ST0701-CS081219
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THE.CITY.OF
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MEMORANDUM
TO:
FROM:
Clay Phillips, City Manager
Kenneth M. Griffin, P.E., Director of Engineering/Public Works ~
December 19,2008
DATE:
RE:
Southwestern Boulevard Bridge Closure
This is a follow-up to the briefing on the construction challenges associated with the
bridge construction on Southwestern Blvd. presented at the November 11 th Council
meeting. We have reviewed various construction alternatives with the design engineer
that would allow at least one way traffic across the bridge during construction.
As mentioned at the Council briefing, there is an increased cost associated with building
the bridge one half at a time. To offset some of the increased cost, we had the design
engineer review potential cost savings if the width of pavement were reduced.
Southwestern is shown as a 4 lane undivided collector (C4U) on our Thoroughfare Plan.
The paving width is generally 45 feet wide on C4U streets. However, most of the C4U
streets in this area (Wrangler, Airline and improved portion of Southwestern) operate as
C2U streets. Using more of the C2U approach to the design, the current design for
Southwestern has only 2 through lanes and a center turn .lane for vehicle stacking at
Pinkerton Elementary. The paving width for a C2U ranges from 33 feet to 41 feet.
Therefore, we are recommending that the paving width be reduced to 41 feet. The cost to
reduce the paving width should result in a net cost savings of about $18,500. This is
broken out as follows: 1) increase in design fee - $36,500; 2) cost savings in reduced
paving width - $20,000; and 3) cost savings in reduced bridge width - $35,000.
The obvious benefit to having one way east bound traffic across the bridge during
construction is two-fold. One, it allows the Fire Department to meet response times when
leaving from Fire Station # 1. Two, it continues to allow school traffic to reach Pinkerton
from two directions, thus not creating additional traffic congestion on westbound
Southwestern Blvd.
However, there is a cost for the safety of Fire response and access to Pinkerton. The cost
to build the bridge in two phases should result in a net cost increase of $285,000. This
includes a $35,000 redesign fee and a $250,000 cost increase in the actual construction of
the bridge. There is also about a six week increase in design time.
To summarize: The total increase in construction cost to maintain east bound traffic on
Southwestern during construction is about $266,500 (+ $36,500 - $20,000 - $35,000 +
$35,000 + $250,000 = $266,500)
If it is our desire to proceed with the one way traffic, then I will need to take an agenda
item to Council on January 13, 2009 for a $71,500 ($36,500 for reduced paving width
and $35,000 for the bridge redesign) contract amendment to the design contract that we
have with Halff and Associates.
Let me know your thoughts.
cc: Jennifer Miller, Finance Director
Keith Marvin, P.E., Project Engineer