American Society of Military Engineers

Transcription

1 Presentation to American Society of Military Engineers Runway 9-27 Rehabilitation Project POHNPEI INTERNATIONAL AIRPORT, FSM Presented by Wadgy A. Guirguis, P.E. President August 14, 2012 PROJECT SCOPE OF WORK New Runway Turn-around New Runway & Taxiway Edge Lights New Runway Shoulders New Security Perimeter Fence & Road New Runway Turn-around Asphalt Overlay New Electrical Vault New ARFF Location Proposed JICA Funded Expansion 1

2 Distressed Runway Pavement Areas Existing Runway Dilemma: Two specific areas within the Runway are known to have continually settled for decades. Airlines have complained about the EXCESSIVE RUNWAY DIP prompting safety concerns. Topographic survey indicates a 6 inch difference between low-point and finish grade elevation. GMP is tasked to provide a PERMANENT SOLUTION to the settlement problem. Distressed Runway Pavement Areas Distressed Runway Pavement Areas 2

3 Geotechnical Investigation Subsurface conditions at the distressed areas were identified through geotechnical investigation by Geolabs Inc. Subsurface profiles show the pavement distressed areas is underlain by fill materials consisting of the following feet: Loose to medium dense gravel and sand with varying amounts of silt feet: Very soft alluvial deposits of silty clay feet: Lagoonal deposits of loose silty and clayey sand. Medium hard to hard basalt rock formation. 143 feet and below: Subsurface Soil Profile RUNWAY SURFACE 0 ELEVATION FEET (MSL) 20 FILL CORALLINE DETRITUS 40 FILL RECENT ALLUVIUM RECENT ALLUVIUM LAGOONAL DEPOSIT 60 CORALLINE DETRITUS DISTRESSED RUNWAY PAVEMENT AREAS LAGOONAL DEPOSIT ALLUVIUM BASALT ROCK FORMATION CROSS--SECTION CROSS 3

4 Distressed Runway Pavement Areas Probable Causes of Pavement Settlement: Due to consolidation settlement of the soft Alluvium soils between depths of feet below the existing runway surface. Estimated ultimate settlement in the range of 6-7 feet in approximately 25 to 30 years. Distressed Runway Pavement Areas Remedial Measures Considered: RECURRING PAVEMENT OVERLAY DEEP COMPACTION GROUTING CONCRETE PILES WITH CONCRETE PILE CAP 4

5 Distressed Runway Pavement Areas PAVEMENT OVERLAY Installation of new asphalt pavement course over the existing asphalt pavement. Advantages: Low risk with known construction variables. Short construction time duration. Lowest initial cost of alternatives considered. Disadvantages: Temporary resolution of settlement problem. Overlay roughly every 3 years. Financial burden of funding maintenance program. Distressed Runway Pavement Areas DEEP COMPACTION GROUTING Injection of a low-slump grout or cement into the very soft alluvial soils. Mixture densifies the highly compressible Alluvium soil. Advantages: Soil stabilization with minimal disruption to operations. Easier setup and quicker installation time for shorter overall construction duration than pile system. Lower initial cost than concrete pile alternative. Successfully used for soil densification of feet depths. 5

6 Distressed Runway Pavement Areas DEEP COMPACTION GROUTING(continued) Disadvantages: Method has not been proven for depths beyond 50 feet. Higher initial cost than the pavement overlay alternative. No successful track record. This option eliminated from further analysis. Distressed Runway Pavement Areas CONCRETE PILES WITH PILE CAP Installation of 16 inch concrete piles to 140 feet depth with continuous concrete pile cap slab over piles. Advantages: PERMANENT RESOLUTION of settlement problem. Disadvantages: Highest initial cost of alternatives considered. The longest construction duration of alternatives considered. May require extended closure of Runway. 6

7 Life Cycle Cost Analysis BASE CASE: Recurring asphalt overlay every 3 years as part of a maintenance program. ALTERNATIVE CASE: Installation of concrete piles and pile cap for a PERMANENT SOLUTION. Life Cycle Cost Analysis OVERLAY Base Case Estimated Costs: Initial Capital Cost: $ 00 Repair & Maintenance Cost: Construction Cost $ 420,000 Administration (5%) $ 21,000 Settlement Monitoring (5%) $ 21,000 Design (10%) $ 42,000 CM (10%) $ 42,000 Total Cost (in 2006 dollars) $ 546,000 7

8 Life Cycle Cost Analysis PILING Alternative Case Estimated Costs: Initial Capital Cost: $ 7,800,000 Repair & Maintenance Cost: $ 00 Total Cost (in 2006 dollars) $ 7,800,000 Life Cycle Cost Analysis Repair Alternatives Live Expectancy: Use life expectancy of subgrade to reach 100% consolidation. Estimate 50 years. Inflation Rate: Estimate 4.0%, based on report from January 2006 Pacific Magazine. 8

9 Life Cycle Cost Analysis SUMMARY OF PRESENT WORTH VALUES Discount Rate 3% 4% 5% OVERLAY Base Case NPV $11,755,613 $9,100,000 $7,197,932 PILING Alternative Case NPV $7,800,000 $7,800,000 $7,800,000 Life Cycle Cost Analysis FINDINGS Piling alternative is a cost effective remedial method. Relieves financial burden of maintenance funding. Eliminates future disruption to airport operations. Reinforces Public confidence in Runway safety. 9

10 Recommended Remedial Measure CONCRETE PILE CAP RUNWAY SURFACE 0 ELEVATION FEET (MSL) 20 FILL CORALLINE DETRITUS 40 RECENT ALLUVIUM FILL 140 feet long piles LAGOONAL DEPOSIT RECENT ALLUVIUM 60 CORALLINE DETRITUS DISTRESSED RUNWAY LAGOONAL DEPOSIT PAVEMENT AREAS ALLUVIUM BASALT ROCK FORMATION CROSS--SECTION CROSS DESIGN CONSTRAINTS OPERATIONAL CONSIDERATIONS Keeping Runway open for all flights. Minimizing interruptions to airport operations. CONSTRUCTION CONSIDERATIONS Installation of piles and pile cap without continuous, extended closure of the Runway. 10

11 RUNWAY DESIGN CRITERIA Current Runway Data: Length: 6,000 feet Width: 150 feet Surface: Asphalt FAA Airplane Design Group (ADG): , : III FAA Airport Approach Category (AAC): Pohnpei Airport: C FAA Minimum Runway Design Width: Pohnpei Airport: 100 feet width Runway DESIGN PLAN DESIGN RESOLUTION Provide for operational use of 100 feet wide Runway. Phase construction activities to allow use of Runway with concurrent installation of piles and pile cap. 11

12 DESIGN PLAN DESIGN ISSUES TO RESOLVE Construction of additional Runway pavement. Temporary work to the Runway airfield lights and navigational aids. Piles and pile cap installation. FAA approval of the Design Plan. Airlines approval of the Design Plan. PHASE 1 CONSTRUCTION STEP 1 Construction of Haul Road (location of new access road) Construction of Staging Area (site of new ARFF) 12

13 PHASE 1 CONSTRUCTION STEP 2 Construct new 25 feet pavement shoulders PHASE 1 CONSTRUCTION STEP 2 (continued) Remove existing edge lights and replacement with battery powered, portable lights Install battery powered, portable threshold lights Existing REIL to remain Existing PAPI system to remain Install new edge light base and conduit bank for final installation Install new threshold light base and conduit bank for final installation 13

14 PHASE 1 CONSTRUCTION STEP 3 Re-stripe Runway for southern 100 feet use prior to next flight operation Relocate battery powered, portable edge lights to new Runway configuration Relocate battery powered, portable threshold lights and REIL to new Runway configuration PHASE 1 CONSTRUCTION STEP 4 Close northern half of Runway 14

15 PHASE 1 CONSTRUCTION STEP 5 Drive new concrete piles on 10 feet spacing and construct pile cap on northern half of Runway PHASE 2 CONSTRUCTION STEP 1 Re-stripe Runway for 100 feet northern half use prior to next flight operation Relocate battery powered, portable edge lights to Runway configuration Relocate battery powered, portable threshold lights to new Runway configuration 15

16 PHASE 2 CONSTRUCTION STEP 2 Close southern half of Runway. PHASE 2 CONSTRUCTION STEP 3 Phase I completes construction on the northern half of the Runway. Drive new concrete piles on 10 feet spacing and construct pile cap on southern half of Runway. 16

17 PHASE 3 CONSTRUCTION Re-stripe Runway for full 150 feet wide use prior to next flight operation. Install 2 inch asphalt overlay over entire 150 feet width of Runway, including shoulders. Resurface in foot width paving lanes during temporary closure of runway. ADDITIONAL WORK TO BE PHASED IN New Runway Turn-around New Taxiway Edge Lights New Security Perimeter Fence & Road New Runway Turn-around Taxiway and Apron Asphalt Overlay New Electrical Vault New ARFF Location Proposed JICA Funded Expansion 17

18 POST DESIGN CHALLENGES Two Bid opening events with no Bidder. Third Bid opening event with only one Bidder. Bid price was $86 million. Initial estimate was $56 million. AIP Grants were to be re-allocated. POST DESIGN CHALLENGES (continued) Re-Phase Construction activities according to AIP Funding. Re-Design the ARFF to eliminate pile foundation. Negotiating with the sole source proved to be difficult. Construction schedule was delayed. 18

19 PRE-CONSTRUCTION PHASE 1 19

20 PHASE 2 PHASE 3 20

21 PHASE 4 POHNPEI RUNWAY

22 POHNPEI INTERNATIONAL AIRPORT ARFF Mahalo! 22