Go with the Flow
The city of Houston, Texas is growing at a rapid pace, adding about 95,000 new residents each year and is the fifth largest metropolitan area in the U.S. To keep up with this population boom, the city realized a need to double its current water output. A redesign project of the East Houston Water Treatment Facility was needed to update the water treatment plant and piping to increase water flow and meet the growing population demand.
In March 2018, CSDA member Aggregate Technologies of Houston was contracted by General Contractor CYMI to core drill three very large holes into two of the concrete walls of the water treatment plant to allow for new piping to be installed. The biggest challenge of this job was that the holes were to be drilled 15 feet above the ground, creating a challenge for maneuvering the needed equipment into place and handling the weight of the large cores. Diamond core drilling was determined to be the best method for this job because the holes needed to have clean, smooth edges so that a water-tight seal could be created when the piping and link seals were installed. Additionally, these output pipes would be visible from the road, and other methods such as jackhammering or chiseling would not have created the smooth edges needed for the seal or for a visually appealing finish.
The first step for Aggregate Technologies was to plan the set up of the core drill. The existing piping on the wall needed to be removed, and a meeting with the General Contractor was required to plan out the precise drilling plan to ensure the holes were drilled to the correct tolerances. The new piping was temporarily placed so Aggregate could mark the core drill setup on the wall, and then removed so the core drill rig could be mounted.
To mount the rig, a crane was provided to lift the core drill post into place and placed against the wall, so the two anchors could be set. Hilti roto hammers and drop-in anchors were used on this project. Once the anchors and post were set, the drill bit was hoisted by the crane and attached to the rig. To keep the drill bit level, Aggregate fabricated a wheel system that mounted on the drill rig post which eliminated the need to set boards on the wall. This ended up saving several hours of set-up time as well as provided a smoother startup when starting the bit into the wall.
Using a Diamond Products M-6 hydraulic core drill and M-2 stand, the two 56 inch diameter holes could now be drilled. The holes took a day to a day and a half each to complete, which ended up being ahead of the planned two day per core schedule. The Aggregate team consisted of one operator and one helper, working in 12-hour shifts. To avoid the core getting stuck in the bit, a small hole was roto-hammered in the middle of each core to about one inch of breaking through the end of the 14 inch depth. The bit was then removed, and the core broken out of the wall. This was no small task, as each core weighed 7,400 pounds. Even though the cores were completed ahead of schedule, Houston concrete is very hard, and this wall had been poured in the 1960’s with heavy rebar. The wheel system fabricated by Aggregate to keep the drill bit level and make for a smoother start helped save valuable time in cutting this hard concrete and allowed the cores to be drilled out ahead of schedule.
Once the two 56 inch holes were completed, another 50 inch diameter core, also 14 inches deep, needed to be drilled using the same technique. In total, three large cores were drilled, as well as several smaller holes in 12 to 18 inches thick river rock slab. Three holes 36 inch diameter holes and three 24 inch diameter holes were drilled in the 14 foot-thick slab, as well as several smaller holes four to eighteen inches thick. To take down the drill rig, the crane was again brought in to lift all equipment down safely.
Aggregate’s main concern on this job was the large diameter holes needed. These large holes, due to their size and weight, can cause the drill rig to break off the wall if not planned out and secured properly. To prevent that from happening, Aggregate set multiple anchors into the wall at different depths and set them as far away from each other as possible. Since operators were working from a height on a boom lift, all standard PPE was worn, and operators were tied off to prevent falls.
This CSDA contractor completed their portion of this job ahead of schedule and within budget. Aggregate Technologies was chosen for this job due to their relationship and history of successful projects with the General Contractor. Project Manager for Aggregate Chris Allen stated “I was very pleased with this job. We expected each hole to take two days due to the large size and the hardness of the concrete. We have drilled smaller holes at the same site that took longer than expected due to the concrete hardness, so it was a testament to our team that this job was completed ahead of schedule.”
Houston aggregate, especially river rock, is notoriously difficult to cut. Selecting diamond tools was the only way to ensure a precise, clean cut and ensure that this job would be a success. Aggregate Technologies’ experience with this type of concrete was one of the main reasons they were chosen for this job, and their knowledge and expertise was crucial in creating the clean cut needed.
Precision and quality, not quantity, were the most important parts of this job and Aggregate Technologies proved they can handle even the most challenging projects.
In business since 1997, Aggregate Technologies has been a CSDA member since 2013. They are based in Houston, Texas. Aggregate runs 15 trucks and offers core drilling, slab sawing, wall sawing, wire sawing, selective concrete demo, hydrodemolition and load and haul out services.
Sawing and Drilling Contractor