Conforming to Design
SVT Contractors' company policy states that each project superintendent is responsible for recording locations of all newly installed features including any changes or deviations from the plans during construction. Each day, he (or she) does his best to make notes on a set of paper plans kept in the truck. As with every construction project, problems arise-equipment fails, workers call in sick and other unforeseen conditions are encountered. The super tries his best to make appropriate notes on the plans to indicate any deviations from the proposed design. Some days he is successful, some days he is not.
Although the school project dragged on for three months longer than planned, it was finally completed. The project manager called the superintendent for his documentation. "I'll look for that plan set I've been making notes on," the superintendent replied. "Last time I cleaned out my pickup, I thought I saw them in back of the seat." Shivers ran down the project manager's spine.
Two days later the superintendent walked into the office and plunked down a roll of war-torn plans, spotted with hydraulic oil, on the project manager's desk. "Here ya go!" he said, and walked out of the office. A quick inspection revealed a barely legible drawing with lines and numbers penned in with red ink. It didn't take long for the PM to realize that there was a lot of information missing, and several days' work to be done to create the as-built information required by contract.
There's got to be a better way, he thought-and there is.
Two months later, SVT Contractors purchased a GPS system to perform layout and grade checking tasks. With a little training, the superintendent learned to use the system. As part of his daily routine, he uses the GPS system to locate everything his crews install. At the end of the week, he downloads his data files to the PM's office computer. At the end of a job, a comprehensive, accurate as-built drawing can be created in less than an hour. As-builts are no longer a hit-or-miss proposition, but a smoothly integrated part of the daily work flow.
As-builts: Important DocumentsThere is probably no other document in the design and construction process that has as wide a variety of purposes as the as-built-or as long of a life expectancy. While there are many different forms of as-builts, a simple definition is "a permanent record of the location of constructed improvements."
As-built documents verify that a completed project conforms to the planned design and applicable regulations. A subdivision plat, for example, is an as-built confirming that lot sizes and setbacks meet zoning standards, and that roads and utilities are located in the right place. Most home mortgage companies conduct as-built surveys as part of every residential closing before funds are released. They protect the new owner and lending institution from future lawsuits.
As-builts can control cash flow in construction projects. Some construction permits, such as those for new sanitary sewers, require a monetary deposit to ensure that new installations will be constructed according to design standards and be compatible with existing facilities. The as-built drawings, in combination with final inspections, serve as a guarantee to the utility owner that the standards have been met. Deposits are not released until the drawings are submitted.
The usefulness of as-builts extends far beyond the day the project is completed. While designers take the perspective that their creations meet all the needs of the intended user, that they will function perfectly and that they will never be changed, this is often not the case.
Sometimes, a few years down the road the owner decides to expand his office building and parking lot. The designer will need to know if the flowline of that storm sewer manhole is low enough to accept a new pipe from the parking expansion. His team will also need to be armed with information showing whether the planned finish floor elevation of the new wing will allow gravity flow to the sanitary sewer system. These questions can be quickly answered by referencing a comprehensive set of as-built drawings.
This new trend in lifecycle design provides valuable information to an owner well beyond the initial design and construction phase. When construction is completed, the owner receives a complete set of documents that provides essential information for maintenance and reference purposes.
Digital Data-A Better WayThe computer age and CAD software have made digital data the preferred method of creating design information. Even until recently, putting that design on the ground was still accomplished with paper drawings. Some firms still use this method. Others have turned to technology such as GPS to enable digital workflow from design to construction-and on through to the recording and creation of as-builts. Most progressive contractors now equip their field engineers and superintendents with GPS rovers for layout and grade staking chores. Having these instruments available on a daily basis enables them to record as-built information-horizontal and vertical positions-quickly and easily.
After digital position data is recorded in the field, it's a simple matter to download it to an office PC. If the contractor has obtained the original design file in digital format, the as-built information can be imported on a separate layer. The previously laborious process of recording and documenting as-built information has become seamless and nearly effortless. Surveyors across the country are benefitting from this effective lifecycle design and are producing as-builts easier and faster these days.
GPS Expedites Construction As-builtsSteve Walton, construction supervisor with Shaw Brothers Construction, Gorham, Maine, has worked in his position for 18 years and has used many different methods for as-built documents. This past year, Shaw Brothers was involved in the major I-295 Connector road construction project in Portland, Maine. To expedite and automate the project, Walton used Topcon's (Livermore, Calif.) HiPer+ rover and FC-100 field computer to perform all stakeout for this complex project.
Walton built a comprehensive digital record of installed improvements in the course of his daily routine using Topcon's Pocket 3D jobsite management software. Walton describes how Topcon's system helps him organize data as the job progresses: "It's like a filing cabinet. You can as-built the gas line, as-built the water line-anything you want on separate layers. I add each day's completed work as I go."
Having this information available at a moment's notice can prevent accidental damage to newly installed underground lines. Walton recalled a modification that had to be made in close proximity to underground lighting lines. "We know exactly where the electrical conduits are located," he says. "I just walk down through the area with my Topcon HiPer + rover and paint it out on the ground."
Mathiowetz Construction is one of the leading highway contractors in the state of Minnesota. The contractor, in its fourth generation, is building a new four-lane section of Highway 14 from Smith's Mill to Waseca.
The Minnesota Department of Transportation provided Mathiowetz with 3D surface fills for 20 detention basins located along the 13-mile length of the new road. The files were loaded into Topcon's 3D-GPS+ machine control system that automatically controls the cutting edge of his Caterpillar (Peoria, Ill.) dozer.
"MNDOT just wants proof that we built it in reasonable conformity to the plan grades," explains Brian Mathiowetz, president. "They take the file and compare it to their design and give us the approval or "corrections needed.' By using GPS, we are confident we will never have any "corrections needed.'" Dale Schweiss, GPS manager for Mathiowetz, explains how the contractor provided as-built information on the basins: "A person with a GPS rover walks the area and takes point shots at various locations within the pond. This file is then given to me in the office. Using our software, I export these shots to a text point file with northings, eastings and elevations. This file is then forwarded to MNDOT for verification of the as-built."
GPS Reduces the Surveyor's RisksArnold Carson owns and operates a land surveying firm located in Wilmington, N.C. In this low-lying coastal area, first floor elevations of buildings must be constructed above FEMA flood level. The height above flood level varies with the county and municipality where the structure is located. A large amount of Carson's work involves preparing elevation certificates to verify that the floor elevations of structures meet the requirements of the regulatory agencies.
Residential development is spreading out into rural areas where monumentation and reliable elevation bench marks are few and far between. Transferring an elevation cross-country from a known, reliable bench mark is impractical and uneconomical. Carson needed a solution that would enable him to determine accurate vertical positions in remote areas.
"Land is becoming more expensive with every breath we take-every breath," he says with intensity. "The liability associated with surveying that land is compounded just like the value of the land is. Even with the flux in demand, you're talking about charging three or four hundred dollars for work that can cost you millions of dollars. We carry a lot of insurance here. We haven't had to use it. I hope we never have to.
"I do a lot of elevation certificates, which is a high liability issue in flood zones. It's a scary thing for a surveyor to do. You can drive up and down the road and look around town here. You'll see a railroad spike driven in a power pole and a stake with an elevation written on it. It's a huge liability risk to take that elevation for gospel and sign a flood elevation certificate based on that."
Carson sought the advice of his local survey instrument dealer, Southern Photo Print and Supply. Working with survey product specialist Dean Howell, Carson explored the possibility of using a GPS survey system to expedite his rural survey work. Howell recommended installing a Topcon Odyssey-RS GPS+ reference station at Carson's office in downtown Wilmington. This GPS receiver incorporates Topcon's advanced dual-constellation GPS+GLONASS tracking for improved performance and accuracy.
For field work, Carson prefers Topcon's HiPer Lite+ survey rover. To extend the range to outlying areas, cellular communications are used between the base and rover. In researching cellular service providers, Carson found that Sprint provided the best coverage and service in his area. In the office, Carson uses TopNET software to configure and manage his reference station.
Carson builds his confidence level in the accuracy of Topcon's TopNET RTK system while performing routine tasks in his day-to-day operations. "I had to do an elevation certificate about ten miles from here out in the middle of the country in an unnumbered zone," Carson explains. "I proceeded to set up and acquired a fixed solution-about ten miles out from the base at my office. I took a folding six-foot ruler, taped it to it, set the level up, shot it, shot the house, found the reference line on the house and measured it up.
"I shot one elevation with the HiPer Lite+ before, one halfway through the time I was doing the elevation certificate and one at the end. I had about three or four hundredths difference during that 30-minute cycle. It's hard to argue that degree of accuracy with a fixed solution, especially when you're out in a rural area where there are no bench marks." Now that Carson has taken steps to insure reliable elevation information, his concerns about liability issues with as-built information for elevation certificates are reduced.