Alchatek Blog

One Atlanta Plaza experienced significant settling of sidewalks and approach slabs around the perimeter of the building, creating safety hazards for pedestrians and visitors. The multi-story structure includes underground parking levels supported by piles, which remained stable, but the transition areas connecting to surrounding sidewalks were built on compacted fill. Over time, differential settlement occurred between the pile-supported structure and the soil-supported approach slabs, with some areas dropping approximately half an inch. Building management had previously attempted fixes by creating concrete "ramps" at transition points, but these temporary solutions continued to deteriorate as settlement progressed.

Initial Assessment

Engineers inspected the site and identified that the compaction difference between the soil immediately adjacent to the building foundation and the surrounding area was causing uneven settlement. This resulted in cracking of curbs, trip hazards at entrance points, and visibly sagging pavement sections, particularly noticeable at the approach to the parking garage. The most affected areas showed clear separation between the stable pile-supported structures and the settling exterior slabs. Entrance points where the differential settlement created ADA (Americans with Disabilities Act) compliance issues, and potential liability for trip-and-fall incidents were of particular concern. This problem stemmed primarily from inadequate soil compaction during the original construction.

Proposed Solution

Alchatek recommended a two-phase approach to address both the underlying soil conditions and the visible settlement. First, AP Soil 600, a single-component polyurethane product designed for soil stabilization and permeation, would be injected to densify the loose soil beneath the affected slabs. Following soil treatment, two-component polyurethane foam, AP Lift 475, would be used to lift the settled concrete sections back to their proper elevation. This non-invasive approach would eliminate the need for demolition and replacement of concrete, allowing for minimal disruption to building operations while providing a long-lasting solution.

Procedures

1. Technicians established injection points in a grid pattern, spacing them approximately 3-4 feet across the affected areas.
2. Saw cuts were made at key joints to free slabs from binding against adjacent concrete, allowing for controlled lifting without creating additional stress.
3. In the initial phase, AP 600 was injected through small drilled holes to stabilize the underlying soil and prevent future settlement.
4. After the soil stabilization phase, AP 475 was injected in multiple passes, starting from the areas closest to the building and moving outward.
5. Elevation was carefully monitored throughout the lifting process using zip levels and dial indicators to ensure proper alignment and prevent cracking.

Results

The rehabilitation project restored proper elevations at all transition points around the building, eliminating tripping hazards and improving aesthetics and safety. The lightweight polyurethane material added minimal load to the treated areas while effectively compacting and stabilizing the underlying soil.

From a financial perspective, this approach delivered significant cost savings compared to traditional repair methods. Concrete replacement would have required demolition, disposal, and new concrete installation, which is why the two-phased remediation project resulted in a 90% reduced cost compared to traditional replacement methods.

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A property in Atlanta featured a multi-level parking structure with a split-level design. The upper-level parking area began showing signs of significant distress, with visible cracking and pavement deterioration. Investigation revealed that soil was actively migrating through a lower retaining wall of the parking structure, creating voids behind the wall and compromising support for the pavement above. The color change in the asphalt surface clearly marked the affected area, and the problem was getting progressively worse, posing both functional and safety concerns for vehicles using the facility.

Initial Assessment

Engineers determined that soil was passing through the precast concrete retaining wall that separated the lower parking level from the surrounding earth. Testing revealed substantial voids had formed behind the wall, primarily involving clay soils that had become soft and unstable. While the wall itself remained structurally sound, the continued migration of soil threatened to create more significant issues if left untreated. Traditional repair methods would have required extensive excavation and potential wall replacement, a prohibitively disruptive and expensive approach for an active parking facility. The challenge was stabilizing the soil and filling the voids without impeding parking operations.

Proposed Solution

Alchatek recommended using two-component polyurethane foam (AP Lift 475) to stabilize the soil and fill the voids behind the wall. This material was selected specifically because of its high compressive strength and ability to effectively fill large voids in clay soil conditions. Since the wall was precast concrete and structurally sound, there was no concern about the polyurethane's strength pushing or damaging the wall. The expansive properties of the material would ensure complete penetration into irregular void spaces, while its closed-cell structure would prevent future water migration that could cause additional soil loss. This approach would stabilize the subsurface conditions without requiring excavation or disrupting the facility's operations.

Procedures

1. Established a precise injection grid with tighter three-foot spacing in the first row close to the wall and slightly wider spacing in the second row.
2. Drove injection pipes through the soil to reach the void areas behind the wall.
3. Injected approximately 15 pounds of two-component polyurethane every 1.5 feet vertically, ensuring complete filling from bottom to top.
4. A hydraulic pipe puller was used to extract injection pipes during material placement for controlled distribution.
5. Monitored for any structural movement throughout the process using zip levels and dial indicators to prevent over-pressurization.
6. Injected material systematically across the affected area, adjusting quantities based on observed soil conditions.

Results

The project successfully halted soil migration through the retaining wall and stabilized the pavement above. The two-component polyurethane effectively filled all voids while creating a waterproof barrier to prevent future erosion. Most importantly, the solution eliminated the need for disruptive and costly excavation, allowing the parking structure to remain operational throughout the repair process. Post-treatment monitoring showed complete stabilization with no further signs of settlement or cracking in the pavement. The property owner avoided significant reconstruction costs that would have been incurred with traditional methods, while also preventing potential revenue loss from parking facility closure. This case demonstrates how polymer injection technology can provide effective structural solutions with minimal operational impact, a key consideration for commercial property remediation.

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US Highway 98 is the main coastal route along Florida’s panhandle, connecting Panama City Beach, Destin, and Fort Walton Beach. Over time, the Florida Department of Transportation (FDOT) faced persistent issues with groundwater infiltrating the stormwater system. This infiltration carried exceptionally fine “sugar sand” into pipes and manholes, gradually reducing capacity and causing flooding on roadways during heavy rains. The situation escalated when a vehicle was damaged after falling into a void created by soil loss beneath the roadway, highlighting the urgent need for a lasting solution.

Initial Assessment

Inspections found that groundwater was entering through pipe joints, manhole connections, and cracks in concrete structures, transporting fine sand and creating sizable voids beneath the infrastructure. The affected system included concrete pipes ranging in diameter from 36 to 84 inches, with numerous manholes spread along a three-mile stretch of highway. Traditional repair would have required full excavation and replacement—a disruptive and prohibitively expensive process for such a critical transportation corridor. Based on the extent of sand loss and the depth of infrastructure, voids were estimated to range from several inches to several feet around key structures.

Proposed Solution

Alchatek recommended Spetec PUR H100, a semi-rigid polyurethane grout, for comprehensive rehabilitation. This material was chosen for its ability to expand and fill voids, while remaining flexible enough to accommodate minor ground movement and maintain a watertight seal. The approach involved direct injection into leaking joints and cracks, followed by creating a curtain wall around critical structures to prevent further sand migration and stabilize the surrounding soils. FDOT required a five-year warranty on the repair, underscoring both the severity of the problem and their confidence in the solution.

Procedures

1. Technicians drilled directly into each pipe joint, installing injection ports for precise placement of H100 grout.
2. Additional holes were drilled about one foot from each joint in a clock-pattern to encapsulate the joints and stabilize the surrounding soil.
3. Injection began at the lowest point of each structure and progressed upward to ensure complete filling and displacement of water.
4. Manholes received perimeter injections to form a waterproof curtain wall, with special attention to all pipe penetrations.

Results

Over the course of 18 months, approximately 2,000 pipe joints and numerous manholes were treated along a three-mile stretch of US 98. Since the project's completion in 2017, there have been no warranty claims or reported issues, even during multiple heavy storm seasons. The highway has remained free of flooding and sand accumulation, and no further undermining of the roadbed has occurred. By choosing polyurethane injection over full excavation, the FDOT avoided estimated replacement costs of $7 million to $16.5 million, while keeping the highway open and safe throughout the process.

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The US Army Corps of Engineers (USACE) required a solution to fill the annular spaces between eight 84-inch ductile iron pipes and the concrete bulkhead at a new pump station along the Mississippi River in Port Sulphur, Louisiana. Traditional methods, such as pouring non-expanding resin, were cost-prohibitive (approximately $50,000 per void) and lacked the necessary performance characteristics. The voids posed a risk of instability and water infiltration, demanding a material that combined strength, adhesion, and environmental safety.

Initial Assessment

Inspections revealed significant annular gaps around the pipes, necessitating a material that can bond to both ductile iron and concrete while forming a waterproof seal. The USACE prioritized a solution that avoided excavation, minimized downtime, and provided long-term durability. Based on the scale of the pipes and typical annular space requirements, the voids were estimated to range from 6 to 12 inches in width around each pipe, although exact dimensions would depend on site-specific conditions.

Proposed Solution

Alchatek’s AP Lift 430, a high-density, two-component polyurethane foam, was selected for its compressive strength of 7,200 psf, ensuring structural support while adhering tightly to both ductile iron and concrete. Its hydrophobic nature prevents water infiltration,  and its expansion capability allows for complete void filling without precise volume calculations. AP Lift 430 provided a balanced solution for strength, durability, and cost efficiency.

Procedures

1. Material Application: AP Lift 430 was free-sprayed into the annular spaces using a Graco Fusion spray foam gun, ensuring deep penetration and adhesion to both the ductile iron pipes and the concrete bulkhead.
2. Curing and Expansion: The foam expanded to fill the voids, creating a seamless and waterproof barrier.
3. Surface Finishing: Excess foam was ground flush with the concrete surface to allow secure installation of flanges and gaskets.

Results

The project was completed in two days, with no disruptions to ongoing site operations. AP Lift 430 formed a durable, watertight seal, meeting all USACE requirements for strength and longevity. Total material costs were approximately $30,000, representing a 90% cost savings compared to other resin-based alternatives. The USACE supervisor conducted daily inspections and praised the efficiency and quality of the repair.

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Buchanan Dam, located on the Colorado River in Texas, is a critical infrastructure built in 1937 to form Lake Buchanan. The dam is one of the longest multiple-arch dams in the world and serves as a vital resource for hydropower generation and flood control. Over time, the dam developed high-pressure water leaks in its concrete arches, particularly in Arch 47. These leaks were exacerbated by seasonal temperature fluctuations, which caused thermal expansion and contraction, leading to recurring cracks and water infiltration. Restek, Inc., a contractor specializing in structural repairs, collaborated with Alchatek to implement a polyurethane grouting solution to address these issues.

Initial Assessment

An inspection of the dam revealed severe water infiltration concentrated in Arches 45-47. Arch 47 presented the most aggressive leaks, with water flowing under high pressure. Previous injection efforts had only provided temporary relief due to insufficient grout penetration and equipment limitations. The concrete structure’s thickness and seasonal movement posed additional challenges for effective leak sealing.

Proposed Solution

Alchatek recommended using a combination of advanced polyurethane products tailored to the dam’s specific conditions. Spetec PUR HighFoamer was selected for high-pressure leaks due to its rapid reaction time and expansive properties. Spetec PUR H100 and Spetec PUR F1000 were chosen for lower-flow areas requiring flexibility to accommodate joint movement. Higher-capacity airless pumps, such as the Titan 640 and Titan 8900, were utilized to ensure effective grout delivery.

Procedures

1. Preparation:

• To reach the midpoints of the concrete structure, deeper injection points were drilled using 24-inch and 36-inch masonry drill bits.
• Oakum rope saturated with grout was packed into joints to slow water flow during the injection.

2. Injection Process:

• Spetec PUR HighFoamer mixed with Alchatek Gen Cat was injected into high-flow leak areas using upgraded pumps capable of handling high pressure.
• Flexible grout mixtures (Spetec PUR H100/PUR F1000) were injected around rigid plugs to reinforce sealed areas and accommodate seasonal joint movement.

3. Post-Sealing Monitoring:

• The team monitored material expansion within cracks and adjusted injection pressure as necessary to ensure complete sealing.

Results

The grouting crew successfully sealed leaks throughout Arches 45-47. High-flow leaks in Arch 47 were effectively stopped using Spetec PUR HighFoamer, while lower-flow leaks were addressed with flexible polyurethane grout mixtures. Equipment upgrades allowed deeper injections, overcoming previous limitations and ensuring long-term durability against thermal stresses. Subsequent inspections confirmed substantial reductions in water infiltration, with no major leak recurrence reported.

Conclusion

The Buchanan Dam leak-sealing project demonstrated the importance of combining advanced materials with appropriate equipment upgrades to address complex infrastructure challenges. Restek, Inc.'s collaboration with Alchatek resulted in a sustainable repair strategy that restored the dam’s structural integrity while accommodating environmental factors such as temperature fluctuations. This case underscores polyurethane grouting’s effectiveness as a solution for high-pressure leak repair in large-scale concrete structures.

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Gerace Construction undertook a gate replacement project at the Tom Miller Dam in Austin, Texas. While working on Large Gate #6, and after installing a needle beam cofferdam system to lower the water level, a continuous wet spot was discovered under the metal gate sill. This indicated a crack in the concrete extending under the sill plate. Sealing the leak was necessary to prepare and coat the steel sill plate, which was crucial for the overall gate replacement.

Initial Assessment

The primary challenge was water seeping through a crack, less than one linear foot in length, located in the concrete beneath the steel gate sill. The cofferdam system had created approximately 18 feet of head pressure upstream, with the water level pumped down about two feet below the sill. As per the project specifications, a dry surface was required to apply coatings to the steel sill plate.

Proposed Solution

Alchatek recommended Spetec PUR H100 to seal the crack. This hydrophobic polyurethane resin was chosen for its ability to rapidly seal cracks with reasonable water flow and minimal anticipated movement. The solution involved injecting the resin into the crack to create a watertight seal, allowing the steel surface to dry for coating application. Alchatek also provided an on-site representative during the injection process, as required by the project specifications.

Procedures

1. Preparation:

• The contractor established the cofferdam system and lowered the water level to expose the leaking area.
• Injection ports were installed along the crack at 12-inch centers on alternating sides.

2. Injection Process:

• Spetec PUR H100 mixed with Alchatek Gen Cat was injected into the crack using positive displacement equipment capable of maintaining a minimum pressure of 250 psi.
• Injection began at the lowest port and continued sequentially upward until grout filled the crack and seepage ceased.
• Inline pressure was monitored throughout to ensure it did not drop below 190 psi during injection.

3. Post-Injection:

• The injected resin was allowed to cure fully, forming a watertight seal.
• Excess surface seal material was removed, and the repaired area was inspected to confirm no further water intrusion.
• The injection ports were removed, and holes were patched flush with hydraulic cement as per project guidelines.

Results

The application of Spetec PUR H100 successfully sealed the leak under the steel gate sill, allowing Gerace Construction to proceed with surface preparation and coating application. The fast-reacting properties of Spetec PUR H100 minimized delays while ensuring long-term durability against water infiltration. The Lower Colorado River Authority (LCRA) engineering staff approved of the product, and the Alchatek representative provided the required on-site supervision ensured compliance with all quality assurance measures, resulting in a successful repair that restored functionality and structural integrity to Gate #6 at Tom Miller Dam.

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Gerace Construction was contracted for a project at the Pat Mayse Dam in Paris, Texas, to repair and seal leaks in the discharge conduit. The project involved addressing cracks and weeps within a concrete pipe structure. The United States Army Corps of Engineers (USACE) was overseeing the project, requiring strict adherence to specifications, including the presence of a manufacturer’s representative on-site during the grout injection process.

Initial Assessment

The primary challenge was to stop active water leaks within the concrete conduit pipe. A site visit identified the locations of cracks and weeps, as documented in the photo report included in the specification. The photos showed typical leaking monolith joints on the sides and top of the structure, as well as leaking monolith cracks. These leaks required a solution that could effectively seal actively flowing water in both vertical and horizontal orientations.

Proposed Solution

Alchatek proposed the use of Spetec PUR F400, a flexible polyurethane grout, to address the leaking cracks. This product was selected for its ability to penetrate narrow cracks, its flexibility to accommodate movement, and its compatibility with wet concrete surfaces. The plan included supplying the necessary materials, equipment, and a qualified manufacturer’s representative to supervise the installation.

Procedures

1. Preparation:

• Injection ports were installed along the identified cracks and weeps in the concrete pipe.
• Holes approximately 12 inches deep were drilled at a 45-degree angle.

2. Injection Process:

• Spetec PUR F400, along with Alchatek Gen Cat to control reaction time, was injected through the installed packers using a suitable pump.
• Injection began at the lowest packer for vertical joints or cracks, working upwards.
• The process continued until the grout traveled between packers, and the leaks were sealed.
• An approved epoxy adhesive paste was used to seal the surface of the cracks, allowing grout to travel.

3. Post-Injection:

• Re-injection was performed to ensure all voids were properly sealed off.
• Each installed packer was re-injected with a small amount of water to allow the resin in the drill hole to react.
• The injection ports were removed and cut flush, and packer holes were filled with approved epoxy paste.
• Once cured, the remaining materials were removed from the concrete surface with a wire brush or handheld grinder.

Results

The Alchatek solution, implemented by Gerace Construction, effectively sealed the cracks and stopped the leaks in the Pat Mayse Dam discharge conduit. The on-site presence of a qualified manufacturer’s representative ensured the proper application of the product, meeting the requirements of the USACE. The project was completed in accordance with the specifications, resulting in a successful repair and improved structural integrity of the dam’s discharge conduit.

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The Cave Buttes Dam, located in Phoenix, Arizona, required modifications that involved installing a 60-inch diameter steel conduit pipe beneath the dam through bedrock. During tunneling operations, a 15-foot-wide fault zone containing water and composed of clay was encountered. After the excavation and grouting of the annular space between the pipe and the rock with cementitious grout, leaks began to emerge from some of the welded grout packer plugs. SSC Underground was the contractor for this project, with engineering oversight provided by AECOM and the U.S. Army Corps of Engineers.

Initial Assessment

The primary issue was leaking grout plugs, which were 2-inch diameter, straight-threaded plugs welded into place after the initial grouting process. These plugs exhibited varying degrees of water seepage, with flow rates estimated at a few gallons per minute. The leaks were attributed to anticipated movement between the steel pipe and the surrounding rock due to temperature changes and vibrations. Based on these conditions, a flexible chemical grout was determined to be the best solution to seal the leaks while accommodating future movement.

Proposed Solution

Alchatek recommended injecting Spetec PUR F400, a flexible polyurethane grout, to seal the leaks. This grout was selected because of its ability to bond effectively while maintaining flexibility to withstand differential movement between the steel pipe and surrounding materials. The plan involved drilling into the existing grout plugs and injecting Spetec PUR F400 through packers to confine the grout and ensure a complete seal. The project utilized packers for controlled injection and a Titan Impact 440 pump to deliver the grout. Alchatek Gen Cat was used to manage the grout’s reaction time based on the specific site conditions.

Procedures

1. Preparation:

• The team drilled into the center of each leaking grout plug to create access points for injection.
• Packers were installed into these drilled holes to facilitate the controlled injection of the grout.

2. Injection Process:

• Spetec PUR F400 was injected through the packers using a Titan Impact 440 pump.
• Alchatek Gen Cat was added to the grout mixture to adjust reaction times as needed.
• The injection process was monitored to ensure proper confinement of the grout within the leaking areas.

3. Post-Repair Monitoring:

• After sealing each leaking port, inspections were conducted to confirm the cessation of water infiltration.
• New leaks that emerged from previously sealed or new locations were identified for subsequent treatment.

Results and Conclusion

The initial injection process sealed most of the identified leaking grout ports, effectively stopping water infiltration at those locations. However, water subsequently found new paths, resulting in additional leaks from previously sealed ports. The team used the same materials and procedures to address these additional leaks through follow-up injections. Ultimately, all leaks were successfully sealed, restoring the integrity of the steel pipe installation.

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The City of Sand Springs, Oklahoma, identified a foundation leak in Bay 10 of the Shell Lake Dam, necessitating repairs to ensure the dam’s structural integrity. The city’s Public Works Department contracted with a qualified firm to address the issue, and Keithline Engineering Group was retained to provide engineering design and oversight for the project.

Initial Assessment

An inspection by Keithline Engineering revealed an active boil, or leak, in the concrete footing of Bay 10. The leak, measuring approximately 5” by 7”, exhibited increasing water movement and was deemed a priority for repair. The engineering team determined that the water was likely traveling between the concrete footing and the porous sandstone underlayment before exiting through the hole in the concrete. This leak was transporting a small amount of material under low pressure. It was also determined the owner had made prior unsuccessful attempts to seal the area with bentonite.

Proposed Solution

After consulting with Alchatek, Keithline Engineering specified a leak-sealing solution centered around the injection of Spetec PUR H100. Alchatek recommended this hydrophobic polyurethane grout for its ability to expand and create a dense, impermeable seal upon contact with water. The repair strategy involved drilling through the concrete and injecting the grout into the concrete/sandstone interface to create a grout curtain. This approach aimed to stop the leak at its source and prevent further water migration.

Procedures

1. Preparation:

• Hammer-drilled 1/2-inch injection ports were installed into the concrete foundation at designated locations.
• Saturated oakum rope or hydraulic cement was applied to temporarily plug the hole during the injection.

2. Injection Process:

• Spetec PUR H100 was injected through installed packers using positive displacement pumps.
• Injection proceeded until the grout formed a complete polyurethane barrier around the boil and stopped water infiltration.
• The process included monitoring grout expansion and ensuring proper confinement within the concrete/sandstone interface.

3. Post-Sealing:

• Following the injection, all nipples were removed, and drilled holes were patched with hydraulic cement to a minimum depth of 12 inches.

Results and Conclusion

The injection grouting successfully sealed the foundation leak in Bay 10 of Shell Lake Dam. Spetec PUR H100 formed a durable polyurethane barrier, effectively stopping water flow and preventing further erosion of material from beneath the dam footing. The swift and effective repair was achieved in a matter of hours. Restek, Inc. precisely executed the specifications. The result is a solution that preserves the long-term structural integrity of the Shell Lake Dam, showcasing the value of proactive maintenance in preserving critical water resources.

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A Utah-based geotech specialist partnered with a general contractor to address a critical DOT infrastructure challenge involving the replacement of an existing culvert on a major roadway in Utah. The project involved the installation of precast concrete slabs on both sides of the box culvert, designed to create a seamless transition from the culvert to the compacted road base.

Site Investigation and Challenge

During the design phase, engineers identified that constructing a compacted road base beneath the slab would inevitably leave voids underneath. These voids posed a risk of uneven support and potential rocking of the slab when subjected to heavy traffic load.

Proposed Solution

To address this, ¾” holes were drilled four feet apart to allow for injection rods to be inserted through the slab. The foam selected for this slab was AP Lift 440 structural foam due to its rapid expansion and high strength needed for DOT projects. This foam expands 17-19 times its original volume within 8-10 seconds of injection, ensuring comprehensive void filling. Dial indicators were used to ensure that there was no vertical movement of the slab during the injection process.  

Results and Conclusion

The entire operation was executed in approximately three hours, utilizing about 400 lbs of structural foam. This successful application filled all of the voids, providing uniform support for the precast slabs and enhancing overall road stability. The rapid curing properties of the foam allowed for swift project completion with minimal disruption to traffic.

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