Abstract – Dredging is the process of removing sediments from the seabed to deepen the waters for the safe navigation of vessels. The dislodged materials from the seabed, i.e. dredged marine soils, are generally disposed of as a geo-waste. This paper examines the potential reuse of the dredged materials within a comprehensive framework of technological feasibility, environmental soundness and knowledge creation (SAKET management system). The existing multi-discipline knowledge base serves as a vast reservoir of good practices to be adopted and moulded into the proposed system. The environmental background and impact that are related to the reuse mechanism need to be thoroughly investigated and determined too. The background data enables an informed selection of relevant technology to be implemented in the reuse exercise of dredged marine soils, which could lead to technological integration and innovation for optimum outputs. The subsequent monitoring and reviews would then create new insights and understanding to enrich the existing knowledge base, i.e. a full circle return. The proposed SAKET framework aims to provide a handling and management system of dredged marine soils which is simultaneously proactive and responsive, while being sufficiently flexible and predictive to ensure effective operational outputs with efficient utilization of the resources available. In short, the framework would embrace existing know-how in the folds of technological advances and innovations to develop an all-encompassing management system for reusing the dredged marine soils in a responsible manner for long term benefits.

Keywords – Dredged marine soils, management, reuse,

knowledge, environment, technology

I. INTRODUCTION Dredging is a necessity in the development of maritime industry and economy. Whether it is capital dredging to enlarge, deepen or create new ports and shipping channels, maintenance dredging to keep the navigation pathways sufficiently wide and deep, or clean-up dredging to remove contaminated sediments, the activity has seen a dramatic rise in recent years. Indeed, the category of dredging activity is not always easily discernible, especially at sites with combined natural and induced sedimentation caused by man-made coastal alterations, like reclamation works along the coastline. Historically a maritime kingdom dating back to the 15th century, Malaysia’s maritime industry has recorded continuous expansion driven by a thriving economy. For 2013 alone, the Marine Department of Malaysia reported

an estimated total dredged volume of 4 million m3 [1]. The dredged materials are generally disposed of 10 nautical miles (1 nautical mile = 1.853 km) offshore in waters of at least 20 m deep. Haulage to the dumping site is often time-consuming and could incur transportation cost which constitutes up to 20 % of the total dredging cost. While thorough Environmental Impact Assessment (EIA) is conducted prior to a dredging project, much remains unknown of the long term consequences of the disposal alternative adopted. To create upland landfills or contained disposal facilities appear to be unfavourable due to the additional construction and maintenance costs incurred as well as other environmental issues that may arise (Fig. 1). In addition, the removal and placement of the dredged materials from sea to land is unlikely to be well received considering the general public awareness of contamination risks and health hazards. That leaves seemingly limited options on the handling and management of the dredged marine soils but disposal. Adhering to existing practices is understandable within the context of avoiding disruptive changes, but it can also inadvertently stifle technological incorporations and advancements which could improve operations. A stagnant knowledge and talent pool could create blind spots to the exacerbating influences of the affected site, and hold back the implementation of advanced scientific mitigation measures before further damage is done. This leads to an urgent and timely need to review the management of dredged marine soils in Malaysia, particularly in terms of proposing a more sustainable ‘waste-to-wealth’ approach involving reuse of the materials instead of disposal.

Fig. 1. On-land and offshore disposal.

Strategic and Adaptive Knowledge-Environment-Technological (SAKET) Management System for Sustainable Reuse of Dredged Marine Soils

C-M. Chan1, A. Shamsuddin2, A. Suratkon3 1Faculty of Engineering Technology, Universiti Tun Hussein Onn Malaysia, Johor, Malaysia

2Faculty of Technology Management & Business, Universiti Tun Hussein Onn Malaysia, Johor, Malaysia 3Faculty of Civil & Environmental Engineering, Universiti Tun Hussein Onn Malaysia, Johor, Malaysia

1chan@uthm.edu.my, 2alina@uthm.edu.my, 3azeanita@uthm.edu.my

To landfills and contained disposal facilities

To offshore dumping site

Land Offshore Dredging site

526978-1-4799-5529-9/14/$31.00 ©2014 IEEE

Fig. 2. SAKET basic framework. This paper proposes an integrated Strategic and Adaptive Knowledge-Environment-Technology (SAKET) dredged marine soils management system to address the reuse possibilities and delivery mechanism (Fig. 2). The framework is underlain by a foundation of the existing information and knowledge base, and evaluated against environmental soundness and acceptability to determine the technological selection, development and innovation. The framework involves a 3-level interaction, i.e. Level 1: knowledge base and environmental acceptability cross-check, Level 2: knowledge and environmental input to the technological options, and Level 3: enrichment of the existing knowledge and environmental database with lessons learnt and new breakthroughs. This close-loop and interactive framework allows continuous improvement of the existing system to take place with minimal disruption to the overall management system. The relevant aspects of each component is examined and discussed within the context of the Malaysian cultural, environmental and legislation background.

II. KNOWLEDGE BASE As the sea has its own self-cleansing ability, hypothetically speaking, any adverse environmental and ecological effects from the dumping of dredged marine soils offshore would heal with time. Nonetheless, with the increasing volumes of dumping and escalating contamination risks from anthropogenic activities, the damage to the marine ecosystem could be very severe and irreversible. While offshore dumping sites are usually isolated to avoid disrupting local fishery economy, disturbance to the aquatic ecosystem is almost unavoidable [2]. Bogers and Gardner [3] reported on the effect of light attenuation by suspended sediments on the seagrass plants, coral reefs and other marine organisms. In addition, the response of soft bottom macro-benthic assemblages to the disturbance associated with the dumping process could affect the overall marine ecosystem [4].

Fig. 3. Possible contamination risk of granular dredged materials in concrete due to complex chemical reactions at the concrete-soil

interface. Dredged materials may contain toxic chemicals which are not easily degradable. These could have adverse effects on marine organisms at the disposal area and surrounding waters. As established by Kapsimalis [5], uncontrolled dumping in coastal or marine areas can cause severe degradation of the natural ecosystems, which effects are long term and irreversible on the sensitive marine food chain [6]. This is not to mention the sometimes critical levels of heavy metals and hydrocarbon present in dredged materials, such as reported by Simonini et al. [7] and Leotsinidis and Sazakli [8], which cause damaging pollution when released to the surrounding waters. Knowing that the dredged marine soils are commonly contaminated, and that dumping offshore can cause negative consequences, an obvious alternative is to dispose of the materials in landfills or contained disposal facilities upland. However these facilities incur additional costs, e.g. according to Japan Port and Harbour Association [9], the dredged soils for port and harbour construction constituted almost 50 % of the total wastes stored in specially built bulkheads, and incurred tens of billions of Japanese Yen in construction costs. The containment exercise also inadvertently extends the possible contamination trail inland. Close monitoring and preventive measures are necessary in case of leaching to surrounding agriculture land and groundwater sources. The dredged materials are readily usable if they are of the granular type, i.e. sand and gravels, as per reports by Dolage et al. [10] and Limeira et al. [11]. This is notwithstanding the fact that thorough environmental safety assessments need to be carried out before dispatching the materials to end users. Considering that most of the reused sand and gravels are incorporated in the production of concrete, contamination risks could be effectively reduced. Nonetheless long term chemical processes at the interface of the concrete element and soil envelope for a subsurface element may still lead to leaching of contaminants from the dredged materials (Fig. 3). If the dredged materials are fine-grained, i.e. clay and silt, potential for direct beneficial reuse is significantly reduced [12]. This is very much attributed to the inherent soft and weak nature of the material, not unlike soft soils normally encountered on problematic upland sites.

Soil

Concrete

Granular dredged materials

Leaching of contaminants Foundation

(submerged)

GWT

Ground surface

KNOWLEDGE Base

ENVIRONMENTAL Acceptability

TECHNOLOGICAL Development and

Innovation

Level 1

Level 2 Level 2 Level 3 Level 3 Continuous Quality

Improvement (CQI)

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Moreover these fine-grained materials are susceptible to harbouring contaminants within their microstructure, with greater affinity towards certain adverse chemical bonds and their larger contact surface due to the fine particles.

III. ENVIRONMENTAL ACCEPTABILITY As offshore dumping remains the main disposal method for dredged marine soils in Malaysia, the dump site selection is of utmost importance. Some of the basic information required to make the selection include the physic-chemical and biological properties of the seabed and water column, proximity to surrounding facilities and activities, practicality and economic considerations. The size of the dumpsite is to be determined by weighing the following factors: sufficient buffer zone for the dumped material, adequate for the designated dumped volume, compatible and feasible long term monitoring. Details on dump site selection and management have been recorded in a number of guidelines, such as the ones by the International Maritime Organisation, IMO [13] and US Army Corps of Engineers [14]. An exposure assessment is rudimentary in the environmental risk assessment of dredging activities and material handling. While the assessment is dependent on site and project specifics, it always begins with the ‘source’ and ends with the ‘receptors’ (Fig. 4). The endpoints of an exposure path involve the human and ecological aspects. From the human’s perspective, the primary concern is ingestion of potentially contaminated food or drinking water. The local traditional and cultural preferences which may influence seafood intake habits, such as fish processing for preservation, ingestion rate and commercial activities, need to be taken into account too in the assessment. Secondary concerns may include recreational and tourism activities, with close relationship with the primary factors mentioned earlier. The ecological impact is examined from several points of view, including the affected natural habitats, food chain, flora and fauna. For the reuse of dredged marine soils, the contamination levels and inherent risks to the receptors are the most critical factors to be considered. The applications may be within a recreational or residential area, or fulfilling an industrial need. The Minnesota Pollution Control Agency [15] further stipulated conditions for various applications of dredged materials, such as beach amendments, storage prior to use or reuse, co-mingling of dredged materials, and in-water backfilling.

The reuse potential of dredged marine soils is also recommended by IMO [13], with 3 main categories of beneficial uses: engineered, agricultural and product uses as well as environmental enhancement applications. The engineered uses category includes creation of artificial land, improvement of existing sub-par lands, beach nourishment and rehabilitation, offshore capping and berm construction. Applications in aquaculture, lining backfill sites and simply as building materials fall into the

second category. Environmental enhancement reuse is found in wetlands restoration and creation, development of fisheries and nesting islands. The reuse possibilities of dredged marine soils depend very much on the health and ecological risk factor than the engineered feasibility. The former usually outweighs the latter due to the uncertainties in predicting and anticipating the consequences of miscalculations and negligence. Therefore environmental acceptability is arguably the most dominant factor in the design and operations of the SAKET management system. The environmental impact, peripheral influences and even remote catastrophe, no matter how unlikely it may be, can be a hindrance to the reuse of dredged marine soils. As such, it is crucial to identify the calculated risks and provide a balanced view of what is known and unknown to ensure public acceptance and long term feasibility of the chosen applications.

IV. TECHNOLOGICAL DEVELOPMENT AND INNOVATION

Taking into account the preference for the reuse of granular dredged materials due to their favourable engineering properties and ready-to-use versatility, the vacuum of technological advancement apparently lies in the limited reuse potential of the fine-grained materials. Similar to fine-grained soils found on land, i.e. clay and silt or soils with over 50 % of clay constituent, these materials are generally low in load-bearing capacity and high in compressibility upon loading over a long period of time. Structures built on these grounds are also prone to failures and damages due to excessive and non-uniform subsidence of the soft soil deposits (Fig. 5).

SOURCE RECEPTOR Exposure path

Physical, chemical and biological characteristics - Sediments - Water column

Human: ingestion, agriculture, recreation, economic activities Ecology: natural habitats, food chain, flora and fauna

Fig. 4. Environmental risk assessment- exposure model.

Fig. 5. Subsidence of soft soil deposits causing structural failures.

Soft soil

Bedrock (deep-seated)

Initial condition Excessive settlement:

leading to loss of building’s height

Non-uniform settlement: leading to ‘leaning’ effect in building

Progress of time…

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Chan [16] discussed at length on the various ground improvement methods applicable to strengthen and stiffen these weak soil deposits. These techniques can be potentially adopted for treating dredge marine soils of the fine-grained category too. For instance, the solidification technique uses chemical binders to partially dehydrate the soils and to induce bonding of the soil particles. The chemical reactions also produce gelatinous compounds which effectively fill up the inter-particle voids to create a structured mass for load-bearing (Fig. 6). Of course, for treating the dislodged dredged material, issues pertaining to storage, mixing, transportation and placement require careful planning and execution. Indeed, most of the reported reuse of fine-grained dredge marine soils is in environmental enhancement projects, such as creating wildlife habitats, improving fisheries and restoring wetlands [17]. The selection, adoption and adaptation of existing technologies for on land applications can be the starting point for developing tailor-made technology for dredged marine soils. It necessarily entails innovation and creativity to transform the existing techniques to suit the relevant and specific site conditions. Besides, it is imperative that a constant supply of raw material (i.e. dredged fine-grained soils) for mass production and delivery is in place, such as by scheduling dredging works in parallel with the production timeline. On the other hand, current technology of using fine-grained soils as the primary raw material for manufacturing various construction materials, like lightweight aggregates, bricks and ceramic, can be adopted without significant modifications. Nevertheless scheduling for continuous and regular supply of the raw material remains the crucial operational feasibility and success factor.

V. CONCLUSIONS Based on the discourse on the 3 major inter-related components of the SAKET management system above, clearly optimization of the resources available to address the challenges of reusing dredge marine soils is the way forward. The existing knowledge base and technological know-how can evolve into environmentally acceptable

and economically viable solutions by establishing cross-talk among the resources. It is a multi-disciplinary industry, hence a multi-faceted approach is recommended to implement the SAKET system. This paper has highlighted the issues involved and the possible strategies to be espoused.

ACKNOWLEDGMENT

Financial support for the work presented is provided by ORICC, UTHM via the Multidisciplinary Research Grant 1319.

REFERENCES [1] Marine Department of Malaysia, personal communications,

2014. [2] Snyder, G. R., “Effect of dredging on aquatic organisms

with special application to areas adjacent to the northeastern Pacific Ocean,” A Marine Fisheries Review, 1976.

[3] Bogers, P. and Gardner, J., Dredging near live coral, 17th World Dredging Congress, Hamburg, Germany. WODCON XVII 2004, Paper A31, 2004.

[4] Cruz-Motta, J. J. and Collins, J., Impacts of dredged material disposal on a tropical soft-bottom benthic assemblage, Mar Pollut Bull, vol. 48, no. 3-4, pp. :270-80, 2004.

[5] Kapsimalis, V., Panagiotopoulo,s I., Kanellopoulus, T., Hatzianestis, I., Antoniou, P. and Anagnostou, C., A multi-criteria approach for the dumping of dredged material in the Thermaikos Gulf, Northen Greece, Journal of Environmental Management, no. 91, pp. 2455-2465, 2010.

[6] Harvey, M., Gauthier, D. and Munro, J., Temporal changes in the composition and abundance of macro-benthic invertebrate communities at dredged material disposal sites in the Anse a Beaufils, Baie de Chaleurs, Eastern Canada, Marine Pollution Bulletin, no. 36, pp. 41-55, 1998.

[7] Simonini, R., Ansaloni, I., Cavallini, F., Graziosi, F., Iotti, M., Massamba N’Siala, G., Mauri, M., Montanari, G., Preti, M. and Prevedelli, D., Effects of long-term dumping of harbour-dredged material on macrozoobenthos at four disposal sites along the Emilia-Romagna coast (Northen Adriatic Sea, Italy), Marine Pollution Bulletin, no. 50, pp. 1595-1605, 2005.

[8] Leotsinidis, M. and Sazakli, E., Evaluating contamination of dredges and disposal criteria in Greek coastal areas, Chemosphere, no. 72, pp. 811-818, 2008.

[9] Japan Port and Harbour Association, “Technical standard for port facilities,” 1999. (in Japanese)

[10] Dolage, D. A. R., Dias, M. G. S. and Ariyawansa, C. T., Offshore sand as a fine aggregate for concrete production, British Journal of Applied Science and Technology, vol. 3, no. 4, pp. 813-825, 2013.

[11] Limeira, J, Etxeberria, M., Agullo, L. and Molina, D., Mechanical and durability properties of concrete made with dredged marine sand, Journal of Construction and building Materials, no. 25, pp. 4165-4174, 2011.

[12] Sheehan, C., Harrington, J. R. and Murphy, J. D., An investigation into potential beneficial uses of dredged material in Ireland, WEDAXXVIII and Texas TAMU 39th

Fig. 6. Solidification of fine-grained dredged marine soils.

Before solidification After solidification

Soil particles

Voids

Cementitious bonds

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Dredging Seminar, St. Loius, USA, 2008 [13] International Maritime Organisation, “Specific guidelines

for assessment of dredged material,” 2000, www.imo.org. [14] US Army Corps of Engineers, “Environment risk

assessment and dredged material management: Issues and Applications,” 1998.

[15] Minnesota Pollution Control Agency, “Managing dredged materials in the state of Minnesota,” 2012.

[16] Chan, C-M., “The sinking earth: How do we survive?” Publisher’s Office, Universiti Tun Hussein Onn, 2012.

[17] US Army Corps of Engineers, “Beneficial uses of dredged material,” 2006.

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