20221344 Ver 1_More Info Received_20221108

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November 7, 2022

Re: Response to NC DNER DWR Comments on 09/23/22 PCN Submittal for Ranlo Avenue Street & Waterline Extension (TWC Project No. 3374-I & 3374-L)

Dear Mr. Alan Johnson,

Thank you for your comments on the project.

Attached is our response along with related attachments as given below and described herein.

On your first comment, we chose the standard engineering “road embankment” design for a number of reasons, which we will describe herein. We still believe that is the most suitable design
for this project for a variety reasons. The latter design approach was done according to good engineering practices with an objective to keep the length of the creek culvert as short
as possible. We knew it was of primary importance to minimize the impact to Houser’s Branch and the surrounding environment for both the short-term and long-term. With that in mind,
we considered alternate designs as described in the attached PDF “Response to NC DNER Comments…”. Two road designs that would allow a shorter length of culvert to be used, are the
Alternate #1 and #2 designs. The Alternate #1 design included the use of “tall (18 ft in ht) reinforced concrete vertical embankment wall” just off the edge of the road. Alternate #2
consisted of the construction of a “structural/abutment bridge” over the creek for this project. Although the shorter culvert length could be achieved by either of these two alternatives,
the engineering and construction cost associated with either of these road design approaches would make the project economically infeasible. Having to proceed with either Alt #1 or
Alt #2 will result in the project being canceled for now, and the project would not be considered again unless there was an infrastructure funding project that pay for this type of
road creek crossing.

Upon reflection and consideration of your second comment, we agree that the design should include features that minimize “direct” and cross-directional stormwater discharges to the stream
to the degree economically feasible. With that objective, we evaluated two alternatives (shown below) to the PCN Submittal design: Alt #1 has stormwater pipe discharges that are completely
parallel to the stream (cross-sectional sketch of Alt #1 is attached); and Alt #2 involves stormwater discharge pipes (15” & 24” RCP) on either side of the creek culvert that discharge
at a less abrupt angle to creek to lower road embankment rip-rap areas, which then secondarily discharge to the stream in an almost parallel manner. Even though Alt #1 is slightly more
costly than Alt #2 and the original PCN Submittal design, we are in favor of using Alt #1 design because it best meets both objectives of not being a direct stream discharge, while
also being a discharge that smoothly merges in a parallel direction to the stream.

Besides the PDF Response to NC DNER Comments, also attached are two matrices (one for each DNER comment) that we prepared that does a comparison of various aspects of the alternatives
to the original PCN Submittal design.

We look forward to hearing back from you on our response to your comments and continuing with this very worthwhile community project on the Town’s behalf to move the project forward
to the bidding and award phase.

Sincerely,

Jim

James P Lamancusa, PE

Senior Project Manager

[phone] x301 • Office
[phone] • Fax
1430B Old Lenoir Rd. NW
Hickory, NC 28601

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ALTERNATIVE No. 1 to DNER Comment No. 2:

ALTERNATIVE No. 2 to DNER Comment No. 2:

From: Slade Harvin <[e-mail]>
Sent: Wednesday, November 2, 2022 3:24 PM
To: Johnson, Alan D <[e-mail]>
Cc: [e-mail]; Lisa Bradshaw <[e-mail]>; Jim Lamancusa <[e-mail]>
Subject: Re: Ranlo culvert replacement #22-1344

Alan,

Thank you for the comments.

We will review and respond soon.

Is an email response sufficient or is there another requested format?

Thank you,

Slade

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________________________________

From: Johnson, Alan D <[e-mail] <mailto:[e-mail]> >
Sent: Wednesday, November 2, 2022 3:10:51 PM
To: Slade Harvin <[e-mail] <mailto:[e-mail]> >
Cc: [e-mail] <mailto:[e-mail]> <[e-mail] <mailto:[e-mail]> >
Subject: Ranlo culvert replacement #22-1344

1. Why the necessity to extend the culvert and additional 115 ft. Are headwalls utilized to shorten the impact and steep slopes. The original culvert was 40 ft.

2. Is it not possible to discharge the stormwater parallel to the channel and dissipate over riprap, rather than a direct discharge into the stream

TWC (Ranlo engineer) Response to NC DENR Comments on 9/23/22 Ranlo Ave St/ WM Ext Project PCN
PCN Submittal comments received from Alan Johnson or NC DENR:
1. Why the necessity to extend the culvert and additional 115 ft. Are headwalls utilized to shorten
the impact and steep slopes. The original culvert was 40 ft.
2. Is it not possible to discharge the stormwater parallel to the channel and dissipate over riprap,
rather than a direct discharge into the stream
RESPONSE TO Comment #1:
In order to have a smooth transition on the two connecting points of the road, it is necessary to build up
the road profile. Other considerations were to have adequate cover for the proposed water main, while
at the same time building into the design adequate vertical separation distance between new and
existing pipelines (sanitary sewer, storm sewer). Given all of that, the vertical height of the road was
established at the stream cross -over point.
Next, given the height at the edge of the proposed road at the creek cross over point, it was necessary
to transition from that elevation point down to existing grades on both sides of the road in a manner
that met standard road good engineering design practices (NC DOT, AASHTO etc.), taking into
consideration long-term erosion control (limiting steepness of side grades) and safety for vehicles,
pedestrians (sidewalk) and bicycle traffic. In general, the latter limited the side slope to 3:1 maximum,
and at the narrower horizontal section of the proposed road in close vicinity to the creek, it was
necessary to even have a 2:1 side slope grade, which is achievable by using Double -Net Erosion Control
Matting in combination with the final seeding to establish a sturdy vegetative cover (for the 3:1 side
slopes, a Single -Net Erosion Control Matting is used).
So, given all the grade transitions that are necessary from edge of proposed road going outward and the
streambed connecting points for the proposed culvert vertical profile ("IE" invert elevations at upstream
and downstream ends set 12" below streambed), the necessary length of the creek culvert was 115 LF.
Embankment retaining walls at the two ends of the creek culvert will be achieved using pre-engineered
NC DOT standard culvert end walls with wing walls.
On the safety aspects of the project as designed and described above at the creek crossing, there was
concern about not having excessively steep of side slopes or drop-off to the creek, especially on the
north edge of the road, where there is a proposed sidewalk (pedestrian barrier used there as an
additional safety feature).
So, an embankment type design following good engineering practices as described above and shown on
the plans requires that the prior culvert length of 40 LF on the two -track, non -engineered, unsafe dirt
road be increased to 115 LF in order to provide a two-lane paved road with curb and gutter and a
sidewalk on one side. Alternatives to the latter are much more expensive, both for engineering
(structural engineering design) and construction costs. Examples of alternatives would be a design that
has tall reinforced concrete retaining walls up close to the edge of the road on both sides, which would
give a culvert having a length maybe half the length as proposed, but would be more expensive, and
would have to have additional other expensive design features to safeguard vehicle, pedestrian, and
bicycle traffic (high profile guard rails, etc.). The next even more expensive alternative would be to
design and install a structural steel or reinforced concrete abutment type "bridge" at the creek crossing,
Page 1 of 2 NC NDER DWR/US ACE 401/404 Permit Application 11/07/22

TWC (Ranlo engineer) Response to NC DENR Comments on 9/23/22 Ranlo Ave St/ WM Ext Project PCN
which would bring forth other complexities to the design, such as how to transition the roadway vertical
curves into this bridge design given the short span of paved road that is connecting to the existing paved
roads in the adjoining subdivisions.
Both of these alternatives are associated with increased carbon footprint due to large volumes of
concrete, as well as being eyesores for residents. Attached is a matrix evaluation/comparison of the
three different designs as described below:
• Longer creek culvert: PCN Submittal, Standard Road Embankment Design
Shorter creek culvert: Alternate #1, Tall Vertical Reinforced Concrete Retaining Wall
• No creek culvert: Alternate #2, Structural/Abutment Creek Bridge
The matrix clearly shows that the current road creek crossing design given in the PCN submittal is the
design best suited for this project.
RESPONSE TO Comment #2:
Current PCN Submittal Design: The current design has the road stormwater discharge pipes
Discharging to End Wall (EW) and lower road embankment on W side of Creek (Cr), and directly to the
creek through a headwall (HW) on the downstream side of the Cr culvert for the E side of the creek.
For new road stormwater inlet collection system as shown on the plans for the PCN submittal, system
on the W side of creek there is a 15" RCP pipe that discharges to a concrete end wall (EW) in the lower
road embankment area, and from there it flows to the creek (Cr) itself after passing through a
stormwater energy dissipator/erosion control area consisting of rip -rap laid over geotextile fabric. In
contrast, the road drainage system discharge pipe (24" RCP) on the E side of the creek discharges more
directly to the creek through the concrete headwall (HW) on the downstream end of the creek culvert,
where the discharges passes through a rip -rap area as previously described in vicinity of the top of bank
for the creek.
In order to lessen the angle that the road stormwater discharges to the creek and make it more parallel
to the creek, the following two alternatives could be used:
Alternative #1: 100% parallel discharge to the creek by modifying the street stormwater collection
system by installing junction boxes close to and at both sides of the creek discharge culvert, and then
running the discharge pipe from those two junction boxes directly south to and through the headwall
(HW) on the downstream end of the creek culvert, where the two storm pipes discharge directly into
two separate gabion formed channels (on E & W side of creek culvert) parallel and adjacent to the
stream, which then passes through an erosion protected rip -rap area before merging with the stream
Alternate #2: This alternative has stormwater discharges more parallel to stream flow than the PCN
Submittal design, but however is not as parallel as Alternative #1. Alternative #2 consists of lessening
the creek discharge angle on both the W and E sides of the creek by shifting the location of junction
boxes and street inlets, and then directing the discharge pipe flow from the junction boxes to endwalls
(EW) located in the lower embankment area on both the W and E side of the creek, after which the
flow continues to the creek after first passing over a rip -rap area.
Page 2 of 2 NC NDER DWR/US ACE 401/404 Permit Application 11/07/22

Ranlo Ave St WM Extension
NC NDER Comment #2 Alternatives
Alternate #2 More Parallel than PCN
Item #
PCN Submittal Design
Alternate #1 100% Parallel
Submittal Design
Minor increase over PCN
1
Construction Cost
Similar to Alternative #2
Submittal Design (less than
Similar to PCN Submittal Design
$20K)
Minor increase over PCN
2
Maintenance Cost
Similar to Alternative #2
Submittal Design (less than
Similar to PCN Submittal Design
$20K)
Milder discharge angle to Cr and
3
Road Drainage RCP Discharge
Worst - Steepest on angle to Cr,
o
100% parallel to Creek
closer to parallel than PCN Submittal
Angle to Creek
and the least parallel to creek
design
Discharges in line with andNo
E side of creek direct, W side
parallel to Cr from both E & W&
direct discharges to creek: Both E
4
Is it Direct Discharge to creek?
discharges to lower road
W side of creek discharges to
sides of creek, and then merges
embankment area
into stream flow
lower road embankment areas
Both E & W side road drainageDirect
Lower road embankment area on
to lower road embankment
pipes discharge to erosion
5
Erosion Impact Area
W side & creek secondary after
area, and secondary (indirect) to
protected channels than merge
that, and direct to creek on E side
Creek after that
inward to Cr centerline
TWC Project 3374-I, L NC DNER DWR/US ACE 401/404 Permit App 11/07/2022

Ranlo Ave St WM Extension
NC NDER Comment #1 Alternatives
PCN Submittal, Std Road
Alternate #1 Tall Vertical
Alternate #2 Structural/Abutment
Item #
Embankment Design
Retaining Wall
Creek Bridge
1
Culvert Length
115 feet
Reduced in half approx.
N/A
2
Engineering Design Cost
Moderate
High
Highest
3
Construction Cost
Moderate
High
Highest
Public Safety Concerns &Cost
4
Lowest concern, Lowest costs
Higher concern, Higher costs
Higher concern, Higher costs
to Address
Compatibility to
5
Neighborhood/Community
Best
Poor
Worst
Related Energy Use for
6
Moderate
High
Highest
Materials
7
Maintenance Costs
Moderate
Moderate
Moderate
Blending into Natural
S
Best
Poor
Worst
Environment
Economic compatibility to
9
Best
Poor
Worst
Smaller Community
TWC Project 3374-I, L NC DNER DWR/US ACE 401/404 Permit App 11/07/2022

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