14-CHRI_217021-244555_Bulkhead_Inspection_Report_Collins-Engineers_10-25-18.pdf

CHRISTIANSTED NATIONAL HISTORIC SITE

GALLOWS BAY

CHRISTIANSTED, ST. CROIX, U.S.V.I.

September 2018

WATERFRONT INSPECTION

AND MATERIAL TESTING

Prepared by:

124 Venture Court, Suite 10

Lexington, Kentucky 40511

859.367.0097 • www.collinsengr.com

Prepared for:

WATERFRONT INSPECTION AND TESTINGS

CHRISTIANSTED NATIONAL HISTORIC SITE, CHRISTIANSTED, U.S.V.I.

TABLE OF CONTENTS

EXECUTIVE SUMMARY

1.0 INTRODUCTION

1.1 Background and Objectives

1.2 Scope of Work

1.3 Inspection Methods and Techniques

1.3.1 General Inspection Tasks

1.3.2 Schmidt Hammer Readings

1.3.3 Bulkhead Core Samples

1.3.4 GPR Readings

2.0 EXISTING CONDITIONS

3.0 EVALUATION AND RECOMMENDATIONS

EXHIBIT 1 – FIGURES

LOCATION MAP

CONCRETE BULKHEAD

WEST END

EXHIBIT 2 – DATA TABLES

TABLE 2-1: CONCRETE CORE TESTING RESULTS

TABLE 2-2: GPR-REBAR LOCATION/SIZING

EXHIBIT 3 – INSPECTION PHOTOGRAPHS

Photograph No. 1: Overall View of Christiansted National Historic Site Bulkhead, Looking

Southwest.

Photograph No. 2: Overall View of Christiansted National Historic Site Bulkhead, Looking

Southeast.

Photograph No. 3: View of Typical Bent Cap and Pile at STA 0+00, Looking South.

Photograph No. 4: View of the Typical Ledger Wall from STA 0+00 to 0+14, Looking South.

Photograph No. 5: View of the Typical Concrete Cleaning at STA 5+50, Looking South.

Photograph No. 6: View of the Typical Undermining Under the Concrete Wall at STA 5+55, Looking South.

Photograph No. 7: View of the Typical Concrete at the Waterline, Looking South.

Photograph No. 8: View of the Joint at the Waterline at STA 5+39, Looking South.

Photograph No. 9: View of the Joint Underwater at STA 5+39, Looking South.

Photograph No. 10: View of the Typical Undermining at STA 5+39, Looking South.

Photograph No. 11: View of the Typical Timber Fenders at STA 5+30, Looking South.

Photograph No. 12: View of the Typical Tieback Hole, Looking South.

Photograph No. 13: View of the Fort Wall and Bulkhead Interface, Looking Southwest.

Photograph No. 14: View of the Fort Wall and Bulkhead Interface, Looking Southwest.

Photograph No. 15: View of the Coring Hole at STA 5+25, Looking South.

Photograph No. 16: View of the Coring Hole at STA 5+72, Looking South.

Photograph No. 17: View of the Coring Hole at STA 6+22, Looking South.

Photograph No. 18: View of the Coring Hole at STA 6+85, Looking South.

Photograph No. 19: View of the Typical Bulkhead at Waterlevel, Looking South.

Photograph No. 20: View of the Typical Curb End Fender, Looking East.

Photograph No. 21: View of Typical Under Curb, Looking West.

Photograph No. 22: View of Typical Honeycombing, Looking South.

Photograph No. 25: View of a Typical Coring Hole Repair Using Marine Grade Grout, Looking

South.

Photograph No. 26: View of the Change in Construction at STA 5+02, Looking Southeast.

Photograph No. 27: View of the Change in Construction at STA 5+02, Looking Southeast.

Photograph No. 28: View of Typical Horizontal Cracking Above Water, Looking South.

EXECUTIVE SUMMARY

Project: Christiansted National Historic Site Bulkhead Inspection

Purpose of Project: To perform a detailed visual and tactile above and underwater investigation of the accessible surfaces of the Christiansted National Historic Site bulkhead in Christiansted, U.S.V.I., and to acquire and test concrete samples of the bulkhead.

Inspection Team: Team Leader – Kurt Lingo, E.I.T. – Collins Engineers, Inc.

Team Member – Matthew Rogers, E.I.T. – Collins Engineers, Inc.

Team Member – Brad Mitchell, E.I.T. – Collins Engineers, Inc.

Inspection Date(s): September 11, 2018

Water Visibility: 30 ft Water Velocity: <1 ft/s Water Temperature: 85 °F Weather: Sunny – 90 °F Waterline Elevation: 0.00 ft. Type of Boat: N/A Coordinates: 17.47417°N, -64.702494°W Access Location: Along bulkhead Dive Mode: Commercial SCUBA/Wading Maximum Depth at SSU: 6.0 ft – East End of Bulkhead

Summary of Findings:

• The channel bottom material consisted of sand and gravel with up to approximately 2 in. probe rod penetration.

• The submerged portions of the concrete bulkhead were typically sound and smooth with no defects observed.

• A 12 in. diameter outfall was located at STA 5+03.

• A 6 in. stepout was located 1 ft above the channel bottom from STA 5+03 to 5+20.

• From STA 5+20 to 5+80, concrete was poured directly onto the channel bottom, causing minor undermining between 2 to 4 in. vertical by 6 in. horizontal.

• The bulkhead exhibited random honeycombing at less than 2% of the overall surface area.

• Typical horizontal hairline cracking, 1/16 in. wide, spread from STA 5+00 to 7+00.

• The sheetpile exhibited a hole, 3 ft wide by 1 ft deep, located at the northwest corner of the concrete apron at the West End of the bulkhead.

1.0 INTRODUCTION

1.1 Background and Objectives

This report consists of the results of a detailed above water and underwater investigation performed at the Christiansted National Historic Site bulkhead located in Gallows Bay in St. Croix, U.S.V.I. Collins

Engineers, Inc. (Collins) conducted the underwater investigation for HDR Engineering (HDR) on September

11, 2018.

The Christiansted National Historic Site is an urban national park held under protection of the National

Park Service. Previous underwater inspection reports, as-built drawings, or material/component specs of previous repairs were not available prior to mobilizing to the site to begin inspection work.

1.2 Scope of Work

A visual and tactile field inspection was conducted to determine the general condition of both the concrete apron and bulkhead structure from STA 5+00 to 7+00. The inspection included observations of existing damage to the concrete cap, sinkholes, spalls, cracks, and holes in the deck. Schmidt Hammer readings were performed three (3) times at four determined locations along the 200 ft bulkhead. A GPR device was used in 25 sq. ft. locations along the concrete bulkhead to determine reinforcing steel sizes and locations. Core samples of the concrete bulkhead were obtained at 4 locations, STA 5+25, 5+71, 6+22, and 6+85, with marine grade grout used to seal the voids created. The western termination of the bulkhead was examined and general layout was conveyed to onsite HDR staff.

The condition of all structural elements was documented with field notes and photographs. All of the inspection findings are included in this inspection report, which also contains evaluation of the structural elements, inspection drawings, inspection photographs, and repair recommendations.

1.3 Inspection Methods and Techniques

1.3.1 General Inspection Tasks

A detailed field inspection was conducted to determine the physical condition of the concrete bulkhead.

A three-person team consisting of a team leader (Kurt Lingo, E.I.T.), an engineer-diver (Matthew Rogers, E.I.T.), and a tender (Brad Mitchell, E.I.T.) conducted the inspection. The inspection was conducted using commercial SCUBA equipment and through wading. During the inspection, the inspectors worked from the shore and a note taker on the shore recorded the inspection notes.

The underwater inspection consisted of a visual and tactile examination of the accessible surfaces of the bulkhead from the waterline to the channel bottom with particular attention given to any observed areas of deterioration or apparent distress. Approximately 10 percent of the bulkhead received a Level II inspection.

This equates to cleaning a 1 ft horizontal by 1 ft vertical patch at the waterline, mid-depth, and the mudline at every 100 ft station.

The above water inspection consisted of a visual and tactile examination of the bulkhead above the waterline. The examination included mapping and quantifying any observed defects, documenting overall measurements of each element, and taking photographs of general conditions and observed deficiencies.

1.3.2 Schmidt Hammer Readings

Schmidt Hammer readings were performed three (3) times at four determined locations along the 225 ft bulkhead. These locations were at STA 5+25, 5+71, 6+22, and 6+85. The values of the compressive strengths were calculated using a conversion curve provided by the Schmidt Hammer that interprets the average rebound values emitted from the hammer. Refer to Table 2-1 in Exhibit 2 for these readings.

1.3.3 Bulkhead Core Samples

Concrete core samples were obtained at four determined locations along the 225 ft bulkhead. These locations were at STA 5+25, 5+71, 6+22, and 6+85. A 2 in. diameter sample was removed and the remaining hole was filled with marine grade grout to prevent deterioration of the bulkhead. These samples were transported to Lexington, KY and submitted to a subconsultant for chloride penetration and compressive strength testing.

Refer to Table 2-1 in Exhibit 2 for results of this testing.

1.3.4 GPR Readings

Ground penetrating radar (GPR) was used in 25 sq. ft. locations along the concrete wall to determine reinforcing steel sizes and locations. Refer to Table 2-2 in Exhibit 2 for locations, rebar sizes, and rebar spacing.

2.0 EXISTING CONDITIONS

The channel bottom material consisted of sand and gravel with up to approximately 2 in. of probe rod penetration. The submerged portions of the concrete bulkhead were typically sound and smooth with no defects observed. A 12 in. diameter outfall was located at STA 5+03. A 6 in. stepout was located 1 ft above the channel bottom at STA 5+03 to 5+20. From STA 5+20 to 5+80, concrete was poured directly onto the channel bottom, causing minor undermining between 2 to 4 in. vertical by 6 in. horizontal. The bulkhead exhibited random honeycombing at less than 2% of the overall surface area. Typical horizontal hairline cracking, 1/16 in. wide, spread from STA 5+00 to 7+00. In the western corner of the bulkhead, the sheetpile exhibited a hole, 3 ft diameter by 1 ft deep, at STA 0+10.

3.0 EVALUATION AND RECOMMENDATIONS

Overall, the inspected elements of the bulkhead were found to be in good condition. The results of the concrete testing proved that the bulkhead is in good condition. An average of 6507 psi compressive strength was found from the concrete core compressive tests. The chloride penetration test was conducted using the rapid chloride testing method, which provided an average value of 1.54% by weight. Typically, 1% chloride by weight in a concrete composition is the maximum percentage, with a recommended percentage between 0.05 and 0.1%. Therefore, chloride emitted from rusted reinforcing steel within the concrete will result in corrosion.

It is recommended that concrete repairs be performed on the horizontal cracking and random honeycombing to preserve the life of the bulkhead. Additionally, it is recommended that riprap be placed along the concrete bulkhead to protect the undermined portion of the wall.

Respectfully Submitted, COLLINS ENGINEERS, INC.

Joshua M. Johnson, P.E.

Project Manager

Originated by:

Brad Mitchell, E.I.T.

EXHIBIT 1 – FIGURES

HDR Engineering, Inc.

15450 New Barn Road, Suite 304 Miami Lakes, FL 33014

Phone: 305-728-7400

124 Venture Court, Ste 10 Lexington, KY 40511 Phone: 859-367-0097

Fax: 859-367-0140

CHRISTIANSTED NATIONAL

HISTORIC SITE

BULKHEAD INSPECTION

LOCATION MAP

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EXHIBIT 2 – DATA TABLES

TABLE 2-1: CONCRETE CORE TESTING RESULTS

Station Test

Schmidt Hammer

Rebound Values

Sch. Hammer

Mean Rebound

Sch. Hammer

Compressive

Strength (psi)

Compressive

Strength (psi) from Core Testing

Chloride

Penetration

(mV)

Chloride

Penetration

(% Cl)

5+25

1 52,53,45,51,52,50,54,52

48.88

N/A -46.03 2.267 2 42,34,54,46,47,55,51,53 7066.7

3 53,44,49,49,40,50,45,52

5+71

1 46,46,47,42,39,50,32,43

43.54

6200.0 -26.00 0.958 2 49,50,42,41,38,34,36,50 5783.3

3 43,43,52,50,46,50,34,42

6+22

1 44,40,38,38,40,33,30,40

38.375

6420.0 N/A N/A 2 48,52,38,39,30,26,24,50 4666.7

3 34,32,45,38,40,39,37,46

6+85

1 42,51,42,41,42,38,40,43

40.08

6900.0 -34.97 1.408 2 43,44,38,46,38,43,42,40 5033.3

3 47,43,26,24,33,40,41,35

TABLE 2-2: GPR-REBAR LOCATION/SIZING

Station Rebar Size Rebar Spacing

5+25 #4 2 FT

5+71 #4 2 FT

6+22 #4 2 FT

6+85 #4 2 FT

EXHIBIT 3 – INSPECTION PHOTOGRAPHS

Photograph No. 1: Overall View of Christiansted National Historic Site Bulkhead, Looking

Southwest.

Photograph No. 2: Overall View of Christiansted National Historic Site Bulkhead, Looking

Southeast.

Photograph No. 3: View of Typical Bent Cap and Pile at STA 0+00, Looking South.

Photograph No. 4: View of the Typical Ledger Wall from STA 0+00 to 0+14, Looking South.

Photograph No. 5: View of the Typical Concrete Cleaning at STA 5+50, Looking South.

Photograph No. 6: View of the Typical Undermining Under the Concrete Wall at STA 5+55, Looking South.

Photograph No. 7: View of the Typical Concrete at the Waterline, Looking South.

Photograph No. 8: View of the Joint at the Waterline at STA 5+39, Looking South.

Photograph No. 9: View of the Joint Underwater at STA 5+39, Looking South.

Photograph No. 10: View of the Typical Undermining at STA 5+39, Looking South.

Photograph No. 11: View of the Typical Timber Fenders at STA 5+30, Looking South.

Photograph No. 12: View of the Typical Tieback Hole, Looking South.

Photograph No. 13: View of the Fort Wall and Bulkhead Interface, Looking Southwest.

Photograph No. 14: View of the Fort Wall and Bulkhead Interface, Looking Southwest.

Photograph No. 15: View of the Coring Hole at STA 5+25, Looking South.

Photograph No. 16: View of the Coring Hole at STA 5+72, Looking South.

Photograph No. 17: View of the Coring Hole at STA 6+22, Looking South.

Photograph No. 18: View of the Coring Hole at STA 6+85, Looking South.

Photograph No. 19: View of the Typical Bulkhead at Waterlevel, Looking South.

Photograph No. 20: View of the Typical Curb End Fender, Looking East.

Photograph No. 21: View of Typical Under Curb, Looking West.

Photograph No. 22: View of Typical Honeycombing, Looking South.

Photograph No. 25: View of a Typical Coring Hole Repair Using Marine Grade Grout, Looking

South.

Photograph No. 26: View of the Change in Construction at STA 5+02, Looking Southeast.

Photograph No. 27: View of the Change in Construction at STA 5+02, Looking Southeast.

Photograph No. 28: View of Typical Horizontal Cracking Above Water, Looking South.