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Title:	Supplemental Environmental Assessment : Tampa Harbor - Big Bend Channel, Florida
Authors:	United States. Army. Corps of Engineers. Jacksonville District.
Keywords:	Dredging Dredging spoil Environmental management Environmental protection Tampa Bay (Fla.)
Publisher:	United States. Army. Corps of Engineers. Jacksonville District.
Abstract:	The U.S. Army Corps of Engineers, Jacksonville District, (Corps), is proposing to construct navigation improvements and to conduct periodic maintenance dredging of the Big Bend Channel portion of the Tampa Harbor Federal navigation project in Hillsborough Bay, Hillsborough County, FL consistent with its authorization in Section 101(a)(18) of the Water Resources and Development Act of 1999 (P.L. 106‐53). A detailed description of the Big Bend Channel portion of the Tampa Harbor Federal navigation project can be found in the Feasibility Report and Environmental Assessment, Tampa Harbor – Big Bend Channel, FL (USACE 1997). In summary, the Big Bend Channel’s authorized dimensions are for a 250‐foot wide by ‐41 feet deep plus 2 feet of advanced maintenance plus 2 feet of allowable over‐depth (A.O.) at mean lower low water (MLLW) entrance channel, which extends from the main ship channel 10,200 feet east to connect with the irregularly shaped turning basin. The turning basin would provide a turning diameter of 1,200 feet. The project also contains two 200‐foot wide by ‐41‐feet deep plus 2‐feet of advanced maintenance plus 2‐feet allowable overdepth (A.O.). MLLW channels, one extending from the southern edge of the turning basin 2,700 feet further south (inner channel) and the other extending from the east edge of the turning basin approximately 3,500 feet further east (east channel). See Figure 2 for a graphic representation of these project features. Despite being authorized, the Big Bend project has not yet been fully constructed to authorized dimensions, but from 2005 to 2010, the non‐Federal Sponsor deepened portions of the Big Bend Channel to ‐37 feet MLLW. To fully construct the authorized project, the Corps proposes to widen the north side of the entrance channel by 50 feet (from 200 feet to 250 feet) and deepen it from the current depths of between 36 and 37 feet to 41 feet plus 2 feet of advance maintenance plus 2 feet A.O. MLLW, expand the turning basin approximately 190 feet to the southwest to provide the 1,200 foot turning diameter and deepen it from 37 feet to 41 feet plus 2 feet of advance maintenance plus 2 feet A.O. MLLW, and deepen the inner and east channels from 37 feet to 41 feet plus 2 feet of advance maintenance plus 2 feet A.O. MLLW. The dimensions outlined here for the turning basin are those currently anticipated; however, further coordination with the Tampa Bay pilots and Port Tampa Bay may result in slight modifications to these dimensions as long as they comply with the criteria outlined in the authorizing documents for this project. In addition, two non‐Federal berthing areas located north and south of the east channel and a non‐Federal berthing area south of the inner channel would be deepened from the existing depths (approximately 37 feet) to 41 feet plus 2 feet of advance maintenance plus 2 feet A.O. MLLW at 100 percent non‐Federal cost. Finally, per ER 1130‐2‐520, an additional 1 foot of A.O. MLLW would be dredged in all areas during the initial expansion dredging project due to the presence of rock to ensure future maintenance of the project to the authorized dimensions (41’+2’+2’). The expansion dredging is anticipated to generate approximately 4 million cubic yards (mcy) of material and the anticipated annual shoaling rate of the federal channel after expansion is approximately 80,000 cubic yards (cy) per year. It is anticipated that maintenance dredging would be performed approximately every 9 years; therefore, each future maintenance event would remove approximately 720,000 cy of dredged material. The dredged material from the expansion and maintenance dredging projects would be placed in dredged material management area (DMMA) 3‐D or DMMA 2‐D as described in Section 2.1.3 below.
Description:	Supplemental Environmental Assessment
Rights:	Approved for Public Release; Distribution is Unlimited
URI:	http://hdl.handle.net/11681/27158
Size:	286 pages/26.18 Mb
Appears in Collections:	Environmental Documents