Design and Size your Green Infrastructure Best Management Practices

Overview: This is overview of some general guidance for designing your site and implementing it successfully.

Applicability: Determine is an LID is practice is appropriate for managing runoff from roofs, pavements, sidewalks, or landscapes (Applicability by Runoff Surface Type table) or whether it is appropriate on sites with steep slopes, high groundwater tables, shallow bedrock, inadequate setbacks, slow draining soils, or expansive clay soils (Applicability for Challenging Sites)

LID Infiltration Facility Calculator (xls): Size vegetated facilities including rain gardens, stormwater planters, and vegetated swales with check dams without using complicated proprietary modeling software. Download the model and read about it or watch a  tutorial video on how to enter data and interpret results.

LID Checklist (pdf, xls): The LID Checklist includes over 250 best practices that might be employed during all project phases. A matrix of the practice against a column of different considerations makes it easy to see which practices are applicable with a Y, N, or M (yes, no or maybe, it depends on the implementation).

LID Facility Designs: Download Standard Details of LID facilities including rain gardens, stormwater planters, swales, vegetated filter strips, porous pavements, soakage trenches, and drywells in AutoCAD (dwg), graphic (jpg) or Adobe Acrobat (pdf) format. Tables include additional information for design modifications that might be considered as well as whether the practice:

  • Protects both on- and off-site water quality

  • Substantially reduces runoff volumes

  • Is appropriate in clay soils, and

  • Is regulated as an Underground Injection Control (UIC) (and how to avoid UICs by design)

Seattle Public Utility Design Checklists:
These checklists are helpful for designers and plans reviewers who want to check that sufficient detail has been shown on the plans and that certain conditions are met.

UICs: Underground Injection Control (UIC) facilities are rule authorized by the Oregon Department of Environmental Quality and may include any stormwater facility that infiltrates directly into the soil subsurface. This includes drywells and soakage trenches where volumes of runoff are infiltrated or "injected" into the subsurface via perforated manholes or pipes. Learn how to avoid turning other infiltration facilities that are not usually UICs (like rain gardens, swales, and porous pavement) into UICs.

Porous Pavement Hydrologic Calculator: Size the depth of base rock needed to store and infiltrate the desired storm size in Excel without using proprietary modeling software. Download the model and read about it or watch a  video to learn how to enter data and interpret results.