PUTTING MORE INTO 2242 BACKFILLING
Work section 2242 BACKFILLING (available in Standard, Services and Structural & Civil) has been updated, expanded and provided with a revised question and answer format. The section has been partitioned with sub headings, so as to avoid confusion where a number of similar materials may be specified but for different applications.
Earth fill material clauses have been increased to cover three distinct situations:
- earth fill which is not required to support buildings or surfaces
- earth fill for residential developments
- earth fill for commercial and industrial developments
A new as built document clause has also been added to suit earth fill requirements in relation to items such as the need to record areas of ground that have not meet the required standard.
This as built document clause will automatically be recognised by Masterspec's new scheduling tool. If you have not already heard about this, then click on the link for more information on this new innovation available to Nextgen 2 users.
Some specific material options that were previously included have been removed in favour of a standards based approach. Materials such as granular fill for use under slabs are described as per NZ standard requirements (NZS3604 or NZS 4229), which allows for a number of material options, some of which are described generically. The selections will still allow for the specifiers to nominate specific compliant local materials if desired. The option of specifying granular fill material for projects requiring specific design is also available.
Information for backfilling (sub-base and basecourse requirements) in relation to pavements has been refined to give more specifier options. A distinction is made between flexible pavements (hot laid asphaltic concrete, concrete block pavers, stone block surfacing, chip seals and the like) and non flexible pavements such as concrete slabs. The options for flexible pavements are structured to suit the intended end use, ranging from heavy traffic roads such as would be experienced on state highways through to private residential situations. This provides some options outside of the sections in Structural and Civil, to provide information on sub-base and basecourse aggregates which may be appropriate for situations like industrial pavements that will experience heavy vehicle loading, or office carparks designed just for car parking. For actual civil roading projects, Structural and Civil sections should be used.
Additional fill options such as expanded polystyrene foam light weight fills and self -levelling flowable materials have been added. Self-levelling flowable materials have a number of intended applications, such as filling redundant pipes or other difficult to access voids.
The section has also been expanded to provide a typical service trench bedding and backfill option, and to expand on the available backfill material options that also provide for drainage, e.g. for use behind retaining walls.
Retaining walls & Groundwater drainage - Standard, Landscape, Structural & Civil
In association with the updated 2242 BACKFILLING section, modifications have been made to retaining wall sections. These retaining wall sections have been edited to remove content on backfill material and groundwater drainage (drain coils), other than where the backfill material is integral to the construction of the wall (e.g. crib retaining walls).
Retaining wall backfill and drainage materials are included in section 7441 GROUNDWATER DRAINAGE, and retaining wall backfill is also included in the updated 2242 section mentioned above.
Therefore depending on the type and scale of the project consideration should be given to which section(s) to include. If no other backfill materials are required other than drainage material to retaining walls or basement walls, then section 7441 GROUNDWATER DRAINAGE may suffice, however if the drainage backfill material was part of a more expansive project then section7441 could be altered and reference made to 2242 BACKFILLING, so that the backfill drainage material is included in the same section with other backfill materials used in the project.
The 7441 GROUNDWATER DRAINAGE section has been updated, this section covers gravity flow groundwater drainage for items such as field drains, groundwater drains to basement walls and groundwater drains to retaining walls.
Retaining walls & Groundwater drainage - Basic
To avoid issues with duplication of information, the basic retaining wall section (8110 RETAINING WALLS) has been edited to remove content on backfill drainage material and groundwater drainage (drain coils). This information is contained within the basic section 7430 DRAINAGE.