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Section 5 Formulation of Alternative Plans

EAA Storage Reservoirs Revised Draft PIR and EIS February 2006

5-21

5.3.5 Ogee Spillways

The gated outlet spillways were sized to meet water supply demand in the EAA.

Water supply demand in the EAA was estimated to be approximately 2,000 cfs.

This value was determined by analyzing historical flow data for the S-351, S-352

structures (outlet structures from Lake Okeechobee into Miami, North New

River, and Hillsboro Canals) and the S-6, S-7, and S-8 pump stations. Maximum

monthly flow averages were extracted from periods when releases were made

from the S-351 and S-352 structures and no flows were made to the WCAs (out

of EAA) via the S-6, S-7, and S-8 pump stations. This maximum monthly

average flow value was assumed to be the water supply demand in the EAA.

The capacity for the gated outlet spillways to STA-3/4 was based on

recommendations from the Basin Specific Feasibility Studies Report (September

17, 2002). Based on this report, the capacity of the outlet spillways was sized to

discharge approximately 6,000 cfs. The reservoir outlet spillways to STA-3/4

will discharge into the existing supply canal that is located north of STA-3/4.

5.3.6 Seepage Canals

The seepage canals are located along and parallel to the reservoir’s west, north,

and eastern boundaries. Seepage canal design information is summarized below

in Table 5-7. Seepage rates were based on analyses performed by the

Geotechnical Branch. An approximate safety factor of 2.5 was applied for design

capacities in recognition of the region’s geological irregularities with respect to

seepage rates. The seepage canals convey intercepted seepage by gravity flow

that may then be backpumped into the reservoirs by the seepage return pumps.

The design optimal seepage canal stage and the hydraulic design for seepage

canals will be evaluated, optimized and finalized during the project design

phase.

TABLE 5-7: SEEPAGE CANAL DESIGN SUMMARY.

Design Parameters Values

Slope Vertical to Horizontal 1 on 2

Bottom Width (ft) 10

Depth (ft) 16

Littoral Shelf Width (ft) 35

Average Ground El. (ft NGVD) 12

1 2 ... 170 171 172 173 174 175 176 177 178 179 180 ... 385 386

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