Rainwater management | U.S. Green Building Council
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LEED BD+C: New Construction | v4 - LEED v4

Rainwater management

Possible 3 points

Submittal Tips (click to expand)

SS Credit: Rainwater Management

Option 1. Percentile Rain Events - Paths 1, 2, 3
  • Green infrastructure (GI) and low-impact development (LID) strategies can be either structural or non-structural. Undisturbed natural areas on site could be considered LID/GI strategies and contribute to rainfall runoff management. Ensure that the chosen management practices qualify as LID/GI.

    Projects can use the provided calculator, or can submit their own rainfall data and calculations. If less than 10 years of historical rainfall data is provided, using the most conservative daily rainfall is acceptable, and a narrative explaining the data methodology should be provided by the project team.

    The project must manage rainwater runoff from the entire site, even if there is greenfield area within the project boundary. Note that the runoff volume of the chosen storm, under developed conditions, is what is required to be managed and documented, rather than the rainfall volume. All required runoff volume must be retained (infiltrated, reused, etc) within the project boundary.

    The EPA Technical Guidance 438 is not to be followed in its entirety. Only the method to calculate the percentile storm event would be followed. The Credit Requirements do not allow "to the extent technically feasible", as is allowed in the EPA Standard.

Option 1, Path 3. Zero Lot Line Projects Only
  • Provide the floor area ratio; projects can reference the Floor Area Ratio listed in the local zoning code, if that information is available. A detailed count of all the buildings/parcels on a map, similar to LTc: Surrounding Density and Diverse Uses, is not required.

    If necessary, justify why the project should be considered zero lot line.

Option 2. Natural Land Cover Conditions
  • Green infrastructure (GI) and low-impact development (LID) strategies can be either structural or non-structural. Undisturbed natural areas on site could be considered LID/GI strategies and contribute to rainfall runoff management. Ensure that the chosen management practices qualify as LID/GI.

    Projects can use the provided calculator, or can submit their own rainfall data and calculations. If less than 10 years of historical rainfall data is provided, using the most conservative daily rainfall is acceptable, and a narrative explaining the data methodology should be provided by the project team.

    Documents illustrating natural land cover conditions could include historical land cover maps, soil surveys, historical context of the site, interviews with government officials, universities, or community groups that know the history of land cover conditions.

    This option requires hydrologic analysis and comparison of the site under both natural and proposed conditions. Use representative rainfall data such as an analysis of all rainfall events during a statistically representative period of time.

    The term “natural land cover conditions” refers to the vegetation and soil conditions that would have been present on the site prior to development of any kind. This is not the same thing as “greenfield” for the purposes of this option.
    Multitenant complex projects (all Options/Paths)

  • Show the calculations for the entire multitenant complex area. Take into account the runoff volume from the entire area, and design management facilities based on this number, rather than just the project area's runoff volume.

    Describe the centralized approaches and distributed techniques that are used.

Reducing Rainwater Runoff Volume: Case Example and Calculation Walk-through Part 1

Calculating Percentile of Storm Events