Civil Engineer

What’s that defect…. Rocks and rock faces

Rock faces alongside a road can pose significant risks to road users. These risks can arise from several factors such as rockfall, loose debris, and potential instability. The risks can be heightened in areas with significant weather events, such as heavy rain or snowfall, which can destabilise rock formations. The consequences of rockfall incidents can be severe, including damage to vehicles, injuries or fatalities to road users, and road closures, which can cause significant disruption to traffic flow. As such, it is important for road authorities to implement measures to manage and mitigate the risks posed by rock faces alongside roads.

Here are some likely defects that can be found from rock faces:

Rock falls or debris on the road surface.
Cracks or fissures on the rock face.
Loose or unstable rock formations.
Vegetation or trees growing on the rock face.
Water seepage or drainage issues causing erosion or landslides.
Lack of or damage to protective measures such as rockfall barriers or mesh netting.
Poor visibility or lighting around the rock face area.
Unauthorised access or activity on the rock face.
Signs of wildlife activity, such as burrows or nesting sites, that may pose a hazard to road users.
Obstructions caused by rock or debris buildup in drainage channels or culverts.

Remedial measures to rock faces alongside roads are necessary to reduce the risk of hazards to road users. The risks posed by rock faces can range from loose rock debris to rockfall, which can cause damage to vehicles and injury to drivers and passengers. Additionally, rocks or boulders that have become detached from the rock face can obstruct the roadway, leading to potential accidents or damage to vehicles. Therefore, it is important to implement remedial measures to minimize these risks and ensure the safety of road users. These measures may include slope stabilisation, rockfall protection systems, and regular inspections to identify potential hazards and implement necessary repairs.

Here are some of the remedial measures that can be used to address defects from rock faces:

Scaling: Loose and unstable rock material is removed from the rock face to prevent potential falling hazards.
Rock bolting: This technique involves drilling into the rock face and installing a steel bolt to hold the rock face in place and prevent rock falls.
Shotcrete: This is a process where a layer of sprayed-on concrete is applied to the rock face to stabilise the surface and protect against weathering and erosion.
Mesh and netting: Wire mesh or netting can be installed over the rock face to contain loose rocks and debris.
Catch fences: These are barriers installed at the base of a rock face to catch any falling rocks or debris.
Rockfall barriers: These are steel barriers that are placed on the slope above the road to catch any falling rocks or debris and prevent them from reaching the road.
Slope stabilization: This involves reshaping or modifying the slope to reduce the risk of rock falls or other hazards.

The remedial measures used will depend on the type and severity of the defect, as well as the location and accessibility of the rock face. Inspections of rock faces are typically carried out by qualified engineers who are trained to identify potential hazards and recommend appropriate remedial measures. Inspections may be conducted visually, or may involve the use of specialised equipment such as drones or laser scanning technology to assess the condition of the rock face.

Inspections are carried out by trained personnel who follow guidelines set out by the UK government to identify and document any defects found. These guidelines include specific requirements for the types of defects that may be encountered. The inspections are carried out on a regular basis, and any defects that are identified are addressed through appropriate maintenance and repair measures. The ultimate goal is to ensure the safety of all road users and prevent accidents caused by rock hazards.

What’s that defect…. Ironwork

Ironwork, including manhole covers, gully grates, and utility covers, are critical components of road infrastructure. They provide access to drainage and utility systems and are designed to be strong enough to support vehicular traffic. However, over time, ironwork can deteriorate due to various factors, such as weathering, corrosion, and general wear and tear. Defects in ironwork can pose significant hazards to road users, such as vehicle damage, accidents, and noise pollution. Therefore, it is essential to identify and address these defects as part of a regular maintenance program.

Here are some types of ironwork defects that can be found on UK roads:

Broken or missing covers – this can cause a hazard to vehicles and pedestrians as well as damage to the ironwork below.
Damaged or displaced frames – this can cause noise, vibration, and potential hazards to vehicles and pedestrians.
Inadequate bearings – this can cause problems with movement or rocking, leading to noise and damage.
Corrosion or rusting – this can lead to weakened ironwork and potential failure, as well as aesthetic issues.
Obstructed or blocked gratings – this can lead to ponding, flooding, and damage to the surrounding area.
Incorrect height adjustment – this can cause issues with drainage and may lead to damage to the surrounding road surface.
Insufficient edge clearance – this can cause issues with vehicle and pedestrian access as well as damage to the surrounding ironwork and road surface.
Inadequate sealing or filling – this can cause problems with drainage, and may lead to further issues with corrosion or rusting.

These defects can lead to hazards, damage to infrastructure, and reduced service life of ironwork components. It is important to regularly inspect and maintain ironwork to ensure safe and efficient use of UK roads.

What’s that defect…. Road drainage systems

The drainage system of a highway should be designed, constructed, and maintained to efficiently and effectively manage water and reduce the risk of flooding. The drainage system should be inspected and maintained regularly to prevent defects and ensure functionality. The drainage system plays a crucial role in ensuring the safe use of the highways network. A failure of the drainage system to provide adequate drainage can lead to flooding on the carriageway or adjacent land, which is a significant safety issue for road users.

Drainage Components

There are numerous components of a drainage system, each with specific functions and potential defects. These include piped drainage systems, gullies, catchpits, grit traps, interceptors, soakaways, manholes, piped grips, grips, ditches, filter drains, narrow filter drains, culverts, vegetative drainage systems for highway runoff, ancillary items, linear drainage systems, road-edge surface water channels, grassed surface water channels, and flooding. Defects in these components can include blockages, silt build-up, erosion, damage, incorrect gradient, insufficient capacity, and more. Proper inspection, maintenance, and operation of these drainage components are necessary to prevent flooding, structural damage, and safety hazards on highways.

Drainage General: This covers the general management of the highway drainage system, including the collection, conveyance, storage, treatment, and disposal of highway runoff. It includes the coordination and integration of various drainage assets and features such as gullies, catchpits, ditches, culverts, and filter drains. The drainage system of a highway should be designed, constructed, and maintained to efficiently and effectively manage water and reduce the risk of flooding. The drainage system should be inspected and maintained regularly to prevent defects and ensure functionality. Symptoms of a poorly functioning drainage system include ponding, flooding, erosion, and pavement cracking. Drainage defects may include blockages, damage to pipes or channels, improper gradient or alignment, and erosion of banks or bed.
Piped drainage systems: This includes underground drainage systems that use pipes to convey surface water runoff to a designated outfall. Piped drainage systems are designed to collect and convey surface water runoff away from the highway. Symptoms of a poorly functioning piped drainage system include blockages, ponding, and flooding. Defects may include damage to pipes or channels, joint failure, and silt or debris buildup. The pipes may be made of various materials such as concrete, plastic, or metal, and may range in size from small diameter pipes to large culverts.
Gullies, catchpits, grit traps, interceptors, soakaways, & manholes: These are various types of drainage features that are used to capture and manage surface water runoff. Gullies and catchpits are used to collect runoff from the road surface, while grit traps and interceptors are used to separate and remove sediment and pollutants. Soakaways are used to dispose of excess runoff, and manholes provide access to the underground drainage system for maintenance purposes. Gullies, catchpits, grit traps, interceptors, soakaways, and manholes are critical components of a drainage system. Symptoms of a poorly functioning gully or catchpit include ponding, flooding, and blockages. Defects may include damage to the cover or frame, silt or debris buildup, and joint failure.
Piped grips: These are small-scale drainage channels or ditches that are used to collect and convey surface water runoff. They are typically lined with concrete or other materials and may be covered with grates or other types of covers. Piped grips are designed to convey water away from the highway. Symptoms of a poorly functioning piped grip include ponding and flooding. Defects may include damage to pipes, joint failure, and silt or debris buildup.
Grips: These are open drainage channels or ditches that are used to collect and convey surface water runoff. Grips are unlined channels designed to convey water away from the highway. They are typically unlined with vegetation but may be lined with other materials. Symptoms of a poorly functioning grip include erosion, sediment buildup, and vegetation growth. Defects may include erosion of banks, sediment buildup, and vegetation growth.
Ditches: These are open drainage channels or ditches that are used to collect and convey surface water runoff. Ditches are lined or unlined channels designed to convey water away from the highway. They are typically lined with vegetation and may be designed to provide additional benefits such as flood storage, erosion control, or water quality improvement. Symptoms of a poorly functioning ditch include erosion, sediment buildup, and vegetation growth. Defects may include erosion of banks, sediment buildup, and vegetation growth.
Filter drains & fin/narrow filter drains: These are subsurface drainage systems that are designed to collect and convey surface water runoff to a designated outfall. Filter drains and fin/narrow filter drains are designed to collect and filter surface water runoff. They are typically made of granular material and may be used in conjunction with a geotextile fabric or other materials to filter out sediment and other pollutants. Symptoms of a poorly functioning filter drain include blockages, ponding, and flooding.
Culverts: Culverts are structures designed to convey surface water runoff under roads, railways, or other features. They may be made of various materials such as concrete, plastic, or metal and may be designed to accommodate different flow rates and capacities. Symptoms of a poorly functioning culvert include ponding, flooding, and erosion. Defects may include damage to the culvert or inlet, blockages, and joint failure.
Vegetative drainage systems for highway runoff: These are natural or constructed systems that are designed to collect, treat, and dispose of surface water runoff. They typically consist of vegetation and soil media that help to capture and filter out pollutants and sediments. Symptoms of a poorly functioning vegetative drainage system include erosion, sediment buildup, and vegetation growth. Defects may include erosion of banks, sediment buildup, and vegetation growth.
Ancillary items: These are various components of the drainage system such as access covers, outfalls, weirs, and other features that are used to manage the flow of surface water runoff. Defects may include damage to the item or foundation, silt or debris buildup, and ironwork failure.
Linear drainage systems: These are drainage systems that are designed to collect and convey surface water runoff along the length of a road or other feature. They typically consist of a channel or slot drain that is installed along the edge of the road surface. Symptoms of a poorly functioning linear drainage system include blockages, ponding, and flooding. Defects may include damage to the channel or inlet, silt or debris buildup, and vegetation growth.
Road-edge surface water channels: These are small-scale drainage channels that are installed along the edge of the road surface to collect and convey surface water runoff. They may be made of various materials such as concrete, plastic, or metal and may be covered with grates or other types of covers. Symptoms of a poorly functioning road-edge surface water channel include ponding, flooding, and erosion. Defects include blockages caused by debris or vegetation, damage to the channel lining, and erosion or settling of the channel bed.
Grassed surface water channels: These are open drainage channels or ditches that are lined with vegetation and are used to collect and convey surface water runoff. They may be designed to provide water quality treatment by allowing vegetation to absorb pollutants and sediment, as well as providing habitat for wildlife. Grassed surface water channels should be inspected regularly for any blockages, erosion or damage to the vegetation lining, and any necessary maintenance work should be carried out promptly to ensure effective operation. In addition, excess vegetation growth should be controlled to prevent blockages and ensure the channel remains clear and free-flowing.

One of the most critical aspects of maintenance are Category 1 defects of the drainage system. Category 1 defects in the drainage system are those that pose an imminent safety risk to road users and require immediate attention and repair. These defects are considered to be the highest priority and should be addressed as soon as possible to ensure the safety of the road network.

Examples of Category 1 defects in the drainage system include:

Blocked gully causing standing water on live carriageway: A blocked gully can result in standing water on the live carriageway, creating a potential hazard for road users, particularly during adverse weather conditions such as heavy rain or snow.
Blocked ditch causing flooding on live carriageway or adjacent land: A blocked ditch can result in flooding on the live carriageway or adjacent land, creating a potential hazard for road users.
Pollution of the drainage system: The presence of hazardous or toxic materials within the drainage system can pose a significant risk to the environment and road users.
Flooding of live carriageway: Flooding of the live carriageway can pose a significant hazard to road users and can be caused by a variety of factors, including blocked gullies or ditches, subsidence, or heavy rainfall.

Symptoms of a poorly functioning drainage system include ponding, flooding, erosion, and pavement cracking. Drainage defects may include blockages, damage to pipes or channels, improper gradient or alignment, and erosion of banks or bed, carriageway flooding, blocked ditches, flooded ditch systems, and pollution of the drainage system.

A blocked gully can cause standing water on the live carriageway, which creates a hazard for drivers and can result in reduced visibility and increased braking distances. A blocked ditch can cause flooding on the live carriageway or adjacent land, which can result in the road being temporarily closed.

Category 2 defects in the drainage system refer to those that are less severe than Category 1 defects and do not pose an imminent safety risk to road users. However, they still require attention and repair within a defined timescale.

Examples of Category 2 defects in the drainage system include:

A partially blocked gully, which does not cause standing water on the live carriageway but may reduce the efficiency of the drainage system.
A minor leak in a pipe or ditch, which does not result in significant flooding but may need repair to prevent further deterioration of the asset.
A small depression in the carriageway caused by subsidence, which does not pose an imminent safety risk but may cause water to pond on the surface and affect the efficiency of the drainage system.
A gully or ditch that is partially clogged with debris, which does not cause significant flooding but may need cleaning to maintain the efficiency of the drainage system.

It is important to note that Category 2 defects should still be monitored and repaired in a timely manner to prevent them from becoming Category 1 defects, which can pose an imminent safety risk to road users. Highways agencies are responsible for ensuring that Category 2 defects are repaired within a defined timescale and that the drainage system is functioning effectively.

Pollution Risks to the Drainage System

The pollution of the drainage system can also have serious consequences for the safe use of the highways network. Polluted water can contain toxic chemicals or oil spills, which can be harmful to the environment and can cause a slippery surface on the carriageway, creating a hazard for drivers. Pollution of the drainage system is a serious issue that can have far-reaching consequences for the environment and road users. The pollution of the drainage system can occur from a variety of sources, including trade or industrial waste, hazardous materials, and the dumping of controlled materials. In the event of an incident associated with trade or industrial waste, hazardous materials, or any visible warning signs or chemical symbols displayed on the trade or industrial vehicles involved, it is essential that immediate action is taken to contain and clean up the spill.

Additional consideration should be given to oil or diesel spillages, which can pose a significant risk to the environment and road users. In such cases, it is important to determine whether the pollution observed causes a localised or more extensive network issue. Controlled materials, such as oil and paint drums, organic waste, sharps materials, and refrigerators/freezers, can also contribute to the pollution of the drainage system.

It is crucial to be vigilant in monitoring and preventing the pollution of the drainage system. Regular inspections and prompt action in the event of a spill can help minimize the impact of the pollution on the environment and road users. By taking proactive measures, highways agencies can help ensure the continued safe and efficient functioning of the drainage system.

The maintenance and successful resolution of defects of the drainage system are critical to the safe use of the highways network during winter weather conditions. Service codes outline the maintenance requirements to prevent the occurrence of these defects and ensure that the highways network is safe to use during winter weather conditions. It is important for highways agencies to regularly inspect and maintain the drainage system to prevent the occurrence of these category 1 defects, which can result in the failure of the asset to provide adequate drainage and cause imminent flooding of the carriageway or adjacent land.

Inspection of the Drainage System

Inspecting a drainage system is an important part of ensuring that it is in good working order and that maintenance is being properly carried out. Here are some steps that could be taken to inspect a drainage system:

Check drainage records: Start by checking the records for the drainage system. These records should include the location of the drainage system, its design and construction, and any maintenance or repairs that have been carried out.
Visual inspection: Carry out a visual inspection of the drainage system. Look for any signs of damage, such as cracks or breaks in the pipes, or evidence of blockages, such as standing water or debris in the drainage channels.
Check inlets and outlets: Check that the inlets and outlets of the drainage system are clear and not blocked. Ensure that the inlets are properly connected to the road surface and that there is no evidence of erosion around the outlets.
Test the flow rate: Carry out a flow rate test to check that the drainage system is capable of coping with the amount of water it is designed to handle. This can be done by pouring a known amount of water into the inlet and measuring the time it takes for the water to flow through the system.
Check the surrounding area: Inspect the surrounding area to ensure that there are no signs of flooding or other water damage. Check that any adjacent land is not being affected by the drainage system.
Document your findings: Document your findings from the inspection and use this information to inform any necessary maintenance or repair work.

Regular inspections of the drainage system can help to ensure that it is in good working order and that any necessary maintenance is carried out in a timely manner. By taking a proactive approach to maintenance, potential issues can be identified and addressed before they become more serious problems.

What’s that defect…. Blocked or Collapsed Culvert Assets

Blocked or collapsed culverts can cause significant safety issues for road users and adjacent land. A culvert is a drainage structure that allows water to pass beneath a roadway, and when it becomes blocked or collapses, it can cause flooding on the live carriageway or adjacent land. This can create a hazardous conditions for road users, making the road surface slippery and potentially causing vehicles to skid or aquaplane. It can also damage the road surface, and the surrounding environment, resulting in costly repairs and potentially long-term disruptions and further maintenance issues.

In addition to the safety risks posed to road users, blocked or collapsed culverts can also pose a risk of imminent failure of the carriageway or embankment above the culvert. This can cause serious structural damage to the roadway, leading to significant repair costs and potential closures.

Highways maintainers in the UK are responsible for identifying and repairing blocked or collapsed culverts as part of their maintenance duties. They use various techniques, including unblocking or clearing debris, repairing or replacing damaged sections, and performing regular inspections to ensure the culverts remain in good condition. By proactively addressing these issues, highways maintainers can help prevent accidents and damage to the road surface and surrounding environment, promoting the safety and functionality of the road network.

To mitigate the risk of blocked or collapsed culverts causing safety issues and damage to roadways, it is essential for maintainers to identify and repair these defects promptly. This involves inspecting culverts regularly and cleaning them when necessary, as well as repairing any damage or defects that are found. By doing so, maintainers can help to ensure the safety of road users and prevent costly structural damage to the roadway.

Some of the defects that can occur outside of vegetative and material blockages are;

Concrete culverts: cracking, spalling, delamination, corrosion of reinforcing steel, erosion of concrete, leaks, and joint separation.
Brick arch culverts: cracks in the bricks, sagging or bowing of the arch, voids or cavities in the brickwork, crumbling mortar joints, and erosion of the foundation.
Plastic culverts: deformation, buckling, cracking, splitting, joint separation, abrasion, and crushing.

It’s worth noting that the specific defects that can occur in each type of culvert will depend on factors such as the age and condition of the culvert, the material it’s made from, and the environmental conditions it’s exposed to.

Inspecting culvert assets is an important part of ensuring that they are in good working order and condition. Here are some steps that could be taken to inspect culvert assets:

Conduct a visual inspection: Start by conducting a visual inspection of the culvert. Look for any signs of damage, such as cracks, corrosion, or deformation in the structure, and ensure that there are no signs of wear and tear that could compromise the culvert’s structural integrity.
Check the inlets and outlets: Check that the inlets and outlets of the culvert are clear and not blocked. Ensure that the inlets are properly connected to the road surface, and that there is no evidence of erosion around the outlets.
Check the surrounding area: Inspect the surrounding area to ensure that there are no signs of flooding or other water damage. Check that any adjacent land is not being affected by the culvert, and that there are no signs of soil erosion or instability.
Test the flow rate: Carry out a flow rate test to check that the culvert is capable of coping with the amount of water it is designed to handle. This can be done by pouring a known amount of water into the inlet and measuring the time it takes for the water to flow through the culvert.
Check for debris or blockages: Look for any signs of debris or blockages within the culvert, such as sediment or leaves. This can be done by using a camera or other specialized equipment to inspect the interior of the culvert.
Document your findings: Document your findings from the inspection and use this information to inform any necessary maintenance or repair work.

Regular inspections of culvert assets can help to ensure that they are in good working order and that any necessary maintenance is carried out in a timely manner. By taking a proactive approach to maintenance, potential issues can be identified and addressed before they become more serious problems.

What’s that defect?

There is a central body responsible for the operation, maintenance and improvement of roads. In England it is Highways England who has an obligation to provide safe roads and reliable journeys for the road user, Scottish roads are managed by Transport Scotland, Welsh roads by the Welsh Assembly, local roads by the relevant local authority and roads in London by TfL (Transport for London).

In the English instance Highways England are responsible for the motorways and major trunk roads which totals around 4,300 miles (about 2% of all roads in England by length). Whilst only a small number the roads carry a third of all traffic by milage and two thrids of all heavy good traffic.

Under the Highways (Miscellaneous Provisions) Act 1961, highway authorities have an obligation to maintain public highways to reasonable standards and this is done with the help of a document which is used by the maintainers called the Routine and Winter Service Code (RWSC). This RWSC identifies the Category of the defect, the duration of any hazard mitigation and the permanent repair period duration for the contractual timeframe.

The definition of a Cat 1 defect as defined in the RWSC is;

Defects are those that require prompt attention because there is an immediate or imminent safety risk
Significant disruption to the normal flow of traffic through the Network
Structural deterioration
Damage to the environment
Offence to road users from graffiti that is obscene, blasphemous or otherwise offensive

Pothole – a loss of carriageway surface material resulting in a void being formed

Sign damage preventing function of direction signage

The definition of a Cat 2 defects as defined in the RWSC are sub-divided into two categories;

Category 2.1 – Not superficial
Category 2.2 – Superficial (i.e. does not change the characteristic or function of the asset/item)

Cat 2.1 – Not superficial

Cat 2.2 – Superficial

To keep it interesting we can look at Cat 1 defects which need us to make safe, permanent repairs within a contractual time frame and defects that, due to their nature and/or location, require intervention from an Incident Support Unit (ISU) within the contractual response times. This will all vary depending upon time of day and location and can either be dealt with immediately by a Network Maintenance Crew, an ISU or where it requires a more expansive response; such as lane closures or traffic management to protect the road user whilst hazard mitigation works take place.

Initially Cat 1 defects can be dealt with in 2 different ways: reactive or proactive, and with everything else the second respective is always better.

Reactive maintenance – Cat 1 defects identified by an external third party source…Police, Highways England Traffic Officers, Local Authorities or occasionally even direct via the public.

Proactive maintenance – Cat 1 defects identified by the Incident Support Units, depot based operatives, office based staff or Inspection teams driving the Network.

In addition to those defects listed in the bulleted points above we can look at defects as examples going forward and what constitutes a Category 1 defect. As always the caveat within the RWSC is that any list should not be regarded as exhaustive, because ultimately a defect can appear at anytime with anything on any Network, this ultimately just makes life that little bit more interesting and challenging.

To get a full idea of what to look for under Cat 1 defects (and in no particular order) I am going to ask around for examples from my contacts and look at the following over the coming months;

Potholes and other local defects in the carriageway/footway/cycle track, including defective ironwork
Excessive standing water and water discharging on to and/or flowing across the road
Damaged road restraint systems and other barriers
Debris and spillage in traffic lanes or on hardshoulders
Kerbing, edging and channel defects
Damaged lighting columns and other street furniture
Damaged, defective, displaced or missing traffic signs or signals
Dirty or otherwise obscure traffic signs and signals
Trees, shrubs and hedges which by virtue of their position or condition constitute hazard to road users and the travelling general public
Displaced roadstuds (particularly the cast “Catseye” type) lying in the carriageway, hardshoulder or laybys
Defective, missing or loose roadstuds
Faults in road structures e.g. impact damage to superstructures, supports or parapets, flood damage, insecure expansion joints
Damage and defects in structures carrying water beneath the roads
Difference in level (exceeding 20mm) between abutting concrete slabs at transverse or longitudinal joints in the carriageway/footway/cycle track
Rocking gratings or covers in urban areas causing intrusive noise
Damaged boundary fences where animals or children could gain access
Defective road and sign lighting
Overhead wires in a dangerous condition
Blocked gully and piped grip gratings and obstructed channels, grips and slot drains
Earthslips where debris has encroached or is likely to encroach on to the road
Rocks or rock faces constituting a hazard to road users.

What’s that defect… Potholes

Keeping our roadways in good condition is a challenging problem due to harsh weather, unexpected traffic load, accident damage, changes in wheel load locations and normal wear and tear. All these factors degrade even new roads over relatively short periods of time.

Pre-start – Day 0

Post switch – Day 17

Failure – Day 31

Repair – Day 32

As cost constraints and maintenance budgets tighten under the current austerity measures determining which roads need ﬁxing becomes important process and with the introduction of the new Smart Motorway Systems throughout the country trafficking of the joints in the pavement is becoming more prevalent and giving rise to a greater number of failures on the network.

A pothole is a structural failure in the road surface where there is a loss of carriageway surface material resulting in a void being formed, and/or, a void in the carriageway surface layer that requires prompt attention because there is either a significant safety risk to the travelling public or major disruption to the normal flow of traffic. They need two things to form. Water and traffic, something which we have plenty of. The depression itself penetrates all the way through the surface course down to the base course and is the result of moisture infiltration and usually the end result of untreated crazing. As crazing becomes severe, the interconnected cracks create small chunks of pavement, which can be dislodged as vehicles drive over them. The remaining hole after the pavement chunk is dislodged is called a pothole.

There is no formal definition for a pothole recognised nationally. A pothole for this instance has been defined as a sharp edged depression anywhere in the carriageway where part or all of the surface layers have been removed and is identified when its maximum horizontal dimension is greater than 300mm and is 40mm+ in depth:

The following are for guidance only as smaller voids in more heavily trafficked areas may also be Cat 1 defects from my experience of Maintenance;

Voids with dimensions of 40-50mm in depth and 300mm in any direction should be considered a Cat 1 defect with a 24 hour response.
Voids greater than 50mm in depth and greater than 300mm in any direction should be considered a Cat 1 defect with emergency response and requires immediate attention

Pothole – Wheel Track Failure

Pothole – Manhole surround failure

Pothole – Plated manhole surfaced over

Designing a road…

I’ve not long finished putting a road through planning and I was asked what and how it all comes about. How you justify it, and what is entailed in actually deciding the route and designing it…

When you identify a route to be improved it normally comes about because there are problems with the existing stretch of road. This may be linked to congestion relief, unreliable journey times, a poor safety record or the need for useful access improvements.

The need for improvement will be justified through economic analysis. These economics will normally be analysed by looking at local factors such as the traffic figures. Interrogation of these figures will give traffic predictions and allow models to be produced based on observed numbers (traffic counts, mobile data ect…) by the traffic engineers. The traffic models generated through bespoke software predict various scenarios when looking at suggested improvement schemes. Once the need and the appropriate traffic models have been finalised work can then start on the proposed route.

Proposing a route is carried out by studying the terrain through which the road is to pass and identifying constraints on any route selected. There will be things like buildings, road crossings, rivers, canals, railways, airfields, areas of special landscape or environmental interest, archaeology, strategic utility infrastructure, type of soils or underlying geology etc., all of which will impact in some way on the proposed route under review.

A factor when making any selection of a route will be to recognise the type of road that will be required. For instance will it be single carriageway, dual carriageway, motorway standard. Will it need to change in character along the route? All these decisions are determined by the traffic demands and traffic models. It is logical that a road carrying more traffic will require more lanes and a greater capacity to enable it to flow freely. These matters are all covered by standards.

It then is a matter of making an assessment of the most appropriate routes through/over/under/around the constraints, or, if possible, incorporating some measure to accommodate the constraint within the design by some special feature, i.e. tunnel, bridge, culvert, creation of alternative habitat, etc.

The route selected will have to comply with the standards for minimum curvature required for the type of road required. These are all pre-determined in standards and recognise the type of road and the anticipated speed. This is required for both the horizontal and vertical alignment of the road.

Where there is a need to link back into existing highway networks, junctions will be required. Again, the type of junction will be driven by the traffic demands. There are standards that apply to the type of junction appropriate for the traffic flow and the resulting geometry standards associated with the junction choice. There will be the need to look at the roads crossing the route and decisions made to assess whether to link the road with a junction, take it across the road, but not directly connected, or stop it up altogether.

An important factor in highway construction is the amount and position of where “muck” has to be excavated and transported. This is determined by designing the road’s vertical alignment. It is desirable to obtain a “earthworks balance” for the highway. That is to say, all the material excavated in cutting will have somewhere for it to be placed on a part of the highway on embankment so that no material will need to be imported or taken off site. This assists in the economics of a scheme as “muck shift” is a large portion of the overall cost.

If a number of options for a route are found from the above exercise, these can be tested and compared.

The assessment of alternative routes will be made by comparing each option in turn against a number of factors. These will include things like;

Resulting geometrical layout
Overall affect on traffic in the long term
Economics and benefits
Affect on drivers and whether the layout is complicated
Affect on Non-Motorised Users – footpaths, bridleways, cycle paths
Affect on the local traffic whilst being constructed
Complexity of the construction activities and the impact on the surrounding people
Amount of land required
Affect on property – any buildings require demolition?
Environmental impact and affect on important ecological areas
Affect on Statutory undertakers and possible impacts of diversions
Type and suitability of the terrain – geotechnical considerations

Having made a preferred selection using the process above, the option can then be designed in sufficient detail so that the land required to construct the scheme can be identified.

It is at this point that, subject to on-going public consultation, the scheme could be taken through the planning process. The resulting acceptance (or otherwise) of this process, the scheme would be taken forward to detailed design and construction. At this point the scheme will only be changed in matters of detail brought about by detailed design. The overall layout and scope of the scheme would be unchanged.

makes roads safe and useful
makes roads understandable
fits in context and is restrained
is environmentally sustainable
is long-lasting

Quality Management and Avoiding Common Defects – Seasonal working with concrete

Winter working

Two different temperatures have to be considered when working with concrete in cold weather, firstly the ambient air temperature and secondly the concrete temperature at time of delivery. The definition of cold weather is a period during the day or night when the ambient air temperature will fall below 2°C. The BS and EN standard states that the temperature of the concrete should not fall below 5°C until the concrete achieves a strength of 2 N/mm² and that the temperature of fresh concrete shall not be less than 5°C at the time of delivery.

Therefore general good practice is to only place concrete when the ambient air temperature is 2°C and rising. However, following best practice and through early engagement with the supply chain, concrete could be placed down to 0°C with not unforeseeable risk.

Ensure batching facilities have heated water and heated aggregate bins.
Review sequence, logistics, materials and methodologies to ensure best practice is followed.
Remove frost from rebar and formwork before pouring.
Monitor the concrete temperature as it arrives on site. Reject any that is below 5°C.
Temperature must be 2°C and rising (sometimes 4°C and rising, check specification).
Apply frost blankets quickly at the end of the pour; avoid thermal shock when removing.
Concrete will be frost damaged unless 2 N/mm² or stronger.
Measure the temperature gradient for large pours; thermal gradient control (insulated shutters, quilts etc.) must be designed to control the thermal gradient.
Concrete will ‘go off’ slower. Allow more time for slabs and beams to cure, and measure strength before striking.
In wall pours control the rate of rise to keep shutter pressures as designed. Masonry and Render.
Temperature must be 2°C and rising (sometimes 4°C and rising, check specification).
Provide frost protection for minimum 24hrs.
Avoid retarded mortar.
Special admixtures can be used to accelerate the set.
For rendered elevations, ensure the cement particle board, insulation and render are applied in quick succession; the CPB and insulation will deteriorate in a day or less if exposed to bad weather.
Maintain moisture in wet mortar.
Cover completed work with polythene to avoid desiccation.

Summer working

Again with concrete pours that take place in warm weather the same two different temperatures need to be considered, the ambient air temperature and the concrete temperature at time of delivery. Ambient temperatures up to about 20°C should not on their own cause significant problems, especially in damp or humid conditions but when the ambient temperatures of 20°C and above are in partnership to low humidity and drying winds consideration of a more efficient curing regime is needed.

The target temperature of concrete on delivery from the chute should not be more than 30°C.

Make appropriate modifications to concrete mixtures to manage rate of slup loss, setting time and other characteristics. Retarders, extended set control admixtures, synthetic fibers or other proven local solutions may be helpful.
The consistence of the material is affected. The slump/flow/slump flow of concrete reduces more rapidly. If there is water added to improve the consistence it decreases the concretes compressive strength, potentially increases permeability and ultimately affects the durability of the structure.
The hot weather will accelerate the loss of moisture from the surface and therefore increase the risk of plastic shrinkage cracking. Consideration of some form of protection is needed. If using hessian and water, you will need to rewet the hessian frequently (up to four times per hour) to ensure that it is effective.
On hot or dry days when the conditions are conducive to plastic shrinkage consider dampening the sub-grade, pans and forms and reinforcement prior to pouring concrete, do not allow water to pond however during and after this process.
Check the weather forecast to pick the best time to pour. Consider starting large pours at 6am or earlier avoiding working during the hottest part of the day, often between noon and mid-afternoon.
As the concrete temperatures increase the setting time reduces and impacts the time to place, compact and finish the concrete. Consideration of more labour is needed to achieve the work and schedule the rate of concrete delivery to avoid overloading the labour and/or equipment.
Consideration of how to maintain the labour in hot conditions. On a hot day you need to have access to drinking water at all times to avoid exhaustion during manual work. Also, sunscreen should be applied before starting the pour.
Keeping equipment out of direct sunlight until it is required to lay the concrete is a small but effective measure. This will stop the equipment from heating the concrete while it is being poured.
Concrete will go off quicker. Begin final finishing operations as soon as the water sheen has left the surface. Apply curing measures immediately on finishing an area; on a large slab this will be while pouring is still in progress in other areas.
In large elements or rich mixes faster hydration of cementitious materials down to high ambient temperatures can result in higher maximum concrete temperatures and thermal cracking.
Changes in temperature of the concrete may also result in cracking particularly where concrete is placed on a hot day followed by a cool night.
With the increased rate of hydration the surface of the concrete will dry quicker which leads to premature finish being applied, trapping of bleed water and possible debonding of the top surface with subsequent flaking/de-lamination
Delays in transport should be minimised although in numerous cases this is a difficult task.

None the less when it comes to planning any pour with any amount of concrete you will need the knowledge and advice of an expert. Whether that is you, a contractor or your concrete supplier depends on your project, what you are doing and how much risk it entails. To avoid pouring concrete incorrectly careful consideration and forethought is a must.

Quality Management and Avoiding Common Defects – Pre-work considerations for in-situ reinforced concrete

In-situ reinforced concrete is expensive. Prior to starting there are some key checks, areas to set up, materials and pre-work processes to be considered but foremost to avoid any quality issues on site we should ask, “Has pre-cast concrete been considered as alternative?“.

Despite this we can’t always go with the factory controlled alternative so pre-start and pre-work considerations are essential here I list a few that I consider;

Ensure a complete specification for the site has been received addressing strength and durability; ensure mix designs have the correct cement type, water/cement ratios, work-ability. Its also important to check that all mix designs have been approved by structural engineer, materials engineer and designer, before works commence. Test the mix… if not then you’re not ready.

Ensure an adequate clean storage area is available before reinforcement is delivered. Rebar can get dirty, bent, lost and damaged from poor storage…

Poor Rebar Storage — Dirty, damaged and bent from passing traffic and mud splatter makes expensive delays from reordering or cleaning prior to concrete or fixing

Ensure that the cement type and delivered concrete temperature have been considered in the shutter design and the rate of pour. – We can look at winter working and summer working in more detail later but all these things factor into a successful defect free pour.
Have the number of mix designs been kept to a minimum? Its all well that you have multiple options and are they clearly named as more than once a wrong mix has gone into a pour only to have it broken out at a later date when you discover that the blinding mix is in a column.
Is testing equipment on site and operational and has the Lab been certified and checked? Do you have a cube tank and is that heated and operational?

Concrete cube testing to determine the strength of concrete.

If you have not carried out a plant inspection then it is well worth doing so as seeing the set up, location, routes to site and facilities is vitally important.

Right set up for the job… go and look and check it out before you start. Remember if you have not carried out a plant inspection then it is well worth doing so as seeing the set up and facilities is vitally important and the purchaser assumes the responsibility for ensuring technical correctness
Plan large pours meticulously and early with concrete suppliers, your onsite batching facility, plant suppliers and subcontractors, etc. Be aware of the time between placing fresh concrete on already placed fresh concrete, taking into consideration heat developing in the concrete during curing. as the last thing that is needed is a defect.

Pour Planning... — Delays between deliveries, breakdowns and a lack of contingency can result in real quality issues.

Make sure that your method statements take into account precautions to protect against cold/hot weather, rain and drying wind and ensure the operatives and supervisors are aware of what needs to be done to protect the work.

This isn’t an exhaustive list and nothing can prepare you more than knowledge, experience and planning and just one last thing if that wasn’t enough… it is also important to note that it is the purchaser that assumes the responsibility for technical correctness of the concrete specification.

Quality Management and Avoiding the Common (and less common) Defects

Dip visible in NW kerb line — Structures settlement and the after effects on kerbs and surfacing can also affect the bridge joints, making this an expensive fix for the contractor if he has not managed to sew up the earthworks package and does not have supporting quality compaction records.

Poor quality in the construction industry is one of the most common issues that results in lost time and additional costs to a contract. Year on year it costs contractors millions of pounds, damages relationships with Clients, places additional pressures on Site Teams attempting to complete a contract or results in further intervention from Designers through lengthy reports. The implication of finding such workmanship issues can be carefully navigated through controls and an understanding of what is required and what is expected from the specification/design prior to putting people to work. As with most things any defects in construction require re-work to correct the problem and the longer defects remain uncorrected, the more rework we are likely to encounter and the more rework there is likely to be involved. Ensuring that the work force and supervision have the right skills and knowledge, right tools and materials and, following completion, the right protection will all help prevent this from happening.

In the next series of posts I have decided to look at specific issues with different activities and to compile a list of checks that can be undertaken by the Engineer or Supervisor, with some examples, to help check and ensure that we are identifying the major and sometimes minor details that people miss when planning or executing an activity. As suggested earlier defects can be avoided by sufficient planning and adequate monitoring. Allowing enough time for the work to be done properly and in the correct sequence is always particularly important.

Excessive distance to the top step from finished level (maximum 675mm)

Poor control with cutting joints damaging permanent mesh on a parapet rail

Structures settlement to the parapet due to poor compaction

The first at avoiding common defects will look at one of the most common and versatile construction materials used in civil engineering – reinforced concrete. Following on from that I will go through various other trades and activities which include;

Formwork
Falsework and Temporary Works
Pre-concrete Checks
Concrete Checks
Earthworks Planning, Bulk Cut/Fill Operations and Finishes
Drainage Planning, Pipelaying and Chambers
Roadworks – Type 1 Sub-base
Roadworks – Kerbs and Finishes
Surfacing
Sheet and Bearing Piles
Setting Out Checks
Landscaping
Safety Fencing
Signs
Temporary Works
Bridge Bearings

Whilst we review the checks that we should look in the coming weeks there are some simple first steps that can be implemented to ensure the right ethos is achieved with the team to achieve good planning, good leadership and a culture that promotes good quality.

Ensure everyone knows and understands the contractual project requirements and specifications from the designer and the client or clients representative. No client wants a bad job.
Always read the label – People should be encouraged to refer to British Standards, European Standards and Trade or Manufacturer literature. Instructions are there for a reason, if you don’t follow them it will not go well.
Learn to recognise what good looks like. If it doesn’t look right, it probably isn’t and don’t be afraid to stop the work if anything looks wrong. Allowing it to continue could cost more money.
Make sure that everyone is qualified, competent and capable for the activity that you are planning to execute. Hiring a bricklayer when you need a joiner will never work. You should never assume specialist trades know what acceptable quality is, just because they come in a van with a logo on it does not mean they know what they are doing.
Don’t assume a manufactured product is correct, always check what you pay for. Quality is still an issue in a factory, even where quality controls are stricter.
Follow the Inspection and Test Plan set out by the Quality Team and Quality Manager, get involved with its production and complete quality inspection records as the work progresses. Quality can be as onerous as you like and sometimes those with the most letters after their name don’t always realise the workload they are enforcing on people.
Ensure everyone understands the activity, the sequence and what is expected and always take photographs of the works as they progress and get sign off from those accountable or executing the work.

vlcsnap-2011-08-31-19h22m38s214 — The Hidden Cost – Pipe damage – Early CCTV can avoid the need to excavate drainage well after installation, reducing costs and identifying defects early.

Making sure that we have enough competent supervision for the normal working week is essential before we move to increase working time to either weekend and/or night work as these are times when defects occur most frequently. We should also scrutinise our reliance on our supply chain and their ability to supervise and correct defects in the manor that we require, from painful experience there will always be a percentage that will not return to undertake the work so early intervention is essential.

Effectively its down to you to ensure that you are right first time because if you think quality is expensive…try building it twice.