Laserfiche WebLink
1 <br /> ARCADIS GERAGHTY&MILLER <br />' Work Plan Comments by SJCPHS <br />' SJCPHS <br /> Comment In paragraph 3, your letter states, " the depth to groundwater at <br />' the time of the release(s) is not known" <br /> Response ARCADIS Geraghty and Nbller will work with the SJCPHS, the <br /> California State Department of Water Resources (DWR), and other <br />' relevant agencies, to identify records on the elevation of, or depth <br /> to, shallow groundwater relevant to the site between the dates of <br /> the first installation of the UST's, or the date of the UNOCAL's <br /> site lease, and the present <br />' SJCPHS <br /> Comment In paragraph 4, your letter states, "The investigation should not be <br /> limited to current dissolved-phase hydrocarbons The potential for <br />' future releases to the groundwater from contaminated soil should <br /> also be investigated by sampling of the soil above and below current <br /> groundwater until the vertical extent of soil contamination has been <br /> demonstrated " <br /> Response ARCADIS Geraghty and NLller respectfully disagrees with the need <br />' to, or the appropriateness of, sampling soils beneath groundwater <br /> It is our experience at many sites in numerous locations that <br /> delineation of the vertical extent of impact to groundwater can be <br />' accomplished using the technique described in the workplan <br /> Further, the method indicated in the work plan will go beyond <br /> allowing the assessment of potential for future groundwater impacts <br />' from soils It will allow a real-time assessment of the actual <br /> impacts of groundwater on an ongoing basis <br /> Sampling of soils in the saturated zone will provide data on the <br /> total amount of constituents sorbed onto the soil particle surfaces <br /> and that which exists in the dissolved phase <br />' A quantified assessment of the future potential for groundwater <br /> impacts based on data provided from a saturated soil sample <br /> requires an investigator to make a calculation which partitions the <br />' total amount reported in the sample analysis into the amount sorbed <br /> and the amount in the sample which exists m the pore liquids as a <br /> dissolved fraction Next a calculation must be made which relates <br />' the constituent amount sorbed to the amount that is desorbed and <br /> the rate at which the desorption (into the dissolved phase) occurs <br /> Next, the rate of advection in the moving groundwater must be <br /> identified Next, the rate of migration of a constituent must be <br /> related to the rate of movement of site groundwater by a <br />' 2 <br />