Finding the best water source for your construction site

SRK - Alternative water supplies for construction sites: pros and cons

26 March 2018 – Cape Town: Drought in the Western Cape and other parts of South Africa is forcing construction projects to change the way they source and use water; the good news is that there are various opportunities in the construction sector to do this, according to Xanthe Adams, principal engineer at SRK Consulting (SA).

“It sometimes falls to contractors to ensure water supply for a range of on-site requirements but they face rising costs and reputational issues if their water use is not well managed,” said Adams. “The traditional solution of just tapping into a municipal source may not be optimal for every operation, and alternatives should be considered.”

She highlighted that an important starting point for contractors is to establish well in advance where the construction contract will place the responsibility for water supply; will it lie with the employer or the contractor?

“Early consideration by all parties would allow for better planning of the best option, and would also help to identify potential cost-related risks resulting from an unexpected rise in water tariffs, for example,” she said. “Engineers need to consider this during the design phase and advise the employer accordingly as there could be long permitting processes required in the use of certain water sources.”

When considering alternative water sources for a site, a long-term project could warrant the cost of sinking a borehole – but there are various details that should be borne in mind. While borehole water is often of a good quality, it can have quality problems. Common issues include high levels of iron, manganese or even salt, so testing would need to be conducted to establish if further treatment is necessary and practical under the circumstances. Testing the yield of the borehole is also important to ensure that the water source can sustainably provide the required water volumes.

“Most water use options will require some form of permit or licence, so professional advice at an early stage is vital when considering the borehole option for site water,” said Adams. “Depending on the nature of these applications, the process could be a long one – with impacts on the project timeline. The borehole option may also be attractive for large projects in remote locations, where access to municipal or other sources of treated water is difficult or expensive.”

Another alternative is treated sewage or effluent, but this has not always been well received as it still perceived as poor quality water; however, the use of treated effluent can be a simple and cost-effective strategy to reduce reliance on increasingly costly and scarce drinking water.

“This is a great option for contractors in a city like Cape Town, where people are more water conscious than ever and the city council has made treated effluent easy to access,” she said. “It is already being used by the city in applications such as irrigation, and its quality standards for retreated water are high – as much of it needs to be discharged into rivers. Quality problems can occur, of course, especially if an individual treatment plant is not running optimally, so professional advice and testing is recommended.”

Applying to use this water from a local municipality’s treatment plant is usually a quick and straightforward process, and the water comes at an economical price. Contractors will generally just need to assume responsibility for the transport arrangements, and need to provide clear signage to show that the water is not for drinking. Common applications for this quality of water include dust suppression and compaction, but it can also be used for mixing concrete.

“When considering treated effluent for mixing concrete, it is important to have the water tested in terms of the national standard SANS 51008:2006, and the engineer on the project would have to give permission,” she said.

A common temptation for contractors is to use water from rivers, dams or canals – but Adams highlighted that there are both compliance and quality issues that must first be addressed; again, talking to an expert is the best route for avoiding risk and ensuring smooth project roll-out. More recently, another factor has become important: public visibility. She notes that residents in places like Cape Town are today much more vigilant about non-compliant extraction of water from public sources; this activity therefore holds considerable reputational risk if a user is found to be in contravention of any water use regulations.

While seemingly mundane, there are various other ways that water can be saved on construction sites – including the use of hand sanitiser for hand washing, the installation of chemical toilets, and the capturing of rain water using drains and storage tanks. Greater awareness of water conservation – to prevent wastage through unattended hosepipes, for instance – also goes a long way, said Adams.

How water savvy are you?
 
Take the 5-minute challenge for the most water-savvy site
 Ever wondered how your on-site water management strategies rate when compared to your peers in the sector? Now you can take a test and find out!

Just go to the SRK-supported ‘Water War’ website at: http://www.waterwars.co.za/construction-competition/ and answer some simple questions about the way you use water on your current project.
 
The Civil Engineering Contractor will track your responses and publish the most interesting results, including the most water-wise entry.

The Best Water Source for Construction
Acknowledgement: The Civil Engineering Contractor

SRK Africa