USCG STA Tybee_Geotech Report_Final May 2020.pdf

Prepared for:

United States Coast Guard Facilities Design and Construction Center 5505 Robin Hood Rd., Suite K, Norfolk, VA 23513-2431

Contract No. 70Z05019DPHEBKE06 Task Order No. 70Z04719FATYBEE00, Conduct A/E Services for Topographic and Hydrographic Surveys, Geotechnical Investigation, and Site Soil Evaluation for On-site Sewer Management at USCG Station Tybee, GA

GE OTECHNICAL S ITE CHARACTERIZATION REPORT

U.S. COAST GUARD STATION TYBEE ISLAND

FINAL

MAY 2020

Prepared by:

PHE-BAKER JV LLC

77 Upper Rock, Suite 302 Rockville, MD 20850

This Page Intentionally Left Blank

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Table of Contents 1 Background

2 Site Geology

2.1 Soils

2.2 Geology

2.3 Groundwater

2.4 Seismicity

3 Geotechnical Investigation

3.1 Field Activities

3.2 Laboratory Testing Program

4 Findings

4.1 Subsurface Soil Conditions

4.1.1 New Station Building and Parking Lot Area

4.1.2 Area C

4.2 Groundwater

4.2.1 New Station Building and Parking Lot Area

4.2.2 Area C

4.3 Potential Geologic & Seismic Hazards

4.3.1 Liquefaction Potential

5 Recommendations

5.1 Parameters

5.1.1 New Station Building and Parking Lot Area

5.1.2 Area C

5.2 Foundation Design

5.2.1 Deep Foundations

5.2.2 Shallow Foundations

5.3 Pavement Design

5.3.1 New Station Building and Parking Lot Area

5.3.2 Area C

6 References

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LIST OF TABLES

Table 1. Boring Summary Table Table 2a. Laboratory Summary – USCS Classifications and Atterburg Limits - Table 2b. Laboratory Summary – California Bearing Ratio & Modified Proctor Tests

LIST OF FIGURES

Figure 1 Topographic Map Figure 2a Soil Map- New Station Building and Parking Lot Area Figure 2b Soil Map- Area C Figure 3 Nautical Map c.1852 Figure 4 Nautical Map c.1855 Figure 5 Nautical Map c.1926 Figure 6 Nautical Map c.1944 Figure 7 Nautical Map c.1954 Figure 8 Nautical Map c.1974 Figure 9 Geologic Map Figure 10 Groundwater Map Figure 11 Generalized Subsurface Section- New Station Building and Parking Lot Area Figure 12 Generalized Subsurface Section- Area C

APPENDICES

Appendix A: Geotechnical Exploration Letters (written by Cal-tech)

Appendix B: Liquifaction Analysis

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ACRONYMS

USCG United States Coast Guard

FDCC Facilities Design and Construction Center JV PHE-Baker JV, LLC

ASCE 7-16 ASCE/SEI 7-16, Minimum Design Loads and Associated Criteria for Buildings and Other Structures (2017)

AASHTO American Association of State Highway and Transportation Officials ASTM ASTM International Cal-Tech

CBR

Cal-Tech Testing, Inc.

California Bearing Ratio

DRI Double Ring Infiltrometer FPGA Site Amplification Factor at PGA Fa Site Amplification Factor at 0.2 second k Subgrade Modulus MCE Maximum Considered Earthquake msl Mean Sea Level MW Design Earthquake Magnitude NRCS Natural Resources Conservation Service OSHPD California’s Office of Statewide Health Planning and Development pci Pounds per Cubic Inch PGA MCEG Peak Ground Acceleration PGAM Site Modified Peak Ground Acceleration SM1 Site-Modified Spectral Acceleration Value SD1 Numeric Seismic Design Value at 1.0 Second SA SMS Site-Modified Spectral Acceleration Value SDS Numeric Seismic Design Value at 0.2 Second SA SPT Standard Penetration Test SPT-N Standard Penetration Test N Value

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1 BACKGROUND

The PHE-Baker JV, LLC (JV) performed a geotechnical site characterization in support of proposed facility improvements at the United States Coast Guard (USCG) Station Tybee at Cockspur Island, Georgia. This work was completed for the USCG Facilities Design and Construction Center (FDCC), under Contract Number 70Z05019DPHEBKE06, Order Number 70Z04719FATYBEE00.

A new station building and parking lot is proposed at the project site. The PHE-Baker JV understands that the station building will be an elevated three-story building consisting of a high bay ground-supported boat bay at the ground level with a mix of administrative and dormitory living spaces on the second and third floors. The parking lot is expected to have HS-20 loading due to semi-trailer traffic.

Updates to the current NPS picnic shelter, water well, underground storage tanks (10,000 and 15,000 gallons), and pump house are proposed in the location designated as Area C (see Figure 1 and Appendix A). The PHE-Baker JV understands that the Area C updates will include relocation of the existing pump house and an elevated well head and emergency generator to increase flood resiliency.

2 SITE GEOLOGY

2.1 Soils

A topographic map of the site is included as Figure 1. The soils at the project site are identified by the Natural Resources Conservation Service (NRCS) web soil survey as Made Land (MAE) (Figures 2a and 2b).

The Made Land is considered to have been produced from previously dredged material placed onto former marshland. Review of historic mapping of the Savannah River delta supports this claim. Since the mid-1800’s the shape of the island has changed as a result of maintenance dredging of the channel north of Cockspur Island and development along the Savannah River up to and including the Savannah River harbor, located upstream at Savannah, GA. Material from the Savannah River navigational channel was most likely dredged from the main river channel that outlets into the Atlantic Ocean to provide the necessary depth for larger marine vessels to navigate the river channel and access the harbor. Since the site is thought to be “made land” from river channel dredging and assumed to be close to the dredging site, it is anticipated that the material at the project site will likely be stratified with layers of varying thicknesses of alluvial soil ranging in type from coarse sand to clay-size fraction. Other than the stratification as a result of dredging, the material is most likely devoid of any uniform gradational structure.

A sequence of the Island’s evolution can be seen on Figure 3 though Figure 8. The oldest retrievable nautical map, circa 1852 (Figure 3), identifies the depth of water in the area near the project site between 2 and 10 feet. Over the years, this depth of water in the channel has increased to over 40 feet (April 2017).

According to Climate.gov, sea level has risen approximately 1 foot since 1850. Assuming that no dredge material had been placed at the location prior to 1852 and that the map was drawn using depths taken at mean sea level, the dredged material thickness is estimated to range from approximately 11 to 21 feet, or more. With shallow water depths present at the northern shore of the island, salt marshes may have existed to a lesser extent as they do at the southern and eastern boundaries of the island, as the northern shore is adjacent to the main river channel and the velocity of the water and channel dredging to deepen the channel would likely hinder marsh development. Buried marsh soils would be expected to be identified as material with high organic material and could include organic silt (OL), and organic clay (OH), with varying amounts of sand.

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2.2 Geology

The project site is in the Barrier Island Sequence District physiographic province of Georgia. The Barrier Island Sequence District is at the state’s lowest elevation and contains numerous tidal salt marshes, brackish marshes, and bottomland hardwood swamps. It is flat and grades to low rolling hills at the inner margin. Underlying bedrock is not mapped on geologic maps at the project site. The surficial material is mapped as recent coastal deposits (Figure 9).

2.3 Groundwater

According to the Georgia Geological Survey, the potentiometric surface of the principal artesian aquifer at the project site is approximately -20 feet-msl (mean sea level) (Figure 10). Heavy pumpage from the aquifer has drawn the piezometric surface to a point that is below sea level, which means that it is believed that there is no artesian condition present at the project site. However, the project site is located within the Savannah River at the discharge point to the Atlantic Ocean. It is likely that brackish groundwater will be encountered at mean sea level.

2.4 Seismicity

Seismic design for the project location considers the regional seismicity of the area. The project site is near one of the most seismically active zones in the eastern United States, the Middleton Place- Summerville Seismic Zone (MPSSZ). Seismicity in the region surrounding the 7.3 magnitude earthquake recorded in 1886 has been higher than typical for the southeastern U.S. as a whole since 1886, but was markedly lower during the preceding half century than it has been since 1886.

In the past century, the four largest earthquakes to occur within 250 km of the site include:

November 22, 1974 a Magnitude 4.7 earthquake occurred approximately 75 miles northeast of Tybee Island.

August 03, 1959 a Magnitude 4.4 earthquake occurred approximately 85 miles northeast of Tybee Island.

February 03, 1972 a Magnitude 4.4 earthquake occurred approximately 95 miles north of Tybee Island.

July 26, 1945 a Magnitude 4.3 earthquake occurred approximately 120 miles north of Tybee Island.

3 GEOTECHNICAL INVESTIGATION

The subsurface investigation was completed in two phases:

Phase 1 was performed for the proposed station building and parking lot;

Phase 2 was performed for the proposed updates in Area C.

The Phase 1 subsurface investigation was completed in September 2019 by Cal-Tech Testing, Inc. (Cal- Tech) of Lake City, Florida. The investigation consisted of drilling two Standard Penetration Test (SPT) borings (B-1 and B-2) to depths of 75 ft each for a total of 150 feet, performing one Double-Ring Infiltration (DRI) Test in accordance with ASTM D-3385, and collecting one bulk sample (CBR-1) of near-surface soils for determination of a soaked California Bearing Ratio (CBR).

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The Phase 2 subsurface investigation was completed in March 2020 by Cal-Tech. The investigation consisted of drilling one SPT boring (T1-01) to depth of 75 ft.

See Appendix A for the boring location plans.

3.1 Field Activities

The sampling and penetration procedures of the SPT borings were in general accordance with ASTM D 1586 Penetration Test and Split-Barrel Sampling of Soil, using a mud rotary drill rig. Mud rotary drilling began after the water table was encountered. The standard penetration tests were performed by driving a standard 1.375-inch I.D. and 2 inches O.D. split-spoon sampler with a manual 140-lb hammer falling 30 inches. The number of hammer blows required to drive the sampler a total of 24 inches (upper 10 ft) and 18 inches, in 6-inch increments, were recorded in the boring logs. The penetration resistance, SPT N-value, is the summation of the second and third 6-inch increments. Borings B-1 and T1-01 were sampled continuously to 12 feet and boring B-2 was sampled continuously to 10 feet; after continuous sampling, the boring was sampled at generally 5-foot intervals to the termination depth. At completion, each bore hole was backfilled with fluid mixed with cement grout.

Boring B-1 was drilled in the southeastern corner of the existing parking lot; CBR-1 was also collected in the parking lot at the median. Boring B-2 was drilled in the immediate vicinity of the existing building.

Boring T1-01 was drilled west of the existing picnic shelter structure.

All locations were staked by the on-site surveyor. See Table 1 for the boring summary table. Detailed boring logs are included in Appendix A

3.2 Laboratory Testing Program

Select soil samples from Borings B-1, B-2, and T1-01 were tested in the laboratory by Cal-Tech in general accordance with the following ASTM Test methods:

Unified Soil Classification System (ASTM D2487) Sieve analysis (ASTM D6913) Moisture content (ASTM D2216) Atterberg limits (ASTM D4318)

Additionally, two near-surface bulk soil sample was tested in the laboratory to complete a soaked CBR test (CBR-1 and CBR-T101) in general accordance with ASTM D1883 Standard Test Method for CBR of Laboratory-Compacted Soils.

See Tables 2a and 2b for a summary of the laboratory testing. Detailed laboratory testing results are included in Appendix A.

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4 FINDINGS

4.1 Subsurface Soil Conditions

4.1.1 New Station Building and Parking Lot Area

The subsurface soils primarily consisted of light gray to dark gray sand with varying amounts of silt and clay. Shells and organics were encountered at Boring B-1. Standard Penetration Test (SPT) N-values indicated a generally loose to medium dense condition. Test boring logs are included in Appendix A. A generalized subsurface section is presented as Figure 11.

4.1.2 Area C

The subsurface soils primarily consisted of light gray to dark gray SAND with varying amounts of silt and clay, with the exception of two five-foot layers with elevated fines content and high plasticity; the boring encountered two layers of dark gray sandy CLAY at 18.5 to 23.5 feet below ground surface (bgs) and 38.5 to 43.5 feet bgs. SPT N-values indicated a generally very loose to medium dense condition. Test boring logs are included in Appendix A. A generalized subsurface section is presented in Figure 12.

4.2 Groundwater

Water level measurements were made in the test borings at the times and under the conditions indicated herein. It should be noted that ground water levels might fluctuate due to variations in season, rainfall, temperature, site grading and other factors not evident at the time these measurements were made.

4.2.1 New Station Building and Parking Lot Area

Water levels encountered during drilling were 8.0 and 6.0 feet below the existing ground surface at Borings B-1 and B-2, respectively

4.2.2 Area C

Water levels encountered during drilling were 2.0 feet below the existing ground surface at Boring T1-01.

4.3 Potential Geologic & Seismic Hazards

Using the OSHPD (California’s Office of Statewide Health Planning and Development) Seismic Design Maps web application, summary and detailed reports were generated that provide earthquake ground motion parameters for designing structures in accordance with ASCE 7-16. The depth to the top of rock is greater than 75 feet at the site. The site is classified as Site Class E by its soil stiffness as identified by the SPT blow counts in accordance ASCE 7-16.

The mapped acceleration parameters for the project, according to standard, ASCE/SEI 7-16, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, are presented below:

Site Class E – Soft Clay Soil (based on a weighted average of the N values of the upper 100 feet of soil at B-2 and T1-01 - see Appendix B for the full calculation) Risk Category IV (designated operation center per UFC 3-301-01 Table 2-2) Maximum Considered Earthquake (MCE) Spectral Response Acceleration for peak ground acceleration, PGAM:

o Mapped spectral acceleration at peak ground acceleration (PGA) is 0.184g

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o Site coefficient based on site class for peak ground acceleration (FPGA) = 1.979 o PGAM = .365g

MCE Spectral Response Acceleration for short periods, SMS:

o Mapped spectral acceleration (short period, 0.2 seconds), SS, is 0.337g o Site coefficient based on site class for short periods (Fa) = 2.156 o SMS = 0.727g o SDS = 0.485g (design spectral response acceleration parameter)

MCE Spectral Response Acceleration for 1-second periods, SM1:

o Mapped spectral acceleration (1-second period), S1, is 0.12g o Site coefficient based on site class for 1-second periods (Fv) = 1.7 o SM1 = 0.089g o SD1 = 0.060g (design spectral response acceleration parameter)

4.3.1 Liquefaction Potential

Seismic design was conducted in accordance with the 2019 Unified Facilities Criteria Section C-1.1, which states that Risk Category IV structures shall be designed based on earthquake ground motions that have a one percent probability of exceedance in 50 years, equal to a 5,000-year return period. The design earthquake ground motions used in the analysis were interpolated from seismic coefficients derived from the USGS Unified Hazard Tool Deaggregation calculation. The design earthquake magnitude (Mw) of 6.9 occurs at 76.85 km distance with a peak ground surface acceleration of 0.1834g.

A liquefaction analysis was performed in accordance with the simplified procedure established in Youd et.

al. 2001 and complemented by Cetin et al 2009. Liquefaction potential at the site is considered low when the capacity to demand ratio is calculated higher than 1.3, medium when calculated between 1.1 and 1.3, and high when calculated at 1.1 or lower. Shear wave velocity in the soil was assumed to be 175 m/s (575 feet per second) for the analysis.

4.3.1.1 New Station Building and Parking Lot Area

The liquefaction analysis determined the liquefaction potential at the New Station Building location as high between 10 and 70 feet bgs. Total soil settlement due to seismic-induced consolidation is estimated to be approximately 22 inches. See Appendix B for the detailed liquefaction analysis.

4.3.1.2 Area C

The liquefaction analysis determined the liquefaction potential at the building location as high between 2 and 75 feet bgs with the exception of two dense layers encountered at 45 to 50 feet bgs and 55 to 60 feet bgs. Total soil settlement due to seismic-induced consolidation is estimated to be approximately 34 inches. See Appendix B for the detailed liquefaction analysis.

5 RECOMMENDATIONS

5.1 Parameters

5.1.1 New Station Building and Parking Lot Area

Cohesionless Soils (light gray to brown SAND, dark gray sandy SILT with organics, and dark gray silty SAND) o Friction Angle (ɸ) = 30 degrees

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o Moist Unit Weight = 120 pcf o Cohesion = 0 psf

Cohesive Soils (gray to dark gray CLAY with sand and organics) o Friction Angle (ɸ) = 18 degrees o Moist Unit Weight = 120 pcf o Cohesion = 50 psf o Undrained Shear Strength (Su) = 250 psf

5.1.2 Area C

Based on EM 1110-2-504 correlations with SPT-N Values, and experience with similar soils, consider the following soil parameters:

Cohesionless Soils, upper 45 feet of soil profile (gray SAND and dark gray silty to clayey SAND) o Friction Angle (ɸ) = 26 degrees o Moist Unit Weight = 110 pcf o Cohesion = 0 psf

Cohesionless Soils, greater than 45 feet bgs (gray SAND to dark olive-green silty SAND) o Friction Angle (ɸ) = 32 degrees o Moist Unit Weight = 120 pcf o Cohesion = 0 psf

Cohesive Soils (dark gray sandy CLAY) o Friction Angle (ɸ) = 20 degrees o Moist Unit Weight = 115 pcf o Cohesion = 50 psf o Undrained Shear Strength (Su) = 200 psf

5.2 Foundation Design

5.2.1 Deep Foundations

Based on the extent of potentially liquefiable soils at the proposed building location, traditional deep foundations (i.e piles) are not feasible due to the extreme lateral forces exerted during liquefaction.

PHE-Baker JV recommends consideration for rammed aggregate stone columns as a deep foundation alternative. Stone columns are typically considered a ground improvement method but also have been successfully used to support lightly loaded structures. The advantages of stone columns include the following:

Bearing Capacity Improvement Reduction of Total and Differential Settlement Reduction in Liquefaction Potential of Sands

Typical column layout would include a rectangular grid pattern with 24-inch diameter stone columns spaced on 10-foot centers. Estimated depth would be approximately 50 feet. Typical stone specification for this application is naturally rounded AASHTO #8 coarse aggregate, or equivalent. Refer to a specialty contractor for site specific design requirements.

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5.2.2 Shallow Foundations

Due to the liquefaction concerns at the site, a shallow mat foundation may be advantageous. A mat foundation would maximize the bearing resistance of the onsite soils and minimize risk of catastrophic failure under an extreme seismic event due to liquefaction.

5.3 Pavement Design

Prior to construction of new pavement, the exposed subgrade should be proof rolled and compacted to at least 95 percent of the modified Proctor maximum dry density. Any areas of soft, unsuitable material should be removed and replaced with suitable fill. All proof-rolling and compaction operations should be monitored by an on-site representative that is under the direct supervision of a registered Geotechnical

Engineer. Consider 0-inches of frost penetration in accordance with the UFC 3 301-01, 2013 edition.

Provide adequate drainage within the pavement system to avoid ponding of water and subgrade softening.

5.3.1 New Station Building and Parking Lot Area

Based on the available data, consider a CBR value of 15 and a modulus of subgrade reaction (k) of 225 pci for fill that is compacted in accordance with the subgrade preparation recommendations presented above.

5.3.2 Area C

Based on the available laboratory data, and published presumptive CBR values for poorly graded sand, consider a CBR value of 15 and a modulus of subgrade reaction (k) of 225 pci for fill that is compacted in accordance with the subgrade preparation recommendations presented above.

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Table 1. Boring Summary Table

Approximate Ground Surface

Elevation

Depth to Top of

Bedrock

Total Depth of

Boring

0-hr Water Level

Reading

Test Boring

Approximate Northing

Approximate Easting

(ft-msl) (ft) (ft) (ft) B-1 741981.9 1046560.4 9.2 N/E 75.2 8.0 B-2 742165.6 1046743.3 10.2 N/E 75.0 6.0

T1-01 740938.2 1048438.9 0 N/E 75.0 2.0 N/E = Not Encountered

Table 2a. Laboratory Summary – USCS Classifications and Atterberg Limits

Test Boring

Depth Below Ground

Surface (ft)

USCS

Group

Symbol

Percent Passing No.

200 Sieve (%)

LL PL PI

As-Received Moisture

Content (%)

B-1 2.0-4.0 SW 2.6 -- -- -- 5.1

B-1 4.0-6.0 SW-SM 9.6 -- -- -- 10.6

B-1 6.0-8.0 SW 3.4 -- -- -- 19.1

B-1 8.0-10.0 SM 22.0 -- -- -- 58.5

B-1 10.0-12.0 CH 94.0 71 23 48 47.9

B-1 13.5-15.0 MH 94.7 74 38 36 50.6

B-1 18.5-20.0 SM 27.6 -- -- -- 53.5

B-1 23.5-25.0 SM 15.1 -- -- -- 60.7

B-1 28.5-30.0 SM 16.0 -- -- -- 28.4

B-1 33.5-35.0 SM 23.9 -- -- -- 35.3

B-1 38.5-40.0 ML 59.9 -- -- -- 30.6

B-1 43.5-45.0 CH 74.4 70 32 48 38.8

B-1 48.5-50.0 CH 72.5 66 20 46 42.5

B-1 53.5-55.0 SP 3.9 -- -- -- 19.0

B-1 58.5-60.0 SP 2.2 -- -- -- 13.7

B-1 63.5-65.0 SP-SM 11.8 -- -- -- 21.6

B-1 68.5-70.0 SP-SM 9.1 -- -- -- 27.2

B-1 73.5-75.0 SP-SM 8.7 -- -- -- 23.3

B-2 4.0-6.0 SP 2.1 -- -- -- 3.9

B-2 8.0-10.0 SP 3.3 -- -- -- 6.6

B-2 13.5-15.0 SP 1.5 -- -- -- 15.3

B-2 18.5-20.0 ML 92.2 37 34 3 40.0

B-2 23.5-25.0 SM 24.8 -- -- -- 38.3

B-2 28.5-30.0 SP-SM 8.2 -- -- -- 25.2

B-2 33.5-35.0 NA NA -- -- -- NA

B-2 38.5-40.0 SM 19.8 -- -- -- 26.8

B-2 43.5-45.0 SM 18.6 -- -- -- 35.4

B-2 48.5-50.0 SM 12.7 -- -- -- 26.9

B-2 53.5-55.0 SW 4.6 -- -- -- 22.1

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Test Boring

Depth Below Ground

Surface (ft)

USCS

Group

Symbol

Percent Passing No.

200 Sieve (%)

LL PL PI

As-Received Moisture

Content (%)

B-2 58.5-60.0 SW 4.8 -- -- -- 14.1

B-2 63.5-65.0 SM 24.2 -- -- -- 29.1

B-2 68.5-70.0 SP-SC 10.3 -- -- -- 27.2

B-2 73.5-75.0 SP-SC 9.4 -- -- -- 23.3

T1-01 1.0-3.0 SP 1.7 NA NP NP 17.1

T1-01 4.0-6.0 SP 4.4 NA NP NP 25.4

T1-01 6.0-10.0 SP 2.5 NA NP NP 22.5

T1-01 10.0-12.0 SM 34.3 43 38 5 67.5

T1-01 13.5-15.0 SM 46.6 33 29 4 42.9

T1-01 18.5-20.0 CH 53.0 61 16 45 95.8

T1-01 23.5-25.0 SC 41.6 65 30 35 98.1

T1-01 28.5-30.0 SW-SM 8.4 NA NP NP 23.7

T1-01 33.5-35.0 SC 39.0 NA NP NP 26.3

T1-01 38.5-40.0 CH 86.9 67 39 28 98.7

T1-01 43.5-45.0 SM 13.2 NA NP NP 17.7

T1-01 48.5-50.0 SW 2.8 NA NP NP 15.4

T1-01 53.5-55.0 SW 3.0 NA NP NP 15.9

T1-01 63.5-65.0 SM 20.1 NA NP NP 40.7

T1-01 68.5-70.0 SM 16.5 NA NP NP 37.9

CBR-

T101 1.0-3.0 SP-SM 6.4 NA NP NP NA

Table 2b. Laboratory Summary – California Bearing Ratio & Modified Proctor Tests

Test Boring

Depth Below Ground

Surface (ft)

Dry Density

(pcf)

Compaction Effort (%) CBR (%)

Optimum Moisture Content

CBR-1 1.0-3.0 118.0 95.0 15 8.4

T1-01 1.0-3.0 120.6 95.0 33 9.5

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6 REFERENCES

NOTE: Sources for Figures are referenced in the title block and contain web links, where applicable.

“USGS Store.” Map Locator | USGS Store, USGS. Accessed online at:

https://store.usgs.gov/map-locator

NRCS. Web Soil Survey, United States Department of Agriculture. Accessed online at:

https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm

Wilson, G. (1997, January 3). Coast Guard Station Tybee. Accessed online at:

http://tybee.com/tour/uscg_station_tybee_island/welcome.html

USGS. Quaternary Fault and Fold Database of the United States. Accessed online at:

https://earthquake.usgs.gov/cfusion/qfault/show_report_AB_archive.cfm?fault_id=2657&sectio n_id=

Barksdale, R.D. State of the Art for Design and Construction of Sand Compaction Piles. November 1987.

USCG STATION TYBEE ISLAND GEOTECHNICAL SITE CHARACTERIZATION REPORT

FIGURES

USCG STATION TYBEE ISLAND GEOTECHNICAL SITE CHARACTERIZATION REPORT

MBAKERINTL.COM

FIGURE 1

TOPOGRAPHIC MAP

USCG -Tybee Station

Chatham County, Tybee Island, GA Approximate Scale - Contour Interval 10’ Source: USGS US Topo 7.5 Minute Map for Fort Pulaski Quadrangle, GA. 2017.

AREA C

N

NEW STATION BUILDING

AND PARKING LOT AREA

FIGURE 2A

SOIL MAP (NEW STATION BUILDING AND

PARKING LOT AREA)

Source: Google Earth. NRCS, Web Soil Survey, Accessed from: https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm.

PROJECT

LOCATION

Legend Mae: Made Land

FIGURE 2B

SOIL MAP (AREA C)

Source: Google Earth. NRCS, Web Soil Survey, Accessed from: https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm.

Legend Mae: Made Land Tml: Tidal Marsh, salty

FIGURE 3

NAUTICAL MAP c.1852

Approximate North Arrow, No Scale Provided Source: NOAA Office of Coast Survey Historical Map and Chart Collection, Chart of Savannah River c. 1852. Retrieved from:

https://historicalcharts.noaa.gov/#map

AREA C

N

FIGURE 4

NAUTICAL MAP c.1855

Approximate Scale Source: NOAA Office of Coast Survey Historical Map and Chart Collection, Preliminary Chart of Savannah River, Georgia with a Continuation from Savannah to Head of Argyle Island c. 1855. Retrieved from: https://historicalcharts.noaa.gov/#map

FIGURE 5

NAUTICAL MAP c.1926

Approximate Scale Source: NOAA Office of Coast Survey Historical Map and Chart Collection, Savannah and Wassaw sound c. 1926. Retrieved from:

https://historicalcharts.noaa.gov/#map

AREA C

N

FIGURE 6

NAUTICAL MAP c.1944

Approximate Scale Source: NOAA Office of Coast Survey Historical Map and Chart Collection, Savannah and Wassaw sound c. 1944. Retrieved from:

FIGURE 7

NAUTICAL MAP c.1954

Approximate Scale Source: NOAA Office of Coast Survey Historical Map and Chart Collection, Savannah and Wassaw sound c. 1954. Retrieved from:

NEW STATION BUILDIG

FIGURE 8

NAUTICAL MAP c.1974

Approximate Scale Source: NOAA Office of Coast Survey Historical Map and Chart Collection, Savannah and Wassaw sound c. 1954. Retrieved from:

NEW BUILDING STATION

FIGURE 9

GEOLOGIC MAP

Approximate Scale Source: Cooke, C. Wythe, Georgia Division of Mines, Mining, and Geology, Geologic Map of the Coastal Plain of Georgia, Reprint. 1944.

AND PARKING LOT AREA/

FIGURE 10

GROUNDWATER MAP

Source: Department of Natural Resources Environmental Protection Division Georgia Geologic Survey, Environmental Geologic Atlas of Coastal Georgia, Geologic Atlas 5, 1986.

AND PARKING LOT AREA/

USCG STATION TYBEE ISLAND GEOTECHNICAL SITE CHARACTERIZATION REPORT

NEW STATION BUILDING AND PARKING LOT AREA

USCG STATION TYBEE ISLAND GEOTECHNICAL SITE CHARACTERIZATION REPORT

APPENDIX A

Geotechnical Exploration Letter (written by Cal-tech)

USCG STATION TYBEE ISLAND GEOTECHNICAL SITE CHARACTERIZATION REPORT

- Borings B-1 and B-2

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USCG STATION TYBEE ISLAND GEOTECHNICAL SITE CHARACTERIZATION REPORT

/Manual Hammer

/Manual Hammer

REPORT OF: Sieve Analysis - ASTM D6913 PROJECT: U.S. Coast Guard Tybee Island Survey CLIENT: Michael Baker International

USCG STATION TYBEE ISLAND GEOTECHNICAL SITE CHARACTERIZATION REPORT

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USCG STATION TYBEE ISLAND GEOTECHNICAL SITE CHARACTERIZATION REPORT

USCG STATION TYBEE ISLAND GEOTECHNICAL SITE CHARACTERIZATION REPORT

USCG STATION TYBEE ISLAND GEOTECHNICAL SITE CHARACTERIZATION REPORT

APPENDIX B

Liquefaction Analysis

USCG STATION TYBEE ISLAND GEOTECHNICAL SITE CHARACTERIZATION REPORT

New Station Building and Parking Lot

Area C

USCG STATION TYBEE ISLAND GEOTECHNICAL SITE CHARACTERIZATION REPORT

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Appendix B Liquefaction Analysis