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Wetland Trail Development

Wetland identification, working with wetlands regulation, and trail development in riparian areas.

From THE TRAIL FORUM, Colorado State Trails Program

If you are considering development of trails in a possible wetland area or along a river or lake, Federal regulations may apply. The following information, while not intended as a definitive guide to wetlands regulation, is from two publications of the U.S. Army Corps of Engineers: "Recognizing Wetlands" and "Caring For Our Nation's Waters". If there is any question as to whether your specific project will impact a wetland area, you should contact the regulatory field office in your area.

WHAT IS A WETLAND?

The U.S. Army Corps of Engineers (Corps) and the U.S. Environmental Protection Agency (EPA) jointly define a wetland as follows:

Those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal conditions do support a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas.

HOW CAN WETLANDS BE RECOGNIZED?

The Corps uses three characteristics when making wetland determinations: vegetation, soil, and hydrology. Nearly 5,000 plant types in the United States, known as "hydrophytic" vegetation, may occur in wetlands. Several Corps offices have published pictorial guides of representative wetland plant types. There are approximately 2,000 named soils in the U.S. that may occur in wetlands. Such soils are called "hydric soils" by the Soil Conservation Service. Most of these hydrologic indicators can be observed during a field inspection. One or more indicators of wetland vegetation, hydric soil, and wetland hydrology must be present for an area to be defined as a wetland. If you observe definite indicators of any of these characteristics, you should seek assistance from the local Corps District Office.

PERMITS ARE REQUIRED

The Corps has regulatory authority under two laws: Section 404 of the Clean Water Act, and section 10 the Rivers and Harbors Act of 1899. There are four different forms of authorization which the Corps can issue to conduct work in wetland areas. These are:

  1. Individual Permit
  2. Letter of Permission
  3. Nationwide Permit
  4. General Permit

If you plan any work in or near a wetland, river, or stream you should contact the Corps Regulatory Field Office in your area early in the planning phase of your project. The field office can determine what type of permit, if any, is required.For projects which exist within the Omaha District, contact the Corps office nearest you at one of the following numbers for further information and assistance:

Nebraska (308) 234-1403
Colorado (303) 979-4120
Wyoming (307) 772-2300
Montana (406) 444-6670
North Dakota (701) 255-0015
South Dakota (605) 224-9371

TECHNIQUES FOR TRAIL DEVELOPMENT IN SEASONALLY WET AREAS

CURTAIN DRAINS

By Jeff Bartlett

In spring 1992 Jefferson County Open Space began a project involving the construction of a multi-use crusher fines trail in rural Jefferson County just north and east of Golden, Colorado. The trail specifications called for a trail tread 8 feet wide, excavated to a depth of 6 inches, then filled with crusher fines and compacted.

The construction process in this instance was complicated by several factors, including a corridor easement only 20 feet in width and a location just downslope from a soil water-supply ditch which in spring and summer carries an average of 80 cubic feet per second of water. We quickly realized that when this ditch was active, it allowed a surprising amount of leakage and generated several seasonal bogs in the middle of our trail corridor.

Because of the narrow confines of the easement, we were forced to develop a means of construction that would maintain the integrity of our trail through these boggy areas. Our solution was to build a drainage system to catch the water before it could percolate onto the trail, and, instead, channel it underneath.

First, we dug a trench along the uphill side of the trail with intermittent drains crossing the tread and emptying below the trail. This trench was approximately 2 feet deep and a foot wide. Next, we lined the bottom and the trail-ward side of the trench with heavy plastic and anchored it. This plastic constitutes the "curtain" or barrier. On top of the plastic we placed a geotextile fabric to line the entire trench as well as the excavated subgrade of the trail tread. Four-inch perforated drain tile was then laid in the bottom of the trench and 1" rock brought in to fill it up to the level of the subgrade. With this complete, we were ready for the crusher fines.

As of this writing, the curtain drain system appears to be doing an adequate job of keeping the leakage from the ditch away from our trail.

From Jefferson County Open Space (Colorado) Trails Program

TURNPIKE TRAIL CONSTRUCTION

Within the Jefferson County Open Space trail system, we have several areas where spring runoff creates seasonal bogs or marsh-like areas. Since many of these areas have trails running through them, we have developed a somewhat unique form of "turnpike" or elevated trail. These turnpikes consist of treated timber "rails" resting on timber risers, filled with rock, and finished with crusher fines as the final trail tread which will bridge the entire boggy area.

Turnpike construction is most effective if completed in late summer or early fall, when the soil is driest. We use 6x8 treated timbers as risers, or supports for the elevated trail. These must be dug down to firm ground and then laid in place perpendicular to the trail (just like railroad ties). On top of these we line or edge what will be our final trail tread with a second (or third) layer of 6x8 timbers. These are like the rails of a railroad. The empty space between and beneath the "rails" is filled, within 3 or 4 inches of the top, with 6-12 inch rip-rap. The rip-rap is then covered with geotextile and the remaining space filled with crusher fines. In the end, we have a solid elevated trail which allows spring runoff to seep or flow easily beneath it.

From Jefferson County Open Space (Colorado) Trails Program

DEVELOPING A PHYSICALLY CHALLENGED RIPARIAN NATURE TRAIL AT ARAPAHO NATIONAL WILDLIFE REFUGE

How do you decide the best location to build a nature trail? In our case, access to the Illinois River riparian area was a critical factor. We also wanted a route that would cause the least soil disturbance. Two existing fishing access areas with parking facilities offered the best alternatives. We decided on the fishing access area that had restrooms and the largest parking area. These were then converted to be accessible for the disabled.

We then looked for the best area to construct the trail. We took into consideration such things as minimal habitat impact, using existing man-made features (pond dike), avoiding wildlife nesting areas and adding the least amount of man-made structures (boardwalks and bridges). With these factors in mind, the trail was laid out to provide as many interesting interpretive stops as possible, while following the highest elevation and disturbing the least amount of willow and wet meadow areas.

To meet accessibility criteria for the physically challenged, the trail was designed to be approximately one-half mile long and 5 feet wide with a hardened surface. We looked into several options for hardening the trail. One option was to mix concrete with a gravel base and compact it; the other was to mix calcium chloride with the gravel and compact it. We used calcium chloride, but at this time we do not feel it will harden enough for our needs. This may partly be due to the fact that we used a gravel base and it may not have contained enough small particles (silt and clay).

By placing a hardener on the trail, wetlands were lost and had to be mitigated. In compliance with Section 404 of the Clean Water Act, we contacted the U.S. Army Corps of Engineers to obtain a permit for depositing fill in a wetland. A representative from the Corps of Engineers made a site inspection and designated what portion of the trail involved filling wetlands. The refuge created a new wetland on an upland site which more than mitigated the area lost.

We completed the trail last fall and plan to install interpretive signs, benches, and rails on several bridges this summer.

For more information on this project, contact Pam Rizor, U.S. Fish and Wildlife Service, Arapaho National Wildlife Refuge (MS-65520), P.O. Box 457, 953 Jackson County Rd. #32, Walden, CO 80480. Phone: (303) 723-8202; Fax: (303) 723-8528.

August 8, 2003

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