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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 ...
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25 Comments
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...
Alicja, I don't see any reason you can't pursue this credit in the way you describe.
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 ? )
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.
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?
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?
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.
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.
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.
Jason, yes I would enter such a value, maybe err on the side of high run off.
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!
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?
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?
Yes, I would say so. You might run it by GBCI if it's key to your project situation.
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!
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?
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.
Great - thanks for the information and responses. I'd love to know for future reference how your project does with the ID credits.
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.
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?
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.
how to compute the runoff rate?
If a project is two towers with podium on the 4th floor with hardscape 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?
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.
where is the 'Checklists' tab?
Kathleen, it is at the top of this page, in the gray bar.
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