OF-15-11 Geology and Groundwater Resources of Park County, Colorado


This report provides a regional overview with the general public in mind: it also contains detailed background that will benefit more technical users. The multiyear (2011-2016) project was made possible via several funding sources, including grants from the Colorado Water Conservation Board (CWCB) as well as the Park County Land and Water Trust Fund (LWTF). The CGS — through its Severance Tax Operational Funds, Colorado General Fund, and CUSP — provided matching funds. Digital PDF/GIS/ZIP download. OF-15-11D

An online map — ON-OF-15-11 Geology and Groundwater Resources of Park County, Colorado — is also available.

Included in the Zip file is the primary report with figures, accompanied by the individual plates (listed below). In addition, there is a map package file (.mpk) with ArcGIS 10.0 compatibility.

List of Individual Plates included in the Zip file:

1. Geologic Map of Park County
2. Cross-sections Through Park County
3. Hydrogeologic Unit Map: Precambrian Crystalline Bedrock
4. Hydrogeologic Unit Map: Tertiary and Cretaceous Intrusive and Volcanic Igneous Rocks
5. Hydrogeologic Unit Map: Older Paleozoic Formations
6. Hydrogeologic Unit Map: Belden Formation
7. Hydrogeologic Unit Map: Minturn Formation
8. Hydrogeologic Unit Map: Maroon Formation
9. Hydrogeologic Unit Map: Garo Sandstone
10. Hydrogeologic Unit Map: Morrison Formation
11. Hydrogeologic Unit Map: Dakota Sandstone
12. Hydrogeologic Unit Map: Benton/Niobrara
13. Hydrogeologic Unit Map: Pierre Shale
14. Hydrogeologic Unit Map: Laramie-Fox Hills Aquifer
15. Hydrogeologic Unit Map: Laramide Sedimentary Units
16. Hydrogeologic Unit Map: Tallahassee Creek Conglomerate
17. Hydrogeologic Unit Map: Antero Formation
18. Hydrogeologic Unit Map: Wagontongue-Trump Formation
19. Hydrogeologic Unit Map: Unconsolidated Quaternary Deposits
20. Water Quality Stiff Diagram Map: Countywide
21. Water Quality Pie Chart Map with TDS: Countywide
22. Water Quality Pie Chart Map With TDS: Precambrian Crystalline Bedrock
23. Water Quality Pie Chart Map with TDS: Tertiary Intrusive and Volcanic Rocks
24. Water Quality Pie Chart Map with TDS: Older Paleozoic Formations
25. Water Quality Pie Chart Map with TDS: Belden Formation
26. Water Quality Pie Chart Map with TDS: Minturn Formation
27. Water Quality Pie Chart Map with TDS: Maroon Formation
28. Water Quality Pie Chart Map with TDS: Garo Sandstone
29. Water Quality Pie Chart Map with TDS: Morrison Formation
30. Water Quality Pie Chart Map with TDS: Dakota Sandstone
31. Water Quality Pie Chart Map with TDS: Benton & Niobrara Formations
32. Water Quality Pie Chart Map with TDS: Pierre Shale
33. Water Quality Pie Chart Map with TDS: Laramie-Fox Hills Formations
34. Water Quality Pie Chart Map with TDS: Laramide Sedimentary Units
35. Water Quality Pie Chart Map with TDS: Tallahassee Creek Conglomerate
36. Water Quality Pie Chart Map with TDS: Antero Formation
37. Water Quality Pie Chart Map with TDS: Wagontongue-Trump Formation
38. Water Quality Pie Chart Map with TDS: Quaternary Deposits

From the Introduction:

Park County has experienced considerable population growth in recent decades with development becoming increasingly reliant on local groundwater resources. A diverse geologic setting characterizes the county and groundwater may be found in many of those settings. This product compiles the most recent geologic mapping and interpretations focusing on groundwater occurrences in the various geologic formations found in the area. The revisions in the 2017 update include a discussion of groundwater types and quality, as presented in more detail below.

The county straddles two very different geologic terrains that share a long and complex history. The east side of the county extends into the Precambrian-cored Front Range uplift of the Rocky Mountains. The west side of the county covers the South Park topographic basin, a 35 by 50 mile structural feature shaped by a long and varied history of geologic processes. It contains a wide variety of crystalline igneous and metamorphic rocks, volcanic rocks, and sedimentary units, ranging in age from Precambrian through Cenozoic. Based on differences in hydrologic properties, the aquifers and confining units in Park County can be grouped into three general categories: 1) crystalline-rock aquifers, 2) sedimentary bedrock aquifers and confining units, and 3) unconsolidated Quaternary deposits. Within these categories, there were 19 mapped hydrogeologic units.

More that 7,500 completed water wells are inventoried in Park County as of December 19, 2012 and are available in the Colorado Division of Water Resources (CDWR) database. Permitted uses include: domestic or household use only, livestock, commercial, industrial, municipal, irrigation, monitoring and other (such as evaporative, fire, geothermal, gravel, or unspecified). Wells and springs were assigned a hydrogeologic unit. Due to various sources of uncertainty, hydrogeologic unit designations were assigned a confidence level value of 1, 2, or 3, with 3 representing the least confidence.

A Park County groundwater quality database was compiled from publicly available databases, reports, and samples collected in 2011, 2012, 2014 and 2016 by the Coalition for the Upper South Platte (CUSP) with some assistance by CGS. The primary electronic data source was the Water Quality Portal (WQP) from the National Water Quality Monitoring Council. Groundwater data was also manually compiled from other publicly available publications not in the WQP. A total of 689 sample sites had groundwater quality data through 2016. A limited number of sample locations have data from multiple sampling events at the same well or spring. Data analysis for these locations used the maximum value detected, unless it was identified as an anomalous outlier. Where feasible, dissolved water quality data was used preferentially over total data.