Rainwater Management - No discharge at all or No immediate discharge?

I also have the same question! any guidance is appreciated.

This article explains it nicely: https://leeduser.buildinggreen.com/blog/reality-rainwater-leed-v4-green-roof-may-not-help-you

"Manage" means infiltrate on site or reused within the building. No runoff may leave the site - so no discharge at all.

Be careful with the reuse...it has been denied many times, as reuse in a building mechanical is not "natural hydrologic conditions."

The best approach is to use Option 2 for this credit, so you only need to manage the increase in runoff from the pre-development condition.

Regarding the discharge requirement, I'm curious what everyone thinks the significance is of the addition of the word "surface" that was added as a Reference Guide Correction in the Addendum dated October 2014. As far as I can tell, this was the only change in this addendum, which now reads, "All runoff from the chosen percentile of precipitation events must be managed such that there is no surface discharge from the site."

More specifically, I am working on a project where rainwater from the 98th percentile event is treated onsite, temporarily stored, and then discharged at less than the predevelopment rate via underground piping. There is no "surface" discharge from the project site. Does our project qualify for the 3 available points via Option 1 due to the absence of surface discharge? 

Any updates on whether no surface discharge, but slow discharge from GI (such as microbioretention) will be acceptable to comply the requirement? Would like to hear whether anyone has a success story..

Thanks in advance!

Michael - can  you explain why you are not recommending Option 1 re-use? The guide specifically says re-use is considered acceptable "All runoff from the chosen percentile of precipitation events must be managed such that there is no discharge from the site. Techniques include, but are not limited to, infiltration, storage and re-use, bioretention, open-grid pavement, and the reduction of impervious area." and "For projects following Path 3, green roofs and rainwater harvesting approaches are the most likely GI and LID strategies to help zero lot line projects meet the credit requirements."

Option 2 is even harder because you have to show pre-settement (not pre-development) vs post-development, and good luck finding the pre-settlement natural land cover condition.

Mike and Seonhee,

The v4.1 language may be a little more clear, but in both v4 and 4.1 detaining stormwater and releasing it slowly from the site - whether at the surface, or to stormwater infrastructure (storm sewer, pipes, etc) - is not allowed as a management/ reduction strategy. The requirement to "manage" now means "infiltrate" with the goal to drastically limit any water leaving the site. Water reuse for can help reduce the total volume of water that needs to be managed, but by itself may not be enough to reach the thresholds. 

Thanks for your reply, David, and just to close the loop on our project's experience with demonstrating compliance utilizing discharge via underground piping, for those who are interested; The Reviewer's accepted our project team's response to their initial comments and awarded 3 points via the Option 1 compliance path.

The response cited Reference Guide Correction 100001951 dated October 1, 2014, which added the word "surface" to the original language, as noted in my original post above, as well as correction 100001952 (also dated October 1, 2014), which indicates that, "...detaining rainwater runoff at or close to its source" is an acceptable approach.

No further comments were provided by the reviewers as our Final Design Review report came back simply stating "awarded", however this approach was accepted by our particular review team at the time of submission - Hope this helps!

Mike - I was preparing a post and I think that you may have aided our team in understanding how to manage our rainwater.  Our project is the El Portal Visitors Center located on a previously developed site in the El Yunque National Forest in Puerto Rico, the only tropical rainforest in the U.S. National Park system.  El Yunque is located in a heavily forested mountainous area with poorly drained clayey soils.  So the pre-development hydrological condition of our site indicates that rainwater naturally does not stay on-site.  So normal LIDs such as permeable pavement, cisterns, and bio-retention ponds for this site are not technically feasible considering the volume of rainwater. 

So, the strategy we are considering is very similar to your solution.  We are applying Option 2 and designing a series of detention ponds that will slowly release rainwater collected from the roadways, surface parking, and Visitors Center roofs to simulate the pre-development conditions.  Any feedback is welcome.