Report Meissner CCE BMC 200015 SRT.pdf

BLACK MOUNTAIN CONSULTING LLC

22566 SW Washington St., Ste. 206 Sherwood, OR 97140

2418 SE Ivon St. Portland, OR 97202 503.625.2517 www.blkmountain.com

Black Mountain Consulting LLC SHERWOOD Office - 22566 SW Washington St., Ste. 206 Sherwood, OR 97140

PORTLAND Office - 2418 SE Ivon St. Portland, OR 97202

503.625.2517 www.blkmountain.com

March 21, 2020

Black Mountain Project No. 200015-SRT

Columbia 911 c/o Cushing Civil Engineers 909 North Beech Street, Suite D Portland, Oregon 97227

Attn: Mr. Kenny McManaway

Subject: Soil Resistivity Survey Meissner Tower Site Lookout Road Deer Island, Oregon 97054

At your request, a representative of Black Mountain Consulting LLC (Black Mountain) visited the above referenced site on March 4, 2020 to perform soil resistivity testing. Two surveys were completed, at the approximate locations and orientations described in this report. We understand others will use these test results in their design of the antenna grounding system.

Attention: Due to the high resistivity values at the planned tower site, a standard grounding design may not be appropriate and a site-specific grounding design may be required.

We appreciate this opportunity to be of service.

Sincerely, Black Mountain Consulting LLC

Robert Nystrom, R.G.

Staff Geologist

BLACK MOUNTAIN CONSULTING LLC

2 | P a g e Black Mountain Consulting LLC | Project 200015-GEO| March 21, 2020

Methods:

The resistivity survey was completed using the Wenner Four-Electrode Method and the Miller Model 400A Soil Resistance Meter. The Wenner Four-Electrode Method requires that four metal electrodes be placed in a straight line, equal distance from one another. Each electrode is driven approximately 6 -12 inches below ground surface at 5, 10, 20, 30 and 40-foot spacing intervals. A current of known amperage is subsequently circulated into the soil through the end electrodes and the resulting voltage drop between the inner electrodes is measured, yielding the resistance (in ohms) of the soil. The correct unit for resistivity is the ohm-centimeter (Ω-cm). The following equation is used to calculate the resistivity (Ω-cm).

ρ = 191.5 aR

Where:

ρ = soil resistance in ohm-cm (Ω-cm) a = electrode separation (in feet)

R = resistance measured in ohms (Ω)

This method is in general accordance with ASTM method G57-06 (IEEE Standard 81).

Site Conditions:

Two equally spaced electrode arrays were established on the subject property. Array 1 was configured along a NW-SE axis that extended through the planned communication compound. Array 2 was configured along an NE-SW axis that also extended through the planned communication compound.

The planned communication compound is located in a recently logged area and is undeveloped. The area is approximately level and there were no structures or underground utilities in the area. Soils consist of silty clay and forest duff (soils heavily disturbed by logging activity). No standing water was observed in the area.

Black Mountain conducted a geotechnical exploration in the lease area on March 19, 2020 and encountered 8 feet of silty clay mantling severely decomposed basalt at about 8 feet below ground surface (bgs). We encountered moderately weathered basalt below about 10 feet and we terminated our exploration on the moderately weathered basalt at 15 feet bgs. There was sufficient space to perform 40-foot spacing on both arrays and the arrays were oriented approximately 90° to one another.

Soil Resistivity Survey Results

Site Name & Address:

Company Performing Test (Include Name of Person & Date):

Test Instrument (Model #, Serial #, Date of Last Calibration):

Areas to be Measured Data Recordings

5 10 20 30 40

Array 1 Measured Resistance (Ω): 27.0 15.0 7.2 5.2 4.0

Calculated Resistivity (Ω-cm): 25,853 28,725 27,576 29,874 30,640

Array 2 Measured Resistance (Ω): 42.0 18.0 8.1 5.1 3.9

Calculated Resistivity (Ω-cm): 40,215 34,470 31,023 29,300 29,874

Weather:

Silty clay over severely to moderately weathered basalt bedrock at 8 feet

Damp

Clear at time of survey, 40° F, scattered showers last 24 hours

Additional Site Information

Table 1: Soil Resistivity Data

Description of Soil as Seen as Site:

Soil Condition (Wet, Damp, or Dry):

Meissner, Lookout Road, Deer Island, Oregon 97054

Black Mountain Consulting LLC, Robert Nystrom, 3-4-2020 Miller Model 400A Soil Resistance Meter, #44500, Calibrated January 2019

Distance Between Test Rods in Feet