Native Village of Atka: Atka IRA Council - 1995 Project
|Tribe/Awardee:||Atka, Native Village of/Atka IRA Council|
|Project Title:||Hydropower Feasibility Study and Preliminary Facility Design|
|Type of Application:||Feasibility|
|DOE Grant Number:||DE-FG48-95R810574|
|Project Status:||Complete More|
This study was performed to determine the feasibility of a source of hydroelectric power for Atka, Alaska, which would be significantly more economical than the current diesel-generated electricity. The results of the analysis conclude that hydroelectric power can reduce the cost of power generation. This feasibility study discusses in detail the data and the analyses used to form this conclusion. Information derived from this work is summarized as follows:
Estimated cost for design, acquisition of permits, and construction is $765,747.
Present cost of generating power with the hydro plant for 30 years is $1,161,000.
Projected cost of continuing to generate power with diesels for the same period is $1,489,000.
Net capacity of the plant is approximately 271 kW.
Estimated average power generation for the hydro plant, based upon analysis, is 1,757,412 kWh per year.
Community power consumption, for the analysis, is estimated at 260,144 kWh per year.
Using the hydro plant, average yearly savings are $17,713.
The recommended plant will consist of the following: small impoundment dam; 1,060 feet of high density polyethylene pipe (HDPE); 271 kW turbine and generator; powerhouse; 7.2/12.4 kV electrical cable connecting to the existing system. The plant can be constructed using primarily local labor. Basic characteristics of the recommended project are provided below:
|Installed Capacity:||271 kW|
|Type of Turbine:||Cross-flow|
|Hydro Average Annual Energy:||1,757,412 kWh|
|Atka's Energy Consumption:||260,144 kWh|
|Estimated Hydro Available Energy:||260,144 kWh|
|Design Flow:||36 cfs|
|Static Head:||116 feet|
|Penstock Inside Diameter:||28.2 inches|
|Penstock Length:||1,060 feet|
|Dam Height:||13 feet|
|Project Construction Cost:||$765,747|
|Average Savings per year:||$17,713|
|Total Savings, present worth:||$328,000|
|Total Excess Energy, present worth:||$4,388,000|
This project analyzes the feasibility of hydroelectric power production from Chuniisax Creek. The project location is approximately 0.6 mile southwest of Atka. The community has a population of approximately 90 people, and is located 1,100 miles southwest of Anchorage. Previous reports on Chuniisax Creek have been compiled by Nortec, the Alaska Energy Authority, the Department of Natural Resources, and Polarconsult Alaska, Inc. The Nortec report is a comprehensive analysis of potential for hydropower from Chuniisax Creek. Nortec identified this creek as having the best potential for hydroelectric development. This location is used in the analysis for this report.
The intake is at an elevation of about 174 feet above sea level. The creek will be dammed and the water raised 10 feet. Water will flow from the dam to the powerhouse through 1,060 feet of 30-inch HDPE pipe. The powerhouse is located at an elevation of about 68 feet. Access to the plant will be via a four-wheel drive trail. A 2,625-foot electrical transmission route will tie the plant to Atka's existing electrical system.
Goals and Objectives
The goal of this project is to assess the feasibility of hydroelectric power production from Chuniisax Creek for use by the Native Village of Atka.
Project Actions and Resultant Data
Hydrology and Power
Streamflow measurements of Chuniisax Creek were performed for use in this study as well as for two previous studies. A summary of the information obtained and the analysis used in determining the streamflows are outlined in the following sections.
The following sources of streamflow data were obtained for Chuniisax Creek:
- Data collected by Nortec in 1983 for its 1984 report;
- Data collected by the Alaska Department of Natural Resources (DNR) and included in its Feb. 10, 1992, preliminary report;
- Data collected in 1995 by Polarconsult for presentation in this report.
Nortec performed a feasibility study for hydropower at Atka for the Alaska Power Authority. Stream-gauging consisted of installing a recorder and doing numerous in-stream measurements to develop a rating curve. The rating curve was used with the level measurements to develop a hydro-graph for the stream. Measured data extends from May 1983 through November 1983. Data is missing during the months of December 1982 through April 1983. Nortec estimated the streamflow for this period.
The DNR installed a level recorder in September 1989. It was removed two years later. Data is missing or invalid from Jan. 22, 1991, to June 10, 1991, due to a flood that washed away the pressure transducer. This data has a noticeable trend over time.
Currently, Polarconsult has a level recorder installed in the same location that was used by Nortec. The recorder was installed on May 25, 1995. Two in-stream flow measurements were taken: one on Nov. 15, 1995, and the other on Nov. 4, 1996. An average of these two values was used to linearly scale depth values from the recorder to obtain flow values.
Due to the short period during which streamflows were measured, it is possible that flows may differ substantially from the long-term average for the stream. Because records of precipitation over an 18-year period exist, the measured data can be compared with the precipitation record by converting rainfall to streamflow based on basin size. This will indicate whether the measured data needs to be adjusted.
The size of the basin has not been accurately determined. Nortec estimated the basin size to be 9 square miles. The Department of Natural Resources estimated the basin size to be 5 square miles. For this study, an average of 7 square miles is used.
Four sets of monthly average flows were developed using four different data sources:
- Flow based on rainfall
- Flow from Polarconsult stream gauging
- Flow from Nortec, 1983
- Data selected from DNR stream gauging
Given the amount of water that can flow through the penstock at a specified head (pressure differential due to the change in elevation of the confined water), one can calculate the maximum amount of power that can be produced. For this plant, the value is 337 kilowatts (kW). Due to the net efficiency of the turbine, generator, and transmission losses (80%), the maximum usable power available is 271 kW. Approximately 100% of the time there is more power available than Atka's maximum peak of 70 kW. This means that there will not be any need for supplementing the hydro plant's output with diesel power.
A 10-foot-high dam will store water in sufficient quantity to run the plant at 270 kW for an entire day without inflow. This means a community with twice Atka's power demand would not have to run diesels at any time. In addition, the added water makes it feasible to handle peaks created from starting motors at the fish-processing plant.
The reservoir will have a surface area of approximately 12.5 acres. Incorporated in this area will be an existing 6.3-acre lake. The total storage will be about 69 acre-feet. Additional storage can be added by deepening the channel between the lake and the creek to four feet throughout. Because the divide is at approximately the same height as the lake surface elevation, during normal flows it may be necessary to construct a dam of wooden sheet piles, about two feet in height, to prevent bypassing during flood-stage.
The hydro plant will produce energy in excess of the community's traditional power needs. This energy is wasted unless a use for it is found. No economic credit is given for use of excess energy. Even though it is difficult to quantify, its value should not be ignored when comparing alternate designs.
The equivalent amount of fuel that can be displaced by the excess hydropower will be dependent on water-flows and the ways in which the excess power is used by Atka. It is estimated that the equivalent of 176,149 gallons of oil would be available on average each year if all of the energy were used. A realistic assumption is that one-quarter of the energy can be readily put to useful purpose. The basis for this estimate is founded on previous work with district heating systems.
One way to use excess energy is to employ an inexpensive computer equipped with a load-management device that can determine, by changes in electrical frequency, when there is surplus energy. When surplus electricity is sensed, a relay is closed, sending the excess to an electric resistance load. Such a resistance load can be hot water heaters for the school, community center, or electric hot air or water heaters for buildings. These loads can be arranged to turn off and on, on a priority basis as programmed into the computer. The cost estimate includes load-management devices for using excess energy.
Water is forced into the intake by a small dam that raises the water 10 feet above the streambed. The increased water depth will create a small amount of storage that can be used during low-flow periods to supply extra energy during periods of increased demand. The reservoir will also provide a settling basin that will keep sand and rocks from entering the penstock. There are no trees on Atka, so a screen to filter out leaves and twigs is not required; however, there will be a trash rack to prevent large objects from damaging the turbine.
The dam is constructed from Douglas Fir timbers. The intake pipe, gate, and trash rack are located in the lower section of the dam. The dam is equipped with a spillway to discharge excess water. The spillway is designed for a flood of about 500 cfs. The maximum recorded flow for Chuniisax creek is 101 cfs.
A walkway that is capable of supporting a four-wheel drive vehicle will be constructed across the crest of the dam to provide access for maintenance of the dam and pipeline. The walkway will be protected by a locked gate to discourage unwarranted use.
HDPE pipe will be used for the penstock. It comes in 40-foot lengths and is joined by butt fusion. This pipe has the advantages of being flexible, having good flow characteristics, and being easy to install. It has the disadvantage of requiring a fusion machine to assemble it. The fusion machine required for this type of pipe is expensive. It rents for approximately $10,000 per month.
An alternative to renting the fusion machine is to rent and assemble the pipe at Dutch Harbor by having the pipe and fusion machine shipped there via Sea Land. The pipe can be assembled into three sections, each more than 330 feet. The pipe would be capped and launched into the harbor during the fusion process. A small boat would then tow it to Atka. This will save approximately $5,000.
The three lengths of pipe will be dragged up the hillside to their proper positions, joined mechanically using inner steel sleeves and then the exterior will be wrapped with fiberglass.
The powerhouse will contain the turbine, generator, load-governor, and switchgear. A pad-mounted transformer will be located outside the powerhouse. The powerhouse will be located so that the generator floor is above flood stage. The floor of the powerhouse will be concrete poured over a wood floor. The floor joists will rest on glulam beams that will span to column supports at the corners. The walls and roof will be wood framing, with T1-11 on the exterior and green board on the interior.
The turbine for this plant will be a cross-flow type. This turbine is highly efficient at varying power outputs and over a wide range of flows. The following pictures show the arrangement of the water-flow through the turbine and its main components.
The proposed generator will produce a minimum of 271 kW, at a 0.99 power factor. Electrically, it will be a three-phase 480-volt unit. It will have static excitation and will use a Basler (or equivalent) voltage regulator.
The generator for the turbine will be manufactured in the U.S. and will operate at 1,200 rpm. It will have ball bearings and the shaft will be connected to the turbine through a speed increaser. A speed increaser is a gear or belted transmission that increases the shaft rpm at the generator. This makes the generator less expensive and enables the turbine to be more efficient in matching the fixed rpm requirements of a generator.
The generator rpm must be controlled to produce 60 cycles. In earlier hydro plants, the speed of the turbine was controlled with a governor that varied the amount of water the machine received and, in turn, controlled the speed. There is another way to control the speed of the machine; it is to add or subtract electrical loads so the output remains at 60 cycles. A device called a "load governor" can now do this electronically. There are a number of load governors operating in Alaska, including Burnett Inlet on Alaska Aquaculture's project, Larsen Bay, Ouzinkie, Rainbow Creek, and others. An electronic load governor can be located anywhere on the three-phase electrical distribution system. It takes power in excess of that being used by the community and shunts it to resistance heaters. Resistance heaters can be hot water heaters, hvdronic-heating systems, and electric air heaters that are located wherever heat is required. Loads are prioritized by the load governor. For example, the governor can be programmed to supply excess electricity first to the school heating system, secondly to the school hot water, and then to the green house or the city hall.
In addition to the load governor, there will be an electronic-head level controller that governs the turbine-flow control gate based on the level of the water at the dam. It does this by reading the water pressure (depth), which in turn is converted to an electrical signal provided to a computer. The computer directs the operation of a hydraulic pump driving a cylinder that controls the flow of water to the turbine. Usually for a run-of-the-river plant, the turbine runs at the maximum electrical production commensurate with its capacity or the flow of water, which ever is less.
The switchgear will consist of several elements. One element will be a circuit breaker that will protect the plant if there is over-current. It will also have electronic equipment with relays to shut the plant off if there is over-or-under voltage or frequency. In addition, transducers can be provided, as they were at Larsen Bay, so it is possible to monitor the status of the plant from town or anywhere else. In a small plant such as this, the switchgear and the electronic controls for a load governor can be incorporated within a single enclosure, thereby saving space and costs.
Modern low-cost electronic equipment can be installed to monitor the operation of a small hydro plant. For example, there is an inexpensive device that, when connected to the telephone system, will call designated people if the temperature is too high or too low or if there is too much noise. This device also has contacts where a fire detector or other detection devices may be connected. One can also call and listen to the sound level at the plant. This is useful for periodic monitoring. The cost for this device is about $500 and is included in the cost estimate.
Equipment that facilitates monitoring but is not included in the cost estimate is a real-time monitoring device. Transducers can be installed in the switchgear that will enable the operator to electrically determine what is happening at the plant. This type of system was installed at Larsen Bay. It is possible to install a pair of the new video phones, which will provide an inexpensive way of looking at the powerhouse, intake, or other plant features. The picture is transmitted over the telephone lines. Since the operator will be living in town and the weather is not always conducive to inspecting the plant, these remote devices will reduce the number of field inspections. Considerable time and effort will be saved. After the operator gains experience handling the plant, fewer observations will be needed. For example, the operator might find from experience, that after a heavy rain the screens require cleaning. So, the operator will not bother investigating the screens on a daily basis if the rain has been moderate. This means that the amount of labor required to keep the plant in operation will decrease with time.
The diesel back-up in the existing plant can be started and synchronized either manually or automatically when a power deficiency occurs. Using a load governor simplifies manual startup for diesel back-up. Since the hydro plant is always producing all of the power possible (up to 271 kW), reading the power output gauges will provide the operator with the information to determine if there is sufficient water to produce the required (estimated) daily power. Early in the morning, given the traditional use patterns for the time of year, day of the week, and weather conditions (rain, snow, cold, cloud cover), a skilled operator will know if a diesel generator will have to be added during the day. There will be times, while the engine is operating, when rain rapidly increases the flow and the hydro begins to generate sufficient power so that the diesel is no longer needed. Unless this condition is observed or there are automatic controls to shut off the diesel, there will be an occasional waste of diesel fuel. This condition is more likely than is one where a diesel must be added due to an unforeseen, sudden reduction in flow. This is because flow reductions occur more gradually than flow increases. Therefore, automatic diesel controllers are not included in the cost estimate.
Different power line designs are possible. The most desirable one, considering aesthetics and potential damages, is buried cable. Buried cable is also the type of distribution used throughout Atka. An alternative design would be bare overhead wire. For this study, it was assumed that the transmission line would be a buried line.
An alternative intake for the hydro site is located about 1,000 feet further upstream above the last two falls. This intake location results in a project that has about 20% more head and will produce 20% more power. From appearances, it will have equivalent storage to the lower site. It is estimated the cost to build at this site is essentially that of the additional pipeline; the rest of the project will cost nearly the same. This dam site is better as it is carved through rock without overburden. If money is available (an estimated additional $100,000), this site should be considered as it uses all of the available resource.
Power Generation Costs
The value of hydropower is based on the cost to build the hydro plant versus the least expensive alternate means of providing the same service. Diesel generation is currently the only feasible alternative to hydro. Diesel-generation costs were obtained from State of Alaska, Department of Community and Regional Affairs' Power Cost Equalization Program (PCE).
Project costs comprise two major elements. One element is material costs. These costs, if based on good quantities, can be fairly accurate. The second element is labor cost. This is a variable cost and is more difficult to estimate accurately. For example, heavy rain might reduce productivity to 36% of productivity during dry conditions. However, if most work is done during the months of June, July, and August, and the weather is not unusually wet, productivity can be good.
The following describes how project cost was estimated:
All of the material costs shown in the cost estimate derive from actual quotes or published price information. Frequently, quoted prices can be improved when an order is placed. Substitute items can also reduce the cost. As a general rule, these quotations are rounded to higher values.
Quantities of materials are based on the design and construction materials shown in the drawings. Quantities have been rounded up, and additional material is included where warranted. For instance, a significant amount of extra wood is listed in the cost estimate because this item usually has some waste.
Equipment costs include purchasing the equipment that is new or slightly used. The only pieces of equipment that need to be rented are the fusion machine, vehicles for handling the pipe in Dutch Harbor, and a backhoe.
Freight costs are based on a single barge hauling in the majority of the material during one trip from Seattle. Costs are based on quotes from a barge operator. Rates ranged from $150 to $205 per ton/short ton. All rates have been set uniformly at $200 per ton/short ton for this analysis.
With the exception of the equipment and the piping, all material costs and their associated shipping cost incorporate a 20% contingency. This is somewhat conservative but given the brevity of the cost estimate it is appropriate.
Title 36 is enforced when a contractor or subcontractor performs work on public construction in Alaska. Title 36 requires that contractors be paid the prevailing wage in the locality. This prevailing wage is set by the Labor Department's Labor Standards and Safety Division. For Atka, the average wage plus the fringes under Title 36 will be more that $35 per hour. Project costs for labor would increase by $44,000. Additionally, a contractor's profit would further raise this by $81,000. Savings in administration and inspection would be replaced by increased engineering design and specification costs, as well as bid and contractor management costs.
Force account, or turnkey work, is the only practical and cost effective way to construct a project such as this. Wage rates for Title 36, Little Davis Bacon, are high enough to make the project uneconomical. Force account optimize the situation for local employment and avoids all of the added costs that contracting brings.
Generally, force account works well if it is well-managed. For the best interest of the project, the manager generally should not be from the community, as tough personnel decisions need to be made. It is better to be stern and bring the project in under budget returning money to the rate-payer or the workers with a bonus, than it is to compromise during the execution of the project. A good manager, with experience in force account, can strike the balance between sensitivity for local feelings and needs, and the absolute need to complete the project on or under budget.
The potential negative aspects of using force account are:
- Primary risk is from cost overruns during construction.
- A project such as this could be conceived as increasing stress within the community, because of the requirement to complete it on time and on budget. Further, if the community is divided on the project, there is always a possibility of increased political disagreements.
A considerable portion of production efficiency depends on the quality of management and the authority granted to the management to remove unproductive workers. Labor costs are based on an estimate of the time to do the work assuming a five-person crew and one supervisor. Wages are based on current private sector wages (non-Davis Bacon) and force account work in other communities. For wages, the following assumptions are made: two skilled laborers at $21/hr; three laborers at $17/hr; and one foreman at $30/hr. The average of these wages is $20.50. Fringes estimated as follows: workers compensation - 8.5%; Alaska unemployment - 3.1%; employer Social Security - 7.65%; Total - 19.25%. The average rate per hour calculated is $24.45. The lowest wage used in this analysis is $25.00 per hour. In some instances a higher wage is used where it is anticipated that specialized work is involved.
Diesel-generation costs used in this analysis are derived from existing information and from detailed information from similar-sized communities. The primary cost with diesel generation is the fuel. Other considerable costs include the operator's salary, parts and labor for maintenance, and lube oil costs.
Fuel is the single most expensive component in producing power with diesel-generating units. It is estimated that total-plant average yearly expenditures are approximately $59,380 (including generator replacement payments). Using a past fuel cost of $1.10 per gallon, $34,676 is estimated to purchase the 31,523 gallons consumed. This represents more than half of the yearly cost of operating the diesel-electric plant. For this reason, it is important to have an idea of what fuel prices will do in the future.
Recently, oil prices have dropped and leveled out to pre-1970 prices (adjusted for inflation). In the recent past, there was significant fluctuation (Gas Research Institute (GRI)) of the history of oil prices.
The Energy Information Administration's 1996 Annual Energy Outlook has one of the highest predictions for oil prices in the year 2025, with $25.43 per barrel of oil as compared with other organizations. The Gas Research Institute has one of the lowest predictions, with $16.17 per barrel of oil. For this analysis, an average price of $20.80 is used for the price of oil in 2025. Given the current price of around $18 a barrel this gives a growth rate of 0.5% per year. This value is used in the economic analysis.
Equipment and Labor Costs
Equipment and labor costs have been estimated from 1994 and 1995 PCE reports.
Parts and lube oil costs are assumed a direct function of the amount of power that the diesel generator produces. The cost for lube oil is assumed to be $0.0022I per kWh. Replacement parts are also assumed to be directly related to the power produced and are $0.02000 per kWh. Thus, the cost for equipment amounts to $0.022.
The cost for the plant operator amounts to $15,000 per year. The plant operator salary remains constant for increases in diesel production but is lowered to $1,000 per year when the hydro plant is added. Hydro maintenance salary is assumed to be $10,000 in addition to the plant operator salary so there is little change in plant operator salaries.
The cost of replacing the diesel generators is also included. They are assumed to be a part of the reported PCE operating cost and are estimated as follows. Replacements are scheduled every six years, when operating just the diesel plant. When using the hydro plant, replacement of the diesel generators is assumed to occur every 18 years. The cost for replacing the diesel generators is assumed to be $20,000. This cost is amortized over the replacement period and is included in the economics.
A hydro plant has high initial costs. Therefore, the hydro is more sensitive than other forms of generation to high interest rates. This analysis assumes that the hydro plant can be funded through a 30-year loan, with a basic discount rate of 3.5% above inflation.
All of the monetary values in this analysis have been adjusted to present value using the discount rate. This means that inflation is not taken into account. This gives clearer resolution of variations in the dollar-quantities as it shows all costs in current values without the distortion of inflation.
An explanation of some of the selected values follows:
Interest rates: A system was selected that does not use standard interest rates, which include assumed factors for inflation. Everything is reduced to the opportunity cost of interest, which traditionally has been approximately 3.5%. This results in costs that are in today's dollars throughout the analysis period. This achieves a more accurate understanding of project costs.
Power demand: A conservative figure is 1.5% growth. More growth favors the hydro over the diesel. Current energy-use growth rates are approximately 1% per year.
Other economic values for the project cannot be quantified. Some of these values are:
Money is retained within the community. When oil is purchased, most of the money leaves the community and goes to the transporters, refiners, producers, and resource owners. The labor associated with hydro will result in employment for people in the community.
People receive training in construction by doing the work. This training is valuable. It makes for salable skills and fosters independence.
Because less fossil fuels will be used, there is less strain on the environment.
Due to decreased handling of fossil fuels, there is less risk for environmental liability.
Fuel storage requirements are lower.
Because the hydro plant is located above and just below falls that prevent the passage of fish, it is anticipated that the construction of the plant will have little impact on the fish habitat.
Federal Energy Regulatory Commission (FERC)
Because this project is on a non-navigable stream and is located on private property, a FERC license will not be needed. A request for non-jurisdiction from FERC will be required.
Other Permits and Considerations
Permits will be required as follows:
A water-use permit will be required from the Alaska Department of Natural Resources (DNR). DNR will ask for comments by the Alaska State Department of Fish and Game (ADF&G) and the Department of Environmental Conservation (DEC) in the review of these permits. It is unlikely, but ADF&G may ask for special conditions such as minimum stream flows.
Alaska Coastal Zone Management Consistency Review Compliance.
DEC Clean Water Certification 401, which is done in conjunction with DNR's review. This permit is required only if a federal permit is needed. A typical federal permit, which will require a 401, is a 404 permit for action involving a wet land or fill in a stream. Without fill, a 404 permit will not be needed. Therefore, a 401 permit will not be required either.
A 404 permit will be required for stream excavation.
Results, Conclusions, Findings, and Recommendations
The analyses conclude that, economically speaking and under conservative assumptions, a hydro plant is superior to the current diesel-generation (benefit to cost ratio = 1.28).
A modest increase in fuel price, or a need for substantially more power in the community, would make the project significantly superior economically over current diesel-generation. Other advantages, which cannot be quantified or may be subjective, include:
An environmentally superior plant, as it will not discharge carbon dioxide, nitrogen oxides, and sulfur oxides into the atmosphere; Less dependence and concern with fuel cost and handling.
Less dependence on outside expertise (maintenance of engines). A plant design which, in addition to reducing costs, fits into the terrain and requires the very minimum of earthwork.
A generation facility located outside the community, which will considerably reduce air and noise pollution in Atka.
There are a number of advantages that can accrue to the people of Atka if a hydro plant is constructed. To attain these advantages, the following steps are recommended:
Continue recording the streamflow using a level recorder combined with in-stream flow gauging.
If the people believe continuing the project is favorable, then the following steps should be taken:
Obtain a grant from the Legislature to design and construct a portion of the plant. King Cove has a grant that funds a large portion of their hydro plant's cost. The Railbelt has been granted money for Bradley Lake. Tazimina received $3.4 million in state grants and $5 million in federal grants. The four-dam pool has received great amounts of largess from the state. It would seem equitable for Atka to receive equal consideration. Governor Knowles likes to keep money within Alaska and philosophically supports the concept of the plant.
Money can be borrowed from the revolving power loan fund at low interest or from the Alaska Industrial Development and Export Authority, the Farmers Home Administration, the Municipal Bond Bank, or other sources.
Consider doing the work only with force account. Be very careful with management of the project. Non-innovative construction people, who are accustomed to high-cost state government projects, can ruin this type of small project. Paraphrasing Ernst Schumacher, think small. Give the project manager absolute authority to fire people who are not performing.
Plan and execute methods of taking advantage of excess energy that becomes available to reduce costs, decrease pollution, and improve the quality of life in the community.
For additional information, contact the project contact.
Atka IRA Council
P.O. Box 47030
Atka, AK 99547
Telephone: (907) 272-5969