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    Corridor Management: A Means to Elevate Understanding of Geotechnical8

    Impacts on System Performance9


    Scott A. Anderson1, Ph.D., P.E. and Benjamin S. Rivers2, P.E.1112

    1Corresponding Author, Team Manager, Geotechnical Technical Service Team,13Resource Center, Federal Highway Administration, 12300 West Dakota Avenue,14Suite 340, Lakewood, CO; [email protected]: 720-963-324416

    Fax: 720-963-323217


    192Geotechnical Engineer, Geotechnical Technical Service Team, Resource Center,20Federal Highway Administration, 61 Forsyth St. SW, 17T26, Atlanta, GA 30303;[email protected]: 404-562-392623Fax: 404-562-370024

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    ABSTRACT: The primary assets of a transportation agency are the transportation25corridors that have been established to provide means for moving people and goods26safely and efficiently. A corridors performance in this regard is only as good as its27weakest link. Therefore, the way an agency can manage an asset such as a corridor to28a standard for system performance is to consider its components concurrently, not by29

    individual asset classes. A corridor has embankments, slopes, walls, bridges, and30

    pavements, and considering these geotechnical features separately just doesnt make31sense from a system performance perspective. Settlement, slope instability, rockfall,32erosion and corrosion are events which can be surprising, or recognized in advance33and managed. The corridor concept can bring geotechnical assets into consideration34and result in better management for system performance. It also provides a means for35rational prioritization that allows for a phased approach to the daunting task of36collecting inventory and condition assessment for features that have not previously37been managed. Geo-professionals are developing tools and practices for38inventorying, assessing performance, predicting life-cycle costs and degradation, and39evaluating risk associated with geotechnical features. These tools and practices will40

    contribute to effective corridor management.41


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    A geotechnical feature is defined here as a part of a highway right-of-way45comprised largely of soil or rock, or another improvement that has direct bearing on46soil or rock performance or influence over the effects of their performance. Examples47

    are cut slopes, embankments, retaining walls and the soil or bedrock foundation upon48

    which all structures and roadway are built. Improvements are things such as surface49or subsurface drainage ditches, pipes and trenches, rock bolts or ground anchors, and50rockfall mitigation systems. When a geotechnical feature is performing well it goes51unnoticed but when it is not performing well it causes escalation in maintenance costs52or catastrophic failure. Either way, it causes a drain on limited resources, a potential53safety hazard, and a reduction in performance. A few recent slope and embankment54examples illustrate this point well (Anderson and Rivers, 2013).55


    Embankment Failure on I-75 in Campbell County, TN March, 201257


    In March, 2012, a slope failure within a 150-ft high side-hill embankment section59

    propagated into the southbound travel lanes of I-75 in Campbell County, TN, forcing60southbound traffic to be rerouted for five days until one southbound travel lane could61be reestablished along the northbound side. The investigation of the failure revealed62a deteriorated corrugated metal pipe (CMP) culvert and saturated weathered-shale63clay embankment material and underlying natural soils to be primary factors64contributing to the failure (TDOT 2012a). An emergency repair contract was65executed in mid-April, 2012 with an estimated repair cost between $9.4M and66$12.6M and an estimated completion date of September 28th (5.5 months).67




    Figure 1. Aerial photograph of the I-75 embankment slope failure site in TN as71construction repairs were on-going in May, 2012. (Photograph courtesy of Tennessee72Department of Transportation).73

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    A detour was created within the right of way and one southbound lane remained74closed during most of the repair. In addition, two alternative routes approximately 2075and 30 miles in detour length were recommended to travelers. Even so, with an76annual average daily traffic (ADT) volume of approximately 28,000 vehicles, long77delays and traffic back-ups in excess of 20 miles along the interstate were generally78

    expected during holidays and peak travel times (TDOT 2012b). An aerial photograph79

    of the embankment failure site taken by Tennessee Department of Transportation80(TDOT) in May, 2012, shortly after a localized failure occurred near the upper81southern end of the site during construction, is shown in Figure 1. Traffic was82reduced to one-lane northbound and closed to southbound traffic for 14 days until the83localized failure was stabilized.84


    Rockslide on I-40 in Haywood County, NC October, 200986


    In October, 2009 a large rockslide occurred near mile post 3 along the I-40 Pigeon88River Gorge corridor in North Carolina essentially closing a 53-mile section of the89

    interstate between North Carolina and Tennessee for 6 months while debris could be90

    removed and the rock-slope was stabilized. An aerial view of the rockslide soon after91failure occurred is shown in Figure 2.92




    Figure 2. Rockslide within the Pigeon River Gorge on I-40 in North Carolina,96October, 2009 (Photograph courtesy of North Carolina Department of97Transportation).98

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    A second failure occurred in January 2010 near mile post 7 while the interstate was100still closed. The interstate reopened in April, 2010 to limited traffic for an additional1016 months until repairs for the two failures and mitigation measures for five other102high-risk sites were completed The total cost for all slope repairs, mitigation103

    measures and operations was $19.2M (NCDOT 2010; Joel Setzer, personal104

    communication, July 9, 2012).105106

    During the I-40 closure, an ADT of approximately 24,000 vehicles per day was107rerouted approximately 130 miles along I-81 and I-26. Frequent traffic back-ups in108excess of 7 miles were commonly observed in Asheville, NC due to increased109congestion. Coincidently, US Highway 64 near the NC/TN border was also closed110from November 2010 to April 2011 due to rock-slope failures. The total repair cost111for the US-64 slides was approximately $3M. Local economic impacts due to the112closures of two regional national highway corridors are difficult to quantify.113However, a report examining the economic impacts of these two coincidental114

    rockslides was prepared for the Appalachian Regional Commission. The report115

    suggests that rural businesses within the surrounding area experienced reductions in116revenue ranging between 30 to 90 percent compared to previous years. The regional117economic and transportation costs were estimated to be $197M due to increased118congestion, additional travel times, vehicle operating costs and pavement119maintenance. Approximately 90 percent of those costs were attributed to the I-40120closure (HDR 2010).121


    The I-40 Pigeon River Gorge corridor has a history of rockfall and rockslide123activity since its original construction in the late 1960s. Significant failures causing124closures and partial closures for five or more months occurred in 1985 and in 1997.125Most recently, three failures and two partial closures of two weeks or less occurred in126January and March, 2012. Closures of this frequency and duration almost certainly127mean the performance of this corridor and perhaps network of corridors is controlled128by geotechnical feature performance.129


    Rockfall on I-70 in Glenwood Canyon, CO March, 2010131132

    In March, 2010, a rockfall event occurred on I-70 within Glenwood Canyon,133Colorado. The rockfall covered all travel-lanes in both directions, damaging the134bridge-deck that elevates the roadway through this section. One boulder completely135ripped through the deck, damaging a support beam and retaining wall below the deck;136the aftermath of the rockfall is shown in Figure 3. The corridor was closed for four137days and re-opened to limited traffic for two-months while debris was removed and138repairs were made. The repair costs for this event totaled $1.6M. A significant139impact of this closure involved the necessary 200-mile detour to connect local140communities and to reroute an ADT volume of approximately 27000 vehicles per141day.142


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    This corridor has seen two other recent events with similar closures. Another144rockfall event occurred in November, 2004, and in June, 2003, a culvert failure145occurred that completely destroyed an embankment section of roadway. The repair146cost for the culvert failure was $4.2M. Again, the frequency suggests that147geotechnical features likely control the performance of the corridor.148




    Figure 3. (A) Rockfall debris on I-70 elevated deck. (B) Portion of deck torn-152through by boulder (Photographs courtesy of Colorado Department of153Transportation).154



    In summary, these recent examples from three different interstate highways show157the significant impact to the performance of a highway system caused by closing a158highway corridor. The large impact from these examples is not in safety, as one159might first think, as there were no serious injuries or fatalities from these events. The160

    impact is in direct repair costs, which are higher for emergency situations than for161programmed work, and indirect costs associated with closure and reduced mobility162for the community. These are impacts to system performance from geotechnical163features that can be managed.164





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    In July, 2012, a new highway bill entitled Moving Ahead for Progress in the 21st171Century Act,or MAP-21, was enacted into law. This new legislation reestablished172national goals for the federal-aid highway program and established requirements for173

    performance management and associated performance measures (MAP-21, 2012).174

    Under this new legislation, State Departments of Transportation are required to175develop a risk-based asset management plan for the National Highway System176(NHS) to improve or preserve the condition of the assets and the performance of the177system, and will need to set targets and track progress toward achieving those targets178based on the established national goals and performance measures. States are179required to include performance management of bridges and pavements within their180asset management plans, and are encouraged to include all infrastructure assets181within the right-of-way corridor in such plans (MAP-21, 2012).182


    Performance Management is a systematic approach to making investment and184

    strategic decisions using information about the condition and performance of the185

    system and developing an approach to achieve goals. The MAP-21 goals are as186follows:187


    Safety reduce fatalities and injuries;189 Infrastructure Condition maintain the highway infrastructure asset system190

    in a state of good repair;191

    Congestion Reduction reduce congestion on NHS;192 System Reliability improve efficiency;193 Freight Movement and Economic Vitality improve the freight network,194

    strengthen ability of rural communities to access national and international195

    trademarks, support regional economic development;196 Environmental Sustainability enhance performance of transportation197

    system while protecting and enhancing the natural environment; and198

    Reduced Project Delivery Delays reduce project costs, promote jobs and199economy, and expedite the movement of people and goods by accelerating200project completion through elimination of delays in project201development/delivery process.202


    All of these can in some way be impacted by geotechnical features and for some of204these goals the connection is significant. Given that the applications of asset205management systems and principles are intended to assist highway agencies with206

    achieving these performance goals the risk is this: If established indicators, measures207and state-developed asset management plans do not collectively consider the impacts208of all manageable features having significant influence on the effective performance209of the highway system and its corridors, then established standards and targets might210well be met while the impacts due to other significant features and their associated211costs may be left ineffectively managed, resulting in inadequate performance to the212system and its components. From the geotechnical perspective, this risk can be213mitigated by educating those establishing and evaluating the measures and putting214

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    Figure 4. (a) A hypothetical inventory organized by asset class and, (b)264hypothetical values of assessed condition or performance, also organized by asset265class.266


    A corridor is a defined section of transportation pathway (Right-of-Way) that268traverses and crosses natural and manmade obstacles and provides for economic269vitality by allowing for the safe and efficient movement of people and goods. The270asset types are like pieces of equipment along the way that are needed to accomplish271this mission. There may be good reasons to define a corridor as a limited part of a272highway or a sequence of highways linked together. Wyoming has addressed this and273has a good example of a statewide corridor system (WYDOT, 2010). At a national274level, a logical collection of corridors is the Interstate Highway System (IHS) and275there are some recent advances and publications on the management of this system.276


    In 2009, NCHRP publishedReport 632: An Asset-Management Framework for the278Interstate Highway System that proposed a framework for an integrated, performance-279based and system-wide approach, recognizing the critical significance of the interstate280highway system to global, national, regional, and local movements of people and281goods. The report identified the need for comprehensive management strategies, and282focused on 1) how to incorporate assessment of the risks of system failure into the283

    Asset Class














    1 100 30 80 100 50 60 10

    2 200 50 40 150 30 40 20

    3 300 70 20 50 10 20 40

    4 200 40 20 100 60 50 20

    5 400 60 30 100 40 30 10

    6 600 80 70 150 20 20 20

    1800 330 260 650 210 220 120

    (a) Inventory, with total for each Asset Class shown.


    SUM (units)

    Asset Class














    1 6 7 6 6 8 6 6

    2 7 9 7 9 6 9 5

    3 5 7 8 6 7 9 8

    4 9 6 8 8 9 7 7

    5 8 7 7 8 8 8 8

    6 6 5 9 7 8 8 9

    6.8 6.8 7.5 7.3 7.7 7.8 7.2

    (b) Condition (performance) rating or level of service (LOS), with average shown for each Asset Class.



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    asset management framework; 2) guidance for handling all interstate highway system284assets, particularly those other than bridges and pavements; and 3) recommended sets285of measures and approach to performance management for highway assets (NCHRP,2862009). Importantly, the report identifies retaining walls, tunnels and drainage287structures as asset types and it does call for consideration of natural hazards as a288

    source of risk, but the report is silent with respect to slopes and embankments, for289

    example. Natural hazards are limited here too. For example, there is no mention of290swelling or collapsing soils, sink holes or other geohazards that wouldnt likely291impact an existing bridge but could have a large impact on a corridor. The292framework does, however, incorporate a risk assessment approach within the asset293management plan development process, whereby risks to system failure affecting294safety, property damage and system/mission disruption from identified threats,295including natural hazards and deficit conditions of assets, can be managed.296


    A continuation of the NCHRP Report 632 effort resulted in Report 677:298Development of Levels of Service for the Interstate Highway System. This report299

    presents a standard template and it recommends asset classes and elements to300

    communicate critical funding needs to decision-makers, direct resources to problem301areas, and demonstrate accountability to taxpayers (NCHRP, 2010). However,302noticeably absent from this report are indicators and measures of any real significance303relating the condition of geotechnical features to system performance for decision-304makers.305


    The conclusions here are that there is movement in TAM to include recognition of307geotechnical features but there is still a ways to go. The movement towards308performance of corridors and systems promises to help integrate geotechnical features309into TAM, especially as TAM is applied to performance. Looking back at Figure 4b,310the hypothetical entries represent condition for different asset types, often called asset311classes as in the figure, and the tendency is to look at the asset classes individually,312as in stovepipes separated from one another. Because many geotechnical assets are313not yet inventoried or assessed, and the term itself is not defined or established (for314example, it is not mentioned in the recent NCHRP reports), now is the opportunity to315consider what benefit there is of creating or defining geotechnical features as asset316classes that might become additional stovepipes. While assessing a population of317individual asset classes certainly could have value for tracking preservation efforts for318those classes, the approach is limited when attempting to provide any significant319collective indication of system performance.320


    The corridor concept, which is shown conceptually as rows in Figure 5, provides a322rational approach to using TAM for optimizing system performance. The stovepipes323(columns), as in Figure 4, are deemphasized and identified as features of a corridor.324The corridor (row) is the meaningful asset. This allows states to phase in the three325implementation steps, focusing on high priority corridors first. In this approach,326corridors are identified based on meaningful characteristics and they are prioritized327based on their significance to the performance of the system.328


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    Figure 5. Level of Service (LOS) for a hypothetical inventory of corridors listed in332priority order and evaluated for the Feature Type with minimum LOS.333


    One could imagine that corridors on the IHS would be near the top of this list and335

    systems of corridors could be grouped in priority categories. For each priority336category, targets and tolerances would be established for the LOS of each asset class337(feature type). The LOS rating scale for all asset classes can be made similar such that338it would be possible to compare the LOS between different assets. Given that the339performance of a corridor is only as effective as its weakest link, risks to safety,340property damage and system/mission disruption could be assessed/reassessed for341assets with LOSs falling below established tolerances, and for other identified threat342sources, such as geohazards. Similarly, for preservation purposes, decisions can be343based on LOS and corridor priority. So, rather than emphasis being placed on the344LOS of an asset class, asset classes are evaluated horizontally and screened within345corridors, and according to corridor priority for low LOS, as shown hypothetically in346

    Figure 5. The prioritized corridor approach also allows for meaningful information to347come from an incomplete survey of geotechnical assets, thus allowing states to348proceed gradually into the inventory and assessment of geotechnical assets.349


    As can be seen, the Asset Class term in Figure 4 has been replaced with Feature351Type in Figure 5 to introduce terminology that emphasizes the corridor as the asset.352The shading indicates that the horizontal approach includes many types of353geotechnical features, even in this simple hypothetical example. Since the data in354Figure 5 for LOS are static, they are a snapshot in time, and the influence of time355needs to be considered as well. A third recent NCHRP report, Report 713:356Estimating the Life Expectancy of Highway Assets, provides a guidebook approach on357

    how this can be done. In concept, every asset has a deterioration curve that represents358how condition (or performance) changes through time and how it can be impacted by359actions during its life. A classic example is for pavement and is shown in Figure 6,360where PCI is the Pavement Condition Index.361


    Feature Type

















    1 6 5 4 8 6 2 7 4.0

    2 5 8 3 6 3 7 2 2.0

    3 7 8 6 7 5 5 7 6.0

    4 7 3 3 5 7 3 6 3.0

    99 4 6 7 4 2 6 4 2.0

    Inventory evaluated as a list of corridors prioritized for system performance




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    anchored wall, or corrosion of steel reinforcements in MSE are all things that the389profession hasnt established or hasnt developed means for measuring or recording390in consistent ways. There is some important activity in these areas, for example the391ongoing NCHRP Project 24-35 titled Guidelines for Certification and Management of392Flexible Rockfall Protection Systems addresses performance life-cycle expectations393

    for these mitigation measures. The Long-term Bridge Performance program394

    administered by the Federal Highway Administration includes performance395expectations and monitoring of approach embankments. The Alaska DOT&PF has396been instrumental in advancing the discussion on performance measures and LOS for397slopes (Stanley and Pierson, 2011, 2012a).398


    The third challenge mentioned previously the one that has had the least attention 400is the need for predicting how performance changes through time and identification of401the most advantageous times for investment for long-term optimization of the level of402service. Stanley and Pierson (2012b, 2013) and Vessely (2013) have made some403predictions on how these curves might generally look for some geotechnical features,404

    but there is a unique challenge for many geotechnical features in that there405

    performance curves may be more like step functions where natural but rare events406have a dominant impact on performance. This is primarily where risk enters in the407process for geotechnical features. NCHRP Report 713 has excellent coverage of408many types of curves that may be applicable to geotechnical features. NCHRP Report409675: LRFD Metal Loss and Service-Life Strength Reduction Factors for Metal410Reinforced Systems looks at the reliability of corrosion rate models and metal loss for411metal reinforced systems, and provides the ground work for addressing long-term412performance expectations for mechanically stabilized geotechnical features and413mitigation systems, including walls, anchors and bolts.414


    Bear in mind that tools and protocols for assessment of all feature types are needed416but it is not necessary to identify the entire inventory or assess the entire inventory, or417do it for all corridors with equal frequency. The prioritization for optimizing system418performance relieves us of that burden and should be helpful to states looking at419insurmountable challenges to inventory and assess all of their geotechnical and other420ancillary assets.421




    The slope and embankment failure examples described in the Geotechnical Feature426Performance section of this paper demonstrate how significant the impact of427geotechnical features can be on the performance of a transportation system. Starting428in 2013, state transportation agencies will be required to use asset management429approaches to demonstrate that the investment of federal dollars into their systems430leads to improved system performance. Most asset management is currently focused431on asset classes and reporting on their individual performance and level of service. A432corridor approach is described whereby the significant impact of geotechnical433features on system performance could be captured and the adoption of asset434

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    management principles for geotechnical features could be introduced gradually, in a435meaningful and more affordable way.436


    There are challenges to managing geotechnical features as part of a corridor asset438and solutions to these challenges are needed by the transportation industry. These439

    challenges are good opportunities for research and development now. There has440

    already been a trend for agencies to use TAM approaches to manage their441infrastructure, but it has just now been written into law. A melding of existing442geotechnical solutions to (a) inventory and condition rating, (b) risk assessment, and443(c) performance monitoring with the practice of TAM and performance management444is the future. Someday it will be possible, for example, to identify the deterioration of445the embankment on I-75 in Tennessee and take timely steps to improve drainage, and446thereby the LOS, without such a large negative impact to performance. Or, for447example, it may be possible to demonstrate the value, from a performance448perspective, of multi-million dollar solutions to mitigate the hazard from the rock449slopes above I-40 in North Carolina or I-70 in Colorado.450




    American Association of State Highway and Transportation Officials (2011).455Transportation Asset Management Guide: A Focus on Implementation.456Washington, D.C.457

    Anderson, S.A., Alzamora, D.E., and DeMarco, M.J. (2009). Asset Management458Systems for Retaining Walls. Geotechnical Practice Publication No. 5: GEO-459velopment, 214p.460

    Anderson, S.A. and Rivers, B. R. (2013). Capturing the impacts of geotechnical461features on transportation system performance. In review, ASCE Geo-Congress4622013.463

    Galehouse et al. (2006). FHWA-IF-06-049, Pavement Preservation Compendium II464p67-73465

    HDR (2010). Economic Impact of Rockslides in Tennessee and North Carolina.466Prepared for Appalachian Regional Commission. May 2010.467

    Huang, S.L., Darrow, M. (2009). Unstable Slope Management Program Phase I.468University of Alaska Fairbanks, INE/AUTC RR09.16/G5491, FHWA-AK-RD-46909-04, 2009.470

    Lindemann, M. (2011). Retaining Wall Database and Inspection Program.471Presented at 2011 Midwest Geotechnical Conference, October 11-14, 2011, Saint472Louis, Mo.473

    NCHRP (2012). NCHRP Report 713: Estimating the Life Expectancy of Highway474Assets475

    NCHRP (2011). NCHRP Report 675: LRFD Metal Loss and Service-Life Strength476Reduction Factors for Metal Reinforced Systems477

    NCHRP (2009). NCHRP Report 632: An Asset-Management Framework for the478Interstate Highway System479

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    North Carolina DOT (NCDOT 2010). NCDOT I-40 Rockslide Fact Sheet.480 (April 27, 2012)481

    Stanley, D.A. and Pierson L.A. (2012a). Performance measures for rock slopes and482appurtenances. 11th International Symposium on Landslides and Engineered483Slopes, Banff, Alberta, June 2-8, 2012.484

    Stanley, D.A. and Pierson L.A. (2012b). Estimating the Inestimable: Incorporating485

    Geotechnical Assets into Transportation Asset Management. Presentation only,4869th National Conference on Transportation Asset Management, April 16-18, San487Diego, CA.488

    Stanley, D.A. and Pierson L.A. (2013). Geotechnical asset management of slopes:489condition indices and performance measures. In review, ASCE Geo-Congress4902013.491

    Stanley, D.A. and Pierson L.A. (2011). Geotechnical asset management performance492measures for an unstable slope management program. 62nd Highway Geology493Symposium, Lexington, KY, July 2011.494

    Tennessee DOT (TDOT 2012a). Landslide Report, Campbell County I-75 SBL @495

    Mile Marker 143. Internal report. April 10, 2012.496

    Tennessee DOT (TDOT 2012b). Backups Anticipated on I-75 Southbound from497Kentucky into Tennessee. Tennessee DOT press release. April 3, 2012.498Vessely, M. (2013). Risk based methods for management of geotechnical features in499

    transportation infrastructure. In review, ASCE Geo-Congress 2013.500Washington State Department of Transportation (2010). WSDOTs Unstable Slope501

    Management Program, 10-01-0001.502Wyoming Department of Transportation (2010). Long Range Transportation Plan503