Shadowridge P1-3-CS 920914MEMO
TO:
FROM:
SUBJECT:
DATE:
Alan D. Ratliff, City Manager
Kenneth M. Griffin, P.E., City Engineer
Existing Earthen Channel North of Shadowridge Subdivision/
South of Devonshire Estates
September 14, 1992
As you may recall, Mr. Robert Delvo has written previously concerning the existing earthen
channel behind his property. The correspondence went to the Mayor. In June of 1992, I was
asked to investigate the possibility of installing a drainage system in the channel. Based on both
my investigation and Michael Martin's investigation of this situation, there are two constraints
to constructing a closed drainage system in the existing channel:
1)
2)
The grade is too flat.
The channel is too shallow.
Basically, the two constraints go hand-in-hand. Approximately a 36" diameter pipe increasing
to a 42"diameter pipe at the east end is needed. However, because of the shallowness of the
channel, a system of this size cannot be installed in the channel without building a berm over
the top of it for the appropriate cover. In some areas the existing channel is only a foot and a
half deep. The flatness of the channel is critical because even if you try to deepen the channel
to accommodate a system, ie., a zero percent grade on the channel section, there still would be
inadequate cover to install a closed system. Also, with a zero percent grade, the pipe sizes
would have to be increased to handle the drainage.
After looking at several alternatives, the recommendation for this ditch section is to install a
concrete pilot channel in the bottom of the existing channel. The main purpose of the concrete
pilot channel would be to stabilize the bottom section of the channel. Currently, with the
earthen channel bottom, there is erosion creating pockets of water making it difficult to mow and
maintain the earthen channel.
I am unsure what additional direction needs to be provided to staff, i.e., should we prepare a
set of construction plans, should we pursue this project, should we contact the property owners
to relay this information, should we do nothing, etc. Currently, the developer of the Devonshire
Estates Subdivision is regrading the earthen channel.
Memo to Alan D. Ratliff, City Manager
September 14, 1992
Page 2
A set of construction plans could be prepared in house within a matter of two to three months.
This would include the survey and drafting necessary to design the system. It is difficult to
ascertain correct cost estimates. However, based on some previous projects, the construction cost
of the pilot channel could range from $ 20,000.00 to $40,000.00, depending on the width of
concrete pilot channel designed. The channel is approximately 1,060 feet long.
I would be happy to discuss this project with you at your convenience and the engineering
department would be willing to proceed with any direction given on this project.
KMG/bd
cc: Mike Martin
ADRSHADO