SW0001-CS000324 MEMORANDUM
FROM THE
DEPARTMENT OF ENGINEERING
COPY
To:
From:
Jim Witt, City Manager
Kent Collins, P.E., Civil Engineer/C(_
Date: March 24, 2000
Riverchase Elementary School / MacArthur Park Sidewalk Crossing
In the days since our last meeting with the CFBISD and TXU Electric personnel, I have had the
opportunity to study the proposed crossing. Specifically, I have exarnined the potential locations
in the field and in terms of topographic information. If the crossing is pursued in the future, the
best location would likely be the cul-de-sac at the end of Bradford Drive. Although this is not the
most direct route across to Starleaf, it would provide the shortest run across private property and
have the shortest drop from the street to the elevation of the TXU property. That said, there are
several problems with construction of the sidewalk regardless of the location.
The first obstacle is the drop from the street. Any sidewalk intended for public use will have to
meet ADA requirements. Therefore, one option to deal with this drop would be to run a ramp to
the south or north along the property line and then mm to the west when the ramp is at-grade
with the TXU property. The problem with this option is that the City has very little or no right-
of-way in which to locate the ramp. This option would require the purchase of an easement or
right-of-way. The other option to deal with the elevation difference is to simply run a ramp from
the cul<le-sac directly west into the TXU property. Again, this ramp would have to meet ADA
requirements. However, construction of any streetore in the floodplain will necessitate a flood
study.
Mother concern is the condition of the soil along the proposed path. Based on observations, this
soil is wet for much of the time. This could create a problem from a use standpoint. Water on or
running across the sidewalk would be not only a nuisance but a safety haTard. Elevating the
sidewalk may keep it dry, but it would dam water adjacent to it. This would eventually
compromise the integrity of the sidewalk. The dammed up water could also become a health
issue. Although the School District has agreed to accept these conditions and maintain the
sidewalk, this may not be as simple as sweeping or washing the sidewalk.
A more serious issue with the soil conditions is the ability to actually construct ~e sidewalk. It is
doubtful that the soil is stable enough to support the sidewalk or the machinery necessary to
excavate the soil and pour the sidewalk. There are no inexpensive methods for remedying this
problem. It may be overcome by excavating deep enough to reach stable soils, but that depth is
unknown at this point. Another option might be l'nne stabilization or other soil modification
processes, but again the soil must be stable enough to support the necessary machinery. An
investigation by a Gooteclmical consultant would be advisable prior to pursuing construction of
"CrrY OF COPPELL ENGINEERING - EXCELLENCE BY DESIGN"
the sidewalk. Also, keep in mind that any variance granted to the Floodplain Management
Ordinance would necessitate a balance between soil removed and soil/concrete added. In other
words, no material could be placed Within the floodplain without the removal of a like amount of
material.
Another potential problem with comtmcting a crossing at thi.~ time is the potential for existing
Wetland~ along the proposed route. A requirement of the City's Floodplain Management
Ordinance is that all applicable Federal or State regulatory permit~ must be completed prior to
issuance of a floodplain development permit. The City or CFBISD would need to contract with
an environmental consultant to perform a weftands determination on the land prior to
construction. If it was determined that weftands existed where the crossing was proposed, then a
weftands mitigation plan would have to be developed and submitted for approval by the U.S.
Corps of Engineers. Any wetland mitigation would increase the cost of the coustmction.
These issues are problematlc, The problems can be dealt with but would likely entail significant
additional cost and/or delay. One alternate design that could overcome most of the construction
and use problems would be a "boardwalk' option as illustrated in the attached exhibit. The
design would be a wooden plank walkway on piles such as is commonly used on beaches. This
option would still requke a soil/foundation analysis to determine the depth and number of piles.
Routine maintenance would also be necessary. Obviously, this option would be very costly if this
is to be a temporary walk, but it would solve most of the problems associated with a concrete
sidewalk.
Again, all options will have problems f~om a use, construction, maintenance, or cost standpoint.
I would welcome the opportunity to discuss this with you further at your convenience.
"CITY OF COPPELL ENGINEERING ~ EXCELLENCE BY DESIGN"
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