Shotcrete Contractor Takes His Show On The Road With World Class Results
For nearly thirty years Desert Shotcrete in Tucson, AZ has ridden the wave of growth in the southwest. Along the way, the company has earned a reputation for being a first class rebar and shotcrete contractor, with more than 19 thousand residential and commercial installations to show for their efforts. “There was always so much to do right here in Tucson,” explains Desert owner, Joe Schmieder, “I would get calls from general contractors asking if I would be interested in being the shotcrete sub on large out of state pool projects but I just couldn’t break away to pursue them.” Schmieder kept getting the calls from the generals and when the migration to the southwest slowed along with home construction, Schmieder decided to take his shotcrete show on the road.
Wescon, a 34 year old general contractor in Albuquerque, New Mexico that specializes in aquatic facilities had admired Desert’s work after using them for an Olympic sized pool project in Tucson more than 17 years ago. “They are a very professional operation, “according to Steve Kraft, president of Wescon, “They work very well with the close tolerances required with these competition pools and their work is very high quality.” The general contractor and Desert stayed in touch over the years and the two companies are working together again on some new projects in New Mexico, starting with a 50-meter pool at the University of New Mexico in Albuquerque. No stranger to large pools, Wescon has built similar size pools throughout the southwest and travels as far as Texas to build pools for universities or municipalities.
Because most of the university-owned pools are used for competitions, the tolerances are critical. “Really there is zero tolerance. The pool dimensions must be right on the money,” explains Schmieder. Electronic timing with touch pads verifies a world record only if the dimensions are true. Wescon hired surveyors to set the dimensions of the excavation for the 50 x 25 meter pool. Desert uses grade wire between the corners to maintain the correct shotcrete depth. “Every square inch is set to a grade and elevation,” Schmieder noted. When the project is finished, the NCAA will certify the results for competition.
Schmieder brought six of his workers, an air compressor and a Schwing SP 750-18 trailer pump to the university which is 400 miles from Tucson. “Arizona has a good labor supply of experienced workers because so many pools are built here,” according to Schmieder, “We have an enthusiastic group of men that recognize the importance of the work we do.” In addition to Joe, one operator runs the concrete pump outside and five men work inside applying the shotcrete, striking off the built-up material and finishing the bottom and walls to the correct dimensions. In some cases, Desert will place the reinforcing steel depending on available manpower.
Shotcreting from the bottom up with their all-hydraulic pump, the company had 250-feet of 2-inch flex hose laid out on the project. Ready-mix trucks delivered the stiff mix to the pump located outside of the pool enclosure. Because this pool would also be used for diving competitions one end of the pool was to be 14-feet deep. “We needed a strong and stiff mix to allow us to build up the tall walls of the pool structure,“ explained Schmieder, “ The shotcrete mix consisted of a 3/8-inch basaltic rock, known to be a difficult pump mix. This very coarse shotcrete mix helped provide 4,000 plus psi strength at a three inch slump.” The pump’s 70-cubic yard per hour output and 100 horsepower combined with its 1100psi pressure on the shotcrete mix to pump everyday for two weeks and get the project completed without an incident. Schmieder reports, “The boys like the smaller housing on the Rock Valve, because it cleans up faster at the end of the day than some of our other pumps with swing tubes.”
When shotcreting far from home, reliable equipment is essential to maintaining the schedule and the company’s reputation. “When I saw the all-hydraulic design of the 750, I knew I liked it, “ Schmieder stated, “ Electronic switching problems with my other pumps can take valuable time to troubleshoot. With an all-hydraulic pump, if you see a leak, there’s the problem. It’s that simple.”
After saturating the subgrade, the bottom is shotcreted first in a checkerboard pattern of 10-foot wide sections. The Desert crew prefers a two-inch nozzle with a longer boot which seems to aid in proper placement of shotcrete, according to Schmieder. The workers screed the freshly blown sections while standing on the ground. The men then stand on the completed rectangles to strike off the remaining sections. “The bottom goes fast – maybe 80 to 90 cubic yards per day, “stated Schmieder, “It’s the walls that take time because they have to be shaved from bottom to top in four foot high lifts with cutting rods. We spray about 40 to 50 yards per day on the walls because of all the details.” The crew shotcretes around the stubbed out p.v.c. piping that have flared fittings to prevent water from infiltrating through all pipe openings. A large Olympic-sized pool consumes 500 plus yards of shotcrete.
The pool walls are built up from the bottom in three to four foot lifts. The two curtains of rebar in the deep end are covered in two passes of the nozzle. The walls are shaved and checked for dimensional accuracy shortly after spraying. The finish of the walls must have an even but open face texture for the tile and plaster to adhere properly. The Desert experts have to adjust the lights that are embedded in the shotcrete at intervals around the pool. Unusual for Desert, was that the University specified steps for egress instead of cut-in steps or ladders. “Some companies will form and pour steps but we spray a mound of shotcrete and trim and carve the steps, “ explains Schmieder, “It goes much faster and saves extra labor costs in forming.”
In competitive swimming pools, waves are kept to a minimum by installing a gutter around the perimeter that acts as a weir to circulate the pool water and also absorb any waves generated by the swimmers. The gutter shape is acquired by using a foam template. Desert had started with 300-feet of the reusable foam form on hand to shape 500-feet of gutter on this job. The company also utilized templates for the correct radius for the wall to floor transition.
At the end of every day, the crew sprays a 45-degree angled joint which was wetted prior to the next day’s shooting. This insured maximum overlap and the best joint possible. Working for two weeks straight, the pool was finished and the Desert Shotcrete crew was on their way back to Tucson.
Next stop a municipal pool for the City of Las Cruces, New Mexico.
As Schmieder remarks as he heads out the door, “On large projects such as this, where no down time is acceptable, the reliability of my Schwings have been a big part of our success in completing these large commercial pools that are a long distance from our home base in Tucson, Arizona”
Project: Lower North Outfall Sewer Rehabilitation, Los Angeles California
Owner: Public Works Department, City of Los Angeles
Contractor: Joint venture Colich & Sons/J.R. Pipeline, Los Angeles
Equipment; Schwing WP 1250-18X stationary concrete pump