Presentation on theme: "Biological Assessment for the Use of Bed-Leveling Devices in Port Canaveral – Baseline Research and Data Compilation Presented by: Nadia Lombardero Prepared."— Presentation transcript:
Biological Assessment for the Use of Bed-Leveling Devices in Port Canaveral – Baseline Research and Data Compilation Presented by: Nadia Lombardero Prepared by: Michelle Rau and Christine Smith In cooperation with: Terri Jordan, USACE, Jacksonville District
Outline Bed Levelers – Definitions Bed Levelers and Sea Turtles – Background Consultation History Biological Assessment Objectives Data Compilation Dredging History Sea Turtle Takes Sea Turtle Strandings USACE ERDC Survey Composite Findings Dredging Strandings Conclusions and Future Research
What Is a Bed Leveler? A device (plow, I-beam, old spud) used to smooth out peaks and trenches left by dredging equipment Process also called “Barring” or “Knockdown” Considered an economic way to achieve final grade Not a new dredging technique, dates back as far as 1565
Example of drag-beam devices used for material movement, bed leveling, and agitation dredging (Mohammed 1994). A barge and workboat performing bed leveling by trailing where a hopper dredge has been excavating is a relatively inconspicuous activity; accordingly, the utilization of bed levelers by contractors working in U.S. waters has previously received benign neglect (ERDC 2003). What is a Bed Leveler?
Background: Bed-leveling and Sea Turtles Pre-2003: Bed leveling was mentioned in some early Canaveral observer reports but was not an issue of concern. Early 2003: USACE personnel became aware that regulatory agencies were concerned about the potential impact of bed levelers on sea turtles during the Brunswick Harbor Deepening Project. GA DNR reported to Savannah District that six sea turtle strandings with odd, traumatic, crushing-type injuries were found along the Georgia coast at about the same time bed-leveling was being conducted. Although no conclusive evidence, this incident raised the possibility that operation of a bed leveler might result in takes of sea turtles.
Background: Bed-Leveling and Sea Turtles Turtle Take: A turtle that has been entrained and killed by a dredge. Turtle Stranding: A turtle that has been found either washed up on the beach or floating in the water. Definitions
Consultation History 1997: In the Regional Biological Opinion (SARBO) on hopper dredging; bed-leveling was not considered. Districts had not assessed potential effects of bed leveler use on sea turtles, and acknowledged this info would be difficult to ascertain (Hales et al. 2005). Nov 2003: NMFS issued hopper dredging opinion (GRBO) stating that although bed levelers were suspected of potentially resulting in turtle takes, their use is probably still preferable to use of hopper dredges. Mar 2003 and Feb 2005: USACE ERDC conducted survey of Corps districts and hopper dredge contractors to ascertain extent of bed leveler use (ERDC 2003; Hales et al. 2005) 2005: USACE-SAD reinitiated consultation with NMFS on the 2003 GRBO. Biological Assessments would be the next step in evaluating potential effects and USACE would initiate consultation under ESA.
Biological Assessment Objectives Objective: Research, collect, and compile baseline information regarding use of bed-leveling devices and potential effects on sea turtles to initiate consultation under ESA of 1973. Tasks: Research documents and dredging history reports to determine use of bed levelers at several ports (Port Canaveral, Port of Palm Beach, Port Everglades, Port of Miami) in Florida over last 15 years Compile stranding reports for turtles within a 4-mile radius of port entrance channels for dates coinciding with dredging projects Summarize results of interviews conducted with dredging industry professionals regarding use of bed levelers
Data Compilation: Dredging History Dredging history reports for projects conducted from 1990-2005 were reviewed to determine the amount, type of dredging, and whether bed leveler use was documented.
Data Compilation: Sea Turtle Takes & Strandings Loggerhead Sea TurtleKemp’s Ridley Sea Turtle Green Sea Turtle Hawksbill Sea Turtle Photos courtesy of USFWS and FWRI
Data Compilation: Sea Turtle Takes Data regarding sea turtle takes directly attributable to dredging operations were compiled from USACE Sea Turtle Data Warehouse website.
Data Compilation: Sea Turtle Strandings Sea turtle stranding reports from STSSN databases were compiled. Search focused on those involving impact- or crushing-type injuries coinciding with dredging project timeframes.
1. FWC provided initial database file with all strandings occurring in Brevard County during 1990-2005 that involved non-propeller type injuries. 2. Data were converted to GIS format and clipped geographically to include only those strandings within 4-mile radius of entrance channel. 3. Strandings that occurred during specific dredging timeframes of interest were identified. 4. Data were mapped to depict the number of strandings and proximity to port entrance channel.
Data Compilation: USACE ERDC Survey ERDC questionnaire regarding bed leveler use distributed to: 1.Charleston, Wilmington, Savannah, Jacksonville, and Mobile Districts 2.Selected dredging industry contractors (Bean, Manson, Great Lakes, and Weeks Marine) Data included information regarding the variety of bed-leveling devices currently utilized by the industry and how they are used Additional information included drawings, schematics, and photos of devices Findings summarized in ERDC (2003) and Hales et al. (2005)
Composite Findings: Dredging History Since 1990, dredging has been conducted annually in Canaveral Harbor channels and turning basins. Of 18 total projects, 5 involved hopper dredges. All turtle takes reported occurred during 3 of the 5 hopper dredging projects which resulted in 13 takes (9 greens, 4 loggerheads). USACE Hopper Dredge: McFarland Photo courtesy of Philadelphia District
Composite Findings: Strandings 54 turtle strandings exhibiting crushing- or impact-type injuries within a 4-mile radius of entrance channel. Of these 54, 16 either occurred during a dredging project or within 2 weeks after dredging project completed. These 16 strandings coincided with 7 different dredging projects over the 15- year period. Although strandings occurred within dredging timeframe, there is insufficient evidence to link the strandings with dredging operations as bed leveler use was not documented.
Composite Findings: Strandings Regardless of whether dredging activities are being conducted within the harbor, it appears that strandings occur much more frequently in the spring and summer months.
Composite Findings: Industry Survey Bed levelers are used most often in soft sediments (silts and clays) Routinely used following dredging by conventional methods to achieve final grade Efficient and cost-effective method for lowering high spots H-beam method typically used following cutterhead or excavator dredging operations Drag bar typically used following hopper dredging operations.
Composite Findings: USACE SAD Survey Bed levelers are used to a limited extent in Jacksonville District because much of the hopper dredging is performed in entrance channels with sandy materials Bed-leveling has been used effectively in Canaveral Harbor; associated with mechanical, not only hopper dredging Bed-leveling has not been performed following dredging by U.S. government fleet Contract language in operation logs have not documented bed leveler use
Conclusions and Future Research It is difficult to ascertain the frequency of bed leveler use during dredging projects. Historically, bed levelers have not been a specific pay item; therefore, they are not included in plan and equipment lists of contractor’s bids. Currently, there is insufficient evidence to link bed leveler use with sea turtle takes. In some cases, bed-leveling is preferable. It is more economical and can potentially reduce the risk of sea turtle takes when used in conjunction with hopper dredging. USACE ERDC and SAD have proposed devising studies to evaluate the potential impacts of bed levelers on sea turtles during cleanup phase of dredging projects. USACE Jacksonville District has added language in its dredging contracts to help document bed leveler use. Effects Determination was performed by the USACE.
ANAMAR would like to thank you for attending today’s presentation. email@example.com http://el.erdc.usace.army.mil/seaturtles/docs/SAJ06-BA- Canaveral.pdf
Hopper Dredging and Bed Levelers Draghead, especially one equipped with a TED, will tend to fall off ridges, dig deep trenches, and follow the same path with successive passes. It is thought that sea turtles may rest in these trenches and become susceptible to entrainment when the dredge attempts to level the remaining high spots (Hales et al. 2005). Hopper dredges move faster than bed levelers and they use suction, increasing chance of turtle takes. Bed-leveling is considered the most efficient method for lowering these high spots, being far less costly than returning with a hopper dredge for multiple passes. Bed leveler use during hopper dredging projects can minimize trench formation and perform clean-up operations, conceivably shortening duration of dredging and reducing turtle takes. Bed levelers move slower than hopper dredges and do not use suction, potentially decreasing chance of turtle takes.