TMDL Stormwater Implementation Resources

This webpage provides a set of technical resources for Maryland jurisdictions developing Stormwater WLA Implementation Plans. The guidance documents on this page were developed by MDE's Water and Science Administration and are recommendations only.

General Guidance

Maryland's Stormwater Management Program website provides guidance on accounting for stormwater waste load allocations (SW-WLAs) and implementing environmental site design practices. A good starting point for developing a stormwater implementation plan is the Stormwater Management Program's guidance document, Accounting for Stormwater Wasteload Allocations and Impervious Acres Treated.

Additional guidance has also been developed by Maryland Department of the Environment's Water Science Administration, which expands upon and provides recommendations for many of the technical aspects included in the accounting for SW-WLAs document.

The Maryland Department of the Environment presented a webinar on the features of the new TMDL Data Center website on June 11, 2014. This presentation gives an overview of the function and use of the resources available on the TMDL Data Center website for developing SW-WLA Implementation Plans.

In addition, web-based nitrogen, phosphorus and sediment load estimator tools have been developed to streamline environmental planning. These tools provide estimates of nitrogen, phosphorus, and sediment load reductions with user-specified BMPs and other scenario criteria.
NEW! Maryland Forest Financing Implementation Tool (MD FFIT)
 
Maryland Forest Financing Implementation Tool (MD FFIT), a calculator designed to assist MD local governments, counties, and their partners seeking loans to fund forestry efforts and earn restoration credits for permits. The video shows how MD FFIT can be used to review different implementation scenarios, evaluate how much a forestry project would cost, estimate how many MS4 credits and environmental co-benefits can be achieved.  The slides in the video and a user guide are also below.

Nutrients and Sediment TMDL Guidance

NEW! TMDL Implementation Progress and Planning Tool (TIPP)
 
The TMDL Implementation Progress and Planning (TIPP) spreadsheet tool is meant to accompany the submission of Stormwater Wasteload Allocation (SW-WLA) Implementation Plans to MDE. It estimates load reductions at various points in the watershed planning process, allowing users to assess current progress and future BMP implementation for both local and the Chesapeake Bay TMDL. Local jurisdictions are not required to use this spreadsheet, however it is provided to simplify the county planning process. The spreadsheet uses Chesapeake Bay Phase 6 CAST-2017d Watershed Model No Action (No BMP) scenario loading rates with disaggregated Stream Bed and Bank (STB) loads at the county-8 digit and Chesapeake Bay Segment watershed scale.
 
In an effort to improve and streamline the SW-WLA implementation planning process, jurisdictions are encouraged to provide feedback and suggest improvements for this spreadsheet tool to mde.tmdlcoordinator@maryland.gov​.​
 
Updated Nutrient and Sediment Guidance is being developed and will be published in Summer 2021.  

This guidance applies to any approved Nutrient or Sediment TMDL for which a SW-WLA Implementation Plan needs to be developed under an MS4 Permit. It provides recommendations for identifying sources of nutrients and sediments, selecting management strategies for reducing nutrient/sediment loads, developing a monitoring plan, and tracking implementation progress.

PCBs TMDL Guidance

This guidance applies to any approved PCB TMDL for which a SW-WLA Implementation Plan needs to be developed under an municipal separate storm sewer system (MS4) Permit. It provides recommendations for PCB source identification, source monitoring, accounting for WLA credit and consideration of alternative or adaptive approaches. A slideshow presentation on MDE's PCB guidance, as it relates to Montgomery County, is provided here.

Bacteria TMDL Guidance

This guidance applies to any approved Bacteria TMDL for which a SW-WLA Implementation Plan needs to be developed under an MS4 Permit. It provides recommendations for identifying sources of bacteria, selecting management strategies for reducing bacteria loads, and modeling load reductions from selected management strategies.

Mercury TMDL Guidance

This guidance applies to any approved Mercury TMDL for which a SW-WLA Implementation Plan needs to be developed under an MS4 Permit. It provides recommendations for identifying sources of mercury (both local and atmospherically deposited) and creating systems to account for reductions in mercury air deposition from state and federal programs and potential reductions in local sources.

Trash TMDL Guidance

This guidance applies to any approved Trash/Debris TMDL for which a SW-WLA Implementation Plan needs to be developed under an MS4 Permit. It provides recommendations for identifying sources of trash and debris, selecting management strategies for reducing trash and debris loads, and modeling load reductions from selected management strategies.

This guidance provides additional recommendations for monitoring programs associated with Trash/Debris TMDLs. Because trash is a new and emerging pollutant in the TMDL program, limited data is available. Additional trash loading rate data will provide MDE with updated information on how trash loads may be changing over time. It can also be used by MS4 permit holders to evaluate effectiveness of selected management strategies in reducing trash.

Federal Facility Loading Targets

Per EPA requirements, Maryland has set interim nutrient loading targets for federal facilities. These targets represent loading reductions associated with a 20% retrofit of impervious surfaces with stormwater management that does not provide adequate water quality treatment. This is consistent with implementation strategies outlined in Maryland's Phase II WIP for Phase II MS4s. These planning targets represent an interim goal towards overall 2025 load reductions. Revised planning targets to meet 2025 goals will likely be provided to the federal facilities in 2018 as part of Maryland's Phase III WIP process. The planning targets are available for download below for all facilities that submitted land-use or BMP data to MDE.

MS4 Monitoring Data and Analyses​

MDE's Integrated Water Planning Program (IWPP), in conjunction with the Interstate Commission on the Potomac River Basin (ICPRB), has compiled a comprehensive database of historic MS4 permit required monitoring information, including chemical, biological, habitat, and geomorphic data for targeted sub-watersheds.  MDE, ICPRB, and the Center for Watershed Protection (CWP) have conducted pilot trend analyses of historic chemical monitoring data for three targeted sub-watersheds, which had the longest periods or record, fewest data quality issues, and ideal monitoring designs to relate any changes in ambient water quality to watershed restoration.  The comprehensive database and report summarizing the pilot trend analyses of the chemical data are available for download below.  MDE IWPP intends to conduct further pilot analyses of the biological and habitat data.  MDE IWPP is currently working with ICPRB to populate the database with the geomorphic monitoring data.  The version of the database below only contains the chemical, biological, and habita data.  Once the geomorphic data is added to the database, an updated version will be posed.  Once MDE and ICPRB conclude the analysis of the biological and habitat data, those final reports will be posted as well. 

Glossary

Contact Information

Please direct questions or comments concerning Maryland's TMDL Program to mde.tmdlcoordinator@maryland.gov at (410) 537-3818.​

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