A04_100__Statement_of_work_TrailsPortion.docx

Statement of Work Water Canyon Trails Bridge Approaches

1.0 Overview

· The Bureau of Land Management (BLM), Winnemucca District Office has the requirement for two pre-manufactured steel pedestrian bridges and precast abutments for bridges. The pedestrian bridges will require clearing of the nature trail at ADA acceptable grades while providing a firm and stable surface. A firm trail surface resists deformation by indentations. Approximately 750 feet on the south side of the creek and approximately 210 feet on the north side of the creek is estimated to be required. The equipment allowed for use of the trail clearing will need to conform with the Water Canyon Bridge and Trail Improvement Environmental Assessment and be approved by the COR.

2.0 Materials

It is anticipated that the trail will not require new materials but only clearing of the natural existing surface.

3.0 Trail Requirements

· Meets ABA Access Guide Chapter 10 Guidelines for Outdoor Developed Areas “Trails.” The stable trail surface will be established to the extent possible. Other recommendations must be met. Highlights reproduced for convenience include:

· A stable trail surface is not permanently affected by expected weather conditions and can sustain normal wear and tear from the expected uses between planned maintenances. Scope of work does not include importing materials for reestablishment of this trail.

· The clear tread width of trails must be a minimum of 36 inches. Additional clearance outside of the 36-inch path will be considered incidental to the contract.

· A trail tread width less than 60 inches does not permit two people using mobility devices to pass each other. Consequently, where the tread width is less than 60 inches, passing spaces must be provided at intervals of at least 1000 feet.

· The limit on the height of tread obstacles on trails, passing spaces, and resting intervals is based on the surface material used. When the trail surface is constructed of concrete, asphalt, or boards, tread obstacles cannot exceed one-half inch in height at their highest point. When the trail surface is constructed of materials other than concrete, asphalt, or boards, tread obstacles are permitted to be a maximum of 2 inches high.

· Running slope, also referred to as grade, is the lengthwise slope of a trail, parallel to the direction of travel. Trails or trail segments of any length may be constructed with running slopes up to 1:20 (5 percent). To accommodate steep terrain, trails may be designed with shorter segments that have a running slope and length, as shown in table 2, with resting intervals at the top and bottom of each segment.

· To ensure that a trail is not designed as a series of steep segments, no more than 30 percent of the total length of the trail may have a running slope exceeding 1:12 (8.33 percent). The running slope must never exceed 1:8 (12 percent). Resting intervals must be provided more frequently as the running slope increases (figure 8).

· Cross slope is the side-to-side slope of a trail tread. Some cross slope is necessary to provide drainage and to keep water from ponding and damaging the trail surface, especially on unpaved or natural surfaces.

· When the trail surface is constructed of concrete, asphalt, or boards, the cross slope must be no steeper than 1:48 (2 percent). When the trail surface is constructed of materials other than asphalt, concrete, or boards, cross slopes no steeper than 1:20 (5 percent) are allowed when necessary for drainage.

· The contractor is encouraged to follow the natural contour of the land and to minimize the limits of disturbance to existing vegetation to the extent possible.

· Contractor to encourage positive drainage.

· Trail layout to be flagged by contractor prior to construction and accepted by project inspector before alignment is cleared. If deviations are required the contractor will submit request in writing to the Contractor’s Officer Representative in writing three-days before continuing.

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