Page 208 - Urban Construction Project Management

Logistics 163
of the water surrounding the site increases as the water table is lowered at the construc-
tion site, and therefore the watertight barrier system must withstand the additional
lateral pressure with a strong system of bracing and tiebacks.

Once the water table is lowered and the foundation is put in place at the site, the
CM/GC must be careful as to when and at what rate the water table can be raised to its
original elevation. The new foundation is like a watertight bathtub, which will experi-
ence hydrostatic uplifting pressure once the water table is raised. The building has to
have a sufficient weight to counteract this uplifting force, which has to be properly
engineered and sequenced.

SUMMARY

• A good logistics plan is one of the key ingredients for a successful urban project.
• Protection of the public by fences, bridges, and other barriers is a paramount consid-
eration for an urban construction project.
• In order to be efficient and to meet critical schedules, the movement of trades people
and material must be analyzed. Thus, the location and number of hoists and cranes
must be determined by the CM/GC and related subcontractors.
• Signs must be placed around the site for directing the public around the site, notifi-
cation in case of emergency, traffic flow, and safety considerations on the site.
• In urban settings, storage of material, cylinders, and dumpsters is extremely difficult
due to the limited amount of space at the site. Therefore, off-site storage must be
considered and space must be set aside on site for dumpster and cylinder storage.
• Urban sites require the evaluation of structures adjacent to the proposed site.
Underpinning of the adjacent structures may be required for stability. Several methods
could be used, such as minipiles, shoring, and needling.
• When excavation takes place, the side walls have to be stabilized. This could entail
soldier beams, sheeting, or slurry walls.
• Since urban centers are located near major waterways, the groundwater table may be
close to where the site will be excavated. Thus, several methods are used to remove
the water from the site, such as sump pumps and well points.