... When so directed by the Engineer the bottom of the trench shall be excavated to the exact form of the lower half of the sewer or of the foundation under the sewer.
The bottom width of the trench for a brick or concrete sewer shall be ... not less in any case than the overall width of the sewer, as shown on the plans. In case the trench is sheeted this minimum width will be measured between the interior faces of the sheeting as driven, but in no case shall bracing, stringers, or waling strips be left within any portion of the masonry of the sewer except by permission of the Engineer; and such braces, stringers and waling strips shall not, in any case, be allowed to remain within the neat lines of the masonry as shown on the plans. In case that the distance between faces of the sheeting is less than that called for by the width of the sewer to be laid in the trench, the Engineer may direct the sheeting to be drawn and redriven, or otherwise changed and altered; or he may direct that the sewer be reinforced in such manner and to such an extent as he may deem necessary without compensation to the Contractor, even though such narrower trench was not caused by negligence or other fault on the part of the Contractor.
Trenches for vitrified pipe shall be at all points at least six inches wider in the clear on each side than the greatest external width of the sewer, measured over the hubs of the pipe.... Bell holes shall be excavated in the bottoms of trenches for vitrified pipe sewers wherever necessary.
Not more than three hundred feet of trench shall be opened at any one time or place in advance of the completed building of the sewer, unless by written permission of the Engineer and for a distance therein specified....
The excavation of the trench shall be fully completed at least twenty feet in advance of the construction of the invert, unless otherwise ordered.
During the progress of construction the Contractor will be required to preserve from obstruction all fire hydrants and the carriageway on each side of the line of the work.
The streets, cross-walks, and sidewalks shall be kept clean, clear, and free for the passage of carts, wagons, carriages and street or steam railway cars, or pedestrians, unless otherwise authorized by special permission in writing from the Engineer. In all cases a straight and continuous passageway on the sidewalks and over the cross walks of not less than three feet in width shall be preserved free from all obstruction.
Where any cross walk is cut by the trench it shall be temporarily replaced by a timber bridge at least three feet wide, with side railings, at the Contractor’s expense. The placing of planks across the trench without proper means of connection or fastenings, or pipe or other material, or the using of any other makeshift in place of properly constructed bridges, will not be permitted.
This is equally applicable to certain wagon bridges to be fixed upon by the Engineer, on the basis of traffic requirements.
In streets that are important thoroughfares or in narrow streets the material excavated from the first one hundred feet of any opening or from such additional length as may be required, shall upon the order of the Engineer, be removed by the Contractor, as soon as excavated. The material subsequently excavated shall be used to refill the trench where the sewer has been built.