U.S. Army Corps of Engineers Los Angeles District
Preliminary Design Report, Conceptual Design, Topographic Mapping, Environmental Surveys, Environmental Assessment, Hydrogeological Modeling, Hydrologic and Hydraulic Models, Environmental Compliance, Reports, Meetings
As prime consultant, DRC engineers developed a Preliminary Design Report to address alternatives for flood control measures in the U.S./Mexico border communities of Nogales, AZ, and Nogales, Sonora. The study coordinated and reviewed existing data and literature, hydrologic and hydraulic models for Arroyo Nogales, delineated three concept designs and cost estimates for structural improvements to reduce the potential for flooding, project schedules for major phases of design and construction activities for each alternative, and listed potential environmental requirements.
DRC reviewed existing information and previously published documents pertaining to flood damage, runoff, and flood control measures in Nogales, Sonora and Nogales, Arizona. The information contained existing watershed scale topographic mapping for use in rainfall-runoff analyses, topographic mapping for use in hydraulic analyses and preliminary design of alternatives, topographic cross section data for Arroyo Nogales in Nogales Sonora. Information included historical stream flow data on Arroyo Nogales and tributaries and regional discharge frequency relationships for the project area in the United States and Mexico. Our engineers attended meetings with IBWC Staff at the Nogales Project Field Office to discuss flooding issues in the Nogales area, potential project alternatives and coordinated with pertinent offices at the Los Angeles District, including the Plan Formulation Branch (Planning Division), Hydrology and Hydraulics Branch (Engineering Division), Engineering Design Branch (Engineering Division).
DRC developed the with-project hydrologic models by modifying the existing Corps without-project models for concentration points in Nogales, Sonora to include detention facilities, diversions, pumping, and channel improvements in the three alternatives. We performed hydraulic analyses for the 5-, 10-, and 25-year events for the three alternatives.
DRC prepared conceptual designs of the proposed features in the three alternatives which included enough detail in regards to location, dimension, foundation, and materials so that the element could be evaluated in terms of performance at the given flood level, overtopping, and long term stability; so that DRC can prepare cost estimates for construction, operations, and maintenance of each alternative. DRC also prepared cost estimates for each alternative.
DRC presented the preliminary project results to the USACE, the International Boundary and Water Commission (IBWC), and stakeholders at two project meetings in Nogales. These meetings determined the final outcome. DRC coordinated with IBWC to identify requirements for environmental compliance documents and other project permits for work in Mexico, and any applicable National Environmental Policy Act (NEPA) requirements for each alternative. DRC also prepared a comprehensive report that documents the approaches, methodologies, alternatives, and results of the analyses.