Annex 11

Contents

1. Introduction

Devon County Council (the Council) has the largest Local Authority managed highway network in the UK and is responsible for a bridge stock of over 3000 Council owned and unknown ownership bridges and nearly 2000 retaining walls with a Gross Replacement Cost of just under £1.5 billion. As Highways Authority, the Council also has an interest in other owner structures that span or support the highway, which include 724 bridges. Highway structures include bridges, culverts, subways, footbridges, retaining walls and miscellaneous structures such as reinforced earth embankments, sea walls, rockfaces and cuttings, sign and signal gantries, and traffic signal masts. In addition to the Highway structures, the Council owns Public Rights of Way (PROW) structures which are discussed in Annex 10 – Public Rights of Way.

The Engineering Design Group (EDG) Bridges and Structures Group is part of the Climate Change, Environment and Transport Group of the Council and provides the following services:

Bridges and Structures Asset Management,
Bridge and Structures Inspection and Maintenance,
Design of new Highway and Cycleway bridges and structures, and
Technical Approval Authority (TAA).

In accordance with the National Code of Practice ‘Well-Managed Highway Infrastructure’1 the following highway structures are the responsibility of the EDG Bridges and Structures Asset Management Team:

Council bridges (footbridges, subways, underpasses, tunnels, cellars, vaults, culverts, pipes etc) with a span of 1.5m or more,
Retaining walls associated with the highway with a retained height of 1.35m or more, and
Gantries / cantilever structures / masts for signage, CCTV and traffic signals classed as a structure in CS 450 – Inspection of highway structures2,

In addition to the above, the EDG Bridges and Structures Asset Management Team are also responsible for the following:

Corrugated steel pipes with a span of 0.9m or more, and
Specific culverts with a span of less than 1.5m that are considered by the Flood Risk team to present a significant flood risk should they block.

Data on the actual current condition and performance of assets is obtained from inspections, testing and monitoring and assessment of structures. Since 2016 significant work has been undertaken by the EDG Bridges and Structures Asset Management Team to determine the condition and performance of the highway structures assets. This work has ensured that maintenance strategies and annual maintenance programmes of work focus on high risk and critical condition structures on key networks such as the Resilient Network and Major Road Network (MRN). Increasing pressure on budgets and resources combined with external factors such as climate change means that achieving asset management objectives and the levels of service that deliver a road network which is as safe, reliable and as fit for purpose as possible is becoming more challenging. Reviews have been undertaken and actions have been identified to ensure that where possible asset management objectives are achieved.

2. Inventory

2.1 Asset Types

Highway structures are split into different asset types and comprise bridges (both vehicular and pedestrian), culverts, subways, retaining walls and miscellaneous structures such as reinforced earth embankments, sign and signal gantries, and traffic signal masts. The extent of Council owned and other owner Highway structures assets as of September 2022 is shown in Figure 11.1 below.

Type of Asset	Council owned & unknown ownership	Other owners
Bridge	3079	1086
Retaining Wall	1723	42
Gantry	2	0
Signal Cantilever	22	0
Slope Stabilisation & Rockface Management	55	2
Sea Walls	78	19
Art Sculpture/Monument	2	0
TOTAL	4961	1149

Fig. 11.1: Extent of Council owned and other owner Highway structures assets (Sept 2022)

Within Devon the type of bridge varies from traditional masonry arches to reinforced concrete, steel and timber bridges. Over a third of the County’s bridges are masonry arches. Figure 11.2 below shows the number of bridges per construction type.

Primary Construction Type	Number
Arch	1931
Beam; Beam & jack arch; Beam and slab	237
Box; Box Girder	170
Cable stayed	3
Cantilever; Cantilever and suspended span	2
Clapper	95
Composite slab	76
Corrugated steel	2
Filler beam	2
Laminated beam	5
Opening	4
Pipe	76
Portal frame	5
Solid slab	335
Suspension bridge	1
Through girder	28
Troughing/Metal plate	31
Truss	12
Tunnel	3
Unknown	29
Voided slab	32
Grand Total	3079

Fig. 11.2: Number of Council and other unknown ownership bridges per construction type (Sept 2022)

2.2 Asset Data

The Council holds detailed asset information about its structure assets in the Bridge Management System (BMS) known as WDM’s Structures Management System (SMS). The asset data held within the system can be summarised as follows:

Basic Inventory Data

This includes age, construction type, dimensions, location information; obstacle crossed i.e. road over rail. General and Principal Inspections are also used to check the validity of data held on individual structures. More detailed data is provided by Special Inspections and testing. Further information on the various types of inspection can be found later in this Section.

Legal Data

This includes ownership information, licences and legal agreements.

Condition data

General and Principal Inspections, supplemented by Special Inspections, testing and monitoring provide condition data.

Structural Assessment & Review data

Principal Inspections identify structures which need a structural assessment. The assessment quantifies the load bearing capacity of the structure in accordance with the appropriate current standards and identifies substandard structures, which require improving or monitoring or a weight restriction.

Workbank

This is a list of all identified work by the inspectors, which they either undertake or is put into a works programme.

Repair history

This is updated when works are undertaken and includes the date, type and cost of repair, including details of the element repaired.

Health and Safety File Information

On completion of a scheme relevant health and safety information to be taken into account during any subsequent project, such as as-built drawings and maintenance manuals, is uploaded into SMS.

The Asset inventory is also updated following significant maintenance work; completion of developer schemes; creation of new assets; or ‘discovery’ of existing structures. 

2.3 Inspections

Inspections are carried out in accordance with the requirements of CS 450 – Inspection of highway structures2 and the Council Inspection of Highway Structures Policy.

There are five types of maintenance inspection as detailed in CS 4502.

Safety Inspections

As defined in CS 4502, safety inspections are not specific to highway structures and generally cover all fixed assets on the highway network, including carriageways, footways, structures, drainage, verges and lighting. They are undertaken in addition to planned maintenance inspections either routinely by Bridge Inspectors, Neighbourhood Highway Officers and the Term Maintenance Contractor when driving the network or in response to reports of a defect by a third party such as accident/impact damage to a structure. Safety Inspections identify significant deficiencies or signs of damage which represent, or can lead to, a danger to the public or high maintenance costs and therefore require immediate or urgent attention. Actions from the inspections are dealt with as an immediate risk to public safety or prioritised for action in accordance with asset management principles.

General Inspections

General Inspections (GI’s) of the entire bridge stock are currently undertaken on a nominal 2-yearly cycle to provide information on the physical condition of all visible elements to ensure the structures remain fit for purpose and safe to use.

Principal Inspections

More detailed Principal Inspections (PI’s) are undertaken every 6 to 12 years, depending on bridge type and other risk-based factors, to provide information on the physical condition of all accessible parts of a highway structure. The Council has adopted a risk-based approach to Principal Inspections to increase the inspection interval on non-critical structures in accordance with the risk-based approach described in Chapter 8 of CS 4502. Critical structures and those structures that are managed under Sub-standard structures managed under CS 470 – The Management of sub-standard highway structures3 are not eligible for increased Principal Inspection intervals.

As well as adopting the CS 4502 risk-based approach to Principal Inspection intervals on non-critical structures, a risk-based priority framework has been developed as a means of prioritising structures for Principal Inspection when the number of structures due a principal inspection is more than the number of inspections which will be undertaken. Focus has been on PI’s of complex and higher risk structures such as post-tensioned bridges, where undetected defects could result in sudden collapse, and road over rail bridges due to significant consequence of bridge failure over a live railway line.

GI’s and PI’s include dive inspection of underwater elements; roped access; and confined space inspections, which are all undertaken on a 2-year cycle.

Special Inspections

Special Inspections are required to provide more detailed information in response to the specific characteristics of the structure such as post-tensioned bridges; a recommendation identified by a GI or PI; certain events, such as the transit of a significant abnormal load, or a flood; or a recommendation to consider parts of the structure more closely or at a more frequent interval than the normal general and principal inspection regime. Types of Special Inspection include defect monitoring, defects are monitored in accordance with the Council’s defect monitoring procedure as described in the Council’s Inspection of Highway Structures Policy. The procedure includes structures where there is an issue i.e. major cracking, short term until a scheme is implemented and longer term to determine whether there is an issue that needs to be resolved and included in a future programme. A rolling programme of Post-Tensioned Special Inspections (PTSI’s) is undertaken in accordance with CS 465 – Management of post-tensioned concrete bridges4.

Inspection for assessment

As part of the Principal Inspection reporting, a structural review in accordance with CS 451 – Structural review and assessment of highway structures5 is undertaken to determine if an assessment is required. An Inspection for assessment provides the information required to undertake a structural assessment.

The results of inspections are recorded in accordance with the CSS (County Surveyors Society) Bridge Condition Index (BCI) procedures6, which is described in more detail in Section 3.0 Performance.

3. Performance

Data on the actual current condition and performance of assets is obtained from inspections, testing and monitoring and assessment of structures as described in Section 2 Inventory. Gathering good quality asset condition data enables the bridges and structures asset team to identify changes in condition of the assets, monitor performance and to respond to any urgent needs or emergencies. The data also informs the development of a Highway Structures Asset Programme and lifecycle plans as discussed in Section 6 Programme Development. This section describes the performance targets set by EDG Bridges and Structures Group, the performance measures used and the historical and current performance in relation to these measures.

3.1 Performance Measures

The Code of Practice1 recommends that the following should be considered when identifying performance measures for use in asset management planning:

Performance measures for highway structures that are already in use, such as Condition Performance Indicator (PI);
Performance measures that have been developed, or are under development, for highway structures, such as Availability PI, Reliability PI and Structures Backlog; and
Additional performance measures that may be needed to reflect the levels of service for the overall network and for measuring the effectiveness and efficiency of the planning and delivery processes.

The Condition PI is also referred to as the Bridge Condition Indicator (BCI) and is a measure of the physical condition of a structure, ranging from 100 (best condition) to 0, (worst condition).

The Bridge Stock Condition Index (BSCI) is the numerical value of all the bridge stock condition evaluated as an average of the BCI values weighted by the deck area (m2) of each bridge.

The interpretation of the Bridge Condition Indicator (BCI) values is given in Figure 11.3 below.

BCI Range	Condition BCI Score (all bridge elements)	Additional Comments
100 to 90 Very Good	The structure is in a “Very Good” condition overall.	Likely to be no significant defects in any elements.
90 to 80 Good	The structure is in a “Good” condition overall.	Mostly minor defects/damage but may also be some moderate defects.
80 to 65 Fair	The Structure is in a “Fair” condition.	Minor to moderate defects / damage. One or more functions of the structure may be significantly affected
65 to 40 Poor	The Structure is in a “Poor” condition.	Moderate to severe defects / damage. One or more functions of the structure may be severely affected
40 to 0 Very Poor	The Structure is in a “Very Poor” condition.	Severe defects / damage to a number of elements. One or more elements may have failed. Structure may be unserviceable.

Fig. 11.3: Interpretation of CSS BCI Values

The Availability PI is a measure of the reduction in the Level of Service provided, on a highway network, due to restrictions placed on highway structures. The Reliability PI is a representation of the ability of the structure stock to support traffic, and other appropriate loading, taking into account the consequence of failure. The structures backlog is the monetary value of work required to close the gap between the actual performance provided by an asset and the current required performance. Detailed guidance on performance measures is provided in the suite of Guidance Documents for Performance Measurement of Highway Structures7.

The use of the Condition Performance Indicator is now established and based upon reasonable experience, however, further work is required before the other three indicators can be adopted.

ADEPT (formerly The CSS Bridges Group) has developed the following suggested performance indicators:

Bridges not meeting highway authority’s required carrying capacity as a percentage of total stock,
Annual maintenance expenditure on bridges as a percentage of stock value, and
Annual maintenance expenditure on retaining walls as a percentage of stock value.

The EDG Bridges and Structures Group have set the following high level performance targets:

All bridges and retaining walls on the MRN, Resilient Network and ‘A’ roads shall be BCI good +80 condition by 2028,
All road over rail bridges shall be BCI good +80 condition by 2028;
All bridges on the remaining network with a severe score shall be BCI fair +65 condition by 2028,
All bridges on the remaining network with a poor and very poor score shall have a management plan in place by 2028,
All bridges with a capacity less than 40T shall have a management plan in place by 2025 and where required shall be weight restricted or strengthened by 2028,
Reduce the backlog of bridge GI’s to all in date by 2025 and thereafter to maintain all GI’s in date,
All bridges identified as requiring a PI in accordance with the risk management approach shall have an in date PI in place by 2028,
All Post Tensioned bridges shall have in date PTSI’s by 2024 and a longer term management strategy in place by 2024, and
95% of vegetation shall be removed from retaining walls on the MRN, Resilient Network and ‘A’ roads to allow thorough inspection to be carried out by 2028.

The performance indicators for the high-level targets currently adopted by the EDG Bridges and Structures Group are shown in Figure 11.4 below.

PI Ref	Performance Area	Target	Performance Indicator (PI)	Accountable Manager	Frequency of data capture	Support actions and key strategies
B1a	Bridge Condition	All bridges on the MRN, Resilient Network and ‘A’ roads shall be BCI ≥ 80 by 2028	Report on condition of the bridge stock using the CSS BCI performance measure	Principal Engineer (SAM)	Yearly	Management Plan Review meeting
B1b		All road over rail bridges shall be BCI ≥ 80 by 2028		Principal Engineer (SAM)	Yearly	Management Plan Review meeting
B1c		All bridges on the remaining network with a severe score shall be BCI≥ 65 by 2028		Principal Engineer (SAM)	Yearly	Management Plan Review meeting
B1d		All bridges on the remaining network with a poor and very poor score shall have a management plan in place by 2028		Principal Engineer (SAM)	Yearly	Management Plan Review meeting
B2	Retaining Wall Condition	All retaining walls on the MRN, Resilient Network and ‘A’ roads shall be BCI≥ 80 by 2028	Report on condition of the retaining wall stock using the CSS BCI performance measure	Principal Engineer (SAM)	Yearly	Management Plan Review meeting
B3a	Capacity	All bridges with a capacity less than 40T shall have a management plan in place by 2025	Report on % of bridge stock not meeting the required carrying capacity without a management plan in place	Principal Engineer (SAM)	Yearly	Management Plan Review meeting
B3b	Capacity	All bridges with a capacity less than 40T shall be weight restricted or strengthened by 2028	Report on % of bridge stock not meeting the required carrying capacity without a weight restriction	Principal Engineer (SAM)	Yearly	Management Plan Review meeting
B4	General Inspections (GI’s)	All bridge GI’s shall be in date by 2025	Report on % of bridge stock with an overdue GI	Principal Engineer (SAM)	Yearly	Management Plan Review meeting
B5	Principal Inspections (PI’s)	All bridges identified as requiring a PI in accordance with the risk management approach shall have an in date PI in place by 2028	Report on % of bridges requiring a PI with an overdue PI	Principal Engineer (SAM)	Yearly	Management Plan Review meeting
B6a	Post Tensioned Special Inspections (PTSI’s)	All Post Tensioned bridges shall have in date PTSI’s by 2024	Report on % of Post Tensioned bridges with an overdue PTSI	Principal Engineer (SAM)	Yearly	Management Plan Review meeting
B6b	Post Tensioned Special Inspections (PTSI’s)	All Post Tensioned bridges shall have a longer term management strategy in place by 2024	Report on % of Post Tensioned bridges without a management strategy in place	Principal Engineer (SAM)	Yearly	Management Plan Review meeting
B7	Vegetation Cover	95% of vegetation shall be removed from retaining walls on the MRN, Resilient Network and ‘A’ roads to allow thorough inspection to be carried out by 2028	Report on % of retaining walls with extensive (>50%) vegetation cover.	Principal Engineer (SAM)	Yearly	Management Plan Review Meeting

Fig. 11.4: Asset Management Performance Indicators (2022/28)

B1: Bridge Condition using BCI

Figure 11.5 below shows that there are 2523 bridges in the very good to good condition; 308 in fair condition; 19 in poor condition; 2 in very poor condition and 227 with either a calculation error or no score (September 2022).

DCC are not following the CSS document strictly as concerns have been raised nationally leading to the recently completed consultation for a revised document. The Bridge Stock Condition Index (BSCI) is the numerical value of a bridge stock condition evaluated as an average of the BCI values weighted by the deck area (m2) of each bridge. The score is a measure of durability and structural safety (capacity).  

As it’s not possible to easily differentiate between these two factors (durability and structural safety), the Councils bridge engineers have undertaken a review (which is ongoing) of the 329 bridges with a fair to very poor score and no issues relating to safety have been discovered thus far which aren’t already being dealt with. For example, 3 bridges supporting the MRN have low scores, two of these have been subsequently strengthened and one is being strengthened. The improvement actions in Performance Section 11 have been included to address this issue:  Documented management plan to be put in place for all bridges with a poor and very poor score. Any national changes to the BCI scoring regime will be considered for implementation and updated as necessary to reflect any future amendments to the CSS guidance documents.

Bridges are subject to a General Inspection every 2 years and the Councils bridge inspectors ensure any serious safety related issues are raised with the Bridges and Structures Asset Management Team and dealt with urgently.

BCI Range	Condition	No.
100 to 90	Very Good	1397
90 to 80	Good	1126
80 to 65	Fair	308
65 to 40	Poor	19
40 to 0	Very Poor	2
-999	calculation error	189
no score		38
	TOTAL	3079

Fig. 11. 5: BCI scores for Council owned bridges (Sept 2022)

B3: Load Carrying Capacity

This percentage only relates to bridges that support vehicles i.e. footbridges are not included. The 77 signed weight restriction bridges (July 2022), where the required capacity has been reduced with agreement of the local community, are deemed to be meeting the required capacity.

When an assessment shows a bridge to be sub-standard or provisionally sub-standard then the risk management procedures contained in CS 470 – Management of sub-standard highway structures3 are followed. This means that interim measures such as a weight restriction; traffic management restrictions or a regime of monitoring is imposed on the structure to minimise the risk of asset failure. Weight limits may be accepted by the Highway Authority as a permanent measure.

All restrictions affect the performance of the network and availability to all users.

A recent high level review (July 2022) of the signed weight restriction against the assessed load capacity for Council and non- Council owned bridges identified that there are 83 bridges, excluding clapper bridges, that have an assessed capacity less than 40T (3 – 38T) without any signage and 15 bridges that have signage different to the assessed capacity. There are also 145 Council owned and unknown ownership bridges, excluding clapper bridges, without assessed capacity information in SMS, 11 of which are on ‘A’ roads

A clapper bridge is a simple bridge consisting of slabs of stone or planks laid across a series of rocks or piles of stones. The Council owns 94 clapper bridges, the majority of which have an assessed capacity less than 40T (3 – 38T). The load carrying capacity of clapper bridges is difficult to assess reliably because of the dimensional and material property variability of the individual units. A conservative model is used for the assessment combined with conservative material properties resulting in very low load capacities that are far below the vehicle loadings that the bridges will have carried over many years of use without signs of failure. Some clapper bridges have been strengthened where they carry higher class roads that have greater traffic flows. The remainder carry lower class routes, and as they are small span structures with generally low headroom, they are considered at low risk of failing.

B4: Overdue Bridge General Inspections (GI’s)

Attention has been focussed on reducing the number of overdue bridge GI’s. In 2018 there were 1268 Bridge GI’s overdue (in excess of the 2-year inspection interval), which has been reduced to 438 as of June 2022.

B5: Risk Management Approach for Bridge Principal Inspections (PI’s)

As stated in Section 2, the Council has adopted a risk-based approach to PI’s to increase the inspection interval on non-critical structures in accordance with the risk-based approach described in Chapter 8 of CS 4502. Work is ongoing to risk assess all bridges requiring a PI as per the risk management approach.

B6: Post Tensioned Special Inspections (PTSI’s)

As stated in Section 2, post-tensioned bridges are complex, high risk structures, where undetected defects could result in sudden collapse. Attention has been focussed on eliminating the backlog of overdue PTSI’s and reviewing Stage 1 PTSI reports that have been carried out in accordance with the old code to bring them in line with CS 4654 to ensure that all are current and in date by 2024. A project is currently being undertaken to produce a longer term management strategy for all post-tensioned bridges.

B2 & B7: Retaining Walls

The condition of the retaining wall stock reflects the lack of inspection & maintenance this asset class has had. There is also a problem with carrying out an adequate inspection because of vegetation growth to a significant proportion of the stock, which consequently affects the Condition Indicator score. Performance indicator B7 has been introduced to resolve this issue on the MRN, Resilient Network and ‘A’ roads.

Work Bank

The structures work bank documents the maintenance needs and costs and should form the basis of the subsequent Value Management and Value Engineering processes. There is currently a high degree of under reporting as up until November 2021 the SMS workbank and repair history only contained data for works identified and undertaken from General Inspections of bridges. The aim is that all maintenance tasks required on highway structures (Revenue and Capital) and the associated cost estimates are documented in the structures workbank and the repair history is linked to the work bank so that completed works are recorded.

Actions to address the findings from the above reviews and improve condition and performance are described in Chapter 8 Improvement Actions.

4. Maintenance Strategy

Highway Authorities have a statutory duty to maintain assets. Maintenance of bridges and other highway structures is undertaken to ensure that they do not deteriorate to a standard that compromises the functionality of the highway network through closures and weight restrictions

Section C.6 of the Code of Practice1 states: “The purpose of maintenance is to repair damage caused by deterioration, vehicle impact or vandalism, slow down or prevent the deterioration process and, where appropriate, meet the changing demands of users.”

Different bridge types require different maintenance and inspection regimes. Some are very robust and require minimal maintenance, whilst others such as post tensioned bridges and moveable bridges require significant ongoing costs.

Masonry arch bridges are very robust and deteriorate very slowly provided they are protected from scour of their foundations. The main cause of masonry arch bridge failure is from scour often caused by debris build-up against the bridge during a flood event. Inspections are required to keep a check on any structural issues and scour inspections following flood events. Hence there is a continual risk which will need to be managed.

Higher risk structures, such as post tensioned bridges are maintained and inspected more frequently, to prevent unpredicted collapse. The potential for loss of life, disruption and financial consequences could be significant if these bridges are not maintained in a good condition.

Steel bridges and reinforced concrete bridges have a range of maintenance issues depending upon the quality of materials used, workmanship and types of exposure. They are generally designed for 120-year lifespan, but some show significant issues within half of their operational lifespan.

Timber bridges have a lesser lifespan (typically 15 – 30 years) than masonry and concrete and tend to be on cycleways and PROW’s. Regular maintenance of these structures is required to prevent closures of cycleways and footpaths.

The Council is responsible for 335 listed bridges, 147m of listed retaining walls and 14 scheduled ancient monuments, 6 of which are also listed.

Movable Bridges such as the Exeter Canal Swing and Bascule bridges on Bridge Road Exeter, Shaldon Bridge Lifting Span and River Yeo Cycle & Footbridge in Barnstaple cross a navigable waterway. These need to be maintained to ensure they remain operable.

Maintenance is considered at all stages of the project workflow through integration of design and construction knowledge with operations and maintenance experience to ensure the ease, accuracy, safety, and economy of future maintenance tasks.

The majority of activities associated with the management of highway structures are carried out in accordance with the standards and advice contained within the National Highways Design Manual for Roads and Bridges (DMRB)8. However, there are circumstances where lesser standards are acceptable such as undertaking repair to part of an element or repair of accident damage. Further details are provided in Section C.4. of the Code of Practice1.

Contract documents and procedures for all tendered contracts associated with the management of highway structures are generally prepared in accordance with the National Highways Manual of Contract Documents for Highway Works (MCHW)9, which includes the Specification for Highway Works. Departures from the advice contained in the standard documents are recorded in Feasibility Reports, Approval in Principle (AIP) documentation or Tender Appraisal Reports as appropriate.

EDG Bridges and Structures Group also produce Policy, Procedure and Good Practice Guides where appropriate. A good example of this is the good practice guide ‘Dealing with graffiti on Highway Structures’ which can be found in Appendix 11-1.

4.1 Creation of a new asset

New highway structures assets are created from new highway and cycleway schemes, highway stabilisation schemes or adoption of structures from developer schemes.

The Council Policy and Procedure documents for the maintenance audit of bridges and structures schemes10,11 define a process to ensure that as far as reasonably practicable future maintenance requirements and costs of new and improved bridges and highway structures schemes are carefully considered at the earliest stage to minimise future network disruption and lifecycle costs without compromising other important aspects such as access arrangements, environmental and sustainability issues, etc.

The Policy requires that information for future maintenance is recorded and passed to the maintainer in the form of as built drawings and maintenance manuals and stored in the structures asset management system SMS.

Technical approval is required for all new and existing structures with potential highway implications whether or not they are eventually intended to be adopted by the County Council. The process relates to design, construction, assessment, alteration, strengthening and repair to ensure that all structures are safe, durable, and in the case of structures proposed for adoption, are designed to require minimal maintenance. EDG Bridges and Structures acts as the Technical Approval Authority (TAA) on behalf of the County Council.

4.2 Routine and Reactive Maintenance

Regular and/or cyclical routine maintenance of bridges and other highway structures is undertaken to maintain their condition and functionality by protecting them from deterioration or slowing down the rate of deterioration, and thus reducing the need for reactive maintenance.

Regular maintenance undertaken by EDG Bridges and Structures includes routine electrical, hydraulic and mechanical maintenance of moving bridges, such as the Bridge Road Canal Swing and Bascule bridges, Shaldon Bridge Lifting Span and River Yeo Cycle & Footbridge.

In addition, minor maintenance, such as vegetation clearance and cleaning out of expansion joints is overseen by the Bridge Inspectors using the Revenue Budget.

Reactive maintenance includes emergency work that must be dealt with immediately on safety grounds such as parapet repairs following a bridge strike or removal of debris build up following a flood event, and essential maintenance work. Defects are identified through inspections (refer to Section 2.0 above) or reports of a defect by a third party. Work includes major concrete, masonry and steelwork repairs and scour repairs that must be carried out to prevent the structure becoming unsafe. If works cannot be carried out immediately, temporary or permanent restrictions such as weight or traffic management restrictions are applied.

The Bridges and Structures (BAS) Revenue Budget is used for emergency repairs, whilst the BAS Capital Budget is used to invest in Devon County Council’s assets either by creating new assets or improving existing assets.

4.3 Renewal or replacement

Refurbishment and/or strengthening of structures are determined from inspections and assessments.

Structures are replaced when they reach the end of their serviceable life; when refurbishment and/or strengthening of a structure is more costly than replacement; or when structural failure occurs.

4.4 Decommissioning of the asset

Highway structures are decommissioned when they become redundant either due to the creation of an alternative structure or due to the extinguishment of a highway or PROW.

5. Levels of Service and Investment Strategy

5.1 Levels of Service

Figure 11.6 below documents the Levels of Service that demonstrate the relationship between the Council’s corporate objectives, including the Strategic Plan for 2021 – 2025, and the performance of highway structures assets in terms of stakeholder requirements. The Levels of Service represent the fundamental service aimed at helping to deliver a road network which is as safe, reliable and as fit for purpose as possible within the current funding and resource constraints.

Levels of Service	Responding to the climate emergency	Support Sustainable economic recovery	Improve health and wellbeing	Help communities to be safe, connected, and resilient
Carry out structures inspections in accordance with the National Code of Practice1.		√		√
Monitor those structures considered to be below standard.		√		√
Using condition data develop and deliver an annual programme of bridge and retaining wall maintenance and structural repairs to maintain structures within available budgets.	√	√	√	√
Target structures which are in the Poor/Very Poor condition band where this has a potential impact on safety.		√		√

Fig. 11.6: Levels of Service.

Construction activity results in production of CO2. Future management processes of the highway network are vital to the Council’s contribution to a Net-Zero Devon, and exploiting the economic opportunities presented by green technology will be central to bringing more higher value and sustainable employment to the County.

Highway structures contribute to the achievement of responding to the climate emergency, improving health and wellbeing by maintaining and improving walking and cycling infrastructure such as cycle/footbridges and boardwalks. Over the next few years budget has been allocated to replacing the Gem Aerial Walkway on the Drakes trail and improving Courtlands Boardwalk, which is part of the Exe Estuary trail. This is in addition to the budget allocated yearly to the refurbishment or replacement of footbridges.

The environmental review process is undertaken for all highway structures schemes.

As discussed in the HIAMP, Devon has developed a carbon calculator in conjunction with Exeter University. This tool will be used by designers on larger highway structures schemes as part of the design process to estimate both carbon emissions and carbon cost against various treatment solutions. Carbon data from Contractor’s working on highway structures schemes will come through the carbon web form.

Carbon reductions using alternative design solutions, materials and working practices have already been used in Devon to reduce our carbon footprint, including the use of fibre reinforced plastics for new bridges rather than high carbon options such as steel and concrete. The use of recycled tyre bales for constructing retaining structures provides a significant reduction in the use of concrete and aggregate as well as less transportation of materials. Advances in concrete technologies and the use of admixes reduces the cement content and less quarrying activity. Other innovations, which have been used many times in Devon over the past 10 years, including soil nailing and anchored piled walls to stabilise highway embankments and reinforced earth, also reduce the reliance on traditional concrete retaining walls, which have a higher carbon footprint.

Work is currently being undertaken on a research project with Brunel University to consider the use of masonry arch bridges rather than modern concrete and steel bridges, to replace weak bridges in Devon, as they perform well and have a much longer lifespan and lower carbon footprint than concrete and steel bridges.

Sustainable economic recovery is supported by ensuring network availability and condition supports freight distribution and commuter travel to work, whilst maintaining access arrangements for all communities helps communities to be safe, connected, and resilient. These objectives are achieved by carrying out structures inspections in accordance with the Code of Practice1; monitoring those structures considered to be below standard; using condition data to develop and deliver an annual programme of bridge and retaining wall maintenance and structural repairs to maintain structures within available budgets; and by targeting structures which are in the Poor/Very Poor condition band where this has a potential impact on safety. Focus is on maintaining those structures on the Resilient Network.

5.2 Investment Strategy

Any reduction in the current BAS Revenue and Capital budgets will result in difficult decisions regarding the continual usage of bridges in Devon with some bridges requiring closure as their condition deteriorates.

Different bridge types require different maintenance and inspection regimes. Some are very robust and require minimal maintenance, such as masonry arch bridges, whilst others such as post tensioned bridges and moveable bridges require significant ongoing costs.

Masonry arch bridges deteriorate very slowly and could accommodate a reduced maintenance regime for a considerable time period without becoming unsafe. Inspections would be required to keep a check on any structural issues and scour inspections following flood events.

Higher risk structures, such as post tensioned bridges need to be maintained and inspected, as unpredicted collapse could otherwise occur. The potential for loss of life, disruption and financial consequences could be significant if these bridges are not maintained in a good condition.

Steel bridges and reinforced concrete bridges have a range of maintenance issues depending upon the quality of materials used, workmanship and types of exposure. They are generally designed for 120-year lifespan, but some are showing significant issues within half of their operational lifespan.

Timber bridges have a lesser lifespan (newer bridges found to be less than 30 years) than masonry and concrete and tend to be on cycleways and public rights of way (PROW’s). If these are not maintained closures of cycleways and footpaths will occur over time.

Council owned bridges of historical importance (listed and scheduled monuments) could be lost for ever if they are not maintained. The Council has a moral obligation, if not a statutory duty, to maintain the County’s heritage

Movable Bridges such as the Exeter Canal Swing and Bascule bridges on Bridge Road Exeter cross a navigable waterway. These need to be maintained to ensure they remain operable. Major investment in upgrading these bridges is required within 5 years, without which the bridges will become more unreliable for canal openings and, it is likely a weight restriction on the Bascule bridge would be required within 10 to 20 years. A bid to the Department for Transport (DfT) has been made to upgrade the bridges and to undertake further improvements to Bridge Road. If this bid is unsuccessful the implications are additional funding will be needed within 5 years to refurbish or replace the existing bridges. This is not currently included in the future BAS budget.

It is envisaged the do minimum position would be undertaking safety inspections and monitoring of bridges that fall below the ‘good’ condition and into the ‘fair’ to ‘poor’ condition. Reactive rather than preventative maintenance would only be possible.

The longer term aspiration should be to increase the level of funding to allow the bridges in the fair to poor condition to be improved, thus reducing the safety risk to the public.

6. Programme Development

Part B of the UKRLG Highway Infrastructure Asset Management Guidance Document (HIAMG)12 states that the objectives of works programmes are:

“Develop effective and efficient works programmes to meet the approach to asset management and deliver the service,
Identify potential maintenance works – candidate schemes,
Develop works programme of candidate schemes,
Prioritise and optimise schemes in the works programme to meet the available budgets, and
Monitoring of works to ensure it meets the approach to asset management”

6.1 Identifying Schemes for an Initial Works Programme

Schemes are identified for an initial works programme through the following means:

Asset data from Inspections,
Assessments,
Component life expectancy,
Evaluation of sub-standard structures,
Reports of a defect from an NHO or Third party, and
Unplanned works.

As stated in Section 3 Performance, the structures work bank should document the maintenance needs and costs and form the basis of the subsequent Value Management and Value Engineering processes. At present the workbank in SMS lists all identified work by the inspectors, which they either undertake using the bridges and retaining walls revenue budgets or their Minor Refurbishments Capital budget, or is put into current or future works programmes depending on criticality.

Some components with a finite life are replaced purely according to their age, whilst other components are replaced when significant planned highway works are carried out.

Whilst every effort is made to plan works in advance, unplanned works are always likely to occur due to flooding, vehicle strike and sudden component failure.

The schemes are collated into the appropriate programme of work for the highway structures assets such as bridge strengthening; retaining wall strengthening; sub-standard parapets; joints, bearings and waterproofing; and major refurbishments etc.

6.2 Prioritising the Works Programme

The schemes in the initial works programme are reviewed and prioritised using a systematic, risk-based approach taking into consideration the following:

Safety critical schemes;
Structures with a low condition score;
Locality i.e. road over rail, Resilient Network; route maintenance category;

Structures hierarchy and critical infrastructure assets;
Defined levels of service for the asset; and
Local needs and priorities.

Safety critical schemes include those that are required to safeguard the highway user or where the function of the structure may be compromised if repairs are not carried out such as re-pointing work to an arch barrel or providing anti scour measures.

Strengthening works are prioritised in accordance with the factors listed in Annex E/1. of CS 470 – Management of sub-standard highway structures3.

As stated in Section 2 Inventory a priority framework has been developed for the Principal Inspection programme. These inspections are identifying short term, medium term and long term works and assessments.

Focus is also given to those structures where either the average condition of the bridge or the condition of a critical element in the bridge drops below a certain BCI score.

In addition to complex and high risk structures, where the consequence of failure is severe, such as post-tensioned bridges and road over rail bridges, reference is made to the highway network layers national defined routes13 to identify those structures that are on specific routes such as the Major Road Network (MRN), Resilient Network, primary and secondary salted networks, heavy load and high load routes. Figure 11.7 below shows the number of Council owned bridges and length of retaining walls for the route type supported. Figure 11.8 below shows the number of Council bridges and length of retaining walls per route classification supported.

Route Type Supported	Number of Council owned & unknown ownership Bridges	Length of Council owned & unknown ownership Retaining Walls (m)
MRN Supported	118	3,617
MRN Spanned	40	N/A
Primary Salted Supported	916	Data unavailable
Secondary Salted Supported	134	Data unavailable

Fig.11.7: Number of Council bridges and length of retaining walls per route type supported. Note does not include retaining walls above the highway and retaining wall lengths for primary and secondary salted routes.

Route Classification Supported	Number of Council owned & unknown ownership Bridges	Length of Council owned & unknown ownership Retaining Walls (m)
‘A’ Class	426	41,458
‘B’ Class	250	21,972
‘C’ Class	1069	28,901
Unclassified	994	17,438
Footpath, Cycleway, Bridleway	330	3,385
Aqueduct	2	N/A
Arch in wall	1	N/A
Closed	3	N/A
Dismantled Railway	2	N/A
Unknown	2	N/A
Grand Total	3079	113,154

Fig. 11.8: Number of Council bridges length of retaining walls per route classification supported. Note not all retaining wall lengths are currently recorded.

All bridges that are on the Resilient Network have been identified as critical infrastructure assets as failure would result in a significant impact to the local, and potentially the national, economy. Priority is given to those structures on the MRN, then the Council’s Resilient Network and salted routes (Primary then Secondary). Maintenance categories within those routes may be used to further prioritise schemes.

Selecting and Optimising Schemes for the Forward Programme

The prioritised programme of works is further optimised for the forward programme to ensure that the value of works is within the available budget for the current year and future years.

Where feasible, forward design is undertaken a year ahead of the works, allowing flexibility of scheme delivery and works to take place earlier in the next financial year during better weather. A three-year forward programme is currently being developed to provide flexibility for coordination of works and to allow for unforeseen schemes. As stated above, identified safety critical works are undertaken in year as soon as possible either using the Revenue or Capital budgets depending on the type of work or temporary restrictions are put in place until the works can be carried out. If budget is unavailable, other schemes are deferred to allow the safety critical works to be undertaken.

Where possible schemes are grouped and/or coordinated with other highway infrastructure asset schemes to provide cost savings in delivery. Work is ongoing to coordinate maintenance schemes on the highway network at an early stage to minimise disruption to travel and the economy and to reduce costs to the authority from multiple road closures. Schemes in the same area may be deferred or brought forward to ensure that they are delivered at the same time. Where surfacing schemes traverse a bridge, waterproofing and joint replacement schemes may be brought into the programme to ensure that they are undertaken simultaneously.

6.3 Structures Asset Valuation and Investment Tool (SAVI)

The Structures Asset Valuation and Investment Tool (SAVI) supports asset owners, operators and managers with the management of their structure stock. SAVI is a multi-functional, condition-based decision support tool. It can be used to: carry out valuation of structures stock; develop prioritised short-term programmes of work; and develop long-term asset management plans. EDG Bridges and Structures Asset Management Team intend to incorporate SAVI into the SMS database to assist with developing short-term programmes and lifecycle plans.

The Toolkit will ultimately be used to provide a longer term works programme and lifecycle plans which are derived from inspections, using deterioration profiles and intervention trigger levels.

7. Risks

The HIAMP lists key risks pertinent to the highway network, which may prevent asset management objectives being achieved. Those risks pertinent to the highway structures assets are discussed in more detail below.

7.1 Climate change

Climate change is a major factor influencing the future of Devon’s structures. Greater occurrence of flooding is increasing the risk of bridges being washed away and damage due to scour of bridge foundations. As experience shows from the 2009 flooding events in Cumbria, loss of bridges causes major disruption to communities and businesses. In Devon several bridges have collapsed due to damage following flooding, such as Waterstave and Collard Bridges in 2012. The Council’s bridges identified at potential risk of scour following a flood event are surveyed and assessed to ensure that foundations are investigated and protected or the risks managed.

EDG Bridges and Structures Asset Management Team has undertaken a programme of Stage 1 assessments in accordance with BD 97/12 – The Assessment of Scour and Other Hydraulic Actions at Highway Structures14. This work has now progressed to carrying out Stage 2 assessments where specific works are proposed. The impact of debris accumulation on bridges during flood events, which is known to cause scour, is also being investigated.

During major flooding incidents when a number of bridges may be seriously damaged, the Bridges and Structures Emergency Plan, which is under development, will come into effect.

Investment in highway surface water drainage systems is required to minimise damage to highway embankments and retaining walls. Extreme rainfall events cause surface water to wash away embankments, which support the highway, requiring significant repairs including new retaining walls and other structural solutions to shore up the highway. This is an expensive and disruptive process and can be avoided if preventative actions such as maintaining and improving highway drainage systems are implemented. Future policies and preventative actions are required to ensure the highway network can cope with more frequent extreme weather events due to climate change.

7.2 Defects in Hidden Bridge Components

Two high profile cases in recent years have emphasised the importance of defects in hidden bridge components. In 2009, the Stewarton rail bridge, Ayrshire collapsed during passage of a freight train. Corrosion to half-through girder webs was so severe that complete loss of section had occurred in areas of high shear load. The corroded areas were hidden under ballast and had not been inspected. The A4 Hammersmith Flyover on one of London’s busiest roads, had been subject to limited inspections of its post-tensioning tendons since the mid-1990s. During investigation works in 2011, two of the eight tendons over one particular pier were found to be badly corroded and the flyover was closed while further investigation of the remaining six tendons and assessment was undertaken. The flyover was reopened with restricted traffic loading while emergency strengthening works were undertaken before the implementation of a full strengthening scheme. The full strengthening works, plus bearing and joint replacement, were completed in 2015 at a cost in the order of £120m.

CIRIA has recently published C764 – Hidden defects in bridges: Guidance for detection and maintenance15. EDG engineers will use the document to review and update current inspection practices, and to start a hidden defects programme to identify hidden components in bridges.

7.3 Funding

The Council is facing unprecedented financial pressures and with current high inflation this is impacting available funding and increasing the construction cost of schemes. Any further reduction in the BAS budget will mean the bridge condition is unlikely to be improved and it is more likely they will continue to deteriorate with potential for weight restrictions or closures at some point in the future.

Failure to maintain the Council’s highway structures will result in the structures residual life reducing with potential need to replace sooner.  Depending on the period of time and severity of the reductions, it could eventually result in closure of some bridges as it would not be possible to maintain them in a safe state and an escalation of costs to claw back the condition of other structures in future years.

Major investment in upgrading the Exeter Bridge Road Canal Bascule and Swing bridges is required within 5 years.  Without this investment the bridges will become more unreliable for canal openings and, it is likely a weight restriction on the Bascule bridge will be required within 10 to 20 years. A bid to the Department for Transport (DfT) has been made for to upgrade the bridges and to undertake further improvements to Bridge Road.  If this bid is unsuccessful the implications are additional funding will be needed within 5 years to refurbish or replace the existing bridges.

7.4 Bridge Safeguarding

It is a sad reality that bridges in Devon have been used to end life by suicide. Two major bridges in North Devon crossing the Rivers Taw and Torridge have had their parapets replaced with higher ones and to date the evidence is they have had a significant impact in reducing the number of incidences at these locations. Several other bridges have been identified and work continues to incorporate higher parapets as a means of preventing suicide. Nationally more work needs to be done to tackle the root cause to prevent vulnerable people from taking this course of action.

8. Improvement Actions

The EDG Bridges and Structures Group are continually seeking to improve the efficiency and effectiveness of its maintenance planning and asset management process with particular focus on developing a long-term Maintenance Strategy.

The need to analyse cost-effective maintenance strategies for Devon’s highway bridges is becoming increasingly important as the age of the bridge stock continues to increase whilst the availability of maintenance funding reduces.

Figure 11.9 below documents the improvement actions identified to meet the high-level performance targets and other targets to help ensure that asset management objectives are achieved. The improvement actions will be subject to an annual review to ensure compliance with the target dates. The work required will be incorporated into forward works programmes and resources and budget allocated accordingly.

Ref	Target	PI Ref (if applicable)	Improvement Action	Date to be achieved
1	All bridges on the MRN, Resilient Network and ‘A’ roads shall be BCI good +90 condition	B1a	As a result of the findings of the BCI review undertake further work focussing on how the associated elements are reported to give a more accurate condition score. All BCI structures are to be looked at in more detail and works prioritised for the forward works programme in accordance with risk-based approach. Undertake all GI’s and PI’s. Ensure sufficient resources and Capital budget are allocated.	March 2028
2	All road over rail bridges shall be BCI good +90 condition	B1b	Undertake all GI’s and PI’s. Ensure sufficient resources and Capital budget are allocated.	March 2028
3	All bridges on the remaining network with a severe score shall be BCI fair +80 condition	B1c	Undertake all GI’s and PI’s. Ensure sufficient resources and Capital budget are allocated.	March 2028
4	All bridges on the remaining network with a poor and very poor score shall have a management plan in place by 2028	B1d	Undertake all GI’s and PI’s. Ensure sufficient resources and Capital budget are allocated. Documented management plan to be put in place for all bridges with a poor and very poor score.	March 2028
5	All retaining walls on the MRN, Resilient Network and ‘A’ roads shall be BCI good +90 condition	B2	Complete retaining wall inventory survey. Reduce Retaining Wall Stock with an overdue General Inspection. Ensure sufficient resources and Revenue budget are allocated for inspections and sufficient resources and Capital budget are allocated to undertake the works. Consideration to be given to establishing an assessment programme using CS 459 – The assessment of bridge substructures, retaining structures and buried structures16	March 2028
6	All bridges with a capacity less than 40T shall have a management plan in place and shall be weight restricted or strengthened	B3	Detailed review of capacity and weight restrictions to be undertaken including checking assessments are still current and valid. Where weight restrictions are in place, ensuring that they are as per assessed capacity and TRO and signage are correct. Where no weight restrictions are in place applying for TRO and installing signage or putting in place a documented management plan with monitoring regime. Use risk-based approach to prioritise those structures where assessment is not still current and valid or where there is no assessment.	Management Plan: March 2025 Weight restriction / strengthened: March 2028
7	Reduce the backlog of GI’s to all in date and maintain all GI’s in date	B4	Ensure sufficient resources and Revenue budget are allocated for inspections.	March 2025
8	All bridges identified as requiring a PI in accordance with the risk management approach shall have an in date PI in place by 2028;	B5	Risk assess all bridges requiring a PI as per the risk management approach. Ensure sufficient resources and Capital budget are allocated to undertake PI’s.	March 2024
9	All Post Tensioned bridges shall have in date PTSI’s and a longer term management strategy in place	B6	Undertake PTSI’s in accordance with CS 4654. Produce Risk Review Report; Risk Assessment & Management Report; and Special Inspection Report. Review any existing Stage 1 PTSI reports which have been carried out in accordance with the old code and produce a separate report to bring them in line with CS 4654. Develop a longer term management strategy.	March 2024
10	95% of vegetation shall be removed from retaining walls on the MRN, Resilient Network and ‘A’ roads to allow thorough inspection to be carried out	B7	Allocate funding to vegetation clearance from annual Revenue budget.	March 2028
11	Develop reporting through the Work Bank	N/A	Collect missing data i.e. component material types. Develop Work Bank performance measure to report on the condition of the bridge stock. Document in the structures work bank all maintenance tasks required on highway structures (Revenue and Capital) and the associated cost estimates. Link repair history to the work bank so that completed works are recorded. Prioritise works as per risk-based approach.	March 2028
12	Capture carbon data for all highway structures schemes	N/A	Use carbon calculator on all highway structures schemes as part of the design process to estimate both carbon emissions and carbon cost against various treatment solutions. Use carbon web form to capture carbon data from Contractor’s working on highway structures schemes	October 2023
13	Develop Lifecycle Plans	N/A	SAVI toolkit to be incorporated within the Structures Management System Database and used to develop Lifecycle Plans.	March 2028
14	Develop a long-term Maintenance Strategy	N/A	Review current procedures in place for determining when maintenance work on different structures within the stock should take place. Develop a long term plan. Give consideration to prioritising works in alignment with Highway goals. Schedule of elements with finite life, with dates for replacement and programme in conjunction with highway maintenance works	March 2028
15	Reduce scour susceptibility of those bridges identified through assessment programme.	N/A	Use the results of the risk assessments to investigate bridge foundations to determine if further interventions are required.	March 2028
16	Develop Bridges Emergency Plan.	N/A	Update historical emergency plan to take into consideration current practices and to align with the highways Winter Service and Emergency Plan.	March 2023
17	Identify hidden components in bridges		Use CIRIA document C764 – Hidden defects in bridges: Guidance for detection and maintenance17. to review and update current inspection practices and to start a hidden defects programme to identify hidden components in bridges.	March 2028
18	Improve coordination of highway structures schemes with other highway infrastructure schemes.		Develop and adopt the Good Practice Guide – Coordination of BAS and Highways Schemes. Asset teams to meet to discuss forward works programmes and possibilities for coordination.	Ongoing

Fig. 11.9: Improvement actions identified to achieve asset management objectives

9. References

UK Roads Liaison Group. National Code of Practice ‘Well-Managed Highway Infrastructure, DfT, 2016
National Highways. CS 450 – Inspection of highway structures
National Highways. CS 470 – The Management of sub-standard highway structures
National Highways. CS 465 – Management of post-tensioned concrete bridges
National Highways. CS 451 – Structural review and assessment of highway structures
CSS (County Surveyors Society) Bridge Condition Index (BCI) procedures, 2002
CSS. Guidance Documents for Performance Measurement of Highway Structures, Atkins, 2007
National Highways. Design Manual for Roads and Bridges (DMRB)
National Highways. Manual of Contract Documents for Highway Works (MCHW)
Devon County Council. Maintenance Audit of Bridges and Structures Schemes Policy, 2020
Devon County Council. Maintenance Audit of Bridges and Structures Schemes Procedure, 2020
UK Roads Liaison Group Highway Infrastructure Asset Management Guidance Document (HIAMG), DfT, 2013
Highway network layers national defined routes
National Highways. BD 97 – The Assessment of Scour and Other Hydraulic Actions at Highway Structures
National Highways. C764 – Hidden defects in bridges: Guidance for detection and maintenance
National Highways. CS 459 – The assessment of bridge substructures, retaining structures and buried structures
National Highways. C764 – Hidden defects in bridges: Guidance for detection and maintenance

Appendix 11-1 Good Practice Guide BM3 Dealing with Graffiti

11-1.1 Scope

This guide is intended to be used by anyone working on Devon County Council Bridges and Structures and its prime purpose is ensure a consistent approach to dealing with assets that have been subjected to graffiti. This is not a specification or safe working guide; the responsibility for safety planning will rest with the project manager. The Guide will cover the various aspects of dealing with graffiti including:

Removal of offensive material
Protection of new and existing structures with anti graffiti coatings
Use of street art and murals for reducing the occurrence or impact of graffiti

11-1.2 The Problem

The majority of graffiti on Devon’s bridges is considered unwanted and anti-social. Members of the public complain of unsightly appearance, offensive material and of feeling intimidated when walking through badly affected subways or retaining walls in urban areas. One option for dealing with graffiti is regular removal or overpainting in the hope that those responsible will lose interest and either desist or move elsewhere. This however can be a costly approach with weekly visits by cleaning teams needed in heavily used areas such as the subways at Exe Bridges in Exeter.

11-1.3 Removal of offensive material

There is a need to quickly remove offensive material such as swear words, racist remarks and obscene drawings. This is usually best achieved by painting over the offending material as soon as it is reported and then programming a graffiti removal task. Structures that are frequently targeted will usually have an anti graffiti coating applied; it is important to check the structure records to identify the product so that the correct removal process can be used.

The two main methods of removal are high pressure water jetting and the use of chemicals. Care must be taken not to pollute the environment with chemicals or effluent from the water jetting operation which may contain paint or other contaminants. Removal operations can usually be carried out without restricting public access totally but a safety zone must be used to minimise public risk.

After the removal operation it will usually be necessary to reapply an anti graffiti barrier.

11-1.4 Anti-graffiti coatings

If existing structures are being affected by graffiti the area Bridge Inspector will recommend a treatment process to the Principal Engineer Bridge Maintenance (PE (BM)) who will assess the cost implications and if necessary, add to the revenue programme.

New structures that will become the responsibility of the Council will receive a maintenance audit by the PE (BM) when graffiti protection using a surface finish such as ‘knocked off rib’ on walls to create an uneven surface or proprietary coatings to make it easier to remove graffiti will be considered.

11-1.5 Use of street art and murals

The application of murals and street art is growing in popularity in Devon and can considered for reducing the occurrence or impact of graffiti. The benefits are many including reduced cost to the Council for cleaning operations, involvement of local community groups particularly schools and art colleges and the creation of a more pleasant environment.

The materials used for murals and street art should be carefully considered and agreed with the PE (BM). Whilst damage to a structure from the application of paint is unlikely, it is often sensible to use water based or low volatile content paints to ensure the existing structure is not damaged or the anti carbonation treatment on surfaces is not compromised.

The content of the art work should also be carefully considered to ensure it cannot easily be defaced; the adding of appendages or speech balloons are two common ways to ruin a piece of street art.

It is quite common for local organisations or individuals to volunteer to paint subways and other structures as a school/college art project. This can work but the scale of the task involved can be under-estimated. The Tarka Trail scheme shown at the end of this paper was one such project. A local 6th form college had a competition amongst the students to create suitable designs for two newly opened subways that were being targeted. The Council provided the materials and pedestrian management for what was expected to be a two week project. It soon became apparent that the students would not complete the task and the Council had to take over. The cost of using contracted services for this type of operation is not insignificant.

The second example of Renslade Subway was carried out by a street artist at no cost to The Council and was completed in just over a week so volunteers should be encouraged provided they fully understand the task involved.

11-1.6 Consultees Prior to new street art/murals

Street art on Council owned structures does not require planning permission, however it is advisable to liaise with various parties to ensure stakeholders are aware of the project. The following list assumes a project may not necessarily be led by the Bridge Maintenance team; the project manager will need to consider if there are other stakeholders relevant to the particular project:

Consultees