Geotechnical Report.doc

GEOTECHNICAL ENGINEER’S REPORT

11-14-2008

Date:

November 14, 2008 To: Wayne Clayton, Facilities Engineer B-T From:

J. Humble, P.E.

Geotechnical Engineer

Subject:

Big Piney Foundation Investigation, Bridger-Teton N F

INTRODUCTION

A geotechnical foundation investigation was conducted at the Big Piney Administrative Site on 11-12-2008. The purpose of the investigation was to determine the subsurface profile in the vicinity of the proposed facility and in the proposed drain field area and to provide foundation design criteria to the facility design team.

SITE INVESTIGATION

The investigation included visual observation of a subsurface back hoe pit excavations. Tests pits were excavated near the area proposed for new facility construction and within the proposed drain field location. The facility site is relatively flat with a gradual slope towards the north. The proposed drain field location is along the northern edge of the property. Suitable foundation conditions and materials were found. Surface material was silty sand top soil USCS SM. The material at bearing depth is silty gravel GM. The soils were dry and no groundwater was encountered.

DRAIN FIELD DESIGN

The test pits identified 4-6 ft of silty gravel overlying 6 ft of sandy silt in the area proposed for a drain field. Perc tests and design will be completed by Doug Wewer. See figures and attached soil profile.

Figure 1 Silty Gravel spoils pit #1.

Figure 2 pit #2

Figure 3 Sandy Silt pit #3.

FOUNDATION DESIGN RECOMMENDATION

The allowable foundation bearing pressure for these materials is 2,000 psf for a standard strip footing which is recommended. All foundation design shall be in accordance with the International Building Code.

Settlement is expected to be less than 1 inch at this site due to the anticipated light to moderate loads which will be applied.

The proposed facility should be constructed in accordance with the seismic design criteria contained in the IBC. Site Class D shall be used to calculate seismic design forces. The following mapped spectral responses may be used: Ss = .40g & S1 = 0.12g. No other geologic hazards (flood, landslide, etc…) were identified during this investigation.

The foundation design recommendations within this report should allow the facility design team to complete the design without further geotechnical study.

If site conditions different from those mentioned in this report should be encountered, I am available for consultation. I am also available to review foundation details if needed.

SOIL PROFILE

SOIL EXPLORATION - Big Piney Admin Site

SOIL PROFILE INTERPRETATION FROM 4 TEST PITS

Elevation

Pit 1

Dense cemented gravel

50-70% gravel with cobble up to 5”

Sandy Gravel

Coarser Gravel Lense

Uniform Soil to elev 87

Gravel & Cobble

BOH @ elev 85

J. HUMBLE P.E.