20140761 Ver 1_Application_20140722

SR 1425 Smith Road
Pipe Liner Proposal Location34.778494N 77.226430W
SR 1423
Grants Creek C
UT to Grants Ck
1
4
2
8
14 251423
14
26
1427
Riggs Rd
S m ith R d
Old 30 Rd
Grants Creek Rd
G
allo
w
ay Jones R
d
A n i t a D r
Sm ith Road SR 1425 Pipe Liner Proposal located at2.2 miles East of SR 1423North of Hubert in O nslow County
¹
0 1,600 3,200 4,800 6,400800Feet
SR 1425 Smith Road
Pipe Liner Proposal Location34.778494N 77.226430W
SR 1423
Grants Creek C
UT to Grants Ck
1
4
2
8
14 251423
14
26
1427
Riggs Rd
S m ith R d
Old 30 Rd
Grants Creek Rd
G
allo
w
ay Jones R
d
A n i t a D r
Sm ith Road SR 1425 Pipe Liner Proposal located at2.2 miles East of SR 1423North of Hubert in O nslow County
¹
0 1,600 3,200 4,800 6,400800Feet
SR 1425 Smith Road
Pipe Liner Proposal Location34.778494N 77.226430W
SR 1423
Grants Creek C
UT to Grants Ck
1
4
2
8
14 251423
14
26
1427
Riggs Rd
S m ith R d
Old 30 Rd
Grants Creek Rd
G
allo
w
ay Jones R
d
A n i t a D r
Sm ith Road SR 1425 Pipe Liner Proposal located at2.2 miles East of SR 1423North of Hubert in O nslow County
¹
0 1,600 3,200 4,800 6,400800Feet
Onslow County SR 1425 Smith Road Pipe Liner Proposal Narrative
The existing 60 inch diameter by 37 feet long corrugated metal pipe at the subject location is
deteriorated and a solution is needed to maintain the safety and mobility of the traveling public. A pipe
liner of HDPE material of 54 inch diameter by 45 feet long is proposed. NCDOT considered pipe
replacement rather than the pipe liner, however, the total costs of pipe replacement is approximately
fifty-four thousand dollars more than the proposed pipe liner (eighty-seven thousand dollars for
replacement as compared with thirty three thousand dollars for the pipe liner) and as such the pipe liner
is the least environmentally damaging practicable alternative as further described. The extended pipe
length of the proposed pipe liner is proposed in order to create a safer shoulder typical section in this
area. SR 1425 is proposed to be widened by 1.5 feet on each side in the near future, however, per
interview of the Bridge Maintenance Supervisor, he said that he would be requesting the same length of
proposed pipe liner independent of the proposed widening as the existing shoulder section in this area
needs to be improved for safety.
The proposed pipe liner inlet would be six feet further upstream than the existing pipe inlet and the
proposed pipe liner outlet would be two feet further downstream than the existing outlet. The existing
inlet is buried 0.9 feet relative to the upstream stream bed measurements. The proposed inlet would be
buried approximately 0.56 feet relative to the upstream stream bed measurements. The existing outlet
is buried approximately 0.45 feet relative to the stream bed at the immediate outlet end of the pipe,
then there is a slight blow hole just outside of the outlet of which the existing outlet invert is only buried
0.05 feet when compared to the bottom elevation of the slight blow hole. Approximately 30 feet
downstream is a stream bed reading of 93.6 which makes the existing outlet invert buried
approximately 0.35 feet relative to that 93.6 reading, then further downstream the streambed drops to
93.0. The proposed outlet invert would create a slightly perched situation at the immediate outlet of
the pipe liner, if no further remedy was proposed, since the proposed invert is approximately 4.1 inches
higher than the existing due to the thickness of the HDPE liner (approximately 3.52 inches) and the need
to use an approximate 0.5 inch rail to slide the liner into place coupled with the fact of the proposed
outlet end being two feet further downstream which happens to be right over the slight blow hole. In
order to rectify what would otherwise be a proposed perched situation at this proposed outlet, NCDOT
proposes to use native material (either from the existing pipe cleanout or the material proposed to be
removed from the inlet or both) to fill in the blow hole and create a new proposed stream bed. The new
proposed stream bed would be tied in at twelve feet downstream of the proposed outlet. The proposed
stream bed would be somewhat similar to the existing situation. The pipe liner outlet invert
(approximate elevation 93.58 would be approximately at grade although perhaps ever so slightly buried)
with the proposed stream bed at the immediate outlet end of the pipe (approximate elevation 93.6).
The proposed stream bed would then slope slightly downward and tie into the existing streambed at
elevation 93.4 and then raise slightly up again in elevation to the existing 93.6 (which matches the
proposed stream elevation at the proposed outlet) before starting to fall off in elevation again further
downstream. This is similar to the existing situation in which the stream bed at the outlet of the existing
pipe falls off in elevation outside of the pipe outlet and then raises back up to the 93.6 prior to dropping
off further downstream. NCDOT believes this is an acceptable solution and proposes to perform this
work under Nationwide Permits 3 and 13 and corresponding Water Quality Certifications 3883 and
3885. Please read on.
First, the bypass pumping operation and dewatering operation setup would be installed. Then the
existing sediment in the existing pipe would be removed in order to facilitate the placement of the pipe
liner. The sediment would be removed partly by personnel with wheel barrows, buckets, and shovels
and the like working inside the pipe and then remaining sediment would be washed out of the pipe by
means of pressurized water through a hose; this cleanout would all occur within the confines of the dam
structures. It is likely that some of this native material would be used to create the proposed stream
bed on the outlet end as further described in this proposal. Material from the pipe cleanout that is not
used for the creation of the proposed outlet end streambed would be collected on a tarp(s) placed
within the stream bed and then removed to a proper disposal site. It may also be that material
proposed to be dug out of the inlet end in order to place the proposed pipe liner at the proposed
elevation would also be used for creation of the proposed stream bed on the outlet end as well. For the
next step of installing the liner, bypass pumping would need to be ceased for a period of approximately
four hours. The reason for the ceasing of the bypass pumping for this period is that the bypass hose is
proposed to be ran thru the existing pipe during construction in order to prevent having to close the
road. During the actual placing of the liner (approximately 4 hours timeframe), NCDOT would want the
bypass hose out of the way of placing the liner and sliding it into place. Considering the low flow system
at this location, this is thought by NCDOT to be acceptable. Upon the liner being slid into place, the hose
would be inserted through the pipe liner under the road and the bypass pumping operation would begin
again. To install the liner, a twenty-four foot section of liner would be layed out in the upstream
temporary impact area. This section of liner would be slid into the existing pipe with a minimal amount
of this section left protruding from the inlet of the existing pipe. Then the next section of liner would be
layed in the temporary impact area upstream and attached to the previously installed section of liner.
Then the attached sections of liner would be slid further into their final position and the excess pipe
liner would be cut off to create the proposed 45 foot length of liner. Soil material would need to be
removed from the inlet and the slightest bit from the outlet end in order to get the proposed liner to the
proposed grade (please see the permit drawings for more clarity in this regard). Once the liner is in
position, then the gaps (inlet and outlet end) between the existing pipe and the liner would be filled
with a quick setting concrete or the like with pipe ports installed between the existing pipe and the liner.
Then very fluid grout would be pumped into the pipe ports in order to fill in the void between the
existing pipe and the liner. The inlet side would be stabilized with rip rap bank stabilization. This rip rap
bank stabilization would not extend any further upstream than the proposed pipe liner inlet. However,
some of the rip rap bank stabilization would likely be below the ordinary high water mark of the stream
that extends to the sides of the proposed pipe liner and therefore the Nationwide Permit 13 and Water
Quality Certification 3885 are proposed. NCDOT requests a waiver from the use of filter cloth for this rip
rap bank stabilization as NCDOT believes that we can create a more stable situation by pressing the rip
rap into the bank in this location without the use of the filter fabric. The bypass pumping operation
would continue for twenty four hours after completion of the grout pour to fill the void between the
existing pipe and the proposed liner in order to minimize/eliminate the potential of elevated pH water
entering the stream environment. The dams would then be removed and temporarily impacted areas
would be restored to preconstruction conditions as much as possible.
A waiver is requested, if necessary, from burial requirements of the Nationwide Permit 3 and the Water
Quality Certification 3883. Again, the proposed liner would be buried approximately 0.5 to 0.6 feet on
the inlet side and would be practically at grade (although perhaps ever so slightly buried) on the outlet
end. NCDOT requests the USACE and the NCDWR review this proposal for consistency with the burial
requirements of the NWP3 and the WQC 3883 respectively and advise whether a waiver is needed. I
foresee potential conflict with the USACE NWP3 Regional Condition 3.6 in the second paragraph
regarding CAMA counties in which Stephen Lane has said he is not claiming this area, however, the
regional condition speaks of a one foot burial for streams appearing as blue lines on the USGS in those
coastal counties and this location does appear as a light blue line, but not a bold blue line on the USGS
map. Also, the sixth paragraph of Regional Condition 3.6 speaks of the issuing of waivers if it can be
demonstrated that the proposal would result in the least impacts to the aquatic environment. NCDOT
proposes that there would be minimal impacts to the aquatic environment from the proposal and the
proposal would be very similar to the existing situation. Also, the NCDOT proposes that the proposal
presented is the least environmentally damaging practicable alternative as previously described. Also, I
foresee potential conflict with regard to burial requirements in the WQC 3883 Condition 8 specifically in
regard to the one foot burial requirement in the second paragraph of condition 8. Please advise
whether the full application submittal is needed and I would be glad to supply.
Sincerely,
Stonewall Mathis
Hand Existing Existing
Permanent Temp. Excavation Mechanized Clearing Permanent Temp. Channel Channel Natural
Site Station Structure Fill In Fill In in Clearing in SW SW Impacts Impacts Stream
No.(From/To)Size / Type Wetlands Wetlands Wetlands in Wetlands Wetlands impacts impacts Permanent Temp.Design
(ac)(ac)(ac)(ac)(ac)(ac)(ac)(ft)(ft)(ft)
1 Smith Road Pipe Liner Proposed 54" Dia. X - - - - -<0.01 (A)<0.01 (B)20 (A)38 (B)-
45 ft. length HDPE liner
TOTALS:0 0 0 0 0 <0.01 (A)<0.01 (B)20 (A)38 (B)0
Notes: (A) The temporary stream impact is for dewatering the stream and installing the pipe liner. The proposal is for 30 feet of temporary impacts on the inlet side
and 8 feet of temporary impacts on the outlet side. The reason for the rather extensive length of temporary impacts on the inlet side
is that the proposal is to lay out the twenty four foot sections of pipe in the inlet side stream bed and slide the liner into place. The first section
would be layed and then slid into the existing pipe. The second section would be layed and connected to the first section. Then that would be
slid into place and the excess three feet of pipe liner would be cut off. The area of impacts was calculated using 4.5 feet width of stream, so
4.5 feet x 38 feet equals 171 sq. ft.
(B) The permanent impacts are for the increased pipe length of six feet on the inlet and two feet on the outlet, rip rap bank stabilization on the inlet,
and creating the proposed streambed on the outlet an additional 12 feet beyond the proposed pipe outlet. So we have six feet of permanent
impacts on the inlet for the pipe extension and rip rap bank stabilization. The rip rap bank stabilization would not extend further upstream than
the proposed inlet. And we have 14 feet of permanent impacts on the outlet, two feet of which are for the pipe extension and the additional
12 feet are for the creation of the proposed stream bed. This twelve feet for the creation of the proposed stream bed is not a loss of waters.
So we have a loss of waters of 8 feet (6 feet on the inlet and 2 feet on the outlet). Area calculated by 4.5 ft wide by 20 ft long equals 90 sq.ft.SHEET 1 OF 1 7/17/2014
ONSLOW COUNTY SMITH RD PIPE LINER
NC DEPARTMENT OF TRANSPORTATION
DIVISION OF HIGHWAYS
WBS # 3B.206711
WETLAND PERMIT IMPACT SUMMARY
SURFACE WATER IMPACTSWETLAND IMPACTS