Agenda - 09-15-2009 - 6a - Laserfiche WebLink

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55 Orange Well Net Timeline August 2009 A. Introduction As discussed in my presentation to the BOCC in January 2009, a combination of regolith and bedrock wells spread across the eight main types of generalized bedrock geology present in Orange County is planned for the establishment of a groundwater observation well network, which is proposed to be known as the Orange Well Net. Regolith wells, completed in the unconsolidated material present above bedrock in the subsurface, will be utilized to monitor natural stresses on the quantity of groundwater available in storage which are caused by variations in climatic conditions, while bedrock wells will be used to monitor changes in groundwater levels in the bedrock across the county. B. Situation to Date The main categories of bedrock present in the county have been identified in those portions of the county which have recently been geologically mapped in detail by the North Carolina Geological Survey. Additional mapping is on-going and a complete, detailed geologic map of Orange County is scheduled to be available in June of 2011. As previously presented, the groundwater observation well network is proposed to utilize a combination of bedrock wells and regolith (unconfined subsurface material) wells to monitor groundwater conditions in Orange County. The bedrock wells should be located in each of the main bedrock lithologies present in the recently mapped portion of the county. The drilling of regolith wells is temporarily delayed as a cost saving strategy. The use of existing bedrock wells is desirable because of the considerable cost savings which can be achieved versus drilling new wells. However, existing bedrock wells which appear to be suitable for inclusion in the network must be checked to determine if the surface casing present in the well is leaking or not, thereby insuring that the water present in the well is actually representative of bedrock conditions. County-owned properties which contain existing bedrock wells which appear to be suitable candidates for inclusion in Orange Well Net are (the bedrock geology at each of these well locations is listed): • The former 911 Center on New Hope Church Road (slated for divestiture) (altered tuff); • The Blackwood Farm on NC 86 (felsic lavas and tuffs);