Integrated Stormwater Facility Design to Address Hydromodification on a College Campus, Livermore, California: Fid-Bau Portal

Integrated Stormwater Facility Design to Address Hydromodification on a College Campus, Livermore, California

Paz, Lucas / Beaman, William / Kramer, Hans

LFR provided civil engineering services to the Chabot-Las Positas Community College District ("the District") to support the proposed Las Positas College Facilities Master Plan ("the Master Plan") development with respect to the design and integration of campus-wide low impact development (LID) stormwater management and drainage improvements. Activities included technical studies, the preparation of civil improvement plans, and technical services needed to support the detailed engineering design of the proposed watershed drainage improvements and associated tasks as required by local, state, and federal regulatory agencies (USACE, USFWS, CDFG, Alameda County, City of Livermore, etc.). The work included the development of conceptual design options for new stormwater management facilities required to satisfy Alameda County's hydromodification and water quality treatment standards. The proposed stormwater facilities consisted of an integrated suite of measures including landscape based bioretention cells, vegetated swales, flow duration control basins, and subsurface storage elements. The Bay Area Hydrology Model (BAHM) was utilized to address hydromodification management goals and to determine sizing and design for each of the distributed, stormwater storage and treatment facilities. Following initial BAHM modeling, LFR developed a detailed Hydrology and Drainage Study ("the Study") to support the conceptual design by characterizing existing hydrology and to model proposed conditions using the BAHM continuous simulation approach. Following issuance of the Study, LFR and the District met and reviewed the conceptual design. Consensus on revisions to the proposed conceptual design was reached and LFR prepared 75% civil design and grading plans for the proposed stormwater control facilities, including connections to the existing storm drain system, accommodations for design around existing utilities, re-runs of the modified BAHM model, and finalization of the Hydrology and Drainage Study. In parallel, in order to evaluate potential flooding impacts associated with the campus storm drain system and the new facilities, a StormCAD hydraulic model was developed and used to determine the extent to which the hydraulic grade line would be impacted. By modeling in this fashion, the effect of re-routing flows in the existing campus stormdrain system through the planned stormwater treatment and flow duration control facilities could be accounted for in the final facility design. Subsequently, LFR prepared final civil engineering design documents for the initial portions of the project slated for construction including the surrounding piping system and hydraulic structures.