| Wastewater | Deer Island, Boston Harbor - Page 2 |
| Construction begins on Deer Island |
| On Deer Island digging for the first trench across the island began in June of 1890 with the first brick work laid in July. Initially the contractor was able to use the hospital’s wharf to land brick and other supplies on the island, but that privilege was denied when it resulted in delays for the hospital’s own vessels. Landing bricks on the beach using small boats was not efficient and work was quickly started on a new wharf. Delays building it occurred when piles ran into large boulders. |
| Contractors excavating trenches on Deer Island, in some places to a depth of nearly 30 feet deep, had to contend with areas of clay, gravel, and sand. Blasting by powder was used in some areas to loosen the earth. In other areas sea water infiltration required pumps be run continually to keep the trench dry. On flatter sections of the island the contractor was able to use a Carson Trenching Machine. The wharf was completed by February of 1891, the final sections of the sewer pipe on the island by the end of that year. Still to be completed on Deer Island were two of the most difficult to construct portions of the whole project, crossing Shirley Gut, and extending the pipe to the outlet in the harbor. |
| Photographs and artwork from the Fourth Annual Report of the Metropolitan Sewerage Commission - 1893 |
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Shirley Gut at that time was 315 feet wide at mean high tide and 105 feet across at low tide. The depth of water at high tide was 25 feet. The tidal current through it was swift and practically continuous. By the end of 1892 the sewer pipes were completed on both the Winthrop and the Deer Island sides of the Gut, and a decision had been made to connect the two by means of a curved pipe dropped into a trench that was to be dug 12 to 25 feet below the bed of the Gut. Though not mentioned in the Commission’s Annual Reports, other options had been considered. Howard Carson, in an 1893 article he wrote for the MIT publication Technology Review, identified them. One was to drop shafts 70 feet down into the clay on either side and dig a tunnel between them. This was rejected because it would make it difficult to inspect the tunnel at a later date. The other option, and the one preferred by Carson, was to fill the Gut and make a permanent causeway across allowing the sewer pipe to be on a straight grade. Nautical interests objected, and it was thought that required approvals by federal and state officials would take too long and might be rejected. It would be not long after Carson’s death in 1931 that a storm would close Shirley Gut and then a causeway would be built across. |
| The already completed sewer pipes on either side of Shirley Gut were 9 feet in diameter and like all except smaller diameter connecting pipes, made of brick, at this point, three layers thick. Concrete was widely used, often as a base or invert for the bottom half of the sewer pipes, but this was before concrete-only pipes were in common use (Carson would use all-concrete construction in the Blue Line tunnel completed in 1904). The pipe under Shirley Gut was unique in that it was the only section in the whole system where steel was used. Not as a main structural element, instead as a shell to ensure the strength and tightness of the two layers of bricks laid inside. Construction of crossing involved blocking all water flowing through the Gut with a coffer dam, digging a trench up to 18 feet deep below its bed, constructing two manhole and four 250,000 lb. curved pipe sections on land, dragging them into the water, floating and dropping them into position. In the spring of 1894, after all connections were made and checked to ensure that pipe was water-tight, the trench was backfilled to restore the Gut to its previous condition. It would be one of the first used in the United States of an immersed tube for tunnel.Detailed descriptions of the work and challenges faced appear in the 1893 and 1894 Annual Reports. |
| Photographs from the Fifth Annual Report of the Metropolitan Sewerage Commission - 1894 |
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| Crossing Shirley Gut |
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Photographs from the Bradford Family Collection
The Drew Archival Library of the Duxbury Rural and Historical Society, Duxbury, Mass. |
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Photographs from Historic Point Shirley & Deer Island.
A selection of photos from the book “Photographs Metropolitan Sewerage Works 2” and Old Deer Island. |
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| In spring of 1893 work also had began on the section of sewer pipe that lead to the terminus of North Metropolitan system at the outlet near the Deer Island Beacon. The first part of the almost 2,000-foot section was on dry land before extending into the ocean. Like for the Shirley Gut crossing, a trench was dug inside a coffer dam. But unlike Shirley Gut, where the trench was flooded and pipe sections dropped into it, the trench to the outlet was to be kept dry and the 6-foot masonry pipe constructed on its floor. The pipe across the Belle Isle was constructed this way. Unlike the protected, relatively calm Belle Isle marsh, the sewer pipe to the outlet was in the open ocean. Storms resulted in delays, as did seawater leaking through porous soil underneath the dam’s planking. Multiple pumps were kept running continuously, and only when the trench was dry could masonry work continue. Work ground to a half at the end of 1893 having reached the 600-foot mark. |
| Photographs and artwork from the Fifth Annual Report of the Metropolitan Sewerage Commission - 1894 |
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| Constructing the outfall - 1893 |
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| With the realization that it would be impossible to build a coffer dam that could be kept dry all the way out to the outlet, a new plan was devised. Like the Shirley Gut solution, the decision was made to build the masonry pipes in sections, float them out to the site, then drop them into a pre-dug trench where they would be connected. Instead of using a steel shell, tests were run, and it was determined that pipe sections constructed with 8-inches of brickwork, a 6-inch concrete liner, surrounded by 4-inch spruce lagging supported by white oak hoops, would be satisfactory, and save money. Each section was 52-feet long a weighed 210,000 pounds. There was no beach nearby, so sections were built on the wharf and then floated out to the site in specially constructed cradles. |
| Artwork from the Sixth Annual Report of the Metropolitan Sewerage Commission - 1895 |
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| Constructing the outfall - 1894 |
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| Photographs from the Sixth Annual Report of the Metropolitan Sewerage Commission - 1895 |
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| Constructing the outfall - 1894 |
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| Pipe laying continued through-out the summer of 1894 with the hope that the section would be completed by the end of year. Problems arose when the same strong currents in the area that made the site desirable for the outlet made it difficult to lower the sections accurately. A temporary breakwater was built that solved the problem until a series of storms hit in the fall. Sections of pipe that had been installed but not backfilled broke away. Repairs were made but it wouldn’t be until May of 1895 that the outlet would be completed. |
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