Laserfiche WebLink
Lorertciro Cam~an Mine - GraunGwarer Teclmical ReOOrt <br />• <br />Comparing this value to the established values determined in the regional study by Howard (Table <br />GW 7), this value is one order of magnimde lower. Based upon field data from bailing the wells <br />at the site, the value determined from site specific slug test would appear extremely low. <br />Comparison of field data, the potential pumping rates based upon site-specific data, and the data <br />from the regional study indicates that the regional values may be more consistent with field data <br />from bailing. The potential pumping rate from the well can be estimated from the equation <br />Q=Ts/2000 (derived from Fetter, 1980). In this calculation Q is the flow rate, T is the <br />transmissivity (determined from the hydraulic conductivity T=Kb), s the available drawdown, and <br />2000 is a constant (accounts for conversion of T in g/d/ft). Therefore: <br />Q = (4.78 x 10"Z g/d/fr) [187 ft (for MW-41)]/2000 <br />Q = 0.0045 gpm (for site-specific data) <br />Q = 36.6 g/d/ft [187 ft (for MW-41)J/2000 <br />Q = 0.14 gpm (for regional data) <br />Generally, the rate of evacuation for the wells during the sampling events is estimated as 1.0 gpm. <br />This value and the potential pumping rate for the well (determined above utilizing regional data) <br />compare more favorably; therefore the range of the transmissivity in this zone is 4.78 x lOZ g/d/fr <br />to 0.14 g/d/fr. <br />• Storativity estimated by this method (Cooper, Pappadapoulous) was 2.25 x 10°. The storage value <br />is within the range for a confined zone (heath, 1983). The hydraulic conductivity determined was <br />one order of magnitude higher than the value determined by Howard (1982) for the Raton <br />Formation sandstone. <br />Groundwater seepage velocity (v,) can be determined from the gradient (dh/dl, or I), effective <br />porosity (rte, and hydraulic conductivity (K). Seepage velocity represents the rate at which water <br />actually moves through the pore spaces. The relationship v,=Ki/ttt, is utilized to determine this <br />value (Fetter, 1980). From the above analyses: <br />K = 1.28 x 10-' ft/day (for site specific tests), 0.0408 ft/day (for regional values) <br />I = 0.0055 ft/ft <br />nt=10% <br />Therefore: <br />v, = Ki/r4 <br />vs = (1.28 x 10' ft/day) (0.0055 ft/ft)/10 % <br />v, = 7.04 x 10"5 ft/day or 2.56 x 10-Z ft/yr (for site-specific) <br />vs = (0.0408ft/day) (0.0055 ft!ft)/10 <br />v~ = 2.24 x 10' ft/day or 0.82 ft/yr (from regional data) <br />u <br />Groundwmer.a75\Dcttmber 9. 1996 41 <br />