Two kinds of rock
Most of upcounty Montgomery sits on Piedmont phyllite and schist, with water in fractures. Around Poolesville, Dickerson and Boyds, the ground changes to the red sandstones and shales of the Culpeper basin, where wells draw from fractured sedimentary rock and water chemistry is different again: often harder, sometimes with more iron or manganese.
Radon country
The Maryland Geological Survey specifically names the phyllite zone running through central Montgomery County as a place where homes can have radon well above safe levels. Radon in well water adds to it at the shower. A lab test of the water settles the question.
Typical calls
Farmhouse pumps that have run for decades, pressure tanks in old stone basements, iron filters and softeners, and water testing for buyers in the Reserve.
Permits and rules
In Montgomery County, the Department of Permitting Services (DPS) Well & Septic Section permits wells on behalf of MDE. County guidance sets wells at least 100 feet from septic systems and 30 feet from foundations. Statewide, home sales with wells need lab water quality testing unless the buyer waives it in writing.
140 ftQuestions from Montgomery County
Local answers.
Who permits wells in Montgomery County?
The Department of Permitting Services (DPS) Well & Septic Section, acting for the Maryland Department of the Environment. In most other Maryland counties the health department does this.
Is radon in well water a concern in Damascus or Laytonsville?
It can be. The Maryland Geological Survey names the phyllite belt through central Montgomery County as an area of elevated radon. Test the water through a State-certified lab; treatment is only needed if the number is high.
Why is my Poolesville-area water harder than my friend’s in Damascus?
Different rock. The red sandstone and shale around Poolesville tends to give harder, more mineral water than the phyllite and schist farther east.