SUPPLEMENT TO JULY 1963 REPORT

1-01 Authority

CHAPTER I. INTRODUCTION

At Eastport, Maine, the large tidal range has long intrigued observers as a natural resource that could be used for the development of electric power. There are two large natural tidal bays that are connected by water passages between a string of islands which stand between the bays and the open ocean. Passamaquoddy Bay, the larger of the two, is mainly located across the international boundary in Canada while Cobscook Bay lies entirely in the United States. By connecting the islands with a series of dams in designed pattern separate tidal pools can be formed and water elevations regulated to maintain the pools at different levels. If a powerhouse is placed between the two pools and water permitted to pass from the higher to the lower the induced head differential will produce power.

The development of tidal power at Passamaquoddy has been studied periodically since 1919 by both private and public engineers. The most comprehensive report undertaken was that of the International Joint Commission completed in April 1961 after 3 years of study and a cost of $3 million. The project was developed as a two-pool scheme interconnected with a powerplant that would operate continuously but with varying output. The powerhouse was a 30unit plant with vertical-axis turbine and generator units with a capacity of 10,000 kilowatts each. The Commission found the project not economically feasible under the then existing conditions.

In early July 1963, as a result of an earlier request to review the International Joint Commission (IJC) report to ascertain whether developments in engineering techniques and/or economic conditions would make the project feasible, the Secretary of the Interior presented to President John F. Kennedy a report on "The International Passamaquoddy Tidal Power Project and Upper St. John River Hydroelectric Power Development." This report proposes to use the power output to meet the demand for peak power in the New England area, and when coupled with the advancement in engineering techniques and integrated with a hydroelectric plant on the upper St. John River would make the project economically feasible. The same structures were used for the tidal project, except for the powerhouse where an inclined-axis turbine was substituted for the more conventional vertical-axis turbine. From the studies made of pow. er potential. it was proposed that an ultimate installation of 100 to 10,000 kilowatt units could be installed at Passamaquoddy. Integration with another source of power is necessary since tidal output varies with the tide range, a minimum occurring about every 2 weeks at periods of neap tides when the available head is lowest. In order to supplement and maintain power output at these periods an auxiliary hydroelectric plant with an ultimate capacity of 750,000 kilowatts would be established on the St. John River at Dickey. The Dickey Dam site was selected by the Department of the Interior in lieu of the Rankin Rapids project considered by the IJC in order to preserve the recreational values of the Allagash River. Integrated operation of the two plants would assure dependable peaking capacity of the planned magnitude of 1 million kilowatts and 250,000 kilowatts capacity at 60 percent load factor for energy output.

On July 16, 1963, the President directed the Departments of the Interior and Army to proceed immediately with such additional studies and plans as are necessary and that the studies be coordinated in all respects by the Secretary of the Interior. Pursuant to this general understanding, Lt. Gen. W. K. Wilson, Jr., the Chief of Engineers, by letter of July 29, 1963, proposed an eight-member Army-Interior Advisory Board on Passamaquoddy and upper St. John River, with four representatives from each agency. The purpose of the Board is to advise and guide both field agencies in their preparation of additional studies, plans, and reports to supplement the July 1963 report to the President by the Secretary of the Interior on the international Passamaquoddy tidal power project and upper St. John River hydroelectric power development. By letter of July 30, 1963, Mr. Kenneth Holum, Assistant Secretary, Department of the Interior, agreed

to this procedure. The Board was later increased to 14 members by adding representatives from the Federal Power Commission, Department of Commerce, Bureau of the Budget, Office of Science and Technology, Council of Economic Advisers, and the Atomic Energy Commission. Membership of the Board is given in appendix I.

1-02 Scope of engineering studies

The division of work between the Corps of Engineers and the Department of the Interior, as indicated by the initial agreement between the agencies and confirmed by the Advisory Board, was to the effect that power studies, power transmission, marketing, benefits, and other economic aspects of the project would be the responsibility of the Department of the Interior and that the development of the physical components, other than transmission lines, would be the responsibility of the corps. The detailed engineering studies and requisite field work were to be performed by the division engineer, New England Division, Waltham, Mass.

The studies undertaken for this report to attest to the engineering feasibility and soundness of the engineering structures of this project were as follows: (a) Geologic investigations and field explorations at the sites of all structural components.

(b) Field surveys.

(c) Hydrologic investigations of the St. John River.

(d) Layout and design of facilities for powerplants at Passamaquoddy; power dam and closure dikes at Dickey: and reregulating and power dam at Lincoln School.

(e) Studies of use of inclined-axis turbines at Passamaquoddy in cooperation with the Bureau of Reclamation.

(f) Planning appraisal of all lands and damages for the entire project. (g) Cost estimates of facilities, except transmission facilities.

The layouts of the construction proposed and the cost estimates for the entire project are presented in the following chapters.

CHAPTER II. SITE INVESTIGATIONS AND FOUNDATION CONDITIONS, PASSAMAQUODDY 2-01 General geology

Bedrock of the project area includes sedimentary and igneous rocks of upper Silurian age known as the Eastport formation. The sedimentaries are shales and conglomerates and the igneous rocks are represented by rhyoltic and diabasic varieties and associated volcanic tuffs. These rocks have been much folded to present a complex distribution of alternating beds of igneous and sedimentary rocks.

Prior to glaciation, the bedrock topography was subjected to a long period of erosion featured by development of deep-stream valleys. The land was greatly depressed by the advance of thick glacial ice in Pleistocene time, and with retreat of the ice came invasion by the sea. Since glaciation full emergence has not been attained and the preglacial stream valleys are partly drowned to form the deep marine channels, while the numerous islands are high areas of the old erosional surface.

The preglacial topography was slightly modified by movement of the ice mass in the removal of the weathering mantle and in the plucking and smoothing of the rock surface. More pronounced modification resulted from deposition of rock debris carried in and on the ice. Materials that were deposited directly from the ice generally occur as a veneer over the rock surface in the form of glacial till, a compact mass mixture of all sizes of rock and earth materials. Coarse materials that were outwashed from the ice occur as remnant deposits of sorted sands and gravels. The fine materials that were outwashed to settle in quiet waters of the invading sea occur as thick deposits of marine clay and silt. Since glacial time, the outwash deposits exposed to sea attack have been reworked by waves and transported by currents to form bars and beaches. Minor deposition by streams has occurred and peat has locally accumulated in bogs and marshes.

2-02 Explorations

Investigations previously made over a number of years for powerhouse No. 1 and channels are sufficiently complete as to preclude need for further exploratory work. These investigations, which include concrete aggregate studies applicable to powerhouse No. 2, are detailed in "Report to the International Joint Commission, 1959," Appendix 2: Geology, Foundations, and Materials.

Previous subsurface explorations pertinent to the areas of powerhouse No. 2 and channels have consisted of the following:

(a) Eight scattered wash borings indicating elevation of bedrock made for the Cooper study of 1926-28.

(b) Three drive-sample and core borings made by the Corps of Engineers in 1935 on alinements of the Carlow Island and Pleasant Point Dams.

(c) Marine geophysical exploration extending into a portion of the tailrace channel in the vicinity of Spectacle Island, cooperatively made on a trial basis in 1951 by the Corps of Engineers and U.S. Geological Survey.

Current explorations made for the purpose of this report specifically for powerhouse No. 2, included geological reconnaissance on land and water and the drilling of two test borings recovering 2-inch drive samples and 2-inch diameter rock cores made to investigate foundation and excavation conditions for the powerhouse structure. Boring FD-1 was drilled and hydraulically pressuretested in rock to elevation minus 89 mean sea level or slightly below maximum required depth of structure excavation. Although this boring is located off the structure because of subsequent adjustment in layout, the conditions encountered are considered pertinent. Boring FD-2, which was made to establish depth to bedrock on the west end of the original layout for the powerhouse, is now located nearly 1,000 feet southwest where it becomes more applicable to excavation conditions in the tailrace channel. Other explorations consisted of 29 machine-driven probings to preliminarily determine division of earth and rock materials to be excavated in the headrace and tailrace channels. These probings were distributed in water areas of the channels lacking in surficial and subsurface data and were driven to below proposed grades or to refusals above grades.

The locations and records of previous and current explorations and the distribution of bedrock exposures for powerhouse No. 2 are shown on plate No. 4 entitled "Plan and Record of Explorations."

2-03 Structure excavations and foundations, powerhouse No. 2

Ground elevations will vary from a few feet to nearly 60 feet above mean sea level on the powerhouse alinement. Structure excavation will amount to over 2 million cubic yards, principally rock, and deepest excavation will be about 140 feet in reaching lowest invert of about 80 feet below mean sea level.

Overburden excavation will vary from a skimming to an estimated maximum depth of 30 feet to reach the rock surface. Overburden is principally glacial till with the major exception of the marsh area along about the southeasterly third of alinement where marine clay attains a thickness of 15 or more feet.

Reconnaissance geologic mapping and the rock cores recovered from boring FD-1 indicate that rock excavations will principally encounter igneous rocks, rhyolite and diabase in flows, sills and dikes with subordinate occurrences of sedimentary rock (shale) and tuffs (cemented volcanic fragments). These rocks singly or in their various complex associations present no apparent problems as to their competency for bearing heavy foundation loads. However, the many contacts of rock types, occasional fault zones and the presence of numerous open and healed fractures and cracks may relate to problems of water pressures and inflows requiring grouting during and after excavation, and to difficulties in producing any close tolerances that may be required for precise or shaped excavations. The fractured condition of the rock as recovered in cores from the deep test boring FD-1 is pictured on figure 1 (p. 52) and a graphic record of tests for holed leakage using water under pressure is shown on plate No. 4. These tests indicate openness in some zones by flows of up to 16 gallons per minute under maintained pressures of 20 to 50 pounds per square inch. 2-04 Channel excavations

Excavations for the headrace and tailrace channels will involve over 50 million cubic yards with a greater proportion in the headrace channel where grade is constant at minus 40.7 mean sea level. Deepest excavation, to minus 67 mean sea level and mainly in rock, will occur in the beginning of the tailrace channel near the southerly shore of Moose Island.

Overburden of the land and islands and their fringes is glacial till, except for localized marsh areas and clay deposits. The overburden of the water areas is clay overlying the till which veneers the rock surface.

All of the igneous and sedimentary rock types previously discussed will be encountered. From available surficial and subsurface geologic data, it is preliminarily estimated that 50 percent of channel excavations will involve rock.

2-05 Tidal dam

A low tidal dam would connect from the powerhouse westerly across Bar Harbor to the Perry mainland. The elevation of bottom near midchannel is about minus 30 mean sea level making maximum height of embankment about 50 feet. A single machine-driven probing near this point shows about 4 feet of soft material, followed by increasing resistance to penetration and refusal indicative of bedrock at minus 38.3 mean sea level. Materials required for embankment construction amount to approximately 400,000 cubic yards and perhaps except for special gravel requirements can be selectively obtained from required excavations for powerhouse and channels.

2-06 General geology

DICKEY DEVELOPMENT

The wilderness area which comprises much of the upper St. John River basin in the United States, was not mapped topographically until 1953. Geologic mapping has been only of limited reconnaissance scope except for the published detailed investigations in the igneous rock area at Deboullie Mountain. In the Canadian part of the upper basin, detailed geologic mapping of correlative value is available for the area bordering the St. Francis River in Quebec.

The upper St. John River basin is a maturely dissected upland region which has been modified by glaciation. The headwaters area is predominantly a region of low relief with wide, flat plains, mostly swamps, and low, broadly domed hills with occasional, widely scattered monadnocks. Downstream from the headwaters of the reservoir along the main river and throughout the Allagash and Little Black River drainage areas, the relief is greater and the topography is rougher with steep hills and narrow-crested, broken ridges rising above generally narrow, trough-like valleys. Till consisting of variable, gravelly, silty to clayey sand with cobbles and boulders, deposited by the last glacier blankets the bedrock throughout most of the region. The till is generally thin on the upper slopes and crests of the hills and in these areas bedrock is occasionally exposed. The valley botton and lower hillsides are generally deeply filled with till and outwash left by the wasting glacier. The outwash deposits composed of variable, roughly stratified, silty sands and gravels occur in thick outwash plains in the valley bottoms and extensive terraces on the lower valley walls. Because the St. John River drains northward, it was dammed at successive locations against the retreating ice front. In the sluggish pools thus formed, thick deposits of laminated fine sand, silt and clay were laid down. As a consequence of the thick filling in the valley bottoms, the rivers now flow high above the deep preglacial valleys in bedrock, and rock is exposed only in uncovered bedrock spurs high on the old valley walls.

Bedrock throughout the basin consists of slaty shale with local thin beds of sandstone and limestone. These Silurian sediments have been folded so that ciently so that the shale in many areas grades to poor slate. The only major occurrence of igneous rocks in the upper basin is the syenite and granodiorite in the vicinity of Deboullie Mountain.

No occurrences of mineral deposits of economic value have been reported in the upper basin.

2-07 Explorations

At the initiation of work on the Dickey project, reports of all previous investigations on the upper St. John River were reviewed. The review included study of reports of sites at Lincoln School, Rankin Rapids, Cross Rock Rapids, and Big Rapids. Reports of investigations by Canadian agencies at Glazier Lake on the St. Francis River were also reviewed. Field investigations were made initially for a designated dam alinement immediately downstream from the Dickey highway bridge. At this location, hereafter discussed as the upper site, explorations consisted of a total of 11 borings including 3 borings made for the Dickey highway bridge by the Maine State Highway Commission in 1950. Unfavorable foundation conditions developed by these explorations led to investigation of an indicated more favorable site approximately 11⁄2 miles downstream and just above the mouth of the Allagash River. Seven borings were completed at this site for preliminary exploration of foundation conditions. The locations of explorations and bedrock outcrops at both sites are shown on plan of exploration, plate No. 11. Foundation conditions at the Fall Brook dike site were explored by three borings, and one boring was completed at the Hafey Brook dike site. Subsurface explorations were not made at the Campbell Brook dike site or at the very remote minor dike sites.