This paper summarizes a twelve month examination of full-scale filters under normal backwash conditions and a second twelve month study under test backwash conditions. Factors contributing to initial filter breakthrough were investigated. These findings were then used to develop planning level estimates of capital and operating costs necessary to implement filter to waste at the CWW Richard Miller Treatment Plant (RMTP). In 1995 CWW equipped the effluents of the 47 RMTP rapid sand filters with continuous turbidimeters. The outputs from the turbidimeters were transmitted to a supervisory control and data acquisition system. Each month for one year CWW collected turbidity tracers for an entire filter run for each of the 47 filters. Steady state turbidity, maximum initial breakthrough turbidity and final turbidity were collected. The time required for initial breakthrough to decline to 0.3, 0.2 NTU and return to steady state were also recorded in addition to several other parameters. Grab samples were taken to determine the correlation between iron levels and turbidity in the filter effluent during initial breakthrough.