Excavation and backfilling specifications, 10th Ave Tunnel

NYC 9/11 Public Portal Document

3. In earth areas, excavate so that foundation^nd base slabs bear on 'I undisturbed subgrade. F. Unsuitable Subgrades: 1. If unsuitable materials are encountered at the design subgrades, the Engineer may authorize the removal of such unsuitable materials and I replacement with suitable compacted fill or with concrete. 3.07 ROCK EXCAVATION A. Where rock is encountered, expose the rock surface and notify the Engineer rI so that rock surfaces may be surveyed and cross-sectioned if required bythe. Engineer. /i B. Excavate in rock strata to lines and grades shown on Drawings. Use line ■y drilling at locations indicated on Drawings. Line drilling shall consist ofj 2 inch diameter holes at 6 inches on center drilled to required sUbgrade j h' level; No explosives shall be placed in line - drilled holesir«-j C. Remove rock in a manner that will avoid shattering of rock formations J outside the limits of line-drilled excavation. Remove loose or fractured J rock in the vertical face of rock excavation along the perimeter of the structurej and fill the spaces with 3000 psi concrete. D. Work rock excavation down to a satisfactory bottom. Only drilling, picking^! barring, wedging, chipping or similar methods, that will leave the rock adjacent to foundations in an entirely solid and unshattered condition shalM be Used on rock surfaces which are to receive or be in contact with Jy concrete; SlC

E. Inspection of exposed rock surf aces/will be conducted/ bytheEngineer during a .H all phases of rock excavation. Loose or fractured rock on faces of excavations shall be removed or adequately anchored to prevent; collapse.^ • -v ‘ ' ■ . . , ■ : ; ■ • ® r-'/ M

Where necessaryi the Contractor shall install posting, bracing, rock anchors 9 or use other measures to prevent5collapse oft the rock faces. The methods /I used by the Contractor shall be subject to approval by the Engineer. ; F. Thejsurface of rock at subgrade shall be cleared and leveled / t J ' r f •'I • 6. Exercise;care so that excavations are not carried below required/elevations shown on the Drawings. If excavations are carried too low, backfill to the design elevations indicated with 3000 psi concrete. as approved by the s Engineer,Sat no additional coSt to the Authority.

I H. Footings shall bear on undisturbed rock having the bearing capacities . approved by the Engineer. Bottoms of footings shall be level or stepped 1 where so indicated'and excavated to elevations shown on the Orawingsi ordf authorized* to other elevations where proper bearing exists^ - I. Where broaching is shown on the Drawings, 2 inch diameter holes shall be drilled at 4 inches on center to subgrade level, the rock between the

Contract 02220-7 Excavation and 1-02-21064-0-0 Backfilling

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