December 2010 Final Indian Creek, Dago Slough, and Prairie Creek LRS/TMDL
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6.3.3 Existing and Recommended BMPs
Existing BMPs contribute to reducing upland sediment and nutrient loadings. After the
various upland loading models were developed, localized drainage areas were
delineated for each individual BMP. Based on existing literature (STEPL Spreadsheet
Tool, 2004) and field observations, pollutant removal efficiencies (percentage efficiency)
were use to determine what percentage of pollutants are removed by each BMP; the
result is the remaining loading after runoff and sediment drains through the given
BMP.
Table 73 - Pollutant Removal Efficiencies Used for Existing and Potential BMPs
BMP
Removal Efficiency Range
Sediment (sheet and rill
erosion)
Removal Efficiency Range
N
Removal Efficiency
Range P
Diversion 70% 45-65% 65-70%
Filter Strip 45-75% 40-75% 40-80%
Grade Control 55-75% 35-40% 55-65%
Large Habitat
Block 58-75% 65-75% 60-80%
Livestock
Practices 38-95% 35-95% 35-95%
Pond 95% 95% 95%
Terrace 65-80% 15-30% 45-70%
WASCB 35-85% 20-75% 40-75%
Waterway 35-75% 40-78% 40-82%
Any new BMP will reduce sediment and nutrient loading and are critical in helping to
meet water quality targets. After the various upland loading models were developed,
localized drainage areas were delineated for each individual BMP. Based on existing
literature, pollutant removal efficiencies (percentage efficiency) were use to determine
what percentage of pollutants are removed by each BMP; the result is the remaining
loading after runoff and sediment drains through the given BMP. Additionally,
streambank erosion, streamside gully erosion and nutrient loading were calculated and
BMPs were identified. All gully and streambank stabilization used 100% removal
efficiency for all pollutants, assuming the gully and streambank is entirely stabilized.
Observations were also made in the field using aerial imagery and adjustments were
made for the efficiency percentages based on the quality of the BMP.
In addition to reccomended BMPs that have been field varified, other BMPs should also
be considered or encouraged in both watersheds. Implementing these practices, where
appropriate will lead to additional load reductions and help to improve overall water
quality. Additional BMPs are discussed at the end of this section.
