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PZ-1 Falling Head Permeablity Test Calculations, Hvorslev Method <br /> The following calculations were made using the Hvorslev method (Fetter, 1994). The <br /> falling head permeability test was perfo'rmed.by lowering a solid PVC slug to just below <br /> the static water Ievel and measuring the subsequent fall of the water level over time using <br /> an INSITU 10-psi pressure transducer and a Hermit.3000 data logger. The static water level <br /> L was at 10.5 feet below the top of the casing and the pressure transducer was placed at 25.5 <br /> feet below the top of the casing. The piezometer was installed in an 8-inch diameter <br /> borehole,had an inner casing and screen diameter of 2 inches, and a screen length of 15 <br /> 1� feet. The calculations are based on the assumption that the piezometer screen interval <br /> partially penetrates an unconfined aquifer. <br /> The Hvorslev Method states that if the length f the piezometer g o e p e ometer screen is more than 8 times <br /> the radius of the well screen, the following formula applies: <br /> { <br /> K= r21n L R <br /> 2L,To <br /> K =hydraulic conductivity = ? <br /> Y <br /> r = inner radius of the piezometer casing= 0.0833 ft <br /> R= radius of the borehole (if annulus surrounding screen is filled with gravel pack) <br /> = 0.3333 ft <br /> 4 = length of the well screen (includes gravel pack portion of the well above the screen) <br /> = 18 ft <br /> To= time for water level to fall to 37% of the initial rise in water level after slug is inserted <br /> = 7 <br /> Inspection of the head/initial head (h ho)vs time plot indicates: <br /> To = 2.8s <br /> therefore, <br /> K= 0.0833 ft %)�.18 ft..._/0 333 ft) <br /> 2(18£t)(2.8 s) <br /> K <br /> 0.0002746 ft/s <br /> K = 23.7 ft/day or K = 0.00837 cm/s <br /> A.hydraulic conductivity of 0.00837 cm/s falls within the range typical of well sorted sand <br /> to well sorted gravel (Fetter, 1994) <br /> r � . <br /> I'E - <br />