When a water body is impaired, a TMDL (Total Maximum Daily Load) Action Plan is developed and implemented to limit pollution. Arlington's MS4 Stormwater Permit requires E. coli bacteria and PCB Action Plans, updated most recently in 2022. PCBs (polychlorinated biphenyls) are man-made legacy pollutants banned for their toxicity.
The Action Plans:
- Assess and identify pollutant sources,
- Outline strategies to reduce pollution from these sources,
- Aim to keep pollutants out of the County’s storm drain system and streams.
Actions focus on controlling E. coli bacteria and PCBs from controllable, human sources to the maximum extent practicable as part of a long-term comprehensive pollution prevention program.
The entire Four Mile Run watershed is considered impaired for E. coli bacteria.
The goal of the Bacteria TMDL Action Plan is to reduce E. coli bacteria from controllable, human sources to the maximum extent practicable. This goal is part of a long-term comprehensive, multi-pollutant watershed management program.
The Bacteria TMDL Action Plan includes an outreach program with multiple strategies to help Arlington's residents and visitors keep E. coli bacteria out of the storm drain system and local streams. Reducing bacteria from urban watersheds is extremely challenging given the pre-dominance of uncontrollable wildlife sources, bacteria re-growth and re-suspension, weather volatility, aging public and private infrastructure, and human behavior.
The County continues to implement a suite of programs and practices to address bacteria loading to the storm drain network and is exceeding permit requirements as the outreach programs cover the entire County and are not limited to the Four Mile Run watershed.
View the Bacteria TMDL Action Plan(PDF, 2MB)
Polychlorinated Biphenyls (PCBs) are man-made chlorinated chemicals that are legacy pollutants. The U.S banned the manufacture of PCBs in 1979 after 50 years of production. The ban was due to the toxicity of PCBs. Many industrial and commercial businesses used PCBs in lubricants, coolants, electrical equipment, and hydraulic equipment. PCBS were also used as plasticizers in paints, plastics, and rubbers; and in pigments, dyes, and inks.
The Potomac River is considered impaired for PCBs, which also affects tidal portions of Four Mile Run (Mount Vernon Avenue to the Potomac River).
The County’s PCB TMDL Action Plan assesses potentially significant sources of PCBs owned or operated by the County that drain to the storm drain system. The plan focuses on:
- Strategies to minimize and manage pollution to minimize PCB exposure to stormwater,
- Reducing controllable PCB loadings from County-owned properties and facilities to the maximum extent practicable,
- Combining these strategies with a long-term and comprehensive watershed management program.
Reducing PCB loading from urban watersheds is extremely challenging, given the legacy, non-active source status of PCB contamination, slow chemical breakdown of PCB compounds, and the lack of established stormwater treatment systems with quantifiable PCB removal efficiencies.
Additionally, Arlington's efforts to reduce sediment also helps reduce PCBs. These efforts complement the gradual reduction of PCB loads from atmospheric deposition and long-term chemical breakdown. Arlington also continues to provide information about proper disposal of various waste materials and debris. PCBs can be found in older transformers and capacitators, coolants in electrical equipment, lubricants and hydraulic fluids, old fluorescent light ballasts, thermal insulation materials, adhesives and tapes, caulk, roofing materials and asphalt, pesticides, plastics, inks pigments and dyes, and paints.
Outreach on proper disposal and recycling practices and providing programs such as the Household Hazardous Waste Collection and metal and white goods collection programs as well as events such as E-CARE are important steps to help prevent PCBs from getting into the environment via improper disposal.
View the PCB TMDL Action Plan(PDF, 2MB)