Soil_Logs-_13_25683_.pdf

Geotechnical Engineering Report Taxiway A Reconstruction

Gallup Municipal Airport ACI No. 186484

2111 W. Historic Highway #66 Gallup, New Mexico

May 3, 2019 Terracon Project No. 66175219

Prepared for:

Armstrong Consultants, Inc.

Albuquerque, New Mexico

Prepared by:

Terracon Consultants, Inc.

Albuquerque, New Mexico

May 3, 2019

Armstrong Consultants, Inc.

861 Rood Avenue Grand Junction, Colorado, 81501

Attn: Mr. Eric Rivera P: (970) 242-0101 E: erivera@armstrongconsultants.com

Re: Geotechnical Engineering Report

Taxiway A Reconstruction Gallup Municipal Airport ACI No. 186484 2111 W. Historic Highway #66 Gallup, New Mexico

Terracon Project No. 66175219

Dear Mr. Rivera:

Terracon has completed geotechnical engineering exploration for the Taxiway A Reconstruction Project located at the Gallup Municipal Airport in Gallup, New Mexico. Refer to Figure A1, Site Location Map, for the project location.

The scope of the services performed for this project included site reconnaissance by a geotechnical field engineer, a subsurface exploration program, and laboratory testing. These services were performed in general accordance with our proposal number P66175219 (revision No. 2) dated October 10, 2018 and the Request for Proposal (RFP) entitled “Gallup Municipal Airport; Gallup, NM, Taxiway A Reconstruction, ACI No. 186484” dated October 8, 2018, which included project information, boring location map and scope of work prepared by Armstrong Consultants, Inc. (Armstrong). The purpose of this study will be to evaluate the pertinent geotechnical conditions at the site and to assist Armstrong in the design and construction of new pavements and other site development elements.

1.0 PROJECT DESCRIPTION

Site Location

ITEM DESCRIPTION

Location Gallup Municipal Airport in Gallup, New Mexico.

Existing improvements Municipal airport with existing runway, taxiway, aprons, and structures.

Existing pavement surface Asphalt concrete

Taxiway A Reconstruction – Gallup Municipal Airport ■ Gallup, NM May 3, 2019 ■ Terracon Project No. 66175219

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ITEM DESCRIPTION

Current ground cover Building footprints, soil, vegetation, and asphalt and Portland cement concrete pavement.

Existing topography Relatively flat to gently sloping down to the south and southwest (assumed).

Project Description

ITEM DESCRIPTION

Pavements The project will include the design and reconstruction of Taxiway A at the existing regional airport.

Grading Maximum cut and fills on the order of about 1 to 2 feet (assumed).

Cut and fill slopes Maximum of about 1 to 2 feet (assumed)

2.0 SUBSURFACE EXPLORATION AND TESTING PROCEDURES

A total of 37 test borings were drilled at the site during the period from February 6 to February 9, 2019 using a CME-75 truck-mounted drilling rig utilizing a hollow stem auger equipped with a center bit. The test borings were drilled to depths ranging from about 1 to 15 feet below existing grade. Borings were performed at the locations designated by Armstrong and were located along paved areas of Taxiway A. Refer to Figure A2, Exploration Location Map, for the boring locations.

The station number and centerline offset are shown on each individual boring log.

Lithologic logs of the test borings were recorded by a geotechnical field engineer during the drilling operations. At selected intervals designated by the RFP (1/2 foot or directly below pavement, 2, 3.5, 5, and 10 feet), samples of subsurface materials and penetration tests were taken by driving split-spoon or ring-lined barrel samplers using a 140-pound hammer falling 30 inches. The number of blows required to advance the samplers the last 12 inches, or less if hard materials were present, of an 18-inch sampling interval was recorded as the standard penetration resistance value (N). An automatic SPT hammer was used to advance the split-spoon or ring-lined barrel samplers.

The effect of the automatic hammer's efficiency has been considered in our interpretation and analysis.

In addition, four (4) bulk samples of the subgrade materials were obtained at the designated locations in the RFP (Boring Nos. B-06, B-14, B-27 and B-35). All samples were sealed in the field and then returned to our laboratory for testing and classification.

Groundwater measurements were made in the test borings during and at the completion of drilling.

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Upon the completion of the drilling operations, the borings were backfilled with auger cuttings, compacted, and a heated asphalt cold patch (matching the existing pavement section thickness where applicable) was placed at the top of each boring.

3.0 LABORATORY TESTING PROGRAM

Selected soil samples were tested for the following engineering properties in accordance the referenced ASTM Standards:

Gradation (ASTM D422) Water Content (ASTM D2216) Consolidation (ASTM D2435) Atterberg Limits (ASTM D4318) Dry Density (ASTM D7263) Moisture/Density Relationship (ASTM D1557) California Bearing Ratio (ASTM D1883) Soluble Sulfate Content

As part of the testing program, the soil samples were examined in the laboratory by the field engineer. Based on the material’s texture and plasticity, the soil samples were described and classified in accordance with the attached General Notes and the Unified Soil Classification System, respectively. The estimated group symbols for the Unified Soil Classification System are shown in the appropriate column on the boring logs.

The AASHTO and FAA Frost Group classifications were determined for the four (4) bulk samples of the subgrade. A brief description of the Unified System is included in Appendix A.

4.0 SURFACE AND SUBSURFACE CONDITIONS

4.1 Existing Pavement Conditions

Cursory pavement observations were performed during the period from February 6 to February 9, 2018. Based on limited field observations, the existing taxiway appears to be in relatively poor to good condition. The approximate western ¼ of the taxiway was observed to exhibit less distress than the other portions of the taxiway. Observed surficial pavement distress of the taxiway included transverse and longitudinal cracking, block cracking, patching, overlays, surface treatments, as well as oxidation, weathering of the pavement surface. The as-built plans and maintenance records for the pavement were not provided; however, it appeared that crack filling of the pavement surface may have been performed.

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4.2 Subgrade and Subsurface Soil Conditions

Specific conditions encountered at the boring locations are indicated on the individual boring logs.

Stratification boundaries on the boring logs represent the approximate location of changes in soil types; in-situ, the transition between materials may be gradual. Details for the borings can be found on the attached boring logs. Based on the results of the borings, subsurface conditions on the project site can be generalized as follows:

Description Approximate

Depth to Bottom of Stratum (feet)

Material Encountered Consistency/Density

Stratum 1 0.6 to 1.8 Asphalt concrete – 3.75” to 10” Aggregate base coarse – 3” to 12” N/A

Stratum 2 3 Silt. The sand and gravel content varied* Medium Stiff

Stratum 3 2 to 5 Sand. The silt, clay and gravel content varied** Very Loose to Loose

Stratum 4 3 to 7 Lean Clay. The sand and gravel content varied*** Medium Stiff to Stiff

Stratum 5 6.5 to 15 Fat Clay. The sand and gravel content varied. Soft to Hard

* Encountered in Boring No. B-36 ** Encountered in Boring Nos. B-01, B-07, B-08, B-25, B-26 and B-28 *** Encountered in Boring Nos. B-11 and B-14

Laboratory tests were conducted on selected soil samples and the test results are presented on the attached laboratory test sheets in Appendix B.

The four (4) bulk samples that were retrieved during the field exploration and taken to the laboratory for further observation by the project geotechnical engineer were classified in accordance with the Unified Soil Classification System (USCS), the American Association of State Highway and Transportation Officials (AASHTO) classification system, and by the FAA Frost Group (AC 150/5320-6E) as outlined below.

Boring No.

USCS

Classification

AASHTO

Classification

FAA Frost Group

B-06 CH A-7-6 FG-3

B-14 CL A-7-6 FG-3

B-27 CH A-7-6 FG-3

B-35 CH A-7-6 FG-3

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Four (4) Atterberg limits tests were performed on the bulk samples obtained. Liquid Limit (LL) values for the subgrade materials ranged from 47 to 64. The plasticity index (PI) values for the subgrade materials ranged from 27 to 40. The percent fines of the bulk samples ranged from 51 to 84.

The in-situ dry densities and moisture contents of the subgrade soils ranged from about 68 to 99 pounds per cubic foot (pcf) and 17 to 59 percent, respectively.

Laboratory test results indicate that the surface and near surface soils typically exhibit low to high consolidation/compression potential at in-situ moisture contents. The near surface soils exhibit a low to moderate tendency for consolidation and expansion (swell) when wetted under heavy pavement loads. When water is added to samples of laboratory compacted near-surface soils, we anticipate that the compacted soils will exhibit non- to moderate expansive potential and non-to low consolidation potential when subjected to light loading conditions such as those imposed by pavements.

Four (4) moisture density relations (Proctor) tests were performed on selected samples of the subgrade obtained from depths ranging from 1 to 5 feet below existing site grades. The results of this testing is summarized below:

USCS

Classification

AASHTO

Classification

Maximum Dry Density

(pcf)

Optimum Moisture

Content (%)

B-06 CH A-7-6 85 16

B-14 CL A-7-6 99 14

B-27 CH A-7-6 106 21

B-35 CH A-7-6 96 21

Four (4) California Bearing Ratio (CBR) tests were performed on the bulk samples obtained. The CBR tests were performed on subgrade samples compacted at approximately 95% maximum dry density and at or near optimum moisture content determined by ASTM D1557. A standard surcharge load of 10 pounds and saturated conditions were used for the tests. CBR values for the subgrade materials are summarized below:

USCS Classification

AASHTO

Classification

CBR

Value

(0.100”)

CBR

Value

(0.200”)

B-06 CH A-7-6 1 1

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AASHTO

Classification

CBR

Value

(0.100”)

CBR

Value

(0.200”)

B-14 CL A-7-6 1 1

B-27 CH A-7-6 3 3

B-35 CH A-7-6 3 3

The results of the soluble sulfate testing on the three (3) bulk samples are summarized below:

AASHTO

Classification Soluble Sulfates

(mg/kg)

B-06 CH A-7-6 160

B-14 CL A-7-6 180

B-27 CH A-7-6 1,200

B-35 CH A-7-6 300

5.0 GROUNDWATER INFORMATION

Groundwater was not observed in the test borings at the time of field exploration, nor when checked upon completion of drilling. These observations represent groundwater conditions at the time of the field exploration and may not be indicative of other times, or at other locations.

Groundwater conditions can change with varying seasonal and weather conditions, and other factors.

Fluctuations in groundwater levels can best be determined by implementation of a groundwater monitoring plan. Such a plan would include installation of groundwater monitoring wells, and periodic measurement of groundwater levels over a sufficient period of time.

The possibility of groundwater fluctuations should be considered when developing design and construction plans for the project.

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6.0 ANALYSIS AND RECOMMENDATIONS

6.1 Geotechnical Considerations

The site appears suitable for the proposed taxiway reconstruction based upon existing pavement, subgrade and geotechnical conditions encountered in the test borings. The on-site subsurface subgrade soils are considered to be poor quality subgrade materials for aircraft support indicated by the low CBR values.

Variable subsurface subgrade conditions were encountered that will require particular attention in the design and construction. The shallow subgrade soils typically consisted of soft to stiff, high plasticity (CH) clays. The dry densities and field penetration resistance values of the subgrade soils ranged from 68 to 99 pcf and 3 to 14, respectively. In addition, elevated moisture contents and likely unstable subgrade soils were encountered in the majority of the borings. Moisture contents of the subgrade soils were typically near or above 30 percent and as high as 59 percent.

Therefore, stabilization or drying of the subgrade materials will be required during construction.

Potential stabilization measures are outlined in subsequent sections of this report.

Based upon existing pavement material thickness, consideration could be given to full depth reclamation (FDR) to provide a stable platform for construction and to eliminate material export operations. If pavement grades cannot be adjusted due to geometric constraints, consideration could be given to reusing the processed pavement materials for subgrade stabilization and/or improvement.

6.2 Corrosivity

Laboratory test results indicate the on-site soils exhibit a soluble sulfate concentrations ranging from 160 to 1,200 mg/kg. Results of soluble sulfate testing indicate that ASTM Type I-II or Type II Portland cement should be considered for all project concrete on and below grade. Foundation concrete should be designed for low sulfate exposure in accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4.

7.0 EARTHWORK

7.1 Site Preparation

Strip and remove existing pavement materials, and other deleterious materials from proposed new pavement reconstruction areas. Exposed surfaces should be free of mounds and depressions which could prevent uniform compaction.

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Evidence of underground facilities and utilities were observed within and near the project site during the site reconnaissance. Therefore, such features could be encountered during construction. If unexpected fills or underground facilities are encountered, such features should be removed and the excavation thoroughly cleaned prior to backfill placement and/or construction.

7.2 Excavation

It is anticipated that shallow excavations for the proposed construction can be accomplished with conventional earthmoving equipment. Heavy duty excavation equipment may be necessary for the hard and/or very dense soils.

Based upon the borings, we do not anticipate groundwater will be encountered in excavations up to 15 feet in depth. Pumping from sumps may be utilized to control water within excavations.

Based upon the subsurface conditions determined from the geotechnical exploration, subgrade soils exposed during construction will likely encounter unstable conditions. Soft to medium stiff subgrade conditions along with elevated moisture contents were encountered in majority of the borings. Moisture contents of the subgrade soils were typically near or above 30 percent and as high as 59 percent. Therefore, subgrade stabilization or drying should be anticipated during construction.

The stability of the subgrade may be affected by precipitation, repetitive construction traffic or other factors. If unstable conditions develop, workability may be improved by scarifying and drying. Overexcavation of wet zones and replacement with granular materials may be necessary.

Use of lime, fly ash, kiln dust, cement or geotextiles/geogrids could also be considered as a stabilization technique. Laboratory evaluation is recommended to determine the effect of chemical stabilization on subgrade soils prior to construction. Lightweight excavation equipment may be required to reduce subgrade pumping.

As an option for subgrade stabilization and to improve subgrade improvement, consideration could be given to reusing the existing processed pavement materials.

The individual contractor(s) is responsible for designing and constructing stable, temporary excavations as required to maintain stability of both the excavation sides and bottom.

Excavations should be sloped or shored in the interest of safety following local, and federal regulations, including current OSHA excavation and trench safety standards.

7.3 Pavement Maintenance and Surface Drainage

Preventative maintenance consists of both localized maintenance (e.g. crack sealing and patching) and global maintenance (e.g. surface sealing). Preventative maintenance is usually the

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Pavement design methods are intended to provide structural sections with adequate thickness over a particular subgrade such that wheel loads are reduced to a level that subgrade can support.

The support characteristics of the subgrade for pavement design do not account for the shrink movements of the soils encountered on this project. Thus the pavement may be adequate for a structural standpoint, yet still experience cracking and deformation due to shrink related movement of the subgrade. It is, therefore, important to minimize moisture changes in the subgrade to reduce collapse/consolidation movements.

Future performance of pavements constructed at the airport facility will be dependent upon several factors, including:

■ Maintaining stable moisture content of the subgrade soils.

■ Providing for a planned program of preventative maintenance.

The performance of all pavements can be enhanced by minimizing excess moisture which can reach the subgrade soils. The following recommendations could be considered:

■ site grading at a minimum 2% grade away from the pavements;

■ subgrade and the pavement surface have a minimum ¼ inch per foot slope to promote proper surface drainage.

■ consider appropriate edge drainage and pavement under drain systems,

■ install pavement drainage surrounding areas anticipated for frequent wetting

■ install joint sealant and seal cracks immediately,

■ compaction of any utility trenches for landscaped area to the same criteria as the pavement subgrade.

■ seal all landscaped areas in, or adjacent to pavements to minimize or prevent moisture migration to subgrade soils;

8.0 GENERAL COMMENTS

Terracon should be retained to provide observation and testing services during grading, excavation, pavement construction and other earth-related construction phases of the project.

The analysis and recommendations presented in this report are based upon the data obtained from the borings performed at the indicated locations and from other information discussed in this report. This report does not reflect variations that may occur between borings, across the site, or due to the modifying effects of construction or weather. The nature and extent of such variations may not become evident until during or after construction. If variations appear, we should be

APPENDIX A

FIELD EXPLORATION

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A-38

UNIFIED SOIL CLASSIFICATION SYSTEM

Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests Soil Classification

Group Symbol Group Name

Coarse Grained Soils:

Gravels: Clean Gravels:

Gravels with Fines:

Sands: Clean Sands:

Sands with Fines:

Fine-Grained Soils:

Silts and Clays:

Inorganic:

Organic:

Silts and Clays:

Inorganic:

Organic:

Highly organic soils:

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APPENDIX B

LABORATORY TESTING

PROJECT: Taxiway A Reconstruction - Gallup Municipal Airport JOB NO: 66175219 LOCATION: Gallup, NM WORK ORDER NO: 66175219 MATERIAL: Sandy Fat Clay (CH) LAB NO: 2510

SAMPLE SOURCE: B-06 @ 1.3'-5' DATE SAMPLED: 3/5/19

COMPACTION(%) 102 PENETRATION 0.100 0.200

COMPACTION METHOD D698 STANDARD HAMMER CORRECTION 0.00 0.00

3 LIFTS @ 35 BLOWS/LIFT CORRECTED CBR 1 1

SAMPLE CONDITION SOAKED

PERCENT SWELL 1.16%

% MOISTURE (TOP 1") 24.2% CBR (SOAKED) 1

SURCHARGE WEIGHT 10 lbs % RETAINED 19mm SIEVE 0%

DRY DENSITY 86.7 lbs./cu.ft

PERCENT MOISTURE 16.8 %

REVIEWED BY

CBR(CALIFORNIA BEARING RATIO) OF LABORATORY-COMPACTED SOILS

ASTM D1883 (SOAKED)

BEFORE SOAK

0.000 0.100 0.200 0.300 0.400 0.500 0.600

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PENETRATION (inches)

Exhibit B-59

LOCATION: Gallup. NM WORK ORDER NO: 66175219 MATERIAL: Lean Clay with Sand (CL) LAB NO: 2510

SAMPLE SOURCE: B-14 @ 1'-5' DATE SAMPLED: 3/5/19

COMPACTION(%) 96 PENETRATION 0.100 0.200

COMPACTION METHOD D698 STANDARD HAMMER CORRECTION 0.00 0.00

3 LIFTS @ 20 BLOWS/LIFT CORRECTED CBR 1 1

SAMPLE CONDITION SOAKED

PERCENT SWELL 5.72%

% MOISTURE (TOP 1") 34.8% CBR (SOAKED) 1

SURCHARGE WEIGHT 10 lbs % RETAINED 19mm SIEVE 0%

DRY DENSITY 95.0 lbs./cu.ft

PERCENT MOISTURE 13.7 %

REVIEWED BY

CBR(CALIFORNIA BEARING RATIO) OF LABORATORY-COMPACTED SOILS

ASTM D1883 (SOAKED)

BEFORE SOAK

0.000 0.100 0.200 0.300 0.400 0.500 0.600

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Exhibit B-60

MATERIAL: Sandy Fat Clay LAB NO: 2510

SAMPLE SOURCE: B-27 @ 1.8'-5' DATE SAMPLED: 3/5/19

COMPACTION(%) 95 PENETRATION 0.100 0.200

COMPACTION METHOD D1557 MODIFIED HAMMER CORRECTION 0.00 0.00

3 LIFTS @ 56 BLOWS/LIFT CORRECTED CBR 3 3

SAMPLE CONDITION SOAKED

PERCENT SWELL 1.42%

% MOISTURE (TOP 1") 33.7% CBR (SOAKED) 3

SURCHARGE WEIGHT 10 lbs % RETAINED 19mm SIEVE 0%

DRY DENSITY 101.0 lbs./cu.ft

PERCENT MOISTURE 21.0 %

REVIEWED BY

CBR(CALIFORNIA BEARING RATIO) OF LABORATORY-COMPACTED SOILS

ASTM D1883 (SOAKED)

BEFORE SOAK

0.000 0.100 0.200 0.300 0.400 0.500 0.600

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Exhibit B-61

MATERIAL: Fat Clay with sand (CH) LAB NO: 2510

SAMPLE SOURCE: B-35 @ 1.4'-5' DATE SAMPLED: 3/5/19

COMPACTION(%) 100 PENETRATION 0.100 0.200

COMPACTION METHOD D698 STANDARD HAMMER CORRECTION 0.00 0.00

3 LIFTS @ 56 BLOWS/LIFT CORRECTED CBR 3 3

SAMPLE CONDITION SOAKED

PERCENT SWELL 1.35%

% MOISTURE (TOP 1") 31.2% CBR (SOAKED) 3

SURCHARGE WEIGHT 10 lbs % RETAINED 19mm SIEVE 0%

DRY DENSITY 95.8 lbs./cu.ft

PERCENT MOISTURE 21.2 %

REVIEWED BY

CBR(CALIFORNIA BEARING RATIO) OF LABORATORY-COMPACTED SOILS

ASTM D1883 (SOAKED)

BEFORE SOAK

0.000 0.100 0.200 0.300 0.400 0.500 0.600

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Exhibit B-62

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