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LEED v2009
New Construction
Sustainable Sites
Stormwater Design—Quantity Control

LEED CREDIT

NC-2009 SSc6.1: Stormwater design - quantity control 1 point

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LEEDuser expert

Michael DeVuono

PE, CPESC, LEED AP BD+C

Arcadis North America
Senior Water Engineer

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Credit language

USGBC logo

© Copyright U.S. Green Building Council, Inc. All rights reserved.

Intent

To limit disruption of natural hydrology by reducing impervious cover, increasing on-site infiltration, reducing or eliminating pollution from stormwater runoff and eliminating contaminants.

Requirements

Option 1. Design storms
Case 1. Sites with existing imperviousness 50% or less
Path 1

Implement a stormwater management plan that prevents the postdevelopment peak discharge rate and quantity from exceeding the predevelopment peak discharge rate and quantity for the 1- and 2-year 24-hour design storms.

OR

Path 2

Implement a stormwater management plan that protects receiving stream channels from excessive erosion. The stormwater management plan must include stream channel protection and quantity control strategies.

Case 2. Sites with existing imperviousness greater than 50%

Implement a stormwater management plan that results in a 25% decrease in the volume of stormwater runoff from the 2-year 24-hour design storm.

OR

Option 2. Percentile rainfall events
Case 1. Non-zero lot line projects

In a manner best replicating natural site hydrology1 processes, manage onsite2 the runoff from the developed site for the 95th percentile of regional or local rainfall events using Low Impact Development (LID)3 and green infrastructure4.
Use daily rainfall data and the methodology in the United States Environmental Protection Agency’s 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

CASE 2: zero lot line projects

For zero lot line projects located in urban areas with a minimum density of 1.5 FAR (13,800 square meters per hectare net), in a manner best replicating natural site hydrology processes, manage onsite the runoff from the developed site for the 85th percentile of regional or local rainfall events using LID and green infrastructure.

1Natural Site Hydrology is defined as the natural land cover function of water occurrence, distribution, movement, and balance.

2Manage 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.

3Low Impact Development (LID) 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, preserving 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 assistance.

4Green Infrastructure is a soil and vegetation-based approach to wet weather management 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).

Streamlined path available

Achievement of this credit can be documented via a LEED ND v2009 submittal. For more information check out this article.

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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Frequently asked questions

Why do the requirements focus on 1-year and 2-year, 24-hour storms?

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Why include the 1-year storm in the credit requirements? Won't management practices for the 2-year storm be effective?

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How can green roofs count as a stormwater control measure?

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How can I achieve compliance if my project's stormwater control measures are outside the LEED project boundary?

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I have 100-year data—how do I convert to 2-year?

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Is it an acceptable strategy to capture the rainwater into tanks and discharge it into the public sewers after the rainstorm reducing the peak discharge?

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Are there special considerations for international projects?

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What performance threshold do I need to achieve for an Exemplary Performance point?

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The calculations for this credit are always a headache! While our projects are usually awarded the credit, the equations in the LEED Reference Guide are helpful mostly for sizing a reservoir or cistern, but don't help you get to the final results. Does USGBC provide any step-by-step guidance that would make submitting these credits more predictable?

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Documentation toolkit

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Credit achievement rate

XX%

Upgrade to LEEDuser Premium to see how many projects achieved this credit. Try it free »

LEEDuser expert

Michael DeVuono

PE, CPESC, LEED AP BD+C

Arcadis North America
Senior Water Engineer

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USGBC logo

© Copyright U.S. Green Building Council, Inc. All rights reserved.

Intent

To limit disruption of natural hydrology by reducing impervious cover, increasing on-site infiltration, reducing or eliminating pollution from stormwater runoff and eliminating contaminants.

Requirements

Option 1. Design storms
Case 1. Sites with existing imperviousness 50% or less
Path 1

Implement a stormwater management plan that prevents the postdevelopment peak discharge rate and quantity from exceeding the predevelopment peak discharge rate and quantity for the 1- and 2-year 24-hour design storms.

OR

Path 2

Implement a stormwater management plan that protects receiving stream channels from excessive erosion. The stormwater management plan must include stream channel protection and quantity control strategies.

Case 2. Sites with existing imperviousness greater than 50%

Implement a stormwater management plan that results in a 25% decrease in the volume of stormwater runoff from the 2-year 24-hour design storm.

OR

Option 2. Percentile rainfall events
Case 1. Non-zero lot line projects

In a manner best replicating natural site hydrology1 processes, manage onsite2 the runoff from the developed site for the 95th percentile of regional or local rainfall events using Low Impact Development (LID)3 and green infrastructure4.
Use daily rainfall data and the methodology in the United States Environmental Protection Agency’s 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

CASE 2: zero lot line projects

For zero lot line projects located in urban areas with a minimum density of 1.5 FAR (13,800 square meters per hectare net), in a manner best replicating natural site hydrology processes, manage onsite the runoff from the developed site for the 85th percentile of regional or local rainfall events using LID and green infrastructure.

1Natural Site Hydrology is defined as the natural land cover function of water occurrence, distribution, movement, and balance.

2Manage 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.

3Low Impact Development (LID) 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, preserving 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 assistance.

4Green Infrastructure is a soil and vegetation-based approach to wet weather management 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).

Streamlined path available

Achievement of this credit can be documented via a LEED ND v2009 submittal. For more information check out this article.

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.

XX%

Upgrade to LEEDuser Premium to see how many projects achieved this credit. Try it free »

Got the gist of SSc6.1 but not sure how to actually achieve it? LEEDuser gives step-by-step help. Premium members get:

  • Checklists covering all the key action steps you'll need to earn the credit.
  • Hot tips to give you shortcuts and avoid pitfalls.
  • Cost tips to assess what a credit will actually cost, and how to make it affordable.
  • Ideas for going beyond LEED with best practices.
  • All checklists organized by project phase.
  • On-the-fly suggestions of useful items from the Documentation Toolkit and Credit Language.

In the end, LEED is all about documentation. LEEDuser’s Documentation Toolkit, for premium members only, saves you time and helps you avoid mistakes with:

  • Calculators to help assess credit compliance.
  • Tracking spreadsheets for materials purchases.
  • Spreadsheets and forms to give to subs and other team members.
  • Guidance documents on arcane LEED issues.
  • Sample templates to help guide your narratives and LEED Online submissions.
  • Examples of actual submissions from certified LEED projects.

Why do the requirements focus on 1-year and 2-year, 24-hour storms?

The answer to this question is available to LEEDuser premium members. Start a free trial »

(If you're already a premium member, log in here.)

Why include the 1-year storm in the credit requirements? Won't management practices for the 2-year storm be effective?

The answer to this question is available to LEEDuser premium members. Start a free trial »

(If you're already a premium member, log in here.)

How can green roofs count as a stormwater control measure?

The answer to this question is available to LEEDuser premium members. Start a free trial »

(If you're already a premium member, log in here.)

How can I achieve compliance if my project's stormwater control measures are outside the LEED project boundary?

The answer to this question is available to LEEDuser premium members. Start a free trial »

(If you're already a premium member, log in here.)

I have 100-year data—how do I convert to 2-year?

The answer to this question is available to LEEDuser premium members. Start a free trial »

(If you're already a premium member, log in here.)

Is it an acceptable strategy to capture the rainwater into tanks and discharge it into the public sewers after the rainstorm reducing the peak discharge?

The answer to this question is available to LEEDuser premium members. Start a free trial »

(If you're already a premium member, log in here.)

Are there special considerations for international projects?

The answer to this question is available to LEEDuser premium members. Start a free trial »

(If you're already a premium member, log in here.)

What performance threshold do I need to achieve for an Exemplary Performance point?

The answer to this question is available to LEEDuser premium members. Start a free trial »

(If you're already a premium member, log in here.)

The calculations for this credit are always a headache! While our projects are usually awarded the credit, the equations in the LEED Reference Guide are helpful mostly for sizing a reservoir or cistern, but don't help you get to the final results. Does USGBC provide any step-by-step guidance that would make submitting these credits more predictable?

The answer to this question is available to LEEDuser premium members. Start a free trial »

(If you're already a premium member, log in here.)

LEEDuser expert

Michael DeVuono

PE, CPESC, LEED AP BD+C

Arcadis North America
Senior Water Engineer

See all LEEDuser forum discussions about this credit » Subscribe to new discussions about NC-2009 SSc6.1