Geothermal Generation Contact Geothermal 2 Wairakei Tauhara Geothermal

Geothermal Generation

Contact Geothermal 2

Wairakei –Tauhara Geothermal System: Wairakei Field (west side) > Production from Wairakei Field began in 1958 and comprises Wairakei, a Binary Plant, Poihipi and Te Mihi Stations (combined approx 333 MW). > Wairakei Station was reconsented 2001 – 2007. > For Wairakei, cooling water is taken from the Waikato River and cooling water/condensate and used or ‘separated’ geothermal water are discharged to the Waikato River. > A bioreactor (completed 2012) takes out 85 90% of the H 2 S from Wairakei cooling water discharge. > The most recent station, Te Mihi (commissioned 2014), maximises reinjection; no increase in river discharges. > Secondary uses of extracted fluid are the Huka Prawn Park (takes residual heat from sgw) and the Wairakei Terraces (utilises hot fluid). > Key Resource Consents expire in 2026 and 2043.

Wairakei –Tauhara Geothermal System: Tauhara Field (east side) > Some electricity generation and large scale energy use. > Comprises Te Huka Binary Plant (26 MW), Tenon direct heat (20 MWth) and the consented but unbuilt 250 MW Tauhara II power station. > There is a small water take consent from the Waikato River for drilling purposes but no River discharge. > Key Resource Consents expire in 2026 and 2045.

Geothermal Power Stations 5

6 Geothermal Power Stations - Wairakei

Geothermal Power Stations – Te Mihi 7

The Resource Management Act (RMA) and Resource Consents • Waikato Regional Council - through the Regional Policy Statement and Regional Plan set rules around: – Take and use of water (including geothermal fluid) – Air discharges – Discharges to land – Discharges to water – Protection of significant natural areas • District (Taupo and Rotorua Districts) - through District Plans set rules around: – Land use – Subdivision – Noise – Landscape 8

Resource Consents – Geothermal Contact holds a set of: • 108 resource consents for its geothermal operations, covering such things as: – Geothermal takes and discharges – Air discharges – Take and discharge of cooling water – Condensate irrigation – Land use – Drilling – Earthworks – Structures in waterways – Other discharges to land waterways – Fresh water takes 9

The Environment Effective environmental management is crucial to the continued operation of Contact’s generation facilities. All generation sites pose unique environmental challenges. 10

Wairakei challenges • 55 year old plant. • Reconsenting – ceasing river discharges. completely not technologically feasible. • Sought continuation of discharge of separated geothermal water and cooling water/steam condensate to the Waikato River. • But with staged reductions of key contaminants. 11

Reductions Achieved Separated Geothermal water • From the 1990 s increased reinjection and reduced geothermal water discharges to River. • By August 2012 - 35, 000 tpd sgw. • By August 2017 – 23, 000 tpd - pre development – natural – discharge level of geothermal water run off from the System. • Arsenic and boron will be at approx natural levels. • Geothermal water is naturally hot but heat also reduced as discharges reduce. 12

Reductions Achieved Cooling water • Absorbs H 2 S, mercury and heat from condensed steam in the cooling process. • By August 2012 - H 2 S – 85 -90% reduction achieved. • By August 2017 – further H 2 S reduction. • Best endeavours obligation re mercury – 25% reduction achieved by reducing total discharge following Te Mihi commissioning. • Heat – max 5˚C rise in river temperature or 25˚ ambient • Cooling water flow rates decline as power station output is constrained by the geothermal take consent. 13

Solving H 2 S – the Bioreactor • Uses sulphur-oxidising bacteria to reduce the levels of H 2 S in cooling water absorbed from condensate • pumps the used cooling water through 378 km of pipes under a field next to the power station at the rate of 13, 000 litres per second • Inside the pipes, the bacteria absorb the H 2 S from the water, removing up to 90% of it before discharge to River • cost some $30 million and involved years of trials and a year of construction • Depends on temperature – reduce the temperature and the bacteria die • Not possible to materially reduce both heat and H 2 S 14

The Bioreactor üCompleted in August 2012 üRemoves H 2 S from cooling water üReduced H 2 S from >10, 000 kg/wk to ± 1500 kg/wk 15

Ohaaki Geothermal System • Ohaaki Power Station has operated since 1988 (generates 45 MW). • Reconsented 2013 for a further 35 years. • Landmark relationship established with Ngati Tahu as part of reconsenting. • River water is used for cooling transformers and auxiliary plant then discharged, with stormwater, via a series of separation ponds to the Waikato River. • Mitigation project on the Waikato River wetlands – ongoing enhancement and improvement. • Cascade (secondary) user: Ohaaki kilns • Key Resource Consents expire 2048. 16

Ohaaki geothermal power station

Ohaaki Wetland - Recently completed project – 18

Geothermal Environmental Interactions Overall, our geothermal operations are a benefit to the environment: üRenewable energy üLow greenhouse emissions üSustainable energy source üDomestic energy source Geothermal fluid use Water discharges Natural habitat protection Energy Use Thermotolerant vegetation 19