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The MAPP Transmission Project

First proposed in 2008, the Mid-Atlantic Power Pathway (MAPP) was a 152-mile extra-high voltage transmission line that would have extended from Possum Point, VA to Southern Maryland under the Chesapeake Bay, and across the lower Eastern Shore into Southern Delaware.

Utility giant Pepco Holdings, Inc. (PHI) argued that MAPP was necessary to prevent blackouts, lower electricity costs, and increase access to other sources of renewable energy, but local residents were skeptical.

Parents, in particular were alarmed. Extra-high voltage transmission lines are associated with an increased risk for childhood leukemia. Pepco’s installation of these transmission lines would have also predisposed Maryland and Delaware to the construction of new coal power plants, exposing residents to increased levels of air pollution.

Concerns weren’t limited to public health. They were also environmental. MAPP would have been the first time transmission cables crossed the Chesapeake Bay from shore to shore. Under Pepco’s plan, grapnel anchors would have been dragged along both proposed trench locations to remove any large objects buried up to three feet below the Bay and River bottom and a jet plow would be used to excavate two 3×6 foot trenches in which the transmission cables would be laid.

Scientists pointed to effects including the alteration of the behavior of some fish species by the electromagnetic field (EMF) emitted from the cables. This effect could have extended a thousand feet from the cables over a total of 9,500 acres of the Chesapeake Bay.

Compounding damage and disturbance to the Chesapeake Bay addition was the prospect of long-term maintenance activities. For example, portions of a similar transmission line – the Cross Sound Cable between Connecticut and New York – had to be reburied only several years after its initial installation. 

When Pepco applied for a low-interest loan from the federal government to complete phase two of the project in 2011, it triggered the need for an Environmental Impact Statement (EIS) under the National Environmental Policy Act (NEPA). Passed in 1970, NEPA protect local communities and the environment communities by requiring project sponsors to engage in a review process designed discover any significant environmental and public health impacts before construction begins on a new project. In a word, NEPA requires the government to “look before it leaps.”

An essential part of this review process is a mandated public comment period that gives members of the local communities that stand to be most impacted by a project a chance to voice their concerns and influence government decision-making.

Throughout the fall of 2012, the Maryland Public Service Commission held evening hearings in Calvert, Charles, Dorchester, Prince George’s, and Wicomico counties. These hearings were a critical opportunity for concerned citizens to voice their concerns regarding the MAPP project. Residents proposed a series of viable project alternatives that would have maintained reliable, affordable electricity while mitigating serious environmental and public health concerns:

Upgrade Existing Transmission Lines-Substations
A number of improvements to existing transmission lines and substations could allow for greater power flows. For instance, “reactive compensation” would resolve the deficiencies that exist in the transmission grid serving Southern Maryland. Reactive compensation changes the natural characteristics of the flow of electricity to make it more compatible with the amount of electric load required at any given moment.

Expand Generating Capacity
Maryland imports 30% of its electricity – this was one of the major justifications for MAPP. By expanding generating capacity in the eastern portions of the state by 200-300 megawatts (MW), however, MAPP would not be needed.

Northern Route
If it is determined that a genuine need exists for the MAPP project, then consideration should be given to routing the project on existing transmission right-of-way around the head of the Chesapeake Bay. The Northern Route would have crossed 3 miles of the Delaware River and approximately 1 mile of the Susquehanna, for a total of 4 miles of waterway crossings, whereas Pepco’s original plans would have crossed 42 miles of water: 2 miles of the Potomac River, 1 mile of the Patuxent River; 16 miles of the Chesapeake Bay; and 23 miles of the Choptank River.

Although the Northern Route would have limited disturbance to the Chesapeake Bay, Pepco was opposed to the proposed re-route because it would have been more expensive. As public opposition from individuals and citizen groups began to trickle upwards, elected officials began asking their own questions and Pepco reneged – the project was eventually cancelled in late 2012.


[1] “Notice of Intent To Prepare an Environmental Impact Statement for a Proposed Federal Loan Guarantee To Support Construction of the Mid-Atlantic Power Pathway Transmission Line Project, in Maryland and Delaware.” Federal Register 76:43 (March 4, 2011). pp. 12088-9. Available at:

[2] “Scoping Meeting For Phase II of the Mid-Atlantic Power Pathway (MAPP) Transmission Project.” Capital Reporting Company. March 23, 2011. Available at:

[3] “Mid-Atlantic Power Pathway & Delmarva Expert Witness Testimony Presented Before the Maryland Public Service Commission.” Prepared by Community & Environmental Defense Services. Available at:

[4] “Decision on 152-mile high-voltage transmission line getting down to wire.” Bay Journal. May 1, 2011. Available at:


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