Alchatek Blog

An interior elevator pit needed for ADA retrofit in a multi‑level building, inside an old stairwell beside a load‑bearing wall on sandy soils. Conventional shoring wasn’t feasible indoors with tight footprint and headroom limits.​ Stable Soils of Florida was called in to assess and remedy the situation.

Initial Assessment

• Sandy, below‑water‑table soils at a planned 7 ft pit depth.​

• Footing and slab at risk of undermining if excavated untreated.​

• No practical option for sheet piling, slurry wall, or trench box.​

Proposed Solution

Engineers designed a perimeter grout “box” using AP Soil 600, a low‑viscosity, single‑component permeation resin that bonds wet sands into a rock‑like, load‑bearing mass.

Procedures

1. Lay out pit and grout‑box perimeter around the planned excavation.​

2. Drill and set probes to depths below the final pit grade.​

3. Inject AP Soil 600 while slowly extracting probes to form overlapping treated columns.​

4. Allow cure, then excavate the pit inside the treated zone.​

5. Grind exposed treated face flat and use it as the outer form for the concrete pit.​

Results

Stable excavation adjacent to the load‑bearing wall with no observed soil loss.​
Interior elevator pit completed without conventional shoring or large equipment.​
Enabled ADA‑compliant vertical access using permeation‑stabilized in‑place soils.

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A below-grade warehouse loading ramp had water infiltration at the slab-to-wall cold joint. Hydrostatic pressure forced water and sandy soil through the joint during rainfall, clogging the French drain and requiring manual removal after each storm.

Initial Assessment

The cold joint leak allowed water and sediment infiltration. Soil erosion created voids beneath the slab. Traditional solutions proved impractical. Slab replacement entailed demolition at 5–6 times the cost. Exterior waterproofing required excavation below the water table. And interior drains merely treated symptoms, not root causes.

Proposed Solution

Spetec PUR HighFoamer was selected for its 50x expansion ratio and hydrophobic properties. This single-component polyurethane resin reacts with water to create a curtain grout while filling voids. Safe for potable water contact with NSF/ANSI 61-5 certification, it delivers a rapid 15-minute cure time.

Procedures

1. Drilled 3/8" injection holes at 2.5' spacing along the cold joint.
2. Installed threaded nylon packers with zerk fittings for controlled injection.
3. Initiated injection at the lowest elevation using a gas-powered hydraulic pump.
4. Injected foam progressively upward, monitoring emergence at adjacent ports.
5. Sealed ports after 15-minute cure.

Results

• Eliminated 100% of water infiltration and sediment transport. 
• Achieved 80% cost savings versus traditional slab replacement and 75% savings versus exterior membrane installation. 
• Completed in one day with zero operational downtime—the facility remained fully functional. 
• Eliminated recurring French drain maintenance.

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Developers working on a new CVS Pharmacy in Orlando, Florida, encountered critical soil stability issues during the construction process. The project managers faced a significant challenge when geotechnical testing revealed unsuitable soil conditions between 5 and 10 feet below the surface, posing a threat to the structural integrity of the planned parking lot. This issue was discovered after site preparation had already begun, adding urgency to finding an effective solution that would allow construction to proceed on schedule.

Initial Assessment

A geotechnical analysis revealed that although the upper soil layers had been replaced, a layer of muck remained at depth, posing significant risks of settlement and potential structural failure in the parking lot. The site required comprehensive soil stabilization to proceed with construction. Traditional methods of excavation and replacement were deemed too time-consuming and costly, necessitating an alternative approach.

Proposed Solution

A comprehensive soil stabilization plan utilizing AP Lift 475, a two-component polyurethane foam, was proposed. This solution was chosen for its ability to:

• Consolidate soil throughout the parking lot area.
• Provide a stable foundation for the structure.
• Avoid extensive excavation and soil replacement.

AP Lift 475 was selected for its high strength and excellent expansion properties, which would allow it to effectively fill voids and stabilize the muck layer without adding significant weight to the unstable soil.

Procedures

1. Establish a 5-foot grid pattern across the entire parking lot area.
2. At each grid point, inject 25 pounds of AP Lift 475 at a depth of 10 feet.
3. Inject an additional 25 pounds at a depth of 5 feet at each point.
4. Monitor soil consolidation and adjust injection amounts as needed.
5. Perform post-injection testing to confirm soil stability.

Results

The polyurethane injection solution proved highly effective, successfully stabilizing the soil without the need for extensive excavation. This approach allowed the construction schedule to be maintained, avoiding costly delays that would have been incurred with traditional soil replacement methods. Post-injection testing confirmed that the treated area passed all required stability tests, demonstrating the effectiveness of polyurethane injection for large-scale soil stabilization projects in commercial construction.

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A municipal wastewater treatment facility in New York had catastrophic water loss in five interconnected tanks, including two Sequencing Batch Reactors (SBR) and a digester. One SBR alone lost 20–22 inches of water daily, threatening its compliance with environmental regulations and risking $25,000/day in regulatory fines. The facility’s partially buried concrete structure was built just five years prior, with cracks linked to defective cold joints and curing errors. Traditional demolition/replacement was estimated at $1.5M, but the client sought a less expensive and minimally invasive solution to avoid shutdowns. All County Spray Foam Solutions was brought in to do the job.

Initial Assessment

Technicians documented dozens of active leaks through crack networks at tank walls and floor transitions. Water migrated horizontally across tanks due to cold-joint defects in the buried structure. Larger cracks (up to ⅛") required stabilization to prevent material blowout during injection. A structural inspection confirmed no risk of wall collapse but highlighted the urgent need for crack sealing.

Proposed Solution

The engineering team selected Spetec AG200, an ultra-low-viscosity (3–4 cP) acrylic resin with NSF 61 certification for use in contact with potable water. Key advantages:

• Microscopic penetration: Fluid enough to fill hairline cracks without high-pressure injection.
• Flexible sealing: Creates elastic barriers tolerant of concrete movement.
• Cold operation: Reacts fully at substrate temperatures of 30–35°F.

The method avoided:

• Tank evacuation/excavation beneath the structure.
• Long-term downtime for concrete replacement.

Procedures

1. Crack Identification: Mapped moisture patterns and active leaks using towels/paper.
2. Port Drilling: Drilled 45° angles to intersect cracks, avoiding direct surface drilling.
3. Crack Stabilization: Used hydraulic cement to plug larger cracks, retaining oakum-soaked material.
4. Material Application:
   1. Injected Spetec AG200 at 1:12 to 3:00-minute gel times with accelerators.
   2. Monitored breakthrough (material appearing at adjacent ports).
   3. Verification: Confirmed leaks reduced to “moist areas” post-injection.

Results

The injection process, which used approximately 20 gallons of resin, sealed all major leaks within under a week. Post-repair inspections confirmed dry conditions. The approach averted months of tank shutdown, $1.5 million in replacement costs, and thousands more in potential fines.

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A public park in New York had critical erosion issues at its waterfront staircase and adjacent beach, which were built over a landfill. Over the years, natural erosion pulled back sand, exposing uneven foundation areas and creating safety hazards for visitors. The partially buried concrete staircase exhibited significant subsidence and shifting soil, posing a threat to structural collapse. The New York City Parks Department required a rapid solution to stabilize the site before further degradation occurred.

Initial Assessment

The staircase and surrounding sand exhibited signs of differential settlement, likely due to uneven soil compaction and erosion. Technicians identified voids beneath the stairs and along the beachfront, with sand migration exacerbating instability. Traditional excavation or pier-and-casing methods were impractical due to limited access and the need to avoid displacing adjacent structures.

Proposed Solution

The team selected AP Fill 720 (a single-component polyurethane) for soil compaction/stabilization and AP 430 (a two-component foam) for structural void filling. AP Fill 720 addressed loose sand through permeation and consolidation, while AP Lift 430 filled critical voids beneath the staircase, providing lift and support.

Procedures

1. Stabilization Pattern: Injected AP Fill 720 every 4 feet at 6–8 feet depth to bond sand particles and prevent further migration.
2. Structural Foam Injection: Applied AP Lift 430 directly beneath the staircase’s granite slabs through strategic ports, filling void spaces with approximately 1 gallon per linear foot.
3. Final Treatment: Reserved excess AP Fill 720 to seal surface gaps around the staircase, preventing sand washout.

Results

The dual-material injection rapidly stabilized the waterfront staircase, eliminating soil migration and structural risk without closing the park. Compared to traditional heavy reconstruction, the approach cut costs by an estimated 97% and completed the work in under two weeks with minimal marine or community disruption. Post-repair inspections confirmed lasting results with no recurrence of erosion.

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AT&T Plaza in downtown Dallas had persistent water infiltration issues in its basement and sub-basement levels, resulting in structural concerns and operational disruptions. The building's below-grade concrete walls developed multiple active leaks, allowing groundwater to penetrate the structure and causing dampness at wall-floor transitions, which raised concerns about potential corrosion of the reinforcing steel. Building management required an immediate solution that would effectively seal the leaks while minimizing disruption to commercial operations.

Initial Assessment

Engineering inspections by B|S|A Design Group revealed multiple active leak points throughout the basement and sub-basement concrete walls, with water infiltration occurring through cracks, joints, and penetration points. The moisture intrusion patterns indicated that several leak locations had been active for an extended period. Traditional waterproofing methods would require extensive excavation and reconstruction, making them impractical for a busy downtown commercial building. The assessment concluded that targeted injection would be most effective while allowing the building to remain operational.

Proposed Solution

The engineering team specified Spetec PUR F400, a hydrophobic polyurethane grout designed for water cut-off applications in concrete structures. This single-component material was selected for its ability to react with water to form a flexible, closed-cell polyurethane seal that permanently stops water infiltration. The material's low viscosity allows deep penetration into crack networks while its hydrophobic nature ensures effective sealing in wet conditions. This approach would eliminate disruptive excavation while providing a permanent solution.

Procedures

1. Engineers identified and mapped all visible leak points, prioritizing the most severe infiltration locations.
2. Injection ports were drilled at strategic locations to intersect water migration pathways through the concrete structure.
3. Spetec PUR F400 was mixed with appropriate catalyst ratios and injected using controlled pressure techniques.
4. Technicians monitored for complete crack filling and leak cessation, with post-injection inspections confirming successful sealing.
5. Work was coordinated to minimize disruption to building tenants throughout the process.

Results

The injection process successfully eliminated all water infiltration throughout the treated areas. Post-repair monitoring following significant rainfall events confirmed the complete cessation of leaks, with previously wet areas remaining dry. The project was completed with minimal disruption to building operations. The injection approach achieved 98%+ cost savings compared to traditional excavation and membrane installation methods. Additionally, avoiding a building evacuation prevented an estimated $25,000-$ 50,000 in lost rental income and tenant relocation costs.

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A persistent water infiltration was observed in a below-grade tunnel in Houston, TX. Staining on the sheetrock ceiling indicated the leak originated at the joint between the tunnel shell and the building wall, specifically at the interface with the flashing. The tunnel was situated on the negative pressure side of the structure, resulting in recurring water intrusion issues. The property management team sought technical advice to resolve the leak without extensive demolition or disruption to the building’s operations.

Initial Assessment

Visual inspection confirmed that water was entering through the wall/flashing joint and migrating into the tunnel ceiling. The stains and moisture patterns suggested a continuous leak path exacerbated by negative hydrostatic pressure. The location and nature of the leak made traditional surface repairs ineffective, as water was entering from behind the structure and not from an exposed face.

Proposed Solution

Alchatek recommended injecting the joint between the tunnel shell and the building wall with Spetec PUR F400, a hydrophobic polyurethane grout. This product was chosen for its ability to react with water and expand, effectively sealing active leaks even under negative pressure. The material’s low viscosity allows it to penetrate tight joints and bond with both concrete and steel, creating a durable, watertight seal. The recommended installation method involved using a Titan 440 electric injection pump, ensuring the grout was injected until the joint could no longer accept any more material.

Procedures

1. The team identified the leaking joint at the wall/flashing interface as the primary injection target.
2. Injection ports were installed along the joint to provide access for the polyurethane grout.
3. Spetec PUR F400 was injected using an electric injection pump, with technicians monitoring for material refusal and observing for any signs of milky fluid or foam, which indicated grout migration.
4. Injection continued until the joint was fully saturated and would not accept additional material, ensuring complete sealing of the leak path.
5. The process required no pre-pumping or removal of water from the joint, as the hydrophobic grout was designed to react in wet conditions.

Results

The polyurethane injection successfully sealed the leak at the tunnel shell/building wall joint. Post-repair observations showed no further water staining or active intrusion in the tunnel ceiling, and the tunnel remained dry even during subsequent rain events. The method enabled targeted remediation with minimal disruption to building occupants and eliminated the need for costly demolition or exterior excavation. The use of Spetec PUR F400 provided a cost benefit of 96% compared to traditional invasive repair methods. The property management team was satisfied with the outcome and the efficiency of the repair process.

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At Antwerp Airport, a section of the runway slab had settled by 1–2 inches, creating a hazardous rocking effect that endangered aircraft landing gear and led to grounded flights. Aircraft wheels hitting the depressed area like a pothole generated dangerous jolts. Although the settlement had persisted for years, mounting operational demands finally compelled immediate action.

Initial Assessment

Initial investigations revealed voids beneath the 8-inch-thick concrete slab. Replacing the entire slab proved impractical because it would require a multi-day runway shutdown, extended project timelines, and substantially higher costs.

Proposed Solution

The contractor selected Alchatek’s AP Lift 430 polyurethane foam for its hydro-insensitivity, rapid strength development, 22x expansion ratio, and compressive strength of 7,200 psf. These properties enabled efficient lifting and stabilization with minimal downtime.

Procedures

1. Marked the slab and established 8 injection points in a grid pattern.
2. Drilled through the 8-inch slab and installed injection ports.
3. Injected 16 gallons of AP Lift 430 in staged passes.
4. Monitored elevations with dial indicators.
5. Sealed the drill holes and restored the surface.

Results

• The slab was lifted to specifications, resulting in zero differential settlement with adjacent panels.
• The project was completed in just 4 hours—over 90% faster than a full slab replacement.
• The international airport resumed its full flight schedule the same day, avoiding over $100,000 in losses from runway closures.

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A single-story office building settled over organic soils beneath its post-tensioned slab. With access restricted to the interior, a fast and clean repair was essential. Geotech experts from Helicon were called in to assess the situation.

Initial Assessment

Borings showed dense to very loose strata and differential movement under interior columns and slab zones; uniform densification and code‑level lift tolerance were required. Traditional underpinning inside an occupied shell would extend schedules and raise costs versus targeted polyurethane injection.

Proposed Solution

The contractor selected AP Lift 440 for hydro‑insensitivity, rapid reaction, and ~80 psi compressive strength. This material was ideal to permeate, densify, and lift with minimal downtime.

Procedures

1. Inject 30,000 lbs over 635 interior points per geotech layout.
2. Apply tight grid spacing, pressure/volume control, and real‑time elevation checks.
3. Coordinate QA/QC with the Engineer of Record for sign‑offs.

Results

• Restored slab support and column bearing
• Zero exterior disruption; interior‑only access.
• Approximately 97% cost savings vs interior underpinning/piering, with faster completion.

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A critical downtown Houston pedestrian tunnel had persistent water infiltration affecting the ceiling, walls, and floor throughout the structure. The tunnel serves as vital underground infrastructure in Houston's urban core, where any significant disruption would impact pedestrian traffic and building access. Initial observations revealed widespread moisture intrusion, but the full extent of the problem remained unclear until interior finishes could be removed for proper assessment. The facility required a rapid, effective solution that would minimize downtime and restore the tunnel's watertight integrity.

Initial Assessment

Once sheetrock was removed from affected areas, engineers discovered extensive water infiltration through multiple pathways in the concrete structure. Moisture intrusion was occurring through joints, cracks, and penetrations, creating a complex leak pattern that compromised the tunnel's structural integrity and usability. Traditional repair methods would have required extensive excavation from above or complete tunnel closure for membrane installation - both prohibitively disruptive options in Houston's dense downtown corridor. The assessment revealed that targeted injection could address the root cause of infiltration without major structural modifications.

Proposed Solution

Alchatek recommended using Spetec PUR GT350, a hydrophilic polyurethane grout specifically designed for active leak sealing in underground structures. This single-component material was selected for its ability to react with water to form an expanding, flexible foam that creates a permanent, waterproof barrier. The injection approach would allow precise targeting of leak sources while maintaining tunnel accessibility throughout the repair process. The polyurethane's expansion properties would ensure complete void filling and crack sealing, even in areas with irregular geometries or active water flow.

Procedures

1. Mapped all visible leak points and moisture intrusion areas throughout the tunnel structure.
2. Drilled strategic injection ports at locations determined to intercept water infiltration pathways.
3. Injected polyurethane grout through ports using positive displacement pumps, monitoring for material refusal and leak cessation.
4. Conducted systematic injections across all identified problem areas, adjusting techniques based on local conditions.
5. Verified complete sealing through visual inspection and moisture monitoring following cure completion.

Results

The polyurethane injection process successfully eliminated water infiltration throughout the tunnel structure, restoring its watertight integrity without requiring facility closure or major structural modifications. Post-treatment inspections confirmed the complete cessation of leaks, with the tunnel remaining dry even during subsequent heavy rain events. The minimally invasive approach allowed the tunnel to remain operational throughout the repair process, avoiding costly service interruptions. For a typical tunnel section, this represents over 95% cost savings compared to traditional methods. Additionally, avoiding tunnel closure prevented an estimated $10,000 to $ 25,000 in daily economic losses due to disrupted pedestrian traffic and building access, further amplifying the financial benefits of this innovative approach.

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