS, 2000)

The following text is quoted from the document.

The Murray-Darling Basin Commission ordered a report in 1994 on the benefit to roads and other infrastructure of providing drainage in the irrigated areas of the Murray-Darling Basin. This was one of the first attempts to quantify the benefits (costs that would be avoided) of undertaking either surface or subsurface drainage.

Road maintenance costs in Victoria were found to be higher ($200/km/yr for gravelled roads and $400/km/yr for main sealed roads) in irrigation areas than in dryland areas. Amortised construction costs in NSW at a discount rate of 5% were also higher in irrigation areas relative to dryland areas ($980/km/yr for gravelled roads and $6,500/km/yr for highways). However, the impact of salinity on roads could not be completely mitigated by improved drainage. Estimates of the value of achievable benefits attainable in 1993 dollars per kilometre per year are summarised in Table 3.

ARRB Transport Research Ltd published a report (McRobert & Foley 1999) on the impacts of waterlogging and salinity on road assets in south western WA in 1999. The report reviews roads that were initially constructed on free-draining sites but are now affected by rising saline groundwater. It was commissioned by Main Roads WA to help make informed decisions about the optimal level of investment in remedial measures.

The report estimated that 230km of state main roads (plus more kilometres of local roads) were affected in 1999, with this expected to double over the next 20 years.

Methods of remediation are discussed, including highway reconstruction, pavement rehabilitation, improved drainage, groundwater pumping and revegetation. The estimated effectiveness of these methods was given along with an expected cost of $200,000 to $400,000 per km (McRobert and Foley 1999). The report also discusses the risk of roads causing or exacerbating salinity outside the road reserve. In many cases this will be due to inadequate culvert capacities restricting overland flows and causing ponding of water along the upslope side of roads.

A later ARRB Transport Research Ltd report focuses on salinity impacts on local roads in Victoria. Road structure impacts, options for remediation and sample costs are covered. The effectiveness and cost of revegetation as a remediation option is discussed in detail. Site investigation and monitoring are particularly emphasised where revegetation is being considered (McRobert and Robinson 2000).

Although the report does not attempt to further quantify costs it concisely captures many of the issues relevant to road managers in areas of salinity. Where options are discussed there are approximate ‘rule of thumb’ costs to assist a manager in deciding whether an option warrants further investigation.

The 2004 Ausroads document is the most recent on cost. It draws extensively from the other documents referenced here and is referred to extensively in earlier section of this document.



4.2 COST OF SALINITY TO LOCAL GOVERNMENT

Most work to assess the cost of dryland salinity to local government and non-agricultural sectors generally has been implemented by Dr Suzanne Wilson and colleagues, generally in co-authored papers. The following text in this section is in part condensed from the paper of Wilson S M. titled ‘Assessing the cost of dryland salinity to non-agricultural stakeholders in selected Victorian and NSW catchments. A methodology report’ prepared for MDBC in December 2000. That document collates information from a range of catchment specific studies conducted for the Murray Darling Basin Commission and Land and Water Australia.

This section also draws on content from other material including the 2004 Austroads document Salinity and Rising Water Tables - Risks For Road Assets Publication No. Ap-R246/04.

4.2.1 Local Government studies

The studies conducted by Dr Wilson et al into the impacts and costs of dryland salinity to Local Governments surveyed all 111 Local Governments wholly or in part of the following MDBC catchments:

• Victoria: North Central (Campaspe, Loddon and Avoca River catchments) and Goulburn-Broken Regions;

• NSW: Central West; North West; Murrumbidgee; and Lachlan Regions .

The study objective that is relevant to this literature review, was to collect information on the impact costs of dryland salinity and on the average annual amount currently spent on preventative works.

The survey (with follow-up contact) used 26 questions covering the following four themes, and other relevant data was obtained from other available sources including other recent Local Government surveys, Local Action Plans and other catchment reports:

• Perceptions of the severity and causes of dryland salinity;

• The type and extent of the physical impacts;

• The estimated costs and benefits of dryland salinity;

• The impact of dryland salinity on the operations of Local Governments.

A 67% written response was achieved, and follow up consultation was made with all 111 municipalities. Processes were developed to extrapolate the results within each catchment to provide a regional perspective of the likely nature and cost of salinity problems to Local Governments in each area.

In summary, it was found that:

• most costs to Local Governments (excluding road costs) occurred in urban areas.

• understanding of salinity matters including costs, varies across Local Government,

To counter for the varied understanding of salinity across local government, ‘extensive manipulation of digitised Geographical Information Systems (GIS) datasets and other information were used to improve the accuracy of the data compiled’.



Increased repair and maintenance costs on roads

To estimate Local Governments’ additional repair and maintenance expenditure on roads due to high saline watertables, Dr Wilson used GIS datasets to show:

• the location of minor sealed and non-sealed roads in the catchments;

• the areas affected by severe, moderate, slight and very slight dryland salinity outbreaks;

• Local Government Area and catchment boundaries.

The average cost arising from the reduced expected lifespan of rural roads subject to high saline watertables was then calculated by the following process and is identified in Table 16.

• Each council was asked to specify the expected lifespan of minor sealed roads and non-sealed roads that are not affected by high saline watertables. They were also asked to specify the expected lifespan of minor sealed roads and non-sealed roads that are affected by high saline watertables. These figures were used to derive an average estimate of the expected lifespan of the two road types that ‘are’ and ‘are not’ affected by high saline watertables.

• Each council was also asked to specify the average ‘per kilometre’ cost of constructing minor sealed roads and non-sealed roads. Again, these figures were used to derive an average annual figure for all Local Governments in the catchments being studies.

• The information provided by the respondents was again compared to and, where appropriate, enhanced with information obtained from other published reports to generate the following assumptions:

Table 16: Estimated costs for repair and maintenance rural cost on roads in salt affected areas in the Murray Darling Basin.

Road class Additional annual R&M expenditure due to high saline watertables

Severe impacts ($/km/yr)

Moderate impacts ($/km/yr)

Slight impacts ($/km/yr)

Very slight impacts ($/km/yr)

Minor sealed road

$1,200 $700 $300 $100

Non-sealed road

$800 $500 $200 $75

Source: Assessing the cost of dryland salinity to non-agricultural stakeholders in selected Victorian and NSW catchments: A methodology report. Wilson S M. 2006.

It was determined that different costs are applicable to the repair and maintenance of roads in urban areas, and the following four stage process was used to assess these.

Stage one - The data compiled for the urban household study was again used to identify those urban town centres affected by high saline watertables, their population, and the percentage of each affected by very slight, slight, moderate and severe salinity.

Stage two - The data presented in a report by Hardcastle and Richards (2000) was used to estimate the length of urban roads located in each of these urban centres. In their study, Hardcastle and Richards estimated the typical length of urban roads that can be found in urban centres of different sizes (see the table below).



Table 17: Length of urban roads used in Murray Darling Basin study of salinity damage to infrastructure.

Urban centre population Length of urban roads (km)

5,000 60 km 20,000 150 km

100,000 875 km

Source: Assessing the cost of dryland salinity to non-agricultural stakeholders in selected Victorian and NSW catchments: A methodology report. Wilson S M. 2006

Stage three - The data compiled in Stages one and two were combined to estimate the total length of urban roads in each affected town centre, and the length of roads affected by very slight, slight, moderate and severe high saline watertables.

Stage four - The information compiled in Stage three was combined with the cost estimates shown below to estimate the added cost of repairing and maintaining urban roads subject to high saline watertables in each affected town.

Table 18: Severity categories for salinity damage to roads

Severity of salinity Urban road R&M cost ($/km/yr)

Severe $150 Moderate $375

Slight $1,150 Very slight $2,400

Source: Assessing the cost of dryland salinity to non-agricultural stakeholders in selected Victorian and NSW catchments: A methodology report. Wilson S M. 2006

Full details of these results are presented in the related regional-level reports in the series of cost estimate reports prepared by Dr Wilson (refer to reference list).

Assessing the cost of shortened expected lifespans of roads

To estimate the cost of shortened expected lifespans of salinity-affected roads, the digitised GIS datasets used in the study were again overlaid to estimate the length of minor sealed and non-sealed roads intersecting sites with high saline watertables.

The average cost arising from the reduced expected lifespan of roads subject to high saline watertables was then calculated:

• Each council was asked to specify the expected lifespan of minor sealed roads and non-sealed roads that are not affected by high saline watertables. They were also asked to specify the expected lifespan of minor sealed roads and non-sealed roads that are affected by high saline watertables. These figures were used to derive an average estimate of the expected lifespan of the two road types that ‘are’ and ‘are not’ affected by high saline watertables.

• Each council was also asked to specify the average ‘per kilometre’ cost of constructing minor sealed roads and non-sealed roads. Again, these figures were used to derive an average annual figure for all Local Governments in the catchments being studies.

The information provided by the respondents was again compared to and, where appropriate, enhanced with information obtained from other published reports to generate the following assumptions:



Table 19: Estimated salinity damage to roads

Road class Construction cost

Expected lifespan (No high saline

watertables)

Expected lifespan

(yrs)

($/km) (yrs) Slight to very slight impacts

(yrs)

Severe to moderate

impacts (yrs)

Minor sealed road $80,000 30

20 27

Non-sealed road

$30,000 15 10 13.5

Source: p16. Wilson S M. 2006

By combining the GIS generated information on the length of road types affected by salinity with the cost functions specified above, it was possible to then estimate the total cost fully incurred within the boundaries of each catchment, at the LGA scale. The full results of this analysis are presented in the Regional-level reports in this series.

As noted above, the GIS datasets provided by the State Agencies did not provide details of dryland salinity outbreaks in the urban areas. Hence, it can be assumed that the data generated using the approach outlined above relates primarily to the increased cost of shortened lifespans in rural areas.

To estimate the cost of shortened expected lifespans of salinity-affected roads in urban areas, the following process was adopted.

Stage one - The data compiled for the urban household study was used to identify those urban town centres affected by high saline watertables, their population, and the percentage of each affected by very slight, slight, moderate and severe salinity.

Stage two - The data presented in a recent report by Hardcastle and Richards (2000)14 of Dames and Moore, was used to estimate the total length of urban roads located in each affected town centre, and the lengths affected by very slight, slight, moderate and severe high saline watertables.

Stage three - The above information was combined with the cost estimates shown below to estimate the cost of shortened expected lifespans of salinity-affected urban roads in each affected urban town centre.

Table 20: Salinity costs to road infrastructure. Road class Construction

cost ($/km)

Expected lifespan (No high saline watertables)

(yrs)

Expected lifespan (yrs)

Severe to moderate impacts

Slight to very slight impacts

Urban road

$110,000 30 20 27(yrs)

Source: p18. Assessing the cost of dryland salinity to non-agricultural stakeholders in selected Victorian and NSW catchments: A methodology report. Wilson S M. 2006

14 Hardcastle and Richards. (2000). Impact of rising water and salinity on infrastructure, Draft report prepared for Dames and Moore Pty Ltd.



Full details of these results are presented in the related Regional-level reports in the ‘Wilson’ salinity costs series.

The Austroads report in part used Dr Wilson’s results in its analysis findings. It determined indicative costs for the staged maintenance of damaged roads as presented here in Table 21.

Table 21: Example staged maintenance program for roads

Maintenance cycle stage

Indicative cost Maintenance activity

Year 1 $2 per m2 Undertake drainage works to reinstate and improve table drains, clean culverts, minor patching and shoulder maintenance

Year 2 $10 per m2 Stabilise pavement base following drainage improvements the previous year. - for very moist perennial conditions, stabilise the subbase/subgrade in addition to the base.

Year 3 $3 per m2 Carry out surface correction, eg. Asphalt regulate, fabric seal

Year 4 $4 per m2 Reseal the pavement




Site management

General

The following text is refined in part from the Cement Concrete and Aggregates Australia document titled Guide to Residential Slabs and Footings in Saline Environments, and from other literature. It primarily relates to the design of large scale and /or small scale developments that could impact on salinity or be impacted upon by salinity rather than on the sites of existing infrastructure development, and is not fully relevant to the current literature review topic.

It does however provide context for consideration of technical remedial measures where salinity is an issue for built infrastructure. The use of concrete in saline environments, requires assessment of the degree of exposure to provide appropriate concrete strength and cover.

Subdivisions

The Guide to Residential Slabs and Footings in Saline Environments proposes that if existing or potential problems are identified on development sites, the following matters should be considered:

• Salt loading. Groundwater (containing salts) flows downward, to emerge in low-lying areas such as creeks and rivers, or at the base of a slope. If groundwater is intercepted along the slope by cut-and-fill construction, provision of retaining walls or installation of roads or services, and diverted to stormwater drains, a similar salt loading should reach the creek/river. However, intercepting groundwater can create some opportunities, potentially including diversion of salts to evaporation basins, controlling the height of the water table and leaching salts out of the soil15.

• Levels. The finished surface levels on blocks should fall to the street sufficient to allow for water runoff to prevent ponding, waterlogging of the soil, and to reduce water infiltration into the ground.

• Cut-and-fill. While this may expose some saline material, concrete elements such as house slabs, drains and retaining walls, and infrastructure, can be designed to provide the required durability. Depending on the salinity levels, the greatest impact may be the short-term effect on the vegetation such as trees, lawns and gardens. Careful design of the major earthworks may be able to overcome such problems such as by keeping the saline materials covered. For the long term, the ground levels and design of the drainage system may be able to control watertable level.

• Concrete retaining walls. Adequate drainage should be provided behind walls. In saline soils a plastic membrane behind the wall will also help reduce or eliminate the risk of efflorescence on the exposed face of the wall. Such walls should have appropriate concrete strength and cover to the reinforcement.

• Stormwater/subsoil drains. For level or low-lying areas, stormwater drains along roads can assist to control groundwater levels, Depending on the

15 Authors note: In Victoria such activities are subject to regulation in order to control water pollution, and cannot be implemented without authority. In most cases discharge of free draining water is not be permitted



situation, these could be installed at greater depth to further lower the watertable16. Alternatively, to reduce the distance between drains, subsoil drains could be installed along property boundaries.

• Filling. If the level of a low-lying area is to be built up by filling (with non-saline material), a drainage layer should be provided beneath the fill to prevent groundwater rising to the surface.

• Capping layers. Covering saline soils with a layer of non-saline material (perhaps an impermeable clay material) may be an option to avoid disturbance of the affected soil horizon/material, but the long-term effectiveness needs to be evaluated. Capillary action through clay materials that might be used as capping could draw groundwater and associated salts closer to the surface to affect building elements and landscaping.

Where salinity problems exist, all of the above need to be considered in design and management of developments. Where possible, design should enable reduced salinity over time through procedures such as planned tree planting and drainage design to lower groundwater levels and allow leaching of the salts.

Where there is potential for a salinity hazard to develop, the design should provide for no future problems (where feasible), or require that basic measures are incorporated into the design of, say, house footings to ensure their long term (eg 50 year) durability.

Single-lot Developments

The opportunities to respond to salinity on single-lot developments are likely to be limited to on-site actions such as building and service design, stormwater management and landscaping. However, the impact on the overall salinity system should not be underestimated as each single lot can contribute to the recharging of the water table.

In areas affected by urban salinity, some items to consider are:

• Cut and fill. The majority of sloping sites will be cut-and-filled to create a level building platform. This may expose some saline material, in which case the concrete footings, retaining walls and paving should be designed to provide the required durability.

• Suspended floors. Note that the strip footings used to support suspended floors are generally deeper than the edge beams for stiffened-raft type footings, and extend further into the ground, increasing the risk of exposure to saline conditions, especially if there is a high groundwater table.

• Strip and pad footings. As a damp-proofing membrane is seldom provided for strip or pad footings, the concrete for these should be designed for the exposure conditions present on the site. If a damp-proofing membrane is installed, and a reduced concrete strength and cover used, the member should be completely encased by the membrane.

• External paving. Where paving (including driveways) is being placed on saline soils, the provision of a plastic membrane such as a damp-proofing membrane under the paving will assist in preventing salts coming through the paving materials. These salts may cause efflorescence and possible physical, chemical and corrosion damage to paving.

16 As noted in the footnote 15, such activities are generally subject to regulation in order to control water pollution, and cannot be implemented without authority from the local water authority.



• Concrete retaining walls. As for subdivisions, adequate drainage should be provided behind concrete retaining walls. A plastic membrane behind the wall will also reduce the risk of efflorescence and possible physical damage to the exposed face of the wall. Concrete retaining wall systems should be designed with the appropriate concrete strength and cover to the reinforcement.

• Drainage. Ground and paving levels should ensure that water does not pond to increase infiltration to raise the water table. Subsoil drains behind retaining walls and around buildings, and drains at the base of batters should be effectively drained to avoid water ponding within the trenches/drains. For flat sites, subsoil drainage can be installed to control the level of the groundwater table.

• Landscaping. Planting suitable deep-rooted vegetation can assist in controlling the level of the water table by reducing infiltration. Depending on the salinity level, salt-resistant turf and plants could be considered.

• Sundry buildings and retaining walls. For items such as garden sheds and small retaining walls, the required design life may only be 10 to 20 years, instead of the nominal 50 years required of new houses. In these circumstances, the normal 20-MPa concrete strength may be satisfactory. In saline environments, it is, however, still recommended that the concrete be placed on a membrane such as a vapour barrier to control moisture and efflorescence from the salts.

Source: Guide to Residential Slabs and Footings in Saline Environments

Roads



5 CONCLUSIONS The following conclusions are drawn from the contents of this report.

The key findings on the costs of salinity on public infrastructure are presented in the Tables in the Executive Summary.

The main work investigation the cost of salinity to infrastructure has been done by Dr Suzanne Wilson and colleagues, mainly across the Murray Darling Basin, based on survey methodologies developed by Dr Wilson. Other key work has been done by the firm Dames and Moore (now URS) and the Australian Bureau of Agricultural and Resource Economics (ABARE). The extensive work of Dr Wilson has occurred mainly across the Murray Darling Basin as a series of regional survey and interpretation studies and a catchment wide collation has occurred.

The above works have largely provided the data base has provided base data from which most other documents that discuss the costs of salinity to built infrastructure are derived.

The results presented in the Executive Summary and in the body of this report should not be considered literally. They have been heavily qualified by the respective authors as there confidence levels need to be considered against a number of variables and uncertainties including the following: • Respondents to surveys in municipalities across the Murray Darling Basin and

Western Australia from where much data has been derived will have varying knowledge of salinity and of its appearance on the ground and in infrastructure.

• The margins of impacts caused by dampness and salinity can blur.

• Much data was obtained by surveys that provided incomplete primary data coverage across target municipalities, and assumptions and extrapolations have needed to be made to complete studies.

• Environmental and hydrogeological conditions differ between regions. For example groundwaters in northern Victoria generally have substantially higher salinities than do those in southern Victoria including the Corangamite CMA Region.

On the basis of the above it is concluded that the cost implications for salinity damage to infrastructure as presented in this report should be regarded in relative and order of magnitude contexts. They should be regarded as reasonable determinations but should not be regarded as a definitive guide for Corangamite Region municipalities participating in the current review of the costs of salinity on public infrastructure.

Other content in this report identifies the types of impacts that salinity has on built infrastructure, and on remedial measures. These components of the report are included as a general guide to place infrastructure costs in their broader real context. The contents of these sections cannot be regarded as definitive information and advice on the control and management of salinity and its effects on built infrastructure, need to be considered on a case by case basis.



6 REFERENCES The following list identifies contemporary Australian literature on the topic of salinity and infrastructure damage. While not all listed documents are quoted in the text of this document nor used directly in its preparation, all documents listed are referenced in documents sourced for the current project and are thereby considered in the preparation of this report.

Abbott T S. (1990). Soil Test Interpretation Proceedings of a Symposium, Dubbo, NSW, February.

ACTEW (1997). Economic Benefits Assessment – Wagga Wagga Integrated Water Cycle Management Project, Report prepared in support of National Heritage Trust project funding.

Australian Building Code Board. (2004). Housing Provisions (Building Code of Australia - Volume Two),.

Houghton N, McRobert J, Styles E (2004) Salinity and Rising Water Tables - Risks for Road Assets. Publication No. AP-R246/04) Austroads. Prepared by ARRB Transport Research Ltd for Austroads Incorporated

Booth Associates, (1996). Economic, environmental and sociological baseline, Report prepared for the West Hume Land Care Group.

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Cement and Concrete Association of Australia and Standards Australia. (2002). Guide to Concrete Construction (T41/HB64),

Cement Concrete & Aggregates Australia. Guide to Residential Slabs and Footings in Saline Environments

Christiansen, G. (1995) An Economic Report on the Costs of Urban Salinity in the City of Wagga Wagga. Department of Land and Water Conservation, Wagga Wagga, NSW.

Clifton, C. (2000). Final Report Victorian Salinity Audit, Prepared for the National Land and Water Resources Audit by Sinclair Knight Merz and Agriculture Victoria.

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Department of Land and Water Conservation. (1997). Windows on Water: The State of Water in NSW 1996/97.



Department of Land and Water Conservation. (1998). Windows on Water: The State of Water in NSW 1997/98.

Department of Land and Water Conservation. (1998). Economic No Plan Scenario for the Wagga Wagga Natural Resource Management Plan – A draft Scoping Study, DLWC, Parramatta, NSW.

Department of Land and Water Conservation. (1998). Natural Resource Management Plan, Impact of urban salinity and waterlogging in Wagga Wagga – the no plan scenario – a Scoping Study. Resource Economics Centre for Natural Resources, Department of Land and Water Conservation, Parramatta, NSW.

Department of Land and Water Conservation. (1999). Kyeamba Valley Landcare Area Land and Water Management Plan: Economic Evaluation, DLWC, Sydney.

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Department of Infrastructure Planning and Environment, and Department of Primary Industries (2005). Costs of Urban Salinity NSW .

Local Government Salinity Initiative - Booklet No.10

ISBN: 0 7347 5469 8

Electricity Association of NSW (1997) Corrosion in the electricity supply industry, Report to the NSW Electrolysis Committee.

EnPlan Partners (2007) Permit Application Requirements for Developments in Salinity Management Overlay areas. Prepared for Corangamite Catchment Management Authority.

EnPlan Partners. (2007) Building in Saline Environments Prepared for Corangamite Catchment Management Authority.

Flaherty K. (2002). Local Government Salinity Initiative – Broad Scale Resources for Urban Salinity Assessment. Department of Land and Water Conservation Sydney,

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Hajkowicz, S. and Young, M. (1999). Interim estimates of dryland salinity impact cost associated with agricultural land use in South Australia, CSIRO Land and Water Report prepared for the Department of Primary Industries and Resources, South Australia.

Hamilton, S. (1995). Urban salinity in the Murray-Darling Basin, DLWC report to the Murray-Darling Basin Commission Groundwater Working Group.

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Hill, C.M. (1998). Assessing economic impacts of salinity in rural and urban areas, In: Managing saltland into the 21st Century: Dollars and sense from salt, Proceedings, 5th National PUR$L Conference, Tamworth, NSW, 9-13th March, 1998 pp. 110-13.

Institute of Public Works Engineering Australia (IPWEA). (2001). The Local Government Salinity Management Handbook – A Resource Guide for the Public Works Professional. .Prepared by Albury City Council’s Asset Design Services Section.

Ivey-ATP. (1998a). Determining the costs of dryland salinity: Dryland salinity survey of the Talbragar and Little River catchments – Central West NSW: Volume 3 of 5: Costs to the Little River catchment, Report prepared for the Murray-Darling Basin Commission, Wellington NSW.

Ivey-ATP. (1998b). Determining the costs of dryland salinity: Dryland salinity survey of the Talbragar and Little River catchments – Central West NSW: Volume 2 of 5: Costs to the Talbragar catchment, Report prepared for the Murray-Darling Basin Commission, Wellington NSW.

Ivey-ATP. (1998c). Determining the costs of dryland salinity: Dryland salinity survey of the Troy Creek catchment – Central West NSW, Report prepared for Salt Action New South Wales, Wellington NSW.

Institute of Public Works Engineering Australia. (2001). The Local Government Salinity Management Handbook – A Resource Guide for the Public Works Professional [Draft]. Prepared for the IPWEA by Albury City Council’s Asset Design Services Section (Available: http://www.ipwea.org.au/members/documents/#6.

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McRobert, J. and Foley, G. (1997). An investigation of the impact of waterlogging and salinity on the road asset in Western Australia, Report to Main Roads WA.

McRobert, J. and Foley, G. (1999).The impacts of waterlogging and salinity on road assets: a Western Australian case study. ARRB Transport Research Ltd Special Report 57, Vermont South, VIC.

McRobert, J. and Robinson, P. (2000). Salinity Impacts on Local Roads, ARRB Transport Research Ltd Report RC 1420 to the Department of Natural Resources and Environment, Vermont South, VIC..

Murray-Darling Basin Commission. (1994). A study into the benefits of roads and other infrastructure of providing drainage in the irrigation areas of the Murray-Darling Basin, Drainage Program, Technical Report no. 1, Canberra.

Murray-Darling Basin Commission. (1997). Salt Trends: Historic Trend in Salt Concentration and Salt Load of Stream Flow in the Murray-Darling Drainage Division, Dryland Technical Report No. 1, Canberra.

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Oliver, M., Wilson, S., Gombosso, J. and Muller, T. (1996). Costs of Salinity to Government Agencies and Public Utilities in the Murray-Darling Basin, Australian Bureau of Agricultural & Resource Economics Research Report 96.2, Canberra, ACT.

Pelikan, M.R.P. (2000) Cost of dryland salinity: GIS Methodology Paper, In-Confidence Draft Report prepared for the Murray-Darling Basin Commission.



PPK Environment and Infrastructure Pty Ltd. (2001) The ex-situ impacts to industrial and commercial water users due to degradation in the quality of water resources, Report prepared for CSIRO Land & Water, Adelaide.

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Slinger, D. (1998) Urban salinity in Wagga Wagga: A community problem, being addressed by our community, Wagga Wagga, NSW.

Spennemann, D.H.R. (1997) Urban salinity as a threat to cultural heritage places, Charles Sturt University, Albury, NSW.

Standards Australia. (1997). AS 1379 Specification and supply of concrete. a,

Standards Australia. (1995) AS 2159 Piling – Design and installation.

Standards Australia. (2001) AS 3600 Concrete structures.

Standards Australia. AS 3735 Concrete structures for retaining liquids..

Stark D. Longtime Study of Concrete Durability in Sulphate Soils. Portland Cement Association, Research and Development Bulletin RD086.01T.

Wagga Wagga City Council. Urban Salinity Annual Status Report 1999–2000.

Western Sydney Salinity Working Party. (2003) Western Sydney Salinity Code of Practice. Western Sydney Regional Organisation of Councils,

Wilson, S.M. (1999). Dryland Salinity: What are the impacts and how do you value them?, Guidelines prepared for the Murray-Darling Basin Commission and the NDSP.

Wilson, S.M. (2000). The cost of dryland salinity to non-agricultural stakeholders in selected Victorian and New South Wales catchments: Interim Report – Part 1, A Wilson Land Management Report prepared for the Murray-Darling Basin Commission and the National Dryland Salinity Program, Canberra.

Wilson, S.M. (2001a). Dryland salinity: What are the costs to non-agricultural stakeholders?: North Central Region, A Wilson Land Management Services Report prepared for the Murray-Darling Basin Commission and National Dryland Salinity Program, Canberra.

Wilson, S.M. (2001b)., Dryland salinity: What are the costs to non-agricultural stakeholders?: Goulburn-Broken Region, A Wilson Land Management Services Report prepared for the Murray-Darling Basin Commission and National Dryland Salinity Program, Canberra.



Wilson, S.M. (2001c), Dryland salinity: What are the costs to non-agricultural stakeholders?: Central West Region. A Wilson Land Management Services Report prepared for the Murray-Darling Basin Commission and National Dryland Salinity Program, Canberra.

Wilson, S.M. (2001d). Dryland salinity: What are the costs to non-agricultural stakeholders?: North West Region, A Wilson Land Management Services Report prepared for the Murray-Darling Basin Commission and National Dryland Salinity Program, Canberra (draft).

Wilson, S.M. (2001e). Dryland salinity: What are the costs to non-agricultural stakeholders?: Murrumbidgee Region, A Wilson Land Management Services Report prepared for the Murray-Darling Basin Commission and National Dryland Salinity Program, Canberra.

Wilson, S.M. (2001f), Dryland salinity: What are the costs to non-agricultural stakeholders?: Lachlan Region, A Wilson Land Management Services Report prepared for the Murray-Darling Basin Commission and National Dryland Salinity Program, Canberra.

Wilson, S.M. and Laurie, I. (2001). Assessing the full impacts and costs of dryland salinity, an Ivey ATP and Wilson Land Management Services report prepared for the Salinity Economics Workshop, 22-23 August 2001, Orange, NSW.

Wilson S.M. (2002). Assessing the costs of dryland salinity to non-agricultural stakeholders, the environment and cultural heritage in selected catchments across the Murray-Darling Basin – Methodology report 2, Report to the Murray-Darling Basin Commission and the National Dryland Salinity Program, Canberra.

Wilson S.M. and Laurie, I. (2002). Costs functions to assess the cost of saline town water supplies to households, commerce and industry, A Wilson Land Management Services and Ivey ATP Report prepared for the Murray-Darling Basin Commission, Canberra.

Wilson, S.M. (2003). Determining the full costs of dryland salinity across the Murray-Darling Basin: Final Project Report, a Wilson Land Management Services report to the Murray-Darling Basin Commission and National Dryland Salinity Program. (MDBC Project D9008)

Wilson, S.M. and Ivey ATP (2003) Dryland and urban salinity: What are the impacts and how do you value them? Version 2, Report to the MDB Commission and the National Dryland Salinity Program, Canberra.

Wilson S M. (Undated). Understanding and Preventing Impacts of Salinity on Infrastructure in Rural and Urban Landscapes (Wilson Land Management Services Pty Ltd.

Wooldridge, A. (1998). Dryland salinity 1998 – the view from the ground, In: Managing saltland into the 21st Century: Dollars and sense from salt, Proceedings, 5th National PUR$L Conference, Tamworth, NSW, 9-13th March, 1998 pp. 20-23

(Note: Many of the referenced documents are available on the internet)

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