Docket No. 217
Connecticut Light & Power Company
Development and Management Plan
Norwalk Substation 345-kV Expansion

On September 19, 2003, Connecticut Light Power Company (CL&P) submitted a segment of the Development and Management (D&M) Plan for the Norwalk Substation 345-kV Expansion.

The D&M Plan outlines the installation of a new 345-kV Gas Insulated Substation (GIS) facility and 345-kV line terminations, modifications, including removal, to an existing 115-kV substation facility and transmission lines, and switchgear enclosures. Such site development details include, line relocation [previously approved]; Phasing and erosion and sediment controls; Spill Prevention, Control, and Countermeasure Plan; Environmental Sound Evaluation; Landscaping Plan; and Project schedule.

This D&M Plan is consistent with the substation expansion plan submitted in the Certificate proceeding that also included the City of Norwalk's Zoning and Conservation Commissions recommendations. These commissions recommended reducing the area of expansion on the west side providing a buffer to the Norwalk River, making provision for a bike trail on the site, installing water contamination monitoring wells for the protection of the First Norwalk Taxing District public water supply well field located just west and north across the Norwalk River, additional landscaping, eliminating some new 115-kV lime terminating equipment, and enclosing the new gas-insulated substation equipment within a long building.

CL&P proposes to access the substation expansion area via the existing substation access road off New Canaan Avenue with two additional temporary access points, one located off Broad Street and another located off the Route7 New Canaan/Route 123 southbound exit. CL&P has a permit from the Department of Transportation for the construction and use of a temporary access road contingent that guardrails be installed to protect construction workers and adjacent temporary transmission line poles. Because the temporary access roads pass under existing or relocated transmission and/or distribution lines and will be used by construct vehicles, Council staff recommends these lines be identified with high-visibility markers.

Approximately eight acres of undeveloped land will be cleared and graded. About 1.4 acres is forested land and the remaining acreage consists of shrubs and low growing vegetation within an existing 115-kV line right-of-way north of the existing substation. Three acres require a cut of 8,000 cubic yards and five acres require fill of 45,000 cubic yards to establish a substation elevation of 53 feet above mean sea level. Existing elevations range between 37 feet and 50 feet amsl. To create the elevation change CL&P proposes to construct approximately 2,500 linear feet of concrete retaining walls. Site development is planned in five phases. The first three phases are dedicated to site work [physical alteration of topographic features] and the last two phases is for installation of substation equipment. CL&P has reduced the expansion on the west side of the substation to create a bike path and provide for more buffer between the substation and the Norwalk River.

Four 200 MVA, 345-kV-115kV single phase transformers (3 active, 1 spare), two 90-180 MVAR 345-kV shunt reactors and one 345-kV HPFF cable oil pressurization station within an ascoutical enclosure, associated capacitors, breakers, and overhead to underground transition equipment. Traprock filled concrete sumps will be constructed beneath oil-filled equipment with a capacity to hold 110 percent of the equipment's volume. A 20-foot by 220-foot 345-kV GIS facility building is proposed. A steel "hip roof and glazed clerestory over approximately one-half of the building is required". While a narrative specification for the GIS building has been provided no elevation drawings would be available until eight weeks after a contract has been awarded. Council staff recommends that elevation drawings and color of the GIS building be submitted when available for review and approval.

The existing property discharges all storm water runoff to the Norwalk River, primarily by surface flow. The proposed development incorporates both surface flow and pipe discharge (ie. catch basins with sumps, sand/oil collectors and stone lined stilling pools). An existing DOT culvert discharge located on the east side of the substation will be intercepted and integrated into the newly piped storm water collection system.

Also, CL&P proposes to install a stone lined overbank mitigation channel between the substation and the Norwalk River to manage the flow of a hypothetical 100-year floodwaters. This stone lined channel will be used as a temporary storm water detention basin during construction. This will be constructed during a period when the Norwalk River is at low flow to minimize impact to the riparian habitat. The only wetlands to be disturbed are located at the north and south ends of the overbank channel where it intersects with the banks of the Norwalk River; otherwise a vegetative buffer of 50 to 150 feet would be maintained between the disturbed area and the wetlands along the western portion of the site. CL&P filed for and has received a Federal Emergency Management Agency (FEMA) acknowledgement for flood boundary map revision for the Norwalk Substation expansion. While no Army Corp of Engineer permit is required, a Department of Environmental Protection Stream Channel Encroachment permit is required. DEP was waiting for the FEMA conditional letter of map revision. Now that this letter is part of the DEP permitting process, CL&P expects a permit will be issued shortly after a 30-day public comment period. Council staff recommends CL&P provide a copy of the DEP permit prior to construction of the mitigation channel/temporary storm detention basin.

All work proposed will conform with the Connecticut Guidelines for Soil Erosion and Sediment Control dated 2002. Such techniques, but not limited to, include use of stone lined tracking pads at construction access points, synthetic and/or haybale erosion and sediment controls, moistening areas for dust control, and loaming and seeding areas of no construction activity. Council staff recommends the erosion and sediment controls be inspected weekly and after every major storm event with deficiencies corrected within 24 hours.

A Spill Prevention, Control, and Countermeasure Plan that exists for the present-day operations at the Norwalk Substation would be amended to encompass the expanded substation. Because the substation is within an aquifer protection area CL&P agreed with the First Taxing District Water Company to use Construction Best Management Practices, test all fill to brought on site, complete a hydrogeological investigation report, install post-construction ground water monitoring measures, provide access to the First Taxing District personnel, and mitigate impacts of contamination caused by leakage from construction or operation of the substation. Secondary containment for refueling operations and periodic meetings and literature dispersal to contract supervisors and workers of aquifer protection areas will be employed. Council staff recommends CL&P shall fulfill its agreement with the First Taxing District Water Company.

The Environmental Sound Evaluation modeled sound levels that would be emitted by the expansion of the operations at the Norwalk Substation and concluded the new 345-kV substation would be in full compliance with the State and Local Noise Regulations.

A Landscape Plan has been provided identifying locations of sidewalks, bike path, vegetative plantings and stream channel mitigation. Also, CL&P would cover an approximate 2,000 square foot area within the fenced facility and north of the GIS building with grass and trees. While this plan was substantially reviewed and approved by the Norwalk's Conservation and Zoning Commissions, Council staff recommends that tree and shrub plantings not native to New England be eliminated and/or substituted with plantings native to New England, berming to reduce visibility from Route 7, and defers action on the landscaping plan until such revisions are made.

Council staff recommends that no construction shall commence until an Environmental Inspector has been provided for Council approval, as per Order 3 of the Decision and Order.

A Project Schedule for the Norwalk Substation expansion has been provided and CL&P expects site work and underground infrastructure installation be completed within 16 months and an additional ten months for cabling and connections. Expected completion for all work is November 2005.

Council staff recommends approval of the Norwalk Substation 345-kV expansion D&M Plan subject to the following conditions:

• Transmission and distribution lines crossing construction access points be identified with high-visibility markers.
• Elevation drawings and color (dark green is suggested) of the GIS building be reviewed with the City of Norwalk prior to filing with the Council for review and approval.
• Copy of the DEP stream channel encroachment permit be submitted to the Council prior to construction of the mitigation channel/temporary storm detention basin.
• The erosion and sediment controls be inspected weekly and after every major storm event with deficiencies corrected within 24 hours.
• CL&P shall fulfill its agreement with the First Taxing District Water Company.
• Tree and shrub plantings not native to New England be eliminated and/or substituted with plantings native to New England and berming to reduce visibility from Route 7, and defers action on the landscaping plan until such revisions are made.
• No construction shall commence until an Environmental Inspector has been provided for Council approval.