R4 Green River Lakes Kendall Pit Investigation (5-9-2023).pdf

LVR Consultants LLC Missoula Montana

4-27-2023

Green River Lakes Road Gravel Pit Inves�ga�on, Observa�ons, Tes�ng and Recommenda�ons – Kendall Pit

Project: USDA FS A/E Contract 1240LR21D0010 Award 1240LT22F0069 – Supplemental Work on R4 Pavement Surveys (CLH 22143)

Execu�ve Summary

The purpose of this inves�ga�on is to locate a source of gravel surfacing for the Green River Lakes Road.

The inves�ga�on of three loca�ons was completed November 1, 2022, and test results were provided by Inberg-Miller Engineers on March 28, 2023. Two loca�ons had poor durability and all three did not contain clay needed to meet plas�city index requirements for gravel surfacing.

The bulk of this report is on test results and recommenda�ons for the Kendall source since it had much beter coarse aggregate durability and four test pits had grada�ons where mee�ng specifica�ons was realis�c. Mee�ng a good gravel surfacing grada�on will require a considerable amount of exper�se in selec�ve u�liza�on (feeding the crusher) to avoid excessive sands and considerable amount of crushing and screening equipment to u�lize most of the large rock necessary to meet grada�on requirements.

Since this source loca�on does not have sufficient clay for plas�city index, an addi�onal inves�ga�on of clay deposits is planned for late May 2023.

Detailed recommenda�ons for pit u�liza�on, specifica�ons, contract administra�on and use of Sublete County Road crew versus contract crushing are provided below.

Field Inves�ga�ons

The field inves�ga�on work was conducted on October 312022, and November 1, 2022 at three loca�ons shown in Appendix 1. Test results were completed in late March 2023 at Inberg-Miller Engineers. Coarse aggregate durability test results (sodium sulfate soundness) at the Warm Springs and Forest Boundary sources failed so no further analysis of the test results was done. Appendix 2 shows Pit Inves�ga�on Notes for the three sources and Appendix 3 shows laboratory test results for aggregate quality, plas�city index and 1 inch minus grada�ons. Grada�ons shown do not include a significant amount of plus one inch aggregate in the form of cobbles, typically in the 10-to-12-inch maximum size range that would normally be crushed to meet aggregate surfacing specifica�ons.

Kendall Source Test Data Discussion

Sodium Sulfate Soundness (Na2SO4) test results of 11.8% loss is borderline, based on tradi�onal spec requirement of 12% max assuming the test was conducted with 5 cycles. Normally, borderline test results would jus�fy retes�ng at a different lab. In this case, since only 1" minus was tested, and there is a significant amount of plus 1" material that will be crushed, the final crushed gravel would normally have less loss a�er Na2SO4 tes�ng the composite material. The larger rock in this type of source is normally more durable.

The lab grada�on test data for minus #4 material was converted to pit run grada�ons using the percent passing #4 es�mated for each of the pits during sampling. See Appendix 4. The grada�on of minus #4 is cri�cal because that grada�on is normally not modified significantly during crushing. The grada�on curves for Test Pits 1 and 2 have too much coarse and intermediate size sands. Test Pits 3, 4, 5 & 6 are closer to the center of the grada�on band, so those areas are suggested for the mining area. These test pits have sand layers that were not part of the test pit samples. Grada�on test results indicate this sand layer should be stripped and stockpiled as reject to stay in specs.

Kendall Source Pit U�liza�on

Recommend mining areas represented by Test Pits 3, 4, 5 & 6 as shown in Appendix 5. The black rectangle on the Google Earth image is provided to show the approximate area needed to obtain 50,000 tons of aggregate. Locate ini�al pit boundaries that provide the desired visual screen. Boundaries should be large enough to accommodate 1.5 �mes the planned extrac�on quan�ty, one acre for the crusher and addi�onal areas for stockpiling of crushed aggregate, reject sand layers, boulders (rocks over 12”) and topsoil. U�lize stockpiled topsoil as visual screen where needed. Do not start revegeta�on of slopes un�l the gravel has been depleted in that area of the source. Revegeta�on may need to be delayed for several years depending on how well the crushing contractor is able to meet specifica�ons.

Strip and stockpile sand layers to stay in spec and reduce wash boarding problems in gravel surfacing.

Since pit sample test results of minus #200 are low and minus #40 is non-plas�c, plan to add clay to extend gravel life and reduce dust, washboards & raveling. Suggest up to 8% natural clay from a roadside source (to be inves�gated in late May 2023) to achieve a plas�city index and exceed 12 percent minus #200. Another op�on is to add 3 to 4% bentonite clay from a commercial source. See addi�onal informa�on in "Specs and Contract Admin" and Reference 1 (TRB Paper # 19-06145).

Crush larger rocks to offset high amounts of natural sands in the source and to reduce wash boarding and improve coarse aggregate resistance to weathering.

Appendix 1 – Source Inves�ga�on and Sampling Loca�ons

Appendix 2 - Source Inves�ga�on Notes

Green River Lakes Source Investigations Source Name: Kendall Guard Station (Bridger Teton NF Personnel: Monlux, Snyder Source Name: Kendall Guard Station (Bridger Teton NF

N W From To 43o 15'00.50" 110o 01'24.36" 1 SA & PI Silt, Sand 0 8 80

2 SA & PI 6" minus 0 10 65 NP

3 SA & PI 8" minus 10 18 55 NP

Topsoil 0 1.25

1 & 1A SA & PI (Combine both samples) 8" minus 1.25 13 65 NP

Wet Clay Layer

13 17 100 20

Topsoil 0 0.5

1A 0.5 8 40 NP

1B 8 12 NP

Topsoil 0 0.5 1A 10" minus 0.5 4.5 50 NP

Sand 4.5 6.5 NP

1B 12" minus 6.5 13 50 NP Topsoil 0 1

1 & 1A SA & PI (Combine both samples)

12" minus w/5% boulders

1 12 50 NP

Topsoil 0 0.75 1A & B SA & PI 10" minus 0.75 6.5 45 NP

Sand 6.5 8 NP 2A & B SA & PI 8" minus 8 15+ 35 NP

5 43o 15'07.72" 110o 01'29.67"

43o 15'03.44"

3 43o 15'04.41" 110o 01'26.93"

2 110o 01'24.78"

Est PI

This site is a existing pit run borrow area. Water table rose to one foot depth in trench (Sample 3)

4 43o 15'06.06" 110o 01'26.04"

Unsuitable Materials

6 43o 15'05.03" 110o 01'29.30"

SA: Washed Sieve Analysis PI: Plasticity Index LAA: Los Angeles Abrasion DI: Durability Index (AASHTO T210) Na2SO4 Sodium Sulfate Soundness NP: Non Plastic Note: If questions, call Steve Monlux at 406-544-1919

(a) Samples from Sites 1 thru 6 should be scalped on 1" sieve prior to SA and PI testing. After splitting to test sample size, save unused split material for one composite aggregate quality test (LAA, Durability Index or NaSO4) that should represent the whole gravel source

12" minus w/10% boulders

SA & PI (Combine both samples)

SA & PI (Combine both samples)

Test Hole

Coordinates Sample # Testing (a)

Materials Description

Depth below Ground Surface, Ft

% Minus #4

Appendix 3- Laboratory Test Results

Appendix 3 – Laboratory Test Results (Con�nued)

Appendix 4 – Pit Run Grada�on Es�mate

Kendall Guard Station Pit Run Gradation Estimate Pit Run Grad Rating:

80 1/2" 65 6 55 8 65 8 40 12 50 12 50 12 45 10 35 8 Lab Test

Pit Run

Lab Test

Pit Run

Lab Test

Pit Run

Lab Test

Pit Run

Lab Test

Pit Run

Lab Test

Pit Run

Lab Test

Pit Run

Lab Test

Pit Run

Lab Test

Pit Run mm .45 Power Std High Low 300 13.02281 12 250 11.99701 10 200 10.85084 8 150 9.533252 6 75 6.978749 3 25 4.2567 1 100 100 19 3.762176 3/4 98 70

12.5 3.116087 1/2 88 58

4.75 2.0161 #4 57 80 66 65 52 55 68 65 71 40 68 50 73 50 67 45 65 35 60 36

2.36 1.47167 #8 49 69 52 51 41 43 56 54 61 34 56 41 62 42 55 37 59 32 47 25

0.600 0.794636 #30 35 49 20 20 23 24 29 28 30 17 29 21 31 21 31 21 42 23 31 12

0.074 0.309852 #200 2.7 3.8 3.3 3.3 6.4 6.8 9.2 8.8 7.6 4.3 4.2 3.1 8.2 5.6 7.6 5 19.9 11 20 8

Test Pit % minus #4 & Max Size, Sieve Sizes (mm, inch & mesh #)

Test Pit # (Sample #) TP3 (A&B)

GradationsGradations

TP1 (1) TP1 (2)

Gradations

TP1 (3)

Gradations

TP2 (1&1A)

Gradations Gradations Gradations GradationsGradations

Best OptionNext Best OptionAvoid Poor option, expect wash

TP6 (2A&B)TP6 (1A&B)TP5 (A&B)TP4 (A&B)

Spec Limits

0.01 0.1 1 10 100 1000

Pe rc en t P as si ng

Sieve Size, mm

Kendall Pit Run Gradation Plot

High Spec Limit Low Spec Limit

TP1 (1)

TP1 (2)

TP1 (3)

TP2 (1&1A)

0.01 0.1 1 10 100 1000

Pe rc en t P as si ng

Sieve Size, mm

Kendall Pit Run Gradation Plot

High Spec Limit Low Spec Limit

TP1 (3)

TP3 (A&B)

TP4 (A&B)

TP5 (A&B)

TP6 (1A&B)

TP6 (2A&B)

Appendix 5 – Kendall Source U�liza�on

Note: Pit Boundaries could include Test Pits 3, 4, 5 & 6, and be any shape depending on desired screen.

Rectangle shown is 2.7 AC.

Tons Aggregate = 50,000 if 10 � deep, 15 � depth may be realis�c