Long-Term Performance and Life-Cycle Costs of Stormwater Best Management Practices (2014) / Chapter Skim
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Pages 130-143
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130 C H a P T E r 9 This chapter discusses the use of the BMP Evaluation Tool (located on the CD-ROM that accompanies this report) that can be used for planning-level estimates of BMP treatment performance and whole life costs.
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131 Figure 9-2. NCDC climate divisions for tool rain gauge selection.
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132 defaults are customizable by the user to adapt to site-specific needs. Appendix F: Planning Tool Handbook provides detailed information on tool organization, project set up, entering project data, and general information such as saving, editing, and printing multiple scenarios.
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133 • Treated Effluent Concentration -- The pollutant concentration in the BMP effluent, calculated using influent/ effluent performance curves. • Whole Effluent Concentration -- The pollutant concentration for the total discharge to the receiving water body, calculated by dividing the total discharge load by the total discharge volume.
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134 and then selecting the project location by clicking on the region where the site under consideration is located.
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135 median parallel to the travel lanes with outlet structures installed in the swale every 150 ft to collect treated runoff. This layout is effectively equivalent to having 8 individual swale segments (total length of 1,150/150 = 8 swales)
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136 size. The PFC was assumed to be installed over the four 12-ft travel lanes for an approximate total installed footprint area of 1.26 acres (55,200 ft2)
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137 Average Annual Volume (f3/year) Percent of Baseline Runoff Volume Average Annual Pollutant Loads Pathogens (colonies /year)
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138 lowest unit cost may be the preferred solution. Also, the sizing and related costs of the BMPs are not completely equitable because hydrologic routing was not performed.
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139 not account for hydrologic routing, therefore, tend to be conservative and result in BMPs with larger footprints or storage volumes than needed to provide a cost-effective level of treatment. This section briefly evaluates the effect of routing on the performance and cost of the BMPs.
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140 Volume Pathogens Loads Metals Loads Nutrients Loads Sediment Loads Captured1 Reduced2 E Coli FC TCu TPb TZn NO3 TKN TN DP TP TSS Swales 98.5% 37.5% 37% 37% 64% 67% 80% 38% 38% 37% 38% 51% 75% Bioretention 96.9% 96.9% 97% 97% 97% 97% 97% 97% 97% 97% 97% 97% 97% Wet pond 98.9% 0.0% 88% 58% 69% 91% 74% 51% 43% 48% 49% 54% 83% Filter strip >99.9% 72.3% 72% 72% 90% 92% 93% 80% 72% 74% 72% 84% 93% Dry detention 98.9% 12.3% 87% 55% 52% 67% 63% 25% 28% 27% 12% 42% 74% PFC >99.9% 0.0% 0% 0% 69% 98% 86% 0% 52% 36% 0% 43% 90% Sand filter >99.9% 0.0% 70% 71% 56% 88% 86% 0% 57% 33% 22% 56% 89% 1 The captured volume is the percent of the runoff that enters the BMP and either receives treatment and is released or is infiltrated.
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141 Volume Pathogens Metals Nutrients Sediment Captured Reduced E Coli FC TCu TPb TZn NO3 TKN TN DP TP TSS Swales 80.0% 12.9% 13% 13% 42% 46% 70% 13% 13% 13% 13% 28% 54% Bioretention (without underdrain)
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142 did not change because they are still based on 100% capture (an underlying assumption for these BMPs)
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143 statistics include the 85th percentile and 95th percentile, 24-hour precipitation depths, and average annual precipitation depths. These statistics are provided after the user selects the gauge that best represents the project.
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