B08_Attachment_7_Central_Wharf_Dock_Condition_Report_(2).pdf

34 William Way

Bellingham, MA 02019

(508) 966 9092 childseng.com

National Park Service

Salem, MA

Central Wharf Floating Dock Inspection November 2022

Submitted to:

National Park Service

Denver Service Center

Design & Construction Division

12795 W. Alameda Parkway

Lakewood, CO 80228

Submitted by:

National Park Service, Salem, MA

Central Wharf Floating Dock Inspection

Submitted by:

Childs Engineering

34 William Way

Bellingham, MA 02019

508-966-9092 www.childseng.com

Submitted to:

National Park Service

Denver Service Center

Design & Construction Division

12795 W. Alameda Parkway

Lakewood, CO 80228

Childs Project: 2983-22.03

Inspection Date: November 7-8, 2022

TABLE OF CONTENTS

1.0 Introduction

2.0 Inspection Procedure…………………………………………………………………...2

3.0 Condition of Existing Structures

4.0 Recommendations

APPENDIX A – Photographs

APPENDIX B – Existing Conditions Plan

National Park Service, Salem, MA – Floating Dock Inspection

November 2022

1.0 Introduction

Childs Engineering (Childs) performed an above and below water inspection of

National Park Service’s floating dock and related elements on Central Wharf on the dates of November 7 and 8, 2022, in Salem, MA. The inspection was performed by a team of three engineers led by Nicholas B. Sarata, P.E. The inspection was intended to assess the current conditions of the floating dock and to provide recommendations and design solutions of the floating dock structure. The inspected elements included the floating dock, guide piles, guide pile assemblies, gangways, and the support pier. The information contained in this report is based on a visual inspection only. No destructive or partially destructive testing of the structural members was done. Also included with this report are photos outlining the general and specific conditions encountered. To conduct the inspection, Childs Engineering deployed a dive team using SCUBA from the shore and utilized methods outlined in the ASCE Waterfront Facilities Inspection and Assessment manual and assigned ratings to the structural elements based on the following table:

Assessment Ratings Description

''Good'' No problems or only minor problems noted. Structural elements may show some very minor deterioration, but no significant reduction in structural capacity.

''Satisfactory'' Minor to moderate defects and deterioration observed, but no significant reduction in structural capacity.

''Fair''

All primary structural elements are sound; but minor to moderate defects and deterioration observed. Localized areas of moderate to advanced deterioration may be present but do not significantly reduce the structural capacity.

''Poor'' Advanced deterioration or overstressing observed on widespread portions of the structure. Some reduction in structural capacity.

''Serious''

Advanced deterioration, overstressing or breakage may have significantly affected the load bearing capacity of primary structural components. Local failures are possible.

''Critical''

Very advanced deterioration, overstressing, or breakage has resulted in localized failure(s) of primary structural components. More widespread failures are possible or likely to occur.

2.0 Inspection Procedure

To conduct the inspection, Childs deployed a diver utilizing SCUBA equipment conforming to all necessary OSHA standards. The underwater inspection included a visual inspection of 100% of the structure, partial removal of marine growth on a representative sample for a more in-depth inspection, and nondestructive testing in the form of ultrasonic steel thickness measurements to determine steel thickness remaining and electrical potential readings to determine the effect the anodes are having on the underwater steel elements. A topside inspection was performed on the floating dock as well as within the floating dock. The confined space inspection was performed conforming to all necessary OSHA standards. The confined space inspection included a visual inspection of 100% of the structure and nondestructive testing in the form of ultrasonic steel thickness measurements to determine steel thickness remaining.

3.0 Condition of Existing Structures

3.1 Overview

Overall, the engineering assessment indicates that the floating dock and support elements were found to be in fair condition with some structural elements ranging into poor. In general, the structural elements of the floating dock were found to be sound but with minor to major defects found throughout the elements. The floating dock has a rectangular footprint of 50 feet in the north-south direction, by 20 feet. The western edge of the float is located approximately 3 feet from Central Wharf. The floating dock structure consists of ¼ inch thick steel plating as well as ¼ inch thick steel angle members within the floating dock. The floating dock consists of eight individual tanks either 150 square feet or 100 square feet in area. There are fourteen sacrificial anodes around the under water portion of the exterior of the float.

The floating dock is able to move vertically on two guide piles, an interior guide pile in the northwest corner of the floating dock and an exterior guide pile connected with a guide pile assembly, on the southeast corner. The guide piles are 24 inches in diameter and ½ inch thick. The guide piles are approximately 29 feet in length from their top to the mudline. The guide pile assembly consists of HSS bolted welded to the float with the use of steel angles. Accessible gangways cover the western half of the float and part of the eastern half. The gangway supports are connected by bolts to the top of the float. The gangway system connects the support pier and wharf to the floating dock. The support pier is made of four 12 inch diameter timber piles with timber cross bracing. The piles support timber split pile caps, timber stringers, and composite decking.

3.2 Summary of Findings

The floating dock is in fair condition with minor to major defects found throughout the inspection. The exterior of the floating dock has a 1 foot wide band of moderate corrosion in the splash zone (see Photos 02 and 03). There is approximately a 25% loss of cross sectional area within the band of corrosion. There is moderate corrosion with

10% section loss over the entire length of the flange that supports the rubber fenders (see

Photo 04). The sacrificial anodes placed around the floating dock typically have 15% section loss (see Photo 05). Based on visual observations and electrical potential readings the anodes do not appear to be providing enough protection to the floating dock.

This could be due to a loss of electrical connectivity at the stainless steel bolts that connect the anodes to the float. The hangers that support the four anodes on the western side have moderate corrosion and up to 50% loss of cross sectional area in the splash zone. There is a tripping hazard at the northeast tank of the float that is caused by a pump out drain. Typically, the hatch covers have moderate corrosion with no significant loss of section (see Photo 06). Typically, welds that have been added to the float post construction are uncoated. On the interior of the two northern tanks of the float there is corrosion on the welds connecting the vertical scantling (see Photo 07). The corrosion reaches from the float base and up 3 feet. In the northern two tanks there is a one foot wide strip, 2 feet off the ground with heavy pitting, up to an inch in diameter and 3/16th inch deep (see Photo 08). The vertical members on the interior of the northeast middle tank have moderate corrosion and up to 60% loss of cross sectional area (see Photo 09).

In the southeast tank, there is an 18 inch long by 2 inch wide strip of corrosion, 18 inches off the bottom (see Photo 10). This corrosion is due to the welding of the guide pile assembly to the floating dock, over hating the steel coating on the float’s interior. There is minor corrosion and 10% loss of cross sectional area on the welds in the corner of the northwest middle tank (see Photo 11). This corrosion is in the northwest corner and is 2 inches thick by 6 feet long. The bulkhead separating the southwest tank from the middle tank has buckled up to ½ inch over a 2 foot length (see Photo 12). There are three cleats located on the eastern edge of the floating dock. One is located under the gangway and is not optimal for mooring. The other 2 cleats have 5% coating loss and minor corrosion around the base (see photo 13).

The guide piles are in satisfactory condition with minor to moderate defects found

(see Photo 14). There are 2 inch wide by 14 foot long strips of abrasion on all four sides of each guide pile (see Photo 15). The abrasion is due to the floating dock moving vertically on the piles. There is a 3 square foot area of corrosion on the southeast pile at the high water mark (see Photo 16). This area of corrosion has a 20% loss of cross sectional area. Ultrasonic steel thickness measurements taken show the remainder of the piles have no significant section loss. The northwest guide pile has a loose protective cover (see Photo 17).

The guide pile assembly is in poor condition with minor to major defects found.

The lower section of the guide pile assembly where the HSS member is bolted to the steel angles has major corrosion and up to 100% section loss (see Photo 18). In general, the guide pile assembly has complete coating loss and moderate corrosion in the splash zone

(see Photo 19).

The gangways are in good condition with minor defects found. Gangways have coating loss and minor corrosion on 20% of the gangway base plates (see Photo 20).

There is no significant loss of cross sectional area on the base plates. The lower end of ramp D has an aluminum hand grip that has broken off at the weld location (see Photo

21).

The support pier is in fair condition with minor to major defects found. The timber members are typically sound and hard with no defects (see Photo 22). The lower bolts connecting the cross braces to the piles typically have up to 25% section loss (see Photo

23). The lower bolt on the northern cross brace has 75% loss of cross sectional area and is missing the nut (see Photo 24). The cross bracing upper bolts have 100% loss of galvanization with minor surface corrosion. The bolts connecting the piles to the split timber pile caps typically have 20% loss of galvanization with no significant surface corrosion. The lower pile cap bolt on the southern side has 100% loss of galvanization with minor surface corrosion (see Photo 25). The bolts connecting the stringers to the pile caps typically have complete loss of galvanization with minor corrosion and 10% loss of cross sectional area of the nut (see Photo 26). The composite decking is beginning to show wear and planks are deflecting when stepped on. The location where the decking meets the wharf is not flush and is a tripping hazard (see Photos 27 and 28).

4.0 Recommendations

Childs recommends the following repairs be conducted to the floating dock to ensure it remains a viable waterfront structure. The recommended repairs include:

Clean and recoat areas of corrosion and coating loss on the float and guide piles.

Provide electrical continuity between anodes and float.

Replace the hangers that support the western anodes.

Reroute the pump out drain through the bulkhead and out of the float under the gangway to avoid a tripping hazard.

Clean and recoat the hatch covers.

Recoat all uncoated welds.

Clean and recoat areas of minor corrosion on the interior of the floating dock.

Clean, add a steel plate, and recoat areas of significant section loss.

Repair the buckled bulkhead to prevent further deflection of the bulkhead.

Clean and recoat the corroded cleat bases.

Replace the loose protective pile cover.

Cut, remove, and replace the corroded section of the HSS members of the guide pile assembly.

Clean and recoat the corroded gangway base plates.

Replace the end of the gangway handrail that has broken off.

Replace the support pier bolts with section loss.

Galvanize the support pier bolts with loss of galvanization.

Replace the composite decking on the support pier.

Replace the ramp stringers to ensure the ramp provides a flush transition from the wharf to the pier.

Increase the height of guide piles to ensure float does not rise above the top of the guide piles during extreme highwater levels.

Childs Engineering appreciates the opportunity to present our findings and recommendations from our recent investigation. If you have any questions or comments on this report, please do not hesitate to contact the undersigned.

Nicholas B. Sarata, P.E.

Vice President

508 966 9092 saratan@childseng.com

APPENDIX A

Photographs

Photo 01: Overall of floating dock and related elements.

Photo 02: 1 foot band of corrosion around the floating dock within the splash zone.

Photo 03: 1 foot band of corrosion around the floating dock within the splash zone.

Photo 04: Typical corrosion of the flange supporting the rubber fender.

Photo 05: Typical anode with 15% loss of section.

Photo 06: Typical hatch cover with moderate corrosion.

Photo 07: 3 foot length of corrosion on scantling weld.

Photo 08: Pitting on bulkhead up to an inch in diameter and 3/16 inch deep.

Photo 09: Up to 60% loss of section on vertical members.

Photo 10: Loss of steel coating on bulkhead interior due to welding on float exterior.

Photo 11: Minor corrosion of the weld in corner of the north west middle section.

Photo 12: Bulkhead has buckled a ½ inch over a 2 foot length in southwest section.

Photo 13: Typical cleat with minor corrosion at the base.

Photo 14: Typical guide pile below water.

Photo 15: Typical 2 inch wide abrasion strip on guide piles.

Photo 16: 3 square foot area of corrosion on southeast guide pile.

Photo 17: Loose protective pile cover on northwest pile.

Photo 18: Lower HSS member of the guide pile assembly with up to 100% section loss.

Photo 19: Guide pile assembly with moderate corrosion in the splash zone.

Photo 20: Minor corrosion on gangway base plates.

Photo 21: Broken handrail at the lower end of ramp D.

Photo 22: Typical timber member on the support pier is sound and hard below water.

Photo 23: Typical cross brace lower bolt with 25% loss of cross sectional area.

Photo 24: Bolt on northern brace with 75% loss of cross sectional area and no nut.

Photo 25: Pile cap bolt with 100% loss of galvanization and minor surface corrosion.

Photo 26: Typical stringer bolt with minor corrosion and 10% section loss of the nut.

Photo 27: Tripping hazard between the wharf and the support pier.

Photo 28: Tripping hazard between the wharf and the support pier.

APPENDIX B

Existing Conditions Plan

SCALE OF FEET

SCALE A

FLOAT DECK PLAN

SCALE A

PROJECT

NORTH

M

IT

C H

E L L

R

K

-2

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A M

A C

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T R

A L W

H A

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\C A

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\C U

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IN

G D

W G

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A M

A \P

M

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\C A

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IN

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\S

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:2 p m

NOTES:

1. DIMENSIONS AND LOCATIONS ARE APPROXIMATE.

2. DRAWINGS REFERENCED FROM DRAWING SET TITLED

"CENTRAL WHARF LANDING - CITY OF SALEM - SALEM,

MASSACHUSETTS" DATED JANUARY, 2000 BY NUCCI VINE

ASSOCIATES.

DATE:

DESIGNED:

TECH. REVIEW:

SUB SHEET NO.

PMIS/PKG NO.

DRAWING NO.

SHEET

OF

TITLE OF SHEET

A/E FIRM

PRIME:

CHILDS

ENGINEERING

BELLINGHAM, MA FLOATING DOCK PLANS

131837

2 3

NBS

TEQ

NBS

11/14/22

SALEM MARITIME NATIONAL HISTORICAL SITE

SALEM MASSACHUSETTS

FOSU 211428S1 TITLE OF PROJECT

FLOAT LAYOUT PLAN

SCALE A

4 40 128

TIMBER PLATFORM P1

SEE DETAIL

S2

C

S2

50'-0"

'-0

" 30'x3' CLEAR FIXED RAMP

30'x3' CLEAR FIXED RAMP

30'x3' CLEAR FIXED RAMP

PLATFORM

P3

60" HIGH

PLATFORM

P2

90" HIGH

PLATFORM

P4

30" HIGH

STAIRS

PLATFORM P1

DECK EL.

+13.0' (MLW)

30'x5' CLEAR GANGWAY

W/30" TRANSITION PLATE

30'x3' CLEAR GANGWAY

W/30" TRANSITION PLATE

24" CLEAT (TYP)

8" RUBBER

D-FENDER (TYP)

24"Ø x 0.5" WALL

STEEL SPUD PILE

24"Ø x 0.5" WALL

STEEL GUIDE PILE

W/GUIDE ASSEMBLY

HANDRAIL

LADDER

LADDER

24" CLEAT (TYP)

4"x4"x1/4" TUBE SUPPORT COLUMN WITH 10"x10"x1/2"

BASE PLATE (TYP)

OUTLINE OF

RAMP/PLATFORM SYSTEM

12" BAND OF

CORROSION IN

SPLASH ZONE

AROUND FLOAT

EXTERIOR

4 ANODE STRAPS WITH UP TO 50%

LOSS OF SECTION IN SPLASH ZONE

FLOAT

3 SQUARE FOOT AREA OF

CORROSION AT

HIGHWATER

MINOR CORROSION ON

20% OF BASE PLATES

END OF HAND RAIL

BROKEN AT WELD

STRIP OF COATING LOSS

18" OFF THE BOTTOM, 18"

LONG, AND 2" WIDE

INTERIOR BULKHEAD

BUCKLED UP TO 1/2"

OVER 2' LENGTH

1' STRIP OF HEAVY

PITTING UP TO 1" Ø WITH

3/16" DEPTH

5% COATING LOSS AND

MINOR CORROSION AT

CLEAT BASE

TRIPPING HAZARD DUE TO

PUMP OUT DRAIN

CORRODED WELDS ON

INTERIOR VERITCAL

SCANTLING FROM BASE

OF FLOAT UP 3 FEET

2" WIDE MINOR

CORROSION AND 10%

SECTION LOSS ON WELD

OVER A 6' LENGTH

LOOSE

PROTECTIVE

PILE COVER

10% SECTION LOSS OF

LOWER D-FENDER

FLANGE SUPPORT

VERTICAL MEMBERS IN

SECTION HAVE UP TO 60%

LOSS OF CROSS

SECTIONAL AREA

TYPICAL PILE

ABRASION STRIP 2"

WIDE AND 14' LONG

100% LOSS OF CROSS

SECTIONAL AREA ON

HORIZONTAL HSS

MEMBER

MODERATE CORROSION

OF HSS MEMBERS IN

THE SPLASH ZONE

SCALE OF FEET

SCALE B

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N o v

:2 p m

NOTES:

1. DIMENSIONS AND LOCATIONS ARE APPROXIMATE.

2. DRAWINGS REFERENCED FROM DRAWING SET TITLED

"CENTRAL WHARF LANDING - CITY OF SALEM - SALEM,

MASSACHUSETTS" DATED JANUARY, 2000 BY NUCCI VINE

ASSOCIATES.

DATE:

DESIGNED:

TECH. REVIEW:

SUB SHEET NO.

PMIS/PKG NO.

DRAWING NO.

SHEET

OF

TITLE OF SHEET

A/E FIRM

PRIME:

CHILDS

ENGINEERING

BELLINGHAM, MA

PLATFORM PLAN

AND SECTIONS

131837

3 3

NBS

TEQ

NBS

11/14/22

SALEM MARITIME NATIONAL HISTORICAL SITE

SALEM MASSACHUSETTS

FOSU 211428S2 TITLE OF PROJECT

4 40 128

S1

PLATFORM FRAMING PLAN

SCALE A

B S2

A S2

A S2

PLATFORM SECTION

SCALE A

B S2

PLATFORM SECTION

SCALE A

10'-0"

'-0

'-1

10'-0" 12'-0"6'-0"

6"x12" TIMBER

SPLIT CAP (TYP)

ALUMINUM

HANDRAIL

3"x12" TIMBER

BRACING (TYP)

6"x12" LOW

WATER WALE

6"x10" TIMBER

STRINGERS

TIMBER BULKHEAD

DENSE

GRAVEL FILL

3"x12" TIMBER

BRACING (TYP)

6"x10" TIMBER

STRINGERS FASTENED

WITH 3/4"Ø GALV. BOLTS

(2) 2"x FASCIA

ALUMINUM

HANDRAIL

6"x12" TIMBER LOW

WATER WALE (TYP)

12"Ø CCA TREATED

TIMBER PILE (TYP)

12"Ø TIMBER

PILE (TYP)

2"x8" WOOD POLYMER

COMPOSITE DECKING

6"x12" TIMBER SPLIT CAP (TYP)10"x10" TIMBER

STRINGER

APPROXIMATE

FACE OF CURB

6"x10" TIMBER

STRINGER (TYP)

TRIPPING HAZARD AT

PIER TO WHARF

CONNECTION

TYP. MINOR CORROSION

WITH 10% LOSS OF THE NUT'S

CROSS SECTIONAL AREA

TYP. 20% LOSS OF

GALV.

100% LOSS OF GALV. WITH

MINOR CORROSION ON

LOWER SOUTHERN BOLT

TYP. 100% LOSS OF GALV.

WITH MINOR SURFACE

CORROSION

12" Ø PILE

TYP. 25% SECTION

LOSS ON BOLTS

75% LOSS OF

SECTION ON

NORTHERN BOLT

COMPOSITE

DECKING

BEGINNING TO FAIL

C S1

PLATFORM/FLOAT ELEVATION

SCALE B

TIMBER PLATFORM P1

EL. +13.0' (MLW)

PLATFORM P2

PLATFORM P4

PLATFORM P3

TOP OF 24"Ø x 0.5" WALL

STEEL PIPE GUIDE PILE

EL. +20.0' (MLW)

20'x50' STEEL FLOAT

W/48" FREEBOARD

SCALE OF FEET

SCALE A

2 20 64

100% SECTION LOSS ON

HSS AT HORIZONTAL