Difference between revisions of "Test page mtds"
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| − | == | + | ===Methodology for phosphorus credits=== |
| − | + | A tiered approach to crediting allows flexibility in selecting practices and associated conditions that may affect performance, such as influent water quality, and operation and maintenance. However, data from the TERs indicate differing performance levels for each device. It is therefore not possible to develop uniform credits across all devices. It is not desirable to conduct an in depth analysis of each device. We therefore chose the following approach to crediting. | |
| − | + | *Tier 1 applies a 50 percent reduction for TP. This is the TAPE-approved value. Basic conditions required to receive this credit are provided in the support documents for each device. These base conditions are generally the same as in the Washington State approval document, tailored for Minnesota. | |
| + | *Tier 2 is based on an assessment of 95% lower confidence limits (LCLs) for the device. Since the LCL varies when all data are considered compared to just data used by TAPE, we typically select the more conservative value, though this may be adjusted based on additional analysis and professional judgement. The credit is based on specific conditions in addition to conditions described for the Tier 1 credit. | ||
| + | *Tier 3 is based on an assessment of medians for the device. Since the medians vary when all data are considered compared to just data used by TAPE, we typically select the more conservative value, though this may be adjusted based on additional analysis and professional judgement. The credit is based on specific conditions in addition to conditions described for the Tier 1 credit. | ||
==Calculating annual volume treated by a device== | ==Calculating annual volume treated by a device== | ||
Revision as of 21:28, 1 February 2021
Manufactured treatment devices (mtds) remove pollutants from stormwater runoff. This page provides pollutant removal credits for mtds and includes guidance on determining credits for mtds.
Contents
Overview
Credits are provided for total phosphorus and total suspended solids. Credits refer to the amount of pollutant reduced by treatment with a stormwater best management practice (BMP). For more information on credits, link here.
Abbreviations
- TP – total phosphorus
- DP – dissolved phosphorus
- OP – orthophosphorus
- TSS – total suspended solids
- TAPE - Technology Assessment Program – Ecology
- TER – Technical Evaluation Report
- GULD - General Use Level Designation
- LCL – Lower confidence limit of the mean (usually the 95% LCL)
- MTD (mtd) – manufactured treatment device
What manufactured treatment devices are credited?
Only Washington State Technology Assessment Protocol - Ecology (TAPE) devices that received General Use Level Designation (GULD) are credited for pollutant reductions. TAPE-approved devices include devices that are considered pretreatment devices in Minnesota, as well as permanent structural practices not designed specifically for pretreatment. In Minnesota, pretreatment is required for permanent treatment practices and therefore pretreatment devices are not credited for pollutant removal.
Pollutant removal credits are provided for the following devices.
| Device name | Manufacturer | TAPE approval date | Total suspended solids | Total phosphorus |
|---|---|---|---|---|
| BayFilter w/EMC Media | BaySaver Technologies, Inc. | 7/10/19 | Basic | Basic |
| BioPod Biofilter with Curb Inlet | Oldcastle Infrastructure, Inc. | 10/28/19 | Basic | Basic |
| Compost-Amended Biofiltration Swale | WSDOT | 8/26/13 | Basic | |
| ecoStorm plus | Watertectonics, Inc. | 1/9/13 | Basic | |
| Filterra Bioscape | CONTECH Engineered Solutions, LLC. | 9/16/19 | Basic | Basic |
| Filterra System | CONTECH Engineered Solutions, LLC. | 6/11/20 | Basic | Tiered |
| FloGard Perk Filter | Oldcastle Infrastructure, Inc. | 8/9/18 | Basic | Basic |
| Media Filter Drain | WSDOT | 5/22/14 | Basic | Basic |
| Media Filtration System | CONTECH Engineered Solutions, LLC. | 11/15/16 | Basic | |
| MWS-Linear Modular Wetland | Bio Clean Environmental Services, Inc. (A Forterra Company) | 12/16/19 | Basic | Tiered |
| StormFilter using PhosphoSorb Media | CONTECH Engineered Solutions, LLC. | 1/2/20 | Basic | Tiered |
| Stormfilter using ZPG Media | CONTECH Engineered Solutions, LLC. | 4/14/17 | Basic | |
| StormGarden Modular Stormwater Bio-filtration System | Environmental Solutions | 8/28/19 | Basic | Basic |
| The Kraken | Bio Clean Environmental Services, Inc. (A Forterra Company) | 12/16/19 | Basic | Basic |
| Up-Flo Filter w/Filter Ribbons | Hydro International | 3/5/19 | Basic | Basic |
Total phosphorus credits
The adjacent table provides phosphorus removal credits for mtds. This credit only applies to the water treated by the device. To calculate annual pollutant mass removal, the removal credit must be multiplied by the volume treated.
| Manufactured treatment device | Total phosphorus | Total suspended solids | ||
| Tier 1 | Tier 2 | Tier 3 | ||
| Filterra | 50 | 58 | 65 | 90 |
| Phosphosorb | 50 | 65 | 75 | 88 |
| UpFlo | 50 | - | - | 75 |
| Modular wetland | 50 | 54 | 60 | 82 |
Methodology for phosphorus credits
A tiered approach to crediting allows flexibility in selecting practices and associated conditions that may affect performance, such as influent water quality, and operation and maintenance. However, data from the TERs indicate differing performance levels for each device. It is therefore not possible to develop uniform credits across all devices. It is not desirable to conduct an in depth analysis of each device. We therefore chose the following approach to crediting.
- Tier 1 applies a 50 percent reduction for TP. This is the TAPE-approved value. Basic conditions required to receive this credit are provided in the support documents for each device. These base conditions are generally the same as in the Washington State approval document, tailored for Minnesota.
- Tier 2 is based on an assessment of 95% lower confidence limits (LCLs) for the device. Since the LCL varies when all data are considered compared to just data used by TAPE, we typically select the more conservative value, though this may be adjusted based on additional analysis and professional judgement. The credit is based on specific conditions in addition to conditions described for the Tier 1 credit.
- Tier 3 is based on an assessment of medians for the device. Since the medians vary when all data are considered compared to just data used by TAPE, we typically select the more conservative value, though this may be adjusted based on additional analysis and professional judgement. The credit is based on specific conditions in addition to conditions described for the Tier 1 credit.
Calculating annual volume treated by a device
Devices tested and approved in Washington State are required to treat 91% or more of the average annual runoff. Because climatic conditions differ between Washington State and Minnesota, the annual average volume to which the credit applies must be determined. The following are acceptable methods for calculating the average annual volume treated by a device.
- Translators
- Modeling
- Monitoring
- Devices approved in similar climatic conditions
- The device is downstream of a retention device that ensures a specified volume is treated by the device
Credits
Credits for manufactured treatment devices
Credit support documents
Although specific guidance and methods for crediting are provided on individual device support documents, an overview of information in these documents is provided here. All devices must meet the following conditions for credit.
- The device must be designed, assembled, installed, operated, and maintained following manufacturers specifications.
- All systems must meet specified