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Woods Hole Coastal and Marine Science Center > Coastal Model Applications and Field Measurements > Research Activities > Palos Verdes Shelf

Coastal Model Applications and Field Measurements

Palos Verdes Shelf

The Palos Verdes Shelf near Los Angeles is the site of an effluent-affected deposit of fine sediment contaminated with DDT, PCBs, metals, and other contaminants, and is a Superfund site being remediated by the U.S. EPA. The USGS has been studying the site since 1992, originally supported by the U.S. Department of Justice, and more recently supported by US EPA Superfund program and in-kind contributions from the Coastal and Marine Geology Program. The overall objective of the project has been to develop a predictive understanding of sediment and chemical dynamics that control the fate of contaminates in PV sediment, which will help the EPA choose among available remediation options. Work under the five-year cooperative agreement with the EPA was completed in 2009 and Open-File reports describing the field programs conducted in the spring of 2004 and the winter of 2007-2008 are in the publication process (see also Sound Waves (http://soundwaves.usgs.gov/2008/07/). Papers providing analysis and interpretation of these data have been published or are in press (Noble et al., 2008; Noble et al., 2009; Ferré et al., 2010; Noble et al., submitted).

We took took 40 samples of bottom sediment during a May 2010 cruise on the RV Sproul and conducted grain-size analysis using techniques originally developed by D. Drake (USGS Menlo Park) during the 1992 Palos Verdes studies. The method used gentle hand sieving to determine grain size without breaking aggregations. This analysis confirmed that significant fraction of most of the samples are durable, low-density fecal pellets. We are presently using these data, along with historical data and a recent baseline survey to evaluate changes in sediment texture, deposition rates, pellet content, and contamination on the Palos Verdes shelf.

Color photos of sand and pellets of various sizes

Fecal pellets from surficial sediment on the Palos Verdes shelf near Los Angeles. Fine silt has been repackaged into low-density sand-sized pellets, which changes the sediment-transport characteristics.

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