Poncha Springs, Colorado

Key Project Information

Purpose: Geothermal Exploration for Electric Power Generation
Method: Magnetotelluric (MT) and Shallow Temperature Probe (STP) surveys / Broadband Magnetotellurics (BMT) and Low-frequency Magnetotellurics (LMT)
Location: Poncha Springs, Colorado, U.S.A.
Client: Mt. Princeton Geothermal, LLC
End-User: Mt. Princeton Geothermal, LLC
Dates: 2011 - 2012
Main Survey Area: 1 km2
Extended Survey Area: 2.25 km2
Total number of MT Stations: 99
Total number of STP Stations: 18
Client Reference: Mr. John H. Held Mt. Princeton Geothermal, LLC 5005 Christensen Dr. Littleton, CO 80123 (303) 748-0001 (M) (303) 789-7604 (O) hheld@burt.com

Project Summary

Dewhurst Group, LLC (DG) was competitively selected by Mt. Princeton Geothermal, LLC to confirm resource potential for geothermal power generation. DG exclusively provided all 3-D resistivity imaging and shallow temperature information used for the project. Poncha Springs, CO is located approximately 7.5km Southwest of Salida, CO, 38.3km South of Buena Vista, CO and 116km West of Colorado Springs, CO. Within the Survey Area, there are known hot springs which feed a municipally operated swimming pool located in Salida, CO. DG was responsible for locating sub-surface structure, potential geothermal source, and plumbing systems for commercial exploitation.

Statement of Work

Work was performed using a phased approach:

™™Phase 1: Test and Design

  • Calibration, geo-electric strike and dimensionality analysis
  • Survey Design

™™Phase 2: Field Work

  • 78 BMT stations (soundings)
  • 21 LMT stations
  • 18 Shallow temperature probe observations
  • Near-real time processing in the field

™™Phase 3: Data Analysis

  • Calculation of transfer functions
  • 1-D station inversions
  • 2-D profile inversions
  • 10 BMT Profiles + 4 variations
  • 15 LMT Profiles
  • 3-D Survey Area inversion

™™Phase 4: 3-D modeling and Final Report

  • 3-D renderings from 1-D results
  • 3-D renderings from 2-D results (e.g., 2.5-D inversion)
  • 3-D unconstrained inversion

™™Phase 5: Comparison of all results for robust resistivity imaging and interpretation.

Environment, Safety, and Cultural Awareness

DG is committed to minimally disrupting the land, stimulating the local economy and respecting native culture. DG’s methods 1.) are non-ground disturbing, 2.) did not require an Environmental Impact Statement under the National Environmental Policy Act of 1969 and 3.) qualified for a casual use permit within the Bureau of Land Management (BLM). Further, DG coordinated all field work with the City of Salida, CO, Town of Poncha Springs, CO, and private stakeholders. Despite adverse winter weather conditions, no significant injuries were incurred during this accident-free survey.

Schedule and Budget

All field work was completed within four weeks and final results delivered within 30 days of data acquisition. All work was completed with a multiple-survey discount of nearly 30 percent. Survey was coincidental with the survey performed at Mt. Princeton, CO.