Dissenting Opinion

The one feature of project configuration that the Council approved that has significantly influenced my decision to cast a negative vote is the use of 345-kV XLPE cable. This type of cable will be used in the area of the Bethel Education Park for a distance of 2.1 miles.

I fully support the need to construct a 345-kV transmission line between Plumtree and Norwalk Substations in order meet electrical demands and maintain reliable service in southwestern Connecticut. The applicant’s preferred alternative, as initially proposed, was to construct an overhead transmission line to meet this need. Overhead transmission lines are the most reliable method of transporting electricity at high voltage. There are alternative underground transmission methods available, which have typically been used only when overhead lines are not practical (e.g. high density urban areas).

During the course of this Docket, a settlement agreement, between the applicant and the Towns of Bethel, Redding, Weston, and Wilton was offered to the Council. This agreement was dubbed Configuration X and called for use of two underground transmission segments of different technologies: a 1.6-mile segment through the Bethel Education Park and a 9.6-mile segment of high-pressure fluid-filled (HPFF) cable between Archers Lane in Redding and Norwalk Junction in Wilton. In the Council's decision, the underground segment through the Bethel Education Park was extended an additional one half mile in order to anchor one end of this underground segment to the grounding system at the Plumtree substation

One measure of the reliability of a transmission method, which can lead to an interruption in service, is its fault rate. The fault rates for overhead, HPFF and XLPE 345-kV configurations are 0.7, 0.5 and 4 occurrences per year per 100 miles, respectively. Faults of overhead transmission lines are primarily caused by lightening strikes and are of limited duration, as well as, generally self-correcting. If a fault requires an overhead line be placed out of service, locating and repairing the fault can be accomplished in hours. The occurrence of a fault in an underground transmission line requires the line to be placed out of service while the cause of the fault is located, which can take several days. The actual repair of the line can take up to 4-6 weeks. A further complication in repairing an XLPE line is the need to bring in foreign crews to perform this work.

In this country, HPFF is the most common type of underground transmission cable used and the only cable typically used above 230-kV. The operational history of XLPE cable is limited and uncertain on a worldwide basis at 345-kV.

The overall fault rate for Configuration X, as originally proposed, is estimated at one occurrence every 4.5 years. While the increased length of the approved XLPE segment will have some improved electrical characteristics, the overall fault rate for the line will be greater than 4.5 years. If the XLPE segment is omitted from this estimate, the fault rate is one occurrence every 20.5 years. I believe that the use of XLPE cable in Configuration X, as well as, in the Council's final decision makes this needed transmission line suffer a significant and unacceptable reduction in reliability. The elimination of visual impacts by using XLPE cable does not warrant the reduction in the reliability of this line. Ultimately, if this transmission line proves not to be reliable, which I hope is not the case, recent experience has demonstrated that short-term reliability enhancements will be under-taken which may have less desirable environmental consequences than constructing this line to a high reliability standard.

Also, while not a basis for my dissent, I remain concerned about the HPFF segment in Configuration X. This concern is focused on the dielectric fluid used as an electrical insulator and to transfer heat away from the cable. This fluid has not been designated a carcinogen or hazardous material and the applicant has attempted to characterize it as a benign material. I remain unconvinced, especially given the clean-up efforts that have been undertaken when spills of this material have occurred.

This HPFF segment will contain under pressure, approximately 130,000 gallons of dielectric fluid, which is subject to potential uncontrolled releases. This potential risk due to passive failure of the system is small and, thus, poses a minimal risk to the environment. However, a non-system failure, such as a construction dig-in, has the potential to release thousands of gallons of dielectric fluid. Such a failure would be difficult to clean up and presents an unknown threat to surface and ground water resources.

I feel that this potential risk to public water resources should be balanced with the public resource benefits anticipated. Also, in this instance, the benefit of undergrounding this segment is the avoidance of visual impacts. In the northern portion of this underground segment, the impact avoidance predominantly benefits individual property owners and disproportionately place public resources at risk.

The southern half of this underground segment traverses the Cannondale National Historic District. While the potential risk to public resources and benefits to individual property owners are similar to the northern segment, the presence of a publicly designated historic district, which is significantly influenced by visual qualities, makes this portion of the line different. In this case, I believe the risks to public resources are more appropriately balanced with avoidance of adverse impacts on a public resource.

In summary, I believe it is appropriate to give communities that host public service facilities some deference in siting such facilities, however the approved project configuration goes too far in this respect and does not serve the greater public’s interests in a reliable electrical system.

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Brian J. Emerick