|Ross Dam Issues|
Retyped for clarity and emphasis 8/14/1953 Corps document.
See Seattle District Office Ltr re: Flood Control Requirement and Operating Procedure for Ross Reservoir, Skagit River, Wash. for original document.
|For this document we took the original 8/14/1953 document, retyped it verbatim and added emphasis, footnotes, and a flood CFS table to show what the Corps was studying. The document shows us that among many other things, the Corps used the Sedro-Woolley Stewart figures to compute the Ross Dam storage requirements, this despite the fact the Stewart data wasn’t published yet, and presents a serious question as to why they discarded the Stewart Concrete figures before 1924; if the 1909 flood happened today it would carry approximately only 185,000 CFS not the 220,000 CFS Stewart estimated; and the Corp recommended storage only “start” to be accomplished on November 1st even though 24% of the flood events “studied” happened in October. This document is a must read for everyone interested in storage issues for the Skagit River.|
|7/15/1946||Congressman Henry "Scoop" Jackson Letter to Corps of Engineers, Re: Application to Increase Ross Dam Height and Request for Flood Control||
“As you will note, the Skagit County Planning Commission and the Board
of County Commissioners have requested that any grant of right to
increase the height of the Ross Dan be granted only upon the condition
that the upper 15 feet of the dam, as either completed or partially
completed be reserved as storage for flood waters and for flood control
Note: Upper 15 feet of full pool translates into 170,741 acre-feet of storage. As of 2/2010, Ross Lake has 119,629 acre-feet of flood control storage.
|9/26/1946||Seattle District Corps of Engineers Letter, re: Ross Dam Flood Capacity Needs||“From the tabulation in paragraph 4, it can be seen that 100,000 to 200,000 acre-feet of storage would control the winter floods of record on the upper Skagit.”|
|11/20/1946||Acting Chief of Engineers for the Army Corps of Engineers Letter to Federal Power Commission, Re: Third Step in the Construction of the Ross Dam||“Studies by our District Engineer, Seattle, Washington, indicate that 300,000 acre-feet or more of capacity would be required to control floods comparable to the historical floods of 1851 and 1856, although a reserve capacity of approximately 200,000 acre-feet during the period 1 November to 1 April would have controlled floods of record since 1909.”|
|1/16/1947||Seattle District District Engineer Corps of Engineer Letter to North Pacific Division, Re: Skagit County Planning Commission Meeting on Flood Storage, Ross Dam, Skagit River, Washington||“Several members of the committee objected to the proposed flood control reservation of 200,000 acre-feet from 1 November to 1 April on the grounds that, although the amount of storage was adequate, the period suggested did not include the usual early fall high water in October, nor the snow melt high water in April. In historic times neither of those high waters has exceeded bank-full stage of Skagit River, and anticipated reservoir operations are such that flood storage reservation in the months of October and April would reduce the prime power output of the plant. Nevertheless, the representative of Seattle City Light stated that the City would have no objections to reserving 200,000 acre-feet of flood storage from 1 October to 1 May of each year.”|
|4/29/1947||Federal Power Commission Order Authorizing Amendment of License [to complete Ross Dam]||“Upon installation of the spillway gates it is provided that during the period November 1 to April 1 200,000 acre-feet of storage space in Ross Reservoir shall be reserved by the licensee for flood control and utilized as prescribed herein.”|
|12/27/1948||Seattle City Light Letter, Re: Amendment of License - Project No. 553 - Third Step of Ross Dam||Request due to inadequate data, incomplete dam & powerhouse construction and also “the position that the Skagit Project bears to regional power development rather than an isolated project.”|
|1/26/1950||Col. Itschner Ltr to Seattle Department of Lighting/Seattle City Light on Ross Dam Storage||
“The value of flood storage at Ross was recently demonstrated during the
November 1949 flood when river stages at Mount Vernon were reduced by an
estimated three feet through the fortunate availability of sufficient
storage above Ross Dam.”
See Also: 1/7/1950 Reply to Corps Request for Flood Fight Mapping: At “the peak of the Nov. 27-28 flood... The dikes at Mount Vernon were about 1.5 or 2 feet above the peak at most places, with weak spots developing near Avon.”
|2/8/1950||Corps Seattle District Ltr to North Pacific Division, Re: Standard Project Flood, Skagit River Basin, Washington||“From the hydrograph on Plate 4 and considering 200,000 acre-feet available in Ross Reservoir for reduction of floods, it is calculated that the peak inflow of 97,000 second-feet could be reduced to a constant outflow of about 25,000 second-feet. The Skagit River Report may present data to indicate that a reduction to zero outflow for a short period may be better for flood control, but in any case it is evident that the Ross Reservoir, will be able to accomplish a substantial reduction of flood flows.”|
|7/17/1950||Seattle City Light/Department of Lighting Letter to Corps of Engineers, Re: Costs of 200,000 Acre-Feet of Ross Dam Storage & Discharge Capability Past Gorge Diversion Dam||“The Department has made a study of the operations of the reservoir to effect flood control in the amount of 200,000 acre-feet to be made available continuously from December 1 through February 15 of each seasonal year. In this study it was assumed that the Skagit River plants would be operated as a part of the Northwest Power Pool.”|
|2/21/1952||Report on Survey for Flood Control of Skagit River and Tributaries||“The existing reservoirs are not effective in preventing major flooding in the Skagit Valley, Diablo Reservoir is ordinarily maintained at a high level by Ross storage and has no flood storage, Shannon Lake is likewise held at a high level if stream flow permits, but an incidental degree of minor flood protection might be available if the reservoir should be drawn down because of deficient run-off before a flood, Ross Reservoir above Diablo has a large amount of storage, primarily for power, but the Federal Power Commission has required a reservation of winter flood control storage space. Studies are under way to determine the amount of such storage, and it is believed that it will not exceed 200,000 acre-feet. Because of its far upstream location Ross Reservoir storage cannot greatly reduce major floods on the lower Skagit River, The effectiveness of Ross storage in reducing peak discharges depends upon location of the storm center and other variable storm characteristics, Estimates based on average conditions indicate that crest reductions varying between 15,000 and 25,000 second-feet may be expected at Sedro Woolley.”|
|8/13/1953||Ltr to USACE Corps District Office in Portland fm USACE Seattle District Office re: Flood Control Requirement and Operating Procedure for Ross Reservoir, Skagit River, Wash.||This document provides descriptive detail into how
the USACE determined to lower the required 200,000 acre feet originally required
for flood control storage down to 125,000 acre feet. “All discharges of more
than 65,000 second-feet at either Sedro Woolley (1908
through 1923) and Concrete (1924 to date)
occurring in October, November, and December were studied.”
See also: Retyped for clarity and emphasis 8/14/1953 Corps document.
||USACE Seattle District Plan of Survey Skagit River Flood Control Study||
With regulation at Ross and Upper Baker Dams, a 150,000 cfs flow at SW has a
frequency of about 25 years. ... Flows of 210,000 cfs at
SW have frequencies of about 200 years under existing conditions.
(NOTE: REMEMBER THIS IS BEFORE ADDITIONAL STORAGE BEHIND UPPER BAKER.) ...
damages from flows of this magnitude would total about
$6,600,000. ... objective of this study is to find the most
economically feasible solutions.
See also: Public Hearing on Flood Control for the Skagit River Basin, 8 February 1961
|2/8/1961||Summary of Public Hearing on Flood Control||The Bypass project was favored by the Dept of Game and Fisheries because it would have no effect on the existing Skagit River fishery resources.”|
|2/8/1961||Public Hearing on Flood Control for the Skagit River Basin, 8 February 1961||
“I am particularly interested in securing information on the nature and scope of the flood control improvements desired; the problems and difficulties encountered under the present conditions, and the proposed developments which would utilize the desired improvements that you would suggest.” (Col. Young, US Army Corps of Engineers)
|11/1963||Unregulated 100yr fld 250,000 to 300,000 cfs (pg 2); The 35-year level of flood protection provided by the Avon Bypass with levee and channel improvements would protect against 79 percent of average annual flood damages under present conditions. These flood damages are 75 percent agricultural and only 25 percent urban. Therefore, the project is now required essentially for the protection of agricultural lands, and the 35-year level of protection is well suited to present development. . . . The semi-pervious foundation conditions preclude any general raising of levees without extensive broadening of the levee sections, construction of cutoffs to reduce seepage, and relocation of the road systems adjacent to the levee system. (pg 4) To achieve the same results as the Bypass and levee improvements, the channel would have to be widened from 300 to 600 feet from the downstream limits of Sedro Woolley to the mouth of the river, a distance of over 20 miles. (pg 6) ... At Mt. Vernon the 1932 flood of 140,000 c.f.s. has a 12-year frequency; the 1921 flood of 182,000 c.f.s. has a 30-year frequency; and a flood of 245,000 c.f.s, would have a 100-year frequency. ... 278,000 at SW (Table 2)|
||Series of MFRs & Letters Mostly Addressing 8 Possible Dam Sites and Impacts of Wild and Scenic River Act||
7/9/65 8 sites were Cascade River, Lower Suiattle
River; Upper Suiattle River; Upper Sauk River; Lower Sauk River; Cooper Creek;
Thunder Creek; and Faber site (on Skagit about 6 miles upstream from Baker
River). 7/1/65 "A decision to commit a portion
of the river basin to a Wild (and Scenic) River category appears premature at
this time. 6/18/65 "One hundred year flood
protection is vitally necessary for continued progress in Skagit county.
6/29/65 The purpose of this meeting was to inform
Seattle Light representatives of our proposed upstream storage studies in the
Skagit River basin, determine sites at which City Light has made studies, and
obtain data on power studies made by the city. 4/7/65
Ltr fm private engineering company to Corps re Cape Horn.
See also: 8/12/1965 DF re Skagit River Upstream Storage Geologic Reconnaissance
"This report covers certain geologic phases of upstream storage -sites as viewed
on a 5-day reconnaissance by Messrs. A. S. Cary, F&M Branch and W. R. McKinley,
Project Planning Branch, into the Skagit drainage area." . . . The Skagit
Valley far upstream has a depth of fill near 500 feet and if the rock floors of
the Sauk and Skagit are concordant, the depth is well below sea level."
See also: 7/9/1965 Series of MFRs & Letters Mostly Addressing 8 Possible Dam Sites and Impacts of Wild and Scenic River Act
||Corps DF re Environmental Assessment of Levee Repairs After 1975 Flood Event||Repairs took place on Cockreham Island. Skagit floods "characterized by sharp rises of relatively short duration from October through March." . . . "The Skagit River system produces more runoff than any other river basin in the Puget Sound area." 100 year flood 266,000 cfs. 50-year flood 224,000 cfs. Zero damage 60,000 cfs. Present levee system with 2ft of freeboard 84,000 to 130,000 cfs or 3 to 11 year protection. . . . Ross Dam controls about 30 percent of the basin's runoff with 120,000 acre-ft of storage space. . . . During the 1972-1973 collection period, nearly 14,400 salmon were captured, trucked, and released into Baker Lake and adjoining artificial spawning beaches . They consisted of 10,000 sockeye , 4,000 coho, 250 chinook , and 30 chum. In addition, 50 steelhead trout were captured and released. . . . The damaged areas at the town of Hamilton, and the four damaged portions between Hamilton and Lyman occurred where the high water flow was either restricted or at a sharp change in direction without adequate floodway area to handle the resulting turbulence. The floodwater was most destructive where the levee was breached; in some of these cases the water velocity cut a channel from the river through the vegetated bench and beyond into the agricultural area. . . . The greatest loss to fish will be the loss of eggs placed in the gravels by spawning fish prior to the flood.|
||Corps Public Brochure re Skagit River Levee and Channel Projects||See also Public Meeting Transcript and 3/23/78 SVH for a meeting summary. Pg2...The 100-yr flood at SW is estimated at about 215,000 cfs. Pg3...The existing levees below Burlington vary in level of protection ... from 84,000 cfs to 130,000 cfs with a minimum 2 ft levee freeboard. Pg7...The two "PSE" dams on the Baker river provide flood control for the Baker River Basin which amounts to approximately 10% of the Skagit River drainage ... Skagit River flood damages in Dec 1975 totaled $3,247,000... Skagit County has considered a comprehensive flood control plan to guide future planning and has formed a county-wide flood control district to enable the county to sponsor flood control improvement projects. (See 1973 Comp Plan Alternatives for the Skagit ) which was clearly never enforced.|
||Corps Seattle District ltr to Division Engineer in Portland re City of Seattle's application for a new major license for Skagit River Project||Seattle District states "Article 36 requires the licensee to provide 120,000 acre-feet of flood control storage between October 1 to March 15. By reference Article 36 included "Details of Regulation for Use of Storage Allocated for Flood Control in Ross Reservoir, Skagit River Washington revised May 25, 1967. Reference states that "In the event that the high dam is constructed at Ross (1725-foot pool) or any appreciable change in the economic development of the valley takes place which would necessitate a lower control flow at Concrete, a maximum of 180,000 acre feet of flood control storage may be required. Corps confirmed the need for 180,000 behind Ross Reservoir."|
||nhc Memorandum: Skagit River Gl Study- Seasonality Assessment of Flood Storage||
“Hydrologic analyses of existing condition regulated flows conducted to date
have ignored the seasonal variation of flood control storage and have assumed
that the required maximum amount of storage (74,000 ac-ft at Upper Baker and
120,000 ac-ft at Ross) is available for all floods, regardless of the date of
occurrence. The full amount of flood storage is not required at Upper Baker
until November 15 and at Ross until December 1. The purpose of the work
described in this memo was to assess the impact of lower flood control storage
requirements prior to December 1 on regulated peak flows on the Skagit River
near Concrete (i .e. downstream from the Baker River confluence).
“Operations at Upper Baker have also deviated from expected future operations since 2004. In accordance with the requirements of a relicensing agreement, an Interim Protection Plan (IPP) was introduced in 2004 to improve fish habitat in the Baker River by reducing rapid fluctuations in flow. Under IPP-related project operations, more storage than required would be available in the Baker River project early in the flood control season.
“A further change affecting flood control performance has been the implementation by PSE since about 2006 of flood control pool buffers at both Upper Baker and Lower Baker. The buffers provide additional storage above that required for flood control operations per the operating license. At Upper Baker, this additional storage is 26,000 acre-ft, so that the bottom of the buffer is approximately 7ft below the maximum permissible pool elevation in the flood control season. At Lower Baker, the bottom of the buffer is approximately 5 ft below the spillway crest elevation, representing approximately 9,850 acre-ft of storage below the spillway crest. The purpose of the buffers is to provide PSE with operational flexibility while avoiding, to the extent possible, incursion into the formal flood control storage space at Upper Baker. PSE operates the reservoirs to try to maintain water levels toward the low end of these buffers (water levels are generally maintained 2 to 3 feet above the bottom of the buffer), however there is no formal operating policy for the buffers.
“The Baker Project WCM should be updated to show flood control storage requirements per the current FERC license. Future updates to the WCM should be anticipated and coordinated with PSE to reflect operational changes adopted as a result of future implementation of new FERC license conditions. ”
This document was submitted to the 2011 Skagit River GI Scoping Efforts by the City of Burlington.
||Skagit River General Investigation Study Scoping Meeting Comments - City of Burlington||
34 slide presentation to the
the 2011 Skagit River GI Scoping Efforts by the City
of Burlington. Main focus is flood storage.
“•With additional Baker flood storage in place (139,000 AF in accordance w/ Baker advance drawdown targets), Skagit peak flow reduction will be 13,000 – 18,000 cubic feet per second.
“ – Reduces downstream surface water elevation 1.5 feet
“ – Coordination w/ downstream storage (40,000 – 60,000 acre-feet in the Nookachamps basin) reduces another 1.5 feet.
“•Similar reductions can occur from Ross storage and operation
“• At least 3-4 feet flood reduction in total.”