HomeMy WebLinkAboutCORRESPONDENCE a+ C
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November 20, 2003
40 4 14 , c e
Spencer Thompson
COCS - Development Services
P.O. Box 9960
College Station, TX 77840
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Re: Autumn Chase Sanitary Sewer Line
V , ',I, c v g Dear Spencer,
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oe$ c c Attached please find two sheets of revised sanitary sewer plans for Autumn Chase
E . a a Subdivision. Per your request we have rerouted the sewer line on the project. If
9 c s o t have any questions please give us a call.
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C • ▪ — v ` cerely,
W O z in cn
Veronica J. � Mo an P.E.
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a Managing Partner 1
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December 16, 2003
Spencer Thompson
c o, Development Services
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°' P.O. Box 9960
t -, c College Station, TX 77840
0 co ▪ c "' RE: Autumn Chase Subdivision —Cover over RCP Storm Sewer at Cornell
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U gl • Dear Spencer:
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c c c ia This letter is in response to your question about the cover over the 30" and 36" RCP
E Sol storm drains that cross Cornell Street. In several locations there is only 1 foot of cover
'Di u.1 o a • � from the finished surface of the roadway to the outer diameter of these pipes. This
to u 3:I N cover issue is due to several factors: First, we have a fixed existing outfall elevation.
The second factor is the sanitary sewer that crosses underneath the storm drain further
downstream of Cornell Street. These two factors have caused the storm drain profile
u3 to remain as it is shown on sheet 2. We cannot easily raise the roadway elevations on
o. top of the storm drain since this location of Cornell is close to point where this new
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section of Cornell will tie into the existing section. For the 30" RCP storm drain, the
C a geometry of the road does not allow for more fill on top of the pipe. As you may
s Z a recall, this geometry is necessary to allow the storm water conveyed by the curb and
,,, U c gutter to flow down the side street.
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u o r a We have analyzed the required pipe strength in terms of a 0.01 -inch crack D- loading
� z — given the 1 foot of cover and both pipe sizes. We assumed that the cement stabilized
o backfili load to be 120 pounds per cubic foot. in
a)
The equation for the D-loading +W / B *D)*F.S., where
q g is Do.oi =(WL E) ( f * )
WE =Earth Load,392 lb /LF for 30" RCP, 467 lb /LF for 36" RCP, calculated,
—1 N WL=Live Load, 2830 lb /LF for 30" RCP, 2810 lb /LF for 36" RCP, from Table
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45 of the Concrete Pipe Design Manual,
4 •— h Bf = Bedding Factor, 1.9 for Class B bedding, from Figure 227 of the Concrete
Ce Vl y Pipe Design Manual,
O ui i D= Diameter of Pipe, 2.5' and 3' diameters, and
C 1— tci F.S. =1 due to the reinforced pipe.
� *O r o From this equation, Do.oi(3o»� =678 and Do.oi(36 »)=575, which are below the Class III
W r.0 RCP ASTM C76 D -load of 1350 (see attachment). This shows that the Class III pipes
V • > to ^ f could handle the vehicular loading on Cornell. However, because of the one foot of
- S cu cover there is concern of the pipes busting during construction when compaction
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41
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would occur. The one foot of cover includes two inches of hot mix, eight inches of
flex base, and two inches of lime stabilized subgrade (the regular section of Cornell is
eight inches of lime stabilized subgrade). The concern will be that there will only be
two inches of subgrade protecting the 30" RCP and 36" RCP when the flex base is
c co placed and compacted by the contractor.
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,., The solution to this would be a concrete cap placed on top of the storm drain pipes
c 6 °� �' • where they cross Cornell. This would keep the contractor from rolling over the RCP
H c ` when placing the flex base and give additional strength to the pipe at this location.
0 = 43 rn v, Attached please find an updated sheet 2 showing where the concrete cap will be
E • placed and the concrete cap detail.
as c:
y If you have any further questions or concerns please feel free to contact me.
w • . 0, E o
a 2 a ' — Sincerely,
t
C4 oel 'tchell, P.E.
c LL ! Pa er
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Attachments
V S:\Proj \0322- autumn- chase - villas \docs \conc - cap- 2- spencer.doc
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40 C76
TABLE 3 Design Requirements for Class III Reinforced Concrete Pipe
1 ' NOTE I - -- -See Section 5 for basis of acceptance specified by the owner.
The strength test requirements in pounds -force per linear foot of pipe under the three - edge - bearing method shall be either the D -load (test load
expressed in pounds -force per linear foot per foot of diameter) to produce a 0.01 -in. crack, or the D-Ioads to produce the 0.01 -in. crack and the ultimate
load as specified below, multiplied by the internal diameter of the pipe in feet.
D-load to produce a 0.01 - in. crack 1350
D -load to produce the ultimate load 2000
Reinforcement, in. ft of pipe wall
Wall A
Wall B Wall C
Internal Concrete Strength, 4000 psi
Concrete Strength, 4000 psi Concrete Strength, 4000 psi
Designated Rinforcement Circular Wall Circular
Wall Circular Wall s Reinforcement Elliptical
Diameter, in. e s Reinforcement Elli tical Thick -
Thick- Elliptical Thick- p Cage Cage Reinforcement nesses, Inner Outer Reinforcement D nesses, Inner Outer Reinforcements
in. C
nesses,
Inner Outer in Cage Cage in. Cage Cage
23'4 0.07 ... ...
12 13'4 0.070 2 0.07
15 VA 0.07 ... ... 2' /4 0.07 ° .. 0.07° 3 0.07 3Y< 0.07 ... 0.07
..
18 2 0.07 ... 0.07 2' . 0.07 ... 0.07 3Y 0.07 ... 0.07
21 2Y4 0.14 ... 0.11 2 . 0.07 ° ... D
24 2' 0.17 ... 0.14 3 . 0.07 ... 0.07 33'4 0.07 0.07
0.14 4 0.08 0.07°
27 24'e 0.18 0.16 3Y4 0.16 •• 0.08
30 234 0.19 ... 0.18 3' 0.18 ... 0.15 4'/4 0.10 .
33 21/4 0.21 . 0.20 4 0. .
0.17 4' 0.12 0.10
36 3
0.21 0.13 0.23 4 E 0.17 17 0.10 0,19 43/4 0.08 0.07 0.09
42 31/2 0.25 0.15 0.28 41/2 0.21 0.13 0.23 51/4 0.12 0.07 0.13
48 4 0.32 0.19 0.35 5 0.24 0.14 0.27 53/4 0.16 0.10 0.18
54 41/2 0.38 0.23 0.42 51/2 0.29 0.17 0.32 6% 0.21 0.13 0.23
60 5 0.44 0.26 0.49 6 0.34 0.20 0.38 63/4 0.25 0.15 0.28
7'/4 0.31 0.19 0.34
66 651/2 0.57 0.34 0.55 7'/z 0.41 0.25 0.46 73 0.36 0.22 0.40
72 6 0.57 0.34 0.63 7 0.49 0.29 0.54
Concrete Strength, 5000 psi 8 0.42 0.25 0.47
78 61/2 0.64 0.38 0.71 71/2 0.57 0.34 0.63 83 0.50 0.30 0.56
f 84 7 0.72 0.43 0.80 8 0.64 0.38
Concrete Strength, 5000 psi Concrete Strength, 5000 psi
90 71/2 0.81 0.49
0.90 8' 0.69 0.41 0.77 91/4 0.59 0.35 0.66
96 8 0.93 0.56 1.03 9 0.76 0.46 0.84 934 0.70 0.42 I Circular 0.28
Plus El- 0.42
liptical
102 81/2 1.03 0.62 Inner 0.41 9' 0.90 0.54 Inner 0.36 10'/4 0.83 0.50 I secular 0.33
Circular Circular
Plus El- 0.62 Plus El- 0.54 Plus El- 0.50
liptical
liptical liptical
108 9 1.22 0.73 Inner 0.49 10 1.08 0.65 Inner 0.43 1034 0.99 0.59 I neoular 0.40
Circular Circular
Plus El- 0.73 Plus El- 0.65 Plus El- 0.59
fiptical liptical liptical
114 A - A ...
A ... A
120 ... ... ... ... A
.. A
A
126 ... ... A
132
138
144 A ... ... ... ... ... ...
A For modified or special designs see 7.2 or with the permission of the owner utilize the provisions of Specification C 655. Steel areas may be interpolated between those
shown for variations in diameter, loading, or wall thickness. Pipe over 96 in. in diameter shall have two circular cages or an innr circular
in either of the elliptical
fo i s l manners:
a As an alternative to designs requiring both inner and outer circular cages the reinforcement may be positioned and proportioned
An inner circular cage plus an elliptical cage such that the area of the elliptical cage shall not be less than that specified for the outer cage in the table and the total area
of the inner circular cage plus the elliptical cage shall not be less than that specified for the inner cage in the table,
An inner and outer cage plus quadrant mats in accordance with Fig. 1, or
An inner and outer cage plus an elliptical cage in accordance with Fig. 2.
s Elliptical and quadrant steel must be held in place by means of holding rods, chairs, or other positive means throughout the entire casting operation.
° For these classes and sizes, the minimum practical steel reinforcement is specified. The actual ultimate strength is greater than the minimum strength specified for
nonreinforced pipe of equivalent diameters in Specification C 14.
E As an alternative, single cage reinforcement may be used. The reinforcement area in square in. per linear foot shall be 0.30 for wall 8 and 0.20 for wall C.
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03.252
i f June 14, 2004
Spencer Thompson
Development Services
E' 1
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+ °' P.O. Box 9960
.2 M6 College Station, TX 77840
N YJ as / o'
? �_ n RE: Autumn Chase Subdivision — Oversize Participation Request
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V = a ` A�` . Dear Spencer:
c = as v
L a , a Attached please find a request for oversize participation for the Autumn Chase
o >. g- g Subdivision. As you will recall, this final plat was approved by the Planning & Zoning
• c w - f° • ' > Commission on November 6, 2003. We are requesting the following:
c >
W 1 _ rii a • Oversize participation in the amount of $40,586.00 to reimburse for the cost
difference between a 39' street cross section in a 60' right -of -way and a 49'
ui street cross section on a 70' right -of -way.
n:
c id • Oversize participation in the amount of $51,457.00 to reimburse for the cost
fa o. difference between a storm sewer system designed to carry the runoff from
L' c • Autumn Chase Subdivision and that required to retrofit the drainage design to
E a u correct the flooding occurring at Manuel Drive and Cornell Street.
rn 11 o P Z a As you can see from the Traffic Impact Analysis (attached) performed by Jeff Milburn
'4 with Jeff Milburn Engineering, he indicated that a minor collector (39' cross section)
C S is sufficient for the future needs for traffic in the area. The larger street cross section is
a) n not necessary for the traffic associated with the development of the Autumn Chase
> Subdivision.
We have also attached a series hydraulic modeling runs from XP -SWMM in which we
a 8 analyzed the 10- and 100 -year storm events. These analyses were performed for both
J N 0 the proposed flow (including additional flow from Manuel Drive) and the reduced
Z , 3 flow (excluding flow from Manuel Drive). We believe that City participation should
W ' 3 N be included to pay for the larger pipe size and extra inlets required to correct the
flooding situation at Manuel and Cornell Drive. Although this flooding has occurred
ui for many years, this project has been asked to correct the situation. We are happy to
0 I– e correct the inadequate outfall situation, but feel that the City should also be part of the
4S C ` Q solution. We understand that similar storm sewer oversize participation has been
– -= 0 M p by Y• graphic P accepted b the City. Also attached is a ra hic de ictin g the storm sewer system
J E
W .. �o with the itemization of areas where we are requesting participation. As always thank
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you for your help and consideration. If I can answer any questions or clarify any
portions of our request, please do not hesitate to call.
'i erely,
if f
Veronica J.B. Mor_, n, .E.
Managing Partner
cc: file
Bob Mosley, P.E.
Mark Smith, P.E.
Attachments (7): Oversize Participation Request Estimate
Engineer' s Estimate
Hydraulic Calculations
Traffic Impact Analysis from Jeff Milburn
Planning & Zoning Agenda
Planning & Zoning Minutes
Autumn Chase Subdivision Staff Report
S:1Proj \0322- autumn- chase - villas \docs \0322 - oversized Participation.doc