Grab samples are an arbitrary collection of surficial sediments using a clam-shaped apparatus that can be dropped from a boat to the bottom and recovered using a line. Grab sampling can be used to cover a large area with many samples in a short amount of time and relatively easily. Usually the top ten centimeters are collected during the process and stratigraphic integrity is not maintained, so analysis is usually restricted to bulk characteristics.

This project incorporates a large database of grab samples collected through various efforts from 1973 to present (Figure 16). Most surveys focused on specific areas of interest. For example Landrum, 1994 focused on the area around the Inner Harbor Navigational Canal and Lakefront airport. Some surveys, however, were well distributed across the lake. Flowers, 1987 collected over 100 samples throughout Lakes Pontchartrain and Maurepas for trace metal and grain size analysis, as did Tarver and Savoia, 1976 (grain size analysis). In 1995 the Environmental Protection Agency compiled an extensive collection of surficial samples from throughout the Pontchartrain Basin that were analyzed for organic and trace metal constituents.

Analysis of the grab samples provide physical and chemical characterization of surficial sediments in the Basin, such as lithology, grain size and trace metal distribution. Certain physical parameters such as lithology can be compared between studies to define temporal change. With proper data validation certain geochemical analysis, such as trace metal distribution, can also be compared.