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1/23/2019 State.co.us Executive Branch Mail-Fwd:Twentymile Coal, LLC,TR16-84 TA4 Responses <br /> From: Bays, Jim/TPA<JimoBays jacobs.com> <br /> Sent: Thursday, January 17, 2019 1:58 PM <br /> To: Nettleton, Jerry<JNettleton r@peabodyenergy,com> <br /> Cc: Evans, Derek/HOU <Derek.Evans@jacobs.com> <br /> Subject: Twentymile Passive Treatment System Question <br /> Hi Jerry <br /> Thanks for your patience. I spoke with our design lead, Gary Bowles, and we reviewed the drawings, the information <br /> available and their question. <br /> For item 1, the vortex stones, the answer is that there are none in this drawing and none are called for. Although our <br /> detail No. 1 is called "Crest Stones and Footer Stones", it is intended as a catch-all detail for stone type and placement, <br /> and therefore includes vortex stones in the text. As you know, crest stones and footer stones are called out on our <br /> drawing but vortex stones are not in our design. The velocities are not sufficient to require them, as they are used typically <br /> for energy dissipation. <br /> For item 2, the weep hole, we didn't include them intentionally as we do not see the need for them. This is not a concrete <br /> wall, but instead is grouted riprap and the relatively small size of the structure and the open-sided nature of the structure <br /> indicate there would be no retention of water behind the structure that would have a significant effect. <br /> Please let me know if you have any questions on this response. <br /> Jim <br /> Jim Bays I Jacobs I Technology Fellow I Natural Treatment Systems I + 01.813.281.7705 + 01.813.765.9286 mobile <br /> + 01.813.874.3056 fax <br /> Jiirn..IBays Jacobs„com I w „jacobs„coim <br /> From: Nettleton, Jerry <br /> Sent: Tuesday, January 08, 2019 9:06 AM <br /> To: 'Bays, Jim/TPA' <Jim,Bays jacobs.com> <br /> Cc: Evans, Derek/HOU (Derek,Evans@jacobs.com) <Derek.Evans@jacobs.com> <br /> Subject: Twentymile Passive Treatment System Question <br /> Jim— <br /> As part of the permitting process for the Passive Treatment System, I am responding to some comments <br /> from the Colorado Division of Reclamation, Mining, and Safety. One of their comments (re: the cascade <br /> system at the inlet, Drawing C11 —Sheet 15 of 15) is reproduced below. Would you provide <br /> information/response on the highlighted items. Thanks for your consideration and assistance- <br /> https://mail.google.com/mail/b/AN50xKOKJ ROCsWaEnKNoaNi le8rnVdY8EGJbj5W5_to7gHAFsFyx/u/O?ik=deb7fOcd20&view=pt&search=all&permthi... 2/4 <br />