Toward Infrastructure Improvement: An Agenda for Research (1994)

Infrastructure systems typically require large-scale construction, which involves high-cost, capital-intensive financing, and long time to completion. The work often is carried out in densely populated, highly developed urban areas or environmentally sensitive locations. Research is needed to enhance construction productivity, minimize hazards and environmental impact, and reduce costs.

Effective construction technology and management can reduce the time required to build or repair infrastructure, and thus reduce costs, minimize site disruptions, and improve quality and safety. Off-site fabrication, ''just-in-time'' delivery of materials and labor to the site, reusable form-work, and climbing cranes are examples of performance-enhancing construction techniques introduced in recent years. While many construction innovations are project-specific, research on the broader issues of enhancing construction productivity, for example with computer-aided tools and equipment or new construction materials, could yield substantial returns to the industry and to infrastructure performance.

Improved construction efficiency often depends on better utilization of the substantial capital invested in equipment and materials. More effec-

tive information exchange among on-site operations, fabricators and suppliers, and the central design offices, for example through constructibility assessments and short lead-time scheduling, improves efficiency. Research to improve information and its management in construction could produce further significant improvements.¹

Typical questions for research might include the following examples:

• What tools and procedures could enhance communication and information transfer of as-built construction data between the design office and construction site?

• Can more efficient and accurate construction site documentation improve equipment utilization and control and product quality?

• How can three-dimensional spatial data-management systems and simulations be most effectively used for construction site management?

• Can electronic data interchange reduce costs and improve efficiencies in the business of construction, i.e., transactions among owners, designers, constructors, and vendors?

• What must be done to develop or adapt site-positioning technologies, such as satellite global positioning systems (GPS) and laser- and radio frequency-based systems, for construction site use?

One of the most important recent advances in infrastructure construction, particularly in structural systems, has been in the use of pre-cast or pre-fabricated units mass-produced at a specialized central facility and delivered "as-needed" to the construction site. Research could further enhance the efficiencies and quality improvements of off-site component fabrication, for example by improving construction tolerances and product durability. Research directed at enabling transport of fabricated construction elements from shop to site could also yield substantial benefits.

Effective resource utilization (e.g., skilled labor, specialized materials, advanced equipment, time, and funds) is crucial to construction efficiency. Available resource-scheduling techniques, typically based on critical-path methods and other linear mathematical methods for project activity scheduling, are often inadequate for the multiple-objective, multiple-constraint complexity of large projects. Research could yield improved methods for characterization of project constraints, optimization algorithms, and cost-effective systems for making advanced management methods accessible to project personnel.

Typical questions for research might include the following examples:

• Can the design or installation of a system or component be optimized with respect to financial and other resources?

• Can the physical and resource constraints be balanced to improve the overall cost-effectiveness of the project and completed system?

• How might design of specific infrastructure components or systems better reflect the resource constraints operating in a particular geographical or physical environment?

Infrastructure construction, maintenance, and rehabilitation inevitably produce excavated earth materials (termed "spoil"), nonrecyclable wastes, and other debris. Replacement of old infrastructure produces volumes of demolition debris. Disposal or other disposition of such wastes is often complicated by concerns that the materials may be contaminated by petroleum products, heavy metals, asbestos, or other hazardous substances. Excavations to repair pipes and other buried infrastructure frequently uncover unexpected wastes from long-discontinued industrial activities. The scale of these problems generally falls short of the cases dealt with in the Environmental Protection Agency's Superfund cleanup program, but the experiences are similar.

Federal agencies such as the Corps of Engineers and Environmental Protection Agency have sought to address elements of the problem, but further research is needed to make systematic improvements in construction waste reduction and management. Methods that combine efficient disposal, constructive reuse, and effective recycling would relieve the pressure on dwindling available disposal sites adjacent to urban centers. An extension of this philosophy might encourage the development of more environmentally sensitive facilities.

Past studies, sponsored primarily by the Corps of Engineers, have sought to improve methods for disposal of dredge spoil, and a number of full-scale disposal sites have been established. Containment islands, such as Hart-Miller in Baltimore Harbor, and salt-marsh construction in Chesapeake Bay could point toward more environmentally sensitive means to deal with recurring dredge-spoil problems. However, careful field evaluation of such schemes is needed to characterize their impact and support development of planning and design guidelines for use elsewhere.

Typical questions for research might include the following examples:

• What are fill consolidation rates and related effluent characteristics for containment area design?

• What are the technical and economic comparisons of various forms of spoil containment and salt-marsh construction?

• Could drying procedures enable the use of dredge spoil as soil cover for sanitary landfills, lightweight construction fill, or agricultural soil nutrient?

The accumulated impact of decades of industrial activity has increased the uncertainty in infrastructure activities, regarding the environmental consequences of excavation and construction in areas where toxic or hazardous materials might be encountered. Characterizing and treating these contaminated sites becomes an unanticipated and very costly addition to the work of infrastructure renewal and development.

Research is needed to support better methods for determining the extent and severity of contaminants, for characterizing the threat they pose in soil and groundwater, and for assessing the consequences of alternative abatement strategies. Research is also needed to devise better strategies for decontamination or effectively immobilizing contaminants in situ. Better bases are needed for determining appropriate levels of site investigation and remediation, and for monitoring long-term results of remediation efforts.

Typical questions for research might include the following examples:

• Can risk assessment models be developed to reduce variability and public controversy regarding estimates of contamination and response to such assessments?

• Can remote sensing and nonintrusive on-site reconnaissance and measurement methods be developed to improve characterization of contaminated sites?

• Can remote data-acquisition systems be utilized to monitor long-term performance of treatment and remediation?

Even when sites are not thought to be particularly contaminated, the management of urban soils excavated during infrastructure construction and improvement often requires comprehensive chemical assessment to satisfy stringent governmental solid- and hazardous-waste laws and regulations. Typically, chemical constituents of concern include volatile organ-

ic compounds, semi-volatile organic compounds (including polyaromatic hydrocarbons), metals, and petroleum hydrocarbons. These constituents have entered the soil through such routes as combustion of leaded gasoline (now completely phased out), waste and deterioration from lead-based paints (not generally available now), applications of pesticides and herbicides, leakage and spillage, and residues from industrial activities. The presence of such contamination limits the options for reuse or disposal of these construction wastes.

Soil sampling and testing programs must balance the needs for environmental protection with the realities of demanding construction schedules. Research is needed to facilitate rapid screening for hazard and reduce laboratory costs and response times. Better methods are needed for biological or chemical treatment of contaminated soils to permit their reuse.

Typical questions for research might include the following examples:

• Can new test procedures be found for rapid, cost-effective sampling and testing or in situ evaluation of soil chemical composition?

• Can soil admixtures, injection grouting, or other means be developed for immobilizing contaminant leakage and effectively sealing areas surrounding buried tanks and pipelines?

• Can cost-effective biological or other methods be found to extract and concentrate soil contaminants in order to facilitate their removal?

A major share of infrastructure construction and rehabilitation occurs below ground or deals with underground structures. Many infrastructure facilities now located above ground would be placed below the surface if costs and safety hazards were not so high. Research to facilitate underground construction could yield substantial environmental and economic benefits, particularly in densely developed urban areas.

Robotic control systems have been, as yet, infrequently utilized in U.S. underground construction. There is tremendous potential for their contribution to safety, efficiency, and economy. Research is needed to develop more efficient mechanized tunneling systems, better methods for investigation and characterization of subsurface conditions to match machine features to soil and rock conditions, and improved modeling of excavation, tunnel support, and ground response to determine support requirements and optimal construction procedures.

Typical questions for research might include:

• What kinds of automated control systems are best suited to tunnel boring machines (TBMs), for both hard- and soft-ground tunnels?

• How can robotics be adapted most effectively to TBMs, particularly for such tasks as mechanized shotcreting, continuous casting of concrete tunnel lining, and automated erection of segmented tunnel linings?

Developments in trenchless technology—for installation, renovation, and replacement of underground utility systems without open-cut construction--has been rapid and extensive, and international competition for markets is keen. The benefits of this technology in urban applications include reduced disruption of street traffic and adjacent businesses, longer service life of street pavement, improved safety for construction personnel, and ground movement and vibration hazards to nearby structures. In wetlands and ecological reserve areas, trenchless construction can avoid disrupting natural systems. Problems of construction spoil are reduced or eliminated.

These substantial benefits have motivated proliferation of methods such as pipe jacking, microtunneling, auger boring, pipe ramming, directional drilling, directional fluid jet cutting, percussive tools, rod pushers, and horizontal slurry drilling. In situ renovation procedures for infrastructures include pipe insertions, sprayable seals, structural repair, slip lining, and a variety of polymer lining installations. These various methods have relied, in turn, on advances in drilling technologies and adaptation of microelectronics for guidance and control systems. The field's broad range gives rise to similarly broad opportunities for beneficial research.

Typical questions for research might include:

• Can reliable analytical relationships be developed to link-jacking mechanisms, soil and groundwater conditions, and construction and service loads on pipelines and conduits that are suitable for use by designers selecting pipe materials, dimensions, and installation procedures?

• Can trenchless technologies be used for more cost-effective and safe treatment of contaminated sites?

• Can reliable analytical methods be developed for estimating magnitudes and patterns of ground deformation likely to occur for different trenchless installation methods and different sizes of installed conduit, particularly with regard to volumetric expansion associated with insertion of new or larger diameter piping and conduits?

• How may the economic benefits of reduced business and traffic disruption, pavement damage, and public hazard be most effectively evaluated in order to compare trenchless with alternative construction methods for specific projects?

Risks of fire, explosion, and other hazards to worker safety in underground construction are high in comparison to other types of construction. Research is needed to develop better methods for assessing, managing, and mitigating these risks.

Typical questions for research might include:

• Can better methods be found for exploration and monitoring of underground hazards such as explosive or flammable materials (e.g., methane deposits), for hazard mitigation (e.g., gas-flow deflection or prevention), and for hazard management within the workspace (e.g., nonflammable materials, fire-suppression procedures, explosion-proof equipment)?

• Can new methods be developed to prevent migration of hazardous liquids into work areas, such as by ground freezing, use of compressed air, well-pumping barriers, cutoff procedures, impervious linings, or membranes?

Excavation in soil and rock always disrupts the in situ conditions of equilibrium so that adjustments in the form of ground deformations will take place, even though structural support is installed to promote overall excavation stability. In urban and suburban environments, excavations are often undertaken close to buildings and utilities which will be influenced by the ground deformations that accompany the excavation and support process. Moreover, construction often involves the generation of potentially damaging vibrations from blasting, pile driving, or operation of heavy equipment. Accordingly, the permanent and transient ground deformations caused by construction are of critical importance with respect to cost and feasibility of infrastructure projects.

In some cases, vibrations generated by rail traffic can be transmitted through the ground into overlying structures, causing noise that can seriously impair the use of facilities which depend on a relatively quiet acoustic environment. This noise, which is referred to as re-radiated noise, tends to be heard in basements and properties with concrete floors. The recognition of the phenomenon can be very important when planning and designing for underground transit systems in congested urban settings.

Typical questions for research might include the following:

• What are the most appropriate site-exploration methods and analytical models for characterizing soft soil sites, particularly those in highly deformable clays and silts, with emphasis on predicting permanent ground movements in response to deep excavation and construction activities?

• What are the appropriate soil-structure interaction models to account for high-rise building and underground facility response to excavation-induced ground deformation, and can such models be validated by thorough field instrumentation at actual construction sites?

• How does frequency affect the response of various structures to vibrations from blasting and heavy construction, and how should such effects be measured and reflected in construction specifications?

• What are the most reliable and effective means for evaluating the potential for re-radiated noise, and how can new construction be implemented to dampen such effects or to shield existing structures from vibration?

Safety for the neighbors as well as workers on infrastructure construction and rehabilitation activities is a crucial concern, for work in congested areas, often in proximity to vulnerable or potentially hazardous structures, involving heavy or specialized equipment and long hours of work. Research can enhance construction safety by supporting development of ways to reduce human exposure to hazards and levels of injury and damage if accidents occur. Robotics, automated guidance and control of heavy equipment, and ergonomic design are researchable topics from which benefits could be substantial.

Typical questions for research might include the following examples:

• How can hand-held and operator-controlled construction equipment be designed for more productive use and increased safety with respect to accidents, unsafe environments (e.g., dust or noxious fumes), and the hazards of continued repetitive motion?

• What kind of automatic sensing and control systems can be adapted for heavy construction equipment to reduce the risk of exposing and penetrating hazardous structures, such as high-pressure gas and liquid-fuel pipelines, and contaminated soils?

• Can cost-effective robotic systems be developed for inspection and construction at sites having potentially toxic chemicals, flammable or toxic gases, and high risk settings, such as elevated structures and underwater environments?

Infrastructure rehabilitation and retrofit can cause major disruptions in the functions of a community. Methods to mitigate these problems, such as repair of pavements and replacement of the linings in water pipes, are being developed, but major improvements in rehabilitation methods can still be made.

For instance, new technologies could improve significantly the safety in the work zone as well as minimizing both disruption and community costs.

The key characteristics of rehabilitation and retrofit activities are that major portions of existing systems remain in place, and efforts to repair or replace significant components must be performed in situ and must be compatible with elements retained. For instance, the improvement of a water system may involve replacement of pumps or addition of storage tanks at higher elevations, thereby creating greater pressure in supply mains and distribution pipes, which may then fail. Replacement or repair of the pipe sections that failed may likewise induce failure at other places in the system, creating a cycle of repair, breakdown, and repair.

Several of the previously mentioned research niche areas obviously apply to rehabilitation and retrofit, particularly life-cycle management, condition assessment and monitoring, and new materials. However, certain other research areas are specifically connected to infrastructure in situ repair, and these can offer significant cost savings in both immediate application as well as through their long-term impact on the planning and practice of rehabilitation and retrofit.

To repair existing infrastructure systems in situ, segments of the systems must be isolated. This isolation must be conducted through physical segregation as well as in functions of service performance. A criterion for this isolation is that a segment of the system must be able to be shut off from the system as a whole without causing total system shutdown. Elements that influence the degree of potential isolation for any segment include the size of the segment and redundancy of other elements for service functions, as well as the speed with which work can be performed on the isolated segment.

Some important research questions may include models for effective short- and long-term system isolation, and the selection of appropriate technologies (such as quickly applied remedial materials).

Typical questions for research might include:

• How can a series of rehabilitation activities on an infrastructure system be modeled to decrease the probability of total system shutdown or failure and to minimize system disruption?

• How can temporary redundant systems be used to improve system performance during rehabilitation or retrofit?

• What are some types of mechanisms or components that can temporarily isolate a segment of a system and be easily withdrawn after repair or retrofit?

The in situ repair and retrofit of infrastructure systems usually involves components to which access is difficult. The specific element which has degraded may underlie layers of other systems (such as a failed structural member within a building) or in other regions which are difficult to reach (such as the geomembrane in a landfill). The costs of dismantling the system to get at the degraded element may be extremely high, but failing to repair the segment may induce additional stresses in the system that can cause more serious failure.

Research could build better understanding of the effects of gaining access to degraded segments. Topics in this area could complement activities mentioned earlier in underground construction.

Typical questions for research might include:

• What are effects of gaining access to degraded segments on adjoining infrastructure systems or on neighboring segments?

• What are the performance criteria necessary for localized and non-intrusive repair and rehabilitation methods, such as the expected life of repair and ability to withstand expected loads?

• How may systems explicitly incorporate access for maintenance and repair into their design and construction?

Fluctuating demographics and societal demands have awakened many municipalities to the need to decommission portions of existing infrastructure, or even to close down complete systems. In addition, when severe natural disasters occur, choices must be made on which destroyed or damaged segments will be repaired by order of their priority. Unfortunately, in many disasters, the costs of repairing all damaged elements may be beyond reasonable ranges to replace. For example, the Loma Prieta earthquake destroyed several segments of the highway system in the San Francisco area, including the much publicized and tragic collapse of an elevated interstate highway structure in Oakland. When deciding which segments would be rebuilt with scarce state and federal funds, government agencies decided that the overpass should be completely demolished and not replaced. Other similar choices have been made for the decommissioning of school buildings as the school-age population in a community diminishes, and for water reservoirs as small communities join regional water authorities.

Research in this area could provide immediately applicable insights to agencies contemplating system contraction and decommissioning. It could also provide significant long-term benefits from the improved effec-

tive use of infrastructure systems, encouraging the decommissioning (either temporary or permanent) of unused infrastructure, while preserving flexibility to meet future demands.

As the population in a specific region changes, the demands on infrastructure also change significantly. A region with many small children may require a large school system and plentiful public transportation, while a region with an older population may need more handicapped-accessible public buildings and transportation modes. Some of these changes may be best met with facilities that are not designed to be permanent additions to the capital investment of a region, but are rather marshalled to meet the demands as they occur.

The concept of temporary facilities is to minimize the cost of the facilities' construction and maintenance for abbreviated design lives, such as for only 10 or 20 years. Research can be conducted on the attributes of less costly materials for these temporary structures, as well as the design of systems that improve the efficiency of service operations while minimizing maintenance and repair costs.

Typical questions for research might include:

• What are the attributes of temporary facilities that have a curtailed design life, such as the exclusion of expansion capabilities and the use of specific materials?

• What are the construction methods and procedures that can influence the projected design life of temporary facilities?

• How can the design of temporary facilities best accommodate overflow activities from permanent facilities?

Older urban and suburban areas sometimes find that losses of residents and certain economic activities leave large areas served by infrastructures for which demand no longer exists at the same levels. Agencies responsible for these systems don't have the resources to maintain excess capacity, and often lack the tools to reduce the scale of the subsystem.

Research can explore the issues of infrastructure decommissioning. System elements may be removed from service entirely or their service levels may be reduced, an equivalent of the management strategy of ''downsizing.'' Some elements may be taken out of regular service but maintained for use if unusual needs arise (e.g., during droughts or following earthquakes). Such issues may also be addressed as questions for research on systems life-cycle management (Chapter 3).

Typical questions for research might include the following examples:

• What materials are most conducive to decommissioning, either through lack of maintenance (should the facility be mothballed) or through immediate reuse or recycling?

• What construction equipment, connections, methods, and materials could facilitate the decommissioning of infrastructure systems, for example by increasing ease of disassembly?

• How may the scale of certain infrastructure systems be decreased without reducing the efficiency of adjoining or connected systems?

• What are the acceptable ranges of "overcapacity" for infrastructure systems, and how might the costs for this extra capacity be minimized? Where is this maintenance minimization, rather than decommissioning, appropriate?

The U.S. construction industry is composed of a relatively few large firms and many smaller businesses that operate in limited geographic areas and technical specialties. While larger firms often utilize sophisticated management procedures comparable with other leading industries, the majority of firms have limited access to such procedures. Further, the industry depends largely on management skills that are not widely applicable in other industries. Thus, research is warranted to improve management practices in infrastructure construction.

Increased efficiency and lower cost in these industries, which are largely tied to public service, imply better service and economy for the public. Management improvements for infrastructure construction can serve as an example and can improve practices throughout the construction industry.

Disputes leading to litigation between parties involved in infrastructure construction, as in all civil construction, have led to an adversarial climate that can interfere with legitimate business activities and ultimately increase costs for infrastructure owners and users. The nature of the contractual relationship in infrastructure projects, the assignment of risk and responsibility, and methods of dispute arbitration deserve some priority in research.

Typical questions for research might include:

• Do joint venture agreements between prime contractors and material suppliers affect total job costs?

• Can more cost-effective and equitable risk-apportionment methods be developed for construction and for the completed facility (e.g., con-

struction bonding, workmens' compensation, wrap-up insurance, and designers' warranty)?

• How effective are alternative procedures for contract dispute avoidance and resolution, such as mediation, arbitration, dispute review boards, and partnering concepts?

Apart from avoidance and adjudication of disputes and risks, there are many opportunities for improved management practices assisted by computer and data-handling techniques.² Research is needed to support methods for providing detailed technical information on-site, such as shop drawings, and for monitoring of quantitative measures of construction project productivity on site and at major off-site fabrication locations. Such systems would in turn enable research into decision rules for scheduling and procurement contingency planning and response strategies.