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Mr.Roger Doak <br /> Coal Ash Pilot Project Proposal <br /> June 26,2000 <br /> Page 8 <br /> of the boiler where it is removed using a water discharge system. This "bottom" ash is <br /> conveyed to holding ponds for excavation and removal from the plant site. <br /> Lighter particles of ash are carried in the flue gas stream into collection devices known as <br /> baghouses, which contain fabric filters for removing the ash from the gas stream. The clean <br /> gases are then discharged through stacks and the ash removed from the filters and conveyed to <br /> silos for unloading and removal from the plant site. Typically, ash makes up 10% of the coal. <br /> The Cherokee plant typically burns two million tons of coal a year, generating 200,000 tons of <br /> ash. Of this amount, approximately 80% (or 160,000 tons) is in the form of fly ash and 20% <br /> (40,000 tons) is bottom ash. <br /> Silo ash is unloaded into trucks through a pug mill, which adds 20% water to mitigate dusting. <br /> Some ash is dry unloaded into bulk trucks for resale. Ash trucks leaving the plant site are <br /> covered and the ash delivered to job sites (construction projects) or to disposal locations. <br /> Bottom ash, which will not be used in the Varra project, is excavated using hydraulic shovels <br /> and loaded for off-site transport. <br /> 3. We concur that based on available data it is difficult to ascertain why element concentrations in the <br /> leachates from the SGLP were much lower. It is our opinion the difference in analytical results is <br /> a combination of the interaction of natural water with the ash and extraction and analytical <br /> techniques. There can be no basis for comparison as the leachates from the CSU experiment <br /> were not filtered. As you are aware all the leachates from the modified column test were <br /> filtered to 0.45 microns and are comparable to one another. <br /> 4. The extraction fluid for the TCLP test conducted by Analytica was #I. The pHs of the final <br /> extracts are presented in Attachment H. <br /> 5. The only consensus methodology employed during this study was the TCLP. The SUP was <br /> identical to the TCLP with the exception that natural waters were used as the leaching medium. <br /> Methods and procedures as generated by CSU for this project are presented in Attachment 1. <br /> However, since the samples from the CSU experiment were not filtered the value of these data <br /> and corresponding methodology is uncertain. <br /> The methodology used in the modified column leaching test is presented in the QAPP generated <br /> for the leaching tests. Natural water was used in the test with the exception that fluorescein <br /> was added as a visual aid. Photographs of the modified column leaching tests are presented as <br /> an Attachment A to this submittal. <br /> 6. We agree that in some cases further testing for various elements may have been warranted. <br /> However, budget restraints required us to selectively eliminate elements, which appeared to be <br /> non-issues. The reduction in elements was based on our testing data and available data from <br /> other investigations — none of which indicated mercury or titanium to be a concern in coal <br /> ashes. However, the analytical suite in the modified column test incorporated more elements, <br /> including mercury and titanium, all of which were tested on every occasion, <br />