Prologue to Ground Water Contamination

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Prologue to Ground Water Contamination CIVE 7332 Lecture 2

Darcy permits a gauge of: the speed or stream rate moving inside the aquifer the normal time of go from the leader of the aquifer to a point found downstream

Darcy's Law Darcy's law gives a precise depiction of the stream of ground water in all hydrogeologic situations.

Who Was Darcy? Henry Philibert Gaspard Darcy was conceived June 10, 1803 in Dijon, France. Admitted to the French School of Bridges and Roads in Paris, some portion of the Corps of Bridges and Roads. After graduation, he was in the long run appointed by the Corps to a position in Dijon. In 1828, Darcy outlined a 12.7 km arrangement of reservoir conduits to supply the city of Dijon with surface water. The framework included 28,000 m of pressurized surface lines and required no pumps or channels. Made vital commitments to stream and contact misfortune in channels, made an enhanced pitot tube outline, and was the first to propose the existance of a limit layer in liquid stream. In 1856, completed trials while examining sand channels that prompt to Darcy " s Law. Kicked the bucket out of the blue January 3, 1858 from pneumonia amid an outing to Paris.

Darcy " s Legacy Place Darcy, Dijon, France.

Flow in Aquifers

Darcy's Experiment (1856): Flow rate dictated by Head misfortune dh = h 1 - h 2

Darcy's Law Henri Darcy set up exactly that the flux of water through a porous development is relative to the separation amongst top and base of the dirt section. The steady of proportionality is known as the pressure driven conductivity (K). V = Q/A, V  – ∆h, and V  1/∆L

Darcy's Law V = – K (∆h/∆L) and since Q = VA (A = add up to range) Q = – KA (dh/dL)

Hydraulic Conductivity K speaks to a measure of the capacity for course through permeable media: Gravels - 0.1 to 1 cm/sec Sands - 10 - 2 to 10 - 3 cm/sec Silts - 10 - 4 to 10 - 5 cm/sec Clays - 10 - 7 to 10 - 9 cm/sec

Conditions Darcy's Law holds for: 1. Immersed stream and unsaturated flow 2. Enduring state and transient flow 3. Stream in aquifers and aquitards 4. Stream in homogeneous and heterogeneous systems 5. Stream in isotropic or anisotropic media 6. Stream in rocks and granular media

Darcy Velocity V is the particular release ( Darcy speed). (–) demonstrates that V happens toward the diminishing head. Particular release has units of speed. The particular release is a perceptible idea, and is effortlessly measured. It ought to be noticed that Darcy's speed is distinctive … .

Darcy Velocity ... from the tiny speeds related with the genuine ways if singular particles of water as they wind their way through the grains of sand. The minute speeds are genuine, however are most likely difficult to quantify.

Darcy & Seepage Velocity Darcy speed is an imaginary speed since it accept that stream happens over the whole cross-area of the dirt specimen. Stream really happens just through interconnected pore channels. A v voids A = add up to territory

Darcy & Seepage Velocity From the Continuity Eqn: Q = A v D = A V s Where: Q = stream rate A = add up to cross-sectional range of        material A V = zone of voids V s = leakage velocity V D = Darcy speed

Darcy & Seepage Velocity Therefore: V S = V D ( An/A V ) Multiplying both sides by the length of the medium ( L ) V S = V D ( AL/A V L ) = V D ( V T/V ) Where: V T = add up to volume V = void volume By Definition, v/V T = n , the dirt porosity Thus V S = V D/n

Equations of Groundwater Flow Description of ground water stream is based on: Darcy's Law Continuity Equation - depicts conservation of liquid mass during course through a permeable medium; brings about a fractional differential condition of stream. Laplace's Eqn - most essential in math

Derivation of 3-D GW Flow Equation from Darcy's Law z Fluid thickness Mass In - Mass Out = Change in Storage mass/territory/time y Steady State

Derivation of 3-D GW Flow Equation from Darcy's Law Replace V x , V y , and V z with Darcy utilizing K x , K y , and K z Divide out consistent  , and expect K x = K y = K z = K incompressible liquid, isotropic, homogeneous medium

Permeameters Constant Head Falling Head

Constant head Permeameter Apply Darcy's Law to discover K: V/t = Q = KA(h/L) or: K = (VL)/(Ath) Where: V = volume streaming in time t A = cross-sectional region of the sample L = length of sample h = steady head t = time of stream

Pressure and Elevation Heads - Laboratory  = weight head z = height head h =  + z = add up to head Freeze and Cherry, 1979.

Pressure and Elevation Heads - Field  = weight head z = height head h = add up to head Freeze and Cherry, 1979.

Horizontal and Vertical Head Gradients Freeze and Cherry, 1979.

Two Confined Aquifers with Different Heads Groundwater will tend to spill out of the top aquifer to the base aquifer. (Expecting that level separation between piezometers is little) Charbeneau, 2000.

Hydraulic Head is a Potential Field Hubbert (1940): potential – a physical amount, equipped for estimation at each point in a stream framework, whose properties are to such an extent that stream dependably happens from districts in which the amount has a higher estimations of those in which it has lower, paying little heed to the course in space. Potential fields and related physical laws: Fluid Flux Head (Darcy " s Law) Temperature (Fourier " s Law) Conduction of warmth in solids Concentration (Fick " s Law) Diffusion of chemicals Heat Flux Mass Flux

Horizontal and Vertical Head Gradients Freeze and Cherry, 1979.

Potentiometric Surface – Dakota Sandstone Domenico and Schwartz, 1992.

Drinking Water Standards Primary Standards Maximum Contaminant Level (MCL) Microorganisms Disinfectants Disinfection by-items Inorganic chemicals Organic chemicals Radionuclides

Contaminant Secondary Standard Aluminum 0.05 to 0.2 mg/L Chloride 250 mg/L Color 15 (shading units) Copper 1.0 mg/L Corrosivity noncorrosive Fluoride 2.0 mg/L Foaming Agents 0.5 mg/L Iron 0.3 mg/L Manganese 0.05 mg/L Odor 3 edge scent number pH 6.5-8.5 Silver 0.10 mg/L Sulfate 250 mg/L Total Dissolved Solids 500 mg/L Zinc 5 mg/L List of National Secondary Drinking Water Regulations

BTEX-Related Compounds

Chlorinated Solvents

Chlorinated Solvents (cont'd)

Superfund - CERCLA The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), normally known as Superfund , was established by Congress on December 11, 1980. This law made a duty on the concoction and petroleum businesses and gave expansive Federal expert to react straightforwardly to discharges or undermined arrivals of perilous substances that may imperil general wellbeing or the earth. More than 5 years, $1.6 billion was gathered, and the expense went to a trust subsidize for tidying up surrendered or uncontrolled risky waste locales. Superfund National Priorities List (NPL) locales are the most genuine uncontrolled or relinquished perilous waste destinations that have been distinguished for conceivable long haul healing activity under Superfund. The rundown is construct basically in light of the score a site gets from the Hazard Ranking System . The U.S. Ecological Protection Agency (EPA) is required to refresh the NPL in any event once every year. A site must be on the NPL to get cash from Superfund for long haul healing activity. Long haul medicinal activity is characterized as activity that stops or significantly diminishes a discharge or risk of an arrival of unsafe substances, where such a danger is not kidding yet not a quick danger to general wellbeing. The EPA controls the Superfund program in collaboration with individual States and tribal governments. Source: EPA site

National Priorities List Sites in Texas (Superfund) Triangle – proposed (2) Circle – endorsed (43) Square – erased (9) The NPL is the rundown of national needs among the known discharges or undermined arrivals of risky substances, contaminations, or contaminants all through the United States and its regions