Wynnpage-CS 910807 unziCker · schnurbusch · associates · inc.
civil engineers · surveyors ° planners
~s~too sternrnonSdallas,(2,,~) texas6:s,~...s:~oofreeway'z'..sz,,z'suite ,,oo ~ r~ ~ ~
August ?, 1991 AU~ I
~s. Shohr~)anes~mand, P. E ·
c±ty of/C'oi~pell
~.0. B6x 478
255 Parkway
Coppell, Texas 75019
Re: Wynnpage Estates
Coppell, Texas
90051-0
Dear Shohre:
We have revised the Final Plat and Engineering Plans per your comments
found in your letter dated June 28, 1991, and the markups of the plan
set returned to us by your office. Please find an itemized listing of
the changes made or our response to your comments. They are as
follows:
COVER SHEET
1. A "Plan approval paragraph" has been added to the cover sheet per
your request.
2. The developer is aware of the water/wastewater impact fee
required for this development.
3. The developer is aware that a street light fee will be required
prior to City acceptance of this subdivision.
PAUL :5. UNZICKER, P.E. DAVID M. SCHNURBUSCH, P.E.
PRESIDENT VICE-PRESIDENT
4. The developer has been notified of the required park fee of
$11,700.00 ($150.00/lot) which shall be paid to the City prior to
acceptance of the subdivision.
5. The irrigation and landscape plans have been prepared by Mesa
Design GrouD and was submitted to you under separate cover.
Their plans have been included with our submittal.
6. This sheet as well as all exhibits within this plan set will be
signed and sealed by a Registered Professional Engineer in the
State of Texas before the final plans have been submitted to your
office. All required plan sets will be available at the
preconstruction meeting.
FINAL PLAT
1. Finished floor elevations for all lot adjacent to creek G-1 and
adjacent to the "overflow swales" near alley or street sags have
already been provided. Please see the table on the left hand
side of this exhibit.
2. An offsite drainage easement will be needed from the property
owner to the North (H.T. Ardinger, Jr.). We have submitted these
plans to Mr. Ardinger's Engineer, Nathan D. Maier and Associates,
who is in the process of reviewing them. Once he has reviewed
them, he will advise Mr. Ardinger if it is in his best interest
to dedicate the needed easement.
3. Ail street names have been approved by all reviewing authorities.
These names were revised during the Final Platting process per
the Planning Department request.
WATER PLAN
1. A blow-off valve has been added at the North end of the eight
inch water line in Tealwood Drive per your request. A fire
hydrant is not needed in this area because a fire hydrant (
hydrant number one) already exists less than 150 feet away. All
City codes have been met by this design. A detail of the blow
off valve has also been added to this exhibit.
2. A note has been added to the detail of the water mains connecting
to the line in Denton Tap Road per your request. Please remember
that this entire pavement area will be removed and replaced with
a "streetscape" plan during the paving phase of this development.
3. The developer is aware of all impact fees related to this
project. Please prepare a letter itemizing each fee and submit
to our office at your earliest convenience.
4. An irrigation tap has been added to the eight inch water main in
Wynnp~ge ~rive near the entrance to this subdivision. The size
indicated W~S provided to us by the Landscape Architect.
SANITARY SEWER PLAN
1. The curve in line "S-I" has been eliminated per your request.
This main in this area has been "straightened" and an additional
manhole added.
2. The six inch sewer laterals which will serve the two commercial
tracts along Denton Tap 'Road have been replaced with eight inch
laterals.
3. General notes number 3, 23, and 29 have been replaced with those
notes provided to us by your office.
SANITARY SEWER PROFILES
1. The proposed sewer lines will be concrete encased in those areas
indicated on your returned markups.
2. Line "S-i" has been lowered per your request to provide
additional cover.
3. There are some reaches of sewer main within this addition which
will have more than six foot of cover. This additional depth
(between station 0+00 and 3+30 of line "S-I") is needed in order
to connect into the existing sanitary sewer line in Plantation
Drive and situated so that adequate cover is provided in the
street sag of Wrenwood Drive.
DRAINAGE AREA MAP
1. A note regarding "grade to drain" has been added to the area in
the vicinity of the proposed "Y" inlet at the North end of
Tealwood Drive.
2. A detail of the alley intersection with Tealwood Drive at the
North end of tract has been added to the Paving Plan/Profile of
Tealwood.
3. The grate inlet along the West and South property lines have been
left as shown. It is our request that the City reconsidered this
design for the following reasons:
1. positive overflow has been provided in the event that
these inlets become "clogged";
2. the grate inlets have been overdesigned in case any
portion of the grate becomes ineffective, thus allowing
for the inlet to collect runoff;
3. the amount of runoff into these inlets is minimal and
in our opinion not a critical issue;
4. as part of the zoning of this tract, we will be
building a screening wall along the property lines near
these storm s~w~r collection Doint~. It is more
desirable to have the inlets in the middle of the alley
and not the edge of the alley. Putting the inlets
along the edge of the alley will be in conflict with
the screening walls because the curb inlets extend
approximately 3.5 feet behind the edge of pavement. I
would also like to point out that grate inlets have
been allowed in the past (i.e. Meadows Section Six) and
they appear to be functioning adequately. Also, our
details of these inlets were ,taken directly from "The
City of Coppell Standard Drainage" detail sheets.
4. Additional information regarding the outfall of our proposed
storm sewer system into stream "G-i" has been provided per your
request. This information can be found on the first storm sewer
plan/profile exhibit.
5. The total acreage and runoff form this drainage area has been
provided in the Hydrology Summary Table.
6. As you and David Schnurbusch from our office had discussed, the
"C" valve of 0.55 is adequate for the 8,500 square foot lots.
Please note that the 0.55 "C" valve is higher than those used by
most cities within our metroplex.
7. Drainage area "B-i" will drain into the alley along the East side
of this development as well as Wynnpage Drive. Flow arrows have
been added to this exhibit for clarification.
8. According to our filed survey and per the Engineering Plans of
the subdivision to the South of this tract, the existing pilot
channel in stream "G-I" is five wide (back to back).
9. The design of these drainage facilities is for a 100 year, fully
developed watershed condition. All streets and alleys within our
proposed subdivision contain the 100 year flows. It is our
opinion that no additional inlets are needed since the 100 year
runoff is contained within all streets, alleys, easements, and
Rights-of-Way.
10. The capacity of our outfall channel has been calculated and will
contain the 159.9 cf~. runoff from this drainage area. Please see
the calculation sheets submitted with this letter which shows the
capacity of this channel.
STORM SEWER PLAN/PROFILE (Line "D-1" and "D-1.1")
1. The capacity of the storm sewer outfall channel has been provided
on the enclosed worksheets. Please note that this channel will
contain the entire 100 year discharge from our site.
2. Ail storm sewer capacities and velocities within the pipes have
been checked and verified. Please find attached a copy of these
calculations.
3. As found on our response number three under "Drainage Area Map",
it is our desire to leave the grate inlets as shown. This inlet
has been profiled on this exhibit.
4. The side slopes of the proposed outfall channel will be 4:1 as
requested. The erosion control plan can be found in the notes on
the right side of the channel section. We have also shown staked
hay bales along the top of the proposed channel for additional
protection. The hydromulched side slope will have an established
root system by the time these hay bales "rot" away.
5. Please make reference to the "HEC-2" mode from the Halff Report
which provides all hydraulic data within the stream "G-I"
drainage course. All data was taken from a cross section located
within the area of our proposed storm sewer outfall.
6. The starting hydraulic grade line of line "D-I" was not taking
from the Halff study. The reason being that the "Peak on Peak"
factor of the 100 year storm over the entire watershed versus
that of just our subdrainage area does not occur at the same
time. As you are aware, the 100 year event for stream "G-I" was
prepared by Halff and Associates and begins at the confluence of
the Elm Fork of the Trinity River. The 100 year water surface
adjacent to our tract in the creek is based on a backwater
profile which begins at the downstream end of the streams total
drainage area and works upstream to our property. In general,
the 100 year storm event for our small drainage area will have
passed by the time the 100 year water surface of Stream "G-I"
occurs adjacent to our tract. What generally happens is the
runoff from our site has already passed through our drainage
facilities before the water is backed up through this stretch of
creek. It has been our experience working with other cities such
as Grapevine, Dallas, etc. that the starting hydraulic grade
begins at the top of the pipe. If you are unfamiliar with this
process, please feel free to call Larry Frassinelli with the City
of Grapevine, or Tommie McPherson with the City of Dallas. I
will also be more than happy to meet with you regarding this
issue.
STORM SEWER PLAN/PROFILE
1. Ail utility crossing will be concrete encased per your request.
These crossings have been shown in profile.
2. The velocities through each reach of storm sewer has been double
checked per your request. Please find attached our calculations
for this hydraulic data.
3. It is our opinion that the hydraulic grade line is at an
acceptable elevation through all stretches of storm sewer. The
hydraulic grade line for a 100 year fully developed watershed
condition will remain beneath the proposed street pavement which
is considered acceptable. There will be no surcharge at any
inlet within these drainage facilities. It is also our opinion
that the deeper you place the hydraulic grade line, the better.
However, due to the flat grades throughout this development, it
would be physically impossible to provide a condition with a
deeper hydraulic grade line.
4. A special embedment detail has been added to this sheet for storm
sewer pipe which has less than three feet of cover. This detail
was reproduced for the detail your office provided us as found on
your returned markups.
5. As discussed in item number three under "Drainage Area Map", we
requested that the grate inlets remain as shown. I will be more
than hap~y to meet with you regarding this issue.
PAVING PLAN / PROFILE (Wynnpage Drive, Heatherwood Drive)
1. The total linear feet of pavement has been added to the profile
section of this exhibit.
2. General note number 6 has been completed indicating the street
numbers in which the paving details can be found.
3. Top of curb elevations have been added at every 50 foot interval.
4. Ail valley gutters have been identified on this exhibit.
PAVING PI.AN / PROFILE (Wrenwood Drive)
1. The total linear feet of pavement has been added to the profile
section of this exhibit.
2. General note number 6 has been completed indicating the street
numbers in which the paving details can be found.
3. Top of curb elevations have been added at every 50 foot interval.
4. The proposed inlets have been situated at the lowest point in the
street sag. The paving station of these inlets has also been
shown on the storm sewer Plan/Profiles.
PAVING PT.AN / PROFILE (Tealwood Drive)
1. The total linear feet of pavement has been added to the profile
section of this exhibit.
2. General note number 6 has been completed indicating the street
numbers in which the paving details can be found.
3. Top of curb elevations have been added at every 50 foot interval.
4. The type III barricade at the end of Tealwood Drive has been
replaced with a guard rail as requested.
5. A detail fo the intersection of Alley "A' with Tealwood Drive has
ben added to this exhibit as requested.
PAVING PLAN (Left turn lane, Denton Tap Road)
1. The location of the pavestone entry has been identified on this
exhibit. Several notes have been added to this exhibit directing
the Paving contractor to see other exhibits and detail within
this plan set for these improvements.
2. A note has been added to this exhibit stating that the Paving
contractor's maintenance bond shall include coverage for any
irrigation and landscape relocation/replacement within the median
of Denton Tap Road.
3. An irrigation plan has been submitted to you under separate cover
by the landscape architect. A water tap for irrigation purposes
has been added to the water plan per your request.
ALLEY PROFILES
1. Invert elevations for all alleys have been added at 50 foot
intervals.
If you have any additional comments regarding these plans, please feel
free to call me at your earliest convenience. We have completed the
bidding process for the excavation phase of this project. Brazos
Valley Contracting Company out of Waco, Texas, will be performing this
work beginning shortly after City Council approves our Final Plat. I
would also appreciate it very much if I could schedule a
preconstruction meeting for August 23rd. The bidding process for the
Utilities and Paving phase will begin once you have had a chance to
review the final set of plans.
Sincerely,
Kevin R. Kendrick, P.E.
Project Manager
KRK/bp
xc: Waymon Levell / Wynnpage Estates Limited
Larry Davis / City of Coppell
Greg Rich / Siepiela Interests, Inc.
Dick Pierce / Pierce Lunsford & Associates