Chapter Five |
|
Use of Materials |
Track Construction
The Great Kai'mia Way is based around maximising the use of existing routes, however there are significant links to be made where new sections of track, bridges and structures are necessary.
Track standards should be a function of route, track condition alignment, width, length, steepness of grade and the kind of natural and man made barriers, which must be traversed, combined with the type of use planned for.
Recommendation:
- That a standard be adopted for construction and upgrade of track works, consistent with existing Australian Standards for walking track classification signage and infrastructure AS 2156.1-2001 and AS 2156.2-2001: a combination of Class 2, Class 3 and occasionally Class 4 out of 6 classes, where 6 is the least developed class
This Standard is meant for use by land and recreation managers in parks and reserves and is not as applicable to the urban and shared use sections of the Way. It is recommend that three categories be adopted which cover the majority of routes along the Way based on AS 2156-1978 and adapted by NPWS:
-
Walk - A well-constructed and hard surfaced path designed for high use by persons of all ages and physical condition. Easy grades suitable for disabled use may be required with bridges or boardwalks where necessary. Development costs of "Walks" are high but means lower maintenance costs.
-
Track - Well defined and suitable for people of average fitness with some experience. These routes are benched and drained as necessary to account for erosion and water damage.
-
Route - Lightly marked for well-equipped and experienced walkers. Routes are unconstructed except for erosion control work; there are examples of this in sections in Dharawal State Conservation Area.
Track Surface
Bushland Situation - (Preferred Methods of Bushcare Groups)
The simplest form of track surfacing and the first option always to be considered is to use the mineral soil found in-situ. With correct drainage this will often be adequate to carry normal intermittent foot traffic.
When surfacing is required, a suitable material indigenous to the area, such as local sandstone, should first be considered before importing material. However do not remove habitat!
Edgings to both sides of the track are not recommended as they tend to concentrate gullying, leading to break up of the stone surface.
In a situation where a track is cut along a contour line, the lower track edge can be retained by either fallen timber, provided it is not habitat, or sustainable sourced hardwood sections.
Management Trails
Generally based on roadstone, surfaced with crushed granite or sandstone occasionally bluemetal gravel. These trails are prone to erosion from maintenance vehicle use, stormwater, and trail bike use. Tar-sealed sections often break up under heavy vehicle use.
Roadstone, recycled crushed concrete and blue metal change the ph of the soil in sandstone areas making track edges nutrient rich and promoting weed growth.
Crushed sandstone held together with binding agent should be the preferred material for use on management trails.
The binding agent leaves the surface permeable but resistant to erosion. This technique is particularly suited to repairing gullied steeper grades or as a preventative treatment on steep grades. A less satisfactory solution is to tar seal the steeper sections.
Steps and Stairs
A popular material for constructing steps and stairs has been CCA treated pine product. Recently, however, there are increasing doubts about its safety. Many councils, such as Brisbane City Council now ban its use. It is allegedly connected to cancers in children from exposure in playground areas. When on fire, it releases potentially fatal toxic fumes.
Recommendation:
- That infrastructure on the Great Kai'mia Way is free of all CCA treated pine products.
Alternatives are:
- Durable hardwood - sourced from plantation; for example, tallowood.
- Recycled Plastic - post user HDPE and LDPE - non toxic. Life expectancy is approximately 40 years. It has a lower combustible threshold than timber and is "less toxic" according to research in USA. Kosziosko National Park is rebuilding Charlottes Pass walking track replacing treated pine steps with plastic profiles. Royal National Park is trialing"floating mesh " walkways using plastic profiles to support galvanised metal panels at $120 per metre
- Stone - best for achieving least visual impact. When firmly constructed, it will last indefinitely and survive most flood and bushfire conditions. A concrete bed may be used discreetly to secure rocks in position. Cost $50 per step. Either Sandstone from site (preferable) or imported sandstone can be used.
- Timber - from site.
- ACQ (Alkaline Copper Quad) - treated "naturewood" timber.
Track Structures
Bridges |
Bridges are key elements of any track system for linking previously separate networks and opening up access to new areas, maximising the potential of the network. They are expensive items but their value cannot be underestimated.
- The concept of a pedestrian bridge spanning Heathcote Road is a discreet engineering project in its own right and should be considered as a long-term venture partnership open to all relevant stakeholders.
|
 |
|
- Small bridges are required as tracks are upgraded in the urban bushland areas to span creeks and gullies. Designs should be in keeping with the surroundings and a proper engineering drawing prepared. Materials to be considered are sustainable sourced hardwoods for bearers or steel for larger spans with hardwood or non-slip recycled plastic decking depending on the setting.
Boardwalks
Boardwalks can be an attraction in their own right. A major boardwalk is proposed as a central feature of the Como Heritage and Environment Trail, physically linking the foreshores at the confluence of the Woronora and Georges Rivers under Como Railway Bridge. They require heavy engineering solutions in many instances increasing the cost of installation to as much as $1,200 per linear metre . The cost of a 100m stretch of boardwalk could potentially pay for 1 km of sandstone surfaced track. |
In sub section tables for the Way, they have been proposed for foreshore access where there are physical constraints or where traditional methods of track construction, e.g. cut and fill, are unsustainable - such as cutting a path along a steep gradient, through sensitive wetlands and foreshore vegetation.
Recycled materials such as plastic profiles can be used for decking purposes, but are yet to be proven for structural supports. |
 |
|
N.B. Professional help should be sought in the design of boardwalks and all track structures with regard to foundation bearing, live loadings and stability. Design is to be in accordance with the applicable Australian Standards AS 1170 as referred to in AS 2156.2-2001 section 2.
Raised walkway |
Examples of raised walkways include sections of the Coast Track in the Royal National Park where an innovative Floating Mesh design has been installed where previously a severely eroded track existed on thin heathland soils. Overuse had trampled and fragmented the sensitive vegetation. Mesh sheets are supported on recycled plastic bearers held in place by the weight of the steel alone allowing the vegetation to flourish beneath.
At $120 a metre in construction costs it compares favourably with crushed sandstone and will last longer. This technique can be applied to short stretches such as look out decks.
|
 |
 |
Benches
A simple bench design, 1.8 metres long, is suggested with hardwood planks for durability and aesthetic. Seats to be installed at key access control points where surveillance is possible. Community groups should select on track sites such as at vantage points and look outs suitable for a bench seat, taking account of fire risk, vandalism and safety. |
|
Access Control Infrastructure
Signage
Suitable Signage materials are outlined in the signage section above and summarised in the material application tables below.
Gates and Barriers |
| In aggressive access situations; that is where trail bikes and 4WD activity is a problem, use galvanised pipe for the frame of the gate, such as currently seen blocking fire trail access at several locations of the Great Kai'mia Way. Use galvanised steel double rope for barriers where possible - similar to the barrier surrounding parts of the Dharawal Aboriginal Land Council land. This is the only design that has proved robust enough to cope with attempts to break through by 4WD (winching, etc). |
 |
|
| In situations where there are barriers on either side of a gate and a gap which allows universal access, it is recommended that a kissing gate type structure be installed. A kissing gate is a pedestrian gateway that prevents bikes and horses from passing trough. It allows access to families with pushchairs and some wheelchairs. 2 designs are illustrated - galvanised steel circular and square hardwood timber. |
|
Recommendation:
- Effective measures be implemented to exclude trail bikes and 4WDs from sensitive areas by using, for example, gates made from galvanised steel pipe, fencing made from galvanised steel double rope, and kissing gates to enable access by legitimate users.
Railings and Safety Barriers
AS 2156.2-2001 section 3 states that barriers shall be provided on walking track structures to reduce the risk from falling.
In providing barriers, track managers should:
- carry out site specific risk assessments for each location; and
- calculate "effective fall height" (which varies according to track classification), by adding "actual fall height" within a distance of 2 m from the proposed barrier position to the "impact surface value" - this varies from -0.5 "Benign" (a surface presenting features that will tend to reduce the effect of impact e.g. deep moss) to +3.0 "Hazardous" (a surface presenting features that will seriously harm regardless of the effect of fall to the initial impact point).
|
The most likely application of railings on the Way is where a look out platform is proposed, above a steep drop. e.g. along the Burnum Burnum Track overlooking Mill Creek . It is recommended that type A barriers should be installed. These are a minimum of 1.0 m high and have the following:
No openings anywhere below the top rail which will permit the passage of a sphere 125mm in diameter.
There should be no components providing a toe-hold between the heights of 150mm and 760mm above deck (or stair nosing) level. |
 |
|
Horizontal rails are acceptable if the barrier geometry is such as will prevent children under six climbing over the top.
For steps, the triangular opening formed by the riser, tread and bottom rail at the open side if the stairway shall be such a size that a 125 diameter sphere cannot pass through it.
Recommendation:
- That Type A barriers, as described in AS 2156.2-2001: Track Infrastructure be installed at lookouts and other relevant locations for safety and risk management, at the discretion of track managers, based on an assessment of effective fall height.
|
|
• Exec Summary 
Sutherland Shire Environment Centre | Suite 4 (1st Floor), 2-4 Merton Street, Sutherland NSW 2232
