2021-09-16_REVISION - M1983033 - Laserfiche WebLink

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Walstrum Spur Amendment, Exhibit D—Mining Plan revised September 2021 In general, mining of the Spur Amendment will be done from top to bottom and west to east. Mining will begin at the northwest corner of Parcel H2 adjacent to the Existing Quarry and move east along the north (upslope) side of the Spur Amendment. Mining on the south (downslope) side will occur roughly in tandem with the north side in order to keep elevations roughly the same. Since the south side is generally lower in elevation than the north side, mining of the south side will begin after the north side. Exhibit C-3 illustrates the mining condition with a floor elevation at 7,800 feet. It is meant to serve as an example of how mining will progress down from the existing grade to the quarry floor. In this example, mining will be completed at elevation 7,800 before progressing to elevation 7,700. Throughout mining, the quarry floor elevation topography will be graded to guide runoff from disturbed areas westward to the Existing Quarry. Mining of the affected area of the 8-acre Parcel B2 will occur in conjunction with mining of the west side of the Existing Quarry. A portion of this parcel, depicted on Exhibit C-3, will remain undisturbed as a screening buffer as viewed from Highway 6. The overall timeline for mining the Spur Amendment is 30 to 50 years. Existing Quarry Timetable Mining in the Existing Quarry will occur concurrently with mining in the Spur Amendment area. The reason for mining both areas at the same time is that the resource quality in the two areas is different. Material in the Spur Amendment is of a higher quality and will be blended with material from the Existing Quarry. In this manner, mining in both areas will occur at roughly half the rate that would occur if only one area was being mined. In general, the Existing Quarry will be mined in a counterclockwise manner. Current mining will continue with the existing benches on the east side, then the north side, then the west side. The overall timeline for mining of the remaining areas of the Existing Quarry is 20 to 50 years. 3.6 Nature of Deposit (f) A map (in Exhibit C - Pre-Mining and Mining Plan Maps(s) of Affected Lands, Subsection 6.4.3) may be used along with a narrative to present the following information: (i) nature, depth and thickness of the ore body or deposit to be mined and the thickness and type of overburden to be removed(may be marked "CONFIDENTIAL,"pursuant to Paragraph 1.3(3)); (ii) nature of the stratum immediately beneath the material to be mined in sedimentary deposits. Exhibit C-3 shows the Affected Lands. In the Spur Amendment area, there is typically less than 1 foot of topsoil overlaying 4 feet of silty sand colluvium followed by 5 feet of weather gneiss before hitting competent bedrock at approximately 10 feet. The majority of the disturbed area has a soil classification of Cathedral-Rock outcrop complex. This soil type typically has only a 10-to 20-inch depth to lithic bedrock and no soil over bedrock in the rock outcrop areas which cover a substantial portion of the disturbed area (see Exhibit I Soils Information). Topsoil is relatively absent from this operation as confirmed by test pits dug on-site in 2020 (see Geotechnical Stability Exhibit). The bedrock is a metamorphic rock including layers of Biotite Gneiss, Feldspar Gneiss, Hornblende Gneiss, and Interbedded Gneiss. The average thickness of the deposit is more than 600 feet. The Geotechnical Stability Exhibit included in this application presents a summary of the geologic investigation describing the nature and depth of the aggregate material and overburden in more detail. 3.7 Commodities to be Mined 6.4.4(g) Identify the primary and secondary commodities to be mined/extracted and describe the intended use; The primary products produced from the Existing Quarry are and will continue to be aggregates for use as construction materials. No secondary commodities will be extracted. oTETRA TECH P age 6 1 9