Availability of ground water in Montgomery County, Maryland

Montgomery County, Md., is underlain by consolidated rocks that, on the basis of well yields, have been subdivided into six hydrogeologic units. The distribution of the hydrogeologic units are shown on a map (scale 1:62,500). Most wells drilled in the county yield between 6 and 25 gal/min (0.4 to 1.6 L/s); however, about one-third of the wells drilled in the most productive hydrogeologic unit yielded more than 25 gal/min (1.6 L/s). Water from all units is suitable for domestic, public supply, and most industrial uses, but may require treatment for the removal of iron and hardness.