Confined Disposal Facility Research Articles

Recovery of the NJ marine transportation system in the wake of Superstorm Sandy: A 10-year retrospective

The New Jersey Department of Transportation’s Office of Maritime Resources (NJDOT/ OMR) is responsible for operations and maintenance of more than 200 nautical miles (nmi) of shallow draft navigation channels in the Atlantic coastal region, as well as providing capacity for dredged material management to the U.S. Army Corps of Engineers to maintain the 117-mile New Jersey Intracoastal Waterway. When Superstorm Sandy made landfall in fall 2012, an estimated $65 million in damage was caused to state infrastructure in the form of severe shoaling, shoreline erosion, and berm loss on confined disposal facilities. In the decade since, the NJDOT/OMR has dredged 1.9 million CY of sediment and beneficially used over half of that in resiliency projects ranging from shoreline stabilization and marsh enhancement to restoration of shallow water habitat at a cost of over $120 million. Another 2.0 million CY of sediment has been dredged by the U.S. Army Corps of Engineers (USACE) in the same timeframe, with 60% being used in resiliency projects. In addition to these projects, NJDOT also repaired and strengthened five confined disposal facilities, improved storm preparedness, and created a pathway toward a more sustainable maintenance program for New Jersey’s waterways. A summary of these projects is presented, along with lessons learned and considerations for dredging and beneficial-use practitioners.

Multi-year planning for optimal navigation channel dredging and dredged material management

Navigation channels are critical maritime infrastructure that supports economic and recreational activities and intermodal freight supply chains, impacting broad areas of the hinterland. Maintenance of the maritime infrastructure is vital to the operations of the transportation system. This paper studies a strategic-level maritime infrastructure asset management problem: multi-year planning of navigation channel maintenance dredging and dredged material management. A mathematical model called dredging planning optimization model (DPOM) is developed to optimize channel dredging planning and dredged material management in confined disposal facilities (CDFs), accounting for practical constraints and considerations, including channel linkage and dependency, channel bundling, CDF accessibility and capacity, shoaling and navigability deterioration over time, reimbursable costs, channel economic values, etc. The problem is formulated as a mixed integer nonlinear programming (MINLP) model, with the objective of maximizing the total economic-value-weighted average navigability under fixed budget. The model can be reformulated as an equivalent mixed integer programming (MIP) model, which can be solved by the CPLEX solver, using the branch and bound algorithm. A heuristic algorithm called the dynamic planning prioritization (DPP) algorithm, is proposed in order to solve large-scale problems due to the computational complexity. DPP incorporates a dynamic ranking criterion to overcome the challenge of simultaneously handling all of the practical constraints and considerations, as well as the impact of channel prioritization on future year decisions. Finally, a real-world case study is proposed to illustrate the model results and demonstrate the effectiveness of the MIP model and the DPP algorithm.

Dredged Material Decision Tool (DMDT) for Sustainable Beneficial Reuse Applications

The Dredged Material Decision Tool (DMDT) was developed by the United States Environmental Protection Agency (USEPA) to allow project managers, stakeholders, and communities to quantify environmental, economic, and social considerations of using dredged material for beneficial purposes. Dredged material may be disposed in a confined disposal facility (CDF); however, this option is unfavorable because of the finite capacity problems these facilities pose. A more sustainable option is to use dredged materials beneficially such as construction material, for habitat restoration, or for brownfield remediation projects. This study demonstrates the applicability of the DMDT to three relevant candidate projects: (1) Dog Beach, Greenwood, and Lee Street Beaches (Evanston, IL, USA); (2) New York-New Jersey Harbor (New York/New Jersey); and (3) Poplar Island (Chesapeake Bay). The DMDT requires the project information and then completion of worksheets with each criteria (biophysical environment, economic, governance, social, and built environment) ranked, weighed, and scored. The DMDT is applied for all potential alternatives and the results are then analyzed to select the best beneficial reuse alternative. It was found that for the beaches in Evanston, the most beneficial option was on-beach placement with hydraulic dredging. The best option for the New Jersey Harbor was found to be using for brownfield and landfill remediation. The best option for Poplar Island was the lateral and vertical expansion of 50% uplands and 50% wetlands. Overall, DMDT is found to be a valuable tool to facilitate the evaluation of multi-criteria based on the project-specific data and help select the best beneficial use alternative for the dredged material.

Marmaray (Bosphorus Crossing)

It is possible to construct deeper and longer immersed tunnels when the connection to land, ventilation, emergency evacuation systems, connection details between elements and similar key features are assessed and designed appropriately. Being the deepest and one of the most challenging immersed tunnels constructed to date, the Bosphorus Crossing included various innovative techniques.The Bosphorus Crossing project is located in Istanbul, Turkey, connecting the European and Asian sides of the city. The works included a double-track railway immersed tunnel with a length of 1387 m at a maximum depth of approximately 60 m below sea level. The tunnel consists of a total of 11 tunnel elements 15.3 m wide and 8.6 m high. Elements were constructed as reinforced concrete (RC) with an external steel waterproof membrane and with a transition to sandwich section for the element joint areas. Element no.11 also had a full-sandwich section in the vicinity of the access shaft connection. Design life of the permanent structures is 100 years. Elements were prefabricated in two drydocks approximately 40 km from the immersion site. Due to the expected severe seismic shaking, a sand foundation was unsuitable. A gravel foundation was placed low and roughly levelled using a remotely operated blade. Under-base grouting was injected from inside the tunnel elements to fill all gaps between the gravel foundation and the bottom slab.The tunnel is in a high seismic zone of Magnitude 7.5, which was considered in the design. Towards the Asian end of the tunnel, ground improvement using compaction grouting was used to minimize the risk of soil liquefaction. A total of 1.2 million m3 of seabed was excavated, of which 118,000 m3 was contaminated soil that had to be dumped in a confined disposal facility created on land nearer the Black Sea. The adjacent bored tunnels were constructed using tunnel boring machines (TBMs) that were driven at depth through pre-mixed soil into receiving chambers at the two ends of the immersed tunnel.

Healthy Port Futures: Rethinking Sediments for Rivermouth Landscapes

Throughout the Great Lakes, port cities are often located on the rivermouth and where rivermouths once sorted, shaped, and moved the riverine sediment into the lake. Their current use as industrial navigation channels requires cyclical mechanical maintenance dredging. Past sediment management practices have either placed the riverine sediment nearshore in confined disposal facilities (CDFs) or out in deeper open water. Both practices remove the sediment from the nearshore system, preventing its potential use in coastal protection, habitat creation, wave attenuation, and sediment nourishment. However, novel rivermouth wetlands can draw from both strategies of containment (as in a CDF) and cost-efficiency of non-containment (open lake disposal) to allow for the processing and use of sediment. This article will describe one such attempt, conducted by the Great Lakes Protection Fund-supported Healthy Port Futures project. Through a collaborative design-research process, Healthy Port Futures used a range of tools to generate, speculate, model, visualize, and test wetland forms under a range of social, ecological, and hydrological conditions. This project, understood colloquially as “the Crescent,” proposed a semi-circular, partially open-cell wetland design as a response to the complexity of rivermouth conditions. Throughout this design-research process, the project sought to acknowledge uncertainty, assess risk, and explore a range of outcomes in order to redefine the public expectations around wetland creation and restoration, and reimagine innovation along the Great Lakes coast.

Eco-friendly dredged material-cement bricks

The increasing concerns about natural-resource depletion and environmental degradation have resulted in developing “green” products and switching to sustainable manufacturing processes. The conventional fired clay bricks and concrete masonry still play vital roles in the construction industry. However, the use of virgin materials and carbon emissions associated with their production have raised questions about their environmental sustainability. This study investigates the potential of using dredged material from a confined disposal facility (CDF) in Cleveland, Ohio, to fabricate eco-friendly bricks. The brick samples were made using mixtures of sand, sieved from the dredged material, with 8%, 10%, and 12%, by weight, of Type I/II cement, and compacting the samples using a pressure of 2 MPa or 4 MPa. The compressive strength, water absorption, and freeze–thaw resistance of the bricks were evaluated in the laboratory per American Society for Testing and Materials (ASTM) method C67. The compressive strength of the bricks ranged from 10.3 MPa to 17.2 MPa, whereas absorption ranged from 13% to 18%. The 50-cycle freeze–thaw (F-T) weight loss ranged from 0.1% to 0.4%, demonstrating that durable bricks, meeting the ASTM specifications (0.5% maximum F-T weight loss after 50 cycles), could be produced using the dredged material. Furthermore, a life cycle inventory of dredged material–cement brick (DM-CB) was established to compare its environmental impacts with conventional fired clay brick, concrete masonry units, and compressed stabilized brick. The DM-CB was observed to have the least embodied energy of 1.49 MJ/kg and an embodied greenhouse gas emission of 0.162 kg CO2e/kg, making it the eco-friendliest and environmentally sustainable product compared to conventional bricks.

Application of polyoxymethylene passive air sampler to monitor hydrophobic organics in air around a confined disposal facility

Volatile losses of hydrophobic organic contaminants from a confined disposal facility (CDF) containing dredged contaminated sediments is of substantial concern to surrounding communities. A partitioning passive sampling approach using polyoxymethylene (POM) was applied to measure long-term average (weeks to months) air concentrations resulting from evaporation at a CDF. Measurements at 10 locations surrounding the CDF using the POM air samplers indicated that the highest concentrations of ΣPCBs∼13 ng/m3 and ΣPAHs ∼65 ng/m3 were measured during an active dredge material placement period when the average temperature was 23 °C. The measurements were dominated by the more volatile, lower molecular weight compounds of each type. Partitioning to the POM during the post dredge material placement period with average temperature of 5 °C was corrected for temperature and the measured ∑PCBs and ∑PAHs were ∼3 ng/m3 and 45 ng/m3 respectively. The partitioning passive sampling measurements agreed well with the available weekly 24-h high-volume air samples (HVAS) averaged over the POM equilibration time for lower congener number PCBs (15, 18, 20/28 and 31) and naphthalene but were as much as 10 times lower than HVAS for high molecular weight PAHs. The difference was likely the result of the greater association of these PAHs with particulates and sources other than evaporation from the CDF. The POM air sampler achieved the goal of providing a long-term average air concentration without having to collect, analyze and average multiple HVAS samples although the technique is largely limited to the lower molecular weight PAHs and PCBs and different equilibration times for different compounds complicate its use and analysis.

Development of polyoxymethylene passive sampler for assessing air concentrations of PCBs at a confined disposal facility (CDF)

In this study, 76 μm polyoxymethylene (POM) strips were evaluated as a passive air sampler (PAS) for monitoring the volatile emissions from dredged material placed in confined disposal facilities (CDF). Laboratory evaluations were used to assess the uptake kinetics, average equilibrium time, and estimate the POM-air partition coefficients (KPOM-A) of 16 PCB congeners. The uptake kinetics defined the effective averaging time for air sampling and ranged from about a week for dichlorobiphenyls to 2 weeks or more for tetra- and pentachlorobiphenyls at ∼20 °C under internal mass transfer resistance control which was applicable for Log KPOM-A < 8. The measured Log KPOM-A for PCBs ranged from 5.65 to 9.34 and exhibited an average deviation of 0.19 log unit from the theoretical value of KPOM-W/KAW. The PAS approach was then tested with a preliminary field application (n = 17) at a CDF allowing equilibration over 42 days. The field application focused on lower congener PCBs as a result of the estimated increase in KPOM-A and longer uptake times expected at the low ambient temperatures during the field study (average of 3.5 °C). Total PCB air concentrations around the CDF averaged 0.32 ng/m3 and varied according to proximity to placement of the dredged materials and predominant wind directions. Average PAS concentration of low congener number PCBs (15, 18, 20/28, 31) were compared to available high volume air sampler (HVAS) measurements. The PAS concentrations were within 20% of HVAS in the dominant north and south directions and showed similar trends as east and west HVAS samplers although PAS concentrations were as much as an order of magnitude below the west HVAS.

Mathematical Modeling of Ice Thrusting on the Shore of the Vistula Lagoon (Baltic Sea) and the Proposed Artificial Island

Coastal lagoons are inland and shallow water bodies, separated from the ocean by a barrier. In cold regions, ice phenomena in shallow water coastal lagoons occur every winter season. Ice is predominantly formed on the surface due to density stratification and surface cooling. The ice dynamics in such areas are dominantly affected by winds. Water dynamics also cause ice movement, but due to the large areal scale of lagoons, the effect is usually limited to the direct vicinity of river estuaries. For open lagoons, which are connected to the sea by straits, tides will also cause significant movement of the ice inside the lagoon. Due to the limitation of ice outflow from a lagoon, ice fields will form ridges or hummocks on the shores. In this paper, the case of the Vistula Lagoon, located on the southern Baltic coast, is analyzed. Currently, the project of a new strait connecting the Baltic Sea with the Vistula Lagoon is in progress. As an effect of extensive dredging for the waterway to the port of Elblag, the material will be disposed of at a Confined Disposal Facility (CDF), which will form an artificial island. The island will be located on the western part of the lagoon, limiting the cross-section by about 20%. In consequence, ice cover pushed by winds blowing along the lagoon will create significant force action on the island banks. The DynaRICE mathematical model has been used to evaluate the ice dynamics and to determine the force produced by the ice on the coasts of the lagoon and the artificial island.

Assessment of heavy metal release from dredged materials for different disposal scenarios: Study of Anzali international wetland, Iran

In aquatic systems, heavy metals are accumulated in sediments that can release from loosely bound fractions during dredging and disposal operations. Five sediment samples were collected from the entry of the Pasikhan River to Anzali wetland, where dredging is carried out. The heavy metal distribution in sediments was determined using a sequential extraction procedure that showed Pb and Cd contribution mostly to non-residual phase (>80%). Heavy metal release from dredged materials was assessed for different disposal scenarios using pathway specific leaching tests. The highest release was attributed to Pb and Cd in open-water disposal (232 and 12.6μg/L, respectively), confined disposal facilities (CDF) (180 and 12.2μg/L, respectively), and landfilling (679 and 5.6μg/L, respectively). The metal bioavailability and bioaccessibility were assessed using single extraction methods for agricultural use and other disposal scenarios. The metal bioavailability was in the order of Cd ∼ Pb>Cu>Mn>Zn>Fe>Ni>Cr. In case of open-water disposal, metal concentrations in water column were higher than water quality standards but lower than background amounts at the disposal site. In confined disposal, the concentrations in effluent and leachate of CDF occasionally exceeded the allowable limits. Finally, in case of landfilling, metal concentrations in leachate exceeded that of other methods, but remained below the USEPA recommended limits. According to implemented risk assessment indices, the risk level for heavy metal bioavailability and bioaccessibility was medium and very high, respectively, and Cr had carcinogenic and non-carcinogenic risk for human health.

Design of a GIS-based rating protocol to assess the potential for landfill closure using dredge material in post Hurricane Sandy New Jersey

ABSTRACTNew Jersey is rapidly running out of capacity for storage of dredged material. A potential solution to this lack of storage space is to remove and reuse the dredged material for some beneficial use. Results from a Rutgers University project performed for the New Jersey Department of Transportation, Office of Maritime Resources, designed to assess the potential for closure of New Jersey landfills using dredge material from existing Confined Disposal Facilities (CDFs) are presented and discussed. The project included an update of the existing NJDEP landfill database, the development of a rating system to identify landfills with the highest potential to utilize dredged material for their closure, and the identification and preliminary investigation of the top candidate landfills based on this rating system.

Contaminants of emerging concern in Caspian tern compared to herring gull eggs from Michigan colonies in the Great Lakes of North America

A broad suite of 87 contaminants of emerging concern (CECs), including 26 polybrominated diphenyl ethers (PBDEs), 23 non-PBDEs halogenated FRs (NPHFRs), 16 organophosphate esters (OPEs), 4 perfluorinated sulfonates (PFSAs), 13 perfluorinated carboxylic acids (PFCAs) and 5 emerging perfluoroalkyl acids (PFAAs) or precursors, were determined in 30 individual Caspian tern (listed as a threatened species in the U.S. State of Michigan) eggs collected in 2013 and 2014 from Michigan nesting sites on Two Tree Island (St, Mary's River), Charity Reef (Saginaw Bay) and Channel-Shelter Island (a Confined Disposal Facility (CDF) in Saginaw Bay). The same CEC suite was determined in 10 herring gull eggs on the Pipe Island Twins in the lower St. Mary's River. In tern eggs, the order of concentrations were ΣPFSA (mean: 793 ng/g wet weight (ww); range: 116–4690 ng/g ww) > ΣPFCAs (131; 30.4–506 ng/g ww) ≈ ΣPBDEs (86.7; 32.4–189 ng/g ww) » ΣNPHFRs (0.67; ND-4.3 ng/g ww) ≈ ΣOPEs (0.46; ND-2.89 ng/g ww). Compared to gull eggs collected from the same area, tern egg exposure contained significantly lower concentrations of ΣPBDE, but with up to 10 times greater mean concentrations of ΣPFSAs and ΣPFCAs. This study highlights the importance of consistent monitoring in eggs of different Great Lakes birds of PBDEs, perfluorooctane sulfonate (PFOS) and perfluoro-4-ethylcyclohexane sulfonate (PFEtCHxS) given that: 1) PBDE concentrations in all analyzed avian eggs exceeded or approached a concentration of 29 ng/g ww, which for birds is the current Canadian FEQG (Federal Environmental Quality Guideline); 2) ΣPBDE concentrations were comparable to lowest observed effect concentration (LOEC) values reported in the literature; 3) PFOS concentrations in Caspian tern eggs were extremely high with many eggs across sites exceeding 1 ppm, and with the greatest being up to 4.7 ppm; and 4) PFEtCHxS, a potentially persistent and bioaccumulative substance, showed a detection frequency of 100% in 40 of the analyzed eggs.

Evaluating soil properties and potential nitrate removal in wetlands created using an Engineering With Nature based dredged material placement technique

Many waterways around the globe, including those in southern Louisiana, require periodic dredging to maintain navigability in channels, rivers, and at ports. Traditionally, dredged materials are deposited in confined disposal facilities, relegated to deep open water disposal, or used as fill material to build wetlands. Over the past 15+ years, dredge material from the Atchafalaya River was strategically placed up-river of a small, natural shoal, located mid-channel, resulting in the creation of a wetland exhibiting many structural characteristics of the naturally occurring riverine wetlands within the basin. This construction practice adheres to Engineering With Nature (EWN) concepts which utilize natural processes to produce maximum benefit for navigation, while lowering economic costs and improving habitat features. The current study determined soil physical, nutrient, and biogeochemical properties at the EWN wetland and compares these characteristics to values observed at a traditional dredge shoreline material placement wetland (TDMP), essentially examining the effect of construction technique on soil biogeochemical properties. Soil total carbon and nitrogen at EWN continued to accumulate with time; however, TDMP exhibited a significantly higher degree of soil formation as indicated by lower bulk density, and higher soil organic matter, carbon, and nitrogen. Despite the observed differences, rates of potential nitrate removal and microbial biomass nitrogen did not differ between wetlands, suggesting that the nature based construction technique resulted in nutrient cycling and nitrate removal capacities equivalent to traditionally constructed dredged material wetlands in the region.

Designing dredge: engaging the sediment landscapes of the Great Lakes Basin

In many cities within the Great Lakes region—on the water or next to the old steel mill, water treatment plant, or coal-fired power station—there sits a green behemoth. Likely riddled with invasive biota, these places are sediment dumps; landfills for wet soil. Generally given the name Confined Disposal Facilities (CDFs), these engineered landscapes serve the purpose of containing sediment dredged from an adjacent harbour or ship channel. This process creates landscapes that contain layers of eroded sediment from the surrounding urban watershed. Currently, the Great Lakes have over fortyfive CDFs—some still in operation and others that are at capacity, or otherwise abandoned. This article will examine this process of dredge-land creation in the Great Lakes region as one of incredible ecological and social potential by illuminating key projects and speculating upon the expanded role of the landscape architect in creatively leveraging these potentials.

Stability of Capped Dredged Sediments in a Confined Disposal Facility at Malmøykalven, Oslofjord, SE Norway

Conventional sediment capping is a widely used technique where clean sediments are placed over contaminated sediments to reduce the migration of contaminants to the environment. A concern of the method is initial contaminant transport through the cap during the consolidation of the underlying disposed sediments. The current study was conducted to investigate the efficiency of the cap placed over the Malmøykalven confined disposal facility (CDF). The thickness of the soft disposed sediments reached 6 m in maximum, and was subject to extensive consolidation when the cap was placed. Vertical profiles of trace metals (Cd, Cu, Hg, Pb, Zn) and the structure of the cap layer were studied in six gravity cores. The cap material was clearly distinguishable in the sediment cores, both visually and chemically. The results provided evidence that consolidation-induced pore water advection was able to transport fine particles (<63 µm) and organic material into the cap layer. Metal transport in the particulate phase was suggested to be the main transport process into the cap layer. The study shows the importance of an appropriate cap layer design to prevent any particle transport and to minimize the effects of consolidation-induced advective transport.

Release of Potentially Toxic Elements From Industrial Sludge: Implications for Land Disposal

In recent years, rapid industrial development has led to an increase in various types of industrial waste generation in Vietnam. Potentially toxic elements (PTEs) can contaminate water resources when waste is not properly treated and/or stored in confined disposal facilities. This study characterizes the occurrence and leaching behavior of PTEs from industrial sludge under the influence of oxidation and pH with implications for open dump disposal. Environmental issues related to possible management options are also addressed. Sludge samples from industrial parks at Binh Duong and Dong Nai, Southern Vietnam, were oxidized under atmospheric conditions. The results indicate that Fe and Mn (both samples) and Cu, Ni, and Zn (Binh Duong sample) may pose a potential threat to the water quality for sludge dumped near water bodies. Therefore, we recommend avoiding uncontrolled upland disposal of such sludge. Some preliminary treatment to immobilize PTEs should be applied to the sludge originating from Binh Duong prior to upland disposal. A recovery of Ni and Zn from this sludge could be considered. For the less contaminated sludge from Dong Nai, beneficial use, such as land application for agricultural purposes, is a possible option.

Sand Cap Placement and Cap Thickness Monitoring: A Case Study at a Confined Disposal Facility

Thin sediment capping is a commonly used technique to prevent mobilization of contaminants from sediments into the environment. A 70‐m‐deep subaqueous confined disposal facility (CDF, 350,000 m2) at Malmøykalven, Oslofjord, which received dredged contaminated sediments from Oslo Harbor, was capped with 148,900 m3 of sand in 2009. This research serves as a case study regarding some of the key considerations involved with the cap placement and monitoring of the cap layer. Uncertainty is included in all the cap thickness monitoring methods and a combined use of them provided a better understanding of the cap coverage and structure at the site. An open water disposal model (STFATE) was used to simulate the behavior of the barge‐released cap material. The modeling results were consistent with field observations regarding the material spread, and the results provided insight into the relatively high material losses calculated. Better knowledge obtained of material settling resulted in cap properties and cap monitoring methods that are useful when planning similar operations. ©2015 Wiley Periodicals, Inc.

Methodology and determination of tetradecabromo-1,4-diphenoxybenzene flame retardant and breakdown by-products in sediments from the Laurentian Great Lakes

Tetradecabromo-1,4-diphenoxybenzene (TeDB-DiPhOBz) is a brominated polyphenyl ether flame retardant (FR) that is known to photolytically degrade to produce lower brominated polybrominated-diphenoxybenzenes (PB-DiPhOBzs), which may be precursors to MeO-PB-DiPhOBzs recently reported in the Great Lakes herring gulls eggs. To our knowledge, there are no reports on TeDB-DiPhOBz or other PB-DiPhOBz by-products in any environmental sample. The present study analyzed for the presence of PB-DiPhOBzs (including TeDB-DiPhOBz) and MeO-PB-DiPhOBzs in surficial sediment from sites in Saginaw Bay in western Lake Huron (n=7), and in comparison to southern Lake Huron (open water) (n=5) and Lake Erie (n=3) sediment collected in the summers of 2012 or 2013. To analyze for possible PB-DiPhOBzs (Br14–Br0), the first known analytical method was developed for extraction and cleanup of sediment samples, and analysis by HPLC–atmospheric pressure photoionization (−)-quadrupole time-of-flight-mass spectrometry. The overall recovery efficiency was optimized to on average 33–104% progressing from Br14- to Br10-PB-DiPhOBzs. Br10- to Br14-PB-DiPhOBz detection and quantification limits ranged from 0.05 to 0.15ngg−1 dw and 0.17 to 0.49ngg−1 dw, respectively. Although this is the first report, PB-DiPhOBzs (Br14–Br10) and MeO-PB-DiPhOBzs were not detectable in any sediment sample. This included a site near the mouth of the highly FR-contaminated Saginaw River, near the confined disposal facility (CDF) located in Saginaw Bay at Channel-Shelter Island, which receives dredged sediment from the Saginaw River. Our findings suggest sediments from the presently studied sites in the Great Lakes ecosystem are not a sink for TeDB-DiPhOBz and PB-DiPhOBz by-product contaminants.

Environmental recovery in Sydney Harbour, Nova Scotia: Evidence of natural and anthropogenic sediment capping

Contaminants were assessed in Sydney Harbour during baseline and three years of remediation of a former coking and steel facility. Concentrations of PAHs; PCBs; and lead measured in surface sediments indicate overall spatial distribution patterns of historical contaminants remains unchanged, although at much lower concentrations than previously reported due to natural sediment recovery. Recovery rates were in broad agreement with predicted concentrations; or in some cases lower, despite remediation at the Sydney Tar Ponds (STP) site. Contaminants showed little temporal variability, except for detection of significant increases in PAH concentrations during onset of remediation compared to baseline which represented a short term interruption in the overall long term natural recovery of sediments in Sydney Harbour. Recovery (via “capping”) was enhanced following recent harbour dredging activities where less contaminated outer harbour sediments were discharged into a confined disposal facility (CDF) required for a new container in the inner harbour.

Planning dredging services in contaminated sediments for balanced environmental and investment costs

Dredging of contaminated sediments has shown to be a harmful activity for the environment, because a number of contaminants can be resuspended and become available to the organisms. Furthermore, dredged contaminated sediments may cause significant damages in the dumping site. In order to avoid the drawbacks of this activity, better techniques have to be developed and the present article presents a new procedure for the planning of dredging that reduces the environmental impacts by reducing the amount of dredged sediments and, at the same time, reduces costs. The new technique uses screening of contaminant concentrations in the sediments that are normally part of the environmental impact assessment for dredging activity. A detailed mapping of the contamination, layer by layer is carried out and the areas where the action levels are reached are outlined with polygons, establishing limits within which sediments have to be dredged with safe procedures. In the case presented, construction of a harbor in Sepetiba Bay, Rio de Janeiro, Brazil, the safe procedure is cutter/suction dredging and pumping into a sub-aquatic confined disposal facility (CDF). A detailed evaluation of costs showed that if the whole layers of sediment were to be dumped into the CDF, the cost of the activity would be at least 63.82% more expensive than the proposed procedure, constituting an attractive advantage. Furthermore, as the size of the CDF is significantly smaller, less dredging is necessary, causing smaller environmental impact.