June 9, 1998
MEMORANDUM
SUBJECT: Status of Total Dissolved Gas (TDG) Production, Monitoring and Abatement Plans at Facilities Most Likely to Impact TDG Levels in the Columbia River at the US-Canada Border
FROM: Jack H. Gakstatter
TO: System Configuration and Dissolved Gas Teams
DRAFT DRAFT DRAFT DRAFT
The purpose of this memo is to summarize the status of total dissolved gas (TDG) production, monitoring and gas abatement planning at Columbia Basin dams nearest the US-Canada border and most likely to affect TDG levels in the mainstem river at the border. Border TDG levels are of interest to the United States because, at times each year, they exceed our federal criterion and the State of Washington=s water quality standard of 110%. Further, there is surprising little decrease in TDG levels between the border and Grand Coulee Dam, a distance of about 120 miles.
Annual maximum gas levels at the border monitoring station, operated by the Bureau of Reclamation, ranged from 122-138% TDG over the period of 1984-1997 (US Army Corps of Engineers, 1997). Average monthly TDG levels at the border during the period of April through September of 1997 ranged from 118% (April) to 130% (June). These relatively high TDG levels occuring at the US-Canada border sometimes result in levels at the Grand Coulee forebay station exceeding the State of Washington and Colville Confederated Tribe=s water quality standard.
Dams that most directly affect TDG at the border are located on the Columbia mainstem, the Kootenay River and the Pend Oreille River as shown in Figure 1. Hugh Keenleyside Dam is located on the Columbia mainstem about 28 miles upstream from the border. The Kootenay River joins the Columbia a few miles below Keenleyside. A series of five dams are located on the Kootenay River within the first 20 miles above its junction with the Columbia. Brilliant Dam is the nearest of these five to the Columbia. The Pend Oreille River flows north from the United States to Canada and then meanders westward for a few miles before joining the Columbia a mile or two north of the border. Boundary Dam is the last US dam on the Pend Oreille before it reaches Canada. Two dams are located in the Canadian reach of the Pend Oreille, Waneta Dam just a few hundred yards above the confluence with the Columbia and Seven Mile Dam
located a few miles above Waneta Dam.
Hugh Keenleyside Dam:
This facility can be a major initial source of high TDG levels in the Columbia River, ie in the range of 130-140%, according to studies done by Clark (1977). Currently, Keenleyside has no capability to generate power but there are plans to start construction of two turbines capable of generating a total of 150 MW of power. The earliest the generators would be completed in the year 2003. When these generators come on line, studies indicate that the average number of days per year in which the TDG guideline of 110% is exceeded will be reduced from 132 to 45 (Columbia Power, Consolidated Project Report, 19__). Studies were also conducted during the summer of 1997 to evaluate the effects of different discharge regimes on downstream TDG levels.
There are no permanent TDG monitoring stations immediately below Keenleyside Dam. All monitoring has been of an intermittant nature for the purposes of special studies.
Lower Kootenay River:
Brilliant Dam is the most downstream of five dams (Figure 1) on the Kootenay River between its confluence with the Columbia River and town of Nelson, B.C., a distance of about 20 miles. All of these facilities are operated by the West Kootenay Power Company. Some or all of these facilities produce significant amounts of TDG and the Kootenay River is a significant contributor to Columbia River TDG levels.
West Kootenay Power conducted tests in November, 1997 on the effects of using different Brilliant Dam spillway gates on TDG levels. Depending on the specific gate used in the tests, TDG levels were increased from 13-17% over forebay levels (Kosowan, personal communication). Other TDG monitoring conducted in July, 1997 indicated that Lower Bonnington and South Slocum dams might also be significant producers of TDG.
Monitoring TDG on the lower Kootenay River is intermittant, associated with special projects. There are no permanently operated monitoring stations.
Pend Oreille River:
Boundary Dam, owned and operated by Seattle City Light, is located just 0.9 mile south of the US-Canada border on the Pend Oreille River. Although Boundary is the most direct contributor to TDG being exported from the US to Canada, there are a number of other dams upstream on the Pend Oreille, starting with Box Canyon Dam, that might be responsible for elevated TDG levels reaching Boundary Dam.
Studies commissioned by BC Hydro in 1995, 1996 and 1997 indicate that TDG levels in the mid-140% range may be exported from the US to Canada during times of high flow and high spill. TDG levels of this magnitude were measured in the forebay of Seven Mile Dam during June, 1997 (RL & L Environmental Services, 1998).
Seattle City Light is planning a special study this spring to relate various spill conditions to TDG levels below Boundary Dam (Solonsky, Personal, Communication). Although there are no permanent monitoring stations below Boundary Dam, Seattle City Light and Environment Canada staff are discussing the possibility of initiating a jointly operated monitoring station at the US-Canada border (Binkley, personal communication).
Seven Mile Dam, owned and operated by BC Hydro, is located between Boundary Dam and Waneta Dam. Seven Mile was designed to prevent gas entrainment and actually degasses water at higher flows. Roughly a 10% decrease in TDG levels was observed between the Seven Mile forebay and tailrace in June, 1997 when forebay levels were in the mid-140% range (RL & L Environmental Services, 1998).
Waneta Dam, located on the Pend Oreille a few hundred yards from its confluence with the Columbia River, is owned by Cominco, Ltd and operated by West Kootenay Power. Depending on flows, it appears that Waneta can add significant amounts of TDG (RL & L Environmental Services, 1998) although it should be noted that high levels of TDG are apparently reaching the Waneta forebay from sources in the US. Permanent monitoring stations are located in the forebay and tailrace of Waneta but it is not clear whether data will be continuously collected from these stations.
Proportion of Flow from Columbia, Kootenay and Pend Oreille:
The two major tributaries, the Kootenay and Pend Oreille, are said to account for 60% of the mean annual flow of the Columbia River at the international boundary (MacDonald Environmenatal Sciences Ltd., 1997). Therefore, TDG levels in each of these components could significantly influence levels at the boundary.
TDG Monitoring:
Environment Canada is planning on installing two TDG monitoring stations in the next few months (Ryan, personal communication). One station will be on the Columbia River mainstem at Birchbank and will reflect the combined inputs of the Columbia and Kootenay Rivers above that point. The other station will located on the Pend Oreille River at the US-Canada boundary. Discussions are underway with Seattle City Light regarding joint operation with Environment Canada.
References:
Binkley, K., 1998. Personal communication. Seattle City Light, Seattle, WA 98104.
Clark, M.J.R., 1977. Environmental Protection Dissolved Gas Study: Data Summary - 1977. Ministry of Environment, Pollution Control Branch, Report No. 77-10, 246 pp.
Kosowan, G., 1998. Personal communication. West Kootenay Power, South Slocan, BC VOG 1LO.
MacDonald Environmental Sciences Ltd., 1997. Lower Columbia River from Birchbank to the International Border: Water Quality Assessment and Recommended Objectives, Technical Report. Prepared for Environment Canada and British Columbia Ministry of Environment, Lands, and Parks. 115 pp plus tables and figures.
Ryan, A., 1998. Personal communication. Environment Canada, Vancouver, B.C. V6P 6H9.
R.L.& L. Environmental Services Ltd. 1998. Total gas pressure monitoring at Seven Mile and Waneta Dams, 1995-1997. Information package prepared for BC Hydro.
U.S. Army Corps of Engineers, 1997. 1997 Dissolved Gas Monitoring Columbia and Snake Rivers. Northwestern Division, North Pacific Region, U.S. Army Corps of Engineers report, 158 pp.
Solonsky, A., 1998. Personal communication. Seattle City Light, Seattle, WA 98104.