Long-Term Performance and Life-Cycle Costs of Stormwater Best Management Practices (2014) / Chapter Skim
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Pages 13-33
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From page 13... ...
13 C H a P T E r 2 2.1 Background Since the NPDES program began in 1972 under Section 402 of the Clean Water Act, state DOTs have installed thousands of stormwater treatment facilities in the course of adding to the nation's capacity to meet NPDES permit requirements and other similar state laws. These structural treatment facilities are commonly referred to as treatment BMPs and are designed to control the amount of stormwater runoff pollutants and volumes discharging to receiving waters.
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14 breadth and depth of data contained in the BMPDB, it was a key resource used when developing the BMP spreadsheet tools. 2.2.2.1 BMP Constituent Removal The Water Environment Research Foundation (WERF)
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15 State and BMP Type BMP Study Count by Primary Land Use Total California 15 6 43 64 Biofilter – vegetated strip 2 – 29 31 Biofilter – vegetated swale 1 – 5 6 Detention basin (dry) – concrete or lined basin with open surface – – 1 1 Detention basin (dry)
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16 BMP Type TSS, mg/L (95% CI) a Dissolved Cadmium µg/L (95% CI)
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17 BMP Type Dissolved Zinc µg/L (95% CI) a Total Zinc µg/L (95% CI)
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18 and the lack of any organic material in the ecology mix. While the ecology embankment effluent concentration was higher for total copper, the influent concentrations were also generally much higher (a median influent of 52 µg/L compared to 17 µg/L for the bioretention category and 25 µg/L for the vegetated strip category)
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19 Vegetated Strip Studies, California. Vegetated strip studies in California included: 1.
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20 Moreno Valley 2 also contained the shortest vegetation, approximately 3 cm high, and the lowest vegetation coverage -- average vegetation cover of less than 15%. Dense vegetation decreases runoff velocities and increases the opportunity for straining of particles, facilitating sedimentation and reduction of constituents.
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21 estimates. Other factors may be maintenance and climatic differences.
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22 Inc., performed an analysis of the BMPDB to specifically evaluate volume reduction through selected post-construction BMPs. Volume reduction is an increasingly important issue in TMDL and NPDES permit compliance; however, very little data within the BMPDB address this aspect of performance since the focus tends to be on pollutant concentration reduction.
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23 3. Structural specifications, 4.
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24 various special structures (aprons, end sections, weirs) , and ditches (see Figure 2-2)
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25 system for stormwater management facilities includes an inventory, database, and photo record of all facilities statewide and their maintenance status, within a GIS. Under the rating system, those installations graded "A" or "B" are considered functionally adequate.
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26 subcodes for wet, dry, and other swales -- but the DOT maintenance division is not able to use all of those subcodes in its record keeping or maintenance work. Delaware Department of Transportation (DelDOT)
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27 many DOTs indicated that maintenance is performed on an as-needed basis. Historically, the maintenance of stormwater BMPs included activities such as removing excess sediment, revegetating ditches and embankments, and trash removal that have occurred in response to inspection during a storm event.
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28 maintenance schedules for permanent/post-construction stormwater BMPs. For example, WSDOT's NPDES permit requires annual inspection and maintenance of stormwater BMPs (Baroga, 2012)
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29 Life-cycle cost factors are described in WEF's 2012 manual, Design of Urban Stormwater Controls, which reviews and summarizes unit construction activity costs from standard civil engineering price guides, develops costing models to facilitate generic stormwater control cost estimation, compares actual and predicted costs, and outlines many cost factors, especially in BMP construction (Barrett and WEF, 2012, pp.
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30 b. Medium -- The normal level of maintenance to address function and appearance; it allows for additional activities, including preventative actions, at some facilities; and c.
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31 In WSDOT's case, GPS data will be linked with the agency's Highway Asset Tracking System (HATS) , a tool for managing maintenance activities by asset or roadway section.
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32 provide capital and maintenance information from the Caltrans study. The practitioner may refer to the following website for other detailed BMP capital and maintenance cost information from the Caltrans retrofit study: http://www.dot.ca.gov/ hq/oppd/stormwtr/Studies/BMP-Retro-fit-Report.pdf.
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33 total storage volume (for storage-based BMPs) , peak flow capacity (for flow-based or conveyance BMPs)
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