Triad Engineering
Triad Engineering

Pearl River CSO Client: City of Lafayette, IN

Client:  City of Lafayette, Indiana
Consulting Engineer:  Greeley & Hansen LLC
Contract Amount:  $18,956,607.07
Scope:   2300 feet long tunnel under Second Street in downtown Lafayette, IN.
                12 feet in diameter and 30 feet deep to the invert.
                Tunnel alignment contained three curves.
                Project included an S curve and four access shafts.
                Primary liner designed by Joint Venture engineers in cooperation with Underground Steel. 
Solution: A reinforced steel segment system and was installed behind the tunnel digging machine.
                Final lining is 9.5 feet in diameter, monolithically poured, reinforced concrete.

Triad was the managing partner of the Triad Frontier Kemper Joint Venture.  The Joint Venture completed the Pearl River CSO Tunnel Project in Lafayette, IN in 2010.  The project required soft ground mining in mixed face conditions below the water table.  The soils were a combination of glacial till overlain by water bearing sands and gravels.  The project used a tunnel machine designed with a compressed air pressurized face in front of a steel bulkhead.  This permitted the work space to be in free air.

The tunnel is approximately 2300 feet long under Second Street in downtown Lafayette, IN.  In addition to the challenging soils, the tunnel was 12 feet in diameter, yet only 30 feet deep to the invert.  Tunnel excavation required strict instrumentation and monitoring, as many utilities were very close to the tunnel crown.  In addition, the tunnel crossed under the major rail link between Chicago and the southern United States with approximately one diameter of tunnel cover.  The tunnel alignment contained three curves including an S curve and four access shafts.

A unique primary liner was designed by Joint Venture engineers, in cooperation with Underground Steel Solutions.  A reinforced steel segment system was designed and installed behind the tunnel digging machine.  This solution was more economical and practical than precast concrete segments, due to the short length of the tunnel.  The final lining is a 9.5 feet diameter, monolithically poured, reinforced concrete.

Contact Us

Ohio Office

9715 Clinton Road
Brooklyn, OH 44144
Phone: 440.786.1000
Fax: 216.651.0754

e-mail Triad Engineering

South Carolina Office

480 Jessen Lane, Unit H
Charleston, SC 29492
Phone: 843.416.1112
Fax: 843.416.1192