The terrain represents some particular challenges for the sewer collection and water distribution systems. In particular areas including the main population centre of Bendigo, the sewers are laid in shallow soil that is predominantly shale and rocky, is unstable and has been mined very heavily during the 18th and 19th centuries. As a result there is significant tree root infiltration into the sewer collection system. In the financial year ending June 2006 there were 1,462 sewer blockages reported, of which 632 resulted in a sewer spill. On average there were 88.5 blockages per 100 km of pipe.

Tree root infiltration was found to be the predominant cause of blockages. The dry conditions have contributed to further infiltration. As the ground has dried out, roots are growing aggressively towards vapour trails formed from exfiltration and condensation off the warm pipes. Roots will not grow underwater as they are aerobic organisms. The lower inflows into the treatment plants due to water restrictions and domestic recycling have lowered the flows in the pipes which allow the roots to grow further into the pipe. This gives partially blocked pipes a better chance to clear. When flows pick back up more blockages will result due to the root infiltration during the dry conditions.

The tree root infiltration not only caused the high number of blockages but also contributed to the degradation of the sewer pipes. The cycle of cutting the roots, regrowth, blockage and recutting the roots reduced the life span of the asset. The act of cutting the roots increases the regrowth rate of the roots resulting in more frequent blockages and more customers inconvenienced more often. The cost of reactive maintenance increases proportionally with the number and severity of sewer blockages.

A program of proactive maintenance strategies including routine cleaning, CCTV inspections and root foaming was undertaken in the period assessed year. In January 2007 Coliban Water took delivery of a specially designed jet cleaning truck which incorporated a Drainchem mainline root foamer. The root foamer allowed for the application of Sanafoam Vaporooter II which is part of a strategy of programmed works to reduce tree root infiltration. The Jetter/foaming truck has allowed Coliban Water to develop a proactive strategy to target tree root infiltration on an ongoing basis.

Coliban Water networks engineer Matt Beatty manages the proactive maintenance program. Daily operations for the jet truck start with the application of Vaporooter to 400 m of sewer pipe which had under gone root cutting or cleaning 6 weeks prior. This ensures that the root masses are not too large, as this could reduce the effectiveness of the application of Vaporooter. During the six week waiting period the roots heal and start to regrow. The new root growth allows for good contact between the roots and the Vaporooter herbicide and ensure an effective kill of the roots in the pipe, in the pipe wall and just outside the pipe. The crew were trained by Drainchem, who designed and supplied the mainline root foamer incorporated in the jet truck.

The loading of chemical is done with a closed system to ensure safe mixing. The chemicals are packed in two parts, a 19 litre drum and a water soluble package containing the Dichlobenil. The packaging ensures the correct dosage of chemicals is used to make up each mix. A patented two stage foaming nozzle ensues that the application is efficient and will never require an applicator to lean into or enter a manhole as part of the application process. Each manhole section takes about 30 minutes to complete and in a full day 800 m of 150 mm diameter pipe can be treated with two batches of Vaporooter.

After the batch of Vaporooter is applied the jet truck is free to root cut more lengths of pipe to be treated in six weeks time. Alternatively the truck can respond to emergency call outs such as sewer chokes if required.

The Vaporooter program has been designed to firstly target drains with a history of blocking, particularly those close to waterways were a spill could cause significant contamination. Drains located in backyards and difficult-to-reach areas are also included in the initial program of works. The program is only young, however it is expected that with ongoing applications of Vaporooter blockage rates will decrease. As the program matures drains will be retreated every three years to ensure that roots do not grow back into the pipe and the drains do not reblock.

The program is expected the dramatically decrease the number of sewer blockages and reduce the reactive maintenance costs currently incurred. Very encouraging results have been achieved by water authorities who have mature Vaporooter root foaming programs such as Grampians Wimmera Mallee Water, the GWMW program dates back to 1994 with root foaming being performed by a contractor twice annually. Upon the expiry of the guarantee the drains are retreated to ensure further blockage free performance.

Vaporooter is a non-systemic contact herbicide; the main ingredients of Vaporooter are used in food crops. Vaporooter has been used for more than 30 years with proven success.

One active ingredient in Vaporooter is Metham Sodium. Upon dilution with water the Metham Sodium begins a process of disintegration to produce MITC, a gas which attacks the individual cells of the roots. The herbicide travels only a few centimetres outside the pipe. Vaporooter will not harm trees or plants above the sewer pipe. Trees that rely solely on the moisture and nutrients in the sewer will loose this source and this has seen some trees suffer. The Metham breaks down very rapidly and reverts to its inert ingredients within 12 hours.

The second active ingredient is Dichlobenil, blended specifically for the Vaporooter formula to a 50 W powder, this superfine wettable powder is cationic, causing it to bond to surfaces like the cracks and defects in the pipe and organic matter. Dichlobenil is a sterilant which retards the regrowth of treated tree roots back into the sewer. Dichlobenil will not kill plant tissue but allows for the protection of the sewer pipes for three years.

There are no detrimental effects to employees, customers or the environment when used according to the directions. Vaporooter has now also been approved for use in collection systems that recycle treated sewerage for reuse on food crops and recharging ground water aquifers that supply drinking water for human consumption. There are several sanitation districts in California that now recharge ground water aquifers with treated sewerage from sewer catchments that have had Vaporooter applied.

Vaporooter can be applied to sewer systems draining to WWTP’s with daily inflows as low as 250,000 L/d. A recent Palo Alto (CA) wastewater treatment plant study testing a concentration as high as 32 mg/L with Palo Alto treatment plant organisms found no effect on the plant. In the City of Los Altos, the effluent from the WWTP empties in to environmentally sensitive wetlands on San Francisco Bay, Los Altos applied Vaporooter to approximately 100,000 m of pipe over a period of time of about three months. Palo Alto runs a unique test with the effluent from their plant. They test with kelp to see if the water will kill or damage the kelp prior to discharge. During the treatment of Vaporooter there were no adverse effects to the kelp.

There are more than 120 water authorities and councils in Australia currently using Vaporooter as a proactive maintenance tool. It is common practice in the United States and Canada for Authorities to apply Vaporooter with in-house crews however Coliban Water is the first authority to apply Vaporooter to mainline sewers with in-house crews. There are 45 councils who apply Vaporooter to branch lines using the Drainchem minifoamer. There is a Vaporooter mainline contractor in every state.

Contact details are available from Drainchem.