CHAPTER IV. DICKEY PROJECT, ST. JOHN RIVER

4-01 General plan

The site selected for the river hydroelectric project is on the main river immediately above the confluence with the Allagash River as shown on plate No. 5. The geologic features of the site have been described in a previous chapter. The general plan of the development is shown on plate No. 6. The main dam across the river and the dikes across the adjoining saddles would be of the earthfill type. All structural features would be located on the right bank and in general founded on rock: The low-level outlet tunnels, which would be used for diversion during construction; the powerhouse with tailrace discharging into the St. John River; and the spillway which would discharge at infrequent times through a stilling basin into the Allagash River. The maximum and minimum reservoir elevations would be 910 and 870 feet above mean sea level, thus providing a 40-foot drawdown.

4-02 Hydrology

The drainage area above the Dickey site is 2,725 square miles. Area and capacity curves for the Dickey site, shown on plate No. 10, were developed from the latest available U.S. Geological Survey quadrangle sheets, scale 1: 62,500. At maximum elevation of 910 feet, the reservoir area would be 88,600 acres and its capacity 8,080,000 acre-feet. At drawdown level of 870 the reservoir area would be 58,500 acres and its capacity 5,180,000 acre-feet.

Tailwater rating curves were developed for the spillway and the powerhouse. Since the stilling basin at the end of the spillway chute would discharge into the Allagash River just above the cutoff, its tailwater would be controlled by the new channel. The estimated rating curve is shown on plate No. 10. The rating curve at the powerhouse shows that tailwater levels there would be controlled by the Lincoln School dam. The static maximum, minimum, and average tailwater elevations would be 605, 597, and 601, respectively.

Streamflow at the Dickey site was assumed to be the same as at the Dickey gaging station 2 miles upstream. Records at the gage indicate the following: Drainage area, in square miles: 2,700 (approximately).

Period of record: October 1946 to September 1962.

Average discharge, in cubic feet per second: 4,600.
Minimum discharge, in cubic feet per second: 129.

Date: September 17, 1948.

Maximum discharge, in cubic feet per second: 71,700.

Date: May 15, 1961.

Two important hydrologic events have occurred since the IJC study: The most critical 3-year drought, 1955-58; and the greatest flood, May 1961. These events are taken into consideration in the present study.

The streamflow follows a normal annual pattern. Melting snow produces high rates of runoff in April and May after which the flow diminishes gradually and then remains quite uniform until the following spring, except for occasional rises due to rainfall. Then the cycle repeats. The following tabulation of mean monthly discharge illustrates this cycle:

In order to determine the regulated flow available at the Dickey site storagedraft curves were developed for periods of deficient streamflow, using records of flow at the Dickey gaging station. The critical periods were found to be 1947 to 1948 and 1955 to 1958. The following tabulation gives the storage and regulated flow for various values of drawdown:

In computing the regulated flows, an allowance of 50 cubic feet per second was made for losses by evaporation and leakage. For the selected maximum drawdown of 40 feet, the active storage would be 2.90 million acre-feet, and the regulated flow 4,370 cubic feet per second.

An analysis was made of the time required to fill the Dickey Reservoir. With the intakes built as shown on plate No. 7, the reservoir would have to be filled to elevation 870 before power generation could begin. This would require the accumulation of 5,180,000 acre-feet of water. In filling the reservoir consideration would need to be given to the water requirements of downstream plants, of which Beechwood, with 102,000 kilowatts installed, requires the most water. Assuming that Beechwood operates at 60 percent load factor and an average net head of 58 feet, its average water requirement is 14,600 cubic feet per second. It was assumed that the flow at Beechwood could be reduced to this average, 14,600 cubic feet per second, as a minimum, by storing water at Dickey except that a minimum discharge of 500 cubic feet per second would be released at all times to maintain a reasonable low water riverflow immediately below the dam. It is also assumed that water in storage would not be drawn on during the filling period to make up any deficiency should natural flow at Beechwood fall below the 14,600-cubic-feet-per-second level. Under average flow conditions, filling of the reservoir would begin in April and be completed in about 2 years. 4-03 Reservoir

The extent of the proposed Dickey Reservoir at full pool elevation 910 is shown on plate No. 5. It would extend about 47 miles up the St. John River and cover an area of 88,600 acres. A more detailed description will be given later under the subject of "Lands and Damages," in paragraph 4-09. The reservoir would be contained by the main dam and saddle dikes at five scattered locations, required to prevent flow into adjacent watersheds.

4-04 Embankment and saddle dikes

The top of the main embankment was set at elevation 925 to provide 15 feet of freeboard over the maximum normal operating pool. A 60-mile-per-hour wind (velocity over water) acting on the effective fetch of 3.14 miles from the northwest, would generate 4.6-foot waves. These waves would run up 3.8 feet on the 1-on-3, riprapped slope. In addition, there would be a setup of 0.7 foot, on an effective reservoir length of 23 miles. The sum of setup plus wave runup would be 4.5 feet, leaving a freeboard of 10.5 feet. The freeboard provided above maximum spillway surcharge of 8.6 feet, an extremely rare condition, is 6.4 feet without wind and wave action.

Typical cross sections of the main embankment across the river and the secondary dam on the right bank are shown on plate No. 7. Transition zones between different materials, details of surface protection and control of seepage follow conventional practice.

The upstream face of the embankment would have 4 feet of rock slope protection placed on a 2-foot layer of gravel bedding. Above elevation 860, where the pool is subject to fluctuation, the rock for slope protection would be selected. The downstream slopes would be faced by 3 feet of processed gravel above elevation 610, below elevation 610, the downstream toe would be protected by 4 feet of "select" rock on a 2-foot gravel bedding.

To prevent overflow into the St. Francis River Basin a dike would be required on Falls Brook, and another on Hafey Brook. Dikes would also be required on

Campbell Brook, Blue Brook, and Cunliffe Brook to prevent overflow into the Allagash River Basin. All dikes would be earthfill type, constructed of materials found within 3 or 4 miles of the respective sites. The locations of the dikes are shown on plate No. 5.

4-05 Low-level outlets and river diversion

Two 24-foot tunnels driven through the right abutment would be used during construction to pass riverflows after the spring freshet recedes. A study shows that the 10-year construction-season flood passing through the tunnels would raise the level in the reservoir to elevation 627.2. A closure section across the river would have to be raised above this elevation as rapidly as possible after the spring breakup. The following spring flood could be passed through the tunnels and over a saddle at elevation 662.5 to the right of the powerhouse location. With a gap of about 1,000 feet in the embankment across the saddle the maximum spring flood would raise the level in the reservoir to elevation 672.6. With the flow confined to the two 24-foot tunnels the maximum flood of record would raise the reservoir to elevation 699. The section of the dam closing the 1,000-foot gap would be raised to above this elevation during the construction season.

The two 24-foot tunnels described in the previous paragraph would also be used for releases during reservoir filling. Two 90-inch fixed-cone dispersion valves would be installed in each tunnel to control the discharge. The valves and their vertical-lift emergency gates would be located in a shaft immediately upstream from the centerline of the dam as shown on plate No. 7.

4-06 Spillway

The spillway design flood for the Dickey site was developed in the same way as the spillway design flood for the Big Rapids site. (See report of the International Passamaquoddy Engineering Board; app. 12, "Auxiliary River Hydro Developments"; par. 12-08, f, pp. 12–27). The maximum possible rainfall over the Dickey drainage area is very nearly the same as for the Rankin Rapids drainage area. Figure 5, plate 12-6, same reference, shows the component hydrographs of the Rankin Rapids spillway design flood. The two component hydrographs representing flow from the drainage area of St. John River were added together. Then the ordinates were adjusted to the drainage area above the Dickey site, and base flow was added. This gave the natural hydrograph at the damsite. The hydrograph of inflow to a full reservoir would have a higher and earlier peak because of loss of valley storage and shorter travel time. Accordingly, the peak of the hydrograph was increased by 35,000 cubic feet per second and the hydrograph was reshaped, retaining the same runoff volume, to obtain the inflow hydrograph, show on plate No. 10.

An ungated overflow spillway rather than a gated control structure was chosen for the Dickey development to provide better flood control. In addition, an ungated structure would not require a power supply or operating personnel.

A relationship was developed between maximum surcharge and length of spillway crest by trial routings of the spillway design flood through the Dickey Reservoir. On the basis of this relationship, a crest length of 500 feet was selected. After the shape of the spillway crest and the spillway rating curve was determined, the spillway design flood was again routed through the spillway to check the design. It was assumed that all other outlets would be closed. The routing was started with the reservoir 0.75 foot above spillway crest, corresponding to a spillway discharge equal to the base flow. The maximum surcharge was 8.6 feet, and the maximum discharge was 50,000 cubic feet per second, which were satisfactory.

Since the control structure would be subject to ice thrust, the upstream face of the control weir would have a slope of 1 on 1. The crest would be shaped to conform to the lower nappe of a freely falling sheet of water. A design head of 7 feet was used. Heads in excess of the design head would produce pressures somewhat less than atmospheric on the crest of the weir.

The crest structure would discharge into a rock chute which would gradually converge from a width of 500 feet, spillway crest length, to a width of 250 feet in about 1,500 feet. The upstream 800 feet of the chute would have a slope of 0.2 percent, then 700 feet at a slope of 13.8 percent, then 1,650 feet at a slope of 11.8 percent into a stilling basin with floor at elevation 590. The chute would be unpaved where it is in sound rock and the lower 1,600 feet and stilling basin would be paved with concrete and have concrete sidewalls.

A standard hydraulic jump stilling basin would be provided at the downstream end of the chute, as shown on plate Nos. 6 and 7 to give necessary control of the high flow velocities which would occur in the chute. The horizontal apron at the basin would be at elevation 590, sufficiently below river tailwater elevation to assure the formation of a hydraulic jump at all levels of tailwater. Concrete walls of the stilling basin would rise 50 feet above the floor to provide ample freeboard above spillway design flood tailwater and to serve as abutments for the highway bridge.

The channel of the Allagash River would be improved from the stilling basin to its mouth, a distance of about 8,700 feet. The bottom width would be 400 feet, and the side slopes 1 on 2. The bottom slope would be about 1 foot per thousand feet.

4-07 Intake and penstocks

The most economical arrangement of penstocks and intake structure was found to be with the intake through a high rock knob on the right bank. The invert of the 18-foot penstocks was set at elevation 835, an elevation determined by an economic relationship between width and depth of the approach channel referred to the drawdown level of 870. This elevation provides 17 feet of submergence over the top of the penstocks. The excavated channel from the reservoir to the intake structure would be 10 feet lower in accordance with common practice.

The intake would be a concrete gravity structure with the top elevation the same as the dam crest, elevation 925. The service road across the dam would cross the top of the intake structure. Each intake would have a single water passage with an 18- by 30-foot trashrack and a 12.5- by 25-foot emergency vertical-lift headgate. The gates would be remotely controlled from the powerhouse. Stoplogs, placed in the trashrack slots, would be used when inspection or repair of the gate slots is necessary.

The penstocks from the intake to the powerhouse would be constructed of welded steel. The eight main unit penstocks would be 18 feet in diameter and the station service units would be supplied through a single 4-foot 3-inch penstock which would branch at the powerhouse to the two units. Maximum velocity in the main unit penstocks would be 23 feet per second. Plate thickness would be designed for maximum pressures accompanying emergency interruption of full turbine load with maximum pool head. The length of the penstocks was made as short as possible, 1,230 feet, to obviate the need for surge tanks and thus avoid the problems of icing that would occur with peaking operation of a hydroplant during the extremely cold winters at the Dickey site.

To prevent icing of the penstocks, they would be located in a cut and backfilled to a depth of 5 feet over the top. This would place the centerline well below the frostline with a depth of 6 feet.

4-08 Powerhouse

As stated earlier the powerhouse would have an ultimate capacity of 760 megawatts with eight 95,000-kilowatt generators. The cost estimate includes the structure for the ultimate development in the initial 190-megawatt installation. For the 380-megawatt, 475-megawatt, and the 760-megawatt installations the costs for turbines, generators, penstocks, and accessories are added. The powerhouse would be of the indoor concrete type with ultimate installation of eight generating units driven by vertical shaft, Francis-type, hydraulic turbines spaced 63 feet on centers. Each turbine would be connected by an 18-foot-diameter steel penstock extending approximately 1,230 feet to the intake structure. The switchyard would be located downstream from the powerhouse on the right bank of the tailrace channel and connected by aerial lines to the power transformers on the draft tube deck of the powerhouse. Access would be heavy-duty road from the railhead at St. Francis, Maine, to the south end of the plant where the assembly, control, service, and office areas are located. The powerhouse layout is shown on plate No. 8. The bridge crane would have a rated capacity of 375 tons.

The centerline of turbine distributors would be set at elevation 601. Each of the eight vertical, Francis-type, steel-spiral-case, hydraulic turbines would develop 130,000 horsepower at full gate, at the rated head of 275 feet and at 128.6 revolutions per minute. The governors would be equipped with means for adjusting the rate of gate movement to any value between 5 and 30 seconds for full gate opening or full gate closing stroke.

The generators, directly connected by vertical shafts to the turbines, would each be rated at 105,500 kilovolt-amperes, 60° C. temperature rise, class B insulation, 13.8 kilovolt, 0.90 power factor, 3-phase, 60-cycle and with a directconnected exciter. Reactances, WR, runway speed, and thrust bearing loading would not exceed values available in standard design machines. Power for the station service system would be supplied by two station service generators driven by hydraulic turbines. The generators would be rated at 1,250 kilovolt-amperes, 480 volts, 0.80 power factor, 3-phase, 60-cycle and with a speed of 720 revolutions per minute. Conventional fire protection, cooling, heating, and utility systems would be provided.

Four, 3-phase, 243,000 kilovolt-ampere, 13.2-13.2-230 kilovolt, three winding, delta-delta-star connected, type FOW transformers would be provided. Each transformer would be connected to two generators and sized for 115 percent of the rated generator output. The transformers would be located on the tailrace deck, and each transformer would be connected to the switchyard by an aerial line.

The switchyard would be a 230-kilovolt yard and would be remote controlled from the powerhouse.

4-09 Lands and damages

The site of the Dickey Dam and Reservoir is located at Aroostook County, Maine, as shown on plate No. 5. The damsite is about 13 miles above the town of St. Francis, Maine, and just above the point where the Allagash River enters the St. John River. The reservoir extends from the damsite 57 miles to the farthest point of flooding on the St. John River. The backwater extends 25 miles up the Little Black River and 23 miles up the Shields Branch of the Big Black River. (The Shields Branch is called Riviere St. Roche in Canada.)

Land required for the project is approximately 110,000 acres which consists of water area of approximately 88,600 acres at maximum pool elevation 910, and 2,000 acres for work areas at the dam and saddle dikes with necessary access and adjacent borrow areas. The total area includes some islands that would be formed by the reservoir and a 300-foot buffer and access strip around the perimeter. A separate borrow area of 20 acres at Deboullie Mountain is included as a source for concrete aggregate and stone facing.

The reservoir would extend into the Province of Quebec, Canada, at three places. On the Shields Branch (Riviere St. Roche) of the Big Black River about 1,200 acres in Canada would be flooded. This area is developed with farms, roads, and bridges. On two branches of the Little Black River about 2,400 acres of forest would be flooded. The costs of relocation of the public facilities in Canada are included in the relocation costs.

Most of the land required for the Dickey project is in large tracts of timber held mainly for pulpwood cutting. There are some abandoned farms reverting to woodland. There is a built-up area in the hamlet of Dickey about 11⁄2 miles above the damsite. Highway No. 161 serves the community and terminates above the hamlet of Dickey. The population of the entire project area is estimated at 700. About 240 tracts of land would have to be acquired for the project.

An appraisal of the woodland required for the project was made by an appraiser familiar with timberlands in the region. All land was classified according to its highest and best use, and appraised on the basis of fair market value in January 1964. An allowance was made for the value of standing wood growth on all timberland, and also for severance. Severance costs provide an equal access in cases where present access would be flooded out. To avoid isolation of timberlands on the north side of the St. John River, a ferry with landings on the north and south side of the reservoir is included in the estimate. An access road leads from the ferry landing to connect with the road along the Allagash River and with Route 161 just below the damsite. Improvements on the land were estimated separately. They include dwellings, barns, lumber mills, churches, schools, etc. There are no known mineral rights.

Water rights include two breached dams on the St. John River. International water rights on the St. John River arise from the treaty of August 9. 1842, between the United States and Britain (the Webster-Ashburton Treaty), which provides for common use of the waters of the St. John River to promote commerce and transportation for the benefit of the United States and Canada. The only use made of the river in the sense of the treaty is the floating of logs and pulpwood to downstream points. The design of the dam provides for a logway to maintain this traffic. No fishways would be required since the upstream movement of anadromous fish is blocked downstream by natural obstacles.