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Mr.Bright July 17,2001 <br /> ENVIRONMENTAL AUDIT,INC. 094.01902 <br /> Page 3 <br /> our report dated April 4, 2001. Casing off the upper aquifers to a depth of 260 feet also provides an <br /> extra margin of safety from downward migration of petroleum hydrocarbons. It is important to note <br /> that even though the upper zones of impacted groundwater are isolated from the well, there maybe <br /> some hydrocarbon impacts in the deeper aquifers due to cross-communication created by the RIW over <br /> the past 50 years. <br /> Use of Robinhood Irrigation Well <br /> It was suggested that the existing RIW could be rehabilitated by sealing the upper zones and malting <br /> the well useable. This could be done by setting a packer below the screen and squeezing cement into <br /> the screened or perforated interval. Once set,the cement could be drilled out and the packer removed. <br /> This process would need to be done on at least two screened intervals in the RIW. It is a risky process <br /> and there is no guarantee that the zone would be completely sealed off from the well. In addition, the <br /> existing casing is old and may not be in suitable condition for this type of operation. Because the well <br /> is over 50 years old, SECOR would not recommend rehabilitating the RIW. It could turn into a very <br /> expensive undertaking and may result in making the well completely unusable. <br /> Conclusions <br /> The conclusions of the assessment of the new water supply well are: <br /> • The results of the modeling indicated that benzene-impacted groundwater should not migrate <br /> past a depth of 130 feet bgs if the new water supply well pumps between 600 and 1,000 gpm. <br /> • The new well can be located adjacent to the Robinhood Irrigation Well if the upper 260 feet of <br /> the well is cased and sealed. <br /> • The design of the new water supply well should be as described in the SECOR letter dated <br /> April 4,2001. <br /> • Sealing of the two upper screened or perforated intervals in the RIW would not be <br /> recommended. <br /> • Even though the upper zones are sealed from the well in the new water supply well,there may <br /> be some impacted water in the deeper zones due to cross-communication from the RIW over <br /> the past 50 years. <br /> SECOR appreciates the opportunity to work with you on this project. If you have any questions,give <br /> me a call. <br /> Sincerely, <br /> NYDR <br /> SECORIntemational Incorporated ��p y <br /> R' S�.Q <br /> a <br /> y No. HG123 <br /> UP. �l02 <br /> Stev4&mit, N <br /> R.G.,C.HG. P <br /> f �Q <br /> Principal Hydrogeologist <br /> FOF Cp41Fo <br /> Attachments: Limitations <br /> Table 1 <br /> Appendix A—Model Output <br /> EACHwt Reports\Delm Co11ege\De1taRo.dm-00:jw:I <br />