Taxiways-F and G Geotechnical report 2019.pdf

6650 Pierce Boulevard, O’Fallon, Illinois 62269 ■ 618-624-6969 www.sciengineering.com

SCI ENGINEERING, INC.

EARTH SCIENCE SOLUTIONS

GEOTECHNICAL

ENVIRONMENTAL

NATURAL RESOURCES

CULTURAL RESOURCES

CONSTRUCTION SERVICES

October 10, 2019

Mr. David Phillips, P.E.

Senior Project Manager Mead & Hunt, Inc. | M & H Aviation Services 2440 Deming Way Middleton, Wisconsin 53562

RE: Letter Report South Foxtrot Concrete Repair Scott Air Force Base, Illinois SCI No. 2019-0561.10, .20

Dear Mr. Phillips:

At the request of Mr. David Phillips with Mead & Hunt, Inc. (M&H), SCI Engineering, Inc. (SCI) conducted a geotechnical exploration and environmental soil sampling for the proposed taxiway repairs.

Our services were provided in general accordance with our proposal dated June 17, 2019 and the contract with M&H, executed by both parties on July 16, 2019.

The purpose of our geotechnical and environmental services was to explore and generate subsurface information to be used in developing recommendations for the design and construction of the pavement rehabilitation project.

SITE AND PROJECT DESCRIPTION

The project will consist of pavement improvements along Taxiway F (Foxtrot) near its intersection with Taxiway G (Golf) on the Scott Air Force Base property located in Scott Air Force Base, Illinois. The location of the site is shown on the Vicinity and Topographic Map, Figure 1.

The objective of the scope of work is to remove and replace or mill and replace the identified sections of Taxiway F and G by using UFC 3-260-02 for Airfield Pavements.

FIELD EXPLORATION AND LABORATORY TESTING

The borings were staked in the field using a handheld GPS Trimble unit with submeter accuracy and the ground surface elevations at the boring locations were estimated using available Lidar data from Scott Air Force Base, Illinois. We then explored the site by drilling the requested nine borings at the approximate locations shown on the Aerial Photograph, Figure 2.

Six-inch and ten-inch core barrels were used to advance the borings through the pavement and any crushed rock base if present. A dynamic cone penetrometer (DCP) test was then conducted within the upper 36 inches below the ground surface on the soil subgrade in each boring using the K-100 DCP in accordance with ASTM D 6951. Then, Standard Penetration Tests were advanced continuously to the termination depth of each borings. An engineer from SCI was present on site during the exploration to perform the

Mr. David Phillips, P.E. 2 October 10, 2019 Mead & Hunt, Inc. | M & H Aviation Services SCI No. 2019-0561.10, .20

DCP tests and classify the soils in accordance with ASTM D 2488. Bulk samples of the soils subgrade were also collected for addition laboratory testing. Environmental screening of selected samples was performed by SCI field personnel, which is summarized later in the letter.

Upon completion, each borehole was backfilled with clean aggregate backfill with a gradation of less than 1 inch. The aggregate backfill was compacted in 10-inch lifts using the drilling rig augers and placed to within 12 inches from the surface. At that time, asphalt cold patch was placed and compacted in 4-inch lifts to the surface. This method of backfilling was requested by Scott Air Force Base personnel to minimize the time to backfill the boring due to ongoing airfield traffic.

After completing the field exploration, the samples were transported to our laboratory for further classification and characterization. The moisture content of each cohesive sample was measured. Hand penetrometer values, which provide an indication of strength, were obtained for each apparently intact cohesive samples. Dry densities were also recorded on the initial soil subgrade sample along with an Atterberg limits test. On selected samples, an unconfined compressive strength was recorded using the Illinois Department of Transportation Rimac apparatus. This test method covers the determination of the unconfined compressive strength (Qu) of cohesive soil using a strain-controlled application of axial load with a small, portable compression device. Two modified Proctor tests and two soaked California Bearing Ratio tests were conducted on the bulk samples from the upper 3 feet of subgrade soils.

SUBSURFACE CONDITIONS

Pavement

Nine core samples of the pavement where obtained. The pavement consisted of a combination of asphaltic concrete (AC) and Portland cement concrete (PCC) ranging in thickness from 11.5 to 22 inches as detailed in Table 1. Approximately 3 to 7 inches of crushed rock base was present below the pavement in B-2, B-7, B-8, and B-9, but was absent in the remaining borings. Detailed pavement thicknesses are also shown on the boring logs included in Appendix A. During most of the coring, the upper portions of the pavement remained intact while the lower portions closest to the soil subgrade fractured during the coring process.

Pictures of the pavement cores are enclosed in Appendix B.

Table 1 – Summary of Pavement Thicknesses

Boring Pavement Thickness (inches) Type of Pavement Crushed Rock Base Thickness (inches)

B-1

9.5 AC

NA

6.75 PCC

B-2

5.75 AC

13.5 PCC

B-3

11 AC

NA

11 PCC

B-4

1.5 AC

NA

7.75 PCC

1.25 AC

8 PCC

Mr. David Phillips, P.E. 3 October 10, 2019

Table 1 – Summary of Pavement Thicknesses (continued)

Boring Pavement Thickness (inches) Type of Pavement Crushed Rock Base Thickness (inches)

B-5

1.75 AC

NA 6 PCC

5.75 AC

B-6

3.75 AC

NA

13 PCC

B-7

3.5 AC

3 4.25 PCC

3.75 PCC

B-8

5.25 AC

8.5 PCC

B-9

7.5 AC

8.25 PCC

Soil Subgrade

Existing Fill

Existing fill was encountered in B-1 through B-5, B-7, and B-8 below the pavement extending to depths of

2.5 to 6 feet. The fill in B-1 and B-5 consisted of lean clay while the fill in the remaining borings consisted of fat clay. Standard Penetration Test (SPT) N values ranging from 3 to 7 blows per foot (bpf) and moisture contents of 25 to 30 percent were recorded in the fill. Atterberg limits tests on the fill samples are summarized in Table 2.

Table 2 – Atterberg Limits Tests Results in Fill

Boring Liquid Limit Plasticity Limit Plasticity Index USCS Classification

B-1 41 19 22 Lean Clay (CL)

B-2 56 20 36 Fat Clay (CH)

B-3 52 21 31 Fat Clay (CH)

B-4 64 22 42 Fat Clay (CH)

B-5 38 20 18 Lean Clay (CL)

B-7 63 21 42 Fat Clay (CH)

B-8 71 22 49 Fat Clay (CH)

Natural Soils

Natural soils consisted of interbedded soft to medium stiff, fat to lean clay and silt. SPT N values ranged from 2 to 6 bpf with moisture contents ranging from 24 to 37 percent. Atterberg limits tests on the initial sample of natural soils are summarized in Table 3.

Mr. David Phillips, P.E. 4 October 10, 2019

Table 3 – Atterberg Limits Test Results in Natural Soils

Boring Liquid Limit Plasticity Limit Plasticity Index USCS Classification

B-6 52 22 30 Fat Clay (CH)

B-9 65 21 44 Fat Clay (CH)

Groundwater

Groundwater was observed during drilling at a depth of 6.9 feet in B-8, but was not observed during drilling in the remaining borings. The gray coloration of the samples indicates the groundwater may be present between 5 and 6 feet below the ground surface. The groundwater level depends on seasonal and climatic variations and may be present at different depths in the future. In addition, without extended periods of observation, accurate groundwater level measurements may not be possible, particularly in low permeability soils.

DCP and CBR Testing

Bulk samples of subgrade soils were collected from the upper 0 to 5 feet from each boring except B-3 and B-9. The combined samples from the upper 3 feet in B-1, B-2, and B-5 yielded a liquid limit of 47 and a plasticity index of 26, classifying the soil as a lean clay. The second bulk sample was collected from the upper 5 feet in B-2, B-4, B-6, and B-8 and yielded a liquid limit of 59 and a plasticity index of 34, classifying the bulk sample as a fat clay. A modified Proctor test and a California Bearing Ratio test were completed on each of the bulk samples. Tables 4 and 5 summarized the laboratory testing on each of the bulk samples.

The laboratory results are also included in Appendix C.

Table 4 – Bulk Sample of Fat Clay (B-2, B-4, B-6, and B-8)

Modified Proctor Test Results CBR Results

Maximum Dry Density

(pcf)

Optimum Moisture

Content (%)

Dry Density

(pcf)

Moisture

Compaction

Blow Counts

CBR

Value Swell (%)

109.4 15.5

106.4 17.7 97.2 25 9 1.03

108.8 18.0 99.4 56 9 0.48

109.4 17.6 100.0 75 10 0.48

Table 5 – Bulk Sample of Lean Clay (B-1, B-2, and B-5)

Modified Proctor Test Results CBR Results

Maximum Dry Density

(pcf)

Optimum Moisture

Content (%)

Dry Density

(pcf)

Moisture

Compaction

Blow Counts

CBR

Value Swell (%)

113.0 14.9

103.8 16.9 91.8 20 3 3.99

112.2 16.9 99.3 56 6 2.75

113.0 16.6 100.0 75 7 2.75

Mr. David Phillips, P.E. 5 October 10, 2019

As previously stated, in addition to the laboratory calculated CBRs, blow counts collected in the field via DCP testing were correlated to a CBR value. Where feasible, the DCP tests extended to approximately 36 inches below the soil subgrade. In some cases, the thickness of the pavement limited the ability to extend the DCP test to 36 inches below soil subgrade. The results of the field DCP are summarized per boring in Appendix D.

GEOTECHNICAL RECOMMENDATIONS

Based on our observations in the field and the results of the laboratory testing, we have compiled a list of possible causes of the overall deterioration of the pavement.

Drainage. A crushed rock layer is absent in most of the areas cored. Without a layer of crushed rock present, the surficial water can work its way down through the pavement cracks and become trapped between the pavement and the soil subgrade, allowing the water to saturate the subgrade, which will promote subgrade failure. This may have been evidenced during the coring operations where the upper portions of the core appeared intact while the lower portions of the cores were often broken, almost as if they failed in tension due to lack of support below. This can be compounded by cracks in the existing pavement due to the normal wearing process.

Expansive Clay Soils. Much of pavement subgrade consists of expansive, fat clay. There is a moderate to high risk of volume change of the fat clay with variations in the soil’s moisture content.

This can result in cracking of undamaged pavement and opening of existing cracks in the pavement which can allow for water to seep in, which can further exacerbate the issue.

Proper maintenance. Typically, pavement maintenance is suggested at the following intervals:

routine maintenance for a 5-year period, minor repair and maintenance during the 5- to 10-year life of the pavement, and possibly major repairs and restoration after a 10-year service life. Proper maintenance can include sealing cracks and repairing damaged sections of pavement that may help prevent further water infiltration. As previously discussed, these infiltration points can lead to additional deterioration.

Subgrade and Drainage Recommendations

Based on the discussion above, we would recommend the following to improve drainage and the overall pavement subgrade.

Expansive Clays

Much of pavement subgrade consists of expansive, fat clay. Without remediation, the existing fat clay subgrade could cause heave distress in the new pavement. To reduce long-term maintenance, consideration could be given to remediating the upper 12 inches of subgrade. Alternatives include removal and replacement with 1-inch minus crushed rock per UFC criteria, or lime treatment of the existing subgrade soils. If the removal and replacement option is chosen, an additional measure to bridge over any unstable soil subgrade conditions, would be to add a layer of geogrid (Tensar TX-130S, or equivalent) prior to the placement of the compacted crushed rock. The rock should be compacted to the standards set forth in the UFC guidelines for aggregate base rock for Airfield pavements. Depending on the final pavement design, the addition of crushed rock and geogrid may allow for a reduction in pavement thicknesses.

Mr. David Phillips, P.E. 6 October 10, 2019

If lime stabilization is performed, we recommend thoroughly mixing in hydrated lime at a rate of 7 percent, or approximately 8 pounds of Code L per cubic foot of soil, to the depth described above. Water may need to be added during mixing to allow for proper hydration of the lime. Pulverizing and tilling equipment, such as “gators,” are preferred for mixing the lime into the soil. The treated soil should be compacted to the UFC guidelines for Airfield pavement subgrades.

Drainage

We would recommend that at a minimum 4 inches of drainage material be added within the pavement section. Care should also be taken to grade the subgrade as to not trap water in between the different aggregate base layers and pavement thicknesses. This will also be critical if the subgrade is lime stabilized so that water is not trapped atop the firmer stabilized subgrade and the rock base.

ENVIRONMENTAL SOIL SAMPLING

The soil samples collected as part of the geotechnical study were screened on approximate 1.5-foot vertical intervals using a photo-ionization detector (PID) which is capable of detecting variations in concentrations of various organic trace gases. This screening process aided in determining if soil impact was present. No organic gases were identified with the exception of Borings B-1 and B-3. The PID readings in B-1 ranged from <1 parts per million (ppm) to 1.2 ppm, while the PID readings in B-3 ranged from <1 ppm to 10 ppm.

The samples with the highest PID reading from B-1 and B-3 were selected for analytical testing. The deepest sample or the sample from above the observed perched groundwater saturation zone was selected from the other borings. Each soil sample was placed into laboratory provided containers and transported under proper chain-of-custody procedures to the laboratory in chilled containers.

Soil samples collected from each boring were analyzed by the laboratory for the following constituents of concern:

Volatile organic compounds (VOCs) by U.S. EPA method 8260 and

Semi-VOCs (SVOCs) by U.S. EPA method 8270.

Complete laboratory results from the soil samples as well as the associated chain-of-custody documentation are contained in Appendix E.

Analytical Testing Results – Soil

A summary of the analytes detected by laboratory analysis of soil samples are summarized in Table 6 located in Appendix F. Table 6 also includes a comparison of the detected laboratory results to the Illinois Environmental Protection Agency (IEPA) Tiered Approach to Corrective Action (TACO), Tier 1 Soil Remediation Objectives (SROs) for the ingestion, inhalation, and soil component of the groundwater ingestion exposure routes for residential properties.

As indicated on Table 6 (Appendix F), several constituents were identified at concentrations exceeding the laboratory reporting limits (RLs). Additionally, several constituents had estimated concentrations between the method detection limits (MDLs) and RLs. However, none of the reported or estimated concentrations exceeded the identified IEPA TACO Tier 1 SROs.

It should be noted that one compound (methylene chloride) within the soil sample collected from B-5 had

Mr. David Phillips, P.E. 7 October 10, 2019 an elevated RL due to matrix interference. Although a detectable concentration of the compound was not identified, both the RL and MDL for this compound exceeded the IEPA TACO Tier 1 SRO for the soil component of the groundwater ingestion exposure route. However, the RL and MDL were below the IEPA TACO Tier 1 SROs for ingestion and inhalation.

Based on the results of the other eight samples collected during this assessment, it is likely the actual concentration of methylene chloride within the soil sample from B-5 is below the IEPA TACO Tier 1 SRO for the soil component of the groundwater ingestion exposure route. Therefore, SCI does not consider the elevated RL to be a concern for the subject site.

Quality Assurance/Quality Control

SCI reviewed the Quality Assurance/Quality Control (QA/QC) sections of the analytical reports supplied by Teklab, Inc. for this project. Elevated reporting limits were reported by the lab for several of the samples due to sample extract composition or matrix interference. As such, J-flag results were reported and are summarized in Table 6 (Appendix F). The following qualifiers were also noted for several of the samples:

Laboratory Control Sample (LCS) was recovered outside upper control limit for some compounds.

However, the sample results which would be biased high were below the reporting limit for B-1, B-3, B-4, B-6, B-7, B-9.

Allowable marginal exceedances of several compounds were noted in the LCS. However, the sample results which would be biased high were below the reporting limits for B-1, B-2, B-3, B-5, B-6, B-8, B-9.

Although some qualifiers were noted within the reports, SCI did not identify anything which would have significantly altered the findings of the reports and considers the laboratory results to be in accurate representation of current site conditions.

LIMITATIONS

The recommendations provided herein are for the exclusive use of our client, Scott Air Force Base, and their respective successors and assigns. They are specific only to the project described, and are not meant to supersede more stringent requirements of local ordinances. They are based on subsurface information obtained at nine specific boring locations, and our understanding of the project as presented in the “Site and Project Description” section; and geotechnical engineering practice consistent with the standard of care.

No other warranty is expressed or implied. SCI shall be contacted if conditions encountered are not consistent with those described.

We shall also be provided with a set of construction plans and specifications, once they become available, to review whether our recommendations have been understood and applied correctly, and to assess the need for additional exploration or analysis. Failure to provide these documents to SCI may nullify some or all of the recommendations provided herein. In addition, any changes in the planned project or changed site conditions may require revised or additional recommendations on our part.

Mr. David Phillips, P.E. 8 October 10, 2019

We appreciate the opportunity to be of service to you on this project. If you have any questions concerning the information contained in this transmittal, please call.

Respectfully, SCI ENGINEERING, INC.

Julie A. Miller, P.E.

Senior Engineer

Michelle L. Eaton, P.E.

Senior Engineer

JAM/MLE/SLE/EPG/lf

Enclosures

Figure 1 – Vicinity and Topographic Map Figure 2 – Aerial Photograph Appendix A – Boring Log Legend and Nomenclature, Boring Logs Appendix B – Pavement Core Photographs Appendix C – Proctor and CBR Testing Results Appendix D – Field CBR from DCP Tests Appendix E – Environmental Soil Analytical Results Appendix F – Analytical Results of Detected Analytes – Soil

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APPENDIX A

SCI ENGINEERING, INC.

650 Pierce Boulevard

O’Fallon, Illinois 62269 618-624-6969 www.sciengineering.com

BORING LOG LEGEND AND NOMENCLATURE

Depth is in feet below ground surface. Elevation is in feet mean sea level, site datum, or as otherwise noted.

Sample Type SS Split-spoon sample, disturbed, obtained by driving a 2-inch-O.D. split-spoon sampler (ASTM D 1586).

NX Diamond core bit, nominal 2-inch-diameter rock sample (ASTM D 2113).

ST Thin-walled (Shelby) tube sample, relatively undisturbed, obtained by pushing a 3-inch-diameter, tube (ASTM D 1587).

CS Continuous sample tube system, relatively undisturbed, obtained by split-barrel sampler in conjunction with auger advancement.

SV Shear vane, field test to determine strength of cohesive soil by pushing or driving a 2-inch-diameter vane, and then shearing by torquing soil in existing and remolded states (ASTM D 2573).

BS Bag sample, disturbed, obtained from cuttings.

Recovery is expressed as a ratio of the length recovered to the total length pushed, driven, cored.

Blows Numbers indicate blows per 6 inches of split-spoon sampler penetration when driven with a 140-pound hammer falling freely 30 inches. The number of total blows obtained for the second and third 6- inch increments is the N value (Standard Penetration Test or SPT) in blows per foot (ASTM D 1586). Practical refusal is considered to be 50 or more blows without achieving 6 inches of penetration, and is expressed as a ratio of 50 to actual penetration, e.g., 50/2 (50 blows for 2 inches).

For analysis, the N value is used when obtained by a cathead and rope system. When obtained by an automatic hammer, the N value may be increased by a factor of 1.3.

Vane Shear Strength is expressed as the peak strength (existing state) / the residual strength (remolded state).

Description indicates soil constituents and other classification characteristics (ASTM D 2488) and the Unified Soil Classification (ASTM D 2487). Secondary soil constituents (expressed as a percentage) are described as follows:

Trace <5 Few 5-15 With >15-30

Stratigraphic Breaks may be observed or interpreted, and are indicated by a dashed line. Transition between described materials may be gradual.

Laboratory Test Results

- Natural moisture content (ASTM D 2216) in percent.

- Dry density in pounds per cubic foot (pcf).

- Hand penetrometer value of apparently intact cohesive sample in kips per square foot (ksf).

- Unconfined compressive strength (ASTM D 2166) in kips per square foot (ksf).

- Liquid and Plastic Limits (ASTM D 4318) in percent.

RQD (Rock Quality Designation) is the ratio between the total length of core segments 4 inches or more in length and the total length of core drilled. RQD (expressed as a percentage) indicates insitu rock quality as follows:

Excellent 90 to 100 Good 75 to 90 Fair 50 to 75 Poor 25 to 50 Very Poor 0 to 25

APPENDIX B

APPENDIX C

COMPACTION TEST REPORT

Test Data

Weight of Mold and Soil (g)

Weight of Mold (g)

Weight of Wet Soil & Tare (g)

Weight of Dry Soil & Tare (g)

Weight of Tare (g)

Moisture Content (%)

Dry Density (pcf)

Maximum Dry Density (pcf): Optimum Moisture Content:

1 2 3 4 5 6

Project Name: Project Number:

Project Location: Client:

Sample Location: Sample Number:

Material Description:

Date Sampled:

NM: LL: PI: Soil S.G: % Oversize: %<No.200: Rammer:

Tested By: Date Tested:

Reviewed By: Title:

SCI Engineering, Inc.

Source:

Prep:

Button

113.0 14.9%

6,035.2 6,132.2 6,220.3 6,197.4 6,156.9

4,261.0 4,261.0 4,261.0 4,261.0 4,261.0

367.9 577.0 828.2 826.8 750.3

339.2 521.6 717.9 705.8 628.4

87.9 86.7 88.7 88.9 86.2

11.4 12.7 17.5 19.6 22.5

105.7 110.2 110.7 107.5 102.8

ASTM D 1557 Modified - Method B

South Foxtrot Concrete Repair 2019-0561.10

MEAD & HUNT, INC.Scott Air Force Base, IL

B1, B2, B5, 0-3' Depth

LEAN CLAY (CL): Dark brown

8/22/2019

22.5 47 26 Mechanical

D. Barger

J. Hemphill

8/22/2019

Staff Engineer

N/A

130 Point West Blvd.

St. Charles, Missouri 63301

* The Specific gravity is estimated.

Moist

Remarks:

Button

COMPACTION TEST REPORT

Test Data

Weight of Mold and Soil (g)

Weight of Mold (g)

Weight of Wet Soil & Tare (g)

Weight of Dry Soil & Tare (g)

Weight of Tare (g)

Moisture Content (%)

Dry Density (pcf)

Maximum Dry Density (pcf): Optimum Moisture Content:

1 2 3 4 5 6

Project Name: Project Number:

Project Location: Client:

Sample Location: Sample Number:

Material Description:

Date Sampled:

NM: LL: PI: Soil S.G: % Oversize: %<No.200: Rammer:

Tested By: Date Tested:

Reviewed By: Title:

SCI Engineering, Inc.

Source:

Prep:

Button

109.4 15.5%

6,085.2 6,140.5 6,164.3 6,149.9

4,261.0 4,261.0 4,261.0 4,261.0

438.7 798.3 702.6 734.9

400.5 708.7 604.8 621.7

109.7 90.1 87.7 90.4

13.1 14.5 18.9 21.3

107.1 109.0 106.3 103.4

ASTM D 1557 Modified - Method B

South Foxtrot Concrete Repair 2019-0561.10

MEAD & HUNT, INC. Scott Air Force Base, IL

B2, B4, B6, B8, 0-5' Depth

FAT CLAY (CH): Brown and black

8/22/2019

24.3 59 34 Mechanical

D. Barger

J. Boyd

8/22/2019

Laboratory Supervisor

N/A

130 Point West Blvd.

St. Charles, Missouri 63301

* The Specific gravity is estimated.

Moist

Remarks:

Button

SCI Engineering, Inc.

SCI Engineering, Inc.

APPENDIX D