Low Impact Development Manual for Michigan - OSEH - University ...

Large subsurface filter
Large Subsurface filters (Figure 7.20) receive relatively
large amounts of flow directed into an underground box
that has separate chambers. One chamber settles large
particles, and the other chamber contains media to filter
small particles. The water discharges through an outlet
pipe and into the stormwater system.
Figure 7.20
Large subsurface filter
Source: New York Stormwater BMP Manual
Applications
Constructed filters can be used in a wide variety of
applications, from commercial/industrial developments
to ultra-urban sites and even transportation projects.
Their application in residential settings, especially lowdensity
residential, can be limited because they require
extensive maintenance. Moreover, other BMPs are more
cost effective for stormwater management in residential
projects (constructed filters are generally used for areas
with high impervious cover).
Filters are applicable in urban areas of high pollutant
loads and are especially applicable where there is
limited area for constructing BMPs. Filters may be
used as a pretreatment BMP for other BMPs such as
wet ponds or infiltration systems, but input to many
filters also requires pretreatment to reduce large settled
particulates or debris.
LID Manual for Michigan – Chapter 7 Page 162