Mitigating 15% of stormwater for this credit may be more doable than you think. If a site was not designed with stormwater mitigation in mind, or does not have the benefit of extensive vegetated areas relative to the amount of impervious site area, you may need to make a significant investment in strategies like cisterns, green roofs, water retention features, and detention ponds. However, a typical project site may have a favorable ratio of vegetated area to impervious 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. that would naturally mitigate enough stormwater runoff, eliminating the need for major modifications in order to achieve this credit. While it is important to have a professional calculate the required amount of vegetated area needed, a hardscape-to-vegetated area ratio of as much as five-to-one may be suitable.
Owners and facility managers can assess current conditions and, if necessary, work closely with a stormwater engineer or other professional to determine an effective stormwater management plan that is appropriate to the site’s climate, topography and local stormwater ordinances.
The approach for achieving this credit varies dramatically across different regions and climate zones. The strategies employed in an urban environment, where water is discharged to a municipally controlled and maintained master system, will vary significantly from the approach for a rural project that discharges to smaller streams or lakes with higher water quality standards. Regions that are generally dry and need to retain and reuse rainwater, but also have seasonally heavy rainfall, can benefit greatly from collection and storage strategies.
Stormwater captured in cisterns may be treated and used for irrigation and and indoor uses such as toilet flushing, fire suppression, laundry, and cooling tower make-up water.
NOAA provides a great resource for finding information on the 2-year 24-hour storm. For some locations in the U.S., the site allows you to navigate to a specific locale and generates a table of rainfall intensities, including for the 2-year 24-hour design storm. For the other states, it lets you download isopluvial maps.
This is mostly a judgment call and if you’re concerned about questions during the review process, a great way to make your case is with photos or with a narrative describing your methodology to determine the slope.
If the manufacturer publishes or can provide the runoff coefficient for your system, use that. For other surfaces where the data is not available, chose the closest surface type from the credit form and go with that.
The best place to find this type of data is typically through public agency or semi-public agencies like universities or other organizations. But if you can’t find data specific to the 2-year 24-hour storm, there is an alternative compliance path published by USGBC in the ACP Documentation Guidance for Projects Outside the U.S.
If the water body can contain the rainfall event with no discharge to the sanitary sewer, then the runoff coefficient is essentially zero. If, on the other hand, the rain that falls directly into the water body raises the water level sufficiently to overflow into the sanitary sewer, the runoff coefficient is 1.0. For example, pools will often have a bit of freeboard before the water level rises enough to overflow and this will allow you to capture the rainfall, and even make up for some evaporation that would otherwise be made up using potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems..
Porous pavers used for site hardscape areas can reduce runoff.Perform a site inventory cataloging surface types, such as asphalt, concrete, roof areas, and landscaped areas. Use the LEED template to assess the percent of stormwater managed based on site perviousness.
The LEED Online credit form contains a built-in calculator that uses runoff coefficients of different surface types to determine infiltration volumes.
If the project site contains a number of different surface slopes and grades, you can simplify the calculation process by classifying the majority of appropriate surface areas as “steep.” This will generate the most conservative calculation of stormwater mitigation.
If cisterns, detention ponds, or other stormwater collection systems exist on site, assess their capacity and the area of surfaces from which they collect water, based on design documents or other system information.
Research region-specific data for the total annual rainfall and the 2-year, 24-hour frequency storm. See the Documentation Toolkit for an example of this kind of assessment, and see the step-by-step LEEDuser strategy page on getting the stormwater data you need.
You may use online tools to determine region-specific rainfall amounts. However, since this data is not always readily available online, the best way to track down this information may be to contact your city or county stormwater management officials directly.
Investigate opportunities for increased stormwater mitigation (based on the inventory results) through water harvesting techniques or modifying surface areas to increase the amount of pervious surface.
Substitute porous paving materials in place of conventional asphalt and concrete. This may require installing a new sub-base and is not as simple as repaving.
Harvest stormwater in tanks and cisterns for reuse. Stormwater may be treated and used for irrigation and indoor uses such as toilet flushing, fire suppression, laundry, and cooling tower make-up water.
Install green roofs to reduce the runoff coefficient of the roof area.
For urban buildings with small sites, green roofs and rainwater collection and reuse systems are the most likely strategies to bring the project to compliance with this credit. While it is important to have a professional calculate the required amount of vegetated area needed to mitigate 15% of onsite rainfall, a reasonable rule of thumb is that you’ll need to cover at least 20% of the site area with a green roof or other vegetation.
Convert site area to include infiltration swales, rain gardens, vegetated filter strips and retention ponds.
Consult with local authorities and ordinances to learn about regulations on stormwater detention features that may influence your management plan.
Stormwater capture may be illegal in certain areas of the country, such as Colorado, where existing downstream water rights take precedence.
Develop a preventative maintenance plan to evaluate stormwater management facilities regularly and ensure optimal performance.
Stormwater reuse costs are minimal for irrigation, moderate for make-up water, and significantly higher for use in indoor plumbing fixtures.
Monitor all stormwater mitigation features, including natural areas as well as mechanical harvesting equipment, to gauge retention efficiency and ensure proper function.
Perform all routine required maintenance and repairs within 60 days of inspection and keep an inspection report and maintenance log.
Maintenance costs will vary depending on the equipment and techniques in use, but regular preventative maintenance will help to minimize those costs.
Excerpted from LEED 2009 for Existing Buildings: Operations & Maintenance
To limit disruption of natural hydrology by reducing impervious cover, increasing on-site infiltration, reducing or eliminating pollution from stormwater runoff and eliminating contaminants.
During the performance period, implement a stormwater management plan that infiltrates, collects and reuses runoff or evapotranspirates runoff from at least 15% of the precipitation falling on the whole project site both for an average weather year and for 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..
Implement an annual inspection program of all stormwater management facilities to confirm continued performance. Maintain documentation of inspection, including identification of areas of erosion, maintenance needs and repairs. Perform all routine required maintenance, necessary repairs or stabilization within 60 days of inspection.
Use Low Impact Development (LID)1 practices to capture and treat water from 25% of the 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. for the 95th percentile of regional or local rainfall events.
Collect and reuse stormwater for nonpotable uses such as landscape irrigation, toilet and urinal flushing, and custodial uses. During facility or site alterations or additions, specify the use of alternative surfaces (e.g., vegetated roofs, pervious pavement or 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 improve perviousness, thereby restoring or maintaining natural stormwater flows. Incorporate stormwater management facilities into routine preventive and corrective maintenance programs.
1.The baseline condition is the site condition prior to LEED registration.
2. Low impact development (LID) is an approach to managing stormwater runoff that emphasizes on-site natural features to protect water quality byreplicating the natural land cover hydrologic regime of watersheds and addressing runoff close to its source. Examples include better site design principles such as minimizing land disturbance, preserving vegetation, minimizing impervious cover, and design practices like rain gardens, vegetated swales and buffers, permeable pavement, rainwater harvesting, and soil amendments. These are engineered practices that may require specialized design assistance.
This website provides historic rainfall data and isopluvial maps for various storm events.
A nonprofit dedicated to disseminating watershed-protection information to community leaders and watershed managers, the Center offers online resources, training seminars and a journal, The Practice of Watershed Protection.
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.
EPA offers help on managing stormwater, including fact sheets on the six minimum control measures for best management practices.
This site for practitioners and local government officials provides technical assistance on stormwater management issues.
NRCS provides technical resources and financial assistance to land-users, communities, and local governments for conserving soil, water and natural resources.
This article discusses how to work around Colorado's water use laws when managing stormwater.
You'll need to document stormwater inspections to confirm continued performance.
Perform stormwater management calculations to assess the percentage of precipitation mitigated by the project site.
This sample LEED Online form with tips demonstrates how to document SSc6.
The following links take you to the public, informational versions of the dynamic LEED Online forms for each EBOMEBOM is an acronym for Existing Buildings: Operations & Maintenance, one of the LEED 2009 rating sytems.-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. For more information, visit LEED Online and click "Sample Forms Download."
I am wondering if we can leave the sections below blank on the Stormwater Inspection Checklist due to only having large open turf/landscape areas and no retention ponds (we have ponds, but these are all sealed aside from a drain at the bottom with plastic filters to stormwater drains):
1.) Detention/Retention Management (SITE-SPECIFIC)
2.) Infiltration Facilities Managements (SITE-SPECIFIC)
3.) Filtration Practices (SITE-SPECIFIC)
Basically, I was going to put N/A in the sections above.
The roof rainwater drains into the ponds to fill them, but not for filtration purposes.
I have always avoided this credit, however, I thought i would take a stab at it. Hopefully, my lack of knowledge and background about stormwater won't prevent me from understanding what is required.
I am having a hard time envisioning your stormwater "pond." If it is an underground system, where any problems may not be immediatley apparent, that is all the more reason to perform, at minimum, a visual inspection of the system after larger storms.
There are about eight ponds that all feed into each other (like the Great Lakes between Canada and U.S. and the St. Lawrence Seaway). The water does not actually drain off of the site, they keep their levels even based on how much/little rainfall we receive. If there is not enough, the irrigation is turned on manually. If there is too much, we hope there isn't an overflow (we have an on-site person that watches it). The ponds evaporate 1-2"/day depending on the weather. In the rainy season, the rainwater from the roofs (4 buildings) filters through stones and grassy sections and flows into the ponds, therfore, no need to turn the irrigation lines on to raise the pond levels. Unfortunately, the rainwater comes when we don't really need it (wet season). The ponds all have a drainage system and the plastic filters between the ponds are cleaned as needed (bi-annually). Maybe these ponds are irrelevant because the water never actually leaves the site to go to the stormwater drains off-site? Basically, all of the rainwater stays on site, and we add water for irrigation and raising the pond levels. I do not have a "plan" that shows or proves this, just an older Landscaper that explained how it works. No way to prove this.
The ponds all have cement bottoms that are sealed aside from the drianage pipes between them.
Anyway, I am either way on or way off track here. I think it is a good concept though!
I think I get the gist of it. I would not leave everything blank, summarize what you just told me. Add a little bit about maintenence of the stone filter (cleaning sediment, trash, etc)....you clean the filters bi-annually, you inspect after every significant rainfall...
I've been reading the EB&OM stress test, and felt confused about the "You may get dirty" factor in SSc6. Does it mean if I achieve this credit, it will have a negative environmental impact on the building? Then will this kind of reason affect the target credit selection?
Jun, that factor is partly meant as a fun thing. All it means in this context is that you may have to go outside and get your hands dirty understanding and maintaining your stormwater system to earn the credit. Earning the credt should have a positive impact, and is recommended.
I am trying to verify that the cisterns on site release stormwater quickly enough to capture 2-year 24-hour design storm events by calculating the minimum drawdown rate. However, I cannot figure out what the rainfall event interval is. Is this information that I should be able to find or something that needs to be calculated?
I assume you are talking about back to back storm events here.
This topic comes up a lot in stormwater management, especially with capture and reuse. Calculating back to back events is a complex study, and requires the EPA's SWMM software. However, I don't believe you are being asked to get this involved for LEED.
I have never received clear guidance on how quickly we need to free up volumes for back to back storm events. However I have successfully made the case to the DEP, just last week, that a theoretical 2 yr storm event only occurs every 2 years, and therefore providing volume for back to back events is unrealistic.
I've also come across agencies wanting the water gone in 72 hours.
As far as LEED is concerned, I would follow your local water quality requirements for drawdown, provide the necessary calculations that show all your reductions, and go from there. Show that you have an adequate bypass in place, in the event the cistern is full as well
I see that equation 3 in the reference manual performs the calculation for Q, the peak runoff rate, but I do not see how this value is used to calculate the amount of water retained on site.
How do you take the storm intensity calculated based on NOAA data and calculate the design storm rainfall volume?
Once rainfall volume has been calculated, how do you apply the runoff rate in order to calculate the amount of water mitigated on site?
My project does not currently have any special detention facilities in place, and I would like to assess our liklihood of acheiving this point. It seems to me that the reference manual provides very little support for calculating the volume of runoff using equation 3, is this a valid option?
TR-55 has all the methodology explained to calculate a runoff volume.
My project is pursuing Option 1, stormwater assessment report, of the Full documentation option of the O&M submittal path (what a mouthful!) of SSc6.
The site was designed to infiltrate the stormwater volumes created by a 100 year storm, so has the capacity to infiltrate all volumes created by the 2 year storm.
I'm entering the same volumes into the "Two year, 24 hour design storm onsite rainfall volume" and the "Mitigated design storm rainfall volume." When I do this the calculator (Both on the downloadable form and the LEEDonline version) says that the site mitigates 1% of the design storm rainfall volume. It seems like this should read 100%.
Is this a bug or am I totally missing something?
I haven't personally documented this credit in this way, but I would agree the form's response is puzzling. I would contact GBCI to get further clarification.
At an office park, the stormwater management control is a large retention pond that is managed by an aquatic service vendor. They provide inspection logs for the LEED documentation. Recently, they recommended adding sterile carp to control an outgrowth of vegetation.
1)How and where is the best place to document this?
On one hand, it is part of the maintenance of our stormwater control (SSc6).
On the other hand, it is an organic and low-impact maintenance of the landscape and pest control (SSc3).
2) Is it worth 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. because of a synergy among credits?
The carp themselves do not contribute to SSc6 since they are performing a maintenance function unrelated to stormwater quantity control. It probably falls under SSc3, but may go beyond what is standard there.
I suggest reposting your inquiry under SSc3.
Looking for Precipitation Intensity. New NOAA Site lets me select Precipitation Intensity and location and a site, but doesn't return any data. Old site returns data but the list of available observation sites is unfamiliar to me. How can I locate nearest observatory to my subject property? Thanks in advance.
I don't know if you are still having trouble with the NOAA website, but the HDSC (http://hdsc.nws.noaa.gov/hdsc/pfds/index.html) has data on most states by weather station.
Does installation of mechanical filter media into the storm drain help meet this requirement? (Flogard curb filter inlet)
Mechanical filtration can improve the water quality, but doesn't typically reduce the quantity of runoff during the storm event, which this credit requires. Projects typically achieve this credit with one or more strategies for detention (stormwater ponds, cisterns, large planted areas or green roof), infiltration into the ground (pervious paving, drywells, landscaping) or collection and storage of the water for on-site uses such as irrigation or toilet flushing. Hope that helps.
I'm unclear as to how we show a reduction in stormwater runoff. I see how we calculate the current runoff by figuring the area type and using the formula given, but what does that get compared to?
Emily, you need to find opportunities for onsite stormwater mitigation—giving you a plan to compare your preexistingh runoff to.
In the Volume Captured equation the variable "I" is said to stand for percent impervious of surface. Is this the same thing as the coefficients or is this different? I thought it could mean 2 other things; one being that if 68% of a certain area was impervious then you would put .68. The other option would be that the surface type is 68% impervious so it rejects 68% of all water...which this could actually be the same theory behind the coeffecients. Anyone know?
Generally, when we calculate runoff, we use a runoff coefficient, or in the case of a site with multiple types of surfaces (pavement, grass, gravel, etc.) we calculate the areas of each surface and use a table that provides us with runoff coefficients for each type of surface. Then we develope a combined run-off coefficient value for the site or drainage that can be used with 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.. In the case of storage volume, LEED provides us with an emperical method that essentially calculates the runoff coefficient (Volume of captured runoff) and the "I" stands for the percent of impervious area, as a whole number in the equation. In my opinion, I would rather use a combination of runoff coefficient values and their associated areas to develop a more accurate combined ronoff coefficient volume. This is the same runoff coefficient that is used for the Rational Method. The difference is that you are just calculating a simple volume for storage based on a given rainstorm over an entire area, assuming the surface is impervious, or it isnt, using the LEED storage equation. Runoff coefficients can be easily obtained for various surfaces from the internet.
I have 3 parking lots which are comprised of gravel (chat)....what would the coefficient for this be? I believe it should be less than any kind of pavement but more than grass.
Steve, I'd say this is highly variable. It would depend a lot on the type and size of gravel, and the characteristics of the sub-base. I think you have the right idea, but obviously that leaves a lot of variability.
Our project site is a winery that directs stormwater to ponds which are later used for irrigation. The only thing is that the ponds are sometimes considerably distant from the LEED building. Would we need to expand our LEED boundary to include the ponds? Does the water storage need to take place on site?
Prudence, have you reviewd the MPR supplemental guidance? I think you will find your answer in there. Please post back with further thoughts and questions.
1) How do we consider pools in this credit?
2) If so, how doe we account for runoff coefficient?
I consider a pool the same as a pond or lake. If the pool can contain the rainfall event with no discharge to the sanitary sewer, then the runoff coefficient is essentially zero. If, on the other hand, the rain that falls directly into the pool raises the water level sufficientl6y to overflow into the sanitary sewer, the runoff coefficient is 1.0. Many times the pool will have a bit of freeboard before the water level rises enough to overflow and this will allow you to capture the rainfall, and even make up for some evaporation that would otherwise be made up using potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems.. Much depends on the overflow elevation compared to normal water elevation and the elevation at which makeup water is introduced into the pool to make up for evaporation..
we adapted a vegetated area nearby our project space. i wonder the collected stormwater can be used as irrigation towards this new habitat?
because we would like to make use all our 15% captured stormwater runoff. .
Absolutely, use of captured rainwater for irrigation is a great thing, and contributes to other credits as well.
I am not seeing a default coefficient for pervious concrete or grid pavers. Can you use half of the default for pavers?
The coefficient depends on the kind of pavers.
I would say a "grasscrete" paver with 1/3 vegetation and 2/3 concrete would have a weighted average of 0.66(0.95*2/3 + 0.10*1/3).
Pervious concrete or pavers filled with gravel would be more similar to brick (0.85) in terms of overall permeability.
Amy, How did you come up with a coefficient of 0.85 for pervious concrete? While there can be a great deal of variablility between materials in market areas, the normal range is 500 - 200+ inches per hour permeability. This would seem to equate much closer to zero than to 0.85. Is there testing data that can be required? ASTMVoluntary standards development organization which creates source technical standards for materials, products, systems, and services C 1707 is a permeability test for pervious concrete used to determine when maintenance is required.
0.85 is the runoff coeffecient for brick pavement listed in the reference guide.
For most products I assume that testing data isn't required, but if you are using something that greatly exceeds the permeability expectations of similar products you may wish to provide supporting documentation.
Can you please tell me what the difference is between the percentage listed as "Percentage of storm rainfall volume mitigated" and the second percentage "Design storm rainfall mitagted" ?
I assume you are referring to the two tables on the Credit Form on LEED Online, correct? (the version of the form I am looking at has slightly different wording.)
If so, it is my understanding that table 2.1 is related to volume while table 2.2 is for runoff rate.
there is a question post by our client, and i did not have a definite answer for it. therefore would like to get some advice from here.
the storm water which been collected will be use for irrigation purposes. as to do the irrigation, our client thought of tapping a pipe from the stromwater tank and at the end of the pipe , add a faucet. every day, the gardener will use a long hose , tap onto the faucet and use the collected water for irrigation.
do you think , this concept will be acceptable by usgbc?
James, this is an okay strategy from USGBC's standpoint. To earn SSc6, though, you should focus not on the irrigation system, in my opinion, but in how much stormwater you're capturing from the site, and documenting that.
Would like to know, is 3 days is a default value in all design storm interval?
i unable to locate the interval value because is not stated in the central weather bureau here in Taiwan.
if 3 days is not a default value, what other ways i could calculate the interval value. is there anyone have this issue before?
could you share your thought and sample of calculation.
I'm not sure I totally understand your question, but the 2-year 24 hour design storm is usually shown as either the volume for the entire 24 hour period, or as the average inches per hour over the 24 hour period.
The form wants me to upload documentation of the most recent inspection. My site has no stormwater management facilities - its just a flat site with grass. Do I just need to (annually?) confirm that there have been no changes?
A flat site with grass is a stormwater management facility that according to the credit requirements does need inspection. It could be a pretty simple inspection.
If there were some massive deluge that eroded the grass and led to increased runoff to a local waterway, etc., you would want to be on top of that—so the inspection is that all that frivolous.
After researching this credit for my building, it seems when the building was first constructed it was designed to take advantage of storm water quantity control, pervious services and the green roof but for some reason during the original LEED NC Certification it did not receive the points for storm water management. I think this was a documentation issue but when I looked on the USGBC web site under case studies this is posted under my building's landscape.
The landscape design includes climate-adaptive perennials, groundcovers, flowering shrubs, and trees in mulch beds; a highly efficient irrigation system; and an underground rainwater cistern. This system captures water from 100% of the impervious roof areas of the building for an estimated 47,966 gallons in the peak watering month of July, providing nearly 60% of the July demand. In July, the net potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. demand is reduced to 35,221 gallons compared with the baseline turfgrass case of 176,120 gallons—an 81% reduction during peak periods. Since 95% of the parking is provided in structured parking below the building, the only non-captured stormwater generated by the site is that falling on the impervious driveway and sidewalk areas.
With all this said, what do i have to do to receive this credit? Do I still need to re run all of the calculations and create a storm water management plan?
Thank you again for your help,
In short, you do need to run EBOMEBOM is an acronym for Existing Buildings: Operations & Maintenance, one of the LEED 2009 rating sytems.-specific calculations to earn this credit. I am not an expert on this credit so I can't comment on your chances of earning it, but it does sound like you have a good chance.
Three questions (Sorry about that last inadvertent post!):
1-The corporate campus on which my building sits has an NPDESThe National Pollutant Discharge Elimination System (NPDES) is a permit program that controls water pollution by regulating point sources that discharge pollutants into waters of the United States. Industrial, municipal, and other facilities must obtain permits if their discharges go directly to surface waters. demonstrating that the infiltration is =/> that of the pre-development site. Can we use this to qualify for SSC6 or do we still need to do the stormwater calcs?
2-The building is just one of a multi-building campus that shares impervious and pervious spaces, so whether we can use the NPDES or whether we need to do our own stormwater calcs according to the LEED SSC6 form, we will need to submit for the whole campus -- even though we're seeking certification of just one building. Is this acceptable or would this approach require 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?
3-How exactly can I use the Licensed Professional Exemption in this particular case? I have a stormwater specialist who is a P.E. What's the benefit of this exemption and what's required of him - besides his completing the LPE form?
1. I've seen previously conducted stormwater studies work to document this credit. It kind of depends on what information is included in the report, and whether it can be translated into showing management of at least 15% of the 2-yr, 24-hr volume.
2. In my experience, showing compliance on a campus-wide basis shouldn't be a problem. I'd recommend just making it really clear what the boundary is for the campus included in the stormwater analysis, and that the LEED project boundary falls completely within the larger campus boundary.
3. The form from LEED Online will show you exactly what documentation aspects you do not have to provide if you do an LPE exemption. In generally, the LPE exemption requires that you complete the associated form, and then you get a pass on providing a subset of the usual documentation. Which documentation is excused varies by credit, and the form will show this.
In the calculation section of the guide it says that we need to have the rainfall event interval to calculate the minimum drawdown rate.To what is this event interval refers to? is it the maximum gap within a year or a average gap interval within a year which can be determined by the rainfall data.(we have annual rainfall data).
Further i am unclear of the fact that we need to have the system to address 15% of both AVERAGE YEAR and 2-YEAR,24-HOUR DESIGN STORM..
how to we cater to both of that requirements at once??
please post your ideas..
The rainfall event interval only comes into play if you are collecting rainwater in a cistern or other detention facility as part of your stormwater management strategy. If that is the case, you basically need to know the interval between rainfalls so you can figure out if you empty your cistern before the next rains come. If you aren't collecting rainwater, you don't need to worry about this particular aspect of the calculations.
Regarding the average year vs. 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., in most cases it's appropriate to focus on showing compliance during the 2-year, 24-hour storm, with the idea being that if you can handle that volume on water you'll also be able to deal with the volume of rain that falls during the average year.
Hope this helps.
Thanks Jenny, as you have mentioned it seems like it will be better for us to comply with the 2 year 24 design storm in setting up our rainfall collecting system..
We are collecting rainwater in a cistern or other detention facility as part of our stormwater management strategy...So what IS a reasonable interval between rainfalls? Could one look up the daily average rainfall and assume that the interval is 24 hours? If using the 2 year-24 hour design storm what would the interval be? 2 years?
I see that in LEED Online the only space for retention facilities is a cell asking "Volume captured (cubic feet)" so I'm not even sure where the drawdown information comes into play?
Green roofs help retain stormwater and reduce peak flow.
Use this step-by-step guide to find the data you need for this credit.
Harvesting rainwater, which reduces stormwater runoff, can be used for nonpotable indoor uses like toilet flushing.
Harvested rainwater can be applied landscape irrigation, also reducing stormwater runoff.
Efforts to promote stormwater infiltration by reducing hardscapes can be combined with native habitat restoration.
Vegetated open space can help projects earn SSc7.1.
Vegetated roofs can help meet stormwater goals while reducing the urban heat island effect.
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