Abstract of proposals received and opened May 1, 1900, by Maj. D. W. Lockwood, Corps of Engineers, for dredging Block Island

The commerce arriving and leaving Block Island, Rhode Island, by water during the calendar years ending December 31, 1894-1899, is estimated as follows (based mainly upon reports received from local parties):

New transportation companies established during the year, none reported. The vessels entering and leaving this waterway are as follows (each entrance and departure together being counted as one) :

IMPROVEMENT OF GREAT SALT POND, BLOCK ISLAND, RHODE ISLAND.

Block Island is about 12 miles south of Point Judith and 15 miles northeast of Montauk Point; it is about 5 miles long, with an average width of 2 miles; has a population of 1,300, and the valuation of ratable property, as returned by the board of assessors for 1896, was as follows: Real estate, $614,275; personal estate, $114,850; total, $729,125. About midway of the island north and south is a salt-water pond, known as the Great Salt Pond. Its water surface covers 700 acres, about 150 acres of which has a depth of 18 feet and over.

Plan of improvement. The conversion of this pond into a harbor of refuge by making a channel through the sand strip separating it from the sea on the west side of the island was reported against by Maj. D. C. Houston, Corps of Engineers, under date of January 15, 1868, and again by Capt. W. H. Bixby, Corps of Engineers, under date of June 12, 1893, and Col. Henry L. Abbot, Corps of Engineers, under date of June 15, 1893.

The river and harbor act of August, 1894, provided for a survey of "Great Salt Pond, Block Island, with a view to making harbor of refuge therein." The duty of making this survey was assigned to Col. S. M. Mansfield, Corps of Engineers, and his report is dated October 8, 1895. At the time of this survey work was in progress, under appropriations made by the State of

Rhode Island and town of New Shoreham, on a channel connecting the pond with the ocean. Its condition at the time is fully given in the report

of Colonel Mansfield. A jetty 425 feet long had been built, and up to September 1, 1895, 268,038 cubic yards of material had been removed from the cut.

In his report Colonel Mansfield states as follows:

I assume that the channel of entrance should have at least a central depth of 25 feet and be of ample width, and on the accompanying chart I have projected such a channel through the centre 150 feet wide, thence gradually shoaling to 12 feet in a width of 504 feet, and thence to highwater line, with a slope of 1 on 4. The total width at low water will be 600 feet.

The above plan was authorized by Congress in the river and harbor act of June 3, 1896, which contained the following item: "Improving harbor, Great Salt Pond, Block Island, Rhode Island, in accordance with the report of November 29, 1895," which was the date of the letter of the Chief of Engineers transmitting Colonel Mansfield's report to the Secretary of War. Colonel Mansfield estimated the cost of the improvement at $97,567.94 in addition to the amounts appropriated by the State and town, but this estimate did not include revetting the banks through the beach, and the cost of dredging was figured at 10.7 cents per yard, which was the price being paid by the State and town at the time of the survey.

In April, 1899, a survey was made of the locality, and on June 8, 1899, I had the honor to submit a special report with revised estimate of the cost of completion of this project, of which the following is an extract:

The work remaining to be done to complete the project submitted by Colonel Mansfield in 1895, and upon which Congressional action has to be based, is as follows:

North jetty to 12-foot contour, including riprapping through beach. $35,000 Dredging 470,000 cubic yards from channel, at 16 cents per cubic yard....

75,200

But a comparatively small amount of stone has been placed in the north jetty started by the State and town, and on this account, and for the additional reason that the amount of dredging for the 720-foot channel over that required for the 600 feet wide channel would more than offset this, I would recommend that a new north jetty be built, limiting the width of channel to 600 feet.

The dredging that has been done already has not apparently left the bottom even, as a line parallel to the south jetty and almost any distance up to 400 feet from it will show. Bowlders of varying sizes have been encountered, and some of the large ones have been left, so that 12 feet depth can not be carried into the pond generally, except under a competent pilot. *

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In 1895 dredging in this locality cost 10.7 cents per cubic yard, but this was principally inside work. Since then dredging has cost 143 cents per cubic yard, and as the digging gets deeper, clay and bowlders are met with, so that I do not regard 16 cents per cubic yard as too high.

This revised estimate was approved under date of July 20, 1899.

In a report on this harbor dated May 4, 1900, I stated that—

Owing to changes that have taken place since the survey upon which the estimate of cost of completion was based, I do not regard the estimate of June 8, 1899, and which was published in the Annual Report of the Chief of Engineers for that year as reliable.

This statement was based upon changes observed in the general condition of affairs, and particularly those produced by the storm of March 2 and 3 of this year, during a period of exceptionally high tides. The winds varied from NW. to SW. The height of the south jetty is 5 feet above mean high water, and on the occasion mentioned the seas went over the breakwater into the channel and across the beach sufficiently to partially undermine the oil house belonging to the Light-House Establishment and carrying sand into the channel. The giving way of the outer end of the jetty was due to its being undermined, the cut being from 7 to 8 feet in water that was 18 to 19 feet deep when the head of the jetty was completed, while in advance of the jetty the shoaling amounted to from 6 to 8 feet and extended out a distance of 250 feet. There was some shoaling in the channel, but in less degree.

The low-water shore line on south side of south jetty has advanced 190 feet since the survey of April, 1899, was made, and the sand has been raised back of it so that it is now even with the top of the breakwater and is being carried into the channel when the wind is from south around to west. It would appear from the foregoing that it will be necessary within a

short time to prolong the south jetty, and also to raise it or else resort to sand fences to keep the sand out of the channel.

There is no question in my mind but that if the north jetty is built as planned and the jetties are extended by revetments through to the pond, the depth of the channel between them will be maintained by the tidal flow, at least for a long time; trouble, however, is to be anticipated beyond the jetty ends in the ocean and in the pond. Where the openings widen out, the current diminishes rapidly, and such material as has been carried along by it is deposited. In the small harbors on the Cape Cod coast where attempts have been made to deepen and hold a channel by revetments and jetties the results have always been the same. The channels could be deepened and held between the jetties and revetments, but beyond them inside and outside there were crescent shaped bars which materially lessened the navigable depth. In these small harbors the results were accomplished in a comparatively short time. In a case like that at the Salt Pond, where the depths are greater, deterioration in depth would be slower on account of the large volume and greater force of the tidal flow. There appears to be a movement of sand along the west shore of the island toward the north, as is evidenced by the long sand spit at the north end of the island and the steady advance seaward of the shore line on the south side of the south jetty. Whether this shore line will eventually reach the end of the jetty or not, experience this spring has shown that under certain conditions there is an erosive current around the outer end of the south jetty, and a deposit of sand in advance of it that projects over into the channel way; as a matter of fact, the United States inspector states that to obtain 18 feet depth dredging is necessary 150 feet outside of the 18-foot contour shown on the map of survey of April, 1899. During a southwester the water on the south side and outer end of the south jetty and northward across the channel is discolored with sand.

Dredging in advance of the south jetty can afford but temporary relief, as, owing to the fact that the prevailing winds are from the southwest, there is an almost continual motion of sand along the shore and across the entrance in advance of the jetties.

On the map here with I have indicated an extension to the south jetty amounting to 350 feet and extending over the 14-foot shoal to deep water beyond. The north jetty is shown with an extension of 600 feet beyond what is provided for in the approved project. If extended farther its outer end would catch the drift along the shore.

I am of the opinion that the better plan in the first place would have been to have built the jetties normal to the general trend of the shore in