Brunswick 15 Field Report

DIVISION OF COASTAL MANAGEMENT FIELD INVESTIGATION REPORT

l. APPLICANT'S NAME: North Carolina Department of Transportation

2. LOCATION OF PROJECT SITE: The project is located at Bridge No. 15 over the Calabash
River on NC 179B in Brunswick County (T.I.P. No. BR-0160).

Latitude: 33° 53’ 23” N Longitude: 78° 32’ 58” W

3. INVESTIGATION TYPE: CAMA and D&F

4. INVESTIGATIVE PROCEDURE: Date of Site Visit – December 9, 2022
Was Applicant Present – No

5. PROCESSING PROCEDURE: Application Received Complete: December 5, 2022
Office – Morehead City
6. SITE DESCRIPTION:
(A) Local Land Use Plan – Town of Calabash, Brunswick County
Land Classification From LUP – Conservation, Residential
(B) AEC(s) Involved: EW, PTA, CS, CW
(C) Water Dependent: Yes
(D) Intended Use: Public
(E) Wastewater Treatment: Existing – N/A
Planned - N/A
(F) Type of Structures: Existing – Bridge for public use
Planned - Bridge for public use
(G) Estimated Annual Rate of Erosion: N/A
Source – N/A

7. HABITAT DESCRIPTION: [AREA]
EXCAVATED FILLED OTHER (A) Open Water 950 sf Additional shading 3,171 sf Disturbed by project 261 sf
(B) Coastal Wetlands

10,137 sf

1,119 sf

Hand clearing 4,260 sf
(C) Section 404 Wetlands

585 sf

Mechanized clearing 584 sf
Hand Clearing 60 sf
(D) High Ground 17,424 sf Disturbed by project 95,214 sf

(D) Total Area Disturbed: 133,765 sq. ft.
(E) Primary Nursery Area: Yes
(F) Water Classification: SA; HQW Open: No

8. PROJECT SUMMARY: The applicant proposes to replace the existing 281’ long concrete bridge on
NC 179 Business over the Calabash River with a new 575’ long concrete bridge
including a multi-use path on the bridge and associated infrastructure on the
existing alignment.
FIELD INVESTIGATION REPORT:
N.C.D.O.T. – BRUNSWICK BRIDGE NO. 15 OVER THE CALABASH RIVER
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NARRATIVE DESCRIPTION:

Project Setting

Bridge No. 15 is located over the Calabash River on NC 179 Business (Beach Drive SW),
approximately 0.7 miles south of the intersection of NC 179 Business and NC 179 in the Town of
Calabash, Brunswick County. Typical elevations in the project area range from 0 to 12 feet. The
northern area of the project includes a 75’ wide x 310’ long causeway leading from the north end of
the bridge through Coastal Wetlands to high ground. The land along the sides of the causeway and
the banks of the Calabash River are vegetated with Spartina alterniflora, Juncus roemerianus,
Distichlis spicata, and Spartina patens. The high ground on the north end of the bridge is residential
in nature, with a single-family home site located in the northwest quadrant of the bridge and a
recreational vehicle campground located in the northeast quadrant. The land in the southwest
quadrant of the bridge is owned by the Town of Calabash and is the former site of commercial
fishing docks. The docks are now dilapidated, and the Town has designated the site as Waterfront
Park and plans to develop the park in the future. Waterfront Park is qualified for protection under
Section 4(f) of the U.S. Department of Transportation Act. The land in the southeast quadrant of the
bridge is privately owned and wooded, predominantly with loblolly pines and scattered maple and
gum trees. There are no known historic resources within the project area. One archaeological site,
determined not eligible, will be preserved in place.
The existing bridge was constructed in 1975 and is 281’ long with 29.3’ of clear roadway width,
including a 12’ wide travel lane in each direction. The cored slab bridge consists of seven fixed
spans, with a maximum horizontal distance of approximately 40’ between bents. The bridge is
supported with concrete bent caps on steel I-beams, with lateral bracing at each bent. Stormwater
from the bridge currently drains directly into the Calabash River. The vertical clearance underneath
the bridge is 12’.
The bridge received a 43, out of a possible 100 points during its last sufficiency rating and is
listed as structurally deficient due to severe deterioration of its bent lateral bracing and end bents.
NC 179 Business is a designated hurricane evacuation route and NC Bike Route 1 and 3 both run
along its length. The annual average daily volume of traffic over the bridge in 2018 was
approximately 7,100 vehicles per day and is projected to increase to 14,200 vehicles per day by
2040. A wrack line indicating overtopping of the causeway was observed during the field
investigation of the project.
The utilities in the project area consist of telecommunication lines and an 8” water line on the
west side of the project, as well as an 8” sanitary sewer line, telecommunication lines, and overhead
electric lines on the east side of the project.
The Calabash River is classified SA; HQW in the area of the proposed construction by the
Environmental Management Commission. The stream has been designated as Coastal Waters in the
vicinity of the bridge and has been designated a Primary Nursery Area immediately upstream of the
bridge. The waters adjacent to the bridge are closed to shellfish harvesting by the Shellfish
Sanitation Section of the Division of Marine Fisheries. The Calabash River is approximately 525’
wide at the project site with a maximum water depth of -6’ below normal low water. There was no
submerged aquatic vegetation observed in the project area during the site visit. An oyster reef was
observed under the existing bridge between bent numbers two and four and appears to be well
established.

FIELD INVESTIGATION REPORT:
N.C.D.O.T. – BRUNSWICK BRIDGE NO. 15 OVER THE CALABASH RIVER
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Project Proposal

NCDOT proposes to replace the existing Bridge No. 15 over the Calabash River. The project
involves replacement of the existing bridge and related approaches with a prestressed concrete
bridge and new approaches on the existing alignment. The total project length is 0.313 miles. To
initiate the project, the existing bridge would be closed to traffic and traffic would be directed to an
off-site detour route along NC 179, NC 904, Sunset Boulevard North, and Shoreline Drive West
resulting in a detour approximately 10 miles in length.
The existing bridge would be completely demolished and removed from the project site utilizing
NCDOT’s Best Management Practices for Construction and Maintenance Activities. All demolition
of the existing bridge and all work on the new bridge would be accomplished via top-down
methodology from the existing bridge deck, existing causeway, and new bridge deck. The use of top-
down methodology would eliminate the need to construct a temporary work trestle on the project.
Once the old bridge is removed from the project site, the existing causeway would be excavated
down to adjacent coastal wetland elevations. This would involve excavating a 90’ wide x 310’ long
section of existing roadway fill beginning near the northern terminus of the old bridge to the high
ground on the mainland side of the project. The causeway would be removed down to
approximately 1’ of elevation and require excavation into the existing adjacent coastal wetlands to
blend the removal area smoothly into natural wetland elevations and eliminate high areas at the base
of the causeway. Excavated areas would be ripped and disked prior to planting of the site if
necessary.
The new bridge as proposed would be 575’ in length and 45’ in width, which would be 294’
longer and 15’ wider than the existing bridge. The new bridge would consist of ten spans of
approximately 57’ each and include four bents located within the river. The bridge would provide
for a 12’ wide travel lane in each direction as well as a 10.7’ wide multi-use path on the west side of
the bridge. A 42” tall slotted concrete barrier would be constructed between the travel lanes and the
multi-use path from STA. 17+90 to STA. 25+41. The bridge design would provide approximately
55’ of horizontal clearance through the bridge and 17’ of vertical clearance underneath the bridge.
To allow for the increased height of the new bridge and prevent overtopping during storm events,
the applicant has requested to raise the approach structures to the bridge. The road on the north and
south ends of the bridge would be raised for 483’ and 588’, respectively, by up to 5’ at each end of
the bridge. The road would then be replaced from STA. 13+00 to STA. 18+88 and from STA.
24+67 to STA. 29+50 and include two 12’ wide asphalt travel lanes with eight-foot paved shoulders.
Additionally, a 10’ wide concrete multi-use path would be constructed along the west side of the
new roadway to connect the Town of Calabash’s Waterfront Park into the multi-use path on the new
bridge.
The applicant has proposed to install riprap at several locations on the project. The bases of the
bridge are to be stabilized with Class II riprap. The riprap as proposed would be up to 290’ in length
and 20’ in width around the southern end bent of the bridge and 140’ in length and 20’ in width
around the northern end bent. The slope along the causeway in the southwest quadrant of the project
would also be rock plated for 50 linear feet between Sta. 14+00 and Sta. 14+50 LT.
Stormwater from the bridge would be dispersed into the Calabash River below via deck drains
located in the bridge rails. The stormwater from the roadway is designed to discharge at non-erosive
velocities over grassed shoulders and conveyed to lower elevations by several new pipe additions,
vegetated conveyances, and base swales located adjacent to the roadway along both sides of the
project. Approximately 120 linear feet of Class I riprap would also be placed between Sta. 24+30

FIELD INVESTIGATION REPORT:
N.C.D.O.T. – BRUNSWICK BRIDGE NO. 15 OVER THE CALABASH RIVER
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and Sta. 25+50 RT to help stabilize the cut ditch channeling stormwater to the adjacent wetlands on
the north end of the project. The existing 18” diameter culvert at approximately STA.14+45 would
be replaced with a 24” culvert as part of the project. A channel change is also proposed from Sta.
18+67 to Sta. 19+10 RT due to the fill from the end bend stabilization there.
Multiple utilities would have to be relocated as part of the project. The existing 8” water line on
the west side of the project and the existing 8” sanitary sewer force main on the east side of the
project would each be relocated 15’ further away from the bridge and replaced with 10” diameter
lines via directional drill under the Calabash River. The existing telecommunication lines on the
west side of the road would be abandoned and the existing telecommunication lines and overhead
power lines on the east side of the road would be relocated 30’ further east in a joint bore under the
creek. Utility relocations would be accomplished through a combination of open cuts and directional
bores. All of the directional bores would be constructed at least 15’ under the bottom of the creek,
and bore pits would not be located within wetlands or waters of the State. There is also a new
driveway proposed into Waterfront Park on the south side of the project, as well as new driveway to
serve a utility easement on the north side of the project.

Anticipated Impacts

The proposed riprap stabilization for the bridge would permanently fill 950 sq. ft. of open water
and require disturbing another 261 sq. of open water the during the installation process. The new
bridge would shade 3,171 sq. ft. of open water beyond that which is shaded by the existing bridge.
The removal of the high ground causeway would require the excavation of 9,745 sq. ft. of Coastal
Wetlands to properly match the predominant Coastal Wetland elevations surrounding the causeway.
The channel change adjacent to the riprap on the south side of the project would require 392 sq. ft. of
excavation of Coastal Wetlands. The construction of the riprap stabilization around the proposed
bridge end bents would require filling 1,119 sq. ft. of Coastal Wetlands. An additional 4,260 sq. ft.
of Coastal Wetlands would be hand cleared for the causeway removal and riprap stabilization on the
project.
The construction of the 24” culvert would require filling 585 sq. ft. of Section 404 Wetlands and
require another 584 sq. ft of mechanized clearing within Section 404 Wetlands. An additional 60 sq.
ft. of Section 404 Wetlands would be hand cleared for drainage on the project.
The project would result in a total of 118,464 sq. ft. of high ground disturbance, including the
grading and paving of the new approaches to the bridge, removal of the causeway areas under the
proposed bridge, and relocation of utility lines on the project. The removal of the causeway areas
under the proposed bridge would represent 17,424 sq. ft. of the total proposed high ground
disturbance. The vertical navigable clearance under the bridge would increase by 5’ from 12’ to 17’.
The new bridge would also allow an increase in the maximum horizontal opening under the bridge
from 40’ to 55’.
The wetland impacts from the bridge replacement project would be offset by removal of the
high ground causeway and on-site coastal marsh restoration. The site is estimated to provide a total
of 17,424 sq. ft. of brackish marsh wetlands and would be used as mitigation for impacts from the
project, with the potential to apply any excess credits to other projects as appropriate. The applicant
has proposed a 0.75 mitigation ratio for the entire 0.4 acres causeway removal area which would
result in a total of 0.3 acres of mitigation credits. The causeway removal would also increase the
hydraulic opening under the bridge to allow for increased river flow under the structure during

FIELD INVESTIGATION REPORT:
N.C.D.O.T. – BRUNSWICK BRIDGE NO. 15 OVER THE CALABASH RIVER
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storms.
The applicant has incorporated multiple avoidance and minimization measures into the project
design, including but not limited to maximizing span lengths, the use of steepened slopes,
implementation of BMP’s for Construction and Maintenance Activities, implementation of Design
Standards for Sensitive Watersheds, and the use of top-down methodology with an off-site detour to
avoid the need for temporary bridges and/or trestles. The applicant has agreed to adhere to the U.S.
Fish and Wildlife Service’s “Guidelines for Avoiding Impacts to the West Indian Manatee:
Precautionary Measures for Construction Activities in North Carolina Waters”. An in-water work
moratorium would be implemented from April 1 through September 30 to reduce impacts to
fisheries resources within the Calabash River and construction activity at or below the mean high
water elevation within the Calabash River would not be allowed from April 1 to September 30
without exclusion devises, casings, or other barriers to allow work in the dry.
Deck drain fall heights from the bridge range from 13’ to 14.3’. Deck drains would be removed
from the ends of the bridge to reduce the chances of bank erosion from discharge onto embankment
slopes. The applicant states that deck drains in the bridge rail provide dispersed discharge over the
water providing maximum dilution of stormwater runoff.
No additional closures of shellfishing waters are expected in association with the proposed
project, however, one of the proposed bridge bents may impact the oyster reef located under the
proposed bridge. A localized increase in turbidity can be expected during the in-water construction
portion of the permanent bridge, demolition of the existing bridge, and restoration Coastal Wetlands.
Impacts to the Town of Calabash’s Waterfront Park were determined to be de minimis in accordance
with the requirements of Section 4(f) of the U.S. Department of Transportation Act. The public is
expected to benefit upon completion of the project by the increase in the safety of the new structure.

Submitted by: Stephen Lane –Morehead City District – December 22, 2022