Page images
[ocr errors][ocr errors][merged small][ocr errors][ocr errors]

At Hafey Brook dike approximately 2 million cubic yards of earthfill and rock
are required. The minor dikes have small volumes ranging from 40,000 to 200,000
cubic yards.
(6) Impervious materials.--Foundation testborings made high on the left
abutments at both the sites investigated at Dickey indicate that thick and ex-
tensive deposits of till occur generally above elevation 900. The till is com-
pact, relatively impervious and characteristically variable. It contains scattered
boulders and ranges in gradation from gravelly, silty sand to gravelly, sandy
claç. Preliminary estimates indicate that an area extending upstream along the
Falles 2 miles or more from Dickey Dam site could provide all impervious ma-
terials required for the impervious sections of the dam. Other localities where
extensive deposits of relatively impervious till occur within 242 miles of the
site include the high slopes on the north valley wall downstream from the site
and the higher hillside on the south side of the valley between the upper and
lower Dickey sites.
At the Falls Brook dike impervious materials are available in nearby extensive
till deposits on the east side of the Falls Brook Valley both upstream and down-
stream from the site. Sources of impervious materials for the other dikes were
not specifically located. However, it is expected that deposits of till suitable
for use as impervious fill can be found in proximity to all the sites.
(C) Pervious materials.---Pervious materials for construction of the Dickey
Dam occur in extensive terrace deposits of silty sands and gravels which extend
from river level to about elevation 800 along the north side of the valley. In
some areas the terrace materials are mantled by till. Within these deposits, till
also occurs in scattered small masses and thin lenses. The total thickness of
the pervious materials, including the relatively minor till zones, is generally
more than 100 feet. It is expected that adequate exploration of these deposits
would permit delineation of suitable areas where it would be feasible to obtain
very large quantities of relatively pervious material. Without some selection,
these deposits would probably provide material which overall would be classified
as random All.
Foundation explorations for the southern section of the dam at the lower
Dickey site and in the valley bottom at the upper site encountered more than 40
feet of relatively pervious silty sands and gravels, and similar materials occur
in the extensive outwash plain at the mouth of the Little Black River. The
water table is generally less than 20 feet deep in these areas so that subaqueous
borrow operations would be required to realize more than a nominal percentage
of an indicated large potential.

Other potential sources of pervious borrow occur in a large terrace approxi-
mately 11 miles downstream from the Dickey site and in less extensive terraces
on the east side of the Allagash River from Three Mile Island to Twin Brook
Rapids about 4 miles from the Dickey site.

A nearby source of pervious materials has not been found in the vicinity of Falls Brook dike. For purposes of this report it is assumed that pervious materials will be obtained from deposits in the vicinity of the damsite.

Immeriately north of the Hafey Brook dike site, there is an extensive outwaslı plain indicated to be underlain by gravelly sands in sufficient quantity for pervious fill requirements.

At Campbell Brook dike all pervious materials required will be obtained from pervious deposits at Dickey. At Blue Brook and Cunliffe Brook dike requirements for pervious fill have been kept to a minimum in preliminary designs and it is assumed that they can be found within 5 miles haul distance of the sites,

(d) Gravel bedding, slope protection, and road gravel.-It might be possible to obtain these materials by selective excavations in the areas considered as potential sources for pervious material. Considering the large quantities required, however, it is believed more realistic at this time to assume that all gravel for bedding, slope protection, and roads will be obtained by processing materials from the most suitable pervious borrow areas. Campbell Brook dike is only a short-haul distance from the Dickey site and could be supplied from a processing plant at Dickey. Select gravel materials for the dikes at Falls Brook and Hafey Brook likewise could probably be supplied most readily from a central processing plant located at Dickey.

le) Rock slope protection and rockfill.The slaty shale bedrock will provide most of the required rock for slope protection and rockfills. The shale bedrock from the required rock excavations will be utilized at the dam and adjacent dike. At the remote dikes most of the required slope protection or rockfill will be provided by quarrying in nearby areas.

[ocr errors][ocr errors][ocr errors][merged small]

Cleavage is very well developed in the shale so that it will split easily into thin plates and wafers, and shapes produced by blasting will be elongate, flat slabs. Breakdown of the rock during blasting and handling will result in production of a high proportion of undesirable fines. Processing will, therefore, be required to obtain satisfactory rock for use in rock slope protection. It is expected that the excavated rock will increase in volume by a factor of 1.3 over in situ volume but losses incurred during blasting, handling, and processing will reduce the quantity of available rock so that for in place volume on the embankment a balance factor of 0.8 of the in situ volume is considered reasonable for quantity estimates. A very large volume of shale will be available from required rock excavations so it is planned to incorporate unprocessed excesses in a rolled, rockfill section in the cofferdam or internally in the dam embankment.

Because of the tendency of the shale to break down during freezing and thawing, it will be necessary to use a more durable type of rock where the slope protection will be exposed to fluctuating water levels and atmospheric conditions. Granitic rocks, mainly granodiorite, suitable for this purpose are available in the vicinity of Deboullie Mountain located approximately 12 miles southeast of the Dickey site as shown on plate No. 5. The granodiorite is massive, hard, durable and generally uniform in texture, color, and composition. Access to the Deboullie area is possible for most of the distance on existing poor logging roads but extension by several miles of new road will be required. Total haul distance from the Deboullie area to Dickey is about 18 miles.

(f) Concrete aggregates.-All the natural deposits of sand and gravel in the region contain a high proportion of flat, elongate and friable shale fragments derived from the local bedrock. Because of the slaty character of the shale, both the bedrock and the natural sand and gravel deposits are not considered suitable for use as aggregates in concrete.

At Deboullie Mountain, as previously discussed in conjunction with producing high quality rock slope protection, rock for production of suitable fine and coarse aggregates could be obtained by quarrying. In view of the large volume of concrete required, amounting to approximately 500,000 cubic yards, and the long haul distance from the Deboullie area, consideration will be given to the feasibility of also obtaining fine aggregates from the nearby sand and gravel deposits in the vicinity of the damsite. As a subsidiary operation to processing for selected gravels or by selective excavations, it may be possible, by adequate processing, to eliminate or reduce to tolerable limits the percentage of shale fragments in the natural materials to produce an acceptable fine aggregate.





3-01 General description

The basic plan envisioned by the Department of the Interior proposes Passamaquoddy developerl as a peaking powerplant supplying a substantial portion of the peaking power requirements of an extensive marketing area embracing the New England States and New Brunswick. The plan utilizes the basic two pool concept developed in the IJC's report with the significant modification that inclined shaft turbines would be used in the powerplant in lieu of conventional vertical shaft turbine-generator units, and that the installed capacity would be 1 million kilowatts instead of 300,000 kilowatts.

The components of the IJC's plan, except the powerhouse, are incorporated into the Department of the Interior's plan without change. The unchangel features include tidal dams, the navigation locks, and all filling and emptying gates.


3-02 Layout

The adopted plan proposes the construction of two identical 50-unit powerhouses, one at Carryingplace Cove and the second at Bar Harbor, as shown on plate No. 1. Powerhouse No. 1 would be located on Mathews Island, as in the IJC's plan, with the headrace excavated across a narrow isthmus of Moose Island between Kendall Head and Redoubt Hill. A closure dam would connect the northwest end of the powerhouse to Moose Island. Powerhouse No. 2 would be located on the western peninsula of Moose Island near Bar Harbor with the

headrace excavated across the causeway for Route 190 between Carlow and Joose Islands. A closure dam would connect the west end of the powerhouse to the mainland.

For economic studies cost estimates were required for installations of 30, 50, 70, and 100 power units. The 30-unit powerplant would be located at the same site as powerhouse No. 1. Headrace and tailrace would be narrower to correspond to the smaller powerhouse. The 50 units would be installed in powerhouse No. 1. The 70 units would include an additional 20-unit powerhouse at the location of powerhouse No. 2 with appropriate headrace and tailrace. The 100 units would be contained in the two powerhouses as already described.

The switchyard would be built on an artificial fill near the northwest end of powerhouse No. 1 as shown on plate No. 1 where it would serve both powerhouses.

The powerhouses developed would be identical, and further description of one powerhouse will apply to both. The powerhouse would have 50 main unit bays, each 62 feet wide; two 83-foot assembly bays, one at each end; and four 55-foot service bays, located between groups of 10 units. The total length of the powerhouse would be 3,486 feet. Plate No. 2 shows the general plan of the powerhouse.

The powerhouse would be a reinforced concrete structure. The intake side of the structure housing the turbines is planned as a semioutdoor type of structure with the deck at elevation 20 feet above mean sea level. Access roads and railroad would meet the powerhouse at deck level. Most of the mechanical and electrical equipment would be housed inside the powerhouse. Two outdoor-type 85ton gantry cranes would travel on the concrete deck to unload, install, and service the 50 turbines, and operate the intake gates. Large openings in the deck, each covered with a removable hatch cover, would provide access to the turbines. The portion of the powerhouse over the draft tubes, containing the speed increasers and generators, would be of the indoor type. It would have reinforced concrete walls and a flat roof on steel trusses. Two 100-ton bridge cranes, traveling the full length of the powerhouse, would install and service the 50 speed increasers and generators. Five step-up transformers would be spaced along the deck at 10-unit intervals between the gantry crane tracks and the powerhouse roof. Two 20-ton gantry cranes would travel the deck over the draft tube openings and operate the draft tube gates. 3-03 Turbines and generators Plate No. 2 shows the equipment setting and water passages which are in accordance with a manufacturer's submitted proposal and considered reasonable. The main unit includes a turbine, speed increaser, and generator all on an inThe slightly inclined propeller-type turbine would have adjustable blades, adjustable wicket gates, and fixed stay vanes. Wicket gates are required to prevent leakage. Turbine would have a full-gate rating of 14,000 horsepower at a 13.2foot head and 45 revolutions per minute. A governor and operating mechanism are included with the turbine.

The speed increaser with a 10-to-1 ratio, would increase the shaft speed from 45 to 450 revolutions per minute, permitting the use of a smaller diameter, more efficient, and less costly generator and results in a better design. The generator would be rated at 11,100 kilovolt-amperes, 0.90 power factor, 3 phase, 60 cycle, 13,800 volts, 450 revolutions per minute, complete with exciter. The generator and direct connected exciter would be complete with bear. ing relays. thermometers, waterflow indicators, generator field shunt, space heaters, current transformers, etc.

Included are also air-to-water heat exchangers, a carbon dioxide fire protection system, and thrust bearing to absorb the generator thrust due to inclination of the shaft.

clined axis.

3-04 Main unit bay

The inclined axis turbine, with centerline at elevation —20, is set at a slight angle to the horizontal so as to permit the lacating of the generator and speed inCreaser in the dry. Preliminary structural analysis indicated a thickness requirement of 6 feet for the end piers and 5 feet for the center pier. This requirement plus the water passage exist width of 45 feet established the width of the main unit bays at 62 feet. The generator floor is established at elevation 4 and as such provides 4 feet of concrete, minimum, over the draft tube. The


floor level over the turbines was established at elevation +3 and provides mass concrete around the turbine for the inertia block.

The powerhouse deck was established at elevation 20 which provides 6.5 feet of freeboard above the upper pool maximum elevation of 13.5, and which also provides a working headroom of 14 feet in the mechanical and electrical equipment galleries. The walls for the generator room would extend the entire length of the powerhouse, and support the bridge cranes. The walls for the turbine area would extend the entire length of the powerhouse, and support the deck slab and gantry cranes.

The indoor-type structure over the generator has the advantage that it would provide suitable electrical clearances for the high voltage equipment and transmission line takeoff structures. The indoor-type structure also offers the advantage of a dry inside area for the construction, operation, and maintenance of the major electrical equipment. The powerhouse roof would consist of multiple-ply roofing laid over “Q” decking supported by a steel truss framework. 3-05 Assembly bays

The 83-foot assembly bay provided at each end of the powerhouse would have two floor levels, elevation -4 and +20, as shown on plate No. 3. The lower level would provide two assembly areas. One area for the erection of turbines and transformers would ser iced by one 85-ton gantry crane operating through metal-covered hatches in the deck. The other assembly area for the erection of speed increasers and generators would be serviced by one 100ton bridge crane. A transfer car operating on transverse rails would be used for moving equipment between the two erection areas. The assembly bays would provide space for oil storage and purification, maintenance shop, washroom, and first aid and storage area. An office building, 24 feet by 83 feet, would be located on the elevation 20 floor as shown on plate No. 3. The building at the southeast end would be used for offices for project administrative personnel and facilities for visitors. The building at the northwest end would be used for additional office space and for the powerplant supervisory control room. 3-06 Service bays

A 55-foot service bay would be provided between each group of 10 units as shown on plates Nos. 2 and 3. These four areas, at elevation -4 would provide space for station service auxiliary equipment and space for repair of main unit equipment. These repair areas would be used during construction as additional assembly areas for erection of turbines, generators, and speed increasers. The central portion of the area would be used for station service air compressor rooms. The powerhouse drainage and unwatering sumps and pumps would be located in the downstream area of these service bays. 3-07 General arrangement

The general arrangement of the powerhouse equipment is shown on plate No. 3. The mechanical and electrical systems would be arranged in 5 groups of 10 units each. A group control center would be located on the generator floor at the midpoint of each group. This control center would provide all necessary features for the remote control and operation of each of the 10 units in the group. The generator and station service switchgear for each group of 10 units would be located in the electrical equipment gallery, elevation 3, at the midpoint of the group. The main power transformer for a group would be located on the main deck, elevation 20 directly above the generator switchgear. The mechanical equipment gallery would be used for locating the governors, heat exchangers. piping systems, and other mechanical equipment. A transverse utility gallery would be provided between each unit for the routing of mechanical piping and electrical circuits from the generator room to the mechanical and electrical equipment galleries. The powerhouse roof area would be used for location of high voltage equipment and takeoff structures for aerial lines to the switchyard. 3-08 Gates, trashracks, and stoplogs

Five sets of intake gates would be provided for the 50 units. This would permit the simultaneous unwatering of three units while leaving two reserve sets for emergencies. Each set would consist of one wheeled and one slide gate. The gates, approximately 34 feet 6 inches high by 16 feet 6 inches wide, would each

be constructed in two sections. The gates would be handled by the 85-ton powerhouse gantry crane and when not in use would be stored in the gate slots and supported by latches. The gates would be designed for emergency closure under full flow conditions with wide-open wicket gates. Under these conditions, the slide gate would first be placed in one passage, then the wheeled gate would be placed in the remaining passage. Under these conditions the gates would close under their own weight.

Similarly five sets of draft tube gates would be provided for the 50 units to Dernit the simultaneous unwatering of three units, leaving two reserve sets. This quantity would be adequate to meet the requirement of project maintenance for a 50-unit plant. Each gate, approximately 53 feet 6 inches high by 22 feet 6 inches wide, would be constructed in six sections. The gate sections would be handled by the draft tube 20-ton gantry crane and when not in use would be stored in the gate slots and supported by latches. Because these gates would always be placed under a balanced-head condition, all would be slide gates.

One set of trashracks would be provided for each of the 50 units plus 1 spare set for use in maintenance work. The trashracks would be placed in structural strel guides fastened to the upstream pier noses of the intake and would be handled by a 10-ton auxiliary jib hoist located on the 85-ton powerhouse, gantry crane. This hoist would be equipped with a grab hook for use in removal of trash gathered in front of the trashracks.

One set of intake stoplogs would be provided for the 50 units and would be used for closure under a balanced-head condition of any one of the intake passagerays. This would permit maintenance of the intake gate slots. The stoplogs would be designed to operate in the trashrack guide slots and would be of such dinension and weight as to permit their handling by the 10-ton jib hoist on the 87-ton powerhouse gantry crane.

3-09 Cranes

Two 85-ton gantry cranes with a 52-foot span would be provided for the 50 units and would operate along the entire length of the powerhouse including the unloading areas at each end. The principal function of the cranes would be to handle the turbines and intake gates during construction and maintenance of the powerplant. The cranes would also be used to untank transformers, to unload railroad cars, and to handle trashracks and intake stoplogs. Each crane would have large rolling doors to permit complete enclosure of the area under the crane for use when servicing the turbines during inclement weather. A 115-kilowatt diesel generator set would be installed in each crane to provide power for hoisting and propulsion. Two 100-ton bridge cranes, having a 70-foot span, would be provided in the generator room and would operate along the entire length of the powerhouse including the assembly and service bays. The cranes would handle the generators, speed increasers, turbine shafts, and miscellaneous equipment during the construction and maintenance of the powerplant. They would take their lower from a trolley bus located on the downstream side of the powerhouse.

There would also be two 20-ton draft tube gantry cranes to handle the draft tube gates for the 50 units. Each would be powered by a 115-kilowatt diesel Generator set mounted on the crane. 3-10 Powerhouse control and operation When required for load the powerplant would be operated to generate maximum power during short periods of time and would be under automatic control. The sequence of stopping and starting units could be preprogramed by electronic computer from tide cycle predictions and recorded on punched cards or tapes for use by the automatic controller. The main supervisory control board would be equipped with a 50-unit status board permitting the witholding of selected units from autoinatie control if required. di central supervisory board would be located in the west assembly bay of the plant and would provide equipment for automatic or manual control of all 5 units. Controls would also permit remote manual operation of switchyard breakers and disconnects. A unit-group control center would be located adjacent to each of the 5 groups of 10 generators. From this center, an operator could control all operations for starting, loading, and stopping the generators in his


« ՆախորդըՇարունակել »