Aggregate Surfacing Study.pdf

Project No. - 106662-001_L1.docx

1321 Bannock Street Suite 200 Denver, Colorado 80204-2718 303 825-3800 www.shannonwilson.com

April 26, 2022

Mr. Aaron Swafford, PE Jacobs Engineering 9191 S Jamaica Street Englewood, Colorado 80112

RE: AGGREGATE SURFACING STUDY, CO OMAD 300(67), MINUTEMAN MISSILE

ACCESS ROADS, COLORADO

Dear Mr. Swafford:

This letter summarizes the results of our subsurface exploration and laboratory testing program and presents existing aggregate surfacing thicknesses and grain size distributions for the Minuteman Missile Access Roads Project (the Project) located in northeastern Colorado. Our services were completed in general accordance with our Task Order Agreement No. 148022060 MSA No. 148017721 with Jacobs Engineering, Inc. (Jacobs) dated February 11, 2020.

The objective of our studies was to provide the existing aggregate surfacing thickness and grain size distribution at the Minuteman Missile Access Roads, as presented herein. The authorized scope of services was based on this objective and this letter should not be used for other purposes without Shannon & Wilson’s review. If a service is not specifically indicated in this report, do not assume that it was performed.

PROJECT DESCRIPTION

The project includes gravel roadway improvements at several locations in Colorado within Weld and Logan counties. We understand that the project improvements consist of roadway linear grading, roadway widening, drainage improvement, permitting, and new aggregate surface course.

The roads included in this project are rural county roads which service various agricultural fields and wind farms in addition to the missile silos. The topography in the vicinity of the roads varies from generally flat to rolling hills within the west central province of the Great Plains. We understand that traffic primarily consists of sparse passenger pickup truck or SUV traffic, school buses, and occasional delivery trucks and snow removal trucks or tractors along with the occasional missile delivery vehicle.

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106662-001_L1.docx 106662-001

SUBSURFACE EXPLORATIONS AND LABORATORY TESTING

Field Investigation

Shannon & Wilson conducted a field exploration program from February 15 to 17, 2021 to explore aggregate surfacing thicknesses along the Project roads. The subsurface exploration program consisted of drilling and sampling 36 borings advanced to depths of approximately

1.5 to 4.5 feet below the ground surface.

The boring designations consisted of the missile silo identification followed by the boring number (e.g., M-02b-1) where M-02b is the missile silo identification and the boring identification is 1 in the adjacent road.

Explorations

The borings were coordinated (including subcontractor coordination and utility locates) and observed by Shannon & Wilson. Boring designation, location (latitude and longitude), and approximate aggregate thicknesses are presented in Table 1. This table represents our interpretation of the aggregate thicknesses measured in the field. Field measurements of aggregate thickness were performed by probing the borehole with a flathead screwdriver and measuring with a tape measurer or folding ruler to the nearest inch. The thicknesses should be considered accurate at the locations indicated to the degree implied by the method used.

The borings were drilled by Vine Laboratories, Inc. of Commerce City, Colorado (under subcontract to Shannon & Wilson) using two truck mounted CME-55 drill rigs. The borings were advanced to a depth of up to 4.5 feet using 6-inch diameter solid-stem-auger techniques. On completion of drilling, the borings were backfilled with cuttings to approximately level with the existing road surface.

Soil Classification System

During exploration, our representative collected samples of the explorations and measured aggregate thicknesses. Soil classification for this project was based on ASTM International (ASTM) Designation: D2487, Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System), and ASTM Designation: D2488, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure).

106662-001_L1.docx 106662-001

Grab Sampling

Soil samples were obtained by collecting the drill cuttings from the upper 1.0 to 1.5 feet of the borings. Cuttings were placed in plastic bags and transported to our laboratory for further analysis and testing.

Geotechnical Laboratory Testing

Geotechnical laboratory tests were completed on selected samples retrieved from the borings to estimate index properties. Index tests included natural water content and grain size analysis. Laboratory test results are included in Figure 1.

Laboratory tests were completed on soil samples retrieved from the borings in general accordance with American Association of State Highway and Transportation Officials (AASHTO) test methods. The geotechnical laboratory testing was performed at our laboratory in Denver, Colorado. The following sections describe the laboratory testing procedures.

Water Content

Water content was determined for selected samples in general accordance with AASHTO T265, Standard Method of Test for Laboratory Determination of Moisture Content of Soils.

To perform this test, a sample was weighed before and after oven-drying, and the water content was calculated. Water content determinations are summarized in Figure 1.

Grain Size Analysis

The grain size distribution of selected samples was determined in general accordance with AASHTO T88, Standard Method of Test for Particle Size Analysis of Soils. Results of these analyses are presented as grain size distribution curves on Figure 1.

FINDINGS

The existing road surface consisted of compacted aggregate that ranged in thickness from 6 to 26 inches thick as measured in the 36 borings. Refer to Table 1 for the measured aggregate thicknesses and GPS coordinates for each boring location. Based on laboratory testing the existing aggregate surfacing is classified as Silty Sand with with varying percentages of gravel. In the four samples tested, the fines content of the soil ranged from 20% to 41% and the gravel content ranged from 4% to 19%. The AASHTO soil classification

Aggregate Surfacing Study

CO OMAD 300(67)

Minuteman Missile Access Roads, Colorado

Latitude Longitude

(in)

M-02b-1 40.847564 -103.397012 18

M-02b-2 40.847705 -103.387536 24

M-08a-1 40.696964 -103.492005 8

M-08a-2 40.699514 -103.494978 13

M-08a-3 40.702034 -103.509892 17

M-08a-4 40.702034 -103.509892 15

M-08b-1 40.679724 -103.523941 6

M-08b-2 40.687221 -103.523857 10

M-09a-1 40.803368 -103.666578 15

M-09a-2 40.803357 -103.657304 15

M-09a-3 40.803373 -103.647524 22

M-09a-4 40.803467 -103.638036 17

M-09a-5 40.803519 -103.628472 20

M-09a-6 40.803345 -103.618994 26

M-09b-1 40.791594 -103.611382 25

M-09b-2 40.798925 -103.611122 21

M-10 M-10-1 40.806182 -103.611047 20

M-11-1 40.735563 -103.517102 26

M-11-2 40.742740 -103.517093 22

M-11-3 40.779364 -103.516860 16

NOTE:

M-02b

1. Aggregate thickness was estimated from drill cuttings where noted because it was not possible to visually observe aggregate thickness in borehole.

M-11

M-09b

M-08a

M-08b

M-09a

Table 1 - Approximate Aggregate Thickness

Segment ID Boring ID

Location Approximate Aggregate

Thickness

106662-001 Page 1 of 2 106662-001_T1 - Aggregate Thickness.xlsx - 4/25/2022

Aggregate Surfacing Study

CO OMAD 300(67)

Minuteman Missile Access Roads, Colorado

Latitude Longitude

(in)

Table 1 - Approximate Aggregate Thickness

Segment ID Boring ID

Location Approximate Aggregate

Thickness

J-06-1 40.879438 -103.343604 16

J-06-2 40.872132 -103.343604 18

J-06-3 40.864980 -103.343794 14

J-07b-1 40.960545 -103.286200 19

J-07b-2 40.953418 -103.285750 19

J-08-1 40.964170 -103.331492 20

J-08-2 40.964232 -103.340812 18

J-08-3 40.964232 -103.368835 15

J-08-4 40.964207 -103.378389 16

I-06c-1 40.994961 -102.880354 18

I-06c-2 40.994526 -102.870424 14

I-07 I-07-1 40.985707 -102.904781 14

E-10a-5 41.085616 -104.064382 18

O-01c O-01c-1 40.887042 -104.003496 22

O-11-1 40.975681 -104.067251 18

O-11-2 40.983034 -104.067211 23

NOTE:

O-11

I-06c

1. Aggregate thickness was estimated from drill cuttings where noted because it was not possible to visually observe aggregate thickness in borehole.

J-08

J-07b

J-06

106662-001 Page 2 of 2 106662-001_T1 - Aggregate Thickness.xlsx - 4/25/2022

6 4

P E

R C

E N

T F

IN

E

R B

Y W

E

IG

H T

PL

3/

SM

SM

SM

SM

Silty Sand, few gravel [A-4]

Silty Sand, few gravel [A-2-4]

Silty Sand, trace gravel [A-4]

Silty Sand with Gravel [A-1-b]

7.6

9.7

8.1

8.9

COARSE MEDIUM

GRAVEL

.3

2 1

5/

HYDROMETER ANALYSIS

3/

U.S.C.S.

SYMBOL

.0

1/

.0

12 20

41.0

27.7

35.7

19.6

.0

NAT.

W.C. %

FINE

GRAIN SIZE IN MILLIMETERS

.0

1/

.0 6.8

.0

LL

.0

.0

.0

0.0

0.0

0.0

0.0

DEPTH

(feet)

.1

.0

April 2022

.0

COBBLES

.4

1/

GRAIN SIZE DISTRIBUTION

I-06c-1, G-1

J-08-1, G-1

M-02b-1, G-1

M-09a-5, G-1

SAMPLE ID

Geotechnical and Environmental Consultants

.6

SHANNON & WILSON, INC.

.0

PI

.0

P E

R C

E N

T C

O A

R S

E R

B Y

W E

IG

H

T

.0

.0

SAND

FINES

SIZE OF MESH OPENING IN INCHES

.0

.0

.0

SIEVE ANALYSIS

.0

.2

.0

GRAIN SIZE IN MILLIMETERS

106662-001

.0

.0

FINES: SILT OR CLAY

NO. OF MESH OPENINGS PER INCH, U.S. STANDARD

FIG. 1

SAMPLE

DESCRIPTION

COARSE FINE

.0

FIG

. 1

CO OMAD 300(67)

Minuteman Missile Access Roads

Colorado

G S

A _M

A

IN

106662 -00

1 O M

A D

G R

A V

E L R

O A

D S

_C O

.G P

J 4/25/22