1

2

Briefing Purpose

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

3

Seawall Description• Overall Image of Portsmouth Seawall

4

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

5

Seawall Description• Image of Sheet Pile and Batter Pile Design

6

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

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

7

Installed Batter Steel H Piles

8

Installed Batter Steel H Piles

9

10

City Hall Segment• Image of City Hall Segment

11

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

12

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

13

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

14

15

Renaissance Hotel Segment• Image of Renaissance Hotel Segment

16

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%

17

Holiday Inn Segment • Image of Holiday Inn Segment

18

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

19

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

20

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

21

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)

22

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)

23