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' Slug Test Results - <br /> Stockton Service Center <br /> ' On January 26, 1994, slug tests were conducted in monitoring wells MW-1, <br /> MW-8, and MW-9 at the District's Stockton Service Center site The purpose of the <br /> ' study was to gather data that would allow the estimation of the horizontal hydraulic <br /> conductivity of the underlying aquifer Slug tests can be used to determine to situ <br /> hydraulic conductivity values from tests carried out in a single well <br /> i <br /> Hydraulic conductivities were estimated from slug test data by the Hvorslev <br /> method (Hvorslev, 1951, Freeze & Cherry, 1979) The irutial analysis by Hvorslev <br /> assumed a homogeneous, isotropic, infinite medium in which both soil and water are <br /> incompressible <br /> ' A slug test is initiated by causing an instantaneous change in the water level in <br /> a well by suddenly introducing or removing a solid cylinder of known volume The <br /> ' water levels are measured by a data logger at timed intervals as the water level <br /> returns to static conditions The height of the water level immediately after insertion <br /> of the cylinder is defined as ho The height of the water level above the static level <br /> at some time, t, after the beginning of the test is denoted as h The data are plotted <br /> by computing the ratio h/ho and plotting that versus time on semilogarithinuc paper, <br /> ' as shown in the example The data are normalized to static water levels <br /> Once the curve has been plotted, a value is determined for the basic lag time <br /> ' (Tj To is the time value at which the normalized displacement data is equal to a <br /> value of 0 37 This value is determined in practice by drawing a horizontal line across <br /> ' the graph from a point on the y-axis equal to 0 37 Once the normalized drawdown <br /> versus time curve is intercepted, a perpendicular to the line for which y = 0 37 is <br /> drawn, intersecting the x-axis The time value of the intercept on the x-axis is the <br /> ' time value for To This is demonstrated in the example for MW-8 Falling Head 2 <br /> If the length of the screen is more than 8 times the radius of the well screen, the <br /> ' following formula applies <br /> rz In (LZR) X 1,440 nun/day <br /> K = 2LT9 <br /> 94 R3 East Bay Municipal Utility D1StrlLt <br /> 40429500\slugdata 1 Stockton Service CentLr-Remediation <br />