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HomeMy WebLinkAboutAgenda - 11-10-2015 - 4 - Orange Well Net Update 1 ORANGE COUNTY BOARD OF COMMISSIONERS ACTION AGENDA ITEM ABSTRACT Meeting Date: November 10, 2015 Action Agenda Item No. 4 SUBJECT: Orange Well Net Update DEPARTMENT: Environment, Agriculture, PUBLIC HEARING: (YIN) No Parks and Recreation (DEAPR) ATTACHMENT(S): INFORMATION CONTACT: A. Orange Well Net Well Details B. Map of OWN Well Locations Tom Davis, 245-2510 C. Draft Outreach Document - Waterin David Stancil, 245-2510 Orange County D. Draft Outreach Document - Improving Groundwater Yield from Wells PURPOSE: To receive an update regarding the Orange Well Net (OWN), Orange County's groundwater observation well network. BACKGROUND: DEAPR's groundwater observation well network, Orange Well Net (OWN), uses a combination of bedrock and regolith wells spread across the main types of bedrock geology present in Orange County. Regolith wells measure groundwater levels in the unconsolidated material present above bedrock to monitor natural stresses on the quantity of groundwater available in storage caused by variations in climatic conditions. Bedrock wells monitor changes in groundwater levels in the bedrock across the County. Groundwater level data collection is underway at seven bedrock wells and five regolith wells. In early 2015, a bedrock well on Triangle Land Conservancy property was added to the network. Attachment A is a listing of well construction details for the current OWN observation wells. Attachment B is a map showing the locations of the wells that are currently in use along with the underlying geology. All data collected by OWN is available to the public on the NC Division of Water Resources (DWR) web site provided below. The web site includes maps of well locations, geologic information, and statistical curves that provide monthly minimum, mean, and maximum groundwater level information for each well in the network. This information can be used to compare recent groundwater levels with historical values. ht!g-://www.ncwater.org/Data and M2delin / and Water Data basesfleveltable.php?tl=1&net =orange&inactive= 2 Staff is plans to begin an outreach campaign on groundwater information for County residents in late 2015-early 2016. Informational outreach materials are being designed that will help residents learn a variety of useful information, from basic hydrologic concepts to measures for planning the installation of supply wells which may help increase the yield of water from these wells (please see Attachments C and D). These documents will be used in combination with data gathered from the OWN network to inform residents of common facts about hydrogeology, especially with regard to groundwater occurrence and usage. SOCIAL JUSTICE IMPACT: The following Orange County Social Justice Goal is applicable to this agenda item: • GOAL: ESTABLISH SUSTAINABLE AND EQUITABLE LAND-USE AND ENVIRONMENTAL POLICIES The fair treatment and meaningful involvement of people of all races, cultures, incomes and educational levels with respect to the development and enforcement of environmental laws, regulations, policies, and decisions. Fair treatment means that no group of people should bear a disproportionate share of the negative environmental consequences resulting from industrial, governmental and commercial operations or policies. The information obtained from the Orange Well Net is available on the NC Division of Water Resources web site. The planned outreach materials will be posted to the Orange County DEAPR web site once they are finalized. FINANCIAL IMPACT: There is no financial impact to the County at this time. RECOMMENDATION(S): The Manager recommends that the Board receive the update on the groundwater observation well network (Orange Well Net) and provide feedback as desired. 3 Attachment A. Orange Well Net groundwater observation well details Orange Well Net Well Details Bedrock Wells Casing Total Top of Well Location Depth,ft. Depth,ft. Casing Bedrock Geology Elevation,ft. Millhouse Rd 67 164.7 515.22 Metasedimentary Rocks(Epiclastics) 2 Eno Confluence Property 37 175.5 609.27 Pyroclastic Rocks(Felsic Tuff) 2 Altered Pyroclastic Rocks 3 Former 911 Center 85 400 582 (Altered Tuff) 4 Blackwood Farm 100 302 557.44 Dacite(Felsic Lavas and Tuffs)' 5 Duke Forest 4D 85 400 427.82 Granodiorite(Felsic Intrusives) 6 Brumley East 108 605 Andesite to Basalt (Mafic Lavas and Tuffs) 7 Eubanks Road 33 145.7 531.15 Gabbro(Mafic Intrusives) Regolith Wells Total Top of Well Location Depth,ft. Casing Bedrock Geology Elevation,ft. 1 Andrews Rd. (COL-1) 33.0 528.00 Pyroclastic Rocks (Felsic Tuff) 2 Hwy 54 (COL-3) 43.7 528.18 Diabase(Mafic Intrusives) 3 Orange Grove Road (COL-4) 35.2 504.86 Diabase(Mafic Intrusives) 4 Blackwood Farm(BFS) 45.0 5562 Dacite(Felsic Lavas and Tuffs)' 2 Metasedimentary Rocks 5 Northeast Park (NES) 45.0 624 (Epiclastics) 1 - Main bedrock lithology in the county, by area. 2- Estimated elevation. 4 Attachment B. Orange Well Net groundwater observation well locations f `A b West Fork of + �� Eno River - Reservoir Orange ;- f ■I NES Ena r- ..� F Canlluencr . �3•-'� Corpo ation La " 0 0.75 1-5 3Miies AIF � ■ Gnur". r'J .c Bnpnl.Y d 0 eeawkwo FJFatkwDOa•' In . ReppAnwek DWQ 00e FORS!k0 Gl us cs Stream gage Main ruW . Cane Creek �' ,Duke —Malay s,ream . - '. Forwt�0 -Rearrvd�a is ke Re$ervoir� 1.-.... � '. Opontounrypark ianoa open space - ,,ax`1 ,ANllhouk� County parnanG a oxen space 'y Eu6 k. Crn.ng2.tl COrnpo.iu B�gfOCk llnlrs 1 Aner U Nft - ° I�z EpcwstKrock i Q 3 FMW run caE- . p 0 s Fetsrc rara am tuft COL - 5 Marc'""and ru* 7�9LJ • f O 6 FNac plutonw.fo[k 7 i ntennediate piutpr GnxR 8 MarK pKrIonK nwk Dtah35e Llnrvers[ity' -- - Q rnaMW Segmentary/ock Lake •�3 �' Q aua*tr.a.a aoa12 Creccw SrP"— �• ' .r�aF• � 5 I y� GIN aka yc.Frc Ma N k� v[�waYatoC¢rtp inW 5 Attachment C. DRAFT Water in Orange County information sheet Water in Orange County 1. Each year, Orange County receives approximately 45 inches of precipitation. This equals 1.2 million gallons of water per acre per year, or a total of approximately 308 billion gallons of water each year over the entire county! 2. Much of this precipitation flows over the ground surface as stormwater runoff, and enters waterways shortly after reaching the ground. 3. The amount and velocity of stormwater runoff increases as more impervious surfaces (roads, buildings and other hard materials) are built. 4. Stormwater runoff also increases when wooded areas are turned into lawns or other types of managed landscape. Steeper slopes also produce more runoff than flatter areas. 5. As the amount and velocity of stormwater runoff increases, the amount of soil erosion can increase, leading to more sediment in streams and lakes. Sediment is the main pollutant affecting waterways. Land disturbance, including farming and the construction of residential, commercial and industrial buildings, can also result in increased soil erosion. 6. Increases in the amount and velocity of stormwater runoff can increase the temperature of the water in surface water bodies. Adding impervious surfaces that get very warm during summer months can result in warmer water leaving these sites and affecting the fish and other aquatic organisms that live in this water. 7. Increasing the amount of precipitation that becomes stormwater runoff reduces the amount of water that infiltrates the soil and becomes groundwater, a process known as groundwater recharge. This reduction in infiltration can reduce the amount of groundwater available to residents for use as drinking water. 8. Reducing infiltration (recharge) will decrease the amount of baseflow. Baseflow is shallow groundwater that enters streams and other surface water bodies. During periods of dry weather, baseflow is the main source of water sustaining small streams. Up to 55 percent of the water present in the streams in Orange County is supplied by baseflow. Consequently, baseflow is critically important for maintaining aquatic ecosystems. 6 Attachment D. DRAFT information sheet about groundwater yield Maximizing Groundwater Yield from Water Supply Wells Orange County Each year, many new wells are installed in Orange County. A well may be installed after a site is cleared, graded and a new house is built on the site. Planning the well location may not be as much of a priority as it could be. Achieving a suitable supply of water from a new supply well can be difficult, possibly becoming an ongoing source of frustration for those residents dependent on the well. Research into groundwater yields from fractured rock aquifers in the Piedmont area of North Carolina, including Orange County, has determined several factors that should be considered when attempting to increase the yield of water from a new supply well. 1 . The groundwater system in the Piedmont area of North Carolina is known as a regolith- fractured bedrock aquifer system. Regolith is the unconsolidated material present above the underlying bedrock. Nearly all groundwater storage is within the regolith. As a result, wells should be located in areas that maximize the thickness of saturated regolith. Saturated regolith tends to be thickest beneath valleys and draws (-34 feet), versus that beneath hills and ridges (-20 feet) (Daniel and Dahlen, 2002). l —Stream T unsaturated �--� �Tapsoil :one r Re olith saturate �Top of water table zone a; Fractured Bedrock with groundwater Now in fractures Arrows represent �r direction of groundwater Now (Modified tram Hrrr dwd Usnid,3993) 2. Yield (the amount of water that can be extracted from the well) from a bedrock well depends upon the well intersecting fractures in the rock. As a result, steps to locate wells in areas with more fractures should increase the yield of the well. 3. The geology of the bedrock at a site affects the porosity and weathering characteristics of the fractured bedrock aquifer. More massive rock types are likely to include fewer fractures than rocks that have undergone deformation such as folding and faulting. 7 4. In general the number of fractures, and the size of fracture openings in bedrock both decrease with depth. This means it is usually not cost effective to drill a well deeper than approximately 200 feet. 5. Two (or more) low-yield wells can more effectively extract groundwater from the Piedmont groundwater system than one high-yield well. High-yields typically can only be developed in locations that have abundant and intensive bedrock fracturing and where the bedrock is overlain by thick saturated regolith. 6. Choosing a well location should not be based on the view one desires from the building that will be served by the well. 7. Minimize impervious surfaces (pavement, buildings and other hard surfaces) on the site and leave as much undisturbed forest area as possible to increase the recharge of groundwater in the area. Steep slopes also decrease recharge compared to flatter areas. References: Cunningham, W.L., and Daniel, C.C., III. 2001. Investigation of Ground-Water Availability and Quality in Orange County, North Carolina. U. S. Geological Survey, Water-Resources Investigations Report 00-4286. 59 p. CDM. 2003. Wake County Comprehensive Groundwater Investigation Final Report. Daniel, C.C., 111. 1996. Ground-Water Recharge to the Regolith-Fractured Crystalline Rock Aquifer System, Orange County, North Carolina. U. S. Geological Survey, Water-Resources Investigations Report 96-4220. 59 p. Daniel, C.C., 111, 1990. Evaluation of Site-Selection Criteria, Well Design, Monitoring Techniques, and Cost Analysis for Ground-Water Supply in Piedmont Crystalline Rocks, North Carolina. U. S. Geological Survey, Water-Supply Paper 2341-B. 35 p. Daniel, C.C., 111, 1987. Statistical Analysis Relating Well Yield to Construction Practices and Siting of Wells in the Piedmont and Blue Ridge Provinces of North Carolina. U.S. Geological Survey, Water-Resources Investigations Report 86-4132. 59 p. Penn State Cooperative Extension, College of Agricultural Sciences. 2015. Water Facts 5: Water Well Location by Fracture Trace Mapping. 3 p. State of California, Department of Water Resources, April 1991. Water Facts: Ground Water in Fractured Hard Rock. 4 p.