RFQ Clearwell Tank Design

ECS Florida, LLC
Preliminary Geotechnical Engineering Report
Flagler Beach WTP - Storage Tanks
4680 Seminole Woods Boulevard
Palm Coast, Flagler County, Florida
ECS Project Number 56:2106
MC Project Number 01005-0007
December 29, 2025
January 21, 2026 - Revised

December 29, 2025
January 21, 2026 - Revised
Mr. Matthew Clark, P.E.
McKim & Creed
139 Executive Circle
Suite 201
Daytona Beach, FL 32114
ECS Project No. 56:2106
Reference: Preliminary Geotechnical Engineering Report
Flagler Beach WTP - Storage Tanks
4680 Seminole Woods Boulevard
Palm Coast, Flagler County, Florida
Dear Mr. Clark:
ECS Florida, LLC (ECS) has completed the preliminary subsurface exploration, laboratory testing, and
geotechnical engineering analysis for the above-referenced project. Our services were performed in
general accordance with our agreed-to scope of work. This report presents our understanding of the
geotechnical aspects of the project along with the results of the field exploration and laboratory testing
conducted, and our preliminary foundation design considerations.
It has been our pleasure to be of service to McKim & Creed, Inc. during the conceptual phase of this
project. We would appreciate the opportunity to remain involved during the continuation of the design
phase, and we would like to provide our services during construction phase operations as well to verify
the assumptions of subsurface conditions made for this report. Should you have any questions
concerning the information contained in this report, or if we can be of further assistance to you, please
contact us.
Respectfully submitted,
ECS Florida, LLC
Giovanni Mafiol, E.I. Cody M. Wallace, P.E.
Geotechnical Project Manager Senior Geotechnical Engineer
gmafiol@ecslimited.com Registered FL No. 92248
cwallace1@ecslimited.com
2330 South Nova Road, Suite A., South Daytona, FL 32119 * T: 386-944-9588 * www.ecslimited.com
ECS Carolinas, LLP * ECS Florida, LLC * ECS Midwest, LLC * ECS Mid-Atlantic, LLC * ECS Southeast, LLC * ECS Texas, LLP

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ECS Project No. 56:2106 Page 1
TABLE OF CONTENTS
EXECUTIVE SUMMARY .................................................................................................................. 2
1.0 INTRODUCTION ....................................................................................................................... 3
1.1 General ............................................................................................................................. 3
1.2 Scope of Services ............................................................................................................... 3
1.3 Authorization .................................................................................................................... 3
2.0 PROJECT INFORMATION ......................................................................................................... 4
2.1 Project Location/Current Site Use ...................................................................................... 4
2.2 Past Site History/Uses........................................................................................................ 4
2.3 Soil Survey Mapping .......................................................................................................... 5
2.4 Proposed Construction ...................................................................................................... 6
3.0 FIELD EXPLORATION AND LABORATORY TESTING ................................................................... 6
3.1 Subsurface Characterization .............................................................................................. 6
3.2 Groundwater Observations ............................................................................................... 7
3.2.1 Encountered Groundwater ....................................................................................... 7
3.2.2 Estimated Seasonal High Groundwater ..................................................................... 7
3.3 Laboratory Testing............................................................................................................. 8
4.0 PRELIMINARY DESIGN Considerations .................................................................................... 8
4.1 General ............................................................................................................................. 8
4.2 1-MG Rectangular Clearwell Option ................................................................................... 8
4.2.1 Auger Cast In-Place (ACIP) Piles ................................................................................ 8
4.2.2 ACIP Allowable Capacities ........................................................................................ 9
4.2.3 Lateral Capacities of ACIP Piles ............................................................................... 10
4.2.4 Below Grade Walls ................................................................................................. 10
4.3 1-MG Circular GST Option ................................................................................................ 11
4.3.1 Foundations ........................................................................................................... 11
5.0 ADDITIONAL TESTING RECOMMENDATIONS ........................................................................ 11
5.1 Additional Borings ........................................................................................................... 11
5.2 Infiltration Testing ........................................................................................................... 12
6.0 CLOSING ................................................................................................................................ 12
APPENDICES
Appendix A - Diagrams
* Site Location Diagram
* Boring Location Diagram
* Subsurface Cross Section
Appendix B - Field Operations
* Reference Notes for Boring Logs
* Subsurface Exploration Procedure: Standard Penetration Testing (SPT)
* Boring Logs
Appendix C - Laboratory Testing
* Laboratory Testing Summary
Appendix D - Other Information
* ACIP Allowable Capacity Graph

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ECS Project No. 56:2106 Page 2
EXECUTIVE SUMMARY
The following summarizes the main findings of the subsurface exploration and geotechnical
services, particularly those that may have a cost impact on the project. Information gleaned from
the executive summary should not be utilized in lieu of reading the entire geotechnical report.
* Based on the subsurface conditions encountered and preliminary deep foundation pile
design capacities, we estimate 24-inch Auger Cast-In-Place (ACIP) piles installed between
EL. -30 and -40 (NAVD88) will be suitable for the proposed clearwell structure. Note: Piles
embedded deeper than EL. -45 (NAVD88) may produce high than tolerable settlement due
to the deeper loose stratum.
* We estimate an allowable bearing pressure on the order of 1,500 to 2,500 psf may be used
for design of the 1-MG Circular Ground Storage Tank (GST) structure and adjacent higher
service pump station and deep transfer well mat slab foundations.
* As project plans progress, we recommend we be allowed to review the plans and
implement a supplemental exploration program that evaluates the subsurface conditions
more thoroughly to meet the intent of the proposed project and provide foundation design
and construction recommendations.

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ECS Project No. 56:2106 Page 3
1.0 INTRODUCTION
1.1 GENERAL
The purpose of this preliminary study was to provide limited geotechnical information for the
proposed improvements at the existing Flagler Beach Water Treatment Plant (WTP) facility located
at 4680 Seminole Woods Boulevard. We understand two (2) design options are being considered
to increase water storage capacity at the plant. Associated site improvements will include a new
stormwater retention area, yard piping, and an asphalt driveway. This preliminary report contains
the results of our subsurface exploration, site characterization, engineering analyses, and
preliminary geotechnical engineering considerations for the proposed improvements.
1.2 SCOPE OF SERVICES
Our scope of services included performance of two (2) Standard Penetration Test (SPT) soil borings,
laboratory-testing to characterize the physical and engineering properties of the subsurface soils,
and a preliminary report discussing the following:
a. A review of published soils mapping.
b. Observations from our site reconnaissance and personnel on the drill rig, including current site
conditions, surface drainage features, and surface topographic conditions, and available
satellite imagery.
c. A description of the field exploration and laboratory tests performed.
d. A site location diagram and a boring location diagram.
e. Final logs of the soil borings in accordance with industry standard practices for geotechnical
engineering. Elevations were interpolated from publicly available information.
f. The results of the laboratory tests are plotted on the final exploration logs and included on
separate test report pages.
g. Discussion of the subsurface materials encountered along with groundwater conditions
observed.
h. Subsurface cross sections/profiles are included that graphically represent the subsurface
conditions.
i. Preliminary recommendations for appropriate shallow foundation system and their allowable
bearing pressures as well as estimates of predicted foundation settlement for the 1 MG GST,
HSP, and TPS.
j. Preliminary recommendations for deep foundations for the 1 MG clearwell structure with
consideration of the preliminary design loads provided.
k. Preliminary design recommendations for below-grade walls, including lateral earth pressures.
l. Recommendations for additional subsurface exploration, laboratory testing, and/or
consultation that may be required to complete the geotechnical assessment and engineering
recommendations.
1.3 AUTHORIZATION
Our services were provided in accordance with our Proposal No. 56:2764r, dated October 10, 2025,
as authorized by Charles H. Hill, P.E. via the master subcontract dated October 24, 2025.

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ECS Project No. 56:2106 Page 4
2.0 PROJECT INFORMATION
2.1 PROJECT LOCATION/CURRENT SITE USE
The project site is located at the existing Flagler Beach Water Treatment Plant (WTP) at 4680
Seminole Woods Boulevard in Palm Coast, Forida. The site is shown below and on the Site Location
Diagram in Appendix A. The site was bounded by woods to the east, a power line easement to the
west, Quest Diagnostics to the north, and a residential subdivision to the south.
Figure 2.1.1 Site Location
The existing plant was comprised of several above and below ground treatment plant structures
and an existing wet stormwater facility in the southwestern portion of the facility. Based on
topographic information authored by Mittauer & Associates, Inc dated January 26, 2009, the site is
relatively level, with an approximate low EL. of 24.7 (NAVD88) in the northeast and a high around
EL. 29.05 (NAVD88) near the existing two-story building.
2.2 PAST SITE HISTORY/USES
ECS has reviewed aerial photographs of the subject site on Google Earth. The aerial photographs
reviewed were dated from 1995 to 2025. The facility appears operational in 1995. Between 2006
and 2007, the southern building and southwestern stormwater pond appeared to be constructed.
Between February 2016 and November 2016, new/improved asphalt pavement appeared around
the entrance and parking areas throughout the facility. Between April 2024 and November 2024,
the central pit and northern adjacent treatment structures were removed and the area appeared
to have been backfilled. No apparent changes appeared on the November 2025 aerial.

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2.3 SOIL SURVEY MAPPING
Based on the Web Soil Survey for Flagler County, Florida, as prepared by the U.S. Department of
Agriculture Natural Resource Conservation Service (USDA-NRCS), the predominant soil types
existing within the site area boundaries are described in the following table. The site area is
illustrated superimposed on the USDA-NRCS Soil Survey Map in the following figure.
Web Soil Survey Data
Soil Type Constituents Drainage Class Water Table
12 - Placid, Basinger, and
Very Poorly
St. Johns soils, 0 to 80" fine sand About 0 to 12 inches
Drained
depressional
21 - Smyrna fine sand, 0
0 to 80" fine sand Poorly Drained About 6 to 18 inches
to 2 percent slopes
Site Soil Survey, Flagler County, Florida

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2.4 PROPOSED CONSTRUCTION
Based on McKim and Creed's Geotechnical Request for Proposal - Revision 0 dated September 29,
2025, we understand two (2) options are being considered to increase water storage capacity at
the plant. The option information provided to us is presented below.
Option 1 - 1 MG rectangular clearwell - will be a cast-in-place concrete structure with inside
dimensions of 80' x 110' x 16.25' deep. We estimate existing grades to be between EL. 25' to 27'
(NAVD88). The clearwell will be covered with a top slab matching the existing clearwell to the
southwest at EL. 12.75' (NAVD88), resulting in a top of base slab approximately 15.25' below
existing grade. It is anticipated that the base slab will be supported on a pile foundation with a pile
type that will resist both compression and tension loads. Preliminary design indicates that the
maximum compression and tension loads will be on the order of 124 tons and 40 tons per pile,
respectively. The top of pile is anticipated around EL. 11.5' (NAVD88).
Option 2 - 1 MG circular GST - An 80' inside diameter (ID) x 26'-8" side water depth (SWD)
prestressed concrete Ground Storage Tank (GST) manufactured by a tank contractor such as Crom
or Precon. Soil bearing pressures will be on the order of 1800 psf. The new high service pump
station will consist of ground mounted pumps on a mat foundation with turndowns. The transfer
pump station will consist of ground mounted pumps on a mat foundation with turndowns with
10'x24'x10' deep transfer well. Top of mats will be near finished grade and a uniform live load of
300 psf will be specified for the mats.
Additionally, heavy-duty roadways are anticipated to be constructed in addition to stormwater
improvements which may consist of either a shallow dry swale/detention facility or a wet retention
facility near the central area of the treatment plant facility.
3.0 FIELD EXPLORATION AND LABORATORY TESTING
Our scope of services included drilling two (2) Standard Penetration Test (SPT) borings of
approximately 60 to 75 feet below the existing site grades. Additionally, one (1) temporary
groundwater monitoring well was installed at the B-01 boring location to periodically measure
groundwater levels. Our test locations were located with a handheld GPS unit and their
approximate locations are shown on the Boring Location Diagram in Appendix A. Our exploration
procedures are explained in greater detail in Appendix B including the insert titled Reference Notes
for Boring Logs.
3.1 SUBSURFACE CHARACTERIZATION
The subsurface conditions encountered were generally consistent with published geological
mapping. The following sections provide generalized characterizations of the soil strata. Please
refer to the boring logs in Appendix B.

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General Subsurface Stratigraphy
Approximate
Stratum Description
Depth Range (ft)
Very Loose to Medium Dense
0 - 28.5 I Fine SAND (SP), Fine SAND with Silt (SP-SM), Fine SAND with
Clay (SP-SC)
Medium Dense to Dense
21.5 - 33.5 II
Fine Sand (SP)
Loose to Medium Dense
33.5 - 48 III Fine Sand (SP), Fine Sand with Clay (SP-SC), and Clayey Fine
Sand (SC)
Very Dense to Dense
43.5 - 68.5 IV
Fine SAND (SP)
Medium Dense
68.5 - 73.5 V1
Fine SAND (SP)
Loose
73.5 - 75 VI1
Highly Plastic Clayey Fine SAND (SC)
Notes: (1) Encountered at Boring B-04, only.
3.2 GROUNDWATER OBSERVATIONS
3.2.1 Encountered Groundwater
Groundwater levels were measured in the boreholes during our field exploration and are presented
in our boring logs in Appendix B. Additionally, we visited the site several times to measure the
groundwater levels near the B-01 boring location, which are presented in the table below. Based
on our measurements, groundwater depths ranged from 2.9 to 4.4 feet below the ground surfaces.
Variations in the long-term water table may occur as a result of changes in precipitation,
evaporation, surface water runoff, construction activities, and other factors.
Ground Water Level Measurements Below Existing Grades (ft)
Date B-01
(Installed 11/12/2025)
11/12/2025 4.6
11/14/2025 4.4
11/18/2025 4.6
11/21/2025 4.6
3.2.2 Estimated Seasonal High Groundwater
The normal seasonal high groundwater level (SHGWL) is affected by a number of factors. The
drainage characteristics of the soils, land surface elevation, relief points such as drainage ditches,
lakes, rivers, swamp areas, etc., and distance to relief points are some of the more important factors
influencing the seasonal high groundwater level.
We estimate SHGWL's at the boring locations to be in the range of 1.92 to 3.67 feet below existing
grades. However, based on our interpretation of the site conditions and Web Soil Survey

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information, we estimate the site's SHGWL can be as shallow as 0.5 to 1.5 feet below the ground
surface in some areas. It is possible that groundwater levels may exceed the estimated normal
seasonal high groundwater level as a result of significant or prolonged rain.
3.3 LABORATORY TESTING
Each sample was visually classified on the basis of texture and plasticity in accordance with ASTM
D2488 Standard Practice for Description and Identification of Soils (Visual-Manual Procedures) and
including USCS classification symbols, and ASTM D2487 Standard Practice for Classification for
Engineering Purposes (Unified Soil Classification System (USCS)). After classification, the samples
were grouped in the major zones noted on the boring logs in Appendix B. The group symbols for
each soil type are indicated in parentheses along with the soil descriptions. The stratification lines
between strata on the logs are approximate; in situ, the transitions may be gradual.
The laboratory testing consisted of selected tests performed on samples obtained during our field
exploration operations. Classification and index property tests were performed on representative
soil samples. Laboratory tests performed on the selected samples included percent fines (ASTM
D1140), moisture content (ASTM D2216), and organic content (ASTM D2974) tests. The moisture
content and percent fines test results are shown on the boring logs in Appendix B, and all laboratory
test results are tabulated in Appendix C.
4.0 PRELIMINARY DESIGN CONSIDERATIONS
4.1 GENERAL
Our preliminary geotechnical engineering evaluation of the site and subsurface conditions at the
property, with respect to the anticipated construction, are based upon 1) our site observations; 2)
the limited field data obtained; and 3) our understanding of the project information as presented
in this report.
4.2 1-MG RECTANGULAR CLEARWELL OPTION
We understand the clearwell structure will be founded approximately 15.25' below existing grade,
near EL. 11.50' (NAVD88) and that buoyancy pressures will control foundation design. Therefore,
deep foundations will be necessary to resist uplift pressures considering allowable compressive and
tensile capacities on the order of 124 tons and 40 tons per pile, respectively.
In our experience, Auger Cast In-Place (ACIP) piles are economically effective deep foundation
options that are beneficial at sensitive sites such as treatment facilities due to their minimized
vibration and noise impacts and rapid production rates with relatively small equipment footprints.
4.2.1 Auger Cast In-Place (ACIP) Piles
Based on our experience with similar projects, it is our opinion that 24-inch ACIP piles are a feasible
foundation solution for support, where required. ACIP piles typically develop their axial capacity
through the combination of skin friction and end bearing at the base of the pile. For this project,
the ACIP piles would derive their axial capacity from both friction and end bearing in the medium
dense to very dense sandy soils.