From the Boulder Weekly (Jefferson Dodge):
State regulations prohibit biosolids from being applied to lands where the water table is within five feet of the surface. Over the past couple of years, Licul has identified several farming areas where wetlands and other obvious signs indicate that the water table is higher than the five-foot threshold, and as a result, the use of biosolids has been suspended on hundreds of acres of [Boulder] county open space.
[Boulder County resident Elvis Licul] also pointed out last spring that the depth of the water table can vary by as much as seven feet on his own property between the winter and summer months, so he questioned why water depth is sometimes measured in the winter, when it is lowest. His complaints have prompted state and county officials to begin performing depth measurements in the summer, when irrigation and runoff can raise the water level.
County Water Quality Program Coordinator Mark Williams told Boulder Weekly it is now standard operating procedure to measure water depth in the summer before biosolid application is approved in areas where there is any question whether groundwater approaches the five-foot mark. (In some areas of Colorado, the aquifer can be as deep as 150 feet below the surface.) The same approach is implied, if not explicitly spelled out, in state regulations on biosolid use, which say that no one can apply the human waste in areas where the “annual high groundwater table” is within five feet of the surface.
More water pollution coverage here.