ARCHIVED REPORTS XR0001009 - Laserfiche WebLink

Home Browse Search

Geological recknas Inc Page 8 In Situ Remediation Feasibility Study Project No 5072 • September 20,2002 Heavy Metal Mobilization There is some evidence that the stable trivalent chromium present in the native soils can be oxidized to the less stable, highly soluble hexavalent chromium Thus potentially adding to the list of compounds that would degrade drinking water resources This condition would ' only hold true if chromium is present in the soil at a concentration sufficient to be a threat to water quality if it were mobilized and if the oxidized state were to persist beyond the bounds ' of the study area and migrate into a pumping well To evaluate this situation and the potential for a problem, soil samples will be collected at ' various depths that represent each geologic type and tested for total chromium We will also investigate the potential for off site migration of hexavalent chromium and evaluate the potential for impact to drinking water quality and methods to mitigate that threat Radius of Treatment The tight soils of the site will be a hindrance to any remedial method chosen for the site ' Use of an in-situ oxidation method would have the advantage of easily being modified as the project progressed to obtain a larger cleanup area A likely design would be to install a number of small diameter wells, on five to ten foot centers, using a direct push rig, in a gnd pattern across the highly contaminated area The wells would be used as infection points for the ozone and peroxide as well as monitoring points to determine plume conditions Some wells would be screened in the vadose zone and others would be screened in the water table so both zones would be treated --ozaW4 d+- 0Z -(;- V.Jds, , ' Peroxide is infected into each well and then "chased" with pressurized oxygen The oxygen will serve both to add oxygen to the anoxic soil and groundwater at the site and to force the peroxide out into the formation As discussed above, the peroxide will directly oxidize the ' BTEX and create hydroxyl radicals in the process As the BTEX is consumed and more hydroxyl radicals are needed to consume the remaining gasoline range hydrocarbons and fuel oxygenates, ozone will be added with the peroxide ' Groundwater monitoring would occur weekly to allow for decisions on whether more peroxide and ozone are needed Frequent monitoring will also begin to show what the - 1 radius of influence from each well is If the treatment radius is not large enough, additional wells can easily be installed 1 4.0 CONCLUSIONS AND RECOMIIWNDATIONS Conclusions I Of the several options for in-situ remedial procedures, one using an advanced oxidation process such as described above, has the best potential for effective mass removal at the site 1