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This research improves field based estimates of aquitard compressibility and permeability. A semianalytical model of partially penetrating, overdamped slug tests achieves this objective. The short term solution is an existing fully penetrating model, the long term solution is the polar residue of an inverse Laplace transform, and an exponential spline function patches the solutions together. Large amplitude slug test data from ten pairs of partially penetrating monitoring wells installed in an unweathered till at Scituate Hill in eastern Massachusetts calibrate the model. The deposit is bound by weathered till and the Dedham Granite fracture zone, and both are far more permeable than the unweathered till. The calibrated till permeability of 8.4 × 10-16 m2 is about 25% less than existing model calibrations that include boundary recharge in permeability values. The calibrated till compressibility of 5.1 × 10-10 Pa-1 reflects the proper inclusion of recharge as a long term source of groundwater, rather than the unrealistically large compressibility calibrations required by fully penetrating models. [ABSTRACT FROM AUTHOR]

We extend Bouwer and Rice (1976) slug test theory to incorporate background head trends that may be important in incompressible material of low permeability k. The extension, which features a convolution integral of the background head, is closed form for linear trends. A sensitivity study suggests that a rising background head can diminish the head changes associated with a slug-out test and underestimate k if it is ignored, as does falling background trend with a slug-in test. A falling background head can reinforce slug-in test head change and, if ignored, can overestimate k, as does a rising background head with a slug-out test. The simple extension is verified by field tests in glacial till and stratified drift deposits in eastern Massachusetts. [ABSTRACT FROM AUTHOR]

We incorporate a linear estimate of casing friction into the analytical slug test theory of Springer and Gelhar (1991) for high permeability aquifers. The modified theory elucidates the influence of inertia and casing friction on consistent, closed form equations for the free surface, pressure, and velocity fluctuations for overdamped and underdamped conditions. A consistent, but small, correction for kinetic energy is included as well. A characteristic velocity linearizes the turbulent casing shear stress so that an analytical solution for attenuated, phase shifted pressure fluctuations fits a single parameter (damping frequency) to transducer data from any depth in the casing. Underdamped slug tests of 0.3, 0.6, and 1 m amplitudes at five transducer depths in a 5.1 cm diameter PVC well 21 m deep in the Plymouth-Carver Aquifer yield a consistent hydraulic conductivity of 1.5 x 10-3 m/s. The Springer and Gelhar (1991) model underestimates the hydraulic conductivity for these tests by as much as 25% by improperly ascribing smooth turbulent casing friction to the aquifer. The match point normalization of Butler (1998) agrees with our fitted hydraulic conductivity, however, when friction is included in the damping frequency. Zurbuchen et al. (2002) use a numerical model to establish a similar sensitivity of hydraulic conductivity to nonlinear casing friction. [ABSTRACT FROM AUTHOR]

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Summary: We derive a closed form theory of water level fluctuations caused by slug tests in a well with an annulus that extends to the piezometric surface. This hydraulics can be created by small diameter slug test equipment in a large diameter well, with an annulus established by borehole casing and the riser pipe of the equipment. The conservation of mass equation couples aquifer hydraulics, core hydraulics inside the riser pipe (which include inertia), and annular hydraulics outside the riser pipe (which include inertia and linear friction). The linear friction is needed to attenuate oscillations between the core and annulus, which would otherwise persist indefinitely after damping of aquifer discharge. A characteristic velocity is adopted for the annular friction, so that aquifer permeability is the sole calibration parameter. We calibrate the theory with overdamped and underdamped experiments run in a limestone aquifer at the Hydrogeological Experimental Site of Poitiers in France by Audouin, O., Bodin, J. 2007. Analysis of slug tests with high frequency oscillations. Journal of Hydrology 334, 282–289. The data and analytical theory yield plausible, accurate permeability estimates of 4.1×10−12 and 1.7×10−11 m2. Portable, small diameter slug testing devices may accordingly be used in permanent, large diameter cased boreholes to estimate aquifer permeability, although the annular effects can obscure aquifer hydraulics. The annular effects may also occur in slug tests on wells with skins, bypasses, and packers, although different boundary and matching conditions would be needed to model this hydraulics. [Copyright &y& Elsevier]