Raingardens and permeable pavement

In response to a query I had on raingardens and pervious payment
Gregg Thompson (Izaak Walton League- Bush Lake Chapter) submitted
this:

A Burnsville project involved the City's retrofitting about 17
raingardens into a two-block residential neighborhood on Rushmore
Drive, north of Crystal Lake. This area of the city, like many,
have no stormwater ponds for settling out sediments and nutrients,
so their stormsewers discharge directly into Crystal Lake. The City
worked with Barr Engineering to do an on-the-ground study on the
effectiveness of strategically-placed raingardens to intercept and
infiltrate stormwater runoff. The project ended up reducing the
neighborhood's stormwater discharge by 90% (they have monitoring
equipment in the stormsewer system). I think their goal is to get a
cost-analysis done on the project, with their monitoring results
(measuring sediment, nutrient and pollutant removal, etc.) to
determine how much this method would cost for a certain level of
sediment/nutrient/pollutant removal. Raingardens (Bioretention /
Infiltration Basins) are being used all over the Twin Cities, with
the exception of Bloomington. The city claims two raingardens in
town, but they're simply wet ponds that they are choosing to call
raingardens because they don't seem to understand the function.
Anyway, raingardens are designed to infiltrate stormwater runoff and
treat that runoff through sediment capture, nutrient capture and
absorbtion, and pollutant breakdown by the soil microbes. These
raingardens can work in a variety of locations, from residential to
commercial areas, with priorities being locations that would keep
stormwater runoff out of the stormsewer systems and our wetlands,
lakes, streams and rivers.

Here's a link that has a photo of one of the Burnsville
raingardens:
http://www.metrocouncil.org/Directions/water/water2006/
raingardensApr06.htm and another good link to an article from the
DNR Conservation Volunteer Magazine:
http://www.dnr.state.mn.us/volunteer/mayjun04/raingardens.html



Also, regarding water conservation issues, there are a lot of
sprinkler systems in Bloomington (and everywhere else) that will
often be running during and immediately after rain events -dumping
drinkable water onto the ground.

We would also promote rainbarrels and other water conservation,
and measures for the landscape (and maybe have a couple of hands-on
'make your own rainbarrel' workshops). Anyway, getting back to your
question about permeable / pervious pavement, I don't know of any
good examples in our area, but there are installations in Prior Lake
(driveways), Apple Valley (driveway), UofM Landscape Arboretum in
Chanhassen (parking lot), Ramsey-Washington Metro Watershed District
in Little Canada (parking lot), Schmeltz Volkswagen in White Bear
Lake (huge parking lot), MnDOT-Annandale Roadway Testing Grounds
(interstate road surface) and a few other places. With the
permeable pavements, materials can be special concrete pavers (which
have wider openings between joints), permeable concrete, permeable
asphalt, and some other plastic products that are filled with turf
or crushed rock. The base of these permeable paving systems has
typically been over-excavated and a material with large amounts of
pore-space (like crushed rock or coarse-sand) has been put in to be
able to hold a large amount of stormwater. These systems are quite
interesting. Homeowners could also employ these materials
(specifically the pavers) in patios and sidewalks.

My hope is that eventually Bloomington will follow Minneapolis'
model (slightly revised) that charges people for their stormwater
runoff. If landowners reduce their runoff (and can prove it to the
city) the city will provide stormwater credits to reduce the
stormwater utility fee.

Here's a little on Minneapolis' program that I had previously
sent to another person: The City of Minneapolis has enacted higher
stormwater utility fees. Landowners' stormwater utility fees are
determined by their amount of impervious surfaces. The City is
providing economic incentives to encourage runoff reduction by
offering "credits" for implementing runoff reduction practices
(raingardens, permeable pavement, etc.) along with proof of what
size of storm-event the practices were sized for. Some of the other
cities in the twin cities are in the wait-and-see mode, letting
Minneapolis work out the kinks, but I think this sort of 'pay for
your impact' fee will be utilized by other cities to both reduce
stormwater-runoff from private lands and help them pay for public
runoff-reduction project planning and implementation, as well as
education. Link:
http://www.ci.minneapolis.mn.us/stormwater/what-we-do/StormwaterRate
.asp