2021-03-05_REVISION - M1977141 - Laserfiche WebLink

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Lyons Quarry �� 112d Reclamation Permit Operations Technical Revision property lease area. The area of disturbance extends from South St. Vrain Creek on the north, to the south approximately 1,500 feet. The limits of affected land make up the east and west perimeters of the site reclamation with the east boundary adjacent to the lease property line. A mining map is shown in Attachment A -Figure 4. The site is further described as having a surface elevation (El.)of 5,508 feet near the northeastern entrance of the site to above El. 6,000 feet at the south end of the site. The existing natural slopes in sedimentary rock strata are as steep as 1.75H:1V, where the sedimentary strata are capped by the Lyons Sandstone. Where the sedimentary rocks are not capped by the Lyons Sandstone, slopes ranged from 2H:1V to 4H:1V. The mining plan splits the operation up into two quarries as shown in Attachment A - Figure 5. Quarry 1 is at the east end and at the base of the 300-foot tall high wall. Quarry 1 is bounded on the south and west by the highwall protrusion and on the east and northeast by backfill material. A constructed swale allows access into Quarry 1 between the backfill and an access road ramp that leads to Quarry 2 to the west. The horseshoe-shaped Quarry 2 is in the southwest corner of the operation and is bounded on the east, south and west by quarry highwalls. Quarry 2 was partially backfilled in 2017 but still has highwalls approximately 100 feet in height. The flattest measured slopes were in areas mapped as landslides. Existing natural slopes in the dacite are nearly vertical where the dacite is exposed along the north side of South St. Vrain Creek. Where the dacite outcrops in the drainage along the west side of the site, the existing natural slopes range from 0.3H:1V to 2.2H:1V. This large range in the natural slope was measured along west- facing slopes over a span of approximately 300 feet. Vegetation is generally absent in the leveled and mined areas. Vegetation over the remainder of the site consists of grasses, forbs, and shrubs/brush with various cottonwoods, willows, Virginia creeper and golden currant found along the drainages. Surface water is present along the north edge of the site, in South St. Vrain Creek. Groundwater is present, ponded in low areas and observed as wet areas along the base of the highwall. Groundwater is also anticipated perched above siltstone and shale layers in the Fountain Formation. Under the current reclamation plan, the existing sedimentation pond on the east end of the site will be utilized for dust control, earthen fill moisture conditioning, and watering vegetation as needed. The pond will then be backfilled (requiring approximately 2,200 CY) at the end of construction to blend with the surrounding topography, unless alternatives for future land use dictate otherwise. The final contours will be graded toward South St. Vrain Creek. 3 Exhibit E — Reclamation Plan The post-mining use has come under consideration recently with the purchase of the site by BCPOS. Original plans involved the land being reclaimed to cattle range and pastureland in the production, stockpile and pit floor areas. With these land uses in mind, a Reclamation Plan developed in the 2016 Technical Revision#2 addressed the areas within the quarry, known as Lyons Quarry Reclamation Area 1 (LQRA1 as noted in Technical Revision#4). The plan included re- grading the high walls, backfilling the pit areas, installing runoff erosion control structures around the site perimeter and revegetating approximately 81% of the LQRA1 total 37-acre area. The remaining March 2021 1 4