Post Falls Dam relicensing in contention
Three stretches of concrete in Post Falls sure have a lot of people riled up. Combined, those three slabs make up the three dams that comprise Post Falls Dam. None is large by dam standards, but the three dams have an incredible amount of control over both Lake Coeur d’Alene and the Spokane River – a lot of water, to be sure.
It’s how that water is managed that has so many different groups all trying to have a say in how Post Falls Dam is operated.
In 2005 Avista Corp., owner of Post Falls Dam, began the arduous process of relicensing the dam – its 1981 license was set to expire this past August. That process has been so contentious that a year’s extension of the current license was granted to Avista in September. Meanwhile, multiple water-use issues are being sorted out in negotiations, in state and federal regulatory agencies and in the courts.
It all started innocently enough. As has been the case down through history, whenever man has encountered a narrow spot in a free-running creek, stream or river, a dam has been placed for one of a number of reasons. In the Northwest it has usually been for the generation of electricity. Flood control has been another common reason.
In the past, at least, most everyone considered these dam projects to be a good thing. From Grand Coulee to Bonneville, the Columbia River has been completely controlled by dams. From Lake Coeur d’Alene to Lake Roosevelt, the entire 111 mile length of the Spokane River has likewise been completely controlled by dams.
These days, though, lots of people are not so sure these dams have been such a good idea. In fact, just this past summer, the Marmot Dam on Oregon’s Sandy River was removed at great expense and to great fanfare. Other Northwest dams are set to be destroyed during the next few years.
Thus, how to operate Post Falls Dam over the next 50 years is not a simple question.
Things were less complicated 127 years ago when Frederick Post, founder of Post Falls, the city, set out to harness the power potential of the Spokane River at the falls at Post Falls – a 40-foot cascade over one of the rare bedrock outcrops in the area.
In 1880, Post built a water-powered sawmill at the smaller of the two upper falls. This is the site of the current North Channel Dam, adjacent to Falls Park. Post sold the mill in 1894; it was destroyed by fire in 1899, rebuilt, and again destroyed by fire in 1902.
In 1899, a grist mill was built on the other upper falls at the site of what is today the Middle Channel Dam. It was this site that was converted into an electrical power generating plant in 1906. Its initial purpose was to supply electricity to mining interests in Wallace. This portion of the dam currently includes a six-generator powerhouse and six 11-foot-diameter penstocks.
The third channel at this unique section of the river was closed by the South Channel Dam. This is the dam seen from Q’emiln Park. Both the North and South Channel Dams are spillway-only dams.
The dam complex was sold to Washington Water Power, now Avista, in 1909 to become a part of their growing Spokane River Hydroelectric Project which was begun at Spokane Falls with construction of the Monroe Street Dam in 1890. Between 1906 and 1922, Washington Water Power built four other dams on the Spokane River and the city of Spokane built one dam. The Monroe Street Dam was rebuilt in 1973.
Post Falls Dam, however, is key to the whole system. Its generating capacity is not great, only about 14 megawatts out of a potential 137 megawatts for the entire system (according to Avista, a megawatt is the power needed to serve 750 typical homes), but Post Falls Dam manages input of water into the entire system. And herein lies the controversy.
Apart from power-generation considerations, Post Falls Dam has controlled Lake Coeur d’Alene and Spokane River since all three channels of the river at Post Falls were closed in 1906. The depth of the lake and the volume of the river have been dictated by human interests for the past 101 years.
Of course its impact is huge. Post Falls Dam has the capability of changing the depth of Lake Coeur d’Alene by more than 7 feet and the flow of Spokane River can be increased or decreased as if by spigot.
For example, prior to Post Falls Dam, Lake Coeur d’Alene had a summer surface-elevation that varied between 2,121 and 2,124 feet above sea level. The 1906 dams increased this summer elevation to 2,126 feet. In 1942, the elevation was increased to the present summer level of 2,128 feet.
When the dams closed in 1906, four lakes at the southern end of Lake Coeur d’Alene – Hidden, Round, Benewah and Chatcolet – were flooded by and incorporated into the larger lake, extensive wetland areas around the lake were inundated and Spokane River in the 10 miles between North Idaho College and Post Falls Dam became a mostly currentless extension of the lake.
An extra 7 feet of water over the nearly 50-square-mile surface of the lake means that there is a lot of water that is not going into the Spokane River during the summer. Instead, that water is stored for release in the fall. The result is obvious at Spokane Falls, and Spokane residents are not happy about it.
The result is not so obvious to those of us on Lake Coeur d’Alene today, but just imagine the difference to lakeside property if the summer level of the lake was 7 feet lower. Coeur d’Alene residents would probably not be happy about that.
At least salmon, the bane of so many other dams, are not one of the problems that operators of Post Falls Dam have to contend with. None of the lower six dams on the Spokane River made allowance for fish passage, so salmon were extirpated from the system long ago.