Otta Seals: the under-utilised tool in pavement preservation?

Improving asset management can often come from new or improved technology – not just enhanced processing and reporting of data sets. One such instance where adopting and adapting technology has proved to be a winner, has been in the central NSW regional Shire of Narrandera. Relatively unknown in Australia, Otta seals are a low-volume, low-cost road treatment used predominately in South Africa. Put simply, graded gravel/crushed rock is placed on a relatively thick film of soft bitumen, and then rolled.

They have become attractive to some Australian councils who seek greater sustainability, combined with a view that a number of current standards, if applied directly, would lead to excessive cost and overuse of scarce premium materials ultimately leading to inefficient asset management. The Narrandera Shire Council has 300 km of sealed roads and 800 km of unsealed roads, but the unsealed roads only serve about 10% of the population. The significance of the savings from introducing adapted technology is made clear by referencing against their annual rate revenue, where, to reseal the sprayed seal network on a ten-year return cycle (as recommended by Austroads & ARRB) the annual reseal budget would be in the order of 20 % of the annual rate revenue. If they were to re-sheet the unsealed network at a 5-year interval as recommended, the annual re-sheet budget would be about 90% of the annual rate revenue.

Council have realised considerable lifecycle cost savings with Otta seals for local roads with low traffic volumes due to the use of less-tightly specified materials and a longer period between maintenance interventions.

Narrandera Shire Council completed about 65 km of Otta Seal in last 4 years, 20 km of new otta seal in 2017/2018 alone. Importantly, they have customised the process of Otta seals to suit the Australian environment, including ammending gradation of stone, % of cutter and rolling regime and signage after application. For further information contact the Manager of Works, Narrandera Shire Council, or Kym Neaylon, Executive Manager (Professional Development), CPEE (This email address is being protected from spambots. You need JavaScript enabled to view it. ).

The Centre for Pavement Engineering Education (CPEE) is dedicated to road and pavement engineering education, and because of this dedication regularly provides training in regional centres and the more remote parts of Australia far from capital cities.