2023-02-24_PERMIT FILE - M2022013 (8)

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Page 119 6.4.4 EXHIBIT D — Extraction Plan `... that head cutting/erosion will not progress through the full length of a 100-ft riverside berms. It is important to note that should a flood occur that results in head cutting/erosion of a riverside berm, Varra Companies, Inc. will act diligently to restore the damaged areas to pre- flood conditions. As mentioned, this analysis is conservative and riverside head cutting/erosion is based on the 100-yr flood. There is a small probability that such a flood event could occur during extraction and when the pit is dewatered. The DRMS in a supplemental adequacy response dated November 17, 2022 challenged the validity of the engineered design approach taken by Flow Technologies despite having accepted it as valid in the past. Raptor Materials believes the approach is valid and is in the process of performing an analysis by alternate methods incorporated in HEC-RAS. This, however, will take time. Raptor has per DRMS suggestion decided to adopt the 400-foot setback from the top of the riverbanks to the top of the pit-side slope based on guidance developed using generic and non-site-specific empirical methods as adopted by the Mile High Flood District whose jurisdiction does not include the proposed operation. Raptor Materials intends after permit approval to present the results of the ongoing engineering evaluation as a Technical Revision to obtain relief from what we are confident are extreme setbacks. During extraction, a predominantly vertical advancing pit wall (the extraction front) is not anticipated due to the use of excavators in the removal of the material deposits. Excavators provide a great deal of control over the extraction process. The maximum length of the extraction front will likely never exceed the length of one side of a quarter section of land, or 1,3 20± f eet, or less; in any given direction. The advancing front will result in a moving face with a slope typically equal to or flatter than 1.2 5H:1V, and commonly not greater than 1.2 5H:1V along the perimeter of the extraction limits to depth. The exception to cut perimeter slopes is shown with a distinct Red Boundary on Exhibit C-2: Extraction Plan Map, where cut slopes will not exceed 2H:1V in order to maintain integrity and stability along that designated perimeter area (refer to the AWES Slope Stability Analyses of 23 December 2019, located at the back of this exhibit). Internal transport of extracted materials to conveyor systems or other internal transport; or otherwise by approved public roadways, will be used in the transportation of extracted materials to the designated plant/stockpile location, described in greater detail, below. Acreage to be affected during the first year of extraction activities include the establishment of the initial Wash Pond and attending Settling Pond(s), Plant VARRA COMPANIES, INC. TWO RIVERS SAND GRAVEL AND RESERVOIR PROJECT MARCH 2O22 A REGULAR IMPACT[1121 CONSTRUCTION PERMIT APPLICATION-COLORADO DIVISION OF RECLAMATION MINING&SAFETY OFFICE OF MINED LAND RECLAMATION