Drinking Water Engineering

GWE offers advisory, design and implementation services related to the provision of drinking water including, water source selection, transmission, treatment process and plant design, storage and distribution. We also prepare risk management and water safety plans in accordance with the Drinking Water Standards NZ. Solutions are based on a range of processes and technologies and sized to meet community needs.

In many communities across NZ, public water safety has been catapulted to the forefront of concern.

With awareness of safe drinking water at an all-time high, and regulations becoming more and more stringent, the task of providing new or upgrading existing infrastructure becomes ever more challenging. We offer comprehensive consulting services to public and private clients planning to implement water treatment and supply projects. Our integrated approach to the development of project solutions matches contemporary standards of design and resilience while at the same time adding value for clients.

Drinking Water – What We Do

We undertake the following Drinking Water related work:

  • Small community water supply schemes
  • Water source selection
  • Storage and pretreatment
  • Water treatment process design
  • Process control and compliance programme & monitoring
  • Reticulated water supplies
  • Water safety plans
  • Source water risk management plans

Community Water Supply Schemes

GWE has the experience to design and develop community water supply schemes to the suppliers’ needs and meet regulatory standards as well as environmental and cultural concerns. We can also provide our clients with advice on those small supply schemes that are required to provide safe drinking water but subject to less rigorous compliance standards. Our designs meet the following standards:

  • The Drinking-water Standards for New Zealand 2005 (revised 2018) (DWSNZ)
  • The Guidelines for Drinking-water Quality Management for New Zealand 2017
  • Self-supplied drinking-water systems are subject to the requirements of the Building Act 2004.
  • The Health Act 1956
  • The Water Service Act 2021

Water Source Selection

A major consideration when designing a water supply scheme is the nature of the source water that is to be used which may be a stream or river, groundwater or rainwater collection. GWE will investigate potential sources by assessing the following criteria:

Surface Water

  • Is the abstraction site close to the area to be supplied?
  • Will the flow always be sufficient, or will storage be needed?
  • Is there a downstream minimum flow requirement?
  • How variable is the quality, day-to-day, or seasonally?
  • What is the worst raw water quality to be treated?

Groundwater

  • If bore water, will it be assessed as secure?
  • Will the quality of its waters be difficult to treat?
  • Is the catchment or recharge area vulnerable to contamination?

Resource Consents

Many water treatment plants will require a resource consent for the take of water from a surface water or groundwater resource. GWE will provide advice on the consenting requirements and produce technical and planning reports, including an assessment of environmental effects (AEE) to support applications for new or the renewal of water take applications. The consent application will need to demonstrate:

  • New water supply infrastructure complies with the regional water plan
  • The assessment of effects follows the Fourth Schedule of the RMA
  • Where necessary appropriate consultation has occurred

Water Treatment Plants

GWE engineers are experienced in the design of a variety of treatment processes based on the characteristics of the source water which could be a surface water, a groundwater or rainwater. The plant could be a full-scale water treatment process or just a simple disinfection system. Treatment processes include:

  • Chemical coagulation and sedimentation
  • Sand or membrane filtration
  • Carbon or cartridge filtration
  • pH and hardness adjustment
  • Chlorine or UV disinfection
  • Iron and manganese removal

Distribution Systems

GWE engineers can model and design all of the components of a distribution system serving a small community including, trunk mains connecting treatment plants to service reservoirs, reticulation mains connecting reservoirs to consumers and providing a fire-fighting supply to provide protection for industrial, commercial and domestic properties.

Water Safety Plans

Our engineers have the experience to prepare a Water Safety Plan (WSP) for your community water supply scheme. A WSP is a written document that aims to assess and manage risks to the safety of drinking water associated with that drinking water supply. Risks are identified from the water supply catchment right through when the water is supplied to the public. The WSP should identify barriers to contamination, potential events that could introduce hazards to the scheme, preventative measures and corrective actions and improvements that are necessary to protect public health.

Sanitary Surveys

GWE can undertake sanitary surveys of the water supply scheme including the catchment, abstraction point, treatment plant, and distribution system on behalf of the water supplier as part of any programme of risk management. The surveys should be conducted with sufficient frequency to be useful in interpreting trends or sudden or significant changes in water quality as revealed by routine monitoring.

The surveys identify potential risks, whilst monitoring can record process performance and water quality trends, whether contamination is occurring, and the extent and the intensity of that contamination.

As part of the Water Reform all suppliers will require a source water risk management plan. GWE has the expertise and experience in gathering all the information to produce these plans so that they are relevant and useful to your water supply scheme.