abstracts for
4 Coastal & Island Mines

The main objectives of the workshop were to help train Fiji government staff to appraise environmental documents and reports relating to the submarine tailings disposal (STD) system suggested as part of the proposed Namosi copper mine development, and to increase community awareness of the submarine tailings issue. In the process, an appraisal of Placer Pacific Ltd.'s Final Environmental lnception Report and the Progress Data Report 1992-1993 was made. Representatives from Placer Pacific Ltd. and their environmental consultants, staff and post-graduate students from the University of South Pacific, and representatives of landowner, environmental and tourist industry groups also participated.

The workshop discussed the suggested Namosi STD system in conjunction with proposed screening criteria developed by the USA Bureau of Mines for the suitability of STD for various locations and environmental conditions. Consensus was reached that the Namosi STD system met criteria concerning proximity to coast, appropriate bathymetry and availability of site but that there was, at present, insufficient information to assess whether other criteria concerning potential for contamination, potential for resuspension and upwelling, impacts on other resource uses and socioeconomic impacts would be met satisfactorily. Particular issues of concern involved the need for more data on the depth to which the seawater surface mixed zone will penetrate (particularly during cyclones), the use of a particular (criticised) instrument for oceanographic determinations, and the preliminary information about the levels of copper in the residues from bench scale milling tests.

The appraisal of Placer Pacific Ltd.'s environmental investigations so far used two objective rating models developed in Canada: the ADCAP model which rates the quality of scientific data on a 0-4 scale, and the Clark-Whitfield model which rates the quality of environmental assessment and monitoring processes on 14 separate points. By the ADCAP criteria, the data to date were given a rating of 3-4. The main concerns expressed were that various data gathering procedures were not satisfactorily documented and critical instruments not properly calibrated. However, these concerns do not affect the broad conclusions reported by Placer Pacific Ltd. so far.

By the Clark-Whitfield Criteria, the environmental Design, Plan and Reporting were satisfactory, but there was insufficient information available to determine whether the other criteria, largely concerning documentation of procedures, were met. Discussion indicated that there was considerably more documentation available from Government and other sources which has not yet been incorporated in the environmental assessments.

The workshop was informed that Placer Pacific Ltd's environmental investigations for the STD system are still in an early stage and only long-elapsed-time weather, trapping depth and upwelling investigations are being addressed at present. Other areas such as current metering, bathymetry and the impact on fisheries and benthic biota will be addressed by short-elapsed-time investigations to be initiated once it is more clearly apparent that the mine development will proceed.

Overall, there was consensus in the Workshop that environmental concerns relating to the possible installation of a STD system for the Namosi mine are being satisfactorily addressed at this early stage by Placer Pacific Ltd but that there is a strong need for continual monitoring and assessment of the company's on-going environmental investigations and reporting by Government and the community.

Developments in the mining sector in 1987 were still low keyed even though there were some encouraging indications of greater activities.

Discoveries and development of new oil and gas fields were in progress, which were sub-sequently developed and increasingly private companies have shown and interest in the development of coal and gold, and domestic consumption of some mineral commodities have increased.

As a producer of raw materials for the world market Indonesia has been hard hit by the prevailing low prices of mineral commodities in the world market, particularly those of oil and tin, affecting severely the oil and tin mining industries.

Still the fact remains that 53.31 percent of the country's export earning were derived from the mining sector.

Table 1 illustates Indonesia's minerals production from 1983 through 1987, and Table 2 shows the export earnings over the same period.

1. Based on papers presented during the seminar, conclusions can be made as follows,
2. The Government policies either in environmental management or in other matters shall be immediately adjusted to solve the issues and meet the demand of the public;
3. The results of survey and research concerning environmental impact due to sub marine tailing placement and plan to mitigate its impact shall be made available and socialized to the public;
4. The sub marine tailing placement technology shall adopt geographical and climate conditions in Indonesia. Therefore, in its application, the environmental management becomes the main priority and it shall be undertaken accordingly with local environmental rules and conditions;
5. There are several technical requirements in the application of STPothers, thermoclyne, bathymetry, distance of tailings outfall from shoreline, seabed slope stability and physical and chemical characteristics of the tailing;
6. Detoxification process in the STP system can minimize the toxicity level of the tailing/waste prior its discharge into the environment. Thermoclyne layer is an important factor in STP application, however it is not the main factor in the consideration of sub marine tailing placement mainly in relation with the mitigation of STP's impact on the marine biota;
7. There are failures in tailing placement in the sea. However this happen due to the discharge of tailing into the coastal waters, bay or river that does not meet the requirement of the application of STP. In the case where all technical requirement are met, the sub marine tailing placement is proven safe and the seabed environment can recover in a short time;
8. From coastal engineering point of view, the STP technology is more suitable for area with steep seabed that generally indicated by volcanic uplift such as in Indonesia;
9. Coastal management is also an important aspect that shall be examined thoroughly because the coastal ecology contains high biodiversity including coral reefs that sensitive to the ecological changes. In addition, coastal area shall be protected from the negative impact of STP;
10. Dissemination of research results concerning the impact of tailing on marine park, coastal area and river as sources of tourism, irrigation and drinking water as well as health condition of fish for human consumption shall be done clearly and straight to avoid confusion of the community;
11. The heavy metal content with carcinogenic characteristics that may resulted from sub marine tailing placement will cause heavy metal accumulation which may exceed the prevailing standard. Considering the fish also one of the main export commodities of the North Sulawesi Province, the heavy metal contamination of fish may cause ban for North Sulawesi and even Indonesia fish export. Therefore, concern of conducting deep, accurate and reliable research by independent, professional and credible institution is crucial;
12. Generally, sea water quality in sub marine placement site meet the sea water standard quality for tourism and conservation;
13. Socialization of research and monitoring results concerning impact on sub marine tailing placement shall be undertaken using language that understood by local people;
14. Clarification of research and monitoring data, as well as sources of data is needed as reference to avoid confusion;
15. There is no indication yet on the impact of mining on fish population particularly for species indicator that lives in coral reef;
16. The condition of the existing coral reef is able to support the existence of high fish diversity;
17. There are suspicion on the decrease of some species of fish population at certain time due to catching of decorating fish or maybe bombing,
18. There shall be transparency in monitoring which must be done comprehensively for example: fish population, reefs, tailing deposition etc, that involving local communities.

Environmental management and protection are implicit in the 1945 Constitution of the Republic of Indonesia, and in the five principles of Pancasila which provide the foundation of political and social rule for the state. Indonesia's awareness of the need for environmental management developed in concert with that of other progressive countries in the late 1960s and early 1970s, though the imperatives of a burgeoning population provided an added dimension to Indonesia's environmental issues. The evolution of formal environmental institutions and laws is represented by the formation of the Ministry of Development Supervision and Living Environment (PPLH) in 1978, passage of the Environmental Management Act in 1982, conversion of PPLH into the Ministry of State for Population and Environment (KLH) in 1983, and the promulgation of the Regulations pertaining to the Analysis of Impacts on the Environment (AMDAL) in 1987. These Regulations provide a potentially highly effective tool in the service of environmental management. Political will, functional institutional arrangements and sufficient human and other resources are essential for realizing the potential of this and other KLH environmental management mandates. The current structure and levels of resources are inadequate to the task.

Donor agencies have recognized these needs and, in concert with their own developing awareness of their responsibilities to the environment, have begun to assist the Government of Indonesia in its environmental management initiatives. This assistance may come through ensuring good environmental management practices on projects supported in other sectors, or through assistance directly to the environmental "sector". The Canadian International Development Agency (CIDA) is testing a project model that provides multi-focus support to Indonesia's primary environmental institution, KLH; and through KLH to agencies and institutions that have interests and responsibilities in environmental management in lndonesia. This is the Environmental Management Development in Indonesia (EMDI) Project jointly implemented by KLH and Dalhousie University, Halifax, Canada. Dalhousie University is the Canadian Executing Agency.

Many countries and agencies have developed and implemented environmental assessment processes in the service of environmental management. Definition and implementation of these processes have demonstrated a number of common issues which are relevant to lndonesia as it proceeds with implementation of its own process. These general issues include administrative and procedural matters, the quality of the assessment, public participation, follow-up to assessment statements, education and training, and the fitting of a country's environmental assessment system into the broader international context of environmental assessment and sustainable development. These general issues are examined in greater detail and in the Indonesian context in this paper.

Indonesia has well-informed and potentially highly effective legislation in place in its Environmental Management Act and its AMDAL Regulations. Twelve high priority concerns were identified in conjunction with Indonesia's initial experience with implementing these Regulations. They are:

1. The time has come to shift from "theory" to "practice", i.e. from the conceptualization and consultation associated with developing the legislation to making the AMDAL process work in the service of environmental management.
2. The unit which administers the overall AMDAL process must be established and supported with the mandate, authority, and resources to do its job. Five possible institutional models were considered, only one of which, the status quo (KLH with no additional resources), was rejected as untenable.
3. The administrative unit in charge of implementing the AMDAL process must work effectively across all pertinent units in the central (national) government: sectoral departments; non-departmental agencies, especially Bappenas (the national development planning agency); and the AMDAL Commissions (see below).
4. The AMDAL process administrative unit must also work effectively vertically through the Indonesian government structure, i.e., with the Governors and Executives of Level I Regions, the Bappeda (regional development planning agencies), the BKLH (regional environmental management agencies), the regional AMDAL Commissions, and influencing the district and local levels as appropriate.
5. In setting up the mechanism of the AMDAL Commissions in both the central and regional government systems, Indonesia has selected an innovative and potentially very effective form of "setf-assessment" for the agencies responsible for development, since their Commissions are charged with managing the environment (physical, living and human) sustainably. The individual Commissions must now be made to function effectively. Good working relations must also be established between the Central Commissions and the Regional Commissions.
6. The environmental assessment process for Indonesia is now in place. Experience elsewhere demonstrates that the best and only way to do environment assessment proficiently is to learn by doing. Deliberate selection of demonstration projects and activities is recommended to test the system; test the institutional structures and relationships; train managers, practitioners, reviewers and participants; and direct adjustments as necessary to provide an efficient, smoothly operating, high quality system.
7. In order to avoid overloading the AMDAL process, screening systems will need to be developed, exclusion/inclusion lists established, and/or review priorities will need to be set. Trying to put too many projects through the process too quickly will destroy its credibility just as surely as would exempting too many projects with impacts of concern.
8. Provision is made in the Environmental Management Act and in the AMDAL Regulations and Guidelines for public participation. This can take the form of interventions submitted to the review process, reviews of the AMDAL documents, and for representatives of "seIf-reliant" groups to be appointed to the Commissions and to the Commissions' technical teams.
9. Financial instruments can be used a number of ways in environmental assessment and management. In the AMDAL Regulations, provision is made to ensure participation of all interested parties in the environmental assessment process through provision of subsidies to disadvantaged activity initiators, and compensation to individuals or groups negatively impacted by pollution or other forms of environmental damage.
10. The relationships between environmental management, the AMDAL process, and regional spatial planning with its resulting Regional Plans must be understood. Essentially, both the AMDAL process and Regional Plans are tools used in the implementation of environmental management and sustainable development. There is an interactive dynamic between the AMDAL process and regional planning that should be capitalized for the benefit of both.
11. The AMDAL process is a very necessary one for Indonesia, but a demanding one in terms of human resources and human resource development. Substantial resources will have to be devoted to the process full time, while other technical specialists will be used part time. The human resource needs encompass governments at all levels, universities, the private sector, self-reliant community groups and concerned and/or affected individuals.
12. The credibility of the AMDAL process must be developed and maintained. Priority areas for attention within the next five years include bringing relevant scientists, social scientists and economists into closer contact with the process to ensure the credibility of data collection and interpretation; research and development efforts in AMDAL through departmentally-based Research and Development (Puslitban) units; continued strengthening of the university based environmental study centres (PSLs) so that they can play their roles in AMDAL; training, especially on-the-job training for AMDAL practioners so that high quality AMDAL reports result; and close attention to the administrative and management system to ensure the effective and credible functioning of the AMDAL process at all levels.

The placement of mine tailings in a targeted deposition area deep in the sea has been shown as an environmentally sound practice at several mine-sites over the past 25 years. The case histories now available allow the development of screening procedures to determine whether other sites are suitable for STP. Three criteria have been developed for appraising the suitability of a site for STP.

The screening criteria are (1) the location is physically suitable for Submarine Tailings Placement, (2) a preliminary assessment of environmental and social risks indicates that they are less for STP than for other tailings management systems, (3) a detailed assessment of physical, chemical, biological and social factors confirms the preliminary appraisals. The first two criteria require relatively simple and inexpensive desk-top procedures.

There are several environmental reasons why tailings placement underwater in a tailings impoundment, in a lake or in the sea should be considered at selected sites. Placement of tailings underwater can dramatically reduce the generation of Acid Rock Drainage through reduction of exposure to oxygen. This in turn reduces the risk of contamination affecting fisheries, agriculture, and other resource and habitat use by residents. Placement in the sea adds the buffering power of seawater to the environmental protection, allows the generation of marine bacteria which precipitate metal sulphides thus reducing the risk of trace metal bioactivation, and eliminates the risk of tailings dam collapse in regions of earthquakes and torrential rain storms.

The technology for submarine tailings placement has been proven over 25 years at Island Copper Mine in Canada, and the prototype system developed there has been used successfully elsewhere, e.g. the Misima Gold and Silver Mine, Papua New Guinea. At Island Copper Mine environmental impacts and risks from tailings placed in a targeted area of the seabed near the mine were less than on-land placement due to the site being subject to earthquakes and torrential rainstorms; and the local creeks and rivers being the spawning grounds for the commercially-fished species, the Pacific salmon.

The physical bases for submarine tailings placement (i.e. meeting Screening Criterion 1 above) are (1) it must be possible to target a deposition area large enough to receive the tailings during the mine's lifetime, (2) the targeted area must not be subject to deep sea currents capable of returning tailings in impacting amounts to the surface, and (3) a pipeline can be engineered (with a de-aeration/seawater-mix system) to discharge the tailings slurry below 50 m depth (or deeper if necessary) as a density current to the targeted area. A set of guidelines for making these determinations is included.

During the Dutch East Indies period, environmental legislation could be characterized as "classical", in that it concerned primarily with sectoral aspects. It mainly emphasized environmental control.

A few of the regulations of this period are still valid on the basis of the provisions as contained in Article II concerning Transitional Provisions of the 1945 Constitution.

The environmental legislation in Indonesia today therefore comprises both the laws and regulations of the pre-independence period and those developed during the independence period. The 1972 Stockholm Declaration on the Human Environment gave an impetus to the development of modern environmental legislation.

An important breakthrough in the overall management of the environment is the promulgation on March 11th, 1982 of the Act No.4 of 1982 concerning Basic Provisions for the Management of the Living Environment.

It encompasses all aspects of the living environment in order to form the basis for further regulations. ln addition, It serves as the basis for the evaluation and adjustment of all legislations heretofore valid.

The Act strongly advocates a development, which is based upon environmental consideration as a means of achieving continuity and the well-being of present and future generations.

This paper studies the various implications of the principles contained in the Act.

Misima Mines Pty Limited operates a gold and silver mine on Misima Island, 600 km east of Port Moresby in Milne Bay Province, Papua New Guinea (PNG). The mine is owned by Placer Pacific Limited and the Government of PNG and commenced operation in June 1989.

A five-year period of environmental monitoring, impact assessment and consultation with both landowners and government was carried out immediately prior to development approval. Alternative waste disposal strategies were addressed as a key part of the feasibility process and the PNG Government's decision to allow ocean disposal of tailing, soft waste rock and treated sewage effluent. Ocean disposal was approved as the preferred option after consideration of land and resource use issues, public safety and potential environmental effects.

The Misima Mine utilises submarine tailing disposal from a deep-ocean outfall (112 m water depth) after recovery of process chemicals and pre-discharge dilution of the tailing slurry with seawater. Between 1989 and 1994, soft waste rock was disposed into deep water (>1,000 m) from the shoreline. Since then soft waste rock has been used to backfill mined-out parts of the main pit. Treated sewage effluent is discharged via a shallow-water outfall (7 m water depth) near the mine's accommodation centre (Plate 1).

Environmental planning of the Misima Mine gave greatest emphasis to the protection of resources utilised by Misimans. That emphasis was extended to the design of the monitoring program and today it underpins the environmental management of the mine's operations. With regard to marine effects, greatest importance was placed on monitoring of the fringing coral reefs where there is at least some resource utilisation by Misimans. An environmental baseline was established followed by a commitment to direct measurements and biosurveillance which continues today. A strategy was implemented to ensure the ongoing compliance with ocean water quality criteria for both the tailing discharge and the discharge of treated sewage effluent. While there was no utilisation of deepwater fish by Misimans, data on metal levels in the tissue of deepwater fish was also collected as part of the baseline.

Consistent with Placer's corporate commitment to fully understand and manage the environmental effects of its operations and to demonstrate environmental leadership, a systematic review of the Misima Mine's effects on, and risks to, the marine environment was initiated in 1993 and is ongoing. To assist in the review, a conceptual model of physical and chemical interactions and their associated biological responses was developed. The results of the review can be summarised as follows.

Effects on Water Quality

• As predicted in the Environmental Plan (EP) for the Misima Mine, the construction and operation of the Misima Mine has caused elevated turbidity and increased sedimentation in nearshore waters. However, marine monitoring results show that both have declined since the end of construction (mid 1989), despite the large quantity of soft waste rock (>50 Mt) that was disposed of into deepwater from the shoreline prior to 1994.
• Direct observation of the tailing outfall has confirmed that the tailing slurry flows down the steep submarine slope as a coherent density current which is a similar process to the transport of natural sediments.
• Monitoring has confirmed that the ocean water column is consistently stratified, between the warm surface waters and the deep colder water, above the depth of the tailing discharge. Tailing was predicted not to rise to the surface and no tailing material has been observed upwelling into shallow water in six and a half years of continuous operation.
• Acoustic sensing of subsurface tailing plumes, confirmed by both transmissivity profiling and water sampling, has shown that only subsurface plumes containing very low concentrations of suspended tailing solids occur in the ocean water column and that these are trapped at depth by the ocean's natural stratification. Subsurface plumes are generated by the separation of fine particles from the descending density current as it passes through density discontinuities on its way down the submarine slope.
• Analysis of water samples collected in 1995 from within the subsurface plumes has confirmed that Misima Mine's submarine tailing disposal system complies with regulatory permit conditions, i.e., that ambient seawater standards are met at the edge of an allowed mixing zone 1,200 m from shore. This finding supports the results of two previous validation surveys undertaken in 1989.

Effects on the Ocean Floor

• A marine seismic survey was undertaken to define mine-derived sediment deposition on the ocean floor and the results confirmed that deposition was confined to a semi enclosed oceanic basin at a maximum of 1,500 m water depth immediately to the south of Misima Island.
• The steep submarine slope to the south of Misima Island and gravity flow processes have combined to prevent detectable deposition of mine-derived sediment in water shallower than about 1,000 m.
• Deposits (>1.5 m limit of seismic detection) of tailing soft waste rock and locally displaced natural sediments were interpreted from the seismic survey results. These deposits covered a 20 km2 area on the gently sloping floor of the basin to the southeast of Misima Island between about 1,000 and 1,500 m water depth. Thinner deposits (<0.1 m) of fine sediment were detected by ocean floor coring throughout the basin.

Effects on Marine Biota

• The review of the mine's effects on the fringing coral reef found that:
  • Increased turbidity and sedimen tation has had varying impacts on the fringing coral reef over a 9 km length, but have reduced since construction.
  • The approximate location and extent of the EP predicted impact zones were correct i.e, severe (1 km), transitional (3 km) and minor (5 km).
  • Evidence of coral recruitment in the impact zones highlights the potential for rapid recovery of the affected coral reef communities.
  • There was no evidence of damage to the fringing coral reef from the discharge of treated sewage from the mine's accommodation centre.
• Fish consumption by Misimans is highly variable. Data confirm that a variety of edible freshwater and marine biota continues to be caught and consumed by Misimans, from areas both affected and unaffected by the mine's activities.
• Analysis of the metal content in tissue samples (both flesh and liver) taken from shallow- and deep- water finfish, and pelagic fish, indicates that there has been no increase since mining commenced. While two species of deep-water fish contained levels of mercury that exceed Australian National Food Authority standards, the levels were similarly elevated prior to mining, which suggests naturally occurring bioaccumulation.
• Analyses of the soft body part of two species of shellfish showed that metal levels in shellfish have generally increased near the mine compared to the baseline. The mean cadmium content of one species exceeded the relevant Australian National Food Authority standard. However, a preliminary risk assessment indicated no health risk to Misimans who consume shellfish. In fact, the rate of shellfish consumption would need to increase by 7 to 12 times in order to exceed the World Health Organisation's cadmium guideline for long- term Tolerable Daily Intake.
• The findings of a literature review have confirmed that fish have the ability to detect potential contaminants in the water column and then to respond by swimming away. This process, known as 'behavioural avoidance', is likely to apply to deep- water fish species at Misima Island should they encounter dilute tailing plumes in the ocean water column.
• Deposition of mine-derived sediments has physically smothered the deep- ocean benthos; however, sampling has confirmed that even the thickest deposits are colonised by microscopic organisms.
• Preliminary assessment of deep- ocean benthic biota did not indicate a clear pattern of effect on the abundance and diversity of microscopic organisms, resulting from mine-derived deposition on the ocean floor. The results indicated an extremely heterogenous ocean floor off Misima Island, which is not unusual in the Coral and Solomon sea regions.

Direction of Ongoing Work

Implicit in the mine's environmental impact assessment and this review are the following three hypotheses. The ongoing marine work program in addition to routine monitoring at Misima Island is focused primarily on testing these hypotheses.

Hypothesis 1: Effects on the fringing coral reefs will be temporary

Monitoring results to date support this hypothesis and have shown that sediment impacts are reducing and that coral recruitment is occurring (Plate 2). As a result, the mine's coral reef monitoring program will be modified to address recruitment and recovery.

Hypothesis 2: The Misima Mine does not adversely impact human health through the utilisation of marine resources

A program of work is presently being developed to determine (in greater detail) the concentrations of metals in edible marine biota and to confirm that there is no human health risk to Misimans from the consumption of seafood.

Hypothesis 3: Effects on the deepocean benthic community will be temporary

Case studies of other mining operations have shown rapid recolonisation of shallow-water benthic communities following cessation of submarine tailing disposal. However, as deposition off Misima Island has occurred in deep water (mostly >1,000 m), the rate of recolonisation is expected to be slower because of the consistently low temperatures in the deep ocean. Discussions have commenced with research institutions from which a long-term work program will be developed to enable quantification of both the benthic impact of mine derived sedimentation and the rate of recolonisation (following mine closure).

Misima Mines Pty Limited (MMPL) operates a gold and silver mine on Misima Island, 600 km east of Port Moresby in Mime Bay Province, Papua New Guinea (PNG). The mine is owned by Placer Pacific Limited and the Government of PNG and commenced operations in June 1989.

A five-year period of environmental monitoring, impact assessment and consultation with both landowners and government was carried out immediately prior to development approval. Alternative waste disposal strategies were ad-dressed as a key part of the engineering feasibility and environmental impact assessment process. The PNG Governments decision to allow submarine tailing disposal and ocean disposal of treated sewage effluent and some soft waste rock was made after consideration of land and resource use issues, public safety and potential environmental effects.

The Misima Mine utilises submarine tailing disposal from a deep-ocean outfall (112 m water depth) after recycling of process chemicals by thickening of the tailing and pre-discharge dilution of the thickened tailing slurry with seawater.

Environmental planning of the Misima Mine gave greatest emphasis to the protection of resources utilised by Misimans. That emphasis was extended to the de-sign of the monitoring program and today it underpins the environmental management of the mine's operations. With regard to marine effects, greatest importance was placed on monitoring the shallow water effects, especially of the fringing coral reefs, where there is at least some resource utilisation by Misimans. An environmental baseline was established followed by a commitment to direct measurements and and biosurveillance which continues today. A strategy was implemented to ensure the ongoing compliance with ocean water quality criteria. While there was no utilisation of deep-water fish by Misimans, data on metal levels in the tissue of deep-water fish was also collected as part of the baseline.

Consistent with Placer's corporate commitment to fully understand and manage the environmental effects of its operations and to demonstrate environmental leadership, a systematic review of the Misima Mine's effects on, and risks to, the marine environment was initiated in 1993 and is ongoing. To assist in the review, a conceptual model of physical and chemical interactions and their associated biological responses was developed.

Background

The large quantities of tailings produced as a result of mine operations at Panguna, Bougainville, are transported by pipeline to the Jaba River. Part of the tailings accumulate in the river, while the remainder forms a delta where the river joins the sea at Empress Augusta Bay. These copper-containing deposits are leachable by seawater presenting a potential hazard to aquatic biota.

Objectives

The aim of this investigation was to examine the chemical form and toxicity of copper in seawater samples collected near the tailings delta. Copper speciation is measured using anodic stripping voltammetry combined with physicochemical separations, in an analytical scheme developed in the Division of Energy Chemistry. Toxicity is assessed in algal bioassays and the results related to chemical speciation measurements.

Conclusions

Total copper concentrations were detected in surface and bottom water samples in the range 8 and 88 ug L-1. Greater than 93% of this copper was in the form of weak soluble complexes extractable by the chelating resin Chelex-100. Labile copper concentrations ranged from 33 to 60% of the total copper, with unusually high percentages of lipid soluble copper being detected. Growth factors determined from algal toxicity studies correlated poorly with all the chemical species measured. Despite the high copper concentrations in the surface and bottom waters, in almost all instances the samples were found not to inhibit algal growth, whereas the same copper concentrations, present as the free metal ion, were in many cases highly toxic. Diminished toxicities were shown to result from the presence of the organic additives methyl isobutyl carbinol and polypropylene glycol ether in the process waste streams. Although these compounds may be naturally biodegradable or removed from the water column, it is likely that by the time this occurs, the dispersion of the copper plume will have reduced the soluble copper concentration to a level where it may no longer present a hazard to aquatic organisms.

During the period September 1975 - November 1976, more than 400 sampling hours have been spent collectively at twenty (20) sampling locations in the Pangara, Luluai, Mariropa, Pinei and Arakawau River systems. Samples have been collected using a 4" mesh gill net, 3/8" beach seine net) diving and spearing, night fishing with white lights and baited handlines.

From data collected by each of the three more successful methods, i.e. 3/8" beach seining, diving and spearing and night fishing with white lights, Shannon-Wiener and Brillouin indices of diversity, richness and evenness have been calculated.

The results of diving and spearing and beach seining in the Pangara River show marked reduction in all three indices compared with other streams. Indices calculated from light fishing data are similar among streams, a result which may be due to selectivity of the method.

The overall diversity in all five streams is low (H'{1og10}0.l-0.89) indicating fish communities predominantly controlled by abiotic factors such as current and temperature.

The Shannon-Wiener and Brillouin indices, recalculated substituting biomass units for abundance, were similar among streams. Values in the Pangara River were slightly lower than those of other streams.

A simple graphical analysis of diversity is included which reinforces results of analysis by indices.

Aquatic productivity on Bougainville Island is reviewed. Resources such as molluscs (oysters, clams), crustaceans (crabs, lobsters), sea weed, and beche-de-mer (sea cucumber), are poorly represented. Limited quantities of a freshwater mollusc (kina shell) occur on the east coast of the Island at the mouth of the Pinei River but there are very few in river mouths in Empress Augusta Bay on the west coast. Small numbers of shrimp can also be found in the lower reaches of streams on the east and west coasts.

Mud crab (Scylla serrata) is only found in abundance at the western end of Buka Passage while rock lobster (Panulirus spp.) occurs in association with coral reefs but distribution is patchy. Small blacklip oysters can be obtained from mangrove areas in Tonelei Harbour in the south of the Island and limited areas of eel grass which support dugong are located at Mission Passage (Toniva) and in the littoral zone at Aropa.

Fish and estuarine crocodiles which feed on fish appear to dominate marine and freshwater habitats.

Because of the geology of the area, coral barrier reefs are a dominant feature of the east coast whereas only limited areas of patch reef and fringing reef occur on the west coast. This influences the west coast aquatic resources with the result that reef species (eg. coral trout, rock lobster) are not well represented and estuarine fish assume even greater importance as a source of supplementary protein for west coast villagers.

Quantitative research information about marine and freshwater productivity on Bougainville Island has been compared with international literature to evaluate the magnitude and human importance of aquatic resources in the area. Trophic levels considered in the assessment include primary producers (ie. phytoplankton) together with primary, secondary and tertiary consumers of which fish, especially those of potential importance as food to man, are the major representatives.

It is concluded that aquatic resources are severely limited on Bougainville because of the Island's geographic location, it's geology, and the low levels of essential nutrients in water. Marine phytoplankton production for the Island is estimated at 30-40 gC/m2/yr. Benthic production depentdent on plankton is 4 g/m2/yr. Predicted fish production dependent on benthos is 0.4 g/m2/yr of which 50% or 0.2 g/m2/yr is available as potential yield for man. In Empress Augusta Bay with an area of 360 km2 this translates to a maximum potential annual catch of approximately 70 tonnes. This catch multiplied by a price per kg of fresh fish (price to be established by local market survey) provides an indicator of the potential monetary value of the resource if all the catch was available for sale or trading.

Currently however, there are no commercial fisheries on Bougainville nor are there areas of commercial or tourist recreational value. Fishing on the west coast is conducted by villagers on a subsistence basis. Therefore, the real fish yield to coastal villages is likely to be a small fraction of the potential catch. For example, the exploitation level may be as low as 10% of the potential catch: a figure of much more practical significance.

A questionaire has been designed for distribution to west coast villages to establish levels of historical and current exploitation of the west coast fish resource in terms of frequency of fishing, numbers of vessels involved, numbers of people involved, types of fish caught, types of preferred fish, and sizes of fish eaten.

The information will greatly assist negotiations for compensation in the event of future claims for loss of fish on the west coast as a result of tailings disposal.

An environmental audit of the mine's aquatic resource environmental programme was made through an on-site visit from June 25-29, 1984, through inspection of sampling and laboratory procedures, discussions with environmental staff, and examination of reports and documents. Results of the programme are reviewed, and a preliminary environmental impact assessment made for various proposed new tailings disposal options.

Audit

The aquatic resource environmental programme has emphasized assessments of fish and benthos populations and measures of trace elements in fish tissues. Sampling design and statistical analyses are generally appropriate, and results convincing. More effort is needed on quality control of the programme to ensure greater accuracy and precision.

The existing programme should be continued with extensions to monitor benthic recolonization, water turbidity, wetland, shellfish and aquatic plant contributions to primary productivity and local resource use.

Updated sampling on fish, benthos and trace metal contamination should be implemented in 1984 or 1985, and continued at two year intervals. If and when a new tailings disposal scheme is constructed these programmes should be implemented annually, starting one year before the new system becomes operational and continuing for two years afterwards.

Fully qualified scientific staff with appropriate experience should have continuing responsibility for the design, implementation and quality control of operations.

Projects must be professionally documented, at least by in-house reports, and preferably by appropriate publication in technical journals and conference proceedings.

The environmental group should prepare a detailed annual report each year for mine management and maintain a professional level report library with catalogue.

To maintain quality control there should be continuing environmental audits and reviews. The next audit should be conducted by a specialist in fish resource assessment or biostatistics (preferably both) in 1987. Thereafter the reviews should be at five year intervals. More on-site time than five days should be allowed the auditors.

Review

Analyses of fish survey data from 1977 to 1983 provides no evidence for population differences between east and west coast sampling areas, and no evidence of population declines in estuarine areas affected by tailings. Estuary running harvestable fish have declined in numbers and diversity in rivers now separated from the sea by tailings flowing down the Jaba River.

Analyses of benthos collections from Empress Augusta Bay, the adjacent coast and Rorovana Bay (on the east coast) have shown sufficient similarities that Rorovana Bay can be used as a reference station by which to assess changes in Empress Augusta Bay derived from the tailings discharge. A number of stations near the delta and shoreline in Empress Augusta Bay show population and biomass declines between 1979 and 1981, coincident with tailing spread in the bay. Tailing distribution can be mapped by copper levels in sediments.

Tissue analyses of selected species of fish for 1975 to 1983 provide no evidence for persistent bioaccumulation of copper or other metals nor that fish from Empress Augusta Bay can have significant impact on human health.

A start has been made on compiling a comprehensive baseline data bank on aquatic resources including information on invertebrate shellfish species, primary production, and ecosystem food chain relationships and energy flows.

Environmental Impact Assessment

A preliminary environmental impact assessment has been made for six tailings disposal options now being considered. These are submarine tailings disposal, offshore island disposal, shoreline within lease disposal, extended finger disposal, on-land high stack within the lease and on-land low stack with lease extension.

Both organisms and their supportive ecosystems may be impacted.

The impacts can be derived physically from tailings deposition smothering organisms or creating barriers to river and current flow, and from continuing or episodic water turbidity.

The impacts may be mediated chemically through trace metals, or pH, redox and associated effects.

Biological impacts may be at the level of primary or secondary biological production.

There are complicating factors arising from earthquake risk, the nature of the existing land lease, social perceptions of impact, the expected continuing erosion and river transport of upland deposited tailings, and need to construct river channels.

Finally, there is potential for the amelioration of impacts by natural recovery, enhanced by biological and land-form reclamation engineering, with or without action facilitating prior indigenous use or novel agricultural and aquacultural developments.

The preliminary assessment suggests that marine discharge will have less impact on aquatic resources than land stacking, but definitive assessments will be needed when disposal options are defined in more detail.

Bougainville Copper is currently reassessing its method of tailings disposal. This paper discusses the likely effects of proposed options on the quality of water in the Jaba river and in Empress Augusta Bay.

Two options are considered in detail. One involves the dredging of tailings from the Jaba river and stacking them in coastal swamps; the other involves piping tailings direct to the West coast. Dump management, river training and low cutoff grade are also briefly considered.

While tailings are discharged into the Kawerong river, copper concentrations in the Jaba river will remain very low (i.e. less than 10 ug/l). However without tailings to neutralise acidity from wasterock dumps, concentrations of copper will rise. This will be at the end of mine life if dredging is selected, or 1989 for a pipeline.

A model has been developed to predict future copper concentrations in the Jaba river under various disposal strategies. It is predicted that the pipeline option will result in far better water quality at end of mine life than if dredging is carried. The additional copper in the river with dredging results from the oxidation of sulphide minerals in land stacked tailings.

Recolonisation of the river at end of mine life with freshwater biota will be limited by the high copper content in the river (i.e. 0.1 to 10 mg/l) and will be restricted to copper tolerant species only.

Copper concentrations in Empress Augusta Bay have been surveyed and three types of water, or water quality. have been identified. They are mid-water, the freshwater plume, and bottom water. Concentrations mid-depth are generally less than 1 ug/l, in the plume 10 to 20 ug/l, and in bottom water up to 170 ug/l. Suspended solids and bottom sediments appear to be the principal sources of dissolved copper in the bay.

During mine life it is likely that copper concentration in seawater will not change significantly regardless of the tailings disposal option chosen. The only major change will be a progressive increase in the area of seafloor covered with tailings. A greater volume of bottom water will therefore be affected. A tailings pipeline would accelerate this process.

At end of mine life, input of dissolved copper to the bay from the Jaba river will increase, particularly if tailings are dredged from the river. It is tentatively predicted that the average copper concentration in midwaters of the bay will increase to around 2 ug/l under a pipeline option or to 10 ug/l under a dredging option. At any given site concentration will vary from these means depending on local and general current movements. In particular, water immediately off the delta will have much higher concentrations of copper. To refine estimates of future quality of bay water more detailed information is required on water circulation and mixing patterns in the bay.

Migration habits of fish around the bay will determine their exposure to copper, but there seems little likelihood that concentrations will ever be lethal. In contrast, benthic organisms are being continually smothered by tailings and even after mine closure they may continue to suffer because of toxic concentrations of copper in bottom and interstitial waters. Re-establishment of a bottom community may therefore be slow and limited.

The bathymetry and water quality of Empress Augusta Bay have been mapped from the results of a single survey.

Water quality in the bay has not deteriorated as a result of tailings disposal, although a small water mass was defined in which solar heating (32 degrees C) of suspended particulates was apparent. Plumes from river discharges to the bay seem best defined from salinity and temperature measurements.

Concentrations of suspended solids in near bottom waters show a general movement of sediment northward from the existing delta.

Results of a single traverse across the sediment plume adjacent to the delta showed significantly higher (degrees C>0.05) sediment concentrations in surface waters, compared with layers at five metres depth and near bottom.

Depth contours in the bay show a relatively steep increase in depth (0 - 20 metres) close- to shore, followed by a gradual increase in depth (20 - 60 metres) 15 km offshore.

Using gill netting and haulseining, fish samples have been collected fron seven estuaries on Bougainville Island, four on the west coast and three on the east coast. One of the west coast estuaries is subjected to excessive sedimentation resulting from marine disposal of tailings wastes from the Bougainville Copper Mine. Samples were collected quarterly in 1975/76 and half-yearly in 1977.

Assuming discrete estuarine communities, statistical comparisons among sites were conducted for species diversity (Shannon's formula), species richness, species evenness and biomass. Sites were not significantly different with respect to the measured attributes (P <.05).

The east and west coast assemblages were compared by plotting mean levels of the various indices as a time-series. Weak seasonal fluctuations are apparent which are not significant (P <.05). The slopes of regression lines fitted to these cyclic trends are indistinguishable from zero for all indices and east and west coast regression coefficients are not significantly different from each other (P <.05).

These patterns show that no reduction in diversity is apparent in the west coast population as a result of tailings disposal, when compared to the east coast assemblage.

Suspended solid concentrations were measured in sea water coincident with netting periods during 1976 and 1977.

Correlation coefficients measuring the degree of association between suspended solid concentration and diversity were not significant (P <.05).

It is concluded that the community is tolerant to high suspended solid concentrations as a result of natural estuarine turbidity and salinity stress.

Concentrations of trace elements (Cu, Pb, Zn, Cd, Hg and As) have been measured in muscle tissues and organs of six species of marine fish from 8 sites on Bougainville Island; 5 on the west coast, where mine tailings are discharged and 3 reference sites on the east coast.

Recorded levels of trace elements comply with Australian National Health and Medical Research Council Standards for edible seafoods.

Comparisons of trace element concentrations between coasts were significant in 45% of cases. These were evenly divided into those which showed east coast levels greater than west coast levels and vice versa.

Trends emerged showing west coast concentrations greater than those on the east coast for Pb in muscle tissue (3 cases) and Cu in gills (3 cases). East coast levels exceeded west coast levels for Cd in muscle (2 cases), Hg in muscle (5 cases), and Pb in gills (3 cases). The remaining results including those for liver, kidney and reproductive organs, showed no firm pattern between coasts.

The relationship between weight and metal assay was investigated and corrections made where appropriate. Differences in weight did not significantly influence the outcome of comparisons between coasts.

It is concluded from these results that there is no evidence to indicate increased levels of trace elements in fish tissues and organs from the west coast resulting from tailings disposal.

A preliminary benthic survey of Empress Augusta Bay was conducted in 1979 to assess the effects of tailings deposition on bottom dwelling communities. Benthic organisms continued to exist in tailings sediments at that time but a 40-50% reduction in the numbers of species was recorded. This was accompanied by a 60-70% loss in mean benthic standing crop. This is not as severe as it may seem since benthic biomass over much of the bay was less-than-or-equal-to 5.0g/m2. Total numbers of species ranged from 6 species/0.lm2 in what are thought to be natural areas to 3 species/0.1m2 in tailings areas. The natural background values of both species counts and biomass are extremely low when compared with recorded levels in the literature.

The most difficult part of the survey was distinguishing tailings from natural sediments and it is recommended that the survey be extended to areas beyond Empress Augusta Bay to provide more reliable background information about benthos.

The influence of benthos on fish populations is discussed but no firm conclusions can be drawn from the current information.

Literature dealing with the toxicity of copper in the aquatic environment has been reviewed to assist with environmental research associated with tailings disposal. It is concluded that copper concentrations in sea water adjacent to the delta and within Empress Augusta Bay (> 5 ppb) will not be directly toxic to, or induce serious sub lethal effects in aquaticorganisms. This conclusion is based on evidence for the removal of copper from solution in sea water, together with the scavenging and binding capacities of hydrous oxides of Fe and Mn. High pH, adequate disolved oxygen, constant high temperature and the complexing capacity of sea water also reduces toxicity.

However, there is evidence to suggest that levels of copper in interstitial waters of submarine tailings deposits (>166 ppm) will be toxic to more sensitive benthic organisms resulting in impaired recolonization of tailings in the longer term by bottom dwelling animals.

Concentrations of dissolved copper in the Jaba River at end of mining (>1.0 mgl-1) are also expected to be lethal to a variety of aquatic organisms and some form of control will almost certainly be required to promote biological recovery of the stream.

Using gill netting and haulseining, fish samples have been collected fron seven estuaries on Bougainville Island; four on the west coast and three on the east coast. One of the west coast estuaries is subjected to excessive sedimentation resulting from marine disposal of tailings wastes from the Bougainville Copper Mine. Samples were collected half-yearly during 1977, 1978 and 1979. Water samples were taken concurrent with netting periods and analysed for suspended solid content.

Indices of species diversity, species richness, evenness and biomass were statistically compared among sites and among sampling times. Results show that these indices are not depressed at the tailings disposal site relative to reference sites. Significant differences among sampling times occurred (p < 0.05) but this did not reflect seasonality. In general, correlation coefficients measuring the degree of association between suspended solid concentration and the various indices were not significant (p > 0.05). The range of diversity values recorded (H = 0.7 to 2.0) compares favourably with figures quoted in the literature.

The east and west coast assemblages were also compared using time-series analysis. The regression coefficients of fitted trend lines are indistinguishable from zero indicating that the populations on both coasts have remained stable during the period.

Cluster analysis of sites x species complemented analysis of diversity. Sites are similar in species composition and site groupings did not separate according to areas of tailings disposal or distinguish between coasts.

It is concluded that with respect to fish species, no environmental discontinuities are emerging as a result of tailings disposal.

In 1981, BCL. reviewed its method of river and marine tailings disposal. A flexible long-term strategy was recommended involving lease boundary extension, dredging (with regrind of flotation feed to assist river transport) or a pipeline to the coast. No selection of a particular method was made; however all options involve marine tailings disposal to some extent.

To assist with choices among options, this report presents marine impacts associated with the current method of tailings disposal and identifies aspects of potential concern associated with the alternative options.

Loss of fish resulting from isolation of the Pangara River system from the sea, is the basis of a claim for compensation filed in September, 1975 by local villagers.

The Pangara River system, (P.R.S.), comprising the Oreil Nunopa and Pangara Rivers, is a tributary of the Jaba River system. As a result of tailings disposal, the P.R.S. has become isolated from the marine ecosytem due to high concentrations of suspended solids in the Jaba River.

A study was initiated to compare the species composition of the P.R.S. with that of the Mariropa River system, (M.R.S.). Situated to the north of the Jaba River, the Mariropa River is a natural river unaffected by tailings.

Eleven sampling sites both riverine and estuarine were visited during the period July - October, 1975. A total of 27 riverine species of fish were captured, 24 being recorded from the M.R.S. and 14 from the P.R.S. Sixty-three percent (63%) of the fish fauna of the natural river are estuarine. Sixty-seven percent (67%) of the above are important food fish or estuarine origin.

Ten (10) estuarine species, important as food fish, have been excluded from the P.R.S. as a result of isolation. However, an extremely important fresh water food fish (Tilapia mossambica) has been introduce to the P.R.S. Its rapid growth rate and rate of reproduction tend to diminish the effects of isolation in terms of fresh fish production. However Tilapia are not present in the M.R.S.

Twelve (12) fresh water species remain in the Pangara River. Six (6) of these are food fish with Tilapia being of major importance.

There are two important food species still present in the P.R.S. which are estuarine in origin. These are the Mangrove Jack (Lutjanus argentimaculatus) and the Eel (Anguilla marmorata) and have been included in calculations for compensation.

In the M.R.S. the ten (10) estuarine species not present in the P.R.S. contributed 39% of the edible bromass captured. It is assumed that, had these species been present in the P.R.S. under natural conditions, then their contribution to edible biomass would have been the same.

Therefore, production in the P.R.S. currently represents 60% of what it would have been prior to mining operations.

It is suggested that compensation be paid for loss of the 40% fraction.

An expression for compensation has been derived below.

• C = 0.235 x 1.07 x 0.6 x [(l.67 (A x P x 1/3)) - (A x P x l/3)] K/year.
• C = Compensation
• 0.235 = a cost factor of 23.5 c/tin of fish
• 1.07 = a correction factor to convert recoverable fish weight to number of tins of fish.
• 0.6 = the recoverable fraction of fresh fish weight allowing for skeleton, skin etc. easteage.
• 1.67 = a correction factor for the estuarine contribution to production.
• A = area in Hectares (Ha) of the stream in question.
• P = The maximum standing crop possible based on other tropical ecosystems.
• 1/3 = a factor to calculate maximum sustainable yield from standing crop estimations.

Bougainville Copper Ltd. has been discharging mine tailings into Empress Augusta Bay on the west coast of Bougainville Island for the past 12 years (1972-1983). Macrobenthic surveys have been conducted on both the east and west coasts of Bougainville Island to quantify the effects of marine tailings disposal on bottom dwelling communities. Surveys were conducted in Empress Augusta Bay in 1979 and 1981 and in Rorovana Bay on the east coast in 1982.

The east and west coasts are similar with respect to bottom substrate and benthic species compositon; polychaetes and crustaceans are the major taxa present. Species richness and benthic standing crop have been significantly reduced in areas of tailings deposition. By 1981, after 9 years of deposition, the area of biological influence of tailings extended over 150 km2 of the bay floor. Detrimental biological effects are related to the chemistry of copper in tailings sediments and smothering associated with tailings deposition; the texture of tailings sediment does not appear to adversely affect benthos.

The important role of benthic communities as a source of food for fish is discussed. Benthic standing crop in reference areas fo the east coast ranges from 3 to 4 g/m2. This is low by world standards but not unexpected in view of the fine silts and fine sands which compise the bottom substrates. It appears that similar biomass existed in Empress Augusta Bay in pre-mining years. Benthic productivity in Empress Augusta Bay also seems to be naturally higher than adjacent coastal areas outside the Bay. This establishes the importance of benthos in Empress Augusta Bay in the support of west coast fish populations.

It is possible that continued tailings disposal, with associated loss of benthos could adversely influence fish populations; particularly if a pipeline disposal option is implemented.

To rapidly monitor the ecological effects of increasing areas of tailings deposition, the development of predictive equations was attempted for estimation of biological characteristics based on environmental factors. Concentrations of total copper in sediment and the depth of water at each sampling site have limited value in this regard. It would appear that bottom communities are responding to other abiotic factors which were not measured; for example the depth or thickness of the overlying tailings layer.

It is recommended that core sampling be undertaken to estimate the depth of tailings at various distances offshore in order to gain a better understanding of the cause and effect relationships between tailings deposition and loss of bottom dwelling organisms.

A. EXISTING CONDITIONS

1. The Empress Augusta Bay shoreline is subjected to a very mild wave climate. Short period waves (sea) are less than 0.5 metres high for 75% of the time. They are unlikely to exceed a significant wave height of 1.5 metres. Swell waves are generated in the South Pacific Ocean and Tasman Sea. The Bay is partially protected from Swell by Motupena pt. At the shoreline swell wave heights are less than 0.5 metres for 90% of the time.
2. The highest significant wave heights for the most severe storm possible in the area is 2.5 metres. This would occur on the northern most beaches. In the lee of Motupena Pt. highest waves are restricted to 1 metre.
3. Only fringe effects of cyclones are felt at Empress Augusta Bay. Waves produced by cyclones are significantly smaller than swell waves produced by extreme storms from the South Pacific Ocean and Tasman Sea.
4. Currents in the bay south of the Jaba River are consistently low and usually less than 10 cm/sec. Currents north of the Jaba River are higher and average about 15 cm/sec. Overall currents are too small to initiate or sustain the movement of natural beach sands which have sizes 0.25 <D50 <0.5 mm.
5. Due to the mild wave climate annual sediment transport rates along the shoreline are low except in the vicinity of the Jaba delta. Rates are of the order of 10,000 m3 /year. At the Jaba delta the sediment transport rates are about 3 times greater.
6. The ambient wave climate tends to cause beach growth along all the shoreline from the Hupai River to the Torokina River. The material for beach growth is supplied by rivers discharging into Empress Augusta Bay. Prior to tailings discharge down the Jaba river, the river only had a small delta because the rate of sediment supply from the river was comparable to the longshore sediment transport by waves.
7. The beach growth appears to have occurred over the recent Holocene period (last 6000 years) whilst water levels have remained nearly constant. The shoreline at Motupena Pt. and north of the Jaba has prograded some kilometres over this period.
8. Net sediment transport along the Empress Augusta Bay shoreline is northward from about the Hupai River to the southern tail of the Jaba tailings delta. It is also northward from the western extreme of the delta to the northern end of the Bay.
9. Net sediment transport is southward along the southern face of the Jaba tailings delta and south of the Hupai River.
10. There are localised effects of the existing delta which can cause erosion just to the north and the south of the delta. This is due to the blocking effect of the delta on waves and sediment transport.
11. Major Storms do occur and cause erosion along nearly all the shoreline as evidenced by an erosion scarp behind the existing shoreline. A single storm of approximately 5 days duration can move as much sediment as is moved over 4 to 6 months of ambient wave conditions.
12. Natural beach slopes are steep (1:3 to 1:6) because of a mild wave climate combined with a medium sized beach sand. Tailings delta beach slopes are much flatter because the material is fine sand to silty sand.
13. Sea waves transport sediment in both northerly and southerly directions, depending on the sea direction relative to the shoreline.
14. Swell waves only transport sediment from south to north.
15. For ambient yearly conditions sea waves results in about 50% less beach sand movement than swell waves.
16. There is little mixing of tailings deposited on the delta with the natural beaches. Instead there is a slow encroachment of the delta both north and south.
17. All quoted sediment trasport rates are only semi quantitative since no satisfactory field data exists for verification purposes. However the relative rates of transport between shoreline locations are appropriate.
18. Seismic events have in the past and will continue to cause a slumping of the existing tailings delta. The supply of sediment (tailings) down the Jaba tends to obliterate the effects of seismic slumping within a few months of the event.

B. CONTINUED TAILINGS DISPOSAL VIA THE JABA

1. Sediment transport rates will increase by about 50% on the delta and in the northern part of the bay at year 2025 compared to 1981 conditions. This results because the delta will be 2 to 3 kilometres seaward of its 1981 location by the year 2025. Wave refraction and exposure to swell is increased.
2. The delta will continue to grow, albeit at a slower rate after the end of mining due to the continued degradation of the river bed. This will occur for several hundred years.
3. Local erosion areas will occur in the short term on the beach just north and just south of the delta as it continues to grow. The erosion areas will subsequently be filled by the growth of the delta.
4. There will still be little mixing between the tailings and natural beach sediments.
5. Beach growth to the north of the delta will continue the rate being dependent on the supply of sediment from the northern rivers.
6. On a geological time scale - thousands of years - and provided there are no extreme seismic events or sea level changes, the delta will erode with the material being redistributed along the Bay shoreline. A shelf will remain as a submerged delta.
7. The delta will undergo localised changes in plan form as the level of the sediments build up causing the river to break through to the sea at new locations from time to time.

C. MARINE PIPELINE TAILINGS DISPOSAL

1. The range of marine disposal methods investigated can all be designed so as to prevent adverse geomorphological changes to the Bay shoreline. Adverse changes are taken as being erosion of natural beaches or a significant change in beach character due to the spread of tailings. This conclusison refers to time scales of up to several hundred years.
2. All coastal process sediment transport rates are orders of magnitude slower than the rate of sediment supply down the Jaba even after tailings disposal into the Jaba stops. The sediment supply comes from the degradation of tailings that will be deposited on the river bed up to 1989. Even if mining ceased immediately, the delta would still continue to grow for hundreds of years.

Submerged Offshore Disposal

1. A submerged offshore disposal system which maintains the crest of the spoil level at about -10meters will have negligible effects on sea waves. Swell waves will be transformed so that, outside the company lease boundary, beaches will accrete at a faster rate than occurred in 1981.
2. The submerged disposal area causes wave energy to be focussed on the Jaba river delta and increases sediment transport along the shoreline compared to 1981 conditions. Careful design and management procedures will need to be implemented to ensure that the wave energy focussing is confined to the Jaba delta. Otherwise it could cause severe erosion on natural beach areas.
3. Tailings placed by submarine disposal will not be transported to the beaches on any timescale unless there are major sea level changes.
4. Submarine disposal will have negligible effect on currents within the Bay.

Foreshore Extension Disposal

1. Tailings disposal by extending the shoreline seawards is in essence equivalent to the formation of an artificial delta. Its effects are similar to the effects of continued tailings disposal down the Jaba system.
2. Local erosion on a short term seasonal storm basis can occur north of the Jaba delta. In the long term (years) the area will accrete.
3. Sediment transport rates along the seaward face of a forshore extension are limited to about 50,000 m3/annum. This is compared to a supply of about 40,000,000 m3/annum from the pipeline.
4. At the completion of mining the seaward face of the foreshore extension will erode at an average rate of about 0.5 to 1 metre per year. The eroded material will form a Spit at the northern end of the foreshore extension.
5. All erosion and redistribution of tailings will be limited down to a depth of about 10 metres. Below that depth the waves will have insufficient energy to move noticeable amounts of sediment.
6. Eventually, on a geological time scale of thousands of years, some of the tailings will be redistributed along the Bay shoreline. This will not start to occur for several hundred years.
7. The foreshore extension will change current patterns since it is a definite barrier. However, since currents are small in the south of the bay the consequences of reduced currents are not obvious. They relate to marine biology rather than to sediment processes.
8. Seismic effects on the foreshore extension are likely to be superficial such as slumping and a surface level reduction of the disposal area. Effects on geomorphological processes would be negligible. Engineering pipeline operations need to be designed to allow for seismic activity.

D. THE PRESENT DAY DATA BASE

1. The existing data base is very incomplete. However, because the area is subjected to a mild wave climate and weak currents, reasonable estimates of coastal processes and the geomorphological history have been possible.
2. Bathymetric data is based on sparse 1883 British Admiralty surveys.
3. Wind data is incomplete and there is no wave data. These had to be hindcast for the area from meteorological charts.
4. Current data is available and is sufficient for foreshore extension disposal systems. Further data would be required for submarine disposal methods.
5. Some beach survey data exists. This needs to be consolidated and continued at regular intervals.
6. There is no data available for quantifying sediment transport rates on engineering time scales.

E. FUTURE MONITORING REQUIREMENTS

1. The furture monitoring requirements depend to some extent on the adopted method of tailings disposal.
2. For all methods of tailings disposal the following monitoring is required to quantify sediment transport rates and to design the disposal methods such that they do not have adverse affects on beaches.
   1. Complete hydrographic survey of Empress Augusta Bay.
   2. Measurement of sediment transport along the beach using a groyne as a sediment trap.
   3. A year of wave measurement.
3. For submarine disposal the following monitoring is also required.
   1. Measurements of currents along the pipeline route over a year.
   2. Wind recordings over a year.
   3. Measurement of marine growth on a floating pipeline section.
4. Physical model studies will be required during the design phase of any pipeline tailings disposal method.

A. DATA

1. A complete hydrographic survey coupled wit hpresent day aerial photography is essential before detail design of tailings disposal is commenced.
2. Existing beach profile data obtained by Bougainville Copper Limited needs to be corrected and reduced to common datums. Additional survey may be required. Beach profile surveys should continue.
3. Data is required to quantify sediment transport rates. It is recornmended that at least 1 groyne be constructed to trap longshore sediment transport, and that the rate of sand collection be monitored by regular survey
4. It is recommended that waves be measured including wave direction offshore from the sediment trap groyne. It is essential that a continuous return of good data is obtained for correlation with the measured rates of sediment collected at the groyne.
5. Measurement of waves offshore in deep water using a Datawell Waverider Buoy or equally reliable instrumentation is recommened to obtain confirmation of the hindcast wave climate. Data needs to be recorded for a minimum of one year.

B. WAVES AND CURRENTS

1. Short period waves (sea) are less than 0.5 metres high for 75% of the time. They are unlikely to exceed a significant wave height of 1.5 metres. The predominant sea direction is from the south west.
2. Swell waves are generated in the South Pacific Ocean and Tasman Sea. Their direction offshore from Empress Augusta Bay are from the south to the south south-east. The average swell height is about 1.25 metres with a period of 6 seconds.
3. Extreme storm conditions may produce swell with heights up to 4.5 metres and periods up to 13 seconds seaward of Empress Augusta Bay.
4. After wave refraction and diffraction to the Empress Augusta shoreline, the average swell waves are reduced to about 10% of their offshore size.
5. Averaged over the year there is more sea wave energy reaching the Bay shoreline than swell wave energy.
6. Swell wave height at the shoreline increases moving from south to north.
7. Only fringe effects of cyclones are felt at Empress Augusta Bay. Waves produced by cyclones are significantly smaller than swell waves produced by extreme storms from the South Pacific Ocean and Tasman Sea.
8. Average swell wave heights at the shoreline increase from less than 0.04 metres in Gazelle Harbour to about 0.3 metres at the Torikima River.
9. Currents in theBay south of the Jaba River are consistently low and usually less than 10 cm/sec. Currents north of the Jaba River are higher and average about 15 cm/sec. Overall currents are too small to initiate or sustain the movement of natural beach sands which have sizes 0.25 < D50 < 0.5 mm.

C. SHORELINE AS OF 1981

1. Net sediment transport along the Empress Augusta Bay shoreline is northward from about the Hupai River to the southern tail of the Jaba tailings delta. It is again northward from the western extreme of the delta to about the Reini River.
2. Net sediment transport is southward along the southern face of the Jaba tailings delta, and south of the Torikina River to about the Reini River and south of the Hupai River.
3. Sediment transport rates along the shoreline are low except in the vicinity of the Jaba delta. Rates are of the order of 30,000 m3/year.
4. The ambient wave climate tends to cause beach growth along all the shoreline from the Hupai River to the Torikina River. The material from beach growth is supplied by rivers discharging into Empress Augusta Bay.
5. There are localised effects of the existing delta which cause erosion first to the north and the south of the delta. This is due to the blocking effect of the delta on waves and sediment transport.
6. Continuation of existing disposal methods down the river would result in the erosion areas moving further south and north, with the presently eroding areas accreting due to the extension of the tailings delta tails.
7. Major storms do occur and cause extensive erosion along nearly all the shoreline as evidenced by an erosion scarp many metres behind the existing shoreline.
8. Currents are small and have a negligible effect on beach process of the naturally occurring beaches which have medium grain size sand.
9. Natural beach slopes are steep (1:3 to 1:6) because of a mild wave climate combined with a medium sized beach sand. Tailings delta beach slopes are much flatter because the material is fine sand to silty sand.
10. Sea waves transport sediment in both northerly and southerly directions, depending on the sea direction relative to the shoreline. Since the water in the Bay is deep up to the shoreline (the delta excepted) sea waves are not refracted.
11. Swell waves only transport sediment from south to north.
12. For ambient yearly conditions sea waves result in considerably more beach sand movement than swell waves.
13. An extreme storm has the potential to move orders of magnitude more sand than ambient conditions. These storms do occur but are probably infrequent.
14. The conceptual model predicts accretion of the shoreline between the Jaba entrance and the Torikina River of about 50,000 to 100,000 m3 per year. This is consistent with the extent of beach ridge formation that is evident and would have formed over the holocene period of the last 6,000 years.
15. The beach building sediments would be derived mainly from the Jaba - Pongara River (Pre-mining) and the Torikina River.
16. A conceptual model has been derived for sediment transport which satisfactorily describes existing shoreline features.
17. All quoted sediment transport rates are only semi-quantitative since no satisfactory field data exists for verification purposes. However the relative rates of transport between shoreline locations are believed to be correct.

D. PIPELINE DISPOSAL ALTERNATIVES

Submerged Offshore Disposal

1. A submerged offshore disposal system which maintains the crest of the spoil level of -10 metres will have a negligible effect on waves and therefore on shoreline processes.
2. A suitably large sea bed area is available to accommodate all the tailings up to a mining life of year 2025.
3. Beach processes along the shoreline will continue at natural levels, as dictated by sand supply from the rivers and the wave climate. Degradation of tailings from the Jaba River will result in increased sediment supply in the short term. This will apply to all forms of pipeline disoosal into the Bay.
4. Beach processes are unaffectec\d by the disposal of tailings from 1989 to 2025.
5. If mining is completed at any projected year - 2003, 2015 or 2025 - as soon as mining ceases where will be no noticeable redistribution of tailings within the Bay. All beach processes remain the same as occurred during mining.
6. The effect on currents within the Bay is expected to be small.

Finger Disposal

1. Disposal of tailings on a finger with a surface elevation of +10 metres has only a small effect on the beaches outside the lease area during the life of the mine.
2. Local erosion will occur just to the north and south of the finger if the finger is oriented east-west.
3. If the finger is oriented in a a general south-west direction, erosion to the north can be eliminated but there will still be erosion to the south. The converse occurs for a north westerly finger orientation.
4. A south-westerly finger orientation will result in about 100,000 m3/year or more of sediment being deposited near the Jaba River entrance. This, coupled with deposition out of the river by natural degradation, will result in some worsening of flooding upstream.
5. Since 40,000,000 m3 per year of tailings will be discharged compared to a capacity of sediment transport away from the finger of about 350,000 m3 year, the finger will effectively not be influenced by waves over the mine life.
6. After the completion of mining the tailings finger will change steadily and noticeably: - it will erode from the seaward face at about 4 metres per year; - a spit will form at the northern seaward corner of the finger; - by the year 2050 the finger will be about 100 metres shorter and the spit about 200 metres long.
7. All erosion and redistribution of tailings will be limited down to a depth of about -10 metres. Below that depth the waves will have insufficient energy to move noticeable amounts of sediment.
8. Ultimately, in about 1,500 years assuming no catastrophic geological activity, the finger will be completely eroded away and the sediments distributed on the Bay floor and on the shoreline. However, a shelf will remain at about RL -10 m similar in form to the submerged offshore dump.
9. The shoreline will be in a continual state of change due to time changing shape of the finger. This will result in short term erosion at locations along the beach.
10. The finger will change current patterns since it is a definite barrier. However, since currents are small in the south of the Bay the consequences of reduced currents are not obvious. They relate to marine biology rather than to sediment processes.

Foreshore Extension Disposal

1. The same conclusions apply as for finger disposal except that the rates of sediment transport by waves are reduced marginally.
2. Sedimentation at the entrance to the Jaba River would be more rapid than for the finger disposal method.

The Porgera Joint Venture (PJV) contracted CSIRO to select and manage a team of specialists to review effects of the Porgera gold mine on the riverine environment downstream of Porgera, Papua New Guinea.

As five years had passed since operations commenced, the PJV felt it was appropriate to conduct an independent review in accord with its environmental policy. The policy requires an active program of environmental auditing and independent reviews to identify and evaluate potential risks and to ensure environmental performance meets company policies and regulatory requirements. During the past five years community awareness of environmental protection has also increased world-wide, and this was an added incentive for the review. In addition, the PJV sought specific recommendations on how it could improve environmental performance at Porgera.

The report presented here introduces the independent study team and describes the approach used during the study. The Porgera gold mining operations are outlined and aspects of the processing relevant to the mine's riverine impacts are reviewed. The team's assessment of the riverine environment, first in the upper river system and then in the flood plain and Lake Murray area, and the potential effects of mining operations on them, are integrated into two chapters (4 & 5) to give an overall perspective. Chapter 6 discusses the practical aspects of monitoring, including techniques for sampling, analysis, statistics and reporting, with particular reference to the PJV's Environmental Management and Monitoring Program (EMMP). An important component of the review was the health survey of villagers who live along the river system. The survey findings are reported in Chapter 3, together with a review of the potential for mine-derived riverine impacts on the human population of the regions.

The following terms of reference for the review were developed by the PJV and CSIRO:

• identify and review the riverine impacts associated with the operation of the Porgera mine;
• assess the accuracy of riverine impact predictions;
• assess the quality and scientific rigour of the data generated from the present monitoring and research programs;
• determine whether the monitoring and research programs are adequate for quantifying riverine effects and are able to withstand scientific scrutiny;
• identify any deficiencies in the present monitoring and research programs and recommend any changes necessary to improve the assessment of existing and future effects;
• review the operation's compliance with environmental regulations;
• provide an overview report integrating the findings of the independent review team.

In effect, the terms of reference were formulated to assist the PJV in determining whether:

• all the riverine effects from the mine had been identified;
• the Environmental Management and Monitoring Program (EMMP) was adequate to identify effects;
• the data quality (QAIQC) was sufficient and reliable;
• the Environmental Plan and subsequent predictions were accurate;
• the current EMMP needed any improvement to detect effects on the environment.

To reiterate the report's recommendations as gathered in this Executive Summary, the review team wants to see the PJV:

1. aim for a more detailed understanding of the riverine system and how it functions, so as to better identify potential risks and strategies needed to reduce them;
2. provide the PJV Environment Dept with additional staff to carry out the more rigorous and refocused EMMP we are advocating;
3. employ a better-designed sampling program and select other 'control' catchments nearby, unaffected by upstream land uses, for comparison with the Strickland river system;
4. carefully assess: (i) the effect of increased production on residence times in the neutralisation circuit; (ii) the probability of accidental discharges of incompletely-treated materials; and (iii) the response mechanisms required to manage such eventualities;
5. develop a comprehensive sediment budget for the river system, and initiate a dump monitoring program including the analysis of particle size distributions in the river bed, and more rigorous monitoring of suspended sediment;
6. collect data on benthic invertebrates, the composition of key aquatic-based food chains leading to humans, the importance of side channels, and locally-derived inputs;
7. give priority to 5G2 as a hydrology master station for compliance purposes;
8. undertake a program of integrative investigations in the Hood plain and Lake Murray region, using a risk assessment approach;
9. review the location of hydrological stations in the Strickland/Herbert River region, to improve knowledge of inflows and outflows to the Lake;
10. use a program of core-sampling to estimate inputs of mine-derived sediment to the lower Strickland flood plain and their fate in that region;
11. reconsider the assumptions in the Environmental Plan about the structure of the biological food chain in the Lake Murray region;
12. monitor (and manage) for impacts.

One of the largest open-cut copper and gold mines in the world commenced operation in May 1984 in the Star Mountains of Papua New Guinea. Waste rock and tailings are currently dumped into the Ok Tedi, a tributary of the Fly River. Mine development has been surrounded by controversy concerning the potential environmental impacts of this major development. This paper outlines the environment in which the mine is situated; details traditional resource use in the area; reviews the history of mine development and evaluates the current situation with regard to waste disposal. Details of the current concerns expressed both within and outside the country about the long-term impacts of this project are also presented. As such this paper serves as a background to the other papers in this volume, which examine issues such as tailings toxicity; heavy metal levels in fish; the complexing capacity of waters in the drainage basin; and the limnology of lakes associated with the Fly River flood plain.

Planners of large resource developments in tropical humid countries, resulting in river basin modifications, have an advantage over their colleages in developed countries where development took place some time ago. The worldwide environmental concern stimulates the governments in developing countries to approach new projects cautiously and to request environmental impact studies prior to the approval of such developments. A developing country such as Papua New Guinea, where most of the river basins have not yet been largely modified, has the opportunity to approach resource development with the highest level of management principles and in this way to prevent the major mistakes and disturbances of the environment which have been experienced by a number of other countries. Problems relating to three development projects in Papua New Guinea are discussed.

Two major development projects in Papua New Guinea, while still in the planning stage, are being approached with full awareness of their possible impact on the environment. A copper-mine high up in the catchment of a large river, the Fly, and a large hydroelectric dam on another sizeable river, the Purari, raise a number of questions. The extremely high rainfall in the area of the proposed copper-mine precludes the use of standard methods of tailings disposal. Thus if the tailings were stored behind a darn, it would frequently overflow; alternatively, they could be discharged directly into a stream. Both alternatives would have a negative environmental impact. Downstream dilution by tributaries would, however, be an important mitigating factor of tailing disposal. At present, frequent, naturally occuring landslides in the upper catchment result in a very high input of sediments, with a disastrous impact on the aquatic life.

The major problem connected with the hydroelectric scheme at present appears to be the correct evaluation of its possible impact on the productivity of the delta and adjacent sea. Investigations indicate that the downstream biota survive well on dissolved fractions of nitrogen and phosphorus whose concentrations would not be affected to any great extent by darnming the river. Bacterial production shows considerable increase in the brackish water of the delta as compared with fresh water, and it is probably of significance as food for prawn and fish larvae and juveniles. Sediment retention by the dam might result in some reduction in the deltaic and sea productivity, but it is assumed that input of organic matter and nutrients from the extensive mangroves, together with the continuing release of nutrients from bottom sediments, would maintain the estuarine, and possibly also the coastal, sea-water productivity at the present level. Fish migrations could be affected by the scheme, though, taken as a whole, it would appear likely to have the least darnaging environmental impact of all similar, large, existing schemes situated in the tropics or subtropics.

In both projects, the extremely high rainfall results in small human populations in the affected areas, and this would mean a relatively small social impact.

A quantitative survey of the macrobenthos in the south-west lagoon of New Caledonia was carried out at 35 stations, sampled both with a grab and by diving. The stations were classified by multivariate analysis on the basis of their floral and faunal composition and three major communities, corresponding to muddy bottoms, grey sand bottoms and white sand bottoms, were identifled. At the same time, grain-size analysis performed on sediment samples at each station enabled us to identify the most discriminating grain-size parameters for each type of bottom. Classification of stations with respect to the mud fraction and the very fine + fine sand fraction reproduced the groups identified on the basis of purely taxonomic criteria. Application of these results to the available sedimentological data allowed the main benthic communities in the investigation area to be mapped.

66 sediment samples were taken in the Great Northern Lagoon of New Caledonia with a Neyrpic grab. Samples stations were selected, either according to two transects in the lagoon - one lenghtwise, the other crosswise - or because they belonged to one of the various lagoon compartments. Textural and granulometric characteristics, terrigenous fraction, colour and skeletal composition were studied according to conventional sedimentological methods. A Principal Components Analysis is used to summarize the results. Six sedimentary environments have been so identified: passes, inner barrier reef zone, lagoonal plain, central depositional zones, coastal zone and coastal bays.

The south-western lagoon of New Caledonia covers an area of 5500 sq. km. composed largely of soft bottoms. As part of the biotopes of the New Caledonian lagoons that is being carried out, a study of the distribution of sediments and communities has also been undertaken. Sampling has been done with a 2 nautical miles grid, using a dredge for the benthos and a grab for the sediments. Mapping of the muds and a multivariate analysis have made it possible to define the sedimentological structure of these bottoms. A qualitative inventory of the benthic macrofauna communities has been drawn up in respect of the main zoological groups. Mud distribution is governed by the morphology of the shore, bathymetry and hydrodynamics. Sediments are divided according to two gradients, one relating to grain size, the other to siltation, which reflect a two-fold influence, from the land and from the reef. One of the main factors affecting the distrubution of benthic communities is the mud content of the sediment, which influences the wealth of species and the composition of the fauna. For herbivorous species however, this relationship is indirect, for their distribution is primarily associated with the presence of vegetative cover, which itself is dependent on the nature and the texture of the sediment. Examples of species distribution concerning the Strombidae and Cerithiidae molluscs are described.

Chesterfield lagoon which is located between 19 degrees 00' and 20 degrees 00' latitude south and 158 degrees 10' and 159 degrees 00' longitude east covers an area of about 3500 km3. 105 stations regularly distributed on a 3 nautical miles grid were sampled using a Smith-McIntyre grab. Textural and granulometric characteristics, carbonate content of fine fraction and colour were studied according to conventional sedimentological methods. The northern and the extreme southern parts of the lagoon are relatively sheltered from trade winds by barrier reefs. In these parts fine sedimentation is predominant (moderate to very high mud facies) and textural sediment types range from very fine sand to muddy sand. Backreef sediments are characterized by a bimodal distribution with dominance of gravelly muddy sand. Other parts of the lagoon are much exposed to south east trade winds. Their pecentage of mud in the sediments is generally low (<10 %) and the textural sediment types are chiefly gravelly sand. Carbonate contents of the fine fraction are always greater than 87% with an average value of 93.7% (high carbonate facies). Sediment colours are always white or light yellow.

Uvea atoll is situated in the Eastern part of New Caledonia. The lagoon has a maximum depth of about 40m, and covers an area of 850 km2. In the course of the first general study of the marine resources of Uvea lagoon, scuba divers collected sediment samples from 62 evenly distributed stations. The main sedimentological characteristic of the Uvea lagoon is the paucity of soft substrata (mean thickness = 5.4cm). Sediments always present a light colour, a high carbonate content, and a low mud percentage. The general characteristics of the lagoon speak for homogenous and moderate hydrodynamic conditions, a sediment production of low volume but well balanced between fine and coarse particles, and low sediment displacement. However, the inner barrier reef bottoms and the coastal strip differ from the general conditions.

The opencast nickel mining of ultrabasic mountains in New-Caledonia provoked geomorphological and ecological consequences, especially during cyclonic rains. After a presentation of the mountains geology, of the seam conditions and past and recent ttgarnierite" ore exploitation, a classification of the different surface state is being tested from SPOT imagery.

The tropical perturbations (cyclone and multiannual drought) which condition the hydrological regime of New-Caledonia rivers and the different phases of opencast mining are run in connection with the suspended loads variations, measured in the Pouembout and Ouenghi catchments.

Otherwise, the analysis from the spatial land scanning photography remote sensed allows to precise fluvial and coastal geomorphological modifications (creation of the Thio winding, evolution of the Thio and Ouenghi deltas).

This study shows that evolution of the exploitation conditions leads to a decreasing number of pollution causes, and alluviation goes on.

Two algal communities on unconsolidated sand, dominated by two Caulerpa populations, were studied in the southwestern New Caledonian lagoon. Biomass, growth rates and production were measured at two stations over one year.

Biomass and growth rate of Halimeda were estimated monthly by counting the number of new and lost segments on tagged plants and by weighing them.

Production was assessed monthly by comparing two successive measurements. The average rates measured were 0.60 s f-1 d-1 (segment frond-1 day-1) for Halimeda incrassata and 0.15 s f-1 d-1 for H. discoidea. Production in terms of organic carbon amounted to 3.79 g m-2 y-1 for H. incrassata and 3.37 g m-2 y-1 for H. discoidea. The production of H. discoidea population is subject to seasonal variations.

Since 1876, more than 130 million tons of Nickel ore have been extracted and, consequantly, huge amounts of sterile have accumulated. Before 1950, the mining production level was low; from 1950 to 1975, the extraction was mechanized and the extraction level of ore was increasing and the production of sterile reached a higher level. These steriles were dumped into the nearest valleys and represented major nuisances to the environment. Since 1970, with the increasing interest in environmental studies, the mining society "Le Nickel (SLN)" tried to find a solution to place steriles, mainly laterites, in waste laterite dumps in order to prevent river and lagoon pollution. These new techniques are applied since 1975.

A bionomic mapping survey of the soft bottoms of the south-western lagoon of New Caledonia was carried out by dredging. From analysis of the sediments and the fauna and flora found in 489 dredgings, it was possible to define three main benthic communities. Echinodermata were found in 37.8% of the dredges: 22 species of Echinoidea, 30 Asteroidea species and 26 species of Holothu ro idea. Correlations existed between the presence of principal species, the mud content of the sediments and the bathymetry. Distribution maps are given for the following species. Laganum depressum, Maretia planulata, Gymnechinus epistichus, Brissopsis luzonica, Astropecten polyacanthus, Pentaceraster alveolatus, Echinaster luzonucus and Tamaria fusca. Some species have very particular ecological requirements, such as Brissopsis luzonica which is a mud dwelling; Gymnechinus epistichus and Maretia planulata live in sand but dislike mud. 0ther species such as Laganum depressum and Astropecten polyacanthus are very ubiquitous and their distribution seems to be unaffected by sediments or depth.

The aims and methods of a long running and large scale (23 400 km2) study of the soft bottoms of the lagoon of New Caledoma are presented.

Geomorphological and sedimentological characteristics of each lagoon of the main island and the Chesterfield atoll along with a description of principal communities in relation to substratum type with special reference to molluscs and echinoderms are given. Major results of quantitative studies and ichtyological sampling are reported.

The appendices list all taxonomists who have worked on New Caledonian material and the physical characteristics of dredging stations and location maps.

Three habitats, coral reefs, soft bottoms and mangroves were sampled monthly during 1989 in the St Vincent bay area. A total of 565 species of fish were collected and are distributed as follow 344 species on coral reefs, 233 species on soft bottoms and 140 species in the mangroves. The number of species per habitat showed no noticeable changes with time, however the species composition varied markedly from one month to the next in all three habitats. The overlap between the species composition of these habitats was maximum between soft bottoms and mangroves (Kulczynski's sImilarity index, 1K= 30,87%) and minimum between coral reefs and mangroves (1K= 21,61%). There were important monthly variations in the nature of these overlaps. The data indicate that species in common can be classified into three groups. The first group are sedentary species which may be found in different habitats. Examples are given by species of Holocentridae and Lutjanidae. The second group are species which may be found as juveniles in one habitat and as adults in another. This is the case of several species of Serranidae, Jutjanidae and Sphyraenidae. The third group are species which migrate between habitats for reproduction or for trophic reasons. This has been observed for Sillago spp., Pomadasys argenteus, Trichiurius lepturus, some Leiognathidae, Mullidae and Gerreidae.

A study was made to gauge possible impacts of tailings in three shore coral community areas in Looc, Bato, and Matab-ang which are located at varying distances from a copper mine tailing outfall at Ibo, Toledo City, Cebu. Physico-chemical parameters measured were salinity, temperature, dissolved oxygen, suspended solids, light, sediment load and concentration of trace metals in their sediment. The influx of tailings sediment may be the dominant pollution factor as evidenced by the high copper concentration in the sediments. This could have affected the various community characteristics of the areas studied. These aspects of the community are those of abundance and diversity. Live coral cover may have been reduced to only 8-10% in the proximal areas (to the tailings discharge point) of Bato and Looc as compared to a relatively fair coverage of around 40% at the farther Matab-ang station. Significant differences in diversity indices were found between the areas, with Matab-ang having an H'=2.51154+/- .19942, while Bato has H'=2.09925+/- .41396 and Looc only H'=1.61911 +/- .573724.

A preliminary report on the coral fish fauna and morphological notes on some corals (like Porites and Diploastrea) are presented.

The only environmentally safe clean-up option at this time is dredging the existing channel and placing the dredgate permanently deep underwater. There will then be no risk of tailings subsequently contaminating the coastline due to weathering or from being in shallow well-aerated water.

The only option in the Boac region for such safe placement deep underwater is to draw on the proven technology developed in the past 20 years for placement of mine tailings deep in the sea.

The final deposition area must be well below surface and shallow water fishery and coral zones, and without physical risk of re-suspension and upwelling to those resource use zones by strong currents. This is so offshore from the Boac River delta where tailings will deposit below 450 m depth. There is no physical mechanism, no upwelling currents, that can bring the material back to the surface fishery zones. Oxygen levels are low thus ensuring that the deposits will remain inert indefinitely.

The limited amount of material produced over a 10-day dredging operation will deposit at rates tolerated by seabed organisms. It is to be expected that there will be virtually no loss of biodiversity, since mud and sand bottom creatures can avoid or burrow-up through such slowly depositing material. The proponents have shown that tailings presently deposited off the Boac delta have recolonized the biodiversity sufficiently to support a local fishery. There can be no effect on the fisheries of Tablas Strait.

Deep placement of dredgate in the sea is allowed by the 1996 Protocol to the London Dumping Convention of the United Nations Environmental Programme.

It is urgent that the license to proceed be granted within the next few days due to the increasing environmental and safety risks arising from the approaching typhoon season.

This report reviews the present environmental impacts of tailings disposal, potential alternative tailings disposal methods, provides predictions of long-term impacts, and recommendations for amelioration, reclamation, enhancement and monitoring. The report is based on file information and a site visit by the authors in August 1981. The present mining situation is that the Tapian orebody, now being worked, has a lifetime at existing production rates and grades of only until late 1984. The reserves indicate that lower grade ore will be available from the Tapian pit until 1993. In order to maintain an economical operation, a combination of the San Antonio and the Tapian orebodies will be required. To provide a phased transition to the San Antonio orebody, the existing tailings pond and overburden must be removed and disposed in an environmentally acceptable manner. The present tailings disposal scheme is under governmental and popular (local) criticism.

Tailings are now being surface discharged in Calancan Bay from the end of a causeway constructed in 1975 and subsequently extended with coarse tailings. The discharge produces a turbid plume visible between Hakupan Island and nearly to Santa Cruz Point. The outstanding biological impact of this discharge has been stress on the coral reefs at the area. However, stress on coral reefs is not new to the area as there was documented evidence of damage by river silt and dynamite fishing in the area prior to tailings discharge. Cyanide fishing within the reef areas has also been reported. Coral reefs are conventionally regarded as the major supportive ecosystem of nearshore fisheries, and therefore have to be monitored closely.

Trace metal analyses to date by Marcopper (and their agents) have included the tailings effluent, seawater, marine sediments and tissue analyses of edible marine species sampled in and about Calancan Bay. While copper levels in oysters are apparently elevated, inconsistencies in sampling and inadequate analytical technique do not allow confirmation. A similar situation exists for lead in fish tissue. Problems with analyzing dissolved metals in seawater were evident. Difficulties in trace metal analyses exist in all local laboratories visited (Marcopper Assay, Marcopper Geochemical, MacPhar, and National Pollution Control Commission) due to facilities, equipment, and/or techniques for dissolved metals. The National Pollution Control Commission Laboratory was generally better prepared to do trace metal work but had equipment limitations.

Samples of mill effluent (liquid and solid fractions), marine sediment, seawater, tailings beach interstitial waters, mangrove leaves, oysters and fish were collected for metals analyses in August 1981. The dissolved metals in the fluid portion of the tailings were lower than the National Pollution Control Commission 1981 effluent regulations in all cases except molybdenum. This particular standard is more stringent than those in the United States or Canada. Dissolved metals in seawater were well within the natural variability of marine waters. Interstitial waters from a man-made tailings beach indicated dissolved metal concentrations similar to those within natural beaches. The dissolved manganese was high within this anoxic zone which is a well documented common occurrence in nature. Dissolved lead and cadmium levels were low, indicating no dissolution. Copper, molybdenum and zinc showed slight, but not alarmingly high dissolution levels.Public concerns include both health (metal poisoning diseases) and recovery-reclamation potential of disturbed areas. There is no evidence of metal poisoning in the area, given the metal levels in the tailings discharge and the discharge regime, it is extremely unlikely. However, continued monitoring of biological tissues is recommended to alleviate any public concern. Measures for recovery/reclamation such as coral recolonization, mangrove transplantation and aquaculture are discussed.

Long-term impact predictions of continuing the present mode of discharge are discussed along with alternative schemes. The alternative of a coastal impoundment for all tailings discharged appears unacceptable due to environmental, safety and social considerations. Deep discharge of the tailings is not feasible due to the tailings particle size distribution and the submarine slopes available to the north of Marinduque Island. If the coarse fraction can be feasibly separated, a long-term solution might be to consider deep discharge of the slimes and retention of the coarse fractions. The ultimate place for the coarse fraction should be the exhausted Tapian Pit. The least impacting alternative may be to continue the present surface discharge system until the Tapian pit is available for backfilling with the coarse tailings fraction. This avenue will require further investigation and refinement.Specific recommendations include:

1. Determine the feasibility of separating the coarse fraction of the tailings.
2. Determine the feasibility of a deep discharge for the slimes and the environmental implications of retaining the coarse fraction on land.
3. San Antonio dredging should be increased to a level consistent with economically viable interphasing of the Tapian and San Antonio pits.
4. If a deep discharge scheme is feasible for the slimes, then a revised and extended monitoring program should be implemented to provide a measure of impact prior to discharge relocation and after discharge starts.
5. Upgrading of analytical capabilities, should Marcopper continue the in-house environmental work, and retention of experienced environmental consultants as overseers.
6. Extension of reclamation and enhancement projects.
7. Formation of an Environmental Review Committee with government, local citizen, mine and consultant representatives.
8. Should deep discharge not be feasible, detailed engineering and environmental studies should be undertaken to ameliorate present impacts and develop definite ameliorative measures for the expected duration of the mine.

Lastly, detailed monitoring recommendations are presented together with Appendices of environmental background, analytical procedures and monitoring methods.

Bathymetric, geophysical and sediment sampling surveys were carried out off Rarotonga to gather data for the design of a sewerage outfall pipeline off Avarua Harbour; to assess the quality and quantity of channel fill sediments known to occur off Avarua, Avatiu and Ngatangiia Harbours; and to contribute to a separate sedimentological study of Ngatangiia Harbour and Muri Lagoon.

At Avarua the sediment floored channel widens from 40m at the harbour entrance to a maximum width of 200m at the 20m isobath 420m offshore. Seawards of this the channel narrows and the sides and floor steepen out to the 150m isobath occurring 730m from the entrance, where they again become more gentle. The channel floor at depths of less than 30m is smooth but two large coral reefs occur at between 30 and 40m depth.

At Avatiu the sediment floored channel widens from 60m at the harbour entrance to a maximum width of 170m at the 12m isobath 220m offshore. Seawards of this the channel narrows and the sides and floor steepen. Out to the 30m isobath occurring at 300m offshore the generally smooth channel floor is interrupted by numerous patch reefs up to 25m across and 2-5m in height.

The channel floor surface sediment at both Avatiu and Avarua is a fine to medium sand. This sand formation is thin and is probably underlain by a mixture of broken coral, reef rubble and sand. The base of the channel fill material has not generally been determined but in places at Avarua it appears to lie at up to 14m beneath the sea bed. In the areas of coral outcrop the sea bed relief is rugged with ridges, pinnacles and bosses of living and dead reef material up to 3m or more in height commonly occurring.

At Ngatangiia the channel off the harbour entrance is poorly defined out to a distance of 250m. Between 250m and 350m it is U-shaped, increasing in depth from 20m to 40m, and is about 100m in width. It is here covered by a coarse carbonate sand out of which protrude numerous live coral heads and patch reefs. This sand material is here probably thin and it may everywhere directly overly coral bedrock.

The channel floor sand at Avarua and Avatiu is too fine for concrete making. The sand from off Ngatangiia is acceptable for concrete making but an improved grade would be obtained by blending this with material from Avarua.

The maximum water depth just inside the Ngatangiia harbour entrance is 9m and the channel here is 50m in width with near vertical sides. The channel bed shallows rapidly in the direction of Muri Lagoon and lies at a depth of 2m at a distance of 200m from the harbour entrance. Depths opposite the centre of Motutapo Island are less than 1m, and opposite the southern end of this island depths are zero with respect to chart datum.

A reconnaissance side scan sonar, diving and sea bed sampling survey of the nearshore area north of Nuku'alofa was undertaken in June 1978 as part of an exploration programme for submerged deposits of constructional sand. This was followed in September 1980 by more detailed surveys of selected areas using continuous seismic profiling, echo sounding and sea bed sampling techniques.

The major part of the lagoon north of Nuku'alofa is floored by silty or muddy sediments. Talus slopes of reef debris occur adjacent to the fringing reefs and patch reefs are developed in places, particularly in the main shipping channel east of Atata Island.

A large deposit of fine, shelly sand occurs in a reef embayment on the south side of Fafa and Velitoa islands about 6km north of Nuku'alofa. The deposit lies in between 2.5 and 30m of water, covers an area measuring 2.5km in length and between 200m and 1km in width, and has a thickness of between 1.5 and 9m. The surface is covered by eel grass in the shallow water areas. The volume of shelly sand present is estimated at over 4,000,000m3. Tests carried out on samples of the sand at the Concrete Research Association, Wellington, indicate that it could be used for concrete making, although it is not an ideal material. It will produce a harsh mortar and a high cement demand.

South of Pangaimotu Island on the east side of the lagoon, the sea bed slopes up quite steeply from the lagoon floor at a depth of about 20m to the reef flat lying at about the datum level. Sediments on the lagoon floor and much of the slope are too silty for concrete making but shelly sand occurs on the reef flat here. Although the survey terminated on the edge of the shallow water, and therefore thicknesses of the sand formation were not determined, the reef flat is quite extensive and the volume of material present may be considerable. Live coral heads are developed in places and the flats are colonised by eel grass beds. Tests indicate that the suitability of this sand material for concrete making is similar to that from the Fafa-Velitoa area.

Marcopper Mining Company hereby submits this application for a dredging permit and accompanying supporting documents to the Department of Environment and Natural Resources(DENR).

The main reason for redredging the channel is to increase channel capacity to accommodate up to 400,000 m³ of tailing still left in the Boac River. The existing dredged channel is expected to be at fill capacity early in the 1997 wet season which may result in the uncontrolled release of tailing into the sea.

The main options to increase the dredge channel capacity and contain the tailing are to:

• Redredge the channel and store the dredgate in:
  • Encapsulated landfills or dumps;
  • Submerged landfill; and
  • Managed submarine placement.
• Dredging a parallel channel.
• Do nothing (unmanaged marine disposal).

This application is accompanied by three reports from consultants who investigated the physical, chemical and biological impacts of this proposal to redredge and place the dredgate on the seabed. Their findings indicate that the most environmentally and socially acceptable option is to redredge the channel and to place the dredgate on the seabed. The placement of dredgate must be managed so that it will not form a visible surface plume or deposit any significant amounts of tailing on the coast.

Social impact studies by the University of British Columbia and the University of the Philippines at Diliman conclude that augmented riverine transport, which is currently underway, with submarine placement is the most favorable in terms of socio-economic impact. Discussions with local communities and their leaders also show that redredging with submarine placement is an attractive option, provided the DENR approves the project and the project is conducted in an internationally acceptable manner. The mayor of Boac, Mayor Madla, is opposed to submarine placement preferring the submerged landfill solution.

Hay & Company predict that 99% of the dredgate will settle deeper then 450m in the Tablas Straight and settle in a very thin widespread layer, with an average of 0.5 mm and less than 7 mm thick. Subsequent surveys of the dredge channel indicate that 10-20% of the tailing will be coarser than assumed in the Hay & Company model. This should not significantly affect the dispersion model. Most importantly the model confirmed that tailing will not resurface if placed at 30-35 m below the surface and 500 m off the Boac coast.

Lorax Environmental Consultants provided evidence that ocean currents and stratification of the seawater column will prevent the tailing from rising to the surface. They further demonstrated that the oxygen levels decreased with depth, at 300 m dissolved oxygen was 2 mg/L, therefore reducing the risk of acid generation from the sulphide minerals in the tailing.

Woodward Clyde conducted a baseline survey of the coral and seagrass beds off the coast of Marinduque. This baseline study shows that the coral reef to the south of Boac is damaged from previous human activities in the area but the reefs to the north are in a healthy status. Hay & Company indicate that the dredgate will not settle on coral or seagrass beds and therefore have no impact.

A training exercise for monitoring benthic biota off the Boac coast demonstrated that several small animals have established on tailing which escaped from the river before the original dredge channel was constructed. This survey combined with two earlier surveys on Marinduque and evidence from other mine sites show that there will be little or no impact on benthic organisms in the Tablas Straight.

A commitment is made by the proponents to an extensive monitoring program which will document several physical, chemical and biological parameters throughout the project.

Highlands Pacific Limited is currently seeking finance for the development of a Nickel- Cobalt Mine in Madang Province, Papua New Guinea. The mine will be located near the Ramu River with processing facilities at Basamuk Bay on the Rai Coast. Basamuk Bay is a small embayment of the larger Astrolabe Bay. Highlands Pacific plans to dispose of mill tailings through a submarine outfall into Astrolabe Bay. Oceanographic conditions in Astrolabe Bay make this practise inadvisable if consideration is given to the ecological health of the Madang region.