During the next season, 1872, the water of the river continued remarkably high through the whole summer, so as to render it impracticable to determine to what extent the bars have been benefited by the work done. The extensive improvements around Enfield Rapids which have been proposed would scarcely appear to be warranted, unless the river below could be made navigable for boats of greater draught than at the present time, or the proposed canal continued down to the deep water at Hartford. The present survey has therefore been made to ascertain the cost of continuing the proposed canal around Enfield Rapids down to Hartford. SURVEY. The field-work was commenced about the 1st of November, 1872, and was mostly completed by January 1, 1873. The surveying party consisted of Mr. Charles L. Burdett, civil engineer, principal assistant; Mr. Norman W. Eayrs and Mr. Luther W. Burt, sub-assistants; Oliver Deming, rodman; George W. Newton and Frederick B. Lathrop, chainmen; Wilmot Horton, axman; George V. Wilson and Donald G. Mitchell, flagmen. A line of survey was run from near the railroad-bridge at Warehouse Point, upon the easterly side of the Connecticut, down to the mouth of the Hockanum River, in East Hartford. The line generally follows the side-hill, which limits the meadow overflowed in freshets. This line is very direct, and uncommonly favorable for such a work. The route was carefully leveled over, and the levels compared with bench-marks, the heights of which were determined when taking levels from Hartford to Enfield Rapids for the previous surveys. The total difference of the two lines of levels from the bench-mark on the east abutment of the railroad-bridge at Warehouse Point to the bench-mark on the foundation of house corner of Warwarm avenue and Van Dyke avenue, in Hartford, a distance of about fourteen and one-half miles by the line run, was only .014 foot; and the greatest amount of difference in the comparison of intermediate benches was .030 foot at Scantic River. At about 500 feet distances apart, taken usually at characteristic points, cross-sections were leveled over to aid in making an approximate location of the canal. The side-hill along which the survey was made being in many places irregular and quite steep, a very close approximation to a location by the preliminary line was impracticable without consuming time unnecessarily. From a study of the cross-sections a line of approximate location has been placed upon the map accompanying this report, which, it is believed, is nearly upon the best ground. The character of the side-hill is such that in most places a slight alteration of the position of the center line of the canal will greatly affect the amount of work, and a careful location will make a large part of the work only side-hill excavation, or cutting upon one side and embankment upon the other. The estimated quantities, therefore, of cutting and filling will probably exceed the actual amount required in a final location, and will probably be sufficient to cover all contingencies in the execution of the work. GENERAL DESCRIPTION OF THE ROUTE. The previously proposed canal around Enfield Rapids turned into the river at Warehouse Point, reaching the low-water level by means of three locks. The route at present proposed dispenses with the locks at Warehouse Point, and keeps back from the river-road, leaving the formerly proposed route at the cross-street which passes by the American Hotel and running farther from the bank than the old line, as it is not necessary to reach the river at this place; the object of the change being to keep off the ground covered by freshets. About a mile below Warehouse Point is a rocky point called Red Hill, around which the line passes close to the river. This will probably be the best location, although a perfectly feasible route can be obtained on the flat ground east of the hill. This would necessitate a long cut in which it is probable solid rock will be found. It would, however, be a matter for future determination before a final location should be made. After passing Red Hill, the line follows along the side-hill nearly all the way to the terminus at the Hockanum River in East Hartford. It keeps near the Connecticut River down as far as Prior's Creek, where it diverges to the left and runs at a distance varying from 2,000 to 4,000 feet from it to the lower end. The line is generally outside of the highway up and down the river on the east side, and crosses very few important roads. Those that are crossed are mostly farm-roads to the meadows bordering on the river, which are used only at certain seasons to get in the crops. Narrow swing-bridges at these points that can be left open most of the time, are all that will be required. Some of these roads can be abandoned, or two roads turned over one bridge. The roads that will require heavier and wider bridges are, the main road near Red Hill, the Connecticut River Quarry Company's Railroad, the road to Bissell's Ferry near the Scantic River, and three roads in East Hartford. These will all require permanent structures with draws, and will be at or near the grade of the tow-path of the proposed canal. Very few streams of any importance are crossed. The Seantic River is the largest, and the Podunk River next in size. The others are all small streams. It is proposed to carry them all under the canal by suitable arches and culverts. At the lower end of the canal, for about a mile, the line runs across a nearly level meadow, and out upon a point or spur which reaches nearly to the bank of the Hockanum River, thereby keeping up the grade of the canal until it reaches the point for descending by locks to the level of the river. This seems to be the most feasible place for entering the Connecticut, although somewhat below the most desirable point, opposite Hartford. There appears, however, to be no point on the river above which admits of the entrance of the canal. Above the toll-bridge the river channel is shallow and obstructed by bars, and the bridge has no suitable draw, the existing one being only 17 feet in the clear, and not in working order. Below the bridge, where the navigable water begins, the eastern bank is low, and has an extensive shoal extending half across the river. The meadows are low and overflowed in freshets to a distance of about 4,000 feet from the ordinary river-bank. Carrying the canal across these flats at a high level would be impracticable on account of the expense and the contraction of the water-way of the river, and dropping down by locks to the level of the meadow would submerge the canal and render its navigation impossible whenever there was a high freshet. The point near the Hockanum River, above mentioned, offers a situation protected from the ice and freshets, and gives a good entrance to the canal through the lower part of the Hockanum. The banks are wooded and well defined, and this stream can be entered in any navigable stage of the Connecticut River. The locks can be placed as near together as is desirable so as to reduce the part of the canal submerged in freshets to a minimum. The Hockanum is at the present time navigable up to the point where it is proposed to enter it with the canal; but it is proposed to deepen, widen, and straighten the channel out to the Connecticut River, as shown on the map, so as to make a free entrance to the canal. This would forin a basin where vessels could lie while awaiting a passage through the locks, and would afford a safe harbor for wintering, protected from the ice. SLOPE AND AMOUNT OF WATER REQUIRED. The question whether this canal will be for navigation only, or whether the water will be used for manufacturing purposes also, will materially affect its location and slope. An inclination of the water-surface sufficient only for the waste and lockage is undoubtedly the best for navigation; the current will be slower, and the amount of water required to supply the canal and maintain the slope will be a minimum. If it is desired to have a sufficient amount of water to supply power for manufacturing purposes, a much greater inclination will have to be given to the surface, which will not be so favorable for navigation on account of the increased current in the canal. It also has the disadvantage of requiring a large supply of water at all times to maintain the height at the upper end of the canal. The amount of fall required in the whole length, from Enfield to Hartford, for navigation only, would be about 1.75 feet; while to carry half the water in the river at low-water would take about 7 feet fall between the same points. This difference would materially alter the position of the best location at the lower end. As there is already a canal upon the west side of the river from Enfield Dam down to the village of Windsor Locks, which now supplies a valuable and important manufacturing interest, it is very doubtful if more than half the water at low stages of the river could rightfully be diverted to the east side. On account of this complication with the franchise of the Connecticut River Company, and the somewhat better location for navigation that can be obtained with the less slope, the plan of improvement is made for the purposes of navigation only. If the work should be executed, the location can be made for either navigation alone or for the additional purpose of a water-power, as may then be thought best. It is believed that the cost would not materially differ in the two cases. The amount of water required in the canal for the purposes of navigation will be about as follows: Cubic feet per second. 200 168 3 371 This allows a lockful of water every ten minutes, a filtration and leakage of 10 cubic feet per second per mile, and an evaporation of .02 foot in twenty-four hours. The amount lost by filtration would probably much exceed the above during the first season, but after a certain time the deposit of mud upon the bottom and sides of the canal would greatly diminish the loss from this cause. The slope assumed for the surface of the water is .00002 of the length, or very nearly 14 inches in a mile. This is a somewhat greater inclination than would be required to supply the quantity of water necessary for navigation, and allows for all contingencies and obstructions in the head of the canal. It would give a mean velocity of about 1.2 feet per second in a straight and smooth channel of the section proposed, or a discharge of 1,620 cubie feet per second. In the proposed canal, however, there will be the usual obstructions to the flow of water, resulting from the accidental irregularities of construction, the abutments and piers for road-bridges that may be placed within the water-line, and especially the resistance offered by aquatic plants. These, with the small loss of head due to curves, will probably reduce the mean velocity to about .75 foot per second, or a discharge of 990 cubic feet per second. The canal of the Connecticut River Company has been very much obstructed by eelgrass, which grows abundantly upon the sides and bottom-so much so that a special floating steam mowing-machine has been provided to cut it at intervals. An examination of their canal shows that this grass grows to a depth of about 9 feet. The proposed canal being 10 feet deep, it is thought it will not prove so troublesome. Whether this grass is peculiar to the locality, I am not aware. The slope of the canal has been assumed in excess of the probable requirements of navigation to provide for all contingencies, and if found more than is requisite, the total amount is so small, viz, 1.75 feet in the whole length of the canal from Enfield Dam to East Hartford, that it can be varied to the desired extent by allowing the water to rise at the lower end and fall at the upper, even to becoming level, without damage to the canal. DIMENSIONS OF THE CANAL. The length of that part of the canal around Enfield Rapids which is embraced in the present plan is 23,000 feet, or 4.36 miles. The length, as stated in report of January 10, 1872, was 4.83 miles, but the changes at the lower end and the abandonment of the locks at Warehouse Point, consequent upon the continuation down the river, shorten it about half a mile. The length of the extension at present proposed, from its junction with the previous survey in the village of Warehouse Point to its entrance into the Hockanum River, is 65,700 feet, or 12.44 miles. About 1,800 feet of this at the lower end is occupied by the locks and intermediate reaches. The whole length of the canal, from the Enfield Dam to the Hockanum, is therefore 16.80 miles. That portion of the Hockanum River which it is proposed to dredge ont is about 2,800 feet in length. This is to be deepened to 8 feet below the lowest water, and to have a bottom width of 150 feet, with slopes of 14 horizontal to 1 vertical. It is proposed to make the canal 150 feet wide at the water-line and 10 feet deep. The slopes of the excavations and embankments are estimated at 14 horizontal to 1 vertical. This slope may be somewhat varied in the execution of the work if different materials are encountered than appears upon the surface. Upon the embankments the tow-path is intended to be 2 feet above the surface of the water and 10 feet wide. In the cuttings a berm of 20 feet is allowed at the towpath on each side. This is for the purpose of allowing room for ditches and a short space, with a flatter slope than that named above, at the foot of the main slope and at the water's edge. LOCKS. The locks of the canal would all be at the lower end, except the guard-lock at the upper end, as proposed for the canal around Enfield Rapids in my previous report. The total fall from the level of the lower end of the canal to low-water in the river would be 37.5 feet. It is proposed to arrange this in three lifts, the two upper ones to be 11.5 feet each, and the lower one 14.5 feet. This is done so as to make the lifts about equal at the ordinary summer level of the river. It is intended to make the locks 50 feet wide and 200 feet in length, the same as was proposed for the canal around Enfield Rapids. They are to have 8 feet depth of water upon the miter-sills. This will permit the passage of any boats that would be likely to navigate the Connecticut River above Enfield Rapids. The masonry of the gate-chambers, quoins, miter-sills, and coping is intended to be of cut granite, with the side walls and backing of coursed rubble, all laid in hydraulie cement and grouted. The lock-gates are supposed to be of the ordinary construction, with white-oak timbers and pine sheathing, and to be opened and closed by capstans. BRIDGES. It is proposed to make the faces of the abutments of the bridges in line with the sides of the bottom of the canal, or 120 feet apart, and to place a circular pier in the middle of the water-way, so as to allow a swing-bridge with clear openings of at least 50 feet on each side of the central pier to span the whole canal. The abutments and piers are intended to be of coursed freestone-rubble, with corners and bridge-seats, having cut beds and builds. The bridges are intended to be of iron; those for the main roads 20 feet wide, and those for the farm-crossings 10 feet wide and correspondingly lighter. ARCHES AND CULVERTS. At the crossings of the large streams it is proposed to carry them under the canal through arches, as follows: At the Seantic River, two 20-foot arches. At the Podunk River, one 20-foot arch. At Stoughton's Brook, one 10-foot arch. At Prior's Creek, one 6-foot arch. At Station 103, one 6-foot arch. These arches are to have the abutments, wings, and backing of coursed freestonerubble with cut-stone corners, coping, and arched courses. The smaller streams are carried through the embankment under the canal by box-culverts, varying from 24 to 5 feet opening. WASTE-WEIRS AND RETAINING-WALLS. The masonry of the waste-weirs is to be of rubble with cut corners, similar to that described for the bridge abutments. The retaining-walls at the ends of the locks, and other places where necessary, are to be built of rubble-masonry. MATERIALS. The material encountered in the excavation is mostly a clayey loam, from the village of Warehouse Point down to the Scantic River, a distance of about five miles, after which it becomes more sandy, and for a long distance at the lower end of the route it is almost a pure sand. It is proposed to make the embankments entirely of the material excavated, and to build them up in layers slightly concave, in preference to making puddled walls in the interior, even where the material is entirely sand. The expedi ent of a central puddled wall in an embankment of porous materials has been shown to be of exceedingly doubtful value, and it is believed that the best modern engineering practice is to make the whole embankment of uniform material in the manner proposed. Canals formed even in very porous ground, like coarse gravel, soon become fight from the deposit of silt from the water. The wastage that might occur from filtration during the first year or more, in a canal constructed as proposed, would be of little importance, as there would be an ample supply of water and a sufficient slope to maintain its depth in the canal. The stone for all the rubble-masonry can be obtained in the vicinity. The cut blocks of freestone for the corners and coping, and for the voussoirs of the arches, will probably be best obtained from the quarries at East Windsor, where blocks of any desired size and excellent quality can be procured. The granite used in the locks will have to be brought from Munson, Mass., or Westerly, R. I., at both of which places there are excellent quarries. The latter place is probably the best and easiest of communication. The timber for the lock-gate, weirs, &c., can be best obtained in Vermont and New Hampshire, and brought down by railroad to where it is to be used. It cannot at the present time be rafted down the river from above Holyoke. The iron-work for the bridges and locks can be obtained at Springfield and Hartford, where there are extensive works, and transported by water to near where it is to be used on the river. ALTERATIONS IN THE ENFIELD RAPIDS CANAL. In my report upon the canal around Enfield Rapids of January 10, 1872, a depth of 6 feet upon the miter-sills of the locks was recommended. This was in view of its extending down only as far as the village of Warehouse Point and entering the river at that place. The depth was thus limited, as it was not thought practicable to improve the natural bed of the river between that point and Hartford so as to maintain more than the above-named depth of water in the channel. A greater depth in the canal would likewise make a much greater amount of rock excavation at the head of the canal near the Enfield Dam, and also at the foot, where it enters the river at Warehouse Point. If the canal is to be continued to Hartford, I would recommend that the upper part be made of the same depth as is now proposed for the lower part, viz, 8 feet deep upon the miter-sills, and the canal 10 feet deep. A great part of the previously proposed canal is embanked from the river-bed and is sufficiently deep. A little extra work will be required in the cuttings and in the rock excavation at the upper end. The rock at the lower end will be avoided. These additions will be made to the estimate. There will also be required a little more masonry in the guard-lock, aud some extra work on the gates, which is also provided for in the estimate. The alterations at the lower end will save some work, which becomes unnecessary on account of commencing the new canal about half a mile back from the terminus of the old survey; viz, the excavation from the point of junction to the river; the rock excavation in the bed of the river to make a channel from the lower lock out to the riverchannel; also the masonry, puddling, and gates in the three locks. These are deducted in making the total estimates for the whole length of the canal. Estimate from Warehouse Point to Hartford. 1,862,000 cubic yards earth excavation, at 30 cents per yard..... 98,000 cubic yards dredging in Hockanum River, at 40 cents per yard 6 pairs lock-gates 3 waste-weirs. Superstructure for 6 swing road-bridges. Superstructure for 6 swing farm-bridges.. $558, 600 5,658 39, 200 3,750 14,400 45, 960 13, 900 40, 440 13,900 40, 440 45,990 1.600 54,900 4.480 31, 200 640 2,400 32.600 20,000 13,500 19,000 1.500 48.000 28,800 Coffer-dams, &c..... Land damages, twelve and a half miles, at $20,000 per mile Total...... 6,000 250,000 133, 686 1, 470, 544 Additional cost in canal around Enfield Rapids, 10 feet deep and 8 feet on miter-sills of locks. 5,500 cubic yards rock excavation above dam, at $5. Amount saved from former estimate for canal around Enfield Rapids by alteration. 2,500 cubic yards earth excavation, at 35 cents... 5,500 cubic yards rock excavation, at $5.. ... 1,935 cubic yards cut-stone masonry in locks, at $20. 1,500 cubic yards concrete, at $5.. 1,200 cubic yards clay puddling, at $1.50 . 6 pair lock-gates Total.... 1,800 16, 875 217,0 .045 |