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 Department of the Environment's Water Science Administration has developed guidance which provides recommendations for many of the technical aspects of developing a Total Maximum Daily Load (TMDL) Implementation Plan. This guidance contains checklists for required elements of a permit-required SW-WLA implementation plan and makes recommendations regarding larger scale planning efforts intended to achieve overall TMDL goals.​

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.

Maryland's Stormwater Management Program website provides guidance on MS4 accounting and implementing environmental site design practices. Pollutant load reductions for MS4 accounting are used to derive MS4 credit at the state scale.
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.

MDE initially produced the FITT calculator and then updated it in 2022. Since the tool has changed, MDE would like to give users the benefit of seeing the previous demonstrations, therefore older versions of the training webinar are posted below. Please use the NEWER Version 2 for planning purposes.

Nutrients and Sediment TMDL Guidance

​​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.​

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​.​
The TIPP is also available in the TMDL Implementation Toolkit​.

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.​

Municipal Separate Storm Sewer System (MS4) Monitoring Guidance

MDE has developed monitoring guidance for MS4 jurisdictions collecting water quality, biological, bacteria, and habitat parameters. The MS4 Monitoring Guidance provides additional clarity for the monitoring requirements in the MS4 Permit. MS4 jurisdictions report annual monitoring data through their annual report. Additional guidance has been developed to facilitate the use of a new format for reporting monitoring data. These monitoring data format templates and guide are provided below.

Biological Monitoring

The MS4 Biological Database is intended to collect, archive, and facilitate the querying of biological data collected by MS4 jurisdictions to address their permit requirements. This database has been expanded to include additional biological sampling data that jurisdictions collect and report to MDE (such as fish sampling). This guide provides a general overview of the MS4 Biological Database, which was developed to house biological data collected in support of MS4 permit​​.


Contact Information ​
Please direct questions or comments concerning this project to Maryland's TMDL Program to​ at (410) 537-3884.​​​


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