Ruakura Reservoir

PROJECT DESCRIPTION

Water is the lifeblood of a vibrant growing community, and an essential resource for fast-growing cities like Hamilton. As part of its long term growth strategy, Hamilton City Council engaged with key stakeholders, including local iwi Waikato-Tainui,to fast track development of bulk water infrastructure for the new Ruakura Inland Port, including two new 12ML water reservoirs.

Ruakura’s aim is to be Aotearoa New Zealand’s premium logistics and industrial hub. The 400ha precinct is the top economic priority for Waikato-Tainui, and is a critical factor in the region’s Futureproof Growth Strategy.

Ruakura represents the greatest opportunity for integrated transformational urban development in the Waikato. It will be a truly mixed-use precinct underpinned by an inland port that contributes to lifting Aotearoa New Zealand’s productivity and freight efficiency. It also includes a world class knowledge zone (Waikato University and Innovation Park), freight and logistics land, and new residential and retail land uses.

The Ruakura reservoirs will ensure the continued supply of safe drinking water for Hamilton City in the event of a major natural disaster.

CLIENT BRIEF/PROJECT CHALLENGES

WSP made a contractual commitment to deliver Ruakura Reservoir project by June 2020 (less than three years). The reservoir was also Hamilton City’s first IL4 reservoir for seismic resistance. Meeting the timeline required an innovative approach to reduce the preloading lag time needed in traditional reservoir construction. WSP achieved this through the design of the siteworks, which used the natural terrain to minimise preload downtime for the site.

The service and working life of the reservoirs needed to cater for both current and future (2050) needs for Hamilton City. This presented major challenges, with the expected flow for the reservoir ranging anywhere between 30 and 700 litres per second. The pump-station design configuration needed to incorporate an efficient pump layout that catered for night flows in the fledgling development area in 2020, right through to peak flows from the fully developed growth cell in 2050.

OUR SOLUTION

Ruakura Reservoir was delivered to a tight timeline to meet the commercial needs of key stakeholders. WSP accelerated the preloading phase and earthworks design (ahead of the main construction contract) to make sure a suitable platform onsite was available to the construction contractor to begin construction. WSP also reduced the carbon footprint and costs of the project, by recycling onsite surplus material.

The WSP structural team provided options on seismic resistance, longevity and cost to deliver the reservoir to an IL4 standard. This was based on a design life of 50 years and durability of 100 years,using a post tensioned structural system. WSP’s mechanical design incorporated a staged manifold design using split case pumps,which achieved the required flow flexibility and saved approximately $500,000 in capital costs.

LIST OF PRIMARY SERVICES

WSP provided a broad range of design services for the reservoirs, which followed all best industrial practices and standards, and relevant regulatory requirements.

This included:

• verifying the scope of works and timelines, and planning and programming the design process
• Assessing and identifying information gaps
• Facilitating and documenting workshops with HCC
• Developing cost estimates at key stages

Completing investigations needed to inform design, including geotechnical investigation, survey and service identification.

WSP also designed two 12ML identical, circular, above-ground post-tensioned water reservoirs, to importance Level 4, as well as:

• two 650mm ID bulkmains which connected to the existing bulkmains located in Wairere Drive and Peachgrove Road
• one reservoir pumphouse, to Importance Level 3 and located on-site, which allowed for one reservoir to operate, and provided for the second reservoir to be added later
• associated services, including on-site permanent Emergency Power Generation to 80% of maximum demand and a trunk main, electrical and control system.

WSP’s project management team maintained a local Hamilton representative as key contact to manage the process and provide regular project updates.

OUTCOME/CLIENT BENEFITS

The construction programme for construction was accelerated as the preload (a critical part of any reservoir construction) was staged ahead of the main contract. The design could be duplicated and staged onsite to cater for growth, while giving the city more robust water storage in case of an emergency event. WSP’s staged design catered for the growth of the new development area and had the flexibility to deal with industrial demands, while realising capital cost savings in excess of $500,000.

KEY FACTS

This will be Hamilton's first reservoir with IL4 seismic resistance.