Hospitality-NC-v4 SSc4: Rainwater management

  • Understand your site’s natural hydrology

    This credit is a combination of stormwater quality control and quantity control, and includes site-specific criteria for more frequent, low-intensity storm events. There’s even a pathway for zero-lot-line urban projects.

    Executing this credit may be expensive but it can also be economical; it varies greatly depending on site, soil, and project. Additionally, teams should take some time to better understand the historical conditions of the site; this is important as you’ll need to use low-impact developmentAn approach to managing rainwater runoff that emphasizes on-site natural features to protect water quality, by replicating the natural land cover hydrologic regime of watersheds, and addressing runoff close to its source. Examples include better site design principles (e.g., minimizing land disturbance, preserving vegetation, minimizing impervious cover), and design practices (e.g., rain gardens, vegetated swales and buffers, permeable pavement, rainwater harvesting, soil amendments). These are engineered practices that may require specialized design assistance. (LIDLow-impact development: an approach to managing rainwater runoff that emphasizes on-site natural features to protect water quality, by replicating the natural land cover hydrologic regime of watersheds, and addressing runoff close to its source. Examples include better site design principles (e.g., minimizing land disturbance, preserving vegetation, minimizing impervious cover), and design practices (e.g., rain gardens, vegetated swales and buffers, permeable pavement, rainwater harvesting, soil amendments). These are engineered practices that may require specialized design assistance.) and green infrastructure strategies that mimic the site’s natural pre-development hydrology.

    What’s New in LEED v4

    • This credit combines the LEED 2009 stormwater quality and quantity management credits.
    • A specific credit path has been added that accommodates zero lot line projects with reduced rainwater management opportunities.
    • Am expanded multi-tenant complex path has been added for all types of projects in addition to just retail projects.
    • Projects must use onsite low impact development and green infrastructure rainwater management techniques.
    • The credit now uses a metric for testing compliance that calculates the total volume of runoff for the 95th percentile of regional or local rainfall events, instead of one and two-year storm events.

    FAQs

    What calculations will I need to complete?

    You’ll need to calculate (1) the volume of rainfall for the 95th percentile storm, (2) the total stormwater runoff from impermeable surfaces on your site, and (3) the volume of runoff that gets infiltrated or captured for reuse by your green infrastructure.

    95th percentile storm

    USGBC’s calculator helps teams calculate the 95th percentile storm, but you first need to collect at least 10 years of historic rainfall data from the National Climatic Data Center and paste it into the USGBC calculator. The rainfall data will likely be in the format of daily rainfall amounts over historic years. So, expect to input a lot of data points into the calculator.

    Calculating runoff from impermeable areas

    LEED InterpretationLEED Interpretations are official answers to technical inquiries about implementing LEED on a project. They help people understand how their projects can meet LEED requirements and provide clarity on existing options. LEED Interpretations are to be used by any project certifying under an applicable rating system. All project teams are required to adhere to all LEED Interpretations posted before their registration date. This also applies to other addenda. Adherence to rulings posted after a project registers is optional, but strongly encouraged. LEED Interpretations are published in a searchable database at usgbc.org. #100001950 outlines updated protocol for calculating the total runoff. Generally you need to know the rainfall depth (mm) for the 95th percentile storm, the area of the impermeable spaces, and the runoff coefficient, which is described as “Small Storm Hydrology Method Runoff.” See the interpretation for more details.

     

  • SS Credit 4: Rainwater management

    Intent

    To reduce runoff volume and improve water quality by replicating the natural hydrology and water balance of the site, based on historical conditions and undeveloped ecosystems in the region.

    Requirements

    Option 1. Percentile of rainfall events
    Path 1. 95th percentile (2 points except Healthcare, 1 point Healthcare)

    In a manner best replicating natural site hydrology processes, manage on site the runoff from the developed site for the 95th percentile of regional or local rainfall events using low-impact developmentAn approach to managing rainwater runoff that emphasizes on-site natural features to protect water quality, by replicating the natural land cover hydrologic regime of watersheds, and addressing runoff close to its source. Examples include better site design principles (e.g., minimizing land disturbance, preserving vegetation, minimizing impervious cover), and design practices (e.g., rain gardens, vegetated swales and buffers, permeable pavement, rainwater harvesting, soil amendments). These are engineered practices that may require specialized design assistance. (LIDLow-impact development: an approach to managing rainwater runoff that emphasizes on-site natural features to protect water quality, by replicating the natural land cover hydrologic regime of watersheds, and addressing runoff close to its source. Examples include better site design principles (e.g., minimizing land disturbance, preserving vegetation, minimizing impervious cover), and design practices (e.g., rain gardens, vegetated swales and buffers, permeable pavement, rainwater harvesting, soil amendments). These are engineered practices that may require specialized design assistance.) and green infrastructure.

    Use daily rainfall data and the methodology in the U.S. Environmental Protection Agency (EPA) Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438 of the Energy Independence and Security Act to determine the 95th percentile amount.

    OR
    Path 2. 98th percentile (3 points except Healthcare, 2 points Healthcare)

    Achieve Path 1 but for the 98th percentile of regional or local rainfall events, using LID and green infrastructure.

    OR
    Path 3. Zero lot line projects only – 85th Percentile (3 points except Healthcare, 2 points Healthcare))

    The following requirement applies to zero lot line projects in urban areas with a minimum density of 1.5 FARFloor-area ratio is the density of nonresidential land use, exclusive of parking, measured as the total nonresidential building floor area divided by the total buildable land area available for nonresidential structures. For example, on a site with 10,000 square feet (930 square meters) of buildable land area, an FAR of 1.0 would be 10,000 square feet (930 square meters) of building floor area. On the same site, an FAR of 1.5 would be 15,000 square feet (1395 square meters), an FAR of 2.0 would be 20,000 square feet (1860 square meters), and an FAR of 0.5 would be 5,000 square feet (465 square meters).. In a manner best replicating natural site hydrology processes, manage on site the runoff from the developed site for the 85th percentile of regional or local rainfall events, using LID and green infrastructure.

    OR

    Option 2. Natural land cover conditions (3 points except Healthcare, 2 points Healthcare)

    Manage on site the annual increase in runoff volume from the natural land cover condition to the postdeveloped condition.

    Projects that are part of a multitenant complex only

    The credit requirements may be met using a coordinated approach affecting the defined project site that is within the master plan boundary. Distributed techniques based on a watershed approach are then required.

    SITES-LEED Equivalency

    This LEED credit (or a component of this credit) has been established as equivalent to a SITES v2 credit or component. For more information on using the equivalency as a substitution in your LEED or SITES project, see this article and guidance document.

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Mar 26 2017
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