ETL 1110-2-367
31 Mar 95
e.
Interior storage areas.
system entering the area consisted of 24- to 48-in. pipes. The
Preliminary borrow
invert elevations for each outlet were selected based on
requirements, along with any natural storage available, were
evaluating the stage-duration data available through HEC-IFH
identified at each site. As borrow requirements became more
for the period of record and the necessary interior storage.
specific throughout the course of the levee investigation,
Invert elevations selected represent a 7-percent exceedance
elevation-storage relationships were developed and refined.
duration or less for the Meramec and do not decrease the desired
Elevation-storage relationships are shown in Table E-3.
storage volumes. The gravity outlets would be expected to be
f.
Gravity outlet rating curves.
unblocked at least 93 percent of the time, lessening the need for
Discharge-stage
supplementary pumping. Gravity outlet rating curves are
relationships were developed for 48-, 54-, and 60-in.
generated automatically by HEC-IFH, with typical output
reinforced concrete pipes (RCP). A minimum diameter of
illustrated in Figure E-2.
48 in. was used because each subarea's existing storm outlet
Table E-3
Interior Storage Areas
Fishpot
I-141
Glass Plant
Simpson Lake
Grand Glaize
Elev
Vol
Elev
Vol
Elev
Vol
Elev
Vol
Elev
Vol
(ft)
(acre-
(ft)
(acre-
(ft)
(acre-
(ft)
(acre-
(ft)
(acre-
(NGVD)
ft)
(NGVD)
ft)
(NGVD)
ft)
(NGVD)
ft)
(NGVD)
ft)
405.0
0.0
415.0
0.0
407.0
0.0
408.0
0.0
410.0
0.0
406.0
0.2
416.5
0.2
409.0
5.4
409.0
0.4
412.5
1.0
407.0
0.9
422.0
2.3
413.0
35.8
412.0
6.3
414.0
4.4
408.0
2.0
420.0
119.1
414.0
25.6
419.0
20.2
420.0
26.0
417.0
59.6
420.0
23.5
Figure E-2. Gravity outlet rating table for two 48-in. culverts
E-4
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