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16 Nov, 2008

Case Studies in Sustainable Stormwater – Rainwater as a Resource

Posted by: Skylar In: Stormwater

Sustainable Stormwater - Treepeople

A recent post from the L.A. Creek Freak led me to one very interesting resource for up-and-coming stormwater management practices: Rainwater as a Resource.

Rainwater as a Resource is a report developed by “TreePeople”, a non-profit group from L.A. dedicated to sustainable development.  The report focuses on 3 sites that were chosen as pilot programs for the stormwater technologies.  The first site is a residential parcel, where the report lays out the following objectives:

  • Demonstrate how a single parcel can act as a miniature watershed, and how thousands of similar parcels can be networked to meet a region’s water management and flood prevention needs
  • Capture onsite stormwater falling on the property from up to a 100-year storm
  • Utilize a cistern to store some of the stormwater for later use in irrigation
  • Infiltrate remaining water to recharge the aquifer, thereby virtually eliminating runoff
  • Minimize the solid waste stream and detain irrigation water by reusing greenwaste onsite as mulch

The objectives are quite aggressive, and the BMP’s employed to meet these objectives are as follows:

  • A cistern system, comprising two connected 1,800-gallon tanks that retain stormwater for irrigation use, and a first-flush diversion unit. T his unit collects the “first flush” of water that occurs during a storm and stores it long enough so gravity can settle out pollutants that accumulate on the roof. Remaining water is delivered to the cistern
  • A vegetated and mulched swale filled with yard trimmings that captures and slows rainwater runoff so it can be absorbed by the soil
  • Retention grading in the frontyard and backyard, which allows large quantities of stormwater to be retained onsite and percolate into the ground rather than wash down storm drains
  • A drywell filled with sand and crushed rock, which prevents water that falls on the driveway from reaching the street as runoff. This unit cleanses polluted water from the driveway before it percolates into the ground to recharge the aquifer.

The report goes on to describe some of the design work that was done, and even covers the various cost estimates and benefits for the technologies.  More importantly, the report contains an extensive list of “Lessons Learned”, which is invaluable for these newer and less used technologies.

The second site was an elementary school, where sustainable design BMP’s were applied to an existing establishment.  The report has a similar writeup for this site, including objectives, designs, monitoring, maintenance, and lessons learned.  As stated previously, I personally found the lessons learned to be one of the most beneficial aspects of the report.  The report is very candid, making every attempt to provide realistic and helpful information throughout.  Here’s a portion of the writeup that was quite informative, revealing the importance of continued education to ensure awareness about the site’s functionality:

Challenge: Staff, faculty and students move on and even those who stay cannot always be relied upon to interpret or defend the project. The Broadous project budget did not include funds for signage or other permanent interpretive elements. As a result, knowledge of the project’s meaning – and even its existence – has been lost.

The significance of the project was not sufficiently evident to district personnel, and several disheartening events consequently occurred without notification to the other partners, including improper pruning and care of trees on the campus. In the summer of 2005, the district removed trees and grass from the swale and paved its entire length with concrete in order to accommodate the passage of delivery trucks.

While most reports would be reluctant to admit to obstacles of this type, I appreciate the honesty of this information.

The report covers one additional school project, with some similar objectives but certainly different site-specific designs and challenges.  I highly recommend reading this report, or at least bookmarking the link in case you need some tangible case studies in sustainable design.  To read more of the report, visit the following link:

[Rainwater as a Resource]

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