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CONSTRUCTION METHODSThe first field-scale test of in-situ activated carbon (AC) amendment for contaminated sediment remediation was conducted at Hunters Point Naval Shipyard by researchers at Stanford University (ESTCP Project ER-200510) The equipment for that project was specialized equipment adapted to place and mix the particulate AC (PAC) into the sediment (see Hunters Point Case Study). Since that seminal demonstration, the equipment for placing the AC onto and/or into the sediment has shifted to finding ways of delivering PAC to the sediment surface using conventional marine construction/spreading equipment. |
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The following web pages focus on the placement techniques that are highlighted in the Case Studies section of this web site. The methods are arranged from the simplest methods to specialized equipment developed specifically for PAC placement. The table below provides a list of projects and placement methods.
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Site |
Contaminant |
Year Constructed |
Project summary |
Target AC |
Delivery Methods |
Project Web Link |
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AC Projects Completed in North America |
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USN Hunters Point San Francisco Bay, CA |
PCBs & PAHs |
2015 |
1 acre pilot study that includes ca 0.5 acres of SediMite and 0.5 acres of AquaGate+PAC. |
4 - 6 % |
Telebelt ® |
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USN Sierra 1B Pier Pearl Harbor, HI |
PCBs & mercury |
2015 |
11,000 ft 2 under-pier pilot study with ~ 4,400 ft 2 of SediMite and 4,400 ft 2 of AquaGate+PAC. |
2.5% |
Gravity fed hopper with pneumatic conveyance to an under-pier operator who directed the output over specific 10' x 10' cells. |
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Mirror Lake Restoration Dover DE |
PCBs |
2014 |
Full-scale 4.9 acre remediation of lake and downstream with SediMite. |
5% |
Telebelt® in deeper areas of lake; induction air horn, vortex spreaders, and by hand in nearshore |
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Puget Sound Naval Shipyard Bremerton, WA |
PCBs & mercury |
2012 |
0.5 acre pilot study to evaluate the efficacy of AC application under an active Navy pier. Product was AquaGate+PAC. |
4% |
Telebelt ® over-water and under pier sections of the project. |
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Berry’s Creek, NJ |
Mercury & PCBs |
2012 |
Small test plots (30 x 30 ft) with AC placed on the surface of a phragmites marsh using three approaches: 1) granular carbon only, 2) granular carbon with a 2 inch coarse sand cap, and 3) fine granular carbon in the form of SediMite™. Activated carbon dose was 5 percent by dry weight of sediment in the top 10 cm. SediMite™ application rate was 5 kg/m2 |
AC 5% SediMite™ 5 kg/m 2 |
GAC as a slurry using a hydroseeder. Coarse sand was delivered to plot using a telebelt and manually layered over the treatment area. SediMite™ was applied using a Vortex TR Aquatic spreader. |
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Lower Duwamish Slip 4 Seattle, WA |
PCBs |
2011 |
Dredged areas on the banks and riverbed at the head of the slip included a filter layer of well graded sandy gravel, amended with sand-size granulated activated carbon. |
0.5% |
Sandy gravel with GAC mixed upland and placed using a dredge bucket. |
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Onondaga Lake Pilot Study Onondaga County, NY |
Chlorinated benzenes & PAHs |
2011 |
1 acre capping pilot to demonstrate the implementability of mixing/slurrying GAC and sand on-shore and placing the material over a pre-defined depth and area. The project informed full scale construction planning and implementation. |
0.25 - 1.0 lb/ft 2 |
Sand/GAC slurry mix system mixed with water and pumped through a pipeline and booster pumps to a hydraylic spreader barge. Slurry placed in a series of parallel lands. |
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Canal Creek, MD |
PCBs & mercury |
2010 |
Twenty-four test plots, each 8 meters by 8 meters to evaluate the performance of three AC applications in a wetland: two pelletized AC products (AquaBlok and SediMite, and a PAC slurry . Pilot project under ESTCP ER-200825 and ER-200835. |
3% |
Depending upon the test product, a Vortex spreader, hydroseeder, bark blower, or by hand. Many of the test plots were accessible on-foot, in the submerged wetlands the spreaders were used on a boat. |
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Naval Air Station, Cottonwood Bay, Dallas TX |
PCBs, PAHs, chromium, lead |
2009 |
Small-scale pilot project that tested reactive mats featuring a 0.28 lb/ft2 activated carbon, 0.23 lb/ft2 apatite, 0.28 lb/ft2 organoclay amendment mixture and an AOS 80 geotextile. |
0.28 lb/ft 2 |
Prototype reactive mats rolled up and deployed from a john-boat by divers. Divers secured the mats in the shallow bay with anchors, anchor screws, and blocks. Some of the treatments were further covered with sand. |
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Bailey Creek, Fort Eustice, VA |
PCBs |
2009 |
Pilot-scale studies of SediMite in 225 m 2 plots within a marsh and in the main channel. |
5% |
Vortex spreaders from boat |
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St. Louis River Superfund Site Duluth, MN |
NAPL/PAHs |
2006 |
11 acres of cap that included a reactive core mat withAC to absorb advected PAH-porewater during consolidation. The cross section of the cap was 0.5 ft (15 cm) sand/activated carbon mat/2.5 ft (75 cm) sand. |
0.4 lb/ft 2 |
Reactive mats attached to outer sheet-pile wall and unrolled toward shore from a moveable barge. Overlapping RCMs stapled and allowed to sink, followed by sand placement |
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Grasse River, Massena, NY |
PCBs |
2006 |
0.5 acre pilot project with AC mixed into PCB-contaminated sediment. |
3.2 - 5% |
Two application methods tested: "roto-tiller" and tine sled. The tiller is an enclosed device that first applied (via spraying) activated carbon onto the sediment surface, followed by mixing of the material into near-surface sediments using the roto-tiller (was used with and without mixing). The tine sled device included direct injection of activated carbon into near-surface sediments. |
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Hunters Point 2005 Pilot Project San Francisco Bay, CA |
PCBs & PAHs |
2005 |
Pilot project under SERDP-1207 and ESTCP ER-200510. |
5.1% |
Two types of GAC applications were tested. In the first, the AC was spread onto the surface of the sediments via a backpack spreader located on an Aquamog and then a rotovator arm mixed the GAC into the sediments. WIth the second applicationGAC was sprayed onto the rotovator and mixed. |
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Anacostia River, Washington, DC |
PCBs, PAHs, chromium, lead |
2004 |
1100 m 2 area was capped with a coke-filled RCM and covered with 15 cm of sand. |
24 kg/m 2 |
Twelve 3.1 m x 31 m coke-filled RCMs were placed with a 0.3 m overlap using a crane with a clamshell.A diver followed the unrolling mat to insure proper placement. A sand layer (~15 cm) was then placed above the RCM by particle broadcasting to |
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AC Projects Completed in Europe |
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Grenlandsfjords, Norway |
Dioxins/furans |
2009 |
Pilot project to demonstrate efficacy of a hydraulic application of AC/clay mixture at depth. Plot size was 40,000 m 2 at a depth of 100 m. Comparative plots also included crushed limestone, and clay-only cpas. |
2 kg/m 2 |
Dredged clean marine clay was mixed with a coal-derived powdered AC (d80 < 45 μm) in 10:1 dw ratio. To increase the density of the clay + AC slurries the salinity was increased by adding NaCl, and was pre-mixed for at least one hour in the hopper dredger tank to a water content of 56−70% prior to placement. A hopper dredge was used in reverse mode: the intake pipe was as a tremie with the material released approximately 5 m above the seafloor. To facilitate settling the powdered AC was mixed with a 10% w/w |
Grenlandsfjords Case Study |
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Trondheim Harbor, Norway |
PAHs |
2008 |
Pilot project evaluating three treatments: AC, AC+clay, and AC covered with sand for erosion protection. Test plots were 225 m 2 |
5 kg/m 2 |
NaCl in a 100-L cement blender to saturate the AC pore system with water that was slightly heavier than surrounding water. For the AC-only and AC+sand fields, this slurry was pumped out with a flexible manually operated 5 cm hose For the AC+clay field, AC and bentonite were mixed 1:1:6 with 10%-NaCl and pumped out as described above. |
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