Presidio question and response.doc

(Added on 07/30/2010

1. The Soil-Bentonite Slurry Trench Specification 02 35 27

a. Section 3.8 requires trench cleaning of the prior placed SB Backfill in ceased operations for longer than 24 hours. Can this be increase due to the 40-hour schedule?

Paragraph 3.8 of Specification 02.35.27 has been revised to include the Contractor’s responsibilities in regard to ceasing the backfill fill operation more than 24 hours.

b. Please provide the CM rate so the contractors can allow for this cost in preparing our estimate. How can the contractor provide a rate for the CM for additional working hours without the US IBWC providing the applicable cost?

The CM for this project has not been awarded. However as an average the following hourly rates are provided from previous acquisitions: $66 (Added on 07/31/2010; email from Jose Nunez of USIBWC on 7/31)

1. Question and Answer from 47 and No. 1(7/29/2010) – As stated previously the API reference of 13A [4][5] conflicts and the recent amendment restates that “chemically treat bentonite will not be allowed”. Please consider revising, most Wyoming Grade Bentonite supplies have little or no supply of this material due to no demand. For the construction of Soil-Bentonite Slurry Walls Section 4 material is used nearly 100% of the time.

IBWC is aware of the concern brought up by a few contractors, stating ‘chemically untreated bentonite’ may not be readily available. However, the chemically ‘untreated bentonite’ is a preferred choice of bentonite. In addition, the Geotech has identified a few suppliers (such as CETCO) who can provide ‘untreated bentonite’ for the project.

Note: Based on the latest API spec 13A (effective August 2010), the section [4] has been renamed section [10] in the project specification.

2. It should also be noted that Magnus Pacific is currently working with for the USACOE in the Sacramento District and other USACOE projects is using API 13A Section 4 Bentonite, as such we request that the specification section be revised to include the use of API 13A Section 4 Bentonite.

Not Concur. Only the “Chemically untreated bentonite” will be allowed for this project (Added on 08/02/2010; email from Isela Canava of USIBWC on 8/02)

I know it is too late for questions to be answered, but after opening the file that was attached to amendment 3 “Presidio Urban Levee ‘Request for Information’ Comments – (added in 7/29/2010) page 9 of 11.

Questions 2.A. and 2.B. relates to imported backfill material if the trench material does not meet specs. How does one quantitatively assume a price for something which might not be needed, how do we know bidding the job how many cubic yards of the total 74,000 cubic yards of material excavated need to be imported?

The cost estimate is based on the assumption that approximately 30% of the clay fill backfill material would be imported based on geotechnical assessments of the subgrade conditions by the geotechnical consultants. The Paragraph 2.1.C of Specification 02.35.27 has been revised to state include this information.

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