ESTIMATES. The quantities involved in any drilling and grouting opera-
tion are rarely susceptible to accurate estimating. The estimates needed for
bidding purposes should be the best approximations possible, but should not
be considered more than that. The specifications should make provisions for
increasing or decreasing quantities and for eliminating items as warranted
during progress of work under the contract. Often-used bid items are dis-
cussed in the following paragraphs.
BID ITEMS AND UNITS OF PAYMENT.
a. Mobilization and Demobilization. This is a lump sum item and is
compensation for assembling all necessary drilling and grouting equipment
on the site and removing it therefrom. Payment for this item does not de-
pend upon the amount of drilling and grouting done. Provisions may be made
for partial payment to the contractor after mobilizing the equipment and for
payment of the remainder of the item when the work is completed and the
equipment removed from the jobsite.
b . D r i l l i n g . A bid item should be prepared for each type of drilling re-
quired, i.e., grout-hole drilling, drilling exploratory holes for core recovery,
drilling hardened grout, etc. If more than one size of hole is required, sepa-
rate items are needed for each size. If unusually deep holes are planned for
a part of the job, a separate pay item should be added for this. If stage
grouting is done, it may be desirable to provide separate items for each zone
of drilling. If part of the holes are vertical and part inclined, separate pay
items should be made for each. The size of grout holes and the type of drill-
ing equipment may be left to the option of the contractor if a particular size
is not needed. Adequate control of size for grouting purposes can be main-
tained by specifying that the hole shall be large enough to permit use of
packers with grout openings of a specified minimum size. The plans and
specifications should indicate clearly the location and extent of the work to
be done and should show limiting depths and inclinations of all holes. The
responsibility of the contractor for cleaning cuttings and sludge out of grout
holes after drilling and for keeping them clean and free from surface pollut-
ants until grouted should be cited. Payment is made by the linear foot of hole
drilled. Water and air required for drilling and grouting or any auxiliary
operation are not separate pay items. The contractor is expected to re-
cover the cost of furnishing both air and water under one or more of the
designated pay items.
c. Pipe. Pipe and fittings for use as nipples in grout holes or other use
thatresults in permanent embedment should be paid by the pound.