Initial results from a parametric laboratory investigation are described: the investigation was designed to study the effectiveness of water jetting as a means for removal of anomalous materials from concrete drilled shaft foundations. A primary objective for the investigation was to establish relationships between jetting parameters and the removal of commonly occurring anomalous zone materials, including low-strength concrete, slurry-mixed concrete, grout, and clay soil. The experimental work consisted of water blasting test specimens with rotary jets, nozzles, and pumping equipment typically used in construction practice. During testing, material removal rates were measured as a function of jet pressure and standoff distance for specimens with compressive strengths ranging between approximately 5 and 6,500 psi. Water-blasted specimens were cut apart after testing to confirm erosion measurements and to permit inspection of the water-blasted surfaces. The results show that erosion rates and the effectiveness of water jetting are primarily influenced by compressive strength when standard test equipment and jetting pressures are used. The size and angularity of aggregate in the anomalous material do not appear to influence erosion. The greatest erosion was observed for a semicemented material with a compressive strength of approximately 500 psi. Maximum erosion was observed approximately 12 in. from the axis of the jet.