1. 2 Briefing Purpose To provide an update of the existing condition of the Portsmouth Seawall and...

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Briefing Purpose

To provide an update of the existing conditionof the Portsmouth Seawall and to indicate the status of future projects

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Seawall Description• Overall Image of Portsmouth Seawall

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Seawall Description• Constructed in the 1970’s

Section adjacent to Holiday Inn constructed in 1981

• Approximately 2480 linear feet, excluding High Street andNorth Landing

• Four segments – City Hall, Admiral’s Landing, Renaissance Hotel and Holiday Inn

• Majority of seawall is sheet pile and batter pile design

• Holiday Inn segment is sheet pile with tiebacksand deadman design

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Seawall Description• Image of Sheet Pile and Batter Pile Design

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Seawall Description• Image of Sheet Pile and Tieback/Deadman Design

Seawall Description• Image of Sheet Pile with a batter steel H pile design

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Installed Batter Steel H Piles

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Installed Batter Steel H Piles

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City Hall Segment• Image of City Hall Segment

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City Hall Segment• City Hall to High Street Landing

• Approximately 900 linear feet

• 20-30% material loss, which is consistent with its age

• Scheduled pile repair in summer of 2013

City Hall to North Inlet

Approximately 20 piles

Miscellaneous concrete repairsand pile replacement

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Admiral’s Landing Segment• Image of Admiral’s Landing Segment

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Admiral’s Landing Segment• High Street Landing to Lightship Museum

• Approximately 470 linear feet

• In 2010 approximately 150 linear feet failed because of failed batter piles

Batter piles in the failed section had approximately 75% material loss judging from piles that were removed during the project

Remaining batter piles were inspected

Most were found to have about 30% material loss

Sheet piles were inspected and havesimilar material loss (30%)

Pictures ofReconstructionof Failed Sectionof Seawallin 2010• Failed section of

a batter pile

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Renaissance Hotel Segment• Image of Renaissance Hotel Segment

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Renaissance Hotel Segment• Lightship Museum to North Landing

• Approximately length 460 linear feet

• Timber piles under decking at north inlet (southern corner) need replacement

Some dolphin piles at this location also need to be replaced

Replacement included in upcoming project

• 2010 inspection revealed that steel batter piles wererusted and showing signs of deterioration

Section loss of 25-30%

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Holiday Inn Segment • Image of Holiday Inn Segment

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Holiday Inn Segment North Landing to Tidewater Yacht Club

• Approximately 650 linear feet

• Inspection performed in 2006

Average material loss of 30%, some sectionshave loss of 40-50%

Deterioration of fenders and similar pile deterioration as other parts of seawall

• Started design for replacement in 2009

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Holiday Inn Segment (Cont.)• Discovered significant riprap outboard of seawall in 2011

Underwater inspection conducted in December 2012Riprap extend 15 feet into channelRequires design revision – seawall cannot be

installed seaward

• Current exploratory investigation to verify location oftiebacks and deadmen Information used to finalize design for replacement Estimated replacement cost of $3.5 million dollars

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Condition Summary• City Hall and Renaissance Hotel Segments show deterioration

expected due to age of structure – approximately 30%

• Admiral’s Landing Segment has experienced areas that have exceeded the expected rate of deterioration (section failure in 2009)Pile replacement scheduled for this summer

• Holiday Inn Segment has a different design that the remainder of the seawallDeterioration of 40-50% in some locationsRiprap found seaward of structure will alter design

and increase replacement costs

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Previous Seawall Projects1997-2011

• Six Repair/Improvement Projects Since 1997

• Repair to Seawall and Boardwalk

• Marine Improvements at Downtown Seawall and North Inlet

Installation of 9 dolphins in front of Downtown Seawall

Removal and replacement of copper pile caps and fender guards at North Inlet

• Structural Repairs to Seawall Decking

• North Landing Ferry Dock Repairs and Improvements

• Repairs to Portsmouth Seawall Boardwalk

• Seawall Repairs (Admiral’s Landing Section)

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Recommendations• Proceed with pile replacement project this summer

• Complete investigation of Holiday Inn Seawall andfinalize design based on findings

• Re-inspect seawall from North Landing to City HallDetermine repair options and inspection schedule

based on results

• Estimated cost to replace seawall from North Landingto City Hall: $20 million (minimum)

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