000007A-Conditions Found & Struct Assess Rpt.pdf

MV Thunderbird 18 March 2021 Conditions Found & Structural Assessment Report 1 Job 21020.01, Rev -

MV Thunderbird Conditions Found & Structural Assessment Report

PREPARED FOR:

Moffat and Nichol

Seattle, WA

BY:

Andrew L. Girdler, PE

PROJECT ENGINEER

CHECKED:

Justin M. Morgan, PE

PRINCIPAL

APPROVED:

Justin M. Morgan, PE

PRINCIPAL-IN-CHARGE

DOC:

21020.01-091-01

REV:

FILE:

21020.01

DATE:

18 March 2021

References

1. MV Thunderbird Survey and Recommendations, Pedersen Marine, 12/2/20

2. Thunderbird Ultrasonic Gauging Survey, International Inspection, 3/15/21

Background

Washington State Parks contracted Pedersen Marine to perform a vessel survey of MV

Thunderbird to determine the overall condition of the vessel and the ABYC compliance of vessel systems. Reference 1 documents the conditions found of the vessel at the time of the survey and provides recommendations for corrective action. The overall condition of the vessel’s coatings suggested vessel structure may be corroded. It was recommended that a hull inspection and ultrasonic gauging be performed to determine extent of wastage and to repair as required.

MV Thunderbird was hauled out at Pacific Marine Center on Wednesday, March 10, 2021

(Figure 1) to facilitate the recommended hull inspection. Glosten was contracted to perform the hull inspection of the vessel and sub-contracted International Inspection to perform ultrasonic thickness gauging as required.

Scope of Inspection

Glosten

Glosten performed a visual inspection of the following:

1. Exterior steel hull and decks

2. Major foundations

3. Engine room

4. Bow lockers

5. Forepeak void

International Inspection

International Inspection was originally contracted to perform a thickness gauging of three (3) transverse sections of the hull, but, at the request of Glosten, expanded the scope to include a more thickness readings of the following:

1. Exposed decks

2. Inner bin walls

3. Wind and water strakes

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4. Engine room bilge

5. Transom plating

The resulting scope of gauging generally follows USCG Alternate Compliance and Safety

Agreement (ACSA) guidelines.

Conditions Found

The following describes the overall condition of the coatings and steel structure:

Hull and decks

The predominant features at the time of vessel haul out were the completely wasted anodes and severely biofouled propellers (Figure 2). There was some localized hull deformation on the forward bottom shell (Figure 3), which is not unusual for a landing craft. Otherwise, the hull coatings and structure were in good condition.

The main deck coatings were in poor condition. In fact, most exposed horizontal surfaces exhibited cracking and blistering and in some cases were rust stained (Figure 4) This type of paint degradation is common as these surfaces are more exposed to the elements, e.g., sunlight, dirt, and traffic, which are all caustic to coatings.

Compromised coatings generally result in corrosion of steel in a marine environment. In most cases, and even in the cases of weathered foundations (Figure 5), thickness gauging will be required to determine to which extent the steel material has wasted away. However, in a few instances the severity was apparent, e.g., the through thickness wastage of the unused deck fittings (Figure 6), the port bin wall (Figure 7), and bulwark cap flange (Figure 8).

Engine room

The engine room (Figure 9) bulkheads were in good condition. The bilge and equipment foundations (Figure 10) exhibited a moderate to poor condition. Especially noteworthy were the top of the propeller tunnels and the area under the port side tanks. Similarly, corrosion was observed throughout the bilge and foundations but was concentrated in those areas where the coatings were severely degraded (Figure 11).

Bow locker, forepeak void and misc

The bow lockers were in fair condition with most of the coating failure and accompanying rust and corrosion limited to high traffic areas on the deck (Figure 12). The forepeak was generally in good condition with some localized coating failure and rust (Figure 13).

Thickness Gauging

The following summarizes the thickness gauging results (see Reference 2 for details):

1. Hull (1/4”)

a. Generally minimal to no wastage (Figure 14)

2. Decks (1/4”)

a. Main deck

i. Minimal wastage forward

ii. Evidence of severe to excessive wastage locally amidships and aft

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b. Poop deck

i. Generally minimal to wastage

ii. Evidence of severe wastage locally on starboard side

3. Bin walls (3/16”)

a. Minimal wastage on cap strake

b. Evidence of excessive wastage throughout (Figure 15)

i. Through thickness wastage amidships on port side just above deck and cap flange

4. Wind and water strakes (1/4”)

a. Generally minimal to no wastage

b. Evidence of serve wastage locally in way of vents (Figure 16)

i. Corrosion is likely active within the bin wall

5. Engine room bilge (1/4”)

a. Generally moderate to severe wastage

i. Severe wastage on prop tunnel tops and outboard, especially under port side tanks

6. Transom (1/4”)

a. Generally minimal to no wastage

Structural Assessment and Recommendations

In general, the vessel hull structure is in good condition with some areas of extreme wastage

(>25%) that should be cropped and replaced as per USCG guidance. The bottom deformation of the hull is of little concern as global hull bending is minimal and plate buckling is not expected.

Most importantly, the condition of the vessel coatings needs to be addressed as this is the predominant method of cathodic protection of the vessel. The hull below waterline is in good condition and new anodes were installed at the time of this inspection. Similarly, the forepeak void is in good condition. However, the engine room, decks and topsides exhibit significant coating breakdown.

The inaccessible voids and fuel tanks should be opened and inspected. Based on the condition of the forward void, these areas are likely in good condition.

The vessel’s hull and voids should be cleaned and touch up paint applied as required. The wetted hull should have a new coat of AF paint.

The engine room bilge, decks and foundations should be sand blasted, reinspected, gauged and repaired as required and repainted. This will require temporary removal of equipment. All unused foundations and deck fittings should be removed.

The bin walls may be considered a non-structural liner plate and may be made of sheet metal

(<3/16”), therefore the bin wall plating does not need to replaced in full. Areas of through thickness wastage should be repaired including the cap flange as the knife edge condition may chafe lines or cause injury to personnel. In addition, the topside areas in way of the vents should be repaired as this area exhibits a higher rate of corrosion than elsewhere. The bin walls should be completely sealed to mitigate further corrosion inside the void.

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Figure 1 MV Thunderbird at haul out

Figure 2 Stern bottom after blocking

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Figure 3 Example of bottom shell deformation

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Figure 4 Example of compromised coating and rust staining on main deck

Figure 5 Aft winch foundation

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Figure 6 Unused aft quarter bitt

Figure 7 Port bin wall

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Figure 8 Corroded bulwark cap flange

Figure 9 Engine room

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Figure 10 Generator foundation

Figure 11 Bilge below port side tanks

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Figure 12 Port locker

Figure 13 Forward void

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Figure 14 Hull side thickness gauge measurements

Figure 15 Bin wall thickness gauge measurements

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Figure 16 Topside thickness gauge measurements in way of vents