Chemically Treated Drinking-Water: Environmental Impacts – Rarotonga, Cook Islands

Dragonfly, Turangi Stream.

Chemically Treated Drinking-Water: Environmental Impacts, Rarotonga, Cook Islands.
Compiled by: Andy Kirkwood, Justine Flanagan, 2019.
[www.islandbooth.com/comm/190709-cl2-environmental-impacts.html].
Contact: [firstName] @ islandbooth.com.

Masthead Dragonfly, Turangi Stream

 

This is a working draft. Updated 28 June 2020

 

The Te Mato Vai Project to update Rarotonga’s intakes and water main includes implementation of a 4-stage treatment process. Chemicals have been proposed for Stage 2: Coagulation/Flocculation to remove small particles and protozoa; and Stage 4: Water Disinfection to kill or inactivate micro-organisms.

 

On this page

Stage 2 Coagulation: Polyaluminum Chloride

Polyaluminum chloride (PACl) has been proposed to improve water clarity (turbidity). When added to the source water, the chemical causes smaller particles to clump together; these clumps then fall to the bottom of a settlement tank or are removed by subsequent filtration methods.

Adding a coagulation chemical is one method of treating water to improve clarity. There are alternative physical (non-chemical) treatment methods that can also be used to improve clarity, such as not collecting water in high-turbidity conditions (diversion); centrifugal separation; passing water over a electrical plate; or use of fine filtration.

Disinfection requires that water is clear. Particles in clouded water can prevent the disinfection from deactivating potentially harmful micro-organisms. Clear water improves the effectiveness of disinfectoin whether the disinfection method is chemical (e.g. chlorine solution); or physical (e.g. UV irradiation).

Stage 4 Disinfection: Calcium Hypochlorite

Although the Cook Islands Government has continued to issue the statment that ‘No decision has been made on disinfection’; chlorine solution storage and dosing equipment was ordered in 2018 and installed by contractors at each of the ten intakes from early 2019; prior to the community presentation and discussion of disinfection options in May 2019.

The chlorination chemical preferred by government is calcium hypochlorite.

 

Environmental Impacts of Chemical Treatment

The Cook Islands National Water Policy (2016)“[brings] together government policies for water resources management, infrastructure, water supply, drinking-water safety planning and sanitation.”

This document makes a number of references to water management and environmental considerations that apply to the Te Mato Vai Project and the operations of the new water authority To Tatou Vai.

Precautionary Principle
Taking active measure to prevent serious or irreversible environmental damage or degradation whether the consequences are uncertain or not.

Sustainability & Environmental preservation
Strive to protect and avoid adverse interference with the natural ecology of the Cook Islands’ waters and lagoons and ensure that usage and management of water will be conducted in a manner that will preserve and enhance this resource for generations to come.

Mitigation of the impact of Infrastructure and Development on Ecological Flows
In designing and delivering future water supplies, infrastructure, services and operations will be provided in a manner that ensures that ecological flows are maintained in natural streams and waterways to the greatest extent practicable in order to ensure the protection of freshwater and coastal ecosystems.
Cook Islands National Water Policy (2016)

 

Environment Act 2003 / Te Mato Vai Stage 2 Environmental Impact Assessment

Groundworks and construction in areas of specific concern are subject to regulation in the Cook Islands under the Cook Islands Environment Act 2003; areas of concern include sloping lands and sites in close proximity to waterways/streams. The new Te Mato Vai water treatment plants are located in such areas.

Prior to construction commencing the applicant may be required to complete a report detailing possible environmental impacts of the project and the measures that will be taken to minimise such impacts. The resulting Environmental Impact Assessment (EIA) report must be made available for public consultation to allow for any formal responses prior to a construction permit being issued.

An EIA for the Te Mato Vai Stage 2 construction was produced in August 2015. The only mentions of chemical use are indirect.

  • A reference is made to the engineering standard to be followed when commissioning (sterilising) the new waterworks; and the engineering standard recommends the use of high-strength chlorine solution.
  • An example water treatment process schematic diagram include a note that a “Flocculating Agent may be injected (if required) to aid removal of finer particles”; however no further specific detail is provided regarding the construction or operation of chemical treatment systems.
3.1.2 Water Treatment Upgrade (Schematic).

3.1.2 Water Treatment Upgrade (schematic), Te Mato Vai Detailed Design for Stage 2, Draft Environmental Impact Assessment Report. GHD, August 2015
Accompanying caption: Figure 3 - Indicative flow diagram to illustrate how the proposed gravity operated water supply and treated system works.

With the project now nearing completion, it can now be seen that ommitting detail from the EIA report has prevented the public from raising concerns about the treatment method (prior to the commencement of the construction project), and is a likely violation of the intended consultation and approval process.

Old pipe – new pipe: both on the same pipe

Concerns have been raised as to the pipes and construction of the distribution system with estimates of 17km of the new water main requiring replacement (Cook Islands News, Dec 2018). These concerns were confirmed in Oct 2019 with a contracting company taking up a tender to repair the faulty sections of the main. The repair works have been referred to euphemistically by government as a Stage 1 Upgrade; Remedial, or Resilience works.

Above: Pipes leaking into the Turangi stream, approx 100m from the water treatment plant. June 6 2019.

Turangi Pipe-leak Updates

  • 19 July 2019: The above blue-collar thermo-coupling has been repaired. The older asbestos concrete (AC) pipe length is still leaking. In drought conditions, water leaking from the trunk main is the only water entering this part of the Turangi stream. The PMU have indicated that this length of pipe may be decommissioned when the new system is made live.
  • 4 Sept 2019: Te Mato Vai have advised that the pipework that spans the streams will be the final sections of pipework to be replaced. The above ground pipework will be fibre-coated metal rather than the softer high-density uPVC plastic used for the in-ground network. The weight and vibration of water moving through the pipes require the strong metal pipes to be used. In-ground pipes are bedded in sand.
  • 4 Dec 2019: Still leaking. Along with chlorine; dissolved aluminium and PACl sludge is also toxic to aquatic life. The operation of the new Te Mato Vai system proposes regular discharge into the stream of supernatant (PACl wastewater); and onsite storage of PACl sludge, before transfer to the Arorangi landfill.
    See: PACl on Trial.
  • 22 Apr 2020: Road closure and work underway on new trunkline. Construction of a (temporary?) upstream dam and excavation suggesting the new trunkmain may run underneath the ford?
    •  

    Network failure will result in chemically-treated water contaminating waterways as pipework often follows the stream route out of the valleys.

    Freshwater aquatic life is highly sensitive to chemicals, with acute toxicity to chlorine at very low dosage.

    A chlorine residual concentration of 0.04-0.2mg/L is considered toxic to the majority of fish species.

    Active chlorine is toxic to fish from levels as low as 4 parts chlorine to 100,000,000 parts water. In periods of low waterflow/drought, leakage from the water main may be the only water in the streambed (below the intake point).

    Active chlorine is very toxic to fish. Its toxicity largely depends on water temperature: for example, an active chlorine concentration of 3.5 mg per litre has a sublethal effect on carp at a water temperature of 3–7°C but when exposed to the same concentration at a temperature of 15–20°C they die in 1 to 2 hours. In general, a prolonged exposure to active chlorine concentrations of 0.04 to 0.2 mg per litre is considered to be toxic to the majority of fish species.
    (PDF) Water Quality and Fish Health, United Nations FA0 (1997)

     

    WHO Drinking-Water Standards for Chlorinated Supply

    The WHO standard for residual chlorine disinfection is 0.2-5 mg/L. At this level water ‘from the tap’ will be toxic to the majority of fish species. Leakage nearer the intakes will be more toxic due to the higher levels of active chlorine.

    What will the chlorine level be as water enters the network?

    WHO recommends that the concentration of active chlorine in water entering the network to be at least 0.5mg/L and no greater than 5mg/L. (The concentration of chlorine in pool water is 2-4ppm).

    Chlorine dosage: Leaving Treatment, Entering Network: 0.5-5.0mg/L.
     

    Commissioning: Super-chlorination Disinfection

    Prior to the new Te Mato Vai system being made ‘live’ the network pipes and plant (including storage tanks) are required to be disinfected, using a ‘shock’- or super-chlorinated solution. This is to remove any construction waste and disinfect surfaces that might pose a health-hazard to the public.

    5.11 Disinfection
    5.11.1 General
    When instructed to do so by the Engineer, the Contractor shall disinfect the pipeline by chlorination either in sections or as a whole. The Contractor shall provide a suitable chlorine dose pump and chlorine which is capable of accurately injecting the required concentration of chlorine solution at steady rate into the pipeline.
    The Contractor shall introduce at least 20ppm of chlorine or such greater quantity of chlorine as will produce a residual of at least 1ppm of free chlorine at any point along the pipeline being sterilised 2 hours after the section of pipeline has been filled with water.
    …
    If after 24 hours, the residual chlorine is 1ppm or greater, then disinfection shall be deemed to be complete and the chlorinated water shall be drained and flushed away to a suitable outlet where no harm will result from the flow or its contents. Dispose of disinfected wastewater to meet relevant Regulation and ICI Requirements.…
    -Infrastructure Cook Islands Technical Standards for Water Supply in Partnership with the Institution of Professional Engineers Cook Islands, 30 May 2014

    Specific chlorine dosage values from standard-to-standard, but in New Zealand can reach starting levels of up to 100mg/L (prior to neutralisation). Even when reduced to the recommended disposal dosage of 1ppm, this is still 25 × the level at which the chemical is toxic to freshwater aquatic life.

    Along with the connecting pipework, commissioning includes the sterilisation of the new 1.8–2.3 million litre water storage tanks (some intakes have two such tanks). Given the remote inland locations (lacking a suitable outlet for disposal); logistics of removing the wastewater, sterilisation water will be discharged either into the ground or into the intake valley streams.

     

    Dissolved Aluminium

    The coagulant chemical polyaluminum chloride (PACl) is proposed to remove sediment and fine particles from source water.

    Aluminium in the aquatic environment can have a major impact on aquatic life. Acid precipitation [acid rain] has been implicated in the loss of fish populations from acid sensitive waters through the mobilisation of aluminium… The short-term changes in aluminium concentrations caused by these events can have severe effects on aquatic biota.
    Canadian Water Quality Guidelines for the Protection of Aquatic Life: Aluminium. Candian Council of Ministers for the Environment, 2003 (Withdrawn).

    In the Cook Islands, infrastructure projecs in areas of specific (environmental) concern are required to complete an environmental impact assessment process. This includes public consultation processes. Despite initially claiming that the necessary regulatory processes had been completed, in January 2020 a release was issued through the Te Mato Vai Facebook Page (later attributed to the new water authority - To Tatou Vai), that a stream survey was to be undertaken as part of an EIA into the operational use of PACl. The stream survey was conducted over a 1-2 week period in January 2020 by government consultants GHD (pers. comm. To Tatou Vai).

    Although better-late-than-never, a two-week spot sample is insufficient given that operation of the new system proposes to decant dissolved aluminium wastewater into the freshwater streams (also noting the companion risk of unintended overflow of onsite sludge storage ponds).

    Conditions of pH, total hardness and dissolved organic carbon (DOC) may vary within a waterbody throughout the year, thereby affecting the bioavailability of aluminum over time. To ensure the criteria will be protective during the times when aluminum is most bioavailable (and most toxic), the EPA recommends that the state or authorized tribe collect, if possible, 24 months of monthly sampling data for the three input parameters. This approach will help to account for both intra- and inter-annual variability of the input parameters.
    Implementing the 2018 Recommended Aquatic Life Water Quality Criteria for Aluminum. United States Environmental Protection Agency (EPA).

    Also see: PACl on Trial.

     

    Rarotonga’s Freshwater Biodiversity

    Without surveying the valley streams and waterways prior to chemical use it will be difficult to track or attribute impacts.

    Bodies of freshwater in the Cook Islands are extremely limited, with no large lakes or rivers, only wetlands, streams and a few small freshwater lakes present. Freshwater biodiversity is therefore extremely limited. The Cook Islands National Biodiversity Strategy and Action Plan (NBSAP) lists only nine native and four introduced fish species, two native and three introduced gastropods, and six native and one introduced crustacean.
    Cook Islands 4th National Report to the Convention on Biological Diversity (2011), National Environment Service.

    Cook Islands Biodiversity Database: Freshwater Species.

    Freshwater Species Search Result, Cook Islands Biodiversity Database. The above result include estuarine species, but not insects that may also depend on freshwater ecosystems such as dragonflies and damselflies.

    Potential impacts on plants and insect life should also be further researched.

    NZ: Freshwater Management

    As a regional and regulatory reference-point, the New Zealand policy statement on the management of freshwater ecosystems may help to identify impact areas requiring monitoring:

    In a healthy freshwater ecosystem ecological processes are maintained, there is a range and diversity of indigenous flora and fauna, and there is resilience to change.
    Matters to take into account for a healthy freshwater ecosystem include the management of adverse effects on flora and fauna of contaminants, changes in freshwater chemistry, excessive nutrients, algal blooms, high sediment levels, high temperatures, low oxygen, invasive species, and changes in flow regime. Other matters to take into account include the essential habitat needs of flora and fauna and the connections between water bodies.
    New Zealand: National Policy Statement for Freshwater Management 2014 (amended 2017)

     

    From Ridge-to-Reef

    Impacts of water treatment chemicals on the lagoon, reef and ocean require research specific to Rarotonga. International research indicates linkages between freshwater quality, chemical pollution, and reef health.

    “Citing climate change as the exclusive cause of coral reef demise worldwide misses the critical point that water quality plays a role, too. While there is little that communities living near coral reefs can do to stop global warming, there is a lot they can do to reduce nitrogen runoff… the fight to preserve coral reefs requires local, not just global, action.”
    15 July 2019: Thirty years of unique data reveal what’s really killing coral reefs. Science Daily. Accessed 29 July 2019.

     

    Liability for Environmental Incidents

    Consideration of liability for environmental damage involves analysis of whether the Government has a “power of control” over the work of contractors such that the Government is vicariously liable:

    The test [to prove vicarious liability] involves:

    1. a right to direct the subcontractor in circumstances where the right is capable of exercise and is, or is likely to be effective; and
    2. actual control of a course of action taken by the independent subcontractor; ie, control over the way in which the tasks are to be performed or how they are to be carried out.

    Liability for Environmental Incidents – Are You in Control?. Andrew Petersen and Irene Wales, Findlaw Australia. Accessed 28 July 2019.

    In other words, it is critical whether the Government controls how work is carried out by the consultancy or contracting firm.

     

    Comissioning of the Te Mato Vai Water Treatment System

    The Cook Islands Government announced commissioning in a double-page spread appearing in the Cook Islands News, 30 November 2019.

    The Cook Islands Government has instructed the Te Mato Vai Stage 2 contractor McConnell Dowell to begin commissioning the new intake water supply systems. Currently the public water supply is still connected to the old intake infrastructure.
    Improved water will soon flow through new water supply system. Cook Islands Government Release in Cook Islands News, 30 Nov 2019.

    If the wording seems awkward, it’s likely as result of the vicarious liability issue outlined above; to make clear that the contractor has been directly instructed by government to proceed (and is carrying out works to the specification of the national water supply standards). It is now the government that assumes all responsibility for environmental damage that might occur as a result of the shock-chlorination.

    According to the To Tatou Vai Public Notice appearing in the same paper:

    Matavera Intake Shut Down
    The contractor is undertaking commissioning works for Matavera intake and may require a shut down on the following days
    Monday 2 December, 8am to 1PM…
    -IBID

    Community group Te Vai Ora Maori protested the commissioning the morning the work was scheduled to commence.

    Takuvaine Stream Die-Off: Dec 2019

    The following Wednesday a further notice was published; and the same week letters were delivered to Landowners to notify that the Takuvaine WTP was to be commissioned Fri 13 Dec.

    Landowners visiting the plant on Monday 16 Dec saw operations staff in personal protection equipment dosing the settlement tank with chlorine solution.

    The Landowners had previously been advised that chlorinated water was to be held in the settlement tank for 24 hours and then drained through the treatment plant network to the lower water storage tank, where it would remain for 3-6 weeks to allow the chlorine to disappate / be reduced to non-toxic levels. Instead it appears that chemical water was partially or entirely discharged into the Takuvaine stream.

    Above: Takuvaine Stream Die-off / Shock-cholorination Commissioning Video. Filmed 17 Dec 2019.

    Takuvaine Stream Die-off Updates

    • 20 Dec 2020: Report submitted to authorities requesting formal investigation into potential environmental incident.
    • 24 Dec 2019: Although no investigation has been conducted by the National Environment Service; no formal response tended to the complainant; and despite the eyewitness accounts; the Secretary of Finance issues statements to local and international media: “…the complainants were wrong. There was no evidence to back such claims, he said, with no photos of the supposedly dead fish and eels the landowners say had died.”
    • 27 April 2020: An independent expert review of the Te Mato Vai water treatment system was commissioned by the Cook Islands Ministry of Justice in Feb-Mar 2020. As part of a walk-through of the waterworks, a potential engineering fault was identified: when the settlement tank is full, streamwater will flow through the Inlet Chamber (where PACl is dosed) and then overflow to the stream.
      During disinfection, (if left unattended), the design of the system appears to allow for high-dose chlorinated water to overflow into the stream. If this interpretation is correct, it this would account for the residents’s observations.
      The Expert description of the ‘fault’ and the response from GHD was requested 15 April 2020 but has not been answered as at 28 June 2020.
    Te Mato Vai Settlement tank design, and proposed engineering fault.

    Emptying the Settlement Tank (settlement tank design), adapted (enlargement added) from ‘Information to support approval to commission Te Mato Vai Stage 2’. GHD, Nov 2019.
    The settlement tank diagram suggests that when the tank is full, chemically-treated water can overflow to the stream.

    • 25 June 2020: In a Te Mato Vai photo opportunity staged to coincide with the June session of Parliament it was revealed that the backwash (PACl wastewater) storage pond required reconstruction after it was damaged in a storm event. If the plant had been operational, the consequence of pond failure would be contents of the pond overflowing into the Takuvaine stream.
      OIA request filed: 26 June 2020
      Response 22 July: A culvert outside of the Takuvaine Stage 2 construction site became blocked, causing an overflow of water to run over the road, down past the settling tank to the scour ponds… causing some minor erosion of the scour pond embankments. [Remediation] reshaping of the ground profile upstream and around the culvert area to divert any overflow back into the stream. A concrete ford crossing is also being constructed on top of the culverts to further protect the culvert and access road from future extreme rainfall events      .
     

    Cook Islands Biodiversity Reports

    Water Treatment Chemicals

    Chemicals have been proposed for the ongoing treatment of Rarotonga’s water supply for the purpose of coagulation and disinfection.
    Estimated value of coagulation and disinfection chemical contract: $350-500k / year.

    • Polyaluminum Chloride (PACl): Coagulant. TTV estimate: 75 ~ 100 tonnes / year.
    • Calcium Hypochloride (CaHCl): Disinfectant. TTV estimate: 8 ~ 10 tonnes / year.
    • Sodium Thiosulphate: Neutralises shock-chlorination undertaken when commissioning the new water treatment plants and network pipes. TTV estimate: none provided.

    See also: Chemicals and Pathogens.

     

    References and Further Reading

    News

    • 24 Dec 2019: Chemicals claim wrong: Henderson . Rushneel Kumar, Cook Islands News.
      Government has refuted claims that disinfected water containing chemicals has been released into the Takuvaine stream.
      … financial secretary Garth Henderson assured the public, especially the landowners up at the Takuvaine intake, that “no calcium hypochlorite has been disposed into the stream”.
    • 24 Dec 2019: Another stoush in Cook Islands over chlorine in water. RNZ.
      [Landowner Tere Carr] “What we suspect happened last Monday is that the chlorinated water from one of the tanks was released into the stream that runs past where the works are located. So there’s real concern from the landowners on the Takuvaine Intake that this could have happened. As a result there was evidence of some of the animals in the stream having been affected and having died.”
      However, Secretary of Finance Garth Henderson, speaking for the government, said the complainants were wrong. There was no evidence to back such claims, he said, with no photos of the supposedly dead fish and eels the landowners say had died.
    • 23 May 2020: Andy Kirkwood: Water treatment: Don’t be hasty Letters in Cook Islands News.
      The Government intends to proceed with a separate six-month PACl trial, despite not having a permit to do so. The Government claims the trial is necessary to inform the environmental impact assessment. This claim is not supported by the GHD technical documentation, the Court-expert assessment, or the opinion of the consultancy firm preparing the To Tatou Vai environmental impact assessment submission. The Government’s claim requiring a trial is necessary, is a fiction.
    • 25 Jun 2020: Turning on the taps Katrina Tanirau, Cook Islands News.
      Authorities acknowledge they need to be as transparent as the water they plan to pipe into people’s homes in Rarotonga.…
      Storm damage to the main water storage pond meant it had to be reconstructed, and that delayed the project.
    • 4 July 2020: Pipe gushes despite pleas. Melina Etches, Cook Islands News.
      A large high-pressure water pipe has burst at the Turangi intake road and is being held together by tyre tubes to limit the spill. With the shortage of water issue experienced on the island, a concerned neighbour was upset at the poor effort to fix the problem. “It’s been like this for at least two months, during this time of drought…”

    News Archive: 2011–

    Cook Islands Water Policy and Infrastructure Reports

    All reports are PDFs.

     

    Cook Islands Acts

    Parliament of the Cook Islands

    Legislation

    • Crown Proceedings Act 1950 (New Zealand Leglislation)
    • Judicature Act 1980-81. Pacific Islands Legal Information Institute (PacLII).
    • Dangerous Goods Act 1983. Pacific Islands Legal Information Institute (PacLII).
    • Environment Act 2003. PacLII.
      “Inland waters” means the waters and banks of any stream, river, or lake together with the bed (whether dry or not) of any stream, river or lake (for the purposes of this definition “bank” shall include all that area of land extending away from the stream, river, or lake and measured at right angles to a distance of 5 metres from the bank of that stream, river and lake);
    • Environment (Takuvaine Water Catchment Management Plan) Regulations 2006.
      -The Regulations, Part 2: Activities that Degrade Water Quality
      13. Use of Chemicals - No person shall take any chemical into the Area or use any chemical in the Area unless its use has been approved by the Management Committee.
    • Official Information Act 2008, 2009. PacLII.
      11.(3) If the person making the request asks that his request be treated as urgent, he shall give his reasons for seeking the information urgently.
      13. Transfer of requests – Where –
      …
      (a) a request in accordance with section 11 of this Act is made to a Ministry or Minister of the Crown or organisation; and
      (b) the information to which the request relates —
      (i) is not held by the Ministry or Minister of the Crown or organisation but is believed by the person dealing with the request to be held by another Ministry or Minister of the Crown or organisation; or …
      the Ministry or Minister of the Crown or organisation to which the request is made shall promptly, and in any case not later than 10 working days after the day on which the request is received, transfer the request to the other Ministry or Minister of the Crown or organisation, and inform the person making the request accordingly.
      14. Decisions on requests –
      (1) Subject to this Act, the Ministry or Minister of the Crown or organisation to whom a request is made in accordance with section 11 or is transferred in accordance section 13 of this Act shall, as soon as reasonably practicable, and in any case not later than 20 working days after the day on which the request is received by that Ministry or Minister of the Crown or organisation,…
    • Rarotonga Waterworks Ordinance Amendment Act 2015
    • “Cook Islands” - New Zealand Legislation |Cook Islands Chronological Table of Acts… - PacLII
     

    Working Draft. Updated: 28 June 2020.

 
 

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