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More than ever, heavy-construction contractors are burning the midnight oil. By Dan Brown |
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For one thing, night work helps contractors finish projects sooner. On highway projects, nighttime construction cuts down on traffic disruption and allows construction trucks to move about more freely on the roadways. The same principle applies to airport construction, where working at night is often the only way to avoid shutting down an active runway. And with today's portable light towers, most heavy-construction activities–from surveying to drainage construction to excavation and paving–can be sufficiently illuminated to permit nighttime work. How do you decide how many light towers you need? The answer is important, because OSHA has minimum-illumination standards. For general construction area lighting, OSHA specifies a minimum of 5 foot-candles. And OSHA requires at least 3 foot-candles for "general construction areas, concrete placement, excavation and waste areas, access ways, active storage areas, loading platforms, refueling, and field maintenance areas" (see www.osha.gov). There are rule-of-thumb calculations for determining the number of floodlights needed to put out a given level of illumination. Terex Light Construction publishes one such lighting formula, but it doesn't take into account shadows, glare, light absorption by pavement, and other such factors. Most contractors, in fact, rely on experience and trial-and-error methods to figure the number of light towers they need. "Like a Bic lighter," remarks Rocco Danna, project manager for the E.A. Cox Company, which is doing night construction on a $24-million-plus runway and drainage project at Chicago's O'Hare International Airport. "The runway out here is pitch black. At night it absorbs light like you wouldn't believe. You don't get any light reflected off the pavement. You might think four light towers would do it for a given job. But then you get out there with four towers, and it's like holding a Bic lighter in your hand." At O'Hare, the project owner is the City of Chicago's Department of Aviation, and the department has specified that lighting equipment "shall be trailer-mounted units, each with four 1,000-watt metal halide or high-pressure sodium lights on a winch-lift telescopic mast." Furthermore, the spec requires the contractor to maintain an average of 5 horizontal foot-candles throughout the working area. As general contractor for the O'Hare project, E.A. Cox is responsible for providing the lighting for all of its subcontractors. The job involves milling and resurfacing a 13,000-ft. runway, installing new underdrains, doing shoulder excavation work, and putting in all new runway wiring and fixtures. To light up the project for night work, Cox has rented a total of some 28 light towers for use by project subcontractors. How does Danna figure the number of light towers needed? "There's no real scientific method to do it," he says. "Our underground contractor, who is doing underdrains, has two light plants. He might do 400 feet of sewer a night, and he just tows the light plants with him as he moves along." The underdrain contractor is digging a trench 3.5—4 ft. deep and placing perforated 8-in.-diameter PVC pipe in the trench for drainage. The pipe is wrapped with a geotextile filter fabric, and the trench gets backfilled with stone. "We've got surveyors, and they usually need one light plant to illuminate the areas they're working [in]," notes Danna. "Every night after we pave, we have to provide pavement elevation shots, and the surveyor does those." Danna says subcontractor T.J. Lambrecht of T.J. Lambrecht Construction, with offices in Illinois and Texas, is widening the runway shoulders at night. Using a large excavator and a small dozer, Lambrecht removes a section of earth 12-14 ft. wide and 28 in. deep. Fabric is placed on the bottom of the trench, which is then filled with stone. Lambrecht started out using two light towers, Danna explains. "Once he got over the learning curve, he started getting more distance each night and he needed more light towers. Now he uses three to four light towers a night, and he can light up 400 to 500 feet of shoulder." The city's lighting specifications are enforced by an onsite safety representative, who might tell a subcontractor he needs more light, states Danna. That subcontractor then would pass the word to Cox, who would provide another light tower. For the O'Hare project, Cox included lighting in its bid as an "incidental" item, Danna says. The current project is similar to one Cox did a year earlier at O'Hare, so the contractor had night-work experience at the airport. "We had a clue from last year's job about how many light plants we would need, and we used our experience to gauge how many we would need for this year's job," notes Danna. A Mega-Project
One of the nation's largest current heavy-construction projects, with extensive nighttime earthmoving work, is the $245 million E-470 beltway project near Denver, CO. The project entails building a 12.5-mi. length of four-lane toll road and includes moving about 11 million yd.3 of earth. That total includes both imported borrow material and moving cuts to fills on the job, points out Doug Raitt, deputy project director of construction for MKK Constructors. MKK is a joint venture of the Washington Group International and Kiewit Western Company; it's a design/build project. "We've been working for about a year at night," reports Raitt. "Our scrapers typically work at night, and we've also done some import fill operations by running over-the-road belly dumps at night. Right now we're doing a 3,000-foot scraper operation at night, hauling from a cut to a fill. We've also done some night paving, and we've done some pile driving at night where we couldn't slow down traffic on a busy highway during the daytime." Raitt states that MKK is running 10 scrapers for the nighttime haul. The machines are Caterpillar 631E and 637E units; each hauls about 21 yd.3 To light up the haul road, MKK is using 12 portable light towers; each has four 1,000-watt lamps. MKK has devoted 32 of its towable four-light towers to the project. In addition, the project has two contractor-built 12-ft.-tall light towers, each with 16 1,000-watt lights. Those units are powered by 30-kW generators. What's more, the contractor also put together four 50-ft. light towers, each of which has 32 1,000-watt lamps. Each of the 50-footers is powered by a 60-kW generator. MKK owns all of the light towers. "We have a lot of light," remarks Raitt. "The big lights are good for lighting interchanges where we need to light up a large area," explains Raitt. "We'll soon start back with the big lights when we move from one end of the project to the middle of the project." Does all that light ever create a problem? "We did have to buy blackout curtains for one of our residential neighbors along the toll road," recalls Raitt. "We bought him curtains for his house." Raitt is aware of OSHA's minimum-illumination levels–and says MKK sometimes uses a light meter to check light levels. Do they check lighting levels every time they move the portable towers? "No," says Raitt. "The guys get a feel for it. With the amount of light we use, we've had zero complaints." Raitt says MKK uses all the lights when running two operations: (1) importing earth from a borrow pit 4 mi. away from the project and (2) using scrapers to haul from cut to fill. The contractor has run up to 50 belly-dump trucks at once for the importing operation–all hauling earth from two excavators, a Hitachi EX750 and a John Deere 550, at the borrow pit. "At the borrow pit, the 50-foot light towers come in handy because there the configuration of the haul road changes pretty often," notes Raitt. "The big lights mean we don't have to move lights as often as we would if we used several little towers. We can go for weeks without moving the 50-foot tower in the borrow pit. It lights up the whole borrow area." On scraper haul roads, portable light towers are spaced 500-1,000 ft. apart. Kiewit and Washington Group International have also won a connecting 10-mi. stretch of toll road, a project worth about $180 million. "It will follow the same schedule for nighttime work, so we'll have two and a half years of nighttime construction on the two projects," explains Raitt. Construction on the second project started in September 2001 and is scheduled for completion in late 2003. Task Lighting
On a somewhat smaller scale, contractor Fred Weber Inc. is doing extensive nighttime construction on the $48.3 million relocation of an Interstate 70 interchange in the St. Louis, MO, area. The project entails moving about 1 million yd.3 of earth, building drainage structures and six bridges, and paving the new interchange with concrete. The interchange is being moved mainly to make it safer; there had been several accidents at the former one, reports Bill Vondera, Weber's senior project manager on the job. Grading began in March 2001. "In May we started grading at night, and we went night and day through the summer," notes Vondera. "We moved about 600,000 cubic yards." Weber's equipment of choice: a Komatsu PC600 excavator and 20 Load King belly-dump trucks. "There was a large hill that had to be moved," recalls Vondera. "We had to load the hill out and put the road where the hill was." The only temporary lighting Weber needed was six portable light plants. "That lighting was just put up as needed for trucks to get off the road at the right location, get loaded, and get back on the road," says Vondera. "Our superintendent judges the number of towers needed by experience. The superintendent orders a few towers and sets them up where needed. If they get any problems, they order a couple more light towers. "The portable towers are a few hundred feet apart," describes Vondera. "All the trucks have headlights, so they only need floodlights at corners and strategic locations." Rent vs. Buy Whether a contractor owns or rents light towers depends on pretty much the same factors as for other equipment. If a contractor has an ongoing need for light towers, chances are he owns them. "We have 30-plus light towers," says Tom Besing, equipment coordinator for Traylor Bros. Inc., based in Evansville, IN. The firm mainly builds bridges and tunnels, and it does some earthmoving. "We usually buy 4,000-watt towers," adds Besing. "And we have been buying mostly Coleman units. Their tower raises up 30 feet, and they have 6 kilowatts on the generator. You can fold the tower down for transport; it folds down to 56 inches. "If we rent one of those, say for $750 per month, then over a 60-month life that's $45,000," continues Besing. "I can buy that machine for less than $8,000. Now, you don't have to be a rocket scientist to figure out which of those is the best deal." Sometimes night work is done for the contractor's convenience: There's simply little or no highway traffic to deal with. In San Antonio, TX, contractor H.B. Zachry Company is working on an $18.855 million highway-widening project on IH 410 at Military Road. The main-line pavement is being widened from three to five lanes, and the project includes moving 73,341 yd.3 of earth, states Project Manager Spike Hubenak. "The nighttime earthmoving haul is for our convenience," explains Hubenak. "We have to excavate the median and haul the material to the south header bank for one of the bridges. The haul is about a quarter mile. The convenience of the haul is that we can close the main line at night and load trucks over the portable concrete barrier. The trucks do not have to cycle into traffic or return on a long route. They can just cross the main line into the frontage-road median where we are constructing the header." Zachry's earthmoving equipment consists of one Komatsu 210LC excavator loading four tandem-axle dump trucks. Project lighting is simple enough–one light tower at the excavation area and one at the dump area. "Both the excavation and the dump area are long and narrow, so the lighting is localized and has to be moved along with the work," says Hubenak. Summary So most contractors use experience to decide how much lighting will do the job. A lot depends on what the specific job is. "If you're hauling earth into a fill, you try and light up most of the area," says Weber's Vondera. "You don't need a whole lot of light because you're just putting down dirt in lifts. But if you're doing bridge construction and making measurements, you need more light. We go by experience as to how many light towers are needed. I am aware of calculations for permanent lighting, but for temporary lighting we don't use those. We just get enough light for the guys to work by." Frequent contributor Dan Brown is the owner of TechniComm, a communications business based in Des Plaines, IL.
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