Overcoming Transmission Line Siting Challenges. Case Study Middletown-Norwalk Project

Transcription

1 Overcoming Transmission Line Siting Challenges Case Study Middletown-Norwalk Project NARUC Transmission Workshop April 21, 2011 Albert W. Cretella, III

2 Presentation Overview Project Description Need, Route Options, Steps to ID Best Solution Siting Challenges Overhead Lines Underground Lines Techniques & Technologies Used Route Variations & Bypasses Low Magnetic Field Designs Underground Cable River & Rail Crossing Methods Summary & Closing Thoughts 2

3 Connecticut Energy Situation NY 0 MA Daily total imports are approximately 1,500 MW RI Most of the time Connecticut uses more power than it generates. 0 Long Island Most of Connecticut s imported power moves on a 345-kV system. SWCT consumes half the state s electricity. But the 115-kV system in SWCT limits the movement of power to where it s needed 50% 345-kV 115-kV Power Plant 3

4 Determining a Solution What needs to be done?* What are the components of the solution? What is the best combination of solution components? 1.Strengthen power source to a point in Wallingford Overhead Point-to-Point Options Connect that source to substations in Milford, Bridgeport, and Norwalk Underground Point-to-Point Options * Per regional planning led by ISO-New England. Evaluate each option based on these criteria Evaluate each combination based on these criteria SYSTEM BENEFIT Operability, Reliability TECHNICAL FEASIBILITY Can it be engineered? Can it be built? PROPERTY IMPACT Impact on homes & property; Visual impact ENVIRONMENTAL IMPACT Impact on wildlife, vernal pools, aquifers COST to CUSTOMERS Engineering and Construction Costs Per national and regional reliability standards. 4

5 Step 1: What needs to be done? To meet national and regional reliability standards 1 Middletown S/S 1 2 Norwalk S/S 2 S/S 2 S/S 5

6 Step 2: What are the options? 6

7 Scovill Rock Beseck East Devon? I-91, I-95 Wilbur Cross Amtrak Railroad Conrail Railroad Transmission ROW Secondary Roads 7

8 Step 3: What are the best options? What are the components of the solution? What is the best combination of solution components? 1 Overhead Point-to-Point Options Underground Point-to-Point Options SYSTEM BENEFIT Operability, Reliability Evaluate each option based on these criteria PROPERTY IMPACT Impact on homes & property; Visual impact Evaluate each combination based on these criteria COST to CUSTOMERS Engineering and construction costs TECHNICAL FEASIBILITY Can it be engineered? Can it be built? ENVIRONMENTAL IMPACT Impact on wildlife, vernal pools, aquifers Per national and regional reliability standards. 8

9 Choosing a Route / Design was an Iterative Process System Studies General Electric ISO-NE NU HVDC Black & Veatch Singer Substation Site Routing & Criteria Burns & McDonnell m n Decision Circle Transmission & Substation Design Burns & McDonnell Underground Technology Underground Construction PDC JD Hair Property Impact Black & Veatch CB Ellis Noise Cavanough & Tocci Environmental Review EMF/ Best Practice Exponent Phenix Environmental, Inc. Historical Raber Associates Environmental Topology Water Resources Coastal Area Cultural SSES Marine Options ESS 9

10 M-N Project and Alternatives M-N Project (Budget $1.400 B) Alternative A (Budget $1.350 B) Alternative B (Budget $1.272 B) OH 345-kV (circuit miles) OH 115-kV (circuit miles) UG 345-kV XLPE (circuit miles) UG 115-kV XLPE (circuit miles) Greenfield S/S Sites Upgrade S/S Sites Acquisition Acres Land / # Homes

11 Middletown-Norwalk Summary 69 miles of 345-kV line 24 miles of XLPE underground 45 miles of overhead 57 miles of 115-kV line 1 mile of XLPE underground 56 miles of overhead 3 new substations 2 existing substation upgrades Construction in 18 towns Middletown Haddam Durham Middlefield Wallingford Meriden Cheshire Hamden Bethany Woodbridge Orange West Haven Milford Stratford Bridgeport Fairfield Westport Norwalk In-Service Date: December 2008

12 Why This Solution Why underground from Milford to Norwalk? Going underground is 50% shorter The underground option avoids the environmental and social impacts of having to acquire over 100 acres and up to 29 homes The reduced length, avoided real estate costs, and construction difficulty make going underground virtually cost-neutral to going overhead Why overhead from Middletown to Milford? No ROW expansion is needed except for 2.5 miles in an unpopulated area of Haddam/Middletown Nine of the 13 towns would see a net reduction in the number of poles in the ROW Most towns would experience no discernible increase in pole heights from what exists today 12

13 Design & Construction Challenges Overhead EMF ROW acquisition (condemnation of residential homes) Viewscape Permitting (wetland) Existing ROW rights Constructability 13

14 Magnetic Field Mitigation Connecticut Public Act No New Applicant Requirements: Mapping requirement to identify Statutory Facilities (i.e., residential areas, private or public schools, licensed child day care facilities, licensed youth camps and public playgrounds) in the vicinity of the proposed OH route. Assessment of the impact of electromagnetic fields. 14

15 Protection from Magnetic Fields Electric fields are a function of voltage higher voltage causes higher electric fields Magnetic fields are a function of current (Amps) higher current causes higher magnetic fields Power is a function of Volts times Amps For the same amount of power, higher voltage means less current therefore lower magnetic fields There is no practical way to shield magnetic fields, but there are ways to reduce them 15

16 Strategies to Reduce Magnetic Fields 1. Add Distance Widen the ROW Relocate the Line Increase Pole Height 2. Optimize phasing to maximize field cancellation 3. Optimize combination of the structures A B C C B A 16

17 Split Phase Construction Structure Type B 345 kv Split Phase Structure Type C Combination 345/115kV Split Phase Structure Type E Horizontal Split Phase 17

18 Cross Section 1 Scovill Rock S/S to Chestnut Junction (2.6 miles; 335 ROW) Middletown Existing Proposed Option 1 Option 3 ($2.1M/mile) ($2.1M/mile) ($3.1M/mile) mg on North/West Edge of ROW 33.8 mg on South/East Edge of ROW (15 GW Case) (15 GW Case) Existing Proposed Option 1 Option 3 Existing Proposed Option 1 Option 3 18

19 Cross Section 2 Oxbow Junction to Beseck S/S (7.0 miles; 125 ROW) Haddam, Durham, Middletown, Middlefield, Wallingford kV 115-kV Existing Proposed Option 2 Option ($2.8M/mile) ($6.7M/mile) ($7.5M/mile) Bypass Royal Oak by placing 345-kV on new ROW. Existing 115-kV remains. Option 6 ($TBD M/mile) mg on North/West Edge of ROW mg on South/East Edge of ROW (15 GW Case) (15 GW Case) * * Existing Proposed Existing Proposed * EMF value for 115-kV only 19

20 Royal Oak Neighborhood Bypass Property Condemnation Significant Tree Clearing Significant Wetland Impacts Bypasses may not be Least Environmentally Damaging Practical Alternative 20

21 Cross Section 7B Cheshire Town Line to Cook Hill Junction (0.4 miles; 200 ROW) Cheshire kV 130 Existing Proposed Option 1 Option 2 ($8.4M/mile) ($9.0M/mile) ($12.5M/mile) mg on North/West Edge of ROW 115-kV 150 mg on South/East Edge of ROW (15 GW Case) (15 GW Case) kV Existing Proposed Option 1 Option 2 Existing Proposed Option 1 Option 2 21

22 Cross Section 8-South Pease Road Junction to East Devon S/S (12.0 miles; 165 ROW) Woodbridge, Orange, Milford Existing Proposed Option 4 Option 5 ($3.8M/mile) ($5.0M/mile) ($5.5M/mile) mg on North/West Edge of ROW mg on South/East Edge of ROW (15 GW Case) (15 GW Case) Existing Proposed Option 4 Option 5 Existing Proposed Option 4 Option 5 22

23 Jewish Community Center Bypass 23

24 Design & Construction Considerations Underground System Limitations Operation & Maintenance Concerns Traffic/Public & Worker Safety DOT/Local Constraints Cost Railroad/Bridge/ River Crossing Methods Soil/Water Handling Conflicts w/other Utilities Residential & Business Disruption 24

25 Underground Challenges How much underground cable can system handle What are O&M implications of UG lines Shortest route is always better can it be built? CT Siting Council approved route along 14 miles of State roadways (shortest and straightest route) DOT resisted use of State roadways due to potential traffic impacts and safety concerns DOT originally wanted the duct bank 8 feet deep which would be too deep for the heat to dissipate and would reduce the capacity of the line DOT wanted all vaults to be located outside of the travel roadway needed to find off street locations How to cross rivers and railroads 25

26 Cable Types Cable Type Maximum Voltage High-pressure Fluid-filled (HPFF) 345kV + Electrical Advantages Most Common at >230kV High-pressure Gas-filled (HPGF) 138kV Lower Capacitance Extruded-dielectric (XLPE) 345kV + Extruded-dielectric (EPR) 138kV Higher Rating than HPFF, Lower VAR Consumption, Low Maintenance More Flexible than XLPE Self-contained Fluid-filled (SCFF) 345kV + High Voltages Electrical Disadvantages Higher VAR Consumption, Leaking oil Higher VAR Consumption, Uncommon New to the United States at 345kV+ Higher Electrical Losses than XLPE Dielectric Fluid, Higher VAR Consumption than XLPE, Uncommon 26

27 Factors Impacting Vault Locations Maximizing system reliability minimize splices Cable length that can be loaded on reels maximum 1800 feet Electrical requirement to space each set of 4 vaults about equally Maximum cable pulling tensions Location of water and railroad crossings - fixed or hard coded vault locations due to river crossings Maximizing the number of off-street vault locations Minimizing impacts to existing businesses (condemnation and business disruption claims) Location of off road wetlands Avoidance of existing utilities Avoidance of intersections 27

28 Water / Rail Crossing Methods Horizontal Directional Drill (HDD) Horizontal Auger (Jack and Bore) Self-Supporting Utility Bridge Open Cut (Trenching with Cofferdams) In-Street Trenching Attachment to DOT Bridges Evaluation Criteria Conformance with Siting Council Decision and Order Minimize Impact to the Environment Minimize Social Impact Minimize Construction Risk Minimize Construction Schedule 28

29 UG Route Change Very busy commercial area No feasible crossing method 29

30 Options to Cross Ash Creek ConnDOT Bridge Attachment Structurally Infeasible HDD Unacceptable Risks Unfavorable Subsurface Conditions Mixed Face Soil Conditions / Shallow Drill Path - Risk of Construction Failure Release of drilling mud (Frac-Out) Staging Area - Unsatisfactory Demolition of business at 58 Post Road in Fairfield Eliminates Entire business parking Lot in Bridgeport for 2-3 months Jack & Bore Not Constructible Open Cut Environmentally Devastating 30

31 Ash Creek Crossing Original Proposal Self-Supporting Utility Bridge 160 Foot Clear Span 4-5 Month Construction Duration Bridge Located Outside of Town Public Access Easement Design Provides Shoreline Access Around Bridge Abutments and Under Bridge Minor Impacts to Intertidal Area 31

32 Proposed Utility Bridge at Ash Creek Building Demolition Elimination of Parking for 2-3 months 32

33 Mock-up of Utility Bridge at Ash Creek This attempt to provide residents a visual representation did not go well and resulted in a petition to DEP due to proposed crossing method 33

34 Ash Creek Permitting Background Extensive feasibility / design completed to determine the least environmentally damaging practical alternative DEP hearings conducted due to petition associated with the construction method After DEP hearings and extensive discussion the Town of Fairfield, City of Bridgeport, ConnDOT and DEP eventually agreed to permit an HDD within the State roadway under the existing bridge Town of Fairfield, City of Bridgeport and ConnDOT signed Memorandum of Understanding to ensure that all understood the impacts of an HDD within the roadway 34

35 Ash Creek Horizontal Directional Drill One circuit on each side of road Each circuit bundle of 5 conduits Drill path was steep and deep to get under bridge abutments Circuits separated and spaced far apart to address cable overheating concerns Construction mostly night work in 12- hour shifts 6 days per week 35

36 Ash Creek-Northwest Corner 36

37 Ash Creek-Northeast Corner 37

38 Construction Duration for Each HDD Each HDD took over 5 months to complete 30 days to install traffic control and Mobilize HDD equipment 8 days to drill pilot hole 30 days to ream pilot hole to proper diameter 45 days to fuse conduits for pull back 2 days conduit pull back 12 days to clean/test conduits 30 days to remove traffic control, restore road and demobilize NOTE: Blue items occur in expanded work zone. Typical Horizontal Directional Drill Setup 38

39 Saugatuck River Crossing 39

40 Saugatuck River Crossing Horizontal Directional Drill 1563 feet in length Max 40 deep 2 3 month construction duration Subsurface conditions Marginal Drill side staging area Adequate Conduit side staging area somewhat constrained residential street Result Hit target exit point Frac-outs cleaned up with no impacts to coastal / environmental resources 40

41 Managing Stakeholder Conflicting Priorities State Siting Authority Federal Agencies - ACOE, NPS, USF&W, OLISP (Office of Long Island Sound), etc. Municipal Leaders State Dept. of Transportation State Dept. of Environmental Protection State Dept. of Health Residents Businesses Other Utilities Communication, engagement and compromise for the greater good are essential 41

42 M-N Project Cost Summary Configuration Circuit Miles $ M/Circuit Mile Range / Ave Influencing Factors 345-kV OH 52 $ / $ kV UG 46 $ / $13.2 Single / Double Circuit Low EMF Designs Double Circuit Duct Bank River / RR Crossings 115-kV OH 63 $ / $2.1 Single / Double Circuit 115-kV UG 1 $7.5 / $7.5 Single Circuit Duct Bank Underground transmission lines can cost 4 to 6 times more than overhead transmission lines on an adequately sized existing ROW 42

43 Closing Thoughts Every projects use of various technologies must be evaluated on its own merits Cost/mile comparisons of OH and UG can be deceiving State Siting Regulators should strive to streamline / shorten the siting approval process 2 plus years is too long State Siting Regulators should be cautious about delegating decisions to municipalities Legislators can provide leadership roles in coordinating stakeholders State and Federal agencies, municipal leaders, businesses and residents 43