HomeMy WebLinkAboutNC133CulvertstoBridge.frm 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 on NC 133 over Sand Hill Creek and a UT to
Sand Hill Creek near Boiling Spring Lakes, Brunswick County.
Latitude: 34°6’1” N Longitude: 77°58’11” W
3. INVESTIGATION TYPE: CAMA and D&F
4. INVESTIGATIVE PROCEDURE: Date of Site Visit – October 26, 2023
Was Applicant Present – No
5. PROCESSING PROCEDURE: Application Received Complete: September 28, 2023
Office – Morehead City
6. SITE DESCRIPTION:
(A) Local Land Use Plans – Brunswick County
Land Classification From LUP –Open Space Conservation 1 and Rural-Agriculture
(B) AEC(s) Involved: CW
(C) Water Dependent: Yes
(D) Intended Use: Public
(E) Wastewater Treatment: Existing – N/A
Planned - N/A
(F) Type of Structures: Existing – Site 1 - Twin 36” diameter and one 48” diameter pipes
Site 2 - Single 60” diameter pipe
Planned - Site 1 - 385’ long cored slab bridge
Site 2 - Single 84” diameter pipe
(G) Estimated Annual Rate of Erosion: N/A
Source – N/A
7. HABITAT DESCRIPTION: [AREA]
EXCAVATED FILLED OTHER
(A) Open Water
305 sf
Temp. impacts 279 sf
(B) Coastal Wetlands
(C) Section 404 Wetlands
5,402 sf (for restoration)
1,566 sf (for restoration)
3 sf
9,205 sf
Hand cleared 3,188 sf
Hand cleared 773 sf
Mechanized clearing 5,537 sf
(D) High Ground
Disturbed by project 166,320 sf
(D) Total Area Disturbed: 192,578 sq. ft.
(E) Primary Nursery Area: No
(F) Water Classification: C; Sw Open: No
8. PROJECT SUMMARY: The applicant proposes to replace the existing three pipes on NC 133 over Sand
Hill Creek with a new 385’ long bridge including causeway removal and replacement of the existing
pipe on NC 133 over a UT to Sand Hill Creek with a new larger pipe and associated infrastructure.
FIELD INVESTIGATION REPORT:
NORTH CAROLINA DEPARTMENT OF TRANSPORTATION
NC 133 CULVERTS REPLACEMENT OVER SAND HILL CREEK
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9. NARRATIVE DESCRIPTION:
Project Setting
The project is located on an approximately 2,800’ section of NC 133 (River Road) adjacent to the
road’s intersection with SR 1521 (Funston Road SE) crossing over Sand Hill Creek and a UT to
Sand Hill Creek near Boiling Springs, Brunswick County. Roadway elevations in the project area
range from a low of approximately 6’ above NHW adjacent to Sand Hill Creek to 22’ above NHW
near the southern end of the project. NC 133 floods during storm events at the culvert crossings
creating hazardous conditions for travelers. The area in the vicinity of the project can be
predominantly characterized as Riverine Swamp Forest with Mixed Hardwood/Pine Forest at the
higher elevations adjacent to the project. The side slopes of the elevated causeway through the
project area are maintained and vegetated with sod grasses grading to coastal wetland vegetation
adjacent to Sand Hill Creek, while Section 404 Wetlands reside adjacent to the UT to Sand Hill
Creek. Several houses populate the area beyond the project boundaries.
The existing roadway in the project area is a two-lane road with 12’ wide asphalt travel lanes and
grassed shoulders. Currently two 36” diameter by 50’ long reinforced concrete pipes and one 48”
diameter by 50’ long corrugated metal pipe carries Sand Hill Creek under the roadway. A 60” by
50’ long reinforced concrete pipe carries the UT to Sand Hill Creek under NC 133. The existing
culverts in the project area are buried and undersized resulting in the flooding condition. There are
currently no stormwater runoff controls in the project areas.
Multiple utility lines are located within the project vicinity. Brunswick Electric Cooperative
(BEMC) owns aerial power lines that parallel the west side of the project. Spectrum currently has
telecommunication lines that are attached to the BEMC poles and cross aerially over the project area.
AT&T has telecommunication lines that are buried underground along both sides of NC 133 in the
project area.
The waters of Sand Hill Creek and the UT to Sand Hill Creek both received a classification of C;
Swamp and are classified as Inland Waters in the area of the proposed construction. The
waterbodies are not considered a Primary Nursery Area nor Anadromous Fish Spawning Area and
are closed to shellfishing by the Shellfish Sanitation Section of the Division of Marine Fisheries.
Sand Hill Creek has no defined channel on the west side of the project site and is approximately 10’
wide with depths in the 3’ to 4’ range; it splits into multiple channels immediately downstream of the
culverts (east side of the project). The UT to Sand Hill Creek is approximately 3’ wide with depths
in the 1’ to 2’ range. There were no SAV’s or oyster beds expected or observed in the project area
during the site visit.
There were no historic or archeological resources identified within the project area.
Project Proposal
NCDOT proposes to replace the existing culverts on NC 133 over Sand Hill Creek and a UT to
Sand Hill Creek with a bridge and larger culvert respectively, as well as raise the adjacent roadway
to address flooding issues on NC 133. To initiate the project, NC 133 would be closed to traffic in
the project area and rerouted to an off-site detour utilizing NC 133, US 17, and NC 87,
approximately 43 miles in total length.
FIELD INVESTIGATION REPORT:
NORTH CAROLINA DEPARTMENT OF TRANSPORTATION
NC 133 CULVERTS TO BRIDGE OVER SAND HILL CREEK
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To facilitate construction of the new bridge and for restoration purposes, the applicant would
excavate the culverts and existing causeway at Sand Hill Creek down to match existing Coastal
Wetland elevations. This would entail removal of an approximately 60’ wide x 385’ long section
(23,100 square feet) of the causeway. The excavation would include 5,402 square feet of existing
Coastal Wetlands and 1,475 square feet of Section 404 Wetlands to blend the removal area smoothly
into the natural wetland elevations. Restoration of the area would be carried out in accordance with
the Wetland Restoration Plan submitted with the project application.
The existing pipes over Sand Hill Creek are to be replaced on the existing alignment with a
bridge 385’ in length and 36’ in width utilizing top-down construction techniques. The bridge as
proposed would include two 12’ wide travel lanes, with a 4.75’ shoulder on each side, and 1.25’
wide concrete rails. The bridge would consist of seven 55’ spans and utilize cored slab construction.
The bridge would be approximately 7’ above wetland elevations. Stormwater from the bridge would
be discharged via 34 drains in the deck of the bridge and by two grated inlets at the south end of the
bridge. The outfalls from the deck drains would discharge onto 6’ x 6’ riprap dissipater pads to
prevent erosion of adjacent wetlands.
The existing pipe over the UT to Sand Hill Creek would be replaced with an 84” diameter x 60’
long corrugated aluminum pipe with aluminum headwall and the inverts of the pipe would be buried
1’ below the creek bed. The pipe would be dewatered during replacement utilizing NCDOT Best
Management Practices. The new pipe would be constructed with equipment from the existing
roadway.
The approach structures to the bridge and new culvert would be raised to allow for the increased
height of the new bridge and prevent overtopping of the roadway during storm events. The roadway
on the northern end of the bridge would be elevated by up to 7’ from STA. 12+50 to STA. 18+63,
while the roadway on the southern end of the bridge to the southern terminus of the project would be
elevated by up to 5’ between STA. 22+50 and STA. 40+20. The new roadway would be constructed
with two 12’ travel lanes and 4’ paved shoulders.
Ripap and rock plating would be utilized at several locations on the project. The bases of the
bridge would be stabilized with 80 linear feet of riprap placed 10’ wide. Riprap would also be
utilized to backfill a scour hole at the upstream end of the new 84” pipe. The riprap would be up to
12’ in width and 11’ in length. The banks of the stream downstream from the end of the 84” pipe
would also be stabilized with riprap for 10’.
The increased height of the causeway would necessitate stabilization at areas where the causeway
abuts wetland areas. Immediately adjacent to the riprap placed at the bases of the bridge, rock
plating would be placed along the toe of the causeway up to 15’ wide and total 270 linear feet. Rock
plating up to 10’ wide and up to approximately 600 linear feet would also be used to plate the slopes
in the vicinity of the 84” pipe.
As part of the project, the existing ditches would be regraded in all four quadrants of the bridge
and the southwest quadrant of the new 84” pipe. The ditches would dissipate into wetlands at
existing locations thereby retaining existing drainage patterns.
Two utility line relocations would have to occur with the project. Spectrum would abandon their
telecommunication line on the west side of the project and construct a new line via directional bore.
along Funston Road tying into an existing hand hole in front of the cell tower site. AT&T will
abandon their telecommunication lines on both sides of the road through the project area. They
would tie the existing services into their existing underground lines via a directional bore under
FIELD INVESTIGATION REPORT:
NORTH CAROLINA DEPARTMENT OF TRANSPORTATION
NC 133 CULVERTS TO BRIDGE OVER SAND HILL CREEK
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NC 133 on the north end of the project and via a directional bore along the east side of the road on
the south end of the project. No wetlands or waters of the State would be impacted by the
relocations.
Anticipated Impacts
The riprap associated with the construction of the 84” pipe would permanently fill 306 sq. ft. of
open water and temporarily impact another 279 sq. ft. of open water during the dewatering process.
The removal of the high ground causeway would require the excavation of 5,402 sq. ft. of Coastal
Wetlands and 1,566 sq. ft of Section 404 Wetlands to smoothly match the grade of the adjacent
wetlands. The riprap at the base of the bridge would permanently fill 3 sq. ft. of Coastal Wetlands.
The higher and wider slopes of the roadway would require permanently filling 9,205 sq. ft. of
Section 404 Wetlands and mechanized clearing of 5,537 sq. ft of Section 404 Wetlands.
Additionally, 773 sq. ft. of Section 404 Wetlands and 3,188 sq. ft. of Coastal Wetlands would be
hand cleared due to the higher and wider slopes of the roadway. The project would result in 166,320
sq. ft. of high ground disturbance mainly due to the grading and paving of the roadway, removal of
the culverts, and removal of the causeway for restoration.
There were no historic or archeological resources identified within the project areas, therefore no
impacts to either of these resources are expected. No additional closures of shellfishing waters are
expected in association with the proposed project. Impacts to fisheries resources within the streams
on the project are expected to be de minimis.
The applicant has proposed to offset the unavoidable stream impacts by debiting 78 stream
mitigation credits from the Sneeden Site, a private mitigation bank. Wetland impacts from the
project would be offset by removal of the high ground causeway and on-site wetland restoration.
The on-site restoration and enhancement portion of the project would restore 0.34 acres of high
ground to wetlands and enhance 0.16 acres of existing wetlands by adjusting their grade to match the
adjacent wetlands. The restoration area would include the proposed deck drain dissipator pads under
the new bridge. All mitigation generated by the proposed restoration would only be used for this
project. No banking of any excess mitigation is proposed by the applicant.
The applicant has proposed to construct the bridge and culvert utilizing minimization measures to
reduce the environmental impacts from the project which include but not limited to utilizing an off-
site detour with top-down construction techniques, minimized fill slopes, and sediment and control
measures that adhere to the Design Standards in Sensitive Watersheds criteria.
The replacement of the culverts with larger structures is expected to allow for increased hydraulic
flow and connectivity throughout the Sand Hill Creek System. The increase in height of the
roadway, in conjunction with the increased hydraulic flow is expected to reduce flooding of the
roadway during storm events thereby increasing safety of the traveling public.
Submitted by: Stephen Lane –Morehead City District – November 3, 2023