2025-08-07_PERMIT FILE - C1981019 ‎(2)‎

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 8/7/2025
• Doc Name: Treatment Area Geotech Drilling
• Section_Exhibit Name: Exhibit 07 Item 23
• Media Type: D
• Archive: No

EXHIBIT 27, ITEM 3

Exhibit 7 Item 23 1 Revision Date: 7/22/25
Revision No.: MR-268

I. INTRODUCTION

The Treatment Area Geotech Drilling will consist of drilling seven exploratory geotechnical
holes within the Gossard Rail Loop Area and one exploratory geotechnical hole directly adjacent
to the East Taylor Pond. Two of the exploratory drill holes will have temporary piezometers
installed, and hollow stem auger drilling methods will be employed. Subsurface information
gathered from the drill holes will be utilized in the design of the long-term treatment facility
planned to be constructed in the vicinity of the East Taylor Pond and the Gossard Rail Loop
Area. Please see Figure Exh. 7-23-1 for the seven drill holes locations near the Gossard Rail
Loop, and Figure Exh. 7-23-2 for the drill hole adjacent to the East Taylor Pond.

II. DRILL HOLE SPECIFICS

Specific information for each drill hole is presented on the table below. BH-02 and BH-04 will
have temporary piezometers installed.

Drill Hole Number Approximate Depth
(ft)
BH-01 30
BH-02* 30
BH-03 65
BH-04* 30
BH-05 30
BH-06 65
BH-07 50
BH-08 75
*Piezometers will be 2” Sch 40 PVC

III. ABAONDMENT OF DRILLED HOLES

All borings will be shallow and are not intended to penetrate subsurface coal seams; therefore, the
drill holes that will not be piezometers will be backfilled with drill cuttings and marked with a
wooden stake. The two piezometers (BH-02 and BH-04) will be abandoned in accordance with
Rule 16 of the Colorado Division of Water Resources regulations. All drill-hole locations will be
surveyed and mapped for future reference.