new runway ready for take-off - antigo construction

SUSTAINABLE INSTALLATIONS ♦

New Runway Ready for Take-OffRebuilding acritical runway at Fairchild Air Force Base required attention to every last detail—from theconcrete to the construction technique to the calendar.

BY DAVID SCHILLING, P.E.,M.SAME,CHRISTOPHER J. HOLMES, P.E., M.SAMEandJANELLEZWEIFEL,M.SAME

From bombers to refueling tankers,Fairchild Air ForceBaseoutside Spokane,Wash., for the last 70 years has played avital role in supporting U.S. military missions around the globe. Today, the 92ndAir Refueling Wing, as part of the AirMobility Command, and its associate, the141st Washington Air National Guard(ANG) Air Refueling Wing, are the onlyActive Duty/National Guard teamsdesignated to handle refueling and support forthe entire U.S. fleet.

Pilots, flight crews, airmen and civilian personnel rely on the only runwayon base, Runway 05-23, for all supportactivities. When it began to showsignsofdeterioration, and required increased andcostly maintenance, base civil engineersknew the time had come for extensive

renovation and reconstruction.

To meet its mission requirements forglobal air support, Fairchild AFB neededto relocate both wings—approximately1,300 personnel—to alternate facilities inorder to continue operations. Moreover,theproject needed to becompleted inoneconstruction season to maintain operational efficiency.

With speed and sustainability in mind,Atkins, a global engineering and designconsultancy serving as the lead designconsultant onthe project, set two primaryobjectives tomeetDepartment ofDefense(DOD) "green" goals at the outset of therenovation. The first was to minimize the

amount of excess concrete not used in

the reconstruction (either hauled off-siteor remaining on-site). The second goalwas to maximize the utilization of asphaltmillings and any existing crushed aggregate base materials—thus minimizing theneed for imported materials.

The Military Engineer- No. 677

A RUNWAY IN NEED OF REPLACEMENTPrior to renovation, Runway 05-23

stretched approximately 13,900-ft fromthreshold to threshold, with1,000-ft pavedoverruns on each end. Overall width was

200-ft, with 50-ft of asphalt pavement oneach side. The runway consisted of bothconcrete and asphalt surfaces.

Many of the pavements at FairchildAFB were rebuilt in the 1950s and early1960s, when the property underwent amajor reconfiguration in preparation toaccommodate B-52 aircraft. Tliese pavements remained in service with only occasional maintenance until 2002, whenthe usable pavement was reduced from300-ft to250-ft. The outer 25-ft ofexistingpavement was abandoned in place. Remaining outboard (non-critical) asphaltpavements wereremoved to the aggregatebase layer and new asphalt surfacing wasplaced tocreate a 200-ft wide runway with25-ft shoulders. Along with asphalt pavement replacement, some selective concretepanel replacement also was conducted.

A pavement condition report preparedin November 2005 indicated that the primary load bearing pavementsectionswerebelow the critical Pavement Condition Index (PCI) of 70 for runways. The asphaltsurface showed cracking due to cyclichigh and lowtemperatures at the site. Analkali-silica reaction (ASR) investigationconducted by the U.S. Army Corps ofEngineers also indicated progressive ASR intheconcrete—with thepresence ofASR insample cores with natural-aggregate concreteand the pea-gravel repairmaterials.

ASR is a form of alkali-aggregate reaction found in concrete, caused by a reaction between the alkaline cement and reactive forms ofsilica in the aggregate. Thereaction produces a gel that exerts pressure, resulting incracking, and ultimately,failure. Pronounced ASR deteriorationrequired continuous maintenance to keeptherunway free of foreign debris.

The concrete keel section (center 50-ftof the runway) had been exhibiting signsofsignificant deteriorationand, combinedwith50years of heavy use, was generatingforeign object debris. This deteriorationprompted the need for reconstruction.

THERE-DESIGNWhile keeping the runway length the

same, the design team reduced the widthto the Air Mobility Command standard150-ft of full strength concrete pavement,flanked by 25-ft asphalt shoulders. Thepaved overrunsare 1,000-ft by 150-ft wide.Along with the reduction in the width ofthe runway, reconstructing portions ofthe connector taxiways also was necessary, with replacement of a concrete surface identical to the runway. The renovation was scheduled for a 10-month window

beginning in February 2011.

MATERIALS BALANCING ACTAs part of the strategy to comply with

DOD's sustainability requirements, existing concrete would be removed, crushedand re-used as much aspossible.

The project team knew they would haveto manage ASR-affected concrete withcare. Due to the destructive nature of

ASR material, the Air Force placed tightrestrictions on where it could be reused.

And with ASR-affected crushed concreteonly being placed beneath shoulder andoverrun areas, it was not anticipated thatall concrete materials could be completelyreused in the runway reconstruction. Anearthwork balance exercise helped minimize the amountof existing concrete material left over.

Conversely, insufficient asphalt millingswereavailable to completely fill voids leftby pavement removal. Toavoid the need toimport large volumes of fill material fromoffsite locations, the millings were supplemented with existing crushed aggregatebase typically found in the areas just be-

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♦ SUSTAINABLE INSTALLATIONS

Construction ofthe newrunway at Fairchild Air Force Base wascompleted onschedule inNovember 2011.

neath the existing asphalt pavement. Thiscombination of asphalt millings and reclaimed crushed aggregate base materialwas used to fill the voids beneath the new

concrete pavement structure.

THE TOTAL NUMBERSBy the timeall the work had beencom

pleted, some 146,000-T of concrete hadbeen recycled back in and used as aggregate base material. This accounted forroughly 60 percent of the total amountof concrete removed from the project.In addition to the recycled concrete, theaggregate base material placed under therunway also consisted of approximately4,400-T of recycled asphalt millings. Additionally, another 87,000-T of concreteand 63,000-T of asphalt millings wassalvaged to a local construction company foruse on other projects. Everything on sitethat could be used was; extraneous mate

rials were recycled andtheproject didnotendure anyof thedelays that arecommonon runway renovations in other parts ofthe country.

RAPID PAVING AND PRODUCTIONThe construction season in the Pa

cific Northwest is typically less than 10months, leaving little leeway for delays.In fact, the average low temperatures arebelow freezing from November throughMarch. Surveyors and construction crewsteamedup to reconstruct the new runwaywith greater speed and efficiency than

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might otherwise be typical of a runwayrenovation of similar size and scope.

Throughout construction, the pavingsubcontractor used a stringless guidancesystem for placing the graded crushedaggregate base course, which provideda platform for subsequent material layers. The stringless guidance system consists primarily of a GPS-guided machinecontrol system that tracked elevation andslopeas material was placed.

Advantages to this system were numerous. First, the approach allowed for moretime on actual production and less timewaiting for surveying andgrade checking.Operators could finish jobs faster—andwith minimalsupervision—even in dusty,foggy, or dark conditions. Second, theneed for stakes and stringlines, and thetime needed for their installation, were

alleviated. Personnel and machine costs

also were reduced through the improvedproductivity.

The original schedule for concrete paving assumed production rates for single-lane paving to be on average 1,800-yd3per day, with additional time needed forconcrete curing and dowel barinstallationbetween each lane.

The contractor proposed paving twolanes wide, a width of 37.5-ft, eliminatingthe additional curing and installation timebetween each pour. Furthermore, production rates ended up averaging 2,500-yd3per day. This alone proved a tremendousimprovement in saving time.

ENERGYMANAGEMENTThe Runway 05-23 projectalso included

the installation of a new runway center-lineand edge lightingsystem; runwaydistance markers; airfield signage; precisionapproach path lighting systems; approachlighting systems; electrical duct systemand associated drainage; and revisions tothe airfield lighting vault. The glide slopeantennas, shelters and associated equipment also were relocated due to a changein threshold crossing height.

Through previous design considerations with Air Mobility Command,Atkins designed the airfield lighting systems to incorporate the use of LED lightsand signage. Despite their higher upfrontcost, the long-term benefits far outweighthis expense. LED lights have a longerlifeexpectancy, consume less energy, and reduce stress on the airfield lighting cable.Additionally, the lights have an acute on/offcontrast and produce a pure color thatdoes not fade over time, which means

safer, more reliable conditions. LED technology was used for the runway centerlinelights, touchdown zone lights, runwayguard lights, taxiway edge lights, andrunway and taxiway signage.

The renovation of Runway 05-23 wascompleted on time in November 2011.Soon after, more than 1,300 airmen andcivilians who were temporarily deployedto Grant County International Airportand Spokane International Airport returned to Fairchild AFB. With the con

struction completed, the 92nd Air Refueling Wing and 141st Washington ANGAir Refueling Wing can continue theirsupport to the global mission.

David Schilling, P.E., M.SAME, is a GroupManager, and Chris Holmes, P.E., M.SAME, isa Senior Project Manager, with Atkins AviationServices. Viey can bereached at 615-365-1448,or david.schilling@atkinsglobal.com; and 615-365-1451, or chris.holmes@atkinsglobal.com,

respectively.

Janelle Zweifel, M.SAME, isan Engineer II withAtkins; 615-399-0298, orjanelle.zweifel@atkin-sglobal.com.

The Military Engineer •May-June' 2012

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