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Precast <strong>Polymer</strong> <strong>Concrete</strong><br />
provides “BIG” Solution for the<br />
City of Austin’s “BIG’ Project<br />
Eric Dawson, P.E.<br />
PARSONS<br />
Austin, Texas
Project Summary<br />
• Gravity flow wastewater tunnel, 3.9 miles long<br />
• Relieve major downtown area collectors<br />
• Tunnel bore: 10’ & 8’ dia, with pipes 90” to 36”<br />
• Seven deep tunnel access manholes<br />
• Constructed value: $40 million<br />
• Contractor: JV of SAK Construction and Quest Civil<br />
Constructors<br />
• <strong>Polymer</strong> concrete tunnel access manholes supplied by<br />
U.S. Composite Pipe, Alvarado, Texas
Tunnel Alignment
Geologic Profile
Tunnel Access Manholes<br />
• 70 to 90 feet deep<br />
• 4 with 16’ diameter<br />
• 2 with 8’ diameter<br />
• All anticipated to serve in very corrosive conditions<br />
• Vortex drops installed in 4 of the manholes<br />
• Singular structures<br />
• Tunnel has 100-year + design life
Tunnel Access Manhole Design<br />
• Hydraulic drop from surface sewer to tunnel<br />
• Provide maintenance access to tunnel<br />
• Resistance to corrosion<br />
• Minimize volume of induced air into tunnel<br />
• Selected 16’ ID for manholes<br />
• Accommodate 90” pipes – 7.5 feet across<br />
• Accommodate vortex drop structures<br />
• Provide work space for future inspection/maintenance<br />
• Would fit inside anticipated construction shafts
Tunnel Manhole Design, contd.<br />
• Austin experience with WW tunnel manholes<br />
• Initially cast-in-place concrete with extra sacrificial thickness<br />
• Have had severe corrosion, difficult/expensive rehabilitation<br />
• Later used PVC liner cast inside CIP concrete and applied<br />
coatings<br />
• Better results<br />
• Small defect in liner/coating or damage after installation problematic
Tunnel Manhole Design, contd.<br />
• Design process<br />
• Considered liners and coatings for cast-in-place concrete<br />
• Installation conditions critical and needs strong construction QC<br />
• Investigated polymer concrete<br />
• Uses resin binder in place of Portland cement<br />
• Corrosion resistant across whole cross-section<br />
• Was not available in 16’ ID sections at time of design<br />
• Selected cast-in-place concrete with PVC liner
Construction Changes<br />
• Large diameter polymer concrete sections became<br />
available<br />
• U.S. Composite Pipe – Alvarado, Texas<br />
• Investigated other cities’ experience – Houston, others<br />
• Worked with Contractor – made no-cost change<br />
• Greatly reduced construction effort<br />
• Shortened project schedule<br />
• Cast in place Portland concrete base with protective<br />
coating
<strong>Polymer</strong> <strong>Concrete</strong><br />
• High strength<br />
• 10,000 psi compressive strength<br />
• 1,000 psi tensile strength.<br />
• Material has the desirable properties of standard<br />
concrete<br />
• First time polymer concrete used in such a large<br />
application<br />
• Many millions of dollars in savings on maintenance<br />
possible
Manhole Construction
Manhole Construction
Manhole Construction
Manhole Construction
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Manhole Construction
Manhole Construction
Manhole Construction
Summary<br />
• Use of <strong>Polymer</strong> concrete was win-win change<br />
• Owner: no cost change to superior material<br />
• Contractor: Reduced complexity and duration of<br />
construction<br />
• City of Austin using polymer concrete for wet wells and<br />
critical manholes
Questions<br />
Eric.J.Dawson@Parsons.com<br />
512-719-6029
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