The C-111 Canal with structures marked. Notice

ENP to the west, Florida Bay and Barnes Sound to

the south. Barnes Sound(along with Card Sound)

represents 1/3 of all American crocodile nesting in

the continental U.S. Current water quality: FAIR.

Taylor Slough extends more than 20 miles to the

coastal mangrove fringe along Florida Bay, and

has historically been an important source of fresh

water to the central portion of the Bay.

Southeast District

Assessment and Monitoring Program

Ecosummary Ecosummary

C-111 Canal

Miami-Dade County

March 2003

Currently, the C-111 Canal is the major feature of the

C-111 drainage system. For a significant part of its

length, it runs east southeast just north of the Panhandle

region of Everglades National Park (ENP), in southern

Miami-Dade County. The C-111 Basin includes approximately 100 square miles of agricultural land in the

Homestead/Florida City area and most of the Taylor

Slough Basin, about 100 square miles, mostly within

ENP. Canals in the C-111 Basin are operated to provide water supply and flood protection for urban and

agricultural areas and deliver flows to Taylor Slough

and coastal basins of the Park. At times, the C-111

Canal also receives water from Water Conservation

Area 3 (WCA 3) and seepage from Shark River Slough

and the headwaters of Taylor Slough from the L-31N

Canal through the S-176. It discharges to the Everglades National Park Panhandle, Florida Bay, Manatee

Bay and Barnes Sound. A number of structures are

utilized to control flow in the basin, including the S-174,

S-175, S-176, S-177, S-178, S-18C and, S-197. The S197, located a short distance east of US1, is an outlet

structure from the C-111 Canal to Barnes Sound. During major flood events, all 13 culverts are opened to

provide flood protection for the developed portions of

the basin.

The existing C-111 Basin drainage system is a modification of the original Central and South Florida (C&SF)

project. Initially, the 1947 C&SF Project included levees

to protect the C-111 Basin from hurricane driven tides

on the south and east and high water in the Everglades

on the west. Spillways and culverts in the east and

south walls of the levee would pass flood control discharges from upstream canals and maintain groundwater levels to prevent saltwater intrusion. After later

analysis in 1959, a series of north-south canals that

would extend to Barnes Sound, Long Sound and Florida

Bay (C-107 through C-112) were proposed to replace

the southern levee. Salinity control structures were to

be built between the 1 and 2-foot contours.

Both Everglades National Park and the US Fish and

Wildlife Service (FWS) objected to the canals cutting

through the Park and discharging to tide. Additional

review indicated that the design discharge could not

be passed unless the canals were dug into the open

water of the bays. As an alternative, the FWS suggested an east-west canal to connect the C-111 and

C-110 Canals at their southern end to the C-109 Canal, which would discharge into Barnes Sound. This

would allow some of the water to spread out through

levee gaps and flow across the panhandle of ENP into

Florida Bay. During this period, Aerojet General Corp.

purchased a large tract of land in the area to construct

a rocket engine test facility. Because the canals would
be large enough to allow barges to transport rockets to

Cape Canaveral, Aerojet also supported the idea of a

canal to connect the C-111 and C-110 Canals to the C109 Canal. Today’s alignment is a version of that concept. Aerojet has since sold it’s property to the South

Florida Water Management District (SFWMD).

A design change was also made in the western part of

the basin. ENP requested additional flows for Taylor

Slough to replace water that had already been diverted

from its headwaters by other projects and the lowering

of groundwater levels. The L-31W Canal was added

to deliver flows to Taylor Slough from western south

Dade County. Later the S-332 Pump Station would be

added to assist in this effort.

A major modification was made to the project during

construction: since the S–18C, which was to serve as

the salinity control structure for the C-111 Canal, was

located many miles upstream from the outfall, concerns

were raised regarding saltwater moving up the canal.

If this occurred, saltwater could contaminate the freshwater aquifer or spill over the south canal bank, flow

through the levee gaps and impact the freshwater wetlands in the ENP Panhandle. A national campaign by

environmental groups to add a structure to the end of

the canal reached its peak about the time a US Highway 1 bypass, used during construction of a bridge over

the canal, was to be removed. A temporary solution

was reached that left an earthen plug with three culverts in the canal at the bypass site. Although the plug

was never removed for navigational purposes, it was

removed and replaced a number of times to pass flood

control discharges to protect the C-111 Basin’s developed areas. These massive discharges resulted in much

environmental harm to Manatee Bay and Barnes Sound,

and drained significant amounts of water from ENP

and Southern Everglades. In the early 1990s, the S197 Structure, containing thirteen culverts, was constructed to replace the earthen plug.

Prior to construction of the C-111 Canal, the Panhandle

of ENP served as a source of freshwater flows to

Florida Bay. Even with the gaps placed in the levee

south of the canal, natural surface water flow to adjacent wetland areas was restricted and some flow diverted to the east. The reduction of over-bank hydrologic flow resulted in changes in vegetation composition, saltwater intrusion, and loss of desirable fauna.

Impounding the wetland system north of the canal altered natural hydrology and consequently impacted

water quality throughout the marsh and northeast Florida

Bay. As a result, in the early 1990s, a General Reevaluation Report for the C-111 Canal was begun. The

Final Report recommended the removal of the spoil

mounds from the south side of the east-west leg of the

C-111 Canal upstream of US Highway 1; filling of the

C-109 and C-110 Canals; and a 1000 foot bridge over

Taylor Slough in ENP. Construction of new pump stations S-332A, B, C and D on the L-31N Canal; and a

tieback levee that would extend from S-175 north for

91⁄4 miles to near S-332B were recommended. This

levee would form a retention/detention area into which

the new pump stations would discharge. A new Pump

Station S-332E and C-111N Canal were recommended

to remove water from the C-111 Canal at its junction

with the C-111E Canal and distribute it across the Southern Everglades between the C-111 and US Highway

1. Except for the S-332A and E Pump Stations and

the C-111N Spreader Canal, most of these proposals

have been constructed, although some in a modified

form. The tieback levee system has been partially completed.

Additional changes to the C-111 Canal system were

recommended by the Comprehensive Everglades Restoration Plan (CERP), and are included in the C-111N

Spreader Canal Project. Modifications consist of enlarging pump station S-332E 10-fold, from 50 cfs to

500 cfs, and extension of C-111N Canal into the Model

Lands east of US Highway 1. A stormwater treatment area is proposed to treat water prior to discharging to the Southern Everglades and Model Lands. Additional components of the plan include filling in the

southern reach of C-111 and removal of structures S18C and S-197. These features will improve water

deliveries and enhance the connectivity and sheetflow

in the Model Lands and Southern Glades areas, eliminate damaging discharges to Manatee Bay and Barnes

Sound, and maintain flood protection in the lower south

Miami-Dade County area.

An analysis of 1983-96 data (Walker, 1997) reported

that inflows to the northern section of C-111 averaged

11,000 acre-ft/yr and contained 97 kg/yr of phosphorus

at a concentration of 7 ppb. Inflows to the southern

section of C-111 averaged 45,000 acre-ft/yr and contained 937 kg/yr phosphorus at an average concentration of 17ppb. Walker attributed the higher loads to the

south reach of the C-111 to “a more substantial agricultural watershed”. Water delivered overland from

C-111 through S-18C, S-176, and S-177 structures to
For more informationcontact:

The Southeast District SurfaceWater Quality Section in Port St. Lucie

at 772/398-2806, or by e-mail:

Dana.Fike@dep.state.fl.us

Florida Bay is a triangular shaped, 850 square mile

subtropical estuary with an average depth of three

feet. It lies between the southern edge of the Everglades and the Florida Keys with its western side

opening directly to the Gulf of Mexico. It is almost

entirely enclosed to the south and east except for

tidal channels between the Keys. Approximately

80 percent of the Bay is within the boundaries of

ENP. Until recently Florida Bay was described by

its clear, warm water, lush seagrass beds, and outstanding fishing. In the 1980’s, changes in the Bay’s

ecology became apparent. These changes included

the extensive death of seagrass beds associated with

turbid water, large sustained algal blooms and the

death of sea sponges near the Florida Keys.

Florida Bay

Florida Bay contained median phosphorus concentrations of 11.8, 11.2 and 8.5 ppb, respectively. Estimates

of average annual loads from these three structures

based on 1991-96 data was 2813, 129, and 1211 kg/

year. FDEP’s analysis of 1990-2000 SFWMD data

collected at S-197 (station AR03) showed a relatively

low mean concentration of ammonia and nitrate nitrogen of 0.06 and 0.04 mg/L, respectively. Mean phosphorus concentration at this site was a low 4 ppb, with

only one of the 62 observed values above 10 ppb. Dissolved oxygen (DO) mean concentration of 5.8 was

well above the State standard for DO of 5.0 mg/L, albeit 7% of the reported values were below 2 mg/l.

These low dissolved oxygen concentrations (less than

2 mg/L) all occurred during the warmer months (June

thru October); such low oxygen concentrations values

could potentially result in fishkills in C-111 or in Manatee Bay if water were being released in sufficient quantity. 1990-2000 SFWMD data collected at S-177 (north

of S-197) showed a mean concentration of ammonia

and nitrate nitrogen of 0.13 and 0.09 mg/L , respectively. There was a decreasing trend of nitrate nitrogen of 0.01/yr. Mean phosphorus concentration at this

site was 0.009 mg/L with no apparent trend. DO mean

concentration was 3.5 mg/L with 30 percnet <2.0 and

75 percent <5.0 mg/L. Chlorophyll a mean concentration was 2.1 mg/L.

Most of the discharges from the S-176, S-177 and S18C structures pass to Florida Bay via overland flows

from C-111 southward.