MAY 7,1998


103)Once the Contractor has installed and tested the first two grouted pipe test piles located near Piers 4 & 6 is it permissible to begin production work on Piers 4 through 7 and Piers 9 through 11 prior to installing and testing the two remaining test piles?

Your attention is directed to section 10-1.01 "ORDER OF WORK", section 10-1.21"PILING", sub-section "LOAD TEST PILES" and Section 4, "Beginning of work, Time of Completion and Liquidated damages" of the special provisions. Upon Engineer's approval of test results at any "Load Test Pile Location", production work on corresponding "Control Location" piers can begin. SEE ADDENDUM No. 5 FOR NEW REVISIONS TO SPECIFICATIONS.

104)Note 6 on contract plan sheet 128 of 190 states that no splices will be allowed in the bondbreaker zone and for an additional 5'-0" beyond the ends of the bond breaker zone. The specified 45 foot -long unspliced lengths of 12.75" O.D. x 11/8" wall pipe is not available.

Bid the contract plans and specifications. Equivalent alternative construction methods are subject to the approval of the Engineer. SEE ADDENDUM No. 5 FOR NEW REVISIONS TO SPECIFICATIONS.

105)Is foreign pipe acceptable on this job?


106)Will there be any alternates for the 12 3/4" x 1 1/8"? We are a piling supplier and this is a very unique size. So far we have not found anyone who makes this size. We are currently pursuing the option of foreign pipe.

No. Bid the contract plans and specifications.

107)The 2'- 8" dimension (Sect C-C/B2) that was deleted in Addendum #2 (replacement sheet 132 of 190). We have assumed that this is a varying dimension and the 28'-6", 15'- 0"dimensions should be shown as "VARIES". Also the interior 2'- 0" dimension "VARIES". Please clarify.

Bid the contract plans and specifications. Addendum #2, special provision revisions to Section 10-1.01 "ORDER OF WORK", allows only the work within the interior cells of Piers 3 and 13 to take place prior to foundation work. All other work on each pier should follow completion of foundation work, at that pier. Reference to sheet 132 of 190, section C-C: The transverse dimension of the cut-off triangle at the corners of the pier section, varies from 2'-8" at the base to zero at height shown in "Elevation" view on sheet 131 of 190. The dimension 28'-6"+/- represents the transverse distance from CL bridge to the outside edge of the existing pier, and therefore does not vary. The dimension 15'-0"+/- represents the transverse dimension of the existing external cells of the existing piers (including thickness of the walls) and therefore does not vary.

108)Regarding the drilling specifications on page 91 of the special provisons: "Air assisted reverse circulation rotary drilling methods shall be used during drilling and for final clean-out of the bottom of the drilled shaft before concrete placement." Does this allow for use of conventional drilling methods (i.e. bucket drills) to drill the caisson shafts, provided air tools are used as final clean -out of the bottom of the drilled shaft.

No. Bid the contract plans and specifications. Requirements for drilling into rock, for the drilled shaft are stated in Special Provisions, Section 10-1.21 "PILING", subsection "Drilled Shaft." Alternative construction methods are subject to the Engineer's approval.

109)Do existing surfaces to be covered plated (i.e. Lateral, sway frame, chord & diagonal, vertical truss members, etc.) have to be blasted near white and painted with inorganic zinc primer prior to drilling and bolting?

No. Provisions in section 10-1.37 "Clean and Paint Structural Steel" of the special provisions are required to be completed prior to final installation of the cover plate. SEE ADDENDUM No. 5 FOR NEW REVISIONS TO SPECIFICATIONS.

110)In order to prepare an alternate isolator design for the project cited above, we need clarification of sheet 74/190 (50/76), "Isolator Bearing Details". Specifically, we have two questions:

1. What is the maximum seismic lateral force transferred through the isolator at each of the 22 support locations? The maximum seismic force listed in the table is qualified by note 13 and is apparently not the maximum design force.

2. What is the maximum sum of seismic lateral force transferred through each pair of isolators at each of the 11 substructure locations?

1. Design philosophy has been to design 4 types of bearings, for envelopes of force and displacement demands within each pier group represented by each type. The values of "Maximum Seismic Lateral Force, F" in the table "Isolator Bearing Performance Criteria" on plan sheet 74/190 reports the corresponding Desing Seismic Force for each "Type" of bearing. This value does represent the maximum design force for each type of bearing, and does envelop force demands for all bearings represented by that bearing type.

2. From the "Design" point of view, maximum sum of seismic design lateral forces at 2 columns of each pier ( i.e. through corresponding isolator bearings) equals twice the reported "Maximum Seismic Lateral Force, F" in the table "Isolator Bearing Performance Criteria" on plan sheet 74/190. More detailed analysis results which led to the enveloped "Design Forces" can be obtained by conducting nonlinear time history analysis using representative IAI-NEABS and/or ADINA analytical models. These analytical models can be obtained as noted in sub-section "Alternative Bearing", under Section 10-1.26 "Furnish Seismic Isolator Bearing," in the Special Provisions.

111)Reference addendum #5, page 11, fourth paragraph, Section 10-1.21 ≥Permanent Steel Casing≤- Is the intent to have 2 ft. of penetration of casing into rock? By following the specified tip elevations given, there could be as much as 8 ft. of casing penetration into rock which is very impractical and expensive. Please clarify.

Design intention has been to ensure minimum embedment of 2 ft into the rock per the special provisions/addenda. For quantity purposes, the lowest recorded bedrock elevation at the base of existing caissons within each foundation has been used to establish the specified tip elevation for all new casings in the foundation with a 2 ft minimum embedment into rock. Revisions to the specified tip elevations of individual casings, based on actual rock elevations, are subject to approval of the Engineer after the bid opening.

112)Reference addendum #5, page 12, Section 10-1.21, ≥Grouted Pipe Pile≤ second sentence of twentieth paragraph - Does the statement ≥Percussion type drills shall not be used for drilling through foundation material≤ mean that it is therefore acceptable to use percussion type drills through the existing concrete caissons?

Percussion type drilling is permitted for the 17" hole inside existing caissons, subject to construction requirements as stated in the Special Provisions. See "Construction" Section, under sub-section "Grouted Pipe Pile" in Section 10-1.21"Piling" of Special Provisions.

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