20160299_R-2536 Burial of Pipes on Jurisdictional Features_20160115

Hi Travis,

I wanted to follow-up with you regarding discussions yesterday during
the 4C meeting for Section 2 and burial requirements. There has been
discussions about burial and if it is necessary if aquatic passage is
not viable due to length and slope and the possibility that material
will not stay in the pipe or culvert due to the slope. While there is a
need for additional quantification of this topic, the following are
recommendations for R-2536 only based on existing guidelines and
discussions to date. Please provide comments. Thanks for your
response.

Proposed:

Pipes on JS streams do not need to be buried if either of the following
are true:

1. If the pipe is greater than 250’ in length.

2. If the pipe is on greater than a 3% slope. Velocity in a 36”
pipe on a 3% slope is about 10 fps at 0.5 feet of depth. Depth vs
Velocity of a 36” pipe is shown below.

The plans will say “Pipe not Buried” on the pipe where JS features
enter a pipe with either of the above conditions.

Pipes that are buried will have a sill incorporated into the headwall
to provide stability for the upstream section.

Culverts on JS streams do not need to be buried or backfilled if slope
is greater than 4%

If culverts greater than 4% are buried, then sills are required on both
ends of the culvert.

All other culverts will follow the Hydraulics Unit Guidelines on Sills
and Baffles
<https://connect.ncdot.gov/resources/hydro/Hydraulics%20Memos%20Guidelin
es/01-06-2014%20Guidance%20for%20when%20to%20use%20Sills%20,Baffles%20in
%20Box%20Culverts.pdf>

Examples on R-2536 that came up at the meeting that need your
concurrence include:

Site 43C

54” Pipe over 390 feet would not be buried.

Site 33

54” Pipe over 400 Feet long will not be buried.

Site 35

6X7 RCBC on 4.89% slope will not be backfilled and will have sills if
buried a foot.

Regards,

Matt

Matthew (Matt) Lauffer, PE, CPM

Assistant State Hydraulics Engineer

Hydraulics Unit

Department of Transportation

919 707 6703 office

919 621 0443 mobile

[e-mail]

1590 Mail Service Center

Raleigh, NC 27699-1590

1020 Birch Ridge Dr.

Raleigh, NC 27610

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