Page 13 - TN Public Works May-June Vol. 32 No.1
P. 13
By Jim luebbering and Greg Herold
For some time, Departments within the city of Chatta-
nooga including the Regional Planning Agency, Economic &
Community Development, and the Public Works Depart-
ment have coordinated efforts to bring about a well-man-
aged and hopefully “confusion free” transition from our ex-
isting stormwater management standards to new standards
mandated by the State of Tennessee. Existing development
regulations tied to “grey” stormwater infrastructure systems
will be swapped out for more sustainable and environmen-
tally beneficial stormwater infiltration and stormwater reuse
practices dubbed “green” infrastructure practices.
So why are existing stormwater systems and practices
“grey?” Well, pipe is grey, some of the time. Ditches, heav-
ily armored with grouted rip-rap to sustain high velocity
flows, are grey (until major floods wash away the stone;
then the channels are brown). Detention ponds aren’t
grey unless they’re armored with concrete or incorpo-
rate cinder block walls into their design. Unfortunately,
more than a few of these relics can still This newly constructed road is part of
be seen, across the U.S., never modi- In contrast, newly mandated Chattanooga’s transition from existing
fied for water quality improvements infiltration and reuse practices stormwater management standards to
and still standing as testament to a new standards mandated by the State of
time when flood control was the sole are “green”. The trees, plants, Tennessee. The road, built on a stone bed
stormwater management condition un-compacted subgrade, and with brick pavers on top, actually accepts
placed on new developments. A final good planting soil incorporated more rainwater than the yard next to it.
reason for the title of “grey” is that the into infiltration practices such as
fifty year old, semi-successful technol- rain gardens, bio-retention cells,
ogy of flood control “or peak attenu-
ation if you’re a hydrologist” is pretty vegetated roofs and infiltration
boring and grey is, well, boring. Grey is berms are living stormwater
utilitarian. It is practical. It has served systems. Even cisterns and rain
its purpose. barrels are “green” because
In contrast, newly mandated infiltra-
tion and reuse practices are “green”. The water reuse is as environmentally
trees, plants, un-compacted subgrade, beneficial as it gets.
and good planting soil incorporated
into infiltration practices such as rain gardens, bio-reten-
tion cells, vegetated roofs and infiltration berms are living
stormwater systems. Even cisterns and rain barrels are
“green” because water reuse is as environmentally benefi-
cial as it gets. Research also indicates that the installation
cost of green infrastructure can be less expensive than grey
while the full life cycle cost is almost always less expensive
than grey. Once maintenance, system replacement, land
and utility costs and resulting property values are fac-
tored into the cost equation, green infrastructure can save
money or add to property values. Therefore, “green” also Previously the road flooded with
means affordable. Grey is utilitarian, but maybe green is every rainfall, and there was
also utilitarian, but in a better way. nothing the city could do about it.
Why paint the old and new technologies as either grey
Continued on page 14
TPW May/June 2014 13
For some time, Departments within the city of Chatta-
nooga including the Regional Planning Agency, Economic &
Community Development, and the Public Works Depart-
ment have coordinated efforts to bring about a well-man-
aged and hopefully “confusion free” transition from our ex-
isting stormwater management standards to new standards
mandated by the State of Tennessee. Existing development
regulations tied to “grey” stormwater infrastructure systems
will be swapped out for more sustainable and environmen-
tally beneficial stormwater infiltration and stormwater reuse
practices dubbed “green” infrastructure practices.
So why are existing stormwater systems and practices
“grey?” Well, pipe is grey, some of the time. Ditches, heav-
ily armored with grouted rip-rap to sustain high velocity
flows, are grey (until major floods wash away the stone;
then the channels are brown). Detention ponds aren’t
grey unless they’re armored with concrete or incorpo-
rate cinder block walls into their design. Unfortunately,
more than a few of these relics can still This newly constructed road is part of
be seen, across the U.S., never modi- In contrast, newly mandated Chattanooga’s transition from existing
fied for water quality improvements infiltration and reuse practices stormwater management standards to
and still standing as testament to a new standards mandated by the State of
time when flood control was the sole are “green”. The trees, plants, Tennessee. The road, built on a stone bed
stormwater management condition un-compacted subgrade, and with brick pavers on top, actually accepts
placed on new developments. A final good planting soil incorporated more rainwater than the yard next to it.
reason for the title of “grey” is that the into infiltration practices such as
fifty year old, semi-successful technol- rain gardens, bio-retention cells,
ogy of flood control “or peak attenu-
ation if you’re a hydrologist” is pretty vegetated roofs and infiltration
boring and grey is, well, boring. Grey is berms are living stormwater
utilitarian. It is practical. It has served systems. Even cisterns and rain
its purpose. barrels are “green” because
In contrast, newly mandated infiltra-
tion and reuse practices are “green”. The water reuse is as environmentally
trees, plants, un-compacted subgrade, beneficial as it gets.
and good planting soil incorporated
into infiltration practices such as rain gardens, bio-reten-
tion cells, vegetated roofs and infiltration berms are living
stormwater systems. Even cisterns and rain barrels are
“green” because water reuse is as environmentally benefi-
cial as it gets. Research also indicates that the installation
cost of green infrastructure can be less expensive than grey
while the full life cycle cost is almost always less expensive
than grey. Once maintenance, system replacement, land
and utility costs and resulting property values are fac-
tored into the cost equation, green infrastructure can save
money or add to property values. Therefore, “green” also Previously the road flooded with
means affordable. Grey is utilitarian, but maybe green is every rainfall, and there was
also utilitarian, but in a better way. nothing the city could do about it.
Why paint the old and new technologies as either grey
Continued on page 14
TPW May/June 2014 13
