Informer 283: 9 September 2015

We’ve now standardised our slot-trenching fibre installation approach, adding a new technique to our NGA fibre install methodologies. 

What's happening?

We’ve now standardised the less invasive slot-trenching technique for use when the agreed installation option for your customer’s fibre installation requires a trench to be dug in hard, flexible and soft surfaces. The method is suitable for some surfaces, such as concrete or asphalt but will only be available in areas of the country where our service company has the required skilled operators and machinery.

Slot-trenching has been offered as an alternative technique to end-customers in a controlled area while we standardise this technique. It will now be rolled-out more widely.

There is publically accessible information available on the Chorus website at Getting UFB > Installing fibre and detailed information will be available on the Chorus customer portal from early September. 

What's the detail?

Slot trenching is a rapid trenching technique used to cut a narrow 10mm slot into a soft, hard or flexible surface into which the cable is placed. It is an option that is far less intrusive than current methods where a trench of up to 300mm wide is excavated to accommodate the network infrastructure.

Slot trenching involves the use of a motorised saw to make a small cut along the surface, at a set depth, into which the ruggedised microduct is installed. In hard or flexible surfaces once the ruggedised microduct is in place the slot is filled with a grouting or bituminous compound to maintain the surface and protect the cable. In soft surfaces the slot is filled with a clean material of the same type as surroundings and if dirt the surface sown with grass.

This installation method has a number of advantages for end-customers, including:

• It is far less invasive and messy
• There are fewer problems with getting machinery into premises

Initially, this option will only be available in the parts of Auckland and Wellington where slot-trenching machines are available with trained operators.

Generally, the slot trench in hard or flexible surface will be 10mm wide and 30mm to 40mm deep. The depth depends on the number of ruggedised microducts that need to be installed.

Examples of slot trenching

The above image shows a completed example of a common slot trench in flexible surface

This image shows slot trench cuts completed in hard surface

This image shows a completed example (pre-compaction) of a soft surface

While slot trenching is a solution that is suitable for most surfaces, it is unsuitable for chip seal and tar seal (made up of bituminous tar sprayed) or other similar surfaces where the top layer has insufficient structural integrity to form, or maintain, a slot cut.

Who do I contact?

For further information please talk to your Service Delivery Manager.