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Coastal Structures, Waste Materials and Fishery Enhancement See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/233650401 Coastal Structures, Waste Materials and Fishery Enhancement Article in Bulletin of Marine Science -Miami- · September 1994 CITATIONS READS 32 133 4 authors, including: K.J. Collins A. C. Jensen University of Southampton National Oceanography Centre, Southampton 66 PUBLICATIONS 1,195 CITATIONS 70 PUBLICATIONS 1,839 CITATIONS SEE PROFILE SEE PROFILE All content following this page was uploaded by A. C. Jensen on 19 December 2014. The user has requested enhancement of the downloaded file. BULLETIN OF MARINE SCIENCE, 55(2-3): 1240-1250, 1994 COASTAL STRUCTURES, WASTE MATERIALS AND FISHERY ENHANCEMENT K. J, Collins, A. C. Jensen, A. P. M, Lockwood and S. J. Lockwood ABSTRACT Current U.K. practice relating to the disposal of material at sea is reviewed. The usc of stabilization technology relating to bulk waste materials, coal ash, oil ash and incinerator ash is discussed. The extension of this technology to inert minestone waste and tailings, contam- inated dredged sediments and phosphogypsum is explored. Uses of stabilized wastes arc considered in the areas of habitat restoration, coastal defense and fishery enhancement. It is suggested that rehabilitation of marine dump sites receiving loose waste such as pulverized fuel ash (PFA) could be enhanced by the continued dumping of the material but in a stabilized block form, so creating new habitat diversity. Global warming predictions include sea It:vel rise and increased storm frequency. This is of particular concern along the southern and eastern coasts of the U.K. The emphasis of coastal defenses is changing from "hard" seawalls to "soft" options which include offshore barriers to reduce wave energy reaching the coast. Stabilized waste materials could be included in these and other marine constructions with possible economic benefit. Ministry of Agriculture, Fisheries and Food (MAf'F), the regu- latory authority in England and Wales for marine disposal/construction, policy regarding marine structures and fishery enhancement is outlined. A case is made for the inclusion of fishery enhancement features in future coastal structures. Examples of the producti vity of man-made structures are given. Slight modification of planned structures and inclusion of suitable habitat niches could allow for the cultivation of kelp, molluscs, crustacea and fish. This paper provides an account of marine disposal practice in the U.K. in relation to the requirements of international conventions. Consideration is also given to the potential for stabilization of some of the wastes which are currently dumped loose at sea or in landfill sites. The possible use of such stabilized ma- terial in marine construction, particularly in relation to coastal protection works, is discussed, CURRENT U.K. MARINE DISPOSAL The U.K. is a signatory to the London and Oslo dumping conventions. Within the provisions of these agreements dumping of materials in the marine environ- ment is licensed by the Ministry of Agriculture, Fisheries and Food (MAJ:<f')in England and Wales and by the Scottish and Northern Ireland offices in Scotland and Northern Ireland. Four main categories of waste are currently disposed to the sea around the U.K.; dredged materials, solid waste, sewage sludge and liquid waste. Dredged Materia/s.-In 1989 44,303,995 wet tons of dredged material were dumped at sea around the coast of England and Wales (MAFF, 1991). Most of this material came from harbor maintenance dredging or new port developments. Typically dredged material is mainly silt with lesser amounts of coarse sand and shingle, cobbles, small rocks and heavy clay from capital spoils arising from new port developments. Analysis of dredged spoils indicates that some may contain significant amounts of various metals. For example, Murray and Norton (1979) showed high levels of zinc, copper and chromium in samples taken from the River Tees, River Tyne and Manchester Ship Canal (Fig. 1). Not all these metals 1240 COLLINS ET AI..: COASTAL STRUCfURES FROM WASTES 1241 . LOndOn~] - , •...• -' '-::::-\~~ West B.y " Highelltfe c::;0 Poole B8Y.rtffle'.' reef Figure I. Map showing locations described in the text and areas vulnerable to sea level rise (shaded portions) identified by Borman et a!. (1989). are necessarily freely available to marine organisms as some components may be bound within the mineral structure of the sediments. The practice of disposing of dredged spoil at sea is likely to continue in the U.K. Solid Waste.-In 1989 4,835,6] 0 tons wet weight solid industrial waste were licensed for disposal at sea (MAFF, ]99]), The bulk of this material was stone extracted from coal mines, considered chemically inert in the marine environment. Dumping of mine tailings, a slurry of finely ground stone arising from the washing of coal, has aroused considerable concern at certain disposal sites (e.g., the beach disposal site at Durham on the east coast of Britain). In response to this a con- dition of the ]988 and 1989 British Coal licenses to dispose at sea was to inves- 1242 BULLETIN OF MARINE SCIENCE. VOL 55. NO. 2-3. 1994 tigate the practicality of disposing of colliery waste on land to terminate beach disposal at Durham (a particularly sensitive site) as soon as possible. Similarly, disposal of pulverized fuel ash (PFA) at sea from the coal-fired pow- er-stations of Blythe (309,000 tons per annum) and Stella on the northeast coast of England was recently allowed to continue only on the condition that it should be terminated as soon as practicable, in line with the declaration of the Second International Conference on the Protection of the North Sea, London 1987 (De- partment of the Environment, 1987). Only 50% of the PFA produced in the U.K. is sold commercially (e.g., for road bases, cement filler, etc.). The remainder has to be disposed of by other means. It is currently expected that both loose PFA and minestone waste disposal at sea will be discontinued by 1995. Sewage Sludge.-In 1989 9,642,847 wet tons of sewage sludge were dumped under license into the coastal waters of England and Wales (MAFF, 1991). At present licenses are linked to the quality of sludge, which is related to the amount and type of industrial effluent released into the sewers. This disposal at sea will be stopped by 1998. Liquid Waste.-In 1989 248,454 tons of liquid industrial waste were licensed to be disposed to the marine environment (MAFF, 1991). Following the second In- ternational Conference on the Protection of the North Sea, London 1987, an agree- ment to reduce the number of licenses relating to marine disposal was reached (Department of the Environment, 1987). This has encouraged the development of alternative disposal methods. Stabilization of Wastes Landfill.-The simplest method used to stabilize otherwise mobile wastes is to bury material at a landfill site. This is particularly attractive where disused quarries and mine workings are available. The economics of disposal dictate that while a low cost landfill alternative is available little effort will be made to find alternative, environmentally acceptable practices. Current (1990) U.K. landfi II prices are in the region of £2·m-3 for inert materials and £ 10'01 3 for controlled materials. It would seem likely that as U.K. landfill sites are filled, and the price to dispose increases, that there will be a greater willingness to pursue other options. Stabilization of Urban Waste Material.-Nagasaka et al. (1985) describe a process by which Japanese urban waste can be stabilized by press packaging in steel mesh and encasement in concrete. These materials could then be used to build artificial reefs. Stabilization of Ash.-Research groups in the U.S. and Europe are investigating the use of cement-stabilized waste from coal-fired power-stations (Woodhead et aI., 1985, 1986; Collins et aI., 1990, 1991a, 1991c). Groups in the U.S. are in- vestigating cement stabilized oil ash (Metz and Trefry, 1988; Nelson et aI., 1988) and incinerator ash (Breslin et aI., 1988). The common theme running through this work is the construction of artificial reefs from this stabilized material. In Japan it is usual for artificial reefs to be constructed from prime (not waste) materials. However, Suzuki (1985) describes plans for artificial ridges, designed to enhance nutrient upwelling and improve fishing grounds constructed from a hardened mixture of 65% coal ash, 23% water and 12% cement. Use of this stabilized material would have half the cost of similar structures made from con- crete. COLLINS ET AL.: COASTAL STRUCTURES "ROM WASTES 1243 Stabilization of Contaminated Sediments.-Some harbor dredgings contain high levels of toxic materials. In the Netherlands some 45 million m3 of sediment is dredged annually, over half from the River Rhine. Scouten and Rang (1989) have described a system for high temperature (up to 1,200°C) processing of dredged muds. Organic micro-pollutants are destroyed. Heavy metal loss is slowed by the formation of a glass-like matrix of metal silicates and scintering which reduces the overall surface area of the material. A gravel-sized particulate is produced. Other Materia/s.-At present bulk wastes such as minestone waste and tailings with inherent low toxicity, small particle size which are currently disposed of at sea seem to be ideal subjects for cement stabilization technology. It is possible that other materials, such as phosphogypsum, which pose greater environmental problems, may be suitable for disposal in the sea after stabilization. Phosphogyp- sum is a by-product of the production of phosphate fertilizers from ores which may contain trace constituents such as cadmium and natural radionuc1ides of the uranium-238 family. The conversion of ore to phosphoric acid by sulfuric acid leaves calcium sulfate as a waste product.
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