MEMORANDUM To : Exposure and Effects Workgroup

The 2008 RMP Status and Trends program (RMP S&T) will be collecting benthos, sediment toxicity and chemistry at 27 stations this summer in order to implement and evaluate the Sediment Quality Objectives (SQOs) assessment methods for bays and estuaries that have been approved by the State of California. The RMP S&T conducts both acute and sub-lethal sediment toxicity tests as recommended by the SQO assessment methods. However, the sub-lethal bivalve development test is an elutriate test, which is not recommended by the SQO program. At the March 2008 meeting, the TRC has decided that the RMP should adopt the sediment-water interface (SWI) bivalve test to comply with the SQO protocol recommendations. We would like to obtain guidance from the Exposure and Effects workgroup on this issue. To assist in this decision, we have compiled the following: 1) Background information from the SQO Staff Report; 2) A brief review of the 1999 – 2001 elutriate and SWI side-by-side test comparisons; 3) Description of a new study (by SCCWRP) to determine optimal equilibration time for homogenized sediment for the Sediment-Water Interface Exposure Method as an alternative to collecting intact sediment cores; and 4) General discussion points and suggestions for further evaluation of the SWI method.