CS-2009 SSpc16: Rainwater management

  • Natural, not structural, strategies

    This credit is based upon LEED BD+C 2009 SS Credits 6.1 and 6.2, and is intended to incentivize the use of natural best practices instead of structural practices.

    Definitions:

    The baseline condition is the site condition prior to LEED registration.

    Green infrastructure is a soil and vegetation-based approach to wet weather manage-ment that is cost-effective, sustainable, and environmentally friendly. Green infrastructure management approaches and technologies infiltrate, evapotranspire, capture and reuse stormwater to maintain or restore natural hydrologies (US EPA).

    Low Impact Development (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.) is defined as an approach to managing stormwater 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 such as minimizing land disturbance, pre-serving vegetation, minimizing impervious cover, and design practices like rain gardens, vegetated swales and buffers, permeable pavement, rainwater harvesting, and soil amendments. These are engineered practices that may require specialized design assis-tance.

    “Manage Onsite” refers to capturing and retaining the specified volume of rainfall to mimic natural hydrologic function. This includes, but is not limited to, strategies that manage volume through evapotranspiration, infiltration, or capture and reuse.

    A multi-tenant complex is defined as a site that that was master-planned for the devel-opment of stores, restaurants and other businesses. Retailers may share one or more services and/or common areas.

    Natural Site Hydrology is defined as the natural land cover function of water occurrence, distribution, movement, and balance.

    Credit Submittals

    General

    1. Register for Pilot Credit(s) here.
    2. Register a username at LEEDuser.com, and participate in online forum
    3. Submit feedback survey; supply PDF of your survey/confirmation of completion with credit documentation

    Credit Specific

    NC, CS, SCHOOLS, RETAIL, HEALTHCARE

    Option 1

    • Provide a narrative describing the proposed practices to be implemented on the project site and what qualifies these strategies as LID or green infrastructure techniques that best replicate natural site hydrology processes.
    • Provide any applicable specifications, drawings, and storage and infiltration cal-culations of the LID practices utilized on site.
    • Provide calculations showing the 95th percentile regional or local rainfall event amount and how the runoff is managed onsite by these practices.

    Option 2 – Path 1

    • In addition to the submittals listed in Option 1, provide any applicable specifica-tions, drawings, and water balance calculations describing natural site hydrology and post-development partitioning of annual rainfall volumes. Natural site hydrol-ogy conditions can be determined using a combination of pre-settlement vegeta-tion maps and soil maps. Where detailed pre-settlement vegetation maps do not exist, typical land cover for the project’s EPA Level IV Ecoregion can be used.

    Option 2 – Path 2

    • Provide all submittals listed in Option 1 for the 98th percentile regional or local rainfall event.

    Zero Lot Line Projects:

    • Provide all submittals listed under “NC, CS, Schools, Retail, Healthcare” above, but for the 85th percentile threshold.
      Provide density calculations or density information from the municipality in which the project is located.

    Retail NC Projects:

    • Provide all submittals listed under “NC, CS, Schools, Retail, Healthcare” above.
    • Provide a narrative describing the distributed techniques and watershed ap-proach, if used.

    EBOM

    Establishment:

    • Provide any applicable specifications, drawings and calculations demonstrating that the implemented strategies result in the reduction of impervious surfacesAn area of ground that development and building have modified in such a way that precipitation cannot infiltrate downward through the soil. Examples of impervious surfaces include roofs, paved roads and parking areas, sidewalks, and soils that have been compacted either by design or by use. and/or capture and treat water from the impervious surfaces.
    • Provide a narrative describing the inspection program, including details about timing/schedule, scope, and procedure for identifying and performing any neces-sary repairs or stabilization.

    Performance:

    • Provide documentation and dates of all inspections, maintenance, and repairs performed.

    Additional Questions

    1. The goal is to replicate the natural hydrology and water balance of the site. What obstacles make this difficult? Obstacles may or may not be specific to the proposed credit requirements.
    2. What climate data source is most applicable for your area?
  • USGBC

    Excerpted from LEED 2009 for Core and Shell Development

    SS Pilot Credit 16: Rainwater management

    Intent

    Pilot Credit Closed

    This pilot credit is closed to new registrations

    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

    * This credit language is drawn from the LEED v4 draft. Where other point totals are noted, this pilot credit is worth 1 point in total. *

    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.

    Path 1.

    Achieve Option 1 and manage on site the annual increase in runoff volume from the natural land cover condition to the postdeveloped condition.

    OR

    Path 2.

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

    Zero lot line projects only (3 points)

    The following requirement applies to zero lot line projects in urban areas with a minimum density of 1.5 FAR. 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.

    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.

    General Pilot Documentation Requirements

    Register for the pilot credit

    Credits 1-14

    Credits 15-27

    Credits 28-42

    Credits 43-56

    Credits 57-67

    Credits 68-82

    Credits 83-103

    Credit specific

    Option 1:

    • Provide a narrative describing the proposed practices to be implemented on the project site and what qualifies these strategies as LID or green infrastructure techniques that best replicate natural site hydrology processes.
    • Provide any applicable specifications, drawings, and storage and infiltration calculations of the LID practices utilized on site.
    • Provide calculations showing the 95th percentile regional or local rainfall event amount and how the runoff is managed onsite by these practices.

    Option 2 – Path 1:

    In addition to the submittals listed in Option 1, provide any applicable specifications, drawings, and water balance calculations describing natural site hydrology and post-development partitioning of annual rainfall volumes. Natural site hydrology conditions can be determined using a combination of pre-settlement vegetation maps and soil maps. Where detailed pre-settlement vegetation maps do not exist, typical land cover for the project’s EPA Level IV Ecoregion can be used.

    Option 2 – Path 2:

    Provide all submittals listed in Option 1 for the 98th percentile regional or local rainfall event.

    Zero Lot Line Projects:

    • Provide all submittals listed above, but for the 85th percentile threshold.
    • Provide density calculations or density information from the municipality in which the project is located.

    Retail NC Projects:

    • Provide all submittals listed above.
    • Provide a narrative describing the distributed techniques and watershed approach, if used.
    Additional questions:
    1. The goal is to replicate the natural hydrology and water balance of the site. What obstacles make this difficult? Obstacles may or may not be specific to the proposed credit requirements.
    2. What climate data source is most applicable for your area?
    Changes:
    • 1/15/2013: update with SSc4 from LEED v4 draft

      • BD+C: wording changes, the Stormwater Calculator methodology was removed
      • EBOMEBOM is an acronym for Existing Buildings: Operations & Maintenance, one of the LEED 2009 rating systems.: Revised requirements to allow for rwm practices currently in place on the EBOM project, and to make the credit more performance-based

    16 Comments

    0
    0
    Amir Salehi
    Oct 16 2016
    Guest
    18 Thumbs Up

    how the impact categories are used to evaluate each credit

    I want to know how each credits weight among categories, for example this credit is in which category and the degree of its importance in that category?

    Post a Reply
    0
    0
    Joseph Haupt
    Dec 20 2013
    Guest
    61 Thumbs Up

    SSpc16 - Rainwater Management

    There are local/regional requirements that may be more applicable, but it is not apparent how local/regional requirements could be included in this credit. For example, in my project area the 90% exceedance interval is used as a measure for fully capturing or infilltration of runoff. The 90% exceedance interval rainfall is provided by the local agency. Doing the statistical analysis for this pilot credit is not difficult. Unfortunately, the source links listed in the EPA "Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438" are no longer applicable, so finding the data can be challenging.

    1
    1
    0
    Michael D. DeVuono Senior Staff Engineer, T&M Associates Dec 20 2013 LEEDuser Expert 6000 Thumbs Up

    If you are in the USA, you can use the EPA's National Stormwater Calculator to determine the 95-99 percentile event. Otherwise, pull annual rainfall data from NOAA, and plug it into a spreadsheet.

    Post a Reply
    0
    0
    Anna Korinkova
    Nov 12 2013
    LEEDuser Member
    2199 Thumbs Up

    Time period

    Our building will implement a stormwater harvesting system. 95th percentil of regional or local rainfall event will be retained in a rainwater collection tank and then used for flushing toilets and urinals. My question is, does this credit require us to use the collected water for some specific time period? In our case, the water will be used within 5 days.
    Thank you for any suggestions.

    1
    3
    0
    Michael D. DeVuono Senior Staff Engineer, T&M Associates Nov 12 2013 LEEDuser Expert 6000 Thumbs Up

    Jiri, there is no dewatering requirement that I am aware of. Work with your CE to provide an adequate bypass (or storage) in the event of back to back storms, or more intense storms.

    2
    3
    0
    Michael D. DeVuono Senior Staff Engineer, T&M Associates Nov 12 2013 LEEDuser Expert 6000 Thumbs Up

    You may also want to look at the SSc 6.2 forums where this has been discussed at length, along with some calculations that demonstrate the probability of back to back storms of particular depth as duration.

    3
    3
    0
    John Nichols Senior Sustainability Coordinator, Moseley Architects May 07 2014 LEEDuser Member 208 Thumbs Up

    We often have projects with the same rainwater reuse strategy as Jiri describes. Figuring out how to count these systems towards SSc6.1/6.2 and now Pilot Credit WEpc16 is not very straightforward. I think more guidance should be given to project teams using such rainwater harvesting methods. If there is a particular expectation for how quickly the captured rainwater must be drawn down, it seems like this should be communicated in the credit requirements?

    Post a Reply
    0
    0
    Hannah Sokol Senior Associate, Sustainability Group U.S. Equities Realty
    Aug 15 2013
    Guest
    49 Thumbs Up

    SSc 6.1, 6.2, and SSpc16

    Just to confirm, this pilot credit can be pursued in addition to the current stormwater management credits SSc6.1 and 6.2, is that correct?

    1
    1
    0
    Tristan Roberts LEED AP BD+C, Executive Editor – LEEDuser, BuildingGreen, Inc. Nov 05 2013 LEEDuser Moderator

    Hannah, that's correct.

    Post a Reply
    0
    0
    nancy Charron Principal Traho Architects
    Jul 05 2012
    Guest
    63 Thumbs Up

    Historical uses

    I have a urban site project that has had 2 prior buildings before this one. The most recent prior historical use was all impervious surfacesAn area of ground that development and building have modified in such a way that precipitation cannot infiltrate downward through the soil. Examples of impervious surfaces include roofs, paved roads and parking areas, sidewalks, and soils that have been compacted either by design or by use.. Is there measurement for net improvement from most recent use or just the % and the "undeveloped Eco-system" equivalent.

    1
    1
    0
    Theresa Backhus Sites Technical Specialist, LEED, USGBC Sep 04 2012 Guest 1011 Thumbs Up

    Hi Nancy,
    The pilot credit does not measure the net improvement from the site's most recent use. The goal is to analyze and mimic the natural site hydrology conditions (as much as possible), meaning the conditions found prior to any development. In your case, it sounds like it might be the site conditions prior to both of the buildings (if there was no development or grading before that).

    I hope this answers your question. If you have additional questions about the methodology listed in this pilot credit, I would be happy to help.

    Post a Reply
    0
    0
    Laura Millberg Sustainable Development Minnesota Pollution Control Agency
    Jan 12 2011
    Guest
    205 Thumbs Up

    Options and Paths for Pilot Credit 16

    I'm confused by the Options and Paths for this credit. Does Option 2 achieve more credits than Option 1?

    1
    4
    0
    Chrissy Macken Assistant Project Manager, LEED v4 , U.S. Green Building Council Jan 12 2011 Guest 1799 Thumbs Up

    Hi Laura -

    Thanks for posting. It is anticipated that, once these requirements are part of a balloted and weighted rating system, that Option 2 will likely earn an additional point. Since the requirements are currently in the Pilot Library, you would get only one point, whether your pursue Option 1 or 2. Does this help?

    2
    4
    0
    Laura Millberg Sustainable Development, Minnesota Pollution Control Agency Jan 12 2011 Guest 205 Thumbs Up

    Yes, thanks. I am not working on a project that could apply for the credit, but I do want to bring information about the proposed credit to my state agency's Green Stormwater Infrastructure Team to solicit comments that I can submit to USGBC by the Friday deadline. Is there any more supporting information about the proposed/pilot credit that I could provide to my team this afternoon for review?

    3
    4
    0
    Chrissy Macken Assistant Project Manager, LEED v4 , U.S. Green Building Council Jan 12 2011 Guest 1799 Thumbs Up

    I would suggest that you send them to the USGBC Rating System Development page: www.usgbc.org/leed/development so they can view all of the proposed Sites and Water changes and comment on those credits too. Additionally, there are supporting documents such as summaries of changes and an FAQ document.

    4
    4
    0
    Chris Fleming Senior Project Manager, EMH&T Aug 17 2011 Guest 68 Thumbs Up

    I just finished submitting for this credit, and I agree with Laura's comment. Option 2 is more restrictive than option 1 and should get an additional credit.

    Post a Reply

    Start a new LEED comment thread

    Feb 25 2017
    Type the characters you see in this picture. (verify using audio)
    Type the characters you see in the picture above; if you can't read them, submit the form and a new image will be generated. Not case sensitive.

    Copyright 2017 – BuildingGreen, Inc.