Structural Integrity Evaluation of Buried Concrete Water Reservoir

Services Performed

C3S, INC. conducted a structural integrity evaluation of the buried concrete reservoir, including examination of the roof slab, interior columns, walls, and floor.

The investigation included:

• • Site inspections and condition assessment.
  • Evaluation of concrete cores and samples.
  • Examination of concrete columns, walls, floor, and top slab.
  • Non-destructive testing.
  • Minimally invasive testing.
  • Evaluation of concrete strength and carbonation depth.
  • Petrographic examination of selected concrete samples.

Figure 6 shows some of samples taken from inside the Reservoir.

Testing Methods

The evaluation incorporated two non-destructive testing methods and five minimally invasive testing methods on concrete from various areas of the facility.

Key evaluations included:

• Compressive Strength Testing
• Carbonation Depth Evaluation
• Petrographic Examination
• Concrete Core Examination
• Microscopic Examination of Cement Paste and Aggregate

Findings

Compressive strength testing of the concrete cores produced results ranging from approximately 5,000 to 9,000 psi.

Carbonation testing showed that the depth of carbonation was less than ½ inch. Based on the observed carbonation depth and reported reinforcement cover of approximately ¾ inch, the embedded reinforcement was considered to have substantial protection from carbonation-related corrosion.

Petrographic examination identified dense cement paste with sand particles and some unhydrated cement particles. Iron-bearing gravel aggregate was also identified within the concrete.

The evaluation included examination of the numerous interior concrete columns, floor, walls, and roof slab to assess the condition of the existing structure.

Outcome

C3S, INC. provided a technical evaluation of the existing concrete condition and structural integrity of the 84-year-old underground reservoir. The investigation documented strong concrete core results and limited carbonation penetration, providing important information for stakeholders considering the future use and preservation of the facility.

The evaluation supported subsequent efforts to preserve and repurpose the historic reservoir as the Buffalo Bayou Park Cistern, rather than demolishing the structure.

Featured Services: Structural Integrity Evaluation • Concrete Core Testing • Compressive Strength Testing • Carbonation Evaluation • Petrographic Examination • Non-Destructive Testing • Concrete Condition Assessment

Fun Facts:

• 87,500 square feet or the size of 1.5 football fields
• 221– 25-foot tall, slender concrete columns span the space
• Holds 15 million gallons of water when functioning at capacity
• 8-inch thick concrete roof and tapered concrete walls range from 8 inches at the top to 18 inches at the bottom
  17-second echo
• SWA Landscape Architect Kevin Shanley first called the reservoir “the Cistern” because it reminded him of the ancient Roman cisterns under Istanbul
• https://buffalobayou.org/visit/destination/the-cistern/