Reports
Preliminary assessment of factors affecting well yields in the fractured rock terrane of Frederick County and portions of Carroll and Montgomery Counties
2012, Burgy, K.; Duigon, M.T.
Report of Investigations 79
Abstract
A pilot study was conducted in an area comprising Frederick County and the nearby areas surrounding Poolesville (Montgomery County), Taneytown, Mt. Airy, and Westminster (Carroll County), Maryland, to evaluate factors related to well yields. Data from 2,315 wells were analyzed in a preliminary assessment to determine what, if any, relation exists between well yield and geology, well depth, well construction, or other factors affecting ground-water availability in the fractured-rock terrane. The key results of the study are:
- Well use is a significant factor in the determination of well yield. Differences in the construction of public-supply and industrial wells allow for greater variation in well depth and diameter. These well uses also benefit from better location selection and siting. Well yields are significantly higher (P< 0.05) in public-supply wells and industrial wells than in domestic wells. Commercial and institutional wells do not have statistically different yields, nor do industrial and institutional wells. Domestic well yields are significantly different (lower) from all other well uses.
- Commercial, domestic, industrial, institutional, and public-supply wells in the Piedmont have greater median well yields and variability in well yields than wells in the Blue Ridge, although these differences were not statistically significant.
- Lithology and topography are site factors that may have a statistically significant impact on well yield; however, this is not consistently demonstrated throughout all well-use groups.
- Depth to bedrock (overburden thickness) and position of the water table relative to the bedrockoverburden interface do not demonstrate any statistically significant influence on well yield.
- Distance to a mapped fault appears to have no effect on well yield, but this result may be unduly influenced by the map scale of this study.
