1. Newsletter Page 3
Reducing Bacteria Loading in Urban Watersheds
By Adam Frey, E.I.T.
Phase II MS4 Compliance Specialist
Although relatively new to Houston, communities throughout the United
States are facing the restrictions associated with total maximum daily
loads (TMDLs) for bacteria. The implementation plans for these TMDLs
Bacteria concentrations
require employing best management practices (BMPs) in order to reduce
the levels of E. coli and/or fecal coliform in urban waterways. This in storm water runoff are
proves especially challenging for MS4 permit holders due to the relative well above recreation
infancy of data collection relating to BMPs and their effectiveness in standards.
reducing bacterial levels.
Researchers have found that bacteria concentrations in storm water
runoff are usually well above primary contact recreation standards. Both
human and non-human activities can be blamed for these elevated
levels. In any case, it is still the responsibility of the MS4 to reduce the
loading of the bacteria being discharged from their conveyance system.
Traditional storm water BMPs employed in Houston, such as drainage
swales and detention ponds, have performed poorly in initial trials for
bacteria reduction. In fact, detention ponds may actually increase the
bacteria levels due to the attraction of waterfowl and other wildlife.
Other options, such as bioretention cells and media filtering, have shown
promise. These techniques are effective because of the treatment
processes utilized by the BMP. However, these techniques become futile Detention Ponds may actually
if the BMP is not properly maintained. To retrofit existing municipalities increase bacteria loading.
with these BMPs would most likely be cost-prohibitive due to large capital
outlays and perpetual maintenance requirements.
Current testing and research will hopefully provide an answer to the
bacteria quandary. The International Stormwater BMP Database provides
a large data set that is useful in evaluating the effectiveness of various “By reducing the amount
BMPs. It is the opinion of this author that regardless of the pollutant, be of water you discharge,
it bacteria or TSS or metals, the key is reducing any pollutant is to reduce you reduce every
the quantity of water discharged from the site. Houston’s communities pollutant that the TCEQ
need to focus on retaining more water through infiltration and allowing would fine you for.”
more time for evapotranspiration. Simple practices like bioretention,
vegetated biofilters, and even elongated, dry detention basins can
perform this task. By reducing the amount of water you discharge, you
reduce every pollutant that the TCEQ would fine you for.
You can contact Adam at afrey@stormwatersolutions.com