The U.S. Army Corps of Engineers Jacksonville District announces a 30-day public comment period for the Draft Environmental Assessment (EA) and Proposed Finding of No Significant Impact (FONSI) for the South Florida Water Management District’s (SFWMD) proposed construction of a seepage cutoff wall in the L-357W levee. The Jacksonville District, in response to a request from the SFWMD, is evaluating a modification to an existing Central and Southern Florida (C&SF) Project pursuant to 33 U.S.C. 408 (Section 408) to improve seepage management in the 8.5 Square Mile Area (SMA), also known as the Las Palmas community. The proposed action would be in Miami-Dade County. Improved seepage management would allow for greater operational flexibility of the Central and Southern Florida Project. Comments are due April 9, 2021.
Review the Draft Environmental Assessment (EA) and Proposed FONSI at www.saj.usace.army.mil/408-8.5SMACutoffWall/.
The SFWMD proposed action would include the construction of a 2.3-mile seepage cutoff wall made of a mix of soil, cement and bentonite slurry along the L-357W levee northwest of the S-357 pump station, and along the south side of the C-358 canal. The seepage cutoff wall would be constructed through the approximate center of the L-357W levee. The approximate depth of the curtain wall would be 55 to 65 feet deep below ground, with an approximate thickness of 28 inches. Construction is subject to Corps approval pursuant to 33 U.S.C. 408. If approval is granted, the SFWMD will complete construction at no cost to the Corps.
Operations in the project area are currently governed by the 2020 Combined Operational Plan (COP) Water Control Plan. Providing flood mitigation in the 8.5 SMA can influence regional operations including releases from Water Conservation Area (WCA) 3A to Everglades National Park (ENP). Conditions in October and November of 2020, including Tropical Storm Eta, highlight the role 8.5 SMA flood mitigation has in limiting operation of the WCAs during high water events. Various seepage management alternatives have been evaluated to afford increased system-wide flexibility under the 2020 COP Water Control Plan and future water control plans.
Please submit comments on the Draft Environmental Assessment (EA) and Proposed FONSI via email to Melissa.A.Nasuti@usace.army.mil (recommended subject: “8.5 SMA EA Comments”) by April 9, 2021.
Release no. 21-017