The Heckathorn Superfund Site in Richmond, California, encompasses the property of the former United Heckathorn pesticide packaging plant and the adjacent waterway, Lauritzen Channel. The site was used from 1945 to 1966 by several operators to produce various agricultural chemicals. The site was placed on the National Priorities List of Superfund sites in 1990, which resulted in the removal of pesticide-contaminated soil from the upland portion of the site and dredging the marine portion of the site. Post-remediation marine monitoring and associated studies conducted through 2002 indicate that the contamination in the channel continues to pose a significant risk to biota and human health. This report documents continued marine monitoring and source investigation studies conducted in 2003.