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The height of roadway above low-water will be 60 feet, though with a view of diminishing the cost of approach on the Virginia (south) side, it may ascend from this elevation at its north end toward the Virginia end on a grade not exceeding 1 foot in 100 feet. The clear headway at caual shall not be less than 14 feet.

4. Proposed site about 500 feet abore Aqueduct Bridge. -At this section the width of the river is about 1,500 feet, and the distance between main abutments would be about 1,500 teet, with a further distance of 200 to 225 feet to the smaller abutment at north side of "road. The north half of the river widih has hard bottom, the remainder being soft. The depth to rock is not known at any part of this sertion. The requirements for the structure at this site are the same as for the preceding, except as to the height of roadway, which may be less, and is to be taken at a convenient level as regards approaches, but shall not be less than that of the Aqueduct Bridge. The elear headway at canal shall not be less than 14 feet.

5. Funds arailable. The amount appropriated for the construction of the bridge complete, with approaches and right of way, is $140,000, and proposals exceeding that amount, or which do not include all the work comtemplated in the act of appropriation, cannot be entertained.

6. Examinations and measurements.-Bidders are expected to esamine the sites and ascertain for themselves the character of ground for foundations for piers and abutments, and for approaches, &c., and must inake their own measurements of distances, heights, and grades.

7. Further information.-Any further information in possession of this office will be given persons desiring to bid, on their application.

8. Explanations and corrections.—Any doubt as to the meaning of the specifications, and any obscurity in the wording thereof, shall be explained by the engineer, who shall bave the right of correcting any errors or omissions in them when such correc. tion is necessary for the proper fulfillment of their intention, the action of such correction to date from the time the engineer gives due notice thereof.

9. Extra work, fc.—No claim for extra work or for delay of any kind will be considered or paid, and the contractor will be held responsible for the entire work until every part of it is completed according to the specifications, and accepted by the Secretary of War as in accordance there.with and with the act of February 23, 1881.

10. Payments.-Estimates for payments will be made upon each pier and abutment as soon as safe from damage by freshets, and npon embankmeuts as soon as riprapped above flood line. Therealter monthly estimates will be made, until the structure is completed. Ten per cent. will be reserved from all payments until the entire work is completed. At the end of six months after the entire work shall have been completed, if no fault of construction, use of improper material, or settling of foundations or embankments are apparent on an inspection of the work by the engineer, the reserved percentages will be paid; otherwise they will be retained until the contractor makes good the deticiency, together with all damage that may have been caused thereby.

11. Proposals.- Proposals must be in duplicate for each or either of the sites for which proposals are submitted, and must be on separate forms for each site. Proposals for each site must be accompanied by bidders' plans and specifications in detail. A single set of plans and drawings will suffice for each site bid for.

The proposals, plans, and specifications are to include the construction of piers and abutinents with proper foundations, superstructure complete, approaches connecting with the most accessible road, and right of way for same, together with all other expenditures necessary for the covenient use of the structure by the public.

Each proposal must be accompanied by a copy of these general specifications, which, together with the special specifications, plans, and drawings submitted by the bidder, are to be referred to in the proposal as forming a part thereof.

Each bidder will submit for each or either site three prices as follows: (A.) For constructing bridge with approaches, right of way, &c., as specified, at

** Thrie Sisters": (1.) For piers and abutments, as specified, ..

dollars. (2.) For superstructure complete, as specified,

dollars. (3.) For grading and embankments for approaches, as specified,

dollars. (B.) For constructing bridge with approaches, right of way, &c., as specified,

about 500 feet above Aqueduct Bridge: (1.) For piers and abutinents, as specified,

dollars. (2.) Por superstructure complete, as specified,

dollars. (3.) For grading and embaukonents for approaches, as specified,.

dollars. These prices are to cover all costs whatever for labor, materials, appliances, &c., for the completion of the work as specified.

The right to reject any or all bids is expressly reserved. The right is also reserved to accepi a bid or bids for any one or two of the three classes of work at either site, rejecting the bids for the remaining class or classes made by that bidder, for accept

ance of corresponding bid or bids of another bidder or bidders, provided the bidder does not expressly state with the price for each class that it is conditioned upon the acceptance of the bid or bids for one or both of the other classes.

Bids will also be considered for one or more of the classes of work named at either or each of the sites; also, bids based on plans and estimates differing from those described in the specifications but made in accordance with the act of February 23, 1881, will be received and considered at the same time.

Proposals must be accompanied by a bond, with two sureties, in the sum of $5,000, in accordance with the act of Congress of April 10, 1878, and with the form prescribed. A proposal unaccompanied by such a bond will not be considered.

12. Contract.—The successful bidder will be required to enter into a written contract with the United States, with good and approved security, in the sum of $25,000, within ten days after being notified of the acceptance of his proposal. These specifications will be attached to the contract and form a part of it.

s. T. ABERT, United States Civil Engineer.

Instructions to bidders. No bids will be considered which are not made on blank forms furnished from this office.

Proposals and bonds must be in duplicate, and each accompanied by a copy of these specifications.

All the blank spaces in the proposal and bond must be filled in.

The duplicate proposal must be in a sealed envelope indorsed “Proposals for constructing bridge near Georgetown, D. C.”

Bidders are requested to be present at the opening of the bids.
For further instructions see "General instructions for bidders.”
A copy of the act of Congress referred to is appended for further information.

Abstract of proposals for free bridge across l'otomao River about 500 feet abore 1 queduct Bridge, opened Saturday, October 29, 1881, at 12 m.

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1

Not stated..

Charles H. Bliss & Co* Washington, D. C. Similar and equal to Ana

costia Bridge.

(1)

(t)

(+)

$183, 600

Abstract of proposals for free bridge across the Potomac River at the Three Sisters," opened Saturday, October 29, 1881, at 12 m.

10,000 to

13,400

8,000

20

$36, 000 $100,000 $4,000

$140,000

1 Corrugated Metal East Berlin, Conn. Piers of masonry founded on

73

pounds 12,500 to Company. solid rock. Superstructure, average.

16,000
parabolic truss of wrought-
iron, with pin connections.
Spans 150 to 300 feet. Deck

bridge.
2 King Iron Buidge and Cleveland, Ohio... Superstructure, a wrought- 60 to 80

12, 500
Manufacturing Com-

iron parallel chord, Pratt pounds.
pany.

truss, spans 100 to 300 feet.

Deck bridge. 3 Chas. H. Bliss & Coll - Washington, D.C. Similar and equal to Ana Not stated (t)

costia Bridge.

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* Proposals not accompanied by bond or detailed specifications, and plans informal. Not stated. for approaches. || Proposals not accompanied by bond or plans, and specifications informal.

Same as Aqueduct Bridge.

No bid for piers and abutments nor

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[PUBLIC_No. 38. ] AN ACT to authorize the construction of a bridge across the Potomac River at or near Georgetown in

the District of Columbia, and for other purposes. Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled, That the Secretary of War be, and he is hereby, authorized and directed to cause to be constructed across the Potomac River, at or near Georgetown in the District of Columbia, at such point as he may select, a substantial iron and masonry bridge, with approaches; and the sum of one hundred and forty thousand dollars be, and the same is hereby, appropriated, out of any money in the Treasury not otherwise appropriated, for the construction of said bridge and approaches, the same to be maintained as a free bridge for travel.

[1] Provided, That the said Secretary of War shall construct a bridge upon such plan as shall cost no more than the amount herein appropriated, and which cost shall include the construction of a substantial bridge over the canal, and any and all approaches to the said iron bridge; and no part of this appropriation shall be paid out of the Treasury until contracts shall have been entered into with responsible parties, and with good and sufficient sureties to be approved by the Secretary of War, for the construction and completion of said bridge, including the masonry, iron-work, and approaches, at a cost not to exceed one hundred and forty thousand dollars.

[2] and provided also, That a draw of sufticient width to permit the free passage of vessels navigating that part of the Potomac River shall be constructed in said bridge unless said bridge shall be constructed npon or by the side of, or up the river from, the present aqueduct and at the same or greater elevation above the water.

[3] And provided also, That the sun which may be expended under this act shall be treated and regarded as a part of the general expenses of the District of Columbia, and the United States shall be credited with the amount which it may pay under this act for the erection of said bridge upon its fifty per centum of the expenses of the District of Columbia, as provided in the act of June eleventh, eighteen hundred and seventy-eight, entitled "An act providing a permanent form of government for the District of Columbia."

[4] Provided further, That the Secretary of War shall, as soon as may be, fix and determine the location of said bridge, and cause a survey of the river to be made at such place or location, determine the length, width, and height of said bridge, and the length of draw, if one is required, and thereupon advertise for plans and price for the construction of such bridge; such advertisement to be inserted in one or more daily newspapers published in Washington, District of Columbia, New York, Cleve. land, Ohio, Detroit, Michigan, Philadelphia, Pennsylvania, and Chicago, Illinois, for the space of one week.

SEC. 2. That for the purpose of establishing a free bridge, and in lieu of erecting the bridge provided for in the preceding section, the Secretary of War may, in his discretion, purchase the aqueduct bridge now crossing the Potomac River at Georgetown

[5] Prorided, said bridge with all the appurtevances, rights and franchises connected therewith including piers and real estate for abutments and approaches can be purchased for a sum not exceeding eighty-five thousand dollars; which sum or so much thereof as may be necessary may be paid out of the money appropriated by this act.

[6] Provided further, That a good and sufficient title thereto can be secured to the United States, to be approved by the Attorney-General of the United States.

[7] It is further prorided, That the Alexandria Canal Company or its present lessees shall have the right to maintain at their own cost and expense, a canal aqueduct of the same width and depth as the one now in use, and to attach it to or suspend it from said bridge; and whenever a permanent bridge shall be erected upon said site, the same shall be of sufficient strength to sustain the weight of such canal aqueduct; but the construction attachment and maintenance of such aqueduct shall be such as the Secretary of War may determine and shall be without cost or liability to the United States or the District of Columbia.

[8] And it is further prorided, That if upon the erection of such permanent bridge the said canal company or their present lessees shall neglect or refuse to reconstruct secure and attach the said aqueduct at their own expense, or if at any time for the space of six months, they shall fail to use such aqueduct for the purposes of a canal, or fail to keep the same in good condition and repair, or if at any time, they shall use the same for other than canal purposes, then all rights of said canal company, its lessees or assigns in said bridge and property, shall cease and determine, and the said aqueduct shall be detached and removed by the Secretary of War.

SEC. 3. And the Secretary of War is further authorized, in his discretion, in the event of said purchase, to repair the wooden bridge nowon said piers, and for that purpose is authorized to expend, of the moneys hereinbefore appropriated, a sum not exceeding ten thousand dollars.

Approved February 23, 1881.

REPORT OF MR. S. T. ABERT, UNITED STATES CIVIL ENGINEER, OF

FEBRUARY 27, 1882.

UNITED STATES ENGINEER OFFICE,

Washington, D. C., February 27, 1882. GENERAL: I have the honor to submit herewith the following report upon the modified plans of the Corrugated Metal Company for the construction of the free bridge across the Potomac River at the Three Sisters, near Georgetown, D. C., referred to me by your indorsement of December 20, 1881:

The preparation of this report was unavoidably delayed by reason of the fact that at the time of the receipt of the papers relating to this subject I was engaged in the completion of my report upon the proposed improvement of the barbors of Washington and Georgetown, D. C., which was needed for immediate consideration. As soon as this report was completed the subject of the bridge was taken up. As several modifications of the original plans and specifications had been made, it seemed to be essential, in order to avoid any misunderstanding in the case of the award of a contract, to prepare a complete specification for substructure and superstructure, embodying these various modifications and other provisions which had been omitted, but which were required to make the specifications complete.

These specifications (a copy of which is herewith inclosed), inclosure A were sent to the Corrugated Metal Company on January 31, with the request that they would state whether they would accept them as a basis for a contract, but owing to the illness of Mr. Jarvis, the chief engineer of the company, no reply was received until February 13. The reply made by Mr. W.0. Douglas, agent, is herewith inclosed-Inclosure B.

Referring in detail to the various propositions of the Corrugated Metal Company, I would report as follows:

1. Foundations. In the letter addressed to the Chief of Engineers by the Corrugated Metal Company on December 19 they call attention to the crib foundation shown in Trautwine's Handbook, and ask that they be allowed to construct the piers of the bridge on such foundations. On the 27th of December I addressed a letter to the company inquiring whether this was intended as a substitute for the foundations built by coffer-dam on solid rock. The agent of the company, Mr. Douglas, replied that in case the crib foundations were not accepted the company would still adhere to the original plan of foundations of masonry built in a coffer-dam and starting at the solid rock.

The crib foundations would manifestly be inadequate to give the proper strength and security to the structure, and I would respectfully recommend that this proposition be declined and that the foundations be built by means of a coffer-dam, the masonry starting from the sol a mock as originally proposed, and as provided in the new specifications inclosed. 2. Strains on the iron.—The unit strains on the iron proposed by the Corrugated Metal Company are as follows: For tensile strains, 10,000 pounds per square inch. For sbearing strains, 7,500 pounds per square inch. For compressive strains as per table on page 124, volume IV, of Transactions of American Society of Civil Engineers. An addition should, however, be made to the table of compressive strains, in order to make it complete, as in the report, as follows: When one end is square and the other end rounded, a mean is to be taken between

the two.

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