NC-v2.2 SSc6.1: Stormwater Design—Quantity Control

  • NC CS Schools SSc6.1 Credit Requirements Diagram

  • Beyond standard practice, but cost-effective

     

    Development usually comes with increased stormwater runoff due to impervious surfacesSurfaces that promote runoff of precipitation volumes instead of infiltration into the subsurface. The imperviousness or degree of runoff potential can be estimated for different surface materials. like roofs and parking lots. To earn this credit with previously undeveloped sites, you’ll need to avoid any increase in runoff, while on mostly impervious developed sites, you’ll need to reduce runoff. You will probably need to go beyond standard practice to achieve this credit, and you might see increased costs, although an integrated approach can make this credit  cost-effective.

    Encourage natural infiltration when possible

    Many project teams are reluctant to attempt this credit because engineers typically use conventional methods that might not meet requirements. Although it's readily achievable, this credit can be challenging, particularly in areas with compacted soil, no landscaped area, large parking areas, or areas with water laws that preclude rainwater harvesting. Green roofs will be helpful in these cases, but the simplest and cheapest option, whenever available, is to simply encourage natural infiltration of stormwater into the ground.

    Reducing hardscapes, designing a smaller building footprintBuilding footprint is the area on a project site used by the building structure, defined by the perimeter of the building plan. Parking lots, parking garages, landscapes, and other nonbuilding facilities are not included in the building footprint., increasing landscaping area, using porous paving materials, using natural swales and other low-impact development strategies, and preserving natural site features are all cost-effective methods for promoting natural infiltration. Although natural infiltration may decrease the cost of maintenance compared to other structural and packaged stormwater control systems, keep in mind that it will still require regular maintenance.

    Similar to SSc6.2

    The two stormwater credits, SSc6.1 (stormwater rate and quantity), and SSc6.2 (stormwater quality) involved similar calculations and can be addressed by similar strategies, such as promoting natural infiltration.  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. Both credits focus on smaller, more frequent storms, not the larger ones that are more likely to cause flooding

    Many of the benefits of this credit are indirect and can be difficult to calculate. These include issues like reducing the burden on the municipal stormwater system; reducing contaminants in waterways; reducing peak runoff, which makes stream habitats more consistent; reducing the temperature of runoff, which improves the conditions for aquatic life; and reducing erosion.

     

Legend

  • Best Practices
  • Gotcha
  • Action Steps
  • Cost Tip

Pre-Design

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  • Consider low-impact development (LID) strategies such as bioretention, vegetated swales, a green roof, rainwater cisterns, and porous pavement. LID strategies can have a wide-ranging impact on decisions including site selection, landscaping, addressing off-site drainage onto the site, space and structural requirements, flood protection, and stormwater discharge locations. Consider this full range of factors in creating the stormwater management plan.

  • You will probably need to go beyond standard practice to achieve this credit, requiring deliberate design and the potential for up-front cost increases. Strategies going beyond standard practice but not likely to incur additional costs include infiltration swales and bioretention areas.

  • Overlapping strategies and technologies address both stormwater credits, SSc6.1 (stormwater rate and quantity), and SSc6.2 (stormwater quality). 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.

  • Approach this credit with an integrated design strategy that incorporates the input of the entire site team, including the civil engineer, landscape architect, and architect.

  • The easiest way to achieve credit compliance is by decreasing impervious area. You can do this by reducing the building footprint and hardscape area, and establishing rain gardens or other bioretention areas.

  • 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.

  • Most credit compliance problems are due to stormwater volume reduction, in part because many municipalities are more interested in runoff rate and do not require volume calculations. A civil engineer must run calculations for pre- and post-development runoff rate and quantity, for the one- and two-year, 24-hour design storm. Most jurisdictions don’t require calculations for these specific storm designs.

  • Creative stormwater management techniques such as open channels, eliminating curbs and gutters, and depressed parking islands may reduce construction costs by reducing runoff and the need for more costly infrastructure.

  • 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.

  • Most municipalities require stormwater documentation. In these cases, the documentation for LEED requirements should not represent a significant soft-cost premium.

Schematic Design

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  • Having trouble calculating the 2-year, 24-hour storm event? See LEEDuser's guidance on interpolation of rainfall intensity values. 

  • The owner and civil engineer determine the feasibility and rough costs of appropriate stormwater management techniques. Identifying cost tradeoffs for complementary strategies is a crucial component of the decision process. For example, a rooftop runoff collection system may be more cost-effective when combined with a graywater collection and reuse system. Fully explore the potential for LID strategies such as rainwater cisterns, green roofs, and bioswales.

  • A site visit and tests are integral to understanding the natural hydrology, site topography, and soil infiltration rates.

  • Research local regulations on stormwater reduction requirements, as well as regulations on the collection, storage, and reuse of rainwater. (See Resources for examples.)

  • Determine the imperviousness of the existing site. The Rational Method (see Resources for more information) is most commonly used to determine the weighted runoff coefficient. Then multiply by 100 to get the percent imperviousness. The imperviousness of the site determines which compliance path the project must take.

    • If the average imperviousness of the pre-development site is 50% or less (typically, most of the site is vegetated or permeable), follow requirements for Case 1.
    • If the average imperviousness of the pre-development site is more than 50% (typically, most of the site is hardscape or impermeable), follow requirements for Case 2. Redevelopment projects often fall into this category.

  • The Rational Method is the most common for determining peak discharge rate and runoff volume. It requires the runoff coefficient for each surface type, the total area for each surface type, and the total project area. Runoff rate and volume are directly proportional to landscape or hardscape porosity or perviousness. Undeveloped land has little imperviousness, while previously developed land will have more. However, many materials that seem to be impervious do not necessarily have 100% imperviousness. For example, asphalt will absorb and evaporate some rainfall and has an imperviousness of 85%–95%.

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

  • We recommend that the civil engineer 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.

  • Research historical climate records to understand the frequency, intensity, and duration of the design storm event. A longer record of daily rainfall events (rather than monthly rainfall averages) will result in more accurate sizing of components like cisterns.

  • Some jurisdictions may have stormwater standards that are similar to the LEED requirements. For example, Portland, Oregon's Title 17, Public Improvements, Chapter 17, 17.38.030 Section C, states that the quantity and flow rate of stormwater leaving the site after development shall be equal to or less than the quantity and flow rate of stormwater leaving the site before development, as much as is practicable.

  • Quantity of stormwater is typically the more difficult measurement for project teams to reduce. Detention basins can help reduce peak flow rate, but they may not reduce overall stormwater quantity. This is a common municipal requirement, and you may need to take additional measures to meet the credit requirements.

  • Integrating the stormwater plan into the design at an early stage and calculating the stormwater reduction percentages significantly decreases additional costs. This way, landscaping and building infrastructure can be designed with stormwater reduction in mind.

Design Development

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  • All Cases

  • Explore potential synergies and tradeoffs with other LEED credits or green building strategies. Items to discuss can include the use of parking lots versus parking garages for stormwater management, trees for shading hardscapes, and avoiding impervious surfaces (SSc7.1), trees for passive solar design (EAc1), plantings with native or adapted plants (WEc1), water reuse (WEc3), and rainwater capture (WEc1).

  • The civil engineer and landscape architect collaborate to design the stormwater systems to meet project goals, using the civil engineer's assessment of how much stormwater may be reduced through nonstructural means, such as increased landscape area or bioswales, and how much must be treated through engineered systems such as rainwater cisterns or green roofs.

  • The civil engineer typically uses a computer program or in-house spreadsheets to calculate the current rainfall and infiltration rates, which helps to determine the best practices and best systems for an individual site. Many projects measure peak flow rates and volumes with the National Resource Conservation Service unit hydrograph method outlined in TR-55. (See Resources.)

  • Existing stormwater management systems can be used to demonstrate credit compliance, provided that the system meets the requirements.

  • Involve the whole project team in integrating stormwater strategies with the site design and structure. For example, calculate a cistern size appropriate for water reuse needs and for rainfall patterns, being sure to allocate proper space. If using a green roof, incorporate structural considerations, planting decisions, and energy impacts

  • In place of elevated planters, grade parking lots and walkways to direct runoff to depressed swales or bioretention areas with perforated pipes and other slow-release infiltration mechanisms. This design is better for 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.

  • Detention ponds with controlled release structures only help to reduce the rate of runoff, not the volume. If a detention pond is going to be used onsite, other means of facilitating infiltration must also be used to meet the credit requirements.

  • 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 reduces the amount of stormwater runoff leaving the site as well as outdoor potable water use. Reusing captured rainwater for toilet flushing has similar effects, in addition to reducing potable water use indoors. In some cases, cisterns with open bottoms may be effective in storing stormwater runoff, encouraging infiltration and reducing 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.

  • Green roofs can reduce peak runoff rates on developed sites. However, the volume reduction potential of any green roof will depend on its moisture-retention capacity, which depends on the soil profile. One storm may saturate the soil, leading to a conventional amount of runoff resulting from a second storm in close succession.

  • Mitigate cost premiums by getting the most from stormwater strategies. Onsite treatment and retention strategies like green roofs and rainwater cisterns can be costly, but may serve additional purposes and contribute to other LEED credits, including open space requirements (SSc5.2), mitigating the urban heat island effect (SSc7.2), and reducing potable water use for landscaping (WEc1). Features such as constructed wetlands, green roofs, and bioswales can also increase property value. Mitigate cost premiums by designing strategies for multiple purposes.

  • 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 bioswales and grass filter strips 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.

  • Consider maintenance costs in choosing stormwater strategies. Check with the product manufacturer, designer, or engineer for cost details.

  • Case 1: Existing imperviousness is less than or equal to 50%

  • The civil engineer calculates the pre- and post-development peak rate and total volume of stormwater runoff for the one-year and two-year, 24-hour design storms.

  • The civil engineer verifies that post-development rate and quantity are equal to or less than pre-development.

  • If the stormwater reduction goals are not met, the civil engineer must adjust the design to meet them.

  • If post-development rate and quantity are not equal to or less than pre-development, the option exists for the civil engineer to design stormwater improvements to enable discharge channels from the site to the receiving stream channels to be protected from erosion. The stormwater management narrative must detail the strategies used and how they protect receiving stream channels from excessive erosion. In this plan the civil engineer verifies that post-development stormwater runoff is below critical values for the receiving waterway.

  • Projects using stream protection to achieve the credit must provide a detailed narrative describing how the stormwater management plan protects the receiving waterway from erosion and keeps runoff below critical levels.

  • Projects implementing a stream protection plan must calculate the pre- and post-development runoff rate and quantity for the one- and two-year design storms. The requirements for this plan are fairly vague and dependent on the specifics of the project. Including the percent reductions for rate and quantity along with a description of the project design will help buttress the plan with specifics.

  • Projects using the stream channel protection option need to also implement strategies to reduce the quantity of stormwater runoff, where possible. Typical strategies could include reduced building footprint, reduced hardscape, infiltration areas, or rainwater harvest and reuse. These stategies need to be described in the stormwater management plan and narrative in order to meet the credit requirements.

  • Projects may use a combination of Option 1 (rate and quantity calculations) and Option 2 (stream protection) to meet the requirements of this credit.

  • Option 2: Existing imperviousness is greater than 50%

  • The civil engineer calculates the post-development runoff volume for the two-year, 24-hour design storms.

  • Verify that post-development volume is at least 25% less than pre-development, using site-appropriate stormwater strategies.

  • If the stormwater reduction goals are not met, the civil engineer needs to adjust the design to meet them.

  • Case 2 requires calculating just the volume for the two-year, 24-hour design storm, not the rate or the one-year storm.

Construction Documents

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  • The civil engineer provides final calculations for the stormwater design. Verify that volume and discharge flow rate reduction goals are met. Be sure that any items removed through value-engineering do not impact stormwater calculations.

  • On the project plans, include all stormwater quantity reduction strategies. Indicate where BMPs are located and what areas they serve.

  • For LEED documentation, the civil engineer needs to fill out the LEED Submittal Template, including the pre-development rate and quantity of stormwater runoff, the post-development rate and quantity, and a stream-protection narrative (as applicable). The civil engineer should also provide a copy of the project plans with designated stormwater strategies. (See Documentation Toolkit for samples.)

  • Maintenance is usually needed for stormwater quantity reduction systems. The civil engineer should develop a maintenance plan shortly after design completion.

Construction

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  • Commission any water reuse systems to ensure that they operate as designed. Include this in the commissioning credits EAp1 and EAc3.

  • 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 also helps compliance with SSc5.1). 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 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.

  • USGBC

    Excerpted from LEED for New Construction and Major Renovations Version 2.2

    COPYRIGHT © 2005 BY THE U.S. GREEN BUILDING COUNCIL, INC. ALL RIGHTS RESERVED

    SS Credit 6.1: Stormwater design - quantity control

    1 Point

    Intent

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

    Requirements

    Case 1 - existing imperviousness is less than or equal to 50%

    Implement a stormwater management plan that prevents the post-development peak discharge rate and quantity from exceeding the pre-development peak discharge rate and quantity for the one- and two-year 24-hour design storms.

    OR

    Implement a stormwater management plan that protects receiving stream channels from excessive erosion by implementing a stream channel protection strategy and quantity control strategies.

    OR

    Case 2 - existing imperviousness is greater than 50%

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

    Potential Technologies & Strategies

    Design the project site to maintain natural stormwater flows by promoting infiltration. Specify vegetated roofs, pervious paving, and other measures to minimize impervious surfacesSurfaces that promote runoff of precipitation volumes instead of infiltration into the subsurface. The imperviousness or degree of runoff potential can be estimated for different surface materials.. Reuse stormwater volumes generated for non-potable uses such as landscape irrigation, toilet and urinal flushing and custodial uses.

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

http://www.cleanwaterways.org/professionals/index.html

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.

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.

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.

Hydraulic Design Manual

The Texas Department of Transportation offers this guide to the 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., which, it notes, is appropriate for estimating peak discharges for small drainage areas of up to about 200 acres in which no significant flood storage appears.

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.

Organizations

EPA Low Impact Development Website

EPA provides valuable information on low-impact development through fact sheets, design guides and cost estimates for low-impact development strategies that reduce stormwater runoff.

National Pollutant Discharge Elimination System (NPDES)

EPA offers help on managing stormwater, including fact sheets on the six minimum control measures for best management practices.

Stormwater Manager’s Resource Center

This site for practitioners and local government officials provides technical assistance on stormwater management issues.

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.

Publications

Stormwater — A Journal for Surface Water Quality Professionals

Online magazine for stormwater professionals.

Articles

EPA Urban Stormwater BMP Study

This article provides a preliminary study on BMPs.

LEED Online Sample Template – SSc6.1

This template is the flattened, public version of the dynamic template for this credit that is used within LEED-Online v2 by registered project teams. This and other public versions of LEED credit templates come from the USGBC website, and are posted on LEEDuser with USGBC's permission. You'll need to fill out the live version of this template on LEED Online to document this credit.

USGBC

Official LEED Online Forms

Design Submittal

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

37 Comments

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Patricia Fuertes
Apr 26 2013
LEEDuser Member

Best practice

Which is the best practice? installing vegetated roofs without any irrigation system or harvesting stormwater for reuse in irrigation?

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Michael DeVuono T&M Associates Apr 26 2013 LEEDuser Expert 353 Thumbs Up

Impossible to say unless you elaborate a little more about your project.

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Patricia Fuertes Apr 26 2013 LEEDuser Member

Our project has a vegetated roof without any irrigation system because in our town rains a lot. But we do not know if installing a storage tank to reduce the storwater runoff and use it for irrigation is a better practice.

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Michael DeVuono T&M Associates Apr 26 2013 LEEDuser Expert 353 Thumbs Up

I'm sorry, but this is just way too broad a question to really give you much useful guidance.

If it rains a lot, is there a need for irrigation? If you say you are reusing the water, you have to show the demand and how you will use it. A green roof is a lot more expensive that a simple capture/reuse system, but can have other advantages depending on your situation.

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Dale Hyatt
Mar 13 2013
Guest

Runoff quantity and infiltration

For credit SSc6.1 Option 1 - How do you show reduction in runoff volume for the 1 year and 2 year 24hr storms using infiltration? I understand an increase in impervious area increases post construction runoff volume, such that I have now have a quantity of runoff to infiltrate, how quickly must I show this volume infiltrating? Our soils have very low infiltration rates, such that it may take 3-4 weeks to infiltrate the required volume. I guess my question is just how do you relate a particular storm runoff volume to an infiltration basin that infiltrates over an extended period of time?

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Michael DeVuono T&M Associates Mar 14 2013 LEEDuser Expert 353 Thumbs Up

[(surface area s.f)(infiltration rate in/hr)(x)]/12 = (volume)

x=time to dewater

If your dewatering time is greater than 72 hours, you are either trying to ilfiltrate too much water, or your rates are too low. Typically you need a foot per day (.5"/hr) for infiltration to realistically work, otherwise you will have a mosquito problem.

3-4 weeks is not an acceptable dewatering time.

The volume that you infiltrate is the volume you take credit for.

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Lauren Glasscock Sr. Sustainability Professional DNV KEMA Energy & Sustainability
Nov 12 2012
LEEDuser Expert
8641 Thumbs Up

On-site Storage as compliance path

We received the following comment noted below. Is there a reason that on-site storage cannot count toward compliance?

The LEED Submittal Template has been provided stating that the project has implemented a stormwater management plan that results in a 0% decrease (rate and quantity) in runoff from calculated pre-project conditions. Calculation results have been provided in the template to demonstrate compliance with the requirements of this credit. The Submittal Template indicates that the project is seeking point(s) for this credit using an alternate compliance approach. The narrative states that an additional 4,000 cubic feet of storage has been added to the site. However, additional storage does not demonstrate a decrease in the quantity of runoff released from the project site.

TECHNICAL ADVICE:
Please complete the Submittal Template by providing stormwater calculation results demonstrating that the rate and quantity of stormwater runoff generated from the post-development site decreased by at least 25% as compared to pre-development conditions.

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Michael DeVuono T&M Associates Nov 13 2012 LEEDuser Expert 353 Thumbs Up

What are you doing with the water you are storing? Did you spell it out?

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Alan Jalon
Sep 04 2012
Guest
14 Thumbs Up

Narrative approach

Any advise on narrative approach for compliance with this credit. I'm having one heck of time trying to find IDF curves and substantial data for calcs. My site is a remote island with no population and no sewers. It only rains 3 months out of the year. Neighboring island can't provide accurate weather stats or IDF curves because every island has a distinct micro-climate.

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Michael DeVuono T&M Associates Sep 04 2012 LEEDuser Expert 353 Thumbs Up

So your project is on a remote, unpopulated island? Can I come for a site visit when complete?

Have you checked the GIS at ncdc.noaa.gov

There are thousands of little dots representing climate information all over the world. I'd start there.

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Alicja Florczak Skanska
Jun 09 2011
LEEDuser Member
516 Thumbs Up

storage without reusing

My project is a zero lot line project (it means that the building will cover the whole plot) located on a previusly developed site with impreviousness grater than 50% - option 2. The building will be equiped with a tank located in the basement, that will capture and store stormwater. However, we are not planning to reuse the stormwater, but discharge it in small portions to the municipal sewer system. This is required by local authorities, in order to avoid large amount of stormwater flowing directly into the sewer system during a storm event.
Can I attempt this credit even though I only store stormwater without reusing it? I hope yes, at the end it prevents postdevelopment peak discharge...

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Nov 13 2011 LEEDuser Moderator

Alicja, I don't see any reason you can't pursue this credit in the way you describe.

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Mike Barker Principal : Energy / Electrical Engineer BuildingPhysics South Africa
Feb 09 2011
LEEDuser Member
931 Thumbs Up

5 year design storm ?

Our Civil Engineers say they design around a 5 year storm in our neck-of-the-woods. I will check if 1 and 2 year data is available, but if not could we use 5 year design storm data. ( i imagine a 5 year 24-hr design storm data is more water anyway ? )

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Amy Rider Sustainability Manager, KEMA Services Mar 02 2011 LEEDuser Expert 1360 Thumbs Up

Using a 5 year design storm (which is more severe than a 2 year storm) should be adequate, but the reviewer may balk at this. I highly recommend using 1 and 2 year data if you can find it.

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Michael DeVuono T&M Associates Mar 06 2012 LEEDuser Expert 353 Thumbs Up

The smaller storm targets are typically harder to hit than the larger. I wouldn't count on getting this credit approved using a 5-year storm.

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Greg Kight National Director of Sustainable Design Jacobs
Jan 18 2011
LEEDuser Member
188 Thumbs Up

Credit Denial

Pursued this credit through Option 1 (Narrative approach) for project pre-development impervious is less than or equal to 50%, but project does not comply with first part of Option 1. Credit was denied with comment:

This credit requires that calculations be provided demonstrating that the rate and quantity of stormwater runoff generated from the post-development site does not exceed pre-development conditions for both a one year, AND a two year, 24 hour peak discharge. Calculations must show values for both conditions, and for both discharge events so that it can be confirmed that the appropriate path was taken for credit compliance.

Deciding if it is worth appealing credit. 100% of the water will be retained onsite (within project boundaries) via storm channel, retention basin, rip rap pads, and dry wells. A Stormwater Pollution Protection Plan was provided (this includes erosion control measures). If the pre- and post- development rate and quantity is provided, do you think USGBC will give us this credit through the appeal process?

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Jan 20 2011 LEEDuser Moderator

Greg, was there something missing from the calculations that you can include on appeal, and improve your chances? In other words, does the review comment speak to any reasonable issues that you are able to address?

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Greg Kight National Director of Sustainable Design, Jacobs Jan 31 2011 LEEDuser Member 188 Thumbs Up

Did not include the calculations, as the pursuit was via the narrative approach. However, we have the pre/post development runoff rates and could provide.

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Feb 08 2011 LEEDuser Moderator

Greg, you're right... I would say you got a bum review, not the first time. I would appeal it, include the numbers since you have them, but ask them why you need to provide what they're asking for, since it's not required by the form.

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Chi-Chung Sue Steven Leach International Asia Inc. Taiwan Branch
Dec 23 2010
LEEDuser Member
3415 Thumbs Up

Porosity and Run Off coefficient

I was given a spec about a types of asphalt that has porosity of 15%-25%. but the manufacturer doesnt know the run off coefficient. can we use the percentage as run off coefficient. in this case, the run off might be 0.85 - 0.75.

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Jan 20 2011 LEEDuser Moderator

Jason, yes I would enter such a value, maybe err on the side of high run off.

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Jonathan Dunn
Dec 15 2010
Guest
80 Thumbs Up

Mulit-Tenant Complex - where is the boundary?

I am working on one building of a large multi-tenant commercial project that will be shooting for certification while the rest of the complex will not. I am trying to set the LEED project boundary to capture the stormwater credits SSc6.1 and SSc6.2 that the site will be taking care of and due to project perk rates is a no brainer. I know we need to be consistent with the boundary once we set it, but if I use the Campus boundary to delineate and capture the stormwater that the site is handling do I also have to use it for the WE1.1 credit for landscaping that we are putting around our building? I have read through the slightly useful multi-tenant guide and am still at odds on how to puruse this...Thanks in advance!

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Jan 20 2011 LEEDuser Moderator

I think the answer to your question is to understand the difference between the LEED campus boundary (larger for  SSc6) and the LEED project boundary (smaller, WEc1 is applicable).

Does that help?

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Jonathan Dunn Jan 21 2011 Guest 80 Thumbs Up

Yes. However based on the supplemental guide to the MPR it states that at least in LEED 2009 rating system that "STORM WATER DESIGN CREDITS The nature of storm water calculations often necessitates that land outside the LEED project boundary be considered when determining compliance for these credits. Also, it may be necessary to discharge site runoff to a regional or master stormwater management system, such as a retention pond. This additional real property does not need to be included in the LEED project boundary or be considered for prerequisite, other credit, or other MPR compliance."

Will this logic prevail in V2.2?

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Feb 08 2011 LEEDuser Moderator

Yes, I would say so. You might run it by GBCI if it's key to your project situation.

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Kimberly Cullinane
Oct 14 2010
LEEDuser Member
301 Thumbs Up

EP for this credit

LEED User shows that you can get an EP for this credit - what would be the requirements for the EP? And in general, where do I find this information in LEED User if EP is indicated? (I'm assuming that EP means Extra Point or something like that). Thanks!

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Oct 15 2010 LEEDuser Moderator

Kimberly, EP means Exemplary PerformanceIn LEED, certain credits have established thresholds beyond basic credit achievement. Meeting these thresholds can earn additional points through Innovation in Design (ID) or Innovation in Operations (IO) points. As a general rule of thumb, ID credits for exemplary performance are awarded for doubling the credit requirements and/or achieving the next incremental percentage threshold. However, this rule varies on a case by case basis, so check the credit requirements., which is a bonus point earned via IDc1. Only some credits have EP as an option. SSc6 is notorious in the sense that one is allowed to earn an EP point for it, but there is no established path or guidelines for doing so. I haven't heard of it being done. Anyone?

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Susann Geithner Director of Sustainability, HSB Architects & Engineers Oct 18 2010 LEEDuser Expert 7758 Thumbs Up

We have two project in review both going after an ID credit for a reduction of stormwater quantity and quality by 100%. The buildings have green roofs and an infiltration well, no connection to the sewage for storm water discharge. I will let you know if they get approve or not.

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Kimberly Cullinane Oct 18 2010 LEEDuser Member 301 Thumbs Up

Great - thanks for the information and responses. I'd love to know for future reference how your project does with the ID credits.

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Susann Geithner Director of Sustainability, HSB Architects & Engineers Nov 09 2010 LEEDuser Expert 7758 Thumbs Up

100% reduction in stormwater runoff denied. LEED CS V 3
We just got the review back and this was the comment of the reviewer:
"However, Innovation in Design credits are not awarded when the strategy aids in the achievement of an existing LEED credit (even if the credit was not applied in the project). In this case, the proposed ID strategy aids in the achievement of SSc6.1: Stormwater Design, Quantity Control and SSc6.2 Stormwater Design, Quality Control.... project may attempt a different ID strategy for Final Review.:"
I do agree with the general statement, however achieving a 100% reduction of stormwater runoff especially in a densely developed area, urban center, I think, goes far beyond the achievement of SS6.1-6.2. Next time I would submit a CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide to get this clarified.

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Nov 12 2010 LEEDuser Moderator

I'm surprised it was denied. Did you clearly submit it on the Exemplary PerformanceIn LEED, certain credits have established thresholds beyond basic credit achievement. Meeting these thresholds can earn additional points through Innovation in Design (ID) or Innovation in Operations (IO) points. As a general rule of thumb, ID credits for exemplary performance are awarded for doubling the credit requirements and/or achieving the next incremental percentage threshold. However, this rule varies on a case by case basis, so check the credit requirements. path, as opposed to Innovation?

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Susann Geithner Director of Sustainability, HSB Architects & Engineers Dec 01 2010 LEEDuser Expert 7758 Thumbs Up

I discussed this at the greenbuild with the GBCI staff. They explained that it would be OK to submit it as exemplary performanceIn LEED, certain credits have established thresholds beyond basic credit achievement. Meeting these thresholds can earn additional points through Innovation in Design (ID) or Innovation in Operations (IO) points. As a general rule of thumb, ID credits for exemplary performance are awarded for doubling the credit requirements and/or achieving the next incremental percentage threshold. However, this rule varies on a case by case basis, so check the credit requirements., but not as Innovation and Design. In this case we already reach the limit of 3 EP points, but we will use this credit in another project.

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BWBR Architects BWBR Architects Sep 12 2012 LEEDuser Member 180 Thumbs Up

Is SSc6 really allowed to earn EP under NCv2.2? I submitted for exemplary performanceIn LEED, certain credits have established thresholds beyond basic credit achievement. Meeting these thresholds can earn additional points through Innovation in Design (ID) or Innovation in Operations (IO) points. As a general rule of thumb, ID credits for exemplary performance are awarded for doubling the credit requirements and/or achieving the next incremental percentage threshold. However, this rule varies on a case by case basis, so check the credit requirements. as one of the project ID credits in a recent Design Review submittal and had it denied by the reviewer based on the fact that SSc6 does not have an EP path in NCv2.2.

Can anyone provide me the specific citation or addendum which allows this path? If it is of any note, the reviewer specifically says that 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. 10108 does not apply to projects using the LEED NC v2.2 rating system.

Thanks!

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Mary Ann Santos
Aug 31 2010
LEEDuser Member
1221 Thumbs Up

how to compute the runoff rate?

If a project is two towers with podium on the 4th floor with hardscapeHardscape consists of the inanimate elements of the building landscaping. Examples include pavement, roadways, stone walls, concrete paths and sidewalks, and concrete, brick, and tile patios. and softscape and will have a rainwater storage tank at basement 5 that will collect rainwater from the roof deck of the two towers; how do we compute for the post development runoff rate if we will use rainwater storage tank as a means to control stormwater?

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Aug 31 2010 LEEDuser Moderator

Katherine, the key steps for doing this are shown under the Checklists tab, above.

It's a fairly general question so let's start there and see what specific roadblocks you might be facing.

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Kathleen Bender Aug 01 2011 Guest 19 Thumbs Up

where is the 'Checklists' tab?

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Nov 13 2011 LEEDuser Moderator

Kathleen, it is at the top of this page, in the gray bar.

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