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Dr. Dave Bull and Waikato Regional Council team leader Michelle Begbie were awarded best podium presentation on the second day of the Australasian Land and Groundwater Association's annual Ecoforum conference recently held in Auckland. Michelle and Dave argued that arsenic is the most common contaminant of concern in New Zealand, especially in the Waikato Region. Arsenic contamination is often a result of human activities such as sheep dipping, codling moth control in apples, or timber treatment and use. But elevated arsenic can also be geogenic – naturally occurring – and in these cases the conceptual site model and risk mitigation are always much harder to resolve. They introduced a natural source of arsenic in the Waikato Region; not a new topic in itself, but our approach to identifying the risk it poses and how it should be managed are new. The Waikato Region is blessed with rich volcanic minerals and fluids. It has long been known that the Waikato River itself has elevated arsenic; mostly derived from naturally occurring geothermal inputs, but enhanced by human factors such as geothermal power stations and water extraction and use. Natural groundwater in the region is also elevated with arsenic thanks to our unique combination of geology and enhanced rates of weathering from geothermal heating. Multiple contaminated land investigations in the region have identified naturally occurring arsenic, which has posed significant challenges to land redevelopment. In particular, certain soils of the Hamilton Basin feature an iron pan heavy with naturally enriched arsenic, often exceeding Soil Contaminant Standards (SCS) and at times well into the hundreds of mg/kg. Michelle selected a number of sampling sites in an area currently under heavy development pressure, where arsenic is often reported elevated, in the absence of any obvious man-made source of contamination. Samples were analysed for arsenic bioaccessibility, and for a variety of chemical and mineralogical determinands so as to provide multiple lines of evidence. Dave presented information collated to date. Elevated arsenic in the study area seems strongly associated with Bruntwood type soils, apparently formed on riverbanks deposited after the Oruanui eruption 26,000 years ago, and associated breakout floods from the Lake Taupo area. "Iron pans" that have formed in Hamilton Basin soils also seem to be generally enriched in arsenic. These iron pans can sometimes be broken up and brought to surface, increasing topsoil arsenic concentrations, by ploughing - or as an unintended consequence of soil mixing intended as a remedial action! Initial results suggest that arsenic bioaccessibility and bioavailability in these impacted soils is considerably less than the 100 % assumed in guidance, indicating that the risk these soils pose is lower than a simple comparison with the SCS would suggest. Supporting analysis is still ongoing. Michelle hopes that the project will enable some broader discussions about sustainable land management and how policy might be able to respond in a way that enables practical and risk-based land management before development.
Jimmy Huang

HAIL Environmental is delighted to welcome Jimmy Huang as an associate. Jimmy has nine years' experience in contaminated land following a B.Sc. in Chemistry from Canterbury University. He is a fluent speaker of both Cantonese and Mandarin. Jimmy lives in Auckland with his wife Tian and two exceedingly cute kids, Joyce (4) and Rocco (1). A keen outdoorsman, he loves to fish and has been known to spend holidays as a tramping guide.

Kopeopeo Canal, Whakatane

One of the key challenges of the Kopeopeo Canal remediation project is keeping dioxins from moving around the broader drainage network. The dioxins are adsorbed to fine sediment particles in the canal bed. If the sediment is disturbed, the dioxins can be resuspended into the overlying water column, and transported wherever the water goes next. Even in this flat landscape, flow velocities can exceed silt curtain specifications, so it is not feasible just to enclose the work area in silt curtains.

But the canal sediment can’t be left completely undisturbed. The canal is an integral part of the Rangitaiki Plains flood management system, it needs to be able to convey floodwater during high rainfall events – even during remedial works, if necessary. So how does the project avoid redistributing dioxins back into remediated sections – or, worse still, out onto adjoining land? A mixture of hard controls, and practices that minimise resuspension, is needed.

One key control is the dredging method, which inherently minimises resuspension of sediment – that topic needs an article all to itself. Another is silt curtains around the dredge zone, which are effective at no-low flow. Yet another is canal level management using flood and sediment control structures – earthen/sheetpile walls equipped with floodgates and spillways.

How do we know that these controls are working? Water samples can readily be collected and analysed to see how much sediment and dioxin is in the water column at any given time. But this approach isn’t adequate for real time control. Even under urgency, it takes days to get samples collected, transported to the certified laboratory, and processed. That’s just not fast enough to inform management decisions when the rain is heavy and water levels are rising by the hour. What needs to be done to comply with consent conditions – is there enough storage in the dredge zone? Is it time to stop dredging and let everything settle?

Kopeopeo Canal project manager, HAIL Environmental’s Brendon Love, needed a better management tool. He and the project team could monitor some parameters in real time, such as turbidity – how murky the water is, roughly speaking. Could turbidity be used as a proxy for suspended dioxin loads? Simulation trials showed that they could indeed construct a traffic-light system, setting turbidity levels that give them confidence suspended dioxins are within target levels. With turbidity and water level monitors at ten locations throughout the canal, Brendon and the stakeholders can now be confident that the remedial works aren’t transporting dioxin where it shouldn’t be. Now, with this reliable and well maintained monitoring network, the project team can be confident that compliance can be achieved and remedial works can continue even during rainfall events.

Before 1945, exterior house paint contained up to 50 % lead by weight. While lead levels diminished thereafter, lead-based house paints were not banned until 1965. Metal primers were lead-based until the 1990s. A pre-war house can carry more than 80 kg of lead in exterior paint. Health authorities have estimated more than 250,000 houses are, or have been, painted with lead.

The Ministry of Health and Master Painters New Zealand have produced some great guidance on managing and removing lead-based paint. However, if paint has been removed without following that guidance, soils close to the house can be more than 1 % lead by weight, many times greater than the national Soil Contaminant Standard. Children who happen to swallow soil or indoor dust can suffer subtle neurotoxic effects; at higher levels of exposure, children and pets may experience a range of acute poisoning symptoms. Back in 1986, the Dunedin Longitudinal Study tested more than 500 11-year-olds for elevated blood lead, finding 10 cases of significant exposure. Nine of these ten were apparently associated with renovations in the home in the months before testing. 

Recent media reports have raised concern about lead in backyard chickens and their eggs - see a 'Stuff' article here and the blog at Keeping Chickens NZ.

HAIL Environmental has a particular interest in assessing and managing lead in soil: last year Dr. Dave Bull chaired and organised two sessions on lead contamination at the Australasian Land and Groundwater Association's 2018 New Zealand conference in Christchurch - for full details see the ALGA website. The Waste Management Institute New Zealand (WasteMINZ) has set up a Residential Lead Group in response, and Dave is a founding member of that group. Property owners or regulators needing advice on lead contamination can call Dave on 021 036 7764, or contact their local HAIL specialist.

 

 

 

Naturally Occurring Arsenic

Naturally occurring (geogenic) arsenic seems to be a surprisingly common 'natural hazard' around New Zealand. Dave Bull and Bill Lines have encountered several sites from Otago, Canterbury, Waikato and even Wellington where arsenic exceeds Soil Contaminant Standards and there is no evident man-made (anthropogenic) source. Typically these sites are difficult to remediate because of the sheer volume and extent of impacted soil. HAIL Environmental has had a lot of success applying bioavailability assessment to such sites, to show that the 'contamination' does not pose as much risk as total concentrations might indicate, and hence minimise the need for management. These risk assessments have been accepted by territorial authorities including Thames-Coromandel, Queenstown Lakes and Tasman District Councils, allowing affected developments to proceed.

To find out more call Dave on 021 036 7764.

DBull photoHAIL Environmental’s Dr. Dave Bull was recently interviewed by Industrial Safety News. In their article “Identifying and remedying land contamination a tricky process” (Spring 2017 issue, pages 10-12) Dave talks about naturally occurring ‘contaminants’ such as fluoride, hydrogen sulfide, asbestos and arsenic. Surprisingly common in New Zealand, naturally occurring contaminants are also surprisingly difficult to identify, manage or remediate. He goes on to discuss arsenic bioavailability assessment as a new tool to assist in risk management at naturally arsenic-rich sites. The full article can be found here. Dave is available on 021 036 7764 to help landowners who may have naturally occurring contaminant issues.

Battelle International Sediment Remediation Conference, New Orleans. 9-12 January, 2017

Brendon Love recently attended the Battelle International Sediment Remediation Conference in New Orleans, following acceptance of a paper on the importance of stakeholder engagement in remediation projects. The conference is the largest sediment remediation conference in the world with over 1,190 scientists, engineers, regulators delegates and speakers in attendance. Brendon also attended two very informative workshops prior to the conference which focused on international best practice management in sediment remediation. Both the workshops and the conference provided useful insights into the latest tools that are being implemented on sediment remediation projects throughout the world, and what lessons have been learnt along the way. When asked about the conference Brendon commented, “There is really no other conference in the world that has the same amount of collective knowledge on sediment remediation gathered together.” The conference is of particular relevance to a current HAIL Environmental contract.

Brendon has been Project Manager on one of New Zealand’s largest contaminated site remediation projects, the Kopeopeo Canal Remediation Project for over two years. “The knowledge gathered during the conference will be put to good use on the Kopeopeo Canal Remediation Project”, Mr Love said. “It was a great honour to be selected to present at this conference. The importance of stakeholder engagement is becoming more widely recognised as being critical to the success of remediation projects.” Brendon’s presentation, that was co-authored by Andrew Kohlrusch from GHD Australia, can be viewed here (link to PDF attached). For more information on the Kopeopeo Canal Remediation Project visit https://www.boprc.govt.nz/environment/kopeopeo-canal-contamination-remediation-project/

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