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<td>1. Is Media Mix C or D being used or is the media phosphorus content 30 mg/kg or less per the Mehlich 3 test?
 
<td>1. Is Media Mix C or D being used or is the media phosphorus content 30 mg/kg or less per the Mehlich 3 test?
*If yes, credit as a % = 20 * (depth of media above underdrain/2)
+
*If yes, credit as a % (up to a maximum of 20%) = 20 * (depth of media above underdrain, in feet/2)
 
*If no or unknown, credit = 0%
 
*If no or unknown, credit = 0%
 
2. Does the system include approved P-sorbing soil amendments<sup>2</sup>?
 
2. Does the system include approved P-sorbing soil amendments<sup>2</sup>?

Revision as of 20:07, 16 January 2014

Phosphorus credits for bioretention systems with an underdrain.
Link to this table

Particulate phosphorus Dissolved phosphorus
Is Media Mix C or D being used or is the media phosphorus content 30 mg/kg or less per the Mehlich 3 test1?
  • If yes, credit = 45%
  • If no or unknown, credit = 0%
1. Is Media Mix C or D being used or is the media phosphorus content 30 mg/kg or less per the Mehlich 3 test?
  • If yes, credit as a % (up to a maximum of 20%) = 20 * (depth of media above underdrain, in feet/2)
  • If no or unknown, credit = 0%

2. Does the system include approved P-sorbing soil amendments2?

  • If yes, additional 40% credit

1Other widely accepted soil P tests may be used.
2Acceptable P sorption amendments include

  • 5% by volume elemental iron filings above IWS or elevated underdrain
  • minimum 5% by volume sorptive media above IWS or elevated underdrain
  • minimum 5% by weight water treatment residuals (WTR) to a depth of at least 10 cm
  • other P sorptive amendments with supporting third party research results showing P reduction for at least 20 year lifespan, P credit commensurate with research results