A newly proposed regulation for the Milwaukee area could put new and existing "green" infrastructure on the hook for collecting and processing larger amounts of stormwater runoff every year.
A draft state wastewater discharge permit for the Milwaukee Metropolitan Sewerage District (MMSD) could be the first in the nation to mandate adding the equivalent of 1 million gallons of alternative stormwater storage capacity annually to municipal and private projects.
The regulation change is proposed as an alternative to adding sewer overflows to waterways, while still reducing the risk of sewage backups into area basements. The new permit would bring a variety of alternative stormwater management tools to the area, including rain chains and rain barrels, porous pavement, green roofs, landscaped swales on the sides of streets and additional purchases of wetlands and floodplains by the MMSD.
These systems, all designed to prevent runoff-borne pollutants from reaching sewers and waterways, are less costly per gallon of stormwater collected than digging more sewage tunnels. Porous pavement, for example, only costs 35 cents per gallon of stormwater absorbed and treated, while new tunnels cost about $2.50 per gallon. Adding green roofs costs about $1.10 per gallon, though total costs to the property owner can be higher.
Taxpayers will pay for a portion of each project's cost in the district's annual construction budget, which has allotted just over $2.95 million for green infrastructure spending in 2012 and 2013.
The new additions are meant to move the district closer to the goal of no sewer overflows by 2035, though the permit maintains earlier language allowing up to six overflows a year in the combined sanitary and storm sewers of central Milwaukee and eastern Shorewood. Since deep tunnel operation began in 1994, the district has averaged only 2.5 overflows annually through 2011.
MMSD has been awarding grants to building owners to encourage green roof plantings since 2003. From 2002 through 2011, roughly 118 million gallons worth of green infrastructure storage has been built in the Milwaukee area, according to MMSD sustainability manager Karen Sands.