17-CHRI_217021-244555_Waterfront_Facility_Assessment-Moffatt-Nichol_09-17-2014.pdf

1509 W. Swann Avenue, Suite 225 Tampa, FL 33606

(813) 258-8818 Fax (813) 258-8525 www.moffattnichol.com

September 17, 2014

Damian Cartwright Virgin Islands Port Authority 2nd Floor Henry E. Rohlsen Airport Terminal St. Croix, VI 00821

Re: Waterfront Facility Assessment and Recommendations King’s Wharf, Christiansted, St. Croix, USVI

Dear Mr. Cartwright:

Moffatt & Nichol (M&N) completed a condition assessment of King’s Wharf at the Christiansted National Historic Site in Christiansted, St. Croix. King’s Wharf spans the waterfront between the Christiansted boardwalk and Fort Christiansvaern. The wharf was constructed circa 1983 and comprises a 700 foot long steel sheet pile bulkhead, concrete cap, concrete splash apron, and timber fender system. An overall photograph and aerial of the site can be found in Figures 1 and 2, respectively.

According to the NPS engineering assessment of the wharf provided to VIPA in January 2014, the bulkhead underwent minor repairs in 1989, 1995, and 2005. During Hurricane Omar in 2008, boats broke free and collided with the bulkhead causing damage to the fender system and bulkhead. No known repairs to the bulkhead have been completed since Hurricane Omar;

however, barriers were installed in 2012 to prevent vehicle traffic behind the bulkhead. Mooring along the bulkhead has been prohibited.

Figure 1: King’s Wharf – Looking East from Station 7+03 (End of Bulkhead)

DRAFT

Mr. Damian Cartwright, M&N #7903‐07 Virgin Islands Port Authority

Figure 2: King’s Wharf Aerial View and Stationing

SITE VISIT

M&N (Michael Freiner, P.E. and Nicole Pauly, E.I.) conducted a site visit on July 31st and August 1st, 2014 to observe the condition of King’s Wharf. The site visit entailed an above water visual assessment of the bulkhead and apron with detailed hammer soundings and thickness measurements at isolated locations along the wharf. The bulkhead was stationed from east to west, beginning at Fort Christiansvaern and terminating at the end of the sheet pile wall in front of the King Christian hotel. Stationing is shown on the aerial provided in Figure 2.

Observations and Condition Assessment Three different wall types were observed; (1) steel sheet piles with concrete cap and full height concrete fascia, (2) type “U” steel sheet piles with concrete cap, and (3) type “Z” steel sheet piles with concrete cap. Construction drawings for the various bulkhead sections were not provided.

A timber fender system was installed along the seaward face of all three wall types; however, much of the fender system has failed and large segments are missing. A concrete apron was installed on the landward side of the bulkhead and terminates approximately 35 feet before the end of the sheet pile wall/cap. The different wall types have been depicted on the following page in Photos 1 through 4. Additional photos from the site visit have been provided in Appendix A.

Steel sheet piling with a full height concrete fascia and concrete cap was observed from Stations 0+00 to 1+98 and from Stations 3+89 to 4+00 (Photos 1 and 2). The concrete fascia was formed and poured along the sea bottom, causing variations in the fascia height. Hammer soundings were completed intermittently along the cap and fascia in places where timber fendering did not impede access to the wall. No cracking or delamination of the concrete fascia was noted. The fascia extends from the bulkhead cap to the sea floor; therefore, the type and condition of the sheet piling beneath the fascia could not be observed.

Type “U” sheets with a reinforced concrete cap were observed from Station 1+98 to 3+89 and from Station 4+00 to 4+56 (Photo 3). Type “Z” sheet piles with a reinforced concrete cap were observed from Station 4+56 to 7+03 (Photo 4). Both wall types exhibited signs of advanced corrosion such as heavy rust staining, corrosion by‐product, and major section loss. The bulkhead was tested at isolated locations to determine the extents of the corrosion. From Station 4+00 to the end, the steel was easily penetrated with a hammer at all locations tested. Holes measuring up to 9 inches wide with aggregate exposed were observed. In several locations, the anchor bolts supporting the timber fender system, leaving holes in the sheet piling where they had been welded. The bulkhead also appeared to be out of vertical alignment with the toe of the type “Z” sheet piles rotating seaward. This rotation may be due to insufficient sheet pile depth and/or improper installation.

No indication of a conventional anchoring system was observed in the field. The reinforced concrete cap and concrete apron likely act as the restraining system for the bulkhead. The concrete cap exhibited signs of horizontal cracking and rust staining throughout, and in some sections the concrete has degraded and spalled. Insufficient concrete cover around the steel sheet piles was noted in several locations. Cracking was noted as a typical condition throughout the apron, though it was most significant in areas where the concrete cap had degraded.

Photo 1: Concrete Fascia – STA 0+00 Photo 2: – Type ‘U’ Sheet Piles STA 3+29

Photo 3: Concrete Fascia – STA 3+89’ to 4+00 Photo 4: Type ‘Z’ Steel Sheet Piles – STA 6+50

CONCLUSIONS AND RECOMMENDATIONS

The overall condition of the bulkhead is poor, with the segment between Stations 4+00 and 7+03 being in critical condition due to significant loss of section. M&N recommends that the concrete apron remain restricted to light pedestrian loading and that no vessels be moored along the existing bulkhead from Stations 4+00 to 7+03.

Repair to the existing bulkhead is not cost effective at this stage of deterioration. It is our recommendation to replace the entire bulkhead by driving a new steel sheet pile bulkhead with concrete fascia seaward of the existing bulkhead and anchoring it at the top using a conventional tie‐back/deadman system. The existing bulkhead would be abandoned in place. A concrete fascia extending two feet below the low water level would provide significant corrosion protection and an extended service life. In addition to that, a cathodic protection system using passive anodes may be installed below water and maintained every 10 years to extend the service life to greater than 50 years.

Installation of a new steel sheet pile bulkhead would require demolition of the existing concrete apron and the installation of a new concrete apron, bulkhead, and tie‐back system. Total probable construction cost could range from $1.7 million to $2.5 million based on geotechnical analysis and level of corrosion protection selected (i.e. drop concrete fascia and/or cathodic protection system).

This project should qualify for a Nationwide Permit from the US Army Corps of Engineers if the bulkhead is installed within 18 inches of the existing bulkhead face. A CZM permit would also be required. If a new wall alignment is proposed or future dredging seaward of the bulkhead is desired to accommodate larger vessels, the range of construction costs may change and the permitting effort may increase.

Please give me a call if you have any questions regarding our evaluation.

Sincerely, MOFFATT & NICHOL

Mark A. Pirrello, P.E.

Project Manager

cc. Bill McComb, Joel Tutein, Nicole Pauly, Michael Freiner, APPENDIX A

SITE PHOTOS

APPENDIX A M&N #7903‐07

Concrete fascia and cap – Looking west from STA 0+00

Underwater view of concrete fascia bottom near STA 0+50

APPENDIX A M&N #7903‐07

Hole in Type “U” Steel Sheet Pile near STA 3+35

Underwater view of concrete fascia at STA 3+95

APPENDIX A M&N #7903‐07

Underwater view of hole at interface between Type “U” Steel Sheet Pile & Fascia at STA 4+00

Corroded fender anchor bolt with hole through sheet pile ‐ STA 4+00

Hole in Type “U” Steel Sheet Pile at STA 4+35

APPENDIX A M&N #7903‐07

Hole in Type “U” Steel Sheet Pile near STA 6+00

Major horizontal cracking in cap ‐ Less than 1” concrete clear cover – Fender system degraded and/or missing ‐ Typical condition from 4+56 to 5+32

APPENDIX A M&N #7903‐07

Major Cracking and Degradation of Concrete Cap – Fender system degraded and/or missing

‐ Typical Condition STA 4+00 to STA 6+69

Horizontal Cracking in Cap with Rust Staining – Typical Condition

APPENDIX A M&N #7903‐07

Cracking along concrete apron – Typical Condition STA 0+00 to STA 2+28

Cracking along concrete apron – Typical Condition STA 4+00 to 6+69

APPENDIX A M&N #7903‐07

Timber fender system ‐ Mostly intact from STA 0+10 to STA 3+00

Timber fender system ‐ Mostly intact from STA 3+38 to STA 3+89