The Austin-based Lower Colorado River Authority has begun work on a 2.1 km-long 2.8 m-diameter tunnel for a wastewater treatment plant in Williamson County. The TBM-driven tunnel runs from downtown Round Rock off State Highway 79, under I-35 and continues west of the Georgetown Railroad to connect previously installed upstream and downstream portions of the Brushy Creek Regional Wastewater System. The tunnel is needed for a 27.3 km system that will extend from the Cedar Park Wastewater Treatment Facility to the Brushy Creek Regional Wastewater Treatment Plant, adjacent to Highway 79 just east of the Dell Diamond. The tunnel will be constructed in a stiff, expansive clay and a competent limestone. A complex fault zone marking the contact between the two formations will be crossed. Tunnelling is expected to end in August 2003 and the Brushy Creek Wastewater System Project is to be completed by October 2004. Design by Brierley Associates and PBS&J. Visit www.lcra.org 39/02.