Investigation and Implementation of Sediment Remediation At the An-Shun Remediation Site, Tainan City, Taiwan
Type:
Presented during:
WODCON XX: "The Art of Dredging" - 2013, Brussels, Belgium
Authors:
Mastin B, Moore D, Renfrew D, Chen J
Abstract: Taiwan is in the process of developing sediment and water quality criteria and guidelines to establish sitespecific sediment remediation goals. Without this guidance, it is extremely difficult to obtain consensus among stakeholders on detailed scopes of work and subsequently negotiate achievable performance goals. The overall objective of the An-Shun Remediation Project includes a multi-phased approach for the investigation, design engineering, and implementation of a full-scale project for the mitigation of mercury and dioxin contaminated sediment in Seawater Pond B. This sediment was contaminated by the manufacturing of chlorine, sodium hydroxide, and pentachlorophenol over a greater than 40-year period. The specific objectives of this project were 1) to perform a remedial investigation to determine the extent and magnitude of contaminated sediment in Pond B and 2) implement a full-scale hydraulic excavation and sediment management project to remove/process 100,000-m3 of contaminated sediments. Activities included conducting a comprehensive hydrograph and collection of sediment cores for analyses of mercury, dioxin, particle size, percent solids, and total organic carbon. Mercury and dioxin were analyzed to delineate the horizontal and vertical extent of contamination and results ranged from ND to 862 mg/kg and 0.401 to 36,988 ng/kg dry weight, respectively. Percent solids and TOC ranged from 72.4 to 83.4 and 1.66 to 3.9 μg C/mg, respectively. These results were subsequently used for defining the volume of sediment required for excavation and provide information necessary for a feasibility evaluation, full-scale sediment remediation design and engineering, and implementation of full-scale project work. In November 2012, an IMS 5012 Versi-Dredge, hydrocyclones, a chemical wash plant, and wastewater treatment plant were mobilized, constructed and started in order to process 800 m3/hr of dredge material. System integration, mass balance, operational performance (effectiveness and efficiency), challenges, lessons learned, and progress to date will also be discussed in this presentation.
Keywords: remedial investigation, mercury, dioxin, sediment management