20170239 Ver 1_Temporary Stream Crossing Guidelines_20180328

Practice Standm•ds and S�ec�cations
� T�--�-�- Defin ition A bridge, ford or temporaty structure instatled across a sheam or watercourse
for short-term use by conshuction vehicles or heavy equipment.
Purpose To provide a m.eans for conshuction vehicles to cross skeams or watercourses
without moving sediment into streams, damaging the streambed or channel,
or causing flooding.
Conditions Where Where heavy equipment must be moved from one side of a shcam channel
Praetiee Applies to another, or where light-duty construction vehicles must cross the sheam
channel ftequently for a short period of time.
Planning Cazeful planning can minimize the need for stream crossings. Try to avoid
Considerations crossing streams. Whenever possiUle, complete the development separately
on each side and leave a natural buffer zone along the stream. Temporuy
stream crossings can be a d'u�ect source of water pollution; they may create
flooding and safety hazu�ds, they can be expensive to construct and they can
cause costty const�uction delays if washed out.
Both fords and culverts may involveplacing fill in an intermittent orperienniaL
stream or wetland. The need fm� permits from tlie U.S. Army Cmps of
Engineers or the N. C. Division of Water Qualiry should be deteimined when
planning the project.
Setect locations for stream orossings where erosion potential is low. Evaluate
stream channel conditions, oveiflow areas, aud sw'face runoff coutrol at the
site before choosing the type of crossiug. When practical, ]ocate and design
temporary stream crossings to serve as pennanent crossings to keep stream
disturbance to a minvnum.
Pian stream crossings in advance of need and, when possible, construct them
during dty pei�iods to minimize st��eam dishubance and reduce cost. Ensure
that all necessary materials and equipment are ou-site before any work is
be�nm. Complete const�uction in an expedient manner, and stabilize the area
urunediate(y.
Often sh�eam crossuigs are provided in conjuuction with operations iu a
natural watercoucse. Land disturbing activity in conneclion with conshuction
in, on, over, or undcr a lake or natural watercourse shall minimize the extent
and duration of disruption of the stream channel. Where relocation of a
s[�•eam fmms an esseutial part of the proposed activity, the relocation-shall
miuimize unnecessaiy clianges in the sri�eam flow chu�acteris[ies. Pumping
or diverting stream ftow around a work area is o8en the best way to minimize
the disruption of tlie stream channel. Any diversions should be stabilized with
adequate geotextile fabric or stone.
After the bypass is completed and stable, the stream may be diverted (Practice
6.15, Riprap). Small stream flows may be diverted az�onnd wm�k areas with a
coffer dam and pump instead of conshvction of a byF�ass channel.
Rev. 6/06 (.�Q.j

u
Unlike permanenC sd�eam crossivgs, temporary sri�eam crossings inay be aI-
lowed to overtop during peak storm periods. However, tl�e sGvcture and ap-
proaches should remain stable. Keep any 8ll needed in flood plains to a mini-
mum to preventupstream flooding and reduce erosion potential. Use riprap to
protect locations subject to erosion from overflow.
If permanent utiliry crossings are planned, stream erossinga may be located at
these locations to minimize stream impacts.
Stream crossings are of the three general types: biidges, culverts, and fords.
Cousider which methad best suits the specific site conditions.
Bridges--Where available materials and designs are adequate to bear the ex-
pected loadings, bridges are preferred for temporaiy strcam crossing.
Bridges usually cause the least disturbance to the sh�ea�n bed, banks, and surv
rovudiug area. They provide the least obshvc[ion to flow and fish migra-
tion. Tliey generally reqnire little maintenance, oan be designed to fit most
site conditions, and can be easily removed and inaterials salvaged. However,
bddges are generally the most expensive to design and construct. Fmther,
they may offer the greatest safety hazard if not adequatety designed, installed,
aud maintauied, aud if washed out, they cause a longer conshuetion delay and
are more costly to repair.
Iu steep watersheds it is reeommended to Yie a eable or chain to oue coiner of
tl�e bridge frame wit(i the otlier end secured to a large b�ee or other substantial
object. This will pxevent flood flows from canying the biidge downstream
where it may cause damage to other prope�ty.
Culvert crossings—Culverts are the most common stream crossinga In many
eases, they are the least costly to install, can safely support heavy loads, attd
are adaptable to most site conditious. Coushvction materials are readily avai(-
able and can be salvaged. However, tUe ins[allation aud removal of cnlverts
causes considerable disturbance to t(ie stream and sun'oundin� area. Culverts
also offer the greatest obstruction to flood flows and are subject, tlierefore,
to bloekage and washout. Clean stonc should be used for back fill around
culverts
Cutverts should be used when vehicles wil] make repeated trips across the
sheam dw�ing conshuc[ion, or track mud inro the stream.
Fords—Fords, made of stabilization material such as rock, are often used in
steep areas subject to ftash flooding where no�mal flow is shallow (less than
3 inches deep) or intennittent. Fords should only Ue used where crossings are
infi�equent. Fords are especially adapted for crossing wide, shaltow water-
courses (Figure 6.70a).
6J0.2 Rev. 6/O6

Fr•acfice Standa�ds and Specdfications
Wheu properly installed, fords offer lit8e or no obshvction to flow, can safely
handle heavy loadings, are relatively easy to iustalL and maintain, and in most
cases, may be left in place at the end of the conshuction.
Problems associated with fords iuchide the following:
1. Approach sections are subject to erosion. Geuerally, do not use fords
where the bank height exceeds 5 feet.
2. Excavation for flie installation of tlie riprap-gravel bottom and filter
material causes major stream disturbance. In some cases, fords may be
adequately constructed by shallow filling without excavation.
3. Thc stabilizing material is subject to washing out during storm flows and
may require replacement. '
4. Mud and other contaminants are brought direcUy into tl�e stream� on
vehicles unless crossings are limited to no flow conditions.
Stream Channel
c....o,..... n,....
Figure 670a A well constructed ford offers little obstruction to flow while safely handling heavy loading.
xev. 6/a6 6.70.3

NC[
#57 a
C
Stream
Channel
NCDOT #5 or #57
washed stone
� diameter of pipe or 12"
whichever is greater
Figure 6.70b Temporary culvert backfilled with stone.
Capaciiy of pipe culverts
together = bankfull flow
Filter Cloth
Class B Erosion
Stone
6.70.4 Rev. 6/O6

Practice Standar�ls and Spec�calzons
Permitting requirements from the U.S. Aimy Coips of Engineers and the NC
Division of Water Quality should be determined for stream crossings. Pennit
conditions may require tha[ pipes be buried below stream bottom elevation.
Small stream flows may be diverted arouud work arcas with a cofferdam and
ptunp instead of construction of a bypass channel.
If permanent utility crossings are plawied, stream crossings may be located at
tUese locations to minimize stream impacts.
Design Criteria ln additiou to erosiou and sedimentatiou control, structural stability, utility,
and safery miist also be taken into consideration wheu designing temporaiy
streatn crossings. Bridge designs, in particulaz, should be undertaken by a
qualified engineer.
• The anticipated life of a temyoraiy stream crossing sYructure is usually
considered to be 1 year or less. Reinovc the structure'vnmediately afier it
� is no longer needed. �
• As a miuimum, design the st�ucture to pass baukfull flow or peak flow,
whichever is less, from a 2-year peak srorm, wifliout over toppvig. Ensure
that no erosion will result from flie 10-year peak stoim.
• Evsm�e that design flow velociry at the oufle[ of the crossing stracture
is non-erosive � for the receiving sh�eam chaimel (References: Ontlet
Protection).
• Consider overftow for storms larger than the design stoim, and provide a
protected ovetilow area.
• Design erosion control practices associated with the sheam crossing to
conh�ol erosion from surface runoff at the crossing and dw�ing a 10-year
peak stoim runoff.
Construetion 1. Kecp cleuing and excavafion of the streun banks and bed and approach
sections to a minimum.
Specifications
2. Divert all s�face water from the construction site onto undisturbed areas
adjoining the strcam.
3. Keep sh'eam ctossings at right angles to the streatn flow.
4. Align road approaches with the center line of the crossing for a minimum
dis[ance of 30 feet. Raise bridge abuhnents and culvert fills a minimum of 1
foot above the adjoining approach sections to prevent erosion from su�face
runoff and to allow flood flows to pass around the s[rucNre.
5. Stabi(ize all disturbed areas subject to flowing wa[er, including planned
oveiflow areas, with riprap or other suitable means if design velocity exceeds
the allowablc for the in-place soil (Table B.OSa, Appendix 8.05).
6. Ensure that bypass channels necessary to dewater the crossing site azc
stable before diverting the sd�eam. Upon eompletion of the crossing, fill,
wtnpaet, and stabilize the bypass chaunel appropriately.
7. Remove tempoiuy stream crossings nnmediately when they are no longer
needed. Restore the stream channel to i[s original cross-section, and smoofli
and approprixtely stabilize all disturbed areas.
8. Any in-stream sediment control measures must be removed upon
stabilization of flie area.
Rev. 6/Ofi 6.70.5

�
Maintenance H�spect tempora�y stream crossings after ruuoff-producing rains to check for
blockage in channel, erosiou of abutments, channel scoui; iipiap displacement,
or piping. Make all repairs immediacely Co prevent furthex damage to the
installatiou.
References Su{faceStabilization
6.15, Riprap
Outlet I'��otection
6,41, Outlet Stabilization Structure
Appendices
S.OS, Design of Stable Cl�annels and Diversions
6.70.6 xev. 6/ob