Honolulu Light Rail Stream Crossings – Pearl Highlands Station

As part of a planned 20-mile elevated light rail project on the island of Oahu, WSE has partnered with Northwest Hydraulic Consultants to conduct hydraulic engineering for approximately 20 stream crossings.  The most complex site is Pearl Highlands at Waiawa Stream, where the transit facility will be constructed within a mapped FEMA floodway and is influenced by complex bridge crossings.  The facility consists of a vehicle parking and bus transit facility, guideway station, and the guideway.

Role / Services:  WSE is performing the hydraulic modeling required to assist in the design of the Pearl Highlands facility.  Per local agency criteria, a one-dimensional HEC-RAS model has been developed to evaluate and ensure no-rise; however, for design, a two-dimensional (2D) FST2DH (FESWMS) model has been developed.

Outcome:  The modeling has provided key input to the design of the facility, which includes excavation of the floodplain to maintain no-rise, significant bank protection countermeasures, and floodplain surface treatments to control and prevent lateral erosion and scour.  Both models have been used to refine the grading plan to ensure that no-rise requirements are achieved.