Illinois Environmental Protection Agency Crab Orchard Creek Watershed TMDL Implementation Plan
70 Final Report
Table 6-3. Summary of BMPs Reducing Impairments Due to Urban Land Sources.
BMP Phosphorus
Reduction
(percent)
BOD5
Reduction
(percent)
Manganese
Reduction
(percent)
Fecal
Coliform
Reduction
(percent)
Additional Benefits for
Stream Health and
Dissolved Oxygen
Impairments
Disinfection of
primary effluent from
STPs
unknown na na unknown
the use of this BMP
should result in a
substantial reduction in
fecal coliform loading
Control of CSOs unknown na na unknown
the use of this BMP
should result in a
substantial reduction in
fecal coliform loading
Maintenance of
onsite septic systems 100 6 - 35 na 100 -
Infiltration trench 50 -75 90 75 - 99 90
up to 90 percent removal
of sediments and organic
material
Grassed swales 20 - 65 unknown 40 - 90 unknown Typical TSS removal are
70 – 90 percent
6.4 Summary of BMPs for Stream and Lake Sediment Related Sources
Erosion in streams and lakes is a great concern as it contributes to the overall water quality degradation in
the watershed. In addition, sediment transported by streams (as a result of erosion) accumulates in lakes
as it is deposited onto the lake bottom. Phosphorus and manganese are released from lake bottom
sediments as these pollutants typically adhere to the fine sediment particles. Marion County has
estimated that approximately 8,800 acres of cropland in the watershed is highly erodible. The average
sedimentation rate is 319,200 tons/year and the total deposited sediments in creeks and lakes in the Crab
Orchard Creek watershed are 104,000 tons/year (WCSWCD, 2007). The BMPs that are applicable to
reduce impairments related to sediments are summarized in Table 6-4 and include the anticipated
reductions for each BMP and parameter. If a BMP is not expected to significantly reduce loading of a
specific parameter, then the reduction is labeled not applicable (“na”). If a BMP is expected to reduce
pollutant loading, but no studies were found to quantify the reduction, then the reduction is labeled
“unknown.”
Table 6-4. Summary of BMPs Reducing Impairments Related to Sediments.
BMP Phosphorus
Reduction
(percent)
BOD5
Reduction
(percent)
Manganese
Reduction
(percent)
Fecal
Coliform
Reduction
(percent)
Additional Benefits for
Stream Health and Sediment
Impairments
Inlake Controls 90 unknown 80 - 90 na
May have impacts on DO
balances downstream of water
release structures. TSS
removal of 90 percent
Streambank and
Shoreline
Erosion BMPs
unknown unknown unknown na
Improves temperature and
dissolved oxygen conditions by
allowing vegetation to establish
Stream
Restoration unknown unknown unknown na
Improves aquatic habitat and
increases the amount of re-aeration
from the atmosphere to
the water
