R2 PM Evaluating Short- and Long- Term Effectiveness In Sediment Remediation
Thursday, 17 November 2005: 1:50 PM - 5:30 PM in Ballroom 2

(SEX-1117-854877) Use of Sediment Amendment for Remediation of Organically Enriched Sediments in Ward Cove, Alaska.

Sexton, J.¹, Becker, D.¹, Jacobs, L.², ¹ Exponent, Inc., Bellevue, Washington, USA² Integral Consulting, Inc., Mercer Island, Washington, USA

ABSTRACT- In 2000 and 2001, 28 acres of the bottom of Ward Cove, Alaska were remediated by amending native sediments with 15-30 cm of clean sand. The remediated areas were part of an overall area of concern identified offshore from a former pulp mill. The primary chemicals of concern were those commonly associated with organic enrichment: ammonia and 4-methylphenol. The objective of the remedial action was to 1) reduce the toxicity of the native sediments and 2) stimulate colonization by benthic macroinvertebrates by providing a clean substrate that early colonists could inhabit and begin modifying for succeeding species. It was expected that colonization would follow the classical patterns identified for organically enriched marine environments. In 2004, the first monitoring event for the remediated areas was conducted, and included evaluations of sediment chemistry, sediment toxicity (using the 10-day marine amphipod test with Eohaustorius estuarius), and benthic macroinvertebrate communities. Results of the monitoring event showed that conditions in the remediated areas had improved considerably in the 3 years since remediation occurred. Concentrations of both ammonia and 4-methylphenol were very low and amphipod survival was very high, exceeding 90 percent at most stations. In addition, benthic communities appeared to be recovering rapidly, based on multivariate analysis of community composition (i.e., using classification analysis and multidimensional scaling), evaluations of various benthic metrics (e.g., total abundance, taxa richness, dominance, abundances of major taxa), and evaluations of key indicator species (e.g., the bivalves Axinopsida serricata and Parvilucina tenuisculpta, and the polychaetes Capitella capitata and Nephtys cornuta). It was concluded that the sediment amendment process was successful in remediating the native sediments, and that benthic communities will likely continue to develop in the remediated areas in the future. The next monitoring event will be conducted in 2007.

Key words: Sediment Toxicity, Sediment Remediation, Sediment Monitoring, Benthic Communities