From:	Kenneth Potter [kwpotter@wisc.edu]
Sent:	Tuesday, May 10, 2011 10:54 AM
To:	Hoffman, Jeanne
Subject:	Madison Sustainability Plan

Jeanne,

I congratulate the Sustainable Design and Energy Committee on its 
comprehensive and thoughtful report.  However, I would like to point out that 
the recommendation for a green roof requirement is inconsistent with the goals 
of sustainable water use and stormwater management.  As pointed out in the 
report, groundwater levels in the Madison metropolitan area are declining as a 
result of groundwater pumping .  This adversely affects surface water bodies, 
such as  
lakes, streams, and wetlands.   As recently as 2004 the minimum flow  
in the Yahara River at Windsor was only 10 cubic feet per second,  
which even made canoeing difficult.   The Madison Metropolitan  
Sewerage District diverts about 60 cubic feet per second from the watershed in 
the form of treated wastewater.  Green roofs would divert water from the 
watershed as well.  It is preferable that roof runoff be captured for local 
use or fed to infiltration facilities to recharge groundwater.

While green roofs can provide energy savings, equivalent savings can be 
provided by other means (such as insulation and reflective roof coatings).  
The requirement proposed by the sustainability plan allows for the use of 
alternative approaches, but nonetheless specifies green roofs as the default 
option.  For the reasons given above, I question the wisdom of this proposed 
requirement.

I would be happy to discuss this further.

Ken Potter
Department of Civil & Environmental Engineering University of Wisconsin-
Madison


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