What are the Engineering Guidelines for Subdivisions and Development?

Developers use the guidelines when drawing up designs for new subdivisions and development, deciding what materials to use for infrastructure such as roads, and methods for testing that infrastructure.

The guidelines cover everything from the size, surface and durability of roads to the types of sewer mains that can be used.

They do not dictate the design of houses.


Why is Council reviewing its Engineering Guidelines for Subdivision Developments?

The City of Wagga Wagga is currently reviewing its engineering standards to address recurring issues with subdivisions and development and to bring them in to line with modern standards. The current document, Engineering Guidelines for Subdivisions and Development Standards, was issued in 1996. Ideally such documents should be reviewed after a period of 15-20 years so it is timely to do so now.

The original work on this proposal was coordinated by Consultants GHD and involved consultation with Councils in Albury, Wodonga and Griffith, City of Wagga Wagga staff and North East Water Council (Vic), to provide some commonality in approach. More recent discussion on specifics has been in house at Wagga Wagga City Council and with Councillors in a 2015 workshop.

The 1996 document tended to set out specifically how projects should be designed. With changing source documents, there was a need to re-issue updates when the source documents changed. It is proposed to provide references to the source documents (which may be Australian Standards, Austroads Manuals, RTA/RMS Manuals, Engineers Australia publications such as Australian Rainfall & Runoff, and many others). Designers can then adjust their designs to suit when changes are made in these source documents rather than awaiting advice from Council.

What are some of the recurring issues with the existing guidelines?

Some of the issues with the existing guidelines, as documented by Council, include:

  • There seems to be inadequate supervision and monitoring of the quality of material and construction of a road base.
  • Due to the early cracking of asphalt surfaces, Council is required to undertake maintenance works at an earlier stage than expected. Increasing the asphalt wearing course and more focus on pavement design and construction practices will assist in remedying this issue.
  • The life of a road base is currently only 30 years. If it was thicker this could be extended to 50 years, which in turn means the road needs to be renewed less frequently.
  • Council has had a need to attend to both drainage and sewer pipelines shortly after transfer from contractors to Council as a result of siltation and blockages, particularly in the vicinity of pits and manholes. Upon investigation, it has been found that workmanship at pits and manholes has been such that material is catching at the entry and outlets.
  • Council has received complaints and request for assistance where trenches have sunk after subdivisions have passed out of maintenance. This has caused fences to lean over and in some circumstances has been suspected of causing damage to house footings and brick walls.
  • The installation of pedestrian ramps at intersections has been carried out in an ad-hoc manner with widths, grades and layouts highly variable.
  • In relation to narrow streets, Council has had some complaints from service providers such as the garbage contractor who has difficulty in servicing narrow carriageways, particularly cul-de-sacs where there is limited turning room and if cars are parked out in the street. Removalists and other heavy vehicles such as concrete trucks also have difficulty using such streets. There is also the issue of condoning the illegality of parking on footpaths, which is encouraged by roll kerbs.

What are some of the changes Council is proposing to make?

Some of the changes that Council would like to make to the Engineering Guidelines for Subdivisions and Development Standards include:

  • Early discussion with engineering staff on requirements for the development/subdivision
  • Current minimum asphalt wearing course of 25mm to be increased and consideration being given to 2 coat bitumen seal as final surface
  • Previous Guidelines provided for a 30 year design life, this consultation seeks comment on a 50 year design life
  • Requirement for Traffic Engineering Report
  • More involvement of a Geotechnical Engineer in relation to pavement design and construction
  • Increased requirement on use of appropriate materials in pavement construction
  • Use of CCTV and pressure testing for drainage and sewer pipelines
  • Increased focus on compaction of trenches in easements and road pavements to meet the Australian Standard
  • Consideration of curved sewer lines
  • Footpaths in new developments to be 1.5m in width
  • Maintenance period will be 12 months
  • Roads of 7.5m width to have no more than 10 lots
  • Provision of lot soil classification

What is a narrow street and what are some of the pros and cons to having them in subdivisions?

A narrow street is considered to have a 7.5m wide or smaller road with a 3.5m wide or smaller nature strip and/or footpath on either side.

Some of the pros and cons for adopting narrow streets include:

Pros

  • Traffic is forced to drive slower through high density neighbourhoods where there could be children playing etc.
  • It creates a sense of ‘cosiness’ and a close knit community within a neighbourhood
  • It allows for larger blocks of land to be allocated

Cons

  • Garbage contractors have difficulty in servicing narrow carriageways, particularly cul-de-sacs where there is limited turning room and if cars are parked out in the street
  • Garbage contractors have been subjected to insurance claims for damage to concrete areas and irrigation systems. As a result they have indicated that it may be necessary to introduce smaller compacter units with a commensurate increase in costs
  • Removalists and other heavy vehicles such as concrete trucks also have difficulty using such streets
  • There is also the issue of condoning the illegality of parking on footpaths, which is encouraged by roll kerbs