About road construction and maintenance
Twelve areas to manage:
1 Earthworks
2 Storing materials
3 Bitumen spraying
4 Asphalt laying
5 Pavement patching and repair
6 Concreting
7 Maintaining unsealed roads
8 Bridge maintenance
9 Road line marking and removal
10 Saw cutting
11 Drain and sump cleaning
12 Street cleaning
Case studies
Legislation

About road construction and maintenance

Local government is responsible for the construction and maintenance of many roads and related infrastructure such as bridges, footpaths and stormwater channels. Councils are often involved in maintenance activities such as patching, regrading and street sweeping.

Councils must keep existing roads to a standard acceptable to the community, while in outer urban and growing regional areas they must provide new infrastructure to meet the demands of developing areas.

The following twelve issues cover many aspects of stormwater management for depots. Some of the suggested techniques are for everyday use and some relate more to the need for council planning.

1 Earthworks

• carefully select road routes to avoid sensitive areas, minimise cut and fill etc
• limit the area of land disturbance and avoid disturbance near watercourses, drainage lines and sensitive areas
• consult the council's services plan before beginning work, to avoid damage to services, burst water mains etc
• determine if acid sulphate soils are present and, if they are, develop a management plan to deal with this
• control erosion, e.g. diverting runoff from the site, keeping sediments on-site
• stabilise disturbed areas immediately after final grading has been done
• develop a schedule and implement an inspection and maintenance program
• develop an erosion and sediment control plan (see below).

Erosion and sediment control plan

2 Storing materials

Stockpiles of materials used in road construction and maintenance activities such as sand and gravel, can contribute to stormwater pollution if rain or other water passes through or over them. Many other materials - petroleum products, sealants and paints etc - have the potential to impact on stormwater if they are not correctly stored on site.

To minimise these problems:

• locate stockpiles away from waterways, roads, slopes steeper than 10%, and areas of concentrated water flow.
• prevent runoff from washing through storage areas by locating stockpiles high on the site or diverting runoff around the site or the stockpile areas
• place sediment controls or bunding down the slope from stockpiles and provide weatherproof covering
• stabilise topsoil that is to be stockpiled for extended periods
• store potentially harmful chemicals in safe, secure, on-site storage facilities and in accordance with current regulations.

3 Bitumen spraying

Bitumen spraying is commonly undertaken in order to provide a surface on road pavements and/or as a waterproof membrane between an asphalt surface and the road. This involves spraying a liquid asphalt binder (asphaltic cement derived from the distillation of crude oil that has been thinned to a liquid state).

If it rains before the bitumen can cure, liquid bitumen can get into the drainage system and have an impact of waterways. It can also enter waterways due to excessive application rates, over-spraying, spills, and cleaning of equipment.

During the process of chip-sealing (a method for sufacing roads), the binder is generally combined with an aggregate. The aggregate used in the operation also has the potential to wash into drains.

There are many things you can do to deal with these problems:

• select appropriate sealing material for site conditions such as traffic volume, temperature, gradient, shade and humidity
• use bitumen emulsion where possible (see Case study: Bitumen emulsion vs cutback bitumen)
• try to time spraying so it does not coincide with rainfall during or immediately after sealing
• install sand bags or 'sand sausages' next to stormwater inlets which receive drainage from the site
• ensure correct bitumen application and spray rates to avoid overspraying and waste
• start rolling only after sufficient curing, to prevent pickup of bitumen on the roller tyres
• ensure the pre-coating on aggregate has cured before placing it on the road
• sweep up loose materials from gutters immediately on finishing, and routinely as required
• remove all waste and debris from the site
• clean all equipment at a stockpile site or other safe site, ie one which is least environmentally sensitive
• collect spoil from the uncovering of hydrants and manholes and dispose of it correctly
• ensure soiled tar paper and pavement marker covers are collected and disposed of correctly
• ensure that trucks carrying liquid asphalt, particularly hydrocarbon-thinned materials, carry absorbent spill kits.

4 Asphalt laying

Asphaltic concrete is commonly used as a surface on main roads and pavements that need a smooth finish.

When used as pavement it is generally heated and mixed with aggregate off-site before being transported in a heated state to the site. The material is then deposited in layers using special machinery and compacted before curing into a solid mass.

This has the potential to impact on stormwater if runoff occurs before curing, if compacting is inadequate, or if substances such as kerosene are used for cleaning tools and machinery.

To deal with these problems you can:

• select appropriate sealing material for site conditions - traffic volume, temperature, gradient, shade, humidity etc
• try to time the laying so it does not coincide with rainfall during or immediately after sealing
• install sand bags or sand sausages next to stormwater inlets which receive drainage from the site
• sweep up loose metal from gutters immediately following the laying and routinely as required
• remove all waste and debris from the site
• clean all equipment at stockpile sites or other safe sites.

5 Pavement patching and repair

Faults in the pavement, e.g. potholes and breaking edges, may be a source of sediments that can wash out during rain. Pavement patching principally involves patching a spot with a new surface, or replacing the sub-grade before resurfacing. Repairing pavements can contaminate stormwater with sediments if waste is not properly disposed of, compacting is inadequate, or runoff occurs before curing.

Sometimes reshaping and stabilisation is needed, requiring the mixing of cement and lime before moistening, compacting and replacing the surface. This lime and cement can wash off and enter waterways.

Before patching, it is necessary to do investigation work, using an auger (boring tool) or digging test pits. This can contribute sediments to stormwater if waste is not properly disposed of, test pits are left exposed to rain, or if water mains are hit when using an auger.

To deal with these problems you can:

• monitor roads for potholes and fix them promptly
• do a pavement investigation to identify exactly how much work is needed and how best to do it; after the investigation, replace and compact soil into any auger holes and test pits, and seal them the same day
• when stabilising, mix materials during periods of dry weather and little wind, and seal as soon as possible after dressing
• fill and compact soil, gravel and asphalt in layers
• reuse spoil in repairs; otherwise sweep it up
• eliminate 'edge break' by fully sealing road shoulders
• dispose of used soil samples and excess spoil at a suitable fill site
• use suitable facilities for washing tools, plant etc.

6 Concreting

Concrete residues and wastes can enter waterways in many ways: runoff and water from washing concrete-delivery trucks, on-site mixing, washing tools, and hosing or acid cleaning concrete surfaces, such as exposed aggregate.

To minimise these problems:

• avoid mixing or pumping concrete in areas where excess material could enter the drainage system, or else install containment measures
• have waste concrete taken back to the supplier for reuse
• ensure that concrete residue from washing concrete truck shutes and pumping equipment is either diverted to the area that is being concreted, or deposited in a contained area on site and allowed to set before disposal
• wash tools in the area that is being concreted, or contain washing water in a drum for safe disposal later
• when hosing down concreted areas, e.g. exposed aggregate, use minimal water and allow sediments to settle in an area made with sand bags or sand sausages. For larger jobs a sandbag dam may be needed.

7 Maintaining unsealed roads

Maintaining unsealed roads involves grading, patching and re-sheeting of dirt or gravel. Each of these activities can affect the stormwater system through erosion and flow of sediments. Unsealed road shoulders are a similar source of sediments.

Reducing the potential for erosion is the key to minimising the impact on the environment from unsealed roads. Proper methods of grading, the selection of suitable materials, and good compaction are the key ways to achieve this. Also you can:

• make busy roads a priority for sealing
• avoid grading when the road is extremely dry
• use compacting equipment when grading
• use road materials that bind easily together to minimise sediment runoff
• for road verges, make sure the fill materials are suitably cohesive and thoroughly compacted, and stabilise the surface with techniques such as spraying bitumen emulsion
• maintain a structurally sound surface while providing adequate crown and drainage so that erosion or scattering of gravel is avoided
• implement soil erosion controls where necessary.

8 Bridge maintenance

Bridges that are situated or designed incorrectly may lead to increased erosion of channels and stream banks, and destruction of important aquatic habitats. Maintenance materials - such as paints, solvents, and timber preservatives - can have an impact on stormwater if they enter waterways by runoff or wind drift.

To deal with these problems you can:

• at the design stage, assess maintenance requirements and their possible impact
• do works such as sandblasting and timber treatment off-site, if possible
• when cleaning bridges use suspended nets, tarpaulins, a vacuum or booms in water to capture paint, rust and other chemicals
• avoid spraying chemicals in windy conditions
• paint surfaces regularly, so there is less old paint to remove
• use materials that require minimal maintenance, e.g. galvanised or aluminium rails, resistant hardwood timbers.

9 Road line marking and removal

Line marking is done on new as well as existing roads. Generally it involves applying either paint or thermoplastic material to the road surface by machine or by hand. Line marking can have an impact on stormwater if the site isn't cleaned properly or marking is done in the rain.

Line removal generally involves techniques such as grinding and sandblasting, resulting in residue which can be washed or blown into nearby waters.

To minimise this impact you can:

• use water-based paints or thermoplastics rather than solvent-based ones
• avoid using materials while the pavement is wet, during humid conditions, or if rain is likely
• avoid applying thermoplastics at low temperatures, i.e. below 13°C.
• use a portable drip tray under plant to catch spills when possible
• use a skirt around the blaster to minimise the spraying of material away from the work site
• coordinate street-sweeping with line removal, so that waste material is picked up before it can be transported by rain, wind and traffic.

10 Saw cutting

Saw cutting of concrete, bitumen and brickwork is periodically done by councils or their contractors as part of pavement repair, concreting, bricklaying, and footpath repair or placement. The grinding process produces a fine particle residue that combines with the cooling water to produce a slurry which typically ends up in the stormwater system.

To minimise the impact of saw cutting:

• use as little cooling water as possible; switch the water off when the saw is not in use
• prevent cooling water from flowing across exposed soil or other pollutants
• confine waste water to an infiltration trench or collect it for disposal off-site
• where a stormwater inlet is next to the work area, that drain should be blocked completely and controls put in place between the worksite and the next stormwater inlet
• use sand bags or sand sausages to slow the flow of water and allow sediments to settle; for larger jobs a sandbag dam may be needed
• where sandbags are used, ensure there is enough capacity for materials to settle before treatment, disposal or reuse
• at the end of a job, collect sediment and liquid from behind sandbags and within the gutter and dispose of it where the material will not wash into waters.

11 Drain and sump cleaning

This includes the inspection, cleaning and repair of open and piped drains, sumps, treatment devices and outfall structures.

Inappropriate cleaning practices can affect stormwater if materials are transported downstream. Cleaning sumps and piped drains can put pollutants into the water system. If pollutant traps are not maintained frequently they lose their effectiveness.

The cleaning of open drains can have a similar impact, as well as erosion from disturbing the banks and bed of the drain.

To reduce these problems you can:

• monitor how waste accumulates in each part of the system and develop a routine cleaning program
• use appropriate silt controls
• ensure there are no hazardous chemicals put into drains
• clean only the part of the drain that needs it, and if possible, leave existing vegetation intact to act as natural filter
• remove all materials from sumps, and use a sucker broom where possible
• ensure that no spillage occurs when transporting waste
• if waste is to be kept on-site for some time (e.g. for drying out) ensure suitable silt controls are in place.

12 Street cleaning

Roads, carparks, footpaths and cycleways are places where pollutants accumulate. During rain these pollutants often run off into adjacent stormwater drains.

Pollutants include soil erosion particles, nutrients, litter, organic matter, phenolic compounds (from wearing of asphalt surfaces), and grease, oils and heavy metals from vehicles.

Inadequate disposal of the waste from street sweeping, or using water to flush contaminants into drains can impact on stormwater.

To deal with these problems you can:

• ensure street sweeping techniques collect pollutants rather than putting them into drains
• monitor cleaning areas to determine the 'hot spots' for pollutants, and give these areas more attention
• coordinate street cleaning with other maintenance programs such as grass cutting and tree pruning
• arrange street cleaning to be in off-peak periods, as cleaning is easier with less cars
• identify when 'one-off' cleaning is required, e.g. special events or road works, and plan accordingly
• in areas where a mechanical sweeper cannot reach, either sweep by hand or flush material into a contained area and collect it
• take waste water to a suitable treatment site.

Case studies

Watching the weather

Lake Macquarie City Council recently developed a standard operating procedure for its spray sealing operations. This is aimed at minimising runoff of bitumen emulsion if rain falls before the material is cured.

Procedures which have been adopted include:

• requiring that a four-day forecast is obtained from the Bureau of Meteorology the day before the planned sealing and is made available to all sealing crews
• outlining factors for selecting products, e.g. humidity, threat of rain, wind
• distributing 'seal sheets' to employees the day before proposed works, which detail products and procedures for each job
• distributing hydrocarbon barriers and sediment bags for use on all jobs immediately after sealing
• checking environmental controls daily or twice daily in the event of rain
• removing environmental controls when traffic is allowed back on the road
• avoiding using freshly pre-coated material as this may delay curing time.

Using jutemesh for stabilisation

A number of studies in the Lake Macquarie area revealed that sediment from roads is entering watercourses and having a detrimental impact on water quality. In response to this, Lake Macquarie City Council carried out a trial program of stabilising road shoulders using bitumen emulsion and seed mix.

The procedure involves correcting the shape of a shoulder or table drain (if need be) and then rolling and pegging down jutemesh fabric. Grass seeds suited to the climatic conditions are then cast over the fabric and covered with a layer of bitumen emulsion. The bitumen provides stabilisation for the first few weeks while assisting the growth of the grass by holding warmth and moisture. In areas of gradual slope, additional stabilisation of the jutemesh is not required and the grass seed is put down independently.

The result is the rapid revegetation and stabilisation of a formerly exposed area. This has the added benefits of preventing sediment, nutrients and litter from further upslope entering stormwater drains. The trial generated information about optimum mixtures and application rates. Since the trial Council has started a comprehensive program of stabilisation and made a commitment to stabilise a minimum of 50km of road shoulder per year.

Bitumen emulsion vs cutback bitumen

Lake Macquarie City Council uses large amounts of liquid bitumen in road sealing and other activities.

Liquid bitumen is available in two forms: cutback bitumen and bitumen emulsion. The main difference is that the curing of cutback bitumen relies on the evaporation of a solvent, while curing of bitumen emulsion relies on evaporation of water. Cutback bitumen is widely used but emulsions have traditionally been confined to smaller jobs such as patching.

Lake Macquarie City Council has decided to use bitumen emulsion throughout its operations. This is because it is easier to use, can be applied in a greater range of temperatures, and has a number of environmental benefits, including:

• no petroleum distillate in runoff
• no volatile organic compounds from evaporation
• less energy needed for making the bitumen.

Other benefits include:

• it is safer and easier to use because it is not flammable or explosive,
• it can be used in a greater range of conditions
• it adheres more easily to aggregates.

Simple modifications to equipment

Lake Macquarie City Council's road maintenance crews have identified a number of simple modifications which can be made to their equipment to minimise the potential for polluting stormwater. The council's mechanical services division, in liaison with the field crews, designed these modifications and have successfully installed them.

One modification was to add a waste bin to trucks used for patching so that spoil material can be put in the bin and then taken to an approved facility. Bins are now required on any new patching machines.

Another initiative was to improve the kerosene boxes used to clean asphalt buildup off rakes and other tools. The boxes were modified to make it easier to place rakes inside them, resulting in substantially less kerosene being used to achieve the same job.

Legislation

Local government has responsibility for managing urban stormwater as a result of the Local Government Act 1993 and related legislation, and the Protection of the Environment Operations Act 1997. In addition to these Acts, other pieces of natural resource legislation that have relevance to stormwater management in council operations include the Fisheries Management Act 1994 and Environmental Planning & Assessment Act 1979 (as amended). The following legislation is relevant to managing road construction and maintenance:

NSW Local Government Act 1993

Section 7E of the Local Government Act 1993 requires that Councils have due regard for the protection of the environment in carrying out their responsibilities.

Section 8(1) of the Council's Charter states that a council has 'to properly manage, develop, protect, restore, enhance and conserve the environment for which it is responsible, in a manner that is consistent with and promotes the principles of ecologically sustainable development'.

Councils therefore have an obligation under NSW law to ensure that environmental considerations are taken into account throughout all their 'activities'.

Protection of the Environment Operations Act 1997

Under the Protection of the Environment Operations Act 1997 (POEO Act) the EPA is the Appropriate Regulatory Authority (ARA) for public authorities including councils.

Section 120 of the Act states:

(1) Prohibition on polluting
A person must not pollute any waters

(2) Prohibition on causing pollution
A person must not cause any waters to be polluted

(3) Prohibition on permitting pollution
A person must not permit any waters to be polluted.

Waters are defined as:

(i) any dry bed of any water, or into any drain, channel or gutter used, or is designed to receive or pass rainwater, floodwater or

(ii) any other water that is not polluted.

Water pollution is defined as the placing of any matter (whether solid, liquid, or gaseous) in a position where it

(i) falls, descends, is washed, is blown or percolates, or

(ii) is likely to do the same into any waters.

Severe penalties exist under the POEO Act for pollution of waters. Councils and their employees could be liable depending on the circumstances of the case.

Penalties range from on-the-spot fines of $750 for individuals and $1,500 for corporations through to penalties imposed by the courts of up to $250,000. In addition there are a number of notices which can be issued to councils requiring them to take action to clean up or prevent pollution, each of which involves a cost to the council.