Memorial_Park_Subsidence_Investigation_Revised_Report_ECS1286_digi.pdf

ECS Florida, LLC.

Geotechnical Engineering Report Memorial Park – Subsidence Investigation

76 Dirksen Drive DeBary, Florida

ECS Project Number 56:1286

March 25, 2020 Revised April 6, 2020

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

March 25,2020 Revised April 6, 2020

Mr.Tom Vandehey Parks Superintendent City Of DeBary 16 Colombia Road DeBary, FL 32713

ECS Project No. 56:1286

Reference: Geotechnical Engineering Report

Memorial Park – Subsidence Investigation DeBary, Florida

Dear Mr. Vandehey:

ECS Florida, LLC. (ECS) has completed the subsurface exploration, laboratory testing, and geotechnical engineering analyses for the above-referenced project. Our services were performed in general accordance with our Proposal No.56:1286, dated February 12, 2020. This report presents our understanding of the geotechnical aspects of the project, the results of the field exploration and laboratory testing conducted, our engineering evaluation, and remediation recommendations.

It has been our pleasure to be of service to City Of DeBary during the investigation phase of this project. We would appreciate the opportunity to remain involved during the continuation of the project 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.

Vinay Kumar Arebelli David W. Spangler, P.E Staff Project Manager Geotechnical Department Manager VArebelli@ecslimited.com Registered Florida No.58770 dspangler@ecslimited.com

Memorial Park – Subsidence Investigation April 06, 2020 ECS Project No. 56:1286 Page i

TABLE OF CONTENTS

1.0 PROJECT INFORMATION

1.1 Site location and Project Description

1.2 review of published information

1.2.1 Historical Aerial Photographs

1.2.3 Florida Sinkhole Map

1.3 Past Activities on the site

2.0 FIELD EXPLORATION

2.1 Geophysical Investigation

2.2 Geophysical Survey Results

2.3 SPT Borings

3.0 LABORATORY TESTING

4.0 GENERAL SUBSURFACE CONDITIONS

4.1 General Soil Profile

4.2 Groundwater Level

5.0 DISCUSSION AND EVALUATION

6.0 REPORT LIMITATIONS

PLATES

Plate 1 – Area of Recommended Over-excavation and Compaction

APPENDICES

Appendix A – Drawings & Reports

Site Location Diagram Boring Location Diagram

Appendix B – Field Operations

Boring Logs B-1, B-2 and HA1 Soil Classification Index

Appendix C – Laboratory Testing

Laboratory Test Results Summary

Appendix D – Supplemental Report Documents

Geophysical Investigation Report

Appendix E – Site Photographs

ECS Project No. 56:1286 Page 2

1.0 PROJECT INFORMATION

1.1 SITE LOCATION AND PROJECT SITE DESCRIPTION

The project site is located at 76 Dirksen Drive in DeBary, Florida. The general site location is shown on Figure 1 of 1 in Appendix A. At the time of our exploration, the site was a developed park with five picnic pavilions, a F-15 Eagle tactical fighter aircraft and the USS Langley’s anchor, which are prominently displayed. The F-15 Eagle display area is surrounded by iron fencing with a concrete sidewalk along the perimeter of the fenced area. The F-15 Eagle display area was located along a natural sloping area (sloping down toward the south). Based on site observation, it appears that several feet of elevating fill had been placed along the southern portion of the display to create a level perimeter area. During our site visits we observed no signs of previous movement to the F-15 Eagle display structure. However, several inches of subsidence was observed at the concrete sidewalk at the southwestern side of the F-15 Eagle display. In addition, a depression was evident in the grass landscape area immediately to the west of the concrete sidewalk. We also observed the edges of the concrete slabs at the subsidence area had been previously grinded level to the adjacent concrete slabs (to prevent a trip hazard). Photographs showing the representative site conditions at the time of our site visit and field work are attached in Appendix E.

1.2 REVIEW OF PUBLISHED INFORMATION

1.2.1 Historical Aerial Photographs

We reviewed historical aerial photographs of the site dated 1957, 1994, 1999, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013, 2014, 2016, 2017, 2018, 2019 and 2020. The 1957 and 1994 aerial photographs show the site as undeveloped and heavily wooded with a high voltage power line located north of the site. The 1999 aerial photograph shows the site was developed with the current park features (including picnic pavilions and F-15 aircraft on display). A new segment of concrete sidewalk (the currently settled portion of sidewalk at the area of subsidence) was first clearly observed in the 2008 aerial photograph. The site appeared unchanged through the 2020 aerial images and site features are consistent with the conditions as observed during our site visits.

1.2.2 Florida Sinkhole Map

Based on the map titled Sinkhole Type, Development, and Distribution in Florida, 1985, by William C.

Sinclair and J.W. Stewart of the U.S. Geological Survey, the project site is located in Area II which consists mainly of incohesive and permeable sands of low permeability overlying the limestone. The overburden cover in this area is 30 to 200 feet thick. Sinkholes in this area are few, of varying size, and develop gradually. Cover-subsidence sinkholes dominate in this area. Cover-subsidence sinkholes develop at areas sand covers the bed rock. The sand filters down into openings in the rock, gradually causing land surface to sink.

1.3 PAST ACTIVITIES ON THE SITE

Based on information provided by Mr. Tom Vandehey, the City of Debary Parks Superintendent, and our research of publicly available information, we have developed the following site chronology:

1) May 31, 1999 (Memorial Day) – The opening and dedication of the park occurred.

2) 2008 – A depression at the subject area was documented to have occurred. Mr. David Griffis, the Volusia County Extension Director/Natural Resource Agent at that time, performed several

ECS Project No. 56:1286 Page 3 hand augers to a depth of 6 feet below the existing ground surface. The hand augers revealed soil horizons that indicated disturbed conditions.

3) 2009 - The Volusia County Public Works department reportedly excavated to a depth of approximately 10 feet below the existing grade and found buried organic material. The presence of buried organic materials could have caused subsurface subsidence prior to removal of the organics due to consolidation of the organics as a result of decomposition of the organic material or loss of soil into voids within the organic material.

4) 2011 – Additional subsidence at the subject site area was again noted. We understand that additional studies have not occurred since 2011 prior to our current study.

ECS Project No. 56:1286 Page 4

2.0 FIELD EXPLORATION

Geophysical and geotechnical field explorations were performed between February 24 and March 09, 2020. The approximate boring locations are indicated on the attached Field Exploration Plan (Figure 2).

Our personnel determined the boring locations using taped measurements from existing structures on the site. The boring locations on the referenced Field Exploration Plan should be considered accurate only to the degree implied by the method of measurement used.

2.1 GEOPHYSICAL INVESTIGATION

To explore of the depression features at the site, GeoView, Inc. was retained to perform Electrical Resistivity Imaging (ERI) and Ground Penetrating Radar (GPR) and surveys at the site. The geophysical surveys were performed on February 24, 2020.

During an ERI survey the apparent electrical resistivity of subsurface soil is measured by sending an electrical current into the soil with a pair of current electrodes while the potential difference is recorded with a pair of potential electrodes generally arranged in a linear array. The ERI survey involves several measurements of the soil resistivity using various spacings and placement of the electrodes. Resistivity contour maps at relative changes in the subsurface soil conditions are generated from the ERI survey to show resistivity variations along the horizontal and vertical (depth) planes.

The ERI survey was performed with an Advanced Geosciences, Inc. Sting R8 automatic electrode resistivity system. One ERI transect were performed using up to 28 electrodes with a spacing of 7.5 feet. The ERI data obtained was analyzed using the EarthImager 2D, a computer inversion program, which provides a two-dimensional vertical cross-sectional resistivity model (pseudo-section) of the subsurface. The results of this study provide subsurface information to a maximum depth ranging from 15 feet to 23 feet. Modeled resistivities were compared within profiles to develop an indication of the subsurface conditions.

Ground Penetrating Radar (GPR) equipment transmits high frequency electromagnetic waves into the ground and records the wave energy reflected back to the equipment. The GPR system consists of a dual transmitter/receiver antenna and a profiling recorder to process and provide a graphic display of the field data. The GPR survey provides a graphic cross-sectional view of subsurface conditions.

The GPR survey data obtained during the current exploration was obtained with a GSSI radar system. The position of the GPR data was recorded using an integrated GPS system with a sub-meter accuracy. A copy of the Geophysical Investigation report is included in Attachment D.

2.2 GEOPHYSICAL SURVEY RESULTS

The GPR survey indicated the presence of two well-defined, relatively continuous set of GPR reflectors at depth ranges of 1 to 3 feet and 8 to 11 feet below the existing grade. GeoView concluded the reflector set is likely associated with a change of lithological (soil) conditions at that depth range. The GPR survey also identified one anomaly area in the central portion of the survey area. The GPR anomaly area is identified on Figure 1 of the Geophysical report included in Appendix D. The anomaly was characterized by a downwarping of the GPR reflector set ranging in apparent vertical relief from approximately 2 to 3 feet.

The ERI transects indicate the presence of high resistivity near-surface soil materials to a depth range of approximately 15 to 23 feet bgs. This high resistivity layer was most likely associated with the sandy soils

ECS Project No. 56:1286 Page 5 observed in the borings. The surficial high resistivity layer is underlain by a moderate to low resistivity layer to the maximum depth of investigation of the ERI transects of approximately 49 feet bls. GeoView concluded the moderate to low resistivity layer is most likely associated with an increase in the clay content of the soils or a highly weathered limestone unit at depths. One ERI anomaly was identified at the project site within the area of the survey area near a depression. The ERI anomaly is characterized by the shallow breach of the moderate resistivity soils at depths ranging from approximately 1 to 11 feet bls.

Geoview concluded that there is a poor correlation between the identified GPR and ERI anomalies and that the ERI anomaly is likely associated with localized breach of moderate resistivity soils at a similar shallow depth range of the observed downwarping of the GPR reflector sets. Geoview also concluded it is not possible basd on the geophysical results to determine whether the identified anomaly have a potential for collapse or subsidence that could have an impact on the memorial.

A copy of the Geophysical Investigation Report is included in Attachment D.

2.3 SPT BORINGS

We located and performed 2 Standard Penetration Test (SPT) borings, drilled to depths of approximately 72 to 90 feet below the existing ground surface, in general accordance with the methodology outlined in ASTM D 1586 to explore the subsurface conditions within the site area at selected GPR and ERI anomalies within the surface depression area. Split-spoon soil samples recovered during performance of the borings were visually classified in the field and representative portions of the samples were transported to our laboratory for further evaluation. The borings were grouted at the completion of the drilling activities.

2.4 AUGER BORING

We located and performed one hand auger boring with Dynamic Cone Penetration soundings (DCP), drilled to depth of approximately 5 feet below the existing ground surface in general accordance with the methodology outlined in ASTM D 1452 to explore the subsurface conditions within the anomaly area.

Representative soil samples also were recovered from the auger borings and returned to our laboratory for further evaluation.

ECS Project No. 56:1286 Page 6

3.0 LABORATORY TESTING

A geotechnical engineer classified representative soil samples obtained during our field exploration using the Unified Soil Classification System (USCS) in general accordance with ASTM D 2488. A Key to the Soil Classification System is included in Appendix A.

Selected samples of the soils encountered during the field exploration were subjected to quantitative laboratory testing to better define the composition of the soils encountered and to provide data for correlation to their anticipated strength and compressibility characteristics. The laboratory testing determined the percent fines and natural moisture contents of selected soil samples. The results of the laboratory testing are shown in the Summary of Laboratory Test Data included in Appendix B. Also, these results are shown on the Log of Boring records at the respective depths from which the tested samples were recovered.

ECS Project No. 56:1286 Page 7

4.0 GENERAL SUBSURFACE CONDITIONS

4.1 SOIL CONDITIONS

Detailed boring records are included in Appendix A. It should be understood that the soil conditions will vary between the boring locations. The following discussion summarizes the soil conditions encountered.

SPT Boring B1 encountered a layer of very loose to loose fine sand (SP) to a depth of approximately 12.5 feet below the existing grade (apparent fill soil). Below, medium dense to dense clayey fine sand (SC) and very stiff clay (CH) was encountered above the limestone surface to a depth of about 42.5 feet below the existing grade. Hard limestone was generally penetrated below a depth of 43.5 feet to a depth of 68.5 feet below the ground surface. Hard silty clay (CH) was then countered to depths of approximately 87.5 feet below the ground surface. Limestone was then noted between depths of about 87.5 feet to the boring termination depth of 90 feet below the existing grade. No systematic decreases of N-values were observed at this boring that would indicate a raveled zone in the overburden material.

SPT Boring B2 encountered a layer of very loose to loose fine sand (SP) to a depth of approximately 12.5 feet below the existing grade (apparent fill soil). Below, layers of loose to medium dense clayey sands (SC) and stiff to very stiff clay (CH) was encountered to the top of the limestone layer at approximately 42.5 feet. Generally hard limestone (with a layer of very dense clayey sands (SC) between depths of 47.5 to

52.5 feet) was encountered to the boring termination depth of 72 feet below the existing grade (where slow difficult drilling was encountered due to the relative density of the limestone at that depth). No weight-of-hammer or weight-of-rod events where noted at this boring. In addition, no systematic decreases of N-values were noted in the overburden material at this boring.

The hand auger boring HA1 performed within the depression area also encountered fine sands (SP, apparent fill soil) to the termination depth of 5 feet below the existing grade. The Dynamic Cone Penetration soundings performed within the hand auger boring indicated the sands were very loose to the boring termination depth of 5 feet.

4.2 GROUNDWATER LEVEL

Groundwater was measured at the time of drilling at a depth of 14.5 feet below the existing ground surface at boring B1 location. Groundwater was not measured in Boring B2 before the boring was advanced using wet rotary wash methods. We note that groundwater levels will fluctuate due to seasonal climatic variations, surface water runoff patterns, construction operations, and other interrelated factors.

ECS Project No. 56:1286 Page 8

5.0 DISCUSSION, EVALUATION, AND RECOMMENDATIONS

In central Florida, sinkholes are a common occurrence due to the natural geological conditions in the region. Much of Florida is underlain by thick soluble carbonate deposits of limestone that are susceptible to dissolution from movement of slightly acidic groundwater. Cavities develop in the limestone over geologic time periods due to dissolution of the rock. Siliciclastic marine sediments consisting of sand, silt, and clay overly the irregular limestone surface creating an overburden layer with a variable thickness and permeability. Sinkholes are more common where the limestone and Floridan aquifer is unconfined or thinly confined.

The SPT borings did not reveal a systematic decrease of N-values that would indicate an active raveling zone in the overburden native soil above the limestone layer. In addition, no weight-of-hammer or weight-of-rod events were noted in the borings that would be suggestive of a cavity in the limestone or raveling of overburden soils. The limestone encountered at the boring locations was generally hard and appeared competent providing SPT refusal during several sample intervals (N-values greater than 50 blows per 6 inches of sampler penetration). Based on the results of the geophysical and geotechnical explorations, it is our opinion that sinkhole actively is not currently occurring at the site.

The SPT borings and auger boring with Dynamic Cone Penetrometer (DCP) soundings revealed very loose to loose sandy soils within the upper 6 feet of the borings. The previously backfilled soil appeared to be in a loose condition to the bottom of the backfilled soil at a depth of approximately 12.5 feet below the existing grades. We note that casing was required to be installed at the SPT boring locations through the backfill soil layer to prevent the loss of drilling circulation at the borings. The GPR and ERI anomaly depths of upto 11 feet below the existing grades generally coincided with the very loose to loose fill depths observed at the SPT borings. Typically, this may suggest that the soil backfill was not compacted after removal of the organic materials in 2009. Due to the sandy nature of the backfill soils, we would expect that the majority of the settlement would have occurred fairly quickly after the backfill was replaced (with settling more quickly during/after rain events) and additional significant settlement should not still be occurring. Although, the depression area appeared to be covered with healthy grass cover, we note that some surface erosion from stormwater occurances may be currently deepening the depression area to a small degree.

To reduce the potential for future surface subsidence at the area of the observed depression we recommend the soil be over-excavated to a depth of 6 feet below the existing ground surface and replaced with compacted structural fill soils. The approximate area to be over-excavated and compacted is indicated on the Attached Plate 1. Structural fill is defined as a non-plastic, inorganic, granular soil having less than 15 percent material passing the No. 200 mesh sieve and containing less than 4 percent organic material. Based on the results of the borings the existing fine sands (SP) to be over-excavated are suitable for reuse as the backfill soil. During the excavation operations, any encountered buried objects should be totally removed from the excavaton and ECS should be notified to evaluate the encountered conditions.

Other soil improvement techniques, although not as common as the over-excavation and backfill with compacted structural fill alternative, could include compaction grouting or chemical grouting. These alternatives require injecting grout under pressure through the zone of soil to be improved. Compaction grouting consist of the injection, under pressure, of low slump grout to densify the loose sands adjacent to the injection point. Chemical grouting consist of the injection of grout that will permeate through the

ECS Project No. 56:1286 Page 9 sands creating a cemented (sandstone like) material. Compaction and chemical grouting are both anticipated to be less economically feasible than the over-excavation and backfill with compacted structural fill alternative, and they require a specialty ground improvement contractor to perform the work.

After completing the over-excavation operations, the bottom of the excavation should be compacted with a vibratory drum roller having a minimum static, at-drum weight, on the order of 4 tons to 6 tons.

Typically, the material should exhibit moisture contents within ±2 percentage points of the modified Proctor optimum moisture content (ASTM D 1557) during the compaction operations. Compaction should continue until densities of at least 95 percent of the modified Proctor maximum dry density (ASTM D 1557) have been achieved within the upper 2 feet of the compacted soils at the bottom of the excavation.

The structural backfill should be placed in loose lifts not exceeding 12 inches in thickness when compacted by the use of the vibratory drum roller (to densities of at least 95 percent of the modified Proctor maximum dry density (ASTM D 1557)). ECS should be retained to perform the density testing of the backfill and observations required for this project, to verify that our recommendations have been satisfied.

After the backfilling and compaction operation we anticipate that no additional observable settlement would occur at the depression area. While we did not observe any evidence of previous movement of the monument structure, the structure could be monitoring for any movement over the course of years by surveying a secure monitoring reference point attached to the monument.

All excavations and slopes should be made and maintained in accordance with OSHA excavation safety standards. The contractor is solely responsible for designing and constructing stable, temporary excavations and slopes and should shore, slope, or bench the sides of the excavations and slopes as required to maintain stability of both the excavation sides and bottom. We anticipate that a shoring system will need to be designed along the excavation adjacent to the fence at the F-15 display area. The contractor’s responsible person, as defined in 29 CFR Part 1926, should evaluate the soil exposed in the excavations as part of the contractor’s safety procedures. In no case should slope height, slope inclination, or excavation depth, including utility trench excavation depth, exceed those specified in local, state, and federal safety regulations. ECS is providing this information solely as a service to our client. ECS is not assuming responsibility for construction site safety or the contractor’s activities; such responsibility is not being implied and should not be inferred.

ECS Project No. 56:1286 Page 10

6.0 REPORT LIMITATIONS

ECS has prepared this report of findings, evaluations, and recommendations to guide geotechnical-related design and construction aspects of the project.

The description of the proposed project is based on information provided to ECS by the client. If any of this information is inaccurate, either due to our interpretation of the documents provided or site or design changes that may occur later, ECS should be contacted immediately in order that we can review the report in light of the changes and provide additional or alternate recommendations as may be required to reflect the proposed construction.

We recommend that ECS be allowed to review the project’s plans and specifications pertaining to our work so that we may ascertain consistency of those plans/specifications with the intent of the geotechnical report.

Field observations, monitoring, and quality assurance testing during earthwork and foundation installation are an extension of and integral to the geotechnical design recommendation. We recommend that the owner retain these quality assurance services and that ECS be allowed to continue our involvement throughout these critical phases of construction to provide general consultation as issues arise. ECS is not responsible for the conclusions, opinions, or recommendations of others based on the data in this report.

ECS Project No. 56:1286 Page 11

APPENDIX A – Drawings & Reports

Site Location Diagram Boring Location Diagram

Service Layer Credits: Esri, HERE, Garmin, (c) OpenStreetMap contributors

²

CITY OF DEBARY

MEMORIAL PARK SUBSIDENCE

76 DIRKSEN DR, DEBARY, FLORIDA

Site Location Diagram

0 600300 Feet

3/20/2020

ENGINEER

SCALE

56:1286

PROJECT NO.

SHEET

DATE

DS05

1 " = 300 '

B-1

B-2HA-1

Service Layer Credits: Esri, HERE, Garmin, (c) OpenStreetMap contributors

²

Legend Approximate SPT boring locations

Approximate Auger boring location

CITY OF DEBARY

MEMORIAL PARK DEPRESSION

76 DIRKSEN DR. DEBARY, FLORIDA

Boring Location Diagram

0 5025 Feet

3/25/2020

ENGINEER

SCALE

56:1286

PROJECT NO.

SHEET

DATE

DS05

1 " = 30 '

Observed area of Subsidence at ground surface

ECS Project No. 56:1286 Page 12

APPENDIX B – Field Operations

Soil Classification Index Boring Logs B-1, B-2, H.A-1

Silts and Clays

Consistency

Safety Hammer SPT N-Value (Blow/Foot)

Automatic Hammer SPT N-

Value (Blow/Foot)

Very Soft Less than 2 Less than 1

Soft 2 – 4 1 – 3

Firm 4 – 8 3 – 6

Stiff 8 – 15 6 – 12

Very Stiff 15 – 30 12 – 24

Hard Greater than 30 Greater than 24

SILT/CLAY DESCRIPTION

MODIFIERS

Modifier Silt/Clay Content

Trace <5% With 5% to12%

Silty/Clayey 13% to 35% Very >35%

ORGANIC MATERIAL MODIFIERS

Modifier Organic Content

Trace 1% to 2% Few 2% to 4%

Some 4% to 8% Many >8%

KEY TO SOIL CLASSIFICATION

Description of Compactness or Consistency in Relation To Standard Penetration Resistance

Granular Materials

Relative Density

Safety Hammer SPT N-Value (Blow/Foot)

Automatic Hammer SPT N-Value (Blow/Foot)

Very Loose Less than 4 Less than 3

Loose 4 – 10 3 – 8

Medium Dense 10 – 30 8 – 24

Dense 30 – 50 24 – 40

Very Dense Greater than 50 Greater than 40

DESCRIPTION OF SOIL COMPOSITION**

(Unified Soil Classification System)

LABORATORY CLASSIFICATION CRITERIA

MAJOR DIVISION

Group Symbol FINER THAN

200 SIEVE %

SUPPLEMENTARY

REQUIREMENTS

SOIL DESCRIPTION

GW <5* D60/D10 greater than 4, 2 / (D x D ) between 1 & 3

Well graded gravels, sandy gravels Gravelly soils (over half of

D30 60 10

Coarse coarse fraction larger than

GP <5* Not meeting above gradation for GW

Gap graded or uniform gravels, sandy gravels grained (over 50% by weight coarser

No. 4) GM >12* PI less than 4 or below A-line Silty gravels, silty sandy gravels

GC >12* PI over 7 above A-line Clayey gravels, clayey sandy gravels

D60/D10 greater than 6, than No.

SW <5*

D 2 / (D x D ) between 1 & 3 Well graded sands, gravelly sands

200 sieve) Sandy soils (over half of coarse fraction finer than

30 60 10

SP <5* Not meeting above gradation requirements

No. 4) SM >12* PI less than 4 or below A-line Silty sands, silty gravelly sands

SC >12* PI over 7 and above A-line Clayey sands, clayey gravelly sands

Fine

Low compressibility

ML Plasticity chart

Silts, very fine sands, silty or clayey fine sands, micaceous silts grained (over 50% by weight finer than

(liquid limit less than 50)

CL Plasticity chart Low plasticity clays, sandy or silty clays

OL Plasticity chart, organic odor or color Organic silts and clays of low plasticity

Micaceous silts, diatomaceous silts, No. 200 sieve)

High compressibility

MH Plasticity chart volcanic ash

(liquid limit more than 50)

CH Plasticity chart Highly plastic clays and sandy clays

OH Plasticity chart, organic odor or color Organic silts and clays of high plasticity

Soils with fibrous organic matter PT Fibrous organic matter; will char, burn or glow Peat, sandy peats, and clayey peat

* For soils having 5 to 12 percent passing the No. 200 sieve, use a dual symbol such as SP-SM.

** Standard Classification of Soils for Engineering Purposes (ASTM D 2487)

SAND/GRAVEL DESCRIPTION

MODIFIERS

Modifier Sand/Gravel

Content

Trace <15% With 15% to 29%

Sandy/Gravelly >29%

* = Hand Auger to Avoid Possible Underground Utility Conflict.

Brown Fine SAND (Fill) (SP)

VERY LOOSE Dark Gray Fine SAND (Fill) (SP)

LOOSE Light Brown Fine SAND (Fill) (SP)

LOOSE Brown Fine SAND (Fill) (SP)

MEDIUM DENSE Orange Brown Clayey Fine

SAND (SC)

DENSE to MEDIUM DENSE Orange Clayey Fine

SAND (SC)

See Field Exploration Plan

Boring Completed: 3/4/20

Boring No.: B1

Boring Location:

B L

O W

S P

E R

IN

of 4

Drill Rod: AWJ Drill Mud: Super Gel-X

Time: Drilling

Unconfined Compression

Length of Casing: 20'

S A

M P

L E

T Y

P E

Driller: OtherDrill Rig: Truck Mounted

DESCRIPTION

L

IQ

U

ID

L

IM

IT

N V al u e

M O

IS

T

U R

E C

O N

T E

N T

Remarks

Memorial Park Depression

P E

R C

E N

T O

R G

A N

IC

M

A T

E R

IA

L

Groundwater Depth: 14.5 ft

0 1 20 10 20 30 40

P E

R C

E N

T P

A S

S

IN

G N

O . 2

S

IE

V

E

D E

P T

H , F

E E

T

Casing Size:

Boring Begun: 3/4/20Date: 3/4/20

Triaxial Compression

Project: Client: City of Debary

S A

M P

L E

N O

LOG OF BORING

Project No.: 56-1286

Pocket Penetrometer Disturbed Sample

Torvane

Sheet 1

P

A

S T

IC

L

IM

IT

Pocket Penetrometer Undisturbed Sample

SHEAR STRENGTH

(ksf)

LO

G

O F

B O

R

IN

G

6-

.G

P J

E

LL

IS

A

S S

O C

IA

T

E S

.G D

T

/2

/2

DENSE to MEDIUM DENSE Orange Clayey Fine SAND (SC) (Continued)

MEDIUM DENSE Gray Clayey Fine SAND (SC)

MEDIUM DENSE Brown Clayey Fine SAND (SC)

Gray Moderately to Hard Weathered Limestone

See Field Exploration Plan

Boring Completed: 3/4/20

Boring No.: B1

Boring Location:

B L

O W

S P

E R

IN

of 4

Drill Rod: AWJ Drill Mud: Super Gel-X

Time: Drilling nUnconfined Compressio

Length of Casing: 20'

S A

M P

L E

T Y

P E

U

ID

L

IM

IT

N V al u e

M O

IS

T

U R

E C

O N

T E

N T

Remarks

Memorial Park Depression

P E

R C

E N

T O

R G

A N

IC

M

A T

E R

IA

L

Groundwater Depth: 14.5 ft

0 1 20 10 20 30 40

P E

R C

E N

T P

A S

S

IN

G N

O . 2

S

IE

V

E

D E

P T

H , F

E E

T

Casing Size:

Boring Begun: 3/4/20Date: 3/4/20

Triaxial Compression

Project: Client: City of Debary

S A

M P

L E

N O

LOG OF BORING

Project No.: 56-1286

Pocket Penetrometer Disturbed Sample

Sheet 2

A

S T

IC

L

IM

IT

Pocket Penetrometer Undisturbed Sample

SHEAR STRENGTH

(ksf)

LO

G

O F

B O

R

IN

G

6-

.G

P J

E

LL

IS

A

S S

O C

IA

T

E S

.G D

T

/2

/2

50/6"

50/3"

50/2"

Gray Moderately to Hard Weathered Limestone (Continued)

HARD Gray Silty CLAY (CH)

50/6"

50/3"

50/2"

See Field Exploration Plan

Boring Completed: 3/4/20

Boring No.: B1

Boring Location:

B L

O W

S P

E R

IN

of 4

Drill Rod: AWJ Drill Mud: Super Gel-X

Time: Drilling

Unconfined Compression

Length of Casing: 20'

S A

M P

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Memorial Park Depression

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Groundwater Depth: 14.5 ft

0 1 20 10 20 30 40

P E

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S

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Casing Size:

Boring Begun: 3/4/20Date: 3/4/20

Triaxial Compression

Project: Client: City of Debary

S A

M P

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N O

LOG OF BORING

Project No.: 56-1286

Pocket Penetrometer Disturbed Sample

Sheet 3

A

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Pocket Penetrometer Undisturbed Sample

SHEAR STRENGTH

(ksf)

LO

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/2

HARD Gray Silty CLAY (CH) (Continued)

Gray Weathered Limestone

Boring Terminated @ 90 ft.

See Field Exploration Plan

Boring Completed: 3/4/20

Boring No.: B1

Boring Location:

B L

O W

S P

E R

IN

of 4

Drill Rod: AWJ Drill Mud: Super Gel-X

Time: Drilling

Unconfined Compression

Length of Casing: 20'

S A

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Memorial Park Depression

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Groundwater Depth: 14.5 ft

0 1 20 10 20 30 40

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G N

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Casing Size:

Boring Begun: 3/4/20Date: 3/4/20

Triaxial Compression

Project: Client: City of Debary

S A

M P

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N O

LOG OF BORING

Project No.: 56-1286

Pocket Penetrometer Disturbed Sample

Sheet 4

A

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Pocket Penetrometer Undisturbed Sample

SHEAR STRENGTH

(ksf)

LO

G

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* = Hand Auger to Avoid Possible Underground Utility Conflict.

Gray Brown Fine SAND (Fill) (SP)

VERY LOOSE to LOOSE Brown Fine SAND (Fill)

(SP)

LOOSE Brown Orange Fine SAND (Fill) (SP)

LOOSE to MEDIUM DENSE Gray Clayey Fine

SAND (SC)

See Field Exploration Plan

Boring Completed: 3/4/20

Boring No.: B2

Boring Location:

B L

O W

S P

E R

IN

of 3

Drill Rod: AWJ Drill Mud: Super Gel-X

Time: Drilling

Unconfined Compression

Length of Casing: 20'

S A

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Memorial Park Depression

P E

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Groundwater Depth: NE

0 1 20 10 20 30 40

P E

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H , F

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Casing Size:

Boring Begun: 3/4/20Date: 3/4/20

Triaxial Compression

Project: Client: City of Debary

S A

M P

L E

N O

LOG OF BORING

Project No.: 56-1286

Pocket Penetrometer Disturbed Sample

A

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Pocket Penetrometer Undisturbed Sample

SHEAR STRENGTH

(ksf)

LO

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LOOSE to MEDIUM DENSE Gray Clayey Fine SAND (SC) (Continued)

LOOSE to MEDIUM DENSE Gray Clayey Fine

SAND(SC)

Gray Moderately Weathered Soft Limestone

VERY DENSE Brown Orange Clayey Fine SAND

(SC)

See Field Exploration Plan

Boring Completed: 3/4/20

Boring No.: B2

Boring Location:

B L

O W

S P

E R

IN

of 3

Drill Rod: AWJ Drill Mud: Super Gel-X

Time: Drilling nUnconfined Compressio

Length of Casing: 20'

S A

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Memorial Park Depression

P E

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A N

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M

A T

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Groundwater Depth: NE

0 1 20 10 20 30 40

P E

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A S

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G N

O . 2

S

IE

V

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H , F

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Casing Size:

Boring Begun: 3/4/20Date: 3/4/20

Triaxial Compression

Project: Client: City of Debary

S A

M P

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N O

LOG OF BORING

Project No.: 56-1286

Pocket Penetrometer Disturbed Sample

Sheet 2

A

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Pocket Penetrometer Undisturbed Sample

SHEAR STRENGTH

(ksf)

LO

G

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50/6"

50/6"

VERY DENSE Brown Orange Clayey Fine SAND (SC) (Continued)

Brown Soft to Hard Weathered Limestone

Boring Terminated @ 72 ft.

50/6"

50/6"

See Field Exploration Plan

Boring Completed: 3/4/20

Boring No.: B2

Boring Location:

B L

O W

S P

E R

IN

of 3

Drill Rod: AWJ Drill Mud: Super Gel-X

Time: Drilling

Unconfined Compression

Length of Casing: 20'

S A

M P

L E

T Y

P E

U

ID

L

IM

IT

N V al u e

M O

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Remarks

Memorial Park Depression

P E

R C

E N

T O

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A N

IC

M

A T

E R

IA

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Groundwater Depth: NE

0 1 20 10 20 30 40

P E

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E N

T P

A S

S

IN

G N

O . 2

S

IE

V

E

D E

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H , F

E E

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Casing Size:

Boring Begun: 3/4/20Date: 3/4/20

Triaxial Compression

Project: Client: City of Debary

S A

M P

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N O

LOG OF BORING

Project No.: 56-1286

Pocket Penetrometer Disturbed Sample

Sheet 3

A

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Pocket Penetrometer Undisturbed Sample

SHEAR STRENGTH

(ksf)

LO

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DCP = Dynamic Hand Cone Penetrometer Value.

Boring Terminated @ 5 ft.

See Field Exploration Plan

Boring Completed: 3/9/20

Boring No.: HA1

Boring Location:

of 1

Drill Rod: Drill Mud:

Time: Drilling

Unconfined Compression

Length of Casing:

S A M P L E T Y P E

Driller: VinayDrill Rig: Hand Auger

E s ti m a te d N V a lu e

U

ID

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M O

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C O N T E N T

Remarks

Memorial Park Depression

P E R C E N T O R G A N

IC

M A T E R

IA

L

Groundwater Depth: NE

0 1 20 10 20 30 40

P E R C E N T P A S S

IN

G

N O S

IE

V E

D E P T H F E E T

Casing Size:

Boring Begun: 3/9/20Date: 3/9/20

Triaxial Compression

Project: Client: City of Debary

S A M P L E N O

LOG OF BORING

Project No.: 56-1286

Pocket Penetrometer Disturbed Sample

A S T

IC

L

IM

IT

Pocket Penetrometer Undisturbed Sample

SHEAR STRENGTH

(ksf)

L O G O F B O R

IN

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-1 .G P J

E L L

IS

A S S O C

IA

T E S .G D T

/2 /2

D C P V A L U E P E R /4

VERY LOOSE Brown Fine SAND (Fill) (SP)

VERY LOOSE Dark Gray Fine SAND (Fill) (SP)

DCP = Dynamic Hand Cone Penetrometer Value.

VERY LOOSE Brown Fine SAND (SP)

VERY LOOSE Dark Gray Fine SAND (SP)

Boring Terminated @ 5 ft.

See Field Exploration Plan

Boring Completed: 3/9/20

Boring No.: HA1

Boring Location:

of 1

Drill Rod: Drill Mud:

Time: Drilling

Unconfined Compression

Length of Casing:

S A M P L E T Y P E

Driller: VinayDrill Rig: Hand Auger

U

ID

L

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M O

IS

T U R E

C O N T E N T

Remarks

Memorial Park Depression

P E R C E N T O R G A N

IC

M A T E R

IA

L

Groundwater Depth: NE

0 1 20 10 20 30 40

P E R C E N T P A S S

IN

G

N O S

IE

V E

D E P T H F E E T

Casing Size:

Boring Begun: 3/9/20Date: 3/9/20

Triaxial Compression

Project: Client: City of Debary

S A M P L E N O

LOG OF BORING

Project No.: 56-1286

Pocket Penetrometer Disturbed Sample

A S T

IC

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Pocket Penetrometer Undisturbed Sample

SHEAR STRENGTH

(ksf)

L O G O F B O R

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D C P V A L U E P E R /4

E s ti m a te d N V a lu e

ECS Project No. 56:1286 Page 13

APPENDIX C – Laboratory Testing

Laboratory Test Results Summary

ECS FLORIDA, LLC

Laboratory Testing Summary Date: 3/20/2020

Project Number:56:1286 Project Name:Memorial Park Subsidence Investigation

Percent Boring Sample Depth Moisture Liquid Plastic Plasticity Passing CBR Organics % Number Number (FT) Content USCS Limit Limit Index No. 200 Value

(%) Sieve

B-1 7 20 20.1 SC 13.0

B-2 9 30 32.0 SC 17.2

Summary Key:

V = Virginia Test Method Hyd = Hydrometer UCS = Unconfined Compression Soil OC = Organic Content S = Standard Proctor Con = Consolidation UCR = Unconfined Compression Rock SA = See Attached M= Modified Proctor DS = Direct Shear LS = Lime Stabilization NP = Non Plastic

GS = Specific Gravity CS = Cement Staibilization * = Test Not Conducted

Permeability rate Kh (ft/day)

Lab Workbook and Summary Sheet.xls Page 1

ECS Project No. 56:1286 Page 14

APPENDIX D – Supplemental Report Documents

Geophysical Investigation Report

FINAL REPORT

GEOPHYSICAL INVESTIGATION

MEMORIAL PARK DEPRESSION SITE

DEBARY, FL

Prepared for ECS Florida, LLC South Daytona, FL

Prepared by GeoView, Inc.

St. Petersburg, FL

A Geophysical Services Company

4610 Central Avenue Tel.: (727) 209-2334 St. Petersburg, FL 33711 Fax: (727) 328-2477

February 27, 2020

Mr. Vinay Kumar Arebelli ECS Florida, LLC 2330 South Nova Road, Suite A South Daytona, FL 32119

Subject: Transmittal of Final Report for Geophysical Investigation Memorial Park Depression Site - Debary, FL GeoView Project Number 31157

Dear Mr. Vinay Kumar Arebelli, GeoView, Inc. (GeoView) is pleased to submit the final report that summarizes and presents the results of the geophysical investigation conducted at the Memorial Park Depression site. Ground penetrating radar and electrical resistivity were used to evaluate near-surface geological conditions. GeoView appreciates the opportunity to have assisted you on this project. If you have any questions or comments about the report, please contact us.

GEOVIEW, INC.

Michael J. Wightman, P.G.

Principal Geophysicist, President Florida Professional Geologist Number 1423

Steve Scruggs, P.G.

Senior Geophysicist Florida Professional Geologist Number 2470

1.0 Introduction

A geophysical investigation was conducted at Memorial Park located at 76

Dirksen Drive in Debary, Florida. The project site consisted of the area located west of the memorial where there was reportedly a depression that has subsequently been filled. The total survey area was approximately 30 by 110 feet

(ft) in plan dimension. The investigation was conducted on February 24, 2020.

The purpose of the investigation was to help characterize near-surface geological conditions and to identify subsurface features that may be associated with sinkhole activity within the survey area. The results of the investigation are shown on Figure 1.

2.0 Description of Geophysical Investigation

2.1 Ground Penetrating Radar Survey

The GPR survey was conducted along a series of transects spaced 5 to 10 ft apart (Figure 1). The GPR data was collected with a GSSI radar system. The GPR settings used for the survey are presented in Table 1.

Table 1 GPR Equipment Settings Used for GPR Surveys

Antenna Frequency

Time Range (nano-seconds)

Estimated Depth of GPR Signal Penetration

350 MHz 1/ 165 15 to 20 ft bls 1/ MHz means mega-Hertz and is the mid-range operating frequency of the GPR antenna.

A description of the GPR technique and the methods employed for geological characterization studies is provided in Appendix 2.2.

2.2 Electrical Resistivity Imaging Survey

The ERI survey was conducted using the Advanced Geosciences, Inc. Sting R8 automatic electrode resistivity system. One ERI transect was performed using 28 electrodes with an “a spacing” of 7.5 ft. A dipole-dipole combined with an inverse Schlumberger electrode configuration was used with a maximum “n value” of six. The ERI data was analyzed using EarthImager 2D, a computer inversion program, which provides two-dimensional vertical cross-sectional resistivity model (pseudo-section) of the subsurface. A description of the ERI method and the methods employed for geotechnical characterization studies is provided in Appendix A2.2. A discussion of the modeling process used to create the ERI results is provided in Appendix A2.2.1.

3.0 Identification of Possible Sinkhole Features Using GPR and ERI Methods

3.1 Identification of Possible Sinkhole Features Using GPR

The features observed on GPR data that are most commonly associated with sinkhole activity are:

• A downwarping of GPR reflector sets, that are associated with suspected lithological contacts, towards a common center. Such features typically have a bowl or funnel shaped configuration and can be associated with a deflection of overlying sediment horizons caused by the migration of sediments into voids in the underlying limestone. If the GPR reflector sets are sharply downwarping and intersect, they can create a “bow-tie” shaped GPR reflection feature, which often designates the apparent center of the GPR anomaly.

• A localized significant increase in the depth of the penetration and/or amplitude of the GPR signal response. The increase in GPR signal penetration depth or amplitude is often associated with either a localized increase in sand content at depth or decrease in soil density.

• An apparent discontinuity in GPR reflector sets, that are associated with suspected lithological contacts. The apparent discontinuities and/or disruption of the GPR reflector sets may be associated with the downward migration of sediments.

The greater the severity of these features or a combination of these features the greater the likelihood that the identified feature is a sinkhole. It is not possible based on the GPR data alone to determine if an identified feature is a sinkhole or, more important, whether that feature is an active sinkhole.

3.2 Identification of Possible Sinkhole Features Using ERI

Sinkhole features are typically characterized by one of the following conditions on the ERI profile:

1. The occurrence of highly resistive material that extends to depth in a columnar fashion towards the top of the limestone. Such a feature may indicate the presence of a sand-filled depression or raveling zone.

2. The localized presence of low-resistivity material extending below the interpreted depth to the top of limestone. Such a feature may indicate the presence of a clay-filled void or fracture with the limestone or the presence of highly weathered limestone rock.

3. Any significant localized increase in the depth to limestone. Such a feature may indicate the presence of an in-filled depression (paleo-sink).

When comparing the results of the ERI method, the following considerations should be given. The ERI method, for example, describes the transition from clay to limestone as a transition, rather than a discrete depth. This transition is due to several factors including: a) The vertical density of the resistivity data decreasing with depth and b) The possibility that the upper portion of the limestone is weathered which would create a physical transition zone in terms of resistivity between the clay and competent (non-weathered) limestone and c) The limitations in the modeling process.

4.0 Survey Results

4.1 Discussion of GPR Survey Results

Results of the GPR survey indicated the presence of two well-defined, relatively continuous sets of GPR reflectors at approximate depth ranges of 1 to 3 ft bls and 8 to 11 ft bls. The reflector sets are most likely associated with some change in lithological conditions at those depth ranges.

Description of GPR Anomaly

One GPR anomaly area was identified in the central portion of the survey area. The anomaly is characterized by the observed downwarping of the GPR reflector set ranging in apparent vertical relief from approximately 2 to 3 ft. In addition, a localized increase in the depth of penetration of the GPR signal was also observed within the anomaly area. The apparent center of the feature is characterized as the area of maximum downwarping of the previously referenced GPR reflectors.

In addition, the GPR data identified a suspected buried utility at a depth range of approximately 1 to 3 ft bls in the northern portion of the survey area (Figure 1).

An example of the GPR data collected across the anomaly area is provided in Appendix 1. A discussion of the limitations of the GPR technique in geological characterization studies is provided in Appendix 2.

4.2 Discussion of ERI Survey Results

Results from the ERI survey are presented in Appendix 1. The ERI transect is of acceptable quality (a discussion of the criteria used to determine the quality of an ERI inversion model is provided in Appendix A2.3.1).

Analysis of the ERI transect indicate the presence of high resistivity near-surface soil materials to a depth range of 15 to 23 ft bls (represented in yellow to red on the ERI transect). This high resistivity layer is most likely associated with sand soils. The surficial high resistivity layer is underlain by a moderate to low resistivity layer (represented in green to blue) to the maximum depth of investigation of the ERI transect of approximately 49 ft bls. The moderate to low resistivity soils are most likely associated with an increase in the clay content of the soils at depth.

Discussion of ERI Anomaly

One ERI anomaly was identified at the project site within the retention pond area and area of observed sinkhole activity (Figure 1). The ERI anomaly was characterized by the apparent shallow breach of the moderate resistivity soils at an estimated depth range of 1 to 11 ft bls. It is noted that the underlying low resistivity layer appears to be undisturbed. Accordingly, this ERI anomaly may be associated with naturally-occurring lateral variations in resistivity not related to sinkhole activity.

4.3 Correlation of Geophysical Study Results

There is a poor correlation in the depths between the GPR and ERI identified layers (GPR: 1 to 3 ft bls, 8 to 11 ft bls and ERI: 15 to 23 ft bls). It is suspected that the GPR-identified layers are associated with some minor change in lithological conditions that was not resolved by the ERI method. The maximum depth of the GPR signal does appear to correlate to the presence of the low-resistivity sediments identified by the ERI survey. Since the GPR signal is attenuated (absorbed) within low resistivity sediments there is a good correlation between the two methods from this respect.

The GPR data indicated an anomaly area characterized by the apparent downwarping of the reflector sets coupled with an increase in signal penetration.

The ERI data indicated a corresponding localized breach of moderate resistivity soils at a similar shallow depth range of the observed downwarping of the GPR reflector sets. Accordingly, the geophysical methods were in good agreement in this regard. However, it is not possible based on the geophysical results to determine whether the identified anomalies have a potential for collapse or subsidence that could have an impact on the memorial. It is recommended that the central portion of the anomalies be further evaluated using appropriate geotechnical test methods.

APPENDIX 1

FIGURE, EXAMPLE OF GPR ANOMALY, AND ERI TRANSECT

ERI Anomaly

GPR Transect 4 Showing Example of GPR Anomaly

GPR Anomaly

A2-1

APPENDIX 2

DESCRIPTION OF GEOPHYSICAL METHODS, SURVEY

METHODOLOGIES AND LIMITATIONS

A2.1 On Site Measurements

The measurements that were collected and used to create the site map were made using a fiberglass measuring tape. The degree of accuracy of such an approach is typically +/- 2.5% for lengths and +/- 2.5 degrees for angles.

A2.2 Ground Penetrating Radar

Ground Penetrating Radar (GPR) consists of a set of integrated electronic components that transmits high frequency (200 to 1500 megahertz [MHz]) electromagnetic waves into the ground and records the energy reflected back to the ground surface. The GPR system consists of an antenna, which serves as both a transmitter and receiver, and a profiling recorder that both processes the incoming signal and provides a graphic display of the data. The GPR data can be reviewed as both printed hard copy output or recorded on the profiling recorder’s hard drive for later review. GeoView uses a Mala GPR system.

A GPR survey provides a graphic cross-sectional view of subsurface conditions. This cross-sectional view is created from the reflections of repetitive short-duration electromagnetic (EM) waves that are generated as the antenna is pulled across the ground surface. The reflections occur at the subsurface contacts between materials with differing electrical properties. The electrical property contrast that causes the reflections is the dielectric permittivity that is directly related to conductivity of a material. The GPR method is commonly used to identify such targets as underground utilities, underground storage tanks or drums, buried debris, voids or geological features.

The greater the electrical contrast between the surrounding earth materials and target of interest, the greater the amplitude of the reflected return signal.

Unless the buried object is metal, only part of the signal energy will be reflected back to the antenna with the remaining portion of the signal continuing to propagate downward to be reflected by deeper features. If there is little or no electrical contrast between the target interest and surrounding earth materials it will be very difficult if not impossible to identify the object using GPR.

The depth of penetration of the GPR signal is very site specific and is controlled by two primary factors: subsurface soil conditions and selected antenna frequency. The GPR signal is attenuated (absorbed) as is passes through earth materials.