Specifications

Section 5 Formulation of Alternative Plans
EAA Storage Reservoirs Revised Draft PIR and EIS February 2006
5-13
TABLE 5-2: SUMMARY OF RESERVOIR ALTERNATIVES.
Alternative
Designation
Depth
(ft)
Area
(Ac)
Storage
(acre-feet)
Embankment Type
Alt 2 6 62,000 360,000 Earthen
Alt 3 10 38,000 360,000 Earthen
Alt 4 12 32,000 360,000 Earthen
Alt 5 12 32,000 360,000 RCC
Alt 6 14 26,500 360,000 Earthen
Embankment heights were set approximately 6.7 feet and 7.7 feet (11 feet and
12 feet above normal pool) above maximum surcharge pool elevations for earthen
and RCC levee designs, respectively. An internal embankment that runs north
to south was included to compartmentalize the reservoirs, thus creating 2 cells,
which adds operational flexibility, and reduces perimeter embankment height by
reducing the wind setup/wave run up fetch length. Seepage would be
intercepted and collected in a canal that runs along the reservoir’s western,
northern, and eastern boundaries. The existing STA-3/4 supply canal would be
utilized to intercept seepage to the south. A 35-foot wide littoral shelf was
included along the entire length of the seepage canal. A 200-foot wide seepage
management buffer was included along the entire length of the seepage canal.
In addition to serving as a seepage management measure, this feature could also
could provide environmental benefits (habitat for fish and wildlife). It is
expected that the proposed reservoirs will improve the performance of STA-3/4
by acting as a surge tank to equalize flows. The EAA reservoirs will also
improve water quality by providing residence time for settling of contaminants
prior to input into STA-3/4.
Alternative plans are shown in Figures 5-1 through 5-4. Reservoir design
parameters for each of the alternatives are summarized in Tables 5-3 through 5-
6. The footprint, pumps, and structures are identical for the earthen and RCC
embankment alternatives.