Building a Flume

Bend Bulletin 11 May 1948 Arnold Irrigation district farmers will feel much more secure this season, with a new metal flume carrying water from the Deschutes river to the Arnold ditch. The new flume was rushed to completion this spring by R.P. Syverson, Bend contractor. Standing beside the flume after an inspection of the new installation are: Kenneth Slack, Arnold maintenance superintendent; George T. Murphy, chairman of the Arnold district board; Stanley Kebbe, bureau of reclamation inspector; J.W. Taylor, bureau construction engineer, C.C. Beam, staff member, and Syverson. On top of the flume is Pearl Anderson, ditchrider for the district.

Engineering News-Record April 10, 1924 Vol. 92, No. 15 pgs. 612, 613

Semicircular Wood Flume With Radius of 6 Ft.

Creosoted Staves and Section Giving Minimum Leakage Make for Long Life –
Crew Assembles 500 Ft. per Day

The Central Oregon Irrigation District recently found it necessary to replace the wooden box flume which carried the main canal along the canyon of the Deschutes River, three miles above the city of Bend, Ore. The box flume, a structure 18 ft. wide has been in use for 18 years, a period far beyond the usual life of this class of construction. As the flume box aged and decayed heavy leakage had rotted the substructure and weakened footings so that only by the most thorough patrol and heavy maintenance was the structure kept in service during recent years. Due to the necessity of supplying water to stock on certain sections in the project, the flume was operated at intervals during the winter season and the heavy accumulation of ice from the leaky box was an additional problem.

In planning the renewal of the flume detailed plans were prepared and bids called for on (1) a semicircular, creosoted wood-stave flume, and (2) a semicircular metal flume. After bids were received and compared the former class of construction was adopted. The total length of the flume to be replaced und the plans is 5,820 ft. During the winter and early spring of 1923, 3,920 ft. of the new flume was constructed, leaving 1,900 ft. of flume and reconstruction of the headworks for later attention.

Seimcircular 12-Foot Flume along the Deschutes River

The new semicircular flume is 12 ft. in diameter and the sides extend along the same circular curve to a height of 1 ft. above the diametral line. The depth of water is 6 ft. under the maximum flow and this upper foot, which ads 21 per cent to the area of the cross-section, is considered as freeboard. Due to the necessity of utilizing the headworks and following the location of the old flume, a rather high velocity was used in the semicircular section. The Hydraulic prop0erties are: Capacity, 656 sec.-ft.; slope, 2 in 1,000; N., 0.012; wetted perimeter, 18.85; velocity, 11.6 ft. per second.

The semicircular section has ideal hydraulic properties and careful attention was given to the curvature of the flume. The result is reported to be an exceptionally smooth flow with a minimum of disturbance even through the critical velocity for the depth of flow is approached.

The flume proper is made of Douglas fir staves of 1-½ in. finished thickness and about 5-½ in. width. The edges of the staves have no bead, being simply beveled to radius. These staves are only about two-thirds the thickness that would be used for a pipe of the same diameter, for the reason that the flume does not involve the arch action which exists in the upper half of a pipe when empty. After being milled the staves were given an 8-lb. pressure treatment of creosote. The staves are made tight by edgewise  pressure exerted by ½ in. mild steel rods, spaced 16 in. on centers and passing through the ends of 4×4 in. fir spreaders. The bands have rolled threads and are tightened by nuts and washers resting on top of the spreaders.

The flume is supported independently of the bands by cradles 8 ft. apart cut from fir timber to the exact outside diameter. When the staves were placed, only enough bands were put on to hold the flume proper in shape, the other being added later by crews that worked independently of the driving crew. The final cinching up was done just before the flume was placed in service.

“Buckling in” staves where sections join. Note cradle construction and staggered joints in staves. Bands are laid on each bent ready to be placed.

This cinching was done by the most experienced men, the intention being that the expected swelling of the staves would be allowed for without constant over-stressing. After the water was tuned in only a few leaks were found and these were readily eliminated by a little adjustment of the band pressure. The flume has now been in service for one full season and is reported to be almost absolutely watertight, a condition favorable to long life of the substructure and preservation of the footings.

In the portion of the flume reconstructed, a length of about 800 ft. of the old flume was eliminated and replaced by a concrete lined canal. This section is located in a through cut with a maximum depthe of 42 ft. The material traversed here is largely pumice, having a specific gravity less than that of water. In trimming up the slopes of this cut, the pumice removed was therefore floated out of the cut in the water of the canal.

Ice load on old flume caused by leaks.

In general the location follows a steep rocky canyon above the Deschutes River. The fact that the building of the substructure and the erection of the flume had to be done during the winter season when the flume could be kept out of service made the job rather difficult. On account of the availability of rock and the difficulty in bringing in concrete materials, rubble masonry was adopted for the piers. The flume substructure required a total of 340,000 ft. b.m. of Douglas fir. This material and subsequently the staves for the flume proper were delivered on the rim of the canyon at points several hundred feet above the flume, were lowered to the flume through wooden chutes and were subsequently distributed by hand or means of dollies. The substructure is of standard design and two types: on low portions 8-ft. spans are used without stringers, and on the higher portions of the substructure 16-ft. spans with stringers are adopted.

The construction crew on the flume barrel itself consisted of about twenty men who delivered the material from the chutes, placed the bands and staves, and drove the staves to tightness. After the work was organized this force, divided into two gangs, placed as much as 400 to 500 ft. in an 8-hour shift. At the work was done in two sections, it became necessary in places to join up adjacent sections by “buckling in” or springing the connecting staves into place after they had been accurately cut to the requisite length.

The wrecking of the old flume and building of piers and substructure was done under contract by the Warren Construction Co., Portland, Ore. The flume material, including cradles, wad furnished and the erection of the flume barrel was done by the Continental Pipe Manufacturing Co.

Barr & Cunningham, Portland, Ore., were consulting engineers for the district in charge of design and construction.

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