Laserfiche WebLink
Mr. Michael T. Goldstein <br /> October 28 , 1985 <br /> Page 2 <br /> chloroform transport in the vicinity of the Georgia-Pacific Tracy <br /> plant. Random-Walk is a two-dimensional, finite difference computer <br /> program that can simulate solute transport in groundwater (Prickett , <br /> T. A. , and others; "A Random Walk Solute Transport Model for Selected <br /> Groundwater Quality Evaluations , " Bulletin 65 of the Illinois State <br /> Water Survey) . The effects of dispersion and chemical reactions <br /> ( retardation) are taken into account by this model . <br /> The model can simulate nonsteady or steady flow problems in <br /> hetrogeneous aquifers under confined and/or unconfined and leaky <br /> conditions. The program covers pumping and injection by wells and <br /> allows specification of chemical constituent concentrations in any <br /> segment of the model. Further features of the program include <br /> variable grid size, printout of input data, sequential plots of <br /> solute concentration distributions, concentrations of water recharged <br /> to the modeled area, quantities of chemical constituents removed by <br /> pumpage, and the effects of dispersion and dilution or mixing of <br /> waters having different solute concentrations . <br /> The basis for the solute transport calculation in this model is that <br /> the distribution of concentrations can be represented by the <br /> distribution of a finite number of discrete particles. Each particle <br /> is assigned a mass which represents the weight of pure solute <br /> dissolved in an element of the aquifer to produce a convenient unit <br /> concentration, e.g. , 100 ppb for each particle in an element. <br /> The particles are moved by groundwater flow. The changes in <br /> concentration with assistance from the source are controlled by <br /> dispersion, retardation, dilution, and mixing. The groundwater flow <br /> vector is entered as the regional velocity and modified as the head <br /> distribution is changed. The dispersion is calculated as a random <br /> process tending to a normal distribution moderated by longitudinal <br /> and transverse dispersivity. The retardation is a coefficient that <br /> includes adsorption, organic fixation, and biodegradation. <br /> Basic Transport Coefficient <br /> The basic transport coefficients defined for the shallow aquifer in <br /> the vicinity of the Georgia-Pacific plant are as follows: <br /> Transmissivity = 150 ,000 (gallons per day per foot) <br /> Storage coefficient = 0 . 01 ( dimensionless) <br /> Hydraulic conductivity = 3 ,750 (gallons per day per square foot) <br /> Porosity = 0 . 30 (dimensionless) <br /> Longitudinal dispersivity = 27 ( ft) <br /> Transverse dispersivity = 6 .5 ( ft) <br /> Retardation coefficient = 1 .0 (dimensionless) <br /> Regional X flow = -0 . 53 ( ft/day) <br /> Regional Y flow = 1 . 57 ( ft/day) <br /> Particle mass = 0.7488 ( lbs) <br /> BROWN AND CALDWELL <br /> PO,BOX 8045 WALNUT CREEK,CA 945961220•(415)93]-9010 TELEX 336490 .OFFICE AT 3480 BUSKIRK AVENUE PLEASANT HILL 94523 <br />