CHATHAM ISLANDS CHALLENGES – UPGRADING NEW ZEALAND’S MOST REMOTE COMMUNITY WATER SUPPLIES

Graeme Glasgow

Senior Process Engineer, MWH NZ Ltd, Dunedin, New Zealand

Charles Mellish

Principal Process Engineer, MWH NZ Ltd, Dunedin, New Zealand

Owen Pickles

Chief Executive Officer, Chatham Islands Council, Waitangi, New Zealand

Abstract

The Chatham Islands face significant water challenges despite large surface water lakes. Their remoteness, some 680km south-east of New Zealand presents unique circumstances for the identification, design, construction and operation of water supplies. The settlement of Waitangi with a population of 300 faces shortages and relies upon a single groundwater source. The small community of Te One, 4km north of Waitangi has no public water supply and relies on rain water. Kaingaroa, located on the north-east promontory with a population of 60, relies upon a decaying former fish factory water treatment plant and a lake source prone to runoff. Owenga, in the south- east of the main island with a population of 40, relies upon erratic spring fed ponds, household bores and rain tanks but suffers frequent shortages and quality issues. Achieving the New Zealand Drinking Water Standards, providing quality, sustainability and affordability that can be constructed under the unique conditions on the Islands requires close collaboration between the stakeholders to transform the facilities and deliver solutions. This paper discusses the challenge to secure water supplies, presents details of the options proposed for Waitangi, Te One and Owenga and the design of the recently upgraded supply for Kaingaroa.

Keyword

Chatham Islands, Waitangi, Kaingaroa, Owenga, Water Supply

Introduction

Waitangi/Te One

The Chatham Islands (Rekohu or “misty sun” The community of Waitangi, located on the in the indigenous language of the Moriori) lie southern shore of Petre Bay is supplied with approximately 430 nautical miles East of the groundwater from a 30 to 40 metre deep bore South Island of New Zealand. The population located on Tikitiki Hill (approximately 500m totals approximately 600 residents with the North West of the community). Use of surface main communities located at Waitangi, Te water ceased when a new treatment plant One, Owenga and Kaingaroa (Figure 1). was provided in 2004. The water is currently filtered, softened, disinfected by UV light and which has since requested that Council take it dosed with chlorine before passing into the over for the good of the community. Raw reticulation network. Concerns have been water from the Lake is stored in timber tanks raised over the security of the water supply above the community (Figure 4). The water and the need to make improvements to meet treatment facilities are located inside the old the Drinking Water Standards New Zealand fish factory and comprise pressure filtration, 2005 (amended 2008). It should also be cloth filtration and UV disinfection (Figure 5). noted that one of the pressures on the Since the factory closed a local resident has Waitangi supply is the water that is taken by kept the system running for the benefit of the people resident outside of the reticulated community with no recompense. This area. These are usually people who are requires multiple journeys to the raw water mostly reliant on rain water capture and have pumping station for refuelling and manual run out. operation linked to visual inspection of the contents of the raw water tanks and is laborious. The supply and equipment has fallen into disrepair with few spare parts The nearby community of Te One is remaining and is at the end of its’ asset life. approximately 4km North East of Waitangi Chatham Island Council has now taken over and has no existing public water supply. All the supply. properties typically collect rainwater with groundwater for non-potable use. During periods of water shortage, residents collect water from the Waitangi source. Reliance on Owenga a single bore leaves both communities vulnerable, especially since the single bore is The community of Owenga is located in the believed to be close to its’ sustainable yield South East of the Island, near Cape Fournier limit. Concerns have been raised over and is approximately 18km from Waitangi. security of drinking water supplies and There is no existing water supply scheme at contamination of collected rainwater. In Owenga. Historically, some properties have addition, an Iwi housing development at Te access to spring fed ponds (Figure 6) or One in 2012 saw 6 housing units established abstraction from shallow creeks. Others are all with rain water catchment tanks. These reliant on rainwater tanks and private bores properties constantly run out of water and (Figure 7) and pay for cartage of water from were dry throughout November and Waitangi when supplies run out. The water December 2013. These properties have quality from the bores is highly variable and come to rely on the Waitangi supplies. suffers from high levels of iron. In most Furthermore, a new Marae is proposed for Te cases, there is little storage and water is One. pumped directly to the residence. The pond and creek sources are prone to faecal contamination from surface water runoff from grazed land. Peat beds result in high levels of Kaingaroa dissolved organic matter. None of the water sources receive treatment and E. Coli has Supply for the community at Kaingaroa been detected in tap water. comes from Lake Rangitai, a fresh water lake located on the North East peninsular of Chatham Island. Raw water is pumped from the Lake to the community (approximately Options & Solutions 8km East) by a manually operated diesel pump located on a small island within the Lake (Figure 2). The water supply system at Kaingaroa used to be owned and operated by Waitangi/Te One and Owenga a fishing company and served both the A methodology to identify the preferred factory and local community (Figure 3). When solution, encompassing the 3 communities of the company ceased operations the water Waitangi, Te One and Owenga has been supply assets were transferred to a Trust developed and agreed with Chatham Islands Council (CIC) and the Ministry of Health (MoH). The proposed methodology Te One: comprises:  Pipe in water from Waitangi for  Information collation and desk top potable use (existing and/or new review bores at Waitangi)  Prepare short list of potential options  Retain existing groundwater sources  Selection of preferred solution for non-potable use  Preparation of Preliminary Design  Retain existing rainwater collection for Report to support funding application potable use with potential cartage of potable water from Waitangi or Readily available information will be collated potential new fill point at existing Trust and a high level desktop review conducted. bores The review will briefly consider and provide  Provide a new non-potable bore at Te high level comment upon the following: One based on GNS report recommendations (Begg & Zemansky,  Existing Chatham Islands Enterprise 2012) Trust boreholes located  Provide a new potable bore at Te One approximately 6km from Waitangi and based on GNS report 12km from Owenga recommendations (Begg & Zemansky,  Existing bores and springs located in 2012) Owenga  Existing bores located in Waitangi  Existing bores located in Te One Owenga:  Potential for new bores for Waitangi, Te One and Owenga  Provide a new bore for potable water supply to the east of the community at  Water quality information where Owenga and new reticulation to the available community at Owenga based on GNS

report recommendations (Begg & There are a number of options at each site Zemansky, 2012) with an integrated solution possible. Potential  Retain existing rainwater harvesting options could include the following. and ponds/springs for potable supply  Retain existing private residents’ Waitangi: bores for non-potable use  Cart in potable water when required  Retain the existing bore on Tikitiki Hill from potential new fill point at existing  Provide a new pump at this bore Trust bores (assuming water is  Upgrade the existing treatment plant available) or possibly provide a  Retain the existing storage and pipeline reticulation  Provide an additional new bore on Tikitiki Hill The Ministry commissioned a study (Begg &  Provide additional storage at the Zemansky, 2012) of the potential to develop treatment plant new groundwater sources at Waitangi, Te  Provide additional storage at the One and Owenga. A key feature of the Island existing 4 treated water tanks identified by the study is the extensive  Provide a new bore based on GNS southern upland plateau (Figure 1) that report recommendations (Begg & essentially drains to the North. The three Zemansky, 2012) communities of Waitangi, Te One and  Pipe in water from the existing bores Owenga are located on the northern edge of at the Trust site this plateau. Potential groundwater sites were  Provide pipeline from Waitangi to identified for each of the communities and will be included in the assessment of the options supply Te One described above. Another option in some  Short listed options that have been areas may be larger household rain water considered storage tanks to accumulate rain fall not  Preferred solution identified currently captured and wasted.  Evaluation criteria used  Description of how demand will be

met A short list of potential options will be  Water quality of the proposed source identified and agreed with CIC and MoH. At  Proposed water treatment facilities this stage, it is envisaged that this would including storage comprise:  Pumping and reticulation requirements  Develop new bores at Waitangi, Te  General plans and flow schematics One and Owenga  Power supply and control  Provide pipeline from Trust bores to requirements Waitangi and Te One  Cost estimate  Provide rain tanks for Owenga  Statement of design and procurement method

The short listed options would include an Kaingaroa assessment of their advantages and disadvantages based on the review of Lake Rangitai suffers from low UV available information and where appropriate transmissivity (50 – 60% filtered UVT) sketches of potential sources, treatment sites associated with colour, generally low and pipe routes. The short listed options will suspended solids and moderately high be evaluated using agreed evaluation criteria hardness (150 to 200 mg/l as CaCO3). The and a preferred solution identified. The Kaingaroa water supply is for a community of evaluation criteria will need to be discussed <500 people. CIC therefore pursued and agreed with CIC and MoH and other compliance for this supply as a Participating stakeholders as part of the study at this Supply under Section 10 of DWSNZ 2005/08. stage. Issues that could be considered in This required that: development of the agreed evaluation criteria to be used include the following:  A Public Health Risk Management Plan (PHRMP) must have been  Potential pipeline routes and cost approved by a drinking water  Exploratory drilling, cost and likelihood assessor (DWA) and be in the of success process of being implemented.  Design population and water demand  Appropriate bacterial and chemical  Design water treatment requirements treatment, as determined from the  Risk assessment catchment assessment in the PHRMP, must be in use.  Appropriate protozoal treatment A Preliminary Design Report will need to be (Table 10.1 of DWSNZ 2005/08) must prepared for the preferred solution to support be in use. an application for funding from MoH. The  Water quality must be monitored and preliminary design report will include the meet the requirements of section 10.4 following: of DWSNZ 2005/08.  The remedial actions that have been  Description of the communities served specified in the PHRMP must be  Statement of the design water undertaken when a Maximum demand Allowable Value is exceeded for any  Description of the existing water contaminant or treatment process supplies controls are not met.  Outline of the deficiencies of the existing water supplies The catchment assessment in the PHRMP The proposed methodology for the states: identification and development of the solution(s) for Waitangi/Te One and Owenga The catchment fits the description in Table has been submitted for approval by CIC and 10.1: Microbial treatment requirements for MoH. Work is expected to commence shortly. small supplies of different levels of risk (DWSNZ 2005 revised 2008) “Partially protected catchment with no sewage discharges or human habitations and no Kaingaroa intensive livestock operations harbouring gatherings of pre-weaned and juvenile stock”. The upgraded water supply and treatment The minimum microbial treatment plant is complete and is currently being requirement for this category of catchment commissioning at Kaingaroa (Figure 9). The type is “Bacterial and 3-log protozoa raw and treated water tanks and the new treatment”. treatment plant shed have been installed (Figure 10). The new skid mounted treatment No chemical treatment requirements were units have been assembled and installed. identified in the PHRMP.

References Table 10.1 of DWSNZ 2005/2008 stipulates, inter alia, microfiltration followed by chlorination or UV disinfection. Chlorination of Begg, J.G. and Zemansky, G. (2012) this supply was discarded due to the risk of formation of disinfection by-products from the “Investigation of groundwater potential at colour present. It was recognised that UV Waitangi, Te One, Owenga and Kaingaroa disinfection where the UVT was low as in this Chatham island.” GNS Science Consultancy case would not provide a validated dose and Report 2012/261. hence not achieve full compliance with the requirements of the standards. After Campbell, H.J.; Andrews, P.B.; Beu, A.G.; discussion, it was agreed with MoH that the Maxwell, P.A.; Edwards, A.R.; Laird, M.G.; best practical solution in the circumstances Hornibrook, N.deB.; Mildenhall, D.C.; was a treatment process comprising roughing Watters, W.A.; Buckeridge, J.S.; Lee, D.E.; filtration, Macrolite® filtration, softening and UV disinfection where the Macrolite® filter Strong, C.P.; Wilson, G.J.; Hayward, B.W. was accepted by MoH as delivering 3 log (1993) “Cretaceous-Cenozoic geology and protozoal treatment and with the UV unit biostratigraphy of the Chatham Islands, New selected to compensate for the low UVT Zealand.” Institute of Geological and Nuclear (Figure 8). Sciences Monograph 2.

Forsyth, P.J.; Barrell, D.J.A.; Jongens, R. Conclusion (compilers) (2008) “Geology of the Christchurch area.” Institute of Geological and Nuclear Sciences 1:250 000 geological map 16. Waitangi/Te One and Owenga

Appendix A Figures

Figure 1: Chatham Island (Begg & Zemansky, 2012. After Campbell et al. 1993; Forsyth et al. 2008)

Figure 2: Kaingaroa (Lake Rangitai) raw water pumping station

Coral Filter

Pump Kaingaroa Township Reticulation

2 x Timber Tank Reservoirs

Lake Rangitai 1 x Pressure Filter KAINGAROA WTP

4 x Cloth 4 x UV Filters Units

Figure 3: Kaingaroa existing water supply scheme

Figure 4: Kaingaroa existing timber (raw water) tanks

Figure 5: Kaingaroa existing cloth filters and UV units

Figure 6: Owenga water supply - typical spring fed pond

Figure 7: Owenga water supply – typical household (bore and filter)

Raw water reservoir 1 x 30 m3 tank

Intake Pump WTP Inlet Booster Pump Set Pump Set Macrolite Cartridge UV Treated water filter filter disinfection reservoirs Kaingaroa 4 x 30 m3 tanks reticulation Infiltration gallery KAINGAROA WTP at Lake Rangitai

Figure 8: New Kaingaroa water supply scheme (WTP finalised with MoH as roughing filter, Macrolite® filter, softener and UV, Existing Lake intake retained)

Figure 9: New water treatment plant at Kaingaroa

Figure 10: New raw and treated water storage tanks and treatment plant shed at Kaingaroa

Author Biography

Graeme Glasgow BEng MSc PhD CEng CEnv MCIWEM

Graeme has over 20 years of experience in water and wastewater treatment engineering. He is a Chartered Engineer with the Engineering Council and a Chartered Environmentalist with the Society for the Environment. He is a Member of the Chartered Institute of Water and Environmental Management. He holds a Doctorate in water engineering from Loughborough University in the UK where he undertook research in rapid sand filtration. He has worked as a consultant engineer in both the UK and New Zealand. Graeme joined MWH NZ Ltd in 2009 and is based in the Dunedin Office.