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Home My WebLink AboutR-2822B__Concurrence Point 2A_4B_Packet - June 2022_Final-CombinedCombined Concurrence Point 2A (Revisited) and 4B Meeting NC 143 Improvements From West Buffalo Creek to NC 143 Business, west of Robbinsville Graham County WBS No. 34508.1.1 STIP Project No. R-2822B June 15, 2022, at 1:00 pm North Carolina Department of Transportation Prepared By Stantec Consulting Services, Inc. 801 Jones Franklin Road, Suite 300 Raleigh, NC 27606 919-851-6866 STIP Project R-2822B (NC 143 Improvements): Combined CP 2A (Revisited) & 4B Meeting 1 | Page 1.0 Meeting Purpose • Revisit Concurrence Point 2A (Bridging Decisions) – Hooper Branch Crossing • Conduct Concurrence Point 4B (30% Hydraulic Review) 2.0 Project Description The North Carolina Department of Transportation (NCDOT) proposes to make safety improvements along NC 143 from West Buffalo Creek to NC 143 Business, west of Robbinsville in Graham County. The project corridor is approximately 4.5 miles long. The project location is shown below in Figure 1. This project is included in the 2020 - 2029 State Transportation Improvement Program (STIP) as Project R-2822B. The proposed improvements include upgrading NC 143 to ensure that all vertical and horizontal curves have a minimal design speed of 35-mph. The project will widen the lanes to 11feet and widen the shoulders to 6feet (4-foot paved), which is consistent with the minimal recommendations for a Rural Collector in the NCDOT 3-R guidance. Figure 1: Build Alternative PROPOSED HOOPER BRANCH CROSSING STIP Project R-2822B (NC 143 Improvements): Combined CP 2A (Revisited) & 4B Meeting 2 | Page 3.0 Concurrence Point 2 Recap • During the March 22, 2018, Combined Concurrence Point 1, 2, and 2A Meeting, it was concurred that a 115-foot long, 8x8 reinforced concrete box culvert (RCBC) would be constructed at the new Hooper Branch crossing along each of the Alternatives Carried Forward. • The replacement of Bridge #13 over Snowbird Creek was added to the scope of the LEDPA (Alternative 4A) during the Concurrence Point 3 Meeting, which was conducted on March 20, 2019. Staged construction would be the method of reconstruction for Bridge #13 due to no feasible off-site detours. o Due to the staged construction, the modified alignment would require a new approximately 60-foot long hydraulic structure at Hooper Branch instead of the previously recommended 115-foot long 8x8 RCBC. This would also allow for the removal of the 48-inch Corrugated Metal Pipe (CMP) along existing NC 143. o During the meeting, the US Fish and Wildlife Service (USFWS) and the US Forest Service (USFS) requested a bottomless hydraulic structure be evaluated at this location. The following commitment was developed and included in the draft MCDC: “NCDOT will evaluate the feasibility of a bottomless hydraulic structure at the Hooper Branch crossing. Geotechnical information is required to make a final determination. NCDOT will provide the Merger Team with final hydraulic recommendations once information is available. o NCDOT committed to revisiting CP2A if the geology prohibited the construction of a bottomless culvert and necessitated the need for a standard box culvert at Hooper Branch. 4.0 Concurrence Point 2A Update • NCDOT Hydraulics Unit design guidelines dictate that three-sided culverts must be founded on shallow rock (<3-feet deep). o Geotechnical investigations found that bedrock was approximately 13feet deep at the proposed location of the Hooper Branch crossing. o Based on NCDOT Hydraulic Unit guidelines, a three-sided culvert is not at viable at the proposed location. • It is recommended that a double 8-foot x 7-foot, 82-foot long RCBC, with low and high flow barrels buried one foot in the ground be constructed at Hooper Branch. The low flow culvert will have a 1-foot sill at each end and the high flow culvert will have a 2-foot sill at each end. Figure 2 shows the location of the Hooper Branch Crossing. STIP Project R-2822B (NC 143 Improvements): Combined CP 2A (Revisited) & 4B Meeting 3 | Page • The existing culvert is proposed to be removed and a ditch will be graded from the proposed culvert to the main channel of Snowbird Creek. o During the April 18, 2022, Field Meeting, USFS noted “the final look [of the graded portion of Hooper Branch] should not be a ditch but restored in cohesion with the natural surroundings that exist. “ • Impacts to the EBCI cultural wash site must be coordinated with the US Army Corps of Engineers (USACE). The site is identified as the area bordered by existing NC 143, Snowbird Creek, and Hooper Branch including the picnic area. o USACE noted “impacts [to Hooper Branch] should not exceed what is shown in the current plans as this was the design used during tribal consultation.” PROPOSED HOOPER BRANCH CROSSING Figure 2: Hooper Branch Crossing Plan Sheet Excerpt STIP Project R-2822B (NC 143 Improvements): Combined CP 2A (Revisited) & 4B Meeting 4 | Page • Figure 3 shows the Recommended Hydraulics Design in the vicinity of the Hooper Branch crossing. • Figure 4 is an excerpt from the Culvert Conceptual Design showing the stream profile and the placement of the proposed new culvert in relation to the existing roadbed and culvert. Figure 3: Red Line Hydraulic Plans Sheet Excerpt STIP Project R-2822B (NC 143 Improvements): Combined CP 2A (Revisited) & 4B Meeting 5 | Page Table1: Additional Stream Information Hooper Branch DWQ Index Number 2-190-9-(15.5) Best Usage Classification C; Tr Bank Height (ft) 0.5 Bank full Width (ft) 3 Water Depth (in) 2 – 3 Channel Substrate Cobble, Gravel Velocity Moderate Clarity Clear Classification Perennial River Basin Buffer Rules Not Subject Figure 4: Stream Profile and Culvert Placement 50 0 50150 100200 150250 200100 250 w/ FLOOD BENCH BURIED 1' 2@6'x7' RCBC 120 25yr.50yr.100yr. FREQUENCY PROPOSED ????? ????? ????? NATURAL 500yr. EXISTING 10yr. PERFORMANCE TABLE NCDOTCULVERT SURVEY & HYDRAULIC DESIGN REPORTSITE DATAADDITIONAL INFORMATION AND COMPUTATIONS? FT. FROM US FACE OF CULVERT @SECTION ?169+00170+00171+00172+00173+001,9301,9401,9501,9601,9701 7 2 + 0 0 173+00 174 + 00 PROPOSED GRADEELEV = 1957.55SKEW = 120 DEGREES(BURIED 1' w/FLOOD BENCH)2@8'x7' RC BOX CULVERTCENTERLINE STA. -L- 172+16.00EXISTING GRADESNOWBIRD CREEKEXISTING STRUCTURE OVERSLOPE = 0.039 FT/FTC INVERT = 1947.4' (BURIED 1')LTO BE REMOVEDEXISTING 48" CMP50.00'EXISTING R/W EXISTING R/W 48" CMP18" CMP MTL36" WDGR/SOILHTR S RK WALL S GR ROCK WALL 15" CMP-Y4- POT STA 10+00.00 -L- POC STA 172+64.00 =).DR PAG U I( 8111 RS-4Y-35'R55'R.05.06.06.05.04.03.02.01.00.01.02.03.04.02.02.01.01.00.02.02.0211.02115" CSP15" CSP2GI2GI2GI15" RCP-III SR 1118 I U GAP RD. 18' BST T O MASS E Y B R A N C H R D. PROPOSED CHANNEL CHANGE T O S ANTE ETLAH RD.SPECIAL CUT 'V' DITCH BST REMOVE 48" CMP PROPOSED CHANNEL CHANGE REMOVE 18" CMP G R A D E T O D R AI N GRADE TO DRAIN EXISTING CULVERT TO BE REMOVED 2:1 (NORMAL) 2:1 (NORMAL) 1935 1940 1945 1950 1955 1960 1965 1935 1940 1945 1950 1955 1960 1965 EXIST. 48" CMP ELEV = 1957.55 SKEW = 120 DEGREES (BURIED 1' w/FLOOD BENCH) 2@8'x7' RC BOX CULVERT CENTERLINE STA. -L- 172+16.00 -L- SLOPE = 0.039 FT/FT C INVERT = 1947.4' (BURIED 1')L EXISTING BED PROFILE PROPOSED BED PROFILE Ground Natural FROM -L- STA. 172+35 TO -L- STA. 173+35 LT FROM -Y4- STA. 10+50 TO -Y4- STA. 10+89 RT TO A THICKNESS OF 18” EXISTING CHANNEL AND USE TO LINE PROPOSED CHANNEL BOTTOM NOTE: REMOVE 18” OF NATURAL CHANNEL BOTTOM MATERIAL FROM NATURAL CHANNEL SUBSTRATE BASE: Type of Liner=COIR FIBER MATTING SIDE SLOPES B= 8Ft. Max. d= 1Ft. Min. D= 6Ft. DETAIL 16-4 2:1d D ( Not to Scale) B CHANNEL CHANGE 2:1B Ground Natural Fill Slope Proposed DDE = 250 CY SEE DETAIL 16-4 EST. 135 SY GEOTEXTILE EST. 90 SY COIR FIBER MATTING EST. 22 TONS NATURAL CHANNEL SUBSTRATE WITH 8' BASE & 8' FLOODBENCH PROPOSED CHANNEL CHANGE