Ok Tedi Mining Ltd. (OTML) Environment Peer Review Group (PRG): Comments On Key Issues And Review Comments On The Final Human And Ecological Risk Assessment Documents April 2000

CONTENTS (clickable) 
(The full document is below)


1. Introduction 
In 1997 Ok Tedi Mining Limited (OTML) formed a Peer Review Group (PRG) to provide advice, recommendations and peer review related to a human and ecological risk assessment (HERA) of the terrestrial and aquatic ecosystems of the Ok Tedi/Fly River systems downstream of the mine. The HERA was based on the state of knowledge to July 1999. There are five members of the PRG:

Dr. Peter Chapman, EVS Environment Consultants, North Vancouver (Chair)
Professor Margaret Burchett, University of Technology, Sydney
Professor Peter Campbell, Univestite du Quebec
Professor William Dietrich, University of California, Berkeley
Professor Barry Hart, Water Studies Centre, Monash University

The PRG’s terms of reference are as follows:

The PRG has been involved in the HERA process since August 1997 and have attended all work-shops and provided detailed review comments on individual proposals, projects, and on all aspects of the HERA.

The purpose of this report is two fold. First, in Section 2.0, the PRG comments on key issues, effectively updating our previous report (Fourth PRG Report [20/07/99]). Second, in Section 3.0, the PRG provides summary review comments on the November 1999 report prepared for OTML by Parametrix Inc. and URS Greiner Woodward Clyde “Assessment of Human Health and Eco-logical Risks for Proposed Mine Waste Mitigation Options at the Ok Tedi Mine, PNG”. These summary review comments summarize very detailed review comments provided as working docu-ments to OTML and to the DLRA consultants (Fifth PRG Report [04/02/2000]). Our comments regarding the DLRA include: (1) limitations imposed by the scope mandated by OTML; (2) uncer-tainties; and, (3) errors or omissions. We conclude this report (Section 4.0) with a summary in-tended to provide context to the findings to date.

The DLRA still has a number of inadequacies, some of which could have been addressed (cf. Section 3 of this report). However, the DLRA is still a useful document (though not as useful as it might have been). In addition, the present risk assessment process has substantively advanced the science from the first risk assessment completed by OTML in 1996.

2. Comments On Key Issues
The following Comments on Key Issues expand and develop on similar issues contained in the PRG’s Fourth Report. Our intent in providing these comments here is to continue to emphasize their importance not only for short-term decision-making regarding the future of the mine but also regarding long-term monitoring and possible remediation efforts. For each Key Issue we briefly: explain its importance (Why), what we understand is presently occurring and will occur in the future (Present Situation and Prognosis), what makes this understanding less than perfect (Key Uncertainties), and recommended future actions (What Needs to be Done). We end with a Sum-mary regarding the key issues.
2.1 The Accuracy or Predictive Power of the Sediment Transport Model.
Why
The sediment transport model provides a quantitative causal linkage between sediment input and environmental change throughout the Ok Tedi - Fly River system. An acceptably accurate model is needed to evaluate controls on rates (or frequency) and location of: 1) channel bed level change (aggradation or degradation); 2) bed material grain size; 3) flooding; 4) particulate copper dispersal through the river and floodplain system; 5) floodplain sedimentation; and 6) tie channel closure. The model is the only quantitative means to evaluate various waste management options and the response of the system to eventual mine closure. Understanding and investigation of all other key issues depend on the reliability of this model.

Present Situation
A massive, long-term transformation of the Ok Tedi - Fly River system, driven by mine-derived sediment loading, is underway. Considerable data have been gathered that quantify how the system has changed since mining began. Two downstream tapering aggradation zones have become estab-lished, one in the gravel reach of the Ok Mani - Ok Tedi Rivers and the other in the sand bedded reach in the lower Ok Tedi - Fly Rivers. Mine derived sediment has spread across nearly all of the lower Ok Tedi and Middle Fly floodplain. Rates of floodplain deposition in both the lower Ok Tedi and Middle Fly have been estimated from field data. Monitoring by the OTML Environment de-partment has provided essential data on stream flows, river profiles and cross-sections, floodplain dimensions, sediment inputs (from rock waste, wall erosion from waste dumping, and milling), and sediment discharge at various stations along the system. However, the quality of these data is gen-erally poor in the complicated lower Middle Fly where backwater effects and extensive floodplain water storage influence discharge rating curves and where limited data exist on channel cross-sections and bed material grain size. Although there was a period of intensive monitoring of flood-ing processes on the Middle Fly, inadequate monitoring has occurred to quantify flow and sediment properties below the junction with the Strickland River. Limited data have been collected on tie channel topography or off-river water body infilling.

The sediment transport model used to investigate environmental change by OTML has been con-structed by Drs. G. Parker and Y. Cui. This model has been in development for over 10 years. It is a physics-based model that represents state of the art modelling and was built specifically to ad-dress issues on the Ok Tedi and Fly River system. The most recent modelling results applicable to the HERA are those reported in July 1999 by Cui and Parker. This report and model results were reviewed by the PRG, T.R. Davies (for OTML) and C. R. Dietrich and A. J. Jakeman (for BHP). All three reviews accept the basic approach employed by Cui and Parker. Davies and the PRG con-clude that the model performs reasonably well in the Ok Tedi and upper Middle Fly River in pre-dicting observed bed level changes. Both reviews note (as do Cui and Parker) the apparent poor performance of the model in the lower Middle Fly, where aggradation rates appear to be under predicted, and attribute this to both inappropriate downstream boundary condition data and inad-equate modelling of downstream sorting of sediment. There is, however, considerable uncertainty regarding the extent and magnitude of current (as of the time of this report) aggradation in this reach. The BHP sponsored review emphasized a recommendation by Davies that sensitivity analy-sis of the model should be performed. This has yet to be done.

Only a few model outcomes are mentioned here in this Key Issue analysis: Prognosis The high dredging option, which is the option actively underway, does create tangible benefits. However, quantification of these benefits is not yet possible. These issues were the subject of discussions at a Sediment Transport Workshop on site, the third week of February 2000. Updated information from this workshop and from further modelling and field work will be included in the next PRG report.

The Cui-Parker model can be used to continue to explore waste management options. In order to improve model usefulness and accuracy, however, the downstream lower boundary condition needs to be changed so that the effects of high flow in the Strickland and tidal influences can be directly modelled. Further improvements in the downstream sorting of sediment in the Middle Fly are needed as well. Sorting effects may be important to the prediction of aggradation in the lower Middle Fly. There is evidence such sediment sorting effects are already occurring in the Ok Tedi River.

Key Uncertainties
Field Observations Modelling What Needs to be Done
Field work Modelling
2.2 Dieback Extents and Conversion in Floodplain Vegetation
Why
The ecological structure, composition, biodiversity and resource potential of the different types of vegetation are very different from one another. Any significant ecological disturbance caused by mine activities is human-induced environmental harm, and regrettable from an ecological perspec-tive. The severity of harm is partly a function of area. In addition, the long-term harmful conse-quences (including failure to re-establish to an approximately pre-mine equilibrium of vegetation types and relative abundances), from evidence from other studies, increase as the area involved expands. The vegetation and its fauna are also important resources for the local people, different vegetation types supplying different plant and animal food sources, by different production, har-vesting or catching methods.

Present Situation and Prognosis
Dieback and conversion have occurred, are occurring, and the affected areas are predicted to in-crease. The dieback area may eventually exceed 2,000 km2.

Key Uncertainties And, from the Fourth PRG Report: What Needs to be Done
2.3 Fish Biomass Decline and Loss of Fish Biodiversity
Why
Fish biomass and diversity comprise one index of the health of the aquatic ecosystem; as well, the fisheries are an important food resource for the local people. Declines in fish biomass and diversity have been documented since the late 1980s and, because of a lack of mechanistic understanding of causality, it is not possible to judge whether declines will continue to the point of elimination of species and failure to recover after mine closure.

Present Situation Prognosis
No prognosis is possible. The possibility of a catastrophic collapse of the fisheries in the Fly River is high if bioavailable copper reaches levels that are toxic to algae; this situation is likely to occur before toxicity to fish occurs. This possibility becomes a certainty if copper bioavailability and toxicity increase as a result of widespread acid rock drainage (ARD). The possibility of a collapse as opposed to a stabilization at current low levels of diversity and biomass, if copper toxicity is not an issue, is real but no probabilities can be assigned.

Key Uncertainties What Needs to be Done
2.4 Possible Chemical Stressors of Plants
Why
The DLRA listed a number of metals present in the system that are potential hazards to plants. The document points out that the physical stressors of sedimentation and flooding may be masking the effects of possible chemical toxicities (which may be chronic rather than acute).

Present Situation and Prognosis
To date only one species has been subjected to toxicity testing, and that was an exotic crop plant (maize). The nutrient trials that were carried out with this species, on dredge sediment, indicated that there was no toxicity of this substrate to maize. In addition, sago and cassava were found to be low in Cu and most other metals of concern. It is difficult to predict, however, the possibility of chronic toxicities and this possibility should not be overlooked. It is possible that as flooding recedes as a stressor, other toxicities may be revealed. This matter also relates to the next key issue - ARD.

Key Uncertainties What Needs to be Done
2.5 Possible ARD Hazards
The question of acid rock drainage (ARD) was raised at the first PRG meeting in Melbourne (August 18-20, 1997) and is also one of five major concerns previously identified by the PRG (Third PRG Report to OTML [24/02/99]). A preliminary report on ARD was produced by the Australian-based consulting group EGI and was provided to the PRG on June 29, 1999. This was the first serious treatment of this issue. The preliminary report was the subject of both written PRG comments and intense discussions at the July 6-8, 1999 Brisbane workshop. The PRG has not received any further information on ARD since that time, although ARD was discussed at a technical workshop in Tabubil on January 19, 2000.

There appear to be two possible sources of very serious problems: Why Present Situation Prognosis Key Uncertainties What Needs to be Done
2.6 Cu Chemistry Model/Cu Spikes (and in Relation to ARD Hazards)
Dissolved copper (dCu) is of concern because high concentrations of bioavailable Cu could kill key elements of the aquatic flora and fauna in the Ok Tedi/Fly River systems. Algae are an important component of the aquatic food chain and are well known to be very sensitive to Cu. Thus, they would be particularly adversely affected by any increase in bioavailable Cu. CSIRO modelling and the OTML Cu monitoring data base suggest little likelihood of toxic problems due to Cu unless ARD occurs (assuming that Cu “spikes” detected during monitoring are not real). However, there is a lack of Cu toxicity data for Fly River species. Further, dCu modelling is presently insufficiently sensitive.

Why Present Situation Prognosis Key Uncertainties What Needs to be Done
3.0 Review Comments
This section summarizes the PRG’s detailed review comments (from the Fifth PRG Report [04/02/ 2000]) on both the “Final” Screening Level Risk Assessment (SLRA) and the “Final” Detailed Level Risk Assessment (DLRA) documents.

As noted in our Fourth Report (20/07/99), the SLRA has been previously subjected to review twice in draft format. However, the DLRA has previously only been subjected to one review, and only as an incomplete draft. Our review of this “final” SLRA document only considered whether our previous comments had been adequately addressed. In contrast, our review of the “final” DLRA document considered not only whether our previous comments had been adequately addressed but also involved a complete review of the document.

Our review comments are provided in the context of OTML’s July 1999 cut-off date for information to be included in the HERA. In other words, per OTML’s instructions, neither the HERA nor this report consider new information provided after that date. However, we are aware of some of the results of post-July 1999 studies and believe that those findings are of direct relevance to ultimate decision-making. Further, those findings could well change some of the DLRA results for comparisons between options. We expect that review of post-1999 study findings will be the subject of a future PRG report.

3.1 Screening Level Risk Assessment (SLRA)
The SLRA is set out within the standard risk assessment (RA) format. Many (but not all) of its shortcomings do not arise from the document itself but rather from the terms of reference and the sometimes glaring data gaps. The terms of reference effectively limited the SLRA (and the DLRA) to a comparative RA format; the PRG were asked to identify potential fatal flaws common to all options. Our review of the HERA (Human and Ecological Risk Assessment) consultants’ replies to our previous comments indicates that not all of our comments or concerns have been adequately or completely addressed. However, given the above limitations and time constraints imposed by OTML, we do not believe that there is anything to be gained by further changes to the SLRA. Instead, we focus our attentions on the more important DLRA.

3.2 Detailed Level Risk Assessment (DLRA)
The PRG finds the “Final” DLRA document to have a number of major gaps and deficiencies. The major gaps are due to either limitations on the scope and timing of the DLRA imposed by OTML or due to remaining uncertainties. Deficiencies are due to errors or omissions that could have been addressed in the document.

The major gaps and deficiencies as identified from our detailed review comments (Fifth PRG Report [04/02/2000]) are provided below in bulleted format. After the narrative for each bullet we provide one or more numbers explaining the context of the major gap or deficiency: (1), (2), or (3). A (1) indicates limitations on the scope and timing of the DLRA; a (2) indicates remaining uncertainties; a (3) indicates errors or omissions.

Our review of the HERA consultants’ replies to our previous comments indicates that many of our previous comments (including some they had agreed to address) have not been addressed, and factually incorrect material is still included in the DLRA. In particular, it appears that most previous comments regarding the state of knowledge of the physical system have been ignored. Key points related to our disagreements or reservations include the following: Our detailed review of the “final” DLRA document indicates the following additional major deficiencies: It is in general clear from the DLRA that considerable human and ecological disturbance and harm have been caused by the mining operation, and that the effects will be very long-term, whatever mine option is adopted. However, although any ecological risk assessment will by definition contain uncertainties, in this case some of the uncertainties are vast indeed. This is partly because of the complexity of the system and disturbances being evaluated, but also partly because of the absence of data, some of which could have been acquired by field and laboratory investigations, had more time and resources been available for the purpose. In this regard we note that constraints on the HERA consultants included the fact that many past investigations were not appropriate to the focus of the HERA, and problems with some commissioned studies (timeliness and/or acceptability). However, as noted above, the DLRA still contains serious errors and omissions that should have been rectified.

The DLRA has narrowed the risks to the aquatic ecosystem from the OTML operations to three stressors - Cu toxicity, TSS (total suspended solids) and habitat changes (aggradation). These stressors remained after consideration of the SLRA and available data. Unfortunately, the conclusions from the detailed assessment of the risks from each of these key stressors are largely qualitative. It was disappointing that the DLRA did not provide a more quantitative assessment.

In summary, although the DLRA comprises a great deal of work and is also a useful piece of work, it is not as useful as it should be as either a benchmark document or for decision-making. However, despite the shortcomings, it can still be used by OTML as part of their decision-making process provided the major data gaps and deficiencies noted above (and in more detail in the Fifth PRG Report) are taken into account.

4.0 Summary
The evidence clearly shows that OTML’s activities have to date caused major aggradation and flooding in the river valley which, among other effects, have resulted in extensive forest dieback (>500 km2) which is likely to spread further, possibly exceeding 2,000 km 2 . There has therefore at the same time been some loss of biodiversity, at the genetic (i.e., intra-specific) and ecosystem levels, in at least the rainforest system. Based on international comparisons, some loss of species biodiversity is also likely to have resulted already from the mining activities, however this cannot at present be assessed, because of a lack of detailed data on the New Guinea biota as a whole. The forest dieback has been accompanied by replacement (or conversion) to swamp grasslands and other wetland communities, which are more flood-tolerant. Effects of mine-related activities on diversity, abundance and productivity of these wetter communities are also largely unknown. As the wave of mine-derived sedimentation passes down through the river system, it can be expected that secondary rainforest will be re-established in some areas. Present predictions suggest that no general vegetation type will be lost from the Ok Tedi/Fly valley. However, this is not certain. Further, the patterns of distribution of the dominant vegetation types, their relative abundances, and their exact species compositions cannot be predicted. This is again partly the result of a lack of detailed information on the flora of New Guinea, and partly because the details of the current and future topography and physico-chemical composition of the sediments in this river system are also uncertain.

In addition to widespread adverse effects to the terrestrial environment, the aquatic environment has also been adversely affected over a large area. There are very few fish to be found in the Lower Ok Tedi (an approximate 90% decrease in fisheries biomass). In the middle Fly River, there has been an approximate 75% decrease in fisheries biomass and some species are no longer found in this stretch of the river. Further decreases and possibly even a total collapse of the fishery are possible, however the likelihood of this possibility is unknown because the reason(s) for the original decline are unknown. The primary suspect is aggradation and associated habitat loss in the main river channel. Continued aggradation may threaten the ecologically critical tie channels in the Fly River system. The other major threat to the fisheries is ARD that, if it occurs on more than a localised basis, has the potential to totally eradicate the fisheries either through direct toxicity or indirectly by toxicity to sensitive food chain components (e.g., algae).

ARD also poses a threat to the plant communities living in the floodplain. Surface floodplain sediments presently include tailings and waste rock. Although preliminary modelling and predic-tions indicate that ARD is not an issue on the floodplain, the work is not definitive and future tailings and waste rock will have a greater ARD potential than was the case in the past. There are no easy solutions. Closing the mine is arguably the best option environmentally but not necessarily the best social option. However, decisions must be made. And these decisions require the best possible and most up-to-date information. Post-DLRA work must focus on the key uncer-tainties noted in the DLRA and in the PRG’s present report, related in particular to what can be done to minimize or prevent further environmental damage should the mine either continue to the natural end of its life or shut down earlier. In this regard, the positive effects of dredging need to be fully assessed. So too do the possibility of ARD and methods to prevent this, as well as reason(s) for the fisheries decline (which may provide insights into how to ameliorate this or at least prevent a catastrophic collapse).

The PRG recognizes the social value of OTML’s presence in PNG but are not in a position nor do we have the expertise to evaluate social benefits compared to environmental harm. We commend OTML for the very valuable environmental studies done to date, but caution that more work is needed and almost certainly must continue post-mining if further environmental harm is to be avoided or minimized.

*End*