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Page 1 19 <br /> 6.4.4 EXHIBIT D — Extraction Plan <br /> times, safety will take precedent and over-ride all other conditions in time with <br /> a matter of safety or emergency respective to any and all aspects of the <br /> approved permit. <br /> To minimize the potential of river capture, planned setbacks from the two rivers <br /> was evaluated by Flow Technologies (refer to report at the back of Exhibit G: <br /> Water Information- titled: `Two Rivers Riverside Berm Failure Analysis and Flood <br /> Control Mitigation Plan' of 22 January 2020). The report finds: <br /> '... that head cutting/erosion will not progress through the full length of <br /> a 100-ft riverside berms. It is important to note that should a flood occur <br /> that results in head cutting/erosion of a riverside berm, Varra <br /> Companies, Inc. will act diligently to restore the damaged areas to pre- <br /> flood conditions. <br /> As mentioned, this analysis is conservative and riverside head <br /> cutting/erosion is based on the 100-yr flood. There is a small probability <br /> that such a flood event could occur during extraction and when the pit is <br /> dewatered. <br /> The DRMS in a supplemental adequacy response dated November 17, 2022 <br /> challenged the validity of the engineered design approach taken by Flow <br /> Technologies despite having accepted it as valid in the past. Raptor Materials <br /> believes the approach is valid and is in the process of performing an analysis <br /> by alternate methods incorporated in HEC-RAS. This, however, will take time. <br /> Raptor has per DRMS suggestion decided to adopt the 400-foot setback from <br /> the top of the riverbanks to the top of the pit-side slope based on guidance <br /> developed using generic and non-site-specific empirical methods as adopted by <br /> the Mile High Flood District whose jurisdiction does not include the proposed <br /> operation. Raptor Materials intends after permit approval to present the results <br /> of the ongoing engineering evaluation as a Technical Revision to obtain relief <br /> from what we are confident are extreme setbacks. <br /> During extraction, a predominantly vertical advancing pit wall (the extraction <br /> front) is not anticipated due to the use of excavators in the removal of the <br /> material deposits. Excavators provide a great deal of control over the <br /> extraction process. The maximum length of the extraction front will likely <br /> never exceed the length of one side of a quarter section of land, or 1,320± feet, <br /> or less; in any given direction. The advancing front will result in a moving face <br /> with a slope typically equal to or flatter than 1.25H:1V, and commonly not <br /> greater than 1.25H:1V along the perimeter of the extraction limits to depth. <br /> The exception to cut perimeter slopes is shown with a distinct Red Boundary on <br /> Exhibit C-2: Extraction Plan Map, where cut slopes will not exceed 2H:1V in <br /> order to maintain integrity and stability along that designated perimeter area <br /> VARRA COMPANIES, INC. TWO RIVERS SAND GRAVEL AND RESERVOIR PROJECT MARCH 2O22 <br /> A REGULAR IMPACT[1121 CONSTRUCTION PERMIT APPLICATION-COLORADO DIVISION OF RECLAMATION MINING&SAFETY <br /> OFFICE OF MINED LAND RECLAMATION <br />