RFQ_24_25-10_Attachment_4_-_Geotech_Report_SMWTP_Improvements.pdf

Prepared for:

Carollo 200 Robinson Street, Suite 1400

Orlando, FL 32801

Prepared by:

Nadic Engineering Services, Inc.

601 N. Hart Blvd

Orlando, Florida 32818 407-521-4771

Consultants in: Civil ꞏ Environmental ꞏ Geotechnical Engineering Offices in: Orlando ꞏ Miami

Geotechnical Engineering Report Facility Plan for Sanford Main Water

Treatment Plant (SMWTP) Improvements

City of Sanford, Florida Seminole County, Florida

NADIC Project No.: PR.GEO-CV24061

April 17, 2025

200 Robinson Street, Suite 1400 Orlando, Florida 32801

Attention: Ms. Erica Stone, PhD, P.E.

Project Manager/Vice President

Re: Geotechnical Engineering Report

Facility Plan for Sanford Main Water Treatment Plant (SMWTP) Improvements City of Sanford, Florida

NADIC Project No. PR.GEO-CV24061

Dear Ms. Stone:

Nadic Engineering Services, Inc. (NADIC) is pleased to submit this subsurface exploration and geotechnical engineering report for the proposed improvements at the Sanford Main Water Treatment Plant (SMWTP), located at 3701 Country Club Road in Seminole County, Florida.

This report presents the findings of our field exploration methods and our recommendations to support the preparation of engineering design plans and technical specifications, as well as construction support services for the proposed SMWTP improvements. This evaluation was authorized through a subconsultant agreement between Carollo and NADIC dated February 4th, 2025.

NADIC appreciates the opportunity to be of service to Carollo and the City of Sanford in connection with the SMWTP Improvements in Sanford, Florida. We look forward to a continued association. Please contact us if you have any questions, or if we may be of further assistance to you as this project proceeds.

Sincerely, NADIC ENGINEERING SERVICES, INC.

Engineering Business No. 8214

Maria Bridges, M.S., E.I. Godwin N. Nnadi, Ph.D., P.E.

Staff Engineer Principal Engineer FL Registration No: 50637

C:\...\PR.GEO-CV24061 - City of Sanford Main WTP Upgrades\Project Working File\Report

Facility Plan for SMWTP Improvements April 17, 2025 NADIC Project No.: PR.GEO-CV24061 Page i of ii

NADIC

TABLE OF CONTENTS

1.0 EXECUTIVE SUMMARY

2.0 PROJECT LOCATION AND DESCRIPTION

2.1 Existing Site Condition

3.0 PURPOSE AND SCOPE OF SERVICES

4.0 REVIEW OF AVAILABLE PUBLISHED DATA

4.1 General

4.2 USGS Topographic Map

4.3 USDA/NRCS Soil Survey

4.4 Potentiometric Surface

4.5 Generalized Geology

5.0 FIELD EXPLORATION PROGRAM AND METHOD

5.1 Field Exploration Program

5.2 Field Exploration Methods

5.2.1 Standard Penetration Test (SPT) Borings

6.0 GENERALIZED SUBSURFACE CONDITIONS

6.1 Boring Results

6.2 Groundwater

7.0 LABORATORY TESTING

8.0 EVALUATION AND RECOMMENDATIONS

8.1 General

8.2 Site Suitability

8.3 Groundwater Control

8.4 Geotechnical Design Parameters

8.5 Foundation Considerations

8.5.1 Foundation Settlement

8.5.2 Foundation Construction Considerations

8.5.3 Floor Slab Construction Considerations

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TABLE OF CONTENTS CONTINUED

8.6 Pipeline Foundations

8.7 Pipeline Settlement

8.8 Lateral Earth Pressures

9.0 CONSTRUCTION CONSIDERATIONS

9.1 Site Preparation

9.2 Structural Fill

9.3 Excavations

9.4 Dewatering

10.0 CONSTRUCTION RELATED SERVICES

11.0 REPORT LIMITATIONS

APPENDICES

Appendix A

Figure 1 Vicinity Map Figure 2 USGS Topographic Map Figure 3 USDA/NRCS Soils Map Figure 4 Boring Location Map

Table 4 Summary of Laboratory Test Results Table 5 Summary of Corrosion Test Results Table 7 Soil Design Parameters Historical Aerial Photographs

Appendix B

Sheets 1 to 7 Report of SPT Borings

Appendix C

Settlement Analysis

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NADIC

1.0 EXECUTIVE SUMMARY

Nadic Engineering Services, Inc. (NADIC) was retained by Carollo to conduct geotechnical engineering investigation for the proposed improvements at the Sanford Main Water Treatment Plant (SMWTP) in accordance with the City of Sanford requirements and guidelines. The purpose of the exploration was to explore subsurface conditions and groundwater conditions to provide recommendations for the proposed improvements. Our investigation was in regard to the following improvements:

New building for the Electrical Room, UV AOP Room, and Hydrogen Peroxide Storage and Feed

New Outdoor Slab around Static Mixer New GAC Contactors and Backwash System Two (2) Ground Storage Tanks.

To accomplish the investigation, the following procedures were carried out:

Visited site to evaluate existing conditions Completed five (5) Standard Penetration Test (SPT) borings to a depth of 40 feet below existing grade and 10 SPT borings to a depth of 80 feet below existing grade Measured existing groundwater table Performed engineering evaluation based on the results of the field exploration.

The investigation focused on the evaluation of the subsurface conditions at the location of the proposed improvements to evaluate geotechnical foundation alternatives and site preparation requirements for construction. Based on the results of the exploration, NADIC concluded the following:

Excavation cut for utilities should be a supported vertical cut due to space limitation, where restrictions do not permit excavation to be appropriately sloped

Use a maximum allowable bearing pressure of 2,500 pounds per square foot (psf) for footing bearing on top and laterally against the natural soils

Use unfactored coefficient of subgrade reaction of 130 lb/in3.

Some forms of dewatering may be required to achieve the necessary compaction if construction commences during the wet period Any areas of soft yielding or unsuitable materials encountered at the site shall be excavated and replaced with clean sands and compacted in accordance with the City of Sanford Utilities Standards and Specifications Manual

Site preparations, excavations, structural filling and backfilling should be in accordance with the City of Sanford Utilities Standards and Specifications Manual

A representative number of in-place field density tests should be performed in each lift of structural fill to ensure the required degree of compaction has been achieved in compliance with the City of Sanford Engineering Standards and Requirements.

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NADIC

This summary should be used in conjunction with the entire report for design purposes. The following report presents the results, conclusions, and recommendations resulting from the geotechnical exploration at this site.

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2.0 PROJECT LOCATION AND DESCRIPTION

We understand that the City of Sanford plans to improve the existing SMWTP located at 3701 Country Club Road in Seminole County, Florida. The current SMWTP is an existing 5.3 million gallons per day (MGD) annual average daily flow (AADF) wastewater treatment plant. We further understand that the proposed structures will be supported by shallow foundations and that each Ground Storage Tank will have a 0.7-million-gallon water capacity.

Based on information obtained from Carollo, the SMWTP project consists, among other project elements, preparation of design plans and construction bid documents for the following proposed structures:

New building for the Electrical Room, UV AOP Room, and Hydrogen Peroxide Storage and Feed

New Outdoor Slab around Static Mixer New GAC Contactors and Backwash System Two (2) Ground Storage Tanks.

The proposed improvements are generally located within Section 37, Township 19 South, and Range 30 East in Sanford, Florida. A Vicinity map showing the approximate location of the proposed improvements is shown on Figure 1 in Appendix A.

This report presents the findings of our subsurface exploration program, an evaluation of the soil and groundwater encountered, and provides recommendations to support the design and construction of the proposed improvements. The dimension and loading conditions of the structure as provided by Carollo except otherwise stated are presented on Table 1 below.

Table 1: Foundation Design Loads

Structure Approximate Foundation Footprint

Depth of Foundation

(feet)

Foundation Pressure

(psf) Electrical Room, UV AOP Room, Hydrogen Peroxide Storage and Feed Building 104 ft x 58 ft 2* 1200

Outdoor Slab around Static Mixer 17 ft x 72 ft 2* 500* GAC Contactors and Backwash System 122 ft x 54 ft 2* 800*

Ground Storage Tanks 61 ft diameter each 2* 3200 psf: pounds per square foot *Assumed

The recommendations presented in this report are based on the above information. If any of the information or assumptions are not correct, please contact us immediately to review and/or amend the recommendations presented herein. This exploration was performed in accordance with generally accepted soil and foundation engineering practices. No other warranty expressed or implied is made.

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NADIC

2.1 Existing Site Condition

Project site historical aerials from Google Earth Pro were reviewed. The 1994 aerial photograph show that two (2) Ground Storage Tanks, the Water Treatment Plant structure and Reclaimed Water Operations Building had been constructed, and the rest of the site generally covered with grass and trees. The 2006 aerial photograph show that a Reclaimed Water Ground Storage Tank was constructed. Expansion of the water treatment facility and construction of the Main Water Treatment Plant Operations began in 2021 and was completed by 2024. The Water Treatment Plant structure was demolished by 2025. Selected Historical Aerial Photographs of the project site are presented in Appendix A.

3.0 PURPOSE AND SCOPE OF SERVICES

The purpose of this exploration was to evaluate the shallow subsurface conditions at the site and to provide recommendations related to:

Subsurface soil and groundwater conditions Foundation design and construction Floor slab design and construction Earthwork, including subgrade preparation.

Our approach is in general accordance with the Florida Department of Transportation (FDOT), “Soils and Foundation Manual” and the City of Sanford Utilities Standards and Specifications Manual.

The following services were provided to achieve the preceding objectives:

1. Reviewed readily available published geologic and topographic information. This published information was obtained from the appropriate Quadrangle Maps published by the United States Geological Survey (USGS) and “Soil Survey of Seminole County, Florida.” Published by the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS)

2. Performed site reconnaissance to evaluate existing conditions and drilling accessibility

3. Performed a total of five (5) Standard Penetration Test (SPT) borings to a depth of 40 feet below existing grade for the proposed Electrical Room, UV AOP Room, and Hydrogen Peroxide Storage and Feed Building, Outdoor Slab and GAC Contactors and Backwash System

4. Performed a total of 10 Standard Penetration Test (SPT) borings to a depth of 80 feet below existing grade for the proposed Ground Storage Tanks

5. Measured encountered groundwater table in the borings and estimated normal wet seasonal high groundwater table depths

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NADIC

6. Visually classified and stratified representative soil samples as per ASTM D-3282 and D-

7. Prepared this formal engineering report summarizing the field exploration, laboratory tests, engineering analyses, evaluation and recommendations.

4.0 REVIEW OF AVAILABLE PUBLISHED DATA

4.1 General

To obtain general information on soil and ground water conditions at the project site, NADIC reviewed data including aerial maps, United States Geological Survey (USGS), Quadrangle Topographic Maps, and the United States Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS) Soil Survey for Seminole County, Florida. A summary of this information is presented below in the following report section. A map of the site location is shown on Figure 1 in Appendix A.

4.2 USGS Topographic Map

The "Sanford, Florida" USGS Topographic Map issued in 2024 was reviewed. The map shows the ground surface elevation in the project vicinity of about +50 feet, North American Vertical Datum of 1988 (NAVD-88). The project site is shown on an excerpt of the USGS topographic map presented on Figure 2 in Appendix A.

4.3 USDA/NRCS Soil Survey

The "Soil Survey of Seminole County, Florida" published by the United States Department of Agriculture (USDA), Natural Resource Conservation Service (NRCS) was reviewed for general near-surface soil information within the general project vicinity. More specifically, the following table describes the primary mapping units within the vicinity of the proposed construction. A reproduction of the USDA/NRCS map for the project is presented on Figure 3 in Appendix A.

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Table 2: USDA/NRCS Soil Survey Summary

Soil Unit Depth

(in) Soil Description USCS* USDA

SHGWT** (ft) Risk of Corrosion

Uncoated Steel Concrete Adamsville

(2) 0 – 4 Fine sand SP-SM 2 – 3.5 Low Moderate4 – 80 Fine sand, sand SP-SM, SP

Sparr (2)

0 – 4 Fine sand SP-SM, SM

1.5 – 3.5

Moderate

High

4 – 41 Sand, fine sand SP-SM, SM

41 – 43 Sandy loam, sandy clay loam, fine sandy loam SM-SC, SC, SM

43 – 72 Sandy clay, sandy clay loam, sandy loam SC, SM-SC

72 – 80 Sandy clay loam, sandy loam, fine sandy loam SC, SM-SC, SM

Tavares (31)

0 – 6 Fine sand SP, SP-SM 3.5 – 6 Low High 6 – 80 Sand, fine sand SP, SP-SM

Millhopper (31)

0 – 45 Fine sand SP-SM, SM

3.5 – 6 Low Moderate45 – 80 Sandy loam, fine sandy loam, sandy clay loam SM, SM-SC, SC *USCS: Unified Soil Classification System **SHGWT: Seasonal High Groundwater Table

Information contained in the NRCS Soil Survey is very general and may be outdated due to recent development in the site vicinity. Therefore, it may not reflect the actual soil and groundwater conditions, particularly where developments may have modified soil conditions or surface and near surface drainage.

It should be noted that the NRCS Soil Survey is not intended as a substitute for site-specific geotechnical exploration; rather it is a useful tool for planning a project scope by providing surficial soil types likely to be encountered.

Boundaries between adjacent soil types on the Soil Survey maps are approximate.

4.4 Potentiometric Surface

Based on review of data provided by the Florida Department of Environmental Protection, Florida Geological Survey titled “Upper Floridian Aquifer Potentiometric Surface, Florida, September 2023”, the elevation of the potentiometric surface in the vicinity of the project site appears to be approximately +30 feet, NAVD-88.

4.5 Generalized Geology

The geology of the Central Florida area is characterized by sedimentary strata formed during three distinct geologic periods. The surficial stratum is composed of undifferentiated Holocene/Pleistocene/Pliocene age sands containing varying amounts of silt and clay, which extend typically to depths on the order of 40 feet to 60 feet below the ground surface. This upper, mostly sandy zone contains the surficial aquifer (water table). A Miocene age deposit, the Hawthorn

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NADIC

Formation, frequently underlies the surficial sands and is typically composed of clay, clayey sands and sandy limestone sometimes containing appreciable amounts of phosphate. This stratum extends to typical depths of 80 to 120 feet beneath the existing ground surface and serves as the confining layer for the underlying Floridian Aquifer.

The Eocene age Ocala and Avon Park limestone formations are contained in the Floridian Aquifer, which is one of the most productive aquifers in the world. The extremely high productivity of this aquifer is directly related to its numerous cavities and interconnected channels. The deepest formation of the Eocene age is the Avon Park limestone. The Avon Park limestone consists mostly of hard brown dolostone and tan, granular limestone. Above the Avon Park limestone is the Ocala limestone.

The Ocala limestone is a loose to moderate well cemented mass of very small to large microfossils with much less dolostone than the Avon Park limestone. Typically, the Ocala limestone contains almost pure limestone with no dolostone, although the lower few feet can be partly dolomitized in some areas.

5.0 FIELD EXPLORATION PROGRAM AND METHOD

5.1 Field Exploration Program

To evaluate the subsurface and surface conditions at the proposed construction locations; property access, boring locations and utility location was coordinated through Carollo. The subsurface condition at the project site was evaluated by performing five (5) SPT borings of 40 feet deep each, and 10 SPT borings 80 feet deep each below existing grade within the footprint of the proposed improvements.

The borings were staked in the field by L&S Diversified. Due to utility conflict, some of the borings were relocated about five (5) feet to 15 feet from their original location by NADIC, upon notifying Carollo.

Upon completion of groundwater level measurement, borings were backfilled with natural soils and cement bentonite grout for safety. The results of the exploration program are presented on Sheets 1 through 7 in Appendix B.

5.2 Field Exploration Method

5.2.1 Standard Penetration Test (SPT) Borings

The SPT borings performed at the proposed project site were conducted in general conformance with American Society for Testing and Materials (ASTM) test designation D-1586. The borings were advanced by the rotary wash method with bentonite based mud as the circulating fluid to stabilize the borehole. Borings were performed continuously from the ground surface to 10 feet and at 5-foot depth intervals thereafter. After seating the sampler six inches, the number of successive blows required to drive the sampler 12 inches into the soil constitutes the test result commonly referred to as the “N” value. Adjacent to the SPT boring profiles are the “N” values.

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NADIC

The “N” value has been empirically correlated with various soil properties and is considered indicative of the relative density of cohesionless soils and the consistency of cohesive soils.

All recovered samples were described in the field by the driller and reviewed therein by a senior geotechnical field technician. Representative portions of the samples placed in airtight bags and transported to our office for visual classification by an engineer. Following completion and groundwater measurements, the SPT borings were backfilled for safety.

6.0 GENERALIZED SUBSURFACE CONDITIONS

The results of the field exploration and laboratory testing programs are presented on Sheets 1 through 7 in Appendix B. The profiles include observed soil strata, groundwater levels, and the SPT 'N'-values. The SPT borings were backfilled upon completion of the drilling operation for safety.

The soil classification and stratification shown on the report of SPT Borings are based on visual examination of the recovered soil samples, limited number of laboratory tests and interpretation of the field boring logs by a geotechnical engineer. Stratification lines shown on the boring profiles represent the approximate boundaries between soil types of significantly different engineering properties. The actual transition between soils may be gradual.

The boring profiles indicate subsurface conditions only at the specific boring locations at the time of our field exploration. Subsurface conditions, including groundwater conditions may differ from the conditions we encountered at the boring location at other locations within the project site. In addition, subsurface conditions at the boring locations can change over time.

The following generalized soil descriptions are intended to provide a summary of the observed subsurface conditions at the proposed construction location. A specific description of the soil conditions encountered and relative density is provided with the soil profiles.

6.1 Boring Results

A total of 15 SPT Borings were completed for the new structures as requested. The borings encountered the following general soil profiles and are presented on Sheets 1 to 7 in Appendix B:

Stratification lines… represent the approximate boundaries between soil types... actual transition between soils may be gradual.

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Table 3: Generalized Subsurface Profiles

Structure Boring

ID

Approx.

Latitude & Longitude

Approx.

Layer

Depth (ft) Soil Description

Range of N-Values

(blows/foot) Electrical

Room B-1 28°47'10.35"N, 81°19'6.19"W 0 – 40 Loose to medium dense brown to gray fine SAND with silt (SP-SM) 3* – 12

UV AOP

Room

B-2 28°47'10.33"N, 81°19'6.77"W 0 – 40 Loose to medium dense brown to gray fine SAND with silt (SP-SM) 3* – 14

B-3 28°47'9.83"N, 81°19'6.65"W 0 – 40

Loose to medium dense brown to gray fine SAND with silt (SP-SM) with an interbedded layer of medium dense light brown silty SAND (SM)

3* – 13

Hydrogen Peroxide

Storage and Feed

B-4 28°47'9.49"N, 81°19'6.19"W 0 – 40

Loose to medium dense brown to gray fine SAND with silt (SP-SM) with an interbedded layer of medium dense light brown silty SAND (SM)

3* – 12

GAC

Contactors and Backwash

System

B-5 28°47'9.36"N, 81°19'7.29"W

0 – 12.5

Loose brown to light brown fine SAND, trace silt, roots and limerock fragments (SP) to loose light brown fine SAND with clay (SP-SC) and medium dense light brown fine SAND with silt (SP-SM)

3* – 8

12.5 – 17.5 Stiff light brown with yellow stain clayey SAND

(SC) 10

17.5 – 40 Medium dense light brown silty SAND (SM) to medium dense light brown to light gray fine SAND with silt (SP-SM)

14 – 17

Ground Storage

Tank No. 1

B-7 28°47'5.66"N 81°19'6.68"W

0 – 12.5 Loose brown fine SAND with silt (SP-SM) to firm to stiff yellowish brown clayey SAND (SC)

4 – 10

12.5 – 47.5 Medium dense light brown to light gray fine SAND with silt (SP-SM) to medium dense light brown to light gray silty SAND (SM)

8 – 13

47.5 – 72.5

Interleaved layers of stiff brown to gray clayey SAND (SC) and stiff to very stiff brown to gray sandy CLAY (CL), occasionally with shell and dolostone fragments

8 – 21

72.5 – 80 No sample recovery 50

B-8 28°47'5.78"N 81°19'6.27"W

0 – 12.5 Loose brown fine SAND with silt (SP-SM) to soft to firm yellowish brown to gray clayey SAND (SC)

2 – 5

12.5 – 57.5 Medium dense light brown to light gray fine SAND with silt (SP-SM) to medium dense light brown to light gray silty SAND (SM)

9 – 15

57.5 – 80 Stiff light brown to light gray clayey SAND, trace shell fragments (SC) to stiff to very stiff brown to gray sandy CLAY with phosphate fragments (CL)

10 – 14

3* = Assumed “N” value for hand augered depth

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Table 3 Continued: Generalized Subsurface Profiles

Approx.

Latitude & Longitude

Approx.

Layer

Depth (ft) Soil Description

Range of N-Values

(blows/foot)

Ground Storage

Tank No. 1

B-9 28°47'5.42"N 81°19'6.60"W

0 – 8 Loose light brown fine SAND with clay (SP-SC) to firm to stiff yellowish brown to gray clayey SAND

(SC)

4 – 12

8 – 57.5

Medium dense yellowish brown silty SAND (SM) to loose to medium dense light brown to light gray fine SAND with silt (SP-SM) followed by medium dense light brown to light gray silty SAND (SM)

7 – 13

57.5 – 77.5

Stiff to very stiff light brown to light gray clayey SAND with shell, phosphate and dolostone fragments (SC) followed by stiff to very stiff brown to gray sandy CLAY with phosphate and shell fragments (CL)

12 – 16

77.5 – 80 No sample recovery 50

B-10 28°47'5.18"N 81°19'6.69"W

0 – 8 Loose light brown fine SAND with clay (SP-SC) to stiff yellowish brown clayey SAND (SC) 4 – 11

8 – 57.5

Medium dense yellowish brown silty SAND (SM) to medium dense light brown to light gray fine SAND with silt (SP-SM) followed by medium dense yellowish brown silty SAND with dolostone and shell fragments (SM)

8 – 13

57.5 – 72.5 Stiff gray sandy CLAY, trace shell fragments (CL) to stiff yellowish brown clayey SAND (SC) 10

72.5 – 77.5 Very dense gray silty DOLOSTONE (DS) 50

77.5 – 80 No sample recovery 50

B-11 28°47'5.12"N 81°19'6.20"W

0 – 2 Soft to firm yellowish brown clayey SAND (SC) 3

2 – 52.5

Loose to medium dense light brown to light gray silty SAND (SM) to loose to medium dense light brown to light gray to yellowish brown fine SAND with silt (SP-SM)

4 – 13

52.5 – 72.5

Stiff to very stiff gray to brown sandy CLAY occasionally with phosphate and dolostone fragments (CL) with an interbedded layer of stiff brown clayey SAND (SC)

8 – 15

72.5 – 77.5 Very dense gray silty DOLOSTONE with phosphate fragments (DS) 50

77.5 – 80 No sample recovery 50

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Approx.

Latitude & Longitude

Approx.

Layer

Depth (ft) Soil Description

Range of N-Values

(blows/foot)

Ground Storage

Tank No. 2

B-12 28°47'4.65"N 81°19'6.35"W

0 – 12.5 Yellowish brown to gray clayey SAND (SC) 5 – 12

12.5 – 57.5

Medium dense light brown to light gray to yellowish brown silty SAND occasionally with shell fragments (SM) with an interbedded layer of medium dense light brown to light gray fine SAND with silt (SP-SM)

10 – 13

57.5 – 77.5

Interleaved layers of stiff to very stiff dray to dark brown sandy CLAY (CL) and stiff to hard brown clayey SAND occasionally with shell, phosphate and dolostone fragments (SC)

11 – 50

77.5 - 80 Very dense brown silty DOLOSTONE with phosphate fragments (DS)

B-13 28°47'4.88"N 81°19'6.54"W

0 – 12.5 Firm to very stiff yellowish brown to gray clayey

SAND (SC)

4 – 13

12.5 – 52.5

Medium dense light brown to light gray to yellowish brown silty SAND (SM) with an interbedded layer of medium dense light brown to light gray fine SAND with silt (SP-SM)

10 – 12

52.5 – 72.5

Stiff to very stiff yellowish brown to light brown to light gray clayey SAND with shell fragments (SC) with an interbedded layer of stiff gray sandy CLAY with shell fragments (CL)

9 – 12

72.5 – 80 Very dense gray silty DOLOSTONE with phosphate fragments (DS)

B-14 28°47'4.89"N 81°19'6.26"W

0 – 12.5 Firm to very stiff yellowish brown to gray clayey

SAND (SC)

6 – 13

12.5 – 67.5

Medium dense light brown to light gray to yellowish brown silty SAND occasionally trace organic and phosphate fragments (SM) with an interbedded layer of medium dense light brown to light gray fine SAND with silt (SP-SM)

8 – 12

67.5 – 77.5 Very stiff yellowish brown clayey SAND, trace organic and phosphate fragments (SC) to very stiff dark brown sandy CLAY (CL)

13 – 15

77.5 – 80 Very dense gray DOLOSTONE (DS) 50

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Approx.

Latitude & Longitude

Approx.

Layer

Depth (ft) Soil Description

Range of N-Values

(blows/foot)

Ground Storage

Tank No. 2

B-15 28°47'4.45"N 81°19'6.19"W

0 – 2 Loose brown fine SAND with clay, trace roots (SP-

SC)

2 – 12.5 Stiff yellowish brown to gray clayey SAND (SC) 10 – 11

12.5 – 62.5 Medium dense light brown to light gray silty SAND (SM) to medium dense light brown to light gray fine SAND with silt (SP-SM)

10 – 14

62.5 – 67.5 Stiff gray clayey SAND (SC) 11

67.5 – 80 Very dense gray silty DOLOSTONE with phosphate fragments (DS)

B-16 28°47'4.46"N 81°19'6.73"W

0 – 6 Loose to medium dense light brown to light gray fine SAND with silt (SP-SM)

4 – 8

6 – 22.5 Stiff yellowish brown to gray clayey SAND (SC) 10 – 11

22.5 – 80

Medium dense light brown to light gray fine SAND with silt (SP-SM) with an interbedded layer of medium dense gray to brown silty SAND with shell and phosphate fragments (SM)

10 – 12

Drilling fluid losses were not encountered in the borings.

6.2 Groundwater

Groundwater levels were measured in the boreholes after completion of each boring and prior to backfilling operations. Groundwater was encountered in the borings at depths between 5 feet and

15.5 feet below existing ground surface at the time of our field investigation (February 2025).

It should be recognized that fluctuations of the groundwater table will occur due to the seasonal variations in the amount of rainfall, runoff, and other factors not evident at the time the borings were performed. In addition, perched water can develop within higher permeability soils overlaying less permeable soils. Therefore, groundwater levels during construction or at other times in the future may be higher or lower than the levels indicated on the boring logs.

For the purpose of this report, estimated seasonal high groundwater levels are defined as groundwater levels that are anticipated at the end of wet season of a "normal rainfall year" under current site conditions. The estimated seasonal high groundwater levels presented next in the boring profiles (Sheets 1 to 7 in Appendix B) are based on the soil stratigraphy, measured groundwater levels, USDA/NRCS information, and past experience with similar soil conditions.

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NADIC

7.0 LABORATORY TESTING

Representative soil samples were retained from the strata obtained from each boring and returned to NADIC’s laboratory for visual classification and stratification in accordance with ASTM D-2487 “Standard Classification of Soils for Engineering Purposes” (Unified Soil Classification System).

Selected soil samples were tested to aid in classifying the soils and to help in evaluating the general engineering characteristics of the recovered soils. The results of our laboratory testing are presented on Table 4 in Appendix A and on Sheets 1 to 7 in Appendix B.

Environmental corrosion tests (pH, resistivity, chloride content, and sulfate content) were also performed on selected samples from Borings B-2, B-4, B-5, B-9, and B-12. The corrosion tests were performed in accordance with FDOT Structural Design Guidelines. The environmental classifications for the structures are presented in the Report of SPT Borings on Sheets 1, 2, 4 and 5 in Appendix B and Table 5 in Appendix A and should be classified as follows:

Boring B-2: Moderately aggressive for use of Steel and slightly aggressive for use of Concrete (pH = 7.9 and Resistivity = 6,280 ohm-cm)

Boring B-4: Moderately aggressive for use of Steel and moderately aggressive for use of Concrete (pH = 7.7 and Resistivity = 1,490 ohm-cm)

Boring B-5: Moderately aggressive for use of Steel and slightly aggressive for use of

Concrete (pH = 8.0 and Resistivity = 9,920 ohm-cm)

Boring B-9: Slightly aggressive for use of Steel and slightly aggressive for use of Concrete (pH = 7.6 and Resistivity = 14,230 ohm-cm)

Boring B-12: Moderately aggressive for use of Steel and slightly aggressive for use of

Concrete (pH = 7.2 and Resistivity = 8,900 ohm-cm).

8.0 EVALUATION AND RECOMMENDATIONS

8.1 General

The following recommendations have been developed based on the previously described project characteristics, the results of a limited subsurface exploration, and experience with similar projects. If the proposed improvements change from those previously discussed, NADIC requests to have the opportunity to review and possibly amend our recommendations with respect to those changes.

Furthermore, evaluation and recommendations contained in this report are based in part on the data obtained from a visual classification and groundwater measurements obtained from the borings. The exploration methods used indicate subsurface conditions at a specific boring location, only at the time it was performed and to the depth penetrated. Borings cannot be relied upon to accurately reflect the variations that usually exist between boring locations and these variations

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may not become evident until construction. If variations from the conditions described in this report become evident during construction, or project characteristics described in this report change, NADIC should be retained to re-evaluate the conclusions and recommendations contained in this report in light of such changes.

The following recommendations are provided based on preliminary concept and design assumptions previously described, and on subsurface conditions encountered during our field exploration. Based on the above we feel that conventional earthwork equipment and techniques can be used during the site clearing, grubbing and densification of in-situ and fill materials. They are deemed adequate and should render the site suitable for construction. Design and construction of the proposed project should be cognizant of the groundwater table at the site.

8.2 Site Suitability

Based on the results of our exploration, the encountered subsurface materials are generally suitable for construction and support of the anticipated foundations and floor slabs, provided proper subgrade preparation is performed.

Prior to construction, any underground utilities and impermeable obtrusions within the construction area should be established. In this regard, it should be noted that if buried utility lines and pipes are not properly removed or plugged, they may serve as a conduit for subsurface erosion which subsequently may result in excessive settlement.

It is our recommendation based on the results of the field exploration that the footprints of all new structures plus five (5) feet beyond the outside edge of the footprints should be prepared with the objective being to minimize settlements and differential settlements.

8.3 Groundwater Control

The groundwater table fluctuates seasonally depending upon intensity and duration of rainfall and presence and proximity of any artificial drainage facilities. Based upon our observations at the site, observations in the borings, review of historical ground water level records in Central Florida and the USDA/NRCS Soil Survey of Seminole County, Florida, it is NADIC’s opinion that the seasonal high groundwater level should be as presented next to the boring profiles (Sheets 1 to 7 in Appendix B).

Some form of dewatering may be required to achieve the required compaction if construction commences during the wet period. This can be accomplished through the use of pumps and sumps.

We recommend the groundwater table be maintained at least two (2) feet below all earthwork and bearing level during construction. Control of groundwater should be completed in accordance with the City of Sanford requirements.

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8.4 Geotechnical Design Parameters

Generalized geotechnical design parameters presented below in Table 6 were obtained empirically based on established relationship between the SPT “N” values with various soil properties and statistical averages, and grouped into a single design parameter for each subsurface stratum encountered at the site. However, specific geotechnical soil parameters at each boring location are presented in Table 7 of Appendix B.

Table 6: Geotechnical Design Generalized Parameters

Material Description

Avg.

N60

Value

Unit Weight (γ) (pcf) Soil

Friction Angle

(degrees)

Steel Wall

Friction Angle

(degrees)

Cohesion (pcf)

Earth Pressure Coefficients γtotal γeffective Active

Pressure (Ka)

Passive Pressure

(Kp)

Sand 10 105 42.6 29 14 - 0.3 2.9

Clayey Sand 10 120 57.6 21 14 1000 1.0 1.0

Sandy Clay 13 120 57.6 - 14 1625 1.0 1.0

Dolostone 50 135 72.6 - 17 - 1.0 1.0

In-field subsurface strength of the materials encountered at the site was evaluated during the site exploration by evaluating the penetration resistance by means of SPT. The SPT is characterized by the “N” value with higher resistance, density, and strength associated with higher “N” values.

These “N” values are shown on the Report of SPT Borings on Sheets 1 to 7 in Appendix B.

8.5 Foundation Considerations

We are assuming all construction will be supported by a shallow foundation system bearing on native soils or newly placed fill provided ground modification is performed as stated above. Design recommendations for the shallow foundations are presented below:

Prepare foundation subgrade soil in accordance with the recommendations presented in the Construction Considerations section of this report

Use a net allowable bearing pressure of 2,500 pounds per square foot (psf) for mat foundations. The allowable bearing pressure is a net pressure that will increase over and above that due to the overburdened soils, including dead load plus sustained live load

For non-load bearing walls, a thickened slab can be used for support. As an alternative to strip footings, monolithic thickened edge slabs and/or post-tensioned slabs could be utilized for support

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Monolithic slab or post tension slab foundation should be designed for a maximum allowable net soil bearing pressure of 2,500 pounds per square foot (psf). The allowable net bearing pressure is the pressure that may be transmitted to the soil in excess of the minimum surrounding overburden pressure. The allowable bearing pressure should include dead load plus sustained live load. Per Section 1805.4.1 of the Florida Building Code (FBC), the foundations should be designed for the most unfavorable effects due to the combinations of loads specified in Section 1605.3 of the FBC

For monolithic slab, footing should be embedded a minimum of 12 inches below adjacent compacted grade in accordance with FBC

The unfactored coefficient of subgrade reaction is estimated to be 130 lb/in3.

The foundation slabs should be reinforced with steel mesh or similar reinforcement. To avoid potential problems with cracking because of differential settlement, the slabs should be sufficiently jointed

To avoid slab moisture problems, it is recommended that the monolithic slab bearing soils be covered by lapped polyethylene sheeting and the floor slab placed directly on the vapor retarder. The slab designer or contractor should refer to ACI and Florida Building Code (FBC) regarding moisture and radon for procedures and cautions regarding the selection and placement of a vapor retarder

Any cuts that are made in the building pads for utility installation should be backfilled with clean granular materials that are compacted at least 95 percent of the ASTM D-1557 maximum dry density

Additionally, construction joints that allow relative vertical displacements are recommended when the difference in fill thickness under adjacent portions of the same structure is abrupt and greater than about three (3) feet

Over excavate any areas of soft yielding or unsuitable material encountered in the proposed foundation area and replace with clean sands compacted to at least 95 percent of the ASTM D-1557 maximum dry density and in accordance with City of Sanford requirements

Immediately prior to placement of foundation reinforcing steel, it is suggested that the bearing surfaces of the mat foundations be compacted using hand operated mechanical tampers. In this manner, any localized areas which have been loosened by excavation operations can be adequately re-compacted

Soils exposed in the bases of all foundation excavations should be protected against any detrimental change in conditions such as from physical disturbance or rain. Surface water run-off should be drained away from the excavations and not be allowed to pond. If possible, concrete should be placed the same day the excavation is made. If this is not possible, the excavations should be adequately protected.

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8.5.1 Foundation Settlement

Estimated total settlement for each structure is presented below in Table 8. Differential settlement is estimated to be less than 0.7%. It is anticipated that about 75 percent of the settlement will occur during construction.

Table 8: Estimated Settlement

Structure Estimated Load (psf)

Estimated Foundation

Depth

Total Settlement

(in) Comments

Electrical Room, UV AOP Room, Hydrogen Peroxide Storage and Feed Building 1200 2* 2.0 75% of this settlement will occur during construction

Outdoor Slab around Static Mixer 500* 2* 0.5 75% of this settlement will occur during construction

GAC Contactors and Backwash System 800* 2* 1.4 75% of this settlement will occur during construction

Ground Storage Tanks 3200 2* 4.8 75% of this settlement will occur during construction

1.9 With vibro-compaction

psf: pounds per square foot *Assumed

Estimated Total Settlement for each Ground Storage Tank is about 4.8 inches. If Vibro-compaction is utilized, settlement is reduced to about 1.9 inches. Vibro-compaction will result in increased bearing capacity and significant settlement reduction as illustrated in Table 8 above. It is NADIC’s opinion that vibro-compaction can be used to improve the foundation soils at the proposed location of the Ground Storage Tanks.

Vibro-compaction, is a method of ground improvement whereby a large vibrating probe is lowered into the soil to a specified depth while soils or gravel are backfilled, densifying the soil as the probe is lifted back towards the surface.

This process increases bearing capacity, reduces foundation settlement, and can replace deep unsuitable soils. If the engineer opts for this method of ground improvement, NADIC requests the opportunity to review the improvement plans and confirm adequate compaction through additional soil exploration.

8.5.2 Foundation Construction Considerations

The base of all foundation excavation should be free of water and loose or soft soil, and debris prior to placement of concrete. If the foundation bearing soils are observed to be suitable as load bearing materials, the soils should be compacted to a density of at least 95 percent of the ASTM D-1557 maximum dry density. The required compaction should be achieved for a depth of at least three feet below and 6-inch beyond the foundation bearing level and should achieve a minimum internal friction, 34 degrees.

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If soft pockets of soil are encountered in the foundation, the unsuitable materials should be excavated and backfilled with suitable material. Over excavation should also extend laterally beyond all edges of the foundations at least 8 inches per foot. Backfilling may be done with a well-compacted, suitable fill such as clean sand, gravel, or crushed #57 or #67 stone or with very lean concrete. Sand backfill should be compacted to a density of at least 95 percent of the material’s modified Proctor maximum dry density (ASTM D-1557), as previously described.

Immediately prior to placement of foundation reinforcing steel, it is suggested that the bearing surfaces of the foundations be compacted using hand operated mechanical tampers. In this manner, any localized areas which have been loosened by excavation operations can be adequately re-compacted.

8.5.3 Floor Slab Construction Considerations

We recommend subgrades should be maintained in a relatively moist condition prior to floor slab construction. If the subgrade should become desiccated, saturated or disturbed the area be scarified, moisture conditioned, and recompacted prior to mat foundation placement. The bearing soils should be compacted to a density of at least 95 percent of the ASTM D-1557 maximum dry density. The required compaction should be achieved for a depth of at least one foot below the bottom of the bearing surface. Any soft/loose soil or unsuitable materials should be excavated and backfilled with suitable material. Sand backfill should be compacted to a density of at least 95 percent of the material’s modified Proctor maximum dry density (ASTM D-1557), as previously described.

The slab design should include at least 6 inches of free drainage compacted granular material with less than 5 percent fines as a capillary break.

The slab designer and contractor should refer to ACI and Florida Building Code (FBC) regarding moisture and radon procedures and precautions regarding the use and placement of vapor barrier.

We recommend minimum testing frequency of one field density test per 2500 square feet or fraction thereof for a depth of 12 inches.

8.6 Pipeline Foundations

It is anticipated new pipelines will be installed throughout the site. Pipe diameters, material, and locations were not provided at the time of this report.

Prior to construction, the site should be cleared of unwanted ground cover. Based on the data obtained for this study, over-excavation may be necessary to remove soft/yielding soils and replaced with select materials. Upon removal of the unwanted soils, the exposed subgrade should be compacted and densified. The soils penetrated within the vicinity of the structures consisted mainly of fine sands, clayey sands, silty sands, and sandy silt. This conclusion is contingent on the following recommendations:

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Prepare foundation subgrade soil in accordance with the recommendations presented in the Construction Considerations section of this report

Pipeline foundations may be designed for their actual soil contact pressures

Use a maximum allowable bearing pressure of 2,500 psf for foundation design

Over excavate any areas of soft yielding or unsuitable material encountered along the proposed pipe alignments

The subsoil should be firm and stable prior to placement of pipeline foundation.

8.7 Pipeline Settlement

The primary design concerns with pipeline installation are typically long-term differential settlement and the effective length for settlement. Since the foundation soils are primarily sand, short-term settlement is anticipated to occur rather quickly. If unsuitable soils such as organic sands and plastic soils are encountered along the pipelines, they should be removed to a depth of at least two feet below pipe embedment depth and replaced with clean sands compacted to a density of at least 95 percent of the materials Modified Proctor maximum dry density (ASTM D-1557).

Field control will contribute substantially in minimizing settlements which actually occur. Based on the results of our field exploration and anticipated design loads, we feel that settlement is not a concern provided the recommendations discussed below under CONSTRUCTION CONSIDERATION are followed.

8.8 Lateral Earth Pressures

Any below ground structure including excavations to install the pipeline should be designed to resist pressures exerted by retained soils and hydrostatic head. Any foundation wall constructed below existing grade or which has adjacent compacted fill will be subjected to lateral at-rest or active earth pressure. For walls that are not restrained but are free to rotate at the top, active earth pressure should be used in design. The recommended equivalent fluid densities for each pressure condition are presented below:

Active Pressure Above Water Table – 36 pcf Below Water Table – 77 pcf

At-Rest Pressure

Above Water Table – 54 pcf Below Water Table – 84 pcf

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The above recommended densities do not include effects of surcharge loads such as traffic, construction equipment, etc. The above equivalent fluid densities do not include any factor of safety.

If a uniform surcharge is applied behind the vertical walls, it will produce an additional lateral pressure along the wall equal to about one-third the vertical contact pressure. The values presented herein presume that the walls will be backfilled with well compacted granular materials.

9.0 CONSTRUCTION CONSIDERATIONS

9.1 Site Preparation

Site preparation and construction should be in accordance with the City of Sanford requirements.

Prior to the construction of the proposed development, provisions should then be made to relocate any interfering utility lines within the construction area to appropriate locations consistent with project specifications.

The site should also be cleared and all debris completely removed including vegetation from the ground surface (topsoil, grass, shrubs, stumps and trees identified for removal). At a minimum, extend the clearing and grubbing operations to at least five feet beyond the development perimeter. Any "topsoil" removed from the proposed structure areas should be stockpiled in designated locations and used in areas to be grassed or be removed from the site as directed by the owner.

After the clearing/grubbing operations, the development areas should be proof rolled. Proof rolling should be carried out by making repeated overlapping coverage of the subgrade; to attain a degree of densification of at least 95 percent of the material’s ASTM D-1557 modified Proctor maximum dry density. Undercut any yielding soils such as loose or soft soils and replace with clean sand fill.

9.2 Structural Fill

All structural fill material should consist of clean sands (SP), free of organic matter and other deleterious substances with fine content not exceeding 5 percent (i.e., 5 percent by dry weight passing the U.S. Number 200 sieve). Fills with fines content between 5 percent and 12 percent (SP-SM or SP-SC) may be utilized with strict moisture control during placement. Each lift of the structural fill should be in 12-inch lifts as measured in loose thickness when heavy compaction equipment is used in vibratory mode. Lift thickness should be decreased if static compaction is being used, typically to no more than 8 inches and the required compaction must be achieved. For hand-guided compaction equipment, the fill loose thickness should be between 4 and 6 inches.

Each lift should be uniformly compacted to at least 95 percent of the material’s ASTM D-1557 Modified Proctor maximum dry density, prior to placement of the next lift. The fill should be placed at moisture content within 2 percent of optimum required to attain maximum dry density. Subsequent lifts should be placed and constructed in a similar manner.

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9.3 Excavations

All excavations shall be executed in accordance with the Central Florida Building Codes, the State of Florida Trench Safety Act (TSA), Occupational Safety and Health Administration (OSHA) requirements and all applicable requirements of the City of Sanford Utilities Standards and Specifications. Where required, slope protection should be provided in accordance with the most recent OSHA regulations.

All foundation excavations should be observed by a representative of NADIC to explore the extent of any fill and excessively loose, soft, or otherwise undesirable materials. If the foundation bearing soils are observed to be suitable as load bearing materials, the soils should be prepared for construction by compacting to a density of at least 95 percent of the material’s modified Proctor maximum dry density (ASTM D-1557).