California Creek Hydroelectric Project Pre-feasibility Study

Transcription

1 California Creek Hydroelectric Project Pre-feasibility Study Girdwood, Alaska June 2007 Prepared for the Municipality of Anchorage Heritage Land Bank Brian Yanity

2 1a. Summary A. Description A small hydroelectric plant, with a generation capacity of about 125 kilowatts (kw), appears to be economically and environmentally feasible on California Creek in Girdwood. A power plant of this size would be enough to provide electric power to about forty homes along lower Crow Creek Road. The plant s water intake would be just below the boundary of Chugach State Park, and the penstock (pipe that carries the water from the intake to the powerhouse) would be buried along either side of California Creek for a total distance of 1/3 mile (600 m). The penstock will terminate downhill at a small powerhouse a about ¼ mile (400 m) upstream from Crow Creek Road, with a Pelton water turbine driving an alternating current (AC) generator. B. Conclusions The California Creek site has a potential capacity of 125 kw, with an average annual energy of about 750,000 kilowatt-hours (kwh). Installation cost is estimated to range between $600,000 and $800,000, with the cost of energy produced ranging between 6 and 8 cents/kwh. Permits required include at least a stream discharge and water rights permit, and the cost to acquire them could be $100,000 or more. The electricity demand of the planned residential development near the project site would be several times greater than what California Creek will be able to produce. For the California Creek hydropower site, a high head (vertical drop) Pelton turbine system is preferred. The hydroelectric plant would be designed and operated as a run-of-river facility, as there is no environmentally acceptable way of constructing a water-storage dam and reservoir in California Creek Valley. There would be a small additional cost to local homeowners using California Creek hydroelectric power in addition to that used from the Chugach Electric Association (CEA) power grid. The economic attractiveness of local hydropower is likely to increase in the years ahead along with the cost of CEA power. It is uncertain whether or not CEA would accept electric power generated by a hydroelectric plant on California Creek into the utility s distribution grid. However, the power could be used as a local source supplemental to the power grid without CEA buying any of the power, as long as local residents arrange to purchase the power independently. C. Recommendations The Heritage Land Bank should proceed with a full hydroelectric feasibility study of California Creek, involving preliminary engineering design and field studies of the site s hydrology, environmental/ecologic, and geotechnical issues. Combine a California Creek hydroelectric project with ongoing studies being conducted for the Heritage Land Bank s residential development. 2

3 1b. Key Data General data: Installed Capacity 125 kw Number of Units 1 Type of Turbine Pelton Average Annual Energy 750,000 kwh Design Flow 0.20 m 3 /sec Gross Head 120 m Design (Net) Head 110 m Penstock Length 600 m Penstock Diameter 0.35 m Diversion Structure Height 2 m Economic data: Annual grid power displaced: 750,000 kwh Project cost (hydro plant and electrical distribution): $600,000 to $800,000 Annual project cost (20-year financing period) $45,000 to $60,000 Expected cost per kwh of Electricity Generated: 6 cents/kwh to 8 cents/kwh Figure 1: Map of two possible alternative layouts for a California Creek hydroelectric plant 3

4 1c. Introduction The California Creek hydroelectric project area would be located in the western uplands of the land parcel owned by the Municipality of Anchorage (MOA), which is designated by the Girdwood Area Plan as open-space. Presumably, the vast majority of this project area will remain publicly owned. The hydroelectric facility can be designed to be largely invisible to passers-by. Buried electrical cable and penstock piping is slightly more expensive than above-ground installation, but it is out of sight. No significant ecological impacts on fish and wildlife are expected, although a full environmental study needs to be carried out before site construction is approved. Figure 2: Location of California Creek hydroelectric project in the Crow Creek Road area (map image taken from Crow Creek Neighborhood Land Use Plan study by Agnew::Beck Consulting (2006). ) 4

5 Figure 3: Typical layout for a small-scale, run-of-river hydroelectric plant Examples of similar-sized hydroelectric projects in Alaska: Power Plant Location Owner Installed Capacity Lutak near Haines Alaska Power and Telephone 250 kw Ouzinkie near Kodiak City of Ouzinkie 125 San Juan Lake Evans Island San Juan Fishing and Packing Co. 105 McRoberts Creek near Palmer Polarconsult 100 Armstrong Keta Port Armstrong Armstrong Keta, Inc. 80 Burnett Inlet Hatchery Etolin Island Southern Southeast Regional Aquaculture Assn. 80 Dry Spruce Bay Kodiak Island Wards Cove Packing Co. 75 College Sitka Sheldon Jackson College Energy Demand and Future Demand Trends Power users have a demand that varies throughout the year. For Girdwood, peak demand is in winter. The electric power generated by California Creek would mostly be used by residential units, and perhaps a few small commercial buildings. The proposed hydroelectric plant will be right next to the planned Heritage Land Bank (HLB) residential development areas of North Fan and South Fan, as part of a larger plan for the Crow Creek Road area. According to the 2005 report on HLB s 981 acres, 1000 residential units are planned, between 60 and 75% of which will be occupied year-round. These planned residential units will consist of 650 single-family residences, 270 multi-family units, and 80 additional units as part of a later development reserve. A distribution grid intertie with Chugach Electric Association (CEA) is planned as part of the new residential development on HLB land, and any power demand forecast should be done in conjunction with CEA. Assuming each residential unit uses an average of 1 kw of power continuously, 600 units would require 600 kw of power. This amount of power is several times what a hydroelectric plant on California Creek would be capable of producing. 5

6 3. Water Demand During the highest-demand months of winter, all of the flow may be directed into the hydro plant intake if necessary. Downstream water temperature and silt effects (described in environmental concerns section below) of this total stream diversion need to be studied. The Anchorage Water and Wastewater Utility (AWWU) is considering expanding water and sewer service to the lower Crow Creek Road area. No water for this purpose would need to be diverted from California Creek because AWWU s existing Glacier Valley well system is expected to be sufficient for future needs. In sum, it is unlikely that water from the project area of California Creek would be used for residential water supply or sewage treatment. 4. Energy Supply Options (Alternatives to Hydropower) Utilization of local Chugach Electric Association distribution line: Use of planned and existing distribution lines owned by Chugach Electric Association (CEA) is the base case scenario or no-action alternative. Effective April 1, 2007, CEA s residential electricity rates were 12.7 cents/kwh, and are expected to increase in the years ahead with Cook Inlet natural gas prices. In the early 1980s, a small hydroelectric project was proposed for Bear Creek near Hope, on the south shore of Turnagain Arm. Like Girdwood, the small community of Hope is located on the CEA power grid. The proposed 150 kw plant was not recommended by a U.S. Army Corps of Engineers study because of the site s inability to produce dependable power year-round, and the community chose to stay with CEA grid power. However, the winter flow of California Creek is more favorable compared to that of Bear Creek Onsite electrical generation powered by diesel or natural gas: Even with a small hydroelectric plant on California Creek, residents of the area may want a backup generator on site in the event of a grid outage. While a diesel-powered electric generation plant is much less expensive to install than a hydroelectric plant of equal capacity, the bulk of its energy cost is fuel prices. A major drawback to diesel generators located in a residential area is localized air pollution. Another possibility is a micro-turbine power plant or cogeneration (heat and power combined) facility fired by natural gas. Although more expensive than a diesel generation system, a gas cogeneration system is more energy efficient and emits less air pollution. Natural gas service in Girdwood is provided by the ENSTAR Natural Gas Co., with a gas pipeline connecting to Anchorage. 5. Hydropower Potential Assuming an overall power plant efficiency of 53%, the California Creek site could have an installed capacity of 125 kw. This figure is calculated assuming that the available gross head (vertical drop) of the site is about 120 m, though with a net head (see below) of 110 m. The power plant s design flow is assumed to be 0.20 m 3 (200 liters) per second, or about 7 cubic feet per second. This estimated design flow is based on streamflow measurements conducted in November and December 2004 at a site just upstream of where Crow Creek Road crosses California Creek on a bridge. The town of Girdwood averages about 80 inches (200 cm) of annual precipitation, the majority of which is in the form of snowfall. In the California Creek watershed, melt water from two glaciers is the initial source of the stream, but less of a contributor than snowmelt, rainfall, and groundwater. Future trends of climate change could very likely increase rainfall during winter, and thus boost stream flow during the time of peak demand. 6

7 Figure 4: View of the Northwest side of upper California Creek Valley Figure 5: View of the Northeast side of upper California Creek Valley. 7

8 Figure 6: View of lower California Creek Valley, facing east, with Mount Alyeska behind. The amount of power which can be generated varies greatly during different times of the year. Based on observations and hydrology studies of similar streams in the Chugach region, California Creek s lowest flow period lasts about two months, from March into mid-april. During this period, the hydroelectric plant will only be able to produce a fraction of its installed capacity, or may have to be shut down completely to avoid ice problems during low flow. Power from the CEA grid would then have to make up for the drop in hydropower output. Plant factor: Matching of supply and demand Because a plant on California Creek would be designed for run-of-river operation, the stream s power production potential is opposite of demand curve. This is because the time of year when there is peak energy demand, winter, corresponds to relatively low flow. There are two important factors for the output of an electric power plant: Plant factor = (energy used)/(energy available) Load factor = (average load/peak load) The hydro plant design should aim for the highest possible plant factor (at least 0.6) for highest return on capital invested, and a lower unit cost of energy. The load factor for the California Creek site should be high, because the electricity demand of the planned residential area will far outstrip the hydroelectric plant s maximum capacity. The most significant operating constraint on hydropower production is the March-April period of lowest streamflow, because the forebay and intake must have a minimum head to operate. Minimum flow requirements may also be specified for California Creek, depending upon ecological and visual impacts. Also, yearly inspection outages each summer are common for Alaska hydroelectric plants, for this is when power demand is lowest. 8

9 6. Hydroelectric Plant Design a. Civil Works Prediction of flood levels is important for design of the power plant civil works, because the ultimate test of a hydroelectric plant s durability is during times of exceptionally high stream flow. In addition, a geotechnical/geology site study would be required for a comprehensive feasibility study, as well as recommendations for protection from natural hazards (rock fall, flooding, avalanches). Figure 7: Possible intake area on California Creek, looking upstream. Figure 8: Possible intake area on California Creek, looking downstream. 9

10 Weir: A weir is small and visually unobtrusive dam-like structure used to raise the water level and ensure the intake is deep enough for design flow. For the California Creek site, a weir would have a height about 6 feet (2 m). At least part of the weir structure could be made from natural rock elements found in the streambed. Forebay: A forebay is a silt basin that slows down the flow speed of the water entering the intake. Such a silt basin is needed for California Creek, a stream with a high bedload of glacial and other eroded sediment. Much of this water-bourn sediment is composed of hard abrasive materials, which can cause expensive damage to the turbine. Also, enough sediment may cause blockage of the intake. The finest type of stream sediment, glacial flour, can easily pass through the silt basin and be carried through the turbine. However, glacial flour generally causes less damage than coarser particles of stream sediment. A sluice-type spillway, directed downstream back into California Creek, can be used to periodically clean out the silt basin and handle overflow conditions. Intake: The hydroelectric plant must extract water from California Creek in a reliable and controllable way. The location of the intake structure (including the weir and forebay) would be close to the boundary of Municipality of Anchorage land and the Chugach State Park, or as high up on the valley slope as possible without entering the park. A typical intake structure consists of a trash rack made from metal bars. Penstock: The penstock will consist of a buried pipe, about 600 m (2000 feet) in length, which carries water downhill from the intake to the powerhouse. The penstock pipe to carry the design flow of 0.20 m 3 /sec would have an inner-diameter of 14 (or 0.35 m). The penstock outer-diameter, or pipe wall thickness, needs to increase further downhill, in order handle increasing water pressure. Material choices for the penstock pipe include high-density polyethylene (HDPE) plastic for low pressures, and steel for higher pressure. At 120 m of gross head (vertical drop), assuming a head loss of 10 m due to friction, the net head would be 110 m. As part of a complete feasibility study, much more detailed head loss calculations for the two different penstock alternative layouts (west or east slope) for California Creek. The route of the buried penstock could easily serve as a hiking trail. The plant could even serve as a tourist attraction with an interpretive sign explaining the project features to recreational users of the California Creek Valley. Figure 9: Penstock under construction for 100 kw McRoberts Creek hydroelectric plant, near Palmer (photo courtesy of Polarconsult Alaska, Inc.) 10

11 Figure 10: Typical upper penstock terrain along the ridgeline just south of California Creek. Tailrace: The tailrace conduit carries water out of the powerhouse and back into California Creek, and needs to be oriented downstream to prevent backwash of floodwater, debris, and bed load from reaching the powerhouse. b. Powerhouse For a run-of-river hydroelectric plant of this size, a 12 x 18 (4m x 6m) concrete building would serve as the powerhouse. The location of the powerhouse would be close to the uphill edges of the North Fan and South Fan areas of planned residential development, and needs to be above flood stage along the streambed. Figure 11: Small concrete powerhouse structure for 100 kw McRoberts Creek hydroelectric plant, near Palmer (photo courtesy of Polarconsult Alaska, Inc.) 11

12 Figure 12: Possible location for powerhouse along California Creek Turbine: A single 125-kW Pelton turbine is the most practical type for the California Creek site, which has a low amount of flow relative to its net head. Figure 13: Pelton turbine unit (10 MW size) installed at Terror Lake hydroelectric plant, Kodiak 12

13 Generator: Power generation on the scale of 100 kw and above is generally three-phase, 60-Hz alternating current (ac) synchronous generator. Connected to the generator inside the powerhouse will be a load controller, and additional protective and control equipment. An asynchronous (induction) generator could also be used, which is generally less expensive than a synchronous generator of equal capacity. An induction generator is more easily synchronized with a local distribution grid, though must be self-excited (with capacitors) during a grid outage. Figure 14: Turbine-generator set for 100-kW McRoberts Creek hydroelectric plant, near Palmer, (photo courtesy of Polarconsult Alaska, Inc.) c. Power Distribution Single-phase power is generally the rule for supplying electricity to residences, and the conversion of three-phase power from the generator into one-phase for distribution is a simple process. However, three-phase power requires less copper in a transmission line to carry the same amount of power, and larger electrical loads such as motors (rated over 5 kw) are usually only three-phase machines. In a full feasibility study, the connection to Chugach Electric Association (CEA) s distribution line along lower Crow Creek Road needs to be carefully examined. There is no precedent for CEA buying power from a small, independent hydroelectric plant connected to its distribution system. Important issues of electrical safety and operational control would need to be worked out as part of a power-purchase agreement. d. Other Infrastructure At present, only hiking trails exist along either possible penstock route, and the closest road is Crow Creek Road. The trail on either side of the creek would have to be expanded so that heavy equipment can be brought up to the intake area. 13

14 7. Cold Climate Considerations Intake ice problems: Ice is expected to be a minor problem at the intake compared to glacial silt and rocks, though still needs to be accounted for in the design of the intake structure. Frazil ice is likely to occur in California Creek during the winter. This type of ice consists of small particles which form in turbulent or open water during exceptionally cold temperatures, particularly winter nights. Frazil ice can stick to an intake trashrack, potentially blocking all flow into the power plant. Electricallyheated intake trashrack bars help prevent ice from sticking take up to 10 kw of power consumption for an installation size of California Creek. During winter ice conditions, this heating could result in a net power loss of 10 to 20%, though this only would be turned on during frazil ice supercooled conditions. Frazil and other types of ice may have to mechanically cleared from the intake area during cold weather. Low winter flow: Power plant generation capacity will be defined for a maximum output during the months of November, December, January, and February. Winter flow measurements are the most important for design of the hydroelectric plant, for this is period when the plant s design flow must be optimized. Future climate change is expected to increase winter flow for streams in the Chugach Range, although it is uncertain by how much. 8. Environmental Concerns The most significant environmental benefit of a local hydroelectric plant is that there is no air pollution, in contrast to a diesel or natural gas-powered generator of equal size. Existing environmental conditions: The project site is almost entirely covered by open, mature needleleaf forest. Part of the site near Crow Creek Road includes a small amount of mature broadleaf forest. Construction of the hydroelectric plant would require the clearing of some trees along the penstock route. Visual impacts: During times of peak energy demand (December, January, February) the stream could be dewatered along the reach of the power plant. However, during the peak recreation season of summer, only a small fraction of stream s flow will be diverted into the power plant. The power plant s intake structure and powerhouse are small enough to be easily shield by trees or shrubbery from view of hikers on nearby trails. The penstock route, however, will be buried and cold also serve as a public trail. Fish requirements: The Alaska Department of Fish and Game (ADF&G) has tagged California Creek as State Anadromous Fish Stream No According to ADF&G studies, adult pink, king and coho salmon are found in the upper stretch of California Creek (the project area) during the summer and early fall. Spawning and rearing of anadromous fish have not been observed in the project area, though do occur about one mile downstream. The time of year when fish are present in California Creek also corresponds to a time of relatively high flow, so only a small proportion of the total stream flow would need to be taken away from fish habitat along the length of the project. 14

15 Wildlife habitat: Black and brown bears, moose, lynx and a variety of birds and small mammals can be found in the California Creek Valley. However, most of the valley is in Chugach State Park land, and would be unaffected by a hydroelectric installation. However, any possible construction impacts need to be carefully studied, as heavy equipment would be brought up along the penstock route and the intake area. 9. Operations and Maintenance At the outset, it would have to be decided who would own the hydroelectric plant. The owningentity could be the Municipality of Anchorage, a cooperative organization of local homeowners, or some other type of organization or business. And although the power plant would be remotely operated, a special management committee should be formed to determine the operations and maintenance (O&M) management structure, capabilities and costs. This O&M committee must also prepare operation schedules, the advance ordering of spare parts, and maintenance procedures. Also necessary is the preparation of training procedures and detailed O&M manuals and adequate documentation from equipment manufacturers. O&M must be considered during the design and contracting phase, since the typical lifespan of a hydroelectric plant is 50 years or more. In order to repay its large capital cost of installation, a hydro plant needs to run efficiently and continuously throughout its design life. To this end, O&M training must begin before the plant goes online. The project team must also assess the need for institution building to support the project over the long term. Below are listed some power plant operational issues that need to be worked out: How will the project be financed, and what will be the electric accounting (billing) structure? Who collects revenues from power users? Who keeps accounts and visits the bank? Who should perform maintenance work? If the plant breaks down due to extreme weather, an accident, or an equipment failure, who do you call in order to fix it? What would be in an emergency management plan? 10. Economic Analysis As described above, the economic difference with fossil fuel-powered generation is that hydroelectric plants have higher capital costs of construction, but operate with no fuel costs. Based on an assumed installation cost ranging from $4800 to $6400 per kw, a 125-kW hydroelectric plant on California Creek would have an estimated construction cost of $600,000 to $800,000. Out of this total amount, the combined cost of 2000 feet of penstock pipe (both HDPE or steel) and intake structure could be up to $300,000, and the cost of turbine-generator set between $200,000 to $300,000. Sources of financing for a small hydroelectric project worth investigating include grants and subsidized loans from the state or federal government. The annual power generated by the 125-kW plant, assuming a plant factor of 0.68, would be 750,000 kwh. The annual cost of the power plant, including O&M costs and assuming a 20- year financing period (based on financial of similar-sized hydroelectric plants) is estimated to be between $45,000 and $60,000. Therefore, the expected cost per kwh of electricity generated would range between 6 and 8 cents/kwh. The projected additional cost to local homeowners using California Creek hydroelectric power (in addition to that used from the CEA power grid) appears to be small. These cost estimates need to be investigated in greater detail as part of a comprehensive feasibility study. 15

16 11. Required Permits The estimated costs for acquiring the permits listed below are about $100,000, but could be higher depending on the amount of field studies which need to be conducted. Contact information is listed below each government/regulatory agency that needs to be consulted. Municipality of Anchorage Owner of all land in the project area is the municipal government s Heritage Land Bank. Arrangements involving zoning and rights-of-way would be worked out with other municipal departments. Girdwood Board of Supervisors ( ) State of Alaska Department of Environmental Conservation Division of Water Michelle Bonnet, Section Manager 410 Willoughby Ave., Suite 303 Juneau, AK Phone: Fax: Michelle_Bonnet@dec.state.ak.us Master Permit Application for stream discharge A Certificate of Reasonable Assurance (Water Quality Certification) 401 is required only if a federal permit is needed, such as a discharge permit from the U.S. Army Corps of Engineers (see below). The project may require a consistency review for the Alaska Coastal Zone Management Plan because the greater watershed of Glacier Valley, including the waters of California Creek, drains directly into Turnagain Arm. Department of Natural Resources Division of Mining, Land & Water Water Resources Section 550 West 7th Avenue, Suite 1020 Anchorage, AK Phone: Fax: The Dept. of Natural Resources would likely require a Water Rights Permit on California Creek, and also must approve any weir and civil works construction. 16

17 Department of Fish and Game Division of Wildlife Conservation 333 Raspberry Road Anchorage, AK Phone: (907) California Creek is listed by the Dept. of Fish and Game as State Anadromous Fish Stream No Habitat protection could require specified minimum stream flows in California Creek during certain parts of the year, as determined by qualified biologists. Department of Transportation and Public Facilities Central Region 4111 Aviation Avenue Anchorage, AK Gordon C. Keith, P.E. Central Region Director Phone: (907) Planned road improvements along lower Crow Creek Road may affect the California Creek project area. Regulatory Commission of Alaska 701 West Eighth Avenue, Suite 300 Anchorage, AK Phone: (907) The RCA webpage on Water Power Development: Federal Jurisdiction It is unlikely that a small hydroelectric project on California Creek would fall under the jurisdiction of the United States government. The closest lands of the Chugach National Forest to the California Creek hydroelectric site are about one mile upstream. Federal Energy Regulatory Commission (FERC): If necessary, the project would need to receive a FERC confirmation of no jurisdiction for a hydroelectric plant of under 5000 kw of capacity that is not on federal land, or lands of the United States (Section 32 of the Federal Power Act). U.S. Army Corps of Engineers (USACE): The USACE-Alaska District would need to be consulted regarding Section 404 of the Clean Water Act, which concerns the discharge of fill or other materials in wetlands. The closest wetlands to the California Creek hydroelectric project site are about a half mile downstream. Permitting webpage of USACE-Alaska District: 17

18 14. References Agnew::Beck Consulting (2006). Crow Creek Neighborhood Land Use Plan, Prepared for Heritage Land Bank Harvey, Adam, A. Brown, P. Hettiarachi and A. Inversin (1993). Micro-Hydro Design Manual: A guide to small-scale water power schemes. Intermediate Technology Publications, London. Inversin, Allen (1986). Micro-Hydropower Sourcebook: A practical guide to design and implementation in developing countries. NRECA International Foundation, Arlington, VA. U.S. Army Corps of Engineers- Alaska District (1984). Hydropower Potential of Bear Creek for Hope, Alaska. 18