Difference between revisions of "Test page Filterra"
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*Filterra® Shallow | *Filterra® Shallow | ||
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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== | ||
Revision as of 20:02, 8 February 2021
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.
TP and TSS credits
When conditions described in this section are met, applicable Contech Filterra systems are approved for the following pollutant removals.
- TSS credit: 80 percent. If the LCL exceeds 80 percent, the LCL is used but the credit cannot exceed 85 percent.
- Tier 1 - TP
- Credit: 50 percent reduction
- Conditions for receiving credit: Inspect manufactured treatment device a minimum of twice per year.1 Conduct inspections following manufacturer’s instructions/recommendations. Use maintenance indicators provided by manufacturers to determine if maintenance is needed.2 Maintenance procedures should follow manufacturer’s guidelines.
- Tier 2 - TP
- Credit: based on an assessment of 95% lower confidence limits (LCLs) for the device (see discussion below)
- Conditions for receiving credit: To receive this credit the device must meet Tier 1 conditions and the following conditions.
- DP should be 25 percent or less of TP. If site specific monitoring data do not exist to verify this, acceptable land uses include commercial land use, industrial land use, transportation land use, highly urban and ultra-urban environments (ultra-urban), or combinations of these. The credit should not be applied in residential land use, to roof runoff, areas with extensive tree canopy, or other areas where dissolved phosphorus is likely to exceed 25 percent of total phosphorus (link here for discussion of dissolved phosphorus ratios). Site specific monitoring data collected using following appropriate QA/QC protocols may be used to establish DP:TP ratios.
- Inspect manufactured treatment device monthly during the frost free season for the first year of operation after construction. Conduct inspections following manufacturer’s instructions/recommendations. Use maintenance indicators provided by manufacturers to determine if maintenance is needed. Maintenance procedures should follow manufacturer’s guidelines. Determine future inspection and maintenance schedules from findings during the first year of operation.
- Tier 3 - TP
- Credit: based on an assessment of medians for the device (see discussion below)
- Conditions for receiving credit: To receive this credit the device must meet Tier 1 and Tier 2 conditions the following conditions.
For more information on credits, see TP and TSS credits and guidance for manufactured treatment devices (mtds)
Configurations
Applicable configurations (systems) include
- Filterra Internal Bypass - Pipe (FTIB-P)
- Filterra Internal Bypass – Curb (FTIB-C)
- Filterra® Shallow
Use 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.
- The maximum flow rates through the devices are specified below. Use the lowest applicable infiltration rate depending on the pollutant treatment required.
- 175 inches per hour for TSS
- 100 inches per hour for TP
- Systems are designed to treat a specified water quality volume or annual average runoff volume. The annual average runoff treated can be determined using methods that are specified here.
- Each site plan must undergo Contech Filterra review before approval of the unit for site installation.
- Filterra media shall conform to the specifications described in Filterra Bioretention System Specifications and shall be sourced from Contech Engineered Solutions, LLC with no substitutions.
- Follow maintenance procedures given in the most recent version of the 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.
- Discharges from the Filterra units shall not cause or contribute to water quality standards violations in receiving waters. ===
Derivation of credits
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