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Drainage construction on the Delmarva Peninsula was started in colonial times in the 1700s. Most of the drainage is open ditch drainage with very little tile drainage. Environmental issues became a concern in drainage projects in the 1970s. Some controlled drainage was installed in the late 1980s and 1990s in some of the tax ditches. A number of drainage water quality studies have been reported. Ritter and Chirnside (1986) in a three year study, found phosphorus concentrations were increased by drainage construction. In another study herbicides were leached rapidly to shallow groundwater shortly after they were applied in both controlled and uncontrolled drainage sites. The Soil Conservation Service evaluated the effect of drainage on sediment yield over a 16 year period. Drainage decreased sediment yield. Several more recent studies have shown drainage ditches may release ortho phosphorus from bottom sediments and transport it to the estuaries along with high nitrate loads in baseflow.