20160919 Ver 1_More Info Received_20161024

Homewood, Sue
From:[e-mail]
Sent:Monday, October 24, 2016 7:59 PM
To:Homewood, Sue
Cc:John t thomas jr; Leslie, Andrea J; Charles Anderson
Subject:Re: Big Creek 4 Stream Restoration Project
Attachments:image002.png; stelprdb1046932.pdf; nrcs144p2_052940.pdf; Response to NCDENR 2nd
Comments.docx
Sue,

In response to your e-mail I have prepared the attached letter requesting exemption from the dewatering requirement
for the Big Creek 4 project.
I am attaching the NRCS guidance documents on stream crossings for your review. If you have specific questions
regarding the culvert, you can discuss them with Tommy Burchette when you meet on-site. He prepared the culvert
design criteria.
I also forwarded the application signature page to Debbie Dodson, RI for signing. As soon as I receive it I will forward
that and a revised page 2.

Rocky

From:
"Sue Homewood" <[e-mail]>
To:
[e-mail]
Cc:
"John t thomas jr" <[e-mail]>, "Andrea J Leslie"
<[e-mail]>, "Charles Anderson" <[e-mail]>
Sent:
Monday, October 24, 2016 9:56:07 AM
Subject:
RE: Big Creek 4 Stream Restoration Project

Rocky,

Thanks for the response. I need a couple follow up items in order to issue the 401 approval.


I need the revised Page 2 of the PCN and signature authority (agent authorization) indicating the applicant you would like

to receive the 401 authorization. (you mentioned you’d send it, I just wanted to be clear that I can’t issue the approval

until I receive that)

Cost for dewatering effects all restoration projects. While we recognize that more work can be accomplished when

dewatering doesn’t use up the funding, that is not a sufficient justification for the risk/damage that can be done when a
project is installed “in the wet”. When we spoke on the phone you indicated that the size of Big Creek is the main reason
you were going to request exemption from working in the dry (the risk is greater to try to dewater a channel that
large). Also, that installation of structures is more likely to occur when the stream is flowing during installation and the
designer can make adjustments as needed. Please provide a revised justification for exemption from dewatering Big
Creek. Also, the exemption will not be applicable to either of the tributaries unless you provide justification for those

channels also.


Please provide a copy of the standard detail for the NRCS ford crossing and the culvert crossing for my file.

Thanks,

Sue Homewood

Division of Water Resources, Winston Salem Regional Office

Department of Environmental Quality
1

October 24, 2016
Ms. Sue Homewood
Division of Water Resources, Winston Salem Regional Office
Department of Environmental Quality
450 W. Hanes Mill Rd, Suite 300
Winston Salem NC 27105

Dear Ms. Homewood,
I am responding to your e-mail of October 24, 2016 regarding the Big Creek 4 Stream Restoration Project.
I am requesting that you consider granting an exemption for the pump diversion requirement for the
mainstem portion of the Project. I am requesting that you consider the following logistical issues and
risks associated with requiring the dewatering of a stream this size.
Providing pump diversion for a stream this size (DA = 10.5 square miles) increases the risk associated with
trying to effectively dewater the stream channel. Given that a typical pump diversion scenario involves
dewatering stream channels in manageable 300 - 500 foot increments, the overall length of the Big Creek
4 mainstem restoration (2,172 LF) would require multiple installations and removals of the coffer dam-
pump diversion system. The significant volume of stream flow that must be diverted would require a
system of large coffer dams, large pumps and interconnecting hoses or pipes. This size system requires
the use of heavy equipment to move the cofferdams, pumps and pipes from one set-up location to the
next. Because the dewatering system is setback from the channel, generally along the adjacent
floodplain where it is proximate to the channel but out of the immediate work area, the heavy equipment
utilized to set-up the system would have to travel along the floodplain multiple times. Given your
concerns about the degree to which mechanical clearing would impact the riparian area, setting up this
system has the potential to impact a much greater area than the channel work alone.
Given the size of the dewatering system required it would be unwise to leave the coffer dam in-channel
when storm flows are anticipated. To avoid the potential for the coffer dams to impound significant
volumes of sediment or divert storm flow into existing banks or worse yet, the restored banks, it would
be necessary to incorporate additional set-up and breakdowns into the process to account for multiple
storm events over the several month construction period.

On the other hand, there are significant advantages to working in the wet. The potential impacts to the
riparian area associated with installing the dewatering system are avoided or minimized. As the in-stream
structures are installed the designer and contractor have the ability to immediately assess whether they
are functioning as intended, making adjustments as needed.
We propose that the work along the Big Creek mainstem be exempted from the dewatering requirement.
Given the shorter length and smaller size of Tributaries 1 and 2, a single, smaller sandbag-pump diversion
system set-up could be employed to dewater these streams.
If you have any additional comments or questions, please contact me at my office.
Sincerely,

Rocky Powell
C
Charles Anderson
John Thomas
Andrea Leslie

NATURAL RESOURCES CONSERVATION SERVICE
CONSERVATION PRACTICE STANDARD
STREAM CROSSING
(No.)
CODE 578
DEFINITION
A stabilized area or structure constructed
across a stream to provide a travel way for
people, livestock, equipment, or vehicles.
PURPOSE
• Provide access to another land unit
• Improve water quality by reducing
sediment, nutrient, organic, and
inorganic loading of the stream
• Reduce streambank and streambed
erosion
CONDITIONS WHERE PRACTICE APPLIES
This practice applies to all land uses where an
intermittent or perennial watercourse exists
and a ford, bridge, or culvert type crossing is
needed.
CRITERIA
Apply this standard in accordance with all
local, State, Tribal, and Federal regulations,
including flood plain regulations and flowage
easements.
Identify significant cultural resources or
threatened or endangered species that could
be affected by the implementation of the
practice.
Location. Locate stream crossings in areas
where the streambed is stable or where it can
be stabilized (see NRCS Conservation
Practice Standard, Channel Bed Stabilization,
Code 584). Do not place crossings where
channel grade or alignment changes abruptly,
excessive seepage or instability is evident,
overfalls exist (evidence of incision and bed
instability), where large tributaries enter the
stream, or within 300 feet of known spawning
578-1
areas of listed species. Avoid wetland areas.
Discourage livestock loafing in the stream by
locating crossings, where possible, out of
shady riparian areas or by including gates in
the design.
Install stream crossings perpendicular to the
direction of stream flow where possible. Fully
consider the natural lateral migration pattern of
the stream in the design. Avoid skews on all
but the smallest streams.
Access Roads. Where the stream crossing is
installed as part of a roadway, size the
crossing according to NRCS Conservation
Practice Standard, Access Road, Code 560.
Width. Provide an adequate travel -way width
for the intended use. Make "livestock- only"
crossings no less than 6 feet wide and no
more than 30 feet wide, as measured from the
upstream end to the downstream end of the
stream crossing, not including the side slopes.
Side Slopes. Make all side slope cuts and fills
stable for the channel materials involved. Make
the side slopes of cuts or fills in soil materials
no steeper than 2 horizontal to 1 vertical (2:1).
Make rock cuts or fills no steeper than 1.5
horizontal to 1 vertical (1.5:1).
Stream Approaches. Blend approaches to the
stream crossing with existing site conditions,
where possible. Use streambank soil
bioengineering practices as appropriate and
feasible. Make the approaches stable, with
gradual ascent and descent grades which are
not steeper than 4 horizontal to 1 vertical (4:1),
and of suitable material to withstand repeated
and long term use. Make the minimum width of
the approaches equal to the width of the
crossing surface.
Divert surface runoff around the approaches to
prevent erosion. Direct roadside ditches into a
Conservation practice standards are reviewed periodically and updated if needed. To obtain
the current version of this standard, contact your Natural Resources Conservation Service
State Office or visit the Field Office Technical Guide.
NRCS, NHCP
September 2011

578-2
diversion or away from the crossing surface.
Configure the crossing approaches (gradient
and curves) to properly accommodate the
length and turning radii of vehicles using the
crossing.
Rock. All rock must be able to withstand
exposure to air, water, freezing, and thawing.
Use rock of sufficient size and density to resist
mobilization by design flood flows.
Use appropriate rock sizes to accommodate
the intended traffic without damage to the
livestock, people, or vehicles using the
crossing.
Fencing. Exclude livestock access to the
crossing through the use of fence and gates,
as needed.
Install cross -stream fencing at fords, with
breakaway wire, swinging floodgates, hanging
electrified chain, or other devices to allow the
passage of floodwater and large woody
material during high flows.
Design and construct all fencing in accordance
with NRCS Conservation Practice Standard,
Fence, Code 382.
Vegetation. Plant all areas to be vegetated as
soon as practical after construction. If
completion does not coincide with appropriate
planting dates for permanent cover, use a
cover of temporary vegetation to protect the
site until permanent cover can be established.
Native or functioning -as -native plant species
are preferred. Use NRCS Conservation
Practice Standard, Critical Area Planting, Code
342, where vegetation is unlikely to become
established by natural regeneration, or where
acceleration of the recovery of vegetation is
desired.
In areas where the vegetation may not survive,
use NRCS Conservation Practice Standard,
Heavy Use Area Protection, Code 561.
Bridge Crossings
Design bridges in a manner that is consistent
with sound engineering principles and
adequate for the use, type of road, or class of
vehicle. Design bridges with sufficient capacity
to convey the design flow and transported
material without appreciably altering the
stream flow characteristics. Design bridges to
fully span the stream, passing at least the
bankfull flow where the design flow is not
dictated by regulation.
NRCS, NHCP
September 2011
Bankfull flow is the discharge that fills a stream
channel up to the elevation at which flow
begins to spill onto the floodplain.
Adequately protect bridges protected so that
out -of -bank flows safely bypass without
damaging the culvert or eroding the banks.
Vehicle and pedestrian bridges must be
designed in accordance with the current
American Association of State Highway and
Transportation Officials Load and Resistance
Factor Design (LRFD) bridge design
specifications (AASHTO, 2010).
Evaluate the need for safety measures such as
guardrails and reflectors at bridge crossings.
Acceptable bridge materials include concrete,
steel, and wood.
Culvert Crossings
Design culverts in a manner that is consistent
with sound engineering principles and
adequate for the use, type of road, or class of
vehicle. For culverts associated with a road,
culvert design flow shall meet the criteria in
NRCS Conservation Practice Standard,
Access Road, Code 560. The design flow for
culverts not associated with a road will be the
2 -year, 24-hour storm discharge, or bankfull
flow, whichever is less. Design culverts with
sufficient capacity to convey the design flow
and transported material without appreciably
altering the stream flow characteristics.
Design culverts to minimize habitat
fragmentation and to minimize barriers to
aquatic organism movement.
Do not use culverts where large flows of
sediment or large woody material are
expected, or where the channel gradient
exceeds 6 percent (100 horizontal to 6
vertical).
Evaluate the need for safety measures such as
guardrails at culvert crossings.
Crossings shall be adequately protected so
that out -of -bank flows safely bypass without
damaging the structure or eroding the
streambanks or the crossing fill.
At least one culvert pipe shall be placed with
its entire length set six inches below the
existing stream bottom. Additional culverts
may be used at various elevations to maintain
terrace or floodplain hydraulics and water
surface elevations.

Make the barrel length of the culvert adequate
to extend the full width of the crossing,
including side slopes, and inlet or outlet
extensions.
Acceptable culvert materials include concrete,
corrugated metal, corrugated plastic, new or
used high quality steel, and any other
materials that meet the requirements of NRCS
Conservation Practice Standard, Structure for
Water Control, Code 587.
Ford Crossings
The following criteria apply to all ford
crossings:
Make the cross-sectional area of the crossing
equal to or greater than the natural channel
cross-sectional area. Make a portion of the
crossing depressed at or below the average
stream bottom elevation when needed to keep
base flows or low flows concentrated.
Match ford shape to the channel cross-section
to the extent possible.
Provide cutoff walls at the upstream and
downstream edges of ford -type stream
crossings when needed to protect against
undercutting.
Evaluate the need for water depth signage at
ford crossings.
To the extent possible, the top surface of the
ford crossing shall follow the contours of the
stream bottom but in no case shall the top
surface of the ford crossing be higher than 0.5
foot above the original stream bottom at the
upstream edge of the ford crossing.
Make the downstream edge of the ford
crossing with a low -flow hydraulic drop less
than 0.5 foot above the original stream bottom.
Concrete Fords
Use concrete ford crossings only where the
foundation of the stream crossing is
determined to have adequate bearing strength
Use concrete with a minimum compressive
strength of 3,000 psi at 28 days, with a ratio of
water to cementitious materials of 0.50 or less.
Use coarse aggregate of 0.75 to 1 inch
nominal size. If designed for freezing
conditions, use concrete with 4 to 8 percent
air -entrainment.
578-3
Use a minimum thickness of 5 inches of placed
concrete. Pour the concrete slab on a
minimum 4 -inch thick gravel base, unless the
foundation is otherwise acceptable.
Construct toe -walls at the upstream and
downstream ends of the crossing. Make the
toe -walls a minimum of 6 inches thick and 18
inches deep. Extend the toe -walls in the
stream approaches to the bankfull flow
elevation.
Precast concrete panels may be used in lieu of
cast -in-place concrete slabs. To the extent
possible, the panels shall follow the contours
of the stream bottom in order to avoid potential
problems with sediment accumulation. Use
concrete units that have adequate
reinforcement for transportation and
placement.
Dewatering of the site and toe -walls is required
during placement of the concrete to maintain
the proper water/cement ratio. Flowing water
will erode concrete that is not sufficiently
hardened. The stream must be diverted or
retained from flowing over the concrete for at
least 12 hours after placement of the concrete.
During construction, aquatic species must be
removed from the construction area according
to State protocols.
Rock Fords and the Use of Geosynthetics
Coarse aggregate or crushed rock ford
crossings are often used in steep areas
subject to flash flooding and where normal flow
is shallow or intermittent. When the site has a
soft or unstable subgrade, use geotextiles in
the design of rock ford crossings.
Dewater and excavate the bed of the channel
to the necessary depth and width and cover
with geotextile material. Install the geotextile
material on the excavated surface of the ford
and extend it across the bottom of the stream
and at least up to the bankfull flow elevation.
Cover the geotextile material with at least 6
inches of crushed rock. Use minimum 6 -inch
deep geocells, if geocells are used. Use
durable geosynthetic materials and install them
according to the manufacturer's
recommendations, including the use of staples,
clips, and anchor pins.
NRCS, NHCP
September 2011

578-4
Design all rock ford stream crossings to remain
stable for the bankfull flow. Compute channel
velocities and choose rock size using
procedures in NEH630; NEH654 TS14N; and
EFH Chapter 16 (NEH650), Appendix 16A, or
other procedures approved by the State
Conservation Engineer.
Where rock is used for ford crossings for
livestock, use a hoof contact zone or
alternative surfacing method over the rock.
CONSIDERATIONS
Avoid or minimize the use of or number of
stream crossings, when possible, through
evaluation of alternative trail or travel -way
locations. Assess landuser operations to
consolidate and minimize the number of
crossings. Where feasible, use existing roads.
Evaluate proposed crossing sites for variations
in stage and discharge, tidal influence,
hydraulics, fluvial geomorphic impacts,
sediment transport and flow continuity,
groundwater conditions, and movement of
woody and organic material. Increase
crossing width or span to accommodate
transport of large woody material in the flow.
Design passage features to account for the
known range of variation.
For culvert crossings, consider incorporating
natural streambed substrates throughout the
culvert length for passage of aquatic
organisms (see Bunt and Abt, 2001, for
sampling procedures). Natural streambeds
provide passage and habitat benefits to many
life stage requirements for aquatic organisms
and may reduce maintenance costs.
Consider all life stages of aquatic organisms in
the stream crossing design to accommodate
their passage, in accordance with the species'
requirements. Design criteria are available in
NEH Part 654, Technical Supplement 14N,
Fish Passage and Screening Design; U.S
Forest Service low-water design guidance
(USFS, 2006); and stream simulation guidance
(USFS,2008). Each State also has specific
design criteria for culverts and stream
crossings (e.g., MassDOT, 2010). See also
Harrelson, et al. 1994, for stream reference
site descriptions.
Where a stream crossing is installed to remove
an existing barrier to the passage of aquatic
organisms, consider using NRCS
NRCS, NHCP
September 2011
Conservation Practice Standard, Aquatic
Organism Passage, Code 396.
Consider relevant aquatic organisms in the
design and location of crossings to improve or
provide passage for as many different aquatic
species and age classes as possible.
Consider the habitat requirements of other
aquatic or terrestrial species that may be
affected by construction of a stream crossing.
For example, a crossing may be designed with
features that also promote safe crossing by
terrestrial vertebrates.
Ford crossings have the least detrimental
impact on water quality when their use is
infrequent. Ford crossings are adapted for
crossing wide, shallow watercourses with firm
streambeds. If the stream crossing is to be
used frequently, or daily, as in a dairy
operation, a culvert crossing or curbed bridge
should be used, rather than a ford crossing.
Locate stream crossings to avoid adverse
environmental impacts and consider the
following:
• Effects on upstream and downstream flow
conditions that could result in increases in
erosion, deposition, or flooding. Consider
habitat upstream and downstream of the
crossing to avoid fragmentation of aquatic
and riparian habitats.
• Short-term and construction -related effects
on water quality.
• Overall effect on erosion and
sedimentation that will be caused by the
installation of the crossing and any
necessary stream diversion.
• Effects of large woody material on the
operation and overall design of the
crossing.
• Consider adding a well -graded rock riprap
apron on the downstream edge of concrete
crossings to dissipate flow energy.
• Ford crossings should not be placed
immediately downstream from a pipe or
culvert because of potential damage from
localized high velocity flows.

PLANS AND SPECIFICATIONS
Prepare plans and specifications for stream
crossings in keeping with this standard. The
plans and specifications must clearly describe
the requirements for applying the practice to
achieve its intended purpose.
As a minimum, include the following in plans
and specifications:
• Location of stream crossing.
• Stream crossing width and length with
profile and typical cross sections.
• Design grades or slopes of stream
approaches.
• Design flow calculations.
• Thickness, gradation, quantities, and type
of rock or stone.
• Type, dimensions, and anchoring
requirements of geotextile.
• Thickness, compressive strength,
reinforcement and other special
requirements for concrete, if used.
• Vegetative requirements that include seed
and plant materials to be used,
establishment rates, and season of
planting.
• Location, type, and extent of fencing
required.
• Method of surface water diversion and
dewatering during construction.
• Location of utilities and notification
requirements.
OPERATION AND MAINTENANCE
Develop an operation and maintenance plan
and implement it for the life of the practice.
Include the following items in the operation and
maintenance plan, as a minimum:
• Inspect the stream crossing,
appurtenances, and associated fence after
578-5
each major storm event and make repairs
if needed.
• Remove any accumulation of organic
material, woody material, or excess
sediment.
• Replace surfacing stone used for livestock
crossing as needed.
REFERENCES
AASHTO, 2010. American Association of State
Highway and Transportation Officials Load and
Resistance Factor Design (LRFD) Bridge
Design Specifications, Customary U.S. Units,
5t" Edition, with 2010 edits; ISBN Number: 1-
56051-451-0
Bunte, Kristin; Abt, Steven R. 2001. Sampling
surface and subsurface particle -size
distributions in wadable gravel -and cobble -bed
streams for analyses in sediment transport,
hydraulics, and streambed monitoring. Gen.
Tech. Rep. RMRS-GTR-74. Fort Collins, CO:
U.S. Department of Agriculture, Forest
Service, Rocky Mountain Research Station.
428 p
(http://www.fs.fed.us/rm/pubs/rmrs gtr74.html )
Harrelson, Cheryl C; Rawlins, C. L.; Potyondy,
John P, 1994. Stream channel reference sites:
an illustrated guide to field technique. Gen.
Tech. Rep. RM -245. Fort Collins, CO: U.S.
Department of Agriculture, Forest Service,
Rocky Mountain Forest and Range Experiment
Station. 61 p.
(http://www.stream.fs.fed.us/publications/PDFs
/RM245E.PDF)
MassDOT, 2010. Design of Bridges and
Culverts for Wildlife Passage at Freshwater
Streams. Massachusetts Department of
Transportation, Highway Division.
(http://www.mhd.state.ma.us/downloads/probD
ev/Design Bridges Culverts Wildlife Passage
122710.pdf )
NRCS, NHCP
September 2011

TECHNICAL NOTE
United States Department of Agriculture
NATURAL RESOURCES CONSERVATION SERVICE
Engineering
Engineering Technical Note No. MT -13
February 2001
LIVESTOCK WATER ACCESS AND FORD STREAM CROSSINGS
Forrest Berg, Stream Mechanics Engineer and Sandy Wyman, Rangeland Management Specialist
A livestock water access or ford stream crossing is a trail or travelway constructed across a stream or
at a water access point that allows livestock to cross or to drink with minimal disturbance to the
streambank and channel.
The livestock water access and ford stream crossings are used to:
• prevent or minimize water degradation from sediment, nutrient and organic loading.
• protect the watercourse from restricted capacity, degradation and adverse hydrological impacts.
• protect the land from streambank erosion.
• provide a means for livestock to cross a watercourse or provide a stable area to drink from the
stream.
This practice may be used for all land uses where an intermittent or perennial stream exists and a
crossing or access point for livestock is necessary.
Stream crossings (Figure 1) or access points (Figure 2) should be located in areas where the streambed
is stable. Where practical, crossings should be located just upstream or downstream of any natural
barrier such as a rock seam. Avoid sites where:
• channel grade or alignment changes abruptly
• the channel bed is unstable
• overfalls exist
• large tributaries enter the stream
• there is a newly located or constructed channel, or
• immediately upstream or downstream of a culvert or bridge
• water velocity and depth are excessive.
Figure 1. Stream Crossing
NRCS—Montana—Technical Note—ENGINEERING—MT-13

Engineering Technical Note No. MT -13
February 2001
Figure 2. Livestock Access Point
It is not recommended to install a crossing or access point if the product of the depth x velocity is
greater than six. In this case, a bridge crossing should be considered.
Crossings or access points should be installed perpendicular to the direction of the flow of the stream,
preferably at the midpoint between the stream meanders (riffle section). Special care should be taken
to harden the width and depth of bankfull stream channel dimensions in order to maintain long-term
health and proper stream function. Bankfull is based on the 1-1/2 year return interval. Do not disturb
the stream channel upstream or downstream of the crossing during installation of a stream crossing.
Avoid polluting streams during construction. Temporary diversions may need to be installed to avoid
excess sediment transport.
Shaping of the entrance and exit approaches may be all that is necessary if bank and channel is
comprised of .5 inch diameter or larger materials.
GENERAL DESIGN GUIDELINES
Job sheet drawings can be downloaded from http://www.wcc.nres.usda.gov/wtec/roads.html.
Establishing Grades
Subgrade and finished surface grade are critical factors in the design of a properly functioning
crossing or access point. Materials should be placed in excavated subgrades, which are below
potential scour lines.
Geotextile Filter Fabric
Geotextile should be installed on the excavated surface of the ford according to specifications. The
geotextile should extend across the bottom of the stream including 20 feet of approach on each side of
the stream. Geotextile may be omitted in streambeds with stable rock, gravel, or cobbles. All edges of
the geotextile should be keyed as described under construction specifications and manufacturer's
recommendations.
Geotextile filter fabric should be woven or non -woven, needle -punched, geotextile fabric with a
minimum tensile strength of 180 pounds (minimum average roll value).
NRCS—Montana—Technical Note—ENGINEERING—MT-13 2

Engineering Technical Note No. MT -13
February 2001
Longitudinal ends of the geotextile filter fabric should be lapped back over the top of the backfill toe
trench a minimum of one foot beyond the edge of the trench. The ends should be anchored to the
fabric using anchoring pins placed on five-foot centers. When more than one width of fabric is
required, the downstream panel should be installed first. The next upstream panel should be installed
with a minimum of 18 inches overlap over the first section. Anchoring pins should be installed on
3 -foot centers, 6 inches from the downstream edge of the lap. Pins should penetrate both sections of
fabric in the lap.
Every precaution should be taken to not tear the geotextile filter fabric. Tears should be repaired
immediately by removing all surface material and soil from the tear, for a minimum distance of
18 inches, in all directions from the tear. Spread a new section of fabric over the cleared area and
anchor with anchoring pins around all sides.
Where stream channels are composed of a stable coarse rocky material or solid bedrock, the
requirement to extend filter fabric across the channel bottom may be waived upon the approval of the
engineer.
Anchoring Pins for Geotextile
Anchoring pins should be fabricated using No. 3 reinforcing steel or material of equivalent or greater
size and durability. All anchor pins should be installed with the top width lying perpendicular to the
direction of flow in the stream. Pins should be driven vertically into undisturbed soil to provide
maximum resistance to removal.
Anchoring pins should be installed through all overlapped filter cloth at all excavated trenches and
across the channel bottom widths on approximately 3 -foot centers. For crossings using only one width
of fabric, plan to use a number of pins equal to 0.85 times the total length of the crossing from
entrance to exit end. For crossings using two widths of fabric, use 1.3 times the total length (Table 1).
Table 1. Minimum Number of Anchoring Pins Reauired
Number of
Fabric Strips
Across Channel
1
2
Example: Stream crossing 80 feet in total length using two adjacent strips of 15' wide fabric for a
crossing width of 20 feet. Minimum number of pins is 1.3 times 80 feet for 104 pins. Recommend
110 anchor pins.
Care should be taken not to rip the fabric while installing anchor pins. Pins should be sharpened to
permit easy penetration through the fabric. Also, the fabric will fit tightly around anchor pins with
sharpened ends. If a pin must be removed, plug the opening with a wadded ball of fabric filter cloth.
Light weight wire staples such as used to anchor mulch netting may be used to hold filter cloth in
place temporarily while construction is in progress. Such staples cannot substitute for anchor pins.
Elevation
The design subgrade and finished surface are determined by analysis of the stream channel profile
upstream and downstream of the proposed crossing location. The finished (top) surface of the stream
crossing in the channel should not be higher than the natural stable channel gradeline. If the top
surface is above the stable grade line, the surfacing material may wash off. It is recommended that the
final finished surface should be approximately four inches below natural channel grade.
NRCS—Montana—Technical Note—ENGINEERING—MT-13 3

Engineering Technical Note No. MT -13
February 2001
Width
Width is defined as the crossing surface and does not include the side slopes. "Livestock only"
crossings may be as narrow as 6 feet wide. Multi -use crossings should be no less than 10 feet and no
more than 20 feet wide in the upstream -downstream direction.
Side Slopes
All cuts and fills for the stream crossing should have side slopes that are stable for the soil or soil
material involved. Side slopes of earth fills should be no steeper than 2.5:1. Rock fills should be no
steeper than 1.5:1. Cut slopes should be no steeper than 2.5:1 unless in rock or hard shale, in which
case they should be no steeper than .5:1.
Entrance and Exit Approaches
The entrance and exit approach is defined as the terrace elevation to the five-year rainfall event surface
elevation, where it exists. Materials will be used which are equal to the channel bottom materials from
the channel bottom to the five-year frequency storm or terrace elevation (whichever is less). Use
surfacing material (minimum 6" thick) and geotextile fabric, where necessary, from the five-year to
the terrace elevation (if exists).
Entrance and exit approaches to the crossing or access point should blend in with existing site
conditions where possible, but should not be steeper than 5:1. The entrance and exit approaches
should be underlain with geotextile filter fabric and covered with a minimum 6 inches of crushed
gravel. The minimum width of the approaches to the structure should be equal to the width of the
structure.
Where necessary, a surface flow diversion should be installed across the entrance and exit of the
travelway to prevent sediment -laden runoff from entering the stream (See Figure 3).
Fencing
If necessary, stream channel areas above and below the stream crossing should be fenced to prevent
livestock access to the stream except at the crossing or access point (Figure 2). Fence posts along each
side of fords should be installed inside the area covered with geotextile filter cloth and stone. Fence
posts with sharpened ends should be driven through the filter cloth, in the center of the toe trenches,
along the side of the crossing.
A "break -away" fence may be installed across streams where damage from runoff is likely to occur.
The fencing wire should be placed on the downstream side of the posts on each fence line. Strands of
wire should not be continuous across the crossing, but should be cut and secured lightly to the posts so
a buildup of trash will pull the wire away from the post, allowing the trash to move downstream.
In lieu of "break -away" fences, other appropriate means of preventing livestock access to the stream,
such as swinging gates, electrified chains, or other control measures may be used.
Safe
The specifications contained in this practice pertain primarily to flow capacity and resistance to
washout of the structure. A gauging rod should be installed at ford crossings to determine depth of
flow and safety for crossing. Crossing should not be installed where water velocity and depth are
excessive.
NRCS—Montana—Technical Note—ENGINEERING—MT-13 4

Figure 3. Stream Crossing
5' max
VA. bank height ..
X31 � f f
Stone over
filter cloth
Engineering Technical Note No. MT -13
February 2001
,,,Stream channel
f1"
Surface flow
diversion
POW
Stone approach section
5:1 max, slope on road •�.
Surface flow
diversion
Original streambank
t�oj
_r
w
Q r 1 J
Filter cloth
Stone
Fords Using Stone
Figure 3 shows a typical layout for a well -constructed crossing (fence not shown). The stream
crossing must be designed to remain stable during the bank full event. Bankf ill flow and water
surface slope or channel velocities should be computed or measured, and a stone size chosen from
Figure 4 or Table 2. The surfacing material should consist of 1/2" to 2" rock with a minimum 2-3"
thick layer, where the D50 of the crossing stone is >1 inch. The minimum thickness of rock protection
should be the greater of 6 inches or twice the D50 rock size.
The final elevation of the surfacing stone in the bottom of the stream/watercourse should be no higher
than the original stream bottom on both the upstream and downstream edges of the crossing or access
point. This eliminates any overfall and possible scour problems.
NRCS-Montana-Technical Note -ENGINEERING -MT -13 5

Engineering Technical Note No. MT -13
February 2001
Figure 4. Livestock Crossing DM Rock Size
D50
V
LIVESTOCK CROSSING
Bankfull Depth
D50
D50 ROCK SIZE (inches)
Slope
5.00
inches
fps
4.50
ft
r
4.00
ft/ft
ft
0.5
2.96
F-
F-
3.50
2
13.
0.01
0.84
w
3.00
0.002
J
2
3.91
0.012
2.50
0.5
2.35
0.004
0.52
2
3.81
0.014
0.60
0.5
2.20
0.006
0.35
3
ILL Y
2.00
Dso=•5
Dso=
2.09
Dso=
Dso=3 Dso
3
5.75
0.004
3.15
1
Z
0.001
4.20
3
5.38
0.006
2.10
1
3.73
0.002
2.10
3
Q
0.008
1.57
1
3.32
0.004
1.05
3
4.94
0.01
1.26
1
m
1.50
0.70
3
4.79
0.012
1.05
1
2.96
0.008
0.52
3
4.67
0.014
0.90
1
2.85
0.01
0.42
4
7.45
0.002
8.39
1
2.77
1.00
0.35
4
6.64
0.004
4.20
1
2.70
0.014
0.30
4
6.21
0.006
2.80
2
5.27
0.002
4.20
4
5.92
0.008
2.10
2
4.70
0.50
2.10
4
5.70
0.01
1.68
2
4.39
0.006
1.40
4
5.53
0.012
1.40
2
0.001 0.002
0.004 0.006 0.008 0.010 0.012 0.014
1.05
4
BANKFULL SLOPE
D50
V
Slope
Bankfull Depth
D50
V
Slope
Bankfull Depth
inches
fps
ft/ft
ft
inches
fps
ft/ft
ft
0.5
2.96
0.001
2.10
2
4.03
0.01
0.84
0.5
2.63
0.002
1.05
2
3.91
0.012
0.70
0.5
2.35
0.004
0.52
2
3.81
0.014
0.60
0.5
2.20
0.006
0.35
3
6.45
0.002
6.29
0.5
2.09
0.008
0.26
3
5.75
0.004
3.15
1
4.18
0.001
4.20
3
5.38
0.006
2.10
1
3.73
0.002
2.10
3
5.13
0.008
1.57
1
3.32
0.004
1.05
3
4.94
0.01
1.26
1
3.10
0.006
0.70
3
4.79
0.012
1.05
1
2.96
0.008
0.52
3
4.67
0.014
0.90
1
2.85
0.01
0.42
4
7.45
0.002
8.39
1
2.77
0.012
0.35
4
6.64
0.004
4.20
1
2.70
0.014
0.30
4
6.21
0.006
2.80
2
5.27
0.002
4.20
4
5.92
0.008
2.10
2
4.70
0.004
2.10
4
5.70
0.01
1.68
2
4.39
0.006
1.40
4
5.53
0.012
1.40
2
4.19
0.008
1.05
4
5.39
0.014
1.20
Table 2. Livestock Crossing Ds„ Rock Size
NRCS-Montana-Technical Note -ENGINEERING -MT -13 6

Engineering Technical Note No. MT -13
February 2001
Fords or Access Points Using Geocell and Stone
The minimum height of the geocell is 6 inches but an 8 -inch geocell is recommended (See Figure 5).
The geocell material should not be used if velocities are expected to exceed 6 fps. In order to
minimize velocities; locate the crossing where the stream is not steeply graded.
Install geotextile and geocell as shown in Figure 5. The geotextile and geocell should extend across
the bottom and at least 20 feet up each approach section. Fill geocell with AASHTO
No. 2 stone, (3/4 in. to 3 in.) and, add 2 inches (minimum) of stone above the geocell. Use staples,
clips, anchor pins, or earth anchors as recommended by manufacturer.
The final surface of the stone in the bottom of the watercourse should be the same elevation as the
original watercourse bottom in order to eliminate any overfall and possible scour problems.
Figure 5. Stream Crossing Using Geocell
c O
I
egg e a p Q e r
{� /J1,
streizm>aed � � a"i+ ti.Jl d orf
1S ti I I ri'4 � Jf r¢
� X411
TOP OF BA
FILLED
'GEOCELL•
GRADE RAMP AT
EACH END
PLAN
(Hydmullo Flow diagram PrnYl wLh psmu miwn tram Malo Produce, GHOSYSYEMS 17iVWW.)
NRCS—Montana—Technical Note—ENGINEERING—MT-13 7

Engineering Technical Note No. MT -13
February 2001
Fords Usine Concrete
Concrete may be used as a surface treatment for crossings. The finished surface of the concrete will
be at or slightly below the natural stable channel grade. The subgrade for the concrete will be shaped
and smoothed to provide a uniform 5 inch minimum thickness of concrete. The concrete slab and
toewalls will be reinforced by placing #4 (1/2 -inch diameter) steel reinforcing bars on 24 inch centers
(both directions) at the slab thickness mid -point. The concrete will extend down into toe trenches,
minimum 6 inches wide and 18 inches deep, on the upstream and downstream edge of the crossing.
The toe trenches/walls will extend half way up the streambank approaches.
If the crossing has "soft" or compressible soil, the foundation will be excavated and backfilled with
graded aggregate base (GAB) or crusher run stone to provide a dense subgrade for the concrete.
De -watering of the toe trenches and site should be needed during placement of the concrete to
maintain the proper water/cement ratio. Flowing water will erode concrete that is not sufficiently
hardened. The stream should be diverted or retained from flowing over the concrete for 12 hours after
placement of the concrete.
A three-foot wide and 18 inch thick rock riprap apron should be installed along the downstream edge
of the concrete. This riprap apron serves two purposes; 1) velocity dissipation, and 2) head cut
protection should the stream channel degrade.
The concrete should meet the following minimum requirements:
• Minimum 28 day compressive strength of 3500 psi and maximum water/cement ratio of 0.5
(minimum of 5 1/2 bags of cement per cubic yard).
• Portland cement type I or II should be used.
• A slump of 1.5 to 3 inches - use a concrete super plasticizer admixture to improve workability
during placement and reduce voids and honeycombs.
• The maximum size aggregate should be 1-1/2 inch.
• Air entrainment should be 3 to 6 percent by volume (air entrainment is critical for concrete subject
to freezing and thawing).
• The concrete will be placed within 90 minutes after adding water to the cement/sand/gravel mix.
Construction Equipment
Experience has proved that certain types of construction equipment are more suitable for installation
of crossings than others. Where crossings are on small drains with stable subsoil, equipment choice
may not be critical. Where non -plastic silts and clays or unstable fine sands are anticipated in the
subgrade material, the following observations should be noted:
• Tracked equipment is superior to rubber -tired equipment, when working in streams.
• Crawler tractors with angle dozer or bulldozer blades and fixed bucket front-end loaders should be
avoided.
• Smaller, lighter dump trucks to deliver surfacing material will cause less damage to approaches
than large trucks.
• Track -mounted hydraulic excavators with reaches of 25 feet or more provide the best and fastest
installation.
• A tracked front-end loader with a 4 in I clamshell type bucket and a large rubber -tired backhoe
provide the best installation if a hydraulic excavator is not available.
• A gasoline -powered pump and hose should be available for pumping excess water from trenches.
Landowners and contractors should be advised of the use of proper equipment. Improper equipment
will result in construction difficulties and excessive construction costs.
NRCS—Montana—Technical Note—ENGINEERING—MT-13 8

Engineering Technical Note No. MT -13
February 2001
Vegetation
Disturbed areas not covered or protected should be established to vegetation immediately after
construction. Seed bed preparation, fertilizing, seeding, and mulching should be in accordance with
NRCS Field Office Technical Guide, Section IV, Practice Standard 322, Channel Vegetation or
Practice Standard 342, Critical Area Planting.
PLANNING CONSIDERATIONS
Avoid crossing streams when possible. Crossings can be a direct source of water pollution. They may
create flooding and safety hazards and can be expensive to construct.
Evaluate each specific site carefully to determine if a crossing is most appropriate.
Crossings made of stabilizing material such as rock riprap are often used in steep areas subject to flash
flooding, where normal flow is shallow or intermittent. Crossings have the least detrimental impact on
water quality when crossing is infrequent. Crossings are especially adapted for crossing wide, shallow
watercourses with firm streambeds. Generally, crossings should not be used where bank heights
exceed 5 feet. Mud and other contaminants are brought into the stream by vehicular and animal traffic
where crossings are used. Access to crossings will be prevented during high flows. It is
recommended to shape cut slopes of a minimum of 3:1 or flatter to facilitate re -vegetation and ease of
maintenance.
Livestock access points should be constructed as narrow as possible to allow drinking, but so as not to
encourage loafing in or near the stream.
Where feasible, utilize and stabilize existing livestock crossing areas to ensure livestock are familiar
with and will use the area.
Roads or trails leading to stream crossings will normally slope into the stream. Where necessary,
water diversions should be installed to move sediment -laden runoff from the trail or road and to
disperse the runoff onto an undisturbed area for filtering. Crossings should provide a way for normal
passage of water and aquatic animals within the channel.
Consideration should be given to erosion and sedimentation, which will be caused by the installation
of the crossing and any necessary stream diversion. Construction should be done during the driest part
of the year.
Cultural resources should be considered when planning this practice. This practice has the potential to
adversely affect cultural resources and requires compliance with General Manual 420, Part 401 during
the planning process.
Measures planned shall not adversely affect threatened and endangered species or species of special
concern. If threatened and endangered species or their critical habitats are present at this site, or
downstream, or upstream, General Manual 190, Part 410.22 shall be followed.
Determine and secure necessary permits prior to construction. It may be necessary to obtain permits
such as 310 Permits, 404 permits, etc.
NRCS—Montana—Technical Note—ENGINEERING—MT-13 9

Engineering Technical Note No. MT -13
February 2001
OPERATION AND MAINTENANCE
The crossing or access point and associated fence should be inspected on a frequent basis, especially
after major storm events. Any disturbed materials should be repaired or replaced as soon as possible
to prevent further damage from occurring. Surfacing stone used for crossings or access points should
be replaced as needed. Break -away type fences will need to be repaired after major runoff events.
During high flows, sediment and deposition may occur on approaches to crossings. This berm of soil
and debris will need to be occasionally removed.
REFERENCES
United States Department of Agriculture, Natural Resources Conservation Service, Field Office
Technical Guide, Section IV, Practice Standards and Specifications:
• Alabama Stream Crossing 728
• Access Road 560
• Fence 382
• Channel Vegetation 322
• Georgia Stream Crossing 728
NRCS—Montana—Technical Note—ENGINEERING—MT-13 10