Ohio Underwater Intake Grouting
The Job
The municipality in Portsmouth, Ohio, is upgrading its municipal water system. This critical infrastructure upgrade requires the installation of two new intake pipes drawing from the Ohio River. A microtunneling contractor installed two parallel 60-inch microtunnels. The contractor retrieved the microtunnels from a cofferdam constructed in the river. Following the tunnel excavation, the contractor installed 36-inch ductile iron intake pipes inside the microtunnels. This configuration required annular space grouting to ensure long-term stability and structural integrity.
The parallel intake tunnels.
The Challenge
Underwater intakes and dams present unique environmental and engineering obstacles. The annular grout must resist water intrusion completely. Lower densities of cellular grout can be highly permeable, which allows water to flow through the annular space. The project demanded an impermeable material to prevent river water infiltration. Additionally, the contractor needed a fast installation process to minimize disruptions at the cofferdam. Grouting operations also had to account for the buoyancy of the ductile iron carrier pipes.
The Solution
Based on our extensive experience with underwater intakes, CJGeo proposed CJFill-Standard cellular grout. We selected a 60-pound per cubic foot density for this project. This specific density achieves a permeability of less than 10^-6 centimeters per second. This exceptionally low permeability is crucial for preventing water from flowing through the annular grout. Because the grout is less dense than water, the contractor easily addressed carrier pipe buoyancy by filling the pipes with water.
CJGeo mobilized a dry batch cellular concrete crew to the site. The crew performed the annular space grouting in fewer than four hours. The fast placement time ensured the project stayed on schedule. The water fill successfully held the carrier pipes on grade without any flotation.
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