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PT15 Contaminated Harbour and River Sediment
(PT238) Monitoring the deformation of a low-permeability sediment cap using in-place horizontal inclinometers: Preliminary findings.
Mutch Jr., R.1, 1 HydroQual, Inc., Mahwah, NJ, USA
ABSTRACT- The Hazardous Substances Research Center (HSRC), in conjunction with Battelle, Horne Engineering, and HydroQual, Inc., is conducting a major field study of active sediment caps on the Anacostia River near Washington, DC. As a part of this overall study, the potential uplift and deformation of a low-permeability sediment cap constructed with AquaBlok will be studied using highly sensitive, in-place horizontal inclinometers. The potential for low permeability sediment caps to be uplifted by increases in sediment pore pressures due to the designed restriction of groundwater discharge caused by the cap or by transient tidal fluctuations has been shown to be significant in some riverine and estuarine settings. Uplift can potentially cause cracking and jointing of the low permeability cap substantially increasing its hydraulic conductivity and, consequently, compromising the ability of the cap to restrict contaminant flux. The research project involves construction of several pilot scale sediment caps. One such pilot scale sediment cap consists of six inches of AquaBlok overlain with six inches of sand. Each pilot-scale cap is slated to be 80 by 100 feet. A 100-foot long horizontal inclinometer casing will be constructed within the cap overlying the AquaBlok. A string of ten in-place horizontal inclinometers will be housed in the casing and be equipped to measure and record any uplift or deformation of the cap in real time. Data will be fed to an on-shore measurement and control module. The Inclinometers were installed on March 26, 2004 and deformation data is being collected continuously. Preliminary data and findings will be presented.
Key words: remediation, deformation, sediment, capping
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