HomeMy WebLinkAboutDrainage ReportCafeEccell
Parking Lot Expansion
Drainage
Analysis
April 2001
By
;UrrcHELL.& ;ff oRGAN, LLP
Engineers & Constructors
511 University Drive, Suite 204
College Station, Texas 77840
Office (979) 260-6963
Fax (979) 260-3564
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REVIEWED FOR
Cf"~ .'11")1 II\~
MAY 0 1 2001t)
COLLE:GE STA nu1\J
ENGINEERING
FILE
CERTIFICATION
I hereby certify that this report for the drainage design for Cafe Eccell Parking Lot
Expansion was prepared under my supervision in accordance with the provisions of the
City of College Station Drainage Policy and Design Standards for the o~ thereof. · --:'\.,,
Veronica J.B. Mor , P.
State of Texas No. 77689
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CAFE ECCELL PARKING LOT EXPANSION
DRAINAGE ANALYSIS
INTRODUCTION
This storm drainage report is written to document and analyze the necessary drainage
infrastructure for Cafe Eccell parking lot improvements. The parameters used for design
and analysis of pre-vs. post-developed conditions are incorporated to show how the final
drainage design will accomplish the desired drainage objectives per the City of College
Station Drainage Policy and Design Standards (DPDS).
GENERAL LOCATION AND DESCRIPTION
Cafe Eccell is located in north College Station at the northeast comer of Wellborn Road
and Church A venue as shown on Exhibit A. The existing site is surrounded by
residential property as well as commercial development. The 1.98 acre Drainage Area,
which contributes to the back side of the northern inlet at Church Ave. and Wellborn Rd.,
is comprised of approximately 58% grassland, 35% impervious and 11 % general land
cover (i.e., Ci,re=0.62). The proposed improvements include the expansion of the existing
parking area. The construction of the proposed parking lot expansion will increase the
Drainage Area to a total of2.02 acre, which will consist of approximately 50% grassland,
39% impervious and 11 % general land cover (i.e., Cpost=0.66).
PRIMARY DRAINAGE BASIN DESCRIPTION
In general, the property drains toward the south of the parking lot and is captured by the
Church A venue drainage system, eventually discharging into the storm drain system
crossing FM 2154 and the T AMU West Campus. The existing drainage area and flow
directions are shown on Exhibit B-1. All runoff from this area contributes to the storm
drain system in Church A venue. The post-developed conditions and flow directions are
shown on Exhibit B-2. Like the existing conditions, all drainage from the post-developed
site will drain to the Church A venue drainage system. No portion of the site lies within
2 ________________ Cafe Eccell Parking Lot Expansion Drainage Analysis
the 100-year floodplain per the Federal Emergency Management Agency Flood Insurance
Rate Map as shown in Exhibit B-3.
DRAINAGE DESIGN CRITERIA
All drainage design is in accordance with the City of College Station DPDS. As such:
• the design rainstorm events used are the 10 and 100-year events (10-year to
analyze the gutter flow and inlet/pipe capacity and the 100-year to analyze flow
containment within the right-of-way); and
• flow calculations are based on the Rational Method.
DRAINAGE FACILITY DESIGN
Due to the minor amount of increased runoff and the proximity to the underground storm
drainage system, the expansion of the parking lot is being designed without detention.
The post-developed site conditions can be adequately handled by the downstream storm
drainage system without improvements to the drainage system. The site analysis will
show that the increases runoff will leave the downstream system before the peak runoff
from the Church A venue drainage system reaches the study point.
The rehabilitation project planned for Church A venue includes a better design of the
drainage system to accommodate the higher runoffs quantities created by recent
development in the Northgate Area. The proposed drainage system in Church Ave. will
be composed of 13 inlets; each of which will receive the flow of at least one drainage
area (Exhibit D). From a recent drainage analysis done for the rehabilitation of Church
A venue, it can be shown that there is a lag time of almost 16 minutes for the peak flow
(96.20 cfs) to reach computation point# 86.9, which is the end of the proposed Church
Avenue drainage system (Exhibit C-1).
The Expansion of the Parking Lot at Cafe Eccell will not have a significant impact on the
flow rate leaving this site. The increased Q for the 10-year storm event is less than 1 cfs
while that associated with the 100-year event is less than 1.5 cfs. According to the
Rational Method and using a 10-Year Storm Return Period (Exhibit C-3), the Peak
3 _________________ Cafe Eccell Parking Lot Expansion Drainage Analysis
Runoff increase due to the proposed conditions will be 0.93 cfs. The lag time associated
with this subsystem is shown on Exhibit C-2; it takes approximately 10.14 minutes for
the peak flow of 20.05 cfs to reach computation point #86.9. With a difference of almost
6 minutes in peak flow, there will be adequate time for the runoff of the first peak to
leave the system before the pipes reach maximum capacity from the flow of the whole
system. The hydrograph comparison below illustrates the hydrographs of the Church
A venue Drainage system both under existing conditions (Pre Developed) and proposed
conditions (Post Developed) without detention on the Cafe Eccell parking lot expansion.
Hydrograph Comparison
-Post Developed
-----Pre Developed
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0
Time (min)
CONCLUSION
The improvements to Cafe Eccell Parking Lot will accommodate the minor increase in
runoff due to the difference in time to peak for the Cafe Eccell flow versus the remaining
Church A venue drainage system. Because the runoff from the proposed development can
be handled by the downstream drainage system, no detention or other major drainage
facilities are proposed.
4 Cafe Eccell Parking Lot Expansion Drainage Analysis
~~~~~~~~~~~~~~~~~
VICINITY MAP
SUBJECT
RAYMOND STOTZER PW
UNIVERSITY DR
EXHIBIT A
~~---
\
ZONE X
\ \
r·~--·-·
L--~-
CJ
LEGEND
SPEOAL FLOOD HAZARD AREAS INUNDATED BY llXHEAR FLOOD
ZONE A No base flood......._ clelenrined.
ZONE AE _flood ___ .........
ZONE AH flood clopd'5 of 1 to 3 feec f\n<llly .._ of
ponclina); base flood .ie.mon. ct.rmined.
ZONE AO Flood clopd'5pl1to3 feec (.......,. sheec Row
on sloping -.in); -.e clopd'5 deter-
mined. fot --ol ........ ~ flooding; "9ocilies ..... clmrmined.
ZONE A99 To be prO(ected from .....,_. flood by
redo<.i flood ....-.,_ under CIOl>-
""'<lion; no base flood ...,,._ cku<-
mined.
ZONE V ea-al flood with velocity huard (.....,
.aion); no i...e flood elevadcn~
ZONE VE c:-1 flood with velocity hazard ,.....,
.aion); i...e flood ......... clmrmined.
ROODWAY AREAS IN ZONE AE
OTHER FLOOD AREAS
ZONE X Area ol ~ flood; .._ ol ...,,_
flood witf'l-.eciopd'5ol leB dm.1 fODI or
.......... --... it-1 oquare mile;
one! -proteaed by ie-"""' ~ flood.
OTHER AREAS
ZONE X -deleminodlDbeOUllidem.,_load-
ploin.
ZONE D Area In whidi flood hu.ck •e undece<·
nined.
UNDEVELOPED COAST AL BARRIERS
lone D Boundaiy
laundory DMdlng 5pedal flood ~
1-, and Boundaiy DMdif'I -ol Dif •
..... C-.1 -flood .......... MNrl 5pecW fload tt-d l.ana.
-613--flood Sewlioo> llne; Elevllion in Feel"
@----@ V-Seaion Une
IEL 9871 Bose Rood Elevllion in feel Where Uniform --RM7 X 11ev-. Relermae Mori<
eM1 .5 -Mile
~enced to the Noliorlal Geodetic Vertial Dllum of 19l!J
NOTES
T..,..sb .. ilaadio•"*'•••hdlllianol flood~ Prapam; ii
:~Area. ThecommuniiY~~thOUicibiCmniulied,o;powble
.... flood huardlnfommian prior IO _,ol!Hs mop far praps1y pun:hole ~purpxes.
. bee flood...,,_..opply only llfldwanl of 0.11 NCVD,and indudelhe
.... o1 ...... .a1on;lhae ........ may ..... clffer~framlhme
daolaped by the NadaNI Wellher 5enic:e for hurricMe evacuacion pr.v,ing.
-afspeciolflood~(lOO-,_-flood)includeZonesA.Af,AH,AO,A9!1, V,andVE.
Cercain --in 5peclol flood Hou<d -moy be prooeaed by flood ......,,_
~dlhe ...... -......,...i ..... sealaflSand~ i..-. .... _._. • ........,._ ..... ""..,._._ ..... __
...ithoepdlOi"""" •d6efedorll~ .... --.,,..,,.,,,.
Aaacl.y"6dd&ln __ _, ... _....._..,shawl0 .... ~
wldd&-Pftl'ided In che flood -SIUily lloport.
a..-. .......... ____ ....._ ... the Raad lnlunnaoSIUily 11.epoot.
Corpar-. ..... .._ _ ....,_. d the doee of this map. the -should
Clllilacl apprapo;.e.............., aflidak ID deeerlNne if mrpat* lmics '-t
"'""'"" ............. che-....ce d ... map.
.,.,.___., ............. hiolarypior10munlywidemapp;r.,--Uf' ._flood-.... SIUily llepart.
*Excerpt from FEMA FIRM panel 48041C0143C, effective date July 2, 1992
Exhibit B-3
Pipe Box Box Return From Inlet To Inlet Length Diameter Width Height Period #l !#l !ftl (in) !ftl !ftl !~l 70 70.2 137.49 18 10 70.1 70.2 35 12 10 70.2 71 208.94 21 10 71 72 63.3 21 10 72 74.1 100.25 24 10 73 73.1 20 36 10 74 74.1 65 24 10 74.1 75 109.32 30 10 76 78.1 14.4 30 10 75 76 71.7 30 10 77 73 16 30 10 73.1 78.1 80 36 10 78 83.1 15 24 10 78.1 80.1 280 36 10 80 80.1 18 18 10 80.1 83.1 60 BOX 4 3 10 81 82 1 24 10 82 80.1 0.1 24 10 83 86 255 24 10 83.1 85.1 250 BOX 4 3 10 84 85 1 24 10 85 86 20 24 10 85.1 86 20 BOX 4 3 10 86 t 86!9:'-M 10 BOX 4 3 10 70E 80.1E 15 24 10 73.1E 80.1E 335 36 10 77E 73.1E 30 24 10 78E 70E 50 24 10 80.1E 83.1E 60 BOX 4 3 10 82E 83E 65 24 10 83.1E 85.1E 250 BOX 4 3 10 83E 86E 255 24 10 84E SSE 1 24 10 85.1E 86E 20 BOX 4 3 10 85E 86E 15 24 10 86E 86.9 10 BOX 4 3 10 Church Avenue Rehabilitation Pipe Sizing Calculations Storm Precipitation Peak Duration Rate Sum C*A Flow !min! !in/hrl !cfsl 10.00 8.63 0.311 2.69 10.00 8.63 0.159 1.38 11.21 8.23 0.470 3.87 12.94 7.72 0.906 6.99 13.23 7.64 1.490 11.38 12.95 7.71 3.915 30.20 10.00 8.63 1.192 10.29 13.60 7.54 2.682 20.22 14.30 7.36 3.975 29.26 14.04 7.43 3.053 22.67 12.90 7.73 3.296 25.47 13.03 7.69 3.915 30.12 10.00 8.63 1.148 9.91 14.34 7.35 7.890 58.01 10.00 8.63 0.281 2.42 14.91 7.22 9.050 65.30 10.00 8.63 0.519 4.48 10.01 8.63 0.880 7.60 10.00 8.63 1.663 14.36 15.09 7.17 10.198 73.15 11.80 8.04 1.195 9.61 11.80 8.04 1.638 13.17 15.77 7.02 10.198 71.57 15.83 7.01 13.732 ;:-95!,20r1 15.68 7.04 6.517 45.87 12.94 7.71 3.312 25.55 12.90 7.73 3.312 25.59 12.12 7.95 1.531 12.17 15.69 7.04 9.829 69.16 10.00 8.63 1.486 12.83 15.87 7.00 9.829 68.78 10.21 8.56 3.147 26.93 11.80 8.04 1.694 13.63 16.59 6.84 9.829 67.25 11.80 8.04 2.346 18.87 16.65 6.83 15.652 106.91 Adjusted Peak Flow !cfsl 3.36 1.72 4.84 8.74 14.22 30.20 12.87 20.22 29.26 22.67 25.47 30.12 12.39 58.01 3.03 65.30 5.60 9.49 17.94 73.15 12.01 16.47 71.57 96.20 57.34 25.55 31.99 15.21 69.16 16.04 68.78 33.67 17.03 67.25 23.59 106.91 Flow per Full Flow Full Flow Travel Lag Time Conduit Slope !cfsl !%) 3.36 0.12% 1.72 0.27% 4.84 0.11% 8.74 0.35% 14.22 0.46% 30.20 0.24% 12.87 0.37% 20.22 0.28% 29.26 0.59% 22.67 0.35% 25.47 0.44% 30.12 0.24% 12.39 0.35% 58.01 0.87% 3.03 0.10% 65.30 0.32% 5.60 0.07% 9.49 0.20% 17.94 0.73% 73.15 0.40% 12.01 0.33% 16.47 0.61% 71.57 0.39% 96.20 0.70% 57.34 7.41% 25.55 0.17% 31.99 2.31% 15.21 0.52% 69.16 0.23% 16.04 0.58% 68.78 0.23% 33.67 2.56% 17.03 0.65% 67.25 0.22% 23.59 1.25% 106.91 0.55% Velocity Time @end (ft/s) !minl !min 1.90 1.21 11.21 2.19 0.27 10.27 2.01 1.73 12.94 3.63 0.29 13.23 4.53 0.37 13.60 4.27 0.08 13.03 4.10 0.26 10.26 4.12 0.44 14.04 5.96 0.04 14.34 4.62 0.26 14.30 5.19 0.05 12.95 4.26 0.23 13.26 3.94 0.06 10.06 8.21 0.57 14.91 1.71 0.17 10.17 5.44 0.18 15.09 1.78 0.01 10.01 3.02 0.00 10.01 5.71 0.74 10.74 6.10 0.68 15.77 3.82 0.00 11.80 5.24 0.06 11.87 5.96 0.06 15.83 8.02 0.02 ! '~5J§!?, 18.25 0.01 15.69 3.61 1.54 14.49 10.18 0.05 12.94 4.84 0.17 12.29 5.76 0.17 15.87 5.10 0.21 10.21 5.73 0.73 16.59 10.72 0.40 10.61 5.42 0.00 11.80 5.60 0.06 16.65 7.51 0.03 11.84 8.91 0.02 16.67 Exhibit C-1 Cafe Eccell Parking Lot Expansion Drainage Analysis 3/22/2001
From Pipe Box Box
Inlet Length Diameter Width Height
(#) (ft (in) ft ft)
P1 1 24
SS 1S 24
S6 10 BOX 4 3
E1 SSE 1 24
SSE S6E 1S 24
86E 86.9 10 BOX 4 3
Cate Eccell Parking Lot Expansion
Pipe Sizing Calculations
Return Storm Precipitation Peak
Period Duration Rate Sum C*A Flow
(yrs) min (in/hr (cfs)
10 10.00 S.63 1.344 11.60
10 10.00 S.63 1.996 17.23
10 10.04 S.62 2.326
10 10.00 S.63 1.236 10.67
10 10.00 S.63 1.SSS 16.30
10 10.04 8.62 2.218 19.12
Adjusted
Peak Flow per
Flow Conduit
cfs cfs)
14.SO 14.SO
21 .54 21 .S4
20.0S 20.0S
13.34 13.34 0.40%
20.37 20.37 0.94%
19.12 19.12 0.02%
Full Flow Travel
Velocity Time
(ft/s) min)
4.62 0.00
6.S6 0.04
1.67 0.10
4.2S 0.00 10.00
6.4S 0.04 10.04
1.S9 0.10 10.1S
Exhibit C-2
Cafe Eccell Parking Lot
Expansion Drainage Analysis
3/26/2001
Cafe Eccell Parking Lot Expansion
Rational Method Calculations
Basin Characteristics Precipitation Rates
average
overland
avg runoff flow time of
Identifier coefficient area CA slope velocity concentration 2 5 10 25 50 100
Cacresl (ft/ft) (ft/s) (min) (in/hr) (in/hr) Cin/hr) (in/hr) (ln/hrl (in/hr)
P1 0.664 2.024 1.344 0.010 1.74 10.00 6.33 7.69 6.63 9.66 11.15 12.66
65 0.650 0.767 0.652 0.005 1.23 10.00 6.33 7.69 6.63 9.66 11.15 12.66
66 0.650 0.369 0.331 0.006 1.41 10.00 6.33 7.69 6.63 9.66 11.15 12.66
E1 0.623 1.962 1.236 0.D11 1.52 10.00 6.33 7.69 6.63 9.66 11.15 12.66
65E 0.650 0.767 0.652 0.005 1.23 10.00 6.33 7.69 6.63 9.66 11.15 12.66
66E 0.650 0.369 0.331 0.006 1.41 10.00 6.33 7.69 6.63 9.66 11.15 12.66
Proposed Totals=
Existing Toatals=
Increment=
Peak Runoff Rates
2 5 10
(cfsl (cfsl Ccfsl
6.50 10.34 11.60
4.12 5.02 5.63
2.09 2.54 2.66
7.62 9.51 10.67
4.12 5.02 5.63
2.09 2.54 2.66
14.72 17.90 20.09
14.03 17.07 19.15
0.66 0.63 II · 0.93
25 50 100
(cfsl (cfsl (cfs)
13.25 14.96 17.04
6.43 7.27 6.27
3.26 3.69 4.19
12.19 13.76 15.67
6.43 7.27 6.27
3.26 3.69 4.19
22.94 25.93 29.50
21 .66 24.73 26.13
1.06 1.20 1.37
Exhibit C-3
Cafe Eccell Parking Lot
Expansion Drainage Analysis
3/22/2001
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Drainage Area Designation
Computation Point
Proposed Structures
Existing Structures
Proposed Junction Box
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Civil Engineerinq
Hydraulic~; Hydroloqy;
Utilily Planning & Oesiqn
Site ~~~;~:"i!~slgn
Subdivision Planning & ~sign
Mitchell & Morgan, L.LP .
onsultln<J Engineers and Constructors
11 University Drive East, Suite 204
College Station, TX n B40
(979) 280-6983 Fa.: (979) 260-3564
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