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Mr. Himanshu H . Mehta, P . E . 30 September 2011 Page 2 [DNAPL] ) , pump and treat (P& T) , and natural attenuation monitoring for the downgradient dissolved plume . Based upon the results of post- source removal groundwater monitoring activities and an evaluation of natural attenuation processes , Geosyntec recommended in the June 2006 monitoring report that the existing P&T system , originally installed in 2001 as an interim measure , be permanently shut down . The P& T system was designed to provide hydraulic capture of the source area . With the source area removed via the excavation, the continued operation of the system was no longer justified . Additionally, the natural attenuation evaluation included in the June 2006 report demonstrated that anaerobic degradation processes are actively degrading the CVOC plume . In consideration of the ongoing natural attenuation processes occurring at the site, the enhancement of these biological processes via the injection of an electron donor was proposed , and agreed to in concept by the FDEP in correspondence dated 2 August 2006 . A RAP Modification (RAPM) was submitted to the FDEP outlining the injection of an electron donor, Emulsified Oil Substrate (EOS®) , in May 2007 . Geosyntec implemented the RAPM activities in April through June 2008 , as documented in the RAPM Implementation Report submitted to FDEP as Appendix A to the June 2008 Semi -Annual Groundwater Monitoring Report dated September 2008 . RAPM Addendum implementation , which included bioremediation implementation in the former source area, was completed in June and July 2009 and documented in the July 2009 RAPM Addendum Implementation Report . The ongoing semi-annual groundwater monitoring activities have documented the success of this approach . EOS ® is designed to provide a carbon source to the indigenous bacteria for up to approximately three years . In response to FDEP ' s request dated 3 May 2011 and supported by groundwater monitoring results, a RAPM Addendum No . 2 was prepared and presents an electron donor injection plan to address CVOC impacts in the former source area and to redose the two downgradient biobarriers , which are serving as a permeable reactive barrier (PRB ) to treat a portion of the dissolved plume . Electron donor in the form of emulsified oil will provide a hydrogen source for the indigenous microbes at the site, and the microbes will in turn transform the CVOCs to the harmless byproduct, ethene , via reductive dechlorination . PROPOSED SCOPE OF WORK The proposed scope of work includes the activities required to implement the FDEP-approved RAPM Addendum No . 2 , including the installation of the proposed former source area injection wells, the purchase of 78 drums (55 - gallon capacity) of EOS ® 598 , and the injection of 500 to 1 , 203 gallons of a 5 or 10 percent EOS® solution to each of the 90 existing biobarriers and proposed injection wells . The remainder of this letter provides details regarding the proposed scope of work and a budget estimate to accomplish the work described herein . XR11055\XR11072 er) g1P1cers I scientists iiill0 ators