Dredged Material Disposal Site Research Articles

Spatial distribution and temporal trends of butyltin compounds (TBT, DBT & MBT) in short sediment cores of the SW Portuguese Shelf (western Iberian Margin, NE Atlantic)

Spatial patterns and temporal trends of the butyltin compounds tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) were investigated in a set of sediment samples collected along the SW Portuguese continental shelf. This region did not reach the Good Environmental Status (GES) in accordance with the Marine Strategy Framework Directive (MSFD) during a first evaluation carried out in 2012. Overall, MBT and DBT were the predominant organotin species detected, but high concentrations of TBT were found in and around disposal sites for dredge sludge derived from the dredging in navigation channels, harbours, and shipyard facilities of the Tagus and Sado estuaries. Although Portuguese regulations for monitoring sediment quality in relation to dredging activities consider only PAH, PCB and HCB, they also dictate that other organic contaminants such as butyltin compounds (BTs) should be monitored if suspicion of high values exists, but no action limits are defined for these (MAOTDR, 2007). Without action limits, the monitoring recommendation given in the regulations is not put into practice. Considering their toxicity, BT derivates should be integrated in the legislation, because they represent an environmental threat in the relocation of dredged material, especially when derived from harbour and shipyards areas. Based on this study, we recommend giving more attention to the amounts and impacts of BTs in sediments at dredged material disposal sites (DMDS) and their surroundings. Or even better, in order to be more efficient, monitoring should be done at the source of the dredged materials and not at the sink. In case it is not done, the monitoring of concentrations of TBT (and other BTs) in sediments and organisms, including imposex studies, at all Portuguese sites for disposal of dredged material receiving slightly to strongly contaminated dredged material must be developed.

Field of dreams: Restoring estuarine habitat and structure in Mississippi after the Deepwater Horizon oil spill

This paper presents a Mississippi Department of Marine Resources (MDMR), Office of Coastal Restoration and Resiliency, perspective on adaptation and innovation in restoration permitting, collaboration, and design in an era shaped by the Deepwater Horizon oil spill (DWH). These adaptations and innovations lay groundwork to support Mississippi’s future address of challenges stemming from its ongoing geomorphic evolution and loss of primary landforms. The Round Island project in Jackson County, Mississippi (MS), will serve as a principal example. Completed through the efforts of four agencies via a Memorandum of Understanding (MOU) and funded by the National Fish and Wildlife Foundation (NFWF) this project helped break a long-standing practice of dumping large quantities of federal navigation channel dredged materials in an Offshore Dredged Material Disposal Site (ODMDS). Not only were 220 acres of new island and marsh habitat created in the Mississippi Sound, the Round Island project saved millions in federal navigation dollars because it could be more efficiently accessed than the ODMDS site. The Round Island project represents a collective, multi-agency step toward strategic scale, nature-based approaches more capable of managing Mississippi’s burgeoning restoration and resource needs.

Video sleds effectively survey epibenthic communities at dredged material disposal sites

This research assessed the effectiveness of benthic video sleds for monitoring the impacts of dredged material disposal on epifauna at shallow and deep water disposal sites near the mouth of the Columbia River, USA. Video sleds collected visual transects at the two disposal sites and comparable reference areas during 2014 and 2015 within a Before-After, Control-Impact (BACI) experimental design. These flat, soft-bottom habitats are populated by demersal fish and benthic invertebrates, including the economically important Dungeness crab (Cancer magister). At the shallow site, results from multivariate Similarity Profile Analysis (SIMPROF) and univariate ANOVA tests on prominent species did not detect any significant differences between disposal and reference communities. At the deep site, the multivariate and univariate analyses detected differences in communities and abundances between years, rather than between disposal and reference locations. At the scale of this research, there was no detectable impact of dredged material disposal on the epifauna communities at these two Pacific Northwest disposal sites. While the species resolution of cryptic or small organisms was found to be limited, the video sled technique had sufficient power to detect potential differences in most epifaunal species densities with a BACI statistical design. We found the video sleds were an effective tool to assess potential impacts of dredged material disposal on epifauna.

WORKING THROUGH STATE DIFFERENCES TO CREATE A REGIONAL DREDGED MATERIAL MANAGEMENT PLAN FOR FEDERAL HARBORS IN LONG ISLAND SOUND

On January 11, 2016 the U.S. Army Corps of Engineers (USACE) New England District (NAE) completed a Final Dredged Material Management Plan (DMMP) for Long Island Sound (LIS). The DMMP was requested by the Governors of Connecticut and New York, in their letter of February 8, 2005 to the Chief of Engineers, following the U.S. Environmental Protection Agency’s (EPA) publication in April 2004 of the Long Island Sound Dredged Material Disposal Site Designation Study Final Environmental Impact Statement. The LIS is a large coastal estuary located between Long Island, New York on the south, and the shores of New York, Connecticut and southwestern Rhode Island on the north. A total of nearly 240 harbors, coves, bays and rivers supporting various levels of navigational access are located along these shores. Twelve Congressional districts and 112 municipalities border the Sound and its adjacent waters in the three states. The ideals, goals, and needs along the LIS do not always align and thus the need for open communication throughout each dredging project.

Impact of disposal of dredged material on sediment quality in the Kaohsiung Ocean Dredged Material Disposal Site, Taiwan

Kaohsiung Ocean Dredged Material Disposal Site (KODMDS) that located in the southwest offshore of Taiwan, has been annually disposed about 500,000 ton dredged sediments of Kaohsiung Harbor from 2003 to 2012. Five sediment cores collected from KODMDS and three from nearby reference sites were analyzed to evaluate their sedimentation rates, vertical profiles of heavy metal, and heavy metal pollution indices to assess the impact of dumping harbor dredged sediments into the ocean on the sediment quality in KODMDS. The sedimentation rate of 0.24 cm/y was estimated by the 210Pb method, which means that the effected depth of the top layer of a core of D1 was affected in the period of dumping dredging sediments. The vertical distribution of heavy metals in the sediment cores from KODMDS showed the concentrations of most heavy metals were slightly elevated in the top layers of the sediment cores, which may be affected by the dumping of harbor dredged sediments. According to the analyzed results of the heavy metal pollution indices, the level of heavy metal pollution, the potential eco-toxicity and the potential ecological risk of the sediments in KODMDS exhibited only a slight increase, which indicated that the increase in concentration of heavy metals may potentially pose the insignificant impact on benthos inhabiting the disposal site.

Phthalate ester distributions and its potential-biodegradation microbes in the sediments of Kaohsiung Ocean Dredged Material Disposal Site, Taiwan

The aim of this study was to examine the effect of dumping harbor dredged sediments into the ocean on the phthalate esters distribution in the sediments of Kaohsiung Ocean Dredged Material Disposal Site (KODMDS). Compared with the sediments outside the disposal site (Area R), the particle size distribution of sediment in disposal site has no significant difference, because the pattern of particle size distribution in the dredged sediments is similar to that in the sediments of KODMDS. Results indicated that the mean phthalate ester content in the centres of the four disposal areas (Area I) were significantly (p < 0.05) higher than those in Area R, whereas those in the vertex angles of disposed area (Area II) were no significantly higher than those in Area R. This result implied that the dredged sediments were mainly deposited inside the disposal area, and the surface sediments in KODMDS may be impacted by the disposal of dredged sediments. The percentage of sediment samples for phthalate esters content exceeding Maximum Permissible Concentrations (MPC) and/or Ecotoxicological Serious Risk Concentrations (SRCeco) in Areas I and II was higher than that in Area R, indicated that the disposal of dredged sediments may increase the potentially ecological risks for benthic organisms that lived in the surface sediments of KODMDS. However, the present study has found the bacteria have the ability to degrade PAEs in KODMDS, indicating PAEs in KODMDS could be biodegraded eventually.

Metal distributions in the Kaohsiung Ocean dredged material disposal site, Taiwan

Metal distributions in the Kaohsiung Ocean dredged material disposal site, Taiwan

The application of Diffusive Gradients in Thin Films (DGT) for improved understanding of metal behaviour at marine disposal sites

Assessment of the effects of sediment metal contamination on biological assemblages and function remains a key question in marine management, especially in relation to disposal activities. However, the appropriate description of bioavailable metal concentrations within pore-waters has rarely been reported. Here, metal behaviour and availability at contaminated dredged material disposal sites within UK waters were investigated using Diffusive Gradient in Thin films (DGT). Three stations, representing contrasting history and presence of dredge disposal were studied. Depth profiles of five metals were derived using DGT probes as well as discrete analysis of total metal concentrations from sliced cores. The metals analysed were: iron and manganese, both relevant to sediment biogeochemistry; cadmium, nickel and lead, classified as priority pollutants. DGT time-integrated labile flux profiles of the metals display behaviour consistent with increasingly reduced conditions at depth and availability to DGT (iron and manganese), subsurface peaks and a potential sedimentary source to the water column related to the disposal activity (lead and nickel) and release to pore-water linked to decomposition of enriched phytodetritus (cadmium). DGT data has the potential to improve our current understanding of metal behaviour at impacted sites and is suitable as a monitoring tool. DGT data can provide information on metal availability and fluxes within the sediment at high depth-resolution (5mm steps). Differences observed in the resulting profiles between DGT and conventional total metal analysis illustrates the significance of considering both total metals and a potentially labile fraction. The study outcomes can help to inform and improve future disposal site impact assessment, and could be complemented with techniques such as Sediment Profile Imagery for improved biologically relevance, spatial coverage and cost-effective monitoring and sampling of dredge material disposal sites. Additionally, the application of this technology could help improve correlative work on biological impacts under national and international auspices when linking biological effects to more biologically relevant metal concentrations.

Polycyclic aromatic hydrocarbons in sediments at dredged material disposal sites around England: Concentrations in 2013 and time trend information at selected sites 2008–2013

The maintenance of navigation channels to ports and the development of their facilities present a need to conduct dredging operations, and the subsequent disposal of dredged material at sea. Contaminant concentrations in candidate dredged material are determined and their possible impacts considered during the licensing process, which can result in the exclusion of some material from sea disposal. Monitoring of disposal sites is conducted in order to ensure that no undesirable impacts are occurring. In this study we consider the levels of polycyclic aromatic hydrocarbons (PAHs) in sediments at a number of disposal sites monitored in 2013 and variations in concentrations over time at three sites during the period 2008–2013. These were assessed using established sediment quality guidelines. Elevated PAH concentrations were generally observed only within the boundaries of the disposal sites studied.

A temporal and spatial assessment of TBT concentrations at dredged material disposal sites around the coast of England and Wales

Despite legislative interventions since the 1980s, contemporary concentrations of organotin compounds in marine sediments still impose restrictions on the disposal of dredged material in the UK. Here, we analyse temporal and spatial data to assess the effectiveness of the ban on the use of TBT paints in reducing concentrations at disposal sites.At a national scale, there was a statistically significant increase in the proportion of samples in which the concentration was below the limit of detection (LOD) from 1998 to 2010. This was observed for sediments both inside and outside the disposal sites. However, this temporal decline in organotin concentration is disposal site-specific. Of the four sites studied in detail, two displayed significant increases in proportion of samples below LOD over time. We argue that site-specificity in the effectiveness of the TBT ban results from variations in historical practices at source and unique environmental characteristics of each site.

Estimating the biological value of soft-bottom sediments with sediment profile imaging and grab sampling

Biological value estimation is based on a set of assessment questions and several thresholds to delineate areas of ecological importance (e.g. biodiversity). An existing framework, that was specifically designed to assess the ecosystem biodiversity, was expanded by adding new questions on the productivity, functionality and biogeochemical status of benthic habitats. The additional ecological and sedimentological information was collected by using sediment profile imagery (SPI) and grab sampling. Additionally, information on the performance and comparability of both techniques is provided in this study. The research idea was tested at a site near the harbor of Zeebrugge, an area under consideration as a new disposal site for dredged material from the harbor entrance.The sedimentology of the area can be adequately described based on the information from both SPI and Van Veen grab samples, but only the SPI revealed structural information on the physical habitat (layering, a-RPD). The latter information represented the current status of the benthic habitat, which was confirmed by the Van Veen grab samples. All information was summarized through the biological valuation framework, and provided clear evidence of the differences in biological value for the different sediment types within the area. We concluded that the installation of a new dredged material disposal site in this area was not in conflict with the benthic ecology. This area has a low biological value and the benthic system is adapted to changing conditions, which was signaled by the dominance of mobile, short living and opportunistic species.This study showed that suitable sedimentological and ecological information can be gathered by these traditional and complementary techniques, to estimate the biological value of an area in the light of marine spatial planning and environmental impact assessments.

Impacts of dredged material disposal on macrobenthic invertebrate communities: A comparison of structural and functional (secondary production) changes at disposal sites around England and Wales

Although the impacts of dredged material disposal in the marine environment have been well studied, there is currently a limited understanding of the associated impacts on benthic function. This study compares macrofaunal structural and functional (based on secondary production estimates) responses to dredged material disposal at 14 sites across the coast of England and Wales.Disposal resulted in significant reductions of total secondary production at seven sites; no sites exhibited significant increases in production estimates. These seven sites were generally those which displayed significant structural impacts. There was no clear relationship between multivariate structural changes and taxonomic contribution to total production, indicating that a lack of change in the former (regarded as a sensitive indicator of change) does not always signify a lack of a significant functional impact. The need to evaluate functional changes, in addition to structural impacts, with respect to dredged material disposal site monitoring is discussed.

Novel Application of Cyclolipopeptide Amphisin: Feasibility Study as Additive to Remediate Polycyclic Aromatic Hydrocarbon (PAH) Contaminated Sediments

To decontaminate dredged harbor sediments by bioremediation or electromigration processes, adding biosurfactants could enhance the bioavailability or mobility of contaminants in an aqueous phase. Pure amphisin from Pseudomonas fluorescens DSS73 displays increased effectiveness in releasing polycyclic aromatic hydrocarbons (PAHs) strongly adsorbed to sediments when compared to a synthetic anionic surfactant. Amphisin production by the bacteria in the natural environment was also considered. DSS73’s growth is weakened by three model PAHs above saturation, but amphisin is still produced. Estuarine water feeding the dredged material disposal site of a Norman harbor (France) allows both P. fluorescens DSS73 growth and amphisin production.

Channel Shoaling with Deepening of Houma Navigation Channel at Cat Island Pass, Louisiana

ROSATI, J.D. and LAWTON, C., 2011. Channel Shoaling with Deepening of Houma Navigation Channel at Cat Island Pass, Louisiana. In: Roberts, T.M., Rosati, J.D., and Wang, P. (eds.), Proceedings, Symposium to Honor Dr. Nicholas C. Kraus, Journal of Coastal Research, Special Issue, No. 59, pp. 256-265. West Palm Beach (Florida), ISSN 0749-0208. This study evaluated the potential increase in shoaling and associated sources of sediment as a result of proposed channel improvements for the Houma Navigation Channel in the vicinity of Cat Island Pass, Louisiana. Using morphologic change data and historical maintenance dredging rates, historical and forecasted with-deepening sediment budgets were developed. Conclusions from this study were that deepening the channel from 5.5 m to 6.1 m relative to Mean Low Gulf, a local low water datum, would increase the shoaling rate from the present 191,000 m 3 /year to 220,000 m 3 /year, and the likely source of shoaling would be sediment that is presently bypassed naturally. It was recommended that all environmentally-acceptable sediment dredged from Cat Island Pass be placed on the downdrift barrier island, East Island, part of the Isle Dernieres barrier island system. Clays and silts should be placed on the bayside of the island and sand similar to or coarser than the existing beach sand should be placed downdrift of the nodal zone on the Gulf side of East Island. Historically, sediment dredged from Cat Island Pass has been placed in designated dredged material disposal sites located 760 m west of the channel. Based on morphologic change in the region from 1980 to 2006, it appears that sediment may be transported from this placement site to deposit back into the channel. It is recommended that, if sediment cannot be placed on either East Island or Timbalier Island, that the dredged material disposal site be moved further to the west, away from the channel. Finally, based on movement of Timbalier Island and Cat Island Pass over the past 100 years, it is recommended that the channel be moved further to the west to avoid future impingement by Timbalier Island. Based on the results of this and other studies of the Houma Navigation Channel, channel realignment was approved in 2009, and authorization of the deepened channel is being requested during 2010.

Establishment of a Dredged Material Disposal Site in the Exclusive Economic Zone: New Zealand

Disposal options for muddy dredged material, especially if lightly contaminated, is an issue facing many countries, particularly if environmental protection and adherence to the Protocols of the London Dumping Convention is a regulatory requirement. For the case of the oceanic islands of New Zealand, disposal of muddy dredged material has become an issue for the prime city of Auckland. Accordingly, it has been necessary to investigate a suitable marine disposal site outside of the territorial seas in the exclusive economic zone (EEZ). Ideal properties for such a disposal site include a near flat surface on the continental shelf, with sediments of similar textural characteristics to the material being disposed, a site of non-critical benthic ecology, water depths sufficient to enable the disposal site to be monitored (as required under the London Dumping Convention), a site experiencing low shelf currents, not affected by significant wave agitation, and a site not of cultural significance. The approach for site establishment and gaining consent for disposal activities is reviewed. Preliminary investigations supporting a proposed site on the continental shelf in the EEZ are presented.

Impact of the Charleston Ocean Dredged Material Disposal Site on nearby hard bottom reef habitats

The deepening of shipping and entrance channels in Charleston Harbor (South Carolina, USA) was completed in April 2002 and placed an estimated 22 million cubic yards (mcy) of material in the offshore Charleston Ocean Dredged Material Disposal Site (ODMDS). To determine if sediments dispersed from the ODMDS were negatively affecting invertebrate and/or finfish communities at hard bottom reef areas around the disposal area, six study sites were established: three close to and downdrift of the ODMDS and three upcurrent and farther from the ODMDS. These sites were monitored biannually from 2000 to 2005 using diver surveys and annually using simultaneous underwater video tows and detailed sidescan-sonar. In general, the sediment characteristics of downdrift sites and reference sites changed similarly over time. Overall, the hard bottom reef areas and their associated communities showed little evidence of degradation resulting from the movement of sediments from the Charleston ODMDS during the study period.

Effects of dredged material disposal on benthic macrofauna near Itajaí Harbour (Santa Catarina, South Brazil)

From July 2006 to November 2007 the effects of sediment disposal on a macrobenthic association were evaluated at the dredged material disposal site, located 3 km northeast of Itajaí Harbour navigation channel. Seven sample sites were chosen, five inside the licensed disposal area and two outside. Five samples were collected from each site with a 0.042 m 2 Van-Veen grab. Nine sampling campaigns took place, one before, one during, and seven after the disposal operations. Evaluations were carried out through sediment and macrofauna composition analysis. An increase in coarse fractions of sediments was found during the first months, mainly within the licensed disposal area. Sites outside the area kept the same granulometric characteristics. Nested ANOVA showed that abundance, taxa richness and Shannon–Weaver diversity were significantly smaller after the disposal, and recovered the initial mean values after the disposal ends. PERMANOVA showed a high heterogeneity between the sites. It decreased until the fifth month after disposal operations, mainly in the sites inside the licensed area. These sites were characterized by low abundance and high variability among the samples. Eight to 16 months after disposal sites recovered their heterogeneity, indicating less variability among the samples of each site and distinct benthic macrofaunal composition. The high volume and frequency of sediment disposal were the main factors of environmental modifications, since the amount of deposited sediment on the seabed probably exceeded the natural sedimentation rates. The presence of a benthic macrofauna adapted to natural/human disturbances was crucial to the fast recovery verified in the area.

Long-term benthic infaunal monitoring at a deep-ocean dredged material disposal site off Northern California

One hundred and thirty-five benthic infaunal samples were collected from the San Francisco Deep-Ocean Disposal Site (SF-DODS) over a 10-year period from January 1996 to September 2004. Each sample was 0.1 m2, cut to a depth of 10 cm, and sieved through a 300-μm mesh. A total of 810 species of benthic invertebrates were identified; the majority of taxa (65.4%) new to science. The fauna represents a rich lower slope infaunal assemblage that rivals similarly studied locations in the western North Atlantic. No regional impact or degradation of benthic infauna due to dredged material disposal was detected. All reference stations and stations on the site boundary maintained high species richness and diversity during the monitoring period. Exceptions included an occasional sample with anomalously high numbers of one or two species that reduced the diversity and/or equitability. Within SF-DODS species richness and diversity were often reduced. Stations within the disposal site were recolonized by the same taxa that normally occurred in adjacent reference areas. Initial colonizers of fresh dredged material included spionid and paraonid polychaetes that were typical dominants at the site. At least one polychaete species, Ophelina sp. 1, sometimes colonized dredged materials containing coarse sand. One sample at Station 13, located in the middle of SF-DODS (September 2002), contained 57 species of benthic invertebrates, suggesting that colonization of fresh dredged material is rapid. It seems unlikely that larval dispersal and settlement account for this rapid recolonization; therefore it is postulated that adult organisms from adjacent areas move to the disturbed sites via boundary layer currents. The steep continental slope adjacent to SF-DODS is subject to turbidity flows and the resident fauna are likely pre-adapted to rapidly colonize disturbed sediments. Larval dispersal, especially by spionid polychaetes such as Prionospio delta, may also be important in colonizing newly deposited sediments. Subtle year-to-year shifts in faunal assemblages were evident at stations on the boundary of SF-DODS. At these stations species richness and diversity remained high, but numerically dominant taxa differed, possibly due to changes in sediment grain size associated with the dredged material. However, some year-to-year changes appeared to be regional in nature. Large epifaunal organisms such as the elasapoid holothurian Scotoplanes globosa appeared to be locally important in modifying surficial sediments: it moves through the sediment like a bulldozer, disturbing the surface and disrupting resident infauna as it ingests sediment. Other deposit-feeding holothurians such as Ypsilothuria bitentaculata were found throughout the study area including sediments with fresh dredged material. A long, narrow-bodied tube-like agglutinated foraminiferan of the genus Bathysiphon is commonly found in sediments containing dredged material. This foraminiferan is poorly understood, but may be opportunistic on soft dredged material.

Biological indicators of disturbance at a dredged-material disposal site in Liverpool Bay, UK: an assessment using time-series data

Abstract Whomersley, P., Ware, S., Rees, H. L., Mason, C., Bolam, T., Huxham, M., and Bates, H. 2008. Biological indicators of disturbance at a dredged-material disposal site in Liverpool Bay, UK: an assessment using time-series data. – ICES Journal of Marine Science, 65: 1414–1420. The development of reliable indicators of disturbance in the marine environment is essential because of increasing anthropogenic pressures and the need for more effective regulation. Our objective was to evaluate 13 nationally and internationally recommended metrics, using a large dataset derived from annual (1996–2003) macro-invertebrate infaunal surveys of a Liverpool Bay dredged-material disposal site. The primary and derived univariate metrics, along with multivariate derivations, were assessed and scored against six selection criteria. Metrics that did not correlate with the pressure indicator (the annual quantity of material disposed of) were discounted from further analysis. Of the 13 metrics evaluated, only measures of species number and Margalef’s species richness index were significantly correlated. Although assemblage types were significantly different between stations, common time patterns were observed, indicating that underlying larger scale, low-frequency events may have influenced assemblage development at all locations.

Lights, camera and acoustics: Assessing macrobenthic communities at a dredged material disposal site off the North East coast of the UK

This study presents the results of a trial assessment based on a combination of sampling techniques at a dredged material disposal site located off the North East coast of the UK, over 2001 to 2004. The site was surveyed with a high-resolution sidescan sonar system producing a mosaic with 100% coverage of the survey area. Benthic communities and sediments were ground-truthed using a Hamon grab with a video camera. Additionally, the area was also sampled in 2003 with a Sediment Profile Imaging (SPI) camera, which complemented other techniques by providing in situ information on sediment quality, and biogenic activities. An assessment is made of the benefits of combining the results from conventional methods, principally using grab samples, with those from acoustic techniques and optical imaging devices to determine seafloor and macrobenthic conditions. This information has the potential to contribute to the enhancement of routine monitoring programmes within UK waters.