CS-2009 SSc6.2: Stormwater Design—Quality Control

  • NC CS Schools SSc6.2 Credit req's diagram
  • Use natural infiltration

    Many project teams are reluctant to attempt this credit because conventionally engineered solutions don’t always meet LEED requirements. Don’t be deterred. The best and easiest way to improve the quality of stormwater is to let water permeate the ground through increased landscaping and reduced impervious areas. As long as your soil type has a good infiltration rate, letting stormwater seep into the ground will treat 100% of the pollutants associated with the stormwater runoff. Let natural infiltration do as much of the work possible before using more expensive mechanical methods. In urban sites, infiltration options can be very limited and a rainwater cistern or green roof might be the best approach for credit compliance.

    Pollution Prevention

    This credit deals with the prevention of polluted runoff, and uses Total Suspended Solids (TSSTotal suspended solids (TSS) are particles that are too small or light to be removed from stormwater via gravity settling. Suspended solid concentrations are typically removed via filtration.) as the indicator of level of pollution. Nitrates and phosphates are not accounted for in the credit calculations. Projects can use biological or mechanical treatment methods for smaller and more frequent storms for credit compliance. In order to earn the credit you must be able to show your stormwater treatment system is effective at treating all rainstorms for any year up to 90% of the average annual rainfall event. 

    Numerous environmental benefits

    Retaining and reusing stormwater on-site can provide numerous environmental benefits, along with LEED synergies. In addition to trapping suspended solids, capturing stormwater for reuse can reduce peak runoff rate and volume, helping with SSc6.1: Stormwater Design—Quantity Control, and help with water efficiency credits WEc1, WEc2, and WEc3.

  • FAQs for SSc6.1 and SSc6.2

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

    The 2-year, 24-hour design stormA 2-year, 24-hour design storm is a nationally accepted rate that represents the largest amount of rainfall expected over a 24-hour period during a 2-year interval. The rate is the basis for planning and designing stormwater management facilities and features. is a storm that has a high probability of happening and contributing to stormwater pollution. A 2-year storm has a 50% chance of happening in a given year, whereas a 1-year storm has a 100% chance.

    It should be noted that most state or local programs only require projects to meet regulatory requirements related to flooding and/or water quality.  This type of stormwater management program is designed to control the large, infrequent storm events that cause flooding, but not to manage smaller storm events that we now know cause the majority of the overall erosion and quality concerns because of their much higher frequency. The criteria of SSc6.1 are designed to ensure that both concerns are addressed in LEED projects that achieve this credit.

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

    It depends on how you look at it. Here's how LEEDuser Expert Michael DeVuono describes it: Think about it in terms of a simple pre>post analysis. Your one year "pre" number will be smaller than your 2-year "pre" number. Sometimes that 1-year number is so small that you have to choke back a lot of water, to ensure the "post" 1-year is smaller. This raises the required storage volume for the BMPBest Management Practice. So if you're looking at both the 1- and 2-year events, you may have a greater storage need than if you simply looked at the 2-year event. The 2-year "pre" number will be bigger, so you can let more out in the "post."

    How can green roofs count as a stormwater control measure?

    There are different approaches to this. One approach is to ensure that green roof soil depth and retention capacity allows for the 2-year, 24-hour design storm.

    However, simply taking a “CN credit” for a green roof is usually beneficial enough. (The Curve Number or CN provides a number characterizing the runoff properties for a particular soil and ground cover.) Instead of the roof being modeled as impervious (with a CN of 98 which produces a high rate of runoff) some projects with extensive green roofs have used a lawn CN—usually around 61. In the calculations this results in a lower overall rate of runoff for the site, and is usually a more feasible option that providing stormwater storage in the roof media itself. If you can model your site so there is less runoff, there is less runoff volume that needs to be stored.

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

    Projects with stormwater control measures outside the LEED project boundary may be accepted if the measures appropriately take into account neighboring facilities by demonstrating that the existing stormwater management systems that serve the LEED project boundary meet the LEED requirements for all areas within the site serviced by those systems. LEED 2009 campus projects are required to reference USGBC's AGMBC guidance, which has specific guidelines for stormwater. For more on this see, for example, LI#2275 from 08/22/2008.

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

    Storm intervals don’t convert. These numbers represent specific storm event probability. A 100-year storm has a 1% chance of happening in a given year, while a 2-year storm has a 50% chance of happening in a given year. The best resource for rainfall intensity data is NOAA’s Hydrometeorological Design Studies Center Precipitation Frequency Data Server. Further guidance on interpolating 2-year, 24-hour storm event can be found in LEEDuser's EBOM SSc6 Guidance.

    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?

    This is a common strategy for reducing peak rate, which will help you comply with SSc6.1, but you'll need to add onsite reuse or infiltration to meet SSc6.2 requirements.

    A sample graph illustrating the 95th percentile rainfall event

    Are there special considerations for international projects?

    In 2012, an additional compliance option was added to SSc6.1 that was specifically written with international projects in mind. This can be found in the credit language, and is fully supported on the most recent LEED Online forms. Projects in some countries can have trouble finding the stormwater data they're looking for. Some useful sites are posted in LEEDuser's Resources tab.

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

    LEED Interpretation #10108 dated 11/01/2011 gives guidance in achieving Exemplary Performance. Achievement of the exemplary performance point encompasses both quantity and quality measures, and includes a comprehensive approach to capture and treat stormwater runoff.

    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?

    No. USGBC has indicated that providing step-by-step instructions for this entire calculation process within the context of LEED reference documents is not possible. Various methods and computer-based software programs are available to estimate stormwater runoff rates and volumes, and the exact methods used for a particular project will depend upon the data available for a given site and the preferences of the qualified professional (typically a civil engineer) performing the calculations.

    LEEDuser has heard from LEED project teams that the LEED expert on the project is sometimes expected to do the calculations for these credits, even if that person isn't a stormwater expert. We recommend a more integrated process in which the civil engineer documents this credit.


  • Best Practices
  • Gotcha
  • Action Steps
  • Cost Tip


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  • Explore low-impact development strategies such as bioretention, vegetated swales, a green roof, rainwater cisterns, and porous pavement. These strategies  reduce hardscape and impervious areas, thereby reducing runoff. Some strategies such as green roofs and rainwater cisterns have space needs, so be sure to consider their requirements. The owner and civil engineer should work together to determine the feasibility and rough cost increase of including rainwater cisterns or a green roof.

  • The easiest way to earn this credit is through decreasing your project’s impervious area by reducing the building footprint, increasing landscaped areas, and disconnecting impervious areas—designing sidewalks, roofs, and parking areas so that the runoff is not directed to a drainage system or other hardscapes. Use natural infiltration, promoted by strategies like green roofs, downspout disconnection (disconnecting the downspouts so that runoff is directed to softscape area instead of storm drains), softscapes, bioswales, porous paving, and rain gardens.

  • Overlapping strategies and technologies address SSc6.1: Stormwater Design—Quantity, as well as SSc6.2. Vegetative swales, for example, can contribute to both credits—integrate the requirements of both for best results. Keep in mind, however, that each credit requires different calculations and methodologies. Reducing the quantity of stormwater runoff for SSc6.1 does not always equate to a quality improvement for SSc6.2.

  • Using site space for stormwater management is often a must. Architects and owners may see stormwater best management practices (BMPs) as wasting valuable land—a mentality that can make this credit difficult. It may help to stress that stormwater BMPs can act as aesthetic features that enhance the quality of the site and add value to the project. Creative, integrated approaches can even reduce space-hogging, unattractive strategies like detention ponds while adding amenities with multiple benefits, like green roofs.

  • Use an integrated design strategy to improve the quality of stormwater runoff. True integration requires the input and collaboration of the entire site team, including the civil engineer, landscape architect and architect. Don’t leave stormwater management solely in the hands of the civil engineer.

  • Make sure that all team members understand landscape and hardscape tradeoffs. All team members should know how these details affect stormwater generation, runoff, and possible capture, treatment, and reuse strategies.

  • Indirect benefits of stormwater systems are just as real as direct costs to the project, but can be harder to quantify. These include issues like reducing the burden on the municipal system; reducing contaminants in waterways; reducing peak runoff, making stream habitats more consistent; reducing the temperature of runoff, which improves the conditions for aquatic life; and reducing erosion. If your municipal codes are more stringent and come with higher fees, there may be a more direct cost benefit to the project from stormwater mitigation. Any additional costs in this case are likely to be for documentation purposes, although most municipalities require similar stormwater documentation.

Schematic Design

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  • Familiarize yourself with natural hydrology, site topography and soil infiltration rates by conducting site visits and tests. Confirm that soils are capable of infiltrating 90% of annual rainfall. If the porous site area cannot infiltrate 90% of rainfall, you will need to add structural controls or soil amendments to achieve the target.

  • Research local regulations on the stormwater quality requirements, as well as regulations on the collection, storage and reuse of stormwater, including water rights.

  • Research historical climate records to understand expected storm event frequency, intensity, and duration.

  • Runoff Treatment EquivalentsThe civil engineer determines the degree of stormwater management required by LEED based on average annual rainfall. The engineer uses these calculations to determine the type and size of systems needed. Managing 90% of the average annual rainfall is equivalent to treating the amounts listed on this table.

  • Develop a project-wide water budget and a landscape irrigation water budget. This will help teams decide if reusing rainwater may be appropriate and where to use it—typically either in irrigation or toilet flushing.

  • The civil engineer can conduct a cost-benefit analysis of stormwater-reduction strategies, including cisterns, porous pavement, rain gardens, parking garages (instead of parking lots), detention ponds, green roofs, sand filters, or detention tanks. Some of these strategies may be perceived as added costs, but this analysis may show that with reduced infrastructure, these environmental strategies are cost-neutral, or better.

  • Depending on local regulations, this credit may be standard practice. For example, new developments following the Commonwealth of Massachusetts Stormwater Policy must provide at least 80% of TSS removal rates through BMPs. Also, any projects areas that are required to follow the U.S. Environmental Protection Agency, Section 6217(g) of the 1900 Coastal Zone Management Act Reauthorization Amendments, are required to meet these same TSS standards.

  • In locations where local stormwater regulations are similar to or more stringent than LEED requirements, implementation of this credit will incur minimal additional cost for documentation purposes. In locations where it goes beyond standard practice, it may require additional design and documentation costs.

  • Some municipalities require documented stormwater management. The documentation for LEED requirements should not represent a significant soft cost premium.

  • Integrating the stormwater plan into the design at an early stage and calculating the pollution reduction percentages will decrease additional costs as the landscape and building infrastructure can be designed accordingly.

Design Development

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  • Explore potential synergies and tradeoffs with other LEED credits or green building strategies. Items to discuss can include the use of parking lots vs. parking garages (SSc7.1) for stormwater management, rain gardens, trees for shading hardscapes (also SSc7.1), tress for passive solar design (EAc1), impervious surfaces, planting material (WEc1), wind-break opportunities, water reuse (WEc3), rainwater capture (WEc1) and acoustical barriers

  • The civil engineer calculates the minimum volume of stormwater that must be treated through infiltration, reuse or mechanical treatment to meet the 80% TSS removal rates after development. Base this calculation on the average annual rainfall for the project.

  • Calculate the potential for stormwater reuse and corresponding cistern sizes to accommodate stormwater reuse for irrigation or other applications like toilet flushing. Be sure to allocate proper space for rainwater cisterns.

  • The civil engineer develops a stormwater management plan for post-development suspended sediment loads, detailing acceptable BMPs and their associated TSS removal rates. Reference the LEED 2009 Reference Guide’s table of Effectiveness of Management Practices for Total Suspended Solids Removal from Runoff. (Also shown here.)

    Management practices for removing TSS

  • The civil engineer and the landscape architect design the landscape and stormwater systems to maximize infiltration and collect water where possible. These systems must be designed based on the watershed region, and the BMPs employed must in combination remove 80% of the TSS for the post-construction design. The civil engineer will need to verify that the design meets the LEED requirements.

  • Find TSS removal rate data in state or local best management practice manuals.

  • You must design any BMPs to local standards that have adopted an 80% TSS removal rate criterion, or use existing data that has monitored the TSS removal rates of different stormwater controls.

  • Previously existing stormwater management systems on the project site can be used towards credit compliance as long as requirements are met.

  • The stormwater design should reflect unique site features, attempt to minimize impacts on natural stormwater hydrology, and promote infiltration and treatment of stormwater runoff.

  • Treating captured stormwater to the quality standards required for this credit provides the potential for a clean water source for irrigation or toilet flushing, and a further reduction of the burden on municipal treatment facilities.

  • Consider contouring the land to direct stormwater to planting beds to reduce irrigation needs of potable water in locations where stormwater capture and reuse is not allowed. Parking lots and walkways can be graded to direct runoff to depressed swales or bioretention facilities with perforated pipes and other slow release infiltration mechanisms. This design offers better stormwater management than typical elevated or impervious planters.

  • Soil type, planting medium and plant species must be considered for their capacity to promote infiltration. For example, clay soils do not allow for good infiltration rates and an engineered soil or compost could be added to allow for better absorption.

  • Stormwater storage and biofiltration can be incorporated into landscape features and can also include educational elements for occupant and community benefits.

  • All design methods must consider the soil type and infiltration rates to show that soils are capable of treating the appropriate amount of rainfall.

  • In urban areas and sites with little land, use a variety of features to achieve project goals. For example, green roofs and rainwater cisterns may be effective in these situations. Capturing rainwater for irrigation will reduce the amount of stormwater runoff leaving the site as well as outdoor potable water use. Reusing captured rainwater for toilet flushing will have similar effects, in addition to reducing potable water use indoors. In some cases, cisterns with open bottoms may be effective in storing stormwater runoff and will encourage infiltration and reduce the peak flow rate discharge. These cisterns may be incorporated under parking areas or other hardscape.

  • Porous pavement can be incorporated into many sites and climatic conditions. Proper design, installation, and maintenance is important. Work with an experienced contractor, and verify that porous paving will work with your site’s climate and soil conditions. For example, snowplowing, sanding, and salting can damage porous paving.

  • Stormwater systems can range from bioswales to cisterns to green roof systems, and range greatly in cost and effectiveness depending on the application. Certain on-site stormwater treatment technologies can be costly but serve additional environmental purposes and may contribute to various other LEED credits related to open space and heat island effect. See ‘Related Credits.’ These strategies should be considered and designed for multiple purposes.

  • Stormwater features such as constructed wetlands, green roofs, and bioswales can be designed as a site asset (aesthetic, habitat, etc.) and provide valuable amenities. Including these features can also increase property value.

  • The most cost-effective stormwater management strategies are those that preserve or restore natural site features and promote natural infiltration: reducing hardscapes, designing a smaller building footprint, increasing landscaping area, using porous paving materials, natural swales, and other low impact development strategies. Natural infiltration may also decrease the cost of maintenance compared to other structural and packaged stormwater control systems.

  • Bioinfiltration strategies on streets and parking lots, such as vegetated filter strips and grass swales,  are alternatives to typical curb and gutter design that allow for infiltration of stormwater, as opposed to conveying the runoff to storm drains. Reducing the number of curbs, storm drains, and piping systems can substantially reduce construction costs.

  • Installing a green roof is one successful way to control and treat stormwater. Different types of green roofs provide varying levels of stormwater management, amenity, benefits and maintenance requirements. While green roofs can be expensive, they can often reduce the costs of traditional stormwater systems for a net savings.

  • Stormwater collection, storage and reuse equipment will increase costs, but will reduce the expenses of potable water.

  • There are fewer codes and associated costs for collecting and reusing stormwater for irrigation than for interior water reuse. Captured stormwater can often be reused for irrigation without much treatment. Reuse for toilet flushing and cooling tower make-up usually requires treatment.

Construction Documents

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  • The civil engineer runs final calculations for the project’s stormwater design. Be sure to address all value engineered items and the finalized design.

  • The civil engineer verifies that TSS removal and infiltration rate goals are met.

  • The civil engineer includes all stormwater treatment strategies on the project plans.

  • The civil engineer fills out the LEED documentation including a list of the BMPs used, descriptions of their function, expected annual percentage of rainfall infiltrated by each and a list of the structural controls used, descriptions of TSS removal performance, and expected annual percentage of rainfall treated by each. The civil engineer should also provide a copy of the project plans with designated stormwater strategies, detailing where the BMPs or structural controls are located along with the area the serve. It’s helpful to include an optional narrative naming the local standard that the stormwater system is designed to match or surpass.

  • Stormwater quality control systems require a maintenance plan for proper functioning. Ideally this is developed by the civil engineer shortly after design completion.


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  • Commissioning water reuse systems will help ensure they operate as designed. This step can be incorporated EAp1: Fundamental Commissioning, or EAc3: Enhanced Commissioning.

  • Compacted soil from high vehicle traffic prior to or during construction can severely limit natural infiltration of stormwater. Avoid site compaction during construction as much as possible—this will also help compliance with SSc5.1: Site Development—Protect or Restore Habitat. Aerating soils is not a substitute for avoiding compaction, but can be used to improve infiltration rates.

Operations & Maintenance

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  • Provide maintenance personnel with plans and operations manuals for the operation of all structural control systems.

  • Implement a maintenance plan to ensure ongoing, as-designed performance of stormwater systems and equipment. Doing so will also contribute to LEED-EBOM SSc6: Stormwater Management credit compliance.

  • If using porous paving, implement a plan to maintain its porosity. Vehicle use, sand and organic matter, and snowplowing can all damage or reduce the effectiveness of porous paving.

  • If relying on natural infiltration in landscaped areas, keep the plants in those areas healthy and avoid soil compaction from vehicle use.

  • Maintenance will be required for most stormwater systems. If the project uses structural controls, check with the product manufacturer, designer, and engineer for details on additional cost for maintenance requirements. If the project uses non-structural controls, have the designer confirm the associated maintenance practices for facility manager or additional contracts required. Maintenance costs will vary depending on the strategies employed.


    Excerpted from LEED 2009 for Core and Shell Development

    SS Credit 6.2: Stormwater design - quality control

    1 Point


    To limit disruption and pollution of natural water flows by managing stormwater runoff.


    Implement a stormwater management plan that reduces impervious cover, promotes infiltration and captures and treats the stormwater runoff from 90% of the average annual rainfall1 using acceptable best management practices (BMPs).

    BMPs used to treat runoff must be capable of removing 80% of the average annual postdevelopment total suspended solids (TSSTotal suspended solids (TSS) are particles that are too small or light to be removed from stormwater via gravity settling. Suspended solid concentrations are typically removed via filtration.) load based on existing monitoring reports. BMPs are considered to meet these criteria if:

    • They are designed in accordance with standards and specifications from a state or local program that has adopted these performance standards.


    • There exists infield performance monitoring data demonstrating compliance with the criteria. Data must conform to accepted protocol (e.g., Technology Acceptance Reciprocity Partnership [TARP], Washington State Department of Ecology) for BMP monitoring.
    1 There are 3 distinct climates in the United States that influence the nature and amount of annual rainfall. Humid watershedWatershed that receives at least 40 inches of rainfall each year. are defined as those that receive at least 40 inches of rainfall each year, Semiarid watersheds receive between 20 and 40 inches of rainfall per year, and arid watersheds receive less than 20 inches of rainfall per year. For this credit, 90% of the average annual rainfall is equivalent to treating the runoff from the following (based on climate): Humid Watershed - 1 inch of rainfall Semiarid Watersheds - 0.75 inches of rainfall Arid Watersheds - 0.5 inches of rainfall.

    Potential Technologies & Strategies

    Use alternative surfaces (e.g., vegetated roofs, pervious pavement, grid pavers) and nonstructural techniques (e.g., rain gardens, vegetated swales, disconnection of imperviousnessResistance to penetration by a liquid and is calculated as the percentage of area covered by a paving system that does not allow moisture to soak into the ground., rainwater recycling) to reduce imperviousness and promote infiltration and thereby reduce pollutant loadings.

    Use sustainable design strategies (e.g., low-impact development, environmentally sensitive design) to create integrated natural and mechanical treatment systems, such as constructed wetlands, vegetated filters and open channels to treat stormwater runoff.

Technical Guides

Stormwater Best Management Practices Design Guide, Vegetated Biofilters (EPA/600/R-04/121A)

This guide provides design strategies and techniques on incorporating biofilters in projects.

Bioretention (Rain Gardens) – EPA’s Stormwater Menu of BMPs

This website gives designers and planners information on the appropriate application of bioretention areas.

Model Low Impact Development Strategies for Big Box Retail Stores

This report describes low-impact development approaches to stormwater management for big-box stores.

Urban Drainage and Flood Control District

Technical manuals on stormwater BMP’s as they relate to Denver and surrounding counties.

Clean Water Ways, Stormwater Implementation BMP Guidelines


Effectiveness of Urban Stormwater BMPs in Semi-Arid Climates

This design manual provides stormwater information specific to semi-arid climates, including Denver, Colorado.

Denver Water Quality Management Plan, Stormwater Quality BMP Implementation Guidelines, Chapter 6

This design manual provides stormwater information specific to Denver, Colorado.

City and County of Denver, Department of Public Works Wastewater Management Division Storm Drainage Design and Technical Criteria

This design manual provides stormwater information specific to Denver, Colorado.

EPA’s National Pollutant Discharge Elimination System (NPDES) Overview

This portion of the EPA’s website provides general information on stormwater, including technical information specific to NPEDS.

Stormwater Best Management Practices Design Guide, Vegetated Biofilters (EPA/600/R-04/121A)

This guide provides design strategies and techniques on incorporating biofilters in projects.

Stormwater Management Manual (Portland Bureau of Environmental Services)

This website provides stormwater information specific to the Portland, Oregon area.

Rain Garden Handbook for Western Washington Homeowners: Designing your Landscape to Protect our Streams, Lakes, Bays and Wetlands

A guide to low-impact development for residences.

Maryland Stormwater Design Manual

This design manual provides stormwater information specific to Maryland.

Massachusetts Stormwater Technology Evaluation Project

This website provides stormwater information specific to Massachusetts.

Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438 of the Energy Independence and Security Act

This technical manual from the U.S. EPA contains background on documenting stormwater requirements through capturing the 95th percentile storm using onsite management practices.

International Stormwater Best Management Practices (BMP) Database

Features a database of over 500 BMPBest Management Practice studies, performance analysis results, tools for use in BMP performance studies, monitoring guidance and other study-related publications.

Web Tools

International Stormwater Management Best Practices Database

This database provides studies and analysis on BMPs and is intended to improve design.

Technology Acceptance and Reciprocity Partnership

This website provides information on the performance of technologies in a number of states across the U.S.


Stormwater — A Journal for Surface Water Quality Professionals

Online magazine for stormwater professionals.

Storm Water Solutions

Online magazine for stormwater professionals.

American Society of Civil Engineers Online Research Library

This online research center for civil engineers of all backgrounds includes stormwater information.


Low Impact Development Center

This website provides a comprehensive overview of LID strategies including design manuals and case studies.

Stormwater Quality Narrative

Provide narrative documentation like this to demonstrate structural and non-structural stormwater control measures.

Stormwater Management Report

All Options

A stormwater management and drainage report covering both SSc6.1 and SSc6.2 can document all aspects of credit compliance.

LEED Online Forms: CS-2009 SS

The following links take you to the public, informational versions of the dynamic LEED Online forms for each CS-2009 SS credit. You'll need to fill out the live versions of these forms on LEED Online for each credit you hope to earn.

Version 4 forms (newest):

Version 3 forms:

These links are posted by LEEDuser with USGBC's permission. USGBC has certain usage restrictions on these forms; for more information, visit LEED Online and click "Sample Forms Download."

Design Submittal

PencilDocumentation for this credit can be part of a Design Phase submittal.


Agata Mozer GO4IT SP Z OO SP K
Apr 10 2014
LEEDuser Member
28 Thumbs Up

Rainwater used for irrigation

Does reusing rainwater for irrigation complies with this credit's requirements? Does rainwater that is collected in a rainwater tank and then reused for irrigation, has to be also cleaned by filters that remove TSSTotal suspended solids (TSS) are particles that are too small or light to be removed from stormwater via gravity settling. Suspended solid concentrations are typically removed via filtration. with efficiency of 80%? Or is it enough if it will be just initially cleaned accoriding to local requirements because it won't be dischrged to the sewage system?

Michael DeVuono Senior Staff Designer, T&M Associates Apr 16 2014 LEEDuser Expert 1918 Thumbs Up

This should comply with the credit, as it is commonly accepted that 100% of TSSTotal suspended solids (TSS) are particles that are too small or light to be removed from stormwater via gravity settling. Suspended solid concentrations are typically removed via filtration. is removed when capture/reuse is proposed.

Agata Mozer GO4IT SP Z OO SP K Apr 16 2014 LEEDuser Member 28 Thumbs Up

Thank you for your reply. Do you know any project that used this approach for credit documentation and had this solution accepted by GBCI? Then while filling in the credit form what shuold be selected as "Source of TSSTotal suspended solids (TSS) are particles that are too small or light to be removed from stormwater via gravity settling. Suspended solid concentrations are typically removed via filtration. Removal Efficiency data" if there are no filters applied? Or maybe should it be described as an alternative compliance path?

Amanda Ross Apr 16 2014 LEEDuser Member 177 Thumbs Up

Be careful about the type of filter you use. We used a first flush filter, which essentially took the dirtiest water at the start and it was "flushed" down into the city storm system, which resulted in all of our TSSTotal suspended solids (TSS) are particles that are too small or light to be removed from stormwater via gravity settling. Suspended solid concentrations are typically removed via filtration. going down the city storm (but not into the water re-use). Of course the intent of the credit is that you remove the TSS from the water going to the city storm, so this filter and our water re-use didn't do anything to address water quality. We got caught on this on our first design review, but were fortunately able to address water quality with a bioswale instead.

Alternatively, if you use a filter that captures the TSS and requires clean-out, or goes somewhere other than city storm, then you are removing TSS from city storm.

Michael DeVuono Senior Staff Designer, T&M Associates Apr 16 2014 LEEDuser Expert 1918 Thumbs Up

I have always just designed a cistern with slightly more volume required. The thought process here is that the TSSTotal suspended solids (TSS) are particles that are too small or light to be removed from stormwater via gravity settling. Suspended solid concentrations are typically removed via filtration. settles out at the bottom of the cistern, and this is cleaned out during the dry season.

Depending on the means of conveyance to the cistern, you could always add a snout or something similar to ensure the bulk of your WQ occurs upstream of the cistern.

Post a Reply
wendy zhao engineer qidi
Feb 19 2014

SSc6.2 form

I'm very confused by the calculation methods about the TSSTotal suspended solids (TSS) are particles that are too small or light to be removed from stormwater via gravity settling. Suspended solid concentrations are typically removed via filtration. removal efficiency . Especially the TSS removal efficiency for BMPs in series.
Can someone tell me what the default calculation methods is used in the SSc6.2 credit form?

Michael DeVuono Senior Staff Designer, T&M Associates Feb 20 2014 LEEDuser Expert 1918 Thumbs Up

Can you be more specific? Removal efficiencies vary by BMPBest Management Practice, several suggested efficiencies are outlined in the reference guides.

Post a Reply
BH .
Sep 06 2013
LEEDuser Member
869 Thumbs Up

SSc6.2 in urban areas


there is a sentence in LEED Reference Guide which makes me really confused (page 103):

“For existing sites with greater than 50% imperviousnessResistance to penetration by a liquid and is calculated as the percentage of area covered by a paving system that does not allow moisture to soak into the ground., structural techniques may include restoring and repairing deteriorated storm sewers or separating combined sewers”

Does it mean that we can discharge rainwater to the sewer system without treating it ?

Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Nov 04 2013 LEEDuser Moderator

Interesting. I take this to mean that these are measures that could be a part of a plan for improving stormwater quality by fixing broken or outdated infrastructure. Based on where this appears in the Reference Guide, I take it as helpful suggestion for improving general conditions, and not an alternate compliance path for those sites.

Post a Reply
Michele Otazua CSHQA
Apr 11 2013
LEEDuser Member
21 Thumbs Up

SSc6.2 form

The credit form for SSc6.2 has apparently changed. The table 1 for TSSTotal suspended solids (TSS) are particles that are too small or light to be removed from stormwater via gravity settling. Suspended solid concentrations are typically removed via filtration. has been removed, and in its place a description of BMPs is required. Is this the case?

Michele Otazua CSHQA Apr 16 2013 LEEDuser Member 21 Thumbs Up

I was looking at the preliminary form, not the actual form.

Why does LEED have preliminary forms where you have to fill out a lot of information, and then complete the real forms for certification? It seems like a colossal waste of time, which it has been for me.

Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Apr 16 2013 LEEDuser Moderator

Michele, are you preferring to the form for LEED-CS precertification, as opposed to the actual certification form and process?

If so, precertification is optional, and typically pursued by developers who want to build interest in a project. It is not a LEED requirement to do both processes. If a project does choose to go through both, I wouldn't be at all surprised if GBCI could set it up more efficiently, though.

Post a Reply
michelle xuereb quadrangle architects limited
Feb 12 2013
24 Thumbs Up

Pollutant Management Plan

As part of this credit, LEED Canada 2009 requires the owner to implement a management plan to minimize pollution and eutrophication1. Eutrophication is the increase in chemical nutrients, such as the nitrogen and phosphorus often found in fertilizers, in an ecosystem. The added nutrients stimulate excessive plant growth, promoting algal blooms or weeds. The enhanced plant growth reduces oxygen in the land and water, reducing water quality and fish and other animal populations. 2. The process by which bodies of water are starved of oxygen and light by algae and other plants that multiply due to excessive concentrations of nutrients such as nitrogen and phosphorous. Typical sources include fertil­izer runoff and poorly managed wastewater treatment systems, frequently including home septic systems. of waterways from excess nutrient pollutants such as nitrogen and phosphorus. My civil engineer who had agreed to provide this initially is no longer answering my emails. As such I am attempting to write this myself. My site is a commercial office building on a sea of parking with a cistern, inimal landscaping and permeable pavers at the low end. My plan addresses the cleaning agent for the building exterior meeting Greenseal or Ecologo annual testing of soil (for nutrient levels) followed by aeration and minimal fertilizers on sod. Is this adequate?

Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Mar 22 2013 LEEDuser Moderator

I don't know—I wouldn't want to be in your shoes. You might try posting this to our LEED Canada forum.

Michael DeVuono Senior Staff Designer, T&M Associates Aug 06 2013 LEEDuser Expert 1918 Thumbs Up

They are looking for surface runoff to be routed through structural BMPs, such as raingardens, wetlands, swales, etc. in a treatment train.

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Dan Wise RLA Wise Land Design
Feb 22 2012
40 Thumbs Up

6.2 90% Rainfall Trtmnt vs. Drainage Boundaryvs. Leed Boundary

Does anyone know if Drainage Areas tributary to Treatment BMPs used to atain the 90% rainafall treatment and 80% TSSTotal suspended solids (TSS) are particles that are too small or light to be removed from stormwater via gravity settling. Suspended solid concentrations are typically removed via filtration. removal must be contained within the LEED Boundary. Also must the BMP facilities be contained within the LEED Boundaries? Is there regulatory language that specifies this?
Its seems beneficial to keep the LEED Boundary as reasonably small as possible to enable the & open Space % and Resortation % high but this excludes some drainage areas.

Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Feb 22 2012 LEEDuser Moderator

Dan, you may have stormwater treatment area outside the LEED boundary. See the LEED Minimum Program Requirements supplemental guidance document from USGBC for detail on this.

Dan Wise RLA, Wise Land Design Feb 22 2012 Guest 40 Thumbs Up

I presume you're referencing this language: ?
I take "any land" to mean any Stormwater BMPBest Management Practice used for Treatment or Draiange Area thereto.

When land included in submittals may be excluded from the LEED project boundary
Land described in this section is not required to be included in the LEED project boundary,
and therefore is not subject to consideration for prerequisite, other credit, or other MPR
Any land used to earn this credit.

Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Feb 22 2012 LEEDuser Moderator

Dan, you got it. Does that help?

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Amanda Ross
Sep 27 2011
LEEDuser Member
177 Thumbs Up

Estimating credit acheivement

1) Does anyone know of any local/regional programs with the 80% standard in the Vancouver, BC area? Our project is located in Surrey, BC.

My civil engineer tells me that he knows of no local/regional stormwater programs that have adopted the 80% TSSTotal suspended solids (TSS) are particles that are too small or light to be removed from stormwater via gravity settling. Suspended solid concentrations are typically removed via filtration. removal standard. Therefore, we need to provide field measurements after the installation.

2) Does anyone know of any good tools to estimate stormwater TSS removal? We have mostly non-structural measures (a lot of green roofs). It would be very helpful to know if we're getting close to this point.



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Hansong Sun
Apr 20 2010
207 Thumbs Up

How to determine the 90% of the average annual rainfall

I'm very confused by the methods determining the 90% of the average annual rainfall in SSS Credit 6.2 LEED guide.
In p103 of LEED guide, they said "For this credit, managing 90% of the average annual rainfall is equivalent to treating the runoff from the amounts listed in Table:
Watershed Rainfall per 24 Hours(ins)
Humid 1
Semiarid 0.75
Arid 0.5
I wondered Why the 90% of average rainfall is equivalent to treating the runoff of 1,0.75 and 0.5 (this is the quantity of 24 hours? not entire year?).


Jean Marais b.i.g. Bechtold DesignBuilder Expert Apr 20 2010 LEEDuser Member 7165 Thumbs Up

1) Intensity-Duration-Frequency (IDF) Charts. These charts show the relationship between the rainfall intensity (rate) and the corrisponding rainfall duration (minutes). This data is required for 1 and 2 year statistical return periods.
2) Depth-Duration-Frequency (DDF) Charts. These charts show the relationship between the rainfall depth (volume) and the corrisponding rainfall duration (minutes). This data is required for 1 and 2 year statistical return periods.
3) Volume of the 90% rainfall event, i.e. only 10% of rainfall events have a cummilative depth of more than this amount.
4) 90% Shortest Time between rainfall events, i.e. only 10% of rainfall events have between them a dry time less than this time.
5) Volume of yearly rainfall for "water shed" classification as per LEED.

in plain english this means that it is the volume of rain coming down for an entire rainfall 24 hour equivalent event AND the event is the one that statistically happens most of the time.

I think the reason the userguide wording is comfusing is because the statistical concepts are confusing and these calculations are usually done by an expert civil engineer. I also am not 100% certain of this area.


also google
Stromwater Retention Volume - Schueler's Simple Method
RUN-OFF RATE CALCULATION - Rational MethodA formula that can be used for calculating stormwater flow rates. Q = CIA, where C represents a coefficient for physical drainage area, I is the rainfall intensity, and A is area. The method is suitable for watersheds smaller than 300 acres in size.

Hansong Sun Apr 26 2010 Guest 207 Thumbs Up

Hello Jean,
Thanks very much for your detailed explanation. I think what you said is right.

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