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Tuesday, January 31, 2012

Stormwater Visionary Tom Holz Has an Opinion on Proposed Regulations

Tom Holz is an engineer.
For decades he's been promoting the concept of "Zero Impact Design" to educate the stormwater community about the destructive impacts of stormwater runoff to our ecosystems and especially to Puget Sound. He was among a group called the "14 Scientists"  that crafted a letter to Department of Ecology, that ended up rocking their world. The group was sounding the alarm to that the Northwest ecosystem was crashing into serious decline, with salmon and other iconic wildlife listed as "Threatened Species" by the ESA.

Tom Holz is a Board Member for
People for Puget Sound
To make a long story short, that letter and Tom's testimony in a case brought by People for  Puget Sound and Earthjustice to the Pollution Control Hearings Board, ended up drastically changing the Stormwater Regulations for Cities.  In the Boards ruling in 2009, cities were required to implement "Low-Impact Development" techniques. PCHB’s so-called Phase II stormwater ruling
The Board concludes the (Washington Department of) Ecology must modify the permit to require permittees to identify barriers to the implementation of (low-impact development) and identify actions taken to remove those barriers, to establish goals for the future use of (low-impact development), and to require other specific actions on reasonable and flexible time frames, both during this permit cycle and in anticipation of future permits.
In other words, cities must clean up their acts!

Now Tom Holz is raising the alarm again. The Department of Ecology is again asking for comments on their latest round of regulations. People for Puget Sound is urging citizens to submit comments by Friday to DOE to

Stop polluted runoff and save our Sound

Tom Holz says they are still not getting it.


Washington State Department of Ecology Stormwater Management Manual for Western Washington, 2012 Update
Thomas W. Holz
The manual is based on deeply flawed assumptions.  Stormwater management depends on a computer program (WWHM) to impose a standard for development.  Although the program is derived from HSPF, a venerable and reasonably reliable stream flow simulation program, it was modified (originally by King County) to become a pond-sizing program for development projects.  The assumptions made in coding the pond-sizing program are unjustified, and the program is thus invalid for the purpose of serving as a test for acceptability of a development project. 
For example, it is assumed in the coding of ECY’s program, that a stream flow model (HSPF), which requires calibration to two years of stream flow to be valid, can somehow be converted to model runoff on discrete sites.  On such sites, stream flow data is non-existent and, more often than not, there is no stream to calibrate to.  The most egregious and invalid assumption buried in the WWHM model is that predevelopment overland flow is defined as the sum of predevelopment surface overland flow (near zero) plus groundwater flow.  This totally invalid assumption allows the developer to collect all precipitation on a site and route it as overland flow to the nearest stream (with catastrophic results on streams and aquatic life).
If WWHM is to continue to serve as the standard for development, it must be converted to a water balance model.  The water balance model would recognize the predevelopment fate of precipitation that falls on most discrete sites in a watershed:
1.    Evapotranspiration (ET) comprises about 18 inches per year (Beyerlein, 1999).  Maintenance of ET is critically important to a healthy watershed.
2.    Precipitation exceeding the volume evapotranspired is infiltrated (usually up to the 100-year storm event).
3.    Overland flow runoff in a typical watershed is less than 1% of stream flow.
Thus the water balance model would provide the developer with the tools to assess whether the practices employed on his project will maintain a water balance in close approximation to predevelopment water balance.  It is clear that, in this paradigm, evapotranspiration is the important parameter and its decline must be severely limited.
Without this change, and others that tend to reinforce low impact development practices, Puget Sound and its watersheds will continue on a path of steep decline.

1 comment:

  1. Interesting stuff. I'm all for it if it makes construction site cleanup more efficient!