Home Sustainable Land Development Today January 2005

Turning Projects from Red to Black

Written by Greg Yoko

Sunday, 02 January 2005

Effective data management can save development project millions. Whether you call the job he performs a CADD Design Analyst, ConstructionSurvey Analyst, Data Manager, orConstruction Data Analyst, the bottomline is that Steve Moore is hired to makesure that the geometric informationneeded to construct large landdevelopment projects is geometricallysound and is made available to the manyparties that will make use of it.Moore has been in the middle of the land development business as a surveyor and geometric specialist for over 25 years. His job is to ensure the mathematical integrity of a project’sdesign and to put it in a form that isusable by the project’s survey team aswell as the many subcontractors,vendors, and consultants that typicallyare involved in large constructionprojects.   “The construction world is moremathematically challenging than it hasever been,” explains Moore. “For anumber of reasons, including budgetconstraints, much of the geometricdetail that traditionally has beenprovided by designers has become thecontractor’s responsibility. Additionally,certain “computationally intense”projects, such as segmental bridges,require geometric number crunchingcapabilities far beyond anything requiredjust a few years ago. In the world ofheavy construction, this can stretch theresources of a contractor to the limit.”   In any single land development project,data can take many forms. Among themost common are spreadsheets,database files, text point files, textalignment files, digital terrain models,Land XML files, and of course, CADfiles.   CAD files are likely the most common,and most important method of sharingdata in the industry.   “We all understand that CAD is adrafting tool,” explains Moore, “but ofmuch greater importance to me are itscapabilities as a geometric calculator anddatabase. The Cartesian coordinatesystem that we learned about in highschool is at the heart of all CADprograms. And, because every aspect ofa land development project has an exactlocation with respect to such a system,CAD is the ideal environment tocalculate, store, and visualize thisinformation.”Moore emphasizes that although mostCAD software can work with geometricdata to a high degree of precision, muchof the work that he sees fails to maintainthis precision and is of little value in theconstruction world.   “When used properly, CAD cancompute distances, areas, volumes, andperform a wide range of geometrictasks, and at the same time, can maintainthe exact spatial location of every aspectof a complex project,” Moore relates.   However when improperly used, CAD is just an expensiveEtch A Sketch® that creates little more than cartoons!”“Cartoons” is Moore’s term for CAD drawings that look finein appearance but that lack the mathematical integrity to beuseful engineering tools. He claims that cartoons are thenemesis of the CAD and land development world.   All of the major projects that Moore has worked on in recentyears have provided the design CAD files to the contractor.But, he claims, “Few of these files have been of any value forlayout as most fall into the ‘cartoon’ category. Further, thesefiles are generally provided ‘for information only’ and are notlegal contract documents” so he generally develops his CADmodels from the ground up working from paper documents.     A Project Example Perhaps the best way to explain Moore’s role is to relate hisexperience on a recent project - a complicated quarter-milesection of Boston’s seemingly never-ending $15 billion “BigDig.” This section of the project is the $377 million C15A1contract in the North End that was undertaken by a jointventure of J.F. White, Slattery, and Perini.   This 1,300-foot-long by 300-foot-wide project extended toover 100 feet below grade and involved the construction oftwo mainline tunnels of four lanes each as well as eightconnecting tunnels. Toward this end, the constructionincluded 4,000 feet of SPTC slurry walls, temporary vehicularand pedestrian decking, temporary bridges and ramps,massive bracing for support of excavation, underpinning ofthe existing elevated Central Artery, groundwater control, anda maze of utility relocations.   As sponsor, J.F. White was responsible for the actualexecution of the work and, early on, recognized the geometriccomplexities of the project. The sheer volume of designdocuments for this project was staggering. Nearly 1,500 Dsizesheets detailed the work to be done and, before theproject was complete, a similar number of revised drawingswere generated and provided to the contractor. Moore wasretained to help untangle the project’s geometry and disseminate it for project-wide use.    The Data Management Process The first step in dealing with all this information, according toMoore, is to get the designer’s intent put into a series ofcomputer models. Because of the “cartoon issue”, thisprocess generally involves reconstructing project geometryworking from hardcopy contract documents.   The first models to be created are generally only in 2-D andinclude the most fundamental features such as projectbaselines. Next, major structural feature such as walls andinverts are added, still working in two dimensions.   On this particular project, the geometry of this 2-D‘footprint’ was complicated by the fact that few of the tunnelwalls were parallel and even the roadway widths wereconstantly varying. Effectively, each tunnel was controlled byfive separate alignments (one to carry the stationing, two todefine the edges of roadway, and two more to define thetunnel walls).     The Missing Link “For a number of reasons, including the‘cartoon issue,’ the land developmentindustry is not ready for this first step tobe simply a transfer of electronic databetween designer and contractor. Andfor liability reasons, I doubt that theprocess will ever be fully electronic,”states Moore. “Translation issuesbetween different CAD systems havealso caused problems historically, butthis seems to be improving.”   According to Moore, this is why officialcontract documents will likely stay inpaper form for the foreseeable future.   During this early stage of the process,the contractor has many opportunities todetect and remedy any geometricproblems in the design. On thisparticular project, Moore found andisolated over 2,000 significant numericalerrors in the contract documents. Theseincluded coordinates, dimensions,elevations, etc that were often wrong byfeet and sometime much more.   “Some of these errors,” admits Moore,“would have been caught by others intime for corrections to be made withoutsignificant costs. However, many wouldnot have been discovered until theaffected work was well under way. Thiswould have involved more than aninconvenience, it can cost anunbelievable amount of time, money,and/or litigation.”     Going to 3-D Remember that the project extends fromwell above grade to more than 100 feetbelow, Moore found it essential toemploy 3-D methods to resolve all of itsintricacies. Although a few particularlytricky areas called for solids modeling,the bulk of the work in the thirddimension was handled by digital terrainmodeling. More than 100 differentDTMs were developed representingroadways, tunnel roofs, slurry walls,existing ground, top of rock, andnumerous other surfaces. These surfacesdrove the entire construction process inthe third dimension including liftdrawing development, excavation, rebardetailing, formwork, concrete placementand earthwork.   Collectively, the 2-D and 3-D modelsbecame the single source of geometricinformation for the manysubcontractors, consultants, and vendorsinvolved in the process. The sharing ofthis information minimized duplicationof effort and helped to ensure that thework of each member of the teamwould be compatible with that of all theothers.   Data flow was almost entirely electronic,with the project network, data collectors,and email attachments being the mostcommon means of communication. Atthe extremes of data sharing technology,the “sneaker-net” (disk) and the projectFTP site are other possible means.Among those working with thisinformation, CAD consultant Johnson& Leasure handled the development ofthe thousands of lift drawings byresolving fine details and addingannotation to the basic geometry,Weidlinger Associates was retained asstructural engineer for the decking andsupport of excavation, and CarolinaSteel provided the thousands of tons ofsteel for the roof girders. All dependedheavily on shared electronic information.    Other Benefits Among the related tasks that all thistechnology supports, is the computationof earthwork quantities. Combining datafrom the field with the project’s digitalterrain models can quickly provideaccurate quantities for paymentpurposes. In addition to a finalbreakdown of earth and rockexcavation, earlier projections based onavailable geotechnical data were madefor project management needs.   Another mundane but necessary task isthe maintenance of accurate utility asbuiltinformation. According to Moore,increasingly, utility owners are requiringthis in electronic form thus providingexact spatial locations without theguesswork of older methods. Themarriage of total stations, datacollectors, and CAD is perfect foraccomplishing this task with minimal effort.    Summary “With the help of the data paths we used(see Figure 1),” states Moore, “we tookthe geometry of 245,000 cubic yards ofconcrete, 18,000 tons of rebar, and13,000 tons of permanent structuralsteel, interwoven with countlesstemporary structures and utilities andmade all the pieces of the puzzle fittogether properly.”Moore summarizes by stating that thereare five primary benefits of diligent datamanagement:• Early resolution of problems andconflicts• A common data base improvesinterdisciplinary compatibility• Visualization of the complex orproblem areas is enhanced• Survey layout efficiency is improved• Duplication of effort is largelyeliminated“Perhaps the greatest benefit is also themost difficult to quantify,” concludesMoore. “It is the increase in productivitythat comes from having the rightinformation available to all the partiesthat need it in a timely manner.” SLDT