Document 44: Seattle Regrade

Louis P. Zimmerman, "The Seattle Regrade, With Particular Reference to the Jackson St. Section,"
Engineering News
60:20 (12 November 1908): 509-11.

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By Louis P. Zimmerman*

Seattle, Wash., is confronted with an immense problem that is and must be solved in order that the city may continue to flourish and grow. This problem consists briefly in regrading and leveling the hilly streets and adjacent property on which the city is built.

Commercially, Seattle has every advantage. Here terminate the transcontinental railway systems of the Pacific Northwest; here are the terminal wharves of the steamship lines running to Alaska, the Asiatic ports, the west coast of South America, the Pacific Islands and Canada; and here is found cheap and convenient transportation between many growing towns on the numerous islands and natural harbors of the Puget Sound country.

Seattle fronts on Elliott Bay, a branch of Puget Sound, which forms an extensive deep-water harbor protected from storms, and accessible to the largest vessels afloat, at all times and at all stages of tide. On the east side is Lake Washington, a body of fresh water twenty-five miles long, from two to four miles wide and of great depth. Lake Union and Green Lake, smaller fresh water bodies, lie wholly within the city limits. The surface of the city is hilly, consisting principally of long ridges, which rise to an elevation of about 300 ft. above the level of the sound, with a few higher butters.

These long, hill ridges present a problem to Seattle, the magnitude of which has seldom or never been equaled in any city of the world. To accommodate the great, growing business districts of the city, new ground areas must be produced, with a maximum grade so low that the retail traffic can be moved by teams without exhaustive effort. To get these areas Seattle is carrying out the most extensive regrade of any city in the country. Whole sections are being cut down from 10 to 100 ft., and new blocks are being built up on the hitherto worthless tide flats.

Steam shovels, cars and wagons were so inadequate for this project that, except in special cases, they were not considered. Water, both fresh and salt, is unlimited here in quantity. Hydraulic sluicing was adopted to level Seattle's hills and convert almost worthless buttes into valuable property. Two methods of disposing of the vast amount of earth presented themselves. One, was to waste it into the sound; the other, to sluice it onto the tide flats.

The regrade work in Seattle may be divided into three large and three small areas. The ultimate aim is to level the entire business and abutting sections. . . .

Considerable difficulty was found in laying the pipe. As laid, it passes under two heavy traffic streets, two street car tracks and several railroad tracks. For a considerable distance over the tide flats it is supported on blocks or suspended from the bridges. Although salt water is obtainable in any quantity and is more effective than fresh water, due to its greater specific gravity, there is the objection of the water foaming and air bubbles being carried in, thus reducing the effective area of the pipe. Four branches lead from this line to four giant cast-iron nozzles, varying in effective diameter from 2.5 to 4 ins. Each giant is mounted on a reducer and a ball and socket joint, so that a sweep of a full circle can be obtained. The nozzles are fitted with handles at the nozzle end, and with a board and box counterweight by means of which adjustment can be made in any direction and at almost any angle.

The operators of these nozzles have all seen service sluicing in Alaska. The streams are directed only toward the bottom strata and worked to within a foot of the final grade (see Fig. 2 and view on p. 509). This leaves little surfacing to be done by hand. The soil in being undermined works well together, lubricating itself fairly well under the guidance of a skillful operator. About 60% is blue clay. The yellow clay, loam and sand wash away fairly easily, but the lower strata of hardpan or blue clay requires blasting. In shooting, the clay carries the concussions along the strata and people living on the other side of the hill complain, while those directly above are not affected. Gravel is the hardest to handle. The fine sand washes out and leaves the heavier gravel. This and occasional boulders are disposed of to builders and contractors who haul them away in wagons. . . .

With the disposal of this immense amount of material and the work on the tide flats, several problems of exceptional engineering interest are encountered. This district is covered with places of business, access to which must be provided by temporary bridges, built on piles and moved as required. New streets are constantly being laid out in the filled tide lands. . . .

The problem of sanitation and sewage disposal is important because the district is thickly settled. The people living in the district regraded have the choice of tearing down their houses or moving them off, , either of which entails crowded and unnatural conditions. On the adjoining streets and lots houses are crowded together and temporary sewage disposal becomes necessary. This is well effected by means of 1 x 1-ft. box sewers 3 [?] feet underground, leading to the tide flats. These wooden boxes are buried beneath the fill and permanent brick sewers will be installed after the work has been finished. The temporary sewers are suspended under the traffic bridges or placed on piles, and have uprights so that a higher level connection can be made into them, after the filling is completed, and before the permanent sewers are finished. The temporary sewers are put in by the contractors at 75 cts. per lin. ft.

One very striking and beneficial effect has been the cleaning up of the district in which the work is going on. Before, the buildings were all on the low, wet grounds adjoining the tide flats. At high tide they were soaked , and the result was a dirty, filthy region that naturally became the immoral center of Seattle. Since the regrade began, the buildings have been raised from 20 to 40 ft., are now on piles and have plenty of dry air around them. House moving has developed into an important business. The cost is often excessive, in some cases more than the building is worth. A three-story frame building, 60 x 120 ft. in plan, can be raised 40 ft. and blocked for about $2,000. . . .

This gigantic work so carefully laid out and so faithfully being carried out by R. H. Thomson, M. Am. Soc. C. E., who has been city engineer for sixteen years, will lay the foundations to make Seattle one of the greatest cities in the United States.

*302 Pioneer Building, Seattle, Wash.

Center for the Study of the Pacific Northwest