Can extra-high voltage transmission cable be placed beneath 39 miles of the Bay & Choptank without undue harm?
On August 8th PJM staff recommended a halt to both the MAPP and PATH transmission line projects. This action resulted from modeling that showed neither project was needed to maintain the reliability of electric service for at least the next 15 years. A combination of declining energy use and new generating facilities have resolved issues that once threatened reliability. PJM is scheduled to act on the staff recommendation on August 24th.
When both projects first emerged numerous individuals and citizen groups began raising questions about need and alternatives that might satisfy that need without such sweeping impacts to homes, farms, the environment, electricity prices, and other factors. This prompted elected officials to pose these same questions. This in turn slowed down the permitting process while essential studies were initiated. Had citizens not acted then these multi-billion dollars transmission lines could have been in the midst of construction by the time we learned that neither was needed.
A truly comprehensive energy planning process is urgently needed to prevent such unwarranted, ultra-expensive projects from taking our energy future in the wrong direction. We sincerely hope the MAPP and PATH near-disasters serve as a wake-up call.
A proposal has been made to bury extra-high voltage transmission cables beneath 16 miles of the Chesapeake Bay and 23 miles of the Choptank River. This action could set a precedent leading to similar projects in the future along this same route. There are clear, viable alternatives to the proposed Mid-Atlantic Power Pathway (MAPP) project. However, we are concerned that reviewing agencies will lack the information needed to compare the pros and cons of the Chesapeake-Choptank cable option with the other alternatives. This is why Dorchester Citizens for Safe Energy hopes you will join with us in signing our petition. For further detail please read on or contact us at 410-654-3021 or Help@ceds.org.
The proposed transmission line route is shown with a redline in the photo below. A more detailed map can be viewed by clicking the following text: Detailed Map. With the exception of where the cables come ashore in Goose Creek, just south of Secretary, the transmission line will be at least 1,000 feet from the Choptank River shoreline and buried at a depth greater than 20 feet.
Submerged transmission cable
In 2009, 26 national, statewide and local organizations wrote to Governor Martin O'Malley about the potential negative impacts of the MAPP project. At that time MAPP would be placed beneath ten miles of the Chesapeake with none slated for the Choptank. The current proposal has heightened concerns about Bay and River impacts. This is why we are calling upon Governor Martin O'Malley to convene a panel of independent, leading Bay scientists to:
We are concerned that without such an independent evaluation the Maryland Public Service Commission, the Maryland Department of the Environment, the Maryland Department of Natural Resources, and the Maryland Wetlands Administration will lack the information essential to a thorough review.
On November 12, 2010, Baltimore Gas & Electric Company, Delmarva Power & Light Company, and Potomac Electric Power Company filed a Supplemental Application with the Maryland Public Service Commission regarding the proposed Mid-Atlantic Power Pathway (MAPP). Part of the proposal includes placing transmission cable beneath 39 miles of the Chesapeake Bay and Choptank River.
Barge used to lay transmission cable
According to the application, the placement would begin on the western shore three miles north of the Calvert Cliffs Nuclear Power Plant, cross beneath 16 miles of the Chesapeake Bay to the mouth of the Choptank River, continue 23 miles upriver to Goose Creek, and come ashore about a mile south of the Town of Secretary. Prior to laying the cables grapnel anchors would be dragged along the 39-mile route to remove obstructions buried to a depth of two- to three-feet beneath the Bay and River bed. Along this 39-mile route two 500 kilovolt Direct Current (DC) circuits would be buried in separate trenches a minimum of six-feet beneath the Bay and River bed. The trenches would by excavated with a jet plow. Each would be two- to three-feet wide and a minimum of 80 feet apart. A three-foot wide depression would also be created along both sides of each trench as jet-plow skids are dragged along. Each trench would hold one DC circuit consists of two 5.25-inch cables. Additional bottom disturbance may result from other activities, such as moving kedging anchors. Maintenance and other activities may result in additional physical disturbance of the Bay and River bottom throughout the service life of the project. The application indicates that a number of vessels will be operating during cable installation. These vessels include: freighter transporting cable, main lay barge, river lay barge, and tug boats.
Cross-section of submerged transmission cable
The MAPP transmission line is also proposed to cross over the Nanticoke River. The crossing would be made with the cables supported on 90-foot towers. Presently the viewshed to the north of the Route 50/Nanticoke crossing is that of a wide river meandering past extensive wetlands and a few farms. The overhead cables would despoil this view. This would be true for where the transmission lines cross the River and for the area several miles to the east and west of the Nanticoke where the lines would still be visible. If the independent review shows that the cables can be submerged without undue impact and other possible River impacts are resolved, then we would like consideration given to placing the transmission line underground and submerged from the Choptank River to a point east of the Nanticoke outside the river viewshed.
MAPP was originally proposed to run from Virginia, through Southern Maryland, cross the Bay to travel through central Dorchester County, then pass through Wicomico County before traveling the length of Delaware to end at Salem, New Jersey. MAPP offers the possibility of improving the reliability and reducing the cost of Delmarva electric service. However, a number of state agencies have also asked the applicants to explore other options which could provide these same benefits but at lower cost to both electricity users and our fragile environment. For example, rather then crossing the Bay and running up the Choptank River the transmission lines could be built along existing right-of-way around the head of the Chesapeake. Again, we are asking for a review by an independent panel of leading Bay scientists to determine if extra-high transmission cable can safely cross the Bay and, if yes, where. We also want the panel to consider the pros and cons of no Bay crossing.
Because extra-high voltage DC transmission cables have never been placed beneath the Chesapeake Bay the potential impacts are not completely known. While somewhat similar projects have been carried out elsewhere, shortcomings in monitoring studies and the unique character of the Bay provide a less than complete understanding of impacts. Following are some of the basic effects that could result from this precedent setting action. Further detail may be found in Mid-Atlantic Power Pathway & The Chesapeake Bay: A Preliminary Review of the Impact of Placing Portions of an Extra-High Voltage Transmission Line Beneath the Chesapeake Bay & Other Waters.
Physical Disturbance: Assuming disturbances are confined to two, three-foot wide trenches and three-foot wide skid areas on each side of the trenches, a minimum of 35 acres of Bay bottom and 50 acres of Choptank River bottom would be disturbed during initial cable installation.
Turbidity: Considerable quantities of fine-grained sediments and other particulate matter could be resuspended as the grapnel anchor is dragged through the upper two- to three-feet of the Bay and River bottom. Subsequent trench excavation could further increase turbidity.
Thermal Effects: Submerged DC cables are designed to operate at a temperature of up to 158 F. It is possible that adjoining sediments and water could be heated. The heating may then induce current flows through the sediments increasing the release of nutrients and other substances from bottom sediments. It is also be possible that waters overlying the cable trenches would heat to some degree with potential negative effects to bottom-dwelling organisms in the vicinity.
Electromagnetic Field Effects: The application indicates that electromagnetic field strength will be higher in the vicinity of the cables. There is a possibility that the altered fields could interfere with the behavior of some aquatic species at a distance of up to 1,000 feet which could affect 9,500 acres of the Chesapeake and Choptank. EMF may also interfere with compass readings. A possibility also exists of effects to bottom sediment chemistry.
Cable Exposure: While the application states that the cables will be buried a minimum of six feet below the Bay and River bottom, subsequent exposure of the cable is possible. In fact, the direct current Cross Sound Cable was exposed two years after being placed nine feet beneath the bed of Long Island Sound. Exposed cable could increase temperature and electromagnetic field effects. Also an exposed cable may pose a greater threat to aquatic organisms, commercial fishing activities, anchored vessels, vessels dragging anchor during storm events, and navigation.
The five basic effects listed above may cause the following impacts.
Nutrient Release: Nitrogen and phosphorus release could increase from sediments in the vicinity of the cable due to the physical disturbances, increased turbidity, and thermal effects.
Increased Oxygen Demand: The cable route passes through areas plagued by very low dissolved oxygen concentrations. Oxygen-demanding materials could also be released from Bay and River sediments, which could exacerbate the deficiency.
Release of Other Pollutants: There are likely a number of other potential pollutants which could also be released from the sediments.
Oyster Sanctuaries & Planting Areas: A number of oyster sanctuary and planting areas are located in the vicinity of the proposed cable route. The project could negatively affect these resources through physical disturbance, increased turbidity, elevated levels of nutrients and other pollutants, reduced oxygen concentrations, and elevated temperature.
Other Benthic Communities: In addition to oysters, a number of other organisms - annelids, crustaceans, etc. - inhabit the Bay and River bottom. These organisms are a vital component of the Bay and River ecosystem. As with oysters, the project could negatively affect these organisms through physical disturbance, increased turbidity, elevated levels of nutrients and other pollutants, reduced oxygen concentrations, and elevated temperature.
Submerged Aquatic Vegetation (SAV): Grasses and other SAVs provide critical habitat to Bay and River fin and shellfish. These plants are also essential to improving water clarity. SAV beds along the route could be negatively affected through physical disturbance, increased turbidity, and elevated levels of nutrients.
Boating Safety: The vessels used to lay the cable may cause some short term interference with recreational boating. Post-installation effects may include interference with magnetic compasses and limiting areas where boaters feel comfortable anchoring. As mentioned above, the Cross Sound Cable was exposed two years following installation. Perhaps the greatest boating concern may result from the possibility of cable exposure and vessels dragging anchor over the cables during a storm.
Commercial Fishing: Large portions of the 85-acres of Bay and River directly impacted by the project are important commercial fishing areas. Impacts to commercial fishing may result from direct disturbance of oyster or SAV beds, declines in fin and shellfish due to increased pollutant levels, concerns on the part of watermen about working near the cables, and the possibility of anchors, dredges or other equipment coming in contact with exposed cables particular in heavy weather. The possibility exists of altering fish behavior within a thousand feet of the cables or 9,500 acres of the Bay and River.
Cultural Resources: There may be a number of submerged archaeological or historic features present within the minimum 85-acre area directly impacted by the project. A thorough evaluation of potential impacts should include not only the initial placement but the possibility of future maintenance, cable exposure then lateral movement, and additional cables, pipelines, etc. being placed along the proposed route.
Unknown Effects: Again, the preceding is a listing of some of the possible impacts. The proposed panel of leading Bay scientists would likely identify other impacts which are presently unknown.