1.5 km underground rapid transit system with two stations in weathered alluvium below water table. Jacobs Associates handling tunnel design as part of design and build jv of Kiewit-Kenny-Zachry with CMA Architects and Engineers and local designers. Rio Piedras station under construction using concrete-filled stacked drifts and extensive compensation grouting. Lovat EPB and segmental concrete lining for twin 430 m tunnels to University and sprayed concrete lining elsewhere. Nov 1998.   Four NATM tunnels for Carolina and Bayamon lines completed and twin EPB tunnel completed and lined. South cut and cover section fully excavated and concrete walling underway. Remaining stacked drifts for Rio Piedras station under excavation and concreting. E-mail contact mguzman@kkz-cma.com Sept 1999.   URS Greiner Woodward Clyde is project geotechnical and instrumentation engineer for design and construction phases of the Rio Piedras project, as part of the KKZ JV. More from www.urscorp.com December 1999.  Preliminary design of Phase 2 underway. $600 million, 1.7 km design/build extension involves 1.255 km of twin tunnels, crossover and stations at Minillas and San Mateo at 10-15 m depth in soft, sandy clay and clayey sand. Visit www.jenny-engineering.com 35/01.