2019-07-09_REVISION - C1981035 (2)

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4.09.2—Valley Fill 4.09.2(2)(d) As originally stated in my memo dated May 3, 2019, "[p]er this rule...the Division has approved an alternative sizing with the currently approved underdrain...Please have King(GCC)provide a demonstration or analysis that ensures the proposed underdrain expansion size is sufficient in alleviating water within the entire refuse pile including the proposed expansion per Rule 4.10.3(5)." In GCC's response (see GCC Reponses#6), they state that the currently proposed underdrain sizing is based upon the original refuse pile underdrain analysis in Appendix 10(1) and a July 2014 Trautner Geotech report. The July 2014 Trautner Geotech report(Report)has not been provided as part of TR-27 but after discussions with Joel Riggins of GCC, he was able to forward this report for our review. The Report was originally submitted under TR-20, however, withdrawn in 2017. This Report is a geotechnical study conducted by Trautner for a waste bank similar to that proposed under TR-27 in response to violation CV2012003. In the Report, the underdrain design for TR-20 was based on Appendix 10(1) as well as an on-site investigation done by Trautner. It should be noted that the waste bank proposed in TR-20 is considerably smaller than the Lower Refuse Pile proposed in TR-27. From GCC's Response#6, in order to address the difference in size, it appears that GCC used a linear relation between the Reports recommended underdrain size and pile footprint area to size the proposed underdrain in TR-27. While this may be acceptable,this information needs to be updated and included with TR-27 for the Division's review. Additionally, it appears that the underdrain in the Report is designed as an independent underdrain. In TR-27, the underdrain proposed is an extension to the existing underdrain of the Refuse Pile. With the linear relationship used for sizing the underdrains between TR-20 and TR-27, it appears that this method does not take into account the addition of potential groundwater flow from the current underdrain of the Refuse Pile into the Lower Refuse Pile for TR-27. o If GCC is using part of the information in the Report as its demonstration to justify alternative criteria used for an underdrain per Rule 4.10.3(5), please have GCC submit this information as part of TR-27. While the information used as part of the Report is applicable, the entirety of the Report should not be submitted as is due to conflicting designs. This information/analysis should come amended specifically for TR-27. o Please have GCC provide additional explanation on whether the currently proposed underdrain sizing for the Lower Refuse Pile takes into account the potential groundwater flow from the current underdrain of Refuse Pile. All other information required under 4.09.2 has been met. 2