20180749 Ver 1_More Info Received_20180703

Johnson, Alan
From:Wilson, Robert <[e-mail]>
Sent:Tuesday, July 03, 2018 5:49 PM
To:Johnson, Alan; [e-mail]; [e-mail]; Aliisa
Harjuniemi; 'Dustin Ledford ([e-mail])'; Cloninger, Robert
Subject:\[External\] Court Drive/Wellman Street - Permit Site Visit - Meeting Notes
CAUTION: External email. Do not click links or open attachments unless verified. Send all suspicious email as an attachment to
Report Spam.

Good Afternoon:

An on-site meeting was held on June 26, 2018, at the Court Drive/Wellman Street site. Attendees are listed below:
 Robert Cloninger, Gastonia Storm Water
 Dustin Ledford, Gastonia Engineering
 Alan Johnson, NCDWQ
 Catherine Janiczak, USACE
 Aliisa Harjuniemi, Carolina Wetland Services
 Christine Geist, Carolina Wetland Services
 Bob Wilson, LaBella

The following topics were discussed:
1. Regional conditions for a 404/401 permit require burying culverts. For Court Drive, there is an existing 8” sewer
line that is less than 6’’ below the existing culvert. The existing 48” pipe is being replaced with dual 48” pipes
along the same vertical alignment. Unfortunately, the existing sewer line prevents the culvert from being
buried. For Wellman Street, there is an existing 24” sewer force main just below the existing pipe. The
proximity of the 24” force main prevents the proposed dual 42” pipe from being buried. Also, these pipes are
part of an existing pipe system and not a true culvert crossing.
2. The rip rap stilling basins are needed to dissipate the energy from the high velocity flow (greater than 10 feet
per second) leaving the proposed pipe culverts. The stilling basins force a hydraulic jump at the pipe outlet, and
reduce the velocity to the downstream channel. The stilling basin at Wellman Street is designed to tie in to the
side channel before reaching the main stream.
3. The dual pipes will widen the channel at the upstream end of the Court Drive culvert. Ideally, one of the dual
pipes would be set at the floodplain elevation. Due to utility conflicts and for capacity needs, a 1’ high sill will be
placed across the western most 48” pipe. The sill will be a steel plate that is attached to the endwall at both the
upstream and downstream ends of the western 48” pipe. A flood shelf will be graded in front of this culvert
barrel, and the pipe will be filled with channel substrate material excavated from the channel during the rip rap
installation.
4. Because the pipes at Wellman Street are part of a pipe system, a sill is not required.
5. The filter fabric under the rip rap prevents the normal interaction between the channel and the soil
below. Filter fabric was first included in rip rap channel details in the late 1980s in North Carolina, when the
Land Quality Section published the Sediment & Erosion Control Planning & Design Manual. The concern
expressed at the time was that piping of groundwater into the channel could lead to soil loss and settling or
failure of the rip rap protection. The filter fabric or other filter media is needed to prevent this from
happening. This is primarily an issue for the side slopes, so the detail will be changed as follows:
a. Filter fabric will be deleted from the detail.
b. For the channel banks, a 6” layer of gravel (#57 washed stone) will be placed under rip rap.
c. For the channel bottom, the gravel would be lost in the muck, so no filter barrier will be used.
1

6. Along Court Drive, there is a proposed pipe system that discharges directly into the main channel at the outlet of
the pipe culverts. There was much discussion on this topic. Listed below are the main points:
a. A grass swale is preferred from a water quality perspective rather than a direct pipe discharge to the
channel.
b. The pipe system is intended to intercept runoff that currently floods the crawlspace of a house at 2843
Court Drive.
c. We discussed deleting a portion of the pipe system from the first driveway to the main
channel. Because of the 2:1 slope into the channel, there is too much flow to dump this swale directly
into the main channel. We proposed to collect the flow at an inlet just beyond the top of bank and drop
down to an outlet pipe that could safely discharge into the main channel.
d. The City had its stormwater team meeting on June 28, 2018, and the team prefers to leave the Court
Drive pipe system as currently proposed for the following reasons:
i. The City has no plans to install curb and gutter along Court Drive. Street runoff will continue to
flow through the grass shoulder along the road. There are only two (2) points where the pipe
system collects street runoff: the pipe inlet at S5A at the upstream end of the run, and inlet S3
just upstream of the last driveway.
ii. The grass swale discussed at the site would only be about 80’ long. The water quality benefits
would be minimal at best.

The above represents my understanding of the topics discussed, both at the site meeting and as relayed to me from the
City’s stormwater team meeting. Please let me know of any questions or concerns.

Bob Wilson, PE
LaBella Associates | Civil Group Leader

704-342-3007 ext. 112
9140 Arrowpoint Boulevard, Suite 200
Charlotte, NC 28273
labellapc.com

2