ARCHIVED REPORTS_XR0004215 - Laserfiche WebLink

Home Browse Search

In general, the selected values for these input parameters represent conservative � estimates of the actual values. Assuming that the highest concentration occurs at a point i �,j source at MW-9 is more conservative than the actual field conditions based on the monitoring data. The mass of contaminant has been conservatively estimated using the entire area of the plume and a depth of 10 feet (3.05 meters) as described earlier in this t section. An effective porosity of 0.25 was calculated using the step draw down test results. The calculated porosity was compared to established ranges for the type of aquifer materials + encountered at the site. An effective porosity of 0.20 was ultimately selected from the low end of the range of values for a sand and gravel mixed aquifer (Fetter,Applied Hydro eolo , g �y 1980). The low end of the range was selected to reflect the most conservative porosity value for the model. The hydraulic conductivity is based on the highest end of transmissivity range values (35 W/day) obtained during the step draw down test divided by the aquifer thickness. These conservative assumptions provide the highest hydraulic conductivity and transport rates from the empirical range of data. The longitudinal dispersivity is assumed to be 0.1 times the flow path and the transverse dispersivity is 0.1 times the longitudinal dispersivity. The vertical dispersivity is estimated at 0.05 times the longitudinal dispersivity. (Bioscreen Natural Attenuation Decision Support System Users Manual, Version 1.3, June 1996.) The fractional organic carbon content was not measured for soils at the site. Soils 1 with lower organic carbon content provide less retardance to chemical transport.. One z, percent represents a very low organic content in soil and is in keeping with the conservative values used for all other model input parameters. � P i � 96R7 D-5 East Bay Municipal Utility District 40429700.fcr Final Closure Report I 3