The Environmental Protection Agency, Region III (EPA) is issuing this Second Explanation of Significant Differences (ESD), for the September 30, 1992, Record of Decision (ROD) (no. 189, Section III, in the Administrative Record Index for the Site) issued for the Tonolli Corporation Superfund Site (Site) in Nesquehoning, Pennsylvania. This ARAR requires that 'a minimum distance of 4 feet shall be maintained between the top of the subbase (of the landfill) and any seasonal high water table without the use of any artificial or manmade groundwater drainage or dewatering systems' and that the 'distance between the top of the subbase and the regional groundwater table shall be a minimum of 8 feet'. The 1995 ESD also required further data collection to determine if the ARAR was being achieved or if the need to evaluate an artificial system existed. The Tonolli Site Technical Committee, through their consultant, Advanced GeoServices Corporation, has submitted a Technical Memorandum (October 1996) which presented the findings of the data collection required by the 1995 ESD. The data shows that the minimum 4 feet ground water isolation distance is not achieved during all seasons. However, the data also show that the groundwater did not contact the liner during the remedial design investigation. Therefore, EPA believes an equivalent standard of performance to that required by the groundwater isolation distance regulation presently exists and has determined that an evaluation of a manmade groundwater drainage or dewatering system is unnessary.