Attachment_F_LS-1_Geotechnical_Report.pdf

REPORT OF GEOTECHNICAL

CONSULTING SERVICES

Gainesville Regional Utilities – Lift Station #1

Generator Fuel Storage Pad – P.O. No. 4510055624 3311 SW 2nd Avenue

Gainesville, Alachua County, Florida

UES Project No. 0230.2200091 UES Report No. 1969830

Prepared for:

Gainesville Regional Utilities Water/Wastewater Engineering

301 SE 4th Avenue Gainesville, FL 32614

(352) 393-1618

Prepared by:

Universal Engineering Sciences, LLC 4475 SW 35th Terrace

Gainesville, Florida 32608

(352) 372-3392

August 15, 2022

Consultants in: Geotechnical Engineering • Environmental Sciences • Construction Materials Testing Offices in: Orlando • Gainesville • Ocala • Fort Myers • Rockledge • Daytona Beach • West Palm Beach

UNIVERSAL

ENGINEERING SCIENCES

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

August 15, 2022

Gainesville Regional Utilities Water/Wastewater Engineering 301 SE 4th Avenue Gainesville, FL 32614

Attention: Mr. Chris Krpan, P.E.

Reference: Report of Geotechnical Consulting Services

Gainesville Regional Utilities – Lift Station #1 Generator Fuel Storage Pad - P.O. No. 4510055624

3311 SW 2nd Avenue Gainesville, Alachua County, Florida

UES Project No.: 0230.2200091 UES Report No.: 1969830

Dear Mr. Krpan:

Universal Engineering Sciences, LLC (UES) has completed the geotechnical engineering services for the subject project in Gainesville, Alachua County, Florida. This Geotechnical Report is submitted in satisfaction of the contracted scope of services as summarized in UES Proposal No. 1963474, dated June 29, 2022.

This Report presents the results of our field subsurface exploration and laboratory soil testing programs, and recommendations for geotechnical site preparation, foundation design and construction, and fill suitability.

We appreciate the opportunity to have assisted you on this project and look forward to a continued association. Please do not hesitate to contact us if you should have any questions, or if we may further assist you as your plans proceed.

Respectfully submitted, UNIVERSAL ENGINEERING SCIENCES, LLC

Certificate of Authorization 549

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

Project Geotechnical Engineer Senior Geotechnical Engineer Florida P.E. No. 86444 Florida P.E. No. 60272

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

ENGINEERING SCIENCES

UNIVERSAL

OFFICES IN

• Daytona Beach, FL

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This item has been electronically signed and sealed by Eduardo Suarez, PE on the date adjacent to the seal using 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

EXECUTIVE SUMMARY

1.0 INTRODUCTION

1.1 GENERAL

2.0 SCOPE OF SERVICES

2.1 PROJECT INFORMATION

2.2 PURPOSE

2.3 FIELD EXPLORATION

2.3.1 Standard Penetration Test (SPT) Boring

2.4 LABORATORY TESTING

2.4.1 Visual Classification

2.4.2 Index Testing

3.0 FINDINGS

3.1 REGIONAL GEOLOGY

3.2 KARST TOPOGRAPHY

3.3 GENERAL AREA SOILS 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 Moisture Content

3.7.3 Permeability Testing

4.0 RECOMMENDATIONS

4.1 GENERAL

4.2 GEOTECHNICAL CONSIDERATIONS

4.3 GROUNDWATER CONSIDERATIONS

4.4 FOUNDATION DESIGN RECOMENDATIONS

4.5 SITE PREPARATION

4.6 SUITABILITY OF EXCAVATED SOILS

5.0 REPORT LIMITATIONS

APPENDIX A

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

APPENDIX B

Important Information About Your Geotechnical Engineering

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

LIST OF TABLES

Table 1 – Relevant Engineering Properties of Arredondo Sand Soils Table 2 – Laboratory Soil Test Results

Project No.: 0230.2200091 Report No.: 1969830 Date: August 15, 2022

EXECUTIVE SUMMARY

We have prepared this executive summary solely to provide a general overview. Do not rely on this executive summary for any purpose except that for which it was prepared. Rely on the full report for information about findings, recommendations, and other concerns.

Project Location and Description

The subject parcel is located at 3311 SW 2nd Avenue in Gainesville, Alachua County, Florida.

The project site lies on Section 1, Township 10 South and Range 19 East, adjacent to the Mark Bostick Golf Course. Our office was provided a copy of a Site Plan prepared by CDM Smith. We understand that the proposed construction includes a pad for a 500 kW generator and fuel tank, with anticipated dimensions of 12’ x 24’. Maximum loading includes a 1,000 gallon (about 7,500

lb) fuel tank at full capacity, and approximately 18,000 lbs for the generator.

Soil and Groundwater Considerations

The soil boring encountered very loose to dense silty sand [SM] to a depth of 8.5 feet, followed by medium dense clayey sand [SC] to the boring termination depth of 20 feet below existing grade. The groundwater level was not apparent in the open borehole at the time of our exploration. Fluctuations of groundwater level conditions on this project parcel should be expected to occur seasonally as a result of rainfall, surface runoff, nearby construction activities, and other factors.

Foundation Recommendations:

Based on the results of our exploration, we consider the subsurface conditions at the site adaptable for support of the proposed structure when constructed on a properly designed conventional shallow foundation system.

The foundations in areas adjacent to the existing structure may need special consideration. It is recommended that the addition should be structurally independent of the existing building since additional loads of the new structure on existing footings may cause detrimental settlement and unsightly cracking. For the same reason, new footings 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 footings in the critical zone which extends about 5 feet laterally from the existing footings. 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 overlying structure. Pipes and underground utilities shall be removed and properly abandoned.

Following completion of the recommend geotechnical site preparation and building pad preparation activities, the proposed structure may be supported on a shallow mat foundation system designed with a maximum average soil bearing pressure of 1,500 pounds per square foot (psf). We recommend utilizing a modulus of subgrade reaction of 75 pci beneath the proposed mat foundation, and coefficient of (sliding) friction of 0.4, beneath the proposed mat foundation.

1.0 INTRODUCTION

1.1 GENERAL

In this report, we present the results of the subsurface exploration of the site for proposed Generator Fuel Storage Pad at Gainesville Regional Utilities’ Lift Station No. 1 in Gainesville, Alachua County, Florida. We have divided this report into the following sections:

SCOPE OF SERVICES - Defines what we did FINDINGS - Describes what we found 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 INFORMATION

The subject parcel is located at 3311 SW 2nd Avenue in Gainesville, Alachua County, Florida.

The project site lies on Section 1, Township 10 South and Range 19 East, adjacent to the Mark Bostick Golf Course. Our office was provided a copy of a Site Plan prepared by CDM Smith. We understand that the proposed construction includes a pad for a 500 kW generator and fuel tank, with anticipated dimensions of 12’ x 24’. Maximum loading includes a 1,000 gallon (about 7,500

lb) fuel tank at full capacity, and an approximately 18,000 lbs for the generator.

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. If our assumptions are incorrect we should be advised so that we may review our engineering evaluations, conclusions and recommendations.

The above constitutes all of the project information provided to our office at the time of this Report preparation.

We note that, our authorized scope of services and this Report do not address any other specific project elements, such as retaining walls, sidewalks, or slope stability issues that may be part of the overall project site plan. Since other side improvements could have detrimental effects on the performance of a foundation system at this site, UES, or another qualified geotechnical consultant, should be consulted to review the entire site development plan and conduct additional services as required to minimize any impact of associated improvements on foundation performance.

Our recommendations are based upon the above considerations. If any of this information is incorrect, or if you anticipate any changes, please inform Universal Engineering Sciences so that we may review our recommendations.

2.2 PURPOSE

To explore the prevailing site subsurface conditions within the proposed addition area, To perform a series of laboratory tests 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 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.

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 investigation 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 and completed on July 19, 2022. Field tests for this portion of the geotechnical study included one (1) soil test boring performed at the locations shown on the attached Boring Location Plan. The actual test locations shown were approximate and were staked in the field by UES engineering personnel using existing landmarks and site features. The boreholes were grouted to grade upon field work completion.

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 away from the soil test boring location, and between the subsurface soil strata interfaces which have been shown on the Boring Logs. The soil test boring data reflect information from the specific test locations only.

2.3.1 Standard Penetration Test (SPT) Boring

Penetration tests were performed in accordance with ASTM Procedure D-1586, Standard Test Method for Penetration Test and Split-Barrel Sampling of Soils. This test procedure generally involves 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.

2.4 LABORATORY TESTING

2.4.1 Visual Classification

The soil samples recovered from the soil test boring 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 observation, and our review of the field boring log we classified the soil boring 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 evaluate soil composition and properties. Testing was performed in accordance to ASTM procedures and included Percent passing No. 200 Sieve (ASTM D-1140), natural moisture content (ASTM D-2216), and Permeability (ASTM D-2434). The test results have been presented on the attached Boring Logs.

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.

The Hawthorn Group includes a highly variable mixture of interbedded quartz sands, clays, carbonates, pebbles and grains occurring with thicknesses of up to 150 feet. In the general area of the subject project, it is anticipated that the Hawthorn Group is laterally discontinuous and perforated.

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. Water exists under confined conditions.

3.2 KARST TOPOGRAPHY

About 10% of the earths 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. Per contract scope of services, 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, such as sinkhole development related to karst activity. This evaluation requires a more extensive range of field services than performed in this study.

3.3 GENERAL AREA SOILS INFORMATION

The United States Department of Agriculture (USDA) Soil Survey of Alachua County, Florida describes the near-surface soil profile in the project parcel as Arredondo-Urban Land complex soils. Urban Land soil classification indicates that 85 percent of the area is covered with shopping centers, parking lots, buildings, streets, sidewalks and other facilities. Many of these open areas have been altered by cutting and shaping or by having fill material spread on surfaces. Arredondo sand is nearly level to gently sloping and well drained. The water table is at a depth of more than 72 inches. Engineering properties for Arredondo soil are summarized below in Table 1.

Table 1 – Relevant Engineering Index Properties of Arredondo Sand Soils

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 portion of this geotechnical study. The proposed project area is currently developed with existing water management facilities. Surface organic soils, surface debris, unusual ground depressions, or rock outcroppings were not observed on the project site. Information provided to our office suggests the presence of buried services and utility lines within the proposed addition.

The above constitutes all of the project information provided to our office at the time of this report preparation.

3.5 SUBSURFACE CONDITIONS

Soil classifications and descriptions for this geotechnical study are 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 boring have been summarized in the attached Boring Log and described below.

The soil boring encountered very loose to dense silty sand [SM] to a depth of 8.5 feet, followed by medium dense clayey sand [SC] to the boring termination depth of 20 feet below existing grade.

3.6 GROUNDWATER DEPTH

The groundwater level was not apparent in the open boreholes at the time of our exploration.

Fluctuations of groundwater level conditions on this project parcel should be expected to occur seasonally as a result of rainfall, surface runoff, nearby construction activities, and other factors.

The potentiometric surface map of the upper Floridan aquifer suggests groundwater elevations, outside perched zones, on the order of +50 feet NGVD in the general site area.

3.7 LABORATORY TESTING

The soil samples recovered from the 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, and permeability testing. The test results have been presented on the attached Boring Logs and summarized in Table 2.

Table 2 – Laboratory Soil Test Results

Soil Test Boring Sample Depth Type of Test Results Soil Description

B-1 2 feet % Finer #200 19 %

Silty Sand Moisture Content 13 %

B-1 5 feet

% Finer #200 19 %

Silty Sand Moisture Content 15 %

Permeability 1.1 feet/day

B-1 8 feet % Finer #200 15 %

Silty Sand Moisture Content 14 %

B-1 10 feet

% Finer #200 23 %

Clayey Sand Moisture Content 16 %

Permeability 0.3 feet/day

B-1 15 feet

% Finer #200 30 %

Clayey Sand Moisture Content 21 %

Permeability < 0.1 feet/day

B-1 20 feet

% Finer #200 22 %

Clayey Sand Moisture Content 24 %

Permeability 0.3 feet/day

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 sample was 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. This test was 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 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.

3.7.3 Permeability Testing

Representative soil sample were selected to determine the permeability rate of the soils.

Constant head permeability test were performed on representative samples of the near surface soils from the proposed stormwater management area. These tests were conducted following the concepts outlined in ASTM D-2434, Standard Test Method for Permeability of Granular Soils (Constant Head).

4.0 RECOMMENDATIONS

4.1 GENERAL

In this section of the report, we present our recommendations for groundwater control, structure foundation, site preparation, and construction related services. The following recommendations are made based upon a review of the attached soil test data, our understanding of the proposed construction, and experience with similar projects and subsurface conditions.

4.2 GEOTECHNICAL CONSIDERATIONS

Recommendations for foundation design are dependent on the amount of total settlement and more importantly, differential settlement between various structural elements, that can be safely tolerated by the individual structures. Total and/or differential settlements beyond specified tolerable limits often dictate the use of deep foundation systems, or appropriate deep subsurface improvement techniques in order to support the structure on a shallow foundation system.

It should be noted that differential settlement underneath structures is a function of the uniformity or variability of the subsurface conditions within the zone of influence of the structure/building footprint. The more uniform the subsurface conditions, the less the differential settlement will be. We recommend that the connections and joints of various pipes, and utility lines selected must be flexible enough to allow for anticipated vertical settlement of the structure.

Based on our exploration, the primary geotechnical consideration for the design and construction of the proposed structural addition is the presence of very loose sandy layers in the shallow subsurface soil profile. Subsurface sandy soils will undergo immediate settlements upon application of surface loads, and this could be a result of both fill placement for building pad construction and building construction. In light of the above, it becomes important to compact the subgrade soils as much as possible prior to both building pad fill placement and foundation construction.

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. If at the time of construction the contractor encounters or suspects that clay soils may be near the grade slab or foundation bearing elevations, UES should be contacted to prepare appropriate recommendations. Where encountered, shallow deposits of clay soils must be addressed through site grading, over-excavation and replacement. The over-excavated areas should be backfilled with a compacted, low permeability, non-plastic engineered fill material. The low permeability backfill should continue to an elevation consistent with the top of the adjacent clay layers to minimize the potential for surface water to become trapped in the previously excavated areas. Low permeability, engineered 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, and be free of organics. A crushed limerock base material could be used as the low permeability material.

We recommend that we be provided the opportunity to review the project plans and specifications to confirm that our recommendations have been properly interpreted and implemented. If the structural loadings or the location change significantly from those discussed previously, we request the opportunity to review and possibly amend our recommendations with respect to those changes. The discovery of any subsurface conditions during construction which deviate from those encountered in the borings should be reported to us immediately for observation, evaluation, and recommendations.

4.3 GROUNDWATER CONSIDERATIONS

The groundwater level will fluctuate seasonally depending upon local rainfall. The rainy seasons in North Central 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 will be deeper than 6 feet below the ground surface in the general area of the project site; however, stormwater can perch on the clayey sands when sandy soils are present at the surface. 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. The groundwater level is anticipated to perch, for short periods of time, above the clayey sand and clay zones in the shallow subsurface profile following wet period during the year. 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.

4.4 FOUNDATION DESIGN RECOMENDATIONS

We understand that the structure consists of a reinforced concrete platform that will provide support bases for equipment. Based on information provided: maximum loading includes a 1,000 gallon (about 7,500 lb) fuel tank at full capacity, and approximately 18,000 lbs for the generator. We understand that the proposed construction includes a building pad with anticipated dimensions of 12’ x 24’.

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 structure when constructed on a properly designed conventional shallow foundation system. Provided the site preparation and earthwork construction recommendations outlined in Section 4.5 of this report are performed, the following parameters may be used for foundation design.

Foundation System

Based on the results of our exploration, we consider the subsurface conditions at the site adaptable for support of the proposed structure when constructed on a properly designed conventional shallow foundation system. Provided the site preparation and earthwork construction recommendations are performed, the following parameters may be used for foundation design.

We are recommending the use of shallow foundation systems on this project as a sound, practical and cost effective solution for support of the various proposed structural and building systems. Based on our past project experience, it is our professional opinion that the structure addressed in this geotechnical study can be designed to withstand the estimated foundation settlements summarized in this Report. We believe this to be a cost effective approach in light of the alternative solutions. However, we will address alternative foundation design options and provide appropriate recommendations if in fact the estimated total and differential settlements exceed design tolerances set forth by the project’s Structural Engineer and/or the manufacturer.

If so requested, we will evaluate the use of deep (pile) foundations such as driven concrete or auger cast piles.

The foundations in areas adjacent to the existing structure may need special consideration. It is recommended that the addition should be structurally independent of the existing structure since additional loads of the new structures on existing footings may cause detrimental settlement and unsightly cracking. For the same reason, new footings 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 footings in the critical zone which extends about 5 feet laterally from existing footings.

Bearing Pressure

We estimate that mat foundation designed with an average net contact pressure not exceeding 1,500 psf will provide satisfactory performance on this project. The foundations should be designed based on the maximum load which could be imposed by all loading conditions. We recommend utilizing a modulus of subgrade reaction of 75 pci beneath the proposed mat foundation, and coefficient of (sliding) friction of 0.4, beneath the proposed mat foundation.

The foundations should bear at a depth of at least 12 inches below the finish floor elevation to provide confinement to the bearing level soils. The thickened sections should have minimum width of 12 inches and be embedded a minimum of 12 inches.

Should the proposed addition be structurally connected, additional movement and stresses imposed on existing structural elements must be considered by the Structural Engineer. Further additional bearing pressures applied on existing footings should not exceed the maximum allowable bearing capacity previously recommended/use in design. Our recommendations provide for prudent geotechnical site preparation and foundation construction methods in light of the above conditions. Additional loads should not be imposed on the existing foundations.

Bearing Material

The foundations may bear in either the compacted suitable existing soils or compacted structural fill. 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 two feet below the foundation bearing level.

Settlement Estimates

Post-construction settlement of the structure 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. Any deviation from these recommendations could result in an increase in the estimated post-construction settlement of the structure.

Using the recommended allowable bearing pressure, the assumed maximum structural loads and the field data which we have correlated to geotechnical strength and compressibility characteristics of the subsurface soils, we estimate that total settlements of the structures could be on the order of 1 inch or less. Differential settlement result from differences in applied bearing pressures and variations in the compressibility characteristics of the subsurface soils.

Because of the subsurface conditions and the recommended site preparation and earthwork construction techniques outlined in Section 4.5, we anticipate that differential settlement of the structure could be on the order of ½ inch or less over a lateral distance of 20 feet. It should be noted that the total settlement of the proposed addition will be differential settlement with respect to the existing structure.

4.5 SITE PREPARATION

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

stripping the site of existing vegetation and topsoil, compacting the subgrade and placing necessary fill or backfill to grade with engineered fill. We recommend that the bottom of all footings be probed as 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 overlying structure. Pipes and underground utilities shall be removed and properly abandoned as per State and Local regulations. Areas disturbed by the removal of existing pipes should be backfilled in accordance with the specifications applicable to the construction.

2. Where cut operations must extend below existing buildings’ foundation/structures bearing elevations, and extend laterally within five feet of the same existing foundations, the stability of the existing foundations should be addressed by the Structural Engineer.

If excavation extends below an imaginary plane projecting downward at 1:1 (horizontal to vertical) from existing foundations, the existing foundations should either be underpinned or shoring should be designed to keep settlements of the foundations within acceptable limits. The design and installation of all necessary underpinning and shoring would be the responsibility of the contractor.

3. We recommend that existing structures in close proximity (within 50 feet) to the proposed building/construction area should be monitored for cracks or signs of distress during adjacent new excavation and building construction operations. As a prudent measure, we recommend that a pre-construction survey of the existing structures be performed to assess those buildings for current architectural and structural distress, as may be evidenced by exterior/interior vertical and horizontal surface cracking, unusual separation of building elements, and out-of-level conditions. The pre-construction survey results would provide a baseline for comparison and decision making during the building construction process.

4. If required, perform remedial dewatering prior to any earthwork operations. Dewatering operations scheduled immediately adjacent to existing structure footings should be carefully evaluated for possible impacts to the existing foundation systems. Dewatering system 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 minimize ponding of stormwater runoff.

5. Strip/demolish the proposed construction limits of all grass, roots, topsoil, above and below grade structures (foundations, etc.), debris, and other deleterious materials within and 5 feet beyond the perimeter of the proposed construction footprint. Demolition should include complete removal of all above and below grade foundations and other improvements. Excavated areas should be set back to a stable configuration or shored, in either case in accordance with OSHA requirements. Adequate bracing should be provided if necessary to prevent side slope failures.

6. Following 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.

7. Weak subgrade soils identified during proof-rolling operations should be excavated and removed from the site, and replaced with granular fill soils. We recommend that the bottom of all footings be probed as to confirm the suitability of the bearing soils. We recommend that the bottom of all footings be probed as to confirm the suitability of the bearing soils. Perform hand auger borings or cone penetrometer probe in the structures/building areas that will be constructed near the existing grade to investigate for clayey soils. If encountered, expansive clays should be removed to a minimum of 4 feet below the bottom of the footings/floor slabs. The over-excavated clayey soils should be backfilled with a compacted, low permeability, non-plastic engineered fill material (as described in Section 4.2).

8. 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.

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. Place fill material, as required. The fill material can consist of material as illustrated in the “Fill Suitability” section of this report. Offsite fill (import) shall consist of sand with less than 10 percent soil fines, unless a low-permeability backfill material is needed. Place backfill and 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. Compaction operations should extend to the limits of the cleared/grubbed project areas. Compaction operation 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 structure/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.

11. Care should be exercised to avoid damaging any nearby structures while the compaction operation is underway. Compaction should cease if deemed detrimental to adjacent structures. Universal Engineering Sciences 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.

12. Test the subgrade for compaction at a frequency of not less than one test per 2,500 square feet in the structure area, or a minimum of three test locations per structure, whichever is greater.

4.6 SUITABILITY OF EXCAVATED SOILS

The recovered soil samples were classified using visual and textural means, and limited laboratory testing. We offer below preliminary guidelines for the use of on-site soils, such as those excavated from the proposed structure, as fill material for the project.

Soil materials excavated and classified as fine sands to slightly silty fine sands (SP, SP-SM), with typically 12% fines or less (silt/clay fraction), may be considered suitable for use as utility trench backfill, as well as building pad and pavement subgrade structural fill, provided said materials are properly dried, placed, and compacted.

Soil materials excavated and classified as silty to slightly clayey fine sands (SM, SP-SC), with typically 12% to 25% fines, may also be considered suitable for use as utility trench backfill, as well as building pad and pavement subgrade structural fill, after significant drying and some mixing with the fine sand material described above. Proper placement, proof rolling and compaction must also be performed.

Soil materials excavated and classified as clayey sand silt or clay (SC, ML, MH, CL, and CH) and any organic-laden soils (5% or greater organics by weight) should not be reused as fill beneath buildings or pavement sections. These materials could be used in green areas, if applicable and in non-structural applications where excessive ground subsidence will not create functional or aesthetic problems.

5.0 REPORT LIMITATIONS

This Report has been prepared for the exclusive use of Gainesville Regional Utilities, and members of the Design/Construction Team for the specific project discussed in this Report. This Report has been prepared in accordance with generally accepted local geotechnical engineering practices; no other warranty is expressed or implied.

Because of the natural limitations inherent in working with the subsurface, it is not possible for a geotechnical engineer to predict and address all possible problems. A GBA publication, "Important Information About Your Geotechnical Engineering Report" appears in Appendix B, and will help explain the nature of geotechnical issues. Additional limitations are presented in General Conditions also included in Appendix B. Further, we present documents in Appendix B:

Constraints and Restrictions, to bring to your attention the potential concerns and the basic limitations of a typical geotechnical report.

APPENDIX A

Boring Location Plan

Boring Logs

Key to Boring Logs

APPENDIX B

Important Information About Your Geotechnical Engineering Report

Constraint and Restrictions

Geotechnical-Engineering Report Important Information about This

Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes.

While you cannot eliminate all such risks, you can manage them. The following information is provided to help.

The Geoprofessional Business Association (GBA) has prepared this advisory to help you – assumedly a client representative – interpret and apply this geotechnical-engineering report as effectively as possible. In that way, clients can benefit from a lowered exposure to the subsurface problems that, for decades, have been a principal cause of construction delays, cost overruns, claims, and disputes. If you have questions or want more information about any of the issues discussed below, contact your GBA-member geotechnical engineer.

Active involvement in the Geoprofessional Business Association exposes geotechnical engineers to a wide array of risk-confrontation techniques that can be of genuine benefit for everyone involved with a construction project.

Geotechnical-Engineering Services Are Performed for Specific Purposes, Persons, and Projects Geotechnical engineers structure their services to meet the specific needs of their clients. A geotechnical-engineering study conducted for a given civil engineer will not likely meet the needs of a civil-works constructor or even a different civil engineer. Because each geotechnical-engineering study is unique, each geotechnical-engineering report is unique, prepared solely for the client. Those who rely on a geotechnical-engineering report prepared for a different client can be seriously misled. No one except authorized client representatives should rely on this geotechnical-engineering report without first conferring with the geotechnical engineer who prepared it. And no one

– not even you – should apply this report for any purpose or project except the one originally contemplated.

Read this Report in Full Costly problems have occurred because those relying on a geotechnical-engineering report did not read it in its entirety. Do not rely on an executive summary. Do not read selected elements only. Read this report in full.

You Need to Inform Your Geotechnical Engineer about Change Your geotechnical engineer considered unique, project-specific factors when designing the study behind this report and developing the confirmation-dependent recommendations the report conveys. A few typical factors include:

• the client’s goals, objectives, budget, schedule, and risk-management preferences;

• the general nature of the structure involved, its size, configuration, and performance criteria;

• the structure’s location and orientation on the site; and

• other planned or existing site improvements, such as retaining walls, access roads, parking lots, and underground utilities.

Typical changes that could erode the reliability of this report include those that affect:

• the site’s size or shape;

• the function of the proposed structure, as when it’s changed from a parking garage to an office building, or from a light-industrial plant to a refrigerated warehouse;

• the elevation, configuration, location, orientation, or weight of the proposed structure;

• the composition of the design team; or

• project ownership.

As a general rule, always inform your geotechnical engineer of project changes – even minor ones – and request an assessment of their impact. The geotechnical engineer who prepared this report cannot accept responsibility or liability for problems that arise because the geotechnical engineer was not informed about developments the engineer otherwise would have considered.

This Report May Not Be Reliable Do not rely on this report if your geotechnical engineer prepared it:

• for a different client;

• for a different project;

• for a different site (that may or may not include all or a portion of the original site); or

• before important events occurred at the site or adjacent to it; e.g., man-made events like construction or environmental remediation, or natural events like floods, droughts, earthquakes, or groundwater fluctuations.

Note, too, that it could be unwise to rely on a geotechnical-engineering report whose reliability may have been affected by the passage of time, because of factors like changed subsurface conditions; new or modified codes, standards, or regulations; or new techniques or tools. If your geotechnical engineer has not indicated an “apply-by” date on the report, ask what it should be, and, in general, if you are the least bit uncertain about the continued reliability of this report, contact your geotechnical engineer before applying it. A minor amount of additional testing or analysis – if any is required at all – could prevent major problems.

Most of the “Findings” Related in This Report Are Professional Opinions Before construction begins, geotechnical engineers explore a site’s subsurface through various sampling and testing procedures.

Geotechnical engineers can observe actual subsurface conditions only at those specific locations where sampling and testing were performed. The data derived from that sampling and testing were reviewed by your geotechnical engineer, who then applied professional judgment to form opinions about subsurface conditions throughout the site. Actual sitewide-subsurface conditions may differ – maybe significantly – from those indicated in this report. Confront that risk by retaining your geotechnical engineer to serve on the design team from project start to project finish, so the individual can provide informed guidance quickly, whenever needed.

This Report’s Recommendations Are Confirmation-Dependent The recommendations included in this report – including any options or alternatives – are confirmation-dependent. In other words, they are not final, because the geotechnical engineer who developed them relied heavily on judgment and opinion to do so. Your geotechnical engineer can finalize the recommendations only after observing actual subsurface conditions revealed during construction. If through observation your geotechnical engineer confirms that the conditions assumed to exist actually do exist, the recommendations can be relied upon, assuming no other changes have occurred. The geotechnical engineer who prepared this report cannot assume responsibility or liability for confirmation-dependent recommendations if you fail to retain that engineer to perform construction observation.

This Report Could Be Misinterpreted Other design professionals’ misinterpretation of geotechnical-engineering reports has resulted in costly problems. Confront that risk by having your geotechnical engineer serve as a full-time member of the design team, to:

• confer with other design-team members,

• help develop specifications,

• review pertinent elements of other design professionals’ plans and specifications, and

• be on hand quickly whenever geotechnical-engineering guidance is needed.

You should also confront the risk of constructors misinterpreting this report. Do so by retaining your geotechnical engineer to participate in prebid and preconstruction conferences and to perform construction observation.

Give Constructors a Complete Report and Guidance Some owners and design…