Attachment 15 - Geotechnical Report.pdf

REPORT OF GEOTECHNICAL

CONSULTING SERVICES

Malcom Randall VA Hospital – Administration Building 1601 SW Archer Road

Gainesville, Alachua County, Florida

UES Project No. 0230.1800060.0000 UES Report No. 1582115

Prepared for:

Alliance Design & Construction, Inc.

P.O. Box 1296

Winter Park, FL 32790

(407) 907-0367

Prepared by:

Universal Engineering Sciences, Inc.

4475 SW 35th Terrace

Gainesville, Florida 32608

(352) 372-3392

July 3, 2018

Consultants in: Geotechnical Engineering • Environmental Sciences • Construction Materials Testing Threshold Inspection • Private Provider Inspection Offices in: Daytona Beach • Ft. Myers • Gainesville • Jacksonville • Miami • Ocala • Orlando • Palm Coast •

Panama City • Pensacola • Rockledge • Sarasota • Tampa • West Palm Beach

UNIVERSAL

ENGINEERING SCIENCES

4475 S.W. 35th Terrace • Gainesville, FL 32608-2526 • (352) 372-3392 • Fax (352) 336-7914

July 3, 2018

Alliance Design & Construction, Inc.

P.O. Box 1296 Winter Park, FL 32790

Attention: Mr. Douglas Sangster, AIA, CGC President

Reference: Report of Geotechnical Consulting Services

Malcom Randall VA Hospital – Administration Building 1601 SW Archer Road Gainesville, Alachua County, Florida Section 7, Township 10 S, Range 20 E

UES Project No: 0230.1800060.0000 UES Report No: 1582115

Dear Mr. Sangster:

Universal Engineering Sciences, Inc. (UES) has completed the geotechnical exploration program for the subject project in Gainesville, Florida in accordance with the authorized scope of services as summarized in UES Proposal No. 1456762v2, dated May 25, 2018. This Report presents the results of our field subsurface exploration and recommendations for geotechnical site preparation, and foundation design and construction.

We appreciate the opportunity to have assisted you on this project and look forward to a continued association. Please do not hesitate to contact our office if you should have any questions, or to assist your office with the remaining phases of project design and construction.

Respectfully submitted, UNIVERSAL ENGINEERING SCIENCES, INC.

Certificate of Authorization 549

Timothy Kwiatkowski, E.I. Eduardo Suarez, P.E.

Staff Geotechnical Engineer Senior Geotechnical Engineer Florida P.E. No. 60272 Date:

Consultants in: Geotechnical Engineering • Environmental Engineering Construction Materials Testing • Threshold Inspection • Private Provider Inspection

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

TABLE OF CONTENTS

EXECUTIVE SUMMARY

Project Location and Description Soil and Groundwater Conditions Groundwater Considerations

1.0 INTRODUCTION

1.1 GENERAL

2.0 SCOPE OF SERVICES

2.1 PROJECT DESCRIPTION

2.2. STRUCTURAL CONDITIONS

2.2 PURPOSE

2.3 FIELD EXPLORATION

2.3.1 Standard Penetration Test (SPT) Borings

2.3.2 Radon Testing and Corrosion Bulk Sampling

2.4 LABORATORY TESTING

2.4.1 Visual Classification

2.4.2 Index Testing

2.4.3 Corrosion Testing

3.0 FINDINGS

3.1 REGIONAL GEOLOGY

3.2 KARST TOPOGRAPHY

3.3 GENERAL AREA SOIL INFORMATION

3.4 SURFACE CONDITIONS

3.5 SUBSURFACE CONDITIONS

3.6 GROUNDWATER DEPTH

3.7 LABORATORY TESTING

3.7.1 Percent Passing No. 200 Sieve

3.7.2 Atterberg Limits

3.7.3 Moisture Content

3.7.4 Organic Content

4.0 RECOMMENDATIONS

4.1 FOUNDATION SYSTEM EVALUATION

4.2 GROUNDWATER CONSIDERATIONS

4.3 SHALLOW BUILDING FOUNDATION

4.3.1 Mat Foundation System

4.3.2 Bearing Material

4.3.3 Settlement Estimates

4.3.4 Shallow Foundation Site preparation

4.4 DEEP FOUNDATION SYSTEM

4.4.1 Augered Cast-in-place Pile (ACIP) Recommendations

4.4.1.1 ACIP Axial Load Analysis

4.4.1.2 ACIP Lateral Load Analysis

4.4.1.3 ACIP Pile Construction Techniques

4.4.1.4 Installation Sequence

4.4.1.5 ACIP Pile Load Test Considerations

4.4.2 Steel Placement

4.4.3 Pile Group Effects

4.4.4 Settlement

4.5 CORROSION SERIES – ENVIRONMENTAL CLASSIFICATION

4.6 RADIUM SAMPLE ANALYSIS AND RECOMMENDATIONS

4.7 CONSTRUCTION RELATED SERVICES

5.0 REPORT LIMITATIONS

APPENDIX A

Boring Location Plan ..................................................................................................... A-1 Boring Logs ...................................................................................................... A-2 to A-11 Key to Boring Logs ........................................................................................................... A

APPENDIX B

ACIP Allowable Capacities .............................................................................................. B

APPENDIX C

Lab Testing Summary ..................................................................................................... C Corrosion Series Test Results ........................................................................................ C Radium Sample Test Results.…………………………………………………………………C

APPENDIX D

Important Information About Your Geotechnical Engineering

Report, Constraints and Restrictions, General Conditions ............................................... D

LIST OF TABLES

Table 1 – Description of Structures Table 2 – Relevant Engineering Index Properties of Arredondo Soil (4B) Table 3 – Allowable ACIP Pile Capacities

Project No.: 0230.1800060 Report No.: 1582115 Date: July 3, 2018

EXECUTIVE SUMMARY

We have prepared this executive summary as a general overview. Please refer to, and rely on, the full report for information about findings, recommendations, and other considerations.

Project Location and Description

The subject property is located within the Malcom Randall Veterans Affairs (VA) Hospital complex at 1601 SW Archer Road in Gainesville, Alachua County, Florida. The project site lies within Section 7, Township 10 South and Range 20 East. The location for the proposed structure is currently occupied by planter areas and sidewalks. The new structure will be adjacent to the existing Building 12 that is supported by a 3’-4” thick mat foundation.

Our office was provided a copy of a drawing titled, “ALTA/ACSM Land Title Survey, Boundary and Topographic Survey, Malcom Randall VA Medical Center,” which presented the parcel location and proposed building location; and a drawing titled, “VA Administration Building Option B Section,” prepared by Alliance Design & Construction, Inc. Our office was also provided as-built drawings of the adjacent Building 12, which include typical sections of the existing mat foundation and bearing levels. Current plans include the two-phase construction of a six-story, composite steel frame administration building. The first phase will consist of constructing the first two stories.

Soil and Groundwater Conditions

The soil test borings generally encountered sand with silt to silty sand [SP-SM/SM] to depths of 4 to 6.5 feet, followed by interbedded layers of silty/clayey sands [SM-SC/SC] and sandy clay [CH] to maximum boring termination depths of 100 feet. As an exception, soil boring B-6 encountered weathered limestone at a depth of 97 feet to the boring termination depth of 100 feet below grades. The groundwater level was generally encountered at a depth of 30 feet at the time of our exploration.

Groundwater Considerations

Groundwater levels and seasonal high groundwater levels may be affected by the proposed construction which will modify the surface and subsurface hydrology. We found shallow deposits of clayey sands and sandy clays across the site during our site exploration. Due to the poor permeability characteristics of these clayey soils, these soils tend to act as an aquiclude (a sediment through which groundwater cannot pass) to the natural infiltration of the rainwater.

Therefore, rainfall will most likely temporarily perch on top of these relatively impermeable soils causing isolated areas with temporary groundwater levels significantly higher during periods of heavy or extended rainfall.

Perched groundwater levels can generally be expected to occur at the ground surface to about 2 feet above the top of hydraulically restrictive soils, where present, if the groundwater level is unable to drain and/or percolate into a more pervious layer. It should be noted that undercutting of the hydraulically restrictive materials will impact the depth of the perched water level. The potential for groundwater to perch will be directly related to rainfall and irrigation, as well as site grading. The potential for transient perched groundwater levels should be considered during the design of the site grades and during construction.

Foundation Design

Our office was supplied with structural loading information. We anticipate that maximum column loads may range from 600 kips to 900 kips.

We understand that the structure may be supported on a reinforced concrete mat foundation system. The anticipated column load for the structures, provided by TLC ranges from 600 kips to 900 kips, for a column spacing of approximately 30’ x 30’, with an estimated average net bearing pressure of less than 1,500 psf. A preliminary finished floor elevation of EL 89.5 feet was provided at the time of this report, with the bottom of mat elevation approximately 8 feet below building 12 level slab. We estimate that a mat foundation designed with an average net contact pressure not exceeding 1,500 psf will provide satisfactory performance on this project.

We recommend utilizing a modulus of subgrade reaction for the mat system of 12 kcf beneath the proposed mat foundation. The subgrade reaction is used to compute node springs and flexural rigidity of the mat/raft foundation system. Due to presence of clayey soils it should be anticipated that some undercutting of clay may be required.

Due to the relatively high loads, adjacent buildings and site restrictions, a deep foundation system may be used to support the structures. We recommend, a deep foundation system consisting of augered cast in-place piles, be utilized for support of the structure. Presented in this report are recommendations for augered cast-in-place piles, including allowable compression and tension pile capacities. The floor slab could be designed as a floating slab (independent of the grade beams). Potentially expansive clayey soils shall be removed to a minimum of 4 feet below the bottom of the footing/floor slab. The over-excavated/fill areas shall be backfilled with a compacted, low permeability, engineered fill material.

1.0 INTRODUCTION

1.1 GENERAL

In this report, we present the results of the subsurface exploration of the site for the proposed construction of the Malcom Randall VA Hospital Administration Building in Gainesville, Florida.

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

The subject property is located within the Malcom Randall Veterans Affairs (VA) Hospital complex at 1601 SW Archer Road in Gainesville, Alachua County, Florida. The project site lies within Section 7, Township 10 South and Range 20 East. The location for the proposed structure is currently occupied by planter areas and sidewalks. The new structure will be adjacent to the existing Building 12 that is supported by a 3’-4” thick mat foundation.

Our office was provided a copy of a drawing titled, “ALTA/ACSM Land Title Survey, Boundary and Topographic Survey, Malcom Randall VA Medical Center,” which presented the parcel location and proposed building location; and a drawing titled, “VA Administration Building Option B Section,” prepared by Alliance Design & Construction, Inc. Our office was also provided as-built drawings of the adjacent Building 12, which include typical sections of the existing mat foundation and bearing levels. Current plans include the two-phase construction of a six-story, composite steel frame administration building. The first phase will consist of constructing the first two stories.

2.2. STRUCTURAL CONDITIONS

Current plans include the two-phase construction of a six-story, composite steel frame administration building. The first phase will consist of constructing the first two stories.

Estimated foundation type and loading addressed in this report have been specified by TLC Engineering for Architecture, and are summarized in Table 1.

Table 1 – DESCRIPTION OF STRUCTURES

Structure Estimated Maximum Foundation Loading

Administration Building

Column Spacing 30’x30’ Maximum Interior Column Load: 900 kips Maximum Exterior Column Load: 600 kips

We understand the structure is proposed to be supported on a mat foundation system or a deep foundation (pile cap and grade beam) system. Our office was not provided with Foundation Plans or any other construction-related information other than that discussed herein. If our understandings and assumptions of project issues are incorrect our conclusions and recommendations will not be considered valid until we have had the opportunity to review all pertinent issues. The above constitutes all of the project information provided to our office at the time of this report preparation.

2.2 PURPOSE

The purposes of this exploration were:

To explore the prevailing site subsurface conditions within the proposed administration building footprint area, To perform a series of laboratory tests, including radon potential and corrosion series, on selected subsurface soil specimens, recovered from the field exploration program to assist with engineering soil classifications, To evaluate the subsurface response to anticipated structural loadings and discuss the groundwater table characteristics, To evaluate and discuss geotechnical issues deemed relevant to the proposed on-site building construction, To prepare foundation design and construction recommendations.

This report presents an evaluation of site conditions on the basis of 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 you desire.

By contract, 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 conduct an exploration to evaluate the probable effect of the regional geology upon the proposed construction, if you desire.

2.3 FIELD EXPLORATION

The field geotechnical testing activities were started on June 16, 2018 and completed on June 18, 2018. Field testing for this portion of the geotechnical study included six (6) soil test borings to depths of 50 to 100 feet below the ground surface within the limits of the proposed administration building footprint. The actual test locations shown are approximate and were staked in the field by UES personnel using existing landmarks and site features. All boreholes were grouted/backfilled upon field work completion. The soil test boring locations have been presented on the attached Boring Location Plan.

Representative portions of the subsurface soil samples recovered were transported to our Gainesville soils laboratory. The soil samples were visually classified by an experienced geotechnical engineer. It should be noted that soil conditions might vary between soil test boring locations, and between the subsurface soil strata interfaces which have been shown on the Boring Logs. The soil test boring data reflects information from the specific test locations only.

Due to the weathered condition of the upper limestone stratum, obtaining rock core samples was not attainable.

2.3.1 Standard Penetration Test (SPT) Borings

Penetration tests were performed in accordance with ASTM Procedure D-1586, Penetration Test and Split-Barrel Sampling of Soils. This test procedure generally involved driving a 1.4-inch I.D. split-tube sampler into the soil profile in six inch increments for a minimum distance of 18 inches using a 140-pound hammer free-falling 30 inches. The total number of blows required to drive the sampler the second and third 6-inch increments is designated as the N-value, and provides an indication of in-place soil strength, density, and consistency.

2.3.2 Radon Testing and Corrosion Bulk Sampling

Radon and corrosion test samples were collected from the subgrade between depths of 1 to 2 feet below existing grades. The corrosion testing sample was brought back to our laboratory for further testing. The radon testing was performed by Radon Professional Services, Inc.

2.4 LABORATORY TESTING

2.4.1 Visual Classification

The soil samples recovered from the soil test borings were returned to our laboratory where an engineer visually reviewed the field descriptions in accordance with ASTM D-2488. We then selected representative soil samples for laboratory testing. Using the results of the laboratory tests, our visual examination, and our review of the field boring logs we classified the soil borings in accordance with the current Unified Soil Classification System (USCS).

2.4.2 Index Testing

Laboratory testing was performed on selected samples of the soils encountered in the field exploration to better define soil composition and properties. Testing was performed in accordance to ASTM procedures and included Percent Passing No. 200 Sieve (ASTM D-1140), Atterberg Limits (ASTM D-4318), Organic Content (ASTM D-2974), and Natural Moisture Content (ASTM D-2216). The test results have been presented on the attached Boring Logs.

2.4.3 Corrosion Testing

Selected soil samples were tested for corrosion potential. Testing was completed in accordance with ASTM procedures and included pH (ASTM D-1293), electrical resistivity (ASTM D-1125), chloride (ASTM D-512) and sulfate content (ASTM D-4130). Test results are shown in Appendix C.

3.0 FINDINGS

3.1 REGIONAL GEOLOGY

The general geology of central Alachua County is characterized by a surface veneer of Pleistocene and Pliocene sands and sandy clays overlying the Miocene age Hawthorn Group, a highly variable mixture of interbedded quartz sands, clays, carbonates, pebbles and grains occurring in thickness of up to 150 feet. Underlying the Hawthorn Group is the upper Eocene age Ocala Formation, occurring as a uniform limestone, which is approximately 200 feet thick and overlies the Eocene age Avon Park Formation, which can be up to 500 feet thick. Both the Ocala and Hawthorn Formations dip to the northeast by approximately one degree.

The general hydrogeology of Alachua County consists of three aquifer systems; a surficial aquifer, an intermediate aquifer, and the Floridan Aquifer system. The surficial aquifer exists as an unconfined water table situated over the impermeable Hawthorn Group and is usually a subdued reflection of surface topography. The intermediate aquifer system includes all rocks that collectively retard the exchange of water between the overlying surficial aquifer system and the underlying Floridan Aquifer system. Water in this system is contained under confined conditions. The Floridan Aquifer system is a thick carbonate sequence that functions regionally as a water-yielding hydraulic unit. The direction of shallow groundwater flow is generally toward surface water bodies.

The surface of the upper Floridan Aquifer in the general project site area is estimated in the elevation range of +50 to +60 feet, NGVD, based on the 2009 St. John’s River Water Management District (SJRWMD) Potentiometric Surface Map. USGS topography maps indicate ground surfaces in the area of the site are from +85 to +90 feet, NGVD.

3.2 KARST TOPOGRAPHY

About 10% of the earth’s land (and 15% of the United States) crust is composed of, or underlain by, soluble limestone. When limestone interacts with underground water, over time, the water dissolves the limestone to form karst topography, a mix of caves, underground channels, and rough and undulating ground surfaces. The underground water of karst topography carves channels and caves that become susceptible to collapse from the surface. When enough limestone is eroded from underground, a sinkhole may develop. Sinkholes can range in size and depth from a few feet to over 300 feet.

The topography of North Central Florida is characteristic of karst terrain, with sinkholes caused by natural climatic variability, as well as, man-made activities, such as, the drop in groundwater levels from well pumping.

3.3 GENERAL AREA SOIL INFORMATION

The United States Department of Agriculture (USDA) Soil Survey of Alachua County, Florida describes the near-surface soil profile in the general project area as Arredondo soil. Arredondo soil is characterized as nearly level to gently sloping, well-drained, and has a water table at a depth of more than 72 inches. In addition, the soil classification for this site indicates that between 30 and 45 percent of the area is “urban land,” which is made up of sidewalks, driveways, and existing buildings. The soil may have been previously impacted by other construction work. Relevant engineering index properties of these soils have been summarized in Table 2 below.

Table 2 – Relevant Engineering Index Properties of Arredondo Soil (4B)

Depth, Inches

Texture Classification % Passing #200 Sieve

Plasticity Index

Shrink-swell Potential

Permeability

0-49 Fine sand SP-SM, SM 5-15 NP Low 6.0-20 in/hr

49-54 Loamy sand, loamy fine sand, sandy loam

SM, SM-SC 13-25 NP-7 Low 2.0-6.0 in/hr

54-86 Sandy loam, fine sandy loam, sandy clay loam

SM-SC, SC 20-40 NP-20 Low 0.2-2.0 in/hr

3.4 SURFACE CONDITIONS

UES engineering personnel visited the project site prior to and during the performance of the field portions of this geotechnical study. At the time of our initial exploration, the proposed construction area consisted of planter areas, and adjacent buildings. Surface organic soils, unusual ground depressions, or rock outcroppings were not observed on the project site.

3.5 SUBSURFACE CONDITIONS

The field exploration performed for this project disclosed subsurface conditions that were somewhat consistent with the local geology and general area soils information described above.

The soil test borings performed beneath the proposed structure were reviewed to evaluate the subsurface soil strata lateral continuity and uniformity, both parameters that would have an impact in foundation system selection and performance. Soil classifications and descriptions for this geotechnical study have been based both on the results of the laboratory soil testing programs and on visual examinations of soil specimens by the Geotechnical Engineer. The subsurface soil conditions encountered in the soil test borings have been summarized in the attached Boring Logs and described below.

The soil test borings generally encountered sand with silt to silty sand [SP-SM/SM] to depths of 4 to 6.5 feet, followed by interbedded layers of silty/clayey sands [SM-SC/SC] and sandy clay [CH] to maximum boring termination depths of 100 feet. As an exception, soil boring B-6 encountered weathered limestone at a depth of 97 feet to the boring termination depth of 100 feet below grades.

3.6 GROUNDWATER DEPTH

The groundwater level was generally encountered at a depth of 30 feet at the time of our exploration. It should be noted that the groundwater levels may not have been fully stabilized in the boreholes when the readings were recorded upon boring completion.

Based upon our review of regional hydrogeology and the Alachua County Soil Survey, we estimate the normal seasonal high groundwater level will be at depths of 3 feet to more than 5 feet below the ground surface at the boring locations, as a result of perched conditions.

3.7 LABORATORY TESTING

The soil samples recovered from the previous and recent field exploration program were placed in plastic containers and returned to our soils laboratory, where the Geotechnical Engineer visually examined and classified the samples. Laboratory soil tests are performed to aid in the classification of the soils, and to help in the evaluation of engineering characteristics of the soils.

Representative soil samples were selected for percent fines determination, moisture content, organic content, and Atterberg Limits testing. The test results have been presented on the attached Boring Logs and summarized in Appendix C.

3.7.1 Percent Passing No. 200 Sieve

Certain recovered soil samples were selected to determine the percentage of fines. In these tests the soil samples were dried and washed over a U.S. No. 200 mesh sieve. The percent of soil by weight passing the sieve was the percentage of fines or portion of the sample in the silt and clay size range. The tests were conducted in accordance with ASTM Procedure D-1140, Standard Test Methods for Amount of Material in Soils finer than the No. 200 Sieve.

3.7.2 Atterberg Limits

Certain recovered soil samples were selected for Atterberg Limits testing to evaluate the soil plasticity characteristics. The soil’s Plasticity Index (PI) was the range of moisture content over which the soil deforms as a plastic material. It was bracketed by the Liquid Limit (LL) and the Plastic Limit (PL). The LL was the moisture content at which the soil will flow as a heavy viscous fluid. The PL was the lowest moisture content at which the soil is sufficiently plastic so as to be manually rolled into a 1/8-inch diameter thread. These tests were conducted in accordance with ASTM Procedure D-4318, Standard Test Methods for LL, PL and PI of Soils.

3.7.3 Moisture Content

Certain recovered soil samples were selected to determine their moisture content. The moisture content was the ratio expressed as a percentage of the weight of water in a given mass of soil to the weight of the solid particles. These tests were conducted in accordance with ASTM Procedure D-2216, Standard Test Method for Laboratory Determination of Water (Moisture) Content of Soil and Rock.

3.7.4 Organic Content

A recovered soil sample was selected to determine the organic content. This test was conducted in accordance with ASTM Procedure D-2974. This test method evaluates the moisture content, ash content, and organic matter in peats and other organic soils, such as organic clay, silt, and sand. The soil specimen is first dried to measure the initial moisture content, and then transferred to a high temperature kiln that burns off the organic materials. The organic content is then calculated as the ratio of the weight loss to the dry weight of the soil measured from the low temperature oven; it is expressed as a percent.

4.0 RECOMMENDATIONS

In this section of the report, we present our recommendations for building foundation design, site preparation, and construction related services. The following recommendations are made based upon a review of the attached soil test data, and our understanding of the proposed preliminary information provided and cited herein.

4.1 FOUNDATION SYSTEM EVALUATION

A geotechnical consideration for the design and construction of the proposed structure is the presence of very loose sand layers in some of the soil borings. Significant variations in depth, thickness and consistency of the soil strata were also encountered at individual boring locations and between borings. The amount of silt and clay fines present in the soil strata varied significant between boring locations.

Some of the soil borings encountered a surficial layer of clayey sand; laboratory testing indicates that these soils have a low plasticity. These soils are considered suitable; however our past experience has shown that clayey sands with more than 30 percent fines will require stringent moisture control during compaction, particularly during rainy season. Special compaction equipment (I.e. sheep-foot roller) and strict moisture control may be required to achieve the minimum compaction specifications. Footings should be visually inspected and tested to verify the in-place density and condition of the subgrade bearing soils.

The sand-clay mixtures and clayey sand soils may require stringent moisture control during compaction, particularly during rainy periods. Footings that are excavated through the upper layer of compacted sand fill soils into the native clayey sands should be visually inspected and tested to verify the in-place density and condition of the subgrade bearing soils.

Our local experience has found that clay layers are often laterally discontinuous, which make it more difficult to ascertain their presence on a given project parcel with a few soil test borings.

Near-surface active clay soils which change volume; i.e., shrink and swell, with variations in moisture content have the potential to impact foundation performance. As such, both natural variations, such as rainfall, and man-made variations, such as landscape details and irrigation habits, can affect the upward and downward movement of these clays and consequent emulation of this movement by ground supported improvements. If encountered, these shallow deposits of clay soils must be addressed through site grading, over-excavation and replacement, site drainage and stiffened foundation.

The available data suggests that conventional concrete slab-on-grade (grade slab or ground floor slab) construction on this project is technically feasible. A concrete grade slab differs from a concrete structural slab in that the former fully relies on the underlying soils for structural support. The base soils beneath the slab-on-grade must be carefully selected and compacted to provide uniform and solid support beneath the slab section. The floor slab can be constructed as a slab-on-grade provided any potentially expansive soils are undercut a minimum of 4 feet below the bottom of the slab and the subsequent lifts of engineered structural backfill are compacted and tested in accordance with the recommendations included in this report.

4.2 GROUNDWATER CONSIDERATIONS

The groundwater level will fluctuate seasonally depending upon local rainfall. The rainy seasons in North Florida are normally between June and September and December and February.

Based upon our review of regional hydrogeology and the Alachua County Soil Survey, we estimate the normal seasonal high groundwater level could perch 3 feet to more than 5 feet below the ground surface in the general area of the project site. The perched groundwater will be a transient condition, directly related to rainfall and site grading.

It should be noted that the normal estimated seasonal high water levels do not provide any assurance that groundwater levels will not exceed these estimated levels during any given year in the future. Should the impediments to surface water drainage be present, or should rainfall intensity and duration, or total rainfall quantities, exceed the normally anticipated rainfall quantities, groundwater levels might once again exceed our seasonal high estimates. We recommend positive drainage be established and maintained on the site during construction.

We further recommend permanent measures be constructed to maintain positive drainage from the site throughout the life of the project.

4.3 SHALLOW BUILDING FOUNDATION

We understand that the structure may be supported on a reinforced concrete mat foundation system. The anticipated column load for the structures, provided by TLC ranges from 600 kips to 900 kips, for a column spacing of approximately 30’ x 30’, with an estimated average net bearing pressure of less than 1,500 psf. A preliminary finished floor elevation of EL 89.5 feet was provided at the time of this report, with the bottom of mat elevation approximately 8 feet below building 12 level slab.

Assuming a subgrade improvement program is implemented and the total and differential settlement are within acceptable limits, we consider the subsurface conditions at the site adaptable for support of the proposed structures when constructed on a properly designed mat foundation system. Provided the site preparation and earthwork construction recommendations outlined in Section 4.3.4 of this report are performed, the following parameters may be used for foundation design.

4.3.1 Mat Foundation System

We estimate that a mat foundation designed with an average net contact pressure not exceeding 1,500 psf will provide satisfactory performance on this project. We recommend utilizing a modulus of subgrade reaction for the mat system of 12 kcf beneath the proposed mat foundation. The subgrade reaction is used to compute node springs and flexural rigidity of the mat/raft foundation system. Due to presence of clayey soils it should be anticipated that some undercutting of clay may be required.

The foundations in areas adjacent to the existing structure may need special consideration. It is recommended that the building should be structurally independent of existing buildings since additional loads of the new structure on existing footings may cause detrimental settlement and unsightly cracking. For the same reason, new foundations should be located in such a way that the stresses under new footings will not overstress the soil under existing footings. This problem applies to new foundation system/footings in the critical zone which extends about 5 feet laterally from the existing footings.

4.3.2 Bearing Material

The foundations should bear in either the compacted suitable native soils or compacted structural fill. The bearing level soils should be compacted to at least 95 percent of the Modified Proctor maximum dry density (ASTM D 1557) to a depth of at least two feet below the foundation bearing level.

As previously mentioned soil test borings encountered surficial clayey sands. The clayey sand soils may require stringent moisture control during compaction, particularly during rainy periods.

If this material is degraded by construction equipment or pumped due to rainy weather it should be undercut and replaced with structural fill as described in section 4.3.4.

4.3.3 Settlement Estimates

Post-construction settlement of the structures will be influenced by several interrelated factors, such as (1) subsurface stratification and strength/compressibility characteristics; (2) footing size, bearing level, applied loads, and resulting bearing pressures beneath the foundations; and (3) site preparation and earthwork construction techniques used by the Contractor. Our settlement estimates for the structures are based on the use of site preparation/earthwork construction techniques as recommended in Section 4.3.4 of this report. Any deviation from these recommendations could result in an increase in the estimated post-construction settlement of the structures.

Using the recommended allowable bearing pressure, the assumed maximum structural loads and the limited field/laboratory data which we have correlated to geotechnical strength and compressibility characteristics of the subsurface soils, we estimate that total elastic settlements of the structure could be on the order of 1¾ inches or less, which should be a common allowable value for mat foundations. Differential settlement result from differences in applied bearing pressures and variations in the compressibility characteristics of the subsurface soils.

Because of the subsurface conditions, we anticipate that differential settlement of the structures could be on the order of 1 inch to or less over a lateral distance of 30 feet between the mat center and the perimeter).

4.3.4 Shallow Foundation Site preparation

We recommend normal, good practice site preparation procedures. These procedures include:

stripping the site of existing construction (footings, utilities, etc) vegetation and topsoil, compacting the subgrade and placing necessary fill or backfill to grade with engineered fill. The structural borings indicated that clayey soils (fill) were present to depths of less than 10 feet below existing grades beneath the building footprint. We recommend that foundation excavations be augered/probed to confirm the suitability of the bearing soils. A more detailed synopsis of this work is as follows:

1. Prior to construction, the location of any existing underground utility lines within the construction area should be established. Provisions should then be made to relocate interfering utilities to appropriate locations. It should be noted that if underground pipes are not properly removed or plugged, they may serve as conduits for subsurface erosion which may subsequently lead to excessive settlement of the overlying structure(s).

2. If required, perform remedial dewatering prior to any earthwork operations. Dewatering operations scheduled immediately adjacent to existing structural footings should be carefully evaluated for possible impacts to the existing foundation systems. Dewatering systems should not be decommissioned until the excavation is backfilled two feet above the groundwater level at the time of construction. Further, the site should always be graded to prohibit ponding of stormwater runoff. Dewatering means and methods are the sole responsibility of the Contractor.

3. Strip/demolish the proposed construction limits of all grass, roots, topsoil, asphaltic concrete, concrete and other deleterious materials within 5 feet beyond the perimeter of the proposed structure(s). Demolition should include complete removal of all above and below grade foundations and other improvements. Expect typical stripping at this site to depths of 6 to 12 inches. Deeper clearing and grubbing depths may be encountered in heavily vegetated areas. Also all utilities, foundations and other below grade structures should be removed and the excavation backfilled as described herein.

4. We recommend that existing structures in close proximity to the proposed building addition should be monitored for cracks or signs of distress during adjacent new excavation and building construction operations.

5. Following demolition/site clearing, grubbing and rough grading, the same project areas should be proof-rolled using a large, fully loaded rubber-tired vehicle (dump truck) or similar equipment. Proof-rolling will help locate any surficial zones of especially loose or soft or unsuitable soils not encountered in the soil test borings, and should help provide more uniformity in the sandy subsurface soil profile. Unusual or unanticipated conditions identified during this process must be immediately brought to the attention of the UES Geotechnical Engineer. Field density testing is not required during proof-rolling operations. Proof-rolling operations should be observed by a representative of UES.

6. Weak subgrade soils identified during proof-rolling operations shall be excavated and removed from the site, and replaced with granular fill soils. Excavate the site to the proposed grades. Stockpile the surficial sandy soils for later use as fill. We recommend that the bottom of foundation/footings be probed to confirm the suitability of the bearing soils. If encountered, potentially expansive clayey soils shall be removed to a minimum of 2 feet below the bottom of the mat/slab. The over-excavated areas should be backfilled with a compacted, low permeability, engineered fill material. Fill material shall consist of poorly draining, silty-clayey sand with between 15% to 30% material passing the No. 200 sieve, a Liquid Limit (LL) value less than 30, and a Plasticity Index (PI) value less than 15. Limerock base material may be used as a substitute for a low permeability fill, if availability is an issue. Special compaction equipment and strict moisture control may be required to achieve the minimum compaction specifications. Loose lift thicknesses of 8 to 12 inches are recommended. Should the Contractor experience difficulty in achieving the appropriate level of compaction, a thinner lift should be utilized.

7. Proof-rolling operations should be followed by subgrade compaction operations.

Compaction operations should be implemented with a compactor of appropriate size.

Subgrade compaction operations should be run until an in-place soil density of 95 percent of the Modified Proctor maximum dry density (ASTM D-1557) is achieved to a depth of 2 feet below the final subgrade, or foundation bearing elevations, whichever is greater. If necessary to achieve the recommended soil compaction at depth, the entire project area may be undercut, the exposed subgrade soils compacted, and then the areas backfilled using 6-inch lifts to final subgrade elevation.

8. Compaction operations should extend to the limits of the cleared/grubbed project areas.

Compaction of the existing, near-surface soils will provide for uniformity of foundation/slab settlements and improve the soils’ bearing capacity conditions. Typically, the soils should exhibit moisture contents within ± 2 percent of the modified Proctor optimum moisture content during compaction. A minimum of eight (8) complete coverages (in perpendicular directions) should be made in the building area with the roller to improve the uniformity and increase the density of the underlying sandy soils. It should be anticipated that moisture will need to be added to the subgrade in order to achieve the required compaction.

9. Should the bearing level soils experience pumping and soil strength loss during the compaction operations, compaction work should be immediately terminated and (1) the disturbed soils removed and backfilled with dry structural fill soils which are then compacted, or (2) the excess pore pressures within the disturbed soils allowed to dissipate before recompacting.

10. Care should be exercised to avoid damaging any nearby structures while the compaction operation is underway. Prior to commencing compaction, occupants of adjacent structures should be notified and the existing conditions of the structures be documented with photographs and survey (if deemed necessary). Compaction should cease if deemed detrimental to adjacent structures. UES can provide vibration monitoring services to help document and evaluate the effects of the surface compaction operation on existing structures. In the absence of vibration monitoring it is recommended the vibratory roller remain a minimum of 50 feet from existing structures.

Within this zone, use of a vibratory roller operating in the static mode is recommended.

11. Place fill material, as required. Offsite fill (import) shall consist of sand with less than 10 percent soil fines, unless a low permeability engineered fill material is required. Place fill in uniform 10- to 12-inch loose lifts and compact each lift to a minimum density of 95 percent of the modified Proctor maximum dry density (ASTM D1557).

12. In the building areas, test all footing cuts for compaction to a depth of two feet and probe footing to confirm suitability of bearing soils. We recommend you test every column footing, and conduct one test for every 100 lineal feet of wall footing.

13. If difficult compaction conditions are encountered during the site work operations, the compaction efforts shall stop and a qualified representative of Alliance Design & Construction, Inc.’s testing agency shall be consulted for recommendations

14. If site preparation is performed during the rainy season (June through September, reference historic data and Climatic Atlas of the United States), special care shall be taken to maintain positive drainage from the building pad areas to drains or ditches around the site. Unexpected wet periods can also occur in Florida during the “dry” season. Such events can raise water levels above seasonal highs without the associated high temperatures to evaporate ponded water. Therefore, the Contractor shall practice wet weather means and methods for earthwork during the “dry” season as well. Groundwater and surface water control, use of granular fill material and aeration are the normal means to accommodate wet weather construction. All fill materials that are excavated from below the water level shall be stockpiled and/or spread out for a sufficiently long period to allow drainage.

4.4 DEEP FOUNDATION SYSTEM

Due to the relatively high loads, adjacent buildings and site restrictions, a deep foundation system may be used to support the structures. The following sections provide recommendations utilizing augered cast-in-place (ACIP) piles, and include allowable compression and tension pile capacities. The pile diameters and depths provided are typical for structures of this size and type and are based on past experience with similar loading requirements for projects in the local area.Note that prestressed concrete piles were considered and eliminated as an option due to the proximity of buildings, and the vibrations and noise caused by driving piles.

The project areas should be cut level to the bottom of pile cap bearing elevations in preparation for pile installation. Unusual or unanticipated conditions identified during this process will be addressed by the UES Geotechnical Engineer. Recommendations contained in section 4.3.4 should be followed to reduce the potential for intolerable settlements.

We strongly recommend the Foundation Contractor selected for this project have a minimum of five (5) years of continuously successful project experience with similar geological conditions in the North Central Florida Region. The Contractor should provide documentation on successfully completed similar projects to be reviewed by the Design Team. The Geotechnical Report should be made available to foundation contractors in order to determine the best installation methodology for this site.

The floor slab can be a floating slab in conjunction with undercutting of the surficial potentially expansive clays. The floor slab may be supported upon the compacted fill and should be structurally isolated from other foundation elements and adequately reinforced to prevent distress due to differential movement. The shrink-swell behavior of the clays can cause significant distress to the interior of the structure, namely in non-load bearing walls and floor undulations. To minimize the effect of the clayey soils on the floor slab we have provided the following recommendations.

The floor slab could be designed as a floating slab (independent of the grade beams).

Potentially expansive clayey soils shall be removed to a minimum of 4 feet below the bottom of the footing/floor slab. The over-excavated/fill areas shall be backfilled with a compacted, low permeability, engineered fill material. Fill material shall consist of poorly draining, silty sand or clayey sand with between 15% to 30% material passing the No. 200 sieve, a Liquid Limit (LL) value less than 30, and a Plasticity Index (PI) value less than 15. Limerock base material may be used as a substitute for a low permeability fill if availability is an issue. Special compaction equipment and strict moisture control may be required to achieve the minimum compaction specifications. Loose lift thicknesses of 8 to 12 inches are recommended. Should the Contractor experience difficulty in achieving the appropriate level of compaction, a thinner lift should be utilized. Additionally, we recommend that the floor slab be at least 6-inches thick so that it may act more rigid (than a typical 4-inch thick slab) and better distribute stresses. Please note the control of water-cement ratios and joint locations will be necessary to control cracking. In conformance with the Florida Building Code, we recommend the use of a vapor barrier beneath the floor slab.

4.4.1 Augered Cast-in-place Pile (ACIP) Recommendations

Augered cast-in-place (Auger-cast) piles (ACIP) are a common foundation type in the State of Florida. This pile type uses a hollow-stem auger to reach the specified bearing stratum. Sand-cement grout is pumped, under pressure, through the hollow stem as the auger is slowly withdrawn after reaching the pile tip elevation forming a cast-in-place auger pile. Loads are resisted primarily by shaft skin friction, with limited end bearing capacity also available beneath the pile tip dependent upon soils present at and beneath the tip elevation.

The ACIP option provides for a relatively vibration free installation process, produces reasonable settlements, affords favorable compression and tension capacities, and has demonstrated foundation economy on other projects in the State of Florida and in the local area.

4.4.1.1 ACIP Axial Load Analysis

Auger-cast piles with nominal diameters of 16-inches to 18-inches can be utilized for the support of the proposed structures(s). The augercast piles are anticipated to derive their load bearing capacity primarily from shear (skin friction). As a reference, our estimated allowable pile capacities are presented on attached graphs in Appendix B. Pile allowable compression and tension capacities are shown in Table 3. The graphed results and engineering experience indicate that 16-inch ACIP piles should achieve an allowable pile capacity of approximately 75 tons at a pile tip elevation of +25 feet, NGVD. The results of our axial load analysis have been summarized in Table 3. The estimated pile lengths have been based on pile cut off elevations of approximately +85 feet, NGVD.

Table 3 – Allowable ACIP Pile Capacities

Augercast Pile Nominal Diameter

Working Compression Capacities

Working Tension Capacities

Estimated Average Pile Lengths 1(Feet)

16 inches 75 Tons 45 Tons 60 feet

18 inches 85 Tons 50 Tons 60 feet

*1 Estimated Ground Surface Elevation = +85 feet

4.4.1.2 ACIP Lateral Load Analysis

Vertically aligned deep foundations, embedded in subsurface conditions similar to those at this site, can typically support horizontal and lateral loads on the order of 5 percent of their compressive capacity without experiencing lateral deflections greater than about ½ inch. If requested, once final design loads become available UES can provide a lateral capacity analysis.

4.4.1.3 ACIP Pile Construction Techniques

Auger-cast piles concrete…