United States Department of Agriculture
Forest Service
Tech Tips
National Technology & Development Program • Recreation • October 2013 • 2300 • 1223–2315P–MTDC
Plastic Bottomless Arch Culverts for Trails
Jerry D. Barrow, Civil Engineer and James Scott Groenier, Project Leader
S
torm water chambers currently are installed under
parking lots to retain storm water runoff. These chambers prove most useful where space for retention
ponds is limited. The chambers (figure 1) also can be used on
trails as bottomless arch culverts as an alternative to round
plastic or metal culverts.
Figure 1—Plastic storm water chambers are increasingly being used as
bottomless arch culverts on trails.
Advantages and Disadvantages
Plastic bottomless arch culverts have several advantages
and some disadvantages.
Advantages
• Installation requires less digging than a traditional culvert and causes less disturbance to the stream bottom.
• The plastic and resin-based products are noncorrosive
and do not rust.
• The storm water chambers are lightweight and easily
carried to remote jobsites.
Highlights…
• Storm water chambers can be
used on trails as an alternative to
round plastic or metal culverts.
• Storm water chambers used as
bottomless arch culverts are
available in several sizes and
types of material.
• Arch culverts must be properly
sized to handle water flows
effectively. A culvert that is
buried correctly will withstand
heavy loads, including 10,000pound trail dozers.
• Bottomless arch culverts are cost effective when compared with bridges or steel culverts.
• Heavy loads for maintenance equipment can be supported with only 1 to 1½ feet of compacted fill cover.
• The culverts are a good option for maintaining trail
grades in rolling mountain terrain drainages where
bridges are not the best option.
Disadvantages
• Bottomless arch culverts are not resistant to ultraviolet light. Exposed ends must be covered or coated.
• Bottomless arch culverts, like round plastic culverts,
melt if exposed to wildfires or prescribed burns.
• The currently available colors (bright yellow, bright
green, and black) must be coated to blend with the natural surroundings.
For additional information, contact: USDA Forest Service, MTDC; 5785 Hwy. 10 West; Missoula, MT 59808–9361.
Phone: 406–329–3900; fax: 406–329–3719; email: wo_mtdc_pubs@fs.fed.us
Construction Process
Sizing and Product Selection
Storm water chambers used as bottomless arch culverts are
available in several sizes and types of material. The chambers
are designed for use as storm water retention systems under
parking lots or in other areas where volumes of storm water
runoff must be stored underground for a short time. The products typically are made of polypropylene or high-density polyethylene, such as those sold by StormTech, Inc., and Hydrologic Solutions, Inc. (StormChamber). A chamber from Triton
Stormwater Solutions, LLC, is made from soy-based resin.
When properly buried, storm water chambers can withstand
heavy loads, including 10,000-pound trail dozers. In engineering terms, this is equivalent to American Association of State
Figure 2—Excavate to provide a flat, mineral soil base for the bottomless
arch culvert, disturbing the drainage area as little as possible.
Highway and Transportation Officials (AASHTO) HL-93 load
and resistance factor design (LRFD) methodology.
Sizing the arch culvert properly is essential. The culvert
size determines the flow it can handle in a storm event. If the
arch is undersized, trail damage may result or the arch itself
may be washed out. On national forests, a hydrologist and
engineering staff can be consulted to determine sizing. District
rangers may be concerned with the arch culvert installation
(including the finishing details), such as headwalls and the
color coating used for the exposed ends of the culvert.
Excavation and Placement
Excavate to mineral soil and provide a smooth, straight
surface for the edges of the arch culvert to rest on (figure 2).
Set the bottomless arch culvert in place and secure it with
2-foot sections of No. 4 steel rebar pins. Drive steel rebar
pins through the arch culvert slots (in the middle and at each
of the four corners) to secure the culvert while backfill is
placed. This also secures the culvert in case the edges of the
stream erode and the arch settles.
Figure 3—Compact each lift with compactors or handtools until there is no
visible sign of displacement.
Backfilling
Backfill in 6-inch lifts beginning along the outside bottom of the arch culvert. Fill both sides in equal lifts, progressing to the top. Compact each lift as it is placed until no signs
of displacement are visible (figure 3).
Continue backfilling over the top of the arch culvert.
With a minimum of 1 to 1½ feet of compacted suitable fill
over the top, the arch culvert should meet the loading requirements of a 10,000-pound trail dozer, mini-excavator, or other
trail machinery (figure 4).
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Figure 4—Backfill the culvert with 6-inch lifts along the sides and over the top.
Headwalls
Install headwalls at each end of the arch culvert to prevent backfill from sloughing (figure 5). Headwalls can be
rock, blocks, or timber retaining (soldier pile) walls (figure
6) designed to remain in place and blend aesthetically with
the surrounding landscape. Placing nonwoven geotextile fabric between the rock headwall and the backfill reduces the
chance of fine materials washing out of the fill.
Figure 6—Rock headwalls help keep backfill in place. Place nonwoven
geotextile fabric between the headwall and the backfill so fine materials will
not wash out of the fill.
Painting/Coating
Most plastic storm water chambers are available in bright
yellow, bright green, or black. Color has not been an issue in
the past because the chambers normally are completely covered. Colors may be changing as the chambers are used for
bottomless arch culverts and for other uses.
Apply black or brown spray paint that adheres to plastic
(or use an automobile undercoat spray) for parts of the culvert exposed to view and to sunlight. Numerous auto body
paints are available for painting plastic car parts. Painting
improves aesthetics and provides ultraviolet protection to
exposed ends.
Figure 5—Rock headwalls usually blend in with the natural environment,
but headwalls also can be formed from timber soldier pile retaining walls.
Product Sources
The U.S. Department of Agriculture, Forest Service does not endorse products to the exclusion of other suitable products.
The listing of companies below is provided as a source of places to compare similar products.
StormTech, a Division of ADS, Inc.
70 Inwood Road, Suite 3
Rocky Hill, CT 06067
Phone: 888–892–2694
http://www.stormtech.com
HydroLogic Solutions, Inc.
(StormChamber)
12301 Beechnut Ct.
Woodbridge, VA 22192
Phone: 877–426–9128
http://stormchambers.com
Triton Stormwater Solutions, LLC
9864 E. Grand River, Suite 110, No. 176
Brighton, MI 48116
Phone: 810–222–7652
http://www.tritonsws.com
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About the Authors
Library Card
Jerry D. Barrow joined the Trails Unlimited enterprise
team in 2007 as a civil engineer specializing in trail bridge
construction. Barrow began his career with the Forest Service
in 1985 after 8 years in the private sector and the U.S. Army
Corps of Engineers. He earned degrees in forestry and civil
engineering from Virginia Tech and the University of Tennessee. He has worked on the Cherokee, Chattahoochee-Oconee,
and George Washington National Forests. He served as the
project construction engineer for the 1996 Olympic Venue at
the Cherokee National Forest.
James Scott Groenier began working for MTDC during
2003 as a civil engineer. Groenier earned a bachelor’s degree
from the University of Wisconsin at Madison and a master’s
degree from Montana State University. He worked for the Wisconsin and Illinois State Departments of Transportation before
starting his career with the Forest Service. He worked as the
east zone structural engineer for the Eastern Region and as a
civil engineer for the Ashley and Tongass National Forests.
Barrow, Jerry D.; Groenier, James Scott. 2012. Plastic
bottomless arch culverts for trails. Tech Tip 1223–2315P–
MTDC. Missoula, MT: U.S. Department of Agriculture, Forest Service, Missoula Technology and Development Center.
4 p.
This tech tip explains some of the advantages and disadvantages of using storm water chambers on trails as an
alternative to round plastic or metal culverts. Information is
provided on sizing, product selection, excavation, and placement. Some sources also are provided as a place to begin
comparing similar products.
Additional single copies of this publication may be
ordered from:
USDA Forest Service
Missoula Technology and Development Center
5785 Hwy. 10 West
Missoula, MT 59808–9361
Phone: 406–329–3978
Fax: 406–329–3719
Email: wo_mtdc_pubs@fs.fed.us
For additional technical information, contact MTDC:
Phone: 406–329–3900
Fax: 406–329–3719
Keywords: arch culverts, headwalls, storm water chambers, trail damage, trails
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documents, CDs, DVDs, and videos on their internal computer networks at:
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This document was produced in cooperation with the Recreational Trails Program of the U.S. Department of Transportation’s Federal Highway Administration in the interest of information exchange. The
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