Water Management Planning Guidance for Construction Projects

Water Management Planning Guidance for Construction Projects

 

head Site-measurement-and-monitoring

Measurement and monitoring of water use is the most important step in being able to manage consumption on site. The site should be planned to allow adequate information on water use to be regularly collected and reported on so that decisions with regard to consumption can be made.

A useful guide to metering technologies, and specific requirements with regard to metering of abstractions can be found on the Environment Agency at

http://a0768b4a8a31e106d8b0-50dc802554eb38a24458b98ff72d550b.r19.cf3.rackcdn.com/geho0910btao-e-e.pdf

This guidance may be useful for other forms of metering in addition to abstraction.

Identifying sources

Ideally all water sources supplying a site should be metered. This may include mains water (which may already be metered by the supplier), standpipes, recycled water and directly abstracted water from rivers or groundwater.

Meter

Selecting meters

Selection of the correct meter for any particular site is the first step to obtaining reliable data. This means making sure the meter being fitted is the right technology and the right size. It is necessary to consider all aspects of installation when selecting a meter. BS 7405:1991 (Guide to selection and application of flowmeters for the measurement of fluid flow in closed conduits) defines five basic areas which should be considered in the selection of any meter. Of most relevance to construction sites would be:

  • Suitability for clean (mains, borehole) or other water;
  • Meter size, based on the flow rates to be measured;
  • How, and how often, the meter is to be read.

The only instances where there are set requirements for accuracy in clean water meter applications are:

  • Meters used for household revenue metering; and
  • Some abstraction metering

The ability of a meter to interface with other systems may be a consideration. Meters are available that can directly interface with a number of common reporting systems and some are available with internal logging capacity. This can help reduce the complexity of an installation and hence minimise equipment and installation costs.

The manufacturer’s fitting instructions should be followed, for instance although most types of meter can be fitted in vertical, inclined or horizontal pipelines there are some, particularly jet types, where performance is compromised if they are not mounted horizontally.

The availability of power, or lack of, may limit meter choice. Mechanical meters do not require any electrical power supply, drawing the energy needed to drive the meter from the flow itself. However, power may be needed if an electrical pulse unit, data-logger or AMR transmitter is attached to the meter for remote reading.

Most types of meter require little or no maintenance.

Meter reading

The measurements made by a meter need to be recorded in some way and transmitted to where they are to be used. Common methods of taking a reading from the meter are:

  • Visual read. The meter reader looks at the visual display (register) and transcribes the reading manually onto paper or into a computer system. The colours of the digits on mechanical registers have been standardised as:
    • Black digits on a white background or white digits on a black background signify cubic meters; and
    • Red digits on a white background or white digits on a red background signify litres.
    On electronic displays there is typically a black frame around the digits representing cubic meters and a red frame around the digits representing litres.
    Visual reads are suitable for weekly or monthly meter read frequency.
  • Generating pulses from mechanical meters. The rotation of the meter operates a switch, the opening and closing of which is detected by circuitry within an external data logger. Meters may have options for different resolution (pulses/litre) depending on the type of system or where it is positioned on the meter.
  • This technology may be appropriate where there is a need for more frequent or detailed meter reads.
  • Automatic meter reading (AMR). The term AMR is used to encompass a range of technologies used for obtaining readings usually via a radio link. A small battery powered transmitter is positioned on, or in the meter register. It counts the pulses from the meter register and sends the total within a data packet to a remote receiver.
    This technology may be appropriate where there is a need for frequent meter reads with information sent to a central location.

Locating meters

As a minimum each water source should be metered. A better granularity of information could be provided by sub-metering particular uses which allows benchmarks for consumption both within and between sites to be identified along with opportunities for reductions in water use. Sub-metering could be considered for:

  • Critical sections of the site.
  • Points where different parts of a site are in different phases of work.
  • Points prior to specific draw off points for a particular purpose e.g. welfare facilities.
  • Points downstream of a specific draw off point so that consumption for a specific purpose can be identified.

A sub metering plan should be prepared to ensure everyone knows where to access the relevant meters.

Frequency of monitoring

More frequent monitoring of water use will result in a better picture of how water is used on site being derived and provide earlier warning of unusually high, or low consumption.

As a minimum it is suggested that monthly meter reads are obtained. In some circumstances it may be useful to collect reads more frequently than this, for instance where there is:

  • A critical period on site.
  • Periods of extreme weather (wet or dry).
  • A need for specific investigation of night use (to identify and quantify leaks).
  • A highly variable schedule on site e.g. by number of people or activity.

The monitoring can be set up on a half hourly basis allowing virtual real time monitoring.

Reporting requirements – how, when and who

At the outset reporting requirements should be determined and agreed. Reporting requirements may include:

  • To site managers
  • To environmental managers
  • For corporate reporting systems
  • To site staff, to encourage particular behaviours

Reporting will be clearest, and most clearly understood by the audience where water use values are documented in relation to factors such as:

  • Number of staff on site
  • Value of construction work
  • Activities carried out on site during the reporting period
  • Other influencing factors during the reporting period (e.g. unusually dry, or wet weather).

A number of online systems for reporting of water are available that may interface directly with appropriate meters. These have the advantage of allowing easy access to a variety of staff and managers through an online login and graphics of performance and targets can easily be visualised.

Reporting against baseline and target

Initially it is useful to derive baseline water use on site, against which future consumption can be assessed. This may be reported against a number of factors such as number of staff on site, or value of construction work.

It is good practice to set a target water use figure appropriate to the site against which progress can be measured. This may be set following identification of the baseline or may reflect a sector or industry specific target which already exists. Reporting should then be carried out against the target at an appropriate, regular, period.

Procedure for investigating unusual consumption

A procedure for investigating unusual consumption should be devised. The need for this may arise from unusually high, or low meter readings that could indicate problems perhaps through leaks, or a faulty meter.

The procedure should be clearly documented and include:

  • Identification of a person who should be notified of an unusual reading & takes the decision for investigation.
  • Identification of who is responsible for investigation once a decision has been made.
  • Activities to be conducted as part of the investigation, for instance:
    • More regular routine meter reads
    • Site walk-around to identify cause of consumption
    • Review/testing of meters
    • Use of leak detection technology
    • Discussions with site staff to identify unusual activities.
  • Reporting route following completion of investigation
  • Identification of a person who is responsible for taking the decision to resolve any issues identified.

Meters should require relatively little maintenance, although regular review of meter reads to ensure they are within expected bounds should be undertaken. Monitoring, reporting, and investigation of unusual consumption should be carried out in accordance with the plan.

If meters are to remain on site following handover to the site owner upon completion then the location should be clearly marked on a site plan, along with details of isolation valves and other relevant pipework or ancillaries. It is useful also to provide details of the make and model of meter, and any calibration information pertinent to it.

Where there is an on-going requirement for metering e.g. of an abstraction which is to continue following handover, this should be made clear to the site owner along with any relevant contact information and historical logs that exist.