Remediation: Techniques and Cost - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 398

Common remedial methods for remediating contaminated sediment include (USEPA
2005b; Sediments Focus Group 2007):
• Source control
• Excavation
• Dredging
• Bioremediation
• Capping
• Natural attenuation
• Institutional control
11.7.1 Source Control
Source control may be more difficult to achieve with contaminated sediments, because the
contamination may have a distant origin and/or emanate from numerous locations. To
ensure recontamination does not occur, careful evaluation and study are necessary before
initiating remedial activities (USEPA 2005c).
11.7.2 Excavation
Excavation of contaminated sediments is usually conducted within floodplains, stream
and river banks, and beach areas when water does not cover the contaminated materials.
Access to these areas is relatively easy when they are contaminated and require reme-
diation, and excavation is usually preferred over other technologies if the volume of con-
tamination is manageable. In these cases, the impacted sediments can be removed quickly
before they become covered with water; otherwise excavation becomes potentially impos-
sible and much more costly (USEPA 2005c).
11.7.3 Dredging
Dredging involves excavating submerged contaminated sediments. Multiple techniques
and a variety of dredging equipment have been developed to address the array of situa-
tions encountered. Figure 11.24 shows a common dredging technique with an excavator on
a floating barge (USEPA 2005c).
Dredging submerged sediment often causes contaminated sediment particles to become
suspended in the water column. This may cause contamination to spread in the downgra-
dient direction of water flow.
To avoid this situation, extreme measures are sometimes conducted (USEPA 2005c;
Sediments Focus Group 2007):
• Temporarily draining the surface water requiring remediation
• Rerouting the surface water around the affected area in small streams or rivers
requiring remediation
• Installing sheet pile walls around the affected areas and pumping the water from
inside the sheet pile wall to provide access to the affected area