Project At-a-Glance
- 60-inch Diameter Steel Casing Trenchless Crossing by MTBM
- Prepared Geotechnical Baseline Report, Tunnel Design, Pipe Stress and Jacking Load Calculations
- Clays with moderate to high clogging potential, sand, gravel and swelling claystone
The Alliance Regional Water Authority (ARWA) in a multi-phase project is supplying water to portions of Central Texas including Buda, Kyle and San Marcos. This trenchless crossing was constructed beneath the San Marcos River by Micro-tunnel Boring Machine (MTBM) , which utilized installation of a 60-in welded steel casing with a length of 300-ft with water-tight shafts. The casing pipe contains a 42‑in water transmission main.
Brierley Associates served as Trenchless Specialist subconsultant to the lead designer of this phase of the project. Brierley prepared the Geotechnical Baseline Report (GBR), tunnel design, specifications, risk assessment, pipe stress calculations, jacking load calculations, and opinion of probable construction cost (OPCC).
The subsurface conditions in the project area contained Fluviatile Terrace deposits composed of clays with moderate to high clogging potentials as well as granular layers of sand, gravel, and cobbles. Below the Fluviatile Terrace deposits is the Navarro Group and Marlbrook Marl , a swelling claystone with a high clogging potential.
Additionally, Brierley aided the design team. during construction reviewing submittals, RFI’s, construction site visits with corresponding reports.
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