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==Abbreviations==
 
==Abbreviations==
TP – total phosphorus
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*TP – total phosphorus
DP – dissolved phosphorus
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*DP – dissolved phosphorus
OP – orthophosphorus
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*OP – orthophosphorus
TSS – total suspended solids
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*TSS – total suspended solids
TAPE - Technology Assessment Program – Ecology
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*TAPE - Technology Assessment Program – Ecology
TER – Technical Evaluation Report
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*TER – Technical Evaluation Report
GULD - General Use Level Designation
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*GULD - General Use Level Designation
LCL – Lower confidence limit of the mean (usually the 95% LCL)
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*LCL – Lower confidence limit of the mean (usually the 95% LCL)
MTD (mtd) – manufactured treatment device
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*MTD (mtd) – manufactured treatment device
  
 
==What manufactured treatment devices are credited?==
 
==What manufactured treatment devices are credited?==

Revision as of 20:15, 1 February 2021

Guidance for MTD crediting

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.

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 Tiered 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 Basic
StormFilter using PhosphoSorb Media CONTECH Engineered Solutions, LLC. 1/2/20 Basic Basic
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

Credit documentation

Each of the above devices has a supporting document that explains the credits and conditions necessary to receive the credit. Some devices have multiple credit tiers, that is they receive a basic credit or a higher credit if certain conditions are met. The above table indicates which practices have tiered credits. The individual supporting documents contain specific information about the device. This information should be carefully read and understood before assigning the appropriate credit to a device.

Credit levels

If conditions described in individual support documents are met, all devices receive base credits for total suspended solids (TSS) and total phosphorus (TP). These are TAPE-approved values as summarized below.

  • TSS – 80% removal for the annual volume treated by the device
  • TP – 50% removal for the annual volume treated by the device

MPCA analyzed available data from testing done for Washington State. Some devices may receive higher credit if conditions in support documents are met. Derivation of these credits is provided in the support documents.

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.

  1. The device must be designed, assembled, installed, operated, and maintained following manufacturers specifications.
  2. All systems must meet specified

Contech Filterra