Hills, Hollows, and Honeycomb Rock On a rolling countryside with
grassy ridges and wooded hollow, farmers till neatly around
bowl-shaped depressions. Layers of limestone crop out where
pasture sinks into a hole. Streams spring out of the ground,
meander along awhile, then dip underground again. The water runs
clear in dry weather but swirls with much when it rains.
Sinkholes appear where soil has been slipping down cracks in the
bedrock below. The hollowed-out crevices often turn into caves
and subsurface channels, growing larger every time rainwater or
melting snow surges through them. No wonder there are few
surface streams. Rainfall and snowmelt disappear down sinkholes
and flow through underground passages. So pollution from surface
or near-surface sources, such as septic systems, may drain into
the groundwater that supplies private wells. In rural areas,
there are no sanitary sewers. Each household has a septic system
to handle human waste, and most have a private well to supply
drinking water. But is th