Contamination and other issues  Source Point sources Point sources Non-point sources Non-point sources Naturally occurring Naturally occurring  Reactions (chemical and biological)  Transport

Potential sources of contamination

Point sources Fuel storage tanks Landfill Septic tank Leaking tank in gas station Truck fuel spill Dry cleaner Factory wells, spills, emissions Households

Non-Point sources Naturally occurring Farm Brought by river Brought from outside area by groundwater

Cannot be traced to a specific spot Multiple sources Large area Source activities related either to land or water use Examples water runoff from urban areas construction sites agricultural failing septic tanks improper animal-keeping practices Improper forestry practices Non-Point source pollution

How Does Groundwater Contamination Move? Can be filtered if flows slowly, like through sands With groundwater down water table Not filtered if flows rapidly, like in limestone caves a

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LNAPL - Light Non-Aqueous Phase Liquids lighter than water generally petroleum NAPL - Non-Aqueous Phase Liquids v/definitions/lnapls. html

DNAPL - Dense Non-Aqueous Phase Liquids denser than water chlorinated compounds PAHs igconference/wj w_preliminaryco ncept.htm

(from USGS WRIR )

Arsenic in groundwater  Depends on rock type (sulfide minerals)  Oxidation state  pH  Presence of Fe

Arsenic accumulation over time Tiles on cement block Increased coating on tiles with time 41a7-9cc e7de5e&groupId=38364

Bottom: Reducing Top: Oxidizing Arsenic accumulation 10 cm Reid, Haven, Eudy, Milosh, Stafford, 2007, Arsenic in Groundwater Investigations – Eastern Slate Belt (ESB): Nash and Halifax Counties, North Carolina

Source: DENR “North Carolina State of the Environment Report 2011” 2010 State-Wide Private Well Sampling Results NitratepHArsenicChromiumIronManganese State Groundwater Standard 10 mg/L ug/L 300 ug/L50 ug/L Number of samples 4,1104,9014,8704,8924,8964,900 Percent of samples exceeding standard 0.7%18.4% below pH of %1.5%57.6%39.9% NC population 10,000,000 ½ drink groundwater 2/4% of 5,000,000 people is 120,000 people

Arsenic Probability from Private Well Data (Pippin, 2005) Probability of a groundwater sample exceeding mg/L Pippin, 2005, Arsenic Occurrence in the Unconfined Fractured Bedrock Aquifer System of the North Carolina Piedmont

Arsenic Probability from Private Well Data (Pippin, 2005) Probability of a groundwater sample exceeding mg/L Carolina Slate Belt Kings Mountain Belt Charlotte Belt Inner Piedmont Belt Eastern Slate Belt

Probability of a groundwater sample exceeding mg/L USGS Estimated Use of Water in the US County-Level Data for 2010 Population using private wells

Take-aways  It’s easier to keep groundwater clean than to clean up contamination  Groundwater – Surface Water all one thing  Understanding the geology is critical to Public Health  Not all contamination is caused by humans  Well construction is different under certain geologic conditions

Take-aways Test your well! Learn what to test for – Depends on geology Depends on geology Land use practices Land use practices History of land use History of land use Contamination events Contamination events

Porosity and permeability The space between the grains “best extreme caving video” Mammoth Cave, Kentucky Geology of Mammoth Cave Groundwater – good, but long Wish we had this for eastern NC -

How Do We Depict the Water Table? Contour: water table at same elevation; blue arrows show flow Numbers show elevations of the water table: what is the pattern? Compare water table to other features b

 Amy Keyworth NCDENR Division of Water Resources Division of Water Resources