Pecan Hollow-CS 900404 ', DAN M. DOWDEY & ASSOCIATES
CIVIL ENGINEERS
16250 DALLAS PARKWAY SUITE 100
DALLAS, TEXAS 75248
(214)~;-%694 ~
April 4, 1990 ~ %'¥ '%'~%'¢f~
Mr. Steve Goram
Public Works Director
City of Coppell
255 Parkway Boulevard
Coppell, Texas 75019
REF: Pecan Hollow Addition
Dear Steve:
We are in the process of addressing your concerns regarding the street
alignment, the sanitary sewer alignment and the depth of the sanitary
sewer main (Line "A").
The street align)-~ent uas finalized based on the zoning site plan and the
preliminary plat as previously approved. I understand that for a 30 MPH
zone you have a 7~inimum center!ine ra(~ius of 425 ft. The reduction in
radius that we have designed, primarily involves intersection tie-ins.
Where we are not at intersections, the only reduced radius is at extremely
critical locations regarding lot configurations.
As I previously noted in a separate letter, the areas that I have reduced
the radius is similar to situations in the majority of the subdivisions
in Coppell. I am asking that you consider these issues in the review
of this final plat. Had I known that you were opposed to this layout
I would have revised the layout at the zoning level.
In regards to the radius of the sanitary sewer mains, I addressed several
general reasons for the alignment to remain as submitted. After discussing
the issue with Howard Pafford, his concern was that cleaning mains with
the equi ........... the City has,
~]=~u u~= that were constructed on minimum radii,
created a more difficult maintenance situation. There are additional
problems with the straight alignment on this project. Due to the extremely
large amount of storm sewer and inlets, the straight alignment creates
additional conflicts with inlets. I am requesting that you work with
us on this issue and only require the straight alignment where you
definitely have a major problem. If adjustment of manholes can help,
I would like to explore this option. At this final stage of the design,
I would like to minimize the adjustments.
There is an area, sanitary sewer line"A" that is very shallow. The concern
that Mr. Pafford had was the problem of other utilities being located
adjacent to the sanitary sewer laterals in the shallow area. In addition
to encasing the main in concrete, we could restrict the other utilities
to locating their facilities at the rear of the lots or in conduit if
necessary.
Page 2
Mr. Steve Goram
April 4, 1990
I have a concern regarding the minimum 100 ft. vertical length for grade
differential in excess of 1%. The only areas that I did not impose
vertical curves, was in areas approaching the 1% criteria. This length
is difficult to maintain during the construction phase, especially in
sag locations, i.e. "birdbaths" are created.
On behalf of our client, we would appreciate your help regarding the
exceptional matters and hope that we can resolve these concerns with
current acceptable engineering design principles.
Please call me upon review of this letter.
Very truly yours,
William A. Anderson, P.E.
WAA:hc