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HomeMy WebLinkAboutRussell Creek Hydropower Preliminary Feasibility Study - Jan 2018RUSSELL CREEK HYDROPOWER PRELIMINARY FEASIBILITY STUDY COLD BAY, ALASKA 1/2/2018 Douglas Ott, P.E. INTRODUCTION The City of Cold Bay, Alaska with its 10,000 foot runway serves as a transportation hub for neighboring remote communities located nearby at the western tip of the Alaska Peninsula. Additionally, it serves as a base community for governmental employees of the US Fish and Wildlife Service Wildlife Refuges, US Weather Service, Alaska Department of Fish and Game, etc. This study looks at the preliminary feasibility of developing a hydroelectric project on nearby Russell Creek as an alternative source to the existing diesel generation to supply electricity for Cold Bay. BACKGROUND INFORMATION A preliminary reconnaissance hydropower study was conducted by the Department of the Army, Alaska District, Corps of Engineers in 1980 (Regional Inventory and Reconnaissance Study for Small Hydropower Projects – Aleutian Islands, Alaska Peninsula, Kodiak Island, Alaska (SSH-1980-0226)). It looked at four potential hydropower sites located near Cold Bay at a high and a low estimated plant utilization factor. One of the four sites considered was on the east branch of Russell Creek. HYDROLOGY Cold Bay is located on the west end of the Alaska Peninsula. The terrain is dominated by Frosty Peak (elev 5803) which is glaciated. The Russell Creek drainage basin lies southwest of Cold Bay. Basin characteristics were determined through publicly available information, including annual precipitation, topographic maps and land cover. The basin drains into Cold Bay, a part of the Pacific Ocean. About half of the basin consists of is low, flat valleys and low gradient streams, while the upper reaches are steep terrain that is snow-covered much of the year. Cold Bay receives an average annual precipitation of 36”, with a fairly uniform distribution of rainfall/snowfall of 2.4” (water equivalent) per month from January through August and 4.15” per month from September through December. (http://www.cold-bay.climatemps.com/). See Attachment #1. The United States Geological Survey has operated a continuous stream gage on Russell Creek for 27 years from October 1981 through October 2016. (USGS 15297610 Russell Creek Near Cold Bay AK). Monthly mean discharge data for this gage period range from 144 cfs in March to 341 cfs in September. (https://waterdata.usgs.gov/nwis/monthly?referred_module=sw&site_no=15297610&por_15297610_9 2 01=623744,00060,901,1981-10,2016-11&format=html_table&date_format=YYYY-MM- DD&rdb_compression=file&submitted_form=parameter_selection_list). See Attachment #2. The gaged basin area is 31 square miles. A location for a hydropower intake structure was identified on Russell Creek approximately 3.4 miles upstream of the gage. This location was selected because it is just below the confluence of three tributary branches of Russell Creek, with an approximate elevation of 150 feet. The area of the basin above this intake site is estimated at 20.7 square miles. The mean monthly discharge data for the hydro basin drainage were calculated by proration of the gage data by a factor determined from the ratio of the two basin areas (20.7/31 = 0.67). The mean monthly hydro basin discharges are found in Table 1. The estimated mean annual flow of Russell Creek hydro basin for WY 82 through WY 2016 is 171 cfs. Table 1 – Hydro Basin - Mean of Monthly Discharge (cfs) PROJECT CONSIDERATIONS As currently envisioned the project would be a run–of-the-river hydropower project with almost no storage. See Attachment #3 for a map of the key project features. Its intake would consist of a low height diversion structure to create a small stilling headwater basin to drop out sediment, where water would enter a trash rack, screened intake chamber for connection to the penstock. Gates would be provided to control penstock flow and a downstream sluice gate in the intake chamber for sluicing sediment to below the diversion structure. Depending on the amount of sediment movement in the Creek, a pneumatically operated inflatable gate (Obermeyer), such as installed at the Falls Creek intake structure at Gustavus, may be an option to allow for occasional flushing of sediment, debris, rocks and boulders during high flow events. Special provisions would need to be made in the structure to allow for environmental releases and upstream and down-stream movement of salmon, Dally Varden and steelhead. (See LAND OWNERSHIP, LICENSING AND ENVIRONMENTAL CONSIDERATIONS). 3 Because no field visit was made to support this study, a thorough examination of the site geology would be necessary to establish the optimal location for inlet structure. Key factors in this decision include: creek width, strength/stability of abutments, vertical bearing strength of the streambed to support structures’ weight and the need to grout or provide cut-off walls to reduce water leakage. POWERHOUSE EQUIPMENT AND PENSTOCK SIZING From review of the gage hydrology data, it is clear that in most months sufficient water is available to satisfy the load on a year round basis. The intake structure is proposed to be at elevation 150 and the powerhouse at elevation 15. A penstock length of 3 miles (required due to the low gradient terrain found between the intake and the powerhouse) will represent a significant capital cost for the project. The current annual load at Cold Bay (FY 16 PCE records) See Attachment #4 is 2300 MWh of diesel generation. Allowing for all 119 customers to convert to electrical space heating and a 25% allowance for future growth in load, brings to total design load for the new hydroelectric plant to be 4700 MWh. If 100 cfs is used for the design penstock flow, the turbine-generator equipment will be sized at 900 kW. With a 60% capacity factor, the annual net hydropower generation will be 4700 MWh. Allowing for a 10 ft/sec limiting velocity in the penstock will require a 42” diameter penstock. See Attachment #5. COST ESTIMATE A preliminary construction cost estimate of $17,000,000 has been prepared and is shown in Attachment #62. The unit cost for this project is estimated at $18,889 per kW. (Note the estimate does not include cost allowances for land transfer, licensing, feasibility study/preliminary design and final design). LAND OWNERSHIP, LICENSING AND ENVIRONMENTAL CONSIDERATIONS The Russell Creek basin and the facilities to be constructed under this project, (diversion structure, penstock, access roads, powerhouse and transmission lines, etc.) lie within the Alaska Peninsula National Wildlife Reserve (APNWR) as managed by the U.S. Fish and Wildlife Service. Therefore, at present FERC jurisdiction does not extend to this federal land holding and so licensing the hydropower project will be problematic. It is anticipated a land swap of the federal lands needed to construct the hydropower project within the Refuge could be negotiated for lands held by the State of Alaska. This would allow authority for FERC to issue a license for the hydropower project under the provisions of the Federal Power Act. There remain ongoing discussions for road access between the City of King Cove and Cold Bay through the Izembeck National Wildlife Refuge that abuts the APNWR which might also be an opportunity to explore. Several reaches of Russell Creek are listed in the Alaska Department of Fish and Game’s Anadromous Waters Catalog (AWC). The one most directly associated with the proposed hydro project has the following AWC Number of Waterway: 283-34-10200. See Attachment # for map of Cold Bay and local rivers from the AWC. Four species of salmon (chum, sockeye, coho and pink), Dolly Varden and 4 steelhead have been documented to utilize sections of this creek. See Attachment #8. There are no barrier falls or other natural impediments in the low gradient portion of this river system to restrict fish passage. Impacts from anadromous designation to licensing are: (1) environmental flows are anticipated to be required, (2) upstream/downstream fish passage for chum salmon will be required and (3) FERC licensing will be mandated (presuming land transfer takes place) under the presumption that salmon habitat impacts will trigger international and interstate commerce. OTHER CONSIDERATIONS The utility customers of Cold Bay are dominated by employees of state and federal agencies and transportation-related companies (77 total), versus residential customers (38) and community facility customers (4). The school in Cold Bay closed in May 2015. Cold bay is considered the cloudiest place in the U. S., with an average of 304 days of heavy overcast (covering over ¾ of the sky). There is no “dry” season in Cold Bay. Cold Bay is reported to have a relatively constant moderate wind so there may be merit in studying the feasibility of using a wind turbine to provide renewable energy for the community. CONCLUSIONS Russell Creek has a 27 year history of continuous stream gaging by the USGS. In the portion of the basin that would supply a hydropower project, the Russell Creek has a relatively robust year (nearly) round average flow of 170 cfs (monthly averages run from a low 96 cfs in March to a high of 228 cfs in September) and is not expected to experience continuous ice cover in the winter. These are positive aspects for a run-of-the –river hydropower project. Negative considerations regarding project development include: 1) since it is located within a federal Wildlife Refuge, it would require a land transfer to State of Alaska; 2) Russell Creek is anadromous with 4 species of salmon, steelhead and Dolly Varden leading to licensing complications and environmental releases which will require fish passage and environmental flows to maintain connectivity in the reach between the intake and the powerhouse; and 3) is at very expensive location to construct.