HomeMy WebLinkAbout1.17 Gravel Extraction
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Section 7-1002 Gravel Extraction
1. Water Quantity and Quality Impacts/ Floodplain Impacts
The North Hangs Mine shall comply with the applicable standards of section 3-301, Floodplain
Overlay Regulations, and will be subject to section 4-109, Development in 100-Year Floodplain.
The following sections will discuss specific items in more detail.
Flammable or Explosive Solids or Gases
No flammable or explosive solids or gases will be stored on site.
Storage of Materials
Stockpiles of materials will be located within the processing and stockpiling area and will be
contained within stormwater berms to prevent the movement of materials offsite. No materials
will be stored or placed outside of stormwater berms. No permanent overburden or product piles
will be generated during the course of the North Hangs Mine operation. Topsoil will be either
used immediately for reclamation or placed in temporary stockpiles in the stockpile area, until
needed for reclamation.
Floodplain/Floodway
The North Hangs Mine affected area is located adjacent to the Colorado River. The disturbance
area of the site will be a minimum of 100 feet from the river during mining. The entire site is
within the Federal Emergency Management Administration (FEMA) Floodplain Zone A (100-YR
event). No floodway is mapped in this area, according to FEMA. The 100-year floodplain is
shown on Exhibit C and F maps. A Floodplain Analysis can be found earlier in this application.
Dewatering pathways and methodologies are detailed on Map C-2 of the CDRMS application.
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2. Air Quality
The CDPHE regulates both air pollution and fugitive dust that are sourced from businesses in
Colorado. A general air permit will be obtained for fugitive dust, and any required Air Pollutant
Emission Notices (APEN) will be submitted prior to the commencement of mining.
Air Quality Protection
. The following best management practices will be in place for the operation:
• All mining will occur below the existing topography, which will act to limit the migration of
dust and air pollution from the site.
• Disturbance footprint will be limited to the smallest for feasible operations
• Crushing and screening equipment will be equipped with water sprays in order to keep
material wet
• Haul roads, processing and stockpiles floor, and the mining area floor will be watered as
needed
• Haul roads and processing and stockpiles floor will be graveled once they have been
constructed
• Product stockpiles will be maintained moist either from processing or from truck watering
• Product stockpiles will be de-peaked.
• Topsoil stockpiles to be in place longer than 90 days will be seeded with the permanent
seed mix
• Site access will be paved to the main entrance
• Topsoiled reclaimed slopes will be seeded in the first favorable season following the
placement of topsoil
• All internal roads will be gravel
If additional dust suppression is needed at any time, additional watering will take place. This will
be determined by the Facility Manager. In the event of a dust ‘incident’, the Facility Manager will
determine if the incident can be corrected via additional controls or if operation shut down is
needed. The Facility Manager, and his/her designees will be responsible for maintaining a day-
to-day, hour-by-hour sense of the conditions on site and their propensity to generate dust.
Similarly, the Facility Manager would be aware that high afternoon temperatures during the
summer dry out watered areas of the site faster and increase the likelihood of dust generation at
that time of day. Therefore, the Facility Manager would task the water truck to spray active
areas of the site additional times in the hot summer afternoon. It is in this flexible manner that
the dust coming from the North Hangs Mine can and will be minimized. The fact that the
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majority of the excavation will be conducted below the water table will also greatly reduce the
generation of air pollution.
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3. Noise/Vibration
Prior to the initiation of mining activities, Hankard Environmental Inc (HEI) conducted a noise
impact analysis for the proposed North Hangs Mine. Hankard Environmental Inc. gathered
detailed information regarding the noise sources, including makes and models of mining
equipment, crushers, screens, etc., as well as existing and future topography, and mining and
reclamation details. Based on this data, source noise levels were drawn from the HEI
measurement database of similar equipment. Where data was limited, HEI made assumptions
based on their experience and/or gather publicly available GIS data. Noise source
measurements were also conducted by HEI and are included in the attached report. Hankard
Environmental Inc. created a map of the applicable noise limits surrounding the Project per CRS
§25-12 for review and approval by the North Hangs Mine. Hankard Environmental Inc. created
noise models (i.e.: pre-mining, full-mining, reclamation) as necessary to determine the worst-
case model. Mitigation was modeled as needed for the worst-case model. The noise models
include point predictions at noise sensitive receptors and noise level contours. Noise models
were created using SoundPLAN v8.2 software that applied the International Organization for
Standardization 9613-2. See the attached HEI report for further details and results of the noise
impact analysis.
A variety of best management practices will be employed to mitigate noise and vibration
impacts. They include:
• No use of explosives
• Non-beeping back up alarms
• Containing all mining activity behind the topsoil berm and the natural and augmented
screen of trees as much as possible
• Containing all processing activity behind berms as much as possible
• Locating all processing plants as far away from neighbors as possible
• All mining will be conducted below the existing grade
• Mining and plant activities are limited to daylight hours (half an hour before sunrise to
half an hour after sunset)
• Haul trucks will not use J-brakes
In the event that equipment or activity generates nuisance noise in a manner that was
unanticipated, such activity or equipment will be taken offline until it can be operated in a non-
nuisance manner. The Facility Manager can be contacted by anyone in the area or by any
Garfield County personal that detects a nuisance noise. Contractor equipment will be required
to operate under the same constraints as that of the operator.
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4. Visual Mitigation
Due to the fact that the North Hangs Mine is larger than 30 acres, it will be sequenced in a
logical manner so as to minimize the visual impact of the operation. This will entail beginning the
mining in the south portion of the permit area and progressing northwards. In order to minimize
the visual impacts, reclamation will occur as soon as possible in all mined out areas, and will
begin no later than 6 months after the commencement of a new phase of mining. Additionally,
landscaping along the south side of the operation will be developed in advance of mining
operations.
Visual renders were created of the North Hangs site to demonstrate what the mine will
potentially look like through all phases of mining and reclamation. Photos were captured at six
key observation points to demonstrate what is visible of the mine from the nearest neighbors
and adjacent highway with the visual mitigation measures in place. Four of the observation
points are located along the adjacent I-70 highway to the south as these are the closest views
the public will see of the North Hangs mine. These locations are dispersed along the spread of
the site in the areas where the mine is most visible to show what the public will see as they drive
by. The remaining two observation points are located to the north of the site along Highway 6
where the closest neighbors will be able to see the mine.
The site is most visible to the public from I-70. Screening from trees will hide the majority of the
processing area near the site entrance. The trees that will be used for screening during mining
will be transplanted from the existing vegetation on site prior to mining. Transplanting large
vegetation maximizes its effectiveness as a screening tool. Some smaller vegetation will be
planted from seed as well and provide infill screening over time. In the areas without berms and
trees in place, the pit will be visible from the road. However, the topography will provide natural
cover from the activities occurring on the mining floor.
The key observation point (KOP) locations and the directions they were taken in are shown in
Figure 7. For each location, renders were created to show mining and final reclamation. Each
key observation point is described in more detail below.
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Figure 7. Key Observation Point Locations Surrounding North Hangs
KOP 6
KOP 3
KOP 5
KOP 4
KOP 1
KOP 2
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Key Observation Point 1
The first key observation point is located on westbound I-70 near the site entrance facing west.
This location is facing the western portion of the processing area with the mining area in the
background. During mining, transplanted trees near the site entrance screen the view of the
processing area and pit. After reclamation, the lake will be visible in the distance with screening
from the trees placed during mining and as well as newly planted trees. The original image is
shown in Figure 8 while the renders are shown in Figure 9. KOP 1 Mining Render and Figure
10.
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Figure 8. KOP 1 Baseline Photo
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Figure 9. KOP 1 Mining Render
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Figure 10. KOP 1 Reclamation Render
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Key Observation Point 2
The second key observation point is at the same location as KOP 1 on westbound I-70 facing
east. This point is in view of the processing area and site entrance, with the mining area in the
background. The background vegetation will be thinned out and more of the ridge in the
distance will become visible as the trees within the mining area are removed. After final
reclamation, the eastern portion of the reclamation pond and some wetlands will be visible
through the trees. The original photo from this view is shown in Figure 11 while the renders of
mining and reclamation conditions are shown in Figure 12. and Figure 13.
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Figure 11. KOP 2 Baseline Photo
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Figure 12. KOP 2 Mining Render
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Figure 13. KOP 2 Final Reclamation Render
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Key Observation Point 3
The third key observation point is located at the western end of the site along westbound I-70,
facing west. This point is facing the southwest portion of the site where the southern portion of
the pit will extend. After final reclamation, the area will show rangeland and wetlands. The
original photo of this observation point can be seen in Figure 14 while the renders can be seen
in Figure 15. And Figure 16.
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Figure 14. KOP 3 Baseline Photo
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Figure 15. KOP 3 Mining Render
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Figure 16. KOP 3 Reclamation Render
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Key Observation Point 4
The fourth key observation point is located on the eastern side of the site on eastbound I-70
facing northeast. It is facing the northeastern portion of the mine and the furthest east portion of
the processing area. The original photo of this observation point can be seen in Figure 14
Figure 17 while the renders of mining and reclamation can be seen in Figure 15. and Figure 16.
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Figure 17. KOP 4 Baseline Photo
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Figure 18. KOP 4 Mining Render
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Figure 19. KOP 4 Reclamation Render
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Key Observation Point 5
The fifth key observation point is located on the ridge to the north of the site along Highway 6.
The North Hangs site can be seen in the distance to the southwest. This location represents the
view from residents on the western end of the Town of Silt. As shown in the photo, the
topography along the south side of Highway 6 obscures a significant amount of the view. The
eastern half of the site is visible from the nearest neighbor showing most of the processing area
and the eastern portion of the pit. Because the site is barely visible in the distance, few changes
between the different areas of mining will be visible. After final reclamation, the entire visible
area is rangeland and wetlands. The original photo of this observation point can be seen in
Figure 20. while the renders of mining and reclamation are shown in Figure 21. and Figure 22.
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Figure 20. KOP 5 Baseline Photo
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Figure 21. KOP 5 Mining Render
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Figure 22. – KOP 5 Final Reclamation Render
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Key Observation Point 6
The sixth observation point is located on the ridge off Highway 6 to the northwest of the site.
The photo was taken from the driveway of the other nearest neighbor that can view the mine.
The North Hangs site can be seen in the distance to the southeast. The western side of the site
can be seen in this direction showing the site during mining. After reclamation the lake is
primarily what will be seen from this view. The original photo from this observation point can be
seen in Figure 23. while the renders of mining and reclamation can be seen in Figure 24.
through Figure 25.
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Figure 23. KOP 6 Baseline Photo
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Figure 24. KOP 6 Mining Render
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Figure 25. KOP 6 Reclamation Render
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Screening Trees
Trees will be planted in two locations on the site in order to provide a visual screen for the Town
of Silt and the I-70 corridor. Trees will be planted to in-fill the existing trees on the north side of
the site along the Colorado River in order to mitigate the visual impacts to the Town of Silt.
These infill trees will be planted near the Colorado River in locations that will not be affected by
mining. Trees will also be planted along the south edge of the processing area and stockpile
area to mitigate the visual impacts to the I-70 corridor. These trees will be a mix of new seeding
and transplanted trees removed from areas to be mined. See Map F-1 for the locations of tree
plantings. In addition to the installation of screening trees, the phasing of the mining operation
will contribute to the mitigation of the visual impacts of the operation. Mining will maintain the
natural tree stands on the site along the Colorado River. Tree removal will be limited to those
trees that are within the proposed mining areas.
5. County Road System
Prior to the commencement of mining activities, a traffic study was conducted by Kimley-Horn
and Associates Inc. (Kimley-Horn) for the proposed North Hangs Mine, a copy of which is
attached to this application. Based on the analysis presented in the report, Kimley-Horn believes
North Hangs Mine will be successfully incorporated into the existing and future roadway network
without the need for any traffic improvements. All project intersections are expected to operate
acceptably throughout the 2037 study horizon with their existing lane configuration and control.
Operational practices to control traffic will include:
• Installation of any improvements at the intersection of North County Road 346 and
Mamm Creek Road (County Road 315) as required by Garfield County
• Maintenance of signage and speed limits for truck traffic entering and leaving the County
Road 346
• Usage of a one-way traffic routing in the facilities area to minimize customer truck travel
distance and time
• Maintenance of a designated parking area away from stockpiles and internal traffic
• Usage of a designated maintenance area for all minor equipment maintenance such as
greasing and refueling in the facilities area
• Tracking pads will be used at all entrances to the site to ensure sediment and mud
control
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6. Compatibility with Surrounding Land Uses
The North Hangs Mine is compatible with the surrounding land uses which include; an existing
gravel pit, the I-70 transportation corridor, and rangeland. The final uses of the North Hangs
Mine after reclamation will be rangeland, a groundwater lake, and wetlands. These uses are
also compatible with the current surrounding land uses.
7. Revegetation and Reclamation
Revegetation and Reclamation of the North Hangs Mine will be conducted as described in
Exhibit E of the CDRMS permit application in Appendix 4.
Prior to mining, a weed survey will be conducted and an inventory of county and state-listed
weeds along with a detailed weed management plan will be provided to Garfield County.
8. Wildlife/Vegetation
Prior to the commencement of mining activities, a wildlife/vegetation study was conducted for
the proposed North Hangs Mine by Steve D. Dahmer, Principal Ecologist at Environmental
Solutions, Inc., a copy of which is attached to this mitigation plan. The proposed project will
result in removal of a significant amount of rock and gravel resources below the existing grade,
which will result in the creation of one large groundwater lake on the Property. As part of the
mitigation measures, pond depth, shoreline slopes and layout as well as submerged slopes will
all be designed to establish a variety of habitat types to meet requirements of a diverse array of
wildlife species. This will include creation of fish habitat, including deepwater habitats, as well as
perennial wetland vegetation communities, both emergent and wet-meadow types. Mitigation
will include planting of a broad selection of wetland and upland species to maximize the
productivity and diversity of habitats on the Property. Creation of the lake will result in increased
diversity by adding a variety of fish habitat, including deep water, and a great deal of “edge”,
which is how biologists define the convergence of two or more habitat types. In general, the final
use of the site will increase the value of the Property as a wildlife area.
9. Section 7-1002.I.1. Waiver
Western Slope Materials requests a waiver from the requirement outlined in Section 7-1002(I) of
the Garfield County LUDC. Several Local, State, and Federal permits cannot be applied for
without conditional land use approval from Garfield County. These permits are:
- Colorado Div. of Water Resources Water Augmentation Plan
- US Army Corps of Engineers Wetlands Permit
- Colorado Dept. of Transportation Access Permit
- Colorado Dept. of Public Health and Environment Discharge Permit
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- Colorado Dept. of Public Health and Environment Fugitive Dust Permit
- Garfield County Floodplain Permit
Western Slope Materials will not begin operations without all applicable permits in place at the
North Hangs site.