8-0.6 Geotechnical Report.pdf

CAL-TECH TESTING, INC.

P.O. BOX 1625

Lake City, Florida 32056-1625 Phone: (386) 755-3633

Fax: (386) 752-5456

BORING LOCATION PLAN

Suwannee County Airport-8 Unit Hangar

Live Oak, Florida

N

Boring Location Coordinates Provided in the Logs

Florida Registry No. 33930 100 S.W. 75th St. Ste. 201 Gainesville FL 32607 Telephone: 800.770.9990 Admin@Geohazards.com

Expert Solutions. Exceptional Service.

November 12, 2024

GEOPHYSICAL INVESTIGATION OF THE SUBSURFACE AT

SUWANNEE COUNTY AIRPORT

8 UNIT T-HANGAR STRUCTURE

LIVE OAK, FLORIDA

Geohazards Investigation No. 241225FL

INTRODUCTION

Purpose

Geohazards was tasked by Mr. Ivan Marcano from Cal-Tech Testing Inc. to conduct a geophysical investigation at the above referenced site. In particular, our efforts are designed to determine the presence of subsurface cavities and subsurface zones of disruption that may contribute to subsidence in a proposed area for the construction of additional T-Hangars and taxilanes on the property.

Scope

The investigation included the following activities:

A review of available geologic maps and other published data to establish the general probable lithology and regional conditions for the site.

A reconnaissance of the property to identify surface conditions pertinent to the purpose of the investigation.

An Electrical Resistivity Imaging (ERI) investigation of the site to assist in the recognition of site-specific geological conditions at the subject property and to determine evidence for the presence of anomalous subsurface features or conditions.

A final report summarizing the results and conveying our professional opinions.

Suwannee County Airport, Live Oak, Florida November 12, 2024 Geohazards Project No. 241225FL Page 2 of 6

Site Information

The initial reconnaissance and geotechnical investigation was conducted on October 30, 2024 by Geohazards geologists, Mr. Hunter Moran, Mr. Will Skipper, and Ms. Mia Luna.

The area of investigation involved a region north of the existing T-Hangars present on the property where an additional T-Hangar is proposed to be constructed. The survey area measured approximately 1.25 acres.

REGIONAL CONDITIONS

Geology

Based on map consultations and personal inspection, the surficial geologic materials at the study site are undifferentiated Pleistocene/Holocene sediments overlying the Statenville Formation of the Hawthorn Group. The Pleistocene/Holocene sediments are composed of a varying thickness of undifferentiated sediments consisting of siliciclastics, organics and freshwater carbonates. The siliciclastics are light gray, tan, brown to black, unconsolidated to poorly consolidated, clean to clayey, silty, unfossiliferous, variably organic-bearing sands to blue green to olive green, poorly to moderately consolidated, sandy, silty clays. Organics occur as plant debris, roots, disseminated organic matrix, and beds of peat. Freshwater carbonates, often referred to as marls, are buff to tan, unconsolidated to poorly consolidated, fossiliferous carbonate muds. Sand, silt, and clay may be present in limited quantities. These carbonates often contain organics.

The Miocene-age Statenville Formation consists of interbedded sands, clays and dolostones with common to very abundant phosphate grains. The sands predominate and are light gray to light olive gray, poorly indurated, phosphatic, fine to coarse grained with scattered gravel and with minor occurrences of fossils. Clays are yellowish gray to olive gray, poorly consolidated, variably sandy and phosphatic, and variably dolomitic. The dolostones, which occur as thin beds, are yellowish gray to light orange, poorly to well indurated, sandy, clayey and phosphatic with scattered mollusk molds and casts. Phosphate occurs in the Statenville Formation in economically important amounts. Silicified fossils and opalized claystones are also found in the Statenville Formation.

The Oligocene-age Suwannee Limestone underlies the Statenville Formation, and consists of a white to cream, poorly to well indurated, fossiliferous, vuggy to moldic limestone (grainstone and packstone). The dolomitized parts of the Suwannee Limestone are gray, tan, light brown to moderate brown, moderately to well indurated, finely to coarsely crystalline, dolostone with limited occurrences of fossiliferous beds. Silicified limestone is common in the Suwannee Limestone. Fossils present in the Suwannee Limestone include mollusks, foraminifers, corals and echinoids. In places, this limestone has experienced significant dissolution and the creation of an intricate cavernous system. Problems in the development of sinkholes are related to the size and nearness to the surface of the limestone and these underground cavities. The upper surface of the limestone is highly irregular and in some places, no sediments will overlie the Suwannee Limestone.

Geohazards Project No. 241225FL Page 3 of 6

Topography

The subject property is located in Section 21 of Township 2 South, Range 13 East. Elevation information available on the United States Geological Survey (USGS) Live Oak West, Florida 7.5-minute series topographic quadrangle map is attached. The immediate neighborhood of the subject property ranges from approximately 95 to 100 feet North American Datum of 1983 (NAD83). The subject property is situated at approximately 97 feet NAD83.

Hydrology

Based on the September 2017, USGS potentiometric surface map of the Upper Floridan aquifer, the expected potentiometric surface in the area of the subject property is approximately 50 feet

NGVD.

Soils

The U.S. Department of Agriculture Soil Conservation Service (SCS) Soil Survey of Suwannee County indicates that the soil underlying the subject property is the Falmouth-Bonneau-Blanton Complex.

This soil unit consists of 0 to 5 percent slopes, and generally forms on hills or knolls on marine terraces. The parent material for the Falmouth-Bonneau-Blanton Complex is clayey and sandy marine deposits. Typical soil profiles consist of fine sand within the upper 10 to 41 inches, overlying sandy loam and sandy clay loam. This soil ranges from somewhat poorly drained to well drained. The available water storage in profile ranges from low to moderate (from approximately

5.9 inches to 8 inches).

GEOLOGICAL AND GEOTECHNICAL

Geophysical Surveys

Electrical Resistivity Imaging

An electrical resistivity imaging (ERI) survey was completed for the purpose of identifying possible subsurface anomalies, which may be related to karst or sinkhole activity. Color prints of the modeled ERI cross sections are included. The ERI survey was conducted in general accordance with ASTM D6431 “Standard Guide for Using Direct Current Resistivity Method for Subsurface Investigation,” as applied to a multi-electrode resistivity system.

Electrical resistivity measurements involve the passing of an electric current underground and measuring its resistance to flow. Different earth materials (e.g. clay, sand, limestone) and subsurface cavities resist the flow of electrical current differently. Substantially greater contrasts in the degree of resistance (anomalies) are used to identify and locate boundaries among different materials as well as the presence of cavities.

Geohazards Project No. 241225FL Page 4 of 6

The ERI data were collected using Dipole/Gradient array type sequencing. The depth limits of the modeled ER data are primarily dependent on the type of array (Dipole-Dipole, Schlumberger, Wenner, etc.) and the total spread of the electrode array.

Measurements of ERI were made with Advanced Geosciences, Inc. SuperSting R8 8-channel Resistivity Meter with an incorporated switchbox and a passive electrode cable system. The resulting data was processed utilizing EarthImager 2D, a computer program that produces two-dimensional vertical cross section models of the subsurface. The quality of these models was assessed by root mean square (RMS) and L2 values.

The orientation, configuration and distribution of the ERI traverses were designed to provide representative coverage of the site of investigation (see ERI location map). Six traverses were measured. The maximum depth of penetration was 58.1 feet.

RESULTS

Geophysical Investigation

Electrical Resistivity

1. Displayed calculated resistivity values at the subject property ranged from approximately 1 to 1,000 Ohm-meters for the traverses conducted. A color print-out of the modeled two-dimensional ERI cross sections are included. The quality of the resistivity model is considered to be satisfactory.

2. ERI traverses conducted in the investigation area were generally interpreted to contain a surficial layer of highly resistive sands (reds, oranges, yellows). Overlying lower resistivity clayey material (greens and blues). Followed by an upper limestone surface with varying degrees of weathering (greens, yellows, oranges, reds).

3. The data collected on ERI traverse 1 was interpreted to contain a surficial layer of sand generally continuing to approximately 12 feet depth, overlying clayey material which continues to depths ranging from approximately 22 feet to 35 feet depth. Limestone is interpreted to be present at depth ranges beginning from approximately 13 feet to 35 feet and continuing to the maximum depth of penetration of 58.1 feet depth. An anomaly is interpreted to be present in ERI traverse 1 from 0 to 70 feet along the traverse. This anomaly is characterized by a thickened sequence of surficial highly resistive sands which suggests the potential presence of a paleosink.

4. The data collected on ERI traverse 2 was interpreted to contain a surficial layer of sand ranging from approximately 5 feet to 15 feet depth, overlying clayey material which continues to depths ranging from 25 feet to the maximum depth of penetration of 52.3 feet. A limestone pinnacle is interpreted to be present from 50 feet to 162 feet along the traverse beginning at depths of approximately 25 feet and continuing to the maximum depth of penetration. No anomalous features were interpreted to be present in ERI traverse 2.

Geohazards Project No. 241225FL Page 5 of 6

5. The data collected on ERI traverse 3 was interpreted to contain a surficial layer of sand ranging from approximately 3 feet to 25 feet depth, overlying clayey material which continues to depths ranging from approximately 22 feet to the maximum depth of penetration of 52.3 feet depth. A limestone pinnacle is interpreted to be present from approximately 55 feet to 142 feet along the traverse, beginning at a depth of approximately 22 feet. No anomalous features were interpreted to be present within ERI traverse 3.

6. The data collected on ERI traverse 4 was interpreted to contain a surficial layer of sand ranging from approximately 2 feet to 13 feet depth, overlying clayey material which continues to depths ranging from 20 feet to 30 feet. Limestone is interpreted to be present beginning at a depth of approximately 20 feet and continues to the maximum depth of penetration of

46.5 feet depth. No anomalous features were interpreted to be present within ERI traverse 4.

7. The data collected on ERI traverse 5 was interpreted to contain a surficial layer of sand ranging from approximately 3 feet to 15 feet depth, overlying clayey material which continues to depths ranging from 25 feet to the maximum depth of penetration of 58.1 feet. Two limestone pinnacles are interpreted to be present from approximately 40 feet to 110 feet along the traverse and again from 180 feet to 250 feet along the traverse beginning at depths of 30 feet and 20 feet respectively. This central portion of the traverse may be indicative of a paleosink, or relic sinkhole. This area appears stable due to the defined clayey layer between the thickened sand sequence and underlying limestone.

8. The data collected on ERI traverse 6 was interpreted to contain a surficial layer of sand ranging from 3 feet up to the maximum depth of penetration of 58.1 feet depth. These highly resistive sands are underlain by clayey material and/or weathered limestone which continues to 58.1 feet depth within the northeastern portion of the traverse. Low resistivity clay is interpreted to be present from approximately 90 feet to 140 feet along the traverse beginning at a depth of 18 feet and continuing to the maximum depth of penetration. An anomalous feature is interpreted to be present from 0 feet to 110 feet along the traverse characterized by a thickened sequence of sand suggesting the presence of a paleosink. This feature is interpreted to be present in ERI traverse 1 as well.

Geohazards Project No. 241225FL Page 6 of 6

CONCLUSIONS

On October 30, 2024, an initial reconnaissance and geophysical survey was conducted at the Suwannee County Airport in a region north of the existing T-Hangars present on the property where an additional T-Hangar is proposed to be constructed.

The ERI survey indicated a variable upper limestone surface and instances of interpreted thickened sand sequences suggesting the presence of a paleosink generally located in the southwestern portion of the survey area. This is illustrated in ERI figures for traverses 1 and 6.

Geohazards recommends SPT borings within the areas indicated to be anomalous within our ERI survey to determine the potential for future settlement of structures constructed in this region.

A third boring could be situated to verify the geophysically identified paleosink in ER Traverse 5, but Geohazards does not opine the feature is active.

LIMITATIONS

While due care has been exercised in the performance of these measurements and their interpretation, Geohazards can make no representations, warranties, or guarantees with respect to latent or concealed conditions which may exist that may be beyond the limits of detection with the methodologies used. This report is prepared for the exclusive use of Cal-Tech Inc., their agents and assigns. Any use by other parties for any purposes is not authorized.

James Olson, P.G.

Professional Geologist Florida License No. PG2795

This item has been electronically signed and sealed by James Olson, P.G., on November 12, 2024, using a Digital Signature.

Printed copies of this document are not considered signed and sealed and the SHA authentication code must be verified on any electronic copies.

APPENDIX A

Maps and Figures

Suwannee County Airport 13302 80th Terrace Live Oak, Florida 32060

TOPOGRAPHIC MAP

Suwannee County Airport 13302 80th Terrace Live Oak, Florida

100 SW 75th Street, Ste. 201, Gainesville, FL

(352) 371-7243 1-800-770-9990 www.geohazards.com

Suwannee County Airport Elevation: 97 ft.

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