Attachment 8 - B90145 GEOTech Report 03-31-20.pdf

GEOTECHNICAL

EXPLORATION REPORT

BUILDING 90145 ADDITION

HURLBURT FIELD

OKALOOSA COUNTY, FLORIDA

UES PROJECT NO. 1730.2000003.0000

UES REPORT NO. 1750983

FEBRUARY 28, 2020

Prepared For:

Bullock Tice Associates, Inc.

909 East Cervantes Street Pensacola, Florida 32501

Prepared By:

Universal Engineering Sciences 1985 Cope Lane

Pensacola, Florida 32526

(850) 944-5555

UNIVERSAL

ENGINEERING SCIENCES

Consultants in: Geotechnical Engineering • Environmental Sciences • Construction Materials Testing • Threshold Inspection Offices in: Orlando • Daytona Beach • Fort Myers • Gainesville • Jacksonville • Ocala • Palm Coast • Rockledge • Sarasota • Miami

St. Augustine • Pensacola • Panama City • Fort Pierce • Leesburg • Tampa • West Palm Beach • Atlanta, GA • Tifton

1985 Cope Lane • Pensacola, Florida 32526 • (850) 944-5555 • Fax (850) 944-5885 www.universalengineering.com

LOCATIONS:

Atlanta Daytona Beach Fort Myers Fort Pierce Gainesville Jacksonville Kissimmee Leesburg Miami Ocala Orlando (Headquarters) Palm Coast Panama City Pensacola Rockledge Sarasota Tampa West Palm Beach

February 28, 2020

Bullock Tice Associates, Inc.

909 East Cervantes Street Pensacola, Florida 32501

Attention: Mr. Robert C. Rice, RA

Senior Associate | Project Manager r.rice@bulltice.com

Reference: Geotechnical Exploration Report Building 90145 Addition Hurlburt Field, Okaloosa County, Florida UES Project Number 1730.2000003.0000

UES Report Number 1750983

Mr. Rice:

Universal Engineering Sciences, Inc. (UES) has completed a geotechnical exploration at the above referenced site on Hurlburt Field in Okaloosa County, Florida. The scope of our exploration was planned in conjunction with and authorized by you. This exploration was performed in accordance with generally accepted geotechnical engineering practices. No other warranty, express or implied, is made.

The following report presents the results of our field exploration, laboratory testing services, and a geotechnical engineering interpretation of the results with respect to the project characteristics provided to us. We have included geotechnical engineering recommendations for foundation design, site preparation, and construction related services.

We appreciate the opportunity to have worked with you on this project, and look forward to our continued association. Please contact us if you have any questions or if we may further assist you as your plans proceed.

Respectfully Submitted, UNIVERSAL ENGINEERING SCIENCES, INC.

Certificate of Authorization No. 549

Michael A. Johnson, P.E Guy H. Rabens, M.S., P.E.

Senior Geotechnical Engineer Vice President /Principal Engineer Florida P.E. No. 35974 Florida P.E. No. 60917

This item has been electronically signed and sealed by Guy H. Rabens, M.S., P.E. using a digital signature. Printed copies of this document are not considered signed and sealed, and the signature must be verified on any electronic copies.

TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 GENERAL

2.0 SCOPE OF SERVICEs

2.1 PROJECT DESCRIPTION

2.2 PURPOSES

2.3 GEOTECHNICAL EXPLORATION

2.3.1 Field Procedures

2.4 LABORATORY TESTING PROGRAM

2.4.1 Visual Classification

2.4.2 Laboratory Index Testing

3.0 FINDINGS

3.1 REGIONAL GEOLOGY

3.2 USDA NRCS SOIL SURVEY

3.3 SURFACE CONDITIONS

3.4 SUBSURFACE CONDITIONS

3.5 NOTABLE FINDING – BURIED HIGHLY ORGANIC SOILS

4.0 RECOMMENDATIONS

4.1 GEOTECHNICAL ASSESSMENT

4.2 GROUNDWATER CONSIDERATIONS

4.3 BUILDING FOUNDATIONS

4.3.1 General

4.3.2 Allowable Net Soil Bearing Pressure

4.3.3 Foundation Sizes

4.3.4 Bearing Depths

4.3.5 Bearing Material

4.3.6 Settlement Estimates

4.3.7 Foundation Evaluations

4.4 FLOOR SLABS

4.5 FLEXIBLE PAVEMENTS

4.5.1 Pavement Stabilized Subgrade

4.5.2 Base Course

4.5.3 Hot Mix Asphalt (HMA) Surface Course

4.5.4 Effects of Groundwater

4.5.5 Curbing

4.5.6 Construction Traffic

4.6 SITE PREPARATION

4.6.1 Temporary Groundwater Control

4.6.2 Nearby Structures and Vibrations

4.6.3 Existing Underground Utilities

4.6.4 Site Preparation and Grading

4.6.5 Fill Placement

4.6.6 Earth Fill Materials

4.6.7 Compaction Recommendations

4.6.8 Test Criteria to Evaluate Fill and Compaction

4.7 CONSTRUCTION RELATED SERVICES

4.8 EXCAVATION AND SAFETY

5.0 LIMITATIONS

LIST OF TABLES

TABLE 1: SUMMARY OF SOIL SURVEY INFORMATION

TABLE 2: GENERAL SOIL PROFILE

TABLE 3: STANDARD DUTY PAVEMENT SECTION

TABLE 4: HEAVY DUTY PAVEMENT SECTION

LIST OF APPENDICES

SITE LOCATION PLAN ................................................................................................................ A USDA NRCS SOIL SURVEY MAP ............................................................................................... A

BORING LOCATION PLAN .......................................................................................................... B BORING LOGS ............................................................................................................................. B KEY TO BORING LOGS ............................................................................................................... B FIELD PROCEDURES ................................................................................................................. B

LABORATORY PROCEDURES .................................................................................................. C

GEOPROFESSIONAL BUSINESS ASSOCIATION (GBA) DOCUMENTS ................................. D CONSTRAINTS AND RESTRICTIONS ....................................................................................... D

Building 90145 Addition UES Project No. 1730.2000003.0000 Hurlburt Field, Okaloosa County, Florida UES Docs Report No. 1750983

1.0 INTRODUCTION

1.1 GENERAL

In this report, we present the results of the geotechnical exploration of the site for the proposed project. We have divided this report into the following sections:

SCOPE OF SERVICES - Defines what we did FINDINGS - Describes what we encountered RECOMMENDATIONS - Describes what we encourage you to do LIMITATIONS - Describes the restrictions inherent in this report APPENDICES - Presents support materials referenced in this report

2.0 SCOPE OF SERVICES

2.1 PROJECT DESCRIPTION

Project information was provided to us via email correspondence from the client from July 19, 2019 to December 23, 2019. The subject project is located on Hurlburt Field in Okaloosa County, Florida. We were provided with the following documents and information for our use in performing the geotechnical exploration:

Request for Proposal Google Earth Aerial Survey Limits Google Earth Aerial B90145-4 Google Earth Aerial B90145-Survey 2 Boring Location Plan

We understand that the proposed project will consist of constructing a 3,600 SF 1-story, detached, pre-engineered metal building adjacent to Building 90145 – A Squad Ops Facility.

Site improvements will also include paved parking and access drives. No new stormwater management facilities will be required for this project.

The following information regarding loads and foundations for the addition was provided by the structural engineer, Mr. Josh Greenwell, P.E., S.E. with Joe DeReuil Associates, LLC:

Approximate PEMB column service reactions are -12 kip (uplift) and 15 kip (gravity); using a 24”X24” turndown slab edge, we get about 1,500 PSF (maximum) soil pressure.

End wall turndown is 30”wide x 24” thick with 3 klf service wall load.

Isolated canopy footings have service reactions of +/- 2 kips.

We have assumed that 1 foot or less of cut/fill will be required to achieve desired finished grades in the building addition area.

Our engineering recommendations are based upon the previously discussed supplied or assumed information. If any of this information is incorrect or changes, please inform Universal Engineering Sciences (UES) so that we may review our recommendations. Without such a review, the recommendations herein may not be valid. No other site or project facilities should be designed using the soil information contained herein. As such, UES will not be responsible for the performance of any other site improvement designed using the data in this report.

2.2 PURPOSES

The purposes of this exploration program were:

To explore the general subsurface conditions in the proposed building addition area;

To interpret and review the subsurface conditions with respect to the proposed construction;

To perform a series of laboratory tests on selected subsurface soil samples to assist with engineering soil classification, and to establish relevant soil engineering characteristics;

To provide geotechnical engineering recommendations for foundation design, site preparation, and construction related services; and

Prepare a report that documents the results of our exploration and analysis with geotechnical engineering recommendations.

This report presents an evaluation of site conditions based on traditional geotechnical procedures for site characterization. The recovered samples were not examined, either visually or analytically, for chemical composition or environmental hazards. Universal Engineering Sciences would be pleased to perform these services, if desired.

Our exploration was confined to the zone of soil likely to be stressed by the proposed construction. Our work did not address the potential for surface expression of deep geological conditions. This evaluation requires a more extensive range of field services than performed in this study. We will be pleased to provide a proposal for an exploration to evaluate the probable effect of the regional geology upon the proposed construction, if desired.

2.3 GEOTECHNICAL EXPLORATION

The field exploration program was initiated and completed on February 7, 2020. The approximate boring locations are shown on the attached Boring Location Plan in Appendix B.

The approximate boring locations were determined in the field by our personnel using the provided boring location plans, Google Earth aerial imagery, existing field reference points on and adjacent to the site, and a tape measure and/or measuring wheel. As such, the locations shown on the Boring Location Plan in Appendix B should be considered accurate only to the degree implied by the method of measurement used.

Upon completion of the field tests and sampling, recovered soil samples were placed in labeled plastic containers, sealed, and transported to our laboratory where they were classified by a member of our geotechnical staff. Various samples of the soils were then selected for specific laboratory testing. The recovered soil samples will be held in our laboratory for your inspection for 90 days following the issue date of this report, and then discarded unless we are notified and other arrangements are made.

2.3.1 Field Procedures

The field exploration for this project consisted of performing three (3) Standard Penetration Test (SPT) borings in the area of the proposed structure and one (1) SPT boring in an area of new asphalt. The borings were drilled to an approximate termination depth of 6 and 30 feet below existing grade (BEG).

2.4 LABORATORY TESTING PROGRAM

2.4.1 Visual Classification

The soil samples collected were visually classified in general accordance with the Unified Soil Classification System (ASTM D2487). A summary of the resulting soil descriptions is shown on the Boring Logs presented in Appendix B.

2.4.2 Laboratory Index Testing

Laboratory soil tests were performed on selected soil samples obtained from the borings to aid in the classification of the soils, and to help in the evaluation of pertinent engineering characteristics of the soils. The classifications and laboratory testing completed for this project consisted of performing the following procedures/tests in general accordance with the methods listed.

Soil Classification per the Unified Soil Classification System (USCS) – ASTM D2487

Natural Moisture Content Tests – ASTM D2216

Percent -200 Soil Fines Content Tests – ASTM D1140

Organic Content Determination Tests – ASTM D2974

The results of the tests are summarized on the appropriate boring logs presented in Appendix B.

3.0 FINDINGS

3.1 REGIONAL GEOLOGY

Okaloosa County is divided into two physiographic provinces (Vernon 1964). The northern portion is the Western Highlands subdivision of the Northern Highlands, and the southern portion is the Gulf Coastal Lowlands, a subdivision of the Coastal Lowlands The Western Highlands is characterized by gently sloping plateaus at the relatively higher elevations separated by lower, large stream valleys. Dendritic streams drain the margins of the Highlands. The northern two-thirds of Okaloosa County are in this subdivision. At the southern edge of the Western Highlands, and separating it from the Gulf Coastal Lowlands, is a south-facing scarp called the Cody Scarp. This scarp represents the most persistent topographic break in Florida.

The Gulf Coastal Lowlands is that portion of the Coastal Lowlands physiographic province that is adjacent to the Gulf of Mexico. This area is much lower in average elevation than the Highlands to the north. Marine terraces, formed when the sea level was higher than at present, are characteristic, and most features are parallel to the coast. Landforms typical of this subdivision include barrier islands, such as Santa Rosa Island; lagoons such as Santa Rosa Sound; estuaries, such as Choctawhatchee Bay; coastal ridges; sand dune ridges; relict spits and bars; and valleys (US Dept. of Agriculture 1995).

3.2 USDA NRCS SOIL SURVEY

Based on the Web Soil Survey for Okaloosa County, Florida, as prepared by the USDA NRCS, the predominant soil type at the site is identified as 27 – Urban Land. A summary of the characteristics of this soil series was obtained from the Soil Survey and is included in Table 1. Please note the soils presented in the following table are the predevelopment soils and may have been altered during the past development of the site.

Table 1 – Summary of Soil Survey Information

Soil Name Constituents Internal

Drainage Hydrologic Soil Group

Soil Permeability Seasonal High Water Table

(ft)

Corrosion Potential

Depth

(in)

Perm

(in/hr) Steel Concrete

27 – Urban Land

Notes: --- denotes no data reported for Urban Land by USDA NRCS

3.3 SURFACE CONDITIONS

UES personnel visited the project site during the performance of the field portion of this geotechnical study. At the time of the UES field exploration program, the groundcover at the boring locations consisted of topsoil and/or asphalt pavement. In the area of the proposed addition, there was a covered pavilion/picnic table area. Throughout the area of proposed construction, there were a number of metal storage containers present. Surface water was not observed on the property at the time of our field exploration. Site-specific topographical information was not provided.

3.4 SUBSURFACE CONDITIONS

The general subsurface conditions encountered during the subsurface exploration are described in the following Table 2. For more detailed soil descriptions and stratifications at the boring locations, the Boring Logs presented in Appendix B should be reviewed. Also, see the Key to Boring Logs in Appendix B for further explanation of the symbols and placement of data on the Boring Logs.

The Boring Logs represent our interpretation of the subsurface conditions based on a review of the field logs, an engineering examination of the samples, and a limited number of laboratory tests. The horizontal stratification lines designating the interface between various strata represent approximate boundaries. Transition between different strata in the field may be gradual in both the horizontal and vertical directions. Groundwater, or lack thereof, encountered in the borings, and noted on the Boring Logs, represents conditions only at the time of the exploration.

Table 2 – General Soil Profile

Stratum No.

Depths (ft) Soil Descriptions

Range of SPT “N” Blow Counts From To

1 0 0.3 to 0.9 4 to 6 inches of sandy topsoil with roots and organics (B-1 and B-2) or 2.1 to 2.5 inches of asphalt pavement over 6.4 to 8.5 inches of limerock base (B-3 and B-4)

N/A

2 0.3 to 0.9 10 Loose to medium dense sand [SP], sand with silt [SP-SM] with varying amounts of shell, limerock, and small gravel fragments

5 to 26

3 10 12 Very loose Organic Sand [SP/PT] 2 to 3

4 12 30* Very loose to dense sand [SP], sand with silt [SP-SM] and silty sand [SM]

3 to 49

* Termination depth of the borings

[ ] Brackets indicate USCS classification (ASTM D 2487)

A stabilized groundwater table was encountered at approximate depths of 4.5 to 5 feet BEG at the boring locations.

3.5 NOTABLE FINDING – BURIED HIGHLY ORGANIC SOILS

A notable finding during the exploration program was the presence of a buried layer of highly organic soils underlying the site. The organic soils were found between the depths of about 10 to 12 feet below current site grades. An undisturbed/Shelby tube sample was attempted from the depths of 10 to 12 feet at boring location B-1, but no sample was recovered. Representative samples from the split-spoon sampler were selected for laboratory organic content determination. The organic contents of the tested samples ranged from about 26 to 31 percent with corresponding moisture contents of 269 and 202 percent, respectively. The organic soil layer had SPT “N” values of 2 to 3 blows per foot indicating a relative density of very loose. .

In general, soils with organic contents greater than about 5 percent are not considered suitable to remain in-place without special site and/or structure design considerations due the risk of intolerable settlements over the useful life of the project. Further discussion about the buried organic soils is presented in Section 4.3 Building Foundations.

4.0 RECOMMENDATIONS

4.1 GEOTECHNICAL ASSESSMENT

In this section of the report, we present recommendations for foundation design, site preparation, and construction related services. The following geotechnical design recommendations have been developed based on the previously described project characteristics, and the subsurface conditions encountered. If there are any changes in these project criteria, a review should be made by UES to determine if modifications to the recommendations are warranted.

Once final design plans and specifications are available, a general review by UES is recommended as a means to check that the evaluations made in the preparation of this report are correct, and that earthwork and foundation recommendations are properly interpreted and implemented.

4.2 GROUNDWATER CONSIDERATIONS

The groundwater table will fluctuate seasonally depending upon local rainfall. The typical wet season groundwater level is defined as the highest groundwater level sustained for a period of 2 to 4 weeks during the "wet" season of the year, for existing site conditions, in a year with average normal rainfall amounts. Based on historical data, the rainy season in Northwest Florida is typically between June and September of any given year.

At the time of our field exploration, a stabilized groundwater table was found at approximate depths of 4 to 5.5 feet BEG at the boring locations. Based upon our review of USGS data, the Okaloosa County Soils Survey, regional hydrogeology, our exploration boring data, and experience, our best estimate for the stabilized seasonal high groundwater table is approximately 2.5 to 3 feet BEG (approximately 2 feet above the groundwater levels encountered in the borings) at the boring locations.

Please note that groundwater levels could temporarily exceed these estimated levels during any given year in the future. Should impediments to surface water drainage exist on the site, or should rainfall intensity, duration, and/or quantities exceed the normally anticipated conditions, then the groundwater levels may exceed our previously noted estimate. We recommend positive drainage be established and maintained on the site during construction. We further recommend permanent measures be constructed to maintain positive drainage throughout the life of the project. All site improvement designs should incorporate the seasonal high groundwater levels as appropriate.

4.3 BUILDING FOUNDATIONS

4.3.1 General

The following information regarding loads and foundations for the addition was provided by the structural engineer, Mr. Josh Greenwell, P.E., S.E. with Joe DeReuil Associates, LLC:

Approximate PEMB column service reactions are -12 kip (uplift) and 15 kip (gravity); using a 24”X24” turndown slab edge, we get about 1,500 PSF (maximum) soil pressure.

End wall turndown is 30” wide x 24” thick with 3 klf service wall load.

Isolated canopy footings have service reactions of +/- 2 kips.

In addition, it is our understanding that the proposed structure will not be structurally attached with the existing building.

As discussed previously, buried highly organic soils were found on site at all of the borings between the depths of about 10 to 12 feet below current site grades. These soils have likely been in-place for a long period of time. It is unknown if similar organic soils are also present beneath the existing 90145 building, but may be present due to the close proximity. We understand the existing 90145 building is supported on shallow foundation with slab-on-grade construction, and we were not made aware of any on-going settlement issues with the existing building. However, we were unable to ascertain whether or not a surcharge program was performed to pre-load any buried highly organic soils present beneath the existing 90145 building prior to vertical construction. The buried organic soils are considered to be at the threshold depth of the anticipated stress zone of influence, and are not expected to experience a significant increase in stress based on the provided structural loading and foundation design information. However, the buried organic soils found on site do represent a potential risk for long-term secondary consolidation due to creep of the organic soils.

Based upon our understanding of the intended use of the building (i.e. maintenance operations) and conversations with the design team members, we have assumed some risk is acceptable for this project, and the following recommendations are for conventional shallow foundation and slab-on-grade floor systems. If the risk of settlement is not acceptable, a deep foundation design for support of the foundations and slab or a stiffened structural slab should be considered for this project.

4.3.2 Allowable Net Soil Bearing Pressure

The allowable net soil bearing pressure of 1,500 pounds per square foot used for design of the continuous wall/strip foundations for the proposed building addition is acceptable for the project site based on the boring data obtained from our exploration. Depending on loads, this bearing pressure could also be used for the design of isolated column foundations, if any. The presented bearing pressure is suitable for code dead and live loads plus any short duration loadings, and assumes that the surficial soils to a depth of 1 foot below the base of foundations are densified to at least 95 percent of the Modified Proctor maximum dry density (ASTM D 1557) prior to foundation construction.

The net bearing pressure is defined as the soil bearing pressure at the base of the foundation in excess of the natural overburden pressure. The foundations should be designed based upon the maximum load that could be imposed by all loading conditions.

4.3.3 Foundation Sizes

The minimum widths recommended for isolated column foundations (if any) and continuous wall foundations are 24 inches and 18 inches, respectively. Even though the maximum allowable net soil bearing pressure may not be achieved, these width recommendations should control the minimum size of the foundations to prevent “shear punch” deformations.

4.3.4 Bearing Depths

The exterior foundations should bear at a depth of at least 24 inches below the finished exterior grades, and the interior foundations should bear at a depth of at least 18 inches below the finish floor elevation to provide suitable confinement for the bearing level soils. Stormwater should be diverted away from the building exteriors to reduce the possibility of erosion beneath the exterior foundations.

4.3.5 Bearing Material

The foundations may bear in either the compacted suitable native soils or compacted structural fill. The foundation excavation bottoms should be level or suitably benched, and free of any loose soils that have been disturbed by seepage or the construction process. Furthermore, the foundation excavation bottoms should be free of standing water. The bearing level soils, after compaction, should exhibit densities equivalent to at least 95 percent of the Modified Proctor maximum dry density (ASTM D 1557) to a depth of at least 1 foot below the foundation bearing level.

4.3.6 Settlement Estimates

Post-construction settlement of the addition will be influenced by several interrelated factors, such as the following: subsurface stratification and strength/compressibility characteristics;

foundation sizes, bearing levels, applied loads, and resulting bearing pressures beneath the foundations; and site preparation and earthwork construction techniques, as well as building construction operations used by the contractor. Our settlement estimates for the addition are based on the provided structural loading and foundation design information, and compliance with the site preparation/earthwork recommendations in Section 4.5 of this report. Any deviation from this information or recommendations could result in an increase in the estimated post-construction settlement of the structure.

Based on the subsurface conditions found in the borings and the recommended earthwork operations, we expect the majority of settlement to occur rapidly during construction. Using the recommended bearing pressure, the provided structural loading and foundation design conditions, and the field data (which we have correlated to geotechnical strength and compressibility characteristics of the subsurface soils), we estimate that total elastic settlement for the addition could be approximately ½ inch or less.

Differential settlements result from differences in applied bearing pressures and variations in the compressibility characteristics of the subsurface soils. Because of the general uniformity of the subsurface conditions, and pending compliance with the recommended site preparation and earthwork construction techniques outlined in Section 4.5, we anticipate that differential elastic settlement of the addition should be within tolerable magnitudes on the order of approximately ¼ inch or less over a 40 feet long portion of a continuous foundation, or between similarly spaced foundations.

The estimated differential settlements are considered structurally tolerable; however, aesthetic cracking in masonry and brick walls may occur. If such cracking is not desirable, the structural engineer should design the wall/foundation system with sufficient stiffness to minimize such cracking.

As discussed previously, the buried organic soils found on site do represent a potential risk for long-term secondary consolidation due to creep of the organic soils. Although no samples were secured for laboratory consolidation testing, it is estimated that the structure could experience up to 1 inch of additional settlement over the useful life of the structure. If the risk of this additional settlement is not acceptable, a deep foundation design for support of the foundation and slab and/or stiffened structural slab should be considered for this project.

4.3.7 Foundation Evaluations

All foundation excavations should be evaluated by a geotechnical engineer prior to placement of steel reinforcement and concrete. It should be anticipated that undercutting of select areas may be required because of variations in the soil matrix, fill quality, and/or contractor means and methods. If undercut, the unsuitable material may be replaced with No. 57 crushed stone, over-poured with lean concrete, or placed back with clean structural fill.

4.4 FLOOR SLABS

Conventional floor slabs may be supported upon the compacted fill and should be structurally isolated from other foundation elements or adequately reinforced to prevent distress due to differential movements. For the slab design, we recommend using a subgrade modulus (k) of 125 pounds per cubic inches, which can be achieved by compacting the subgrade soils as recommended in this report.

UES recommends the use of a vapor barrier which covers the bearing soils beneath ground supported floor slabs in accordance with Florida Building Code (FBC) requirements. The FBC recommends a minimum 6-mil thick polyvinyl chloride or polyethylene sheet membrane for this purpose. The performance of the vapor barrier is ultimately dependent upon its proper installation, including lapping and sealing plus repair of tears and punctures prior to placement of concrete.

4.5 FLEXIBLE PAVEMENTS

We anticipate flexible pavements will be used for the access roads and parking areas associated with this project. Project specific traffic data has not been provided for this project.

Therefore, we have provided recommendations for standard and heavy-duty flexible pavement sections.

Standard duty pavement sections should be used for traffic volumes with estimated Equivalent Single-Axel Loads (ESALs) less than 0.3 million. We recommend using the following minimum design section presented in Table 3 for standard duty pavement areas.

Table 3 – Summary of Standard Duty Pavement Section

Pavement Layer Thickness

(in.)

Minimum Requirements

Asphalt Wearing & Structural Course

(SP-9.5)

1.5

Minimum field density of 93.5% of the laboratory maximum theoretical density (Gmm)

Limerock or GAB Base Course

98% of Modified Proctor Maximum Dry Density and Limerock Bearing Ratio (LBR) of at least 100

Stabilized Subgrade 12 98% of Modified Proctor Maximum Dry Density and stabilized to a California Bearing Ratio (CBR) of at least 32

Notes:

GAB = Graded Aggregate Base Traffic Level A for HMA selection

Heavy-duty pavement sections should be used for traffic volumes with estimated Equivalent Single-Axel Loads (ESALs) between 0.3 to less than 3.0 million. We recommend using the following minimum design section presented in Table 4 for heavy-duty pavement areas

Table 4 – Summary of Heavy Duty Pavement Section

Pavement Layer Thickness

(in.)

Minimum Requirements

Asphalt Wearing & Structural Course

(SP-12.5 or SP-9.5)

Minimum field density of 93.5% of the laboratory maximum theoretical density (Gmm)

Limerock or GAB Base Course

98% of Modified Proctor Maximum Dry Density and Limerock Bearing Ratio (LBR) of at least 100

Stabilized Subgrade 12 98% of Modified Proctor Maximum Dry Density and stabilized to a California Bearing Ratio (CBR) of at least 32

Notes:

GAB = Graded Aggregate Base Traffic Level B for HMA selection

4.5.1 Pavement Stabilized Subgrade

The subgrade is the top surface of a roadbed upon which the pavement structure and shoulders are constructed. The primary function of the subgrade is to provide a stable and firm platform for construction of the pavement without undue deflection that would affect the pavement’s performance. In addition, the subgrade enhances the overall strength of the pavement section.

Beneath the base course materials, we recommend a subgrade having a minimum California Bearing Ratio (CBR) (ASTM D1883) of 32 percent and a minimum compacted thickness of 12 inches. The subgrade material should be compacted to at least 98 percent of the Modified Proctor maximum dry density (ASTM D 1557) value for the upper 12 inches of the subgrade below the pavement base. As evident from the CBR testing performed for this exploration, it is anticipated that the clean sands predominant on the project site will not meet the minimum stabilized CBR criterion previously discussed. It is anticipated that improvement (by mixing with silty and/or clayey sands or aggregate materials) or replacement of these sands (with suitable materials capable of meeting the CBR requirement) will be required.

Some owners/contractors opt to forgo using a stabilized subgrade and, instead, prefer to use additional pavement base material for time savings, although typically at a significantly higher cost. For this project, we would recommend substituting the 12 inches of stabilized subgrade (CBR 32) with 6 inches of base material (LBR 100). The recommended base course thickness presented in the previous tables would still apply. For instance, for a light duty pavement section: 1.5 inches of asphalt, 6 inches of base (LBR 100), and an additional 6 inches of base (LBR 100) would be used in lieu of 12 inches of a stabilized subgrade (CBR 32) material. The additional base course material used in lieu of the stabilized subgrade should also meet the recommendations presented in the following Section 4.5.2.

4.5.2 Base Course

The base course is a layer or layers of select or specified material of designed thickness placed on a subbase or stabilized subgrade to provide uniform and stable support for binder and surface courses. The base course typically provides a significant portion of the structural capacity in a flexible pavement system.

For this project, we recommend the base course consist of locally available limerock complying with the requirements of the FDOT SSRBC, Section 200 and Section 911. Alternatively, we recommend the use of graded aggregate base (GAB) in accordance with Section 204 of the latest edition of the FDOT SSRBC. A LBR of 100 should be used for limerock and graded aggregate base (GAB) courses. Regardless of the material selected, the base course should be compacted to 98 percent of the Modified Proctor maximum dry density value.

4.5.3 Hot Mix Asphalt (HMA) Surface Course

The surface course should consist of FDOT SuperPave (SP fine) asphaltic concrete having a minimum field density of 93.5 percent of the laboratory maximum density (Gmm). Specific requirements for the SuperPave asphaltic concrete structural course are outlined in the current edition of the FDOT SSRBC, Section 334.

The allowable layer thickness for Type SP Asphalt Concrete mixtures for Type SP-9.5 is 1 to 1-½ inches and for Type SP-12.5 is 1-½ to 2-½ inches. Type SP-9.5 is limited to the top two structural layers and is limited to a maximum of two layers.

Hot mix asphalt (HMA) mixes should be FDOT approved, assigned an FDOT Mix Design Number, and current HMA mixes should have a “fine” gradation classification. We recommend the percent of Reclaimed Asphalt Pavement (RAP) be limited to less than 30 percent. The Asphalt Binder Grade for HMA with less than 20 percent RAP is PG 67-22. The Asphalt Binder Grade for HMA with 20 to 29 percent RAP is PG 64-22.

After placement and field compaction, the asphaltic concrete should be cored to evaluate material thickness and to perform laboratory densities. Cores should be obtained at frequencies of at least one core per 10,000 square feet of placed pavement, or a minimum of two cores per day’s production, whichever is greater.

4.5.4 Effects of Groundwater

One of the most critical factors influencing pavement performance in Northwest Florida is the relationship between the pavement subgrade and the groundwater level. Roadways and parking areas have been damaged because of deterioration of the base conditions and/or the base/surface course bond. We recommend that the seasonal high groundwater table and the bottom of the flexible pavement base course be separated by at least 18 inches.

If this separation cannot be established, the site subgrades should be sloped to drainage points (i.e. perimeter swales and collection areas) to prevent stormwater from collecting under the pavement areas. Additionally, underdrains could be incorporated into the design to capture groundwater and route it away from pavement base and subgrade materials. Based upon the results for the test borings performed on the site, we anticipate that obtaining this separation will not be an issue for this site.

4.5.5 Curbing

Typical curbing is extruded and placed atop the pavement surface. This type of curbing does not act as a horizontal cutoff for lateral migration of storm and irrigation water into the base material. Because of this, it is common for base and subgrade materials adjacent to these areas to become saturated, promoting subsequent localized pavement deterioration. Consequently, we recommend that all pavements abutting irrigated landscape areas be equipped with an underdrain system that penetrates a minimum depth equal to the bottom of stabilized subgrade to intercept trapped shallow water and discharge it into a closed system or other acceptable discharge point.

Alternatively, curbing around any landscaped sections adjacent to the parking lots and driveways could be constructed with full-depth curb sections to reduce horizontal water migration. However, underdrains may still be required dependent upon the soil type and spatial relationships. UES should review final grading plans to evaluate the need and placement of pavement and landscape underdrains.

4.5.6 Construction Traffic

Incomplete pavement sections will not perform satisfactorily under construction traffic loadings.

We recommend that construction traffic (e.g., construction equipment, concrete trucks, sod trucks, dump trucks, etc.) be rerouted away from these pavements during construction of the development or, alternatively, that the pavement section be only partially completed until the need for most of the construction traffic has gone away (i.e., allow construction traffic to drive over the compacted base course, and then repair the base course locally as needed and install the pavement section after the need for the majority of the construction traffic has gone away).

4.6 SITE PREPARATION

We recommend only normal, good practice site preparation procedures. These procedures include: stripping the proposed construction area of topsoil, vegetation, and existing structures (sidewalks, pavilion, etc.); proofrolling and compacting the exposed subgrade; verifying subgrade compaction; and placing engineered fill to the desired grades. An expanded and more detailed synopsis of this work is provided in the following sections.

4.6.1 Temporary Groundwater Control

As previously discussed, groundwater was present at approximate depths of 4.5 to 5 feet BEG in the proposed construction area, on the date the borings were drilled. During periods of seasonal high groundwater conditions, groundwater levels on the order of 2.5 to 3 feet BEG could be prevalent in the proposed construction area. Therefore, it is anticipated that temporary groundwater control could be required during earthwork and/or construction operations.

To minimize problems with elevated groundwater conditions, it would be prudent to schedule, as much as is practical, all site work, grading, and construction operations during extended periods of dry weather. If such operations are performed during extended periods of wet weather, such as may be encountered during the late summer and early fall months of hurricane season, then possible problems with elevated groundwater conditions could occur.

If groundwater is encountered, we recommend that the groundwater table be lowered and maintained at a depth of at least 2 feet below bearing levels and excavation bottoms during construction. Dewatering may consist of ditching, well points, or other means. However, groundwater control means and methods are the sole responsibility of the contractor.

Furthermore, we recommend that the Contractor determine the actual groundwater levels at the time of construction to determine the groundwater impact on the construction procedures. If groundwater is encountered during trenching or foundation installation, the Geotechnical Engineer of Record should be notified so that they can determine whether there is a need for underslab drainage, perimeter drains, or other recommendations for dewatering.

4.6.2 Nearby Structures and Vibrations

Care should be exercised to avoid damaging any nearby structures while the site preparation, earthwork, and building construction operations are underway. Prior to commencing site work operations in areas of this site that will be constructed near adjacent structures and/or developments, we recommend that occupants of adjacent structures should be notified, and the existing conditions of the structures be documented with photographs and survey. Compaction or construction operations should cease if deemed detrimental to adjacent structures.

Pre-construction building surveys of all off-site adjacent structures are recommended, but, absent these surveys, we recommend that the vibratory function of the compaction equipment be turned off when operating within 50 feet of any adjacent structures. UES can provide vibration monitoring services to help document and evaluate the effects of the surface compaction operations on existing structures.

4.6.3 Existing Underground Utilities

The location of any existing underground utility lines within the proposed construction areas should be established prior to initiating construction. Provisions should then be made to relocate or abandon interfering utilities. It should be noted that if underground pipes are not properly removed or plugged, they might serve as conduits for subsurface erosion, which may subsequently lead to excessive settlement of overlying pavements and structures.

4.6.4 Site Preparation and Grading

Prior to placing fill, existing structures, pavement materials (including base), and vegetation, should be removed. Care should be taken to remove all appurtenances associated with the removal of existing structures (e.g., foundations, underground utilities, septic tanks, etc.). All excavations required to remove any underground appurtenances should be extended down to undisturbed soils, and the excavations backfilled to finished elevations in accordance with the recommendations presented in subsequent sections of this report.

Complete stripping of any topsoil should be performed in the proposed addition area, and should extend a minimum of 5 feet beyond the perimeter of the proposed foundations, where possible. Materials removed in conjunction with the initial stripping operations should be removed from the site. In the case of topsoil, the topsoil may be stockpiled for later use and placement in landscaped areas, if required. Based on the boring data obtained, approximate depths of surficial topsoil will range from about 4 to 6 inches.

Following completion of the initial stripping operations, and after rough grade has been established in areas at or below finished subgrade elevations, a visit should be made to the site by the Geotechnical Engineer of Record or his representative. The Geotechnical Engineer will observe proofrolling of the exposed soil subgrades. The purposes of the proofrolling will be to densify loose surficial soils, and identify pockets of unsuitable material which may require densification in-place or undercutting and replacement.

The proofrolling should be performed using a loaded tandem axle dump truck, or similar rubber-tired equipment, weighing between 15 and 20 tons. The vehicle should make at least four passes over each location, with the last two passes perpendicular to the first two. Areas that wave, rut, or deflect significantly and continue to do so after several passes of the proofrolling equipment should be undercut to firmer soils. Undercut areas should be backfilled in thin lifts with approved, compacted fill materials. For any required undercutting operations, undercut volumes should be determined by field measurement. Methods such as counting trucks should not be used for determination of undercut volume, as they are less accurate.

Following completion of any proofrolling operations, it is recommended that the proofrolled subgrades be moisture conditioned and compacted to at least 95 percent of the materials’ modified Proctor (ASTM D1557) maximum dry densities. This proofrolling and compaction process will help provide a stable base for the compaction of new structural fill.

Based on our understanding of the proposed construction, it is anticipated that there will not be extensive areas where excavation operations, beyond the initial site stripping operations, will be required to achieve final site grades. However, in areas where excavation operations are required to achieve final site grades, it is recommended that the final exposed subgrade elevations be checked and proofrolled in a manner similar to the operations discussed in the previous paragraphs.

It is recommended that all exposed subgrades, following initial stripping operations, be checked and observed by the Geotechnical Engineer of Record or his representative. In addition, it is recommended that all proofrolling operations be observed by the Geotechnical Engineer.

During general construction operations, loose sandy soils will likely be encountered at the stripped subgrade level. As a result, unstable subgrade conditions may be anticipated during general construction operations. The use of light construction equipment would aid in reducing subgrade disturbance. The use of remotely operated equipment, such as a backhoe, would be beneficial to perform cuts and reduce subgrade disturbance. Where unstable subgrade conditions develop, stabilization measures will need to be employed.

Subgrade improvement should include scarification, moisture conditioning (e.g., aerate or wet), and compaction of the exposed subgrade soils. The success of this procedure will depend primarily upon favorable weather conditions. Even with adequate time and favorable weather conditions, stable subgrades may not be achieved if the thickness of the unstable material is greater than about 1 to 1.5 feet. A UES representative should observe subgrade preparation, and could assist in developing appropriate stabilization procedures based on conditions encountered during construction.

Upon completion of grading, care should be taken to maintain the subgrade moisture contents prior to subsequent construction. Construction traffic over the completed subgrade(s) should be avoided to the extent practical. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. If the subgrade(s) should become frozen, desiccated, saturated, or disturbed, the affected materials should be removed or these materials should be scarified, moisture conditioned, and recompacted prior to any subsequent construction.

4.6.5 Fill Placement

Once the site has been stripped and prepared, place fill material as required to meet finished grades. The recommended criteria for soil fill characteristics (both on-site and imported materials) and compaction procedures are listed in a subsequent section. The project design documents should include the following recommendations to address proper placement and compaction of project fill materials. Earthwork operations should not begin until representative fill and/or native soil samples are collected and tested (allow 3 to 4 days for sampling and testing) to determine maximum dry density and optimum moisture values.

4.6.6 Earth Fill Materials

Engineered fill should meet the following material properties.

Imported fill and on-site material satisfactory for structural fill should include clean soil material with USCS classifications of SP, SP-SM, and/or SP-SC. The fill material should have a modified Proctor (ASTM D1557) maximum dry density of at least 100 pcf, and contain less than 10 percent passing the No. 200 sieve.

Organic content or other foreign matter (debris) should be no greater than 3 percent by weight, and no large roots (greater than ¼ inch in diameter) should be allowed.

Material utilized as fill should not contain rocks greater than 3 inches in diameter or greater than 30 percent retained on the ¾-inch sieve.

4.6.7 Compaction Recommendations

The following recommendations are presented for fill placement and compaction. The recommendations are also applicable for the compaction of existing soil materials on the project site.

Maximum loose lift thickness – 10 inches, mass fill. Loose lifts of 4 to 6 inches in trenches and other confined spaces where hand operated equipment is used.

Compaction requirements – 95 percent of the maximum dry density as determined by the modified Proctor (ASTM D 1557) compaction test.

Soil moisture content at time of compaction – within ±2 percent of the optimum moisture content.

4.6.8 Test Criteria to Evaluate Fill and Compaction

The following minimum criteria for the evaluation of fill materials, and the compaction of the fill materials are recommended. The recommendations are also applicable for the evaluation and compaction of existing soil materials on the project site.

One modified Proctor compaction test and one No. 200 sieve analysis test for each soil type compacted and/or used as project fill.

Building area – One density test for every 2,000 square feet for each lift or two tests per lift, whichever is greater.

Foundation areas – Test all foundation bearing subgrades for compaction to a depth of 1 foot below bearing subgrade elevation prior to the placement of reinforcing steel and concrete. We recommend testing every column foundation, and one test per every 50 linear feet of wall foundation. Additionally, we recommend checking the bottom of all the column foundations and continuous wall foundations at a frequency of every 50 lineal feet with Dynamic Cone Penetrometer (DCP) or Static Cone Penetrometer to assess the suitability of the bearing level soils. Recompaction of the foundation excavation bearing level soils, if loosened by the excavation process, can typically be achieved by making several passes with a walk-behind vibratory sled or jumping jack compactor. If recompaction is not possible or unsuccessful, then loosened soils can be undercut to more firm underlying soils, and the undercut excavations backfilled with compacted suitable structural fill, flowable fill, lean concrete, or compacted No. 57 stone.

Trench fill areas – One density test every 75 linear feet per lift or two tests per lift, whichever is greater.

4.7 CONSTRUCTION…