Victoria’s Western Water established a program in 2010 to prevent sewer spills, which has reduced the number of incidents by 54 per cent in three years. Here we take a closer look at their strategy and the inspection works that have been carried out to date.
Western Region Water Corporation, trading as Western Water – one of Victoria’s 13 regional urban water corporations – provides water, recycled water and sewerage services to 58,200 properties over an area of 3,000 square km and a population of 158,300. The organisation’s service area is characterised by high growth to the north and west of Melbourne.
Western Water also maintains more than 1,185km of sewer mains, which transferred more than 8,400 million litres of sewage to its recycled water plants in 2012. If one of these mains becomes blocked or cracked, raw sewage can spill out into streets, backyards, creeks, rivers and even into people’s homes.
In 2009 and 2010, there were three serious sewage spills. In response, the Western Water Board endorsed and implemented a Sewage Spill Prevention Strategy (SSPS) in August 2010. This innovative strategy has reduced sewer spills by 54 per cent in its first three years.
The strategy began with a review of all previous sewer spills to find out what had caused them.
Two key parts of the strategy were determined to be: enhanced CCTV of critical sewers, and known and arising repeat blockage areas; and the appointment of a sewer renewal contractor to respond to defects as they are identified.
Appointing a contractor
Western Water awarded a schedule of rates contract to Kembla Watertech to carry out the rehabilitation of sewers from financial year 2011/12 to financial year 2012/13.
As the contract approached the end of its term, the need to extend the program was justified based on the findings of the ongoing CCTV program.
Tenders were publicly invited. The successful contractor was selected based on a multi-criteria assessment, which included value for money, experience and rehabilitation methods proposed.
Western Water wanted to ensure there would be minimal lead time from completing the liner to inserting the house branch connection liner (top hats or tees). Western Water also wanted to make use of the contractor’s expertise in pipeline condition to provide a third-party review of the rehabilitation requirements for the pipes identified.
These recommendations, reviewed by Western Water staff, provide another expert review to form an input to the rehabilitation decision process.
A region-wide CCTV program is being undertaken to ensure all sewers (300mm diameter and greater), and all problematic reticulation sewers are inspected. The data from the CCTV program provides justification for pipe rehabilitation, and is used to prioritise rehabilitation works. Priority is decided based on a combination of the sewer size and structural condition.
A schedule of rates contract for the work was chosen, because Western Water wants to ensure that the rehabilitation contractor only carries out works which are identified as being the highest priority works at the time of the works orders. This flexibility is necessary since the rehabilitation priority is constantly changing based on the CCTV data being collected.
At the end of financial year 2014/15, Western Water expects to complete the inspection of 100 per cent of all sewers (300 mm diameter and greater) and 100 per cent of all problematic reticulation sewers.
Contract benefits
According to Western Water, there are a number of benefits to the long-term rehabilitation contract. The long-term contract allows Western Water to rehabilitate priority sewers annually, without the time and cost impacts of tendering the works under separate contracts.
It also means that sewers with poor structural condition can be rehabilitated quickly – upon receipt of CCTV data, thereby promptly and efficiently reducing the risk of sewer collapse for the business, customers, the community and the environment.
Through the long-term contract, Western Water can benefit from the knowledge of the specialist contractor, and build a good working relationship. This working relationship allows both Western Water and the contractor to better understand each other’s issues, as well as building agreed key performance indicators to measure the contract’s success.
This type of contract also provides the contractor with surety of work, and allows for a dedicated team (from both Western Water and the contractor) to deliver the project efficiently.
Factors to consider
When embarking on such a project, it can be useful to get an idea of what strategies have been used before by other companies, as well as which have been successful or unsuccessful and why.
Western Water sought feedback from numerous water corporations on their experience in delivering sewer rehabilitation contracts, and this knowledge was used in developing its own program.
The corporation says the interesting part of this program is that the more CCTV is conducted, the more issues are discovered. So far, Western Water has found a light pole, gas and Telstra lines through its systems, just to name a few.
