Hi All,
Can there be absolutely no uncontrolled flow to achieve this credit? For example, if the required retention volume for the 95th percentile storm is 100 CF, can I oversize practices to have a storage volume of 100 CF but only capture 75% of the site within the LEED boundary? This is a situation I am running into on a historical site. I cannot add practices in certain areas within the LEED boundary.
If not, that means 100% of the area within the LEED boundary needs to drain to an LID practice for this credit no matter what percentile storm you select. For urban projects, this is pretty difficult to achieve.
Thanks in advance!
Petra Holoubkova
2 thumbs up
May 13, 2021 - 5:29 am
Hi Teresa,
have found any answer on this? I have a similar case - urban project in historical site, where covering 100% of LEED boundary is simply not feasible. Therefore I wonder if there is any chance to earn points for covering at least majority of the project site with GI/LID strategies..
Teresa Lin
Senior Project Engineer3 thumbs up
May 13, 2021 - 10:22 am
Hi Petra, yes according to our LEED coach 100% of the area within the LEED boundary needs to be directed to a GI/LID practice of some kind and you cannot overretain in other areas to make up for uncontrolled area within the LEED Boundary. We decided to forgo the rainwater credit as it was not feasible for our project.
Gustavo De las Heras Izquierdo
LEED Expert185 thumbs up
May 13, 2021 - 11:06 am
Hi Teresa, if you want to follow Option 1 you can't have uncontrolled runoff. In Option 2 there is more flexibility and it is usually easier to fulfil the requirements.
Petra Holoubkova
2 thumbs up
May 18, 2021 - 8:21 am
Hi Gustavo,
since you mention Option 2. - do you have an experience with documenting natural land cover conditions for projects in historical sites? Our project is in area where first settlings/developement dates back to centuries ago. So pre-developed site run off volume would seem to be like a rough guess rather than a proper calculation based on some detailed evidence..
Gustavo De las Heras Izquierdo
LEED Expert185 thumbs up
May 18, 2021 - 11:30 am
Hi Petra,
Yes, I have experience documenting Option 2 in many projects. You can either take a guess observing the surronding landscape or use historical satellite photos.
Teresa Lin
Senior Project Engineer3 thumbs up
August 13, 2021 - 10:04 am
For option 2, do you have to manage the increase in 95th percentile storm compared to predevelopment for LEED v4.1? Or is the threshold lower for option 2 similar to option 1?
Afogreen Build
www.afogreenbuild.comGreen Building Consultant
247 thumbs up
August 23, 2021 - 5:50 am
Hi Teresa,
LEED v4 SSc4 Rainwater Management Option 2 Natural Land Cover Condition needs you to compare the runoff volume under natural land cover conditions with the runoff volume under the post-developed conditions (95th percentile). You need to subtract the natural land cover volume from the post-developed volume. The difference is what must be managed on-site.
If you want to substitute with LEED v4.1, Option 2 Natural Land Cover Condition is no longer available.
To comply with LEED v4.1 SS Rainwater Management:
Thanks and regards,