• 38.5km of pipe
• pumping up to 150,000 cu. m per day
• using 7.9MW
• of which 5.5MW at the high lift pump station

Estimated number of truck movements to construct:

• 1300 pipe trucks
• 34650 cleanfill truck movements/loads
• 5550 granular backfill trucks
• 3485 hardfill trucks
• 880 basecourse trucks
• 4650 general trucks
• 890 reinstatement trucks
• TOTAL 62,090

Total car movements 35,100

Carbon emissions: not quantified (surely this should be part of an AEE)

I suppose that these figures (or preferably actual figures from the project and operation) could be compared with the figures for installing on-site rainwater storage and greywater recycling, but that’s only part of the picture as the increased water supply (as opposed to demand management, on-site supply and recycling) was also part of the reason that an upgrade of the Mangere Wastewater Treatment Plant was required, so some part of that project would have to be included as well…

Copy of newsletter text:

Coomera Cross-Connection Incident

A cross-connection incident at Pimpama Coomera has marred the introduction of Class A+ recycled water to this major development site in southeast Queensland. The incident, which occurred in early December 2009, is a significant public relations setback for the implementation of the Pimpama Coomera Waterfuture Master Plan (1) which has governed regional water supply strategies since August 2005.

The Master Plan, which has won a number of national and international awards for excellence and innovation, was developed in anticipation of projected population growth from a base of 5,000 residents in 2004 to around 150,000 residents by 2056. The aim of the Master Plan is to provide sustainable water management through utilisation of multiple water sources, and improved management of stormwater and sewerage systems.

Since implementation of the Master Plan, new residential developments in the region have been required to have a rainwater tank and a dual reticulation water supply capable of providing non-potable recycled water as well as conventional drinking water. In addition, sewage collection systems have been designed to minimise stormwater intrusion and reduce sewage treatment costs, and water sensitive landscaping provides an attractive environment while protecting local waterways from the adverse impacts of stormwater runoff. Other expected benefits include a reduction in sewage and nutrient discharge to the Pimpama river, and a reduction in greenhouse gas emissions. The Master Plan is expected to reduce demand for conventional drinking water supplies to as little as 16% of typical demand for conventional residential developments which use drinking water for all purposes.

To date about 4,400 homes with dual reticulation plumbing have been constructed. In keeping with normal practice in such developments, households have been initially supplied with drinking water through both pipe systems while the recycled water treatment plant at Pimpama was constructed. The plant was designed to supply Class A+ recycled water (2) to homes for toilet flushing and outdoor taps, however soon after recycled water was supplied to households for the first time on Tuesday 1 December, a number of residents complained that water from kitchen and bathroom taps had a foul taste and odour. Investigations by Gold Coast Water revealed that that a cross-connection had allowed recycled water to mix with the drinking water supply in over 630 homes. The problem was detected on Friday 4 December and affected residents were advised by door-knock and letter drop not to drink tap water until further notice. The recycled water supply was turned off and tap water flushed through both systems until water quality parameters returned to normal levels for drinking water. After extensive testing of the potable and recycled water networks, residents were advised they could resume drinking tap water the following Monday 7 December. The potable and recycled water supplies were restored on Friday 4 December at 6pm, about 11 hours after the problem was detected.

The cross-connection incident is being investigated by the Queensland Office of the Water Supply Regulator, the South East Queensland Water Grid Manager and Queensland Health as well as Gold Coast Water. None of these bodies has yet released their findings about the cause of the incident. While some media reports have speculated that the contamination could have been caused by deliberate illegal cross-connections within one or more households, the scale of the incident makes it appear more likely that the cross-connection occurred at the mains pipe level.

According to media reports, a number of residents reported gastroenteritis symptoms during the period of the cross-connection, and have attributed this to consuming the contaminated water. However, the Chief Medical Officer for Queensland stated that health risks would have been minimal due to the low numbers of microorganisms and high residual chlorine levels in the water. Nevertheless, media reports suggest that a number of legal firms are preparing class action claims against Gold Coast City Council.

An earlier cross-connection incident at the recycled water treatment plant also came under the media spotlight, when it was revealed that up to 375 council workers, contractors and visitors had potentially been exposed to recycled water of much lower quality for a period of nine weeks during 2008. During this time the water supply to a building at the plant was contaminated with partially treated wastewater with quality ranging from predominantly Class B to Class D. The water was used for drinking, laundry and showering. An investigation by Queensland Health found that 73 of those exposed had suffered illnesses possibly related to their exposure. The Queensland government took legal action against the construction company over this cross-connection incident.

These incidents have caused anxiety among Pimpama Coomera residents about the safety of their water supplies and this was further heightened in January this year when, following another customer complaint about taste and odour, inspection of a home revealed a household level cross-connection. This prompted Gold Coast Water to inspect all dual reticulation properties, revealing seven more residences with cross-connections. Five of the cross-connections were at the water meter connection to the house, two within houses and one at the sub-meter for a residential home unit.

The focus on water also led to media speculation that another cross-connection could be responsible for a gastroenteritis outbreak at a childcare centre where 30 children fell ill over a two week period in late January. The investigation by Gold Coast Water showed no problems with water quality or plumbing, and in fact the centre was not even connected to the dual reticulation water supply. There was no evidence to support the idea that the outbreak was related to water, however the incident highlights the difficulty in restoring public confidence in the safety of water supplies, once it has been damaged. Gastroenteritis is a relatively common illness and on average it is expected that around 2% to 4% of people in Australian communities would experience gastroenteritis symptoms in any given week. Outbreaks in childcare centres are common, and not entirely preventable even with the best hygienic practices. Gastroenteritis pathogens have many routes of transmission but adverse publicity about one potential source of risk may lead people to attribute all cases of illness to this source, or to be more aware of the illness and thus perceive an apparent increase in frequency in the community when none has actually occurred. A small number of cross-connection incidents have previously happened at other dual reticulation residential developments in Australia, however investigations by health authorities have not conclusively linked such incidents with adverse health effects. This is not surprising given that the microbial quality requirements for water supplied to dual reticulation developments are relatively high. These requirements have been set in recognition of the risk of occasional household level cross-connections or inadvertent consumption of water from recycled water taps.

Risk management for dual reticulation systems is a challenging undertaking given the complexity of water supply networks and the involvement of multiple organisations and individuals in construction, commissioning and operation of these developments. In an effort to detect household level cross-connections, some water suppliers have elected to perform audits of individual households before a Certificate of Occupancy is issued (a legal requirement before residents are permitted to move into a newly built property). In such audits each internal and external tap is tested to ensure that they are supplying the intended type of water (either potable water or recycled water) by turning off the supply at the respective meters. This will reveal whether a complete cross-connection exists (incoming supply pipes connected to wrong meters). Water quality tests (for example electrical conductivity tests) may also be done to ensure there is not a partial cross-connection within the household allowing the two types of water to mix.

However, the experience of Sydney Water Corporation at the Rouse Hill dual reticulation development illustrates that even this approach is not foolproof. A household audit prior to turning on the recycled water supply revealed around 50 cross-connections among 12,000 houses inspected, and a policy was introduced to ensure subsequent newly built homes were subject to inspection before a Certificate of Occupancy was issued. However some householders move in prior to obtaining their Certificate of Occupancy. Between 2001 and 2007, three such households were found to have cross-connections which had exposed residents to drinking recycled water not intended for potable use. In a subsequent incident, a cross-connection in a home still under construction (and therefore not yet audited) allowed recycled water to enter the drinking water supply of 82 occupied homes in the local area. Residents were exposed for a period of three weeks before taste and odour complaints triggered an investigation which revealed the problem.

It would be expected that mains level cross-connections resulting in complete switching of the two water supplies would be rapidly picked up by routine water quality monitoring if they were not first detected by a sharp rise in customer complaints, however cross-connections which result in intrusion of recycled water into the potable supply present a more complex problem for detection. In these cases the proportion of recycled water present in the potable supply will vary over time due to the changing pressure differential between the two systems. Movement of water through the pipes and storage reservoirs in the distribution network and inflows from other connecting mains will also produce a variable spatial pattern of mixing. In addition the physico-chemical properties of individual recycled water and potable water supplies may also vary somewhat over time, and this will affect the degree of contrast between potable water and the potable/recycled mixture for any given water quality parameter that might be measured by water suppliers or detected by customers. Given the increasing adoption of dual reticulation for greenfield residential sites in response to water shortages in Australia, developing methods to reliably and rapidly detect cross-connections between recycled water and potable water systems is a high priority research area for the water industry.

(1) Information on the Pimpama Coomera Master Plan can be found at: http://www.goldcoastwater.com.au/t_gcw.aspx?PID=5885

(2) Different categories of recycled water used in the state are defined under the Queensland Public Health Regulation 2005. Class A+ recycled water must contain less than one of all of the following microorganisms per 100 ml of water in 95% of samples over a 12 month period – E. coli, Clostridium perfringens, F-RNA bacteriophages, somatic coliphages. In addition water turbidity must be less than 2 NTU and a free chlorine residual of more than 0.5 mg/L must be maintained at the point of supply to households. The recycled water treatment chain for the Pimpama plant includes membrane ultra-filtration, disinfection with ultra-violet light and chlorination

Water under the sustainability microscope

The Carbon Footprint of Water (download pdf).

The Water-Energy Nexus | River Network

• Victoria’s Desal plant figures don’t hold water  (SMH) “Public or private, the 150-gigalitre desal plant is not needed. The additional water could be produced at a sixth to a quarter of the cost by a judicious mixture of conservation, recycling and diversion dams.”

The system was no doubt subject to some very rigourous proceedures and thorough checking but it appears to be very hard to avoid cross-connections at this scale of development.

See also my paper on risk and scale in water recycling.

More on water footprinting:

http://watermiles.org/2008/12/23/water-footprint-network-launches/
http://watermiles.org/2009/06/30/water-footprint-of-bioenergy/
http://watermiles.org/2008/12/04/plumbers-journal-article/

The September 2009 newsletter carries a copy of my NZLTC conference paper, on water reuse and system scale.