ST9401-CS 981118NOV
18
'98
09: 08AM WIER & ASSOCIATES P. 2/5
67S4ol
MEMORANDUM
TO: Ken Griffin
FROM: U!ys Lane
DATE: 11-18-98
PROJECT: Denton Tap Road; Coppell, Texas
W&A #: 94093
The purpose of this memo is to document the decisions regarding changes to the bridge
design to eliminate the interior vertical guard rail. The change of the guard rail to a solid
design partially blocks sight visibility to the new park entry drive. In the meeting we
determined that the best solution would be to connect the two bridges eliminating the
need for internal guard rail. The decisions made are demonstrated partially by the
attached section exhibit and are discussed in the following:
1. The west bridge is nearly completed and the out to out dimensions will be left as
designed, Modifications will need to be made to the section and reinforcing steel at the
east edge of the bridge.
2. The east bridge and columns wilt be uniformly moved to the west to reduce the span
width between the outside beams of the two bddges. The two bridges will be connected.
The amount of movement of the east bridge will depend on the span length between the
two outside beams. Martin Ledford estimated the maximum span iength between
beams to be about 10'. The east bridge will be moved to the west about three feet.
Martin will evaluate and determine the span length which will establish the amount the
east bridge is moved to the west.
3. There will be a construction joint between the two bridges located at the east side of
the west bridge. Reinforcing steel will need to be extended at the joint to connect the
east bridge in the future.
4. A solid concrete barrier rail or some other form of temporary rail will be needed
along the east side of the west bridge once traffic is moved to the west bridge. There is
substantial width on the bridge for two lanes of traffic and multiple options are available
for temporary rail systems.
5. The east bridge lane width will be increased to 35' 10" to agree identically to the
west bddge. This will result in the same inside curb elevations and the median cap
being at the same elevation. The center of the median will be raised and form a roof top
shape (but relatively fiat at a 0.02 ~. per ft. cross-slope).
6. The median will be covered with pavement treatment and the edge border at the
back of curb is anticipated to be one foot wide. The border width needs to be
confirmed with the City immediately so the edge of the west bridge can be
detailed,
7. The sheet piles, gabions and trail systems under the bridge will be left as per current
plans with no changes. The movement of the bridge will result in slightly more riprap
and a slightly flatter slope at the northeast and southeast abutments.
4300 Beltway Place, Suite 130 Arlington, Texas 76010 metro (817) 467-7700
NOV 18
'98 09:09AM WIER &
Memorandum
W&A #
ASSOCIATES
P.3/5
November 18, 1998
Page 2 of 2
8. The pier in the northeast corner of the east bddge approach will be in conflict with
the as-built storm drain pipe system. Martin Ledford will need to design a special offset
pier and cap and footing detail for this specific condition.
9. The water line air relief valve will be .relocated and placed in a vault. An alternate
design will be made to relocate the valve and vault.
10. The changes to the west bridge east edge will be accomplished immediately by
Martin Ledford to avoid delays to the work ongoing.
11. The east bridge changes and changes to the paving plans will come latter in
approximately four weeks time. Once the amount the east bridge is moved to the west
is determined, we can immediately compute new coordinates for the bridge columns.
Once the column locations are established, the work under the bridge will take several
months and the re-design should not delay work.
12. The hike and bike plans will be left as currently designed. Any changes under the
bridge at the east side (which are not anticipated to change at all) will be addressed in
the construction phase. The connections at overpasses on the east side of the bridge
will be addressed in the field. The horizontal changes are not significant and the
pavement will be in place before the trail connections are made. It should be rather
simple to address any horizontal alignment changes in the field.
Please contact me if the comments above in not as you understand from our meeting. I
will forward this memo to Robert Bibby immediately so he will be aware of the changes
and schedule of changes.
On a separate item, we agreed in the meeting to re-consider the slopes on the west side
of the roadway north of the bridge where 'gravity retaining walls are now planned.
Garreth we evaluate whether some of the walls can be eliminated. This decision will
impact the hand rail for which shop drawings are now being reviewed.
END OF MEMO
Copy to:
Martin Ledford
Garreth Cambell
Robert Bibby
4300 Beltway Place, Suite 130 Arlington, Texas 76018 metro (817) 467-7700
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