Key Biscayne Master Plan 043944000.18w_Key_Biscayne_MP(forJooMag) | Page 125

12.0 OVERALL PROGRAM OPINION OF PROBABLE CONSTRUCTION COST

It is assumed that new utility infrastructure related to the conversion
process will be installed in public right-of-ways and easements. It
is further assumed this infrastructure will be installed in a manner
that minimizes relocation of existing utilities in these same locations.
These potential impacts cannot be accurately quantified at this time
and are therefore not included in this OPC.
12.7.3 Construction Methods: Directional Bore
vs. Open Trenching
Conduit for electrical and cable/telephone infrastructure are typically
installed using open-cut trenching or directional boring. Costs for these
methods for installation within a typical residential area within the Village
were analyzed to determine the most cost-effective installation method.
Directional Boring
 Due to the conduit separation requirements for AT&T, FPL, and
Comcast infrastructure, a typical installation within the roadway
by directional bore would require a minimum of three separate
bores, each containing multiple conduits—FPL primary/service
conduit, AT&T mainline/service conduit, and Comcast mainline/
service conduits. FPL feeder conduit may or may not be
bored separately from the other FPL primary/service conduits
depending on the site-specific factors.
 Restoration will be required at each “bore pit” and within areas
of the roadway that need to be excavated to intercept primary
conduits for transformers, feeder conduits for switches, and
service conduits for each building. One restoration area per
property was assumed in the analysis.
Open Cut
 This method assumes AT&T, FPL, and Comcast infrastructure
will be installed in a joint trench with the required separation
between each utility. Asphalt trench repair is assumed
to be required for most joint trench installations as the
opportunities for an off-roadway joint trench installation
within the Village is limited due to right-of-way and property
improvement restrictions.
Based on these assumptions, costs for installing a typical conduit run by
directional bore was estimated to carry an appreciably higher cost than
installation of those same conduits within a joint trench (via the open-
cut installation method), despite the lack of pavement repair required.
Additionally, there are technical challenges with boring on many of the
Village’s roadways that can be overcome using the open cut method
These challenges include:
 Narrow right-of-ways with a high level of utility congestion
 Significant number of electrical and communications conduits to
occupy a corridor with very limited space
 Spacing requirements between electrical and communications
facilities requiring separate bores
 Bore spacing required for constructability to prevent multiple bores
from converging together as often happens in sandy conditions and
tight spacing
Based on the analysis above, it is assumed by this OPC that open-trench
installation methods will be used for most of the joint trench conduit
installation within Village right-of-way. It is further assumed the FPL,
AT&T, and Comcast service conduit installation on private property will
be installed via directional bore, minimizing private property disturbances
and related restoration costs for the many high-end finishes that exist on
private property. FPL service conduit was assumed to be installed as a
separate bore to maintain the required separation to avoid electromagnetic
interference issues.
An exception to this may be the multi-family condominiums on the east
side in Phase 2 between Galen Drive and E. Enid Drive. This project area
includes large properties with long distances between service points.
These buildings are also fed from rear yard overhead poles in easements.
Because most properties are large, multi-family condominiums, there is
relatively little service conduit to be installed. Many of the service drops are
also already undergrounded, therefore it may be possible to intersect these
lines and refeed through existing conduit. Most runs are anticipated to be
either feeder or primary electric and/or communications backbone. This
reduces the number of entry/exit pits required throughout the area, which
in turn reduces the anticipated cost of bore machine setups related to
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