THE IMPROVEMENT OF RIVERS. 



to bring its top to the level of the bottom of the concrete. The price bid per square- 

 yard for this paving must include the cost of furnishing and placing the bed of spalls 

 or gravel upon which it is laid.) 



37. Cement Sidewalk. Ik-foro the completion of the paving a cement walk 3$ 

 feet wide shall be built from the bark of the slope paving to the back of the land-wall, 

 with steps where required. For this walk a trench shall be excavated 12 inches deep 

 below the finished surface of the paving; the bottom shall be well rammed, then cov- 

 ered with spalls or gravel also well rammed, up to 6 inches below the finished grade; 

 this stone or gravel shall then be covered with 4 inches of cement concrete, 

 of the same composition as that in the lock-walls, well rammed and topped with 

 cement mortar, two parts of sand to one of cement, to the required grade, all divided 

 into blocks 3 feet long, and finished in the most approved manner by skilled sidewalk 

 finishers. The sidewalk and steps will be paid for as " Paving," only the horizontal 

 surfaces of the treads being estimated for payment; the layer of broken stone or 

 gravel will not be paid for, but must be included by the contractor in his general price 

 for " Paving." 



28. Puddling. An embankment of heavy moist clay, thoroughly cut, worked, 

 and rammed in 6-inch horizontal layers, shall be placed at the end of and on both 

 sides of the upper wing-wall of the lock, as directed by the Engineer. This clay will 

 be classified as "Puddling." 



FOUNDATIONS. 



29. Changes or Modifications. The character and positions of the proposed foun- 

 dations for the different parts of the work are shown in general on the drawings and 

 cross-sections ; the United States shall have the power to make any changes in the 

 plans of the foundations which, in the judgment of the Engineer, may be consid- 

 ered advisable, after examinations made during or after excavation, and the con- 

 tractor shall have or make no claim against the United States on account of any such 

 changes or modifications, or on account of any increase or decrease in the depth of 

 foundations from those referred to herein or shown on the drawings, other than that 

 for payment for the actual amount of work ordered by the Engineer, and completed 

 at the unit price bid. 



30. Cleaning for Foundations. All rock surfaces for foundations must be freed 

 from loose pieces and be worked down to the firm and solid rock, and be cut out and 

 roughened as required by the Engineer, to give good bond for the masonry. The 

 foundations shall be thoroughly scrubbed and then washed clean by jets of water under 

 heavy pressure before any masonry is laid. Laying masonry will not be permitted 

 on any surface that is not thoroughly clean. Any seams or crevices appearing in the 

 rock must be scraped out and filled to the satisfaction of the Engineer, with concrete 

 or mortar thoroughly rammed or worked in. 



