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HomeMy WebLinkAbout10153-OFC-DC_Project_Narrative-050120Carteret County Shallow Draft Navigation Waterways Old Ferry Channel & Deer Creek Maintenance Dredging Project Narrative Carteret County intends to maintenance dredge the navigation systems referenced as Old Ferry Channel and Deer Creek adjoining Bogue Sound in Cape Carteret. The dredging operations will help enhance recreational navigation access for residents and visitors in Cape Carteret and Emerald Isle to the Atlantic Intracoastal Waterway (AIWW). The Old Ferry Channel spans approximately 6,750 linear feet (lf) (1.3 miles) across the AIWW to connect the townships of Cape Carteret and Emerald Isle. The channel supported a ferry operation from 1961 to 1971, until the B. Cameron Langston Bridge, otherwise known as the Emerald Isle Bridge, was constructed. Since 1971, the Old Ferry Channel has served as a primary recreational navigation access for the Cape Carteret boating community. The proposed work stipulates the first known maintenance event for the Old Ferry Channel since the original construction by W.B. McLean as a developmental action for Cape Carteret. Deer Creek includes a system of navigation channels facilitating access to multiple residential areas in Cape Carteret. The Deer Creek system covers approximately 12,200 lf (2.3 miles) inclusive of a connection to the Old Ferry Channel. Deer Creek provides recreational navigation access to five (5) separate residential areas containing an estimated 18,300 lf (3.5 miles) of shoreline. Maintenance dredging occurred in sections of Deer Creek in 2001 and 2007, although the records do not indicate maintenance ever occurred throughout the entire system. Figure 1 below shows the proposed Old Ferry Channel and Deer Creek maintenance areas. Figure 1. Old Ferry Channel and Deer Creek Maintenance Dredge Areas Old Ferry Channel Deer Creek System Carteret County Shallow Draft Navigation Waterways Old Ferry Channel and Deer Creek Maintenance Dredging Project Narrative Page 2 of 8 Construction Methodology The proposed maintenance dredging project will restore the Old Ferry Channel to a 50-ft width at -7-ft (- 6+1) MLW with 3H:1V side slopes. Although the main alignment of the Old Ferry Channel maintains the 50-ft width, both the Cape Carteret and Emerald Isle inaugural sections begin with a 30-ft width to help minimize potential shoreline impacts. The dredging project will remove approximately 9,675 cubic yards (CY) of fine grained sand and silt from the shoaled areas of the Old Ferry Channel. A clamshell or excavator type dredge will remove the spoil material for placement in an upland site. The dredge spoil will be placed on a floating barge or bin for transport from the dredge area to a material transfer site on Cape Carteret. At the transfer site, material will be ‘transferred’ from the floating barge to dump trucks (or other hauling equipment) for hauling to one of three (3) placement sites. Tab E (Permit Drawings) shows the proposed Old Ferry Channel dredge area, the material transfer site, and the upland material placement sites in Cape Carteret. The material transfer site is located at 314 Live Oak Drive and the material placement sites are located at 312, 314, & 324 Live Oak Drive (1 site), 307 Bayshore Drive, and 916 WB McLean Drive (Hwy 24). Tab F (Consent of Use Agreements) provides the consent of use agreements for the transfer site and placement of the dredge material at each of the three (3) respective placement sites. Tab E (Permit Drawings) also shows the proposed dredge footprints for the Deer Creek channel segments. Deer Creek consists of four (4) branches and a connecting channel extending from the Old Ferry Channel. The project will remove a maximum of 29,058 CY from the Deer Creek system. The connecting channel originates from a 150-ft widener positioned along the northern segment of the Old Ferry Channel. The widener begins with an approximate 300-ft width and narrows to a 50-ft width over a 150-ft length. The connecting channel then extends approximately 2,000 lf at -6-ft (-5+1) MLW to the main branch of Deer Creek. The main branch extends in both a north and south direction with a 30-ft width at -6-ft (-5+1) MLW. The northern extension covers approximately 500-ft before diverting to the northwest and branching again to School House Creek (also referenced as Rocky Run). Both the Deer Creek (North) and School House Creek continue with a 20-ft width at -4.5-ft (-4 +0.5) MLW. These channels have a decreased navigation space available within the residential areas of Deer Creek due to lower anticipated vessel density. The Deer Creek (North) channel continues in a northwest direction for approximately 2,200 lf to reach the terminus near Yaupon Drive and Highway 24 in Cape Carteret. School House Creek also extends approximately 2,200 lf and terminates at Highway 24. The southern extension of the main Deer Creek channel, referenced as Deer Creek (South), increases from the 30-ft width identified at the confluence with the connecting channel to the Old Ferry Channel, to a 50- ft width approximately 300 lf from the confluence area. A west branch originates where the main channel expands to a 50-ft width. This branch, referenced as Deer Creek (West), extends approximately 1,100 lf with a 20-ft width at -4.5-ft (-4 +0.5) MLW to the terminus at Yaupon Road. Deer Creek (South) continues from the branch point with a 50-ft width at -6-ft (-5+1) MLW for approximately 3,750 lf to a deep-water path in Bogue Sound that accesses the AIWW. Deer Creek (South) follows the Cape Carteret shoreline near Hunting Island and makes a western directional turn towards the Emerald Isle Bridge. Deer Creek (South) then merges with the deep-water path which adjoins the AIWW. The increased width for Deer Creek (South) provides additional maneuverability for vessel traffic anticipated from the AIWW. As the multiple Deer Creek channels access predominately residential canals, the widths decrease in expectations of slower navigation speeds and vessel density. Table 1 provides the design standards for both the Deer Creek and Old Ferry Channel navigational systems. Both the Deer Creek and Old Ferry Channel maintenance operations will utilize the three (3) material placement sites and one (1) transfer site located at the Cape Carteret terminus of the Old Ferry Channel. Erosion control structures, such as silt fencing, biodegradable wattles, and earthen berms, will be Carteret County Shallow Draft Navigation Waterways Old Ferry Channel and Deer Creek Maintenance Dredging Project Narrative Page 3 of 8 implemented and maintained until vegetation cover establishes enough to stabilize the placed material. Material may be placed in the designated facilities up to six (6-ft) feet above the pre-construction grade for either site. However, the final grading for each site will provide a steepest slope of 3H:1V for slope stabilization. In addition, the sites will be smooth graded to discourage water ponding. Figure 2 shows the referenced material transfer site and the three (3) placement areas for the Old Ferry Channel and Deer Creek maintenance operations. Table 1. Old Ferry Channel and Deer Creek Design Elements Channel Depth (MLW-ft) Width (ft) Length (ft) Side Slopes H:V Volume (CY) Old Ferry Channel -7 (-6+1) 30-ft 50-ft 600-ft 6,150-ft 3:1 9,675 Deer Creek Connecting Channel -6 (-5+1) 50-ft 2,150-ft 3:1 10,372 Deer Creek (North) Main Channel -6 (-5+1) -4.5 (-4 +0.5) 30-ft 20-ft 500-ft 2,200-ft 3:1 4,984 Deer Creek (South) Main Channel -6 (-5+1) 30-ft 50-ft 300-ft 3,750-ft 3:1 10,882 School House Creek -4.5 (-4 +0.5) 20-ft 2,200-ft 3:1 689 Deer Creek (West) Branch -4.5 (-4 +0.5) 20-ft 1,100-ft 3:1 2,131 Figure 2. Old Ferry Channel & Deer Creek Material Transfer Site and Placement Facilities Material Placement Facility 307 Bayshore Drive (0.6 Ac) Material Placement Facility 916 WB McLean (0.6 Ac) Material Transfer and Placement Site 312, 314, & 324 Live Oak Drive (1.0 Ac) Cape Carteret Carteret County Shallow Draft Navigation Waterways Old Ferry Channel and Deer Creek Maintenance Dredging Project Narrative Page 4 of 8 The volumetric calculations stem from a hydrographic survey Carteret County conducted in August 2018. Tab G (Hydrographic Survey) shows a color-coded depiction of the reference survey. The survey shows several ‘hotspots’ or shoaled areas in the Old Ferry Channel and Deer Creek system. The shoaled areas reflect a red or yellow color and indicate elevations approaching 0 MLLW (-0.15 MLW)1. The shoaled areas will be prioritized during the maintenance event to minimize dredging costs and potential impacts. Carteret County most likely will not dredge the complete navigational system as described due to budget limitations. However, Carteret County requests authorization to dredge the full footprint, as described for the Old Ferry Channel and Deer Creek, in the event additional funds become available in out-year budgets. Obtaining and preserving the appropriate state and federal authorizations through one permitting process, for the complete Old Ferry Channel and Deer Creek system, provides a future potential cost savings by avoiding multiple permit submittals. Carteret County will also limit the construction activities to daytime hours between November 16th and March 31st. Limiting the construction timeframe to the cooler winter months will reduce the injury risk to potential migrating species such as West Indian manatee, and juvenile fish species. Scheduling the work in the winter months will also reduce the potential risk of injuring or harassing sea turtles, which generally show a greater presence density in the summer months. The dredging will also maintain a 10-ft buffer from aquatic vegetation such as marsh grass or vegetated wetlands. Implementing the buffer will help minimize the potential for the channel side slopes to erode the vegetation through tidal scour or boat wake impacts. Carteret County also acknowledges the potential existence of oyster habitat within School House Creek. In order to minimize the potential impacts to oyster in this area, Carteret County will conduct an oyster relocation prior to dredging School House Creek. Carteret County will coordinate with the N.C. Division of Marine Fisheries (DMF) during the develop and implementation of the oyster relocation plan. Carteret County will also provide the N.C. Division of Coastal Management (DCM) with notice of satisfactory completion of the relocation efforts from DMF, prior to initiating dredging activities in School House Creek. Previous Permits As referenced above, the proposed work will be the first known maintenance dredging event for the Old Ferry Channel since the original construction in 1961. W. B. McLean conducted the original dredging to promote ferry travel between Cape Carteret and Emerald Isle2. Subsequently, North Carolina operated a ferry service through the navigation channel until 1971, when the B. Cameron Langston Bridge replaced the ferry service as the primary access between Emerald Isle and Cape Carteret. The Old Ferry Channel has maintained navigation depth, presumably due to the boating traffic and tidal currents helping to flush shoaled sediment from the waterway. The original construction also did not fall under permit review. The original dredging occurred prior to 1972 and the enactment of the North Carolina Dredge and Fill Law and the federal Coastal Zone Management Act. Portions of the Deer Creek system have been previously maintained. Tab H (Previous Permits) contains records of maintenance events proposed during 2001 and 2007. The previous permits concentrate on localized shoaling within the residential neighborhoods of Deer Creek and do not encompass the complete recreational navigable system. However, the current proposal stems from the previous maintenance attempts and concentrates on minimizing potential dredging impacts. The previous dredging projects allowed excavation to -4-ft Normal Water Level (NWL) and the current plan limits dredging to -4.5-ft (-4   1 Datum’s reference benchmark sheets established for NOAA station 8656483, Beaufort, Duke Marine Lab  2 Cape Carteret (2019). History of the Town of Cape Carteret, NC. URL www.townofcapecarteret.org/town-history.html (visited 2019, September 25). Carteret County Shallow Draft Navigation Waterways Old Ferry Channel and Deer Creek Maintenance Dredging Project Narrative Page 5 of 8 +0.5) MLW. Accounting for the elevation difference between NWL and MLW (0.17-ft), the current plan extends the dredging depth approximately 0.67-ft below the previously authorized dimensions to provide a minimal (0.5-ft) overdredge allowance and a 0.17-ft conversion to the MLW datum. The overdredge allowance provides additional workspace for the contractor to help prevent excavation below the authorized limits. Sediment Composition Sediment analysis results indicate silty and fine grain sands comprise a large percentage of Old Ferry Channel and Deer Creek. As a result, the material most likely does not meet state standards for beach placement as beneficial reuse. Tab I (Sediment Analysis) shows the complete sediment composition for the samples collected for Old Ferry Channel and the Deer Creek system. For reference, Table 2 and Table 3 provide a summary of each dredge area and Figure 3 shows the sediment sample locations in planview. Table 2. Sediment Analysis for Old Ferry Channel Sample Sediment Classification (% by weight) % Gravel % Granular % Sand % Fines OFC-01 - - - - OFC-02 0.44 0.38 83.79 15.39 OFC-03 0.00 0.03 94.21 5.77 OFC-04 0.13 0.31 78.95 20.61 OFC-05 0.22 0.01 96.00 3.77 OFC-06 0.63 0.63 83.54 15.19 OFC-07 1.20 0.20 94.30 4.31 OFC-08 21.07 2.13 52.87 23.94 OFC-09 - - - - OFC-10 0.00 0.03 29.23 70.75 OFC-11 - - - - OFC-12 0.12 0.58 58.48 40.83 OFC-13 0.00 0.07 82.79 17.14 Composite 2.38 0.44 75.42 21.77 Notes: Sediment Classification determined in accordance with 15A NCAC 07H.0312 (1) e. (-) indicates the sample depth was below the max. (deepest) dredge elevation. Composite characteristics determined by simply arithmetic mean. Table 3. Sediment Analysis for Deer Creek Sample Sediment Classification (% by weight) % Gravel % Granular % Sand % Fines DC-01 0.31 0.41 70.19 29.09 DC-02 0.96 0.56 64.67 33.81 DC-03 0.00 0.18 19.28 80.54 DC-04 - - - - DC-05 0.36 1.16 83.67 14.81 DC-06 0.90 1.58 72.51 25.01 DC-07 0.00 0.01 96.92 3.07 DC-08 2.52 0.25 95.28 1.95 DC-09 17.33 2.18 61.59 18.91 Composite 2.80 0.79 70.51 25.90 Notes: Sediment Classification determined in accordance with 15A NCAC 07H.0312 (1) e. (-) indicates the sample depth was below the max. (deepest) dredge elevation. Composite characteristics determined by simply arithmetic mean. Carteret County Shallow Draft Navigation Waterways Old Ferry Channel and Deer Creek Maintenance Dredging Project Narrative Page 6 of 8 Figure 3. Old Ferry Channel & Deer Creek Sediment Sample Locations (Not To Scale) Cape Carteret Bogue Sound AIWW Sediment Sample Location (Typ.) Emerald Isle OFC-01 OFC-13 OFC-11 OFC-09 OFC-07 OFC-05 OFC-03 DC-09 DC-04 DC-05 DC-03 DC-01 DC-06 DC-07 DC-08 DC-02 Carteret County Shallow Draft Navigation Waterways Old Ferry Channel and Deer Creek Maintenance Dredging Project Narrative Page 7 of 8 Table 2 and Table 3 indicate approximately 25% of the dredge material consists of silty sands. Although the project did not evaluate a native beach for comparison, generally any site with greater than 10% fines will not meet North Carolina state criteria for beach placement. Carteret County also understands the financial burden and economic cost of transferring the dredge material via truck haul to a nearby beach, assuming the material could satisfy the NC requirements for beneficial reuse placement. Therefore, Carteret County refrained from exploring if the material would be appropriate as beneficial reuse based on the sediment results and general knowledge of sand quality at the nearby beaches and overall cost implications. Summary Carteret County requests authorization to maintenance dredge the Old Ferry Channel and the Deer Creek waterways in efforts to enhance recreational navigation access for residents and visitors of Cape Carteret and Emerald Isle. The proposed project will improve navigation access through the Old Ferry Channel to the AIWW from both Cape Carteret and Emerald Isle. The Old Ferry Channel has served as a recreational navigation throughway for both communities since the 1971 construction of the B. Cameron Langston Bridge. The bridge construction reduced the need for a state operated ferry system to provide the primary travel option between Emerald Isle and Cape Carteret. As the ferry system became less used, Old Ferry Channel became a recreational asset for providing navigational access for local boaters in Cape Carteret and Emerald Isle to the AIWW. Old Ferry Channel extends approximately 6,750 lf (1.3 miles) to connect Emerald Isle with Cape Carteret. The waterway also crosses the AIWW in Bogue Sound to provide navigable access to deep-water. The maintenance project will remove a maximum of approximately 9,675 CY from the Old Ferry Channel alignment. The excavation will occur down to a maximum (deepest) elevation of -7-ft (-6+1) MLW over an approximate 50-ft channel width. The Old Ferry Channel alignment narrows from the 50-ft width to 30- ft at both the Emerald Isle and Cape Carteret terminus. The change in width occurs in response to slower vessel speeds anticipated within the mooring areas and to help limit potential dredging impacts. The proposed maintenance will help improve navigation depths through the residential community adjoining the Deer Creek system. Deer Creek consist of four (4) branches extending from a connecting channel that originates at the Old Ferry Channel. The complete Deer Creek system extends approximately 12,200 lf (2.3 miles) and contains approximately 29,058 CY of shoaled material. Maintenance operations will dredge to a maximum (deepest) elevation of -6-ft (-5+1) MLW in the main channels and -4.5-ft (-4 +0.5) MLW in the residential canal areas. The channel widths vary from 50-ft wide in the main channel segments to 20-ft wide in the residential portions. The varying design dimensions stem from the vessel traffic density anticipated within each navigable waterway. Records indicate this will be the first documented maintenance event for Old Ferry Channel since the original construction in 1961. However, portions of the Deer Creek system have incurred at least two (2) prior maintenance events. The proposed action will be the first to encapsulate the full extents of the Deer Creek system and will help provide a documented channel alignment for future maintenance events. Due to available funding, actions remain unlikely to remove the complete dredge volume proposed for the maintenance event. However, obtaining the necessary permits and authorizations under the current efforts will assist the County in future maintenance operations by defining a channel alignment and operational plan. The sediment placement plan provides three (3) dredge material placement facilities. The dredge material composition most likely falls below the necessary standards for beneficial reuse; and therefore, will be placed in upland facilities. The proposed placement facilities cover approximately 2.2 acres and material will not be placed higher than six (6) feet above pre-construction conditions in either site. Expectations Carteret County Shallow Draft Navigation Waterways Old Ferry Channel and Deer Creek Maintenance Dredging Project Narrative Page 8 of 8 suggest the project will not remove a significantly greater volume than the available capacity can maintain. However, if additional financial resources become available a greater volume may be removed. In this event, material will be stockpiled for dewatering in the placement facilities and removed prior to raising either site more than 6-ft above the existing elevations. Dewatered material will be truck hauled to a landfill facility to create or restore capacity for the additional material. Material remaining in the placement facilities will be smooth graded to discourage water ponding and will also be graded at a maximum slope of 3H-1V for slope stability. Erosion control structures, such as silt fencing, biodegradable wattles, and earthen berms, will be implemented and maintained until vegetation cover establishes enough to stabilize the placed material. The maintenance project will occur during the winter months of November 16th through March 31st. Constricting the construction to this period will help reduce the potential for environmental impacts. The dredging operations will also maintain a 10-ft buffer from wetland vegetation. Implementing the buffer will help minimize the potential for the channel side slopes to erode the vegetation through tidal scour or boat wake impacts. The County will also relocate potential oyster habitat in School House Creek, prior to dredging activities occurring in the referenced waterway. These considerations coupled with the channel design should provide a reasonable and environmentally acceptable enhancement to the navigation systems within the Old Ferry Channel and Deer Creek systems.