Abstract: Oil and/or other material on the walls of a sample tube of an oil-in-water monitoring device is washed with a cleaning solution. In operation, a water sample is directed into the sample cell. Ultra-violet light is directed through the sample tube to the water sample. A detector detects energy emanating from the sample tube characteristic of oil. Valve means channels the cleaning solution through the sample tube to remove oil and/or other material that has accumulated on the walls of the sample tube. The valve means may be operated manually or by a programmable device.

Abstract: An earthworks is constructed by consolidating solids and/or slurries and using the consolidated material for constructing the earthworks. A quantity of less than 150 grams of hydraulic cement and a quantity of soluble alkali metal silicate containing less than 11 grams of SiO.sub.2 are mixed with each liter of the solids and/or slurry to produce a water insoluble solidified material. The material thus produced is used for the construction of the earthworks. The material can be worked in with other solids, the material will not leach chemicals and the material does not break down into colloidal size particles that would remain suspended in water.