TX FTFW LAAT 10(3)_Geotechnical Engineering Report Laguna NWR.pdf

Geotechnical Engineering Report

Steve Thompson Wildlife Drive

Laguna Atascosa National Wildlife Refuge

Los Fresnos, Texas

Yeh Project No.: 220-065

January 8, 2021

Prepared for:

Mr. Scott Marshall, PE

HDR

835 N Post Street, Suite 101 Spokane, WA 99201

Prepared by:

Yeh and Associates, Inc.

627 Elkton Dr.

Colorado Springs, CO 80907

Phone: 719-434-1643 Fax: 303-781-9583

Geotechnical Engineering Report

Steve Thompson Wildlife Drive

Laguna Atascosa National Wildlife Refuge

Los Fresnos, Texas

Yeh Project No.: 220-065

January 8, 2021

Prepared by:

JG T. McCall, PE (CO) Project Engineer

Martin L. Skyrman, P.E.

Senior Project Manager

Reviewed by:

Robert F. LaForce, PE Senior Project Manager i

Table Of Contents

1. PURPOSE AND SCOPE OF STUDY

1.1 PROJECT UNDERSTANDING

2. SUBSURFACE EXPLORATION

2.1 FIELD EXPLORATION

2.2 LABORATORY TESTING

3. SITE AND SUBSURFACE CONDITIONS

3.1 SITE CONDITIONS

3.2 GEOLOGIC SETTING

4. SUBSURFACE CONDITIONS

4.1 GROUNDWATER

5. CONCLUSIONS AND RECOMMENDATIONS

5.1 EXPANSIVE SUBGRADE SOILS

5.2 CONSTRUCTION CONSIDERATIONS

5.2.1 Subgrade Preparation

5.2.2 Excavation Characteristics

5.2.3 Structural Fill

5.2.4 Compaction Requirements

5.2.5 Construction in Wet Weather

5.3 ANALYTICAL TEST RESULTS

5.3.1 Concrete Sulfate Resistance

5.3.2 Corrosion Potential

5.4 PAVEMENT DESIGN

5.4.1 Reclaimed and Subgrade Materials and Strength

5.4.2 Traffic Information

5.4.3 Pavement Design Parameters

5.4.4 Minimum Pavement Thickness

5.4.5 Pavement Materials

5.4.6 Pavement Drainage

5.4.7 Pavement Maintenance

5.5 STWD SOUTH LOOP

6. LIMITATIONS

i i

List Of Figures

FIGURE 1. PROJECT LOCATION

FIGURE 2. PROJECT SITE PLAN

FIGURE 3. GEOLOGIC MAP

FIGURE 4. SUMMARY OF EXISTING PAVEMENT THICKNESS

List Of Tables

TABLE 5-1. IMPORTED STRUCTURAL FILL CRITERIA

TABLE 5-2. COMPACTION SPECIFICATIONS

TABLE 5-3. ANALYTICAL TEST SAMPLES

TABLE 5-4. RESISTIVITY AND CORROSIVITY CATEGORIES

TABLE 5-5. SUMMARY OF PAVEMENT DESIGN PARAMETERS

TABLE 5-6. SUMMARY OF STRENGTH COEFFICIENTS

TABLE 5-7. RECOMMENDED MINIMUM PAVEMENT SECTIONS

List Of Appendices

FIGURE A-1 EXPLORATION LOCATION PLAN...................................................................................................A

KEY TO BORING LOGS............................................................................................................................................ B

BORING LOGS ........................................................................................................................................................... B

LABORATORY TEST RESULTS ............................................................................................................................. C

PAVEMENT DESIGN OUTPUTS ............................................................................................................................ D file:///D:/Projects/220-065%20ES%20HDR%20Laguna%20National%20Wildlife%20Refuge/08%20Reports/Draft/220-065_Laguna%20National%20Wildlife%20Refuge%20Pavement_DRAFT_hml.docx%23_Toc42507579 file:///D:/Projects/220-065%20ES%20HDR%20Laguna%20National%20Wildlife%20Refuge/08%20Reports/Draft/220-065_Laguna%20National%20Wildlife%20Refuge%20Pavement_DRAFT_hml.docx%23_Toc42507580 file:///D:/Projects/220-065%20ES%20HDR%20Laguna%20National%20Wildlife%20Refuge/08%20Reports/Draft/220-065_Laguna%20National%20Wildlife%20Refuge%20Pavement_DRAFT_hml.docx%23_Toc42507581 file:///D:/Projects/220-065%20ES%20HDR%20Laguna%20National%20Wildlife%20Refuge/08%20Reports/Draft/220-065_Laguna%20National%20Wildlife%20Refuge%20Pavement_DRAFT_hml.docx%23_Toc42507582

Steve Thompson Wildlife Drive Improvements YA Project No. 220-065 Laguna Atascosa NWR, Los Fresnos, Texas January 8, 2021

1. PURPOSE AND SCOPE OF STUDY

This report presents the results of Yeh and Associates, Inc. (Yeh) geotechnical engineering study and pavement thickness design for the proposed improvements on Steve Thompson Wildlife

Drive (STWD) at the Laguna Atascosa National Wildlife Refuge (NWR) in Los Fresnos, Texas.

The Central Federal Lands Highway Division (CFLHD) project number for this project is TX FTFW

LAAT 10(3). The approximate location of the project site is presented in Figure 1.

Figure 1. Project Location

The purpose of our study was to evaluate the existing pavement and subsurface conditions at the project site and provide pavement thickness design and construction recommendations of the proposed roadway improvements.

Our engineering study was completed in general accordance with the Scope of Work in Task

Order Number: DTFH68-16-D-00006/TBD, dated December 4, 2019. Yeh has completed the following scope of services for this project:

• Review available geotechnical and geological information about the site including mapped geology, and NRCS soil survey.

• Conduct a site observation and subsurface exploration to evaluate the existing pavement and subsurface conditions. The subsurface exploration consisted of 28 geotechnical borings performed at the approximate locations shown on Figure A-1 in

Appendix A.

• Perform laboratory testing on soil samples obtained during the subsurface exploration to evaluate the engineering characteristics.

• Prepare a report that presents the results of our field and subsurface exploration, geotechnical engineering analyses, encountered site and subsurface conditions, and pavement thickness design and construction recommendations.

The conclusions and recommendations presented herein are based on our limited site explorations and the subsurface conditions encountered at our boring locations during the time of our exploration. Our findings, conclusions, and recommendations should not be extrapolated to other areas of the site or used for other projects without our prior review. Additionally, they should not be used if the site has been altered or if more than two (2) years has elapsed since the date of this report without our prior review to determine if they remain valid.

1.1 Project Understanding

Steve Thompson Wildlife Drive (STWD) previously known as Bayside Wildlife Drive begins at the intersection with Buena Vista Road and proceeds to Redhead Parking Area along the north loop

(7.1 miles). Based on our discussions with the project team and project summary provided in the

SOW document, we understand that the proposed project is to:

1. Improve the existing roadway with new two (2) lanes roadway and new pavement;

2. Add new turn lanes on General Brant Rd., at the southwest entrance to the NWR;

3. Repair or reconstruct the existing pavement at the visitor center and the maintenance and hunter station;

4. Improve existing pavement at the existing parking lots (Plover Point and Redhead) and add additional parking areas within the NWR.

5. The remaining part of the STWD south of this project limit (south loop) will be overlaid with a new chip seal surface. However, south loop is beyond the scope of the work of this project.

The approximate limits of the proposed roadway and parking area improvement are presented in

Figure 2.

Figure 2. Project Site Plan

If the proposed construction is different than as described above, we should be contacted and provided the opportunity to evaluate our recommendations presented herein and evaluate if they remain valid based on the proposed construction.

2. SUBSURFACE EXPLORATION

2.1 Field Exploration

Our site observation and subsurface exploration was completed on April 15, and April 16, 2020.

Our subsurface exploration consisted of advancing 28 exploratory borings to a maximum depth of 5 feet below the existing ground surface (BGS). Approximate locations of borings were recorded using a hand help GPS unit with an accuracy of 10 feet and are presented on Figure A-

1, Exploration Location Plan, in Appendix A. The borings were located along the proposed roadway and parking lot improvement areas. Table 2-1 shows a summary of the boring locations.

Table 2-1. Summary of Exploration Locations

Boring ID Location Description Latitude (°) Longitude (°)

P-1 SW Entrance and Parking Area 26.18225 97.35175

P-2 STWD Main Roadway 26.18528 97.34508

P-3 STWD Main Roadway 26.19248 97.34629

P-4 STWD Main Roadway 26.19965 97.34748

P-5 STWD Main Roadway 26.20687 97.34600

P-6 STWD Main Roadway 26.21395 97.34410

P-7 STWD Main Roadway 26.21726 97.34267

P-8 STWD Main Roadway 26.21373 97.33447

P-9 STWD Main Roadway 26.21583 97.32994

P-10 STWD Main Roadway 26.21561 97.31977

P-11 STWD Main Roadway 26.21581 97.31315

P-12 STWD Main Roadway 26.20941 97.30966

P-13 STWD Main Roadway 26.20329 97.30553

P-14 STWD Main Roadway 26.19900 97.29945

P-15 STWD Main Roadway 26.19366 97.29574

P-16 STWD Main Roadway 26.18648 97.29637

P-17 Redhead Ridge Parking Lot 26.17962 97.29778

P-18 Redhead Ridge Parking Lot 26.17941 97.29787

P-19 Plover Point Parking Lot 26.21767 97.31348

Boring ID Location Description Latitude (°) Longitude (°)

P-20 Plover Point Parking Lot 26.21740 97.31346

P-21 Visitor Center Parking Lot 26.22917 97.34733

P-22 Visitor Center Parking Lot 26.22900 97.34687

P-23 Visitor Center Parking Lot 26.22936 97.34689

P-24 Maintenance Building Parking Lot 26.22836 97.34827

P-25 Hunter Station Parking Lot 26.22698 97.34869

P-26 Hunter Station Parking Lot 26.22611 97.34870

P-27 General Brandt Road Turn Lanes 26.18372 97.35174

P-28 General Brandt Road Turn Lanes 26.18104 97.35284

The borings were advanced using a truck-mounted, CME-45 drill rig equipped with 4-inch diameter, continuous flight, solid stem augers. Soil samples were collected at regular intervals by driving a standard penetration test (SPT) split barrel sampler or Modified California (MC) split barrel sampler into the strata with an automatic, 140-pound hammer falling 30-inches. Shelby tube sampler was also used to obtain clay samples in the selected strata.

The SPT is a 1.375-inch I.D. standard split barrel sampler following ASTM D1586. The Modified

California (MC) Sampler is a 2.5-inch O.D., 2.0-inch ID (1.95-inch ID with liners), split barrel sampler with internal liners, following ASTM D3550. The blows required to drive the SPT sampler the final 12-inches is known as the SPT N-value. The MC Sampler “Penetration Resistance” refers to the sum of all blows required to drive the sampler the drive length of 12-inches or portion thereof. The SPT N-value and the MC penetration resistance represent the consistency or relative density the strata. Thin walled shelby tube samplers are nominally 3-inches diameter and pushed into the strata using hydraulic jack on the drill rig, the thin walled samplers were typically pushed

18-inches to 24-inches in the strata.

Additionally, grab samples were collected from the auger cuttings in the upper 5-feet of the borehole.

The borings were logged and sampled by a qualified representative of Yeh. The boring logs and key to the boring logs are presented in Appendix B.

2.2 Laboratory Testing

Representative soil samples were selected for geotechnical and analytical laboratory testing.

Laboratory testing was performed following industry standards and consistent with local practice.

Laboratory soil testing included the following:

• natural moisture-density

• gradation analysis

• Atterberg limits

• swell/collapse potential

• Hveem Stabilimeter

• Standard Proctor compaction

• water soluble sulfates and chlorides, soil resistivity, redox potential, and pH

Results of the laboratory testing are shown on the boring logs and presented in the Laboratory

Summary in Appendix C.

3. SITE AND SUBSURFACE CONDITIONS

3.1 Site Conditions

The project site is located within the Laguna Atascosa National Wildlife Refuge (NWR) in

Cameron County, Texas. The NWR is mostly natural habitat and terrain that comprise coastal prairies, beaches, mudflats, and dense brush and grassland.

At the time of our exploration, the existing STWD consisted of a single lane, one-way road with chip seal surfacing. The pavement surface was generally in moderate to poor condition. The chip seal surface at the entrance at General Brant Rd. at P-1 was generally in better condition than the most of the STWD and appears to be placed relatively recently.

General Brant Road is a TxDOT highway and consisted of a two-lane asphalt pavement roadway that appears to have been paved recently and the asphalt pavement is generally in good condition. The existing pavement at the existing visitor center, maintenance building and hunter station consists of chip seal surface and appears in moderate condition.

Photographs below show the general site and pavement conditions at the time of our exploration.

Photograph 1. SW Entrance and Parking Area

Photograph 2. General Brant Road. North of NWR Entrance

Photograph 3. Pavement Condition STWD Between Borings P-4 and P-5

Photograph 4. Pavement Condition STWD Between Borings P-13 and P-14

Photograph 5. Pavement Condition STWD Between Borings P-8 and P-9

3.2 Geologic Setting

Review of the Preliminary geologic map of southernmost Texas, United States, and parts of

Tamaulipas and Nuevo Leon, Mexico: environmental health investigations in the United States -

Mexico border region, Page, W.R., VanSistine, D.P., and Turner, K.J., 2005, U.S. Geological

Survey, indicates the project site is mapped to have near surface that comprise of muddy flood-plain alluvium and clay dune and clay to sand dune deposits. The muddy flood-plain alluvium comprises clay soils. The clay dune and clay to sand dune deposits comprises clay and sand soils. The mapped units at the project site and a key to the unit descriptions are presented in

Figure 3, Geologic Map.

Review of the near surface soils mapped by the Natural Soil Conservation Service (NRCS), indicates the surficial soils are generally classified as clayey loam soils. The clay to silty loam units are mapped are generally are 5 to 6 feet thick or more.

Photograph 6. STWD at Readhead Ridge Parking Area

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4. SUBSURFACE CONDITIONS

The subsurface soils encountered in our borings are generally consistent with the mapped geology and NRCS descriptions. The subsurface soils generally comprise clayey soils along most the STWD alignment, visitor center, maintenance building and hunter station. Silty sand soils were encountered along the eastern edge of the site at borings P-16 to P-18 (Redhead Ridge parking area). Along the STWD roadway, thin chip seal surfacing with thickness typically less

Figure 3. Geologic Map

1 1 than 1 inch over 4 to 12 inches of granular subbase was encountered above the clay and sand subgrade. Two (2) inches of asphaltic concrete pavement was encountered in Borings P-27 and

P-28 along General Brant Road. Figure 4 below shows the summary of the thickness of chip seal, asphalt, and subbase thickness encountered in each boring.

The clay soils are medium to high plasticity with relatively high moisture contents and observed to be soft to medium stiff. Individual boring logs in Appendix B present detailed subsurface conditions encountered at each boring.

4.1 Groundwater

Groundwater was not encountered during our exploration. However, high moisture content was encountered in borings P-1 to P-5, P-7 and P-8, which indicates the potential of perched water table at these locations. Groundwater observations are representative of conditions at the time of our field exploration, and therefore may not be indicative of groundwater levels at other times of the year or at other locations across the site. Groundwater conditions may fluctuate with seasonal precipitation, site grading and improvements, and ocean water levels.

P -1

P -2

P -3

P -4

P -5

P -6

P -7

P -8

P -9

P -1

P -1

P -1

P -1

P -1

P -1

P -1

P -1

P -1

P -1

P -2

P -2

P -2

P -2

P -2

P -2

P -2

P -2

P -2

P av em en t Th ic kn es s, in ch es

Boring ID

Asphalt Chip Seal Subbase

Figure 4. Summary of Existing Pavement Thickness

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5. CONCLUSIONS AND RECOMMENDATIONS

Based on the results of our subsurface exploration, laboratory testing, and engineering analysis, it is our opinion that the project is geotechnically feasible provided the recommendations presented in the following sections are incorporated into the design and construction of the project.

Our primary geotechnical concern at the site is the presence of soft, lean-to-fat, and fat clays with high in-situ moisture. These soils generally provide poor support for pavements and will be difficult to compact properly and hard to achieve required minimum density.

The following sections present our construction and design recommendations for the site.

5.1 Expansive Subgrade Soils

Medium to high plastic soils were encountered beneath the existing pavement sections along majority of the proposed pavement improvement areas, except on the eastern part of the STWD near Borings P-16 to P-18. These clayey soils have liquid limits ranging from 32 to 82, and plasticity index ranging from 18 to 59. One-dimensional swell/consolidation tests performed on selected samples indicated swell potential of 0.4% to 6.1% under load of 200 pounds per square foot (psf).

To evaluate the impact of the medium to high plastic soils to the performance of the pavement, Yeh has reviewed the followings:

- Conditions of the existing pavement condition where no obvious negative impact was observed from the existing pavement surface.

- FHWA FLH Project Development and Design Manual (PDDM), Chapter 11 Pavements.

Section 11.3.2.1.3 “Swelling soils and/or soils with high PI (>15)” of PDDM recommends that subexcavation of up to 6 feet for this project site where fat clay was encountered.

- Texas DOT Pavement Manual, October 2019. Following the procedures from Test

Method, Tex-124-E, the potential vertical rise (PVR) of the subgrade can be up to 2.5 inches. The TxDOT Pavement Manual recommends maximum allowable amount of PVR of 2.0 inches for frontage roads.

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- Laboratory one-dimensional swell/consolidation test indicates potential vertical rise of up to 6 inches.

Based on the review, Yeh recommend the following approaches to mitigate the PVR of the clay subgrade soils.

- If PVR up to 2.5 inches is acceptable, no additional mitigation is recommended to the existing clay subgrade soils. Cracks and wavy pavement is possible and should be anticipated.

- If PVR up to 2 inches is acceptable, the existing subbase and clay subgrade soils should be over-excavated to 2.5 feet below the proposed pavement grade, and replaced with structural fill and pavement section.

5.2 Construction Considerations

Unless other Federal or local agency requirements or specifications apply or are specifically incorporated into the project, roadway construction should be performed per the 2014 FHWA

Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects (FP-

14). The following sections provide recommendations associated with design and performance of the proposed pavement section as provided herein.

5.2.1 Subgrade Preparation

Site preparation for areas to receive new pavement of fill should be prepared by removal of any obviously unsuitable materials present (e.g. debris, organic materials, waste) larger than 6 inches should be completely removed from the top 6 inches of subgrade. Remove the stripped materials for offsite disposal in accordance with Section 204.14 of FP-14.

Prior to placement of new embankment fill or pavement sections, processing of the subgrade should be performed per Section 303 of FP-14. Per subsection 204.11 of FP-14, the subgrade should be scarified to a minimum depth of 6-inches, and surface irregularities removed. The subgrade surface should be moisture conditioned to moisture content and density requirements shown in Table 5-2.

Prior to placing new pavement sections including new subbase or aggregate base courses, the pavement subgrade should be proof-rolled with compression type rollers at speeds less than 6 feet per second and vibratory rollers at speeds less than 3 feet per second Areas that pump or

1 4 deform significantly under heavy wheel loads are not suitable for pavement support and should be removed and replaced to achieve a firm and uniform subgrade prior to paving. Care should be taken to ensure areas around manholes or other utility protrusions are proof-rolled adequately.

Any soft and/or wet areas exposed during the excavation process may need to be stabilized prior to placement of new fill and pavement sections to create a stable, unyielding construction platform per Section 204.07 of FP-14. The method and extent of stabilization will depend on the actual conditions encountered, and the more appropriate method of stabilization will likely be best determined in the field at the time of excavation, by Yeh representatives. Typical stabilization methods may include mechanical stabilization utilizing geo-grid such as Tensar TX160, and

Aggregate Base Course (or similar) to form a stable base on which to place the pavement section.

The widening of the existing roadway will require either on-site soils or imported materials.

The construction of the widening areas will encounter clay soils that were encountered in majority of the project limits. If the construction is performed during the wet seasons, soft and unstable subgrade soils should be anticipated. Undercutting or stabilization methods described above should be anticipated. The modifications to the subgrade soils can impact the budget of the project significantly and should be taken into considerations.

5.2.2 Excavation Characteristics

Excavations into the on-site soils will encounter a variety of conditions, the soils encountered during our exploration may be excavated with conventional standard duty earth moving equipment.

All excavations must comply with Section 204 of FP-14 and applicable local, State, and Federal safety regulations, and particularly with the excavation standards of the Occupational Safety and

Health Administration (OSHA). Construction site safety, including excavation safety, is the sole responsibility of the Contractor as part of its overall responsibility for the means, methods, and sequencing of construction operations. Yeh recommendations for excavation support is provided for the Client’s sole use in planning the project, in no way do they relieve the Contractor of its responsibility to construct, support, and maintain safe slopes. Under no circumstances should the following recommendations be interpreted to mean that Yeh and Associates is assuming responsibility for either construction site safety or the Contractor’s activities.

We believe the overburden soil encountered on this site will classify as a Type C material, using

OSHA criteria. OSHA requires that unsupported cuts be no steeper than 1½:1 for Type C for

1 5 unbraced excavations up to 20 feet in height. In general, we believe that these slope ratios will be temporarily stable under unsaturated conditions. Flattened slopes may be required if excavations encounter groundwater or the slopes will be exposed for an extended period of time.

Please note that the Contractor’s OSHA-qualified “competent person” must make the actual determination of soil type and allowable sloping in the field.

The soils encountered by the proposed excavations may vary significantly across the site. The preliminary classifications presented above are based solely on the materials encountered in widely spaced exploratory test borings. The contractor should verify that similar conditions exist throughout the proposed area of excavation.

As a safety measure, it is recommended that all vehicles and soil piles be kept to a lateral distance equal to at least the depth of the excavation from the crest of the slope. The exposed slope face should be protected against the elements and monitored by the contractor on at least a daily basis.

5.2.2.1 Dewatering and Shoring

Groundwater was not encountered in our borings during our exploration. However, based on our experience in the area, close proximity to ocean and swamp land, and high moisture content in subgrade soils, localized areas of shallow groundwater or surface runoff could be encountered, and localized groundwater seepage is possible at random locations and elevations within the soils and subject to seasonal precipitation and ocean level events. Therefore, where operations encounter shallow groundwater or surface water, construction dewatering may be required.

Utilizing appropriate construction dewatering equipment/systems, such as well points, sumps, and trenches, will be the responsibility of the trenching contractor. A dewatering expert should be retained as appropriate. In addition, trenching into wet and/or saturated overburden soils will require temporary shoring, where the construction of safe un-shored slopes is not feasible.

5.2.3 Structural Fill

Structural fill refers to material that is appropriate for placement beneath structure components, embankment fill, and pavement subgrade. Based on the results of our subsurface explorations and laboratory testing, the on-site granular soils are appropriate for this use provided any particles greater than 3-inches are removed. If imported fill is required to meet proposed site grades, it should consist of a non-expansive, mainly granular material meeting the requirements presented in Table 5-1, per Section 704.04 of FP-14.

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A sample of any proposed imported structural fill should be submitted to our office for review and testing at least 3 days prior to stockpiling at the site. The native subgrade to receive structural fill should be prepared in accordance with Section 5.2.1.

Table 5-1. Imported Structural Fill Criteria

Gradation Requirements

Standard Sieve Size Percent Passing

3 inch 100

No. 200 15 or less

Plasticity Requirements (Atterberg Limits)

Plasticity Index 6 or less

We recommend that a qualified geotechnical representative visit the site for observation during excavation and during placement of the structural fill to verify the soils exposed in the excavations are consistent with those encountered during our subsurface exploration and that proper pavement subgrade preparation and placement is performed.

5.2.4 Compaction Requirements

Soil and aggregate materials should be placed on a horizontal plane in loose lifts not to exceed

6-inches in compacted thickness, unless otherwise accepted by the geotechnical engineer.

Materials should be moisture-conditioned and compacted according to following criteria.

Table 5-2. Compaction Specifications

Fill Location Material Type Percent

Compaction (Test Method)

Moisture Content

Pavement Subgrade/ Embankment Fill

On-site granular soils / Imported Structural Fill

95 minimum

(AASHTO T180)

± 2 % of optimum

Pavement Subgrade On-site clay soils with

LL<40

95 minimum

(AASHTO T99)

± 2 % of optimum

Pavement Subgrade On-site soils with LL >40 95 minimum

(AASHTO T99)

0 to +3% of optimum

Granular Subbase & Reclaimed Materials

Granular Subbase Materials /Pulverized Pavement (See Section 5.4.5.2)

95 minimum

(AASHTO T180)

2 % of optimum

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5.2.5 Construction in Wet Weather

During construction, grade the site such that surface water can drain readily away from the pavement and subgrade work area. Promptly pump out or otherwise remove any water that may accumulate in excavations or on subgrade surfaces and allow these areas to dry before resuming construction. Berms, ditches, and similar means may be used to prevent stormwater from entering the work area and to convey water off site efficiently.

5.3 Analytical Test Results

Analytical testing was completed on four representative subsurface soil samples. The location of the samples and test results are presented in Table 5-3 and in Appendix C.

Table 5-3. Analytical Test Samples

Boring and Depth

Soil Type Sulfate (%) Chloride pH

Resistivity (ohm-cm)

Redox Potential

(mv)

P-5 @ 2.0

ft. BGS

Fat Clay 0.215 0.2653 7.7 122 331.7

P-8 @ 3.5

ft. BGS

Fat Clay 0.312 0.2413 7.9 127 243.8

P-15 @ 3.0

ft. BGS

Lean Clay 0.022 0.0558 8.0 536 215.3

P-22 @ 2.0

ft. BGS

Lean-to- Fat Clay

0.037 0.1680 7.4 233 227.7

A qualified corrosion engineer should review test results and determine the appropriate corrosion protection measures at the site.

5.3.1 Concrete Sulfate Resistance

The concentration of water-soluble sulfates was observed to be between 0.022 and 0.312 percent based the test results. This concentration of water-soluble sulfates represents a Class 0 and Class

2 degree of sulfate attack on concrete exposed to these geologic materials. The degree of attack is based on a range of Class 0 (negligible) to Class 3 (very severe) as described in the American

Concrete Institute (ACI) Standard 201.2R, “Guide to Durable Concrete”.

Based on the sulfate test results, the tested soils present a severe potential for sulfate attack on concrete and cementitious material meeting requirements for class 2 sulfate resistance should be incorporated in the project. ASTM Type V, Portland cement is appropriate for class 2 sulfate resistance.

1 8

5.3.2 Corrosion Potential

Test results indicate a measured pH value between 7.4 and 8.0, and resistivity of 122 to 536 ohm-cm for the tests soils. Corrosion of buried metal is an electrochemical process in which the amount of metal loss due to corrosion is directly proportional to the flow of electrical current (DC) from metal into the soil. As resistivity decreases, the corrosivity of the soil increases. The following table provides a correlation between soil resistivity and corrosivity towards ferrous metal, as recommended by “Underground Corrosion, NBS Circular 579”, Melvin Romanoff, 1957.

Table 5-4. Resistivity and Corrosivity Categories

Resistivity in Ohm-centimeters Corrosivity Category

0 to 1,000 Severely Corrosive

1,000 to 2,000 Corrosive

2,000 to 10,000 Moderately Corrosive

Greater than 10,000 Mildly Corrosive

Based on the resistivity test results, the soils encountered at the site are anticipated to be severely corrosive to unprotected buried ferrous structures. A qualified corrosion engineer should review test results and determine the appropriate corrosion protection measures at the site.

5.4 PAVEMENT DESIGN

A pavement section is a layered system designed to distribute concentrated loads from traffic to the subgrade. The performance of a pavement structure is directly related to the physical properties of the subgrade soils, pavement materials and thicknesses, surface drainage, and traffic loading. For pavement design, parameters were chosen in general accordance with

Chapter 11 of the FHWA Project Development and Design Manual, 2018 Edition (PDDM). Yeh performed the flexible pavement design based on the 1993 AASHTO Guide for Design of

Pavement Structures (AASHTO 93).

Based on the subgrade conditions, existing pavement sections, and anticipated traffic loading, we have developed four (4) pavement segments as follows:

Segment 1: STWD mainline roadway and parking areas from the SW entrance to the site extending to the eastern edge of site. Borings within this segment include P-1 to P-15, P-19, and

P-20.

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Segment 2: STWD mainline roadway along eastern edge of site and including Redhead Ridge

Parking Area. Borings within this segment include P-15 to P-18.

Segment 3: Northern parking lots including Visitor Center, Maintenance Building, and Hunter

Station. Borings within these areas include P-21 to P-26.

Segment 4: General Brant Road Turn Lanes and tie into to SW entrance to site. Borings within these areas include P-27 and P-28.

5.4.1 Reclaimed and Subgrade Materials and Strength

Based on the field exploration and laboratory test results, the subgrade soils are anticipated to be primarily lean to fat clays with limited areas of sand. The strength of the subgrade soils was estimated based on the in-situ SPT blows and laboratory R-value test results. The subgrade resilient moduli (MR) was calculated from the R-values for each pavement segment. The estimated subgrade strength for each of the segment is summarized below:

Segment 1, 3 and 4: MR = 5,400 psi based on R-value of 8

Segment 2: MR = 9,500 psi based on R-value of 19

We recommend to recycle the existing chip seal surface and granular subbase by pulverizing the existing pavement surface layer and subbase to 6 inches below the existing pavement surface.

Yeh has performed the R-value test on the mixture of existing chip seal and subbase materials with the composite sample from Borings P-3, P-4, P-21, P-23 and P-36. An R-value of 22 was estimated from the composite sample.

5.4.2 Traffic Information

Design traffic loading is based on a 20-year pavement design period and average daily traffic

(ADT) provided by HDR. ADT was provided as follows:

• STWD: 2020 ADT = 50 and 2040 ADT = 150 with 1% trucks.

• General Brant Road: 2013 ADT = 600 and 2033 ADT = 800. Truck counts not provided, 3% trucks assumed.

Based on the provided traffic, we calculated a 5.6 percent annual growth rate for STWD and 1.45 percent annual growth rate for General Brand Rd. Traffic counts were then projected to 2021

2 0 volumes which is the assumed traffic opening year. An average 20 year, 18-kip Equivalent Single

Axel Loads (ESAL) was calculated for each segment and is shown on in Table 5-5 below.

5.4.3 Pavement Design Parameters

Pavement design parameters are based on laboratory test results for the subgrade soils, AASHTO 93 design criteria, and our experience. Tables 5-5 and 5-6 below present our design parameters and strength coefficients that are utilized in the pavement thickness calculations.

Table 5-5. Summary of Pavement Design Parameters

Parameter STWD and Parking Lots General Brant Rd

Design Period 20 years 20 years

18-kip ESAL 3,126 23,300

Reliability 75% 90%

Overall Standard Deviation 0.45 0.45

Initial Serviceability Index 4.2 4.5

Terminal Serviceability Index 2.0 2.0

Table 5-6. Summary of Strength Coefficients

Parameter Section 1 Value

HACP Structural Coefficient 0.44

HACP Drainage Coefficient 1.0

Aggregate Base Structural Coefficient 0.12

Aggregate Base Drainage Coefficient 1.0

Reclaimed Subbase Material Coefficient 0.10

Reclaimed Subbase Material Drainage Coefficient 1.0

Structural coefficients for the Hot Asphalt Concrete Pavement (HACP) and Aggregate Base were chosen in accordance with Exhibit 11.2-C in Section 11.2.1.4 of the 2018 FHWA PDDM.

The Reclaimed Material (RM) is defined as the material that will be generated during the pulverization of the existing pavement surface and subbase layers to a depth of 6 inches.

2 1

5.4.4 Minimum Pavement Thickness

Based on the results of our subsurface exploration, laboratory testing, engineering analysis and the design parameters and strength coefficients presented above, we recommend the minimum pavement sections presented in Table 5-7. We expect that the General Brant Road will be widened for the new turn lanes, and the widening area will have new pavement. The existing pavement is fairly new and in good condition, Yeh recommend to overlay the existing pavement with HACP to meet the pavement design requirements.

Table 5-7. Recommended Minimum Pavement Sections

Design Segment New HMA over Reclaimed

Materials/Granular Subbase

Segment 1 (STWD from Borings P-1 to P-15)

3” HACP

3” Reclaimed Materials

Segment 2 (STWD From Borings P-15 to P-18)

3” HACP

3” Reclaimed Materials

Segment 3 (Visitor Center, Maintenance Building and

Hunter Station)

3” HACP

3” Reclaimed Materials

Segment 4 New Pavement (General Brant Widening) – Optional Section

3” HACP

8” Granular Subbase

Segment 4 New Pavement (General Brant Widening) – Existing Section

1.5” HACP

One Coat Surface Treatment 10” 2% Lime treated flexbase 12” 3% lime treated subgrade

Segment 4 Existing Pavement (General Brant Turn Lane)

1” HACP Overlay 2” Existing HACP

10” Granular Subbase

2 2

5.4.5 Pavement Materials

5.4.5.1 Asphalt Mix

We recommend an HACP Superpave design mix, or a State Department of Transportation asphalt concrete pavement mixture as specified in Section 403 of the FP-14, Standard

Specifications for Construction of Roads and Bridges on Federal Highway Projects. A commercially produced, heat stable liquid antistrip additive should be added to the asphalt mix to prevent separation of the asphalt from the aggregates. The HACP pavement should be compacted to between 92 percent and 96 percent of its maximum theoretical (Rice) density.

5.4.5.2 Granular Subbase

Untreated granular subbase in accordance with Section 301 of the FP-14, is recommended with a maximum size of 2.5-inch. Granular subbase materials should be uniformly graded, and free of organic matter, lumps or balls of clay, and other deleterious materials. The maximum dry density of the granular subbase should be determined according to AASHTO T 180. Granular subbase should be compacted to at least 95 percent of maximum density and within 2 percent of the optimum moisture content and should be spread in layers not exceeding 6 inches in compacted thickness.

5.4.5.3 Tack and Prime Coat

Per Section 412 of the FHWA FP-14, a tack coat should be applied if the HACP is applied in more than one lift at a rate of 0.03 to 0.15 gal/yd2 between each lift of HACP. Prior to application, prepare the existing surface by removing deleterious substances and ensure that the surface is dry and unfrozen and that the air temperature in the shade is above 35 degrees F and rising. Allow tacked surfaces to cure and place the covering course within 4 hours of placing tack coat. Acceptable emulsified asphalt grades include CSS-1, CSS-1h, SS-1, and SS-

1h per the FHWA PDDM.

In accordance with Section 411 of the FP-14, prime coat should also be applied to prepare the

ABC and RM at a rate of 0.1 to 0.5 gal/yd2. Application should take place when it is not foggy or rainy and when air temperature in the shade above 50 degrees F and rising. Allow tacked surfaces to cure for at least 24 hours before placing the covering course within 4 hours of placing tack coat.

2 3

5.4.6 Pavement Drainage

Proper drainage is critical to pavement performance. To limit the potential for future distress to pavement from wet, soft subgrade soils, we recommend the maintenance of good drainage away from all pavements. Possible water sources include storm runoff, irrigation of landscaping adjacent the pavement and localized groundwater seepage, among others. Joints in the pavement or at asphalt/concrete interfaces should be sealed. Any cracks or openings in the finished pavement surface should be sealed and/or repaired as quickly as possible.

5.4.7 Pavement Maintenance

Annual maintenance generally refers to crack filling and general surface sealers. We recommend implementation of an at least annual if not more frequent pavement crack sealing program. This is very important to prevent surface water (especially from slow infiltration from sources such as snow melt and surface run-off) from entering cracks and wetting the subgrade. Any cracks or openings in the finished pavement surface should be sealed and/or repaired as quickly as possible.

5.5 STWD South Loop

The STWD south loop from boring P-18 extend south and connect back to the entrance at Boring

P-1 is beyond the scope of this project. It is our understanding that the south loop with be overlaid with new chip seal layer, and minor repair to certain areas where severe damages are present.

At the request of CFL, Yeh has visually observe the pavement condition along the south loop.

Pavement surface damages including loss of chip seal, potholes and cracks were observed on the south loop. Yeh has prepared a summary of the field visual observation and present the results on Figure A-7 in Appendix A.

2 4

6. LIMITATIONS

The findings and recommendations presented in this report are based upon data obtained from borings, field observations, laboratory testing, our understanding of proposed construction, and other sources of information referenced in this report. It is possible that subsurface conditions may vary between or beyond the locations explored. The nature and extent of such variations may not become evident until construction. If during construction conditions appear to be different from those described herein, Yeh should be advised and provided the opportunity to observe and evaluate those conditions and provide additional recommendations, as necessary. Yeh should also be contacted if the scope of construction changes from that generally described within this report. The conclusions and recommendations contained in this report shall not be considered valid unless Yeh reviews all proposed construction changes and either verifies or modifies the conclusions of this report in writing.

This report was prepared in in a manner consistent with that level of care and skill ordinarily exercised by other members of our profession practicing in the same locality, under similar conditions and at the date the services are provided. Yeh makes no other representation, guarantee, or warranty, express or implied, regarding the services, communication (oral or written), report, opinion, or instrument of service provided.

This report may be used only by the Client and the registered design professional in responsible charge and only for the purposes stated for this specific engagement within a reasonable time from its issuance, but in no event later than two (2) years from the date of the report.

A

Appendix A

FIGURE A-1 EXPLORATION LOCATION PLAN

220-065 Date: 6/5/2020

BHL Yeh Office: Colorado Springs

HML

Exploration Location Plan

FIGURE

A-1 Project No.:

Laguna Atascosa National Wildlife Refuge

Los Fresnos, TX Figure By:

Checked By:

LEGEND

Approximate Boring Location

N

HML

FIGURE

A-2

Exploration Location Plan

Laguna Atascosa National Wildlife Refuge

Visitor Center and Maintenance Building

Los Fresnos, TX

Project No.:

Figure By:

Checked By:

LEGEND

HML

Exploration Location Plan

FIGURE

A-3 Project No.: Laguna Atascosa National Wildlife Refuge

Hunter Station

Los Fresnos, TX

Figure By:

Checked By:

LEGEND

HML

Exploration Location Plan

FIGURE

A-4 Project No.: Laguna Atascosa National Wildlife Refuge

Southwest Entrance

Los Fresnos, TX

Figure By:

Checked By:

LEGEND

HML

Exploration Location Plan

FIGURE

A-5 Project No.: Laguna Atascosa National Wildlife Refuge

Plover Point Parking Lot

Los Fresnos, TX

Figure By:

Checked By:

LEGEND

HML

Exploration Location Plan

FIGURE

A-6 Project No.: Laguna Atascosa National Wildlife Refuge

Redhead Ridge Parking Lot

Los Fresnos, TX

Figure By:

Checked By:

LEGEND

HML

FIGURE

A-7

Exploration Location Plan

Laguna Atascosa National Wildlife Refuge

South Loop Pavement Condtion Map

Los Fresnos, TX

Project No.:

Figure By:

Checked By:

LEGEND

Loss of chip seal

Pot hole

Patch

Low pavement distress

Moderate pavement distress

High pavement distress

B

Appendix B

KEY TO BORING LOGS

BORING LOGS

Laguna Atascosa National Wildlife Refuge

Project Number: 220-065

Legend for Symbols Used on Borehole Logs

Project:

Lab Test Standards Other Lab Test Abbreviations

Notes

Moisture Content ASTM D2216 Dry Density ASTM D7263 Sand/Fines Content ASTM D421, ASTM C136, ASTM D1140

Atterberg Limits ASTM D4318 AASHTO Class. AASHTO M145, ASTM D3282

USCS Class. ASTM D2487 (Fines = % Passing #200 Sieve Sand = % Passing #4 Sieve, but not passing #200 Sieve)

Sample Types

Asphalt USCS Fat/High Plasticity Clay

USCS Lean/Low Plasticity Clay

Fill with Sand as major soil

Low Plasticity Sandy Clay USCS Silty Sand

Lithology Symbols

Drilling Methods

Modified California Sampler (2.5 inch OD, 2.0 inch

ID)

Shelby Tube Standard Penetration Test

(ASTM D1586)

SOLID-STEM

AUGER

(see Boring Logs for complete descriptions)

2. "Penetration Resistance" on the Boring Logs refers to the uncorrected N value for SPT samples only, as per ASTM D1586. For samples obtained with a Modified California (MC) sampler, drive depth is 12 inches, and "Penetration Resistance" refers to the sum of all blows. Where blow counts were > 50 for the 3rd increment (SPT) or 2nd increment (MC), "Penetration Resistance" combines the last and 2nd-to-last blows and lengths; for other increments with > 50 blows, the blows for the last increment are reported.

4. "ER" for the hammer is the Reported Calibrated Energy Transfer Ratio for that specific hammer, as provided by the drilling company.

1. Visual classifications are in general accordance with ASTM D2488, "Standard Practice for Description and Identification of Soils (Visual-Manual Procedures)".

3. The Modified California sampler used to obtain samples is a 2.5-inch OD, 2.0-inch ID (1.95-inch ID with liners), split-barrel sampler with internal liners, as per ASTM D3550. Sampler is driven with a 140-pound hammer, dropped 30 inches per blow.

pH Soil pH (AASHTO T289-91) S Water-Soluble Sulfate Content (AASHTO T290-91, ASTM D4327)

Chl Water-Soluble Chloride Content (AASHTO T291-91, ASTM D4327)

S/C Swell/Collapse (ASTM D4546) UCCS Unconfined Compressive Strength

(Soil - ASTM D2166, Rock - ASTM D7012) R-Value Resistance R-Value (ASTM D2844) DS (C) Direct Shear cohesion (ASTM D3080) DS (phi) Direct Shear friction angle (ASTM D3080) Re Electrical Resistivity (AASHTO T288-91) PtL Point Load Strength Index (ASTM D5731)

SOLID-STEM

AUGER

A-7-6 (61)

CH99.0 79 5335.0 84.49

4-5

3-3-4

0.0 - 0.2 ft. Chip Seal (2 inches).

0.2 - 0.7 ft. SUBBASE (poorly graded SAND with gravel) (6 inches), brownish yellow, moist, medium dense.

0.7 - 5.5 ft. Fat CLAY (CH), gray to brownish gray, moist to wet, soft.

Bottom of Hole at 5.5 ft.

0.0 1.0100

Night Work:

Logged By: B. Lykins

Final By: J. McCall

Symbol Depth Date

Total Depth: 5.5 ft

Ground Elevation:

Coordinates: Lat: 26.18225 Long: 97.35175

Location: SW Entrance and Parking Area

Weather Notes: 66°F/Overcast

Inclination from Horiz.: Vertical

Boring Began: 4/15/2020

Boring Completed:

Drilling Method(s): Solid-Stem Auger

Driller: Millenium Engineers Group, Inc

Drill Rig: CME 45

Hammer: Cathead and rope, ER: 60%

Groundwater Levels:

Project Number: 220-065 Boring No.: P-1

D ril lin g

M et ho d

S am pl e

T yp e/ D ep th

Project Name:

D ep th (f ee t)

Laguna Atascosa National Wildlife Refuge

Atterberg Limits

E le va tio n (f ee t)

PAGE

AASHTO

& USCS

Classifi-cations

Field Notes and

Other Lab Tests

F in es C on te nt

Li qu id Li m it

P la st ic ity In de x

B O

R

IN

G L

O G

S P

T C

D O

T S

T Y

LE

-0

_L

A G

U N

A A

T A

S C

O S

A N

A T

IO

N

A L

W

IL

D

LI

F E

R E

F U

G E

.G P

J

Y E

H C

O

LO

R A

D O

T E

M P

LA

T

E .G

D T

Y

E H

C O

LO

R

A D

O L

IB

R

A R

Y .G

LB

/6 /2

M oi st ur e C on te nt

D ry

D en si ty

(p cf

Soil Samples P en et ra tio n R es is ta nc e

Blows per 6 in

Material Description Li th ol og y

G ra ve l C on te nt

S an d C on te nt

R ec ov er y

R Q

D

Rock

A-7-6 (64)

CH

A-7-6 (65)

CH

S/C=3.9%

100.0

98.0

32.7

42.4

87.99

4-5

2-2

0.0 - 0.1 ft. Chip Seal (1 inches).

0.1 - 0.6 ft. SUBBASE (poorly graded SAND with gravel) (6 inches), brownish yellow, moist, medium dense.

0.6 - 5.0 ft. Fat CLAY (CH), brown, moist to wet, soft.

Bottom of Hole at 5.0 ft.

0.0

0.0

0.0

2.0

Night Work:

Logged By: B. Lykins

Final By: J. McCall

Symbol Depth Date

Total Depth: 5.0 ft

Ground Elevation:

Coordinates: Lat: 26.18528 Long: 97.34508

Location: STWD Main Roadway

Weather Notes: 66°F/Overcast

Inclination from Horiz.: Vertical

Boring Began: 4/15/2020

Boring Completed:

Drilling Method(s): Solid-Stem Auger

Driller: Millenium Engineers Group, Inc

Drill Rig: CME 45

Hammer: Cathead and rope, ER: 60%

Groundwater Levels:

Project Number: 220-065 Boring No.: P-2

D ril lin g

M et ho d

S am pl e

T yp e/ D ep th

Project Name:

D ep th (f ee t)

Laguna Atascosa National Wildlife Refuge

Atterberg Limits

E le va tio n (f ee t)

PAGE

AASHTO

& USCS

Classifi-cations

Field Notes and

Other Lab Tests

F in es C on te nt

Li qu id Li m it

P la st ic ity In de x

B O

R

IN

G L

O G

S P

T C

D O

T S

T Y

LE

-0

_L

A G

U N

A A

T A

S C

O S

A N

A T

IO

N

A L

W

IL

D

LI

F E

R E

F U

G E

.G P

J

Y E

H C

O

LO

R A

D O

T E

M P

LA

T

E .G

D T

Y

E H

C O

LO

R

A D

O L

IB

R

A R

Y .G

LB

/6 /2

M oi st ur e C on te nt

D ry

D en si ty

(p cf

Soil Samples P en et ra tio n R es is ta nc e

Blows per 6 in

Material Description Li th ol og y

G ra ve l C on te nt

S an d C on te nt

R ec ov er y

R Q

D

A-7-6 (62)

CH98.0 79 5542.0 76.6

2-3-3

3-3

0.0 - 0.0 ft. Chip Seal (0.5 inches).

0.0 - 0.7 ft. SUBBASE (poorly graded SAND with gravel) (8 inches), brownish yellow, moist, medium dense.

0.7 - 5.0 ft. Fat CLAY (CH), brown to light brown, moist to wet, soft.

Bottom of Hole at 5.0 ft.

0.0 2.0

Night Work:

Logged By: B. Lykins

Final By: J. McCall

Symbol Depth Date

Total Depth: 5.0 ft

Ground Elevation:

Coordinates: Lat: 26.19248 Long: 97.34629

Location: STWD Main Roadway

Weather Notes: 66°F/Overcast

Inclination from Horiz.: Vertical

Boring Began: 4/15/2020

Boring Completed:

Drilling Method(s): Solid-Stem Auger

Driller: Millenium Engineers Group, Inc

Drill Rig: CME 45

Hammer: Cathead and rope, ER: 60%

Groundwater Levels:

Project Number: 220-065 Boring No.: P-3

D ril lin g

M et ho d

S am pl e

T yp e/ D ep th

Project Name:

D ep th (f ee t)

Laguna Atascosa National Wildlife Refuge

Atterberg Limits

E le va tio n (f ee t)

PAGE

AASHTO

& USCS

Classifi-cations

Field Notes and

Other Lab Tests

F in es C on te nt

Li qu id Li m it

P la st ic ity In de x

B O

R

IN

G L

O G

S P

T C

D O

T S

T Y

LE

-0

_L

A G

U N

A A

T A

S C

O S

A N

A T

IO

N

A L

W

IL

D

LI

F E

R E

F U

G E

.G P

J

Y E

H C

O

LO

R A

D O

T E

M P

LA

T

E .G

D T

Y

E H

C O

LO

R

A D

O L

IB

R

A R

Y .G

LB

/6 /2

M oi st ur e C on te nt

D ry

D en si ty

(p cf

Soil Samples P en et ra tio n R es is ta nc e

Blows per 6 in

Material Description Li th ol og y

G ra ve l C on te nt

S an d C on te nt

R ec ov er y

R Q

D

A-7-6 (47)

CH96.0 64 4428.9

2-4-4

3-4

0.0 - 0.0 ft. Chip Seal (0.5 inches).

0.0 - 0.7 ft. SUBBASE (poorly graded SAND with gravel) (8 inches), brownish yellow, moist, medium dense.

0.7 - 3.5 ft. Lean-to-Fat CLAY (CL-CH), gray-brown, moist, soft.

3.5 - 5.0 ft. Fat CLAY (CH), brown, moist to wet, soft.

Bottom of Hole at 5.0 ft.

0.0 4.0

Night Work:

Logged By: B. Lykins

Final By: J. McCall

Symbol Depth Date

Total Depth: 5.0 ft

Ground Elevation:

Coordinates: Lat: 26.19965 Long: 97.34748

Location: STWD Main Roadway

Weather Notes: 67°F/Overcast

Inclination from Horiz.: Vertical

Boring Began: 4/15/2020

Boring Completed:

Drilling Method(s): Solid-Stem Auger

Driller: Millenium Engineers Group, Inc

Drill Rig: CME 45

Hammer: Cathead and rope, ER: 60%

Groundwater Levels:

Project Number: 220-065 Boring No.: P-4

D ril lin g

M et ho d

S am pl e

T yp e/ D ep th

Project Name:

D ep th (f ee t)

Laguna Atascosa National Wildlife Refuge

Atterberg Limits

E le va tio n (f ee t)

PAGE

AASHTO

& USCS

Classifi-cations

Field Notes and

Other Lab Tests

F in es C on te nt

Li qu id Li m it

P la st ic ity In de x

B O

R

IN

G L

O G

S P

T C

D O

T S

T Y

LE

-0

_L

A G

U N

A A

T A

S C

O S

A N

A T

IO

N

A L

W

IL

D

LI

F E

R E

F U

G E

.G P

J

Y E

H C

O

LO

R A

D O

T E

M P

LA

T

E .G

D T

Y

E H

C O

LO

R

A D

O L

IB

R

A R

Y .G

LB

/6 /2

M oi st ur e C on te nt

D ry

D en si ty

(p cf

Soil Samples P en et ra tio n R es is ta nc e

Blows per 6 in

Material Description Li th ol og y

G ra ve l C on te nt

S an d C on te nt

R ec ov er y

R Q

D

A-7-6 (66) pH=7.7 S=0.215% Chl=0.2653% S/C=1.9% Re=122ohm·cm

97.0 82 5937.8 84.2

52-3

0.0 - 0.0 ft. Chip Seal (0.5 inches).

0.0 - 0.6 ft. SUBBASE (poorly graded SAND with gravel) (6 inches), brownish yellow, damp to moist, medium dense.

0.6…