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BAY OF PLENTY REGIONAL COUNCIL TOI MOANA

FAQs – Kopeopeo Canal Remediation Project

Contaminants in the Canal

  • What contaminants are present in the Kopeopeo Canal?
  • How did the contamination get there?
  • What are dioxins?
  • Why were dioxins made?
  • Are the dioxin levels in the Kopeopeo Canal a risk?
  • Is dioxin still flowing into the stream?
  • Is it just sediment in the canal that shows unacceptably high levels of dioxin?
  • Will the treatment sites or the groundwater below them become contaminated?

Human Health

  • Is anyone being exposed to the dioxin?
  • When will the eels be safe to eat again?
  • What level of dioxin exposure is considered safe and why?

Bioremediation

  • What is bioremediation?
  • Does this bioremediation plan use proven technology?
  • Why was bioremediation chosen as the treatment method?
  • How long will the sediment bioremediation treatment take?
  • Why not use one instead of three sites for bioremediation?
  • Will there be a smell associated with the geobags either open or closed? Is bioremediation a “smelly” process?

What to do with the sediment

  • Why don’t you leave the sediment in place? Won’t most of it have washed into the sea or broken down?
  • Why not take the sediment to landfill instead of remediating it?
  • Is there any urgency to get sediment removed?
  • Why not realign the canal and fill it in? Wouldn’t that be cheaper?
  • Will the treatment sites or the groundwater below them become contaminated?
  • Did you trial a new methodology?
  • What will happen to the sediment after treatment?
  • What will this work mean for the drainage scheme?

Sediment handling

  • Will the dioxin escape while it’s being transferred? How will the dioxin be contained and not end up spread in the air?
  • How much of the canal will sediment be removed from?
  • Who will monitor what happens during physical works? 
  • Why was the extraction and containment method changed?
  • What is different about this method?
  • How does the varied consent differ to the original consent? 
  • Why is this new method considered better?

Project team, timelines and monitoring

  • Who will do the work?
  • When will the work start and when will it be completed? 
  • Who can I contact if I’ve got questions? 
  • How can the council be the consent holder and consent authority? 
  • What can I expect to happen if I raise a complaint? Issue escalation?
  • What happens during physical works if there is a breach of a consent condition?
  • How will public be informed of human health risks during physical works?
  • Human health monitoring during physical works; what is available and to whom?

Physical Works

  • How will you measure dioxin in the Canal water during works so you know when there has been a breach of the consent conditions? 
  • What will you put in place to ensure that the geobags aren’t vandalised? 
  • When you open the geobags, will dioxin be released into the air? 
  • What will happen to the eels during the process? Will their carcases be able to be eaten by birds/vermin? 
  • How we will deal with contaminated debris? 

Contaminants in the Canal

What contaminants are present in the Kopeopeo Canal?

The contaminants of concern are dioxins and furans. Because there are many different dioxins and furans they are often collectively referred to as dioxins. Dioxins belong to a family of chemicals called organochlorines. Further information can be found on the World Health Organisation website

Testing for other contaminants, including timber treatment chemicals, has not revealed any other elevated contaminants of concern.

How did the contamination get there?

Between 1950 and 1989 surface run-off and storm water from the NZ Forest Products Ltd Sawmill was discharged into the canal. The discharge contained wastes from the sawmill, where technical-grade Pentachlorophenol or PCP was used as a wood preservative. It wasn’t known at the time, but the PCP imported into New Zealand contained impurities (dioxins).When the potential health risks were identified the timber industry voluntarily withdrew PCP from use in New Zealand.

What are dioxins?

Dioxins refer to a particular group of chemicals that can harm human health under certain conditions. The likelihood of risk to human health increases as the concentration and exposure duration increases. Dioxins are part of a wider group of contaminants called persistent organic pollutants. They break down very slowly (decades) and remain in the environment for a long time. More information can be found on the Ministry for the Environment website or the Ministry of Health website.

Why were dioxins made?

Dioxins are an unwanted by-product from the production of other chemicals, in this case PCP, which was used historically as a wood preservative. Other sources include discharges from smelting and chlorine bleaching of paper pulp. There are also naturally occurring sources of dioxins such as volcanic eruptions and forest fires. Further information can be found on the World Health Organisation website.

Are the dioxin levels in the Kopeopeo Canal a risk?

Investigations dating back to 2005 have concluded that dioxin levels in the sediment are elevated and have resulted in eel tissue concentrations of dioxin posing a risk to human health if consumed. A human health risk assessment concluded that a 5.1km section of the canal had sediment that required remediation to ensure the risks to human health could be eliminated. Until the canal is remediated, health advisory warnings have been put up along the canal to discourage people from catching and consuming eels from the canal. While concentrations of dioxins in the canal sediment are also above the National Environmental Standards for the Assessment and Management of Land to protect human health, direct exposure to the sediment is limited due to its location in the canal. The sediment has now built up so it is affecting the canal's ability to convey floodwater. Removal of the sediment is also necessary to ensure an extreme flood event would not result in the canal water overtopping the flood banks and flowing on to surrounding land.

Is dioxin still flowing into the stream?

No. PCP and its contaminant dioxin has not been used for timber treatment for decades. The old sawmill site was closed and decommissioned in the mid-1980s. The site is mostly vacant land now and stormwater generated on it no longer contains dioxins.

Is it just sediment in the canal that show unacceptably high levels of dioxin?

Results from several investigations between December 2014 and February 2015 showed there are elevated concentrations of dioxins in surface soils on Bay of Plenty Regional Council land around the Kopeopeo Canal, near the former mill discharge area into the canal. See flyer discussing the stop bank surface soils.

This area is currently outside of the scope of the Kopeopeo Canal remediation project. The area has been fenced off and signs put up to warn anyone accessing this private land. The risks to human health associated with the dioxin impacted stop banks is considered to be minor due to the current limited use of the land.  In the longer term, trials are proposed to assess the effectiveness of using bioremediation to breakdown the dioxins in-situ.

Human Health

Is anyone being exposed to the dioxin?

While the contaminated sediment remains in the Kopeopeo Canal, the main exposure route is through the food chain. At the bottom of the food chain, filter feeders accumulate dioxin. This accumulation of dioxin increases with every step up the food chain. This means eels may be unsafe to eat. People are advised not to eat eels from the contaminated stretch of the Kopeopeo Canal, as doing so could expose them to human health risks.

Historical dredging of the canal has also resulted in dioxin-contaminated spoil being placed on the top of the canal banks. Further investigations to determine the extent of the contamination associated with this historical activity are ongoing. At present the risk to adjoining landowners and the community is minimal because no one regularly accesses the area. The council intends to install better boundary fences along the canal to further minimise public access. In the long-term, options for remediation or management of the stopbank material will be considered.

Steps will be taken during this project to reduce the risk to remediation contract staff and the community. We will ensure dioxin is contained within the pipeline when it is being transferred from the canal to the containment sites and undertake regular monitoring to ensure the proposed control measures have been effective.

When will the eels will be safe to eat again?

We expect this will be 2-5 years after the dioxin-contaminated sediment has been removed from their environment. The eels will be monitored annually and the data shared with the consent authority and the Community Liaison Group (CLG). Once sufficient data confirms the eels are safe to eat health advisory warnings will be lifted.

What level of dioxin exposure is considered safe and why?

Dioxin laboratory analysis and evaluation of laboratory data is a complex process.  There are a large number of different dioxins and furans which each have their own chemical structure and toxicity.

To account for this, a system was developed by international experts that applies a ‘toxicity equivalence factor’ to each individual dioxin or furan congener (a related chemical substance). These values are then added together to provide a total dioxin concentration expressed as the International Toxic Equivalency (I-TEQ) or World Health Organisation Toxic Equivalency (WHO-TEQ) derived value.

The data presented on our website is based on the I-TEQ values and reported in pictograms per gram (pg/g). There are also three levels reported in each result; lowerbound, mediumbound, and upperbound.  We use the more conservative ‘upperbound’ values for the concentrations presented on the website because these assume that a concentration might be present just below the laboratory method of detection, rather than absolute zero.  This will result in a value that could be zero, being expressed as 0.00 pg I-TEQ/g for the lower bound, 10.0 pg I-TEQ/g for the medium bound, and 20.0 pg I-TEQ/g for the upper bound.

The table below provides a list of Soil Contaminant Standards (SCS) that came into effect in New Zealand in 2012. These values are based around different land uses where a variety of specific exposure pathways and occupant durations are considered. For example a residential land use scenario considers a 30 year exposure duration and exposure pathways such as dermal or direct contact, inhalation of dust, consumption of home grown produce, and ingestion. When long term or chronic exposure to levels above the SCS occurs there is an increase in cancer risk to 1 in 100,000 people exposed.

The Kopeopeo Canal Remediation Target is a site specific human health based target and has been defined to ensure that there is no human health risk associated with direct contact through recreational use, and consumption of eel tissue following the completion of the remediation project.

The USEPA drinking water standard is based on the most toxic dioxin congener; Tetrachlorodibenzo-p-dioxin 2,3,7,8- (TCDD) and is therefore expressed in pictograms per litre (pg/L).

Contaminant  Media  Land Use  Concentration  Units  Source
Total Dioxin  Soil  High-density residental  330  pg/g WHO-TEQ  NES 1
Total Dioxin  Soil   Lifestyle block  90  pg/g WHO-TEQ   NES 1
Total Dioxin   Soil   Parkland/Recreational  520  pg/g WHO-TEQ   NES 1
Total Dioxin   Soil   Residental  120  pg/g WHO-TEQ   NES 1
Total Dioxin   Sediment  Kopeopeo Canal Remediation Target  60  pg/g l-TEQ   BOPRC 2

Tetrachlorodibenzo-p-dioxin

2,3,7,8 - (TCDD) 

Water  Drinking Water  30  pg/L l-TEQ   USEPA 3

1 – National Environmental Standards Contaminated Land (NES CS, 2012).  Note values are those based on the Methodology for Deriving Soil Guideline Values Protective of Human Health (MfE, 2011). The values are considered to be conservative and assume chronic exposure (30 year duration for residential land uses) will increase cancer risk by 1 in 100,000

2 - Bay of Plenty Regional Council Consent 67173

3 - USEPA Drinking Water Standards 2012

Bioremediation

What is bioremediation?

Bioremediation enhances the natural degradation process that breaks down contaminants. For the sediment a combination of fungi, bacteria and plants are proposed to help speed up the natural degradation of the dioxins.

You can also read more about bioremediation in the presentation to the CLG

Does this bioremediation plan use proven technology?

This proposal to bioremediate using a combination of naturally occurring fungi and trees (poplars and natives) is innovative. However we are confident that it will work, following a trial involving a range of organisations and led by Te Runanga o Ngāti Awa in conjunction with Bay of Plenty Regional Council. Variations to the trial were completed and the conditions proposed at the containment sites indicate further research is warranted. The project team is currently undertaking additional trials that reflect the new geotube containment method to eliminate any uncertainty. The results of these trials will be shared with the community prior to beginning the full-scale treatment process associated with remediation works. 

Why was bioremediation chosen as the treatment method?

Often remediation of dioxin impacted soil or sediment is undertaken on former industrial sites as part of urban renewal. Develops commonly fund these clean ups using thermal desorption units. These units effectively cook the soil/sediment and drive off the dioxins.  This treatment method is often favoured because the contaminated site is proposed for redevelopment and there are time constraints in the redevelopment schedule. In comparison to other treatment methods, thermal desorption is a fairly costly due to its energy requirements. In the case of the Kopeopeo Canal, the concentrations are much lower than commonly found on industrial or manufacturing sites and there are no time constraints.  In addition, the project is funded by rate payers and tax payers, not developers, and this was a consideration in the treatment selection process. Overall, the use of bioremediation was considered to have the right balance following the consideration of costs, treatment timeframes, and cultural and community views.

How long will the sediment bioremediation treatment take?

We have estimated it will take 12 years. Bay of Plenty Regional Council will carry out regular monitoring to assess progress until completion. Regular monitoring will provide an indication of how remediation is progressing and a basis for reporting.

Why not use one instead of three sites for bioremediation?

Three sites were selected for the original excavation and transport using heavy trucks and trailers so that the cartage distance was shorter and therefore the risk of any spillage occurring was minimised. Potential traffic effects also played a big part in the selection of the containment site locations and three sites were selected to avoid crossing any major roads, such as SH30. Now that the dredging consent variation has been granted, the sediment can be pumped along a pipeline to the containment site, eliminating any traffic-related effects and allowing consideration of using fewer containment sites.

Will there be a smell associated with the geobags either open or closed? Is bioremediation a “smelly” process?

There may be some minor odour associated with the bioremediation process and changes in chemistry of the canal sediments when they dewater.  This should be addressed via the addition of lime during the dredging process which will help stabilise the pH, and also because the sediment is contained in geobags. The consent holder intends to monitor odour during the process.

What to do with the sediment

Why don’t you leave the sediment in place? Won’t most of it have washed into the sea or broken down?

Dioxins bind strongly to the sediment and, once bound, do not release to the water. The flat grade of the Kopeopeo Canal means the sediment doesn’t readily move downstream. This, coupled with the slow breakdown of dioxins in this environment, mean the problem will remain unless we do something about it. Dioxins can also accumulate in the food chain which is one of the key drivers for carrying out the remediation project. The sediment has now built up so it is affecting the canal’s ability to convey floodwater. Removal of the sediment is also necessary to ensure an extreme flood event does not result in the canal water overtopping the flood banks and affecting surrounding land.

Why not take the sediment to landfill instead of remediating it?

Landfill burial was evaluated along with many other remediation options in 2010, prior to the current consents being applied for and granted. This option was eliminated from further consideration due to costs and potential traffic effects. Due to the type of contaminant, the dewatered sediment would need to go to a landfill at Hampton Downs (North Waikato) or Tirohia (near Te Aroha). The long cartage distances involved increase the risk of spilling as the result of an accident. Cultural beliefs have also been taken into consideration during final selection of the remediation process. Ngāti Awa are strongly opposed to removing material from their rohe and prefer that the process of ‘healing the land’ occurs locally. 

Is there any urgency to get sediment removed?

As well as addressing the contaminant problem, the build-up of sediment in the canal reduces its drainage capacity and is contributing to drainage problems on the plains that flow into the Kopeopeo Canal. Typical drain maintenance - removing sediment to restore drainage capacity - cannot take place as long as contaminated sediments are in place.

The consent holder (Bay of Plenty Regional Council’s Rivers and Drainage Group) has the necessary funding and consents to undertake the remediation. Significant delays could jeopardise the funding agreements or result in the works not being completed within the consented time period. Removal of the sediment is also necessary to ensure an extreme flood event does not result in the canal water overtopping the flood banks and impacting surrounding land.

Why not realign the canal and fill it in? Wouldn’t that be cheaper?

This option was also considered. However physical constraints on moving the canal and underground infrastructure (wastewater, fibre optic, power cables) along the canal corridor mean this is not viable and the expense would be prohibitive.

Will the treatment sites or the groundwater below them become contaminated?

The sediment will be placed into goetubes (geotextile bags) which will be placed within fully enclosed ‘containment cells’. These cells will be formed using high density polyethylene (HDPE) liner which will eliminate sediment-bound contaminants’ movement into the surrounding soil or groundwater. There are extensive monitoring conditions the consent holder needs to comply with, including the monitoring of the containment sites and the groundwater beneath them.

The contaminant is hydrophobic and does not result in impacts to groundwater. Results recently obtained from historical dredge spoil placed along a stopbank indicate dioxins at the surface have not migrated through the soil profile, even when exposed to the environment for at least 30 years.   

Did you trial a new methodology?

Many submissions on the consent indicated the community was concerned about various elements of the project. The key concerns were associated with traffic, dust and spillage during removal and transportation of partially dewatered sediment to the containment sites. Additional concerns were raised about potential releases to the environment during the filling and addition of bioremediation components before the containment sites were sealed.

Cutter suction dredging and geotube dewatering has been available in many parts of the world for decades but has only become available in New Zealand during recent years. The technique involves disturbing the sediment using a mechanical cutter head directly adjacent to a suction intake. As the sediment is disturbed the suction pump draws it up into a pipeline and transfers it to the containment site. At the containment site the water/sediment slurry is dosed with chemicals that separate the solids from the water. The separation occurs in the pipeline prior to it being pumped into geotubes. These tubes are designed to allow the water out but keep the sediment in. The discharged water (filtrate) collects in the base of the HDPE-lined containment site before it is tested. It then discharges back into the canal. Further details of this process can be viewed here.

On the basis of the trial results and positive community feedback, a variation to the existing consents was applied for. The variation was recently granted on a non-notified basis by an independent commissioner. 

What will happen to the sediment after treatment?

Sediment will be left in place at the containment sites following treatment. The final land use of each site will be determined by the treatment level achieved and other site specific controls put in place. 

What will this work mean for the drainage scheme?

When the sediment has been removed the water flow in the canal will be increased. This means better land drainage and greater flood protection.

Sediment handling 

Will the dioxin escape while it’s being transferred? How will the dioxin be contained and not end up spread in the air?

The newly-consented, cutter-suction dredge method eliminates that bulk of the risks associated with potential spillages of contaminated material and dust generation. This is because sediment is transferred from the canal directly to the containment sites via a pipeline. While technical assessments carried out in support of the variation application indicated that there would be little to no risk of air quality effects the consent holder has retained air quality monitoring in the consent to provide piece of mind to surrounding residents and the general community during the works. This is a condition of the consent and there will be ongoing monitoring and reporting of air quality to ensure compliance.

How much of the canal will sediment be removed from?

Approximately 5km of canal will be remediated between State Highway 30 at Kope Drain Road and the confluence of the Kopeopeo and Orini Canals. This area was defined using sediment and eel tissue sampling and analysis. Recent sediment testing to the west of SH30 has shown sediment concentrations at levels above the remediation target. This area is on privately owned land and outside of the scope of the current project. Further discussions with landowners and testing is underway to define the extent of the elevated concentrations in order to determine appropriate management or remediation options.

Who will monitor what happens during physical works?

The physical works contractor will be required to put the control measures in place and carry out monitoring in accordance with the consent conditions. The consent authorities will undertake compliance testing and spot checks of their own, and ensure the project remains compliant with the conditions. An Independent Monitor has also been appointed to oversee the works programme and will review and report on compliance monitoring data.

Monitoring results will be assessed against predetermined limits designed to ensure health risks are eliminated. This data will be uploaded on to the project website. A Cultural Monitor has also been appointed to oversee the works and manage the recovery of any koiwi or taonga unearthed during the Kopeopeo Canal Remediation Project. The Cultural Monitor will also advise contractors and staff on cultural matters associated with works on the project.

Why was the extraction and containment method changed?

Many people in the community were concerned about the number of truck and trailer movements during carting the sediment from the canal to the containment sites, and the potential for spills and contaminated dust to be generated.  An alternative extraction and transfer method was identified in late 2014 that addressed these concerns.  The method was trialled and in October 2015 a pilot study was carried out which the community and various stakeholder group representatives were invited to attend. 

What is different about this method?

The method approved under the existing resource consents involves dewatering the canal in sections before excavating the sediment and transporting to the containment sites on trucks. The alternative method being evaluated uses:

  • A cutter suction dredge to suck up the sediment and water from the canal into a pipeline, from where it is transferred to the containment sites;
  • A water treatment system to separate the water from the sediment at the containment site; and
  • A geotextile bag called a geotube, to provide a primary sediment containment system at the containment site. The geotubes are located within an high density polyethylene (HDPE) lined cell.

How does the varied consent differ to the original consent?

There are several changes to the current consent conditions. The key changes are associated with the need to monitor water quality discharging from the containment sites, and the canal during the dredging activity. There are also different techniques that need to be utilised during the dredging to manage and treat any floodwater that passes through the site. The Flood Management Plan and Dredge Management Plan are currently being prepared by experts in this field and will document the processes that need to be implemented during the physical works. These plans will be submitted to the consent authority and the independent monitor for approval prior to the commencement of dredging activities. 

Why is this new method considered better?

This methodology brings a range of benefits to the project. These include:

  • Elimination of potential spillage of sediment during transfer from the canal to the trucks, and when the trucks are transporting the sediment to the containment sites.
  • There would be no need for heavy traffic movements between the canal and the containment sites. All sediment would be contained within a pipeline while being transferred from the canal to the containment site.
  • Because the dredge operates beneath the water there would be no need to block off and dewater sections of the canal. This makes it easier to manage floodwaters within the canal system and eliminates the need to use sprinkler systems to prevent the dewatered canal banks from drying out and potentially generating dust.
  • With no heavy traffic there would be no potential for dust to be generated on public roads with the associated impact on air quality.
  • The geotubes would be contained within a specially designed high-density polyethylene-lined (HDPE-lined) cell that would collect any water discharging from the geotubes and avoids potential groundwater effects.
  • The use of barge-mounted dredges for the eastern end of the canal may eliminate the need for significant disturbance of the saltmarsh.

Projects works, timelines and monitoring

Who will do the work?

The work to transfer the sediment to the containment cells will be awarded to a suitable contractor as a result of a competitive tendering process. A multi-disciplinary team will carry out the bioremediation implementation, led by research organisations and specialists.

Conditions will be included in contracts to ensure a high level of care to be taken throughout the works to ensure safety of workers and the community.

When will the work start and when will it be completed?

The original project schedule was delayed while the project team evaluated the alternative cutter suction sediment extraction and removal technique. Now that a variation for the consent has been granted to implement this method the project schedule is currently being finalised with physical works expected to commence in summer 2016/2017.  

Who can I contact if I’ve got questions?

The Community Liaison Group has been formed to provide a conduit for information transfer between the project and the community. Members of the public are welcome to attend CLG meetings and to raise any concerns they may have in relation to the project.

The Independent Monitor has also been appointed to provide independent technical advice in relation to the project.

There is also a complaints register and contact page on the website so members of the community can reach the  project team. 

How can the council be the consent holder and consent authority?

As landowner of the canal, the Bay of Plenty Regional Council Rivers and Drainage Group needs to maintain the canal and is the consent holder. Given the rules under the regional and district plan, consents were required from the Bay of Plenty Regional Council and the Whakatāne District Council to remediate the canal.

Bay of Plenty Regional Council is aware of the need to maintain a degree of separation between the consent authority and the applicant, and to avoid even the perception of a conflict of interest. For the Kopeopeo Canal Remediation Project this has been achieved by engaging independent experts for the processing of consents and the peer review of technical reports submitted in support of the application. The decision to allow the variation to the consent was approved by an independent commissioner.  In addition, an Independent Monitor (IM) has been appointed to oversee the project and review and comment on compliance-related data that will be collected during the physical works programme. A Community Liaison Group (CLG) has been formed and represents a broad and diverse range of community groups and members. The IM will prepare regular reports for the CLG so its members can get impartial feedback on compliance and progress throughout the project.

Any Regional Council regulatory compliance and/or enforcement action will be undertaken by Council officers with no previous involvement with the consent process. They will liaise closely with the IM so any compliance issues are promptly addressed.

What can I expect to happen if I raise a complaint? 

Complaints can be registered using the project’s complaints register or using the contact page to get in touch with the project team. 

Alternatively, concerns can be logged with the Consent Authority here or by contacting Council’s regulatory compliance group via phone. The regional council’s pollution hotline is 0800 884 883, or you can phone Whakatāne District Council on (07) 306 0500. Once a complaint is lodged it will be investigated by the appropriate council staff and will generally involve discussions with project staff members, contractors and/or the Independent Monitor. The method to close out the issue identified will be recorded and shared with the complainant. A register of complaints will form part of the reporting to the CLG.

What happens during physical works if there is a breach of a consent condition?

This depends on the level of non-compliance. In every case it is a decision made by the individual council’s regulatory team. In minor cases that are unlikely to impact public health or generate environmental effects, the consent authority may seek ways to work with the consent holder and contractors to rectify the situation so that similar issues do not arise again in the future.

In significant or regular non-compliance situations the regulatory compliance team may take more formal action. This can include issuing an abatement notice on the consent holder that lists actions required to be undertaken within a specified timeframe, or requiring the consent holder to cease an activity. Failure to meet the conditions of abatement notices may result in escalated enforcement being considered.

Other forms of enforcement action include the issuing of an infringement notice (fine), the issuing of an enforcement order (a Court-ordered document, more formal than an abatement notice) or the start of a prosecution.

How will public be informed of human health risks during physical works?

Health risks depend on the activity being carried out and the location where the activity is being carried out. It is expected that once the physical works contractor is appointed a detailed understanding of the proposed physical works will be documented and can be used to prepare health and safety plans and information for distribution to the public. The consent holder intends to discuss this at future Community Liaison Group (CLG) meetings and inform members of the public that own or occupy land directly adjoining the project site via letter box drops and meetings. Accurate and timely communication forms a big component of the project implementation phase. A communications plan has been prepared by the consent holder and approved by the CLG.  This document outlines the various phases of the project and communication methods that the applicant will use during the project physical works.  

Human health monitoring during physical works; what is available and to whom?

Implementing the project according to the consent conditions and within compliance limits is the first priority for the consent holder and in doing so should eliminate any human health effects. The change to a cutter suction dredge extraction technique has also eliminated many of the potential human health effects that needed to be managed under the original consented method.

The assessment of best practice human health monitoring is under review. Determining what is appropriate for the project is also very dependent on the methodology selected to remove and transport sediment to the containment sites. The consent holder will consider community health monitoring on a case–by-case basis once a better understanding of the methodology and best practice review is complete. 

Physical Works

How will you measure dioxin in the Canal water during works so you know when there has been a breach of the consent conditions?

Getting a sample analysed for dioxins can take up to 2-3 weeks. In order to provide real time data, turbidity, total suspended solids, and dioxin proxies will be determined in accordance with consent conditions.  This will provide an understanding of dioxin levels in the canal water based on turbidity values. Data will be collected from turbidity meters mounted on buoys within the canal. The turbidity buoys can be programmed to record readings a set time intervals and then transfer that data to onshore data capture and management systems via telemetry. Compliance triggers can also be programmed in to ensure that the contractors and compliance monitoring staff are aware if turbidity levels are approaching a compliance limit.   

What will you put in place to ensure that the geobags aren’t vandalised?

Fences and other security measures will be in place at the containment sites to ensure that the containment systems are not vandalised.

When you open the geobags, will dioxin be released into the air?

The only time that this is likely to occur is for sampling or bioremediation. If this activity occurs it will be for a short duration and measures will be in place to minimise dust generation and monitor air quality. As long as the mitigation measures are in place the consent holder expects that the very low air quality compliance limits can be met.

What will happen to the eels during the process? Will their carcases be able to be eaten by birds/vermin?

The eels will all be fished out of the canal prior to the dredging, euthanized, frozen, minced, and then fed into the geotubes thereby eliminating birds and other vermin feeding on the contaminated eel tissue.

How we will deal with contaminated debris?

Existing debris will be removed from the canal prior to dredging, cleaned off, and disposed of at containment sites. Any debris that flows down the canal should be captured by the sheet pile control structure on the western end of the project site.