2023-08-03_PERMIT FILE - M2023025 ‎(32)‎

• Permit No: M2023025
• IBM Index Class Name: Permit File
• Doc Date: 8/3/2023
• Doc Name Note: Exhibit G - Water Information
• Doc Name: Application
• From: J & T Consulting Inc.
• To: DRMS
• Email Name: RDZ
• Email Name: MAC
• Email Name: AWA
• Media Type: D
• Archive: No

Bernhardt Pit Groundwater Evaluation Page 10 of 31
May 2023
APPENDIX A—GROUNDWATER EVALATION AND MODELING
The proposed Bernhardt gravel pit mine is located approximately 1 mile south of Milliken,
Colorado in Section 24, Township 4 North, Range 67 West (6th PM). The proposed pit and
surrounding slurry wall are located approximately 200 feet west of the South Platte River(SPR).
Figure 1 and la— ld (located before Appendix A) show: the overall study area, model area, pit
property, permitted wells color coded by use, well permit numbers and the Bernhardt pit private
monitoring wells.
Available Data
We compiled hydrogeologic data from:
• Existing reports from the US Geological Survey, Colorado Geological Survey and
Colorado Division of Water Resources (see Sources below);
• Permitted well "completion reports" filed with the State Engineer's Office ("SEO"wells)
located within approximately 1.5 miles of the proposed pit; and
• Four monitoring wells installed around the Bernhardt pit that were provided by J&T.
Table Al includes well data from 224 registered wells extracted from the State's well database
(CDWR, 2023). This includes 25 monitoring wells and 28 production wells that have been
abandoned but still have useful information in the permit well completion report such depth to
bedrock or well yield (these wells were not included in the impact evaluation). Most of the
existing wells are used for domestic water supply, irrigation, monitoring or as stock wells.
Compiled data includes: the permit number,well owner, Colorado State Plane coordinate, USGS
Digital Elevation Model (DEM) elevation, registered use, well depth, depth to bedrock, yield in
gallons per minute (gpm) and reported static water level (SWL). The depth to bedrock was
documented if bedrock was identified in the well driller's"geologic" log.
Well statistics are shown at the bottom Table Al. The well depth from 200 wells ranged from 5
to 98 ft and averaged 54 ft. The observed depth to bedrock from 92 wells ranges from 19 to 95 ft
and averages 50 feet, 4 feet less than the average well depth. Well yields from 109 wells range
from 5 gpm(domestic well)to 2,150 gpm for irrigation. The reported static water level depths for
134 wells ranges from 4 to 39 feet and averages 21 ft. Seasonal water level variability is discussed
below.
Table A2 shows monitoring well data for the four Bernhardt borehole monitoring wells. The
wells were drilled by Cesare, Inc./CMT Technical Services in March, 2023. The depth to
bedrock ranges from 33 to 40 ft which is approximately 10 feet less than the average (50 ft).
This is because the pit is located along the western edge of the SPR alluvial aquifer at the
bedrock contact with the Fox-Hills sandstone. The depth to water ranges from 4.42 ft to 8.0 ft
which is much shallower than average (21 ft) due to the wells close proximity to the SPR.
HYDROGEOLOGY
The hydrogeology of the SPR alluvial aquifer is described in detail by the US Geological Survey
(Smith and Others, 1964,Hurr and Schneider, 1972,Robson,2000,Lindsay and Others, 1998 and
2005). More recently,the Colorado State University, (CSU, 2013)updated the surface water and
groundwater hydrology, while the Colorado Water Conservation Board prepared an extensive
McGrane Water Engineering,LLC
1669 Apple Valley Rd. 0 Lyons,CO 80540 0 Phone:[phone];email:[e-mail]