CHAPTER IV PLANS AND ESTIMATES The Talent division plan provides an adequate water supply for 17,890 acres of irrigable land, develops 10,000 kilowatts of nominal power, reduces flood damages, and produces incidental benefits associated with recreation and propagation of fish and wildlife. The official cost estimate, including the cost of new construction, rehabilitation of existing works, and costs of past and future investigations, amounts to $19,894,000, based on January 1953 price levels. PLAN OF DEVELOPMENT Storage for irrigation and for generating power will be provided in Howard Prairie and existing Hyatt Prairie Reservoirs in Klamath River Basin, east of the Cascade Divide. Irrigation and flood-control storage will be made available in an enlarged Emigrant Reservoir in Rogue River Basin. Waters released from Howard Prairie and Hyatt Prairie Reservoirs will be carried by Howard Prairie delivery canal and the power canal to the Green Springs powerplant penstock. During winter powergenerating months, this water, together with divertible flows from streams which the delivery canal crosses, will pass through Green Springs powerplant at a constant rate of 78 cubic feet per second to produce 10,000 kilowatts of nominal power. Ashland lateral diversion dam on Emigrant Creek, just below Green Springs powerplant, will divert water requirements of Ashland lateral from power discharges or spills from the power canal and flows in Emigrant Creek. Water in excess of the needs of Ashland lateral will flow down Emigrant Creek and into Emigrant Reservoir. An enlarged Emigrant Reservoir will be constructed at the site of the existing reservoir to reregulate releases from Howard Prairie and Hyatt Prairie Reservoirs, and to capture additional available runoff from Emigrant Creek. The filling schedule for Emigrant Reservoir provides sufficient flood-control space during high runoff months to materially reduce flood damages in Bear Creek Valley. Irrigation releases will be made from Emigrant Reservoir as needed to satisfy water demands of the east, west, and Talent laterals, and Phoenix Canal. A bifurcation structure, in the outlet works, will route releases into the east lateral or into Bear Creek, as may be required. Water for the east and west laterals will be diverted into the east lateral and releases for Talent lateral and Phoenix Canal will be routed into Bear Creek for diversion by their respective diversion dams downstream. Existing works of Talent Irrigation District will be used wherever possible. Hyatt Prairie Dam and Reservoir, canal alinement, turnouts, and sublateral systems will be used with very little change. Emigrant Dam will require major reconstruction to increase the capacity of the reservoir from 8,300 acre-feet to 45,000 acre-feet. Canals and practically all canal structures will have to be rebuilt to handle larger flows. Keene Creek Canal, Sampson Creek diversion dam, and Emigrant Creek siphon on Ashland lateral will be abandoned. The upper west and Frederick laterals divert unregulated runoff of Wagner Creek augmented by transbasin diversions from McDonald Creek, a tributary of Little Applegate River. Lands served by these two laterals are included in the present Talent Irrigation District, but will not receive additional benefits under the division plan of development. Accordingly, these lands and the structures to serve them have not been included in the division plan. Principal items of construction include: Howard Prairie Dam and Reservoir; collection canals; Howard Prairie delivery canal; power canal; penstock; Green Springs powerplant; enlargement of Emigrant Dam and Reservoir; extensions of Ashland and west laterals; rehabilitation and enlargement of irrigation distribution system; and drainage works. Locations of features described above and others described in more detail in this chapter are shown on the storage and canal system map. DIVISION WORKS COLLECTION CANALS Runoff from South Fork of Little Butte Creek, Daley, Big Draw, and Deadwood Creeks will be diverted into Howard Prairie Reservoir by the South Fork-Big Draw collection canal. Runoff from Dead Indian Creek will be diverted into the reservoir by Dead Indian Canal. A large part of the runoff will be collected by the canals during winter and early spring. Inspection and patrolling of the canals will be difficult during this period because the canals are located in a heavily timbered and relatively inaccessible area. Hand auger holes and other evidence along the canal alinements indicate excavation for the canals will be mostly broken and weathered basalt. To minimize possible losses from washouts, slides, and seepage, all canals except the 0.5-mile Dead Indian Canal will be concrete lined. At each creek crossing mentioned in the preceding paragraph, diversion structures will direct the divertible flows of the creeks into the canals. The diversion structures have been designed to pass floods of a magnitude to be expected once in 50 years. Simple slide regulating gates will control flows entering the canal. South Fork collection canal South Fork collection canal will have a capacity of 75 cubic feet per second and will extend from South Fork diversion dam to the outlet of Big Draw siphon, a distance of 16,400 feet. Major structures on the canal will be an overchute, diversion, and spillway at Pole Bridge Creek and a spillway at Big Draw siphon. Big Draw siphon will be 1,430 feet long and will have a maximum static head of 230 feet.. Big Draw collection canal The first section of Big Draw collection canal will begin at the Daley Creek diversion dam. After crossing Big Draw and Deadwood Creeks at diversion structures to be built there, the canal will join the South Fork collection canal at the outlet of Big Draw siphon. From Daley to Big Draw Creek, the canal will have a capacity of 30 cubic feet per second and from Big Draw Creek to the outlet of Big Draw siphon, it will have a capacity of 75 cubic feet per second. The length of this stretch of canal will be 19,000 feet. From the outlet of Big Draw siphon to Howard Prairie Reservoir, a distance of 46,100 feet, Big Draw collection canal will have a capacity of 150 cubic feet per second. The major structures which will be required for this section of the canal are 1 tunnel 1,100 feet long, and 2 overchute and diversion structures with spillways. Dead Indian collection canal Dead Indian collection canal will be 2,600 feet long, beginning at Dead Indian diversion dam and discharging into Howard Prairie Reservoir. It will have a capacity of 60 cubic feet per second and, except for a short concrete flume at the head of the canal, will be in earth and will not require lining. RESERVOIRS Three reservoirs in Talent division will have a total capacity of 123,200 acre-feet of which 120,000 acre-feet will be active storage. Howard Prairie and Hyatt Prairie Reservoirs will be operated in the interests of irrigation and power. Enlarged Emigrant Reservoir will capture natural flows of Emigrant Creek and its tributaries and will also store power releases from Green Springs powerplant for later release for irrigation. Emigrant Reservoir will contribute significant flood-control benefits to Bear Creek Valley based on the effect the schedule of joint-use irrigation and flood-control storage will have on flows in Bear Creek. Howard Prairie Dam Howard Prairie Dam site is located about 0.5 mile below the mouth of Willow Creek on Beaver Creek, a tributary of Jenny Creek in the Klamath River Basin. The dam site is 24 miles from Ashland, Oreg., the nearest rail terminal and is reached over the Dead Indian road. The preliminary design for Howard Prairie Dam is an earth-fill structure which will rise 86 feet above the bed of Beaver Creek and about 94 feet above the lowest excavation in the cutoff trench. Crest elevation will be 4,536 feet above sea level. Details of the dam are shown on drawing 415-100-1. Dam site geology.-The dam site is located at the southern and constricted end of a troughlike basin formed by the eastward dip of rocks of the Western Cascade series and more recent lava flows from the east. The basin has been broadened and deepened by erosion and affords the most economical storage for the division. The valley floor at the dam site is covered with sand, silt, and clay to an average depth of 10 feet. The underlying rock is a jointed and altered andesite. The right abutment has from 2 to 4 feet of a reddish-brown topsoil overlying a layer of basalt about 20 feet thick. The basalt rests upon lake deposits which fill an old depression approximately 165 feet deep at its deepest part. Overburden on the left abutment is 2 to 10 feet deep over a vesicular basalt. Underlying the basalt are, first, a tuff breccia which is related |