Stormwater Library

resources for stormwater professionals

Identifying the roadblocks to LID – 2008 Puget Sound Study

In 2008, a research study was sponsored by the State of Washington to survey the progress being made by 19 local governments in adopting LID controls into their building codes. A representative from each of the 19 municipalities was asked the same set of questions regarding the barriers seen to LID implementation. Some of the trends they found in the responses include the following:

  • Perception that LID is not a proven technology
  • General public and government officials lack understanding of LID
  • Perception that LID is more expensive when compared to traditional BMPs
  • Planning departments lack training to review and inspect LID controls
  • Developers lack knowledge of LID
  • LID difficult to use in urban settings, difficult to retrofit

One of the more interesting solutions to the obstacles focused on funding of “high traffic” demonstration projects to help provide a local proof of benefit.

The report can be read in its entirety here.



Stormwater Factoid: City of San Francisco

On a rainy day in San Francisco over 400 million gallons of stormwater runoff enters the city’s combined sewer system.


Watershed Imperviousness: 3 Recent Studies

Numerous studies have been conducted over the years that correlate the degree of imperviousness of a watershed to overall quality of surface waters fed by that same watershed.  Three studies completed in the last few years are worth noting:

Stormwater Factoid: New York City

More than 27 billion gallons of raw sewage and polluted stormwater discharge out of 460 combined sewage overflows (“CSOs”) into New York Harbor each year.

Source: SUSTAINABLE RAINDROPS – Cleaning New York Harbor by Greening the Urban Landscape

Neighborhood Sidewalk/Street Watering Survey

This is a little impromptu survey that I ran over the last two nights in my neighborhood. While walking the dog at 11pm, I found roughly 10% of my neighbors were overwatering their lawns or missing their lawns altogether – and watering the sidewalks and streets.


If I estimate that each house had 6 half circle nozzles (1 GPM) and 4 quarter circle nozzles (0.5 GPM), that gives me a total rate of 8 GPM.  The total average cycle appeared to be 10 minutes – resulting in 80 gallons per household.  In most cases sprinklers were completely overspraying, but I will estimate that only half of this volume was runoff.  If I make the assumption that each of these households operated sprinklers on a 3 day a week program, then that would give me 120 gallons of runoff per household per week.  This results in a total annual runoff volume of 6240 gallons.  Take the 23 homes that I surveyed (represented by the yellow blobs on the aerial photo) and you get a total anual runoff volume of 143,520 gallons for my neighborhood during the 11 o’clock hour.

And that’s just one hour in the day.

Update: Stormwater Equipment Manufacturers Association

A couple of days ago, I provided a brief introduction to the Stormwater Equipment Manufacturers Association. It was interesting to see their rollout in the press through a distribution of a press release, “A New Voice for Stormwater“.

I was looking forward to seeing the content develop on their website. Two days later, my wish has been granted. Please review the new content on the association’s website. They have broken it out into the following sections:

  • Membership – I was pleased to see a very reasonable level granted to professionals outside of the manufacturing arena at $100
  • Committees – Maintenance and Government/Regulatory
  • Buyer’s Guide – broken down by BMP categories and services
  • Future Publications – a list of future publications pertaining to their initiatives
  • News – upcoming events, including conferences
  • Links – associations, publications, government agencies.

I plan on profiling the group to talk more about their initiatives and to discuss progress to date. The discussion they are trying to facilitate is important and should bring many of the stakeholders to the table.

Developing a Stormwater Credit System for Using Trees

The following four municipalities have developed a stormwater credit system for developers who incorporate trees into their stormwater plans:

The issue of quantifying reduction rates can be a difficult one due to the different capacities of tree species. For more information on use of trees as a stormwater BMP, please refer to the recent study on Trees and Structural Soils by the Department of Urban Forestry at Virginia Tech University. Developers and design professionals can also refer to the Green Values Calculator, which allows you to create hypothetical designs using trees and other green interventions and quantifies the results in terms of costs savings and reduction in stormwater discharge.

Over the next several weeks, I will be presenting a series on how the municipalities of Pine Lake, Sacramento, Portland, and Indianapolis each went about changing the local building code to include stormwater credits for trees.