Chesapeake Bay TMDL Action Plan

In 2010, the EPA established the Chesapeake Bay Total Maximum Daily Load (TMDL), a comprehensive pollution diet for the Chesapeake Bay with accountability measures to restore clean water in the Bay and local streams and rivers.

The Chesapeake Bay TMDL requires Arlington and other Municipal Separate Storm Sewer System Permit Holders to achieve specific nutrient and sediment reductions—defined in terms of pounds of sediment, phosphorus, and nitrogen—through local stormwater management programs.  As established by the Virginia Department of Environmental Quality (DEQ), Arlington must reduce its share of TMDL pollution by 5% during the current MS4 permit cycle (2013–2018), an additional 35% (40% total) during the second permit cycle (2018–2023), and the final 60% (100% total) during the third permit cycle (2023–2028).

The County’s overall strategy to meet the TMDL requirements includes stream restoration projects and watershed retrofits as two key strategies to meet the pollution reduction requirements.  In addition, stringent regulation of the stormwater runoff from development/redevelopment will continue to achieve incremental and cumulative reductions in stormwater pollutants.

The County’s current MS4 permit required a detailed plan to meet the 5% reduction requirements.  This plan, called the Chesapeake Bay TMDL Action Plan, outlines the specific projects and programs that will be implemented to meet the 5% reduction, and was approved by the Virginia Department of Environmental Quality (DEQ) in September, 2015.

Public comment was received on the plan and is summarized in Appendix G.

Final Chesapeake Bay TMDL Action Plan document


Summary of Arlington’s Chesapeake Bay TMDL Action Plan:

  • The implementation strategy outlined in the document is consistent with the overall strategy outlined in the adopted Stormwater Master Plan.
  • With projects and programs implemented since 2006 (the crediting baseline established by DEQ), Arlington County has already met the 5% pollution reduction requirement for this permit cycle (including FY15 progress).
    • These projects include two stream restoration projects in the Donaldson Run watershed, extensive retrofits at the Arlington County Trades Center, and pollutant reductions achieved through redevelopment activity.
    • The pollutant reductions computed using the DEQ guidance methodology are: nitrogen—5.3%; phosphorus—17%; and sediment—13%.
    • The estimated cost to date of the projects implemented is $3 million.
  • Two additional stream restoration projects and multiple watershed retrofit projects (including the large Ballston Pond project) are planned for implementation by the end of the permit cycle (2018)
  • The Action Plan document explains that any reductions achieved beyond the 5% requirement will be credited to the next permit cycle (and into the third permit cycle in the case of phosphorus). It is important to exceed the 5% requirement during this permit cycle to stay on pace to meet the full requirement in three permit cycles—rather than following the progressively steep implementation curve (5%, 35%, 60%).
  • It should also be noted that EPA will be evaluating overall Bay restoration progress in 2017, and it is anticipated that there may be changes to the pollutant reduction requirements for local governments across Virginia and the Bay watershed. More reduction may be required.