R2 AM Contaminated Harbor and River Sediment
Thursday, 17 November 2005: 8:00 AM - 11:40 AM in Ballroom 2

(REI-1117-511061) Organoclay for the control of NAPLs in sediments.

Reible, D¹, Lu, X¹, Blischke, Heidi², ¹ University of Texas, Austin, TX, USA² Oregon Department of Environmental Quality, Portland, OR, USA

ABSTRACT- Conventional capping of contaminated sediments with sand or other inert materials may not be effective in areas where sediments contain nonaqueous phase liquids (NAPLs) due to displacement or continued migration of NAPLs. Organoclays have been proposed as an active capping material for control of NAPLs and were used at the McCormick & Baxter Creosoting Company site on the north shore of the Willamette River in Portland OR. The Oregon Department of Environmental Quality, in cooperation with the University of Texas, undertook a simultaneous laboratory study of organoclay in order to 1) to better understand the effectiveness of organoclay to control NAPLs and 2) to obtain information that will shape the long-term monitoring and maintenance plan for the McCormick and Baxter organoclay cap. The flow and sorption characteristics in the organoclay after exposure to site water and NAPLs were monitored and used as a basis for understanding the feasibility and effectiveness of organoclays for NAPL control. Organoclays were found to provide good control of both dissolved and nonaqueous phase contaminants. Contact with organoclay gave rise to significant swelling and a simultaneous reduction in effective permeability of the organoclay. This could serve to enhance effective utilization of organoclays by forcing lateral migration around seeps but also discourage subsequent migration of NAPLs into a treatment layer. Implications of these results for the design and implementation of organoclays for NAPL control in sediments were assessed.

Key words: organoclay, mccormick and baxter, napl