Section 3 Project Location, Facilities and Operation

Transcription

1 Section 3 Project Location, Facilities and Operation 3.1 General Basin Overview Extending from Olympia north to the Canadian border, and from the Strait of Juan de Fuca east to the lowlands that sit at the foot of the Cascade Mountains, Puget Sound is an immense basin encompassing more than 33,200 square kilometers of land and 8,300 square kilometers of water (Taylor 2000). Its fluid expanse courses through broad waterways, close passages, and intricate recesses to enclose dozens of islands and to give a complex character to 3,700 kilometers of inland coastline that separates it from the surrounding landscape (Gustafson et al. 2000). Puget Sound is a semi-enclosed body of water in which salt water from the nearby Pacific Ocean mixes with fresh water runoff from the surrounding watershed. Ocean salt water enters Puget Sound through the Strait of Juan de Fuca. Although it averages 62.5 meters deep, Puget Sound has a maximum depth of 390 meters slightly to the north of Seattle with 60-meter sills at Admiralty Inlet and Tacoma Narrows. The second-largest estuary in the United States, Puget Sound has 3,790 kilometers of shoreline. The average difference between high and low tide is about 1.6 meters in Admiralty Inlet, increasing to 2.6 meters during the stronger spring tides (NOAA 2007). The tidal range drives a large volume of water in and out of the Sound with the tide. The tidal regime is mixed, mainly semi-diurnal with two high and two low waters daily, but with inequalities in range and timing. In many cases, a particularly strong tide is followed by a very weak one. In places where the depth and width decrease, conservation of mass dictates that currents must increase. These constrictions are the most promising sites for potential Tidal In- Stream Energy Conversion (TISEC) installations. 3-1 January 31, 2008

2 3.2 Project Locations The District s tidal energy permits are located in the northwestern section of Washington State, at several locations in Puget Sound. In general, the seven locations are: Rich Passage west of the City of Seattle, separating the southern end of Bainbridge Island from the mainland of the Kitsap Peninsula (Kitsap County). Agate Passage a high-current tidal passage connecting Port Madison and Port Orchard, lying between the north end of Bainbridge Island and the mainland of the Kitsap Peninsula (Kitsap County), northwest of the City of Seattle. Admiralty Inlet in the northwestern portion of Puget Sound, between the Olympic Peninsula on the mainland of the State of Washington (Jefferson County, Kitsap County) and Whidbey Island (Island County), where the northwestern end of Puget Sound connects to the Strait of Juan de Fuca. Deception Pass in the northern portion of Puget Sound, separating Whidbey Island (Island County) from Fidalgo Island (Skagit County) and connecting the Strait of Juan de Fuca with Skagit Bay. Guemes Channel a narrow pass in northwestern Washington State separating Guemes Island from Fidalgo Island (Skagit County) and connecting the Rosario Strait with Fidalgo Bay and Padilla Bay. San Juan Channel in northwestern Washington State in the San Juan Islands, east of Victoria, British Columbia, Canada, between the southeastern portion of San Juan Island and the west/southwestern portion of Lopez Island (San Juan County), connecting Griffen Bay to the Strait of Juan de Fuca at the southern entrance of San Juan Channel (sometimes referred to as San Juan Channel (southern entrance) or as Cattle Pass ), and lying near the intersection of the Strait of Georgia and the Strait of Juan de Fuca. Spieden Channel on the northwestern edge of the state of Washington in the San Juan Islands, east of Victoria, British Columbia, Canada, separating the northern shore of San Juan Island from Spieden Island (San Juan County), and connecting the northern portion 3-2 January 31, 2008

3 of San Juan Channel with Haro Strait, near the intersection of the Strait of Georgia and the Strait of Juan de Fuca. The currently described boundary for each site is equivalent to the area reserved under the District s preliminary permits. The precise locations of these boundaries, including coordinates of each of their four corners, are depicted in the maps located in Appendix C. The ultimate project boundaries will likely include a subset of the preliminary permit boundaries, but may also include areas surrounding any facilities required for the operation of, and transmission of electricity from, the tidal energy projects. As discussed in this document, the project area or permit area includes the lands and waters within each of the locations described above. The project vicinity includes the lands, waters, towns, and roads outside of and surrounding each project area which in the District s assessment may reasonably affect or be affected by one or more of the projects and their operation. 3.3 Description of Project Areas The District is investigating seven sites in Puget Sound for their potential to support the generation of electricity from tidal currents. The locations of these sites are shown on the map of Puget Sound in Figure 3-1. More-detailed project mapping for the Admiralty Inlet site, expected to be the site chosen for an initial pilot installation, is provided in Appendix C, which depicts preliminary permit boundaries, legal boundaries, proximal towns, federal lands, tribal lands and potential transmission interconnect sites. A number of the District s project sites also serve as usual and accustomed tribal fishing areas. These are described in Sections 4.10 and 4.12 and depicted by the maps in Appendix F. 3-3 January 31, 2008

4 Figure 3-1. Preliminary Permit sites in Puget Sound (Polagye 2006) 3-4 January 31, 2008

5 In preparation for submitting preliminary permit requests to FERC for tidal energy exploration in Puget Sound, the District conducted a high-level study of the Puget Sound estuary to identify potentially viable sites, focusing on the availability of the kinetic resource. As a result of this study, preliminary permits for seven sites within the Puget Sound were requested from FERC in June Upon receipt of the preliminary permits in February and March of 2007, an expanded study was launched to thoroughly investigate all seven sites for tidal energy generation feasibility. Criteria included in the study and discussed in this section are: In-stream resource; Bathymetry and seabed geology; Port facilities; Maritime use; and Electrical interconnection. While currently less than one year into an anticipated three-year study, the District does not necessarily assume that all seven sites will be found viable for cost-effective, utility-scale tidalpower generation. The Admiralty Inlet site has, however, already been deemed a site with excellent potential even at this early stage of investigation, and as a result was selected for the first feasibility study. Accordingly, this document contains relatively more information for the Admiralty Inlet site than for other locations. An overview of site information is presented in Tables 3-1 and 3-2 below. These tables provide a broad, high-level, site characterization summary; additional more-detailed information is presented site by site following the tables. 3-5 January 31, 2008

6 Table 3-1. General summary of area, county, maritime use, presence of dams and general site coordinates by project area Project Admiralty Inlet FERC No Spieden Channel FERC No Area (mi.²) Counties 117 Island, Kitsap, Jefferson Maritime Use Shipping, Ferry, Navy, Fishing, Diving, Recreational Boating 4.82 San Juan Fishing, Ferry, Recreational Boating Dams and Diversions None None Site Boundary Coordinates Latitude Longitude NW Corner 48 08' 17" N ' 12" W SW Corner 48 58' 05" N ' 38" W NE Corner 48 13' 20" N ' 19" W SE Corner 48 58' 22" N ' 15" W NW Corner 48 39' 02" N ' 01" W SW Corner 48 37' 16" N ' 56" W NE Corner 48 38' 09" N ' 54" W San Juan Channel FERC No San Juan Fishing, Recreational Boating None SE Corner 48 36' 54" N ' 55" W NW Corner 48 28' 12" N ' 22" W SW Corner 48 26' 53" N ' 59" W NE Corner 48 29' 01" N ' 45" W Guemes Channel FERC No Skagit Oil tankers, Ferry, Recreational Boating None SE Corner 48 27' 17" N ' 59" W NW Corner 48 32' 07" N ' 16" W SW Corner 48 30' 36" N ' 04" W NE Corner 48 31' 42" N ' 21" W Deception Pass FERC No Skagit, Island Diving, Recreational Boating None SE Corner 48 30' 43" N ' 51" W NW Corner 48 24' 26" N ' 20" W SW Corner 48 24' 09" N ' 46" W NE Corner 48 25' 36" N ' 58" W Agate Passage FERC No Kitsap Fishing, Diving, Recreational Boating None SE Corner 48 23' 56" N ' 44" W NW Corner 47 43' 57" N ' 56" W SW Corner 47 42' 29" N ' 33" W NE Corner 47 43' 14" N ' 47" W Rich Passage FERC No Kitsap Navy, Fishing, Recreational Boating None SE Corner 47 42' 15" N ' 56" W NW Corner 47 35' 39" N ' 27" W SW Corner 47 34' 54" N ' 23" W NE Corner 47 34' 31" N ' 05" W SE Corner 47 33' 37" N ' 23" W 3-6 January 31, 2008

7 Table 3-2. General summary of terrestrial land use by project area General Land Use Admiralty Inlet Agate Passage Deception Pass Guemes Channel Rich Passage San Juan Channel Spieden Channel Bays and estuaries X X X X X X X Commercial and Services X X X X Cropland and pasture X X Deciduous forest land X X X Evergreen forest land X X X X X Industrial X X X Lakes X Mixed forest land X X X X X X X Mixed rangeland X X Mixed urban or built-up land Nonforested wetland X X Other urban or built-up land X X X Reservoirs X Residential X X X X X X X Streams and canals Transitional areas Transportation, communications and services Source: Price et al. (2006) X X X 3.4 Admiralty Inlet The preliminary permit area for Admiralty Inlet is shown in Figure 3-2. Nearly the entire tidal exchange in the Puget Sound passes across this relatively narrow, shallow sill, except a relatively small flow through Deception Pass. While Admiralty Inlet is a constriction in comparison to the Strait of Juan de Fuca to the west and the main basin to the south, it is quite large in absolute terms, nearly five kilometers across with an average depth of 65 meters. As a result, the District s investigation has divided Admiralty Inlet into two sections: Northern Admiralty Inlet and Southern Admiralty Inlet. Each is described separately below. 3-7 January 31, 2008

8 Admiralty Head Point Wilson Marrowstone Point Indian Island Nodule Point Bush Point Figure 3-2. Admiralty Inlet Preliminary Permit Area (Snohomish County PUD 2006) Northern Admiralty Inlet The northern region of Admiralty Inlet may be loosely thought of as the area encompassing Point Wilson, Admiralty Head on Whidbey Island, and Marrowstone Point, as shown in Figure 3-3. The District is proposing to initially develop a pilot demonstration project in this region. 3-8 January 31, 2008

9 Figure 3-3. Northern Admiralty Inlet (Polagye et al. 2007) The blue rectangle drawn on the Admiralty Head nautical chart in Figure 3-4 below indicates the likely area of high power density and is, therefore, the general area being considered for locating the initial pilot installation. Water depths are shown in fathoms (1 fathom = 1.8 meters or 6 feet). The precise location of the pilot turbine(s) will be determined by the District based on an evaluation of all available environmental, social, technical, and economic data, considering the views of federal and state agencies, Indian tribes, and other stakeholders. The area outlined in Figure 3-4 is about 2 km wide by 2.5 km long. The marine-based structures for a pilot project will likely include one to five TISEC devices rated at 0.3 to 1 MW each, associated foundations, and one or more subsea transmission cable(s). Potential land-based structures may include an overhead transmission line to an existing substation, or potentially the construction of a new substation. 3-9 January 31, 2008

10 Figure 3-4. Admiralty Head nautical chart (Polagye et al. 2007) Fort Worden State Park occupies a high point to the west of Point Wilson. Its high bluffs command a view of the inlet towards Admiralty Head, as shown in Figure 3-5. Fort Casey State Park and Ebey s Landing National Historical Reserve occupy most of the land on Admiralty Head. The coastline is dominated by high, sandy bluffs, the highest near Point Wilson, west from Ebey s Landing on Whidbey Island, and near Marrowstone Point. The beaches on both sides of Northern Admiralty Inlet tend to be sand and cobbles. There are extensive kelp beds to the northwest of Point Wilson January 31, 2008

11 Figure 3-5. Admiralty Inlet from Fort Worden (Polagye et al. 2007) In-Stream Resource The surface power density predicted by the National Oceanic and Atmospheric Administration (NOAA) for Northern Admiralty Inlet sites is shown superimposed on a bathymetric plot in Figure 3-6. Red hues indicate shallow water, while blue hues indicate deep water. The NOAA current stations indicate the following: Power densities in the central, deep water channel are consistently on the order of kw/m 2. In the shallows outside of the deep water channel, power densities are much lower generally less than 0.4 kw/m 2. This is likely due to eddy currents. Additionally, the District conducted acoustic Doppler current measurements in Admiralty Inlet during the summer of 2007 and the resulting data were analyzed by team members at the University of Washington. Results were encouraging for turbine deployment in the inlet, 3-11 January 31, 2008

12 reflecting substantially higher currents then were indicated by the NOAA predictions (see Figure 3-6 for the NOAA predictions (NOAA 2006)). Based on this analysis, the surface power density can be inferred to exceed 1.6 kw/m 2 over a large area of Admiralty Inlet between Point Wilson and Admiralty Head. Thus, previous estimations of the in-stream resource should be considered to be conservative. Figure 3-6. Power density and bathymetry in Northern Admiralty Inlet (Polagye 2006) Bathymetry and Seabed Geology Site bathymetry is shown in Figure 3-6. Northern Admiralty Inlet is dominated by a central channel approximately 60 meters deep. While the inlet is quite deep in absolute terms, it is relatively shallow in comparison to the rest of the Puget Sound, and thus is a relative sillcontrolling inflow and outflow. Bathymetric data corresponds to multiple NOAA surveys of the region. In addition, 10-meter-resolution bathymetry is available for the seabed to the northwest of Admiralty Head (NOAA NGDC 2007) January 31, 2008

13 Figure 3-7. Monthly variations in depth-averaged power density in Admiralty Inlet (University of Washington 2007) While U.S. Geological Survey (USGS) publications for Admiralty Inlet show several hundred feet of sediment overlying bedrock, seabed surveys for a pipeline proposed in the 1970s indicate exposed bedrock or bedrock covered by only a thin layer of sediments along some transects (Jones 1999). Since the published USGS data is known to be more accurate on land and less accurate on the seabed, the District considers the pipeline survey to be more authoritative. Seabed profile and composition from the pipeline surveys is shown in Figure 3-8 (Report to the 44 th Legislature of the state of Washington, 1975; Point Wilson to Ebey s Landing) and Figure 3-13 January 31, 2008

14 3-9) (Point Wilson to Admiralty Head). The surveys demonstrate that there is considerable variability in the seabed profile between the two transects. Figure 3-8. Pipeline geologic survey Point Wilson to Ebey s Landing (Polagye et al. 2007) Figure 3-9. Pipeline geologic survey Point Wilson to Admiralty Head (Keystone Landing) (Polagye et al. 2007) 3-14 January 31, 2008

15 In general, surface sediments are estimated to be gravel in the mid-channel, gravel and sand to the channel edges, and sandy gravel on the left edge of the channel between Marrowstone Point and Point Wilson as shown in Figure 3-10 (PSWQA 1992). Puget Sound Water Quality Authority (PSWQA) report does not provide information as to the underlying structure of the seabed. Figure Surface Sediments in Northern Admiralty Inlet (PSWQA 1992) This characterization of the seabed is corroborated by the WSDE sediment sampling program (WSDE 1999) Port Facilities The substantial port facilities in Seattle and Everett to the south and east and Port Angeles to the west could serve as a staging area for installation work. Though Port Townsend, closest to the site, has only limited infrastructure, it might be suitable as a staging area for basic maintenance activities. Water depths at the Port Townsend wharves range from 8 to 30 feet and the only commercial traffic of note is for a paper plant southwest of the city January 31, 2008

16 Maritime Use The high currents in Admiralty Inlet exist because the relatively narrow, shallow sill regulates the flow into the main basin of Puget Sound. This also means that the inlet serves as a main route for all shipping traffic for the ports of Everett, Seattle, Tacoma, and Olympia. Deception Pass, the other entrance to Puget Sound, is too narrow to support large commercial vessels or significant marine traffic (McCurdy 2007). Admiralty Inlet is also traversed by a ferry route: the Port Townsend-Keystone ferry runs between Port Townsend and Admiralty Head on Whidbey Island. Shipping and ferry lanes are shown in Figure 3-11 (PSWQA 1992). Figure Shipping lanes in Northern Admiralty Inlet (PSWQA 1992) Admiralty Inlet also supports substantial Navy traffic. In Northern Admiralty Inlet, the Navy has noted two potential concerns. First, sea-space availability must not be unduly restricted for surface vessels and submarines (Melaas 2007). As a subset to this concern, the Navy requests that any turbine installation not push the Keystone ferry route further to the south (into restricted area 7/R-6701), conflicting with the Admiralty Bay Mining Range (Melaas 2007). Second, the Navy wishes to ensure that magnetic fields, radio frequency interference, and/or acoustic 3-16 January 31, 2008

17 interference/noise caused by turbines and generators do not interfere with navigation or other equipment aboard surface vessels and submarines (Melaas 2007) Electrical Interconnection The nearest transmission circuits to sites in Northern Admiralty Inlet are at 115 kv and are operated by Puget Sound Energy (PSE). The District has been informed that, in general, the lines have sufficient capacity to transmit generation from a project in Northern Admiralty Inlet. The only circuits at lower voltages are all at 12.5 kv, serving customer loads, and unsuitable for megawatt-scale generation. It is expected that underground collector circuits at a voltage such as 34 kv will be used to connect the proposed generation to the regional electrical grid (Polagye et al. 2007). For an array close to Admiralty Head, the nearest substation is in Coupeville (several miles from shore), which is impractical for direct interconnection. The Whidbey-Greenback #2 115kV line is the nearest possible point of interconnection. Construction of a new substation would be required, with the new substation located as near as possible to PSE 115 kv lines, while allowing for the shortest length of collector circuit from the offshore array (Polagye et al. 2007). Interconnection is complicated by the Ebey s Landing National Historic Reserve which occupies most of the Whidbey Island coast in the immediate vicinity of the proposed pilot project area, as well as high bluffs to the west of Admiralty Head. For these reasons, the most feasible routing for the power take-off cable may be to the east of Admiralty Head, either at the Keystone ferry terminal or further along the shoreline. PSE believes interconnection is feasible at this site (J. Seabrook, Personal Communication). A map of the existing electrical infrastructure near Admiralty Head can be obtained from PSE, and will be released according to the criteria established by PSE. For an array closer to Point Wilson, the Kearney Street substation in Port Townsend is approximately 1,500 feet from the shoreline and direct connection might be feasible. A right-of January 31, 2008

18 way would have to be obtained for cable landfall. The waterfront in this area is not very developed, though there is a marina in close proximity that could possibly facilitate the right-ofway. At the substation, interconnection would be with the Port Townsend #1 115 kv line. An array to the northwest of Point Wilson would require several miles of undersea cable to come ashore near the Kearney Street substation. While there is a waste-water discharge to the west of Point Wilson (PSWQA 1992) which could help to bring the power cables ashore, there are no high-voltage transmission lines on the northern shore of the peninsula. A map of the existing electrical infrastructure near Point Wilson can be obtained from PSE, and will be released according to the criteria established by PSE Southern Admiralty Inlet At the southern end of Admiralty Inlet there is a secondary constriction between Bush Point and Nodule Point, as shown in Figure 3-12 (Google Maps 2007). Nodule Point Bush Point Figure Admiralty Inlet constriction between Nodule Point and Bush Point (Polagye et al. 2007) 3-18 January 31, 2008

19 In-Stream Resource The velocity and power assessment conducted by the University of Washington in 2007 on Admiralty Inlet is discussed in the Northern Admiralty Inlet section above, Section The following discussion is based upon data gathered in surveys conducted by NOAA. A bathymetric plot showing the location and power density of current stations on a transect from Bush Point (east side) to Nodule Point (west side) is given in Figure 3-13 (NOAA 2006; NOAA NGDC 2007). Currents in the vicinity of Bush Point are less energetic than in Northern Admiralty Inlet. Figure Power density and bathymetry near Bush Point (Polagye 2006) Bathymetry and Seabed Geology Site bathymetry is shown in Figure In general, the constricted channel is very deep along the transect of interest. The thin bright green regions on the left and right edges of the channel represent depth contours of approximately 70 meters. The strongest currents in the channel, at the midpoint, are in water deeper than 100 meters January 31, 2008

20 The seabed is characterized as gravel and sand, and thus should not pose significant barriers to turbine installation. This transect was also considered for a pipeline project in the mid-1970s and a basic geological survey is available (Anonymous 1975). To the south of Bush Point, a series of sand dunes are slowly migrating north with the current. The dunes are approximately 20 meters high, with a wavelength of 375 meters, and are migrating northwest at approximately 10 meters per year (Seim 1993). These do not pose a present concern for initial siting of turbines in Northern Admiralty Inlet Port Facilities As previously documented in the Northern Admiralty Inlet description, there are port facilities in Seattle and Everett to the south and east and Port Angeles to the west. Port Townsend is the closest to the site, but provides only limited infrastructure Maritime Use Shipping traffic for the ports of Everett, Seattle, Tacoma, and Olympia passes through the potential project area along a designated navigation channel (see Figure 3-11). Overhead clearance requirements indicate a minimum overhead clearance of 23 meters Electrical Interconnection The nearest transmission circuit to Bush Point is a 115 kv line operated by PSE (South Whidbey-Greenbank #2). The District has been informed that, in general, the lines have sufficient capacity to transmit generation from a project in Northern Admiralty Inlet. The only circuits at lower voltages are all at 12.5 kv, serving customer loads, and unsuitable for megawatt-scale generation. It is expected that underground collector circuits at a voltage such as 34 kv will be used to connect the proposed generation to the regional electrical grid (Polagye et al. 2007) January 31, 2008

21 The nearest substation is in Freeland (several miles from shore). The South Whidbey-Greenback #2 115 kv line is the nearest possible point of interconnection. Construction of a new substation may be required, with the new substation located as near as possible to PSE 115 kv lines, while allowing for the shortest length of collector circuit from the offshore array. The shoreline at Bush Point is residential in nature. Provided a right-of-way can be secured, interconnection with PSE infrastructure should not pose undue challenge. A map of the existing electrical infrastructure near Bush Point can be obtained from PSE, and will be released according to the criteria established by PSE. 3.5 Deception Pass Deception Pass is a narrow constriction separating Whidbey and Fidalgo Islands (see Figure 3-14). The area is a spectacularly rugged state park, with sheer rock cliffs plunging down to the water on all sides. At its narrowest point, where the pass is obstructed by the bedrock outcropping of Pass Island, water flows rapidly around the north and south of the island through Canoe and Deception Passes respectively. Deception Pass is often used to refer to the general area, but is properly the 350-meter-long constriction in the channel to the south of Pass Island. State Route 20 crosses the pass high above the water on a steel truss bridge. The preliminary permit area is shown in Figure 3-15 and covers both approaches to Deception Pass, as well as a secondary constriction at Yokeko Point to the east (Snohomish County PUD 2006) January 31, 2008

22 Fidalgo Island Canoe Pass Pass Island State Route 20 Deception Pass Whidbey Island Figure Deception Pass (Polagye et al. 2007) Fidalgo Island Deception Pass Canoe Pass Whidbey Island Figure Deception Pass Preliminary Permit Area (Snohomish County PUD 2006) In-Stream Resource The District conducted acoustic Doppler current measurements in Deception Pass during the summer of 2007 and the resulting data were analyzed by team members at the University of 3-22 January 31, 2008

23 Washington. Power densities in Deception Pass were found to be very high, as expected from looking at NOAA predictions and the bathymetry in the area. These densities exceed 6 kw/m 2 on an annual basis in the middle of the water column and closer to 5 kw/m 2 near the surface. The observations and measurements suggest the importance of determining the turbulence level at potential turbine sites with future computer modeling as well as potentially additional current measurements. The figures below depict some of the data analyzed. Figure Time-mean power density in waters surrounding the Deception Pass channel, shown in logarithmic scale (University of Washington 2007) 3-23 January 31, 2008

24 Figure Measured depth-averaged power density in Deception Pass (kw/m 2 ) (University of Washington 2007). Figure Monthly variation in depth-averaged power density in Deception Pass (University of Washington 2007) January 31, 2008

25 Due to the exceptionally strong currents and rapidly changing channel cross-section, there are substantial eddies both north and south of Pass Island (see Figure 3-19). Deception Pass from Pass Island Canoe Pass from Pass Island Figure Eddy currents in Deception Pass and Canoe Pass (Polagye et al. 2007) Bathymetry and Seabed Geology Deception Pass averages 30 meters in depth in the region of interest, with very steep shorelines. Canoe Pass is substantially shallower, averaging only 8 meters in depth at its narrowest point. A bathymetric plot showing the location and power density of current stations in Deception Pass is given in Figure 3-20 (NOAA 2006; NOAA NGDC 2007) January 31, 2008

26 Figure Power density and bathymetry in Deception Pass (Polagye 2006) While no formal geologic survey exists for Deception Pass, it can be inferred that the seabed is solid rock. Both the northern and southern shores are very rocky and Pass Island is itself solid rock (Krynvtzky 2005; Jones 1999). Given the extreme currents which scour the channels, at most a thin layer of cobbles and gravel overlying bedrock are expected on the seabed Port Facilities Anacortes to the north is a substantial port which could serve as a staging area for maintenance activities. However, the limited infrastructure of the Port of Anacortes may necessitate that larger-scale activities be conducted out of the nearby Seattle or Everett port facilities Maritime Use Deception Pass is primarily used by recreational craft. However, there is intermittent tug traffic and the Victoria Clipper ferry and touring vessels make use of the channel if the water in Admiralty Inlet is too rough January 31, 2008

27 3.5.5 Electrical Interconnection Two 115-kV lines cross Deception Pass just east of the tidal site. These lines (March Point- Whidbey #1 and #2) are operated by PSE. Given the high cliffs in the vicinity of the site, the most feasible interconnection option appears to be to run a cable east along the seabed toward Millar Bay where the shoreline is more hospitable, as shown in Figure The nearest substation is on March Point, approximately 7.5 miles northeast of Deception Pass. A new substation may be required at the interconnection point with the 115 kv line and rights of way would need to be obtained. The land adjacent to Millar Bay is not part of the state park, so all electrical infrastructure associated with the project would likely be either on the seafloor or private land. Millar Bay Cliffs (potential cable landing) (line crossing) Yokeko Point Pass Island Deception Pass Figure Deception Pass east of bridge crossing (Polagye et al. 2007) A map of the existing electrical infrastructure in the vicinity of Deception Pass can be obtained from PSE, and will be released according to the criteria established by PSE January 31, 2008

28 3.6 Guemes Channel Guemes Channel is a narrow body of water separating Guemes and Fidalgo Islands and connects the Rosario Strait to Padilla Bay. The permit area is shown in Figure The area of greatest interest is the narrow constriction midway along the channel where currents are estimated to be strongest. Figure Guemes Channel Preliminary Permit Area (Snohomish County PUD 2006) An aerial image of the region is shown in Figure 3-23 (Google Maps 2007). The southern shore of the channel is relatively industrialized, while the northern shore on Guemes Island is distinctly pastoral. The beach on the Anacortes side of the channel is sand and cobbles with a number of old pilings in shallow water, as shown in Figure January 31, 2008

29 Guemes Island Guemes Channel Anacortes March Point Figure Guemes Channel (Polagye et al. 2007) Figure Guemes Channel from Anacortes shoreline (Polagye et al. 2007) In-Stream Resource NOAA has a single current reference station at the western end of Guemes Channel. A bathymetric plot showing the location and power density of the current station in the Guemes Channel is given in Figure The channel has a region of potentially incomplete bathymetric 3-29 January 31, 2008

30 data noted by the large shaded region on the southeastern shoreline. This appears to correspond to the shallow, pile-filled area pictured in Figure 3-24 (NOAA 2006; NOAA NGDC 2007). Figure Power density and bathymetry in the Guemes Channel (Polagye 2006) Table 3-3. Guemes Channel Site Parameters (Polagye et al., 2007) Tidal Energy Statistics Depth Averaged Power Density (kw/m 2 ) 1.5 Average Power Available (MW) 34.9 Average Power Extractable (MW) 5.2 # Homes equivalent (1.3 kw/home) 3, January 31, 2008

31 250 Channel Power (MW) Annual Average = 35 MW 0 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 Day Source: Polagye et al Figure Tidal cycle channel power variation in Guemes Channel (2006) Channel Power (MW) Annual Average = 35 MW Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Source: Polagye et al Figure Monthly average channel power in Guemes Channel (2006) The Coast Pilot reports currents in the channel in excess of 5 knots (NOAA OCS 2007); that rate is substantially greater than that predicted by NOAA for the station at the western entrance (3.9 knots). Therefore, an estimate of currents in the narrower part of the channel has been made. Considering the shape of the shoreline in the channel, one would anticipate the observed eddy which forms on flood to the east of Anacortes (NOAA OCS 2007), and on ebb one would expect 3-31 January 31, 2008

32 a comparable eddy to the west of Guemes Island. Neither of these eddies affects the project area. Given the uniform bathymetry and cross-section of the channel, flows should be bi-directional Bathymetry and Seabed Geology The Guemes Channel has a relatively regular cross-section with an average depth of nearly 15 meters. The channel is deepest at the center and drops off relatively quickly from the shoreline in the area of interest. Bathymetry for the channel is shown in Figure The seabed in the Guemes Channel is estimated to be gravel (Seacore LTD). This is confirmed by the rocky strata encountered during failed sediment sampling (WSDE 1999). No detailed information regarding the nature of the sediments underlying the gravel is available Port Facilities The Port of Anacortes lies to the north of the project area and is a relatively substantial port. However, its limited infrastructure may necessitate that larger-scale activities be conducted out of the nearby Seattle or Everett Port facilities Maritime Use The Guemes Channel is used by oil tankers making deliveries to the Shell and Tesoro refineries on March Point. The tankers dock at long wharves visible in Figures 3-23 and Tankers are a bit more than 50 meters (170 feet) in width, compared to 1,000 meters for the channel at its narrowest point. While pilots attempt to keep the tankers in the center of the channel while traversing it, the strong currents can cause the tankers to crab to one side or the other (McCurdy 2007). There is also a small ferry which operates in the most constricted part of the channel between Guemes and Fidalgo Island January 31, 2008

33 Figure Guemes Channel ferry, crossing on flood tide (Polagye et al. 2007) The U.S. Army Corp of Engineers (COE) does undertake some dredging on the Anacortes shore of the channel (Fox 2007), possibly to maintain seabed clearance along the docks Electrical Interconnection 115-kV lines and two substations are relatively close to the channel: Anacortes and Burrows Bay. The 115-kV lines and substations are operated by PSE. The two most-feasible options for interconnection are: (1) running a subsea cable west from the project site to come ashore and interconnect at Burrows Bay substation; and (2) running a subsea cable around the head of Anacortes to make landfall directly south of the marina and interconnect at the Anacortes substation. Both options require substantial marine cabling, but are likely to be less expensive than building above-ground transmission capacity or building a new substation in the city of Anacortes. There is a waste-discharge facility on the southern shore of the channel near the project site (PSWQA 1987), but it is unclear whether making use of it to bring the cable onshore will be more cost-effective than extending a marine cable closer to the substations. A map of the existing electrical infrastructure near Guemes Channel can be obtained from PSE, and will be released according to the criteria established by PSE January 31, 2008

34 3.7 Spieden Channel Spieden Channel is a 3.5-kilometer-long constriction between Spieden Island and San Juan Island, as shown in Figure Currents are moderate, but the channel has a large crosssectional area, and therefore is potentially a substantial in-stream resource. Currents are highest at the eastern end of the project area where the cross-sectional area of the channel is at a minimum. Figure Spieden Channel Preliminary Permit Area (Snohomish County PUD 2006) In-Stream Resource The power density of the currents in Spieden Channel is shown in Figure 3-30 (NOAA 2006; NOAA NGDC, 2007) superimposed on a bathymetric map of the region. Beyond Limestone Point, the channel deepens rapidly; however, the cross-sectional area of the channel decreases to the west of the current station at Limestone Point. This should result in higher velocities and power densities than at Limestone Point January 31, 2008

35 Spieden Island Limestone Point Figure Power density and bathymetry in Spieden Channel (Polagye 2006) Table 3-4. Spieden Channel Site Parameters (Polagye et al. 2007) Tidal Energy Statistics Depth Averaged Power Density 0.6 kw/m 2 Average Power Available 56 MW Average Power Extractable (15 percent) 8.3 MW # Homes equivalent (1.3 kw/home) January 31, 2008

36 A representative plot of channel power over a tidal cycle is given in Figure Monthly averaged channel power is shown in Figure Channel Power (MW) Annual Average = 56 MW 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 Day Source: Polagye et al Figure Tidal cycle channel power variation in Spieden Channel (2006) Annual Average = 56 MW Channel Power (MW) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Source: Polagye et al Figure Monthly average channel power in Spieden Channel (2006) Bathymetry and Seabed Geology As shown in Figure 3-30, Spieden Channel is quite deep, except on the southern shore. In the central channel depths are typically greater than 80 meters January 31, 2008

37 Very little information is available regarding the seabed composition, though the sparse data indicates gravel (PSWQA 1992) Port Facilities While Roche Harbor is the closest port to the site, it has extremely limited infrastructure and is probably not suitable for either maintenance or installation of a TISEC array. Friday Harbor, on the eastern side of San Juan Island, has more-extensive facilities, but is still probably not suitable for more than maintenance of an existing array. Installation could be staged out of Port Angeles Maritime Use The channel is extensively used by pleasure craft and is occasionally used by tugs and barges (NOAA OCS 2007). The Anacortes-Sidney, BC ferry also traverses the channel (PSWQA 1992). Overhead clearance of 6 meters should be sufficient to accommodate existing traffic (McCurdy 2007). There is commercial fishing throughout the San Juan Islands from July through December for pink and sockeye salmon (McCurdy 2007) Electrical Interconnection In the vicinity of Spieden Channel, the only electrical infrastructure is 15-kV distribution lines operated by the Orcas Power and Light Cooperative (OPALCO). This limits the maximum output of an array utilizing these lines, without constructing upgrades, to no more than a few megawatts, though further analysis is required for complete specification. The nearest highervoltage line is 69 kv, which terminates at the Roche Harbor substation. Although this substation is approximately six miles from the shoreline, it would allow for greater project output than the lower-voltage 15-kV OPALCO line. Extension of the 69-kV line would likely have to be trenched (M. Tilstra, Puget Sound Energy, Personal Communication; Polagye et al. 2007) January 31, 2008

38 3.8 San Juan Channel San Juan Channel is a long, wide body of water along the east side of San Juan Island. At its southern end, the channel is constricted between San Juan and Lopez Islands and the flow reaches its highest power density here. The preliminary permit area is shown in Figure Figure San Juan Channel Preliminary Permit Area (Snohomish County PUD 2006) In-Stream Resource The power density of the currents in San Juan Channel is shown in Figure 3-34, (NOAA 2007; NOAA NGDC, 2007) superimposed on a bathymetric map of the region. Table 3-5. San Juan Channel Site Parameters (Polagye et al. 2007) Tidal Energy Statistics Depth Averaged Power Density 0.6 kw/m 2 Average Power Available 45 MW Average Power Extractable (15 percent) 6.8 MW # Homes equivalent (1.3 kw/home) January 31, 2008

39 Figure Power density and bathymetry in San Juan Channel (Polagye 2006) A representative plot of channel power over a tidal cycle is given in Figure Monthly averaged channel power is shown in Figure Channel Power (MW) Annual Average = 45 MW 0 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 Day Source: Polagye et al Figure Tidal cycle channel power variation in southern San Juan Channel (2006) 3-39 January 31, 2008

40 60 Annual Average = 45 MW Channel Power (MW) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Source: Polagye et al Figure Monthly average channel power in southern San Juan Channel (2006) Bathymetry and Seabed Geology As shown in Figure 3-34, San Juan Channel is relatively shallow on the edges and extremely deep in the center. Very little information is available regarding the seabed composition, though the available data indicates gravel (PSWQA 1992) Port Facilities Friday Harbor is the closest port lying on the eastern side of San Juan Island. The Friday Harbor port has relatively basic facilities and may be suitable for general maintenance of an existing array. More-extensive or larger-scale activities would likely be staged out of Port Angeles, which is still relatively proximal to the project area Maritime Use The channel is extensively used by pleasure craft and is occasionally used by tugs and barges (NOAA OCS, 2007). Overhead clearance is six meters (McCurdy 2007). There is commercial fishing throughout the San Juan Islands from July through December for pink and sockeye salmon (McCurdy 2007) January 31, 2008

41 3.8.5 Electrical Interconnection In the vicinity of San Juan Channel, the only electrical infrastructure is 15-kV distribution lines operated by OPALCO. This limits the maximum output of an array using existing infrastructure to no more than a few megawatts, with further analysis required for complete specification. The nearest higher-voltage line is 69 kv which terminates near Friday Harbor, approximately 8 miles to the north. Interconnection would require a significant length of marine cable from the array site (M. Tilstra, Personal Communication; Polagye et al. 2007), but could connect with an existing 69-kV line at a nearshore location, allowing for greater project output January 31, 2008

42 3.9 Agate Passage Agate Passage separates the northern end of Bainbridge Island from the Kitsap Peninsula. The project area is shown in Figure 3-37 (Snohomish County PUD 2006). The region of greatest interest is at the southern end of the passage. Figure Agate Passage Preliminary Permit Area (Snohomish County PUD 2006) At the southern end of the passage, State Route 305 crosses the passage on a steel truss bridge. At the bridge, there are minor bluffs on both sides of the channel. The beach is a mix of cobbles and sand. On the western shore, to the south of the highway, there is a large tribal casino. Figure 3-38 shows Agate Passage looking north from the bridge January 31, 2008

43 Figure Agate Passage north of Agate Pass bridge In-Stream Resource While the channel is deepest at its southern end, the maximum depth is approximately 10 meters at mean lower low water (MLLW). At the southern end of Agate Passage, current velocities (and corresponding power densities) are relatively high. However, since the cross-sectional area increases substantially from south to north, currents at the northern end of the channel are much slower. Kinetic power densities and bathymetry are shown in Figure 3-39 (NOAA 2006; NOAA NGDC 2007) for the northern and southern end of the channel. Figure Power density and bathymetry in Agate Passage (Polagye 2006) 3-43 January 31, 2008

44 Table 3-6. Agate Passage Site Parameters (Polagye et al. 2007) Tidal Energy Statistics Depth Averaged Power Density 1.5 kw/m 2 Average Power Available 2.7 MW Average Power Extractable (15 percent) 0.4 MW # Homes equivalent (1.3 kw/home) 280 A representative plot of channel power over a tidal cycle is given in Figure Monthly averaged channel power is shown in Figure Channel Power (MW) Annual Average = 3 MW 0 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 Day Source: Polagye et al Figure Tidal Cycle Channel Power Variation in southern Agate Passage (2006) 3.5 Annual Average = 3 MW Channel Power (MW) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Figure Source: Polagye et al Monthly Average Channel Power in southern Agate Passage (2006) 3-44 January 31, 2008

45 3.9.2 Bathymetry and Seabed Geology As shown in Figure 3-39, the channel is quite shallow with a maximum depth of only ten meters. Seabed geology for the site was assessed during the construction of the Agate Pass Bridge. On the west side of the channel, fifteen meters of moderately consolidated sediments and gravel overlie a harder stratum. On the east side, sediments are significantly more consolidated, though the physical composition is similar (M. Tilstra, Personal Communication; Polagye et al. 2007). These two samplings are only separated by only 150 meters and speak to the variability of seabed geology. The top layer of sediments in both cases consists of coarse sand and gravel Port Facilities The Puget Sound Naval Shipyard is located in Bremerton. This port facility has extensive resources that should provide sufficient support for both installation and maintenance of turbines in Agate Passage. The shipyards are available for private use under certain conditions. In the case that activities cannot be based out of Bremerton, the Port of Seattle is a viable nearby alternative Maritime Use Agate Passage is traversed primarily by pleasure craft. A reasonable overhead clearance requirement to allow this type of traffic to safely pass is 6 meters (McCurdy 2007). In addition, drift diving is common in Agate Passage (Fischnallar 1990) Electrical Interconnection PSE operates multiple 115-kV lines which cross Agate Passage just north of the bridge (M. Tilstra, Personal Communication). The nearest substation is in Port Madison, which is impractically distant to interconnect directly. Given the maximum size of a possible array, interconnection at 115 kv is probably not necessary and the project could be connected to 3-45 January 31, 2008

46 distribution lines at 12.5 kv. This would reduce the interconnection cost and obviate the need for a new substation Rich Passage Rich Passage separates the southern end of Bainbridge Island from the Kitsap Peninsula, as shown in the preliminary permit area map (Figure 3-42) (Snohomish County PUD 2006). The channel is narrowest at the western end and currents are correspondingly highest there. Point White Bainbridge Island Kitsap Peninsula Figure Rich Passage Preliminary Permit Area (Snohomish County PUD 2006) At Point White, the beach is primarily cobbles and is only a few feet lower than the mainland (see Figure 3-43). A residential street runs along the perimeter of Point White. To the east of the point houses have beachfront access. To the west of Point White a road separates the beach from houses. The shoreline on the Kitsap Peninsula is similarly developed January 31, 2008

47 Channel Marker Kitsap Peninsula Bainbridge Island beach Figure Rich Passage from Point White (Polagye et al. 2007) In-Stream Resource Kinetic power densities and bathymetry are shown in Figure 3-44 (NOAA 2006; NOAA NGDC 2007) for the western end of the channel. Figure Power density and bathymetry in Rich Passage (Polagye 2006) 3-47 January 31, 2008

48 Table 3-7. Rich Passage site parameters (Polagye et al., 2007) Tidal Energy Statistics Depth Averaged Power Density 0.9 kw/m 2 Average Power Available 9.0 MW Average Power Extractable (15 percent) 1.4 MW # Homes equivalent (1.3 kw/home) 940 A representative plot of channel power over a tidal cycle is given in Figure Monthly averaged channel power is shown in Figure Channel Power (MW) Annual Average = 9 MW 0 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 Day Source: Polagye et al., 2007 Figure Tidal cycle channel power variation in western Rich Passage (2006) 12 Annual Average = 9 MW 10 Channel Power (MW) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Source: Polagye et al., 2007 Figure Monthly average channel power in western Rich Passage (2006) 3-48 January 31, 2008

49 Bathymetry and Seabed Geology As shown in Figure 3-44, the western end of Rich Passage has a relatively uniform depth, averaging fifteen meters. Depths are greatest in the center of the channel. The seabed is gravel (PSWQA 1992) but there is little information pertaining to the structure of the underlying sediments Port Facilities As it would for Agate Passage, the Puget Sound Naval Shipyard located in Bremerton would provide extensive services for both installation and maintenance of turbines in Rich Passage. The shipyards are available for private use under certain conditions. In the case that activities can not be based out of Bremerton, the Port of Seattle is a viable alternative Maritime Use Aircraft carriers are piloted through Rich Passage to reach the Puget Sound Naval Shipyards at Bremerton. The transit through the western end of Rich Passage is reported to be the most difficult part of getting a carrier to Bremerton. Transit is carried out at high water and requires much of the channel for maneuvering purposes (Street 2007; Melaas 2007). The Seattle-to- Bremerton ferry traverses Rich Passage. In addition to Navy vessels and ferries, Rich Passage sees substantial commercial traffic. The density of vessel traffic and strong currents contribute to a considerable collision hazard (NOAA 2007). There is recreational shore diving at Fort Ward State Park to the north of the project site (Jordan 2007) and drift diving in the western end of the channel (Racine 2007) January 31, 2008

50 Electrical Interconnection There are no high-voltage transmission lines in the vicinity of Rich Passage. There is, however, a 12.5-kV distribution line running along the beach at Point White. Were an array to be constructed, it could be interconnected to distribution lines within a hundred yards of shore at Point White. Similar interconnection possibilities may exist on the Kitsap Peninsula-side of the channel General Project Facilities Tidal In-Stream Energy Converters (TISEC) Devices The District is proposing to use a TISEC-type of technology to generate power, and is currently assessing the most appropriate technology for each of the seven locations. The basic principal of TISEC conversion is that a fluid moves past a configuration of blades on an axis, causing them to spin a generator, which results in electricity being transmitted either to a grid or directly to a source requiring electrical power. Tidal energy conversion has many similarities to wind energy conversion; however, there are three major differences: 1) the density of water is approximately one thousand times greater than the density of air; 2) tidal velocities are less than wind velocities; and 3) tidal current velocity is much more predictable than wind velocities. In general, modern wind turbines are divided into two categories: horizontal-axis turbines and vertical-axis turbines. A horizontal-axis turbine, which is the most common configuration, consists of a tall tower atop of which sits a fan-like rotor that faces into or away from the wind, the generator, the controller, and other components. Most horizontal-axis turbines built today are three-bladed, although some have fewer or more blades (EPRI, 2006 TP-004 NA Survey and Characterization of TISEC Devices). Vertical-axis wind turbines are not widely used today. There are numerous TISEC designs that are either in the conceptual phase of development or are being tested in the water. The industry itself is quite immature when compared to the wind 3-50 January 31, 2008

51 industry; therefore, there is no particular design or device that has proven to be more reliable, efficient or desirable than any other design or device. Like wind turbines, TISEC designs consist of blades on either a vertical or horizontal axis which are connected to a generator. Several of the designs have rotor blades, which may be ducted or non-ducted. Some of the duct designs have wider openings at the mouth to increase the current velocity at the blade location and result in an increase of power. Some designs incorporate variable-pitch blades, which is a common design in many conventional hydropower turbine applications. The District has not selected the specific technology and technology provider for the tidal project at this time. However, available TISEC technology is currently represented mainly by horizontalaxis water turbines, both open-rotor and ducted, fixed to the seabed using either a monopile or gravity base. The District has met with a number of providers including Verdant Power, Clean Current Power Systems, Marine Current Turbines, OpenHydro, Ocean Renewable Power Company, Swan Turbines, Lunar Energy, and Tidal Sails. The District has also conducted a site visit to the European Marine Energy Center in Orkney, Scotland as part of its overall technology assessment and selection process. A selection of TISEC technologies under consideration by the District are depicted below. Figure Lunar Energy TISEC Device 3-51 January 31, 2008

52 Figure Verdant Power TISEC Device Figure Marine Current Turbine TISEC Device 3-52 January 31, 2008

53 Figure OpenHydro TISEC Device Figure Clean Current TISEC Device 3-53 January 31, 2008

54 Potential Foundations In order for utility-scale TISEC devices to effectively extract kinetic energy from tidal exchange, they must be secured to the seafloor. Although conceptual designs exist for free-floating and chain-anchor turbines, they are currently not in use by leading device developers (EPRI 2007). While tripod foundations and tension legs may represent economically viable attachment options for deeper sites in the future, most projects envisioned at present employ either monopiles or gravity foundations to secure tidal energy devices and turbines to the seafloor (EPRI 2007). Of these two systems, monopiles are the more costly and complicated to emplace. Although they have been utilized successfully for offshore wind projects, monopile foundations are economically viable in only waters shallower than 60 m, and from a cost perspective their optimal usage is in waters less than 30 m deep (EPRI 2007). Prior to the installation of monopiles, the seafloor of the selected location must be surveyed in detail, and trial cores must be taken to determine the specific design of the pile (Faber Maunsel and METOC PLC 2007). Drilling a sub-bottom rock socket, which eventually houses the pile and frequently exceeds 20 m in depth, generally begins following this initial survey. However, in many instances the seabed must first be leveled to accommodate the feet of the jack-up rigs typically used to accomplish the drilling stage of installation (Faber Maunsel and METOC PLC 2007). It may take as many as three to seven days for the jack-up vessel to drill, set, and cement a pile in place, and another one to four days to attach the turbine to the pile (Faber Maunsel and METOC PLC 2007). The entire operation, including the removal of the attendant vessels, is weather-dependant. In addition, strong currents can limit the use of jack-up rigs, both geographically and temporally. As a result, the use of monopiles as a means of seafloor attachment can at times be significantly restricted (Faber Maunsel and METOC PLC 2007). In contrast to monopiles, gravity foundations are relatively quick and more straightforward to install. Although they also require a site survey, gravity foundations generally require less site preparation than monopiles. Typically constructed of cement and aggregate or steel, they are heavy and bulky and can measure up to 20 x 40 m in rectangular or oblong cross section (Danish Wind Industry Association, 2008; Faber Maunsel and METOC PLC 2007). Their aspect ratio 3-54 January 31, 2008

55 depends on the specific tidal-energy device to which they are to be coupled (Faber Maunsel and METOC PLC 2007). Following site survey and preparation, the foundations and the attached devices are made buoyant and floated between two tugs out to the site, which is typically marked by buoys and/or sonic instruments (Faber Maunsel and METOC PLC 2007). Once on location they are lowered to the seafloor. The whole process can be accomplished in less than two days from start to finish, given favorable weather (Faber Maunsel and METOC PLC 2007). Given these advantages, the District currently envisions using a gravity foundation for a pilot installation Directional Drilling Horizontal directional drilling (HDD), otherwise referred to as directional boring, is a maneuverable trenchless method of installing underground pipes, conduits and cables in a shallow arc along a defined path by using surface-launched drilling equipment (nodigconstruction.com 2008). Directional boring is used when trenching or excavation is not practical and when environmental issues are of concern. Directional boring minimizes environmental disruption by impacting only a small portion of seabed surface area. It is suitable for a variety of soil conditions. Installation lengths up to 2,000 m (6,500 feet) have been completed, and diameters up to 1,200 mm (48 inches) have been installed in shorter runs (nodigconstruction.com 2008). Pipes can be composed of a variety materials that may include PVC, polyethylene, ductile iron, and steel as long as the pipes can be pulled through the drilled hole. Location and guidance of the drilling is a very important part of the drilling operation as the drilling head is under the ground while drilling and in most cases is not visible from the ground surface. If a drilling operation is not appropriately controlled or guided it can lead to unnecessary damage. Significant engineering and planning paired with the appropriate equipment ensures accurate execution. The District envisions using horizontal directional drilling to minimize any potential envirnomental effects of a pilot installation January 31, 2008

56 Underwater Power Cable TISEC Device Each TISEC device houses a step-up transformer to increase the voltage from generator voltage to a suitable array-interconnection voltage. The choice of the voltage level of this energycollector system is driven by the grid interconnection requirements and the array electrical interconnection design, but is typically below 36 kv. For the pilot-scale unit, an interconnection voltage level of 12 kv may be appropriate. This will allow the device interconnection on the distribution level and also will reduce some of the subsea electrical engineering challenges. For commercial-scale arrays, voltage levels of 36 kv are used. This allows the interconnection of an array with a rated capacity of up to about 50 MW on a single cable. A fiber core is used to establish reliable communication between the devices and a shore-based supervisory system. Remote diagnostic and device management features are important from an O&M standpoint as they allow operators and maintenance staff to pin-point specific issues or failures on each unit, reducing the physical intervention requirements on the device and optimizing operational activities Subsea Cabling Umbilical cables to connect turbines to shore are being used in the offshore oil and gas industry. To make these cables suitable for in-ocean use, they are equipped with water-tight insulation and additional armor, which protects the cables from the harsh ocean environment and the high stress levels experienced during the cable-laying operation. Submersible power cables are vulnerable to damage and need to be buried into soft sediments on the ocean floor. While subsea cables traditionally have been oil-insulated, recent offshore wind projects in Europe showed that environmental risks prohibit the use of such cables in the sensitive coastal environment. XLPE insulations have proven to be an excellent alternative, having no such potential hazards associated with their operation. Figure 3-52 shows the cross-sections of armored XLPEinsulated submersible cables January 31, 2008

57 Figure Armored submarine cables (Source: EPRI 2007) For this project, three-phase cables with double armor and a fiber core would likely be used. The fiber core allows data transmission between the units and an operator station on shore. In order to protect the cable properly from damage, such as from an anchor of a fishing boat, the cable is buried into soft sediments along a predetermined route. There are different technologies available to bury the cable along the cable route; all of them require the creation of a trench in which the cable can be laid. To protect the cable, this channel is then back-filled with rocks. Various trenching technologies exist, such as the use of a plough in soft sediments, the use of a subsea rock-saw in rock (if going through hard rock), or the use of water jets. All of these cablelaying operations can be carried out from a derrick barge that is properly outfitted for the particular job. The best-suited technology will depend largely on the outcome of detailed geophysical assessments along the cable route Cable Landing An important part of bringing power back to shore is the cable landing. Horizontal directional drilling is the method with the least impact on the environment and shoreline aesthetics, and the District envisions assessing feasibility of directional drilling for any pilot installation Project Facilities for a Pilot Installation The District envisions a phased approach for development of tidal projects in Puget Sound. This will involve first a pilot project in Northern Admiralty Inlet, potentially to be followed by 3-57 January 31, 2008

58 additional installations if environmental and economic feasibility is demonstrated by the pilot installation. The footprint of the pilot project is expected to be small, consisting of one to five devices with a capacity of less than 5 MW. Grid connection will likely be to either Whidbey Island or Port Townsend. The blue rectangle drawn on the Admiralty Head nautical chart (Figure 3-53) indicates the likely area of high power density and, therefore, the general area for locating the initial pilot demonstration and the future commercial scale plant. Water depths are shown in fathoms (1 fathom = 6 feet). The precise location for installation of the pilot project turbines will be determined based on further investigation by the District and consultation with federal and state agencies, Indian tribes, local governments, and other stakeholders. Figure Admiralty Head nautical chart (Polagye et al. 2007) The area identified for the pilot project is about 2 km wide by 2.5 km long. The marine-based structures in the pilot project include one to five TISEC devices rated at 0.3 to 1 MW each, and associated foundations and one or more subsea transmission cable(s). Land-based structures may include an overhead transmission line to an existing substation, or potentially the construction of a new substation January 31, 2008

59 Shore Station and Grid Interconnection Traditional overland transmission is proposed to transmit power from the shoreline to a suitable grid interconnection point. Grid interconnection requirements are driven by local utility requirements. Breaker circuits will be installed to protect the grid infrastructure from system faults. VAR compensation voltage step-up and other measures might be introduced, depending on particular local requirements. The two grid interconnection options that appear to be suitable for a pilot-sized plant as well as a commercial-sized plant are located on the opposite ends of the channel in Port Townsend and at the ferry terminal close to Admiralty Head. These are shown in Figure Figure Grid interconnection options suitable for both a pilot and a commercial plant (Google Earth 2007) The first option consists of installing a subsea cable from the pilot turbine deployment site to the ferry terminal and interconnecting the pilot plant at the ferry terminal at a distribution-voltage level. For a commercial-scale installation, the same subsea transmission route and cable landing could be used. However, a new 115-kV transmission line would need to be built from the ferry terminal to the nearest existing 115-kV transmission line a few miles inland. It may also require 3-59 January 31, 2008

60 a new substation located near the ferry terminal. Figure 3-55 shows a possible route for a new 115-kV line to the nearest transmission line (in red) and the directionally drilled portion, allowing the landing of the subsea cables to shore (in yellow). Figure Possible overland transmission route at Admiralty Head (Google Earth 2007) The second option is to interconnect at the Port Townsend substation, which is located about 500 m from the water. Figure 3-56 shows the location of the substation and the potential cable route. The red line shows the overland portion and the yellow line shows the directionally drilled portion. The power could be brought to the substation at 36 kv with a buried cable and stepped up to 115 kv there to interconnect with the transmission line January 31, 2008

61 Figure Potential Port Townsend cable landing and interconnection with substation (Google Earth 2007) The following table summarizes the relevant distances associated with these two main grid interconnection options. Table 3-8. Pilot 12 kv grid interconnection distances (Polagye et al. 2007) Port Townsend Admiralty Head Overland Transmission Distance 500m 500m Directional Drilling Length 500m 1,000m Subsea trench distance (incl. 20 percent cont.) 7,200m 0m 3 Subsea cable length 8,200m 1,200m Energy Projection The proposed pilot plant is expected to have a rated power of 1 to 3 MW and an average power output of about 300 kw to 1 MW. This is a very small fraction of the total kinetic power available in the tidal current stream at Admiralty Inlet. 3 For an interconnection near Admiralty Head, the cable could be brought directly to the deployment area using directional drilling only, eliminating any further subsea trenching January 31, 2008