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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