RFI - Attachment F - Engineering Report

Ortho-P with iron to form iron phosphate in aerobic conditions. Depending on the type of
treatment system, organic phosphorus can transform to Ortho-P and be released later. For
example, leaves trapped in a sump can decompose or fall senescence of wetland plant can
release Ortho-P.

Results
         Performance data for removal of total phosphorus were summarized from ongoing field
evaluations. These field evaluations are a combination of first and third party investigations.
Data were collected from 9 sites located in different geographic locations (primarily from the
West Coast (WA, OR, CA) and a single Midwest site) and configured with different media types
at different flow rates. Available reports are listed in the reference section.
         This performance summary focuses on Total Phosphorus removal only. The following
information presented in Figure 3 contains data collected since 2001, mostly during the late
spring, summer, and fall for total phosphorus removal by the Stormwater Management
StormFilter®. Fifty-five data points are presented in Figure 3. The mean removal efficiency
using linear regression was 62% with 95% confidence limits of 53% and 78% (lower and upper
limits, respectively). Sixteen data points that were included in the analysis did not have a
positive removal. Overall these systems demonstrated statistically significant removal (P<0.001;
99.9% probability of net removal) of Total Phosphorus.




       Figure 3. Total phosphorus removal performance summary collected from 9 sites, in multiple geographic
       locations, with different media. The linear regression produced an equation of y = 0.38x + 0.065, which
       translates to a 62% removal with a 95% confidence interval of 53% and 78% (lower and upper limits,
       respectively). Data was statistically significant with a P < 0.001. Data was current as of July 2003.
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