Design Resources

Hartman, E.; Kim, K.; Santiago, R.; Joyner, R.; Grahm, M.. (2014). “The use of a thin-layer cap to manage Hg and PCB Contaminated Sediments in Peninsula Harbor, Ontario, Canada..” Presentation

Keywords:Mercury, PCBs, Pulp Mill, Chlor-Alkali Plant, Capping

Summary:The slide show describes thin-layer capping for in-situ remediation of mercury and PCB contaminated sediments in Peninsula Harbor, Ontario. Engineering design, contracting, environmental mitigation measures, implementation and monitoring are covered. Descriptive photographs are included.

What You Will Find Here:Slides

Wilson, David; Rudolfo, Nicholas’ Noble, Bruce; Lally, John; Hewitt, Ronald; Kim, Kay; Grover, Barry.. (2014). “Implementation of a Thin Layer Cap on Lake Superior in Marathon, Ontario” Presenation RPIC-FCS Workshop April 14-16, 2014 Ottawa

Keywords:Construction, Monitoring

Summary:Principal discharges resulted from untreated pulp mill effluent and treated effluent from a chlor-alkali plant which operated from 1977 to 1984. Marathon Pulp and Paper filed for bankruptcy in 2009 and ceased operation. Investigations dating back to 1980 have measured elevated mercury and PCBs in Cove sediments. Sediments not toxic to benthic organisms, but affect upper trophic community including reproductive success of bottom feeding fish. Options considered included dredging and capping alternatives. Presence of higher levels of contamination at depth and risk of resuspension were concerns with dredge options. Thin layer sand cap provided ability to achieve adequate risk reduction and to provide enhanced natural recovery of the site. Prescribed remedy is placement of 15 – 20 cm layer of clean sand over defined contaminated “hot spots”.

What You Will Find Here:Construction p. 13; Monitoring p. 20

Lin, D.; Cho, Y-M; Werner, D. Luthy, R.G.. (2014). “Bioturbation Delays Attenuation of DDT by Clean Sediment Cap but Promotes Sequestration by Thin-Layered Activated Carbon.” Environ. Sci. Technol. 48, 1175-1183

Keywords:Thin Layer Activated Carbon, DDT, Bioturbation

Summary:A thin-layer of clean sediment does not reduce DDT flux when bioturbation is occurring. In contrast, a thin layer of activated carbon is more effective at reducting DDT flux with bioturbation than not having bioturbation. A mass transfer and biodynamic model were used to simulate DDT flux and bioaccumulation.

What You Will Find Here:Methods and Materials p. 1176, Modeling p. 1177, Results and Discussion p. 1178

Algar et al. . (2013). “Processes, Assessment, and Remediation of Contaminated Sediments.” Ed. Reible, D.D. Springer. New York.

Keywords:Sediment Deposition, Enhanced Monitored Natural Recovery, Thin-Layer Placement and Stability

Summary:Engineered thin-layer placement is best for remediating moderately elevated concentrations, under quiescent conditions, and where there is minimal natural background sedimentation. A variety of placement techniques are discussed. Lessons from a few case studies are mentioned. The usefullness of SPI camera survies is highlighted.

What You Will Find Here:Sediment Deposition p. 243, Thin-Layer Placement and Stability p. 248

Delaware Department of Natural Resources and Environmental Control. (2013). “DNREC’s first beneficial-reuse marsh restoration project succeeds with thin-layer spray application.” Press Release. Vol. 43, No 212, p. 30, 5-21-13

Keywords:thin-layer placement, marsh restoration, Delaware

Summary:Thin-layer placement of dredged materials was to restore marsh in Pepper Creek satisfied multiple objectives and will serve as a model for similar projects in Delaware.

What You Will Find Here:Webpage

Graham, M.; Hartman, E.; He, C.; Droppo, I.G. . (2013). “Examining thin layer cap behaviour in a freshwater industrial harbor.” J Soils Sediments. 13, 1515-1526

Keywords:Bottom shear stress, Critical shear stress, Dredging, Randle reef, Residuals, Thin layer capping

Summary:A 60 ha remediation area in Hamilton Harbor, Lake Ontario will involve dredging, capping, and thin-layer capping. The site is contaminated with PAHs and heavy metals. The study focused on predicting bottom shear stress that could compromise the thin-layer cap. Bottom shear stresses exceeded critical shear stresses from both weather conditions in shallow areas and from large cargo vessels. The thin cap may require larger grain sizes in some areas to prevent erosion. The overall effect on the remediation area is expected to be minimal from localized erosion events of up to 8 mm on a 16 cm thin layer cap.

What You Will Find Here:Materials and Methods p. 1517, Results p. 1520, Discussion p. 1522

St. Clair Region Conservation Authority. (2013). “St. Clair River Contaminated Sediment Management Options.

Keywords:monitored natural recovery, thin-layer capping, activated carbon, capping, dredging

Summary:The contaminated sediment remedy options are defined for the St. Clair River. The options include: monitored natural recovery, thin-layer placement (including possibly activated carbon amendment), isolation capping, and dredging. The risks of dredging are explained.

What You Will Find Here:Webpage

Samuelsson, G. . (2013). “In situ remediation of contaminated sediment using thin-layer capping – efficiency in contaminant retention and ecological implication.” Stockholm University. Printed by US-AB, distributed by Department of Ecology, Environment and Plant Science (DEEP)

Keywords:Sediment Remediation, Benthic Resilience, Activated Carbon Amendment, Thin-Layer Capping

Summary:Boxcores were taken from Langangsfjord, Norway. Test capping materials included activated carbon, Kraft lignin, sand, hyperite, clay, plaster, and marble. Four papers were reviewed: on ecological effects of the capping materials, on reductions of contaminant flux by capping materials, on bioaccumulation reductions by capping materials, and on a field experiment in Grenlandfjords, Norway.

What You Will Find Here:Background p. 10, In situ remediation techniques Figure 1 p. 16, General findings p.17, Discussion p. 23

Kay Kim, Sue-Jin An, Roger Santiago, Victoria Renner, Rupert Joyner, Anne Borgmann, Matthew Graham, and Erin Hartman. (2012). “The Use of Thin-Layer Cap to Manage Hg and PCB Contaminated Sediments in Jellicoe Cove, Peninsula Harbour, Ontario, Canada.” Environment Canada Sediment Remediation Unit Presentation

Summary:Case study of Thin-Layer Cap in Jellicoe Cove, Peninsula Harbour, Ontario, Canada. Planning, design, construction, and monitoring is discussed.

What You Will Find Here:Remediation (Hg & PCB) p. 6, Planning p. 7, Monitoring p. 13, 56, Construction p. 30,

Näslund, J.; Samuelsson, G.S.; Gunnarsson, J.S.; Nascimento, F. J. A.; Nilsson, H. C.; Cornelissen, G.; Schaanning, M. T.. (2012). “Ecosystem effects of materials proposed for thin-layer capping of contaminated sediments.” 449, 27-39

Keywords:Remediation in situ, Activated carbon, Clay, Structural and functional effects, Benthic organisms, Sediment, Mesocosm

Summary:Boxcosms with intact sediment fauna were used to assess ecosystem effects of thin-layer capping with different materials. Clay (suspended and lumps), sand, hyperite, powdered activated carbon (AC), Kraft-lignin, marble (coarse and fine) and plaster were used as capping materials. Structural endpoints such as: macrofauna community, meiofauna community, and bacterial community were assessed. Functional endpoints such as: bacterial production, biogeochemical fluxes, and oxygen penetration depth in the sediment were also assessed. Based on the results, marble, plaster, and Kraft-lignin should not be used unless modified. AC had fewer negative ecological effects and has a high sorption capacity for hydrophobic organic contaminants. AC may be more effective if mixed with clay or applied directly before phytoplankton blooms in the spring.

What You Will Find Here:Materials and Methods p. 28, Results p. 31, Discussion p.35

Palermo, M.R.; Maynard, S.; Miller, J.; Reible, D.D.. (2012). “Guidance for In Situ Subaqueous Capping of Contaminated Sediments.” USEPA.

Keywords:Capping, Contaminated Sediments

Summary:This webpage provides guidance on: direct mechanical placement, surface discharge of material, spreading by barge movement, piping with baffle plate or sand box, submerged diffusers, spreader barges, tremies and hopper dredges. Armoring layers, geomembranes and fabrics are also discussed.

What You Will Find Here:Webpage

Cornelissen, G.; Krusa, M.E.; Breedveld, G.D.; Eek, E.; Oen, A.M.P.; Arp, H.P.H.; Raymond, C.; Samuelsson, G.; Hedman, J.E.; Stokland, O.; Gunnarsson, J.S.. (2011). “Remediation of Contaminated Marine Sediments Using Thin-Layer Capping with Activated Carbon – A Field Experiment in Trondheim Harbor, Norway.” Environ. Sci. Technol. 45, 6110-6116

Keywords:Thin-Layer Caps, Activated Carbon, PAHs, Norway

Summary:Thin-layer caps of activated carbon (AC) mixed with clay, AC alone, and AC with a sand covering were domonstrated in Norway as a remediation strategy for PAH contaminated marine sediment. The site was in 4-6 m depth water that had a tidal amplitude of 1-2 m with currents of up to 20 cm/sec. The AC slurries were made denser than surrounding water by soaking in a 10% w/w NaCl solution, and was applied using a flexible manually opperated hose. Application rates were 20 L/min. AC mixed with clay worked best for reducing contaminant flux and minimizing effects to benthic communities. Costs of AC material was about $10/m^2 and placement costs were on the same order-of-magnitude.

What You Will Find Here:Field experiment p. 6111, Results on carbon application p. 6112, Results on reduced PAH concentrations and flux p. 6113, Effects on benthic community p. 6114

Winther, Aina. (2011). “Thin layer capping with biochar on marine sediments contaminated with PAHs, and the effect of different caps on marine sediment contaminated with dioxins.” Thesis Norwegian University of Life Sciences

Keywords:Remediation, Thin layer, Design

Summary:Capping contaminated sediment with clean materials is a remediation method that has proved efficient. Passive capping materials physically isolate the contaminated sediment from the receiving environment and active materials sorb the contaminants, thereby making them inaccessible. Activated carbon is one active capping material that is effective in reducing the diffusion of contamination from the sediment. The objective of this thesis was to investigate if biochar could be applied as an active capping material in remediating contaminated sediment. Another part of the thesis was to investigate thin layer capping with three different materials on dioxin contaminated sediment in the Grenland fjords, as a part of the Opticap project. Field work was conducted in the Ormerfjord and the Eidangerfjord in the Grenland fjords. The aim was to test the efficiency of the capping materials 1) activated carbon and clay, 2) crushed limestone, and 3) clay in order to reduce dioxin diffusion. According to the results, all caps were efficient in reducing the dioxin flux from the sediment, and the flux was the lowest in the crushed limestone field, though there are variations between the measurements. Dioxins in free aqueous phase were also reduced in the capped fields, but there were no clear trends in which cap was the most efficient, due to currents and exchange of sea water. The dioxin flux from the sediment was measured with semi-permeable membrane device (SPMD) and the dioxins in free aqueous phase were measured with polyoxymethylene (POM). The measurements were done by employing a flux chamber which was put on the sea floor and collected at different time points.

What You Will Find Here:Remediation p. 10, Thin layer capping p. 21, 40, 59 Design p. 15, (Freundlich Isotherms p. 35 )

Lampert, D.J.; Sarchet, W.V.; Reible, D.D.. (2011). “Assessing the Effectiveness of Thin-Layer Sand Caps for Contaminated Sediment Management through Passive Sampling.” Envion. Sci. Technol. 45, 8437-8443

Keywords:Thin-Layer, Sand Caps, PAHs, Pyrene, Modeling, Analytical Solution, Passive Sampling, Microcosm

Summary:Passive sampling using polydimethylsiloxane coated fibers was used to monitor PAH migration in thin-layer sand caps with bioactivity in the lab. The method for monitoring allowed for freely dissolved pore water concentrations at 1 cm increments in the cap. Measurements were compared to models where analytical solutions were provided. The passive sampling measurements were correlated with bioaccumulation in the worm, Ilyodrilus templetoni.

What You Will Find Here:Introduction p. 8437, Materials and Methods p. 8438, Analytical Solution for Bioturbation Layer p. 8440, Analytical Solutions for Isolation Layer and Combined Bioturbation and Chemical Isolation p. 8441, Bioaccumulation Predictions p. 8442

ECC and HDR. (2011). “Design Document Report, RECOVERY Houston-Galveston Navigation Channel, Multiple Site Repairs – Phase II.” Prepared for USACE Galveston District. HSC 401-528. September 9th 2011

Keywords:Houson-Galveston Navigation Channel, HGNC, placement, beneficial use, Bolivar Marsh, Evia Island, marsh construction, beach restoration, Hurricane Ike

Summary:This is a design report of a marsh and support structures.

What You Will Find Here:Settlement Estimates for 288 acre Marsh Figure 301 p. 3-3, Data Collection Instrument Locations Figure 4-1 p. 4-2, Measured Water Level at Boilvar Marsh Figure 4-2 p. 4-4, Current Speeds Figure 4-3 p. 4-5, Wind Rose Figure 5-1 p. 5-1, Wind Speeds during Hurricane IKE Figure 5-3 p. 5-3, Waterlevel excedance Figure 5-7 p. 5-6, Shipwaves p. 5-10, Breakwater transmitted wave heights at varying water levels Figure 6-11 p. 6-21, Channels and Ponds p. 7-2, Placement Areas Figure 7-4 p. 7-5, Proposed Pond and Channel Layout Figure 7-8 p. 7-7, 288 Acre Cell at Bolivar Marsh Figure 8-2 p. 8-4, Marsh Layout and Slopes Based on Construction Method p. 8-8, Marsh and borrow layout and weathering p. 8-9, Bay Circulation and Sediment Transport p. 8-12, Ebb Tidal Currents past the Marsh Figure 8-13 p. 8-15, Summary p. 10-1

Bray, R.N. (editor). (2008). “Environmental Aspects of Dredging.” Taylor & Francis Balkema. AK Leden

Keywords:dredged material, beneficial use, aquatic placement, CDFs

Summary:The chapter “Reuse, Recycle, Relocate” defines: benefical use, confined placement, convined disposal facility, and containment measures. Steps in the decision making process for dredged material are provided. Potential uses, aquative placement techniques, and CDFs are covered in detail. The chapter concludes with treatment methods for contaminated dredged material.

What You Will Find Here:Management Alternatives p. 192, Beneficial Use p. 200, Unconfined Aquatic Placement p. 215, Semiconfined Aquatic Placement p. 215, Placement in CDFs p. 228

Ray, G.L.. (2007). “Thin Layer Placement of Dredged Material on Coastal Wetlands: A Review of the Technical and Scientific Literature.” ERDC/EL Technical Notes Collection (ERDC/EL TN-07-1), Vicksburg, MS: U.S. Army Engineer Research and Development Center

Keywords:Thin-Layer Placement, Review

Summary:Thin-layer placement of sediment appears to be generally beneficial for combating sediment depletion, subsidence, and sea-level rise. When hydraulically dredged, liquified, and pumped through a high-pressure spray nozzle, well mixed slurries of uniform layers can be easily placed up to 100 meters from the dredging site. If tranportation costs are not an issue, sediment can be shipped by barge or pumped longer distances. Recovery of different plant species following placement varies. It is often a function of the desired elevation and substrate of the particular species. Placement depth does seem to effect individual plant species on a site specific basis. Water from a sediment slurry has been found to drain rapidly without high levels of turbidity. Oyster larvae can be prevented from settling by just 1mm layers of sediment.

What You Will Find Here:Background p. 1, Discussion p. 5

McDonough, K. M.; Murphy, P.; Olsta, J.; Zhu, Y.; Reible, D.; Lowry, G.V.. (2007). “Development and Placement of a Sorbent-amended Thin Layer Sediment Cap in the Anacostia River.” Soil and Sediment Contamination. 16, 313-322.

Keywords:Sorbent Amendments, Coke, Geotextiles, Remediation, Thin Capping

Summary:Laminated polyester fabrics (geotextiles) can be used to apply thin layer sorbant materials followed by 15 cm of sand placement. A 1100 m^2 area, 1.1 to 5.6 m deep area in the Anacostia River was used to demonstrate this technology in 2004. Flow velocities ranged from 0.003 to 0.4 m/s and plots were contained in a silt curtain during placement. The technique did not lead to significant resuspension or recontamination of the placement area, with the exception of slight elevations of naphthalene. The mats could be placed at a rate of 100 m^2/hr with a crane and divers. Overall placement costs ranged from $29-33/m^2.

What You Will Find Here:Materials and Methods p. 316, Results and Discussion p. 319

Murphy, P., Marquette, A., Reible, D., and Lowry, G.. (2006). “Predicting the Performance of Activated Carbon-, Coke-, and Soil-Amended Thin Layer Sediment Caps..” J. Environ. Eng., 132(7), 787–794

Keywords:Design, Capping, Remediation, Model Development, Attenuation

Summary:This study compares the effectiveness of commercially available sorbents that can be used to amend sand caps to improve their ability to prevent contaminant migration from the sediments into the bioactive zone. Amendments evaluated include coke, activated carbon, and organic-rich soil. The properties relevant to advective-dispersive transport through porous media sorption, porosity, dispersivity, and bulk density are measured for each material, and then used as inputs to a numerical model to predict the flux of 2,4,5-polychlorinated biphenyl PCB through a sand cap amended with a thin 1.25-cm sorbent layer. Systems with and without groundwater seepage are considered.

What You Will Find Here:Design (material selection p. 789, material characterization p. 788, groundwater seepage p. 790), Capping, Remediation (PCB), Model Development (Freundlich p. 789, Flux p. 789 – sorption, porosity, dispersivity, bulk density, simulated cap performance, half-life p. 792), Attenuation p. 791

Joseph Gailani, Douglas Clarke,Timothy Welp. (2006). “Working With Nature Beneficial Use Studies.” Presentation

Keywords:Beneficial Use Case Study, Regulatory, Planning, Cost, Monitoring, Construction

Summary:Overview presentation on beneficial use methods of placement and case study discussion.

What You Will Find Here:Beneficial Use Case Study p. 12, p. 13, p. 16, Long Distance Conveyance p. 6, Regulatory p. 8, Planning p. 9, Cost p. 10, Monitoring p. 17, Thin-Layer Placement p. 23

Murphy, P.J.; Lowry, G.V. (2006). “PCBs in Freshwater and Marine Sediments: Transport, Transformation, and Treatment.” Symposia Papers Presented Before the Division of Environmental Chemistry, American Chemical Society

Keywords:Surface Area Weighted Average Concentration (SWAC), In-Situ Capping, Thin Sand Caps, 1,2 DCB, Tracer Studies, Soil, Coke, Activated Carbon, Partitioning Coefficients, Advection, Dispersion, Retardation, Reactive Core Mat (RCM)

Summary:Traditional methods, such as particle broadcasting, can not accurately deploy thin layers of high sorption materials, such as: soil, coke, or activated carbon. Therefore, the use of a reactive core mat was used to lay down a thin-layer of these materials at the Anacostia field demonstration. Sorption and hydrodynamic properties of the materials were quantified to be applied to sites contaminated with PCBs.

What You Will Find Here:Introduction p. 2, Materials and Methods p. 3, Conclusions p.7

USACE/Interagency Coordination Team (ICT). (2002). “Laguna Madre GIWW Dredged Material Management Plan.

Keywords:Dredged Material Management Plan (DMMP), Interagency Coordination Team (ICT), Corps of Engineers (USACE), Placement Areas (Pas)

Summary:Each placement area for the Laguna Madre Gulf Intracoastal Waterway is reviewed. Best management practices are used for dispersing dredged material such ase energy dissipating devices for spreading out thin layers and decreasing the chance of burying sea grasses. Dredging windows are set from November through February when seagrass is dormant and less effected by turbidity. Generally elevated turbidity due to dredging activity is limited to an area 3/4 to 1 mile from the discharge point and remains up to 3 months after disposal is complete. It has been determined that if no more than 3 inches of dredged material is placed seagrass can recover in 3-5 years. Typical issues in the placement areas involve: hauling or pumping distances being too long for ocean disposal, recuirements of protecting seagrass, or critical habitat for piping plover or black skimmer. The preservation of cabins are also common issues with dredge material placement. The use of the placement areas for dredged material was surveyed between 1949 and 1995.

What You Will Find Here:General Guidelines p. 2, Reach 1 issues with Ocean Placement p. 3, Pas 213-219 issues p. 17, PA 221 Circulation problems p. 18, Issues with Thin-Layer Placement in Reach 5 p. 19, Erosive Currents PA 233 p. 23

Turner, R.E.. (2002). “Approaches to Coastal Wetland Restoration: Northern Gulf of Mexico.” Kugler Publications.

Keywords:Dredged Material, Thin-Layer Placement

Summary:The history of thin-layer placement is covered. Thin-layer placement thicknesses for revegetation are discussed. A case of a failed thin-layer placement on very soft sediments is disscussed. The ability to convert shallow open water to vegetated marsh is possible. Important planning considerations are listed. Cost comparisons relating high-pressure spray placement to bucket dredging are provided. Monitoring of thin-layer placement may involve different attributes of plant health and several different soil/sediment parameters.

What You Will Find Here:Dredged Material Wetlands p. 77, Thin-Layer Placement p. 115

de Leeuw, H.A.; Smits, E.P.T.; Mathijssen, F.A.J.M.; Estourgie, A.L.Ph. . (2002). “Reclamation on Soft Subsoil by Spraying Thin Layers of Sand: The “Ijburg” Project near Amsterdam.” Terra et Aqua. 89. December 2002

Keywords:Sand Excavation, Thin-Layers, Reclaiming Soft Soils, Shear Strength, Pilot Project, Hydraulic Placement

Summary:A stable platform was created on soft subsoil using thin-layer placement of sand. This was accomplished using a custom built spray pontoon. A consolidation period of four weeks was allowed between each layer of sand (50 cm layers). Run off suspended solids were minimized to 400 mg/L using large settlement basins and high flow water pumps. The soft subsoil was a young Halocene clay layer over a Halocene peat and clay-layer (total thickness ranging from 6-12 meters). Vertical drains allowed consolidation periods to be 10 times faster. The geotechnical success of the placement project relied on accurately placing the first thin-layer of sand.

What You Will Find Here:Introduction p. 9, Main Features of the Project and its Design p. 12, Geotechnical Aspects p. 17, Sand Extraction and Overburden Removal by “Clay Relocation” Method p. 26, Spraying Sand p. 28, Reducing Dredging Delays p. 30

Talbert, B.; Thibodeaux, L.J.; Valsaraj, K.T.. (2001). “Effectiveness of Very Thin Soil Layers in Chemical Release from Bed Sediment.” Environ. Progress. 20, 2, 103-107.

Keywords: Thin-Layers, Chemical Flux, Diffusion, Advection

Summary: Natural deposition of clean sediment is a significant part of natural recovery of contaminated sediment sites. Thin-layer placement can be engineered. Physical-chemical processes of diffusion are modeled to estimate flux. Physical experiments showed that, on average, flux was 1.7 times greater than model predictions. Surface-water flows induce advection in the upper layers of the cap and is the likely cause for the underprediction of the model.

What You Will Find Here: Theory using Biot Number p. 104, Experimental Findings p. 106

Anchor Environmental, Inc.. (1999). “Kings County Department of Natural Resources Year 2000 CSO Plan Update Project Sediment Mangement Plan: Preliminary Review of Sediment Alternatives.” Task 1000 Draft Technical Memorandum, January 1999

Keywords:Thin-layer capping

Summary:This document presents a draft compilation on sediment remediation technologies pertaining to the Puget Sound region. Thin-layer capping is specifically addressed in a section of one chapter. The document relates to the Kings County combined sewer overflow (CSO) program. Thin-layer capping by: windrows, clam shell bucket, split hull barge, wash off flat barge, and by hydraulic means are discussed. Also, materials and example sites of thin-layer capping are listed.

What You Will Find Here:Summary p. ii, Sediment Remediation Technology Matrix Table 1 p. ii, Introduction p. 1, Sediment Remediation Technologies Figure 1 p. 5, In Situ Containment Technologies p. 6, Enhanced Natural Recovery/Thin-layer Capping p. 6, Capping Material Sources and Availability p. 9

Palermo, M.R.; Clausner, J.E.; Rollings, M.P.; Williams, G.L.; Myers, T.E.; Fredette, T.J.; Randall, R.E.. (1998). “Guidance for Subaqueous Dredged Material Capping.

Keywords:Guidance, Dredged Material, Capping, Subaqueous

Summary:This document provides guidance for subaqueous dredged material capping. Carefully considered design, construction, and monitoring are needed. There is an interdependence between all components. The basic requirement is that the cap thickness is placed and maintained. Biological, physical, and chemical characteristics of sediment are needed. Site selection is important and should be a low-energy environment. Compatability between equipment and placement technique is required. Many types of equipment are available. Scheduling must consider both exposure of contaminated material to the environment, and other constraints. Evaluation of potential wate column effects due to placement of contaminated material must be performed. Capping is less costly than confined disposal.

What You Will Find Here:Sediment Characterization p. 16, Equipment and Placement Techniques p. 26, Sediment Dispersion and Mound Development and Site Geometry p. 51, Cap Design p. 64, Longterm Cap Stability p. 79, Cap Monitoring p. 98, Chemical Containment p. B1, LTFATE p. F1, Frequency of Erosion p. G1,

Stevenson Environmental Services, Inc.. “Silver Lake Pilot Study Sediment Capping.

Keywords:subaqueous cap, thin-layer lifts, geotextile, pilot study, turbidity curtain, armor stone

Summary:A one acre area was capped in Silver Lake. The pilot area was sectioned into 3 units that each received different capping treatments. Two of the areas had a geotextile placed before sand-soil mixtures. The placement of the mixtures utilized a conveyor system, mix tank, pumps, pipeline, a slurry dissipator barge, and barge structures. Turbidity curtains were installed to keep suspended solids in the remediation area. There were some challenges placing the geotextiles in the wind and waves.

What You Will Find Here:Webpage

Wilber, D. H.; Clarke, D.G.. “Defining and Assessing Benthic Recovery Following Dredging and Dredged Material Disposal.” Western Dredging Association (WEDA) conference paper

Keywords:Meta-Analysis, infauna, thin-layer, salt marsh, mud flat habitat

Summary:Benthic recovery rates range from several months to several years. If depths of placed material is limited to 20-30 cm, pre-existing benthos can migrate vertically. Areas with high wave and current energy are often held at early successional stages, and therefore recover more rapidly. Mud habitats recover faster (6-8 months) than sand and gravel (2-3 years). Proximity to unaffected areas also influences recovery time. Thin layer (< 15 cm) of beneficial use sediment in marsh habitats typically takes two growing seasons for plant recovery. Summary tables are provided. What You Will Find Here:Physical factors affecting recovery p. 604, Beneficial use p. 611