20200427 Ver 1_Additional information for PCN_20200424

Additional Information from PCN:
B. Project Information and Prior Project History
3e. Purpose and Need-
The project purpose is to realign a portion of the existing Crabtree Creek Trail (wooden boardwalk structure)
that has failed in 3 locations, and to remove the greenway trail from the floodway of Crabtree Creek. Moving the
existing section of the trail will also result in a safer structure for the public and increase the longevity of the trail
and decrease maintenance.
Project Description-
The proposed project is a re-alignment of the existing Crabtree Creek trail that includes Structure 106, an
approximately 1,150 feet long boardwalk located along the steep bluffs of Crabtree Creek. The existing section
of trail has failed three times and is presently closed. The realignment will replace approximately 1,150 linear
feet of the existing wooden boardwalk section, by realigning the Crabtree Creek Trail as an asphalt path along
Ratchford Drive, then through an existing City of Raleigh sanitary sewer easement before tying back into the to
the existing greenway trail near the intersection of Capital Boulevard and Ratchford Drive. The asphalt path
along Ratchford Drive will be placed within the public right-of-way from the Capital Boulevard crossing to the
existing terminus of Ratchford Drive north. The asphalt greenway will continue to the end the existing Ratchford
Drive right-of way, where it will then follow the existing sanitary sewer access drive (within a 40’ existing
easement), crossing two unnamed tributaries to Crabtree Creek with box culverts that are buried 1’ deep. After
the terminus of sewer access drive, the trail will continue as an asphalt greenway section along the existing
sanitary sewer easement, until it meets the existing asphalt greenway (approximately 700’).
The project area along the existing sanitary sewer easement will be fine graded, and a new greenway trail
with a typical section of 2" S9.5B surface course on 6” ABC stone will be provided (top of pavement will match
existing grades). The type of equipment will likely be conventional construction equipment (backhoes and
trucks with some mini excavators) for this project. Construction entrances will be established before work
begins to prevent transport of sediment from vehicle activity. Mats will be placed within the construction area
to allow vehicle access during wet soil conditions and to reduce the disturbance to established vegetation. Hand
clearing would be conducted outside the fill areas, so impact will be minimal. Silt fencing will be installed at the
top of the banks within the project area prior to land disturbing activities to prevent sedimentation into the
tributaries. Silt fencing will be removed after the area has been stabilized. There will be minimal removal of
trees, as the path follows an existing sanitary sewer easement, however there will grading and ground
stabilization.
D. Impact Justification and Mitigation
1. Avoidance and Minimization
1a Utilizing existing easements and areas that are cleared and maintained will minimize impacts. Areas will be
hand cleared. The improvements will include bank and slope stabilization. All other area will be re-vegetated for
natural stabilization and regrowth. The flatter tie in grades along the existing sanitary sewer easement should
minimize erosion upon revegetation.
Coffer dams/impervious dikes will be used during culvert construction with pump arounds to ensure all work
occurs in the dry. Areas will be hand cleared. Silt fence will be provided along the tributary side of the
construction. After construction is complete the area will be covered with matting, seeded, and mulched. The
riparian buffer area will be re-seeded with native plant species. The limits of construction will constrain the
width along either side of the existing greenway to minimize impact.
6i. Comments
This project is utilizing the existing sanitary sewer easement to relocate the existing Crabtree Creek out of the
existing floodway. The existing greenway is presently closed and has been closed multiple times in this area due
to the existing greenway collapsing and failing. The greenway has been repaired twice and has now failed in a
third location. Due to the safety of the public and minimizing impacts to the area, we are utilizing an existing
easement that is cleared and maintained. The trail grades will match closely to existing grades. All areas that are
disturbed will be stabilized with riparian seeding.
Several options were considered, including a boardwalk crossing, but the only location that crosses once has a
2.2:1 slope that is over 25’ tall. This option would require large retaining walls and large amounts of cut and fill.
The trail alignment follows an existing gravel access drive at 8.78% to the tributary crossing within the existing
access easement. Then the 2nd crossing is within the existing sanitary sewer easement with a 12” sanitary sewer
pipe and multiple manholes. The crossings are culverts to allow for vehicular access to the sanitary sewer for
maintenance purposes.