Green Infrastructure Retrofits: Rapid Identification and Conceptual Design
During 2015, with budget provided by the San Francisco Estuary Project and San Francisco Estuary Institute under a Proposition 84 grant, the author identified and prepared conceptual designs for eight green infrastructure retrofits in San Francisco Bay region communities. This presentation summarizes the approach and methods developed for the purpose, and lessons learned. Existing tools and knowledge for planning green infrastructure are at two distinct scales: At a watershed scale, GIS-based planning tools for green infrastructure retrofits can help identify general areas—neighborhoods or city blocks—where Low Impact Development (LID) is needed, or where LID could make a difference by reducing runoff pollutant loads. At a project scale, built retrofit projects provide experience and insight into the engineering requirements and obstacles that may be encountered “on the ground.” This project identification and conceptual design process links these two scales and enables the planner or engineer to rapidly and cost-effectively scope potential on-the-ground projects. The resulting information may be used to select among alternative projects, to apply for grants, to solicit design/build proposals, to budget costs, to conduct community outreach, to process environmental clearances, and/or as the first step in producing construction drawings. Methods and resources include: • Using maps and satellite imagery to rapidly identify suitable locations for bioretention facilities • Using storm drain maps to locate catch basins and manholes, and to get a sense of general topography • Using Google Street View to gain an understanding of existing surfaces and drainage, and to confirm locations of drainage structures • Reconnoitering the site • Using a rotating construction laser level and rod to confirm drainage areas and direction of flow • Procedure for analysis and design for flat streets and for sloped streets • Sizing ratios; coordinating drainage areas with facility areas Design strategies include: • Identifying bioretention facility locations that will minimize costs and impacts • Designing facilities to be flat while minimizing the need for high curbs or retaining walls • Adapting existing catch basins and piped infrastructure for facility inlets and outlets • Using existing gutters, removed catch basins, and new trench drains to expand the area tributary to a bioretention facility The presentation will include a summary of key lessons learned that will be of interest to green infrastructure planners and designers, as well as to those evaluating the potential of green infrastructure retrofits to make a difference in surface water quality in their communities. The presenter will engage the audience through structured questions directed to the audience (show of hands/invitation to answer or comment) at the beginning, during, and at the end of the technical presentation.
Dan Cloak has assisted California municipalities with stormwater NPDES compliance since 1992. He has been Principal of Dan Cloak Environmental Consulting since 2002. Dan is the author of several guidebooks used to implement Low Impact Development for stormwater NPDES compliance, including the Bay Area Stormwater Management Agencies Association's Post-Construction Manual for Phase II municipalities.