Fracture Density Distributions and Well Yields in Coastal Maine |
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| Authors: | Marc Loiselle David Evans |
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| Institution: | Maine Geological Survey, State House Station 22, Augusta, Maine 04333 (Internet: ).;Department of Marine, Earth &Atmospheric Sciences, Box 8208, North Carolina State University, Raleigh, North Carolina 27695 (Internet: ). |
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| Abstract: | Understanding the distribution of water-bearing fractures in crystalline rock is an important component in evaluating the availability and vulnerability of water resources throughout the northeastern U.S. The State of Maine requests well drillers to report estimates of fracture depths and fracture yields for all bedrock wells drilled in the state. Using these data we analyze fracture-depth and fracture-yield data from 227 bedrock wells in coastal Maine in order to understand how fracture locations and yields are distributed with depth. Numerical simulations and statistical tests show that it is not possible to infer how fractures are distributed with depth: fracture depths are consistent with several distributions, including uniform fracture density with depth. In order to understand how fracture yield varies with depth, we group yield data into 50 foot depth intervals and compare distributions in each interval using nonparametric statistical tests. These tests show that the distribution of fracture yield in different depth intervals are statistically equivalent. These results imply that there is no empirical justification for limiting well depth when drilling for water resources in fractured bedrock in coastal Maine. |
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