Has anyone managed to achieve this credit for an urban site in Colorado, with pre-development imperviousness greater than 50%? our water laws prevent any water harvesting. We will provide retention which significantly decreases the release rate for a 2-year 1-hour event (the local design criteria). My civil engineer also tells me that reductions due to infiltration and evotranspiration "not easily quantifiable", so we have left that out in computing run-off, which basically shows that while the run-off rate is greatly improved, we have not reduced the total run-off quantity.
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Gregory Hurst
Office ManagerRobert Peccia & Associates
66 thumbs up
October 11, 2010 - 4:13 pm
It is very difficult in Colorado. We have two examples, one in Colorado and one in Wyoming. The one in Colorado was a project with a low run-off coefficient after development and the reduction in volume was used to maintain a treatment wetlands that was developed as part of the project for water quality. The wetlands needs a constant source of water to maintain viability. This was an opportunistic situation and is not very land efficient. This project is the Gardens at Spring Creek in Fort Collins. This was not a previously developed site and a portion of the project is in flood plain, but the reduction in volume is achieved, even though we did not have to document it for LEED points.
The project in Wyoming collected all the stormwater for the LEED boundary area and routed it to the center of the project where there is a aesthetic lake that needs water to overcome evaporation and seepage, This is the Cheyenne Children's Garden. This was documented for LEED and was a previously developed site.
Deborah Lucking
Director of SustainabilityFentress Architects
LEEDuser Expert
245 thumbs up
October 14, 2010 - 6:54 pm
I would like to relate this discussion to the question posed earlier by Randall Brookshire (June 15 2010 thread). Given that the design criteria in Colorado is a 1-hr event, what if we provide detention so that the run-off takes more than 24 hours to clear? ! would argue that this has the same effect as 2 separate events, for which runoff has been decreased by 50%. I know - it sounds desperate, but it doesn't make any sense that the entire state of Colorado is precluded from achieving this point (and the regional priority point as well!).
Tristan Roberts
RepresentativeVermont House of Representatives
LEEDuser Expert
11474 thumbs up
October 29, 2010 - 2:10 pm
Deborah, I think this is a great question, and for some discussion on it, see the thread below started by Lucy Williams.