88 CHAPTER NINE
The trees and shrubs required for the project will gener-
ally be handled by a subcontractor who specializes in land-
scaping. The estimator should note the number, size, and
species required. The landscape contractor may submit a
proposal to perform all the landscape work; however, it is up
to the estimator to make a preliminary decision about how it
will be handled.
In the estimate, there must also be an allowance for the
maintenance of the landscaping for whatever period is
required in the specifications. Many specifications also
require a guarantee period during which the contractor
must replace landscaping that fails to grow or dies.
9–15 Pumping (Dewatering)
Almost all specifications state that the contractor provides
all pumping and dewatering required. The estimator should
examine any soil investigation reports made on the property
for the possibility of a high water table. Also to be considered
is the time of year when the soil investigation was made, as
the water table varies throughout the year depending on the
particular area in which the project is located.
Water can present a problem to the contractor in almost
any location. Even if the groundwater table presents no
problem, the possibility exists of rainfall affecting the con-
struction and requiring pumps for its removal.
Some projects require constant pumping to keep the
excavation dry, whereas others require a small pump simply
to remove excess groundwater. The variation in costs is
extreme, and the estimator must rely on past experience in a
given area as a guide. If the area is unfamiliar, the problem
should be discussed with people who are familiar with the
locale. Who should the estimator ask? If the contacts in a
given area are limited, the following may be good sources of
information: the local building department or any retired
construction engineers, superintendents, surveyors (who are
the most readily available source of information)—generally,
these people will be most honest in their appraisal of a situa-
tion and will be delighted to be of help. Other sources might
be local sales representatives, the architect/engineer, and any
local subcontractor, such as an excavator.
The problem of water will vary depending on the season
of the year, location, type of work, general topography, and
weather. The superintendent should be certain that during
construction the general slope of the land is away from the
excavation so that, in case of sudden rainfall, it is not
“washed out.”
9–16 Rock Excavation
The excavation of rock differs from the excavation of ordi-
nary soils. Rock is generally classified as soft, medium, or
hard, depending on the difficulty of drilling it. Almost all
rock excavation requires drilling holes into the rock and
then blasting the rock into smaller pieces so that it may be
handled on the job. Types of drills include rotary and core
jackhammers. The drill bits may be detachable, carbide, or
have diamond-cutting edges, solid or hollow. Among the
types of explosives used are blasting powder and dynamite.
When a contractor has had no experience in blasting, a
specialist is called to perform the required work. The esti-
mator working for a contractor who has had blasting expe-
rience will make use of the cost information from past
projects.
Factors that affect rock excavation include the type of
rock encountered, the amount of rock to be excavated,
whether bracing is required, the manner of loosening the
rock, equipment required, length of haul, delays, and special
safety requirements. Also, the estimator must decide
whether it is to be an open cut or a tunnel in which water
might be encountered. Once loosened, a cubic yard of rock
will require as much as 70 percent more space than it occu-
pied initially, depending on the type of rock encountered.
The cost of blasting will be affected by the type of rock,
equipment, explosive, and depth of drilling. Only the most
experienced personnel should be used, and all precautions
should be taken. Mats are often used to control the possibil-
ity of flying debris.9–17 Subcontractors
Contractors who specialize in excavation are available in
most areas. Specialized subcontractors have certain advan-
tages over many general contractors. They own a large variety
of equipment, are familiar with the soil encountered
throughout a given area, and know where fill can be obtained
and excess cut can be hauled. The subcontractor may bid the
project as a lump sum or by the cubic yard. Either way the
estimator must still prepare a complete estimate—first, to
check the subcontractor’s price to be certain that it is neither
too high nor too low, and second, because the estimator will
need the quantities to arrive at a bid price. All subcontractors’
bids must be checked, regardless.
The estimator should always discuss with subcontrac-
tors exactly what will be included in their proposals and put
this in writing so that both parties agree on what is being
bid. It is customary for the general contractor to perform all
hand excavation and sometimes the trenching. Selection of a
subcontractor is most often based on cost, but also to be
considered are the equipment owned by the subcontractor
and a reputation for speed and dependability.
If the subcontractor does not meet the construction
schedule, it will probably cost far more than the couple
of hundred dollars that may have been saved on the
initial cost.9–18 Excavation Checklist
Clearing site:
removing trees and stumps
clearing underbrush
removing old materials from premises