Vashon Parks District

Tramp Harbor Pier Vashon, WA

Tramp Harbor Pier Condition

Assessment Memorandum

2407 N 31st St, Suite 100

Tacoma, WA 98407

January 16, 2015

Tramp Harbor Pier Condition Assessment Memo January 16, 2015

2407 North 31st Street, Suite 100, Tacoma, WA 98407 (253) 396-0150 Fax (253) 396-0162

Seattle Everett Tacoma Lacey Portland Eugene Sacramento San Francisco Walnut Creek Los Angeles Long Beach Pasadena Irvine

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BACKGROUND AND SCOPE OF WORK

At the request of the Vashon Parks District, KPFF Consulting Engineers performed a maintenance

level condition assessment of the Tramp Harbor Pier on January 12, 2015. Tide levels at the time

of observations ranged between approximately +3.8 to +5.5 feet (MLLW) which allowed

reasonable access for viewing of piling above the water level. The pier is composed of a timber

deck supported by timber stringers. The stringers span between bents and each bent is

supported by a timber pile cap and timber piles. The majority of the pier is supported by bents

10 feet on center, with (2) piles per bent. The outboard end of the pier is supported by bents 10

feet on center, with (4) piles per bent.

KPFF had previously performed a condition assessment in May-June of 2009. The purpose of this

new assessment was to re-evaluate the previously noted structural deficiencies of the visible

portions of the piling, pile caps, and stringers for further deterioration and to look for damage

that has occurred since the 2009 assessment. The immediate life safety of the pier and

remaining service life were also evaluated, taking into account any additional deterioration

observed.

APPROACH AND METHODS

Observations were performed by foot and boat, noting signs of distress such as pile rot and

holes that could be an indicator of current or previous marine borer activity. Observations were

primarily visual in nature, with occasional hand sounding of the timber piling with a hammer or

probing with a screwdriver.

Field notes and digital photos were taken of conditions observed. Appendix A includes the

original condition assessment record plan drawing from the 2009 report with additional

annotation in red indicating further deterioration or damage observed. An attempt was made

to document any deterioration or damage observed even if it does not pose an immediate risk

or maintenance concern at this time. The following summary and recommendations sections

identify areas of primary concern. Appendix B includes representative photographs of the

additional deterioration observed. It should be noted that photographs were not taken to

document every case of distress observed. The intent of the photos is to document the types of

damage discovered, illustrate typical conditions observed and to identify atypical conditions or

damage. A complete digital photo record has been provided with this report.

Marine growth existed on large portions of the piling. Thorough cleaning of structural elements

to enhance visual observations was not within the scope of this project. However, we do not

anticipate that this additional marine growth obscured damage from our attention enough to

significantly affect our ability to assess the structural condition of the pier.

SUMMARY OF ADDITIONAL STRUCTURAL DETERIORATION OR DAMAGE OBSERVED

The pile rating system and description previously defined in the 2009 report was used in this

addendum. In general, the structure is in roughly the same condition as the 2009 report

indicates, which suggests that the rate of decay is relatively slow. However, there is further

section loss in previously noted areas of decay from the 2009 report and other minor locations

of deterioration that were not observed in 2009 as discussed below. The additional locations of

damage or deterioration are shown in Appendix A, in red.

Tramp Harbor Pier Condition Assessment Memo January 16, 2015

2407 North 31st Street, Suite 100, Tacoma, WA 98407 (253) 396-0150 Fax (253) 396-0162

Seattle Everett Tacoma Lacey Portland Eugene Sacramento San Francisco Walnut Creek Los Angeles Long Beach Pasadena Irvine

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The pile caps, stringers and deck are generally in good condition. There are a few locations

where the blocking has shifted or is missing between stringers and should eventually be

repaired. There are also a few locations where the ends of stringers are either splitting or

indicating signs of deterioration. These areas should be monitored for further section loss. There

are four locations where the pile cap is either not bearing on the vertical pile below or only

approximately half of the pile is providing bearing support. These locations should be

completely shimmed to prevent further damage.

There are (98) vertical structural piles supporting the structure. In general, the piling are in good

to fair condition, with the exception of the (6) previously noted 0% capacity piles, which are in

poor condition. In addition to the noted (6) piles in poor condition from the 2009 report, (5)

additional pile locations were observed to either be in fair or poor condition from section loss or

non-bearing between the top of pile and pile cap. The most typical types of deterioration

observed were nearly complete section loss of the piling and smaller holes indicating potential

mariner borer activity.

RECOMMENDATIONS FOR FURTHER ACTION

It appears that the rate of deterioration observed between the 2009 assessment and the

current assessment is slow. In general, areas of deterioration previously observed appeared

similar in size and severity to what was observed in 2009 with slight increases. Some new areas of

deterioration were observed, but it is possible that these areas were obscured by marine

growth during the 2009 observations. The structural members that are not showing current

deterioration could potentially have a number of years of remaining service life, as it appears

completely new deterioration is not quickly developing.

However, KPFF strongly recommends that the Vashon Park District take action to repair current

known damaged pile locations where near complete section loss has occurred. Currently,

there is no calculable capacity for these piles. Any demand in addition to the load that the

piles are currently under could result in pile failure. The ability of the piles to carry the current

loads can’t be accounted for analytically. For a majority of the pier, each bent is supported by

only two piles. If any single pile fails, it will likely result in the collapse of at least 20 feet of pier.

Examples of conditions that could cause increased loading and failure are high wind events,

assembly loading where multiple people are over areas of distress at one time, vessel collision,

or seismic events. However, potential for failure is not limited to these events and could occur at

any time.

At a minimum, the Park District should consider posting warning signs on the pier indicating that

the pier may not be safe. Consideration should also be given to barricading the pier during

known high wind or wave events.

KPFF recommends that at a minimum the following repairs be performed as soon as possible.

These items pose an immediate life safety concern. It is also recommended that the Park District

consider a full underwater dive inspection at some point to determine if deterioration below the

intertidal zone exists.

Bent -1 – Central pile replacement, decay of pile at mudline

Bent 0 – South pile replacement, decay of pile at mudline

Bent 6 – South pile replacement, decay at and above mudline

Bent 13 – South pile replacement, major section loss at mid-pile

Bent 16 – North pile replacement, major section loss just above mudline

Bent 31 – South pile replacement, major section loss at mid-pile

Tramp Harbor Pier Condition Assessment Memo January 16, 2015

2407 North 31st Street, Suite 100, Tacoma, WA 98407 (253) 396-0150 Fax (253) 396-0162

Seattle Everett Tacoma Lacey Portland Eugene Sacramento San Francisco Walnut Creek Los Angeles Long Beach Pasadena Irvine

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KPFF recommends the following repairs be monitored and performed as a secondary priority. If

the piles noted above are replaced, the Park District may want to consider replacing the piles

on this list to gain economy. It should be noted that pile replacement refers to replacement of

deteriorated portions of piling and may not require pile driving. Options beyond those

presented in the previous conditions assessment exist and can be discussed with the Park

District should replacement be desired.

Bent -1 – North pile shim for uniform bearing of pile cap

Bent -1 – South pile repair or replacement, minor section loss at mudline

Bent 4 – North pile repair or replacement, minor section loss at mudline

Bent 5 – South pile repair or replacement, minor section loss just above mudline

Bent 19 – North pile repair or replacement, minor deterioration

Bent 20 – North pile repair or replacement, minor deterioration

Bent 23 – Stringer is bearing on small shim, replacement shim required

Bent 23 – Install new blocking and repair rotated blocking

Bent 28 – South pile repair or replacement, minor section loss at mid-pile

Bent 30 – North pile shims are loose, provide new shim

Bent 32 – North pile shims are loose, provide new shim

Bent 38 – Third pile from the west is not bearing on the pile cap, shim required

We appreciate the opportunity to assist you with this task. If there are any questions or if you

would like to discuss potential pile repair or replacement details, please feel free to contact me

at 253-396-0150.

Sincerely,

Adam Bergman, PE

Associate

Tramp Harbor Pier Condition Assessment Memo January 16, 2015

2407 North 31st Street, Suite 100, Tacoma, WA 98407 (253) 396-0150 Fax (253) 396-0162

Seattle Everett Tacoma Lacey Portland Eugene Sacramento San Francisco Walnut Creek Los Angeles Long Beach Pasadena Irvine

San Diego Boise Phoenix St. Louis New York

Tramp Harbor Pier Structural Condition Assessment

Appendix A

Existing Condition Plan Drawings and Additional Locations

of Damage or Deterioration

Tramp Harbor Pier Condition Assessment Memo January 16, 2015

2407 North 31st Street, Suite 100, Tacoma, WA 98407 (253) 396-0150 Fax (253) 396-0162

Seattle Everett Tacoma Lacey Portland Eugene Sacramento San Francisco Walnut Creek Los Angeles Long Beach Pasadena Irvine

San Diego Boise Phoenix St. Louis New York

Tramp Harbor Pier Structural Assessment

Appendix B

Photo Record

File # Extra Photo File # Photo # Description

0504 1 Looking North at Sea Side of Pier

0505 2 Looking South at Sea Side of Pier

0506 0507 3 Global View - Top of Deck Looking West From Sea Side of Pier

0508 4 Global View - Top of Deck Looking East From Shore Side of Pier

0509 5 Global View - Looking South East

0510 -5011 6 - 7 Bent 34 Batter Pile Decay at End

0512 & 0514 0513, 0515 8 - 9 Bent 40 at East End of Bent - Extra Pile

0516 0517 10 Bent 40 at East End looking North

0518 - 0522

0525, 0526,

0528

0521, 0524,

0527, 0529

11 - 17 Typical View of Pile Cap Splice at Bents 34-37

0530, 0531 18 - 19 Half of Pile is In Bearing (Pile Has Shifted)

0532 0533 20 Bent 40 West End Hole in Edge Beam

0534, 0535 21 - 22 Bent 37 West End Pile Split at Top

0537 0536 23 Bent 32 North Pile is Non Bearing On Pile Cap

0538 24 Bent 30 North Pile is Non Bearing on Pile Cap

0539 0540 25 Bent 26 Cross Bracing Pile is Deteriorated at End

0541 26 Global Picture of South Face of Pier

0542 0543 27 Bent 23 Blocking is Missing or Shifted

0544, 0545 28 - 29 Bent 23 Pile Cap is Non Bearing On South Side. Shim is in place

0546, 0548 0547, 0549 30 - 31 Bents 8 and 9 Piles are Fully Shimmed with Wood for Pile Cap Bearing

0550, 0551 32 - 33 Bent 7 South Pile - New Pile is Strapped to Existing Deteriorated Pile

0552 0553 34 Bent 5 South Pile - Deterioration

0554 0555 35 Bent 4 - South Pile Split At Top

0556, 0557 0558 36 - 37 Bent 0 - South Pile Section Loss

0559, 0560 38 - 39 Bent 20 - North Pile Section Loss

0561 0562, 0563 40 Bent 6 - South Pile Deterioration

0564 0565 41 Bent 2 - South Pile Cap End Deterioration

0566, 0567 41a, 41b Misc Pictures of Bulkhead

0568 - 0570 42 - 44 Bent 31 - South Pile Deterioration

PHOTO 6: TYPICAL DECAY AT TOP OF A BATTER PILE

PHOTO 28: TYPICAL NON-BEARING BETWEEN STRINGERS AND PILE CAP; TYPICAL PILE CAP END SPLITTING

PHOTO 34: TYPICAL PILE SECTION LOSS

PHOTO 41: TYPICAL PILE CAP END DECAY

PHOTO 42: TYPICAL EXTREME PILE SECTION LOSS; 90% OF PADDLE PENETRATES THE PILE

PHOTO 44: ORIGINAL SIZE OF PADDLE