Client: Orange County Public Facilities and Resources Department
Location: Westminster and Huntington Beach, Orange County

Project Features:

• An eight-mile long regional system extremely deficient in storm water carrying capacity from Freeway 22 to its confluence with Bolsa Chica Channel.
• In addition to deficient channel and culvert sections, hydraulic constraints exist at more than 20 street crossings which have low clearance and are extremely undersized.
• Fundamental problems exist in facility enlargement both vertically and horizontally. The rights-of-way may limit vertical enlargement and adjacent ground and street elevations may restrict deepening or raising the banks.
• The southern watershed boundary borders with levees and banks; overflows will escape to the adjacent downstream drainage basins causing compound flooding problems.
• Significant efforts were made to database establishment for channel facilities, storm laterals, and utilities by data collection, collation, and conflict resolution using as-built data as well as supplemental survey.
• Hydraulic calculations were complicated due to current model limitation in simulating backwater with significant momentum changes at deficient culverts and bridges.
• Detention alternatives are most desirable, considering the unique problems with this drainage system. Low impact land use areas, such as parks, parking, and playfields, were identified. Cumulative storage and infiltration using these areas may provide benefits for water quality improvement, however, it can not reduce the peak discharges to the manageable levels.
• Conveyance alternatives were recommended for various reaches and project phasing plans were developed considering the cost and hydraulic efficiency as well as protection of residents and properties along the unimproved downstream reaches. interim protection for the downstream reaches.

WRC staff played important roles not only in the technical tasks but also in the development of strategies for public involvement, permitting and approval.

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