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ADDITIONAL SPECIFICATIONS

For sections advertised for contract July 15th, 1867.

The length of the section stated in the advertisement is the exact length of the wall of masonry designed to be constructed in that locality.

To give stability to the foundation, the rock embankment must extend beyond the end of the wall, and the dredged channel must be continued to the full width and depth thirty-five feet beyond the wall.

The rock embankment will then be filled in, at first to the same height as the adjoining embankment, (one foot above high tide,) the foot of the slope extending to the termination of the bottom of the dredging, and the top being nine feet from the end of the wall.

The embankment will be allowed to settle, and, if necessary, heavy stones will be placed upon it to protect it from being washed away before the adjacent section is constructed.

A deposit of stone four feet in thickness must also be placed along the slope of the earth embankment at its termination, to prevent its displacement by the water. These requirements apply to the termini of all the walls in the sections proposed to be placed under contract, except the end of the wall near Vallejo street.

At this point it will be observed that there is a right angle in the course of the sea wall. The end of the wall will be a continuation of the back of the wall of the adjoining section, which is parallel to Vallejo street.

The dredged channel must be continued to the full width and depth sixteen feet from the end of the wall, and the stone and earth embankment filled in to the centre line of the water front on both Front and Vallejo streets. The culverts on the sections advertised will all be three feet in width and five feet bigh in the clear.

The cost of constructing the brick culverts through the masonry must be included in the contract price for the masonry, and of the framed culverts through the carth embankments, in the contract price for embankment. When bids are made for the entire work per foot lineal, the absolute amount to be paid on the contract will be the price per lineal foot multiplied by the number of feet in length of the wall of masonry, which corresponds for the several sections with the lengths stated in the advertisement. This amount must be considered to include full compensation for the dredging and embankment required beyond the termini of the wall, as described in the preceding specifications, and of all work and materials required for the completion and security of the work proposed to be constructed.

The plans and drawings herein referred to may be seen at the office of William J. Lewis, Engineer, number three hundred and two Montgomery street, room five, fourth story, directly over the office of the Harbor Commissioners.

REPORT OF THADDEUS R. BROOKS,

Civil Engineer.

R E PORT.

SAN FRANCISCO, March 8th, 1866.

TO TIIE Hon. BOARD OF STATE HARBOR COMMISSIONERS :

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GENTLEMEN :- I had the honor of receiving at your hands the appointment as Engineer for making a survey of the water front of this city, extending from the north line of Harrison street to the south line of Chestnut street, indicating the depths (in feet) of water and mud. The surveys, maps, and profiles having been completed, I beg respectfully to make the following report :

The time designated in the contract for the commencement of this work was the fifteenth day of November last; and on that day I commenced with some experiments to determine the most effectual method of making the soundings. In the surveys of this character which I had previously made, I used a sounding rod of gas pipe, three quarters of an inch in diameter; but the great depth of mud along the water front rendered this apparatus entirely inadequate for the purpose. I then decided upon using pipe of one and a half inches in diameter, with à pair of scows and a pile driver, with leaders thirty-five feet long, and a bammer weighing fifteen hundred pounds. An experiment tried with this apparatus before finally commencing work, proved entirely satisfactory; and on the twenty-seventh day of November last, the survey was commenced and steadily prosecuted to its completion

A great deal of delay was necessarily met with, as in even ordinary rough weather no soundings could be taken. The scows were obliged to be firmly anchored or secured to the wharves, before it was safe to commence work. It was tedious and vexatious in very many cases; and to facilitate the work, I employed Mr. Thomas D. Parkinson, a Civil Engineer, as my assistant, whose skill, perseverance, and good judgment, were at all times manifested.

The soundings of the depth of water and mud are taken upon the inner, centre, and outer lines of the water front, each seventy-five feet apart, and also on a line distant about sixty feet from the outer line of the front, which is denominated the “slope line.”. Specimens of the bottom are also submitted for your examination, each one being lettered, and the point where it was obtained indicated on the profiles. A great deal of difficulty was experienced in getting to some of the points where

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