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Varra Coal Ash Pilot Project <br /> May 3, 1999 <br /> Page 3 <br /> 13. The proposal states that the disposal trench will have one-half filled with only fly ash and the <br /> J other half with bottom ash and fly ash. The bottom ash will be placed in the lower one-half of <br /> the saturated portion of the trench and fly ash placed within one foot below ground surface. <br /> Describe how the monitoring points will be constructed to evaluate the bottom ash/fly ash half of <br /> the trench. <br /> 14. The applicant has estimated a groundwater flow rate of 100ft. /day below the site. The <br /> groundwater sampling sequence must be appropriate to evaluate the potential rapid changes in <br /> groundwater quality. <br /> 15. If the objective of the pilot project is to demonstrate that coal ash exhibits "inert" <br /> characteristics in a saturated medium, than coal ash should be compared to an industry <br /> recognized inert material under identical environmental conditions. With this in mind, CDPHE <br /> suggests that a "control' trench be constructed at this site. This trench would be backfilled with <br /> inert material such as, concrete or gravel. The hydrologic properties would be evaluated and <br /> compared to the coal ash trench. In addition, groundwater quality could be sampled <br /> downgradient of the control trench and this data compared to the groundwater quality of the coal <br /> ash trench. <br /> 16. Some trace elements in coal are naturally radioactive. These radioactive elements include <br /> uranium, thorium, radium and their numerous decay products. There are questions concerning- <br /> possible risk from radiation. In order to accurately address questions regarding radioactive of <br /> coal ash, it is important to determine the concentration and distribution of radioactive elements in <br /> the different sources of bottom and fly ash proposed for this project. <br />