Work was completed in early 1992 to clean up a 5.5 acre (2.2 ha) stormwater sludge basin for an oil refinery company. The basin, which had served as a stormwater collection and settling pond for over 40 years, contained oily sludges with high concentrations of certain metals and volatile organic compounds. The closure plan included a combination cement-bentonite slurry wall and jet grouting along the perimeter of the basin. The sludge and contaminated soil beneath the basin were solidified in place using a specially developed soil mixing technique.