Nashville Raw Water Intake Contact Grouting
The Job
The West Wilson Utility District required a new raw water intake from the Cumberland River to serve the eastern Nashville suburbs. The initial phase involved a contractor microtunneling a 60-inch outside diameter steel casing 420 linear feet. This tunnel extended from a solid rock shaft on the riverbank to an underwater retrieval point. CJGeo mobilized to the site after the microtunneling machine was retrieved. Our objective was to perform contact grouting on the annular space separating the casing and the surrounding rock.
Preparing for the contact grouting placement.
The Challenge
The primary challenge was achieving long-term stability for the newly installed 420-foot steel casing. The tunnel path was through solid rock. Even in rock, microtunneling leaves a small, critical annular space around the casing. This space creates a potential pathway. River water could migrate back to the land-side shaft. This compromises the structure’s integrity and introduces unwanted infiltration. Sealing this annular space was essential to ensure the structure’s longevity.
The Solution
CJGeo did the contact grouting to completely fill the gap around the pipe. We injected the grout from the solid rock shaft on the riverbank. Divers watched the work the whole time at the underwater exit point. The injection successfully pushed the air and water out of the space. Grout traveled the full 420 feet from the shaft to the river-bottom area. This successful job sealed the space, which will keep the pipe stable and stop water from leaking in.
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