Government EngineeringThe Digital Journal for Public Infrastructure

Highway Project Meets Tough ChallengesDesign improvements to Virginia highway streamline two complex interchanges.

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rlington Boulevard, Arlington,Virginia’s portion of Route 50,was constructed in the 1930s.

Interchanges at 10th St. and atCourthouse Road were added in 1954,but over the years had become dated.They were tightly spaced by currentstandards, the merge areas did not haveacceleration lanes, and alternative trans-portation modes were not accommo-

dated. In all, the design could no longerprovide sufficient capacity for rapidlyrising traffic volumes, which currentlyreach 65,000 vehicles a day.

AECOM (www.aecom.com) wasretained by the Virginia Department ofTransportation (VDOT) as the primedesign consultant to manage and coor-dinate a multi-discipline, in-housedesign team to provide design and con-

struction engineer-ing services for theurban interchangefacilities. Engineeringtasks included:study of bridge androadway alterna-tives; bridge design;traffic analysis; in-terchange design;sign and signalplans; hydraulic a-nalysis; citizeninformation andpublic hearings;staged constructiondetails; roadwaylighting; multi-use

Highway Project MeetsTough ChallengesDesign improvements to Virginiahighway streamline twocomplex interchanges.

A

By Angela A. Adams,Michael Jelen, and

James Kawchak

Multiuse trail, landscape plantings, anddecorative retaining walls on Route 50interchange.

Government Engineering ■ March-April 2015 ■ 28

trails; and geotechnical investigations.Custom-designed concrete panels andbridge accents in the form of LEDback-illuminated patterned metal grill-work were introduced to the project byartist Vicki Scuri, of Seattle-based VickiScuri Siteworks, working withArlington County Cultural Affairs’Public Art Program.

Poor Soil ConditionsA tight site footprint and poor soil

conditions were significant challenges.The soils were unable to support theloads for MSE walls. Given extreme siteconstraints, the design reduced the loadby using low-density cementatious fill(LDCF) to mitigate adverse conditionswith an earth retention system that sup-ports the retaining walls and the publicart incorporated into the walls. Thistechnique provided the additional spacenecessary for the interchange designthat improved safety, increased public

access, and increasedvehicle capacity withinessentially the sameright-of-way as the out-dated interchanges.

The artistic conceptswere integrated intostructural, civil, andlighting design compo-nents. VDOT’s mandatefor low maintenance,

long-life highway bridge infrastructurehad to be integrated with ArlingtonCounty’s desired aesthetic presentation.The decorative fascia girder panels wereconstructed of weathering steel and areilluminated by LED accent lighting,which meets VDOT’s goals of long-lifeand low maintenance.

Overcoming ObstaclesAECOM implemented an innovative

engineering technique to address sub-standard roadway geometric condi-tions. To correct sight and curvaturedeficiencies, the westbound roadwayelevation had to be raised nearly fourfeet. This was achieved by phased con-struction involving the intermittentplacement of four-in. pavement lifts.The result was an unrestricted flow ofdaily rush-hour traffic through travellanes as the roadway was raised whileremaining within the existing right-of-way.

Installation of low-densitycementious fill was donein lifts to mitigate adverseconditions.

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In addition to dealing with hazardscreated by the highly constricted lanes,the project’s proximity to historic FortMyer required other considerations. Forone, the implementation of a standarddeceleration lane would have resulted inunfavorable and costly consequences,causing the need for additional right-of-way acquisition and replacement ofexisting retaining walls. The solutionwas to simply mill and overlay to staywithin the available right-of-way, miti-gate the need to document environ-mental impacts, and avert additionaldesign problems that would negativelyaffect retaining walls and cantilever signstructures.

Fraught with deficiencies, the existinginterchanges were in dire need of recon-figuration. Acceleration lanes for traffic

entering mainline Route 50 were absentand weaving areas in both directionswere extremely short and did not havethe benefit of a dedicated weaving lanebetween ramps. Resolving those sub-standard conditions was compoundedby limited right-of-way squeezing theproject from both sides.

The key to addressing these issues wasthreefold: 1) the development of aninterchange configuration that added1.67 newly constructed lane-miles; 2)providing three through lanes in eachdirection; and 3) separating collector-distribution roads on each side thatserve local traffic heading forCourthouse Road, Fairfax Drive, or10th Street. This configuration, whichincluded acceleration lanes, improvedweaving areas, and reduced congestion,

10th Street bridge abutment piles under construction while maintaining existing bridge.

Government Engineering ■ March-April 2015 ■ 30

was accomplished within the limitedproject footprint. Implementing a mul-tidiscipline approach, AECOM andVDOT integrated a roadway designscheme that resolved traffic problemsthrough the use of a retaining wall sys-tem that used LDCF to address poorsoil conditions.

Health, Safety, andEnvironmental Issues

Highway and interchange designs inurban settings are typically divisive bar-riers that separate areas within the com-munity because they focus primarily onsafety and effectively moving traffic.Arlington County spearheaded the pro-ject’s public art components in a collab-orative effort with VDOT and the

design consultant. This collaborativeapproach resulted in successful, high-quality civic design and communityappreciation for high-traffic urbaninterchanges that now serve as a modelfor similar projects. In addition to theimproved safety and traffic capacity, theArlington Boulevard project connectsneighborhoods, providing enhancedcommunity access while creating a visu-ally attractive feature markingArlington’s government center. Theenhanced landscaping creates a park-like atmosphere and encourages use ofthe pedestrian/bike trails that are con-tinuous throughout the area of the proj-ect on both the north and south sides ofRoute 50.

The new, dedicated multi-use trailscontribute to enhanced safety, health,

Decorative retaining wall panels and low density cementious fill under construction.

31 ■ Government Engineering ■ March-April 2015

and public welfare. A new trail was cre-ated on the south side of Route 50 andthe existing trail on the north side wasimproved and extended under the new10th Street bridge. The trails are part ofArlington’s Bike and Pedestrian pro-grams and a county-wide effort to pro-vide a choice in the mode of travel.

Continuous roadway lighting wasprovided throughout the project toimprove nighttime visibility. The high-color rendering index afforded by theLED luminaires improved the qualityof lighting as opposed to traditionalsodium lighting, mitigating hazardsassociated with roadway and trail inter-sections. Colored LED fascia panelaccent lighting in conjunction withlong-life, energy efficient LED roadwaylighting are appealing to the eye, day ornight, while also enhancing public safe-ty. The roadway lighting uses ArlingtonCounty standard LED luminaires thatreduce energy consumption by 35 per-cent compared to high-pressure sodi-um. In addition, the LED luminaireshave three times the life expectancy oftraditional light sources, reducingmaintenance and the traffic impactsassociated with lamp replacement.

Aesthetic EnhancementsInspired by the native redbud trees

found near the site, project artist VickiScuri carved heart-shaped leaf patternsand seed pods to add pattern and tex-ture to concrete walls and two bridges,offering a transition from pedestrian-scale while softening the impact of theinfrastructure (wall heights rise to 25

ft). The pattern sequences and transi-tions follow the site terrain.

Bridge spans are clad with laser-cutweathering steel grills that are back-illu-minated with LED lights. A light showon a 15-minute loop fades and transi-tions gradually across the span in arange of non-highway colors, suggest-ing stained glass. The county, localpolice, and VDOT had representativeson site when the light show was final-ized, in an effort to guarantee bothbeauty and safety.

All told, the project required carefulbalance and attention to address trafficcongestion; unsafe conditions for vehi-cles, pedestrians, and bicyclists; multi-modal access improvements; and inte-gration into a dense array of residential,commercial, and government proper-ties. It required multi-agency coordina-tion and briefings to community inter-est groups. The project redefinedVDOT’s views about the value of incor-porating artwork into road and bridgeprojects. The context-sensitiveapproach offers a new model forVDOT, which is already being replicat-ed on other projects.

Ms. Adams is Director, Arlington PublicArt; Mr. Jelen, P.E., is Vice President, andMr. Kawchak, is Project Manager,AECOM.

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