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WA9302-CS 931123 (2)· THE six-million gallon buried I:eservoir in Addison is designed to be inconspicuous. AWARD WINNING WATER TANKS IN TEXAS TWO Dallas area water tanks won awards, and for different reasons: one is exposed and has an attractive ap- pearance; the other is hidden and is barely visible. Both tanks received Portland Cement Association 1991 commendations as out- standing prestressed concrete tanks. They were constructed by Preload Inc. of Garden City, New York. The 6-MG buried reservoir in Addison, Texas, engineered by Ginn, Inc., was named the winner for Distinguished Environmental Treatment. The 10-MG reservoir built for the City of Dallas, Texas, and engineered by Riewe & Wischmeyer, Inc. was named winner for Distinguished Architectural Treatment. The circumstances of the planning, engineering, and construction of the two tanks show both similarities and differences. The Dallas tank is the first AWWA DII0 design for potable water storage ever utilized by Dallas Water Utilities (DWU). The DWU's previous prestressed tanks were constructed in the early 1950s before the D110 standard and with dif- ferent technology than the new type tanks. Other ground storage tanks in the city are made of cast-in-place reinforced concrete in a rectangular or circular shape. The reservoir supplies the new Abrams Road Pump Station. This new installation in the North High Pressure District of the city was built under Dallas' Capital Im- provement Program. Michael Marcotte, Director of DWU, pointed out that the department has the responsibility to prepare for the anticipated future demand in this residential/commercial area. The tank's parameters were 238 ft in diameter and 30 ft side water depth with 10 ft of that below grade. After analyz- ing various alternatives, according to DWU's Project Manager Robert F. Thrash, P.E., the reservoir was specified to be per AWWA DII0, Type III. Clearwater Constructors, Inc. (now known as Hensel Phelps) of Austin, was awarded the contract in February 1989 and the entire project was completed by October 1990. John Rosenwinkel, P.E., of Riewe & Wischmeyer, Inc. was the project engineer. There were no extraordinary problems in the tank construction, except that Mother Nature was apparently not anx- ious to see it completed. Heavy rains flooded the excavation during construc- tion and a deep freeze caused a delay in pouring the roof. The project site landscaping and the tank's architectural treatment were in- tensely evaluated, since the installation faces Forest Lane, a high volume east- west thoroughfare adjacent to the Lyn- don B. Johnson Freeway. "This is an at- tractive area of town," said Marcotte, "and the tank is probably as highly ex- posed to the public as anything around here, so we wanted it to be especially at- tractive. ' ' DWU has received many compliments on the tank, including one from a · RESERVOIR in Dallas is the first in the city built with AWWA Dl10 design technology. PUBLIC WORKS for June, 1992 tourist/engineer who drove past the tank and telephoned Thrash to comment that "that's the best looking tank I've ever seen." It is faced in three kinds of masonry: smooth brick above a horizon- tal white cast stone feature strip, and rough split concrete block below. "Win- dows" with horizontal and vertical mullions enhance the tank's "lived in" look, accented with cast stone lintels and sills on each window. In addition to the tank's esthetically pleasing appearance, Project Manager Thrash anticipates that the new storage facility will be cost-effective for the city. He consulted with officials in surrounding cities who have used prestressed concrete tanks for years. They all reported that their tanks had good track records with limited or no maintenance down time or expense. Another Tank-- Different Approach A few miles away, the town of Addison faced a similar problem. An expanding population required a new ground storage reservoir and pump station, but the most suitable location was within an exclusive residential area. A large plot of vacant land near an existing 84-in. water trans- mission line precluded consideration of any other locations. Residents in the area, whose homes are valued as high as $900,000, were con- cerned about the appearance of the stor- age and pumping facility. They wanted to retain the upscale residential atmos- phere of their neighborhood. Ginn, Inc., Consulting Engineers of Dallas developed a design that is inconspicuous and har- monizes with the surroundings. The 6-MG reservoir is buried 25 ft below grade, so that only its 206-ft diameter roof is visible. Prestressed con- crete construction was chosen for its cor- rosion resistant properties since there is no easy way to inspect the outside of a buried tank. Said Wayne Ginn, "you would have to either excavate around the tank or X-ray from the inside." Excavation was difficult because of the hard rock in the area. However, once the excavation was completed there was an Modern-Day Magic Carpet WENTY years ago, convention cen- T ters were small enough that mainte- nance and custodial crews were able to use ladders and scaffolding to handle most overhead chores. Crawling up and down a ladder might have been a slow process, but it was the most economical way to put work crews in the air. As convention centers became larger and more complex, the serious shortcom- ings of ladders and scaffolding began to outweigh their short-term economy. There were three main problem areas. · It took two or three men to set up a tall ladder. And when it was finally up, only one man could get to the actual work area. · Setting up scaffolding was even more labor-intensive, usually requiring four or more men. It was also considerably more time-consuming. On some jobs, it could take longer to set up and dismantle the scaffolding than it would take to do the actual maintenance or custodial work. · Ladders and scaffolding were con- sidered to be potentially dangerous. Many slips and falls that occurred on ladders and scaffolding resulted in injuries, lost time, and lost productivity. There were other problems, too. On the really high overhead jobs, for example, only the youngest and strongest person- nel would make the climb--while the older and more experienced personnel tended to stay below to hoist tools or materials to the crew in the air. Before too many years had passed, managers of municipal facilities were ac- tively looking for ways to expand their crews' overhead work capabilities, ira- .. · CHANGING light bulbs and ballasts has become quicker and safer. prove their productivity, and enhance their work-area safety. In the late 1970s, the Kansas City, Missouri Special Facilities Department researched new ways to handle the over- head maintenance and custodial functions at the Kansas City Convention Center. The complex covers four square blocks and includes a music ha!l, an exhibition hall, an auditorium, and a multi-faceted convention/exhibition facility (H. Roe Bartie Hall) that encompasses more than 186,000 sq ft of exhibit space, not count- ing the many meeting rooms. The department's final choice of equip- ment to handle the overhead work was the Snorkelift TB-42, a self-propelled aerial work platform from Snorkel-Economy, A Figgie International Company, St. Joseph, Missouri. The TB-42 can position a 30- by 60-in. steel platform 42 ft above the floor, thus providing a working height of 48 ft. The rated capacity of the plat- form is 500 Ib. When compared with other municipal facilities of similar size, the Kansas City Convention Center probably has just as many overhead lights and ballasts to 62 PUBLIC WORKS for June, 1992 exce|lent foundation. The contractor then came in to erect the tank. There was room ,to precast the tank sections on site, posi- tion them, and wind the prestressing wire. The pump station is constructed to look like a residential home. Wood rafters sup- port a gable-ended hip roof, wood studs frame the interior walls, and brick fac- ing covers the concrete block outer walls. In the early planning of the facility, a tennis court and park area was considered for the tank's roof. The village residents, however, wanted to avoid the extra traf- fic and night lights, so that plan was drop- ped. The facility is screened from the road by a wrought iron fence with brick pilas- ters and extensive planrings of trees and shrubs. vo similar community goals--to 1,..,ntain the upscale appearance of a neighborhood--were achieved in two dif- ferent ways. The Dallas tank was de- signed to be contextual with its surround- ings through an attractive architectural treatment. Conversely the Addison reser- voir was almost completely buried beneath grade, so that only the conrex- tual pump house remained visible. Both projects represent the latest in en- vironmentally sensitive public works. Besides the two award winning tanks, there is one more Texas water storage facility that deserves mention. In contrast to the excavation problems in Addison, Ginn encountered even more difficult rock conditions on a site in Coppell, change, fire-sprinklers to check, and ceil- ing tiles to repair or replace. The big dif- ference is that the building-maintenance personnel in Kansas City spend almost no time at all climbing on shaky ladders or assembling labor-intensive scaffolds. In- stead, the maintenance crew relies on the self-propelled work platform to lift a worker quickly, easily, and safely. According to John F. McCord, main- tenance superintendent with the Special Facilities Department, this piece of equip- ment may have been the first self'pro- pelled work platform ever used on a full- time basis by a municipality. "You would expect to see a tool like this on a construction site or in a fac- tory," said McCord, "but the mainte- nance and custodial crews in most cities tend to use ladders and scaffolds for their overhead and elevated work. In this respect, our operation is different because we have almost totally eliminated our reliance on ladders and scaffolds. "With its operating speed and safety features, we find that we can use the Snorkeli~ effectively on many jobs within 15 ft of floor level, as well as those much higher." McCord thinks his department's lift might be unique among municipalities. "There may be other cities out there which use self-propelled work platforms like this one--but I'm not aware of them. If there are, I'd bet that they don't use theirs as much as we use ours. We have our work platform busy almost con- stantly-probably more than 300 days a year. ' ' High Utilization Such high utilization of a work plat- form is what one might expect only in a commercial application. But a large, busy convention center can be just as busy as a construction site or a factory, and some- times, it can be even busier. The work platform is kept busy just changing lights and ballasts in the overhead lights. The Kansas City Convention Center has more than 24,000 lights of different wattages. Most of those lights are located from 16 to 33 ft above floor level. The lift is very maneuverable. It is com- pact enough when the boom is stored that it can easily be driven anywhere in the building, through doorways and along pedestrian ramps. It will fit through an · WORK platform Is used an average of four times a week to change signs. Texas. 'l7 avatiuonni ~u~ virtually impossi- ble because of u q e geological condi- tions at the site. The solution was to drill piers to different depths to reach bedrock. Then a Preload tank was built on the piers. The tank floor was reinforced and made thicker than normal to assure suf- ficient rigidity to support the weight of the water and transfer the forces to the piers. The two award winning projects repre- sent design solutions to esthetic considera- tions. In contrast, the Coppeil facility was engineered to accommodate structural limitations. All of the projects, however, represent the latest in structural and engineering ingenuity and environmental sensitivity. [] [] [] 8-ft doorway--both height and width. The ability to maneuver is particularly im- portant because the Kansas City Conven- tion Center's individual exhibit halls and meeting facilities are connected by a net- work of underground passageways. Someone is always finding a use for the lift--both maintenance and custodial chores--literally dozens of different jobs. The lift is appreciated for three main reasons. First, all it takes for operation is one worker. Second, it can be brought into use at a moment's notice. And third, it is much safer than either a ladder or a scaffold. In addition to replacing ceiling lights and ballasts, crews routinely use the work platform for checking overhead fire sprinklers, replacing ceiling tiles, and replacing or repairing windows. There are some other more unusual jobs that can only be done with the work platform. Curtainwalls are used to divide the large (600- by 300-ft) exhibit hall into three smaller (200- by 300-ft) halls. These curtainwall-panels are suspended from ceiling-mounted trolleys that roll back and forth. The work platform is used to access those trolleys for preventive maintenance and emergency repair. The building's maintenance and custodial crews also use the work platform for everyday dusting, cleaning air conditioner ducts, and painting walls. Since the work platform is self-pro- pelled, it is also a simple matter to use it for jobs that are located outside the building. It is used to change bulbs and glass in the numerous outdoor fixtures along sidewalks and pedestrian walkways. The biggest application for the plat- form outdoors is changing lettering on the marquees. There are three different mar- quees outside the Center--one for the arena, one for the music hall, and one for the theater--so frequently there are three different simultaneous events. The plat- form can be at the marquees 200 days a year, making sure the events are up in lights and displayed prominently. [] [] [] 63