Guido Perla and Assoc., Inc., has recently completed contract design for Crowley Maritime Corp.'s subsidiary Vessel Management Services' series of three PRT Class (Prevention and Response) Tanker Assist/General Towing Z-Drive tugs. GPA is also furnishing complete detail modular construction engineering for the 140 ft. x 10,192 hp Caterpillar-powered PRT Class, which are currently under construction at Dakota Creek Industries in Anacortes, Wash. The vessels are designed as diesel powered twin Z-Drive propulsion tugboats, outfitted for tanker rescue, ocean towing, emergency oil spill response, fire fighting and harbor service. Propulsion is provided by two Caterpillar 3612B diesel engines, each rated 5,096 bhp @ 900 rpm, driving two Kamewa Aquamaster U.S.