Minutes - 20090127 - Laserfiche WebLink

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V. Orange County Geology, cont. •NCGS geologic mapping of Orange County ongoing. Four main quadrangles complete: •White Cross, Hillsborough, Efland and Chapel Hill quadrangles. •Nine main bedrock lithologies are present in the recently mapped area of Orange County. VI. Observation Well Design •Objectives determine well design. •Observation wells can monitor: —Natural stresses (drought, terrane differences, etc) —Man-made stresses (Over-pumping, interference, etc) A. Primary Goal of Observation Well Network: Monitor natural stresses on the quantity of groundwater available in storage which are caused by variations in climatic conditions. Observation Well Network should mainly utilize climatic effects (regolith or shallow) observation wells to monitor the response of groundwater storage to variations in climate that occur over time. B. Secondary Goal of Observation Well Network: Monitor variations in groundwater levels across the nine main bedrock lithologies. Terrane effect (bedrock) observation wells should be completed in each of the nine main bedrock lithologies. •The bedrock wells should also be utilized to gain water quality information, including: •Arsenic and radon concentrations in groundwater •Groundwater quality near biosolids application areas VII. Summary •Combination of bedrock and regolith wells proposed. Wells should be spread across the County and bedrock wells should be located in each of the nine main bedrock lithologies. •A bedrock and regolith well pair could be installed in the same location where possible. •Network will be able to monitor the quantity of groundwater in storage as well as monitor variations in groundwater levels in different bedrock lithologies. VIII. Additional Information •No land purchases are anticipated to be necessary for the observation well network. •Existing wells will be utilized where possible. •Partners and cooperative arrangements are possible and should be explored: