Civil and Environmental Engineering

A nonpoint-point source lumped-parameter pollutant loading model appropriate for prediction of average yearly loads on small suburban watersheds has been developed. Three numerical physical process models describing transport processes observed in such watersheds are included; a build up-wash off model, a stream bank erosion model, and a land surface erosion model are implemented in a program written for general use with a Microsoft® Excel Graphical User Interface. The functionality of this model, Swarthmore Subwatershed-Scale Nonpoint Source Pollutant Model (SSSN) is demonstrated through a case study application to the Little Crum Creek Watershed, located in the suburban area near Philadelphia, Pennsylvania. The predicted loads are found to be within a reasonable margin of hourly simulation models and previous applications of more complex models, indicating its utility as a tool for TMDL regulation. This has been coupled with a resource optimization model, StormWISE, and combined results are presented.

The Parade Game illustrates the impact work flow variability has on the performance of construction trades and their successors. The game consists of simulating a construction process in which resources produced by one trade are prerequisite to work performed by the next trade. Production-level detail, describing resources being passed from one trade to the next, illustrates that throughput will be reduced, project completion delayed, and waste increased by variations in flow. The game shows that it is possible to reduce waste and shorten project duration by reducing the variability in work flow between trades. Basic production management concepts are thus applied to construction management. They highlight two shortcomings of using the criticalpath method for field-level planning: The critical-path method makes modeling the dependence of ongoing activities between trades or with operations unwieldy and it does not explicitly represent variability. The Parade Game can be played in a classroom setting either by hand or using a computer. Computer simulation enables students to experiment with numerous alternatives to sharpen their intuition regarding variability, process throughput, buffers, productivity, and crew sizing. Managers interested in schedule compression will benefit from understanding work flow variability's impact on succeeding trade performance.

A database program called WorkPlan has been created to systematically develop weekly work plans. Such work plans are used by crew foremen in scheduling work packages and allocating available labor and equipment resources. WorkPlan adopts the Last Planner methodology, which implements several lean construction techniques. A week prior to conducting work, WorkPlan guides the user step by step through the process of spelling out work packages, identifying constraints, checking constraint satisfaction, releasing work packages, and allocating resources; then at the end of the week, collecting field progress data and reasons for plan failure. This systematic approach helps the user create quality work plans and learn from understanding reasons for failure. The lean planning philosophy underlying WorkPlan and the functionality of the computer program implementation are detailed in this paper. Various ways of displaying work package data are illustrated. WorkPlan's job-shop scheduling view complements the view traditionally adopted by project management, as is reflected in scheduling tools using the critical-path method.

This paper explains concepts underlying a just-in-time production system. Just-in-time production systems as implemented by Toyota are pull systems in which 'kanban' convey the need to replenish the right inventory at the right time and in the right amount. In this paper, symbols from manufacturing are introduced to map resource flows in order to help distinguish traditional-from lean production processes. These symbols are then applied to construction. Ready-mix concrete provides a prototypical example of a just-in-time construction process. Ready-mix concrete is a perishable commodity, batched to specifications upon customer demand. This makes just-in-time delivery necessary. Based on data from industry case studies, alternative forms of vertical supply chain integration were investigated. The most common one is where the batch plant also delivers the mix to the contractor's project site. An alternative is for the contractor to haul the mix from the batch plant to the project site with their own revolving-drum trucks. One alternative is favored over the other depending on the amount of control the contractor wants in terms of on-time site delivery of concrete and the variability in the contractor's demand for concrete project after project. Insights can be gained from these two examples on how the construction industry has adopted a just-in-time production system for at least one part of the concrete supply chain. The examples provided will help the reader think through issues pertaining to the need for having information, materials, and time buffers at strategic locations in construction processes.

The erection of a building's structural steel frame is a major construction phase on many a project. The main resource in this process, the steel erector's crane, defines not only the pace of erection of steel, but also the pace for handling and installing many other structural and non-structural materials. This production system cannot afford any delays. Some claim that structural steel therefore is managed as a just-in-time (JIT) process with materials being delivered to site as needed and installed promptly. This is the case only in appearance as is clear when one considers the JIT principles that were developed as part of Toyota's lean production philosophy. To illustrate the point, this paper draws on examples of typical structural steel supply chains from the industrial-and building construction sector. The use of symbols from manufacturing is investigated to map key production steps as well as buffers in-between them in order to elucidate where resources do and do not flow. Industry practices in these two construction sectors vary significantly. Neither one is lean. This paper reports on a preliminary investigation into the location of buffers in the structural steel supply and construction process. The reasons for having buffers at various locations are explored. A more in-depth investigation is recommended to gain a deeper understanding of the buffer sizing criteria and steel component sequencing rules that govern current practices. Insight into these will then help determine which buffers can be trimmed in order to reduce work in progress and cycle time. This will support the effort of achieving "more JIT" by making processes within individual companies as well as across the entire steel supply chain leaner.

Waste is omnipresent in construction supply chains. It often occurs at the interface between processes, disciplines, or organizations. To illustrate several causes of waste, this paper focuses on a case study that documents the most common configuration of the supply chain for pipe supports used in the power plant industry. Using value-stream mapping across organizational boundaries, this paper illustrates how work flows throughout the design, procurement, and fabrication phases of pipe supports. Industry data obtained through tens of interviews helps to evaluate value-added and non-value-added times, batch sizes, and lead times for this particular supply chain configuration. The paper provides considerations for eliminating waste in order to reduce the total delivery lead time of pipe supports and thereby improve supply chain performance. It concludes by summarizing the case study findings and identifying additional research opportunities to achieve further improvement.

SightPlan is an expert system that lays out temporary facilities on construction sites. It demonstrates how one can closely model the steps taken by a person performing layout design, and how interactive graphics combined with an expert system can augment human decision-making.

Work structuring means developing a project's process design while trying to align engineering design, supply chain, resource allocation, and assembly efforts. The goal of work structuring is to make work flow more reliable and quick while delivering value to the customer. Current work structuring practices are driven by contracts, the history of trades, and the traditions of craft. As a result, they rarely consider alternatives for making the construction process more efficient. To illustrate current practice and the opportunities provided by work structuring, this case study discusses the installation of metal door frames at a prison project. Because the project is a correctional facility, the door frame installation process involves a special grouting procedure which makes the installation process less routine. Those involved recognized the difficulty of the situation but better solutions were impeded by normal practice. This case study thus provided the opportunity to illustrate how one may come up with alternative ways to perform the work without being constrained by contractual agreements and trade boundaries. By doing so, we illustrate what work structuring means. Local and global fixes for the system comprising walls and doors are explored. In addition, we discuss the importance of dimensional tolerances in construction and how these affect the handoff of work chunks from one production unit to the next.

This paper presents "work structuring," a term used to describe the effort of integrating product and process design throughout the project development process. To illustrate current work structuring practice, we describe a case study involving the installation of door frames into walls in a prison. We analyze why various problems existed. To improve the work structuring effort, we apply the "five whys" to develop local and global fixes for the system of precast walls and door frames. The five whys is a technique to elicit alternative ways of structuring work without being constrained by contractual agreements, traditions, or trade boundaries. We discuss the importance of dimensional tolerances in construction and how these affect the handoff of work from one group of workers to the next. We argue that these constraints and tolerance management practices are so embedded that project participants can miss opportunities to better integrate product and process design. We propose shifting the focus of work structuring from maximizing local trade efficiency to improving overall performance in the delivery system of a capital project.

Industrial buyers of capital facilities have experienced and continue to experience pressure to reduce facility design and construction lead time. This pressure arises both internally (due to successes in manufacturing lead time reductions) and externally (due to competitive forces including narrowing product delivery windows). This paper presents a case study detailing one owner's efforts to reduce the length and variability of delivery time for long-lead construction materials in order to improve overall project lead time. The owner adopted a long-term multiproject perspective, procuring material in advance of specific projects and holding it at a position in the supply chain selected to allow flexibility for customization. Reduction in lead time of 75% from order to delivery of the material resulted for individual projects within the owner's capital plan. As a result, the material was available at the construction site well in advance of its need for erection. To study if holding material at alternative locations in the supply chain could provide a better match between delivery quantities and the demand for erection, the supply chain was simulated. In this case study, demand information was imprecise, allowing only the quantity of material delivered to be considered rather than matching specific items to specific locations. Nonetheless, the results demonstrate the utility of simulation in the capital projects supply chain and the value of improving demand forecasts.