2019-12-05_HYDROLOGY - M1999058 (4)

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would collect water flows from the road fill as temperatures warm in the late spring. A more detailed description of the work completed to date is provided under heading 'Mitigation and Remediation Efforts'. Soil and water sample results are included in 'Appendix G: Colorado Stone Quarries — Master Data Tracker 1 1.12.19.' 4. Results of the operator's investigation to assess the conditions or circumstance that led to the spill, and what protective measures will be taken to prevent a similar event from occurring in the future. Response: The results of the investigation, to date, detailing the cause of the spill are included under heading `Timeline.' The spill does not appear to have been the result of a single cause, but rather resulted from several potentially contributing factors which are discussed more fully under the heading `Factors Contributing to the Spill.' Protective measures to be implemented are detailed under the heading `Plan to Mitigate Diesel Spill Reoccurrence' and include: (i) installation of a liner under all permanent fuel tanks and transfer points (the tanks in issue were double-walled to satisfy spill containment requirements; however, the transfer points were not included within the overall containment system), (ii) increased training of appropriate CSQ staff regarding proper fuel handling and procedures associated with fuel handling, (iii) and installation and certification of all systems involving hydrocarbons will be conducted by appropriately authorized fuel services specialists. Timeline of Events A schematic timeline is presented in Appendix B and should be used in conjunction with the following text narrative. The timeline begins a few months before the spill occurred, with the earliest factors occurring in July 2019. As noted above, the fuel configuration of the prime power genset relies on a relatively small 100 gallon day tank to provide fuel to the C27 engines. The 100 gallon tank is filled by a float and pump system that feeds from a 12,000 gallon above-ground bulk tank. Both tanks are double walled, and the day tank is located within the genset Conex and the 12,000 gallon bulk tank is located adjacent to the Conex. The original installation of the prime power genset and related tanks in 2014 is depicted in Figure IA. As initially installed, the Conex was located at an elevation slightly above or level with the bulk tank. The 100 gallon day tank was equipped with a return flow system and a vent pipe that exited the Conex through the roof. The top of the vent pipe was higher than the `elbow' of the return pipe system. The vent pipe was capped by a pressure release cap meant to keep precipitation out of the vent pipe, but at the same time allow for the release of pressure buildup in the system. In the event of an overfill of the day tank, the fuel pump would continue to feed the day tank, but the pressure of the pump would push the overflow back into the bulk tank through the return flow system. At the same time fuel was being pushed through the return system into the bulk tank, fuel would rise in the vent pipe until it reached equilibrium with the `elbow' height of the return pipe (depicted as the red fuel line in Figure 1 A). 4