The contract was awarded to P. W. Myers, of Stamford, Connecticut, for all but the removal of Drew's Rock, which it was thought best not to attempt with the present appropriation.

Mr. Myers commenced work in dredging on Drew's Bar in July, and has continued at work since. The wing-dam at Sow and Pigs Reef will be commenced in September.

I recommend an additional appropriation of $15,000 to continue the improvement and make a thorough survey at the mouth.

The Housatonic River is the boundary between New Haven and the Fairfield collection district.

The revenue collected during the fiscal year ending June 30, 1871, was, at New Haven $349,726 76, and at Bridgeport, in the other district, $7,193 96. Bridgeport is the nearest port of entry.

I have annexed hereto my report made last January upon the survey of the river, to which I have added the tide observation at Stratford and Derby. Mr. Edwards's report does not describe the bench-marks to which this mean level has been referred, but it is my design to have a permanent mark made, if it has not already been done, so that this level can hereafter be readily found.

Record of tide observations at Stratford and Derby, on the Housatonic River, Connecticut,

made in 1870.

T 14.

ENGINEER OFFICE, UNITED STATES ARMY, Newport, Rhode Island, January 23, 1871. GENERAL: I have the honor to submit the following report, with maps, of the "survey of the Housatonic River below Derby," authorized by section 2 of the act making appropriations for rivers and barbors, approved July 11, 1870.

The Housatonic River from Derby to the outer bar is thirteen miles long.

A special report on the general character and capacities for commerce of this river was made to you by Major D. C. Houston, brevet colonel, January 8, 1870, printed in H. Ex. Doc. No. 62, second session Fortyfirst Congress. In that it is estimated that a thorough survey of the river below Derby would cost $5,000. The amount allowed to me for all the surveys I had to make (though a liberal one, considering the amount of the appropriation from which it was taken, and the great number of surveys expected to be made with it) was at first but $6,000, and, in making a due apportionment to the different surveys intrusted to me, I found that $2,000 was all that I could spare to the survey of the Housatonic River. A preliminary examination by General Theodore G. Ellis, civil engineer, designated the points to which the survey should be confined, and it was placed in charge of Mr. W. S. Edwards, civil engineer, formerly an assistant on the United States Coast Survey. His report, dated January 1, 1871, and maps, in three sheets, on a scale of 24 inches to the mile, are transmitted herewith, and made a part of my report. He made detailed surveys at the Sow and Pigs-Reef, TwoMile Island, Crofut's Bar, Drew's Rock and Bar, and Mill Bar and Rock. His report is clear and brief, and I refer to it for information with regard to these localities. His estimate for improving the river so as to secure a draught of 7 feet at mean low water is $24,486, which I approve. The above surveys and plans of improvement were directed with a view to meeting the wants of the case as presented in Colonel Houston's report on January 8, 1870, already referred to, and quoted in your report, January 14, 1870, to wit:

The river is now considered navigable for vessels drawing 7 feet, i. e., by taking advantage of the tides; but, owing to the variation between the times of high water between Derby and the mouth, (by our survey in 1870, one hour,) delays are experienced in crossing the upper bars. It is considered that if the depth of water on the upper bars can be increased, a great improvement would be made, even if the lower bar should remain untouched. It may be found, however, after a detailed examination that the latter admits of improvement.

Mr. Edwards made an estimate that it would require about $700 to make a proper survey of the mouth of the river, and on this representation to you the additional allowance was made to me. It came however so late that it was not practicable to present the result of such survey to Congress at this session, and the season had become very unfavorable to such work. I, however, had some soundings and measurements made by Mr. Edwards at an expense of $115, which have just reached me in time to be available for this report.

The result of this examination is shown in red on the accompanying copy of the United States Coast Survey of the Housatonic below Derby made in 1837. This map also has the location of the three sheets of detailed survey made by Mr. Edwards the past year.

It will be seen by examining this map that considerable changes have taken place at the mouth since 1837. The sand-spit on the east side of

the harbor has lengthened like all others that I have examined. A new outlet has been formed near this east side sand-spit, and a portion of the land formerly dry at low water has been washed away near the main entrance, as has also a small low-water island formerly in the main channel.

But the depth of the water on the bar is substantially the same, viz, 3 to 4 feet at low water, according to the kind of tide, thus showing that this depth is the result of certain forces not materially modified by any natural changes in the form of the outlet.

I am, therefore, firmly of the opinion that, unless we change the operations of these natural forces by artificial barriers to the action of the

waves, there is but little hope of any improvement by dredging, and I regard it as an essential preliminary to dredging at the mouth to build a breakwater there, however expensive this latter may be.

My plan is to close up the new outlet and build a sea-wall from the sand spit on the east side out to the line of lowest water, a distance of 2,100 feet. This wall to be 8 feet wide on top, 14 feet wide at mean low-water level, and to rise 12 feet above mean low water. It is to be built of large blocks of rubble-stone, except the top course, which must be of single stone, 2 feet thick, 8 feet long, clamped together, and the bottom course, which must be made of stone so long that two of them shall reach entirely across the bottom.

To fill the new outlet
with riprap and brush,
540 cubic yards, at $5
To build the wall, 12,800
cubic yards, at $10...

$2,700

128, 000

130, 700

From extreme low-water line out to the 6-foot curve, a distance of 2,100 feet, I would build a breakwater on the following plan, being the same I have recommended for Bridgeport and Port Jefferson Harbors.

Section of breakwater. Spring tides rise 9 feet above mean low water. The top of the wall to rise 2 feet above high water of spring tides.

Wall to be 6 feet wide on top; batter 4 upon 1, down to 12 feet above low water; to be composed of granite blocks of from 2 to 4 cubic yards

783

each, of a thickness from 18 inches to 2 feet; to be doweled throughout with gun-metal dowels, and top course securely clamped with wrought iron of suitable size, (cost, say, $25 per yard.)

This wall to rest on a bed formed by throwing in large irregular blocks of stone of not less than 14 tons weight, having a slope seaward of one upon three, and shoreward one upon one, and to be 15 feet wide on top at level of mean low water. This foundation to be brought to even surface by small angular stones, and paved on the sea slope with large granite blocks 14 feet thick, and not less than 2 tons weight, clamped with wrought iron. The foot of the paved to be protected by large riprap stone, same as for the body of the breakwater; to contain about 4 cubic yards per lineal yard of breakwater. All the riprap to cost, say, $6 per yard, the pavement, $25 per yard.

The above wall is proportioned so as to be about the same cost as a rough breakwater would be made of the same height, namely, 11 feet. As the height increases, there is a great saving in combining them as I have.

This particular form is adapted as the basis of calculation. It may be modified in practice as may be necessary. The body of the work may not need paving.

From the experience with the sea-wall at Southport, the thickness of wall adopted will be sufficient to stand the waves of Long Island Sound. The Southport sea-wall is 9 feet above ordinary low water, and it is thought that 2 feet additional height should be given it. That is the reason a height of 11 feet is taken above mean low water for this design. The waves in heavy storms and high tides will break over such wall, but not enough to cause any swell, and if the wall be well built, it will probably stand the shock. However this wall may answer, it is probable that a higher structure of stone should not be adopted.

To build the body of the breakwater, 2,800 cubic yards of large riprap stone, at $6

$16,800

15, 750

To pave the outer slope, if necessary, 630 cubic yards, at $25.. For 1,400 cubic yards riprap at base of outside slope, (if paved,) at $6

To build top wall, 7,875 cubic yards, at $25.

8,400 196, 825

Total for breakwater

237, 775

For dredging to secure depth of 7-foot over the outer bar of a width of 200 feet, 40,000 cubic yards, at 30 cents.

$12,000

Making a total for improving the mouth of the river as fol lows:

For sea-wall from high-water line to low-water line, filling up
uneven places, &c...

For building breakwater out to the 6-foot curve.

For dredging on the outer bar.

Total

$130, 700 237,775 12,000

380, 475