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*Filterra® Shallow | *Filterra® Shallow | ||
− | ==Use conditions== | + | ===Use conditions=== |
To receive the full credit, Filterra systems must comply with the following conditions. | To receive the full credit, Filterra systems must comply with the following conditions. | ||
#Design, assemble, install, operate, and maintain Filterra systems in accordance with applicable Contech Filterra manuals. | #Design, assemble, install, operate, and maintain Filterra systems in accordance with applicable Contech Filterra manuals. | ||
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#Follow maintenance procedures given in the most recent version of the [https://www.conteches.com/Portals/0/Documents/Maintenance%20Guides/Filterra%20OM%20Packet.pdf?ver=2018-05-31-143300-750 Filterra Operation and Maintenance Manual]. | #Follow maintenance procedures given in the most recent version of the [https://www.conteches.com/Portals/0/Documents/Maintenance%20Guides/Filterra%20OM%20Packet.pdf?ver=2018-05-31-143300-750 Filterra Operation and Maintenance Manual]. | ||
#Install the Filterra in such a manner that flows exceeding the maximum Filterra operating rate are conveyed around the Filterra mulch and media and will not resuspend captured sediment. | #Install the Filterra in such a manner that flows exceeding the maximum Filterra operating rate are conveyed around the Filterra mulch and media and will not resuspend captured sediment. | ||
− | #Discharges from the Filterra units shall not cause or contribute to water quality standards violations in receiving waters. | + | #Discharges from the Filterra units shall not cause or contribute to water quality standards violations in receiving waters. === |
==Derivation of credits== | ==Derivation of credits== |
Contech's Filterra is an engineered bioretention system designed to filter pollutants from stormwater runoff. This page provides information on pollutant removal credits for Filterra.
When conditions described in this section are met, applicable Contech Filterra systems are approved for the following pollutant removals.
For more information on credits, see TP and TSS credits and guidance for manufactured treatment devices (mtds)
Applicable configurations (systems) include
To receive the full credit, Filterra systems must comply with the following conditions.
The base credits are equal to TAPE-approved credits. However, due to differences between Washington State and Minnesota climates, the credits cannot be directly applied as an average annual removal. The applicable treatment volume must be determined using one of the methods described here.
Tier 2 and Tier 3 credits were determined by analyzing water quality data collected at Bellingham, Washington. The site consisted of residential land use with 0.4 acres of impervious draining to the device. The device was 4 ft by 6.5 ft, with a filter media depth of 1.8 feet and a ponding depth of 0.75 feet.
MPCA compiled data from Appendix K of the report TECHNICAL EVALUATION REPORT - FILTERRA SYSTEM PHOSPHORUS TREATMENT AND SUPPLEMENTAL BASIC TREATMENT PERFORMANCE MONITORING. Summary statistics are shown in the adjacent image. TAPE means and medians represent values meeting TAPE criteria for TP (inflow concentrations of 0.1 to 0.5 mg/L) and TSS (inflow concentrations greater than 20 mg/L). Thus, of the 22 samples, TAPE medians and means represent 10 samples for TP and 18 samples for TSS, while the remaining data in the figure are for all 22 events.
The Tier 2 value of 58% for TP is slightly below the median concentrations for all 22 sampling events. The Tier 3 value of 65% for TP is below the median TAPE value (78.5%). Since the TAPE median is based on samples with TP concentrations greater than 0.100 mg/L, a criteria for receiving the Tier 2 credit for TP is that median average annual inflow concentrations are greater than 0.100 mg/L. This value can be verified with water quality sampling or providing supporting documentation.NOTE - we will have to develop guidance on this.
To link to the Excel spreadsheet containing water monitoring data click here - File:Water quality data for MTDs Feb 4.xlsx