Hello all,
Our project is intending to use a LEED boundary that is only a portion of a larger site. The larger site is a National Cemetery and the LEED boundary includes only the areas that are immediately servicing the buildings on site. As part of meeting credits SSc6.1 and 6.2 (stormwater) we are designing a wet retention pond outside the LEED project boundary that will capture the runoff for the LEED project boundary land as well as a majority of the larger site.
The larger site's irrigation system will be drawn from this wet pond, and is intended to supply the irrigation needs for the larger site, which then includes the land within the LEED boundary. Only in times of drought would the irrigation be supplied by a potable source, but based on our calculations we should easily reduce the need for potable water for irrigation by 50%.
Since this wet pond is collecting the stormwater from the LEED site and the larger site, and supplying the irrigation for both the LEED site and larger site, can this constructed retention pond water be considered "captured on-site rainwater"?
Any advice would be most appreciated, thank you.
William Weaver
LEED Fellow, WELL APJLL
181 thumbs up
June 23, 2016 - 10:11 am
Hi Derek,
We had a similar instance wherein we developed an office building as part of a larger office park. The irrigation system was not specific to our project's boundaries and was continuous throughout the entire park. Likewise, it was supplied by a large retention pond in the park, that was also not within our boundary.
For the purpose of documenting this credit, we provided a narrative explaining that we were calculating the irrigation water use for the entire area served by the irrigation system, not just the vegetated area within our LEED boundary. To demonstrate that the pond met the irrigation demand, we provided the following:
1. Topographical as-built of the pond that illustrated the pond's normal permanent pool elevation, and maximum elevation;
2. Calculations showing the permanent pool volume - used to compare against the calculated demand to show that the pond's normal permanent capacity exceeded that of the irrigation demand;
3. Copy of the irrigation consumptive use permit confirming that the irrigation system is supplied from the pond. Irrigation system drawings could have been used for the same purpose, but we were unable to locate any irrigation system design drawings for the existing irrigation system, hence we had to provide the consumptive use permit as our means of proof.
That may be more than was necessary to sufficiently document credit compliance, but we were able to demonstrate 100% reduction in potable water use, and 52% reduction in total water applied with this strategy. We received no review comments.
Derek Seifert
LEED Green Associate, Landscape Architectural InternAnderson Engineering of MN
1 thumbs up
June 29, 2016 - 9:37 am
Thank you William, this was very insightful for me and my team! We will proceed by presenting the information in the same way.